• Title/Summary/Keyword: quadrilateral

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DISCRETE COMPACTNESS PROPERTY FOR GENERAL QUADRILATERAL MESHES

  • KIM, JI HYUN
    • Journal of applied mathematics & informatics
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    • v.40 no.5_6
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    • pp.949-958
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    • 2022
  • The aim of this papaer is to prove the discrete compactness property for modified Raviart-Thomas element(MRT) of lowest order on quadrilateral meshes. Then MRT space can be used for eigenvalue problems, and is more efficient than the lowest order ABF space since it has less degrees of freedom.

A Study on the Comparison of Triangular and Quadrilateral Elements for the Analysis of 3 Dimensional Plate Structures (3차원 판구조물 해석을 위한 삼각형요소와 사각형 요소의 비교에 관한 연구)

  • 왕지석;김유해;이우수
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.3
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    • pp.344-352
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    • 2002
  • In the analysis of the 3 dimensional plate structures by the finite element method, the triangular elements are generally used for the global stiffness matrix of the analyzed system. But the triangular elements of the plates have some problems in the process of formulation and in the precision of analysis. The formulation of the finite element method to analyze 3 dimensional plate structures using quadrilateral elements is presented in this paper. The degree of freedom off nodal point is 6, that is, the displacements in the direction off-y-z is and the rotations about x-y-z axis and then the degree of freedom off element is 24. For the comparison of the analysis using triangular elements and quadrilateral elements, the rectangular plates subjected to the uniform load and a concentrated load on the centroid of the plate, for which the theoretical solutions have been obtained, are analyzed. The calculated deflections of the rectangular plates using the finite element method by the triangular elements and the quadrilateral elements are also compared with the deflections of the plates calculated by theoretical solutions. The defections of the rectangular plates calculated by the finite element method using the quadrilateral elements are closer to the theoretical solutions than the defections calculated by the finite element method using the triangular elements. The deflection of the centroid of plate, calculated by the finite element method, converges to that of theoretical solution as the number of elements is increased. This convergence is much more rapid for the case of using the quakrilateral elements than fir the case of using triangular elements.

An Analytic Solution to Projector Pose Estimation Problem

  • Lee, Joo-Haeng
    • ETRI Journal
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    • v.34 no.6
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    • pp.978-981
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    • 2012
  • We present an analytic solution to the projector pose estimation problem for the pinhole projection model in which the source image is a centered rectangle with an unknown aspect ratio. From a single quadrilateral given as a target image, our solution gives the position and orientation of a projector as well as the aspect ratio of a source image. The proposed method decomposes the problem into two pose estimation problems of coupled line projectors aligned at each diagonal of the given quadrilateral and then computes the common solution that satisfies the relevant geometric constraints. The solution is formulated as simple analytic equations. We also provide a determinant of projectability of an arbitrary quadrilateral.

An Algorithm of Automatic 2D Quadrilateral Mesh Generation with the Line Constraints (라인(line) 제약조건을 가지는 2차원 사각 메쉬의 자동 생성 알고리즘)

  • 김인일;이규열;조두연;김태완
    • Korean Journal of Computational Design and Engineering
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    • v.8 no.1
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    • pp.10-18
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    • 2003
  • FEM (Finite Element Method) is a fundamental numerical analysis technique in wide spread use in engineering application. As the solving time occupies small portion of entire FEM analysis time because of development of hardware, the relative lime to the whole analysis time to make mesh mod-els is growing. In particular, in the case of stiffeners such as features attached to plate in ship structure, the line constraints are imposed on mesh model together with other constraints such as holes. To auto-matically generate two dimensional quadrilateral mesh with the line constraints, an algorithm is pro-posed based on the constrained Delaunay triangulation and Q-Morph algorithm in which the line constraints are not considered. The performance of the proposed algorithm is evaluated. And some numerical results of our proposed algorithm ate presented.

A study on horizontal positing for the seashore reclamation (해안매립을 위한 수평위치 결정에 관한 연구)

  • 문두열
    • Journal of Ocean Engineering and Technology
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    • v.11 no.2
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    • pp.113-121
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    • 1997
  • With the increase use of electromagnrtic distance measuring equiment, is is required that we need to study the higher dimensional applications and detail technical methods. The purpose of this paper is to improve the accuracy of ocean construction surveying and computer programming for determining of horizontal position of a quadrilateral by measuring line on traverse surveyng, trigulation and trilateration. Aa long distance measurements with high accuracy became possible by the apperance of EDM distance measuring instruments, we induced correct adjustment equation through angle condition and area conditionequation. After that we compared and experimental model. From its a result of the practical applicationto quadrilateral, it has been found that its triangulation and traverse surveying algorithms provide better accuracy than trilateration.

