Showing papers by "Amirkabir University of Technology published in 2015"
TL;DR: The paper mainly covers the fundamental algorithmic frameworks such as decomposition and non-decomposition methods, and their current applications in the field of large-scale global optimization.
382 citations
TL;DR: In this paper, surface modification of graphene oxide (GO) has been performed by grafting of polyisocyanate (PI) resin, and the PI functionalized GO sheets were incorporated into the polyurethane (PU) matrix.
297 citations
TL;DR: In this article, a review on the traditional techniques and recent advances in the separation of phenol from its contaminated streams is carried out, and the most commonly used methods classified based on the phenol concentrations (high, medium, and low), and also, their advantages and disadvantages that should be considered in the design of industrial wastewater treatment systems are discussed.
Abstract: The toxicity of phenol even at low concentrations in industrial effluents is high enough to meet its needs for separation. In this paper, a review will be carried out on the traditional techniques and recent advances in the separation of phenol from its contaminated streams. The most commonly used methods classified based on the phenol concentrations (high, medium, and low), and also, their advantages and disadvantages that should be considered in the design of industrial wastewater treatment systems will be discussed. Finally, the best methods will be suggested for each concentration range at the influent and, of course, that is allowable in the final effluent. The survey results recommended that biodegradation, chemical, electrochemical, and photocatalytic oxidation, solid phase extraction, ozonation, reverse osmosis/nanofiltration, and wet air oxidation are useful methods in low phenol concentrations, whereas liquid–liquid extraction, pervaporation, membrane-based solvent extraction, adsorption...
281 citations
TL;DR: A novel meta-heuristic algorithm called Grey Wolf Optimizer (GWO), which is inspired by living and haunting behavior of wolves, is proposed and it is shown that the GWO outperforms the other employed well-known meta- heuristic algorithms.
217 citations
TL;DR: In this paper, the authors present several types of rare chaotic flows with hidden attractors, including those with no equilibrium, rare flows with a line of equilibrium points, and rare flow with a stable equilibrium.
Abstract: Hidden attractors represent a new interesting topic in the chaos literature. These attractors have a basin of attraction that does not intersect with small neighborhoods of any equilibrium points. Oscillations in dynamical systems can be easily localized numerically if initial conditions from its open neighborhood lead to a long-time oscillation. This paper reviews several types of new rare chaotic flows with hidden attractors. These flows are divided into to three main groups: rare flows with no equilibrium, rare flows with a line of equilibrium points, and rare flows with a stable equilibrium. In addition we describe a novel system containing hidden attractors.
213 citations
TL;DR: In this paper, a multi-depot location-routing model considering network failure, multiple uses of vehicles, and standard relief time is proposed to determine the locations of local depots and routing for last mile distribution after an earthquake.
Abstract: We propose a multi-depot location-routing model considering network failure, multiple uses of vehicles, and standard relief time. The model determines the locations of local depots and routing for last mile distribution after an earthquake. The model is extended to a two-stage stochastic program with random travel time to ascertain the locations of distribution centers. Small instances have been solved to optimality in GAMS. A variable neighborhood search algorithm is devised to solve the deterministic model. Computational results of our case study show that the unsatisfied demands can be significantly reduced at the cost of higher number of local depots and vehicles.
199 citations
TL;DR: Results of cell behavior study indicated that the heat stabilized nanofibrous mat CS/PVA 30/70 was able to support the attachment and proliferation of the fibroblast cells.
Abstract: Electrospinning process has been widely used to produce nanofibers from polymer blends. Poly(vinyl alcohol) (PVA) and chitosan (CS) have numerous biomedical applications such as wound healing and tissue engineering. Nanofibers of CS/PVA have been prepared by many works, however, a complete physicochemical and mechanical characterization as well as cell behavior has not been reported. In this study, PVA and CS/PVA blend solutions in acetic acid 70% with different volume ratios (30/70, 50/50, and 70/30) were electrospun in constant electrospinning process parameters. The structure and morphology of nanofibrous mats were characterized by SEM, FTIR, and XRD methods. The best nanofibrous mat was achieved from the CS/PVA 30/70 blend solution regarding the electrospinning throughput. The dynamic mechanical thermal analysis (DMTA) of PVA and CS/PVA 30/70 nanofibrous mats were measured which were not considered in the previous studies. DMTA results in accordance to the DSC analysis approved the partial compatibility between the two polymers, while a single glass transition temperature was not observed for the blend. The tensile strength of PVA and CS/PVA nanofibers were also reported. Results of cell behavior study indicated that the heat stabilized nanofibrous mat CS/PVA 30/70 was able to support the attachment and proliferation of the fibroblast cells.
