• Structural Engineering and Mechanics
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• 제15권1호
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• pp.135-149
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• 2003

The bubble packing method is implemented for adaptive mesh generation in two and three dimensions. Bubbles on the boundary of a three-dimensional domain are controlled independently of the interior bubbles in the domain, and a modified octree technique is employed to place initial bubbles in the three-dimensional zone. Numerical comparisons are made with other mesh generation techniques to demonstrate the effectiveness of the present bubble packing scheme for two- and three-dimensional domains. It is shown that this bubble packing method provides a high quality of mesh and affordable control of mesh density as well.

• 대한기계학회논문집A
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• 제24권10호
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• pp.2469-2476
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• 2000

The meshing of the domain has long been the major bottleneck in performing the finite element analysis. Research efforts which are so-called meshfree methods have recently been directed towards eliminating or at least easing the requirement for meshing of the domain. In this paper, a new meshfree method for solving nonlinear boundary value problem, based on the bubble packing technique and Delaunay triangle is proposed. The method can be efficiently implemented to the problems with singularity by using formly distributed nodes.

• 대한기계학회논문집A
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• 제25권12호
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• pp.1926-1932
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• 2001

In this second part of the paper, the automatic mesh generation and remeshing algorithm using bubble packing method is applied to the nonlinear problem. The remeshing/refinement procedure is necessary in the large deformation process especially because the mesh distortion deteriorates the convergence and accuracy. To perform the nonliear analysis, the transfer of state variables such as displacement and strain is added to the algorithm of Part 1. The equilibrium equation based on total Lagrangian formulation and elasto-viscoplastic model is used. For the numerical experiment, the upsetting process including the contact constraint condition is analyzed by two refinement criteria. And from the result, it is addressed that the present algorithm can generate the refined meshes easily at the largely deformed area with high error.

• 대한기계학회논문집A
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• 제25권6호
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• pp.1004-1014
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• 2001

The fully automatic algorithm from initial finite element mesh generation to remeshing in two dimensional geometry is introduced using bubble packing method (BPM) for finite element analysis. BPM determines the node placement by force-balancing configuration of bubbles and the triangular meshes are made by Delaunay triangulation with advancing front concept. In BPM, we suggest two node-search algorithms and the adaptive/recursive bubble controls to search the optimal nodal position. To use the automatically generated mesh information in FEA, the new enhanced bandwidth minimization scheme with high efficiency in CPU time is developed. In the remeshing stage, the mesh refinement is incorporated by the control of bubble size using two parameters. And Superconvergent Patch Recovery (SPR) technique is used for error estimation. To verify the capability of this algorithm, we consider two elasticity problems, one is the bending problem of short cantilever beam and the tension problem of infinite plate with hole. The numerical results indicate that the algorithm by BPM is able to refine the mesh based on a posteriori error and control the mesh size easily by two parameters.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.371-378
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• 2000

In this study an adaptive node generation procedure in the Element-free Galerkin (EFG) method using bubble-meshing technique is proposed. Based on the error function that obtained by projected error estimation method, the initial node arrangement is defined along the background cell that is used in the numerical integration. To obtain the smooth nodal configuration, the nodal configuration are regenerated by bubble-meshing technique. This bubble meshing technique was originally developed to generate a set of well-shaped triangles and tetrahedra. Its basic idea is packing circles or spheres, called bubble, into the specified area or space naturally using some dynamic equations with attracting and repelling force. To demonstrate the performance of proposed scheme, the convergence behaviors are investigated for several problems.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.763-768
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• 2001

The purpose of this study is to research a specific material characteristics of top down concrete at column joint and to reduce column joint opening. Based on the established top down study, the experiment to apply an real construction case is performed. When the concrete placed into joint of top down column, raised air bubble is left as opening. This study is examined the incomplete packing reason in the top down column and found to air deflation method. The result of study is below (1) As the method to minimize column opening caused from confined air, it is required that an air exhaust port installation in joint column. (2) From air exhaust port installation, most of air bubble in column part is exhausted. As the concrete placing height is going up, air bubble size is going smaller.

