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sheikhan-soudani--amene
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Anderson Localization of Electromagnetic Waves
, Ph.D. Dissertation Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
The electrons scatter by the impurities during propagation through the media and become localized by increasing the impurities. So the metal insulator transition occurs. This phenomenon was first proposed by W. Anderson and is known as Anderson Localization. In this thesis the Anderson localization of electromagnetic waves is investigated. The disordered media with random dielectric constant is studied by considering Maxwell’s equations. There are different numerical methods to study this phenomenon such as transfer matrix method and level statistics we have used in this thesis. In three dimension, different scaling behavior shows the phase transition from localized states to extended states...
Predicting Novelty Concepts in Data Streams
, M.Sc. Thesis Sharif University of Technology ; Beigy, Hamid (Supervisor)
Abstract
Many real-world environment challenges are not considered in laboratory-controlled models. Although different and powerful models have been developed for object detection and classification in diverse applications, many fail in the real world. One of the most important challenges is dealing with unknown data at the inference time. The second challenge is to change the characteristics of the data distribution over time, known as concept drift. These two important challenges are explored in the Data Stream environment, along with many of the events that a model may face in the real world. To address the challenges of learning in a data stream environment, this thesis first designs a...
Coherent backscattering of electromagnetic waves in random media
, Article EPL ; Volume 98, Issue 1 , 2012 ; 02955075 (ISSN) ; Maass, P ; Rahimi Tabar, M. R ; Sharif University of Technology
2012
Abstract
The single and multiple scattering regimes of electromagnetic waves in a disordered system with fluctuating permittivity are studied by numerical simulations of Maxwell's equations. For an array of emitters and receivers in front of a medium with randomly varying dielectric constant, we calculate the backscattering matrix from the signal responses at all receiver points j to electromagnetic pulses generated at each emitter point i. We show that the statistical properties of the backscattering matrix are in agreement with the recent experimental results for ultrasonic waves (Aubry A. and Derode A., Phys. Rev. Lett., 102 (2009) 084301) and light (Popoff S. M. et al., Phys. Rev. Lett., 104...
Numerical simulations of localization of electromagnetic waves in two- and three-dimensional disordered media
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 80, Issue 3 , 2009 ; 10980121 (ISSN) ; Rahimi Tabar, M. R ; Sahimi, M ; Sharif University of Technology
2009
Abstract
Localization of electromagnetic waves in two-dimensional (2D) and three-dimensional (3D) media with random permittivities is studied by numerical simulations of the Maxwell's equations. Using the transfer-matrix method, the minimum positive Lyapunov exponent γm of the model is computed, the inverse of which is the localization length. Finite-size scaling analysis of γm is carried out in order to check the localization-delocalization transition in 2D and 3D. We show that in 3D disordered media γm exhibits two distinct types of frequency dependence over two frequency ranges, hence indicating the existence of a localization-delocalization transition at a critical frequency ωc. The critical...
Localization properties of acoustic waves in the random-dimer media
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 78, Issue 13 , 2008 ; 10980121 (ISSN) ; Esmailpour, M ; Sheikhan, A ; Elahi, M ; Rahimi Tabar, M. R ; Sahimi, M ; Sharif University of Technology
2008
Abstract
Propagation of acoustic waves in the one-dimensional (1D) random-dimer (RD) medium is studied by three distinct methods. First, using the transfer-matrix method, we calculate numerically the localization length ξ of acoustic waves in a binary chain (one in which the elastic constants take on one of two values). We show that when there exists short-range correlation in the medium-which corresponds to the RD model-the localization-delocalization transition occurs at a resonance frequency ωc. The divergence of ξ near ωc is studied, and the critical exponents that characterize the power-law behavior of ξ near ωc are estimated for the regimes ω> ωc and ω< ωc. Second, an exact analytical analysis...
Anderson localization and propagation of electromagnetic waves through disordered media
, Article Waves in Random and Complex Media ; Volume 20, Issue 1 , 2010 , Pages 191-200 ; 17455030 (ISSN) ; Abedpour, N ; Sepehrinia, R ; Niry, M. D ; Reza Rahimi Tabar, M ; Sahimi, M ; Sharif University of Technology
2010
Abstract
We have used the dynamic method to calculate the frequency dependence of the localization length in a disordered medium, using the amplitude change and the redshift of the spectral density of the propagating incident pulse. The frequency dependence of the localization length in an effectively one-dimensional disordered medium is computed in terms of the strength of the disorder. The results obtained with the dynamic method are confirmed by computing the same results using the transfer-matrix method