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Feed provided by Scientia Iranica. Click to visit.Robust optimization for the resource-constrained multi-project scheduling problem with ...
http://scientiairanica.sharif.edu/article_20801_1119.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.Fri, 31 Jan 2020 20:30:00 +0100A multi-stage stochastic programming model for sustainable closed-loop supply chain network ...
http://scientiairanica.sharif.edu/article_21531_1119.html
This paperproposes a multi-objective, multi-stage programming model to design a sustainable closed-loop supply chain network considering financial decisions. A multi-product, sustainable closed-loop plastic supply chain network design problem which encompasses economic, environmental and social objectives is modeled in a mathematical manner. The decisions to be made are concerned with location of facilities; the flow of products, loans to take and investments to make. Uncertainty issue is about demand of customers and investment's rate of return. The decision making model is formulated as a multi-objective, multi-stage mixed integer linear programming problem and is solved by implementing path formulation and augmented Ɛ-constraint methods. Computational analysis, is provided based on the subject company to determine the significance of the proposed model and the efficiency regarding integrating financial decisions with supply chain network design decisions.Fri, 31 Jan 2020 20:30:00 +0100Extended TOPSIS method for multi-criteria group decision-making problems under cubic ...
http://scientiairanica.sharif.edu/article_20821_1119.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.Fri, 31 Jan 2020 20:30:00 +0100Resilient supplier selection and order allocation under uncertainty
http://scientiairanica.sharif.edu/article_20831_1119.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.Fri, 31 Jan 2020 20:30:00 +0100A joint determination of production cycle length, maintenance policy, and control chart ...
http://scientiairanica.sharif.edu/article_20729_1119.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.Fri, 31 Jan 2020 20:30:00 +0100Economic evaluation of investment projects under uncertainty: A probability theory perspective
http://scientiairanica.sharif.edu/article_20779_1119.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.Fri, 31 Jan 2020 20:30:00 +0100Partnership of contractors in cooperative game theory approach to project resource management
http://scientiairanica.sharif.edu/article_20897_1119.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, 31 Jan 2020 20:30:00 +0100A novel fuzzy multi-objective method for supplier selection and order allocation problem using ...
http://scientiairanica.sharif.edu/article_21063_1119.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.Fri, 31 Jan 2020 20:30:00 +0100Optimizing decisions on under- and out-of-warranty products in a finite planning horizon
http://scientiairanica.sharif.edu/article_20895_1119.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.Fri, 31 Jan 2020 20:30:00 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 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 +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 +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 +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 water to cement ratio on mechanical properties 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 +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 +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 +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 +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 +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 +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 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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 +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 appropriate labeling of the clusters based on ...
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 +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 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 +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 +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
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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 +0100An integrated lot-sizing model with supplier and carrier selection and quantity discounts ...
http://scientiairanica.sharif.edu/article_21362_0.html
Because of growing competition in the global markets and the vital role of suppliers in business success, the subject of supplier selection has attracted many researchers and practitioners during the recent years. In addition to the supplier selection, the order quantity discount provided by the suppliers, is considered through a new mixed-integer linear programming (MILP) model involving a manufacturer with multiple products and multiple purchasing items over multiple periods. According to the proposed model, the manufacturer purchases different amount of raw materials from selected suppliers in order to produce different products. Customers’ demands are fulfilled by minimizing the total purchase, inventory, production, and transportation costs over a multi-period planning horizon. Since the problem is NP-hard, an efficient genetic algorithm (GA) is used to solve the large-scale real-world instances. The results are compared with results from the exact approach wherever possible in order to investigate the efficiency of the algorithm.Sat, 06 Apr 2019 19:30:00 +0100Investigating the effects of impact directions to improve head injury index
http://scientiairanica.sharif.edu/article_21363_0.html
Traumatic brain injury (TBI) is one of the most important causes of death and disability. The objective of this study is to develop new head injury criteria which can predict the greatest principal strain and shear stress in the brain considering the impact directions and magnitudes. So, 150 head impact simulations were performed for 3 magnitudes and 50 directions of impact using head finite element model (FEM). Simulations were performed in order to assess the strain and shear stress created in the brain tissues due to different impact directions and magnitudes. Next, new head injury criteria were developed through performing statistical analysis. The simulation results showed that TBI risks in the sagittal and frontal planes were higher than those with impacts in transverse plane. Furthermore, new brain injury indices were developed to predict maximum principal strain and shear stress in the brain, which had correlation coefficients of 0.85 and 0.89 with head FEM responses, respectively. However, finding of present research showed the effects of impact directions on TBI risks. They also demonstrate that impact magnitude, direction, and duration should be used to develop a brain injury index.Sat, 06 Apr 2019 19:30:00 +0100Technology valuation of NTBFs in the field of cleaner production with regard to the ...
http://scientiairanica.sharif.edu/article_21365_0.html
Technology valuation, especially in the early stages of new technology-based firms (NTBFs) growth is one of the most critical challenges, which most often hinders the investor and entrepreneur's deals during the venture capital (VC) financing process. It is clear that uncertainties arising from the likelihood of implementing public policies could significantly affect the volatility of NTBFs cash flows in the field of cleaner production. Commonly, these kinds of technologies require public supportive policies for achieving success. Consequently, their technology valuation is more challenging and traditional valuation methods are not suitable anymore because of the definitive assumption of cash flow and ignoring the investors’ flexibilities and uncertainties. Therefore, this paper proposes a method by introducing a framework based on the decision tree and the real options analysis which is tailored to meet the technology valuation of such firms during all stages of their growth. Furthermore, unlike previous papers that have utilized the compound options, option to choose has been used to apply investors’ flexibilities. Then, the proposed framework is supported by a case study, which has been conducted to verify and validate it. Finally, the conclusion section discusses the contributions and limitations of the study and provides directions for future research.Sat, 06 Apr 2019 19:30:00 +0100The application of wavelet theory with denoising to estimate the parameters of earthquake
http://scientiairanica.sharif.edu/article_21368_0.html
In this paper, strong ground mot (SGM) parameters are calculated using discrete wavelet transform (DWT) in different kinds of soils with different magnitudes. The main earthquake record (MER) is divided into approximation and detailed signals using wavelet transform with denoising. The high and low frequencies of MER are separated from each other. Previous studies showed that the approximation signal has the greatest effect on dynamic response and it is very similar to the main signal. Then SGM parameters of the new signal are calculated by DWT decomposition. This process continues over five levels and, in each level, SGM parameters are calculated and compared with the MER and its error percentage is presented. In DWT with the denoising method, the curve becomes softer such that the calculation time reduces. Results show that the error percentage in the first two levels is less than 1% and for the third level, this index is less than 3%. In addition, the reduction percentage of calculation time is 1%, 4%, and 8%, respectively, in the first to third levels. The best result is relative to the third decomposition level in which error value as well as computational time reduction is nearly 3% and 8%.Mon, 08 Apr 2019 19:30:00 +0100Experimental and Numerical Study on Proposed T-Form Semi-Precast Moment-Resisting Concrete ...
http://scientiairanica.sharif.edu/article_21369_0.html
This paper presents the results of experimental and numerical study on a proposed exterior semi-precast moment-resisting concrete connection. Steel linkage element connects precast concrete beam to column in two cases of bolted and welded connections. These connections were compared to monolithic connection based on stiffness, strength, energy dissipation capacity and ductility factor. An accurate 3D nonlinear finite element model has been simulated to study the behavior of these connections. A good agreement was observed between numerical results and experimental ones in behavior and damage mode. Although, all samples satisfied all the code criteria, but the trend of failure in bolted and welded connection was observed on the weld and bolts area, at the connection zone between beam and steel linkage. However, in monolithic connection, the yielding was observed in rebars and crushing of concrete at the end of beam. The initial stiffness of bolted and welded connection specimen was less than that of monolithic connection specimen. But, the beam moment capacity factors of these samples were a little more than monolithic sample; so, the ductility factors of them were a little less than that of monolithic sample.Mon, 08 Apr 2019 19:30:00 +0100Parametric study from laboratory tests on twin circular footings on geocell-reinforced sand
http://scientiairanica.sharif.edu/article_21370_0.html
Bearing capacity (BC) test results are presented for bounded and unbounded twin circular footings on unreinforced and geocell-reinforced (GCR) sand. Analysis of the results demonstrate material, scale and size effects on the BC for a given combination in materials (sand-GCR), footing (single-twin) and the problem geometric dimensions. The significance of these combinations on BC and settlements is used to arrive at suitably modified BC factors for design that could be generalized. Plots given relative to reference cases for which BC design solutions are available provide correction factors to modify classical BC equations. Values of the BC and BC factors represent the lumped effect of all or separate problem variables including scale and any experimental limitations. Compared with previous works, these results give deeper critical depths for twin footings on unreinforced and GCR sand and BC higher than 4 times the reference case.Mon, 08 Apr 2019 19:30:00 +0100Modeling Vibrational Behavior of Silicon Nanowires Using Accelerated Molecular Dynamics Simulations
http://scientiairanica.sharif.edu/article_21372_0.html
The classical methods utilized for modeling the nano-scale systems are not practical because of the enlarged surface effects that appear at small dimensions. Contrarily, implementing more accurate methods results in prolonged computations as these methods are highly dependent on quantum and atomistic models and they can be employed for very small sizes in brief time periods. In order to speed up the molecular dynamics (MD) simulations of the silicon structures, coarse-graining (CG) models are put forward in this research. The procedure consists of establishing a map between the main structure’s atoms and the beads comprising the CG model and modifying the systems parameters such that the original and the CG models reach identical physical parameters. The accuracy and speed of this model is investigated by carrying out various static and dynamic simulations and assessing the effect of size. The simulations show that for a nanowire with thickness over 10a, where parameter a is the lattice constant of diamond structure, the Young modulus obtained by CG and MD models differs less than 5 percent. The results also show that the corresponding CG model behaves 190 time faster compared to the AA model.Sun, 14 Apr 2019 19:30:00 +0100Determination of Weibull parameters with using Standard Deviation Method and performance ...
http://scientiairanica.sharif.edu/article_21381_0.html
This study analyzed the harmony of the Weibull Distribution Function (WDF) and the real data obtained from three different locations. The Standard Deviation Method (SDM) was used to determine the coefficients of the WDF at Adana, Osmaniye and Hatay regions. One of the important purposes of this study is to observe how the performance of the SDM changes in regions with different mean wind speeds. The statistical fittings of the calculated and measured wind speed data were evaluated for justifying the performance of the SDM. The obtained results were compared with such error analyses as Coefficient of Determination (R2), Mean Percentage Error (MPE) and Root Mean Square Error (RMSE). Obtained data were examined on monthly, seasonal and annual bases. The power density is a major key issue for suitability use of wind energy. The calculated power densities of all selected regions were compared with wind power density derived from measured wind data. The performance of the method mentioned in this study was examined in detail at different regions with different geographic characteristics. For the selected three regions, the performance of the SDM was evaluated at different mean wind speeds varying over the years.Sun, 21 Apr 2019 19:30:00 +0100ON NEW FAMILY OF KIES BURR III DISTRIBUTION: Development, Properties, Characterizations, and ...
http://scientiairanica.sharif.edu/article_21382_0.html
In this paper, a flexible lifetime distribution with increasing, decreasing, increasing-decreasing-increasing and bathtub hazard function, called New Family of Kies Burr III (NFKBIII) distributions is proposed. The density function of the NFKBIII is arc, J, reverse-J, U, bimodal, left-skewed, right-skewed and symmetrical shaped. The NFKBIII distribution is developed on the basis of the T-X family technique. The NFKBIII distribution is also obtained from compounding mixture distributions. Some structural and mathematical properties including moments, inequality measures, order statistics and reliability measures are theoretically established. The NFKBIII distribution is characterized via different techniques. Parameters of the NFKBIII distribution are estimated using maximum likelihood method. A simulation study is performed to illustrate the performance of the maximum likelihood estimates (MLEs). The potentiality of the NFKBIII distribution is demonstrated via its application to real data sets.Sun, 21 Apr 2019 19:30:00 +0100Bi-objective optimization of non-periodic preventive maintenance strategy by considering time ...
http://scientiairanica.sharif.edu/article_21384_0.html
Recently, design of preventive maintenance (PM) policies during the warranty period has attracted the attention of researchers. The methods mainly design warranty servicing strategies in a way that reduce the cost imposed on the manufacturer without considering the impact of customer dissatisfaction. While dissatisfaction with a product is an important issue which may result in the loss of potential buyers and switching existing buyers to competitors. Therefore, this study develops a bi-objective model which simultaneously minimizes the manufacturer and the buyer cost under a Non-homogeneous Poisson Process framework. Also, a non-periodic preventive maintenance strategy is presented in which PM actions are performed at discrete time instants in a way that the expected number of failures remains a constant value over all PM intervals. Furthermore, it is a known fact that the value of money reduces over time due to different reasons and has a significant impact on long-term contracts. Since PMs and repairs are conducted at different times, the time value of money is considered to estimate the cost more accurately. A comparative study is conducted to support this claim that the presented non-periodic reliability-based PM policy has a better performance in comparison with a periodic PM policy.Sun, 21 Apr 2019 19:30:00 +0100Pulsed Nd: YAG Laser Dissimilar Welding of Ti/Al3105 Alloys
http://scientiairanica.sharif.edu/article_21385_0.html
Overlapped strips of titanium grade 2 and aluminum 3105-O alloy were welded together by an innovative spot-like pulse laser procedure. The tactile seam tracking on ring paths yielded reliable weld fit-up of 1 and 0.5 mm thickness strips. Since the welding parameters of Ti-Al were narrow, three welding speeds of 4, 5 and 6.67 mm•s-1 were chosen for the pretest conditions. The microstructural investigations showed that intermetallic compound Ti3Al, formed in Ti-rich fusion zone. Cracks formed in the Al-rich fusion zone as a result of TiAl3 precipitation. Dimple fracture occurred at 6.67 mm•s-1 welding speed. Longer mixing time at Ti-Al interface occurred at lower welding speeds of 4 and 5 mm•s-1, which led to the formation of thicker intermetallic compounds and more massive crack generation. It also increases the hardness of the fusion zone and results in brittle fracture type during the tensile test. The highest strength was achieved with a welding speed of 4 mm•s-1 which was a result of more massive weld nugget and lower porosity.Sun, 21 Apr 2019 19:30:00 +0100FREIGHT MODAL POLICIES TOWARD A SUSTAINABLE SOCIETY
http://scientiairanica.sharif.edu/article_21386_0.html
Freight transport policy analysts struggle to shift truck freight movements to rail to diminish transportation externalities including environmental costs and safety issues. Therefore, policy-makers need to be aware of the consequences of their decisions beforehand. This study is mainly focused on two policies targeting fuel price and access to rail transportation. A nation-wide freight mode choice model is developed for Iran, and shippers’ tendency to choose rail or truck freight transportation is analyzed by considering the shipping time and cost, commodity weight, commodity type, and rail accessibility. Total fuel consumption and air pollution costs are compared in various scenarios. Based on the results, environmental transportation costs are significantly reduced as a result of the modal shift from truck to rail freight transportation, if the government reallocates the gasoline subsidy to the construction of prioritized railroads.Mon, 22 Apr 2019 19:30:00 +0100Forecasting natural gas production and consumption using grey model with latent information ...
http://scientiairanica.sharif.edu/article_21391_0.html
The aim of the paper is to develop a grey model for short term forecasting of natural gas consumption and production in China and USA respectively. To enhance its prediction accuracy, the outliers are found by the error of the latent information function, and then corrected according to the test sample and the future trend. The sequence with corrected outliers is used to construct a grey model. The proposed model is employed to predict the natural gas consumption and production in China and USA. The results have demonstrated that the proposed model can raise the forecast accuracy of the grey model, and it also indicates that China will inevitably face a massive expansion in natural gas imports.Tue, 30 Apr 2019 19:30:00 +0100On the Performance of Median Based Tukey and Tukey-EWMA Charts Under Rational Subgrouping
http://scientiairanica.sharif.edu/article_21392_0.html
Control chart (CC) is used to monitor the special causes that arise during the process monitoring. These special causes produce continual shifts in the process parameters that last until it is identified and removed. There is a need for such techniques, which present the true representation of the entire process. Rational subgrouping is an essential concept in Statistical Process Control (SPC) which is seldom overlooked by the practitioner. Hence, most of the manufacturing, engineering, and production processes give output products in the form of batches over smaller intervals of time. The aim of this study is to provide a median based design for Tukey and Tukey-EWMA control charts under subgrouping. It will use the idea of boxplot to monitor the process behavior. This study also provides a brief discussion regarding selecting and forming subgroups from the process data. The performance of the median based Tukey and Tukey-EWMA charts are judged using Average, Median and Standard-Deviation run-length as performance measures. We have considered subgroup sizes of m=1,5 &10 at pre-specified ARL0 equal to 370. To real-life applications of the median based tukey designs are also presented to show their implementation in food manufacturing and hard-bake processes.Tue, 30 Apr 2019 19:30:00 +0100Experimental evaluation of solar integrated water heater
http://scientiairanica.sharif.edu/article_21393_0.html
This paper presents an experimental evaluation of portable modified conventional buckets of 10 l capacity. Out of ten modified portable storage, best three cases (viz. Non-insulated open plastic bucket (OPB), Non insulated plastic bucket top surface covered with a transparent cover (CPB), and Insulated plastic bucket closed with a transparent cover (ICPB)) are discussed. Maximum temperature rise after two hour time duration OPB, CPB, and ICPB are 29.82%, 47.36%, and 21.49% respectively as compared with the initial value the temperatures (22.8 ℃). At 14:45 hour CPB temperature reaches 35.6 °C which is 17.88 and 23.61% higher values as compared to the OPB and ICPB units. Net saving due to utilization solar energy in CPB for a range of 35-50°C is net saving increased by 12.34%, 25.76%, 40.73%, 57.93%, 76.45%, and 97.18% from 2017 to 2022 as compared with the saving in 2016.Tue, 30 Apr 2019 19:30:00 +0100Extended Economic Production Quantity Models with Preventive Maintenance
http://scientiairanica.sharif.edu/article_21394_0.html
This paper generalizes the standard economic production quantity (EPQ) model in process manufacturing industry by incorporating regular preventive maintenance (PM) activities into classic EPQ model. The PM program improves the condition of the production to an acceptable level, and avoids potential stoppages and disruptions, hence, it is a vital task in every production process. However, the standard EPQ model does not consider PM activities and then is not applicable to real-world situations. We consider manufacturer which produces a product under EPQ setting with a defective production process, in which every production cycle involves a number of sub-production cycles. Two models are proposed, based on the disposal time of defective items, to determine optimal number of sub-production cycles. In model I, the disposal of defective items is performed once per cycle at the end of each production cycle, while in model II, the disposal of defective items is performed multiple times per cycle, at the end of each sub-production cycle. The total cost functions are derived for each model separately, and then simple solution algorithms are designed. A numerical example is presented and discussed to evaluate proposed models. The results illustrate that model II is more cost effective than model I.Tue, 30 Apr 2019 19:30:00 +0100Novel aspects of Soret and Dufour in entropy generation minimization for Williamson fluid flow
http://scientiairanica.sharif.edu/article_21395_0.html
Soret and Dufour effects on MHD flow of Williamson fluid between two rotating disks are examined. Impacts of stratification, viscous dissipation and activation energy are also considered. Bejan number and entropy generation for stratified flow is discussed. The governing PDE's are converted into ODE's by using Von Kármán transformations. Convergent solution of complicated ODE's is found by homotopic procedure. The results of physical quantities are discussed through plots and numerical values. It is noted that axial and radial velocities are more for greater Weissenberg number. Temperature and concentration profiles are decreasing functions of thermal and solutal stratification parameters respectively. Entropy and Bejan number show the opposite trends for higher Weissenberg number and Brinkman number.Tue, 30 Apr 2019 19:30:00 +0100PM10 and CO Dispersion Modeling of Emissions from the Four Thermal Power Plants in Mashhad-Iran
http://scientiairanica.sharif.edu/article_21397_0.html
In this study, we present an evaluation of the (PM10) and carbon monoxide (CO) particulate matter exposure level originated from the four power plants in the area using Air Pollution Dispersion Model. Combined use of AREMOD (The American Meteorological Society/Environmental Protection Agency Regulatory Model), ArcGIS and health risk assessment were applied to estimate the level of pollution in thirteen municipal receptors in the city. The results indicated the long-range transport of the pollutants from the power plants expected to impose significant health impacts on residential receptors. Almost 80000 inhabitants of the city were exposed to PM10 concentration, ranging between 50-75 µg/m3 and 100000 were exposed to CO concentration, ranging between 40-45 µg/m3. Approximately, 1200 hectares of the city were exposed to PM10 concentration, ranging from 40 to 50 µg/m3 and 370 hectares of the city area were exposed to CO concentration between 50-75 µg/m3. Comparison between simulated and observed concentrations of pollutants shows a little overestimation by model.Tue, 30 Apr 2019 19:30:00 +0100Chaotic Vibrating Particles System for Resource-Constrained Project Scheduling Problem
http://scientiairanica.sharif.edu/article_21398_0.html
Project scheduling in the resource-constrained situation is one of the key issues of project-oriented organizations. The aim of resource-constrained project scheduling problem (RCPSP) is finding a schedule with minimum makespan by considering precedence and resource constraints. RCPSP is a combinatorial optimization problem and belongs to the class of NP-hard problems. The exact methods search the entire search space and are unable to solve large-sized project networks. Thus metaheuristics are used to solve this problem with less computational time. Due to the probabilistic nature of metaheuristics, it is a challenging problem to balance between exploitation and exploration phases. The literature review shows that embedding with chaos improves both the convergence speed and the local optima avoidance of metaheuristics. This paper presents a Chaotic Vibrating Particles System (CVPS) optimization algorithm for solving the RCPSP. Vibrating Particles System (VPS) is a physic inspired metaheuristic which mimics the free vibration of single degree of freedom systems with viscous damping. The performance and applicability of the CVPS is compared with the standard VPS, and five well known algorithms on three benchmark instances of the RCPSPs Experimental studies reveals that the proposed optimization method is a promising alternative to assist project managers in dealing with RCPSP.Fri, 03 May 2019 19:30:00 +0100Sensitivity Analysis of Economic Variables using Neuro-Fuzzy Approach
http://scientiairanica.sharif.edu/article_21402_0.html
Sensitivity analysis (SA) is a vital task for decision making in economic management. In this paper, a novel fuzzy sensitivity analyzer (FSA) is proposed to analyze the sensitivity of economic variables. The proposed FSA algorithm consists of an adaptive neuro-fuzzy inference system (ANFIS) that is adjusted for forecasting economic time series. Based on the output of ANFIS, FSA can determine the importance degree of parameters. In the numerical studies, the proposed method is applied for the sensitivity analysis of oil and gold time series. According to the results, FSA indicates that oil price is highly dependent upon the inflation rate, dollar index and market index while OPEC production level and gold price have less impact. Furthermore, in the gold price modeling, the highest sensitivity is obtained from silver price while demand for gold is more a function of market index and inflation rate. The proposed method can be used in many SA applications.Sat, 04 May 2019 19:30:00 +0100Weight determination and ranking priority in interval group MCDM
http://scientiairanica.sharif.edu/article_21403_0.html
In this study, we propose a method to determine the weight of decision makers (DMs) in group multiple criteria decision making (GMCDM) problems with interval data .Here, we obtain an interval weight for each DM and the relative closeness of each decision from the negative ideal solution (NIS) and the positive ideal solution (PIS) is then computed. In the proposed method, after weighting the decision matrix of each DM, the alternatives are ranked using interval arithmetic. A comparative example together with a real world problem on air quality assessment is given to illustrate our method. Our findings show that the proposed approach is a suitable tool to solve GMCDM problems.Sat, 04 May 2019 19:30:00 +0100A game theoretic approach to coordinate pricing, ordering and co-op advertising in supply ...
http://scientiairanica.sharif.edu/article_21404_0.html
This paper combines the newsboy problem with the cooperative advertisement problem in the presence of uncertain demand which depends on retail price as well as both local and national advertising expenditures to coordinate pricing, ordering, and advertising decisions in a manufacturer-retailer supply chain. A game theoretic approach is adopted to determine the equilibrium values of the decisions. Three different game scenarios based on the newsboy problem model are developed and analyzed: 1) Stackelberg manufacturer game in which manufacturer as the dominant power plays the role of leader in the market and the follower retailer makes its own best decisions after observing the leader decisions, 2) Nash game wherein both manufacturer and retailer have equal power in the market and make their decisions simultaneously to find their own best strategies and 3) centralized scenario in which retailer and manufacturer make the best decisions by information sharing and joint cooperation. The equilibrium decisions are obtained exactly in the three scenarios. Some corollaries are also presented and theoretically proved to show the relationships among the variables in centralized vs. decentralized supply chain. Finally, some numerical examples are randomly generated and a sensitivity analysis is carried out to show capabilities of the proposed models.Sat, 04 May 2019 19:30:00 +0100Risk-based Switch Placement in Electric Distribution Network in Presence of Performance Based ...
