@article { author = {Afjei, E. and Arbab, M. H. and Rashed-Mohassel, Jalil}, title = {Significant Error Propagation in the Finite Difference Solution of Non-Linear Magnetostatic Problems Utilizing Boundary Condition of the Third Kind}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {319-330}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This paper poses two magnetostatic problems in cylindrical coordinates with different permeabilities for each region. In the first problem the boundary condition of the second kind is used while in the second one, the boundary condition of the third kind is utilized. These problems are solved using the finite element and finite difference methods. In second problem, the results of the finite difference method show low magnetic vector potential as well as the magnetic field density when compared to the finite element results and in the linear case, to the analytical solution. This paper investigates the reason behind the low magnetostatic field computation in cylindrical coordinates using the finite difference method when boundary condition of the third kind is used. It then, presents a technique to overcome the problem of low magnetic field calculation using the finite difference method. The results obtained by the new technique are in close agreement with the finite element method as well as the analytical solution. Finally, it analyzes the possible source of error in modeling magnetostatic boundary conditions in finite difference formulation of vector Poisson or Laplace’s equation in cylindrical coordinates.}, keywords = {Nonlinear Magnetic Field,finite difference,Finite Element,Electromagnetics}, url = {https://www.ije.ir/article_71467.html}, eprint = {https://www.ije.ir/article_71467_0cbf292226d420b6228deddea1d5cc46.pdf} } @article { author = {Aghabozorgi, M. R. and Doost Hoseini, A. M.}, title = {Blind Separation of Jointly Stationary Correlated Sources}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {331-346}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The separation of unobserved sources from mixed observed data is a fundamental signal processing problem. Most of the proposed techniques for solving this problem rely on independence or at least uncorrelation assumption for source signals. This paper introduces a technique for cases that source signals are correlated with each other. The method uses Wold decomposition principle for extracting desired and proper information from the predictable part of the observed data, and exploits approaches based on second-order statistics to estimate the mixing matrix and source signals. Simulation results are provided to illustrate the effectiveness of the method.}, keywords = {Blind Source Separation,Wold Decomposition,Second,Order Statistics}, url = {https://www.ije.ir/article_71469.html}, eprint = {https://www.ije.ir/article_71469_6d0d2c72ab75b86a1c37caeec4944af5.pdf} } @article { author = {Menhaj, M.B. and Kazemi, M.H. and Karrari, M.}, title = {A New Class of Decentralized Interaction Estimators for Load Frequency Control in Multi-Area Power Systems}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {347-356}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Load Frequency Control (LFC) has received considerable attention during last decades. This paper proposes a new method for designing decentralized interaction estimators for interconnected large-scale systems and utilizes it to multi-area power systems. For each local area, a local estimator is designed to estimate the interactions of this area using only the local output measurements. In fact, these interactions are the information of other area. A new scheme is developed to construct an approximate model for the interaction dynamics and design a local estimator. The designed local estimator exploits the model of each area and its actual inputs and outputs to produce a good estimation of unknown states and interactions. It is shown that in the proposed method the errors of estimation are globally ultimately bounded with respect to a specific bound. Our scheme is used to design decentralized estimator for a three-area power system to illustrate the effectiveness of the proposed method.}, keywords = {Multi Area Power System,Load Frequency Control,Large Scale Systems,Estimation}, url = {https://www.ije.ir/article_71472.html}, eprint = {https://www.ije.ir/article_71472_d7f783096621077673cf3dc0b6de1bd0.pdf} } @article { author = {Rostamy, Z.}, title = {Determination of Resonance Frequency of Dominant and Higher Order Modes in Thin and Thick Circular Microstrip Patch Antennas with Superstrate by MWM (RESEARCH NOTE)}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {359-366}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {An accurate model named as the Modified Wolff Model (MWM) is presented as an efficient CAD tool for determination of resonant frequency of the dominant and higher order modes under the multi-layer condition in thin and thick circular microstrip patch antennas. The effects of dielectric cover on the resonant frequency obtained from MWM have been compared against the result of theoretical method of Spectral Domain Analysis (SDA). The accuracy of calculated resonant frequency by the MWM for dominant mode is about 0.5% and the average error for higher order modes is about 0.88%. Sensitiveness of higher order modes and also uncertainty effect on the resonant frequency are calculated by the MWM.