Search for: time-domain-analysis
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    Time domain analysis of graphene nanoribbon interconnects based on transmission line model

    , Article Iranian Journal of Electrical and Electronic Engineering ; Volume 8, Issue 1 , Dec , 2012 , Pages 37-44 ; 17352827 (ISSN) Nasiri, S. H ; Moravvej-Farshi, M. K ; Faez, R ; Sharif University of Technology
    Time domain analysis of multilayer graphene nano ribbon (MLGNR) interconnects, based on transmission line modeling (TLM) using a six-order linear parametric expression, has been presented for the first time. We have studied the effects of interconnect geometry along with its contact resistance on its step response and Nyquist stability. It is shown that by increasing interconnects dimensions their propagation delays are increased and accordingly the system becomes relatively more stable. In addition, we have compared time responses and Nyquist stabilities of MLGNR and SWCNT bundle interconnects, with the same external dimensions. The results show that under the same conditions, the... 

    Distributed measurement of signal power evolution in a phase sensitive parametric amplifier

    , Article Conference on Optical Fiber Communication, Technical Digest Series ; March , 2014 ; 978-1-55752-993-0 Alishahi, F ; Vedadi, A ; Soto, M. A ; Denisov, A ; Mehrany, K ; Thevenaz, L ; Bres, C.-S ; Sharif University of Technology
    A method to measure the signal power evolution along phase-sensitive parametric amplifiers is proposed using Brillouin optical time-domain analysis. Different evolutions along the fiber are reported by varying input wave phases, including amplification and de-amplification  

    Simulation of chatter vibrations in reaming

    , Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 3 , 2008 , Pages 441-447 ; 0791842975 (ISBN); 9780791842973 (ISBN) Sajjadi, M ; Movahhedy, M. R ; Sharif University of Technology
    A time domain approach is used to study the cutting conditions in reaming process that leads the system to regenerative chatter vibrations. The dynamic analysis of the system includes inertia of the tool, centripetal and Coriolis terms, damping and the first mode bending of reamer. A model of cutting forces proportional to chip cross sectional area and process damping proportional to cutting speed is considered. Numerical simulation based on the Euler integration scheme is carried out to obtain time domain solution of the equation. Despite linearization in force modelling, the model is nonlinear due to the change in the tool engagement area. Another nonlinearity included in the model jumping... 

    Reflection analysis of the end-facet dielectric slab waveguide by FDTD method

    , Article ICCEA 2004 - 2004 3rd International Conference on Computational Electromagnetics and its Applications, Beijing, 1 November 2004 through 4 November 2004 ; 2004 , Pages 453-456 ; 0780385624 (ISBN) Vahidpour, M ; Shishegar, A. A ; Sharif University of Technology
    The Finite Difference Time Domain (FDTD) method has been applied to the analysis of abruptly-ended dielectric waveguides. In these waveguides, incident propagating wave undergoes reflection in an interaction with the end-facet. As a result of the discontinuity, all possible propagating modes may be excited. The constituent propagating modes are extracted from the reflected wave by the least square method. Thus, we present a good estimation of the amplitudes of the reflected modes. This full wave analysis technique is also capable of analyzing any arbitrarily shaped facet. © 2004 IEEE  

    Sensitive and accurate dispersion map extraction of HNLFs by frequency tuning of a degenerate FWM

    , Article Journal of Lightwave Technology ; Volume 34, Issue 18 , 2016 , Pages 4197-4204 ; 07338724 (ISSN) Alishahi, F ; Vedadi, A ; Shoaie, M. A ; Bres, C. S ; Mehrany, K ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    A sensitive and accurate method for dispersion map extraction along an arbitrarily profiled highly nonlinear fiber (HNLF) is proposed. High sensitivity is achieved by positioning the wavelength of a signal at the band edge of the modulation instability (MI) spectrum generated by an intense degenerate four wave mixing (FWM) pump. In doing so, the to-be-extracted dispersion fluctuations leave a more drastic effect on the FWM-generated power since they either inflate or deflate the MI spectrum. The accuracy of the method is increased by monitoring the distribution of power along the fiber. Once the power distribution is measured along the fiber, dispersion map of the HNLF is extracted using an... 

