• Journal of International Society for Simulation Surgery
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• v.2 no.2
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• pp.67-70
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• 2015

We propose an automatic vessel segmentation method of vertebral arteries in CT angiography using combined circular and cylindrical model fitting. First, to generate multi-segmented volumes, whole volume is automatically divided into four segments by anatomical properties of bone structures along z-axis of head and neck. To define an optimal volume circumscribing vertebral arteries, anterior-posterior bounding and side boundaries are defined as initial extracted vessel region. Second, the initial vessel candidates are tracked using circular model fitting. Since boundaries of the vertebral arteries are ambiguous in case the arteries pass through the transverse foramen in the cervical vertebra, the circle model is extended along z-axis to cylinder model for considering additional vessel information of neighboring slices. Finally, the boundaries of the vertebral arteries are detected using graph-cut optimization. From the experiments, the proposed method provides accurate results without bone artifacts and eroded vessels in the cervical vertebra.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.455-459
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• 1997

A methodology which supports the feature used from design to manufacturing for sculptured pocket is newly devlored and present. The information contents in a feature can be easily conveyed from one application to another in the manufacturing domain. However, the feature generated in one application may not be directly suitable for another whitout being modified with more information. Theobjective of the paper is to parsent the methodology of decomposing a bulky feature of sculptured pocket to be removed into compact features to be efficiently machined. In particular, the paper focuses on the two task: 1) to segment horizontally a bulky feature into intermediate features by determining the adequate depth of cut and cutter size and to generate the temporal precedence graph of the intermediate features and 2)to further decompose each intermediate feature vertical into smaller manufacturing features and to apply the variable feed rate to each small feature. The proposed method will provid better efficiency in machining time and cost than the classical method which uses a long string of NC codes necessary to remove a bulky fecture.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.203-206
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• 2009

This paper represents an efficient algorithm to segment objects from the background using multiple images of distinct luminous intensities. The proposed algorithm obtains images with different luminous intensities using a camera flash. From the multiple intensities for a pixel, a saturated luminous intensity is estimated together with the slope of intensity rate. Then, we measure the sensitivities of pixels from their slopes. The sensitivities show different patterns according to the distances from the light source. Therefore, the proposed algorithm segments near objects using the sensitivity information by minimizing an energy function. Experimental results on various objects show that the proposed algorithm provides accurate results without any user interaction.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.71-76
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• 2020

Various machining methods are being studied to improve the processing quality of the spherical R shape in press die. In this paper, we confirmed that changes in machining quality were associated with changes in cutting direction, path, and cutting angle, which are commonly used in the machining of molds. We obtained a surface roughness graph with each condition change in one specimen using an instrument that measured geometry and surface roughness simultaneously. The results of the study showed that the best surface roughness in the finish cut of the spherical surface was obtained using upward pick feed machining.

• 한국IT서비스학회:학술대회논문집
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• 2003.05a
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• pp.623-628
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• 2003

제품의 개발 및 생산 과정에는 설계, 해석, 가공, 검사 등의 많은 부문이 서로 밀접하게 연계되어 있고 각 부문 간에는 각기 서로 다른 형태의 정보를 필요로 하기 때문에 이들의 유기적인 통합을 위해서는 각각의 응용 분야에서 요구되는 다양한 정보가 효과적으로 제공될 필요가 있다. 본 연구에서는 특징형상을 이용하여 설계 기능과 다른 응용 부분을 유기적으로 연계할 수 있는 알고리즘을 제시한다. ISO에서 진행 중인 STEP의 Form Feature을 기준으로 일반적인 분류를 하고 이를 기초로 특징형상을 인식하고자 하였다. 이를 위해 B-Rep 데이터로부터 Face-Edge Graph를 구성하고 다중 절점(Cut Node)을 인식하였으며, 본 연구를 바탕으로 하여 향후 몇 가지 단점을 보완하고 대상 영역을 확대시켜 감으로써 Computer-aided Design 시스템으로부터 얻어지는 3차원 형상 데이터로부터 Computer-aided Process Plan을 위해 필요한 특징형상을 컴퓨터에 의해 자동으로 추출하기 위한 발판을 구축할 수 있을 것이다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.712-714
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• 2001

