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Thu, 31 Jan 2019 20:30:00 +0100An experimental study on the seismic behavior of infilled RC frames with opening
http://scientiairanica.sharif.edu/article_4150_0.html
Infill walls are generally not taken into account in structural analysis due to their complex behavior at seismic actions. As it is known, they increase the stiffness as well as the lateral load capacity of the system. Sometimes, infill walls may have window and door openings in their planes. In the present study, behavior of reinforced concrete (RC) frames with infill wall which have openings is investigated under cyclic lateral loadings. Location and size of the openings in the infill wall are selected as investigation parameters. Test specimens are constructed and experimentally analyzed. The infill wall changes the behavior of the frames under cyclic lateral loads significantly. Location and size openings in the infill wall are two main parameters which affect the behavior of the infill walls as well as on that of the frame. The test results clearly show that the contribution of the infill wall to the behavior of RC frame has diminished significantly when the opening ratio is larger than 9%. Therefore, the effect of the opening in the infill wall must be taken into account in the structural modeling when the opening ratio is larger than 9%.Sat, 12 Aug 2017 19:30:00 +0100Increasing stability in model-mediated teleoperation approach by reducing model jump effect
http://scientiairanica.sharif.edu/article_20007_1067.html
Model-mediated teleoperation is a predictive control approach for controlling haptic teleoperation systems whereby the environment force is virtually located on master side in order to increase the stability and transparency of the system. This promising approach, however, results in new challenges. One pivotal challenge is the model jump effect, which stems from the delay in correct creation of the virtual environment. Previous works have endeavored to reduce this effect; however, they either led to transparency decrease or assumed simplified environment models. In this paper, we propose a control approach for this aim based on the idea of decoupling. This means that when a new environment has been identified, the operation is interrupted and no signal is transmitted between master and slave sides. During this time, both sides are controlled by their own sliding mode controllers until the system reaches stability. The main advantage of this method is its independence from environment type, which makes it usable for different kinds of applications. To verify the effectiveness of the proposed approach simulation tests are conducted. The results show the system is stable in interaction with hard and soft environments in presence of large time delays in communication channels.Thu, 31 Jan 2019 20:30:00 +0100Lean design management using a gamified system
http://scientiairanica.sharif.edu/article_20325_1067.html
Design process, due to its information- and innovation-intensive nature, is highly susceptible to change, thus waste. This attracted the attention of lean design/construction professionals in the past few years. However, limited, if any, researches have addressed this issue from the human behavior perspective. This research proposes a method that exploits the potential of the Last PlannerÒ System (LPS) in design management. The main contribution of this paper is improving the applicability of the LPS to design processes by incorporating a gamified pay-for-performance system to the normal practice of the LPS. It encourages motivating design engineers by granting them single point, autonomous responsibility to perform their tasks. To this end, the proposed method shifts the focus of design managers away from predicting the workflow and chronologies of design tasks towards motivating design engineers to eliminate non-value-adding works/time. To bolster the concept and examine the method, it was put into practice by construction design teams. Findings corroborate the efficiency of the method in eliminating the non-value-adding works from design processes. The findings are of practical value to consulting firms, especially design team managers who seek to maximize innovation, competency and quality outcome.Thu, 31 Jan 2019 20:30:00 +0100A statistical approach to knowledge discovery: Bootstrap analysis of language models for ...
http://scientiairanica.sharif.edu/article_20198_1067.html
In this paper, we propose a novel approach for knowledge discovery from textual data. The generated knowledge base can be used as one of the main components in the cognitive process of question answering systems. The proposed model automatically extract relations between named enti- ties in Persian. Our proposed model is a bootstrapping approach based on n-gram model to nd the representative textual patterns of relations as n-grams in order to extract new knowledge about given named entities. The main motivation for this work is the characteristic of the sentence structure in Persian which, in contrary to English sentences, is in subject- object-verb format. The proposed approach is a purely statistical one and no background knowledge of the target language is required. This makes our method applicable to any open domain relation extraction task. How- ever, as for our test-bed, we focus on the domain of biographical data of international poets and scientists to build a knowledge base about them. Qualitative evaluations based on human assessment is an evidence for the ecacy of our method.Thu, 31 Jan 2019 20:30:00 +0100Teaching music to children with autism: A social robotics challenge
http://scientiairanica.sharif.edu/article_4608_1067.html
Utilizing a humanoid social robot to systematically teach music to children with autism has not received wide attention to date. In this study, a novel robot-assisted music-based scenario has been designed in order to: 1) teach fundamentals of music via a xylophone-/drum-player robot as a teacher assistant, and 2) improve social/cognitive skills through active music games in children with autism. The educational-therapeutic interventions were conducted in an eleven-session case study program on three high-functioning and one low-functioning children with autism taking into consideration the children’s, parents’, and therapists’ experience during the program. The results indicated that as a tool and facilitator, the NAO robot does have the ability to teach musical notes/rhythms to the participants with high-functioning autism. It was also observed that the severity of the participants’ autism as well as the stress of the parents decreased somewhat during these sessions. Furthermore, noticeable improvements were seen in social/cognitive skills of all four participants; as well as the positive effect of this program on fine motor imitation skills of two subjects after the interventions. The progress reported from this preliminary exploratory study confirmed the potential benefits of using social robots and intelligent technologies as a facilitator in music-teaching and cognitive-rehabilitation.Thu, 31 Jan 2019 20:30:00 +0100An intelligent system for paper currency verification using support vector machines
http://scientiairanica.sharif.edu/article_21194_1067.html
In recent years, with the advent of digital imaging technology such as color printers and color scanners, it has become easier for counterfeiters to produce fake banknotes. The spread of counterfeit money causes loss to everyone involved in financial transactions. Therefore, an effective and reliable verification technique is necessary for successful and reliable financial transactions. This paper presents a cognitive computation based technique for paper currency verification. In this regard, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analysis of counterfeit and genuine banknotes are performed. This experimentation confirmed that, material used in preparation of genuine and counterfeit banknotes is totally different from each other. Based on these findings, a set of discriminative and robust features is proposed to reflect these differences in currency images. The proposed features represent the material of the banknote such as printing ink, chemical composition, and surface coarseness of the banknotes. With these robust features, Support Vector Machines (SVMs) is employed for classification. In order to evaluate the performance of proposed technique, experimentations are performed on a self-constructed dataset of Pakistani banknotes, comprised of 195 currency images, including 35 counterfeit banknotes. The results confirm that proposed system achieves 98.57% verification ability on properly captured images. Thu, 31 Jan 2019 20:30:00 +0100An efficient hardware implementation for a motor imagery brain computer interface system
http://scientiairanica.sharif.edu/article_20830_1067.html
Brain Computer Interface (BCI) systems, which are based on motor imagery, enable human to command artificial peripherals by merely thinking to the task. There is a tremendous interest in implementing BCIs on portable platforms, such as Field Programmable Gate Arrays (FPGAs) due to their low-cost, low-power and portability characteristics. This article presents the design and implementation of a Brain Computer Interface (BCI) system based on motor imagery on a Virtex-6 FPGA. In order to design an accurate algorithm, the proposed method avails statistical learning methods such as Mutual Information (MI), Linear Discriminant Analysis (LDA) and Support Vector Machine (SVM). It also uses Separable Common Spatio Spectral Pattern (SCSSP) method in order to extract features. Simulation results prove achieved performances of 73.54% for BCI Competition III-dataset V, 67.2% for BCI Competition IV-dataset 2a with all four classes, 80.55% for BCI Competition IV-dataset 2a with the first two classes, and 81.9% for captured signals. Moreover, the final reported hardware resources determine its efficiency as a result of using retiming and folding techniques from the VLSI architecture perspective. The complete proposed BCI system not only achieves excellent recognition accuracy but also remarkable implementation efficiency in terms of portability, power, time, and cost.Thu, 31 Jan 2019 20:30:00 +0100Investigating the effect of long trip on driving performance, eye blinks, and awareness of ...
http://scientiairanica.sharif.edu/article_20195_1067.html
A total of 120 commercial drivers from four age groups participated in the expressway driving test in Shandong, China to perform 2, 3, and 4 h continuous driving tasks and collect the data on the driver's blinking, driving performance and self-reported level of sleepiness. Two-way repeated measures ANOVA was used to evaluate the effects of driving duration on the variation of the eye-blink behavior, driving performance and subjective feeling of sleepiness across the different age groups over the time periods tested. Additionally, Pearson product-moment correlation was used to quantify the association between the variations of the dependent variables. The results showed that there was significant difference between groups, significant effect over time and significant interaction between the age and driving duration in the variations of the driver’s blink frequency, blink duration, closure duration, speed perception, choice reaction time, number of incorrect action judgments and subjective level of sleepiness. However, a significant difference varied over time, but no effect of the interaction between groups and time were found in the variation of the driver’s attention allocation value. Furthermore, driver’s eye blink measures were more sensitive to sleepiness and older drivers were more likely to get sleepy in long distance driving.Thu, 31 Jan 2019 20:30:00 +0100EDU-DRM: A Digital Rights Management (DRM) system for K-12 education
http://scientiairanica.sharif.edu/article_20205_1067.html
The technological achievements in digital publishing have made paperless education possible even in K-12 education. Aside from high bandwidth distribution infrastructure, main problems of digital publishing are preserving personal information and protecting the rights of copyrighted contents. Although, specially designed digital rights management (DRM) systems can be used to control distribution and usage of private and/or copyrighted contents in K-12 education, dealing with large number of bursty concurrent access requests and changing the access rights of large amount of students from one content class to another at the end of each education period makes the problem different from existing ones. This paper introduces a new DRM system, called EDU-DRM, that includes a novel bit based authorization approach that reduces the processing time for authorization requests and automatize the access right adjustments with predefined rules for K-12 education. During the study, an experimental framework is designed using Apache Bench to analyze the proposed approach and its evaluation. The system is compared with XML based authorization approach and the results are presented in the paper.Thu, 31 Jan 2019 20:30:00 +0100Pilot workload assessment under different levels of autopilot failure
http://scientiairanica.sharif.edu/article_21097_1067.html
One of the most interesting topics in the field of human machine interaction is workload. In this paper, using information theory concepts, baud rates generated in all subsystems of a generic simulator of piloting tasks were calculated and then, a unique numerical index presenting an estimation of overall workload was extracted. To examine the effectiveness of offered criteria, three tests with different levels of autopilot failure were designed in which existing workload were labeled based on involving baud rates. A group of subjects performed these tests as the pilots while recording their own idea about perceived workload. Results confirmed that there were statistically significant differences between the averages of scores assigned by subjects to the overall workload for three levels of difficulty. Consequently, the proposed quantitative index is effective enough for determination of workload levels in the simulator environment and facilitates creation of needed scenario noticeably.Thu, 31 Jan 2019 20:30:00 +0100Case based reasoning for green information systems infusion and assimilation among IT ...
http://scientiairanica.sharif.edu/article_20600_1067.html
Information Technology (IT) usage in university campuses consume enormous amount of power and incur other costs in cooling and related operations. Currently, universities are infusing environmental friendly initiatives in their campus. However, IT professionals in most universities are still not sure how to infuse and assimilate environmental friendly practices. Hence, Green Information Systems (IS) is suggested as the utilization of technologies and systems for a Greener and more sustainable planet. Accordingly, this study carried out a review on existing Green IS practices and further proposes a decision support framework based on Case Based Reasoning (CBR) technique. The proposed framework utilizes CBR to support the decision making of IT professionals in infusing and assimilating Green IS within university campuses. Findings from this study show how the framework utilizes CBR to support IT professionals in assimilating Green IS lifecycle and infusing Green IS determinants. Furthermore, findings from this study show how IT professionals can Green their university campuses. Moreover, this research study would also be of interest to data and knowledge management community as well as environmental scientists and sustainability researchers.Thu, 31 Jan 2019 20:30:00 +0100Acceptance of online social networks as technology-based education tools among higher ...
http://scientiairanica.sharif.edu/article_21100_1067.html
Educational institutes are adopting Online Social Networks (OSNs) to facilitate learning activities in university campuses. However, before implementation a new technology there is need to identify and measure the factors that influence users' acceptance of the new technology. This will aid to critically predict the success or failure of the new technology that is to be adopted. Therefore, this study aims to identify the factors that influence student’s acceptance of online social networks as learning tool. Besides, a research model is developed based on the identified factors grounded on Technology Acceptance Model (TAM). In addition, Structural Equation Model (SEM) was employed to validate the developed model hypotheses based data collected by employing online survey from 537 students in University Malaysia Pahang (UMP). Furthermore, findings from this study have significant implications and considerable value for higher educational institutes to devise better strategies for adoption of OSNs' as a learning tool.Thu, 31 Jan 2019 20:30:00 +0100Axial translation of a rigid disc inclusion embedded in a penny-shaped crack in a transversely ...
http://scientiairanica.sharif.edu/article_4237_0.html
In this paper, an analytical solution for the axisymmetric interaction of a rigid disc inclusion embedded in bondedcontact with the surfaces of a penny-shaped crack and a transversely isotropic medium is investigated. By using amethod of potential functions and treating dual and triple integral equations, the mixed boundary value problem iswritten in the form of two coupled integral equations, which are amenable to numerical treatments. The axial stinessof the inclusion and the shearing stress intensity factor at the tip of the penny-shaped crack for dierent degrees ofmaterial anisotropy are illustrated graphically. Useful limiting cases such as a rigid disc inclusion in an uncrackedmedium and in a completely cracked solid are recoveredFri, 18 Aug 2017 19:30:00 +0100Three-dimensional repositioning of jaw in the orthognathic surgery using the binocular stereo vision
http://scientiairanica.sharif.edu/article_4351_0.html
In recent years, the binocular stereo vision has become more popular in many different areas because of the latest developments in three-dimensional (3-D) image processing technology that ensures rich information in comparison with other sensor types. This study presents a novel method based on the binocular stereo vision system to reduce the measurement error encountered frequently in the orthognathic surgery. The main aim is to enhance the level of the accuracy of this sensitive operation. The developed system is not only useful for the preoperative assessment or the postoperative process but also can be utilized during the real-time operation. Additionally, this system provides a broader working field, more practical and healthier environment and less expensive setup. Therefore, the developed binocular stereo vision system may be acceptable for most surgeons. Experimental results show that the average error rate for all of X, Y and Z coordinates in the Cartesian system is 0.25 mm which is clinically acceptable (< 1.00 mm). The binocular stereo vision system would be a helpful throughout the orthognathic surgery to improve precision of the measurement and satisfy the healthy surgical operating environmentTue, 29 Aug 2017 19:30:00 +0100A new modulation scheme in polymer optical fiber communications using Jacket matrix spreading
http://scientiairanica.sharif.edu/article_4382_0.html
To mitigate the high peak-to-average power ratio (PAPR) of discrete multi-tone (DMT) modulation in polymer optical fibers (POF) communication systems, a novel DMT scheme based on Jacket matrix spreading (JS) is proposed. Approximations of PAPR distribution for DMT signals are accurately presented. Single band JS-DMT and multi-band (MB)-JS-DMT are introduced in POF transmission link for PAPR reduction. Offline processing and simulations are adopted to investigate the performance of these new schemes with regard to the PAPR reduction, power spectral density (PSD), data rate and bit error rate (BER). The results demonstrate that, applying the JS methodology, up to 4dB PAPR reduction is achieved. JS-DMT is sensitive to the bandwidth range whereas MB-JS-DMT owns the robustness ability against fiber nonlinearity. Compared with some well known PAPR reduction techniques, the proposed schemes can be easily applied to the DMT modem and achieve the PAPR reduction efficiently without degrading the BER, data rate and PSD performance, which demonstrate the feasibility and validity of these two methods in POF transmission.
Fri, 01 Sep 2017 19:30:00 +0100An efficient observer design method for singular discrete-time systems with time-delay and ...
http://scientiairanica.sharif.edu/article_4383_0.html
In this paper, the observer design method for linear and nonlinear singular discrete-time systems with constant time-delays is proposed. By constructing appropriate Lyapunov–Krasovskii functional and using linear matrix inequality (LMI) technique, the asymptotic convergence criterion is developed in terms of LMIs, which can be solved numerically using MATLAB® LMI® toolbox. The sufficient condition for the existence of a full-order observer is obtained and the states are estimated using Schur complement and S-procedure lemma very well. Moreover, an extension procedure for observer design of singular linear system with time-varying delay is presented. Simulation results are included to prove the efficiency of the suggested approach.Fri, 01 Sep 2017 19:30:00 +0100Performance and stability analysis of grid connected single phase inverters used in solar ...
http://scientiairanica.sharif.edu/article_4384_0.html
Single-phase voltage source inverters (SP-VSIs) are widely used in grid connected solar photovoltaic (PV) systems. This paper deals with the dynamic modeling and stability analysis of single-phase grid connected PV inverters taking the PLL dynamics into account. The PLL structure employed in this paper includes two control branches; the main branch, known as phase estimation loop, extracts the phase and frequency of the grid voltage and the other branch, known as voltage peak estimation loop, determines the grid voltage amplitude. In this way, the paper first proposes design considerations for the dc-link voltage control and PLL control loops. Then, unified dynamic modeling of the SP-VSI system comprising PLL, dc-link dynamics and grid is presented and linearized block diagram of the whole system is extracted. The linearized block diagram depicts the interaction between the control loops of the PLL and dc-link system, where the PLL control loops consist of phase/frequency and amplitude estimation loops of the grid voltage. Next, the small signal stability of the full system is presented, and impacts of grid strength, operating point, and PLL closed loop bandwidth on the performance of SP-VSI are investigated by the modal analysis and time domain simulations.Fri, 01 Sep 2017 19:30:00 +0100Dynamic Negawatt Demand Response Resource Modeling and Prioritizing in Power Markets
http://scientiairanica.sharif.edu/article_4406_0.html
In recent years, integrated use of demand- and supply-side resources has been performed by electric utilities, because of its potential attractiveness, both at operation and economic levels. Demand Response Resources (DRRs) can be used as demand side options which are the consequence of implementing Demand Response Programs (DRPs). DRPs comprise the actions taken by end-use customers to reduce their electricity consumption in response to electricity market’s high prices; and/or reliability problems on the electricity network. In this paper, a dynamic economic model of DRPs is derived based upon the concept of flexible elasticity of demand and the customer benefit function. Precise modeling of these virtual negawatt resources helps system operators to investigate the impact of responsive loads on power system studies. This paper also aims to prioritize multifarious DRPs by means of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and entropy methods. Performance of the proposed model is investigated through numerical studies using a standard IEEE test system.Fri, 01 Sep 2017 19:30:00 +0100Project safety evaluation by a new soft computing approach-based last aggregation hesitant ...
http://scientiairanica.sharif.edu/article_4439_0.html
In recent years, the implementation of safety management has been increased in construction projects by institutions, and many companies have recognized environmental and social effects of injuries at project work systems. In this regard, a novel decision model is presented based on a new version of complex proportional assessment method with last aggregation under a hesitant fuzzy environment. The decision makers (DMs) assign their opinions by hesitant linguistic variables that are converted to the hesitant fuzzy elements. Also, the DMs’ judgments are aggregated in last step of decision making to decrease information loss. Since weights of the DMs or professional safety experts and evaluation criteria are not equal in practice, a new version of hesitant fuzzy compromise solution method is proposed to compute these weights. In addition, the criteria weights are determined based on proposed hesitant fuzzy entropy method. A real case study in developing countries about the safety of construction projects is considered to indicate the suitability and applicability of the proposed new hesitant fuzzy decision model with last aggregation approach. In addition, an illustrative example is prepared to show that the proposed approach is suitable and reliable in larger size safety problemsSat, 02 Sep 2017 19:30:00 +0100Probabilistic Seismic Demand Assessment of Steel Moment Resisting Frames with Mass Irregularity ...
http://scientiairanica.sharif.edu/article_4468_0.html
Ductility with direct effect on the response modification factor of buildings can influence their seismic performance. Moreover, some factors such as geometry and different types of irregularity can affect the ductility and seismic performance of structures. In this study, the effects of mass irregularity in height on the over strength, ductility, response modification factors and probabilistic seismic performance in steel Moment Resisting Frames (MRFs) are assessed. Then, the obtained results are compared with those of regular structures. For this purpose, incremental dynamic analysis (IDA) is implemented using ten records out of past worldwide earthquakes. The location of mass concentration in height is studied assessing 8-, 12- and 16-storey buildings with their mass concentrated at the first floor, mid-height and roof. Then, the probabilistic seismic responses of these structures are evaluated using the outputs of IDA. In this regard, probabilistic seismic demand analysis is conducted on each model. The obtained results are used to plot the seismic fragility and demand curves for both regular and irregular models. Based on the findings, mass irregularity causes the reduction of ductility and response modification factors. This effect increases when the heavier storey is located either at the first floor or at roof. Moreover, mass irregularity brings about the increase in probability of damage occurrence or its exceedance from a certain level.Sun, 17 Sep 2017 19:30:00 +0100Liquefaction Prediction Using Rough Set Theory
http://scientiairanica.sharif.edu/article_4507_0.html
Evaluation of liquefaction is one of the most important issues in geotechnical engineering. Liquefaction prediction depends on many factors and the relationship between these factors is non-linear and complex. Different methods have been proposed by different authors for liquefaction prediction. These methods are mostly based on statistical approaches and neural network.
In this paper a new approach based on Rough Set data mining procedure is presented for liquefaction prediction. The Rough set theory is a mathematical approach for analysis of imperfect knowledge or unclear description of objects. In this approach the decision rules are derived from conditional attributes in Rough Set analysis and the results are compared with actual field observations. The results of this study indicate that using this method can be helpful for liquefaction prediction and can reduce unnecessary costs in site investigation process.Mon, 02 Oct 2017 20:30:00 +0100Development of predictive models for shear strength of HSC slender beams without web ...
http://scientiairanica.sharif.edu/article_4509_0.html
Shear failure of slender beams made of high strength concrete (HSC) is one of the most crucial failures in design of reinforced concrete members. The accuracy of the existing design codes for HSC unlike the normal strength concrete (NSC) beams seems to be limited in prediction of shear capacity. This paper proposes a new set of shear strength models for HSC slender beams without web reinforcement using conventional multiple linear regression, advanced machine learning methods of multivariate adaptive regression splines (MARS) and group method of data handling (GMDH) network. In order to achieve high-fidelity and robust regression models, this study employs a comprehensive database including 250 experimental tests. Various influencing parameters including the longitudinal steel ratio, shear span-to-depth ratio, compressive strength of concrete, size of the beam specimens, and size of coarse aggregate are considered. The results indicate that the MARS approach has the best estimation in terms of both accuracy and safety aspects in comparison with regression methods and GMDH approach. Moreover, the accuracy and safety of predictions of MARS model is also remarkably more than the most common design equations. Furthermore, the robustness of proposed models is confirmed through sensitivity and parametric analyses.Mon, 02 Oct 2017 20:30:00 +0100Providing Transient Stability by Excitation System Response Improvement Methods through Long ...
http://scientiairanica.sharif.edu/article_4511_0.html
Maintaining network stability and encouraging generation companies to involve in stability maintaining are major concerns of independent system operator (ISO) in deregulated power system. Excitation system of synchronous generators is effective and well-known equipment which has a significant effect on network stability. Therefore, improving performance of this system can enhance network stability. But utilizing of the methods, which improve performance of excitation system, imposes cost on generation companies. This paper proposes a motivation mechanism for enhancing transient stability which encourages generation companies to improve performance of excitation system. In this mechanism beside excitation system response improving methods, a transient stability constrained optimal power flow is solved in order to ensure maintaining transient stability in different contingencies. A 4-buses test system, the IEEE 14-buses test system, and the IEEE 118-buses test system are used to illustrate effectiveness of the proposed mechanism. Implementation results show that the proposed mechanism not only provides required transient stability margin with minimum operation cost, but also does not restrict generators production capability.Sat, 07 Oct 2017 20:30:00 +0100An Attribute-Based Anonymous Broadcast Encryption Scheme with Adaptive Security in the Standard ...
http://scientiairanica.sharif.edu/article_4517_0.html
In broadcast encryption schemes, a distribution center broadcasts an encrypted message to a subset chosen from a universe of receivers and only the intended users are able to decrypt the message. Most broadcast encryption schemes do not provide anonymity and the identities of target receivers are sent in plaintext. However, in several applications, the authorized users’ identities have the same sensitivity as the broadcasted messages. Yu, Ren and Lou (YRL) considered this issue and introduced an eicient anonymous aribute-based broadcast encryption scheme. In this paper, we first propose an aack on the YRL scheme and showthat the unauthorized receivers can also decrypt the broadcasted message. Next, we propose the Improved-YRL scheme and prove that it achieves anonymity and semantic security under adaptive corruptions in the chosen ciphertext seing. The proof is provided using the dual system encryption technique and is based on three complexity assumptions in composite order bilinear maps. The Improved-YRL scheme is a step forwardin solving the long-standing problem of secure and low overhead anonymous broadcast encryption.Sat, 14 Oct 2017 20:30:00 +0100A COMBINATION OF COMPUTATIONAL FLUID DYNAMICS, ARTIFICIAL NEURAL NETWORK AND SUPPORT VECTORS ...
http://scientiairanica.sharif.edu/article_4520_0.html
This study show the combination of computational fluid dynamics (CFD) and soft computing techniques to make viewpoint for two-phase flow modelling and accuracy evaluation of soft computing methods in the three-dimensional flow variables prediction in curved channels. Therefore, artificial neural network (ANN) and support vectors machines (SVM) models with CFD is designed to estimate velocity and flow depth variable in 60° sharp bend. Experimental results in 6 different flow discharges of 5, 7.8, 13.6, 19.1, 25.3 and 30.8 l/s to train and test, ANN and SVM models is used. The results of numerical models with experimental values are compared and the models accuracy is confirmed. The results evaluation show that all three models ANN, SVM and CFD perform well in flow velocity prediction, with correlation coefficient (R) of 0.952, o.806, and 0.680, and flow depth (R) of 0.999, 0.696, and 0.614 respectively. ANN model to predict both velocity and flow depth variables with mean absolute relative error (MARE) of 0.055 and 0.004 is the best model. Then SVM and CFD models with MARE of 0.069 and 0.089 in velocity prediction and in flow depth prediction CFD and SVM models with MARE of 0.007 and 0.011 are the best models, respectively.Sat, 14 Oct 2017 20:30:00 +0100Core impact force of vertical water jets on smooth and rough surfaces
http://scientiairanica.sharif.edu/article_4522_0.html
A normal way to dissipate energy of the dam released high velocity jets is to allow them to free-fall in to a plunge pool or impact a plane surface in case of dam site limitations. The water jets have an undisturbed core from nozzle outlet to a certain falling height, which has more impact force and less turbulent intensity than the developed part of the free jet. Experiments are conducted to determine core impact pressure coefficient of a vertical jet on smooth and rough plane surfaces. The experiment results for different jet diameters and falling heights showed considerable increase of the mean dynamic pressure coefficient with increase of the jet Froude number for both smooth surface and rough surface. A simple Froude based mathematical model is correlated for estimation of jet core impact force on the smooth and rough plane surfaces. In addition, a considerable increase of the jet core length was indicated with increase of the jet Froude number. Results also showed a strong correlation between turbulence intensity coefficient and the jet core length.Sat, 14 Oct 2017 20:30:00 +0100The Effects of Demand Response on Security-Constrained Unit Commitment
http://scientiairanica.sharif.edu/article_4536_0.html
This paper aims to study the effect of the hourly demand response (DR) on security-constraint unit commitment (SCUC) problem with considering economic and security objectives. The demand side participation can solve some of the electricity market problems. Here, DR is take into consideration as one of the demand side management (DSM) parts. The DR is consist of fixed and responsive loads. The fixed loads satisfy in any circumstance and responsive loads can curtail or shift to other operating hours. The combination of SCUC with DR is a complex and the mixed integer non-linear problem. The bender’s decomposition is used as an optimization technique for solve this problem. This technique solves the problem by decompose it into master and sub problems. One of the effective of this manner is reducing the processing time. The performance and effectiveness of the proposed method are demonstrated on 6-, 24- and 118-bus test systems.Sat, 14 Oct 2017 20:30:00 +0100Strength development of binary cement concrete, using Pulverized Fly Ash (PFA) under various ...
http://scientiairanica.sharif.edu/article_4537_0.html
Binary Cement incorporating Supplementary Cementitious Material (SCM) is widely used in concrete to reduce the cement consumption in construction industry. Cement production is a major source for the emission of Green House Gases (GHG) and there is an increasing pressure to reduce its consumption to avoid further Global Warming and Climate changes etc. In this research, Pulverised Fly Ash was used to partially replace cement in the concrete. Three levels of replacement of cement by PFA were selected and the specimens were cured under summer and winter environments. The strength development characteristics of the blended concrete were compared with the control mix without PFA. The strength gain under winter curing condition was observed as slower. At water cement ratio of 0.35, concrete with 30 % replacement of cement by PFA achieved high early age strength. PFA concrete gained more strength than the PC concrete after the age of 28 days. The 28 days compressive strengths of blended concrete for 30 % of cement replacement by PFA has been observed as nearly the same as that of control concrete mix. Sat, 14 Oct 2017 20:30:00 +0100Reliability analysis of a vertical cut in unsaturated soils using sequential Gaussian simulation
http://scientiairanica.sharif.edu/article_4571_0.html
This paper proposed a practical approach for reliability analysis of vertical cut in unsaturated soil. This approach extends the application of conditional random field into the unsaturated soils. A real case study of vertical cut was considered and three boreholes were drilled to investigate the subsurface layers. The Sequential Gaussian Simulation (SGS) was used to generate conditional random field with considering the possible fluctuation of soil properties between known data. The undersampled parameters were estimated by cokriging method, while Kriging method was used to estimate other stochastic parameters. In order to verify the efficienty of simulations, it was checked that all data were reproduced at their locations and the input semivariogram model was reproduced within acceptable fluctuations. To predict the unsaturated soil behaviour, the Soil Water Retention Curve (SWRC) was estimated using physico-empirical method with the aim of determining suction stress for finite element stability analysis. The vertical cut was analyzed with and without considering suction. It was concluded that considering unsaturated condition shifts the mean of safety factor from the unsafe ranges to the safe ranges. It was illustrated that the number of known data effects the construction of conditional random fields and leads to different probability of failure.Tue, 24 Oct 2017 20:30:00 +0100Investigation of geotechnical properties of clayey soils contaminated with gasoil using ...
http://scientiairanica.sharif.edu/article_4574_0.html
Oil and its derivatives such as gasoline, motor oil and gasoil are using in various industrial and non-industrial sectors as the main energy sources all over the world. However, within the process of exploration, transportation and storage they may spill or leaking into the soil. Among them the gasoil which is more widely used in different parts and machineries has the largest contribution in contaminating lands. Purgation of these areas is not always feasible or possible. Instead, they can be used in many engineering practices if the level of contamination is not high. In such cases knowing the geotechnical properties of these areas are of great necessity and importance. In this study, extensive laboratory tests were performed on remolded clayey samples mixed with gasoil to evaluate their geotechnical properties. The Response Surface Methodology (RSM) was used to analyze the data and find behavioral equations. According to testing results and RSM outputs a decrease in Atterberg limits, and increase in maximum dry density happen by increasing contamination. Also their shear strength parameters (c and f) both exhibit a turning change point at 8% gasoil content, while their variations trends are quite in opposite directionsTue, 24 Oct 2017 20:30:00 +0100Optimal design of grid-connected hybrid renewable energy systems using multi-objective ...
http://scientiairanica.sharif.edu/article_4578_0.html
The optimal design of grid-connected hybrid renewable energy systems (HRESs) is studied by using multi-objective evolutionary algorithm in this paper. With the total system cost and fuel emissions to be minimized, a two-objective optimization model of the hybrid system is established. Then the modified preference-inspired coevolutionary algorithm is, for the first time, applied to find the optimal configuration of a grid-connected hybrid system. As an example, a grid-connected hybrid system including PV panels, wind turbines and diesel generators has been designed and good results are obtained which show that the proposed method is effective.Fri, 27 Oct 2017 20:30:00 +0100Multi-Laminate Rate-Dependent Modelling of Static and Dynamic Concrete Behavior through Damage ...
http://scientiairanica.sharif.edu/article_4581_0.html
Mathematical simulation of the nonlinear tri-dimensional mechanical behavior of quasi-brittle materials like concrete is one of the biggest challenges in the engineering science. It is vital to have the knowledge of the response of concrete specimens subjected to low and high strain rate deformation for the analysis of concrete structures under the static and dynamic loading cases. The behavior of this material is generally known to be strain rate sensitive. Among phenomena of different orientation, the multi plane models, like multi-laminate models using a constitutive equation in a vectorial form rather than tensorial form by means of capturing interactions, can meet this goal adequately. This paper suggests a robust rate dependent damage based model in the multi-planes framework accomplished with minimum parameters for calibration and appropriate for engineering purposes. This damage formulation has been built on the basis of two types of essential damage, axial damage and shear damage, that basically can happen on each sampling plane and based on this concept two new axial and shear damage functions are proposed. Model verification has been studied under different compressive and tensile loading rates, comparing the results of the proposed model with the experimental data and Mohr-Coulomb failure criterion envelope line.Mon, 30 Oct 2017 20:30:00 +0100Numerical modeling of flood waves in a bumpy channel with the different boundary conditions
http://scientiairanica.sharif.edu/article_4582_0.html
In this paper, the Incompressible Smoothed Particle Hydrodynamics (ISPH) method is presented to simulate flood waves in uneven beds. The SPH method is a mesh free particle modeling approach that is capable of tracking the large deformation of free surfaces in an easy and accurate manner. Wave breaking is one of the phenomena that its free surface is complicated. Therefore, ISPH method is robust tool for the modeling of this kind of free surface. The basic equations are the incompressible mass conservation and Navier–Stokes equations that are solved using a two-step fractional method. In the first step, these equations are solved to compute velocity components by omitting the pressure term and in the absence of incompressible condition. In the second step, the continuity constraint is satisfied and the Poisson equation is solved to calculate pressure terms. In the present model, a new technique is applied to allocate density of the particles for the calculations. By employing this technique, ISPH method is stabled. The validation by comparison with laboratory data is conducted for bumpy channel with various boundary conditions. The numerical results showed good agreement with available experimental data. Also relative error is calculated for two numerical cases.Mon, 30 Oct 2017 20:30:00 +0100Investigation of the short-term behaviour of silty sand stabilized by colloidal silica
http://scientiairanica.sharif.edu/article_4583_0.html
Injection in soils using traditional materials, such as cement grout, has its inherent problems and has not shown the potential for further development in industrial applications. Accordingly, application of novel materials for injection in soils with considerable content of fines for stabilizing and even making them impermeable is suggested. Among different stabilizers that are injectable in soils with fine, colloidal silica seems very suitable due to its very low viscosity, nontoxicity in the nature, and adjustability of the setting time for slow injection in soils with fine. Based on laboratory tests performed in this research, the effect of colloidal silica on the strength parameters and the short-term behaviour of silty sand was examined. For characterizing the soil stabilized by colloidal silica, the silty sand samples with different silt values, in both unstabilized and stabilized conditions, were prepared with different concentrations of the stabilizer. 45 Uniaxial tests and 75 unconsolidated- undrained compressional triaxial tests were conducted. An increase in the undrained cohesion of all samples was observed. On the other hand, two different trends were observed in the alteration of the undrained internal friction angle of soils with low and high fines content.Mon, 30 Oct 2017 20:30:00 +0100Investigation of bridge abutment displacements constructed on piles and geogrid reinforced soil ...
http://scientiairanica.sharif.edu/article_4591_0.html
One of the major problems in highway and railway bridges is the settlement of the bridge abutments, which its reduction has always been set as the research target. Two methods which have been widely used for controlling the settlement are either reinforcing the abutment subsoil with geogrid orconstructing the abutments on piles. This paper describes the application of a two-dimensional finite element method (FEM) by using Plaxis2D V8.5 for comparing the performance of these two methods. The effect of the geogrid normal stiffness, length and depth of reinforcement on the horizontal and vertical displacement of abutment is also investigated. Data from an instrumented bridge abutment has been used for the model verification. The reduction of the bridge abutment,the vertical settlement and the horizontal displacement by pile and geogrid have been analysed and compared.It is found that constructing the abutment on piles has a better performance in reducing the vertical settlement of the bridge abutment. However, lower lateral displacement can be obtained by using a geogrid with a higher normal stiffness. It is also found that, while the vertical settlement is not affected by the geogrid stiffness, the horizontal displacement of the abutment decreases with increasing the stiffness.Sat, 11 Nov 2017 20:30:00 +0100Strengthening and shape modification of fire-damaged concrete with expansive cement concrete ...
http://scientiairanica.sharif.edu/article_4592_0.html
This paper reports the results of an experimental study where the axial capacity of fire-damaged specimens repaired by expansive cement concrete and CFRP wrap were investigated. Specimens were subjected to axial compressive loading and their resulting stress-strain curves were recorded. Since the flat sides of the square samples remained unconfined then the cross sections of the tested specimens largely remained unconfined. The FRP jacket was effective only along the two diagonals of the cross-section. Confinement is generally more effective in specimens with circular cross-section than those with square cross-section. The change in cross section for some of the specimens from square to circle was implemented. To modify the shape, expansive cement concrete has been utilized to fill the gap between the circular and the square cross sections. The test results indicated that heating up to 500 °C caused a severe decline in compressive strength and the elastic modulus of concrete. Two layers of CFRP wrap around the concrete not only compensated the drop in compressive strength but furthermore it increased the strength beyond that of unheated specimen. However, the effect of wrapping alone on the stiffness and the elastic modulus is negligible. The heated square specimens that were first subjected to shape modification and then wrapped by CFRP sheet, experienced increase in the strength and the elastic modulus. Therefore, the stiffness and the compression strength of fire-damaged square concrete specimens could be compensated fully by the use of shape modification and CFRP wrapping of the cross section.Mon, 13 Nov 2017 20:30:00 +0100Development of a new integrated method for generation IDF curves based on three climatic ...
http://scientiairanica.sharif.edu/article_4593_0.html
Climate change can change the intensity-duration-frequency (IDF) curves. This research evaluates IDF curves changes of the Baghmalek climatic station in Iran's southwest. Developed integrated method extracts the IDF curves using of the Gumbel and log-Pearson III probability distributions and observed maximum annual precipitations. Durations of these precipitations are 15, 30, 45 minutes and 1,2,3,6 and 12 hours.
For this purpose, this method utilizes the recorded precipitation data of the Baghmalek climatic station in a 40-year period (1974-2013). Then mean square error method determines the probability distribution that has the best fitting with this data. The HadCM3 prepares precipitation data for a 30-year period (2021-2050) based on A1B, B1 and A2 scenarios. Also this method selects an optimum artificial neural network to extraction of maximum annual rainfall intensity for different durations and scenarios. Then selected network and the chosen probability distribution produce IDF curves for different return periods and scenarios. Produced IDF curves for different scenarios are compared to IDF curves of base time period. Because of increasing carbon dioxide and its greenhouse effects in these scenarios, rainfall intensity will increase for return periods less than 2.33 years while it will decrease for return periods more than 2.33 years.Mon, 13 Nov 2017 20:30:00 +0100Effects of aging on dynamic properties of MSW: A case study from Kahrizak Landfill, Tehran, Iran
http://scientiairanica.sharif.edu/article_4594_0.html
The effect of aging on dynamic properties of Municipal Solid Waste (MSW) including damping ratio and shear modulus was investigated in current research. For this purpose, a series of cyclic consolidated undrained (CU) triaxial tests performed on fresh and old reconstituted cylindrical specimens, taken from Mansoory Prototype Landfill (MPL), placed in Kahrizak landfill, Tehran, Iran.
The results show that the shear modulus of old samples (7.5 years old) was more than the fresh ones. This trend can be attributed to decomposition of waste over time which leads to reduction in organic content and, consequently, increment in fibrous waste particles (plastics) of the old samples. On the other hand, the results also state that the damping ratio is partially dependent on the composition of the specimen, and slightly decreases with increasing the age of MSW. The high percentage of organic content in fresh specimens can be considered as the main reason for this behavior. Finally, the normalized shear modulus reduction and strain-dependent material damping curves were proposed for both ages of retrieved MSW from Kahrizak Center Landfill (KCL). The results of current study are in the range reported in technical literature and can be used as reliable data in seismic purposes.Mon, 13 Nov 2017 20:30:00 +0100Applying Materials Waste Quantification to Cement Waste Reduction in Tehran’s Residential ...
http://scientiairanica.sharif.edu/article_4598_0.html
Purpose of this research is twofold. Study’s first part focuses on developing quantitative wastage models for rebar, concrete, brick and cement, as major bulk traditional building materials, used in Tehran residential buildings. Primary results indicate that multiple linear regression is an apt tool to model studied variables’ effects on materials wastage. In every developed wastage model, subtractive or accumulative effect of each studied variable is recognized by its coefficient value and sign. Developed models resulted in adjusted R2 values of 0.907, 0.875, 0.920 and 0.790 respectively for rebar, cement, brick and concrete waste. Cement, with average wastage of 8.57% by weight, is identified as the most wasted material verified by the case study.
In study’s second part, previously developed models as well as project management experts’ opinions were combined to structure a cement waste reduction guideline for traditional building construction which is common in Tehran, Iran. With this purpose in mind, for projects’ initiating phase, choosing lump-sum contract instead of cost-plus contract is suggested. Moreover a financial incentive reward scheme, with its economic viability and environment friendliness, has been tested with positive results and hence is proposed for construction phase. Applicability of proposed scheme is verified through a case study.Mon, 27 Nov 2017 20:30:00 +0100Reinforcement dependent long term deflection response of baked clay beams
http://scientiairanica.sharif.edu/article_4601_0.html
Reinforced Baked Clay (RBC) might serve as low cost material of building construction to substitute Reinforced Cement concrete (RCC). Deflection of a beam under a sustained load is considered an important parameter. It is not yet reported in literature what is the effect of reinforcement on long-term deflection response of RBC beams and relative comparison to that of RCC beams. For this purpose, RBC beams were manufactured, baked, and post-reinforced in tension zone only with three ratios of reinforcement (i.e., 0.003, 0.006, and 0.009). All the beams were subjected to a sustained load of 50 kN for one year. The results indicate that long-term deflection of RBC beams was reduced to 20%, and 50% when the reinforcement ratio was increased to 2 and 3 times of the initial reinforcement ratio of 0.003, respectively. The ultimate load carrying capacity of the RBC beams was similar to that of RCC beams. The deflection of RBC beams was thrice of the deflection of RCC beams. This paper shows that RBC beams could be utilized instead of RCC ones with no sacrifice on strength.Fri, 01 Dec 2017 20:30:00 +0100The effect of Non-Darcy Flow on Induced Stresses Around a Wellbore in an anisotropic in-situ ...
http://scientiairanica.sharif.edu/article_4603_0.html
After drilling a well, the stresses will be altered and the induced stresses present the new state of stress. These induced stresses which result in geomechanical problems. The studies indicate that the flow of hydrocarbon into the wellbore influences the induced stresses. Darcy equation has been used in the past; however, the laminar flow assumption embedded in this equation cannot correctly model the flow of fluid when a non-Darcy flow dominates near a wellbore. Example of such situation includes the gas wells. In this study, analytical equations are developed to incorporate the effect of non-Darcy flow on the induced stresses around a wellbore. These equations developed based on Forchheimer flow equation. Then the simplified solutions were presented by considering the second term of Forchheimer flow equation. It was found that the difference between the results from Darcy and non-Darcy flow models is proportional to the drawdown pressure. Further studies included numerical simulation of non-Darcy fluid flow in a typical reservoir. Comparison of the results with the analytical models indicated that the magnitude of stresses in non-Darcy flow is larger than of Darcy flow. Finally, sensitivity of the reservoir properties on the induced stresses in the non-Darcy flow regime was investigated.Sat, 02 Dec 2017 20:30:00 +0100Using genetic algorithms for long-term planning of network of bridges
http://scientiairanica.sharif.edu/article_4604_0.html
Bridge maintenance activities are often budgeted, scheduled and conducted for networks of bridges with different ages, types and conditions, which can make bridge network maintenance management challenging. In this study, we propose an improved maintenance planning model based on genetic algorithm for a network of bridges to bring a long-term perspective to the lifespan of bridges. To test the applicability and efficiency of the model, it is applied to a network of 100 bridges in one of the south-western provinces of Iran. The results of the model implementation show considerable potential for improvement over the currently adopted model for bridge maintenance planning.Sat, 02 Dec 2017 20:30:00 +0100Uncertainty Management in Time Estimation of Construction Projects: A Systematic Literature ...
http://scientiairanica.sharif.edu/article_4605_0.html
Nowadays, the very low reliability of the project planning in certainty-based approaches, caused to use more intelligent methods for uncertainty management in construction projects. This systematic study aims to survey the methods which have been used to manage the uncertainties in time estimation of construction projects. A series of steps were undertaken during the review. The study was started with determining the purpose of the study, selecting appropriate keywords, and reducing the selected papers using some criteria. A deeper analysis was carried out on the final paper that meets the criteria for this review. The study is limited solely to papers referred in six top online databases. It aims to review how the papers have been distributed by a period of publishing and by country and the domains that these methods have been applied for. The result confirms that uncertainties which affect any project are based probability and possibility theories controlled by Risk Management and Fuzzy Logic. Finally, a hybrid method for uncertainty management in project scheduling is proposed. The result of the implementation of this method in the construction project of Iranian Gas Company shows that proposed method increases the accuracy of time estimation about 8 to 24 percent.Sat, 02 Dec 2017 20:30:00 +0100Uncoupled Analysis of Rc-Slabs under Near-Field Air Explosions: Examination of Various ...
http://scientiairanica.sharif.edu/article_4609_0.html
In an uncoupled analysis, blast loads can be evaluated by empirical models, and then applied to the structure in a separate response analysis. The literature includes a variety of empirical models. However, the potentials of these models may not be fully realized due to a wide variation that may exist in their outcomes, particularly at detonations with a relatively close standoff distances from the target. As such, the selection of an appropriate model should be made with special considerations. This paper investigates the efficiency of various empirical models in blast analysis of the RC-slabs that are subjected to near-field air-detonations. The blast loads resulted by the empirical models are employed in a set of nonlinear FEA-runs. Due to the proximity of detonations, the distribution of blast-overpressure across the concrete slab at any instant in time is nonuniform. A simplified approach that accounts for this nonuniform distribution has been developed and verified in this study. To examine the effectiveness of the empirical models, the FEA-results are compared with the observations made in a set of previous experimental studies. Based on this comparative study, the most effective empirical model is identified, and remarks are made on the performance of the other models.Sat, 09 Dec 2017 20:30:00 +0100Experimental study of the effect of water to cement ratio on mechanical and durability ...
http://scientiairanica.sharif.edu/article_20014_0.html
In the present paper, the effect of Nano silica on mechanical properties and durability of concrete containing polypropylene fibers has been investigated. Here, the length and length to diameter ratio of used polypropylene fibers were considered to be fixed and equal to 18 mm and 600 respectively and the cement content was 479 kg/m3. The effect of fibers and Nano silica in four different percentages at 0.1, 0.2, 0.3 and 0.4 percent by volume for fibers and 3 percent for Nano silica in concrete with water to cement ratio of 0.33, 0.36, 0.4, 0.44 and 0.5 have been compared and evaluated. In total, more than 425 cubic and cylindrical specimens were made according to ASTM standards. Finally, samples of polypropylene fiber containing Nano-silica were tested under compressive loads, flexural strength, indirect tensile strength (Brazilian test), abrasion resistance, permeability and porosity and their mechanical properties were evaluated. The test results showed a significant increase in mechanical properties improvement and durability of concrete. Compressive strength, tensile strength, flexural strength and abrasion resistance (of concrete) increased up to 55%, 25%, 49%, and 45% respectively. Also, considerable reduction of hydraulic conductivity coefficient to 50% indicates high durability of these types of concrete.Sat, 23 Dec 2017 20:30:00 +0100An effective approach for structural damage localization in flexural members based on ...
http://scientiairanica.sharif.edu/article_20019_0.html
This paper presents a method for structural damage localization based on signal processing using generalized S-transform (SGS). The S-transform is the combinations of the properties of the short-time Fourier transform (STFT) and wavelet transform (WT) that has been developed over the last few years in an attempt to overcome inherent limitations of the wavelet and short time Fourier transform in Time-Frequency representation of non-stationary signals. The generalized type of this transform is the SGS-transform that has adjustable Gaussian window width in the time-frequency representation of signals. In this research, the SGS-transform has been employed due to its favorable performance in detection of the structural damages. The performance of the proposed method has been verified by means of three numerical examples and also the experimental data obtained from the vibration test of 8-DOFs mass–stiffness system. By way of the comparison between damage location obtained from the proposed method and simulation model, it was concluded that the method is sensitive to the damage existence and clearly demonstrates the damage location.Mon, 25 Dec 2017 20:30:00 +0100Airline delay prediction by machine learning algorithms
http://scientiairanica.sharif.edu/article_20020_0.html
Flight planning, as one of the challenging issue in the industrial world, is faced with many uncertain conditions. One such condition is delay occurrence, which stems from various factors and imposes considerable costs on airlines, operators, and travelers. With these considerations in mind, we implemented flight delay prediction through proposed approaches that are based on machine learning algorithms. Parameters that enable the effective estimation of delay are identified, after which Bayesian modeling, decision tree, cluster classification, random forest, and hybrid method are applied to estimate the occurrences and magnitude of delay in a network. These methods were tested on a U.S. flight dataset and then refined for a large Iranian airline network. Results showed that the parameters affecting delay in US networks are visibility, wind, and departure time, whereas those affecting delay in Iranian airline flights are fleet age and aircraft type. The proposed approaches exhibited an accuracy of more than 70% in calculating delay occurance and magnitude in both the whole-network US and Iranian. It is hoped that the techniques put forward in this work will enable airline companies to accurately predict delays, improve flight planning, and prevent delay propagation.Mon, 25 Dec 2017 20:30:00 +0100Phenol Removal from Aqueous Solution by Adsorption Process: Study of The Nanoparticles ...
http://scientiairanica.sharif.edu/article_20023_0.html
This study was performed to measure the potential utilization of agro-waste to generate nanoparticles and evaluate the capability of it’s as a low cost adsorbent for removal of phenol. Adsorption studies for phenol removal by using Aloe vera and Mesquite leaves nanoparticles carried out under various experimental conditions including pH, nano-bioadsorbent dosage, phenol concentration, contact time, temperature and ionic strength in a batch reactor. The adsorption kinetics by pseudo-first order and pseudo-second order models and isotherm technique by Freundlich and Langmuir isotherms models were applied. The results showed that the rate of phenol adsorption increases in both nano-bioadsorbents with an increase of pH up to 7, adsorbent dosage up to 0.08 gL-1, phenol initial concentration up to 32 mgL-1, contact time up to 60 min and raising in temperature. The adsorption data followed the Freundlich isotherm model. The kinetic studies indicated that the adsorption of phenol with nano-bioadsorbents was best described by the pseudo second order kinetics. We found that the nanoparticles prepared from Aloe vera and Mesquite leaves had a high capability in adsorption of phenol, beside the point that they could be accessed at a low cost. These agro-wastes can be used to remove phenol from aqueous environments.Tue, 26 Dec 2017 20:30:00 +0100Soil behaviour around the stub abutment of an integral bridge and buried piles in the ...
