Scientia IranicaScientia Iranica
http://scientiairanica.sharif.edu/
Thu, 15 Nov 2018 18:14:34 +0100FeedCreatorScientia Iranica
http://scientiairanica.sharif.edu/
Feed provided by Scientia Iranica. Click to visit.Modeling and analyzing pricing and inventory problem in a closed-loop supply chain with return ...
http://scientiairanica.sharif.edu/article_4459_1011.html
This paper focuses on determining ordering and pricing policies in a single-period closed loop supply chain. The assumed supply chain includes a number of manufacturers who provide their different but substitutable products for their customers via a common retailer; however the manufacturers can have their own internet-based sales channel in order to provide products for the customers. The customers can return products if they are not satisfied with. The return products are collected in a repair center, are repaired and sold as second-hand product through the retailer channel or through an internet-based sale channel. The customer demand is assumed to be stochastic. This study aims to determine the optimum prices for the internet-based and retailer sales channels for the initial and second hand products. It also tries to determine the optimal values of retailer order and production rates of manufacturers and repair centers. Three types of game strategies for the supply chain including Nash, Stackelberg game with retailer as the leader and Stackelberg game with manufacturers and repair center as the leaders are studied in decentralized condition. The analytical equilibrium solutions, equations and constraints are extracted for these strategies. Finally, the effect of variations in key parameter is investigated. Sun, 30 Sep 2018 20:30:00 +0100An experimental study on the seismic behavior of infilled RC frames with opening
http://scientiairanica.sharif.edu/article_4150_0.html
Infill walls are generally not taken into account in structural analysis due to their complex behavior at seismic actions. As it is known, they increase the stiffness as well as the lateral load capacity of the system. Sometimes, infill walls may have window and door openings in their planes. In the present study, behavior of reinforced concrete (RC) frames with infill wall which have openings is investigated under cyclic lateral loadings. Location and size of the openings in the infill wall are selected as investigation parameters. Test specimens are constructed and experimentally analyzed. The infill wall changes the behavior of the frames under cyclic lateral loads significantly. Location and size openings in the infill wall are two main parameters which affect the behavior of the infill walls as well as on that of the frame. The test results clearly show that the contribution of the infill wall to the behavior of RC frame has diminished significantly when the opening ratio is larger than 9%. Therefore, the effect of the opening in the infill wall must be taken into account in the structural modeling when the opening ratio is larger than 9%.Sat, 12 Aug 2017 19:30:00 +0100A capital Flow-constrained lot-sizing problem with trade credit
http://scientiairanica.sharif.edu/article_4444_1011.html
This paper incorporates capital flow constraints and trade credit to lot sizing problems. Capital flow constraint is different from traditional capacity constraints: when a manufacturer begins to produce a certain number of products, its present capital should not be less than its total production costs of that period; otherwise, the manufacturer must decrease production quantity or suspend production, or it could delay payment using trade credit. Moreover, the capital of each period should also be greater than zero to avoid bankruptcy. We formulate a mathematical model for the single-item lot sizing problem. Based on dynamic programming, we approximate this mixed integer problem to a traveling salesman problem finding the longest route, divide the model into sub-linear problems without integer variables, and propose a dynamic programming algorithm with heuristic adjustment to solve it. The sub-linear problems can be easily solved by interior point algorithm. Our algorithm could obtain optimal solutions under certain situations. Numerical analysis shows our algorithm has small optimality deviation percentage under other situations and holds computation efficiency advantage compared with CPLEX 12.6.2. It also indicates capital flow constraints and the application of trade credit in lot sizing problems could affect optimal production decisions.Sun, 30 Sep 2018 20:30:00 +0100Wall and Bed Shear Force in Rectangular Open Channels
http://scientiairanica.sharif.edu/article_4222_0.html
This paper studies the effects of velocity gradients and secondary currents on distribution of the shear force between the walls and bed of rectangular open channels. We show that neglecting the effect of secondary currents and assuming zero-shear division lines does not yield acceptable results. We, accordingly, introduce a method to determine the percentage of the total shear force acting on the walls and bed of rectangular open channels, which takes both the velocity gradients and secondary currents into account. Using the channel bisectors, along which there is no secondary flows effect, and orthogonal trajectories to isovels, along which there is no shear stress, we divide the channel cross-section into three major subsections, namely bed area, wall area, and shared area. The geometry of each subsection is derived given the location of the maximum velocity. The share of the bed and wall shear forces from the shared area are calculated afterward. The results for bed and walls shear forces agree with the experimental data with an average relative error less than 5% for regular flows and flows carrying suspended sediment. This method also provides a physics-driven range for the wall and bed shear forces which nicely covers the experimental data.Fri, 18 Aug 2017 19:30:00 +0100Developing simulation based optimization mechanism for a novel stochastic reliability centered ...
http://scientiairanica.sharif.edu/article_4461_1011.html
This research investigates joint scheduling of maintenance and production planning. This novel integrated problem takes benefit of reliability-centered maintenance (RCM) for monitoring and managing maintenance function of a stochastic complex production-planning problem namely flexible job shop scheduling problem (FJSP). The developed RCM works based on stochastic shocking of machines during their process time. In fact, it implements condition based maintenance approach regulated according to stochastic reliability concept. Comparison of the system reliability with critical levels determines the failure statues of the machines. It activates two main types of reaction called preventive and corrective maintenance. Considering breakdown of the system between inspection intervals makes the proposed model more realistic. Moreover, maintenance activity times and their duration are considered stochastically. Because of the high complexity level for this joint system, simulation-based optimization (SBO) approach is proposed for solving the problem. This SBO searches the feasible area through genetic algorithm (GA) and biogeography based optimization (BBO) algorithm. Different test problems, statistical methods, novel visualizations are used to discuss the problem and the algorithm explicitly. Sun, 30 Sep 2018 20:30:00 +0100Influence of grain shape and gradation on the shear behavior of sand mixtures
http://scientiairanica.sharif.edu/article_4223_0.html
In this paper, triaxial and cyclic direct shear behaviour of different sand mixtures were investigated by considering variations of shape, size and mixture content. In most studies, investigations on stress-strain properties of soils are carried out using clean sands. However, granular soils in the field may contain a considerable amount of grains in different physical characteristics (i.e., shape, size). Therefore, behaviour of the various sand mixtures in triaxial compression and cyclic direct shear testing apparatuses has received attention in this study. Two different sizes (0.25 mm-0.5 mm, and 1.0 mm-2.0 mm) of sands with distinct shapes (rounded and angular) were tested in triaxial and cyclic direct shear apparatuses. The mixtures of coarser and finer geomaterials were tested in various mix ratio values from 5% to 50% by weight. Based on the examinations during shearing of these materials, it was observed that behavior of the sand mixtures are closely related to the grain shape of host materials as well as fines content in both testing apparatuses, whilst size of the sands was not found to be significantly effective on the results.Fri, 18 Aug 2017 19:30:00 +0100A multi-objective SCOR-based decision alignment for supply chain performance management
http://scientiairanica.sharif.edu/article_4463_1011.html
A dynamic integrated solution for three main problems through integrating all metrics using SCOR are proposed in this research. This dynamic solution comprises strategic decisions in high-level, operational decisions in low-level and alignment of these two decision levels. In this regard, a human intelligence-based process for high level decisions and machine-intelligence based decision support systems (DSSs) for low-level decisions is then proposed using a novel approach. The operational presented model considers important supply chain features thoroughly such as different echelons, several suppliers, several manufacturers and several products during multiple periods. A multi-objective mathematical programming model is then developed to yield the operational decisions with Pareto efficient performance values and solved using a well-known meta-heuristic algorithm, i.e., NSGAII where its parameters is tuned using Taguchi method. Afterward, an intermediate machine-intelligence module is used to determine the best operational solution based on the strategic decision maker’s idea. The efficiency of the proposed framework is shown through numerical example where a sensitivity analysis is then conducted over the obtained results so as to show the impact of the strategic scenario planning on the considered supply chain’s performance.Sun, 30 Sep 2018 20:30:00 +0100BEHAVIOR AND DESIGN OF FIN WALLS AT THE PERIPHERY OF STRONG CORE WALL STRUCTURE IN HIGH-RISE ...
http://scientiairanica.sharif.edu/article_4224_0.html
In high-rise buildings, lateral loads, such as wind and seismic loads, are frequently resisted by reinforced concrete (RC) structural walls. Behavior and design of fin walls at the periphery of strong core wall structure in high-rise buildings were not analyzed seriously despite their structural importance. Using elastic design/analysis methodologies for the design of high-rise RC fin walls, it is shown that elicited reinforcement ratios are too high, the economic feasibility and constructability thus becomes worse and the ductile failure mode can not be assured. In the present study, the current design process of these fin walls is investigated by analyzing their structural behavior. According to the investigation of the current design and elicited results, high-rise RC fin walls are coupled by beams although they are located on another line and apart from each other, which is main cause of high reinforcement in high-rise RC fin walls. In the present study, a literature review has been conducted to recommend the alternative design method for high-rise RC fin walls under lateral loads, and inelastic analysis has been performed to verify the design method. Fri, 18 Aug 2017 19:30:00 +0100A two-stage stochastic model for designing cellular manufacturing systems with simultaneous ...
http://scientiairanica.sharif.edu/article_4460_1011.html
In recent decades, many researchers have studied the cellular manufacturing system with consideration of various issues such as scheduling, production planning, layout, reliability, etc. However, limited research papers have investigated this problem in an uncertain environment. The present paper addresses a stochastic problem in cellular manufacturing systems considering simultaneous multiple routings and subcontracting. In the developed problem, each part can be simultaneously produced in multiple processing routes. It is also assumed that the unsatisfied part demands as a result of limited machine capacity or high manufacturing cost could be outsourced. A two-stage stochastic programming approach is employed to take the uncertainty into consideration and to formulate the problem. The objective function is to minimize the summation of production, subcontracting, material handling, and machine idleness costs. A sample average approximation method is applied as a solution method. Also, for further illustration of the problem, a numerical example is solved and sensitivity analyses are conducted. Finally, through some numerical examples extracted from related literature, the advantages of constructing a stochastic optimization model for the problem are demonstrated.Sun, 30 Sep 2018 20:30:00 +0100Empirical Evaluation of Cyclic Behavior of Rotational Friction Dampers with Different Metal Pads
http://scientiairanica.sharif.edu/article_4225_0.html
. Passive energy dissipation devices have been widely used to reduce the maximum responses of structures under seismic loading. Recently, different types of passive energy devices are developed to improve seismic behavior of structures in new construction and retrofitting existing structures. Friction dampers are displacement dependent passive devices which dissipate energy using friction mechanism. Many different types of friction dampers have been proposed in recent years. This paper aims at investigating the cyclic behavior of a rotational friction damper with different friction pads under cyclic loading. To this end, experimental analysis is performed on a friction damper with four friction materials. The tested damper consists of steel plates, friction pads, preloaded bolts and hard washers. Cyclic loads are applied on damper specimens with four friction pads include: aluminum, galvanized steel, stainless steel, steel (St-37). The experimental results are studied according to FEMA-356 acceptance criteria to select the appropriate friction materials as friction pads for using in the friction damper. Fri, 18 Aug 2017 19:30:00 +0100Optimality of network marketing integrated in a dual-channel distribution system
http://scientiairanica.sharif.edu/article_4462_1011.html
This paper provides a framework to study the integration of network marketing in a dual channel distribution system. We develop an approach to optimize the main decision variables of this system simultaneously. These decision variables include the price paid by the customers of both channels, confidence level, the effort level of active distributors of network marketing and also whole sale price. Although both channels compete, it is vital to have a balanced pricing system to make both channels motivated. However, the price in network marketing and traditional retailer system is not necessarily equal, due to the difference of their nature. Furthermore, it is also required to develop an appropriate system of commissioning for the payoff of distributers at different levels of network marketing to make them motivated. We also examine different scenarios of dual distribution systems, centralized and decentralized operation of network marketing. Furthermore, in case of decentralized system, we also investigate revenue or profit sharing for all parties involved (manufacturer; retailer and network marking distributers). To illustrate the proposed approach, we present some numerical studies and also investigate the impact of customer loyalty degree to retail channel on decisions.Sun, 30 Sep 2018 20:30:00 +0100Simulation analysis of the effect of doubling and electrification on the reliability of the ...
http://scientiairanica.sharif.edu/article_4226_0.html
The reliability assessment of the railway services is a complex procedure that is affected by many different factors. A railway system is reliable when the trains arrive at their destination within the allowed delay threshold. The objective of this study is to investigate the effect of the infrastructure doubling and electrification on the reliability of the train schedules. In this study, advanced event-driven stochastic simulation software is developed to determine the reliability of the train movements. The calculation of the average train delay as a benchmark is provided to evaluate performance. We compared average train delay with the acceptable delay to define a new benchmark to determine the reliability of the train movements. We also analyzed the delay cascading effect along the railway line in order to better illustration of a number of correlations between the arrival and departure delays at different stations. The model has been validated through a real-world case study of Iranian railway. Successful validation of the developed simulation system demonstrated that the model provides accurate reliability estimations in both congested and non-congested situations. Furthermore, the experimental results showed that electrification and doubling improve the reliability significantly.Fri, 18 Aug 2017 19:30:00 +0100Finding an improved region of efficiency via DEA-efficient hyperplanes
http://scientiairanica.sharif.edu/article_20004_1011.html
The analysis of efficiency is conducted for two vital purposes: firstly, in order to evaluate the current level of efficiency; and secondly, to provide information on how to improve the level of efficiency, which is to provide benchmarking information. The inefficient Decision Making Units (DMUs) are usually able to improve their performance and Data Envelopment Analysis (DEA) projections provide a prescription for improvement. However, sometimes an inefficient DMU cannot move its performance toward best practice by either decreasing its inputs or increasing its outputs. On the other hand, it can scarcely reach its efficient benchmark. This research suggests a method to find an improved region of efficiency through DEA-efficient hyperplanes by providing an algorithm for detecting an improved efficiency path. In addition to the production of reasonable benchmarking information, the proposed algorithm provides the general requirements that, satisfy the demands which every professional decision-maker should meet. Finally, we provide a more detailed description of some of the new issues, extending the insights from this analysis of the benchmark region from the under-evaluated inefficient DMU. Finally, numerical examples are provided to demonstrate the results of the analysisSun, 30 Sep 2018 20:30:00 +0100Dynamic analysis of concrete gravity dam-reservoir systems by Wavenumber approach for the ...
http://scientiairanica.sharif.edu/article_4227_0.html
Different approaches are utilized for dynamic analysis of concrete gravity dam-reservoir systems. The rigorous approach for solving this problem employs a two-dimensional semi-infinite fluid element (i.e., hyper-element). Recently, a technique was proposed for dynamic analysis of dam-reservoir systems in the context of pure finite element programming which was referred to as the Wavenumber approach. Of course, certain limitations were imposed on the reservoir base condition in the initial form of this technique to simplify the problem. However, this is presently discussed for the general reservoir base condition, contrary to the previous study which was merely limited to the full reflective reservoir base case. In this technique, the wavenumber condition is imposed on the truncation boundary or the upstream face of the near-field water domain. The method is initially described. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by this approach, and the results are compared against the exact response. Based on this investigation, it is concluded that this approach can be envisaged as a great substitute for the rigorous type of analysis under the general reservoir base condition.Fri, 18 Aug 2017 19:30:00 +0100A 'basic form'-focused modeling and a modified parameter estimation technique for grey ...
http://scientiairanica.sharif.edu/article_4465_1011.html
Grey modeling is an alternative approach to time series forecasting with growing popularity. There is no theoretical limitation for grey prediction models to adapt to almost every process by taking the appropriate order. However, deficiencies of traditional higher-order models have made researchers overlook such flexibility and make use of first-order models by default. In order to bridge the mentioned gap, this paper makes two contributions. First, a novel discrete modeling is developed with the basic form equation at its heart, which reconciles estimation and prediction processes. Second, the traditional least-squares estimation technique is modified by shifting the focus from nominal parameters to parameters practically employed in the prediction process. The new approach named ‘Basic Form’-focused Grey Model (BFGM) is applied to first-order, second-order, and Verhulst grey models. Then, it is validated through comparing its performance with the traditional approach. Results show that in most cases BFGM makes considerable improvements in simulation and prediction accuracy, while it has reasonable computational complexity. Improvements are especially dramatic when BFGM is applied to GM (2, 1). The resultant BFGM (2, 1) is superior in simulation and short-term prediction and, therefore, can be regarded as the basis for developing efficient higher-order grey formulations.Sun, 30 Sep 2018 20:30:00 +0100Closed loop supply chain network design for the paper industry: A multi-objective stochastic ...
http://scientiairanica.sharif.edu/article_4464_1011.html
Closed loop supply chain design is to provide an optimal platform for efficient and effective supply chain management. It is an essential and strategic operation management problem in supply chain management, and usually includes multiple and conflicting objectives. A new mixed integer non-linear programming model for a multi-objective closed loop supply chain network design problem in the paper industry is developed under uncertainty. The objective functions are to minimize the total cost, maximize the total volume flexibility and minimize the total number of vehicles hired in order to fulfill the paper industry’s policies towards a cleaner and green environment. Also, a novel hybrid solution is presented based on stochastic programming, robust optimization and fuzzy goal programming. A numerical example utilizing the real data from the paper industry in East Azerbaijan of Iran is designed and the model performance is assessed. Furthermore, a recently developed Dragonfly Algorithm (DA) employed to solve the given problem in large scales and compared with Genetic Algorithm (GA). The results indicated that the DA achieved better performance compared with the GA.Sun, 30 Sep 2018 20:30:00 +0100Hybrid cluster and data envelopment analysis with interval data
http://scientiairanica.sharif.edu/article_4482_1011.html
Data envelope analysis (DEA) is an approach to estimate the relative efficiency of decision making units (DMUs). Several studies were conducted in order to prioritize efficient units and some useful models such as cross-efficiency matrix (CEM) were presented. Besides, a number of DEA models with interval data have been developed and ranking DMUs with such data was solved. However, presenting an obtained crisp data derived interval data is a critical problem, so that many researches were implemented so as to compute weights and averaging the interval data. In this paper we propose the new algorithm to find more suitable weight applying a data mining approach of DMU’s data. For this purpose, we employed clustering and pair-wise comparison matrix on given relative efficiency from CEM. Results indicate there is meaningful different between efficiency of DMUs with lower bound and that of DMUs with upper bound.Sun, 30 Sep 2018 20:30:00 +0100Simulating Structural Responses of a Generic AAR-Affected Arch Dam Considering Seismic Loading
http://scientiairanica.sharif.edu/article_4230_0.html
Alkali-Aggregate Reaction (AAR) is a deteriorative phenomenon for concrete that impresses the performance of structures. This study focuses on the seismic and post-earthquake behavior of an AAR-affected dam. A computer program is developed for simulating the structural behavior of AAR-affected dams including the seismic and post-earthquake durations. A thin high double-curvature arch dam is selected as case study and is modeled in a series of analyses within the assumed 30-year operating period. Each analysis includes an earthquake excitation in a different specified time. In each analysis, the seismic record is applied to the dam at different status of AAR progression considering the proposed ARI index. The results show that AAR affects seismic performance of the dam, i.e. with the AAR progression; the dynamic responses are significantly changed. On the other side, the effect of earthquake occurrence time on the dam post-earthquake behavior is not noticeable. This may be explained by the linear elastic behavior assigned to the body material in the provided FE model.Fri, 18 Aug 2017 19:30:00 +0100Effects of the first reinforcement depth for different types of geosynthetics
http://scientiairanica.sharif.edu/article_4231_0.html
In this study, the performance of the first reinforcement layer depth for sand subbase of a road or construction was investigated with plate load laboratory tests. Unreinforced and reinforced experiments for different reinforcement types were made by changing the first reinforcement layer depth ratio. One type of geotextile and two different geogrid specimens were used in the research. Load-settlement curves and Bearing Ratios were studied by measuring the results for different settlement ratios. Finally, laboratory measurements of unreinforced and reinforced soil using geotextile reinforcement were compared with Finite Element Model (FEM) analyses modeled under similar conditions. The results demonstrated the effects of different types of reinforcements for different first reinforcement layer locations. The number of reinforcement layers was another parameter which affected the bearing ratio along with the first reinforcement layer depths. It was also observed that the Bearing Ratio (BR) and load-settlement behavior changed significantly with the first reinforcement depth and settlements. Effects on failure modes for unreinforced and reinforced sand soils were compared for each test.Fri, 18 Aug 2017 19:30:00 +0100Uncertainty analysis through development of seismic fragility curve for a SMRF structure using ...
http://scientiairanica.sharif.edu/article_4232_0.html
Abstract. The present study is mainly focused on development of the fragility curves for the sidesway collapse limit state. One important aspect of deriving fragility curves is how uncertainties are blended and incorporated into the model under seismic conditions. The collapse fragility curve is influenced by different uncertainty sources. In this paper in order to reduce the dispersion of uncertainties, Adaptive Neuro Fuzzy Inference System (ANFIS) based on fuzzy C-means algorithm used to derive structural collapse fragility curve, considering effects of epistemic and aleatory uncertainties associated with seismic loads and structural modeling. This approach is applied to a Steel Moment Resisting Frame (SMRF) structural model whose relevant uncertainties have not been yet considered by the others in particular by using ANFIS method for collapse damage state. The results show the superiority of ANFIS solution in comparison with excising probabilistic methods e.g., First Order Second Moment Method (FOSM) and Monte Carlo (MC)/Response Surface Method (RSM) to incorporate epistemic uncertainty in terms of reducing computational effort and increasing calculation accuracy. As a result, it can be concluded that comparing with proposed method rather than Monte Carlo method, the mean and the standard deviation are increased 2.2 % and 10 % respectively.Fri, 18 Aug 2017 19:30:00 +0100Near-Fault Effects on RC Buildings’ Demand in Linear and Nonlinear Analyses
http://scientiairanica.sharif.edu/article_4233_0.html
Strong ground motions of near-fault earthquakes are mostly generated by forward-directivity effects. Forward-directivity effects develop energetic pulses particularly in horizontal velocity history of fault-normal component. The narrow-band nature of the pulses results in revealing at least two peaks on the response spectra and also increasing seismic demand especially for mid-rise and high-rise buildings. Iranian seismic code (IS 2800-14) presents the coefficient N, for considering near-fault effects. It seems that the N is not efficient for designing in near-fault zone. The accurate near-fault demands can be determined by using nonlinear response history analyses. In the present paper, two 3-D reinforced concrete framed structures (RC buildings) are designed according to ACI 2014 and IS 2800-14. Then, the demands are estimated by employing linear response history analysis (LRHA) and also nonlinear response history analysis (NRHA) under an ensemble of 11 near-fault ground motions. The results reveal that the design spectrum of IS 2800-14 is incompatible with near-fault spectra and underestimates demands in the long periods range. Further, implementation of LRHA using response modification factor (Ru) and deflection amplification factor (Cd) leads to insufficient inter-story drift ratios. Finally, the influence of enhancing ductility is studied by determining ductility reduction factors for near-fault records.Fri, 18 Aug 2017 19:30:00 +0100Antecedent rainfall induced shallow landslide-A case study of Yunnan landslide, China
http://scientiairanica.sharif.edu/article_4234_0.html
We present a case study of antecedent rainfall-induced failure of engineering slope. The impact of pore-water pressure, the increment of pore-water pressure, and water content, the factor of safety are investigated by numerical models for an actual slope in Yunnan, China. The results indicate that antecedent rainfall played an important role in the stability of the slope. The model reasonably explains the time lag between the occurrence of rainfall and landslides. Pore-water pressures have significantly changed at the upper layer of red clay slope, the cracks phenomenon at the upper of the slope agrees with the field observations before landslide. The saturated zone of the slope gradually expands from the top to bottom of the slope, the major reason for landslide is that the surface stagnant water after rainfall gradually infiltrates into the weathered gneiss rock, resulting in the decrease of the strength of weathered gneiss rock, and then the weight of later rainfall caused the landslide of the slope. The factor of safety of the slope was evaluated by the modified limit equilibrium methods, it was shown that the actual failure occurred when the calculated factor of safety approaches its minimum 0.97. The landslide is characterized by shallow landslides.Fri, 18 Aug 2017 19:30:00 +0100Application of smoothed finite element method in coupled hydro-mechanical analyses
http://scientiairanica.sharif.edu/article_4235_0.html
Smoothed finite element method (SFEM) was introduced by application of the stabilized conforming nodal integration in the conventional finite element method. In this method, integration is performed on “smoothing domains” rather than elements. Smoothing domains are created based on cells, nodes or edges for two dimensional problems. Based on the smoothing domain creation method, different types of SFEM are developed that have different properties. It has been shown that these methods are insensitive to mesh distortion and are generally more computationally efficient than mesh-free and finite element methods for the same accuracy level. Because of their interesting features, they have been used to solve different problems. This paper investigates the performance of these methods in coupled hydro-mechanical (consolidation) analysis, by solution of some problems using a developed SFEM/FEM code. Biot’s consolidation theory is reviewed, and after introduction of the idea and formulation of SFEMs, discretized form of equations is given. Requirements for creation of stable coupled hydro-mechanical models are discussed and based on them, two methods for creation of stable SFEM models are introduced. To investigate the effectiveness of the methods, a number of examples are solved and results are compared with the finite element and analytical ones.Fri, 18 Aug 2017 19:30:00 +0100Evaluation of Peak Ground Acceleration for the City of Kerman through Seismic Hazard Analysis
http://scientiairanica.sharif.edu/article_4236_0.html
In this paper, Probabilistic Seismic Hazard Analysis (PSHA) approach is used to evaluate the distribution of Peak Ground Acceleration (PGA) and their corresponding probabilities for Kerman region in S-E of Iran. The geological and seismological data were integrated into a probabilistic seismic hazard model for the region. Historical and instrumental earthquake data, geology, tectonics, fault activity and seismic source models related to seismic events are taken into account. Foreshocks and aftershocks are rationally eliminated and main shock records are used to evaluate seismicity parameters using Kijko method. The use of such method is advantageous since it accounts for incomplete or inaccurate seismic data related to various seismic sources in the region. CRISIS2007 software is also used to carry seismic hazard analysis for the region and to develop the maps of iso-acceleration contours and for various return periods. The results have been displayed as the probabilistic estimates of PGA for the return periods of 50, 75 and 475 years. Comparison of the results obtained here with those suggested by Iranian Code of Practice for Seismic Resistance Design of Buildings (Standard No. 2800 Version 1393) are also presented. Results obtained in this study provides the basis for the preparation of seismic risk maps.Fri, 18 Aug 2017 19:30:00 +0100Axial translation of a rigid disc inclusion embedded in a penny-shaped crack in a transversely ...
http://scientiairanica.sharif.edu/article_4237_0.html
In this paper, an analytical solution for the axisymmetric interaction of a rigid disc inclusion embedded in bondedcontact with the surfaces of a penny-shaped crack and a transversely isotropic medium is investigated. By using amethod of potential functions and treating dual and triple integral equations, the mixed boundary value problem iswritten in the form of two coupled integral equations, which are amenable to numerical treatments. The axial stinessof the inclusion and the shearing stress intensity factor at the tip of the penny-shaped crack for dierent degrees ofmaterial anisotropy are illustrated graphically. Useful limiting cases such as a rigid disc inclusion in an uncrackedmedium and in a completely cracked solid are recoveredFri, 18 Aug 2017 19:30:00 +0100Structural damage detection using time domain responses and teaching–learning-based ...
http://scientiairanica.sharif.edu/article_4238_0.html
Nowadays, structural health monitoring has attracted much attention, due to the construction of important and complex structures and their safety. One branch of structural health monitoring is damage detection, estimating the location and extent of eventual damages in the structural systems. In this study, an efficient method is introduced to determine the location and extent of damage in the frame, beam and truss structures using time domain response and an optimization algorithm. First of all, the structural damage detection problem is formulated as a standard optimization problem. So that, the optimization objective function is defined by using the acceleration of damaged structures and analytical model acceleration. The acceleration is obtained using Newmark method. Damage is simulated by reducing the elasticity modulus of structural members. Then, damage problem converted to an optimization problem are solved by teaching–learning-based optimization (TLBO) algorithm therefore, the exact location and extent of damage in structure can be determined. In order to show the capabilities of the proposed approach for identifying structural damage, four illustrative test examples are considered with considering measurement noise effect. The results clearly show that the proposed method is as a powerful method to detect multiple damage in structures.Fri, 18 Aug 2017 19:30:00 +0100A New Fourier series solution for free vibration of non-uniform beams, resting on variable ...
http://scientiairanica.sharif.edu/article_4239_0.html
In this research, the combination of Fourier sine series and Fourier cosine series is employed to develop an analytical method for free vibration analysis of an Euler-Bernoulli beam of varying cross- section, fully or partially supported by a variable elastic foundation. The foundation stiffness and cross section of the beam are considered as arbitrary functions in the beam length direction. The idea of the proposed method is to superpose Fourier sine and Fourier cosine series to satisfy general elastically end constraints and therefore no auxiliary functions are required to supplement the Fourier series. This method provides a simple, accurate and flexible solution for various beam problems and is also able to be extended to other cases whose governing differential equations are nonlinear. Moreover, this method is applicable for plate problems with different boundary conditions if two-dimensional Fourier sine and cosine series are taken as displacement function.Numerical examples are carried out illustrating the accuracy and efficiency of the presented approach.Fri, 18 Aug 2017 19:30:00 +0100Determining Shear Capacity of Ultra-high Performance Concrete Beams by Experiments and ...
http://scientiairanica.sharif.edu/article_4264_0.html
In this research, nineteen specimens of ultra-high performance fiber-reinforced concrete rectangular beams are made and their shear resistance is determined experimentally. The results are compared with estimations by ACI 318, RILEM TC 162-TDF, Australian guideline and Iranian national building regulations. To compare the code estimations, the ratio of experimental shear strength to predicted shear strength is calculated for each code. This ratio is actually a measure of safety factor on one hand and a measure of precision of the estimation on the other hand. Based on the results of both studies, the authors conclude that the Australian guideline with a ratio of 2.5 provides the minimum experimental to predicted ratio while the Iranian National Building Regulations with a ratio of about 10 provides the highest experimental to predicted ratio. This ratio obtained for ACI and RILEM was about 8 and 3.6 respectively. The Iranian and ACI codes provide basically the same strength estimation but both are very conservative, which may be interpreted as mainly because the codes are dubious about the precision of their own estimations. However, RILEM and Australian codes, estimate the shear resistance with reasonable margin of safety. Tue, 22 Aug 2017 19:30:00 +0100Enhanced vibrating particles system algorithm for damage identification of truss structures
http://scientiairanica.sharif.edu/article_4265_0.html
Vibrating particles system (VPS) optimization is a recently developed metaheuristic algorithm for optimization. This algorithm is inspired by the free vibration of freedom systems’ single degree with viscous damping. In this method, each answer is modeled as a particle that moves to its equilibrium position; new positions of the vibrating particle system are updated according to a historically best position. Enhanced Vibrating Particles system (EVPS) uses new approaches to improve the performance of the VPS algorithm. In this study, a dynamic method and modal based approach consisting of natural frequencies and mode shapes are used in the objective function formulation. To demonstrate the performance of the VPS and EVPS, different truss structures including several multiple elements scenarios with noise and without noise in modal data are considered for detecting damage problems. Additionally, all scenarios are studied with significant mutations. Results show that the EVPS algorithm has reached better answer compared to the VPS algorithm for damage detection problems.Tue, 22 Aug 2017 19:30:00 +0100Three-dimensional repositioning of jaw in the orthognathic surgery using the binocular stereo vision
http://scientiairanica.sharif.edu/article_4351_0.html
In recent years, the binocular stereo vision has become more popular in many different areas because of the latest developments in three-dimensional (3-D) image processing technology that ensures rich information in comparison with other sensor types. This study presents a novel method based on the binocular stereo vision system to reduce the measurement error encountered frequently in the orthognathic surgery. The main aim is to enhance the level of the accuracy of this sensitive operation. The developed system is not only useful for the preoperative assessment or the postoperative process but also can be utilized during the real-time operation. Additionally, this system provides a broader working field, more practical and healthier environment and less expensive setup. Therefore, the developed binocular stereo vision system may be acceptable for most surgeons. Experimental results show that the average error rate for all of X, Y and Z coordinates in the Cartesian system is 0.25 mm which is clinically acceptable (< 1.00 mm). The binocular stereo vision system would be a helpful throughout the orthognathic surgery to improve precision of the measurement and satisfy the healthy surgical operating environmentTue, 29 Aug 2017 19:30:00 +0100Power System Thévenin Equivalent Estimation Based on Phasor Measurements
http://scientiairanica.sharif.edu/article_4373_0.html
This paper presents a novel algorithm based on phasor measurements to online estimation of power system Thévenin Equivalent (TE) from a generator terminal. Three consecutive phasor measurements of generator terminal voltage and current are used to estimate the system TE. In a real network, system frequency deviation from its nominal value will produce some phase drift in consecutive phasors reported by Phasor Measurements Units (PMUs). To correct the phase drift and synchronizing the reported phasors to the same reference, an improved triangulation method is developed. The improved method uses a virtual vector in its structure. Using this vector alleviates the negative impacts of improper data resulting from noise or disturbances which make the simple triangulation method to be useless. The algorithm is tested on standard NE-39 network and is implemented in Shahid Beheshti University (SBU) protection laboratory to verify the results in a practical area. The obtained results show that the new method can efficiently estimate the in online mode in steady-state and transient conditions.Tue, 29 Aug 2017 19:30:00 +0100Bayesian Hypothesis Testing for One Bit Compressed Sensing with Sensing Matrix Perturbation
http://scientiairanica.sharif.edu/article_4374_0.html
This paper proposes a low-computational Bayesian algorithm for noisy sparse recovery in the context of one bit compressed sensing with sensing matrix perturbation. The proposed algorithm which is called BHT-MLE comprises a sparse support detector and an amplitude estimator. The support detector utilizes Bayesian hypothesis test, while the amplitude estimator uses an ML estimator which is obtained by solving a convex optimization problem. Simulation results show that Bayesian hypothesis testing in combination with the ML estimator has more reconstruction accuracy than that of only an ML estimator and also has less computational complexity.Tue, 29 Aug 2017 19:30:00 +0100Shannon Entropy And Tracking Dynamic Systems Over Noisy Channels
http://scientiairanica.sharif.edu/article_4375_0.html
This paper is concerned with the estimation of state trajectory of linear discrete timedynamic systems subject to parametric uncertainty over the compound erasure channelthat uses feedback channel intermittently. For this combined system and channel,using the data processing inequality and a robust version of the Shannon lower bound,a necessary condition on channel capacity for estimation of state trajectory at thereceiver giving almost sure asymptotically zero estimation error is presented. Then,an estimation technique over the compound erasure channel that includes an encoder,decoder and a sucient condition under which the estimation error at the receiveris asymptotically zero almost surely is presented. This leads to the conclusion thatover the compound erasure channel, a condition on Shannon capacity in terms ofthe rate of expansion of the Shannon entropy is a necessary and sucient conditionfor estimation with uniform almost sure asymptotically zero estimation error. Thesatisfactory performance of the proposed technique is illustrated using simulation.Tue, 29 Aug 2017 19:30:00 +0100INVESTIGATION OF DISPERSION ORDER ON CHIRP MICROWAVE GENERATION USING MICROWAVE PHOTONIC LINK ...
http://scientiairanica.sharif.edu/article_4376_0.html
In this work, we investigate the influence of the second order-(2OD) and third order-(3OD) dispersion terms on chirp signal generation and transmission through RF photonic link without optical filter. Dispersion equations are formalised using Taylor series and Bessel function to study the link performance. Our result (Eye diagrams) shows that the 2OD+3OD have significant impact on chirp mm-wave propagating through fiber of different lengths. In this paper chirp mm signal is controlled at photo detector by individual phase term of external modulators. Moreover, we also demonstrated experimentally that the chirp rate can be significantly controlled by properly choosing the type of fiber in the experiments. We discussed the RF photonic link performance in terms of Optical Sideband Suppression Ratio (OPSSR), Radio Frequency Spurious Suppression Ratio (RFSSR), Bit Error Rate (BER). Theoretical results are verified using MATLAB Software.Tue, 29 Aug 2017 19:30:00 +0100Quadrature oscillator based on novel low-voltage ultra-low-power quasi-floating-gate DVCC
http://scientiairanica.sharif.edu/article_4377_0.html
In this work, a new realization topology of the low-voltage ultra-low-power quadrature oscillator is presented. This quadrature oscillator utilizes only two active elements, namely differential voltage current conveyor (DVCC), and five passive ones, all of them are grounded, which is recommended for the integrated circuit implementation. The DVCC is based on quasi-floating-gate MOS transistor, which is a distinct technique from the conventional one, featuring with operation at low-voltage and ultra-low-power conditions; hence the proposed DVCC works with low supply voltage of ± 400 mV and consumes power of merely 6.6 µW. Thanks to these features the total power dissipation of the oscillator is only 0.28 mW. The simulation results using 0.18 µm TSMC CMOS technology are included in order to prove the design correctness.Tue, 29 Aug 2017 19:30:00 +0100Symbiotic Organisms Search algorithm for economic load dispatch problem with valve-point effect
http://scientiairanica.sharif.edu/article_4378_0.html
Symbiotic Organisms Search (SOS) is a brand new and effective metaheuristic optimization algorithm. This paper proposes the SOS algorithm to solve the Economic Load Dispatch (ELD) problem with valve-point effect, which is one of the essential optimization problems in modern power systems. The proposed algorithm is tested on five different test cases consisting 3-machines 6-bus, IEEE 5-machines 14-bus, IEEE 6-machines 30-bus, 13 and 40 unit test systems including both transmission loss and without transmission loss. These test cases show that SOS is able to converge to the global optima successfully. Moreover results obtained from proposed algorithm are compared through different methods used in solving the ELD problem existing in the literature. According to these results, SOS produces better values than all.Fri, 01 Sep 2017 19:30:00 +0100DTC-SVPWM of an Energy Storage Flywheel Associated with a Wind Turbine Based on the DFIM
http://scientiairanica.sharif.edu/article_4379_0.html
In this article we will control the energy storage inertial noted inertial energy storage system to partner with a wind energy conversion system that aims to improve the power quality transit network. Inertial storage is considered a flywheel coupled to an induction motor and controlled by a voltage inverter type power converter. First step, a model of inertial energy storage system (flywheel + asynchronous machine) is presented, then two control methods are proposed: the direct torque control (DTC and DTC-conventional SVPWM) (space vector pulse with modulation). The two control methods give similar performance, but the DTC-SVPWM requires less computation time. The two regulators and the proportional integrator SVPWM technique were used to determine the switching frequency. Using direct control with vector modulation strategy has enabled the inertial energy storage system of demonstrating good continuation even under rather severe operating conditions, and the torque ripples are significantly reduced compared to the case of conventional DTC. Then we come to the presentation of simulation results obtained.Fri, 01 Sep 2017 19:30:00 +0100Design of Alternating Magnetic Field Generator for Magnetic Fluid Hyperthermia Research Application
http://scientiairanica.sharif.edu/article_4380_0.html
Hyperthermia utilizing nanoparticles is a novel cancer therapy which relies on the heat released when nanoparticles inside a tumor are exposed to an alternating magnetic field. The field strength and frequency are the main variants affect performance of nanoparticles for heat generation. Besides the characteristics of nanoparticle, which is the main criteria for tuning amplitude and frequency of magnetic field generated by an alternating magnetic field generator (AMFG), several parameters should be considered for an optimum design, which is related to AMFG design. These parameters are input voltage range, copper tube resistance used for solenoid coil, coil number of turns, and etc. According to these criteria, design procedure of AMFG for research applications is performed to maximize the heat released by nanoparticles. In order to validate the design, an experimental set up of AMFG is prepared which is used for in vivo hyperthermia tests. The experimental results are shown and compared to the simulations.Fri, 01 Sep 2017 19:30:00 +0100Portfolio Optimization in Electricity Market Using a Novel Risk Based Decision Making Approach
http://scientiairanica.sharif.edu/article_4381_0.html
This paper provides generation companies (GENCOs) with a novel decision-making tool that accounts for both long term and short term risk aversion preferences and devises optimal strategies to participate in energy, ancillary services markets and forward contracts where possibility of involvement in arbitrage opportunities is also considered. Because of the imprecise nature of the decision maker’s judgment, appropriate modelling of risk aversion attitude of the GENCO is another challenge. This paper uses fuzzy satisfaction theory to express decision maker’s attitude toward risk. Conditional value at risk methodology (CVaR) is utilized as the measure of risk and uncertainty sources include prices for the day-ahead energy market, automatic generation control (AGC) and reserve markets. By applying the proposed method, not only trading loss over the whole scheduling horizon can be controlled, but also the amount of imposed loss during every time period can be reduced. An illustrative case study is provided for further analysis.Fri, 01 Sep 2017 19:30:00 +0100A new modulation scheme in polymer optical fiber communications using Jacket matrix spreading
http://scientiairanica.sharif.edu/article_4382_0.html
To mitigate the high peak-to-average power ratio (PAPR) of discrete multi-tone (DMT) modulation in polymer optical fibers (POF) communication systems, a novel DMT scheme based on Jacket matrix spreading (JS) is proposed. Approximations of PAPR distribution for DMT signals are accurately presented. Single band JS-DMT and multi-band (MB)-JS-DMT are introduced in POF transmission link for PAPR reduction. Offline processing and simulations are adopted to investigate the performance of these new schemes with regard to the PAPR reduction, power spectral density (PSD), data rate and bit error rate (BER). The results demonstrate that, applying the JS methodology, up to 4dB PAPR reduction is achieved. JS-DMT is sensitive to the bandwidth range whereas MB-JS-DMT owns the robustness ability against fiber nonlinearity. Compared with some well known PAPR reduction techniques, the proposed schemes can be easily applied to the DMT modem and achieve the PAPR reduction efficiently without degrading the BER, data rate and PSD performance, which demonstrate the feasibility and validity of these two methods in POF transmission.
Fri, 01 Sep 2017 19:30:00 +0100An efficient observer design method for singular discrete-time systems with time-delay and ...
http://scientiairanica.sharif.edu/article_4383_0.html
In this paper, the observer design method for linear and nonlinear singular discrete-time systems with constant time-delays is proposed. By constructing appropriate Lyapunov–Krasovskii functional and using linear matrix inequality (LMI) technique, the asymptotic convergence criterion is developed in terms of LMIs, which can be solved numerically using MATLAB® LMI® toolbox. The sufficient condition for the existence of a full-order observer is obtained and the states are estimated using Schur complement and S-procedure lemma very well. Moreover, an extension procedure for observer design of singular linear system with time-varying delay is presented. Simulation results are included to prove the efficiency of the suggested approach.Fri, 01 Sep 2017 19:30:00 +0100Performance and stability analysis of grid connected single phase inverters used in solar ...
http://scientiairanica.sharif.edu/article_4384_0.html
Single-phase voltage source inverters (SP-VSIs) are widely used in grid connected solar photovoltaic (PV) systems. This paper deals with the dynamic modeling and stability analysis of single-phase grid connected PV inverters taking the PLL dynamics into account. The PLL structure employed in this paper includes two control branches; the main branch, known as phase estimation loop, extracts the phase and frequency of the grid voltage and the other branch, known as voltage peak estimation loop, determines the grid voltage amplitude. In this way, the paper first proposes design considerations for the dc-link voltage control and PLL control loops. Then, unified dynamic modeling of the SP-VSI system comprising PLL, dc-link dynamics and grid is presented and linearized block diagram of the whole system is extracted. The linearized block diagram depicts the interaction between the control loops of the PLL and dc-link system, where the PLL control loops consist of phase/frequency and amplitude estimation loops of the grid voltage. Next, the small signal stability of the full system is presented, and impacts of grid strength, operating point, and PLL closed loop bandwidth on the performance of SP-VSI are investigated by the modal analysis and time domain simulations.Fri, 01 Sep 2017 19:30:00 +0100GAIT GENERATION AND TRANSITION FOR BIPEDAL LOCOMOTION SYSTEM USING MORRIS-LECAR MODEL OF ...
http://scientiairanica.sharif.edu/article_4404_0.html
In this paper, we intend to improve the CPG network presented by Pinto et al. based on 4-cell model for bipedal locomotion systems. This model is composed of four coupled identical cells which internal dynamics of each one is described by the Morris-Lecar nonlinear differential equation and the couplings between the cells follow the synaptic type. We exploit an elitist non-dominated sorting genetic algorithm (NSGA II) to find the best set of coupling weights by which the phase differences become optimally close to the ones required for a primary bipedal gait. Thus, we achieve the rhythmic signals associated with four primary bipedal gaits of walk, run, two-legged jump, and two-legged hop. Also, we successfully obtain all secondary gaits corresponding to the bipedal locomotion identified by Pinto et al. from the 4-cell model, by symmetry breaking bifurcations of primary gaits. Particularly, we are able to produce the secondary gait called “hesitation walk” through transition from primary gaits of run and two-legged jump.Fri, 01 Sep 2017 19:30:00 +0100Dynamic Negawatt Demand Response Resource Modeling and Prioritizing in Power Markets
http://scientiairanica.sharif.edu/article_4406_0.html
In recent years, integrated use of demand- and supply-side resources has been performed by electric utilities, because of its potential attractiveness, both at operation and economic levels. Demand Response Resources (DRRs) can be used as demand side options which are the consequence of implementing Demand Response Programs (DRPs). DRPs comprise the actions taken by end-use customers to reduce their electricity consumption in response to electricity market’s high prices; and/or reliability problems on the electricity network. In this paper, a dynamic economic model of DRPs is derived based upon the concept of flexible elasticity of demand and the customer benefit function. Precise modeling of these virtual negawatt resources helps system operators to investigate the impact of responsive loads on power system studies. This paper also aims to prioritize multifarious DRPs by means of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and entropy methods. Performance of the proposed model is investigated through numerical studies using a standard IEEE test system.Fri, 01 Sep 2017 19:30:00 +0100Project safety evaluation by a new soft computing approach-based last aggregation hesitant ...
http://scientiairanica.sharif.edu/article_4439_0.html
In recent years, the implementation of safety management has been increased in construction projects by institutions, and many companies have recognized environmental and social effects of injuries at project work systems. In this regard, a novel decision model is presented based on a new version of complex proportional assessment method with last aggregation under a hesitant fuzzy environment. The decision makers (DMs) assign their opinions by hesitant linguistic variables that are converted to the hesitant fuzzy elements. Also, the DMs’ judgments are aggregated in last step of decision making to decrease information loss. Since weights of the DMs or professional safety experts and evaluation criteria are not equal in practice, a new version of hesitant fuzzy compromise solution method is proposed to compute these weights. In addition, the criteria weights are determined based on proposed hesitant fuzzy entropy method. A real case study in developing countries about the safety of construction projects is considered to indicate the suitability and applicability of the proposed new hesitant fuzzy decision model with last aggregation approach. In addition, an illustrative example is prepared to show that the proposed approach is suitable and reliable in larger size safety problemsSat, 02 Sep 2017 19:30:00 +0100Identifying the time of step change and drift in Phase II monitoring of autocorrelated logistic ...
http://scientiairanica.sharif.edu/article_4466_0.html
In some profile monitoring applications, the independency assumption of consecutive binary response values within each profile is violated. To the best of our knowledge, estimating the time of a change in the parameters of an autocorrelated binary profile is neglected in the literature. In this paper, two maximum likelihood estimators are proposed to estimate the real time of step changes and drift in Phase II monitoring of binary profiles in the case of within-profile autocorrelation, respectively. Our proposed estimators, not only identify the change point in the autocorrelated logistic regression parameters, but also in autocorrelation coefficient. The performance of the proposed estimators to identify the time of change points either in regression parameters or autocorrelation coefficient is evaluated through simulation studies. The results in terms of the accuracy and precision criteria show the satisfactory performance of the proposed estimators under both step changes and drift. Moreover, a numerical example is given to illustrate the application of the proposed estimators. Sun, 03 Sep 2017 19:30:00 +0100Probabilistic Seismic Demand Assessment of Steel Moment Resisting Frames with Mass Irregularity ...
http://scientiairanica.sharif.edu/article_4468_0.html
Ductility with direct effect on the response modification factor of buildings can influence their seismic performance. Moreover, some factors such as geometry and different types of irregularity can affect the ductility and seismic performance of structures. In this study, the effects of mass irregularity in height on the over strength, ductility, response modification factors and probabilistic seismic performance in steel Moment Resisting Frames (MRFs) are assessed. Then, the obtained results are compared with those of regular structures. For this purpose, incremental dynamic analysis (IDA) is implemented using ten records out of past worldwide earthquakes. The location of mass concentration in height is studied assessing 8-, 12- and 16-storey buildings with their mass concentrated at the first floor, mid-height and roof. Then, the probabilistic seismic responses of these structures are evaluated using the outputs of IDA. In this regard, probabilistic seismic demand analysis is conducted on each model. The obtained results are used to plot the seismic fragility and demand curves for both regular and irregular models. Based on the findings, mass irregularity causes the reduction of ductility and response modification factors. This effect increases when the heavier storey is located either at the first floor or at roof. Moreover, mass irregularity brings about the increase in probability of damage occurrence or its exceedance from a certain level.Sun, 17 Sep 2017 19:30:00 +0100Liquefaction Prediction Using Rough Set Theory
http://scientiairanica.sharif.edu/article_4507_0.html
Evaluation of liquefaction is one of the most important issues in geotechnical engineering. Liquefaction prediction depends on many factors and the relationship between these factors is non-linear and complex. Different methods have been proposed by different authors for liquefaction prediction. These methods are mostly based on statistical approaches and neural network.