http://scientiairanica.sharif.edu/article_21406_0.html
A reward and penalty scheme (RPS) is used for setting up the service quality which exposes the distribution companies to financial benefits caused by demand for the reliability of customers. In this paper, an algorithm for the optimal switch number and placement in distribution networks in the presence of RPS is presented. The primary objective is reliability improvement and minimization of the cost of sectionalizing switches (SS) and tie switches (TS) for a given regulatory period considering acceptable financial risk. In this algorithm, the uncertainty in the reliability is appeared as financial risk. A genetic algorithm is adopted to solve the optimization problem. The number and location of SS and TS is found while financial incentives of RPS, capital investment and annual operation and maintenance costs are considered. The performance of the proposed approach is assessed and illustrated on a real distribution network. The results show the efﬁciency of the proposed algorithm.Mon, 06 May 2019 19:30:00 +0100Estimation of 80 kW Solar Generating Station in Kabudrahang Iran: A Comparative Study
http://scientiairanica.sharif.edu/article_21407_0.html
Estimation of solar energy generation in the integrated power systems must be performed for power system the long-term planning and the short-term control. Irradiation is one of the main factors affecting the out coming energy of solar system. Hence, investigation of solar irradiation on the horizontal surface helps in proper and efficient implementation of solar energy system. Capturing much more energy from the irradiation, by the Photovoltaic (PV) cells, results in enhancement of out coming energy of PV station. This paper is going to study the impact of implementation two topologies for energy harvesting in PV stations. The topologies are as follows: (a) PV station with multilevel boost converters and inverters, (b) PV station with only multilevel inverters. Studies have been performed on 80 KW PV test station, located in Kabudrahang, Iran. The comparison between the results demonstrates much more solar energy harvesting in the case of applying multilevel converters in the output of PV arrays. Simulation results show the promising result of the proposed topology in harvesting maximum power from a PV station.Mon, 06 May 2019 19:30:00 +0100Effects of Seismic Pounding between Adjacent Structures Considering Structure-Soil-Structure ...
http://scientiairanica.sharif.edu/article_21408_0.html
Structures located beside each other interact under dynamic loads both through the underlying soil and possibly by impact. In this paper, this dynamic cross-interaction phenomenon is studied parametrically. While simultaneous modeling of different adjacent buildings would be possible from the beginning, by resorting to simple physical models the cases susceptible to impact under harmonic loads are identified first with much less effort. Then comprehensive models containing two nonlinear multistory shear buildings connected at the base with suitable springs & dampers and impacting at story levels are developed. The system is analyzed under selected ground motions. It is shown that impact and cross-interaction have an increasing effect on lateral displacements for stiff and heavy structures and a decreasing effect for other cases. Also, the shear forces of stories increase and decrease in upper and lower stories, respectively, as a result of the mentioned mutual effect. Finally, the study shows that under a sample ground motion, simultaneous impact and cross-interaction increase the ductility demands of stories for taller structures while it decreases the ductility demand of shorter buildings.Mon, 06 May 2019 19:30:00 +0100A New Active Snubber Cell for Soft Switched Power Factor Correction Boost Converters
http://scientiairanica.sharif.edu/article_21413_0.html
This paper introduces a new active snubber cell for soft switched power factor correction (PFC) boost converters. In the new converter, the main switch turns on by zero voltage transition (ZVT) and turns off by zero voltage switching (ZVS). The main diode turns on by ZVS and turns off by zero current switching (ZCS). In the active snubber cell, the auxiliary switch turns on by ZCS and turns off by zero current transition (ZCT). Any semiconductor device does not expose the addition voltage stress. The theoretical analysis of the proposed converter is presented, and also verified with both simulation and experimental study at 100 kHz switching frequency and 600 W output power. Furthermore, the new converter has 95.7% efficiency and 0.99 power factor at soft switching operation.Sun, 12 May 2019 19:30:00 +0100Powder Metallurgy Mg-Sn alloys: Production and characterization
http://scientiairanica.sharif.edu/article_21414_0.html
In this study, Mg-Sn alloys were produced through the powder metallurgy (P/M) method by adding Sn in different ratios into Mg powder. A new mixing technique has been used in production to prevent the disadvantages of high reactivity that the Mg powders have. The prepared powder mixtures were turned into components by processing through hot pressing. The produced components were characterized by density measurements, microstructure examinations and mechanical tests. The density measurements were made according to the Archimedes principle. The microstructural characterization was performed by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) investigations and energy dispersive spectrometry (EDS) analyses. The hardness measurements and the tensile tests were used for the determination of mechanical properties. Densities close to the theoretical density were obtained in the produced parts. XRD and SEM investigations have shown that the components produced are composed of α-Mg and Mg2Sn phases of the microstructure consisting of coaxial grains. The rising Sn content increased the amount of discrete Mg2Sn precipitates at the grain boundaries, thereby ensuring higher hardness and strength values.Sun, 12 May 2019 19:30:00 +0100Optimization of Manipulator Drive Mechanisms in Hydraulic Excavators on the Basis of the ...
http://scientiairanica.sharif.edu/article_21430_0.html
The paper analyzes functional, structural and tribological parameters of kinematic pairs (joints) of the kinematic chain and manipulator drive mechanisms in hydraulic excavators. On the basis of the conducted analysis the tribological criterion is defined, as one of a number of criteria, for the optimal synthesis of manipulator drive mechanisms in hydraulic excavators. The criterion indicator is determined as a mechanical degree of efficiency of drive mechanisms, to reflect the tribological loss of power of the excavator drive system due to friction between the elements of the joints in manipulator drive mechanisms. As an example, the paper provides experimental results of tribological research and tribological criterion indicators during examination and synthesis of manipulator drive mechanisms in a hydraulic excavator of 17,000 kg in mass.Mon, 20 May 2019 19:30:00 +0100An e-commerce facility location problem under uncertainty
http://scientiairanica.sharif.edu/article_21431_0.html
Facility location problem is a branch of operational research and computational geometry. It involves the best allocation of facilities to minimize transportation costs, while considering factors such as avoiding placing dangerous materials near the premises and the facilities of competitors. According to B2C e-commerce unique customer characteristics and fierce market competition, two facility location models in e-commerce under uncertainty are proposed, i.e., expected value model and pessimistic value model. It is proved these models can be converted into equivalent models based on inverse uncertainty distribution method. A hybrid algorithm is proposed to solve these models. Some numerical experiments are used to demonstrate the effectiveness of the proposed models and approach.Mon, 20 May 2019 19:30:00 +0100A Genetic Algorithm based framework for mining quantitative association rules without ...
http://scientiairanica.sharif.edu/article_21432_0.html
Discovering association rules is a useful and common technique for data mining in which relations and co-dependencies between datasets are shown. One of the most important challenges of data mining is to discover the rules of continuous numerical datasets. Furthermore, another restriction imposed by algorithms in this area is the need to determine the minimum threshold for the support and confidence criteria. In this paper a multi-objective algorithm for mining quantitative association rules is proposed. The procedure is based on the Genetic Algorithm, and there is no need there is no need to determine the extent of the threshold for the support and confidence criteria. By proposing a multi-criteria method, the useful and attractive rules and the most suitable numerical intervals are discovered, without the need to discrete numerical values and the determination of the minimum support threshold and minimum confidence threshold. Different criteria are used to determine appropriate rules. In this algorithm, the selected rules are extracted based on confidence, interestingness, and cosine2. The results obtained from real-world datasets demonstrate the effectiveness of the proposed approach. The algorithm is used to examine three datasets and the results show the performance superiority of the proposed algorithm compared to similar algorithms.Mon, 20 May 2019 19:30:00 +0100Numerical Investigation of the Mechanical Performance of NiTi stent for application in Thoracic ...
http://scientiairanica.sharif.edu/article_21433_0.html
Nowadays, Superelastic NiTi stent is used in Thoracic Aortic Aneurysm (TAA) because of its effects on minimizing such problems as low twistability, unsuitable dynamic behavior, and the shortage of radial mechanical strength. In our simulations, NiTi superelasticity is modeled based on Auricchio theory and Tanaka, Liang and Rogers theory. Auricchio Model show more consistency with the experimental data than Tanaka and Liang and Rogers Models. In the present study, a Finite Element Analysis (FEA) was used to evaluate the impacts of the applied strain on the superelastic behavior of the new geometry designed for Z-shaped TAA NiTi wire stent, for which axial strain (crushing) and radial strain (crimping) force are applied. The results showed that NiTi stent with 50% crimping and 90% crushing displayed the highest mechanical performance owing to suitable Chronic Outward Force(COF), appropriate Radial Resistive Force(RRF), complete mechanical hysteresis loop pertaining to superelastic behavior, and the lower stress and higher strain on the internal curvature of the NiTi stent. Finally, this FEM model can provide a convenient way for evaluating the biomechanical properties of TAA stents given the influences of strain applied.Mon, 20 May 2019 19:30:00 +0100A hybrid Approach in Metaheuristics for a Cross-dock Scheduling Considering Time Windows and ...
http://scientiairanica.sharif.edu/article_21434_0.html
Recent years have envisaged a great deal of interest in optimizing of logistics and transforming systems. One of important challenges in this regard is the cross dock scheduling with several real-life limitations such as the deadline for both perishable and imperishable products. This study is a new cross-dock scheduling problem by not only considering a time window but also for all shipping trucks, the deadline is assumed by the presence of perishable products for the first time in this research area. Based on these suppositions, a new mathematical model is developed. The last but not the least is to propose a new hybrid metaheuristic by combining a recent nature-inspired metaheuristic called Keshtel Algorithm (KA) and a well-known algorithm named Simulated Annealing (SA). The proposed hybrid algorithm not only is compared with its individual ones but also some other well-known metaheuristic algorithms are used. Finally, the performance of the proposed algorithm is validated by several experiments with different complexities and statistical analyses.Mon, 20 May 2019 19:30:00 +0100Efficiency Evaluation of a Three-Stage Leader-Follower Model by the Data Envelopment Analysis ...
http://scientiairanica.sharif.edu/article_21435_0.html
In this paper, a three-stage network with optimal desirable and undesirable inputs and outputs has been taken into consideration by us. This network comprises of a leader and two followers. Four diverse models of Data Envelopment Analysis (DEA) to measure the efficiency or the performance, of this three-stage network have been taken under contemplation; these are namely, a Black Box Model and three Stackelberg Game (Theory) Models. A multiplicative DEA, with a double-frontier approach, to measure the efficiency of the entire system and the performances of the decision making units (DMUs), from both the optimistic and pessimistic views have been utilized. In this paper attempts have been made to present the goals of the managers in the models. Hence, aspects of goal programming have been manipulated so as to define cooperation between the leader and followers, such that, we are able to include the objectives of the managers in the models. In actual fact, a non-cooperative collaboration is deliberated upon. In addition to which, in the second and third scenarios, the leader-follower, nonlinear models are present. Thereby, a heuristic approach is suggested to convert the nonlinear models into linear ones.Mon, 20 May 2019 19:30:00 +0100Free vibration response of functionally graded carbon nanotubes double curved shell and panel ...
http://scientiairanica.sharif.edu/article_21439_0.html
This paper presents free vibration of the double-curved shells and panels with piezoelectric layers in a thermal environment. Vibration characteristics of elliptical, spherical, cycloidal, and toro circular shells of revolution are studied in detail. Vibration behavior of carbon nanotubes (CNTs) reinforced composite shells embedded with piezoelectric layers at the upper and lower surfaces is scrutinized. It is supposed that temperature changes linearly through-thickness direction. Reissner- Mindlin and the first order shear deformation (FSDT) theories are implemented to derive the governing equations of the considered structures. The distribution of nanotubes is assumed to be linear along the thickness direction. For solving the equation, the General Differential Quadrature (GDQ) method is used to obtain a numerical analysis for the dynamics of the objective structures. Finally, the effects of boundary conditions, the thickness of piezoelectric layers, functional distribution of CNTs, thermal environment and kinds of the circuit (opened-circuit and closed-circuit) are analyzed. Eigenvalue system is solved to obtain natural frequencies. It is delineated that the obtained fundamental frequency by the closed -circuit is smaller than those obtained by the opened-circuit. Another interesting result is that the natural frequency is decreased by increasing temperature.Mon, 27 May 2019 19:30:00 +0100Variance-based Features for Keyword Extraction in Persian and English Text Documents
http://scientiairanica.sharif.edu/article_21440_0.html
This paper address automatic keyword extraction in Persian and English text documents. Generally, for keyword extraction in a text, a weight is assigned to each token and words having higher weights are selected as the keywords. We have proposed four methods for weighting the words and have compared these methods with five previous weighting techniques. The previous methods used in this paper are term frequency (TF), term frequency inverse document frequency (TF-IDF), variance, discriminative feature selection (DFS), and document length normalization based on unit words (LNU). The proposed weighting methods are based on using variance features and include variance to TF-IDF ratio, variance to TF ratio, the intersection of TF and variance, and the intersection of variance and IDF. For evaluation, the documents are clustered using the extracted keywords as feature vectors, and K-means, expectation maximization (EM), and Ward hierarchical clustering methods. The entropy of the clusters and pre-defined classes of the documents are used as the evaluation metric. For the evaluations, we have collected and labelled Persian documents. Results show that our proposed weighting method, variance to TF ratio, has the best performance for Persian. Also, the best entropy is resulted by variance to TD-IDF ratio for English.Mon, 27 May 2019 19:30:00 +0100Investigating the effect of learning in set-up cost for imperfect production systems by ...
http://scientiairanica.sharif.edu/article_21444_0.html
In the modern industrial environment, there is a continuous need for the advancement and improvement of the organization’s operations. Learning is an inherent property which is time-dependent and comes with experience. In view of this, the present framework considers the process of learning for an imperfect production system which aids in reducing the setup cost with the level of maturity gained, hence, providing positive results for the organization. Because of machine disturbances/ malfunctions, defectives are manufactured with a known probability density function. To satisfy the demand with good products only, the manufacturer invests in a two-way inspection process with multiple screening constraints. The first inspection misclassifies some of the items and delivers inaccuracies, viz., Type-I and Type–II. The loss due to inspection at the first stage is managed efficiently through a second inspection which is presumed to be free from errors. The study mutually optimizes the production and backordering quantities in order to maximize the expected total profit per unit time. Numerical analysis and detailed sensitivity analysis is carried out to validate the hypothesis and further cater to some valuable implications.Mon, 27 May 2019 19:30:00 +0100Phase II Monitoring of Generalized Linear Profiles Under Different Types of Changes
http://scientiairanica.sharif.edu/article_21445_0.html
Various control charts have been proposed to monitor generalized linear profiles in Phase II. However, robustness of the proposed methods in detecting different types and especially different directions of changes is not well-studied in the literature. In real-world applications different kinds of changes such as drift and multiple change are likely to happen which can be isotonic (increasing) or antitonic (decreasing). This paper studies the robustness of Rao Score Test (RST) method, T2, and multivariate exponential weighted moving average (MEWMA) in different types, drift and multiple, and directions of changes. Rao Score Test method also benefits from a change-point detection approach whose performance is studied as well. According to the results, generally RST method shows a better performance in detecting different types of changes. Moreover, the performance of the RST method is robust to direction of the change, while T2 and MEWMA are not ARL-unbiased and show different performances under isotonic and antitonic changes. Therefore, to address this issue, we proposed a bias-reduced estimator to be used in T2. Our results demonstrate that the proposed control chart outperforms T2 and is less biased than T2. Finally, a real-world problem is presented in which aforementioned methods are applied to real data.Sun, 02 Jun 2019 19:30:00 +0100Inverse Design of a Centrifugal Pump on the Meridional Plane Using Ball-Spine Algorithm
http://scientiairanica.sharif.edu/article_21446_0.html
In this work, an inverse design algorithm called Ball-Spine (BSA) is developed as a quasi-3D method and applied to the meridional plane of a centrifugal pump impeller in an effort to improve its performance. In this method, numerical analyses of viscous flow field in the passage between two blades are coupled with BSA to modify the corresponding hub and shroud geometries. Here, full 3D Navier-Stokes equations are solved within a thin plane of flow instead of solving inviscid, quasi-3D flow equations in the meridional plane. To demonstrate the validity of the present work, the performance of a centrifugal pump is first numerically investigated, and then compared against available experimental data. Defining a target pressure distribution on the hub and shroud surfaces of the flow passage, a new impeller geometry is then obtained in accordance with the modified pressure distribution. The results indicate a good rate of convergence and desirable stability of BSA in the design of rotating flow passages. Overall, the proposed design method resulted in the following major improvements: an increase in static pressure along the streamline, 5% of increase in the pump total head and delay in the onset of flow cavitation inside the impeller.Sun, 02 Jun 2019 19:30:00 +0100Controlling the deflection of long beams using different patterns of pre-tensioning cables
http://scientiairanica.sharif.edu/article_21450_0.html
Despite appropriate design of beams under bending and shear, the deflection of long steel beams usually exceeds the allowable range, and therefore the structural designers encounter challenges in this regard. Considering significant features of the cables, namely, low weight, small cross section, and high tensile strength, they are used in this research so as to control the deflection of beams. 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 as well as the deflection of steel beam with different support conditions and different patterns of cable. Moreover, required cross-sectional area of steel cable has been calculated to reach allowable deflection in steel beams with different support conditions and different patterns of cable. The obtained results show that the theoretical relations can appropriately predict the deflection of beam with different support conditions and different patterns of cable. 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 V-shaped pattern one.Sat, 08 Jun 2019 19:30:00 +0100Investigation of interaction between quartz nanostructures and human cell lines for tissue ...
http://scientiairanica.sharif.edu/article_21464_0.html
Control of interaction between nanostructures and living cells is important for tissue engineering. The topography and hydrophilicity of nanotextured surfaces can provide information on the in vitro interactions between cells and the surrounding environment, which is of great importance in bio-applications. This study proposes a reactive ion etching (RIE) to texture the quartz surfaces with 5 and 10 nm surface roughnesses. The interaction of human cell lines (human breast cancer cells, MCF-7, and human dermal microvascular endothelial cells, HDMVEC) with the nanostructured surfaces exhibited different levels of morphogenesis when the cells adhered on the bare and nanotextured quartz surfaces. The chemical composition of the surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and results showed that cells preferred to grow on hydrophilic surfaces with hydroxyl groups. Moreover, the cellular processes, such as adhesion and spreading, were affected by the combination of physical and chemical properties of the surface, namely, surface topology and hydrophilicity. These results demonstrated the potential applications of quartz nanostructure surfaces with high microscopic image quality in tissue engineering for controlling cell growth via appropriate surface modifications.Sun, 16 Jun 2019 19:30:00 +0100A novel grey object matrix incidence clustering model for panel data and its application
http://scientiairanica.sharif.edu/article_21466_0.html
In order to fully excavate the information contained in the multi-index panel data, one take decision objects as the research object, and the development state matrix and the development speed matrix of the decision objects are defined by considering the cross-section information and time information of the decision objects, and then the distances among the objects over the indexes are given. Based on grey incidence analysis, the absolute difference and relative difference between the measure value matrices are used to characterize and measure the close degree of the development state matrix and the development level matrix of the decision objects, so that the grey object matrix absolute incidence analysis model is established, and then according to the grey incidence degree between the objects, the objects can be clustered based on hierarchical clustering algorithm. Finally, a clustering problem of regional patent research and development (R&D) efficiency is used to verify the validity and rationality of the proposed model.Mon, 17 Jun 2019 19:30:00 +0100Analytical Model of Recirculation Influence on Premixed Combustion of Lycopodium Dust Particle: ...
http://scientiairanica.sharif.edu/article_21467_0.html
In this work, a comprehensive mathematical method is developed to model the flame propagation through organic particles with air as a two-phase mixture, considering random distribution and particles thermal resistance. For this purpose, the structure of flame contains a preheat-vaporization zone, a reaction zone where vaporization and convection rates of particles are negligible and a post flame zone where diffusive terms are negligible in comparison of other terms zone. In order to enhance the combustion efficiency, the exhausted heat from the post flame zone is recirculated back to the preheat zone. Since this stream consists of high temperature gaseous mixture, it can enhance the temperature of the initial two-phase mixture entering the combustion chamber. The obtained results show great compatibility with the experimental findings. Apart from the randomness distribution of particles and heat recirculation phenomena, the effect of thermal resistance on the combustion properties such as flame temperature and burning velocity is studied through non-zero Biot numbers in this model. Additionally, the variation of several parameters including equivalence ratio, particle diameter and Lewis number are studied in this research.Mon, 17 Jun 2019 19:30:00 +0100Adaptive Radar Signal Detection in Autoregressive Interference using Kalman-based Filters
http://scientiairanica.sharif.edu/article_21468_0.html
This paper deals with the adaptive detection of radar target signal with unknown amplitude embedded in Gaussian interference which has been modelled as an AR process. Considering such model for the interference decreases the number of parameters that must be estimated and therefore less or even no secondary data is needed to obtain a detector with desired performance. Herein the detection is based on only the primary data. The authors resorting to the modern Kalman filtering technique develop the conventional GLRT-based detection in the presence of AR interference and propose two new detectors; AREKF based on extended Kalman filter and ARUKF based on unscented Kalman filter. The performance assessment conducted by Monte Carlo simulation compares the proposed detectors with the existing detectors based on generalised likelihood ratio test and Kalman filter. The results show that the ARUKF detector significantly has better detection performance than that of other detectors for the low number of primary data and high signal to noise ratio (SNR).Mon, 17 Jun 2019 19:30:00 +0100On use of Ranked Set Sampling for estimating Super-population Total: Gamma Population Model
http://scientiairanica.sharif.edu/article_21469_0.html
Utilization of superpopulation models for estimation of population parameters is an advantageous practice, when it is easy to recognize the relationship between the study variable with one or more auxiliary variables. This article is concerned with estimation of finite population total under a new ranked set sampling approach, ranked set sampling without replacement (RSSWOR), using so called gamma population model (GPM). Behavior of the proposed estimator, in term of relative efficiency, is studied for various choices of a constant γ via Monte Carle experiment. The provided simulation study shows the superiority of the proposed estimator over existing estimator under same model. The sampling procedure, especially, aids in collecting data from a continuous production process.Mon, 17 Jun 2019 19:30:00 +01000.3V Tunable OTA and Gm-C Filter in 0.13µm CMOS
http://scientiairanica.sharif.edu/article_21470_0.html
This paper presents an ultra-low-voltage operational transconductance amplifier (OTA) and Gm-C filter, both working with 0.3V single supply voltage. Using pseudo-differential structure, the common mode rejection is the main challenge in low voltage condition which is overcome by a new common mode feedback circuit. The OTA can be tuned through the gate terminal of body-driven PMOS input transistors. Post-layout simulation shows 23.4 dB differential gain and 47.4 dB CMRR at low frequencies. By changing the tune voltage from 50mV to 0V, the OTA's transconductance can be tuned from 7.9 to 17.4 uA/V. By applying input voltages up to 0.36 Vpp, the THD of output current remains less than -60 dB. The proposed OTA is employed to implement a tunable low-pass Gm-C filter. The cutoff frequency of Gm-C filter can be tuned from 1.13 to 1.9 MHz that makes it applicable in the multi-standard direct conversion receivers as channel selection filter. The power consumption of filter is 111.3 uW and its input referred voltage noise is 168.7 nV/sqrt(Hz), as results of post-layout simulations. The post-layout simulation shows the IIP3 of 8.5 dBm for the cutoff frequency of 1.9 MHz.Tue, 25 Jun 2019 19:30:00 +0100Experimental Evaluation of Shape Factor of Axis Symmetric Sunken Structures
http://scientiairanica.sharif.edu/article_21471_0.html
This paper presents the dependence of a shape factor for the fully sunken axis symmetrical structures (viz. cubical, square prismatic, pyramidal, and cylindrical) corresponding to the depth and their orientation. Experimental evaluations of the shape factor on reduce scale models are carried out in laboratory using thermal simulation method for different sets of conditions. The method has been used to determine shape factor, which can be used to determine heat loss from ground to structure or structure to groud fully sunken with the different orientation. Maximum and minimum value of shape factor for set-I and II condition are recoded as 90.18 and 9.93 respectively. In set –III it will varies from 16.49 to 35.28. At D/L=2 shape factor of set-VI leads by 17.26% as compared to set VII. Where as set- IX leads by 33.47% as compaired to set VIII. It would help for designing building structure of fully buried nature for creating thermal comfort.Tue, 25 Jun 2019 19:30:00 +0100DNA Sequencing Based On Physical Properties at Single Nucleotide Resolution
http://scientiairanica.sharif.edu/article_21472_0.html
To realize objectives such as genome-based medicine, it is required to develop economical and fast methods for DNA sequencing at single-nucleotide resolution. In this paper a novel approach is developed to significantly improve efficiency of DNA sequencing based on physical differences between nucleotides. Here it is claimed that the reason for rather low resolution of sequencing based on physical differences, is the extremely nonlinear and complex dynamics of the DNA; it causes great dependence of DNA translocation with respect to detectors on initial conditions and environmental disturbances. In various sequencing, the position and orientation of nucleotides would thus be different in detection time. By decreasing signal-to-noise ratio, these different dynamics of nucleotides prevent detecting slight differences in physical properties of DNA bases. The correctness of this claim is verified by designing a sequencing nanodevice in which motion of a stretched single-stranded DNA (ssDNA) is constrained in such a way that axis of ssDNA backbone is fixed and in detection time each nucleotide lies in a fixed plane. Also nonlinear effects in ssDNA and detectors interactions are reduced as low as possible. Results indicate that under these constrained conditions, specific and distinct signal for each type of nucleotide will be generated.Tue, 25 Jun 2019 19:30:00 +0100Pricing in Two Competing Supply Chains Based on Market Power and Market Size under Centralized ...