http://scientiairanica.sharif.edu/article_20030_0.html
The change in the deck length under temperature load affects the upper part of integral bridge abutments and causes abutments rotation. The deck contraction makes the abutment move away from the backfill and causes a failure wedge. To prevent the failure wedge, a new method has been proposed. In this method, the inhibition of integral bridges under contraction is done by cables connected from each abutment to the buried piles outside the bridge along the abutments. In the analysis, the behaviour of soil around the abutment and buried piles is an important parameter which has a great influence on the results. In this paper, the soil behaviour around a laterally loaded stub abutment and buried piles was studied on laboratory stub abutment models using the PIV (particle image velocimetry) method. The PIV analysis was carried out to obtain the deformation pattern and shear strains of the soil around the stub abutment and buried piles. The effects of piles number and soil – pile interaction on the soil deformation pattern were investigated. The results showed that the use of buried piles connected by the cable avoided creating a failure wedge in the backfill.Sat, 06 Jan 2018 20:30:00 +0100TIME SERIES PREDICTION WITH A HYBRID SYSTEM FORMED BY ARTIFICIAL NEURAL NETWORK AND COGNITIVE ...
http://scientiairanica.sharif.edu/article_20033_0.html
Time series prediction is a remarkable research interest, which is widely followed by scientists / researchers. Because many fields include analyzing processes over such time series, different kinds of approaches, methods, and techniques are often employed in order to achieve alternative prediction ways. It seems that Artificial Intelligence oriented solutions have strong potential on providing effective and accurate prediction approaches in even most complicated time series structures. In the sense of the explanations, this study aims to introduce an alternative, Artificial Intelligence based approach of Artificial Neural Networks, and Cognitive Development Optimization Algorithm, a recent intelligent optimization technique introduced by the authors. Here, it has been aimed to predict different kinds of time series, by using the introduced system / approach. In this way it has been possible to discuss about application potential of the hybrid system and report findings related to its success on prediction. The authors believe that the study has been a good chance to support the literature with an alternative solution approach and see potential of a newly developed, Artificial Intelligence oriented optimization algorithm on different applications.Sat, 06 Jan 2018 20:30:00 +0100Chaos and Bifurcation in Nonlinear Inextensional Rotating Shafts
http://scientiairanica.sharif.edu/article_20041_0.html
In this paper, bifurcation and chaotic behavior of in-extensional rotating shafts are investigated. The shaft is modeled as a Rayleigh simply supported beam, spinning with constant rotational speed. Using two–mode Galerkin truncation, the partial differential equations of motion are discretized and then with the aid of numerical simulations, the dynamical behavior of the rotating shaft is studied. Using tools from nonlinear dynamics, such as time history, bifurcation diagram, Poincaré map, Lyapunov exponents, and amplitude spectra, a comprehensive analysis is made to characterize the complex behavior of the rotating shaft. Periodic (synchronous), quasi-periodic, chaotic and transient chaotic responses are observed in the neighborhood of the second critical speed. The effect of rotary inertia and damping on the dynamics of the rotating shaft is considered. It is shown that the chaotic response is possible for a shaft with weak nonlinearity without the existence of any internal resonance.Sat, 06 Jan 2018 20:30:00 +0100Cement grain size effect on the Geotechnical properties of Stabilized Clay
http://scientiairanica.sharif.edu/article_20042_0.html
In this study, some geotechnical properties of microfine and ordinary Portland cements stabilized high plasticity clayey soil (HPCS) were investigated. The results showed that liquid limit, permeability, swelling potential and compressibility of HPCS were reduced and HPCS’s plastic limit and unconfined compressive strength (UCS) was increased by both microfine Portland cement (MPC) and ordinary Portland cement (OPC) stabilizations. Besides, liquid limit, permeability, swelling potential and compressibility of HPCS were further reduced by MPC. Although dry UCS of MPC stabilized HPCS was almost the same as the dry UCS of OPC stabilized HPCS, the plastic limit and wet cured UCS of MPC stabilized HPCS was higher than that of wet cured UCS of OPC stabilized HPCS. In general, as the size of cement particles became finer, the stabilization of HPCS became more effective.Sat, 06 Jan 2018 20:30:00 +0100Using an optimized RBF neural network to predict the out-of-plane welding distortions based on ...
http://scientiairanica.sharif.edu/article_20043_0.html
This study deals with the effect of locator positioning in 3-2-1 locating scheme to control the out-of-plane distortion in gas tungsten arc welding of sheet metals. To apply this locating scheme on the sheet metals, a suitable fixture is designed. The distortion of the welded plates has been predicted using the radial basis function (RBF) neural network. To gather the experimental data employed in the RBF modeling process, a set of welding tests is performed on the sheet specimens by varying the positions of the three locators. The parameters of the network are optimally selected using the simulated annealing (SA) optimization algorithm. The average and maximum error computed for the test dataset were respectively 2.43% and 5.30% while in some cases the error falls below 1%. The results of the RBF network show very good agreement with the experiments and it can be concluded that this modeling technique can be utilized successfully in predicting the welding distortions when the 3-2-1 locating scheme is used.Sat, 06 Jan 2018 20:30:00 +0100Investigation on effect of using rubber as core material in sandwich composite plate subjected ...
http://scientiairanica.sharif.edu/article_20044_0.html
In this article, the structural performance of composite plate under low velocity impact is studied. Two forms of layup sequence namely jute-epoxy laminate (JE) and jute-epoxy-rubber sandwich (JE-R-JE) are considered for evaluation. Special emphasis is provided for evaluating the influence of normal and oblique loading. The various dynamic parameters such as energy, peak load, and deformation are analysed in detail to study the effect of impact angle on both laminate and sandwich. Stress analysis of both the laminate and sandwich structure is carried out to discuss the effect of introducing rubber as a core material. The results reveal that using rubber as a core material has a significant effect on energy absorption. In addition, it is noticed that increasing the angle of impact yields better performance of the composite plate. The results presented here may serve as benchmark for the effective utilization of composite plates in low velocity impact applications.Sat, 06 Jan 2018 20:30:00 +0100Optimal design of monopile offshore wind turbine structures using CBO, ECBO, and VPS algorithms
http://scientiairanica.sharif.edu/article_20090_0.html
Considering both size and dimensions of the offshore wind turbine structures, design optimization of such structures is a fruitful yet, simultaneously, onerous task due to the tempestuous complexity of the problem, which mostly comes from their environment. However, in this study, a computerized methodology based on meta-heuristic algorithms, consisting of the Colliding Bodies Optimization (CBO), Enhanced Colliding Bodies Optimization (ECBO), and Vibrating Particle System (VPS), is presented such that more economic upshots can be accomplished. Hence, minimization of the total weight of the structure subjected to a number of structural constraints, including a frequency constraint, by applying the above mentioned algorithms is the underlying goal of this study. Using the data from Horns Rev I offshore wind farm, which is located in the coastlines of Denmark in the North Sea, this study is performed based on a simplified structural model of a monopile offshore wind turbine structure, which can be utilized in preliminary stages of pertinent projects for conducting suitable comparisons.Tue, 09 Jan 2018 20:30:00 +0100Reference Tracking of Nonlinear Dynamic Systems over AWGN Channel Using Describing Function
http://scientiairanica.sharif.edu/article_20108_0.html
This paper presents a new technique for mean square asymptotic reference tracking of nonlineardynamic systems over Additive White Gaussian Noise (AWGN) channel. The nonlinear dynamic systemhas periodic outputs to sinusoidal inputs and is cascaded with a bandpass filter acting as encoder.Using the describing function method, the nonlinear dynamic system is represented by an equivalentlinear dynamic system. Then, for this system, a mean square asymptotic reference tracking techniqueincluding an encoder, decoder and a controller is presented. It is shown that the proposed referencetracking technique results in mean square asymptotic reference tracking of nonlinear dynamic systemsover AWGN channel. The satisfactory performance of the proposed reference tracking technique isillustrated using practical example simulations.Sat, 13 Jan 2018 20:30:00 +0100Modeling of a PIN Diode RF Switch for Re configurable Antenna Application
http://scientiairanica.sharif.edu/article_20110_0.html
The paper proffers the procedure to model a PIN diode RF switch using full-wave EM solver, HFSS and utilizes the switch to built a simple partial ground plane antenna with omnidirectional radiation pattern. The proposed antenna has ability to tune it from ultra-wideband to narrowband mode. The frequency reconfigurability is accomplished by incorporating a rectangular slot resonator and a PIN diode RF switch embedded in the partial ground plane. The antenna demonstrates -10 dB impedance bandwidth from 500 MHz to 6 GHz in the ultra-wideband mode and 1.125 GHz to 2 GHz in the narrowband mode. A parasitic is stacked in the ground plane to improve the impedance matching and a rectangular slot is fused to explore the bandwidth-limiting possibility of the antenna. The optimization of the antenna is done by full-wave EM solver, HFSS and Specific Absorption Rate (SAR) of the antenna is examined using the equivalent flat tissue phantom. A prototype of the proposed antenna is fabricated and execution is accepted by measured results. The proposed antenna has simple and miniature structure, low SAR (0.41 W/Kg), omnidirectional pattern and low cross-polarization (<-15dB in E-plane and <-30dB in H-plane).Sat, 13 Jan 2018 20:30:00 +0100Hypercube Queuing Models in Emergency Service Systems: A State-of-the-Art Review
http://scientiairanica.sharif.edu/article_20141_0.html
This study provides a review of hypercube queuing models (HQMs) in emergency service systems (ESSs). This survey presents a comprehensive review and taxonomy of models, solutions and applications related to the HQM after Larson [12]. In addition, the structural aspects of HQMs are examined. Important contributions of the existing research are addressed by taking into account multiple factors. In particular, the integration of location decisions with HQMs for designing an ESS is discussed. Finally, a list of issues for future studies are presented.Fri, 19 Jan 2018 20:30:00 +0100A local differential transform approach for the cubic nonlinear Duffing oscillator with damping term
http://scientiairanica.sharif.edu/article_20142_0.html
Nonlinear behaviour of various problems is described by the Duffing model interpreted as a forced oscillator with a spring which has restoring force. In this paper, a new numerical approximation technique based on differential transform method has been introduced for the nonlinear cubic Duffing equation with and without damping effect. Since exact solutions of the corresponding equation for all initial guesses do not exist in the literature, we have first produced an exact solution for specific parameters by using the Kudryashov method to measure the accuracy of the currently suggested method. The innovative approach has been compared with the semi-analytic differential transform method and the fourth order Runge-Kutta method. Although the semi-analytic differential transform method is valid only for small time intervals, it has been proved that the innovative approach has ability to capture nonlinear behaviour of the process even in the long-time interval. In a comparison way, it has been shown that the present technique produces more accurate and computationally more economic results than the rival methods.Fri, 19 Jan 2018 20:30:00 +0100Effects of welding parameters on penetration depth in mild steels A-TIG welding
http://scientiairanica.sharif.edu/article_20145_0.html
A-TIG welding is a welding method in which TIG welding is conducted by covering a thin layer of activating flux on the weld bead beforehand. The most benefit of this process is the gain in weld penetration depth. A-TIG welds were produced on mild steel plates with TiO2 flux. The emphasis of this paper lies in introducing the effects of various process parameters (welding current, welding speed, powder/acetone ratio of the flux, arc length and electrode angle) in mild steel A-TIG welding. The weld penetration depth was the measured metallographically. An optimum value was determined for each welding parameter.Fri, 19 Jan 2018 20:30:00 +0100Performance investigation of a Diesel engine under effective efficiency-power-power density ...
http://scientiairanica.sharif.edu/article_20146_0.html
A performance analysis of a Diesel engine in terms of effective power (EP), effective power density (EPD) and effective efficiency (EE) has been performed using a novel realistic finite-time thermodynamics (FTT) modeling. The effects of design and operating parameters of the diesel cycle such as bore-stroke length ratio (d/L), equivalence ratio (ER), compression ratio (CR), cycle temperature ratio (CTR), cycle pressure ratio (CPR), stroke length (L), friction coefficient (FRC), engine speed (N), mean piston speed, inlet pressure and inlet temperature on the engine performance have been investigated. In addition, the energy losses depending on incomplete combustion (IC) , friction losses (FRL), heat transfer losses (HTRL) and exhaust output losses (EOL) have been described as fuel input energy. In order to acquire reasonable results, variable specific heats with respect to temperature for working fluid have been used. The results presented could be an essential tool for Diesel engine designers.Fri, 19 Jan 2018 20:30:00 +0100Plasma based surface modification of Poly (dimethylsiloxane) electrospun membrane proper for ...
http://scientiairanica.sharif.edu/article_20148_0.html
Constructing of the scaffolds for cell culture applications has long been of interest for engineering researchers and biologist. In this study, a novel process is utilized for construction of suitable membrane with a high mechanical strength and appropriate surface behavior. Poly (dimethylsiloxane) (PDMS) is electrospun into fine fibers using poly (methyl methacrylate) (PMMA) as the carrier polymer in different weight ratios. Since the surface behavior of all PDMS substrates is moderately hydrophobic (120 < contact angle (CA) < 150), the electrospun membranes with higher PDMS ratios show slightly higher hydrophilicity. Direct plasma treatment is utilized to change the interfacial wettability of the membrane. Applying plasma changes the surface energy and renders the PDMS/PMMA substrates superhydrophilic (CA<5). In the following, the mechanical properties of the membrane are evaluated by the tensile test, and the results confirm the suitable mechanical strength of electrospun PDMS for cell culturing objectives (yield stress of more than 10 kPa). Also, changing the PDMS ratio doesn’t significantly affect the total stiffness of the membrane. Thus, applying the proposed fabrication protocol provides a proper platform for cell viability and proliferation which have been proven by the results of MTT assay.Fri, 19 Jan 2018 20:30:00 +0100Redundancy allocation problem with a mixed strategy for a system with k-out-of-n subsystems and ...
http://scientiairanica.sharif.edu/article_20152_0.html
Reliability improvement for electronics and mechanical systems is vital for engineers in order to design of these systems. For this reason, there are many researches in this scope to help engineers in real world applications. One of the useful methods in reliability optimization is redundancy allocation problem (RAP). In the most previous works, the failure rates of system components are considered to be constant based on negative exponential distribution; whereas, nearly all systems in real world have components with time-dependent failure rates; i.e., the failure rates of system components will be changed time by time. In this paper, we have worked on a RAP for a system under k-out-of-n subsystems with time-dependent components failure rates based on Weibull distribution. Also, the redundancy policy of the proposed system is considered as mixed strategy and the optimization method was based on the simulation technique to obtain reliability function as implicit function. Finally, a branch and bound algorithm has been used to solve the model, exactly.Fri, 26 Jan 2018 20:30:00 +0100Procedure for Setting up 180 Degree Sharp Bend Flume Including Construction and Examinations ...
http://scientiairanica.sharif.edu/article_20157_0.html
A laboratory flume in the hydraulics laboratory is necessary in order to investigate and model different hydraulic and hydrodynamic phenomena which govern the river. Hence, this article provides a description on construction and setting up a 180 degree flume, as the first 180 degree sharp bend flume containing multiple lateral intakes, in the Hydraulic Laboratory of Persian Gulf University, Iran. Also, employing the constructed flume, it includes a number of case studies which have been conducted on flow pattern. Such experiments utilized a Vectrino velocimeter in order to obtain the 3D flow velocity. As the primary stage, an experiment was conducted without any hydraulic structures installed at the bend so that flow characteristics could be analyzed in a 180 degree sharp bend. An increase was revealed in the secondary flow strength and velocity as a result of an increase in the flow depth. Therefore, it can result in an attack towards the outer wall. Consequently, a T-shaped spur dike was installed at the apex of the bend in order to provide protection for the outer wall against streams of high velocity, and a study of the flow pattern around the protective structure was conducted under clear water conditions.Mon, 29 Jan 2018 20:30:00 +0100A new method for eliminating membrane compliance in cyclic triaxial tests on gravelly soils
http://scientiairanica.sharif.edu/article_20159_0.html
A new computer controlled flow pump is developed to continuously mitigate the adverse effects of membrane compliance in conjunction with implementation of image processing for volume change measurement. The flow pump eliminates the membrane compliance by injecting or pumping out the required volume of water into or from the gravelly specimens to compensate for the erroneous volume change associated with the membrane compliance during undrained cyclic triaxial tests. This error is compounded in gravelly soils due to the large size of the grains and voids. In order to measure the volume of the specimen during the isotropic consolidation stage and calibrate the flow pump for cyclic loading, an image processing technique was used for measuring the volume change during the isotropic consolidation stage of loading while calculating membrane compliance associated with the amount of input water from the flow pump into the specimen. The results of image processing show that the increase in density of the specimens leads to an increase in the ratio of volumetric skeletal strains to axial strains and a decrease in the normalized membrane penetration. The study yields promising results for minimizing the errors associated with membrane compliance during undrained cyclic loading on gravels.Mon, 29 Jan 2018 20:30:00 +0100New Operations for Interval-valued Pythagorean Fuzzy Set
http://scientiairanica.sharif.edu/article_20160_0.html
Interval-valued Pythagorean fuzzy set (IVPFS), originally proposed by Peng and Yang, is a novel tool to deal with vagueness and incertitude. As a generalized set, IVPFS has close relationship with interval-valued intuitionistic fuzzy set (IVIFS). IVPFS can be reduced to IVIFS satisfying the condition $mu^++nu^+ leq 1$. However, the related operations of IVPFS do not take different conditions into consideration. In this paper, we initiate some new interval-valued Pythagorean fuzzy operators ($diamondsuit, Box, spadesuit, clubsuit, maltese, rightarrow, $ $) and discuss their properties in relation with some existing operators $(cup, cap, oplus, otimes)$ in detail. It will promote the development of interval-valued Pythagorean fuzzy operators. Later, we propose an algorithm to deal with multi-attribute decision making (MADM) problem based on proposed $spadesuit$ operator. Finally, the effectiveness and feasibility of approach is demonstrated by mine emergency decision making example.Mon, 29 Jan 2018 20:30:00 +0100Systematic Approach for the Design of Modular Military Housing Units Using Six-Sigma
http://scientiairanica.sharif.edu/article_20162_0.html
Military quarters and barracks are representative of housing units where the same plan is repeated, and thus prefabricated housing production can be effectively applied. These housing units are required to be disassembled and recycled as military forces are frequently reorganized and deployed to perform military actions. In order to meet these needs, this study proposes a systematic approach for the design of modular military housing units based on Six-Sigma concept. The application of the Six-Sigma to modular military housing units allows customers’ needs to be reflected on the critical to quality, which summarizes the main design requirements, and the design concept of the modular units can be developed based on the derived critical to qualities. To evaluate the effectiveness of the proposed approach, a representative example of military housing units is chosen and designed by utilizing the new modular units developed through this procedure. The weight of frames per unit area and factory manufacturing ratio of the new design are analyzed. The results of the comparison show that the use of the new modular units not only reduces construction cost significantly, but also greatly improves the quality of construction.
Mon, 29 Jan 2018 20:30:00 +0100Profile and wavefront optimization by metaheuristic algorithms for efficient finite element analysis
http://scientiairanica.sharif.edu/article_20163_0.html
For an efficient solution of the equations arising from finite element analysis, the stiffness matrix of the model should be structured. This can be done by reducing the profile or wavefront of the corresponding graph matrix of the structure depending on whether skyline or frontal method being used, respectively. One of the efficient methods to achieve this goal is the use of the method of King, extended by Sloan. In this paper the coefficients of the priority function utilized in the generalized Sloan’s method are optimized using the recently developed metaheuristic algorithm, so-called vibrating particles system. The results are compared to those of other metaheuristic algorithms consisting of the particle swarm optimization, colliding bodies optimization, enhanced colliding bodies optimization, and tug of war optimization. These metaheuristics, are used for optimum nodal numbering of the graph models of the finite element meshes to reduce the profile and wavefront of the corresponding sparse matrices. Comparison of the results achieved by these metaheuristic algorithms and those of the King and Sloan, demonstrates the efficiency of the new metaheuristic utilized for profile and wavefront optimization.Mon, 29 Jan 2018 20:30:00 +0100Application of Ordinary Fiber-Reinforced Concrete Layer for In-plane Retrofitting of ...
http://scientiairanica.sharif.edu/article_20164_0.html
The masonry walls should have sufficient in-plane strength and stiffness to withstand the seismic loads during strong ground shakings. Different retrofitting techniques are proposed for improving in-plane behavior of the Unreinforced Masonry (URM) walls. This study focuses on experimental evaluation and numerical simulation of a simple practical retrofitting technique employing Fiber Reinforced Concrete (FRC) surface layer. The simple FRC mix has conventional available fiber, low fiber content, ordinary mix design and applicable construction procedure. Effect of FRC mix including fiber type and fiber content and surface layer thickness on in-plane behavior of masonry panels made up of conventional solid clay bricks are evaluated through experimental study in accordance with ASTM E-519 diagonal tension strength of masonry panels. In addition, numerical simulation model of this retrofitting technique in ABAQUS software is proposed and validated with test results of bare and retrofitted panels.Mon, 29 Jan 2018 20:30:00 +0100Investigating the Impact of Simple and Mixture Priors on Estimating Sensitive Proportion ...
http://scientiairanica.sharif.edu/article_20166_0.html
Randomized response is an efficacious and effective survey method to collect subtle information. It entitles respondents to respond to over-sensitive issues and defensive questions (such as criminal behavior, gambling habits, addiction to drugs, abortions, etc) while maintaining confidentiality. In this paper, we conducted a Bayesian analysis of a general class of randomized response models by using different prior distributions, such as Beta, Uniform, Jeffreys and Haldane, under squared error, precautionary and Degroot loss functions. We have also expanded our proposal for the case of mixture of Beta priors under squared error loss function. The performance of the Bayes and maximum likelihood estimators is evaluated in terms of mean squared errors. Moreover, an application with real data set is also provided to explain the proposal for practical considerations.Mon, 29 Jan 2018 20:30:00 +0100Resilient Network Design in a Location-Allocation Problem with Multi-Level Facility Hardening
http://scientiairanica.sharif.edu/article_20167_0.html
There are many sources of risk affecting the network elements may lead to network failure, so planners need to consider them in the network design. One of the most important strategies for disruption risk management is the static resilience. In this strategy, the network functionality is maintained after the disruption event by the prevention and hardening actions. In this paper, a resilient capacitated fixed-charge location-allocation model is proposed. Both facility hardening and equipping of the network to backup facilities for disrupted elements are considered together to avoid supply network failure due to random disruption. Facilities are decided to be hardened in multiple levels before disruption events. The problem is formulated as a non-linear integer programming model, then its equivalent linear form is presented. A Lagrangian decomposition algorithm (LDA) is developed to solve large-scale instances. Computational results confirm the efficacy of the proposed solution approach comparing to classical solution approaches in large-scale problems. Moreover, the superiority of the proposed model is confirmed by comparing to the classical models.Tue, 30 Jan 2018 20:30:00 +0100Design of axisymmetric aerospike nozzle based on modified MOC
http://scientiairanica.sharif.edu/article_20168_0.html
In this study a direct method based on the method of characteristics with the assumptions of non-viscous flow and thermal perfect gas is provided to design of axisymmetric plug nozzle. Inputs for numeric code are including output Mach number, specific heat ratio, global gas constant and the number of discrete steps of Prandtl–Meyer expansion fan. In the design process, there has been no simplification and only to create unique spike geometry. Based on the criterion of locating the tip of the spike on the axis of symmetry, for each output Mach number, a correction factor has been extracted that it was the sole source of theoretical errors. Studied parameters include spike geometry, exhaust nozzle flow parallelism and uniformity. In the results by numerical analysis, consistent results with desired output Mach number and parallel of output flow with the axis of symmetry are obtained. The simple and direct formulation is used and so it performs very fast. Due to recognizing of the error resulted in the surface slope reduction factor, some movement in spike geometry relative to ideal conditions was raised so the effect of reduction factor will tend to zero by increasing of the design Mach number.Tue, 30 Jan 2018 20:30:00 +0100Study of swelling behavior of temperature sensitive hydrogels considering inextensibility of network
http://scientiairanica.sharif.edu/article_20169_0.html
In this work, the equilibrium swelling of temperature sensitive hydrogel networks is studied with an emphasis on the chain locking of the network. Using Gent model for elastic part of free energy and modifying the mixing part of the free energy, a continuous model is developed which consider inextensibility of the network chains and has a good agreement with the experimental data particularly for smaller values of crosslinking density of the network and larger values of the swelling ratio. After validating the modified model, it is employed for the studying the inhomogeneous swelling of a spherical shell on a hard core both analytically and numerically. The analytical solution is used for validating the numerical method. Finally, the inhomogeneous swelling of a bilayer beam with an active temperature sensitive hydrogel is investigated and the results are presented. The obtained results show the importance level of considering the chain locking in swelling of the network in the applied problems.Tue, 30 Jan 2018 20:30:00 +0100Numerical investigation of thermal contact conductance between linear and curvilinear contacts
http://scientiairanica.sharif.edu/article_20170_0.html
Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of thermal contact resistance in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, Inverse problem method solution is utilized as a proper method for estimation of thermal contact resistance value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of thermal contact resistance. In conclusion, the final results establish the fact that the inverse problem method solution can predict thermal contact resistance values between contacting surfaces.Fri, 02 Feb 2018 20:30:00 +0100Investigation of moisture susceptibility of SBS modified asphalt containing Alumina Trihydrate ...
http://scientiairanica.sharif.edu/article_20171_0.html
Although several studies have been carried to discover the asphalt mixture performance when Alumina Trihydrate (ATH) as a flame retardant was added into, the moisture susceptibility of asphalt mixture containing ATH is still not fully clear. In this study, the moisture susceptibility of binders containing ATH were assessed through the surface free energy (SFE) obtained by the sessile drop method. A commonly used SBS modified asphalt with different dosages (0%, 6%, 8%, 10%, 12%, and 14%) of ATH were prepared to determine the physical properties, flame retardancy and SFE parameters. Experimental results indicated that the addition of ATH increased the viscosity, softening point, G*/sinδ and limiting oxygen index, but decreased the penetration and ductility. What's more, increases in total SFE, cohesive energy and work of adhesion were observed with the addition of ATH. Conversely, the work of debonding, wettability and energy ratio decrease due to the addition of ATH. It is concluded that the ATH has a significant negative effect on the moisture-induced damage potential of asphalt mixture from the view of micromechanisms. The recommended percentage of ATH was 6-8% in consideration of physical properties, flame retardation and moisture susceptibilitySun, 04 Feb 2018 20:30:00 +0100IMPROVEMENT ON STRUCTURE OF FIRE ALARM SYSTEMS ALARM BELL STOP SWITCH
http://scientiairanica.sharif.edu/article_20172_0.html
Fire alarm systems are essentially installed in specific firefighting equipment and serve as one of important alarm equipments which senses fire early. The main goal of the study is to find methods for improving the structure of fire alarm needs. This study is about false alarms of fire indicating equipment in fire alarm systems. It is found that false alarms false alarms by fire alarm systems are constantly occurring and fire safety manager is neglecting his duty of work by turning alarm bell stop switch on even during usual times. To prevent this, the alarm bell stop switch should be changed into an automatically resettable manual operation type so that it can automatically reset to its original state even though fire safety manager turns the switch on. As a result, aid in correcting fire safety managers' wrongful practices by making the alarm bell ring whenever an actual fire occurs, and ultimately reduce false alarms by eliminating fundamental causes when false alarms occur.Sun, 04 Feb 2018 20:30:00 +0100Evaluation of shear strength parameters of granulated waste rubber using artificial neural ...
http://scientiairanica.sharif.edu/article_20173_0.html
Utilizing rubber shreds in civil engineering industry such as geotechnical structures can accelerate generated waste tire recycling process in an economical and environmentally friendly manner. However, understanding the rubber grains strength parameters is required for engineering designs and can be acquired through experimental tests. In this study, small and large direct shear test was implemented to specify shear strength parameters of five rubber grains group which are different in gradation and size. Moreover, artificial neural networks (ANN) are developed based on the test results and optimized networks which best captured the shear stress (τ), and vertical strain (εv) behavior of rubbers, are introduced. Additionally, a prediction model using the combinatorial algorithm in group method of data handling (GMDH) is proposed for the shear strength and vertical strain in the arrangement of closed-form equations. The performance and accuracies of the proposed models were checked using correlation coefficient (R) between the experimental and predicted data and the existing mean square error (MSE) was evaluated. R-values of the modeled τ and εv are equal to 0.9977 and 0.9994 for ANN, and 0.9862 and 0.9942 for GMDH models, respectively. The GMDH proposed models are presented as comparatively simple explicit mathematical equations for further applications.Sun, 04 Feb 2018 20:30:00 +0100Soft Computing-based Approach on Capacity Prediction of FRP Strengthened RC Joints
http://scientiairanica.sharif.edu/article_20177_0.html
Shear failure of the RC beam-column joints is a brittle failure which has no priorwarning and can induce tremendous damages because of collapse of column and joint before theconnected beam. This paper is focused on one particular method of strengthening the RC joints,that is, the use of FRP composites as confining element. The results of previous studies have shownthat strengthening the RC beam-column joints with FRP composites can improve their shearcapacity. In this study, the data collected from the existing standards and studies regarding the FRPstrengthened RC joints were used to develop an artificial neural network model for predicting theshear strength contribution of FRP jacket. The developed model was then used to evaluate the roleof different parameters on this contribution, and finally derive a formula for contribution of FRPjacket to the shear strength of the RC beam-column joints.Tue, 06 Feb 2018 20:30:00 +0100Modelling Multi Tour Inventory Routing Problem for Deteriorating Items with Time Windows
http://scientiairanica.sharif.edu/article_20178_0.html
In recent decades, there are intensive researches on deteriorating inventory. However, only a few researchers focus on the inventory routing problem for deteriorating item. There are many items such as foods, electronic products that deteriorate with time, and many other products in the market also have perishable characteristic. The items not only decay during the stockpiling period but they also deteriorate throughout transportation time. Since deteriorated rate and time is necessary, in this paper, an inventory routing problem with time windows for deteriorating items is developed. Particle Swarm Optimization (PSO) is used to solve the problem since PSO can solve problems in a reasonable period with near optimal solutions. We use two examples to illustrate the model. In a sensitivity analysis, way parameters that impact costs are demonstrated. Our results show that the deteriorating rate in inventory has bigger effects than deteriorating rate in the vehicle, so this research has a significant contribution and managers can give more effort to reduce deteriorating in inventory than the deteriorating rate in vehicles.Tue, 06 Feb 2018 20:30:00 +0100Quasi-reflection based symbiotic organisms search algorithm for solving static optimal power ...
http://scientiairanica.sharif.edu/article_20179_0.html
This paper offers a novel variant to the existing symbiotic organisms search (SOS) algorithm, to address optimal power flow (OPF) problems considering effects of valve-point loading (VE) and prohibited zones (POZ). Problem formulation includes minimization of cost, loss, voltage stability index (VSI) and voltage deviation (VD) and simultaneous minimization of their combinations. Quadratic cost function, effects of VE and effects of both VE and POZ have been considered. OPF formulation considering effects of both VE and POZ are not yet available in the literature. Efficacy of SOS in resolving OPF is recognized in the literature. An opposition based learning technique named quasi-reflection, is merged into existing SOS to enhance its prospects of getting nearer to superior quality solution. The proposed algorithm, named quasi-reflected symbiotic organisms search (QRSOS), is assessed for IEEE 30 and IEEE 118 bus test systems. It shows promising results in reducing the objective function values of both the systems by large margins (78.98 % in case of VD when compared to SOS and NSGA-II and 46.06 % in case of loss as compared to QOTLBO in IEEE 30 and IEEE 118 bus respectively). QRSOS also outperformed its predecessors, in terms of convergence speed and global search ability.Tue, 06 Feb 2018 20:30:00 +0100Application of Multi-objective Charged System Search Algorithm for Optimization Problems
http://scientiairanica.sharif.edu/article_20184_0.html
The charged system search algorithm is a relatively new optimization algorithm developed based on some principles from physics and mechanics. This paper presents an approach in which Pareto dominance is incorporated into the charged system search in order to allow this algorithm to handle problems with some multi-objective functions; the proposed algorithm will be called Multi-Objective Charged System Search (MOCSS). Well-known mathematical and engineering benchmarks are used to evaluate the proposed algorithm and the results have been compared with other new approaches. The results of implementing the new algorithm on some test problems show that the proposed algorithm outperforms the other algorithms in terms of Generational Distance, Maximum Spread, Spacing, Coverage of two Set and Hypervolume Indicator. Results of well-known mathematical examples indicate that the new approach is highly competitive and can be considered as a viable alternative to solve multi-objective optimization problems. These results encourage the application of the proposed method to more complex and real-world multi-objective optimization problems. The proposed method can deal with highly nonlinear problems with complex constraints and diverse Pareto optimal sets.Sun, 11 Feb 2018 20:30:00 +0100Influence of bladed and glazed entrance on the performance of solar air heaters
http://scientiairanica.sharif.edu/article_20185_0.html
The performance of a flat plate single-pass solar air heater (SAH) modified at the entrance region of the heater was experimentally investigated. The entrance region was covered with glass cover instead of steel cover. The aim of using glass at the entrance region is increasing the heating area exposed to solar irradiation. In addition, replacing the steel cover with glass reduces the shading effect occurred due to steel which decreases the temperature of the surface of the absorber and hence the outlet temperature of the air. Also, guide blades were placed in the entry region to ensure well air distribution on the absorber surface and hence enhancing the thermal performance of SAH. The modified SAH was compared with another one without air blades and without glass cover at the entrance. The experiments were performed at four air flow rates ranged from 0.013 kg/sec to 0.04 kg/sec. The modifications led to good enhancement in both the air temperature difference and the efficiency. The glazed-bladed SAH showed a good improvement in the daily thermal efficiency by 6.72 % to 10.5 % over the conventional heater and by 2.16 % to 3.25 % over the glazed SAH.Mon, 12 Feb 2018 20:30:00 +0100Multiflute Drill-Broach for Precision Machining of Holes
http://scientiairanica.sharif.edu/article_20186_0.html
This paper deals with hole-enlarging multiflute drill processing. The analysis of existing structures, their advantages and disadvantages is carried out. Cutting conditions during hole-enlarging multiflute drill processing are shown. A new design of hole-enlarging multiflute drill as a hole-enlarging multiflute drill-broaching tool from broaching-speed steel with carbide plates, as well as a new way of handling the new tools is offered. Hole-enlarging multiflute drill-broaching combines the features of hole-enlarging multiflute drill (in cross section) and the features of broaching tool (in longitudinal section). In this way, it was possible to increase the quality of hole making (size variance, surface roughness), to facilitate the cutting conditions and to increase the durability. The results of prototypes testing are presented.Mon, 12 Feb 2018 20:30:00 +0100Sustainable Procurement Decision of Electric Coal under Fuzzy Information Environment
http://scientiairanica.sharif.edu/article_20194_0.html
Green supply chain management is a crucial challenge for the sustainable development of the enterprises. In this paper, we study the problem of supplier selection for the multi-attribute and multi-source green procurement of electric coal under fuzzy information environment. Concretely, we establish a new index system of supplier selection by considering both the economic factors and environmental factors, and then present a multi-attribute decision making method based on 2-tuple deviation degree to rank all alternative suppliers in the green procurement of electric coal. We also highlight the implementation, availability, and feasibility of the green procurement decision method of electric coal by using an example of the multi-source procurement of electricity coal. We try to provide theoretical basis and decision-making reference for the thermal power enterprise to implement scientific green procurement management of electric coal.Sat, 17 Feb 2018 20:30:00 +0100Rolling contact fatigue analysis of rails under the influence of residual stresses induced by ...
http://scientiairanica.sharif.edu/article_20196_0.html
This study aims to analyze the rolling contact fatigue influenced by residual stresses caused by the contact of the wheel and rail and its manufacturing process. For this purpose, a rail available in Iran railway is used with an exact profile geometry. The location of maximum stress caused by the contact of wheel/rail for rail profiles can be calculated by three-dimensional elastic-plastic finite element model. Then, in order to estimate the stress distribution caused by rail manufacturing process, a thermal analysis with finite element method will be performed. Afterwards, the results of performed stress analysis will be used as input for three-dimensional crack growth and rail fatigue life estimation model to calculate the stress intensity factors and fatigue life according to the set of related parameters with boundary element method. Finally, three-dimensional finite element analysis results obtained show good agreement with those achieved in field measurements.Sat, 17 Feb 2018 20:30:00 +0100Modeling Stock-out Loss and Overstocking Loss Generated by Bullwhip Effect
http://scientiairanica.sharif.edu/article_20199_0.html
Although the literature of the supply chain is teemed with the analysis of the bullwhip effect, few studies regarding the impact of the bullwhip effect or demand distortion on the supply chain profit have been done. Hence, we introduce the concept of Distance to Loss (DL), which is a function of the retailer’s selling price, the manufacturer’s wholesaler price, the end item’s salvage value, the retailer’s expected demand and the retailer’s variance of demand. This concept can perfectly model both stock-out loss and overstocking loss emanated by the bullwhip effect and combines both the newsvendor model and credit risk concepts. Our findings are based on an experimental design and are profoundly in line with previous research. In particular, our model indicates that variations in demand parameters, retailer’s selling price and manufacturer’s wholesaler price impinge on the retailer’s DL, whereas a slight increase in the salvage value negligibly affect the retailer’s DL.Fri, 02 Mar 2018 20:30:00 +0100Predicting the Effective Stress Parameter of Unsaturated Soils Using Adaptive Neuro-Fuzzy ...
http://scientiairanica.sharif.edu/article_20200_0.html
The effective stress parameter (χ) is applied to obtain the shear strength of unsaturated soils. In this study, two adaptive neuro-fuzzy inference system (ANFIS) models, including SC-FIS model (created by subtractive clustering) and FCM-FIS model (created by Fuzzy c-means (FCM) clustering), are presented for prediction of χ and the results are compared. The soil water characteristic curve fitting parameter (λ), the conﬁning pressure, the suction and the volumetric water content in dimensionless forms are used as input parameters for these two models. Using a trial and error process, a series of analyses were performed to determine the optimum methods. The ANFIS models are constructed, trained and validated to predict the value of χ. The quality of the ANFIS prediction ability was quantiﬁed in terms of the determination coefﬁcient (R2), Root Mean Square Error (RMSE) and Mean Absolute Error (MAE). These two ANFIS models are effectively able to predict the value of χ with reasonable values of R2, RMSE and MAE. Sensitivity analysis was used to acquire the effect of input parameters on χ prediction, and the results revealed that the conﬁning pressure and the volumetric water content parameters had the most influence on the prediction of χ.Fri, 02 Mar 2018 20:30:00 +0100Seismic force modification factors for partitions in low- rise reinforced concrete buildings
http://scientiairanica.sharif.edu/article_20201_0.html
Present codes of practice do not consider the effect of arrangement of partitions in the plan of structure on the seismic demands of these non-structural components. In this paper, a modification factor has been proposed to modify provisions for those seismic demands. Seventy two regular low-rise reinforced concrete moment frames, supporting some partitions, exposed to seven appropriate ground motions. The nonlinear seismic response history analysis considering out-of-plane behavior of partitions has been conducted using the OpenSees platform. The average values of peak responses from those earthquakes were obtained. The forces generated using the analytical method, which some of them verified with existing study results, were compared with the values from the code and a factor denoted as seismic force modification factor, W, was proposed. A parametric study has been carried out to study the effect of dominent parameters such as the arrangement of partitions, partition to structure height ratio, and length to height ratio of partitions on the W values. For the majority of the models, the W values are larger for partitions located further with respect to the center of floor. Moreover the modification factor could be as large as 1.85 for the partitions located in the middle floors.Fri, 02 Mar 2018 20:30:00 +0100Strength and Durability Studies on High Volume Readymade Ultrafine Slag based High Strength Concrete
http://scientiairanica.sharif.edu/article_20202_0.html
Steel industries produces ground granulated blast furnace slag (GGBFS) as a waste material and has enormous scope to be made use of in concrete as partial substitute to cement. The average particle size of GGBFS used was 17.5 µm. It fills voids and modifies the microstructure in turn enhancing the strength and durability of concrete. In the present work commercially available ultra fine slag (readymade ultrafine slag - RUFS) with an average size of 5 µm was used as mineral admixture in three different percentages of 30, 40 and 50 as substitute to cement. Results of present work were compared to precursor slag of author’s earlier works. From the experimental results it was understood that RUFS with 40% substitution to cement gave better performance among three different percentages used. Comparing with author’s earlier works, RUFS performed better than precursor slag and had slightly higher results than that of concrete with 5 to 15% of RUFS. Hence it is suggested that cement could be replaced with readymade ultrafine in high volume as much of 40% without compromising its performance.Fri, 02 Mar 2018 20:30:00 +0100Usability of Arc Fault Circuit Interrupters with Network Function
http://scientiairanica.sharif.edu/article_20203_0.html
The existing arc fault circuit interrupters have the function to interrupt overloads, ground fault, arc fault and all but neither is there the monitoring function to allow external monitoring nor the notification function to notify the fire safety manager. This is a study on arc fault circuit interrupters with the network function that have not been studied so far. We intend to install these arc fault circuit interrupters in places such as server rooms, pigsties, chicken farms, markets, cultural assets, skyscrapers, and facto-ries where large loss may occur if the fire safety managers do not recognize the electricity shutdown in order to increase the efficiency of electricity management. If an overload, a short circuit or an arc is detected while power is supplied to the load, the microprocessor generates a trip signal and cuts off the power by this trip signal. This situation is monitored in real time by ex-ternal monitoring and notified to the fire safety manager. The fire safety manager can immediately recognize the situation where the arc fault circuit interrupter interrupts the circuit and take the necessary action to manage the electricity efficiently.Sat, 03 Mar 2018 20:30:00 +0100Design an analog CMOS fuzzy logic controller for the inverted pendulum with novel triangular ...
http://scientiairanica.sharif.edu/article_20204_0.html
In this paper,a fuzzy analog controller circuit is provided for the inverted Pendulum problem which resulted in a simple analog circuit simply does the act of controlling without requiring to any processing structure.In other words,in case of constructing the proposed circuit,a small analog chip controls the inverted pendulum.For this purpose,the first step is the study of the dynamic model of the inverted pendulum and then a fuzzy controller is designed systematically.In the following,the number of membership functions and the formation of them are designed.In addition,the different MFs and different numbers are examined for each variable and the most efficient structure is selected as fuzzy controller.To assess efficiency of designed fuzzy controller,the controller is simulated in Simulink and then this design is implemented at transistor level in TSMC 0.18µm CMOS technology.In this work,the MFs,the circuits for realization of the knowledge-based and defuzzification circuits are designed in current mode.The proposed circuits are simulated and evaluated in Advanced Design System software based on CMOS technology.Simulation results show that the inverted pendulum is controlled with high accuracy and high speed,meanwhile the controllers have low power consumption and good robustness to outer large and fast disturbance rather than the previous works.Sat, 03 Mar 2018 20:30:00 +0100Laboratory and Numerical Study of the Behavior of Circular Footing Rested on Sand Contaminated ...
http://scientiairanica.sharif.edu/article_20206_0.html
This research studies the behavior of circular foundations rested on the soils contaminated with gas oil and kerosene oil under cyclic loading. The final goal of this study was to determine the influence level of the foundation of the reservoirs rested on oil-contaminated sand due to their filling and discharging. The contaminated sand layers were mixed with different percentages of contamination from 2 to 6 of kerosene oil and gasoline. The effect of the contamination percentage, the value of the applied load, as well as the depth and type of contamination is investigated in this study. To validate the numerical studies performed by finite element software, small-scale laboratory tests is carried out. The results showed that the pollutants could affect the amount of final settlement and the number of loading cycles to reach this value. Increasing depth, the number of load cycles and the contamination content increased the final settlement and the number of loading cycles to reach that level increases. Numerical results showed a good compatibility in the load-settlement charts with the experimental results.Sat, 03 Mar 2018 20:30:00 +0100Numerical simulation of thermal radiative heat transfer effects on Fe3O4- Ethylene glycol ...
http://scientiairanica.sharif.edu/article_20207_0.html
Electrohydrodynamic Fe3O4- Ethylene glycol nanofluid forced convection is simulated in existence of thermal radiation. The porous lid driven cavity has one moving positive electrode. Single phase model has been applied to simulate nanofluid behavior. Control Volume based Finite Element Method is employed to obtain the results which are the roles of Darcy number , radiation parameter , Reynolds number , nanofluid volume fraction and supplied voltage . Results depict that maximum values for temperature gradient is obtained for platelet shape nanoparticles. Nusselt number enhances with rise of Darcy number and supplied voltage. Convection mode enhances with increase of permeability of porous media and nanofluid volume fraction but it decreases with rise of Hartmann number.Sat, 03 Mar 2018 20:30:00 +0100On the measurement of transverse shear stress on a rectangular open channel using optimal ...
http://scientiairanica.sharif.edu/article_20209_0.html
The laboratory studies have been carried out in this research. Determining the sensitivity analysis of the Preston tube diameter in shear stress, four Preston tubes with external diameters of 3.2, 3.9, 4.7 and 6.3 mm were used. The aspect ratios of 2.86 to 13.95 were examined. For measuring the pressure difference of the Preston tube a 200 millibar differential pressure transducer with 0.01 accuracy of the original scale was used. Laboratory results demonstrated that Preston tubes with a diameter of 3.9 mm present the minimum difference in the average value of the shear stress resulting from the Bechert and Patel calibration equations. Therefore, using the Preston tube with an optimal diameter, transverse distribution of shear stress in channels bed and wall were determined. The outcome of this part of study is two dimensionless relationships for determining the local shear stress both in the bed and wall. These relationships are a function of the aspect ratio B/H and the bed relative coordinates b/B in cross section and Z/H sidewall. The survey showed that the dimensionless bed shear stress distribution is considerably influenced by the aspect ratio. The transverse distribution of wall shear stress is independent from the aspect ratio for B/H>3.Mon, 05 Mar 2018 20:30:00 +0100A laboratory investigation on suppression of dust from wind erosion using biocementation with ...
http://scientiairanica.sharif.edu/article_20220_0.html
Dust events are among the serious environmental challenges in some countries. Sustainable solutions can be applied to tackle this problem by considering soil as a living ecosystem. Biocementation based on production of carbonates by heterotrophic bacteria is one of the favored methods to suppress the dust from wind erosion because this type of bacteria produces calcium carbonate (main product) as well as water and carbon dioxide (by-products). In present research, bacterial species of Bacillus amyloliquefaciens was used. First, bacteria were cultivated to reach toa pre-determined concentration. Next, bacterial cells and nutrients in the form of solution were sprayed on the soil surface. Then, samples were tested in a closed circuit wind tunnel. Three main groups of samples were tested: without sand bombardment and undisturbed soil surface, with sand bombardment and undisturbed soil surface, and without sand bombardment and with disturbed soil surface. The results show that the implemented method for stabilization of soil was efficient. Moreover, based on the results of second group of tests, curing duration, amount of water, temperature-water interaction and water -bacterial cells interaction were found to be of considerable significance.Tue, 13 Mar 2018 20:30:00 +0100Adapted Design Of Experiments for Dimension Decomposition Based Meta Model in Structural ...
http://scientiairanica.sharif.edu/article_20221_0.html
Reliability analysis of structures is often problematic for the structures with nonlinear and complex limit state functions (LSF). For these cases, simulation methods often provide accurate failure probability, but with high number of structure’s LSF analysis. This paper presents an efficient combination of Monte Carlo Simulation (MCS) method and Univariate Dimension Reduction (UDR) based Meta-model to approximate the failure probability of structures with few LSFs evaluation. For this purpose, the design of experiment used in the Meta model is adapted such that the expected failure samples in MCS being approximated with higher accuracy. Several numerical and engineering reliability problems are solved by the proposed approach and the results are verified by MCS. Results show that the proposed approach highly reduces the required number of structural analysis to provide proper results.Tue, 13 Mar 2018 20:30:00 +0100Centrifuge modelling of monopiles subjected to lateral loading
http://scientiairanica.sharif.edu/article_20222_0.html
Monopiles are the most common foundation type used for fixed-bottom substructures in offshore wind installations. In an offshore environment, the predominant load is cyclic, which affects the stiffness and deformation properties of foundation systems, especially monopiles. To investigate the effect of cyclic loading on a short (rigid) steel monopile, a set of displacement-controlled ηg laboratory tests were designed. This paper presents the procedure and results of eight centrifuge tests investigating monopile behaviour when subjected to lateral monotonic and cyclic loading. The general trend of monotonic response is in good agreement with the results of similar experimental studies, however, much softer behaviour was observed compared to the equivalent Winkler model on API p-y curves. The cyclic tests focused on the stiffness and deformation properties of a soil-pile system under fatigue loading. Increases, decreases or no changes in secant stiffness were observed depending on the regime of the applied cyclic displacements which are in contradiction to current design methodology where only cyclic degradation is assumed. Influence of load cycling on cyclic bending moments along the pile shaft was discussed and found to be of minor significanceTue, 13 Mar 2018 20:30:00 +0100Experimental Behavior of Circular Foundations on Oil Contaminated Sand
http://scientiairanica.sharif.edu/article_20223_0.html
This paper studies the behavior of circular footings placed on the gasoil and kerosene-contaminated soil. The ultimate objective of this study is to determine the effect that oil contamination has on the sand bearing capacity. The contaminated sand layers were mixed with different levels of between 1 and 4 percent of gasoil and kerosene contamination. The influence of the contamination depth and type of contamination was examined in this study. Laboratory tests were conducted on small scale models and performed in load-controlled manner. The results showed that the contamination can influence the load-settlement curves and lead to a reduction in its load-bearing capacity. An increase in the depth and percentage of contamination decreased the bearing capacity. Some formulas have been provided in which by knowing the depth and percentage of contamination one can predict the third bearing capacity factor of a circular foundationTue, 13 Mar 2018 20:30:00 +0100Trajectory modification of a transonic spherical projectile under Hop-up mechanism
http://scientiairanica.sharif.edu/article_20224_0.html
Improvement of shooting accuracy of air gun pellets is important in sport competitions which is questioned by shooting enthusiasts. Hence, the performance of a transonic spherical projectile as an air gun pellet with 4.5 mm-caliber under a mechanism known as Hop-up is numerically examined in the present study. Hop-up mechanism is resulted in a rotational motion of spherical projectile, so a Magnus Force is generated which prevents the altitude loss of the projectile caused by its weight. The motion of the projectile is assumed in four degrees of freedom including three translational motions and one transverse rotational motion. The projectile confronts the continuous variations of velocity due to the influence of the aerodynamic forces so experiences an unsteady flow. In order to numerical analysis of the problem, the 3-D compressible turbulent Navier-Stokes equations based on “Roe” scheme and dynamic equations of the projectile motion are solved in a coupled form as a fluid-structure interaction and in a moving computational grid. The results obtained from these studies show that the proper rotation of the projectile for a certain distance, can neutralize the altitude loss. It is also demonstrated that the momentum of the projectile is decreased by increasing its angular velocity.Tue, 13 Mar 2018 20:30:00 +0100An Optimization Framework for Risk Response Actions Selection Using Hybrid ACO and FTOPSIS
http://scientiairanica.sharif.edu/article_20225_0.html
This paper presents a framework for solving risk response action selection problem by considering: (1) the impact of risk events on the project objectives, (2) the interactions between risk events and (3) management criteria and preferences. For these purposes, a framework is developed by combining an optimization-based model and a Multi Criteria Decision Making (MCDM) approach. First, in the optimization-based model, Ant Colony Optimization (ACO) is used to find the best combination of response actions which have more effects on time, cost and quality. Also, in this model, to overcome the imprecision situation resulting from lack of knowledge or insufficient data, risk parameters are determined using the fuzzy set theory. Moreover, the Design Structure Matrix (DSM) is used to capture the effect of interactions between risk events. Second, the Fuzzy Technique for Order Preference by Similarity to Ideal Solution (FTOPSIS) method is used to analyze the obtained solutions by ACO, based on the other management criteria. Finally, the efficiency of the proposed framework is examined by its implementation in a real building construction project. Discussions through the case study show that using the proposed framework decision makers can evaluate more aspects of response actions.Tue, 13 Mar 2018 20:30:00 +0100A stochastic multi-objective model based on the classical optimal search model for searching ...