In this paper a new approach based on Rough Set data mining procedure is presented for liquefaction prediction. The Rough set theory is a mathematical approach for analysis of imperfect knowledge or unclear description of objects. In this approach the decision rules are derived from conditional attributes in Rough Set analysis and the results are compared with actual field observations. The results of this study indicate that using this method can be helpful for liquefaction prediction and can reduce unnecessary costs in site investigation process.Mon, 02 Oct 2017 20:30:00 +0100Development of predictive models for shear strength of HSC slender beams without web ...
http://scientiairanica.sharif.edu/article_4509_0.html
Shear failure of slender beams made of high strength concrete (HSC) is one of the most crucial failures in design of reinforced concrete members. The accuracy of the existing design codes for HSC unlike the normal strength concrete (NSC) beams seems to be limited in prediction of shear capacity. This paper proposes a new set of shear strength models for HSC slender beams without web reinforcement using conventional multiple linear regression, advanced machine learning methods of multivariate adaptive regression splines (MARS) and group method of data handling (GMDH) network. In order to achieve high-fidelity and robust regression models, this study employs a comprehensive database including 250 experimental tests. Various influencing parameters including the longitudinal steel ratio, shear span-to-depth ratio, compressive strength of concrete, size of the beam specimens, and size of coarse aggregate are considered. The results indicate that the MARS approach has the best estimation in terms of both accuracy and safety aspects in comparison with regression methods and GMDH approach. Moreover, the accuracy and safety of predictions of MARS model is also remarkably more than the most common design equations. Furthermore, the robustness of proposed models is confirmed through sensitivity and parametric analyses.Mon, 02 Oct 2017 20:30:00 +0100Providing Transient Stability by Excitation System Response Improvement Methods through Long ...
http://scientiairanica.sharif.edu/article_4511_0.html
Maintaining network stability and encouraging generation companies to involve in stability maintaining are major concerns of independent system operator (ISO) in deregulated power system. Excitation system of synchronous generators is effective and well-known equipment which has a significant effect on network stability. Therefore, improving performance of this system can enhance network stability. But utilizing of the methods, which improve performance of excitation system, imposes cost on generation companies. This paper proposes a motivation mechanism for enhancing transient stability which encourages generation companies to improve performance of excitation system. In this mechanism beside excitation system response improving methods, a transient stability constrained optimal power flow is solved in order to ensure maintaining transient stability in different contingencies. A 4-buses test system, the IEEE 14-buses test system, and the IEEE 118-buses test system are used to illustrate effectiveness of the proposed mechanism. Implementation results show that the proposed mechanism not only provides required transient stability margin with minimum operation cost, but also does not restrict generators production capability.Sat, 07 Oct 2017 20:30:00 +0100Medical Tourism Destinations Prioritization using Group Decision Making Method with ...
http://scientiairanica.sharif.edu/article_4514_0.html
Medical tourism has developed rapidly worldwide, especially in Asia, and one of the most important problems facing the patient-tourists is the selection of the optimum destination. In this paper, we present a novel multiple criteria group decision making (MCGDM) methodology to evaluate and rank the medical tourism destinations vague based on vague information. A systematic assessment and selection model was constructed by investigating MCGDM problems with neutrosophic fuzzy preference relations (NFPRs). We began by defining NFPRs which allow the patient-tourists lacking information, time or patience, to express their uncertainty and hesitancy about the given preference values. The additive consistency and acceptable consistency for NFPRs were then proposed. Furthermore, the approach to improve the consistency for NFPRs was also validated and a series of aggregation operators were developed. In addition, we presented a systematic MCGDM method using NFPRs (MCGDM-NFPRs) in this paper to rank the medical tourism destinations. Then our proposed approach was applied to two cases considering different kinds of original data to prioritize medical tourism places. Finally, the applicability and feasibility of proposed approach were verified by the comparison with other previous methods, along with some analyses and a comprehensive discussionSat, 14 Oct 2017 20:30:00 +0100An Attribute-Based Anonymous Broadcast Encryption Scheme with Adaptive Security in the Standard ...
http://scientiairanica.sharif.edu/article_4517_0.html
In broadcast encryption schemes, a distribution center broadcasts an encrypted message to a subset chosen from a universe of receivers and only the intended users are able to decrypt the message. Most broadcast encryption schemes do not provide anonymity and the identities of target receivers are sent in plaintext. However, in several applications, the authorized users’ identities have the same sensitivity as the broadcasted messages. Yu, Ren and Lou (YRL) considered this issue and introduced an eicient anonymous aribute-based broadcast encryption scheme. In this paper, we first propose an aack on the YRL scheme and showthat the unauthorized receivers can also decrypt the broadcasted message. Next, we propose the Improved-YRL scheme and prove that it achieves anonymity and semantic security under adaptive corruptions in the chosen ciphertext seing. The proof is provided using the dual system encryption technique and is based on three complexity assumptions in composite order bilinear maps. The Improved-YRL scheme is a step forwardin solving the long-standing problem of secure and low overhead anonymous broadcast encryption.Sat, 14 Oct 2017 20:30:00 +0100A COMBINATION OF COMPUTATIONAL FLUID DYNAMICS, ARTIFICIAL NEURAL NETWORK AND SUPPORT VECTORS ...
http://scientiairanica.sharif.edu/article_4520_0.html
This study show the combination of computational fluid dynamics (CFD) and soft computing techniques to make viewpoint for two-phase flow modelling and accuracy evaluation of soft computing methods in the three-dimensional flow variables prediction in curved channels. Therefore, artificial neural network (ANN) and support vectors machines (SVM) models with CFD is designed to estimate velocity and flow depth variable in 60° sharp bend. Experimental results in 6 different flow discharges of 5, 7.8, 13.6, 19.1, 25.3 and 30.8 l/s to train and test, ANN and SVM models is used. The results of numerical models with experimental values are compared and the models accuracy is confirmed. The results evaluation show that all three models ANN, SVM and CFD perform well in flow velocity prediction, with correlation coefficient (R) of 0.952, o.806, and 0.680, and flow depth (R) of 0.999, 0.696, and 0.614 respectively. ANN model to predict both velocity and flow depth variables with mean absolute relative error (MARE) of 0.055 and 0.004 is the best model. Then SVM and CFD models with MARE of 0.069 and 0.089 in velocity prediction and in flow depth prediction CFD and SVM models with MARE of 0.007 and 0.011 are the best models, respectively.Sat, 14 Oct 2017 20:30:00 +0100Core impact force of vertical water jets on smooth and rough surfaces
http://scientiairanica.sharif.edu/article_4522_0.html
A normal way to dissipate energy of the dam released high velocity jets is to allow them to free-fall in to a plunge pool or impact a plane surface in case of dam site limitations. The water jets have an undisturbed core from nozzle outlet to a certain falling height, which has more impact force and less turbulent intensity than the developed part of the free jet. Experiments are conducted to determine core impact pressure coefficient of a vertical jet on smooth and rough plane surfaces. The experiment results for different jet diameters and falling heights showed considerable increase of the mean dynamic pressure coefficient with increase of the jet Froude number for both smooth surface and rough surface. A simple Froude based mathematical model is correlated for estimation of jet core impact force on the smooth and rough plane surfaces. In addition, a considerable increase of the jet core length was indicated with increase of the jet Froude number. Results also showed a strong correlation between turbulence intensity coefficient and the jet core length.Sat, 14 Oct 2017 20:30:00 +0100The Effects of Demand Response on Security-Constrained Unit Commitment
http://scientiairanica.sharif.edu/article_4536_0.html
This paper aims to study the effect of the hourly demand response (DR) on security-constraint unit commitment (SCUC) problem with considering economic and security objectives. The demand side participation can solve some of the electricity market problems. Here, DR is take into consideration as one of the demand side management (DSM) parts. The DR is consist of fixed and responsive loads. The fixed loads satisfy in any circumstance and responsive loads can curtail or shift to other operating hours. The combination of SCUC with DR is a complex and the mixed integer non-linear problem. The bender’s decomposition is used as an optimization technique for solve this problem. This technique solves the problem by decompose it into master and sub problems. One of the effective of this manner is reducing the processing time. The performance and effectiveness of the proposed method are demonstrated on 6-, 24- and 118-bus test systems.Sat, 14 Oct 2017 20:30:00 +0100Strength development of binary cement concrete, using Pulverized Fly Ash (PFA) under various ...
http://scientiairanica.sharif.edu/article_4537_0.html
Binary Cement incorporating Supplementary Cementitious Material (SCM) is widely used in concrete to reduce the cement consumption in construction industry. Cement production is a major source for the emission of Green House Gases (GHG) and there is an increasing pressure to reduce its consumption to avoid further Global Warming and Climate changes etc. In this research, Pulverised Fly Ash was used to partially replace cement in the concrete. Three levels of replacement of cement by PFA were selected and the specimens were cured under summer and winter environments. The strength development characteristics of the blended concrete were compared with the control mix without PFA. The strength gain under winter curing condition was observed as slower. At water cement ratio of 0.35, concrete with 30 % replacement of cement by PFA achieved high early age strength. PFA concrete gained more strength than the PC concrete after the age of 28 days. The 28 days compressive strengths of blended concrete for 30 % of cement replacement by PFA has been observed as nearly the same as that of control concrete mix. Sat, 14 Oct 2017 20:30:00 +0100Experimental Investigation of Bond Characteristics of Deformed and Plain Bars in Low Strength ...
http://scientiairanica.sharif.edu/article_4570_0.html
The use of inferior quality materials, inadequate detailing and poor construction practices are responsible for most of the brittle failure modes of non-engineered reinforced concrete structures. Bond failures in non-engineered reinforced concrete elements due to short anchorages or low concrete cover result in large slip deformations prevent the development of plastic deformations and reduce energy dissipation capacity. Until now, little work has been carried out that can lead to the development of bond-slip relationships for low strength non-engineered reinforced concrete structures. To address this, experiments have been carried out on pullout and splitting specimens under monotonic loading to investigate bond characteristics of typically used steel bars in non-engineered reinforced concrete structures. Various deficient parameters are considered in the experiments in order to develop multi-parameter bond strength relations for low strength concrete ≤15MPa. The key parameters examined in the experiments are low strength concrete, bar development length, concrete cover, re-bar types (deformed and plain) and re-bar diameter. This paper presents the experimental details and results which are further processed to develop bond strength equations for different bar types in low strength concrete. These equations can be used to define the bond-slip relation for conducting seismic vulnerability assessment of non-engineered structures.Tue, 24 Oct 2017 20:30:00 +0100Reliability analysis of a vertical cut in unsaturated soils using sequential Gaussian simulation
http://scientiairanica.sharif.edu/article_4571_0.html
This paper proposed a practical approach for reliability analysis of vertical cut in unsaturated soil. This approach extends the application of conditional random field into the unsaturated soils. A real case study of vertical cut was considered and three boreholes were drilled to investigate the subsurface layers. The Sequential Gaussian Simulation (SGS) was used to generate conditional random field with considering the possible fluctuation of soil properties between known data. The undersampled parameters were estimated by cokriging method, while Kriging method was used to estimate other stochastic parameters. In order to verify the efficienty of simulations, it was checked that all data were reproduced at their locations and the input semivariogram model was reproduced within acceptable fluctuations. To predict the unsaturated soil behaviour, the Soil Water Retention Curve (SWRC) was estimated using physico-empirical method with the aim of determining suction stress for finite element stability analysis. The vertical cut was analyzed with and without considering suction. It was concluded that considering unsaturated condition shifts the mean of safety factor from the unsafe ranges to the safe ranges. It was illustrated that the number of known data effects the construction of conditional random fields and leads to different probability of failure.Tue, 24 Oct 2017 20:30:00 +0100Multi-objective open location-routing model for relief distribution networks with split ...
http://scientiairanica.sharif.edu/article_4572_0.html
In this study, the response phase of the management of natural disasters is investigated. One of the important issues in this phase is determining the distribution areas and timely distribution of relief to affected areas in which transportation routing is of a critical matter. In the event of disasters, especially flood and earthquake, terrestrial transportation is not that much easy due to the damage to many infrastructures. For this reason, we propose that delivering relief from the distribution areas to disaster stricken places should be done simultaneously by terrestrial as well as aerial transportation modes to increase route reliability and reduce travel time. In this study, for relief allocation after earthquake, we offer a mixed-integer nonlinear open location-routing model in uncertainty condition. This model includes several contradictory objectives and variety of factors such as travel time, total costs, and reliability. In order to solve this model, a hybrid solution by combining robust optimization and fuzzy multi-objective programming has been used. The performance and effectiveness of the offered model and solution approach has been investigated through a case study on the earthquake in East Azerbaijan, Iran. Our computational results show the solution we have offered for real problems has been effective.Tue, 24 Oct 2017 20:30:00 +0100Investigation of geotechnical properties of clayey soils contaminated with gasoil using ...
http://scientiairanica.sharif.edu/article_4574_0.html
Oil and its derivatives such as gasoline, motor oil and gasoil are using in various industrial and non-industrial sectors as the main energy sources all over the world. However, within the process of exploration, transportation and storage they may spill or leaking into the soil. Among them the gasoil which is more widely used in different parts and machineries has the largest contribution in contaminating lands. Purgation of these areas is not always feasible or possible. Instead, they can be used in many engineering practices if the level of contamination is not high. In such cases knowing the geotechnical properties of these areas are of great necessity and importance. In this study, extensive laboratory tests were performed on remolded clayey samples mixed with gasoil to evaluate their geotechnical properties. The Response Surface Methodology (RSM) was used to analyze the data and find behavioral equations. According to testing results and RSM outputs a decrease in Atterberg limits, and increase in maximum dry density happen by increasing contamination. Also their shear strength parameters (c and f) both exhibit a turning change point at 8% gasoil content, while their variations trends are quite in opposite directionsTue, 24 Oct 2017 20:30:00 +0100Optimal design of grid-connected hybrid renewable energy systems using multi-objective ...
http://scientiairanica.sharif.edu/article_4578_0.html
The optimal design of grid-connected hybrid renewable energy systems (HRESs) is studied by using multi-objective evolutionary algorithm in this paper. With the total system cost and fuel emissions to be minimized, a two-objective optimization model of the hybrid system is established. Then the modified preference-inspired coevolutionary algorithm is, for the first time, applied to find the optimal configuration of a grid-connected hybrid system. As an example, a grid-connected hybrid system including PV panels, wind turbines and diesel generators has been designed and good results are obtained which show that the proposed method is effective.Fri, 27 Oct 2017 20:30:00 +0100Multi-Laminate Rate-Dependent Modelling of Static and Dynamic Concrete Behavior through Damage ...
http://scientiairanica.sharif.edu/article_4581_0.html
Mathematical simulation of the nonlinear tri-dimensional mechanical behavior of quasi-brittle materials like concrete is one of the biggest challenges in the engineering science. It is vital to have the knowledge of the response of concrete specimens subjected to low and high strain rate deformation for the analysis of concrete structures under the static and dynamic loading cases. The behavior of this material is generally known to be strain rate sensitive. Among phenomena of different orientation, the multi plane models, like multi-laminate models using a constitutive equation in a vectorial form rather than tensorial form by means of capturing interactions, can meet this goal adequately. This paper suggests a robust rate dependent damage based model in the multi-planes framework accomplished with minimum parameters for calibration and appropriate for engineering purposes. This damage formulation has been built on the basis of two types of essential damage, axial damage and shear damage, that basically can happen on each sampling plane and based on this concept two new axial and shear damage functions are proposed. Model verification has been studied under different compressive and tensile loading rates, comparing the results of the proposed model with the experimental data and Mohr-Coulomb failure criterion envelope line.Mon, 30 Oct 2017 20:30:00 +0100Numerical modeling of flood waves in a bumpy channel with the different boundary conditions
http://scientiairanica.sharif.edu/article_4582_0.html
In this paper, the Incompressible Smoothed Particle Hydrodynamics (ISPH) method is presented to simulate flood waves in uneven beds. The SPH method is a mesh free particle modeling approach that is capable of tracking the large deformation of free surfaces in an easy and accurate manner. Wave breaking is one of the phenomena that its free surface is complicated. Therefore, ISPH method is robust tool for the modeling of this kind of free surface. The basic equations are the incompressible mass conservation and Navier–Stokes equations that are solved using a two-step fractional method. In the first step, these equations are solved to compute velocity components by omitting the pressure term and in the absence of incompressible condition. In the second step, the continuity constraint is satisfied and the Poisson equation is solved to calculate pressure terms. In the present model, a new technique is applied to allocate density of the particles for the calculations. By employing this technique, ISPH method is stabled. The validation by comparison with laboratory data is conducted for bumpy channel with various boundary conditions. The numerical results showed good agreement with available experimental data. Also relative error is calculated for two numerical cases.Mon, 30 Oct 2017 20:30:00 +0100Investigation of the short-term behaviour of silty sand stabilized by colloidal silica
http://scientiairanica.sharif.edu/article_4583_0.html
Injection in soils using traditional materials, such as cement grout, has its inherent problems and has not shown the potential for further development in industrial applications. Accordingly, application of novel materials for injection in soils with considerable content of fines for stabilizing and even making them impermeable is suggested. Among different stabilizers that are injectable in soils with fine, colloidal silica seems very suitable due to its very low viscosity, nontoxicity in the nature, and adjustability of the setting time for slow injection in soils with fine. Based on laboratory tests performed in this research, the effect of colloidal silica on the strength parameters and the short-term behaviour of silty sand was examined. For characterizing the soil stabilized by colloidal silica, the silty sand samples with different silt values, in both unstabilized and stabilized conditions, were prepared with different concentrations of the stabilizer. 45 Uniaxial tests and 75 unconsolidated- undrained compressional triaxial tests were conducted. An increase in the undrained cohesion of all samples was observed. On the other hand, two different trends were observed in the alteration of the undrained internal friction angle of soils with low and high fines content.Mon, 30 Oct 2017 20:30:00 +0100Parameters Controlling Tensile Strength of Zeolite-Cemented Sands
http://scientiairanica.sharif.edu/article_4585_0.html
Treating soil with cement and zeolite is widely used in soil stabilization. This research intends to quantify the impact of cement and zeolite contents, porosity index, voids/cement ratio on zeolite cemented sands by the splitting tensile strength (σt) assessment. A program of splitting tensile tests using specimens by different zeolite replacement percentages is performed. Results indicate that cement replaces by zeolite at optimum proportion of 30%, then the value of improved σt of the cement sand specimens due to zeolite and cement chemical properties are exploited. Zeolite can effect more on a compacted mixture if its cement content and porosity increase. In this paper, it is shown that for the zeolite cemented sands, σt increases by cement content (C) raise and porosity (n) reduction and a power function is well-adapted to fit both σt-C and σt-n. Afterwards, good correlations are observed between voids/cement ratio (n/c) and the splitting tensile strength(σt)of the sand-zeolite-cement studied. Finally, based on a number of input variables as porosity (n), replacement of cement by zeolite (Z) and cement content (C), considering the regression approach, an equation is suggested to predict σt. Moreover, it is shown that the evolved equation could successfully predict .Mon, 06 Nov 2017 20:30:00 +0100The 3-D finite element analysis of press fitting process in railway wheel-set
http://scientiairanica.sharif.edu/article_4586_0.html
Variations in loadings of rolling contact components lead to a change in contact forces between surfaces. These forces are the main cause of rolling contact damages such as fatigue. Residual stresses are a major issue in railway wheel structures and it is appropriate to reduce such stresses. The aim of this paper is to estimate residual stresses in railway wheel due to hub to rim and axle to hub fitting process. a nonlinear three-dimensional model of stress is applied for analyzing stress field during press fitting process. An elastic-plastic finite element model is developed to model variable thermal loading in railway wheel. Finally, results of three dimensional finite element analysis showed a good agreement to field observations.Mon, 06 Nov 2017 20:30:00 +0100Optimizing insuring critical path problem under uncertainty based on GP-BPSO algorithm
http://scientiairanica.sharif.edu/article_4587_0.html
This study considers a novel class of bi-level fuzzy random programming problem about insuring critical path. In this study, each task duration is assumed as a fuzzy random variable and follows the known possibility and probability distributions. Because there doesn’t exist an effective way to solve the problem directly, we first reduce the chance constraint to two equivalent random subproblems under two kinds of different risk attitudes. Then, we may use sample average approximation (SAA) method for reformulating the equivalent random programming subproblems as their approximation problems. Since the approximation problems are also hard to be solved, we explore a hybrid genotype phenotype binary particle swarm optimization algorithm (GP-BPSO) for resolving two equivalent subproblems, where dynamic programming method (DPM) is used for finding the solution in the lower level programming. At last, a series of simulation examples are performed for demonstrating the validity of the hybrid GP-BPSO compared with the hybrid BPSO algorithm.Tue, 07 Nov 2017 20:30:00 +0100Investigation of bridge abutment displacements constructed on piles and geogrid reinforced soil ...
http://scientiairanica.sharif.edu/article_4591_0.html
One of the major problems in highway and railway bridges is the settlement of the bridge abutments, which its reduction has always been set as the research target. Two methods which have been widely used for controlling the settlement are either reinforcing the abutment subsoil with geogrid orconstructing the abutments on piles. This paper describes the application of a two-dimensional finite element method (FEM) by using Plaxis2D V8.5 for comparing the performance of these two methods. The effect of the geogrid normal stiffness, length and depth of reinforcement on the horizontal and vertical displacement of abutment is also investigated. Data from an instrumented bridge abutment has been used for the model verification. The reduction of the bridge abutment,the vertical settlement and the horizontal displacement by pile and geogrid have been analysed and compared.It is found that constructing the abutment on piles has a better performance in reducing the vertical settlement of the bridge abutment. However, lower lateral displacement can be obtained by using a geogrid with a higher normal stiffness. It is also found that, while the vertical settlement is not affected by the geogrid stiffness, the horizontal displacement of the abutment decreases with increasing the stiffness.Sat, 11 Nov 2017 20:30:00 +0100Strengthening and shape modification of fire-damaged concrete with expansive cement concrete ...
http://scientiairanica.sharif.edu/article_4592_0.html
This paper reports the results of an experimental study where the axial capacity of fire-damaged specimens repaired by expansive cement concrete and CFRP wrap were investigated. Specimens were subjected to axial compressive loading and their resulting stress-strain curves were recorded. Since the flat sides of the square samples remained unconfined then the cross sections of the tested specimens largely remained unconfined. The FRP jacket was effective only along the two diagonals of the cross-section. Confinement is generally more effective in specimens with circular cross-section than those with square cross-section. The change in cross section for some of the specimens from square to circle was implemented. To modify the shape, expansive cement concrete has been utilized to fill the gap between the circular and the square cross sections. The test results indicated that heating up to 500 °C caused a severe decline in compressive strength and the elastic modulus of concrete. Two layers of CFRP wrap around the concrete not only compensated the drop in compressive strength but furthermore it increased the strength beyond that of unheated specimen. However, the effect of wrapping alone on the stiffness and the elastic modulus is negligible. The heated square specimens that were first subjected to shape modification and then wrapped by CFRP sheet, experienced increase in the strength and the elastic modulus. Therefore, the stiffness and the compression strength of fire-damaged square concrete specimens could be compensated fully by the use of shape modification and CFRP wrapping of the cross section.Mon, 13 Nov 2017 20:30:00 +0100Development of a new integrated method for generation IDF curves based on three climatic ...
http://scientiairanica.sharif.edu/article_4593_0.html
Climate change can change the intensity-duration-frequency (IDF) curves. This research evaluates IDF curves changes of the Baghmalek climatic station in Iran's southwest. Developed integrated method extracts the IDF curves using of the Gumbel and log-Pearson III probability distributions and observed maximum annual precipitations. Durations of these precipitations are 15, 30, 45 minutes and 1,2,3,6 and 12 hours.
For this purpose, this method utilizes the recorded precipitation data of the Baghmalek climatic station in a 40-year period (1974-2013). Then mean square error method determines the probability distribution that has the best fitting with this data. The HadCM3 prepares precipitation data for a 30-year period (2021-2050) based on A1B, B1 and A2 scenarios. Also this method selects an optimum artificial neural network to extraction of maximum annual rainfall intensity for different durations and scenarios. Then selected network and the chosen probability distribution produce IDF curves for different return periods and scenarios. Produced IDF curves for different scenarios are compared to IDF curves of base time period. Because of increasing carbon dioxide and its greenhouse effects in these scenarios, rainfall intensity will increase for return periods less than 2.33 years while it will decrease for return periods more than 2.33 years.Mon, 13 Nov 2017 20:30:00 +0100Effects of aging on dynamic properties of MSW: A case study from Kahrizak Landfill, Tehran, Iran
http://scientiairanica.sharif.edu/article_4594_0.html
The effect of aging on dynamic properties of Municipal Solid Waste (MSW) including damping ratio and shear modulus was investigated in current research. For this purpose, a series of cyclic consolidated undrained (CU) triaxial tests performed on fresh and old reconstituted cylindrical specimens, taken from Mansoory Prototype Landfill (MPL), placed in Kahrizak landfill, Tehran, Iran.
The results show that the shear modulus of old samples (7.5 years old) was more than the fresh ones. This trend can be attributed to decomposition of waste over time which leads to reduction in organic content and, consequently, increment in fibrous waste particles (plastics) of the old samples. On the other hand, the results also state that the damping ratio is partially dependent on the composition of the specimen, and slightly decreases with increasing the age of MSW. The high percentage of organic content in fresh specimens can be considered as the main reason for this behavior. Finally, the normalized shear modulus reduction and strain-dependent material damping curves were proposed for both ages of retrieved MSW from Kahrizak Center Landfill (KCL). The results of current study are in the range reported in technical literature and can be used as reliable data in seismic purposes.Mon, 13 Nov 2017 20:30:00 +0100Experimental Evaluation of Effective Parameters on Characteristic Curves of Hydraulic Ram-Pumps
http://scientiairanica.sharif.edu/article_4597_0.html
Abstract
The effects of non-dimensional parameters on the characteristic curves of a ram pump were evaluated in this study using an experimental model. To do so, after providing dependent and independent parameters using dimensional analysis, effect of each independent parameter was examined on the dependent parameter. Experimental observations showed that relative pumping discharge (q/QT), relative wasting discharge (Q/QT) and pump efficiency (η) were depended on length to diameter ratio of drive pipe (L/D) and pressure head ratio (h/hm). Impulse valve parameter (nD/v0) was depended on L/D, h/hm and Reynolds number of flow in drive pipe. Characteristic curves were presented for ram pump used in this study to estimate dependent parameters as function pressure head ratio for various ratios of length to diameter. In addition, characteristic equations of the used ram pump were introduced using nonlinear regression. Evaluation of results showed that the characteristic curves and equations can be designed a ram pump system with high accurate, and this design method can be proposed for any kinds of ram pumps to use in engineering purpose.Mon, 27 Nov 2017 20:30:00 +0100Applying Materials Waste Quantification to Cement Waste Reduction in Tehran’s Residential ...
http://scientiairanica.sharif.edu/article_4598_0.html
Purpose of this research is twofold. Study’s first part focuses on developing quantitative wastage models for rebar, concrete, brick and cement, as major bulk traditional building materials, used in Tehran residential buildings. Primary results indicate that multiple linear regression is an apt tool to model studied variables’ effects on materials wastage. In every developed wastage model, subtractive or accumulative effect of each studied variable is recognized by its coefficient value and sign. Developed models resulted in adjusted R2 values of 0.907, 0.875, 0.920 and 0.790 respectively for rebar, cement, brick and concrete waste. Cement, with average wastage of 8.57% by weight, is identified as the most wasted material verified by the case study.
In study’s second part, previously developed models as well as project management experts’ opinions were combined to structure a cement waste reduction guideline for traditional building construction which is common in Tehran, Iran. With this purpose in mind, for projects’ initiating phase, choosing lump-sum contract instead of cost-plus contract is suggested. Moreover a financial incentive reward scheme, with its economic viability and environment friendliness, has been tested with positive results and hence is proposed for construction phase. Applicability of proposed scheme is verified through a case study.Mon, 27 Nov 2017 20:30:00 +0100Reinforcement dependent long term deflection response of baked clay beams
http://scientiairanica.sharif.edu/article_4601_0.html
Reinforced Baked Clay (RBC) might serve as low cost material of building construction to substitute Reinforced Cement concrete (RCC). Deflection of a beam under a sustained load is considered an important parameter. It is not yet reported in literature what is the effect of reinforcement on long-term deflection response of RBC beams and relative comparison to that of RCC beams. For this purpose, RBC beams were manufactured, baked, and post-reinforced in tension zone only with three ratios of reinforcement (i.e., 0.003, 0.006, and 0.009). All the beams were subjected to a sustained load of 50 kN for one year. The results indicate that long-term deflection of RBC beams was reduced to 20%, and 50% when the reinforcement ratio was increased to 2 and 3 times of the initial reinforcement ratio of 0.003, respectively. The ultimate load carrying capacity of the RBC beams was similar to that of RCC beams. The deflection of RBC beams was thrice of the deflection of RCC beams. This paper shows that RBC beams could be utilized instead of RCC ones with no sacrifice on strength.Fri, 01 Dec 2017 20:30:00 +0100The effect of Non-Darcy Flow on Induced Stresses Around a Wellbore in an anisotropic in-situ ...
http://scientiairanica.sharif.edu/article_4603_0.html
After drilling a well, the stresses will be altered and the induced stresses present the new state of stress. These induced stresses which result in geomechanical problems. The studies indicate that the flow of hydrocarbon into the wellbore influences the induced stresses. Darcy equation has been used in the past; however, the laminar flow assumption embedded in this equation cannot correctly model the flow of fluid when a non-Darcy flow dominates near a wellbore. Example of such situation includes the gas wells. In this study, analytical equations are developed to incorporate the effect of non-Darcy flow on the induced stresses around a wellbore. These equations developed based on Forchheimer flow equation. Then the simplified solutions were presented by considering the second term of Forchheimer flow equation. It was found that the difference between the results from Darcy and non-Darcy flow models is proportional to the drawdown pressure. Further studies included numerical simulation of non-Darcy fluid flow in a typical reservoir. Comparison of the results with the analytical models indicated that the magnitude of stresses in non-Darcy flow is larger than of Darcy flow. Finally, sensitivity of the reservoir properties on the induced stresses in the non-Darcy flow regime was investigated.Sat, 02 Dec 2017 20:30:00 +0100Using genetic algorithms for long-term planning of network of bridges
http://scientiairanica.sharif.edu/article_4604_0.html
Bridge maintenance activities are often budgeted, scheduled and conducted for networks of bridges with different ages, types and conditions, which can make bridge network maintenance management challenging. In this study, we propose an improved maintenance planning model based on genetic algorithm for a network of bridges to bring a long-term perspective to the lifespan of bridges. To test the applicability and efficiency of the model, it is applied to a network of 100 bridges in one of the south-western provinces of Iran. The results of the model implementation show considerable potential for improvement over the currently adopted model for bridge maintenance planning.Sat, 02 Dec 2017 20:30:00 +0100Uncertainty Management in Time Estimation of Construction Projects: A Systematic Literature ...
http://scientiairanica.sharif.edu/article_4605_0.html
Nowadays, the very low reliability of the project planning in certainty-based approaches, caused to use more intelligent methods for uncertainty management in construction projects. This systematic study aims to survey the methods which have been used to manage the uncertainties in time estimation of construction projects. A series of steps were undertaken during the review. The study was started with determining the purpose of the study, selecting appropriate keywords, and reducing the selected papers using some criteria. A deeper analysis was carried out on the final paper that meets the criteria for this review. The study is limited solely to papers referred in six top online databases. It aims to review how the papers have been distributed by a period of publishing and by country and the domains that these methods have been applied for. The result confirms that uncertainties which affect any project are based probability and possibility theories controlled by Risk Management and Fuzzy Logic. Finally, a hybrid method for uncertainty management in project scheduling is proposed. The result of the implementation of this method in the construction project of Iranian Gas Company shows that proposed method increases the accuracy of time estimation about 8 to 24 percent.Sat, 02 Dec 2017 20:30:00 +0100Nano grain refinement and strengthening of copper under room temperature RUE process
http://scientiairanica.sharif.edu/article_4607_0.html
In this investigation repetitive upsetting-extrusion (RUE) process was used to investigate the effect of severe plastic deformation on the microstructural changes and flow behavior of commercial pure copper. Initial material together with two passes, four passes and eight passes of RUE in annealed and non-annealed condition were studied. Results show that grain refinement, in the scale of nano meter, has mostly been achieved only after two passes of RUE which is essentially a combination of one upsetting and one extrusion path. Increasing the number of passes after four passes of RUE did not have discernible effect on the grain refinement. Such a behavior is explained to be due to saturation of dislocations and the formation of high angle grain boundaries after only two passes of RUE. The grains after eight passes of RUE process even became slightly larger than the two and the four passes of RUE. This was related to restoration phenomena occurring during high number of passes of RUE. Flow strength of the material after different passes substantially increased, though the rate at which the flow stress increased declined by increasing the number of passes. ETMB model were used to explain the deformation behavior of the RUE samples.Sun, 03 Dec 2017 20:30:00 +0100Teaching Music to Children with Autism: A Social Robotics Challenge
http://scientiairanica.sharif.edu/article_4608_0.html
Utilizing a humanoid social robot to systematically teach music to children with autism has not received wide attention to date. In this study, a novel robot-assisted music-based scenario has been designed in order to: 1) teach fundamentals of music via a xylophone-/drum-player robot as a teacher assistant, and 2) improve social/cognitive skills through active music games in children with autism. The educational-therapeutic interventions were conducted in an eleven-session case study program on three high-functioning and one low-functioning children with autism taking into consideration the children’s, parents’, and therapists’ experience during the program. The results indicated that as a tool and facilitator, the NAO robot does have the ability to teach musical notes/rhythms to the participants with high-functioning autism. It was also observed that the severity of the participants’ autism as well as the stress of the parents decreased somewhat during these sessions. Furthermore, noticeable improvements were seen in social/cognitive skills of all four participants; as well as the positive effect of this program on fine motor imitation skills of two subjects after the interventions. The progress reported from this preliminary exploratory study confirmed the potential benefits of using social robots and intelligent technologies as a facilitator in music-teaching and cognitive-rehabilitation.Mon, 04 Dec 2017 20:30:00 +0100Uncoupled Analysis of Rc-Slabs under Near-Field Air Explosions: Examination of Various ...
http://scientiairanica.sharif.edu/article_4609_0.html
In an uncoupled analysis, blast loads can be evaluated by empirical models, and then applied to the structure in a separate response analysis. The literature includes a variety of empirical models. However, the potentials of these models may not be fully realized due to a wide variation that may exist in their outcomes, particularly at detonations with a relatively close standoff distances from the target. As such, the selection of an appropriate model should be made with special considerations. This paper investigates the efficiency of various empirical models in blast analysis of the RC-slabs that are subjected to near-field air-detonations. The blast loads resulted by the empirical models are employed in a set of nonlinear FEA-runs. Due to the proximity of detonations, the distribution of blast-overpressure across the concrete slab at any instant in time is nonuniform. A simplified approach that accounts for this nonuniform distribution has been developed and verified in this study. To examine the effectiveness of the empirical models, the FEA-results are compared with the observations made in a set of previous experimental studies. Based on this comparative study, the most effective empirical model is identified, and remarks are made on the performance of the other models.Sat, 09 Dec 2017 20:30:00 +0100Increasing stability in model-mediated teleoperation approach by reducing model jump effect
http://scientiairanica.sharif.edu/article_20007_0.html
Model-mediated teleoperation is a predictive control approach for controlling haptic teleoperation systems whereby the environment force is virtually located on master side in order to increase the stability and transparency of the system. This promising approach, however, results in new challenges. One pivotal challenge is the model jump effect, which stems from the delay in correct creation of the virtual environment. Previous works have endeavored to reduce this effect; however, they either led to transparency decrease or assumed simplified environment models. In this paper, we propose a control approach for this aim based on the idea of decoupling. This means that when a new environment has been identified, the operation is interrupted and no signal is transmitted between master and slave sides. During this time, both sides are controlled by their own sliding mode controllers until the system reaches stability. The main advantage of this method is its independence from environment type, which makes it usable for different kinds of applications. To verify the effectiveness of the proposed approach simulation tests are conducted. The results show the system is stable in interaction with hard and soft environments in presence of large time delays in communication channels.Mon, 18 Dec 2017 20:30:00 +0100Sensitivity analysis of the effective centrifugal pump parameters using the EFAST method
http://scientiairanica.sharif.edu/article_20008_0.html
In the present study, the effective parameters of centrifugal pumps are investigated using the EFAST Sensitivity Analysis (SA) method. The SA is performed using GMDH type artificial neural networks (ANN) which are based on validated numerical data of flow field in centrifugal pumps. There are four design variables namely: leading edge angle of blades on hub section (β1 Hub), leading edge angle of blades on shroud section (β1 Shroud), trailing edge angle of blades (β2), and the stagger angle of blades on mid span (γ mid) and there are two objective functions namely: efficiency (h) and the required NPSH of impeller. The results show that among design variables, β2 has the highest effect on variations of h (46%) and NPSH (45%). Except β2, β1 Hub and γ mid has the highest effect on NPSH (33%) and h (28%) respectively. The effects of all of the design variables on objective functions are shown in the results.Mon, 18 Dec 2017 20:30:00 +0100Relief commodities distribution planning considering the features of demand areas: a robust ...
http://scientiairanica.sharif.edu/article_20009_0.html
Logistics planning plays an important role in providing services to the disaster -stricken areas. In this study, a scenario-based multi-objective model is presented to locate the distribution and evacuation centers and distribute the relief commodities with an appropriate allocation. It aims to serve the earthquake-stricken areas that are classified according to their construction qualities. The objective functions of cost, responsiveness and demand coverage are considered in the proposed optimization model. Moreover, due to the uncertain nature of a disaster and uncertainty in some model parameters, a robust optimization approach is utilized. A revised multi-choice goal programming method is applied to solve the multi-objective model. The proposed model is validated through a case study conducted in the city of Amol. The computational results show the efficiency of the proposed model in a real–world disaster situation.Mon, 18 Dec 2017 20:30:00 +0100Hydroelastic analysis of surface piercing hydrofoil during initial water entry phase
http://scientiairanica.sharif.edu/article_20010_0.html
In the current paper, numerical simulations of Fluid structure interaction (FSI) of a SP (Surface Piercing) hydrofoil are conducted in order to study the influence of elasticity on the initial water entry ventilation. Using ANSYS multi physics solvers, two-way FSI analyses are conducted by the implicit coupled URANS (Unsteady Reynolds averaged Navier–Stokes) equations and finite element method. Numerical result is validated by the well known rigid and elastic wedge water entry problems. Subsequently, computational results are presented for different velocity ratios range [0.38, 0.64] and elasticity factor range [0, 4]. Similar to the Surface Piercing Propeller (SPP), performance curves of a wedge water entry are defined. The obtained similar trend of propeller and wedge performance curves in fully ventilated, transition, and partially cavitated operation modes shows that the adopted approach (2D-study) can be appropriate for future related studies. FSI simulation results indicate that structural deformation can highly affect the location of transition point and shifts it toward the fully ventilated part at high Froude number and elasticity factor. The overall efficiency loss due to increase of foil elasticity is observed and overshoot time of the foil deformation related to the variation of Froude number and elasticity factor, is evaluated.Mon, 18 Dec 2017 20:30:00 +0100Experimental study of the effect of water to cement ratio on mechanical and durability ...
http://scientiairanica.sharif.edu/article_20014_0.html
In the present paper, the effect of Nano silica on mechanical properties and durability of concrete containing polypropylene fibers has been investigated. Here, the length and length to diameter ratio of used polypropylene fibers were considered to be fixed and equal to 18 mm and 600 respectively and the cement content was 479 kg/m3. The effect of fibers and Nano silica in four different percentages at 0.1, 0.2, 0.3 and 0.4 percent by volume for fibers and 3 percent for Nano silica in concrete with water to cement ratio of 0.33, 0.36, 0.4, 0.44 and 0.5 have been compared and evaluated. In total, more than 425 cubic and cylindrical specimens were made according to ASTM standards. Finally, samples of polypropylene fiber containing Nano-silica were tested under compressive loads, flexural strength, indirect tensile strength (Brazilian test), abrasion resistance, permeability and porosity and their mechanical properties were evaluated. The test results showed a significant increase in mechanical properties improvement and durability of concrete. Compressive strength, tensile strength, flexural strength and abrasion resistance (of concrete) increased up to 55%, 25%, 49%, and 45% respectively. Also, considerable reduction of hydraulic conductivity coefficient to 50% indicates high durability of these types of concrete.Sat, 23 Dec 2017 20:30:00 +0100Optimization of the aerodynamic configuration of a tubular projectile based on blind Kriging
http://scientiairanica.sharif.edu/article_20015_0.html
Based on optimal Latin hypercube design for computer experiments, blind Kriging surrogate model and sequential quadratic programming method, the optimal design of the aerodynamic configuration of a 30mm tubular projectile is carried out with the use of commercial softwares, such as UG, ICEM CFD, FLUENT etc. The aerodynamic configuration has been optimized to minimize the drag coefficients at different Mach numbers and maximize the kinetic energies at given flight ranges. The optimal configuration is obtained and discussed. Finally, the similarities and differences of the flow structure and aerodynamic characteristics between the original and optimal tubular projectiles are compared. The numerical optimal method proposed in this paper for optimizing the tubular projectile can provide important guidances for the aerodynamic configuration design of projectiles.Mon, 25 Dec 2017 20:30:00 +0100An improved model and a heuristic for capacitated lot sizing and scheduling in job shop problems
http://scientiairanica.sharif.edu/article_20016_0.html
This paper studies the problem of capacitated lot-sizing and scheduling in job shops with a carryover set-up and a general product structure. After analyzing the literature, the shortcomings are easily realized; for example, the available mathematical model is unfortunately not only non-linear but also incorrect. No lower bound and heuristic is developed for the problem. Therefore, we first develop a linear model for the problem on-hand. Then, we adapt an available lower bound in the literature to the problem studied here. Since the problem is NP-hard, a heuristics based on production shifting concept is also proposed. Numerical experiments are used to evaluate the proposed model and algorithm. The proposed heuristic is assessed by comparing it against other algorithms in the literature. The computational results demonstrate that our algorithm has an outstanding performance in solving the problem.Mon, 25 Dec 2017 20:30:00 +0100Sustainability Assessment of Supply Chains by Inverse Network Dynamic Data Envelopment Analysis
http://scientiairanica.sharif.edu/article_20017_0.html
This paper focuses on assessing sustainability of supply chains. In this paper, at first, we propose network dynamic range adjusted measure (RAM) model. Then, inverse version of network dynamic RAM model is proposed. Our inverse network dynamic data envelopment analysis (DEA) model changes both inputs and outputs of decision making units (DMUs) so that current efficiency scores of DMUs remain unchanged. We change inputs and outputs without any change in efficiency score of DMU under evaluation while inputs and outputs may have large ranges. A case study shows efficacy of our proposed model.Mon, 25 Dec 2017 20:30:00 +0100Lagrangian relaxation approach to minimize makespan for hybrid flow shop scheduling problem ...
http://scientiairanica.sharif.edu/article_20018_0.html
This research addresses scheduling problem of n jobs on a Hybrid Flow Shop (HFS) with unrelated parallel machines in each stage. A monolithic mixed integer linear programming (MILP) model is presented to minimize the maximum completion time (makespan). As the research problem is shown to be strongly NP-hard, a Lagrangian relaxation (LR) algorithm is developed to handle the HFS scheduling problem. We design two approaches, simplification of subproblems and dominance rules, to solve the subproblems which are generated in each iteration. For evaluation purposes, numerical experiments with small and large size problems are randomly generated with up to 50 jobs and four stages. The experimental results show that the Lagrangian relaxation approaches outperform the MILP model with respect to CPU time. Furthermore, from the results, it can be conclude that the simplification of subproblems shows slightly better solutions in comparison with dominance rules to solve the subproblems.Mon, 25 Dec 2017 20:30:00 +0100An effective approach for structural damage localization in flexural members based on ...
http://scientiairanica.sharif.edu/article_20019_0.html
This paper presents a method for structural damage localization based on signal processing using generalized S-transform (SGS). The S-transform is the combinations of the properties of the short-time Fourier transform (STFT) and wavelet transform (WT) that has been developed over the last few years in an attempt to overcome inherent limitations of the wavelet and short time Fourier transform in Time-Frequency representation of non-stationary signals. The generalized type of this transform is the SGS-transform that has adjustable Gaussian window width in the time-frequency representation of signals. In this research, the SGS-transform has been employed due to its favorable performance in detection of the structural damages. The performance of the proposed method has been verified by means of three numerical examples and also the experimental data obtained from the vibration test of 8-DOFs mass–stiffness system. By way of the comparison between damage location obtained from the proposed method and simulation model, it was concluded that the method is sensitive to the damage existence and clearly demonstrates the damage location.Mon, 25 Dec 2017 20:30:00 +0100Airline delay prediction by machine learning algorithms
http://scientiairanica.sharif.edu/article_20020_0.html
Flight planning, as one of the challenging issue in the industrial world, is faced with many uncertain conditions. One such condition is delay occurrence, which stems from various factors and imposes considerable costs on airlines, operators, and travelers. With these considerations in mind, we implemented flight delay prediction through proposed approaches that are based on machine learning algorithms. Parameters that enable the effective estimation of delay are identified, after which Bayesian modeling, decision tree, cluster classification, random forest, and hybrid method are applied to estimate the occurrences and magnitude of delay in a network. These methods were tested on a U.S. flight dataset and then refined for a large Iranian airline network. Results showed that the parameters affecting delay in US networks are visibility, wind, and departure time, whereas those affecting delay in Iranian airline flights are fleet age and aircraft type. The proposed approaches exhibited an accuracy of more than 70% in calculating delay occurance and magnitude in both the whole-network US and Iranian. It is hoped that the techniques put forward in this work will enable airline companies to accurately predict delays, improve flight planning, and prevent delay propagation.Mon, 25 Dec 2017 20:30:00 +0100A knowledge-based algorithm for supply chain conflict detection based on OTSM-TRIZ problem flow ...
http://scientiairanica.sharif.edu/article_20021_0.html
The coordination and integration of efforts and activities of supply chain (SC) members that is a key component of supply chain management success has become a challenging activity due to conflicts in such systems. Lack of proper detection of conflicts in a SC and therefore mismanagement of them will increase disruption risk in the SC. In this article, a knowledge-based algorithm is presented based on the OTSM-TRIZ (general theory of powerful thinking) problem flow network approach to identify, formulate and solve the conflicts of SCs before they occur and cause harmful effects. The proposed algorithm involves analyzing and developing network of problems (NoP) in order to transfer it into a network of conflicts. This study validated the proposed algorithm through a case demonstration. Through the implementation and application, the result demonstrated that this knowledge- based algorithm was able to identify and formulate supply chain conflicts before they occur and more importantly it greatly increased the coordination between supply chain entities.Mon, 25 Dec 2017 20:30:00 +0100An Optimization Model for Emergency Vehicle Location and Relocation with Consideration of ...
http://scientiairanica.sharif.edu/article_20022_0.html
The main purpose of emergency medical services is providing fast medical care, as well as transporting patients to the hospital, in the shortest possible time. Healthcare managers try to improve healthcare systemsthrough reducing the response to demand time. In this paper, we seek to propose an optimization model in order to cover as much demand as possible in the shortest possible time using the available ambulance fleet. To do so, considering the response and service time, amount of demand during the time periods, limitation in the number of available emergency vehicles and the capacity of ambulance stations, we have proposed a mixed integer linear programming optimization model, aiming to minimize the total response time. In this paper we take into account fleet relocation and unavailability time, the time interval in which the vehicle is on its way or doing a service at a demand point. Then, a sensitivity analysis is conducted on the model by manipulating the parameters, so as to observe the effects on the outputs. In order to evaluate the model, several articial test problems were generated and solved. The results depict the capability of the proposed model in dealing with emergency cases.Mon, 25 Dec 2017 20:30:00 +0100Phenol Removal from Aqueous Solution by Adsorption Process: Study of The Nanoparticles ...
http://scientiairanica.sharif.edu/article_20023_0.html
This study was performed to measure the potential utilization of agro-waste to generate nanoparticles and evaluate the capability of it’s as a low cost adsorbent for removal of phenol. Adsorption studies for phenol removal by using Aloe vera and Mesquite leaves nanoparticles carried out under various experimental conditions including pH, nano-bioadsorbent dosage, phenol concentration, contact time, temperature and ionic strength in a batch reactor. The adsorption kinetics by pseudo-first order and pseudo-second order models and isotherm technique by Freundlich and Langmuir isotherms models were applied. The results showed that the rate of phenol adsorption increases in both nano-bioadsorbents with an increase of pH up to 7, adsorbent dosage up to 0.08 gL-1, phenol initial concentration up to 32 mgL-1, contact time up to 60 min and raising in temperature. The adsorption data followed the Freundlich isotherm model. The kinetic studies indicated that the adsorption of phenol with nano-bioadsorbents was best described by the pseudo second order kinetics. We found that the nanoparticles prepared from Aloe vera and Mesquite leaves had a high capability in adsorption of phenol, beside the point that they could be accessed at a low cost. These agro-wastes can be used to remove phenol from aqueous environments.Tue, 26 Dec 2017 20:30:00 +0100Soil behaviour around the stub abutment of an integral bridge and buried piles in the ...
http://scientiairanica.sharif.edu/article_20030_0.html
The change in the deck length under temperature load affects the upper part of integral bridge abutments and causes abutments rotation. The deck contraction makes the abutment move away from the backfill and causes a failure wedge. To prevent the failure wedge, a new method has been proposed. In this method, the inhibition of integral bridges under contraction is done by cables connected from each abutment to the buried piles outside the bridge along the abutments. In the analysis, the behaviour of soil around the abutment and buried piles is an important parameter which has a great influence on the results. In this paper, the soil behaviour around a laterally loaded stub abutment and buried piles was studied on laboratory stub abutment models using the PIV (particle image velocimetry) method. The PIV analysis was carried out to obtain the deformation pattern and shear strains of the soil around the stub abutment and buried piles. The effects of piles number and soil – pile interaction on the soil deformation pattern were investigated. The results showed that the use of buried piles connected by the cable avoided creating a failure wedge in the backfill.Sat, 06 Jan 2018 20:30:00 +0100Optimal Production and Ordering Strategies with Defective Items and Allowable Shortage under ...
http://scientiairanica.sharif.edu/article_20032_0.html
This study investigated a production-inventory model with defective items under a two-part trade credit where the agreement of conditionally freight concession is considered in the integration supply chain. We assume the inspection process is conducted by the retailer before selling incoming items. All the defective items are discovered, stored and then sold as a single batch to a secondary market at a decreased price. Furthermore, shortages are allowed and completely backlogged for the retailer. The purpose of this study is to determine the optimal number of shipments per production cycle for the supplier, and the optimal length of time wherein there is no inventory shortage and replenishment cycle for the retailer such that the total profit function has a maximum value. In theoretical analysis, the existence and uniqueness of the optimal solutions are shown and an algorithm is developed to find the optimal solutions. Furthermore, numerical examples are presented to demonstrate the solution procedures and a sensitivity analysis of the optimal solutions regarding all parameters are also carried out.Sat, 06 Jan 2018 20:30:00 +0100TIME SERIES PREDICTION WITH A HYBRID SYSTEM FORMED BY ARTIFICIAL NEURAL NETWORK AND COGNITIVE ...
