• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.199-207
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• 2001

In this paper, we suggest an edge-based surface segmentation algorithm of 3D image using curvature. For the first, in this proposed method, we approximate 3D depth data to second order curves by each scan line and decide splitting points of 3D edges by curvature of the approximated curves. And finally make a group as 3D surface with the region of input image by the 3D edges. In the conventional algorithms, there are some difficulties in detecting 3D edge with the separated processes for the jump edge and the crease edge and especially, in deciding the ambiguous discontinuity of surface directions about the crease edge. The proposed algorithm decides curvature discontinuity using curvature which is simply calculated by a geometrical approximation. Furthermore, the algorithm has a cooperated process to calculate the jump and crease edges. The results of computer simulations with several 3D images show that the proposed method yields better performance as comparing with the conventional methods.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.426-429
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• 2003

This paper proposes the threshold value selection for surface classification of 3-dimensional objects. Pre-existing method which uses the H-curvature and K-curvature has limitation in the practical threshold value selection. For this, this paper proposes the threshold value selection by the statistical method. Finally, the effectiveness of this paper demonstrated by experiment.

• The Journal of Korean Association of Computer Education
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• v.11 no.4
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• pp.85-93
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• 2008

This paper proposes a method for generating low-level geometric models with retaining salient features during decimation. Our method employs feature extraction technique for extracting feature lines defined via curvature derivatives on the model (we divide features into ridges and valleys). We add the extraction method to simplification technique (Feature Quadric Error Metric) for making coarse model with features. This paper clearly shows that experimental results have better quality and smaller geometric error than previous methods.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.6
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• pp.748-754
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• 2010

To reduce the computational cost required for assembling vessel fragments using surface geometry, this paper proposes a fast axis estimation method. Using circular constraint of pottery and local planar patch assumption, it finds the axis of the symmetry. First, the circular constraint on each cylinder is used. A circular symmetric pot can be thought of unions of many cylinders with different radii. It selects one arbitrary point on the pot fragment surface and searches a path where a circumference exists on that point. The variance of curvature will be calculated along the path and the path with the minimum variance will be selected. The symmetric axis will pass through the center of that circle. Second, the planar patch assumption and profile curve is used. The surface of fragment is divided into small patches and each patch is assumed as plane. The surface normal of each patch will intersects the axis in 3D space since each planar patch faces the center of the pot. A histogram method and minimization of the profile curve error are utilized to find the probability distribution of the axis location. Experimental results demonstrate the improvement in speed and robustness of the algorithms.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1027-1034
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• 2014

The shear stress on a surface due to the thin film fluid flow is an important issue. In case of a rotating disk, the fluid is delivered to the edge of the disk by centrifugal force, which acts as a body force on the fluid. Wear of a surface is affected by the shear stress acting on the surface and curvature. In this study, we utilize computational fluid dynamics software to model the ratio of curvature and local shear stress on solid surfaces. The key goal of the study is to determine an optimized curvature for the thin film fluid flow on a solid surface in order to minimize the local shear stress affecting the wear of this surface. Our results on the effects of curvature will be utilized for the design of devices that utilize thin film fluid flow on a solid surface, such as rotating-disk spray systems and thin film coating.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3
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• pp.20-25
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• 2000

This paper proposes the method of surface classification and threshold value selection for surface classification of the three-dimensional object recognition. The processings of three-dimensional image processing system consist of three steps, i.e, acquisition of range data, feature extraction and matching process. This paper proposes the method of shape feature extraction from the acquired rage data in the entire three-dimensional image processing system. In order to achieve these goals, firstly, this article proposes the surface classification method by using the distribution characteristics of sign value from range values. Also pre-existing method which uses the K-curvature and K-curvature has limitation in the practical threshold value selection. To overcome this, this article proposes the selection of threshold value for surface classification. Finally, the effectiveness of this article is demonstrated by the several experiments.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.500-503
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• 2009