http://scientiairanica.sharif.edu/article_20226_0.html
Although after an earthquake the injured person should be equipped with food, shelter and hygiene activities, before anything must be searched and rescued. But disaster management (DM) has focused heavily on emergency logistics and developing an effective strategy for search operations has been largely ignored. In this study, we suggest a stochastic multi-objective optimization model to allocate resource and time for searching the individuals who are trapped in disaster regions. Since in disaster conditions the majority of information is uncertain, our model assumes ambiguity for the locations where the missing people may exist. Fortunately, the suggested model fits nicely into the structure of the classical optimal search model. Hence, we use a stochastic dynamic programming approach to solve this problem. On the other hand, through a computational experiment, we have observed that this model needs heavy computation. Therefore, we reformulate the suggested search model as a multi-criteria decision making (MCDM) problem and employ two efficient MCDM techniques, i.e. TOPSIS and COPRAS to tackle this ranking problem. Consequently, the computational effort is decreased significantly and a promising solution is produced.Tue, 13 Mar 2018 20:30:00 +0100Nonlinear free vibration analysis of functionally graded plate resting on elastic foundation in ...
http://scientiairanica.sharif.edu/article_20227_0.html
This paper deals with nonlinear vibration analysis of functionally graded plate resting on Pasternak elastic foundation in thermal environment. A mathematical model is developed based on higher-order shear deformation theory using Green-Lagrange type nonlinearity. The model includes all the nonlinear terms to obtain a general form and to present the original flexure of the plate. The material properties are considered as temperature dependent and graded along thickness direction obeying a simple power law distribution in terms of volume fraction of the constituents. The compression/traction free condition is employed to obtain the simplified model with seven parameters instead of nine parameters. The plate model has been discretized into C0 eight noded quadratic elements with seven degrees of freedom per node. The governing equation of the functionally graded plate has been derived using Hamilton’s principle and is solved using direct iterative method. The present model is validated by comparing the obtained results with those published in the literature. The effects of volume fraction index, aspect ratio, thickness ratio, support conditions, elastic foundation modulus and temperature on the nonlinear frequencies of the functionally graded plates are discussed. It has been found that the intermediate material property does not necessarily give intermediate nonlinear frequencyTue, 13 Mar 2018 20:30:00 +0100Effect of Stress Direction on the Undrained Monotonic and Cyclic Behaviour of Dense Sands
http://scientiairanica.sharif.edu/article_20318_0.html
Geotechnical design may be unsafe if the anisotropic behaviour of soil is not considered. The behaviour of anisotropic materials depends on the principal stresses and their directions. A detailed experimental programme was conducted to study the effect of stress direction on the monotonic and cyclic behaviour of dense sand. A total of 20 undrained tests were performed at a constant mean confining stress (σ'0m) constant intermediate principal stress ratio (b= (σ2-σ3)/(σ1-σ3)), and principal stress directions (α). Two fine sands, Babolsar and Toyoura, were selected as the test materials. The isotropic consolidated specimens were prepared using the wet tamping technique. The results showed that the major principal stress direction had little considerable effect on the mobilized friction angle at steady state or phase transformation. The results showed that stress direction had a significant effect on the non-coaxiality between the principal strain increment direction and the principal stress direction. The soil fabric was led to significant non-coaxiality value before the peak shear strength. Increasing the octahedral shear strains decreased the non-coaxiality value due to destruction of the soil particle interlock (soil fabric). The effect of stress direction on non-coaxiality and excess pore water pressure generation was also investigated.Tue, 17 Apr 2018 19:30:00 +0100MHD PERISTALTIC SLIP FLOW OF CASSON FLUID AND HEAT TRANSFER IN CHANNEL FILLED WITH A POROUS MEDIUM
http://scientiairanica.sharif.edu/article_20319_0.html
We examine the effect of velocity slip on hydromagnetic peristaltic flow of a Casson fluid and heat transfer through an asymmetric channel fluid filled a porous medium.The model governing equations are obtained, simplified using long wavelength and low Reynolds number assumptions and then tackled analytically.Numerical result for effects of embedded parameters on the stream function, axial velocity, pressure drop, temperature, skin friction and Nusselt number are presented graphically and discussed. It is found that thepermeability parameter enhances the size of the trapped bolus while velocity slip diminishes it. A rise in magnetic field intensity and Cason fluid parameters decrease the both velocity and temperature profiles.The present problem is of substantial importance in crude oil refinement and biomedical engineering.Tue, 17 Apr 2018 19:30:00 +0100Impact of nonlinearity on bolt forces in multi-bolted joints: A case of the assembly stage
http://scientiairanica.sharif.edu/article_20320_0.html
This article concerns modeling, computation and analysis of multi-bolted joints in the assembly stage. The physical joint model is introduced as the assembly of the following three basic subsystems: a set of fasteners (bolts), a flexible joined flange and a contact layer between it and a rigid support. The finite element method (FEM) is used for modeling. Bolts are replaced by the bolt models of the spider type. The joined flange is modeled with spatial finite elements. As a model of the contact layer, the Winkler contact layer model is adopted. The truth of the theorem has been tested, according to which nonlinear characteristics of the contact layer may have an insignificant impact on computational final values of bolt preloads in the case of sequential tightening of the joint. The results of the calculations for the selected multi-bolted joint are given and compared with the experimental results. Conclusions of paramount importance to the engineering practice are comprised.Tue, 17 Apr 2018 19:30:00 +0100Different Operational Alternatives of Aquifer Thermal Energy Storage System for Cooling and ...
http://scientiairanica.sharif.edu/article_20323_0.html
In this research, a confined aquifer with low groundwater flow was considered to meet the cooling and heating requirement of residential complexes. The complexes were located in the cities of Ahvaz, Ardabil, Bandar Abbas, Esfahan, Kerman, Rasht, Tehran and Zahedan. The complex in Ardabil required mostly heating, the ones in Ahvaz and Bandar Abbas required mostly cooling, whereas the complex in other cities required both heating and cooling. Four different alternatives of aquifer thermal energy storage (ATES) were analyzed in this study. These alternatives were:1) using ATES alone for cooling 2) for cooling coupled with a conventional refrigeration system or a chiller 3) for heating by employing flat plate solar collectors and 4) for heating by employing flat plate solar collectors and a heat pump. Thermal energy recovery factor and the annual coefficient of performance (COP) of the alternatives were determined. The results showed that, for buildings located in cities with mild climatic conditions(such as Esfahan), where the annual heating and cooling energy requirements are early equal, the use of ATES is highly recommended when employing any of the alternatives considered in this investigation.Tue, 17 Apr 2018 19:30:00 +0100Immune Based Evolutionary Algorithm for Determining the Optimal Sequence of Multiple ...
http://scientiairanica.sharif.edu/article_20324_0.html
This paper presents a new multiple disinfection operation problem (MDOP) in which several buildings have to be sprayed with various disinfectants. The MDOP seeks to minimize the total cost of disinfection operations for all buildings. The problem is different from the typical vehicle routing problem since: (a) each building has to receive multiple spray applications of disinfectants; (b) the final spray application of disinfectant in each building is fixed; and (c) for safety, the time interval between two consecutive spray applications of disinfectants for each building must meet or exceed a specified minimum. The MDOP problem is NP-hard and difficult to solve directly. In this paper, we firstly develop an efficient encoding of spray operations to simultaneously determine the optimal sequence of buildings and their respective treatments with spray disinfectants. Secondly, we adopt immune algorithm to solve the presented MDOP. Finally, as a demonstration of our method, we solve the problem for a campus case to determine the optimal disinfection strategy and routes assuming both single and multiple vehicle scenarios. Numerical results of immune algorithm are discussed and compared with those of genetic algorithm and PSO to show the effectiveness of the adopted algorithm.Tue, 24 Apr 2018 19:30:00 +0100New aspect of transition between line and continuous spectrum and its relation to seismic ...
http://scientiairanica.sharif.edu/article_20326_0.html
We considered a new view on transition process from periodic to aperiodic signals, in time and spectral domains, pointing out how the concept of infinity is involved. It contributes to better understanding of the nature of both spectral descriptions, and conditions of their practical use, particularly in unusual cases. There we highlight the invariance in spectrum convergence by introducing some numerical parameters which exactly describe such process. Their behaviour is numerically examined to detail. Also, we considered the opposite transition, from aperiodic to periodic, to clarify the meaning of spectral line. To suggest applicability of our analysis we used an actual seismic signal. By extracting the most prominent waveform part, regarding influence on structures, we formed a periodic signal which line spectrum can clearly show possible resonance with vibrating tones of structures.Tue, 24 Apr 2018 19:30:00 +0100Numerical investigation on natural convection of nanofluids in an inclined square enclosure ...
http://scientiairanica.sharif.edu/article_20327_0.html
Studying on natural convection of nanofluids in enclosures with non-uniform heated walls is important for many engineering applications such as solar energy collection. In this article, we develop a fully higher-order compact (FHOC) finite difference method to investigate the natural convection and heat transfer of nanofluids in an inclined square enclosure with sinusoidal temperature distributions. Numerical simulations have been performed over a range of amplitude ratio, inclination angles, phase deviation, nanoparticles volume fraction, and Rayleigh number. Results show that heat transfer can exchange significantly by increasing the amplitude ratio and inclination angles in nanofluids. Moreover, elevating the nanoparticles volume fraction doesn't always enhance the heat transfer of nanofluids. When the Rayleigh number is low ( = ), the average Nusselt number decreases as the solid volume fraction parameter increases. On the other hand, elevating has favorable effects on the heat transfer of nanofluids when is high (e.g., , ). When , the total heat transfer rate decreases in the order of nanoparticles arranged as Cu, CuO, Al2O3, and TiO2. Finally, a correlated expression of the total average Nusselt number, the Rayleigh number and the solid volume fraction of nanoparticles is empirically obtained.Tue, 24 Apr 2018 19:30:00 +0100Hybrid fuzzy-stochastic approach for multi-product, multi-period, and multi-resource master ...
http://scientiairanica.sharif.edu/article_20329_0.html
Master production scheduling is an effective phase of production planning which leads to scheduling and magnitude of different products production in a company. This problem requires investigating a wide range of parameters, regarding demand, manufacturing resource usage and costs. Uncertainty is an intrinsic characteristic of these parameters. In this paper, a model is developed for master production scheduling under uncertainty, in which demands, as time-dependent variables, are considered as stochastic variables, while cost and utilization parameters, with cognitive ambiguity, are expressed as fuzzy numbers. A hybrid approach is also proposed to solve the extended model. The application of the proposed method is examined in a practical problem of a polyethylene pipe and fitting Co. in Iran. The result showed a high degree of applicability.Tue, 24 Apr 2018 19:30:00 +0100Optimal Location of Stone Column in Stabilization of Sand Slope: An Experimental and 3D ...
http://scientiairanica.sharif.edu/article_20331_0.html
Utilization of numerical and analytical methods to stabilize earth slopes applying piles or stone columns is subject commonly discussed by numerous researchers. Various researchers have practiced optimization of the location of pile or stone column, to stabilize earth slope through numerical and analytical approaches. Their efforts have led to various results raising the question of what the optimal place for installation of a pile or stone column is. It is look like that no experimental studies are conducted in this regard; the point which is discussed in this article. Experimental study conducted in this article is new topic and it can solve the problem caused by varying and sometimes contradictory results of numerical analyses to find the optimal pile (or stone column) location. In this article, an experimental study is conducted for two-layer sand earth slope, which is saturated through precipitation and failure after saturation over time. Installing stone columns in different locations and saturating the earth slope through precipitation, rational acceptable results were obtained that can appropriately assist designers. All of the experimental models were modeled and compared using the 3D finite difference method (3D FDM), which are compliant with each other.Tue, 24 Apr 2018 19:30:00 +0100Assessment of Mechanical and Durability Properties of Concrete Containing PET Waste
http://scientiairanica.sharif.edu/article_20334_0.html
Plastic waste is a silent threat to the environment, and their disposal is a serious issue. To sort out this issue, many efforts were made to reuse the plastic waste, but no significant results were achieved. On the contrary, concrete being the widely used construction material is facing problem due to unavailability of ingredient material (sand and coarse aggregate). In this study PET (polyethylene terephthalate) aggregates manufactured from the waste un-washed PET bottles in shredded form were used to partially replace fine aggregate and coarse aggregate in concrete in various percentages (0%, 5%, 10%, 15% and 20%). Various tests like workability, compressive strength, flexural strength, water permeability, abrasion resistance, dynamic and static modulus of elasticity were performed. The micro-structural analysis of the specimens was carried out using an optical microscope. It was found that the workability, compressive strength, flexural strength, dynamic and static modulus of elasticity decreased with the increasing amount of PET waste in concrete. Water permeability of concrete was found to increase with increasing amount of PET waste. In both the cases, i.e., when fine and coarse aggregates were replaced with PET waste, an improvement in the abrasion resistance of concrete was found.Tue, 24 Apr 2018 19:30:00 +0100Analytic Solution of a System of Linear Distributed Order Differential Equations in the ...
http://scientiairanica.sharif.edu/article_20335_0.html
In this paper, solution of a system of linear differential equations of distributed order in the Riemann-Liouville sense is analytically obtained. The distributed order relaxation equation is a special case of the system investigated in this paper. The solution of the mentioned system is introduced on the basis of a function which can be considered as the distributed order generalization of the matrix Mittag-Leffler functions. It is shown that this generalized function in two special cases of the weight function can be expressed in terms of the multivariate Mittag-Leffler functions and the Wright functions.Tue, 24 Apr 2018 19:30:00 +0100Effects of viscous dissipation and convective heating on convection flow of a second grade ...
http://scientiairanica.sharif.edu/article_20414_0.html
The effects of viscous dissipation and convective boundary condition on the two-dimensional convective flow of a second grade liquid over a stretchable surface with suction/injection and heat generation are investigated. The governing partial differential equations are reduced into a dimensionless coupled system of nonlinear ordinary differential equations by appropriate similarity transformation. Then, they are solved analyticallyby homotopy analysis method (HAM) and by numerically with fourth order Runge-Kutta method with shooting technique. The HAM and numerical results of the local skin friction and local Nusselt number are compared for various emerging parameters. It is found that the momentum boundary layer thickness grows with rising the values of the viscoelastic parameter.Mon, 30 Apr 2018 19:30:00 +0100Experimental Investigation of Magnetic Abrasive Polishing of Paramagnetic Workpieces
http://scientiairanica.sharif.edu/article_20415_0.html
In the current paper application of magnetic abrasive polishing process, on paramagnetic workpieces is investigated. A magnetic disc which comprises of six magnetic coils and is electrified with three phase AC current is used to perform the experiments. In the experimental setup various parameters including; rotational speed of abrasive pins, quantity of abrasive pins, working gap, abrasive pins' dimensions and process's time can be changed. Changing this parameters surface quality is investigated. Two kinds of workpieces with different mechanical properties are examined. It is observed that both increasing the rotational speed and using smaller pins improve final surface quality but the rotational speed has a sharper effect. There are optimum abrasive pins quantity and working gap in which the best surface quality is obtained. The results are similar for the both selected materials.Mon, 30 Apr 2018 19:30:00 +0100Optimized design of adaptable vibrations suppressors in semi-active control of circular plate ...
http://scientiairanica.sharif.edu/article_20417_0.html
Due to flexibility of thin plates, high amplitude vibrations are observed when they are subjected to severe dynamic loads. Due to the extensive application of circular plates in industry, attenuating the undesired vibrations is of foremost importance. In this paper, adaptable vibration suppressors (AVSs) as a semi-active control approach, are utilized to suppress the vibrations in a free circular plate; under the concentrative harmonic excitation. Using mode summation method, mathematical model of the hybrid system, including the plate and an arbitrary number of vibration suppressors is analyzed. By developing a complex multiple-loops algorithm, optimum values for the AVSs’ parameters (stiffness and position) are achieved such that the plate deflection is comprehensively minimized. According to the results, AVSs act efficiently in suppressing the vibrations in resonance/non-resonance conditions. It is also observed that optimum AVSs reduce the plate deflection over a broad spectrum of excitation frequencies. Finally, since the algorithm is developed in a general user friendly style, AVSs’ design can be extended to other shapes of plates with various boundary conditions and excitations.Mon, 30 Apr 2018 19:30:00 +0100Mechanical properties of soft tailings from different depths of a Swedish tailings dam: Results ...
http://scientiairanica.sharif.edu/article_20418_0.html
In an upstream tailings dam, loose layers might occur at different depths due to melting of frozen layers deposited during freezing temperature in Sweden. Reduced shear strength of such layers in a tailings dam might cause stability problems. Due to slow consolidation process, it is unknown, whether self-weight of a high tailings dam could have influence on strength and stiffness of soft tailings located at different depths. For numerical modelling, appropriate strength and stiffness properties of soft tailings are needed. For this purpose, loose layers in an upstream tailings dam were identified based on results of cone penetration tests. Consolidated Drained (CD) triaxial tests were conducted on undisturbed soft tailings collected from different depths of the dam. The results indicated that depth did not have considerable influence on strength and stiffness of tailings. Hardening Soil Model (HSM), at high confining pressures and axial strains underestimated stiffness of soft tailings under CD triaxial state. This study shows that: (i) proper care is needed in evaluating strength and stiffness parameters for soft tailings, and (ii) use of the HSM is likely to predict more deformations which could give an early warning before an actual failure of a tailings dam.Sat, 05 May 2018 19:30:00 +0100THE USE OF NEURAL NETWORKS FOR THE PREDICTION OF THE FACTOR OF SAFETY OF THE SOIL AGAINST ...
http://scientiairanica.sharif.edu/article_20423_0.html
In this study, the performance of the artificial neural network (ANN) and multiple regression (MR) models to predict the factor of safety, Fs, values of soil against liquefaction was investigated and compared. To achieve this, two earthquake parameters, namely, earthquake magnitude (Mw) and horizontal peak ground acceleration (amax ), and six soil properties, namely, standard penetration test number (SPT-N), saturated unit weight (γsat), natural unit weight (γn), fines content (FC), the depth of ground water level from the ground surface (GWL), and the depth of the soil from ground surface (d) varied in the liquefaction analysis and then the Fs value was calculated for each case by using the Excell program developed and used in the development of the ANN and MR models. The results obtained from the simplified method were compared with those obtained from both the ANN and MR models.It was found that the predicted values from the ANN model matched the calculated values much better than those obtained from the MR model. Moreover, the performance indices such asthedetermination coefficient, variance account for, mean absolute error, root mean square error, and the scaled percent error were computed to evaluate the prediction capacity of the models developed. The study demonstrates that the ANN model is able to predict the Fs value of the soil against liquefaction, quite efficiently, and is superior to the MR model.Sat, 05 May 2018 19:30:00 +0100A queuing theory- based approach for designing cellular manufacturing systems
http://scientiairanica.sharif.edu/article_20425_0.html
This paper presents a new cell formation and cell layout problem considering multiple process routings and subcontracting using the principles of queuing theory. It is assumed that each machine operates as an M/M/1 queuing system and a queuing network is used to obtain in-process inventories and machine utilization. The problem is formulated as a mixed-integer nonlinear program with the objective of minimizing the total costs, including the production, subcontracting, material handling, machine idleness, and holding costs. Due to the computational complexity of the problem, a heuristic method is suggested to effectively solve the problem. A numerical example is given to clarify the proposed approach, and finally, further instances are solved to verify the performance of the solution method and to accomplish comparisons. The computational results show that the proposed heuristic is both effective and efficient.Sat, 05 May 2018 19:30:00 +0100A vacuum-refilled tensiometer for deep monitoring of in-situ pore water pressure
http://scientiairanica.sharif.edu/article_20428_0.html
Real-time measurement of soil water pressure has been recognized as an essential part of investigating water flow in unsaturated soils. Tensiometry, amongst different measuring techniques, is a common method for direct evaluation of water pressure. However, the lower limit of measurable water pressure by a conventional tensiometer becomes even more limited by increasing its length in the vertical installation. This paper describes development of a vacuum-refilled tensiometer (VRT) for monitoring soil water pressure independent of installation depth. This is achieved by fixing the distance between pressure sensor and ceramic cup together with incorporating an ancillary vacuum-refilling assembly into its design. The assembly allows for more efficient replacement of diffused air into the ceramic cup and reservoir with water. The new tensiometer is designed to withstand both negative and positive water pressure of up to almost one bar. In addition, the response time of the tensiometer to a change in negative water pressure for its working range (≥ -80 kPa) is very quick, in the order of seconds and one minute at most. The long-term performance of the new tensiometer is evaluated through a five-month monitoring program in the laboratory, simulating cyclic wetting and drying in the field.Sat, 05 May 2018 19:30:00 +0100SCF distribution in FRP-strengthened tubular T-joints under brace axial loading
http://scientiairanica.sharif.edu/article_20430_0.html
The present article is dedicated to study of the effects of different parameters of fiber reinforced polymers (FRP), as strengthening material, on a tubular T-joint subjected to brace axial loading using finite element analyses. The effectiveness of FRP materials on enhancing the fatigue life of tubular T-joints was investigated through computing the ratio of the stress concentration factors (SCFs). FRP parameters which is considered include fiber orientation, FRP thickness, effective wrapping length and FRP material properties. The FRP materials were modeled and applied onto a basic numerical FE model which was validated in the past against well-known experimental results on weld-toe SCFs. Promising results were derived from the analyses showing that the FRP strengthening method can effectively decrease the SCF values for tubular T-joints.Sat, 05 May 2018 19:30:00 +0100Dynamic finite element analysis of shot peening process of 2618-T61 aluminium alloy
http://scientiairanica.sharif.edu/article_20431_0.html
Shot peening is one of the surface treatment processes usually used for the improvement of fatigue strength of metallic parts by inducing residual stress field in them. The evaluation of shot peening parameters experimentally is not only very complex but costly as well. An attractive alternative is the explicit dynamics finite element (FE) analysis having the capability of accurately envisaging the shot peening process parameters using a suitable material’s constitutive model and numerical technique. In this study, ANSYS/LS-DYNA software was used to simulate the impact of steel shots of various sizes on 2618-T61 aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The effect of shot velocity and size on the induced compressive residual stress and plastic deformation were investigated. The results demonstrated that increasing the shot velocity and size yielded in an increase in plastic deformation of the aluminium target. However, as observed, the effect of shot velocity and size was small in magnitude on the target's subsurface compressive residual stress.Sat, 05 May 2018 19:30:00 +0100Modeling and optimization of friction stir welding parameters in joining 5086 H32 aluminium alloy.
http://scientiairanica.sharif.edu/article_20432_0.html
The present manuscript focuses on developing a mathematical model to predict the intergranular corrosion rate of friction stir welded AA5086 H32 aluminium alloy joints. Six factors-Five levels central composite design matrix, having 52 experiments, is used for design of experiments. The developed model is used to examine the impact of studied process parameters i.e. rotational speed, welding speed, tool shoulder diameter, tool hardness, tilt angle , and pin profile on intergranular corrosion rate of the welded joints. Response surface methodology is used to optimize the process parameters for minimizing the susceptibility to intergranular corrosion attack. The optimum combination of studied parameters, to have minimum corrosion rate i.e. 3.2 mg/cm2, is obtained as 1296 rpm rotational speed, 79.4 mm/min welding speed, 14.9 mm tool shoulder diameter, 47.4 HRC tool hardness, 2.380 tilt angle, and square pin profile.Sat, 05 May 2018 19:30:00 +0100Structural Control of RC Buildings Subjected to Near-Fault Ground Motions in terms of Tuned ...
http://scientiairanica.sharif.edu/article_20433_0.html
To design a proper structure against earthquake in modern systems, control systems are of special importance. Added passive tuned mass damper is one of such systems which will be discussed in this paper. In this regard, the effect of adding this damper to a 10-floor concrete structure under six near-fault earthquakes is investigated. To do this, a code has been written in MATLAB which receives ground motion record of the occurring earthquake as well as the structure specifications such as matrix of mass, stiffness and damping as an input. As output, it presents time-history of responses for top floor, a diagram for the floor displacement and drift of the structure at the time that the top floor has reached the maximum displacement. Also, these diagrams are compared both when the added damper is present and absent. It is observed that the added passive control of TMD is highly effective in the reduction of structure response against earthquake which in turn depends on the properties of the earthquake and therefore should be chosen based on the site seismic conditions.Sat, 05 May 2018 19:30:00 +0100On the Equivalency of Reliability and Security Metrics for Wireline Networks
http://scientiairanica.sharif.edu/article_20434_0.html
In this paper, we consider a secure network coding problem in which some secret keys are shared among legitimate nodes, and there exists an eavesdropper which is able to hear a subset of links. We show the equivalency of secure network coding under weak and strong secrecy conditions. For linear network coding, we show a stronger result: equivalency of "perfect secrecy and zero-error constraints" to "weak secrecy and $epsilon$-error constraints". This is a secure version of the result obtained by Langberg and Effros, on the equivalence of zero-error and $epsilon$-error regions in the network coding problem with co-located sources. Jalali and Ho exploit extractor functions to prove the weak and strong rate region equivalency for this network; however, to prove this equivalency, we develop some tools in random binning and prove the equivalency in a slightly more general setting.Sat, 05 May 2018 19:30:00 +0100Optimal Lot Size in a Manufacturing System with Imperfect Raw Materials and Defective Finished ...
http://scientiairanica.sharif.edu/article_20436_0.html
In real-world manufacturing systems, encountering with imperfect raw materials and generation of defective finished products are inevitable. In order to cope with these practical problems, this paper studies a manufacturer which orders raw materials from external source (supplier), and then produces a finished product. The raw materials contain imperfect quality items and, in addition, the production process is defective. The imperfect raw materials are sold after screening process, while the defective finished products go under a further rework process. It is also assumed that defective rate of machine is a random variable, resulting three possible cases regarding occurrence of backordering shortage. The aim is to determine economic order/production lot sizes for each case in such a way that the total cost of system is minimized. The optimal closed form solution is derived for each case separately. Moreover the applicability of the proposed manufacturing model is illustrated via a numerical example.Sat, 05 May 2018 19:30:00 +0100Water Flow Stabilization Using Submerged Weir for Draft Tube Reaction Hydraulic Turbine
http://scientiairanica.sharif.edu/article_20437_0.html
In turbine practice engineering, draft tube downstream running under extreme water flow pressure and velocity. This is causing a vibrations and pressure variation during different operation frequencies. The practical challenge of obtaining a stabilized water flow is ongoing domain of research. In this paper, a proposition of initiating submerged weir in the downstream of draft tube reaction turbine is inspected. The main goal of this research is to reduce the water flow pressure variation, velocity and shear distribution in accordance to the upstream water level influence. Two types of turbines including vertical Kaplan and Francis turbine units are examined. ANSYS CFX software tool is used to build three-dimension (3D) numerical models for the Kaplan and Francis turbines with building a submerged weir at the outlet of the draft tubes at three deferent height suggestions. The influence of the proposed submerged weir is studied the flow through these turbines by considering the dimensions of their components including the penstock with inlets, spiral casing, shafts and blades, and the draft tube with outlets. The findings of this research were tremendous proposition to solve the problem of negative pressure pulsation in draft tube of Kaplan and Francis turbines types.Sat, 05 May 2018 19:30:00 +0100The Algebraic Structures of Complex Intuitionistic Fuzzy Soft Sets Associated with Groups and ...
http://scientiairanica.sharif.edu/article_20438_0.html
In recent years, the theory of complex fuzzy sets has captured the attention of many researchers, and research in this area has intensified in the past five years. However, almost all of the researchers in this area have focused on the development of various complex fuzzy based models as well as constructing decision making processes using current decision making approaches and tools. In this spirit, this paper focuses on developing the algebraic structures pertaining to groups and subgroups for the complex intuitionistic fuzzy soft set model. This paper was constructed based on the complex intuitionistic fuzzy soft set model which is characterized by a membership and a non-membership structure for both the amplitude and phase terms of the elements. This model was chosen due to its dual-membership structure that is better able to handle the uncertainties and partial ignorance that exists in most complex data, whilst retaining all the characteristics and advantages of complex fuzzy sets. Besides examining the properties and structural characteristics of the algebraic structures, the relationship between the algebraic structures introduced here and the corresponding algebraic structures in fuzzy group theory and classical group theory were also discussed and verified.Sat, 05 May 2018 19:30:00 +0100A regression-based approach to predict crest settlement of embankment dams under earthquake shaking
http://scientiairanica.sharif.edu/article_20440_0.html
Settlement and deformation of the embankment dams are among the major damages caused by earthquakes, eventually leading to dam instability. Therefore, accurate assessment of the seismic settlement of embankment dams is of particular concern. This study aims to evaluate the settlement of embankment dams subjected to earthquake loads using regression-based methods. A wide-ranging real data on crest settlement of embankment dams caused by earthquakes was collected and analyzed. Yield acceleration of dam, maximum horizontal earthquake acceleration, fundamental period of dam body, predominant period of earthquake, and earthquake magnitude were considered as the most influential parameters affecting the seismic crest settlement of embankment dams. Using support vector regression method as well as multiple linear regression method, two models were developed to estimate earthquake induced crest settlement of embankment dams. Subsequently, sensitivity analysis was conducted in order to assess the behavior of the proposed models under different conditions. Finally, the accuracy of the proposed models was compared with the existing relationship for estimation of earthquake induced crest settlement of embankment dams. Although both MLR- and SVR-based models have an acceptable accuracy in estimation of the crest settlement of embankment dams under earthquake loading, the SVR-based model has a higher accuracy.Sat, 05 May 2018 19:30:00 +0100Recognizing Involuntary Actions from 3D Skeleton Data Using Body States
http://scientiairanica.sharif.edu/article_20446_0.html
Human action recognition has been one of the most active fields of research in computer vision over the last years. Two dimensional action recognition methods are facing serious challenges such as occlusion and missing the third dimension of data. Development of depth sensors has made it feasible to track positions of human body joints over time. This paper proposes a novel method for action recognition which usestemporal 3D skeletal Kinect data. This method introduces the definition of body states and then every action is modeled as a sequence of these states. The learning stage uses Fisher Linear Discriminant Analysis (LDA) to construct discriminant feature space for discriminating the body states. Moreover, this paper suggests the use of the Mahalonobis distance as an appropriate distance metric for the classification of the states of involuntary actions. Hidden Markov Model (HMM) is then used to model the temporal transition between the body states in each action. According to the results, this method significantly outperforms other popular methods, with recognition (recall) rate of 88.64% for eight different actions and up to 96.18% for classifying the class of all fall actions versus normal actions.Sat, 05 May 2018 19:30:00 +0100Bonferroni harmonic mean operators based on 2-dimension uncertain linguistic information and ...
http://scientiairanica.sharif.edu/article_20447_0.html
The Bonferroni mean (BM) has the advantages that it can capture the interrelationship among the input arguments, and the Harmonic mean is a conservative average lying between the max and min operators. The 2-dimension uncertain linguistic variables add a subjective evaluation on the reliability of the evaluation results given by decision makers, so they can better express fuzzy information. In this paper, in order to combine the advantages of them, we first propose the 2-dimensional uncertain linguistic weighted Bonferroni mean (2DULWBM) operator. However, it cannot consider the case when the given arguments are too high or too low. So we further proposed the 2-dimensional uncertain linguistic improved weighted Bonferroni harmonic mean (2DULIWBHM) operator, which combine the 2DULWBM with Harmonic Mean. Furthermore, we study some desirable properties and some special cases of them. Further, we develop a new method to deal with some multi-attribute group decision making (MAGDM) problems under 2-dimension uncertain linguistic environment based on the proposed operators. Finally, an illustrative example is given to testify the validity of the developed method by comparing with the other existing methods.Sat, 05 May 2018 19:30:00 +0100Study of the correlation between oil price and exchange rate under the new state of the economy
http://scientiairanica.sharif.edu/article_20448_0.html
Aiming at the problem of small sample modelling of oil price and exchange rate with time-delayed causality, a grey multivariate time lag model and its solution are proposed against the new economic background of economic development, structural optimization and power conversion. Considering the difficulty of solving q-order differential equations analytically, we obtain a numerical solution. On the basis of this solution, the validity of the model is proved. The numerical results show that the model can describe and predict the operating rules of oil price and exchange rate economic systems with time delay, and it is concluded that the development of oil price and exchange rate is not coordinated under the new state of the economy. The relationship of oil prices and the exchange rate has changed in this state, oil prices have a positive effect on the rise of the exchange rate.Sat, 05 May 2018 19:30:00 +0100Adaptive dynamic surface control of flexible-joint robot with parametric uncertainties
http://scientiairanica.sharif.edu/article_20492_0.html
A new kind of adaptive dynamic surface control (DSC) method is proposed to overcome parametric uncertainties of flexible-joint (FJ) robots. These uncertainties of FJ robots are transformed into linear expressions of inertial parameters which are estimated based on the DSC, and the high-order derivatives in DSC are solved by using first-order filter. The adaptation laws of inertial parameters are designed directly to improve the tracking performance according to the Lyapunov stability analysis. Simulation results for a two-link FJ robot show the better tracking accuracy against model parametric uncertainties. The method used does not need aid of Neural Network (NN), and is simpler and calculation faster than the other adaptive methodsSun, 13 May 2018 19:30:00 +0100A Tabu Search Algorithm for Multi-Period Bank Branch Location Problem: A Case Study in a ...
http://scientiairanica.sharif.edu/article_20493_0.html
Banks need to open new branches in new sites as a result of increase in the population, individual earnings and the growth in national economy. In this respect, opening new branches or reorganizing the locations of current branches is an important decision problem for banks to accomplish their strategic objectives. This paper presents a decision support method for multi-period bank branch location problems. Our aim is to find bank branch location based on transaction volume, distance between branches, and cost of opening and closing branches. The proposed method not only develops an Integer Program and a Tabu Search algorithm to find the exact places of branches but also presents a structuring method to identify the related criteria and their importance. We demonstrate the effectiveness of the method on random data. In the final stage, the method is applied in a Turkish bank’s branch location problem considering the current and possible places of the branches, availability of the data, and the bank’s strategies for a four-year strategic planning.Sun, 13 May 2018 19:30:00 +0100Seismic Behavior of Chevron Concentrically Braced Frames with Weak Beam
http://scientiairanica.sharif.edu/article_20494_0.html
Concentrically braced frames provide ductility and imparted seismic energy dissipation through yielding of tension braces and buckling of compression braces. In braced frames with chevron configuration, difference of actions in tension and buckled brace results in considerable unbalanced force at brace-beam intersection, which is addressed in modern seismic design provisions. In this paper, effect of flexural capacity of beam to carry this unbalanced force and consequently seismic behavior of braced frame is investigated by finite element analysis. Two-story and four-story chevron braced frames were modeled in ABAQUS software and studied by means of nonlinear cyclic pushover and nonlinear response history analysis methods. Results showed that inadequate flexural strength of the beams reduce lateral stiffness and strength of braced frame significantly as lateral drift increases; therefore, concentration of lateral deformation in one story may cause formation of soft and weak story. Furthermore, seismic behavior of chevron braced frame and two-story X braced frames were compared.Sun, 13 May 2018 19:30:00 +0100Size Effect Investigation on Lateral Vibrations of a Micro Drill Subjected to an Axial Load ...
http://scientiairanica.sharif.edu/article_20496_0.html
In this paper, the modified couple stress theory is used to capture size effect on dynamic behavior in a micro drill subjected to an axial load and a concentrated mass which is attached at its free end. Governing equations of lateral vibrations of the system and also associated boundary conditions are derived by obtaining the total kinetic and potential energies of the system and then using Hamilton’s principle. The Assumed Modes method has been applied to transform the governing partial differential equations into a set of infinite ordinary differential equations. Considering two terms of the equations, first two natural frequencies and also instability rotational speeds of the micro drill system are determined semi-analytically. Finally, numerical results of natural frequencies and also the threshold of instability speeds of the system are presented with respect to different values of the system parameters such as rotational speed, axial load, rotor length, concentrated mass, and also material length scale. The results show that the material length scale parameter is extremely effective on natural frequencies and also the threshold of instability speeds of the micro drill.Sun, 13 May 2018 19:30:00 +0100Robust parameter design of supply chain inventory policy considering the uncertainty of demand ...
http://scientiairanica.sharif.edu/article_20499_0.html
The uncertainty of demand and lead time in inventory management has posed challenges for the supply chain management. The purpose of this paper is to optimize the total profit and customer service level of supply chain by robust parameter design of inventory policies. This paper proposes to use system dynamics simulation, Taguchi method and Response Surface Methodology (RSM) to model a multi-echelon supply chain. Based on the sequential experiment principle, Taguchi method combining location and dispersion modeling method is adopted to locate the optimum area quickly, which is very efficient to optimize the responses in discrete levels of parameters. Then, fractional factorial design and full factorial design are used to recognize significant factors. Finally, RSM is used to find the optimal combinations of factors for profit maximization and customer service level maximization in continuous levels of parameters. Furthermore, a discussion of multi-response optimization is addressed with different weight of each response. Confirmation experiment results have shown the effectiveness of the proposed method.Sun, 13 May 2018 19:30:00 +0100Effect of HCl on the structure and catalytic activity of Pt/Al2O3 nanocatalyst prepared in ...
http://scientiairanica.sharif.edu/article_20500_0.html
Now a day preparation of special and effective nanocatalysts is a hot research topic. Obviously the size and structure of the active site of a catalyst plays the key role in catalytic activity. In this novel research the Pt nanocatalyst supported on γ-Al2O3 was prepared in two different microemulsion systems to clarify the effect of microemulsion essence on catalyst character and activity. Two types of microemulsion systems were constructed from Triton X-100/2-butanol as surfactant and co-surfactant, n-heptane as organic phase and H2O + H2PtCl6 (or HCl(aq) + H2PtCl6) as aqueous phase to investigate the effect of HCl on the shape and structure of the prepared nanocatalysts. Shape, size and size distribution of the Pt nanoparticles on the alumina were monitored by cyclic voltammetry and SEM analysis. Activity of the nanocatalysts was determined by reduction of p-nitrophenol as a reaction model.Sun, 13 May 2018 19:30:00 +0100Determining project characteristics and critical path by a new approach based on modified NWRT ...
http://scientiairanica.sharif.edu/article_20501_0.html
In this paper with respect to the importance of risks in real-world projects and ability of interval type-2 fuzzy sets (IT2FSs) to tackle the uncertainty, a new approach is introduced to consider risks and the correlation among risk factors by subjective judgments of experts on the probability and impact under IT2FSs. Furthermore, a new impact function for considering the correlation among the risk factors are extended under an IT2F environment. Moreover, a new subtraction operator is introduced for the critical path analysis. The node-weighted rooted tree (NWRT) method is modified based on the proposed new operator to avoid producing negative number for characteristics of each activity. Also, in order to cope with the uncertainty of the projects, NWRT method is developed under the IT2FSs. Eventually, to illustrate the validity and capability of the proposed method, two examples from the literature are solved and compared.Sun, 13 May 2018 19:30:00 +0100The experimental assessment of the effect of polypropylene fibers on improvement of Nano-silica ...
http://scientiairanica.sharif.edu/article_20502_0.html
In this study the influence of water-cement ratio on the mechanical properties (compressive, abrasion, tensile, flexural strength and permeability) of Nano-silica concrete reinforced with polypropylene fibers is evaluated. The specimens contain 4% of Nano-silica, 0.30, 0.35, 0.40, 0.45 and 0.50 of water-cement ratios and 0, 0.10, 0.15, 0.25 and 0.35 percent by volume of polypropylene fibers. Other design features remained fixed in all concrete samples. The results of the experiments showed that with decreasing the ratio of water to cement from 0.50 to 0.30, all the mechanical properties of the concrete were improved. In addition, the test results showed a significant increase in mechanical properties improvement of concrete by using polypropylene fibers. Tensile strength, flexural strength and abrasion resistance of concrete increased up to 22%, 40%, and 27% respectively for 28 days age specimens. Also, considerable reduction of hydraulic conductivity coefficient to 51% indicates high durability of these types of concrete. Compressive strength had increment of 22%, 15% and 14% for 7, 28 and 90 days age specimens respectively.Sun, 13 May 2018 19:30:00 +0100Sagittal Range of Motion of the Thoracic Spine Using Standing Digital Radiography; A throughout ...
http://scientiairanica.sharif.edu/article_20503_0.html
Previous studies have measured thoracic range of motion (RoM) using either skin-mounted devices or supine CT-imaging and have reported quite different RoMs. Given the inherent shortcomings of measurements of vertebrae movements from the overlying skin, the present study aims to measure normal RoM of the thoracic spine in the sagittal plane using the upright digital radiography. Lateral radiographs of the thoracic spine were acquired from eight asymptomatic male subjects in upright standing and full forward flexion using a mobile U-arm digital radiographic system. Total (T1-T12), upper (T1-T6), and lower (T6-T12) thoracic RoMs were measured. A throughout comparison with available skin-based measurements in the literature was carried out. Mean of total (T1-T12) thoracic RoM was 22.5° (SD 4.1°), most of which was generated by the lower (T6-T12) as compared to upper (T1-T6) thoracic spine (15.5° versus 7.1°, p<0.001). These RoMs were within the lower range of data previously reported by other skin-based approaches. While skin-based measurements suffer from the inter sensor-skin-vertebra movements and supine imaging techniques do not allow maximal trunk flexion, standing radiography remains as the gold-standard technique. Evaluation of thoracic spine RoM has implications in both patient discrimination for diagnosis and in biomechanical models for estimation of spinal loadsMon, 14 May 2018 19:30:00 +0100Lattice Boltzmann solution of advection-dominated mass transport problem: a comparison
http://scientiairanica.sharif.edu/article_20514_0.html
This article addresses the abilities and limitations of the Lattice Boltzmann (LB) method in solving advection-dominated mass transport problems. Several schemes of the LB method, including D2Q4, D2Q5, and D2Q9, were assessed in the simulation of two-dimensional advection-dispersion equations. The concept of Single Relaxation Time (SRT) and Multiple Relaxation Time (MRT) in addition to linear and quadratic Equilibrium Distribution Functions (EDF) were taken into account. The results of LB models were compared to the well-known Finite Difference (FD) solutions, including Explicit Finite Difference (EFD) and Crank-Nicolson (CN) methods. All LB models are more accurate than the aforementioned FD schemes. The results also indicate the high potency of D2Q5 SRT and D2Q9 SRT in describing advection-controlled mass transfer problems. The numerical artificial oscillations are observed when the Grid Peclet Number (GPN) is greater than 10, 25, 20, 25, and 10 regarding D2Q4 SRT, D2Q5 SRT, D2Q5 MRT, D2Q9 SRT and D2Q9 MRT, respectively, while the corresponding GPN values obtained for the EFD and CN methods were 2 and 5, respectively. Finally, a coupled system of groundwater and solute transport equations were solved satisfactorily using several LB models. Considering computational time, all LB models are much faster than CN method.Sun, 20 May 2018 19:30:00 +0100Shear Strength Prediction of RC Beams Using Adaptive Neuro-Fuzzy Inference System
http://scientiairanica.sharif.edu/article_20515_0.html
In complex engineering problems, there are some inexact conceptions, or a lot of parameters which must be considered. Soft computing is an approach that successfully applied to solve such problems. Determination of fuzzy rules for many problems has not been quite possible by an expert human. In this case, a neuro-fuzzy system which is the combination of neural network (for its ability to learn by datasets) and fuzzy system (for solving the drawback of the neural network) can be enhancing the performance of the system with several parameters or complex conditions. This paper shows the capability of a neuro-fuzzy system namely ANFIS to predicting the shear strength of reinforced concrete beams with steel stirrups. For this propose, the collection of laboratory results which was published in literatures used to train and finally test the proposed system. For this purpose, the sub-clustering approach (SC) applied for generating ANFIS. The results indicated that the considered neuro-fuzzy system was able to predict the shear strength of the RC beams which have been reinforced with steel stirrups.Sun, 20 May 2018 19:30:00 +0100Mitigating the uneven settlement of nearby strip footings on loose saturated sand using ...
http://scientiairanica.sharif.edu/article_20517_0.html
Abstract: Adjacency and interfering of footings are a matter of importance in geotechnical engineering. The researchers have focused on the adjacency of the footings by several approaches, but the mechanism of nearby footings under unequal and non-simultaneous surcharges have not been explored to date. In this study, two series tests were conducted using small scale 1g models to investigate the behavior of the two adjacent footings under reinforced and unreinforced soil conditions. The footings were installed with different spacing and rested on loose saturate sand. The ultimate bearing capacity, settlement, and tilting of footings were evaluated when the footings are rested on unreinforced sand as well as the sand bed reinforced by concrete pedestals. The results indicate that reinforcing the new footing by three concrete pedestals in the spacing to footing's width ratio (S/B) of 0 (i.e., two coherent footings) results in 67% increase of the bearing capacity of the new footing compared to that of the unreinforced condition. Also, the settlement and tilting of the old footing adjacent to the new footing decrease respectively up to 250% and 600% in comparison to those of the unreinforced condition.Fri, 25 May 2018 19:30:00 +0100Multi Stage Investment Planning and Customer Selection in A Two Echelon Multi-Period Supply Chain
http://scientiairanica.sharif.edu/article_20524_0.html
In the supply chain of Fast-moving consumer goods, logistics costs are a main part of the expenses. In low levels of these chains, we usually face with a Vehicle Routing Problem. In practice, due to the high cost of service in many cases, some customers are not chosen for serving. Restrictions associated with the investment in many cases makes impossible serve to some potential clients. In this problem, design a supply chain network, including a location-allocation problem in the warehouse, Multiple Depot Vehicle Routing Problem at the level of distribution and customer selection at the retail level in several periods of time is considered. In this issue, in addition to certain methods that can be used in small sizes, Meta-heuristic algorithms to solve large-scale model have been used. With the aim of improving performance, if not improve in a few diversifications, algorithms are temporarily enhanced. In GA this change leads to improve 1.2 percent and 1.6 percent about the mean of solutions and the best solution and in SA algorithm, this change is led to improving by 2.1% and 2.4% in average solutions and the best solutions. Finally, this approach about a real problem in Sepahan Oil Company is employed.Sun, 27 May 2018 19:30:00 +0100A class Hotelling model for sequential auctions of close substitutes
http://scientiairanica.sharif.edu/article_20546_0.html
Against the background of supply chains, this paper constructs a class Hotelling model to describe and explore sequential auctions of close substitutes with slightly more general associated valuations. In this generalized model, both close substitutes and bidders are hypothetically distributed in the interval [0, 1], types of bidders are continuous, and each bidder’s valuations for close substitutes are not independent. And with the aid of this model, equilibriums are explored and efficiencies of the auctions are analyzed under second-price sealed-bid auction formats. Further considering two typical information policies, we investigate some concrete bids and revenues of the efficient sequential auctions while bidders’ valuations are linear functions of distances between them and close substitutes. Results show that efficiencies of the sequential auctions are conditional, and influences of information policies on revenues of the auctions are related to both numbers of bidders and locations of items.Sat, 02 Jun 2018 19:30:00 +0100Full vs. partial coordination in serial N-echelon supply chains and a new profit sharing contract
http://scientiairanica.sharif.edu/article_20547_0.html
Despite the significance of full coordination of N-echelon supply chains in real-world decision-making situations, the relevant literature has rarely addressed this issue. Furthermore, there is a scarcity of mathematical models in the supply chain management literature for partially coordinated cases. To address these shortcomings, this study concerns both the full and partial coordination in serial N-echelon supply chains facing stochastic demand. In particular, three general cases including decentralized (no coordination), sub-supply chain coordination (partial coordination) and centralized (full coordination) cases are examined to support decisions on ordering and pricing. In addition, this study adds to the literature by investigating how to coordinate a serial N-echelon supply chain through a new spanning profit sharing contract, which can coordinate the entire supply chain through only one contract. Furthermore, we analytically prove the occurrence of externality benefit in partially coordinated cases, which is a paradoxical phenomenon suggesting that small coalitions are unstable. Two numerical examples extracted from the literature are given to verify the effectiveness and validity of the proposed contracts and models. The results show that the proposed contracts can be applied in a rather simple and convenient way and is reliable enough for use in real-world applications.Sat, 02 Jun 2018 19:30:00 +0100An Analytical Approach to Estimate Optimum River Channel Dimensions
http://scientiairanica.sharif.edu/article_20552_0.html
Extremal hypotheses without bank stability constraint typically over-predict and under-predict channel width in large rivers and natural streams, respectively. In general, results obtained from unconstrained extremal hypotheses are indicative of inappropriate agreement between predicted and observed dimensions of the rivers. One of the important factors in disparity of the data may be lack of appropriate relationships to assess bank vegetation of the rivers. For this reason, a modified analytical model has been developed to reduce the effect of bias by considering bank stability and vegetation. The model takes into account channel shape factor, a wide range of bed load equations in the form excess shear stress and vegetation quantification is able to predict optimal channel geometry dimensions. Finally, developed model was calibrated using the field data of the United Kingdom and Iran. In addition to indicating the effect of bank stability and vegetation on estimation of the geometric characteristics of the channel, obtained results also confirmed the efficiency of the constrained model in comparison to the unconstrained model. This study also provides support for the use of the concepts of maximum sediment transporting capacity and minimum stream power for understanding the operation of alluvial rivers.Sat, 02 Jun 2018 19:30:00 +0100Robust and sustainable full-shipload routing and scheduling problem considering variable speed: ...
http://scientiairanica.sharif.edu/article_20561_0.html
This paper presents a sustainable multi objective routing and scheduling for maritime transportation considering ship variable speeds under uncertainty. The proposed model is aimed to satisfy three individual dimensions of sustainability including economic, environmental and social aspects simultaneously while it is finding the best routes and schedule for each ship. The first objective is placed to meet economic goal by minimizing shipping cost. The second objective goes to social respect of sustainability by maximizing job creation due to number of intransitive workers in ships and ports and, the third one is minimizing CO2 emission to cover environmental target. Several test problems are applied to validate the proposed model and sensitivity analysis is used to demonstrate effects of model’s parameters on objective function value. Augmented ɛ-constraint is implemented as a solution method to solve the multi-objective mathematical model. This is the first ship routing and scheduling paper which is considered three aspect of sustainability under uncertainty and solved by augmented ɛ-constraint. To solve the model in larger size, factual input data from a real case study is considered. Computational results show a significant positive managerial effects of this paper contributions.Fri, 08 Jun 2018 19:30:00 +0100A New Heuristic Method for Improved Structuring of the Work Transformation Matrix (WTM)
http://scientiairanica.sharif.edu/article_20562_0.html
The design structure matrix (DSM) is a potent tool in the management of product design processes. Although the compactness and ability to represent design cycles are the main advantages of DSMs over existing traditional tools, the intact whole DSM is not always an understandable piece of information. To overcome this shortcoming, certain analyses have been proposed for a better understanding of the matrix in which partitioning and tearing have significant importance. There are several algorithms for these two analyses that mainly focus on a few rules of thumb. Although partitioning and tearing were originally developed for binary DSMs, they can be extended to numerical variants in which the work transformation matrix (WTM) is of the highest fame and application. In this paper, the authors have proposed an algorithm inspired by the formation of sugar crystals in saturated syrup for reordering the activities in a coupled block of activities (CBAs) based on their level of coupling. To implement this approach, a code was developed to achieve pseudo-optimum solutions. By using a discrete-time simulation, which was applied to an aerospace case study, it was demonstrated that the method produces restructured schemes of the WTM that are comparable/superior to the classical methods.Fri, 08 Jun 2018 19:30:00 +0100A bi-level bi-objective mathematical model for cellular manufacturing system applying ...
