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    Effect of axially graded constraining layer on the free vibration properties of three layered sandwich beams with magnetorheological fluid core

    , Article Composite Structures ; Volume 255 , 2021 ; 02638223 (ISSN) Omidi Soroor, A ; Asgari, M ; Haddadpour, H ; Sharif University of Technology
    Elsevier Ltd  2021
    The free linear vibration of an adaptive sandwich beam consisting of a frequency and field-dependent magnetorheological fluid core and an axially functionally graded constraining layer is investigated. The Euler-Bernoulli and Timoshenko beam theories are utilized for defining the longitudinal and lateral deformation of the sandwich beam. The Rayleigh-Ritz method is used to derive the frequency-dependent eigenvalue problem through the kinetic and strain energy expressions of the sandwich beam. In order to deal with the frequency dependency of the core, the approached complex eigenmodes method is implemented. The validity of the formulation and solution method is confirmed through comparison... 

    A modal coupling procedure to improve residual modal effects based on experimentally generated data

    , Article Journal of Sound and Vibration ; Volume 331, Issue 1 , 2012 , Pages 66-80 ; 0022460X (ISSN) Hosseini Kordkheili, S. A ; Momeni Massouleh, S. H ; Kokabi, M. J ; Bahai, H ; Sharif University of Technology
    In this paper a modal coupling procedure is developed to improve residual modal effects based on experimentally generated data. While showing that CraigChangs proposed approximation function for higher frequency modes does not compare well with the exact function, a new procedure is developed in order to re-express the dynamic residuals. For this purpose, all frequency dependent terms of the Maclaurin series in CraigChangs proposed method are replaced by a general compatible function, which includes the neglected higher order terms. However, this function no longer appears in final equation of motion. Results from case studies for the discrete, continuous and experimental models are... 

    Investigation of partial discharge propagation on compac t three phase XLPE cables

    , Article 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, Sydney, NSW, 14 December 2008 through 17 December 2008 ; 2008 ; 9781424441624 (ISBN) Vakilian, M ; Blackburn, T. R ; Johnson O., H. N ; Phung, B. T ; Sharif University of Technology
    This paper presents the measurements results of simulated partial discharge propagation on a compact three phase XLPE cable, and shows how the high frequency signal on one phase of the cable is induced on the other two phases. A frequency dependent three phase cable model is employed to simulate this phenomena. © 2008 Australasian Universities Power Engineering Conference (AUPEC'08)  

    Multi-port frequency-dependent network equivalent for electromagnetic transient studies

    , Article 37th Annual North American Power Symposium, 2005, Ames, IA, 23 October 2005 through 25 October 2005 ; Volume 2005 , 2005 , Pages 287-295 ; 0780392558 (ISBN); 9780780392557 (ISBN) Porkar, B ; Vakilian, M ; Feuillet, R ; Ghassemi, M ; Akhavan, A ; Sharif University of Technology
    Network equivalents can be used to represent parts of a power system to reduce the complexity and the computation time during the simulation of electromagnetic transients. The goal is to simplify the representation while preserving the accuracy of transients in the remainder. In this work a method is developed for construction of single and multi-port Frequency Dependent Network Equivalent (FNDE). In this equivalent model the input admittance matrix is approximated by a rational function in the frequency domain. This method is developed for both single and multi phase systems. Several examples showing the accuracy and efficiency of the developed FDNE is presented  

    Analysis of frequency-dependent network equivalents in dynamic harmonic domain

    , Article Electric Power Systems Research ; Volume 193 , 2021 ; 03787796 (ISSN) Karami, E ; Hajipour, E ; Vakilian, M ; Rouzbehi, K ; Sharif University of Technology
    Elsevier Ltd  2021
    Rational function-based models have proved to be very efficient for accurate frequency-dependent modeling of power system components. These models are able to characterize the components terminal behaviours (analysing the admittance matrix) for nodal analysis. This provides a fast convergence and inherent stability to the solution routine of the model. This work presents a general framework for interfacing the dynamic phasor method to the rational models. That would be promising for the electromagnetic transient analysis (under harmonic distortion), in the frequency domain. Therefore, Y-element rational pole-residue models (employing the vector fitting method) are developed. Moreover, the... 

