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Extraction of effective constitutive parameters of artificial media using Bloch modes
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 36, Issue 11 , 2019 , Pages 3226-3235 ; 07403224 (ISSN) ; Rejaei, B ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
The effective constitutive parameters of a three-dimensional periodic structure are calculated using its Bloch modes. These modes and their propagation constants are obtained from eigenvectors and eigenvalues of the generalized transfer matrix of a unit layer of the structure. Effective bulk permittivity and permeability tensors of the medium are obtained when two of the Bloch modes are dominant, i.e., propagate without significant decay inside the medium. The effect of the strongly decaying Bloch modes, which are excited at the interface with a conventional medium, are included by means of surface impedance matrices. The results are in excellent agreement with full-wave electromagnetic...
Extraction of effective constitutive parameters of artificial media using bloch modes
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 36, Issue 11 , 2019 , Pages 3226-3235 ; 07403224 (ISSN) ; Rejaei, B ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
The effective constitutive parameters of a three-dimensional periodic structure are calculated using its Bloch modes. These modes and their propagation constants are obtained from eigenvectors and eigenvalues of the generalized transfer matrix of a unit layer of the structure. Effective bulk permittivity and permeability tensors of the medium are obtained when two of the Bloch modes are dominant, i.e., propagate without significant decay inside the medium. The effect of the strongly decaying Bloch modes, which are excited at the interface with a conventional medium, are included by means of surface impedance matrices. The results are in excellent agreement with full-wave electromagnetic...
Numerical modeling of die filling of semi-solid A356 aluminum alloy
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 605-610 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Narimannezhad, A ; Khosravani, A ; Kiani, M ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
Computer base and simulation technique have been applied for modeling the semi-solid die filling and part of the solidification process of aluminum A356 alloy. A fairly simple one-phase rheological model has been implemented into a fluid flow finite element software Procast, to solve the partial differential equations. This model is purely viscous nature and is implemented in the power law cut-off model of Procast. The constitutive parameters of this model were determined for a rheocast A356 alloy. Using these parameters and comparing the simulation results with experimental data showed good correlation with the model prediction. The designed die for rheocasting was applied for the...
Guided-Wave Components Based on Bianisotropic Metamaterials
, Ph.D. Dissertation Sharif University of Technology ; Rejaei, Behzad (Supervisor) ; Khavasi, Amin (Co-Supervisor)
Abstract
In its most general form, analysis of macroscopic electromagnetic behaviour of a medium must include the dependence of magnetic flux density on the electric field and electric flux density on the magnetic filed. This new degree of freedom can lead to new propagation phenomena and result in novel microwave and optical devices. In recent years, numerous theoritical and exprimental studies have been carried out to fabricate these bi-anisotropic materials and understand their behaviour. A particular class of bi-anisotropic materials is electromagnetically equivalent to an anisotropic medium with gyrotropic permittivity and permeability tensors that operate on pseudo-electromagnetic fields. In...
Unidirectional surface waves in bi-anisotropic media
, Article IEEE Journal of Quantum Electronics ; Volume 54, Issue 6 , 2018 ; 00189197 (ISSN) ; Rejaei, B ; Khavasi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
We show theoretically that unidirectional surface waves can propagate on the surface of homogeneous bi-anisotropic layers with an anti-symmetric chirality tensor. These materials mimic the electromagnetic behavior of an anisotropic medium with gyrotropic permittivity and permeability tensors that operate on pseudo-electromagnetic fields. The unidirectional waves have transverse pseudo-electric or magnetic polarizations and pass through an obstacle without backscattering if the obstacle does not cause polarization change. The bi-anisotropic medium can be realized as a metamaterial comprising omega particles tailored to achieve the constitutive parameters desired. © 2018 IEEE
Analyses on the flow stress of an Al-Mg alloy during dynamic recovery
, Article Journal of Materials Engineering and Performance ; Volume 22, Issue 3 , March , 2013 , Pages 700-705 ; 10599495 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2013
Abstract
A comprehensive analysis on flow stress of a wrought Al-Mg alloy is performed to examine the effect of strain. For this study, hot compression tests were carried at different temperatures and strain rates. Corrections of friction and adiabatic heating effects lead to the true stress-true strain curves in the form of dynamic recovery, which reach to a steady-state condition. After correction, constitutive analysis at a constant strain is carried out using hyperbolic-sine equation. The effect of strain on each constitutive parameter is studied to derive a strain-dependent constitutive equation based on hyperbolic-sine equation. Some of constitutive parameters reach to the constant values at...
Evaluation of the geo-mechanical parameters of the interface between asphalt concrete and sand with applying direct shear test and numerical modeling
, Article Advanced Materials Research ; Volume 587 , 2012 , Pages 116-121 ; 10226680 (ISSN) ; 9783037855133 (ISBN) ; Rostami, A ; Karimi, M. M ; Taherkhani, H
2012
Abstract
Asphaltic concrete has been used as waterproofing core in embankment dams, since 1948. In this application, the asphaltic core is surrounded by granular filter materials. The interaction of the asphaltic concrete and the granular materials has not been sufficiently investigated. In this paper the mechanical behavior of the interface between a natural smooth sand filter and asphaltic concrete at different levels of normal stresses and a constant shear strain rate has been studied. Small scale direct shear test has been conducted in this study, in which the shear surface is considered as the interface. Asphalt concrete specimens used in the shear test were cut in square shape (10×10×2.5 cm)...