본 논문에서는 이중곡률을 갖은 막구조물의 동적 불안정 현상을 연구하였다. 풍하중을 받는 막구조물의 지배방정식을 정식화할 경우 가장 중요한 것은 막 표면의 공기 압력을 합리적으로 산정하는 것이다. 베르누이 윈리에 의하여 유체 압력은 속도 퍼텐셜과 관계를 가지며 얇은 날개 원리에 의해 막 표면 공기의 움직임을 일련의 와류로 간주하고 속도 퍼텐셜을 구할 수 있다. 이 논문에서는 가장 많이 쓰이는 3 절점 삼각형 막요소를 이용하여 가중 잔여치 갤러킨법을 적용한 안정 평가의 판별식을 유도하였다. 임계 풍속에 대한 초기인장력, 풍방향과 곡률의 영향도 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1717-1726
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• 1991

본 연구에서는 낮은 레이놀즈수 영역에도 적용될 수 있는 레이놀즈응력모델의 개발을 위해, 우선 벽근처 영역에서 사용되는 실험식(벽법칙)을 Hassid와 Poreh에 의 해 개발된 1-방정식모델로 대체하고 이를 레이놀즈응력모델과 접속시키는 방식을 사용 하였다. Hassid-Poreh의 1-방정식모델은 이미 Gibson등에 의해 그 성능이 평가되어 압력구배가 크지 않은 경계층유동의 낮은 레이놀즈수 영역에서 매우 좋은 결과를 보여 줌이 밝혀졌다. 본 연구에서는 곡면위의 난류경계층에 대해 위에서 설명한 바 있는 난류모델을 적용함에 있어 Gillis등과 Gibson등에 의해 실험된, 각각 곡률이 큰 경우 와 작은 경우의 대표적인 유동을 선택하여 모델의 성능을 시험하였다. 1-방정식모델 내에 포함된 길이차원(length scale)에 대해서는 곡률을 고려한 수정이 이루어졌다.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.628-631
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• 2016

본 연구에서는 플라잉디스크의 윗면 곡률과 끝단두께에 따른 공력특성의 변화 및 유동 흐름을 EDISON_CFD를 통해 해석하고자 한다. 플라잉디스크는 받음각이 증가할수록 윗면 표면에서는 박리 거품이 발생하게 되고 아랫면에서 윗면으로 올라 갈려는 유동의 흐름이 발생하게 되어 뒷전과 후류에서 거대한 박리 거품이 발생하게 되어 공력특성 및 유동흐름에 큰 변화를 주게 된다. 총 5가지의 형상에 대해서 받음각을 $0^{\circ}{\sim}25^{\circ}$까지 마하수 0.0588, 해석모델은 KFLOW에서 k-w SST를 레이놀즈수 $3.78{\times}10^5$을 조건으로 각 형상의 공력특성과 유동의 흐름의 비교를 분석하였다. 그 결과 윗면의 곡률이 증가 할수록 앞전박리가 활발해지고, 끝단두께가 두꺼워 질수록 뒷전박리가 활발해진다. 이로 인해 곡률은 완만할수록 두께는 얇을수록 양력계수와 실속각을 증가 시킬 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.5_6
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• pp.288-296
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• 2004

This paper proposes a new mesh simplification algorithm using differential error metric. Many simplification algorithms make use of a distance error metric, but it is hard to measure an accurate geometric error for the high-curvature region even though it has a small distance error measured in distance error metric. This paper proposes a new differential error metric that results in unifying a distance metric and its first and second order differentials, which become tangent vector and curvature metric. Since discrete surfaces may be considered as piecewise linear approximation of unknown smooth surfaces, theses differentials can be estimated and we can construct new concept of differential error metric for discrete surfaces with them. For our simplification algorithm based on iterative edge collapses, this differential error metric can assign the new vertex position maintaining the geometry of an original appearance. In this paper, we clearly show that our simplified results have better quality and smaller geometry error than others.