Sharif Digital Repository

Analytic Hierarchy Process (AHP) is a multiple criteria decision making approach which is widely used in different engineering domains. The hierarchical structure of AHP makes it a very suitable approach for behavior design in artificial life-based games. But the details of an AHP is always designed by a series of interviews with experts of the domain, and this is not possible for problems in which an expert does not exist such as computer simulations. In such cases, the behavioral engineering of agents is a very complicated task because the designer may not be able to see all different aspects of agents' life. To overcome this problem, this paper has used an artificial life algorithm to... 

This paper proposes two enhanced cross-diamond-hexagonal search algorithms to solve the motion-estimation problem in video coding. These algorithms differ from each other by their second step search only, and both of them employ cross-shaped pattern in first step. Proposed method is an improvement over CDHS, eliminating some checking points of CDHS algorithm. Experimental results show that the proposed methods perform faster than the diamond search (DS) and CDHS, whereas similar quality is preserved. © 2005 IEEE  

This paper analyzes the problem of transient-error recovery of several protecting techniques used in fault-tolerant cache memories. In this paper, reliability and mean-time-to-failure (MTTF) equations for several protecting techniques are derived and estimated. The results of the considered techniques are compared with those of cache memories without redundancies and with only parity codes in both tag and data arrays of caches. Depending on the error rate under which a cache memory will operate, and the size of the cache memory, one of the analyzed cases could be used. If the transient-error rate is very small or the size of cache memory is relatively small, then a protected with only single... 

A new analytical method for finding the general solution of the nth-order linear differential equation with variable coefficients is given based on generalizing the idea of differential transfer matrix method already proposed for solving the second order Helmholtz equation. Our generalization has two aspects. First, the given formulation copes with the nth-order linear differential equations, rather than the special case of second order wave equations. Second, the proposed approach is generalized in several different ways each yielding different types of differential transfer matrices with correspondingly different numerical accuracies. The presented methods can be applied to problems such... 

In this paper, a new software is introduced that is developed to give the most appropriate solution for the component selection and design of a hybrid electric bus. There are several simulation programs that can simulate behavior of a hybrid electric bus, but most of them are not able to suggest the best design and the best choice of the components. Customer requirements are dissimilar and there are several different parameters that they may need. Cost, pollution, driving cycle, battery type, DC link voltage, weight, volume, fuel consumption, and acceleration are some parameters that vary from one customer to the other. The stated software that is developed and presented by this paper will... 

This paper presents a new approach for optimal operation of distribution networks with regard to Distributed Generators (DGs). The objective function in this problem includes cost of active and reactive electrical energy generated by DGs, electrical energy markets and capacitors. Also, this paper presents both application and comparison of the metaheuristic techniques such as the Genetic Algorithm (GA), differential evolution, Ant Colony Optimization (ACO), Particle Swarm Optimization (PSO), tabu search, to optimal operation of distribution networks. These methods are tested on two examples distribution network containing an IEEE 34 distribution test feeders and a practical distribution... 

Optical character recognition of cursive scripts present a number of challenging problems in both segmentation and recognition processes and this attracts many researches in the field of machine learning. This paper presents a novel approach based on a combination of MLP and SVM to design a trainable OCR for Persian/Arabic cursive documents. The implementation results on a comprehensive database show a high degree of accuracy which meets the requirements of commercial use. © Springer-Verlag Berlin Heidelberg 2005  

Symmetry reduction is a promising technique for combatting state space explosion in model checking. The problem of finding the equivalence classes, i.e., the so-called orbits, of states under symmetry is a difficult problem known to be as hard as graph isomorphism. In this paper, we show how we can automatically find the orbits in an actor-based model, called Rebeca, without enforcing any restriction on the modeler. The proposed algorithm solves the orbit problem for Rebeca models in polynomial time. As a result, the simple actor-based Rebeca language can be utilized efficiently for modeling and verification of systems, without involving the modeler with the details of the verification... 

The ODYSSEY design methodology has been recently introduced as a viable solution to the increasing design complexity problem in the ASICs. It is an object-oriented design methodology which models a system in terms of its constituting objects and their corresponding method calls. Some of these methods are implemented in hardware; others are simply executed by a general purpose processor. One fundamental element of this methodology is a network on chip that implements method invocation for hardware-based method calls. However this network is prone to faults, thus errors on it may result into system failure. In this paper an architectural fault-tolerance enhancement to the ODYSSEY design... 

