• Interaction and multiscale mechanics
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• 제7권1호
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• pp.543-561
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• 2014

We present a full energy and force formulation of the quasicontinuum method with non-local and local transition elements. Non-local transition elements are developed to transmit inhomogeneity from the atomistic to the continuum regions. Local transition elements are developed to resolve the mathematical mismatch between non-local atoms and the local continuum. The rationale behind these transition elements is provided by analyzing the energy and force transitions between atoms and continuum under the Cauchy-Born rule. We show that breakdown of the Cauchy-Born rule occurs for slaved atoms of local elements within the cutoff of non-local atoms. The inadequacy of the Cauchy-Born rule at the transition region naturally leads to the need of atomistic treatment of transition slaved and transition representative atoms. Such an atomistic treatment together with a full or cutoff sampling allows non-local transition elements containing these transition entities to transmit inhomogeneity. Different force formulations for transition representative atoms and pure local representative atoms allow the local transition elements to resolve non-local and local mismatches. The method presented herein is validated by force calculations in an unstressed perfect crystal as well as an unrelaxed grain boundary model. A nanoindentation simulation in 3D is conducted to demonstrate the accuracy and efficiency of the proposed method.

• 한국기록관리학회지
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• 제22권3호
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• pp.21-36
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• 2022

최근 기록이 지닌 정보로서의 속성에 주목해야 한다는 논의가 활발히 제기되고 있다. 이는 전자기록 환경을 맞아 행위에 대한 증거로서의 속성에만 초점을 맞추어 온 동향에 대한 반향이다. 하지만 아직까지 기록이 지닌 정보로서의 속성에 대한 명확한 개념은 정립되지 않은 상태이다. 이에 본고에서는 기록과 정보 간의 관계 정립을 위한 일환으로 정보 컨티뉴엄 모델을 분석하고자 한다. 정보 컨티뉴엄은 레코드 컨티뉴엄을 기반으로 레코드키핑 관점에서의 새로운 정보 개념을 정립하기 위해 고안된 이론 체계로, 레코드키핑 내에 존재하는 정보관리를 위한 요소들을 파악할 수 있는 하나의 개념적 틀을 제공해준다. 이에 2장에서는 레코드 컨티뉴엄 개발 이후 정보 컨티뉴엄이 개발된 배경 및 과정을 살펴본 다음, 구조주의 이론 등 정보학 이론을 차용해 정립한 정보의 개념을 레코드 컨티뉴엄과 연계하여 고찰하였다. 이어 3장에서는 정보 컨티뉴엄의 개념적 구조와 함께 정보의 활용 목적 및 방식을 고찰한 후, 레코드키핑 내에 존재하는 정보관리를 위한 요소들을 구조적으로 도식화한 정보 컨티뉴엄 모델상의 4개 차원 및 속성을 분석하였다. 이러한 분석을 기반으로 4장에서는 정보 컨티뉴엄이 지닌 의의 및 한계를 제시하고자 하였다.

• Structural Engineering and Mechanics
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• 제19권6호
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• pp.619-637
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• 2005

The objective of this research was to determine the Vlasov soil parameters for quadratically varying elasticity modulus $E_s$(z) of the compressible soil continuum and discuss the interaction affect between two close plates. Interaction problem carried on for uniformly distributed load carrying plates. Plate region was simulated by Kirchhoff plate theory based (mixed or displacement type) 2D elements and the foundation continuum was simulated by displacement type 2D elements. At the contact region, plate and foundation elements were geometrically coupled with each other. In this study the necessary formulas for the Vlasov parameters were derived when Young's modulus of the soil continuum was varying as a quadratic function of z-coordinate through the depth of the foundation. In the examples, first the elements and the iterative FE algorithm was verified and later the results of quadratic variation of $E_s$(z) were compared with the previous examples in order to discuss the general behavior. As a final example two plates close to each other resting on elastic foundation were handled to see their interaction influences on the Vlasov foundation parameters. Original examples were solved using both mixed and displacement type plate elements in order to confirm the results.

• Structural Engineering and Mechanics
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• 제58권2호
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• pp.231-242
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• 2016

To minimize the compliance of frame, a method to optimize the topology of bracing system in a frame is presented. The frame is first filled uniformly with a truss-like continuum, in which there are an infinite number of members. The frame and truss-like continuum are analysed by the finite element method altogether. By optimizing the distribution of members in the truss-like continuum over the whole design domain, the optimal bracing pattern is determined. As a result, the frame's lateral stiffness is enforced. Structural compliance and displacement are decreased greatly with a smaller increase in material volume. Since optimal bracing systems are described by the distribution field of members, rather than by elements, fewer elements are needed to establish the detailed structure. Furthermore, no numerical instability exists. Therefore it has high calculation effectiveness.

