• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.133-135
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• 2006

단층촬영영상(Tomographic cross-section images)으로부터 임의의 등밀도 표면(iso-density surface)을 재구성하기 위한 새로운 방법을 제안하였다. 이 방법에서는 마칭큐브 알고리즘에 비해 정밀도는 떨어지지만 안정적인 표면을 생성하는 셀경계 알고리즘(Cell-Boundary Method)을 이용하여 초기메쉬를 구하고 이를 표면축소포장(Shrink-wrapping)처리를 통해 정밀한 등밀도 표면을 생성하게 된다. 이는 마칭큐브와 같이 단층영상에서 등밀도 표면을 직접 추출하는 것이 아니라 등밀도점(iso-density Point)을 먼저 추출하고 표면의 모호성이 없는 안정적인 초기메쉬를 이들 방향으로 축소하여 정확한 표면모델링을 가능하게 한다. 이를 통해 마칭큐브에서 발생하는 표면 결정의 모호성이 없이 보다 안정적인 표면을 정확하게 만들 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.1
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• pp.28-37
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• 2007

This paper addresses a new surface reconstruction scheme for approximating the isosurface from a set of tomographic cross sectional images. Differently from the novel Marching cube algorithm, our method does not extract iso-density surface(isosurface) directly from the voxels but calculates the iso-density point(isopoint) first. After building the relatively coarse initial mesh by the Cell-boundary algorithm approximating the isosurface, it produces the final isosurface by iteratively shrinking and smoothing the initial mesh. Comparing with the Marching Cube algorithm, our method is robust and does not make any crack in resulting surface model. Furthermore, the proposed method surmounts the O(1)-adjacency limitation of MC in defining the isopoints by permitting the O(2) and O(3)-adjacent isopoints in surface reconstruction, and can produce more accurate isosurface. According to experiments, it is proved to be very robust and efficient for isosurface reconstruction from cross sectional images.

• The KIPS Transactions:PartB
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• v.14B no.6
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• pp.413-422
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• 2007

This paper addresses a new technique for constructing surface model from a set of wire-frame contours. The most difficult problem of this technique, called contour triangulation, arises when there are many branches on the surface, and causes lots of ambiguities in surface definition process. In this paper, the branching problem is reduced as the surface reconstruction from a set of virtual belts and virtual canyons. To tile the virtual belts, a divide-and-conquer strategy based tiling technique, called the BPA algorithm, is adopted. The virtual canyons are covered naturally by an iterative convex removal algorithm with addition of a center vertex for each branching surface. Compared with most of the previous works reducing the multiple branching problem into a set of tiling problems between contours, our method can handle the problem more easily by transforming it into more simple topology, the virtual belt and the virtual canyon. Furthermore, the proposed method does not involve any set of complicated criteria, and provides a simple and robust algorithm for surface triangulation. The result shows that our method works well even though there are many complicated branches in the object.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.494-496
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• 1999

본 논문에서는 SV(Support Vector Machine)과 3단의 칼라 원형 조명장치를 이용한 효율적인 납땜 검사 시스템을 제안한다. 원형 조명장치를 이용하여 납땜부의 표면의 경사도에 의해서 생기는 명암의 분포로부터 납땜 검사를 위한 특징값을 추출한다. SVM은 추출된 특징값을 이용하여 납땜 영상을 정의된 타입중의 하나로 분류한다. SVM은 두 부류의 경계를 최대로 하는 최적경계를 학습하므로 납땜 영상과 같이 각 부류의 경계가 모호한 문제에 대해서 적은 수의 학습 데이터를 사용해도 우수한 성능을 나타낸다. 제안된 시스템은 현산업에서 사용되고 있는 다양한 표면실장형 부품에 대해서 적용해 본 결과 적은 학습 데이터에도 효율적으로 적용될 수 있음을 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.607-609
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• 2000

본 논문에서는 SVM(Support Vector Machine)과 3단의 칼라 원형 조명장치를 이용한 효율적인 납땜 검사시스템을 제안한다. 원형 조명장치를 이용하여 납땜부의 표면의 경사도에 의해서 생기는 명암의 분포로부터 납땜 검사를 위한 특징값을 추출한다. SVM은 추출된 특징값을 이용하여 납땜 영상을 정의된 타입중의 하나로 분류한다. SBM은 두 부류의경계를 최대로 하는 최적경계를 학습하므로 납땜 영상과 같이 각 부류의 경계가 모호한 문제에 대해서 적은 수의 학습 데이터를 사용해도 우수한 성능을 나타낸다. 제안된 시스템은 현산업에서 사용되고 있는 다양한 표면실장형 부품에 대해서 적용해 본 결과 적은 학습 데이터에도 효율적으로 적용될 수 있음을 보였다.