http://scientiairanica.sharif.edu/article_20033_0.html
Time series prediction is a remarkable research interest, which is widely followed by scientists / researchers. Because many fields include analyzing processes over such time series, different kinds of approaches, methods, and techniques are often employed in order to achieve alternative prediction ways. It seems that Artificial Intelligence oriented solutions have strong potential on providing effective and accurate prediction approaches in even most complicated time series structures. In the sense of the explanations, this study aims to introduce an alternative, Artificial Intelligence based approach of Artificial Neural Networks, and Cognitive Development Optimization Algorithm, a recent intelligent optimization technique introduced by the authors. Here, it has been aimed to predict different kinds of time series, by using the introduced system / approach. In this way it has been possible to discuss about application potential of the hybrid system and report findings related to its success on prediction. The authors believe that the study has been a good chance to support the literature with an alternative solution approach and see potential of a newly developed, Artificial Intelligence oriented optimization algorithm on different applications.Sat, 06 Jan 2018 20:30:00 +0100Steady state Thermal and Mechanical stresses in two-Dimensional functionally graded ...
http://scientiairanica.sharif.edu/article_20037_0.html
In this paper, the general analysis of two-dimensional steady-state thermal and mechanical stresses for a hollow thick cylinder made of functionally graded piezoelectric materials (2D-FGPMs) is developed.The general form of thermal ,mechanical and electrical boundary conditions is considered on the inside and outside surfaces. A direct method is used to solve the heat conduction equation and the non-homogenous system of partial differential Navier equations, using the complex Fourier series and the power law functions method.The material properties are assumed to depend on the radial and circumferential variables and are expressed as power law functions along the radial and circumferential direction.Sat, 06 Jan 2018 20:30:00 +0100An Imperfect Multi-Item Single Machine production system with Shortage, Rework, and Scrapped ...
http://scientiairanica.sharif.edu/article_20038_0.html
In this paper, we consider a deficient production system with permissible shortages. The production system consists of a unique machine that manufactures a number of products that a part of them are imperfect in form of rework or scrap. These defective products are identified by 100% inspection during production, then, they are whether reworked or disposed of after normal production process. Like real-world production systems, there are diverse kinds of errors creating dissimilar breakdown severity and rework. Moreover, reworks have non-zero setup times that makes the problem closer to real-world instances where machines require some preparations before starting a new production cycle. Thus, we introduce an economic production quantity (EPQ) problem for an imperfect manufacturing system with non-zero setup times for rework items. The rework items are classified into several categories based on their type of failure and rework rate. The aim of this study is to obtain optimum production time and shortage in each period that minimizes inventory system costs including setup costs in reworks, holding costs, production costs, inspection costs, disposal costs, and shortage. Finally, a numerical example is proposed to assess efficiency and validation of the proposed algorithm.Sat, 06 Jan 2018 20:30:00 +0100Static and Dynamic Path Planning of Humanoids using an Advanced Regression Controller
http://scientiairanica.sharif.edu/article_20039_0.html
With an ability to mimic the human behaviour, humanoid robots have become a topic of major interest among research fellows dealing with robotic investigation. The current work is focussed on the design of a novel navigational controller based on the logic of the regression analysis to be used in the path planning and navigation of humanoid robots. In the current investigation, static and dynamic path planning of humanoid NAOs are encountered. The static path planning represents a single NAO navigating through random static obstacles. The dynamic path planning represents multiple humanoid NAOs navigating through random static obstacles and acting as dynamic obstacles for each other. A Petri-Net controller is designed to avoid the collision among the multiple NAOs in dynamic path planning. To reduce the path length and time travel and to provide the shortest possible path, an advanced regression controller is implemented in the NAOs in both simulation and experimental environments. Finally, a comparison has been performed between the simulation and experimental results, and a good agreement is observed between both the results with a minimal percentage of error. The proposed navigational controller is also tested against other existing navigational technologies to validate better efficiency.Sat, 06 Jan 2018 20:30:00 +0100Estimating the Parameters of Mixed Shifted Negative Binomial Distributions via an EM Algorithm
http://scientiairanica.sharif.edu/article_20040_0.html
Discrete phase-type (DPH) distributions have one property that is not shared by continuous phase-type (CPH) distributions, i.e., representing a deterministic value as a DPH random variable. This property distinguishes the application of DPH in stochastic modeling of real-life problems such as stochastic scheduling where service time random variables should be compared with a deadline that is usually a constant value. In this paper, we consider a restricted class of DPH distributions, called Mixed Shifted Negative Binomial (MSNB) and show its flexibility in producing a wide range of variances as well as its adequacy in fitting fat-tailed distributions. These properties render MSNB applicable to represent data on certain types of service time. Therefore, we adapt an expectation-maximization (EM) algorithm to estimate the parameters of MSNB distributions that accurately fit trace data. To present the applicability of the proposed algorithm, we use it to fit real operating room times as well as a set of benchmark traces generated from continuous distributions as case studies. Finally, we illustrate the efficiency of the proposed algorithm by comparing its results to that of two existing algorithms in the literature. We conclude that our proposed algorithm outperforms other DPH algorithms in fitting trace data and distributions.Sat, 06 Jan 2018 20:30:00 +0100Chaos and Bifurcation in Nonlinear Inextensional Rotating Shafts
http://scientiairanica.sharif.edu/article_20041_0.html
In this paper, bifurcation and chaotic behavior of in-extensional rotating shafts are investigated. The shaft is modeled as a Rayleigh simply supported beam, spinning with constant rotational speed. Using two–mode Galerkin truncation, the partial differential equations of motion are discretized and then with the aid of numerical simulations, the dynamical behavior of the rotating shaft is studied. Using tools from nonlinear dynamics, such as time history, bifurcation diagram, Poincaré map, Lyapunov exponents, and amplitude spectra, a comprehensive analysis is made to characterize the complex behavior of the rotating shaft. Periodic (synchronous), quasi-periodic, chaotic and transient chaotic responses are observed in the neighborhood of the second critical speed. The effect of rotary inertia and damping on the dynamics of the rotating shaft is considered. It is shown that the chaotic response is possible for a shaft with weak nonlinearity without the existence of any internal resonance.Sat, 06 Jan 2018 20:30:00 +0100Cement grain size effect on the Geotechnical properties of Stabilized Clay
http://scientiairanica.sharif.edu/article_20042_0.html
In this study, some geotechnical properties of microfine and ordinary Portland cements stabilized high plasticity clayey soil (HPCS) were investigated. The results showed that liquid limit, permeability, swelling potential and compressibility of HPCS were reduced and HPCS’s plastic limit and unconfined compressive strength (UCS) was increased by both microfine Portland cement (MPC) and ordinary Portland cement (OPC) stabilizations. Besides, liquid limit, permeability, swelling potential and compressibility of HPCS were further reduced by MPC. Although dry UCS of MPC stabilized HPCS was almost the same as the dry UCS of OPC stabilized HPCS, the plastic limit and wet cured UCS of MPC stabilized HPCS was higher than that of wet cured UCS of OPC stabilized HPCS. In general, as the size of cement particles became finer, the stabilization of HPCS became more effective.Sat, 06 Jan 2018 20:30:00 +0100Using an optimized RBF neural network to predict the out-of-plane welding distortions based on ...
http://scientiairanica.sharif.edu/article_20043_0.html
This study deals with the effect of locator positioning in 3-2-1 locating scheme to control the out-of-plane distortion in gas tungsten arc welding of sheet metals. To apply this locating scheme on the sheet metals, a suitable fixture is designed. The distortion of the welded plates has been predicted using the radial basis function (RBF) neural network. To gather the experimental data employed in the RBF modeling process, a set of welding tests is performed on the sheet specimens by varying the positions of the three locators. The parameters of the network are optimally selected using the simulated annealing (SA) optimization algorithm. The average and maximum error computed for the test dataset were respectively 2.43% and 5.30% while in some cases the error falls below 1%. The results of the RBF network show very good agreement with the experiments and it can be concluded that this modeling technique can be utilized successfully in predicting the welding distortions when the 3-2-1 locating scheme is used.Sat, 06 Jan 2018 20:30:00 +0100Investigation on effect of using rubber as core material in sandwich composite plate subjected ...
http://scientiairanica.sharif.edu/article_20044_0.html
In this article, the structural performance of composite plate under low velocity impact is studied. Two forms of layup sequence namely jute-epoxy laminate (JE) and jute-epoxy-rubber sandwich (JE-R-JE) are considered for evaluation. Special emphasis is provided for evaluating the influence of normal and oblique loading. The various dynamic parameters such as energy, peak load, and deformation are analysed in detail to study the effect of impact angle on both laminate and sandwich. Stress analysis of both the laminate and sandwich structure is carried out to discuss the effect of introducing rubber as a core material. The results reveal that using rubber as a core material has a significant effect on energy absorption. In addition, it is noticed that increasing the angle of impact yields better performance of the composite plate. The results presented here may serve as benchmark for the effective utilization of composite plates in low velocity impact applications.Sat, 06 Jan 2018 20:30:00 +0100Design of prototype dual axis tracker solar panel controlled by geared dc servo motors
http://scientiairanica.sharif.edu/article_20045_0.html
Sunlight sensing for maximum illumination, providing initial position and delays of PV panel, design of an adequate control unit for minimal consuming servo motors are the main challenges of solar tracking systems. That is the objective of this paper to design and implement an automatic control for directing maximum solar illumination to a photovoltaic (PV) panel. The proposed prototype dual axis solar tracker panel is used to optimize the conversion of solar energy into electricity by orienting the panel toward the real position of the sun, at a cost of mechanical complexity and maintenance need, for the best efficiency. In hardware development, two geared DC servo motors are pulse width modulation (PWM) controlled by a drive unit moving the panel using four light dependant resistors (LDR) to provide analog signals processed by a simple and low energy ATMEGA328P microcontroller with Arduino. For the software part, after data processing, a C++ programming controls two DC servo motors to position light sensors in the most favorable direction, where solar panel and sensors will be perpendicular to the sunlightSat, 06 Jan 2018 20:30:00 +0100Optimal design of monopile offshore wind turbine structures using CBO, ECBO, and VPS algorithms
http://scientiairanica.sharif.edu/article_20090_0.html
Considering both size and dimensions of the offshore wind turbine structures, design optimization of such structures is a fruitful yet, simultaneously, onerous task due to the tempestuous complexity of the problem, which mostly comes from their environment. However, in this study, a computerized methodology based on meta-heuristic algorithms, consisting of the Colliding Bodies Optimization (CBO), Enhanced Colliding Bodies Optimization (ECBO), and Vibrating Particle System (VPS), is presented such that more economic upshots can be accomplished. Hence, minimization of the total weight of the structure subjected to a number of structural constraints, including a frequency constraint, by applying the above mentioned algorithms is the underlying goal of this study. Using the data from Horns Rev I offshore wind farm, which is located in the coastlines of Denmark in the North Sea, this study is performed based on a simplified structural model of a monopile offshore wind turbine structure, which can be utilized in preliminary stages of pertinent projects for conducting suitable comparisons.Tue, 09 Jan 2018 20:30:00 +0100Efficient estimation of Pareto model using modified maximum likelihood estimators
http://scientiairanica.sharif.edu/article_20107_0.html
In this article, we have proposed some modifications in the maximum likelihood estimation for estimating the parameters of the Pareto distribution and evaluated performance of these modified estimators in comparison to the existing maximum likelihood estimators. Total Relative Deviation (TRD) and Mean Square Error (MSE) have been used as performance indicators for goodness of fit analysis. The modified and traditional estimators have been compared for different sample sizes and different parameter combinations using a Monto Carlo simulation in R-language. We have concluded that the modified maximum likelihood estimator based on expectation of empirical Cumulative Distribution Function (CDF) of first-order statistic performs much better than the traditional ML estimator and other modified estimators based on median and coefficient of variation. The superiority of the said estimator is independent of sample size and choice of true parameter values. The simulation results were further corroborated by employing the proposed estimation strategies on two real-life data sets.Sat, 13 Jan 2018 20:30:00 +0100Reference Tracking of Nonlinear Dynamic Systems over AWGN Channel Using Describing Function
http://scientiairanica.sharif.edu/article_20108_0.html
This paper presents a new technique for mean square asymptotic reference tracking of nonlineardynamic systems over Additive White Gaussian Noise (AWGN) channel. The nonlinear dynamic systemhas periodic outputs to sinusoidal inputs and is cascaded with a bandpass filter acting as encoder.Using the describing function method, the nonlinear dynamic system is represented by an equivalentlinear dynamic system. Then, for this system, a mean square asymptotic reference tracking techniqueincluding an encoder, decoder and a controller is presented. It is shown that the proposed referencetracking technique results in mean square asymptotic reference tracking of nonlinear dynamic systemsover AWGN channel. The satisfactory performance of the proposed reference tracking technique isillustrated using practical example simulations.Sat, 13 Jan 2018 20:30:00 +0100Modeling of a PIN Diode RF Switch for Re configurable Antenna Application
http://scientiairanica.sharif.edu/article_20110_0.html
The paper proffers the procedure to model a PIN diode RF switch using full-wave EM solver, HFSS and utilizes the switch to built a simple partial ground plane antenna with omnidirectional radiation pattern. The proposed antenna has ability to tune it from ultra-wideband to narrowband mode. The frequency reconfigurability is accomplished by incorporating a rectangular slot resonator and a PIN diode RF switch embedded in the partial ground plane. The antenna demonstrates -10 dB impedance bandwidth from 500 MHz to 6 GHz in the ultra-wideband mode and 1.125 GHz to 2 GHz in the narrowband mode. A parasitic is stacked in the ground plane to improve the impedance matching and a rectangular slot is fused to explore the bandwidth-limiting possibility of the antenna. The optimization of the antenna is done by full-wave EM solver, HFSS and Specific Absorption Rate (SAR) of the antenna is examined using the equivalent flat tissue phantom. A prototype of the proposed antenna is fabricated and execution is accepted by measured results. The proposed antenna has simple and miniature structure, low SAR (0.41 W/Kg), omnidirectional pattern and low cross-polarization (<-15dB in E-plane and <-30dB in H-plane).Sat, 13 Jan 2018 20:30:00 +0100A numerical model for predicting hepatocytes ureagenesis and its related inborn enzyme ...
http://scientiairanica.sharif.edu/article_20140_0.html
One of the important functionality of liver cells is ammonia detoxification and urea production. In this study, a numerical model of urea cycle in hepatocytes have been developed. Navier Stokes along with convection equations have been employed to study the process of ammonia elimination and urea production using a microfluidic channel.The concentration of urea and ammonia throughout the channel were obtained. Furthermore, the urea cycle was modeled regarding its four main enzymes. This resulted in twelve rate equations which were solved to determine the concentration of each metabolites participating in the urea cycle. Application of results were implied to common disorders such as Hyperammonemia type I and II and argininosuccinicaciduria type I and II. Result of this study indicated that there is 80% of reduction in concentration of Citrulline, Argininosuccinate, Arginin, Carbamoyl phosphate, Phosphate and Fumarate in hyperammonemia type II. A 10 fold increase of Argininosuccinate concentration was observed in both argininosuccinicaciduria I and II. The predicted result may be useful in better understanding and control of metabolite deficiencies in patient abnormalities.Fri, 19 Jan 2018 20:30:00 +0100Hypercube Queuing Models in Emergency Service Systems: A State-of-the-Art Review
http://scientiairanica.sharif.edu/article_20141_0.html
This study provides a review of hypercube queuing models (HQMs) in emergency service systems (ESSs). This survey presents a comprehensive review and taxonomy of models, solutions and applications related to the HQM after Larson [12]. In addition, the structural aspects of HQMs are examined. Important contributions of the existing research are addressed by taking into account multiple factors. In particular, the integration of location decisions with HQMs for designing an ESS is discussed. Finally, a list of issues for future studies are presented.Fri, 19 Jan 2018 20:30:00 +0100A local differential transform approach for the cubic nonlinear Duffing oscillator with damping term
http://scientiairanica.sharif.edu/article_20142_0.html
Nonlinear behaviour of various problems is described by the Duffing model interpreted as a forced oscillator with a spring which has restoring force. In this paper, a new numerical approximation technique based on differential transform method has been introduced for the nonlinear cubic Duffing equation with and without damping effect. Since exact solutions of the corresponding equation for all initial guesses do not exist in the literature, we have first produced an exact solution for specific parameters by using the Kudryashov method to measure the accuracy of the currently suggested method. The innovative approach has been compared with the semi-analytic differential transform method and the fourth order Runge-Kutta method. Although the semi-analytic differential transform method is valid only for small time intervals, it has been proved that the innovative approach has ability to capture nonlinear behaviour of the process even in the long-time interval. In a comparison way, it has been shown that the present technique produces more accurate and computationally more economic results than the rival methods.Fri, 19 Jan 2018 20:30:00 +0100Cost Function and Optimal Boundaries for a Two-level Inventory System with Information Sharing ...
http://scientiairanica.sharif.edu/article_20144_0.html
In this paper, we consider a two-echelon inventory system with a central warehouse and two identical retailers employing information sharing. Transportation times to each retailer and the warehouse are constant. Retailers face independent Poisson demand and apply continuous review policy, -policy. The warehouse initiates with m batches (of given size ) and places an order to an outside supplier when a retailer’s inventory position reaches , where is the inventory position considered by central warehouse and is a non-negative constant. So far, an approximate cost function as well as exact analysis of system for only one retailer has been proposed. However, the derivation of the exact value of the expected total cost of this system for more than one retailer, is still an open question. This paper attempts to meet this challenge and derive the exact cost function for two retailers. To achieve this purpose, we resort to conditional probability to split the problem into two simpler problems then we obtain the exact expected total cost of the system.Fri, 19 Jan 2018 20:30:00 +0100Effects of welding parameters on penetration depth in mild steels A-TIG welding
http://scientiairanica.sharif.edu/article_20145_0.html
A-TIG welding is a welding method in which TIG welding is conducted by covering a thin layer of activating flux on the weld bead beforehand. The most benefit of this process is the gain in weld penetration depth. A-TIG welds were produced on mild steel plates with TiO2 flux. The emphasis of this paper lies in introducing the effects of various process parameters (welding current, welding speed, powder/acetone ratio of the flux, arc length and electrode angle) in mild steel A-TIG welding. The weld penetration depth was the measured metallographically. An optimum value was determined for each welding parameter.Fri, 19 Jan 2018 20:30:00 +0100Performance investigation of a Diesel engine under effective efficiency-power-power density ...
http://scientiairanica.sharif.edu/article_20146_0.html
A performance analysis of a Diesel engine in terms of effective power (EP), effective power density (EPD) and effective efficiency (EE) has been performed using a novel realistic finite-time thermodynamics (FTT) modeling. The effects of design and operating parameters of the diesel cycle such as bore-stroke length ratio (d/L), equivalence ratio (ER), compression ratio (CR), cycle temperature ratio (CTR), cycle pressure ratio (CPR), stroke length (L), friction coefficient (FRC), engine speed (N), mean piston speed, inlet pressure and inlet temperature on the engine performance have been investigated. In addition, the energy losses depending on incomplete combustion (IC) , friction losses (FRL), heat transfer losses (HTRL) and exhaust output losses (EOL) have been described as fuel input energy. In order to acquire reasonable results, variable specific heats with respect to temperature for working fluid have been used. The results presented could be an essential tool for Diesel engine designers.Fri, 19 Jan 2018 20:30:00 +0100Plasma based surface modification of Poly (dimethylsiloxane) electrospun membrane proper for ...
http://scientiairanica.sharif.edu/article_20148_0.html
Constructing of the scaffolds for cell culture applications has long been of interest for engineering researchers and biologist. In this study, a novel process is utilized for construction of suitable membrane with a high mechanical strength and appropriate surface behavior. Poly (dimethylsiloxane) (PDMS) is electrospun into fine fibers using poly (methyl methacrylate) (PMMA) as the carrier polymer in different weight ratios. Since the surface behavior of all PDMS substrates is moderately hydrophobic (120 < contact angle (CA) < 150), the electrospun membranes with higher PDMS ratios show slightly higher hydrophilicity. Direct plasma treatment is utilized to change the interfacial wettability of the membrane. Applying plasma changes the surface energy and renders the PDMS/PMMA substrates superhydrophilic (CA<5). In the following, the mechanical properties of the membrane are evaluated by the tensile test, and the results confirm the suitable mechanical strength of electrospun PDMS for cell culturing objectives (yield stress of more than 10 kPa). Also, changing the PDMS ratio doesn’t significantly affect the total stiffness of the membrane. Thus, applying the proposed fabrication protocol provides a proper platform for cell viability and proliferation which have been proven by the results of MTT assay.Fri, 19 Jan 2018 20:30:00 +0100Redundancy allocation problem with a mixed strategy for a system with k-out-of-n subsystems and ...
http://scientiairanica.sharif.edu/article_20152_0.html
Reliability improvement for electronics and mechanical systems is vital for engineers in order to design of these systems. For this reason, there are many researches in this scope to help engineers in real world applications. One of the useful methods in reliability optimization is redundancy allocation problem (RAP). In the most previous works, the failure rates of system components are considered to be constant based on negative exponential distribution; whereas, nearly all systems in real world have components with time-dependent failure rates; i.e., the failure rates of system components will be changed time by time. In this paper, we have worked on a RAP for a system under k-out-of-n subsystems with time-dependent components failure rates based on Weibull distribution. Also, the redundancy policy of the proposed system is considered as mixed strategy and the optimization method was based on the simulation technique to obtain reliability function as implicit function. Finally, a branch and bound algorithm has been used to solve the model, exactly.Fri, 26 Jan 2018 20:30:00 +0100Procedure for Setting up 180 Degree Sharp Bend Flume Including Construction and Examinations ...
http://scientiairanica.sharif.edu/article_20157_0.html
A laboratory flume in the hydraulics laboratory is necessary in order to investigate and model different hydraulic and hydrodynamic phenomena which govern the river. Hence, this article provides a description on construction and setting up a 180 degree flume, as the first 180 degree sharp bend flume containing multiple lateral intakes, in the Hydraulic Laboratory of Persian Gulf University, Iran. Also, employing the constructed flume, it includes a number of case studies which have been conducted on flow pattern. Such experiments utilized a Vectrino velocimeter in order to obtain the 3D flow velocity. As the primary stage, an experiment was conducted without any hydraulic structures installed at the bend so that flow characteristics could be analyzed in a 180 degree sharp bend. An increase was revealed in the secondary flow strength and velocity as a result of an increase in the flow depth. Therefore, it can result in an attack towards the outer wall. Consequently, a T-shaped spur dike was installed at the apex of the bend in order to provide protection for the outer wall against streams of high velocity, and a study of the flow pattern around the protective structure was conducted under clear water conditions.Mon, 29 Jan 2018 20:30:00 +0100A new method for eliminating membrane compliance in cyclic triaxial tests on gravelly soils
http://scientiairanica.sharif.edu/article_20159_0.html
A new computer controlled flow pump is developed to continuously mitigate the adverse effects of membrane compliance in conjunction with implementation of image processing for volume change measurement. The flow pump eliminates the membrane compliance by injecting or pumping out the required volume of water into or from the gravelly specimens to compensate for the erroneous volume change associated with the membrane compliance during undrained cyclic triaxial tests. This error is compounded in gravelly soils due to the large size of the grains and voids. In order to measure the volume of the specimen during the isotropic consolidation stage and calibrate the flow pump for cyclic loading, an image processing technique was used for measuring the volume change during the isotropic consolidation stage of loading while calculating membrane compliance associated with the amount of input water from the flow pump into the specimen. The results of image processing show that the increase in density of the specimens leads to an increase in the ratio of volumetric skeletal strains to axial strains and a decrease in the normalized membrane penetration. The study yields promising results for minimizing the errors associated with membrane compliance during undrained cyclic loading on gravels.Mon, 29 Jan 2018 20:30:00 +0100New Operations for Interval-valued Pythagorean Fuzzy Set
http://scientiairanica.sharif.edu/article_20160_0.html
Interval-valued Pythagorean fuzzy set (IVPFS), originally proposed by Peng and Yang, is a novel tool to deal with vagueness and incertitude. As a generalized set, IVPFS has close relationship with interval-valued intuitionistic fuzzy set (IVIFS). IVPFS can be reduced to IVIFS satisfying the condition $mu^++nu^+ leq 1$. However, the related operations of IVPFS do not take different conditions into consideration. In this paper, we initiate some new interval-valued Pythagorean fuzzy operators ($diamondsuit, Box, spadesuit, clubsuit, maltese, rightarrow, $ $) and discuss their properties in relation with some existing operators $(cup, cap, oplus, otimes)$ in detail. It will promote the development of interval-valued Pythagorean fuzzy operators. Later, we propose an algorithm to deal with multi-attribute decision making (MADM) problem based on proposed $spadesuit$ operator. Finally, the effectiveness and feasibility of approach is demonstrated by mine emergency decision making example.Mon, 29 Jan 2018 20:30:00 +0100Systematic Approach for the Design of Modular Military Housing Units Using Six-Sigma
http://scientiairanica.sharif.edu/article_20162_0.html
Military quarters and barracks are representative of housing units where the same plan is repeated, and thus prefabricated housing production can be effectively applied. These housing units are required to be disassembled and recycled as military forces are frequently reorganized and deployed to perform military actions. In order to meet these needs, this study proposes a systematic approach for the design of modular military housing units based on Six-Sigma concept. The application of the Six-Sigma to modular military housing units allows customers’ needs to be reflected on the critical to quality, which summarizes the main design requirements, and the design concept of the modular units can be developed based on the derived critical to qualities. To evaluate the effectiveness of the proposed approach, a representative example of military housing units is chosen and designed by utilizing the new modular units developed through this procedure. The weight of frames per unit area and factory manufacturing ratio of the new design are analyzed. The results of the comparison show that the use of the new modular units not only reduces construction cost significantly, but also greatly improves the quality of construction.
Mon, 29 Jan 2018 20:30:00 +0100Profile and wavefront optimization by metaheuristic algorithms for efficient finite element analysis
http://scientiairanica.sharif.edu/article_20163_0.html
For an efficient solution of the equations arising from finite element analysis, the stiffness matrix of the model should be structured. This can be done by reducing the profile or wavefront of the corresponding graph matrix of the structure depending on whether skyline or frontal method being used, respectively. One of the efficient methods to achieve this goal is the use of the method of King, extended by Sloan. In this paper the coefficients of the priority function utilized in the generalized Sloan’s method are optimized using the recently developed metaheuristic algorithm, so-called vibrating particles system. The results are compared to those of other metaheuristic algorithms consisting of the particle swarm optimization, colliding bodies optimization, enhanced colliding bodies optimization, and tug of war optimization. These metaheuristics, are used for optimum nodal numbering of the graph models of the finite element meshes to reduce the profile and wavefront of the corresponding sparse matrices. Comparison of the results achieved by these metaheuristic algorithms and those of the King and Sloan, demonstrates the efficiency of the new metaheuristic utilized for profile and wavefront optimization.Mon, 29 Jan 2018 20:30:00 +0100Application of Ordinary Fiber-Reinforced Concrete Layer for In-plane Retrofitting of ...
http://scientiairanica.sharif.edu/article_20164_0.html
The masonry walls should have sufficient in-plane strength and stiffness to withstand the seismic loads during strong ground shakings. Different retrofitting techniques are proposed for improving in-plane behavior of the Unreinforced Masonry (URM) walls. This study focuses on experimental evaluation and numerical simulation of a simple practical retrofitting technique employing Fiber Reinforced Concrete (FRC) surface layer. The simple FRC mix has conventional available fiber, low fiber content, ordinary mix design and applicable construction procedure. Effect of FRC mix including fiber type and fiber content and surface layer thickness on in-plane behavior of masonry panels made up of conventional solid clay bricks are evaluated through experimental study in accordance with ASTM E-519 diagonal tension strength of masonry panels. In addition, numerical simulation model of this retrofitting technique in ABAQUS software is proposed and validated with test results of bare and retrofitted panels.Mon, 29 Jan 2018 20:30:00 +0100Rheology of Burgers’ model with Cattaneo-Christov heat flux in the presence of heat ...
http://scientiairanica.sharif.edu/article_20165_0.html
This investigation presents the characteristics of Cattaneo-Christov heat flux model for the boundary layer flow of Burgers’ fluid model. Instead of simple Fourier’s law of heat conduction, we presented the Cattaneo-Christov model to analyze the thermal relaxation properties when the heat source/sink is present in the system. Mathematical modeling the laws of momentum and energy are presented under the order analysis approach. It is revealed that the term “” is for the hydro-magnetic rheology of the Newtonian model whereas the generalized magnetic field term (as mentioned in Eq. 2) is for the Burgers’ model which is incorporated in the current analysis. Suitable transformations are utilized for the conversion of partial differential system into coupled nonlinear set of ordinary differential equations which are tackled analytically through homotopy analysis technique. The plots of various physical quantities are presented showing the dynamics of the considered analysis. Streamlines for Burgers’ and Newtonian model are presented which show a difference of rheology. Numerical values for skin friction and surface heat transfer rate are presented in the form of tables.Mon, 29 Jan 2018 20:30:00 +0100Investigating the Impact of Simple and Mixture Priors on Estimating Sensitive Proportion ...
http://scientiairanica.sharif.edu/article_20166_0.html
Randomized response is an efficacious and effective survey method to collect subtle information. It entitles respondents to respond to over-sensitive issues and defensive questions (such as criminal behavior, gambling habits, addiction to drugs, abortions, etc) while maintaining confidentiality. In this paper, we conducted a Bayesian analysis of a general class of randomized response models by using different prior distributions, such as Beta, Uniform, Jeffreys and Haldane, under squared error, precautionary and Degroot loss functions. We have also expanded our proposal for the case of mixture of Beta priors under squared error loss function. The performance of the Bayes and maximum likelihood estimators is evaluated in terms of mean squared errors. Moreover, an application with real data set is also provided to explain the proposal for practical considerations.Mon, 29 Jan 2018 20:30:00 +0100Resilient Network Design in a Location-Allocation Problem with Multi-Level Facility Hardening
http://scientiairanica.sharif.edu/article_20167_0.html
There are many sources of risk affecting the network elements may lead to network failure, so planners need to consider them in the network design. One of the most important strategies for disruption risk management is the static resilience. In this strategy, the network functionality is maintained after the disruption event by the prevention and hardening actions. In this paper, a resilient capacitated fixed-charge location-allocation model is proposed. Both facility hardening and equipping of the network to backup facilities for disrupted elements are considered together to avoid supply network failure due to random disruption. Facilities are decided to be hardened in multiple levels before disruption events. The problem is formulated as a non-linear integer programming model, then its equivalent linear form is presented. A Lagrangian decomposition algorithm (LDA) is developed to solve large-scale instances. Computational results confirm the efficacy of the proposed solution approach comparing to classical solution approaches in large-scale problems. Moreover, the superiority of the proposed model is confirmed by comparing to the classical models.Tue, 30 Jan 2018 20:30:00 +0100Design of axisymmetric aerospike nozzle based on modified MOC
http://scientiairanica.sharif.edu/article_20168_0.html
In this study a direct method based on the method of characteristics with the assumptions of non-viscous flow and thermal perfect gas is provided to design of axisymmetric plug nozzle. Inputs for numeric code are including output Mach number, specific heat ratio, global gas constant and the number of discrete steps of Prandtl–Meyer expansion fan. In the design process, there has been no simplification and only to create unique spike geometry. Based on the criterion of locating the tip of the spike on the axis of symmetry, for each output Mach number, a correction factor has been extracted that it was the sole source of theoretical errors. Studied parameters include spike geometry, exhaust nozzle flow parallelism and uniformity. In the results by numerical analysis, consistent results with desired output Mach number and parallel of output flow with the axis of symmetry are obtained. The simple and direct formulation is used and so it performs very fast. Due to recognizing of the error resulted in the surface slope reduction factor, some movement in spike geometry relative to ideal conditions was raised so the effect of reduction factor will tend to zero by increasing of the design Mach number.Tue, 30 Jan 2018 20:30:00 +0100Study of swelling behavior of temperature sensitive hydrogels considering inextensibility of network
http://scientiairanica.sharif.edu/article_20169_0.html
In this work, the equilibrium swelling of temperature sensitive hydrogel networks is studied with an emphasis on the chain locking of the network. Using Gent model for elastic part of free energy and modifying the mixing part of the free energy, a continuous model is developed which consider inextensibility of the network chains and has a good agreement with the experimental data particularly for smaller values of crosslinking density of the network and larger values of the swelling ratio. After validating the modified model, it is employed for the studying the inhomogeneous swelling of a spherical shell on a hard core both analytically and numerically. The analytical solution is used for validating the numerical method. Finally, the inhomogeneous swelling of a bilayer beam with an active temperature sensitive hydrogel is investigated and the results are presented. The obtained results show the importance level of considering the chain locking in swelling of the network in the applied problems.Tue, 30 Jan 2018 20:30:00 +0100Numerical investigation of thermal contact conductance between linear and curvilinear contacts
http://scientiairanica.sharif.edu/article_20170_0.html
Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of thermal contact resistance in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, Inverse problem method solution is utilized as a proper method for estimation of thermal contact resistance value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of thermal contact resistance. In conclusion, the final results establish the fact that the inverse problem method solution can predict thermal contact resistance values between contacting surfaces.Fri, 02 Feb 2018 20:30:00 +0100Investigation of moisture susceptibility of SBS modified asphalt containing Alumina Trihydrate ...
http://scientiairanica.sharif.edu/article_20171_0.html
Although several studies have been carried to discover the asphalt mixture performance when Alumina Trihydrate (ATH) as a flame retardant was added into, the moisture susceptibility of asphalt mixture containing ATH is still not fully clear. In this study, the moisture susceptibility of binders containing ATH were assessed through the surface free energy (SFE) obtained by the sessile drop method. A commonly used SBS modified asphalt with different dosages (0%, 6%, 8%, 10%, 12%, and 14%) of ATH were prepared to determine the physical properties, flame retardancy and SFE parameters. Experimental results indicated that the addition of ATH increased the viscosity, softening point, G*/sinδ and limiting oxygen index, but decreased the penetration and ductility. What's more, increases in total SFE, cohesive energy and work of adhesion were observed with the addition of ATH. Conversely, the work of debonding, wettability and energy ratio decrease due to the addition of ATH. It is concluded that the ATH has a significant negative effect on the moisture-induced damage potential of asphalt mixture from the view of micromechanisms. The recommended percentage of ATH was 6-8% in consideration of physical properties, flame retardation and moisture susceptibilitySun, 04 Feb 2018 20:30:00 +0100IMPROVEMENT ON STRUCTURE OF FIRE ALARM SYSTEMS ALARM BELL STOP SWITCH
http://scientiairanica.sharif.edu/article_20172_0.html
Fire alarm systems are essentially installed in specific firefighting equipment and serve as one of important alarm equipments which senses fire early. The main goal of the study is to find methods for improving the structure of fire alarm needs. This study is about false alarms of fire indicating equipment in fire alarm systems. It is found that false alarms false alarms by fire alarm systems are constantly occurring and fire safety manager is neglecting his duty of work by turning alarm bell stop switch on even during usual times. To prevent this, the alarm bell stop switch should be changed into an automatically resettable manual operation type so that it can automatically reset to its original state even though fire safety manager turns the switch on. As a result, aid in correcting fire safety managers' wrongful practices by making the alarm bell ring whenever an actual fire occurs, and ultimately reduce false alarms by eliminating fundamental causes when false alarms occur.Sun, 04 Feb 2018 20:30:00 +0100Evaluation of shear strength parameters of granulated waste rubber using artificial neural ...
http://scientiairanica.sharif.edu/article_20173_0.html
Utilizing rubber shreds in civil engineering industry such as geotechnical structures can accelerate generated waste tire recycling process in an economical and environmentally friendly manner. However, understanding the rubber grains strength parameters is required for engineering designs and can be acquired through experimental tests. In this study, small and large direct shear test was implemented to specify shear strength parameters of five rubber grains group which are different in gradation and size. Moreover, artificial neural networks (ANN) are developed based on the test results and optimized networks which best captured the shear stress (τ), and vertical strain (εv) behavior of rubbers, are introduced. Additionally, a prediction model using the combinatorial algorithm in group method of data handling (GMDH) is proposed for the shear strength and vertical strain in the arrangement of closed-form equations. The performance and accuracies of the proposed models were checked using correlation coefficient (R) between the experimental and predicted data and the existing mean square error (MSE) was evaluated. R-values of the modeled τ and εv are equal to 0.9977 and 0.9994 for ANN, and 0.9862 and 0.9942 for GMDH models, respectively. The GMDH proposed models are presented as comparatively simple explicit mathematical equations for further applications.Sun, 04 Feb 2018 20:30:00 +0100An Electromagnetism-like Algorithm to Solve Three-dimensional Highway Alignment Problem
http://scientiairanica.sharif.edu/article_20175_0.html
Road alignment design is an important determinant of the development cost of road networks. On the one side, it affects road construction and maintenance costs, which constitute a significant part of country-wide infrastructure development, management and operation budget each year. On the other side, it affects road user-related costs of travel time and vehicle use, which comprise a significant portion of the total transportation cost. This study adapts the existing Electromagnetism-like meta-heuristic algorithm to solve a three-dimensional highway alignment problem, which explores and finds a good route between two given points on a terrain. It detects the potentials of the given initial routes, which are enhanced and shaped toward better positions by the help of the local and global search. The final good solution is, then, fine-tuned for a better alignment. Several example problems are designed to show the behavior of the algorithm. The results show that the algorithm satisfactorily maneuvers to by-pass obstacles, and build highway structures where necessary. The set of the example problems in this paper may also serve to found a basis for evaluation of the performance of alternative algorithmsTue, 06 Feb 2018 20:30:00 +0100Predicting the Collapsibility Potential of Unsaturated Soils Using Adaptive Neural Fuzzy ...
http://scientiairanica.sharif.edu/article_20176_0.html
Soil collapsibility is one of the important phenomena in unsaturated soil mechanics. This phenomenon can impose extensive financial damages on civil engineering structures due to soil subsidence. Because of uncertainties in effective parameters and their measurements, no precise mathematical relation has been proposed for collapsibility potential evaluation. Therefore, soft computing techniques such as fuzzy logic could be a suitable choice to account for different factors. Adaptive neural fuzzy inference system (ANFIS) was used in this study. To predict the collapsibility potential, hybrid algorithm and particles swarm optimization (PSO) were employed by ANFIS for system training. Gaussian membership functions were utilized for fuzzifying the data. Also, data classification was performed in a subtractive form in the fuzzy inference system. A total of 327 laboratory data was used in particles swarm algorithm, 266 of which were chosen for training and 66 for testing. The obtained results showed the effects of different parameters and the rate of their changes in collapsibility potential. Moreover, comparison of different approaches of system training was done using correlation coefficient. The superiority of the proposed method and the utilized techniques was shown by comparing the results with the ones obtained by other researches.Tue, 06 Feb 2018 20:30:00 +0100Soft Computing-based Approach on Capacity Prediction of FRP Strengthened RC Joints
http://scientiairanica.sharif.edu/article_20177_0.html
Shear failure of the RC beam-column joints is a brittle failure which has no priorwarning and can induce tremendous damages because of collapse of column and joint before theconnected beam. This paper is focused on one particular method of strengthening the RC joints,that is, the use of FRP composites as confining element. The results of previous studies have shownthat strengthening the RC beam-column joints with FRP composites can improve their shearcapacity. In this study, the data collected from the existing standards and studies regarding the FRPstrengthened RC joints were used to develop an artificial neural network model for predicting theshear strength contribution of FRP jacket. The developed model was then used to evaluate the roleof different parameters on this contribution, and finally derive a formula for contribution of FRPjacket to the shear strength of the RC beam-column joints.Tue, 06 Feb 2018 20:30:00 +0100Modelling Multi Tour Inventory Routing Problem for Deteriorating Items with Time Windows
http://scientiairanica.sharif.edu/article_20178_0.html
In recent decades, there are intensive researches on deteriorating inventory. However, only a few researchers focus on the inventory routing problem for deteriorating item. There are many items such as foods, electronic products that deteriorate with time, and many other products in the market also have perishable characteristic. The items not only decay during the stockpiling period but they also deteriorate throughout transportation time. Since deteriorated rate and time is necessary, in this paper, an inventory routing problem with time windows for deteriorating items is developed. Particle Swarm Optimization (PSO) is used to solve the problem since PSO can solve problems in a reasonable period with near optimal solutions. We use two examples to illustrate the model. In a sensitivity analysis, way parameters that impact costs are demonstrated. Our results show that the deteriorating rate in inventory has bigger effects than deteriorating rate in the vehicle, so this research has a significant contribution and managers can give more effort to reduce deteriorating in inventory than the deteriorating rate in vehicles.Tue, 06 Feb 2018 20:30:00 +0100Quasi-reflection based symbiotic organisms search algorithm for solving static optimal power ...
http://scientiairanica.sharif.edu/article_20179_0.html
This paper offers a novel variant to the existing symbiotic organisms search (SOS) algorithm, to address optimal power flow (OPF) problems considering effects of valve-point loading (VE) and prohibited zones (POZ). Problem formulation includes minimization of cost, loss, voltage stability index (VSI) and voltage deviation (VD) and simultaneous minimization of their combinations. Quadratic cost function, effects of VE and effects of both VE and POZ have been considered. OPF formulation considering effects of both VE and POZ are not yet available in the literature. Efficacy of SOS in resolving OPF is recognized in the literature. An opposition based learning technique named quasi-reflection, is merged into existing SOS to enhance its prospects of getting nearer to superior quality solution. The proposed algorithm, named quasi-reflected symbiotic organisms search (QRSOS), is assessed for IEEE 30 and IEEE 118 bus test systems. It shows promising results in reducing the objective function values of both the systems by large margins (78.98 % in case of VD when compared to SOS and NSGA-II and 46.06 % in case of loss as compared to QOTLBO in IEEE 30 and IEEE 118 bus respectively). QRSOS also outperformed its predecessors, in terms of convergence speed and global search ability.Tue, 06 Feb 2018 20:30:00 +0100Application of Multi-objective Charged System Search Algorithm for Optimization Problems
http://scientiairanica.sharif.edu/article_20184_0.html
The charged system search algorithm is a relatively new optimization algorithm developed based on some principles from physics and mechanics. This paper presents an approach in which Pareto dominance is incorporated into the charged system search in order to allow this algorithm to handle problems with some multi-objective functions; the proposed algorithm will be called Multi-Objective Charged System Search (MOCSS). Well-known mathematical and engineering benchmarks are used to evaluate the proposed algorithm and the results have been compared with other new approaches. The results of implementing the new algorithm on some test problems show that the proposed algorithm outperforms the other algorithms in terms of Generational Distance, Maximum Spread, Spacing, Coverage of two Set and Hypervolume Indicator. Results of well-known mathematical examples indicate that the new approach is highly competitive and can be considered as a viable alternative to solve multi-objective optimization problems. These results encourage the application of the proposed method to more complex and real-world multi-objective optimization problems. The proposed method can deal with highly nonlinear problems with complex constraints and diverse Pareto optimal sets.Sun, 11 Feb 2018 20:30:00 +0100Influence of bladed and glazed entrance on the performance of solar air heaters
http://scientiairanica.sharif.edu/article_20185_0.html
The performance of a flat plate single-pass solar air heater (SAH) modified at the entrance region of the heater was experimentally investigated. The entrance region was covered with glass cover instead of steel cover. The aim of using glass at the entrance region is increasing the heating area exposed to solar irradiation. In addition, replacing the steel cover with glass reduces the shading effect occurred due to steel which decreases the temperature of the surface of the absorber and hence the outlet temperature of the air. Also, guide blades were placed in the entry region to ensure well air distribution on the absorber surface and hence enhancing the thermal performance of SAH. The modified SAH was compared with another one without air blades and without glass cover at the entrance. The experiments were performed at four air flow rates ranged from 0.013 kg/sec to 0.04 kg/sec. The modifications led to good enhancement in both the air temperature difference and the efficiency. The glazed-bladed SAH showed a good improvement in the daily thermal efficiency by 6.72 % to 10.5 % over the conventional heater and by 2.16 % to 3.25 % over the glazed SAH.Mon, 12 Feb 2018 20:30:00 +0100Multiflute Drill-Broach for Precision Machining of Holes
http://scientiairanica.sharif.edu/article_20186_0.html
This paper deals with hole-enlarging multiflute drill processing. The analysis of existing structures, their advantages and disadvantages is carried out. Cutting conditions during hole-enlarging multiflute drill processing are shown. A new design of hole-enlarging multiflute drill as a hole-enlarging multiflute drill-broaching tool from broaching-speed steel with carbide plates, as well as a new way of handling the new tools is offered. Hole-enlarging multiflute drill-broaching combines the features of hole-enlarging multiflute drill (in cross section) and the features of broaching tool (in longitudinal section). In this way, it was possible to increase the quality of hole making (size variance, surface roughness), to facilitate the cutting conditions and to increase the durability. The results of prototypes testing are presented.Mon, 12 Feb 2018 20:30:00 +0100Sustainable Procurement Decision of Electric Coal under Fuzzy Information Environment
http://scientiairanica.sharif.edu/article_20194_0.html
Green supply chain management is a crucial challenge for the sustainable development of the enterprises. In this paper, we study the problem of supplier selection for the multi-attribute and multi-source green procurement of electric coal under fuzzy information environment. Concretely, we establish a new index system of supplier selection by considering both the economic factors and environmental factors, and then present a multi-attribute decision making method based on 2-tuple deviation degree to rank all alternative suppliers in the green procurement of electric coal. We also highlight the implementation, availability, and feasibility of the green procurement decision method of electric coal by using an example of the multi-source procurement of electricity coal. We try to provide theoretical basis and decision-making reference for the thermal power enterprise to implement scientific green procurement management of electric coal.Sat, 17 Feb 2018 20:30:00 +0100How does long trip affect on driving performance, eye blinks and awareness of sleepiness among ...
http://scientiairanica.sharif.edu/article_20195_0.html
A total of 120 commercial drivers from four age groups participated in the expressway driving test in Shandong, China to perform 2, 3, and 4 h continuous driving tasks and collect the data on the driver's blinking, driving performance and self-reported level of sleepiness. Two-way repeated measures ANOVA was used to evaluate the effects of driving duration on the variation of the eye-blink behavior, driving performance and subjective feeling of sleepiness across the different age groups over the time periods tested. Additionally, Pearson product-moment correlation was used to quantify the association between the variations of the dependent variables. The results showed that there was significant difference between groups, significant effect over time and significant interaction between the age and driving duration in the variations of the driver’s blink frequency, blink duration, closure duration, speed perception, choice reaction time, number of incorrect action judgments and subjective level of sleepiness. However, a significant difference varied over time, but no effect of the interaction between groups and time were found in the variation of the driver’s attention allocation value. Furthermore, driver’s eye blink measures were more sensitive to sleepiness and older drivers were more likely to get sleepy in long distance driving.Sat, 17 Feb 2018 20:30:00 +0100Rolling contact fatigue analysis of rails under the influence of residual stresses induced by ...
http://scientiairanica.sharif.edu/article_20196_0.html
This study aims to analyze the rolling contact fatigue influenced by residual stresses caused by the contact of the wheel and rail and its manufacturing process. For this purpose, a rail available in Iran railway is used with an exact profile geometry. The location of maximum stress caused by the contact of wheel/rail for rail profiles can be calculated by three-dimensional elastic-plastic finite element model. Then, in order to estimate the stress distribution caused by rail manufacturing process, a thermal analysis with finite element method will be performed. Afterwards, the results of performed stress analysis will be used as input for three-dimensional crack growth and rail fatigue life estimation model to calculate the stress intensity factors and fatigue life according to the set of related parameters with boundary element method. Finally, three-dimensional finite element analysis results obtained show good agreement with those achieved in field measurements.Sat, 17 Feb 2018 20:30:00 +0100A Statistical Approach for Knowledge Discovery: Bootstrapped Analysis of Language Models for ...
http://scientiairanica.sharif.edu/article_20198_0.html
In this paper, we propose a novel approach for knowledge discovery from textual data. The generated knowledge base can be used as one of the main components in the cognitive process of question answering systems. The proposed model automatically extract relations between named enti- ties in Persian. Our proposed model is a bootstrapping approach based on n-gram model to nd the representative textual patterns of relations as n-grams in order to extract new knowledge about given named entities. The main motivation for this work is the characteristic of the sentence structure in Persian which, in contrary to English sentences, is in subject- object-verb format. The proposed approach is a purely statistical one and no background knowledge of the target language is required. This makes our method applicable to any open domain relation extraction task. How- ever, as for our test-bed, we focus on the domain of biographical data of international poets and scientists to build a knowledge base about them. Qualitative evaluations based on human assessment is an evidence for the ecacy of our method.Sat, 24 Feb 2018 20:30:00 +0100Modeling Stock-out Loss and Overstocking Loss Generated by Bullwhip Effect
http://scientiairanica.sharif.edu/article_20199_0.html
Although the literature of the supply chain is teemed with the analysis of the bullwhip effect, few studies regarding the impact of the bullwhip effect or demand distortion on the supply chain profit have been done. Hence, we introduce the concept of Distance to Loss (DL), which is a function of the retailer’s selling price, the manufacturer’s wholesaler price, the end item’s salvage value, the retailer’s expected demand and the retailer’s variance of demand. This concept can perfectly model both stock-out loss and overstocking loss emanated by the bullwhip effect and combines both the newsvendor model and credit risk concepts. Our findings are based on an experimental design and are profoundly in line with previous research. In particular, our model indicates that variations in demand parameters, retailer’s selling price and manufacturer’s wholesaler price impinge on the retailer’s DL, whereas a slight increase in the salvage value negligibly affect the retailer’s DL.Fri, 02 Mar 2018 20:30:00 +0100Predicting the Effective Stress Parameter of Unsaturated Soils Using Adaptive Neuro-Fuzzy ...
