• 한국CDE학회논문집
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• 제17권4호
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• pp.246-252
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• 2012

The piping route of hydraulic hose is designed with avoiding interferences to surrounding components. However, in a real practice, the piping route is mostly decided with an expert's experiences on site due to the complexity of design. Thus, this paper proposes a design methodology of the optimized route of a hose. We use NURBS representation to describe the piping route, which is possible to be locally modified, and an energy minimization method is applied to avoid interferences to the surroundings. In other words, the NURBS curve describing a piping route is modified to meet the desired positions from minimizing the perturbation of the control points, and the strain energy of the curve is then optimized to make the curve natural. The proposed method is implemented and its feasibility is validated using the commercial CAD software, CATIA V5.

• 한국CDE학회논문집
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• 제4권1호
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• pp.32-42
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• 1999

Approximate lofting or skinning is one of practical surface modeling techniques well used in CAD and reverse engineering applications. Presented in this paper is a method for approximately lofting a given set of curves wihin a specified tolereance. It is based on refitting input curves simultaneously on a common knot vector and interpolating them to get a resultant NURBS surface. A concept of reducing the number of interior knots of the common knot vector is well adopted to acquire more compact representation for the resultant surface. Energy minimization is newly introduced in curve refitting process to stabilize the solution of the fitting problem and get more fair curve. The proposed approximate lofting provides more smooth surface models and realizes more efficient data reduction expecially when the parameterization and compatibility of input curves are not good enough. The method has been successfully implemented in a new CAD/CAM product VX Vision? of Varimetrix Corporation.

• 한국멀티미디어학회논문지
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• 제22권4호
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• pp.491-501
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• 2019

Variational methods, which cast deformation as an energy-minimization problem, are known to provide a good trade-off between practicality and speed. However, the time required to deform a fully detailed shape means that these methods are largely unsuitable for real-time applications. We simplify a 2D shape into a curve skeleton, which can be deformed much more rapidly than the original shape. The curve skeleton also provides a simplified control for the user, utilizing a small number of control handles. Our system deforms the curve skeleton using an energy-minimization method and then applies the resulting deformation to the original shape using linear blend skinning. This approach effectively reduces the size of the variational optimization problem while producing deformations of a similar quality to those obtained from full-scale nonlinear variational methods.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.65-71
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• 2006

Based on the smoothness criterion of minimum curvature variation of the curve, tangent angle constraints guaranteeing an optimized geometric Hermite (OGH) curve both mathematically and geometrically smooth is given, and new methods for constructing composite optimized geometric Hermite (COH) curves are presented in this paper. The comparison of the new methods with Yong and Cheng's methods based on strain energy minimization is included.

• International Journal of CAD/CAM
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• 제5권1호
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• pp.11-18
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• 2005

The traditional method of manipulation of knots and degrees gives poor quality of surface, if compatibility of input curves is not good enough. In this work, a new algorithm of multiple refitting of curves has been developed using minimum energy based formulation to get compatible curves for skinning. The present technique first reduces the number of control points and gives smoother surface for given accuracy and the surface obtained is then skinned by compatible curves. This technique is very useful to reduce data size when a large number of data have to be handled. Energy based technique is suitable for approximating the missing data. The volumetric information can also be obtained from the surface data for analysis.

• 한국CDE학회논문집
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• 제10권1호
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• pp.40-48
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• 2005

A hydraulic hose is an important part of the hydraulic system which transmits power using pressurized fluids. It allows relative motion between components at each end of the hose assembly, and it is much easier to route a hose assembly than it is to bend and install a rigid tubing assembly. Unnecessary loads, which drop the hose's pressure capability and shorten service life, depend on a hose-routing. Therefore, the Hydraulic system designers must be aware to consider unnecessary load does not affect the here. For this consideration in an early stage of the design process, CAD system must support the hose assembly routing design function which is to generate routing path and design fitting angle properly. This paper proposes 2 methods. One is to generate curves that are similar to routing paths of the real hose assembly using the energy minimization method and the optimization method. The other is to design fitting angles that are important design elements of a hose assembly using the Parallel Transport Frame. To implement the proposed methods above, commercial CAD software, CATIA has been integrated with our program.

