• The Transactions of the Korea Information Processing Society
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• v.3 no.6
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• pp.1616-1623
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• 1996

In general, in order to recognize and modelling the 3-D object, it is necessary to have the method to express the shape of 3-D object. In case of 2-D like silhouette image, the extraction of vertex on the boundary of the object can be obtained by using the 2-D curvature function. But, in case of 3-D curvature function that can calculate the surface curvature values of 3-d object doesn't exist, it is difficult to express the share of 3-D object. Therefore, in this paper, a new method is presented. With this presented method, the approximated surface curvature values and vertex of 3-D object can be obtained effectively using the principle of 2-D curvature and the least square method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.2
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• pp.187-195
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• 1992

This paper propose on the determination of threshold values for extracting shape information of the objects. First, surface curvatures such as mean curvature and gaussian curvature is calculated from given range data. And then local surface regions are classified into the one of 8 primitives by using the sign of mean curvature H and gaussian curvature K. Also from the statistical viewpoint. the range of the zero of H and K in the range is obtained through the analysis of the relation between mean curvature and gaussian curvature. Finally, the effectiveness of the proposed mithod in this paper is demonstrated by comparing with a case, where the zero threshold is arbitrarily obtained.

• Journal of Korea Multimedia Society
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• v.12 no.1
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• pp.50-57
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• 2009

This paper proposes a extraction of feature lines on a polygonal model using local implicit surface fitting technique. To extract feature lines on a polygonal model, the previous technique addressed to compute the curvature and their derivatives at mesh vertices via global implicit surface fitting. It needs a user-specified precision parameter for finding an accurate projection of the mesh vertices onto an approximating implicit surface and requires high-time consumption. But we use a local implicit surface fitting technique to estimate the local differential information near a vertex by means of an approximating surface. Feature vertices are easily detected as zero-crossings, and can then be connected along the direction of principal curvature. Our method, demonstrated on several large polygonal models, produces a good fit which leads to improved visualization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.200-206
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• 2002

A new wiregrid modeling scheme is proposed for a curvature varying scatterer A 2-dimensional conducting elliptic cylinder is modelled by wires with the different size of radius considering the radius of curvature on the surface. The magnitude of the internal field in the conducting elliptic cylinder is used as an indicator to check the accuracy of solutions between two methods. Numerical results show that this new wiregrid model scheme can be reduced the number of wires and applied to enhance the accuracy of solutions for a curvature varying scatterer.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.129-137
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• 2006

In this research, we made a one and two-dimensional analysis of numerical data collected from the bend curvature of a bended river section. According to the result from the numerical analysis, the inflow ＆ output angle caused a water level deviation which increased with an increase of the flood discharge. From the water level deviation of our two-dimensional numerical model, we obtained the maximum slope of 6,67% when the inflow and output angle was 105 degrees and the flood discharge was 500 CMS. As for the right side, the differences with the one-dimensional numerical model were reduced when the angle was more than $90^{\circ}$. As for the left side the differences were reduced when the angle was more than $105^{\circ}$. For a river with more than 90 degrees bend curvature, a hydraulic experiment would be more appropriate than a numerical analysis.

• Nonlinear Functional Analysis and Applications
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• v.26 no.2
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• pp.225-236
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• 2021

In this paper, we determine position vector of a line of curvature of a regular surface which is relatively normal-slant helix, with respect to Darboux frame. Then, a vector differential equation is established by means Darboux formulas, in the case of the geodesic torsion is vanishes. In terms of solution, we determine the parametric representation of a line of curvature which is relatively normal-slant helix, with respect to standard frame in Euclidean 3-space. Thereafter, we apply this result to find the position vector of a line of curvature which is isophote curve.

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.131-135
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• 1997

Effect of wall curvature on flow characteristics is studied for mildly and strongly curved duct flows. The ducts are S-shaped, and the flow is partially blocked at the rear of the downstream. The presence of blockage in combination with curvature generates secondary flows on the concave surface; the magnitude of the secondary flow being dependent on the degree of wall curvature. Objectives are to compare the flow structures for mild and strong cases and to illuminate the changes in flow structure as the flow turns. Sensitivity on numerical solutions due to different inflow boundary conditions is also examined.

• Honam Mathematical Journal
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• v.46 no.2
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• pp.249-266
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• 2024

In this work, we study time-like and space-like surfaces invariant by a group of translation isometries of the half-space model ℋ³₁ of the anti-de Sitter space ℍ³₁ . We determine all such surfaces with constant mean curvature and constant Gaussian curvature. We also obtain umbilical surfaces of ℋ³₁.

• The KIPS Transactions:PartA
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• v.11A no.5
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• pp.391-400
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• 2004

Within multimodal medical image registration techniques, which correlate different images and Provide integrated information, surface registration methods generally minimize the surface distance between two modalities. However, the features of two modalities acquired from one subject are similar. So, it can improve the accuracy of registration result to match two images based on optimization of both surface distance and shape feature. This research proposes a registration method which optimizes surface distance and surface curvature of two brain modalities. The registration process has two steps. First, surface information is extracted from the reference images and the test images. Next, the optimization process is performed. In the former step, the surface boundaries of regions of interest are extracted from the two modalities. And for the boundary of reference volume image, distance map and curvature map are generated. In the optimization step, a transformation minimizing both surface distance and surface curvature difference is determined by a cost function referring to the distance map and curvature map. The applying of the result transformation makes test volume be registered to reference volume. The suggested cost function makes possible a more robust and accurate registration result than that of the cost function using the surface distance only. Also, this research provides an efficient means for image analysis through volume visualization of the registration result.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.99-103
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• 1998

The curved surface machined by plate end mill causes a excess non-cutting volume, in these cases ball end mill is used for the curved surfaces. This study is aimed to obtain the optimum cutting conditions of various cutting speed, table speed, tool diameter, radius of curvature roughness on the conditions of various cutting speed, tool diameter, radius of curvature when machining the curved surface using the ball end mill. After designing curve rates, obtaining NC data by CAD/CAM system through CC-Cartesian method and transferred the data through DNC system, we machined the specimens by the CNC machining center, The surface roughness of specimens was measured by surface roughness tester and CNC 3D coordinate measuring machine. The cutting condition were the same as follow velocity; 15, 20, 25 30m/min, feed rate;40, 60, 80, 100m/min and radius of curvature; 30,40,50,60mm, tool diameters; ø8, ø12, ø16, ø 20mm. Analizing the working results, we can acquire the optimum cutting condition of curved specimen at the cutting velocity of 20~25m/min and the feed rate of 80mm/min. As the same cutting condition the best surface roughness was showed at ø16mm of the tool diameter. But the tool diameter was smaller than ø8mm. we could improve for the surface roughness by controlling the cusp.