    Ramsey interferometry with a two-level generalized Tonks-Girardeau gas

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 76, Issue 3 , 2007 ; 10502947 (ISSN) Mousavi, S. V ; Del Campo, A ; Lizuain, I ; Muga, J. G ; Sharif University of Technology
    We propose a solvable generalization of the Tonks-Girardeau model that describes a coherent one-dimensional (1D) gas of cold two-level bosons which interact with two external fields in a Ramsey interferometer. They also interact among themselves by idealized, infinitely strong contact potentials, with interchange of momentum and internal state. We study the corresponding Ramsey fringes and the quantum projection noise which, essentially unaffected by the interactions, remains that for ideal bosons. The dual system of this gas, an ideal gas of two-level fermions coupled by the interaction with the separated fields, produces the same fringes and noise fluctuations. The cases of time-separated... 

    Design of a gain-scheduling anti-swing controller for tower cranes using fuzzy clustering techniques

    , Article CIMCA 2006: International Conference on Computational Intelligence for Modelling, Control and Automation, Jointly with IAWTIC 2006: International Conference on Intelligent Agents Web Technologies and International Commerce, Sydney, NSW, 28 November 2006 through 1 December 2006 ; 2006 ; 0769527310 (ISBN); 9780769527314 (ISBN) Sadati, N ; Hooshmand, A ; Sharif University of Technology
    IEEE Computer Society  2006
    The main objective of this paper is to design a fast,non-expensive and practical controller for towercranes. The controllers are designed to transfer theloads from point to point, as fast as possible, and at thesame time the load swing is kept small during thetransfer process. Moreover, variations of the systemparameters such as cable length are taken intoconsideration. It is shown how the state feedbackcontrollers along with the gain scheduling could beused for a time varying linear model with varyingparameters. For this reason, linear controllers aredesigned for a number of operating points, where theirparameters are interpolated for conditions in between.In this way, a globally nonlinear... 

    Speech enhancement by adaptive noise cancellation in the wavelet domain

    , Article 2005 Fifth International Conference on Information, Communications and Signal Processing, Bangkok, 6 December 2005 through 9 December 2005 ; Volume 2005 , 2005 , Pages 719-723 ; 0780392833 (ISBN); 9780780392830 (ISBN) Akhaee, M. A ; Ameri, A ; Marvasti, F. A ; Sharif University of Technology
    Adaptive filtering has been used for speech denoising in the time domain. During the last decade, wavelet transform has been developed for speech enhancement. In this paper we are proposing to use adaptive filtering in the Wavelet transform domain. We propose a hybrid method of using adaptive filters on the lower scales of a wavelet transformed speech together with the conventional methods (Thresholding, Spectral Subtraction, and Wiener filtering) on the higher scale coefficients. Experimental results demonstrate that the suggested approach is computationally efficient and has a good performance. © 2005 IEEE  

    Per Tone equalization analysis in DMT based systems

    , Article IEEE TENCON 2004 - 2004 IEEE Region 10 Conference: Analog and Digital Techniques in Electrical Engineering, Chiang Mai, 21 November 2004 through 24 November 2004 ; Volume A , 2004 , Pages A539-A542 Rezaei, S. S. C ; Pakravan, M. R ; IEEE Region 10 ; Sharif University of Technology
    Time domain equalizers are used in the receiver of a discrete multitone (DMT) receiver to compensate the channel effects on the received signal. There are a lot of DMT equalization algorithms presented in the literature, but recently a novel Per Tone equalizer structure was proposed which offers some advantages over the previous traditional ones. The objective of this paper is to provide an overview of the important concepts of this technique and evaluate its initialization complexity. The performance of this technique is also compared with typical time-domain equalization algorithms in different simulation environments. © 2004IEEE  

    Incommensurate order fractional optimal control: Application to treatment of psychiatric disorders

    , Article 2013 21st Iranian Conference on Electrical Engineering ; May , 2013 , Page(s): 1 - 5 ; 9781467356343 (ISBN) Tabatabaei, S. S ; Yazdanpanah, M. J ; Tavazoei, M. S ; Sharif University of Technology
    The main point of this paper is to present a time domain strategy for drug dosage to treat psychiatric disorders. A time domain model of emotion is obtained from an extension of a recently developed fractional nonlinear dynamic model of happiness. First, the Fractional Optimal Control law for incommensurate multi state systems is obtained. It will be then applied as an optimal drug administration procedure in the line of psychiatric disorders treatment. Results of this paper show that optimal control scheme is a proper approach to face the difficulties of analysis and control the incommensurate systems. It can be also clearly seen from the simulation results that this approach is very... 

