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discrete-fourier-transform
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Design And Simulation Of Fast Spectrum Sensing For Cognitive Radio Networks
, M.Sc. Thesis Sharif University of Technology ; Fotowat Ahmadi, Ali (Supervisor)
Abstract
Deployment of demands, increase in users and new services highlight the necessity of effective frequency allocation i.e. dynamic allocation instead of fixed allocation. Cognitive radio is a proper solution for dynamic frequency allocation. Cognitive radio can scan the spectrum and use the idle bands for transmitting and receiving data. The main part of this radio which is responsible for the most pivotal task is spectrum sensing. Recently, varied methods have been proposed to sense the spectrum. The scope of this research is on designing a very high-speed spectrum sensing system. In this thesis, in order to meet the required scan rate, a tunable complex filter with 40MHz pass-band has...
Blow-up For Chemotaxis Models
, Ph.D. Dissertation Sharif University of Technology ; Hesaaraki, Mahmoud (Supervisor)
Abstract
Moving of living organisms appears in many interesting problems, e.g. the growth of bacteria colonies, tumor growth, wound healing, color patterns of animals and etc. There are many ways to model such problems and PDE theory is widely used to investigate these problems. In this thesis, we study two well-known classic models. First, macroscopic “Keller–Segel” model and then kinetic “Othmer–Dunbar–Alt” System. Since these models have a nice behavior in two dimensions that they don’t have in other dimensions, we propose a way to alter them such that they behave in this way in all dimensions. Also none of the known models have the suitable dynamics in one dimension, so our model has the property...
Identifying the Main Factors Affecting Road Accidents in Iran Through Data Mining, Determining the Optimal Solution in Mitigation and Forecasting its Effectiveness Through Arima Models
, M.Sc. Thesis Sharif University of Technology ; Akhavan Niaki, Taghi (Supervisor)
Abstract
Road accidents are unfortunate events that cause more thanl16000 deaths each year in Iran. Intercity accidents require a comprehensive plan to reduce casualties because the number of roads users are increasing and the accidents account for nearlyl65% of fatalities. In this study, we first tried to identify the status of Iran through a study of traffic accidents in the world, and then the research and activities carried out in Iran were analyzed to find new and effective solutions. Using the daily fatalities data froml2008 tol2014, and using the new methodology presented in this research based on the Discrete Fourier Transformation (DFT), the Box-Jenkins models and the Secant method, the...
Speech signal modeling using multivariate distributions
, Article Eurasip Journal on Audio, Speech, and Music Processing ; Volume 2015, Issue 1 , 2015 , Pages 1-14 ; 16874714 (ISSN) ; Veisi, H ; Sameti, H ; Mafakheri, Z ; Sharif University of Technology
Springer International Publishing
2015
Abstract
Using a proper distribution function for speech signal or for its representations is of crucial importance in statistical-based speech processing algorithms. Although the most commonly used probability density function (pdf) for speech signals is Gaussian, recent studies have shown the superiority of super-Gaussian pdfs. A large research effort has focused on the investigation of a univariate case of speech signal distribution; however, in this paper, we study the multivariate distributions of speech signal and its representations using the conventional distribution functions, e.g., multivariate Gaussian and multivariate Laplace, and the copula-based multivariate distributions as candidates....
Hidden markov model-based speech enhancement using multivariate laplace and gaussian distributions
, Article IET Signal Processing ; Volume 9, Issue 2 , 2015 , Pages 177-185 ; 17519675 (ISSN) ; Veisi, H ; Sameti, H ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In this paper, statistical speech enhancement using hidden Markov model (HMM) is studied and new techniques for applying non-Gaussian distributions are proposed. The superiority of using non-Gaussian distributions in online adaptive noise suppression algorithms has been proven; however, in this study, this approach is formulated in an HMM-based mean-square error estimator (MMSE) estimator in which a priori models are trained in an off-line manner. In addition, an analytical study of using different distributions other than autoregressive (AR) Gaussian distribution, such as Laplace, is presented in order to construct an accurate HMM as a priori model for discrete Fourier transform and...