    Blind identification of soil-structure systems

    , Article Soil Dynamics and Earthquake Engineering ; Volume 45 , February , 2013 , Pages 56-69 ; 02677261 (ISSN) Ghahari, S. F ; Ghannad, M. A ; Taciroglu, E ; Sharif University of Technology
    Surrounding soil can drastically influence the dynamic response of buildings during strong ground shaking. Soil's flexibility decreases the natural frequencies of the system; and in most cases, soil provides additional damping due to material hysteresis and radiation. The additional damping forces, which are in non-classical form, render the mode shapes of the soil-structure system complex-valued. The response of a soil-foundation system can be compactly represented through impedance functions that have real and imaginary parts representing the stiffness and damping of the system, respectively. These impedance functions are frequency-dependent, and their determination for different... 

    Anderson localization and propagation of electromagnetic waves through disordered media

    , Article Waves in Random and Complex Media ; Volume 20, Issue 1 , 2010 , Pages 191-200 ; 17455030 (ISSN) Sheikhan, A ; Abedpour, N ; Sepehrinia, R ; Niry, M. D ; Reza Rahimi Tabar, M ; Sahimi, M ; Sharif University of Technology
    We have used the dynamic method to calculate the frequency dependence of the localization length in a disordered medium, using the amplitude change and the redshift of the spectral density of the propagating incident pulse. The frequency dependence of the localization length in an effectively one-dimensional disordered medium is computed in terms of the strength of the disorder. The results obtained with the dynamic method are confirmed by computing the same results using the transfer-matrix method  

    A tunable-Q 4-path bandpass filter with Gm-C second-order baseband impedances

    , Article 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 244-248 ; 9781509059638 (ISBN) Rezvanitabar, A ; 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... 

    Modeling, Analysis and Experimental Investigation of Energy Harvesting via Magnetic Shape Memory Alloys

    , Ph.D. Dissertation Sharif University of Technology Askari Farsangi, Mohammad Amin (Author) ; Sayyadi, Hassan (Supervisor) ; Zakerzadeh, Mohammad Reza (Co-Advisor)
    Vibration based energy harvesting is the process of trapping and collecting vibrational energy from ambient sources which seem unusable at first sight. The smart materials with the capability of coupling two different fields can be used in converting vibrational energy to electrical one. One of this smart material which has been taken into account recently is the Magnetic Shape Memory Alloy (MSMA) and it can couple the magnetic and mechanical fields. In MSMAs the total magnetization vector changes with the application of stress and make it possible to harvest energy from Faraday law’s of induction. An important phenomena that exist in MSMA is the dependency of magnetization-strain behavior... 

    Controllable single-mode random laser using stimulated Raman gain

    , Article Optics Letters ; Vol. 39, issue. 15 , August , 2014 , pp. 4537-4540 ; ISSN: 01469592 Shojaie, E ; Mirzaei, A ; Bahrampour, A ; Sharif University of Technology
    The present study demonstrates numerically a novel approach to perform a controllable single-mode random laser, using stimulated Raman gain. Due to the narrow linewidth of the Raman line shape, only one of the modes of the passive random system can lase. The robust control on the emission spectrum was achieved through the selection of any desired quasi-modes, by adjusting the pump wavelength in order to place the center of Raman line shape on desired quasi-modes. This approach was proved using a developed nonlinear transfer matrix method for a 1D Raman random system. The proposed method includes the Raman gain saturation and the frequency-dependent index of refraction  

    Propagation noise calculations in VVER-type reactor core

    , Article Progress in Nuclear Energy ; Volume 78 , January , 2015 , Pages 10-18 ; 01491970 (ISSN) Malmir, H ; Vosoughi, N ; Sharif University of Technology
    Elsevier Ltd  2015
    Neutron noise induced by propagating disturbances in VVER-type reactor core is addressed in this paper. The spatial discretization of the governing equations is based on the box-scheme finite difference method for triangular-z geometry. Using the derived equations, a 3-D 2-group neutron noise simulator (called TRIDYN-3) is developed for hexagonal-structured reactor core, by which the discrete form of both the forward and adjoint reactor dynamic transfer functions (in the frequency domain) can be calculated. In addition, both types of noise sources, namely point-like and traveling perturbations, can be modeled by TRIDYN-3. The results are then benchmarked in different cases. Considering the... 

