Search for: signal-to-noise
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    An improved spectral subtraction speech enhancement system by using an adaptive spectral estimator

    , Article Canadian Conference on Electrical and Computer Engineering 2005, Saskatoon, SK, 1 May 2005 through 4 May 2005 ; Volume 2005 , 2005 , Pages 261-264 ; 08407789 (ISSN) Ayat, S ; Manzuri, M. T ; Dianat, R ; Kabudian, J ; Sharif University of Technology
    Spectral subtraction is one of the most famous and common-used methods for speech enhancement. The main weakness of this method is the production of an annoying noise called musical noise. In this paper, we have reduced the musical noise and improved the quality of enhanced speech by increasing the accuracy of the system spectral estimator. This method is useful for speech enhancement systems in which the speech signal is degraded by stationary or near-stationary noises. Different experimental results in different SNRs confirmed the better performance of our system from both objective and subjective views, which means better quality and more SNR improvement. © 2005 IEEE  

    Asymptotic eigenvectors, topological patterns and recurrent networks

    , Article Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science ; Volume 14, Issue 2 , 2013 , Pages 95-100 ; 14549069 (ISSN) Bahraini, A ; Sharif University of Technology
    The notions of asymptotic eigenvectors and asymptotic eigenvalues are defined. Based on these notions a special probability rule for pattern selection in a Hopfield type dynamics is introduced. The underlying network is considered to be a d-regular graph, where d is an integer denoting the number of nodes connected to each neuron. It is shown that as far as the degree d is less than a critical value dc, the number of stored patterns with m μ = O(1) can be much larger than that in a standard recurrent network with Bernouill random patterns. As observed in [4] the probability rule we study here turns out to be related to the spontaneous activity of the network. So our result might be an... 

    Signal and noise analysis in sliced model of a fet mixer

    , Article 2nd International Conference on Microwave and Millimeter Wave Technology, ICMMT 2000, 14 September 2000 through 16 September 2000 ; 2000 , Pages 5-8 ; 0780357434 (ISBN); 9780780357433 (ISBN) Moradi, G ; Abdipour, A ; Ghorbani, A ; Farzaneh, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2000
    This paper presents nonlinear signal and noise analysis of a wide gate FET mixer. The study is performed using nonlinear sliced modeling. The FET is taken into account as a distributed element and divided into several smaller pieces so that in each slice a lumped model can be applied. Calculation of passive and active elements of each slice is performed using proper scaling approach. For noise analysis, appropriate noise sources are added to the distributed circuit The wide gate FETs have been suggested for high power, wideband and high gain devices such as travelling wave amplifier. The nonlinear application is suggested for a novel device named travelling wave mixer. © 2000 IEEE  

    Compensating interpolation distortion by new optimized modular method

    , Article 2011 18th International Conference on Telecommunications, ICT 2011 ; 2011 , Pages 346-350 ; 9781457700248 (ISBN) Ayremlou, A ; Tofighi, M ; Marvasti, F ; IBM Cyprus; University of Cyprus; Cyprus Tourism Organisation ; Sharif University of Technology
    A modular method was suggested before to recover a band limited signal from the sample and hold and linearly interpolated (or, in general, an nth-order-hold) version of the regular samples. In this paper a novel approach for compensating the distortion of any interpolation based on modular method has been proposed. In this method the performance of the modular method is optimized by adding only some simply calculated coefficients. This approach causes drastic improvement in terms of signal-to-noise ratios with fewer modules compared to the classical modular method. Simulation results clearly confirm the improvement of the proposed method and also its superior robustness against additive... 

    Achievable rate regions for many-to-one Gaussian interference channel with a fusion centre

    , Article IET Communications ; Volume 9, Issue 6 , April , 2015 , Pages 880-887 ; 17518628 (ISSN) Baianifar, M ; Behroozi, H
    Institution of Engineering and Technology  2015
    This paper considers a many-to-one Gaussian interference channel with a fusion centre (FC) where there is a K -user interference channel in which only one relay (receiver) faces interference while the remaining K-1 receivers are interference free. All the relays communicate information about their observed sequence to the FC through noiseless links at communication rate R0. First, by analysing traditional relaying schemes, i.e., Decode and Forward, Compress and Forward and Compute and Forward, three rate-regions for this setting are derived. Then, based on nested lattice codes, a new achievable rate-region is provided. Based on the proposed scheme, one can design a transmission scheme that... 

