• 품질경영학회지
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• 제40권1호
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• pp.49-59
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• 2012

In computer simulation models the output from the computer code is often deterministic, i.e., running the code twice with the same values for the input variables would give the same output. It is discussed why the response surface method with polynomial approximation for the true response function is a good approximation to the computer experiments model. A sequential strategy to find the proper reduced quadratic polynomial model is illustrated with a case study in the military war game computer simulation model.

• 한국전자파학회논문지
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• 제15권4호
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• pp.345-352
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• 2004

본 논문은 페라이트 필름을 기반으로 하는 마이크로스트립 선로로부터 여기되는 정자표면파의 복사 임피던스를 full-wave모멘트 해석법을 이용하여 계산하였다. 마이크로스트립 선로 폭과 페라이트 필름 두께 변화에 따른 여 기 특성 변화도 분석하였다. 정자파 근사에 의하여 계산된 복사 저항값은 주파수가 증가할수록 실험 값과 차이가 심해지나, full-wave 해석에 의하여 계산된 복사 저항값은 실험값에 매우 근접함을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1023-1028
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• 2004

A micro-pressure wave is generated by the high-speed train which enters a tunnel, and it causes explosive noise and vibration at the exit. It is known that train speed, train-tunnel area ratio, nose slenderness and nose shape mainly influence on generating micro-pressure wave. So it is required to minimize it by searching optimal values of such train shape factors and tunnel condition. In this study, response surface model, one of approximation models, is used to perform optimization effectively and analyze sensitivity of design variables. Owen's randomized orthogonal array and D-optimal Design are used to construct response surface model. In order to increase accuracy of model, stepwise regression is selected. Finally SQP(Sequential Quadratic Programming) optimization algorithm is used to minimize the maximum micro-pressure wave by using built approximation model.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.1103-1106
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• 2000

Recently, the research on computer graphics (CG) has been actively studied and developed. Namely, many surface/solid models have been proposed in the field of computer aided geometric design as well as the one of CG. Since it is difficult to visualize the complex shape exactly, an approximation by generating a set of meshes is usually used. Therefore it is important to guarantee the quality of the approximation in consideration of the computational cost. In this paper, a mesh generation algorithm will be proposed for a surface defined by linear tie algebra The proposed algorithm which considers the quality in the meaning of validation of invariants obtained by the mesh.

• 한국CDE학회논문집
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• 제4권3호
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• pp.173-179
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• 1999

In reverse engineering, when a shape containing multi-patched surfaces is digitized, the boundaries of these surfaces should be detected. The objective of this paper is to introduce a computationally efficient segmentation technique for extracting edges, ad partitioning the 3D measuring point data based on the location of the boundaries. The procedure begins with the identification of the edge points. An automatic edge-based approach is developed on the basis of local geometry. A parametric quadric surface approximation method is used to estimate the local surface curvature properties. the least-square approximation scheme minimizes the sum of the squares of the actual euclidean distance between the neighborhood data points and the parametric quadric surface. The surface curvatures and the principal directions are computed from the locally approximated surfaces. Edge points are identified as the curvature extremes, and zero-crossing, which are found from the estimated surface curvatures. After edge points are identified, edge-neighborhood chain-coding algorithm is used for forming boundary curves. The original point set is then broke down into subsets, which meet along the boundaries, by scan line algorithm. All point data are applied to each boundary loops to partition the points to different regions. Experimental results are presented to verify the developed method.

• International Journal of CAD/CAM
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• 제8권1호
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• pp.21-28
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• 2009

In the present work, an attempt has been made to construct branching surface from 2-D contours, which are given at different layers and may have branches. If a layer having more than one contour and corresponds to contour at adjacent layers, then it is termed as branching problem and approximated by adding additional points in between the layers. Firstly, the branching problem is converted to single contour case in which there is no branching at any layer and the final branching surface is obtained by skinning. Contours are constructed from the given input points at different layers by energy-based B-Spline approximation. 3-D curves are constructed after adding additional points into the contour points for all the layers having branching problem by using energy-based B-Spline formulation. Final 3-D surface is obtained by skinning 3-D curves and 2-D contours. There are three types of branching problems: (a) One-to-one, (b) One-to-many and (c) Many-to-many. Oneto-one problem has been done by plethora of researchers based on minimizations of twist and curvature and different tiling techniques. One-to-many problem is the one in which at least one plane must have more than one contour and have correspondence with the contour at adjacent layers. Many-to-many problem is stated as m contours at i-th layer and n contours at (i+1)th layer. This problem can be solved by combining one-to-many branching methodology. Branching problem is very important in CAD, medical imaging and geographical information system(GIS).

• 한국광학회지
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• 제17권4호
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• pp.359-365
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• 2006

광학계의 파면오차는 광학계의 성능을 나타내는 주요 지표이며, 광학면의 변형에 의해 발생한다. 광기계의 개발에 있어서 주요 하중조건에서 발생하는 파면오차 양은 중요 규격으로 설정되고 관리되어 진다. 광학면의 변형은 유한요소해석 등의 발달과 더불어 정확한 수준까지 계산할 수 있게 되었다. 유한요소해석 결과로부터 파면오차를 계산하기 위해서는 광학면에서의 변형량을 근사하고 분석해야 한다. 이를 위해 추가적인 격자나 요소망으로 결과를 변화하여 근사하는 방법이 사용되고 있으나, 격자 구성의 번거로움과 변환으로 인한 오차 발생 소지를 가지고 있다. 본 연구에서는 추가적인 격자의 구성없이 절점 정보만으로 효과적인 근사를 할 수 있는 이동 최소제곱 근사법을 사용하여 변형량을 근사하고 파면오차를 계산하는 방법을 제안하였다. 제안된 방법의 효용성을 보이기 위하여 해양탑재체 스캔 미러의 자중에 의한 파면오차를 계산하였고, 기존의 방법과 비교 분석하였다.

• 대한수학회지
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• 제13권1호
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• pp.79-86
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• 1976

• Bulletin of the Korean Chemical Society
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• 제22권8호
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• pp.795-796
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• 2001

• 한국CDE학회논문집
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• 제5권2호
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• pp.144-154
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• 2000

We propose an algorithm for obtaining a triangular approximation of a trimmed NLRBS surface. Triangular approximation is used in the pre-processing step of many applications such as RP(Rapid Prototyping), NC(Numerical Control) and FEA(Finite Element Analysis), etc. The algorithm minimizes the number of triangular elements within tolerance and generates a valid triangular mesh for STL file and NC tool path generation. In the algorithm, a subdivision method is used. Since a patch is a basic element of triangular mesh creation, boundary curves of a patch are divided into line segments and the division of curves is applied for the interior of the surface. That is, boundary curves are subdivided into line segments and two end points of each line segment are propagated to the interior of the surface. For the case of a trimmed surface, triangulation is carried out using a model space information. The algorithm is superior because the number of elements can be controlled as the curvature of the surface varies and it generates the triangular mesh in a trimmed region efficiently. To verify the efficiency, the algorithm was implemented and tested for several 3D objects bounded by NURBS surfaces.