http://scientiairanica.sharif.edu/article_20563_0.html
The present study aimed to design a bi-objective bi-level mathematical model for multi-dimensional cellular manufacturing system. Minimizing the total number of voids and balancing the assigned workloads to cells are regarded as two objectives of the upper level of the model. However, the lower level attempts to maximize the workers' interest to work together in a special cell. To this aim, two nested bi-level metaheuristics including particle swarm optimization (NBL-PSO) and a population-based simulated annealing algorithm (NBL-PBSA) were implemented to solve the model. In addition, the goal programming approach was utilized in the upper level procedure of these algorithms. Further, nine numerical examples were applied to verify the suggested framework and the TOPSIS method was used to find the better algorithm. Furthermore, the best weights for upper level objectives were tuned by using a weight sensitivity analysis. Based on computational results, all three objectives were different from their ideal goals when decisions about inter and intra-cell layouts, and cell formation to balance the assigned workloads by considering voids and workers' interest were simultaneously madeby considering a wide assumption-made problem closer to the real world. Finally, NBL-PBSA could perform better than NBL-PSO, which confirmed the efficiency of the proposed framework.Fri, 08 Jun 2018 19:30:00 +0100Numerical investigation of Cover Plate in RCS connections
http://scientiairanica.sharif.edu/article_20564_0.html
Due to the growing popularity of Reinforced Concrete column with Steel beam (RCS) moment frame system in recent years, there are lots of publications about the performance of this structural system. In this paper, fifteen RCS joints with practical details are studied using a verified finite element method. Joint details of the models include Cover Plate, Additional Bearing Plate, Steel Doubler Plate, and joint stirrups. The results show that Cover Plate can be used instead of a combination of steel doubler plate and joint stirrups; it improves the joint performance by increasing the confinement of joint region and contributing to joint shear strength.Sat, 09 Jun 2018 19:30:00 +0100Voltage and reactive power control in distribution network considering optimal network ...
http://scientiairanica.sharif.edu/article_20565_0.html
In order to reduce energy losses and improve voltage stability index in distribution system, two different approaches have been proposed and employed including voltage and reactive power control (volt/var control) and distribution network reconfiguration. In the present paper, volt/var control and network reconfiguration in distribution system considering voltage security constraints is modelled as a multi-objective optimization problem. Total electrical energy losses, voltages deviations and voltage stability have been considered as objectives. Also, a new method for distribution network reconfiguration has been utilized for implementation of these two problems simultaneously. In this way, the two problems can be solved in less time. In addition, different nature of loads in each bus is considered in network load modelling. Non-dominated sorting genetic algorithm-II is used to solve this problem. Finally, the effectiveness of the proposed method is evaluated by implementation on the IEEE 33-bus system and a real 77-bus distribution system.Sat, 09 Jun 2018 19:30:00 +0100Group multiple criteria ABC inventory classification using TOPSIS approach extended by Gaussian ...
http://scientiairanica.sharif.edu/article_20585_0.html
The traditional ABC inventory classification is one of such approaches in which items are classified into three classes: A, very important; B, moderately important; and C, relatively unimportant based on annual dollar usage. However, other qualitative or quantitative criteria in real world may affect grouping items in the ABC inventory classification. Hence, multiple criteria ABC inventory classification (MCABCIC) is applied to classify items, instead of using the traditional ABC inventory classification. Hence, it can be taken into account as a multiple-criteria decision making (MCDM) problem due to using different criteria. The aim of this paper is to the extent TOPSIS approach with Gaussian interval type-2 fuzzy sets (GIT2FSs) as an alternative to the traditional triangular membership functions (MFs) for the MCABCIC in which GIT2FSs are more suitable for stating curved MFs. For this purpose, a new limit distance is presented for prioritizing GIT2FSs which is based on alpha cuts. The proposed method determines the positive and negative ideal solutions as left and right reference limits and then calculates distances between assessments and these limits. In our approach, the weights of the quantitative and qualitative criteria are attained via two linear programming, respectively. The model is illustrated using a real case.Mon, 18 Jun 2018 19:30:00 +0100Pulse extraction of pulselike ground motions based on particle swarm optimization algorithm
http://scientiairanica.sharif.edu/article_20586_0.html
Considering the devastating effects of near-fault earthquakes, seismologists and engineers have, qualitatively and quantitatively, represented the strong velocity pulse of near-fault ground motions using models including physical parameters associated with the wave propagation process. In some mathematical models, the derivation of physical parameters is required to fit time history and response spectrum of the simulated record to the actual record through trial and error process, which limits the scope of these models. In the current study, the particle swarm optimization (PSO) algorithm is replaced with the trial and error procedure. In this way, an automatic and quantitative process with the minimal judgment of the analyst is prepared to extract a wide range of pulselike records. Then, the proposed approach is applied to simulate and represent mathematically a set of 91 pulselike records from the Next Generation Attenuation (NGA) project ground motion library. The obtained results show that a velocity pulse of each pulselike record could be extracted using the proposed approach, and it can therefore be considered as a powerful tool in pulse parametric studies and the relationship between velocity pulse and structure’s response.Mon, 18 Jun 2018 19:30:00 +0100Analysis of change in the state of hydraulic drive of machines while in operation according to ...
http://scientiairanica.sharif.edu/article_20587_0.html
Technical diagnostics is a sphere of knowledge embracing theory, methods and means for defining the technical state of the objects. It is necessary for provision of security, functional reliability and efficiency of the technical object operation, as well as for reduction of the costs for its technical maintenance and reduction of the idle time losses caused by failures and premature shutdowns for maintenance. Therefore the objective of the paper is to analyze the change in the state of hydraulic drive of machines while in operation according to the diagnostic results. In order to achieve the set objective the authors used various experimental methods. The paper considers mutual influence of maintenance and technical diagnostics of hydrostatic drives of construction, track and some other mobile machines. It is shown that introduction of technical diagnostics allows transferring from the system of planned preventive repairs to the system of servicing the machines according to their actual technical state, which allows completely using the resource of a series of expensive aggregates. The authors described several main basic characteristics of change in the volume effectiveness of the hydraulic sets while in operation.Mon, 18 Jun 2018 19:30:00 +0100Effect of Several Heated Interior Bodies on Turbulent Natural Convection in Enclosures
http://scientiairanica.sharif.edu/article_20588_0.html
In this study, turbulent natural convection in a square enclosure including one or four hot and cold bodies is numerically investigated in the range of Rayleigh numbers of . The shape of the internal bodies is square or rectangular with the same surface areas and different aspect ratios. In all cases, the horizontal walls of the enclosure are adiabatic and the vertical ones are isothermal. It is desired to investigate the influence of different shapes and arrangements of internal bodies on the heat transfer rate inside the enclosure with wide-ranging applications such as ventilation of buildings, electronic cooling and industrial coldbox packages. Governing equations including Reynolds-averaged-Navier-Stokes equations have been solved numerically with finite volume method and turbulence model in a staggered grid. The boundary condition for turbulence model is based on the standard wall function approach. Strongly implicit method is employed to solve the discretized systems of algebraic equations with a remarkable rate of convergence. The effects of several parameters such as distance between the bodies, aspect ratio and Rayleigh number on heat transfer rate have been investigated. The most change in heat transfer rate at high values of Rayleigh numbers is associated with alteration in distance between square bodies. Moreover, the horizontal installation of rectangular bodies with h/w = 1/3 is accompanied by a maximum reduction of heat transfer at low Rayleigh numbers. The present results have been compared with previous experimental and numerical works regarding enclosures with or without internal bodies and reasonable agreement is observed.Mon, 18 Jun 2018 19:30:00 +0100Attitude-Based Conflict Management for Resolving Disputes over Water Quality of the Seymareh ...
http://scientiairanica.sharif.edu/article_20599_0.html
A strategic negotiation methodology for managing complex water-related conflicts is presented in order to consider the decision makers' attitudes. The developed approach systematically exploits the Graph Model for Conflict Resolution (GMCR) as an analytical and practical technique, and helps decision makers find the most beneficial outcomes for negotiating their disputes, assuming the competing needs, wants, and attitudes of decision makers. A real case study of a water-related dispute in Iran is used to demonstrate the implementation of the developed methodology and to emphasize the significance of decision makers' attitudes in identifying feasible negotiation outcomes for resolving complex disputes. In fact, the developed attitude-oriented methodology proposes an innovative engineering approach to help stakeholders address a wide range of conflicts, especially in complex water disputes in developing countries where human factors such as attitude play a significant role. The research can also help decision makers with the shortcomings of conventional decision making systems, such as original GMCR, through incorporating attitudes into conflict resolution tools in order to better clarify needs and interests, obtain equilibrium results, and generate more equitable solutionsFri, 22 Jun 2018 19:30:00 +0100Dynamic Behavior of Worn Wheels in a Track Containing Several Sharp Curves Based on Field Data ...
http://scientiairanica.sharif.edu/article_20601_0.html
Study of the wheel and rail wear phenomenon can provide the optimal use of wheel profile which results cost efficiency, dynamic stability, travel comfort, and safety to prevent the derailment especially in curves. In this paper, the experimental data is recorded in the from the field measurements worn wheels of a passenger wagon in the “Southern line” of Iran’s railway system and is combined with the dynamic simulations to study the effects of severe wheel flange wear on the dynamics of wagon. The results show that the amount of wheel wear (especially the wheel flange) directly impacts the dynamic behavior of the wagon in curves. In addition, based on the history of wear index and the peak derailment ratio, the appropriate range of the wheel flange thickness in order to repair or replace the worn wheels is suggested in the range of 25 to 27 mm.Sat, 23 Jun 2018 19:30:00 +0100The surgical case scheduling problem with fuzzy duration time: An ant system algorithm
http://scientiairanica.sharif.edu/article_20602_0.html
In this paper, we address the surgical case scheduling problem in multi operating theater environment with uncertain service times in order to minimize makespan. In surgical case scheduling, not only the hospital resources are allocated to surgical cases but also the start time of performing surgeries is determined based on sequence of cases in a short-term time horizon. We consider fuzzy numbers for duration times of all stages and hereafter the problem called fuzzy surgical case scheduling. Since the operational environment in the problem is similar to no-wait multi-resource fuzzy flexible job shop problem, we consider constraints of that for formulating and solving problem. This problem is strongly an NP-hard optimization problem, hence we employ ant system algorithm to tackle problem. The proposed approach is illustrated by detailed examples of three test cases, and numerical computational experiments. Therefore, the performance of proposed algorithm is compared with a schedule constructed by first-come-first-service rule on all test instances. Also, a real case is provided from Isfahan’s hospital to evaluate proposed algorithm. Consequently, computational experiments state that algorithm outperforms results obtained by hospital planning as well as fuzzy rule, and these indicate efficiency and capability of our algorithm for optimizing the makespan.Mon, 25 Jun 2018 19:30:00 +0100Finite element modeling and design of pH/temperature sensitive hydrogel based biphasic twisting ...
http://scientiairanica.sharif.edu/article_20603_0.html
In this article, a pH/temperature sensitive hydrogel based biphasic twisting actuator is presented and studied in various environmental conditions. The actuator consists of a neutral incompressible elastomeric phase attached to pH/temperature sensitive hydrogel phase which twists, when subjected to pH/temperature variation. The deformation of the actuator depends on the cross-section of the actuator as well as geometrical and environmental parameters. To have a guideline for the design of the biphasic twisting actuator, a finite element model of the mentioned structure is developed. A thermodynamic based constitutive model is used to describe the behavior of the hydrogel. The finite element method is used to resolve the homogeneous and inhomogeneous swelling of the pH/temperature responsive hydrogel to check the validity of the method. Finally, how various parameters affect the torsional behavior of the actuator is discussed in detail. According to the results, to get the maximum twisting angle it is recommended to use the actuator with the square cross-section. Also, the twisting angle can even increase more by decreasing the hydrogel size as well as increasing the length of the actuator.Mon, 25 Jun 2018 19:30:00 +0100Improved Ratio Estimators of Variance Based on Robust Measures
http://scientiairanica.sharif.edu/article_20604_0.html
In this study, we develop some new estimators for estimating the population variance by utilizing the information on midrange and inter decile range of an auxiliary variable. A general class of estimators is also suggested. The derivations of the bias and the mean squared error are presented. Conditions are determined to verify the efficiency of the proposed estimators over existing estimators considered in this study. An Empirical study is also provided for illustration and verification. Moreover, a robust study is also carried out to evaluate the performance of proposed estimators as compared to existing estimators in case of extreme values. From the theoretical and empirical study, it is found that the suggested estimators perform more efficiently as compared to the existing estimators considered in this study.Mon, 25 Jun 2018 19:30:00 +0100Demand Response as a Complement for Wind Energy from System Well-being Viewpoint
http://scientiairanica.sharif.edu/article_20605_0.html
The risk imposed by the stochastic nature of wind energy sources has always been a major barrier despite their proliferation in power systems. To further penetrate these sources, this paper draws upon dynamic prices, which realize demand response potentials along with decimating the risk involved. To do so, a model is first established to study the impacts of activating demand response, on the risk index in a system with a high penetration of wind resources. Then, the model is used to estimate the extra wind capacity that can be hosted by the system such that the risk remains within the acceptable range. The well-being indices are calculated via sequential Monte Carlo simulation approach and Fuzzy theory. The demand response with dynamic prices is modeled by self and cross elasticity coefficients of different load sectors. The performance and applicability of the proposed model are verified through simulations on the IEEE Reliability Test System. (IEEE-RTS).Mon, 25 Jun 2018 19:30:00 +0100Bayesian Analysis of Heterogeneous Doubly Censored Lifetime Data using the 3-Component Mixture ...
http://scientiairanica.sharif.edu/article_20606_0.html
This article is about Bayesian estimation of parameters of a heterogeneous 3-component mixture of Rayleigh distributions (3-CMRD) generating a mixture data. Being the most popular and reasonable sampling scheme in reliability and survival analyses, the doubly censored sampling scheme is considered. The Bayes estimators and their posterior risks are derived under various situations. In addition, elicitation of hyperparameters is presented. Algebraic expressions for posterior predictive distribution and Bayesian predictive intervals are derived. Assuming the informative and the non-informative priors, a comprehensive Monte Carlo simulation is conducted to examine the performance of the Bayes estimators under symmetric and asymmetric loss functions. Finally, to highlight the practical importance, the proposed 3-compnent mixture model is applied to a doubly censored lifetime data from a real life situation. It is observed that the analysis of doubly censored data in Bayesian framework, the SRIGP paired with SELF (DLF) is suitable choice for estimating mixing proportion (component) parameters.Mon, 25 Jun 2018 19:30:00 +0100Experimental Study of the Wedge Effects on the Performance of a Hard-chine Planing Craft in ...
http://scientiairanica.sharif.edu/article_20607_0.html
In this paper, effects of a wedge on the performance of planing craft in calm water are experimentally investigated. Experiments are carried out on three different cases distinguished by the wedge type. The model, built of fiberglass, is a prismatic planing hull with deadrise angle of 24 degrees. Towing tests are conducted at different Froude numbers ranging from 0.21 to 2.1. The total trim angle, resistance, rise up at the CG as well as stern and bow, keel wetted length, chine wetted length, stagnation angle, and the length of stagnation line are measured. They are used to study the effect of installing a wedge on the performance as well as the effect of height on the hydrodynamic characteristics. Based on the observations made, it is concluded that, when the wedge is applied to the hull, the risk of model exhibiting instability diminishes, while total trim angle largely decreases, keel wetted length is enlarged, wetted surface becomes thinner, CG rise up is lowered, and the resistance is reduced. Moreover, experimental measurements and theoretical 2D+T theory are combined to bring deeper insight about physics of the flow and pressure distribution when a wedge is installed on the bottom of a planing hull. Mon, 25 Jun 2018 19:30:00 +0100Implementation of a curved wall- and an absorbing open-boundary condition for the D3Q19 lattice ...
http://scientiairanica.sharif.edu/article_20608_0.html
In this work, a three-dimensional lattice Boltzmann method is developed for numerical simulation of the fluid flows around the arbitrary geometries in the wide range of Reynolds numbers. For efficient simulation of high Reynolds number flow structures in the turbulent regime, a large eddy simulation (LES) approach with the Smagorinsky subgrid turbulence model is employed. An absorbing boundary condition based on the concept of sponge layer is improved and implemented to damp the vorticity fluctuations near the open boundaries and regularize the numerical solution by significantly reducing the spurious reflections from the open boundaries. An off-lattice scheme with a polynomial interpolation is used for implementation of curved boundary conditions for the arbitrary geometries. The efficiency and accuracy of the numerical approach presented are examined by computing the low to high Reynolds number flows around the practical geometries, including the flow past a sphere in a range of Reynolds numbers from 102 to 104 and flow around the NACA0012 wing section in two different flow conditions. The present results are in good agreement with the numerical and experimental data reported in the literature. The study demonstrates the present computational technique is robust and efficient for solving flow problems with practical geometries.Mon, 25 Jun 2018 19:30:00 +0100A robust bi-level programming model to design a closed loop supply chain considering government ...
http://scientiairanica.sharif.edu/article_20609_0.html
This study aims in providing a new approach regarding design of a closed loop supply chain network through emphasizing on the impact of the environmental government policies based on a bi-level mixed integer linear programming model. Government is considered as a leader in the first level and tends to set a collection rate policy which leads to collect more used products in order to ensure a minimum distribution ratio to satisfy a minimum demands. In the second level, private sector is considered as a follower and tries to maximize its profit by designing its own closed loop supply chain network according to the government used products collection policy. A heuristic algorithm and an adaptive genetic algorithm based on enumeration method are proposed and their performances are evaluated through computational experiences. The comparison among numerical examples reveals that there is an obvious conflict between the government and CLSC goals. Moreover, it shows that this conflict should be considered and elaborated in uncertain environment by applying Min-Max regret scenario based robust optimization approach. The results show the necessity of using robust bi-level programming in closed loop supply chain network design under the governmental legislative decisions as a leader-follower configuration.Mon, 25 Jun 2018 19:30:00 +0100Dynamic TOC-based approach for planning and control of accessories in MTO environments
http://scientiairanica.sharif.edu/article_20610_0.html
In make-to-order systems, customers expect to have more freedom to choose the accessories. But demand variations and internal disorders induce some uncertainties. Hence, a different inventory system is needed for such items that dynamically manage those variations. In this paper, a dynamic approach based on the theory of constraints is proposed for inventory planning and control of accessories. First, the risk of processing time variation is balanced while keeping cycle time balancing. Second, the ribbons of buffer control charts are determined by a buffer planning model in which a multi-criteria ABC analysis is used to apply different customer service levels. To detect demand variations and monitor the buffer, trend of consumption in each monitoring window is carefully traced. Also, simulation-based procedures are recommended to update control ribbons. Comparing the performance of proposed approach to common methods using the data of an automobile company as well as several random test problems confirms that it can significantly reduce the costs and improve the efficiency of inventory system.Mon, 25 Jun 2018 19:30:00 +0100Medium-term planning of vehicle-to-grid aggregators for providing frequency regulation service
http://scientiairanica.sharif.edu/article_20612_0.html
Utilization of electric vehicles’ battery to provide frequency regulation service in electricity markets is a technically feasible and economically attractive idea. The role of aggregators as a middleman between electric vehicle owners and the frequency regulation market has been discussed in literature. However, the economic interaction between the aggregator and the vehicle owners on division of interests is still a missing point. In this paper, a new pricing model for aggregators of electric vehicles is proposed in a way, that not only maximizes its profit, but also the vehicle owners have sufficient incentives to take part in the offered Vehicle-to-Grid program. In our proposed model, the aggregator takes into account the depreciation cost of electric vehicle batteries and the cost of net energy transaction between the electric vehicles and the grid, and considers these items in settling accounts with vehicle owners. The proposed model has been implemented on PJM frequency regulation market and the results are discussed in the paper.Fri, 29 Jun 2018 19:30:00 +0100The effect of friction stir welding parameters on the microstructure, defects, and mechanical ...
http://scientiairanica.sharif.edu/article_20614_0.html
This study aims to examine how friction stir welding parameters, such as welding speed and rotational rate, affect the microstructure, defects, and mechanical properties of AA7075-T651 aluminum alloy joints. It also assesses the relation of the defects and microstructure to the mechanical properties. Microstructural investigations using optical microscopy (OM) and scanning electron microscopy (SEM) indicated remarkable grain structure variations among the different welding zones. Especially, it was found out that the interface between welding nugget zone (WNZ) and thermo-mechanically affected zone (TMAZ) is a dominant determinant of the mechanical properties of joints. The importance of the interface comes from the fact that it is the most prone region to cracks, micro-cavities and tunneling defects. WNZ and TMAZ interfaces as well as their grain structures can be influenced by the heat generated from the friction between rotating tool and workpiece material. Therefore, coarser grain structures observed at the WNZ-TMAZ interfaces of the samples welded at higher rotational rates or lower welding speeds is due to the greater heat generated in such cases. Besides, microstructural variations in the weld zone affect the hardness and mechanical properties of weld joints. Thus, samples with coarse-grained structures display lower values of yield stress and microhardness.Fri, 29 Jun 2018 19:30:00 +0100An intelligent model to predict the day-ahead deregulated market clearing price: a hybrid NN, ...
http://scientiairanica.sharif.edu/article_20615_0.html
Under restructuring of electric power industry and changing traditional vertically integrated electric utility structure to competitive, market clearing price (MCP) prediction models are essential for all generation company (GenCos) for their survival under new deregulated environment. In this paper, a hybrid model is presented to predict hourly electricity MCP. The model contains a Neural Network (NN), Particle swarm optimization (PSO) and Genetic Algorithm (GA). The NN is used as the major forecasting module to predict the electricity MCP values and PSO applied to improve the traditional neural network learning capability and optimizing the weights of the NN and GA applied to optimize NN architecture. The main contribution includes: presenting a hybrid intelligent model for MCP prediction; applying K-Means algorithm to clustering NN’s test set and seasonality pattern detection; and evaluation of its performance by improved MAE with penalty factor for positive error. It has been tested on Iranian real-world electricity market for the one month of the year 2010-2013 that result shown average weighted MAE for day ahead MCP prediction is equal to 0.12 and forecasting of MCP can be improved by more than 6.7% and 4%in MAE in compare of simple NN and combination of NN and bat algorithm.Fri, 29 Jun 2018 19:30:00 +0100New Shewhart-EWMA and Shewhart-CUSUM Control Charts for Monitoring Process Mean
http://scientiairanica.sharif.edu/article_20637_0.html
In this paper, we propose new Shewhart-EWMA (SEWMA) and Shewhart-CUSUM (SCUSUM) control charts using the varied L ranked set sampling (VLRSS) for monitoring the process mean, namely the SEWMA-VLRSS and SCUSUM-VLRSS charts. The run length characteristics of the proposed charts are computed using extensive Monte Carlo simulations. The proposed charts are compared with their existing counterparts in terms of the average and standard deviation of run lengths. It is found that, with perfect and imperfect rankings, the SEWMA-VLRSS and SCUSUM-VLRSS charts are more sensitive than their analogous charts based on simple random sampling, ranked set sampling (RSS) and median RSS schemes. A real dataset is also used to explain the implementation of the proposed control charts.Mon, 02 Jul 2018 19:30:00 +0100A Modified Variant of Grey Wolf Optimizer
http://scientiairanica.sharif.edu/article_20638_0.html
The original version of Grey Wolf Optimization (GWO) algorithm has small number of disadvantages of low solving accuracy, bad local searching ability and slow convergence rate. In order to overcome these disadvantages of Grey Wolf Optimizer, a new version of Grey Wolf Optimizer algorithm has been proposed by modifying the encircling behavior and position update equations of Grey Wolf Optimization Algorithm. The accuracy and convergence performance of modified variant is tested on several well known classical further more like sine dataset and cantilever beam design functions. For verification, the results are compared with some of the most powerful well known algorithms i.e. Particle Swarm Optimization, Grey Wolf Optimizer and Mean Grey Wolf Optimization. The experimental solutions demonstrate that the modified variant is able to provide very competitive solutions in terms of improved minimum objective function value, maximum objective function value, mean, standard deviation and convergence rate.Mon, 02 Jul 2018 19:30:00 +0100An Endochronic-based approach for simulating pore water pressure variation during liquefaction ...
http://scientiairanica.sharif.edu/article_20639_0.html
Liquefaction is one of the consequences of earthquake in soil layers comprised of saturated loose sands. Various aspects of liquefaction have been investigated using different methods of field, laboratory, and numerical studies. Numerical simulation of liquefaction constitutes a major part of these researches. Application of a proper constitutive law in the numerical analysis is crucial for modeling thecomplicated undrained behavior of saturated sands during dynamic loading. Simplicity of formulation, limited number of parameters, and good performance are the main features of a proper constitutive law. In this study, an Endochronicbased model for simulating liquefaction of sand is implemented into the finite element program, PISA. Coupled dynamic field equations of Biot’s theory with u-p formulation are used to determine pore fluid and soil skeleton responses. Generalized Newmark method is employed for integration in time. The developed code is capable of predicting the magnitude of the generated pore water pressure, coupled with advanced constitutive laws such as critical state twosurface plasticity as well as simple models such as Mohr- Coulomb. Simulating cyclic simple shear and centrifuge tests using Endochronic model showed favorable performance of this model for predicting the variation of pore water pressure in saturated soil layers subjected to earthquake excitations.Tue, 03 Jul 2018 19:30:00 +0100Effects of recycled Polyethylene terephthalate fibers on strength behavior of cemented Babolsar sand
http://scientiairanica.sharif.edu/article_20640_0.html
Construction of structures on sandy soils of northern part of Iran encounters problems due to lack of proper strength properties. In recent years, bottles of Polyethylene terephthalate (PET) such as water bottles caused an environmental threat due to their prolonged persistence. Utilization of these materials for soil improvement seems to be a sustainable approach. In this study, the effect of recycled PET on mechanical properties of Babolsar sandy soil is investigated through an experimental program using direct shear and consolidated drained (CD) triaxial compression tests. Various contents of PET were added to sand with 3%, 5% and 7% cement contents. Curing time and relative density of samples were 7 days and 70%, respectively. Results showed that addition of fiber improves strength parameters such as cohesion and internal friction angle. Furthermore, the effect of the fiber is less marked with an increase in cement content. The samples with 3% cement demonstrated better results in both direct shear and tiaxial tests. By adding 0.5% and 1% PET fibers to the samples containing 3% cement at 100 kPa pressure, the ratio of strength in direct shear tests increased 13% and 24%, respectively, and in the triaxial test, it increased 50% and 93%, respectively.Tue, 03 Jul 2018 19:30:00 +0100An improvement on feature extraction via time series modeling for structural health monitoring ...
http://scientiairanica.sharif.edu/article_20641_0.html
Feature extraction by time series modeling based on statistical pattern recognition is a powerful approach to structural health monitoring. Determination of an adequate order and identification of an appropriate model play prominent roles in extracting sensitive features to damage from time series representations. Early damage detection under statistical decision-making via high-dimensional features is another significant issue. The main objectives of this article are to improve a residual-based feature extraction method by time series modeling and propose a multivariate data visualization approach to early damage detection. A simple graphical tool based on Box-Jenkins methodology is presented to identify the most compatible time series model with vibration time-domain measurements. Furthermore, k-Means and Gaussian mixture model clustering techniques are utilized to examine the performance of the residuals of the identified model in damage detection. A numerical concrete beam and an experimental benchmark model are applied to verify the improved and proposed methods along with comparative analyses. Results will show that these approaches are successful in obtaining a sufficient order superior to a state-of-the-art order determination technique, generating uncorrelated residuals, extracting sensitive features to damage, and accurately detecting early damage by high-dimensional data.Tue, 03 Jul 2018 19:30:00 +0100Cooperative Control of a Gripped Load by a Team of Quadrotors
http://scientiairanica.sharif.edu/article_20642_0.html
In this paper, an output tracking controller is proposed for cooperative transport of a gripped load by a team of quadrotors. The proposed control law requires measurement of only four state variables; position and yaw angle of the system. Moreover, the controller provides rejection of step and ramp external force disturbances. Also, the control basis vectors derived via optimization facilitate real time determination of quadrotors' control inputs. Numerical simulations show effectiveness of the proposed control scheme and its superiority over formerly designed controllers for such systems.Tue, 03 Jul 2018 19:30:00 +0100Dynamic response of concrete funicular shells with rectangular base under impulse loads
http://scientiairanica.sharif.edu/article_20643_0.html
Funicular shells are thin doubly curved shallow shells which are in compression under dead weight due to their shape. In this study, an analytical approach is employed to consider forced linear vibration of concrete funicular shells with rectangular base under impulse loads based on shallow shells theory. Two boundary conditions simply supported and clamped, both are considered. The solution is obtained by Lagrangian approach. Accuracy of the results has been considered by comparing the results with those of finite element method. The results indicate that under impulse loads, stresses in funicular shells are not only compressive, but also tensile stresses are formed.Tue, 03 Jul 2018 19:30:00 +0100Effects of content and thickness on the microstructure, optical and electrical properties of ...
http://scientiairanica.sharif.edu/article_20644_0.html
It is crucial to control conductivity and optical transmittance of Al doped ZnO (AZO) thin films in application of optoelectronic materials. In this paper, AZO thin films are prepared by oxidizing thermal evaporated Zn-Al thin films in open air. Then, the effects of Al contents and film thicknesses on microstructure, optical and electrical properties of the AZO films are studied. The results show that the optical and electrical properties of the AZO films are affected by the Al content and thickness changing. The Haacke figure of merit reaches 2.91×10-4 Ω-1. The film surface morphology is changed by the Al content. Nanowire is formed when the Al content is 9.58%. The Al2O3 phase appears with an excessive Al content. The transmittance of the AZO films is less than 25% when the Al content is more than 9.58%. The grain size first increases and then decreases with the increase of film thickness when the Al contents remain at 2%. Within the limits of available transmittance, the sheet resistance and transmittance of the AZO thin film decrease exponentially with the film thickness increasing.Tue, 03 Jul 2018 19:30:00 +0100A review on SPT-based liquefaction potential evaluation to assess the possibility of performing ...
http://scientiairanica.sharif.edu/article_20645_0.html
Liquefaction is a serious natural hazard in susceptible regions which are prone to earthquakes. According to empirical and field studies, insufficiency of liquefaction assessment methods in determining liquefaction through clays and high prediction errors has caused an unceasing new development. In this article we present a comprehensive history review to organize literature on the liquefaction potential evaluation published prior to 2017. We consider deterministic approach based on SPT (Standard Penetration Test) records to create an appropriate connection between the different methods, facilitate reviewing the development of correlations in the past and current decades, assess both the cyclic stress and the flow liquefactions in a unified system, compile the latest research developments and identify the main sources as a database for the future investigators. The study attempts to assess cyclic stress method (1971) and Chinese criteria (1982) in evaluating the liquefaction potential and to discuss the insufficiencies of these methods with reference to the liquefactions caused by the Chi-chi (Taiwan) and Adapazari (Turkey) earthquakes in 1999. Besides, the absence of soil improvement on the basis of vulnerability and performance is identified as a research gap in this study.Tue, 03 Jul 2018 19:30:00 +0100Analysis on influencing factors of rutting resistance for stone matrix asphalt mixtures
http://scientiairanica.sharif.edu/article_20646_0.html
The rutting deformation not only shortens the service life of asphalt pavement, but also brings great risks to the drivers. The rutting resistance of Stone Matrix Asphalt (SMA) is affected by many factors. This study aims to thoroughly discuss the main factors of rutting resistance and establish the dynamic stability prediction model that based on the experimental data from Marshall testing and wheel tracking test in SMA mixtures. The results show that the optimal dosage bitumen of rutting test is 0.1~0.3% more than that of Marshall testing in SMA mixtures. With the temperature increases 0.5℃, the dynamic stability of SMA mixtures decreases by an average of 18.6%. The more amount of aggregate and mineral powder donnot mean the better rutting resistance in SMA mixtures. It causes to reduce the rutting resistance of SMA mixtures as compaction work is too much or too little. There is a positive correlation between the dynamic stability of SMA mixtures and fractal dimension, relative coefficient and asphalt content, while it is a negative correlation between the dynamic stability of SMA mixtures and rolling times, testing temperature.Tue, 03 Jul 2018 19:30:00 +0100Combination of Marx and Capacitor Diode Voltage Multiplier for Pulsed Power Applications
http://scientiairanica.sharif.edu/article_20689_0.html
Recently, the pulsed power and pulsed electric field systems used in various industries and these systems have found wide applications. For this reason, using the pulsed power generators that in addition to responding to the needs of the user, are providing the advantages of compactness, high flexibility, high repetition rate and cost efficiency is inevitable. In this paper a hybrid solid state pulsed power generator is introduced that is modular and very flexible. This converter which is a combination of Marx and capacitor diode voltage multiplier, is capable of producing high voltage pulses with varying amplitudes at different frequencies. This proposed converter due to having high reliability, low cost, low weight, and structure’s simplicity can cover a wide area of applications. In this paper after introducing the proposed topology, its analytical design is described and its verification is proved by the simulation results in MATLABSIMULINK and by presenting the measurement results taken from the experimental prototype in low voltages.
Mon, 16 Jul 2018 19:30:00 +0100Effect of FRP Strengthening on the SHS brace collapse mechanism
http://scientiairanica.sharif.edu/article_20690_0.html
During an earthquake diagonal braces are designed to dissipate energy by yielding in tension and buckling in compression. However, local buckling occurring in the middle of the brace leads to immediate fracture. With the aim of strengthening braces against local buckling, wrapping FRP sheets in transverse direction is proposed in this study. Hitherto, the effect of FRP strengthening on the post-buckling behaviour of Square Hollow Section (SHS) tubes has not been investigated. A numerical model was generated and verified by previous research. Then, a comprehensive parametric study was conducted and the effect of slenderness ratio, number of FRP layers and FRP coverage percentage on post-buckling response of strengthening brace was explored within the study. Results indicate that utilising FRP is certainly successful at mitigating local buckling mode of long SHS braces Moreover, for short braces, applying enough numbers of FRP layers can change the mode of buckling from local to overall. Finally, an optimized length of FRP was suggested for strengthening of braces in accordance with their slenderness ratio.Mon, 16 Jul 2018 19:30:00 +0100Effect of damped outriggers arrangement on the seismic response of high-rise steel structures
http://scientiairanica.sharif.edu/article_20691_0.html
Recently, a novel structural system, which is defined as damped outrigger system, has been proposed to control dynamic vibration of tall buildings. This paper examines seismic performance of tall buildings involving multiple outriggers equipped with viscous dampers. In this respect, a dual structural system (braced moment frame) is selected as a bare structure. In addition, the number and position of outriggers are assumed to be variable along the height of structure. Nonlinear response history analysis (RHA) is performed to evaluate the efficiency of damped-outrigger system under eight scaled ground motions. The results are presented based on the average of all ground motions. The mean inter-story drift ratio and maximum base shear force are compared in order to determine the best arrangement of damped outriggers. Conclusively, based on minimizing base shear force, the optimal location of damped outriggers under dynamic excitation is generally the same as that made for conventional outriggers. According to the inter-story drift ratio parameter, it is recommended to place one of the outriggers at the roof level.Mon, 16 Jul 2018 19:30:00 +0100Influence of Tool Material on Forces, Temperature and Surface Quality of Ti-15333 Alloy in CT ...
http://scientiairanica.sharif.edu/article_20692_0.html
Ultrasonically assisted turning (UAT) is a progressive machining method in which vibration is applied to the cutting insert in the direction of the cutting tool velocity to reduce the cutting forces, significantly and increase the surface finish noticeably. However, the key question about the tool damage caused by the vibration and its effect on the cutting forces, surface roughness and process zone temperature is still unknown in UAT.
This paper presents experimental analysis of the effect of worn tool in UAT and conventional-turning (CT) of β-Ti-15V-3Al-3Cr-3Sn (Ti-15333) alloy on surface quality of a machined surface, temperature of the process zone and cutting forces using KC5510 (PVD TiAlN) and CP500 (PVD (Ti,Al)N-TiN) cutting inserts. In UAT, the tool edge damages in CP500 inserts increased with tested machining time resulted a growth of 8 N and 10 N in tangential force component in CT and UAT, respectively. Similarly, with the progression of tool edge damage, a growth of 1.7% and 9.3% in process zone temperature was observed in CT and UAT, respectively. The surface roughness results revealed a gradual degradation with machining time, however, the results UAT with a worn tool was significantly better when compared to CT, with a virgin tool.Mon, 16 Jul 2018 19:30:00 +0100Numerical study of Jet Impingement Subcooled Boiling on the Superheated Surfaces
http://scientiairanica.sharif.edu/article_20693_0.html
Cooling techniques of superheated surfaces by jet impingement with taking advantage of phase change phenomena i.e. boiling heat transfer has proven to be an efficient method because of its high rates of heat transfer. Furthermore, at a specified heat transfer coefficient, flow required for cooling purposes can reduce two orders of magnitude comparing to free-wall parallel flow which is important regarding to energy and water sustainability issues in various industries. This research mainly concerns numerical simulation of hydrodynamics and heat transfer phenomena regarding phase-change jet impingement on nucleate boiling region. Rensselaer Polytechnic Institute wall boiling model based on Eulerian multiphase model and RNG K-ɛ turbulence model were employed. Each interfacial term was considered and selected based on proximity to real physical phenomena. The selected model in this research was validated by a previously done confined jet impingement subcooled boiling experiment (dielectric fluid-PF5060). Minimum error of 4% and maximum error of 15% were reached at stagnation point. As parametric study, the effect of jet Reynolds number based on nozzle hydraulic diameter at Re 2500 to 10000 and the effect of standoff distance of jet nozzle from target surface at H/D 2, 4 and 6 were investigated.Mon, 16 Jul 2018 19:30:00 +0100Sustainable Supplier Selection and Order Allocation: An Integrated Delphi Method, Fuzzy TOPSIS ...
http://scientiairanica.sharif.edu/article_20697_0.html
The purpose of the current study is to select suppliers and determine their order allocation in a way that the performance of the sustainability of the supply process gets optimized on the whole. In this research, after reviewing the literature and investigating the supply chain of the case study (Iran Khodro’s supply chain) through Delphi method, a set of evaluation criteria related to the performance of the suppliers in economical, social and environmental terms was identified. In the next stage, by using the identified criteria, the multi-objective mathematical integer programming was presented to solve the problems of suppliers’ selection and order allocation. The suggested mathematical programming in this research is designed to be multi-product, single-period and multiple sourcing. Fuzzy TOPSIS method is applied to calculate the qualitative parameters that are used in the suggested mathematical programming. Ultimately, the mathematical model suggested in the research will be solved by two methods, i.e. Epsilon Constraint Method and Weighted Sum Method. Moreover, the total value of the sustainable purchasing (TVSP) will be calculated for both cases. Comparing these two methods indicates that in this research the results of weighted sum method are better than those epsilon constraint method.Mon, 16 Jul 2018 19:30:00 +0100A Malmquist Productivity Index with Directional Distance Function and Uncertain Data
http://scientiairanica.sharif.edu/article_20698_0.html
We present an integrated data envelopment analysis (DEA) and Malmquist productivity index (MPI) to evaluate the performance of decision making units (DMUs) by using a directional distance function with undesirable interval outputs. The MPI calculation is performed to compare the efficiency of the DMUs in distinct time periods. The uncertainty inherent in real-world problems is considered by using the best and worst-case scenarios, defining an interval for the MPI and reflecting the DMUs’ advancement or regress. The optimal solution of the robust model lies in the efficiency interval, i.e., it is always equal to or less than the optimal solution in the optimistic case and equal to or greater than the optimal solution in the pessimistic case. We also present a case study in the banking industry to demonstrate applicability and efficacy of the proposed integrated approach.Mon, 16 Jul 2018 19:30:00 +0100Determination of limit-states for near-fault seismic fragility assessment of concrete gravity dams
http://scientiairanica.sharif.edu/article_20701_0.html
Fragility curve, based on the performance-based earthquake engineering (PBEE), is a fundamental tool in assessing the probabilistic seismic performance of concrete gravity dams. Determination of the dam limit-states (LSs) is necessary for estimation of fragility curve. In this research, four LSs in seismic performance of massive structure have been utilized for Pine Flat dam. To address this, the Incremental Dynamic Analysis (IDA) method has been applied to the integrated dam-reservoir finite-element model. Evaluation of seismic behavior, demand and capacity of the tallest monolith has been investigated by implementing IDA. A new comprehensive method in terms of IDA and statistical analysis has been used for determination of each defined LS based on the certain value of the engineering demand parameter (EDP). To assess probabilistic performance of the dam, the exceeding probability of the LSs curves has been developed at various intensity measures based on the tree EDPs. It was found that the defined LSs have the capability indeed to be used in probabilistic framework.Mon, 16 Jul 2018 19:30:00 +0100Developing New Algorithm (G-JPSO) for Optimal Control of Pumps in Water Distribution Networks
http://scientiairanica.sharif.edu/article_20703_0.html
Meta-heuristic methods have been widely used for solving complex problems recently. Among these methods, JPSO is regarded as a promising algorithm. However, in order to achieve more robust performance, the probability to solve the graph-based problems is modified by changing the jumping nature of this algorithm and a new algorithm called G-JPSO is presented which is evaluated by solving Fletcher-Powell function and optimal control of pumps in water distribution network problems. In addition to reduction of electricity cost and the problem limitations such as minimum required pressure in each node, minimum and maximum height of tanks, should also be considered. Moreover, another limitation was performed on the objective function which includes the maximum times of turning the pumps on and off. In order to determine the pumps optimal operation, an optimization-simulation model based on the optimization algorithms G-JPSO and JPSO is developed. This proposed model is used for determination of optimal operation program of Van Zyl distribution network. The comparison carried out between the results of our proposed algorithm and those of the similar algorithms including ant colony, genetic and JPSO shows the high ability of the presented algorithm in finding solutions near the optimal solutions with reasonable computation costs.Mon, 16 Jul 2018 19:30:00 +0100A bi-objective multi-echelon supply chain model with Pareto optimal points evaluation for ...
http://scientiairanica.sharif.edu/article_20724_0.html
Selecting the most suitable optimal point among the Pareto optimal points could help the experts to make an appropriate decision in an uncertain and complex situation. In this paper, an evaluating and ranking approach is proposed based on hesitant fuzzy set environment to assess the obtained Pareto optimal points from the proposed bi-objective multi-echelon supply chain model with locating distribution centers. In this respect, the proposed model has elaborated for perishable products based on fuzzy customers' demand. To address the issue, the possibilistic chance constraint programming approach has manipulated based on the trapezoidal fuzzy membership function. Moreover, the proposed hesitant fuzzy ranking approach is constructed based on group decision analysis and the last aggregation approach. Thereby, the last aggregation approach by aggregating the experts' opinions in last step could prevent the data loss. However, a case study about the perishable dairy products is considered to indicate the applicability of the proposed bi-objective multi-echelon supply chain model with locating distribution centers. Finally, a comparative analysis is provided between the obtained results and the current practice to show the feasibility and efficiency of the proposed model.Sat, 21 Jul 2018 19:30:00 +0100Hartley-Ross Type Unbiased Estimators of Population Mean Using Two Auxiliary Variables
http://scientiairanica.sharif.edu/article_20726_0.html
In survey sampling, most of the research work based on the fact that utilizing the information of auxiliary variable(s) boosts the efficiency of estimators. Keeping this fact in mind we used the information of two auxiliary variables to propose a family of Hartley-Ross type unbiased estimators for estimating population mean under simple random sampling without replacement. Minimum variance of the new family is derived up to first order of approximation. Three real data sets are used to verify that the new family acts efficiently than the usual unbiased, Hartley and Ross (1954), Grover and Kaur (2014), Singh et al. (2014), Cekim and Kadilar (2016), Muneer et al. (2017) and Shabbir and Gupta (2017) estimators.Sat, 21 Jul 2018 19:30:00 +0100A joint determination of production cycle length, maintenance policy, and control chart ...
http://scientiairanica.sharif.edu/article_20729_0.html
Statistical process monitoring, maintenance policy, and production cycle length usually have been investigated separately while they are three dependent aspects in the industrial systems. Moreover, most of the papers that integrated simultaneously these aspects, suffer from three major drawbacks as follows: (1) Optimizing the production cost without considering the time value of money to simplify the model; (2) Considering the fixed shift size while it is a random variable in the real condition; (3) Economic design of control charts ignoring the statistical properties that lead to reduce the control chart power, extremely. To eliminate these weaknesses, this paper presents an integrated model of production cycle length, maintenance policy, and economic-statistical design considering the time value of money and the stochastic shift size. Furthermore, to maintain the reliability of the system at an acceptable level, the presented model uses non-uniform sampling. Finally, three comparative studies on the main contributions are presented to illustrate the advantages of the model and a sensitivity analysis is implemented on the several parameters to extend insights into the matter.Sat, 21 Jul 2018 19:30:00 +0100High-performance controller design and evaluation for active vibration control in boring
http://scientiairanica.sharif.edu/article_20731_0.html
High quality manufactured components with fast production rate is an increasing demand of modern machine tool industry. Internal machining operations due to the large length to diameter ratio are most prone to intolerable chatter vibrations and proved to be an extremely challenging process. This paper presents a new method for proper design of direct velocity feedback (DVF) controller in order to extend boundaries of stable cutting for internal turning with minimum control effort. Control effort and active damping performance are two counteracting parameters that affect the results of active vibration control. After properly implementing the DVF active control algorithm on the internal turning setup, stable boundaries for different control gains of DVF controller are thoroughly studied. The comparison shows that although high DVF gains may considerably improve dynamic stiffness of the tool, it leads to the maximum control effort and actuator saturation and consequently process instability. The proposed gain selection method results in a significant increase in stable machining over the desired range of cutting conditions. The suggested design approach of the DVF controller can considerably improve limitations of rough machining on long over hang boring bars.Sat, 21 Jul 2018 19:30:00 +0100Dynamic adaptive mesh refinement of fluid structure interaction using immersed boundary method ...
http://scientiairanica.sharif.edu/article_20738_0.html
The application of the immersed boundary method (IBM) coupled with adaptive mesh refinement (AMR) is considered one of the powerful tools for solving complex viscous incompressible flow problems. In this paper, the IBM was combined with AMR to solve complex incompressible and viscous fluid with elastic and rigid body problems concerning large structural deformations. In the IBM, the solid and fluid motions at the interface are united by a body force which can be compared to a fraction of a solid volume. The work aims to develop an automatic adaptive mesh refinement strategy to improve the solution near the fluid-structure interface. This is necessary as the flow field might be significantly affected by the structure; therefore, it was essential to precisely capture the boundary layers. The computational results highlighted the capability of this method to improve the flow resolution near the fluid structure. The proposed approach is validated using 2D numerical examples. The approach is validated in terms of its superior performance. The combined IBM-Adaptive mesh refinement approach showed a promising outcome for the investigated mechanical problem. The performance of the method in achieving a solution within a reasonably low computation time is also commendable.Sat, 21 Jul 2018 19:30:00 +0100Mathematical modeling of thermal contact resistance for different curvature contacting geometry ...
http://scientiairanica.sharif.edu/article_20739_0.html
Nowadays having deep knowledge on thermal contact conductance (TCC) and thermal conduct resistance (TCR) existed between various type metals is interesting during heat transfer occurrence in the nuclear reactor, thermal control system of spacecraft, and heat exchangers. In this present contribution, artificial neural network (ANN) coupled with multi-layer perceptron (MLP) modeling was utilized for the prediction of transient temperature contour in various contacting surface such as flat-flat, flat-cylinder, cylinder-cylinder. In order to develop accurate transient model, position, time, and roughness parameter of metal was used as input parameter and temperature of solid bodies decided as target parameter of model. Modeling results indicates that ANN base modeling show great accuracy in comparison with other numerical methods. Also, values of average absolute relative deviation (AARD), coefficient of determination (R2) for the overall data is 0.056 and 0.996 respectively which clarifies the accuracy and robustness of the proposed model.Sat, 21 Jul 2018 19:30:00 +0100The Deformation Mechanism of a High Rockfill Dam during the Construction and First Impoundin
http://scientiairanica.sharif.edu/article_20778_0.html
The Masjed-e-Soleyman dam is a high rockfill dam with clay core, located in Iran. During construction and first impounding, a considerably high excess pore water pressure has been developed inside the core and has been being dissipated with a very slow rate, so the consolidation deformations have been insignificant. However, there have been reports of noticeable internal deformations in the dam, the crest has also exhibited quick settlements during the first impounding. The main objective of this paper was to identify the deformation mechanism of this dam. For this purpose, the data recorded by its instruments were carefully studied and then a three-dimensional numerical model of the dam was developed. The mechanical behavior of materials was idealized by a hardening strain constitutive model. A numerical method was proposed, based on this constitutive model and Rowe’s stress–dilatancy theory, to simulate the deformation behavior of coarse-grained materials, like rockfills, due to particle size distribution, particle breakage, rotation, and rearrangement under shearing. The results show that significant development of pore pressure in the core and its insignificant dissipation, plastic shear deformations inside the core and extensive collapse settlements of the upstream shell are the main causes influencing the deformation mechanism.Mon, 23 Jul 2018 19:30:00 +0100Economic Evaluation of Investment Projects Under Uncertainty: A Probability Theory Perspective
http://scientiairanica.sharif.edu/article_20779_0.html
In the current competitive economy, the investors are facing increased uncertainty while evaluating new investment projects. This uncertainty caused from existence of insufficient information, oscillating markets, unstable economic conditions, obsolescence of technology and so on, and hence uncertainty is inevitable in reality. In such conditions, the deterministic models, while easy to use, do not perfectly represent the real situations and might lead to misleading decisions. When the cash flows for an uncertain investment project, over a number of future periods, are discounted using the traditional deterministic approaches, it may not provide investors with an accurate estimation of the project value. Therefore, this paper utilizes the probability theory tools to derive closed-form probability distribution function (PDF) and related expressions of the net present worth (NPW), as a useful and frequently used criterion, for cost-benefit evaluation of projects. The random cash flows follow normal, uniform or exponential distributions in our analysis. The probability distribution function of the NPW is an important tool that helps investors to accurately estimate the probability of being economic for projects, and hence, it is important tool for investment decision-making under uncertainty.Mon, 23 Jul 2018 19:30:00 +0100Microstructure and fatigue fracture mechanism for a heavy-duty truck diesel engine crankshaft
http://scientiairanica.sharif.edu/article_20780_0.html
The main goal of this research is the experimental and numerical study on the fatigue function and failure of the crankshaft of diesel engine of a heavy truck. To do this, a crankshaft of the diesel engine of a heavy truck that has gone under failure after traveling 955000 km, has been used. To examine the sources of this failure, several experimental studies have been carried out including chemical composition, the strength of the material, determining the hardness and the microstructure of the material. Besides, using an elastic–plastic three dimensional finite element method (FEM) model, the location of the maximum stress in the crankshaft was determined using the ‘‘complete crankshaft model’’ and ‘‘one crank model’’. Using the results of stress analysis, was a basis for the three-dimensional crack growth model and fatigue life estimation to determine the stress intensity factor and fatigue life considering the related parameters and boundary conditions method. At the final stage, using the results gotten from the given model for the fatigue crack growth, comparing it with experimental results, and examining the whole process, it was concluded that the scratches in crankpin region, was the main reason for the fatigue failure got from bending-torsional load-combination.Mon, 23 Jul 2018 19:30:00 +0100A collocation algorithm based on quintic B-splines for the solitary wave simulation of the GRLW ...
http://scientiairanica.sharif.edu/article_20781_0.html
In this article, a collocation algorithm based on quintic B-splines is proposed for the numerical solutionof the non-linear generalized regularized long wave (GRLW) equation. Also, to analyse the linearstability of the numerical scheme, the von-Neumann technique is used. The numerical approach isdiscussed on three test examples consisting of a single solitary wave, the collision of two solitarywaves and the growth of an undular bore. The accuracy of the method is demonstrated by calculatingthe error in the L2 and L¥ norms and the conservative quantities I1, I2 and I3. The findings arecompared with those of previously reported in the literature. Finally, the motion of solitary waves isgraphically plotted according to different parameters.Tue, 24 Jul 2018 19:30:00 +0100Multi-objective mathematical modeling of an integrated train makeup and routing problem in an ...
