AMIRKABIR
Year:2006 | Volume:17 | Issue:64-A|Papers Count:9

One of the main research problems in multiage systems is designing effective and efficient negotiation mechanisms to help the agents to negotiate with each other in order to come to a mutually acceptable division/exchange of scare resources and manage their task interdependencies. For constructing these mechanisms, the developer should determine and specify all the necessary elements, concepts and parameters that are important for negotiation and then based on this specification build the negotiation constructs for performing negotiation in the multiage system. In this paper, we present a conceptual framework for modeling and developing automated negotiation systems. This framework represents and specifies all the needed concepts and entities that are crucial for developing a negotiation system and existing relationships among these concepts. In addition to the role of this framework in development of a computational negotiation system, it is used in modeling human negotiations scenarios for analysis these types of negotiations and simulating them with multiage systems. The work reported in this paper is the first unified framework that considers all the needed elements for modeling and developing negotiation systems and existing influence relationships among them.

In this paper, we give two new optimal parallel algorithms for matrix multiplication which are designed to run on a Fibonacci hypercube structure. At first, we present a broadcast algorithm on Fibonacci hypercube with O (n) time complexity. We use this broadcast algorithm and algorithms presented by Gunnels, Lin, Morrow and Geijn on a mesh structure, in order to present two optimal parallel matrix multiplication algorithms on a Fibonacci hypercube structure. We show these algorithms are cost-optimal. The performance of the algorithm has been tested on a simulative parallel system.

This paper describes simulation of the cardiovascular system using a complex electronic circuit. In this study, we have taken a slightly different approach to the modeling of the system and tried to advance existing electrical models by increasing more segments and parameters. The model consists of 42 segments representing the arterial system which are active. Anatomical and physiological data for circuit parameters have been extracted from medical articles and textbooks. The frequency of heart is 1 Hz and the system operates in steady state condition. Each artery is modeled by one capacitor, resistor and inductor. The left and right ventricles are modeled using AC power suppliers and diodes. The results of the simulation including pressure and volume graphs exhibit operation of the cardiovascular system under normal condition. The results of the simulation have been compared with the relevant experimental observation and are in good agreement with them.

Power electronics converters, because of their nonlinear dynamics and switching operation, are the main source of harmonic injection to the utility, which results in poor power factor. Boost rectifier due to its simple topology and good performance in power factor correction is the most used scheme. Design of a single input fuzzy controller for high power factor boost converter is described in this article. The computer simulation of the proposed fuzzy controller held in MATLAB-SIMULINK on a 500W boost rectifier and closed loop performance of the Converter in respect to Line and Load Regulations are evaluated. Experimental measurements of closed loop performance validate the proposed scheme.

Availability of reliable data is an essential part of any scientific investigation. Many of data records contain inaccurate information, not only due to measurement errors but also for ambiguity of the measuring concept. This occurs especially in human science fields, where instead of softly varying signals sharp signals are observed. Since the conventional smoothing methods do not make sense when applying to such fields, fuzzy smoothing methods are preferred. This paper proposes a novel smoothing procedure based on a single fuzzy rule for smoothing out sharpness of data curves, and analyzes the method focusing on power spectrums. The proposed method smoothes out sharp points found in the signal by sharing their value with the neighboring points. A survey of both time domain and frequency domain performances shows superiority of the proposed method compared to the other classical smoothing methods cited in the literature. Some applications are also introduced to highlight better the merit of the proposed method.

The effect of cellular phone handset dimensions on radiation pattern, impedance and resonance frequency is investigated. The hand-set body is modeled by an appropriate three-dimensional wire-grid structure with a λ/4 monopole antenna as its radiating source. The governing electric field integral equation (EFIE) is solved in the time domain, using the method of moments (MoM). The validity of the model is demonstrated by comparing the wide-band results of the antenna input impedance with those available in the literature. It is shown that at current operating frequencies, a regular handset dimensions has minimal effect on the antenna radiation pattern and impedance, and hence modeling of a handset by its antenna (monopole) is sufficient.

This paper proposes a novel approach to determine optimal location of static synchronous compensator in power system for improving voltage profile, minimizing power system total loss and maximizing system loadability with and without considering generators Mvar limit. An accurate and efficient model for static synchronous compensator in steady state studies is presented and implemented in advanced load flow program with embedded flexible alternating current transmission systems. A simultaneous Genetic Algorithm and Continuation Power Flow was used to determine maximum number of static synchronous compensator's, and steady state stability margin, based on closing to point of voltage collapse. As an important result in this paper we obtain a maximum number of static synchronous compensator beyond which the power system performances such as loadability can not be increased, and hence, increasing loading level leads to static voltage collapse phenomena. A case study and simulation are done on IEEE57 Bus Test System. In Genetic Algorithm optimization procedure the voltage profile flattening, maximizing system loadability and minimizing total loss of power system are used as power system performance Index.

This paper presents the study of shunt active filters which inject compensating current into the network with time delays. It is shown that the performance of the filter is influenced by the variations of the nonlinear load harmonic contents. Measurement results are obtained from several industrial and domestic loads. The samples of the load currents are analyzed by fast Fourier transform. The delay in the compensating current injection is simulated by Matlab software and harmonics of the source current after compensation are compared with the standard permitted harmonic levels (IEEE 519). It is shown that the compensation is not completed for nonlinear loads and, in some cases, does not satisfy the standard requirements. Thus, it is concluded that before selecting a control strategy for the active filter (even, before selecting an active filter for compensation purpose), behavior of the nonlinear load must be studied and inspected from harmonic content variations point of view.

In this paper, a modified analytic approach to the calculation of magnetic field in a slot-less, two-rotor axial-flux permanent magnet machine is presented. The analytic-modeling is based on calculation of scalar and vector magnetic potentials which are produced by the armature windings and the magnets. The magnet and the armature windings are modeled by a magnetization vector and a two-dimensional current sheet, respectively. The effects of the armature reaction and the harmonics of field are also considered. The simulation of magnetic field by the analytic model is compared with that of a two-dimensional finite element analysis. The proposed analytic model predicts the magnetic field within 5% compared to the finite element method. Ultimately, by using the analytic model in a genetic algorithm method, which is a known method in optimization, an optimum design of an axial-flux permanent magnet machine is presented.