• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.38-45
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• 1998

It is a tedious and excessive time consuming process to model the local area of crack tip part of structures in calculation of stress intensity factors by FEM. So, in this paper, the hybrid method of FEM and BEM approach was formulated to overcome this type of problems. The multi-domained BEM was adopted to simplify the modelling process of complex geometry and singularity characteristics of crack tip part and the ordinary FEM modelling was used in the rest part. The example calculations shows very good results compared with analytic solutions and other numerical method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.6
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• pp.865-871
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• 2022

In this paper, we propose a method of extracting prostate region using morphological characteristics of ultra-sonic image of prostate. In the first step of the proposed method, the edge area of the prostate image is extracted. The histogram of ultra-sonic image is used to extract base objects to detect the upper edge of prostate region by altering the contrast of the image, then, the lower edges of the extracted base objects are connected by using monotone cubic spline interpolation to extract the upper edge. Step 2, Otsu's binarization is applied to the region under the extracted upper edge of the prostate ultra-sonic image to extract the lower edge of prostate. In the last step, the upper and the lower edges are connected to extract prostate region and by comparing the extracted region of prostate with the one measured manually, the result showed that the morphological characteristics of prostate in ultrasonic image can be utilized to extract the prostate region.

• The Transactions of the Korea Information Processing Society
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• v.4 no.2
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• pp.596-605
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• 1997

The synamic systrm emplohing the self-squared function, , $f(Z)=z^2+c$, provides the Mandelbrot set which classifies constants c using the divergence of the sequence starting from the origin.To speed-up the generation of Mandelbrot set images, two approaches , called as the divide-and-conquer technique and the triangular boundary tracing technique, have been developed.However , the divede-and-conquer technique genrates sequences of some pixels that so not affect graphical representations of the Mandelbrot set.The triangular boundary tracing tech-mique does noot represent some 8-connected components of the Mandelbrost set.In this paper, we prorose a new ;method which solves the 8-connectivity problem of triangular boundary tracing technique.This algorithm considers the divergence for only pixels which are essential to the graphical repressentation of the Mandelbrot set.It also foves good representations for 8-connected components like hairly structures.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.55-59
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• 2004

유한요소법을 이용하여 전자장을 해석할 경우 전류원이 전 영역에 비해 극히 작은 영역이면, 요소분할 과정에서 소스부분을 세분하여야 하므로 결국 미지수의 증가를 가져오게 된다. 또한, 선전류 문제의 경우 2차원 유한 요소 해석이 용이하지 않다. 이를 보안하기 위해 본 논문에서는 소스가 선전류이고 관심 영역이 선전류원으로부터 떨어져 있는 경우, 소스 영역은 해석해를 적용하여 유한요소법과 결합하는 방법을 제시하였다. 해석적인 해는 원통좌표계에서 반정에 대한 멱함수와 회전각도에 대한 삼각함수의 곱의 형태로 표현된다. 이때 두 종류의 적분 상수가 있는데, 이는 경계상의 포텐셜값과 유한요소법의 경계 적분항을 푸리에급수로 전개한 계수로 표현된다. 제안한 알고리즘의 검증을 위하여 해석해가 존재하는 모델을 설정하여 해석적인 방법, 기존의 유한요소 법 및 결합 방법에 의한 해를 비교 검증하였다.

• Journal of Korea Multimedia Society
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• v.13 no.11
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• pp.1698-1705
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• 2010

In this paper, we propose a fast liver segmentation method from magnetic resonance(MR) images. Our method efficiently divides a MR image into a set of discrete objects, and boundaries based on the normalized gradient magnitude information. Then, the objects belonging to the liver are detected by using 2D seeded region growing with seed points, which are extracted from the segmented liver region of the slice immediately above or below the current slice. Finally, rolling ball algorithm, and connected component analysis minimizes false positive error near the liver boundaries. Our method was validated by twenty data sets and the results were compared with the manually segmented result. The average volumetric overlap error was 5.2%, and average absolute volumetric measurement error was 1.9%. The average processing time for segmenting one data set was about three seconds. Our method could be used for computer-aided liver diagnosis, which requires a fast and accurate segmentation of liver.