176 citations
TL;DR: In this article, a novel electrospun chitosan/graphene oxide (GO) nanofibrous adsorbent was successfully developed by an electrospinning process.
Abstract: A novel electrospun chitosan/graphene oxide (GO) nanofibrous adsorbent was successfully developed by an electrospinning process. The adsorption behaviors of Cu2+, Pb2+ and Cr6+ metal ions from aqueous solutions using chitosan/GO nanofibers were investigated. The composite nanofibers were characterized by FTIR and SEM and TEM analysis. Kinetic and equilibrium studies showed that the experimental data of Cu2+, Pb2+ and Cr6+ were best described by double-exponential kinetic and Redlich–Peterson isotherm models. The maximum monolayer adsorption capacity of Pb2+, Cu2+and Cr6+ metal ions using chitosan/GO nanofibers was found to be 461.3, 423.8 and 310.4 mg g−1 at an equilibrium time of 30 min and temperature of 45 °C. Evaluation of the thermodynamic parameters (ΔG° 0 and ΔS° > 0) showed that the nature of the metal ions sorption by chitosan/GO nanofibers was endothermic and spontaneous. The reusability studies indicated that the chitosan/GO nanofibers could be reused frequently without almost any significant loss in adsorption performance. This study provides a promising chitosan/GO nanofibrous adsorbent with an efficient adsorption property for heavy metal ions removal.
176 citations
TL;DR: In this article, a review and comparison of several low voltage ride through (LVRT) capability enhancement methods for wind turbines is performed, and several modified controller based methods have been proposed for LVRT capability enhancement.
Abstract: Wind energy is rapidly growing in recent years. Among different types of wind turbines, due to several advantages, permanent magnet synchronous generator (PMSG) is attractive concept. Since the penetration level of wind power in the grid is increased, therefore, wind power can influence to the grid and vice versa. Some of the important problems in the grid are fault condition and voltage sags. These conditions may affect the operation of wind turbine. In order to enhance low voltage ride through (LVRT) capability in PMSG-based wind turbines, various approaches have been proposed in the last years. In this paper, the review and comparison of several LVRT capability enhancement methods is performed. The two foremost types of LVRT capability enhancement methods are external devices based methods and modified controller based methods. The main objectives of this paper are to introduce performances of different LVRT capability enhancement methods and use of some LVRT capability enhancement methods in PMSG based wind turbine which are applied in other kind of wind power generators. The external devices based methods can be effective but some of these methods are of significant cost. According to the literatures, modified controller based methods can reduce the LVRT capability enhancement cost. Several modified controller based methods have been proposed for LVRT capability enhancement. To compare the mentioned methods, several simulations are performed in MATLAB software. From the review of simulation results, series connection of FACTS devices and modification of back-to-back converter controllers are the highly efficient LVRT capability enhancement approaches.
175 citations
TL;DR: In this paper, composite electrospun nanofibers mats, as a nano- generator, were fabricated through one-step electrospinning method, where the structure of fibers is composed of Poly(vinylidene fluoride), PVDF, as the matrix, and Zinc ox- ide (ZnO) nanoparticles; the nanocomposite were produced using electro-spinning technique in order to have the benefit of piezoelectric properties and non-brittle behavior of ZnO and PVDF for the application in wearable electronic devices
Abstract: Composite electrospun nanofibers mats, as a nano- generator, were fabricated through one-step electrospinning method. The structure of fibers is composed of Poly(vinylidene fluoride), PVDF, as the matrix, and Zinc ox- ide (ZnO) nanoparticles; the nanocomposite were produced using electrospinning technique in order to have the benefit of piezoelectric properties and non-brittle behavior of ZnO and PVDF for the application in wearable electronic devices. Characteristics of these structures were evaluated by using X- ray diffraction (XRD), Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Elec- tron Microscopy (SEM). Impedance and the electrical con- ductivity of the fabricated composites were also evaluated by Keithley instruments. Electrical response of samples was measured using an impedance analyzer made in Aims Lab (http://aims.aut.ac.ir) at room temperature. Results showed that incorporating the ZnO nanoparticles into the PVDF nanofibers improved the piezoelectric properties of samples compared to PVDF samples. The electrical output of composite samples was improved as high as 1.1 V compared with 0.351 V for the pure PVDF samples. These results imply promising applications, as an enhanced- efficiency energy-scavenging interface, for various wearable self-powered electrical devices and systems.
