Search for: low-pass-filter
Total 22 records
A high-order compact finite-difference lattice Boltzmann method for simulation of steady and unsteady incompressible flows, Article International Journal for Numerical Methods in Fluids ; Vol. 75, Issue. 10 , 2014 , Pages 713-746 ; ISSN: 02712091 ; Ezzatneshan, E ; Sharif University of Technology
A high-order compact finite-difference lattice Boltzmann method (CFDLBM) is proposed and applied to accurately compute steady and unsteady incompressible flows. Herein, the spatial derivatives in the lattice Boltzmann equation are discretized by using the fourth-order compact FD scheme, and the temporal term is discretized with the fourth-order Runge-Kutta scheme to provide an accurate and efficient incompressible flow solver. A high-order spectral-type low-pass compact filter is used to stabilize the numerical solution. An iterative initialization procedure is presented and applied to generate consistent initial conditions for the simulation of unsteady flows. A sensitivity study is also...
Article Proceedings - 2011 UKSim 13th International Conference on Modelling and Simulation, UKSim 2011, 30 March 2011 through 1 April 2011, Cambridge ; 2011 , Pages 299-303 ; 9780769543765 (ISBN) ; Rahmati, A ; Babaie Zadeh, M ; Sharif University of Technology
This paper proposes an image watermarking scheme for copyright protection based on Independent Component Analysis (ICA). In the suggested scheme, embedding is carried out in cumulative form in spatial domain and ICA is used for watermark extraction. For extraction there is no need to access the original image or the watermark, and extraction is carried out only with two watermarked images. Experimental results show that the new method has better quality than famous methods , ,  in spatial or frequency domain and is robust against various attacks. Noise addition, resizing, low pass filtering, multiple marks, gray-scale reduction, rotation, JPEG compression, and cropping are some...
An ant-based rate allocation algorithm for media streaming in peer to peer networks: Extension to multiple sessions and dynamic networks, Article Journal of Network and Computer Applications ; Volume 34, Issue 1 , 2011 , Pages 327-340 ; 10848045 (ISSN) ; Salavati, A. H ; Pakravan, M. R ; Sharif University of Technology
In this paper, we introduce a novel algorithm for rate allocation in media streaming P2P networks where multimedia contents are distributed among network members and streamed toward any requesting peer. The proposed algorithm is based on ant-colony optimization. It is capable of handling network dynamism, which is an inherent property of unstructured P2P networks. Another advantage of our algorithm is its ability to get over uncertainties in network state information, particularly the rate of supplying peers that could happen due to lack of accurate measurements. In addition, the suggested method does not rely on any information about the topology of the network. We have investigated both...
Simulation of two-phase liquid-vapor flows using a high-order compact finite-difference lattice Boltzmann method, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 5 , November , 2015 ; 15393755 (ISSN) ; Ezzatneshan, E ; Sharif University of Technology
American Physical Society 2015
A high-order compact finite-difference lattice Boltzmann method (CFDLBM) is extended and applied to accurately simulate two-phase liquid-vapor flows with high density ratios. Herein, the He-Shan-Doolen-type lattice Boltzmann multiphase model is used and the spatial derivatives in the resulting equations are discretized by using the fourth-order compact finite-difference scheme and the temporal term is discretized with the fourth-order Runge-Kutta scheme to provide an accurate and efficient two-phase flow solver. A high-order spectral-type low-pass compact nonlinear filter is used to regularize the numerical solution and remove spurious waves generated by flow nonlinearities in smooth regions...
On application of high-order compact finite-difference schemes to compressible vorticity confinement method, Article Aerospace Science and Technology ; Volume 46 , October–November , 2015 , Pages 398-411 ; 12709638 (ISSN) ; Hejranfar, K ; Ebrahimi, M ; Sharif University of Technology
Elsevier Masson SAS 2015
The main goal of this study is to assess the application of high-order compact finite-difference schemes for the solution of the Euler equations in conjunction with the compressible vorticity confinement method on both uniform Cartesian and curvilinear grids. Here, the spatial discretization of the governing equations is performed by the fourth-order compact finite-difference scheme and the temporal term is discretized by the fourth-order Runge-Kutta method. To stabilize the numerical solution, appropriate dissipation terms are applied and a detail assessment is performed to study the effects of the values of confinement and dissipation coefficients on the solution to reasonably preserve the...
