• Title/Summary/Keyword: Green function method

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Approximate Method of Multi-Layer Green's Function Using FDTD Scheme and Rational Function Approximation (FDTD 방법과 분수 함수 근사법을 이용한 다층 구조에서의 Green 함수 근사화)

  • Kim, Yong-June;Koh, Il-Suek;Lee, Yong-Shik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.2
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    • pp.191-198
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    • 2011
  • In this paper, a method to approximate a multi-layer Green's function is proposed based on a FDTD scheme and a rational function approximation. For a given horizontal propagation wavenumber, time domain response is calculated and then Fourier transformed to the spectral domain Green's function. Using the rational function approximation, the pole and residue of the Green's function can be estimated, which are crucial for a calculation of a path loss. The proposed method can provide a wideband Green's function, while the conventional normal mode method can be applied to a single frequency problem. To validate the proposed method, We consider two problems, one of which has a analytical solution. The other is about multi-layer case, for which the proposed method is compared with the known normal mode solution, Kraken.

An Accurate Closed-form Green's Function for the Planar Structure with General Sources (일반적인 전원을 포함하는 평판구조에 대한 정확한 Closed-form 그린함수)

  • Kang Yeon-Duk;Lee Taek-Kyung
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.41 no.6 s.324
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    • pp.79-86
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    • 2004
  • In the integration of Sommerfeld type for space domain Green's function, a accurate closed-from Green's function method provides more exact solution than the typical complex image method and two-level method. The accurate closed-form Green's function method is applied to obtain the space domain Green's functions of planar structures with general sources. Please put the abstract of paper here.

Non-Equilibrium Green Function Method in Spin Transfer Torque

  • You, Chun-Yeol
    • Journal of Magnetics
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    • v.12 no.2
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    • pp.72-76
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    • 2007
  • We investigate the spin transfer torque in metallic multilayer system by employing Keldysh non-equilibrium Green function method. We study the dependences of the spin transfer torque on the detailed energy configuration of ferromagnetic, spacer, and lead layers. With Keldysh non-equilibrium Green function method applied to a single band model, we explore spin transfer torque effect in various layer structures and for various material parameters.

Prediction of Sound Field Inside Duct with Moving Medium by using one Dimensional Green's function (평균 유동을 고려한 1차원 그린 함수를 이용한 덕트 내부의 음장 예측 방법)

  • Jeon, Jong-Hoon;Kim, Yang-Hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.915-918
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    • 2005
  • Acoustic holography uses Kirchhoff·Helmholtz integral equation and Green's function which satisfies Dirichlet boundary condition Applications of acoustic holography have been taken to the sound field neglecting the effect of flow. The uniform flow, however, changes sound field and the governing equation, Green's function and so on. Thus the conventional method of acoustic holography should be changed. In this research, one possibility to apply acoustic holography to the sound field with uniform flow is introduced through checking for the plane wave in a duct. Change of Green's function due to uniform flow and one method to derive modified form of Kirchhoff·Heimholtz integral is suggested for 1-dimensional sound field. Derivation results show that using Green's function satisfying Dirichlet boundary condition, we can predict sound pressure in a duct using boundary value.

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A more efficient numerical evaluation of the green function in finite water depth

  • Xie, Zhitian;Liu, Yujie;Falzarano, Jeffrey
    • Ocean Systems Engineering
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    • v.7 no.4
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    • pp.399-412
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    • 2017
  • The Gauss-Legendre integral method is applied to numerically evaluate the Green function and its derivatives in finite water depth. In this method, the singular point of the function in the traditional integral equation can be avoided. Moreover, based on the improved Gauss-Laguerre integral method proposed in the previous research, a new methodology is developed through the Gauss-Legendre integral. Using this new methodology, the Green function with the field and source points near the water surface can be obtained, which is less mentioned in the previous research. The accuracy and efficiency of this new method is investigated. The numerical results using a Gauss-Legendre integral method show good agreements with other numerical results of direct calculations and series form in the far field. Furthermore, the cases with the field and source points near the water surface are also considered. Considering the computational efficiency, the method using the Gauss-Legendre integral proposed in this paper could obtain the accurate numerical results of the Green function and its derivatives in finite water depth and can be adopted in the near field.

