• Title/Summary/Keyword: 수치 적분

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3-D EM Modeling Using Approximate Integral Equation Method for the Models with Non 1-D Background Conductivity (1차원 이외의 배경 전기전도도 구조에서 근사 적분방정식을 이용한 3차원 전자탐사 모델링)

  • Lee Seong Kon;Zhdanov Michael S.
    • Geophysics and Geophysical Exploration
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    • v.8 no.3
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    • pp.207-217
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    • 2005
  • We present a new approximate formulation of the integral equation (IE) method for models with variable background conductivity. This method overcomes the standard limitation of the conventional If method related to the use of a horizontally layered background only. The new approximate IE method still employs the Green's functions for a horizontally layered 1-D model. However, the new method allows us to use an inhomogeneous background with the IE method. The method was carefully tested for modeling the EM field for complex structures with a known variable background conductivity. It can find wide application in modeling EM data for multiple geological models with some common geoelectrical features, like a known inhomogeneous overburden, or salt dome structures.

Explicit Transient Simulation of SH-waves Using a Spectral Element Method (스펙트럴 요소법을 이용한 SH파 전파의 외연적 시간이력해석)

  • Youn, Seungwook;Kang, Jun Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.2
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    • pp.87-95
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    • 2018
  • This paper introduces a new explicit spectral element method for the simulation of SH-waves in semi-infinite domains. To simulate the wave motion in unbounded domains, it is necessary to reduce the infinite extent to a finite computational domain of interest. To prevent the wave reflection from the trunctated boundaries, perfectly matched layer(PML) wave-absorbing boundary is introduced. The forward problem for simulating SH-waves in PML-truncated domains can be formulated as second-order PDEs. The second-order semi-discrete form of the governing PDEs is constructed by using a mixed spectral elements with Legendre-gauss-Lobatto quadrature method, which results in a diagonalized mass matrix. Then the second-order semi-discrete form is transformed to a first-order, whose solutions are calculated by the fourth-order Runge-Kutta method. Numerical examples showed that solutions of SH-wave in the two-dimensional analysis domain resulted in stable and accurate, and reflections from truncated boundaries could be reduced by using PML boundaries. Elastic wave propagation analysis using explicit time integration method may be apt for solving larger domain problems such as three-dimensional elastic wave problem more efficiently.

Open Boundary Modeling for Fully Nonlinear Wave Simulation in a 3-D Numerical Wave Tank (3-D 수치 파수조에서 비선형파 시뮬레이션을 위한 방사경계조건의 모델링)

  • Boo, Sung-Youn
    • Journal of Ocean Engineering and Technology
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    • v.12 no.1
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    • pp.99-106
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    • 1998
  • 3차원 파수조에서 완전 비선형파를 시뮬레이션하기 위하여 우선 랜킨 소스를 기저로한 적분방정식을 고차경계요소법을 이용하여 이산화하였다. 그리고 방사경계조건은 파흡수 비치와 포텐셜 스트레칭 기법을 이용하여 모델링하였으며, 비선형 자유표면과 경계조건식은 고차 예측 및 보정 기법을 이용하여 시간 적분하였다. 파흡수 비치는 파의 진행방향 특성에 따라 수조내에 다양하게 배치할 수 있으며 비칭서 흡수가 덜된 파는 수조의 길이 방향 끝단에서 포텐셜 스트레칭 기법에 의하여 반사없이 진행하도록 하였다. 수치실험 결과 일-에너지 보존법칙과 모멘텀-임펄스 보존 법칙이 만족됨으로써 본 수치기법의 효용성이 검증되었다.

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라틴-하이퍼큐브 실험게획 간의 거리 계산과 비교

  • 박정수;황현식
    • The Korean Journal of Applied Statistics
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    • v.13 no.2
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    • pp.477-488
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    • 2000
  • A distance measure between two Latin-hypercube designs is defined and its expected value is computed. It was computed by using mathematical statistics, numerical analysis (multidimensional numerical integration), Monte-carlo method, and the theory of asymptotic normal distribution. For the comparison of two Latin-hypercube designs with same structure but different randomness, the difference of expected values of response function and information mass of experimental designs are considered. These methods may be useful in comparison between two general experimental designs.

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Boundary Integral Equation Method by Cubic Spline (Cubic Spline을 사용한 경계요소법)

  • 서승남
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.2 no.1
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    • pp.11-17
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    • 1990
  • Dirichlet boundary value problems originated from unsteady deep water wave propagation are transformed to Boundary Intergral Equation Methods by use of a free surface Green's function and the integral equations are discretized by a cubic spline element method. In order to enhance the stability of the numerical model based on the derived Fredholm integral equation of 1 st kind, the method by Hsiao and MacCamy (1973) is employed. The numerical model is tested against exact solutions for two cases and the model shows very good accuracy.

