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Amirkabir University of Technology , formerly called the Tehran Polytechnic, is a public research university located in Tehran, Iran. AUT is one of the most prestigious universities, and the first established technical university in Iran, referred to as "Mother of Industrial Universities".The university was first founded by Habib Nafisi in 1958 and then developed by Dr. Mohammad Ali Mojtahedi, during the reign of the Pahlavi dynasty. Originally named the Tehran Polytechnic, it began its activities with five engineering departments. Six months before the victory of 1979 Iranian Revolution, Tehran Polytechnic was renamed after the famed Iranian prime minister Amir Kabir . With its expansion, the university now boasts fifteen science and engineering departments, and two other affiliated centers, located in Bandar Abbas and Mahshahr. There are currently around 9,100 students enrolled in the undergraduate and graduate programs. AUT has 480 full-time academic faculty members and 550 administrative employees. This gives AUT the highest staff-to-student ratio among the country's universities. The executive branch consists of four departments which receive active participation from various councils in planning and administering affairs.AUT has signed mutual agreements with international universities for research and educational collaboration. There is a joint program between AUT and the University of Birmingham.AUT is one of the leading universities in E-Learning systems in Iran which has begun its activities in 2004.Amirkabir University is the pioneer of sustainable development in Iran and established the AUT's Office of Sustainability on July 2011. The activities of the Office of Sustainability contribute to AUT's campus by reducing energy consumption, costs, and emissions, and also student coursework, volunteer opportunities for students, as well as research and education academic activities on sustainable development. Wikipedia.


Anani Y.,Sharif University of Technology | Alizadeh Y.,Amirkabir University of Technology
Materials and Design | Year: 2011

This paper proposes a new visco-hyperelastic constitutive law for modeling the finite-deformation strain rate-dependent behavior of foams as compressible elastomers. The proposed model is based on a phenomenological Zener model, which consists of a hyperelastic equilibrium spring and a Maxwell element parallel to it. The hyperelastic equilibrium spring describes the steady state response. The Maxwell element, which captures the rate-dependency behavior, consists of a nonlinear viscous damper connected in series to a hyperelastic intermediate spring. The nonlinear damper controls the rate-dependency of the Maxwell element. Some strain energy potential functions are proposed for the two hyperelastic springs. compressibility effect in strain energy is described by entering the third invariant of deformation gradient tensor into strain energy functions. A history integral method has been used to develop a constitutive equation for modeling the behavior of the foams. The applied history integral method is based on the Kaye-BKZ theory. The material constant parameters, appeared in the formulation, have been determined with the aid of available uniaxial tensile experimental tests for a specific material. © 2010 Elsevier Ltd. Source


Mozaffari A.,Babol Noshirvani University of Technology | Gorji-Bandpy M.,Babol Noshirvani University of Technology | Samadian P.,Product Control Section | Rastgar R.,Amirkabir University of Technology | Rezania Kolaei A.,University of Aalborg
Swarm and Evolutionary Computation | Year: 2013

Optimizing and controlling of complex engineering systems is a phenomenon that has attracted an incremental interest of numerous scientists. Until now, a variety of intelligent optimizing and controlling techniques such as neural networks, fuzzy logic, game theory, support vector machines and stochastic algorithms were proposed to facilitate controlling of the engineering systems. In this study, an extended version of mutable smart bee algorithm (MSBA) called Pareto based mutable smart bee (PBMSB) is inspired to cope with multi-objective problems. Besides, a set of benchmark problems and four well-known Pareto based optimizing algorithms i.e. multi-objective bee algorithm (MOBA), multi-objective particle swarm optimization (MOPSO) algorithm, non-dominated sorting genetic algorithm (NSGA-II), and strength Pareto evolutionary algorithm (SPEA 2) are utilized to confirm the acceptable performance of the proposed method. In order to find the maximum exploration potentials, these techniques are equipped with an external archive. These archives aid the methods to record all of the non-dominated solutions. Eventually, the proposed method and generalized regression neural network (GRNN) are simultaneously used to optimize the major parameters of an irreversible thermal engine. In order to direct the PBMSB to explore deliberate spaces within the solution domain, a reference point obtained from finite time thermodynamic (FTT) approach, is utilized in the optimization. The outcome results show the acceptable performance of the proposed method to optimize complex real-life engineering systems. © 2012 Elsevier B.V. All rights reserved. Source


Jamshidi M.,Building Research Institute, Egypt | Ramezanianpour A.A.,Amirkabir University of Technology
Construction and Building Materials | Year: 2011

Asbestos fibers have been used in cement based materials to improve tensile strength and controlling crack formation and propagation. Asbestos-cement sheets are produced by the Hatschek technique in a number of developing countries. Due to the health and safety issues in the asbestos products, attempts have been made to substitute other fibers using the Hatschek system for cement sheets. The quality and homogeneity of the products depend on the type of fibers and varies substantially in the Hatschek system during production. In this investigation acrylic and glass fibers in separate and hybrid forms were used for manufacture of flat and corrugated sheets. Higher strength and ductility were obtained for the sheets containing glass fibers. Performance was even better when hybrid system of acrylic and glass fibers was used. The hybrid system was used for production of fiber-cement sheets in factory. This system is proposed as an appropriate alternative for substituting asbestos in the Hatschek process. © 2010 Elsevier Ltd. All rights reserved. Source


Nekoubin N.,Amirkabir University of Technology
International Journal of Thermal Sciences | Year: 2016

In this study, the conjugate conduction-convection heat transfer in the thermally developing region of a parallel plate microchannel with the constant heat flux at the walls is investigated. The flow is forced to move by applying the pressure difference and is assumed to be fully developed. Moreover, the effects of electrical double layer (EDL) with low zeta potential on the fluid flow and on the temperature field are taken into account. To do so, an analytical/numerical method is proposed to solve the energy equation in a single domain formulation. The energy equation is split and a series solution based on the variational calculus is employed to determine the temperature field. The effects of various parameters such as Peclet number, non-dimensional wall thickness, thermal conductivity ratio, and the zeta potential are studied in details. The obtained results show that the increasing of zeta potential decreases the heat transfer rate. Moreover, the Nusselt number has a non-monotonic behavior when the wall thickness varies. © 2016 Elsevier Masson SAS Source


Rahimian M.,Islamic Azad University at Semnan | Parvin N.,Amirkabir University of Technology | Ehsani N.,Malek-Ashtar University of Technology
Materials and Design | Year: 2011

Aluminum matrix composite is one of the most conventional types of metal matrix composites. This paper deals with the effect of production parameters on wear resistance of Al-Al2O3 composites. Alumina powder with a particle size of 12, 3 and 48μ and pure aluminum powder with particle size of 30μ were used. The amount of added alumina powder was up to 20%. Ball milling was utilized to blend the powders. The range of sintering temperature and time were 500, 550 and 600°C and 30, 45, 60 and 90min respectively. It was found that increasing sintering temperature results in increasing density, hardness and wear resistance and homogenization of the microstructure. However at certain sintering temperatures and time, considerable grain growth and reduction of hardness value occurred, leading to the degradation of wear resistance. The results showed that at high alumina content, relative density of the composite increases. However, after raising the particle size of alumina, relative density initially increases and then drops to lower values. Increasing weight percent of alumina powder leads to higher hardness and consequently improves the wear resistance of Al-Al2O3 composite. The use of fine alumina particles has a similar effect on hardness and the wear resistance. Finally, a finer grain size was observed, at high amount and low size of the reinforcement particle. © 2010 Elsevier Ltd. Source


Saadatmandi A.,University of Kashan | Dehghan M.,Amirkabir University of Technology
JVC/Journal of Vibration and Control | Year: 2011

A numerical method for solving the linear and non-linear fractional integro-differential equations of Volterra type is presented. The fractional derivative is described in the Caputo sense. The method is based upon Legendre approximations. The properties of Legendre polynomials together with the Gaussian integration method are utilized to reduce the fractional integro-differential equations to the solution of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the presented technique and a comparison is made with existing results. © The Author(s) 2011 Reprints and permissions. Source


Pouranvari M.,Islamic Azad University at Dezful | Marashi S.P.H.,Amirkabir University of Technology
Science and Technology of Welding and Joining | Year: 2011

One of the most important issues in resistance spot welding of three-sheet stack joints is the insufficient growth of the weld nugget, which may cause problems in places needing larger weld nuggets (i.e. sheet/sheet interface). In this paper, the effect of sheet thickness on the pattern of weld nugget development during resistance spot welding of three-steel sheets of equal thickness is studied. Results showed that there is a critical sheet thickness of 1.5 mm at which the fusion zone size at the sheet/sheet interface is nearly equal to the fusion zone size at the geometrical centre of the joint. Increasing the sheet thickness beyond the critical size causes a shift in the location of weld nugget formation from the geometrical centre to the sheet/sheet interfaces. Below the critical sheet thickness, the weld nugget growth in the geometrical centre of the joint is higher than that in the sheet/sheet interface. © 2011 Institute of Materials, Minerals and Mining. Source


Behnam B.,Amirkabir University of Technology
Structural Design of Tall and Special Buildings | Year: 2016

Post-earthquake fires (PEF) may result in a catastrophe in urban regions even worse than the earthquake itself. Most urban structures are not designed to resist two subsequent extreme loads such as earthquake and fire. Thus, these types of structures are too weak when subjected to the PEF loads. On the other hand, it is well understood that irregular building structures are more susceptible to sustain earthquake damage than regular buildings. Investigating irregular buildings can therefore be more important when there is a high possibility of PEF. While there are various irregularities, here, vertical irregularity is considered. The study is performed on one irregular seven-story tall moment-resisting steel frame designed based on the American Society of Civil Engineers code. The frame is firstly subjected to an earthquake load with the peak ground acceleration of 0.35 g and then is exposed to a generalized exponential fire curve. To make a comparison between the results, the PEF analysis is also performed for the regular frame. The results show that there is a marked difference between the PEF of the regular frame with that of the irregular frame. In addition, two types of failure—local and global—were observed during the analysis, where the local collapse is related to the deflection of beams, and the global collapse is pertained to the considerable movement of the columns. It is observed during the analysis that the irregular frames are more susceptible to collapse globally. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd. Source


Pouranvari M.,Islamic Azad University at Dezful | Marashi S.P.H.,Amirkabir University of Technology
Materials Science and Engineering A | Year: 2011

Failure mode of resistance spot welds is a qualitative indicator of weld performance. Two major types of spot weld failure are pull-out and interfacial fracture. Interfacial failure, which typically results in reduced energy absorption capability, is considered unsatisfactory and industry standards are often designed to avoid this occurrence. Advanced High Strength Steel (AHSS) spot welds exhibit high tendency to fail in interfacial failure mode. Sizing of spot welds based on the conventional recommendation of 4t0.5 (t is sheet thickness) does not guarantee the pullout failure mode in many cases of AHSS spot welds. Therefore, a new weld quality criterion should be found for AHSS resistance spot welds to guarantee pull-out failure. The aim of this paper is to investigate and analyze the transition between interfacial and pull-out failure modes in AHSS resistance spot welds during the tensile-shear test by the use of analytical approach. In this work, in the light of failure mechanism, a simple analytical model is presented for estimating the critical fusion zone size to prevent interfacial fracture. According to this model, the hardness ratio of fusion zone to pull-out failure location and the volume fraction of voids in fusion zone are the key metallurgical factors governing type of failure mode of AHSS spot welds during the tensile-shear test. Low hardness ratio and high susceptibility to form shrinkage voids in the case of AHSS spot welds appear to be the two primary causes for their high tendency to fail in interfacial mode. © 2011 Elsevier B.V. Source


Ahmadlou M.,Amirkabir University of Technology | Ahmadlou M.,Dynamic Brain Research Office | Adeli H.,Ohio State University | Adeli A.,Ohio State University
International Journal of Psychophysiology | Year: 2012

EEGs of the frontal brain of patients diagnosed with major depressive disorder (MDD) have been investigated in recent years using linear methods but not based on nonlinear methods. This paper presents an investigation of the frontal brain of MDD patients using the wavelet-chaos methodology and Katz's and Higuchi's fractal dimensions (KFD and HFD) as measures of nonlinearity and complexity. EEGs of the frontal brain of healthy adults and MDD patients are decomposed into 5 EEG sub-bands employing a wavelet filter bank, and the FDs of the band-limited as well as those of their 5 sub-bands are computed. Then, using the ANOVA statistical test, HFDs and KFDs of the left and right frontal lobes in EEG full-band and sub-bands of MDD and healthy groups are compared in order to discover the FDs showing the most meaningful differences between the two groups. Finally, the discovered FDs are used as input to a classifier, enhanced probabilistic neural network (EPNN), to discriminate the MDD from healthy EEGs. The results of HFD show higher complexity of left, right and overall frontal lobes of the brain of MDD compared with non-MDD in beta and gamma sub-bands. Moreover, it is observed that HFD of the beta band is more discriminative than HFD of the gamma band for discriminating MDD and non-MDD participants, while the KFD did not show any meaningful difference. A high accuracy of 91.3% is achieved for classification of MDD and non-MDD EEGs based on HFDs of left, right, and overall frontal brain beta sub-band. The findings of this research, however, should be considered tentative because of limited data available to the authors. © 2012 Elsevier B.V. Source


Dilamian M.,Islamic Azad University at South Tehran | Montazer M.,Amirkabir University of Technology | Masoumi J.,Shahid Beheshti University
Carbohydrate Polymers | Year: 2013

Here, antimicrobial nanofibrous membranes were produced by electrospinning of chitosan/poly(ethylene oxide) (PEO) solution in the presence of poly(hexamethylene biguanide) hydrochloride (PHMB). The influence of PHMB on the electrospinnability and antimicrobial properties of chitosan/PEO nanofibers were studied. Further, viscosity of the solutions as well as morphology of the nanofibrous structures were investigated. Results revealed that incorporation of PHMB in chitosan/PEO solutions led to decrease in the zero-shear rate viscosity up to 20%. Moreover, increasing PHMB from 0.5 mM to 1 mM led to formation of thinner fibers with diameters ranging from 240 nm to 60 nm, respectively. Fourier transform infrared (FT-IR) spectrums indicated the functional groups of chitosan, PEO and PHMB in nanofibrous structure. Differential scanning calorimetry (DSC) thermograms indicated interaction of PHMB with PEO and chitosan through alteration in the thermal behavior of the nanofibers. Inhibition of the bacteria growth for both Escherichia coli and Staphylococcus aureus were achieved on the PHMB loaded nanofibers. Also, a burst release of PHMB from mats has been observed in the first hour. These findings suggest that there is a great potential in fabrication of biomaterials with incorporation of PHMB using electrospinning. © 2013 Elsevier Ltd. All rights reserved. Source


Kowsari E.,Amirkabir University of Technology
Journal of Nanoparticle Research | Year: 2011

Nanosheet-based microspheres of ZnO with hierarchical structures, hollow prism, and coralline-like ZnO nanostructures were successfully prepared by ultrasonic irradiation in acidic ionic liquids (AILs). The hollow spherical is made up of many thin petals, the thickness of which is only about 90 nm. In the presence of AIL2, the one prepared at a frequency of 40 kHz is a mixture of nanofibers with diameters ranging from less than 30 nm to about 100 nm. ZnO nanostructure (with AIL1) reveals lozenge-shape hollow prism structures. The products were hollow prism structure covered with some nanometric-size nanoparticles. The average size of the nanoparticles is in the range of 40-80 nm. It is found that the ultrasonic irradiation time, ultrasonic frequency, and the AILs influence the growth mechanism and optical properties of ZnO nanostructures. Producing Zno nanostructures by different traditional methods (e.g., hydrothermal method) requires basic media. These methods are not economical and environmentally friendly in many industrial processes. In so doing, a critical problem has been the point that, normally, a high concentration of base causes reactor metal corrosion. This is a simple and low-cost method, which can be expected to be applied in industry in the future. Also, importantly, the structures synthesized in this experiment can indicate a new way to construct nanodevices by self-organization in one step. © 2011 Springer Science+Business Media B.V. Source


Hosseinabadi Farahani M.,University of Tehran | Hosseini L.,Amirkabir University of Technology
International Journal of Advanced Manufacturing Technology | Year: 2013

This paper considers the single machine scheduling problem with a new version of time-dependent processing times. The processing time of a job is defined as a piecewise linear function of its start time. It is preferred that the processing of each job be started at a specific time which means that processing the job before or after that time implies additional effort to accomplish the job. The job-processing time is a nonmonotonic function of its start time. The increasing rate of processing times is job independent and the objective is to minimize the cycle time. We show that the optimal schedule is V shaped and propose an optimal polynomial time algorithm for the problem. © 2012 Springer-Verlag London Limited. Source


Jalal M.,Amirkabir University of Technology | Fathi M.,Razi University | Farzad M.,Islamic Azad University at Shahrood
Mechanics of Materials | Year: 2013

In the present study, strength enhancement and durability-related characteristics along with rheological, thermal and microstructural properties of high strength self compacting concrete (HSSCC) containing nano TiO 2 and industrial waste ash namely as fly ash (FA) have been investigated. With this respect, Portland cement was replaced by up to 15 wt% waste ash and up to 5 wt% TiO2 nanoparticles and the properties of HSSCC specimens were measured. It was found that with the aim of energy saving and recycling of waste materials, addition of FA as a natural pozzolan can improve the rheological, mechanical and durability properties of concrete at higher ages. TiO2 nanoparticles as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence improve the microstructure of concrete leading to improved durability-related properties and strength enhancement of the concrete. Several empirical relationships for predicting flexural and split tensile strength of concrete based on compressive strength for HSSCC containing FA and nano TiO2 at different ages have been obtained. Finally, an energy-based assessment of strength enhancement of nano-containing concrete has been presented. © 2013 Elsevier Ltd. All rights reserved. Source


Barati E.,Malek-Ashtar University of Technology | Alizadeh Y.,Amirkabir University of Technology
Fatigue and Fracture of Engineering Materials and Structures | Year: 2011

The main purpose of the paper is to propose a numerical method for evaluation of J-integral in plates made of functionally graded materials (FGM) with sharp and blunt V-notches under Mode I loading. The material properties have been assumed to be varied exponentially along the specimen width (notch direction). Using the proposed method, the effect of material gradient on the J-integral for two cases of sharp and blunt V-notches has been studied. The results have shown that in FGMs with sharp V-notches, the J-integral is not proportional to. So, the parameter J L is path dependent. It has been observed that the material gradient has larger effect on the J-integral in sharp V-notch compared with that in blunt V-notch. © 2011 Blackwell Publishing Ltd. Source


Zare Y.,Amirkabir University of Technology
Waste Management | Year: 2013

Currently, the growing consumption of polymer products creates the large quantities of waste materials resulting in public concern in the environment and people life. Nanotechnology is assumed the important technology in the current century. Recently, many researchers have tried to develop this new science for polymer recycling. In this article, the application of different nanofillers in the recycled polymers such as PET, PP, HDPE, PVC, etc. and the attributed composites and blends is studied. The morphological, mechanical, rheological and thermal properties of prepared nanocomposites as well as the future challenges are extensively discussed. The present article determines the current status of nanotechnology in the polymer recycling which guide the future studies in this attractive field. © 2012 Elsevier Ltd. Source


Eslahchi M.R.,Tarbiat Modares University | Dehghan M.,Amirkabir University of Technology
Computers and Mathematics with Applications | Year: 2011

In this research first we explicitly obtain the relation between the coefficients of the Taylor series and Jacobi polynomial expansions. Then we present a new method for computing classical operational matrices (derivative, integral and product) for general Jacobi orthogonal functions (polynomial and rational). This method can be used for many classes of orthogonal functions. © 2011 Elsevier Ltd. All rights reserved. Source


Kowsari E.,Amirkabir University of Technology | Faraghi G.,Malek-Ashtar University of Technology
Materials Research Bulletin | Year: 2010

Flower-like Y2O3 nano-/microstructured phosphors without metal activators have successfully been fabricated by an ionic liquid (IL)-assisted method involving temperature (600 8C) annealing. In this paper, the effect of IL concentration on themorphology of the product has been investigated. The IL plays a crucial role in the formation of various morphologies of Y2O3. The structural and morphological features of the obtained samples have been characterized by means of X-ray powder diffraction (XRD) analysis, photoluminescence spectra (PL), Fourier-transform infrared (FT-IR) spectra and X-ray photoelectron spectra (XPS). The photoluminescence spectra of the products exhibit an intense bluish-white emission (ranging from 405 to 430 nm and centered at 418 nm). The luminescent mechanisms have been ascribed to the carbon impurities in the Y 2O3 host. The effect of the ILs cation and the counter anions on the Y2O3 morphology of these nanostructures was studied experimentally. It was observed that Y2O3 morphology and PL of these nanostructures were strongly influenced by the type of cation and anion. As the length of the subsidiary chain of cation section of IL (imidaziole ione) reduces, the thickness of the nano-sheets increases. It is expected that the present method may easily be extended to similar nano-/microstructures of other oxide materials. Such investigations are currently underway. © 2010 Elsevier Ltd. All rights reserved. Source


Raiesdana S.,Islamic Azad University at Qazvin | Goplayegani S.M.H.,Amirkabir University of Technology
Neurocomputing | Year: 2013

This paper explores a computational dynamic solution for epileptic seizure control. A neuronal model of epileptiform activity which is driving to periodicity, simulating seizures, is chaotified via two chaos anti-control algorithms. Anti-control of some in vivo measurements is also put to test. The perspective is that in an epileptic disorder, a transition of the state of the neuronal system from being chaotic to being patho-physiologically periodic can cause this dynamical disorder. The aim is to retrieve the chaotic state which was running before the seizure start. Based on identifying loss regions for period orbits in the state space, the first control method acts by avoiding the system trajectories entrance into the defined loss regions. On the other hand, the second method, based on intra-attractor (orbit) control concept, is an attempt to steer trajectories to the unstable manifold of a target unstable period orbit solution embedded within the system dynamic. The presented anti-control methods make use of a novel strategy to model chaotic time series' return map with radial basis function to improve the estimation of the dynamics under investigation. Our results show that both methods are successful in driving the model's dynamical activity away from the periodic direction while the second one seems to be faster and more efficient. Moreover, testing both methods on some hippocampal recordings of epileptized rats yields fairly acceptable results in dynamic modulation. This opens ways for further online experimental stimulations based on chaos concept. © 2013 Elsevier B.V. Source


Naderi B.,Amirkabir University of Technology | Ruiz R.,Polytechnic University of Valencia | Zandieh M.,Shahid Beheshti University
Computers and Operations Research | Year: 2010

This paper deals with a realistic variant of flowshop scheduling, namely the hybrid flexible flowshop. A hybrid flowshop mixes the characteristics of regular flowshops and parallel machine problems by considering stages with parallel machines instead of having one single machine per stage. We also investigate the flexible version where stage skipping might occur, i.e., not all stages must be visited by all jobs. Lastly, we also consider job sequence dependent setup times per stage. The optimization criterion considered is makespan minimization. While many approaches for hybrid flowshops have been proposed, hybrid flexible flowshops have been rarely studied. The situation is even worse with the addition of sequence dependent setups. In this study, we propose two advanced algorithms that specifically deal with the flexible and setup characteristics of this problem. The first algorithm is a dynamic dispatching rule heuristic, and the second is an iterated local search metaheuristic. The proposed algorithms are evaluated by comparison against seven other high performing existing algorithms. The statistically sound results support the idea that the proposed algorithms are very competitive for the studied problem. © 2009 Elsevier Ltd. All rights reserved. Source


Hosseinzadeh A.,Amirkabir University of Technology | Reza A.M.,University of Wisconsin - Milwaukee
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2012

A classifier combining strategy, virtual voting by random projection (VVRP), is presented. VVRP takes advantage from the bounded distortion incurred by random projection in order to improve accuracies of stable classifiers like discriminant analysis (DA) where existing classifier combining strategies are known to be failed. It uses the distortion to virtually generate different training sets from the total available training samples in a way that does not have the potential for overfitting. Then, a majority voting combines the base learners trained on these versions of the original problem. VVRP is very simple and just needs determining a proper dimensionality for the versions, an often very easy task. It is shown to be stable in a very large region of the hyperplane constructed by the dimensionality and the number of the versions. VVRP improves the best state-of-the-art DA algorithms in both small and large sample size problems in various classification fields. © 2012 IEEE. Source


Miandoabchi E.,Institute for Trade Studies and Research | Daneshzand F.,Amirkabir University of Technology | Szeto W.Y.,University of Hong Kong | Zanjirani Farahani R.,Kingston University
Computers and Operations Research | Year: 2013

This paper addresses the problem of designing urban road networks in a multi-objective decision making framework. Given a base network with only two-way links, and the candidate lane addition and link construction projects, the problem is to find the optimal combination of one-way and two-way links, the optimal selection of network capacity expansion projects, and the optimal lane allocations on two-way links to optimize the reserve capacity of the network, and two new travel time related performance measures. The problem is considered in two variations; in the first scenario, two-way links may have different numbers of lanes in each direction and in the second scenario, two-way links must have equal number of lanes in each direction. The proposed variations are formulated as mixed-integer programming problems with equilibrium constraints. A hybrid genetic algorithm, an evolutionary simulated annealing, and a hybrid artificial bee colony algorithm are proposed to solve these two new problems. A new measure is also proposed to evaluate the effectiveness of the three algorithms. Computational results for both problems are presented. © 2013 Elsevier Ltd. Source


Yazdchi K.,University of Twente | Salehi M.,Amirkabir University of Technology
Composites Part A: Applied Science and Manufacturing | Year: 2011

Based on the new simplified 3D Representative Volume Element (RVE) for a wavy carbon nanotube (CNT), an analytical model has been developed to study the stress transfer in single-walled carbon nanotube (SWCNT) reinforced polymer composites. The model is capable of predicting axial as well as interfacial shear stresses along a wavy CNT embedded in a matrix. Based on the pullout modeling technique, the effects of waviness, aspect ratio, CNT diameter, volume fraction, Poisson's ratio and matrix modulus on axial and interfacial shear stresses have also been analyzed in details. The results of the analytical model are in good agreements when compared with the corresponding results for straight CNTs. © 2011 Elsevier Ltd. All rights reserved. Source


Masoumi B.,Islamic Azad University at Qazvin | Meybodi M.R.,Amirkabir University of Technology
Expert Systems with Applications | Year: 2011