• Structural Engineering and Mechanics
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• 제30권4호
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• pp.467-480
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• 2008

An aggregation multigrid method (AMM) is a leading iterative solver in solid mechanics. Recently, AMM is applied for solving Schur Complement system in the FE analysis of shell structures. In this work, an extended application of AMM for solving Schur Complement system in the FE analysis of continuum elements is presented. Further, the performance of the proposed AMM in multiple load cases, which is a challenging problem for an iterative solver, is studied. The proposed method is developed by combining the substructuring and the multigrid methods. The substructuring method avoids factorizing the full-size matrix of an original system and the multigrid method gives near-optimal convergence. This method is demonstrated for the FE analysis of several elastostatic problems. The numerical results show better performance by the proposed method as compared to the preconditioned conjugate gradient method. The smaller computational cost for the iterative procedure of the proposed method gives a good alternative to a direct solver in large systems with multiple load cases.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.24-27
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• 1997

In the present work, rigid-plastic continuum elements employing the shape change and anisotropic effects are derived for the purpose of applying more realistic blankholding force condition in three-dimensional finite element analysis of sheet metal forming process. In order to incorporate the effect of shape change effectively in the derivation of finite element equation using continuum element for sheet metal forming, the convected coordinate system is introduced, rendering the analysis more rigorous and accurate. The formulation is extended to cover the orthotropic material using Hill's quadratic yield function. For the purpose of applying more realistic blankholding force condition, distributed normal and associated frictional tangent forces are employed in the blankholder, which is pressed normal and associated frictional tangent forces are employed in the blankholder, which is pressed against the flange until the resultant contact force with the blank reaches the prescribed value. As an example of sheet metal forming process coupling the effect of planar anisotropy and that of blankholding boundary condition, circular cup deep drawing has been analyzed considering both effects together.

• Journal of the Optical Society of Korea
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• 제9권2호
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• pp.39-44
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• 2005

Unlike for the bound states, several different boundary conditions are used for the continuum states above the barrier in semiconductor quantum wells. We employed three boundary conditions, infinite potential barrier boundary condition, periodic boundary condition and scattering boundary condition, and calculated the local number of states, wavefunctions and optical matrix elements for the symmetric and asymmetric quantum wells. We discussed how these quantities are related in the three boundary conditions. We argue that the scattering boundary condition has several advantages over the other two cases. These results would be useful in understanding quantum well lasers and detectors involving continuum states.

• 한국농공학회지
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• 제22권2호
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• pp.83-100
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• 1980

This study was intended to computerize the structural analysis of two-dimensional continuum by finite element method, and to provide a preparatory basis for more sophisticated and more generalized computer programs of this kind. A computer program, applicable to any shape of two-dimensional continuum, was formulated on the basis of 16-degree-of- freedom rectangular element. Various computational aspects pertaining to the implementation of finite element method were reviewed and settled in the course of programming. The validity of the program was checked through several case studies. To assess the accuracy and the convergence characteristics of the method, the results computed by the program were compared with solutions by other methods, namely the analytical Navier's method and the framework method. Through actual programming and analysis of the computed results, the following facts were recognized; 1) The stiffness matrix should necessarily be assembled in a condensed form in order to make it possible to discretize the continuum into practically adequate number of elements without using back-up storage. 2) For minimization of solution time, in-core solution of the equilibrium equation is essential. LDLT decomposition is recommended for stiffness matrices condensed by the compacted column storage scheme. 3) As for rectangular plates, the finite element method shows better performances both in the accuracy and in the rate of convergence than the framework method. As the number of elements increases, the error of the finite element method approaches around 1%. 4) Regardless of the structural shape, there is a uniform tendency in convergence characteristics dependent on the shape of element. Square elements show the best performance. 5) The accuracy of computation is independent of the interpolation function selected.

• 한국도서관정보학회지
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• 제53권3호
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• pp.25-46
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• 2022

본고에서는 레코드 컨티뉴엄에서의 평가 논리를 분석하였다. 전자기록 환경에서의 평가가 지닌 보다 근원적인 함의를 파악하기 위해서는 레코드 컨티뉴엄에 내재되어 있는 평가 논리에 대한 분석이 필수적으로 요구된다. 레코드 컨티뉴엄은 기존의 라이프사이클을 기반으로 한 평가 논리 및 여기서 연유한 양분화된 기록관리체제에 대한 반론에서 출발한 이론체계라는 점에서, 전자기록 환경에서의 평가에 관한 이론적 기반을 제공해 줄 수 있다. 특히 평가는 기록이 지닌 의미를 모색하는 합목적적 행위임을 감안할 때, 레코드 컨티뉴엄에서 의도한 기록의 개념 및 의미에 대한 재해석은 이전과는 다른 평가상의 논리들을 도출할 수 있게 해준다. 이에 본고에서는 라이프사이클 평가 논리와의 비교 및 레코드 컨티뉴엄에서 제시한 새로운 기록에 대한 인식을 기반으로, 레코드 컨티뉴엄 평가 논리상의 핵심 요소를 세 가지 측면에 초점을 맞추어 분석하였다.

• Structural Engineering and Mechanics
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• 제43권4호
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• pp.411-437
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• 2012

In this paper, we propose a continuum mechanics based 3-D beam finite element with cross-sectional discretization allowing for warping displacements. The beam element is directly derived from the assemblage of 3-D solid elements, and this approach results in inherently advanced modeling capabilities of the beam element. In the beam formulation, warping is fully coupled with bending, shearing, and stretching. Consequently, the proposed beam elements can consider free and constrained warping conditions, eccentricities, curved geometries, varying sections, as well as arbitrary cross-sections (including thin/thick-walled, open/closed, and single/multi-cell cross-sections). We then study the modeling and predictive capabilities of the beam elements in twisting beam problems according to geometries, boundary conditions, and cross-sectional meshes. The results are compared with reference solutions obtained by analytical methods and solid and shell finite element models. Excellent modeling capabilities and solution accuracy of the proposed beam element are observed.