An Adaptive Time Domain Approach to Characterize Dispersive Elastodynamic Media

2017 ◽  
Author(s):  
Reza Abedi
Keyword(s):  
Time Domain ◽  
Scattering Problem ◽  
Equivalent Material ◽  
Scattering Parameters ◽  
Retrieval Method ◽  
Linear Solution ◽  
Transmission And Reflection Coefficients ◽  
Adaptive Time ◽  
Constitutive Parameters ◽  
Transmission And Reflection

A time domain approach is presented to compute the transmission and reflection coefficients of a unit cell. The solution of a wave scattering problem to an ultra-short incident wave enables the derivation of these scattering parameters with only one time domain solution. The adaptive operations of a spacetime discontinuous Galerkin method and several or its unique properties, such as linear solution complexity and local / asynchronous solution features, enable accurate computation of scattering parameters. An inverse parameter retrieval method, from the equivalent material impedance and wave speed to dispersive elastic constitutive parameters, is uniquely solved by using the continuity of the wavenumber.

Obtaining Directly Quasi-Square Open Ring FSS Constitutive Effective Parameters by Using Coupled WCIP - Retrieval Method

2019 ◽  
Vol 397 ◽  
pp. 187-199
Author(s):  
Saida Mellal ◽  
Toufik Ziar ◽  
Hichem Farh ◽  
Khalid Hati ◽  
Badreddine Zemmal ◽  
...  
Keyword(s):  
Frequency Selective Surface ◽  
Electric Permittivity ◽  
Scattering Parameters ◽  
Effective Parameters ◽  
Retrieval Method ◽  
Matlab Program ◽  
Open Ring ◽  
Analytical Formulas ◽  
Frequency Selective ◽  
Constitutive Parameters

We propose here a method witch analyze the behavior of Quasi-square open ring frequency selective surface (FSS) by using an approach based on the wave iterative concept procedure method (WCIP) coupled to Retrieval from Scattering Parameters method . The scattering parameters calculated by WCIP for a Quasi-square open ring FSS are used, in analytical formulas, to calculate directly observable effective constitutive parameters (relative electric permittivity εreff , magnetic permeability μreff and refractive index n ) of a frequency selective surface. Results of effective constitutive parameters for a Quasi-square open ring FSS structure are presented by Simulation using MATLAB program codes translating the implementation of the proposed approach.

scholarly journals Transmission, Reflection and Dissipation of Microwaves in Magnetic Composites with Nanocrystalline Finemet-Type Flakes

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3499
Author(s):  
Anatoly B. Rinkevich ◽  
Dmitry V. Perov ◽  
Yuriy I. Ryabkov
Keyword(s):  
Composite Material ◽  
Microwave Absorption ◽  
Nanocrystalline Alloy ◽  
Reflection Coefficients ◽  
Magnetic Composites ◽  
Transmission And Reflection Coefficients ◽  
Wave Interference ◽  
Microwave Losses ◽  
Frequency Dependences ◽  
Transmission And Reflection

The microwave properties of a composite material containing flakes of finemet-type nanocrystalline alloy placed in the epoxy matrix have been investigated. Two compositions have been studied: with 15% and 30% flakes. Frequency dependences of transmission and reflection coefficients are measured in the frequency range from 12 to 38 GHz. The dielectric permittivity and magnetic permeability are obtained, and the microwave losses are calculated. The dependences of transmission and reflection coefficients have been drawn as functions of wave frequency and thickness of the composite material, taking into account the frequency dependences of permittivity and permeability. The regions of maximal and minimal microwave absorption have been defined. The influence of wave interference on the frequency dependence of microwave absorption is studied.

Terahertz time-domain spectroscopy characterization of nitrocellulose in transmission and reflection configurations

Optik ◽  
2020 ◽  
Vol 224 ◽  
pp. 165711
Author(s):  
Noureddine Maamar ◽  
Mohamed Lazoul ◽  
Feriel Yasmine Latreche ◽  
Djalal Trache ◽  
Jean-Louis Coutaz
Keyword(s):  
Time Domain ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Transmission And Reflection

Analytical Study of Cylindrical P-Wave Propagation across Jointed Rock Masses

2014 ◽  
Vol 988 ◽  
pp. 502-507 ◽  
Author(s):  
Shao Bo Chai ◽  
Jian Chun Li ◽  
Hai Bo Li ◽  
Ya Qun Liu
Keyword(s):  
Wave Propagation ◽  
Rock Joint ◽  
Jointed Rock ◽  
P Wave ◽  
Displacement Discontinuity ◽  
Linear Elastic ◽  
Transmission And Reflection Coefficients ◽  
Conservation Of Momentum ◽  
Elastic Rock ◽  
Transmission And Reflection

According to the displacement discontinuity method and the conservation of momentum at the wave fronts, analysis for cylindrical P-wave propagation across a linear elastic rock joint is carried out. Considering the energy variation for wave propagation in one medium, the wave propagation equation was derived and expressed in an iterative form. The transmission and reflection coefficients are then obtained from the equation. By verification, the results agree very well with those from the existing results.

scholarly journals Convergence of the uniaxial PML method for time-domain electromagnetic scattering problems

2021 ◽  
Author(s):  
Changkun Wei ◽  
Jiaqing Yang ◽  
Bo Zhang
Keyword(s):  
Time Domain ◽  
Electromagnetic Scattering ◽  
Scattering Problem ◽  
Three Dimensional ◽  
Scattering Problems ◽  
Laplace Transform Technique ◽  
The Laplace Transform ◽  
Time Domain Electromagnetic ◽  
Numer Anal ◽  
The Time Domain

In this paper, we propose and study the uniaxial perfectly matched layer (PML) method for three-dimensional time-domain electromagnetic scattering problems, which has a great advantage over the spherical one in dealing with problems involving anisotropic scatterers. The truncated uniaxial PML problem is proved to be well-posed and stable, based on the Laplace transform technique and the energy method. Moreover, the $L^2$-norm and $L^{\infty}$-norm error estimates in time are given between the solutions of the original scattering problem and the truncated PML problem, leading to the exponential convergence of the time-domain uniaxial PML method in terms of the thickness and absorbing parameters of the PML layer. The proof depends on the error analysis between the EtM operators for the original scattering problem and the truncated PML problem, which is different from our previous work (SIAM J. Numer. Anal. 58(3) (2020), 1918-1940).

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