http://scientiairanica.sharif.edu/article_21473_0.html
In this paper, we considered the competition between two multi-echelon supply chains with identical structures on price under two market power structures. For this purpose, we developed two different scenarios. In the first scenario, both supply chains decided simultaneously (the Nash game). In the second scenario, due to the imbalance of power between the two supply chains, we adopted the Stackelberg game in the model. Price equilibrium is obviously obtained through the Game Theory. The paper investigated the effects of different relations between the market sizes of supply chains and the supply chain structures on price and profit along with the analysis of power in the market. Based on these assumptions, it was found that the supply chains did not always involve the second-mover advantage in the price Stackelberg game. Furthermore, having the centralized structure, both of the supply chains benefited from presence of a leader in the market for different combinations of market size. Finally, we presented significant managerial insights for the market with two competitive supply chains when the structures were similar. Moreover, the relationship between price and profit was analyzed given the size of the market in different scenarios rather than through provision of numerical examples.Tue, 25 Jun 2019 19:30:00 +0100Eigen Spherical Fuzzy Set and its Application in Decision Making Problem
http://scientiairanica.sharif.edu/article_21476_0.html
Eigen fuzzy set of a fuzzy relation often occurs to be invariant under different computational aspects. The present communication introduces the novel concept of eigen spherical fuzzy set of spherical fuzzy relation along with various composition operators for the first time. We have proposed two algorithms to determine the greatest eigen spherical fuzzy sets and least eigen spherical fuzzy sets using the $max-min$ and $min-max$ composition operators respectively and illustrated the steps with the help of flow charts. Further, two numerical examples related to different fields of decision-making problems have been taken into account for illustrating the proposed methodology. The scope of future work in the field of image information retrieval, genetic algorithm for image reconstruction and notion of eigen spherical fuzzy soft sets/matrices has been duly outlined. The comparative remarks and advantages of the proposed eigen spherical fuzzy sets have also been included for a better readability.Tue, 25 Jun 2019 19:30:00 +0100T-spherical Fuzzy Soft Sets and its Aggregation Operators with Application in Decision Making
http://scientiairanica.sharif.edu/article_21477_0.html
In the present manuscript, we introduce a novel concept of T-spherical fuzzy soft set with various important operations and properties. In the field of information theory, an aggregation operator is a structured mathematical function which aggregates all the information received as input and provides a single output entity, which are found to be applicable for various important decision making applications. Some averaging aggregation operators and geometric aggregation operators (weighted, ordered and hybrid) for T-spherical fuzzy soft numbers have been proposed with their various properties. Further, utilizing the proposed aggregation operators of various types along with the properly defined score function/accuracy function, an algorithm for solving a decision making problem has been provided. The proposed methodology has also been well illustrated with the help of a numerical example. Some comparative remarks and advantages of the introduced notion of T-spherical fuzzy soft set and the proposed methodology have been listed for a better motivation and readability.Tue, 25 Jun 2019 19:30:00 +0100An Evaluation of Inventory System via Evidence Theory for Deteriorating Items under Uncertain ...
http://scientiairanica.sharif.edu/article_21478_0.html
The inventory model for deteriorating items, which is developed by The Evidential Reasoning Algorithm (ERA) and the imprecise inventory costs, is one of the most important factors in complex systems which plays a vital role in Payment. The ERA is able to strengthen the precision of the model and give the perfect interval-valued utility. In this model, during lead-time and reorder level two different cases can be happened which the mathematical model turns into an imposed nonlinear mixed integer problem with interval objective for each case. Placement of an order, which is overlooked by many researchers till now, is normally connected with the advance payment (AP) in business. Specifying the optimal profit and the optimal number of cycles in the finite time horizon and lot-sizing in each cycle, are our goals so. In order to solve this model, we apply the real-coded genetic algorithm (RCGA) with ranking selection. By the model, we represent some numerical examples and also a sensitivity analysis with the variation of different inventory parameters.Tue, 25 Jun 2019 19:30:00 +0100Performance Improvement of AC-DC Power Converters under Unbalanced Conditions
http://scientiairanica.sharif.edu/article_21479_0.html
In this paper, a single synchronous reference-frame based control method is proposed to improve the performance of AC-DC interlink converters feeding DC loads under unbalanced AC grid conditions. Unbalanced grid voltages cause undesirable double frequency (2ω0) oscillations on the DC link voltage in AC-DC converters. In the medium/high power applications, low switching frequency, and the oscillatory power of the input filter considerably degrade the functionality of the existing methods for removing 2ω0 ripples from DC link voltage. In this paper, an analytical equation for the terminal active power is derived considering the input filter inductance. Accordingly, suitable current references are proposed to eliminate the undesirable 2ω0 ripples from DC-link voltage considering low switching frequency. It is shown that the filter inductance adds a non-linear term to the active power equation which complicates the current reference calculation. Accordingly, a real-time recursive method is proposed to solve the equations and find the current references. To evaluate the performance of the proposed method, different grid unbalanced conditions, including asymmetrical short circuit faults, are applied to a test system in the PSCAD/EMTDC environment. Furthermore, the functionality of the proposed method is compared with that of the existing method for unbalanced conditions in the literature.Tue, 25 Jun 2019 19:30:00 +0100A fuzzy solution approach for supplier selection and order allocation in green supply chain ...
http://scientiairanica.sharif.edu/article_21483_0.html
In the field of supply chain, selecting a suitable green supplier could significantly help us to decrease the cost and the risk involved in the operations as well as increase in the quality and green. In this paper, we develop an integrated two-stage approach based on fuzzy analytic hierarchy process (FAHP) and multi-objective mixed-integer linear programming to select suppliers and order allocation in green supply chain. In the first stage, suppliers are evaluated using FAHP method, and in the second stage, a multi-product multi-period supply chain considering green location-routing problem, discounting, and time window under uncertainty is developed. Then, a fuzzy solution approach is applied to solve proposed model using the data of a pharmaceutical chain in Iran. Results will verify the efficiency of the proposed model.Mon, 01 Jul 2019 19:30:00 +0100Numerical investigation of the effect of viscosity on bubble dynamics in a narrow channel
http://scientiairanica.sharif.edu/article_21484_0.html
In this paper, dynamic behavior of a vapor bubble inside a narrow channel filled with a viscous liquid has been studied numerically. The boundary integral equation method (BIEM) and the procedure of viscous correction of viscous potential flow (VCVPF) have been employed for obtaining the vapor bubble profiles during its pulsations inside the narrow channel filled with a viscous liquid. In the present paper a new method has been proposed for considering the effects of viscosity in a viscous liquid flow in the framework of the Green's integral formula together with the modified form of unsteady Bernoulli equation. The reported experimental and numerical results of the problem under investigation have been used for verification of the results of the present work. Numerical results show that, by increasing the viscosity of liquid around the vapor bubble, the bubble lifetime increases. Numerical results also indicate that for Reynolds numbers with the order of , the viscosity effects are extremely reduced. Furthermore, the dynamic behavior of the bubble in water and oil is investigated at different Reynolds numbers and at different so-called dimensionless channel radii.Mon, 01 Jul 2019 19:30:00 +0100A Real-Time Exhaustive Search Algorithm For Weapon-Target Assignment (WTA) Problem
http://scientiairanica.sharif.edu/article_21489_0.html
Weapon-Target Assignment (WTA) as an important part of aerial defense cycle has long been ‎studied. Challenges are usually finding fast-computing methods to search optimal or near-‎optimal solution in cases of a large number of weapons and targets. This viewpoint is more ‎mathematically considerable but practically has limited usage in the mentioned context. A ‎real-time search algorithm is proposed which decomposes the WTA problem and by ‎decreasing the size of solution space and deleting impossible solutions, enables real-time ‎exhaustive search algorithm. Implementation of the algorithm for three typical scenarios shows ‎excellent real-time performance and the possibility of finding exact solutions for large-scale ‎problems.‎Sat, 06 Jul 2019 19:30:00 +0100Computational optimization of a UFAD system using large eddy simulation
http://scientiairanica.sharif.edu/article_21490_0.html
In the present study, the Large Eddy Simulation (LES) turbulence closure is implemented, for the first time, to the best of our knowledge, to investigate the air conditioning system in a large space. The results of LES simulations are validated against experimental measurements and the model is used to study the effect of different design variables, including the Air Changes per Hour (ACH), supply temperature, and return air vent height, on design objectives, such as local and global thermal comfort indexes and the energy saving parameter, via a systematic multi-objective optimization approach. The sensitivity analysis shows that the global and local thermal comfort indexes are most sensitive to the air supply temperature while the energy saving is sensitive to ACH and the supply temperature to the same extent. In addition, the return air vent height affects the energy saving more than the other objectives. Finally, with the best design proposed by the multi-objective optimization, an energy saving of 22.9% is achievable while keeping the thermal comfort indexes within the allowable range.Sat, 06 Jul 2019 19:30:00 +0100The effects of hygro-thermal loading on the two-dimensional response of a functionally graded ...
http://scientiairanica.sharif.edu/article_21494_0.html
In this article, a semi-analytical solution is presented in order to analyze a functionally graded piezomagnetic (FGP) cylinder resting on an elastic foundation exposed to hygro-thermal loading. All mechanical, hygro-thermal and magnetic properties are considered to vary according to the power-law function through the thickness. The steady-state heat conduction and moisture diffusion equations are employed to attain the moisture concentration and temperature distributions in the FGP cylinder. The constitutive equations, and magnetic and mechanical equilibrium equations are combined in order to derive three second-order differential equations in terms of magnetic potential and mechanical displacements. The separation of variables and complex Fourier series method are utilized to solve governing equations. Numerical results reveal the effects of hygro-thermal loading, elastic foundation and non-homogeneity constants on hygro-thermo-magneto-elastic response of the functionally graded piezomagnetic cylinder. It is concluded that hygro-thermal loading has remarkable effects on the behavior of the cylinder leading to increase the absolute values of the radial magnetic induction, radial, circumferential and shear stresses.Sat, 13 Jul 2019 19:30:00 +0100An analysis on the effect of temperature on the morphology of egg shell CaO catalyst: Caytalyst ...
http://scientiairanica.sharif.edu/article_21496_0.html
The increase study on the usage of egg shell derived CaO being used as catalyst during biodiesel production have paved way for the need to study the effects of temperature on the calcination of egg shells. Therefore, the authors in the present study have undertaken calcination of chicken egg shells and duck egg shells at various temperatures of 800 °C, 900 °C and 1000 °C exposed at one hour. The synthesized CaO were characterised using X-ray diffraction (XRD), Fourier transform infra-red spectrometry (FT-IR), Scanning electron microscope (SEM) and Energy Dispersive X-ray analysis (EDX). The study have shown that there is changes in the distribution and formation of calcium, oxides and naturally occurring substance carbon, during calcination of the samples. It was observed in both the cases of chicken as well as duck egg shells that 800 °C is a decent temperature for calcinating the egg shells in producing calcium oxide catalyst.Sat, 13 Jul 2019 19:30:00 +0100Series solution of slip flow of Al2O3 and Fe3O4 nanoparticles in a horizontal channel with ...
http://scientiairanica.sharif.edu/article_21497_0.html
In this problem, we present a theoretical study for the slip effects on the two-dimensional flow of a nano liquid in a semi-porous channel designed by two long rectangular plates having porous media. One of the channel walls is porous and other is rigid as well as slippery. A magnetic field of homogenous strength is also applied transversely to direction of flow. Magnetic nanoparticles and non-magnetic nanoparticles are considered with ethylene glycol and water as base fluids. Least Square method and Galerkin method are adopted to solve the equations transformed from partial differential equations to ordinary ones by Berman’s similarity transformations. The obtained results from the two analytical methods are compared with the results obtained by fourth order Runge-Kutta numerical method(NM). By comparing the results of GM and LSM it is observed that variation in velocity profiles is minimal however the accuracy of GM is higher than LSM. The contributions of various flow parameters on flow field are presented through graphs. Results show a decrease in the fluid velocity with an increase in the slip parameter and porosity parameter. Flow field is less for the case of magnetic nanoparticles as compared to nonmagnetic particles for different base fluids.Sat, 13 Jul 2019 19:30:00 +0100Effect of Welding Parameters on Dissimilar Pulsed Laser Joint between Nickel-Based Alloy ...
http://scientiairanica.sharif.edu/article_21499_0.html
This paper investigates the strength and microstructure of dissimilar weld joints between Hastelloy X, which is a nickel-based superalloy, and austenitic stainless steel 304L. Nd-YAG solid-state pulsed laser is used to perform the welding between these two alloys. Two pieces of Hastelloy X and AISI 304L sheets of 1 mm thickness, are placed edge to edge to form a butt welding configuration with each other and are welded using a pulsed laser beam with a maximum power of 400 watts. The effect of welding speed, laser power and pulse width on the strength of the joint, were investigated by changing mentioned parameters values, while the laser beam frequency and the protective gas flow rate were kept constant. Then, test samples are produced to conduct uniaxial tensile tests at room temperature. Results show that the highest-quality dissimilar joint can be found by optimizing the welding power, beam pulse width, and welding speed.Sun, 14 Jul 2019 19:30:00 +0100Low Power 10-Bit Flash ADC with Divide and Collate Subranging Conversion Scheme
http://scientiairanica.sharif.edu/article_21501_0.html
The sampling rate plays a key role in wireless applications at very high-frequency range. Flash analog-to-digital converter (ADC) betters the slow converter counterparts in this regard but bulky at inevitable high resolutions. A state-of-the-art Divide and Collate (DnC) algorithm is proposed to design the flash ADC at subranging levels. The offset voltage is kept at a minimum through the comparators used for coarse and fine conversion separately. The kick-back noise is also reduced by using sample and hold switches at the input. The 10-bit ADC architecture is designed with 45-nm CMOS technology and analyzed in the SPECTRE environment. A trivial variation in the transconductance with temperature is observed and consequently the offset drift with temperature is found to be 0.015 mV/'C. The design improves the INL by 0.42 LSB and DNL by 0.3 LSB. Signal-to-noise-and-distortion (SNDR) ratio and spurious-free dynamic range (SFDR) are 51.8 dB and 62 dB respectively at a frequency range near the Nyquist rate with a supply voltage of 1 V and input frequency of 500 MHz. Subranging scheme minimizes the comparator requirements which is reflected in the 44% reduction in the power dissipation.Mon, 15 Jul 2019 19:30:00 +0100A new decision approach for the sustainable transport investment selection based on the ...
http://scientiairanica.sharif.edu/article_21502_0.html
Finding the most suitable transport project is one of the most important tasks in transport planning. This task gets more complicated as the sustainable criteria get involved in the process. In this paper, a new multi-criteria group decision-making method with unknown expert and attribute weights is proposed to address the sustainable transport investment selection problem. To make the method more powerful in dealing with uncertain elements, an Interval-Valued Pythagorean Fuzzy (IVPF) set is used as an attractive and useful tool to handle uncertainty. First, a generalized entropy measure under an IVPF environment is introduced, which enables the method to determine the fuzziness of the attribute values, which are expressed by Interval-Valued Pythagorean Fuzzy Numbers (IVPFNs). To determine the fuzziness of IVPFNs with identical membership and non-membership degrees, a generalized knowledge measure of the IVPFNs is also introduced. Based on this measure and considering the deviation between attribute assessments, a new optimization model is presented to obtain unknown attribute weights. In addition, based on the extension of the VIKOR method, a new algorithm is presented to determine the unknown expert weights. Finally, a real case study is considered to show the efficiency of the proposed methods.Mon, 15 Jul 2019 19:30:00 +0100Integration of Machine Learning Techniques and Control Charts for Multivariate Processes
http://scientiairanica.sharif.edu/article_21503_0.html
Using multivariate control chart instead of establishing univariate control chart for all variables in processes provides time and labor advantage. In addition, it is considered in the relations between variables. However, the statistical calculation of the measured values of all variables is seen as a single value in the control chart. Therefore, it is necessary to determine which variable(s) is the cause of the out of control signal. Effective corrective measures can only be developed when the causes of the fault(s) are determined correctly. The aim of the study is to determine the machine learning techniques that will accurately estimate the type of fault. With the Hotelling T2 chart, out of control signals are identified and the types of faults affected by the variables are defined. Various machine learning techniques are used to compare classification performances. The developed model was applied in the evaluation of the paint quality in a painting process. ANN was determined as the most successful techniques according to performance criteria. The novelty of the study is to classify the fault according to the types of faults, not the variables. Defining the faults according to its types will enable to take effective corrective actions quickly.Mon, 15 Jul 2019 19:30:00 +0100Applying a change-point control chart based on likelihood ratio to supply chain network monitoring
http://scientiairanica.sharif.edu/article_21505_0.html
In this paper, a supply chain network system is viewed as a serial-parallel multistage process; and the application of a change point control chart based on likelihood ratio is explored to monitor this system. Firstly, state-space modeling is used to characterize complexity of the supply chain network system. Then, a change point control chart based on likelihood ratio is built to trigger potential tardy orders in the system. A case study is illustrated to indicate that the change point control charts can effectively signal process mean shift, and accurately estimate the change point and the out-of-control stage in term of power of detection and the accuracy of estimation of change point. We also investigate the effect of misspecified parameters of state space equations on the performance of the change point control chart. The results show that the performance of the change point control chart is relatively stable.Sun, 21 Jul 2019 19:30:00 +0100A case study on the coordination scheduling for integrated production and distribution
http://scientiairanica.sharif.edu/article_21506_0.html
An integrated coordination scheduling problem considering production and distribution in integrated energy enterprise aims at coordinating the production plan and distribution plans to eliminate the conflict between them. The research is motivated by the challenges encountered in the practice. Practice has indicated that conflicts are common existing among the plans which are made by production and distribution departments respectively. We propose a scheduling model which considers two aspects. On one hand, we try to maximize the company profit. On the other hand, we expect to minimize the difference between the separate plans and the coordinating ones. A genetic algorithm is developed to solve this problem. A case study of the largest integrated energy enterprise in China shows that once conflicts occurs in separate plans, the most effective way to adjust the separate plans from a global perspective that has strong coordinating relationships with the overall interests. The proposed model would neutralize the influence of the conflict.Sun, 21 Jul 2019 19:30:00 +0100Integrated supply chain decisions with credit-linked demand-A Stackelberg approach
http://scientiairanica.sharif.edu/article_21507_0.html
Market demand mostly possibly affected by the seller’s credit in many industrial practice, this study aims to investigate the beneficial performance of the supply chain considering the credit-linked demand under three different circumstance. We firstly develop a demand model which is a function of the trade credit period. Moreover, the supplier determines optimal trade credit period and the retailer determines optimal replenishment cycle time. Under these conditions, we first present optimal solutions for the centralized decision and the decentralized decision in Stackelberg models. Then, we develop a set of theorems to determine the optimal results. Finally, we provide a numerical example and sensitivity analysis to illustrate the efficiency of the proposed models and optimal solutions. The finding reveals that the trade credit period, replenishment cycle time, retailer’s profit, supplier’s profit and profit of the supply chain are strongly influenced by ordering cost, retail price, production cost, holding cost and the interest rate. In addition, we also find that under the condition of the trade credit, the supply chain that the supplier dominated has a better performance than that the retailer dominated. While when the supplier don’t provide the trade credit period, the result is the opposite.Sun, 21 Jul 2019 19:30:00 +0100A Robust Model for Daily Operation of Grid-connected Microgrids During Normal Conditions
http://scientiairanica.sharif.edu/article_21508_0.html
Microgrids (MGs) are designed to be able to serve hosting critical load in island-mode during major events. However, during normal condition when they are in grid-connected mode, MGs may have opportunity to achieve monetary profits through optimizing operation of energy resources and their participation in wholesale markets. This paper proposes a model to optimize MGs participation in the markets and operation of energy resources. Since MGs usually host renewable energy resources, making decision without considering the uncertainties may prone MGs to risk. So, the model considers uncertainties associated with generation of renewable DGs, demand, and market prices via robust optimization technique. The model is a max-min problem which is modelled as a bi-level optimization problem. The problem is solved in two iterative steps. In the first step, a genetic algorithm (GA) is applied to obtain the worst case wherein uncertain parameters are determined such that MG profit is minimized. Then, a mixed-integer linear problem is solved to maximize the profit over MG decision variables considering the values determined in the first step. The steps are iterated to converge to the best solution. To verify performance of the approach, it is applied to a typical MG and the results are reported.Sun, 21 Jul 2019 19:30:00 +0100A mathematical model for an integrated airline fleet assignment and crew scheduling problem ...
http://scientiairanica.sharif.edu/article_21509_0.html
Fleet assignment and crew scheduling are the most complex airline optimization problems. In this research, an optimized crew pairing set considered as an input, and a crew is chosen for assigning to each certain crew pairing. This paper presents a novel model to integrate fleet assignment and crew scheduling problems. In this model, closed routes for crews and fleet are considered simultaneously. Also, the model considers two consecutive flight legs and some characteristics such as time lag, Minimum permitted time lag and Maximum Economic time. Also, a vibration damping optimization (VDO) algorithm is introduced to find good solution for this problem in a reasonable time. Experimental design based on the Taguchi method is taken into account. To compare the proposed VDO algorithm performance, four designed test problems are solved by proposed VDO and compared with optimal solution and Particle Swarm optimization (PSO) algorithm. Then, 10 generated test problems in large scale are solved using VDO and PSO. The results show that in four designed test problems, VDO and PSO solutions have 1.62% and 2.95% gaps in average with optimal solution. Moreover, based on 10 generated test problems, in average VDO give 6.71% better solution in less time compare to PSO.Sun, 21 Jul 2019 19:30:00 +0100Optimal Winding Selection for Wound-Rotor Resolvers
http://scientiairanica.sharif.edu/article_21510_0.html
Wound-rotor (WR) resolvers are the most commercially used resolvers in industrial applications. In this paper, the effect of different winding arrangements on the accuracy of WR resolvers is discussed. Three windings are proposed for the stator of the resolver that are involved on-tooth overlapping winding, distributed lap winding and distributed concentric winding. Those windings are also applied to the rotor. All the rotor windings are assumed to be single phase and two-phase. Therefore, the effect of damper winding is also studied in the paper. The analysis is done using time stepping finite element method and the most accurate resolver is built and tested. Close agreement between the experimental measurements and the finite element results confirms the obtained results.Sun, 21 Jul 2019 19:30:00 +0100A Novel Transverse Flux Permanent Magnet Generator for Small-Scale Direct Drive Wind Turbine ...
http://scientiairanica.sharif.edu/article_21511_0.html
This study focuses on a special topology of Transvers Flux Permanent Magnet Generator which benefits from low PM cost due to using cheap Ferrite PMs. In this structure, only one PM per phase is used where leads to easy manufacturing process. In spite of the above mentioned advantages of the topology, there are some disadvantages such as unbalanced voltage, high demagnetisation risk of the PM, and high cogging torque. Aiming to solve these problems while maintaining the advantages of the topology, a new structure is proposed. The stator of this structure contains two series connected coils which eliminates all the even order harmonics and balances the voltage waveform. This trick reduces the armature reaction as well as demagnetisation of the PMs, significantly. Additionally, the rotor teeth of the proposed structure are skewed where leads to a noticeable reduction in cogging torque. The output results of the proposed structure are compared with the original one in terms of harmonic components, cogging torque profile, and PM demagnetisation.Sun, 21 Jul 2019 19:30:00 +0100An Investigation into Skill Leveled Operators in a Multi-Period Cellular Manufacturing System ...
http://scientiairanica.sharif.edu/article_21513_0.html
Many works published in the area of cellular manufacturing system are based on the assumption that machines are reliable in the whole production horizon without any break down. As such assumptions often are not realistic, to contribute to closing this gap to reality, the model has been modified by additionally including machine reliability, alternative process routings and workforce assignment in a dynamic environment. In this research to integrate this aspects, the modified problem has been defined and formulated and an extended mixed integer multi-period mathematical model has been proposed.
