The Modares Journal of Electrical Engineering
Volume:11 Issue: 3, 2011

This paper presents a multiobjective power control algorithm that updates the transmitted power based on local information. The proposed algorithm is expanded by using multiobjective optimization schemes. The objectives to be optimized in this paper are determined so as to reduce the SINR fluctuations as well as maintaining the SINR to an acceptable level with minimizing an average transmitted power. The convergence properties of the proposed algorithm are studied theoretically and with numerical simulations. The results indicate that the algorithm converges more rapidly and has lower average transmitted power than other existing algorithms. The current study also suggests a practical version of the proposed algorithm and compares it to the existing totally distributed bang-bang power control (B-BPC) or fixed step power control (FSPC) and multiobjective totally distributed power control (MOTDPC) algorithms. Numerical results show that the proposed algorithm is potentially much more efficient in terms of convergence speed and average consumption power than the other two algorithms.

In this paper، a novel directional super wide band micro strip antenna based on a simple and new geometry has been proposed. The antenna exhibits the widest bandwidth ever reported to the authors’ knowledge from 50 GHz to 200 GHz. Its radiation pattern is approximately steady in the frequency ranges of 50 GHz to 200 GHz. The antenna consists of a club-like radiating patch، a combination of three circular patches، and a partial ground structure. Moreover، the proposed antenna has a compact volume of 24 mm × 18 mm × 0. 787 mm on a RT Duroid substrate with a relative dielectric constant of 2. 2. RT Duroid has very low loss characteristic and therefore the loss of the antenna will be very little. The simulation is performed by CST Microwave Studio simulator. Antenna design and the simulation results of radiation pattern and gain are presented and discussed in detail. Results show that the performance is very excellent in full band.

An ideal fusion method preserves the spectral information in fused image without spatial distortion. The PCA is believed to be a well-known pan-sharpening approach and being widely used for its efficiency and high spatial resolution. However، it can distort the spectral characteristics of multispectral images. The current paper tries to present a new fusion method based on the same concept. In the conventional standard PCA method، PCA transform is applied to spectral bands of multispectral images، but we applied the PCA transform to pixel blocks instead. Since PCA coefficients are extracted from statistical properties of the image، it is more consistent with type and texture of remotely sensed image compared to other kernels such as wavelets. After that، a new hybrid algorithm is proposed which uses both the spatial PCA and the spectral PCA method to improve the quality of the merged images. Visual and statistical analyses show that the proposed algorithm clearly improves the merging quality in terms of RASE، ERGAS، SAM، correlation coefficient and UIQI; compared to fusion methods such as IHS، Brovey، PCA، HPF، and HPM.

The paper tries to present an improved mathematical model for distribution companies (DISCOs) in order to solve Distribution Network Expansion Planning (DNEP) problems in the presence of certain resources of Distributed Generations (DGs) entitled small scale Gas Engines in the medium voltage grids. With the aim of minimizing investment and operation costs، the recommended model combines a comprehensive multi-objective optimization model with grid designer’s experience and power transit possibility in retail trading. The proposed model determines the optimal capacity of new transformers، and the most efficient type and route of the expandable medium voltage feeders under probable power transit condition in retail markets. In addition، this model maintains system reliability along with an innovative formulation. The scenario-based results obtained after implementing this method on a typical distribution grid modeled under GAMS software platform indicate that the proposed model is really suitable for expanding distribution grids.

This paper presents the results of a study on the radiation characteristics of a plasma triangular antenna in the VHF band (30-300MHz) applying the method of moment. Deriving the current distribution of the antenna، it shows the relationship between radiation characteristics of the plasma antenna and the plasma parameters. Both theoretical and numerical results indicate that if the plasma frequency is sufficiently higher than the operating frequency and the collision frequency is correspondingly low، the radiation treatment of the plasma antenna will be close to a metal one. Also the consequence of simulations reveals the proposed plasma antenna has better peak gain than the conventional plasma column on the operating band. The results of the current study are checked by using full wave HFSS simulator.

Increasing overall liberalization and improving reliability indexes are the two prime but often conflicting objectives of electricity markets. Proper embedding of regulatory intervention of price caps provides an effective means to tradeoff between these two objectives. Surprisingly، in the context of the infinitely repeated game paradigm، as in the case of actual electricity markets، the dominance of tacit collusion and capacity withholding highlights the role of non-pivotal firms in frustrating price caps and deteriorating reliability indexes. An agent-based simulation framework is proposed to evaluate both individual behavior of non-pivotal firms within the market and the emergent collusive behavior arising from interaction between firms. Mathematically speaking، to put the capacity withholding into action، we propose embedding a hybrid-control problem in the supply function equilibrium (SFE) modeling assumptions. As a consequence، non-pivotal firms are granted supply curves with vertical segments that obviate the slope constraint of the SFE modeling. A simulation using the generation portfolio of the Iranian electricity industry illuminates the impacts of tacit collusion on reliability indexes.