Showing papers by "Iran University of Science and Technology published in 2003"
TL;DR: In this paper, a FilmTec FT30 membrane as a reverse osmosis membrane and a synthetic emulsion using an Iranian crude oil have been employed to investigate the mechanism of flux decline.
182 citations
TL;DR: In this article, a four-leaf steel spring used in the rear suspension system of light vehicles is analyzed using ANSYS V5.4 software and the finite element results showing stresses and deflections verified the existing analytical and experimental solutions.
175 citations
TL;DR: A Taylor method is developed to find an approximate solution for high-order nonlinear Volterra-Fredholm integro-differential equation.
169 citations
TL;DR: In this paper, the size/topology optimization of trusses is performed using a genetic algorithm (GA), the force method and some concepts of graph theory, which makes the generation of a suitable initial population well-matched with critical paths for the transformation of internal forces feasible.
Abstract: In this article size/topology optimization of trusses is performed using a genetic algorithm (GA), the force method and some concepts of graph theory. One of the main difficulties with optimization with a GA is that the parameters involved are not completely known and the number of operations needed is often quite high. Application of some concepts of the force method, together with theory of graphs, make the generation of a suitable initial population well-matched with critical paths for the transformation of internal forces feasible. In the process of optimization generated topologically unstable trusses are identified without any matrix manipulation and highly penalized. Identifying a suitable range for the cross-section of each member for the ground structure in the list of profiles, the length of the substrings representing the cross-sectional design variables are reduced. Using a contraction algorithm, the length of the strings is further reduced and a GA is performed in a smaller domain of design space. The above process is accompanied by efficient methods for selection, and by using a suitable penalty function in order to reduce the number of numerical operations and to increase the speed of the optimization toward a global optimum. The efficiency of the present method is illustrated using some examples, and compared to those of previous studies. Copyright © 2003 John Wiley & Sons, Ltd.
103 citations
TL;DR: In this paper, a very small experimental electrodialysis cell has been designed and built to study the effects of different operating conditions such as flow rate, voltage and concentration, on treatment of seawater with electrodes have been studied.
85 citations
TL;DR: In this paper, the effect of zirconia addition at various loading ratios on the performance of 10 wt% Co/SiO2 catalysts for the so-called reaction of Fischer-Tropsch synthesis has been studied.
79 citations
TL;DR: In this article, the authors proposed a tapered slot antenna (TSA) profile and geometry, which is achieved through its modeling by a stepline terminated in free space intrinsic impedance, and the impedance matching of the TSA input impedance to the generator impedance is achieved by minimizing an error criterion constructed as the magnitude squared of the difference between the generator and input impedance over the desired bandwidth.
Abstract: The optimum design of the tapered slot antenna (TSA) profile and geometry is achieved through its modeling by a stepline terminated in free space intrinsic impedance. The impedance matching of the TSA input impedance (obtained by the transmission matrix properties) to the generator impedance is achieved by minimizing an error criterion constructed as the magnitude squared of the difference between the generator and input impedances over the desired bandwidth. The attenuation constant of the stepline is computed by the broadside radiation of TSA (which is an endfire antenna) and the longitudinal power flow. The spectral domain immitance approach is used to compute the broadside radiation, by first determining the electric field components in the slot by the Galerkin's method and then obtaining the equivalent magnetic surface current densities. The power flow in the endfire direction of TSA may be computed by the Poynting's vector in the substrate. The attenuation constant is calculated for various values of slot width. Finally, the minimization procedure gives the slotline widths and lengths.
78 citations
TL;DR: A combination of Legendre and Block-Pulse functions on the interval [0,1], to solve the linear integral equation of the second kind, and converts the integral equation, to a system of linear equations.
77 citations
TL;DR: In this paper, the authors used the continuous Legendre wavelets on the interval [0, 1] in the manner of M. Razzaghi and S. Yousefi, to solve the linear second kind integral equations.
Abstract: Uses the continuous Legendre wavelets on the interval [0,1) in the manner of M. Razzaghi and S. Yousefi, to solve the linear second kind integral equations. We use quadrature formula for the calculation of inner products of any functions, which are required in the approximation for the integral equations. Then, we reduced the integral equation to the solution of linear algebraic equations.
