• Title/Summary/Keyword: surface-approach

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Composite $G^{1}$ surface construction from 2D cross-sections (2차원 단면 데이터로부터 복합 $G^{1}$ 자유곡면 생성)

  • Park, Hyung-Jun;Na, Sang-Wook;Bae, Chae-Yeol
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2004.05a
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    • pp.44-47
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    • 2004
  • This paper proposes an approach for composite surface reconstruction from 2D serial cross-sections, where the number of contours varies from section to section. In a triangular surface-based approach taken in most reconstruction methods, a triangular $G^{1}$ surface is constructed by stitching triangular patches over a triangular net generated from the compiled contours. In the proposed approach, the resulting surface is a composite $G^{1}$ surface consisting of three kinds of surfaces: skinned, surface is first represented by a B-spline surface approximating the serial contours of the skinned region and then serial contours of the skinned region and then transformed into a mesh of rectangular Bezier patches. On branched and capped regions, triangular $G^{1}$ surfaces are constructed so that the connections between the triangular surfaces and their neighboring surfaces are $G^{1}$ continuous. Since each skinned region is represented by an approximated rectangular $G^{2}$ surface instead of an interpolated triangular $G^{1}$ surface, the proposed approach can provide more visually pleasing surfaces and realize more efficient data reduction than the triangular surface-based approach. Some experimental results demonstrate its usefulness and quality.

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A new approach for B-spline surface interpolation to contours (윤곽선들의 B-spline 곡면 보간을 위한 새로운 방식)

  • Park Hyungjun;Jung Hyung Bae;Kim Kwangsoo
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2003.05a
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    • pp.474-479
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    • 2003
  • This paper addresses the problem of B-spline surface interpolation to serial contours, where the number of points varies from contour to contour. A traditional lofting approach creates a set of B-spline curves via B-spline curve interpolation to each contour, makes them compatible via degree elevation and knot insertion, and performs B-spline surface lofting to get a B-spline surface interpolating them. The approach tends to result in an astonishing number of control points in the resulting B-spline surface. This situation arises mainly from the inevitable process of progressively merging different knot vectors to make the B-spline curves compatible. This paper presents a new approach for avoiding this troublesome situation. The approach includes a novel process of getting a set of compatible B-spline curves from the given contours. The process is based on the universal parameterization [1,2] allowing the knots to be selected freely but leading to a more stable linear system for B-spline curve interpolation. Since the number of control points in each compatible B-spline curve is equal to the highest number of contour points, the proposed approach can realize efficient data reduction and provide a compact representation of a B-spline surface while keeping the desired surface shape. Some experimental results demonstrate its usefulness and quality.

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AUTOMATED TRIANGULAR SURFACE GRID GENERATION ON CAD SURFACE DATA (CAD 형상 데이터를 이용한 물체 표면 삼각형 격자의 자동 생성 기법)

  • Lee, B.J.;Kim, B.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.04a
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    • pp.103-107
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    • 2007
  • Computational Fluid Dynamics (CFD in short) approach is now playing an important role in the engineering process recently. Generating proper grid system for the region of interest in time is prerequisite for the efficient numerical calculation of flow physics using CFD approach. Grid generation is, however, usually considered as a major obstacle for a routine and successful application of numerical approaches in the engineering process. CFD approach based on the unstructured grid system is gaining popularity due to its simplicity and efficiency for generating grid system compared to the structured grid approaches. In this paper an automated triangular surface grid generation using CAD surface data is proposed According to the present method, the CAD surface data imported in the STL format is processed to identify feature edges defining the topology and geometry of the surface shape first. When the feature edges are identified, node points along the edges are distributed. The initial fronts which connect those feature edge nodes are constructed and then they are advanced along the CAD surface data inward until the surface is fully covered by triangular surface grid cells using Advancing Front Method. It is found that this approach can be implemented in an automated way successfully saving man-hours and reducing human-errors in generating triangular surface grid system.

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AUTOMATIC GENERATION OF UNSTRUCTURED SURFACE GRID SYSTEM USING CAD SURFACE DATA (CAD 형상 데이터를 이용한 비정렬 표면 격자계의 자동 생성 기법)

  • Lee, B.J.;Kim, B.S.
    • Journal of computational fluids engineering
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    • v.12 no.4
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    • pp.68-73
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    • 2007
  • Computational Fluid Dynamics (CFD) approach is now playing an important role in the engineering process in these days. Generating proper grid system in time for the region of interest is prerequisite for the efficient numerical calculation of flow physics using CFD approach. Grid generation is, however, usually considered as a major obstacle for a routine and successful application of numerical approaches in the engineering process. CFD approach based on the unstructured grid system is gaining popularity due to its simplicity and efficiency for generating grid system compared to the structured grid approaches, especially for complex geometries. In this paper an automated triangular surface grid generation using CAD(Computer Aided Design) surface data is proposed. According to the present method, the CAD surface data imported in the STL(Stereo-lithography) format is processed to identify feature edges defining the topology and geometry of the surface shape first. When the feature edges are identified, node points along the edges are distributed. The initial fronts which connect those feature edge nodes are constructed and then they are advanced along the CAD surface data inward until the surface is fully covered by triangular surface grid cells using Advancing Front Method. It is found that this approach can be implemented in an automated way successfully saving man-hours and reducing human-errors in generating triangular surface grid system.

