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    Classification of normal and dysphagic swallows by acoustical means

    , Article IEEE Transactions on Biomedical Engineering ; Volume 51, Issue 12 , 2004 , Pages 2103-2112 ; 00189294 (ISSN) Lazareck, L. J ; Moussavi, Z. M. K ; Sharif University of Technology
    This paper proposes a noninvasive, acoustic-based method to differentiate between individuals with and without dysphagia or swallowing dysfunction. Swallowing sound signals, both normal and abnormal (i.e., at risk of some degree of dysphagia) were recorded with accelerometers over the trachea. Segmentation based on waveform dimension trajectory (a distance-based technique) was developed to segment the nonstationary swallowing sound signals. Two characteristic sections emerged, Opening and Transmission, and 24 characteristic features were extracted and subsequently reduced via discriminant analysis. A discriminant algorithm was also employed for classification, with the system trained and... 

    Analysis of Effect of Parametric Oscillation in Phase Noise Degradation in Frequency Multipliers

    , Ph.D. Dissertation Sharif University of Technology Ahmadi, Arash (Author) ; Banai, Ali (Supervisor)
    Variation of the input driving power can cause in some varactor and BJT frequency multipliers parametric instability. If parametric oscillations are present in the circuit, output phase noise of the multiplier degrades remarkably in some specific driving levels. Phase noise of the varactor and BJT multiplier is calculated by the conversion matrix method using generalized nodal analysis. By the conversion method the phase noise degradation can be predicted precisely. In the calculation of phase noise the effect of the noise sources that are modulated by the large signal drive and the conversion of components of the internal noise sources of the device to the output spectrum due to circuit... 

    Dynamic modeling of a wind turbine with brushless doubly fed induction generator

    , Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 490-494 ; 9781467301114 (ISBN) Tohidi, S ; Zolghadri, M. R ; Oraee, H ; Oraee, A ; Sharif University of Technology
    Brushless Doubly Fed Induction Generator (BDFIG) has been recently proposed to be used in variable speed wind turbines. This paper intends to investigate the influence of certain model simplifications to obtain a reduced-order model of a wind turbine with BDFIG suitable for transient studies. To achieve this goal, small signal analysis is performed for a recently manufactured 250 kVA BDFIG to obtain system modes and their participation factors. Identifying highly damped modes, influences of neglecting dynamics of their participated states are studied through time-domain simulation in MATLAB/Simulink  

    Time-domain signal analysis using adaptive notch filter

    , Article IEEE Transactions on Signal Processing ; Volume 55, Issue 1 , 2007 , Pages 85-93 ; 1053587X (ISSN) Mojiri, M ; Karimi Ghartemani, M ; Bakhshai, A ; Sharif University of Technology
    Noise reduction and signal decomposition are among important and practical issues in time-domain signal analysis. This paper presents an adaptive notch filter (ANF) to achieve both these objectives. For noise reduction purpose, the proposed adaptive filter successfully extracts a single sinusoid of a possibly time-varying nature from a noise-corrupted signal. The paper proceeds with introducing a chain of filters which is capable of estimating the fundamental frequency of a signal composed of harmonically related sinusoids, and of decomposing it into its constituent components. The order of differential equations governing this algorithm is 2n + 1, where n is the number of constituent... 

    A novel two frequency MTI radar

    , Article Proceedings of the IEEE Radar Conference, Philadelphia, PA, 26 April 2004 through 29 April 2004 ; 2004 , Pages 589-591 Esfandyarpour, H ; Norouzi, Y ; Nayebi, M. M ; Sharif University of Technology
    The paper introduced a new design for two-frequency MTI radar is introduced. The suggested system can change its frequencies, in each pulse. Therefore, the system is very resistive to electronic war. The analytical results of our calculation show that the system has very high blind speed and in realistic situations, it increases signal to noise ratio, although it widens clutter bandwidth and detects some spurious targets  