Learning automata (LA) were recently shown to be valuable tools for designing Multi-Agent Reinforcement Learning algorithms and are able to control the stochastic games. In this paper, the concepts of stigmergy and entropy are imported into learning automata based multi-agent systems with the purpose of providing a simple framework for interaction and coordination in multi-agent systems and speeding up the learning process. The multi-agent system considered in this paper is designed to find optimal policies in Markov games. We consider several dummy agents that walk around in the states of the environment, make local learning automaton active, and bring information so that the involved learning automaton can update their local state. The entropy of the probability vector for the learning automata of the next state is used to determine reward or penalty for the actions of learning automata. The experimental results have shown that in terms of the speed of reaching the optimal policy, the proposed algorithm has better learning performance than other learning algorithms. © 2011 Elsevier Ltd. All rights reserved. Source


Sohrabi M.,Amirkabir University of Technology
Radiation Protection Dosimetry | Year: 2015

A 'Universal Radiation Protection System' (URPS) is proposed in this paper with a novel philosophy, concept and methodology. It applies a 'Standardised Integrated Dose System' (SIDS) based on health risk limits for workers and public, no matter where they live in the world. The URPS assigns equal radiation health risk limit to an individual by integrating doses from national natural background (NBG) radiation and from man-made sources. For public, the SIDS integrates doses from planned exposure situations within a dose limit (e.g. 1 mSv y-1) on top of the mean national NBG dose in a country. For workers, the SIDS integrates within a dose limit (e.g. 20 mSv y-1) of occupational dose and doses from mean national NBG and from planned exposure situations as a member of public within the public dose limit. A panorama overview and the rationale in support of the URPS are presented and discussed with a hope to ignite further thoughts and ideas towards establishing the URPS for universal use. © The Author 2015. Published by Oxford University Press. All rights reserved. Source


Ahmadlou M.,Amirkabir University of Technology | Adeli H.,Ohio State University | Adeli A.,Ohio State University
Clinical EEG and Neuroscience | Year: 2012

This article presents a new methodology for investigation of the organization of the overall and hemispheric brain network of patients with attention-deficit hyperactivity disorder (ADHD) using theoretical analysis of a weighted graph with the goal of discovering how the brain topology is affected in such patients. The synchronization measure used is the nonlinear fuzzy synchronization likelihood (FSL) developed by the authors recently. Recent evidence indicates a normal neocortex has a small-world (SW) network with a balance between local structure and global structure characteristics. Such a network results in optimal balance between segregation and integration which is essential for high synchronizabilty and fast information transmission in a complex network. The SW network is characterized by the coexistence of dense clustering of connections (C) and short path lengths (L) among the network units. The results of investigation of C show the local structure of functional left-hemisphere brain networks of ADHD diverges from that of non-ADHD which is recognizable in the delta electroencephalograph (EEG) sub-band. Also, the results of investigation for L show the global structure of functional left-hemisphere brain networks of ADHD diverges from that of non-ADHD which is observable in the delta EEG sub-band. It is concluded that the changes in left-hemisphere brain's structure of ADHD from that of the non-ADHD are so much that L and C can distinguish the ADHD brain from the non-ADHD brain in the delta EEG sub-band. © 2012 EEG and Clinical Neuroscience Society. Source


Akbari Torkestani J.,Islamic Azad University of Arak | Meybodi M.R.,Amirkabir University of Technology | Meybodi M.R.,Institute for Studies in Theoretical Physics and Mathematics IPM
Expert Systems with Applications | Year: 2011

Vertex coloring problem is a combinatorial optimization problem in which a color is assigned to each vertex of the graph such that no two adjacent vertices have the same color. Cellular learning automata (CLA) is an effective probabilistic learning model combining cellular automata and learning automata. Irregular cellular learning automata (ICLA) is a generalization of cellular learning automata in which the restriction of rectangular grid structure in traditional CLA is removed. In this paper, an ICLA-based algorithm is proposed for finding a near optimal solution of the vertex coloring problem. The proposed coloring algorithm is a fully distributed algorithm in which each vertex chooses its optimal color based solely on the colors selected by its adjacent vertices. The time complexity of the proposed algorithm is computed for finding a 11- optimal solution of the vertex coloring problem in an arbitrary graph. To show the superiority of our proposed algorithm over the existing methods, simulation experiments have been conducted. The obtained results show that the proposed algorithm outperforms the others in terms of the required number of colors and running time of algorithm. © 2011 Published by Elsevier Ltd. Source


Mohebbi A.,University of Kashan | Abbaszadeh M.,University of Kashan | Dehghan M.,Amirkabir University of Technology
Journal of Computational Physics | Year: 2013

The aim of this paper is to study the high order difference scheme for the solution of modified anomalous fractional sub-diffusion equation. The time fractional derivative is described in the Riemann-Liouville sense. In the proposed scheme we discretize the space derivative with a fourth-order compact scheme and use the Grünwald-Letnikov discretization of the Riemann-Liouville derivative to obtain a fully discrete implicit scheme. We analyze the solvability, stability and convergence of the proposed scheme using the Fourier method. The convergence order of method is O(τ+h4). Numerical examples demonstrate the theoretical results and high accuracy of the proposed scheme. © 2013 Elsevier Inc. Source


Mohammadi M.,Kharazmi University | Fatemi Ghomi S.M.T.,Amirkabir University of Technology
Expert Systems with Applications | Year: 2011

This paper proposes a genetic algorithm-based heuristic for the capacitated lotsizing problem in flow shops with sequence-dependent setups. The proposed heuristic combines genetic algorithm with rolling horizon approach. To evaluate the effectiveness of the proposed heuristic, some numerical experiments are conducted and corresponding results are compared with those of previously developed heuristics by authors. The comparative results indicate the superiority of genetic algorithm-based heuristic specially in solving the large-sized problem instances. © 2010 Elsevier Ltd. All rights reserved. Source


Tatari M.,Isfahan University of Technology | Dehghan M.,Amirkabir University of Technology
JVC/Journal of Vibration and Control | Year: 2012

In this work, multi-point boundary value problems are considered. These problems have important roles in the modelling of various problems in physics and engineering. Although numerous works have been carried out on the existence and uniqueness to the solution of these problems, the numerical or analytical methods are not established for solving them. In this paper the well-known He's variational iteration method is applied for solving the multi-point boundary value problems. The method is modified and the results are shown using some test problems. These results show the efficiency of the new approach. © 2011 The Author(s). Source


Mokhtari A.,Iran University of Science and Technology | Moghadas Nejad F.,Amirkabir University of Technology
Construction and Building Materials | Year: 2012

In this study, different additives such as mineral fiber, cellulose fiber and styrene-butadiene-styrene (SBS) were used to modify stone matrix asphalt (SMA) mixtures, and performance tests were performed for modified and unmodified mixtures. A mechanistic-empirical design procedure was employed to assess the effect of different additives in improving the service life of the pavement or reduction in thickness of pavement layers. Based on the results, SBS was more effective in improving the performance of asphalt mixtures compared to the fibers. According to the results of mechanistic-empirical design, the service life of the pavement system modified with mineral, cellulose and SBS were 1.07, 1.081 and 1.243 times more than unmodified mix, respectively. © 2012 Elsevier Ltd. All rights reserved. Source


Kamani D.,Amirkabir University of Technology
Annals of Physics | Year: 2015

Using the boundary state formalism we investigate the effect of tachyon condensation process on a rotating and moving D. p-brane with various background fields in the bosonic string theory. The rotation and motion are inside the brane volume. We demonstrate that some specific rotations and/or motions can preserve the brane from instability and collapse. © 2015 Elsevier Inc. Source


Nejad F.M.,Amirkabir University of Technology | Aghajani P.,University of Tehran | Modarres A.,Babol Noshirvani University of Technology | Firoozifar H.,Pasargad Oil Company Research Center
Construction and Building Materials | Year: 2012

Considerable effect of crumb rubber on improving the original bitumen properties along with environmental and economical advantages, encouraged using this additive as an effective modifier. In this research, due to lack of enough information about the effects of crumb rubber produced in Iran on 0/70 bitumen properties, extensive laboratory investigations have been carried out using classic and SHRP testing methods. The results of classic tests showed that adding crumb rubber reduced penetration, temperature susceptibility, ductility and fraass breaking point and increased the softening point, elastic recovery and vialit adhesion. Rheological properties of modified specimens were investigated with DSR in temperature sweep and frequency sweep and creep tests before and after aging in RTFO. Results indicated that there was an inflection point or inflection interval in G, G/sinδ and G·sinδ diagrams. At higher temperatures and lower frequencies than the inflection point or inflection interval the aforementioned parameters increased by increasing the crumb rubber content and at lower temperatures and higher frequencies the reverse was true. Furthermore, increasing the crumb rubber content and aging in RTFO lead to reduce of creep and increase of viscosity quantity. © 2011 Elsevier Ltd. All rights reserved. Source


Yasavol N.,Tarbiat Modares University | Mahboubi F.,Amirkabir University of Technology
Materials and Design | Year: 2012

Plasma nitriding is a surface treatment process, which is widely used to improve wear, fatigue and corrosion resistance of the industrial parts. Nevertheless, corrosion resistance can be enhanced by oxidizing of the nitrided components. This paper considers the duplex treatment of plasma nitriding and post-oxidizing of AISI 4130 low alloy steel. After plasma nitriding, the post-oxidizing treatment was done in the various gas mixtures of O2/H2 and temperatures. The treated samples were characterized using metallographic techniques, XRD, SEM, micro-hardness and potentiodynamic test. The X-ray diffraction confirmed the development of gamma prime and epsilon iron nitride phases during the nitriding, and hematite (Fe2O3) and magnetite (Fe3O4) phases under the oxidizing process. The sample oxidized under O2/H2 volume ratio of 1/3 showed the best corrosion resistance, which is attributed to the formation of an almost single phase magnetite oxide layer on the top of the compound layer. © 2012. Source


Dehghan M.,Amirkabir University of Technology | Hajarian M.,Shahid Beheshti University
Engineering Computations (Swansea, Wales) | Year: 2011

Purpose: The purpose of this paper is to find the efficient iterative methods for solving the general matrix equation A1X + XA2 + A3XH + XHA4 = B (including Lyapunov and Sylvester matrix equations as special cases) with the unknown complex (reflexive) matrix X. Design/methodology/approach: By applying the principle of hierarchical identification and the Hermitian/skew-Hermitian splitting of the coefficient matrix quadruplet A1; A2; A3; A4 the authors propose a shift-splitting hierarchical identification (SSHI) method to solve the general linear matrix equation A1X + XA2 + A3XH + XHA4 = B. Also, the proposed algorithm is extended for finding the reflexive solution to this matrix equation. Findings: The authors propose two iterative methods for finding the solution and reflexive solution of the general linear matrix equation, respectively. The proposed algorithms have a simple, neat and elegant structure. The convergence analysis of the methods is also discussed. Some numerical results are given which illustrate the power and effectiveness of the proposed algorithms. Originality/value: So far, several methods have been presented and used for solving the matrix equations by using vec operator and Kronecker product, generalized inverse, generalized singular value decomposition (GSVD) and canonical correlation decomposition (CCD) of matrices. In several cases, it is difficult to find the solutions by using matrix decomposition and generalized inverse. Also vec operator and Kronecker product enlarge the size of the matrix greatly therefore the computations are very expensive in the process of finding solutions. To overcome these complications and drawbacks, by using the hierarchical identification principle and the Hermitian = skew-Hermitian splitting of the coefficient matrix quadruplet (A1; A2; A3; A4), the authors propose SSHI methods for solving the general matrix equation. © Emerald Group Publishing Limited. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology
International Communications in Heat and Mass Transfer | Year: 2012

In this paper heat transfer and flow field analysis in a wavy channel linked to a porous Gas Diffusion Layer (GDL) is numerically studied. The domain is very similar to our earlier computations of proton exchange membrane fuel cells (see Khakbaz-Baboli and Kermani (2008)). The fluid temperature at the channel inlet (T in) is taken less than that of the walls (T w). The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique (1972). A wide spectrum of numerical studies is performed over a range of Reynolds number Re H: 100≤Re H≤1000, wave number β: 0≤β≤10, the wave amplitude α: 0≤α≤0.3 and Darcy number Da: 0.1≤Da≤0.001. Simulations show that heat transfer in channels can enhance up to 100%, depending on the duct α, β and flow Re H. Computations show excellent agreement with the literature. The present work can provide helpful guidelines to the manufactures of the compact heat exchangers. © 2011 Elsevier Ltd. Source


Shariyat M.,K. N. Toosi University of Technology | Asemi K.,Amirkabir University of Technology
Composites Part B: Engineering | Year: 2014

In the present paper, shear buckling analysis of the orthotropic heterogeneous FGM plates is investigated for the first time. Moreover, influence of the Winkler-type elastic foundation is considered. The material properties are assumed to have in-plane orthotropy and transverse heterogeneity. The most accurate approach, i.e., the three-dimensional elasticity is employed instead of using the approximate plate theories. In contrast to all of the available displacement-based buckling analyses that have employed C0-continuous commercial finite element codes or semi-analytical methods, present formulations are C2-continuous due to using the proposed 3D cubic B-spline element. Results are derived based on principle of minimum potential energy and a non-linear finite element procedure utilizing a Galerkin-type 3D cubic B-spline solution algorithm. Buckling loads are detected based on a generalized geometric stiffness concept. In this regard, effects of both the prebuckling and buckling states are considered. To present a better imagination and more detailed discussions, details of the buckling mode shapes and the foundation interaction are discussed for plates with simply-supported edges. In addition, the more practical free and clamped edge conditions are also considered. © 2013 Elsevier Ltd. All rights reserved. Source


Ataeefard M.,Iran Institute for Color Science and Technology | Moradian S.,Amirkabir University of Technology
Polymer - Plastics Technology and Engineering | Year: 2011

The effects of clays as nanoscale fillers have been rarely addressed. Influence of the amount of organoclay (ranging between 1 and 10 wt.%) on the nanocomposites structure, i.e., intercalated or exfoliated, and on the enhancement of mechanical, rheological and morphological properties of polypropylene (PP) nanocomposites was studied in this work. The fundamental material characterization was conducted using XRD, SEM, TEM, DSC, POM,DMTA as well as RMS. Overall mechanical properties determined by tensile tests showed improvements. DSC andPOMresults demonstrated decrease of nanocomposites crystallinity. XRD and TEM Showed intercalate/ exfoliate structures in the resultant nanocomposites. © Taylor & Francis Group, LLC. Source


Keshavarz E.,Islamic Azad University at Sirjan | Khorram E.,Amirkabir University of Technology
Computers and Industrial Engineering | Year: 2011

In this paper, a fuzzy bi-criteria transportation problem is studied. Here, the model concentrates on two criteria: total delivery time and total profit of transportation. The delivery times on links are fuzzy intervals with increasing linear membership functions, whereas the total delivery time on the network is a fuzzy interval with a decreasing linear membership function. On the other hand, the transporting profits on links are fuzzy intervals with decreasing linear membership functions and the total profit of transportation is a fuzzy number with an increasing linear membership function. Supplies and demands are deterministic numbers. A nonlinear programming model considers the problem using the max-min criterion suggested by Bellman and Zadeh. We show that the problem can be simplified into two bi-level programming problems, which are solved very conveniently. A proposed efficient algorithm based on parametric linear programming solves the bi-level problems. To explain the algorithm two illustrative examples are provided, systematically. © 2011 Elsevier Ltd. All rights reserved. Source


Shamsi M.,Amirkabir University of Technology
Optimal Control Applications and Methods | Year: 2011

In the present contribution, a modified Legendre pseudospectral scheme for accurate and efficient solution of bang-bang optimal control problems is investigated. In this scheme control and state functions are considered as piecewise constant and piecewise continuous polynomials, respectively, and the switching points are also taken as decision variables. Furthermore, for simplicity in discretization, the integral formulation of the dynamical equations is considered. Thereby, the problem is converted into a mathematical programming problem which can be solved by the well-developed parameter optimization algorithms. The main advantages of the present method are that: (i) it obtains good results even by using a small number of collocation points and the rate of convergence is high; (ii) the switching times can be captured accurately; and (iii) the wrongly chosen number of switching points can be detected by the results of the method. These are illustrated through a numerical implementation of the method on three examples and the efficiency of the method is reported. © 2010 John Wiley & Sons, Ltd. Source


Behnamian J.,Amirkabir University of Technology | Zandieh M.,Shahid Beheshti University
Expert Systems with Applications | Year: 2011

Recently introduced colonial competitive algorithm (CCA) has shown its excellent capability on different optimization problems. The aim of this paper is to propose a discrete version of this method to determine a schedule that minimizes sum of the linear earliness and quadratic tardiness in the hybrid flowshops scheduling problem with simultaneously considering effects of sequence-dependent setup times and limited waiting time. In other word we assume that the waiting time for each job between two consecutive stages cannot be greater than a given upper bound. Also for this problem, a mixed integer program is formulated. Computational results are presented to evaluate the performance of the proposed algorithms for problems with different structures. © 2011 Elsevier Ltd. All rights reserved. Source


Ovesy H.R.,Amirkabir University of Technology | Kharazi M.,Sahand University of Technology
Computers and Structures | Year: 2011

In this paper, the compressive, i.e. bucking and post-buckling, behavior of composite laminates with through-the-width and embedded delaminations is investigated analytically. The analytical method is based on the first order shear deformation theory (FSDT) and its formulation is developed on the basis of the Rayleigh-Ritz approximation technique. In the case of the multiple delaminations, the contact phenomenon has significant effects on the compressional behavior of the laminates. Thus, the contact between the delaminated sublaminates is also considered in the presented FSDT analytical method. The method can handle both local buckling of the delaminated sublaminates and global buckling of the whole plate. Also, the three-dimensional finite element analysis is performed by using ANSYS5.4 general purpose commercial software, and the results are compared with those obtained by the analytical model. The agreement between the results is very good. © 2010 Civil-Comp Ltd and Elsevier Ltd. All rights reserved. Source


Hosseinzadeh S.A.A.,Golestan University | Tehranizadeh M.,Amirkabir University of Technology
Journal of Constructional Steel Research | Year: 2014

The overall behavior of steel plate shear wall (SPSW) dual systems comprises the contributions of the infill plate tension field and boundary frame moment resisting actions. In the literature, a moment frame acting as SPSW boundaries (SPSW boundary frame) is treated as the same frame acting alone (bare frame). However, due to an interaction effect between the infill wall and the boundary frame, the actual behavior of SPSW boundary frame is different from the behavior of the same bare frame. In the present paper, a number of code designed single and multi-story SPSWs and the corresponding bare frames are numerically analyzed (a) to study the influence of infill walls on the behavior of boundary frames and (b) to evaluate the effectiveness of infill walls. Results show that the presence of infill walls can significantly improve the performance of moment-resisting frame systems, especially for multi-story ones, in terms of strength, stiffness, ductility and energy dissipation capability. In turn, the better performance of the SPSW system than the corresponding bare frame is not only due to the contribution of the infill wall, but also due to the improvement in the performance of the frame resulted from the wall-frame interaction. © 2014 Elsevier Ltd. Source


Andakhshideh A.,Ferdowsi University of Mashhad | Maleki S.,Ferdowsi University of Mashhad | Aghdam M.M.,Amirkabir University of Technology
Composite Structures | Year: 2010

Non-linear static analysis of laminated sector plates with any combination of clamped, simply supported and free edges is presented using Generalized Differential Quadrature (GDQ) method. Particular interest of this study is large deformation of asymmetric sector plates with free edges. Based on the first-order shear deformation theory and von Kármán type non-linearity, the governing system of equations include a system of 13 partial differential equations (PDEs) in terms of unknown displacements, forces and moments. Successive application of the GDQ technique to the governing equations resulted in a system of non-linear algebraic equations. The Newton-Raphson iterative scheme is then employed to solve the system of non-linear equations. Illustrative examples are presented to demonstrate accuracy and rapid convergences of the method with small number of grid points. Predictions of the presented method show very good agreement with other numerical studies available in the literature. Further results for asymmetric laminated sector plates with free edges are also presented for future references. © 2009. Source


Ahmad R.R.,Amirkabir University of Technology
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2013

Stiffened plate buckles in different modes, including web/flange buckling, torsional buckling, plate buckling, and interactions of them. Generally, interactions of different buckling modes in stiffened plates are ignored and elastic buckling analysis of each mode is treated separately. In some design codes, to cope with interactions of different buckling modes, the influence of adjacent elements are considered as rotational springs. The main aim of this study is to compare literature- and rule-based expressions to assess the elastic buckling strength of T-bar stiffened plates and to identify the applicability of selected expressions for certain conditions. Different buckling modes and their interactions are investigated, and critical Euler stresses are evaluated. Upon comparison with given expressions and the finite element method, it is found that some of the proposed expressions are not applicable in certain conditions. © IMechE 2012. Source


Sajadieh M.S.,Amirkabir University of Technology | Fallahnezhad M.S.,University of Yazd | Khosravi M.,Tarbiat Modares University
International Journal of Production Economics | Year: 2013

This paper considers an integrated production-inventory model for a three-stage supply chain involving multiple suppliers, multiple manufacturers and multiple retailers. The suppliers/manufacturers produce the raw materials/final goods at a finite rate and deliver the materials/goods in a number of batches to the manufacturers/retailers. We analyze the problem where the lead times from the manufacturers to the retailers are stochastic and shortage is allowed. We also explicitly include the transportation costs from the manufacturers to the retailers into the model. The numerical analysis shows that the coordination mechanism employed is more beneficial for the cases with less unpredictable lead times, lower shortage prices, and no transportation cost. © 2013 Elsevier B.V. Source


Ovesy H.R.,Amirkabir University of Technology | Fazilati J.,Astronautics Research Institute
Composite Structures | Year: 2014

The parametric instability regions of laminated composite plate and cylindrical shells subjected to non-uniform in-plane axial end-loadings are studied. The static as well as varying parts of the end-loading assumed to vary according to parabolic distribution in the width of the panel. The dynamic instability of panels has been investigated by using a developed finite strip method (FSM). The problem has been formulated on the basis of principle of virtual work. The effects of loading distribution as well as boundary conditions and static loading on the instability regions of load frequency are studied by applying Bolotin's first order approximation. In order to demonstrate the capabilities of the developed formulations and methods in predicting the structural parametric dynamic behavior, some representative results are obtained and compared with those in the literature wherever available. © 2013 Elsevier Ltd. Source


Dehghani K.,Amirkabir University of Technology
Materials Science and Engineering A | Year: 2011

In the present work, the bake hardening of nanostructured AA7075 aluminum alloy was compared with that of its coarse-grain counterpart. Surface severe plastic deformation (SSPD) was used to produce nanograin layers on both surfaces of workpieces. The nanostructured layers were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The thickness of nanostructured layer, having the grains of 50-110. nm, was about 75. μm on each side of workpiece. The bake hardenability of nanograin and coarse-grain AA7075 was then compared by pre-straining to 2, 4 and 6% followed by baking at 100. °C and 200. °C for 20. min. Comparing to coarse-grain case, there was about 88-100% increase in bake hardenability and about 36-38% increase in yield strength after the bake hardening of present nanograin AA7075. Such an increase in bake hardenability and strength was achieved when the thickness of two nanograin layers was about only one-tenth of the whole thickness. © 2011 Elsevier B.V. Source


Nazari A.,Islamic Azad University at Saveh | Mohandesi J.A.,Amirkabir University of Technology
Journal of Materials Engineering and Performance | Year: 2010

Charpy impact energy of functionally graded steels produced by electroslag remelting composed of graded ferrite and austenite layers together with bainite or martensite intermediate layer in the form of crack arrester configuration has been investigated. The results obtained in the present study indicate that the notch tip position with respect to bainite or martensite layer significantly affects the impact energy. The closer the notch tip to the tougher layer, the higher the impact energy of the composite due to increment of energy absorbed by plastic deformation zone ahead of the notch and vice versa. Empirical relationships have been determined to correlate the impact energy of functionally graded steels to the morphology of layers. © ASM International. Source


Mahmoodi N.M.,Iran Institute for Color Science and Technology | Arami M.,Amirkabir University of Technology
Journal of Alloys and Compounds | Year: 2010

In this paper, the feasibility and performance of degradation, modeling of degradation, mineralization and toxicity reduction of agricultural organic pollutants (Alachlor and Fenitrothion) have been studied using immobilized titania nanophotocatalysis. Total organic carbon (TOC) and ion chromatography (IC) analyses were employed to obtain the details of the photocatalytic degradation and mineralization of both pesticides. Daphnia magna bioassay has been used to test the diminution of toxicity during the treatment process. Computational fluid dynamics (CFD) model was used to solve the mathematical equation describing degradation process. The model predictions were compared to those results obtained from experimental tests for the degradation of both pesticides and close agreement was achieved. Kinetic studies revealed that the degradation rate followed first-order model for both pesticides. Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO2. Inorganic anions such as nitrate and sulphate were detected as the photocatalytic mineralization of Alachlor and Fenitrothion. The results showed that immobilized titania nanophotocatalysis was an environmentally friendly method of degradation and toxicity reduction of agricultural organic pollutants (Alachlor and Fenitrothion). © 2010 Elsevier B.V. All rights reserved. Source


Momeni A.,Amirkabir University of Technology | Abbasi S.M.,University of Tehran
Materials and Design | Year: 2010

Hot deformation behavior of the alloy Ti-6Al-4V was investigated via conducting hot compression tests at temperatures of 800-1150°C and at strain rates, ranging from 0.001s-1 to 1s-1, at an interval of an order of magnitude. The apparent differences of flow stress curves obtained in dual phase α+β and single phase β regions were analyzed in term of different dependence of flow stress to temperature and strain rate and different microstructural evolutions. The values of strain rate sensitivity and apparent activation energy were obtained respectively as 0.20 and 530kJ/mol for two phase microstructure. However, for single phase β microstructure they were approximated as 0.19 and 376kJ/mol, respectively. It was found that in two phase region the values of strains corresponding to peak point, εp, and the highest rate of flow softening, ε*, are almost independent to Zenner-Hollomon parameter. In single phase region, εp and ε* exhibited a direct relationship to Z parameter and the corresponding empirical equations were proposed. © 2010 Elsevier Ltd. Source


Talebi H.A.,Amirkabir University of Technology | Khorasani K.,Concordia University at Montreal
IEEE Transactions on Control Systems Technology | Year: 2013