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Implicit Time Integration Scheme for Real-Time Hybrid Test System (실시간 하이브리드 실험 시스템을 위한 Implicit 시간적분법)

  • Jung, Rae-Young
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.5 s.51
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    • pp.99-106
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    • 2006
  • The Real-Time Hybrid Test system presented in this paper is based on the pseudodynamic test method, and it combines physical testing with model-based simulation. The system is designed to achieve a rate of loading that is significantly higher than that of a conventional pseudodynamic test approaching the real-time response of a structure subjected to earthquake loads. To provide robust computation environment for the analysis of many degree-of-freedom structures, the system adopts an implicit time integration scheme in the model-based simulation. This paper presents an overview of the developed system and numerical simulations that were conducted to evaluate the performance of the computation scheme adopted here. Results of these studies have demonstrated the good performance of the computation scheme for real-time multiple-degree-of-freedom tests.

A Study on Integraion Method for Improvement of Numerical Stability of Meshfree Method (무요소법의 수치적 안정성 개선을 위한 적분기법 연구)

  • Kang, JaeWon;Kang, Da Hoon;Cho, Jin Yeon;Kim, Jeong Ho
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.3
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    • pp.210-218
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    • 2018
  • In order to generate meshes automatically for finite element analysis of complex structures such as aircraft, a large number of triangular elements are typically created. However, triangular elements are less accurate than rectangular elements, so it is difficult to obtain a reliable solution. This problem can be improved through the meshfree method using the back cell integration. However, this method also causes some problems such as over-use of the integration points and inefficiency of the integral domain. In order to improve these problems, a method of performing integration by setting the integral area based on a node basis has been proposed, but in the case of incompressible material problems, the numerical accuracy deteriorates due to the vibration phenomenon of the solution. Therefore, in this paper, the modified meshfree method is proposed which sets the integral domain as an element domain instead of the nodal domain, and the proposed method improves the numerical instability caused by the conventional meshfree method without decreasing the accuracy regardles of the shape of integral domain. The effectiveness of the modified meshfree method is verified by using 2-D examples.

Stress Intensity Factor of Single Edge Cracked Plates Considering Materials and Geometry of Patch by p-Convergent Partial Layerwise Model (p-수렴 부분층별모델에 의한 일변균열판의 패치재료 및 기하형상에 따른 응력확대계수)

  • Ahn, Hyeon-Ji;Ahn, Jae-Seok;Woo, Kwang-Sung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.2
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    • pp.191-198
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    • 2010
  • This study investigated that the stress reduction of single edge cracked plates with patch repairs according to different type of patching such as material, size and thickness of patch and adhesive as well as single sided or double sided patches. As a numerical tool, the p-convergent partial layerwise model has been employed. The proposed model is formulated by assuming piecewise linear variation of in-plane displacement and a constant value of out-of-plane displacements across thickness. The integrals of Legendre polynomials are chosen to define displacement fields and Gauss-Lobatto numerical integration is implemented in order to directly obtain maximum values occurred at the nodal points of each layer without other extrapolation techniques. Also, total strain energy release rate method is adopted to obtain stress intensity factors. Numerical examples are presented not only to demonstrate the stress reduction effect in terms of non-dimensional stress intensity factor and deflection with respect to different type of patch repairs, but also the accuracy of proposed model.

Numerical Modeling of Elastic Wave Scattering in an Isotropic Medium Containing an Orthotropic Inclusion (직교이방성 함유체를 포함하는 등방성 기지에서의 탄성파 산란 수치해석 모델)

  • Lee, Jung-Ki
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.1
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    • pp.69-79
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    • 2001
  • A volume integral equation method(VIEM) is applied for the effective analysis of elastic wave scattering problems in unbounded solids containing general anisotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only the Green's function for the unbounded isotropic matrix is Involved In their formulation for the analysis. nis new method can also be applied to general two-dimensional elastodynamic problems with arbitrary shapes and number of anisotropic inclusions. Through the analysis of plane elastodynamic problems in unbounded isotropic matrix with an orthotropic inclusion, it is established that this new method is very accurate and effective for solving plane elastic problems in unbounded solids containing general anisotropic inclusions.

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A Study on the Boundary Element Method for Numerical Analysis of Nonlinear Free Surface Waves(I) (비선형 자유표면파의 수치해석을 위한 경계요소법에 대한 연구 (I))

  • Sung, Hong G.;Hong, Sa Y.;Choi, Hang S.
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.4
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    • pp.53-60
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    • 1997
  • Nonlinear free surface flow phenomena have teen studied by several kinds of numerical methods, of which boundary element method has been known as most promising one. There, however, remain many difficulties to be solved in the numerical procedures by boundary element analysis. In this paper, an efficient calculation of elemental integrals and iterative solution algorithm for the resulting system of equations were thoroughly investigated in order to enhance the procedure of the boundary element analysis. Advantages of the herein developed boundary element analysis code are demonstrated in terms of accuracy and convergence for typical boundary-value problems with free surface.

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