In order to evaluate the effectiveness and capability of the extended model, some hypothetical numerical instances are generated and computational experiment are carried out using Gams optimization package. Experimental results demonstrate that the demand value can affect the machine breakdown rate, and a machine with a minimum breakdown rate is implemented more often than others. Moreover, the observed trade-off between the workforce-related costs and the cell-formation costs indicates that workforce-related issues have a significant impact on the total efficiency of the system. The proposed model can be implemented in medium- and large-scale manufacturing companies.Sun, 21 Jul 2019 19:30:00 +0100Performance evaluation of aluminium oxide nano particles in cutting fluid with MQL technique in ...
http://scientiairanica.sharif.edu/article_21514_0.html
The current research comprises various machinability aspects of 4340 hardened alloy steel which are scrutinized with in context of improvements in main cutting force, tool flank wear, crater wear, surface roughness, microhardness, machined surface morphology, chip morphology, chip reduction coefficient and apparent coefficient of friction under three different cutting fluid applications i.e. compressed air, water soluble coolant based MQL, and nanofluid (using eco-friendly radiator coolant as the base fluid and Al2O3 as the nanoparticle) based MQL technique using cermet cutting inserts and a comparative assessment was performed to select which fluid performed better in terms of various machining attributes among three cutting fluids. The minimum quantity lubrication technique was used in which a smaller volume of coolant sprinkled at high pressure. This method is found as the most effective alternative to minimize health risks and machining costs, which is quite high in other setups. The test specimen was machined at three different cutting speeds i.e. 100,120 and 140m/min along with two machining parameters i.e. feed and depth of cut were kept constant respectively at 0.2mm/rev and 0.4mm. Outcomes made a conclusion that Al2O3 enriched ecofriendly nano-coolant outperformed both compressed air and water soluble coolant in terms of every machinability aspects.Sun, 21 Jul 2019 19:30:00 +0100Synchronized Timetables for Bus Rapid Transit Networks in Small and Large Cities
http://scientiairanica.sharif.edu/article_21515_0.html
The quality of public transportation service has major effects on people’s quality of life. During frequency and timetable setting, synchronization is a very important and complicated issue which can directly influence the utility and attractiveness of the system. In this paper, a mixed-integer nonlinear programming model is proposed that aims at setting timetables on a bus transit network with the maximum synchronization and the minimum number of fleet size. The proposed model is shown to be applicable for both small and large-scale transit networks by employing it for setting timetables on two samples of both sizes. As an illustrative example, a simple version of the model is coded and run in GAMS Software and a completely reasonable timetable is obtained. As the second example, the proposed model is used to set timetables on Tehran BRT networks through the genetic algorithm; then the NSGA-II is used to obtain the Pareto optimal solutions of the problem for five different scenarios. The Pareto optimal solutions are used to draw the Pareto optimal fronts which act as an essential decision making tool. The overall results show that the proposed model is efficient enough to be employed setting timetables on transit networks with different sizes.Sun, 21 Jul 2019 19:30:00 +0100Fatigue and fracture behavior of A516 steel used in thick-walled pressure vessels
http://scientiairanica.sharif.edu/article_21516_0.html
In this paper, the growth of semi elliptical crack in the walls of thick walled cylindrical pressure vessels has been investigated. Considering the importance of the crack growth problem in cylindrical pressure vessels provides a numerical and experimental 3D model for the growth of fatigue crack and estimating the fatigue life of pressure vessels. Because of available geometric geometric and physical parameters, it can be predicted the problem of the fatigue life of these pressure vessels more precisely in comparison with existing standard tests which are experimental and numerical. A most common specimen of thick walled tanks, steel, is analyzed for conducting experimental tests. The mechanical properties and fatigue behavior of A516 steel have been determined experimentally. For estimating the crack growth and calculation of fatigue life, boundary element method and linear fracture mechanics equations have been used. Finally, the experimental results for fatigue crack growth were compared with numerical method, which yielded acceptable results. The overall results show a good agreement between the experimental data and the numerical results.Sun, 21 Jul 2019 19:30:00 +0100Improved Multi-Ant-colony algorithm for solving Multi-Objective Vehicle Routing Problems
http://scientiairanica.sharif.edu/article_21517_0.html
Classical vehicle routing problems (VRP) involves supply of goods/services from a central depot to geographically scattered customers. Besides the classical objective of minimizing the total travelled distance, the present work also considers simultaneous optimization of two additional objectives namely minimizing make span and minimizing distance imbalance. A mathematical model for this multi-objective version of VRP (MO-VRPTW) has been developed. A meta-heuristic based on multiple ant colony system for solving this MO-VRPTW has also been proposed. Firefly algorithm (FA) has also been applied to avoid local optima. Two new migration operators named Migration-I and Migration-II and multi-pheromone matrices have been developed to further improve the solution set. The proposed algorithm has been tested on a number of benchmark problems and its superiority over other state of art approaches and NSGA-II one of the commonly used method for multi-objective optimization problems is demonstrated.Mon, 29 Jul 2019 19:30:00 +0100Effects of initial suction and degree of saturation on dynamic properties of sand at large strain
http://scientiairanica.sharif.edu/article_21521_0.html
Soil deposits may experience different hydraulic states in terms of suction (ψ) and degree of saturation (Sr) while subjected to large strain caused by dynamic loading during earthquakes. This phenomenon is investigated by considering the effects of initial ψ, initial Sr, sample preparation method, drainage condition, and cycle number (N) on dynamic properties. Shear modulus (G) and damping ratio (D) are specifically studied for an unsaturated sand using a modified cyclic simple shear device for all zones of soil water retention curve (SWRC). Results revealed the relative significance of both ψ and Sr in relation to SWRC on observed trends in G and D. Through analyzing some results from the literature, it was shown that most of the data follow a sigmoid function in the plane of normalized stiffness (G/Gsat) versus suction normalized to the air entry value. It was also revealed that minimum damping is not in conjugation with maximum stiffness due to the contribution of other mechanisms in damping like inter-particle water lubrication. Comparison between results of two testing methods indicated a notable influence of initial fabric on G. Furthermore, the overall trends in G and D against N are marginally influenced by initial ψ and Sr.Mon, 05 Aug 2019 19:30:00 +0100Model Reference Adaptive Control (MRAC) of a Small Satellite in the Presence of Parameters ...
http://scientiairanica.sharif.edu/article_21522_0.html
An accurate control algorithm for small satellites is critical to the mission's success. In this paper, a novel discrete-time Model Reference Adaptive Control algorithm (MRAC) is developed based on unified approach for attitude control of a three-axis stabilized nonlinear satellite model. The linearized model of satellite with unknown dynamic parameters is derived and Recursive Least Squares (RLS) algorithm is used to identify the linear model’s unknown parameters. In order to take into account the nonlinear model of satellite dynamics, the proposed MRAC strategy is used considering the linear model, the estimation error; and the difference between the actual nonlinear system and the linear model outputs. The actual nonlinear model of satellite includes moments of inertia uncertainties, external disturbances, and sensor noise on the outputs. The introduced controller performance is compared with a conventional discrete -time MRAC which demonstrates excellent simultaneous regulation and tracking capabilities.Fri, 09 Aug 2019 19:30:00 +0100Two Low Computational Complexity Improved Multiband Structured Subband Adaptive Filter Algorithms
http://scientiairanica.sharif.edu/article_21523_0.html
The improved multiband-structured subband adaptive filter (IMSAF) applies the input regressors at each subband to speed up the convergence rate of MSAF. When the projection order is increased, the convergence rate of the IMSAF algorithm improves at the cost of increased complexity. The present research introduces two new IMSAF algorithms with low computational complexity feature. In the first algorithm, the selective partial update approach (SPU) is extended to IMSAF algorithms and SPU-IMSAF is established. In SPU-IMSAF, the filter coefficients are partially updated at each subband for every adaptation. In the second algorithm, the set-membership (SM) strategy is utilized in IMSAF and SM-IMSAF is established. The SM-IMSAF has fast convergence rate, low steady-state error and low computational complexity features at the same time. Also, by combining SM and SPU methods, the SM-SPU-IMSAF is introduced. Simulation results demonstrate the good performance of the proposed algorithms.Fri, 09 Aug 2019 19:30:00 +0100Constructing Automated Test Oracle for Low Observable Software
http://scientiairanica.sharif.edu/article_21524_0.html
Using machine learning techniques for constructing automated test oracles have been successful in recent years. However, existing machine learning based oracles have deficiencies when applied to software systems with low observability, such as embedded software, cyber-physical systems, multimedia software programs, and computer games. This paper proposes a new black box approach to construct automated oracles which can be applied to software systems with low observability. The proposed approach employs an Artificial Neural Network (ANN) algorithm which uses input values as well as corresponding pass/fail outcomes of the program under test, as the training set. To evaluate the performance of the proposed approach, we have conducted extensive experiments on several benchmarks. The results manifest the applicability of the proposed approach to software systems with low observability as well as its higher accuracy in comparison to a well-known machine learning based method. We have also assessed the effect of different parameters on the accuracy of the proposed approach.Fri, 09 Aug 2019 19:30:00 +0100An Improved Red Deer Algorithm to Address a Direct Current Brushless Motor Design Problem
http://scientiairanica.sharif.edu/article_21525_0.html
The Red Deer Algorithm (RDA) is one of recent metaheuristic algorithms inspired by the behavior of red deers during a breading season. The RDA revealed its performance for a variety of combinatorial optimization problems in different real-world applications. In this paper, the parameters and operators of RDA using some adaptive strategies have been modified to improve the performance of this optimizer. To prove the efficiency of Improved RDA (IRDA), not only some benchmarked functions are utilized but also a Direct Current (DC) brushless motor design as one of real-world engineering design issues. The results of developed IRDA have been compared with its general idea and existing algorithms from the literature. This comparative study confirms that the offered IRDA outperforms the other algorithms and provide very competitive results.Fri, 09 Aug 2019 19:30:00 +0100The effect of transportation and safety attitudes, personality, and lifestyle on vehicle type ...
http://scientiairanica.sharif.edu/article_21526_0.html
In recent years, researchers have paid specific attention to safety, air pollution, and energy consumption, which are all affected by the vehicle type. The primary objective of this study is to achieve a thorough understanding of the relationships between transportation attitudes, safety attitudes, personality, as well as lifestyle and vehicle type for the first time in Iran, as a developing country. For this purpose, an interview questionnaire was designed, and 740 participants were interviewed in Tehran. Vehicle types are categorized into seven groups: mini, compact, medium, heavy, SUV, pickup, and motorcycle. In the first stage, factor analysis was used to identify the latent variables regarding transportation attitudes, safety attitudes, personality, and lifestyle. In the second step, by using these latent variables, individuals are classified, and a two-level clustering is formed. The correlation analysis performed in the third step shows a significant relationship between each category of people and the type of car. Likewise, the analyses carried out in this study reveal the significant relations between the vehicle type (classified based on fuel economy level, production country, vehicle emission, and vintage) and the attitudes of its owner. This information is beneficial to both vehicle manufacturers and transportation planners.Fri, 09 Aug 2019 19:30:00 +0100A Methodology for Examining the Chaotic Behavior of the CoP Signal during the Quiet Standing ...
http://scientiairanica.sharif.edu/article_21532_0.html
A key parameter for analyzing the human balance dynamics during standing is the center of pressure (CoP). But, so far no conclusive idea has been posed with respect to elicited dynamics of the CoP signal during quiet standing. In this paper, a heuristic algorithm has been proposed to prove the chaotic behavior of the CoP signal with high confidence. In the proposed algorithm, at first the deterministic and non-deterministic (may be stochastic or may be chaotic) components of CoP signal are extracted using the empirical mode decomposition (EMD) method. Then the nonlinear features of the extracted components such as fractal dimension, Lyapunov exponent, correlation dimension, and alpha parameter are computed. Then according to the quantitative value of the computed features, the chaotic component is selected among the extracted components. Finally, using the recurrence quantitative analysis (RQA), the selected chaotic component is reanalyzed to give assurance of correct selecting the chaotic component. In this manner, the kind of CoP dynamics can be determined with high confidence. The analyzed CoP signals were recorded through some experiments on 12 healthy subjects being between 20 to 70 years old. The results of this study show that CoP is a chaotic signal whit high confidence.Sun, 25 Aug 2019 19:30:00 +0100An Integrated Quay Crane Assignment and Scheduling Problem with Several Contractors in ...
http://scientiairanica.sharif.edu/article_21533_0.html
The last decade has seen an important role of container terminals in the global trade centers. By another point of view, the high cost of quay cranes on the other hand is a motivation for a set of real-world problems including of Quay Crane Assignment Problem (QCAP) and the Quay Crane Scheduling Problem (QCSP) in the hotspot of research. The main innovation of this proposal is to integrate both QCAP and QCSP to improve Quay Crane (QC) performance by an optimization goal, i.e., QCASP. A real case study in Iran has been applied to validate the proposed problem which has been formulated by a mixed integer linear programming (MILP). Due to inherent complexity of problem proposed in the real-world cases, the Teaching-Learning-Based-Optimization (TLBO) algorithm has been used to find an optimal/global solution in a reasonable time. The applied TLBO has been tuned by Taguchi method and validated in small instances in comparison with an exact method. The computational results show that our proposed TLBO algorithm can solve QCASP, especially in large size instances, successfully. Finally, a set of managerial implications has been recommended to consider the benefits of proposed methodology and algorithm regarding the real case study presentedSun, 25 Aug 2019 19:30:00 +0100A hybrid model for online prediction of PM2.5 concentration: A case study
http://scientiairanica.sharif.edu/article_21538_0.html
In this paper, we aim at developing a model to predict the daily average concentration of particulate matters with a diameter of less than 2.5 micrometers (PM2.5). In the introduced model, we incorporate Weather Research and Forecasting (WRF) meteorological model, Monte Carlo simulation, wavelet transform, and multilayer perceptron (MLP) neural networks. In particular, the MLP and wavelet transformation are combined for prediction. In order to predict the model’s input parameters, including wind speed, wind direction, temperature, rainfall, and temperature inversion, the WRF meteorological model is used. Finally, according to the available uncertainty in the input data and in order to achieve a more accurate prediction, the Monte Carlo simulation is utilized. In order to assess the effectiveness of the model in the real world, it has been conducted in an online mode for 35 days. Numerical results give an acceptable accuracy in terms of some widely used measures. In particular, taking into account the R measurements, it is equal to 0.831 over the set of test instances.Sun, 01 Sep 2019 19:30:00 +0100Polygonal Tubular Linear Permanent Magnet Generator Analysis and Experimental Test
http://scientiairanica.sharif.edu/article_21539_0.html
Free piston generators are of interest due to their efficiency,compact construction, homogeneous nature,and multiple options for combustion.Much of the research into this type of generator has been facilitated by highly-developed internal combustion engine technology.This study was concerned with the design and application of tubular generator.The design model was developed using the matrix laboratory graphical user interface (MATLAB GUI) programming tool, and the designed interface was of the dynamic type.The sizing of the generator was determined in accordance with the main parameters specified via the interface. In addition, as a benefit of using sizing data, the automatic geometry was formed and analyzed using ANSYS Maxwell software.The magnets and the dynamic part of the tubular-structured generator were shaped polygonally.Numerical analyses were made by adopting the finite element method in the software, and construction of the prototype model was based on the results from these findings.The generator was excited by use of the crank rod mechanism to imitate the conditions of a functioning free piston mechanism.Current and voltage values were obtained at mechanical frequencies of 10Hz and 20Hz, and this data was subsequently analyzed.Global code translation was given in attachment in order to allow communication between the ANSYS Maxwell and MATLAB GUI software.Sun, 01 Sep 2019 19:30:00 +0100Development of an Ensemble Learning-based intelligent model for Stock Market Forecasting
http://scientiairanica.sharif.edu/article_21540_0.html
The use of artificial intelligence-based models have shown that the market is predictable despite its uncertainty and unstable nature. The most important challenge of the proposed models in the stock market is the accuracy of the results and increasing the forecasting efficiency. Another challenge, which is a prerequisite for making decision and using the results of the forecast for profitability of transactions, is to forecast the trend of stock price movements in forecasting price. To overcome the mentioned challenges, this paper employs ensemble learning (EL) model using intelligence-based learners and metaheuristic optimization methods to maximize the improvement of forecasting performance. In addition, in order to consider the direction of price change in stock price forecasting, a two-stage structure is used. In the first stage, the next movement of the stock price (increase or decrease) is forecasted and its outcome is then employed to forecast the price in the second stage. In both stages, genetic algorithm (GA) and particle swarm optimization (PSO) technique are used to optimize the aggregation results of the base learners. The evaluation results of stock market dataset show that the proposed model has higher accuracy compared to other models used in the literature.Sun, 01 Sep 2019 19:30:00 +0100On the Bayesian Analysis of Two-Component Mixture of Transmuted Weibull Distribution
http://scientiairanica.sharif.edu/article_21541_0.html
Transmuted distributions are skewed distributions and recently attracted a great attention of researchers due totheir applications in reliability and statistics. In this article, our main focus is on the Bayesian estimation of two-component mixture of Transmuted Weibull Distribution (TWD) under type-I right censored sampling scheme. In order to estimate the unknown parameters, non-informative and informative priors under Squared Error Loss Function (SELF), Precautionary Loss Function (PLF) and Quadratic Loss Function (QLF) are assumed when computing the posterior estimations. In addition the Bayesian credible intervals (BCI) were also constructed. Markov Chain Monte Carlo (MCMC) technique is adopted to generate samples from the posterior distributions and in turn computing different posterior summaries including Bayes estimates(BEs), posterior risks(PRs) and Bayesian credible intervals (BCI). As an illustration comparision of these Bayes estimators are made through simulated under different loss functions in terms of their respective posterior risks assuming different sample sizes and censoring rates. Two real-life examples; the first being the survival times of hepatitis B & C patientswhile the second being the hole diameter of 12 mm and the sheet thickness is 3.15 mm are also discussed to illustrate the potential application of the proposed methodology.Sun, 01 Sep 2019 19:30:00 +0100Estimation of General Parameter Under Stratified Adaptive Cluster Sampling Based on Dual Use of ...
http://scientiairanica.sharif.edu/article_21543_0.html
Auxiliary information is mostly used together with study variable to enhance efficiency of estimators for population mean, total and variance. Thompson introduced adaptive cluster sampling as an appropriate sampling scheme for rare and clustered populations. In present article, difference-type and difference-cum-exponential-ratio-type estimators are presented utilizing two auxiliary variables for estimation of general parameter under stratified adaptive cluster sampling. Proposed estimators utilize auxiliary information in terms of ranks, variances and means of auxiliary variables in $h^{th}$ stratum. Expressions for bias and mean square error of proposed estimators are derived using first order of approximation. Numerical study is conducted to evaluate the performance of proposed estimators.Sun, 01 Sep 2019 19:30:00 +0100Resilient supplier selection in complex product and its subsystems’ supply chain under ...
http://scientiairanica.sharif.edu/article_21544_0.html
Recently, the manufactures of complex product and its subsystems have faced a series of disruptions and troublesome behaviors in supplying goods and items. Likewise, suppliers in this area are more likely to be affected by external risks, in turn eventuating in disturbances. Selecting resilient and expedient suppliers dramatically decreases the delay time and costs and contributes to the competitiveness and development of the companies and organizations in this field. In this regard, this paper aims at proposing a bi-objective robust mathematical model to provide resilience supplier selection and order allocation for complex products and its subsystems in response to uncertainty and disruption risks. In the proposed model, a robust optimization approach is deployed, providing stable decisions for the proposed problem. Also, different resilience strategies including restoring supply from occurred disruptions, fortification of the suppliers, using backup suppliers, and utilizing the extra production capacity for suppliers have been devised to tolerate disruptions. Meanwhile, the augmented ε-constraint method is used, ensuring the optimal strong Pareto solutions and preventing the weak ones for the proposed bi-objective model. The evaluation of the effectiveness and desirability of the developed model is explored by discussing a real case study, via which helpful managerial insights are gained.Sun, 01 Sep 2019 19:30:00 +0100A Dual- Stator Machine with Diametrically Magnetized PM: Analytical Air-gap Flux Calculation, ...
http://scientiairanica.sharif.edu/article_21545_0.html
This paper presents a design and optimization procedure for a dual-stator machine with a diametrically magnetized PM to improve the electromagnetic performance. First, analytical design equations are presented based on MEC analysis; they are used to design a basic dual-stator machine. Then, by applying an artificial intelligence algorithm, the machine is optimized to achieve high efficiency and torque density, and low pulsating torque for direct-drive applications. A quantitative comparison is performed between the optimized new machine and conventional dual-stator machines to evaluate the performances and improvements of the understudy machine. The machine performance, including air-gap flux density distribution, back electromotive force, electromagnetic torque, cogging torque, and torque ripple are analyzed by the finite element method. The analysis results have demonstrated that benefiting from its topology, the optimized dual-stator machine with diametrically magnetized PM has the comprehensively better performance, including higher torque density, higher efficiency, and lower torque ripple and cogging torque compared to conventional dual-stator machines.Sun, 01 Sep 2019 19:30:00 +0100An incentive-based policy on reduction of GHG emissions and loss minimization using adaptive ...
http://scientiairanica.sharif.edu/article_21546_0.html
A transactive strategy to purposeful pricing distributed energy resources (DERs) in distribution networks is proposed in this paper. This strategy is presented as a novel heuristic optimization approach. The total network loss and released greenhouse gases (GHGs) emissions are considered as objective functions. In addition, the locational marginal prices (LMPs) and power factors of DERs are considered as decision variables. Each DER, which is more participated in the mitigation of afore-mentioned objectives, will contribute a larger excitement form benefits consequently. Therefore, more contribution consequent to more generation leads to a higher price for DERs bus in comparison to substation market price. Also, the earned benefits from loss/emission mitigations are allocated to DERs directly. The fairness of this pricing process is supervised by the Independent Distribution System Operator (IDSO). Because the problem has two contradictory objective functions, a reliable Multi-Objective method called Chaotic search and Covariance matrix (MGSOACC) is proposed to solve the problem. To evaluate the proposed method, the pricing procedure is applied on modified IEEE-33 and IEEE-69 bus test networks. Furthermore, in order to the validation of the proposed optimization method, the result-oriented comparisons between four conventional Multi-Objective optimization methods and proposed optimization method are presented.Sun, 01 Sep 2019 19:30:00 +0100Flexible flow shop scheduling problem to minimize makespan with renewable resources
http://scientiairanica.sharif.edu/article_21547_0.html
This paper deals with a flexible flow shop (FFS) scheduling problem with unrelated parallel machines and renewable resource shared among the stages. The FFS scheduling problem is one of the most common manufacturing environment in which there is more than a machine in at least one production stage. In such a system, to decrease the processing times, additional renewable resources are assigned to the jobs or machines, and it can lead to decrease the total completion time. For this purpose, a mixed integer linear programming (MILP) model is proposed to minimize the maximum completion time (makespan) in an FFS environment. The proposed model is computationally intractable. Therefore, a particle swarm optimization (PSO) algorithm as well as a hybrid PSO and simulated annealing (SA) algorithm named SA-PSO, are developed to solve the model. Through numerical experiments on randomly generated test problems, the authors demonstrate that the hybrid SA-PSO algorithm outperforms the PSO, especially for large size test problems.Sun, 01 Sep 2019 19:30:00 +0100A chaotic iterative fuzzy modeling of circulating a simple sentence
http://scientiairanica.sharif.edu/article_21548_0.html
In this paper, we propose a new model to describe variations in interpretation and perception of a simple sentence by different people. To show the understandability of a simple sentence in the prediction of future situations, the meaning of a sentence is modeled as a fuzzy if-then rule, and the fuzzy model is investigated in an iterative process. The main goal of the paper is modeling a linguistic rule. This is done using an if-then rule and its variation through one person to another. The model predicts that the interpretation reaching the final person in the following years can be chaotic and thus unpredictable.Sat, 07 Sep 2019 19:30:00 +0100“Plant-mediated green synthesis of Ag nanoparticles using Rauvolfia tetraphylla (L. ...