The problem of fault detection and isolation/identification (FDI) of nonlinear systems using neural networks is considered in this paper. The proposed FDI approach employs recurrent neural network-based observers for simultaneously detecting, isolating and identifying the severity of actuator faults in presence of disturbances and uncertainties in the model and sensory measurements. The neural network weights are updated based on a modified dynamic backpropagation scheme. The proposed FDI scheme does not rely on the availability of full state measurements. In most works in the literature the fault function acts as an additive term on the actuator, whereas in this work the fault acts as a multiplicative term. This will make the formal stability and convergence analysis of the overall FDI scheme nontrivial and challenging. Our stability analysis considers the presence of plant and sensor uncertainties through the use of Lyapunov's direct method with no restrictive assumptions on the system and/or the FDI algorithm. The performance of our proposed FDI approach is evaluated through simulations that are performed for two case studies, namely FDI of 1) reaction wheel type actuators that are commonly utilized in the attitude control subsystem (ACS) of a satellite and 2) actuators in a two-link flexible joint manipulator. © 1993-2012 IEEE. Source


Ebadi Amooghin A.,Tarbiat Modares University | Omidkhah M.,Tarbiat Modares University | Kargari A.,Amirkabir University of Technology
RSC Advances | Year: 2015

A novel mixed matrix membrane (MMM) was fabricated by incorporating micro-sized nano-porous sodium zeolite-Y (NaY zeolite) into Matrimid®5218 matrix. The filler and the prepared membranes were characterized by X-ray diffraction (XRD), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), and thermal gravimetric and derivative thermal gravimetric (TG/DTG) analyses. The effects of filler content (0-20 wt%), feed pressure (2-12 bar), operating temperature (35-75°C) and mixed feed gas on CO2/CH4 transport properties of Matrimid/NaY were investigated. The results revealed that the Matrimid/NaY (15 wt%) displayed a CO2 permeability of 17.52 Barrer, more than two-fold increase with respect to the NaY-free counterpart. The corresponding CO2/CH4 selectivity was increased from 36.3 for Matrimid to 43.3 for Matrimid/NaY (15 wt%), (about 20%). The CO2 permselectivities of MMMs were greater than that of the Matrimid over the entire pressure range. As the operating temperature increased from 35 to 75°C, CH4 permeability increased about 175% and 215% for Matrimid and Matrimid/NaY (15 wt%), respectively. While the CO2 permeability enhanced about 78% and 98%. The corresponding decreases in the CO2/CH4 selectivities were 35.27% and 37.14%, respectively. Moreover, the mixed gas experiment results indicated that CO2 permeability and CO2/CH4 selectivity for all membranes were lower than those of pure gas experiments, but with less severity for MMMs. The best CO2-selective membrane, Matrimid/NaY (15 wt%), represented the CO2 permeability of 15.19 Barrer with CO2/CH4 selectivity of 39.5 for a 10/90 vol% mixture of CO2 and CH4. © The Royal Society of Chemistry 2015. Source


Rikhtegar F.,Iran University of Science and Technology | Ketabchi M.,Amirkabir University of Technology
Materials and Design | Year: 2010

The thixoextrusion process is a new method for manufacturing complicated and net shape components through which high strength materials can be formed more easily. In this study 7075 Al alloy which has low extrudability has been thixoformed by forward extrusion process. As it is known conventional extrusion of 7075 Al alloy has been very difficult due to high strength and multi-phase microstructural characterization. In this research, by applying the advantages of semisolid processing, the applied pressure for extrusion is decreased and desired mechanical properties were reached near the standard predictable properties for wrought 7075 Al alloy under T6 tempering conditions, for example tensile and yield strength and hardness of samples of thixoextrusion product sufficiently agree with same expected properties of wrought 7075 Al alloy and only elongation is decreased along this process. © 2010 Elsevier Ltd. Source


Rahbar-Ranji A.,Amirkabir University of Technology
Ocean Engineering | Year: 2012

Corrosion is one of the time dependent detrimental phenomena which reduces strength of structures and leads to catastrophic failures. All rules and regulations concerning strength of corroded plates are based on uniform thickness reduction. To estimate residual strength of corroded structures, typically a much higher level of accuracy is required, since, the actual corroded plate has irregular surfaces. There is little study on strength analysis of corroded plate with irregular surfaces especially as a function of corrosion parameters. It is the main aim of present work to study ultimate strength of corroded steel plates with irregular surfaces under in-plane compression. Nonlinear finite element method is employed to determine ultimate strength of corroded steel plates with irregular surfaces. Comparing the results with ultimate strength of corroded plates with uniform thickness, a reduction factor is introduced. Having done this, ultimate strength of corroded plates could be evaluated easily as a function of corrosion conditions. © 2012 Elsevier Ltd. Source


Naderi B.,Amirkabir University of Technology | Tavakkoli-Moghaddam R.,University of Tehran | Khalili M.,Islamic Azad University at Karaj
Knowledge-Based Systems | Year: 2010

This paper presents an efficient meta-heuristic algorithm based on electromagnetism-like mechanism (EM), in which has been successfully implemented in a few combinatorial problems. We propose the EM for scheduling the flow shop problem that minimizes the makespan and total weighted tardiness and considers transportation times between machines and stage skipping (i.e., some jobs may not need to be processed on all the machines). To show the efficiency of this proposed algorithm, we also apply simulated annealing (SA) and some other well-recognized constructive heuristics, such as SPT, NEH, (g/2, g/2) Johnson' rule, EWDD, SLACK, and NEH_EWDD for the given problems. To evaluate the performance and robustness of our proposed EM, we experiment a number of test problems. Our computational results show that our proposed EM in almost all cases outperforms SA and other foregoing heuristics applied to this paper. © 2009 Elsevier B.V. All rights reserved. Source


Kazemi Nia Korrani H.R.,Amirkabir University of Technology
Journal of Constructional Steel Research | Year: 2010

Lateraltorsional buckling may occur in an unrestrained beam where its compression flange is free to displace laterally and rotate. This paper presents the results of the theoretical and finite element analyses of the lateraltorsional buckling of I-girders with corrugated webs and lateral bracing, under uniform bending. It is well known that an elastic lateral brace restricts partially the lateral buckling of slender beams and increases the elastic buckling moment. However, a full study of the effect of lateral braces on lateraltorsional buckling has not been made especially for I-girder with corrugated webs. This paper develops a three-dimensional finite element model using ANSYS [User's manual, version 10.0] for the lateraltorsional buckling analysis of I-girder with corrugated webs and uses it to investigate the effects of elastic lateral bracing stiffness on the critical moment of simply supported I-girders with corrugated webs under pure bending. It was found that for plastic and inelastic I-girder with corrugated webs, the effect of bracing initially is increased to some extent as the lateral unbraced length increases and then decreased until the beam behaves as an elastic beam. In other words, the effect of bracing depends not only on the stiffness of the restraint but also on the modified slenderness of the I-girder. Also, the results show that Winter's simplified method to determine full brace requirements cannot be applied to I-girders with corrugated webs. Therefore, a general equation is proposed to determine the value of optimum stiffness (Kopt) in terms of the I-girder's slenderness. © 2010 Elsevier Ltd. All rights reserved. Source


Mahootchi M.,Amirkabir University of Technology | Ponnambalam K.,University of Waterloo
Journal of Water Resources Planning and Management | Year: 2013

In this paper, a recently developed stochastic programming technique that includes reliability constraints is used to solve the operations optimization problem of the Parambikulam-Aliyar project (PAP), a multireservoir system in India. The use of reliability constraints as chance constraints in reservoir operations optimization have been around for some time, but is still a challenging problem because either the results are not good or they cannot be applied in problems with more than one or two reservoirs when such techniques depend on discretization. The new implementation of chance constraints based on a previous model extended to multireservoir systems provides better results than so far known. This work is easy to apply because it requires only a standard nonlinear programming solver.©2013 American Society of Civil Engineers. Source


Mirzaei M.,Amirkabir University of Technology | Dehghan M.,Semnan University
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2013

Laminar flow and heat transfer of water-Al2O3 nanofluid under constant heat flux have been investigated numerically. Single-phase with temperature dependant effective properties has been assumed for fluid. Enhancement in heat transfer and increase in friction factor have been obtained by the use of nanofluid. Heat transfer enhancement is more obvious by the use of variable properties. Also, effects of temperature variation on nanofluid heat transfer are greater than the pure water. © 2013 Springer-Verlag Berlin Heidelberg. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology
International Journal of Thermal Sciences | Year: 2012

In this study heat transfer and fluid flow analysis in a channel with blocks attached to bottom wall and utilizing Nano-fluid is numerically studied. The fluid temperature at the channel inlet (T in) is taken less than that of the walls (T w). The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. A wide spectrum of numerical simulations has been done over a range of Reynolds number, Nano-fluid volume fraction and the block number. The influence of these parameters is investigated on the local and average Nusselt numbers. From this study, it is concluded that heat transfer in channels can enhance by addition of Nano-particles, and usage of block on hot walls. Simulations show that heat transfer in channels can enhance up to 60% due to the presence of nano-particles and the blocks in channels, but there exist a saturated number of blocks, beyond which, the average Nu do not increase. The present work can provide helpful guidelines to the manufactures of the compact heat exchangers. © 2012 Elsevier Ltd. All rights reserved. Source


Habibi M.,Amirkabir University of Technology
Journal of Fusion Energy | Year: 2012

In order to improve the HXR emission from APF plasma focus device we have investigated the effect of insulator sleeve outer diameter (O.D.) and its length. Fourteen different insulator sleeve geometries at three different filling gas pressures of 6, 7 and 8 Torr of neon are used in the present investigation. The average HXR yield, measured using scintillation detector, has been found to increase with the increase in insulator sleeve O.D. from 31 to 34 mm. Further increase in insulator sleeve diameter to 37 mm, however, decreased the HXR yield. The highest magnitude of 234.5 kA was achieved for 34 mm O.D. of sleeve at filling gas pressure of 7 Torr and voltage of 12 kV. © Springer Science+Business Media, LLC 2011. Source


Maryan A.S.,Islamic Azad University at Ardabil | Montazer M.,Amirkabir University of Technology
Journal of Cleaner Production | Year: 2013

Denim garment is one of the most important and highly used textile clothing, regarding its exclusive features including color, versatile appearance and high strength that are widely used by young people. To create diversity in denim garment it is necessary to apply special techniques and new substances to respond the huge market demand. In this paper, bio-treatment process, using amylase, cellulase, laccase, and their combinations applied on denim garment to conduct one step bio-desizing and bio-washing producing old-look appearance garment is proposed and analyzed. The color changes of denim samples and the whiteness of the back and staining on the pocket was measured and the surface morphology of the samples were observed using Scanning Electron Microscope. The results indicated successful treatment regarding one step bio-desizing and enzymatic bio-washing using mixture of amylase and cellulase and laccase. The obtained color on the samples treated with the three enzymes has not been differed significantly with the bio-desized garment treated with cellulase or laccase and cellulase/laccase (cellulase and laccase). Source


Lakestani M.,University of Tabriz | Dehghan M.,Amirkabir University of Technology
Computer Physics Communications | Year: 2010

Two numerical techniques are presented for solving the solution of Riccati differential equation. These methods use the cubic B-spline scaling functions and Chebyshev cardinal functions. The methods consist of expanding the required approximate solution as the elements of cubic B-spline scaling function or Chebyshev cardinal functions. Using the operational matrix of derivative, we reduce the problem to a set of algebraic equations. Some numerical examples are included to demonstrate the validity and applicability of the new techniques. The methods are easy to implement and produce very accurate results. © 2010 Elsevier B.V. All rights reserved. Source


Parand K.,Shahid Beheshti University | Dehghan M.,Amirkabir University of Technology | Rezaei A.R.,Shahid Beheshti University | Ghaderi S.M.,Shahid Beheshti University
Computer Physics Communications | Year: 2010

In this paper we propose a collocation method for solving some well-known classes of Lane-Emden type equations which are nonlinear ordinary differential equations on the semi-infinite domain. They are categorized as singular initial value problems. The proposed approach is based on a Hermite function collocation (HFC) method. To illustrate the reliability of the method, some special cases of the equations are solved as test examples. The new method reduces the solution of a problem to the solution of a system of algebraic equations. Hermite functions have prefect properties that make them useful to achieve this goal. We compare the present work with some well-known results and show that the new method is efficient and applicable. © 2010 Elsevier B.V. All rights reserved. Source


Lakestani M.,University of Tabriz | Dehghan M.,Amirkabir University of Technology
Computer Physics Communications | Year: 2010

Two numerical techniques based on the finite difference and collocation methods are presented for the solution of nonlinear Klein-Gordon equation. The operational matrix of derivative for the cubic B-spline scaling functions is presented and is utilized to reduce the solution of nonlinear Klein-Gordon equation to the solution of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the new techniques. © 2010 Elsevier B.V. All rights reserved. Source


Nejati A.,Sharif University of Technology | Hosseini Jenab S.M.,Amirkabir University of Technology
Scientometrics | Year: 2010

The quantity and quality of scientific output of the topmost 50 countries in the four basic sciences (agricultural & biological sciences, chemistry, mathematics, and physics & astronomy) are studied in the period of the recent 12 years (1996-2007). In order to rank the countries, a novel two-dimensional method is proposed, which is inspired by the H-index and other methods based on quality and quantity measures. The countries data are represented in a "quantity-quality diagram", and partitioned by a conventional statistical algorithm into three clusters, members of which are rather the same in all of the basic sciences. The results offer a new perspective on the global positions of countries with regards to their scientific output. © 2009 Akadémiai Kiadó, Budapest, Hungary. Source


Ahmadi-Javid A.,Amirkabir University of Technology
IEEE International Symposium on Information Theory - Proceedings | Year: 2011

In the past decade, the new concept of coherent risk measure has found many applications in finance, insurance and operations research. In this paper, we introduce a new class of coherent risk measures constructed by using information-type pseudo-distances that generalize the Kullback-Leibler divergence, also known as the relative entropy. We first analyze the primal and dual representations of this class. We then study entropic value-at-risk (EVaR) which is the member of this class associated with relative entropy. We also show that conditional value-at-risk (CVaR), which is the most popular coherent risk measure, belongs to this class and is a lower bound for EVaR. © 2011 IEEE. Source


Kanan H.R.,Islamic Azad University at Qazvin | Faez K.,Amirkabir University of Technology
Image and Vision Computing | Year: 2010

In this paper, we propose a new approach for face representation and recognition based on Adaptively Weighted Sub-Gabor Array (AWSGA) when only one sample image per enrolled subject is available. Instead of using holistic representation of face images which is not effective under different facial expressions and partial occlusions, the proposed algorithm utilizes a local Gabor array to represent faces partitioned into sub-patterns. Especially, in order to perform matching in the sense of the richness of identity information rather than the size of a local area and to handle the partial occlusion problem, the proposed method employs an adaptively weighting scheme to weight the Sub-Gabor features extracted from local areas based on the importance of the information they contain and their similarities to the corresponding local areas in the general face image. An extensive experimental investigation is conducted using AR and Yale face databases covering face recognition under controlled/ideal condition, different illumination condition, different facial expression and partial occlusion. The system performance is compared with the performance of four benchmark approaches. The promising experimental results indicate that the proposed method can greatly improve the recognition rates under different conditions. © 2009 Elsevier B.V. All rights reserved. Source


Khajeh A.,Islamic Azad University at Birjand | Modarress H.,Amirkabir University of Technology
Journal of Hazardous Materials | Year: 2010

A quantitative structure property relationship (QSPR) study was performed to develop a model for prediction of flash point of esters based on a diverse set of 95 components. The most five important descriptors were selected from a set of 1124 descriptors to build the QSPR model by means of a genetic function approximation (GFA). For considering the nonlinear behavior of these molecular descriptors, adaptive neuro-fuzzy inference system (ANFIS) method was used. The ANFIS and GFA squared correlation coefficient for testing set was 0.969 and 0.965, respectively. The results obtained showed the ability of developed GFA and ANFIS for prediction of flash point of esters. © 2010 Elsevier B.V. Source


Hossain E.,University of Manitoba | Rasti M.,Amirkabir University of Technology | Tabassum H.,University of Manitoba | Abdelnasser A.,University of Manitoba
IEEE Wireless Communications | Year: 2014

The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, for example, higher data rates, excellent end-to-end performance, and user-coverage in hot-spots and crowded areas with lower latency, energy consumption, and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g. power control, cell association) in these networks with shared spectrum access (i.e. when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems. © 2002-2012 IEEE. Source


Ovesy H.R.,Amirkabir University of Technology | Fazilati J.,Aerospace Rresearch Institute
Computers and Structures | Year: 2012

In the current paper, it is the first time that a dynamic stability analysis of moderately thick cylindrical panels made from FG materials is conducted by employing finite strip formulations based on a Reddy-type third order shear deformation theory (HSDT). Two versions of finite strip methods (FSM), namely semi-analytical and B-spline methods are developed. The mechanical properties of FGM are assumed to change in thickness direction according to a power-law function. The temperature effects are ignored. The strain terms are expressed in terms of the Koiter-Sanders theory of shallow shells. In order to demonstrate the capabilities of the developed methods in predicting parametric behavior of the subject structures, some representative results are obtained and compared with those in the literature wherever available. © 2012 Civil-Comp Ltd. and Elsevier Ltd. All rights reserved. Source


Saadatinejad M.R.,Amirkabir University of Technology | Sarkarinejad K.,Shiraz University
Marine and Petroleum Geology | Year: 2011

The Abadan plain in southwestern Iran has important petroleum reservoir potential but poorly defined structural setting. It is located at the Mesopotamian foredeep basin, bounded by the Arabian plate and the Dezful Embayment. The main reservoir in this field is the Fahliyan formation, composed of reef carbonates. Most of the Abadan area is flat and covered by recent alluvial deposits with no outcrops. Studies of the structures in this area have provided information about the structural history and allowed better reservoir and drilling management. Seismic spectral decomposition techniques have been utilized as a quick and effective interpretation tool. Fast Fourier transform (FFT) and continuous wavelet transforms (CWT) have been used to convert time to frequency domain, and have been applied to detect fault systems in the reservoir. Application of the Fast Fourier transform (FFT) and continuous wavelet transforms (CWT) indicate that the Abadan reservoir consists normal extensional system of the reservoir which display paralleling of contour common depth in two sides of extensional system in some regions and large displacement between two sides of contours indicate that system is normal in which hanging wall moved over footwall. Various displacements between sides indicate parallel strike-slip movements which are associated with reverse faulting and inversion tectonics. © 2011 Elsevier Ltd. Source


Kamani D.,Amirkabir University of Technology
Journal of Experimental and Theoretical Physics | Year: 2011

We express the covariant actions of a super p-brane and the corresponding equations of motion, in flat and curved superspaces, in terms of the Nambu (p + 1)-brackets. These brackets make the (p + 1)-algebra structure of a super p-brane manifest. For the flat superspace, this reconstruction of the action also allows reformulating it in terms of two sets of differential forms. © 2011 Pleiades Publishing, Inc. Source


Aziz M.,Amirkabir University of Technology | Tayarani-N. M.-H.,University of Birmingham
Swarm and Evolutionary Computation | Year: 2016

Magnetic Optimization Algorithm (MOA) has emerged as a promising optimization algorithm that is inspired by the principles of magnetic field theory. In this paper we improve the performance of the algorithm in two aspects. First an Opposition-Based Learning (OBL) approach is proposed for the algorithm which is applied to the movement operator of the algorithm. Second, by learning from the algorithm's past experience, an adaptive parameter control strategy which dynamically sets the parameters of the algorithm during the optimization is proposed. To show the significance of the proposed parameter adaptation strategy, we compare the algorithm with two well-known parameter setting techniques on a number of benchmark problems. The results indicate that although the proposed algorithm with the adaptation strategy does not require to set the parameters of the algorithm prior to the optimization process, it outperforms MOA with other parameter setting strategies in most large-scale optimization problems. We also study the algorithm while employing the OBL by comparing it with the original version of MOA. Furthermore, the proposed algorithm is tested and compared with seven traditional population-based algorithms and eight state-of-the-art optimization algorithms. The comparisons demonstrate that the proposed algorithm outperforms the traditional algorithms in most benchmark problems, and its results is comparative to those obtained by the state-of-the-art algorithms. © 2015 Elsevier B.V. All rights reserved. Source


Farahani R.Z.,Kingston University | Hekmatfar M.,Amirkabir University of Technology | Fahimnia B.,University of Sydney | Kazemzadeh N.,Iowa State University
Computers and Industrial Engineering | Year: 2014

The primary objective in a typical hierarchical facility location problem is to determine the location of facilities in a multi-level network in a way to serve the customers at the lowest level of hierarchy both efficiently (cost minimization objective) and effectively (service availability maximization objective). This paper presents a comprehensive review of over 40 years of hierarchical facility location modeling efforts. Published models are classified based on multiple characteristics including the type of flow pattern, service availability, spatial configuration, objective function, coverage, network levels, time element, parameters, facilities, capacity, and real world application. A second classification is also presented on the basis of solution methods adopted to solve various hierarchical facility location problems. The paper finally identifies the gaps in the current literature and suggests directions for future modeling efforts. © 2013 Elsevier Masson SAS. All rights reserved. Source


Rashvand M.,Iran Institute for Color Science and Technology | Ranjbar Z.,Iran Institute for Color Science and Technology | Rastegar S.,Amirkabir University of Technology
Progress in Organic Coatings | Year: 2011

Nano zinc oxide (ZnO) was co-deposited together with a cathodic electrodeposition paint onto phosphated normal steel panels. The films containing nano zinc oxide were compared with blank films regarding their stability against UV radiation. SEM micrographs show that nano-ZnO can stop the formation of cracks in the film. On the other hand, AFM, surface roughness and loss of gloss studies showed that the presence of nano zinc oxide particles reduces the photo-degradation of the aromatic polyurethane binder. It was also found that the presence of the nano-sized ZnO particles in the films reduces the tendency of the films to yellowing. © 2011 Elsevier B.V. All rights reserved. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology
International Journal of Hydrogen Energy | Year: 2013

In this paper, a method called "bipolar plate duct indentation" is introduced, in which some partial blocks (indents) are recommended to be placed along the fluid delivery channels being machined in bipolar plates (BPPs) of fuel cells (FCs). The indents are to enhance the over-rib convections and the kinetics of reactions in catalyst layers to improve the cell performance. As an initial step to numerically model this problem, a partially porous channel of BPP of a Direct Methanol FC (DMFC) is taken as the model geometry, and the level of heat exchange enhancement due to channel indentation is examined in this geometry. The performed parametric studies show that channel indentation enhances the heat exchange by 40%; with some minor increases in fluid delivery pumping power. From the analogy between the heat and mass transfer problems in dynamically similar problems, it is believed that the mass exchanges between the core channel and the catalyst layer in FC will enhance the same order as that in the pure heat transfer problem. The present work provides helpful guidelines to the bipolar plate manufactures of low-temperature FCs to considerably alleviate the losses on the side(s) of slow reaction electrodes. Crown Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source


Chehrazi E.,Amirkabir University of Technology | Taheri Qazvini N.,University of Tehran
Iranian Polymer Journal (English Edition) | Year: 2013

The influence of nanoconfinement on segmental relaxation behavior of poly(methyl methacrylate) and poly(styrene-ran-acrylonitrile) miscible blend and its nanocomposites with spherical and layered nanoparticles have been investigated. Dynamic mechanical analysis was employed to examine the effect of geometry of nanoparticles on the temperature dependence and relaxation function breadth of segmental dynamics (α-relaxation) in the glass transition region. The maxima of the loss modulus curves were used to fit to the Vogel-Fulcher-Tamman equation to describe the temperature dependence of the characteristic relaxation times. Furthermore, the T g-normalized semi-logarithmic Arrhenius plots (fragility plots) were exploited to indicate the changes in cooperative segmental motions across the glass transition. The master curves for relaxation modulus were also constructed for each sample as a function of time using the time-temperature superposition principle. The investigated nanocomposites showed a narrower segmental dispersion in the glass transition region compared to the neat systems. The relaxation modulus master curves were fitted by the Kohlrausch-Williams-Watts (KWW) function. It was observed that the distribution parameter of segmental relaxation time increased with addition of nanoparticles which was correlated with a decrease in fragility index. In addition, the increase of the KWW distribution parameter (β KWW) for spherical silica nanocomposites was less than that for nanocomposites prepared with layered silicates (organoclay). © 2013 Iran Polymer and Petrochemical Institute. Source


Danyali S.,University of Tabriz | Hosseini S.H.,University of Tabriz | Gharehpetian G.B.,Amirkabir University of Technology
IEEE Transactions on Power Electronics | Year: 2014

This paper presents a new extendable single-stage multi-input dc-dc/ac boost converter. The proposed structure comprises of two bidirectional ports in the converter's central part to interface output load and battery storage, and several unidirectional input ports to get powers from different input dc sources. In fact, the proposed topology consists of two sets of parallel dc-dc boost converters, which are actively controlled to produce two independent output voltage components. Choosing two pure dc or two dc-biased sinusoidal values as the converter reference voltages, situations of the converter operating in two dc-dc and dc-ac modes are provided, respectively. The proposed converter utilizes minimum number of power switches and is able to step up the low-level input dc voltages into a high-level output dc or ac voltage without needing any output filter. The converter control system includes several current regulator loops for input dc sources and two voltage regulator loops for generating the desired output voltage components, resulting in autonomously charging/discharging the battery to balance the power flow. Due to the converter inherent multi-input multioutput control system, the small signal model of the converter is extracted and then the pole-placement control strategy via integral state feedback is applied for achieving the converter control laws. The validity and effectiveness of the proposed converter and its control performance are verified by simulation and experimental results. © 1986-2012 IEEE. Source


Malvandi A.,Amirkabir University of Technology | Ganji D.D.,Babol Noshirvani University of Technology
Journal of the Brazilian Society of Mechanical Sciences and Engineering | Year: 2014

Thermally fully developed mixed convection flow of nanofluids in a vertical annular pipe was investigated. Because of the non-adherence of the fluid–solid interface in the presence of nanoparticles, known as slip condition, the Navier’s slip condition was considered at the pipe walls. The Buongiorno’s model was employed for nanofluids that incorporate the effects of Brownian motion Nb and thermophoresis Nt numbers. Using the similarity variables, the governing partial differential equations were transformed into a system of ordinary ones with a constraint parameter and a solution was prepared via a reciprocal numerical algorithm. The effects of Grashof number Gr and slip parameter λ on nanoparticle volume fraction, velocity, temperature, average Nusselt number Nuavg, and pressure coefficient σ have been investigated in details. Results indicate that an increase in Gr and λ reduces the peak value of the dimensionless velocity profile in the core region of the annulus, away from the pipe walls, however, the velocity closer to the pipe walls increases. Furthermore, it was shown that nanofluids can transfer heat more efficiently in a slip condition than in a no-slip condition. © 2014, The Brazilian Society of Mechanical Sciences and Engineering. Source


