• Title/Summary/Keyword: Inhomogeneous medium

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Wave propagation in an Inhomogeneous Anisotropic Medium through Variational Finite Element Method (변분 유한요소법에 의한 비균질 비등방성 매질에서의 전파특성)

  • 김현준;홍용인;김두경;김정기
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.3 no.1
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    • pp.33-41
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    • 1992
  • In this paper the propagation problems of waves nomally incident upon an anisotropic medium with arbitrary permittivity tensors are analyzed through the variational finite element method. First, a variational equation is derived from the new approach basd on the induction theorm, reactions, and reciprocity. Next, by using the finite element method, the propagation problems are solved from the obtained functional. Specially, the reflection and transmission coefficient and axis ratio are obtained on the case of normally incident upon a homogeneous and inhomogeneous anisotropic medium such as cold mgnetoplasma slab and showed agreement with those of the previous method.

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ESTIMATION OF THE SINGULAR COEFFICIENT IN THE STEADY STATE DIFFUSION EQUATION

  • Cho, Chung-Ki
    • Journal of applied mathematics & informatics
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    • v.10 no.1_2
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    • pp.309-323
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    • 2002
  • This paper studies the parameter estimation problem for a steady state flow in an inhomogeneous medium. Our approximation scheme could be used when the diffusion coefficient is singular. The function space parameter estimation convergence(FSPEC) is considered and numerical simulations are performed.

Evaluation of Effective Soil Moisture From Natural Soil Surfaces (지표면 토양의 유효 수분함유량 산출에 관한 연구)

  • 오이석
    • Korean Journal of Remote Sensing
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    • v.11 no.3
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    • pp.117-127
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    • 1995
  • In this paper several methods for retriving appropriate values of effective soil moisture contents from natural soil surfaces are introduced and compared each other. The soil medium has usually a nonuniform moisture profile; i.e., relatively dry at the top layer and relatively wet at the bottom layer. The effective soil moisture represents the quantitative value of soil moisture of the inhomogeneous soil medium in an average sense. A simple method is an arithmetic averaging of soil moisture values obtained from several layers of a soil surface. Otherwise, the penetration depths can be computed from a homogeneous and an inhomogeneous soil surfaces and compared in order to obtain the effective soil mosture. The other method is to obtain the effective soil moisture by comparing the reflectivities from both of a homogeneous and an inhomogeneous surfaces. Those methods are compared and the reflectivity technique is examined in more detail since the rader scattering is dominated by the reflectivity instead of the penetration.

Wave Propagation Analysis in Inhomogeneous Media by Using the Fourier Method

  • Kim, Hyun-Sil;Kim, Jae-Seung;Kang, Hyun-Joo;Kim, Sang-Ryul
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.3E
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    • pp.35-42
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    • 1998
  • Transient acoustic and elastic wave propagation in inhomogeneous media are studied by using the Fourier method. It is known that the fourier method has advantages in memory requirements and computing speed over conventional methods such as FDM and FEM, because the Fourier method needs less grid points for achieving the same accuracy. To verify the proposed numerical scheme, several examples having analytic solutions are considered, where two different semi-infinite media are in contact along a plane boundary. The comparisons of numerical results by the Fourier method and analytic solutions show good agreements. In addition, the fourier method is applied to a layered half-plane, in which an elastic semi-infinite medium is covered by an elastic layer of finite thickness. It is showed how to derive the analytic solutions by using the Cagniard-de Hoop method. The numerical solutions are in excellent agreements with analytic results.

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Formation of a Stationary Light Pulse in a Doppler-Broadened EIT Medium

  • Chough, Y.T.
    • Journal of the Korean Physical Society
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    • v.73 no.10
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    • pp.1479-1485
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    • 2018
  • A number of experiments have been performed on light slowing and stopping in the electromagnetically induced transparency (EIT) media of hot atomic gases where the Doppler-shift may add detunings to the field frequencies in an inhomogeneous fashion. We provide here a theoretical analysis as to the effect of such a Doppler-broadened environment on the dynamics of the system in comparison to a cold atomic medium. We will show that one of the most critical factors in the formation of a stationary light pulse is the enhancement of the excited-state decay rate caused by the collisions between the atoms of the medium and the molecules of the buffer gas.

Analytical Solutions of Birefringence and Dichroism Spectroscopy for the Jg = 0 → Je = 1 Transition

  • Noh, Heung-Ryoul
    • Journal of the Optical Society of Korea
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    • v.18 no.4
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    • pp.365-369
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    • 2014
  • We present accurate analytical solutions of the lineshapes of birefringence (rotation) and dichroism (absorption) spectroscopy for a circular anisotropic medium composed of atoms of the transition $J_g=0{\rightarrow}J_e=1$. The susceptibility of a weak probe beam was analytically calculated and was averaged over a Maxwell-Boltzmann velocity distribution. The lineshapes of the two spectroscopies were then presented in analytical forms at arbitrary values of the linewidths of the inhomogeneous (Doppler) broadening and the homogeneous (natural) broadening of the atoms.

Analysis and Design of Asymmetric Coupled Line Directional Couplers for Microwave Integrated Circuits (마이크로파 집적회로(MIC)를 위한 비대칭 방향성 결합기의 해석과 설계)

  • 진연강
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.12 no.3
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    • pp.298-308
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    • 1987
  • It is shown that ideal directional couplers consisting of coupled asymmetric lines in an inhomogeneous medium can be realized equalizing the inductive and capacitive coefficients of coupling. Design procedures and examples of the couplers are presented.

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Electro-magneto-thermoelastic surface waves in non-homogeneous orthotropic granular half space

  • Kakar, Rajneesh;Kakar, Shikha
    • Geomechanics and Engineering
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    • v.7 no.1
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    • pp.1-36
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    • 2014
  • The effect of various parameters on the propagation of surface waves in electro-magneto thermoelastic orthotropic granular non-homogeneous medium subjected to gravity and initial compression has been studied. All material coefficients are obeyed the same exponent-law dependence on the depth of the granular elastic half space. Some special cases investigated by earlier researchers have also been deduced. Dispersion curves are computed numerically and presented graphically.

An Analysis of the Wave Properties in an Inhomogeneous Anisotropic Medium using Variational Reaction Theory (변분 리액션 이론을 이용한 비균질 비등방성 매질에서의 전파특성 해석)

  • 김현준;홍용인;김정기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.10
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    • pp.1461-1468
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    • 1993
  • In this paper the propagation problem of waves obliquely incident upon an anisotropic medium with arbitrary permittivity tensors is analyzed through a partial variational finite element method. First, a variational equation is derived from the new approach based on the induction theorem, reactions, and reciprocity. Next, by using the finite element method, the propagation problems are solved from the obtained functional. Also included are numerical results for the problem of waves incident upon a magnetoplasma slab.

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Use of Time Reversal Techniques for Focusing of Ultrasonic Array Transducer Beams

  • Kim, Hak-Joon;Song, Sung-Jin;Thompson R. Bruce;Kim, Jae-Hee;Eom, Heung-Sup
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.3
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    • pp.190-197
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    • 2006
  • For enhancement of flaw detactability using array transducers, focusing of ultrasonic waves on a target in an inhomogeneous medium or through a complex geometry is important. But focusing can be strongly degraded by geometrical distortion of field radiated by the array transducers or by sound speed fluctuations in the propagating medium. In recent years, the time reversal technique has been proposed. Thus, in this paper, we describe the basic principal of the time reversal technique for focusing. Then, the implementation results of the time reversal technique for ultrasonic inspections using bulk waves and guided waves generated by array transducers are presented.