• The Journal of the Acoustical Society of Korea
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• v.24 no.2
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• pp.87-96
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• 2005

In matched field processing (MEP), the observed acoustic field data is basically correlated with the replica produced by the modeling. therefore the results of source localization and correlation is limited by the mismatch of the environment and sensor location. In this paper. the effects of mismatch in environment and system on the bias in estimating the source location are investigated in the context of source localization. In the Pekeris waveguide, the simulation shows that the mismatches in environment and system, can cause a significant biases in the source localization and a degradation in MFP correlation. Mismatch caused by uncertainties in array tilt and depth, bottom depth, bottom sound speed, etc. causes degradation in source localization performance.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.277-291
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• 2023

To analyze the crustal velocity structures beneath 21 broadband seismic stations in Gangwon Province, South Korea, we first applied the H-κ stacking method to 139 teleseismic event data (Mw ≥ 5.8 and the epicentral distance of 30° - 90°) occurring between March 18, 2019 and December 31, 2022 to estimate the Moho depths and V_p/V_s ratios beneath each station. The Moho depths and V_p/V_s ratios from the H-κ stacking method range from 24.9 to 33.2 km depth and 1.695 - 1.760, respectively, and the estimated V_p/V_s ratios were applied to the joint inversion of receiver functions and surface wave dispersion to obtain 1-D crustal velocity models beneath each station. The resulting Moho depths range from 25.9 to 33.7 km depth, similar to the results from the H-κ stacking method. Moho depth results from the both methods are generally consistent with Airy's isostasy. The 1-D crustal velocity models confirm that the existence of 2 km thick low-velocity layers with P-wave velocities of 5 km/s or less at some stations in the Taebaeksan basin, and at the stations CHNB and GAPB in northern Gangwon Province, which are located above the Cenozoic sedimentary layer. The station SH2B, although not overlying a sedimentary layer, has a low P-wave velocity near the surface, which is probably due to various factors such as weathering of the bedrock. We also observe a velocity inversion with decreasing velocity with depth at all stations within 4 - 12 km depths, and mid-crustal discontinuities possibly due to density differences in the rocks at around 10 km depth below some stations.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.235-244
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• 2000

This paper addresses a new method for constructing surface representation of 3D structures from a sequence of tomographic cross-sectional images, Firstly, we propose cell-boundary representation by transforming the cuberille space into cell space. A cell-boundary representation consists of a set of boundary cells with their 1-voxel configurations, and can compactly describe binary volumetric data. Secondly, to produce external surface from the cell-boundary representation, we define 19 modeling primitives (MP) including volumetric, planar and linear groups. Surface polygons are created from those modeling primitives using a simple table look-up operation. Comparing with previous method such as Marching Cube or PVP algorithm, our method is robust and does not make any crack in resulting surface model. Hardware implementation is expected to be easy because our algorithm is simple(scan-line), efficient and guarantees data locality in computation time.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.2
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• pp.123-134
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• 2000

This paper addresses a new triangulation method for constructing surface model from a set of wire-frame contours. The most important problem of contour triangulation is the branching problem, and we provide a new solution for the double branching problem, which occurs frequently in real data. The multiple branching problem is treated as a set of double branchings and an algorithm based on contour merging is developed. Our double branching algorithm is based on partitioning of root contour by Toussiant's polygon triangulation algorithml[14]. Our double branching algorithm produces quite natural surface model even if the branch contours are very complicate in shape. We treat the multiple branching problem as a problem of coarse section sampling in z-direction, and provide a new multiple branching algorithm which iteratively merge a pair of branch contours using imaginary interpolating contours. Our method is a natural and systematic solution for the general branching problem of contour triangulation. The result shows that our method works well even though there are many complicated branches in the object.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.199-207
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• 2013

Spin images representing efficiently surface features of 3D mesh models have been used to detect facial landmark points. However, at a certain point, different normal direction can lead to quite different spin images. Moreover, since 3D points are projected to the 2D (${\alpha}-{\beta}$) space during spin image generation, surface features cannot be described clearly. In this paper, we present a method to detect 3D facial landmark using improved spin images by partitioning the search area with respect to angle. By generating sub-spin images for angular partitioned 3D spaces, more unique features describing corresponding surfaces can be obtained, and improve the performance of landmark detection. In order to generate spin images robust to inaccurate surface normal direction, we utilize on averaging surface normal with its neighboring normal vectors. The experimental results show that the proposed method increases the accuracy in landmark detection by about 34% over a conventional method.