http://scientiairanica.sharif.edu/article_21551_0.html
Various plant extracts have been currently used for the bioproduction of nanoparticles that find enormous applications. Rauvolfia tetraphylla flower extracts were employed to obtain silver nanoparticles (Ag NPs) by bioproduction. The biologically produced nanoparticles were characterized by XRD, FTIR, UV-Vis, BET, SEM, EDAX and TEM analysis. The phytochemical screening of the Rauvolfia tetraphylla flower extracts indicated presence of nine different constituents. The bioreduction of Ag NPs by phytochemicals was revealed by FTIR analysis. The elemental composition of Ag NPs was reported by EDAX spectral analysis. The Ag NPs exhibited anti-bacterial activity against Pseudomonas aeruginosa, Staphylococus aureus, Klebsiella aerogenes and Escherichia coli, anti-fungal activity against Penicillium citrinum and Aspergillus flavus and anti-mitotic activity. The response of amines through formic acid within the sight of an Ag NPs catalyst in dissolvable free condition provides high yielded convention for the N-formylation to shape the comparing formamide derivatives. N-fromylation includes incite recyclability, clean strategy and naturally neighbourly under milder response conditions and straightforward work-up to brilliant yield of the coveted items.Fri, 13 Sep 2019 19:30:00 +0100An Efficient Mixed-Memory-Type Control Chart for Normal and Non-Normal Processes
http://scientiairanica.sharif.edu/article_21552_0.html
Statistical process control techniques are commonly used to monitor process performance. Control charting technique is the most sophisticated tool of SPC and is categorized as memory-less and memory-type control charts. Shewhart-type control charts have low efficiency in detecting the small changes in the process parameters and named as memory-less control charts, and memory-type control charts (for example cumulative sum (CUSUM) and exponentially weighted moving average (EWMA) charts) are very sensitive to small persistent shifts. In connection with enhancing the performance of CUSUM and EWMA charts, an efficient variant of memory-type charts for the location parameter is developed based on mixing the double exponentially weighted moving average (DEWMA) chart and CUSUM chart by performing exponential smoothing twice. Performance of the proposed efficient variant is compared with existing counterparts under normal and non-normal (heavy tails and skewed) environments. The study also provides an industrial application related to the monitoring of weights of quarters made by mint machine placed into service at U.S. Mint. From theoretical and numerical studies, it is revealed that proposed variant of memory-type charts outperforms the counterparts in detecting shifts of small and moderate magnitude.Fri, 13 Sep 2019 19:30:00 +0100Price, delivery time and retail service sensitive dual channel supply chain
http://scientiairanica.sharif.edu/article_21555_0.html
This study deals with a dual channel supply chain where selling price of each player, delivery time for direct channel and retail service dependent demand structures are considered for manufacturer and retailer. In the direct channel, the manufacturer sells the products directly to the customers with a maximum mentioned delivery time. The delivery time of the products is adjustable according to customers’ demand with extra delivery charge. In the retail channel, the customers are extra benefited by the retail service and direct connection with the products. Selling price for direct market is considered as lower than the retail market selling price. The behavior of the model under integrated system is analyzed. In the decentralized structure, vertical Nash and manufacturer Stackelberg models are also discussed. The sensitivity of the key parameters is examined to test feasibility of the model. Finally, a numerical example with graphical illustrations is provided to investigate the proposed model.Fri, 13 Sep 2019 19:30:00 +0100Control and stability analysis of VSC-HVDC based transmission system connected to offshore wind farm
http://scientiairanica.sharif.edu/article_21556_0.html
Offshore wind farms (WFs) with significant capacities have been installed recently all over the world. In order to transmit the WF power to the onshore grid, high voltage direct current (HVDC) transmission system is appropriate technology. This paper analytically studies the impact of system parameters, controllers and operating conditions on the dynamic behavior of HVDC transmission systems based on three-level neutral point clamped voltage source converters (VSC). Also, it investigates modeling, control and stability analysis of VSC-HVDC system connected to the offshore wind farms. The VSC-HVDC system comprises offshore and onshore converters and high voltage dc transmission lines. The paper extracts VSC-HVDC system dynamics at the dc-side and argues the interaction between onshore converter control and HVDC transmission line dynamics. Moreover, the paper presents controller design for the dc-link voltage regulation by the onshore converter and examines the impacts of HVDC line length and dc voltage control bandwidth (BW) on the system stability by the modal analysis and time domain simulations.Fri, 13 Sep 2019 19:30:00 +0100A Comparative Analysis of The New Excitation Controlled Synchronous Generator-Based Wind Turbine
http://scientiairanica.sharif.edu/article_21559_0.html
Excitation Controlled Synchronous Generator-based Wind Turbine (ECSG WT) is a recently proposed wind turbine scheme which has not been fully investigated in detail. This paper is devoted to analyze performance of the ECSG WT scheme and to compare it with two mainstream wind turbine schemes based on electrically excited synchronous generator, i.e. VSC-based full converter wind turbine and diode bridge rectifier-based wind turbine equipped with boost converter on its DC link. The aim of this comparison is to demonstrate great potentials of ECSG WT for being considered in wind industry. To do so, two successful WT schemes at the market which are structurally close to ECSG WT are selected. The comparison includes different technical and economic aspects of the three schemes, assuming DC grid connection for the wind turbines. In addition, another comparison is made between the recently introduced Siemens 2nd generation DC Grid Access Offshore wind farm and a wind farm with similar structure, but using ECSG WTs. The results of these comparisons declare that ECSG WT scheme has promising characteristics, especially regarding economic, reliability and efficiency aspects.Mon, 16 Sep 2019 19:30:00 +0100Design and Optimization of a Large-Scale Permanent Magnet Synchronous Generator
http://scientiairanica.sharif.edu/article_21561_0.html
Direct drive permanent magnet synchronous generators have numerous advantages such as improved reliability, low maintenance, long life, and developed performance characteristics. Focus of this paper is on the development of a step-by-step method for the design of a permanent magnet synchronous generator. Then the winding function method is used to model the generator and to analytically calculate its output characteristics. The analytical results of the designed generator are evaluated with the finite element analysis (FEA) results and it is demonstrated that the achieved results from both methods are well matched with the experimental measurements of the Northern Power direct-drive generator. The sensitivity analysis and the optimization based on the genetic algorithm are used to achieve an optimum generator. The optimization goal is obtaining higher efficiency and power factor with lower required permanent magnet (PM) volume and voltage regulation for the optimum machine compared to the initial design. In addition, the calculation of the voltage total harmonic distortion (THD) is presented and the optimum skew angle for the optimum generator is computed to reduce the voltage THD.Mon, 16 Sep 2019 19:30:00 +0100Size dependent analysis of tapered FG micro-bridge based on a 3D beam theory
http://scientiairanica.sharif.edu/article_21564_0.html
In the current study, an analytical solution based on the modified couple stress theory for a nonlinear model describing the couple 3D motion of a functionally graded tapered micro-bridge is presented. The small scale effects and the nonlinearity arising from the mid-plane stretching are taken into consideration. Governing equations of motions are derived utilizing the modified couple stress theory and applying Hamilton principle. Dynamic and static analyses to determine the effects of lateral distributed forces and mid-plane stretching are investigated. To this aim, analytical Homotopy-pade technique is employed to capture the nonlinear natural frequencies in high amplitude vibrations of tapered micro-bridges with different types of geometries and material compositions. The obtained results of frequencies propose that there is a good agreement between the present analytical results and the numerical ones in opposed to well-known multiple-scale method. Furthermore, comparing the results in 2D and 3D analyses shows that in 2D analysis, the stiffness and natural frequency of the micro-beam is underestimated and it is found that increasing the tapered ratio has different impacts on natural frequencies for micro-beams with different slender ratios.Mon, 16 Sep 2019 19:30:00 +0100Exergy, exergoeconomic and exergoenvironmental assessments and optimization of a novel solar ...
http://scientiairanica.sharif.edu/article_21581_0.html
In this research, a combined cascade organic Rankine cycle (CORC) and ejector refrigeration loops incorporated with the concentrating linear Fresnel solar collector (LFSC) is proposed as a pre-cooling section to reduce electricity work consumption in a mixed refrigerant (MR) hydrogen liquefaction process. The exergy, exergoeconomic and exergoenvironmental analyses of the system during a year and special days are conducted in detail. Moreover, the annual thermodynamic, economic and environmental impact (EI) performances of the proposed system are evaluated by varying the substantial design parameters. Parametric study indicates that increasing the back pressure of turbine in the low temperature (LT) loop improves all aforementioned performances of the system. Meanwhile, bi-objective optimization based on non-dominated sorting genetic algorithm (NSGA-II) and LINMAP, TOPSIS and Shannon entropy decision makers are used to ascertain the optimum COPEx and economic/EI factors of the system concerned. Referring to the results, COPEx is improved by 10% and the cost and EI per exergy unit of LH2 reduce to 0.0309 $/MJ and 1.361 Pts/MJ through TOPSIS method.Fri, 27 Sep 2019 20:30:00 +0100Designing a sustainable agile retail supply chain using multi-objective optimization methods ...
http://scientiairanica.sharif.edu/article_21582_0.html
This paper aimed to design a sustainable agile retail supply chain using multi-objective optimization methods. To this end, a mathematical model was presented for the sustainable agile supply chain with five objectives, including "minimizing costs", "minimizing unanswered demand", "maximizing the quality of goods purchased from suppliers," "maximizing social responsibility or social benefits", and "minimizing environmental impacts". The NSGA-II, PESA and SPEA-II algorithms were used to solve the proposed model, which were run in MATLAB software. After collecting data from the SAIPA Company’s supply chain, the model was solved using the three algorithms. The results indicate that the SPEA-II algorithm produces more high quality responses, compared to the other two algorithms. Furthermore, the SPEA-II algorithm was found to be among the Pareto Front responses. A decrease of environmental impacts had no effect on the problem responses due to the lack of a specific structure in the current system.Fri, 27 Sep 2019 20:30:00 +0100Economic Order Quantity for Imperfect Quality Items Under Inspection Errors, Batch Replacement ...
http://scientiairanica.sharif.edu/article_21591_0.html
In classical inventory control problems, it is usually assumed that all of items are of perfect quality, and the inspection process works perfectly well. However, in practice, the order lots often contain imperfect quality items, and the inspection process, for recognition of these items, is not necessarily error-free. In this article, we extend the economic order quantity model under imperfect quality items where the inspection process involves type I and II errors. The type I error can lead to recognition of perfect quality items as defective, while the type II error can lead to delivery of imperfect quality items to customers even for several consecutive times. We present two cases depending on the length of special inspection process and determine optimal order sizes, analytically, for maximizing total profit per unit time for both cases. A numerical example is provided to compare two cases and a sensitivity analysis is discussed to assess the effect of main parameters on the total profit per unit time.Mon, 07 Oct 2019 20:30:00 +0100A heuristic method for choosing 'virtual best' DMUs to enhance discrimination power of ...
http://scientiairanica.sharif.edu/article_21593_0.html
Despite its intrinsic advantageous features as a tool for increasing discrimination power of the basic DEA (data envelopment analysis) model, augmented DEA has two main drawbacks including the presence of unrealistic efficiency scores and the presence of great distance between its efficiency scores and scores obtained by primary model. In this regard, this paper extends a heuristic method for dealing with both issues and improving the power of augmented DEA model in performance evaluation. Since different virtual DMUs lead to different results for ranking, the hierarchical clustering algorithm is applied in this study to select the best virtual DMUs in order to reduce the possibility of having inappropriate efficiency scores. Finally, to demonstrate the superiority of the proposed approach over previous approaches in literature, two numerical examples are provided.Mon, 07 Oct 2019 20:30:00 +0100On the well-posedness, equivalency and low-complexity translation techniques of discrete-time ...
http://scientiairanica.sharif.edu/article_21594_0.html
The main contribution of this paper is to present the systematic and low-complexity translation techniques between a class of hybrid systems referred to as automaton-based DHA and piecewise affine (PWA) systems. As an starting point the general modeling framework of the automaton-based DHA is represented which models the controlled and uncontrolled switching phenomena between linear continuous dynamics including discrete and continuous states, inputs and outputs. The basic theoretical definitions on the state trajectories of the proposed DHA with forward and backward evolutions which yield forward and backward piecewise affine (FPWA and BPWA) systems are given. Next, the well-posedness and equivalency properties are proposed and the sufficient conditions under which the well-posedness property is achieved with the automaton-based DHA and PWA systems are given. It is shown that the graphical structure of the proposed automaton-based DHA makes it possible to obtain analytically the equivalent PWA system with a polynomial complexity in contrast to the existing numerical translation techniques via decomposed structure of the DHA with an exponential complexity. Examples are presented to confirm the effectiveness of the proposed translation techniques.Mon, 07 Oct 2019 20:30:00 +0100MHD Micropolar Fluid over Curved Stretching Surface with modified Fourier law
http://scientiairanica.sharif.edu/article_21602_0.html
The present study describes MHD micropolar fluid as a result of curved stretching surface with Cattaneo-Christov theory of heat diffusion. The new heat model with the relaxation time is employed in this paper, in spite of classical theory of heat flux presented by Fourier. The curvilinear coordinates are used to model the governing equations. The nonlinear PDE’s are changed into ODE’s by using suitable transformation. The nonlinear ODE’s are solved with the help of OHAM by using BVPh2. The variation of several parameters are indicated and examined graphically. We observed that the pressure and velocity rises by enhancing the radius of curvature.Sat, 12 Oct 2019 20:30:00 +0100Simulations of nonlinear advection-diffusion models through various finite element techniques
http://scientiairanica.sharif.edu/article_21603_0.html
In this study, the Burgers equation is analyzed in both numerically and mathematically by considering various finite element based techniques including Galerkin, Taylor-Galerkin and collocation methods for spatial variation of the equation. The obtained time dependent ordinary differential equation system is approximately solved by α-family of time approximation. All these methods are theoretically explained using cubic B-spline basis and weight functions for a strong form of the model equation. Von Neumann matrix stability analysis is performed for each of these methods and stability criteria are determined in terms of the problem parameters. Some challenging examples of the Burgers equation are numerically solved and compared with the literature and exact solutions. Also, the proposed techniques have been compared with each other in terms of their advantageous and disadvantageous depending on the problem types. The more advantageous method of the three, comparison to other two, has been found out for the special cases of the present problem in detail.Sat, 12 Oct 2019 20:30:00 +0100A Numerical Investigation of Synthetic Jet Effect on Dynamic Stall Control of Oscillating Airfoil
http://scientiairanica.sharif.edu/article_21604_0.html
At high angles of attack, the dynamic stall phenomenon could be appearing owing to the vortex shedding particularly in an oscillating airfoil. The consequences of this event are a considerable decrease in the lift and an increase in the drag as well as the pitching moment coefficients. The flow was assumed to be unsteady and turbulent at a Mach number 0.2 and for Reynolds number 1million. This research was done for a range of angle of attack 15o±10o. In order to carry out the numerical analysis of the problem, the 2-D compressible turbulent Navier-Stokes equations based on “Roe” scheme with second-order accuracy were solved. Turbulence modeling was carried out using the three-equation k-kL-ω model. Regarding the obtained results, it was observed that this flow control method had a significant ability in eliminating the dynamic stall. It was also revealed that the phase difference between the jet and airfoil oscillations is more affected by the dynamic stall decrement. In these changes, use of the SJ with 0.1 momentum coefficient, led to the highest amplitude of lift at φ=-30°, and the multiplication of drag amplitude and amplitude of moment coefficient at φ=-10° offered the best performance in addition to the considerable decrease.Sat, 12 Oct 2019 20:30:00 +0100An approximate methodology to simulate combined conduction-radiation heat transfer for ...
http://scientiairanica.sharif.edu/article_21605_0.html
A quasi-analytical methodology was developed to model combined conduction-radiation heat transfer through the thickness of a reflective multi-layer insulator. This methodology was validated by the experimental result. It could be used for earlier steps of the design process of the high-temperature multi-layer insulators. Traditionally, radiation thermal conductivity approximation is used in the earlier stages of design. Despite the accuracy of this approach in steady-state cases, it yields to some unacceptable errors when the thermal load is transient. It was shown that old methodology can not predict maximum temperature and time of occurrences in acceptable margins. The developed model originated from the radiation thermal conductivity approximation. But unlike the primitive one, the developed model seems acceptable in transient cases. This model is based on consideration of thermal emittance through the thickness of the insulator. It can predict the maximum temperature of the structure and occurrences time with an error of less than 4%.Sat, 12 Oct 2019 20:30:00 +0100POSTFATIGUE LIFE PREDICTION OF GLARE SUBJECTED TO LOW-VELOCITY IMPACT
http://scientiairanica.sharif.edu/article_21606_0.html
In this study, at first, the dynamic progressive failure of Glass-Fiber-Reinforced aluminum laminates (GLARE) under low-energy impact with intra laminar damage models implementing strain-based damage evolution laws, Puck failure criteria using ABAQUS-VUMAT,were modeled. For interface delamination, bilinear cohesive model; and for aluminum layers the Johnson-Cook model was implemented;and the fatigue life of the fiber metal laminates of GLARE subjected to impact was obtained; and the numerical and experimental results of the model were compared with each other. With regard to the very good match betweenthe numerical and experimental results, the results of the finite element model were generalized and expanded, and with the use of the multilayer neural network, the numerical model was extracted and then, by applying the meta-innovative algorithm, the maximum fatigue life of GLARE was determined atthe highest level with very low-velocity impact,and the best configuration of three-layer GLARE was selected.The findings indicated that the best configuration of hybrid composite GLARE based on conventional commercial laminates that can tolerate low-velocity impacts with 18J impact energy and a 349MPa fatigue load with a frequency of 10Hz was [Al/0-90-90-0/Al/0-90-0/Al/0-90-90-0/Al] with 13016 cycle lifetime.Sat, 12 Oct 2019 20:30:00 +0100Government subsidies in manufacturing and remanufacturing with consumer segment and ...
http://scientiairanica.sharif.edu/article_21607_0.html
Waste products have double properties of environmental hazard and resource recovery, while recycling behavior has greater positive external effect of economic, which often results in the low enthusiasm for enterprises to engage in remanufactured activity. For price decisions on whether government subsidizes closed-loop supply chain or not, Stackelberg game model were constructed under three scenarios: none is subsidized (Model N), subsidize to manufacturer (Model M) and subsidized to recycler (Model R) to obtain the optimal government subsidy and price decision, as well as analyze the difference among the equilibriums of four scenarios. From the conclusion, we can find that the government subsidy improve the social welfare, as well as the government implement different subsidy policies based on the needs for economic and social progress.Sat, 12 Oct 2019 20:30:00 +0100Fuzzy Cognitive Mapping Approach for Assessing Industry 4.0 Tendency
http://scientiairanica.sharif.edu/article_21608_0.html
The correct understanding of the conceptual and practical counterpart of Industry 4.0 is of great importance because global competition has made technology-based production a necessity. However, Industry 4.0 studies have not sufficient explanatoriness in terms of their understanding. The aim of this study is to propose a model that will predict the companies' existing and predicted Industry 4.0 levels.The changes of the concepts are examined and interpreted for 3 different hypothetically prepared scenarios. In the first scenario, an organization that is poorly managed in terms of the development of Industry 4.0 is considered. The industry 4.0 tendency was obtained as 0.04 reaching steady state after 12 time periods using the FCM algorithm. Moderate and well-managed organizations are considered in Scenario 2 and 3 respectively. The industry 4.0 tendency reached 0.12 after 15 time periods for Scenario 2. The tendency is calculated as 0.95 at the end of 5 iterations in the third scenario, which has well-managed concept values in the current situation. In addition to the scenario analysis, strategy and organization, smart operation, and smart factory concepts are found to provide the most significant contribution over the industry 4.0 level as a result of static analysis section.Sat, 12 Oct 2019 20:30:00 +0100What can fuzziness do for capability analysis based on fuzzy data
http://scientiairanica.sharif.edu/article_21609_0.html
An advantage of process incapability index over the classical process capability index is that it provides uncontaminated separation between process accuracy and process precision. However, the value of the index is hard to be obtained accurately when process parameters cannot be determined precisely. In such case fuzzy set theory can be applied to get more flexible and more sensitive information. In this article a fuzzy process incapability index is proposed when the specification limits are assumed to be type-2 fuzzy. When the process mean and variance are unknown and when the data collected is fuzzy, three fuzzy estimators are considered. A simulation study is conducted based on a TFT-LCD fuzzy process. By employing the total integral value method to the membership function of a fuzzy index, the comparisons of quality among different processes become easier.Sat, 12 Oct 2019 20:30:00 +0100Novel Exponential divergence measure of complex intuitionistic fuzzy sets with an application ...
http://scientiairanica.sharif.edu/article_21610_0.html
As a generalization of the intuitionistic fuzzy sets (IFSs), complex IFSs (CIFSs) is a powerful and worthy tool to realize the imprecise information by using complex-valued membership degrees with an extra term, named as phase term. Divergence measure is a valuable tool to determine the degree of discrimination between the two sets. Driven by these fundamental characteristics, it is fascinating to manifest some divergence measures to the CIFSs. In this paper, we explain a method to solve the multi-criteria decision-making (MCDM) problem under CIFS environment. For it, firstly, the divergence measures are introduced between two CIFSs and examined their several properties and relations. Secondly, a novel algorithm is given based on the proposed measures to solve the problems in which weights corresponding to criteria are resolved using maximizing deviation method. Thirdly, a reasonable example is provided to verify the developed approach and to exhibit its practicality and utility with a comparative analysis to show its more manageable and adaptable nature.Sat, 12 Oct 2019 20:30:00 +0100Balancing the Portfolio of Urban and Public Projects with Distance-Dependent Coverage Facilities
http://scientiairanica.sharif.edu/article_21613_0.html
The portfolio of urban and public projects should be balanced in terms of completion time, districts and strategic objectives. For this purpose, we suggest a mixed integer nonlinear programming model based on the goal programming approach. Projects are selected so as to minimize the squared deviation of urban and regional development indicators from their respective targets. In the proposed model there are two category of indicators: coverage indicators that are measured based on the distance of each neighborhood from the nearest covering facility, and general indicators that are usually measured based on the capacities and capabilities of each district. It is assumed that the location of covering facilities have already been selected, but the construction of these facilities will be prioritized and planned according to budget constraints and in competition with other regional development projects. Numerical results indicate superior performance of proposed genetic algorithm in comparison to GAMS solvers. Finally, the application of the model is illustrated by an example.Sun, 13 Oct 2019 20:30:00 +0100Modified Seismic Design Lateral Force Distribution for the Performance-Based Plastic Design ...
http://scientiairanica.sharif.edu/article_21616_0.html
It is well recognized that structures designed by conventional seismic design codes experience large inelastic deformations during strong ground motions. Realistic estimation of force distribution based on inelastic response is one of the important steps in a comprehensive seismic design methodology in order to represent expected structural response more accurately. This paper presents an extensive parametric study to investigate the structural damage distribution along the height of the steel moment-resisting frames (SMRFs) designed based on the stat-of-art constant-ductility performance-based plastic design (PBPD) approach considering soil flexibility effects when subjected to 20 strong ground motions. To this end, the effect of fundamental period, target ductility demand and base flexibility level are investigated and discussed. Based on the numerical results of this study, simplified equations are proposed for practical purpose to refine and modify the lateral force distribution pattern already suggested by researchers based on the study of inelastic behavior developed for fixed- and flexible-base structures by using relative distribution of maximum story shears of the selected structures subjected to various earthquake ground motions. It is demonstrated that the proposed equations can be adequately estimated the optimum values of shear proportioning factor for both fixed-based and soil-structure systems.Mon, 14 Oct 2019 20:30:00 +0100A modular Takagi-Sugeno-Kang (TSK) system based on a modified hybrid soft clustering for stock ...