Abbassi M.,Institute for Trade Studies and Research | Abbassi M.,Tafresh University | Ashrafi M.,Amirkabir University of Technology | Sharifi Tashnizi E.,Tafresh University
Technovation | Year: 2014

The intensive growth of technology makes firms rely on research and development (R&D) activities in order to adapt to technology changes in an ever-changing and uncertain environment. Due to R&D budget constraints and limited resources, firms are often forced to select a subset of all candidate projects by means of project portfolio selection techniques mitigating the corresponding risks and enhancing the overall value of portfolio. Projects' interdependencies and types were rarely considered in existing models of R&D portfolio selection that may result in selecting wrong projects. This flaw hinders the projects alignment with corporate objectives and strategy and leads to excessive risk and missing the promised values. In this paper, a balanced set of R&D project evaluation criteria was proposed. Next, to construct R&D project portfolio, a 0-1 nonlinear mathematical programming method for balancing portfolio values and risks was proposed, in which research projects' interdependencies, types and other constraints were all considered. Finally, a Cross-Entropy algorithm was developed to solve the proposed model and results were reported. The algorithm proved to be very effective in terms of solution quality and computational time. The proposed algorithm especially suits large scale instances while exact approaches are doomed to fail. © 2013 Elsevier Ltd. Source


Rahbar-Ranji A.,Amirkabir University of Technology
Journal of Mechanical Science and Technology | Year: 2014

Tripping of stiffeners is one of the buckling modes of stiffened panels which could rapidly lead to its catastrophic failure. Loss of thickness in the web and flange of stiffeners due to corrosion reduces elastic buckling strength. It is common practice to assume a uniform thickness reduction for corroded surfaces. To estimate the remaining strength of a corroded structure, a much higher level of accuracy is required since corroded surfaces are irregular. Finite element method is employed to analyze elastic tripping stress of corroded stiffeners with irregular surfaces. Comparing the results with elastic tripping stress of un-corroded stiffener, a reduction factor is introduced. It is found that for flat-bars and angle-bars the reduction factor increases by increasing corrosion loss; however, for tee-bars remains almost unchanged. Surface roughness has no significant effect on reduction of tripping Euler stress of angle-bars and flat-bars; however, it has an effect on reduction of tripping Euler stress of small flat-bars. For high values of corrosion loss, reduction of tripping Euler stress is higher in flat-bars than angle-bars. Corrosion at the mid-length or ends of flat-bars is more detrimental than full length. Corrosion at the ends of angle-bars is more detrimental than full length and mid-length. © 2014, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source


Yavari M.,Amirkabir University of Technology
Electronics Letters | Year: 2010

A single-stage class AB multipath operational amplifier is presented. The proposed amplifier uses the previously idle devices in a folded-cascode amplifier in the signal path and a flipped-voltage follower cell to build the class AB operation. It results in enhanced unity-gain bandwidth and DC gain and large slew rate with the same power consumption as the folded-cascode amplifier. Circuit level analysis and simulation results are provided to verify the effectiveness of the proposed amplifier. © 2010 The Institution of Engineering and Technology. Source


Sadigh A.K.,University of Tabriz | Hosseini S.H.,University of Tabriz | Sabahi M.,University of Tabriz | Gharehpetian G.B.,Amirkabir University of Technology
IEEE Transactions on Power Electronics | Year: 2010

Multilevel converters are very interesting alternatives for medium and high-power applications. The main reason is the increase in the number of output voltage levels and its apparent frequency. This paper presents a new configuration of flying capacitor multicell (FCM) converter. The main advantages of the proposed converter, in comparison with FCM and stacked multicell converters, are doubling the rms and the number of output voltage levels, improving the output voltage frequency spectrum, and canceling the midpoint of dc source. This progress is achieved by adding only two low-frequency switches to the conventional configuration of FCM converter while the number of high-frequency switches and capacitors, voltage ratings of capacitors and switches, and the number of high-frequency switchings during a full cycle are kept constant. This converter is controlled by a modified phase-shifted pulsewidth modulation, therefore, the self-balancing property of the flying capacitor converter is maintained in the proposed converter. The circuit is simulated using power systems computeraided design/electromagnetic transients in DC systems (EMTDC) software and simulation results are presented to validate the effectiveness and advantages of the proposed configuration as well as its control strategy. Additionally, measurements taken from an experimental setup are presented in order to study the practical configuration. © 2006 IEEE. Source


Managing and reusing knowledge in engineering and construction sectors can lead to greater competitive advantage, improved designs, and more effective management of constructed facilities. The use of Information Technology (IT) in design and construction can exploit strategic opportunities for new ways of integration, sharing and facilitating information and knowledge in any field of engineering. The integrating of separate areas of IT can be used to bring a group of experts and specialists in any field of engineering closer together by allowing them to communicate and exchange information and expertise that facilitate knowledge capture, sharing, and reuse. A lack of an advisory management system and a need to marshal all available data in a common format has indicated the need for an integrated engineering computing environment to investigate concrete repair problems. The research described in this paper is based upon an evaluation management system (EMS) which comprising a database management system (REPCON) alongside visualisation technologies and evaluation system (ECON) is developed to produce an innovative platform which will facilitate and encourage the development of knowledge in educational, evolution and evaluation modes of concrete repair. This allows us to create assessment procedures that will allow the current condition of the concrete structure and its components to be expressed numerically using a confidence level (CL) so as to take the best course of action in the repair and maintenance management. The explained rating system, which is related to structural integrity and serviceability of the structure, allows the confidence level to be determined by visual inspection and the descriptive information and pictures taken from an available REPair of CONcrete (REPCON) database. Source


Jahan A.,Amirkabir University of Technology
Modern Physics Letters A | Year: 2010

We derive the one-loop vacuum energy of the bosonic string theory in a system of non-parallel D1-branes using the path integral method. © 2010 World Scientific Publishing Company. Source


Mirhabibi A.,Islamic Azad University at Parand | Soroush A.,Amirkabir University of Technology
Tunnelling and Underground Space Technology | Year: 2013

Buildings are usually modeled as elastic beams in plane strain finite element (FE) simulation of tunnel-building interaction. However, neither tunnel nor surface buildings behave in a plane strain manner. In order to assess the effect of building modeling type on twin tunneling-induced ground settlement, some full three-dimensional FE models were analyzed and the effect of building modeling type was reviewed. Two dimensional (2D) plane strain interaction and green-field situation models were also analyzed to compare the results with the three dimensional (3D) models and assess the influence of modeling type. Outcomes of the studies showed that three-dimensional modeling has great influence on the results and equivalent surface beam, which is used in common practice of two-dimensional plane strain models, over-estimates the stiffness of building and leads to less settlement prediction in comparison with 3D simulation. © 2013 Elsevier Ltd. Source


Rahimi A.,University of Isfahan | Niksiar A.,Amirkabir University of Technology
International Journal of Mineral Processing | Year: 2013

The general model developed in the first part of this study is based on the grain model. In order to determine the overlapping range of this kinetic model and the unreacted shrinking core model the attempt is made in this part of the article to identify the simplest and most accurate model. Although under certain circumstances the found results in both the models are almost similar, the developed model based on grain model predicts the experimental data much better than the shrinking core model. The simplicity of the model's results in the outcome is due the predominant diffusional regime. This regime is revealed where the pellet size is big; nevertheless, the results of two models are not similar even in small values of pellet porosity. Two correlations for determining effective diffusivity are tested and it shows a direct effect on the overlapping range of both the models. © 2013 Elsevier B.V. Source


Nazari A.,Islamic Azad University at Saveh | Mohandesi J.A.,Amirkabir University of Technology | Tavareh S.,Islamic Azad University at Saveh
Computational Materials Science | Year: 2011

In the present study, the Vickers microhardness profile of functionally graded steel austenitic steel produced by electroslag remelting process has been investigated. To produce functionally graded steels, two different slices from plain carbon steel and austenitic stainless steels were spot welded and used as electroslag remelting electrode. Functionally graded steel containing graded layers of austenite may be fabricated via diffusion of alloying elements during remelting stage. Vickers microhardness profile of the specimen has been obtained experimentally and modeled with mechanism-based strain gradient plasticity theory. In this regard, the density of the statistically stored dislocations and that of geometrically necessary dislocations was related to the Vickers microhardness profile of each layer. The experimental results are in good agreement with those obtained from the theory. © 2010 Elsevier B.V. All rights reserved. Source


Rezaei M.,HEC School of Management | Zarandi M.H.F.,Amirkabir University of Technology
Applied Soft Computing Journal | Year: 2011

This paper presents a continuous facility location model with fuzzy methodology. The developments concern mainly to some drawbacks in the initial model which takes it far from being used in practice. A fuzzy modeling method is proposed to estimate the required functions in the initial model. Structure identification in the proposed fuzzy modeling method is carried out using subtractive clustering, and parameter identification is conducted via some heuristics as well as an optimization problem. Furthermore, a simulation method along with some heuristic relations is used for implementation and evaluation of the modified model. Efficiency of the proposed method to fuzzy modeling as well as the proposed simulation method is presented by a numerical example. © 2011 Elsevier B.V. All rights reserved. Source


Nazari A.,Islamic Azad University at Saveh | Mohandesi J.A.,Amirkabir University of Technology | Tavareh S.,Islamic Azad University at Saveh
Computational Materials Science | Year: 2011

Functionally graded austenitic steel was produced by setting the austenitic and carbon steels with appropriate thickness as electrode through electroslag refining. Tensile stress of specimen has been studied and modeled regarding the mechanism-based strain gradient plasticity theory. Tensile strength of the composites depends on the composition and volume fraction of the layers. The yield stress of each element was related to the density of the statistically stored dislocations of that element and assuming Holloman relation for the corresponding stress-strain curves, tensile strengths of the composites were determined via numerical method by applying the rule of mixtures. The obtained results of the proposed model are in good agreement with the experimental results. © 2010 Elsevier B.V. All rights reserved. Source


Saeedi M.,Amirkabir University of Technology | Wille R.,University of Bremen | Drechsler R.,University of Bremen
Quantum Information Processing | Year: 2011

While a couple of impressive quantum technologies have been proposed, they have several intrinsic limitations which must be considered by circuit designers to produce realizable circuits. Limited interaction distance between gate qubits is one of the most common limitations. In this paper, we suggest extensions of the existing synthesis flow aimed to realize circuits for quantum architectures with linear nearest neighbor interaction. To this end, a template matching optimization, an exact synthesis approach, and two reordering strategies are introduced. The proposed methods are combined as an integrated synthesis flow. Experiments show that by using the suggested flow, quantum cost can be improved by more than 50% on average. © 2010 Springer Science+Business Media, LLC. Source


Rahbar-Ranji A.,Amirkabir University of Technology
Engineering Structures | Year: 2014

Stiffened plate buckles in different modes, including web/flange buckling, torsional buckling, plate buckling and interaction of these. Design codes ignore interaction of different buckling modes and each mode is treated separately. By introducing an effective breadth/web concept, coupled plate-torsional-web buckling in flat-bar stiffened plates is simply analyzed by torsional buckling analysis of equivalent cross section. The model provides a tool that is more accurate than existing design codes, and more efficient than finite element method. An expression for effective breadth/web of flat-bar stiffened plate has been derived and Euler stress for coupled buckling mode in flat-bar stiffened plate are calculated and compared with finite element method and rule-base equation. It is found that this method has better agreement irrespective of dominant mode of buckling. © 2014 Elsevier Ltd. Source


Mohebbi A.,University of Kashan | Dehghan M.,Amirkabir University of Technology
Computer Physics Communications | Year: 2010

The problem of finding the solution of partial differential equations with source control parameter has appeared increasingly in physical phenomena, for example, in the study of heat conduction process, thermo-elasticity, chemical diffusion and control theory. In this paper we present a high order scheme for determining unknown control parameter and unknown solution of parabolic inverse problem with both integral overspecialization and overspecialization at a point in the spatial domain. In these equations, we first approximate the spatial derivative with a fourth order compact scheme and reduce the problem to a system of ordinary differential equations (ODEs). Then we apply a fourth order boundary value method for the solution of resulting system of ODEs. So the proposed method has fourth order accuracy in both space and time components and is unconditionally stable due to the favorable stability property of boundary value methods. Several numerical examples and also some comparisons with other methods in the literature will be investigated to confirm the efficiency of the new procedure. © 2010 Elsevier B.V. All rights reserved. Source


Maslov D.,University of Waterloo | Saeedi M.,Amirkabir University of Technology
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems | Year: 2011

For years, the quantum/reversible circuit community has been convinced that: 1) the addition of auxiliary quantum bits (qubits) is instrumental in constructing a smaller quantum circuit, and 2) the introduction of quantum gates inside reversible circuits may result in more efficient designs. This paper presents a systematic approach to optimizing reversible (and quantum) circuits via the introduction of auxiliary qubits and quantum gates inside circuit designs. This advances our understanding of what may be achieved with 1) and 2). © 2011 IEEE. Source


Mohammadi A.,Amirkabir University of Technology | Ghannouchi F.M.,University of Calgary
IEEE Communications Magazine | Year: 2011

The main limitation of using multiple antenna architecture is the complexity and high cost of the hardware in the RF section. One solution to reduce the extra hardware cost and RF circuit imperfection is the utilization of a single RF front-end in a MIMO system. This article discusses the different alternatives to realize single RF front-end transceivers, including the antenna selection technique, time-division multiplexing, code-division multiplexing, and the parasitic antenna method. The implementation technique for each approach is presented, and a performance study has been conducted. The practical limitations of a single RF front-end design alternative are also discussed. © 2006 IEEE. Source


Forsati R.,Shahid Beheshti University | Mahdavi M.,Sharif University of Technology | Shamsfard M.,Shahid Beheshti University | Reza Meybodi M.,Amirkabir University of Technology | Reza Meybodi M.,Institute for Studies in Theoretical Physics and Mathematics IPM
Information Sciences | Year: 2013

Clustering has become an increasingly important and highly complicated research area for targeting useful and relevant information in modern application domains such as the World Wide Web. Recent studies have shown that the most commonly used partitioning-based clustering algorithm, the K-means algorithm, is more suitable for large datasets. However, the K-means algorithm may generate a local optimal clustering. In this paper, we present novel document clustering algorithms based on the Harmony Search (HS) optimization method. By modeling clustering as an optimization problem, we first propose a pure HS based clustering algorithm that finds near-optimal clusters within a reasonable time. Then, harmony clustering is integrated with the K-means algorithm in three ways to achieve better clustering by combining the explorative power of HS with the refining power of the K-means. Contrary to the localized searching property of K-means algorithm, the proposed algorithms perform a globalized search in the entire solution space. Additionally, the proposed algorithms improve K-means by making it less dependent on the initial parameters such as randomly chosen initial cluster centers, therefore, making it more stable. The behavior of the proposed algorithm is theoretically analyzed by modeling its population variance as a Markov chain. We also conduct an empirical study to determine the impacts of various parameters on the quality of clusters and convergence behavior of the algorithms. In the experiments, we apply the proposed algorithms along with K-means and a Genetic Algorithm (GA) based clustering algorithm on five different document datasets. Experimental results reveal that the proposed algorithms can find better clusters and the quality of clusters is comparable based on F-measure, Entropy, Purity, and Average Distance of Documents to the Cluster Centroid (ADDC). © 2012 Elsevier Inc. All rights reserved. Source


Nazari A.,Islamic Azad University at Saveh | Aghazadeh Mohandesi J.,Amirkabir University of Technology
Computational Materials Science | Year: 2011

Tensile strength of oblique layer functionally graded austenitic steel produced by electroslag remelting has been modeled. For a constant angle of oblique layer, tensile strength of the composite depends on the composition and number of layers. Tensile strength of the composite has been modeled based on tensile behavior of individual layers. By assuming a power-law relation for stress-strain curve of each layer, the differences between tensile strength of neighboring elements maybe related to the tensile strength of the composite by means of an additional parameter which is equal to the ratio of stress level differences to strain level differences of two adjacent elements at a given layer. Accordingly, tensile strength of the oblique layer functionally graded austenitic steel was determined via a numerical method. The obtained result is in good agreement with the experimental data. © 2010 Elsevier B.V. All rights reserved. Source


Markov I.L.,University of Michigan | Saeedi M.,Amirkabir University of Technology
Quantum Information and Computation | Year: 2012

Reversible circuits for modular multiplication Cx%M with x < M arise as components of modular exponentiation in Shor's quantum number-factoring algorithm. However, existing generic constructions focus on asymptotic gate count and circuit depth rather than actual values, producing fairly large circuits not optimized for specific C and M values. In this work, we develop such optimizations in a bottom-up fashion, starting with most convenient C values. When zero-initialized ancilla registers are available, we reduce the search for compact circuits to a shortest-path problem. Some of our modular-multiplication circuits are asymptotically smaller than previous constructions, but worst-case bounds and average sizes remain Θ(n 2). In the context of modular exponentiation, we offer several constant-factor improvements, as well as an improvement by a constant additive term that is significant for few-qubit circuits arising in ongoing laboratory experiments with Shor's algorithm. © Rinton Press. Source


Molladavoodi H.,Amirkabir University of Technology
Archives of Mining Sciences | Year: 2013

Analysis of stresses and displacements around underground openings is necessary in a wide variety of civil, petroleum and mining engineering problems. In addition, an excavation damaged zone (EDZ) is generally formed around underground openings as a result of high stress magnitudes even in the absence of blasting effects. The rock materials surrounding the underground excavations typically demonstrate nonlinear and irreversible mechanical response in particular under high in situ stress states. The dominant cause of irreversible deformations in brittle rocks is damage process. One of the most widely used methods in tunnel design is the convergence-confinement method (CCM) for its practical application. The elastic-plastic models are usually used in the convergence-confinement method as a constitutive model for rock behavior. The plastic models used to simulate the rock behavior, do not consider the important issues such as stiffness degradation and softening. Therefore, the use of damage constitutive models in the convergence-confinement method is essential in the design process of rock structures. In this paper, the basic concepts of continuum damage mechanics are outlined. Then a numerical stepwise procedure for a circular tunnel under hydrostatic stress field, with consideration of a damage model for rock mass has been implemented. The ground response curve and radius of excavation damage zone were calculated based on an isotropic damage model. The convergence-confinement method based on damage model can consider the effects of post-peak rock behavior on the ground response curve and excavation damage zone. The analysis of results show the important effect of brittleness parameter on the tunnel wall convergence, ground response curve and excavation damage radius. Source


Jam J.E.,Composite Materials and Technology Center | Kiani Y.,Amirkabir University of Technology
Composite Structures | Year: 2015

A linear buckling analysis is presented for nanocomposite conical shells reinforced with single walled carbon nanotubes (SWCNTs) subjected to lateral pressure. Material properties of functionally graded carbon nanotube reinforced composite (FG-CNTRC) conical shell are assumed to be graded across the thickness and are obtained based on the modified rule of mixture. Governing equilibrium equations of the shell are obtained based on the Donnell shell theory assumptions consistent with the first order shear deformation shell theory. General form of the equilibrium equations and the complete set of boundary conditions are obtained based on the concept of virtual displacement principle. Shell is assumed to be under lateral pressure. Prebuckling load of the shell is estimated based on the linear membrane analysis. Stability equations of the shell are extracted via the adjacent equilibrium criterion. Resulting stability equations are discreted by suitable trigonometric functions in circumferential direction and generalized differential quadrature method in axial direction. An eigenvalue problem is established to obtain the buckling pressure and circumferential buckling mode of the conical shell. It is shown that, CNTs volume fraction and CNTs distribution law are important factors on the buckling mode and buckling load of the FG-CNTRC conical shells. © 2015 Elsevier Ltd. Source


Tatari M.,Isfahan University of Technology | Dehghan M.,Amirkabir University of Technology
Engineering Analysis with Boundary Elements | Year: 2010

In this work a technique is proposed for solving partial differential equations using radial basis functions. The approach is different from the traditional schemes. The radial basis functions are very suitable instruments for solving partial differential equations of various types. However, the matrices which result from the discretization of the equations are usually ill-conditioned especially in higher-dimensional problems. In the current paper, a stable method will be proposed for solving the partial differential equations and will be generalized to solve higher-dimensional problems. To the contrast of most existing methods, the new technique provides a closed form approximation for the solution. Another advantage of the developed method is that it can be applied to problems with nonregular geometrical domains. © 2009 Elsevier Ltd. All rights reserved. Source


Azadi M.,Islamic Azad University at Qazvin | Mir Mohammad Hosseini S.M.,Amirkabir University of Technology
Tunnelling and Underground Space Technology | Year: 2010

Many studies have focused on the effects of earthquake loading on the forces and displacements of underground structures. As part of the analysis of these forces and displacements, seismic loading effects are considered when designing underground structures, and so the equations are measured under small strains. Thus, the real results in surrounding tunnels and underground structures cannot be expressed by applying these equations when large strains due to some phenomena such as liquefaction occur. In other words, the mechanism of underground structure seismic behavior has not been fully recognized, and despite the presence of several studies that have been conducted already, many others are still needed. So the present study strives to assess the effect of liquefaction on shield tunnels. © 2010 Elsevier Ltd. Source


Abolhasani M.M.,University of Kashan | Naebe M.,Deakin University | Jalali-Arani A.,Amirkabir University of Technology | Guo Q.,Deakin University
PLoS ONE | Year: 2014

In this paper, intercalation of nanoclay in the miscible polymer blend of poly(vinylidene fluoride) (PVDF) and acrylic rubber(ACM) was studied. X-ray diffraction was used to investigate the formation of nanoscale polymer blend/clay hybrid. Infrared spectroscopy and X-ray analysis revealed the coexistence of β and γ crystalline forms in PVDF/Clay nanocomposite while α crystalline form was found to be dominant in PVDF/ACM/Clay miscible hybrids. Flory-Huggins interaction parameter (B) was used to further explain the miscibility phenomenon observed. The B parameter was determined by combining the melting point depression and the binary interaction model. The estimated B values for the ternary PVDF/ACM/Clay and PVDF/ACM pairs were all negative, showing both proper intercalation of the polymer melt into the nanoclay galleries and the good miscibility of PVDF and ACM blend. The B value for the PVDF/ACM blend was almost the same as that measured for the PVDF/ACM/Clay hybrid, suggesting that PVDF chains in nanocomposite hybrids interact with ACM chains and that nanoclay in hybrid systems is wrapped by ACM molecules. © 2014 Abolhasani et al. Source


Behnamian J.,Bu - Ali Sina University | Fatemi Ghomi S.M.T.,Amirkabir University of Technology
Journal of Intelligent Manufacturing | Year: 2014

Because of current globalization trend, production has shifted from the single factory production to multi-factory production network. To become competitive in today's rapidly changing market requirements, factories have shifted from a centralized to a more decentralized structure, in many areas of decision making including scheduling. In multi-factory production network, each factory can be considered as an individual entity which has different efficiency and is subject to different constraints, for example, machine advances, worker cost, tax, close to suppliers, and transportation facilities, etc. Since limited resources make scheduling an important decision in the production, for several decades, researchers focused on determining an efficient schedule to improve the productivity. The recent remarkable attention in distributed production management in both academia and the industry has demonstrated the significance of multi-factory scheduling. For the first time, this paper provides a review on the multi-factory machine scheduling. For this, first, the paper classifies and reviews the literature according to shop environments, including single machine, parallel machines, flowshop, job shop, and open shop. Then the reviewed literature is quantified and measured. At the end, the paper concludes by presenting some problems receiving less attention than the others and proposes several research opportunities in the field. © 2014 Springer Science+Business Media New York. Source


Ghodousian A.,University of Tehran | Khorram E.,Amirkabir University of Technology
Fuzzy Sets and Systems | Year: 2012

In this paper, optimization of a linear objective function with fuzzy relational inequality constraints is investigated whereby an arbitrary function is considered as fuzzy composition. The feasible solution set is determined and compared with some common results in the literature. A necessary and sufficient condition and three other necessary conditions are presented to conceptualize the feasibility of the problem. It is shown that in general a lower bound is always attainable for the optimal objective value. Moreover, we prove that the optimal solution of the problem is obtained if the problem is defined by a non-decreasing or non-increasing function. An algorithm is presented to summarize the process and an example is described to illustrate the algorithm. © 2012 Elsevier B.V. Source


Hosseini M.,Amirkabir University of Technology
Journal of Natural Gas Science and Engineering | Year: 2016

Continuous estimation of pore-size can be very helpful to use in optimization of well completion and effective production of hydrocarbon reservoirs. This paper shows the application of two new empirical models derived of the Kozeny-Carman equation to estimate the mean pore-size. The models are: The formation evaluation model, and the Stoneley slowness model. The main objective of this work is to give a general framework to develop the number of methods that provide a continuous estimation of formation mean pore-size along the well.In the final form of the derived equations, the calibration factors for minerals were the only constants that had to be determined using a calibration method. Therefore, the proposed models were calibrated with core data using the least squares method. Fortunately, all the required core data were accessible to be used for the calibration process. Moreover, the effects of some parameters such as the shape factor were ignored. The shape factor value is influenced by the pore shape. The calibrated models were then used to re-compute the mean pore-size in the logged intervals. The results showed that, in many points, there was a relatively low difference between the estimated mean pore-size and the core pore-size. According to the calculated calibration factors for two methods, illite had a very negative effect upon the pore-size values among all the minerals. The proposed models could be used as an index for determining the permeable and non-permeable layers. As a result of the calibration of the proposed models (particularly for the Stonely model), the RMSE values calculated for the permeabilities of less than 100 mD were lower than that of the permeabilities of greater than 100 mD. The least RMSE values were calculated for the permeabilities ranged in 10-100 mD. Moreover, the simultaneous assessments of the presented pore-size models, and comparing their results with the core data, helped us to evaluate the correctness of the calculated pore-size as well as the permeability. © 2016 Elsevier B.V. Source


Hekmati P.,Amirkabir University of Technology | Mirsalim M.,St. Marys University
IEEE Transactions on Energy Conversion | Year: 2013

This paper presents a novel limited-angle torque motor as a modified double-sided slotless axial-flux permanent-magnet motor (DSAPM) with a trapezoidal cross section for the stator. A new approach to the magnetic equivalent circuit and semi-three-dimensional (3-D) analytical armature reaction field modeling for the proposed actuator are derived and implemented in the design process. Designing is done based on avoidance of saturation at maximum torque production to prevent distortion of torque characteristic in short-time operations. Next, finite-element analysis is utilized to confirm the accuracy of the design equations and to compare the proposed actuator with conventional industrial limited-angle torque motors and the conventional DSAPM structure. Finally, the proposed actuator is prototyped and its experimental results are presented and discussed. Finite-element analysis and experimental data show better accuracy of the model, electromagnetic capability improvements by this new structure and excellent applicability of the proposed rotary actuator. © 1986-2012 IEEE. Source