174 citations
TL;DR: A novel system with an exponential nonlinear term, which can exhibit hidden attractors, is proposed in this work, and although new system possesses no equilibrium points, it displays rich dynamical behaviors, like chaos.
Abstract: Studying systems with hidden attractors is new attractive research direction because of its practical and threoretical importance. A novel system with an exponential nonlinear term, which can exhibit hidden attractors, is proposed in this work. Although new system possesses no equilibrium points, it displays rich dynamical behaviors, like chaos. By calculating Lyapunov exponents and bifurcation diagram, the dynamical behaviors of such system are discovered. Moreover, two important features of a chaotic system, the possibility of synchronization and the feasibility of the theoretical model, are also presented by introducing an adaptive synchronization scheme and designing a digital hardware platform-based emulator.
19 Jan 2015
TL;DR: In this paper, the progress of research on sustainable tourism and to outline and identify the key disciplines, journals, articles and authors is studied through a wide, in-depth, and structured examination of published scholarly papers.
Abstract: This paper aims to study the progress of research on Sustainable Tourism and to outline and identify the key disciplines, journals, articles and authors. This is carried out through a wide, in-depth, and structured examination of published scholarly papers. In recent decades, sustainable tourism has been one of the most significant subjects among academics and practitioners. In this paper, a classification scheme and a comprehensive literature review are presented in order to clarify, categorise, and interpret the current research on sustainable tourism definitions and applications. The classification scheme for this review contains 132 scholarly papers from 47 journals since the year 1993 up to 2013 categorised into 14 application areas. The five major topics are Paradigm, Sustainable Tourism Development, Market research and Economic, Policy-making, and Infrastructure. The scholarly papers are also sorted by (we suggest using the exact order used later in the paper) (1) year of publication; (2) publicati...
TL;DR: In this paper, a linear buckling analysis is presented for nanocomposite conical shells reinforced with single walled carbon nanotubes (SWCNTs) subjected to lateral pressure.
TL;DR: In this paper, the effect of boron incorporation into H-ZSM-5 nanocatalyst on the stability, product distribution and hydrocarbons selectivity in methanol to olefins (MTO) reaction was investigated.
TL;DR: The cell viability results indicated that DOX loaded PEO/CS/GO/DOX nanofibrous scaffold could be used as an alternative source of DOX compared with free DOX to avoid the side effects of freeDOX.
TL;DR: In this paper, the results of linear polarization and electrochemical impedance spectroscopy proved the effectiveness of Aloe Vera extract as concentration increased, and different aspects like transient analysis, noise resistant and characteristic charge were characterized.
01 Apr 2015
TL;DR: The results show that BNNMAS significantly performs accurate and reliable, so it can be considered as a suitable tool for predicting stock price specially in a long term periods.
Abstract: Creating an intelligent system that can accurately predict stock price in a robust way has always been a subject of great interest for many investors and financial analysts. Predicting future trends of financial markets is more remarkable these days especially after the recent global financial crisis. So traders who access to a powerful engine for extracting helpful information throw raw data can meet the success. In this paper we propose a new intelligent model in a multi-agent framework called bat-neural network multi-agent system (BNNMAS) to predict stock price. The model performs in a four layer multi-agent framework to predict eight years of DAX stock price in quarterly periods. The capability of BNNMAS is evaluated by applying both on fundamental and technical DAX stock price data and comparing the outcomes with the results of other methods such as genetic algorithm neural network (GANN) and some standard models like generalized regression neural network (GRNN), etc. The model tested for predicting DAX stock price a period of time that global financial crisis was faced to economics. The results show that BNNMAS significantly performs accurate and reliable, so it can be considered as a suitable tool for predicting stock price specially in a long term periods.
TL;DR: In this paper, a polyisocyanate-functionalized graphene oxide (PI-GO) was synthesized at various functionalization reaction times of 24, 48 and 72 h. The results obtained from X-ray diffraction analysis also revealed that the interlayer distance of the GO increased after modification.
TL;DR: In this article, the authors investigated linear thermal buckling of a composite conical shell made from a polymeric matrix and reinforced with carbon nanotube fibres, under the assumption of first order shear deformation shell theory, Donnell kinematic assumptions and von Karman type of geometrical nonlinearity.