http://scientiairanica.sharif.edu/article_21618_0.html
This study presents a new hybrid intelligent system with ensemble learning for stock selection using the fundamental information of companies. The system uses the selected financial ratios of each company as the input variables and ranks the candidate stocks. Due to the different characteristics of the companies from different activity sectors, modular system for stock selection may show a better performance in comparison with an individual system. Here, a hybrid soft clustering algorithm is proposed to eliminate the noise and partition the input data set into more homogeneous overlapped subsets. The proposed clustering algorithm benefits from the strengths of the fuzzy, possibilistic and rough clustering to develop a modular system. An individual Takagi-Sugeno-Kang (TSK) system is extracted from each subset using an artificial neural network and genetic algorithm. To integrate the outputs of the individual TSK systems, a new weighted ensemble strategy is proposed. The performance of the proposed system is evaluated among 150 companies listed on Tehran Stock Exchange (TSE) regarding information coefficient, classification accuracy and appreciation in stock price. The experimental results show that the proposed modular TSK system significantly outperforms the single TSK system as well as the other ensemble models using different decomposition and combination strategies.Sat, 19 Oct 2019 20:30:00 +0100Developing an Iterative Procedure to Estimate Origin-Destination Matrix Based on Two-Point ...
http://scientiairanica.sharif.edu/article_21619_0.html
Origin-Destination Matrix, one of the most important elements in transportation planning, is usually estimated by various techniques such as mathematical modeling, statistical methods, and heuristic approaches. Since using electronic devices is rapidly increased to help decision makers to improve models’ capabilities, an iterative procedure is proposed in this paper to estimate the O-D Matrix according to vehicles’ license plates detection. The main concept is to track vehicles on the first and the last links equipped by plate camera over the shortest path from origins to destinations. A two-step procedure and mathematical models are developed to adjust assigned the passing traffic to the network links by minimizing deviations between the observed and estimated truck traffic volumes. The proposed procedure is explained by an illustrative example followed by validation using experimental road network that covers seven eastern provinces of Iran including 310 nodes, 400 two-way edges, and around 3600 origin and destination pairs. Results revealed that the proposed procedure is capable to estimate O-D matrix when the network links are optimally located and equipped by road camera detection systems. In addition, such as the other heuristic approaches, the proposed procedure is sensitive to the number of iterations on the estimation accuracy.Sat, 19 Oct 2019 20:30:00 +0100Thermodynamic analysis of a novel solar trigeneration system
http://scientiairanica.sharif.edu/article_21621_0.html
Loop heat pipes (LHPs) are high efficiency devices which can be used in solar systems. The main objectives of this research are to propose a novel solar combined cooling heating and power (SCCHP) system based on loop heat pipe (LHP) evaporator, and to present thermodynamic analyses to effectively improve the utilization of loop heat pipes for distributed renewable energy sources. Also a parametric analysis is carried out to investigate the effect of the key variable parameters on the system performance for three operation modes (solar mode, solar and storage mode and storage mode). The results showed that, for the solar and solar and storage operation modes, the main source of the exergy destruction is the solar loop heat pipe evaporator while for the storage operation mode, the main source of the exergy destruction is the hot storage tank. The energy efficiency of the proposed system is 70.52% for the solar mode, 72.09% for the solar and storage mode, and 64.77% for the storage mode and the exergy efficiency of the proposed system is 12.36% for the solar mode, 14.78% for the solar and storage mode, and 47.45% for the storage mode.Mon, 21 Oct 2019 20:30:00 +0100Effect of distribution pattern of DSM columns on the efficiency of liquefaction mitigation
http://scientiairanica.sharif.edu/article_21647_0.html
Liquefaction during earthquakes can result in severe damage to structures, primarily from excess pore water pressure generation and subsoil softening. Deep Soil Mixing (DSM) is a common method of soil improvement and is also used to decrease shear stress in liquefiable soils to control liquefaction. The current study evaluated the effect of Deep Soil Mixing (DSM) columns and implementation of different column patterns on controlling liquefaction and decreasing settlement of shallow foundations. A series of shaking table physical modelling tests were conducted for three different distribution patterns of Deep Soil Mixing (DSM) columns (i.e.: square, triangular and single) with a treatment area ratio of 30%. The treatment was applied to a liquefiable soil under a shallow model foundation. The results showed that the excess pore water pressure decreased 20% to 50% in comparison with the unimproved soil, depending on the Deep Soil Mixing (DSM) column pattern used. For improved soil, the shallow foundation settlement was about 10% that of the unimproved soil in the best case. The increase in soil shear stiffness after use of the Deep Soil Mixing (DSM) columns was compared with the results of existing practical relations to increase soil shear strength.Sun, 27 Oct 2019 20:30:00 +0100Implementing new variables RGS plan based on EWMA yield index
http://scientiairanica.sharif.edu/article_21648_0.html
This paper develops a new variables repetitive group sampling plan using the exponentially weighted moving average (EWMA) statistic based on the yield index for the submitted lot. The optimal parameters of the proposed plan are determined under three scenarios based on the average sample number. Average sample number (ASN) is minimized to decrease inspection's cost and time by using the optimization problem for the required quality levels and sundry combinations of producer's and consumer's risks. The comparison study is provided to specify the efficiency of the proposed plan. Furthermore, the proposed plan is presented with an example which indicates its applicability in the industry. The proposed plan is compared with the single sampling plan and repetitive group sampling plan based on the yield index. The upshots are tabulated for various quality levels. The obtained outcomes demonstrate that the performance of the proposed sampling plan is more lucrative than the existing sampling plans in terms of ASN.Sat, 02 Nov 2019 20:30:00 +0100Hot-film/hot-wire anemometer calibration for low velocities using image processing
http://scientiairanica.sharif.edu/article_21649_0.html
Calibration of hot-wire and hot-film probes at low velocities is a difficult task because the dynamic pressure at these velocities is very low and may not be measured easily. To overcome this problem, substituent techniques have been presented in the literature that rely on other phenomena and utilize different hardware. This paper describes a simple and low-cost method which proposes to move the anemometer probe in quiescent air (here by means of a swinging arm) and track this motion with a camera. After processing of the images, velocity time history of the probe is found by numerical calculations. Calibration curve is then obtained without any predetermined relationship. Using a medium-speed video camera that is often found in laboratories would avoid the need to a position sensor and a complicated arm on which this sensor is mounted. This technique can be used not only for pendulums but also for other means of moving probes in quiescent medium.Sat, 02 Nov 2019 20:30:00 +0100Gas Separation Properties of Polyacrylonitrile-Polysulfone-Iron Oxide Nanocomposite Membrane
http://scientiairanica.sharif.edu/article_21663_0.html
Gas separation process by the membrane is performed without changing the phase. For this reason, the costs are decreased. This study examined gas separation in Polyacrylonitrile (PAN) and Polysulfone (PSF) blend membranes. The ratio of polymers to mixed matrix membranes was considered 100% PAN, 100% PSF, (95% PAN -5% PSF), (90% PAN-10% PSF), (85% PAN-15% PSF). The best combi-nation of mixture was determined. Then, iron oxide nanoparticles with different weight percentages were placed on the membrane. The impact of adding different values of iron oxide nanoparticles in membrane was examined on separation of gas. Adding iron oxide nanoparticles to the membrane by 10% weight and measuring the value of permeability, it was observed that the permeability of this membrane for carbon dioxide, oxygen, nitrogen, and methane gases increased by 117%, 137%, 95%, and 53% compared to membranes without iron oxide nanoparticles. Examining the findings, it was re-vealed that the optimal value of adding iron oxide to improve the membrane properties was 10% by weight.Mon, 11 Nov 2019 20:30:00 +0100Global optimization for Cross-domain aircraft based on Kriging model and par-ticle swarm ...
http://scientiairanica.sharif.edu/article_21664_0.html
To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathe-matical model for calculations. The architecture of the water-air amphibious aerial vehicle is especially crucial to the whole product, which impacts its performances in many different sides. a new architecture of low-submerged ducted water-air amphibious aerial vehi-cle with double rotor wings is designed on the basis of the studies home and abroad. Both of the system architecture and the dynamic model are established and both of the water-flow and airflow are analyzed with Fluent based on the 3D structure models built by Solidworks software, which mainly aims at the impact factors of body thrust force and lift force. And the CFD simulations of the layout are also accomplished based on the former analysis results as well. Compared with the results from PSO algorithm, kriging model and orthogonal test, the most suitable shape architecture is optimized. Finally, the optimized results were simulated by Fluent. The results show that the Global optimization thought based on the Kriging model and the PSO algorithm significantly improve the lift and drive performance of cross-domain aircraft and computer operational efficiency.Mon, 11 Nov 2019 20:30:00 +0100Modeling the CO gas response of PEDOT:PSS/ Fe(salen) thin film for a gas sensor
http://scientiairanica.sharif.edu/article_21665_0.html
Abstract. A thin film carbon monoxide (CO) gas sensor based on PEDOT:PSS/Fe (salen) has been developed using the spin coating technique on several glass pieces with interdigitated Au electrodes. The change in electrical resistance of the sensors with various content of dopants was measured in different CO gas concentrations and temperatures. It is found that Fe (salen) as a dopant can significantly improve the performance of PEDOT:PSS based gas sensors. Least square support vector regression (LSSVM) method was applied to predict the gas response characteristics of the films for different testing conditions. Modeling results show a satisfactory agreement with experimental findings.Mon, 11 Nov 2019 20:30:00 +0100Expansion Planning of Automated Sub-transmission and Distribution Networks integrated by ...
http://scientiairanica.sharif.edu/article_21666_0.html
This paper presents sub-transmission and distribution network expansion planning (S&DEP) including distributed generation (DG) and distribution automation (DA) considering reliability indexes. The objective function is to minimize investment, operation, maintenance and reliability costs subjected to AC power flow, system operation and generating units and DG limits, reliability, and distribution automation constraints (including the constraints of protection devices and volt/VAr control mechanism). The proposed model is a mixed integer non-linear programming (MINLP) model which is hard to solve. For this reason, a MINLP problem is transformed to mixed integer linear programming (MILP) model. The validity of the proposed method is investigated in the two synthetic test networks.Mon, 11 Nov 2019 20:30:00 +0100Variable Sample Size EWMA Chart With Measurement Errors
http://scientiairanica.sharif.edu/article_21667_0.html
The effect of measurement errors on adaptive Shewhart charts have been investigated by several researchers. However, the effect of measurement errors on the performance of variable sample size EWMA control charts has not so far been investigated. In this paper, the performance of the VSS EWMA chart in the presence of measurement errors is investigated using a linear covariate error model and a Markov chain method. It is shown that the performance of the VSS EWMA chart is significantly affected by the presence of measurement errors. The effect of taking multiple measurements for each item in a subgroup on the performance of the VSS EWMA chart is also investigated. Moreover, the performance of the VSS EWMA control chart is compared with several other control charts in the presence of measurement errors. At last, an illustrative example is presented to show the application of the VSS EWMA control chart with measurement errors.Mon, 11 Nov 2019 20:30:00 +0100Scheduling of periodic services to customers in dispersed locations from heterogeneous ...
http://scientiairanica.sharif.edu/article_21668_0.html
The scheduling problem of periodic services from service providers to customers located in different places and need different services. The service centers are also located in different positions, each of which has limited number of teams with the capability of performing one or some services. The goal is to simultaneously minimize ‘total service costs’ and ‘total earliness/tardiness’ in providing services to customers. Providing an optimal maintenance schedule is a big challenge in those companies with dispersed supply centers. In this paper, a novel bi-objective mixed integer linear programming model along with augmented epsilon constraint method is presented to exactly solve this problem. Then, a bi-objective meta-heuristic technique based on genetic algorithm is proposed and its performance in solving large-scaled problems is assessed. The uncertain parameters are faced through robust possibilistic programming approach to diminish the risk of decision making. Finally, the performance of the proposed model and solution approaches are evaluated through a real case study in maintenance scheduling of CNG stations equipment in Iran.Mon, 11 Nov 2019 20:30:00 +0100Designing and analyzing two non-invasive current sensors using Ampere Force Law (AFL)
http://scientiairanica.sharif.edu/article_21670_0.html
Here two different non-invasive current sensors are proposed, modeled and analyzed. The current sensors are based on the Ampere Force Law (AFL), defining the magnetic force between two parallel wire carrying currents. These current sensors can be used for detecting/sensing DC and AC currents as well as their combination in a single wire or multiple wires, and they do not rely on any permanent magnets for operation. In the first configuration, there are two microbeams, in which one of them is at the vicinity of the wire and undergoes the mechanical vibrations due to magnetic force between the wire and the microbeam. The movement of the microbeam while it is generating a magnetic field induces a current inside the another microbeam, which is stationary, as the output signal of the current sensor. In the second configuration, a single composite piezoelectric microbeam is used. The magnetic force between the wire and the piezoelectric microbeam leads the piezoelectric microbeam to move, thus it produces a voltage. Both configurations present an extremely low power consumption, which is not dependent on the sensitivity of the current sensors. The dynamic response, sensitivity and power consumption of the current sensors are investigated, compared and discussed.Sat, 16 Nov 2019 20:30:00 +0100Predicting primary energy consumption using NDGM(1,1,k,c) model with Simpson formula
http://scientiairanica.sharif.edu/article_21671_0.html
Energy consumption plays a key role in economics development for all countries. Catching the future trend of energy consumption is very important for the governments and energy companies. In this paper, the primary energy consumption of Saudi Arabia, India, Philippines and Vietnam are systematically studied by various forecasting models. Based on the actual data from 2006 to 2016, a novel grey forecasting model termed NDGM_S (1,1,k,c) is proposed where the Simpson numerical integration formula is applied to construct the background value. The time response function and the restored value of the present model are deduced, and then the unbiased property is proved. As shown in the computational results, the NDGM_S (1,1,k,c) model can achieve better prediction accuracy than other forecasting models, and it is quite suitable for predicting sequence with homogeneous/non-homogeneous exponential law.Sun, 17 Nov 2019 20:30:00 +0100Development of MEMS gas actuator for analyzing a gas mixture
http://scientiairanica.sharif.edu/article_21672_0.html
In this study, a computational technique is used to investigate the ability of a new MEMS gas actuator (MIKRA) for detection and sensation of the gas mixture. In this actuator, the temperature difference of two arms inside a rectangular domain at rarefied condition induces a Knudsen force which is relative to physical properties of the gas. Both 2d and 3D approaches are applied for the simulation of the flow inside the model. In order to define the flow feature of a low-pressure gas inside the micro gas actuator, a high order equation of Boltzmann should be solved to attain reliable results. Since the domain of this micro gas is non-equilibrium, Direct Simulation Monte Carlo (DSMC) method is applied for the simulation of the model. According to obtained results, a three-dimensional model presents more reliable results and the effect of a gap for three-dimensional model clearly demonstrates the impact of this parameter on the effective Knudsen forceSun, 17 Nov 2019 20:30:00 +0100Experimental, Numerical and Finite Element Vibration Analysis of Delaminated Composite Plate
http://scientiairanica.sharif.edu/article_21673_0.html
The vibration of the delaminated composites concerns the structure safety and dynamic behavior of the composite structures as it can be vital in the presence of delamination. In this research paper, the finite element simulations, numerical simulations and the experimental work are combined to analyze the vibration behavior at different delamination size, different stacking sequences and different boundary conditions. The finite element analysis software packages like Ansy and Abqus are used to fetch the vibration response of carbon fiber reinforced polymer composite plate for different boundary conditions, stacking sequences and delamination sizes. Experiments are carried out to study the vibration behavior. Numerical results were obtained using the first order shear deformation theory. Rayleigh-Ritz method was used to derive the governing equations to find the natural frequencies and the results were computed using Matlab tool. The results from finite element, numerical and experimental analysis were then compared and verified that the maximum percentage of error is ignorable. It is seen that the natural frequencies of carbon fiber reinforced polymer decreased with an increase in delamination size subjected to all boundary conditions. The higher values of natural frequencies found for all sides clamped boundary conditions.Sun, 24 Nov 2019 20:30:00 +0100Assessment of Optimum Slurry Pipe Design for Minimum Erosion
http://scientiairanica.sharif.edu/article_21681_0.html
Particulate erosion is a major concern in slurry handling unit of a thermal power plant. The pipe bends are the most erosion affected element of a pipeline unit thus, a cost-effective method to reduce pipeline erosion is highly desirable. This work aims to suggest the optimal pipe bend design to minimize the particulate erosion by analyzing the erosion wear in geometrically different pipe bends for bottom ash slurry flow by using Computational Fluid Dynamics code FLUENT. A Three-dimensional simulation study of erosion wear is carried out by implementing Euler-Lagrange modeling along with the standard k-ε turbulence model to solve the complex multi-phase flow. Pipe bends of different bending angle (30°, 45°, 60°, and 90°), diameter (50 to 250 mm) and bending ratio (r/D = 1 to 2.5) are evaluated at different flow condition. The wear location gets shifted to the upper section of the bend and its magnitude is significantly reduced with the increase in pipe diameter and bending angle. The dynamics of multiphase slurry through different bends is analyzed to understand the complex wear phenomenon. The simulation result shows good agreement with the published findings. Finally, a least erosion affected pipe bend profile is suggested for slurry transport unit.Fri, 06 Dec 2019 20:30:00 +0100Mathematical modeling for a new portfolio selection problem in bubble condition, using a new ...
http://scientiairanica.sharif.edu/article_21682_0.html
A portfolio selection model is developed in this study, using a new risk measure. The proposed risk measure is based on the fundamental value of stocks. For this purpose, a mathematical model is developed and transformed into an integer linear programming. In order to analyze the model's efficiency, the actual data of the Tehran Stock Exchange market are used in 12 scenarios to solve the proposed model. In order to evaluate the scenarios, data mining approaches are employed. Data mining methods which are used in this paper include ANFIS, decision tree, random forest, ADF, and GEP. The best method for scenario evaluation is GEP based on numerical results. Hence, the market values are evaluated by this algorithm. Software packages like MATLAB, GEP xpero tools, and LINGO are used to solve the model. Different trends of market value and fundamental value volatility in the optimum stock portfolio are determined. It is possible to examine the optimum portfolio profitability in different scenarios. By using real-world data, trends are extracted and analyzed. Results show that the developed model can be effectively applied in bubble situations.Fri, 06 Dec 2019 20:30:00 +0100Experimental Investigation of Effects of Mach number and Boundary Layer Bleed on the Flow ...
http://scientiairanica.sharif.edu/article_21683_0.html
A series of experiments were conducted to study impacts of the free stream Mach number, back pressure and bleed on the stability of a supersonic intake. The flow stability is related to the buzz phenomenon; oscillation of all shock waves of the intake and it may further occur during the time when the intake mass flow rate is decreasing. The present intake is an axisymmetric intake for Mach number of 2.0. The results showed that the stability margin of the intake decreases when the freestream Mach number increases for both bleed off and bleed on cases. For the configuration without bleed, the frequency of buzz oscillation is increased when the freestream Mach number is decreased or when the back pressure is increased. By applying the bleed and consequently preventing the flow separation, the intake is more stable and the shocks oscillate with a smaller amplitude during the buzz phenomenon. When the bleed is applied, the buzz triggering mechanism varied from the Dailey criterion to that of the Ferri one, a phenomenon that changes the stability characteristics of the intake considerably.Mon, 09 Dec 2019 20:30:00 +0100Robust parameter design based on response surface model under considering measurement errors
http://scientiairanica.sharif.edu/article_21684_0.html
Response surface approach is effective for robust parameter design. Previous response surface methodology assumes that the independent variables are measured without errors. However, this assumption might be violated due to the low capability of measurement system. This paper is concerned with applying response surface method for robust parameter design when there are measurement errors in variables. We present an unbiased estimator when there are some measurement errors and an optimal setting which is determined to minimize the expected quadratic loss. An example is illustrated to verify the effectiveness of the proposed approach. The results show that the proposed method can achieve better operating conditions under situations with measurement errors than the conventional method.Sat, 21 Dec 2019 20:30:00 +0100A NEW GROUND MOTION RECORD SELECTION PROCEDURE BASED ON THE EFFECTS OF SPECTRAL SHAPE AND ...
http://scientiairanica.sharif.edu/article_21685_0.html
One of the most prevalent ground motion Intensity Measures (IMs) is the spectral acceleration at the fundamental period of the structure. Previous research has shown that vectorizing scalar IMs leads to a more reliable structural response, particularly in the nonlinear region and near collapse. Furthermore, nonlinear behavior of ductile structures results in an elongation in the "effective period" of the structure. Therefore, this paper proposes a new approach for selecting ground motion records considering the effect of spectral shape and period elongation. This method contains two disaggregation analyses at the fundamental and elongated period of the structure. Nonlinear dynamic analysis is conducted on a set of reinforced concrete moment resisting frames designed based on ACI 318-05 as representatives of modern structures. Results show a considerable decrease in the median collapse prediction, margin against collapse and dispersion of the structural response. The presented approach can give a better prediction for the vulnerability of the structure toward collapse.Sat, 21 Dec 2019 20:30:00 +0100Tuning the Implementable Structures of Fractional-Order PID Controllers for Control of FOPDT ...
http://scientiairanica.sharif.edu/article_21686_0.html
This study presents a set of rules for optimal tuning a class of integer-order controllers, known as implementable fractional-order PID controllers, to be applied in control of first-order-plus-dead-time (FOPDT) processes. To this aim, the approach of so-called “tuning based on the implementable form of the controller” is applied instead of the common approach of “tuning based on the ideal form of the controller”. Consequently, no contradiction is found between the behavior of the tuned controller and that of the implemented controller. Also, algebraic relations between the values of cost functions, which are defined based on integral square error (ISE) and integral square time error (ISTE) performance indices, and free parameters of the implementable controller are established. Tuning implementable fractional-order PID controllers via the proposed rules guarantees that the values of performance indices are reduced in comparison with the case of using optimal PID controllers. In addition to numerical results, experimental results are also provided to demonstrate the effectiveness of the proposed tuning rules in practical applications.Sat, 21 Dec 2019 20:30:00 +0100Damping estimation of a double layer grid with ball joint system by output-only modal identification
http://scientiairanica.sharif.edu/article_21687_0.html
Modal parameters of large civil engineering structures such as modal damping ratios (MDRs) are determined mainly by output-only modal identification. In this paper, MDRs of a double layer grid were obtained using output-only modal identification. For this purpose, a double layer grid constructed from ball-joint system was tested. Doing some random tapping on the structure, the acceleration response in multiple locations was measured. The acquired data was processed using output-only modal identification to arrive at MDRs. The MDRs corresponding to the first eight modes of the grid were extracted by five output-only modal identification techniques; namely enhanced frequency domain decomposition (EFDD), curve-fit frequency domain decomposition (CFDD) and three different methods of data-driven stochastic subspace identification. To determine the appropriate model order used in SSI methods, a sensitivity analysis was carried out and the resulting number of order was 200. The proper frequency resolution of 1600 was also determined to estimate the MDRs of the grid by EFDD and CFDD. The results showed that the MDRs of the grid, obtained from different methods, are in good agreement with each other. The grid has very low MDRs, as the MDRs of the modes measured from different methods varied from 0.06% to 0.11%.Sat, 21 Dec 2019 20:30:00 +0100A multi-attribute decision making method based on the third generation prospect theory and grey ...
http://scientiairanica.sharif.edu/article_21688_0.html
Considering the uncertainty of the natural state and the convenience of calculation, based on the third generation prospect theory (3-PT) and grey correlation analysis (GRA), we propose a method to solve the multi-attribute decision-making (MADM) problems where the attributes are described by the linguistic intuitionistic fuzzy numbers (LIFNs). Firstly, we transform the LIFNs into the belief structure that includes identity value and belief degree. Then, the evaluation information represented by belief structure is calculated by using the 3-PT, and the prospect matrix is gotten. The alternatives are ranked by the GRA. Finally, we use the proposed method to calculate an example and compare it with other methods to prove its effectiveness and superiority.Sat, 21 Dec 2019 20:30:00 +0100An LMI approach to short-term memory discrete-time FIR controller design for integrating ...
