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radiation-power
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Optimum acoustical design of muffler using numerical simulation
, Article 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life ; Volume 1 , September , 2013 , Pages 306-313 ; 9781632662675 (ISBN) ; Jahani, K ; Sharif University of Technology
OAL-Osterreichischer Arbeitsring fur Larmbekampfung
2013
Abstract
The level and character of noise emitted by exhaust system has significant effect on the overall acoustic performance of vehicle powertrain and sound quality which is received by occupants. In addition to meeting aforementioned objective, the exhaust system must meet exterior noise regulation which is ordered by governments. In this study, acoustic performance of the vehicle exhaust system is investigated. Numerical simulation is applied for this aim that is the fastest and the most economical method in early design stages of vehicle development process. Thickness optimum design is performed in order to improve acoustic performance of exhaust system. Robust parameter design, based on Taguchi...
Terahertz radiation power characterization and optimization of stack of intrinsic Josephson junctions
, Article IEEE Transactions on Applied Superconductivity ; Volume 22, Issue 4 , 2012 ; 10518223 (ISSN) ; Kamrani, H ; Fardmanesh, M ; Sharif University of Technology
2012
Abstract
Terahertz radiation of the stack of intrinsic Josephson junctions in the mesa structure of the layered high- T c superconductors is analyzed and presented in this paper. The dependence of the radiated power to the geometrical parameters, cavity-waveguide boundaries, and magnetic and electric biases has been investigated. This has been done by numerical calculation of the previously proposed coupled sine-Gordon equations, which characterize the electromagnetic dynamics of the stack of the intrinsic Josephson junctions. Using the obtained numerical results from these coupled equations, the effect of the design parameters, such as dimensions of the mesa structure, the magnitude of the applied...
Improving the efficiency and directivity of THz photoconductive antennas by using a defective photonic crystal substrate
, Article Optics Communications ; Volume 412 , April , 2018 , Pages 74-79 ; 00304018 (ISSN) ; Ahmadi Boroujeni, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
One of the shortcomings of photoconductive (PC) antennas in terahertz (THz) generation is low effective radiated power in the desirable direction. In this paper, we propose a defective photonic crystal (DPC) substrate consisting of a customized 2D array of air holes drilled into a solid substrate in order to improve the radiation characteristics of THz PC antennas. The effect of the proposed structure on the performance of a conventional THz PC antenna has been examined from several aspects including radiation efficiency, directivity, and field distribution. By comparing the radiation performance of the THz antenna on the proposed DPC substrate to that of the conventional solid substrate, it...
A superconductor THz modulator based on vortex flux flow
, Article IEEE Transactions on Applied Superconductivity ; Volume 19, Issue 4 , 2009 , Pages 3653-3657 ; 10518223 (ISSN) ; Hosseini, M ; Chalabi, H. R ; Moftakharzadeh, A ; Zandi, H ; Khorasani, S ; Fardmanesh, M ; Sharif University of Technology
2009
Abstract
A terahertz modulator based on the Type-II superconductor flux flow oscillator has been proposed. Analytical calculations are presented and the effects of intrinsic and extrinsic parameters such as disorder strength of crystal, penetration depth, frequency, and amplitude of the modulated current on the radiation power spectrum have been studied. The proposed structure also exhibits a mixer-like behavior, in the sense that its output harmonics range from the washboard frequency up to the superconductor gap frequency, so the input signal is practically mixed with the washboard frequency and its harmonics. The modulation index for each harmonic of this modulator has also been investigated. This...
2D analysis of the effects of geometry on the response of high-T c superconductive bolometric detectors
, Article IEEE Transactions on Applied Superconductivity ; Volume 19, Issue 3 , 2009 , Pages 484-488 ; 10518223 (ISSN) ; Kokabi, A. R ; Pourhashemi, A ; Moftakharzadeh, A ; Khorasani, S ; Banzet, M ; Schubert, J ; Sharif University of Technology
2009
Abstract
We present a new approach for analytical modeling and calculating the response of high-Tc superconductive transition edge sensors in a wide range of modulation frequencies for different configurations of the film patterns. The method used here is based on solving the heat transfer differential equation for two different time varying heat sources, which are related to the absorbed radiated power. The used method employs two-dimensional boundary conditions for describing meander-line patterned devices. The results from the applied method are in better agreement with those obtained from the frequency response measurements of the characterized samples, than the previously developed models. In...