Search for: frequency-domain-analysis
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    Design and Implementation of Time and Frequency Synchronization in LTE

    , Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 23, Issue 12 , January , 2015 , Pages 2970-2982 ; 10638210 (ISSN) Golnari, A ; Shabany, M ; Nezamalhosseini, A ; Gulak, G ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    A novel architecture for efficient time and frequency synchronization, applied to the long-term evolution (LTE) standard, is proposed. For symbol timing, we propose applying a symbol-folding method on top of the sign-bit reduction technique, leading to a novel algorithm for the cyclic prefix-type recognition in LTE. Following the symbol timing, the fractional carrier frequency offset is estimated and compensated using an adaptive gain loop, which allows for a high-accuracy compensation in a short interval. In the frequency domain, for cell search, we propose a sign-bit reduction technique on top of the matched filter method for the primary synchronization signal detection. In addition, we... 

    Performance evaluation of asynchronous multi-carrier code division multiple access for next-generation long-reach fibre optic access networks

    , Article IET Optoelectronics ; Volume 9, Issue 6 , 2015 , Pages 325-332 ; 17518768 (ISSN) Shoreh, M. H ; Beyranvand, H ; Salehi, J. A ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    In this study, the authors evaluate the performance of asynchronous optical multi-carrier code division multiple access (MC-CDMA) for intensity modulated/direct detection systems to be used in next-generation optical access networks. The proposed system employs Gold sequence in frequency-domain to provide asynchronous resource sharing. In long-reach passive optical networks, fibre impairments degradation to the performance of ordinary optical CDMA can be avoided by frequency-domain digital compensation methods in the proposed MC-CDMA. In comparison with orthogonal frequency division multiple access, peak-to-average power ratio in the proposed MC-CDMA is reduced and asynchronous resource... 

    Stockwell transform for epileptic seizure detection from EEG signals

    , Article Biomedical Signal Processing and Control ; Volume 38 , 2017 , Pages 108-118 ; 17468094 (ISSN) Kalbkhani, H ; Shayesteh, M. G ; Sharif University of Technology
    Epilepsy is the most common disorder of human brain. The goal of this paper is to present a new method for classification of epileptic phases based on the sub-bands of electroencephalogram (EEG) signals obtained from the Stockwell transform (ST). ST is a time-frequency analysis that not only covers the advantages of both short-time Fourier transform (FT) and wavelet transform (WT), but also overcomes their shortcomings. In the proposed method, at first, EEG signal is transformed into time-frequency domain using ST and all operations are performed in the new domain. Then, the amplitudes of ST in five sub-bands, namely delta (δ), theta (θ), alpha (α), beta (β), and gamma (γ), are computed. In... 

    Detection of inappropriate working conditions for the timing belt in internal-combustion engines using vibration signals and data mining

    , Article Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering ; Volume 231, Issue 3 , 2017 , Pages 418-432 ; 09544070 (ISSN) Khazaee, M ; Banakar, A ; Ghobadian, B ; Agha Mirsalim, M ; Minaei, S ; Jafari, S. M ; Sharif University of Technology
    SAGE Publications Ltd  2017
    Abnormal operating conditions for the timing belt can lead to cracks, fatigue, sudden rupture and damage to engines. In this study, an intelligent system was developed to detect and classify high-load operating conditions and high-temperature operating conditions for timing belts. To achieve this, vibration signals in normal operating conditions, high-load operating conditions and high-temperature operating conditions were collected. Time-domain signals were transformed to the frequency domain and the time-frequency domain using the fast Fourier transform method and the wavelet transform method respectively. In the data-mining stage, 25 statistical features were extracted from different... 

    Identification of the equivalent linear dynamics and controller design for an unmanned underwater vehicle

    , Article Ocean Engineering ; Volume 139 , 2017 , Pages 152-168 ; 00298018 (ISSN) Banazadeh, A ; Seif, M. S ; Khodaei, M. J ; Rezaie, M ; Sharif University of Technology
    Elsevier Ltd  2017
    This paper investigates the applicability of frequency-domain system identification technique to achieve the equivalent linear dynamics of an autonomous underwater vehicle for control design purposes. Frequency response analysis is performed on the nonlinear and coupled dynamics of the vehicle, utilizing the CIFER® software to extract a reduced-order model in the form of equivalent transfer functions. Advanced features such as chirp-z transform, composite window optimization, and conditioning are employed to achieve high quality and accurate frequency responses. A particular frequency-sweep input is implemented to the nonlinear simulation model to achieve pole-zero transfer functions for yaw... 

    Effect of whole-body vibration and sitting configurations on lumbar spinal loads of vehicle occupants

    , Article Computers in Biology and Medicine ; Volume 107 , 2019 , Pages 292-301 ; 00104825 (ISSN) Amiri, S ; Naserkhaki, S ; Parnianpour, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Whole-body vibration (WBV) has been identified as one of the serious risk factors leading to spinal disorders, particularly in professional drivers. Although the influential factors in this area have been investigated epidemiologically, finite element (FE) modeling can efficiently help us better understand the problem. In this study, a modified HYBRID III dummy FE model which was enhanced by detailed viscoelastic discs in the lumbar region was utilized to simulate the effect of WBV on lumbar spine loads. Spinal responses to the vertical sinusoidal vibrations of a generic seat were obtained and spinal injury risk factors were calculated. Effects of variation of excitation frequencies, three... 

    A novel numerical solution to the diffraction term in the KZK nonlinear wave equation

    , Article Proceedings of the 38th Annual Symposium of Ultrasonic Industry Association, UIA 2009, 23 March 2009 through 25 March 2009, Vancouver, BC ; 2009 ; 9781424464296 (ISBN) Hajihasani, M ; Farjami, Y ; Gharibzadeh, S ; Tavakkoli, J ; Sharif University of Technology
    Nonlinear ultrasound modeling is finding an increasing number of applications in both medical and industrial areas where due to high pressure amplitudes the effects of nonlinear propagation are no longer negligible. Taking nonlinear effects into account makes the ultrasound beam analysis more accurate in these applications. One of the most widely used nonlinear models for propagation of 3D diffractive sound beams in dissipative media is the KZK (Khokhlov, Kuznetsov, Zabolotskaya) parabolic nonlinear wave equation. Various numerical algorithms have been developed to solve the KZK equation. Generally, these algorithms fall into one of three main categories: frequency domain, time domain and... 

    Experimental and analytical model analysis of Babolsar's steel arch bridge

    , Article 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost, Porto, 16 July 2006 through 19 July 2006 ; 2006 , Pages 235-237 ; 0415403154 (ISBN); 9780415403153 (ISBN) Beygi, M. H. A ; Kazemi, M. T ; Lark, B ; Tabrizian, Z ; Sharif University of Technology
    Taylor and Francis/ Balkema  2006
    The paper presents the experimental and analytical model analysis of a steel-girder arch bridge. The field test is carried out by ambient vibration testing under traffic excitations. Both the peak picking method in the frequency domain and the stochastic subspace identification method in the time domain are used for the output-only model identification. A good agreement in identified frequencies has been found between the two methods. It is further demonstrated that the stochastic subspace method provides better mode shapes. The three-dimensional finite element models are constructed and an analytical model analysis is then performed to generate natural frequencies and mode shapes in the...