Firouzi M.,University of Tehran | Gharehpetian G.B.,Amirkabir University of Technology
IEEE Transactions on Energy Conversion | Year: 2013

The interaction between wind turbines and grid results in increasing short-circuit level and fault ride-through (FRT) capability problem during fault condition. In this paper, the bridge-type fault current limiter (FCL) with discharging resistor is used for solving these problems. For this FCL, a control scheme is proposed, which uses the dc reactor current as control variable, to adjust the terminal voltage of induction generator (IG) without measuring any parameters of system. In this paper, the wind energy conversion system (WECS) is a fixed-speed system equipped with a squirrel-cage IG. The drivetrain is represented by a two-mass model. The analytical and simulation studies of the bridge-type FCL and proposed control scheme for limiting the fault current and improving FRT capability are presented and compared with the impact of the application of the series dynamic braking resistor (SDBR). © 1986-2012 IEEE. Source


Karami M.,Amirkabir University of Technology
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2012

Nowadays, pipelines are the most important transportation artery and researches indicate that the pipelines will be a secure tool for energy transmission for over 50 years, which is more significant for petrochemical, oil, and gas industries. The large part of chemical fluids, especially natural gas, transmits with pipelines. These pipelines manufactured with large pipes that they can bear high pressures about several thousand kilogram per cubic centimeter. The gas pressure is obtained by high pressure station in long distances. The function of gas pipelines is very important and vital; therefore, they have to be safe. But unfortunately, utilization of old pipelines in operation increases probability of occurrence. The most important reasons of making these occurrences are the internal and external corrosions that are very effective in damaging gas pipelines, hence safety decreases. So, controlling of corrosion in gas pipelines needs to use cathodic protection with cathodic potential, substance becomes a cathode, and this system decreases the rate of corrosion. Periodic inspections of pipelines are essential, through a method called pigging. A pig is a device inserted into a pipeline which travels freely through it and is driven by the product flow to do specific tasks within the pipeline. In this paper, first, corrosion and its types, as one of the most important threats in gas pipelines, will be investigated. Then methods of controlling corrosion will be explained by stating that cathodic protection is the most important method. Finally, pigs will be investigated because it needs continuous inspections in the performance of pipelines for security reasons. © 2012 American Society of Mechanical Engineers. Source


Akbari Torkestani J.,Islamic Azad University of Arak | Meybodi M.R.,Amirkabir University of Technology
Journal of Network and Computer Applications | Year: 2011

Recently, several studies have been conducted to design mobility-based multicast routing protocols for wireless mobile ad hoc networks (MANET). These protocols assume that the mobility parameters of the network are fixed, and so they cannot perform well under real MANET scenarios in which the mobility parameters of the hosts vary over time at random. Finding the optimal solution to the multicast routing problem is incredibly hard, if the mobility parameters are assumed to be random variables. This becomes more difficult when the probability distribution function of these random variables is assumed to be unknown. In this paper, we propose a weighted multicast routing algorithm for MANET in which the mobility parameters are supposed to be random variables with unknown distribution. In this method, the multicast routing problem is first transformed into an equivalent stochastic Steiner tree problem in which the random weight associated with a communication link is its expected duration time. Then, a learning automata-based algorithm is proposed for solving the proxy Steiner tree problem. The aim of the proposed algorithm is to find the most stable multicast route (with the maximum duration) against the host mobility. Experimental results confirm the superiority of the proposed method over the best existing mobility-based multicast routing protocols in terms of the packet delivery ratio, multicast route lifetime, control message overhead, and end-to-end delay. © 2010 Elsevier Ltd. All rights reserved. Source


Pacheco-Torgal F.,University of Minho | Abdollahnejad Z.,University of Minho | Camoes A.F.,University of Minho | Jamshidi M.,Amirkabir University of Technology | Ding Y.,Dalian University of Technology
Construction and Building Materials | Year: 2012

The alkali activation of alumino-silicate materials is a complex chemical process evolving dissolution of raw materials, transportation or orientation and polycondensation of the reaction products. Publications on the field of alkali-activated binders, state that this new material is likely to have high potential to become an alternative to Portland cement. While some authors state that the durability of these materials constitutes the most important advantage over Portland cement others argue that it's an unproven issue. This paper presents a review of the literature about the durability of alkali-activated binders. The subjects of this paper are resistance to acid attack, alkali-silica reaction, corrosion of steel reinforcement, resistance to high temperatures and to fire, resistance to freeze-thaw. Special attention is given to the case of efflorescences, an aspect that was received very little concern although it is a very important one. © 2011 Elsevier Ltd. All rights reserved. Source


Sohrabi M.K.,Islamic Azad University at Semnan | Barforoush A.A.,Amirkabir University of Technology
Knowledge-Based Systems | Year: 2013

Since extraction of frequent itemsets from a transaction database is crucial to several data mining tasks such as association rule generation, so frequent itemset mining is one of the most important concepts in data mining. One of the major problems in frequent itemset mining is the explosion of the number of results which is directly effecting on the execution time of itemset mining algorithms. To address this problem, closed itemsets have been proposed, which provides concise lossless representations of the original collection of frequent itemsets. Henceforth, the frequencies of all itemsets in the original collection can be reconstructed from the reduced collection. However, the reduction provided by this exact method is not sufficient to solve the pattern explosion problem, mainly because of high dimensional datasets which have large number of items in each transaction. Colossal itemset mining is another solution to reduce the output size which will not be useful if the set of all frequent itemsets have been required. Higher level of performance improvement can be obtained from efficient scalable parallel mining methods. In this paper we represent an efficient scalable parallel algorithm using systolic arrays to conduct mining of frequent itemsets in very large, such as high dimensional, datasets. In our algorithm, we use a bit matrix to compress the dataset and mapping the mining algorithm on the systolic arrays architecture. For this purpose, each transaction of dataset represents as a row in the bit matrix. We use this bit matrix structure to model the pattern mining as a systolic array problem. Our experimental results and performance study show that this algorithm outperforms substantially the best previously developed parallel algorithms. © 2012 Elsevier B.V. All rights reserved. Source


Zareian M.,Amirkabir University of Technology | Tohidypour H.R.,University of British Columbia
IET Image Processing | Year: 2013

In this study, a robust image watermarking based on the quantisation index modulation (QIM) method is proposed. Conventional QIM methods employ a fixed quantisation step-size that results in poor robustness of the algorithm. Here, the quantisation step-size in the QIM method is adaptively selected using a power-law function and with the aid of the side information, the proposed method is invariant to gain and rotation attack. To keep the watermark imperceptible and increase its robustness, the low-frequency components of high-entropy image blocks are used for data hiding. The analytical error probability and embedding distortion are derived and assessed by simulations on artificial signals. The optimum parameter in the power-law function is obtained based on minimising the error probability. Experimental results confirm the superiority of the proposed technique against common attacks in comparison with the recently proposed methods. © The Institution of Engineering and Technology 2013. Source


Pouranvari M.,Islamic Azad University at Dezful | Marashi S.P.H.,Amirkabir University of Technology
Science and Technology of Welding and Joining | Year: 2010

Quasi-static tensile shear mechanical properties of resistance spot welds of three dual phase (DP) grades including DP600, DP780 and DP980 are investigated. Results showed that weld fusion zone size, failure mode and the strength/ductility of failure location are the main factors governing the peak load and the energy absorption of spot welds. Heat affected zone (HAZ) softening plays an important role in mechanical properties of DP steels with higher volume fraction of martensite (i.e. DP780 and DP980). It was shown that the peak load of the spot welds is not proportionally correlated to the tensile strength of the base metal. Pronounced HAZ softening in DP980 resulted in reducing its tendency to fail in interfacial failure mode in comparison to DP780. In addition, despite its lower base metal ductility, DP980 weld exhibits enhanced ductility and energy absorption than DP780 due to its pronounced HAZ softening. © 2010 Maney Publishing. Source


Ovesy H.R.,Amirkabir University of Technology | Ghannadpour S.A.M.,Shahid Beheshti University
Computers and Structures | Year: 2011

This paper presents the theoretical developments of an exact finite strip for the buckling and initial post-buckling analyses of channel section struts. The presented method provides an efficient and extremely accurate buckling solution. The Von-Karman's equilibrium equation is solved exactly to obtain the buckling loads and mode shapes for the channel section struts. The investigation of buckling behavior is then extended to an initial post-buckling study with the assumption that the deflected form immediately after the buckling is the same as that obtained for the buckling. Through the solution of the Von-Karman's compatibility equation, the in-plane displacement functions which are themselves related to the Airy stress function are developed in terms of the unknown coefficient in the assumed out-of-plane deflection function. All the displacement functions are then substituted in the total strain energy expressions. The theorem of minimum total potential energy is subsequently applied to solve for the unknown coefficient. The developed method is subsequently applied to analyze the initial post-buckling behavior of some representative channel sections for which the results were also obtained through the application of a semi-energy finite strip method. Through the comparison of the results and the appropriate discussion, the knowledge of the level of capability of the developed method is significantly promoted. © 2010 Civil-Comp Ltd and Elsevier Ltd. All rights reserved. Source


Qaurooni D.,Amirkabir University of Technology | Akbarzadeh-T M.-R.,Ferdowsi University of Mashhad
Applied Soft Computing Journal | Year: 2013

Timetabling is the problem of scheduling a set of events while satisfying various constraints. In this paper, we develop and study the performance of an evolutionary algorithm, designed to solve a specific variant of the timetabling problem. Our aim here is twofold: to develop a competitive algorithm, but more importantly, to investigate the applicability of evolutionary operators to timetabling. To this end, the introduced algorithm is tested using a benchmark set. Comparison with other algorithms shows that it achieves better results in some, but not all instances, signifying strong and weak points. To further the study, more comprehensive tests are performed in connection with another evolutionary algorithm that uses strictly group-based operators. Our analysis of the empirical results leads us to question single-level selection, proposing, in its place, a multi-level alternative. © 2012 Elsevier B.V. All rights reserved. Source


Noroozian R.,University of Zanjan | Gharehpetian G.B.,Amirkabir University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2013

In this paper, the combined operation of the active power filter with the photovoltaic generation system has been studied. The proposed system consists of a PV power plant, a DC-DC boost converter, and an active power filter. A novel control strategy for the DC-DC converter has been developed in order to extract the maximum amount of power from PV arrays. Also, a novel control strategy, which is based on generalized instantaneous reactive power theory, has been proposed for the active power filter. The simulation results, based on PSCAD/EMTDC, show that the proposed system can provide the power factor correction, load balancing, harmonic elimination, reactive power compensation and simultaneously inject the maximum power available from the PV array into the grid. © 2012 Elsevier Ltd. All rights reserved. Source


Nazari A.,Islamic Azad University at Yazd | Montazer M.,Amirkabir University of Technology | Dehghani-Zahedani M.,Islamic Azad University at Yazd
Industrial and Engineering Chemistry Research | Year: 2013

Wool protection against moths is an important concept in wool finishing that can obtained through application of various chemicals with different mechanisms of actions. In this paper, a novel mothproofing method is introduced through treatment of wool fabric with nano titanium dioxide (NTO) and citric acid (CA). Citric acid (CA) helps to enhance the washing durability, antifelting, and antibacterial properties of the NTO treated wool. Mothproofing was assessed through the study of damages on the wool surface by the larvae of the carpet beetle, Anthrenus verbasci, feeding on protein fibers. The damage intensity of wool fabric and TiO2 nanoparticles on the fabric surface were confirmed with scanning electron microscopy images and energy-dispersive spectrometry. X-ray diffraction (XRD) of NTO treated fabrics indicated the crystal structure of NTO on the wool surface. Overall, the wool fabrics treated with CA and NTO indicated the highest protection against moths compared with raw and bleached wool fabrics. © 2012 American Chemical Society. Source


Kateb M.,Tarbiat Modares University | Ahmadi V.,Tarbiat Modares University | Mohseni M.,Amirkabir University of Technology
Solar Energy Materials and Solar Cells | Year: 2013

The present work reports preparation of an electrochromic device based on poly(3,4-ethylenedioxythiophene) (PEDOT) modified ZnO nanowires. The vertically aligned ZnO nanowires, being 70 nm in diameter, were prepared as a template by hydrothermal process on 65 nm ZnO seed layer sputtered on transparent conductive fluorine doped tine oxide substrate. PEDOT was synthesized by electropolymerization using two approaches. The first was prepared at 1.6 V constant potential (CP) and the second by 0-2 V cyclic voltammetry (CV). The PEDOT nanotubes were successfully grown on ZnO nanowires array by CV electrochemical polymerization but CP method led to formation of PEDOT thin film. The average wall thickness of nanotubes was 20 nm. The CV and CP electrodes and devices were characterized by scanning electron microscope, cyclic voltammetry analysis and UV-visible spectrophotometery to study the effect of preparation method on electrode morphology and device stability, response time (tR) and contrast. The CV approach gave rise to t R and contrast of 66 ms and 46.1%, respectively; CP method resulted in tR and contrast of 300 ms and 37.84%, respectively. While the conventional thin films had response time in order of second. © 2013 Elsevier B.V. Source


Salamat-Talab M.,Iran University of Science and Technology | Nateghi A.,University of Tehran | Torabi J.,Amirkabir University of Technology
International Journal of Mechanical Sciences | Year: 2012

In this paper, Modified couple stress theory is developed for third-order shear deformation functionally graded (FG) micro beam. Classical Continuum theories are not able to capture size effects while higher order continuum theories consider material length scale parameters to improve the results in micro scales by interpreting size dependencies. By applying Hamilton's principle, governing equations, boundary and initial conditions are derived for a FG micro beam. It is assumed that properties of the FG micro beam follow a power law form through thickness. In addition, Poisson's ratio is assumed constant in the current model. Bending and free vibration of the simply supported FG micro beam is analyzed to illustrate size effects. It is observed that if the thickness of the beam is in the order of the material length scale parameter, size effects are more considerable. It is shown that size dependencies of FG micro beams are quite different from isotropic homogeneous beams as they have maximum and minimum size effects for certain values of power index of material distribution and Poisson's ratio. Moreover, it is shown that the results obtained by the present model deviates significantly from those in which Poissons effect is neglected. Also, the effect of Poisson's ratio on the deflection and natural frequency based on modified couple stress theory is proven to be different from Classical one. The numerical results for simply supported thin beams show that the first natural frequency estimated by the current model is higher than the classical one. In addition, it is observed that size effect is more significant for higher vibration modes. © 2012 Elsevier Ltd. All rights reserved. Source


Mozaffari A.,Babol Noshirvani University of Technology | Gorji-Bandpy M.,Babol Noshirvani University of Technology | Gorji T.B.,Amirkabir University of Technology
International Journal of Bio-Inspired Computation | Year: 2012

In the current investigation, a new optimisation technique called mutable smart bee algorithm (MSBA) is used for optimal design of real-life engineering systems that are subjected to different types of constraints. MSBA is a memory-based diversified optimisation technique that hires mutable smart bee (MSB) instead of conventional bee. MSB heuristic agents are capable of maintaining their historical memory for the location and quality of food sources and also a little chance of mutation is considered for them. Exerted experiments reveal that these features are really effective for optimising multi-modal constraint problems. To elaborate on the authenticity of MSBA, obtained results are compared to state-of-the-art optimisation techniques. © 2012 Inderscience Enterprises Ltd. Source


Pourmousavi Kani S.A.,Montana State University | Ardehali M.M.,Amirkabir University of Technology
Energy Conversion and Management | Year: 2011

As the objective of this study, artificial neural network (ANN) and Markov chain (MC) are used to develop a new ANN-MC model for forecasting wind speed in very short-term time scale. For prediction of very short-term wind speed in a few seconds in the future, data patterns for short-term (about an hour) and very short-term (about minutes or seconds) recorded prior to current time are considered. In this study, the short-term patterns in wind speed data are captured by ANN and the long-term patterns are considered utilizing MC approach and four neighborhood indices. The results are validated and the effectiveness of the new ANN-MC model is demonstrated. It is found that the prediction errors can be decreased, while the uncertainty of the predictions and calculation time are reduced. © 2010 Elsevier Ltd. All rights reserved. Source


Molladavoodi H.,Amirkabir University of Technology
Computers and Geotechnics | Year: 2015

In this paper, a micromechanical damage model formulation for closed frictional microcracks considering the coupling between frictional sliding and damage evolution was reviewed. Then, the sliding criterion for closed microcracks was modified to consider the matrix containment of sliding on microcracks. Then, the adjusted model was programmed as a constitutive model to simulate the UCS test. On the other hand, some different forms of damage criteria have been proposed in phenomenological way in literature for micromechanical damage models. The effect of damage criterion on simulated sample behavior was studied with a variation of damage criterion input parameter. The exponential and tangential damage criteria are capable to control the hardening and softening behavior. Furthermore, the influence of matrix containment of sliding on microcracks faces on the simulated sample behavior was studied in this paper. According to the numerical results, the calculated strength of the simulated sample is sensitive to the matrix resistance parameter against sliding on microcracks. The simulation results are in agreement with the experimental data. © 2015 Elsevier Ltd. Source


Abdechiri M.,Islamic Azad University at Qazvin | Meybodi M.R.,Amirkabir University of Technology | Bahrami H.,Islamic Azad University at Qazvin
Applied Soft Computing Journal | Year: 2013

In recent years, different optimization methods have been developed for optimization problem. Many of these methods are inspired by swarm behaviors in nature. In this paper, a new algorithm for optimization inspired by the gases brownian motion and turbulent rotational motion is introduced, which is called Gases Brownian Motion Optimization (GBMO). The proposed algorithm is created using the features of gas molecules. The proposed algorithm is an efficient approach to search and find an optimum solution in search space. The efficiency of the proposed method has been compared with some well-known heuristic search methods. The obtained results confirm the high performance of the proposed method in solving various functions. © 2012 Elsevier B.V. All rights reserved. Source


Azizi S.,University of Tehran | Gharehpetian G.B.,Amirkabir University of Technology | Dobakhshari A.S.,Sharif University of Technology
IEEE Transactions on Smart Grid | Year: 2013

This paper presents an integer linear programming (ILP) framework for the optimal placement of phasor measurement units (PMUs), in the presence of conventional measurements. Furthermore, by the proposed method, the power system remains completely observable during all possible single contingencies for lines and measurement devices. In doing so, the potential of circuit equations associated with both PMUs and conventional measurements as well as the network topology are fully utilized by a system of equations to reach the minimum possible numbers of required PMUs. The limitation of communication channels is also taken into account in the proposed ILP-based framework. The method is implemented on several IEEE test systems which have already been equipped with conventional measurements. The comparison between obtained results of the proposed method and those of other methods reveals its superiority in the modeling of robust PMU placement problem (OPP) in the presence of conventional measurements. As such, a smooth transition from the SCADA-based monitoring system to the PMU-dominated WAMS is ensured. Moreover, this method is successfully applied on three large-scale test systems, which demonstrates it can effectively be employed for robust OPP in realistic power systems. © 2010-2012 IEEE. Source


Zare Y.,Amirkabir University of Technology
International Journal of Adhesion and Adhesives | Year: 2014

In this paper, various micromechanics models are applied to evaluate the interfacial characteristics between the matrix and the nanofiller phases in shape memory polymer nanocomposites (SMPNs). The models analyze the interfacial adhesion by yield strength and tensile modulus of several SMPNs from literature. In addition, the effect of interfacial adhesion on the shape memory behavior of SMPNs is discussed. All calculated parameters by modeling process demonstrate an acceptable interfacial bonding in the reported SMPNs. It is confirmed that the SMPNs, which show a good shape memory behavior, include a strong adhesion at the polymer-nanofiller interface. © 2014 Elsevier Ltd. Source


Malvandi A.,Amirkabir University of Technology | Ganji D.D.,Babol Noshirvani University of Technology
Journal of Magnetism and Magnetic Materials | Year: 2014

The present study is a theoretical investigation of the laminar flow and convective heat transfer of water/alumina nanofluid inside a parallel-plate channel in the presence of a uniform magnetic field. A modified two-component, four-equation, nonhomogeneous equilibrium model was employed for the alumina/water nanofluid, which fully accounted for the effect of the nanoparticle volume fraction distribution. The no-slip condition of the fluid-solid interface is abandoned in favor of a slip condition which appropriately represents the non-equilibrium region near the interface at micro/nano channels. The results obtained indicated that nanoparticles move from the heated walls (nanoparticles depletion) toward the core region of the channel (nanoparticles accumulation) and construct a non-uniform nanoparticles distribution. Moreover, in the presence of the magnetic field, the near wall velocity gradients increase, enhancing the slip velocity and thus the heat transfer rate and pressure drop increase. © 2014 Elsevier B.V. Source


Malvandi A.,Amirkabir University of Technology | Hedayati F.,Islamic Azad University at Neyshabur | Ganji D.D.,Babol Noshirvani University of Technology
Powder Technology | Year: 2014

Unsteady two-dimensional stagnation point flow of a nanofluid over a stretching sheet is investigated numerically. In contrast to the conventional no-slip condition at the surface, Navier's slip condition has been applied. The behavior of the nanofluid was investigated for three different nanoparticles in the water-base fluid, namely copper, alumina and titania. Employing the similarity variables, the governing partial differential equations including continuity, momentum and energy have been reduced to ordinary ones and solved via Runge-Kutta-Fehlberg scheme. It was shown that a dual solution exists for negative values of the unsteadiness parameter A and, as it increases, the skin friction Cfr grows but the heat transfer rate Nur takes a decreasing trend. The results also indicated that, unlike the stretching parameter ε, increasing in the values of the slip parameter λ widen the ranges of the unsteadiness parameter A for which the solution exists. Furthermore, it was found that an increase in both ε and λ intensifies the heat transfer rate. © 2013 Elsevier B.V. Source


Esfandiari A.,Amirkabir University of Technology
Structural Control and Health Monitoring | Year: 2016

This paper presents an innovative sensitivity equation to detect changes of stiffness parameters using mode shape data. Most of the sensitivity-based model updating methods use changes of mode shapes for structural model updating. However, the proposed method uses the mode shape data to estimate changes of the structural parameters directly. The proposed method sets up a relation between the change of structural parameters and the mode shapes of the damaged structure. The proposed formula uses the measured natural frequencies of the damaged structure and the mode shapes of the intact structure. The formulation yields to a set of accurate sensitivity equations. The proposed method is successfully applied to a plane truss and a frame structure using simulated error-contaminated mode shapes data. Results prove robustness of the proposed method against mode shape, natural frequency, and mass modeling errors. © 2016 John Wiley & Sons, Ltd. Source


Beigy H.,Sharif University of Technology | Meybodi M.R.,Amirkabir University of Technology
Computers and Electrical Engineering | Year: 2011

In this paper, we first propose two learning automata based decentralized dynamic guard channel algorithms for cellular mobile networks. These algorithms use learning automata to adjust the number of guard channels to be assigned to cells of network. Then, we introduce a new model for nonstationary environments under which the proposed algorithms work and study their steady state behavior when they use LR-I learning algorithm. It is also shown that a learning automaton operating under the proposed nonstationary environment equalizes its penalty strengths. Computer simulations have been conducted to show the effectiveness of the proposed algorithms. The simulation results show that the performances of the proposed algorithms are close to the performance of guard channel algorithm that knows all the traffic parameters. © 2011 Elsevier Ltd. All rights reserved. Source


Mozafari M.,Iranian Materials and Energy Research Center | Moztarzadeh F.,Amirkabir University of Technology
Ceramics International | Year: 2014

In this study, a new class of bioactive glass scaffolds was prepared through freeze casting method for bone tissue engineering applications. After analyzing the structural characteristics of the scaffolds, in vitro biological evaluations were assessed through monitoring alkaline phosphatase (AP) activity of osteoblast cells and soaking in simulated body fluid (SBF) for different time intervals. It was shown that the scaffolds consisted of bioactive glass plates with interconnected pores between them, aligned along the ice growth direction. The ability of the scaffolds for supporting the growth of human fetal osteoblastic cells (hFOB 1.19) was approved. Moreover, inductively coupled plasma-atomic emission spectrometry (ICP-AES) showed meaningful compositional changes of calcium, phosphorus and silicon in SBF solution, indicating the apatite forming ability of the scaffolds. The present investigation revealed that freeze casting could be an effective method for the preparation of highly bioactive scaffolds. In addition, the scaffolds proved to be highly compatible for the proposed works in vivo. © 2013 Elsevier Ltd and Techna Group S.r.l. Source


Dehghan M.,Amirkabir University of Technology | Hajarian M.,Shahid Beheshti University
Engineering Computations (Swansea, Wales) | Year: 2012

Purpose - Solving the non-linear equation ITf/IT(ITx/IT)=0 has nice applications in various branches of physics and engineering. Sometimes the applications of the numerical methods to solve non-linear equations depending on the second derivatives are restricted in physics and engineering. The purpose of this paper is to propose two new modified Newton's method for solving non-linear equations. Convergence results show that the order of convergence of the proposed iterative methods for a simple root is four. The iterative methods are free from second derivative and can be used for solving non-linear equations without computing the second derivative. Finally, several numerical examples are given to illustrate that proposed iterative algorithms are effective. Design/methodology/approach - In this paper, first the authors introduce two new approximations for the definite integral arising from Newton's theorem. Then by considering these approximations, two new iterative methods are provided with fourth-order convergence which can be used for solving non-linear equations without computing second derivatives. Findings - In this paper, the authors propose two new iterative methods without second derivatives for solving the non-linear equation ITf/IT(ITx/IT)=0. From numerical results, it is observed that the new methods are comparable with various iterative methods. Also numerical results corroborate the theoretical analysis. Originality/value - The best property of these schemes is that they are second derivative free. Also from numerical results, it is observed that the new methods are comparable with various iterative methods. The numerical results corroborate the theoretical analysis. Copyright © 2012 Emerald Group Publishing Limited. All rights reserved. Source


Ahmadi A.,Amirkabir University of Technology | Karray F.,University of Waterloo | Kamel M.S.,University of Waterloo
Information Sciences | Year: 2012

