• Title/Summary/Keyword: plane wave

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Generation of a plane-wave field by point focusing of acoustic potential energy on the radiation sphere in the wavenumber domain (파수 영역의 방사 구면에서 음향 에너지 집중을 통한 평면파 생성 방법)

  • Chang, Ji-Ho;Kim, Yang-Hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.820-823
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    • 2007
  • In the wavenumber domain, each point on a radiation sphere indicates a plane wave of the frequency corresponding to radius of the sphere and the position on the sphere shows propagating direction of the plane wave. This concept is extended from the research by Choi[1] where he focus acoustic potential energy at a point on a radiation sphere. Here we propose the method to focus the energy at a point on the radiation sphere, as a result, we can easily generate a plane wave which propagates to any direction that we want.

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Determination of Plane-wave Reflection Coefficient in Underwater Acoustic Pulse Tube Using Two-dimensional Fourier Filtering (이차원 푸리에 필터링을 이용한 수중음향 펄스 튜브에서의 평면파 반사계수 결정)

  • Kim, Wan-Gu;Kang, Hwi Suk;Yoon, Suk Wang
    • The Journal of the Acoustical Society of Korea
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    • v.34 no.6
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    • pp.493-498
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    • 2015
  • Complex acoustic signals can be formed in a water-filled acoustic pulse tube under some exciting conditions. It makes difficult to measure plane-wave reflection coefficient with the pulse tube for low frequency bands. In this study, using COMSOL Multiphysics we show that the tube wall excitation generates complex acoustic field of nonplanar mode as well as planar one. From such field incident or reflected planar mode can be decomposed respectively with a modal decomposition method, two-dimensional Fourier filtering. It makes possible to more accurately determine the plane-wave reflection coefficient of acoustic specimen with time gating.

Measurement of Reflection Coefficient of Sound Absorbent Material with Respect to Angle of Incidence and Its Associated Errors (입사각에 따른 흡음재의 반사 계수 측정 방법론 및 오차에 대한 고찰)

  • 이수열;김상렬;김양한
    • Journal of KSNVE
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    • v.4 no.3
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    • pp.295-305
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    • 1994
  • The reflection coefficient of a material at oblique incidence is measured in a free field. The sound pressure distributions are measured at discrete points on two measurement lines and then decomposed into plane wave components by using spatial Fourier transform. The inciedent and reflected plane wave components are obtained from a set of "decomposition equations" of which uses the plane wave propagation theory. Numerical simulations and experiments have been performed to see the effect of finite size of measurement area. To reduce this effect, a window fuction has been performed to see the effects of finite size of mesurement area. To reduce this effect, a window function has been proposed and its effect on the measurement of sound absorbing material property has been studied as well. The reflection coefficient obtained by this method is compared with those obtained from other methods; 2-microphone method in a duct and an expirical equation of which determines the characteristic impedance .rho.c and propagation constant k of a material from flow resistance information.formation.

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Propagation of plane wave in transversely isotropic magneto-thermoelastic material with multi-dual-phase lag and two temperature

  • Lata, Parveen;Kaur, Iqbal;Singh, Kulvinder
    • Coupled systems mechanics
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    • v.9 no.5
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    • pp.411-432
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    • 2020
  • This research is devoted to the study of plane wave propagation in homogeneous transversely isotropic (HTI) magneto-thermoelastic rotating medium with combined effect of Hall current and two temperature due to multi-dual-phase lag heat transfer. It is analysed that, for 2-D assumed model, three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal) are present. The wave characteristics like phase velocity, specific loss, attenuation coefficients, energy ratios, penetration depths and amplitude ratios of transmitted and reflected waves are computed numerically and illustrated graphically and compared for different theories of thermoelasticity. Some particular cases are also derived from this research.

Analysis of Infinite Periodic Frequency Selective Surface using Method of Moment (모멘트법을 이용한 주기적 배열을 갖는 무한 크기의 주파수선택 표면(FSS) 해석)

  • 강봉수;강부식;김흥수
    • Proceedings of the IEEK Conference
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    • 2003.07a
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    • pp.290-293
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    • 2003
  • In this paper, infinite frequency selective surface comprised with rectangular plates which are arranged periodically is analyzed using Method of Moment based on Galerkin's method. In analysis, it is assumed that the plates are infinite thin perfect conductors. Based on this assumption, the reflection characteristics of the FSS is compared according to the polarization of plane-wave and the direction of incidence. In the results, the variation of reflection characteristics of the FSS highly depends on the direction of incidence when the polarization of the plane-wave is parallel to the plane of incidence, but the variation is nearly independent upon direction of incidence when the polarization of the plane-wave is perpendicular to the plane of incidence.