    Linear motion blur parameter estimation in noisy images using fuzzy sets and power spectrum

    , Article Eurasip Journal on Advances in Signal Processing ; Volume 2007 , 2007 ; 11108657 (ISSN) Ebrahimi Moghaddam, M ; Jamzad, M ; Sharif University of Technology
    Motion blur is one of the most common causes of image degradation. Restoration of such images is highly dependent on accurate estimation of motion blur parameters. To estimate these parameters, many algorithms have been proposed. These algorithms are different in their performance, time complexity, precision,and robustness in noisy environments. In this paper, we present a novel algorithm to estimate direction and length of motion blur,using Radon transform and fuzzy set concepts. The most important advantage of this algorithm is its robustness and precision in noisy images. This method was tested on a wide range of different types of standard images that were degraded with different... 

    Adaptive secure channel coding based on punctured turbo codes

    , Article IEE Proceedings: Communications ; Volume 153, Issue 2 , 2006 , Pages 313-316 ; 13502425 (ISSN) Payandeh, A ; Ahmadian, M ; Reza Aref, M ; Sharif University of Technology
    Both security and error control coding are very extensive subjects, each with a variety of sub-disciplines. A secure channel coding (joint encryption-channel coding) scheme provides both data secrecy and data reliability in one process to combat problems in an insecure and unreliable channel. In this paper, an adaptive secure channel coding scheme based on serial or parallel concatenated turbo codes is developed. Recent results indicate that the turbo principle delivers near-to-optimal strategies for the channel coding. Reliability and security are achieved by adapting the pseudo-random puncturing strategy to the conditions of the noisy channel. Simulation results show the relevance and... 

    Motion blur identification in noisy images using fuzzy sets

    , Article 5th IEEE International Symposium on Signal Processing and Information Technology, Athens, 18 December 2005 through 21 December 2005 ; Volume 2005 , 2005 , Pages 862-866 Moghaddam, M. E ; Jamzad, M ; Sharif University of Technology
    Motion blur is one of the most common blurs that degrades images. Restoration of such images are highly dependent to estimation of motion blur parameters. Many researchers have developed algorithms to estimate linear motion blur parameters. These algorithms are different in their performance, time complexity, precision and their robustness in noisy environments. In this paper we have presented a novel algorithm to estimate linear motion blur parameters such as direction and extend by using Radon transform to find direction and fuzzy set concepts to find its extend. The most benefit of this algorithm is its robustness and precision in noisy images. Our method was tested on a wide range of... 

    Bayesian denoising framework of phonocardiogram based on a new dynamical model

    , Article IRBM ; Volume 34, Issue 3 , 2013 , Pages 214-225 ; 19590318 (ISSN) Almasi, A ; Shamsollahi, M. B ; Senhadji, L ; Sharif University of Technology
    In this paper, we introduce a model-based Bayesian denoising framework for phonocardiogram (PCG) signals. The denoising framework is founded on a new dynamical model for PCG, which is capable of generating realistic synthetic PCG signals. The introduced dynamical model is based on PCG morphology and is inspired by electrocardiogram (ECG) dynamical model proposed by McSharry et al. and can represent various morphologies of normal PCG signals. The extended Kalman smoother (EKS) is the Bayesian filter that is used in this study. In order to facilitate the adaptation of the denoising framework to each input PCG signal, the parameters are selected automatically from the input signal itself. This... 

