• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.26-34
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• 2003

In this paper, a novel technique is proposed to arbitrarily activate the nodal points in finite element model through the meshless approximation methods such as MLS(moving least squares method), and theoretical investigations are carried out including the consistency and boundeness of numerical solution to prove the validity of the proposed method. By using the proposed node activation technique, one can activate and handle only the concerned nodes as unknown variables among the large number of nodal points in the finite element model. Therefore, the proposed technique has a great potential in design and reanalysis procedure.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.877_878
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• 2009

이 논문에서는, 편미분 방정식을 풀기위한 수치해석 기법들 가운데, 유한요소법과 달리 요소를 사용하지 않는 방법인 무요소법중의 하나인 FMLSRKM을 소개하고자한다. 이 방법의 근사화 과정과정전계 해석, 축대칭, 비균일매질에의 적용을 보임으로써 FMLSRKM이 훌륭한 근사해를 만들어낸다는 것을 검증하였다.

• Journal for History of Mathematics
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• v.18 no.4
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• pp.49-66
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• 2005

Finite element Methods(FEM) have been the primary computational methodologies in science and engineering computations for more than half centuries. One of the main limitations of the finite element approximations is that they need mesh which is an artificial constraint, and they need remeshing to solve in some special problems. The advantages in meshfree Methods is to develop meshfree interpolant schemes that only depends on particles, so they relieve the burden of remeshing and successive mesh generation. In this paper we describe the development of meshfree particle Methods and introduce the numerical schemes for Smoothed Particle hydrodynamics, meshfree Galerkin Methods and meshfree point collocation mehtods. We discusse the advantages and the shortcomings of these Methods, also we verify the applicability and efficiency of Meshfree Particle Methods.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.756-759
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• 2011

일반적으로 컴퓨터를 이용한 수치 해석에는 격자 수치 해석 방법인 유한요소법 또는 유한차분법이 주로 사용되어 왔다. 그러나 이러한 방법들은 해석하고자 하는 영역을 요소나 격자 등으로 분할해야 하기 때문에 복잡한 현상들을 다루는 데 어려움을 갖게 된다. 이를 극복하기 위해 개발된 방법이 무요소법(Meshfree Method)이며 본 논문에서는 다양한 무요소법들 중 SPH(Smoothed Particle Hydrodynamics)가 고려되어진다. SPH는 라그랑지안 수치 근사 기법을 사용하는 입자법(Particle Method)으로 SPH를 정확하게 실행하기 위해서는 적절한 경계 처리법이 요구된다. 그러나 기존의 경계 처리법은 유체 입자의 침투현상 및 커널(Kernel) 끊김 현상이 발생하기 때문에 적합하지 않다. 따라서 지금까지 SPH의 경계 처리법을 향상시키기 위해 다양한 접근법들이 제안되었으며 본 논문에서는 이러한 접근법들 중 정반사(Specular Reflection), 재회복(Bounce-back), 재도입(Reintroduce) 방법 및 경계 반발력(Repulsive Force)과 가상 입자(Ghost Particle)의 적용이 분석되고 현상 접목을 통해 적절한 경계 처리법이 제안되어진다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.35-43
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• 2003

In this paper, an efficient computational algorithm for the implementation of the newly proposed node activation technique is presented, and its computational aspects are thoroughly investigated. To verify the validity, convergence, and efficiency of the node activation technique, various numerical examples are worked out including the problems of Poisson equation, 2D elasticity problems, and 3D elasticity problems. From the numerical tests, it is verified that one can arbitrarily activate and handle the nodal points of interest in finite element model with very little loss of the numerical accuracy.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.410-415
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• 2013

Acoustic target strength (TS) is one of the most considerable design elements for survival capacities of the submarine. It needs to reduce acoustic TS that submarines are getting larger and larger, Alberich anechoic coatings are widely used as the representative method. In this paper, the finite element method (FEM) is used to analyze the reflection and transmission coefficients of Alberich anechoic coatings, which have periodic unit cells. The FEM results are compared with experimental results in the literature. Moreover, acoustic TS for the submarine is analyzed by using that result. Finally, it is shown that acoustic TS (Case 1: 10dB, Case 2: 6dB) are reduced due to the use of Alberich anechoic coatings.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.719-722
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• 2011

본 연구에서는 이동최소제곱 차분법을 2차원 동적고체문제를 해석하기 위하여 확장시켰으며 Newmark ${\beta}$ 방법을 통해 explicit와 implicit 시간적분법을 모두 적용하여 그 차이를 비교하였다. 이동최소제곱 차분법은 Taylor 다항식을 이용하여 미분계산을 근사화 함으로써 내부 및 경계에서도 강형식을 그대로 이용할 수 있다. 그래서 계산이 빠르고 수치적분이 필요하지 않아 무요소법의 장점을 잘 살릴 수 있고 해석차수를 손쉽게 조정할 수 있어 cubic 등의 고차 근사계산이 간편하다. 두 가지 수치예제를 통하여 동적해석에 대한 이동최소제곱 차분법의 적용성과 안정성을 검증하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.143-151
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• 1989

An equation to predict the ground settlement caused by tunneling through granular soils is proposed, The equation is developed modifying the Murayama equation using the results of elastic finite element analysis. Ground settlements at the underground structures in Korea and other countries are analyzed. From the results of the settlement analysis, it is found that the ground settlement associated with tunneling through granular soils is not only affected by tunnel geometry but also related to volume change characteristics of soils. It is also found that the widths of shear band, t in field conditions are 2 to 6 times greater than the values proposed in the Murayama's model. Calculated settlements using the proposed equation show reasonable agreement with the observed settlements and the results from the elasto-plastic finite element analysis. Murayama equation seems to underestimate the ground settlement.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.2
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• pp.139-148
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• 2012

The MLS(Moving Least Squares) Difference Method is a numerical scheme that combines the MLS method of Meshfree method and Taylor expansion involving not numerical quadrature or mesh structure but only nodes. This paper presents an dynamic algorithm of MLS difference method for solving transient solid mechanics problems. The developed algorithm performs time integration by using Newmark method and directly discretizes strong forms. It is very convenient to increase the order of Taylor polynomial because derivative approximations are obtained by the Taylor series expanded by MLS method without real differentiation. The accuracy and efficiency of the dynamic algorithm are verified through numerical experiments. Numerical results converge very well to the closed-form solutions and show less oscillation and periodic error than FEM(Finite Element Method).

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.647-654
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• 1985

A computer aided design package is developed that can perform such functions as computer aided inputing/drafting/modifying/outputing, automatic determination of volumetric properties, finite element analysis and post processing for the design of axisymmetric shell with slight asymmetry. In order to make the design modification easy and to accelerate the computation time for analysis, developed is a new finite element analysis which utilizes an approximate solution method and a conical ring eleement with slight asymmetry. Also proposed is a computer aided process planning algorithm which is based on the axiomatic approach.