    Pairing and non-Fermi liquid behavior in partially flat-band systems: Beyond nesting physics

    , Article Physical Review B ; Volume 101, Issue 1 , 2020 Sayyad, S ; Huang, E. W ; Kitatani, M ; Vaezi, M. S ; Nussinov, Z ; Vaezi, A ; Aoki, H ; Sharif University of Technology
    American Physical Society  2020
    While many-body effects in flat-band systems are receiving renewed hot interest in condensed-matter physics for superconducting and topological properties as well as for magnetism, studies have primarily been restricted to multiband systems (with coexisting flat and dispersive bands). Here we focus on one-band systems where a band is "partially flat," comprising flat and dispersive portions in k space to reveal whether intriguing correlation effects can already arise on the simplest possible one-band level. For that, the two-dimensional repulsive Hubbard model is studied for two models having different flat areas in an intermediate-coupling regime with the dynamical mean-field theory... 

    A discrete model for response estimation of soil-structure systems with embedded foundations

    , Article Earthquake Engineering and Engineering Vibration ; Volume 10, Issue 2 , June , 2011 , Pages 263-276 ; 16713664 (ISSN) Khodabakhshi, P ; Jahankhah, H ; Ghannad, M. A ; Sharif University of Technology
    The need for simplified physical models representing frequency dependent soil impedances has been the motivation behind many researches throughout history. Generally, such models are generated to capture impedance functions in a wide range of excitation frequencies, which leads to relatively complex models. That is while there is just a limited range of frequencies that really influence the response of the structure. Here, a new methodology based on the response-matching concept is proposed, which can lead to the development of simpler discrete models. The idea is then used to upgrade an existing simple model of surface foundations to the case of embedded foundations. The applicability of... 

    Frequency-dependent energy harvesting via magnetic shape memory alloys

    , Article Smart Materials and Structures ; Volume 24, Issue 11 , October , 2015 ; 09641726 (ISSN) Sayyaadi, H ; Askari Farsangi, M. A ; Sharif University of Technology
    Institute of Physics Publishing  2015
    This paper is focused on presenting an accurate framework to describe frequency-dependent energy harvesting via magnetic shape memory alloys (MSMAs). Modeling strategy incorporates the phenomenological constitutive model developed formerly together with the magnetic diffusion equation. A hyperbolic hardening function is employed to define reorientation-induced strain hardening in the material, and the diffusion equation is used to add dynamic effects to the model. The MSMA prismatic specimen is surrounded by a pickup coil, and the induced voltage during martensite-variant reorientation is investigated with the help of Faraday's law of magnetic field induction. It has been shown that, in... 

    Microstructural, optical, and electrical characteristics of Ni/C doped BST thin films

    , Article Ceramics International ; Volume 45, Issue 5 , 2019 , Pages 5503-5510 ; 02728842 (ISSN) Emadi, F ; Nemati, A ; Hinterstein, M ; Adabifiroozjaei, E ; Sharif University of Technology
    Elsevier Ltd  2019
    In the present work the effect of simultaneous doping of carbon and nickel on the microstructural, optical, and electrical properties of barium strontium titanate (BST) is investigated. Thin films of BST were prepared by the sol-gel method in six different compositions ((Ba0.6Sr0.4)(NixCyTi1-x-y)O3): x = y = 0.00 (BST), x = 0.04 y = 0.00 (BST4N), x = 0.04 y = 0.01 (BST4N-1C), x = 0.04 y = 0.02 (BST4N-2C), x = 0.04 y = 0.03 (BST4N-3C), and x = y = 0.04 (BST4N-4C). Structural features and chemical bonds of the films were studied by TGA/DSC, XRD, FT-IR, and FE-SEM. The electrical and optical properties of the films were analysed by impedance spectroscopy and UV–VIS spectroscopy. The results... 

    Revised guided mode expansion on dispersive photonic media

    , Article Photonic and Phononic Crystal Materials and Devices IX, San Jose, CA, 27 January 2009 through 29 January 2009 ; Volume 7223 , 2009 ; 0277786X (ISSN) Eftekharian, A ; Sodagar, M ; Khoshnegar, M ; Khorasani, S ; Chamanzar, M. R ; Adibi, A ; Sharif University of Technology
    A novel plane-wave-based approach for analytical treatment of dispersive relation is developed and applied to analyze the behavior of electromagnetic waves in plasmonic-photonic-crystal slabs. Here Drude model is used for describing frequency dependent permittivity of plasma rods in host dielectric medium. In the present work, dispersion relation below and above the light line is calculated approximately by means of Maxwell-Garnett effective medium and Revised Plane Wave Method (RPWM). The eigen-functions are then used in Revised Guided Mode Expansion (RGME) as the set of orthonormal bases. Following this procedure, the accurate band structure is obtained. In these kind of methods there are...