List of Articles
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Open Access Article
1 - Analyzing Weighted Attack Graphs Using Genetic Algorithms
M. Abadi Saeed JaliliEach attack graph represents a collection of possible attack scenarios in a computer network. In this paper, we use weighted attack graphs (WAGs) for vulnerability assessment of computer networks. In these directed graphs, a weight is assigned to each exploit by the sec MoreEach attack graph represents a collection of possible attack scenarios in a computer network. In this paper, we use weighted attack graphs (WAGs) for vulnerability assessment of computer networks. In these directed graphs, a weight is assigned to each exploit by the security analyst. The weight of an exploit is proportionate to the cost required to prevent that exploit. The aim of analyzing a weighted attack graph is to find a critical set of exploits such that the sum of their weights is minimum and by preventing them no attack scenario is possible. In this paper, we propose a greedy algorithm, a genetic algorithm with a greedy mutation operator, and a genetic algorithm with a dynamic fitness function for analyzing the weighted attack graphs. The proposed algorithms are used to analyze a sample weighted attack graph and several randomly generated large-scale weighted attack graphs. The results of experiments show that the proposed genetic algorithms outperform the greedy algorithm and find a critical set of exploits with less total weight. Finally, we compare the performance of the second genetic algorithm with an approximation algorithm for analyzing several randomly generated large-scale simple attack graphs. The results of experiments show that our proposed genetic algorithm has better performance than the approximation algorithm and finds a critical set of exploits with less cardinality. Manuscript profile -
Open Access Article
2 - Adaptive Inverse Controller Design for Teleoperation Systems
M. Sha Sadeghi H. R. Momeni R. Amirifar S. GanjefarThis paper presents a new robust adaptive inverse control approach for a force-reflecting teleoperation system with varying time delay. In this approach, using the Smith predictor idea, an impedance controller and an adaptive inverse controller are designed, respectivel MoreThis paper presents a new robust adaptive inverse control approach for a force-reflecting teleoperation system with varying time delay. In this approach, using the Smith predictor idea, an impedance controller and an adaptive inverse controller are designed, respectively, for the master and slave robots such that the stability and performance of the closed-loop system are achieved in the presence of communication channels varying time delay. Also, based on robust control theory, two sufficient conditions for the stability of overall system are derived. The time domain desired specifications are contained in the design problem using the standard characteristic polynomials. Also, the proposed approach is compared with the sliding mode control. The simulation results show the proposed approach successfully compensates the position drift although time delay is randomly varying. Manuscript profile -
Open Access Article
3 - Optimization of Shunt Active Power Filter and Load Current with an Improved Sliding Mode Control
M. Nayeripour A. Yazdian Varjani M. MohamadianIn this paper, the compensation of load harmonic current is investigated using Lagrange function and minimization of load current active component. The results are compared with load harmonic current compensation using instantaneous three phase reactive power theory. N MoreIn this paper, the compensation of load harmonic current is investigated using Lagrange function and minimization of load current active component. The results are compared with load harmonic current compensation using instantaneous three phase reactive power theory. Next the PI and sliding mode controller are modified such that RMS value of error signal is minimized and state variables reach the sliding surface faster than conventional sliding mode controller. This improves the dynamic response of active power filter under load unbalance and harmonics conditions. Manuscript profile -
Open Access Article
4 - A New Method for Ripple Reduction of DC Voltage Using Active Filter
S. M. Dehghan A. Yazdian Varjani M. MohamadianFluctuations and ripples in voltage or current of DC power systems cause different malfunctions in operation of equipments and systems which are supplied by low quality distribution power systems. Therefore ripple reduction of voltage or current in DC power systems is v MoreFluctuations and ripples in voltage or current of DC power systems cause different malfunctions in operation of equipments and systems which are supplied by low quality distribution power systems. Therefore ripple reduction of voltage or current in DC power systems is very important. In this paper a new method is proposed to reduce ripple of DC voltage in high power system using an active power noise cancellation filter (APNCF). In the proposed method a hybrid system including series and parallel active filters for ripple reduction of load voltage and source current is used. Simulation and experimental results show the performance of the proposed method in dynamic and static states. Manuscript profile -
Open Access Article
5 - Detection of Coherent Radar Signals with Unknown Doppler Shift in Non-Gaussian Clutter
