فهرست مطالب

  • Volume:7 Issue: 3, 2013
  • تاریخ انتشار: 1392/08/02
  • تعداد عناوین: 8
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  • Zahra Mohammadian, Mostafa Shahabinejad, Siamak Talebi Page 1
    Multi-input multi-output-orthogonal frequency-division multiplexing (MIMO-OFDM) is known as a proper solution for wideband wireless communication. Numerous space-frequency block codes (SFBCs) and space-time-frequency block codes (STFBCs) have been proposed so far for implementing MIMO-OFDM systems. In this paper, a new full-diversity STFBC is proposed for two transmit antennas, which could benefit from the maximum coding advantage when delay and power profiles (DPPs) of the channel are available at the transmitter. Furthermore, simulation results confirm that the proposed STFBC outperforms other recently proposed STFBCs with the same order of the receiver complexity.
  • Shahriar Abasi, Farid Karbalaei Page 8
    Drawing PV curve path by Continuation Power Flow (CPF) runs is the commonly used method for voltage stability studies. Although time-consuming, it can carefully determine the distance between the current operating point and the collapse point. To drive the power flow equations, the bus admittance matrix and the electrical characteristics of the generators and loads are needed. The presented method in this paper is based on this fact that, PV-curves are approximately quadratic functions and become exactly quadratic in close neighborhood of the collapse point. So, to draw the PV curve path at a load bus, the calculation of all points is not needed. Instead, using some points, the other points can be determined by the quadratic approximation of the PV curve path. The needed points can be determined using the local measurements of the voltage magnitude and the active power at the corresponding load bus. Now, having static load characteristics, the Saddle-Node Bifurcation (SNB) point can be predicted. The simulations performed on the IEEE 30-bus test system show that the voltage collapse point can be determined using only local measurements (the thing is usually claimed in model-based methods).
  • Farhad Samaie, Mohammad Hasan Moradi Page 14
    In this paper a hybrid and practical method is provided to allocation and capacity determination combined heat and power (CHP) generator at a bus. This method consists of two stages. Firstly, Through the bus thermal coefficient, the suitable buses will be found for CHP installation. This coefficient indicates the possibility of heat selling around each buses and will be calculated using the fuzzy method. Then, for the appropriate buses, considering the obtained heat capacity and electrical power to heat ratio of CHPs on the market, several CHPs is recommended. Secondly, On the one hand, the amount of loss reduction and improve the voltage due to proposed CHPs installation using nodal pricing method as financial benefit of distribution company to be derived, and on the other hand, the financial benefit for investors by selling CHP heat output is determined Finally, using the Game Theory and consider the distribution company and investors as players, the suitable location and capacity for CHP installation based on the Game strategy set is obtained. The proposed method, is implemented to a sample distribution feeder in the Hamadan city and the results are shown.
  • Mohammad Mehdi Fakharian, Pejman Rezaei, Ali Shahzadi Page 25
    An integration technique based on use of Monte Carlo Integration (MCI) is proposed for the analysis of electromagnetic radiation from apertures. The technique that can be applied to the calculation of aperture antenna radiation patterns is the equivalence principle followed by physical optics, which can then be used to compute far-field antenna radiation patterns. However, this technique is often mathematically complex, because it requires integration over the closed surface. This paper presents an extremely simple formulation for calculating the far-fields from some types of aperture radiators by using MCI technique. The accuracy and the effectiveness of this technique are demonstrated in three cases of radiation from apertures and results are compared with the solutions using FE simulation and Gaussian quadrature rules.
  • Khaled Mammar Page 35
    Electrochemical impedance spectroscopy (EIS) is a very powerful tool for exploitation as a rich source of Proton Exchange Membrane Fuel Cell (PEMFC) diagnostic information.A primary goal of this work was to develop a suitable PEMFC impedance model, which can be used in the analysis for flooding and drying of fuel cell. For this one a novel optimization method based on factorial Design methodology is used. It was applied for parametric analysis of electrochemical impedance Thus it is possible to evaluate the relative importance of each parameter to the simulation accuracy. Furthermore this work presents an analysis of the PEMFC impedance behavior in the case of flooding and drying
  • Mohamed B. El, Mashade Page 43
    The deriving force in the design and performance analysis of all radar systems is the target''s characteristics. The fluctuation rate of such a target may vary from essentially independent return amplitudes from pulse-to-pulse to significant variation only on a scan-to-scan basis. The correlation coefficient between the two consecutive echoes in the dwell-time is equal to unity for the SWI and SWIII cases while it is zero for the SWII and SWIV models. An important class of targets is that represented by the so-called moderately fluctuating Rayleigh and c2 targets, which, when illuminated by a coherent pulse train, return a train of correlated pulses with a correlation coefficient in the range 0
  • Reza Baghipour, Mehdi Hosseini Page 58
    In this paper optimum size and location of capacitors and distributed generators (DGs) are determined for reliability improvement and power loss reduction using genetic algorithm (GA). The main innovation of this paper is using both of DG and Capacitor for the reliability improvement and power loss reduction. For this purpose an objective function consisting of reliability cost, power loss cost and also DG's and capacitor's investment cost are considered. The effectiveness of the proposed method is examined in the 10 and 33 bus test systems and comparative studies are conducted before and after DG and Capacitor installation in the test systems. The results obtained show the effectiveness of the proposed method.
  • Esmaeel Ghaedi, Ghazanfar Shahgholian, Rahmat Allah Hooshmand Page 66
    In this paper, the multi-machine power system is simulated and in addition, VURPSO optimization algorithm is used to optimize the parameters of simultaneous controllers of Static Var Compensator (SVC) and power system stabilizer (PSS) in order that the power system stability increases. By SVC, the transferrable power in steady state can be increased and the voltage profile can be controlled along the line. The main role of PSS is damping the generator oscillations by controlling its stimulation by use of auxiliary supplementary signals. If it is assumed in this paper that a three phase short circuit fault with the ground has occurred in a four-machine power system, SVC and PSS simultaneous controllers are used to damp the oscillations and stabilize the system.