    Discrete multitone modulation with biorthogonal filter bank

    , Article 3rd IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2003, 14 December 2003 through 17 December 2003 ; 2003 , Pages 34-37 ; 0780382927 (ISBN); 9780780382923 (ISBN) Maleki, A ; Shamsollahi, M. B ; Abdi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Discrete multitone (DMT) modulation is used for the efficient transmission of data over nonideal channels. By nonideal channel, we mean that the channel with the frequency response is not flat. Also the noise is present in this kind of channel. In recent years, optimization of filter banks for the DMT systems is considered. Recent researches focused on the orthonormal filter banks have shown that the principal component filter bank (PCFB) is optimal for this application. We focus on one class of biorthogonal filter banks and find the optimum solution for this class. We also have shown that the performance of this structure is better than the optimum orthonormal filter bank. © 2003 IEEE  

    Feature extraction from optimal time-frequency and time-scale transforms for the classification of the knee joint vibroarthrographic signals

    , Article 3rd IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2003, 14 December 2003 through 17 December 2003 ; 2003 , Pages 709-712 ; 0780382927 (ISBN); 9780780382923 (ISBN) Eskandari, H ; Shamsollahi, M. B ; Rahimi, A ; Behzad, M ; Afkari, P ; Zamani, E. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    In this study knee joint vibroarthrographic (VAG) signals are recorded during active knee movements, which are essentially non-stationary. Because of this nature, common frequency methods are unable to represent the signals, accurately. Both time-frequency and time-scale transforms are used in this research which are good tools for studying non-stationary signals. By optimizing the utilized transforms, it was concluded that the wavelet packet, having the ability of multiresolutional analysis, is a more promising method to extract features from the VAG signals. The performance of different feature extraction techniques were compared by using three new recorded and extensive databases,... 

    Composite pnlms & nlms adaptation: A new method for network echo cancellation

    , Article 14th International Conference on Digital Signal Processing, DSP 2002, 1 July 2002 through 3 July 2002 ; Volume 2 , 2002 , Pages 757-760 ; 0780375033 (ISBN) Nekuii, M ; Atarodi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2002
    This paper describes an improved version of the recently proposed fast converging algorithm. PNLMS, for network echo cancellers. We have introduced a simple analysis of the PNLMS convergence behavior to show why after the fast initial convergence, it slows down. Also, the method has been worked out to overcome this deficiency is presented. Improvement is shown by several simulation results. © 2002 IEEE  

    Generalizability of trunk muscle EMG and spinal forces

    , Article IEEE Engineering in Medicine and Biology Magazine ; Volume 20, Issue 6 , 2001 , Pages 72-81 ; 07395175 (ISSN) Sparto, P. J ; Parnianpour, M ; Sharif University of Technology
    The generalizability of trunk muscle EMG and spinal loading estimates obtained from an EMG-assisted biomechanical model was assessed over three occasions and three repetitions. The greatest sources of variability consisted of the intersubject differences and the interaction between subject and occasion. The ID (reliability coefficient) was less for trunk muscle activity compared with estimates of anteroposterior shear force, compression force, and gain computed from the biomechanical model. In order to obtain an ID of 0.8, we recommend five testing occasions for submaximal EMG measurements and three testing occasions for biomechanical estimates. Reproducible estimates of maximal trunk... 

    A two dimensional wavelet packet approach for ECG compression

    , Article 6th International Symposium on Signal Processing and Its Applications, ISSPA 2001, Kuala Lumpur, 13 August 2001 through 16 August 2001 ; Volume 1 , 2001 , Pages 226-229 ; 0780367030 (ISBN); 9780780367036 (ISBN) Moghaddam, A. R. A ; Nayebi, K ; Sharif University of Technology
    IEEE Computer Society  2001
    An improved compression algorithm for ECG signals is presented using temporal alignment of beats and 2-D wavelet packet transform (WPT). This 2-D transform based approach utilizes the fact that the electrocardiogram (ECG) signals generally show two types of correlation, namely correlation between subsequent samples within each ECG cycle (intrabeat) and correlation between subsequent cycles (interbeat). One simple compression algorithm in the 2-D WPT domain, which is applied to some records in the MIT-BIH arrhythmia database shows lower percent root mean square difference (PRD) than 1-D wavelet based compression methods for the same compression ratio (CR). © 2001 IEEE  

    Peak to mean envelope power ratio of oversampled OFDM signals: An analytical approach

