• 호남수학학술지
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• 제40권4호
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• pp.785-794
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• 2018

In [8] they introduced a new finite element method for accurate numerical solutions of Poisson equations with corner singularities. They consider the Poisson equations with homogeneous Dirichlet boundary condition with one corner singularity at the origin, and compute the finite element solution using standard FEM and use the extraction formula to compute the stress intensity factor, then pose a PDE with a regular solution by imposing the nonhomogeneous boundary condition using the computed stress intensity factor, which converges with optimal speed. From the solution they could get an accurate solution just by adding the singular part. This approach uses the polar coordinate and the cut-off function to control the singularity and the boundary condition. In this paper we consider Poisson equations with multiple singular points, which involves different cut-off functions which might overlaps together and shows the way of cording in FreeFEM++ to control the singular functions and cut-off functions with numerical experiments.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권4호
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• pp.281-292
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• 2009

The solution of the interface problem or Poisson problem with concave corner has singular perturbation at the interface corners or singular corners. The decoupled dual singular function method (DDSFM) which exploits the singular representations of the solutions was suggested in [3, 9] and estimated optimal accuracy in [10]. The convergence rates consist with theoretical results even for the problems with very strong singularity, with the efficiency depending on parameters used in the methods. Furthermore the errors in $L^2$ and $L^\infty$-spaces display some oscillation, in the cases with meshsize not small enough. In this paper, we present an answer to remove the oscillation via numerical experiments. We observe the effects of parameters in DDSFM, and show the consisting efficiency of the method over the strong singularity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.286-291
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• 2001

Applications of bonded dissimilar materials such as IC package, ceramic/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edges in bonded joints of dissimilar materials. In orer to understand the package crack emanating from the edge of Die pad and Resin, fracture mechanics of bonded dissimilar materials and material properties are obtained. In this paper, the thermal stress and its singularity index for the IC package were analyzed using 2-dimensional elastic boundary element method. Crack propagation angle and path by thermal stress were numerically simulated with boundary element method.

• 대한전자공학회논문지
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• 제26권6호
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• pp.7-14
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• 1989

본 논문에서는 R-P 시스템의 특이성 회피 기능을 갖는 경로제어 방법에 관하여 논하였다. 먼저 R-P 시스템을 하나의 기구학적 모델로 하여 여유자유도를 갖는 Manippulator 제어 문제로 유도하였다. 또한 R-P 시스템의 특이성을 해식적으로 분석 고찰한 후 (내부)특이성일때 이를 회피하면서 경로오차를 허용범위내에 있도록 하기 위하여 DLS(damped least square)의 Damping Factor를 가변시켜 주는 방법을 제시하였다. 제시된 방법의 타당성을 보이기 위하여 5자유도를 갖는 Rhino 로보트와 2자유도를 갖는 포지셔널을 대상으로 조작성능지수(manipulability)를 최대화하는 방법, 고정 Damping Factor를 갖는 DLS 방법과 제시된 가변 Damping을 갖는 DLS 방법을 컴퓨터 시뮬레이션을 통하여 경로오차와 성능지수 및 관절속도에 관점을 두어 비교 검토하였다.

• Structural Engineering and Mechanics
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• 제14권5호
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• pp.565-574
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• 2002

This paper presents a method for predicting premature separation of carbon fiber reinforced plastic (CFRP) plates from strengthened steel beams. The fracture criterion based on material-induced singularity is formulated in terms of a singular intensity factor. Static test on double strap joints was selected to provide the critical stress intensity factor in the criterion because good degree of accuracy and consistency of experimental data can be expected compared with the unsymmetrically loaded single lap joints. The debond/separation loads of steel beams with different CFRP lengths were measured and compared with those predicted from the criterion. Good agreement between the test results and the prediction was found.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2277-2286
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• 2002

