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Zabihzadeh D.,Asrar Institute of Higher Education | Moattar M.H.,Islamic Azad University at Mashhad
International Journal of Speech Technology | Year: 2014

Speaker verification has been studied widely from different points of view, including accuracy, robustness and being real-time. Recent studies have turned toward better feature stability and robustness. In this paper we study the effect of nonlinear manifold based dimensionality reduction for feature robustness. Manifold learning is a popular recent approach for nonlinear dimensionality reduction. Algorithms for this task are based on the idea that each data point may be described as a function of only a few parameters. Manifold learning algorithms attempt to uncover these parameters in order to find a low-dimensional representation of the data. From the manifold based dimension reduction approaches, we applied the widely used Isometric mapping (Isomap) algorithm. Since in the problem of speaker verification, the input utterance is compared with the model of the claiming client, a speaker dependent feature transformation would be beneficial for deciding on the identity of the speaker. Therefore, our first contribution is to use Isomap dimension reduction approach in the speaker dependent context and compare its performance with two other widely used approaches, namely principle component analysis and factor analysis. The other contribution of our work is to perform the nonlinear transformation in a speaker-dependent framework. We evaluated this approach in a GMM based speaker verification framework using Tfarsdat Telephone speech dataset for different noises and SNRs and the evaluations have shown reliability and robustness even in low SNRs. The results also show better performance for the proposed Isomap approach compared to the other approaches. © 2014 Springer Science+Business Media New York. Source


Mahdinejad K.,Islamic Azad University at Bojnurd | Seghaleh M.Z.,Asrar Institute of Higher Education
Life Science Journal | Year: 2013

Time delay estimation (TDE) has been a research topic of significant practical importance in many fields (radar, sonar, seismology, geophysics, ultrasonic, hands-free communications, etc.). It is a first stage that feeds into subsequent processing blocks for identifying, localizing, and tracking radiating sources. This paper presents an implementation of TDE using different weighted generalized cross correlation and make a comparison between them. We will discuss the effect of length of observation interval on accuracy and speed of estimation and the influence of distance of microphones and sound source on estimation error based on some experimental results in room acoustic environments with reverberation and noise. Source


Reihani E.,Asrar Institute of Higher Education | Sarikhani A.,Florida International University | Davodi M.,Asrar Institute of Higher Education | Davodi M.,Florida International University
International Journal of Electrical Power and Energy Systems | Year: 2012

With the growth of electrical energy demand, providing reliable energy without interruption has become very important nowadays. Maintenance scheduling of generating units is one of the crucial factors in delivering reliable electrical energy to the vital industrial and urban loads. As number of generating units and constraints over their operation is increasing, there is growing need for developing new methods for planning optimal outage of generating units for maintenance. This paper presents a hybrid evolutionary algorithm to tackle the reliability based generator maintenance scheduling problem. Uncertainties in the generating units and the load variations are included so that a more realistic scheduling is obtained. Maintenance scheduling problem is a large scale constrained optimization problem with a large number of variables which needs novel methods to cope with it. A new local search method which is derived from Extremal Optimization (EO) and Genetic Algorithm (GA) is presented to tackle the problem. The proposed method can be used as a local optimizer to further improve the potential solutions in the GA. The proposed method, Hill Climbing Technique (HCT), GA and their hybrid approaches are applied to the IEEE Reliability Test System (RTS) and the obtained results are discussed. © 2012 Elsevier Ltd. All rights reserved. Source

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