http://scientiairanica.sharif.edu/article_21689_0.html
Short-term memory discrete-time finite impulse response (FIR) controller design along with an optimized tuning method is presented in this paper. For this purpose, the loop shaping scheme is employed in the linear matrix inequalities (LMIs) framework for adjusting some characteristics of the open-loop frequency response such as phase margin and bandwidth to the desired values at appropriate frequencies. Unlike the conventional methods which work based on state-space models, the proposed procedure generates LMIs directly in the frequency domain. The proposed controller design procedure was applied to several integrating time-delay systems to illustrate its performance and the results were compared with some other competing methodsSat, 21 Dec 2019 20:30:00 +0100Generation Rejection Scheme Based-on a Combinational Rotor Angle Trajectory Prediction
http://scientiairanica.sharif.edu/article_21690_0.html
This paper presents a response-based generating rejection scheme (GRS) based on an angular stability prediction logic to initiate the outage of accelerated generating units while saving the rest of generating units from the loss of synchronism. First trigonometric, polynomial, and hybrid models of rotor angle trajectory based on the reasonable assumptions are proofed. Then, by taking these models in the prediction step, through the maximum use of measured data based on defining the forecast horizon (FH) and data window with incremental length, the stability/instability of generating units is separately predicted. Next, the status of tripping signal based on a combinational logic of the output results of the angular stability prediction method is specified. In the developed logic, if at least two models of the three designated models yield the same response about the unit stability status, the trip signal is accordingly fired or blocked. The proposed method is examined on the one machine infinite bus and the WSCC standard test bed under different operation and fault scenarios. The obtained results demonstrate that beside simplicity, low computational burden, and very short processing time, the proposed combinatorial method outperforms the existing ones working with individual prediction models.Sat, 21 Dec 2019 20:30:00 +0100A Fuzzy Multi-Criteria Approach for Sustainable Island-based Tourism Development
http://scientiairanica.sharif.edu/article_21691_0.html
This paper aims to propose a framework by which decision-makers can evaluate and compare alternatives for sustainable island-based tourism development. The uncertainties and risks involved in information and judgment within the evaluation process are taken into account by using a hybrid approach, which combines the Delphi method, fuzzy set theory, and a discrete multi-criteria method based on prospect theory called TODIM (an acronym in Portuguese of interactive and multiple criteria decision making). The decision making model examines three different techniques of aggregating the viewpoints of different decision-makers and explores how the aggregation technique affects the ranking of the alternatives. To demonstrate the potential application of the proposed approach, it is examined for development of Hendourabi Island (Iran) for tourism. Results show that among the three development alternative plans, decision-makers prefer the medium-size development alternative, since it offers a balance between benefits of tourism market and costs of project development under an uncertain future. It also allows for adaptive management. Results also showed that the proposed approach which reduces loss regret in decision-making under uncertain future can be used effectively for planning the island development under an uncertain dynamic future considering the risk and uncertainty associated with human judgment.Sat, 21 Dec 2019 20:30:00 +0100Comparison of Static Pushover Analysis and IDA-Based Probabilistic Methods in Assessing the ...
http://scientiairanica.sharif.edu/article_21692_0.html
This study attempts to reliably quantify the seismic response parameters of the steel diagrid structural systems. In that regard, in addition to the conventional static pushover analysis (SPA), the dynamic pushover analysis (DPA) based on the incremental dynamic analysis (IDA) technique is also considered. FEMA P-695 recommends a methodology for establishing seismic performance factors (SPFs). The present study tries to propose a simpler framework for estimating and validating SPFs while applying the concepts of FEMA P-695 guideline. The results show that the R-factors obtained with the SPA procedure for steel diagrid systems are conservative and the IDA-based probabilistic method gives a more rational value for the R coefficient. Furthermore, the proposed simplified method has good agreement with FEMA P-695 in predicting the collapse capacity of diagrid models.Sat, 21 Dec 2019 20:30:00 +0100Tunable Active Grounded Lossless and Lossy Inductance Simulators with Single Grounded Capacitor ...
http://scientiairanica.sharif.edu/article_21694_0.html
In this paper, three active-C synthetic grounded inductance simulator circuits are presented, which realize tunable lossless and lossy series and parallel RL-type inductances. Each of which employs two voltage differencing buffered amplifiers (VDBAs) as active components, and a single grounded capacitor as a passive component. In all the proposed circuits, the simulated equivalent resistance and inductance values can be adjusted electronically through the transconductance gains of the VDBAs. They also do not require any critical component matching conditions and cancellation constraints. Detail non-ideal analysis including transfer errors of the VDBA has been analyzed. For circuit performance verification and comparison, some application examples are given together with computer simulation results by PSPICE program.Sun, 22 Dec 2019 20:30:00 +0100Multi-criteria group decision-making method based on generalized power harmonic aggregation ...
http://scientiairanica.sharif.edu/article_21695_0.html
Normal intuitionistic fuzzy number (NIFN), which is introduced based on intuitionistic fuzzy sets and normal fuzzy numbers, is a useful tool for presenting uncertain information under complicated situations. This study focuses on the development of an effective method by combining NIFNs with the power average and harmonic mean operators to address multi-criteria group decision-making (MCGDM) problems, wherein weight information is completely unknown. First, an effective ranking method for NIFNs is provided in view of defects of the existing comparison method of NIFNs. Subsequently, three normal intuitionistic generalized power harmonic aggregation operators are proposed based on the operations of NIFNs. Next, a new MCGDM method is developed. Finally, a numerical example concerning coal mine safety evaluation is provided for demonstration. The feasibility and validity of the proposed method are further verified by sensitivity analysis and comparison with other existing methods.Sun, 22 Dec 2019 20:30:00 +0100Estimating Prevalence of Sensitive Attribute with Optional Unrelated Question Randomized ...
http://scientiairanica.sharif.edu/article_21696_0.html
In this study, we propose optional randomized response technique (RRT) models in binary response situation. The utility of proposed optional RRT models under stratification are also explored. Gupta et al.cite{Singh} introduced an ingenious idea of optional RRT model, that a question may be sensitive for one respondent but may not be sensitive for another. This study focus on estimating $ pi $, the prevalence of sensitive attribute, $ omega $, the sensitivity level of the underlying sensitive question when the proportion of unrelated innocuous attribute $ pi_{{x}} $ is unknown. A new multi-question approach are proposed and used for estimation of parameters $ (pi,omega) $. A comparison between proposed optional RRT models and corresponding full RRT models are carried out numerically under simple and stratified random sampling.Sun, 22 Dec 2019 20:30:00 +0100Electricity Market Assessment in Wind Energy Integrated Power Systems with the Potential of ...
http://scientiairanica.sharif.edu/article_21697_0.html
This paper focuses on a dynamic equilibrium considering the flexible ramp market and demand response resources. With ever-swelling installation of variable renewable energies, demand response programs can play an important role in mitigating the system ramping deficiency. Hence in this paper, the ramping capability of demand response resources in procuring system ramp requirement is considered. The strategic behavior of different players is modeled through a multi-leader-common-follower game, in which suppliers and demand response aggregators are laid as the leaders and market operator is considered as the single follower of the game. In addition, a dynamic forward rolling process to find equilibria at the real-time market is proposed. The effect of considering demand response resources and flexible ramp penalty price on the strategic behavior of players in equilibrium is evaluated. Finally, the effectiveness of the proposed approach is verified on a three-firm system. While revealing demand response resources roles in mitigating ramping deficiency, the results show that how penalty price on flexible ramp violation can lead uplift payments to be formed.Sun, 22 Dec 2019 20:30:00 +0100Metaheuristics for A New MINLP Model with reduced response time for On-line Order Batching
http://scientiairanica.sharif.edu/article_21698_0.html
With increase in the inventory of stored items and in the number of orders received, the picking process and the response time gain greater importance. It should be noted that, in order to enhance the efficiency of warehouse management system, effective correlation and coordination between order batching and order picking process is of crucial role. In this paper, novel mixed integer nonlinear programming for on-line order batching is proposed for improving performance of the warehouse which in turn results in reducing the response time and idle times. The proposed method is based on a blocked warehouse using a zoning system, which is called Online Order Batching in Blocked Warehouse with One Picker for each Block (OOBBWOPB). The mentioned model is solved by using two algorithm of artificial bee colony (ABC) and Ant-colony (ACO). For proving the analyses and claims, two numerical examples as cases 1 and 2 are defined and analyzed by this algorithms in MATLAB environment. Based on the results, the proposed warehouse shows better performance with a substantial reduction in the average response time of a set of customer orders compare to zhang et al. (2017) results. It’s noteworthy that the ACO yields better results than ABC.Sat, 28 Dec 2019 20:30:00 +0100An integrated fuzzy QFD-MCDM framework for personnel selection problem
http://scientiairanica.sharif.edu/article_21699_0.html
In today’s competitive and high technology world, companies are forced to differentiate themselves with continuous improvement. They need creative, well-educated and self-confident human resource more than ever. Hiring the right person to the right job plays a significant role on firm’s growth. The goal of this paper is to propose a systematic approach for personnel selection problem (PSP) of a textile company in Turkey by considering various performance requirements and criteria. The proposed framework consists of three phases. Initially, Fuzzy Decision Making Trial and Evaluation Laboratory (DEMATEL) method is used for weighting social criteria. Then, weights of technical requirements are calculated by applying Fuzzy Quality Function Deployment (QFD) method allowing to evaluate the interrelationships and correlation of social and technical criteria. Finally, Fuzzy Grey Relational Analysis (GRA) method has been applied to rank the alternatives by considering criteria scores acquired in the previous phase. The method has been illustrated by a case study and compared to the current approach used in the company. The results indicate that this proposed approach can deal with the PSP effectively and help companies to establish a systematic and unbiased way for the problem.Sat, 28 Dec 2019 20:30:00 +0100Preparation of Pt-ZSM-5 zeolite membrane catalysts for isomerization of linear alkane
http://scientiairanica.sharif.edu/article_21700_0.html
A ZSM-5 supported membrane was synthesized by secondary growth method. The Pt-ZSM5 membrane was prepared by impregnation method. The membrane was characterized by single gas permeation step at room temperature. The isomerization of n-pentane was chosen as a probe reaction for evaluating the catalytic performance of the membrane. In particular, the effect of the space velocity and the time on stream were considered. After the catalytic tests, the membrane was characterized by SEM, EDX and XRD. N2 permeance for the membrane, after calcination, was equal to 2.9 × 10-7 mol/m2.s.Pa indicating a coverage of the larger support pores by the zeolite crystals. This results was also confirmed by the SEM investigation. In addition, XRD analysis showed as the ZSM-5 was the desired zeolite-type. During the catalytic tests, it was observed a decrease of the nC5 conversion and an increase of the iC5 selectivity with WHSV. The nC5 conversion was decreased from 2.5 to less than 0.5, with an enhancement in weight hourly space velocity (WHSV), while the selectivity increases from 30 to over 70. On the other hand, it's conversion on catalyst enhanced from 10% to approximately 38%, with an increase in the reaction temperature from 250 to 450°C.Sat, 28 Dec 2019 20:30:00 +0100Measuring congestion in data envelopment analysis without solving any models
http://scientiairanica.sharif.edu/article_21701_0.html
One of the important topics in Data Envelopment Analysis is congestion. Many scholars research in this field and represent their methods. In most of the represented methods, we have to solve lots of models or its used for a special aim like negative data, integer data, different Production Possibility Set and etc. Here we represent our method that measures the congestion without solving a model. It can be used for different Production Possibility Set (different technology) like T_{New} and FDH; different data like negative data and integer data. Also, we can distinguish strongly or weakly congestion of Decision Making Unit. Furthermore, each DMU has congestion, efficient and inefficient, we can measure it by this method. Finally, we represent some numerical example of our purpose method and compare our method with other methods then show the results in tables.Sat, 28 Dec 2019 20:30:00 +0100Numerical Simulation of a Neuron under Blast Load Using Viscoelastic Material Models
http://scientiairanica.sharif.edu/article_21702_0.html
Traumatic brain injury is caused by physical brain injury. A computational model for considering the response of a neuronal cell under blast loading is presented. The neuronal cell consists of four components including the nucleus, cytoplasm, membrane, and also the network of microtubules with different arrays including crossing, stellate as well as random orientations. The effect of the sub-cellular components, specifically the network of microtubules, on a Traumatic Brain Injury’s consequences was studied as a novel and state-of-the-art innovation. Nucleus, cytoplasm, and membrane are assumed viscoelastic, while the network of microtubules follows elastic behavior. Finite element methods and fluid-structure interactions are considered to solve the coupled equations of the solid and the fluid. The results show that the presence of a network of microtubules, regardless of the types of arrays, reduces the total displacement of the cell as well as the von Mises stress. The membrane von Mises stress decreases 50 percent from 30 to 15 Pascal in presence of the network of the microtubules. Results of this research could be used in different fields including treatment of some diseases and pathological conditions such as kidney stones, sports injuries, traumatic astronauts, and ultimately prevention and treatment of traumatic brain injuries.Sat, 28 Dec 2019 20:30:00 +0100Performance Evaluation in Aggregate Production Planning Using Integrated RED-SWARA Method under ...
http://scientiairanica.sharif.edu/article_21714_0.html
It is widely felt that the performance evaluation in aggregate production planning provides a theoretical and practical overview. The present study aimed to evaluate the performance in the aggregate production planning. In this regard, the optimal values were determined by the multi-objective grey aggregate production planning model and the weights of the input and output indicators of the performance evaluation were characterized by the step-wise weight assessment ratio analysis (SWARA) technique. Further, the efficiency of the decision-making units was determined by the ratio efficiency dominance (RED) model. Then, the ranking of decision-making units was conducted. In the case study of automobile parts manufacturing industry in Iran, the sensitivity analysis was performed on the model and its effects were evaluated, in addition to evaluating the proposed model. The results indicated that the proposed model had a high degree of accuracy in evaluating performance compared to previous models and helps managers to make better decisions to increase the efficiency and reduce the waste of resources.Fri, 03 Jan 2020 20:30:00 +0100Forecasting and making policies for Postal Services: system dynamics approach (Iran Post ...
http://scientiairanica.sharif.edu/article_21715_0.html
The main activity in postal services is to deliver letter mails and parcels. By changing customers’ needs and behaviors along with emerging new technologies, postal services have to be renovated. Thus, understanding the changing environment, forecasting the performance, identifying key drivers, and making effective interventions are critical for any further actions. Performing these actions for Iran Post Company is the focus of this paper. Therefore, system dynamic approach is chosen, effective variables are determined and causal-loop diagram (CLD) and stock and flow diagram (SFD) are developed. The results are then validated using expert panels and historical data and the developed model is utilized for policy making. Therefore, two scenarios are designed based on changes in postal rates, quality of services and e-service market share. These scenarios could provide CEOs with critical information to make effective interventions.Fri, 03 Jan 2020 20:30:00 +0100Macrophage+: a Game With a Purpose for Applying Human Intelligence in Control Mechanisms
http://scientiairanica.sharif.edu/article_21719_0.html
Originally, control mechanisms were proposed to replace the need for human intervention in operational environments, and thus, enhance the precision and reaction time. Nowadays, new requirements in computer systems such as adaptation have made the design of control mechanisms more challenging. The Observer/Controller pattern is one of the control mechanisms proposed to control many interacting independent elements by making intelligent decisions. An important challenge in designing these mechanisms is that the knowledge needed for decision making is provided by experts; therefore, the process becomes time consuming and costly, depending on the availability of experts and their costs. In this paper, we hypothesize that employing a Game With A Purpose can help to improve the process of providing knowledge in such control mechanisms by using crowd-sourcing and involving non-expert humans in an enjoyable manner. This hypothesis has been investigated by Macrophage+, a Game With A Purpose implemented for this goal. We conducted experiments evaluating Macrophage+, focusing on both its applicability and effectiveness in the context of the observer/controller pattern as well as its enjoyability for the players. The results show that Macrophage+ is a successful Game With A Purpose that involves non-expert humans in the application of the observer/controller pattern.Sat, 11 Jan 2020 20:30:00 +0100Comparison of disparate solid volume fraction ratio of hybrid nanofluids flow over a permeable ...
http://scientiairanica.sharif.edu/article_21720_0.html
Over the past decade preparation, characterization and modeling of nanofluids plentifully deliberated to improve the heat transfer effects. Hence to gratify the advancements this paper focuses on heat transfer effects of three distinct hybrid nanoparticles and with a base fluid (water). So this work numerically investigated the influence over a permeable flat surface with aligned magnetic field in the presence of suction or injection or impermeable together with the Marangoni convection of different hybrid nanofluids. The present results are validated with previous experimental and numerical results. The effect of solid volume fraction of hybrid nanoparticles, angle of inclination, magnetic parameter and wall mass transfer parameter are deliberated and offered through graphs together with the surface velocity and rate of heat transfer is presented in tabular form. It is found that the rate of heat transfer is increased with an increment of wall mass transfer parameter and an opposite effect of the rising of magnetic parameter. Among the three hybrid nanofluids water hybrid nanofluid has higher surface velocity, water hybrid nanofluid has higher temperature profile and water hybrid nanofluid has higher heat transfer rate.Sat, 11 Jan 2020 20:30:00 +0100Kinetic study of acetone acidic oxidation with KMnO4 in the absence and presence of ...
http://scientiairanica.sharif.edu/article_21721_0.html
The kinetic studies for acetone acidic oxidation with potassium permanganate in the absence and presence of CuO based nanocatalysts were carried out. The rate law and activation energy as kinetic parameters were evaluated for reaction with no catalyst and with 0, 2.5, 5 and 10 weight percentages of CuO on γ-Al2O3. Catalysts were prepared with impregnation method and were characterized using ICP-OES, XRD, BET, and TEM techniques. Products were analyzed with UV-VIS technique and examinations were performed with changing in concentration of a reactant and keeping constant the others to determine the order of the reaction for targeted one. Results showed that in the absence and presence of nano-catalysts, the order of reaction for all KMnO4, (CH3)2CO and H2SO4 were one. The rate constants for the reaction in the absence of catalyst and the presence of 0, 2.5, 5 and 10 wt% CuO were 0.0022, 0.0023, 0.0025, 0.0026 and 0.0029 L2.mole-2.min-1 as well as the relationship between the rate constants and temperature was investigated for each experiment and the activation energies for them were 56.767, 56.807, 53.978, 50.075 and, 46.774 kJ.mol-1, respectively. Also it was demonstrated that there was no relationship between the products concentrations and the rate of reaction.Sat, 11 Jan 2020 20:30:00 +0100Solving a new bi-objective model for relief logistics in a humanitarian supply chain by ...
http://scientiairanica.sharif.edu/article_21722_0.html
One of the most important factors in a humanitarian supply chain during a disaster is to respond quickly and efficiently. Delivering emergency commodities to the affected areas is critical in reducing consequences. Moreover, transferring the injured people through the fastest and the shortest time by using all available resources is vitally important. To this aim, a multi-echelon, multi-objective forward and backward relief network is proposed that considers the location of hospitals, local warehouses and hybrid centers, which are hospital-warehouse centers in the pre-disaster phase. In the post-disaster phase, the routing of relief commodities is considered in the forward route. In the backward route some vehicles that can transfer injured people after delivering commodities; hybrid transportation facilities; will take injured to hospitals and hybrid centers. According to the degree of hardness, a hybrid non-dominated sorting genetic algorithm (NSGA-II) with simulated annealing (SA) and variable neighborhood search (VNS) algorithms is proposed to solve the given problems. The results of this hybrid algorithm are compared with NSGA-II and multi-objective SA-VNS using five metrics (i.e., a number of Pareto, mean ideal distance, spacing, diversity and time) in order to emphasize that the proposed hybrid algorithm outperforms the two foregoing algorithmsSat, 11 Jan 2020 20:30:00 +0100N-(2-Pyridylmethyl)-L-Histidine Functionalized Fe3O4 Magnetic Nanoparticles, as an Efficient ...
http://scientiairanica.sharif.edu/article_21723_0.html
N-(2-Pyridylmethyl)-L-histidine functionalized Fe3O4 magnetic nanoparticles (PMHis@Fe3O4 MNPs) efficiently catalyzed three-component Mannich-type reaction of ketones, aromatic aldehydes and anilines, to synthesize β-amino ketones in good to high yields. Mannich adducts were obtained in moderate to high diastereoselectivity, favoring anti isomer. The imidazole moiety of PMHis residue on catalyst plays an important role in the diastereoselectivity. PMHis@Fe3O4 MNPs were prepared via simple coprecipitation from an aqueous solution of Fe2+ and Fe3+ ions using NH4OH in the presence of L-histidine, followed by reductive amination with 2-pyridine carbaldehyde in the presence of NaBH4. Obtained PMHis@Fe3O4 MNPs were characterized by FT-IR, XRD, VSM, BET, TGA, SEM, EDX and TEM analysis.Sat, 11 Jan 2020 20:30:00 +0100Design of optimum vibration absorbers for a bus vehicle to suppress unwanted vibrations against ...
http://scientiairanica.sharif.edu/article_21724_0.html
Unwanted vibrations of the vehicles are regarded as harmful threats to the human health from various biomechanical and psychophysical aspects. Road roughness has been considered as the main cause of unwanted vibrations in bus vehicles. Vertical seat vibrations have been found via simulation of a ten degree of freedom (10-DOF) model of an intercity bus vehicle under harmonic and random excitations caused by road roughness. To suppress undesirable vibrations, mass-spring-damper passive absorbers are proposed in a thirteen degrees of freedom (13-DOFs) model of the bus. By optimizing the characteristics of the embedded passive absorbers under each seat, and implementation of the designed absorbers, it is observed that the vertical displacement amplitudes in the frequency response of the seats are reduced especially near the bus resonance frequencies. In addition, the vertical displacement and acceleration amplitudes are decreased in the random excitation of the road roughness. According to the results, optimized mass-spring-damper absorbers are suggested as a practical solution to suppress the unwanted vibration effects in the bus vehicle.Sat, 11 Jan 2020 20:30:00 +0100Prediction of discharge flow rate beneath sheet piles using gene expression programming based ...
http://scientiairanica.sharif.edu/article_21725_0.html
Sheet piles are of general water retaining structures. The discharge flow rate beneath sheet plies is an important parameter in the design of these structures. In this study, the Gene Expression Programming (GEP) as an Artificial Intelligence (AI) method is used for developing a model to predict the discharge flow rate. The input parameters include the sheet pile height, upstream head and hydraulic conductivity anisotropy ratio. In order to achieve better performance, the flow rate is normalized and selected as an output of the model. A database including 1000 cases are created from the Scaled Boundary Finite Element Method (SBFEM) for the seepage beneath sheet plies is employed to develop the model. The GEP-based model predictions demonstrate a reasonable agreement with the simulated data, which indicates the efficiency of the developed model. The results of the sensitivity analysis indicate that the upstream head is the most influential parameter in the discharge flow rate beneath the sheet piles. Furthermore, the outputs of the parametric analysis show the reasonable performance of the model in the prediction of normalized discharge flow rate.Sat, 11 Jan 2020 20:30:00 +0100Sensitivity Analysis and Optimization of the surface Roughness in the Incremental Forming of ...