http://scientiairanica.sharif.edu/article_20200_0.html
The effective stress parameter (χ) is applied to obtain the shear strength of unsaturated soils. In this study, two adaptive neuro-fuzzy inference system (ANFIS) models, including SC-FIS model (created by subtractive clustering) and FCM-FIS model (created by Fuzzy c-means (FCM) clustering), are presented for prediction of χ and the results are compared. The soil water characteristic curve fitting parameter (λ), the conﬁning pressure, the suction and the volumetric water content in dimensionless forms are used as input parameters for these two models. Using a trial and error process, a series of analyses were performed to determine the optimum methods. The ANFIS models are constructed, trained and validated to predict the value of χ. The quality of the ANFIS prediction ability was quantiﬁed in terms of the determination coefﬁcient (R2), Root Mean Square Error (RMSE) and Mean Absolute Error (MAE). These two ANFIS models are effectively able to predict the value of χ with reasonable values of R2, RMSE and MAE. Sensitivity analysis was used to acquire the effect of input parameters on χ prediction, and the results revealed that the conﬁning pressure and the volumetric water content parameters had the most influence on the prediction of χ.Fri, 02 Mar 2018 20:30:00 +0100Seismic force modification factors for partitions in low- rise reinforced concrete buildings
http://scientiairanica.sharif.edu/article_20201_0.html
Present codes of practice do not consider the effect of arrangement of partitions in the plan of structure on the seismic demands of these non-structural components. In this paper, a modification factor has been proposed to modify provisions for those seismic demands. Seventy two regular low-rise reinforced concrete moment frames, supporting some partitions, exposed to seven appropriate ground motions. The nonlinear seismic response history analysis considering out-of-plane behavior of partitions has been conducted using the OpenSees platform. The average values of peak responses from those earthquakes were obtained. The forces generated using the analytical method, which some of them verified with existing study results, were compared with the values from the code and a factor denoted as seismic force modification factor, W, was proposed. A parametric study has been carried out to study the effect of dominent parameters such as the arrangement of partitions, partition to structure height ratio, and length to height ratio of partitions on the W values. For the majority of the models, the W values are larger for partitions located further with respect to the center of floor. Moreover the modification factor could be as large as 1.85 for the partitions located in the middle floors.Fri, 02 Mar 2018 20:30:00 +0100Strength and Durability Studies on High Volume Readymade Ultrafine Slag based High Strength Concrete
http://scientiairanica.sharif.edu/article_20202_0.html
Steel industries produces ground granulated blast furnace slag (GGBFS) as a waste material and has enormous scope to be made use of in concrete as partial substitute to cement. The average particle size of GGBFS used was 17.5 µm. It fills voids and modifies the microstructure in turn enhancing the strength and durability of concrete. In the present work commercially available ultra fine slag (readymade ultrafine slag - RUFS) with an average size of 5 µm was used as mineral admixture in three different percentages of 30, 40 and 50 as substitute to cement. Results of present work were compared to precursor slag of author’s earlier works. From the experimental results it was understood that RUFS with 40% substitution to cement gave better performance among three different percentages used. Comparing with author’s earlier works, RUFS performed better than precursor slag and had slightly higher results than that of concrete with 5 to 15% of RUFS. Hence it is suggested that cement could be replaced with readymade ultrafine in high volume as much of 40% without compromising its performance.Fri, 02 Mar 2018 20:30:00 +0100Usability of Arc Fault Circuit Interrupters with Network Function
http://scientiairanica.sharif.edu/article_20203_0.html
The existing arc fault circuit interrupters have the function to interrupt overloads, ground fault, arc fault and all but neither is there the monitoring function to allow external monitoring nor the notification function to notify the fire safety manager. This is a study on arc fault circuit interrupters with the network function that have not been studied so far. We intend to install these arc fault circuit interrupters in places such as server rooms, pigsties, chicken farms, markets, cultural assets, skyscrapers, and facto-ries where large loss may occur if the fire safety managers do not recognize the electricity shutdown in order to increase the efficiency of electricity management. If an overload, a short circuit or an arc is detected while power is supplied to the load, the microprocessor generates a trip signal and cuts off the power by this trip signal. This situation is monitored in real time by ex-ternal monitoring and notified to the fire safety manager. The fire safety manager can immediately recognize the situation where the arc fault circuit interrupter interrupts the circuit and take the necessary action to manage the electricity efficiently.Sat, 03 Mar 2018 20:30:00 +0100Design an analog CMOS fuzzy logic controller for the inverted pendulum with novel triangular ...
http://scientiairanica.sharif.edu/article_20204_0.html
In this paper,a fuzzy analog controller circuit is provided for the inverted Pendulum problem which resulted in a simple analog circuit simply does the act of controlling without requiring to any processing structure.In other words,in case of constructing the proposed circuit,a small analog chip controls the inverted pendulum.For this purpose,the first step is the study of the dynamic model of the inverted pendulum and then a fuzzy controller is designed systematically.In the following,the number of membership functions and the formation of them are designed.In addition,the different MFs and different numbers are examined for each variable and the most efficient structure is selected as fuzzy controller.To assess efficiency of designed fuzzy controller,the controller is simulated in Simulink and then this design is implemented at transistor level in TSMC 0.18µm CMOS technology.In this work,the MFs,the circuits for realization of the knowledge-based and defuzzification circuits are designed in current mode.The proposed circuits are simulated and evaluated in Advanced Design System software based on CMOS technology.Simulation results show that the inverted pendulum is controlled with high accuracy and high speed,meanwhile the controllers have low power consumption and good robustness to outer large and fast disturbance rather than the previous works.Sat, 03 Mar 2018 20:30:00 +0100EDU-DRM: A digital rights management (DRM) system for K-12 education
http://scientiairanica.sharif.edu/article_20205_0.html
The technological achievements in digital publishing have made paperless education possible even in K-12 education. Aside from high bandwidth distribution infrastructure, main problems of digital publishing are preserving personal information and protecting the rights of copyrighted contents. Although, specially designed digital rights management (DRM) systems can be used to control distribution and usage of private and/or copyrighted contents in K-12 education, dealing with large number of bursty concurrent access requests and changing the access rights of large amount of students from one content class to another at the end of each education period makes the problem different from existing ones. This paper introduces a new DRM system, called EDU-DRM, that includes a novel bit based authorization approach that reduces the processing time for authorization requests and automatize the access right adjustments with predefined rules for K-12 education. During the study, an experimental framework is designed using Apache Bench to analyze the proposed approach and its evaluation. The system is compared with XML based authorization approach and the results are presented in the paper.Sat, 03 Mar 2018 20:30:00 +0100Laboratory and Numerical Study of the Behavior of Circular Footing Rested on Sand Contaminated ...
http://scientiairanica.sharif.edu/article_20206_0.html
This research studies the behavior of circular foundations rested on the soils contaminated with gas oil and kerosene oil under cyclic loading. The final goal of this study was to determine the influence level of the foundation of the reservoirs rested on oil-contaminated sand due to their filling and discharging. The contaminated sand layers were mixed with different percentages of contamination from 2 to 6 of kerosene oil and gasoline. The effect of the contamination percentage, the value of the applied load, as well as the depth and type of contamination is investigated in this study. To validate the numerical studies performed by finite element software, small-scale laboratory tests is carried out. The results showed that the pollutants could affect the amount of final settlement and the number of loading cycles to reach this value. Increasing depth, the number of load cycles and the contamination content increased the final settlement and the number of loading cycles to reach that level increases. Numerical results showed a good compatibility in the load-settlement charts with the experimental results.Sat, 03 Mar 2018 20:30:00 +0100Numerical simulation of thermal radiative heat transfer effects on Fe3O4- Ethylene glycol ...
http://scientiairanica.sharif.edu/article_20207_0.html
Electrohydrodynamic Fe3O4- Ethylene glycol nanofluid forced convection is simulated in existence of thermal radiation. The porous lid driven cavity has one moving positive electrode. Single phase model has been applied to simulate nanofluid behavior. Control Volume based Finite Element Method is employed to obtain the results which are the roles of Darcy number , radiation parameter , Reynolds number , nanofluid volume fraction and supplied voltage . Results depict that maximum values for temperature gradient is obtained for platelet shape nanoparticles. Nusselt number enhances with rise of Darcy number and supplied voltage. Convection mode enhances with increase of permeability of porous media and nanofluid volume fraction but it decreases with rise of Hartmann number.Sat, 03 Mar 2018 20:30:00 +0100On the measurement of transverse shear stress on a rectangular open channel using optimal ...
http://scientiairanica.sharif.edu/article_20209_0.html
The laboratory studies have been carried out in this research. Determining the sensitivity analysis of the Preston tube diameter in shear stress, four Preston tubes with external diameters of 3.2, 3.9, 4.7 and 6.3 mm were used. The aspect ratios of 2.86 to 13.95 were examined. For measuring the pressure difference of the Preston tube a 200 millibar differential pressure transducer with 0.01 accuracy of the original scale was used. Laboratory results demonstrated that Preston tubes with a diameter of 3.9 mm present the minimum difference in the average value of the shear stress resulting from the Bechert and Patel calibration equations. Therefore, using the Preston tube with an optimal diameter, transverse distribution of shear stress in channels bed and wall were determined. The outcome of this part of study is two dimensionless relationships for determining the local shear stress both in the bed and wall. These relationships are a function of the aspect ratio B/H and the bed relative coordinates b/B in cross section and Z/H sidewall. The survey showed that the dimensionless bed shear stress distribution is considerably influenced by the aspect ratio. The transverse distribution of wall shear stress is independent from the aspect ratio for B/H>3.Mon, 05 Mar 2018 20:30:00 +0100A laboratory investigation on suppression of dust from wind erosion using biocementation with ...
http://scientiairanica.sharif.edu/article_20220_0.html
Dust events are among the serious environmental challenges in some countries. Sustainable solutions can be applied to tackle this problem by considering soil as a living ecosystem. Biocementation based on production of carbonates by heterotrophic bacteria is one of the favored methods to suppress the dust from wind erosion because this type of bacteria produces calcium carbonate (main product) as well as water and carbon dioxide (by-products). In present research, bacterial species of Bacillus amyloliquefaciens was used. First, bacteria were cultivated to reach toa pre-determined concentration. Next, bacterial cells and nutrients in the form of solution were sprayed on the soil surface. Then, samples were tested in a closed circuit wind tunnel. Three main groups of samples were tested: without sand bombardment and undisturbed soil surface, with sand bombardment and undisturbed soil surface, and without sand bombardment and with disturbed soil surface. The results show that the implemented method for stabilization of soil was efficient. Moreover, based on the results of second group of tests, curing duration, amount of water, temperature-water interaction and water -bacterial cells interaction were found to be of considerable significance.Tue, 13 Mar 2018 20:30:00 +0100Adapted Design Of Experiments for Dimension Decomposition Based Meta Model in Structural ...
http://scientiairanica.sharif.edu/article_20221_0.html
Reliability analysis of structures is often problematic for the structures with nonlinear and complex limit state functions (LSF). For these cases, simulation methods often provide accurate failure probability, but with high number of structure’s LSF analysis. This paper presents an efficient combination of Monte Carlo Simulation (MCS) method and Univariate Dimension Reduction (UDR) based Meta-model to approximate the failure probability of structures with few LSFs evaluation. For this purpose, the design of experiment used in the Meta model is adapted such that the expected failure samples in MCS being approximated with higher accuracy. Several numerical and engineering reliability problems are solved by the proposed approach and the results are verified by MCS. Results show that the proposed approach highly reduces the required number of structural analysis to provide proper results.Tue, 13 Mar 2018 20:30:00 +0100Centrifuge modelling of monopiles subjected to lateral loading
http://scientiairanica.sharif.edu/article_20222_0.html
Monopiles are the most common foundation type used for fixed-bottom substructures in offshore wind installations. In an offshore environment, the predominant load is cyclic, which affects the stiffness and deformation properties of foundation systems, especially monopiles. To investigate the effect of cyclic loading on a short (rigid) steel monopile, a set of displacement-controlled ηg laboratory tests were designed. This paper presents the procedure and results of eight centrifuge tests investigating monopile behaviour when subjected to lateral monotonic and cyclic loading. The general trend of monotonic response is in good agreement with the results of similar experimental studies, however, much softer behaviour was observed compared to the equivalent Winkler model on API p-y curves. The cyclic tests focused on the stiffness and deformation properties of a soil-pile system under fatigue loading. Increases, decreases or no changes in secant stiffness were observed depending on the regime of the applied cyclic displacements which are in contradiction to current design methodology where only cyclic degradation is assumed. Influence of load cycling on cyclic bending moments along the pile shaft was discussed and found to be of minor significanceTue, 13 Mar 2018 20:30:00 +0100Experimental Behavior of Circular Foundations on Oil Contaminated Sand
http://scientiairanica.sharif.edu/article_20223_0.html
This paper studies the behavior of circular footings placed on the gasoil and kerosene-contaminated soil. The ultimate objective of this study is to determine the effect that oil contamination has on the sand bearing capacity. The contaminated sand layers were mixed with different levels of between 1 and 4 percent of gasoil and kerosene contamination. The influence of the contamination depth and type of contamination was examined in this study. Laboratory tests were conducted on small scale models and performed in load-controlled manner. The results showed that the contamination can influence the load-settlement curves and lead to a reduction in its load-bearing capacity. An increase in the depth and percentage of contamination decreased the bearing capacity. Some formulas have been provided in which by knowing the depth and percentage of contamination one can predict the third bearing capacity factor of a circular foundationTue, 13 Mar 2018 20:30:00 +0100Trajectory modification of a transonic spherical projectile under Hop-up mechanism
http://scientiairanica.sharif.edu/article_20224_0.html
Improvement of shooting accuracy of air gun pellets is important in sport competitions which is questioned by shooting enthusiasts. Hence, the performance of a transonic spherical projectile as an air gun pellet with 4.5 mm-caliber under a mechanism known as Hop-up is numerically examined in the present study. Hop-up mechanism is resulted in a rotational motion of spherical projectile, so a Magnus Force is generated which prevents the altitude loss of the projectile caused by its weight. The motion of the projectile is assumed in four degrees of freedom including three translational motions and one transverse rotational motion. The projectile confronts the continuous variations of velocity due to the influence of the aerodynamic forces so experiences an unsteady flow. In order to numerical analysis of the problem, the 3-D compressible turbulent Navier-Stokes equations based on “Roe” scheme and dynamic equations of the projectile motion are solved in a coupled form as a fluid-structure interaction and in a moving computational grid. The results obtained from these studies show that the proper rotation of the projectile for a certain distance, can neutralize the altitude loss. It is also demonstrated that the momentum of the projectile is decreased by increasing its angular velocity.Tue, 13 Mar 2018 20:30:00 +0100An Optimization Framework for Risk Response Actions Selection Using Hybrid ACO and FTOPSIS
http://scientiairanica.sharif.edu/article_20225_0.html
This paper presents a framework for solving risk response action selection problem by considering: (1) the impact of risk events on the project objectives, (2) the interactions between risk events and (3) management criteria and preferences. For these purposes, a framework is developed by combining an optimization-based model and a Multi Criteria Decision Making (MCDM) approach. First, in the optimization-based model, Ant Colony Optimization (ACO) is used to find the best combination of response actions which have more effects on time, cost and quality. Also, in this model, to overcome the imprecision situation resulting from lack of knowledge or insufficient data, risk parameters are determined using the fuzzy set theory. Moreover, the Design Structure Matrix (DSM) is used to capture the effect of interactions between risk events. Second, the Fuzzy Technique for Order Preference by Similarity to Ideal Solution (FTOPSIS) method is used to analyze the obtained solutions by ACO, based on the other management criteria. Finally, the efficiency of the proposed framework is examined by its implementation in a real building construction project. Discussions through the case study show that using the proposed framework decision makers can evaluate more aspects of response actions.Tue, 13 Mar 2018 20:30:00 +0100A stochastic multi-objective model based on the classical optimal search model for searching ...
http://scientiairanica.sharif.edu/article_20226_0.html
Although after an earthquake the injured person should be equipped with food, shelter and hygiene activities, before anything must be searched and rescued. But disaster management (DM) has focused heavily on emergency logistics and developing an effective strategy for search operations has been largely ignored. In this study, we suggest a stochastic multi-objective optimization model to allocate resource and time for searching the individuals who are trapped in disaster regions. Since in disaster conditions the majority of information is uncertain, our model assumes ambiguity for the locations where the missing people may exist. Fortunately, the suggested model fits nicely into the structure of the classical optimal search model. Hence, we use a stochastic dynamic programming approach to solve this problem. On the other hand, through a computational experiment, we have observed that this model needs heavy computation. Therefore, we reformulate the suggested search model as a multi-criteria decision making (MCDM) problem and employ two efficient MCDM techniques, i.e. TOPSIS and COPRAS to tackle this ranking problem. Consequently, the computational effort is decreased significantly and a promising solution is produced.Tue, 13 Mar 2018 20:30:00 +0100Nonlinear free vibration analysis of functionally graded plate resting on elastic foundation in ...
http://scientiairanica.sharif.edu/article_20227_0.html
This paper deals with nonlinear vibration analysis of functionally graded plate resting on Pasternak elastic foundation in thermal environment. A mathematical model is developed based on higher-order shear deformation theory using Green-Lagrange type nonlinearity. The model includes all the nonlinear terms to obtain a general form and to present the original flexure of the plate. The material properties are considered as temperature dependent and graded along thickness direction obeying a simple power law distribution in terms of volume fraction of the constituents. The compression/traction free condition is employed to obtain the simplified model with seven parameters instead of nine parameters. The plate model has been discretized into C0 eight noded quadratic elements with seven degrees of freedom per node. The governing equation of the functionally graded plate has been derived using Hamilton’s principle and is solved using direct iterative method. The present model is validated by comparing the obtained results with those published in the literature. The effects of volume fraction index, aspect ratio, thickness ratio, support conditions, elastic foundation modulus and temperature on the nonlinear frequencies of the functionally graded plates are discussed. It has been found that the intermediate material property does not necessarily give intermediate nonlinear frequencyTue, 13 Mar 2018 20:30:00 +0100Type-2 Fuzzy Rule-Based Expert System for Diagnosis of Spinal Cord Disorders
http://scientiairanica.sharif.edu/article_20228_0.html
The majority of people have experienced pain in their low back or neck in their lives. In this paper a type-2 fuzzy rule based expert system is presented for diagnosing the spinal cord disorders. The interval type-2 fuzzy logic system permits us to handle the high uncertainty of diagnosing the type of disorder and its severity. The spinal cord disorders are studied in five categories using historical data and clinical symptoms of the patients. The main novelty of this paper lies in presentation of the interval type-2 fuzzy hybrid rule-based system, which is a combination of the forward and backward chaining approaches in its inference engine and avoids unnecessary medical questions. Using of parametric operations for fuzzy calculations increases the robustness of the system and the compatibility of the diagnosis with a wide range of physicians’ diagnosis. The outputs of the system are comprised of type of disorder, location and severity as well as the necessity of taking a M.R. Image. A comparison of the performance of the developed system with the expert shows an acceptable accuracy of the system in diagnosing the disorders and determining the necessity of the M.R. Image.Tue, 13 Mar 2018 20:30:00 +0100Effect of Stress Direction on the Undrained Monotonic and Cyclic Behaviour of Dense Sands
http://scientiairanica.sharif.edu/article_20318_0.html
Geotechnical design may be unsafe if the anisotropic behaviour of soil is not considered. The behaviour of anisotropic materials depends on the principal stresses and their directions. A detailed experimental programme was conducted to study the effect of stress direction on the monotonic and cyclic behaviour of dense sand. A total of 20 undrained tests were performed at a constant mean confining stress (σ'0m) constant intermediate principal stress ratio (b= (σ2-σ3)/(σ1-σ3)), and principal stress directions (α). Two fine sands, Babolsar and Toyoura, were selected as the test materials. The isotropic consolidated specimens were prepared using the wet tamping technique. The results showed that the major principal stress direction had little considerable effect on the mobilized friction angle at steady state or phase transformation. The results showed that stress direction had a significant effect on the non-coaxiality between the principal strain increment direction and the principal stress direction. The soil fabric was led to significant non-coaxiality value before the peak shear strength. Increasing the octahedral shear strains decreased the non-coaxiality value due to destruction of the soil particle interlock (soil fabric). The effect of stress direction on non-coaxiality and excess pore water pressure generation was also investigated.Tue, 17 Apr 2018 19:30:00 +0100MHD PERISTALTIC SLIP FLOW OF CASSON FLUID AND HEAT TRANSFER IN CHANNEL FILLED WITH A POROUS MEDIUM
http://scientiairanica.sharif.edu/article_20319_0.html
We examine the effect of velocity slip on hydromagnetic peristaltic flow of a Casson fluid and heat transfer through an asymmetric channel fluid filled a porous medium.The model governing equations are obtained, simplified using long wavelength and low Reynolds number assumptions and then tackled analytically.Numerical result for effects of embedded parameters on the stream function, axial velocity, pressure drop, temperature, skin friction and Nusselt number are presented graphically and discussed. It is found that thepermeability parameter enhances the size of the trapped bolus while velocity slip diminishes it. A rise in magnetic field intensity and Cason fluid parameters decrease the both velocity and temperature profiles.The present problem is of substantial importance in crude oil refinement and biomedical engineering.Tue, 17 Apr 2018 19:30:00 +0100Impact of nonlinearity on bolt forces in multi-bolted joints: A case of the assembly stage
http://scientiairanica.sharif.edu/article_20320_0.html
This article concerns modeling, computation and analysis of multi-bolted joints in the assembly stage. The physical joint model is introduced as the assembly of the following three basic subsystems: a set of fasteners (bolts), a flexible joined flange and a contact layer between it and a rigid support. The finite element method (FEM) is used for modeling. Bolts are replaced by the bolt models of the spider type. The joined flange is modeled with spatial finite elements. As a model of the contact layer, the Winkler contact layer model is adopted. The truth of the theorem has been tested, according to which nonlinear characteristics of the contact layer may have an insignificant impact on computational final values of bolt preloads in the case of sequential tightening of the joint. The results of the calculations for the selected multi-bolted joint are given and compared with the experimental results. Conclusions of paramount importance to the engineering practice are comprised.Tue, 17 Apr 2018 19:30:00 +0100Numerical study of particulate turbulent flow to investigate recovery period in cleanrooms
http://scientiairanica.sharif.edu/article_20322_0.html
The Clean room is a controlled space and is used in various industries such as electronics, medical and military industries. One of the most important tests to evaluate the performance of the cleanroom is recovery test. Recovery test determines the time period during which a clean room returns to its designated cleanliness level after an instant or a period of deliberate or unintentional contamination. In this paper, a thorough investigation of recovery period has been implemented. In this study, air change rate and its pattern were studied using the Eulerian and Lagrangian approaches and LES, DES and k-ω SST turbulent models. Simulation results were evaluated against control volume analysis. Parameters such as the air change rate, the number of particles, and pressure and energy consumption in various radial and tangential angles of diffusers were studied Results showed that radial angle had little positive and occasionally negative effect on recovery period. On the contrary, tangential angle improved decontamination rate, at maximum performance (β=45°), it could reduce recovery period as much as 25% which in turn reduces energy consumption. In addition the DES model provides the best and most coinciding answers between all turbulence models.Tue, 17 Apr 2018 19:30:00 +0100Different Operational Alternatives of Aquifer Thermal Energy Storage System for Cooling and ...
http://scientiairanica.sharif.edu/article_20323_0.html
In this research, a confined aquifer with low groundwater flow was considered to meet the cooling and heating requirement of residential complexes. The complexes were located in the cities of Ahvaz, Ardabil, Bandar Abbas, Esfahan, Kerman, Rasht, Tehran and Zahedan. The complex in Ardabil required mostly heating, the ones in Ahvaz and Bandar Abbas required mostly cooling, whereas the complex in other cities required both heating and cooling. Four different alternatives of aquifer thermal energy storage (ATES) were analyzed in this study. These alternatives were:1) using ATES alone for cooling 2) for cooling coupled with a conventional refrigeration system or a chiller 3) for heating by employing flat plate solar collectors and 4) for heating by employing flat plate solar collectors and a heat pump. Thermal energy recovery factor and the annual coefficient of performance (COP) of the alternatives were determined. The results showed that, for buildings located in cities with mild climatic conditions(such as Esfahan), where the annual heating and cooling energy requirements are early equal, the use of ATES is highly recommended when employing any of the alternatives considered in this investigation.Tue, 17 Apr 2018 19:30:00 +0100Immune Based Evolutionary Algorithm for Determining the Optimal Sequence of Multiple ...
http://scientiairanica.sharif.edu/article_20324_0.html
This paper presents a new multiple disinfection operation problem (MDOP) in which several buildings have to be sprayed with various disinfectants. The MDOP seeks to minimize the total cost of disinfection operations for all buildings. The problem is different from the typical vehicle routing problem since: (a) each building has to receive multiple spray applications of disinfectants; (b) the final spray application of disinfectant in each building is fixed; and (c) for safety, the time interval between two consecutive spray applications of disinfectants for each building must meet or exceed a specified minimum. The MDOP problem is NP-hard and difficult to solve directly. In this paper, we firstly develop an efficient encoding of spray operations to simultaneously determine the optimal sequence of buildings and their respective treatments with spray disinfectants. Secondly, we adopt immune algorithm to solve the presented MDOP. Finally, as a demonstration of our method, we solve the problem for a campus case to determine the optimal disinfection strategy and routes assuming both single and multiple vehicle scenarios. Numerical results of immune algorithm are discussed and compared with those of genetic algorithm and PSO to show the effectiveness of the adopted algorithm.Tue, 24 Apr 2018 19:30:00 +0100Lean design management using a gamified system
http://scientiairanica.sharif.edu/article_20325_0.html
Design process, due to its information- and innovation-intensive nature, is highly susceptible to change, thus waste. This attracted the attention of lean design/construction professionals in the past few years. However, limited, if any, researches have addressed this issue from the human behavior perspective. This research proposes a method that exploits the potential of the Last PlannerÒ System (LPS) in design management. The main contribution of this paper is improving the applicability of the LPS to design processes by incorporating a gamified pay-for-performance system to the normal practice of the LPS. It encourages motivating design engineers by granting them single point, autonomous responsibility to perform their tasks. To this end, the proposed method shifts the focus of design managers away from predicting the workflow and chronologies of design tasks towards motivating design engineers to eliminate non-value-adding works/time. To bolster the concept and examine the method, it was put into practice by construction design teams. Findings corroborate the efficiency of the method in eliminating the non-value-adding works from design processes. The findings are of practical value to consulting firms, especially design team managers who seek to maximize innovation, competency and quality outcome.Tue, 24 Apr 2018 19:30:00 +0100New aspect of transition between line and continuous spectrum and its relation to seismic ...
http://scientiairanica.sharif.edu/article_20326_0.html
We considered a new view on transition process from periodic to aperiodic signals, in time and spectral domains, pointing out how the concept of infinity is involved. It contributes to better understanding of the nature of both spectral descriptions, and conditions of their practical use, particularly in unusual cases. There we highlight the invariance in spectrum convergence by introducing some numerical parameters which exactly describe such process. Their behaviour is numerically examined to detail. Also, we considered the opposite transition, from aperiodic to periodic, to clarify the meaning of spectral line. To suggest applicability of our analysis we used an actual seismic signal. By extracting the most prominent waveform part, regarding influence on structures, we formed a periodic signal which line spectrum can clearly show possible resonance with vibrating tones of structures.Tue, 24 Apr 2018 19:30:00 +0100Numerical investigation on natural convection of nanofluids in an inclined square enclosure ...
http://scientiairanica.sharif.edu/article_20327_0.html
Studying on natural convection of nanofluids in enclosures with non-uniform heated walls is important for many engineering applications such as solar energy collection. In this article, we develop a fully higher-order compact (FHOC) finite difference method to investigate the natural convection and heat transfer of nanofluids in an inclined square enclosure with sinusoidal temperature distributions. Numerical simulations have been performed over a range of amplitude ratio, inclination angles, phase deviation, nanoparticles volume fraction, and Rayleigh number. Results show that heat transfer can exchange significantly by increasing the amplitude ratio and inclination angles in nanofluids. Moreover, elevating the nanoparticles volume fraction doesn't always enhance the heat transfer of nanofluids. When the Rayleigh number is low ( = ), the average Nusselt number decreases as the solid volume fraction parameter increases. On the other hand, elevating has favorable effects on the heat transfer of nanofluids when is high (e.g., , ). When , the total heat transfer rate decreases in the order of nanoparticles arranged as Cu, CuO, Al2O3, and TiO2. Finally, a correlated expression of the total average Nusselt number, the Rayleigh number and the solid volume fraction of nanoparticles is empirically obtained.Tue, 24 Apr 2018 19:30:00 +0100Hybrid fuzzy-stochastic approach for multi-product, multi-period, and multi-resource master ...
http://scientiairanica.sharif.edu/article_20329_0.html
Master production scheduling is an effective phase of production planning which leads to scheduling and magnitude of different products production in a company. This problem requires investigating a wide range of parameters, regarding demand, manufacturing resource usage and costs. Uncertainty is an intrinsic characteristic of these parameters. In this paper, a model is developed for master production scheduling under uncertainty, in which demands, as time-dependent variables, are considered as stochastic variables, while cost and utilization parameters, with cognitive ambiguity, are expressed as fuzzy numbers. A hybrid approach is also proposed to solve the extended model. The application of the proposed method is examined in a practical problem of a polyethylene pipe and fitting Co. in Iran. The result showed a high degree of applicability.Tue, 24 Apr 2018 19:30:00 +0100Optimal Location of Stone Column in Stabilization of Sand Slope: An Experimental and 3D ...
http://scientiairanica.sharif.edu/article_20331_0.html
Utilization of numerical and analytical methods to stabilize earth slopes applying piles or stone columns is subject commonly discussed by numerous researchers. Various researchers have practiced optimization of the location of pile or stone column, to stabilize earth slope through numerical and analytical approaches. Their efforts have led to various results raising the question of what the optimal place for installation of a pile or stone column is. It is look like that no experimental studies are conducted in this regard; the point which is discussed in this article. Experimental study conducted in this article is new topic and it can solve the problem caused by varying and sometimes contradictory results of numerical analyses to find the optimal pile (or stone column) location. In this article, an experimental study is conducted for two-layer sand earth slope, which is saturated through precipitation and failure after saturation over time. Installing stone columns in different locations and saturating the earth slope through precipitation, rational acceptable results were obtained that can appropriately assist designers. All of the experimental models were modeled and compared using the 3D finite difference method (3D FDM), which are compliant with each other.Tue, 24 Apr 2018 19:30:00 +0100Assessment of Mechanical and Durability Properties of Concrete Containing PET Waste
http://scientiairanica.sharif.edu/article_20334_0.html
Plastic waste is a silent threat to the environment, and their disposal is a serious issue. To sort out this issue, many efforts were made to reuse the plastic waste, but no significant results were achieved. On the contrary, concrete being the widely used construction material is facing problem due to unavailability of ingredient material (sand and coarse aggregate). In this study PET (polyethylene terephthalate) aggregates manufactured from the waste un-washed PET bottles in shredded form were used to partially replace fine aggregate and coarse aggregate in concrete in various percentages (0%, 5%, 10%, 15% and 20%). Various tests like workability, compressive strength, flexural strength, water permeability, abrasion resistance, dynamic and static modulus of elasticity were performed. The micro-structural analysis of the specimens was carried out using an optical microscope. It was found that the workability, compressive strength, flexural strength, dynamic and static modulus of elasticity decreased with the increasing amount of PET waste in concrete. Water permeability of concrete was found to increase with increasing amount of PET waste. In both the cases, i.e., when fine and coarse aggregates were replaced with PET waste, an improvement in the abrasion resistance of concrete was found.Tue, 24 Apr 2018 19:30:00 +0100Analytic Solution of a System of Linear Distributed Order Differential Equations in the ...
http://scientiairanica.sharif.edu/article_20335_0.html
In this paper, solution of a system of linear differential equations of distributed order in the Riemann-Liouville sense is analytically obtained. The distributed order relaxation equation is a special case of the system investigated in this paper. The solution of the mentioned system is introduced on the basis of a function which can be considered as the distributed order generalization of the matrix Mittag-Leffler functions. It is shown that this generalized function in two special cases of the weight function can be expressed in terms of the multivariate Mittag-Leffler functions and the Wright functions.Tue, 24 Apr 2018 19:30:00 +0100Hypersonic Flow over Hemispherical Blunt Body with Spikes
http://scientiairanica.sharif.edu/article_20339_0.html
Use of spike on a hemispherical body changes the flow field and hence the aerodynamic drag. Computational studies have been made to obtain the flow field around a hemispherical body with spikes at a hypersonic Mach number of 6. The effect of shape of spike tip and length has been studied. Laminar computations have been made adopting structured grid using commercial software Fluent. It is observed that use of a sharp spike itself reduces the drag signicantly. However the use of a hemispherical head spike further reduces the drag. Contribution of dierent components towards drag indicate that the increase in length of a spike do not change the spike contribution. However the flow field on main body is altered which leads to reduction in dragwith change in length. Estimated maximum drag obtained is found to be highest in comparison to any reported drag value in literatures with any spike shape and length.Tue, 24 Apr 2018 19:30:00 +0100Optimal fleet composition and mix periodic location-routing problem with time windows in an ...
http://scientiairanica.sharif.edu/article_20412_0.html
This paper presents a new Mixed-Integer Non-Linear Programming (MINLP) model for a Supply Vessel Planning (SVP) problem. The traditional SVP, which is a maritime transportation problem, is developed to a Maritime Fleet Sizing Mix Periodic Location-Routing Problem with Time Windows (MFSMPLRPTW) by considering suppliers, location of onshore-base(s) and some real life aspects. The objective of this model is to decide the composition of fleets, optimal voyages, schedules and also the optimal location(s) for onshore-base(s) in such a way that the total cost is minimized and the needs of operation regions are fulfilled. The MFSMPLPRTW model is solved by an exact two-phase solution approach for both small and medium cases. Also, two meta-heuristic algorithms are used to solve the large-sized instances. In order to justify and show how the model and solution can lead to significant economic improvements for real life instances, a case study by the IOOC is considered, which is the only offshore oil and gas producer in Iran that has lots of installations and operation regions in the Persian Gulf and the Sea of Oman.
Mon, 30 Apr 2018 19:30:00 +0100Effects of viscous dissipation and convective heating on convection flow of a second grade ...
http://scientiairanica.sharif.edu/article_20414_0.html
The effects of viscous dissipation and convective boundary condition on the two-dimensional convective flow of a second grade liquid over a stretchable surface with suction/injection and heat generation are investigated. The governing partial differential equations are reduced into a dimensionless coupled system of nonlinear ordinary differential equations by appropriate similarity transformation. Then, they are solved analyticallyby homotopy analysis method (HAM) and by numerically with fourth order Runge-Kutta method with shooting technique. The HAM and numerical results of the local skin friction and local Nusselt number are compared for various emerging parameters. It is found that the momentum boundary layer thickness grows with rising the values of the viscoelastic parameter.Mon, 30 Apr 2018 19:30:00 +0100Experimental Investigation of Magnetic Abrasive Polishing of Paramagnetic Workpieces
http://scientiairanica.sharif.edu/article_20415_0.html
In the current paper application of magnetic abrasive polishing process, on paramagnetic workpieces is investigated. A magnetic disc which comprises of six magnetic coils and is electrified with three phase AC current is used to perform the experiments. In the experimental setup various parameters including; rotational speed of abrasive pins, quantity of abrasive pins, working gap, abrasive pins' dimensions and process's time can be changed. Changing this parameters surface quality is investigated. Two kinds of workpieces with different mechanical properties are examined. It is observed that both increasing the rotational speed and using smaller pins improve final surface quality but the rotational speed has a sharper effect. There are optimum abrasive pins quantity and working gap in which the best surface quality is obtained. The results are similar for the both selected materials.Mon, 30 Apr 2018 19:30:00 +0100Master Surgical Scheduling Problem with Multiple Criteria and Robust Estimation
http://scientiairanica.sharif.edu/article_20416_0.html
In this research the master surgical scheduling (MSS) problem at the tactical level of hospital planning and scheduling is studied. Before constructing the MSS, a strategic level problem, i.e. case mix planning problem (CMPP), shall be solved to allocate the capacity of operating room (OR) to each surgical specialty. In order to make an effective coordination between CMPP and MSS, the results obtained from solving the CMPP is used as an input for the respective MSS. In the MSS, frequently performed elective surgeries are planned in a cyclic manner for a pre-defined planning period. As a part of the planning process, it is required to level downstream limited resources such as intensive care unit (ICU) and ward beds with patient flow. In this study, a mathematical model is developed to construct an MSS. The proposed model is based on a lexicographic goal programming approach which is aimed at minimizing the OR spare time while considering the results of the CMPP. In this paper, data required to solve MSS, is collected from a medium-sized Iranian hospital. Hence, a robust estimation method is applied to reduce the effect of outliers in the decision making process. The results testify the performance of the proposed method against the solution put in practice in the hospital.Mon, 30 Apr 2018 19:30:00 +0100Optimized design of adaptable vibrations suppressors in semi-active control of circular plate ...
http://scientiairanica.sharif.edu/article_20417_0.html
Due to flexibility of thin plates, high amplitude vibrations are observed when they are subjected to severe dynamic loads. Due to the extensive application of circular plates in industry, attenuating the undesired vibrations is of foremost importance. In this paper, adaptable vibration suppressors (AVSs) as a semi-active control approach, are utilized to suppress the vibrations in a free circular plate; under the concentrative harmonic excitation. Using mode summation method, mathematical model of the hybrid system, including the plate and an arbitrary number of vibration suppressors is analyzed. By developing a complex multiple-loops algorithm, optimum values for the AVSs’ parameters (stiffness and position) are achieved such that the plate deflection is comprehensively minimized. According to the results, AVSs act efficiently in suppressing the vibrations in resonance/non-resonance conditions. It is also observed that optimum AVSs reduce the plate deflection over a broad spectrum of excitation frequencies. Finally, since the algorithm is developed in a general user friendly style, AVSs’ design can be extended to other shapes of plates with various boundary conditions and excitations.Mon, 30 Apr 2018 19:30:00 +0100Mechanical properties of soft tailings from different depths of a Swedish tailings dam: Results ...
http://scientiairanica.sharif.edu/article_20418_0.html
In an upstream tailings dam, loose layers might occur at different depths due to melting of frozen layers deposited during freezing temperature in Sweden. Reduced shear strength of such layers in a tailings dam might cause stability problems. Due to slow consolidation process, it is unknown, whether self-weight of a high tailings dam could have influence on strength and stiffness of soft tailings located at different depths. For numerical modelling, appropriate strength and stiffness properties of soft tailings are needed. For this purpose, loose layers in an upstream tailings dam were identified based on results of cone penetration tests. Consolidated Drained (CD) triaxial tests were conducted on undisturbed soft tailings collected from different depths of the dam. The results indicated that depth did not have considerable influence on strength and stiffness of tailings. Hardening Soil Model (HSM), at high confining pressures and axial strains underestimated stiffness of soft tailings under CD triaxial state. This study shows that: (i) proper care is needed in evaluating strength and stiffness parameters for soft tailings, and (ii) use of the HSM is likely to predict more deformations which could give an early warning before an actual failure of a tailings dam.Sat, 05 May 2018 19:30:00 +0100THE USE OF NEURAL NETWORKS FOR THE PREDICTION OF THE FACTOR OF SAFETY OF THE SOIL AGAINST ...
http://scientiairanica.sharif.edu/article_20423_0.html
In this study, the performance of the artificial neural network (ANN) and multiple regression (MR) models to predict the factor of safety, Fs, values of soil against liquefaction was investigated and compared. To achieve this, two earthquake parameters, namely, earthquake magnitude (Mw) and horizontal peak ground acceleration (amax ), and six soil properties, namely, standard penetration test number (SPT-N), saturated unit weight (γsat), natural unit weight (γn), fines content (FC), the depth of ground water level from the ground surface (GWL), and the depth of the soil from ground surface (d) varied in the liquefaction analysis and then the Fs value was calculated for each case by using the Excell program developed and used in the development of the ANN and MR models. The results obtained from the simplified method were compared with those obtained from both the ANN and MR models.It was found that the predicted values from the ANN model matched the calculated values much better than those obtained from the MR model. Moreover, the performance indices such asthedetermination coefficient, variance account for, mean absolute error, root mean square error, and the scaled percent error were computed to evaluate the prediction capacity of the models developed. The study demonstrates that the ANN model is able to predict the Fs value of the soil against liquefaction, quite efficiently, and is superior to the MR model.Sat, 05 May 2018 19:30:00 +0100A Novel Robust Possibilistic Cellular Manufacturing Model Considering Worker Skill and Product ...
http://scientiairanica.sharif.edu/article_20424_0.html
Design of an appropriate cellular manufacturing system (CMS) leads to system flexibility and production efficiency by using the similarities in the manufacturing process of products. One of the main issues in these systems is to consider product quality level and worker’s skill level in the production process. This study proposes a comprehensive bi-objective possibilistic nonlinear mixed-integer programming model under uncertain environment to design a suitable CMS with aims of minimizing the total costs and total inaction of workers and machines, simultaneously. In this respect, the demand of each product with a specific quality level and linguistic parameters such as product quality level, worker’s skill level and job hardness level on machines are considered under fuzzy environment. To this end, the robust possibilistic programming approach is tailored to cope with fuzzy impute parameters. Finally, a real case study is provided to show the efficiency and applicability of the proposed model. In this respect, the proposed approach could be improved the total costs by 23.6% and the total inaction of workers and machines by 11.7% regarding the real practice. In addition, the performance of the presented model is demonstrated by comparing between the results obtained from the proposed model and actual practice.Sat, 05 May 2018 19:30:00 +0100A queuing theory- based approach for designing cellular manufacturing systems
http://scientiairanica.sharif.edu/article_20425_0.html
This paper presents a new cell formation and cell layout problem considering multiple process routings and subcontracting using the principles of queuing theory. It is assumed that each machine operates as an M/M/1 queuing system and a queuing network is used to obtain in-process inventories and machine utilization. The problem is formulated as a mixed-integer nonlinear program with the objective of minimizing the total costs, including the production, subcontracting, material handling, machine idleness, and holding costs. Due to the computational complexity of the problem, a heuristic method is suggested to effectively solve the problem. A numerical example is given to clarify the proposed approach, and finally, further instances are solved to verify the performance of the solution method and to accomplish comparisons. The computational results show that the proposed heuristic is both effective and efficient.Sat, 05 May 2018 19:30:00 +0100A vacuum-refilled tensiometer for deep monitoring of in-situ pore water pressure
http://scientiairanica.sharif.edu/article_20428_0.html
Real-time measurement of soil water pressure has been recognized as an essential part of investigating water flow in unsaturated soils. Tensiometry, amongst different measuring techniques, is a common method for direct evaluation of water pressure. However, the lower limit of measurable water pressure by a conventional tensiometer becomes even more limited by increasing its length in the vertical installation. This paper describes development of a vacuum-refilled tensiometer (VRT) for monitoring soil water pressure independent of installation depth. This is achieved by fixing the distance between pressure sensor and ceramic cup together with incorporating an ancillary vacuum-refilling assembly into its design. The assembly allows for more efficient replacement of diffused air into the ceramic cup and reservoir with water. The new tensiometer is designed to withstand both negative and positive water pressure of up to almost one bar. In addition, the response time of the tensiometer to a change in negative water pressure for its working range (≥ -80 kPa) is very quick, in the order of seconds and one minute at most. The long-term performance of the new tensiometer is evaluated through a five-month monitoring program in the laboratory, simulating cyclic wetting and drying in the field.Sat, 05 May 2018 19:30:00 +0100SCF distribution in FRP-strengthened tubular T-joints under brace axial loading
http://scientiairanica.sharif.edu/article_20430_0.html
The present article is dedicated to study of the effects of different parameters of fiber reinforced polymers (FRP), as strengthening material, on a tubular T-joint subjected to brace axial loading using finite element analyses. The effectiveness of FRP materials on enhancing the fatigue life of tubular T-joints was investigated through computing the ratio of the stress concentration factors (SCFs). FRP parameters which is considered include fiber orientation, FRP thickness, effective wrapping length and FRP material properties. The FRP materials were modeled and applied onto a basic numerical FE model which was validated in the past against well-known experimental results on weld-toe SCFs. Promising results were derived from the analyses showing that the FRP strengthening method can effectively decrease the SCF values for tubular T-joints.Sat, 05 May 2018 19:30:00 +0100Dynamic finite element analysis of shot peening process of 2618-T61 aluminium alloy
http://scientiairanica.sharif.edu/article_20431_0.html
Shot peening is one of the surface treatment processes usually used for the improvement of fatigue strength of metallic parts by inducing residual stress field in them. The evaluation of shot peening parameters experimentally is not only very complex but costly as well. An attractive alternative is the explicit dynamics finite element (FE) analysis having the capability of accurately envisaging the shot peening process parameters using a suitable material’s constitutive model and numerical technique. In this study, ANSYS/LS-DYNA software was used to simulate the impact of steel shots of various sizes on 2618-T61 aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The effect of shot velocity and size on the induced compressive residual stress and plastic deformation were investigated. The results demonstrated that increasing the shot velocity and size yielded in an increase in plastic deformation of the aluminium target. However, as observed, the effect of shot velocity and size was small in magnitude on the target's subsurface compressive residual stress.Sat, 05 May 2018 19:30:00 +0100Modeling and optimization of friction stir welding parameters in joining 5086 H32 aluminium alloy.
http://scientiairanica.sharif.edu/article_20432_0.html
The present manuscript focuses on developing a mathematical model to predict the intergranular corrosion rate of friction stir welded AA5086 H32 aluminium alloy joints. Six factors-Five levels central composite design matrix, having 52 experiments, is used for design of experiments. The developed model is used to examine the impact of studied process parameters i.e. rotational speed, welding speed, tool shoulder diameter, tool hardness, tilt angle , and pin profile on intergranular corrosion rate of the welded joints. Response surface methodology is used to optimize the process parameters for minimizing the susceptibility to intergranular corrosion attack. The optimum combination of studied parameters, to have minimum corrosion rate i.e. 3.2 mg/cm2, is obtained as 1296 rpm rotational speed, 79.4 mm/min welding speed, 14.9 mm tool shoulder diameter, 47.4 HRC tool hardness, 2.380 tilt angle, and square pin profile.Sat, 05 May 2018 19:30:00 +0100Structural Control of RC Buildings Subjected to Near-Fault Ground Motions in terms of Tuned ...
http://scientiairanica.sharif.edu/article_20433_0.html
To design a proper structure against earthquake in modern systems, control systems are of special importance. Added passive tuned mass damper is one of such systems which will be discussed in this paper. In this regard, the effect of adding this damper to a 10-floor concrete structure under six near-fault earthquakes is investigated. To do this, a code has been written in MATLAB which receives ground motion record of the occurring earthquake as well as the structure specifications such as matrix of mass, stiffness and damping as an input. As output, it presents time-history of responses for top floor, a diagram for the floor displacement and drift of the structure at the time that the top floor has reached the maximum displacement. Also, these diagrams are compared both when the added damper is present and absent. It is observed that the added passive control of TMD is highly effective in the reduction of structure response against earthquake which in turn depends on the properties of the earthquake and therefore should be chosen based on the site seismic conditions.Sat, 05 May 2018 19:30:00 +0100On the Equivalency of Reliability and Security Metrics for Wireline Networks
http://scientiairanica.sharif.edu/article_20434_0.html
In this paper, we consider a secure network coding problem in which some secret keys are shared among legitimate nodes, and there exists an eavesdropper which is able to hear a subset of links. We show the equivalency of secure network coding under weak and strong secrecy conditions. For linear network coding, we show a stronger result: equivalency of "perfect secrecy and zero-error constraints" to "weak secrecy and $epsilon$-error constraints". This is a secure version of the result obtained by Langberg and Effros, on the equivalence of zero-error and $epsilon$-error regions in the network coding problem with co-located sources. Jalali and Ho exploit extractor functions to prove the weak and strong rate region equivalency for this network; however, to prove this equivalency, we develop some tools in random binning and prove the equivalency in a slightly more general setting.Sat, 05 May 2018 19:30:00 +0100Optimal Lot Size in a Manufacturing System with Imperfect Raw Materials and Defective Finished ...
http://scientiairanica.sharif.edu/article_20436_0.html
In real-world manufacturing systems, encountering with imperfect raw materials and generation of defective finished products are inevitable. In order to cope with these practical problems, this paper studies a manufacturer which orders raw materials from external source (supplier), and then produces a finished product. The raw materials contain imperfect quality items and, in addition, the production process is defective. The imperfect raw materials are sold after screening process, while the defective finished products go under a further rework process. It is also assumed that defective rate of machine is a random variable, resulting three possible cases regarding occurrence of backordering shortage. The aim is to determine economic order/production lot sizes for each case in such a way that the total cost of system is minimized. The optimal closed form solution is derived for each case separately. Moreover the applicability of the proposed manufacturing model is illustrated via a numerical example.Sat, 05 May 2018 19:30:00 +0100Water Flow Stabilization Using Submerged Weir for Draft Tube Reaction Hydraulic Turbine
http://scientiairanica.sharif.edu/article_20437_0.html
In turbine practice engineering, draft tube downstream running under extreme water flow pressure and velocity. This is causing a vibrations and pressure variation during different operation frequencies. The practical challenge of obtaining a stabilized water flow is ongoing domain of research. In this paper, a proposition of initiating submerged weir in the downstream of draft tube reaction turbine is inspected. The main goal of this research is to reduce the water flow pressure variation, velocity and shear distribution in accordance to the upstream water level influence. Two types of turbines including vertical Kaplan and Francis turbine units are examined. ANSYS CFX software tool is used to build three-dimension (3D) numerical models for the Kaplan and Francis turbines with building a submerged weir at the outlet of the draft tubes at three deferent height suggestions. The influence of the proposed submerged weir is studied the flow through these turbines by considering the dimensions of their components including the penstock with inlets, spiral casing, shafts and blades, and the draft tube with outlets. The findings of this research were tremendous proposition to solve the problem of negative pressure pulsation in draft tube of Kaplan and Francis turbines types.Sat, 05 May 2018 19:30:00 +0100The Algebraic Structures of Complex Intuitionistic Fuzzy Soft Sets Associated with Groups and ...