64 citations
TL;DR: This paper proposes a novel QoS-based multicast routing algorithm based on the genetic algorithms (GA), and the connectivity matrix of edges is used for genotype representation.
Abstract: Computing the bandwidth-delay-constrained least-cost multicast routing tree is an NP-complete problem. In this paper, we propose a novel QoS-based multicast routing algorithm based on the genetic algorithms (GA). In the proposed algorithm, the connectivity matrix of edges is used for genotype representation. Some novel heuristics are also proposed for mutation, crossover, and creation of random individuals. We evaluate the performance and efficiency of the proposed GA-based algorithm in comparison with other existing heuristic and GA-based algorithms by the result of simulation. The proposed algorithm has overcome all of the previous algorithms in the literature.
64 citations
TL;DR: In this article, two maps have been prepared to indicate the earthquake hazard of Tehran and its vicinity in the form of iso-acceleration contour lines, which display the probabilistic estimate of peak ground acceleration (PGA) over bedrock for the return periods of 475 and 950 years.
Abstract: This paper presents a probabilistic seismic hazard assessment of Tehran, the capital of Iran. Two maps have been prepared to indicate the earthquake hazard of Tehran and its vicinity in the form of iso-acceleration contour lines. They display the probabilistic estimate of Peak Ground Acceleration (PGA) over bedrock for the return periods of 475 and 950 years. Tehran is a densely populated metropolitan in which more than 10 million people live. Many destructive earthquakes happened in Iran in the last centuries. It comes from historical references that at least 6 times, Tehran has been destroyed by catastrophic earthquakes. The oldest one happened in the 4th century BC. A collected catalogue, containing both historical and instrumental events and covering the period from the 4th century BC to 1999 is then used. Seismic sources are modelled and recurrence relationship is established. For this purpose the method proposed by Kijko [2000] was employed considering uncertainty in magnitude and incomplete earthqu...
TL;DR: The simulation results clearly demonstrate that the value of maximum allowable load on a given trajectory directly depends on the additional constraint functions which apply to resolve the motion redundancy.
TL;DR: In this article, the effect of calcination temperature on flux and separation factor of kaolin modules that prepared by electrophoresis as a support of zeolite membranes was investigated.
TL;DR: In this article, a methodology based on solving a large-scale nonlinear programming problem is presented for the optimal design and operation of pumping stations, which refers to the selection of pump type, capacity, and number of units as well as scheduling the operation of irrigation pumps that results in minimum design and operating cost for a given set of demand curves.
Abstract: A methodology based on solving a large-scale nonlinear programming problem is presented for the optimal design and operation of pumping stations. Optimum design and operation refers to the selection of pump type, capacity, and number of units as well as scheduling the operation of irrigation pumps that results in minimum design and operating cost for a given set of demand curves. The design criteria for such pumping stations are based fundamentally on some important and critical parameters, such as pump capacity, number of units, types of pumps, and civil works. The optimization process consists of three main steps: ~1! determination of minimum yearly consumed energy; ~2! minimization of the total cost for all sets of pumping stations; and ~3! selection of the least-cost set among the feasible sets of pumping stations, recognizing a combination of the cited criteria. The computational analysis is based upon one major objective function and a computer program, which is developed to solve the generated equations. Application of the model to the Farabi Agricultural and Industrial Project, Iran, shows considerable savings, about 25% in total annual cost of the pumping station.
TL;DR: Soft computing based tools including fuzzy inference systems, artificial neural networks, and genetic algorithms are used here to tackle the minimization of variance of benefits from reservoir operation to demonstrate the usefulness of GA optimized parameters of a T-norm fuzzy operator for variance reduction.
TL;DR: This poster presents a probabilistic model of the response of the immune system to various types of deposits, including “plague” and “sickness”.
TL;DR: In this paper, the effect of different hydrodynamic factors on fouling of polyamide reverse osmosis membrane was investigated and an optimization of the parameters was found to be necessary and optimum values of them and pH were determined.
TL;DR: In this paper, an AR (1) model is proposed to characterize the quality characteristic of interest in a continuous process where autocorrelated observations are generated over time, and the performance of the proposed procedure is evaluated through the use of a numerical example.