매쉬 구조를 갖는 다중 프로세서에서의 오류를 허용하는 라우팅 기법은 구현에 있어 간결함을 제공하는 환경으로, 다수의 오류를 허용하기 위해 직사각형 모양의 오류 블록으로 구성하여 라우팅을 수행한다. 이 경우, 블록 내부의 정상적인 노드 역시 오류 노드로 간주되어 전체 노드의 사용율을 저하시키는데, 오류 블록을 몇 개의 확장된 매쉬로 나누고 DAG(Directed Acyclic Graph)에 적용하여 메시지 전송의 최단 거리를 구하는 RIFP(Routing for Irregular Faulty Pattern)기법으로 이를 해결하였다. 그러나, 이 기법은 노드간에 주고받는 메시지가 거치는 hop의 수가 오히려 증가되는 문제가 발생하게 된다. 본 논문에서는 증가되는 hop의 수를 억제하기 위해 목적 노드와 이웃 노드들로부터 오류블록 경계 부분까지 직선 경로를 찾는 SCP(Short-Cut Path)를 적용한 RIFP를 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.1528-1531
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• 2013

본 논문은 스테레오 시각에서 3차원 정보를 얻기 위해 bilateral filter를 이용한 그래프 컷 기반의 다해상도 스테레오 영상 정합 방법을 제안하고자 한다. 제안한 방법은 변위도에서 물체의 경계를 명확히 구분하기 위해 bilateral filter를 이용하여 그래프의 각 노드들을 연결하는 경로의 가중치를 결정하고 정합 비용을 통합한다. 정합 과정에서 계산복잡도를 줄이기 위해 계층적 다해상도 구조를 적용하여 영상 피라미드를 만들고, 정합의 정확성을 향상시키기 위해 정합 영역에 변위 평활성과 같은 제약 조건을 적용하여 변위를 전파하는 방법을 사용한다. 실험을 통해 제안한 방법이 변위 탐색 시간을 감소시킬 뿐만 아니라 기존의 그래프 컷의 단점을 보완할 수 있음을 확인하고자 한다.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.1
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• pp.89-102
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• 2019

Collagen can be used in building artificial skin replacements for treatment of burns and towards the reconstruction of bone as well as researching cell behavior and cellular interaction. The strength of collagen in connective tissue rests on the characteristics of collagen fibers. 3D confocal imaging of collagen fibers enables the characterization of their spatial distribution as related to their function. However, the image stacks acquired with confocal laser-scanning microscope does not clearly show the collagen architecture in 3D. Therefore, we developed a new method to reconstruct, visualize and characterize collagen fibers from fluorescence confocal images. First, we exploit the tensor voting framework to extract sparse reliable information about collagen structure in a 3D image and therefore denoise and filter the acquired image stack. We then propose to segment the collagen fibers by defining an energy term based on the Hessian matrix. This energy term is minimized by a min cut-max flow algorithm that allows adaptive regularization. We demonstrate the efficacy of our methods by visualizing reconstructed collagen from specific 3D image stack.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.117-126
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• 2010

In the case of failure images with controlling lighting like backlighting and excessive frontlinghting, the compensation scheme for a specific area in an image is required. The interested region is first selected by user in our method to compensate the first frame. Then we define the matching function of brightness and energy function is proposed with weight of matching function and the relationship among the neighbors. Finally, the energy is minimized by the graph-cut algorithm to compensate the brightness of the first frame. Other frames are straightforwardly compensated using the results of the first frame. The brightness variations of the previous frame is transmitted to the next frame via motion vectors. The reliability of the brightness variation is calculated based on the motion vector reliability. Video compensation result is achieved by the process of the image case. Simulation show that the proposed algorithm provides more natural results than the conventional algorithms.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.141-148
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• 2011

Most of the previous works on scene change detection algorithm focus on the detection of abrupt rather than gradual changes. In general, gradual scene change detection algorithms require heavy computation. Some of those approaches don't consider the error factors such as flashlights, camera or object movements, and special effects. Many scenes change detection algorithms based on the histogram show better performances than other approaches, but they have computation load problem. In this paper, we proposed a scene change detection algorithm with fast and accurate performance using the vertical and horizontal blocked slice images and their macro block informations. We apply graph cut partitioning algorithm for clustering and partitioning of video sequence using generated spatio-temporal histogram. When making spatio-temporal histogram, we only use the central block on vertical and horizontal direction for performance improvement. To detect camera and object movement as well as various special effects accurately, we utilize the motion vector and type information of the macro block.