http://scientiairanica.sharif.edu/article_20438_0.html
In recent years, the theory of complex fuzzy sets has captured the attention of many researchers, and research in this area has intensified in the past five years. However, almost all of the researchers in this area have focused on the development of various complex fuzzy based models as well as constructing decision making processes using current decision making approaches and tools. In this spirit, this paper focuses on developing the algebraic structures pertaining to groups and subgroups for the complex intuitionistic fuzzy soft set model. This paper was constructed based on the complex intuitionistic fuzzy soft set model which is characterized by a membership and a non-membership structure for both the amplitude and phase terms of the elements. This model was chosen due to its dual-membership structure that is better able to handle the uncertainties and partial ignorance that exists in most complex data, whilst retaining all the characteristics and advantages of complex fuzzy sets. Besides examining the properties and structural characteristics of the algebraic structures, the relationship between the algebraic structures introduced here and the corresponding algebraic structures in fuzzy group theory and classical group theory were also discussed and verified.Sat, 05 May 2018 19:30:00 +0100Analysis of the secondary vortices in rotating flow induced by a twisted-tape inside a pipe
http://scientiairanica.sharif.edu/article_20439_0.html
Flow through a twisted-tape (swirler) creates a complicated vortex structure downstream in the pipe. Detailed velocity measurements with Laser Doppler Velocimetry (LDV) along horizontal and vertical axes perpendicular to the axial flow direction have shown a strange flow pattern at the center of the rotating flow - a counter-rotating vortex seems to be present at the center with periodically varying magnitude in the axial direction. In more detailed measurements, it is shown that this behavior is the result of a pair of co-rotating secondary vortices that are superimposed on the primary rotating flow in a helical formation. The source of these secondary vortices has remained unclear. This study presents numerical simulations of the flow through 180o twisted-tape in a pipe, complementing the previous experimental results. The simulations reproduce the characteristics of the helical co-rotating vortices observed in experiments and provide details of the flow field. The results provide insight into the formation of the secondary vortices inside the twisted-tape, explaining the experimental observations. Mechanism of the vortex formation is described, showing that the secondary co-rotating helical vortices are produced by a pair of single co-rotating vortex formed on each side of the twisted-tape.Sat, 05 May 2018 19:30:00 +0100A regression-based approach to predict crest settlement of embankment dams under earthquake shaking
http://scientiairanica.sharif.edu/article_20440_0.html
Settlement and deformation of the embankment dams are among the major damages caused by earthquakes, eventually leading to dam instability. Therefore, accurate assessment of the seismic settlement of embankment dams is of particular concern. This study aims to evaluate the settlement of embankment dams subjected to earthquake loads using regression-based methods. A wide-ranging real data on crest settlement of embankment dams caused by earthquakes was collected and analyzed. Yield acceleration of dam, maximum horizontal earthquake acceleration, fundamental period of dam body, predominant period of earthquake, and earthquake magnitude were considered as the most influential parameters affecting the seismic crest settlement of embankment dams. Using support vector regression method as well as multiple linear regression method, two models were developed to estimate earthquake induced crest settlement of embankment dams. Subsequently, sensitivity analysis was conducted in order to assess the behavior of the proposed models under different conditions. Finally, the accuracy of the proposed models was compared with the existing relationship for estimation of earthquake induced crest settlement of embankment dams. Although both MLR- and SVR-based models have an acceptable accuracy in estimation of the crest settlement of embankment dams under earthquake loading, the SVR-based model has a higher accuracy.Sat, 05 May 2018 19:30:00 +0100Recognizing Involuntary Actions from 3D Skeleton Data Using Body States
http://scientiairanica.sharif.edu/article_20446_0.html
Human action recognition has been one of the most active fields of research in computer vision over the last years. Two dimensional action recognition methods are facing serious challenges such as occlusion and missing the third dimension of data. Development of depth sensors has made it feasible to track positions of human body joints over time. This paper proposes a novel method for action recognition which usestemporal 3D skeletal Kinect data. This method introduces the definition of body states and then every action is modeled as a sequence of these states. The learning stage uses Fisher Linear Discriminant Analysis (LDA) to construct discriminant feature space for discriminating the body states. Moreover, this paper suggests the use of the Mahalonobis distance as an appropriate distance metric for the classification of the states of involuntary actions. Hidden Markov Model (HMM) is then used to model the temporal transition between the body states in each action. According to the results, this method significantly outperforms other popular methods, with recognition (recall) rate of 88.64% for eight different actions and up to 96.18% for classifying the class of all fall actions versus normal actions.Sat, 05 May 2018 19:30:00 +0100Bonferroni harmonic mean operators based on 2-dimension uncertain linguistic information and ...
http://scientiairanica.sharif.edu/article_20447_0.html
The Bonferroni mean (BM) has the advantages that it can capture the interrelationship among the input arguments, and the Harmonic mean is a conservative average lying between the max and min operators. The 2-dimension uncertain linguistic variables add a subjective evaluation on the reliability of the evaluation results given by decision makers, so they can better express fuzzy information. In this paper, in order to combine the advantages of them, we first propose the 2-dimensional uncertain linguistic weighted Bonferroni mean (2DULWBM) operator. However, it cannot consider the case when the given arguments are too high or too low. So we further proposed the 2-dimensional uncertain linguistic improved weighted Bonferroni harmonic mean (2DULIWBHM) operator, which combine the 2DULWBM with Harmonic Mean. Furthermore, we study some desirable properties and some special cases of them. Further, we develop a new method to deal with some multi-attribute group decision making (MAGDM) problems under 2-dimension uncertain linguistic environment based on the proposed operators. Finally, an illustrative example is given to testify the validity of the developed method by comparing with the other existing methods.Sat, 05 May 2018 19:30:00 +0100Study of the correlation between oil price and exchange rate under the new state of the economy
http://scientiairanica.sharif.edu/article_20448_0.html
Aiming at the problem of small sample modelling of oil price and exchange rate with time-delayed causality, a grey multivariate time lag model and its solution are proposed against the new economic background of economic development, structural optimization and power conversion. Considering the difficulty of solving q-order differential equations analytically, we obtain a numerical solution. On the basis of this solution, the validity of the model is proved. The numerical results show that the model can describe and predict the operating rules of oil price and exchange rate economic systems with time delay, and it is concluded that the development of oil price and exchange rate is not coordinated under the new state of the economy. The relationship of oil prices and the exchange rate has changed in this state, oil prices have a positive effect on the rise of the exchange rate.Sat, 05 May 2018 19:30:00 +0100Influence Of Masonry Panels With Openings On The Seismic Response Of Reinforced Concrete ...
http://scientiairanica.sharif.edu/article_20483_0.html
Due to architectural considerations, openings are required in masonry infill panels. In this study, a pushover analysis is carried out to assess the behavior of RC infilled frames with emphasis on the effect of openings in the infills. The main parameters that will be considered concern the size, the location and the aspect ratio of the openings. Three reinforced concrete structures representative of rigid, semi-rigid and flexible structures are designed according to the Algerian seismic code. The numerical model of the structures consists of frame elements with concentrated plastic hinges at the ends and a nonlinear layered shell for the infills. The results obtained show that the presence of infills can drastically change the overall behavior of the structures by enhancing the strength capacities but with limited ductility and the presence of openings can modify the hinges locations and patterns according to their size, location and aspect ratio.Fri, 11 May 2018 19:30:00 +0100A multi-component reaction for the direct access to ...
http://scientiairanica.sharif.edu/article_20491_0.html
An efficient synthesis of 4,4'-(phenylmethylene)bis(1H-pyrazol-5-ol)-3-carboxylates is achieved by one pot pseudo five-component reaction of phenylhydrazine, acetylenedicarboxylates and aromatic aldehydes in the presence of nano-NiZr4(PO4)6 at 60°C in water. Nano-NiZr4(PO4)6 has been characterized by powder X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Use of simple and readily available starting materials, excellent yields in short times, reusability of the catalyst, little catalyst loading and simple operational procedures are some of the important features of this protocol.Sun, 13 May 2018 19:30:00 +0100Adaptive dynamic surface control of flexible-joint robot with parametric uncertainties
http://scientiairanica.sharif.edu/article_20492_0.html
A new kind of adaptive dynamic surface control (DSC) method is proposed to overcome parametric uncertainties of flexible-joint (FJ) robots. These uncertainties of FJ robots are transformed into linear expressions of inertial parameters which are estimated based on the DSC, and the high-order derivatives in DSC are solved by using first-order filter. The adaptation laws of inertial parameters are designed directly to improve the tracking performance according to the Lyapunov stability analysis. Simulation results for a two-link FJ robot show the better tracking accuracy against model parametric uncertainties. The method used does not need aid of Neural Network (NN), and is simpler and calculation faster than the other adaptive methodsSun, 13 May 2018 19:30:00 +0100A Tabu Search Algorithm for Multi-Period Bank Branch Location Problem: A Case Study in a ...
http://scientiairanica.sharif.edu/article_20493_0.html
Banks need to open new branches in new sites as a result of increase in the population, individual earnings and the growth in national economy. In this respect, opening new branches or reorganizing the locations of current branches is an important decision problem for banks to accomplish their strategic objectives. This paper presents a decision support method for multi-period bank branch location problems. Our aim is to find bank branch location based on transaction volume, distance between branches, and cost of opening and closing branches. The proposed method not only develops an Integer Program and a Tabu Search algorithm to find the exact places of branches but also presents a structuring method to identify the related criteria and their importance. We demonstrate the effectiveness of the method on random data. In the final stage, the method is applied in a Turkish bank’s branch location problem considering the current and possible places of the branches, availability of the data, and the bank’s strategies for a four-year strategic planning.Sun, 13 May 2018 19:30:00 +0100Seismic Behavior of Chevron Concentrically Braced Frames with Weak Beam
http://scientiairanica.sharif.edu/article_20494_0.html
Concentrically braced frames provide ductility and imparted seismic energy dissipation through yielding of tension braces and buckling of compression braces. In braced frames with chevron configuration, difference of actions in tension and buckled brace results in considerable unbalanced force at brace-beam intersection, which is addressed in modern seismic design provisions. In this paper, effect of flexural capacity of beam to carry this unbalanced force and consequently seismic behavior of braced frame is investigated by finite element analysis. Two-story and four-story chevron braced frames were modeled in ABAQUS software and studied by means of nonlinear cyclic pushover and nonlinear response history analysis methods. Results showed that inadequate flexural strength of the beams reduce lateral stiffness and strength of braced frame significantly as lateral drift increases; therefore, concentration of lateral deformation in one story may cause formation of soft and weak story. Furthermore, seismic behavior of chevron braced frame and two-story X braced frames were compared.Sun, 13 May 2018 19:30:00 +0100Vibrational characteristics of size dependent vibrating ring gyroscope
http://scientiairanica.sharif.edu/article_20495_0.html
In this paper vibrational analysis of size dependent micro-ring gyroscope under electrostatic DC voltage is performed. Based on the modified couple stress theory, Hamilton’s principle and in-extensionality approximation governing equations of size dependent micro rings and corresponding finite element formulation of circular micro ring along with eight half circular stiffeners embedded inside the ring is derived. Frequency analysis indicate that the obtained ring gyroscope mode shape is slightly different from the one previously reported in the literature. Size dependent behavior of the gyroscope is studied and findings confirmed the gap between classic and non-classic natural frequencies and pull-in voltage when the ring thickness is in order of material length scale parameter. Two different orientations for the actuation electrodes of the micro-ring gyroscope are implemented and effect of these orientations on the static deflection, pull-in instability and device frequencies in the sense ( direction) and drive ( direction) directions is investigated. Results reveal that the pull-in phenomena take place under lower voltage for & orientation of electrodes in comparison with orientation and frequency split occurs in higher voltages for & orientation. A comparison between finite element numerical natural frequencies of single ring and previously obtained analytical ones shows excellent agreement.Sun, 13 May 2018 19:30:00 +0100Size Effect Investigation on Lateral Vibrations of a Micro Drill Subjected to an Axial Load ...
http://scientiairanica.sharif.edu/article_20496_0.html
In this paper, the modified couple stress theory is used to capture size effect on dynamic behavior in a micro drill subjected to an axial load and a concentrated mass which is attached at its free end. Governing equations of lateral vibrations of the system and also associated boundary conditions are derived by obtaining the total kinetic and potential energies of the system and then using Hamilton’s principle. The Assumed Modes method has been applied to transform the governing partial differential equations into a set of infinite ordinary differential equations. Considering two terms of the equations, first two natural frequencies and also instability rotational speeds of the micro drill system are determined semi-analytically. Finally, numerical results of natural frequencies and also the threshold of instability speeds of the system are presented with respect to different values of the system parameters such as rotational speed, axial load, rotor length, concentrated mass, and also material length scale. The results show that the material length scale parameter is extremely effective on natural frequencies and also the threshold of instability speeds of the micro drill.Sun, 13 May 2018 19:30:00 +0100Bromodimethylsulfonium bromide: A novel reagent for the one pot synthesis of potent Nα-ureido ...
http://scientiairanica.sharif.edu/article_20497_0.html
Nα-protected ureidopeptides were synthesized efficiently using Bromodimethylsulfonium bromide mediated Curtius rearrangement through the in-situ generation of carboxylated sulfonium intermediate. Conversion of carboxylic acids to ureidopeptides in good yield was obtained in one-pot under mild reaction conditions, through a simple workup. To check the binding modes and binding affinity of urea functional group with target protein, the synthesized compounds were subjected to docking studies. Docking scores confirm that the molecules Boc-Leu-ψ[NHCONH]-Ala-OMe and Leu-ψ[NHCONH]-Ala-OMe have least energy and good agreement with the results of antibacterial studies against Escherichia coli, Staphylococcus aureus and Pseudomonas aeroginosa with respect to Streptomycin sulphate as a standard. The synthesized compounds were well characterized by IR, 1H NMR, 13C NMR and mass spectral studies.Sun, 13 May 2018 19:30:00 +0100Methane Adsorption on Carbonaceous Microporous Materials Prepared from Cellulose and Lignin: ...
http://scientiairanica.sharif.edu/article_20498_0.html
The present investigation highlighted the methane adsorption on synthesized activated carbons (ACs) based upon hydrothermally treated cellulose and lignin followed by a chemical activation utilizing the ZnCl2 as an activating agent. The influence of effective parameters such as; hydrothermal pretreatment, precursor type, carbonization temperature, and impregnation ratio upon the textural properties of synthesized materials as well as adsorption capacities of methane examined. Thermal stability and decomposition procedures of cellulose and lignin determined through the TGA technique while all prepared ACs characterized via the N2 adsorption-desorption analysis utilizing the BET-BJH surface area measurement and field emission scanning electron microscopy (FESEM). FTIR spectra of the prepared species were obtained in order to investigate the existing functional groups and consider effects of the added activating agent upon them. Amongst all prepared materials, the AC produced through hydrothermally treated cellulose impregnated with ZnCl2 possessing a ratio of 1 and carbonized at 600˚C revealed improved surface and textural properties enhancing the methane storage. Furthermore, hydrothermal pretreatment provided micropore diameters ranging from 1.8-2.2nm. These resulted in 6.42mmol/g of methane adsorbed at 298K and 3.65MPa. In order to systematically understand behaviors of adsorbents for the process at hand several kinetic and isotherm models understudied.Sun, 13 May 2018 19:30:00 +0100Robust parameter design of supply chain inventory policy considering the uncertainty of demand ...
http://scientiairanica.sharif.edu/article_20499_0.html
The uncertainty of demand and lead time in inventory management has posed challenges for the supply chain management. The purpose of this paper is to optimize the total profit and customer service level of supply chain by robust parameter design of inventory policies. This paper proposes to use system dynamics simulation, Taguchi method and Response Surface Methodology (RSM) to model a multi-echelon supply chain. Based on the sequential experiment principle, Taguchi method combining location and dispersion modeling method is adopted to locate the optimum area quickly, which is very efficient to optimize the responses in discrete levels of parameters. Then, fractional factorial design and full factorial design are used to recognize significant factors. Finally, RSM is used to find the optimal combinations of factors for profit maximization and customer service level maximization in continuous levels of parameters. Furthermore, a discussion of multi-response optimization is addressed with different weight of each response. Confirmation experiment results have shown the effectiveness of the proposed method.Sun, 13 May 2018 19:30:00 +0100Effect of HCl on the structure and catalytic activity of Pt/Al2O3 nanocatalyst prepared in ...
http://scientiairanica.sharif.edu/article_20500_0.html
Now a day preparation of special and effective nanocatalysts is a hot research topic. Obviously the size and structure of the active site of a catalyst plays the key role in catalytic activity. In this novel research the Pt nanocatalyst supported on γ-Al2O3 was prepared in two different microemulsion systems to clarify the effect of microemulsion essence on catalyst character and activity. Two types of microemulsion systems were constructed from Triton X-100/2-butanol as surfactant and co-surfactant, n-heptane as organic phase and H2O + H2PtCl6 (or HCl(aq) + H2PtCl6) as aqueous phase to investigate the effect of HCl on the shape and structure of the prepared nanocatalysts. Shape, size and size distribution of the Pt nanoparticles on the alumina were monitored by cyclic voltammetry and SEM analysis. Activity of the nanocatalysts was determined by reduction of p-nitrophenol as a reaction model.Sun, 13 May 2018 19:30:00 +0100Determining project characteristics and critical path by a new approach based on modified NWRT ...
http://scientiairanica.sharif.edu/article_20501_0.html
In this paper with respect to the importance of risks in real-world projects and ability of interval type-2 fuzzy sets (IT2FSs) to tackle the uncertainty, a new approach is introduced to consider risks and the correlation among risk factors by subjective judgments of experts on the probability and impact under IT2FSs. Furthermore, a new impact function for considering the correlation among the risk factors are extended under an IT2F environment. Moreover, a new subtraction operator is introduced for the critical path analysis. The node-weighted rooted tree (NWRT) method is modified based on the proposed new operator to avoid producing negative number for characteristics of each activity. Also, in order to cope with the uncertainty of the projects, NWRT method is developed under the IT2FSs. Eventually, to illustrate the validity and capability of the proposed method, two examples from the literature are solved and compared.Sun, 13 May 2018 19:30:00 +0100The experimental assessment of the effect of polypropylene fibers on improvement of Nano-silica ...
http://scientiairanica.sharif.edu/article_20502_0.html
In this study the influence of water-cement ratio on the mechanical properties (compressive, abrasion, tensile, flexural strength and permeability) of Nano-silica concrete reinforced with polypropylene fibers is evaluated. The specimens contain 4% of Nano-silica, 0.30, 0.35, 0.40, 0.45 and 0.50 of water-cement ratios and 0, 0.10, 0.15, 0.25 and 0.35 percent by volume of polypropylene fibers. Other design features remained fixed in all concrete samples. The results of the experiments showed that with decreasing the ratio of water to cement from 0.50 to 0.30, all the mechanical properties of the concrete were improved. In addition, the test results showed a significant increase in mechanical properties improvement of concrete by using polypropylene fibers. Tensile strength, flexural strength and abrasion resistance of concrete increased up to 22%, 40%, and 27% respectively for 28 days age specimens. Also, considerable reduction of hydraulic conductivity coefficient to 51% indicates high durability of these types of concrete. Compressive strength had increment of 22%, 15% and 14% for 7, 28 and 90 days age specimens respectively.Sun, 13 May 2018 19:30:00 +0100Sagittal Range of Motion of the Thoracic Spine Using Standing Digital Radiography; A throughout ...
http://scientiairanica.sharif.edu/article_20503_0.html
Previous studies have measured thoracic range of motion (RoM) using either skin-mounted devices or supine CT-imaging and have reported quite different RoMs. Given the inherent shortcomings of measurements of vertebrae movements from the overlying skin, the present study aims to measure normal RoM of the thoracic spine in the sagittal plane using the upright digital radiography. Lateral radiographs of the thoracic spine were acquired from eight asymptomatic male subjects in upright standing and full forward flexion using a mobile U-arm digital radiographic system. Total (T1-T12), upper (T1-T6), and lower (T6-T12) thoracic RoMs were measured. A throughout comparison with available skin-based measurements in the literature was carried out. Mean of total (T1-T12) thoracic RoM was 22.5° (SD 4.1°), most of which was generated by the lower (T6-T12) as compared to upper (T1-T6) thoracic spine (15.5° versus 7.1°, p<0.001). These RoMs were within the lower range of data previously reported by other skin-based approaches. While skin-based measurements suffer from the inter sensor-skin-vertebra movements and supine imaging techniques do not allow maximal trunk flexion, standing radiography remains as the gold-standard technique. Evaluation of thoracic spine RoM has implications in both patient discrimination for diagnosis and in biomechanical models for estimation of spinal loadsMon, 14 May 2018 19:30:00 +0100Lattice Boltzmann solution of advection-dominated mass transport problem: a comparison
http://scientiairanica.sharif.edu/article_20514_0.html
This article addresses the abilities and limitations of the Lattice Boltzmann (LB) method in solving advection-dominated mass transport problems. Several schemes of the LB method, including D2Q4, D2Q5, and D2Q9, were assessed in the simulation of two-dimensional advection-dispersion equations. The concept of Single Relaxation Time (SRT) and Multiple Relaxation Time (MRT) in addition to linear and quadratic Equilibrium Distribution Functions (EDF) were taken into account. The results of LB models were compared to the well-known Finite Difference (FD) solutions, including Explicit Finite Difference (EFD) and Crank-Nicolson (CN) methods. All LB models are more accurate than the aforementioned FD schemes. The results also indicate the high potency of D2Q5 SRT and D2Q9 SRT in describing advection-controlled mass transfer problems. The numerical artificial oscillations are observed when the Grid Peclet Number (GPN) is greater than 10, 25, 20, 25, and 10 regarding D2Q4 SRT, D2Q5 SRT, D2Q5 MRT, D2Q9 SRT and D2Q9 MRT, respectively, while the corresponding GPN values obtained for the EFD and CN methods were 2 and 5, respectively. Finally, a coupled system of groundwater and solute transport equations were solved satisfactorily using several LB models. Considering computational time, all LB models are much faster than CN method.Sun, 20 May 2018 19:30:00 +0100Shear Strength Prediction of RC Beams Using Adaptive Neuro-Fuzzy Inference System
http://scientiairanica.sharif.edu/article_20515_0.html
In complex engineering problems, there are some inexact conceptions, or a lot of parameters which must be considered. Soft computing is an approach that successfully applied to solve such problems. Determination of fuzzy rules for many problems has not been quite possible by an expert human. In this case, a neuro-fuzzy system which is the combination of neural network (for its ability to learn by datasets) and fuzzy system (for solving the drawback of the neural network) can be enhancing the performance of the system with several parameters or complex conditions. This paper shows the capability of a neuro-fuzzy system namely ANFIS to predicting the shear strength of reinforced concrete beams with steel stirrups. For this propose, the collection of laboratory results which was published in literatures used to train and finally test the proposed system. For this purpose, the sub-clustering approach (SC) applied for generating ANFIS. The results indicated that the considered neuro-fuzzy system was able to predict the shear strength of the RC beams which have been reinforced with steel stirrups.Sun, 20 May 2018 19:30:00 +0100Mitigating the uneven settlement of nearby strip footings on loose saturated sand using ...
http://scientiairanica.sharif.edu/article_20517_0.html
Abstract: Adjacency and interfering of footings are a matter of importance in geotechnical engineering. The researchers have focused on the adjacency of the footings by several approaches, but the mechanism of nearby footings under unequal and non-simultaneous surcharges have not been explored to date. In this study, two series tests were conducted using small scale 1g models to investigate the behavior of the two adjacent footings under reinforced and unreinforced soil conditions. The footings were installed with different spacing and rested on loose saturate sand. The ultimate bearing capacity, settlement, and tilting of footings were evaluated when the footings are rested on unreinforced sand as well as the sand bed reinforced by concrete pedestals. The results indicate that reinforcing the new footing by three concrete pedestals in the spacing to footing's width ratio (S/B) of 0 (i.e., two coherent footings) results in 67% increase of the bearing capacity of the new footing compared to that of the unreinforced condition. Also, the settlement and tilting of the old footing adjacent to the new footing decrease respectively up to 250% and 600% in comparison to those of the unreinforced condition.Fri, 25 May 2018 19:30:00 +0100Multi Stage Investment Planning and Customer Selection in A Two Echelon Multi-Period Supply Chain
http://scientiairanica.sharif.edu/article_20524_0.html
In the supply chain of Fast-moving consumer goods, logistics costs are a main part of the expenses. In low levels of these chains, we usually face with a Vehicle Routing Problem. In practice, due to the high cost of service in many cases, some customers are not chosen for serving. Restrictions associated with the investment in many cases makes impossible serve to some potential clients. In this problem, design a supply chain network, including a location-allocation problem in the warehouse, Multiple Depot Vehicle Routing Problem at the level of distribution and customer selection at the retail level in several periods of time is considered. In this issue, in addition to certain methods that can be used in small sizes, Meta-heuristic algorithms to solve large-scale model have been used. With the aim of improving performance, if not improve in a few diversifications, algorithms are temporarily enhanced. In GA this change leads to improve 1.2 percent and 1.6 percent about the mean of solutions and the best solution and in SA algorithm, this change is led to improving by 2.1% and 2.4% in average solutions and the best solutions. Finally, this approach about a real problem in Sepahan Oil Company is employed.Sun, 27 May 2018 19:30:00 +0100A class Hotelling model for sequential auctions of close substitutes
http://scientiairanica.sharif.edu/article_20546_0.html
Against the background of supply chains, this paper constructs a class Hotelling model to describe and explore sequential auctions of close substitutes with slightly more general associated valuations. In this generalized model, both close substitutes and bidders are hypothetically distributed in the interval [0, 1], types of bidders are continuous, and each bidder’s valuations for close substitutes are not independent. And with the aid of this model, equilibriums are explored and efficiencies of the auctions are analyzed under second-price sealed-bid auction formats. Further considering two typical information policies, we investigate some concrete bids and revenues of the efficient sequential auctions while bidders’ valuations are linear functions of distances between them and close substitutes. Results show that efficiencies of the sequential auctions are conditional, and influences of information policies on revenues of the auctions are related to both numbers of bidders and locations of items.Sat, 02 Jun 2018 19:30:00 +0100Full vs. partial coordination in serial N-echelon supply chains and a new profit sharing contract
http://scientiairanica.sharif.edu/article_20547_0.html
Despite the significance of full coordination of N-echelon supply chains in real-world decision-making situations, the relevant literature has rarely addressed this issue. Furthermore, there is a scarcity of mathematical models in the supply chain management literature for partially coordinated cases. To address these shortcomings, this study concerns both the full and partial coordination in serial N-echelon supply chains facing stochastic demand. In particular, three general cases including decentralized (no coordination), sub-supply chain coordination (partial coordination) and centralized (full coordination) cases are examined to support decisions on ordering and pricing. In addition, this study adds to the literature by investigating how to coordinate a serial N-echelon supply chain through a new spanning profit sharing contract, which can coordinate the entire supply chain through only one contract. Furthermore, we analytically prove the occurrence of externality benefit in partially coordinated cases, which is a paradoxical phenomenon suggesting that small coalitions are unstable. Two numerical examples extracted from the literature are given to verify the effectiveness and validity of the proposed contracts and models. The results show that the proposed contracts can be applied in a rather simple and convenient way and is reliable enough for use in real-world applications.Sat, 02 Jun 2018 19:30:00 +0100An Analytical Approach to Estimate Optimum River Channel Dimensions
http://scientiairanica.sharif.edu/article_20552_0.html
Extremal hypotheses without bank stability constraint typically over-predict and under-predict channel width in large rivers and natural streams, respectively. In general, results obtained from unconstrained extremal hypotheses are indicative of inappropriate agreement between predicted and observed dimensions of the rivers. One of the important factors in disparity of the data may be lack of appropriate relationships to assess bank vegetation of the rivers. For this reason, a modified analytical model has been developed to reduce the effect of bias by considering bank stability and vegetation. The model takes into account channel shape factor, a wide range of bed load equations in the form excess shear stress and vegetation quantification is able to predict optimal channel geometry dimensions. Finally, developed model was calibrated using the field data of the United Kingdom and Iran. In addition to indicating the effect of bank stability and vegetation on estimation of the geometric characteristics of the channel, obtained results also confirmed the efficiency of the constrained model in comparison to the unconstrained model. This study also provides support for the use of the concepts of maximum sediment transporting capacity and minimum stream power for understanding the operation of alluvial rivers.Sat, 02 Jun 2018 19:30:00 +0100Robust and sustainable full-shipload routing and scheduling problem considering variable speed: ...
http://scientiairanica.sharif.edu/article_20561_0.html
This paper presents a sustainable multi objective routing and scheduling for maritime transportation considering ship variable speeds under uncertainty. The proposed model is aimed to satisfy three individual dimensions of sustainability including economic, environmental and social aspects simultaneously while it is finding the best routes and schedule for each ship. The first objective is placed to meet economic goal by minimizing shipping cost. The second objective goes to social respect of sustainability by maximizing job creation due to number of intransitive workers in ships and ports and, the third one is minimizing CO2 emission to cover environmental target. Several test problems are applied to validate the proposed model and sensitivity analysis is used to demonstrate effects of model’s parameters on objective function value. Augmented ɛ-constraint is implemented as a solution method to solve the multi-objective mathematical model. This is the first ship routing and scheduling paper which is considered three aspect of sustainability under uncertainty and solved by augmented ɛ-constraint. To solve the model in larger size, factual input data from a real case study is considered. Computational results show a significant positive managerial effects of this paper contributions.Fri, 08 Jun 2018 19:30:00 +0100A New Heuristic Method for Improved Structuring of the Work Transformation Matrix (WTM)
http://scientiairanica.sharif.edu/article_20562_0.html
The design structure matrix (DSM) is a potent tool in the management of product design processes. Although the compactness and ability to represent design cycles are the main advantages of DSMs over existing traditional tools, the intact whole DSM is not always an understandable piece of information. To overcome this shortcoming, certain analyses have been proposed for a better understanding of the matrix in which partitioning and tearing have significant importance. There are several algorithms for these two analyses that mainly focus on a few rules of thumb. Although partitioning and tearing were originally developed for binary DSMs, they can be extended to numerical variants in which the work transformation matrix (WTM) is of the highest fame and application. In this paper, the authors have proposed an algorithm inspired by the formation of sugar crystals in saturated syrup for reordering the activities in a coupled block of activities (CBAs) based on their level of coupling. To implement this approach, a code was developed to achieve pseudo-optimum solutions. By using a discrete-time simulation, which was applied to an aerospace case study, it was demonstrated that the method produces restructured schemes of the WTM that are comparable/superior to the classical methods.Fri, 08 Jun 2018 19:30:00 +0100A bi-level bi-objective mathematical model for cellular manufacturing system applying ...
http://scientiairanica.sharif.edu/article_20563_0.html
The present study aimed to design a bi-objective bi-level mathematical model for multi-dimensional cellular manufacturing system. Minimizing the total number of voids and balancing the assigned workloads to cells are regarded as two objectives of the upper level of the model. However, the lower level attempts to maximize the workers' interest to work together in a special cell. To this aim, two nested bi-level metaheuristics including particle swarm optimization (NBL-PSO) and a population-based simulated annealing algorithm (NBL-PBSA) were implemented to solve the model. In addition, the goal programming approach was utilized in the upper level procedure of these algorithms. Further, nine numerical examples were applied to verify the suggested framework and the TOPSIS method was used to find the better algorithm. Furthermore, the best weights for upper level objectives were tuned by using a weight sensitivity analysis. Based on computational results, all three objectives were different from their ideal goals when decisions about inter and intra-cell layouts, and cell formation to balance the assigned workloads by considering voids and workers' interest were simultaneously madeby considering a wide assumption-made problem closer to the real world. Finally, NBL-PBSA could perform better than NBL-PSO, which confirmed the efficiency of the proposed framework.Fri, 08 Jun 2018 19:30:00 +0100Numerical investigation of Cover Plate in RCS connections
http://scientiairanica.sharif.edu/article_20564_0.html
Due to the growing popularity of Reinforced Concrete column with Steel beam (RCS) moment frame system in recent years, there are lots of publications about the performance of this structural system. In this paper, fifteen RCS joints with practical details are studied using a verified finite element method. Joint details of the models include Cover Plate, Additional Bearing Plate, Steel Doubler Plate, and joint stirrups. The results show that Cover Plate can be used instead of a combination of steel doubler plate and joint stirrups; it improves the joint performance by increasing the confinement of joint region and contributing to joint shear strength.Sat, 09 Jun 2018 19:30:00 +0100Voltage and reactive power control in distribution network considering optimal network ...
http://scientiairanica.sharif.edu/article_20565_0.html
In order to reduce energy losses and improve voltage stability index in distribution system, two different approaches have been proposed and employed including voltage and reactive power control (volt/var control) and distribution network reconfiguration. In the present paper, volt/var control and network reconfiguration in distribution system considering voltage security constraints is modelled as a multi-objective optimization problem. Total electrical energy losses, voltages deviations and voltage stability have been considered as objectives. Also, a new method for distribution network reconfiguration has been utilized for implementation of these two problems simultaneously. In this way, the two problems can be solved in less time. In addition, different nature of loads in each bus is considered in network load modelling. Non-dominated sorting genetic algorithm-II is used to solve this problem. Finally, the effectiveness of the proposed method is evaluated by implementation on the IEEE 33-bus system and a real 77-bus distribution system.Sat, 09 Jun 2018 19:30:00 +0100Development of Genetically tuned Fuzzy dynamic model for nonlinear dynamical systems: ...
http://scientiairanica.sharif.edu/article_20584_0.html
This work presents a new GA-Fuzzy method to model dynamic behavior of a process, based on Recurrent Fuzzy modeling through Mamdani approach whose inference system is optimized by Genetic Algorithms. By using the Mamdani approach, the proposed method surmounts the need to solve various types of mathematical equations governing the dynamic behavior of the process. The proposed method consists of two steps; i) constructing a startup version of the model, ii) optimizing the shape of membership functions of the fuzzy sets corresponding to the variables exist in the fuzzy model, along with the production rules constituting the inference such that the obtained fuzzy model can predict the dynamic behavior of the process fairly accurately. The proposed method is used to predict the dynamic behavior of the reaction section of the Tennessee Eastman (TE) benchmark. The overall accuracy of the obtained results compared to their corresponding counterparts in TE benchmark. The mean absolute percentage error (MAPE) of the key process variables which are temperature, pressure, and level of the reactor, and the reactor cooling water outlet temperature were calculated as 1.17%, 0.38%, 1.5%, and 1.57%, respectively, showing high prediction capability of the proposed method.Mon, 18 Jun 2018 19:30:00 +0100Group multiple criteria ABC inventory classification using TOPSIS approach extended by Gaussian ...
http://scientiairanica.sharif.edu/article_20585_0.html
The traditional ABC inventory classification is one of such approaches in which items are classified into three classes: A, very important; B, moderately important; and C, relatively unimportant based on annual dollar usage. However, other qualitative or quantitative criteria in real world may affect grouping items in the ABC inventory classification. Hence, multiple criteria ABC inventory classification (MCABCIC) is applied to classify items, instead of using the traditional ABC inventory classification. Hence, it can be taken into account as a multiple-criteria decision making (MCDM) problem due to using different criteria. The aim of this paper is to the extent TOPSIS approach with Gaussian interval type-2 fuzzy sets (GIT2FSs) as an alternative to the traditional triangular membership functions (MFs) for the MCABCIC in which GIT2FSs are more suitable for stating curved MFs. For this purpose, a new limit distance is presented for prioritizing GIT2FSs which is based on alpha cuts. The proposed method determines the positive and negative ideal solutions as left and right reference limits and then calculates distances between assessments and these limits. In our approach, the weights of the quantitative and qualitative criteria are attained via two linear programming, respectively. The model is illustrated using a real case.Mon, 18 Jun 2018 19:30:00 +0100Pulse extraction of pulselike ground motions based on particle swarm optimization algorithm
http://scientiairanica.sharif.edu/article_20586_0.html
Considering the devastating effects of near-fault earthquakes, seismologists and engineers have, qualitatively and quantitatively, represented the strong velocity pulse of near-fault ground motions using models including physical parameters associated with the wave propagation process. In some mathematical models, the derivation of physical parameters is required to fit time history and response spectrum of the simulated record to the actual record through trial and error process, which limits the scope of these models. In the current study, the particle swarm optimization (PSO) algorithm is replaced with the trial and error procedure. In this way, an automatic and quantitative process with the minimal judgment of the analyst is prepared to extract a wide range of pulselike records. Then, the proposed approach is applied to simulate and represent mathematically a set of 91 pulselike records from the Next Generation Attenuation (NGA) project ground motion library. The obtained results show that a velocity pulse of each pulselike record could be extracted using the proposed approach, and it can therefore be considered as a powerful tool in pulse parametric studies and the relationship between velocity pulse and structure’s response.Mon, 18 Jun 2018 19:30:00 +0100Analysis of change in the state of hydraulic drive of machines while in operation according to ...
http://scientiairanica.sharif.edu/article_20587_0.html
Technical diagnostics is a sphere of knowledge embracing theory, methods and means for defining the technical state of the objects. It is necessary for provision of security, functional reliability and efficiency of the technical object operation, as well as for reduction of the costs for its technical maintenance and reduction of the idle time losses caused by failures and premature shutdowns for maintenance. Therefore the objective of the paper is to analyze the change in the state of hydraulic drive of machines while in operation according to the diagnostic results. In order to achieve the set objective the authors used various experimental methods. The paper considers mutual influence of maintenance and technical diagnostics of hydrostatic drives of construction, track and some other mobile machines. It is shown that introduction of technical diagnostics allows transferring from the system of planned preventive repairs to the system of servicing the machines according to their actual technical state, which allows completely using the resource of a series of expensive aggregates. The authors described several main basic characteristics of change in the volume effectiveness of the hydraulic sets while in operation.Mon, 18 Jun 2018 19:30:00 +0100Effect of Several Heated Interior Bodies on Turbulent Natural Convection in Enclosures
http://scientiairanica.sharif.edu/article_20588_0.html
In this study, turbulent natural convection in a square enclosure including one or four hot and cold bodies is numerically investigated in the range of Rayleigh numbers of . The shape of the internal bodies is square or rectangular with the same surface areas and different aspect ratios. In all cases, the horizontal walls of the enclosure are adiabatic and the vertical ones are isothermal. It is desired to investigate the influence of different shapes and arrangements of internal bodies on the heat transfer rate inside the enclosure with wide-ranging applications such as ventilation of buildings, electronic cooling and industrial coldbox packages. Governing equations including Reynolds-averaged-Navier-Stokes equations have been solved numerically with finite volume method and turbulence model in a staggered grid. The boundary condition for turbulence model is based on the standard wall function approach. Strongly implicit method is employed to solve the discretized systems of algebraic equations with a remarkable rate of convergence. The effects of several parameters such as distance between the bodies, aspect ratio and Rayleigh number on heat transfer rate have been investigated. The most change in heat transfer rate at high values of Rayleigh numbers is associated with alteration in distance between square bodies. Moreover, the horizontal installation of rectangular bodies with h/w = 1/3 is accompanied by a maximum reduction of heat transfer at low Rayleigh numbers. The present results have been compared with previous experimental and numerical works regarding enclosures with or without internal bodies and reasonable agreement is observed.Mon, 18 Jun 2018 19:30:00 +0100Attitude-Based Conflict Management for Resolving Disputes over Water Quality of the Seymareh ...
http://scientiairanica.sharif.edu/article_20599_0.html
A strategic negotiation methodology for managing complex water-related conflicts is presented in order to consider the decision makers' attitudes. The developed approach systematically exploits the Graph Model for Conflict Resolution (GMCR) as an analytical and practical technique, and helps decision makers find the most beneficial outcomes for negotiating their disputes, assuming the competing needs, wants, and attitudes of decision makers. A real case study of a water-related dispute in Iran is used to demonstrate the implementation of the developed methodology and to emphasize the significance of decision makers' attitudes in identifying feasible negotiation outcomes for resolving complex disputes. In fact, the developed attitude-oriented methodology proposes an innovative engineering approach to help stakeholders address a wide range of conflicts, especially in complex water disputes in developing countries where human factors such as attitude play a significant role. The research can also help decision makers with the shortcomings of conventional decision making systems, such as original GMCR, through incorporating attitudes into conflict resolution tools in order to better clarify needs and interests, obtain equilibrium results, and generate more equitable solutionsFri, 22 Jun 2018 19:30:00 +0100Case Based Reasoning for Green Information Systems Infusion and Assimilation among IT ...
http://scientiairanica.sharif.edu/article_20600_0.html
Information Technology (IT) usage in university campuses consume enormous amount of power and incur other costs in cooling and related operations. Currently, universities are infusing environmental friendly initiatives in their campus. However, IT professionals in most universities are still not sure how to infuse and assimilate environmental friendly practices. Hence, Green Information Systems (IS) is suggested as the utilization of technologies and systems for a Greener and more sustainable planet. Accordingly, this study carried out a review on existing Green IS practices and further proposes a decision support framework based on Case Based Reasoning (CBR) technique. The proposed framework utilizes CBR to support the decision making of IT professionals in infusing and assimilating Green IS within university campuses. Findings from this study show how the framework utilizes CBR to support IT professionals in assimilating Green IS lifecycle and infusing Green IS determinants. Furthermore, findings from this study show how IT professionals can Green their university campuses. Moreover, this research study would also be of interest to data and knowledge management community as well as environmental scientists and sustainability researchers.Fri, 22 Jun 2018 19:30:00 +0100Dynamic Behavior of Worn Wheels in a Track Containing Several Sharp Curves Based on Field Data ...
http://scientiairanica.sharif.edu/article_20601_0.html
Study of the wheel and rail wear phenomenon can provide the optimal use of wheel profile which results cost efficiency, dynamic stability, travel comfort, and safety to prevent the derailment especially in curves. In this paper, the experimental data is recorded in the from the field measurements worn wheels of a passenger wagon in the “Southern line” of Iran’s railway system and is combined with the dynamic simulations to study the effects of severe wheel flange wear on the dynamics of wagon. The results show that the amount of wheel wear (especially the wheel flange) directly impacts the dynamic behavior of the wagon in curves. In addition, based on the history of wear index and the peak derailment ratio, the appropriate range of the wheel flange thickness in order to repair or replace the worn wheels is suggested in the range of 25 to 27 mm.Sat, 23 Jun 2018 19:30:00 +0100The surgical case scheduling problem with fuzzy duration time: An ant system algorithm
http://scientiairanica.sharif.edu/article_20602_0.html
In this paper, we address the surgical case scheduling problem in multi operating theater environment with uncertain service times in order to minimize makespan. In surgical case scheduling, not only the hospital resources are allocated to surgical cases but also the start time of performing surgeries is determined based on sequence of cases in a short-term time horizon. We consider fuzzy numbers for duration times of all stages and hereafter the problem called fuzzy surgical case scheduling. Since the operational environment in the problem is similar to no-wait multi-resource fuzzy flexible job shop problem, we consider constraints of that for formulating and solving problem. This problem is strongly an NP-hard optimization problem, hence we employ ant system algorithm to tackle problem. The proposed approach is illustrated by detailed examples of three test cases, and numerical computational experiments. Therefore, the performance of proposed algorithm is compared with a schedule constructed by first-come-first-service rule on all test instances. Also, a real case is provided from Isfahan’s hospital to evaluate proposed algorithm. Consequently, computational experiments state that algorithm outperforms results obtained by hospital planning as well as fuzzy rule, and these indicate efficiency and capability of our algorithm for optimizing the makespan.Mon, 25 Jun 2018 19:30:00 +0100Finite element modeling and design of pH/temperature sensitive hydrogel based biphasic twisting ...
http://scientiairanica.sharif.edu/article_20603_0.html
In this article, a pH/temperature sensitive hydrogel based biphasic twisting actuator is presented and studied in various environmental conditions. The actuator consists of a neutral incompressible elastomeric phase attached to pH/temperature sensitive hydrogel phase which twists, when subjected to pH/temperature variation. The deformation of the actuator depends on the cross-section of the actuator as well as geometrical and environmental parameters. To have a guideline for the design of the biphasic twisting actuator, a finite element model of the mentioned structure is developed. A thermodynamic based constitutive model is used to describe the behavior of the hydrogel. The finite element method is used to resolve the homogeneous and inhomogeneous swelling of the pH/temperature responsive hydrogel to check the validity of the method. Finally, how various parameters affect the torsional behavior of the actuator is discussed in detail. According to the results, to get the maximum twisting angle it is recommended to use the actuator with the square cross-section. Also, the twisting angle can even increase more by decreasing the hydrogel size as well as increasing the length of the actuator.Mon, 25 Jun 2018 19:30:00 +0100Improved Ratio Estimators of Variance Based on Robust Measures
http://scientiairanica.sharif.edu/article_20604_0.html
In this study, we develop some new estimators for estimating the population variance by utilizing the information on midrange and inter decile range of an auxiliary variable. A general class of estimators is also suggested. The derivations of the bias and the mean squared error are presented. Conditions are determined to verify the efficiency of the proposed estimators over existing estimators considered in this study. An Empirical study is also provided for illustration and verification. Moreover, a robust study is also carried out to evaluate the performance of proposed estimators as compared to existing estimators in case of extreme values. From the theoretical and empirical study, it is found that the suggested estimators perform more efficiently as compared to the existing estimators considered in this study.Mon, 25 Jun 2018 19:30:00 +0100Demand Response as a Complement for Wind Energy from System Well-being Viewpoint
http://scientiairanica.sharif.edu/article_20605_0.html
The risk imposed by the stochastic nature of wind energy sources has always been a major barrier despite their proliferation in power systems. To further penetrate these sources, this paper draws upon dynamic prices, which realize demand response potentials along with decimating the risk involved. To do so, a model is first established to study the impacts of activating demand response, on the risk index in a system with a high penetration of wind resources. Then, the model is used to estimate the extra wind capacity that can be hosted by the system such that the risk remains within the acceptable range. The well-being indices are calculated via sequential Monte Carlo simulation approach and Fuzzy theory. The demand response with dynamic prices is modeled by self and cross elasticity coefficients of different load sectors. The performance and applicability of the proposed model are verified through simulations on the IEEE Reliability Test System. (IEEE-RTS).Mon, 25 Jun 2018 19:30:00 +0100Bayesian Analysis of Heterogeneous Doubly Censored Lifetime Data using the 3-Component Mixture ...
http://scientiairanica.sharif.edu/article_20606_0.html
This article is about Bayesian estimation of parameters of a heterogeneous 3-component mixture of Rayleigh distributions (3-CMRD) generating a mixture data. Being the most popular and reasonable sampling scheme in reliability and survival analyses, the doubly censored sampling scheme is considered. The Bayes estimators and their posterior risks are derived under various situations. In addition, elicitation of hyperparameters is presented. Algebraic expressions for posterior predictive distribution and Bayesian predictive intervals are derived. Assuming the informative and the non-informative priors, a comprehensive Monte Carlo simulation is conducted to examine the performance of the Bayes estimators under symmetric and asymmetric loss functions. Finally, to highlight the practical importance, the proposed 3-compnent mixture model is applied to a doubly censored lifetime data from a real life situation. It is observed that the analysis of doubly censored data in Bayesian framework, the SRIGP paired with SELF (DLF) is suitable choice for estimating mixing proportion (component) parameters.Mon, 25 Jun 2018 19:30:00 +0100Experimental Study of the Wedge Effects on the Performance of a Hard-chine Planing Craft in ...
http://scientiairanica.sharif.edu/article_20607_0.html
In this paper, effects of a wedge on the performance of planing craft in calm water are experimentally investigated. Experiments are carried out on three different cases distinguished by the wedge type. The model, built of fiberglass, is a prismatic planing hull with deadrise angle of 24 degrees. Towing tests are conducted at different Froude numbers ranging from 0.21 to 2.1. The total trim angle, resistance, rise up at the CG as well as stern and bow, keel wetted length, chine wetted length, stagnation angle, and the length of stagnation line are measured. They are used to study the effect of installing a wedge on the performance as well as the effect of height on the hydrodynamic characteristics. Based on the observations made, it is concluded that, when the wedge is applied to the hull, the risk of model exhibiting instability diminishes, while total trim angle largely decreases, keel wetted length is enlarged, wetted surface becomes thinner, CG rise up is lowered, and the resistance is reduced. Moreover, experimental measurements and theoretical 2D+T theory are combined to bring deeper insight about physics of the flow and pressure distribution when a wedge is installed on the bottom of a planing hull. Mon, 25 Jun 2018 19:30:00 +0100Implementation of a curved wall- and an absorbing open-boundary condition for the D3Q19 lattice ...
http://scientiairanica.sharif.edu/article_20608_0.html
In this work, a three-dimensional lattice Boltzmann method is developed for numerical simulation of the fluid flows around the arbitrary geometries in the wide range of Reynolds numbers. For efficient simulation of high Reynolds number flow structures in the turbulent regime, a large eddy simulation (LES) approach with the Smagorinsky subgrid turbulence model is employed. An absorbing boundary condition based on the concept of sponge layer is improved and implemented to damp the vorticity fluctuations near the open boundaries and regularize the numerical solution by significantly reducing the spurious reflections from the open boundaries. An off-lattice scheme with a polynomial interpolation is used for implementation of curved boundary conditions for the arbitrary geometries. The efficiency and accuracy of the numerical approach presented are examined by computing the low to high Reynolds number flows around the practical geometries, including the flow past a sphere in a range of Reynolds numbers from 102 to 104 and flow around the NACA0012 wing section in two different flow conditions. The present results are in good agreement with the numerical and experimental data reported in the literature. The study demonstrates the present computational technique is robust and efficient for solving flow problems with practical geometries.Mon, 25 Jun 2018 19:30:00 +0100A robust bi-level programming model to design a closed loop supply chain considering government ...
http://scientiairanica.sharif.edu/article_20609_0.html
This study aims in providing a new approach regarding design of a closed loop supply chain network through emphasizing on the impact of the environmental government policies based on a bi-level mixed integer linear programming model. Government is considered as a leader in the first level and tends to set a collection rate policy which leads to collect more used products in order to ensure a minimum distribution ratio to satisfy a minimum demands. In the second level, private sector is considered as a follower and tries to maximize its profit by designing its own closed loop supply chain network according to the government used products collection policy. A heuristic algorithm and an adaptive genetic algorithm based on enumeration method are proposed and their performances are evaluated through computational experiences. The comparison among numerical examples reveals that there is an obvious conflict between the government and CLSC goals. Moreover, it shows that this conflict should be considered and elaborated in uncertain environment by applying Min-Max regret scenario based robust optimization approach. The results show the necessity of using robust bi-level programming in closed loop supply chain network design under the governmental legislative decisions as a leader-follower configuration.Mon, 25 Jun 2018 19:30:00 +0100Dynamic TOC-based approach for planning and control of accessories in MTO environments
http://scientiairanica.sharif.edu/article_20610_0.html
In make-to-order systems, customers expect to have more freedom to choose the accessories. But demand variations and internal disorders induce some uncertainties. Hence, a different inventory system is needed for such items that dynamically manage those variations. In this paper, a dynamic approach based on the theory of constraints is proposed for inventory planning and control of accessories. First, the risk of processing time variation is balanced while keeping cycle time balancing. Second, the ribbons of buffer control charts are determined by a buffer planning model in which a multi-criteria ABC analysis is used to apply different customer service levels. To detect demand variations and monitor the buffer, trend of consumption in each monitoring window is carefully traced. Also, simulation-based procedures are recommended to update control ribbons. Comparing the performance of proposed approach to common methods using the data of an automobile company as well as several random test problems confirms that it can significantly reduce the costs and improve the efficiency of inventory system.Mon, 25 Jun 2018 19:30:00 +0100CuO/WO3/TiO2 photocatalyst for degradation of phenol wastewater
http://scientiairanica.sharif.edu/article_20611_0.html
Cuo/WO3/TiO2 photocatalyst was prepared applying the sol-gel combustion method. It was characterized by X-ray fluorescence spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, porosimetry, and scanning electron microscopy techniques. The activity of CuO/WO3/TiO2 was investigated for the photocatalytic degradation of phenol wastewater. Operating conditions of batch experiments such as initial concentration of phenol, photocatalyst dose, amount of H2O2, and pH were optimized. Rate constants of the pseudo first order reaction for several photocatalysts were determined (TiO2: 0.0054 min-1, WO3/TiO2: 0.0071 min-1, CuO/TiO2: 0.0118 min-1, CuO/WO3/TiO2: 0.0621 min-1). The CuO/WO3/TiO2 had the best performance, and its rate constant was 11.5 times greater than TiO2. The CuO/WO3/TiO2 activity under sun light was considerable. The activity of CuO/WO3/TiO2 for 4-chlorophenol, and 3-phenyl-1-propanol degradation was also successful.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 +0100Application of Ultrasound Wave for Stimulation of Asphaltene Damaged Reservoir Rocks: An ...
