• Title, Summary, Keyword: infinite elements

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A Coupling of Finite Elements and Boundary Elements for Half Plane Problems (반무한영역 문제에 대한 유한요소와 경계요소의 조합)

  • 김문겸;임윤묵
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.49-54
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    • 1988
  • A procedure which may be useful in dealing with problems of half plane is considered. Boundary elements are combined with finite elements to facilitate their merits. Boundary elements for semi-infinite region are composed using the Melan's solution for half plane. Finite elements are used to model irregurarity or the nonhomogeneity of materials, which is usual in underground structures. In order to verify the procedure, a shallow tunnel under internal pressure is analysed using the finite element method, the boundary element method, and the combined method. It is shown that the developed Procedure is accurate enough compared with other method.

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Transposable Elements: No More 'Junk DNA'

  • Kim, Yun-Ji;Lee, Jungnam;Han, Kyudong
    • Genomics & Informatics
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    • v.10 no.4
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    • pp.226-233
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    • 2012
  • Since the advent of whole-genome sequencing, transposable elements (TEs), just thought to be 'junk' DNA, have been noticed because of their numerous copies in various eukaryotic genomes. Many studies about TEs have been conducted to discover their functions in their host genomes. Based on the results of those studies, it has been generally accepted that they have a function to cause genomic and genetic variations. However, their infinite functions are not fully elucidated. Through various mechanisms, including de novo TE insertions, TE insertion-mediated deletions, and recombination events, they manipulate their host genomes. In this review, we focus on Alu, L1, human endogenous retrovirus, and short interspersed element/variable number of tandem repeats/Alu (SVA) elements and discuss how they have affected primate genomes, especially the human and chimpanzee genomes, since their divergence.

Use of finite and infinite elements in static analysis of pavement

  • Patil, V.A.;Sawant, V.A.;Deb, Kousik
    • Interaction and multiscale mechanics
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    • v.3 no.1
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    • pp.95-110
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    • 2010
  • In recent years, study of the static response of pavements to moving vehicle and aircraft loads has received significant attention because of its relevance to the design of pavements and airport runways. The static response of beams resting on an elastic foundation and subjected to moving loads was studied by several researchers in the past. However, most of these studies were limited to steady-state analytical solutions for infinitely long beams resting on Winkler-type elastic foundations. Although the modelling of subgrade as a continuum is more accurate, such an approach can hardly be incorporated in analysis due to its complexity. In contrast, the two-parameter foundation model provides a better way for simulating the underlying soil medium and is conceptually more appealing than the one-parameter (Winkler) foundation model. The finite element method is one of the most suitable mathematical tools for analysing rigid pavements under moving loads. This paper presents an improved solution algorithm based on the finite element method for the static analysis of rigid pavements under moving vehicular or aircraft loads. The concrete pavement is discretized by finite and infinite beam elements, with the latter for modelling the infinity boundary conditions. The underlying soil medium is modelled by the Pasternak model allowing the shear interaction to exist between the spring elements. This can be accomplished by connecting the spring elements to a layer of incompressible vertical elements that can deform in transverse shear only. The deformations and forces maintaining equilibrium in the shear layer are considered by assuming the shear layer to be isotropic. A parametric study is conducted to investigate the effect of the position of moving loads on the response of pavement.

수학의 역사와 오류

  • 이종희
    • Journal for History of Mathematics
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    • v.15 no.3
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    • pp.35-48
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    • 2002
  • In this paper, we explore development of mathematical knowledge, especially calculus, non-Euclidean geometry, Euler's theorem, and the comparison of the number of elements in two infinite sets. And we analyze kinds of errors and the roles for errors with respect to increasing knowledge in mathematics.

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Coupled Nonlinear Finite Element-Boundary Element Analysis of Nuclear Waste Storage Structures Considering Infinite Boundaries (비선형 유한요소-경계요소 조합에 의한 핵폐기구조체의 무한영역해석)

  • 김문겸;허택녕
    • Computational Structural Engineering
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    • v.6 no.4
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    • pp.89-98
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    • 1993
  • As the construction of nuclear power plants are increased, nuclear wastes disposal has been faced as a serious problem. If nuclear wastes are to be buried in the underground stratum, thermo-mechanical behavior of stratum must be analyzed, because high temperature distribution has a significant effect on tunnel and surrounding stratum. In this study, in order to analyze the structural behavior of the underground which is subject to concentrated heat sources, a coupling method of nonlinear finite elements and linear boundary elements is proposed. The nonlinear finite elements (NFE) are applied in the vicinity of nuclear depository where thermo-mechanical stress is concentrated. The boundary elements are also used in infinite domain where linear behavior is expected. Using the similar method as for the problem in mechanical field, the coupled nonlinear finite element-boundary element (NFEBE) is developed. It is found that NFEBE method is more efficient than NFE which considers nonlinearity in the whole domain for the nuclear wastes depository that is expected to exhibit local nonlinearity behavior. The effect of coefficients of the rock mass such as Poisson's ratio, elastic modulus, thermal diffusivity and thermal expansion coefficient is investigated through the developed method. As a result, it is revealed that the displacements around tunnel are largely dependent on the thermal expansion coefficients.