    , Article International Conference on Communications (ICC2001), Helsinki, 11 June 2000 through 14 June 2000 ; Volume 5 , 2001 , Pages 1476-1480 ; 05361486 (ISSN) Sharif, M ; Khalaj, B. H ; Sharif University of Technology
    Orthogonal frequency division multiplexing (OFDM) has a large peak to mean envelope power ratio (PMEPR), which can result in significant signal distortion in presence of nonlinear amplifiers. In this paper, we will show that peak of the continuous envelope of OFDM signal can be bounded by maximum of corresponding oversampled sequence. This fact is then used as the corner stone of our study in two parts. In the first part, statistical analysis is used to find probability upper bound for complementary cumulative distribution function of PMEPR. It is also proven that for large number of subcarriers, only one redundant bit is necessary to limit PMEPR within %10 of its maximum value. In the... 

    Compensating for distortions in interpolation of two-dimensional signals using improved iterative techniques

    , Article ICT 2010: 2010 17th International Conference on Telecommunications, 4 April 2010 through 7 April 2010 ; April , 2010 , Pages 929-934 ; 9781424452477 (ISBN) ParandehGheibi, A ; Rahimian, M. A ; Akhaee, M. A ; Ayremlou, A ; Marvasti, F ; Sharif University of Technology
    In this paper we extended a previously investigated modular method that is designed to compensate for interpolation distortions of one-dimensional signals, to two dimensions (2-D). Next the proposed 2-D modular technique was applied in an iterative fashion and was shown through both simulations and theoretical analyses to enhance the convergence of the iterative technique. In fact, with only a few modules we were able to achieve drastic improvements in signal reconstruction, and with a much less computational complexity. Moreover, both the simulations and the theoretical analysis confirmed the robustness of the proposed scheme against additive noise  

    Toward naturalness in narrow-band speech compression

    , Article 2000 IEEE Internatinal Conference on Multimedia and Expo (ICME 2000), New York, NY, 30 July 2000 through 2 August 2000 ; Issue I/MONDAY , 2000 , Pages 440-443 Ghaemmaghami, S ; Sharif University of Technology
    This paper addresses a new mixed model for characterizing LPC excitation on a 3-band basis through analyzing harmonic structure of the residual signal. In addition, a sub-frame based analysis is developed for detecting both aperiodic pulses and noisy signals, which plays a major role in reduction of perceptual errors introduced by some certain consonants. Preliminary results show that near natural speech is achieved at 1050 bps, allocated to the excitation parameters, suggesting superiority of the proposed coding scheme to the MELP-2400 coding standard, in the sense of perceptual quality of reconstructed speech  

    Estimation of flow rates of individual phases in an oil-gas-water multiphase flow system using neural network approach and pressure signal analysis

    , Article Flow Measurement and Instrumentation ; Volume 66 , 2019 , Pages 28-36 ; 09555986 (ISSN) Bahrami, B ; Mohsenpour, S ; Shamshiri Noghabi, H. R ; Hemmati, N ; Tabzar, A ; Sharif University of Technology
    Elsevier Ltd  2019
    Up until now, different methods, including; flow pressure signal, ultrasonic, gamma-ray and combination of them with the neural network approach have been proposed for multiphase flow measurement. More sophisticated techniques such as ultrasonic waves and electricity, as well as high-cost procedures such as gamma waves gradually, can be replaced by simple methods. In this research, only flow parameters such as temperature, viscosity, pressure signals, standard deviation and coefficients of kurtosis and skewness are used as inputs of an artificial neural network to determine the three phase flow rates. The model is validated by the field data which were obtained from separators of two oil... 

    Piecewise affine large signal modeling of PFC rectifiers

    , Article 2007 IEEE International Symposium on Industrial Electronics, ISIE 2007, Caixanova - Vigo, 4 June 2007 through 7 June 2007 ; 2007 , Pages 3362-3366 ; 1424407559 (ISBN); 9781424407552 (ISBN) Tahami, F ; Molla Ahmadian, H ; Sharif University of Technology
    A problem associated with modeling and control of the power factor correction rectifiers is that the ac variations in duty cycle, as well as in the ac input voltage and current are not small, and hence the traditional small signal analysis is not justified. Nonetheless, the low-frequency components of the converter can be modeled via the circuit averaging technique, but the resulting equivalent circuits are, in general, time varying and highly nonlinear. Nonlinear stability analysis methods are not appropriate for analysis and control design of such complicated circuits. In this paper a piecewise affine approximation is introduced for modeling of switching circuits. This approach makes the... 