On a Symbolic Method for Fully Inhomogeneous Boundary Value Problems

  • Thota, Srinivasarao
    • Kyungpook Mathematical Journal
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    • v.59 no.1
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    • pp.13-22
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    • 2019
  • This paper presents a symbolic method for solving a boundary value problem with inhomogeneous Stieltjes boundary conditions over integro-differential algebras. The proposed symbolic method includes computing the Green's operator as well as the Green's function of the given problem. Examples are presented to illustrate the proposed symbolic method.

Steady Stokes flow analysis using Axial Green's Function Formulation (축그린함수법을 이용한 정상상태의 스톡스유동해석)

  • Kim, D.W.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.256-258
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    • 2011
  • Using the axial Green's function method for Steady Stokes flows, we introduce a new pressure correction formula to satisfy the incompressibility condition, in which the pressure is related to the integral of the second order derivatives of the velocity. Based on this formula, we propose the iterative method for solving the Stokes flows in complicated domains. Even if the domain is complex, this method maintains the second order of convergence for the velocity.

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Analysis of added resistance of a ship advancing in waves (파랑중에서 전진하는 선박의 부가저항 해석)

  • 이호영;곽영기
    • Journal of Ocean Engineering and Technology
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    • v.11 no.2
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    • pp.91-99
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    • 1997
  • This paper presents theoretical formulations and numerical computations for predicting first-and second-order hydrodynamic force on a ship advvancing in waves. The theoretical formulation leads to linearized radiation and diffration problems solving the three-dimensional Green function integral equations over the mean wetted body surface. Green function representing a translating and pulsating source potantial for infinite water depth is used. In order to solve integral equations for three dimentional flows using Green function efficiently, the Hoff's method is adopted for numerical calculation of the Green function. Based on the first-order solution, the mean seconder-order forces and moments are obtained by directly integrating second-order pressure over the mean wetted body surface. The calculated items are carried out for analyzing the seakeeping characteristics of Series 60. The calculated items are hydrodynamic coefficients, wave exciting forces, frequency response functions and addd resistance in waves.

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Analysis of Waveguid Filter Using Green′s Absorbing Layer in three Dimension TLM Method (3차원 TLM 법에서 그린 흡수층을 이용한 도파관 필터의 해석)

  • 김병수;전계석
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.5
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    • pp.1001-1010
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    • 2001
  • In TLM method, Discrete Green's function ABC have been used when improved the exactness of analyzing in wide frequency band. But this technology has a complicated process to apply absorbing boundary, which means it needs additional numerical analyzing process to obtain discrete Green's function data. so, In this paper, we propose new Green's absorbing layer for simple process to apply absorbing boundary. newly proposed Green's absorbing layer is produced by applying of loss operation, loading discrete Green's function with attenuation. A state of optimum absorbing would be obtained by relation between increasing rate of loss, attenuation constant and length of green's absorbing layer. and then Analysts of waveguide BPF is carried out using Green's absorbing layer within state of optimum absorbing, then this result is in corrective agreement with the result applying traditional discrete Green's function ABC.

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Strong Ground Motion Simulation at Seismic Stations of Metropolises in South Korea by Scenario Earthquake on the Causative Fault of the 2016 Gyeongju Earthquake (2016년 경주지진 유발단층 시나리오 지진에 의한 국내 광역 도시 지진관측소에서의 강진동 모사)

  • Choi, Hoseon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.24 no.2
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    • pp.59-65
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    • 2020
  • The empirical Green's function method is applied to the foreshock and the mainshock of the 2016 Gyeongju earthquake to simulate strong ground motions of the mainshock and scenario earthquake at seismic stations of seven metropolises in South Korea, respectively. To identify the applicability of the method in advance, the mainshock is simulated, assuming the foreshock as the empirical Green's function. As a result of the simulation, the overall shape, the amplitude of PGA, and the duration and response spectra of the simulated seismic waveforms are similar with those of the observed seismic waveforms. Based on this result, a scenario earthquake on the causative fault of Gyeongju earthquake with a moment magnitude 6.5 is simulated, assuming that the mainshock serves as the empirical Green's function. As a result, the amplitude of PGA and the duration of simulated seismic waveforms are significantly increased and extended, and the spectral amplitude of the low frequency band is relatively increased compared with that of the high frequency band. If the empirical Green's function method is applied to several recent well-recorded moderate earthquakes, the simulated seismic waveforms can be used as not only input data for developing ground motion prediction equations, but also input data for creating the design response spectra of major facilities in South Korea.