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Showing 4 results for Zaker

M. Mahdavi, Sh. Samavi, N. Zaker, M. Modarres-Hashemi,
Volume 4, Issue 3 (July 2008)

In this paper we present a new accurate steganalysis method for the LSB

replacement steganography. The suggested method is based on the changes that occur in the

histogram of an image after the embedding of data. Every pair of neighboring bins of a

histogram are either inter-related or unrelated depending on whether embedding of a bit of

data in the image could affect both bins or not. We show that the overall behavior of all

inter-related bins, when compared with that of the unrelated ones, could give an accurate

measure for the amount of the embedded data. Both analytical analysis and simulation

results show the accuracy of the proposed method. The suggested method has been

implemented and tested for over 2000 samples and compared with the RS Steganalysis

method. Mean and variance of error were 0.0025 and 0.0037 for the suggested method

where these quantities were 0.0070 and 0.0182 for the RS Steganalysis. Using 4800

samples, we showed that the performance of the suggested method is comparable with

those of the RS steganalysis for JPEG filtered images. The new approach is applicable for

the detection of both random and sequential LSB embedding.

B. Zakeri, H. Bernety,
Volume 10, Issue 4 (December 2014)

Band-notch characteristic has been of great interest recently to overcome the electromagnetic interference of Ultra-wideband systems (UWB) with other existing ones. In this paper, we present a novel microstrip-fed antenna with band rejection property appropriate for UWB applications. Band-notch characteristic has been achieved by adding a rectangular resonant element to the ground section. A prototype was fabricated and measured based upon optimal parameters. Experimental results show consistency with simulation results. Measurement results confirm that the antenna covers the UWB band and satisfies a band rejection in the frequency span of 5 GHz to 5.7 GHz to restrain it from interference with Wireless Local Area Network (WLAN). Then, to achieve better isolation, a rectangular strip is appended to the band-notch creating part of the ground section to enhance obtained VSWR up to 30 through simulation. In addition, by applying a similar technique, a dual band-notched characteristic with an average simulated VSWR of around 13.75 has been achieved for WLAN and the downlink of X band satellite communication systems with each more than 10. Features such as small size, omnidirectional pattern and perfect isolation make the antenna suitable for any UWB applications.
A. A. Khodadoost Arani, B. Zaker, G. B. Gharehpetian,
Volume 13, Issue 1 (March 2017)

The Micro-Grid (MG) stability is a significant issue that must be maintained in all operational modes. Usually, two control strategies can be applied to MG; V/f control and PQ control strategies. MGs with V/f control strategy should have some Distributed Generators (DGs) which have fast responses versus load changes. The Flywheel Energy Storage System (FESS) has this characteristic. The FESS, which converts the mechanical energy to electrical form, can generate electrical power or absorb the additional power in power systems or MGs. In this paper, the FESS structure modeled in detail and two control strategies (V/f and PQ control) are applied for this application. In addition, in order to improve the MG frequency and voltage stability, two complementary controllers are proposed for the V/f control strategy; conventional PI and Fuzzy Controllers. A typical low voltage network, including FESS is simulated for four distinct scenarios in the MATLAB/ Simulink environment. It is shown that fuzzy controller has better performance than conventional PI controller in islanded microgrid.

A. S. Hoshyarzadeh, B. Zaker, A. A. Khodadoost Arani, G. B. Gharehpetian,
Volume 14, Issue 3 (September 2018)

Recently, smart grids have been considered as one of the vital elements in upgrading current power systems to a system with more reliability and efficiency. Distributed generation is necessary for most of these new networks. Indeed, in all cases that DGs are used in distribution systems, protection coordination failures may occur in multiple configurations of smart grids using DGs. In different configurations, there are various fault currents that can lead to protection failure. In this study, an optimal DG locating and Thyristor-Controlled Impedance (TCI) sizing of resistive, inductive, and capacitive type is proposed for distribution systems to prevent considerable changes in fault currents due to different modes of the smart grid. This problem is nonlinear constrained programming (NLP) and the genetic algorithm is utilized for the optimization. This optimization is applied to the IEEE 33-bus and IEEE 69-bus standard distribution systems. Optimum DG location and TCI sizing has carried out in steady fault currents in the grid-connected mode of these practical networks. Simulation results verify that the proposed method is effective for minimizing the protection coordination failure in such distribution networks.

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© 2022 by the authors. Licensee IUST, Tehran, Iran. This is an open access journal distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.