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Total 398 records

    Wide-band VHF nulling by five elements spiral array antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 446-448 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Mousavi, M ; Emadi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE  

    Using neural network for solving of on-line economic dispatch problem

    , Article CIMCA 2006: International Conference on Computational Intelligence for Modelling, Control and Automation, Jointly with IAWTIC 2006: International Conference on Intelligent Agents Web Technologies and International Commerce, Sydney, NSW, 28 November 2006 through 1 December 2006 ; 2006 , Pages 87- ; 0769527310 (ISBN); 9780769527314 (ISBN) Mohammadi, A ; Varahram, M. H ; Sharif University of Technology
    IEEE Computer Society  2006
    Abstract
    In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and X iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield neural network is more efficient and the time required for convergence is considerably smaller compared to classical methods. © 2006 IEEE  

    A new approach for long low autocorrelation binary sequence problem using genetic algorithm

    , Article 2006 CIE International Conference on Radar, ICR 2006, Shanghai, 16 October 2006 through 19 October 2006 ; 2006 ; 0780395824 (ISBN); 9780780395824 (ISBN) Nasrabadi, M. A ; Bastani, M. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    Distinguishing reflected waveforms from two separated targets which are very close to each other is an important challenge in radar signal processing. Pulse compression is a technique used for accounting for this problem. There are several methods for compressing such as phase coding waveform and the goal of this paper is finding these optimal codes. In this paper, by combining several contents, a new optimum method based on Genetic Algorithm is suggested. This method has low computational operation and its speed is faster than the other ordinary algorithms. This method is belonged to local or partial search methods and has following advantages: 1. It uses branch-and-bound strategy; 2. It's... 

    3D numerical analysis of velocity profiles of PD, EO and combined PD-EO flows through microchannels

    , Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 209-214 ; 0791847608 (ISBN); 9780791847602 (ISBN) Yazdi, S ; Monazami, R ; Salehi, M. A ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    In this paper, a three-dimensional numerical model is developed to analyze flow characteristics of pressure driven, electroosmotic and combined pressure driven-electroosmotic flows through micro-channels. The governing system of equations consists of the electric-field and flow-field equations. The solution procedure involves three steps. The net charge distribution on the cross section of the microchannel is computed by solving two-dimensional Poisson-Boltzmann equation using the finite element method. Then, using the computed fluid's charge distribution, the magnitude of the resulting body force due to interaction of an external electric field with the charged fluid is calculated along the... 

    A novel method on singularity analysis in parallel manipulators

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Pendar, H ; Mahnama, M ; Zohoor, H ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a... 

    An architecture for a context-aware service broker in ubiquitous computing environments

    , Article IEEE International Conference on Computer Systems and Applications, 2006, Sharjah, 8 March 2006 through 8 March 2006 ; Volume 2006 , 2006 , Pages 1097-1100 ; 1424402123 (ISBN); 9781424402120 (ISBN) Ganji Saffar, Y ; Abolhassani, H ; Jalili, R ; Sharif University of Technology
    IEEE Computer Society  2006
    Abstract
    In ubiquitous computing environments, many devices and agents interoperate with each other and use services provided by others. But the problem is that there may be requests that can not be fulfilled by available services. A solution to this problem is to use service brokers that compose existing services and create new value added services that can fulfill the clients' requests. In this paper, we present an architecture for a context-aware service broker that not only is able to compose services for responding to new requests, but also considers the context of its clients for providing customized and personalized outputs and behaviors. © 2006 IEEE  

    Tight-binding analysis of coupled dielectric waveguide structures

    , Article Fiber and Integrated Optics ; Volume 25, Issue 1 , 2006 , Pages 11-27 ; 01468030 (ISSN) Khalili Amiri, P ; Ranjbaran, M ; Mehrany, K ; Rashidian, B ; Fathololoumi, S ; Sharif University of Technology
    2006
    Abstract
    Based on the mathematical similarity of the Schrödinger and Helmholtz equations, the tight-binding method has been employed for solving optical waveguide problems, in a manner similar to the methods commonly used in solid-state physics. The solutions (TE mode electric field waveforms and propagation constants) of a single dielectric slab waveguide are considered to be known, and tight-binding is used to compute the propagation constants of several multi-waveguide structures. Analytical solutions are derived for linear and circular arrays of adjacent waveguides. The problem of two similar adjacent waveguides is treated in detail for two cases of similar and different propagation constants of... 

