scholarly journals A Formal Time-domain Approach to Cold Magnetised Plasmas

1988 ◽  
Vol 41 (1) ◽  
pp. 55 ◽  
Author(s):  
Werner Weiglhofer
Keyword(s):  
Differential Equations ◽  
Time Domain ◽  
Scalar Potential ◽  
Coupled System ◽  
Dielectric Tensor ◽  
Tensor Operator ◽  
Transient Wave ◽  
The Time Domain ◽  
Limiting Case ◽  
Wave Phenomena

Representations of the electromagnetic and the average velocity field for a cold magnetised plasma are derived in terms of scalar potential functions. These Hertz potentials are solutions of a coupled system of integro-differential equations of second Qrder. Different from other approaches, the analysis is carried out in the time domain and is therefore especially suited for the investigation of transient wave phenomena. Furthermore, the dielectric tensor operator of the plasma is derived. Mter solving the system of integro-differential equations for a special limiting case, the applicability of the method presented is demonstrated and generalisations are discussed.

Electromagnetic modeling of 3-D sources over 2-D inhomogeneities in the time domain

Geophysics ◽  
1992 ◽  
Vol 57 (8) ◽  
pp. 994-1003 ◽  
Author(s):  
Michael Leppin
Keyword(s):  
Differential Equations ◽  
Diffusion Equation ◽  
Time Domain ◽  
Magnetic Induction ◽  
Host Rock ◽  
Vertical Component ◽  
Wavenumber Domain ◽  
Transient Electromagnetic ◽  
Wide Range ◽  
The Time Domain

A numerical method is presented by which the transient electromagnetic response of a two‐dimensional (2-D) conductor, embedded in a conductive host rock and excited by a rectangular current loop, can be modeled. This 2.5-D modeling problem has been formulated in the time domain in terms of a vector diffusion equation for the scattered magnetic induction, which is Fourier transformed into the spatial wavenumber domain in the strike direction of the conductor. To confine the region of solution of the diffusion equation to the conductive earth, boundary values for the components of the magnetic induction on the ground surface have been calculated by means of an integral transform of the vertical component of the magnetic induction at the air‐earth interface. The system of parabolic differential equations for the three magnetic components has been integrated for 9 to 15 discrete spatial wavenumbers ranging from [Formula: see text] to [Formula: see text] using an implicit homogeneous finite‐difference scheme. The discretization of the differential equations on a grid representing a cross‐section of the conductive earth results in a large, sparse system of linear equations, which is solved by the successive overrelaxation method. The three‐dimensional (3-D) response has been computed by an inverse Fourier transformation of the cubic spline interpolated scattered magnetic induction in the wavenumber domain using a digital filtering technique. To test the algorithm, responses have been computed for a two‐layered half‐space and a vertical prism embedded in a conductive host rock. These examples were then compared with results obtained analytically or numerically using frequency‐domain finite‐element and time‐domain integral equation methods. The new numerical procedure gives satisfactory results for a wide range of 2-D conductivity distributions with conductivity ratios exceeding 1:100, provided the grid is sufficiently refined at the corners of the conductivity anomalies.

scholarly journals Leaky-wave phenomena viewed from the time domain

Radio Science ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 435-441
Author(s):  
Hiroshi Shigesawa ◽  
Mikio Tsuji
Keyword(s):  
Time Domain ◽  
Leaky Wave ◽  
The Time Domain ◽  
Wave Phenomena

scholarly journals On finding a cavity in a thermoelastic body using a single displacement measurement over a finite time interval on the surface of the body

2018 ◽  
Vol 26 (3) ◽  
pp. 369-394 ◽  
Author(s):  
Masaru Ikehata
Keyword(s):  
Time Domain ◽  
Mathematical Formulation ◽  
Three Dimensional ◽  
Coupled System ◽  
The Body ◽  
Time Interval ◽  
Heat Equations ◽  
Time Domain Data ◽  
Thermoelastic Body ◽  
The Time Domain

AbstractA mathematical formulation of an estimation problem of a cavity inside a three-dimensional thermoelastic body by using time domain data is considered. The governing equation of the problem is given by a system of equations in the linear theory of thermoelasticity which is a coupled system of the elastic wave and heat equations. A new version of the enclosure method in the time domain which is originally developed for the classical wave equation is established. For a comparison, the results in the decoupled case are also given.

Time-Domain Poroelastic Green's Functions

2003 ◽  
Vol 11 (03) ◽  
pp. 491-501 ◽  
Author(s):  
Andrzej Hanyga
Keyword(s):  
Differential Equations ◽  
Asymptotic Solution ◽  
Time Domain ◽  
Green's Functions ◽  
Green’S Functions ◽  
Isotropic Case ◽  
The Time Domain ◽  
Singular Memory ◽  
Asymptotic Time

A method previously developed for asymptotic solution of systems of integro-differential equations with singular memory is applied to the determination of the time-domain asymptotic Green's function of Biot's poroelasticity. Asymptotic time-domain Green's functions are constructed in a neighborhood of the wavefronts. The general anisotropic medium as well as the isotropic case are considered.

scholarly journals An accelerated hybrid TLM-IE method for the investigation of shielding effectiveness

2010 ◽  
Vol 8 ◽  
pp. 13-18 ◽  
Author(s):  
N. Fichtner ◽  
P. Russer
Keyword(s):  
Integral Equations ◽  
Time Domain ◽  
Numerical Technique ◽  
Electromagnetic Coupling ◽  
Shielding Effectiveness ◽  
Transient Wave ◽  
Domain Integral ◽  
Tlm Method ◽  
Time Domain Integral Equations ◽  
The Time Domain

Abstract. A hybrid numerical technique combining time-domain integral equations (TD-IE) with the transmission line matrix (TLM) method is presented for the efficient modeling of transient wave phenomena. This hybrid method allows the full-wave modeling of circuits in the time-domain as well as the electromagnetic coupling of remote TLM subdomains using integral equations (IE). By using the integral equations the space between the TLM subdomains is not discretized and consequently doesn't contribute to the computational effort. The cost for the evaluation of the time-domain integral equations (TD-IE) is further reduced using a suitable plane-wave representation of the source terms. The hybrid TD-IE/TLM method is applied in the computation of the shielding effectiveness (SE) of metallic enclosures.

scholarly journals Derivative-Extended Time Domain Reduction for Coupled Systems Using Chebyshev Expansion

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Xiaolong Wang ◽  
Yaolin Jiang ◽  
Jun Liu
Keyword(s):  
Model Reduction ◽  
Time Domain ◽  
Coupled System ◽  
Projection Methods ◽  
Domain Model ◽  
Coupled Systems ◽  
The Time Domain ◽  
Derivative Information ◽  
Projection Matrices ◽  
Domain Information

The time domain model reduction based on general orthogonal polynomials has been presented for linear systems. In this paper, we extend this approach by taking the derivative information of the system into account in the context of model reduction of coupled systems. We expand the derivative terms over the Chebyshev polynomial basis and show that Chebyshev coefficients of the expansion possess a specific structure, making it possible to preserve much more time domain information by employing projection methods. Besides, with the well-defined projection matrices, the resulting reduced model shares the same topological structure with the original coupled system. Two numerical examples are simulated to showcase the accuracy of incorporating the derivative information into model reduction.

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