http://scientiairanica.sharif.edu/article_20613_0.html
In this study, application of ultrasound wave for permeability enhancement of reservoir rocks was experimentally examined. In this regards, a specific core holder apparatus was designed with the ability of in-situ exposure of ultrasound to the plug at high-pressure condition, which is a better representative of ultrasound application in real wellbores. The effect of ultrasound power and exposure time as well as probe-plug distance on permeability stimulation was evaluated. The results showed that ultrasound could stimulate the permeability of asphaltene-damaged rocks, in which its efficiency is significant in sandstone rock. Analysis of asphaltene content in the output fluid showed that, as the result of ultrasound exposure, 84% of deposited asphaltenes in the sandstone plug was removed, which is corresponding to 67% of permeability recovery. It was also found that the stimulated permeability increases with increasing exposure time and power while decreases with increasing probe-plug distance, however an optimum value for exposure time and power, after which the permeability recovery is not significantly enhanced, was observed. Analysis of experiments also showed that probe-plug distance has the most prominent effect on recovery of damaged permeability in comparison to ultrasound time and power.Fri, 29 Jun 2018 19:30:00 +0100The effect of friction stir welding parameters on the microstructure, defects, and mechanical ...
http://scientiairanica.sharif.edu/article_20614_0.html
This study aims to examine how friction stir welding parameters, such as welding speed and rotational rate, affect the microstructure, defects, and mechanical properties of AA7075-T651 aluminum alloy joints. It also assesses the relation of the defects and microstructure to the mechanical properties. Microstructural investigations using optical microscopy (OM) and scanning electron microscopy (SEM) indicated remarkable grain structure variations among the different welding zones. Especially, it was found out that the interface between welding nugget zone (WNZ) and thermo-mechanically affected zone (TMAZ) is a dominant determinant of the mechanical properties of joints. The importance of the interface comes from the fact that it is the most prone region to cracks, micro-cavities and tunneling defects. WNZ and TMAZ interfaces as well as their grain structures can be influenced by the heat generated from the friction between rotating tool and workpiece material. Therefore, coarser grain structures observed at the WNZ-TMAZ interfaces of the samples welded at higher rotational rates or lower welding speeds is due to the greater heat generated in such cases. Besides, microstructural variations in the weld zone affect the hardness and mechanical properties of weld joints. Thus, samples with coarse-grained structures display lower values of yield stress and microhardness.Fri, 29 Jun 2018 19:30:00 +0100An intelligent model to predict the day-ahead deregulated market clearing price: a hybrid NN, ...
http://scientiairanica.sharif.edu/article_20615_0.html
Under restructuring of electric power industry and changing traditional vertically integrated electric utility structure to competitive, market clearing price (MCP) prediction models are essential for all generation company (GenCos) for their survival under new deregulated environment. In this paper, a hybrid model is presented to predict hourly electricity MCP. The model contains a Neural Network (NN), Particle swarm optimization (PSO) and Genetic Algorithm (GA). The NN is used as the major forecasting module to predict the electricity MCP values and PSO applied to improve the traditional neural network learning capability and optimizing the weights of the NN and GA applied to optimize NN architecture. The main contribution includes: presenting a hybrid intelligent model for MCP prediction; applying K-Means algorithm to clustering NN’s test set and seasonality pattern detection; and evaluation of its performance by improved MAE with penalty factor for positive error. It has been tested on Iranian real-world electricity market for the one month of the year 2010-2013 that result shown average weighted MAE for day ahead MCP prediction is equal to 0.12 and forecasting of MCP can be improved by more than 6.7% and 4%in MAE in compare of simple NN and combination of NN and bat algorithm.Fri, 29 Jun 2018 19:30:00 +0100Extraction solvent concentration affecting the anthocyanins and other phytochemicals profile ...
http://scientiairanica.sharif.edu/article_20616_0.html
Different concentrations (100%, 90% and 80%) of extracting solvent methanol were used to determine antioxidant capacities of seven pigmented rice cultivars bran on the basis of phytochemicals and other antioxidants. TPCs of red colored bran (Zag, Kaw quder, Shel kew) were highest in 100% methanol and that of black pigmented (Samarkand), lightly blackish (Kaw kareed) and brown (Gull zag, Teli zag) were highest in 80% and 90% methanol. The higher flavonoid contents in non-pigmented Gull zag and Teli zag were due to luteolin-7-O-glucoside, quercetinhexoside, apigenin-7-O-glucoside, quercetin-3-O-galactoside, apigenin and (epi)catechin rather than anthocyanins in pigmented rice. Higher anthocyanin contents of extracts in lower methanol concentration was due to higher percentage of Cyanidin-3-O-rutinoside, Pelargonidin-3-O-diglucoside, cyanidin-3-O-galactoside. The antioxidant activity had shown a similar trend in which the pigmented cultivars showed higher antioxidant activity in 100% methanol except red colored She lkew having higher value in 90% methanol, while among the light colored brown rice bran, Kaw kareed showed higher activities in 80% methanol and Teli zag in 90% methanol.Fri, 29 Jun 2018 19:30:00 +0100New Shewhart-EWMA and Shewhart-CUSUM Control Charts for Monitoring Process Mean
http://scientiairanica.sharif.edu/article_20637_0.html
In this paper, we propose new Shewhart-EWMA (SEWMA) and Shewhart-CUSUM (SCUSUM) control charts using the varied L ranked set sampling (VLRSS) for monitoring the process mean, namely the SEWMA-VLRSS and SCUSUM-VLRSS charts. The run length characteristics of the proposed charts are computed using extensive Monte Carlo simulations. The proposed charts are compared with their existing counterparts in terms of the average and standard deviation of run lengths. It is found that, with perfect and imperfect rankings, the SEWMA-VLRSS and SCUSUM-VLRSS charts are more sensitive than their analogous charts based on simple random sampling, ranked set sampling (RSS) and median RSS schemes. A real dataset is also used to explain the implementation of the proposed control charts.Mon, 02 Jul 2018 19:30:00 +0100A Modified Variant of Grey Wolf Optimizer
http://scientiairanica.sharif.edu/article_20638_0.html
The original version of Grey Wolf Optimization (GWO) algorithm has small number of disadvantages of low solving accuracy, bad local searching ability and slow convergence rate. In order to overcome these disadvantages of Grey Wolf Optimizer, a new version of Grey Wolf Optimizer algorithm has been proposed by modifying the encircling behavior and position update equations of Grey Wolf Optimization Algorithm. The accuracy and convergence performance of modified variant is tested on several well known classical further more like sine dataset and cantilever beam design functions. For verification, the results are compared with some of the most powerful well known algorithms i.e. Particle Swarm Optimization, Grey Wolf Optimizer and Mean Grey Wolf Optimization. The experimental solutions demonstrate that the modified variant is able to provide very competitive solutions in terms of improved minimum objective function value, maximum objective function value, mean, standard deviation and convergence rate.Mon, 02 Jul 2018 19:30:00 +0100An Endochronic-based approach for simulating pore water pressure variation during liquefaction ...
http://scientiairanica.sharif.edu/article_20639_0.html
Liquefaction is one of the consequences of earthquake in soil layers comprised of saturated loose sands. Various aspects of liquefaction have been investigated using different methods of field, laboratory, and numerical studies. Numerical simulation of liquefaction constitutes a major part of these researches. Application of a proper constitutive law in the numerical analysis is crucial for modeling thecomplicated undrained behavior of saturated sands during dynamic loading. Simplicity of formulation, limited number of parameters, and good performance are the main features of a proper constitutive law. In this study, an Endochronicbased model for simulating liquefaction of sand is implemented into the finite element program, PISA. Coupled dynamic field equations of Biot’s theory with u-p formulation are used to determine pore fluid and soil skeleton responses. Generalized Newmark method is employed for integration in time. The developed code is capable of predicting the magnitude of the generated pore water pressure, coupled with advanced constitutive laws such as critical state twosurface plasticity as well as simple models such as Mohr- Coulomb. Simulating cyclic simple shear and centrifuge tests using Endochronic model showed favorable performance of this model for predicting the variation of pore water pressure in saturated soil layers subjected to earthquake excitations.Tue, 03 Jul 2018 19:30:00 +0100Effects of recycled Polyethylene terephthalate fibers on strength behavior of cemented Babolsar sand
http://scientiairanica.sharif.edu/article_20640_0.html
Construction of structures on sandy soils of northern part of Iran encounters problems due to lack of proper strength properties. In recent years, bottles of Polyethylene terephthalate (PET) such as water bottles caused an environmental threat due to their prolonged persistence. Utilization of these materials for soil improvement seems to be a sustainable approach. In this study, the effect of recycled PET on mechanical properties of Babolsar sandy soil is investigated through an experimental program using direct shear and consolidated drained (CD) triaxial compression tests. Various contents of PET were added to sand with 3%, 5% and 7% cement contents. Curing time and relative density of samples were 7 days and 70%, respectively. Results showed that addition of fiber improves strength parameters such as cohesion and internal friction angle. Furthermore, the effect of the fiber is less marked with an increase in cement content. The samples with 3% cement demonstrated better results in both direct shear and tiaxial tests. By adding 0.5% and 1% PET fibers to the samples containing 3% cement at 100 kPa pressure, the ratio of strength in direct shear tests increased 13% and 24%, respectively, and in the triaxial test, it increased 50% and 93%, respectively.Tue, 03 Jul 2018 19:30:00 +0100An improvement on feature extraction via time series modeling for structural health monitoring ...
http://scientiairanica.sharif.edu/article_20641_0.html
Feature extraction by time series modeling based on statistical pattern recognition is a powerful approach to structural health monitoring. Determination of an adequate order and identification of an appropriate model play prominent roles in extracting sensitive features to damage from time series representations. Early damage detection under statistical decision-making via high-dimensional features is another significant issue. The main objectives of this article are to improve a residual-based feature extraction method by time series modeling and propose a multivariate data visualization approach to early damage detection. A simple graphical tool based on Box-Jenkins methodology is presented to identify the most compatible time series model with vibration time-domain measurements. Furthermore, k-Means and Gaussian mixture model clustering techniques are utilized to examine the performance of the residuals of the identified model in damage detection. A numerical concrete beam and an experimental benchmark model are applied to verify the improved and proposed methods along with comparative analyses. Results will show that these approaches are successful in obtaining a sufficient order superior to a state-of-the-art order determination technique, generating uncorrelated residuals, extracting sensitive features to damage, and accurately detecting early damage by high-dimensional data.Tue, 03 Jul 2018 19:30:00 +0100Cooperative Control of a Gripped Load by a Team of Quadrotors
http://scientiairanica.sharif.edu/article_20642_0.html
In this paper, an output tracking controller is proposed for cooperative transport of a gripped load by a team of quadrotors. The proposed control law requires measurement of only four state variables; position and yaw angle of the system. Moreover, the controller provides rejection of step and ramp external force disturbances. Also, the control basis vectors derived via optimization facilitate real time determination of quadrotors' control inputs. Numerical simulations show effectiveness of the proposed control scheme and its superiority over formerly designed controllers for such systems.Tue, 03 Jul 2018 19:30:00 +0100Dynamic response of concrete funicular shells with rectangular base under impulse loads
http://scientiairanica.sharif.edu/article_20643_0.html
Funicular shells are thin doubly curved shallow shells which are in compression under dead weight due to their shape. In this study, an analytical approach is employed to consider forced linear vibration of concrete funicular shells with rectangular base under impulse loads based on shallow shells theory. Two boundary conditions simply supported and clamped, both are considered. The solution is obtained by Lagrangian approach. Accuracy of the results has been considered by comparing the results with those of finite element method. The results indicate that under impulse loads, stresses in funicular shells are not only compressive, but also tensile stresses are formed.Tue, 03 Jul 2018 19:30:00 +0100Effects of content and thickness on the microstructure, optical and electrical properties of ...
http://scientiairanica.sharif.edu/article_20644_0.html
It is crucial to control conductivity and optical transmittance of Al doped ZnO (AZO) thin films in application of optoelectronic materials. In this paper, AZO thin films are prepared by oxidizing thermal evaporated Zn-Al thin films in open air. Then, the effects of Al contents and film thicknesses on microstructure, optical and electrical properties of the AZO films are studied. The results show that the optical and electrical properties of the AZO films are affected by the Al content and thickness changing. The Haacke figure of merit reaches 2.91×10-4 Ω-1. The film surface morphology is changed by the Al content. Nanowire is formed when the Al content is 9.58%. The Al2O3 phase appears with an excessive Al content. The transmittance of the AZO films is less than 25% when the Al content is more than 9.58%. The grain size first increases and then decreases with the increase of film thickness when the Al contents remain at 2%. Within the limits of available transmittance, the sheet resistance and transmittance of the AZO thin film decrease exponentially with the film thickness increasing.Tue, 03 Jul 2018 19:30:00 +0100A review on SPT-based liquefaction potential evaluation to assess the possibility of performing ...
http://scientiairanica.sharif.edu/article_20645_0.html
Liquefaction is a serious natural hazard in susceptible regions which are prone to earthquakes. According to empirical and field studies, insufficiency of liquefaction assessment methods in determining liquefaction through clays and high prediction errors has caused an unceasing new development. In this article we present a comprehensive history review to organize literature on the liquefaction potential evaluation published prior to 2017. We consider deterministic approach based on SPT (Standard Penetration Test) records to create an appropriate connection between the different methods, facilitate reviewing the development of correlations in the past and current decades, assess both the cyclic stress and the flow liquefactions in a unified system, compile the latest research developments and identify the main sources as a database for the future investigators. The study attempts to assess cyclic stress method (1971) and Chinese criteria (1982) in evaluating the liquefaction potential and to discuss the insufficiencies of these methods with reference to the liquefactions caused by the Chi-chi (Taiwan) and Adapazari (Turkey) earthquakes in 1999. Besides, the absence of soil improvement on the basis of vulnerability and performance is identified as a research gap in this study.Tue, 03 Jul 2018 19:30:00 +0100Analysis on influencing factors of rutting resistance for stone matrix asphalt mixtures
http://scientiairanica.sharif.edu/article_20646_0.html
The rutting deformation not only shortens the service life of asphalt pavement, but also brings great risks to the drivers. The rutting resistance of Stone Matrix Asphalt (SMA) is affected by many factors. This study aims to thoroughly discuss the main factors of rutting resistance and establish the dynamic stability prediction model that based on the experimental data from Marshall testing and wheel tracking test in SMA mixtures. The results show that the optimal dosage bitumen of rutting test is 0.1~0.3% more than that of Marshall testing in SMA mixtures. With the temperature increases 0.5℃, the dynamic stability of SMA mixtures decreases by an average of 18.6%. The more amount of aggregate and mineral powder donnot mean the better rutting resistance in SMA mixtures. It causes to reduce the rutting resistance of SMA mixtures as compaction work is too much or too little. There is a positive correlation between the dynamic stability of SMA mixtures and fractal dimension, relative coefficient and asphalt content, while it is a negative correlation between the dynamic stability of SMA mixtures and rolling times, testing temperature.Tue, 03 Jul 2018 19:30:00 +0100Combination of Marx and Capacitor Diode Voltage Multiplier for Pulsed Power Applications
http://scientiairanica.sharif.edu/article_20689_0.html
Recently, the pulsed power and pulsed electric field systems used in various industries and these systems have found wide applications. For this reason, using the pulsed power generators that in addition to responding to the needs of the user, are providing the advantages of compactness, high flexibility, high repetition rate and cost efficiency is inevitable. In this paper a hybrid solid state pulsed power generator is introduced that is modular and very flexible. This converter which is a combination of Marx and capacitor diode voltage multiplier, is capable of producing high voltage pulses with varying amplitudes at different frequencies. This proposed converter due to having high reliability, low cost, low weight, and structure’s simplicity can cover a wide area of applications. In this paper after introducing the proposed topology, its analytical design is described and its verification is proved by the simulation results in MATLABSIMULINK and by presenting the measurement results taken from the experimental prototype in low voltages.
Mon, 16 Jul 2018 19:30:00 +0100Effect of FRP Strengthening on the SHS brace collapse mechanism
http://scientiairanica.sharif.edu/article_20690_0.html
During an earthquake diagonal braces are designed to dissipate energy by yielding in tension and buckling in compression. However, local buckling occurring in the middle of the brace leads to immediate fracture. With the aim of strengthening braces against local buckling, wrapping FRP sheets in transverse direction is proposed in this study. Hitherto, the effect of FRP strengthening on the post-buckling behaviour of Square Hollow Section (SHS) tubes has not been investigated. A numerical model was generated and verified by previous research. Then, a comprehensive parametric study was conducted and the effect of slenderness ratio, number of FRP layers and FRP coverage percentage on post-buckling response of strengthening brace was explored within the study. Results indicate that utilising FRP is certainly successful at mitigating local buckling mode of long SHS braces Moreover, for short braces, applying enough numbers of FRP layers can change the mode of buckling from local to overall. Finally, an optimized length of FRP was suggested for strengthening of braces in accordance with their slenderness ratio.Mon, 16 Jul 2018 19:30:00 +0100Effect of damped outriggers arrangement on the seismic response of high-rise steel structures
http://scientiairanica.sharif.edu/article_20691_0.html
Recently, a novel structural system, which is defined as damped outrigger system, has been proposed to control dynamic vibration of tall buildings. This paper examines seismic performance of tall buildings involving multiple outriggers equipped with viscous dampers. In this respect, a dual structural system (braced moment frame) is selected as a bare structure. In addition, the number and position of outriggers are assumed to be variable along the height of structure. Nonlinear response history analysis (RHA) is performed to evaluate the efficiency of damped-outrigger system under eight scaled ground motions. The results are presented based on the average of all ground motions. The mean inter-story drift ratio and maximum base shear force are compared in order to determine the best arrangement of damped outriggers. Conclusively, based on minimizing base shear force, the optimal location of damped outriggers under dynamic excitation is generally the same as that made for conventional outriggers. According to the inter-story drift ratio parameter, it is recommended to place one of the outriggers at the roof level.Mon, 16 Jul 2018 19:30:00 +0100Influence of Tool Material on Forces, Temperature and Surface Quality of Ti-15333 Alloy in CT ...
http://scientiairanica.sharif.edu/article_20692_0.html
Ultrasonically assisted turning (UAT) is a progressive machining method in which vibration is applied to the cutting insert in the direction of the cutting tool velocity to reduce the cutting forces, significantly and increase the surface finish noticeably. However, the key question about the tool damage caused by the vibration and its effect on the cutting forces, surface roughness and process zone temperature is still unknown in UAT.
This paper presents experimental analysis of the effect of worn tool in UAT and conventional-turning (CT) of β-Ti-15V-3Al-3Cr-3Sn (Ti-15333) alloy on surface quality of a machined surface, temperature of the process zone and cutting forces using KC5510 (PVD TiAlN) and CP500 (PVD (Ti,Al)N-TiN) cutting inserts. In UAT, the tool edge damages in CP500 inserts increased with tested machining time resulted a growth of 8 N and 10 N in tangential force component in CT and UAT, respectively. Similarly, with the progression of tool edge damage, a growth of 1.7% and 9.3% in process zone temperature was observed in CT and UAT, respectively. The surface roughness results revealed a gradual degradation with machining time, however, the results UAT with a worn tool was significantly better when compared to CT, with a virgin tool.Mon, 16 Jul 2018 19:30:00 +0100Numerical study of Jet Impingement Subcooled Boiling on the Superheated Surfaces
http://scientiairanica.sharif.edu/article_20693_0.html
Cooling techniques of superheated surfaces by jet impingement with taking advantage of phase change phenomena i.e. boiling heat transfer has proven to be an efficient method because of its high rates of heat transfer. Furthermore, at a specified heat transfer coefficient, flow required for cooling purposes can reduce two orders of magnitude comparing to free-wall parallel flow which is important regarding to energy and water sustainability issues in various industries. This research mainly concerns numerical simulation of hydrodynamics and heat transfer phenomena regarding phase-change jet impingement on nucleate boiling region. Rensselaer Polytechnic Institute wall boiling model based on Eulerian multiphase model and RNG K-ɛ turbulence model were employed. Each interfacial term was considered and selected based on proximity to real physical phenomena. The selected model in this research was validated by a previously done confined jet impingement subcooled boiling experiment (dielectric fluid-PF5060). Minimum error of 4% and maximum error of 15% were reached at stagnation point. As parametric study, the effect of jet Reynolds number based on nozzle hydraulic diameter at Re 2500 to 10000 and the effect of standoff distance of jet nozzle from target surface at H/D 2, 4 and 6 were investigated.Mon, 16 Jul 2018 19:30:00 +0100ON-LINE SEISMIC DATABASE WITH SEISMOLOGICAL AND STRUCTURAL PARAMETERS
http://scientiairanica.sharif.edu/article_20694_0.html
In this paper a new free on-line seismic database is presented. The database has 15 seismological and 26 deducted engineering parameters to search for available records for structural seismic analysis. As known, the selection and scaling of seismic records acquire primary importance in seismic analysis. Moreover, the application and development of Performance-based earthquake engineering (PBEE) implies finding records in different levels of the return period. This is a time-consuming and cumbersome procedure and the whole process is affected by great randomness. A database with specific parameters that permit finding best-suited records would prove very useful. As a consequence, both the randomness in the seismic action and in the results of the dynamic behavior of the structure can be strongly reduced. This is the objective of the new database.
In this work the authors describe the new database and develop a numerical application with 3 different bins of parameters of selection for records and results of structural analyses. The great usefulness of the database is shown.Mon, 16 Jul 2018 19:30:00 +0100Discharge and flow field simulation of open channel sewer junction using artificial ...
http://scientiairanica.sharif.edu/article_20695_0.html
One of the most important parameters in designing of sewer structures is the ability to accurately simulation the discharge and velocity field of them. Among the various sewer receiving inflow methods, open channel junctions are mostly occurring. Because of the separation and contraction zone that occur at the open channel junctions, the fluid flow has a complex behavior. Modeling is carried out by Radial Basis Function (RBF) neural network, Gene Expression Programming (GEP), and Multiple Non-Linear Regression (MNLR) methods. Finding the optimum situation for GEP and RBF models are done by examining the various mathematical and linking functions for GEP and different number of hidden neurons and spread amount for RBF. In order to use the models in practical situations, three equations were conducted by using the RBF, GEP, and MNLR methods in modeling the longitudinal velocity. Then, the surface integral of the presented equations is used to simulate the flow discharge. The results showed that the GEP and RBF method perform significantly better than the MNLR in open channel junction characteristics simulations. The GEP method has higher performance in modeling the longitudinal velocity field compare with the RBF. However, the RBF presented more reliable results on the discharge simulations.Mon, 16 Jul 2018 19:30:00 +0100Domain reduction method for seismic analysis of Dam-Foundation-Fault system
http://scientiairanica.sharif.edu/article_20696_0.html
Numerical simulation of dam-foundation-fault system, considering the earthquake source, propagation path and local site effects, was carried out for realistic and reasonable seismic safety analysis of concrete dams. The Domain Reduction Method (DRM) was used for seismic analysis of Dam-Foundation-Fault (DFF) system in which, a modular two-step methodology for reducing the computational costs in large domain analysis is introduced. In this method the seismic excitation is directly applied into the computational domain such that assigning artificial boundary into the finite element models is more comfortable. In order to verify the implementation of the DRM in Finite Element Method (FEM), a simple 2D half-space under the Ricker wavelet excitation was examined. Then to investigate the DRM as an appropriate method in seismic analysis of DFF system, the Koyna concrete gravity dam was modeled. Comparing obtained results from using both the DRM in a small domain and the traditional approach in the large domain containing the source, show the efficiency of the DRM in terms of computational costs such as running time and number of elements for seismic analysis of concrete gravity dams.Mon, 16 Jul 2018 19:30:00 +0100Sustainable Supplier Selection and Order Allocation: An Integrated Delphi Method, Fuzzy TOPSIS ...
http://scientiairanica.sharif.edu/article_20697_0.html
The purpose of the current study is to select suppliers and determine their order allocation in a way that the performance of the sustainability of the supply process gets optimized on the whole. In this research, after reviewing the literature and investigating the supply chain of the case study (Iran Khodro’s supply chain) through Delphi method, a set of evaluation criteria related to the performance of the suppliers in economical, social and environmental terms was identified. In the next stage, by using the identified criteria, the multi-objective mathematical integer programming was presented to solve the problems of suppliers’ selection and order allocation. The suggested mathematical programming in this research is designed to be multi-product, single-period and multiple sourcing. Fuzzy TOPSIS method is applied to calculate the qualitative parameters that are used in the suggested mathematical programming. Ultimately, the mathematical model suggested in the research will be solved by two methods, i.e. Epsilon Constraint Method and Weighted Sum Method. Moreover, the total value of the sustainable purchasing (TVSP) will be calculated for both cases. Comparing these two methods indicates that in this research the results of weighted sum method are better than those epsilon constraint method.Mon, 16 Jul 2018 19:30:00 +0100A Malmquist Productivity Index with Directional Distance Function and Uncertain Data
http://scientiairanica.sharif.edu/article_20698_0.html
We present an integrated data envelopment analysis (DEA) and Malmquist productivity index (MPI) to evaluate the performance of decision making units (DMUs) by using a directional distance function with undesirable interval outputs. The MPI calculation is performed to compare the efficiency of the DMUs in distinct time periods. The uncertainty inherent in real-world problems is considered by using the best and worst-case scenarios, defining an interval for the MPI and reflecting the DMUs’ advancement or regress. The optimal solution of the robust model lies in the efficiency interval, i.e., it is always equal to or less than the optimal solution in the optimistic case and equal to or greater than the optimal solution in the pessimistic case. We also present a case study in the banking industry to demonstrate applicability and efficacy of the proposed integrated approach.Mon, 16 Jul 2018 19:30:00 +0100Determination of limit-states for near-fault seismic fragility assessment of concrete gravity dams
http://scientiairanica.sharif.edu/article_20701_0.html
Fragility curve, based on the performance-based earthquake engineering (PBEE), is a fundamental tool in assessing the probabilistic seismic performance of concrete gravity dams. Determination of the dam limit-states (LSs) is necessary for estimation of fragility curve. In this research, four LSs in seismic performance of massive structure have been utilized for Pine Flat dam. To address this, the Incremental Dynamic Analysis (IDA) method has been applied to the integrated dam-reservoir finite-element model. Evaluation of seismic behavior, demand and capacity of the tallest monolith has been investigated by implementing IDA. A new comprehensive method in terms of IDA and statistical analysis has been used for determination of each defined LS based on the certain value of the engineering demand parameter (EDP). To assess probabilistic performance of the dam, the exceeding probability of the LSs curves has been developed at various intensity measures based on the tree EDPs. It was found that the defined LSs have the capability indeed to be used in probabilistic framework.Mon, 16 Jul 2018 19:30:00 +0100Developing New Algorithm (G-JPSO) for Optimal Control of Pumps in Water Distribution Networks
http://scientiairanica.sharif.edu/article_20703_0.html
Meta-heuristic methods have been widely used for solving complex problems recently. Among these methods, JPSO is regarded as a promising algorithm. However, in order to achieve more robust performance, the probability to solve the graph-based problems is modified by changing the jumping nature of this algorithm and a new algorithm called G-JPSO is presented which is evaluated by solving Fletcher-Powell function and optimal control of pumps in water distribution network problems. In addition to reduction of electricity cost and the problem limitations such as minimum required pressure in each node, minimum and maximum height of tanks, should also be considered. Moreover, another limitation was performed on the objective function which includes the maximum times of turning the pumps on and off. In order to determine the pumps optimal operation, an optimization-simulation model based on the optimization algorithms G-JPSO and JPSO is developed. This proposed model is used for determination of optimal operation program of Van Zyl distribution network. The comparison carried out between the results of our proposed algorithm and those of the similar algorithms including ant colony, genetic and JPSO shows the high ability of the presented algorithm in finding solutions near the optimal solutions with reasonable computation costs.Mon, 16 Jul 2018 19:30:00 +0100Investigation of particle deposition and dispersion using Hybrid LES/RANS model based on ...
http://scientiairanica.sharif.edu/article_20723_0.html
In this study a new hybrid RANS/LES turbulence model within the frame work of the Multi Relaxation Time (MRT) Lattice Boltzmann method (LBM) was used to study particle dispersion and deposition in a room. For the hybrid RANS/LES method the near wall region was simulated by the RANS model, while the rest of the domain was analyzed using the LES model within the framework of the LBM. In the near wall layer where RANS was used, the turbulence model was employed. To simulate the particle dispersion and deposition in the room, particles with diameters of 10nm to 10 µm were investigated. The simulated results for particle dispersion and deposition showed that the predictions of the present hybrid method were quite similar to the earlier LES-LBM. In addition, the predictions of the hybrid model for the particle deposition and dispersion were closer to LES simulation results compared to those of the model.Sat, 21 Jul 2018 19:30:00 +0100A bi-objective multi-echelon supply chain model with Pareto optimal points evaluation for ...
http://scientiairanica.sharif.edu/article_20724_0.html
Selecting the most suitable optimal point among the Pareto optimal points could help the experts to make an appropriate decision in an uncertain and complex situation. In this paper, an evaluating and ranking approach is proposed based on hesitant fuzzy set environment to assess the obtained Pareto optimal points from the proposed bi-objective multi-echelon supply chain model with locating distribution centers. In this respect, the proposed model has elaborated for perishable products based on fuzzy customers' demand. To address the issue, the possibilistic chance constraint programming approach has manipulated based on the trapezoidal fuzzy membership function. Moreover, the proposed hesitant fuzzy ranking approach is constructed based on group decision analysis and the last aggregation approach. Thereby, the last aggregation approach by aggregating the experts' opinions in last step could prevent the data loss. However, a case study about the perishable dairy products is considered to indicate the applicability of the proposed bi-objective multi-echelon supply chain model with locating distribution centers. Finally, a comparative analysis is provided between the obtained results and the current practice to show the feasibility and efficiency of the proposed model.Sat, 21 Jul 2018 19:30:00 +0100One-pot synthesis of benzopyranophenazines using graphene oxide dichlorotriazine (GO-DCT) under ...
http://scientiairanica.sharif.edu/article_20725_0.html
An efficient synthesis of benzopyranophenazines has been presented by one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes and malononitrile with graphene oxide dichlorotriazine (GO-DCT) as an efficient nanocatalyst under microwave irradiation in ethanol. The catalyst has been characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Atomic force microscopy (AFM) and scanning electron microscopy (SEM). Atom economy, experimental simplicity, wide range of products, low amount of catalyst loading, the reusability of the catalyst, excellent yields in short reaction times and applying the microwave methodology as an efficient and green method are some of the substantial features of this method.Sat, 21 Jul 2018 19:30:00 +0100Hartley-Ross Type Unbiased Estimators of Population Mean Using Two Auxiliary Variables
http://scientiairanica.sharif.edu/article_20726_0.html
In survey sampling, most of the research work based on the fact that utilizing the information of auxiliary variable(s) boosts the efficiency of estimators. Keeping this fact in mind we used the information of two auxiliary variables to propose a family of Hartley-Ross type unbiased estimators for estimating population mean under simple random sampling without replacement. Minimum variance of the new family is derived up to first order of approximation. Three real data sets are used to verify that the new family acts efficiently than the usual unbiased, Hartley and Ross (1954), Grover and Kaur (2014), Singh et al. (2014), Cekim and Kadilar (2016), Muneer et al. (2017) and Shabbir and Gupta (2017) estimators.Sat, 21 Jul 2018 19:30:00 +0100A joint determination of production cycle length, maintenance policy, and control chart ...
http://scientiairanica.sharif.edu/article_20729_0.html
Statistical process monitoring, maintenance policy, and production cycle length usually have been investigated separately while they are three dependent aspects in the industrial systems. Moreover, most of the papers that integrated simultaneously these aspects, suffer from three major drawbacks as follows: (1) Optimizing the production cost without considering the time value of money to simplify the model; (2) Considering the fixed shift size while it is a random variable in the real condition; (3) Economic design of control charts ignoring the statistical properties that lead to reduce the control chart power, extremely. To eliminate these weaknesses, this paper presents an integrated model of production cycle length, maintenance policy, and economic-statistical design considering the time value of money and the stochastic shift size. Furthermore, to maintain the reliability of the system at an acceptable level, the presented model uses non-uniform sampling. Finally, three comparative studies on the main contributions are presented to illustrate the advantages of the model and a sensitivity analysis is implemented on the several parameters to extend insights into the matter.Sat, 21 Jul 2018 19:30:00 +0100High-performance controller design and evaluation for active vibration control in boring
http://scientiairanica.sharif.edu/article_20731_0.html
High quality manufactured components with fast production rate is an increasing demand of modern machine tool industry. Internal machining operations due to the large length to diameter ratio are most prone to intolerable chatter vibrations and proved to be an extremely challenging process. This paper presents a new method for proper design of direct velocity feedback (DVF) controller in order to extend boundaries of stable cutting for internal turning with minimum control effort. Control effort and active damping performance are two counteracting parameters that affect the results of active vibration control. After properly implementing the DVF active control algorithm on the internal turning setup, stable boundaries for different control gains of DVF controller are thoroughly studied. The comparison shows that although high DVF gains may considerably improve dynamic stiffness of the tool, it leads to the maximum control effort and actuator saturation and consequently process instability. The proposed gain selection method results in a significant increase in stable machining over the desired range of cutting conditions. The suggested design approach of the DVF controller can considerably improve limitations of rough machining on long over hang boring bars.Sat, 21 Jul 2018 19:30:00 +0100Analysis of asymmetric cold rolling using finite element method to create flat sheet
http://scientiairanica.sharif.edu/article_20735_0.html
In this paper, a simulation of asymmetric cold rolling is being presented by using an explicit analysis procedure. A two-dimensional finite element model with adaptive meshing technique has been employed to simulate asymmetrical condition, due to difference of the roll radius and velocity. Some conditions have been found to make sheet without curvature, in order to achieve this goal, different velocities have been made in rolls in each radius ratio. To validate the simulation, the results of the simulation has been compared with experimental papers which was done in the past. The effects of asymmetric process have been discussed, which is caused by radius ratio and velocity ratio on the rolling force, rolling torque and on the sheet curvature. Also the optimum velocity ratio in each radius ratio that causes the sheet without curvature was obtained. It was found that the appropriate speed ratio to produce flat sheets (i.e. sheets without curvature) is almost 1.067 being independent of the radius ratios between 1 and 1.05.Sat, 21 Jul 2018 19:30:00 +0100A Modified Wavelet Energy Rate Based Damage Identification Method for Steel Bridges
http://scientiairanica.sharif.edu/article_20736_0.html
Strain is sensitive to damage, especially in steel structures. But traditional strain gauge does not fit bridge damage identification because it only provides the strain information of the point where it is set up. While traditional strain gauges suffer from its drawbacks, long-gage FBG strain sensor is capable of providing the strain information of a certain range, which all the damage information within the sensing range can be reflected by the strain information provided by FBG sensors. The wavelet transform is a new way to analyze the signals, which is capable of providing multiple levels of details and approximations of the signal. In this paper, a wavelet packet transform-based damage identification is proposed for the steel bridge damage identifications numerically and with experimental experiment to validate the proposed method. The strain data obtained via long-gage FBG strain sensors are transformed into a modified wavelet packet energy rate index first to identify the location and severity of damage. The results of numerical simulations show that the proposed damage index is a good candidate which is capable of identifying both the location and severity of damage under noise effect.Sat, 21 Jul 2018 19:30:00 +0100Measuring the satisfaction and loyalty for Chinese smartphone users: A simple symbol-based ...
http://scientiairanica.sharif.edu/article_20737_0.html
User satisfaction and loyalty are very important in the mobile communications market because mobile is frequently updated. It is very necessary work that builds up a scientific assessment method to assist product in understanding and knowing well the trend of customers. This paper is intend to build up a scientific assessment method for measuring user satisfaction and loyalty. First, combining the group decision making and TOPSIS (technique for order preference by similarity to ideal solution) technique, a theoretical framework of evaluation method is established. Second, the respondents are allowed to express their opinions by using some simple symbols or by leaving the lack of answers to some measurement questions, even whole questionnaire. Then the symbol information along with the nonresponses in questionnaires are fused into an intuitionistic fuzzy information. Third, the levels of user satisfaction are ranked based on TOPSIS technique and projection measure in an intuitionistic fuzzy environment. Finally, the theoretical and practical implications of current model are discussed, the important limitations are recognized and future research directions are suggested.Sat, 21 Jul 2018 19:30:00 +0100Dynamic adaptive mesh refinement of fluid structure interaction using immersed boundary method ...
http://scientiairanica.sharif.edu/article_20738_0.html
The application of the immersed boundary method (IBM) coupled with adaptive mesh refinement (AMR) is considered one of the powerful tools for solving complex viscous incompressible flow problems. In this paper, the IBM was combined with AMR to solve complex incompressible and viscous fluid with elastic and rigid body problems concerning large structural deformations. In the IBM, the solid and fluid motions at the interface are united by a body force which can be compared to a fraction of a solid volume. The work aims to develop an automatic adaptive mesh refinement strategy to improve the solution near the fluid-structure interface. This is necessary as the flow field might be significantly affected by the structure; therefore, it was essential to precisely capture the boundary layers. The computational results highlighted the capability of this method to improve the flow resolution near the fluid structure. The proposed approach is validated using 2D numerical examples. The approach is validated in terms of its superior performance. The combined IBM-Adaptive mesh refinement approach showed a promising outcome for the investigated mechanical problem. The performance of the method in achieving a solution within a reasonably low computation time is also commendable.Sat, 21 Jul 2018 19:30:00 +0100Mathematical modeling of thermal contact resistance for different curvature contacting geometry ...
http://scientiairanica.sharif.edu/article_20739_0.html
Nowadays having deep knowledge on thermal contact conductance (TCC) and thermal conduct resistance (TCR) existed between various type metals is interesting during heat transfer occurrence in the nuclear reactor, thermal control system of spacecraft, and heat exchangers. In this present contribution, artificial neural network (ANN) coupled with multi-layer perceptron (MLP) modeling was utilized for the prediction of transient temperature contour in various contacting surface such as flat-flat, flat-cylinder, cylinder-cylinder. In order to develop accurate transient model, position, time, and roughness parameter of metal was used as input parameter and temperature of solid bodies decided as target parameter of model. Modeling results indicates that ANN base modeling show great accuracy in comparison with other numerical methods. Also, values of average absolute relative deviation (AARD), coefficient of determination (R2) for the overall data is 0.056 and 0.996 respectively which clarifies the accuracy and robustness of the proposed model.Sat, 21 Jul 2018 19:30:00 +0100Forward Kinematics Analysis of a Novel 3-DOF Parallel Manipulator
http://scientiairanica.sharif.edu/article_20740_0.html
A novel spatial parallel manipulator designed to assemble diagnostic instruments in SG-III is introduced in this paper. Firstly, resorting to screw theory, mobility analysis of this manipulator is investigated. Then the inverse kinematics problem is determined by the method of RPY transformation, with the singularity analyzed. As a key issue in parallel manipulators, it is more difficult to solve the forward kinematics problem, since it is highly nonlinear and coupled. In this work, three different approaches are presented to deal with this issue, which include the back propagation neural network, the simplified ant colony optimization and the proposed improved Newton iterative method. Simulation of each approach is conducted, and their merits and demerits are compared in detail. It is concluded that the improved Newton iterative method which can provide good initial iteration values possesses the best performance to estimate the nonlinear forward kinematic mapping of the considered parallel manipulatorSat, 21 Jul 2018 19:30:00 +0100One-pot solvent-free synthesis of pyranonaphthoquinone-fused spirooxindoles catalyzed by SBA-IL
http://scientiairanica.sharif.edu/article_20741_0.html
In this research article, ionic liquid modified SBA-15 mesoporous material (SBA-IL) as a recyclable, heterogeneous catalyst efficiently catalyzed the synthesis of pyranonaphthoquinone-fused spirooxindoles through the one-pot three-component reaction of isatin derivatives, activated methylene reagents, and 2-hydroxy-1,4-naphthoquinone. The reactions were performed under microwave irradiation and solvent-free conditions. The synthesized SBA-IL was characterized by SEM, FT-IR, nitrogen adsorption-desorption, and thermogravimetric analyses. Excellent chemical yields, short reaction times, mild reaction condition, easy workup procedures and reusability of catalyst are noteworthy advantages of this protocol.Sat, 21 Jul 2018 19:30:00 +0100The Deformation Mechanism of a High Rockfill Dam during the Construction and First Impoundin
http://scientiairanica.sharif.edu/article_20778_0.html
The Masjed-e-Soleyman dam is a high rockfill dam with clay core, located in Iran. During construction and first impounding, a considerably high excess pore water pressure has been developed inside the core and has been being dissipated with a very slow rate, so the consolidation deformations have been insignificant. However, there have been reports of noticeable internal deformations in the dam, the crest has also exhibited quick settlements during the first impounding. The main objective of this paper was to identify the deformation mechanism of this dam. For this purpose, the data recorded by its instruments were carefully studied and then a three-dimensional numerical model of the dam was developed. The mechanical behavior of materials was idealized by a hardening strain constitutive model. A numerical method was proposed, based on this constitutive model and Rowe’s stress–dilatancy theory, to simulate the deformation behavior of coarse-grained materials, like rockfills, due to particle size distribution, particle breakage, rotation, and rearrangement under shearing. The results show that significant development of pore pressure in the core and its insignificant dissipation, plastic shear deformations inside the core and extensive collapse settlements of the upstream shell are the main causes influencing the deformation mechanism.Mon, 23 Jul 2018 19:30:00 +0100Economic Evaluation of Investment Projects Under Uncertainty: A Probability Theory Perspective
http://scientiairanica.sharif.edu/article_20779_0.html
In the current competitive economy, the investors are facing increased uncertainty while evaluating new investment projects. This uncertainty caused from existence of insufficient information, oscillating markets, unstable economic conditions, obsolescence of technology and so on, and hence uncertainty is inevitable in reality. In such conditions, the deterministic models, while easy to use, do not perfectly represent the real situations and might lead to misleading decisions. When the cash flows for an uncertain investment project, over a number of future periods, are discounted using the traditional deterministic approaches, it may not provide investors with an accurate estimation of the project value. Therefore, this paper utilizes the probability theory tools to derive closed-form probability distribution function (PDF) and related expressions of the net present worth (NPW), as a useful and frequently used criterion, for cost-benefit evaluation of projects. The random cash flows follow normal, uniform or exponential distributions in our analysis. The probability distribution function of the NPW is an important tool that helps investors to accurately estimate the probability of being economic for projects, and hence, it is important tool for investment decision-making under uncertainty.Mon, 23 Jul 2018 19:30:00 +0100Microstructure and fatigue fracture mechanism for a heavy-duty truck diesel engine crankshaft
http://scientiairanica.sharif.edu/article_20780_0.html
The main goal of this research is the experimental and numerical study on the fatigue function and failure of the crankshaft of diesel engine of a heavy truck. To do this, a crankshaft of the diesel engine of a heavy truck that has gone under failure after traveling 955000 km, has been used. To examine the sources of this failure, several experimental studies have been carried out including chemical composition, the strength of the material, determining the hardness and the microstructure of the material. Besides, using an elastic–plastic three dimensional finite element method (FEM) model, the location of the maximum stress in the crankshaft was determined using the ‘‘complete crankshaft model’’ and ‘‘one crank model’’. Using the results of stress analysis, was a basis for the three-dimensional crack growth model and fatigue life estimation to determine the stress intensity factor and fatigue life considering the related parameters and boundary conditions method. At the final stage, using the results gotten from the given model for the fatigue crack growth, comparing it with experimental results, and examining the whole process, it was concluded that the scratches in crankpin region, was the main reason for the fatigue failure got from bending-torsional load-combination.Mon, 23 Jul 2018 19:30:00 +0100A collocation algorithm based on quintic B-splines for the solitary wave simulation of the GRLW ...
http://scientiairanica.sharif.edu/article_20781_0.html
In this article, a collocation algorithm based on quintic B-splines is proposed for the numerical solutionof the non-linear generalized regularized long wave (GRLW) equation. Also, to analyse the linearstability of the numerical scheme, the von-Neumann technique is used. The numerical approach isdiscussed on three test examples consisting of a single solitary wave, the collision of two solitarywaves and the growth of an undular bore. The accuracy of the method is demonstrated by calculatingthe error in the L2 and L¥ norms and the conservative quantities I1, I2 and I3. The findings arecompared with those of previously reported in the literature. Finally, the motion of solitary waves isgraphically plotted according to different parameters.Tue, 24 Jul 2018 19:30:00 +0100Multi-objective mathematical modeling of an integrated train makeup and routing problem in an ...
http://scientiairanica.sharif.edu/article_20782_0.html
Train formation planning faces two types of challenges; namely, the determination of the quantity of cargo trains run known as the frequency of cargo trains and the formation of desired allocations of demands to a freight train. To investigate the issues of train makeup and train routing simultaneously, this multi-objective model optimizes the total profit, satisfaction level of customers, yard activities in terms of the total size of a shunting operation, and underutilized train capacity. It also considers the guarantee for the yard-demand balance of flow, maximum and minimum limitations for the length of trains, maximum yard limitation for train formation, maximum yard limitation for operations related to shunting, maximum limitation for the train capacity, and upper limit of the capacity of each arc in passing trains. In this paper, a goal programming approach and an L­p­ norm method are applied to the problem. Furthermore, a simulated annealing (SA) algorithm is designed. Some test problems are also carried out via simulation and solved using the SA algorithm. Furthermore, a sample investigation is carried out in a railway company in Iran. The findings show the capability and performance of the proposed approach to solve the problems in a real rail network.Tue, 24 Jul 2018 19:30:00 +0100Optimization of multiple transmission layouts for minimal energy consumption of a battery ...
http://scientiairanica.sharif.edu/article_20783_0.html
Battery electric vehicles (BEVs) are a promising solution for reducing the impacts of passenger vehicles on the environment. However, their driving range is restricted due to the limitations of battery technologies. This range can be extended by adoption of multiple-speed transmissions. Most of the comparisons in the related studies are based on non-optimal designs or limited to modal driving cycles. Furthermore, the impact of power-split continuously variable transmission (PS-CVT) layout with type III power flow on the power consumption of BEVs has never been examined. In this paper, single, two and three-speed transmissions along with PS-CVTs with type I and III power flows are optimized for a case study BEV. Furthermore, the effect of push belt and full-toroidal CVTs in construction of PS-CVT are compared. The results demonstrate that a PS-CVT with type I power flow equipped with the full-toroidal CVT has the best performance. However, it reduces the energy consumption by 0.36% compared to the optimal two-speed layout. In addition, its ratio range is more limited which can negatively impact the dynamic performance. Finally, simulation of the optimal designs along a different cycle proves that the obtained results are consistent, regardless of the driving cycle.Tue, 24 Jul 2018 19:30:00 +0100Modified quasi-Y-source converter to increase boost factor
http://scientiairanica.sharif.edu/article_20788_0.html
In this paper, a new topology of quasi-Y-source impedance network is presented. This converter utilizes the change of winding factor and shoot through state in order to improve the gain of network. The proposed impedance network employs less turn ratio compared to quasi-Y-source and Y-source network to achieve high voltage gain. The continuous input current of the proposed converter is an advantage particularly for the applications related to the renewable energy sources such as Fuel Cell (FC) and photovoltaic (PV) systems. Furthermore, there is a dc-current-blocking capacitors in the proposed network, which helps to avoid the saturation of the coupled inductor. Operation principles of the converter are discussed and the steady state relations as well as voltage gain and voltage stress across the dc-blocking capacitors are derived. Proposed converter is compared to the conventional quasi-Y-source network, to show the advantages of the converter. Several simulations are done and the results are shown to indicate the performance of the proposed network. In this paper, an experimental prototype of a converter is presented. To prove the validity and consistency of the proposed network, several tests are carried out. This plan, can have a negative gain, similar to the quasi-Y-source network.Sat, 28 Jul 2018 19:30:00 +0100Simulation based optimization of a stochastic supply chain considering supplier disruption: An ...
http://scientiairanica.sharif.edu/article_20789_0.html
Many researchers and practitioners in the recent years have been attracted to investigate the role of uncertainties in the supply chain management concept. In this paper a multi-period stochastic supply chain with demand uncertainty and supplier disruption is modeled. In the model, two types of retailers including risk sensitive and risk neutral, with many capacitated suppliers are considered. Autonomous retailers have three choices to satisfy demands: ordering from primary suppliers, reserved suppliers and spot market. The goal is to find the best behavior of the risk sensitive retailer, regarding the forward and option contracts, during several contract periods based on the profit function. Hence, an agent-based simulation approach has been developed to simulate the supply chain and transactions between retailers and unreliable suppliers. In addition, a Q-learning approach (as a method of reinforcement learning) has been developed to optimize the simulation procedure. Furthermore, different configurations for simulation procedure are analyzed. The R-netlogo package is used to implement the algorithm. Also a numerical example has been solved using the proposed simulation-optimization approach. Several sensitivity analyzes are conducted regarding different parameters of the model. Comparison of the numerical results with a genetic algorithm shows a significant efficiency of the proposed Q-leaning approach.Sat, 28 Jul 2018 19:30:00 +0100Novel Technique for Dynamic Analysis of Shear-Frames Based on Energy Balance Equations
http://scientiairanica.sharif.edu/article_20790_0.html
In this paper, an efficient computational solution technique based on the energy balance equations is presented for the dynamic analysis of shear-frames, as an example of a multi-degree-of-freedom system. After deriving the dynamic energy balance equations for these systems, a new mathematical solution technique which is called Elimination of Discontinuous Velocities is proposed to solve a set of coupled quadratic algebraic equations. The method will be illustrated for the free vibration of a two-story structure. Subsequently, the damped dynamic response of a three-story shear-frame which is subjected to harmonic loading is considered. Finally the analysis of a three-story shear-building under horizontal earthquake load, as one of the most common problems in Earthquake Engineering, is studied. The results show that this method has acceptable accuracy in comparison with other techniques, but is not only faster compared with modal analysis but also does not require adjusting and calibrating the stability parameter as compared with a method of time integration like the Newmark method.Sat, 28 Jul 2018 19:30:00 +0100Experimental study of the effect of polymer fiber based on epoxy resin on compressive and ...