    General noise considerations of amplified photons in lightwave systems with optically bistable elements

    , Article Proceedings - 10th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2010, 12 September 2010 through 14 September 2010 ; 2010 , Pages 93-95 ; 9781424469970 (ISBN) Abediasl, H ; Naqavi, A ; Mehrany, K ; Mousavi, S. M ; Aliakbar, J ; Mousavi, S. M ; Sharif University of Technology
    An optical amplifier followed by a bistable element has been statistically analyzed before [1]. In this manuscript, output noise analysis represents, then signal to noise ratios (SNR) are calculated either for input or output. It will be shown that noise reduction, can be achieved by a proper selection of parameters  

    Gain ripple minimization in fiber Raman amplifiers based on variational method

    , Article Optics Communications ; Volume 281, Issue 6 , 2008 , Pages 1545-1557 ; 00304018 (ISSN) Bahrampour, A. R ; Ghasempour, A ; Rahimi, L ; Sharif University of Technology
    In this paper, the variational method is employed for minimizing the gain ripple of multi-wavelength fiber Raman amplifiers. The variance of gain spectrum of the fiber Raman amplifier is regarded as the cost function, restriction on total pump power and average gain is given as the constraints of the minimization problem. It is shown that the minimization problem with any necessary constraints on the pump powers, average gain and signal to noise ratio, is reduced to a two-point boundary value problem. The method gives the entire possible local and global solutions. The method is applied to different examples of fiber Raman amplifiers with different lengths from 25 km to 100 km and different... 

    Fast and high resolution statistical based algorithm for PCL radar detection in noisy environment

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 1259-1262 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Emadi, M ; Mousavi, M ; Granpayeh, A ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    This paper presents a new statistical based clean algorithm for multiple target detection in noisy environments. For this purpose the variance and average of the ambiguity function as the output of matched filter will be computed. This information used for separating the real targets from the false ones, in noisy environment and heavy clutter up to - 13 dB. © 2006 IEEE  

    A simple and fast analysis of SNR in non-coherent integrators

    , Article 2005 1st International Conference on Computers, Communications and Signal Processing with Special Track on Biomedical Engineering, CCSP 2005, Kuala Lumpur, 14 November 2005 through 16 November 2005 ; 2005 , Pages 5-9 ; 1424400112 (ISBN); 9781424400119 (ISBN) Esfandyarpour, R ; Norouzi, Y ; Parizi, K. B ; Esfandyarpour, H ; Nayebi, M. M ; Sharif University of Technology
    In this paper, an approximate analysis for SNR improvement factor in non-coherent integrators for communication channels is introduced. The SNR improvement factor and loss function of the non-coherent integrator are calculated. Our results are very simple and illustrative. Although calculations are with some approximations and therefore the results are not exact, but the error is negligible, as it is shown. © 2005 IEEE  

    A modified pressure-based algorithm to solve flow fields with shock and expansion waves

    , Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 46, Issue 5 , 2004 , Pages 497-504 ; 10407790 (ISSN) Darbandi, M ; Mokarizadeh, V ; Sharif University of Technology
    The use of collocated grid schemes in control-volume-based methods has resulted in developing different strategies for coupling mass and momentum governing equations. Defining two different velocity components at cell faces is one remedy to suppress the possible checkerboard problem in the solution domain. These velocity components are widely known as convected and convecting velocities which are normally used in the momentum and mass governing equations, respectively. However, the linearization of the nonlinear governing equations generates a number of lagged velocity components which must be carefully treated in a manner to preserve the conceptual definition of the convected and convecting... 

    Design optimisation of aluminium recycling processes using Taguchi technique

    , Article Journal of Materials Processing Technology ; Volume 127, Issue 1 , 2002 , Pages 96-106 ; 09240136 (ISSN) Khoei, A. R ; Masters, I ; Gethin, D. T ; Sharif University of Technology
    In this paper, a robust design method is developed for reducing cost and improving quality in aluminium recycling. An experimental investigation into the process parameter effects is presented to determine the optimum configuration of design parameters for performance, quality and cost. The Taguchi method is applied initially to plan a minimum number of experiments. Orthogonal array techniques are used to investigate the simultaneous variation of several parameters and the investigation of interactions between parameters. Matrix experiments using standard L4 and L9 orthogonal arrays are employed to evaluate the effects of parameters in recycling of aluminium dross and scrap materials. A... 