The application of bonded dissimilar materials to industries as automobiles, aircraft, rolling stocks, electronic devices and engineering structures is increasing gradually because these materials, compared to the homogeneous materials, have many advantages for material properties. In spite of such wide applications of bonded dissimilar materials, the evaluation method of quantitative strength considering the stress singularities for its bonded interface has not been established clearly. In this paper, the stress singularity for Bctors and the stress intensity factors were analyzed by boundary element method(BEM) for the scarf joints of Al/Epoxy with and without a crack, respectively. From static fracture experiments of the bonded scarf joints, a fracture criterion and a evaluation method of interface strength in bonded dissimilar materials were proposed and discussed.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.197-204
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• 1999

The boundary element method was used for studying singularities of an interface crack with contact zones. The iterative procedure is applied to estimate the contact zone size. Because the contact zone size was extremely small in a tension field, a large number of Gaussian points were used for numerical integration of the Kernels. Stress extrapolation method and J-integral were used ofr determining stress intensity factors. When the interface crack was assumed to have opened tips, oscillatory singularities appear near the tips of the interface crack. But the interface crack with contact zone which Comninou suggested had no oscillatory behavior. The contact zone size under shear loading was much larger than that under tensile. The stress intensity factors computed by stress extrapolation method were close to those of Comninou's solution. And the stress intensity factor evaluated by J-integral was similar to that by stress extrapolation method.

• 대한간호학회지
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• 제43권6호
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• pp.791-800
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• 2013

Purpose: This study was done to test a structural equation modeling of case management outcomes in order to identify parameters affecting case management outcomes for the community-dwelling vulnerable elders. Methods: Data were collected from 309 nurses (case managers) and community-dwelling vulnerable elders (clients) from public health centers. For data analysis, descriptive statistics, Pearson correlation analysis, factor analysis, and covariance structure analysis were performed using SPSS Version 18.0 for Windows and Amos 16.0. Results: The hypothetical model had an acceptable fit: GFI=.97, CFI=.95, RMSEA=.02, SRMR=.05. The factor "case managers' singularity" had the greatest impact on case management outcomes in this model. In addition, the factor "case management practice" influenced case management outcomes; however, client characteristics did not. Case managers' singularity affected case management outcomes directly and indirectly, with case management practice mediating the latter effect. Conclusion: These results suggest that the causal relationship between case management outcomes and factors influencing these outcomes should be clarified through longitudinal research including a variety of client characteristics. In addition, in future studies, analysis of the effects of programs to improve manpower quality and examine the relationships among case management outcomes should be done.

• 대한기계학회논문집A
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• 제22권1호
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• pp.206-214
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• 1998

When a crack meets bimaterial interface stress singularity depends on the elastic constants of the adjacent materials. In the present study we are going to describe the finite element formulation for problems with a crack to be embedded in the stiffer material$({\mu}_2/{\mu}_1)$. The cubic isoparametric singular element, represented by adequately shifting the mid-side nodes adjacent to the crack tip is constructed to enclose the crack tip. An alternative method to obtain the optimal position of the mid-side nodes of cubic isoparametric elements is presented. In addition, a proper definition for the stress intensity factors of a crack normal to bimaterial interface is provided. It is based upon near a tip displacement solutions. Models for numerical analysis are two dimensional elastic bodies with a through crack under plain strain. The results obtained are compared with the previous solutions.

• 대한기계학회논문집
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• 제17권10호
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• pp.2398-2406
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• 1993

Abdi's numerical method(ref.13) for representing a stress singularity by shifting the mid-side nodes of isoparametric elements is reviewed. A simple technique to obtain the optimal position of the mid-side nodes in quadratic isoparametric finite element is presented. From this technique we can directly obtain the position of the side-nodes adjacent to the crack tip. It is also observed that the present technique provides good accuracy for the expression of the opening displacement and the determination of the mid-side nodes for more wide range of material properties than that obtained by Abdicant the finite element method is applied to determine stress intensity factors for pressurized crack perpendicular to and terminating at the interface of two bonded dissimilar materials. A proper definition for stress intensity factors of a crack perpendicular to bimaterial interface is provided. It is based upon a near-tip displacement solutions on the crack surface for interface crack between two dissimilar materials. Numerical testing is carried out with the eight-node and six-node elements. The results obtained are compared with the previous solutions.