http://scientiairanica.sharif.edu/article_20782_0.html
Train formation planning faces two types of challenges; namely, the determination of the quantity of cargo trains run known as the frequency of cargo trains and the formation of desired allocations of demands to a freight train. To investigate the issues of train makeup and train routing simultaneously, this multi-objective model optimizes the total profit, satisfaction level of customers, yard activities in terms of the total size of a shunting operation, and underutilized train capacity. It also considers the guarantee for the yard-demand balance of flow, maximum and minimum limitations for the length of trains, maximum yard limitation for train formation, maximum yard limitation for operations related to shunting, maximum limitation for the train capacity, and upper limit of the capacity of each arc in passing trains. In this paper, a goal programming approach and an L­p­ norm method are applied to the problem. Furthermore, a simulated annealing (SA) algorithm is designed. Some test problems are also carried out via simulation and solved using the SA algorithm. Furthermore, a sample investigation is carried out in a railway company in Iran. The findings show the capability and performance of the proposed approach to solve the problems in a real rail network.Tue, 24 Jul 2018 19:30:00 +0100Optimization of multiple transmission layouts for minimal energy consumption of a battery ...
http://scientiairanica.sharif.edu/article_20783_0.html
Battery electric vehicles (BEVs) are a promising solution for reducing the impacts of passenger vehicles on the environment. However, their driving range is restricted due to the limitations of battery technologies. This range can be extended by adoption of multiple-speed transmissions. Most of the comparisons in the related studies are based on non-optimal designs or limited to modal driving cycles. Furthermore, the impact of power-split continuously variable transmission (PS-CVT) layout with type III power flow on the power consumption of BEVs has never been examined. In this paper, single, two and three-speed transmissions along with PS-CVTs with type I and III power flows are optimized for a case study BEV. Furthermore, the effect of push belt and full-toroidal CVTs in construction of PS-CVT are compared. The results demonstrate that a PS-CVT with type I power flow equipped with the full-toroidal CVT has the best performance. However, it reduces the energy consumption by 0.36% compared to the optimal two-speed layout. In addition, its ratio range is more limited which can negatively impact the dynamic performance. Finally, simulation of the optimal designs along a different cycle proves that the obtained results are consistent, regardless of the driving cycle.Tue, 24 Jul 2018 19:30:00 +0100Modified quasi-Y-source converter to increase boost factor
http://scientiairanica.sharif.edu/article_20788_0.html
In this paper, a new topology of quasi-Y-source impedance network is presented. This converter utilizes the change of winding factor and shoot through state in order to improve the gain of network. The proposed impedance network employs less turn ratio compared to quasi-Y-source and Y-source network to achieve high voltage gain. The continuous input current of the proposed converter is an advantage particularly for the applications related to the renewable energy sources such as Fuel Cell (FC) and photovoltaic (PV) systems. Furthermore, there is a dc-current-blocking capacitors in the proposed network, which helps to avoid the saturation of the coupled inductor. Operation principles of the converter are discussed and the steady state relations as well as voltage gain and voltage stress across the dc-blocking capacitors are derived. Proposed converter is compared to the conventional quasi-Y-source network, to show the advantages of the converter. Several simulations are done and the results are shown to indicate the performance of the proposed network. In this paper, an experimental prototype of a converter is presented. To prove the validity and consistency of the proposed network, several tests are carried out. This plan, can have a negative gain, similar to the quasi-Y-source network.Sat, 28 Jul 2018 19:30:00 +0100Simulation based optimization of a stochastic supply chain considering supplier disruption: An ...
http://scientiairanica.sharif.edu/article_20789_0.html
Many researchers and practitioners in the recent years have been attracted to investigate the role of uncertainties in the supply chain management concept. In this paper a multi-period stochastic supply chain with demand uncertainty and supplier disruption is modeled. In the model, two types of retailers including risk sensitive and risk neutral, with many capacitated suppliers are considered. Autonomous retailers have three choices to satisfy demands: ordering from primary suppliers, reserved suppliers and spot market. The goal is to find the best behavior of the risk sensitive retailer, regarding the forward and option contracts, during several contract periods based on the profit function. Hence, an agent-based simulation approach has been developed to simulate the supply chain and transactions between retailers and unreliable suppliers. In addition, a Q-learning approach (as a method of reinforcement learning) has been developed to optimize the simulation procedure. Furthermore, different configurations for simulation procedure are analyzed. The R-netlogo package is used to implement the algorithm. Also a numerical example has been solved using the proposed simulation-optimization approach. Several sensitivity analyzes are conducted regarding different parameters of the model. Comparison of the numerical results with a genetic algorithm shows a significant efficiency of the proposed Q-leaning approach.Sat, 28 Jul 2018 19:30:00 +0100Novel Technique for Dynamic Analysis of Shear-Frames Based on Energy Balance Equations
http://scientiairanica.sharif.edu/article_20790_0.html
In this paper, an efficient computational solution technique based on the energy balance equations is presented for the dynamic analysis of shear-frames, as an example of a multi-degree-of-freedom system. After deriving the dynamic energy balance equations for these systems, a new mathematical solution technique which is called Elimination of Discontinuous Velocities is proposed to solve a set of coupled quadratic algebraic equations. The method will be illustrated for the free vibration of a two-story structure. Subsequently, the damped dynamic response of a three-story shear-frame which is subjected to harmonic loading is considered. Finally the analysis of a three-story shear-building under horizontal earthquake load, as one of the most common problems in Earthquake Engineering, is studied. The results show that this method has acceptable accuracy in comparison with other techniques, but is not only faster compared with modal analysis but also does not require adjusting and calibrating the stability parameter as compared with a method of time integration like the Newmark method.Sat, 28 Jul 2018 19:30:00 +0100Experimental study of the effect of polymer fiber based on epoxy resin on compressive and ...
http://scientiairanica.sharif.edu/article_20791_0.html
In this study, effective parameters on polymer concrete (PC) based on epoxy resin such as filler, hardener and solvent are investigated. Rice husk and broom stem ashes as fillers with mixture of 50-50% Acetone-Toluene as solvent in preparation of PC samples were used. According to experimental results, addition of fillers improved compressive, flexural and chemical strengths of the PC samples. In the sample with 18.4% polymer, additional of rice husk ash with ratio of filler-aggregate 0.075, compressive strength improved by 21%. For the sample with broom stem ash ratio of filler-aggregate 0.09, the flexural strength was improved by 27%. In addition, experimental data proved that addition of optimum amount of solvent improved the performance and enhanced the compressive and flexural strengths. But excess amount of solvent may reduce the adhesiveness of the polymer therefore it may have negative impact on PC. The combination of hardener-resin may influence on the strength of PC. Amine type of hardener with low equivalent weight improved 27 and 13% on compressive and flexural strengths. Also elasticity module was increased in compare with the samples having high equivalent weight of amine type hardener.Sat, 28 Jul 2018 19:30:00 +0100Application of petrographic image analysis in assessment of chemical attack in the concrete ...
http://scientiairanica.sharif.edu/article_20792_0.html
The current paper discusses the petrographic image analysis performed on core specimens that are extracted from a tunnel in the south west of Iran. During tunnel excavation, damages were observed in the inner sections of concrete segments. Due to field observations of damaged segments, environmental parameters and tunnel location, several damage scenarios were proposed. In order to assess damage mechanisms, 69 cores were extracted and a number of standard tests were carried out. Since chemical attacks alter microscopic properties of materials, petrographic image analysis was performed on five of the specimens to evaluate possible microscopic changes in concrete composition. The results show that petrographic image analysis is an efficient method to provide a profound insight into the effects of chemical attacks on concrete members.Sat, 28 Jul 2018 19:30:00 +0100An Architectural Solution for Virtual Computer Integrated Manufacturing Systems using ISO Standards
http://scientiairanica.sharif.edu/article_20799_0.html
Nowadays, manufacturing environments are faced with globalization which urges new necessities for manufacturing systems. These necessities have been considered from different perspectives and Computer Integrated Manufacturing (CIM) is the most popular and effective one. However, considering rapid rate of manufacturing globalization, traditional and current CIM solutions can be criticized by major deficiencies like high complexity for resource allocation over the globe, global facility sharing, and absence of an efficient way to handle lifecycle issues. Recently, Virtual CIM (VCIM) has been introduced as an effective solution to extend the traditional CIM solutions. This paper has investigated recent researches in VCIM/CIM field considering the necessities of todays’ globalized manufacturing environment. The paper shows the lack of traditional and current CIM/VCIM solutions; then, proposes an effective solution to cover them. Because of the complexities in designing such systems, the paper exploits Axiomatic Design (AD) Theory as a promising tools in this field. This theory is applied for validation of the suggested architectural solution and verification of the implementational aspects. The implementation of the architectural solution is considered based on ISO standards. Finally, the results have approved the feasibility of the suggested solution for manufacturing system and its Implementation aspects.Sat, 04 Aug 2018 19:30:00 +0100Solving a multi-objective model toward home care staff planning considering cross-training and ...
http://scientiairanica.sharif.edu/article_20800_0.html
Home care (HC) staff assignment problem is defined as deciding which staff to assign to each patient. In this study, a multi-objective non-linear mathematical programming model is presented to address staff assignment problem considering cross-training of caregivers for HC services. The first objective of the model minimizes costs of workload balancing, cross-training and maintenance. The second objective minimizes the number of employees for each service while the satisfaction level of caregivers is maximized through the third objective function. Several constraints including skill matching, staff preferences, regularity, synchronization, staff absenteeism and multi-functionality are considered to build a service plan. Due to NP-hardness of the problem, a non-dominated sorting genetic algorithm (NSGA-II) with a proposed who-rule heuristic initialization procedure is applied. Due to absence of benchmark available in the literature, a non-dominated ranking genetic algorithm (NRGA) is employed to validate the obtained results. The data required to run the model are gathered from a real-world HC provider. The results indicate that the proposed NSGA-II is superior to the NRGA with regard to comparison indexes. Based on the results obtained, it can be determined which staff should be cross-trained for each service and how the staff are assigned to services.Sat, 04 Aug 2018 19:30:00 +0100Robust Optimization for the Resource Constrained Multi-Project Scheduling Problem with ...
http://scientiairanica.sharif.edu/article_20801_0.html
This paper studies the multi-project scheduling problem which involves multiple projects with different importance weight; with predefined assigned due dates; with activities that have uncertain durations; and with renewable resources that are constrained. The resource sharing policy is applied to share the resources among projects. Due to the environmental rapid changes and also the uniqueness of projects, the probability distribution function of uncertain durations cannot be estimated with confidence. Besides, the multi-project scheduling problem with its large scale investment dictates a conservative approach to deal with the existing uncertainty. Therefore, the Robust Resource-Constrained Multi-Project Scheduling Problem (RRCMPSP) is studied in this paper while the maximum total weighted tardiness of the projects should be minimized. A scenario-relaxation algorithm is implemented which results in optimal solutions for the RRCMPSP. The aim is to find an optimal structure containing all the projects in such a way that it transfers the resources between the activities based on the resource sharing policy while the maximum weighted differences between the projects finish times and their assigned due dates will be minimum.Sat, 04 Aug 2018 19:30:00 +0100Research on the Risk Assessment Method of PPP Project based on the Improved Matter Element Model
http://scientiairanica.sharif.edu/article_20820_0.html
When identifying PPP project risks using the decomposition analysis method, the PPP project risks are considered to include government risk, market risk, and project risk. Based on these facts, a constructed list of PPP project risks is established, which can be divided into three first-class indexes and 27 second-class indexes. Based on the analysis of the traditional matter element model limitations, the evaluation model of PPP project risk assessment of the improved matter element model is established, in order to provide effective support for effective PPP project risk management, contract management and other work. Lastly, the feasibility of theoretical research is verified by a case study.Tue, 07 Aug 2018 19:30:00 +0100Extended TOPSIS method for multi-criteria group decision-making problems under cubic ...
http://scientiairanica.sharif.edu/article_20821_0.html
The objective of this work is to present a novel multi-criteria group decision making (MCGDM) method under cubic intuitionistic fuzzy (CIF) environment by integrating extended TOPSIS method. In the existing studies, the uncertainties which are present in the data are handled either an interval-valued intuitionistic fuzzy sets (IVIFS) or an intuitionistic fuzzy set (IFS) information, which may lose some useful information of alternatives. On the other hand, CIF set (CIFS) handles the uncertainties by considering both the IVIFS and IFS instantaneously. Thus, motivated by this, in the present work, we presented some series of distance measures between the pairs of CIFSs and investigated their various relationship. Further, under this environment, a group decision-making method based on the proposed measure is presented by taking the different priority pairs of the decision makers. A practical example is provided to verify the developed approach and to demonstrate its practicality and feasibility, we compared their results with the several existing approaches results.Tue, 07 Aug 2018 19:30:00 +0100Prediction of Subgrade Reaction Modulus of Clayey Soils using Group Method of Data Handling
http://scientiairanica.sharif.edu/article_20822_0.html
Settlement-based designs for foundations, using subgrade reaction modulus (K_s), is an important technique in geotechnical engineering. Plate load test (PLT) is one of the commonly applied methods to directly determine K_s. As the determination of the K_s from PLT—especially at depths—is relatively costly and time-consuming, it is necessary to develop models that can handle simply determinable properties. In the present study, the suitability of the Group Method of Data Handling (GMDH)-type neural network (NN) to estimate the subgrade reaction modulus of clayey soils has been investigated. In order to derive GMDH models, a database containing 123 datasets compiled from geotechnical investigation sites in Qazvin, Iran, has been used. The performance of the GMDH models has been compared with other available correlations for clayey soils, and it has been demonstrated that an improvement in estimating the K_s has been achieved. Finally, a sensitivity analysis has been conducted on the proposed models, showing that the proposed K_s is considerably influenced by changing the LL value.Tue, 07 Aug 2018 19:30:00 +0100Prediction of meteorological and hydrological phenomena by different climatic scenarios in the ...
http://scientiairanica.sharif.edu/article_20823_0.html
This research evaluates effects of climatic change on future temperature, precipitation and flow discharge in the Karkheh watershed (a watershed in south west of Iran). For this purpose, it utilizes general circulation models (GCMs) and the non parametric Mann-Kendall (MK) trend test. Considered hydrometric station is the Jelogir station at the upstream of the Karkheh dam. Base time period is 1971-2014 and future time period is 2030- 2073 for prediction of meteorological and hydrometric phenomena in the Jelogir station. For GCM model, the Canadian Climate Change Scenarios Network (CCCSN) database represents data of HadCM3 model for A2 and B2 scenarios. For using in a watershed, this research applies SDSM downscaling model and introduces predicted precipitation and temperature of future time period to IHACRES model for prediction of flow discharge. Also the non parametric Mann-Kendall trend test and the Theil–Sen approach (TSA) estimator distinguishes trend of observed and predicted data. Results of scenarios A2 and B2 have not much difference. Different climatic scenarios show that temperature increases and precipitation and flow discharge decrease, also MK test and TSA estimator represent that slope of their variations will slow down in future and most of changes are related to winter and spring.Tue, 07 Aug 2018 19:30:00 +0100Volume Change Behavior of Stabilized Expansive Clay with Lignosulfonate
http://scientiairanica.sharif.edu/article_20824_0.html
This paper presents the swelling and consolidation characteristics of Lignosulfonate (LS) stabilized expansive clay. Expansive clay samples of Amol city in Iran have been used in this research. Based on Atterberg limits and unconfined compressive strength tests, optimum percentage of LS for treatment of this clay was determined 0.75% by soil dry weight. To investigate swelling and consolidation properties of untreated and LS-treated remoulded samples, one dimensional swell and consolidation tests were conducted on these samples. Test results showed that LS has considerable effect on the consolidation and swelling behavior of the expansive clay. Moreover, the effects of compaction water content change and cyclic wetting and drying on the volume change properties of unstabilized and LS-stabilized samples were investigated. Untreated and LS-treated specimens showed different consolidation behavior to the changes of compaction moisture content due to the altering of soil expansivity category from high to moderate. The SEM images of samples showed that the soil specific area was reduced because of stabilization. This reduction in soil specific area was led to the decrease of affinity of samples to moisture increase, so the volume change of expansive clay was decreased.Tue, 07 Aug 2018 19:30:00 +0100A Holistic Day-ahead Distributed Energy Management Approach: Equilibrium Selection for ...
http://scientiairanica.sharif.edu/article_20825_0.html
n this paper, a new holistic distributed day-ahead energy management approach with desired equilibrium selection capability in a smart distribution grid is proposed. The interaction between customers and the distribution company is modeled as a single-leader multiple-follower Stackelberg game. The interaction among customers is modeled as a non-cooperative generalized Nash game because they meet a common constraint. Customers hold the average of the aggregate load in the appropriate domain to reshape it and improve the Load Factor. The strategy of the distribution company is day-ahead energy pricing obtained through maximizing its profit which is formulated as a stochastic conditional value at risk optimization to consider the uncertainty of the price of electricity in the wholesale market. Customers’ strategies are based on hourly consumption of deferrable loads and scheduled charge/discharge rates of energy storage devices in response to price. It is proved that the generalized Nash game has multiple equilibria; hence, the distributed proximal Tikhonov regularization algorithm is proposed here to achieve the desired equilibrium. The simulation results validate the performance of the proposed algorithm with 31.46% increase in the Load Factor besides 45.89 % and 14.23 % reduction in the maximum aggregate demand and aggregate billing cost, respectively.Fri, 10 Aug 2018 19:30:00 +0100A Novel Similar Character Discrimination Method for Online Handwritten Urdu Character ...
http://scientiairanica.sharif.edu/article_20826_0.html
Online handwritten Urdu character recognition is one of the key technologies for intelligent interface on smart phones and touch screens. It is a challenging research topic as Urdu script has many similar character groups. A novel similar character discrimination method for online handwritten Urdu character recognition is proposed in this paper which includes pre-classification, feature extraction and fine classification process. The pre-classifier enables the discrimination of similar characters by putting them in distinct smaller subsets according to stroke number and diacritics. Then structural features and wavelet features are extracted. Finally, Support Vector Machines (SVM), Artificial Neural Networks (ANN), and Recurrent Neural Network (RNN) classifiers are compared for fine classification within subsets. Results of RNN classifier without using the proposed pre-classifier and features have also been obtained to check the end-to-end capability of the RNN classifier. Experimental results show that the proposed method is efficient and achieves an overall accuracy of 96% on a large-scale self-collected dataset. It is feasible to extend this method for other Arabic scripts.Fri, 10 Aug 2018 19:30:00 +0100The Variable Step-Size Wavelet Transform-Domain LMS Adaptive Filter Algorithm
http://scientiairanica.sharif.edu/article_20827_0.html
In this paper, the wavelet transform domain least mean squares (WTDLMS) adaptive algorithm with variablestep-size (VSS) is established. The step-size changes according to the largest decrease in mean square deviation. To keep the computational complexity low, the Haar wavelet transform (HWT) is utilized as a transform. In addition, the mean square performance analysis of the VSS-WTDLMS is studied in the stationary and nonstationary environments and the theoretical relations for transient and steady-state performances are established. The simulation results show that the proposed VSS-WTDLMS has faster convergence rate and lower misadjustment than conventional WTDLMS. The theoretical relations are also verified by presenting various experimental results.Fri, 10 Aug 2018 19:30:00 +0100Design of Mixed Flow Pump Impeller Blade using Mean Stream Line Theory and its Analysis
http://scientiairanica.sharif.edu/article_20829_0.html
Given the importance of blade design in effective performance of the mixed flow pump, the present work demonstrates the designing of the mixed flow pump impeller blade using almost unexplored Mean stream line theory. The Mean stream line theory, though been used sparingly but has found to give comparable results to that of other templates of design. The design process has been carried out in AUTOCAD 2013 and Solid Works Premium 2014 software. The analysis for equivalent stress, equivalent elastic strain, Total deformation and the directional deformation have been carried out in ANSYS 2014 for different construction material of the blade i.e., stainless steel, titanium alloy, bronze, and copper alloy. Total deformation was found to be maximum for impeller blade made from titanium alloy whereas the equivalent stress and strain was least for titanium alloyed impeller blade. Further, a comparison analysis has been carried out for the equivalent stresses in blade designed using mean stream line theory and free vortex theory. It was observed that the equivalent stress in impeller blade designed using free vortex theory was lesser than that designed using mean stream line theory.Sat, 11 Aug 2018 19:30:00 +0100Resilience Supplier Selection and order allocation under uncertainty
http://scientiairanica.sharif.edu/article_20831_0.html
Increasing the number of disasters around the world will decrease the performance of the supply chain. The decision makers should design resilience supply chain network which could encounter with disruptions. This paper develops an integrated resilience model of supplier selection and order allocation. Resiliency measures including quality, delivery, technology, continuity, environmental competences are explored for determining the Resilience Weight of suppliers. Fuzzy DEMATEL and ANP methods are applied to find overall performance of each supplier. Then, the developed mathematical model maximizes overall performance of suppliers while minimizes total cost of network. The proposed mathematical model helps the decision makers to select supplier and allocate the optimum order quantities by considering shortage. Since the disruptive incidents are inevitable events in real world problems, the impact of disruptions on suppliers, manufactures and retailers has been considered in the proposed model. Inherent uncertainties of parameters are taken into account to increase the compatibility of the approach with realistic environments. To tackle the uncertainty and multi-objectiveness of the proposed model, interval Method and TH aggregation function is adapted. The proposed model is validated through application to a real case study in a furniture company. Results demonstrate the usefulness and applicability of the proposed model.Sat, 11 Aug 2018 19:30:00 +0100Design of Conformal Cooling Channels Using Numerical Methods in a Metal Mold and Calculating ...
http://scientiairanica.sharif.edu/article_20894_0.html
Shorter cycle times, better product quality and less product outage can be possible with faster cooling. But mold cooling channels can only be made in linear directions and limited forms via classical manufacturing methods. Therefore, it limits that performance of mold cooling. Developed in recent years additive manufacturing technologies are capable of building complex geometries and monoblock 3D products. With this technology it is possible to produce metal molds with conformal cooling channels in different forms and capable of qualified cooling. In this study, conformal cooling channels were designed in order to achieve optimum cooling in monoblock permanent mold. In this study, CFD (Computational Fluid Dynamic) analyses are performed to steady stead conditions for designed conformal cooling channels and classical cooling channel mold. Pressure drops, cooling channel outlet temperatures and exergy destructions are calculated depending on the flow velocity rate in channels. The numerical investigations of the cooling process have shown that approximately 5% higher cooling performance can be achieved with conformal cooling channels. However, the pressure drop in the conformal cooling is observed to be higher than classical cooling channel. In addition, exergy destruction in the conformal cooling channel is approximately 12% greater than the classical cooling channel.Sat, 18 Aug 2018 19:30:00 +0100Optimizing under and out of warranty products’ decisions in the finite planning horizon
http://scientiairanica.sharif.edu/article_20895_0.html
In this paper, we consider a manufacturer that produces products in a finite horizon time and sells products with non-renewing free replacement warranty policy. The manufacturer is responsible to provide spare parts for failed products, whether the products are under or out of warranty. Previous research on warranty optimization has focused on maximizing manufacturer profit without considering the spare part market for out-of-warranty products. This study proposes a novel nonlinear model that maximizes manufacturer profit by optimization of price, warranty length and spare part inventory for under- and out-of-warranty products in a manufacturing/remanufacturing system. Due to the model’s unique structure, we propose a new two-stage approach that combines metaheuristic and an exact method, in which the first stage is to determine product’s prices and warranty length with metaheuristic algorithm and in the second stage the remaining inventory related problem is transferred to a Minimum Cost Network Flow Problem which is solved for spare part inventory control. To illustrate the effectiveness of the suggested method, the model is solved for a case study of Iranian SANAM electronic company with two different metaheuristic algorithms and a sensitivity analysis is conducted to study the effect of various parameters on the optimal solution.Sun, 19 Aug 2018 19:30:00 +0100Investigation of Transient Numerical Simulation of Solidification and Thermal Behavior of Metal ...
http://scientiairanica.sharif.edu/article_20896_0.html
The cooling process in metal molds is one of the important factors in the solidification process of molten metal. Molding defects such as hot spot defects and warping occur in cast products when the cooling is not uniform. However, qualified and faster cooling affects product quality positively. Molding is one of the important processes both in terms of cycle time and product quality, with permanent mold casting, high quality liquid metal casting, and quality product. Selective Laser Melting (SLM) method has been used to design metal mold cores with unique cooling channels to be compactly produced. The effects of the designed cooling channels, heat transfer and solidification of the molten metal are studied in transient numerical terms. The temperature distributions for 1, 3 and 5 seconds after casting were obtained and the solidification processes were investigated according to the standard cooling channels of the original cooling channels. According to the results obtained, it has been observed that solidification is better in originally designed cooling channels.Sun, 19 Aug 2018 19:30:00 +0100Contractors’ Partnership in Project Resource Management Application of Cooperative Game ...
http://scientiairanica.sharif.edu/article_20897_0.html
It is accepted that project breakdown into several independent subprojects can help to have a successful and effective project management. On the other hand, it can lead to inefficiently use of some renewable resources, and increase the total project cost and time. This article studies the benefits of the horizontal partnering among contractors assigned to subprojects through the sharing renewable resources and proposes a model based on cooperative game theory to solve it. The improvement of the net present value of the project is considered as the benefit of the cooperation among contractors. Therefore, a mixed-integer non-linear programming (MINLP) model is developed for the resource constrained project scheduling with objective function of maximizing the net present value (NPV) of each coalition. Seven widely used cooperative game theory solution methods are used to solve the benefit (NPV) allocation problem and then the stability criteria are suggested to find the best allocation scheme. Finally, an example is represented to more comprehensively illustrate the problem.Fri, 24 Aug 2018 19:30:00 +0100Proposing a new nonlinear hyperviscoelastic constitutive model to describe uniaxial compression ...
http://scientiairanica.sharif.edu/article_20899_0.html
Predicting the nonlinear response of biological tissues is challenging issue, due to strain rate- (short term) and time-dependent (long-term) nature of its response. While many of the tissue properties have already been extensively examined, some are left unnoticed, such as dependence of the stress-relaxation behavior on the strain levels. In this paper, a hyperviscoelastic constitutive model is derived within the integral form presented by Pipkin and Rogers model to remove this limitation. In the suggested model, the hyperelastic and short-term viscous parts are represented by the suitable strain energy function. The long-term viscous function includes the deformation history, which is expressed through a tensorial-relaxation function and has not been considered elsewhere. The constitutive model involves a number of material parameters. The values of those are identified from experimental data for Adiprene-L100 as a tissue-equivalent material. Parameters appearing in constitutive law are estimated by fitting the model with the experimental data. It is assumed that the tissue phantom is slightly compressible, isotropic and homogenous. The obtained results indicate that the presented model can describe the nonlinearity, strain rate- (short-term) and time-dependent (long-term) effects of materials. The validation of the model is investigated and shows very good agreement with the experimental data.Sun, 26 Aug 2018 19:30:00 +0100Lattice Boltzmann Simulation of Blood Flow Properties and Vessel Geometry in an Open and Closed ...
http://scientiairanica.sharif.edu/article_20900_0.html
In the present article, Lattice Boltzmann method is utilized to simulate two-dimensional incompressible viscous flow in an open and closed microchannel (vessel). The main focus of the present research is to study physical parameters of blood flow in a vessel. To find the effect of oscillatory flow inside the vessel, we take account of the Reynolds number from 0.05 to 1.5 for numerical computation in the present manuscript in an open straight vessel. In addition, the accuracy of Poiseuille Law is investigated for blood flow in open vessel too. For this purpose, the effect of the vessel diameter and blood viscosity on the blood flow is studied numerically. As extra results, the effect of blood injection to a coronary bifurcation with two closed ends are studied. The blood pressure drop is high at the beginning of the vessel (pressure variation is high between the adjacent points along the vessel), but after the path along the vessel, the speed of dropping pressure decreases and the pressure difference between the adjoining points decreases along the vessel. Finally, the present results have been compared with the available experimental and numerical results that show good agreements.Sun, 26 Aug 2018 19:30:00 +0100A Bi-Level Programming Model for Energy and Flexiramp Procurement in Day-ahead Market and a ...
http://scientiairanica.sharif.edu/article_20915_0.html
In this paper, we focus on solving the integrated energy and flexiramp procurement problem in the day-ahead market. The problem of energy and ramp procurement could be perfectly analyzed through Stackelberg concept, because of its hierarchical nature of the decision-making process. Such a circumstance is modeled via a bi-level programming, in which suppliers act as leaders and the ISO appear as the follower. The ISO intends to minimize the energy and spinning reserve procurement cost, and the suppliers aim to maximize their profit. To solve the proposed model, a fuzzy max-min approach is applied to maximize the players’ utilities. The objectives and suppliers’ dynamic offers, determined regarding the market clearing prices, are reformulated through fuzzy utility functions. The proposed approach is an effective and simple alternative to the KKT method, especially for problems with non-convex lower-level.Mon, 27 Aug 2018 19:30:00 +0100An Effective League Championship Algorithm for the Stochastic Multi-Period Portfolio ...
http://scientiairanica.sharif.edu/article_20995_0.html
The multi-period portfolio optimization models were introduced to overcome the weaknesses of the single-period models via considering a dynamic optimization system. However, due to the nonlinear nature of the problem and rapid growth of the size complexity with increasing the number of periods and scenarios, this study is devoted to developing a novel league championship algorithm (LCA) to maximize the portfolio’s mean-variance function subject to different constraints. A Vector Auto Regression model is also developed to estimate the return on risky assets in different time periods and to simulate different scenarios of the rate of return accordingly. Besides, we proved a valid upper bound of the objective function based on the idea of using surrogate relaxation of constraints. Our computational results based on sample data collected from S&P 500 and 10-year T. Bond indices indicate that the quality of portfolios, in terms of the mean-variance measure, obtained by LCA is 10 to 20 percent better than those of the commercial software. This sounds promising that our method can be a suitable tool for solving a variety of portfolio optimization problems.Sat, 15 Sep 2018 19:30:00 +0100An Optimal Control Strategy for Parallel Hybrid Electric Vehicles
http://scientiairanica.sharif.edu/article_20996_0.html
This paper proposes a new power management strategy (PMS) for parallel hybrid electric vehicles equipped with continuously variable transmission (CVT). The proposed PMS is established on the basis of electric assist control strategy (EACS) and equivalent consumption minimization strategy (ECMS). This control approach is based on maintaining the battery energy within a recommended range, considering the CVT efficiency in selecting the engine operating point, and finding the best power split between the engine and electric motor at certain moments of the driving. In order to evaluate the effectiveness of this scheme, it is compared with EACS, a modified version of EACS and ECMS. It is shown that, in all of the studied driving cycles, the proposed PMS is superior to the considered rival strategies in terms of the fuel consumption and also HC and CO emissions.Sat, 15 Sep 2018 19:30:00 +0100Soret and Dufour effects on doubly diffusive convection of nanofluid over a wedge in the ...
http://scientiairanica.sharif.edu/article_20997_0.html
This paper is devoted to investigate the influences of thermal radiation, Dufour and Soret effects on doubly diffusive convective heat transfer of nanoliquid over a wedge in the presence of wall suction. The governing equations are transformed to nonlinear ordinary differential equations using similarity transformation. The resulting system is solved numerically using fourth-order Runge-Kutta-Gill method with shooting technique and Newton-Raphson method. The solutions are expressed in terms of velocity, temperature, solutal concentration and volume fraction profiles. The effects of pertinent parameters entering into the problem such as wedge angle, thermal radiation, Brownian motion, thermophoresis, Soret and Dufour numbers on the skin friction coefficient, local Nusselt number and local Sherwood number are discussed in detail.Sat, 15 Sep 2018 19:30:00 +0100Two sufficient conditions for the existence of path factors in graphs
http://scientiairanica.sharif.edu/article_21010_0.html
A graph G is called a (P≥n, k)-factor critical graph if G − U has a P≥ n -factor for any U ⊆ V(G) with|U|=k. A graphG is called a (P≥n, m)-factor deleted graph if.............Sun, 16 Sep 2018 19:30:00 +0100A new image enhancement method considering both dynamic range and color constancy
http://scientiairanica.sharif.edu/article_21011_0.html
This paper proposes an approach to improve color images suffering from low dynamic range, by employing both histogram matching and histogram stretching techniques. Firstly, the color image is transformed from RGB into HSV color space, in which the color information is separated from intensity. Then, an appropriate reference image is selected by comparing component V of the enhancing image with component V of the data base images using a similarity measure. This selected image is used as the goal image in histogram matching algorithm in order to enhance image brightness (Automatic Histogram Matching). Secondly, components V and S are linearly stretched in order to recover the image color information. Finally, using the treated V and S components and untreated component of H, the enhanced image is obtained in RGB color space by inverse transform. The qualitative and quantitative results show that the contrast and color of resultant images are greatly improved using the proposed method, which outperforms the current state-of-the-art methods.Sun, 16 Sep 2018 19:30:00 +0100An Analytical Study on Mechanical Behavior of Human Arteries – A Nonlinear Elastic Double ...
http://scientiairanica.sharif.edu/article_21012_0.html
The focus of this article is on analytical solution for stress and deformation of human arteries. The artery is considered as a long homogeneous isotropic cylinder. Hyperelastic, incompressible stress-strain behavior is used by adopting a classical Mooney-Rivlin material model. The elastic constants of the arteries are calculated by using the reported results of biaxial test. The analysis is based on both single and double layer arterial wall models and. Radial and circumferential stress distribution on the minimum and maximum blood pressure is calculated. Variation of radii due to internal pressure within the arteries is found which is in a good accordance with the experimental results. The results containing the changes in diameter and thickness together with the stress distribution for both single and double layer models have been plotted. It is shown that the major difference between the single and double layer models is in their stress distributions. The circumferential stress distribution for different human’s ages is plotted which shows that the stress increases by increasing the age due to decreasing the flexibility of the artery. It is also shown that despite the artery’s inner layer is softer than the outer layer, the maximum stresses occur at the inner layer.Sun, 16 Sep 2018 19:30:00 +0100Numerical and experimental investigation of impinging turbulent flow of twin jets against a wall
http://scientiairanica.sharif.edu/article_21013_0.html
In the present study, impinging of vertical twin jet against a horizontal plate is numerically and experimentally investigated. Four two equation RANS based turbulence models are used and their capabilities to simulate such complicated turbulent flow were examined. The two fluid jets are separated by a thin membrane. The inlet jet hydraulic diameters are the same and the Reynolds number of external flows of jets is 13500. The ratio of width of nozzles (e) to nozzle-to-plate distance (H) considered as 1:10. The turbulent models used in this work are k-ε, k-ε RNG, k-ω and k-ω SST. The results obtained by the models were compared with each other as well as two-dimensional PIV data to evaluate the capabilities of such models for this kind of flows. By comparing the numerical and experimental results, it is concluded that all of the models can predict acceptable results in the free jet area, but in the near wall region none of the models can predict flow characteristics with reasonable accuracy. It was observed that, at low nozzle-to-plate distances, the prediction results of the turbulence models are approximately in accordance with the experimental data, particularly for a zone near the midline separating the two jets.Sun, 16 Sep 2018 19:30:00 +0100Optimal Production Inventory Decision with Learning and Fatigue Behavioral Effect in Labor ...
http://scientiairanica.sharif.edu/article_21014_0.html
Behavioral economic has received much attention recently. Learning and fatigue are two typical behavioral phenomena in industrial production operation processes. The existence of learning and fatigue result in a dynamic change in productivity. In this paper, a classical economic production quantity model is extended to consider the behavioral economic value of learning and fatigue. Based on a real case study, each production cycle is divided into five phases, i.e, the learning phase, stable phase, fatigue phase, fatigue recovery (rest) phase, and the relearning phase. The new production inventory decision model is incorporated with dynamic productivity and learning-stable-fatigue-recovery effect. Numerical simulation and sensitivity analysis show that appropriate rest alleviates employees fatigue and increases productivity, resulting in a lower average production cost. On the other hand, when the rest time is too high, exceeding a certain value, it leads to the decline of the actual labor productivity, resulting in an increase in the average cost of the system.Sun, 16 Sep 2018 19:30:00 +0100Flood hazard risk evaluation using fuzzy logic and weightage based combination methods in ...
http://scientiairanica.sharif.edu/article_21037_0.html
This study addresses the crucial variables contributing highly to the risk of flooding based on the flood characteristics of the Waverly region and develop a fuzzy logic and geographic information based urban flood map with flood zones in Waverly City, Iowa. The methodology emphasizes on weighting crucial variables using spatial analyst tools and fuzzy logic based GIS mapping. Local elevation, distance from Cedar River, land use and population density in Waverly city are recognized as effective variables to risk of flooding in Waverly city. Twenty three calibration tests for determination of weightages of these variables on the risk of flood were performed and compared to previously produced Waverly flood risk maps. Finally, weightages of these variables were assigned as 70 % for elevation, 20 % for distance from Cedar River, 5 % for Manning’s coefficient, and 5 % for population density. In a fuzzy environment they were assigned different fuzzy membership functions, for elevation, fuzzification technique Small was used, for distance, fuzzification technique MS Small was used, for Manning’s coefficient and population density, fuzzification technique Large was used. The flood hazard maps created were overlaid with 100 and 500-year flood maps of Waverly city for calibration and risk evaluation.Sat, 22 Sep 2018 20:30:00 +0100Localizing Exception Faults in Android Applications
http://scientiairanica.sharif.edu/article_21040_0.html
In software programs, most of the time, there is a chance of faults in general, and exception faults in particular. Localizing those pieces of code which are responsible for a particular fault is one of the most complicated tasks and it can make incorrect results if done manually. Semi-automated and fully-automated techniques have been introduced to overcome this issue. However, despite recent advances in fault localization techniques, they are not necessarily applicable to Android applications because of their special characteristics like context-awareness, use of sensors, being executable on various mobile devices, limited hardware resources, and so on. To this aim, in this paper, we introduce a semi-automated hybrid method that combines static and dynamic analysis to localize exception faults in Android applications. Our evaluations with a number of open source Android applications of different sizes with various exceptions show that our proposed technique can correctly identify the root causes of occurred exceptions. These results indicate that our proposed approach is effective in practice in localizing exception faults in Android applications.Sun, 23 Sep 2018 20:30:00 +0100The Effect of Processing Time on Microstructure of Surface and Corrosion Resistance of Coatings ...
http://scientiairanica.sharif.edu/article_21041_0.html
In this study, the effect of coating processing time on microstructure of surface and corrosion resistance of coatings resulted by plasma electrolytic oxidation (PEO) was investigated on substrate of TiAl6V4 alloy. The coating processes in hydroxyapatite nano-powder electrolytic were carried out in same conditions of constant voltage of 600V and three different times of 125, 250 and 350 seconds. Studying the microstructure of coatings identified that the coating formed in 125 (s) had more compact and steady structure with fine surface cavities and less porosity. X-ray diffraction pattern of coating demonstrates that this coating is consists of oxide phases of titanium (rutile and anatase) and hydroxyapatite. Also, the study of corrosion resistance of coatings by Potentiodynamic polarization and electrochemical impedance spectroscopy in corrosive solution of chloride sodium 3.5% showed that the coating formed in 125 s has the most noble corrosion resitance potential and the least ICorr and finally the highest resistance to corrosion.Sun, 23 Sep 2018 20:30:00 +0100Improvement of Dissipative Particle Dynamics method by taking into account the particle size
http://scientiairanica.sharif.edu/article_21042_0.html
In this paper, flow past a single Dissipative Particle Dynamics (DPD) particle with low Reynolds number is investigated and it is inquired that whether a single DPD particle immersed in a fluid, has an intrinsic size. Then a minimum length scale is determined such that the hydrodynamic behavior based on standard DPD formulation is modeled correctly. Almost all of the previous studies assume the DPD particles as point centers of repulsion with no intrinsic size. Hence to prescribe the size of a simulating sphere, a structure of frozen DPD particles is created. In this paper two effective radii, Stokes-Einstein radius and a radius based on the Stokes law, for DPD particles are introduced. For small Reynolds numbers; it is proved that the two radii approach each other. Finally in spite of the typical simulations which assume DPD particles as point centers of repulsion, it is concluded that each of the individual DPD particles interact with other particles as a sphere with non-zero radius. It results the reduction of the required number of particles and eventuates more economical simulations. Moreover contemplating the radius of the particles is necessary for the new Low-Dimensional model which is derived based on the DPD method.Mon, 24 Sep 2018 20:30:00 +0100The Perils of Group Purchasing in a Competing Supply Chain
http://scientiairanica.sharif.edu/article_21043_0.html
Group purchasing organizations (GPOs) are well-known intermediary firms that play an important role in some supply chains. An important question that arises regarding the GPOs, is whether a GPO that benefits from group buying discounts, always benefit the OEMs in the presence of market competition. In other words, does a GPO always lead to a win-win outcome for OEMs and the GPO? To answer this question, a bargaining framework has been used to investigate competing OEMs' procurement's strategies. The entrance of a GPO in a two tier supply chain that consists of two competing OEMs with a common supplier that has a quantity discount menu is analyzed. The result shows that low purchasing cost GPO may harm OEMs in a cost-benefit perspective. This unintuitive result can be explained by different impacts that a GPO has in purchasing process. Although, it can enlarge the size of trade surplus; but, it has an important influence on the size of the slice of the pie (profit sharing). Moreover, an OEM's procurement strategy in equilibrium not just only depends on his bargaining power; but also depends on his competitor OEM. Interestingly, a strong OEM may not prefer procuring through GPO, as well as a weak OEM does.Mon, 24 Sep 2018 20:30:00 +0100Adaptive Control of a Cable-Actuated Parallel Manipulator Mounted on a Platform with ...
http://scientiairanica.sharif.edu/article_21046_0.html
Cable-actuated parallel Manipulators (CPMs) are widely employed for object handling applications. In order to displace the carried object along the ground to an unlimited distance, the CPMs can be mounted on wheeled mobile robots (WMRs). The derivation of the dynamic equations of motion for this integrated system is presented using Lagrange method. Since in load carrying task, the inertia of the moving load is the main source of uncertainty, an adaptive control approach is considered for the CPM, whereas the WMR uses a feedback linearized sliding mode approach. In order to maintain the end-effector of the CPM in within its relative workspace in the WMR frame, the convergence rate in the two controllers should be similar. Decentralization of the control law can be accomplished if the inertia of the CPM motors are negligible compared with the other inertias of the system. This assumption is shown to be applicable if an introduced index is small enough to have noticeable effect on the tracking error.
Sun, 30 Sep 2018 20:30:00 +0100Reliable Hierarchical Multimodal Hub Location Problem: Models and Lagrangian Relaxation Algorithm
http://scientiairanica.sharif.edu/article_21047_0.html
Hub facility location problems involve the establishment of strategic hub facilities and allocation of demand nodes to them. Meanwhile, with the emergence of new transport and distribution networks with multi-level structures, the design of such networks has been evolved. The diversity in transportation system has added multimodality to these problems. Considering the strategic nature and long-term implications of decision-making in this field, the decisions shall be of high reliability. The present study is an attempt to consider reliability of communication paths in proportion to the volume of transaction through them while covering all of the above-mentioned issues in hub location problems at the same time. Incorporating hierarchical characteristics of the problem into the model, one can obtained a significantly enhanced model in terms of multimodality and reliability. A Lagrangian solution method was developed considering the strategic level of the problem and the importance of the solution accuracy. The model was then validated in terms of time and quality.Mon, 01 Oct 2018 20:30:00 +0100Agricultural tractors of the fifth generation
http://scientiairanica.sharif.edu/article_21048_0.html
The article deals with the problem of substantiation of mobile power units (MPU) – tractors for agriculture of the fifth generation. This issue is quite relevant. The main purpose of the work is to analyze agricultural tractors of the fifth generation. The authors formulated the main requirements for the ecological balance of the technogenic interaction of MPUs with production processes in agro-ecosystems of grain production in the zonal conditions of South-Russian arid agriculture. Proposals for the creation of new MPUs have been developed; the technological structures of machine aggregates based on the MPU of the fifth generation of classes 3, 5-6 and 8 that determined the technical schemes of the named MPU were determined. Analytical models for calculating the power characteristics of MPU of the named classes in deterministic and stochastic modes in relation to the most energy-intensive operations with definitions of the mathematical expectations of MTA’s power and performance. Also, an analysis of the MTAs effectiveness based on new MPUs upon criterion of the time spent on cultivating crop rotations on the examples of peasant farms and agricultural organizations (APC, CAE, etc.)Fri, 05 Oct 2018 20:30:00 +0100Evaluation of the response modification factor of RC structures constructed with Bubble Deck system
http://scientiairanica.sharif.edu/article_21050_0.html
As the concrete material is eliminated from the locations situated around the middle of the cross-sections of bubble decks (BDs), the BD type slabs are lighter than the traditional slabs. In the recent researches, the response modification factor (RMF) is generally determined for the reinforced concrete (RC) structures with the moment-resisting frame (MRF) and dual systems. The dual system comprise mainly the MRF with shear wall (MRFSW), as well as the flat slab having chiefly the BD system. In this paper, the evaluation of values of the RMF of RC structures using BD system are submitted. The obtained results indicate that the lateral strengths of buildings increase by increasing the span length to story height ratio (L/H). Besides, the variations of the span length and the number of the story have more effects than the variation of the usage category buildings on the RMF of structures. Furthermore, the span length has more effect than the number of stories in determining RMF in an MRF. Finally, amongst the building with dual system structures including MRFSW, the low-rise building structures have an RMF equal to 5, and both the mid-rise and high-rise building structures have an RMF of 7.Sat, 06 Oct 2018 20:30:00 +0100Using multivariate analysis approaches in designing NSBM Model with considering undesirable ...
http://scientiairanica.sharif.edu/article_21053_0.html
Due to the competitiveness of banking industry and increasing bargaining power of customers, evaluation of the banks’ performance is crucial to better serve the classified customers in a universal system .In this paper, with consideration of segmenting the customers into personal and business ones, methods such as confirmatory factor analysis (CFA) and structural equation model (SEM) have been used in selecting appropriate variables of the network data envelopment analysis (NDEA) model based on network slacks-based measure and consideration of the undesirable variables and shared resources. The SEM model has been used to establish a proper connection between the different dimension of the NDEA model and CFA model has been used to identify the importance of each dimension. Also, the proposed model has been used to measure the Operational and decomposed universal efficiency of one of the Iranian bank branches (Day Bank). The results show that the extracted model provides managers with a suitable perspective in adopting appropriate policies to promote their performance in the different sectors, including deposit attraction, financial serving personal and business banking customers, and profit generation, and also in comparing them in the different dimensions of the model.Sun, 07 Oct 2018 20:30:00 +0100A novel assessment approach for EFQM driven institutionalization using integrated fuzzy ...
http://scientiairanica.sharif.edu/article_21058_0.html
It is becoming increasingly difficult for enterprises to survive under competitive conditions. Enterprises with high levels of institutionalization are able to survive and benefit more advantages than their competitors. Excellence models are widespread tools for measuring the degree of institutionalization of enterprises. The importance of institutionalization has been increasingly considered in excellence models. EFQM (European Foundation for Quality Management) is a suitable tool to show how successful organizations are in terms of institutionalization. In this study, EFQM criteria are evaluated with fuzzy multi-criteria decision-making techniques. The fuzzy DEMATEL method is used to determine the interactions amongst main EFQM criteria. According to the relationship diagram obtained from the Fuzzy DEMATEL method, the weights of the sub criteria are calculated according to the expert evaluations using Fuzzy Analytic Network Process (FANP) method. The criterion “Business Results” has been determined to be the most important criteria. The criteria weights are taken as input for the VIKOR method. The institutional scores obtained by the proposed method, and the scores given by the EFQM evaluators to the institutions, are statistically analyzed to demonstrate that the proposed method has produced meaningful results.Sun, 14 Oct 2018 20:30:00 +0100Benders Decomposition Algorithm for Robust Aggregate Production Planning Considering Pricing ...
http://scientiairanica.sharif.edu/article_21059_0.html
In operations research, bi-level programming is a mathematical modeling which has another optimization problem as a constraint. In the present research, regarding the current intense competition among large manufacturing companies for achieving a greater market share, a bi-level robust optimization model is developed as a leader-follower problem using Stackelberg game in the field of aggregate production planning (APP). The leader company with higher influence intends to produce new products, which can replace the existing products. The follower companies, as rivals, are also seeking more sales, but they do not have the intention and ability to produce such new products. The price of the new products is determined by the presented elasticity relations between the uncertain demand and price. After linearization, using the KKT conditions, the bi-level robust model is transformed into an ordinary uni-level model. Due to the NP-hard nature of the problem, Benders decomposition algorithm (BDA) is proposed for overcoming the computational complexities in large scale. Finally, using the real data of Sarvestan Sepahan Co as a leader company, the validity of the developed model as well as efficiency and convergence of the BDA are investigated. The computational results clearly show the efficiency and effectiveness of the proposed BDA.Sun, 14 Oct 2018 20:30:00 +0100Residual strain in graphene: study of temperature and crack effect
http://scientiairanica.sharif.edu/article_21060_0.html
Graphene is a thin sheet with special properties and complicated mechanical behavior. It’s important to study graphene experimentally and theoretically. Stone–Wales defects, cracks and atom vacancy are popular defects in carbon allotropes especially in graphene. In this paper, residual strain in graphene was discussed. At first, stress-strain curve of non-defected graphene sheet was obtained using molecular dynamics simulation and effect of temperature on mechanical properties of graphene was obtained. Then, four different cracks were considered in center of graphene sheets. Stress-strain curves of defected graphene sheets with different tension strain rates were plotted. The results showed that cracks lead to the graphene to fracture sooner. Also, increasing temperature lead to the Young’s modulus of graphene decreases and graphene fractured at lower strain. On the other hand, residual strain of non-defected and cracked graphene increased by increasing temperature from 200 K to 1200 K. It means that graphene had more plasticity behavior by increasing temperature.Sun, 14 Oct 2018 20:30:00 +0100Multi-Period Configuration of Forward and Reverse Integrated Supply Chain Networks with the ...
http://scientiairanica.sharif.edu/article_21061_0.html
Today’s competitive business environment has resulted in increasing attention to social responsibilities and customer’s attitudes. Buying and returning have become a common practice for different reasons, including incompleteness or immature failure of the product or its failure to meet the customer’s satisfaction. Before the buying and returning cycle can be handled appropriately, companies need a proper logistics network designed following a proper design strategic. In the present research, a forward and reverse logistics network is proposed for product distribution and collection. The contribution of this paper to the literature is the proposal of a multi-period, multi-echelon, integrated forward and reverse supply chain network design problem with transportation mode selection considered. Different kinds of decisions including the determination of optimum number and locations of facilities, facilities opening time and transportation mode selection among different facilities have been considered in this paper. Due to multi-period nature of the problem, the problem is flexible for future periods. A new mixed integer nonlinear programming model was proposed for the introduced problem considering different levels of facility capacities with the maximum profit objective function. As another contribution, a genetic algorithm was developed to cope with problem’s complexity when the problem size goes large.Sun, 14 Oct 2018 20:30:00 +0100A New Model for Prediction of Liquid Holdup in Two-Phase Flow under Higher Gas and Liquid Velocities
http://scientiairanica.sharif.edu/article_21062_0.html
Existing liquid holdup models are generally based on low gas and liquid velocities. In order to extend the applicable range of existing liquid holdup prediction models and improve its prediction accuracy, a of gas-liquid two-phase flow experiment was carried out using a pipe of inner diameter 60mm and length of 11.5m. The superficial gas and liquid velocity ranges were 14.07~56.50m/s and 0.205~1.426m/s, respectively. The results indicate that the liquid holdup decreases with the increase of the superficial gas velocity and increases with the increase of the superficial liquid velocity. A new annular flow model for calculating low liquid holdup in horizontal pipe was developed and presented considering the relationships between the friction factor ratio of liquid phase and gas-liquid interface as well as the superficial Reynolds number of gas and liquid. The predictions of the model are found to be accurate with an average absolute error of 4.8%. Further, on the basis of the Beggs-Brill model and the horizontal pipe model established in this paper, a new liquid holdup model for different angles was given. It was observed the resultant model is also accurate, and has an average absolute error of 10%.Sun, 14 Oct 2018 20:30:00 +0100A Novel Fuzzy Multi-Objective Method for Supplier Selection and Order Allocation Problem Using ...
