Showing papers by "Amirkabir University of Technology published in 2013"
TL;DR: This paper focuses on reviewing the most recent advances in HLP from 2007 up to now, and a review of all variants of HLPs (i.e., network, continuous, and discrete HLPs) is provided.
471 citations
TL;DR: In this article, the authors used a systematic computer search to find chaotic flows with quadratic nonlinearities that have the unusual feature of having a line equilibrium, which is called hidden attractor chaotic flow.
Abstract: Using a systematic computer search, nine simple chaotic flows with quadratic nonlinearities were found that have the unusual feature of having a line equilibrium. Such systems belong to a newly introduced category of chaotic systems with hidden attractors that are important and potentially problematic in engineering applications.
441 citations
TL;DR: In this article, three methods are used to produce a catalog of seventeen elementary three-dimensional chaotic flows with quadratic nonlinearities that have the unusual feature of lacking any equilibrium points.
391 citations
TL;DR: In this article, the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds is discussed. And a brief review of friction stir spot welding, as an alternative to RSW, is also included.
Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.
369 citations
TL;DR: In this article, the potential of the prepared nanofiber membrane for adsorption of nickel (Ni), cadmium (Cd), lead (Pb) and copper (Cu) from aqueous solution was investigated.
330 citations
TL;DR: In this paper, a nonlinear analysis of EEG signal for discriminating depression patients and normal controls was performed. And the proposed technique is compared and contrasted with the other reported methods and it is demonstrated that by combining nonlinear features, the performance is enhanced.
328 citations
TL;DR: Using the Routh–Hurwitz stability criterion and a systematic computer search, 23 simple chaotic flows with quadratic nonlinearities were found that have the unusual feature of having a coexisting stable equilibrium point.
Abstract: Using the Routh–Hurwitz stability criterion and a systematic computer search, 23 simple chaotic flows with quadratic nonlinearities were found that have the unusual feature of having a coexisting stable equilibrium point. Such systems belong to a newly introduced category of chaotic systems with hidden attractors that are important and potentially problematic in engineering applications.
294 citations
TL;DR: A new PID controller for resistant differential control against load disturbance is introduced that can be used for load frequency control (LFC) application and a comparison between this controller and two other prevalent PI controllers, optimized by GA and Neural Networks, has been done which represents advantages of this controller over others.
Abstract: A new PID controller for resistant differential control against load disturbance is introduced that can be used for load frequency control (LFC) application. Parameters of the controller have been specified by using imperialist competitive algorithm (ICA). Load disturbance, which is due to continuous and rapid changes of small loads, is always a problem for load frequency control of power systems. This paper introduces a new method to overcome this problem that is based on filtering technique which eliminates the effect of this kind of disturbance. The object is frequency regulation in each area of the power system and decreasing of power transfer between control areas, so the parameters of the proposed controller have been specified in a wide range of load changes by means of ICA to achieve the best dynamic response of frequency. To evaluate the effectiveness of the proposed controller, a three-area power system is simulated in MATLAB/SIMULINK. Each area has different generation units, so utilizes controllers with different parameters. Finally a comparison between the proposed controller and two other prevalent PI controllers, optimized by GA and Neural Networks, has been done which represents advantages of this controller over others.
287 citations
TL;DR: This survey reviews algorithmic paradigms—search based, cycle based, transformation based, and BDD based—as well as specific algorithms for reversible synthesis, both exact and heuristic, and outlines key open challenges in synthesis of reversible and quantum logic.
Abstract: Reversible logic circuits have been historically motivated by theoretical research in low-power electronics as well as practical improvement of bit manipulation transforms in cryptography and computer graphics. Recently, reversible circuits have attracted interest as components of quantum algorithms, as well as in photonic and nano-computing technologies where some switching devices offer no signal gain. Research in generating reversible logic distinguishes between circuit synthesis, postsynthesis optimization, and technology mapping. In this survey, we review algorithmic paradigms—search based, cycle based, transformation based, and BDD based—as well as specific algorithms for reversible synthesis, both exact and heuristic. We conclude the survey by outlining key open challenges in synthesis of reversible and quantum logic, as well as most common misconceptions.
278 citations
TL;DR: A novel hydrometallurgical process was proposed for selective recovery of Cu, Ag, Au and Pd from waste printed circuit boards (PCBs) by using two consecutive sulfuric acid leaching steps in the presence of H2O2 as oxidizing agents.
248 citations
TL;DR: In this article, a polyurethane (PU) nanocomposite with highly aligned graphene oxide (GO) is produced, and the agreement between the experiments and theoretical predictions for tensile modulus proves that the graphene sheets are indeed dispersed individually on the molecular scale and oriented in the polymer matrix to form a layered structure.