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표준어 단순 모음의 세대간 차이에 대한 실험음성학적 분석 연구

  • Jeong Il-Jin
    • MALSORI
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    • no.33_34
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    • pp.111-125
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    • 1997
  • This experimental phonetic analysis aims to describe standard Korean simple vowels with a view to presenting the vowel quality change from generation to generation, especially between the 50's and the 20's. This change reflects that the contemporary vowel system has both stable and unstable aspect: the former can be affirmed in the vowels with extreme positions in the vowel quadrilateral. and the latter in some vowels(e.g.,'ㅔ/ㅐ') which have the non-quantal vowel characteristics in the current vowel system. Formant values are measured to show these. And the results of acoustic analysis are presented graphically in the vowel quadrilateral for the convenience' sake. The comparison between the articulatory vowel quadrilateral and the acoustic one shows a lot concerning the current vowel quality change.

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Automatic Mesh Generation with Quadrilateral Finite Elements (사각형 유한요소망의 자동생성)

  • 채수원;신보성;민중기
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.2995-3006
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    • 1993
  • An automatic mesh generation scheme has been developed for finite element analysis with two-dimensional, quadrilateral elements. The basic strategies of the method are to transform the analysis domain into loops with key nodes and the loops are recursively subdivided into subloops with the use of best split lines. Finally by using the basic loop operators, the meshes are completed. In this algorithm an eight-node loop operator is proposed, which is useful in the area where the change of element size is large and the splitting criteria for subdividing the loops have also been modified to the existing algorithms. Lines, arcs, and cubic spline curves are used to define the boundaries of analysis domain. Sample meshes for several geometries are presented to demonstrate the robustness of the algorithm.

Automatic Quadrilateral Mesh Generation for Large Deformation Finite Element Analysis (대변형 유한요소해석을 위한 요소망 자동 생성기법)

  • 김동준;최호준;장동환;임중연;이호용;황병복
    • Transactions of Materials Processing
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    • v.12 no.3
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    • pp.194-201
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    • 2003
  • An automatic quadrilateral mesh generator for large deformation finite element analysis such as metal forming simulation was developed. The NURBS interpolation method is used for modeling arbitrary 2-D free surface. This mesh generation technique is the modified paving algorithm, which is an advancing front technique with element-by-element resolving method for paving boundary intersection problem. The mesh density for higher analysis accuracy and less analysis time can be easily controlled with high-density points, maximum and minimum element size. A couple of application to large deformation finite element analysis is given as an example, which shows versatility and applicability of the proposed approach and the developed mesh generator for large deformation finite element analysis.

Stabilization of pressure solutions in four-node quadrilateral elements

  • Lee, Sang-Ho;Kim, Sang-Hyo
    • Structural Engineering and Mechanics
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    • v.6 no.6
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    • pp.711-725
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    • 1998
  • Mixed finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements. The criterion for the stability in the pressure solution is the so-called Babu$\check{s}$ka-Brezzi stability condition, and the four-node elements based on mixed variational principles do not appear to satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element edges proposed by Hughes and Franca is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. Also, a solid mechanics problem is presented by which the stability of mixed elements can be studied. It is shown that the pressure solutions, although stable, are shown to exhibit sensitivity to the stabilization parameters.

Problem-dependent cubic linked interpolation for Mindlin plate four-node quadrilateral finite elements

  • Ribaric, Dragan
    • Structural Engineering and Mechanics
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    • v.59 no.6
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    • pp.1071-1094
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    • 2016
  • We employ the so-called problem-dependent linked interpolation concept to develop two cubic 4-node quadrilateral plate finite elements with 12 external degrees of freedom that pass the constant bending patch test for arbitrary node positions of which the second element has five additional internal degrees of freedom to get polynomial completeness of the cubic form. The new elements are compared to the existing linked-interpolation quadratic and nine-node cubic elements presented by the author earlier and to the other elements from literature that use the cubic linked interpolation by testing them on several benchmark examples.