Extracting different clusters of a given data is an appealing topic in swarm intelligence applications. This paper introduces two main data clustering approaches based on particle swarm optimization, namely single swarm and multiple cooperative swarms clustering. A stability analysis is next introduced to determine the model order of the underlying data using multiple cooperative swarms clustering. The proposed approach is assessed using different data sets and its performance is compared with that of k-means, k-harmonic means, fuzzy c-means and single swarm clustering techniques. The obtained results indicate that the proposed approach fairly outperforms the other clustering approaches in terms of different cluster validity measures. © 2011 Elsevier Inc. All rights reserved. Source


Eslami A.,Amirkabir University of Technology
Bulletin of Earthquake Engineering | Year: 2015

Explosive compaction (EC) or Blast densification (BD) has been realized as an efficient technique for soil improvement and mitigation of the liquefaction potential in loose saturated sands. Due to providing continuous and precise records, Piezocone (CPTu) is the most applicable in situ test in geotechnical practice for evaluation of liquefaction potential. In this research a data bank including eight case histories in different locations has been compiled for investigation of EC effects on mitigation of loose sands instability. The sites geomaterials are in the category of fine to medium sand, silty sand and mixture of sand and gravel with relative density between 30 and 60 % and thickness of 5–40 m. Four CPT-based criteria have been used including cyclic stress ratio approach, cone tip resistance (qc) variations before and after modification, Qtn and qc1N, and soil behavior classification charts. Analyses have shown that due to EC the state of soil changes from loose to dense, the contractive behavior of sands changes to dilative, and the liquefaction potential diminishes. Also, by using soil behavior classification charts pre and post explosion, it can be observed that improved soils are not in the liquefiable zone, anymore. This improvement has a significant effect on layers where located in deeper zones, whereas in surface layers in some cases, liquefaction phenomenon has been observed. Moreover, by blasting in two stages between first and phases for boreholes, liquefaction potential decreases significantly. © 2015 Springer Science+Business Media Dordrecht Source


Talatahari S.,University of Tabriz | Kaveh A.,Iran University of Science and Technology | Sheikholeslami R.,Amirkabir University of Technology
Structural and Multidisciplinary Optimization | Year: 2012

The imperialist competitive algorithm is a new socio-politically motivated optimization algorithm which recently is applied for structural problems. This paper utilizes the idea of using chaotic systems instead of random processes in the imperialist competitive algorithm. The resulting method is called chaotic imperialist competitive algorithm (CICA) in which chaotic maps are utilized to improve the movement step of the algorithm. Some well-studied truss structures are chosen to evaluate the efficiency of the new algorithm. © 2012 Springer-Verlag. Source


Dehghan M.,Amirkabir University of Technology | Hajarian M.,Shahid Beheshti University
Engineering Computations (Swansea, Wales) | Year: 2012

Purpose - The purpose of this paper is to find two iterative methods to solve the general coupled matrix equations over the generalized centro-symmetric and central antisymmetric matrices. Design/methodology/approach - By extending the idea of conjugate gradient (CG) method, the authors present two iterative methods to solve the general coupled matrix equations over the generalized centro-symmetric and central antisymmetric matrices. Findings - When the general coupled matrix equations are consistent over the generalized centro-symmetric and central anti-symmetric matrices, the generalized centro-symmetric and central anti-symmetric solutions can be obtained within nite iterative steps. Also the least Frobenius norm generalized centrosymmetric and central anti-symmetric solutions can be derived by choosing a special kind of initialmatrices. Furthermore, the optimal approximation generalized centrosymmetric and central anti-symmetric solutions to given generalized centro-symmetric and central anti-symmetricmatrices can be obtained byfinding the least Frobenius normgeneralized centro-symmetric and central anti-symmetric solutions of new matrix equations. The authors employ some numerical examples to support the theoretical results of this paper.Finally, the application of the presented methods is highlighted for solving the projected generalized continuous-time algebraic Lyapunov equations (GCALE). Originality/value - By the algorithms, the solvability of the general coupled matrix equations over generalized centro-symmetric and central anti-symmetric matrices can be determined automatically. The convergence results of the iterative algorithms are also proposed. Several examples and an application are given to show the efficiency of the presented methods. © Emerald Group Publishing Limited. Source


Akbari Torkestani J.,Islamic Azad University of Arak | Meybodi M.R.,Amirkabir University of Technology
Information Sciences | Year: 2012

Finding the minimum weight connected dominating set (MCDS) in an arbitrary graph is an NP-hard problem and several heuristics and approximation methods have been proposed to solve it. Forwarding the messages along the virtual backbone induced by the connected dominating set (CDS) significantly reduces the routing overhead as well as the power consumption by reducing the routing nodes to the backbone nodes. This paper first defines the stochastic MCDS problem where the probability distribution function (PDF) of the random weight associated with the graph vertices is unknown. Then, it presents several learning automata-based algorithms (Algorithms 1-6) to solve the stochastic MCDS problem. Taking advantage of learning automata, the proposed algorithms significantly reduce the number of samples that must be taken from the graph to construct the MCDS. It is proved that by the proper choice of the learning rate, the probability of finding the MCDS is close enough to unity. The standard sampling method (SSM) is the baseline with which we compare the performance of the proposed algorithms. Experimental results show that Algorithm 6 significantly outperforms the SSM and the other proposed algorithms in terms of the sampling rate. © 2012 Elsevier Inc. All rights reserved. Source


Bidabad B.,Amirkabir University of Technology
Differential Geometry and its Application | Year: 2014

In the first part of this work we are going to touch the conformal theory of curves on Finsler geometry, emphasizing on the notion of circles preserving transformations, recently studied by the present author and Z. Shen. Next, the conformal changes of metrics which leave invariant geodesic circles known as concircular transformation are characterized by a second order differential equation. As an application a classification of complete Finsler manifolds admitting such transformations is obtained. © 2014 Elsevier B.V. Source


Mostafaei H.,Islamic Azad University at Urmia | Meybodi M.R.,Amirkabir University of Technology
Wireless Personal Communications | Year: 2013

In wireless sensor networks, when each target is covered by multiple sensors, we can schedule sensor nodes to monitor deployed targets in order to improve lifetime of network. In this paper, we propose an efficient scheduling method based on learning automata, in which each node is equipped with a learning automaton, which helps the node to select its proper state (active or sleep), at any given time. To study the performance of the proposed method, computer simulations are conducted. Results of these simulations show that the proposed scheduling method can better prolong the lifetime of the network in comparison to similar existing methods. © 2012 Springer Science+Business Media New York. Source


Mahjub A.,Amirkabir University of Technology
RSC Advances | Year: 2016

The Monte Carlo kinetic simulation method was performed to simulate the entire process of the dispersion polymerization of styrene stabilized by polyvinyl pyrrolidone (PVP) in ethanol. The equilibrium distributions of each component between the continuous phase and the particle phase were calculated by a thermodynamic model. In order to calculate the time course of the concentration of different species in each phase a kinetic model was proposed for the mechanism of dispersion polymerization which took into account the reactions both in the ethanol phase and particles. The role of the stabilizer and aggregation by Brownian diffusion and aggregation by the shear stress of the fluid was quantified for simulating the time course of particle concentration and particle size. The simulation results indicated that aggregation due to Brownian diffusion was the dominant mechanism of aggregation in dispersion polymerization. The effect of monomer concentration was investigated on the particle formation stage by simulating the monomer conversion, particle diameter and particle concentration. Subsequently, the particle growth stage was simulated after sufficient stabilizer was absorbed on the particle surface. The Monte Carlo simulation results for the monomer conversion, particle diameter and particle concentration were in agreement with experimental data. © 2016 The Royal Society of Chemistry. Source


Poursha M.,Sahand University of Technology | Khoshnoudian F.,Amirkabir University of Technology | Moghadam A.S.,Structural Engineering Research Center
Soil Dynamics and Earthquake Engineering | Year: 2014

This paper aims to extend the consecutive modal pushover (CMP) procedure for estimating the seismic demands of two-way unsymmetric-plan tall buildings subjected to bi-directional seismic ground motions taking the effects of higher modes and torsion into account. Multi-stage and single-stage pushover analyses are carried out in both X and Y directions. Inelastic seismic responses obtained by multi-stage and single-stage pushover analyses for X and Y directions are combined using the SRSS combination scheme. The final seismic responses are determined by enveloping the combined results of multi-stage and single-stage pushover analyses. To evaluate the accuracy of the proposed procedure, it is applied to two-way unsymmetric-plan tall buildings which include torsionally stiff and torsionally flexible systems. The results derived from the CMP procedure are compared with those from nonlinear response history analysis (NL-RHA), as a benchmark solution. Moreover, the advantages of the proposed procedure are demonstrated by comparing the results derived from the CMP to those from pushover analysis with uniform and fundamental effective mode distributions. The proposed procedure is able to accurately predict amplification or de-amplification of the seismic displacements at the flexible and stiff edges of the two-way unsymmetric-plan tall buildings by considering the effects of higher modes and torsion. The extended CMP procedure can accurately estimate the peak inelastic responses, such as displacements and storey drifts. The CMP procedure features a higher potential in estimating plastic hinge rotations at both flexible and stiff sides of unsymmetric-plan tall buildings under bi-directional seismic excitation when compared to the uniform and fundamental effective mode force distributions. © 2014 Elsevier Ltd. Source


Behnamian J.,Bu - Ali Sina University | Fatemi Ghomi S.M.T.,Amirkabir University of Technology
Applied Soft Computing Journal | Year: 2014

This paper considers a bi-objective hybrid flowshop scheduling problems with fuzzy tasks' operation times, due dates and sequence-dependent setup times. To solve this problem, we propose a bi-level algorithm to minimize two criteria, namely makespan, and sum of the earliness and tardiness, simultaneously. In the first level, the population will be decomposed into several sub-populations in parallel and each sub-population is designed for a scalar bi-objective. In the second level, non-dominant solutions obtained from sub-population bi-objective random key genetic algorithm (SBG) in the first level will be unified as one big population. In the second level, for improving the Pareto-front obtained by SBG, based on the search in Pareto space concept, a particle swarm optimization (PSO) is proposed. We use a defuzzification function to rank the Bell-shaped fuzzy numbers. The non-dominated sets obtained from each of levels and an algorithm presented previously in literature are compared. The computational results showed that PSO performs better than others and obtained superior results. © 2014 Elsevier B.V. Source


Sadighi M.,Amirkabir University of Technology | Alderliesten R.C.,Technical University of Delft | Benedictus R.,Technical University of Delft
International Journal of Impact Engineering | Year: 2012

Combining the suitable properties of metals and fiber reinforced composites, as the idea behind the application of new types of materials, called fiber metal laminates (FMLs), have lead to superior impact properties as well as considerable improvement in fatigue performance. The characteristics of FMLs under impact loading and the ways to improve their properties to withstand this type of loading could be of particular importance in aerospace structures and other applications. This paper reviews relevant literature which deals with experimental evidence of "material related" and "event related" impact resistance parameters as well as the articles related to theoretical and numerical simulation of impact loading of FMLs. Relevant results will be discussed and the recommendations that need to be resolved in the future will be addressed. © 2012 Elsevier Ltd. All rights reserved. Source


Hamidi S.,Islamic Azad University at Sanandaj Branch | Kermani M.J.,Amirkabir University of Technology
European Journal of Mechanics, B/Fluids | Year: 2013

Numerical solutions of a compressible two-phase two-component moist-air flow with and without shock waves are investigated in this paper using the high resolution flux difference splitting scheme of Roe (1981) [22]. The solver is spatially third order and temporally second order accurate. The flow is assumed to obey an equilibrium thermodynamic model. For the two-phase flow in dry regions, the pressure (P), temperature (T), and velocity (u) are extrapolated to the cell faces by the MUSCL approach, while in wet regions the steam quality (χ) has been used instead of pressure. Comparisons of the wetness fraction at the nozzle exit show that in the case of moist-air flow rather than pure steam, a much higher wetness fraction, about 30%, can be achieved, while in the case of pure steam and under similar conditions the wetness fraction is limited to about 6%. The present study gives a practical guideline in the production of liquid water in a much higher rate, if an additive gas (like air) is added to steam. Hence it can be used as an alternative approach to produce potable water from atmospheric air in geographically humid regions. For moist-air flow with normal shock, the results show that across the shock the liquid phase rapidly evaporates. © 2013 Elsevier Masson SAS. All rights reserved. Source


Nasiri B.,Islamic Azad University at Qazvin | Meybodi M.R.,Amirkabir University of Technology
International Journal of Artificial Intelligence | Year: 2012

In many optimization problems in real world, objective function, design variable or constraints can be changed during time, so optimal value of these problems also can be changed. These kinds of problems are called dynamic. Algorithms which are designed for optimizing in these environments have some principles that distinguish them from algorithms designed in static environment. In this paper, for the first time, an algorithm based on firefly algorithm is proposed for optimization in dynamic environment. Firefly algorithm is a new meta-heuristic algorithm with a great potential for discovering multiple optima simultaneously. Mentioned ability of this algorithm has been used to propose a novel approach for multi-modal optimization in dynamic environments. The proposed approach evaluated on Moving peaks benchmark problem, which is the most famous benchmark for assessment in dynamic environments. The obtained results show the proper accuracy and convergence rate for the proposed approach in comparison with other well-known approaches. © 2012 by IJAI (CESER Publications). Source


Ganji D.D.,Babol Noshirvani University of Technology | Malvandi A.,Amirkabir University of Technology
Powder Technology | Year: 2014

The present study is a theoretical investigation of natural convective heat transfer of nanofluids, inside a vertical enclosure, in the presence of a uniform magnetic field. A modified Buongiorno's model is employed for the nanofluid, which fully accounts for the effect of nanoparticle migration. The behavior of the nanofluid is investigated for two different nanoparticles in the water-base fluid, namely alumina and titania. It was observed that the nanoparticles move from the heated walls (nanoparticles' depletion) toward the cold wall (nanoparticles' accumulation) and construct a non-uniform nanoparticle distribution. The results also indicate that for smaller nanoparticles, the nanoparticle volume fraction is more uniform and there is no abnormal variation in the heat transfer rate. Moreover, NuB is reduced in the presence of the magnetic field for alumina/water nanofluid; however, for titania/water nanofluid it is vice versa. © 2014 Elsevier B.V. Source


Malvandi A.,Amirkabir University of Technology | Ganji D.D.,Babol Noshirvani University of Technology
Powder Technology | Year: 2014

Mixed convective heat transfer of water/alumina nanofluid inside a vertical microchannel is investigated theoretically. A modified Buongiorno's model is employed for the nanofluid, which fully accounts for the effect of the nanoparticle migration. This model considers the Brownian motion and thermophoresis diffusivities as the predominant slip mechanism. Because of surface roughness in microscale channels, slip condition is considered at the walls, which appropriately represents the hydrodynamic boundary condition. The results obtained indicated that nanoparticles move from the heated walls (nanoparticle depletion) toward the core region of the channel (nanoparticle accumulation) and construct a non-uniform nanoparticle distribution. In addition, increasing the bulk mean volume fraction of nanoparticles φB, slip parameter λ and mixed convective parameter Ng enhances the heat transfer rate. Moreover, in contrast to λ, φB and Ng have a negative effect on the pressure drop of the system. © 2014 Elsevier B.V. Source


Miandoabchi E.,Amirkabir University of Technology | Farahani R.Z.,Kingston University
Advances in Engineering Software | Year: 2011

This paper addresses the problem of designing of street directions and lane additions in urban road networks, based on the concept of reserve capacity. Reserve capacity is identified by the largest multiplier applied to a given existing demand matrix, that can be allocated to a network without violating the arc capacities. Having a two-way streets base network and the allowable street lane additions, the problem is to find the optimum configuration of street directions and two-way street lane allocations, and the optimum selection of street lane addition projects, in a way that the reserve capacity of the network is maximized. The problem is considered in two variations; in the first variation no restriction is imposed on the symmetricity of lane allocations for two-way streets, and in the second variation, two-way street lane allocations are restricted to be symmetric. The proposed problems are modeled as mixed-integer bi-level mathematical problems. A hybrid genetic algorithm and an evolutionary simulated annealing algorithm are proposed to solve the models. Computational results for both problem variations are presented. © 2011 Elsevier Ltd. All rights reserved. Source


Zarandi M.H.F.,Amirkabir University of Technology | Alaeddini A.,Wayne State University
Information Sciences | Year: 2010

Despite their capability in monitoring the variability of the processes, control charts are not effective tools for identifying the real time of such changes. Identifying the real time of the change in a process is recognized as change-point estimation problem. Most of the change-point models in the literature are limited to fixed sampling control charts which are only a special case of more effective charts known as variable sampling charts. In this paper, we develop a general fuzzy-statistical clustering approach for estimating change-points in different types of control charts with either fixed or variable sampling strategy. For this purpose, we devise and evaluate a new similarity measure based on the definition of operation characteristics and power functions. We also develop and examine a new objective function and discuss its relation with maximum-likelihood estimator. Finally, we conduct extensive simulation studies to evaluate the performance of the proposed approach for different types of control charts with different sampling strategies. © 2010 Elsevier Inc. All rights reserved. Source


Forsati R.,Islamic Azad University at Qazvin | Meybodi M.R.,Amirkabir University of Technology | Meybodi M.R.,Institute for Research in Fundamental Sciences
Expert Systems with Applications | Year: 2010

Different efforts have been done to address the problem of information overload on the Internet. Recommender systems aim at directing users through this information space, toward the resources that best meet their needs and interests by extracting knowledge from the previous users' interactions. In this paper, we propose three algorithms to solve the web page recommendation problem. In our first algorithm, we use distributed learning automata to learn the behavior of previous users' and recommend pages to the current user based on learned patterns. By introducing a novel weighted association rule mining algorithm, we present our second algorithm for recommendation purpose. Also, a novel method is proposed to pure the current session window. One of the challenging problems in recommendation systems is dealing with unvisited or newly added pages. By considering this problem and improving the efficiency of first two algorithms we present a hybrid algorithm based on distributed learning automata and proposed weighted association rule mining algorithm. In the hybrid algorithm we employ the HITS algorithm to extend the recommendation set. Our experiments on real data set show that the hybrid algorithm performs better than the other algorithms we compared to and, at the same time, it is less complex than other proposed algorithms with respect to memory usage and computational cost too. © 2009 Elsevier Ltd. All rights reserved. Source


Solimanpur M.,Urmia University | Kamran M.A.,Amirkabir University of Technology
Computers and Industrial Engineering | Year: 2010

Facilities location problem deals with the optimization of location of manufacturing facilities like machines, departments, etc. in the shop floor. This problem greatly affects performance of a manufacturing system. It is assumed in this paper that there are multiple products to be produced on several machines. Alternative processing routes are considered for each product and the problem is to determine the processing route of each product and the location of each machine to minimize the total distance traveled by the materials within the shop floor. This paper presents a mixed-integer non-linear mathematical programming formulation to find optimal solution of this problem. A technique is used to linearize the formulated non-linear model. However, due to the NP-hardness of this problem, even the linearized model cannot be optimally solved by the conventional mathematical programming methods in a reasonable time. Therefore, a genetic algorithm is proposed to solve the linearized model. The effectiveness of the GA approach is evaluated with numerical examples. The results show that the proposed GA is both effective and efficient in solving the attempted problem. © 2010 Elsevier Ltd. All rights reserved. Source


Ataeefard M.,Iran Institute for Color Science and Technology | Moradian S.,Amirkabir University of Technology
Journal of Applied Polymer Science | Year: 2012

Polypropylene (PP) nanocomposites having five different loadings of an organically modified montmorillonite, mineral clay was prepared by a melt mixing technique. The resultant PP nanocomposites were then uniformly dyed using three distinct disperse dyestuffs each at three concentrations. The enhanced dyeability of PP nanocomposite was characterized by spectrophotometric measurements. Good wash fastnesses were obtained after subjection of dyeing to a reduction clear process. It was found that increasing the clay content had a significant effect on dye uptake. Tensile strength tests showed improvements in mechanical properties. Degree of crystallinity of nanocomposites at various nanoclay loadings were investigated using differential scanning calorimeter. Surface behaviors of the resultant nanocomposites as well as the extent of exfoliation and dispersion of the nanoclay particles in PP were studied by various analytical techniques such as polarized optical microscope, X-ray diffraction, and transmission electron microscopy analytical techniques. These showed intercalate/exfoliate structures in the resultant nanocomposites. © 2011 Wiley Periodicals, Inc. Source


Yavari M.,Amirkabir University of Technology
Journal of Circuits, Systems and Computers | Year: 2010

This paper presents two novel active-feedback single Miller capacitor frequency compensation techniques for low-power three-stage amplifiers. These techniques include the active-feedback single Miller capacitor frequency compensation (AFSMC) and the dual active-feedback single Miller capacitor frequency compensation (DAFSMC). In the proposed techniques, only one Miller capacitor in series with a current buffer is utilized. The main advantages of the proposed three-stage amplifiers are the enhanced unity-gain bandwidth and the reduced silicon area. Small-signal analyses are performed and the design equations are obtained. Extensive HSPICE simulation results are provided to show the usefulness of the proposed AFSMC and DAFSMC amplifiers in both large and small capacitive loads. © 2010 World Scientific Publishing Company. Source


Moraveji M.K.,Amirkabir University of Technology | Hejazian M.,Arak University
Numerical Heat Transfer; Part A: Applications | Year: 2014

A numerical inspection based on computational fluid dynamics (CFD) method, with a single phase approach, has been carried out to study and compare the convective heat transfer and pressure drop of nanofluid flowing through a straight tube and a helical coil. The nanofluid consists of CuO nanoparticles, with the average diameter of 50 nm and Particle weight concentrations of 0.5, 1, and 2% dispersed in oil as a base fluid. Using the modeling results, four correlations were developed to estimate the Nusselt number and friction factor, based on the dimensionless numbers. The results showed that the modeling data were in good agreement with experimental data. © 2014 Taylor & Francis Group, LLC. Source


Integral imaging is a technique for displaying three-dimensional images using microlens arrays. In this paper, a method for calculating root mean squared wavefront error and modulation transfer function (MTF) of a defocused integral imaging capture system with hexagonal aperture microlens arrays is introduced. Also, maximum allowable depth of field with Century MTF analyzing and Strehl criterion are obtained. © 2016 Optical Society of America. Source


Nazari A.,Islamic Azad University at Saveh | Mohandesi J.A.,Amirkabir University of Technology | Riahi S.,Islamic Azad University at Saveh
Computational Materials Science | Year: 2011

By utilizing plain carbon and austenitic stainless steels with different thicknesses and arrangements as electrodes of electroslag remelting, functionally graded steels containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers were produced. Fracture toughness of the functionally graded steels in crack arrester configuration has been demonstrated to depend on the position and sense of the graded region in which the crack is located. When a propagating crack experiences an upward gradient of fracture toughness, the fracture toughness of the composite is increased and vice versa. An analytical model has been presented for predicting fracture toughness of the composites. Also 3D numerical simulation by conducting finite element method has been presented. There is a good agreement between experimental results and those obtained by the analytical and numerical models. © 2010 Elsevier B.V. All rights reserved. Source


Karimzadeh A.,Amirkabir University of Technology
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2014

The modulation transfer function (MTF) is the main parameter that is used to evaluate image quality in electrooptical systems. Detector sampling MTF in most electro-optical systems determines the cutoff frequency of the system. The MTF of the detector depends on its pixel shape. In this work, we calculated the MTF of a detector with an equilateral triangular pixel shape. Some new results were found in deriving the MTF for the equilateral triangular pixel shape. © 2014 Optical Society of America. Source


Mirzaei B. E.,Sharif University of Technology | Ramazani S. A. A.,Sharif University of Technology | Shafiee M.,Sharif University of Technology | Danaei M.,Amirkabir University of Technology
International Journal of Polymeric Materials and Polymeric Biomaterials | Year: 2013

Chitosan was crosslinked with different amount of glutaraldehyde to prepare appropriate hydrogels to be used as drug delivery system. The swelling behavior of freeze-dried hydrogels in aqueous media at different temperature and pHs has been examined. The swelling, porosity and biocompatibility behavior of samples were investigated to check effects of polymer/polymer and polymer/drug interactions on these system characteristics. Obtained experimental results illustrates that with increasing crosslinking agent from 0.068 to 0.30, swelling of the prepared samples degrees from 1200% to 600% and pore diameters change from 100 to 500 μm. To investigate systems biocompatibility in gastric conditions, effects of crosslinker concentration on the pepsin enzyme activity have been studied using variation of relative viscosity of the system. Presented results also show that with increasing crosslinker agent concentration activity of enzyme reduces considerably and so crosslinker molar ratio to amine functional groups of chitosan must be less than 0.2. Copyright © 2013 Taylor & Francis Group, LLC. Source


Malvandi A.,Amirkabir University of Technology | Ganji D.D.,Babol Noshirvani University of Technology
Journal of Electroanalytical Chemistry | Year: 2013

The aim of this paper is to find a general mathematical expression for amperometric enzyme kinetics problems. The variational iteration method coupled with Padé approximation (VIM-Padé) is used to attain a reliable mathematical expression based on the rational functions. The accuracy of the results is shown in two cases of the electrochemical polymerization on the electrode surfaces. The comparisons indicated that the presented mathematical expression is not only a general model - which could be used in most amperometric enzyme kinetics problems - but also gives more accurate results than the mathematical expressions previously developed for such problems. © 2013 Elsevier B.V. All rights reserved. Source


Hejazian M.,Arak University | Moraveji M.K.,Amirkabir University of Technology | Beheshti A.,Arak University
Numerical Heat Transfer; Part A: Applications | Year: 2014

In this article, turbulent TiO2/water nanofluid flow and convective heat transfer in a horizontal tube is numerically investigated. Four computer codes were developed for each model (single phase, volume of fluid, mixture, and Eulerian) to simulate this problem. The Finite volume method is applied to solve the two-dimensional steady state governing equations. The results are compared with each other and an experimental work. A model with the most similar results to those of the experimental data and less amount of time for the CPU usage is chosen to develop two correlations for Nusselt number and friction factor based on dimensionless numbers. © 2014 Taylor & Francis Group, LLC. Source


Boroojerdian N.,Amirkabir University of Technology
International Journal of Theoretical Physics | Year: 2013

In this paper we will extend the notion of tangent bundle to a Z 2 graded tangent bundle. This graded bundle has a Lie algebroid structure and we can develop notions semi-Riemannian metrics, Levi-Civita connection, and curvature, on it. In case of space-times manifolds, even part of the tangent bundle is related to space and time structures (gravity) and odd part is related to mass distribution in space-time. In this structure, mass becomes part of the geometry, and Einstein field equation can be reconstructed in a new simpler form. The new field equation is purely geometric. © 2013 Springer Science+Business Media New York. Source


