Sharif Digital Repository

One of the essential usages of adaptive filters is in sparse system identification on which the performance of classic adaptive filters is not acceptable. There are several algorithms that designed especially for sparse systems; we call them sparsity aware algorithms. In this paper we studied the performance of two newly presented adaptive algorithms in which P-norm constraint is considered in defining cost function. The general title of these algorithms is continuous mixed P-norm (CMPN). The performances of these algorithms are considered for the first time in sparse system identification. Also the performance of l0 norm LMS algorithm is analysed and compared with our proposed algorithms.... 

In this paper an iterative method for recovery of the missing samples of signals is investigated in detail, and some novel linear, nonlinear, and adaptive extrapolation techniques are proposed to be used along with it to increase the convergence rate of the recovery system. The proposed methods would remarkably speed up the convergence rate, save processing power, and reduce the delay of the system compared to some well known accelerated versions of the aforementioned iterative algorithm. © 2007 Elsevier B.V. All rights reserved  

In this paper, a flux search controller is proposed to increase the efficiency of a direct torque-controlled induction motor in full load range. The value of the flux reference is determined through a minimization algorithm. The amplitude of stator current is used as the objective function since it is shown that samples of the stator current have better statistical properties than input power. In addition, the stator current has more sensitivity to the flux variation than input power. These two properties allow implementing an adaptive algorithm to determine the proper flux step without waste of time. The minimum allowable value of the flux step has been determined based on this process to... 

In this paper, we study the effect of adaptivity of routing algorithm on the overall performance in a hypercube multicomputer using wormhole switching. To this end, we use three accurate analytical models proposed for deterministic, fully-adaptive, and partially-adaptive routing algorithms in hypercube. Surprisingly, our analysis shows that under uniform traffic load, the partially-adaptive routing exhibits a lower performance compared to the deterministic routing with less adaptivity. ©2006 IEEE  

This paper presents a new algorithm for detecting user-selected objects in a sequence of images based on adaptively lifted wavelet transforms. In our algorithm, we first select a set of object features in the wavelet transform domain and then build a new transform by using the selected features. The new wavelet transform is constructed based on adaptive prediction in a lifting scheme structure. Adaptive prediction is performed such that, the large coefficients in the high-pass component of the old transform, vanish in the high-pass component of the new transform. Finally, both of the old and new transforms are applied to a given test image and the transform domain coefficients are compared... 

The present study aims to evaluate the important issue of elimination of direct path interference and clutter in ambiguity function and detection of passive radars with adaptive filters. The efficiency and performance of each of them were investigated. Finally, by simulation and their learning curve, the best algorithm was proposed for these radars  

A new robust image adaptive digital watermarking algorithm in wavelet transform domain is proposed in this paper. The proposed method exploits Human Visual System (HVS) characteristics and entropy masking concept to determine image adaptive thresholds for selection of perceptually significant coefficients. The mark is embedded in the coefficients of all subbands including the LL subband. Experimental results show that the proposed method significantly improves watermarking performance over conventional methods, in the terms of invisibility and robustness  

Group-testing refers to the problem of identifying (with high probability) a (small) subset of D defectives from a (large) set of N items via a 'small' number of 'pooled' tests (i.e., tests have a positive outcome if even one of the items being tested in the pool is defective, else they have a negative outcome). For ease of presentation in this work we focus the regime when the number of defectives is sublinear, i.e., D = O (N1-δ) for some δ > 0. The tests may be noiseless or noisy, and the testing procedure may be adaptive (the pool defining a test may depend on the outcome of a previous test), or non-Adaptive (each test is performed independent of the outcome of other tests). A rich body... 

Nature has always been a source of great inspiration for engineers and mathematicians. Evolutionary Algorithms are the latest in a line of natural-based innovations which have had a profound effect on the application of optimization in science and engineering. Although based on nature, Evolutionary Algorithms are nonetheless distinctly different from natural evolution in several areas. This paper outlines early and recent developments of Evolutionary Algorithms while covering those areas of difference. Practical issues related to the use of Evolutionary Algorithms, key parameters that affect the quality of the search and impact of user choices in problem formulation are also covered in this... 