Performance comparison of a novel DFT-based method and conventional channel coding methods for clipping noise cancellation in OFDM systems
, Article IEICE Transactions on Communications ; Volume E87-B, Issue 4 , 2004 , Pages 1034-1036 ; 09168516 (ISSN) ; Azmi, P ; Marvasti, F ; Sharif University of Technology
Institute of Electronics, Information and Communication, Engineers, IEICE
2004
Abstract
A DFT-Based method (DBM) has been proposed to compensate for the performance degradation caused by clipping distortion at the expense of bandwidth expansion. On the other hand, in any communication systems, conventional channel coding methods can be employed to improve performance. In this letter, the performance of the DBM and the channel coding methods (CCM) are compared. Furthermore, we introduce a hybrid system which outperforms both the DBM and the CCM
A new method for using a psychoacoustic model with patchwork audio watermarking in DFT domain
, Article 34th Annual Conference of the IEEE Industrial Electronics Society, IECON 2008, Orlando, FL, 10 November 2008 through 13 November 2008 ; 2008 , Pages 1822-1827 ; 9781424417667 (ISBN) ; Tabandeh, M ; Sharif University of Technology
IEEE Computer Society
2008
Abstract
This paper presents a novel patchwork audio watermarking scheme with a psychoacoustic model of HAS in DFT domain that has significantly higher detection robustness compared to standard and modified patchwork watermarking algorithms. In addition, watermark is perceptually tuned, so that its embedding is transparent. The proposed algorithm can be used for transmitting hidden data through telephone channel. Experimental results show that the proposed watermarking algorithm is sustainable against compression algorithms such as MP3, LPF, resampling, requantization and AWGN attacks. © 2008 IEEE
Significant pathological voice discrimination by computing posterior distribution of balanced accuracy
, Article Biomedical Signal Processing and Control ; Volume 73 , 2022 ; 17468094 (ISSN) ; Jahed, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The ability to speak lucidly plays a key role in social relations. Consequently, the role of the larynx is quite important, and timely diagnosis of laryngeal diseases has proved to be crucial. In this study, a simple computational model for inverse of speech production model is employed to extract the glottal waveform using speech signal. This waveform has useful information about vocal folds performance in terms of providing evidence for distinguishing pathological disorders. Furthermore, obtaining the significance of classification results is important, because it leads to reliable inferences. This study utilizes the sustained vowel sound /a/ and a well-referenced database, namely MEEI. In...
OFDM pilot allocation for sparse channel estimation
, Article Eurasip Journal on Advances in Signal Processing ; Volume 2012, Issue 1 , March , 2012 ; 16876172 (ISSN) ; Amini, A ; Marvasti, F ; Sharif University of Technology
2012
Abstract
In communication systems, efficient use of the spectrum is an indispensable concern. Recently the use of compressed sensing for the purpose of estimating orthogonal frequency division multiplexing (OFDM) sparse multipath channels has been proposed to decrease the transmitted overhead in form of the pilot subcarriers which are essential for channel estimation. In this article, we investigate the problem of deterministic pilot allocation in OFDM systems. The method is based on minimizing the coherence of the submatrix of the unitary discrete fourier transform (DFT) matrix associated with the pilot subcarriers. Unlike the usual case of equidistant pilot subcarriers, we show that non-uniform...
Discrete Fourier Transform based approach to forecast monthly peak load
, Article Asia-Pacific Power and Energy Engineering Conference, APPEEC ; 2011 ; 21574839 (ISSN) ; 9781424462551 (ISBN) ; Ranjbar, A. M ; IEEE Power and Energy Society (PES); Chinese Society for Electrical Engineering (CSEE); State Grid Corporation of China; China Southern Power Grid; Wuhan University ; Sharif University of Technology
Abstract
This paper presents a new method in order to predict the monthly electricity peak load of a country based on the prediction of Discrete Fourier Transform (DFT) of monthly peak electricity demand variation using the ARIMA methodology. For validation, the result of this method was used to predict monthly peak load variation of the recent two years in Iranian national grid. The primary goal of this article is to show the application and implementation of Discrete Fourier Transform to predict monthly variation of electricity peak load in national electric power systems. Furthermore, it is elaborated to demonstrate the benefits and shortcomings of DFT approach comparing to the commonly used...
Bounds on discrete fourier transform of random mask
, Article 2017 12th International Conference on Sampling Theory and Applications, SampTA 2017, 3 July 2017 through 7 July 2017 ; 2017 , Pages 327-330 ; 9781538615652 (ISBN) ; Marvasti, F ; Anbarjafari, G ; Kivinukk, A ; Tamberg, G ; Sharif University of Technology
Abstract
This paper proposes some bounds on maximum of magnitude of a random mask in Fourier domain. The random mask is used in random sampling scheme. Having a bound on the maximum value of a random mask in Fourier domain is very useful for some iterative recovery methods that use thresholding operator. In this paper, we propose some different bounds and compare them with the empirical examples. © 2017 IEEE
Realization of constant envelope OFDM using quantization and CPM technique
, Article AEU - International Journal of Electronics and Communications ; Volume 80 , 2017 , Pages 172-178 ; 14348411 (ISSN) ; Mohammadi, A ; Afrashteh, N ; Sanjaroonpouri, V ; Sharif University of Technology
Abstract
Orthogonal frequency division multiplexing (OFDM) is used in many wireless communication. The important drawback of this modulation is its high peak-to-average power ratio (PAPR). In this paper, a new modulation scheme of constant-envelope OFDM (CE-OFDM) is proposed. This scheme uses a combination of OFDM, quantizer and continuous phase modulation (CPM) to achieves 0 dB PAPR. The statistical signatures of signals, based on system parameters such as the length of discrete Fourier transform (DFT) and the number of quantization levels are presented. There are two sources of noise in proposed CE-OFDM scheme: quantization noise and channel noise. The theoretical analysis of these noises is...