    Large signal analysis of double quantum well transistor laser

    , Article Optical and Quantum Electronics ; Volume 45, Issue 5 , 2013 , Pages 389-399 ; 03068919 (ISSN) Horri, A ; Faez, R ; Sharif University of Technology
    In this paper, we present an analytical model for the large-signal analysis of the double quantum well (DQW) transistor laser. Our model is based on solving the continuity equation and the rate equations which incorporate the virtual states as a conversion mechanism. By using the presented model, effects of barrier width on DQW transistor laser static and dynamic performances are investigated. Also the static and dynamic responses of DQW transistor lasers are compared with single quantum well ones. Simulation results are in agreement with the numerical and experimental results reported by other researchers  

    Two-dimensional random projection

    , Article Signal Processing ; Volume 91, Issue 7 , 2011 , Pages 1589-1603 ; 01651684 (ISSN) Eftekhari, A ; Babaie-Zadeh, M ; Abrishami Moghaddam, H ; Sharif University of Technology
    As an alternative to adaptive nonlinear schemes for dimensionality reduction, linear random projection has recently proved to be a reliable means for high-dimensional data processing. Widespread application of conventional random projection in the context of image analysis is, however, mainly impeded by excessive computational and memory requirements. In this paper, a two-dimensional random projection scheme is considered as a remedy to this problem, and the associated key notion of concentration of measure is closely studied. It is then applied in the contexts of image classification and sparse image reconstruction. Finally, theoretical results are validated within a comprehensive set of... 

    Power spectrum and FFT-based signal analysis in turbulence measurements

    , Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 275-278 ; 2010376X (ISSN) Dehghan Manshadi, M ; Tamadonfar, P ; Soltani, M. R ; Ghorbanian, K ; Masdari, M ; Sharif University of Technology
    In this research, the employment of an innovative but simple and cost effective method for turbulent reduction in a low speed wind tunnel is investigated and the effect of this turbulence reduction on the Power Spectrum and FFT-Based signals that obtained from Hot-wire Anemometry is studied. These terms represents the amount of power contained in the signals. Several situations are studied in this paper. One of these situations is when there are four screens in the settling chamber of the wind tunnel and after that by adding the trip strip in the contraction region of the wind tunnel the tests were repeated. In the next stage, three screens were removed from the settling chamber of the wind... 

    On the cramer-rao bound for estimating the mixing matrix in noisy sparse component analysis

    , Article IEEE Signal Processing Letters ; Volume 15 , 2008 , Pages 609-612 ; 10709908 (ISSN) Zayyani, H ; Babaie Zadeh, M ; Haddadi, F ; Jutten, C ; Sharif University of Technology
    In this letter, we address the theoretical limitations in estimating the mixing matrix in noisy sparse component analysis (SCA) for the two-sensor case. We obtain the Cramer-Rao lower bound (CRLB) error estimation of the mixing matrix. Using the Bernouli-Gaussian (BG) sparse distribution, and some simple assumptions, an approximation of the Fisher information matrix (FIM) is calculated. Moreover, this CRLB is compared to some of the main methods of mixing matrix estimation in the literature. © 2008 IEEE  

    Adaptive sparse source separation with application to speech signals

    , Article 2007 IEEE International Conference on Signal Processing and Communications, ICSPC 2007, Dubai, 24 November 2007 through 27 November 2007 ; 2007 , Pages 640-643 ; 9781424412365 (ISBN) Azizi, E ; Mohimani, G. H ; Babaie Zadeh, M ; Sharif University of Technology
    In this paper, a sparse component analysis algorithm is presented for the case in which the number of sources is less than or equal to the number of sensors, but the channel (mixing matrix) is time-varying. The method is based on a smoothed l0 norm for the sparsity criteria, and takes advantage of the idea that sparsity of the sources is decreased when they are mixed. The method is able to separate synthetic and speech data, which require very weak sparsity restrictions. It can separate up to 50 mixed signals while being adaptive to channel variation and robust against noise. © 2007 IEEE