    A new continuous action-set learning automaton for function optimization

    , Article Journal of the Franklin Institute ; Volume 343, Issue 1 , 2006 , Pages 27-47 ; 00160032 (ISSN) Beigy, H ; Meybodi, M. R ; Sharif University of Technology
    2006
    Abstract
    In this paper, we study an adaptive random search method based on continuous action-set learning automaton for solving stochastic optimization problems in which only the noise-corrupted value of function at any chosen point in the parameter space is available. We first introduce a new continuous action-set learning automaton (CALA) and study its convergence properties. Then we give an algorithm for optimizing an unknown function. © 2005 The Franklin Institute. Published by Elsevier Ltd. All rights reserved  

    Time decomposition in batch process integration

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 45, Issue 1 , 2006 , Pages 14-21 ; 02552701 (ISSN) Pourali, O ; Amidpour, M ; Rashtchian, D ; Sharif University of Technology
    2006
    Abstract
    In this work, the concept of problem table decomposition for the thermal integration of continuous processes is extended to batch processes. The approach is based on a combination of time intervals using pinch analysis tools and energy storage system design. Pinch analysis improves energy efficiency for batch processes and it may increase the productivity of a revised plant. Operational and economical constraints may cause some limitation; therefore, in this approach process constraints and flexibilities are carefully considered by defining individual time and heat intervals. The approach is demonstrated on a case study. © 2005 Elsevier B.V. All rights reserved  

    Label updating to avoid point-shaped obstacles in fixed model

    , Article Theoretical Computer Science ; Volume 369, Issue 1-3 , 2006 , Pages 197-210 ; 03043975 (ISSN) Rostamabadi, F ; Ghodsi, M ; Sharif University of Technology
    2006
    Abstract
    In this paper, we present efficient algorithms for updating the labeling of a set of n points after the presence of a random obstacle that appears on the map repeatedly. We update the labeling so that the given obstacle does not appear in any of the labels, the new labeling is valid, and the labels are as large as possible (called the optimal labeling). Each point is assumed to have an axis-parallel, square-shaped label of unit size, attached exclusively to that point in the middle of one of its edges. We consider two models: (1) the 2PM model, where each label is attached to its feature only on the middle of one of its horizontal edges, and (2) the r4PM model, where each label is attached... 

    The single period problem with price discount and probabilistic initial inventory

    , Article 2006 IIE Annual Conference and Exposition, Orlando, FL, 20 May 2006 through 24 May 2006 ; 2006 Haji, R ; Haji, M ; Sharif University of Technology
    2006
    Abstract
    In this paper we consider a newsvendor problem in which the suppliers offer quantity discounts. We assume that the initial inventory at the beginning of the period is a random variable. This assumption, among other applications, may apply to the case where the decision about the order quantity must be made at a time long before the start of the period and the available inventory may decrease due to several factors, such as deterioration, consumption, etc. up to the start of the period. In this paper, we obtain the optimal order quantity that maximizes the total profit for this model  

    Development of a consistent slip boundary condition at the inlet of microchannels

    , Article 44th AIAA Aerospace Sciences Meeting 2006, Reno, NV, 9 January 2006 through 12 January 2006 ; Volume 10 , 2006 , Pages 7087-7096 ; 1563478072 (ISBN); 9781563478079 (ISBN) Darbandi, M ; Vakilipour, S ; Schneider, G. E ; Sharif University of Technology
    2006
    Abstract
    The fast progress in Microelectromechanical systems has drawn the attention of many numerical workers to provide sufficient numerical tools to analyze the micro flows accurately. Besides many ambiguities behind the slip boundary condition research which are normally encountered in the vicinity of the solid walls (and are necessary to provide the suitable bridge between the macro and micro behaviors), there are serious uncertainties at the inlet of channels where the microflow enters into the conduit. Indeed, the macro inlet flow have been long investigated by the past workers; however, there is little effort to clarify the issue in micro inlet flow cases. In this research, we utilize the... 

    On validity assurance of dynamic reconfiguration for component-based programs

    , Article Electronic Notes in Theoretical Computer Science ; Volume 159, Issue 1 , 2006 , Pages 227-239 ; 15710661 (ISSN) Niamanesh, M ; Fekrazad Nobakht, N ; Jalili, R ; Heydarian Dehkordi, F ; Sharif University of Technology
    2006
    Abstract
    Growing the need for long-life and high-available programs, dynamic reconfiguration is going to be an important research issue. Dynamic reconfiguration enables the software systems to change at runtime to decrease their down-time in case of any updating, upgrading or in any changes. Any invalid reconfiguration at runtime may lead programs into invalid states. In this paper, we investigate on validity of dynamic reconfiguration for component-based programs and propose validity conditions for it. We show that the problem of validity assurance in general is undecidable and there is no general-purpose algorithm to verify dynamic reconfiguration validity. To have a computable algorithm for... 