Experimental investigation of the leading edge vortex formation on unsteady boundary layer
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 18 , 2018 , Pages 3263-3280 ; 09544062 (ISSN) ; Abdollahi, R ; Azimizadeh, E ; Sharif University of Technology
Abstract
Extensive experimental studies have been performed to investigate the unsteady boundary layer behavior over a plunging wind turbine blade section. The studies have been undertaken at various combinations of reduced frequencies, Reynolds numbers, and locations. A boundary layer rake has been carefully manufactured and utilized for velocity measurements inside the unsteady boundary layer. The measurement has been conducted in pre-static stall conditions. The reduced frequency and free stream velocity have varied from 0.005 to 0.1, and 30 to 60 m/s, respectively. To cover all possible scenarios, the streamwise positions of measurements have been chosen to be in favorable (x/c = 0.37), almost...
Involving computer science students in real-world problems
, Article ITI 2008 30th International Conference on Information Technology Interfaces, Cavtat/Dubrovnik, 23 June 2008 through 26 June 2008 ; 2008 , Pages 569-573 ; 13301012 (ISSN) ; 9789537138127 (ISBN) ; Shirali ShahrezaMohammad, M ; Sharif University of Technology
2008
Abstract
Today, many students are study computer science. Although they study different courses, they rarely do homework or projects related to real world problems. In this paper, we design a project to show some of the problems which are occured during implementing a real word project to the students. In this project, the students are asked to implement the FFT (Fast Fourier Transform) algorithm on a personal computer and then port the program to a smartphone using J2ME (Java 2 Micro Edition) programming language. By doing this project, the undergraduate computer science students will become familiar with the limitations of small devices such as smartphones. They also learn the process of porting a...
Elastic field of a nano disk shape defect in an fcc thin film
, Article 2007 2nd IEEE International Conference on Nano/Micro Engineered and Molecular Systems, IEEE NEMS 2007, Bangkok, 16 January 2007 through 19 January 2007 ; 2007 , Pages 142-146 ; 1424406102 (ISBN) ; 9781424406104 (ISBN) ; Pahlevani, L ; Hamed, E ; Sharif University of Technology
2007
Abstract
In this paper, we develop a theory to study the nano defects of various geometries within thin films. The considered thin films have face centered cubic (fee) structure. The eigenstrain method is combined with the long-range Sutton-Chen (SC) inter-atomic potential function which is appropriate for fee crystals. The disturbance caused by a defect in a thin film is determined from the equilibrium equation using the discrete Fourier transformation. The disturbed field is also determined using three dimensional (3D) Molecular Dynamics (MD) simulation in which the constant NVT ensemble is applied to the atomic system. For illustration, the problem of nano disk shape defect in thin film is studied...
Robust decoding of DFT-based error-control codes for impulsive and additive white Gaussian noise channels
, Article IEE Proceedings: Communications ; Volume 152, Issue 3 , 2005 , Pages 265-271 ; 13502425 (ISSN) ; Marvasti, F ; Sharif University of Technology
2005
Abstract
A novel decoding technique for DFT-based error control codes that is robust against quantisation noise and additive white Gaussian noise is proposed. The algorithm simultaneously determines the number and the positions of the corrupted samples. In contrast to the conventional decoding technique, the proposed decoding method is stable in the presence of both quantisation noise and additive white Gaussian noise. © IEE, 2005
FFT-based fast Reed-Solomon codes with arbitrary block lengths and rates
, Article IEE Proceedings: Communications ; Volume 152, Issue 2 , 2005 , Pages 151-156 ; 13502425 (ISSN) ; Marvasti, F ; Sharif University of Technology
2005
Abstract
By puncturing the Reed-Solomon codes with the block lengths of 2 m, it is possible to design systematic and nonsystematic codes with arbitrary block lengths and rates that can be decoded using FFT. Because the Reed-Solomon (RS) codes are maximum distance separable (MDS), the resultant codes keep this property as well. The codes are constructed over prime fields as opposed to the conventional practice of extension fields, and hence additions and multiplications are simple mod operations and there is no need to use polynomials and look-up tables. © IEE, 2005
CIROLS: Codec independent recovery of lost speech packets
, Article 2007 9th International Symposium on Signal Processing and its Applications, ISSPA 2007, Sharjah, 12 February 2007 through 15 February 2007 ; 2007 ; 1424407796 (ISBN); 9781424407798 (ISBN) ; Manzuri Shalmani, M. T ; Aghatabar, M. M ; Sharif University of Technology
2007
Abstract
In this paper, we have focused on finding an error resilient method for discontinuity-less transmission of speech signals in the internet. Our proposed method creates artificial correlation between speech samples that pre-distorts the speech signal. The receiver uses this correlation to reconstruct the lost speech packets. A discrete Fourier transform (DFT)-based speech enhancement technique is designed for the reduction of the processing error in the recovered speech caused by the speech codecs. The SegSNR results show the superiority of our proposed method over a recently proposed speech enhancement technique. ©2007 IEEE