Abstract: This paper presents an artificial neural network model for detecting and classifying three types of non-random disturbances referred to as level shift, additive outlier and innovational outlier which are common in autocorrelated processes. To the best of our knowledge, this is the first time that a neural network has been considered for simultaneous detection and classification of such non-random disturbances. An AR (1) model is considered to characterize the quality characteristic of interest in a continuous process where autocorrelated observations are generated over time. The performance of the proposed procedure is evaluated through the use of a numerical example. Preliminary results indicate that the procedure can be used effectively to detect and classify unusual shocks in autocorrelated processes. Copyright © 2003 John Wiley & Sons, Ltd.
TL;DR: In this paper, the method developed for eigensolution for matrices of special structures in Kaveh and Sayarinejad (Commun. Numer. Meth. Engng 2003; 19: 125-136) is extended to a more general special form known as Form III.
Abstract: The method developed for eigensolution for matrices of special structures in Kaveh and Sayarinejad (Commun. Numer. Meth. Engng 2003; 19: 125–136) is extended to a more general special form known as Form III. Efficient methods are presented for evaluating the eigenvalues and eigenvectors of these matrices. Copyright © 2004 John Wiley & Sons, Ltd.
23 Jun 2003
TL;DR: In this article, an adaptive Neuro-Fuzzy Inference System (ANFIS) is proposed for the control of a 2WD electric vehicle with two motor drive motors.
Abstract: This paper, investigates the traction control of an electric vehicle (EV) that is equipped with two motor drives. A new yaw moment control scheme via an Adaptive Neuro-Fuzzy Inference System (ANFIS) is proposed. The ANFIS is an attractive compromise between the adaptability of a neural network and interpretability of a fuzzy inference system. In a 2WD EV, because of independent torque control of the motors, simultaneous torque control of several drive motors is the main objective. Due to nonlinear vehicle model and parameters variations, an intelligent controller on base ANFIS, using emotional learning is presented and is used for tracking the reference yaw rate. The designed controller calculates the reference torque of motor drives. Mechanical differential is eliminated and its operation is done electronically. Because of large magnitude of control effort, assistance brake control also is applied to limit the control effort value. Various simulations with a full nonlinear and uncertain 7-DOF vehicle model show that the proposed controller enhances the vehicle performance and stability.
TL;DR: In this paper, a simple method for obtaining actual unloading behavior of high strength steels is proposed based on this method loading-unloading stress-strain curves for NiCrMoV125 steel is obtained.
Abstract: A simple method for obtaining actual unloading behavior of high strength steels is proposed. Based on this method loading-unloading stress-strain curves for NiCrMoV125 steel is obtained. It is shown that the actual unloading behavior tends to be nonlinear as soon as unloading occurs. Using the variable material properties (VMP) method, residual stresses induced by autofrettage process of a tube made of this type of steel are calculated. Significance of employing actual unloading behavior is demonstrated by comparing the results with ideal models such as isotropic hardening and bilinear models. There is at least 30% over estimation of compressive residual stress at the bore if ideal models are used. Also, the process of material removal is simulated by using commercial FEM soft-ware to evaluate the recommended scenarios of removal on redistribution of residual stresses at the bore. Resulting stresses after machining are also calculated by the VMP method using actual behavior. It is shown that the final residual stress field differs significantly if actual unloading behavior is used.
01 Jan 2003
TL;DR: A general axisymmetric method for elastic-plastic analysis was previously proposed by Jahed and Dubey [ASME J Pressure Vessels Technol 119 (1997) 264] as discussed by the authors.
TL;DR: In this article, a boundary element method based on the Laplace transform technique is developed for transient coupled thermoelasticity problems with relaxation times in a two-dimensional finite domain.