http://scientiairanica.sharif.edu/article_21063_0.html
This paper introduces a supplier selection and order allocation problem in a single-buyer-multi-supplier supply chain in which appropriate suppliers are selected and orders allocated to them. Transportation costs, quantity discount, fuzzy type uncertainty and some practical constraints are taken into account in the problem. The problem is formulated as a bi-objective model to minimize annual supply chain costs and to maximize the annual purchasing value. The fuzzy weights of suppliers, which are the output of one of the supplier evaluation methods, are considered in the second objective function. Then, we propose a novel fuzzy multi-objective programming method for obtaining Pareto solutions. The method is the extension of a single-objective method exist in the literature. This method is based on the decision maker's degree of satisfaction from each fuzzy objectives considering the fulfillment level of fuzzy constraints. In the proposed method, the problem remains multi-objective and, unlike existing methods, does not transformed into a single-objective model. At the last stage of proposed method, the fuzzy results are compared with an index, and decision maker can identify the appropriate or inappropriate solutions. To solve the problem, non-dominated sorting genetic algorithm (NSGA II) is designed and computational results are presented using numerical examples.Sun, 14 Oct 2018 20:30:00 +0100A Comparative Study of Economic Load Dispatch using Sine Cosine Algorithm
http://scientiairanica.sharif.edu/article_21064_0.html
Economic Load Dispatch (ELD) is an important part of cost minimization procedure in power system operation. Different derivative and probabilistic methods are used to solve ELD problems. This paper proposes a powerful Sine Cosine Algorithm (SCA) to explain the ELD issue including equality and inequality restrictions. The main aim of ELD is to satisfy the entire electric load at minimum cost. The SCA is a population based probabilistic method which guides its search agents that are randomly placed in the search space, towards an optimal point using their fitness function and also keeps a track of the best solution achieved by each search agent. SCA is being used to solve the ELD problem with their high exploration and local optima escaping technique. This algorithm confirms that the promising areas of the search space are exploited to have a smooth transition from exploration to exploitation using sine and cosine functions. Simulation results prove that the proposed algorithm surpasses other existing optimization techniques in terms quality of solution obtained and computational efficiency. The final results also prove the robustness of the SCA.Sun, 14 Oct 2018 20:30:00 +0100QUASI-OPPOSITIONAL SYMBIOTIC ORGANISMS SEARCH ALGORITHM FOR DIFFERENT ECONOMIC LOAD DISPATCH ...
http://scientiairanica.sharif.edu/article_21065_0.html
In this paper, an effective meta-heuristic technique called Quasi-Oppositional Symbiotic Organisms Search is applied for solving non-convex economic dispatch problems. Symbiotic Organisms Search is a soft computing technique, inspired by organisms in the ecosystem. This technique is implemented for improving the solution quality in minimum time. In order to improve convergence rate, quasi-reflected numbers are used here instead of pseudo-random numbers. Different equality and inequality constraints such as transmission loss, load demand, prohibited operating zone, generator operating limits and boundary of ramp rate are considered here. Presence of multiple fuels and valve point are also considered in some cases. This algorithm is applied to four different test systems. Simulation results are compared with many recently developed optimization techniques to show the superiority and consistency of this method. Simulation results also show that the computational efficiency of this algorithm is much better than the other meta-heuristic methods available in the literature.Sun, 14 Oct 2018 20:30:00 +0100Natural convection of CNT-water nanofluid in an annular space between confocal elliptic ...
http://scientiairanica.sharif.edu/article_21069_0.html
In this paper, free convection heat transfer in an annulus between confocal elliptic cylinders filled with CNT-water nanofluid is investigated numerically. The inner cylinder is at constant surface heat flux while the outer wall is isothermally cooled. Equations of continuity, momentum and energy are formulated using the dimensionless form in elliptic coordinates for two-dimensional, laminar and incompressible flow under steady state condition, which is expressed in terms of vorticity and stream function. The governing equations are discretized using the control volume method. For the thermo-physical properties of CNTs, empirical correlations are used in terms of the volume fraction of nanoparticles. For the effective thermal conductivity of CNTs, a new model has been used. The study is performed for modified Rayleigh number (103≤ Ram ≤106), volume fraction of nanoparticles (0≤ f ≤0.12). The eccentricity of the inner and outer ellipses and the angle of orientation are fixed at 0.9, 0.6 and 0°, respectively. Results are presented in the form of streamlines, isotherm contours, and distribution of temperature and local and average Nusselt numbers on solid boundaries. The results are also discussed in detail and a very good agreement exists between the present results and those from the literature.Fri, 19 Oct 2018 20:30:00 +0100The Effect of Various Curing Temperatures on Engineering Properties of Chemically Grouted Sands
http://scientiairanica.sharif.edu/article_21070_0.html
In this experimental study, the effect of curing temperature on the engineering properties of sand samples grouted with sodium silicate-glyoxal was investigated. The experiments were started with determination of the gelation times, viscosities and syneresis percentages of the blends prepared for injection, after which the injection experiments were then carried out at the determined mixing ratios. Grouted specimens were subjected to unconfined compressive strength (UCS) and permeability tests being kept at different curing temperatures (+10 °C, +20 °C and +30 °C) in the curing tank. As the temperature was increased, the viscosity values and gelling times decreased, while the syneresis percentages increased. The UCS of the grouted samples decreased with time. This decrease was observed to slow down in the samples kept at +10°C after the 56th day, while the same was on 28th day in those kept at +20°C and on 7th day for those kept at +30 °C. Also, UCS values decreased with the increasing temperature. The permeability values of the grouted samples decreased with time. This decrease has been observed to slow down after the 28th day. The increase in temperature reduced the permeability values.Sun, 21 Oct 2018 20:30:00 +0100Suitability of brick kiln waste as a stabilizer to clayey soils
http://scientiairanica.sharif.edu/article_21071_0.html
Due to increased use of brick masonry for construction of buildings in Pakistan, huge quantities of Brick Kiln Waste (BKW) are generated which not only create disposal problems but are a hazard to the environment. In order to get rid of such problems, it is necessary to investigate suitability of the BKW as a stabilizer to the clayey soils. For this purpose, an experimental program was carried out to stabilize clayey soil with the BKW ranging from 5 to 40%. Basic geotechnical tests were performed on the clayey soil blended with the BKW. The results showed that the clayey soil became coarser and more suitable as a subgrade material with addition of the BKW. There was negligible reduction in dry density up to 7% when the BKW added was 40%. As expected, the cohesion and friction angle of the blended soils respectively decreased and increased with inclusion of the BKW. As compared to the clayey soil, the ultimate bearing capacity of the blended soil having 40% of the BKW increased by 21%. This study shows that clayey soils stabilized with the BKW could be used as a partial fill material for highway embankments and foundations of buildings.Sun, 21 Oct 2018 20:30:00 +0100Uncertainty Quantification in Seismic Collapse Assessment of Iranian Code-Conforming RC Buildings
http://scientiairanica.sharif.edu/article_21072_0.html
Structural collapse is the main concern in the existing structures which are built in the seismic-prone regions. Therefore, the primary goal of the seismic provisions in building codes is to prevent the global collapse. Iran is located in the Alpine-Himalayan belt, and has experienced some of the most destructive earthquakes in the past century. To evaluate the extent to which the Iranian building code provisions meet this objective, the authors have conducted a detailed assessment of collapse risk on a set of moderate moment resisting reinforced concrete (RC) buildings. This study considers P-Delta effects, deterioration in strength and stiffness, and cyclic deterioration in structural components. Structural assessment is performed using OpenSees platform and the multiple-record incremental dynamic analysis (IDA). Results are presented in terms of the IDA capacity curves and the collapse fragility functions at different seismic hazard levels. Results show that probability of instability increases with height of the buildings. Moreover, the collapse confidence level was evaluated considering the available uncertainties. Assuming a minimum confidence level of 90% for the buildings, the collapse prevention limit state under the 2%/50 hazard level is not satisfied for the 9 and 12 story frames, and they need to re-designed.Sun, 21 Oct 2018 20:30:00 +0100Economic efficiency of application of artificial air cooling for normalization of thermal ...
http://scientiairanica.sharif.edu/article_21073_0.html
The work substantiates a technical solution for improving the working conditions for the thermal factor in the extraction of oil by the thermoshaft method using the mine refrigeration technology. The review of manufacturers and technical characteristics of refrigeration technology in Russia, CIS countries and Western Europe was conducted. For the selected set, the economic efficiency of the project was assessed and a conclusion was made about the feasibility of implementing this project solution. It was shown that the use of a water cooling machine in the mine air conditioning system will reduce the air temperature in the oil production gallery to the required values and will allow to abandon the long-term construction of a surface stationary refrigeration station. Normalization of the thermal regime reduces the costs of benefits and compensation for work in harmful labor conditions and improves the quality of service of production wells by operators. The project for the introduction of air conditioning has a high level of profitability, and its payoff will occur in the second year of operation.Sun, 21 Oct 2018 20:30:00 +0100Parameter converting method for bifurcation analysis of nonlinear dynamical systems
http://scientiairanica.sharif.edu/article_21074_0.html
For detecting behavior of a dynamical system, bifurcation analysis is necessary with respect to change in parameters of system. In this work, based on the solution of ordinary differential equations from initial value and parameters, a simple method is presented, which can efficiently reveal different bifurcations of system. In addition to its simplicity, this method does not required to have deep physical and mathematical understanding of the problem, and because of its high precision and the speed of solutions, does not need to reduce the order of models in many complex problems or problems with high degrees of freedom. This method is named parameter converting method (PCM), which has two steps. In the first step the parameter is varied as a function of time and in the second step, time is expressed as inverse of this assumed function. With this method bifurcation and amplitude-frequency diagrams and hidden attractors of some complex dynamics will be analyzed and the sensitivity of the multi potential well systems to initial conditions is studied. With this algorithm, a simple way to find the domain of high-energy orbit in bistable systems is obtained.Sun, 21 Oct 2018 20:30:00 +0100Drivers of Cross-Country Vehicles
http://scientiairanica.sharif.edu/article_21075_0.html
This work offers a new chassis design, namely the wheel-track, represents a mathematical model of this chassis, and also proves the advantage of the proposed design when driving the vehicle on arbitrary terrain - rough off-road. The proposed approach can find application in the design of unmanned research mechanisms for other planets (Mars Rovers, Lunar Rovers etc.), also for design of robots and transport of rescuers at liquidation of consequences of natural or technological disasters. The article presents the analysis of the requirements for the chassis of extraterrestrial research unmanned mechanism demonstrated high compliance of the proposed approach. The analysis of the requirements for the chassis of extraterrestrial research unmanned mechanism demonstrated high compliance of the proposed approach. We proposed and investigated a mathematical model of wheel-track, demonstrated the optimization of the proposed mathematical model to machine computing, demonstrated the flexibility and scalability of the mathematical model. The proposed design is an attempt to combine the advantages of a walking and wheel types of travel in one mechanism.Sun, 21 Oct 2018 20:30:00 +0100Static Performance of Geosynthetic Reinforced Soil Walls with Peripheral Soil–Cement Mixtures
http://scientiairanica.sharif.edu/article_21076_0.html
Recently, much effort has been devoted to improving the performance of geosynthetic reinforced walls under various stress conditions. In this research, the effect of using cemented mixed soil as a backfill material is studied on the static response of geosynthetic reinforced soil (GRS) walls. For this, numerical models based on a finite-difference code are made according to one of the Royal Military College’s (RMC) full scale test walls with a segmental facing. Different arrangements of soil reinforcement are considered in the presence of cemented sandy soil and sandy soil alone. In the cement-treated approach, each reinforcement layer is surrounded by a 30 cm cemented sand soil. The results show that using cement-treated sandy soil decreases the maximum deformation of the wall by as much as 75% compared with the case where untreated sandy soil is used. Moreover, by using cemented soil around reinforcements, the reinforcement forces reduce considerably. Therefore, increasing the number of reinforcement layers in the backfill will decrease the face wall deformation as well as the reinforcement forces, which are not cost-effective in many situations. It is also suggested that using the cement-treated technique can be an efficient cost-saving method compared with common GRS walls.Sun, 21 Oct 2018 20:30:00 +0100Optimization of embedded rail slab track with respect to the environmental vibrations
http://scientiairanica.sharif.edu/article_21077_0.html
This paper is geared toward selection of the trough geometry (width and height) and elastic surrounding materials (elasticity modulus) as the optimization parameters along with selection of minimum environmental vibrations in the critical point of pavement system. The optimum trough geometry and specification of surrounding materials were evaluated as the objective function .To this, a numerical finite element model of embedded slab track rail system was developed in consideration of the components of the substructure and superstructure of system under the plain strain conditions. In the first stepf, the numerical model was calibrated by comparing it with static lab results. In the next step, the vibration behavior was investigated after applying a harmonic load to the system at various amplitudes and frequencies corresponding to the real operation conditions. Maximum velocity of particles vibrations was evaluated at different points in the vertical direction, and the critical point of pavement determined. Then, the best trough section and elasticity modulus of surrounding materials corresponding to the load amplitude and frequency were determined by designing the experiments using the surface response method and limiting the maximum vibrations of critical points to 65 Decibel.Sun, 21 Oct 2018 20:30:00 +0100Determination of Optimum Cross Section of Earth Dams Using Ant Colony Optimization Algorithm
http://scientiairanica.sharif.edu/article_21078_0.html
Earth Dams are one of the most important and expensive civil engineering structures to which a considerable amount of budget is allocated. Their construction costs are mainly related to the size of embankments, which in turn depends on their cross section area. Therefore, reductions in cross section areas of earth dams would cause decreases in embankment volumes leading to a significant reduction in the construction cost of these structures. On the other hand, it is almost impossible to obtain optimum cross section in earth dams with desired stability and acceptable operational dimensions using traditional design methods. In this paper, ant colony optimization algorithm (ACO), a well-known and powerful metaheuristic method used to tackle problems in geotechnical engineering, was used to solve this complicated problem. The results showed that applying ideal and optimum slope and berm arrangements resulted from ACO in designing embankments and earth dams with different heights could lead to decreases in embankment volumes compared to those without any berms or those with berms resulting from usual designs with trial and error.Sun, 21 Oct 2018 20:30:00 +0100A New Approach to Improve Durability of Rice Husk Ash Blended Concrete with Re-Dispersible ...
http://scientiairanica.sharif.edu/article_21079_0.html
An experimental investigation was conducted to improve the limitation of Rice Husk Ash (RHA) blended concrete in terms of durability, by incorporating Re-dispersible Polymer Powder. To examine durability properties of Rice Husk Ash Polymer-Modified Concrete (RHAPMC) matrix, the RHAPMC mix of 1:2:3 proportions was used to prepare the specimens. To prepare Rice Husk Ash-Modified Mix (RHAMM), 10% of RHA was replaced with cement. RHAPMC was made with the inclusion of polymer at the ratio of 1 to 7.5% by the weight of cement. Most common durability related properties, i.e. water absorption, density, water permeability, ultrasonic pulse velocity and compressive strength were experimentally investigated. The results showed a remarkable improvement in durability characteristics in newly developed matrix of rice husk ash polymer modified concrete and could be used as a repair material in aggressive environment.Sun, 21 Oct 2018 20:30:00 +0100Numerical evaluation of the operating room ventilation performance: ultra-clean ventilation ...
http://scientiairanica.sharif.edu/article_21083_0.html
The surgical site infection (SSI) is one of the most important infectious problems in hospitals which may be happened in 2.6% of all surgeries. According to the literature, the primary source of SSI is the flakes released from the exposed skin of surgical staffs or patients. It is well known that appropriate ventilation strategy is the most effective way to control bacteria-carrying airborne particles responsible for SSI. In this research, the effect of the most dominant design parameter, namely inlet air velocity, on the ultra-clean ventilation (UVC) systems performance is evaluated in detail using the computational fluid dynamics (CFD). The results show an optimum value for the inlet air velocity which is mainly due to formation of a thermal plume over the wound tissue. This thermal plume protects the wound from contaminants deposition like a shield and may be disturbed at too high inlet air velocity. In addition, the effect of critical factors including the particle size the wound temperature, the operating lights boundary condition, and the existence of fixed and removable partitions on the optimum inlet air velocity is also investigated and discussed extensively.Sat, 27 Oct 2018 20:30:00 +0100A POMDP framework to find Optimal Policy in Sustainable Maintenance
http://scientiairanica.sharif.edu/article_21084_0.html
The increasing importance of these two subjects, maintenance and cleaner environment, beside the relations between them, encourages us to investigate a mathematical Markovian model for Condition Based Maintenance problem while considering environmental effects. In this paper, the problem of proposing maintenance optimal policy for a partially observable, stochastically deteriorating system is studied, in order to maximize the average profit of the system with consideration of sustainability aspects. The modeling of this Condition Based Sustainable Maintenance (CBSM) problem is done using mathematical methods such as Partially Observable Markov Decision Process (POMDP) and Bayesian theory. A new exact method named Accelerated Vector Pruning method and other popular estimating and exact methods are applied and compared in solving the presented CBSM model and several managerial conclusions were obtained.Sat, 27 Oct 2018 20:30:00 +0100On designing CUSUM charts using ratio-type estimators for monitoring the location of normal ...
http://scientiairanica.sharif.edu/article_21085_0.html
Control chart is one of the important tools in statistical process control (SPC) that plays a significant role in monitoring and identifying disturbances of any production process. The Shewhart, cumulative sum (CUSUM) and exponentially weighted moving average (EWMA) are commonly used control charts for detecting process shifts. CUSUM and EWMA chart are more sensitive in detecting smaller shifts whereas the typical Shewhart chart is known to be only sensitive to large process shifts. The present study incorporates ratio-type estimators based on auxiliary information in CUSUM structure as a substitute of simple mean estimator for monitoring process location. These estimators are more efficient than the simple mean estimator in the presence of high correlation between the study and the auxiliary variables. Average run length (ARL), standard deviation of run length (SDRL) and extra quadratic loss (EQL) are used to measure the performances of the proposed charts. The performance comparison of the proposed chart with the existing CUSUM, CUSUM-FIR and many other control charts are made by using out-of-control ARL. The comparison revealed the superiority of the suggested charts over the other existing charts. An illustrative example is also provided for the performance evaluation of the proposed charts.Sat, 27 Oct 2018 20:30:00 +0100Investigating the behavior factor of coupled concrete shear walls with steel coupling beam
http://scientiairanica.sharif.edu/article_21086_0.html
The behavior factor is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural properties. The more accurate this parameter is estimated, the more exact responses of the structures will be obtained. Recently, coupled walls with steel coupling beams are extensively utilized as an efficient system against lateral forces in high-rise buildings. But, there is not enough information about the behavior of these walls during earthquake, and design codes have not suggested any behavior factor for this structural system. Consequently, this paper is devoted to find the behavior factor of this structural system. To achieve this goal, six-, twelve- and twenty-story buildings are assessed. Except for the number of stories, all characteristics of these buildings are completely similar. Buidlings’ height, the length of the coupling beams and the coupling ratio are key parameters which influence the behavior factor of the aforesaid structural system. In this work, the effect of these parameters on this factor are studied.Sat, 27 Oct 2018 20:30:00 +0100Utilizing new spherical Hankel shape functions to reformulate the deflection, free vibration, ...
http://scientiairanica.sharif.edu/article_21087_0.html
In this study, a new class of shape functions, namely spherical Hankel shape functions, are derived and applied to reformulate the deflection, free vibration, and buckling of Mindlin plates based on finite element method (FEM). In this way, adding polynomial terms to the functional expansion, in which just spherical Hankel radial basis functions (RBFs) are used, leads to obtaining spherical Hankel shape functions. Accordingly, the employment of polynomial and spherical Bessel function fields together results in achieving more robustness and effectiveness. Spherical Hankel shape functions benefit from some useful properties, including infinite piecewise continuity, partition of unity, and Kronecker delta property. In the end, the accuracy of the proposed formulation is investigated through several numerical examples for which the same degrees of freedom are selected in both the presented formulation and the classical finite element method. Finally, it can be concluded that a higher accuracy is reachable by utilizing spherical Hankel shape functions in comparison with the Lagrangian FEM.Sat, 27 Oct 2018 20:30:00 +0100MCM-41-SO3H: as an efficient reusable Nano-ordered heterogeneous catalyst for the synthesis of ...
http://scientiairanica.sharif.edu/article_21088_0.html
An improved and efficient method for the synthesis of 1- & 5-substituted 1H-tetrazole derivatives has been described in the presence of nano-ordered MCM-41-SO3H as an effective heterogeneous catalyst. This metal-free protocol, [2+3] cycloaddition of sodium azide to various nitriles or ethyl N-phenyl formimidate intermediate under mild reaction conditions, afford a wide range of 1H-tetrazoles in good to excellent yields. The catalyst was reused for five times without significant loss of catalytic activity.Sat, 27 Oct 2018 20:30:00 +0100Application of Endurance Time Method in Seismic Analysis of Bridges
http://scientiairanica.sharif.edu/article_21089_0.html
In this paper, the application of Endurance Time method in seismic analysis of bridges is explained. The Endurance Time method is a novel seismic analysis method based on time history analysis in which a structure is subjected to a predefined intensifying acceleration function. First, six concrete bridges were modeled. Three Endurance Time acceleration functions were applied to the models and the average of the responses were calculated. Next, the time history analysis was conducted using seven real accelerograms scaled using the method recommended by FHWA 2006 to be compatible with the design spectrum of seismic AASHTO guideline for a site with soil type C in Berkeley, California. The average of the responses of these seven analyses is considered as reference. Scaling the mentioned accelerograms over a wide range of hazard levels, Incremental dynamic analysis is performed. Finally, the comparison of the response of ET and time history analysis and also comparison of ETA with IDA curves reveals good agreement. The major advantage of ET method over time history and IDA methods is less computational effort needed for the analysis. This saving in time is resulted due to the possibility of predicting response by fewer analyses despite maintaining the necessary accuracy.Sat, 27 Oct 2018 20:30:00 +0100Application of AG method and its improvement to nonlinear damped oscillators
http://scientiairanica.sharif.edu/article_21093_0.html
In this paper, a new and innovative semi analytical technique, namely Akbari-Ganji’s method (AGM), is employed for solving three nonlinear damped oscillatory systems. Applying this method to nonlinear problems is very simple because in solving process only a trial solution, the main differential equation and its derivatives are required. The analytical solutions obtained by the AGM are utilized to study the impact of amplitude on nonlinear frequency and damping ratio. It is found that the AGM leads to acceptable results for the problems considered in this paper. Also, in order to obtain a more accurate solution, instead of using a trial solution with higher-order terms which may result in complicated and time consuming mathematical calculations, the solution obtained by AGM is improved via variational iteration method (VIM). The usefulness and effectiveness of the approach is demonstrated through comparison of the obtained results with those achieved by the numerical method. Hence, the AGM can be applied to nonlinear problems consisting of significant nonlinear damping terms and, if necessary, can be easily improved. Sun, 28 Oct 2018 20:30:00 +0100Mixed-mode fracture parameters estimation by genetic programming
http://scientiairanica.sharif.edu/article_21094_0.html
The linear elastic fracture phenomenon has been characterized with stress intensity factors (SIFs). In this study a general function is obtained in order to predict the fracture parameters. Numerical calculation of the SIFs in a mixed-mode condition is a cumbersome task. In this research, more than 6800 numerical analyses using extended finite element method are conducted to simulate the fracture problem. States are considered for a plate with an arbitrary edge or center crack. Mixed mode SIFs were calculated using of interaction integral. Then, Gene Expression Programming (GEP) method is utilized to extraction of a function. Results show acceptable correlations between numerical calculations and genetic programming functions. R-square (R2) values are in a range of 0.91 to 0.96 that guarantees the accuracy of the inferred functions.Sun, 28 Oct 2018 20:30:00 +0100Iterative Method for Simultaneous Sparse Approximation
http://scientiairanica.sharif.edu/article_21095_0.html
This paper studies the problem of Simultaneous Sparse Approximation (SSA). This problem arises in many applications which work with multiple signals maintaining some degree of dependency such as radar and sensor networks. In this paper, we introduce a new method towards joint recovery of several independent sparse signals with the same support. We provide an analytical discussion on the convergence of our method called Simultaneous Iterative Method (SIM). Additionally, we compare our method with other group-sparse reconstruction techniques, i.e., Simultaneous Orthogonal Matching Pursuit (SOMP), and Block Iterative Method with Adaptive Thresholding (BIMAT) through numerical experiments. The simulation results demonstrate that SIM outperforms these algorithms in terms of the metrics Signal to Noise Ratio (SNR) and Success Rate (SR). Moreover, SIM is considerably less complicated than BIMAT, which makes it feasible for practical applications such as implementation in MIMO radar systems.Sun, 28 Oct 2018 20:30:00 +0100Design and Optimization of Tubular Linear Permanent Magnet Generator with Performance ...
http://scientiairanica.sharif.edu/article_21096_0.html
Linear generators are electric machines which generate electrical energy from linear movement. Since these machines can lift gear wheel or power train, they have begun to be used widely nowadays. Since their working areas differ according to speed and power characteristic, this study contains design and optimization of tubular linear generator for free piston practices. The design performed response surface optimization through design variables acquired as a result of sizing via interface. The association between the determined design variables and the sizes of generator output was examined. In addition, these sizes were used for objective functions of increasing efficiency, decreasing overall volume and increasing general performance and their optimum values were found by using Multi-Objective Genetic Algorithm. Initial and optimum design data were compared with Ansys Maxwell 2D. With overall performance increase, 22,78% decrease was seen in total mass, while 11,7% decrease was seen in cost. In addition, prototype linear generator was made in line with initial geometry data and it was applied with crank slider mechanism.Sun, 28 Oct 2018 20:30:00 +0100Modelling, Control and Simulation of a SCARA PRR-Type Robot Manipulator
http://scientiairanica.sharif.edu/article_21098_0.html
In this study, a SCARA PRR-type robot manipulator is designed and implemented. Firstly, the SCARA robot was designed according to the mechanical calculations. Then, forward and inverse kinematic equations of the robot are derived by using D-H parameters and analytical methods. The software is developed according to obtain cartesian velocities from joint velocities and joint velocities from cartesian velocities. The trajectory planning is designed using the calculated kinematic equations and the simulation is performed in MATLAB VRML environment. A stepping motor is used for prismatic joint of the robot, and servo motors are used for revolute joints. While most of the SCARA robot studies focus on RRP-type servo control strategy, this work focuses PRR-type and both stepper and servo control structures. The objects in the desired points of the workspace are picked and placed to another desired point synchronously with the simulation. So the performance of the robot is examined experimentally.Sun, 28 Oct 2018 20:30:00 +0100Comparative Study on Damage Behaviour of Synthetic and Natural Fiber Reinforced Brittle ...
http://scientiairanica.sharif.edu/article_21099_0.html
In the present study, comparative study on the damage behaviour of Glass-Epoxy (GE), Jute-Epoxy (JE) laminates with [0/90]s orientation and Jute-Rubber-Jute (JRJ) sandwich is carried out using ABAQUS/CAE finite element software. The GE, JE laminate and JRJ sandwich with thickness of 2 mm is impacted by a hemispherical shaped impactor at a velocity of 2.5 m/s. The mechanisms in which the brittle laminate gets damaged are analyzed using Hashin’s 2D failure criteria and flexible composites are analysed by ductile damage mechanism. The energy absorbed and the incipient point of each laminate was compared. It was observed from the results that there is no evidence of delamination in JRJ as opposed to GE and JE. The compliant nature of rubber contributes in absorbing more energy and it is slightly higher than GE. Also it was observed that there is no incipient point in JRJ sandwich which means there is no cracking of matrix since rubber is elastic material. Thus the JRJ material can be a better substitute for GE laminate in low velocity applications. The procedure proposed for the analysis in the present study can serve as benchmark method in modelling the impact behaviour of composite structures in further investigations.Sun, 28 Oct 2018 20:30:00 +0100The stage shop scheduling problem: lower bound and metaheuristic
http://scientiairanica.sharif.edu/article_21119_0.html
Remarkable efforts are made to develop the job shop scheduling problem up to now. As a novel generalization, the stage shop can be defined as an environment, in which each job is composed of some stages and each stage may include one operation or more. A stage can be defined a subset of operations of a job, such that these operations can be done in any arbitrary relative order while the stages should be processed in a predetermined order. In other words, the operations of a stage cannot be initiated until all operations of the prior stage are completed. In this paper, an innovative lower bound based on solving the preemptive open shop (using a linear programming model in polynomial time) is devised for the makespan in a stage shop problem. In addition, three metaheuristics, including firefly, harmony search and water wave optimization algorithms are applied to the problem. The results of the algorithms are compared with each other, the proposed lower bound, and a commercial solver.Fri, 02 Nov 2018 20:30:00 +0100Studying buckling of composite rods made of hybrid carbon fiber/carbon nanotube reinforced ...
http://scientiairanica.sharif.edu/article_21120_0.html
In this paper, the buckling behavior of rods made of carbon fiber/carbon nanotube-reinforced polyimide (CF/CNT-RP) under the action of axial load is investigated based on a multiscale finite element method. A dual-step procedure is first adopted to couple the influences of micro- and nano-scale in order to obtain the equivalent elastic properties of CF/CNT-RP for various volume fractions of CF and CNT. The interphase effect between CNTs and the polymer matrix is taken into consideration. Also, dispersion of CF/CNT into the polymer matrix is assumed to be random. Then, rods with square and circular cross sections are considered whose stability characteristics are analyzed. The finite element modeling is performed using two models including a 3D brick model and a 2D beam model. Selected numerical results are given to study the effects of volume fraction of CNT/CF, interphase and geometrical properties on the axial buckling response of multiscale composite rods.Fri, 02 Nov 2018 20:30:00 +0100Inventory model optimization revisited: Understanding service inventories to improve performance
http://scientiairanica.sharif.edu/article_21121_0.html
Services are increasingly important in the modern economy, for both service and manufacturing firms, yet inventory literature has been focused mainly on physical goods and, only a few studies have included services in optimization. On the other side, traditional service management literature relies on an extremely narrow definition of inventory that excludes services, because they are perishable. Thus, there is a lack of research in the link between inventory optimization and service management. However, according to a new service inventory approach, businesses components such as tasks or information, as different from physical goods, can be performed and stored in anticipation of service demand as a form of service inventory—that is, inventorying by anticipation rather than delaying the service. This article aims to contribute to this lack of research by proposing a service inventory optimization model that integrates a service orientation to optimize tasks and information to be performed in advance. In contrast with traditional inventory models, where the objective is to optimize physical items, in this approach physical products whenever included, constitute only mechanisms for service provision. This service inventory model contributes to optimize the quantity of tasks or information to be anticipated and thus provides benefits for customers.Fri, 02 Nov 2018 20:30:00 +0100Solution of Fractional Order Riccati Differential Equations Using Euler Wavelet Method
http://scientiairanica.sharif.edu/article_21122_0.html
The fractional-order differential equations (FDEs) have the ability to model the real-life phenomena better in a variety of applied mathematics, engineering disciplines including diffusive transport, electrical networks, electromagnetic theory, probability and so forth. In most cases, there are no analytical solutions therefore a variety of numerical methods have been developed for the solution of the FDEs. In this paper, we derive the numerical solutions of the various fractional-order Riccati type differential equations using the Euler Wavelet Method (EWM). The Euler wavelet operational matrix method converts the fractional differential equations to a system of algebraic equations. Illustrative examples are included to demonstrate the validity and efficiency of the technique.Fri, 02 Nov 2018 20:30:00 +0100Damage detection in frame structures using noisy accelerometers and Damage Load Vectors (DLV)
http://scientiairanica.sharif.edu/article_21123_0.html
In the area of damage detection, there have been many notable methods introduced in the past years. Damage Load Vectors (DLV) is among the most powerful methods, which computes a set of load vectors from variations in flexibility matrices of a frame in the undamaged and damaged conditions. These flexibility matrices are derived from acceleration responses of the frame which can be captured using accelerometers. The DLV method then scrutinizes this shift among the flexibility matrices, which ultimately enables locating the damaged member(s). This study holistically conducted seven experimental tests, with seven damage scenarios of a test frame installed on a semi-harmonic shaking table. The DLV method was subsequently employed to locate the damaged members using recorded frame vibration data obtained from ‘noisy’ accelerometers positioned on the frame at eight predefined locations. The Eigen Realization Algorithm (ERA) alongside Pandy’s recommendations were adapted herein to facilitate generation of accurate flexibility matrices derived from the noisy accelerometers. The outcome is very encouraging with accurate identification of damaged members in all seven damage scenarios without any ‘positive-false’ and ‘negative-false’ findings. Additionally, there is a decrease (from 0.045 to 0.289) in the accuracy of WSI index when the number of damaged members is increased.Sat, 03 Nov 2018 20:30:00 +0100Mathematical models and an elephant herding optimization for multiprocessor-task flexible flow ...
http://scientiairanica.sharif.edu/article_21125_0.html
Shop floor control (SFC) is one of the main concepts in manufacturing resource planning (MRPII) and production scheduling is a key element in SFC. This paper studies the hybrid flow shop scheduling problem where jobs are multiprocessor. The objective is to minimize total completion time. Although there are several papers considering hybrid flow-shop scheduling problem with multiprocessor tasks, but none propose a mathematical model for this problem. At first, the two problems (fixed and selective cases) are mathematically formulated by mixed integer linear programming models. Using commercial software, the model is used to solve the small instances of the problems. Moreover, an elephant herding optimization is developed to solve large instances of the problems. To numerically evaluate the proposed algorithm, it is compared with two available algorithms in the literature, simulated annealing and shuffled frog-leaping algorithm in the literature.Sun, 04 Nov 2018 20:30:00 +0100Optimal Objective Function in Simulating Endurance Time Excitations
http://scientiairanica.sharif.edu/article_21127_0.html
Endurance Time (ET) method is a dynamic analysis procedure in which increasing excitations are imposed on structures; these excitations are known as Endurance Time excitation functions (ETEF). This study presents a method to find the optimal objective function for simulating ETEFs which unconstrained optimization problems are. In optimization problems, equations are defined in term of an objective function. In the problem of simulating ETEFs, the objective function can be defined in many different ways regarding considered intensity measures and respective weighting factors. In addition, the type of calculating residuals (absolute way or relative way) diversifies objective function definitions. The proposed method for determining optimal objective function includes quantifying the accuracy of ETEFs in a scalar quantity regardless of their objective functions and introducing an approach to overcome the dependence of results on initial points of optimizations. The proposed method is applied and results are then presented. It is observed that considering only acceleration spectra and calculating residuals in the relative way creates more accurate ETEFs.Sat, 10 Nov 2018 20:30:00 +0100Economic evaluation of energy-efficient engineering systems
http://scientiairanica.sharif.edu/article_21128_0.html
The paper shows the aspects of introducing energy-efficient equipment for engineering systems within the context of productivity enhancement in general. The author as research relevance brings a thesis that each of production members reach after implementing possibility for increasing general effectiveness of business operation. The paper reveals the issues of factor and expert assessments for introducing innovations at the enterprise and economic evaluation of the place of energy-efficient technologies in the general medium of production enterprise modernization. The novelty of the study is an aspect that under conditions of energy products’ cost increase and significant energy intensity of present-day production, the issue of energy conservation and choice of priorities of investment into the project of energy efficiency increase at enterprises is a major concern. Reduction of production cost is one of the most important ways of effective competition and increasing of productiveness of an enterprise in the modern conditions. The authors offer to evaluate the process of energy conservation in a complex way, taking into account all investment consequences: economic, technical, ecological, organizational, commercial, and others. The prospect areas of research: cost-to-use analysis from the introduction of personally developed systems of energy conservation.Sat, 10 Nov 2018 20:30:00 +0100Intelligent Navigation of a Self-Fabricated Biped Robot using a Regression Controller
http://scientiairanica.sharif.edu/article_21129_0.html
With increasing demand towards use of biped robots in industrial automation and other related applications, navigation and path planning has emerged as one of the most challenging research topic over the last few decades. In this paper, a novel navigational controller is designed and implemented in a self-fabricated biped robot. After fabricating the biped equipped with a large set of sensors, a regression controller is implemented in it for obstacle avoidance and path optimization purpose. The obstacle distances detected by the sensory network of the biped are fed as input parameters to the regression controller and the output obtained from the controller is the necessary heading angle required to avoid the obstacles present randomly in the environment. The biped is tested in a simulation environment for obstacle avoidance and target following behaviour. Along with that, to validate the simulation results, a real-time experimental set up is designed under laboratory conditions. The results obtained from both the environments are compared in terms of navigational parameters and a good agreement between them is observed. Being a relatively new area of research, the navigation of bipeds can serve as a pioneer act towards industrial automation.Sun, 18 Nov 2018 20:30:00 +0100A new numerical application of the generalized Rosenau-RLW equation
http://scientiairanica.sharif.edu/article_21130_0.html
In this article, a collocation finite element method based on septic B-splines as a tool has been carried out to obtain the numerical solutions of the nonlinear generalized Rosenau-RLW equation. One of the advantages of this method is that when the bases are chosen at a high degree, better numerical solutions are obtained. Effectiveness of the method is demonstrated by solving the equation with various initial and boundary conditions. Also, in order to detect the performance of the method we have computed L2 and L1 error norms and two lowest invariants IM and IE: The obtained numerical results have been compared with some of those in the literature for similar parameters. This comparison clearly shows that the obtained results are better than and found in good conformity with the some earlier results. Stability analysis denotes that our algorithm, based on a Crank Nicolson approximation in time, is unconditionally stable.Sun, 18 Nov 2018 20:30:00 +0100Technical and Economic Considerations for using of Permanent Magnet Brushless Motors in ...
http://scientiairanica.sharif.edu/article_21131_0.html
Evaporative coolers due to their low cost are used in hot and dry regions of many countries especially in Iran. Conventional evaporative coolers use single-phase induction motors (SPIMs). But the benefits of these motors are very low, and their substitution with high efficient electrical motors is considered by industrial parties. In this paper, the details of using the brushless motor in the application of evaporative cooler are presented. A 1/2 hp brushless motor and drive are designed and built. This motor- drive is tested by a dynamometer and standard testing equipment. Also, for the approval of this motor-drive, a 5000 m3/h direct evaporative water cooler equipped with this motor is examined under the airflow rate test in the reference laboratory. The results obtained in both tests are compared with the test results of a typical SPIM. The results verify an increase of at least 60% for energy efficiency compared to evaporative coolers equipped with SPIM. Moreover, a new control scheme based on power control instead of speed control is proposed to stabilize the outlet airflow rate. The results indicate that use of brushless motors in this application can offer considerable energy saving, and helps to protect environment.Sun, 18 Nov 2018 20:30:00 +0100A NOVEL PROCEDURE FOR MICROMECHANICAL CHARACTERIZATION OF WHITE MATTER CONSTITUENTS AT VARIOUS ...
http://scientiairanica.sharif.edu/article_21132_0.html
Optimal hyperplastic coefficients of the micromechanical constituents of human brain stem were investigated. An evolutionary optimization algorithm was combined with a Finite Element (FE) model of a Representative Volume Element (RVE) to find the optimal material properties of axon and Extra Cellular Matrix (ECM). The tension and compression test results of a previous experiment were used for optimizing the material coefficients and the shear experiment was used for validation of the resulting constitutive model. Periodic Boundary Conditions (PBC) were applied to ensure the symmetry of displacements on the opposite faces of the RVE. The optimization algorithm searched for optimal shear moduli and fiber stiffness of axon and ECM by fitting the average stress in axonal direction. The resulting constitutive model was validated against the shear stress results of the same experiment. The results were in strong agreement with those of the shear test. In addition, we concluded that the instantaneous shear moduli and fiber stiffness of both axon and ECM rise at higher strain rates, and more importantly, the shear modulus ratio of axon to ECM decreases from the value of 10 at low strain rate of 0.5/s to the value of 5 at the strain rate of 30/s.Sun, 18 Nov 2018 20:30:00 +0100Trapezoidal neutrosophic aggregation operators and its application in multiple attribute ...
http://scientiairanica.sharif.edu/article_21133_0.html
The aim of this paper is to introduce interval trapezoidal neutrosophic set which is a combination of trapezoidal fuzzy numbers and interval neutrosophic set. The paper presents some operational rules, the score and accuracy functions of interval trapezoidal neutrosophic numbers. Then, some aggregating operators under interval trapezoidal neutrosophic information which are called interval trapezoidal neutrosophic number weighted arithmetic averaging (ITNNWAA) operator and interval trapezoidal neutrosophic number weighted geometric averaging (ITNNWGA) operator, are proposed, and their properties are investigated in detail. Furthermore, based on these operators a multi-attribute decision making method is developed. Finally, a numerical example is presented to illustrate the application and effectiveness of the proposed method.Sun, 18 Nov 2018 20:30:00 +0100Presenting a Series-Parallel Redundancy Allocation Problem with Multi-State Components Using ...
http://scientiairanica.sharif.edu/article_21134_0.html
Redundancy Allocation Problem (RAP) is one of the most important problems in the field of reliability. This problem aims to increase system reliability, under constraints such as cost, weight, etc. In this paper, we work on a system with series-parallel configuration and multi-state components. To draw the problem nearer to real condition, we merge this problem with discount levels in purchasing components. For calculating sub-systems reliability, we used recursive algorithm. Because RAP belongs to Np. Hard problems, for optimizing the presented model a new Genetic algorithm (GA) was used. The algorithm parameters tuned using Response surface methodology (RSM) and for validation of GA an enumeration method was used.Sun, 18 Nov 2018 20:30:00 +0100Fabrication of Bismuth Titanate (Bi4Ti3O12) Thin Films: Effect of Annealing Temperature on ...
http://scientiairanica.sharif.edu/article_21135_0.html
Bismuth Titanate (Bi4Ti3O12) ceramics, so-called BiT, have many modern applications in microelectronics, sensors, and capacitors. In this study, the related solutions for fabricating BiT thin films were prepared and then coated on glass substrates by using the sol-gel technique and the spin coating instrument. The Xray diffraction patterns of our samples indicate that the crystalline phases of BiT are orthorhombic. Based on the transmission-spectra analysis, the samples are transparent in the visible spectrum, and their optical energy gaps are found to be 3.36 eV and 3.41 eV for the BiT thin films annealed at 600◦C and 650◦C, respectively. Other physical quantities such as refractive index, thickness, extinction coefficient and dielectric constant were estimated by swanepol’s method. The results show that as the annealing temperature rises the real part of the dielectric constant becomes larger indicating our samples are good dielectric materialsFri, 23 Nov 2018 20:30:00 +0100Mechanical and Durability Characteristics of Marble Powder Based High Strength Concrete
http://scientiairanica.sharif.edu/article_21138_0.html
Concrete is a construction material consisting of cementitious material, fine aggregate, coarse aggregate and water. Now-a-days, the cost of these materials is increasing. We need to look at a way to reduce the cost of building materials especially cement. One of the recent advancement in construction industry is the replacement of cement with waste materials in concrete. This replacement offers cost reduction, energy savings and protection of environment. To achieve the above objective, an attempt has been made to replace cement with waste marble powder (WMP) produced from marble industries. The present investigation aims to study the mechanical and durability properties of high strength concrete (HSC) with cement partially replaced by waste marble powder. Cement has been replaced with marble powder at 0%, 5%, 10%, 15% and 20% in this study. The properties of concrete such as compressive strength, modulus of elasticity and flexural strength were determined. The durability characteristics such as water absorption, acid resistance and rapid chloride permeability were also determined.Sat, 01 Dec 2018 20:30:00 +0100Gene expression programming models for liquefaction-induced lateral spreading
http://scientiairanica.sharif.edu/article_21139_0.html
Lateral spreading is one of the most significant destructive and catastrophic phenomena associated with liquefaction caused by earthquake and can impose very serious damages to structures and engineering facilities. The aim of this study is to evaluate liquefaction induced lateral spreading and finding new relations using gene expression programming (GEP) that is a new and developed generation of genetic algorithms approaches. Since there are complicated, nonlinear and higher order relationships between many factors affecting the lateral spreading, GEP is assumed to be capable of finding complex and accurate relationships between these factors. This study includes three main stages: (i) compilation of available database (484 data), (ii) dividing data into training and testing categories, and (iii) building new models and propose new relationships to predict ground displacement in free face, gentle slope and general ground conditions. The results of modeling each of the different ground conditions are presented in the form of mathematical equations. At the end, the final GEP models for 3 different cases of ground conditions are compared with multiple linear regression (MLR) and other published models. The statistical parameters indicate the higher accuracy of the GEP models over other relations. Sat, 01 Dec 2018 20:30:00 +0100Cracking effects on chloride diffusion and corrosion initiation in RC structures via finite ...
http://scientiairanica.sharif.edu/article_21140_0.html
Chloride ion ingress into concrete causes steel corrosion over time, thereby ending the service life of structures. Sometimes, it severely reduces the loading capacity of reinforced concrete and may even cause the sudden destruction of concrete structures. Concrete cracking stems from different factors, such as shrinkage and tensile stress due to thermal loading and under loading. Modeling and estimating chloride ion ingress into cracked concrete over different periods can aid the appropriate determination of structural lifetime and maintenance of reinforced concrete structures. Accordingly, this research investigated the effects of the width and depth of concrete cracks on the rate of chloride ion diffusion and rebar corrosion. To this end, different concrete specimens characterized by various cracking conditions were modeled in COMSOL Multiphysics. Analytical results showed that the critical crack that reflected the highest extent of chloride ingress into a specific region at different times was not necessarily the defect with the largest thickness and depth. This finding highlights the importance of investigating crack behavior in the appropriate estimation of structural service life. Nevertheless, over time, considerably wide and deep cracks may ultimately be a reflection of substantial rate of ingress.Sat, 01 Dec 2018 20:30:00 +0100Effect of temperature and time on the structural properties of PbS nanofilms
http://scientiairanica.sharif.edu/article_21141_0.html
Temperature and time are among the effective parameters in thin film preparation. In this research, lead acetate as a source of Pb2+ and thiourea as a source of S2- have been used and effect of deposition time (tDMon, 03 Dec 2018 20:30:00 +0100Mathematical modelling of a decentralized multi-echelon supply chain network considering ...
http://scientiairanica.sharif.edu/article_21142_0.html
We study a multi-time, multi-product and multi-echelon supply chain aggregate procurement, production and distribution planning problem and discuss the implications of formulating a tri-level model to integrate procurement, production and distribution, maintaining the existing hierarchy in the decision process. In our model, there are three different decision makers controlling the procurement, production and the distribution processes in the absence of cooperation because of different optimization strategies. First, we present a hierarchical tri-level programming model to deal with decentralized supply chain problems. Then, an algorithm is presented to solve the proposed model. A numerical illustration is provided to show the applicability of the optimization model and the proposed algorithm. In order to evaluate the application of the model and the proposed algorithm, ten sets of small and large problems are randomly generated and tested. The experimental results show that our proposed fuzzy-stochastic simulation based hierarchical interactive particle swarm optimization (Sim-HIPSO) performs well in finding good approximate solutions within reasonable computation times.Mon, 03 Dec 2018 20:30:00 +0100Improving heat transfer in triplex tube heat exchanger containing phase-change materials by ...
http://scientiairanica.sharif.edu/article_21143_0.html
Heat thermal energy storage is a technique to improve thermal efficiency through reducing discrepancy between energy demand and supply. Latent heat thermal energy storage as a kind of thermal energy storage method has drawn considerable attention from researchers due to its high thermal energy density and constant operating temperature. This study numerically investigates the melting process in a triplex tube heat exchanger containing phase change material (PCM) RT82. A two-dimensional numerical model has been generated using the Ansys Fluent 16 software program to simulate melting process. In this study, conduction and natural convection have been considered. Selected arrangements of rectangular fins, including lengths and positions, were selected according to heat distribution while the total area of fins was kept constant. This new strategy was done to improve heat transfer in PCM which would result in decreasing its melting time. The select optimized model in this article reduces meting time to 28.4% in comparison with the model in Ref. [1]. Numerical results have been validated by numerical and experimental results of this reference and there has been a proper agreement between them.Mon, 03 Dec 2018 20:30:00 +0100OPTICAL SOLITONS IN BIREFRINGENT FIBERS WITH FOUR{WAVE MIXING BY EXTENDED TRIAL EQUATION METHOD
http://scientiairanica.sharif.edu/article_21144_0.html
This paper obtains optical soliton solutions in birefringent bers that are studied in presence of four-wave mixing.The extended trial function scheme is the integration algorithm that is applied. Both Kerr law and parabolic lawsare taken into account. The soliton solutions are presented with relevant integrability criteria.Mon, 03 Dec 2018 20:30:00 +0100Performance of EBFs equipped with an innovative shape memory alloy damper
http://scientiairanica.sharif.edu/article_21145_0.html
Given their unique characteristics, Shape Memory Alloys (SMAs) have significant potential for use in different areas of engineering. The phase shift characteristics of these alloys allow them to memorize a certain shape, and if deformed, revert back to that shape through a thermal process. Given the vast potentials of SMAs, they can be utilized to address the limitation of conventional eccentrically braced frames (EBFs) with vertical links in order to achieve better residual and maximum interstory drifts. This paper presents a vibration control system equipped with SMAs to achieve improved operational domain. The Compared to conventional EBFs, the proposed system named recentering damping device (RDD) is easy to fabricate and implement and allows for the redesign of fuse members. A numerical analysis is performed for a 9-story steel frame building using nonlinear analysis program OpenSees to evaluate the system performance. Results of time history analysis demonstrate better self-centering behavior and lower residual interstory drifts of the proposed system as compared to EBF.Mon, 03 Dec 2018 20:30:00 +0100Seismic evaluation of special steel moment frames undergoing near-field earthquakes with ...
http://scientiairanica.sharif.edu/article_21146_0.html
While the bottom soil of the foundation is supposed to be rigid and the flexibility effect is ignored, the seismic response of the structure is affected by dynamic properties of the structure, and the soil flexibility does not have any effect on the response of the structure. Hence, considering the results obtained by analyses based on the fixed base buildings can lead to the unsafe design of the structure. On the other hand, the proximity of the site to the earthquake production resource causes the most earthquake energy to be reached to the structure as a long-period pulse. Therefore, near-field earthquakes produce many seismic needs so that force the structure to dissipate this input energy with relatively large displacements. Accordingly, the primary objective of the present paper is the determination of the seismic response of the 3, 5 and 8-story steel buildings with special moment frame system and by considering the soil-structure interaction and panel zone modeling as well. The selected records of the near and far-field earthquakes in nonlinear time history analysis have been used, and the response of the structure was compared in both states.Mon, 03 Dec 2018 20:30:00 +0100Government Credit Risk Assessment of Non-profit PPP Projects in China based on the Model of ...