M. R. Taban A. mohammadi M. Modarres HashemiIn this paper the problem of detection of coherent radar signals with slow fluctuating amplitude and unknown Doppler shift in non-Gaussian clutter is considered. Coherent radar signal detection with unknown Doppler shift is rarely considered in the literature. It has be MoreIn this paper the problem of detection of coherent radar signals with slow fluctuating amplitude and unknown Doppler shift in non-Gaussian clutter is considered. Coherent radar signal detection with unknown Doppler shift is rarely considered in the literature. It has been demonstrated that in high resolution radars or in small grazing angles, the pseudo-Gaussian models are more accurate than Gaussian for clutter modeling. Optimum detection of signals with unknown Doppler shift in pseudo-Gaussian clutter contains a complicated multiple integral. Therefore, in this paper, generalized forms of the suboptimum GLR and CGLR detectors are proposed. Also, by estimating the random variable related to the clutter power (τ) in the test cell, GLRTLQ detector for unknown Doppler shift case is introduced and generalized. It is demonstrated that the proposed GLRTLQ detector has a simple structure and does not depend on the clutter distribution. The performances of the proposed detectors are evaluated by computer simulation. Manuscript profile -
Open Access Article
6 - A Nonoblivious Watermarking Scheme for Embedding Spread Spectrum-like Watermarks in the Wavelet Domain Using HVS Characteristics
A. R. zolghadr asli S. RezazadehIn this paper, we introduce a multiresolution watermarking method for copyright protection of digital images. The method is based on the discrete wavelet transform. A noise type Gaussian sequence is used as watermark. To embed the watermark robustly and imperceptibly, w MoreIn this paper, we introduce a multiresolution watermarking method for copyright protection of digital images. The method is based on the discrete wavelet transform. A noise type Gaussian sequence is used as watermark. To embed the watermark robustly and imperceptibly, watermark components are added to the significant coefficients of each selected subband by considering the human visual system (HVS) characteristics. Some small modifications are performed to improve HVS model. The host image is needed in watermark extraction procedure and Normalized Correlation Function (NCF) is used to measure similarities of extracted watermarks. It is shown that this method is robust against wide variety of attacks such as: additive noise, low pass filtering, compression, chopping, histogram equalization, rotation. Comparison with other methods shows the better performance of this suggested method. Manuscript profile -
Open Access Article
7 - A New Method for Short Block Length LDPC Code Design
M. Taki M. B. NezafatiIn this paper, we propose a new method for short block length Low Density Parity Check (LDPC) code design. The experimental results show that codes designed using the proposed algorithm have better performance compare to the other short block length LDPC codes. For LDPC MoreIn this paper, we propose a new method for short block length Low Density Parity Check (LDPC) code design. The experimental results show that codes designed using the proposed algorithm have better performance compare to the other short block length LDPC codes. For LDPC code design in short block length, two problems arise: first analytical estimation of code performance using density evolution method is unusable because of infinity of code length in this method. Second because of high code density, the probability of short loop in code graph (Girth) is high that dramatically reduces the code performance. We propose solution for both problems. First, code structure is designed in such a way that the code performance is near to that of the density evolution method estimates and second by improving Extended Bit Filling algorithm, short block length is controlled. Manuscript profile -
Open Access Article
8 - Fuzzy Evaluation of Long-Term Impacts of Electrical Appliances Efficiency Improvement on Load Pattern
M. Behrangrad M. Parsa-MoghaddamEvaluation of long-term home electrical appliance efficiency improvement scenarios on load and energy pattern needs comprehensive and precise modeling taking to account a variety of uncertainties. In the modeling process, all effective parameters should be considered. E MoreEvaluation of long-term home electrical appliance efficiency improvement scenarios on load and energy pattern needs comprehensive and precise modeling taking to account a variety of uncertainties. In the modeling process, all effective parameters should be considered. Estimation is the main source of information in this process which is a long-term large scale impact assessment procedure. Furthermore, the non homogeneous structure of load behavior in response to DSM policies makes the problem more sophisticated. The presented method implies fuzzy numbers to model the main uncertainties of the demand side reactions to the proposed DSM program. Here, the social classes of customers and their behaviors regarding energy utilization as well as time dependency of the problem parameters are taken into account. The paper focuses on the efficiency improvement of the electric appliances in Iran as a long-term DSM program, due to their considerable share in electricity consumption in residential sector. Finally, the numerical results are presented. Manuscript profile