http://scientiairanica.sharif.edu/article_20791_0.html
In this study, effective parameters on polymer concrete (PC) based on epoxy resin such as filler, hardener and solvent are investigated. Rice husk and broom stem ashes as fillers with mixture of 50-50% Acetone-Toluene as solvent in preparation of PC samples were used. According to experimental results, addition of fillers improved compressive, flexural and chemical strengths of the PC samples. In the sample with 18.4% polymer, additional of rice husk ash with ratio of filler-aggregate 0.075, compressive strength improved by 21%. For the sample with broom stem ash ratio of filler-aggregate 0.09, the flexural strength was improved by 27%. In addition, experimental data proved that addition of optimum amount of solvent improved the performance and enhanced the compressive and flexural strengths. But excess amount of solvent may reduce the adhesiveness of the polymer therefore it may have negative impact on PC. The combination of hardener-resin may influence on the strength of PC. Amine type of hardener with low equivalent weight improved 27 and 13% on compressive and flexural strengths. Also elasticity module was increased in compare with the samples having high equivalent weight of amine type hardener.Sat, 28 Jul 2018 19:30:00 +0100Application of petrographic image analysis in assessment of chemical attack in the concrete ...
http://scientiairanica.sharif.edu/article_20792_0.html
The current paper discusses the petrographic image analysis performed on core specimens that are extracted from a tunnel in the south west of Iran. During tunnel excavation, damages were observed in the inner sections of concrete segments. Due to field observations of damaged segments, environmental parameters and tunnel location, several damage scenarios were proposed. In order to assess damage mechanisms, 69 cores were extracted and a number of standard tests were carried out. Since chemical attacks alter microscopic properties of materials, petrographic image analysis was performed on five of the specimens to evaluate possible microscopic changes in concrete composition. The results show that petrographic image analysis is an efficient method to provide a profound insight into the effects of chemical attacks on concrete members.Sat, 28 Jul 2018 19:30:00 +0100Massive Parallel Digital Micro fluidic Biochip Architecture for Automating Large-Scale ...
http://scientiairanica.sharif.edu/article_20797_0.html
Micro/Nano fluidic biochips are used to automate the clinical diagnosis, DNA sequencing, automated drug discovery and real time bio-molecular recognition. One of attractive usages of biochips is Lab-on-chip (LOC). Lab-on-Chip technology is a promising replacement for biomedical and chemical apparatus. Two main types of micro fluidic based biochips are used: continuous-flow based and digital micro fluidic biochips (DMFB). In DMFBs, liquids, in the form of droplets, are controlled independently and concurrently over a two dimensional array of cells (or electrodes).Digital micro fluidic biochips provide high ability to congure and fault tolerance.In this paper, a new architecture for DMFB with purpose of balancing among the parameters of flexibility, efficiency, cost, and completion time of biological experiments, is presented. In the new architecture, a FPGA-based structure is used, which increase flexibility and paralellizing assay operations. Experiments showthat, the execution time of scheduling, routing, and simulation are improved in comparison with FPPC architecture about 2.54%, 18.76% and 12.52%, respectively in cost of 21% overhead in the number of controlling pins.Sat, 04 Aug 2018 19:30:00 +0100From Object-Z Specification to Groovy Implementation
http://scientiairanica.sharif.edu/article_20798_0.html
So far, valuable researches have been conducted on mapping object-oriented specification notations, such as Object-Z, to different object-oriented programming languages, such as C++. However, the results of selecting JVM-based programming languages for mapping have not covered most of basic Object-Z structures. In this paper, the Groovy language, as a dynamic JVM-based language, is selected to overcome some of the existing limitations. As the main contribution, the rules required for mapping Object-Z specifications to executable Groovy code are introduced. The proposed rules cover notions such as multiple inheritance, inverse specification of functions, functions defined on generic definitions, and free type constructors. These notions have not been covered in previous methods for formal program development from object-oriented specifications, regardless of the selected formal specification language and target programming language. In addition, in this paper, the parallel composition construct is mapped to a parallel, executable code to improve the faithfulness of the final code to the initial specification. We also introduce a mapping rule for the class union construct, which has not yet been provided for any JVM-based language. Unlike previous works, instead of presenting the mapping rules in terms of natural languages, we present them in terms of some formal mapping rules.Sat, 04 Aug 2018 19:30:00 +0100An Architectural Solution for Virtual Computer Integrated Manufacturing Systems using ISO Standards
http://scientiairanica.sharif.edu/article_20799_0.html
Nowadays, manufacturing environments are faced with globalization which urges new necessities for manufacturing systems. These necessities have been considered from different perspectives and Computer Integrated Manufacturing (CIM) is the most popular and effective one. However, considering rapid rate of manufacturing globalization, traditional and current CIM solutions can be criticized by major deficiencies like high complexity for resource allocation over the globe, global facility sharing, and absence of an efficient way to handle lifecycle issues. Recently, Virtual CIM (VCIM) has been introduced as an effective solution to extend the traditional CIM solutions. This paper has investigated recent researches in VCIM/CIM field considering the necessities of todays’ globalized manufacturing environment. The paper shows the lack of traditional and current CIM/VCIM solutions; then, proposes an effective solution to cover them. Because of the complexities in designing such systems, the paper exploits Axiomatic Design (AD) Theory as a promising tools in this field. This theory is applied for validation of the suggested architectural solution and verification of the implementational aspects. The implementation of the architectural solution is considered based on ISO standards. Finally, the results have approved the feasibility of the suggested solution for manufacturing system and its Implementation aspects.Sat, 04 Aug 2018 19:30:00 +0100Solving a multi-objective model toward home care staff planning considering cross-training and ...
http://scientiairanica.sharif.edu/article_20800_0.html
Home care (HC) staff assignment problem is defined as deciding which staff to assign to each patient. In this study, a multi-objective non-linear mathematical programming model is presented to address staff assignment problem considering cross-training of caregivers for HC services. The first objective of the model minimizes costs of workload balancing, cross-training and maintenance. The second objective minimizes the number of employees for each service while the satisfaction level of caregivers is maximized through the third objective function. Several constraints including skill matching, staff preferences, regularity, synchronization, staff absenteeism and multi-functionality are considered to build a service plan. Due to NP-hardness of the problem, a non-dominated sorting genetic algorithm (NSGA-II) with a proposed who-rule heuristic initialization procedure is applied. Due to absence of benchmark available in the literature, a non-dominated ranking genetic algorithm (NRGA) is employed to validate the obtained results. The data required to run the model are gathered from a real-world HC provider. The results indicate that the proposed NSGA-II is superior to the NRGA with regard to comparison indexes. Based on the results obtained, it can be determined which staff should be cross-trained for each service and how the staff are assigned to services.Sat, 04 Aug 2018 19:30:00 +0100Robust Optimization for the Resource Constrained Multi-Project Scheduling Problem with ...
http://scientiairanica.sharif.edu/article_20801_0.html
This paper studies the multi-project scheduling problem which involves multiple projects with different importance weight; with predefined assigned due dates; with activities that have uncertain durations; and with renewable resources that are constrained. The resource sharing policy is applied to share the resources among projects. Due to the environmental rapid changes and also the uniqueness of projects, the probability distribution function of uncertain durations cannot be estimated with confidence. Besides, the multi-project scheduling problem with its large scale investment dictates a conservative approach to deal with the existing uncertainty. Therefore, the Robust Resource-Constrained Multi-Project Scheduling Problem (RRCMPSP) is studied in this paper while the maximum total weighted tardiness of the projects should be minimized. A scenario-relaxation algorithm is implemented which results in optimal solutions for the RRCMPSP. The aim is to find an optimal structure containing all the projects in such a way that it transfers the resources between the activities based on the resource sharing policy while the maximum weighted differences between the projects finish times and their assigned due dates will be minimum.Sat, 04 Aug 2018 19:30:00 +0100Research on the Risk Assessment Method of PPP Project based on the Improved Matter Element Model
http://scientiairanica.sharif.edu/article_20820_0.html
When identifying PPP project risks using the decomposition analysis method, the PPP project risks are considered to include government risk, market risk, and project risk. Based on these facts, a constructed list of PPP project risks is established, which can be divided into three first-class indexes and 27 second-class indexes. Based on the analysis of the traditional matter element model limitations, the evaluation model of PPP project risk assessment of the improved matter element model is established, in order to provide effective support for effective PPP project risk management, contract management and other work. Lastly, the feasibility of theoretical research is verified by a case study.Tue, 07 Aug 2018 19:30:00 +0100Extended TOPSIS method for multi-criteria group decision-making problems under cubic ...
http://scientiairanica.sharif.edu/article_20821_0.html
The objective of this work is to present a novel multi-criteria group decision making (MCGDM) method under cubic intuitionistic fuzzy (CIF) environment by integrating extended TOPSIS method. In the existing studies, the uncertainties which are present in the data are handled either an interval-valued intuitionistic fuzzy sets (IVIFS) or an intuitionistic fuzzy set (IFS) information, which may lose some useful information of alternatives. On the other hand, CIF set (CIFS) handles the uncertainties by considering both the IVIFS and IFS instantaneously. Thus, motivated by this, in the present work, we presented some series of distance measures between the pairs of CIFSs and investigated their various relationship. Further, under this environment, a group decision-making method based on the proposed measure is presented by taking the different priority pairs of the decision makers. A practical example is provided to verify the developed approach and to demonstrate its practicality and feasibility, we compared their results with the several existing approaches results.Tue, 07 Aug 2018 19:30:00 +0100Prediction of Subgrade Reaction Modulus of Clayey Soils using Group Method of Data Handling
http://scientiairanica.sharif.edu/article_20822_0.html
Settlement-based designs for foundations, using subgrade reaction modulus (K_s), is an important technique in geotechnical engineering. Plate load test (PLT) is one of the commonly applied methods to directly determine K_s. As the determination of the K_s from PLT—especially at depths—is relatively costly and time-consuming, it is necessary to develop models that can handle simply determinable properties. In the present study, the suitability of the Group Method of Data Handling (GMDH)-type neural network (NN) to estimate the subgrade reaction modulus of clayey soils has been investigated. In order to derive GMDH models, a database containing 123 datasets compiled from geotechnical investigation sites in Qazvin, Iran, has been used. The performance of the GMDH models has been compared with other available correlations for clayey soils, and it has been demonstrated that an improvement in estimating the K_s has been achieved. Finally, a sensitivity analysis has been conducted on the proposed models, showing that the proposed K_s is considerably influenced by changing the LL value.Tue, 07 Aug 2018 19:30:00 +0100Prediction of meteorological and hydrological phenomena by different climatic scenarios in the ...
http://scientiairanica.sharif.edu/article_20823_0.html
This research evaluates effects of climatic change on future temperature, precipitation and flow discharge in the Karkheh watershed (a watershed in south west of Iran). For this purpose, it utilizes general circulation models (GCMs) and the non parametric Mann-Kendall (MK) trend test. Considered hydrometric station is the Jelogir station at the upstream of the Karkheh dam. Base time period is 1971-2014 and future time period is 2030- 2073 for prediction of meteorological and hydrometric phenomena in the Jelogir station. For GCM model, the Canadian Climate Change Scenarios Network (CCCSN) database represents data of HadCM3 model for A2 and B2 scenarios. For using in a watershed, this research applies SDSM downscaling model and introduces predicted precipitation and temperature of future time period to IHACRES model for prediction of flow discharge. Also the non parametric Mann-Kendall trend test and the Theil–Sen approach (TSA) estimator distinguishes trend of observed and predicted data. Results of scenarios A2 and B2 have not much difference. Different climatic scenarios show that temperature increases and precipitation and flow discharge decrease, also MK test and TSA estimator represent that slope of their variations will slow down in future and most of changes are related to winter and spring.Tue, 07 Aug 2018 19:30:00 +0100Volume Change Behavior of Stabilized Expansive Clay with Lignosulfonate
http://scientiairanica.sharif.edu/article_20824_0.html
This paper presents the swelling and consolidation characteristics of Lignosulfonate (LS) stabilized expansive clay. Expansive clay samples of Amol city in Iran have been used in this research. Based on Atterberg limits and unconfined compressive strength tests, optimum percentage of LS for treatment of this clay was determined 0.75% by soil dry weight. To investigate swelling and consolidation properties of untreated and LS-treated remoulded samples, one dimensional swell and consolidation tests were conducted on these samples. Test results showed that LS has considerable effect on the consolidation and swelling behavior of the expansive clay. Moreover, the effects of compaction water content change and cyclic wetting and drying on the volume change properties of unstabilized and LS-stabilized samples were investigated. Untreated and LS-treated specimens showed different consolidation behavior to the changes of compaction moisture content due to the altering of soil expansivity category from high to moderate. The SEM images of samples showed that the soil specific area was reduced because of stabilization. This reduction in soil specific area was led to the decrease of affinity of samples to moisture increase, so the volume change of expansive clay was decreased.Tue, 07 Aug 2018 19:30:00 +0100A Holistic Day-ahead Distributed Energy Management Approach: Equilibrium Selection for ...
http://scientiairanica.sharif.edu/article_20825_0.html
n this paper, a new holistic distributed day-ahead energy management approach with desired equilibrium selection capability in a smart distribution grid is proposed. The interaction between customers and the distribution company is modeled as a single-leader multiple-follower Stackelberg game. The interaction among customers is modeled as a non-cooperative generalized Nash game because they meet a common constraint. Customers hold the average of the aggregate load in the appropriate domain to reshape it and improve the Load Factor. The strategy of the distribution company is day-ahead energy pricing obtained through maximizing its profit which is formulated as a stochastic conditional value at risk optimization to consider the uncertainty of the price of electricity in the wholesale market. Customers’ strategies are based on hourly consumption of deferrable loads and scheduled charge/discharge rates of energy storage devices in response to price. It is proved that the generalized Nash game has multiple equilibria; hence, the distributed proximal Tikhonov regularization algorithm is proposed here to achieve the desired equilibrium. The simulation results validate the performance of the proposed algorithm with 31.46% increase in the Load Factor besides 45.89 % and 14.23 % reduction in the maximum aggregate demand and aggregate billing cost, respectively.Fri, 10 Aug 2018 19:30:00 +0100A Novel Similar Character Discrimination Method for Online Handwritten Urdu Character ...
http://scientiairanica.sharif.edu/article_20826_0.html
Online handwritten Urdu character recognition is one of the key technologies for intelligent interface on smart phones and touch screens. It is a challenging research topic as Urdu script has many similar character groups. A novel similar character discrimination method for online handwritten Urdu character recognition is proposed in this paper which includes pre-classification, feature extraction and fine classification process. The pre-classifier enables the discrimination of similar characters by putting them in distinct smaller subsets according to stroke number and diacritics. Then structural features and wavelet features are extracted. Finally, Support Vector Machines (SVM), Artificial Neural Networks (ANN), and Recurrent Neural Network (RNN) classifiers are compared for fine classification within subsets. Results of RNN classifier without using the proposed pre-classifier and features have also been obtained to check the end-to-end capability of the RNN classifier. Experimental results show that the proposed method is efficient and achieves an overall accuracy of 96% on a large-scale self-collected dataset. It is feasible to extend this method for other Arabic scripts.Fri, 10 Aug 2018 19:30:00 +0100The Variable Step-Size Wavelet Transform-Domain LMS Adaptive Filter Algorithm
http://scientiairanica.sharif.edu/article_20827_0.html
In this paper, the wavelet transform domain least mean squares (WTDLMS) adaptive algorithm with variablestep-size (VSS) is established. The step-size changes according to the largest decrease in mean square deviation. To keep the computational complexity low, the Haar wavelet transform (HWT) is utilized as a transform. In addition, the mean square performance analysis of the VSS-WTDLMS is studied in the stationary and nonstationary environments and the theoretical relations for transient and steady-state performances are established. The simulation results show that the proposed VSS-WTDLMS has faster convergence rate and lower misadjustment than conventional WTDLMS. The theoretical relations are also verified by presenting various experimental results.Fri, 10 Aug 2018 19:30:00 +0100Determination and preconcentration of trace amounts of Cd(II), Cu(II), Ni(II), Zn(II) and ...
http://scientiairanica.sharif.edu/article_20828_0.html
In this work Fe3O4@SiO2 core-shell nanoparticles functionalized with 2-mercaptobenzothiazole as a magnetic nanosorbent was utilized for the simultaneous extraction of trace amounts of cadmium(II), copper(II), nickel(II), zinc(II) and lead(II) ions. A Box–Behnken design was applied with several variables for optimization of the extraction and elution steps. In the selected conditions, it was observed that limits of detection were 0.14 ng mL−1 for Cd(II), 0.24 ng mL−1 for Cu(II), 0.30 ng mL−1 for Ni(II), 0.27 ng mL−1 for Zn(II) and 0.53 ng mL−1 for Pb(II) and the maximum sorption capacity of this suggested magnetic nanosorbent was 168, 138, 104, 120, and 220 mg g−1 for Cd(II), Cu(II), Ni(II), Zn(II) and Pb(II), respectively. Finally, the suggested procedure was applied for determination of target metal ions at trace levels in different water samples, sugar, edible salts and various vegetables (lettuce, broccoli, and tomato) samples with satisfactory results. Sat, 11 Aug 2018 19:30:00 +0100Design of Mixed Flow Pump Impeller Blade using Mean Stream Line Theory and its Analysis
http://scientiairanica.sharif.edu/article_20829_0.html
Given the importance of blade design in effective performance of the mixed flow pump, the present work demonstrates the designing of the mixed flow pump impeller blade using almost unexplored Mean stream line theory. The Mean stream line theory, though been used sparingly but has found to give comparable results to that of other templates of design. The design process has been carried out in AUTOCAD 2013 and Solid Works Premium 2014 software. The analysis for equivalent stress, equivalent elastic strain, Total deformation and the directional deformation have been carried out in ANSYS 2014 for different construction material of the blade i.e., stainless steel, titanium alloy, bronze, and copper alloy. Total deformation was found to be maximum for impeller blade made from titanium alloy whereas the equivalent stress and strain was least for titanium alloyed impeller blade. Further, a comparison analysis has been carried out for the equivalent stresses in blade designed using mean stream line theory and free vortex theory. It was observed that the equivalent stress in impeller blade designed using free vortex theory was lesser than that designed using mean stream line theory.Sat, 11 Aug 2018 19:30:00 +0100An Efficient Hardware Implementation for a Motor Imagery Brain Computer Interface System
http://scientiairanica.sharif.edu/article_20830_0.html
Brain Computer Interface (BCI) systems, which are based on motor imagery, enable human to command artificial peripherals by merely thinking to the task. There is a tremendous interest in implementing BCIs on portable platforms, such as Field Programmable Gate Arrays (FPGAs) due to their low-cost, low-power and portability characteristics. This article presents the design and implementation of a Brain Computer Interface (BCI) system based on motor imagery on a Virtex-6 FPGA. In order to design an accurate algorithm, the proposed method avails statistical learning methods such as Mutual Information (MI), Linear Discriminant Analysis (LDA) and Support Vector Machine (SVM). It also uses Separable Common Spatio Spectral Pattern (SCSSP) method in order to extract features. Simulation results prove achieved performances of 73.54% for BCI Competition III-dataset V, 67.2% for BCI Competition IV-dataset 2a with all four classes, 80.55% for BCI Competition IV-dataset 2a with the first two classes, and 81.9% for captured signals. Moreover, the final reported hardware resources determine its efficiency as a result of using retiming and folding techniques from the VLSI architecture perspective. The complete proposed BCI system not only achieves excellent recognition accuracy but also remarkable implementation efficiency in terms of portability, power, time, and cost.Sat, 11 Aug 2018 19:30:00 +0100Resilience Supplier Selection and order allocation under uncertainty
http://scientiairanica.sharif.edu/article_20831_0.html
Increasing the number of disasters around the world will decrease the performance of the supply chain. The decision makers should design resilience supply chain network which could encounter with disruptions. This paper develops an integrated resilience model of supplier selection and order allocation. Resiliency measures including quality, delivery, technology, continuity, environmental competences are explored for determining the Resilience Weight of suppliers. Fuzzy DEMATEL and ANP methods are applied to find overall performance of each supplier. Then, the developed mathematical model maximizes overall performance of suppliers while minimizes total cost of network. The proposed mathematical model helps the decision makers to select supplier and allocate the optimum order quantities by considering shortage. Since the disruptive incidents are inevitable events in real world problems, the impact of disruptions on suppliers, manufactures and retailers has been considered in the proposed model. Inherent uncertainties of parameters are taken into account to increase the compatibility of the approach with realistic environments. To tackle the uncertainty and multi-objectiveness of the proposed model, interval Method and TH aggregation function is adapted. The proposed model is validated through application to a real case study in a furniture company. Results demonstrate the usefulness and applicability of the proposed model.Sat, 11 Aug 2018 19:30:00 +0100Molecular Dynamics Simulations of Sessile and Pendant Droplets Shape on Inclined and Curved Surfaces
http://scientiairanica.sharif.edu/article_20832_0.html
In this study, shape of water droplets with different sizes on various inclined smooth surfaces is simulated numerically and advancing and receding contact angles are determined by using the molecular dynamics approach. Experimental measurements are also carried out to validate the numerical predictions of droplet shape on inclined surfaces. Based on the verified code, shape of water droplets in different sizes around smooth circular cylinders with various diameters is simulated. Furthermore, advancing and receding contact angles along with the hysteresis values of the sessile and pendant droplets with various sizes around the cylinders are evaluated. Finally, based on the numerical results, two correlations are developed to predict advancing and receding contact angles of droplets on the circular cylinders. According to the results, maximum advancing and minimum receding angles take place on both sides of the cylinder on a horizontal line passes through the cylinder center. As a result, contact angle hysteresis reaches its maximum value in these two positions. In addition, advancing and receding angles have the same values on the top and bottom of the cylinder. Moreover, droplet size and cylinder diameter have minor effect while drop position has major effect on the shape of droplets over the cylinder.Sat, 11 Aug 2018 19:30:00 +0100Lion Pride Optimization Algorithm: A meta-heuristic method for global optimization problems
http://scientiairanica.sharif.edu/article_20833_0.html
This paper presents a new non-gradient nature-inspired method, Lion Pride Optimization Algorithm (LPOA) for solving optimal design problems. This method is inspired by the natural collective behavior of lions in their social groups "lion prides". Comparative studies are carried out using fifteen mathematical examples, two benchmark structural design problems, in order to verify the effectiveness of the proposed technique. The LPOA algorithm is also compared with other algorithms for some mathematical and structural problems. The results have proven that the proposed algorithm provides desirable performance in terms of accuracy and convergence speed in all the considered problems.Sat, 11 Aug 2018 19:30:00 +0100Brain Tissue Constitutive Material Models and the Finite Element Analysis of Blast-Induced ...
http://scientiairanica.sharif.edu/article_20888_0.html
Traumatic brain injury (TBI) often happens due to assaulting loads such as blast on the human head. Finite elements (FEs) can approximately simulate the blast interactions with the human head. An important parameter in the FE modelling procedures is the accuracy of constitutive formulation of the brain tissue. This paper is focusing on implementation of three brain tissue constitutive relations to measure and compare the dynamic behaviour of the brain under identical blast loads. For the geometry, we employ a simple spherical head model to monitor the brain tissue response and examine the uncertainties in FE brain tissue constitutive modelling. The brain tissue is constitutively modelled as hyperelastic, viscoelastic, and hyperviscoelastic type material. Intracranial pressures (ICP), strains, and shear stresses as the dynamic parameters are measured with time. These biomechanical parameters can be compared against the injury thresholds. Our analyses show that although the results for ICPs and strains are close for the three models, however, shear stresses are considerably different. The study will further provide new insight into selecting a proper constitutive model of the brain tissue under dynamic conditions.Tue, 14 Aug 2018 19:30:00 +0100Numerical modeling of sand particle erosion in return bends in gas-particle two-phase flow
http://scientiairanica.sharif.edu/article_20889_0.html
In gas and oil industry, erosion damages to pipe lines bends and elbows due to the presence of sand particles have been a challenging issue. In this study a computational model approach was for evaluating the erosion rates in different vertical return bends including sharp bend, standard elbow, 180° pipe bend and long elbow. The airflow in the pipe was simulated using the SIMPLE method and the k-ω SST turbulence model. An Eulerian-Lagrangian approach was used for predicting particle trajectories and the corresponding erosion rates. Different particle sizes and mass flow rates were considered and Oka model for evaluating the erosion rate was used in these simulations. Under the same conditions, the simulation results indicated that the sharp return bends experience the highest erosion rates and the 180° bends experience the lowest erosion among the studied configurations. It was also found that the erosion rate is linearly proportional to the mass flow rate of particles for all cases studied.Fri, 17 Aug 2018 19:30:00 +0100Numerical 3D simulation of developing turbulent stratified gas-liquid flow in curved pipes ...
http://scientiairanica.sharif.edu/article_20890_0.html
Predicting multiphase flows in curved pipes is of great importance in industrial equipment. In the present study, a computational model for predicting the velocity profile is developed and used to study the developing turbulent gas-liquid- solid three dimension flow in curved pipes. In order to discretize and solve the three-dimensional steady-state momentum equations, the finite volume scheme on staggered grids besides central difference and QUICK scheme have been used. Moreover, the k-ε model is employed to reflect the nature of turbulence in the flow. In order to address the needs for sooner convergence and convenient mapping of the physical domain, the computations have been performed in an extended toroidal coordinate system. Particle tracking has been done using Lagrangian approach in which two-way coupling regime is considered. In terms of validation, the numerical simulation results for the straight duct (infinite curvature), have been compared with the analytical solution and previous experimental results. Moreover, injection of particles through the flow indicates that, in each section of the bend, trade-off between centrifugal and pressure gradient forces plays a key role on particles motion. In last section, the effects of particle diameter and bend curvature on particle motion have been examined.Fri, 17 Aug 2018 19:30:00 +0100A CLASS OF SYNCHRONIZED NONLINEAR TWO-DOF SYSTEMS WITH CLOSED FORM SOLUTION
http://scientiairanica.sharif.edu/article_20891_0.html
Nonlinear dynamic behaviour of structural systems has a significant role in many engineering applications. The analysis methods are typically numerical. Accordingly, for verification and test of accuracies, availability of nonlinear systems with exact closed form solutions is important. In this paper, a three-parameter system, with exact analytical solution, consisted of two synchronized colliding mass-spring-dashpot systems, is introduced and the validity of the exact solutions is demonstrated. Simplicity of the exact response, and the capability to control the frequency content, are addressed as the main features of the introduced system. Selection of appropriate values of the parameters entailing desired response features is discussed, and practical implementations of the model are described.Fri, 17 Aug 2018 19:30:00 +0100Numerical Simulations on Gas-Liquid-Particle Flows in Three-Phase Slurry Reactors under gravity ...
http://scientiairanica.sharif.edu/article_20892_0.html
Numerical simulations of three-phase gas-liquid-particle flows under 1g and 2g gravitational conditions were performed with an Eulerian-Lagrangian method. In this study, the liquid was treated as continuous phase and modeled by a volume-averaged system of governing equations. Bubbles and particles were modeled as discrete phases using Lagrangian method. Drag, lift, buoyancy, and virtual mass forces were included in the Lagrangian equation. Bubbles were treated as spherical without shape variations. The two-way coupling between bubble-liquid and particle-liquid were included and interactions between bubble-bubble and particle-particle were considered with the hard sphere model. Particle-bubble interactions and bubble coalescences were also included in the analysis. The results under 1g normal gravity condition were compared with the available experimental data in earlier simulation with good agreement. The transient flow characteristics of the three-phase flow under 1g and 2g gravitational condition were studied and the effects of gravity were analyzed. The results show that gravity has magnificent effect on the flow characteristics of three-phase gas-liquid-particle flows in bubble columns. The three-phase velocities under higher gravity are larger than that of the flow under normal gravity. The flow under higher gravity develops fast. Bubbles and bubble volume fraction in the higher gravity flow are smaller.Fri, 17 Aug 2018 19:30:00 +0100Modeling and multivariable active disturbance rejection control of hydraulic looper ...
http://scientiairanica.sharif.edu/article_20893_0.html
Controlling the looper height and strip tension is important in hot strip mills, because these variables affect both the strip quality and strip threading. Many researchers have proposed and applied a variety of control schemes for this problem, but the increasingly strict market demand for strip quality requires further improvements. This paper describes a multivariable active disturbance rejection control (MADRC) strategy that realizes the decoupling control of a hydraulic looper multivariable system. Simulation experiments for a traditional proportion- integration (PI) controller and the proposed MADRC controller were conducted using MATLAB/Simulink software. The simulation results show that the proposed MADRC ensures good robustness and adaptability under modeling uncertainty and external disturbance .It is concluded that the designed MADRC controller produces better dynamic performance than the traditional PI controller, and the proposed looper control system is effective and practical.Sat, 18 Aug 2018 19:30:00 +0100Design of Conformal Cooling Channels Using Numerical Methods in a Metal Mold and Calculating ...
http://scientiairanica.sharif.edu/article_20894_0.html
Shorter cycle times, better product quality and less product outage can be possible with faster cooling. But mold cooling channels can only be made in linear directions and limited forms via classical manufacturing methods. Therefore, it limits that performance of mold cooling. Developed in recent years additive manufacturing technologies are capable of building complex geometries and monoblock 3D products. With this technology it is possible to produce metal molds with conformal cooling channels in different forms and capable of qualified cooling. In this study, conformal cooling channels were designed in order to achieve optimum cooling in monoblock permanent mold. In this study, CFD (Computational Fluid Dynamic) analyses are performed to steady stead conditions for designed conformal cooling channels and classical cooling channel mold. Pressure drops, cooling channel outlet temperatures and exergy destructions are calculated depending on the flow velocity rate in channels. The numerical investigations of the cooling process have shown that approximately 5% higher cooling performance can be achieved with conformal cooling channels. However, the pressure drop in the conformal cooling is observed to be higher than classical cooling channel. In addition, exergy destruction in the conformal cooling channel is approximately 12% greater than the classical cooling channel.Sat, 18 Aug 2018 19:30:00 +0100Optimizing under and out of warranty products’ decisions in the finite planning horizon
http://scientiairanica.sharif.edu/article_20895_0.html
In this paper, we consider a manufacturer that produces products in a finite horizon time and sells products with non-renewing free replacement warranty policy. The manufacturer is responsible to provide spare parts for failed products, whether the products are under or out of warranty. Previous research on warranty optimization has focused on maximizing manufacturer profit without considering the spare part market for out-of-warranty products. This study proposes a novel nonlinear model that maximizes manufacturer profit by optimization of price, warranty length and spare part inventory for under- and out-of-warranty products in a manufacturing/remanufacturing system. Due to the model’s unique structure, we propose a new two-stage approach that combines metaheuristic and an exact method, in which the first stage is to determine product’s prices and warranty length with metaheuristic algorithm and in the second stage the remaining inventory related problem is transferred to a Minimum Cost Network Flow Problem which is solved for spare part inventory control. To illustrate the effectiveness of the suggested method, the model is solved for a case study of Iranian SANAM electronic company with two different metaheuristic algorithms and a sensitivity analysis is conducted to study the effect of various parameters on the optimal solution.Sun, 19 Aug 2018 19:30:00 +0100Investigation of Transient Numerical Simulation of Solidification and Thermal Behavior of Metal ...
http://scientiairanica.sharif.edu/article_20896_0.html
The cooling process in metal molds is one of the important factors in the solidification process of molten metal. Molding defects such as hot spot defects and warping occur in cast products when the cooling is not uniform. However, qualified and faster cooling affects product quality positively. Molding is one of the important processes both in terms of cycle time and product quality, with permanent mold casting, high quality liquid metal casting, and quality product. Selective Laser Melting (SLM) method has been used to design metal mold cores with unique cooling channels to be compactly produced. The effects of the designed cooling channels, heat transfer and solidification of the molten metal are studied in transient numerical terms. The temperature distributions for 1, 3 and 5 seconds after casting were obtained and the solidification processes were investigated according to the standard cooling channels of the original cooling channels. According to the results obtained, it has been observed that solidification is better in originally designed cooling channels.Sun, 19 Aug 2018 19:30:00 +0100Contractors’ Partnership in Project Resource Management Application of Cooperative Game ...
http://scientiairanica.sharif.edu/article_20897_0.html
It is accepted that project breakdown into several independent subprojects can help to have a successful and effective project management. On the other hand, it can lead to inefficiently use of some renewable resources, and increase the total project cost and time. This article studies the benefits of the horizontal partnering among contractors assigned to subprojects through the sharing renewable resources and proposes a model based on cooperative game theory to solve it. The improvement of the net present value of the project is considered as the benefit of the cooperation among contractors. Therefore, a mixed-integer non-linear programming (MINLP) model is developed for the resource constrained project scheduling with objective function of maximizing the net present value (NPV) of each coalition. Seven widely used cooperative game theory solution methods are used to solve the benefit (NPV) allocation problem and then the stability criteria are suggested to find the best allocation scheme. Finally, an example is represented to more comprehensively illustrate the problem.Fri, 24 Aug 2018 19:30:00 +0100Proposing a new nonlinear hyperviscoelastic constitutive model to describe uniaxial compression ...
http://scientiairanica.sharif.edu/article_20899_0.html
Predicting the nonlinear response of biological tissues is challenging issue, due to strain rate- (short term) and time-dependent (long-term) nature of its response. While many of the tissue properties have already been extensively examined, some are left unnoticed, such as dependence of the stress-relaxation behavior on the strain levels. In this paper, a hyperviscoelastic constitutive model is derived within the integral form presented by Pipkin and Rogers model to remove this limitation. In the suggested model, the hyperelastic and short-term viscous parts are represented by the suitable strain energy function. The long-term viscous function includes the deformation history, which is expressed through a tensorial-relaxation function and has not been considered elsewhere. The constitutive model involves a number of material parameters. The values of those are identified from experimental data for Adiprene-L100 as a tissue-equivalent material. Parameters appearing in constitutive law are estimated by fitting the model with the experimental data. It is assumed that the tissue phantom is slightly compressible, isotropic and homogenous. The obtained results indicate that the presented model can describe the nonlinearity, strain rate- (short-term) and time-dependent (long-term) effects of materials. The validation of the model is investigated and shows very good agreement with the experimental data.Sun, 26 Aug 2018 19:30:00 +0100Lattice Boltzmann Simulation of Blood Flow Properties and Vessel Geometry in an Open and Closed ...
http://scientiairanica.sharif.edu/article_20900_0.html
In the present article, Lattice Boltzmann method is utilized to simulate two-dimensional incompressible viscous flow in an open and closed microchannel (vessel). The main focus of the present research is to study physical parameters of blood flow in a vessel. To find the effect of oscillatory flow inside the vessel, we take account of the Reynolds number from 0.05 to 1.5 for numerical computation in the present manuscript in an open straight vessel. In addition, the accuracy of Poiseuille Law is investigated for blood flow in open vessel too. For this purpose, the effect of the vessel diameter and blood viscosity on the blood flow is studied numerically. As extra results, the effect of blood injection to a coronary bifurcation with two closed ends are studied. The blood pressure drop is high at the beginning of the vessel (pressure variation is high between the adjacent points along the vessel), but after the path along the vessel, the speed of dropping pressure decreases and the pressure difference between the adjoining points decreases along the vessel. Finally, the present results have been compared with the available experimental and numerical results that show good agreements.Sun, 26 Aug 2018 19:30:00 +0100A Bi-Level Programming Model for Energy and Flexiramp Procurement in Day-ahead Market and a ...
http://scientiairanica.sharif.edu/article_20915_0.html
In this paper, we focus on solving the integrated energy and flexiramp procurement problem in the day-ahead market. The problem of energy and ramp procurement could be perfectly analyzed through Stackelberg concept, because of its hierarchical nature of the decision-making process. Such a circumstance is modeled via a bi-level programming, in which suppliers act as leaders and the ISO appear as the follower. The ISO intends to minimize the energy and spinning reserve procurement cost, and the suppliers aim to maximize their profit. To solve the proposed model, a fuzzy max-min approach is applied to maximize the players’ utilities. The objectives and suppliers’ dynamic offers, determined regarding the market clearing prices, are reformulated through fuzzy utility functions. The proposed approach is an effective and simple alternative to the KKT method, especially for problems with non-convex lower-level.Mon, 27 Aug 2018 19:30:00 +0100The effect of amine functionalized carbon nanotubes as promising support for platinum ...
http://scientiairanica.sharif.edu/article_20916_0.html
In this study, multiwall carbon nanotubes (MWCNTs) were chemically oxidized (OMWCNTs) and functionalized with ethylenediamine (EDAMWCNTs) and diethylenetriamine (DETAMWCNTs) as amine precursors. The electrocatalysts were prepared through deposition of Pt nanoparticles on the functionalized MWCNTs by polyol method. The average size of Pt nanoparticles was found to lie between 4 and 5 nm. Cyclic Voltammetry (CV), Rotating Disk Electrode (RDE), Electrochemical Impedance Spectroscopy (EIS), and Chronoamperometry (CA) were employed to evaluate the electrochemical properties of the electrocatalysts. The Electrochemical active surface area (EASA), number of electron transferred (n), and onset potential for EDAMWCNTs and DETAMWCNTs were found to be about 32.2 and 45.8 (m2/g Pt), 4.03 and 4.10 (electron per oxygen molecule), and 0.986 and 0.997 (V vs RHE), respectively. However, in the case of Pt-OMWCNTs the above mentioned electrochemical characteristics were calculated to be 24.2 (m2/g Pt), 3.34 (electron per oxygen molecule), and 0.824 (V vs RHE), respectively. Moreover, EIS and CA indicate that introducing amine functional groups lead to less electron transfer resistance and better electrocatalytic activity and stability during oxygen reduction. The results show that the higher number of nitrogen atoms within the amine functional groups the more enhanced electrocatalytic performance of Pt nanoparticles in ORR.Tue, 28 Aug 2018 19:30:00 +0100An Effective League Championship Algorithm for the Stochastic Multi-Period Portfolio ...
http://scientiairanica.sharif.edu/article_20995_0.html
The multi-period portfolio optimization models were introduced to overcome the weaknesses of the single-period models via considering a dynamic optimization system. However, due to the nonlinear nature of the problem and rapid growth of the size complexity with increasing the number of periods and scenarios, this study is devoted to developing a novel league championship algorithm (LCA) to maximize the portfolio’s mean-variance function subject to different constraints. A Vector Auto Regression model is also developed to estimate the return on risky assets in different time periods and to simulate different scenarios of the rate of return accordingly. Besides, we proved a valid upper bound of the objective function based on the idea of using surrogate relaxation of constraints. Our computational results based on sample data collected from S&P 500 and 10-year T. Bond indices indicate that the quality of portfolios, in terms of the mean-variance measure, obtained by LCA is 10 to 20 percent better than those of the commercial software. This sounds promising that our method can be a suitable tool for solving a variety of portfolio optimization problems.Sat, 15 Sep 2018 19:30:00 +0100An Optimal Control Strategy for Parallel Hybrid Electric Vehicles
http://scientiairanica.sharif.edu/article_20996_0.html
This paper proposes a new power management strategy (PMS) for parallel hybrid electric vehicles equipped with continuously variable transmission (CVT). The proposed PMS is established on the basis of electric assist control strategy (EACS) and equivalent consumption minimization strategy (ECMS). This control approach is based on maintaining the battery energy within a recommended range, considering the CVT efficiency in selecting the engine operating point, and finding the best power split between the engine and electric motor at certain moments of the driving. In order to evaluate the effectiveness of this scheme, it is compared with EACS, a modified version of EACS and ECMS. It is shown that, in all of the studied driving cycles, the proposed PMS is superior to the considered rival strategies in terms of the fuel consumption and also HC and CO emissions.Sat, 15 Sep 2018 19:30:00 +0100Soret and Dufour effects on doubly diffusive convection of nanofluid over a wedge in the ...
http://scientiairanica.sharif.edu/article_20997_0.html
This paper is devoted to investigate the influences of thermal radiation, Dufour and Soret effects on doubly diffusive convective heat transfer of nanoliquid over a wedge in the presence of wall suction. The governing equations are transformed to nonlinear ordinary differential equations using similarity transformation. The resulting system is solved numerically using fourth-order Runge-Kutta-Gill method with shooting technique and Newton-Raphson method. The solutions are expressed in terms of velocity, temperature, solutal concentration and volume fraction profiles. The effects of pertinent parameters entering into the problem such as wedge angle, thermal radiation, Brownian motion, thermophoresis, Soret and Dufour numbers on the skin friction coefficient, local Nusselt number and local Sherwood number are discussed in detail.Sat, 15 Sep 2018 19:30:00 +0100Two sufficient conditions for the existence of path factors in graphs
http://scientiairanica.sharif.edu/article_21010_0.html
A graph G is called a (P≥n, k)-factor critical graph if G − U has a P≥ n -factor for any U ⊆ V(G) with|U|=k. A graphG is called a (P≥n, m)-factor deleted graph if.............Sun, 16 Sep 2018 19:30:00 +0100A new image enhancement method considering both dynamic range and color constancy
http://scientiairanica.sharif.edu/article_21011_0.html
This paper proposes an approach to improve color images suffering from low dynamic range, by employing both histogram matching and histogram stretching techniques. Firstly, the color image is transformed from RGB into HSV color space, in which the color information is separated from intensity. Then, an appropriate reference image is selected by comparing component V of the enhancing image with component V of the data base images using a similarity measure. This selected image is used as the goal image in histogram matching algorithm in order to enhance image brightness (Automatic Histogram Matching). Secondly, components V and S are linearly stretched in order to recover the image color information. Finally, using the treated V and S components and untreated component of H, the enhanced image is obtained in RGB color space by inverse transform. The qualitative and quantitative results show that the contrast and color of resultant images are greatly improved using the proposed method, which outperforms the current state-of-the-art methods.Sun, 16 Sep 2018 19:30:00 +0100An Analytical Study on Mechanical Behavior of Human Arteries – A Nonlinear Elastic Double ...
http://scientiairanica.sharif.edu/article_21012_0.html
The focus of this article is on analytical solution for stress and deformation of human arteries. The artery is considered as a long homogeneous isotropic cylinder. Hyperelastic, incompressible stress-strain behavior is used by adopting a classical Mooney-Rivlin material model. The elastic constants of the arteries are calculated by using the reported results of biaxial test. The analysis is based on both single and double layer arterial wall models and. Radial and circumferential stress distribution on the minimum and maximum blood pressure is calculated. Variation of radii due to internal pressure within the arteries is found which is in a good accordance with the experimental results. The results containing the changes in diameter and thickness together with the stress distribution for both single and double layer models have been plotted. It is shown that the major difference between the single and double layer models is in their stress distributions. The circumferential stress distribution for different human’s ages is plotted which shows that the stress increases by increasing the age due to decreasing the flexibility of the artery. It is also shown that despite the artery’s inner layer is softer than the outer layer, the maximum stresses occur at the inner layer.Sun, 16 Sep 2018 19:30:00 +0100Numerical and experimental investigation of impinging turbulent flow of twin jets against a wall
http://scientiairanica.sharif.edu/article_21013_0.html
In the present study, impinging of vertical twin jet against a horizontal plate is numerically and experimentally investigated. Four two equation RANS based turbulence models are used and their capabilities to simulate such complicated turbulent flow were examined. The two fluid jets are separated by a thin membrane. The inlet jet hydraulic diameters are the same and the Reynolds number of external flows of jets is 13500. The ratio of width of nozzles (e) to nozzle-to-plate distance (H) considered as 1:10. The turbulent models used in this work are k-ε, k-ε RNG, k-ω and k-ω SST. The results obtained by the models were compared with each other as well as two-dimensional PIV data to evaluate the capabilities of such models for this kind of flows. By comparing the numerical and experimental results, it is concluded that all of the models can predict acceptable results in the free jet area, but in the near wall region none of the models can predict flow characteristics with reasonable accuracy. It was observed that, at low nozzle-to-plate distances, the prediction results of the turbulence models are approximately in accordance with the experimental data, particularly for a zone near the midline separating the two jets.Sun, 16 Sep 2018 19:30:00 +0100Optimal Production Inventory Decision with Learning and Fatigue Behavioral Effect in Labor ...
http://scientiairanica.sharif.edu/article_21014_0.html
Behavioral economic has received much attention recently. Learning and fatigue are two typical behavioral phenomena in industrial production operation processes. The existence of learning and fatigue result in a dynamic change in productivity. In this paper, a classical economic production quantity model is extended to consider the behavioral economic value of learning and fatigue. Based on a real case study, each production cycle is divided into five phases, i.e, the learning phase, stable phase, fatigue phase, fatigue recovery (rest) phase, and the relearning phase. The new production inventory decision model is incorporated with dynamic productivity and learning-stable-fatigue-recovery effect. Numerical simulation and sensitivity analysis show that appropriate rest alleviates employees fatigue and increases productivity, resulting in a lower average production cost. On the other hand, when the rest time is too high, exceeding a certain value, it leads to the decline of the actual labor productivity, resulting in an increase in the average cost of the system.Sun, 16 Sep 2018 19:30:00 +0100Flood hazard risk evaluation using fuzzy logic and weightage based combination methods in ...
http://scientiairanica.sharif.edu/article_21037_0.html
This study addresses the crucial variables contributing highly to the risk of flooding based on the flood characteristics of the Waverly region and develop a fuzzy logic and geographic information based urban flood map with flood zones in Waverly City, Iowa. The methodology emphasizes on weighting crucial variables using spatial analyst tools and fuzzy logic based GIS mapping. Local elevation, distance from Cedar River, land use and population density in Waverly city are recognized as effective variables to risk of flooding in Waverly city. Twenty three calibration tests for determination of weightages of these variables on the risk of flood were performed and compared to previously produced Waverly flood risk maps. Finally, weightages of these variables were assigned as 70 % for elevation, 20 % for distance from Cedar River, 5 % for Manning’s coefficient, and 5 % for population density. In a fuzzy environment they were assigned different fuzzy membership functions, for elevation, fuzzification technique Small was used, for distance, fuzzification technique MS Small was used, for Manning’s coefficient and population density, fuzzification technique Large was used. The flood hazard maps created were overlaid with 100 and 500-year flood maps of Waverly city for calibration and risk evaluation.Sat, 22 Sep 2018 20:30:00 +0100Localizing Exception Faults in Android Applications
http://scientiairanica.sharif.edu/article_21040_0.html
In software programs, most of the time, there is a chance of faults in general, and exception faults in particular. Localizing those pieces of code which are responsible for a particular fault is one of the most complicated tasks and it can make incorrect results if done manually. Semi-automated and fully-automated techniques have been introduced to overcome this issue. However, despite recent advances in fault localization techniques, they are not necessarily applicable to Android applications because of their special characteristics like context-awareness, use of sensors, being executable on various mobile devices, limited hardware resources, and so on. To this aim, in this paper, we introduce a semi-automated hybrid method that combines static and dynamic analysis to localize exception faults in Android applications. Our evaluations with a number of open source Android applications of different sizes with various exceptions show that our proposed technique can correctly identify the root causes of occurred exceptions. These results indicate that our proposed approach is effective in practice in localizing exception faults in Android applications.Sun, 23 Sep 2018 20:30:00 +0100The Effect of Processing Time on Microstructure of Surface and Corrosion Resistance of Coatings ...
http://scientiairanica.sharif.edu/article_21041_0.html
In this study, the effect of coating processing time on microstructure of surface and corrosion resistance of coatings resulted by plasma electrolytic oxidation (PEO) was investigated on substrate of TiAl6V4 alloy. The coating processes in hydroxyapatite nano-powder electrolytic were carried out in same conditions of constant voltage of 600V and three different times of 125, 250 and 350 seconds. Studying the microstructure of coatings identified that the coating formed in 125 (s) had more compact and steady structure with fine surface cavities and less porosity. X-ray diffraction pattern of coating demonstrates that this coating is consists of oxide phases of titanium (rutile and anatase) and hydroxyapatite. Also, the study of corrosion resistance of coatings by Potentiodynamic polarization and electrochemical impedance spectroscopy in corrosive solution of chloride sodium 3.5% showed that the coating formed in 125 s has the most noble corrosion resitance potential and the least ICorr and finally the highest resistance to corrosion.Sun, 23 Sep 2018 20:30:00 +0100Improvement of Dissipative Particle Dynamics method by taking into account the particle size
http://scientiairanica.sharif.edu/article_21042_0.html
In this paper, flow past a single Dissipative Particle Dynamics (DPD) particle with low Reynolds number is investigated and it is inquired that whether a single DPD particle immersed in a fluid, has an intrinsic size. Then a minimum length scale is determined such that the hydrodynamic behavior based on standard DPD formulation is modeled correctly. Almost all of the previous studies assume the DPD particles as point centers of repulsion with no intrinsic size. Hence to prescribe the size of a simulating sphere, a structure of frozen DPD particles is created. In this paper two effective radii, Stokes-Einstein radius and a radius based on the Stokes law, for DPD particles are introduced. For small Reynolds numbers; it is proved that the two radii approach each other. Finally in spite of the typical simulations which assume DPD particles as point centers of repulsion, it is concluded that each of the individual DPD particles interact with other particles as a sphere with non-zero radius. It results the reduction of the required number of particles and eventuates more economical simulations. Moreover contemplating the radius of the particles is necessary for the new Low-Dimensional model which is derived based on the DPD method.Mon, 24 Sep 2018 20:30:00 +0100The Perils of Group Purchasing in a Competing Supply Chain
http://scientiairanica.sharif.edu/article_21043_0.html
Group purchasing organizations (GPOs) are well-known intermediary firms that play an important role in some supply chains. An important question that arises regarding the GPOs, is whether a GPO that benefits from group buying discounts, always benefit the OEMs in the presence of market competition. In other words, does a GPO always lead to a win-win outcome for OEMs and the GPO? To answer this question, a bargaining framework has been used to investigate competing OEMs' procurement's strategies. The entrance of a GPO in a two tier supply chain that consists of two competing OEMs with a common supplier that has a quantity discount menu is analyzed. The result shows that low purchasing cost GPO may harm OEMs in a cost-benefit perspective. This unintuitive result can be explained by different impacts that a GPO has in purchasing process. Although, it can enlarge the size of trade surplus; but, it has an important influence on the size of the slice of the pie (profit sharing). Moreover, an OEM's procurement strategy in equilibrium not just only depends on his bargaining power; but also depends on his competitor OEM. Interestingly, a strong OEM may not prefer procuring through GPO, as well as a weak OEM does.Mon, 24 Sep 2018 20:30:00 +0100Practical Provably-Secure Authenticated Encryption Schemes Using Lattice-based Pseudorandom ...
http://scientiairanica.sharif.edu/article_21044_0.html
Lattice-based cryptography has received significant attention from security practitioners in the past decade. It exhibits attractive properties, including being a major post-quantum cryptography candidate, enjoying worst-case to average-case security reductions, and being supported by efficient implementations. In this paper, we propose three practical lattice-based authenticated encryption (AE) schemes. These schemes are provably secure assuming hardness of basic lattice problems. The proposed schemes have remarkable motivationsand advantages over widely-used AEs as follows. These schemes are alternatives to current conventional and post-quantum AE schemes in the post-quantum era. Moreover, composing the proposed AEs with a lattice-based asymmetric key distribution scheme results to a hybrid encryption which depends only on one (type of) security assumption. The implementation of such hybrid encryption can make use of specific optimizations regarding, e.g., code size in software, and gate equivalent or FPGA area usage in hardware. That is because the symmetric and asymmetric algorithms have some common primitive computations. To evaluate the performance of the proposed AEs, we implement them on current Intel CPUs and benchmark them to encrypt messages of various sizes. The most efficient proposed scheme is only 12% slower than AES-256-GCM for 40-byte messages on Sandy Bridge, and 34% faster for 1500-byte messages.Sat, 29 Sep 2018 20:30:00 +0100Adaptive Control of a Cable-Actuated Parallel Manipulator Mounted on a Platform with ...
http://scientiairanica.sharif.edu/article_21046_0.html
Cable-actuated parallel Manipulators (CPMs) are widely employed for object handling applications. In order to displace the carried object along the ground to an unlimited distance, the CPMs can be mounted on wheeled mobile robots (WMRs). The derivation of the dynamic equations of motion for this integrated system is presented using Lagrange method. Since in load carrying task, the inertia of the moving load is the main source of uncertainty, an adaptive control approach is considered for the CPM, whereas the WMR uses a feedback linearized sliding mode approach. In order to maintain the end-effector of the CPM in within its relative workspace in the WMR frame, the convergence rate in the two controllers should be similar. Decentralization of the control law can be accomplished if the inertia of the CPM motors are negligible compared with the other inertias of the system. This assumption is shown to be applicable if an introduced index is small enough to have noticeable effect on the tracking error.