• Journal of KIISE:Software and Applications
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• v.30 no.3_4
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• pp.308-315
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• 2003

This paper proposes an approach integrating multiple segmentation methods in a systematic way, which can improve overall accuracy without deteriorating accuracy of highly confident segments of boundaries generated by constituent methods. A segmentation method produces boundary segments, which are then evaluated with an evaluation function considering pros/cons of the current and next methods to apply. Boundary segments with low confidence are replaced by a next method while the other segments are kept. These steps are repeated until all segmentation methods are applied. The proposed approach is implemented for the segmentation of muscles in the Visible Human color images. A Balloon method, a minimum cost path finding method, and a Seeded Region Growing method are integrated. The final segmentation results showed improvements in both overall evaluation and segment-based evaluation.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.805-807
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• 2005

본 논문에서는 동적 계획법(dynamic programming)과 이미지 세그먼트(segment)를 이용한 새로운 스테레오 정합(stereo matching)기법을 제안한다. 일반적으로 동적 계획법(dynamic programming)은 빠르면서도 비교적 정확하고, 조밀(dense)한 disparity map을 얻을 수 있다. 그러나 경계(boundary)근처의 폐색지역(occlusion region)이나, 텍스쳐가 적은 모호한 영역에서는 잘못된 결과를 유도할 수 있다. 본 논문에서는 이러한 문제점들을 해결하기 위해 먼저 이미지를 아주 작은 영역으로 분할(over-segmentation)하고, 이런 작은 영역들이 비슷한 disparity를 가질 것이라고 가정한다. 다음으로 동적 계획법(dynamic programming)을 통해 정합을 수행한다. 여기서 계산비용(cost)은 기존의 정합윈도우 안에서 세그먼트 영역을 적용한 새로운 비용함수를 사용하며, 이 새로운 비용함수를 통해 정확도를 높인다. 마지막으로 동적 계획법을 통하여 얻어진 조밀한 disparity map을 세그먼트 영역들의 시각특성(visibility)과 유사도(similarity)를 이용하여 에러를 찾아내고, 세그먼트 정합을 통해 수정함으로 정확한 disparity map을 찾아낸다.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2006.06a
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• pp.21-24
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• 2006

본 논문에서는 신장조직 영상에서 사구체 영역을 자동적으로 추출하는 방법을 제안한다. 사구체 조직은 신장의 상태를 나타내는 많은 정보를 포함하고 있기 때문에 사구체 영역의 추출은 신장 검사를 자동화하기 위한 첫 번째 단계이다. 그러나 사구체 영역을 단순한 2치화 방법으로 직접 추출함은 어려운 일이다. 이에 본 연구자들은 우선, 가우스 함수에 의한 원영상의 빛바랜 영상을 동적인 임계값으로 사용함으로써 원영상을 2치화한다. 다음으로, 획득한 영상으로부터 간단한 영상처리 기법에 의한 사구체 영역의 경계 에지를 포함하는 모든 에지를 추출한다. 그 다음으로 사구체 영역의 경계 에지를 판별함으로써 사구체 영역을 추출하였다. 이 방법은 다수의 샘플에 적용해서 유효성을 확인한 바 양호한 결과를 얻을 수 있었다.

• Journal of KIISE:Software and Applications
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• v.37 no.4
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• pp.273-281
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• 2010

In this paper, we propose an automatic segmentation method of the endo- and epicardial boundary by using ray-casting profile based on intensity distribution and gradient information in CT images. First, endo-cardial boundary points are detected by using adaptive thresholding and seeded region growing. To include papillary muscles inside the boundary, the endo-cardial boundary points are refined by using ray-casting based profile. Second, epi-cardial boundary points which have both a myocardial intensity value and a maximum gradient are detected by using ray-casting based adaptive gradient profile. Finally, to preserve an elliptical or circular shape, the endo- and epi-cardial boundary points are refined by using elliptical interpolation and B-spline curve fitting. Then, curvature-based contour fitting is performed to overcome problems associated with heterogeneity of the myocardium intensity and lack of clear delineation between myocardium and adjacent anatomic structures. To evaluate our method, we performed visual inspection, accuracy and processing time. For accuracy evaluation, average distance difference and overalpping region ratio between automatic segmentation and manual segmentation are calculated. Experimental results show that the average distnace difference was $0.56{\pm}0.24mm$. The overlapping region ratio was $82{\pm}4.2%$ on average. In all experimental datasets, the whole process of our method was finished within 1 second.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.244-246
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• 2000

x,y평면 위를 자유롭게 구동할 수 있는 서피스 모터(평면 모터)의 디텐트력을 3차원 유한요소 해석을 이용하여 해석한다. 고정자와 이동자를 분리하여 모델링을 하고 접하는 면을 주기 경계조건으로 처리하여 실제로 이동하지 않고도 이동을 고려할 수 있도록 하였다. 고정자와 이동자의 계수 행렬을 분리하여 영역 분할법을 적용하여 계산 시간을 단축하였다.