A General Description of Tool Surface Based on Finite Element Mesh and Its Application to 3-D Sheet Forming Processes (유한요소격자에 기초한 일반적인 금형면 묘사와 3차원 박판성형공정에의 응용)

  • Yun, Jeong-Hwan;Kim, Jong-Bong;Yang, Dong-Yeol;Kim, Seok-Gwan;Yu, Dong-Jin;Lee, Jae-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.3 s.174
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    • pp.550-559
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    • 2000
  • One of the most important factor to be considered for the analysis of sheet metal forming processes is the tool surface description for arbitrarily- shaped sheet metal parts. In the present study , finite element approach is used to describe the arbitrarily shaped tool surface. In finite element mesh approach, tool surfaces ar, described by finite elements. The finite elements mesh description of the tool surface, which is originally described by CAD data, needs much time and time-consuming graphic operation. The method, however, has been widely used to describe a complex tool surface. In the present study, the contact searching algorithm for the finite element mesh approach is developed based on cell strategy method and sheet surface normal scheme. For the verification purpose, a clover cup drawing, Baden-Baden oilpan problem and a trunk floor drawing were investigated. The computational results based on the finite element approach were compared with the results of available parametric patch approach and experiments.

A Study on an Application of the Protection for the Visual Segment of the Approach Procedure focused on Taean Airport (접근절차의 시계구간 보호 적용 연구 - 태안비행장을 중심으로 -)

  • Kim, Dohyun;Hong, Seung Beom
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.22 no.2
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    • pp.9-15
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    • 2014
  • 'Visual segment surface' means a surface that extends from the missed approach point of non precision approaches (or the decision altitude location for approaches with vertical guidance and precision approaches) to the threshold to facilitate the identification of and protection from obstacles in this visual segment of the approach. Validation is the necessary final quality assurance step in the procedure design process, prior to publication. The purpose of validation is the verification of all obstacle and navigation data, and assessment of flyability of the procedure. This paper shows how to apply the protection for the visual segment of the approach procedure, and the results of the validation for visual segment surface conducted at an airport.

Interference-Free Tool Approach Directions in Multi-Axis NC Machining of Sculptured Surfaces (자유 곡면의 다축 NC 가공시 간섭 없는 공구 접근 자세 영역)

  • J.G. Kang
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.7
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    • pp.108-115
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    • 1997
  • In this paper, an algorithm of computing interference-free tool approach directions(visibility cone) with consideration of tool volume at an arbitrary point of a sculptured surface is developed. The surface is first approximated into a polyhedron with smaller subpatches and the tool approach directions are evenly sampled so as to test accessibility. Then the visibility cone is computed by testing if each approach direction is interfered by other surface subpatches. The results are represented as the binary spherical map which transform geometric information on sphere into aogebraic one. The developed algorithm is implemented and tested by several sculptured surfaces, convincing it can be easily used as a tool for not only interference- free tool approach directions but also determining process planning of multi-axis NC machining of sculp- tured surfaces

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Investigation on the Automatic Tool Mesh Generatio for Sheet Metal Stamping Analysis (박판성형해석을 위한 자동 툴 격자 생성에 관한 연구)

  • 유동진
    • Transactions of Materials Processing
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    • v.9 no.2
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    • pp.140-151
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    • 2000
  • The finite element mesh approach for tool surface description is applied effectively to analyze sheet metal stamping processes. To improve the mesh quality and the stability of the mesh generation process, a gybrid method based on the grid approach and the Delaunay triangulation is proposed in the present work. In the present study, a general method for the mathematical description of arbitrarily shaped tool surface is proposed by introducing the parametric surface approach. A polynomial function employed to describe the base parametric surface and the boundary curves are defined to describe arbitrary three-dimensional trimmed surfaces. To verify the validity of the proposed method, automatic mesh generation is carried out for some shosen complicated parts including actual automotive panel.

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Studies on the Adsorption Modeling of Cationic Heavy Metals(Pb, Cd) by the Surface Complexation Model (Surface Complexation Model을 이용한 양이온 중금속(Pb, Cd) 흡착반응의 모델화 연구)

  • 신용일;박상원
    • Journal of Environmental Science International
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    • v.8 no.2
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    • pp.211-219
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    • 1999
  • Surface complexation models(SCMs) have been performed to predict metal ion adsorption behavior onto the mineral surface. Application of SCMs, however, requires a self-consistent approach to determine model parameter values. In this paper, in order to determine the metal ion adsorption parameters for the triple layer model(TLM) version of the SCM, we used the zeta potential data for Zeolite and Kaolinite, and the metal ion adsorption data for Pb(II) and Cd(II). Fitting parameters determined for the modeling were as follows ; total site concentration, site density, specific surface area, surface acidity constants, etc. Zeta potential as a new approach other than the acidic-alkalimetric titration method was adopted for simulation of adsorption phenomena. Some fitting parameters were determined by the trial and error method. Modeling approach was successful in quantitatively simulating adsorption behavior under various geochemical conditions.

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Estimation of Surface Roughness using Neural Network in Polishing Operation of Mold and Die (금형연마작업에서 신경망을 이용한 표면거칠기 추정)

  • Cho, Kyu-Kab;Kang, Yong-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.4
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    • pp.73-78
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    • 2002
  • This paper presents a neural network approach to estimate the surface roughness by considering the relationship between the polishing operation parameters and the surface roughness. The neural network model predicts the post-machining surface roughness by using several factors such as pre-machining surface roughness, pressure, feed rate, spindle speed, and the number of polishing as inputs. In this paper, the several neural network models are implemented to estimate the surface roughness by using actual experimental data. The experimental results show that the neural network approach is more appropriate to represent the polishing characteristics of mold and die compared with the results obtained by the approach using exponential function.