    A multi-objective lead time control problem in multistage assembly systems using an interactive method

    , Article Applied Mathematics and Computation ; Volume 176, Issue 2 , 2006 , Pages 609-620 ; 00963003 (ISSN) Azaron, A ; Kianfar, F ; Sharif University of Technology
    2006
    Abstract
    In this paper, we develop a multi-objective model to optimally control the lead time of a multistage assembly system, using an interactive method. The multistage assembly system is modelled as an open queueing network, whose service stations represent manufacturing or assembly operations. It is assumed that the product order arrives according to a Poisson process. In each service station, there is either one or infinite number of servers (machines) with exponentially distributed processing time, in which the service rate (capacity) is controllable. The transport times between the service stations are independent random variables with generalized Erlang distributions. The problem is... 

    Stochastic optimization using continuous action-set learning automata

    , Article Scientia Iranica ; Volume 12, Issue 1 , 2005 , Pages 14-25 ; 10263098 (ISSN) Beigy, H ; Meybodi, M. R ; Sharif University of Technology
    Sharif University of Technology  2005
    Abstract
    In this paper, an adaptive random search method, based on continuous action-set learning automata, is studied for solving stochastic optimization problems in which only the noisecorrupted value of a function at any chosen point in the parameter space is available. First, a new continuous action-set learning automaton is introduced and its convergence properties are studied. Then, applications of this new continuous action-set learning automata to the minimization of a penalized Shubert function and pattern classification are presented. © Sharif University of Technology  

    Elastic-plastic modeling of the hardening materials based on an Eulerian strain tensor and a proper corotational rate

    , Article 2005 ASME Pressure Vessels and Piping Conference, PVP2005, Denver, CO, 17 July 2005 through 21 July 2005 ; Volume 2 , 2005 , Pages 201-206 ; 0277027X (ISSN) Naghdabadi, R ; Ghavam, K ; Sharif University of Technology
    2005
    Abstract
    In this paper a model for analyzing elastic-plastic kinematic hardening materials is introduced, based on the additive decomposition of the corotational rate of an Eulerian strain tensor In this model, the elastic constitutive equation as well as the flow rule and the hardening equation is expressed in terms of the elastic and plastic parts of the corotational rate of the mentioned Eulerian strain tensor and its conjugate stress tensor. In the flow rule, the plastic part of the corotational rate of the Eulerian strain tensor is related to the difference of the deviatoric part of the conjugate stress and the back stress tensors. A proportionality factor is used in this flow rule which must be... 

    An ACO algorithm for graph coloring problem

    , Article 2005 ICSC Congress on Computational Intelligence Methods and Applications, Istanbul, 15 December 2005 through 17 December 2005 ; Volume 2005 , 2005 ; 1424400201 (ISBN); 9781424400201 (ISBN) Salari, E ; Eshghi, K ; Sharif University of Technology
    2005
    Abstract
    Ant Colony Optimization (ACO) is a well-known metaheuristic in which a colony of artificial ants cooperate in exploring good solutions to a combinatorial optimization problem. In this paper, an ACO algorithm is presented for the graph coloring problem. This ACO algorithm conforms to Max-Min Ant System structure and exploits a local search heuristic to improve its performance. Experimental results on DIMACS test instances show improvements over existing ACO algorithms of the graph coloring problem  

    An improved model for optimal under voltage load shedding: Particle swarm approach

    , Article 2006 IEEE Power India Conference, New Delhi, 10 April 2006 through 12 April 2006 ; Volume 2005 , 2005 , Pages 723-728 ; 0780395255 (ISBN); 9780780395251 (ISBN) Amraee, T ; Mozafari, B ; Ranjbar, A. M ; Sharif University of Technology
    2005
    Abstract
    Under voltage load shedding is one of the most important tools to avoid voltage instability. In this paper an optimal load shedding algorithm is developed. This approach is based on the concept of the static voltage stability margin and its sensitivity value at the maximum loading point or the collapse point. The traditional load shedding objective is extended to incorporate both technical and economical effects of load shedding. The voltage stability criterion is modeled as a soft constraint into load shedding scheme. The proposed methodology is implemented over the IEEE14 bus system and solved using a mathematical (GAMS/CONOPT) and two heuristic (P.S.O & GA) methods. © 2006 IEEE  

    Effects of inlet position and baffle configuration on the hydraulic performance of primary settling tanks

    , Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 261 FED , 2005 , Pages 613-618 ; 08888116 (ISSN); 0791842193 (ISBN); 9780791842195 (ISBN) Firoozabadi, B ; Tamayol, A ; Ahmadi, G ; ASME Fluids Engineering Division ; Sharif University of Technology
    2005
    Abstract
    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  

    Rough terrain rovers dynamics analysis and optimization

    , Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 7 B , 2005 , Pages 903-909 ; 0791847446 (ISBN) Tavakoli Nia, H ; Alemohammad, S. H ; Bagheri, S ; Khiabani, R. H ; Meghdari, A ; Sharif University of Technology
    2005
    Abstract
    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...