Abstract: A boundary element method based on the Laplace transform technique is developed for transient coupled thermoelasticity problems with relaxation times in a two-dimensional finite domain. The dynamic thermoelastic model of Lord and Shulman (LS) is selected to show how mechanical and thermal energy conversion takes place in a coupled field. The Laplace transform method is applied to the time domain and the resulting equations in the transformed field are discretized using the boundary element method. The nodal dimensionless temperature and displacements in the transformed domain are inverted to obtain the actual physical quantities, using the numerical inversion of the Laplace transform method. The creation and propagation of elastic and thermoelastic waves in a finite domain and their effects on each other are investigated for the first time in this paper. Different relaxation times are chosen to show briefly the events that take place in temperature, displacement and stress fields considering the LS theory...
TL;DR: A multi-sensor navigation system is introduced in this paper to address the shortcomings of the existing train positioning systems and utilizes the Global Positioning System (GPS), Doppler radar, gyroscopes, tachometers, digital maps and balises.
Abstract: Onboard train positioning (navigation) plays a vital and safety critical role in advanced Automatic Train Control (ATC) and Automatic Train Protection (ATP) systems. Such onboard systems are also essential for moving block signalling and control systems for railways. The application of multi-sensor fusion algorithms to the vehicle navigation field has made it possible to create inexpensive and accurate positioning systems, which will satisfy the railways' requirements. The state estimation methods involved in Kalman filtering have proved to be some of the most effective techniques in multi-sensor data fusion. A multi-sensor navigation system is introduced in this paper to address the shortcomings of the existing train positioning systems. The proposed system utilizes the Global Positioning System (GPS), Doppler radar, gyroscopes, tachometers, digital maps and balises. In order to provide fault detection and isolation capabilities, a hierarchical structure is proposed for the multi-sensor integration system in which different combinations of navigation systems would function. Several data integration nodes, including DR/GPS, DR/Balise, and DR/GPS/Balise, are studied in more detail and their performances are evaluated.
10 Nov 2003
TL;DR: A new approach to control of HVAC system is presented, which is a hybrid of fuzzy logic and PID controller and simulation results show this method has the better control performance than PID controller.
Abstract: Heating, Ventilating and Air Conditioning (HVAC) plant is a multivariable, nonlinear and non minimum phase system, which control of this plant, is very difficult. This paper presents a new approach to control of HVAC system. The proposed method is a hybrid of fuzzy logic and PID controller. Simulation results show that this control strategy is very robust, flexible and alternative performance. To evaluate the usefulness of the proposed method, we compare the response of this method with PID controller. The simulation results show that our method has the better control performance than PID controller.
TL;DR: In this article, the effect of melt cleanliness on the hydrogen content of the melt has been studied, and it has been found that the melting cleanliness has a significant effect on the reduction of hydrogen content.
Abstract: The effect of Sr-modification on hydrogen content of commercial 319 aluminium alloy melts has been quantified, by using HYSCAN instrument at 685°C and 735°C. In addition, the effect of melt cleanliness on the hydrogen content of the melt has been studied. It has been found that the melt cleanliness has a significant effect on the reduction of hydrogen content of the melt. The hydrogen contents of Sr-modified cleaned melts were significantly lower (30-45%) than uncleaned melts (melts containing surface oxide layers) at both temperatures. Sr-modification had no marked effect on the hydrogen content of the melt at both temperatures, when measurements were carried out in a cleaned melt. Hydrogen content of strontium modified, uncleaned melts has been increased, particularly at 685°C. In order to study the melt hydrogen absorption susceptibility in Sr-modified alloys, the formation of different hydrogen containing compounds such as hydrides and hydroxide of modifiers and other alloying elements in Al-Si melts has been evaluated thermodynamically. It has been found that there is no hydrogen containing compound, which can form in aluminium melts, and if these compounds are introduced into the melt they will dissociated to release hydrogen.
TL;DR: In this article, a two-parameter formulation is used to study how the T-stress influences the isochromatic fringe patterns around the tip of a mode I crack.
TL;DR: In this paper, efficient neural networks are trained for the analysis, design and prediction of the displacements of domes using the Backpropagation and Radial Basis Functions neural networks.
Abstract: In this paper, efficient neural networks are trained for the analysis, design and prediction of the displacements of domes using the Backpropagation and Radial Basis Functions neural networks. The performance of these networks is compared when applied to domes. Programs are developed for accurate distribution of applied forces and wind load to the nodal points of domes. Training and testing pairs are prepared by ANSYS software.
16 Sep 2003