}, keywords = {Modified Wolff Model,MWM,Microstrip Antenna,Microstrip Patch Antenna,Superstrate,Dynamic Dielectric Constant,Transverse Transmission Line,TTL}, url = {https://www.ije.ir/article_71474.html}, eprint = {https://www.ije.ir/article_71474_410a23409b9392c744daf870b8fd4cd0.pdf} } @article { author = {Vaez Zadeh, S. and Zamanian, M.}, title = {Permanent Magnet DC Motor Sliding Mode Control System}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {367-376}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper a sliding mode controller (SMC) is designed for a permanent magnet direct current (PMDC) motor to enhance the motor performance in the presence of unwanted uncertainties. Both the electrical and mechanical signals are used as the inputs to the SMC. The complete motor control system is simulated on a personal computer with different design parameters and desirable system performance is obtained. The experimental implementation of the motor control system by a floating point DSP is also presented. The test results confirm the simulation results and validate the proposed motor control system for high performance applications.}, keywords = {Permanent Magnet,DC Motor,Sliding Mode Controller,SMC}, url = {https://www.ije.ir/article_71476.html}, eprint = {https://www.ije.ir/article_71476_5be1166c90b17e2daf811dcb4fbdaadc.pdf} } @article { author = {Ghimire, R. P.}, title = {M1, M2, ..., Mk/G1, G2,..., Gk/l/N Queue with Buffer Division and Push-Out Schemes for ATM Networks (RESEARCH NOTE)}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {377-382}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper, loss probabilities and steady state probabilities of data packets for an asynchronous transfer mode (ATM) network are investigated under the buffer division and push-out schemes. Data packets are classified in classes k which arrive in Poisson fashion to the service facility and are served with general service rate under buffer division scheme, finite buffer space N is divided in to N1, N2, …, Nk such that N= N1+ N2 +…+ Nk. Under push-out scheme if upon arrival of class 1 packet to the system finds that there are less than N1-1 class 1 packets waiting for service and there is no unoccupied buffer space then one of the packets of other classes is pushed out. The pushed out packet is lost. The packets are served under general service discipline.}, keywords = {Steady State Probability,ATM,Finite Buffer,Push,Out Scheme}, url = {https://www.ije.ir/article_71478.html}, eprint = {https://www.ije.ir/article_71478_ef0557569e4914dbe5a3277127147810.pdf} } @article { author = {Khoshkish, H. and Seyed- Hosseini, S.M.}, title = {Mathematical Programming Approach To Allocate Local Or National Resources For Bridge Maintenance Rehabilitation & Replacement Planning (RESEARCH NOTE)}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {383-392}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Today’s, the transportation facilities such as terminals, street, bridge, etc, represent the major investment in highway network. Every year tremendous resources should be invested to maintain these facilities. Among them, the Bridge Management System (B.M.S.) has been necessitated by large imbalance between extensive bridge repair and maintenance needs and limited available budget. So the main purpose of this research study is to develop an optimization methodology to allocate the limited resource among the most bridge maintenance demanded projects. The reduction of user cost or increased the user benefit can be considered as the main objective function of the developed Dynamic Programming Optimization Model. The results of the implementing of optimization model shows a tremendous cost savings, and as a result, more demanded bridge requiring the maintenance can be selected.}, keywords = {Optimization. Resource Allocation,Bridge Management}, url = {https://www.ije.ir/article_71479.html}, eprint = {https://www.ije.ir/article_71479_3fc9f02687d257d6ae0a29dc8fcf1d0f.pdf} } @article { author = {Wang, Xungai and He, W.}, title = {Modeling the Tensile Behavior of Fibers with Geometrical and Structural Irregularities}, journal = {International Journal of Engineering}, volume = {16}, number = {4}, pages = {393-412}, year = {2003}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Virtually all fibers exhibit some dimensional and structural irregularities. These include the conventional textile fibers, the high-performance brittle fibers and even the newly developed nano-fibers. In recent years, we have systematically examined the effect of fiber dimensional irregularities on the mechanical behavior of the irregular fibers. This paper extends our research to include the combined effect of dimensional and structural irregularities, using the finite element method (FEM). The dimensional irregularities are represented by sine waves with a 30 % magnitude of diameter variation while the structural irregularities are represented by longitudinal and horizontal cavities distributed within the fiber structure. The results indicate that fiber geometrical or dimensional variations have a marked influence on the tensile properties of the fiber. It affects not only the values of the breaking load and extension, but also the shape of the load-extension curves. The fiber structural irregularities simulated in this study appear to have little effect on the shape of the load-extension curves.}, keywords = {Fiber,irregularity,Tensile Behavior,Modeling,Structural Variations}, url = {https://www.ije.ir/article_71481.html}, eprint = {https://www.ije.ir/article_71481_442b90d79baa94474605f2560f1e39bd.pdf} }