    Sparse representation-based super-resolution for diffusion weighted images

    , Article 21st Iranian Conference on Biomedical Engineering, ICBME ; 26-28 November , 2014 , pp. 12-16 ; ISBN: 9781479974177 Afzali, M ; Fatemizadeh, E ; Soltanian-Zadeh, H ; Sharif University of Technology
    Diffusion weighted imaging (DWI) is a non-invasive method for investigating the brain white matter structure. It can be used to evaluate fiber bundles in the brain. However, clinical acquisitions are often low resolution. This paper proposes a method for improving the resolution using sparse representation. In this method a non-diffusion weighted image (bO) is utilized to learn the patches and then diffusion weighted images are reconstructed based on the trained dictionary. Our method is compared with bilinear, nearest neighbor and bicubic interpolation methods. The proposed method shows improvement in terms of Peak Signal-to-Noise Ratio (PSNR) and Structural SIMilarity (SSIM)  

    Optimized compact-support interpolation kernels

    , Article IEEE Transactions on Signal Processing ; Volume 60, Issue 2 , November , 2012 , Pages 626-633 ; 1053587X (ISSN) Madani, R ; Ayremlou, A ; Amini, A ; Marvasti, F ; Sharif University of Technology
    In this paper, we investigate the problem of designing compact-support interpolation kernels for a given class of signals. By using calculus of variations, we simplify the optimization problem from an nonlinear infinite dimensional problem to a linear finite dimensional case, and then find the optimum compact-support function that best approximates a given filter in the least square sense (ℓ 2 norm). The benefit of compact-support interpolants is the low computational complexity in the interpolation process while the optimum compact-support interpolant guarantees the highest achievable signal-to-noise ratio (SNR). Our simulation results confirm the superior performance of the proposed kernel... 

    Fetal ECG extraction using πtucker decomposition

    , Article 2015 22nd International Conference on Systems, Signals and Image Processing - Proceedings of IWSSIP 2015, 10 September 2015 through 12 September 2015 ; 2015 , Pages 174-178 ; 9781467383530 (ISBN) Akbari, H ; Shamsollahi, M. B ; Phlypo, R ; Miah S ; Uus A ; Liatsis P ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    In this paper, we introduce a novel approach based on Tucker Decomposition and quasi-periodic nature of ECG signal for fetal ECG extraction from abdominal ECG mixture. We adapt variable periodicity constraint of the ECG components to main objective function of the Tucker Decomposition and shape it to matrix form in order to simply optimize the objective function. We form a 3rd order tensor by stacking the mixed multichannel ECG and reconstructed fetal and maternal subspaces using BSS methods in order to have the benefit of further artificial observations, and apply our proposed penalized decomposition on it. The proposed method is evaluated on synthetic and real datasets using the criteria... 

    Colour image steganography method based on sparse representation

    , Article IET Image Processing ; Volume 9, Issue 6 , 2015 , Pages 496-505 ; 17519659 (ISSN) Ahani, S ; Ghaemmaghami, S ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    The authors address the use of sparse representation to securely hide a message within non-overlapping blocks of a given colour image in the wavelet domain. All four sub-images of the two-dimensional wavelet transform of two colour bands are used for data embedding without affecting the image perceptibility. Bit error rate of hidden data extraction is reduced to zero by introducing a novel refinement procedure in the proposed algorithm. The refinement procedure introduced solves the hidden bit extraction errors caused by the rounding process, the overflows and the nature of approximation in sparse decomposition. Capacity of the proposed method is calculated using necessary conditions for... 

    A novel image hiding scheme using content aware seam carving method

    , Article ARES 2010 - 5th International Conference on Availability, Reliability, and Security, 15 February 2010 through 18 February 2010 ; Feb , 2010 , Pages 702-707 ; 9780769539652 (ISBN) Toony, Z ; Jamzad, M ; Sharif University of Technology
    In image hiding we embed a secret image into a cover image. In order to minimize the distortion of secret image, we presented a novel steganographic method based on content-aware seam carving. In this paper, we propose a new image hiding method in which, the secret image is initially classified based on image complexity measure. Then it is resized to an appropriate smaller size, but for having the important objects of the image in resized image we use seam carving method that resizes an image whereas the important content of it remains. By applying the seam carving, we have an image that is smaller than the original one, and then we hide it in a cover image. Obviously hiding a smaller secret...