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Time Domain Soil-Structure Interaction Analysis for Earthquake Loadings Based on Analytical Frequency-Dependent Infinite Elements (해석적 주파수종속 무한요소를 사용한 시간영역해석의 지반-구조물의 상호작용을 고려한 지진해석)

  • Kim, Doo-Kie;Yun, Chung-Bang
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.121-128
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    • 1999
  • This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far field soil. The dynamic stiffness matrices of the far field region formulated using the present method in frequency domain can be easily transformed into the corresponding matrices in time domain. At first, the equivalent earthquake forces are evaluated along the interface between the near and the far fields from the free-field response analysis carried out in frequency domain, and the results are transformed into the time domain. An efficient procedure is developed for the convolution integrals to evaluate the interaction force along the interface, which depends on the response on the interface at the past time instances as well as the concurrent instance. Then, the dynamic responses are obtained for the equivalent earthquake force and the interaction force using Newmark direct integration technique. Since the response analysis is carried out in time domain, it can be easily extended to the nonlinear analysis. Example analysis has been carried out to verify the present method in a multi-layered half-space.

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3-D Axisymmetric Fluid-Structure-Soil Interaction Analysis Using Mixed-Fluid-Element and Infinite-Element (혼합형 유체요소와 무한요소를 이용한 3차원 축대칭 유체-구조물-지반 상호작용해석)

  • 김재민;장수혁;윤정방
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.257-266
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    • 1999
  • This paper presents a method of seismic analysis for a cylindrical liquid storage structure on/in horizontally layered half.space considering the effects of the interior fluid and exterior soil medium in the frequency domain. To capture the essence of fluid-structure-soil interaction effects effectively, a mixed finite element with two-field (u, p) approximation is employed to model the compressive inviscid fluid, while the structure and soil medium are presented by the 3-D axisymmetric finite elements and dynamic infinite elements. The present FE-based method can be applied to the system with complex geometry of fluid region as well as with inhomogeneous near-field soil medium, since it can directly model both the fluid and the soil. For the purpose of verification, dominant peak frequencies in transfer functions for horizontal motions of cylindrical fluid storage tanks with rigid massless foundation on a homogeneous viscoelastic half.space are compared with those by two different added mass approaches for the fluid motion. The comparison indicates that the Present FE-based methodology gives accurate solution for the fluid-structure-soil interaction problem. Finally, as a demonstration of versatility of the present study, a seismic analysis for a real-scale LNG storage tank embedded in layered half.space is carried out, and its member forces along the height of the structure are compared with those by an added mass approach developed by the present writers.

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On the Structure of A Matrix for Dynamic Stability Analysis of One Machine to the Infinite Bus (발전기 무한모선계통의 동태안정도 해석시 A행렬의 구조)

  • 권세혁;송길영
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.39 no.1
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    • pp.1-9
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    • 1990
  • The structure of A matrix of one machine connected to the infinite bus is described for a full model. The A matrix can be partitioned to submatrices which depend on the initial operating point and do not depend on it. When the dynamic properties for several different operating points are desired, those submatrices can be obtained through simple column operation. Furthermore, the elements of A matrix can be directly calculated from the manufacturer's data. RMS quantities of the state variables for the initial operating point are used. This approach can save the labor for calculating the elements of A matrix for the dynamic stability analysis.

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An Impact Analysis of Adhesively-Bonded Single Lap Joint (단면 겹치기 접착 조인트의 충돌해석)

  • Lee, Ju-Won;Na, Won-Bae
    • Journal of Ocean Engineering and Technology
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    • v.24 no.1
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    • pp.172-177
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    • 2010
  • This study presents an explicit dynamic analysis of an adhesively bonded single-lap joint under an impact load. The finite element software, ANSYS LS-DYNA, was used for the analysis and Von Mises stresses were obtained from the analysis. To model the adherents, solid elements were used and a rigid body was assumed for impactor modeling. Three impact heights (1 m, 5 m, and 10 m) were applied to consider different impact conditions and infinite boundary conditions were applied to the end-area of each adherent to save computational time in the analysis. In addition to investigating the stresses in the normal state, we also investigated the stresses in a damaged state (elasticity deterioration), simulated by a change in Young's modulus for 36 of the 3600 elements in the upper layer of the adhesive. The results showed that the location of damage is critical to the stress state of each layer (upper, middle, and lower).

Strain-based seismic failure evaluation of coupled dam-reservoir-foundation system

  • Hariri-Ardebili, M.A.;Mirzabozorg, H.;Ghasemi, A.
    • Coupled systems mechanics
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    • v.2 no.1
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    • pp.85-110
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    • 2013
  • Generally, mass concrete structural behavior is governed by the strain components. However, relevant guidelines in dam engineering evaluate the structural behavior of concrete dams using stress-based criteria. In the present study, strain-based criteria are proposed for the first time in a professional manner and their applicability in seismic failure evaluation of an arch dam are investigated. Numerical model of the dam is provided using NSAD-DRI finite element code and the foundation is modeled to be massed using infinite elements at its far-end boundaries. The coupled dam-reservoir-foundation system is solved in Lagrangian-Eulerian domain using Newmark-${\beta}$ time integration method. Seismic performance of the dam is investigated using parameters such as the demand-capacity ratio, the cumulative inelastic duration and the extension of the overstressed/overstrained areas. Real crack profile of the dam based on the damage mechanics approach is compared with those obtained from stress-based and strain-based approaches. It is found that using stress-based criteria leads to conservative results for arch action while seismic safety evaluation using the proposed strain-based criteria leads to conservative cantilever action.