• 한국유체기계학회 논문집
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• 제19권4호
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• pp.39-42
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• 2016

A PFA lined ball valve, which is machined with fluorinated resin PFA to its inner part for improving corrosion resistance, non-stickness, heat-resistance, has been widely used to the chemical/pharmaceutical industries, the semiconductor/LCD manufacturing processes, etc. with the high purity chemicals as working fluid. EPA stated that 60% of all fugitive emissions come from the valve stem packing in a typical petroleum or chemical processing plant. They monitor regulated components for leaks and maintain seal performance at acceptable levels. Korean industrial standards only deals with the bubble test for in-line leakage of valves, which has the detectable leak rate of $10^{-4}$ [$mbar{\cdot}L{\cdot}s^{-1}$], therefore, it is not sufficient to check fugitive emissions. In this study, we conducted Helium leak detection from a PFA lined ball valve and evaluated fugitive emissions according to ISO 15848-1, which has the detectable leak rate of $10^{-9}$ [$mbar{\cdot}L{\cdot}s^{-1}$], for manufacturing the high-reliable PFA lined ball valves against fugitive emissions.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3295-3300
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• 2012

3차원 유한요소법은 구조물에 존재하는 표면균열과 내재균열들의 응력확대계수를 구하는데 이용되어 진다. 기하모델, 즉 솔리드모델은 3차원 균열들을 포함하고 있다. 국부적인 절점밀도가 선택되어 지면 자동적으로 기하모델 영역에 중첩되어 지며 절점은 버블패깅 방법에 의해 생성되어지고 10절점 사변형 솔리드요소는 데라우니 삼각화 기술에 의해 생성하였다. 시스템의 정확도와 효용성을 체크하기 위해 인장하중을 받는 평판에 하나의 균열이 존재하는 경우의 응력확대계수를 구해 Raju-Newnam식과 비교하여 5%이내의 차이를 보였다. 또한, 인장하중을 받는 평판에 두개 균열이 존재하는 경우의 해석을 통해 상호 간섭 효과를 분석하였다.

• 한국식품저장유통학회지
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• 제19권5호
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• pp.626-632
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• 2012

신선편이 슬라이스 더덕의 포장방법 차이에 따른 $7^{\circ}C$ 저장 중 품질 변화를 조사하였다. 진공포장과 PP 필름으로 밀봉포장 한 것은 14일, PE 필름으로 밀봉포장 한 것과 비닐포장은 7일까지 저장 실험이 가능하였다. 저장 7일에 비닐포장은 초기에 비하여 50% 이상의 중량 감소율을 보여 상품성을 상실한 반면, 밀봉과 진공포장구들은 중량 감소를 보이지 않았다. 가용성 고형물 함량은 저장 5일까지 $6.9{\sim}7.0^{\circ}Brix$로 포장방법 차이에 따른 유의적인 차이를 보이지 않았다. 그러나 비닐포장 한 슬라이스 더덕은 저장 7일에 $4.5^{\circ}Brix$로 크게 감소한 반면, PP필름으로 밀봉포장 한 것과 진공포장은 각각 6.4, $6.8^{\circ}Brix$로 함량 변화가 적었다. 슬라이스 더덕의 조직감과 수분함량은 비닐포장을 제외하고 저장 2일까지는 밀봉포장과 진공포장의 유의적인 품질 차이는 보이지 않았다. 이후에는 진공포장을 이용한 슬라이스 더덕의 수분함량이 잘 유지되었으며, 연화가 지연됨에 따라 경도의 변화도 가장 적었다. 전체적인 색은 비닐포장이 저장 2일부터 색 변화를 보였으나, PP 필름 이용 밀봉포장과 진공포장은 저장 14일 후에도 변화율이 가장 적었다. 총균수와 대장균군은 저장 중 진공포장한 것이 품질변화가 가장 적었으며, PP 필름 이용 밀봉포장, PE 필름 이용 밀봉포장 그리고 비닐포장 순이었다. 따라서 슬라이스 더덕의 버블 세척 후 진공포장을 하여 저장 유통하는 것이 품질 유지에 가장 효과적인 것으로 나타났다.