• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2552-2557
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• 2007

Shape optimization of an internal cooling passage with staggered dimples on single surface is performed and performances of surrogates are evaluated in this paper. Optimizations are performed so that turbulent heat transfer can be enhanced compromising with pressure loss due to friction. The three-dimensional governing differential equations have been solved to find the overall Nusselt number and friction factor which are related to the objective functions of this problem. Three design variables were selected among the dimensionless geometric variables. Basic surrogate models such as second order polynomial response surface approximation (RSA), Kriging meta-modeling technique, radial basis neural network (RBNN), and derived press based averaged (PBA) surrogate model are constructed. The optimal points are searched from the above constructed surrogates by sequential quadratic programming (SQP). It is shown that use of multiple surrogates can increase the robustness in prediction of better design with minimum computational cost.

• 한국통신학회논문지
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• 제19권10호
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• pp.1880-1893
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• 1994

본 논문에서는 한 장의 영상으로부터 물체의 형상을 복원하는shape from shading 문제에 접근하기 위한 새로운 알고리즘을 제안하였다. 제안된 반복 알고리즘에서 주어진 3차원 표면이 직교 다항식에 의해 근사화되고 주어진 표면과 그것이 미분치 사이의 관계를 다항식 개수를 이용한 행렬식으로 표현하였다. 또한 표면의 상대적인 높이와 그것이 미분치를 서로 반복적으로 갱신하면서 얻었다. 알고리즘의 성능을 밝기오차, 표면의 방향오차, 높이오차 측면에서 평가하였으며 제안된 방법과 기존의 여러 방법들과의 성능 비교를 보였다.

• 접착 및 계면
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• 제6권1호
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• pp.7-10
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• 2005

Condensation control of nano-particles has become important in order to fabricate minute condensed structures. In this study, we focus our attention on condensation mechanism of polymer aggregates in a resist film. The polymer aggregate is structural component of a resist material which is used in lithography process. The condensation nature of polymer aggregates in the resist film surface is observed by using atomic force microscope (AFM). By using the AFM, the condensation of polymer aggregates can be observed clearly. The condensation of polymer aggregate strongly affects to precise fabrication of resist pattern below 100nm size. The interaction force among polymer aggregates can be analyzed based on Derjaguin approximation. We also discuss about condensation nature of polymer aggregates in the resist film surface with the help of micro sphere model.

• 제어로봇시스템학회논문지
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• 제5권4호
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• pp.481-488
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• 1999

A thermal model based on the chamber geometry of the industry-standard AST SHS200MA rapid thermal processing system has been developed for the study of thermal uniformity and process repeatability thermal model combines radiation energy transfer directly from the tungsten-halogen lamps and the steady-state thermal conducting equations. Because of the difficulties of solving partial differential equation, calculation of wafer temperature was performed by using finite-difference approximation. The proposed thermal model was verified via titanium silicidation experiments. As a result, we can conclude that the thermal model show good estimation of wafer surface temperature distribution.

• 한국CDE학회논문집
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• 제15권3호
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• pp.178-188
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• 2010

This paper addresses the problem of determining if two surfaces intersect tangentially or transversally in a mathematically consistent manner and approximating an intersection curve. When floating point arithmetic is used in the computation, due to the limited precision, it often happens that the decision for tangential and transversal intersection is not clear cut. To handle this problem, in this paper, interval arithmetic is proposed to use, which provides a mathematically consistent way for such decision. After the decision, the intersection is traced using the validated ODE solver, which runs in interval arithmetic. Then an iterative method is used for computing the accurate intersection point at a given arc-length of the intersection curve. The computed intersection points are then approximated by using a B-spline curve, which is provided as one instance of intersection curve for further geometric processing. Examples are provided to demonstrate the proposed method.

• 대한기계학회논문집A
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• 제33권2호
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• pp.114-126
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• 2009

In this paper, a versatile multi-criteria optimization concept for fatigue life prediction is introduced. Multi-criteria decision making in engineering design refers to obtaining a preferred optimal solution in the context of conflicting design objectives. Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a response surface model, the compromise decision support problem, which is a multi-objective formulation based on goal programming. Examples illustrate the concepts and demonstrate their applicability.

• 대한기계학회논문집A
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• 제33권2호
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• pp.127-134
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• 2009

T-splines are recently proposed geometric modeling tools. A T-spline surface is a NURBS surface with T-junctions and is defined by a control grid called T-mesh. Local refinement can be performed very easily for T-splines while it is limited for B-splines or NURBS. Using T-splines, patches with unmatched boundaries can be combined easily without special technique. In this study, the analysis methodology using T-splines is proposed. In this methodology, T-splines are used both for description of geometries and for approximation of solution spaces. Two-dimensional linear elastic and dynamic problems will be solved by employing the proposed T-spline finite element method, and the effectiveness of the current analysis methodology will be verified.

• 오토저널
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• 제7권3호
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• pp.42-55
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• 1985

The study is concerned with the investigation of curved line folding of developable surface from flat sheets of metal. General geometric relations among folding line, folded surface, folded angle are derived. From the derived geometric relations, the required plastic work and punch force are derived for the first approximation. Five methods of forming are suggested and the experiment is carried out using two chosen methods for the prismatic developable surfaces of which cross-sections have 103.deg.arc, 180.deg.arc, sinusoidal shape. In the die design for the tolding of prismatic developable surfaces, a stack of sheets were used to form shapes of the dies by which acceptable folded surfaces were obtained. The computed plastic work and punch force turned out to be in reasonable agreement with the experimental result.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.287-292
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• 2002

This paper presents a reverse engineering method for compound surfaces using vision system. A CNC machining center is used as a measuring station, which is equipped with slit beam generator and vision probe. Since obtained data using slit beam or laser scanner may have much data loss along the edge of compound surfaces, an algorithm is presented in this study to recover missing geometric data at such region. First, b-spline interpolation is applied to extract edge information of the surface, and as a next step, b-spline approximation is applied to recover the missing geometric data. Finally, b-spline skinning method is applied to regenerate the surface information. Appropriate simulation and experimental works are preformed to very the effectiveness of the proposed methods.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.392-399
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• 1997

An approximation technique was developed for the simulation of free surface flows in non-orthogonal coordinates. The main idea of this approach is to approximate VOF by the second order linear equation in the transformed domain on the assumption that the continuity of free surface would be maintained. The method was justified through a set of numerical test to examine if its original shape could be maintained when the circles are convected in uniform velocity in horizontal direction in curvilinear coordinates. Finally a simple problem was solved by applying the method to CFX4.1 general purpose CFDS code.