In this paper we present a general formalism for the establishment and mean-square performance analysis of the family of selective partial update affine projection (SPU-AP), selective regressor affine projection (SR-AP), and selective partial update subband adaptive filter (SPU-SAF) algorithms. This analysis is based on energy conservation arguments and does not need to assume a Gaussian or white distribution for the regressors. We demonstrate through simulations that the results are useful in predicting the performance of these adaptive filter algorithms  

A new adaptive real-coded memetic algorithm has been developed for continuous optimization problems. The proposed algorithm utilizes an adaptive variant of Continuous Ant Colony System for local search. Here new adaptive strategies are utilized for online tuning of the number of local search steps and the width of the search interval over each dimension of the search space. A new crossover scheme is also developed and utilized. The new algorithm has been examined with CEC 2005 benchmarks and compared with three other state of the art works in the field. The comparisons have showed relatively better results. © 2009 IEEE  

OTIS-based architectures appear to have the potential to be an interesting option for future generations of multiprocessing systems. In this paper, we propose a new adaptive unicast routing algorithm and four software-based (unicast-based) broadcast algorithms for the wormhole switched OTI S-hypercube. We then present an empirical performance evaluation of these algorithms in OTIS-hypercube for different topologies, message length and traffic loads. © 2008 IEEE  

Although several analytical models have been proposed in the literature for different interconnection networks with different routing algorithms, there is only one work [M. Ould-Khaoua, An approximate performance model for partially adaptive routing algorithm in hypercubes, Microprocessors and Microsystems 23 (1999) 185-190] dealing with partially adaptive routing. It is not accurate enough especially in heavy traffic regions due to the rough approximation of assuming equal traffic rate over network channels. We show, however, such an approximation can greatly affect the accuracy of the model. This paper proposes an accurate analytical model to predict the average message latency in wormhole... 

Steganography is the art of hiding information in a cover media without attracting attention. One of the cover media which can be used for steganography is speech. In this paper, we propose a new speech steganography in wavelet domain. In this method, lifting scheme is used to create perfect reconstruction Int2Int wavelets. The data is hidden in some of the Least Significant Bits (LSB) of detail wavelet coefficients. The LSB bits for hiding are selected with a new adaptive algorithm. This algorithm does not hide information in silent parts, so there is no need for silent detection algorithms. This method has zero error in hiding/unhiding process, while normal wavelet domain LSB has about 0.2... 

In this paper an indirect adaptive control algorithm is proposed to stabilize the fixed points of discrete chaotic systems. It is assumed that the functionality of the chaotic dynamics is known but the system parameters are unknown. This assumption is usually applicable to many chaotic systems, such as the Henon map, logistic and many other nonlinear maps. Using the recursive-least squares technique, the system parameters are identified and based on the feedback linearization method an adaptive controller is designed for stabilizing the fixed points, or unstable periodic orbits of the chaotic maps. The stability of the proposed scheme has been shown and the effectiveness of the control... 

The necklace hypercube has recently been introduced as an attractive alternative to the well-known hypercube. Previous research on this network topology has mainly focused on topological properties, VLSI and algorithmic aspects of this network Several analytical models have been proposed in the literature for different interconnection networks, as the most cost-effective tools to evaluate the performance merits of such systems. This paper proposes an analytical performance model to predict message latency in wormhole-switched necklace hypercube interconnection networks with fully adaptive routing. The analysis focuses on a fully adaptive routing algorithm which has been shown to be the most... 

In this paper, adaptive model predictive control is applied to schedule differentiated buffers in routers. The proposed algorithm, adaptive model predictive control scheduler (AMPCS), dynamically regulates the service rates of aggregated traffic classes. This algorithm guarantees some required constraints on proportional or absolute delay. The control parameters and the way they are adjusted as well as the problems of implementing the controller at high data rates are investigated. Theoretical analysis and numerical simulations demonstrate stability of AMPCS and its acceptable quality of service differentiations at core routers while maintaining end to end delay constraints. © 2007 Elsevier... 

In this paper, we study the effect of adaptivity of the routing algorithm on the overall performance of a hypercube multicomputer using wormhole switching. To this end, we use three accurate analytical models proposed for deterministic, fully-adaptive, and partially-adaptive routing algorithms in the hypercube. We compare these three different classes of routing algorithms under different working conditions and structural factors. It is widely believed that the level of adaptivity can result in better performance. Our analysis shows that under uniform traffic load, the employed partially-adaptive routing algorithm exhibits a lower performance compared to the considered deterministic routing... 

Partially adaptive routing algorithms are a useful category of routing algorithms due to their simple router logic and restricted adaptivity in selecting the next output channel towards the destination. Several partially adaptive routing algorithms on mesh and hypercube networks have been presented in the literature. But there is no study on evaluating the performance of these algorithms. This paper tries to compare the most important partially adaptive routing algorithms on the mesh and hypercube networks as the most popular topologies for multicomputers. The evaluation has been performed by the use of event driven simulator coded by C++ compiler. © 2006 IEEE