http://scientiairanica.sharif.edu/article_21147_0.html
To reduce the financial pressure on local governments and improve operational efficiency, the Chinese government has introduced the Public-Private Partnership (PPP) model for the development of infrastructure. However, the government credit risk generated by PPP projects may damage private and public interests. Therefore, this study evaluates the government credit risks of non-profit PPP projects by using a systematic and rounded model that employs interval value hesitant fuzzy sets and intuitionistic fuzzy hierarchical analysis (IVHFS-IFAHP). This study employs the perspective of the private sector to establish risk index systems using the dimensions of Wuli-Shili-Renli (WSR) methodology. IFAHP is used to collect expert opinions for the comparison of the importance of the indexes and establish an intuitionistic fuzzy judgment matrix in order to calculate the weight of each index. IVHFSs are adopted to obtain the scores of the indexes coupled with the results acquired by IFAHP to produce comprehensive scores of the indexes. The feasibility and practicability of this method were verified empirically. This study provides an effective method for the private sector to evaluate the government credit risks of non-profit PPP projects and provides a reference for participation in PPP projects.Mon, 03 Dec 2018 20:30:00 +0100Artificial accelerograms to estimate damage of dams by using failure criteria
http://scientiairanica.sharif.edu/article_21148_0.html
The aim of this paper is to analyse dam’s damage by using two recent methodologies. The first method has been used to define the performance and response curves of concrete gravity dams. The second method defines the seismic input which has been obtained from power spectral density function consistent with the response spectrum. Both methods set themselves as efficient, practical and useful to develop quite complicated analysis as the construction of the stochastic process to define the synthetic earthquake and the estimation of cracks in the dam’s body. These methodologies have been explained and revised to improve their use. The fluid behaviour contained by arch-dams is compared with the fluid behaviour in storage tanks by studying the sloshing phenomenon which is usually neglected for dams. For the mathematical modelling, interactive programming language has been used.Mon, 03 Dec 2018 20:30:00 +0100Joint Distribution Adaptation via Feature and Model Matching
http://scientiairanica.sharif.edu/article_21149_0.html
It is usually supposed that the training (source domain) and test (target domain) data follow a similar distribution and feature space in most pattern recognition tasks. However, in many real-world applications, particularly in visual recognition, this hypothesis has been frequently violated. This problem is known as domain shift problem. Domain adaptation and transfer learning are promising techniques to learn an effective and robust classifier to tackle shift problem. In this paper, we propose a novel scheme for domain adaptation, entitled as Joint Distribution Adaptation via Feature and Model Matching (JDAFMM), in which feature transform and model matching are jointly optimized. Due to joint optimization, we can have a robust model with feasible feature transformation and model parameter adaptation. By introducing regularization operated between the marginal and conditional distributions’ shifts across domains, we can successfully adapt data drift as much as possible along with empirical risk minimization and rate of consistency maximization between manifold and prediction function. We conduct extensive experiments to evaluate the performance of the proposed model against those of other machine learning and domain adaptation methods in three types of visual benchmark datasets. Our experiments illustrate that our JDAFMM significantly outperforms other baseline and state-of-the-art methods.Fri, 07 Dec 2018 20:30:00 +0100Nonlinear vibration analysis of partially coated circular microplate under electrostatic actuation
http://scientiairanica.sharif.edu/article_21150_0.html
This paper investigates the optimal configuration for a partially two-layered circular capacitive microplate subjected to AC-DC electrostatic actuation. To this end, the static deflection due to DC electrostatic actuation, natural frequency of vibration about static position and primary resonance response due to AC electrostatic actuation are studied. Primarily, the nonlinear equations of motion are derived through classical laminated plate theory (CLPT). Then, the static position and natural frequency of vibration around static position are obtained using Galerkin approach. The linear mode shapes of non-uniform microplate i.e. a microplate coated as partial by a second layer are used as comparison functions. The forced vibration equations around static position are separated using Galerkin method, and solved by the multiple scale perturbation theory. Firstly, the impact of changes in the second layer radius on the variations of static and dynamic response of the system is studied while its thickness remains constant. Then, the effect of changes in the second layer thickness is studied while its radius remains constant. Finally, the impact of simultaneous change in the radius and thickness of the second layer is studied while its volume remains constant.Fri, 07 Dec 2018 20:30:00 +0100Investigating the Exergy of Flow and Three Dimensional Flow Study within the Vortex Tube Device ...
http://scientiairanica.sharif.edu/article_21151_0.html
In this paper, the effect of inlet pressure on the performance of vortex tube device has been investigated using 3D simulation and CFD technique by Fluent software. The flow inside the device is considered as compressible and turbulent. In order to understand and investigate the effect of inlet pressure, different inlet pressures are entered into the device and the results are extracted and analyzed. The main goal is to achieve the minimum cold exit temperature and maximum swirl velocity in the vortex tube. This paper indicates that inlet pressure of 4.8 bars is an optimal inlet pressure which is justifiable economically and also in terms of the amount of produced cooling. The CFD results show that increase in inlet pressure, increases the entropy production and subsequently the system disorder. Finally, the existing gaps in the previous studies will be filled by examining the inlet and exit exergies in the vortex tube device. Inlet exergy has not considerable changes in terms of α and have a constant value and at α=0.3691 the minimum exergy efficiency is occurred according to the calculations.Fri, 07 Dec 2018 20:30:00 +0100A Mathematical Model for Competitive Location Problem with Product Selection
http://scientiairanica.sharif.edu/article_21152_0.html
In this paper, a new competitive location problem for a chain is considered. The chain’s owner can offer a variety of products. The model’s objective is to determine both the location of the new facilities and the optimal product type for each opened facility. The patronizing behavior of the customers is based on Huff rule and the location of new facilities is selected from a set of potential sites. As a result, the model is a nonlinear integer programming problem and for solving the proposed model, the problem is reformulated as a mixed integer linear programming and therefore a standard optimization solver can be used for obtaining the optimal solutions for small and medium-size problems. To cope with large-size problems, we develop two methods: 1) a heuristic method for a special case and 2) a hybrid heuristic-firefly algorithm for general cases. By using the proposed model, it is shown numerically that in multi-product industries in which owner of the facilities is able to offer different types of products, in addition to the optimal location, it is necessary to determine the best products. In the end, a real-world case study for locating a new bakery is presented.Fri, 07 Dec 2018 20:30:00 +0100The effects of bubble detachment shape on rising bubble hydrodynamics
http://scientiairanica.sharif.edu/article_21153_0.html
Local velocities and aspect ratios of rising bubbles were measured to investigate the effects of bubble detachment shape on rising bubble hydrodynamics. Two types of capillary were employed to generate bubbles of identical volume: one glassy nozzle aligned vertically and the other stainless steel needle aligned horizontally. Horizontally injected bubbles had spherical initial shape and their values of aspect ratio slightly fluctuated around unity. However, vertically injected bubbles had surface-stretched initial shape and their values of aspect ratios decreased sharply from 1.1 to 0.65. There is a notable correspondence between the variation of local velocities and aspect ratios which reflects the relevance of the detachment shape of the bubbles to their surface energy. Correlations of Taylor & Acrivos and Vakhrushev & Efremov for aspect ratio were examined by experimental data.Fri, 07 Dec 2018 20:30:00 +0100Vapor Solidification of Saturated Air in Two-Dimensional Stagnation Flow
http://scientiairanica.sharif.edu/article_21154_0.html
In the present paper, stagnation flow solidification of vapor from saturated air is investigated. Saturated air with strain rate a impinges on a flat plate and, because the plate temperature is below the freezing temperature of water, condensation occurs and an ice layer forms on the plate. The ice surface is modeled as an accelerated flat plate moving toward the impinging fluid. The unsteady Navier-Stokes equations were subjected to a similarity transformation to obtain a single ordinary differential equation for the velocity distribution. Two methods of solution were used for the energy equation: a finite-difference numerical technique and a numerical solution of a similarity equation; these two results were compared to establish accuracy. Freezing time first increases as the far-field temperature decreases from above zero degrees Celcius and then rapidly approaches zero as the far-field temperature approaches zero Celcius. Despite the physical experiment, here the size of the nearest cell to the substrate controls the time at which condensation begins. As a result, maximum time before freezing begins occurs at about 5℃ air temperature, with the cell size 0.01 or 0.02 mm. The air temperature distribution and the ultimate frozen thickness for two saturated air temperatures are also presented.Sun, 09 Dec 2018 20:30:00 +0100A bi-objective hierarchical hub location model with facility failure
http://scientiairanica.sharif.edu/article_21155_0.html
In the most past hub location problem (HLP) studies, failure probability is limited to a constant value; while in reality, it depends on various factors including natural disasters such as floods and earthquakes, commodity flow, institutional elements such as strikes, and etc. This paper looks into the problem of hub network design through a new model. The problem is to maximize the network reliability and to minimize the total routing cost simultaneously. In order to provide a more realistic model, the hub’s failure probabilities were considered as a function of the hub’s incoming traffic. Reserve hub elements are also taken into account in the model with the aim of increasing network reliability. To solve the model, a non-dominated sorting genetic algorithm (NSGA-II) is presented. The parameters of the algorithm are tuned using Taguchi method. The proposed solution is then carried out in a case study where the results confirm the acceptable performance of the model and also sensitivity analysis is performed in order to describe the effects of critical parameters into objective functions.Sun, 09 Dec 2018 20:30:00 +0100Non-Fourier's and Fick's laws applications in the flow of temperature dependent thermal ...
http://scientiairanica.sharif.edu/article_21156_0.html
The current article presents a numerical study for local solutions of Sisko liquid flow by bidirectional stretched surface. Additionally, the analysis of relaxation times for the heat and mass transfer mechanisms are made by utilizing modified heat flux and mass diffusion models. These improved relations are the generalized form of Fourier's and Fick's laws in which the time space upper-convected derivative are employed to portray the heat conduction and mass diffusion mechanisms. Appropriate transformations lead to a strongly nonlinear differential system of equations which is then solved numerically by employing the applications of bvp4c package in Matlab software. Another numerical method namely shooting technique with RK45 Fehlberg and Newton-Raphson method is utilized to authenticate the results. Graphical illustrations demonstrating the impacts of sundry physical parameters with required discussion highlighting their physical effect are also a part of this exploration. It is perceived that the temperature and concentration of Sisko liquid are diminishing functions of relaxation times for the heat and mass transfer mechanisms. It is also fascinating to perceive that the temperature and concentration of Sisko liquid are higher in case of classical form in comparison with an improved constitutive relations.Sun, 09 Dec 2018 20:30:00 +0100Determining the Optimal Conditions for the Catalytic Hydrogenation of a Mixture of Tian Shan ...
http://scientiairanica.sharif.edu/article_21157_0.html
The shortage of natural resources in the power industry, combined with their increasing usage, price, and negative impact on the environment necessitate the search for new techniques of producing liquid fuel. One such possibility is the production of fuel and chemical products from coal via hydrogenation. The transformation of coal into liquid fuel is a complex technical process that requires saturating the initial substance with oxygen. Therefore, the purpose of this study is to determine the optimal conditions for the catalytic hydrogenation of a mixture of coal, primary coal tar (PCT) and heavy oil residues with an end-boiling point of 300°C. The results show the optimal conditions for producing liquid fuel. The proposed technique allows achieving a complete homogenization of all components and producing a highly stable coal paste. This technique also allows significantly reducing the negative impact on the environment.Sun, 09 Dec 2018 20:30:00 +0100Cooperative Search and Localization of Ground Moving Targets by a Group of UAVs Considering ...
http://scientiairanica.sharif.edu/article_21186_0.html
A cooperative task allocation and search algorithm is proposed to find and localize a group of ground based moving targets using a group of Unmanned Air Vehicles (UAVs), working in a decentralized manner. It is assumed that targets have RF emissions. By using an algorithm including Global Search (GS), Approach Target (AT), Locate Target (LT) and Target Reacquisition (TR) modes, UAVs cooperatively search the entire parts of a desired area, approach to the detected targets, locate the targets, and search again to find the targets that stop transmitting their RF emissions during the localization process, respectively. In GS mode, UAVs utilize a cost function to select the best zone for search. In LT mode, each UAV performs a circular motion around the target and uses extended Kalman filter to estimate the target position. Furthermore, a fuel tanker is considered to provide fuel for UAVs during the flight. Therefore, two more operating modes as Approach to Fuel Tanker (AFT) and Fueling (FUE) are added to the operating modes. Before switching to the AFT mode, UAVs take turn using a fueling decision function. In AFT mode, the future position of the fuel tanker is predicted by UAVs to reduce the approach time.Mon, 17 Dec 2018 20:30:00 +0100Riprap design at bridge piers with limited scouring
http://scientiairanica.sharif.edu/article_21187_0.html
In previous studies, sizing riprap layer around bridge pier as scour countermeasure was for 100% protection against scouring. However, in many cases limited scour depth around a pier maybe accepted if only smaller riprap sizes are available. In the present work the effects of smaller size of riprap stones than the stable size on the scour depth is studied. Circular and oval shapes for riprap extent as well as both round and angular stone shape were tested. All tests were conducted at the threshold of bed sediment motion and the maximum scour depth was measured. The results of these experiments showed that with stone sizes closer to stable riprap, the efficiency of both round and angular stone shape was identical. As, size of riprap was reduced, deeper scour holes were observed with both round and angular shape material. The results also indicated that increasing the extent of the riprap layer from circular to oval with 5 times more riprap volume had insignificant effects on scour hole for angular shape riprap meanwhile reduced the scour depth with round shape material. Based on experimental data a method was developed to calculate a smaller riprap size based on an accepted limited scour hole.Mon, 17 Dec 2018 20:30:00 +0100Evaluation of UV aging behaviors of polyphosphoric acid (PPA) modified asphalt and its asphalt ...
http://scientiairanica.sharif.edu/article_21188_0.html
Effects of polyphosphoric acid (PPA) on the ultraviolet (UV) aging properties of asphalt and asphalt mixture were studied. The morphologies of these binders were characterized by FTIR spectra and TG analysis, then the influence of PPA on asphalt and its mixture before and after UV aging were investigated by the physical properties and pavement performances. Results show that the mechanisms of PPA modified asphalt are physical and chemical reactions; both UV aging and PPA additive could prompted the polycondensation of light components in asphalt. Compared with control samples, the introduction of PPA enhances the asphalt properties and intensifies the asphalt mixture performances. Furthermore, the asphalt performance aging variations (penetration aging index, softening point increment, ductility aging index, G*/sinδ aging index) decrease signiﬁcantly due to the introduction of PPA. This manifests that the effects of UV aging on the behaviors of asphalt and asphalt mixture are restricted by the addition of PPA through inhibiting the increase of carbonyl in the oxidation process.Mon, 17 Dec 2018 20:30:00 +0100Microwave aided and plant reduced gold nanoparticles as talented dye degradation catalyst
http://scientiairanica.sharif.edu/article_21189_0.html
Green alternatives prevail over the hazardous and expensive pathways of nanoparticles synthesis. Here we report eco-friendly manufacturing of gold nanoparticles by microwave assistance. The water soluble organic constituents of the tropical herb Elephantopus scaber functioned as the three electron donor and the aggregation preventer. XRD spectra certified fcc crystal lattice and the TEM images supported mixed spherical and triangular geometry to the nanoparticles with an average particle size of 18.97±5.86 nm. Ecological relevance of the gold nanoparticles lies in their ability to degrade methylene blue and methyl orange. The catalytic capacity of the gold nanoparticles is exploited in the reduction of 4-nitrophenol. Large scale production of gold nanoparticles in an easy manner using renewable sources improves the ‘green’ significance of the present synthesis.Fri, 21 Dec 2018 20:30:00 +0100Coordination of traditional and online group-buying channels considering website promotion effort
http://scientiairanica.sharif.edu/article_21190_0.html
The development of modern technology and e-commerce have given rise to the emergence of many new selling channels. Among one of them, group-buying attracts numerous new customers rapidly due to the characters of deep discounts and great convenience. Although deep discounts create sales growth for sellers, it also causes the loss in their profit margins. Meanwhile, the business model of group-buying websites is not thoroughly understood in literature. Based on a Stackelberg game framework, this paper studies the equilibrium between a group-buying website and a seller. The optimal pricing and channel decisions of the seller and the optimal group-buying pricing and promotion effort decisions for the website are investigated to offer guidance for their businesses. We find that the total profit of the whole system could be hurt when the agreement price or revenue sharing contracts are adopted by the firms. We propose a revenue-cost sharing contract that could coordinate the total profit. Finally, we show how the scale of the seller and the website and the unit cost influence the optimal decisions in the equilibrium.Fri, 21 Dec 2018 20:30:00 +0100Innovation and Environment Performance : An empirical study on 31 cities in China
http://scientiairanica.sharif.edu/article_21191_0.html
After its rapid economic growth, China is facing a very serious problem of atmospheric pollution with major long-term atmospheric problems appearing in large cities. Air pollution not only affects people’s normal lives, but also has a greater negative impact on their bodies, causing diseases, impacting productivity, and influencing people’s creativity. Due to past articles, the discussion on the efficiency of innovation and research has not been considered the impact of environmental variables. This study combines energy consumption, economics, environmental variables and innovative research and development capabilities to analyze and explore the relationship between consumption, environment, economy, and innovative R&D capabilities, this is the feature of this article. This study employ the Dynamic Data Envelopment Analysis (DEA) model to calculate energy consumption efficiency, R&D input efficiency, innovation patent output efficiency, carbon dioxide emission efficiency, and AQI efficiency of each city and further compare each city to find their space for improvement. The results of the study show that 10 cities have a total efficiency score of 1, implying the improvement space is already 0, whereas the total efficiency scores of the other 21 cities mean there is still much room for improvement, and there are big differences among the cities.Fri, 21 Dec 2018 20:30:00 +0100Dynamic virtual cell formation considering new product development
http://scientiairanica.sharif.edu/article_21192_0.html
Nowadays, factories should be coordinated with changes in the dynamic environment due to the intense competition in the businesses. Different strategies and systems are existing to help factories in a dynamic situation. In this article, a new multi-objective mathematical model is presented by the implementation of dynamic virtual cellular manufacturing and also considering new product development which enables factories to be successful in their business. This paper contains three objectives including maximizing the total profits of the factory in all the periods, the grouping efficacy and also the number of the new product. After linearization of the proposed model, multi-choice goal programming with utility function is used to solve the model. In addition, a case study has been conducted in the real world to show the effectiveness of the proposed model and finally, the results show that the integration of virtual cellular manufacturing with new product development can be helpful for managers and companies and leads to more efficiency.Fri, 21 Dec 2018 20:30:00 +0100A Novel Inductive Tactile Probe Design for Lump Detection in Soft Tissue Phantoms
http://scientiairanica.sharif.edu/article_21193_0.html
The purpose of this study is the development of a novel tactile probe for detection of lumps in soft tissue. The tactile probe includes an inductive sensor inside of an artificial tissue-like silicon rubber cushioning and a square shaped multi-metal-array to increase sensitivity. Firstly, a thermoplastic polymer probe was fabricated for housing and the mechanical compression test was executed by material testing machine. Secondly, the tactile sensor was calibrated between 2.5N-25N by 2.5N incremental steps and showed 99.49% linear behavior. In order to measure probe’s performance, 16 cylindrical silicon phantoms were used in three different scenarios. Each phantom was embedded by hard plastic inclusions at different depths and sizes. Finally, human palpation experiments were conducted by 10 naive subjects for the same scenarios above. The comparison results showed that especially for deep inclusions at low forces, human subjects had high false diagnose rates, while the tactile sensor could detect the deep inclusions at all force levels (ANOVA, pFri, 21 Dec 2018 20:30:00 +0100Study of the effect of organic binders on 13X zeolite agglomeration and their CO2 adsorption ...
http://scientiairanica.sharif.edu/article_21198_0.html
The aim of the present research is the shaping of zeolite 13X and study the effect of singular and binary system of binders. For this purpose, zeolite 13X was successfully synthesized under hydrothermal conditions. Different combinations of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) have been used for shaping. Physical properties of granules were measured by nitrogen adsorption-desorption and results showed that increasing the binder content up to a certain amount, enhanced the physical properties but with a further increase in binder content surface area decreases. Also it was found that mechanical strength was decreased with increasing binder content after burnoutTue, 25 Dec 2018 20:30:00 +0100Near free-edge stresses in FRP-to-concrete bonded joint due to mechanical and thermal loads
http://scientiairanica.sharif.edu/article_21199_0.html
Over the last few decades, a considerable amount of theoretical and experimental investigations have been conducted on the mechanical strength of composite bonded joints. Nevertheless, many issues regarding the debonding behavior of such joints still remain uncertain. The high near free-edge stress fields in most of these joints are the cause of their debonding failure. In this study, the performance of an externally bonded fiber-reinforced polymer (FRP) fibrous composite to a concrete substrate prism joint subjected to mechanical and thermomechanical loadings is evaluated through employing the principles of lamination theory. An inclusive Matlab code is generated to perform the computations. The bond strength is estimated to take place in a region- also termed the boundary layer- where the peak interfacial shearing and transverse peeling stresses occur; whereas the preceding stress field is observed to be the main failure mode of the joint. The proposed features are validated through the existing experimental data points as well as the commercial finite element (FE) modeling software Abaqus. Comparison between the calculated and experimental results demonstrates favorable accord, producing quite a high average ratio. The current approach is advantageous to failure modeling analysis, optimal design of bonded joints, and scaling analyses among others.Tue, 25 Dec 2018 20:30:00 +0100EXPERIMENTAL INVESTIGATION OF SHOCK WAVE OSCILLATION ON A THIN AIRFOIL
http://scientiairanica.sharif.edu/article_21200_0.html
Experimental results of surface pressure distribution over a thin supercritical airfoil and its wake are presented. All tests were conducted at free stream Mach numbers from 0.27 to 0.85 and at different angles of attacks in a transonic wind tunnel. The model was equipped with static pressure orifices connected to high frequency pressure-transducers. The present paper evaluates variations of shock wave location with both Mach number and angle of attack variation as well as its interaction with the boundary layer leading to the buffet phenomenon. The frequency of the shock wave oscillation and unsteady wake behaviour at a freestream Mach no. of M=0.6 and at different angles of attacks are measured using cross-correlation technique by means of pressure sensors locating on the suction side of the model and via the rake total pressure data that was traversed vertically behind the model respectively. From the analysis of surface pressure distribution and wake data, drag divergence occurred at a certain angle of attack and at a frequency equal to the shock wave oscillation frequency.Tue, 25 Dec 2018 20:30:00 +0100Pulsating flow induced parametric instabilities of a smart embedded micro-shell based on ...
http://scientiairanica.sharif.edu/article_21201_0.html
In this study, the dynamical instabilities of an embedded smart micro-shell conveying pulsating fluid flow is investigated based on nonlocal piezoelasticity theory and nonlinear cylindrical shell model. The micro-shell is surrounded by an elastic foundation which is suitable for both Winkler spring and Pasternak shear modules. The internal fluid flow is considered to be purely harmonic, irrotational, isentropic, Newtonian and incompressible and it is mathematically modeled using linear potential flow theory, time mean Navier Stokes equations and Knudsen number. For more reality of the micro-scale problem the pulsating viscous effects as well as the slip boundary condition are also taken into accounts. Employing the modified Lagrange equations of motion for open systems, the nonlinear coupled governing equations are achieved and consequently the instability boundaries are obtained using the Bolotin’s method. In the numerical results section, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence; flutter and parametric resonance). It is found that applying positive electric potential field will improve the stability of the system as an actuator or as a vibration amplitude controller in the Micro Electro Mechanical Systems.Fri, 28 Dec 2018 20:30:00 +0100Septic B-spline method for solving nonlinear singular boundary value problems arising in ...
http://scientiairanica.sharif.edu/article_21202_0.html
In this paper, we present a numerical method based on septic B-spline function for nonlinear singular second-order two-point boundary value problems, which depend on different physiological processes as thermal explosions problem and the steady state oxygen diffusion in a spherical cell with Michaelis–Menten uptake kinetics and distribution of heat sources in the human head. Septic B-spline method has a truncation error of O(h^8) and converges to the exact solution with O(h^6). The numerical problems show that our method is very effective. The resulting sets of differential equations are modified at the singular point and are treated by using septic B-spline for finding the numerical solution. The maximum absolute errors and the absolute residual errors are acceptable.Fri, 28 Dec 2018 20:30:00 +0100Computational modeling of the operating room ventilation performance in connection with ...
http://scientiairanica.sharif.edu/article_21203_0.html
Surgical site infection (SSI) is a critical source of post-surgical complications in hospitals which affects 2.6% of all surgeries. The primary source of SSI is the deposition of flakes released from the exposed skin of the surgical staff or the patient on the exposed surgical wound. There is considerable interest to design an appropriate ventilation system to minimize SSI. In this study, a computational model for simulating the airflow and thermal conditions in an operating room is developed, and the transport and deposition of particulate contaminants near the surgical wound are analyzed. The results show the formation of a thermal plume over the wound tissue, which is typically at higher temperature than the surrounding. The thermal plume protects the wound from deposition of falling contaminants. The effects of particle size, surgical lights characteristics, and presence of partitions on the optimum inlet air velocity are also studied. Based on the results, the formation of thermal plume over the surgical lamps may easily disturb the ventilation airflow and impresses the optimum inlet air velocity accordingly. The present study provides a better understanding of airflow pattern and transport process in the operating rooms equipped with the UCV systems.Sun, 30 Dec 2018 20:30:00 +0100A holistic framework for lot sizing problem in fast-moving perishable products
http://scientiairanica.sharif.edu/article_21204_0.html
One of the major challenges being faced by manufacturing companies today is the issue of addressing various aspects of perishable products in a supply chain environment. To address this issue, the integrated lot size problem for a perishable product has been investigated in the present work. The problem is modeled as a single vendor multiple buyer system. A variant of the truckload discount scheme is applied and the proposed model is formulated as a mixed integer program (MIP). The traditional warehouses are replaced by ‘cross-docks’ and situations in which, cross-docking would be more beneficial are highlighted. The problem of fleet selection is also addressed and various strategies to minimize the vendor cost are also highlighted for centralized and decentralized supply chains. Sensitivity analysis is then carried out on various input parameters such as setup cost at plant, variable transportation cost, fixed transportation cost, setup cost per order, holding cost and, lost cost, which underscores the significant impact of economies of scale in transportation on the total supply chain cost. Analysis of lead time-cost trade-off reveals that alternate modes of transportation could be explored, which significantly reduces the lead time of transportation, thereby minimizing the total supply chain cost.Sun, 30 Dec 2018 20:30:00 +0100Microwave assisted green synthesis of guar gum esters with enhanced physico-chemical properties
http://scientiairanica.sharif.edu/article_21205_0.html
Several methods have been developed for the modification of natural polymers. Most of the reported methods are expensive since the chemical reactions are carried out using chemical additives along with stabilizers. Microwave assisted synthetic strategies gained significant importance for materials synthesis due their eco-friendly nature. Guar gum is one of the important naturally occurring non-ionic polysaccharide, which has incredible industrial and commercial applications. A rapid method for protecting the hydroxyl group in sterically hindered gum was developed by microwave-assisted synthesis (MAS). An efficient synthesis of different novel guar gum derivatives such as (acetate, butyrate and propionate; GG1-GG3) was performed. A significant higher yield of ester was achieved for 15 min at 600 W using iodine as a reaction promoter. Gum ester formation was carried out at various concentrations and for different reaction intervals. The synthesized products were characterized using FTIR, NMR, and SEM techniques. The efficiency of adopted synthesis method was evaluated based on swelling ratio, gelation ability and solubility. The study indicates that the guar gum can be modified using acid anhydride under microwave irradiation with enhanced physic-chemical properties. Moreover, microwave modification is an eco-friendly approach.Sun, 30 Dec 2018 20:30:00 +0100Numerical and experimental study of the process parameters effect on the void evolution in the ...
http://scientiairanica.sharif.edu/article_21206_0.html
Elimination of defects such as voids and internal cavities is required in metal forming processes to avoid premature failure of mechanical components during service. In this paper, the effect of different parameters on the void closure behavior is studied in the cold extrusion of rods. A three dimensional nonlinear dynamic finite element model is developed for this purpose. Experiments are also performed on aluminum samples to verify the accuracy of the finite element model. Results of the developed model are in good agreement with experimental findings. It is observed that voids contract in all directions during the direct extrusion which is in contrast to some other metal forming processes like forging and rolling. Effect of parameters such as die semi-angle, friction coefficient and void location on the void evolution is systematically investigated and discussed. The results of this study can help industries using metal extrusion for optimized design and control of the process to reduce voids and porosity and increase the strength of their product.Sun, 30 Dec 2018 20:30:00 +0100An effective solution approach for multi-objective fractional fixed charge problem with fuzzy ...
http://scientiairanica.sharif.edu/article_21207_0.html
A multi-objective fixed charge problem in existence of several fractional objective functions with triangular fuzzy parameters is considered in this study. The problem previously has been tackled only by Upmanyu and Saxena (2016) with a method containing wrong mathematical concepts (see the commentary of Kaur and Kumar (2017)). To overcome the shortcomings of the literature, an effective solution approach based on a typical goal programming approach is proposed to solve the problem for obtaining a Pareto-optimal solution. The proposed approach considers the shortcomings of the method of Upmanyu and Saxena (2016) and applies no ranking function of fuzzy numbers. In addition, the goal programming stage considers no preference from decision maker. The computational experiments provided by an example of the literature, prove the effectiveness of the proposed approach.Sun, 30 Dec 2018 20:30:00 +0100Nanoporous metal-organic framework Cu2(BDC)2(DABCO) as an efficient heterogeneous catalyst for ...
http://scientiairanica.sharif.edu/article_21208_0.html
Solvent-free ball-milling synthesized porous metal-organic framework Cu2(BDC)2(DABCO) (BDC: benzene-1,4-dicarboxylic acid, DABCO: 1,4-diazabicyclo[2.2.2]octane) proved to be a practical catalyst for facile and convenient synthesis of 1,2,3–triazole derivatives via multicomponent reaction of terminal alkynes, benzyl or alkyl halides, and sodium azide in ethanol. Avoidance of usage and handling of hazardous organic azides, using ethanol as an easy available solvent and catalyst simple preparation and its recycling makes this procedure truly a scale-up-able method. The high loading of copper ions in the catalyst causes efficient catalytic activity and hence its low weight usage in reaction. The catalyst was recycled and reused several times without significant loss of its activity. Furthermore, novel derivatives were examined to investigate their potential antimicrobial activity via microdilution method.Sun, 30 Dec 2018 20:30:00 +0100Processing Parameter Effects in Gas Tungsten Arc Welding of Thin Titanium Plates
http://scientiairanica.sharif.edu/article_21209_0.html
This work systematically investigated the effects of process parameters on the technological responses, including the tensile force TF and average micro hardness AMH in the gas tungsten arc welding (GTAW) of titanium. Controlled parameters are the welding current I, gas flow rate F, and arc gap G. The objective of this work is to improve the tensile strength with respect to micro hardness constraints. A GTAW welding machine was adopted in conjunction with the Box-Behnken matrix to conduct experimental trails. The nonlinear relationships between welding parameters and responses were developed using response surface method (RSM). Subsequently, an optimization technique entitled desirability approach (DA) was used to solve the trade-off analysis between responses considered and find the optimal parameters. The conformity test was performed in order to evaluate the accuracy of optimizing values. The results showed that the welding current had the greatest influence on the outputs considered, compared to other factors. The measured improvements using optimal parameters of tensile force and average micro hardness are approximately 4.10% and 6.12% in comparison with initial settings. A hybrid approach comprising RSM and desirability approach can be considered as an effective method for parameter optimization and observation of reliable values in GTAW processes.Sun, 30 Dec 2018 20:30:00 +0100Numerical study of hydrothermal characteristics in nanofluid using KKL model with effect of ...
http://scientiairanica.sharif.edu/article_21213_0.html
Finite element method (FEM) is used to study the hydrothermal characteristics of the nano-fluid subjected to Brownian motion. For effective thermal conductivity and effective, viscosity Koo-Kleinstreuer-Li (KKL) model is used. It is observed that the dispersion of nano-particles in Newtonian liquid causes a significant increase in the effective thermal conductivity. This results based on the dispersion of nano-particles help engineers to design an efficient thermal system. A significant role of viscous dissipation on diffusion of momentum of wall into the fluid is observed. Therefore, dissipations effects cannot be ignored while designing thermal systems. The buoyant force is responsible for the effect of electromagnetic thermal radiations on the velocity of fluid convectively heated surface enhances the rate of generation of entropy. This study also recommends that nano-fluids are the best coolants as compare to the base fluids. Imposition of magnetic field causes more entropy generation.Fri, 04 Jan 2019 20:30:00 +0100TF/TA Optimal Flight Trajectory Planning Using a Novel Regenerative Flattener Mapping Method
http://scientiairanica.sharif.edu/article_21215_0.html
In this paper, a new methodology has been proposed to enhance the conformal mapping applications in the process of optimum trajectory planning in Terrain Following (TF) and Terrain Avoidance (TA) Flights. The new approach uses the conformal mapping concept as a flattener tool to transform the constrained trajectory-planning problem with flight altitude restrictions due to the presence of obstacles into a regenerated problem with no obstacle and minimal height constraints. In this regard, the Schwarz–Christoffel theorem has been utilized to incorporate the height constraints into the aircraft dynamic equations of motion. The regenerated optimal control problem then is solved employing a numerical method namely the direct Legendre-Gauss-Radau pseudospectral algorithm. A composite performance index of flight time, terrain masking, and aerodynamic control effort is optimized. Furthermore, to obtain realistic trajectories, the aircraft maximum climb and descent rates are imposed as inequality constraints in the solution algorithm. Several case studies for two-dimensional flight scenarios show the applicability of this approach in TF/TA trajectory-planning. Extensive simulations confirm the efficiency of the proposed approach and verify the feasibility of solutions satisfying all of the constraints underlying the problemFri, 04 Jan 2019 20:30:00 +0100Enhancing the efficiency of the ratio-type estimators of population variance with a blend of ...
http://scientiairanica.sharif.edu/article_21219_0.html
Numerous ratio-type estimators of the population variance are proposed in the existing literature based on different characteristics of the study as well as the auxiliary variable. However, mostly the existing estimators are based on the conventional measures of the population characteristics and their efficiency is dubious in the presence of outliers in the data. This study presents improved families of variance estimators under simple random sampling without replacement assuming that the information on some robust non-conventional location parameters of the auxiliary variable is known besides the usual conventional parameters. The bias and mean square error of the proposed families of estimators are obtained and the efficiency conditions are derived mathematically. The theoretical results are supplemented with the numerical illustrations by using real datasets which indicates the supremacy of the suggested families of estimators.Mon, 07 Jan 2019 20:30:00 +0100Optimal Sizing of Hybrid WT/PV/Diesel Generator/Battery System using MINLP Method for a Region ...
http://scientiairanica.sharif.edu/article_21220_0.html
Abstract— Renewable resources have attracted attention due to different reasons like reducing pollution, improving technical issues. Using several resources along with each other requires studying different aspects. One of the most important issues in hybrid systems is system optimality. Therefore, the most effective approach is to combine components to minimize the cost. Different approaches have been proposed for determining the size of hybrid system components to optimize the proposed system. These methods are classified into three categories: classic, artificial intelligence and computer program methods. In this paper, the optimal size of components is obtained using MINLP method. Outputs of this algorithm are compared with two other algorithms and advantage of this method is proved. This paper gives better responses in a shorter time.Mon, 07 Jan 2019 20:30:00 +0100Exact mathematical solution for nonlinear free transverse vibration of beams
http://scientiairanica.sharif.edu/article_21221_0.html
In the present paper, an exact mathematical solution has been obtained for nonlinear free transverse vibration of beams, for the first time. The nonlinear governing partial differential equation in un-deformed coordinates system has been converted in two coupled partial differential equations in deformed coordinates system. A mathematical explanation is obtained for nonlinear mode shapes as well as natural frequencies versus geometrical and material properties of beam. It is shown that as the s th mode of transverse vibration excited, the mode 2s th of in-plane vibration will be developed. The result of present work is compared with those obtained from Galerkin method and the observed agreement confirms the exact mathematical solution. It is shown that governing equation is linear in time domain. As a parameter, the amplitude to length ratio (Λ⁄l) has been proposed to show when the nonlinear terms become dominant in the behavior of structureMon, 07 Jan 2019 20:30:00 +0100Damage detection in a double-beam system using proper orthogonal decomposition and ...
http://scientiairanica.sharif.edu/article_21222_0.html
This study deals with inverse approach for damage detection in a double-beam system. A double-beam system made of two parallel beams connected through an elastic layer. Degradation in stiffness of beams element, crack occurrence and partly destruction of inner layer has been considered as different types of damage. The time domain acceleration response of the system measured and proper orthogonal decomposition has been applied to the collected data in order to derive the proper orthogonal values (POV) and proper orthogonal modes (POM) of the system. Effect of single damage in different locations on the POV has been analyzed and an objective function has been defined using the dominant POV and POM of each beam separately. In order to increase robustness of the method against noise, the objective function enriched by adding statistical property of time domain response. The teaching-learning based optimization algorithm has been employed to solve optimization problem. Efficiency of the proposed method for detecting single and multiple damages in the system demonstrated with and without noise. Simulation results show good accuracy of the proposed method for detection single and multiple damages of different types in the system.Mon, 07 Jan 2019 20:30:00 +0100Optimal Pricing Strategies in Presence of Advance Booking Strategies for Complementary Supply Chains
http://scientiairanica.sharif.edu/article_21223_0.html
Due to high competition, companies tend to improve their market share by applying different selling mechanisms such as online to offline commerce as an efficient selling mechanism in which the companies sells their products via both online and real stores. This study deals with a selling problem for two complementary supply chains including a supplier and a shopping center where the commodities are sold by a virtual and a traditional shopping center who present items as complementary shopping centers. It is assumed that market demand depends on price and service level so that they can purchase the item via both shopping centers based on their priorities. Also to analyze the reactions of the chain’s partners, different games such as Nash and Stackelberg game are deemed. The aim is to obtain the closed-form solutions of the decision variables of the networks’ members in order to maximize their profits where the prices of different selling periods at each echelon of the chains are the decision variables of the model. The closed-form solutions are derived and the solutions are examined by a numeric example. In following, several sensitivity analyses on key factors are performed to determine efficient ones on the variables and profits.Mon, 07 Jan 2019 20:30:00 +0100Design Modifications for Improving Modulation Flux Capability of Consequent-Pole Vernier-PM ...
http://scientiairanica.sharif.edu/article_21224_0.html
The Vernier PM (VPM) machine is known as a high-torque and low speed drive solution suitable for direct-drive applications such as electric vehicles and wind turbines. The Consequent-Pole Vernier PM (CP-VPM) machine is a special structure of VPM that also introduces high torque density as the conventional VPM incorporating significantly lower volume of PM materials. Although many researches and experiment studies, especially in recent years, reported concerning the conventional structure, there are little publications on the CP-VPM machine. The paper presents the electromagnetic principles of modulation flux occurring in CP-VPM machine. The operating quantities are evaluated using analytical equations and compared with the conventional machine performance. It is concluded that the torque density and back-EMF are much larger than the conventional machine and the torque pulsation magnitude is lower. However, the power-factor is undesirably reduced due to higher spatial harmonics distortion of the CP rotor magnetic field and presence of magnetic field components that do not contribute in the flux modulation. Based on the spatial harmonic analysis, design modifications for enhancing the operational characteristics of the CP-VPM machine are proposed and their effectiveness is verified through comparing the 2D-FE results with the results of the conventional VPM machines.Mon, 07 Jan 2019 20:30:00 +0100PREDICTION OF CRITICAL FRACTION OF SOLID IN LOW PRESSURE DIE CASTING OF ALUMINUM ALLOYS USING ...
http://scientiairanica.sharif.edu/article_21225_0.html
Casting simulation programs are the computer programs that digitally model the casting of an alloy in the sand, shell or permanent mold and then the cooling and solidification processes. However, obtaining consistent results from the casting modeling depends on providing many parameters and boundary conditions accurately. Critical fraction of solid (CFS), which is one of the most important of these parameters, is defined as the point where the solid dendrites do not allow any flow of the liquid metal in the mushy zone. Since the CFS value varies depending on many factors, inconsistent results can be experienced in the modeling applications. In this study, the CFS value obtained during the solidification of various commercial aluminum alloys' casting process carried out using low pressure die casting method, is predicted by using artificial neural network (ANN) method based on alloy type, grain refiner and modifier additions, initial mold temperature, pressure level parameters. In the scope of the study, 162 experiments are conducted. The results obtained from the low pressure die casting experiments using a special model designed for the study are validated by using SOLIDCast casting simulation. The CFS values obtained from this validation range from 33% to 61%.Mon, 07 Jan 2019 20:30:00 +0100Instantaneous Thrust Control of the Linear Switched Reluctance Motors with Segmental Translator
http://scientiairanica.sharif.edu/article_21226_0.html
The linear switched reluctance machine (LSRM) has all advantages of rotary switched reluctance machine including simple and rugged structure, absence of magnetic material and windings on translator, high reliability and appropriate performance over a wide range of speed. Like rotary switched reluctance motor with segmental rotor, segmental translator linear switched reluctance motor (STLSRM) has capability to produce higher output power/weight in comparison to the conventional linear switched reluctance motors. Due to high advantages of the STLSRM drive, various control algorithms including current control, model predictive control, direct force control, universal control and force distribution function are investigated for the first time to control the instantaneous thrust of this motor. Applying these algorithms to a typical three-phase STLSRM, simulation results are presented and they are compared together from the force ripple reduction point of view.Mon, 07 Jan 2019 20:30:00 +0100Continuous Slip Surface Method for Stability Analysis of Heterogeneous Vertical Trenches
http://scientiairanica.sharif.edu/article_21227_0.html
Evaluating the reliability of trenches against sliding failure is complicated by the fact that most alluvial deposits are heterogeneous and spatially variable. This means that instead of perfectly circular or linear failure surfaces, trench failure tends to be more complex, following the weakest path or zones through the material, thereby, a new method named Continuous Slip-Surface (CSS) is adopted for calculating the critical excavation depth. CSS runs an algorithm to seek for continuous slip surface. The Finite Difference Method (FDM) coupled with random field theory and CSS method is well suited to slope stability calculations since it allows the failure surface to seek out the weakest path through the soil. For an unsupported vertical cut, it was shown that the critical excavation depth acquired from CSSM is indeed an upper bound solution. It was further shown both numerically and analytically through an idealized variation model that increasing the un-drained shear strength density fades the effect of shear strength variability. Correlation structure of the input variable was also shown to influence the results, although the behaviour was found different in low and high scales of fluctuation.Mon, 07 Jan 2019 20:30:00 +0100Analysis of RC Beams Strengthened with FRP Sheets under Shear and Flexure Using MCFT
http://scientiairanica.sharif.edu/article_21228_0.html
Shear behavior of reinforced concrete (RC) beams strengthened with fiber reinforced polymers (FRP) sheets is studied in this paper using modified compression field theory(MCFT). The beam is considered to be under the combined effects of shear force and bending moment. Equilibrium and compatibility equations, as well as stress-strain relationships are developed for an element in the strengthened beam. Due to the extensive computations, a computer program wasdeveloped to solve the governing equations. The accuracy of the presented method herewas verified by the experimental results of 84 strengthened RC beams reported in the literature. Comparison between the measured and predicted results shows that the method can predict the shear behavior of the beam throughout its entire range leading up to failure. The method can also incorporate the effect of debonding of the FRP sheets in the analysis. The results of a case study indicates that preventing thedebonding of theFRP sheets from the web of the beam adds significantly to the shear capacity, and in certain cases changes the failure mode from brittle to ductile.Mon, 07 Jan 2019 20:30:00 +0100Preventing SQL Injection Attacks by Automatic Parameterizing Raw Queries Using Lexical and ...
http://scientiairanica.sharif.edu/article_21229_0.html
SQL injection (SQLI) is one of the most important security threats against web applications. Many tech-niques have been proposed for counteracting SQLI attacks; however, second-order attacks and the injectionattacks that are raising data-type mismatch errors have been ignored in most of them. In this paper, wepropose a new anomaly-based method (deploying as a proxy between the application server and its databaseserver) for detection and/or prevention of SQLI attacks without requiring any modication to the sourcecode of vulnerable applications. The majority of attacks, which lead to a change in the syntax of applica-tion queries, are identied in the detection phase by lexical analysis of the queries. The remained types ofattacks, such as second-order attacks and attacks generating data type mismatch errors, are prevented tobe executed in the prevention phase, where each query is automatically converted to a parameterized query(before submitting to its database) using a semantic analysis method.Mon, 07 Jan 2019 20:30:00 +0100Simultaneous analysis and optimal design of truss structures via displacement method
http://scientiairanica.sharif.edu/article_21230_0.html
In this paper, an efficient technique is proposed by displacement method of analysis and three metaheuristic algorithms consisting of the Colliding Bodies Optimization (CBO), Enhanced Colliding Bodies Optimization (ECBO) and Vibrating Particles System (VPS), for the simultaneous analysis and optimal design of truss structures. The presented method is applied to the minimum weight design of some planar and spatial truss structures. For examining the accuracy and efficiency of the proposed method, the problems are also designed by the same metaheuristic algorithms utilizing pure force method and pure displacement method as analysis tools (non-simultaneous) and the resulting structural weights are compared.Tue, 08 Jan 2019 20:30:00 +0100Improving facility management of public hospitals in Iran using building information modeling
http://scientiairanica.sharif.edu/article_21231_0.html
Improving management of complex and congested facilities in hospital buildings is a potential point for both reducing money spent and enhancing quality level of the medical services provided in public hospitals of Iran. Although building information modeling (BIM) is identified as an effective tool for improving facility management (FM), use of advantages it offers to the FM processes of hospitals has been neglected thus far in the country. To address this issue, this research aims to investigate the BIM capabilities and the supporting organizational structure public hospitals in Iran can adopt to improve their FM processes. A comprehensive literature review was conducted on applicable capabilities of BIM to the FM processes. Hierarchical FM structure of public hospitals in the country was recognized through review of the related regulations. A public hospital case was chosen for an in-depth recognition of FM processes operations and validation of the proposed BIM-based improvements. It was argued the use of BIM capabilities can cause substantial improvements in the FM processes of the public hospitals. Reduced duration of FM activities, improved facility layouts, enhanced communication and coordination, facilitated training, and improved emergency management are some expected outcomes.Fri, 11 Jan 2019 20:30:00 +0100Synthesis and characterization of poly(styrene-block-acrylic acid)/Fe3O4 magnetic nanocomposite ...
http://scientiairanica.sharif.edu/article_21232_0.html
A well-defined, amphiphilic poly(styrene-block-acrylic acid) (PSt-b-PAA) block copolymer to prepare a magnetic nanocomposite was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The synthesized PSt and PSt-b-PAA copolymer were characterized using FTIR and 1H NMR spectroscopies as well as GPC analysis. Afterward, a PSt-b-PAA/Fe3O4 magnetic nanocomposite was fabricated through the incorporation of Fe3O4 nanoparticles (NPs) into the synthesized block copolymer. The morphology of the fabricated magnetic nanocomposite was observed using SEM and TEM. The SEM image revealed that the PSt-b-PAA/Fe3O4 magnetic nanocomposite has spherical morphology with the mean diameter of 100 nm approximately. In addition the thermal properties of the synthesized polymers as well as magnetic nanocomposite were studied using DSC and TGA analysis. The developed nanocomposite may be applied for enzyme immobilization and cell separation.Fri, 11 Jan 2019 20:30:00 +0100Influence of Two Different Producers in a Competitive Location Problem
http://scientiairanica.sharif.edu/article_21233_0.html
Facility location of two producers with preference of customers is discussed in this paper. Because of differences between two producers in terms of their influence on the market, the problem is formulated as a bi-level integer mathematical programming model with binary variables. It is considered that both leader and follower have some facilities at first and are going to open new facilities and this may lead to make changes in allocation of facilities and customers. To solve the problem, two metaheuristics algorithm based on genetic algorithm (GA) and hybrid of genetic algorithm and ant colony optimization (ACO) are proposed. In the first section of each algorithm, the location of facilities for two producers is determined and in the second section, each customer selects a facility. Upper bound of the competitive facility location problem is determined by solving the upper-level problem as an integer linear programming model without considering the follower’s decision. To evaluate the efficiency of proposed algorithms, enumeration technique is used to find optimal solution. Computational results show that all of the developed algorithms are capable of achieving optimal solution for small size problems and high-quality solution in reasonable computational time for medium and large-scale problems.Fri, 11 Jan 2019 20:30:00 +0100Coating of B2O3 and Al2O3 containing Hydroxyapatite on Ti6Al4V by HVOF Technique
http://scientiairanica.sharif.edu/article_21234_0.html
Calcium phosphate (Ca-P) based bioceramics has proved to be alluring materials for biomedical applications. Among these, particular attention has been given to hydroxyapatite (HA), Ca10(PO4)6(OH)2. Due to its favorable some physical, mechanical, chemical properties and biocompatibility, HA-coated Ti6Al4V alloy has been approved as one of the most interesting implant materials for orthopedic and dental applications. High Velocity Oxy Fuel (HVOF) is a method used to coat hydroxyapatite (HA) on metallic implants such as titanium (Ti) and its alloy (Ti6Al4V). In this work decreasing the crack occurrence and increasing adhesion strength were investigated. For this purpose, sol-gel synthesized nano sized HA, alumina (Al2O3) and Boron oxide (B2O3) powders were produced. First, a series of HA/Al2O3 HA/B2O3 coatings have been deposited on Ti6Al4V substrate by HVOF method. All specimens’ surfaces were used to characterize by using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD). Adhesion strength of the samples was found to affect with increasing amount of Al2O3 and B2O3 in HA. Furthermore, water contact angles of coating layer were decreased with increasing amount of Al2O3 and B2O3 in HA. This coating surface was expected to combine the advantages of Ca-P (osseointegration) and adhesion strength.Fri, 11 Jan 2019 20:30:00 +0100Developing a deformable model of liver tumor during breathing to improve targeting accuracy in ...
http://scientiairanica.sharif.edu/article_21235_0.html
New advances in computer technology for biomechanical numerical modeling of human body are the basis for the improvement of targeting accuracy. This is especially important for guiding surgeons during interventional procedures and locating of liver tumor for radiotherapy. This paper deals with investigating the motion and deformation of a tumor, embedded into liver, during respiration. Here, a 3D FE model of human liver as a whole is developed to simulate liver behavior during respiration. First, the cloud of point according to CT image data was imported into CATIA software. Then a spherical tumor was embedded into the different segments of liver tissue in ABAQUS. A quasi-linear hyperviscoelastic constitutive model and an elastic behavior were used to define the liver and tumor properties, respectively. Boundary conditions were defined based on the difference between end-exhale and end-inhale states of liver tissue. Deformation and motion of liver tumor was then determined at intermediate states of breathing. Finally, the new position and the deformed shape of the tumor were investigated, considering the increase of tumor stiffness. The results show that if the tumor is located in the segment VII, then maximum displacement in the y-direction is observed.Fri, 11 Jan 2019 20:30:00 +0100Collapse of reticulated domes, a case study of Talakan oil tank
http://scientiairanica.sharif.edu/article_21239_0.html
In this paper, instability of single layer reticulated domes is discussed. This purpose is elaborated by a case study on Talakan oil tank dome which is analyzed in this work with research package. This paper provides technical information related to the design, fabrication and collapse of Talakan dome. The secondary paths, especially in unstable buckling, can play an important role in the loss of stability and led to failure of the structure. The authors show that the stiffness of the dome is not adequate to prevent buckling under the prescribed snow loads. It is also shown that the capacity of the dome to resist eccentric snow load is about half of its capacity to resist symmetric snow loads. Although six combinations of load and support fixity are included in design assumptions, considerable attention has been focused on the bifurcation behavior in Talakan dome. The stiffness of the aluminum sheets of the roof cover have not been taken into account in the stability analysis.Mon, 21 Jan 2019 20:30:00 +0100SUSTAINABLE USE OF STABILIZED FLOOD MUD AS SUBGRADE SOIL FOR LOW VOLUME TRAFFIC ROADS
http://scientiairanica.sharif.edu/article_21240_0.html
This research was carried out to identify the basic properties of flood mud and the efficiency of biomass silica (SH85) as a stabiliser to improve the strength of this mud. Unconfined Compressive Strength (UCS) testing was carried out on untreated soil and soil treated with 2%, 4%, and 9% SH85 at three and seven curing days. The microstructure of SH85 treated flood mud was investigated via field-emission scanning electron microscopy (FESEM) and Energy-Dispersive X-Ray spectrometry (EDX) analyses. It was found that the strength of treated soil increases two to seven times that of the untreated soil strength where the highest strength was recorded at 949 kPa after the soil had been treated with 9% of SH85 for seven days. A polynomial trend was observed with an R2 greater than 95% relationship between SH85 content versus UCS, with different curing periods. The seven-day UCS of SH85 treated flood mud meets the strength requirement of 0.8 MPa for Malaysian subgrade material of low traffic volume roads and the compressibility was significantly reduced when SH85 content was greater than 4%. It was found from the FESEM and EDX results that cementitious products leading to strength improvement fill the voids of the treated soil.Mon, 21 Jan 2019 20:30:00 +0100Experimental and Numerical Comparison of Flow and scour Patterns around a Single and Triple ...