Asemi K.,Amirkabir University of Technology | Shariyat M.,K. N. Toosi University of Technology
Composite Structures | Year: 2013

Buckling of the orthotropic FGM plates has not been investigated so far. In the present paper, a highly accurate nonlinear three-dimensional energy-based finite element elasticity formulation is developed for buckling investigation of anisotropic functionally graded plates with arbitrary orthotropy directions. The material properties are assumed to have in-plane orthotropy and transverse heterogeneity. The formulation and results cover uniaxial compression and compression and tension-compression biaxial loading conditions. The governing equations are developed based on the principle of minimum total potential energy and solved based on finite element orthogonal integral equations. To achieve most accurate results, a full compatible Hermitian element with 168 degrees of freedom, which satisfies continuity of the strain and stress components at the mutual edges and nodes of the element a priori, is employed. A variety of loading combinations, orthotropy directions, and aspect ratios is considered and discussed in the results section to draw practical conclusions. Results reveal that when the external loads are exerted in the principal directions of the materials, higher strengths may be achieved. © 2013 Elsevier Ltd. Source


Mirzaei A.,Isfahan University of Technology | Rahmati M.,Amirkabir University of Technology
IEEE Transactions on Fuzzy Systems | Year: 2010

Clustering-combination methods have received considerable attentions in recent years, and many ensemble-based clustering methods have been introduced. However, clustering-combination techniques have been limited to "flat" clustering combination, and the combination of hierarchical clusterings has yet to be addressed. In this paper, we address and formalize the concept of hierarchical-clustering combination and introduce an algorithmic framework in which multiple hierarchical clusterings could be easily combined. In this framework, the similarity-based description matrices of input hierarchical clusterings are aggregated into a transitive consensus matrix in which the final hierarchy could be formed. Empirical evaluation, by using popular available datasets, confirms the superiority of combined hierarchical clustering introduced by our method over the standard (single) hierarchical-clustering methods. © 2006 IEEE. Source


Mohammadi M.,Amirkabir University of Technology
International Journal of Advanced Manufacturing Technology | Year: 2010

Presenting an integrated lotsizing, loading, and scheduling model for the capacitated flexible flow shops with sequence-dependent setups is the main contribution of this paper. An exact formulation of the problem is provided as a mixed integer program. To solve this problem, mixed integer programming-based heuristics based on iterative procedures are provided. To test the accuracy of heuristics, two lower bounds are developed and compared against the optimal solution. The trade-offs between solution quality and computational time of heuristics are also provided. © 2010 Springer-Verlag London Limited. Source


Sadrabadi M.R.,TU Eindhoven | Zarandi M.H.F.,Amirkabir University of Technology
Applied Soft Computing Journal | Year: 2011

In direct approach to fuzzy modeling, structure identification is one of the most critical tasks. In modeling the nonlinear system, this fact is more crucial. In this paper, a new hybrid method is proposed to cluster the data located in the linear parts on the nonlinear systems. The proposed method can partition the input-output data in two groups: data located in the linear parts and data in the extrema. It is shown that the first group of data is suitable to be clustered by Fuzzy C-Regression Model (FCRM) clustering algorithm and the second group by Fuzzy C-Means (FCM). Then, based on the above findings, a new hybrid clustering algorithm is proposed. Finally, the proposed approach is tested and validated by several numerical examples of nonlinear functions. © 2010 Elsevier B.V. All rights reserved. Source


Tarahomjoo S.,Razi Vaccine and Serum Research Institute | Tarahomjoo S.,Amirkabir University of Technology
Molecular Biotechnology | Year: 2012

Live recombinant bacteria represent attractive antigen delivery systems able to induce both mucosal and systemic immune responses against heterologous antigens. The first live recombinant bacterial vectors developed were derived from attenuated pathogenic microorganisms. In addition to the difficulties often encountered in the construction of stable attenuated mutants of pathogenic organisms, attenuated pathogens may retain a residual virulence level that renders them unsuitable for the vaccination of partially immunocompetent individuals such as infants, the elderly or immunocompromised patients. As an alternative to this strategy, non-pathogenic food-grade lactic acid bacteria (LAB) maybe used as live antigen carriers. This article reviews LAB vaccines constructed using antigens other than tetanus toxin fragment C, against bacterial, viral, and parasitic infective agents, for which protection studies have been performed. The antigens utilized for the development of LAB vaccines are briefly described, along with the efficiency of these systems in protection studies. Moreover, the key factors affecting the performance of these systems are highlighted. © Springer Science+Business Media, LLC 2011. Source


Zamanian M.,Polymer Engineering Group | Mortezaei M.,Polymer Engineering Group | Salehnia B.,Amirkabir University of Technology | Jam J.E.,Polymer Engineering Group
Engineering Fracture Mechanics | Year: 2013

An epoxy resin was modified by the addition of different nanosilica particles. The particles were distributed into epoxy resin with ultrasonic instrument which gave a very well-dispersed phase of nanosilica particles. Tensile test and dynamic mechanical thermal analysis (DMTA) showed that Young's modulus increased and the glass transition temperature was unchanged. The fracture energy increased to about 620 J/m2 for the epoxy with 3.17 vol.% of 12-nm diameter nanoparticles. The responsible toughening mechanisms were recognized to be plastic deformation and plastic void growth. Finally, the toughening mechanisms have been quantitatively modeled and an excellent agreement between the results was found. © 2012 Elsevier Ltd. All rights reserved. Source


Habibi M.,Amirkabir University of Technology
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2016

The distribution of argon ion beam emitted from a small plasma focus device (PFD) with four different anode tips i.e., cylindrical with a flat top, cylindrical with a hollow top, cone with a flat top, and cone with a hollow top is studied at various working pressures. The angular distribution of ions is significantly reduced at angles higher than ±11° and the maximum ion emission is between 0° and 11°. The maximum ion flux of about 5.57 × 1012 ions/steradian is obtained with cylindrical-flat anode tip that increases to 9.82 × 1012 ions/steradian per shot for cone-flat anode tip. © 2015 Elsevier B.V. All rights reserved. Source


Moriniere F.D.,Technical University of Delft | Alderliesten R.C.,Technical University of Delft | Sadighi M.,Amirkabir University of Technology | Benedictus R.,Technical University of Delft
Composite Structures | Year: 2013

A progressive quasi-static approach was developed to study the low-velocity impact response of GLARE fibre-metal laminates. The impacting mass, impact force, and impact duration were assessed for the projectile. Ply-angle orientation, aluminium thickness, plate dimensions, global flexure, and failure modes were addressed for the target plate. The in-plane stress analysis was enhanced by considering residual curing stresses, contact area increase during perforation, and strain rate effect on material properties. In comparison to test results, the model predicted with a precision of 5% contact time, impact force, maximum displacement, perforation energy, and impact velocity. In addition to these common impact characteristics, further evaluation gave relevant insight on the role of the material constituents, i.e. 2024-T3 aluminium and S2-glass/FM94-epoxy prepreg, with respect to energy absorption, plate flexure, and damage progression. The generic nature of the developed method can support the optimisation of high-performance multi-material structures. © 2013. Source


Javadi Y.,Islamic Azad University at Semnan | Najafabadi M.A.,Amirkabir University of Technology
Materials and Design | Year: 2013

This paper presents a comparison of contact and immersion waves used to measure residual stresses. The residual stresses are produced due to a dissimilar welding of stainless steel (304) to carbon steel (A106). Longitudinal critically refracted (LCR) wave propagated by 2. MHz contact and immersion ultrasonic transducers is employed to measure the residual stresses. A Finite Element (FE) model of welding process, which is validated by hole-drilling method, is used to verify the ultrasonic results while an acceptable agreement is achieved. The best agreement is observed in the parent material while the maximum difference is measured in the heat affected zone (HAZ). The results show no considerable difference between using contact and immersion transducers in ultrasonic stress measurement of dissimilar joints. © 2013 Elsevier Ltd. Source


Fazilati J.,Aerospace Research Institute | Ovesy H.R.,Amirkabir University of Technology
Composite Structures | Year: 2013

The dynamic instability of longitudinally stiffened panels having rectangular internal cutouts under parametric in-plane loading is studied by using a developed finite strip method (FSM). The loading is considered as uniform stresses throughout the whole area. The effects of perforations on the instability load frequency regions are investigated using the Bolotin's first order method and a negative stiffness modeling approach. In order to demonstrate the capabilities of the developed methods in predicting the structural dynamic behavior, some representing results are obtained and compared with those in the literature wherever available. © 2012 Elsevier Ltd. Source


Tehrani Dehkordi M.,Shahrekord University | Nosraty H.,Amirkabir University of Technology | Shokrieh M.M.,Iran University of Science and Technology | Minak G.,University of Bologna | Ghelli D.,University of Bologna
Materials and Design | Year: 2013

Low-velocity impact and compression after impact (CAI) tests were performed to investigate the impact behavior of hybrid composite laminates reinforced by basalt-nylon intraply fabrics. The purpose of using this hybrid composite is to combine the good mechanical property of basalt fiber as a brittle fiber with the excellent impact resistance of nylon fiber as a ductile fiber. Five different types of woven fabric with different contents of nylon (0%, 25%, 33.3%, 50% and 100%) were used as reinforcement. The effect of nylon/basalt fiber content on impact parameters, impact damage behavior and CAI strength was studied at different nominal impact energy levels (16, 30 and 40. J). The results indicate that at low impact energy, hybridization and variation in basalt/nylon fiber content cannot improve the impact performance of composite plates. With increasing impact energy, the impact performance becomes more and more dependent on the content of nylon and basalt. © 2012 Elsevier Ltd. Source


Naderi R.,University of Tehran | Mahdavian M.,Sahand University of Technology | Darvish A.,Amirkabir University of Technology
Progress in Organic Coatings | Year: 2013

Protective performance of the epoxy primer containing strontium aluminum polyphosphate (SAPP) as a zinc-free phosphate-based anticorrosion pigment is aimed to assess in this work through taking advantage of electrochemical impedance spectroscopy (EIS) and electrochemical noise method (ENM). The absence of zinc offers an excellent environmentally friendly profile to the class of inhibiting compound. In the pigment extracts, the electrochemical techniques revealed superiority of SAPP compared to the conventional zinc phosphate (ZP). The behavior was connected to precipitation of a protective layer on the surface exposed to SAPP. In comparison with ZP, the most effective SAPP content in the protective primer was then determined using EIS. © 2012 Elsevier B.V. Source


Samadi B.,Amirkabir University of Technology | Rodrigues L.,Concordia University at Montreal
Automatica | Year: 2011

The main objective of this paper is to present a unified dissipativity approach for stability analysis of piecewise smooth (PWS) systems with continuous and discontinuous vector fields. The Filippov definition is considered for the solution of these systems. Using the concept of generalized gradients for nonsmooth functions, sufficient conditions for the stability of a PWS system are formulated based on Lyapunov theory. The importance of the proposed approach is that it does not need any a-priori information about attractive sliding modes on switching surfaces, which is in general difficult to obtain. A section on application of the main results to piecewise affine (PWA) systems followed by a section with extensive examples clearly show the usefulness of the proposed unified methodology. In particular, we present an example with a stable sliding mode where the proposed method works and previously suggested methods fail. © 2011 Elsevier Ltd. All rights reserved. Source


Hajarian M.,Shahid Beheshti University | Dehghan M.,Amirkabir University of Technology
Mathematical Methods in the Applied Sciences | Year: 2011

An n×n real matrix P is said to be a symmetric orthogonal matrix if P = P-1 = PT. An n × n real matrix Y is called a generalized centro-symmetric with respect to P, if Y = PYP. It is obvious that every matrix is also a generalized centro-symmetric matrix with respect to I. In this work by extending the conjugate gradient approach, two iterative methods are proposed for solving the linear matrix equation AYB + CYTD = E and the minimum Frobenius norm residual problem min ∥AYB + CYTD E∥ over the generalized centro-symmetric Y, respectively. By the first (second) algorithm for any initial generalized centro-symmetric matrix, a generalized centro-symmetric solution (least squares generalized centro-symmetric solution) can be obtained within a finite number of iterations in the absence of round-off errors, and the least Frobenius norm generalized centro-symmetric solution (the minimal Frobenius norm least squares generalized centro-symmetric solution) can be derived by choosing a special kind of initial generalized centro-symmetric matrices. We also obtain the optimal approximation generalized centro-symmetric solution to a given generalized centro-symmetric matrix Y0 in the solution set of the matrix equation (minimum Frobenius norm residual problem). Finally, some numerical examples are presented to support the theoretical results of this paper. © 2011 John Wiley & Sons, Ltd. Source


Allahbakhsh A.,Islamic Azad University at Shiraz | Mazinani S.,Amirkabir University of Technology
RSC Advances | Year: 2015

In this study, the influences of sodium dodecyl sulfate (SDS) on the vulcanization process and mechanical performance of ethylene-propylene-diene-monomer rubber (EPDM)/graphene oxide (GO) nanocomposites are investigated. Torque values variations and activation energies of the vulcanization process are used to study possible interactions between GO and EPDM. An increase in physical interactions between EPDM macromolecules and GO nanosheets in the presence of SDS is observed through rheometry studies, as minimum torque and scorch time of the vulcanization process increased noticeably. Moreover, the maximum strength of the EPDM/GO nanocomposite in the presence of SDS is about 137% more than the mechanical strength of the EPDM/GO nanocomposite. Furthermore, the EPDM/GO nanocomposite is elongated up to 700% in the presence of SDS. A mechanism for the physical interactions between EPDM macromolecules and GO nanosheets and influences of SDS presence on such interactions is reported based on Fourier transform infrared spectroscopies. © 2015 Royal Society of Chemistry. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology | Kermani M.J.,Head of Energy Conversion Research Laboratory
International Communications in Heat and Mass Transfer | Year: 2010

In this paper heat transfer and flow field in a wavy channel with nano-fluid is numerically studied. The temperature of input fluid (T c) is taken less than that of the wavy horizontal walls (T w). The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. Copper-water nano-fluid is considered for simulation. A wide spectrum of numerical simulations has been done over a range of Reynolds number, Re H, 5≤Re H≤1500, nano-fluid volume fraction, Φ, 0≤φ≤20% and the wave amplitude, α, 0≤α≤0.3. The effects of these parameters are investigated on the local and average Nusselt numbers and the skin friction coefficient. Simulations show excellent agreement with the literature. From this study, it is concluded that heat transfer in channels can enhance by addition of nano-particles, and usage of wavy horizontal walls. These can enhance the heat transfer by 50%. The present work can provide helpful guidelines to the manufacturers of the compact heat exchangers. © 2010 Elsevier Ltd. Source


Shomali Z.,Institute for Advanced Studies in Basic Sciences | Abbassi A.,Amirkabir University of Technology
International Journal of Thermal Sciences | Year: 2014

The one-dimensional non-linear non-Fourier heat conduction within a thin film of solid argon is numerically investigated under the framework of the Dual-Phase-Lagging (DPL) model including the boundary phonon scattering. The thermal properties of the solid argon including the thermal conductivity and sound group velocity are considered to be temperature-dependent, and the results are compared with those obtained from the Molecular-Dynamics simulation for the following cases: (I) constant applied temperature and (II) constant applied heat flux at the left boundary. In addition, each case is studied under two conditions of constant and temperature-dependent volumetric heat capacity. It is concluded that the combination of the DPL model with the mixed-type temperature boundary condition is able to accurately predict the heat flux and temperature distribution obtained from the molecular dynamics simulation. It is also found that using the temperature jump boundary condition along with the DPL model is essential to precisely capture the nanoscale heat transport. The results of our simulation showed that the Knudsen number increases up to 3.86 near right boundary for the temperature dependent volumetric heat capacity. © 2014 Elsevier B.V. All rights reserved. Source


Taghizadeh M.,Amirkabir University of Technology | Mobki H.,University of Tabriz
Archives of Mechanics | Year: 2014

In this paper, static and dynamic behavior of an electrostatically actuated torsional micro-actuator is studied. The microactuator is composed of a micromirror and two torsional beams, which are excited with two electrodes. Unlike in the traditional microactuators, the electrostatic force is exerted to both sides of micromirror, so the model is exposed to a DC voltage applied from the ground electrodes. The static governing equation of the torsional microactuator is derived and the relation between rotation angle and the driving voltage is determined. Local and global bifurcation analysis is performed, considering torsional characteristics of the micro-beams. By solving static deflection equation, the fixed points of the actuator are obtained. Critical values of the applied voltage leading to qualitative changes in the microactuator behavior through a saddle-node or pitchfork bifurcations for different spatial condition are obtained. Furthermore, the effects of different gap and electrode sizes as well as beam lengths on the dynamic behavior are investigated. It is shown that an increase of the applied voltage leads the structure to an unstable condition by undergoing saddle-node and pitchfork bifurcations when the voltages ratio is zero and one, respectively. © 2014 by IPPT PAN. Source


Esfandiari A.,Amirkabir University of Technology
Journal of Sound and Vibration | Year: 2014

In this paper a model updating algorithm is presented to estimate structural parameters at the element level utilizing frequency domain representation of the strain data. Sensitivity equations for mass and stiffness parameters estimation are derived using decomposed form of the strain-based transfer functions. The rate of changes of eigenvectors and a subset of measured natural frequencies are used to assemble the sensitivity equation of the strain-based transfer function. Solution of the derived sensitivity equations through the least square method resulted in a robust parameters estimation method. Numerical examples using simulated noise polluted data of 2D truss and frame models confirm that the proposed method is able to successfully update structural models even in the presence of mass modeling errors. © 2014 Elsevier Ltd. Source


Monfared M.,Ferdowsi University of Mashhad | Rastegar H.,Amirkabir University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2012

As a cost-effective and reliable alternative to standard three phase PWM converters, the low cost converters have attracted great attentions today. While the research trends mainly focused on using these converters for AC motor drives, some successful efforts in grid connected applications are also reported. These works use the voltage oriented technique to regulate the active and reactive power exchanges with the electric grid. This paper presents a dead beat direct power control strategy for grid integration of low cost three phase PWM converters. While keeping the advantages of fast and accurate power control associated to the VOC technique, the proposed strategy offers a considerably simpler algorithm. Extensive simulation and experimental results are provided which confirm the validity of the proposed technique. © 2012 Elsevier Ltd. All rights reserved. Source


Hajmohammadi M.R.,Amirkabir University of Technology | Poozesh S.,University of Kentucky | Rahmani M.,Arak University | Campo A.,University of Texas at San Antonio
Applied Thermal Engineering | Year: 2013

This paper explores the bearing that a non-uniform distribution of heat flux used as a wall boundary condition exerts on the heat transfer improvement in a round pipe. Because the overall heat load is considered fixed, the heat transfer improvement is viewed through a reduction in the maximum temperature ('hot spot') by imposing optimal distribution of heat flux. Two cases are studied in detail 1) fully developed and 2) developing flow. Peak temperatures in the heated pipe wall are calculated via an analytical approach for the fully developed case, while a numerical simulation based on CFD is employed for the developing case. By relaxing the heat flux distribution on the pipe wall, the numerical results imply that the optimum distribution of heat flux, which minimizes the peak temperatures corresponds with the 'descending' distribution. Given that the foregoing approach is quite different from the 'ascending' heat flux distribution recommended in the literature by means of the entropy generation minimization (EGM) method, it is inferred that the optimization of heat transfer and fluid flow, in comparison with the thermodynamic optimization, may bring forth quite different guidelines for the designs of thermal systems under the same constraints and circumstances. © 2013 Elsevier Ltd. All rights reserved. Source


Sadeghi H.,Amirkabir University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2012

Wind speed variations results in wind farm voltage, frequency and power output fluctuations. Therefore, protection of lines connecting such a farm to the grid is very important and an adaptive system for distance protection of such a line is necessary. In this paper, an adaptive unit which adjusts the relay trip characteristic using local information has been designed for distance relay using artificial neural networks. In this case, in order to prevent wrong operation of relay, changing in wind farm conditions, the set points of different zones of distance relay has to be changed simultaneously. The results obtained from proposed method are verified by computer simulation. © 2012 Elsevier Ltd. All rights reserved. Source


Akbari Torkestani J.,Islamic Azad University of Arak | Meybodi M.R.,Amirkabir University of Technology
Cluster Computing | Year: 2011

In the last decade, numerous efforts have been devoted to design efficient algorithms for clustering the wireless mobile ad-hoc networks (MANET) considering the network mobility characteristics. However, in existing algorithms, it is assumed that the mobility parameters of the networks are fixed, while they are stochastic and vary with time indeed. Therefore, the proposed clustering algorithms do not scale well in realistic MANETs, where the mobility parameters of the hosts freely and randomly change at any time. Finding the optimal solution to the cluster formation problem is incredibly difficult, if we assume that the movement direction and mobility speed of the hosts are random variables. This becomes harder when the probability distribution function of these random variables is assumed to be unknown. In this paper, we propose a learning automata-based weighted cluster formation algorithm called MCFA in which the mobility parameters of the hosts are assumed to be random variables with unknown distributions. In the proposed clustering algorithm, the expected relative mobility of each host with respect to all its neighbors is estimated by sampling its mobility parameters in various epochs. MCFA is a fully distributed algorithm in which each mobile independently chooses the neighboring host with the minimum expected relative mobility as its cluster-head. This is done based solely on the local information each host receives from its neighbors and the hosts need not to be synchronized. The experimental results show the superiority of MCFA over the best existing mobility-based clustering algorithms in terms of the number of clusters, cluster lifetime, reaffiliation rate, and control message overhead. © 2011 Springer Science+Business Media, LLC. Source


Ghatee M.,Amirkabir University of Technology
Computer Communications | Year: 2011

This paper treats with integral multi-commodity flow through a network. To enhance the Quality of Service (QoS) for channels, it is necessary to minimize delay and congestion. Decreasing the end-to-end delay and consumption of bandwidth across channels are dependent and may be considered in very complex mathematical equations. To capture with this problem, a multi-commodity flow model is introduced whose targets are minimizing delay and congestion in one model. The flow through the network such as packets, also needs to get integral values. A model covering these concepts, is NP-hard while it is very important to find transmission strategies in real-time. For this aim, we extend a cooperative algorithm including traditional mathematical programming such as path enumeration and a meta-heuristic algorithm such as genetic algorithm. To find integral solution satisfying demands of nodes, we generalize a hybrid genetic algorithm to assign the integral commodities where they are needed. In this hybrid algorithm, we use feasible encoding and try to keep feasibility of chromosomes over iterations. By considering some random networks, we show that the proposed algorithm yields reasonable results in a few number of iterations. Also, because this algorithm can be applied in a wide range of objective functions in terms of delay and congestion, it is possible to find some routs for each commodity with high QoS. Due to these outcomes, the presented model and algorithm can be utilized in a variety of application in computer networks and transportation systems to decrease the congestion and increase the usage of channels. © 2010 Elsevier B.V. All rights reserved. Source


Akbari Torkestani J.,Islamic Azad University of Arak | Meybodi M.R.,Amirkabir University of Technology | Meybodi M.R.,Institute for Studies in Theoretical Physics and Mathematics IPM
Applied Soft Computing Journal | Year: 2011

Due to the hardness of solving the minimum spanning tree (MST) problem in stochastic environments, the stochastic MST (SMST) problem has not received the attention it merits, specifically when the probability distribution function (PDF) of the edge weight is not a priori known. In this paper, we first propose a learning automata-based sampling algorithm (Algorithm 1) to solve the MST problem in stochastic graphs where the PDF of the edge weight is assumed to be unknown. At each stage of the proposed algorithm, a set of learning automata is randomly activated and determines the graph edges that must be sampled in that stage. As the proposed algorithm proceeds, the sampling process focuses on the spanning tree with the minimum expected weight. Therefore, the proposed sampling method is capable of decreasing the rate of unnecessary samplings and shortening the time required for finding the SMST. The convergence of this algorithm is theoretically proved and it is shown that by a proper choice of the learning rate the spanning tree with the minimum expected weight can be found with a probability close enough to unity. Numerical results show that Algorithm 1 outperforms the standard sampling method. Selecting a proper learning rate is the most challenging issue in learning automata theory by which a good trade off can be achieved between the cost and efficiency of algorithm. To improve the efficiency (i.e., the convergence speed and convergence rate) of Algorithm 1, we also propose four methods to adjust the learning rate in Algorithm 1 and the resultant algorithms are called as Algorithm 2 through Algorithm 5. In these algorithms, the probabilistic distribution parameters of the edge weight are taken into consideration for adjusting the learning rate. Simulation experiments show the superiority of Algorithm 5 over the others. To show the efficiency of Algorithm 5, its results are compared with those of the multiple edge sensitivity method (MESM). The obtained results show that Algorithm 5 performs better than MESM both in terms of the running time and sampling rate. © 2010 Elsevier B.V. All rights reserved. Source


Farivar F.,Amirkabir University of Technology
International Journal of Hydrogen Energy | Year: 2016

In this paper an improved dual chamber photoelectrochemical (PEC) reactor for water splitting is developed. COMSOL Multiphysics (4.2b) software is utilized to simulate two and three-dimensional PEC reactor. Different geometries are studied to have a uniform flow with minimum recirculation zones inside the photoreactor chamber. Furthermore, the gas evolution rate in the photoreactor at different current densities is studied. As expected, the simulation results showed that by increasing the current density, the gas production rate increases. Integration of a thin layer of golden grid on the transparent conductive films (TCFs) is proposed to reduce potential drop across the sheet resistance of TCFs in photoelectrods which is one of the major problems in construction of larger photoelectrods. The simulation results showed that the potential drop is decreased significantly (from about 25% drop to roughly 6% drop) after applying the golden grid on the fluorine doped tin oxide (F-TO) film. Finally, some practical considerations and data are provided for fabrication of the PEC reactor. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source


Poursha M.,Sahand University of Technology | Khoshnoudian F.,Amirkabir University of Technology | Moghadam A.S.,International Earthquake and Seismology Research Center
Engineering Structures | Year: 2011