Article Signal Processing ; Volume 107 , February , 2015 , Pages 407-414 ; 01651684 (ISSN) ; Sharif University of Technology
In this paper, an effective way is proposed for reduction of oscillations in the response of dynamical systems. In this regard, it is analytically shown that the undesirable oscillations in the response of dynamical systems can be reduced using a simple input shaping fractional order filter. The effectiveness of the proposed fractional calculus based technique is numerically verified in reduction of oscillations in a mass-spring-damper system, a low-pass Chebyshev filter, and a PI-controlled two-mass drive system
Article Proceedings - 3rd International Symposium on Information Processing, ISIP 2010, 12 November 2010 through 14 November 2010, Qingdao ; 2010 , Pages 363-367 ; 9780769542614 (ISBN) ; Ghaemmaghami, S ; Sharif University of Technology
This paper proposes an image watermarking scheme for copyright protection based on Independent Component Analysis (ICA). In the suggested scheme, we divide the original image into blocks and use the ICA to project the image into a basis with its components as statistically independent as possible. The data embedding is carried out in cumulative form in the ICA basis and also the ICA is used for watermark extraction. The extraction process could be either non-blind, through a straightforward procedure, or blind, via a tricky method we propose. Experimental results show that the new method outperforms some well-known image watermarking methods , ,  in spatial or frequency domain and...
Article 2017 12th International Conference on Sampling Theory and Applications, SampTA 2017, 3 July 2017 through 7 July 2017 ; 2017 , Pages 552-555 ; 9781538615652 (ISBN) ; Shahsavari, S ; Marvasti, F ; Sharif University of Technology
In this paper, we will provide a comparison between uniform and random sampling for speech and music signals. There are various sampling and recovery methods for audio signals. Here, we only investigate uniform and random schemes for sampling and basic low-pass filtering and iterative method with adaptive thresholding for recovery. The simulation results indicate that uniform sampling with cubic spline interpolation outperforms other sampling and recovery methods. © 2017 IEEE
Ultra-low power frequency-shift keying demodulator based on injection-locking ring oscillator without using phase locked loop for wireless body area networks, Article Electronics Letters ; Volume 53, Issue 16 , 2017 , Pages 1148-1150 ; 00135194 (ISSN) ; Safarian, A ; Sharif University of Technology
An ultra-low power frequency-shift keying (FSK) demodulator based on injection-locking ring oscillator for wireless body area networks is presented. The proposed system uses the power-efficient injectionlocking ring oscillator (ILRO) to replace the LC oscillator which occupies much more area on chip with higher power consumption. In addition, through the ILRO, the frequency modulated input signal is converted to a full swing rectangular signal, which can be directly demodulated by a chain of down-conversion passive mixers, lowpass filters and a comparator. Power efficiency and simplicity of the proposed structure eliminate conventional FSK demodulator based on power-hungry phase locked...
Article 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 244-248 ; 9781509059638 (ISBN) ; Babamir, S. M ; Behmanesh, B ; Atarodi, S. M ; Sharif University of Technology
An active switched-capacitor 4-path bandpass filter suitable for multi-standard applications in ultra-high frequency (UHF) band with different channel bandwidths is designed and simulated in 0.18 μm CMOS technology. The baseband impedance of the filter is implemented as a second-order Gm-C low-pass filter which can be used to tune the channel bandwidth as well as the quality factor (Q) of the RF filter. The center frequency of the filter can be tuned from 100 MHz up to 1.5 GHz by changing the clock frequency applied to the filter while its bandwidth can be tuned by tuning impedance parameters in any center frequency. To do so, the baseband impedance utilizes a frequency dependent negative...
Article Signal, Image and Video Processing ; Volume 3, Issue 4 , 2009 , Pages 363-374 ; 18631703 (ISSN) ; Mirzaee, S. M. A ; Sharif University of Technology
This paper proposes a new method of estimating an orthogonal bounded spectrum wavelet from a given signal. The method is based on minimizing the distance of the wavelet and the given signal in the sense of the metric of the L2 space. In this method, the amplitude and phase of the mother wavelet are optimized simultaneously. The Lagrange multipliers technique is applied to consider the constraints due to the bounded spectrum wavelet and orthogonality conditions. The variational method reduced the optimal matching problem to the solution of a set of functional equations for the amplitude and phase of the optimal-matched bandlimited wavelet spectrum. Continuous functional equations are written...
M.Sc. Thesis Sharif University of Technology ; Atarodi,Mojtaba ; Sharifkhani, Mohammad
Delta-Sigma Analog-to-Digital converters have been positioned themselves as robust reliable converters so far. The magic Of extracting high resolutions from low bit ADC has made them popular between designers. Previously, the noise-shaping magic was used in high-resolution applications such as high-quality audio signal converters. However, as the technology scales and proceeds, these converters are approaching RF applications, too. Power and OSR trade-off limits this progress. To increase OSR in bandpass delta-sigma modulators, more power should be consumed to increase the quality factor of loop filters. In this thesis, a systematic approach has been utilized. An n-path filter is employed...