    Extended finite element modeling of deformable porous media with arbitrary interfaces

    , Article Applied Mathematical Modelling ; Volume 35, Issue 11 , 2011 , Pages 5426-5441 ; 0307904X (ISSN) Khoei, A. R ; Haghighat, E ; Sharif University of Technology
    In this paper, an enriched finite element method is presented for numerical simulation of saturated porous media. The arbitrary discontinuities, such as material interfaces, are encountered via the extended finite element method (X-FEM) by enhancing the standard FEM displacements. The X-FEM technique is applied to the governing equations of porous media for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. In X-FEM, the material interfaces are represented independently of element boundaries and the process is accomplished by partitioning the domain with some triangular sub-elements whose Gauss points are used for integration of the... 

    Computing all the Floquet eigenfunctions of oscillators using harmonic balance Jacobian matrices

    , Article IET Circuits, Devices and Systems ; Volume 5, Issue 4 , July , 2011 , Pages 257-266 ; 1751858X (ISSN) Jahanbakht, S ; Farzaneh, F ; Sharif University of Technology
    Floquet eigenfunctions and Floquet exponents are encountered in stability and noise analysis of circuits operating at large signal periodic regime. It is analytically verified that the spectrum vectors of the left-hand and right-hand Floquet eigenfunctions and the Floquet exponents (Floquet eigenpairs) are members of the harmonic balance eigenvalues and eigenvectors (HB eigenpairs). The relationships between other HB eigenpairs with the Floquet eigenpairs are discussed. This discussion leads to a practical algorithm for computing the Floquet eigenpairs through HB eigenpairs. Furthermore, it is analytically verified that the main arguments of the study are consistent with the... 

    Rescheduling of power systems constrained with transient stability limits in restructured power systems

    , Article Electric Power Systems Research ; Volume 81, Issue 1 , 2011 , Pages 1-9 ; 03787796 (ISSN) Kheradmandi, M ; Ehsan, M ; Feuillet, R ; Hadj-Saied, N ; Sharif University of Technology
    This paper investigates various approaches to relieve the transient stability constraint in restructured power systems. The approaches adopted fall into two broad categories: those based on eliminating the constraint in the least-cost way and those based on eliminating with the least possible rescheduling. The latter group can, on the other hand, emerge in the form of a pool-protected policy in which the bilateral contracts are rescheduled to maintain the stability or in the form of a contract-protected policy in which the realizable bilateral contracts are maximized while minimizing the rescheduling in pool market. Transient energy function (TEF) method is used as a tool to calculate the... 

    Finite-time consensus in undirected/directed network topologies

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 5 , 2010 , Pages 1-6 ; 9780791849194 (ISBN) Doostmohammadian, M. R ; Sayyaadi, H ; Sharif University of Technology
    The main contribution of this paper is to introduce a novel non-Lipschitz protocol that guarantees consensus in finite-time domain. Its convergence in networks with both unidirectional and bidirectional links is investigated via Lyapunov Theorem approach. It is also proved that final agreement value is equal to average of agents' states for the bidirectional communication case. In addition effects of communication time-delay on stability are assessed and two other continuous Lipschitz protocols are also analyzed  

    Experimental identification of closely spaced modes using NExT-ERA

    , Article Journal of Sound and Vibration ; Volume 412 , 2018 , Pages 116-129 ; 0022460X (ISSN) Hosseini Kordkheili, S. A ; Momeni Massouleh, S. H ; Hajirezayi, S ; Bahai, H ; Sharif University of Technology
    Academic Press  2018
    This article presents a study on the capability of the time domain OMA method, NExT-ERA, to identify closely spaced structural dynamic modes. A survey in the literature reveals that few experimental studies have been conducted on the effectiveness of the NExT-ERA methodology in case of closely spaced modes specifically. In this paper we present the formulation for NExT-ERA. This formulation is then implemented in an algorithm and a code, developed in house to identify the modal parameters of different systems using their generated time history data. Some numerical models are firstly investigated to validate the code. Two different case studies involving a plate with closely spaced modes and... 