http://scientiairanica.sharif.edu/article_21241_0.html
Placement of bridge piers along rivers creates a complex 3D flow pattern which disrupts normal river flow and the resulted turbulence erodes alluvial sediments around the pier. In this research, SSIIM model has been used to simulate flow and scour patterns when no pier, one pier, and triple piers are placed at a 180 degrees bend and the results are compared with those of experiments. The piers are vertical. The simulated channel was 1 m wide with a U-turn having the relative curvature radius of 2 carrying a volumetric flow of 70 l/s the flow depth at the beginning of the bend is 18 cm. Results showed that SSIIM is well capable of simulating bed form changes and flow patterns such that at the bend with triple piers error in maximum scour and sedimentation was only 4%, in maximum transverse velocity 12%, in maximum longitudinal velocity 13%, and in maximum vertical velocity 19%. In general, SSIIM model satisfactorily simulates the location and value of local scour arising from single and series piers in numerical simulation of the flow and scour. In flow pattern simulation, the errors and differences are greater under moving bed conditions than a rigid bed.Mon, 21 Jan 2019 20:30:00 +0100Collapse assessment of Protected Steel Moment Frame under Post-earthquake Fire
http://scientiairanica.sharif.edu/article_21242_0.html
This paper investigates the behavior of low-, medium- and high-rise protected steel moment resisting frames under post-earthquake fire through two different methods. In the first method, the pushover analysis is utilized to simulate the response of the sample structures for various target displacements. Then the thermo-mechanical analysis is implemented to evaluate the behavior of the damaged frames under fire, assuming that the fireproofing is delaminated at the end regions of the beams. In the second method, the seismic response of the frames under two sets of the MCE-scaled near and far fault ground motion records is determined employing the time history analysis. In this method, the damage of fireproofing is characterized by the maximum inter-story drift ratio. The results of the study revealed that the method 1 give similar results to the method 2, for most cases. It is also found that for sufficiently large drift demands, the collapse of the frames under post-earthquake fire occurs in side-way mode, while for lower seismic responses, the local failure of beams dominates other failure modes. Moreover, it was found that the reduction of fire resistance time due to the effects of MCE seismic loads ranges 4% to 26% for the considered structures.Mon, 21 Jan 2019 20:30:00 +0100NUMERICAL MODELING OF A NEW REINFORCED MASONRY SYSTEM SUBJECTED TO IN-PLAN CYCLIC LOADING
http://scientiairanica.sharif.edu/article_21243_0.html
This paper describes the behavior of walls under in-plane cyclic shear compression loads of a new reinforced masonry system composed of horizontally and vertically reinforcement based on Iran's national building regulation in two groups. First, steel bars in grid-type are mounted in the cement core between solid clay bricks (Double-Wythe) and in the second group, common steel bars in grid-type are mounted in perforated bricks and trusses as horizontal reinforcement, using advanced numerical simulation (LS-DYNA). A nonlinear finite element discrete modeling according to stress-strain models have been used in order to represent previously modeled masonry walls. Masonry units include perforated bricks and solid clay bricks, the mortar and bonding interfaces have been shown as continuum elements. In order to validate micro-modeling strategy, the input data, based on a reinforced masonry wall was previously tested in the laboratory with a clear identification and justification. That being so, the major purpose of this paper is: (a) the results of specimens in terms of maximum strength, ductility, energy absorption and failure modes (b) influence of aspect ratio and reinforcement type and (c) the comparison of modeled walls with other reinforced systems.Tue, 22 Jan 2019 20:30:00 +0100Laboratory investigation of geotextile position on CBR of clayey sand soil under freeze-thaw cycle
http://scientiairanica.sharif.edu/article_21244_0.html
In cold regions, soil experiences repetitive freeze–thaw cycles that are considered as one of the most important phenomena in cold region engineering. Approximately 30 percent of soils around the world and a large portion of fertile lands are subjected to daily or seasonal freeze-thaw cycles. These cycles cause considerable changes in water content, solute movement, permeability, strength parameters, erosion rate, and other physical or chemical characteristics of the soil. Nowadays, one of the ways for improvement the physical and mechanical characteristics of the soil is to incorporate geosynthetic material as a layer between the embankment and the ground surface. This paper presents results of some California Bearing Ratio tests a clayey sandy soil. Moreover, effect of freeze–thaw cycles on the compressive strength of geotextile-reinforced soil is investigated. The geotextile layer was placed in five positions in different depths of 1.3, 2.6, 3.9, 5.85 and 7.8 cm beneath the surface of the mold and then the sample was exposed to freeze-thaw cycles. It was found that the optimum depth of the geotextile layer is 3.9 cm. In addition, it could be observed that reinforcing the soil can diminish the weakening effect of freeze-thaw cycles up to 41.7%.Tue, 22 Jan 2019 20:30:00 +0100An exact solution to the problems of flexo-poro-elastic structures rested on elastic beds acted ...
http://scientiairanica.sharif.edu/article_21245_0.html
This paper aims to examine flexural vibrations of fully saturated poroelastic structures on an elastic bed subjected to moving point loads via an analytical solution. Using a flexural beam model in conjunction with the Biot’s poro-elasticity theory, the equations of motion of the porous structure are derived. Using assumed mode method and Laplace transform, the explicit expressions of displacement and pore pressure are obtained carefully. For a particular case, the predicted results are also compared with those of another work and a reasonably good agreement is achieved. The influences of the moving load velocity, permeability ratio, transverse stiffness of the foundation, viscosity of the pore fluid, and porosity on the maximum elasto-dynamic fields and pore pressure are conclusively discussed. The velocity pertinent to the maximum possible dynamic response is graphically determined and the roles of influential parameters on this crucial factor are displayed. The present model could be easily extended to multi-layered poroelastic structures under moving loads.Fri, 25 Jan 2019 20:30:00 +0100Numerical simulation of novel trombe wall-assisted desiccant wheel
http://scientiairanica.sharif.edu/article_21246_0.html
In the present study, a novel trombe wall-assisted desiccant wheel system has been modeled, in which the trombe wall is divided into three equal parts and it provides the heat energy needed to regenerate the desiccant wheel. The components of the system, including the desiccant wheel, the trombe wall are separately modeled in MATLAB software and then assembled to investigate the surface area of the trombe wall and the output humidity of the desiccant wheel for attaining air conditioning comfort. It has been discussed that the integrated system presented here, can be utilized in all humid climate conditions around the globe. The results of the present study for some special cases have been compared with results available in open literature. The optimal surface area of the trombe wall has been extracted according to the parameters of the desiccant wheel. Results shows that the solar energy received by the trombe wall is 600-740 W/m2 (1May – 15August) in warm and humid climate of Gilan (Iran), the temperature of the wall surface is obtained 77-86 ºC, and the outlet temperature of regeneration air stream from trombe wall is obtained 60-70 ºC, the output humidity of the desiccant wheel reduces 10-12 gw/kga.Fri, 25 Jan 2019 20:30:00 +0100Heat transfer correlation for a cross-flow jet impingement on a protruded surface
http://scientiairanica.sharif.edu/article_21247_0.html
This paper aimed at developing an empirical correlation for heat transfer from a protruded surface in the presence of a cross-flow jet. Finite volume method has been used to solve the governing differential equations for mass, momentum, energy as well as turbulence by imposing appropriate boundary conditions. Extensive numerical computations have been carried out to vary each of the independent variables to collect data for area-weighted average Nusselt number. Both the duct and the nozzle Reynolds number are varied from 6,000-20,000. The volume fraction and Prandtl number are also varied in the range of and , respectively. The number of protrusion (n) is varied from 1 to 4. A nonlinear regression analysis has been executed using CFD data to develop an empirical correlation for the Nusselt number in terms of pertinent independent parameters. The volume fraction of the nanofluid is found to be the most significant parameter to influence heat transfer rate among all other parameters. It has been observed that the predicted Nusselt number matches well with the computed one. The variations of the Nusselt number as the function of the independent parameters has been demonstrated. The present numerical methodologies have been validated with some open literature.Sat, 26 Jan 2019 20:30:00 +0100Product substitution with customer segmentation under panic buying behavior
http://scientiairanica.sharif.edu/article_21248_0.html
Under conditions of consumer panic buying, satisfying demand with the available products is a complex problem. In reality, most retailers accept alternative products during panic situations. This study considers the case of firm-driven substitution of products (differing in weight) based on retailer preferences over two periods. In the proposed model, panic behavior emerged in the first period and supply disruption occurred in the second period. Under this model, retail stores were segmented into high index (valuable) and low index (less valuable) customers. Before meeting the demand of low-index customers, wholesalers attempt to satiate high-index customer’s panic buying behavior. We determined the optimal number of units to be substituted, order quantities, and leftover units that generated maximum total profits for the wholesaler. The performance of the model was analyzed both with and without customer-segmented substitution. To gain managerial insights, we also examined the influence of both the degree of supply disruption and substitution costs on decisions and profits. The results can assist business managers to improve the decision-making process.Sat, 26 Jan 2019 20:30:00 +0100Optimal Tuner Selection using Kalman Filter for a Real-Time Modular Gas Turbine Model
http://scientiairanica.sharif.edu/article_21249_0.html
In this study, a real-time flexible modular modeling approach for the simulation of gas turbine engines dynamic behavior based on nonlinear thermodynamic and dynamic laws is addressed. The introduced model, which is developed in Matlab-Simulink environment, is an object-oriented high speed real-time computer model and is capable of simulating the dynamic behavior of a broad group of gas turbine engines due to its modular structure. Moreover, a Kalman filter-based model tuning procedure is applied to decrease the modeling errors. Modeling errors are defined as the mismatch between simulation results and available experimental data. This tuning procedure is an underdetermined estimation problem, where there are more tuning parameters than available measured data. Here, an innovative approach to produce a tuning parameter vector is introduced. This approach is based on seeking an optimal initial value for the Kalman filter tuning procedure. Three simulation studies are carried out in this paper to demonstrate the advantages, capabilities and performance of the proposed scheme. Furthermore, simulation results are compared with manufacturer’s published data, and with the experimental results gathered in either turbo-generator or turbo-compressor applications. Computational time requirement of the model is discussed at the end of the paper.Sat, 26 Jan 2019 20:30:00 +0100A Modified Indicial Functions Approximation for Nonlinear Aeroelastic Analysis
http://scientiairanica.sharif.edu/article_21250_0.html
The nonlinear dynamic response, Limit Cycle Oscillations (LCOs), of high aspect ratio wings using a novel indicial aerodynamics in subsonic flow is investigated. Using the nonlinear beam theory, the structural model is derived including the in-plane and out-of-plane bending and torsion motions, all nonlinearities up to cubic order arising from large deformation, mass distribution, and cross-sectional mass imbalance. Based on new approximations of the indicial functions, a comprehensive unsteady aerodynamic model is used. Such an indicial aerodynamics while being coupled to nonlinear structural equations can result in a unified nonlinear aeroelastic formulation in both the incompressible and subsonic compressible flow. The effect of flight conditions, wing tip initial disturbances, stiffness ratio between bending modes, and nonlinearity due to inertia and cross-sectional mass imbalance on the characteristics of LCO are discussed. The results show that the compressibility can affect the LCO boundary up to 12 percent which implies that an appropriate Mach-dependent aerodynamics is required to achieve a more reasonable and realistic description of dynamic behavior of the system. It is shown that the presence of LCO before the linear flutter speed depends on initial disturbances as well as wing characteristics.Sat, 26 Jan 2019 20:30:00 +0100Boundary layer and surface pressure distributions behavior over a submarine nose model with two ...
http://scientiairanica.sharif.edu/article_21251_0.html
Surface pressure distributions and boundary layer profiles are measured over the nose surface of a submarine model in a wind tunnel. The tests are conducted for two different nose shapes in order to study the effects of nose shape on the flow field around the model. The influence of Reynolds numbers, which are 0.5×106, 0.8×106 and 106, and pitch angles, α = 0, 5, 10 and 15°, on the surface pressure distribution over the surface of two nose shapes are investigated. Furthermore, the effect of the longitudinal pressure gradient on the boundary layer velocity profiles and the probability of the separation in the plane of symmetry of the nose are studied. It is found that the Reynolds number does not have a significant influence on the nose surface pressure distribution at all pitch angles. The results show that the presence of the adverse pressure gradient in major portion of the blunter nose shape causes the non-dimensional velocity profiles of boundary layer in locations of 0.1≤X/L≤0.23 are deviated from the log layer profile. Therefore the separation on the blunter nose shape is more likely than the other nose at high pitch angle manoeuvres.Sat, 26 Jan 2019 20:30:00 +0100Numerical study of insulation structure characteristics and arrangement effects on cell ...
http://scientiairanica.sharif.edu/article_21252_0.html
Insulator-based dielectrophoresis is a recently developed technique in which insulating posts are used to produce non-uniformity in the electric field in a microchannel. This study presents the effects of insulating posts geometry and arrangement on the trapping efficiency of red blood cells in an alternating current- Insulator-based dielectrophoresis system. Microchannels containing square, circular and diamond-shaped posts with particles under the influence of positive dielectrophoresis force and fluid flow were considered. Finite element method was used to compute the velocity of the flow and electric field. The numerical method was verified by comparing the numerical results with experimental data. Two distinct criteria for examining particle trapping for distinct shapes and arrangements of insulating posts were introduced. Particle tracing simulation was implemented to observe particle trapping and compare the trapping performance of systems with distinct posts. As shown in the results for the system with circular and square posts, insulators should be narrowed to improve particle trapping, while diamond post should be widened to increase the trapping efficiency. In addition, the particle tracing results showed that microchannel with square posts is more efficient in particle trapping.Sat, 26 Jan 2019 20:30:00 +0100Multiscale Simulation of SU8 and SU8-Graphene Nanocomposite: Bridging Atomistic to Macroscale ...
http://scientiairanica.sharif.edu/article_21253_0.html
SU8 is commercial epoxy-Novolac resin, a negative tone photoresist with outstanding mechanical properties. Its nanocomposites have also been considered as a research material. In order to obtain insights about the SU8 nanocomposites with graphene the present work was conducted to simulate the mechanical properties using multiscale simulation method: atomistic, meso and macro scales. This has started from molecular dynamics, then moved to coarse grain and finally reached to macroscale. Peridynamics is the methodology which is governed throughout the work. Top-down and bottom-up loop has to be employed in order to confirm the total results. A tensile deformation is applied to a 2D plane at the upmost scale to result in an internal pressure. This is transferred to the lower scale in the next step as the external pressure. The procedure continues down until the molecular scale is reached. However, bottom-up strategy requires a bridging model to link the molecular scale to upper scales. The check point is the deformation values which have to be in the same order independent of top-down or bottom-up movement. At 2.1 wt.% of graphene in SU8, increased Young’s, bulk and shear modulus were calculated (62, 200, and 82 % respectively) compared to the neat SU8.Sat, 26 Jan 2019 20:30:00 +0100A framework for Earthquake Emergency Response in Iran
http://scientiairanica.sharif.edu/article_21254_0.html
Earthquake is common natural disaster in Iran, often accompanied by huge damages, losses and casualties. Therefore, focusing on earthquake response management, and improving its effectiveness is an important issue for the national disaster management organization. This paper proposes a framework to improve this process in Iran. The proposed framework attempts to coordinate governmental and non-governmental organizations involved in earthquake response. It also allows governments to systematize the obligations and responsibilities of these organizations, and mitigate the earthquake fatalities and casualties. Moreover, this study discusses the key considerations for implementing the proposed framework, and analyzes it for distinct scales of earthquake.Sat, 26 Jan 2019 20:30:00 +0100Vibrational Analysis of Fullerene Hydrides Using AIREBO Potential
http://scientiairanica.sharif.edu/article_21255_0.html
In this paper, the vibrational properties of fullerene hydrides with the chemical formula C60H2n are investigated using a method based on the potential energy of the molecule. The potential used in this methodology is AIREBO (Adaptive Intermolecular Reactive Empirical Bond Order). Using this interatomic potential, some of the most important frequencies of the fullerene hydrides, such as the breathing mode frequency, were calculated and then analyzed. It was observed that in addition to the number of hydrogen atoms in the structure, their position on the C60 cage has a significant effect on the natural frequency corresponding to a particular mode shape. The results obtained by this method have been compared and validated with quantum mechanics and experimental observations. The simulations results demonstrate that the proposed method is capable of calculating the vibrational properties of fullerene hydrides with high precision and low computational cost.Sat, 26 Jan 2019 20:30:00 +0100On Accuracy Function and Distance Measures of Interval-valued Pythagorean Fuzzy Sets with ...
http://scientiairanica.sharif.edu/article_21256_0.html
The notion of interval-valued Pythagorean fuzzy sets permits four important parameters, i.e., membership degree, non-membership degree, and a pair of values strength of commitment and direction of commitment, to a given set to have an interval value in dealing with imprecise information. In the present communication, a new accuracy function is being provided to overcome the shortcomings of the existing score and available accuracy functions for interval-valued Pythagorean fuzzy sets. The validity of the proposed accuracy function has been discussed in detail through the illustrative examples. Further, a new interval-valued Pythagorean fuzzy $p$-distance measure for interval-valued Pythagorean fuzzy numbers has been proposed and used in context with the existing weighted averaging operators. Finally, in view of the proposed accuracy function, distance measure and weighted averaging operators, a numerical example of multi-criteria decision-making problem has been solved to validate the proposed methodology.Sat, 26 Jan 2019 20:30:00 +0100Spaser Based on Graphene Tube
http://scientiairanica.sharif.edu/article_21257_0.html
In this paper, we propose a structure for graphene spaser and develop an electrostatic model for quantizing plasmonic modes. Using this model, one can analyze any spaser consisting of graphene in the electrostatic regime. The proposed structure is investigated analytically and the spasing condition is derived. We show that spasing can occur in some frequencies where the Quality factor of plasmonic modes is higher than some special minimum value. Finally, an algorithmic design procedure is proposed, by which one can design the structure for a given frequency. As an example, a spaser with plasmon energy of 0.1 eV is designed.Sun, 03 Feb 2019 20:30:00 +0100Fault Detection in Cracked Structure under Moving Load using RNNs based Approach
http://scientiairanica.sharif.edu/article_21258_0.html
The current work is based on the development of an indirect approach in the domain of Recurrent Neural Networks (RNNs) to identify and quantify cracks on a multi-cracked cantilever beam structure subjected to transit mass. At first, the responses of the multi-cracked structure subjected to transit load are determined using fourth order Runge-Kutta numerical method and finite element analysis (FEA) has been executed using ANSYS software to authenticate the employed numerical method. The existences and positions of cracks are identified from the measured dynamic excitation of the structure. The crack severities are found out by FEA as forward problem. The modified Elman’s Recurrent Neural Networks (ERNNs) approach has been implemented as inverse problem to predict the locations and severities of cracks in the structure by applying Levenberg-Marquardt (LM) back propagation algorithm. The present analogy has been carried out in a supervised manner to check the convergence of the proposed algorithm. The proposed ERNNs method converge good results with those of theory and FEA.Sun, 03 Feb 2019 20:30:00 +0100Comparison of γ and δ-Al2O3 supported CoMo catalysts in the hydrodesulfurization of ...
http://scientiairanica.sharif.edu/article_21259_0.html
The effect of two different crystal species of alumina on hydrodesulfurization activity of the corresponding CoMo catalysts was studied. Cylindrical extruded alumina with two different crystal structures i.e. γ-Al2O3 and δ-Al2O3 was prepared using boehmite and nitric acid as a peptizing agent by calcination at 550 ˚C and 900 ˚C, respectively. The Al2O3 support were impregnated with 9 wt.% of Mo and 2 wt.% Co via incipient wetness impregnation method. The CoMo/Al2O3 catalysts were used for hydrodesulfurization (HDS) and hydrodenitrification (HDN) of Iranian straight-run gas oil (ISRGO). The supports and catalysts were characterized by nitrogen adsorption-desorption isotherm, XRD, UV-vis-DRS, TPD, TPR and ICP-OES. The HDS activity of CoMo/γ-Al2O3 catalyst was higher than that of CoMo/δ-Al2O3 and was found to be 95.74%. This result was due to the formation of larger CoMoO4 and MoO3 crystals in CoMo/δ-Al2O3 catalyst which reduces the active metal phase dispersion and the performance of the catalyst. The HDS activity of CoMo/γ-Al2O3 catalyst was remarkable as the metal content of the catalyst was low. The HDN activity of CoMo/γ-Al2O3 was also about 66%.Sun, 03 Feb 2019 20:30:00 +0100ANALYSIS OF SECOND-GRADE FLUID FLOW IN POROUS CHANNEL WITH CATTANEO-CHRISTOV AND GENERALIZED ...
http://scientiairanica.sharif.edu/article_21260_0.html
This attempt executes the combined heat mass transport features in steady MHD viscoelastic fluid flow through stretching walls of channel. The channel walls are considered to be porous. The analysis of heat transport is made by help Cattaneo-Christov heat diffusion formula while generalized Fick’s theory is developed for study of mass transport. The system of partial differential expressions is changed into set of ordinary differential by introducing suitable variables. The homotopic scheme is introduced for solving the resultant equations and then validity of results are verified by various graphs. An extensive analysis has been performed for the influence of involved constraints on liquid velocity, concentration and temperature profiles. It is noted that the normal component of velocity decreases by increasing Reynolds number while retards for increasing viscoelastic constraint. Both temperature and concentration profiles enhanced by increasing combined parameter and Reynolds number. The presence of thermal relaxation number and concentration relaxation number declines both temperature and concentration profiles, respectively.Sun, 03 Feb 2019 20:30:00 +0100Thermodynamics analysis for high temperature hydrogen production system
http://scientiairanica.sharif.edu/article_21261_0.html
Using clean energy sources is considered as a prevention solution for global warming. Hydrogen is one of the most popular clean and renewable fuel which is widely noticed by researchers in different approaches from additive fuel of internal combustion engines to pure feed of fuel cells. Hydrogen production is also one the most interested field of studies and extended efforts are doing to fined high performance, fast and economical ways of its production. In this work, a novel high temperature steam electrolysis system with main solar integrated Brayton cycle core is proposed and numerically simulated to achieve this goal. Energy and exergy analysis having better perception of system performance is done and Rankine and organic Rankine cycles were utilized cooperating with the main core to improve its efficiency. The influences of different parameters such as turbine inlet temperature, inlet heat flux from the sun, compression ratio and also used organic fluid were investigated based first and second laws. Results show the high performance of proposed system, more than 98% energy efficiency of hydrogen production, besides the simplicity of utilizing it.Sun, 03 Feb 2019 20:30:00 +0100Influence of Areca Nut Nano Filler on Mechanical and Tribological Properties of Coir Fiber ...
http://scientiairanica.sharif.edu/article_21262_0.html
The present study is aimed at investigating the effect of incorporating arecanut nano filler on the tribological behaviour of coir reinforced epoxy based polymer matrix composite. Areca nut nano filler is produced by grinding followed by ball milling. Particle size analyzer confirmed the size of nano fillers obtained are in the range of 20-100 nm. Composites with different weight percentage of nano filler (0%, 5%, and 10%) were studied for their mechanical and tribological behaviour using pin on disc rig. Tensile, Flexural, Interlaminar shear and impact tests are carried out on the proposed composite. Taguchi’s technique is used for analysing effect of various factors on the tribological behaviour of the composite. The results showed that inclusion of arecanut nano filler enhanced the microhardness of the composite, with inclusion of arecanut filler the tensile strength increased up to 5 %, later there is a decrease in tensile strength. Flexural strength significantly increases with increase in filler percentage from 0% to 5%, but the variation of flexural strength from 5% to 10% is negligible. Inclusion of filler has negligible effect on the interlaminar shear strength of composites. Impact strength and wear resistance of the composite is enhanced with incorporation of filler.Sun, 03 Feb 2019 20:30:00 +0100Hyperelastic modeling of sino-nasal tissue for haptic neurosurgery simulation
http://scientiairanica.sharif.edu/article_21263_0.html
The aim of this research was to provide a simple yet realistic model of the sino-nasal tissue as a major requirement for developing more efficient endoscopic neurosurgery simulation systems. Ex-vivo indention tests were performed on the orbital floor soft tissue of four sheep specimens. The resulting force-displacement data was incorporated into an inverse finite element model to obtain the hyperelastic mechanical properties of the tissue. Material characterization was performed for Polynomial, Yeoh, Mooney-Rivlin and Neo-Hookean hyperelastic models, using a Sequential Quadratic Programming algorithm. Experimental results indicated a relatively large elastic deformation, up to 6mm, during indentation test with a considerable nonlinearity in the force-displacement response. All hyperelastic models could satisfy the convergence criteria of the optimization procedure, with the highest convergence rate and a close fittings accuracy associated with the Yeoh hyperelastic model. The initial guess of the material constants was found to affect the number of iterations before converging, but not the optimization results. The normalized mean square errors of fitting between the model and experimental curves were obtained as 2.39%, 4.26% and 4.65% for three sheep samples, suggesting that the Yeoh model can adequately describe the typical hyperelastic mechanical behavior of the sino-nasal tissue for surgery simulation.Sat, 16 Feb 2019 20:30:00 +0100Designing a resource-constrained project scheduling model considering multiple routes for ...
http://scientiairanica.sharif.edu/article_21264_0.html
Resource constrained project scheduling problem with multiple routes for flexible project activities (RCPSP-MR) is a generalization of the RCPSP, in which for the implementation of each flexible activity in main structure of the project, several exclusive sub-networks are considered. Each sub-network is regarded as a route for the flexible activity. The routes are considered for each flexible activity that are varied in terms of: 1) Number of activities required to execute; 2) Precedence relationship between activates; 3) Allocation of different renewable and nonrenewable resources to each activity; and 4) Effectiveness on the duration and cost of project completion. In this paper, a new mathematical formulation of RCPSP-MR is firstly presented. Then, two solving approaches based on particle swarm optimization (PSO) and genetic algorithm (GA) are proposed to minimize costs of project completion. To evaluate the effectiveness of these proposed approaches, 50 problems (in very small, small, medium, and large-sized test problems) are designed and then are solved; Finally, comparisons are provided. Computational results show that the proposed GA generates high-quality solutions in a timely fashion.Sat, 16 Feb 2019 20:30:00 +0100A novel selective clustering framework for feature selection and appropriate labeling of the ...
http://scientiairanica.sharif.edu/article_21265_0.html
Clustering is one of the main methods of data mining. K-means algorithm is one of the most common clustering algorithms due to its efficiency and ease of use. One of the challenges of clustering is to identify the appropriate label for each cluster. The selection of a label is done in such a way as to provide a proper description of the cluster records. In some cases, choosing the appropriate label is not easy due to the results and structure of each cluster. The aim of this study is to present an algorithm based on the K-means clustering in order to facilitate the allocation of labels to each cluster. Moreover, in many data mining issues, the data set contains a large number of fields and therefore, the identification of the fields and the extraction of subsets from the required fields is an important issue. With the help of the proposed algorithm, the important and influential variables of the data set would be identified and the subset of the required fields would be selected.Sat, 16 Feb 2019 20:30:00 +0100High Accuracy Power Sharing in Parallel Inverters in an Islanded Microgrid Using Modified ...
http://scientiairanica.sharif.edu/article_21266_0.html
Increasing the penetration level of distributed generation (DG) units in micro grids which feeds the large loads in parallel connections creates the concept of power sharing phenomena in recent researches. In island mode of micro grid the voltage and the frequency control are done using the high inertia inverter. Therefore, the internal control loop is executed in such way to avoid all of DGs not to be overloaded. consequently, the reactive power-sharing error is eliminated and the voltage is also kept constant within the permissible range. This paper, presents a modified control method based on sliding mode approach. The proposed control method is tested using several different disturbances and three scenarios. Also, the fractional order calculus is applied to proposed control strategy to increase the convergence speed and the system accuracy. finally, the proposed method is compared to other well-known controlling approaches while the achieved results confirms the superiority of proposed one.Sat, 16 Feb 2019 20:30:00 +0100Supply Chain Reconfiguration for a New Product Development with Risk Management Approach
http://scientiairanica.sharif.edu/article_21267_0.html
We are living in an era that innovation is increasingly growing and products’ lifetime is decreasing. In this situation new product development is an advantage that makes it possible to survive in the competitive market. However, risks are unavoidable in new product development in any industries. Therefore, identifying, management and mitigation of risks are considered of high significance for companies. By taking risk management into account, this study introduces a new, multi-objective, mathematical model for supply chain configuration in the presence of a new product. The considered supply chain is multi-echelon, multi-resources, multi-period, and multi-product. In order to manage the risk in this supply chain, appropriate mitigation strategies were chosen from various risk response strategies considering their cost and effectiveness as well as influence of each choice on supply chain was also taken into account in the mathematical model. The assumed model explored the optimum tactical and operational SCM decisions. The ability of the model was assessed by solving an example. The result showed that the choice of various response strategies as well as new product production influenced supply chain configuration.Sat, 16 Feb 2019 20:30:00 +0100A green procedure for one-pot synthesis of N, N’-alkylidene bisamides under solvent- and ...
http://scientiairanica.sharif.edu/article_21268_0.html
An effective solvent- and catalyst-free method was introduced for synthesis of symmetrical N, N’-alkylidene bisamides as high usage compounds in organic chemistry. In order to show the generality, the synthesis was done with various benzamides and aldehydes to obtain various derivatives in high yields.Sat, 16 Feb 2019 20:30:00 +0100Modeling the particle deposition in the respiratory system during successive respiratory cycles
http://scientiairanica.sharif.edu/article_21269_0.html
In this study, using a 5-lobe symmetric model, total, lobar and generational particle deposition in the lungs during successive cycles is investigated. It has been found that for the particle size between 0.05 and 2 μm and the tidal volumes greater than 1000 ml, considering the effect of successive cycles predicted more deposition fraction per cycle compared to a single cycle up to about 16 percent. The mentioned range of tidal volume is related to light or heavy physical activities. So, it can be understood that people exposed to particulate matter within the mentioned size range, when acting physically, are at more health risk compared not only to the resting state, but also to the same state calculations based on a single cycle. Finally, total and generational remaining mass fraction suspended in the respiratory tract after the completion of each cycle is calculated. This remaining mass fraction turned out to be negligible except for particles between 0.05 and 2 μm.Sat, 16 Feb 2019 20:30:00 +0100Comparison of Adaptive magnetorheological elastomer isolator and elastomeric isolator in ...
http://scientiairanica.sharif.edu/article_21270_0.html
Magnetorheological elastomer (MRE) materials are widely used in the development of smart isolators and absorbers due to their stiffness and damping adaptability. This study investigates the performance of MRE isolators and elastomeric isolators from near-field and far-field earthquakes in benchmark base isolation buildings. All earthquakes are simultaneously applied in two horizontal directions to the horizontal plan. Vertical earthquakes are not attended in the dynamical analysis of benchmark base isolation buildings. For making an isolator model, the effect of bilateral interaction has been considered. The behaviors of MRE isolators and MR dampers are compared. To this end, three control systems including adaptive isolator, passive isolator and semi-active MR damper are considered. The results show that the MRE isolator has a better performance in near-field earthquakes due to its variable stiffness and damping, as compared to the elastomeric isolator. The semi-active MR damper for both far-field and near-field earthquakes has a better control to reduce base displacement, but causes to increase floor accelerations, story drifts and story shear. According to the results of this study, it can be observed that MRE isolator can be used instead of MR damper. The MRE isolator can reduce the base displacement without increasing other responses.Sat, 16 Feb 2019 20:30:00 +0100Design and Analysis of Solar Photovoltaic fed Z-Source Inverter based Dynamic Voltage Restorer
http://scientiairanica.sharif.edu/article_21272_0.html
Impedance source inverter or Z-source inverter (ZSI) is an emerging power electronic device. The one kind of feature of ZSI is that dissimilar the conventional inverters such as voltage source inverter and current source inverter it can be open and short-circuited which provides a mechanism for the main circuit to step-up and step-down the voltage as wanted. This work introduces a solar photovoltaic fed Z-source inverter (ZSI) based Dynamic Voltage Restorer (DVR) for the alleviation of destructive voltage swell and harmonics under sudden addition of a balanced three-phase nonlinear load. This article also focuses on perturbation and observation (P&O) method for automatically find the PV systems operating voltage that produces a maximum power output. The design, modeling, and simulation of the proposed PV-ZSI-DVR are implemented in MATLAB/SIMULINK for mitigation of voltage swell and harmonics balanced three-phase nonlinear load and the obtained results are compared with traditional SPV fed voltage and current source inverter based DVRs.Sun, 17 Feb 2019 20:30:00 +0100ASYMMETRICAL FUZZY LOGIC CONTROL BASED MPPT ALGORITHM FOR STAND-ALONE PV SYSTEM UNDER PARTIALLY ...
http://scientiairanica.sharif.edu/article_21273_0.html
Partial shading conditions (PSCs) in Photovoltaic (PV) system is an inevasible situation which curtails the PV array output by exhibiting multiple peaks in its Power-Voltage (P-V) curve. The multiple peaks consist of a single global maximum power point (GMPP) and many local maximum power points (LMPP). The presence of multiple peaks makes tracking of maximum power point more difficult and demands an efficient controller to track the global peak of the P-V curve. In the present work, a novel intelligent asymmetrical Fuzzy Logic Control (AFLC) based maximum power point tracking (MPPT) algorithm has been proposed for tracking GMPP. The fuzzy membership functions of the proposed algorithm have been optimized using a heuristic approach. The algorithm has been designed, developed and analyzed using MATLAB/Simulink. Furthermore, to establish the superiority of proposed AFLC algorithm, it has been compared with conventional perturb & observe (P&O) algorithm and intelligent Fuzzy Logic Control (FLC) based algorithm for GMPP tracking and shading losses under standard test condition (STC) and partially shaded conditions.Sun, 17 Feb 2019 20:30:00 +0100The Study of Cavitation Phenomenon in Multistage Centrifugal API BB2 Pump and Reduction of Its ...
http://scientiairanica.sharif.edu/article_21274_0.html
Cavitation Phenomenon in Centrifugal pumps is the main cause of failures in pump components, such as impeller and volute. To evaluate this phenomenon, firs of all the flow field in a BB2 API multistage centrifugal pump with and without cavitation situation is studied. Additionally, to improve impeller inlet condition and reduction of cavitation possibility, Stepannof and Dixon theory is used. This study mainly focuses on the concept of cavitation’s in pump, pump performance curve, system pump curve, and net positive suction head (NPSH). The ultimate goal of this project is to determine the best operating pump range. It is interesting to examine the system pump curve prediction to identify the inception cavitation zone. Therefore, a theoretical system pump curve was generated using Microsoft Excel 2010, in addition, Catia V5 R21 and ANSYS CFX 14. Were applied to create computational fluid dynamic model From simulation results, a decrease of NPSHa values produces the onset of cavitation. The major findings of this thesis present the theoretical and numerical results concerning the pump characteristics and performance breakdown at different flow conditions. Therefore the best operating pump range is identified a flow rate of 330 m3/hr to avoid the occurrence of cavitation in pump.Sun, 17 Feb 2019 20:30:00 +0100Predictive heuristics to generate robust and stable schedules in single machine systems under ...
http://scientiairanica.sharif.edu/article_21276_0.html
The present paper examines the problems of stable and robust scheduling under disruptions with uncertain processing times. In order to handle such problems, in addition to exact solution approaches, a general predictive two-stage heuristic algorithm is proposed. In the first stage of the algorithm, the optimal robust schedule is generated by only considering the uncertain job processing times and forgoing the breakdown disruptions. In the second stage, adequate additional times are embedded in job processing times to enhance stability. Extensive computational experiments are carried out to test the performances of the proposed methods. The achieved results show the superiority of the proposed general predictive heuristic approach over the common methods in the literature.Sat, 23 Feb 2019 20:30:00 +0100Numerical study on the influence of suspended equipments on the ride comfort in high speed ...
http://scientiairanica.sharif.edu/article_21277_0.html
To study how the suspended equipments impact the carbody flexible vibrations in railway vehicle and the ride comfort, a rigid flexible general model is required. The numerical simulations rely on three models, derived from the general model - a reference model with no equipment, a simplified model with one equipment mounted at the carbody centre and another model considering four equipments mounted along the carbody. The intent of this paper arises from the observation that the literature review does not feature any study to highlight the change in the ride comfort, exclusively due to the equipments. Similarly, there is no mention on contrasting the ride comfort results obtained from the simplified model versus the ones coming from the model with more equipments. The main characteristics of the flexible vibrations behaviour in the carbody due to the suspended equipments are made visible by comparing the frequency response functions of the carbody between the no equipment and the one equipment models. The influence of the suspended equipments on the ride comfort is established by a contrastive examination of the ride comfort index calculated in the carbody fitted with one/four equipment/s models with the ride comfort index from the no equipment model.Sat, 23 Feb 2019 20:30:00 +0100An analytical Solution for Bending Problem of micro Plate using New Displacement Potential Function
http://scientiairanica.sharif.edu/article_21278_0.html
In this paper to include small scale effect, the augmented Love displacement potential functions (DPF) are developed for isotropic micro or Nano scales medium based on couple stress theory. By substituting the new DPF in equilibrium equations, governing equations are simplified to two linear partial differential equations of sixth and fourth order. Then the governing differential equations are solved for simply supported rectangular plate using the separation of variable method with satisfying exact boundary conditions without any simplification assumptions. Displacements, bending and torsional moments of rectangular plate are obtained for different length scale parameters, aspect and Poisson’s ratios. The obtained results are compared with other studies which show excellent agreement between them.Sat, 23 Feb 2019 20:30:00 +0100An experimental study regarding Economic Load Dispatch using Search Group Optimization
http://scientiairanica.sharif.edu/article_21279_0.html
Power System network is formed mainly to generate power from all the generators to fulfil total load demand and transmission line losses. The Economic Load Dispatch (ELD) problem is considered to be one of the most important problems of cost minimization in power system operations. Various approaches have been taken to solve the ELD problem. In this paper a powerful Search Group Optimization (SGO) technique is implemented to solve the ELD problem. SGO maintains a good balance between the exploitation and the exploration phases of the technique. This optimization technique tends to find the promising regions of the search space from the first iteration onwards. The algorithm uses five important steps to reach the optimal solution of the ELD problem. Namely, initial population, initial selection of search group, search group mutation, family generation and new search group selection. Using these five steps, the SGO tends to make a smooth transition towards the optimized solution. The SGO is applied to five test systems and the final results obtained have been compared to various other recently developed optimization techniques. The results prove the robustness, feasibility, effectiveness and efficiency of SGO in terms of computational time and proximity to the global optimum solution.Sat, 23 Feb 2019 20:30:00 +0100Using combined artificial neural network and particle swarm optimization algorithm for modeling ...
http://scientiairanica.sharif.edu/article_21299_0.html
In this study Electrical discharge machining (EDM) process, widely used in mold manufacturing, is modeled and optimized using artificial neural network and an optimization heuristic algorithm. Material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) are considered as performance characteristics of the EDM process. Optimization of process parameters in order to find a combination of process parameters to simultaneously minimize TWR and SR and maximize MRR is the objective of this study. In order to establish the relations between the input and the output process parameters, back propagation neural network (BPNN) used. In the last section of this research, particle swarm optimization (PSO) algorithm has been employed for optimization of the multiple response characteristics. A set of verification tests is also performed to verify the accuracy of optimization procedure in determination of the optimal levels of process parameters. Results demonstrate that propose modeling technique (BPNN) can precisely simulate actual EDM process with less than 1% error. Furthermore less than 4% error for PSO algorithm results is quite efficient in optimization procedure.Sat, 02 Mar 2019 20:30:00 +0100Space headway calculation and analysis at turn movement trajectories using hybrid model
http://scientiairanica.sharif.edu/article_21308_0.html
Space headway calculation and analysis play an important role in identifying surrounding obstacles and understanding traffic scene. However, the performance of existing methods is limited by the complexity of computer processing. In addition, it is quite difficult to obtain space headway at turn movement trajectories, mainly owing to the limitation of rectilinear propagation. Therefore, a hybrid model based on spline curve and numerical integration was proposed to estimate distance of the front vehicle and vehicle trajectory in this study. The space headway at turn movement trajectories was analogous to the track of a vehicle, which could be fitted by a quadratic spline curve. Newton-Cotes numerical integration was employed to calculate distance due to its meshing flexibility and ease of implementation. Data collected from Lankershim Boulevard in the city of Los Angeles, California (USA) were used to evaluate performance of the hybrid model. Compared with another algorithm based on computer vision and trilinear method, the results showed that the proposed model worked successfully and outperformed the competing method in terms of accuracy and reliability. Finally, the proposed method was applied to investigate the effects of vehicle speed, relative speed of vehicles, and time period on the spacing of vehicles during car-following.Sun, 03 Mar 2019 20:30:00 +0100Online Nonlinear Structural Damage Detection Using Hilbert Huang Transform and Artificial ...
http://scientiairanica.sharif.edu/article_21309_0.html
Structural Health Monitoring (SHM) as a process in order to implement a damage detection strategy and assess the condition of structure plays a key role in structural reliability. In this paper, we aim to present a methodology for online detection of damages which may occur during a strong ground excitation. In this regard, Empirical Mode Decomposition (EMD) is superseded by Ensemble Empirical Mode Decomposition (EEMD) in the Hilbert Huang Transformation (HHT). Albeit analogous, EEMD brings about more appropriate Intrinsic Mode Functions (IMFs) than EMD. IMFs are employed to assess the first mode frequency and mode shape. Afterward, Artificial Neural Network (ANN) is applied to predict story acceleration based on previously measured values. Because ANN functions precisely, any congruency between predicted and measured acceleration indicates onset of damage. Then, another ANN method is applied to estimate the stiffness matrix. Though the first mode shape and frequency are calculated in advance, the process essentially requires an inverse problem to be solved in order to find stiffness matrix, which is done by ANN. This algorithm is implemented on moment-resisting steel frames, and the results show that the proposed methodology is reliable for online prediction of structural damage.Sun, 03 Mar 2019 20:30:00 +0100Structure, Stability and Electronic Properties of Thin TiO2 Nanowires of Different Novel ...
http://scientiairanica.sharif.edu/article_21312_0.html
This paper investigates on the structural stability and electronic properties of titanium dioxide (TiO2) nanowires of different novel shapes using first- principle based density functional approach. Out of linear, ladder, saw tooth, square, triangular, hexagonal, and octahedron shaped atomic configuration, the ladder shape atomic configuration is energetically most stable. After computation of lattice parameters as well as various mechanical properties of nanowire TiO2, it is seen that highest bulk moduli is obtained for triangular TiO2 nanowire which shows the highest mechanical strength for the structure whereas hexagonal configuration has lowest Bulk moduli which shows the lowest mechanical strength for the structure. Analysis of various electronic properties show that different configurations of TiO2 nanowires can have different utility as solid state materials.Mon, 04 Mar 2019 20:30:00 +0100A STUDY ON REPAIRING PROCEDURES INVOLVED WITH LEADING EDGE CRACKS, OFFSETTING, OVERBITE & ...
http://scientiairanica.sharif.edu/article_21313_0.html
Rotor blades are the most important part of wind turbine system, which are generally made up of polymer matrix based composites. The performance and lifetime of the wind turbine system often depend of the constituent of composite materials, properties of these materials, design of blades and manufacturing techniques. However the inspections after manufacturing of blades do reveal certain defects which need to addressed and fixed before it is sent for real time operations. Further offsetting usually occurs when closure of two blade halves lead to displacement of aerodynamic suction side from the aerodynamic pressure side. This work is concerned with the two main objectives: one is to repair leading edge cracks in the longitudinal direction, outside the area with existing external root over lamination, the second objective is to how offsetting is measured, evaluated and repaired especially in connection with: overbite and underbite. All these repair procedures were conducted on the glass fabric reinforced polyester blades manufactured by Hand lay-up technique. Until aforementioned repair procedures are not performed, the blades will not be sent to assembly stage. Ultrasonic inspection was conducted as per ASTM standards, ASTM E317 and ASTM E1316.Mon, 04 Mar 2019 20:30:00 +0100Instantaneous and Equilibrium Responses of the Brain Tissue by Stress Relaxation and ...
http://scientiairanica.sharif.edu/article_21314_0.html
Human brain and brainstem tissues have viscoelastic characteristics and their behaviours are functions of strains, as well as strain rates. Determination of the equilibrium and instantaneous stresses happening at low and high strain rates provide insights into a better understanding of the behaviour of such tissues. In this manuscript we present the results of a series of stress relaxation tests, at six different values of strains conducted on porcine brainstem tissue samples to indirectly measure the equilibrium and instantaneous stresses. The equilibrium stresses at low strain rates are measured from long-term responses of the stress relaxation test. The instantaneous stresses at high strain rates are determined using Quasi-Linear Viscoelasticity (QLV) theory at six strains. The results show that the instantaneous stresses are much larger (almost 11 times) than the equilibrium stresses and across all the strains. It can be concluded that the instantaneous response can be reasonably estimated from the long-term response which can be easily measured experimentally. The experimental results also show that the reduced relaxation moduli, estimated from the QLV theory, vary for the six strains tested.Mon, 04 Mar 2019 20:30:00 +0100Seismic Behaviour Assessment of Eccentrically Split-X Braced Frames
http://scientiairanica.sharif.edu/article_21325_0.html
Eccentrically braced frames (EBF) are lateral resisting systems with appropriate ductility and strength against earthquakes. An important kind of arranging such systems, recommended by Popov and also presented in AISC, is eccentrically split-X bracing. The axial force applied to the beam outside link beam is reduced causing the improvement of the behaviour of this type of bracing. In this research, for the first time, ductility factor, overstrength factor and response modification factor of eccentrically split-X braces are investigated through nonlinear static and incremental dynamic analyses and fragility curves are presented for different ratios of link beam length to span length. For this purpose, three buildings, 2-, 6- and 10-storey structures with the ratios of link beam length to span length (e/L) of 0.05, 0.1, 0.15 and 0.2 are considered. Ductility factor of R𝛍=3.55, overstrength factor of Rs = 2.31 and response modification factor of RLRFD =8.06 are calculated under 10 earthquake records. It is concluded that the most appropriate values of e/L ratio in the eccentrically split-X bracing are 0.1 for tall structures and 0.05 for small ones. According to the log-normal distribution, the fragility curves are also plotted considering collapse prevention (CP) and immediate occupancy (IO) performance levels.Sat, 09 Mar 2019 20:30:00 +0100Control of Natural Frequency of Beams using Different Pre-tensioning Cable Patterns
http://scientiairanica.sharif.edu/article_21326_0.html
Steel cable is utilized in this research to control the natural frequency of beam due to its important advantages such as low weight, small cross-sectional area and high tensile strength. In this study, for the first time, theoretical relations are developed to calculate the increase in pre-tensioning force of steel cables under external loading based on the method of least work. Moreover, the natural frequency of steel beams with different support conditions without cable and with different patterns of cable is calculated based on Rayleigh’s method. To verify the theoretical relations, the steel beam is modeled in the finite element ABAQUS software with different support conditions without cable and with different cable patterns. The obtained results show that the theoretical relations can appropriately predict the natural frequency of beams with different support conditions and different cable patterns. In this study, simply supported as well as fixed supported beams are pre-stressed with v-shaped and modified v-shaped patterns of the cable. According to the obtained results, the modified v-shaped pattern of the cable is more efficient than the v-shaped pattern one. Furthermore, the effects of the length of horizontal cables on the natural frequency are studied.Sat, 09 Mar 2019 20:30:00 +0100On the assessment of MIDA method for mid-rise steel structures with non-symmetrical plan
http://scientiairanica.sharif.edu/article_21356_0.html
Determination of nonlinear dynamic behavior of structures has always been one of the main goals for both structural and earthquake engineers. One of the newest methods for analyzing seismic behavior of structures is Modal Incremental Dynamic Analysis (MIDA). In fact, this method is an alternative to the Incremental Dynamic Analysis (IDA) which is a difficult and time-consuming method. Despite the MIDA's approximate results, advantages such as adequate accuracy, high speed, and low cost has made this method an efficient and appropriate approach. In all previous studies, the proposed models have had a regularized plan, hence, all the analyses have been carried out on a frame. In this study, the MIDA analysis is developed in an unsymmetric-plan type building by considering three structures with 4, 7, and 10 stories having irregularity in plan and thereafter, the accuracy of work has been examined. In this study, by a simplification, instead of considering an unconventional plan, we used a rectangular plan with an eccentricity of 15% between the center of mass and the center of rigidity. Comparing the results of this study with the IDA method proves the high level of accuracy of this method in assessing seismic demands.Tue, 12 Mar 2019 20:30:00 +0100A computational plastic–damage method for modeling the FRP strengthening of concrete arches
http://scientiairanica.sharif.edu/article_21357_0.html
In this paper, a computational technique is presented based on a concrete plastic-damage model to investigate the effect of FRP strengthening of reinforced concrete arches. A plastic-damage model is utilized to capture the behavior of concrete. The interface between the FRP and concrete is modeled using a cohesive fracture model. In order to validate the accuracy of the damage-plastic model, a single element is employed under the monotonic tension, monotonic compression, and cyclic tension loads. An excellent agreement is observed between the predefined strain-stress curve and those obtained from the numerical model. Furthermore, the accuracy of the cohesive fracture model is investigated by comparing the numerical results with those of experimental data. Finally, in order to verify the accuracy of the proposed computational algorithm, the results are compared with the experimental data obtained from two tests conducted on reinforced concrete arches strengthened with FRP.Tue, 12 Mar 2019 20:30:00 +0100Employing a Novel Gait Pattern Generator on a Social Humanoid Robot
http://scientiairanica.sharif.edu/article_21358_0.html
This paper presents a novel Gait Pattern Generator developed for the “Alice” social humanoid robot whichup to now lacked an appropriate walking pattern. Due to the limitations of this robot, the proposed gatepattern generator was formulated based on a nine-mass model to decrease the modeling errors; and theinverse kinematics of the whole lower-body was solved in such a way that the robot remains staticallystable during the movements. The main challenge of this work was to solve the inverse kinematics of a7-link chain with 12 degrees-of-freedom. For this purpose, a new graphical-numerical technique has beenprovided using the definition of the kinematic equations of the robot joints’ Cartesian coordinates. Thismethod resulted in a significant increase in the calculations’ solution rate. Finally, a novel algorithm wasdeveloped for step-by-step displacement of the robot towards a desired destination in a two-dimensionalspace. Performance of the proposed gate pattern generator was evaluated both with a model of the robot ina MATLAB Simulink environment and in real experiments with the Alice humanoid robot.Tue, 12 Mar 2019 20:30:00 +0100Effect of creep on high-order shear deformable beams
http://scientiairanica.sharif.edu/article_21359_0.html
A powerful and new theoretical approach is used to obtain an expression for the effect of creep on reinforced concrete shear deformable beams. First, a method for Euler-Bernulli beam is proposed to represent long-term behavior of concrete beams based on linear strain theory. Secondly, a formulation is developed for analyzing the strain distribution in shear deformable concrete beams. Finally, three numerical examples are included in order to compare well-known codes with the proposed method. Comparison between proposed method, FEM, codes and experimental works demonstrate that the proposed analytical procedure can effectively simulate creep behavior in reinforced concrete beams.Tue, 12 Mar 2019 20:30:00 +0100