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    Fuzzy wavelet and contourlet based contrast enhancement

    , Article 28th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'06, New York, NY, 30 August 2006 through 3 September 2006 ; 2006 , Pages 6635-6638 ; 05891019 (ISSN); 1424400325 (ISBN); 9781424400324 (ISBN) Nezhadarya, E ; Shamsollahi, M. B ; Sayadi, O ; Sharif University of Technology
    2006
    Abstract
    This paper presents a fuzzy approach for contrast enhancement, based on two multi-scale transforms, namely wavelet and contourlet transforms. Separability and nondirectionality of conventional 2D wavelet transform, makes it unsuitable for sparsely representation of curve or line shaped image objects. On the other hand, the contourlet transform is a good alternative for this purpose. In this paper, coefficient enhancement, both in wavelet and contourlet spaces, is carried out by making use of simple fuzzy rules. These rules make the enhancement procedure more understandable and flexible. With this method, the knowledge and experience of the expert from the distribution of the coefficients can... 

    ECG segmentation and fiducial point extraction using multi hidden Markov model

    , Article Computers in Biology and Medicine ; Volume 79 , 2016 , Pages 21-29 ; 00104825 (ISSN) Akhbari, M ; Shamsollahi, M. B ; Sayadi, O ; Armoundas, A. A ; Jutten, C ; Sharif University of Technology
    Elsevier Ltd 
    Abstract
    In this paper, we propose a novel method for extracting fiducial points (FPs) of electrocardiogram (ECG) signals. We propose the use of multi hidden Markov model (MultiHMM) as opposed to the traditional use of Classic HMM. In the MultiHMM method, each segment of an ECG beat is represented by a separate ergodic continuous density HMM. Each HMM has different state number and is trained separately. In the test step, the log-likelihood of two consecutive HMMs is compared and a path is estimated, which shows the correspondence of each part of the ECG signal to the HMM with the maximum log-likelihood. Fiducial points are estimated from the obtained path. For performance evaluation, the Physionet...