    Single-site source localisation using scattering data

    , Article IET Radar, Sonar and Navigation ; Volume 12, Issue 2 , February , 2018 , Pages 250-259 ; 17518784 (ISSN) Samizadeh Nikoo, M ; Behnia, F ; Sharif University of Technology
    Institution of Engineering and Technology  2018
    Passive localisation of non-cooperative targets through their electromagnetic emissions is an attractive issue. This localisation task can be carried out using multitude of receiver sites being linked together. This multiplicity, however, brings about difficulties in organising and coordinating the sites. One can even claim that the method is no longer passive considering the necessary communication links between the sites. On the other hand, single-site localisation methods basically overcome these difficulties eliminating the need for inter-site communications. In this study, a single-site localisation method is presented and analysed. This method is applicable to scenarios with a large... 

    Spatial heterodyning optical code division multiple access technique for near-field free-space optical communication systems

    , Article Journal of Optical Communications and Networking ; Volume 1, Issue 5 , 2009 , Pages 498-511 ; 19430620 (ISSN) Salehiomran, A ; Salehi, J. A ; Sharif University of Technology
    We present a novel optical code division multiple access (OCDMA) scheme based on spatial optical heterodyning for free-space optical communication systems. In this technique, in particular, the decoding process is established by means of a spatial optical heterodyne receiver. The spatial heterodyning OCDMA introduced can be considered to be in the class of spread-space techniques, which implies that there is no structural limitation on the shape of time domain signals, e.g., digital or analog modulation. For the sake of simplicity and practicality we considered onoff keying modulation. However, there is no limitation on using more advanced modulation schemes such as pulse position... 

    Cellular design for a dense RFID reader environment

    , Article APCCAS 2008 - 2008 IEEE Asia Pacific Conference on Circuits and Systems, Macao, 30 November 2008 through 3 December 2008 ; January , 2008 , Pages 1124-1127 ; 9781424423422 (ISBN) Pourbagheri, S ; Bakhtiar, M. S ; Atarodi, M ; Sharif University of Technology
    This paper presents a method for positioning a large number of readers in an RFID cellular deployment zone while taking advantage of frequency and time domain multiplexing. The safe distance among the readers in the proposed cellular structure is calculated considering features such as collisions, local regulations and propagation issues. Using hexagonal cells, the RFID readers and tags are placed in an assumptive environment such as a warehouse building or a supermarket and the reliability of the implementation is estimated by means of calculating the total Bit Error Rate (BER). © 2008 IEEE  

    Periodic solutions for predator-prey systems with Beddington-DeAngelis functional response on time scales

    , Article Nonlinear Analysis: Real World Applications ; Volume 9, Issue 3 , 2008 , Pages 1224-1235 ; 14681218 (ISSN) Fazly, M ; Hesaaraki, M ; Sharif University of Technology
    This paper deals with the question of existence of periodic solutions of nonautonomous predator-prey dynamical systems with Beddington-DeAngelis functional response. We explore the periodicity of this system on time scales. New sufficient conditions are derived for the existence of periodic solutions. These conditions extend previous results presented in [M. Bohner, M. Fan, J. Zhang, Existence of periodic solutions in predator-prey and competition dynamic systems, Nonlinear. Anal.: Real World Appl. 7 (2006) 1193-1204; M. Fan, Y. Kuang, Dynamics of a nonautonomous predator-prey system with the Beddington-DeAngelies functional response, J. Math. Anal. Appl. 295 (2004) 15-39; J. Zhang, J. Wang,... 

    Designing a fuzzy rule based system to estimate depth of anesthesia

    , Article 1st IEEE Symposium on Computational Intelligence and Data Mining, CIDM 2007, Honolulu, HI, 1 April 2007 through 5 April 2007 ; 2007 , Pages 681-687 ; 1424407052 (ISBN); 9781424407057 (ISBN) Esmaeili, V ; Assareh, A ; Shamsollahi, M. B ; Moradi, M. H ; Arefian, N. M ; Sharif University of Technology
    Estimating the depth of anesthesia (DOA) is still a challenging area in anesthesia research. The objective of this study was to design a fuzzy rule based system which integrates electroencephalogram (EEG) features to quantitatively estimate the DOA. The proposed method is based on the analysis of single-channel EEG using frequency and time domain features as well as Shannon entropy measure. The fuzzy classifier is trained with features obtained from four subsets of data comprising well-defined anesthesia states: awake, moderate, general anesthesia, and isoelectric. The classifier extracts efficient fuzzy if-then rules and the DOA index is derived between 100 (full awake) to 0 (isoelectric)...