http://scientiairanica.sharif.edu/article_21726_0.html
Flexibility and simple tooling make the incremental sheet forming (ISF) a great process to create complex shapes from mild steel sheets. It is a significant issue to reduce the surface roughness (SR) which is a weakness in the manufacturing the mild steel parts in ISF process. The purpose of this study is to investigate the effects of the ISF process parameters on the SR of the mild steel sheets. Feed rate, tool diameter, vertical step and spindle speed are chosen as four input variables in the experimental tests. Taguchi design of experiment (DOE) and the analysis of variance (ANVOA) are used to optimize the SR by investigating the parameters effects and their interactions. According to the obtained results, the vertical step reduction and increase in tool diameter, decrease the roughness on the surface of the mild steel sheets during the single-point incremental forming (SPIF). In addition, the tool speed in term of both rotation and feed have little effect on the surface roughness. The results of a validation test demonstrates that the Taguchi technique and the ANOVA can effectively optimize the level of each variable to ensure the best SR.Sun, 12 Jan 2020 20:30:00 +0100Cooperative cellular manufacturing system: a cooperative game theory approach
http://scientiairanica.sharif.edu/article_21727_0.html
In the cellular industry, the components of products are increasingly being manufactured by multiple companies, which are distributed across different regions resulting in increased production costs. Here, a cooperative cellular manufacturing system is introduced to decrease these costs. A mathematical programming model has been proposed, which evaluates the production cost when companies work independently and the model is then extended to consider coalitional conditions in which the companies cooperate as an integrated cell formation system. A key question that arises in this scenario is how to arrange the cells and machines of multiple companies when their cell formation systems are designed cooperatively. Through a realistic case study of three high-tech suppliers of the Mega Motor Company, we show that these companies can reduce the costs through a cooperative cellular manufacturing system. We then compute the cost saving of each coalition of companies obtained from cooperation to get a fair allocation of the cost savings among the cooperating firms. Four cooperative game theory methods including Shapley value, τ -value, core-center, and least core are proposed to examine fair sharing of cost saving. A comprehensive analysis of the case study reveals important managerial insights.Fri, 17 Jan 2020 20:30:00 +0100Product Acceptance Determination by Two Suppliers with Linear Profiles
http://scientiairanica.sharif.edu/article_21728_0.html
In the management of suppliers, it is an important task to compare the performance of two suppliers using the linear profiles. In this paper, the product acceptance determination procedure is designed using a EWMA statistic based on the process-yield index applied to the linear profiles of two suppliers. The design parameters of the proposed plan are determined to satisfy both the producer’s and consumer’s risks. The efficiency of the proposed sampling plan is compared with the sampling plan developed based on the Wang’s test statistic in terms of the sample size required for the selection of a better supplier. A real example is given to explain the proposed sampling plan.Fri, 17 Jan 2020 20:30:00 +0100Multi-echelon green open-location-routing problem: A robust-based stochastic optimization approach
http://scientiairanica.sharif.edu/article_21729_0.html
In recent years, considering the environmental competencies could help the companies/countries to successfully improve their industries regarding the sustainable development. In this study, a green open location-routing problem with simultaneous pickup and delivery (GOLRPSPD) is considered to minimize the overall costs. In addition to cost minimization, the objective function is provided the environmental competencies regarding the costs of CO2 emissions and fuel consumption. Meanwhile, in complex situation, considering the precise information could lead the results to unreliable in which considering the uncertainty theories could prevent the data loss. In this respect, this study considered the pickup and delivery demand and the travel time as probabilistic parameters. To address the issue, a robust stochastic programming approach is developed to decrease the deviations of imprecise information. Moreover, the proposed approach is implemented based on five scenarios to decide the best decision in different situations. In addition, a practical example about the multi-echelon open-location-routing model is provided to represent the feasibility and applicability of the presented robust stochastic programming approach. Finally, a comparative and sensitivity analysis is considered to indicate the validity of the proposed approach, and also represent the robustness and sensitiveness of the obtained results regarding some significant parameters, respectively.Fri, 17 Jan 2020 20:30:00 +0100Numerical simulation of turbulent oscillating flow in porous media
http://scientiairanica.sharif.edu/article_21730_0.html
Two macroscopic turbulent models, P-dL and N-K, have been proposed in recent years for simulating turbulent unidirectional flow in porous media. In this paper a modification on N-K model has been proposed for turbulent oscillating flow in porous media. To this purpose, Turbulent oscillating flow in porous media has been simulated in microscale employing a periodic array. The k-ε model was applied to solve turbulent oscillating flow in periodic array. Control volume approach has been used to discretize Navier-Stokes and k-ε equations and the well-established SIMPLE method has been conducted to deal with pressure and velocity coupling. To modify N-K model the effect of different parameters such as frequency and Reynolds number has been investigated and the constants in source terms of turbulent kinetic energy and its dissipation rate has been modified versus Re according to microscale results. In order to validate the new modified constants, the modified N-K model was applied to turbulent oscillating flow in porous media and results were compared to original N-K macroscopic model.Fri, 17 Jan 2020 20:30:00 +0100A simplified analytical model to predict heating performance of single U-tube ground heat exchangers
http://scientiairanica.sharif.edu/article_21731_0.html
In underground U-tube heat exchangers (boreholes) it is important to predict its heating performance to design and select the proper parameters such as length, diameter, material etc. to have an optimized borehole from the point of view of heat capacity and economical aspects. For this reason, having trusty equations is vital to foresee borehole heating performance and applying it in design issues. In this study a single vertical U-tube borehole with constant wall temperature is considered and analytical equations for temperature distribution in the surrounding ground around the borehole is evaluated based on one and two dimensional heat conduction respectively. The analytical equation is compared to experimental data for a borehole with 50 m depth in which warm water of 40 C is pumped into it a time period of 120 hours and the heat transfer rate per unit length is recorded. The comparison between analytical expression and experimental data shows a good agreement between them. Also the borehole entropy generation number is studied and the optimized parameters are evaluated to minimize it. It is concluded that for the considered borehole, entropy generation number is decreased by increasing its length and by decreasing the borehole radius and pipe outer radius.Fri, 17 Jan 2020 20:30:00 +0100Measuring skewness: we don’t assume much
http://scientiairanica.sharif.edu/article_21733_0.html
Skewness plays a vital role in different engineering phenomena so it is desired to measure this characteristic accurately. Several measures to quantify the extent of skewness in distributions have been developed over the course of history but each measure has some serious limitations. Therefore, in this article, we propose a new skewness measuring functional, based on distribution function evaluated at mean with minimal assumptions and limitations. Four well recognized properties for an appropriate measure of skewness are verified and demonstrated for the new measure. Comparisons with the conventional moment-based measure are carried out by employing both functionals over range of distributions available in literature. Furthermore, the robustness of the proposed measure against unusual data points is explored through the application of influence function. The Mathematical findings are verified through meticulous simulation studies and further verified by real data sets coming from diverse fields of inquiries. It is witnessed that the suggested measure passes all the checks with distinction while comparing to the classical moment-based measure. Based on computational simplicity, applicability in more general environment and preservation of c-ordering of distribution, it may be considered as an attractive addition to the family of skewness measures.Mon, 27 Jan 2020 20:30:00 +0100Two-stage game-theoretic approach to supplier evaluation, selection and order assignment
http://scientiairanica.sharif.edu/article_21734_0.html
This study proposes a framework for supplier evaluation, selection, and assignment that incorporates a two-stage game-theoretic approach method. The objective is to provide insights to manufacturers in choosing suitable suppliers for different manufacturing processes. The framework applies to the decision logic of multiple manufacturing processes. In the first stage, a non-cooperative game model is utilized for supplier evaluation and selection. The interactive behaviors between a manufacturer and some supplier candidates are modeled and analyzed so that the supplier evaluation value (SEV) can be obtained using the Nash equilibrium. In the second stage, the supplier evaluation values become the input for the Shepley values calculation of each supplier under a cooperative game model. The Shapley values are utilized to create a set of limited supplier allocation. This paper provides managerial insights to verify the proposed approach on supplier selection and allocation. Thus enables SCM manager to optimize supplier evaluation, selection, and order assignment.Sat, 08 Feb 2020 20:30:00 +0100Investigation of Harmonic Effects in Locational Marginal Pricing and Developing a Framework for ...
http://scientiairanica.sharif.edu/article_21735_0.html
Locational Marginal Pricing (LMP) is arguably the most effective and commonly employed mechanism to provide the most reliable economic signal to market participants. Meanwhile, nodal prices depend on active power losses and transmission congestion which may be affected by harmonics pollution. In the conventional method, power system and loads are assumed linear and nodal prices are obtained by results of optimal power flow (OPF) at the power frequency. Harmonics lead to skin effect and increasing loss. Further, harmonic flowing in branches in a power network occupies transmission capacity. For providing more accurate signals to market participants and achieving more accurate nodal prices, harmonic effects on LMP are investigated and a framework is developed for LMP calculation in a harmonic polluted power system. In this framework, skin effect, losses, and congestion which can be arisen by harmonic pollution are modelled in optimal power flow (OPF) and are considered in LMP calculation. The proposed concept is implemented with 9-bus and 30-bus test systems while nodal price changes are also indicated.Sat, 08 Feb 2020 20:30:00 +0100Wardrop’s First Principle: Extension for Capacitated Networks
http://scientiairanica.sharif.edu/article_21736_0.html
In transportation literature, User Equilibrium (UE) has been widely studied since early 1950’s, many studies of which define equilibrium flow of traffic for uncapacitated networks based on Wardrop’s first principle, implying also a Nash Equilibrium (NE). Although, in general, the two equilibria (UE and NE) are not explicitly the same, they are shown to be equivalent under special conditions, for uncapacitated UE, when volume-delay functions are separable, continuous, non-decreasing and non-negative.
A good deal of research is devoted to explain UE in capacitated networks based on Wardrop’s first principle and the concept of generalized costs. However, UE for capacitated networks, even under the defined special conditions, is not equivalent to NE. This paper extends Wardrop’s first principle to explain UE in capacitated networks, which, under the same special conditions of uncapacitated networks, would represent an NE as well. Moreover, a complementarity equilibrium model is proposed for UE, based on an extension of Wardrop’s principle.Tue, 11 Feb 2020 20:30:00 +0100Flexural Retrofitting of the Damaged Reinforced Concrete Beams by Using HPFRCC
http://scientiairanica.sharif.edu/article_21737_0.html
Damaged structures are not usually reliable to tolerate designed loads and therefor, need to retrofit in structural parts. The main purpose of this paper is to utilize HPFRCC as a high-performance material to recover the damaged beams and improve their ductility and moment capacity with experimental approaches. In addition to, a retrofitting method is presented using high-performance fibre reinforced cement-based composite (HPFRCC). The experimental study is performed on three simply supported beams with the same dimension, materials, and reinforcement configuration. The first beam, which is known as the reference beam (RC), is subjected to pure bending condition till its failure and the others are prone to a certain amount of load according to the final capacity of the first beam. Thereafter, two damaged beams are retrofitted using HPFRCC in the created grooves on tensile surface of the beam and finally these retrofitted beams are loaded to determine the bending behaviour. Experimental Results demonstrate that retrofitting can improve the first crack strength, load at yield condition, and maximum load capacity. Also, the proposed method increases the ductility and energy absorption of retrofitted beams.Tue, 11 Feb 2020 20:30:00 +0100Bridge backwater estimation: A Comparison between artificial intelligence models and explicit ...
http://scientiairanica.sharif.edu/article_21738_0.html
Estimation of bridge backwater has been one of practical challenges in hydraulic engineering for decades. In this study, Genetic Programming (GP) has been applied for estimating bridge backwater for the first time based on the conducted literature review. Furthermore, two new explicit equations are developed for predicting bridge afflux using Genetic Algorithm (GA) and hybrid MHBMO-GRG algorithm. The performances of these models are compared with Artificial Neural Network (ANN) and several explicit equations available in the literature considering both laboratory and field data. Based on five considered performance evaluation criteria, the two new explicit equations outperform the ones available in the literature. Furthermore, GP and ANN achieve the best results in favor of four out of five considered criteria for train and test data, respectively. To be more specific, ANN improves the MSE and R2 values of the explicit equation developed using GA by 44% and 12% for the test data while GP enhances the corresponding values by 62% and 9% for the train data. Finally, the results demonstrate that not only artificial intelligence models considerably improve bridge afflux estimation than the explicit equations but also the suggested equations significantly improve the accuracy of the available explicit ones.Tue, 11 Feb 2020 20:30:00 +0100Life-Cycle Cost Analysis (LCCA) of RC Bridges Subjected to Multiple Hazards
http://scientiairanica.sharif.edu/article_21739_0.html
The main structural elements of reinforced concrete (RC) bridges deteriorate with time under such uncertain hazards as scouring and corrosive conditions. In this paper, a multi-hazard framework is proposed to assess the performance of bridges subjected to the main effective uncertain natural hazards during their lifetime. In this assessment, the uncertainties associated with the combined effects of multiple hazards including pier scour, earthquake, carbonation, and corrosion are considered. Therefore, for each of the hazards, their severity relationships have been extracted over time, and the effects of these hazards on concrete elements are presented as resistance dimming parameters. The annual and cumulative losses due to these hazards in unit currency are estimated using the life-cycle costs. For decision making, the present value of the expected cumulative cost associated with the retrofit or design scenarios is evaluated using a cost-benefit analysis. The results for a case study bridge, using the proposed framework, indicate the significant impact of the different scenarios on reducing the expected value of damages or incurred losses due to multiple hazards.Tue, 11 Feb 2020 20:30:00 +0100Dispersion of Stoneley waves through the irregular common interface of two hydrostatic stressed ...
http://scientiairanica.sharif.edu/article_21740_0.html
The present work deals with the mathematical inspection of Stoneley wave propagation through the corrugated irregular common interface of two dissimilar magneto-elastic transversely isotropic (MTI) half-space media under the impression of hydrostatic stresses. For the enumeration of the Lorentz’s force besmeared in the structure, generalized Ohm’s law and Maxwell’s equation have been considered. The interior deformations are calculated analytically to obtain the wave frequency equation using prescribed boundary conditions. To investigate the impacts of irregularity and various affecting parameters such as magnetic couplings and hydrostatic stresses on the wave propagation, frequency curves are framed-up for the phase velocity of the wave.Tue, 11 Feb 2020 20:30:00 +0100Multiple attribute decision making based on Muirhead mean operators under 2-tuple linguistic ...
http://scientiairanica.sharif.edu/article_21744_0.html
In this paper, we expand the Muirhead mean (MM) operator and dual MM (DMM) operator with 2-tuple linguistic Pythagorean fuzzy numbers (2TLPFNs) to propose the 2-tuple linguistic Pythagorean fuzzy MM (2TLPFMM) operator, 2-tuple linguistic Pythagorean fuzzy weighted MM (2TLPFWMM) operator, 2-tuple linguistic Pythagorean fuzzy DMM (2TLPFDMM) operator and 2-tuple linguistic Pythagorean fuzzy weighted DMM (2TLPFNWDMM) operator. Based on the proposed operators and built models, two methods are developed to solve the MADM problems with 2TLPFNs and the validity and advantages of the proposed method are analyzed by comparison with some existing approaches. The method proposed in this paper can effectively handle the MADM problems in which the attribute information is expressed by 2TLPFNs, the attributes’ weights are completely known, and the attributes are interactive. Finally, an example for green supplier selection is used to show the proposed methods.Tue, 18 Feb 2020 20:30:00 +0100A novel fuzzy bi-objective vehicle routing and scheduling problem with time window constraint ...
http://scientiairanica.sharif.edu/article_21745_0.html
In the process of hazardous material transportation, the risk is a significant factor that should be considered due to the potential severe consequence of an incident. Regardless of risks, time is a paramount concern that should be considered in hazardous material transportation. In this way, this paper introduces a bi-objective model for a vehicle routing and scheduling problem of hazardous material distribution problems under the fuzzy condition to minimize both total distribution time and risks. In the proposed model, the fuzzy inference system and fuzzy failure mode and effects analysis are applied to identify and calculate the high-level risks instead of the previous simple methods for the first time. Moreover, Jimenez method and fuzzy goal programming are respectively utilized to convert the fuzzy bi-objective model into the same crisp and single-objective one. Besides, to cope with the NP-hardness of the large-sized problems, two meta-heuristic algorithms namely invasive weeds optimization and genetic algorithm is used, and several sensitivity analyses are performed to prove the efficiency of the proposed approach. The performance of the proposed algorithms is also assessed through a comparative study. Finally, the proposed model is implemented to a real case study to prove the validity of the model.Tue, 18 Feb 2020 20:30:00 +0100A new bi-objective integrated vehicle transportation model considering simultaneous pick-up and ...
http://scientiairanica.sharif.edu/article_21746_0.html
Nowadays, global competition causes that the companies are dealing with the issue of cost reduction besides increasing productivity in business network more than ever. Because of that, today, both researchers and industrial practitioners are focusing on the supply chain network issues. In order to achieve the real word objectives, we attempt to improve the efficiency of a supply chain via not only considering simultaneous pick up and split delivery but also minimizing the total costs and maximizing the customer service in the form of multi-products and multi-period. In addition, to accumulate the data of parameters, a case study in a food industry in the north of Iran has been utilized. Eventually, the proposed mixed-integer linear programming model is addressed by a ε-constraint approach. Finally, related results of this solution are analyzed and also is compared with simple VRP.Tue, 18 Feb 2020 20:30:00 +0100Decision Tree-based Parametric Analysis of a CNC Turning Process
http://scientiairanica.sharif.edu/article_21747_0.html
Computer numerical control (CNC) is a manufacturing concept where machine tools are automated to perform some predefined functions based on the instructions fed to them. CNC turning processes have found wide ranging applications in modern day manufacturing industries due to their capabilities to produce low cost high quality parts/components with very close dimensional tolerances. In order to exploit the fullest potential of a CNC turning process, it should always be operated while setting its different input parameters at their optimal levels. In this paper, two classification tree algorithms, i.e. classification and regression tree (CART) and Chi-squared automatic interaction detection (CHAID) are applied to study the effects of various turning parameters on the responses and identify the best machining conditions for a CNC process. It is perceived that those settings almost match with the observations of the earlier researchers. The CART algorithm outperforms CHAID with respect to higher overall classification accuracy and lower prediction risk.Tue, 18 Feb 2020 20:30:00 +0100Entropy generation analysis in peristaltic flow of magneto-nanoparticles suspended in water ...
http://scientiairanica.sharif.edu/article_21748_0.html
Here consideration is given to the peristalsis of magneto- nanoparticles suspended in water. Explicitly water nanofluid is utilized for two-dimensional flow in a symmetric channel with complaint walls. Uniform magnetic field is applied. Temperature equation is arranged for viscous dissipation. Second order velocity and thermal slip conditions are utilized. Small Grashof number leads to perturbation solution. Examination of entropy generation is also carried out in this study. Maxwell and Hamilton-Crosser models are used. Analysis is based on the comparative study of these two models representing the cylindrical and spherical shaped particles. Graphs for velocity, temperature, entropy generation and Bejan numbers are plotted under the influence of sundry variables. Streamlines are also plotted for the sake of trapping phenomenon.Tue, 18 Feb 2020 20:30:00 +0100Hemodynamic analysis of coronary artery bypass grafting with elastic Walls and different stenosis
http://scientiairanica.sharif.edu/article_21749_0.html
In this study the hemodynamic analysis of complete coronary bypass graft with elastic walls and different percentages of stenosis are investigated numerically. Blood flow is considered Newtonian and unsteady. The objective of this study is to deal with the influence of the wall elasticity, flow pulsatility and stenosis percentage on the flow configuration, Wall Shear Stress (WSS) and rotational flows. By comparing the rigid and elastic wall results of WSS, it is concluded that WSS obtains lower values in toe, heel and bed of the host vessel under the bifurcation in the elastic mode, which is closer to reality. Also it is concluded that with increasing the stenosis percentage, the possibility of occurring rotational flow will increase. The maximum and minimum values of WSS are observed in the stenosis of 70%. From the pulsatility of flow, it is observed that unsteady flow shows more accurate results also velocity and WSS have lower values compared with the steady state results.Tue, 18 Feb 2020 20:30:00 +0100Forecasting Ambient Air Pollutants by Box-Jenkins Stochastic Models in Tehran
http://scientiairanica.sharif.edu/article_21750_0.html
This paper presents a study over the behavior of six air pollutants including PM10, PM2.5, O3, SO2, NO2 and CO in Tehran during a 6-year timespan. In this paper, an iterative procedure based on the univariate Box-Jenkins stochastic models is applied to develop the most effective forecasting model for each air pollutant. Applying a number of widely used criteria, the best model for each air pollutant is selected and the results show that, the proposed models perform accurately and satisfactorily for both fitting and predicting where, the fitted and predicted values are so close to the true values of the related data. Finally, a factor analysis is conducted to investigate the relationships between the air pollutants where the results show that four factors accounts for 93.2704% of the total variance. In this regard, the factor containing PM10 and PM2.5 and the factor containing CO and NO2 are, respectively, the most and the second most affecting factors with proportion of 43.2594% and 21.6500% of total variability. While both factors originate from high number of automobiles which use fossil fuels, decreasing the number of automobiles or increasing the quality of fossil fuels may result in up to 60% improvement in air quality.Fri, 28 Feb 2020 20:30:00 +0100Price and Quality Decisions in Heterogeneous Markets
http://scientiairanica.sharif.edu/article_21751_0.html
This paper analyzes the optimal price and quality decisions of a retailer for its different stores in a heterogeneous market. The consumers are assumed to be heterogeneous in their willingness to pay for quality and are non-uniformly distributed in the market. This type of heterogeneity which is identified based on income disparity can have important implications for a retailer’s optimal policy. The specific objective of this paper is to investigate how the distribution of consumers’ types in the market and their travel costs affect the optimal setting of price and quality levels among different stores of a retailer. Our results express that the geographical disparity of willingness to pay plays a significant role in the differentiation and targeting strategy of a retailer. Comparative analysis shows that the widely adopted assumption of uniform distribution of consumers in the literature leads to non-optimal decisions where the distribution of consumers is non-uniform in a real-world situation.Fri, 28 Feb 2020 20:30:00 +0100Improvement of an acrylic-urethane paint adhesion to PP-EPDM surface by mediated ...
http://scientiairanica.sharif.edu/article_21752_0.html
Adhesion improvement of an acrylic-urethane paint on a bumper surface made from polypropylene/ethylene-propylene-diene monomer was investigated at long term after electrochemical treatment by 2N nitric acid and 0.6M Silver (II)-nitrate /2N nitric acid. The stability of the electrochemically treated samples was examined at different aging times by ATR and SEM. The results were also compared to those of the untreated and flame-treated samples. Accelerated UV weathering analysis along with morphology study by SEM approved the effectiveness of the Ag (II) treatment technique in long term particularly at curvature area of the bumper. For the Ag (II) treated samples, the increase in adhesion strength was sustained even after 650 hours exposure to UV irradiation in wet condition prior to bonding. In addition, the stability of the Ag (II)-treated surface was maintained for at least three months. In case of the flame-treated surface, hydrophobic recovery during aging in environment was found to reduce the polarity of the PP-EPDM surface. The pull-off test showed Ag (II) treatment can enhance adhesion strength of the acrylic-urethane coating on to PP-EPDM in comparison with the flaming method by 20.7%. Moreover the results of zeta potential analysis for Ag (II) treated blend showed a typical acidic surface.Fri, 28 Feb 2020 20:30:00 +0100Evolution of IT, Management and Industrial Engineering research: a topic model approach
http://scientiairanica.sharif.edu/article_21753_0.html
Information Technology (IT), Management and Industrial Engineering are correlated academic disciplines which their publications rose significantly over the last decades. The aim of this study is analyzing the research evolution, determining the important topics and areas and depiction the trend of interdisciplinary topics in these domains. To accomplish this, the text mining techniques are used and the combination of bibliographic analysis and topic modeling approach are applied on their publications in the WOS repository over the last 20 years. In the topic extraction process, a heuristic function was suggested to key extraction, and some new applicable criteria were defined to compare the topics. Moreover, a novel approach was proposed to determine the high-level category for each topic. The results determined the hot-important topics and incremented, decremented and fixed topics are identified. Subsequently, comparing the high-level research areas confirmed the strong scientific relationships between them. This study presents a deep knowledge about internal research evolution of domains and illustrates the effect of topics on each other over the past 20 years. Furthermore, the methodology of this study could be applied to determine the interdisciplinary topics and observe the research evolution of other academic domains.Fri, 28 Feb 2020 20:30:00 +0100Theoretical and experimental investigation of design parameter effects on the slip phenomenon ...
http://scientiairanica.sharif.edu/article_21769_0.html
There are many pieces of research considering slip phenomenon in centrifugal compressors to drive equations for prediction of the slip factor. Inevitably, some simplifications have been imposed on the flow field characteristics and effects of many parameters have been neglected. In this research slip phenomenon is investigated experimentally and numerically in one centrifugal compressor with complex blade curves and splitter blades considering the main effective parameters. Three-dimensional simulation of the compressor viscus flow field with suitable turbulence method was performed using CFD methods. Experimental work was carried out at several rotational speeds and mass flow rates which enabled slip factor results of the compressor as well as, approving accuracy of the simulation results. Effect of main parameters such as rotational speed, mass flow rate, blade number, blade exit angle, diffuser design and tip clearance on slip phenomenon were studied. It was observed that slip factor increases, as rotational speed and flow rate increase. Also changing the blade number from 6 to 9 in constant rotational speed and mass flow rate, caused 27 percent increase in slip factor. For a detailed insight, a variation of performance parameters such as pressure ratio and isentropic efficiency with slip factor were investigated, as well.Tue, 10 Mar 2020 20:30:00 +0100Electrochemical determination of glutathione in hemolysed erythrocytes
http://scientiairanica.sharif.edu/article_21770_0.html
The physiological significance of determining glutathione (GSH) and its oxide form is obvious from their applications in clinical practices such as diagnostic experiments for diabetes, Parkinson’s disease, and cancers. Such an important detemination still needs the development of certain experimental procedures that are easy, fast, and cheap enough to implement. These procedural advantages can be provided through electrochemical methods. Therefore, in this study, at the surface of a glassy carbon electrode (GCE), a composite of functionalized multi-walled carbon nanotubes (MWCNTs) and formazon was used as a mediator to determine GSH electrochemically. The results indicated that this modified GCE is electrocatalytically very active for glutathione oxidation. Several techniques including cyclic voltammetry (CV), scanning electron microscopy (SEM), and differential pulse voltammetry (DPV) were used to characterize the electrode. Also, such kinetic parameters as the charge transfer rate constant and the transfer coefficient were calculated. In optimized conditions, there was a linear relationship between the DPV peak current of GSH oxidation and GSH concentration in the ranges of 1.0-100.0 and 100.0-800.0 µM at pH 7.0. As for the detection limit, it was found to be 0.73 µM.Tue, 10 Mar 2020 20:30:00 +0100