Circulation regions always exist in the settling tanks. These regions reduce the tank's performance and decrease effective volume of the tank. Recirculation zones would also result in short-circuiting and high flow mixing problems. Inlet position would also have effect on these, too. Using good baffle configuration may increase performance of settling tanks. One method for comparison of different tanks with each others is to use FTC. In this paper, by using FTC the effects of inlet position and baffle configuration on the hydraulic performance of primary settling tanks are studied. The best position of baffle is also determined. Copyright © 2005 by ASME  

In this paper a new approach to dynamics optimization of rough terrain rovers is introduced. Since rover wheels traction has a significant role in rover mobility, optimization is based on the minimization of traction at rover wheel-ground interfaces. The method of optimization chosen is Genetic Algorithm (GA) which is a directed random search technique along with the usual optimization based on directional derivatives. GA is a suitable and efficient method of optimization for nonlinear problems. The procedure is applied on a specific rough terrain rover called CEDRA-I Shrimp Rover. Dynamical equations are obtained using Kane's method. Finally, the results are verified by modeling of the... 

This paper presents a recursive approach for solving kinematic and dynamic problem in snake-like robots using Kane's equations. An n-link model with n-nonholonomic constraints is used as the snake robot model in our analysis. The proposed algorithm which is used to derive kinematic and dynamic equations recursively enhances the computational efficiency of our analysis. Using this method we can determine the number of additions and multiplications as a function of n. The proposed method is compared with the Lagrange and Newton-Euler's method in three different aspects: Number of operations, CPU time and error in the computational procedures. Copyright © 2005 by ASME  

In this paper, we consider the problem of computing the visibility of a query point inside polygons with holes. The goal is to perform this computation efficiently per query with more cost in the preprocessing phase. Our algorithm is based on solutions in [13] and [2] proposed for simple polygons. In our solution, the preprocessing is done in time O(n3 log(n)) to construct a data structure of size O(n3). It is then possible to report the visibility polygon of any query point q in time O((1 + h′) log n + |V(q)|), in which n and h are the number of the vertices and holes of the polygon respectively, |V(q)| is the size of the visibility polygon of q, and h′ is an output and preprocessing... 

Transferring image sequences requires a very high bit-rate on the communication channels. However, if we want to use telephone lines as the means of communication, the bandwidth constraint problems limit the bit-rates, and the optimal exploitation of link and resource are required. The statistical analysis of video signals indicates that there is a strong correlation both between successive picture frames as well as within the picture elements themselves. Theoretically, decorrelation of these signals can lead to bandwidth compression without significantly affecting image resolution. In this research, in order to reduce bit-rate, we propose a new algorithm using Bilinear Transformation... 

Persian (Farsi) script is totally cursive and each character is written in several different forms depending on its former and later characters in the word. These complexities make automatic handwriting recognition of Persian a very hard problem and there are few contributions trying to work it out. This paper presents a novel practical approach to online recognition of Persian handwriting which is based on representation of inputs and patterns with very simple visual features and comparison of these simple terms. This recognition approach is tested over a set of Persian words and the results have been quite acceptable when the possible words where unknown and they were almost all correct in... 

Recently, fuzzy variable linear programming problems have attracted some interests. We introduce the dual of fuzzy variable linear programming problem, and then deduce some important duality results. COPYRIGHT © ENFORMATIKA  

In this paper, we show that the stability can not be achieved with current stabilizing MPC methods for some unstable processes. Hence we present a new method for stabilizing these processes. The main idea is to use a new time varying weighted cost function for traditional GPC. This stabilizes the closed loop system without adding soft or hard constraint in optimization problem. By studying different examples it is shown that using the proposed method, the closed-loop stability of unstable nonminimum phase process is achieved. COPYRIGHT © ENFORMATIKA  

In this article a new technique for the dynamic response of structures is investigated. This applied procedure can predict the approximate seismic performance of the structures and it is fast, inexpensive and results are reasonably acceptable. In fact, this novel method logically combines two different techniques, 'incremental dynamic analysis (IDA)' and 'modal pushover analysis (MPA)', presented by other researchers. This method will take advantage of both methodical ideas such as equivalent single degree of freedom of multi-degree structures and the implementation of different scaled level of an earthquake record to the provided equivalent SDF structure. Using this procedure, simple... 

An effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the wave and boundary layer characteristics such as bed shear stress. A mixing-length theory is used for turbulence modeling. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2005 by ASME  

The vibration of a simply supported beam with rotary springs at either ends is studied. The governing equations of motion are investigated considering the nonlinear effect of stretching. These equations are made non-dimensional and then solved to first order approximation using the two methods of the multiple scales and the mode summation. The first five natural frequencies of the beam for few pairs of the boundary condition parameters are evaluated. A multilayer feed-forward back-propagation artificial neural network is trained using these natural frequencies. The artificial neural network used in this study shows high degree of accuracy for the natural frequency of the beam with general...