JOURNAL OF IRANIAN ASSOCIATION OF ELECTRICAL AND ELECTRONICS ENGINEERS
Year:2010 | Volume:7 | Issue:1|Papers Count:8

In this article, a planar multilayered structure is considered as a radar absorber for normal and oblique incidence plane wave. We used actual dispersive material which could be used as a metamaterial for our structure. The formulation can respond any arbitrary polarization i.e. TE or TM. The optimizations are done in a wide frequency band and at a wide range of incident angles that has reached to considerable conclusions. In order to optimize the reflection coefficient, which is a complicated and multi parameter function, we use Genetic algorithm (GA) method.

Using the path integral Monte Carlo method, in this paper, we have calculated energies of a parabolic quantum dot (PQD) under various conditions and the corresponding electron densities. We have studied the effects of parameters such as temperature, number of confined electrons in the PQD, and electron-electron interactions on the PQD's ground state, from which we have described the formation of the Wigner molecule. Moreover, we have investigated the effect of magnetic field on the variations in separation between various energy levels in the PQD.

In this paper two novel steganalysis methods is presented based on co-occurrence matrix of an image. It is shown that by using features extracted from this matrix, we can differentiate between cover and stego images. These features include energy, entropy, contrast, inverse difference moment, maximum probability and correlation. We use SVM classification for separation of cover and stego images. In the second method, we directly use the diagonal elements of co-occurrence matrix as a feature and we remove some bit planes of an image for feature dimension reduction. Experiments on the 1800 images for LSB and LSB matching (LSBM) algorithms are performed with different rates for the same database. By comparing the results, we also show that the detection rates effectively are increased with respect to previous steganalysis techniques.

In this paper, competitiveness of nuclear power plants in comparison with fossil fuel power plants in Iran has been evaluated. For the first step, different factors affecting economic competitiveness of thermal power plants such as Investment, O&M and Fuel Costs, Discount Rate and Environmental Impacts has been studied. To analyse the effect of each parameter, screening curve method has been used. Taking into account that the real nuclear power competitiveness in Iran is against combine-cycle gas fired power plants, therefore the break even points of gas price(as the most important parameter in fossil fuel plants cost) and overnight investment cost as the most important parameter in nuclear power plant cost) has been calculated. Results show that gas price breakeven point for optimistic 1500$/kW nuclear power plant investment cost is 7 cents/m^3. By increasing the investment cost from 1500 to 2500 $/kW the breakeven point changes from 7 to 17 cents/m^3. As the production cost of gas is between 3-4.5 cents/m^3 and its opportunity cost is near zero (as a result of low potential of export in comparison with gas reservoirs), economic competitiveness of nuclear power plants in Iran is questionable. Increase in the gas price and export capability will lead to better competitiveness of nuclear power plants. It should be mentioned that the results are based on latest economic data of year 2005-2007 and can be updated.

In this paper an effective method for the purpose of state estimation of fundamental and harmonics signals in the radial power distribution network is presented. In Addition, the application development of this method to the network observability and data processing is considered and analyzed. One of the most advantages of this method is capability of bad data detection and process of them and application on the harmonic state estimation in practical case. In this paper by testing this algorithm on the example system and partial of Isfahan distribution network, the effectiveness and confirmation of this method for the fundamental and 3rd and 5th harmonic frequencies are investigated.

Natural gas is transmitted at high pressure levels. For industrial and domestic consumptions, this pressure should be reduced. Usually, mechanical valves accomplish this process. Turbo-expanders can replace these equipments and reduce gas pressure at city gate gas pressure reduction stations as well. Besides, they can recover the huge amount of high pressure gas energy and drive electrical generators. But, because of instantaneous varying of domestic consumptions, environment temperature and other effective parameters, turbo-expander inlet gas pressure and mass flow-rate vary with time and consequently, the extracted power has time variant specification. These variations are transferred by coupled generator to the power distribution network and cause voltage flicker at the point of common coupling (PCC). In this paper, we represent a proper model for flicker study of turbo-expander driven synchronous generator in the power distribution network. Also, we assess the amount of voltage flicker at the PCC and show the produced flicker rate is dependent on the inlet gas specification and the power distribution network parameters.

The aging of insulating materials can be estimated by an electrical breakdown occurring in electrical components so that the relationship between lifetime, failure probability and reliability of electrical components may be studied using the life models in high voltage cables networks. In last decades with attention to higher features as electrical, thermal, mechanical characteristic, widely cross-linked polyethylene cables replaced instead of oil-papered cables. However cable networks reliability far higher than overhead transmission networks, but different stresses as thermal, electrical, multi stress and load cycling are reduced useful cable operation life. In this paper, a novel approach is presented to high voltage power XLPE insulated cable life estimation. In this work, for power XLPE cable life estimation, artificial neural networks (ANNs) are used. Inputs of artificial neural networks, thermal, electric field intensity, soil thermal resistivity and other cable layers thermal resistivities are specified. Power cable life under thermal, electrical and multi stresses and different conditions are estimated by ANNs.