Sun, 30 Sep 2018 20:30:00 +0100Reliable Hierarchical Multimodal Hub Location Problem: Models and Lagrangian Relaxation Algorithm
http://scientiairanica.sharif.edu/article_21047_0.html
Hub facility location problems involve the establishment of strategic hub facilities and allocation of demand nodes to them. Meanwhile, with the emergence of new transport and distribution networks with multi-level structures, the design of such networks has been evolved. The diversity in transportation system has added multimodality to these problems. Considering the strategic nature and long-term implications of decision-making in this field, the decisions shall be of high reliability. The present study is an attempt to consider reliability of communication paths in proportion to the volume of transaction through them while covering all of the above-mentioned issues in hub location problems at the same time. Incorporating hierarchical characteristics of the problem into the model, one can obtained a significantly enhanced model in terms of multimodality and reliability. A Lagrangian solution method was developed considering the strategic level of the problem and the importance of the solution accuracy. The model was then validated in terms of time and quality.Mon, 01 Oct 2018 20:30:00 +0100Agricultural tractors of the fifth generation
http://scientiairanica.sharif.edu/article_21048_0.html
The article deals with the problem of substantiation of mobile power units (MPU) – tractors for agriculture of the fifth generation. This issue is quite relevant. The main purpose of the work is to analyze agricultural tractors of the fifth generation. The authors formulated the main requirements for the ecological balance of the technogenic interaction of MPUs with production processes in agro-ecosystems of grain production in the zonal conditions of South-Russian arid agriculture. Proposals for the creation of new MPUs have been developed; the technological structures of machine aggregates based on the MPU of the fifth generation of classes 3, 5-6 and 8 that determined the technical schemes of the named MPU were determined. Analytical models for calculating the power characteristics of MPU of the named classes in deterministic and stochastic modes in relation to the most energy-intensive operations with definitions of the mathematical expectations of MTA’s power and performance. Also, an analysis of the MTAs effectiveness based on new MPUs upon criterion of the time spent on cultivating crop rotations on the examples of peasant farms and agricultural organizations (APC, CAE, etc.)Fri, 05 Oct 2018 20:30:00 +0100Experimental and numerical study of low frequency pulsed Nd:YAG laser heating of slip cast ...
http://scientiairanica.sharif.edu/article_21049_0.html
Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low thermal conductivity. Laser assisted machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, the effect of laser heating in the LAM process on slip cast fused silica (SCFS) ceramics is investigated by presenting a numerical thermal analysis of laser effects on material behavior. A transient three-dimensional heat transfer analysis for laser assisted turning (LAT) of SCFS is performed using finite element method. Temperature distributions in SCFS cylindrical specimens are obtained. Moreover, the influence of laser parameters such as power, translational speed, and feed rate on the temperature field are studied. To increase the absorptivity of the ceramic surface, a coating is applied, and the absorptivity of the coated surface is determined by carrying out a series of experiments. Experiments are performed to validate the numerical transient heat transfer finite element model. In addition, the effects of spot overlapping of pulsed laser on temperature distribution and absorptivity of SCFS workpiece are studied. It is for the first time that effect of laser beam overlapping on low frequency pulsed laser heating in LAT is formulated and completely investigated.Fri, 05 Oct 2018 20:30:00 +0100Evaluation of the response modification factor of RC structures constructed with Bubble Deck system
http://scientiairanica.sharif.edu/article_21050_0.html
As the concrete material is eliminated from the locations situated around the middle of the cross-sections of bubble decks (BDs), the BD type slabs are lighter than the traditional slabs. In the recent researches, the response modification factor (RMF) is generally determined for the reinforced concrete (RC) structures with the moment-resisting frame (MRF) and dual systems. The dual system comprise mainly the MRF with shear wall (MRFSW), as well as the flat slab having chiefly the BD system. In this paper, the evaluation of values of the RMF of RC structures using BD system are submitted. The obtained results indicate that the lateral strengths of buildings increase by increasing the span length to story height ratio (L/H). Besides, the variations of the span length and the number of the story have more effects than the variation of the usage category buildings on the RMF of structures. Furthermore, the span length has more effect than the number of stories in determining RMF in an MRF. Finally, amongst the building with dual system structures including MRFSW, the low-rise building structures have an RMF equal to 5, and both the mid-rise and high-rise building structures have an RMF of 7.Sat, 06 Oct 2018 20:30:00 +0100Using multivariate analysis approaches in designing NSBM Model with considering undesirable ...
http://scientiairanica.sharif.edu/article_21053_0.html
Due to the competitiveness of banking industry and increasing bargaining power of customers, evaluation of the banks’ performance is crucial to better serve the classified customers in a universal system .In this paper, with consideration of segmenting the customers into personal and business ones, methods such as confirmatory factor analysis (CFA) and structural equation model (SEM) have been used in selecting appropriate variables of the network data envelopment analysis (NDEA) model based on network slacks-based measure and consideration of the undesirable variables and shared resources. The SEM model has been used to establish a proper connection between the different dimension of the NDEA model and CFA model has been used to identify the importance of each dimension. Also, the proposed model has been used to measure the Operational and decomposed universal efficiency of one of the Iranian bank branches (Day Bank). The results show that the extracted model provides managers with a suitable perspective in adopting appropriate policies to promote their performance in the different sectors, including deposit attraction, financial serving personal and business banking customers, and profit generation, and also in comparing them in the different dimensions of the model.Sun, 07 Oct 2018 20:30:00 +0100A novel assessment approach for EFQM driven institutionalization using integrated fuzzy ...
http://scientiairanica.sharif.edu/article_21058_0.html
It is becoming increasingly difficult for enterprises to survive under competitive conditions. Enterprises with high levels of institutionalization are able to survive and benefit more advantages than their competitors. Excellence models are widespread tools for measuring the degree of institutionalization of enterprises. The importance of institutionalization has been increasingly considered in excellence models. EFQM (European Foundation for Quality Management) is a suitable tool to show how successful organizations are in terms of institutionalization. In this study, EFQM criteria are evaluated with fuzzy multi-criteria decision-making techniques. The fuzzy DEMATEL method is used to determine the interactions amongst main EFQM criteria. According to the relationship diagram obtained from the Fuzzy DEMATEL method, the weights of the sub criteria are calculated according to the expert evaluations using Fuzzy Analytic Network Process (FANP) method. The criterion “Business Results” has been determined to be the most important criteria. The criteria weights are taken as input for the VIKOR method. The institutional scores obtained by the proposed method, and the scores given by the EFQM evaluators to the institutions, are statistically analyzed to demonstrate that the proposed method has produced meaningful results.Sun, 14 Oct 2018 20:30:00 +0100Benders Decomposition Algorithm for Robust Aggregate Production Planning Considering Pricing ...
http://scientiairanica.sharif.edu/article_21059_0.html
In operations research, bi-level programming is a mathematical modeling which has another optimization problem as a constraint. In the present research, regarding the current intense competition among large manufacturing companies for achieving a greater market share, a bi-level robust optimization model is developed as a leader-follower problem using Stackelberg game in the field of aggregate production planning (APP). The leader company with higher influence intends to produce new products, which can replace the existing products. The follower companies, as rivals, are also seeking more sales, but they do not have the intention and ability to produce such new products. The price of the new products is determined by the presented elasticity relations between the uncertain demand and price. After linearization, using the KKT conditions, the bi-level robust model is transformed into an ordinary uni-level model. Due to the NP-hard nature of the problem, Benders decomposition algorithm (BDA) is proposed for overcoming the computational complexities in large scale. Finally, using the real data of Sarvestan Sepahan Co as a leader company, the validity of the developed model as well as efficiency and convergence of the BDA are investigated. The computational results clearly show the efficiency and effectiveness of the proposed BDA.Sun, 14 Oct 2018 20:30:00 +0100Residual strain in graphene: study of temperature and crack effect
http://scientiairanica.sharif.edu/article_21060_0.html
Graphene is a thin sheet with special properties and complicated mechanical behavior. It’s important to study graphene experimentally and theoretically. Stone–Wales defects, cracks and atom vacancy are popular defects in carbon allotropes especially in graphene. In this paper, residual strain in graphene was discussed. At first, stress-strain curve of non-defected graphene sheet was obtained using molecular dynamics simulation and effect of temperature on mechanical properties of graphene was obtained. Then, four different cracks were considered in center of graphene sheets. Stress-strain curves of defected graphene sheets with different tension strain rates were plotted. The results showed that cracks lead to the graphene to fracture sooner. Also, increasing temperature lead to the Young’s modulus of graphene decreases and graphene fractured at lower strain. On the other hand, residual strain of non-defected and cracked graphene increased by increasing temperature from 200 K to 1200 K. It means that graphene had more plasticity behavior by increasing temperature.Sun, 14 Oct 2018 20:30:00 +0100Multi-Period Configuration of Forward and Reverse Integrated Supply Chain Networks with the ...
http://scientiairanica.sharif.edu/article_21061_0.html
Today’s competitive business environment has resulted in increasing attention to social responsibilities and customer’s attitudes. Buying and returning have become a common practice for different reasons, including incompleteness or immature failure of the product or its failure to meet the customer’s satisfaction. Before the buying and returning cycle can be handled appropriately, companies need a proper logistics network designed following a proper design strategic. In the present research, a forward and reverse logistics network is proposed for product distribution and collection. The contribution of this paper to the literature is the proposal of a multi-period, multi-echelon, integrated forward and reverse supply chain network design problem with transportation mode selection considered. Different kinds of decisions including the determination of optimum number and locations of facilities, facilities opening time and transportation mode selection among different facilities have been considered in this paper. Due to multi-period nature of the problem, the problem is flexible for future periods. A new mixed integer nonlinear programming model was proposed for the introduced problem considering different levels of facility capacities with the maximum profit objective function. As another contribution, a genetic algorithm was developed to cope with problem’s complexity when the problem size goes large.Sun, 14 Oct 2018 20:30:00 +0100A New Model for Prediction of Liquid Holdup in Two-Phase Flow under Higher Gas and Liquid Velocities
http://scientiairanica.sharif.edu/article_21062_0.html
Existing liquid holdup models are generally based on low gas and liquid velocities. In order to extend the applicable range of existing liquid holdup prediction models and improve its prediction accuracy, a of gas-liquid two-phase flow experiment was carried out using a pipe of inner diameter 60mm and length of 11.5m. The superficial gas and liquid velocity ranges were 14.07~56.50m/s and 0.205~1.426m/s, respectively. The results indicate that the liquid holdup decreases with the increase of the superficial gas velocity and increases with the increase of the superficial liquid velocity. A new annular flow model for calculating low liquid holdup in horizontal pipe was developed and presented considering the relationships between the friction factor ratio of liquid phase and gas-liquid interface as well as the superficial Reynolds number of gas and liquid. The predictions of the model are found to be accurate with an average absolute error of 4.8%. Further, on the basis of the Beggs-Brill model and the horizontal pipe model established in this paper, a new liquid holdup model for different angles was given. It was observed the resultant model is also accurate, and has an average absolute error of 10%.Sun, 14 Oct 2018 20:30:00 +0100A Novel Fuzzy Multi-Objective Method for Supplier Selection and Order Allocation Problem Using ...
http://scientiairanica.sharif.edu/article_21063_0.html
This paper introduces a supplier selection and order allocation problem in a single-buyer-multi-supplier supply chain in which appropriate suppliers are selected and orders allocated to them. Transportation costs, quantity discount, fuzzy type uncertainty and some practical constraints are taken into account in the problem. The problem is formulated as a bi-objective model to minimize annual supply chain costs and to maximize the annual purchasing value. The fuzzy weights of suppliers, which are the output of one of the supplier evaluation methods, are considered in the second objective function. Then, we propose a novel fuzzy multi-objective programming method for obtaining Pareto solutions. The method is the extension of a single-objective method exist in the literature. This method is based on the decision maker's degree of satisfaction from each fuzzy objectives considering the fulfillment level of fuzzy constraints. In the proposed method, the problem remains multi-objective and, unlike existing methods, does not transformed into a single-objective model. At the last stage of proposed method, the fuzzy results are compared with an index, and decision maker can identify the appropriate or inappropriate solutions. To solve the problem, non-dominated sorting genetic algorithm (NSGA II) is designed and computational results are presented using numerical examples.Sun, 14 Oct 2018 20:30:00 +0100A Comparative Study of Economic Load Dispatch using Sine Cosine Algorithm
http://scientiairanica.sharif.edu/article_21064_0.html
Economic Load Dispatch (ELD) is an important part of cost minimization procedure in power system operation. Different derivative and probabilistic methods are used to solve ELD problems. This paper proposes a powerful Sine Cosine Algorithm (SCA) to explain the ELD issue including equality and inequality restrictions. The main aim of ELD is to satisfy the entire electric load at minimum cost. The SCA is a population based probabilistic method which guides its search agents that are randomly placed in the search space, towards an optimal point using their fitness function and also keeps a track of the best solution achieved by each search agent. SCA is being used to solve the ELD problem with their high exploration and local optima escaping technique. This algorithm confirms that the promising areas of the search space are exploited to have a smooth transition from exploration to exploitation using sine and cosine functions. Simulation results prove that the proposed algorithm surpasses other existing optimization techniques in terms quality of solution obtained and computational efficiency. The final results also prove the robustness of the SCA.Sun, 14 Oct 2018 20:30:00 +0100QUASI-OPPOSITIONAL SYMBIOTIC ORGANISMS SEARCH ALGORITHM FOR DIFFERENT ECONOMIC LOAD DISPATCH ...
http://scientiairanica.sharif.edu/article_21065_0.html
In this paper, an effective meta-heuristic technique called Quasi-Oppositional Symbiotic Organisms Search is applied for solving non-convex economic dispatch problems. Symbiotic Organisms Search is a soft computing technique, inspired by organisms in the ecosystem. This technique is implemented for improving the solution quality in minimum time. In order to improve convergence rate, quasi-reflected numbers are used here instead of pseudo-random numbers. Different equality and inequality constraints such as transmission loss, load demand, prohibited operating zone, generator operating limits and boundary of ramp rate are considered here. Presence of multiple fuels and valve point are also considered in some cases. This algorithm is applied to four different test systems. Simulation results are compared with many recently developed optimization techniques to show the superiority and consistency of this method. Simulation results also show that the computational efficiency of this algorithm is much better than the other meta-heuristic methods available in the literature.Sun, 14 Oct 2018 20:30:00 +0100Natural convection of CNT-water nanofluid in an annular space between confocal elliptic ...
http://scientiairanica.sharif.edu/article_21069_0.html
In this paper, free convection heat transfer in an annulus between confocal elliptic cylinders filled with CNT-water nanofluid is investigated numerically. The inner cylinder is at constant surface heat flux while the outer wall is isothermally cooled. Equations of continuity, momentum and energy are formulated using the dimensionless form in elliptic coordinates for two-dimensional, laminar and incompressible flow under steady state condition, which is expressed in terms of vorticity and stream function. The governing equations are discretized using the control volume method. For the thermo-physical properties of CNTs, empirical correlations are used in terms of the volume fraction of nanoparticles. For the effective thermal conductivity of CNTs, a new model has been used. The study is performed for modified Rayleigh number (103≤ Ram ≤106), volume fraction of nanoparticles (0≤ f ≤0.12). The eccentricity of the inner and outer ellipses and the angle of orientation are fixed at 0.9, 0.6 and 0°, respectively. Results are presented in the form of streamlines, isotherm contours, and distribution of temperature and local and average Nusselt numbers on solid boundaries. The results are also discussed in detail and a very good agreement exists between the present results and those from the literature.Fri, 19 Oct 2018 20:30:00 +0100The Effect of Various Curing Temperatures on Engineering Properties of Chemically Grouted Sands
http://scientiairanica.sharif.edu/article_21070_0.html
In this experimental study, the effect of curing temperature on the engineering properties of sand samples grouted with sodium silicate-glyoxal was investigated. The experiments were started with determination of the gelation times, viscosities and syneresis percentages of the blends prepared for injection, after which the injection experiments were then carried out at the determined mixing ratios. Grouted specimens were subjected to unconfined compressive strength (UCS) and permeability tests being kept at different curing temperatures (+10 °C, +20 °C and +30 °C) in the curing tank. As the temperature was increased, the viscosity values and gelling times decreased, while the syneresis percentages increased. The UCS of the grouted samples decreased with time. This decrease was observed to slow down in the samples kept at +10°C after the 56th day, while the same was on 28th day in those kept at +20°C and on 7th day for those kept at +30 °C. Also, UCS values decreased with the increasing temperature. The permeability values of the grouted samples decreased with time. This decrease has been observed to slow down after the 28th day. The increase in temperature reduced the permeability values.Sun, 21 Oct 2018 20:30:00 +0100Suitability of brick kiln waste as a stabilizer to clayey soils
http://scientiairanica.sharif.edu/article_21071_0.html
Due to increased use of brick masonry for construction of buildings in Pakistan, huge quantities of Brick Kiln Waste (BKW) are generated which not only create disposal problems but are a hazard to the environment. In order to get rid of such problems, it is necessary to investigate suitability of the BKW as a stabilizer to the clayey soils. For this purpose, an experimental program was carried out to stabilize clayey soil with the BKW ranging from 5 to 40%. Basic geotechnical tests were performed on the clayey soil blended with the BKW. The results showed that the clayey soil became coarser and more suitable as a subgrade material with addition of the BKW. There was negligible reduction in dry density up to 7% when the BKW added was 40%. As expected, the cohesion and friction angle of the blended soils respectively decreased and increased with inclusion of the BKW. As compared to the clayey soil, the ultimate bearing capacity of the blended soil having 40% of the BKW increased by 21%. This study shows that clayey soils stabilized with the BKW could be used as a partial fill material for highway embankments and foundations of buildings.Sun, 21 Oct 2018 20:30:00 +0100Uncertainty Quantification in Seismic Collapse Assessment of Iranian Code-Conforming RC Buildings
http://scientiairanica.sharif.edu/article_21072_0.html
Structural collapse is the main concern in the existing structures which are built in the seismic-prone regions. Therefore, the primary goal of the seismic provisions in building codes is to prevent the global collapse. Iran is located in the Alpine-Himalayan belt, and has experienced some of the most destructive earthquakes in the past century. To evaluate the extent to which the Iranian building code provisions meet this objective, the authors have conducted a detailed assessment of collapse risk on a set of moderate moment resisting reinforced concrete (RC) buildings. This study considers P-Delta effects, deterioration in strength and stiffness, and cyclic deterioration in structural components. Structural assessment is performed using OpenSees platform and the multiple-record incremental dynamic analysis (IDA). Results are presented in terms of the IDA capacity curves and the collapse fragility functions at different seismic hazard levels. Results show that probability of instability increases with height of the buildings. Moreover, the collapse confidence level was evaluated considering the available uncertainties. Assuming a minimum confidence level of 90% for the buildings, the collapse prevention limit state under the 2%/50 hazard level is not satisfied for the 9 and 12 story frames, and they need to re-designed.Sun, 21 Oct 2018 20:30:00 +0100Economic efficiency of application of artificial air cooling for normalization of thermal ...
http://scientiairanica.sharif.edu/article_21073_0.html
The work substantiates a technical solution for improving the working conditions for the thermal factor in the extraction of oil by the thermoshaft method using the mine refrigeration technology. The review of manufacturers and technical characteristics of refrigeration technology in Russia, CIS countries and Western Europe was conducted. For the selected set, the economic efficiency of the project was assessed and a conclusion was made about the feasibility of implementing this project solution. It was shown that the use of a water cooling machine in the mine air conditioning system will reduce the air temperature in the oil production gallery to the required values and will allow to abandon the long-term construction of a surface stationary refrigeration station. Normalization of the thermal regime reduces the costs of benefits and compensation for work in harmful labor conditions and improves the quality of service of production wells by operators. The project for the introduction of air conditioning has a high level of profitability, and its payoff will occur in the second year of operation.Sun, 21 Oct 2018 20:30:00 +0100Parameter converting method for bifurcation analysis of nonlinear dynamical systems
http://scientiairanica.sharif.edu/article_21074_0.html
For detecting behavior of a dynamical system, bifurcation analysis is necessary with respect to change in parameters of system. In this work, based on the solution of ordinary differential equations from initial value and parameters, a simple method is presented, which can efficiently reveal different bifurcations of system. In addition to its simplicity, this method does not required to have deep physical and mathematical understanding of the problem, and because of its high precision and the speed of solutions, does not need to reduce the order of models in many complex problems or problems with high degrees of freedom. This method is named parameter converting method (PCM), which has two steps. In the first step the parameter is varied as a function of time and in the second step, time is expressed as inverse of this assumed function. With this method bifurcation and amplitude-frequency diagrams and hidden attractors of some complex dynamics will be analyzed and the sensitivity of the multi potential well systems to initial conditions is studied. With this algorithm, a simple way to find the domain of high-energy orbit in bistable systems is obtained.Sun, 21 Oct 2018 20:30:00 +0100Drivers of Cross-Country Vehicles
http://scientiairanica.sharif.edu/article_21075_0.html
This work offers a new chassis design, namely the wheel-track, represents a mathematical model of this chassis, and also proves the advantage of the proposed design when driving the vehicle on arbitrary terrain - rough off-road. The proposed approach can find application in the design of unmanned research mechanisms for other planets (Mars Rovers, Lunar Rovers etc.), also for design of robots and transport of rescuers at liquidation of consequences of natural or technological disasters. The article presents the analysis of the requirements for the chassis of extraterrestrial research unmanned mechanism demonstrated high compliance of the proposed approach. The analysis of the requirements for the chassis of extraterrestrial research unmanned mechanism demonstrated high compliance of the proposed approach. We proposed and investigated a mathematical model of wheel-track, demonstrated the optimization of the proposed mathematical model to machine computing, demonstrated the flexibility and scalability of the mathematical model. The proposed design is an attempt to combine the advantages of a walking and wheel types of travel in one mechanism.Sun, 21 Oct 2018 20:30:00 +0100Static Performance of Geosynthetic Reinforced Soil Walls with Peripheral Soil–Cement Mixtures
http://scientiairanica.sharif.edu/article_21076_0.html
ecently, much effort has been devoted to improving the performance of geosynthetic reinforced walls under various stress conditions. In this research, the effect of using cemented mixed soil as a backfill material is studied on the static response of geosynthetic reinforced soil (GRS) walls. For this, numerical models based on a finite-difference code are made according to one of the Royal Military College’s (RMC) full scale test walls with a segmental facing. Different arrangements of soil reinforcement are considered in the presence of cemented sandy soil and sandy soil alone. In the cement-treated approach, each reinforcement layer is surrounded by a 30 cm cemented sand soil. The results show that using cement-treated sandy soil decreases the maximum deformation of the wall by as much as 75% compared with the case where untreated sandy soil is used. Moreover, by using cemented soil around reinforcements, the reinforcement forces reduce considerably. Therefore, increasing the number of reinforcement layers in the backfill will decrease the face wall deformation as well as the reinforcement forces, which are not cost-effective in many situations. It is also suggested that using the cement-treated technique can be an efficient cost-saving method compared with common GRS walls.Sun, 21 Oct 2018 20:30:00 +0100Optimization of embedded rail slab track with respect to the environmental vibrations
http://scientiairanica.sharif.edu/article_21077_0.html
This paper is geared toward selection of the trough geometry (width and height) and elastic surrounding materials (elasticity modulus) as the optimization parameters along with selection of minimum environmental vibrations in the critical point of pavement system. The optimum trough geometry and specification of surrounding materials were evaluated as the objective function .To this, a numerical finite element model of embedded slab track rail system was developed in consideration of the components of the substructure and superstructure of system under the plain strain conditions. In the first stepf, the numerical model was calibrated by comparing it with static lab results. In the next step, the vibration behavior was investigated after applying a harmonic load to the system at various amplitudes and frequencies corresponding to the real operation conditions. Maximum velocity of particles vibrations was evaluated at different points in the vertical direction, and the critical point of pavement determined. Then, the best trough section and elasticity modulus of surrounding materials corresponding to the load amplitude and frequency were determined by designing the experiments using the surface response method and limiting the maximum vibrations of critical points to 65 Decibel.Sun, 21 Oct 2018 20:30:00 +0100Determination of Optimum Cross Section of Earth Dams Using Ant Colony Optimization Algorithm
http://scientiairanica.sharif.edu/article_21078_0.html
Earth Dams are one of the most important and expensive civil engineering structures to which a considerable amount of budget is allocated. Their construction costs are mainly related to the size of embankments, which in turn depends on their cross section area. Therefore, reductions in cross section areas of earth dams would cause decreases in embankment volumes leading to a significant reduction in the construction cost of these structures. On the other hand, it is almost impossible to obtain optimum cross section in earth dams with desired stability and acceptable operational dimensions using traditional design methods. In this paper, ant colony optimization algorithm (ACO), a well-known and powerful metaheuristic method used to tackle problems in geotechnical engineering, was used to solve this complicated problem. The results showed that applying ideal and optimum slope and berm arrangements resulted from ACO in designing embankments and earth dams with different heights could lead to decreases in embankment volumes compared to those without any berms or those with berms resulting from usual designs with trial and error.Sun, 21 Oct 2018 20:30:00 +0100A New Approach to Improve Durability of Rice Husk Ash Blended Concrete with Re-Dispersible ...
http://scientiairanica.sharif.edu/article_21079_0.html
An experimental investigation was conducted to improve the limitation of Rice Husk Ash (RHA) blended concrete in terms of durability, by incorporating Re-dispersible Polymer Powder. To examine durability properties of Rice Husk Ash Polymer-Modified Concrete (RHAPMC) matrix, the RHAPMC mix of 1:2:3 proportions was used to prepare the specimens. To prepare Rice Husk Ash-Modified Mix (RHAMM), 10% of RHA was replaced with cement. RHAPMC was made with the inclusion of polymer at the ratio of 1 to 7.5% by the weight of cement. Most common durability related properties, i.e. water absorption, density, water permeability, ultrasonic pulse velocity and compressive strength were experimentally investigated. The results showed a remarkable improvement in durability characteristics in newly developed matrix of rice husk ash polymer modified concrete and could be used as a repair material in aggressive environment.Sun, 21 Oct 2018 20:30:00 +0100Numerical evaluation of the operating room ventilation performance: ultra-clean ventilation ...
http://scientiairanica.sharif.edu/article_21083_0.html
The surgical site infection (SSI) is one of the most important infectious problems in hospitals which may be happened in 2.6% of all surgeries. According to the literature, the primary source of SSI is the flakes released from the exposed skin of surgical staffs or patients. It is well known that appropriate ventilation strategy is the most effective way to control bacteria-carrying airborne particles responsible for SSI. In this research, the effect of the most dominant design parameter, namely inlet air velocity, on the ultra-clean ventilation (UVC) systems performance is evaluated in detail using the computational fluid dynamics (CFD). The results show an optimum value for the inlet air velocity which is mainly due to formation of a thermal plume over the wound tissue. This thermal plume protects the wound from contaminants deposition like a shield and may be disturbed at too high inlet air velocity. In addition, the effect of critical factors including the particle size the wound temperature, the operating lights boundary condition, and the existence of fixed and removable partitions on the optimum inlet air velocity is also investigated and discussed extensively.Sat, 27 Oct 2018 20:30:00 +0100A POMDP framework to find Optimal Policy in Sustainable Maintenance
http://scientiairanica.sharif.edu/article_21084_0.html
The increasing importance of these two subjects, maintenance and cleaner environment, beside the relations between them, encourages us to investigate a mathematical Markovian model for Condition Based Maintenance problem while considering environmental effects. In this paper, the problem of proposing maintenance optimal policy for a partially observable, stochastically deteriorating system is studied, in order to maximize the average profit of the system with consideration of sustainability aspects. The modeling of this Condition Based Sustainable Maintenance (CBSM) problem is done using mathematical methods such as Partially Observable Markov Decision Process (POMDP) and Bayesian theory. A new exact method named Accelerated Vector Pruning method and other popular estimating and exact methods are applied and compared in solving the presented CBSM model and several managerial conclusions were obtained.Sat, 27 Oct 2018 20:30:00 +0100On designing CUSUM charts using ratio-type estimators for monitoring the location of normal ...
http://scientiairanica.sharif.edu/article_21085_0.html
Control chart is one of the important tools in statistical process control (SPC) that plays a significant role in monitoring and identifying disturbances of any production process. The Shewhart, cumulative sum (CUSUM) and exponentially weighted moving average (EWMA) are commonly used control charts for detecting process shifts. CUSUM and EWMA chart are more sensitive in detecting smaller shifts whereas the typical Shewhart chart is known to be only sensitive to large process shifts. The present study incorporates ratio-type estimators based on auxiliary information in CUSUM structure as a substitute of simple mean estimator for monitoring process location. These estimators are more efficient than the simple mean estimator in the presence of high correlation between the study and the auxiliary variables. Average run length (ARL), standard deviation of run length (SDRL) and extra quadratic loss (EQL) are used to measure the performances of the proposed charts. The performance comparison of the proposed chart with the existing CUSUM, CUSUM-FIR and many other control charts are made by using out-of-control ARL. The comparison revealed the superiority of the suggested charts over the other existing charts. An illustrative example is also provided for the performance evaluation of the proposed charts.Sat, 27 Oct 2018 20:30:00 +0100Investigating the behavior factor of coupled concrete shear walls with steel coupling beam
http://scientiairanica.sharif.edu/article_21086_0.html
The behavior factor is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural properties. The more accurate this parameter is estimated, the more exact responses of the structures will be obtained. Recently, coupled walls with steel coupling beams are extensively utilized as an efficient system against lateral forces in high-rise buildings. But, there is not enough information about the behavior of these walls during earthquake, and design codes have not suggested any behavior factor for this structural system. Consequently, this paper is devoted to find the behavior factor of this structural system. To achieve this goal, six-, twelve- and twenty-story buildings are assessed. Except for the number of stories, all characteristics of these buildings are completely similar. Buidlings’ height, the length of the coupling beams and the coupling ratio are key parameters which influence the behavior factor of the aforesaid structural system. In this work, the effect of these parameters on this factor are studied.Sat, 27 Oct 2018 20:30:00 +0100Utilizing new spherical Hankel shape functions to reformulate the deflection, free vibration, ...
http://scientiairanica.sharif.edu/article_21087_0.html
In this study, a new class of shape functions, namely spherical Hankel shape functions, are derived and applied to reformulate the deflection, free vibration, and buckling of Mindlin plates based on finite element method (FEM). In this way, adding polynomial terms to the functional expansion, in which just spherical Hankel radial basis functions (RBFs) are used, leads to obtaining spherical Hankel shape functions. Accordingly, the employment of polynomial and spherical Bessel function fields together results in achieving more robustness and effectiveness. Spherical Hankel shape functions benefit from some useful properties, including infinite piecewise continuity, partition of unity, and Kronecker delta property. In the end, the accuracy of the proposed formulation is investigated through several numerical examples for which the same degrees of freedom are selected in both the presented formulation and the classical finite element method. Finally, it can be concluded that a higher accuracy is reachable by utilizing spherical Hankel shape functions in comparison with the Lagrangian FEM.Sat, 27 Oct 2018 20:30:00 +0100MCM-41-SO3H: as an efficient reusable Nano-ordered heterogeneous catalyst for the synthesis of ...
http://scientiairanica.sharif.edu/article_21088_0.html
An improved and efficient method for the synthesis of 1- & 5-substituted 1H-tetrazole derivatives has been described in the presence of nano-ordered MCM-41-SO3H as an effective heterogeneous catalyst. This metal-free protocol, [2+3] cycloaddition of sodium azide to various nitriles or ethyl N-phenyl formimidate intermediate under mild reaction conditions, afford a wide range of 1H-tetrazoles in good to excellent yields. The catalyst was reused for five times without significant loss of catalytic activity.Sat, 27 Oct 2018 20:30:00 +0100Application of Endurance Time Method in Seismic Analysis of Bridges
http://scientiairanica.sharif.edu/article_21089_0.html
In this paper, the application of Endurance Time method in seismic analysis of bridges is explained. The Endurance Time method is a novel seismic analysis method based on time history analysis in which a structure is subjected to a predefined intensifying acceleration function. First, six concrete bridges were modeled. Three Endurance Time acceleration functions were applied to the models and the average of the responses were calculated. Next, the time history analysis was conducted using seven real accelerograms scaled using the method recommended by FHWA 2006 to be compatible with the design spectrum of seismic AASHTO guideline for a site with soil type C in Berkeley, California. The average of the responses of these seven analyses is considered as reference. Scaling the mentioned accelerograms over a wide range of hazard levels, Incremental dynamic analysis is performed. Finally, the comparison of the response of ET and time history analysis and also comparison of ETA with IDA curves reveals good agreement. The major advantage of ET method over time history and IDA methods is less computational effort needed for the analysis. This saving in time is resulted due to the possibility of predicting response by fewer analyses despite maintaining the necessary accuracy.Sat, 27 Oct 2018 20:30:00 +0100Application of AG method and its improvement to nonlinear damped oscillators
http://scientiairanica.sharif.edu/article_21093_0.html
In this paper, a new and innovative semi analytical technique, namely Akbari-Ganji’s method (AGM), is employed for solving three nonlinear damped oscillatory systems. Applying this method to nonlinear problems is very simple because in solving process only a trial solution, the main differential equation and its derivatives are required. The analytical solutions obtained by the AGM are utilized to study the impact of amplitude on nonlinear frequency and damping ratio. It is found that the AGM leads to acceptable results for the problems considered in this paper. Also, in order to obtain a more accurate solution, instead of using a trial solution with higher-order terms which may result in complicated and time consuming mathematical calculations, the solution obtained by AGM is improved via variational iteration method (VIM). The usefulness and effectiveness of the approach is demonstrated through comparison of the obtained results with those achieved by the numerical method. Hence, the AGM can be applied to nonlinear problems consisting of significant nonlinear damping terms and, if necessary, can be easily improved. Sun, 28 Oct 2018 20:30:00 +0100Mixed-mode fracture parameters estimation by genetic programming
http://scientiairanica.sharif.edu/article_21094_0.html
The linear elastic fracture phenomenon has been characterized with stress intensity factors (SIFs). In this study a general function is obtained in order to predict the fracture parameters. Numerical calculation of the SIFs in a mixed-mode condition is a cumbersome task. In this research, more than 6800 numerical analyses using extended finite element method are conducted to simulate the fracture problem. States are considered for a plate with an arbitrary edge or center crack. Mixed mode SIFs were calculated using of interaction integral. Then, Gene Expression Programming (GEP) method is utilized to extraction of a function. Results show acceptable correlations between numerical calculations and genetic programming functions. R-square (R2) values are in a range of 0.91 to 0.96 that guarantees the accuracy of the inferred functions.Sun, 28 Oct 2018 20:30:00 +0100Iterative Method for Simultaneous Sparse Approximation
http://scientiairanica.sharif.edu/article_21095_0.html
This paper studies the problem of Simultaneous Sparse Approximation (SSA). This problem arises in many applications which work with multiple signals maintaining some degree of dependency such as radar and sensor networks. In this paper, we introduce a new method towards joint recovery of several independent sparse signals with the same support. We provide an analytical discussion on the convergence of our method called Simultaneous Iterative Method (SIM). Additionally, we compare our method with other group-sparse reconstruction techniques, i.e., Simultaneous Orthogonal Matching Pursuit (SOMP), and Block Iterative Method with Adaptive Thresholding (BIMAT) through numerical experiments. The simulation results demonstrate that SIM outperforms these algorithms in terms of the metrics Signal to Noise Ratio (SNR) and Success Rate (SR). Moreover, SIM is considerably less complicated than BIMAT, which makes it feasible for practical applications such as implementation in MIMO radar systems.Sun, 28 Oct 2018 20:30:00 +0100Design and Optimization of Tubular Linear Permanent Magnet Generator with Performance ...
http://scientiairanica.sharif.edu/article_21096_0.html
Linear generators are electric machines which generate electrical energy from linear movement. Since these machines can lift gear wheel or power train, they have begun to be used widely nowadays. Since their working areas differ according to speed and power characteristic, this study contains design and optimization of tubular linear generator for free piston practices. The design performed response surface optimization through design variables acquired as a result of sizing via interface. The association between the determined design variables and the sizes of generator output was examined. In addition, these sizes were used for objective functions of increasing efficiency, decreasing overall volume and increasing general performance and their optimum values were found by using Multi-Objective Genetic Algorithm. Initial and optimum design data were compared with Ansys Maxwell 2D. With overall performance increase, 22,78% decrease was seen in total mass, while 11,7% decrease was seen in cost. In addition, prototype linear generator was made in line with initial geometry data and it was applied with crank slider mechanism.Sun, 28 Oct 2018 20:30:00 +0100Pilot workload assessment under different levels of autopilot failure
http://scientiairanica.sharif.edu/article_21097_0.html
One of the most interesting topics in the field of human machine interaction is workload. In this paper, using information theory concepts, baud rates generated in all subsystems of a generic simulator of piloting tasks were calculated and then, a unique numerical index presenting an estimation of overall workload was extracted. To examine the effectiveness of offered criteria, three tests with different levels of autopilot failure were designed in which existing workload were labeled based on involving baud rates. A group of subjects performed these tests as the pilots while recording their own idea about perceived workload. Results confirmed that there were statistically significant differences between the averages of scores assigned by subjects to the overall workload for three levels of difficulty. Consequently, the proposed quantitative index is effective enough for determination of workload levels in the simulator environment and facilitates creation of needed scenario noticeably.Sun, 28 Oct 2018 20:30:00 +0100Modelling, Control and Simulation of a SCARA PRR-Type Robot Manipulator
http://scientiairanica.sharif.edu/article_21098_0.html
In this study, a SCARA PRR-type robot manipulator is designed and implemented. Firstly, the SCARA robot was designed according to the mechanical calculations. Then, forward and inverse kinematic equations of the robot are derived by using D-H parameters and analytical methods. The software is developed according to obtain cartesian velocities from joint velocities and joint velocities from cartesian velocities. The trajectory planning is designed using the calculated kinematic equations and the simulation is performed in MATLAB VRML environment. A stepping motor is used for prismatic joint of the robot, and servo motors are used for revolute joints. While most of the SCARA robot studies focus on RRP-type servo control strategy, this work focuses PRR-type and both stepper and servo control structures. The objects in the desired points of the workspace are picked and placed to another desired point synchronously with the simulation. So the performance of the robot is examined experimentally.Sun, 28 Oct 2018 20:30:00 +0100Comparative Study on Damage Behaviour of Synthetic and Natural Fiber Reinforced Brittle ...
http://scientiairanica.sharif.edu/article_21099_0.html
In the present study, comparative study on the damage behaviour of Glass-Epoxy (GE), Jute-Epoxy (JE) laminates with [0/90]s orientation and Jute-Rubber-Jute (JRJ) sandwich is carried out using ABAQUS/CAE finite element software. The GE, JE laminate and JRJ sandwich with thickness of 2 mm is impacted by a hemispherical shaped impactor at a velocity of 2.5 m/s. The mechanisms in which the brittle laminate gets damaged are analyzed using Hashin’s 2D failure criteria and flexible composites are analysed by ductile damage mechanism. The energy absorbed and the incipient point of each laminate was compared. It was observed from the results that there is no evidence of delamination in JRJ as opposed to GE and JE. The compliant nature of rubber contributes in absorbing more energy and it is slightly higher than GE. Also it was observed that there is no incipient point in JRJ sandwich which means there is no cracking of matrix since rubber is elastic material. Thus the JRJ material can be a better substitute for GE laminate in low velocity applications. The procedure proposed for the analysis in the present study can serve as benchmark method in modelling the impact behaviour of composite structures in further investigations.Sun, 28 Oct 2018 20:30:00 +0100The Acceptance of Online Social Networks as a Technology-Based Education Tools among Higher ...
http://scientiairanica.sharif.edu/article_21100_0.html
Educational institutes are adopting Online Social Networks (OSNs) to facilitate learning activities in university campuses. However, before implementation a new technology there is need to identify and measure the factors that influence users' acceptance of the new technology. This will aid to critically predict the success or failure of the new technology that is to be adopted. Therefore, this study aims to identify the factors that influence student’s acceptance of online social networks as learning tool. Besides, a research model is developed based on the identified factors grounded on Technology Acceptance Model (TAM). In addition, Structural Equation Model (SEM) was employed to validate the developed model hypotheses based data collected by employing online survey from 537 students in University Malaysia Pahang (UMP). Furthermore, findings from this study have significant implications and considerable value for higher educational institutes to devise better strategies for adoption of OSNs' as a learning tool.Sun, 28 Oct 2018 20:30:00 +0100The stage shop scheduling problem: lower bound and metaheuristic
http://scientiairanica.sharif.edu/article_21119_0.html
Remarkable efforts are made to develop the job shop scheduling problem up to now. As a novel generalization, the stage shop can be defined as an environment, in which each job is composed of some stages and each stage may include one operation or more. A stage can be defined a subset of operations of a job, such that these operations can be done in any arbitrary relative order while the stages should be processed in a predetermined order. In other words, the operations of a stage cannot be initiated until all operations of the prior stage are completed. In this paper, an innovative lower bound based on solving the preemptive open shop (using a linear programming model in polynomial time) is devised for the makespan in a stage shop problem. In addition, three metaheuristics, including firefly, harmony search and water wave optimization algorithms are applied to the problem. The results of the algorithms are compared with each other, the proposed lower bound, and a commercial solver.Fri, 02 Nov 2018 20:30:00 +0100Studying buckling of composite rods made of hybrid carbon fiber/carbon nanotube reinforced ...
http://scientiairanica.sharif.edu/article_21120_0.html
In this paper, the buckling behavior of rods made of carbon fiber/carbon nanotube-reinforced polyimide (CF/CNT-RP) under the action of axial load is investigated based on a multiscale finite element method. A dual-step procedure is first adopted to couple the influences of micro- and nano-scale in order to obtain the equivalent elastic properties of CF/CNT-RP for various volume fractions of CF and CNT. The interphase effect between CNTs and the polymer matrix is taken into consideration. Also, dispersion of CF/CNT into the polymer matrix is assumed to be random. Then, rods with square and circular cross sections are considered whose stability characteristics are analyzed. The finite element modeling is performed using two models including a 3D brick model and a 2D beam model. Selected numerical results are given to study the effects of volume fraction of CNT/CF, interphase and geometrical properties on the axial buckling response of multiscale composite rods.Fri, 02 Nov 2018 20:30:00 +0100Inventory model optimization revisited: Understanding service inventories to improve performance
http://scientiairanica.sharif.edu/article_21121_0.html
Services are increasingly important in the modern economy, for both service and manufacturing firms, yet inventory literature has been focused mainly on physical goods and, only a few studies have included services in optimization. On the other side, traditional service management literature relies on an extremely narrow definition of inventory that excludes services, because they are perishable. Thus, there is a lack of research in the link between inventory optimization and service management. However, according to a new service inventory approach, businesses components such as tasks or information, as different from physical goods, can be performed and stored in anticipation of service demand as a form of service inventory—that is, inventorying by anticipation rather than delaying the service. This article aims to contribute to this lack of research by proposing a service inventory optimization model that integrates a service orientation to optimize tasks and information to be performed in advance. In contrast with traditional inventory models, where the objective is to optimize physical items, in this approach physical products whenever included, constitute only mechanisms for service provision. This service inventory model contributes to optimize the quantity of tasks or information to be anticipated and thus provides benefits for customers.Fri, 02 Nov 2018 20:30:00 +0100Solution of Fractional Order Riccati Differential Equations Using Euler Wavelet Method
http://scientiairanica.sharif.edu/article_21122_0.html
The fractional-order differential equations (FDEs) have the ability to model the real-life phenomena better in a variety of applied mathematics, engineering disciplines including diffusive transport, electrical networks, electromagnetic theory, probability and so forth. In most cases, there are no analytical solutions therefore a variety of numerical methods have been developed for the solution of the FDEs. In this paper, we derive the numerical solutions of the various fractional-order Riccati type differential equations using the Euler Wavelet Method (EWM). The Euler wavelet operational matrix method converts the fractional differential equations to a system of algebraic equations. Illustrative examples are included to demonstrate the validity and efficiency of the technique.Fri, 02 Nov 2018 20:30:00 +0100Damage detection in frame structures using noisy accelerometers and Damage Load Vectors (DLV)
http://scientiairanica.sharif.edu/article_21123_0.html
In the area of damage detection, there have been many notable methods introduced in the past years. Damage Load Vectors (DLV) is among the most powerful methods, which computes a set of load vectors from variations in flexibility matrices of a frame in the undamaged and damaged conditions. These flexibility matrices are derived from acceleration responses of the frame which can be captured using accelerometers. The DLV method then scrutinizes this shift among the flexibility matrices, which ultimately enables locating the damaged member(s). This study holistically conducted seven experimental tests, with seven damage scenarios of a test frame installed on a semi-harmonic shaking table. The DLV method was subsequently employed to locate the damaged members using recorded frame vibration data obtained from ‘noisy’ accelerometers positioned on the frame at eight predefined locations. The Eigen Realization Algorithm (ERA) alongside Pandy’s recommendations were adapted herein to facilitate generation of accurate flexibility matrices derived from the noisy accelerometers. The outcome is very encouraging with accurate identification of damaged members in all seven damage scenarios without any ‘positive-false’ and ‘negative-false’ findings. Additionally, there is a decrease (from 0.045 to 0.289) in the accuracy of WSI index when the number of damaged members is increased.Sat, 03 Nov 2018 20:30:00 +0100Mathematical models and an elephant herding optimization for multiprocessor-task flexible flow ...
http://scientiairanica.sharif.edu/article_21125_0.html
Shop floor control (SFC) is one of the main concepts in manufacturing resource planning (MRPII) and production scheduling is a key element in SFC. This paper studies the hybrid flow shop scheduling problem where jobs are multiprocessor. The objective is to minimize total completion time. Although there are several papers considering hybrid flow-shop scheduling problem with multiprocessor tasks, but none propose a mathematical model for this problem. At first, the two problems (fixed and selective cases) are mathematically formulated by mixed integer linear programming models. Using commercial software, the model is used to solve the small instances of the problems. Moreover, an elephant herding optimization is developed to solve large instances of the problems. To numerically evaluate the proposed algorithm, it is compared with two available algorithms in the literature, simulated annealing and shuffled frog-leaping algorithm in the literature.Sun, 04 Nov 2018 20:30:00 +0100Optimal Objective Function in Simulating Endurance Time Excitations
http://scientiairanica.sharif.edu/article_21127_0.html
Endurance Time (ET) method is a dynamic analysis procedure in which increasing excitations are imposed on structures; these excitations are known as Endurance Time excitation functions (ETEF). This study presents a method to find the optimal objective function for simulating ETEFs which unconstrained optimization problems are. In optimization problems, equations are defined in term of an objective function. In the problem of simulating ETEFs, the objective function can be defined in many different ways regarding considered intensity measures and respective weighting factors. In addition, the type of calculating residuals (absolute way or relative way) diversifies objective function definitions. The proposed method for determining optimal objective function includes quantifying the accuracy of ETEFs in a scalar quantity regardless of their objective functions and introducing an approach to overcome the dependence of results on initial points of optimizations. The proposed method is applied and results are then presented. It is observed that considering only acceleration spectra and calculating residuals in the relative way creates more accurate ETEFs.Sat, 10 Nov 2018 20:30:00 +0100Economic evaluation of energy-efficient engineering systems
http://scientiairanica.sharif.edu/article_21128_0.html
The paper shows the aspects of introducing energy-efficient equipment for engineering systems within the context of productivity enhancement in general. The author as research relevance brings a thesis that each of production members reach after implementing possibility for increasing general effectiveness of business operation. The paper reveals the issues of factor and expert assessments for introducing innovations at the enterprise and economic evaluation of the place of energy-efficient technologies in the general medium of production enterprise modernization. The novelty of the study is an aspect that under conditions of energy products’ cost increase and significant energy intensity of present-day production, the issue of energy conservation and choice of priorities of investment into the project of energy efficiency increase at enterprises is a major concern. Reduction of production cost is one of the most important ways of effective competition and increasing of productiveness of an enterprise in the modern conditions. The authors offer to evaluate the process of energy conservation in a complex way, taking into account all investment consequences: economic, technical, ecological, organizational, commercial, and others. The prospect areas of research: cost-to-use analysis from the introduction of personally developed systems of energy conservation.Sat, 10 Nov 2018 20:30:00 +0100