TL;DR: In this article, the aminosilane grafting reaction was considered using 3-aminopropyl(diethoxy)methylsilane (APDEMS) as the silane coupling agent.
TL;DR: In this paper, the authors evaluate physical and mechanical properties of pervious concrete including density, strength, porosity, and permeability, and the relationship between properties dependent on coarse aggregate size.
TL;DR: In this article, a method based on dual modality densitometry using artificial neural network (ANN) was presented to first identify the flow regime and then predict the void fraction in two-phase flows.
TL;DR: In this article, mixed mode I/II fracture toughness of five modified asphalt mixtures containing poly phosphoric acid (PPA), Styrene Butadiene Styrene (SBS), anti-stripping agent, crumb rubber (CR) and F-T paraffin wax (Sasobit) was investigated experimentally using a large number of cracked semi-circular bend (SCB) specimens.
TL;DR: Based on a new lexicographic ordering on triangular fuzzy numbers, a novel algorithm is proposed to solve the FFLP problem by converting it to its equivalent a multi-objective linear programming (MOLP) problem and then it is solved by the lexicography method.
TL;DR: A high order difference scheme and Galerkin spectral technique is applied for the numerical solution of multi-term time fractional partial differential equations and it is proved the unconditional stability of the compact procedure by coefficient matrix property is proved.
TL;DR: In this article, the authors review the recent developments in the flame retardant nanocomposites of natural and synthetic textile polymers and survey the application of different nanoparticles or a combination of nanoparticles and conventional flame retardants.
Abstract: Along with the rising trend of stringent fire safety regulations, demands for reduction in the fire hazard caused by highly combustible materials such as textiles and polymers have become a matter of significant importance Therefore, numerous attempts have been made to improve the flame retardation of textiles for a variety of applications The present paper aims to review the recent developments in the flame retardant nanocomposites of natural and synthetic textile polymers We survey the application of different nanoparticles or a combination of nanoparticles and conventional flame retardants Furthermore, a comprehensive discussion on mechanisms and optimized conditions of flame retardation and thermal stability is presented
TL;DR: In this paper, the water uptakes of nanocomposite films were measured at 25°C in three acidic, neutral and alkaline media, and the greatest swellings were observed in the acidic pH but the least water uptake was found in the alkaline medium.
TL;DR: In this paper, an attempt is made to obtain a closed form solution for both natural frequency and buckling load of nonlocal FG beams resting on nonlinear elastic foundation, where the effect of nonlocality is introduced into the Euler-Bernoulli beam theory to obtain the nonlinear governing partial differential equation.
TL;DR: This technical note considers the consensus problem in high-order multiagent systems under undirected networks by employing agents relative positions and proposes a protocol under which the agents reach agreement on a common position while their higher-order states converge to zero.
Abstract: This technical note considers the consensus problem in high-order multiagent systems under undirected networks. By employing agents relative positions, sufficient conditions are proposed under which the agents reach agreement on a common position while their higher-order states converge to zero. Despite introduced consensus protocols in the literature for high-order systems, by using only relative positions, it is possible to achieve consensus on the average of any shared quantities of the agents. By setting the shared quantities properly, the obtained protocol is employed to achieve consensus on the average of the initial positions of the agents. Numerical examples confirm the accuracy of the proposed consensus protocol.
TL;DR: Results indicated desirable bioactivity and hemostasis of the scaffolds with the capability of encapsulation and controlled release of the protein which can be served as skin tissue engineering scaffolds and wound dressings.
Abstract: The novel strategies of skin regenerative treatment are aimed at the development of biologically responsive scaffolds capable of delivering multiple bioactive agents and cells to the target tissues. In this study, nanofibers of poly(lactic-co-glycolic acid) (PLGA) and gelatin were electrospun and the effect of parameters viz polymer concentration, acid concentration, flow rate and voltage on the morphology of the fibers were investigated. PLGA nanofibers encapsulating epidermal growth factor were also prepared through emulsion electrospinning. The core-sheath structure of the nanofibers was verified by transmission electron microscopy. The hemostatic attributes and the biocompatibility of the scaffolds for human fibroblast cell were scrutinized. Furthermore, gene expression of collagen type I and type III by the cells on the scaffolds was quantified using real-time reverse transcriptase polymerase chain reaction. The results indicated desirable bioactivity and hemostasis of the scaffolds with the capability of encapsulation and controlled release of the protein which can be served as skin tissue engineering scaffolds and wound dressings.