A robust short-circuit fault diagnosis for high voltage DC power supply based on multisensor data fusion, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; 2019 , Pages 659-664 ; 9781538692547 (ISBN) ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2019
Short-circuit fault (SCF) detection is mandatory in a high voltage DC power supply (HVPS) to prevent fatal damage. The majority of converters employ a single sensor to detect the SCF. This attribute increases the interference vulnerability of the fault detection (FD) system in the presence of noise. Therefore, miss detections and false alarms are possible to occur. Miss detections and false alarms are harmful catastrophes in most applications. A commonly used method to suppress the noise impacts is using a low-bandwidth low-pass filter. However, the use of the low-bandwidth low-pass filter reduces the speed of FD due to the filter delay. This paper proposes a fast FD algorithm based on...
Article 2019 International Vacuum Electronics Conference, IVEC 2019, 28 April 2019 through 1 May 2019 ; 2019 ; 9781538675342 (ISBN) ; Rahmanian, M ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2019
Vacuum tubes are widely used for various applications. These vacuum tubes are supplied by high voltage power supplies. The amount of delivered energy from the high voltage power supply to the vacuum tube is an important issue during the vacuum arc in the tube. The protection mechanism consists of a shunt crowbar which diverts the fault current from the tube to itself as a parallel path. Detection of the vacuum arc is crucial and only one sensor is usually employed to detect the vacuum arc. This characteristic intensifies the interference susceptibility of the vacuum arc diagnosis system in a noisy environment. As a result of the noise, the arc detection system can report false alarms. False...
A Fast vacuum arc detection method based on the neural network data fusion algorithm for the high-voltage dc power supply of vacuum tubes, Article IEEE Transactions on Plasma Science ; 2020 ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2020
Vacuum arc is one of the most important failure factors of the vacuum tubes. The amount of delivered energy from the high-voltage dc power supply to the vacuum tube is an important issue during the vacuum arc in the tube. Vacuum arc acts as a short-circuit fault (SCF) at the power supply output. The majority of converters use a single current sensor to measure only the converter output current for detecting the SCF. However, the sensor may provide unreliable data because of the noise effect. Application of a low-pass filter reduces the noise effect. Regarding the delay of the low-pass filter, the interval of arc detection increases and more energy is delivered to the tube. In this article, a...
Article Signal Processing ; Volume 88, Issue 10 , 2008 , Pages 2417-2424 ; 01651684 (ISSN) ; Izadnia, S ; Vahedi, M ; Sharif University of Technology
In this paper, we have developed an efficient method for obtaining an orthonormal wavelet that is matched to a given signal. The error between the wavelet and the given signal is minimized subject to the constraints of the amplitude and phase of the band-limited wavelet spectrum. To consider the constraints of the minimization problem, the Lagrange multipliers technique is applied. Variational method reduced the optimal matching problem to the solution of a set of functional equations for the amplitude and phase of the wavelet spectrum. Continuous functional equations were written in terms of Fourier coefficients of the phase of the transfer function of the quadrature low pass filter at the...
Article 2007 IEEE Region 10 Conference, TENCON 2007, Taipei, 30 October 2007 through 2 November 2007 ; 2007 ; 1424412722 (ISBN); 9781424412723 (ISBN) ; Mehrmanesh, S ; Zamanlooy, B ; Atarodi, M ; Sharif University of Technology
A compact low power circuit for implementation of a direct conversion OQPSK modulator is proposed. The circuit consists of a digital to analog converter, a low pass filter and an up-converter mixer. By embedding these three blocks, the circuit performance is enhanced and the total power consumption is reduced. The mixer is designed base on a Gilbert cell with on chip inductor loads. Instead of transconductance transistors of Gilbert cell, a fully deferential current mode DAC is used and proficiently a low pass filter is embedded between them and therefore the linearity of total system is improved. All of circuits are designed based on 0.18 μm CMOS technology with a single 1.8 volt power...
Article 2007 IEEE International Symposium on Circuits and Systems, ISCAS 2007, New Orleans, LA, 27 May 2007 through 30 May 2007 ; 2007 , Pages 717-720 ; 02714310 (ISSN) ; Bakhtiar, M. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2007
this paper presents a new class AB circuit for current-mode signal processing. The proposed circuit provides high-dynamic range, low distortion and accurate definition of quiescent current and it is well suited for high-speed applications. A third-order low-pass filter with a cutoff frequency of 200MHz and 51dB dynamic range is also presented. The Alter consumes 2.7mW from 1.8V supply. © 2007 IEEE
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) ; 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...
Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Saidi, M. H ; Mehrabian, A ; Bazargan, M ; Kenarsari, S. D ; Sharif University of Technology
American Society of Mechanical Engineers 2006
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. The objective of this paper is to obtain the fluid flow response to actuation frequency of a passive diffuser valve under harmonic pressures. In this regards a 2D model of a micropump valves and chambers is analyzed. The analysis is performed for 10Kpa back pressure on micropump chamber and actuation frequencies within the range of 1Hz to 10 KHz. Results show the highest velocity in the direction of diffuser axis occurs at the narrow diffuser neck while flow direction reverses every half period. For low frequencies, a parabolic velocity...