Abstract: Polyurethane (PU) nanocomposite films containing highly-aligned graphene sheets are produced. Aqueous dispersion of ultralarge-size graphene oxide (GO) is in situ reduced in waterborne polyurethane, resulting in fine dispersion and high degree of orientation of graphene sheets, especially at high graphene contents. The PU/reduced GO nanocomposites present remarkable 21- and 9-fold increases in tensile modulus and strength, respectively, with 3 wt.% graphene content. The agreement between the experiments and theoretical predictions for tensile modulus proves that the graphene sheets are indeed dispersed individually on the molecular scale and oriented in the polymer matrix to form a layered structure. The moisture permeability of the nanocomposites presents a systematic decrease with increasing graphene content, clearly indicating the impermeable graphene sheets acting as moisture barrier. The synergy arising from the very high aspect ratio and horizontal alignment of the graphene sheets is responsible for this finding.
TL;DR: The flow refueling location model was reformulated and a flexible mixed-integer linear programming model was presented, which was able to obtain an optimal solution much faster than the previous set cover version and could be solved in the maximum cover form in a reasonable time on the large-sized networks.
Abstract: Serious environmental and economic problems of using fossil fuels in transportation sections force managers to think of alternative fuels such as hydrogen, ethanol, biodiesel, natural gas, or electricity. Meanwhile, lack of fuel network infrastructures is a major problem, which needs to be investigated considering the number and optimal location of alternative fuel stations. In the literature, two different flow-based demand modeling concepts (the maximum cover and set cover) have been proposed for solving this problem. Because of the huge number of combinations of fuel stations for covering the flow of each path, the models are impractical for the real size problems. In this paper, the flow refueling location model was reformulated and a flexible mixed-integer linear programming model was presented, which was able to obtain an optimal solution much faster than the previous set cover version. The model also could be solved in the maximum cover form in a reasonable time on the large-sized networks.
TL;DR: In this article, the impact of climate change on freshwater availability in Africa at the subbasin level for the period of 2020-2040 was analyzed, and the results showed that for Africa as a whole, the mean total quantity of water resources is likely to increase.
TL;DR: This brand-new hybrid MCDM method is presented in this research as a powerful framework for decision making and can be useful as an appropriate framework for solving locating issues in other companies.
Abstract: Shopping malls are one of the glories of metropolises with their attractive shops and a wide variety people who are walking in order to purchase goods. Location of a shopping mall is one of the critical criteria, because it can influence the success of the project. In addition, selecting an appropriate location to establish a new shopping mall is a sophisticated, time consuming and risky decision. Commonly multi-factors should be considered in the decision making model. Thus, a comprehensive model should be considered for similar studies. Moreover, the foresight perspective can be necessary for the future competitiveness of the project. Decision makers need powerful tools for the process of the decision making, for this aim two Multiple Criteria Decision Making (MCDM) methods are applied in our model. Stepwise Weight Assessment Ratio Analysis (SWARA) is applied to decision making in order to prioritize and calculating the relative importance of the criteria. Then, Weighted Aggregated Sum Product Assessment (WASPAS) methodology is used to evaluate potential alternatives. Tehran is considered as a real example of this research and potential places for this mean considered in research. This brand-new hybrid MCDM method is presented in this research as a powerful framework is decision making. This framework can be useful as an appropriate framework for solving locating issues in other companies.
TL;DR: Two modified scaffolds added to the thermosensitive chitosan/glycerophosphate hydrogels to reinforce two hydrogel constructs which were used as scaffold for hyaline cartilage regeneration showed support of the chondrogenic phenotype for chondrocytes and could be employed for cartilage tissue engineering.
TL;DR: In this paper, surface modification of polyethersulfone (PES) ultrafiltration (UF) membranes using corona air plasma in order to reduce membrane fouling during separation of oil/water emulsions was investigated.
TL;DR: In this paper, the effect of polypropylene fiber (PPF) on both durability, and physical and mechanical characteristics of concrete for application in concrete sleepers was investigated, where compressive, splitting tensile, and three-point flexural strength, and VeeBee Consistometer (VB) tests were performed to indicate physical and physical characteristic of PPF reinforced concrete.
TL;DR: In this paper, the authors investigated the properties of high strength self compacting concrete (HSSCC) containing nano TiO 2 and industrial waste ash namely as fly ash (FA) for strength enhancement and durability-related characteristics along with rheological, thermal and microstructural properties.
TL;DR: In this article, an epoxy resin was modified by the addition of different nanosilica particles, which gave a very well-dispersed phase of nanoparticles and the responsible toughening mechanisms were recognized to be plastic deformation and plastic void growth.
TL;DR: In this paper, a multi-mode resource-constrained discrete time-cost-resource optimization (MRC-DTCRO) model is presented to select starting time and the execution mode of each activity satisfying all the project constraints.
TL;DR: This paper proposes a new solution method based on the combination of particle swarm optimization (PSO) algorithm with variable neighborhood search (VNS) to solve the problem of a single-model assembly line balancing problem (ALBP).
TL;DR: In this article, the effects of crosslinker concentration on the pepsin enzyme activity have been studied using variation of relative viscosity of the system and the results showed that with increasing crosslinkers agent concentration activity activity of enzyme reduces considerably and so cross-linker molar ratio to amine functional groups.