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Plane Wave Scattering Induced Resonant Modes of Spherical Resonator (구형태 공진기에서의 평면파 산란 공진모드)

  • Yoo, Hyoungsuk
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.9
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    • pp.1260-1263
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    • 2013
  • Plane wave scattering from a spherical resonator is calculated by solving the combined field integral equation (CFIE) with Rao-Wilton-Glisson (RWG) basis functions and the moment method. The calculations show that magnetic and electric dipoles are found at resonant modes. These characteristics are confirmed by radiation patterns in the far field region. In addition, an analysis of a magnetodielectric sphere is discussed.

A Verification of the Numerical Energy Conservation Property of the FD-TD(Finite Difference-Time Domain) Method by Using a Plane Wave Analysis (평면파 해석을 이용한 시간영역-유한차분법의 수치적 에너지 보존성질의 증명)

  • Ihn-Seok Kim
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.7 no.4
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    • pp.320-327
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    • 1996
  • This paper presents that the lossy or amplification property of the Finite Difference-Time Domain(FD-TD) method based on the leap-frog scheme is theoretically verified by using a plane wave analysis. The basic algorithm of the FD-TD method is introduced in order to help understanding the analysis procedure. Since our analysis is formulated by the Von Neumann's approach, the stability inequality is also produced as an another outcome.

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A Study of Power Absorption in Human Head Exposed to Plane Wave (평면파에 노출된 인체 두부의 전력흡수 해석)

  • 이애경;조광윤;이혁재
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.8 no.6
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    • pp.665-680
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    • 1997
  • The specific absorption rate (SAR) distributions in various models of the human head have been analyzed when the models are exposed to 350 MHz and 900 MHz plane waves. The numerical analysis is performed with the finite-difference time-domain (FDTD) method. A homogeneous sphere including a cylinderical neck, a homogeneous head shaped model, and a heterogeneous realistic model are used as models of human head. The incident plane wave used for these calculations is propagating from the front to the back or from the back to the front of the head model, with its E-field vector orientation being parallel to the major length of the body. The specific findings are: 1) the average SARs of the three models are similar mutually but the local SARs of them differ greatly mutually; 2) the power is deposed more deeply in the head at 350 MHz, which is roughly the resonant frequency of a human head, than at 900 MHz; 3) for a plane wave propagating from the back, "hot spot" is found in the neck region, not in the head; 4) for a plane wave propagating from the front, "hot spot" is found in the nose at 900 MHz, and in the upper part of the lip and the jaw region at 350 MHz.

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A Convergence Test of the Full-potential Linearized Augmented Plane Wave (FLAPW) Method: Ferromagnetic Bulk BCC Fe

  • Seo, Seung-Woo;Song, You-Young;Gul, Rahman;Kim, In-Gee;Weinert, M.;Freeman, A.J.
    • Journal of Magnetics
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    • v.14 no.4
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    • pp.137-143
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    • 2009
  • The convergence behavior of the all-electron full-potential linearized augmented plane-wave (FLAPW) method with the explicit orthogonalization (XO) scheme is tested on ferromagnetic bulk body-centered-cubic Fe. Applying a commonly used criterion relating the plane-wave and angular momentum cutoffs, $l_{max}\;=\;R_{MT}K_{max}$, where $R_{MT}$ is the muffin-tin (MT) sphere radius and $K_{max}$ is the plane-wave cutoff for the basis - the total energy is converged and stable for $K_{max}R_{MT}$ = 10. The total energy convergence dependence on the star-function cutoff, $G_{max}$, is minimal and so a $G_{max}$ of 3$K_{max}$ or a large enough $G_{max}$ is a reasonable choice. We demonstrate that the convergence with respect to $l_{max}$ or a fixed large enough $G_{max}\;and\;K_{max}$ are independent, and that $K_{max}$ provides a better measure of the convergence than $R_{MT}K_{max}$. The dependence of the total energy on $R_{MT}$ is shown to be small if the core states are treated equivalently, and that the XO scheme is able to treat systems with significantly smaller $R_{MT}$ than the standard LAPW method. For converged systems, the calculated lattice parameter, bulk modulus, and magnetic moments are in excellent agreement with the experimental values.

Elastic Wave Propagation in Monoclinic System Due to Harmonic Line Load

  • Kim, Yong-Yun
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.2E
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    • pp.47-52
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    • 1998
  • An analysis of dynamic responses is carried out on monoclinic anisotropic system due to a buried harmonic line source. The load is in the form of a normal stress acting along an arbitrary axis on the plane of symmetry within the orthotropic materials: In case that the line load is acting along the symmetry axis normal to the plane of symmetry, plane wave equation is coupled with verital shear wave and longitudinal wave. However, if the line load is acting along an arbitrary axis normal to the plane of symmetry, plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in a reference coordinate system, where the line load is coincident with a symmetry axis of the orthotropic material. Then the equation of motion is transformed into one with respect to general coordinate system with azimuthal angle by using transformation tensor. Plane wave solutions of monoclinic systems are derived for infinite media. Finally complete solutions for the plane harmonic wave are obtained by calculating the inverse of the integral transforms, in which bulk wave poles are avoided by deforming the contour of the integration to the complex plane. Numerical results for examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

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