Seismic responses of unsymmetric-plan tall buildings are substantially influenced by the effects of higher modes and torsion. Considering these effects, in this article, the consecutive modal pushover (CMP) procedure is extended to estimate the seismic demands of one-way unsymmetric-plan tall buildings. The procedure uses multi-stage and classical single-stage pushover analyses and benefits from the elastic modal properties of the structure. Both lateral forces and torsional moments obtained from modal analysis are used in the multi-stage pushover analysis. The seismic demands are obtained by enveloping the peak inelastic responses resulting from the multi-stage and single-stage pushover analyses. To verify and appraise the procedure, it is applied to the 10, 15, and 20-storey one-way unsymmetric-plan buildings including systems with different degrees of coupling between the lateral displacements and torsional rotations, i.e. torsionally-stiff (TS), torsionally-similarly-stiff (TSS) and torsionally-flexible (TF) systems. The modal pushover analysis (MPA) procedure is implemented for the purpose of comparison as well. The results from the approximate pushover procedures are compared with the results obtained by the nonlinear response history analysis (NL-RHA). It is demonstrated that the CMP procedure is able to take into account the higher mode influences as well as amplification or de-amplification of seismic displacements at the flexible and stiff edges of unsymmetric-plan tall buildings. The extended procedure can predict to a reasonable accuracy the peak inelastic responses, such as displacements and storey drifts. The CMP procedure represents an important improvement in estimating the plastic rotations of hinges at both flexible and stiff sides of unsymmetric-plan tall buildings in comparison with the MPA procedure. © 2011 Elsevier Ltd. Source


Abdollahi F.,Amirkabir University of Technology | Abdollahi F.,Concordia University at Montreal | Khorasani K.,Concordia University at Montreal
IEEE Transactions on Control Systems Technology | Year: 2011

This paper presents a Markovian jump linear (MJL) system framework for developing routing algorithms in mobile ad hoc networks (MANETs) that encounter changes in the number of nodes and/or the number of destinations. A unified ℋ∞ control strategy is proposed by representing the dynamically changing destination nodes as singular switching control systems. A decentralized routing scheme is proposed and designed for the networked multi-agent system in presence of unknown time-varying delays. To solve the corresponding optimization problem the physical constraints are expressed as linear matrix inequality (LMI) conditions. The resulting decentralized ℋ∞ routing control schemes for both regular and singular MJL systems are shown to formally achieve the desired performance specifications and requirements. Simulation results are presented to illustrate and demonstrate the effectiveness of our proposed novel routing control strategies. © 2010 IEEE. Source


Mirzavand B.,Shahrekord University | Eslami M.R.,Amirkabir University of Technology
Acta Mechanica | Year: 2011

A thermal buckling analysis is presented for functionally graded rectangular plates that are integrated with surface-bonded piezoelectric actuators and are subjected to the combined action of thermal load and constant applied actuator voltage. The temperature-dependent material properties of the functionally graded plate are assumed to vary as a power form of the thickness coordinate. Derivation of the equations is based on the third-order shear deformation plate theory. Results for the critical buckling temperatures are obtained in closed-form solution, which are convenient to be used in engineering design applications. The effects of the applied actuator voltage, plate geometry, and volume fraction exponent of the functionally graded material on the buckling temperature are investigated. © 2010 Springer-Verlag. Source


Mirabi M.,University of Yazd | Fatemi Ghomi S.M.T.,Amirkabir University of Technology | Jolai F.,University of Tehran
Robotics and Computer-Integrated Manufacturing | Year: 2010

The paper addresses the problem of multi-depot vehicle routing in order to minimize the delivery time of vehicle objective. Three hybrid heuristics are presented to solve the multi-depot vehicle routing problem. Each hybrid heuristic combines elements from both constructive heuristic search and improvement techniques. The improvement techniques are deterministic, stochastic and simulated annealing (SA) methods. Experiments are run on a number of randomly generated test problems of varying depots and customer sizes. Our heuristics are shown to outperform one of the best-known existing heuristic. Statistical tests of significance are performed to substantiate the claims of improvement. © 2010 Elsevier Ltd. Source


Shirazi M.M.A.,Islamic Azad University at Omidieh | Kargari A.,Amirkabir University of Technology | Tabatabaei M.,Agricultural Biotechnology Research Institute of Iran
Chemical Engineering and Processing: Process Intensification | Year: 2014

In this study, nine flat-sheet commercially available hydrophobic PTFE membranes were used in desalination by direct contact membrane distillation and their characteristics were investigated under different operating conditions including feed temperature, feed flow rate, cold stream flow rate, and feed concentration. Membrane properties, i.e. pore size, thickness, support layer, and salt rejection were also studied. Moreover, membrane module designs including flow arrangements (co-current, counter-current and tangential) for process liquid and depth both on hot and cold sides were tested experimentally. Finally, the long-term performance of the selected membranes for direct contact membrane distillation as a stand-alone desalination process was investigated. The results indicated that increasing feed temperature, hot feed flow rate, and module depth on the cold side led to increase permeate flux. On the other hand, increasing membrane thickness and module depth on the hot side (at constant flow rate) had negative effects on the flux. The highest permeation flux and salt rejection was achieved when the membranes with a pore size of 0.22. μm were used in the cross-current follow arrangement of hot and cold streams. In addition, the requirements for support layer for a successful DCMD process has been extensively discussed. © 2013 Elsevier B.V. Source


Sharifi M.,Amirkabir University of Technology | Kelkar M.,University of Tulsa
Fuel | Year: 2014

Despite computational advances, geo-cellular models are routinely upscaled for reservoir simulation purposes. Geo-cellular models typically incorporate small scale variations obtained from static data; whereas, simulation models capture dynamic data obtained from production of the field. The process of reducing the number of grid blocks in the geological model so that the simulation model can be run efficiently is called the process of upscaling. Upscaling requires combining the small grid blocks from geological model to make a larger grid block, as well as assigning reservoir properties on the coarse scale. Among the physical properties that need to be assigned, the assignment of permeability is the most challenging. Unlike porosity (or saturation), permeability is a dynamic property and capturing the fine scale dynamic displacement requires a non-linear upscaling of fine scale permeability values. The two types of methods used for permeability upscaling can be broadly categorized as static upscaling and dynamic upscaling. Static upscaling methods average fine scale values to calculate an upscaled value. These methods are efficient but may not capture the dynamic behavior. The dynamic upscaling methods are computationally expensive and may be dependent on boundary conditions. In this paper, we propose a new dynamic method for areal upscaling based on the fast marching algorithm. The Fast Marching Method (FMM) accurately captures the propagating pressure front as a function of time. We define the objective function as the difference in the propagation time between fine scale and coarse scale models. By minimizing the objective function, we calculate the permeability of the upscaled model. The Fast Marching Method is an extremely efficient method for calculating the pressure front propagation time based on reservoir properties. This method is based on solving the Eikonal equation using an upwind finite difference approximation. The advantage of this method is that, without running any flow simulation, we can calculate the pressure front location (radius of investigation) as a function of time. In this paper, using 2D and 3D models, we demonstrate that the calculated effective permeability using the new method can reproduce the dynamic behavior of the fine scale model. © 2013 Elsevier Ltd. All rights reserved. Source


Hajmohammadi M.R.,Amirkabir University of Technology | Rahmani M.,Arak University | Campo A.,University of Texas at San Antonio | Joneydi Shariatzadeh O.,Lappeenranta University of Technology
Energy | Year: 2014

When the total amount of thermal energy is fixed in a device, it is important to keep the highest temperatures (hot spots) of the device at the minimum level. The present paper deals with the optimal design of heat flux elements mounted on the outer walls of a rectangular duct. The total amount of heat load is fixed and is transferred by in-duct laminar forced convection. The objective is to minimize the hot spots temperature under the platform of constructal design. A numerical simulation is carried out to calculate the hot spots temperatures. The numerical results suggest that the equal heat flux elements (uniform heating) customarily used in industry must be avoided. By conducting a detailed optimization process, it is shown that there exists an optimum 'descending' distribution for the unequal heat flux elements that minimizes the hot spot temperatures. The influence of Graetz number and the number of unequal heat flux elements on the temperature reduction is studied. For instance, compared with the case of uniform heating, it is shown that the hot spot temperature is reduced up to 25% in the case of four unequal heat flux element under the influence of intermediate values of Graetz number. © 2014 Elsevier Ltd. Source


In this work the complex permittivity and microwave absorption of toxins/sewage gases and functionalized single-walled carbon nanotube sensors in a perturbed microwave resonant cavity are studied with the aid of a kinetic model. The results show that the real permittivity decreases and the imaginary permittivity increases with increasing the electron density; however, the real permittivity increases and the imaginary permittivity decreases with the collision frequency increasing. The results furthermore show that low electron density and high collision frequency can greatly reduce the microwave absorption, while high electron density and low collision frequency can increase the microwave absorption. The microwave absorption shifts to high frequency with increasing the electron density. The microwave absorption, in contrast, shifts to low frequency with the collision frequency increasing. The kinetic model may be used to study the effects of gas pressure on the complex permittivity and microwave absorption. © 2010 American Institute of Physics. Source


Ahmadlou M.,Amirkabir University of Technology | Adeli H.,Ohio State University
Integrated Computer-Aided Engineering | Year: 2010

In recent years the Probabilistic Neural Network (PPN) has been used in a large number of applications due to its simplicity and efficiency. PNN assigns the test data to the class with maximum likelihood compared with other classes. Likelihood of the test data to each training data is computed in the pattern layer through a kernel density estimation using a simple Bayesian rule. The kernel is usually a standard probability distribution function such as a Gaussian function. A spread parameter is used as a global parameter which determines the width of the kernel. The Bayesian rule in the pattern layer estimates the conditional probability of each class given an input vector without considering any probable local densities or heterogeneity in the training data. In this paper, an enhanced and generalized PNN (EPNN) is presented using local decision circles (LDCs) to overcome the aforementioned shortcoming and improve its robustness to noise in the data. Local decision circles enable EPNN to incorporate local information and non-homogeneity existing in the training population. The circle has a radius which limits the contribution of the local decision. In the conventional PNN the spread parameter can be optimized for maximum classification accuracy. In the proposed EPNN two parameters, the spread parameter and the radius of local decision circles, are optimized to maximize the performance of the model. Accuracy and robustness of EPNN are compared with PNN using three different benchmark classification problems, iris data, diabetic data, and breast cancer data, and five different ratios of training data to testing data: 90:10, 80:20, 70:30, 60:40, and 50:50. EPNN provided the most accurate results consistently for all ratios. Robustness of PNN and EPNN is investigated using different values of signal to noise ratio (SNR). Accuracy of EPNN is consistently higher than accuracy of PNN at different levels of SNR and for all ratios of training data to testing data. © 2010 IOS Press and the author(s). All rights reserved. Source


Kamani D.,Amirkabir University of Technology
European Physical Journal C | Year: 2014

Using the dilaton scalar and axion pseudoscalar fields we construct a number of scalars and differential forms which are symmetric under the Z2-subgroup of the group SL(2, R). These invariants enable us to establish various 10-dimensional invariant actions. Other invariants which are not independent from the previous ones will be detached. © 2014 The Author(s). Source


Beigy H.,Sharif University of Technology | Meybodi M.R.,Amirkabir University of Technology
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2010

The cellular learning automaton (CLA), which is a combination of cellular automaton (CA) and learning automaton (LA), is introduced recently. This model is superior to CA because of its ability to learn and is also superior to single LA because it is a collection of LAs which can interact with each other. The basic idea of CLA is to use LA to adjust the state transition probability of stochastic CA. Recently, various types of CLA such as synchronous, asynchronous, and open CLAs have been introduced. In some applications such as cellular networks, we need to have a model of CLA for which multiple LAs reside in each cell. In this paper, we study a CLA model for which each cell has several LAs. It is shown that, for a class of rules called commutative rules, the CLA model converges to a stable and compatible configuration. Two applications of this new model such as channel assignment in cellular mobile networks and function optimization are also given. For both applications, it has been shown through computer simulations that CLA-based solutions produce better results. © 2009 IEEE. Source


Ahmadlou M.,Amirkabir University of Technology | Adeli H.,Ohio State University
Clinical EEG and Neuroscience | Year: 2010

A multi-paradigm methodology is presented for electroencephalogram (EEG) based diagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD) through adroit integration of nonlinear science; wavelets, a signal processing technique; and neural networks, a pattern recognition technique. The selected nonlinear features are generalized synchronizations known as synchronization likelihoods (SL), both among all electrodes and among electrode pairs. The methodology consists of three parts: first detecting the more synchronized loci (group 1) and loci with more discriminative deficit connections (group 2). Using SLs among all electrodes, discriminative SLs in certain sub-bands are extracted. In part two, SLs are computed, not among all electrodes, but between loci of group 1 and loci of group 2 in all sub-bands and the band-limited EEG. This part leads to more accurate detection of deficit connections, and not just deficit areas, but more discriminative SLs in sub-bands with finer resolutions. In part three, a classification technique, radial basis function neural network, is used to distinguish ADHD from normal subjects. The methodology was applied to EEG data obtained from 47 ADHD and 7 control individuals with eyes closed. The Radial Basis Function (RBF) neural network classifier yielded a high accuracy of 95.6% for diagnosis of the ADHD in the feature space discovered in this research with a variance of 0.7%. Source


Sohrabi M.,Amirkabir University of Technology
Radiation Measurements | Year: 2013

Highlights of findings on radiological measurements, radiobiological and epidemiological studies in some main world high background natural radiation (HBNR) areas such as in Brazil, China, India and Iran are presented and discussed with special regard to remediation of radiation exposure of inhabitants in such areas. The current radiation protection philosophy and recommendations applied to workers and public from operation of radiation and nuclear applications are based on the linear non-threshold (LNT) model. The inhabitants of HBNR and radon prone areas receive relatively high radiation doses. Therefore, according to the LNT concept, the inhabitants in HBNR areas and in particular those in Ramsar are considered at risk and their exposure should be regulated. The HBNR areas in the world have different conditions in terms of dose and population. In particular, the inhabitants in HBNR areas of Ramsar receive very high internal and external exposures. This author believes that the public in such areas should be protected and proposes a plan to remedy high exposure of the inhabitants of the HBNR areas of Ramsar, while maintaining these areas as they stand to establish a national environmental radioactivity park which can be provisionally called "Ramsar Research Natural Radioactivity Park" (RRNRP). The major HBNR areas, the public exposure and the need to remedy exposures of inhabitants are reviewed and discussed. © 2012 Elsevier Ltd. All rights reserved. Source


Farahani R.Z.,Kingston University | Hekmatfar M.,Amirkabir University of Technology | Arabani A.B.,Wayne State University | Nikbakhsh E.,Tarbiat Modares University
Computers and Industrial Engineering | Year: 2013

Hub location problem (HLP) is a relatively new extension of classical facility location problems. Hubs are facilities that work as consolidation, connecting, and switching points for flows between stipulated origins and destinations. While there are few review papers on hub location problems, the most recent one (Alumur and Kara, 2008. Network hub location problems: The state of the art. European Journal of Operational Research, 190, 1-21) considers solely studies on network-type hub location models prior to early 2007. Therefore, this paper focuses on reviewing the most recent advances in HLP from 2007 up to now. In this paper, a review of all variants of HLPs (i.e., network, continuous, and discrete HLPs) is provided. In particular, mathematical models, solution methods, main specifications, and applications of HLPs are discussed. Furthermore, some case studies illustrating real-world applications of HLPs are briefly introduced. At the end, future research directions and trends will be presented. © 2013 Elsevier Ltd. All rights reserved. Source


Danaeifar M.,K. N. Toosi University of Technology | Granpayeh N.,K. N. Toosi University of Technology | Mohammadi A.,Amirkabir University of Technology | Setayesh A.,K. N. Toosi University of Technology
Applied Optics | Year: 2013

This paper presents a sheet of graphene as a simple band-pass filter in terahertz and infrared frequencies. The central frequency and quality factor of this band-pass filter can be tuned by changing the physical parameters, such as the substrate thickness, gate voltage, temperature, and conductivity of the graphene. The effects of these parameters on surface plasmon polariton waves and filter specifications are numerically depicted. © 2013 Optical Society of America. Source


Abbasi S.M.,University of Tehran | Momeni A.,Amirkabir University of Technology
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2011

The effects of hot compression, hot rolling and post-rolling annealing on microstructure and tensile properties of Ti-6Al-4V were analyzed. Hot compression tests were conducted in the temperature range of 800-1 075 °C and at strain rates of 0.001-1 s-1, and the relations between the characteristic points of flow curve and processing variables were developed. Two passes of hot rolling test with total reduction of 75 were performed in the temperature range of 820-1 070 °C and at constant strain rate of 2 s -1. After hot rolling, some specimens were subjected to heat treatment at 870 °C and 920 °C for 2 h followed by air cooling. Hot rolling in beta phase field resulted in coarse beta grains transforming to martensite by cooling. Otherwise, rolling in the alpha/beta phase filed gave rise to a partially globularized alpha microstructure. The post-rolling heat treatment completed the partial globularization of alpha phase in two-phase region and otherwise broke down the martensitic structure of beta-rolled samples. Tensile tests showed that the strength characteristics as well as elongation decrease significantly with increasing the rolling temperature from the two-phase to the single-phase region. Increasing heat treatment temperature contributed to lower strength for the specimens rolled in two-phase region and higher strength characteristics for the beta-rolled specimens. © 2011 The Nonferrous Metals Society of China. Source


Ataeefard M.,Iran Institute for Color Science and Technology | Sharifi S.,Amirkabir University of Technology
Progress in Organic Coatings | Year: 2014

The current work deals with the effects of incorporation of silver nanoparticles on the antibacterial and the thermal properties of a flexographic ink. The stable and uniform dispersion of silver nanoparticles in the ink were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal properties of the pure and nanoparticle loaded ink films were also evaluated using TGA and DSC techniques. The results from this study proved acceptable dispersion characteristics, wherein, the flexographic ink showed a significant antibacterial activity against Gram-positive and Gram-negative bacteria. © 2013 Elsevier B.V. All rights reserved. Source


Asadisaghandi J.,National Iranian Oil Company | Tahmasebi P.,Amirkabir University of Technology
Journal of Petroleum Science and Engineering | Year: 2011

This paper presents a new approach to improve the performance of neural network method to PVT oil properties prediction. The true value of PVT properties which is determined based on the accurate data is a challenge of the petroleum industry. The main goal of the following investigation would be the performance comparison of various back-propagation learning algorithms in neural network that could be applied for PVT prediction. Up to now, no procedure has been presented to determine the network structure for some complicated cases, therefore; design and production of neural network would be almost dependent on the user's experience. To prevent this problem, neural network based recommended procedure in this study was applied to present the advantages. To show the performance of this procedure, several learning algorithms were investigated for comparison. One of the most common problems in neural network design is the topology and the parameter value accuracy that if those elements selection was correctly and optimally, the designer would achieve better results. Since, fluids of different regions have varying hydrocarbon properties, therefore, the empirical correlations in different hydrocarbon systems should be investigated to find their accuracies and limitations. In this study, an investigation of different empirical correlations along with the artificial neural networks in Iran oilfields has been presented. Then, the new model of artificial neural network for prediction of PVT oil properties in Iran crude oil presented. To test this new method, it was evaluated by collecting dataset from 23 different oilfields in Iran (south, central, western and continental shelf). In this study, two networks for prediction of bubble point pressure values (Pb) and the oil formation volume factor at bubble point (Bob) were designed. The parameters and topology of the optimum neural networks were determined and in order to consider the effect of these networks designing on results, their performances were compared with various empirical correlations. According to comparison between the obtained results, it shows that the improved method presented has better performance rather than empirical and current methods in neural network designing in petroleum applications for these predictions. © 2011 Elsevier B.V. Source


Naderi R.,University of Tehran | Attar M.M.,Amirkabir University of Technology
Progress in Organic Coatings | Year: 2014

In the field of protective coatings, zinc-free pigments are proposed as promising anticorrosion compounds due to their excellent environmentally- friendly profile. In this paper, cathodic disbonding performance of a solvent-borne epoxy primer incorporating strontium aluminum polyphosphate (SAPP) as a zinc-free phosphate-based anticorrosion pigment was investigated. Regardless of the applied potential, the presence of SAPP in the coating formulation caused slower growth of the delamination area in comparison to ZP. According to the data obtained from EIS and SEM/EDX, this behavior was attributed to locally controlled pH and the precipitated film restricting active zones available for electrochemical reactions. © 2014 Elsevier B.V. Source


Esnaashari M.,Amirkabir University of Technology | Meybodi M.R.,Institutes for Studies in Theoretical Physics and Mathematics IPM
Wireless Networks | Year: 2010

One way to reduce energy consumption in wireless sensor networks is to reduce the number of packets being transmitted in the network. As sensor networks are usually deployed with a number of redundant nodes (to overcome the problem of node failures which is common in such networks), many nodes may have almost the same information which can be aggregated in intermediate nodes, and hence reduce the number of transmitted packets. Aggregation ratio is maximized if data packets of all nodes having almost the same information are aggregated together. For this to occur, each node should forward its packets along a path on which maximum number of nodes with almost the same information as the information of the sending node exist. In many real scenarios, such a path has not been remained the same for the overall network lifetime and is changed from time to time. These changes may result from changes occurred in the environment in which the sensor network resides and usually cannot be predicted beforehand. In this paper, a learning automata-based data aggregation method in sensor networks when the environment's changes cannot be predicted beforehand will be proposed. In the proposed method, each node in the network is equipped with a learning automaton. These learning automata in the network collectively learn the path of aggregation with maximum aggregation ratio for each node for transmitting its packets toward the sink. To evaluate the performance of the proposed method computer simulations have been conducted and the results are compared with the results of three existing methods. The results have shown that the proposed method outperforms all these methods, especially when the environment is highly dynamic. © Springer Science+Business Media, LLC 2009. Source


Kouhikamali R.,Guilan University | Sharifi N.,Amirkabir University of Technology
Applied Thermal Engineering | Year: 2012

Nowadays multiple effect desalination plants are used widely in water treatment processes. They utilize thermal vapor compressors instead of mechanical ones. One of the major complexities about thermo-compressors is related to its unstable operational mode. An experimental malfunctioning occurred in a desalination unit established in south pars gas field phases 9&10 with 1718 cubic meter per day capacity. Some modifications on the thermo-compressor design were applied and well tested. In the current study a numerical investigation was performed on a malfunctioning thermo-compressor and the source of the problem was observed via a numerical simulation. Afterwards, the modifications were conducted on the numerical models and then a perfect analyzed and verified model was selected to manufacture and install. The test results were shown a better performance of thermo-compressor which yields an increase in entrainment ratio and extend the stable region of thermo-compressor working. It is shown that the entrainment ratio is very sensitive to the geometrical parameters of mixing area zone and throat section of thermo-compressor. © 2012 Elsevier Ltd. All rights reserved. Source


Etaati A.,University of Southern Queensland | Dehghani K.,Amirkabir University of Technology
Materials Chemistry and Physics | Year: 2013

To investigate the hot deformation behavior of the Ni-42.5Ti-7.5Cu (wt%) alloy, hot compression tests were carried out at the temperatures from 800 °C to 1000 °C and at the strain rates of 0.001 s-1 to 1 s-1. The results show that the occurrence of dynamic recrystallization (DRX) is the dominate restoration mechanism during the hot deformation of this alloy. There is an increase in peak and steady state stresses with decreasing the deformation temperature and increasing the strain rate. The experimental results were then used to determine the constants of developed constitutive equations. There is a good agreement between the measured and predicted results indicating a high accuracy of developed model. Zener-Hollomon (Z) parameter, calculated based on the developed model, indicates that DRX was postponed when the logarithm of the Zener-Hollomon parameter fell around 33 at strain rate of 0.001 s-1 and temperature of 900 °C. This phenomenon can be regarded as the interactions between solute atoms and mobile dislocations. The established constitutive equations can be used to predict and analyze the hot deformation behavior of Ni-42.5Ti-7.5Cu alloy. © 2013 Elsevier B.V. All rights reserved. Source


Montazer M.,Amirkabir University of Technology | Shamei A.,Islamic Azad University at South Tehran | Alimohammadi F.,Islamic Azad University at South Tehran
Progress in Organic Coatings | Year: 2012

In this study, silver nanoparticles stabilized on the nylon knitted fabric by padding process using 1,2,3,4-butanetetracarboxylic acid (BTCA) and sodium hypophosphite (SHP) without considerable yellowing. This cross-linking combination also dimensionally stabilized the nylon knitted fabric. The SEM images showed the distribution and size of nanosilver within 34 nm. Also, the presence of nanosilver on the fabrics confirmed by EDX and XRD spectrums. The antimicrobial test performed on the treated fabrics against Staphylococcus aureus as a Gram positive and Escherichia coli as a Gram negative bacterium using pour plate test method. A bacterium growth decrease above 96% achieved with 200 ppm nanosilver/BTCA/SHP with standing up to 20 successive rinses. The L*a*b* values had little changes upon increasing the concentration of silver nanoparticles. However the color changes were negligible and the fabric was still white. Moreover, diffuse reflectance spectroscopy, dimensional stability, and water droplet adsorption time as well as statistical analysis of the results investigated and reported. © 2012 Elsevier B.V. Source


Karami A.,Amirkabir University of Technology | Salehi V.,Sharif University of Technology
Journal of Catalysis | Year: 2012

A series of Cr-substituted Fe-Ti compounds were prepared by the co-precipitation method and were systematically investigated as catalysts for the selective catalytic reduction (SCR) of NO by NH 3. A variety of analytical techniques revealed that the Cr substitution amount affects the N 2 selectivity, SCR activity, redox behavior of NH 3/NO x, adsorption ability, and structure of catalysts in terms of surface properties, porosity, mobility of lattice oxygen, oxidative ability of Cr species, ratio of Bronsted acid sites and Lewis acid sites, NO x adsorption capacity, and structural disorder and distortion. In a series of Fe aCr 1-aTiO x (a = 1, 0.75, 0.5, 0.2, 0) catalysts, Fe 0.5Cr 0.5TiO x showed the highest activity because of the optimized interactions of Fe, Cr, and Ti species in this catalyst. © 2012 Elsevier Ltd. All rights reserved. Source


Sofla M.A.,University of Toledo | Gharehpetian G.B.,Amirkabir University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2011

Dynamics are the most important problems in the microgrid operation. In the islanded microgrid, the mismatch of parallel operations of inverters during dynamics can result in the instability. This paper considers severe dynamics which can occur in the microgrid. Microgrid can have different configurations with different load and generation dynamics which are facing voltage disturbances. As a result, microgrid has many uncertainties and is placed in the distribution network where is full of voltage disturbances. Moreover, characteristics of the distribution network and distributed energy resources in the islanded mode make microgrid vulnerable and easily lead to instability. The main aim of this paper is to discuss the suitable mathematical modeling based on microgrid characteristics and to design properly inner controllers to enhance the dynamics of microgrid with uncertain and changing parameters. This paper provides a method for inner controllers of inverter-b