Abstract: 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 ...
TL;DR: In this paper, the corrosion inhibition function of two azole derivatives namely benzotriazole (BTR) and benzothiazoles (BNS) on stainless steel in 1M HCl was investigated using electrochemical techniques and SEM surface analysis as well.
TL;DR: In this paper, a transmission operator operating under different incentives decides about investment in transmission network while anticipating the outcome of a purely competitive electricity market where several rival generation firms complete with each other to determine operating level of their generators, amount of their sales and amount of investment in generation capacity.
Abstract: The main purpose of this paper is to develop methodologies for simultaneous generation and transmission expansion planning problem of power networks while investigating interactions between these two important sections. In the proposed methodologies, a transmission operator (TO) operating under different incentives decides about investment in transmission network while anticipating the outcome of a purely competitive electricity market where several rival generation firms complete with each other to determine operating level of their generators, amount of their sales and amount of their investment in generation capacity. The proposed methodologies rely on bi-level programming models whose upper level model represent the problem of investment in transmission by TO and the lower level problems represent market outcomes obtained from clearing the market. These bi-level models are reduced to mixed-integer linear and nonlinear programming using the duality theory and Karush-Kuhn-Tucker (KKT) optimality conditions. The results of the proposed models are analyzed and compared using two illustrative examples.
TL;DR: In this paper, the authors proposed a numerical method for the solution of the time-fractional nonlinear Schrodinger equation in one and two dimensions which appear in quantum mechanics.
Abstract: In this paper, we propose a numerical method for the solution of the time-fractional nonlinear Schrodinger equation in one and two dimensions which appear in quantum mechanics. In this method we first approximate the time fractional derivative of the mentioned equation by a scheme of order O ( τ 2 − α ) , 0 α 1 then we will use the Kansa approach to approximate the spatial derivatives. The meshless method has already proved successful in standard quantum mechanics as well as for several other engineering and physical problems. The aim of this paper is to show that the meshless method based on the radial basis functions and collocation approach is also suitable for the treatment of the fractional quantum mechanics. The results of numerical experiments are compared with analytical solution to confirm the accuracy and efficiency of the presented scheme.
TL;DR: In this article, the buckling of heated functionally graded material (FGM) annular plates on an elastic foundation is studied analytically, and the equilibrium equations of an annular-shaped plate are obtained based on the classical plate theory.
Abstract: The buckling of heated functionally graded material (FGM) annular plates on an elastic foundation is studied analytically. A conventional Pasternak-type elastic foundation is assumed to be in contact with plate during deformation, which acts in both compression and tension. The equilibrium equations of an annular-shaped plate are obtained based on the classical plate theory. Each thermo-mechanical property of the plate is assumed to be graded across the thickness direction of plate based on the power law form, while Poisson’s ratio is kept constant. Among all combinations of free, simply-supported, and clamped boundary conditions, existence of bifurcation buckling for various edge supports is examined and stability equations are obtained by means of the adjacent equilibrium criterion. An exact analytical solution is presented to calculate the thermal buckling load by obtaining the eigenvalues of the stability equation. Three types of thermal loading, namely; uniform temperature rise, transversely linear temperature distribution and heat conduction across the thickness type are studied. Effects of thickness to outer radii, inner to outer radii, power law index, elastic foundation coefficient, and thermal loading type on critical buckling temperature of FG plates are presented.
TL;DR: In this paper, the authors investigate the biosorption of mercury ions from aqueous solutions using Sugarcane Bagasse (SCB), and the pre-treatment of the biosorbent was determined by NaOH and HCl.
Abstract: The aim of this study was to investigate the biosorption of mercury ions from aqueous solutions using Sugarcane Bagasse (SCB). The pre-treatment of the biosorbent was determined by NaOH and HCl. The parameters affecting the biosorption such as solution pH, contact time and temperature were investigated. The pseudo-first order and pseudo-second order kinetic models were used to describe the kinetic data. The adsorption equilibrium data were analyzed by Freundlich and Langmuir's isotherm models. According to the results, both models were suitable for describing the biosorption equilibrium. The maximum adsorption capacity was found to be 35.71 mg/g. The kinetic was found to be the best-fit pseudo-second order equation. The maximum mercury removal of 97.584% at a pH of 4.0 was observed. Additional chemical treatments of the biosorbent had no significant effect on mercury biosorption.
TL;DR: In this paper, an interactive fuzzy satisfying method based on Hybrid Modified Shuffled Frog Leaping Algorithm is proposed to solve the problem of the multi-objective optimal placement and sizing of DG (distributed generation) units in the distribution network.
TL;DR: Gum tragacanth (GT) is one of the most widely used natural gums which has found applications in many areas because of its attractive features such as biodegradability, nontoxic nature, natural availability, higher resistance to microbial attacks and long shelf-life properties.
TL;DR: In this paper, a logical approach to prevent pressure increase at near well-bore is pore throat physical plugging, and nano-particles have been used for this intent.