• 한국정보처리학회논문지
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• 제6권10호
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• pp.2809-2815
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• 1999

Level set, and active contour(snakes) models are extensively used for image segmentation or shape extraction in computer vision. Snakes utilize the energy minimization concepts, and level set is based on the curve evolution in order to extract contours from image data. In general, these two models have their own drawbacks. For instance, snake acts pooly unless it is placed close to the wanted shape boundary, and it has difficult problem when image has multiple objects to be extracted. But, level set method is free of initial curve position problem, and has ability to handle topology of multiple objects. Nevertheless, level set method requires much more calculation time compared to snake model. In this paper, we use good points of two described models and also apply multi resolution algorithm in order to speed up the process without decreasing the performance of the shape extraction.

• Journal of Computational Design and Engineering
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• 제2권4호
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• pp.218-232
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• 2015

Piecewise linear (G01-based) tool paths generated by CAM systems lack $G_1$ and $G_2$ continuity. The discontinuity causes vibration and unnecessary hesitation during machining. To ensure efficient high-speed machining, a method to improve the continuity of the tool paths is required, such as B-spline fitting that approximates G01 paths with B-spline curves. Conventional B-spline fitting approaches cannot be directly used for tool path B-spline fitting, because they have shortages such as numerical instability, lack of chord error constraint, and lack of assurance of a usable result. Progressive and Iterative Approximation for Least Squares (LSPIA) is an efficient method for data fitting that solves the numerical instability problem. However, it does not consider chord errors and needs more work to ensure ironclad results for commercial applications. In this paper, we use LSPIA method incorporating Energy term (ELSPIA) to avoid the numerical instability, and lower chord errors by using stretching energy term. We implement several algorithm improvements, including (1) an improved technique for initial control point determination over Dominant Point Method, (2) an algorithm that updates foot point parameters as needed, (3) analysis of the degrees of freedom of control points to insert new control points only when needed, (4) chord error refinement using a similar ELSPIA method with the above enhancements. The proposed approach can generate a shape-preserving B-spline curve. Experiments with data analysis and machining tests are presented for verification of quality and efficiency. Comparisons with other known solutions are included to evaluate the worthiness of the proposed solution.

• 한국멀티미디어학회논문지
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• 제20권1호
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• pp.10-16
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• 2017

This paper proposes efficient schemes for image segmentation using the region-based active contour model. The developed methods can approach the boundaries of the desired objects by evolving the curves through minimization of the Mumford-Shah energy functionals, given arbitrary curves as initial conditions. Topological changes such as splitting or merging of curves should be handled for the methods to work properly without prior knowledge of the number of objects to be segmented. This paper introduces how to change topological structure of the curves and shows experimental results by applying the methods to the images.

• 한국의학물리학회지:의학물리
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• 제4권2호
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• pp.49-58
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• 1993

열자극 과정의 수치해석적인 방법을 이용하여 열자극 세기곡선의 kinetic order, 활성화 에너지, 이탈 진동수 그리고 초기 트랩 밀도를 구하기 위하여 혼합된 열자극 세기곡선으로 분해하였고, 비선형 최소 자승법으로 분해된 열자극 곡선 세기와 측정된 세기의 차이를 최소화시켰다. 감마선 선량계로 사용되고 있는 $\alpha$-Al$_2$ $O_3$ 에감마선을 조사시킨 후 ,300K～600K의 온도 구간에서 측정된 $\alpha$-Al$_2$ $O_3$의 열자극 발광 세기곡선은 정점 온도가 381K, 415K, 441K, 460K, 488K 그리고 506K인 6개의 독립된 열자극 발광세기곡선으로 분해되었으며, 381K의 정점온도를 갖는 분해된 열자극 발광 세기곡선의 kinetic order, 활성화 에너지 그리고 이탈 진동수는 각각 1, 1.12eV 그리고 6.79X$10^{12}$sec$^{-1}$로써, 이 결과는 다른 측정법에 의한 값과 유사하였다.