• 한국정밀공학회지
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• 제20권4호
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• pp.174-182
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• 2003

Recently, medical imaging has taken interest on CAD based solution for anatomical part fabrication or finite element analysis of human body. In principle, contours representing object boundary are obtained through image processing techniques. Surface models are then approximated by a skinning method. For this, various methods should be applied to medical images and contours. The major bottleneck of the reconstruction is to remove shape inconsistency between contours and to generate the branching surface. In order to solve these problems, bi-directional smoothing and the composite contour generation method are proposed. Bi-directional smoothing has advantage of removing the shape inconsistency between contours and minimizing shrinkage effect with a large number of iterations. The composite contour by the proposed method ensures smooth transition in branching region.

• 한국주조공학회지
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• 제25권1호
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• pp.16-22
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• 2005

This study aims to investigate the effects of the microstructures and nodule type on the fatigue characteristics of cast iron. Fatigue tests were carried out in tension-tension mode using a servo-hydraulic testing machine with load control mode operating at a frequency of 15 Hz. The tests were conducted at stress ratio R=Kmin/Kmax, of 0.1. Initial crack ${\Dalta}K$ values were highly performed with increase in tensile strength of DCI fatigue specimens. ${\Dalta}K_{th}$ region, fatigue crack propagation was primarily advanced through cell boundary and in periphery of near nodule. Fatigue crack propagation rate of D2 consisted with 2Phase(Ferrite+Pearlite) was slow due to crack closure enhanced by crack deflection and occurred crack branching. The generation of crack branch was occurred due to interaction of crack-nodule. At Threshold and Paris zone, the fractographs of the fatigue fracture surface for DCI show typical striations of a ductile fracture and isolated cleavage planes near graphite. The effect of microstructure on fatigue crack propagation of GC strongly depends on the type of flake. The generation of crack branch occurred due to interaction of crack-nodule. The fractographs of the fatigue fracture surface for GC show cleavage plane along the flake graphite.

• 정보과학회 논문지
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• 제43권4호
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• pp.419-429
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• 2016

최근 관상동맥 영역화 결과로부터 삼차원 표면 모델을 생성함으로써 혈관 구조적 정보의 렌더링 효율성의 증대뿐만 아니라 전산유체역학를 이용한 혈류 역학 시뮬레이션을 통해 혈류분획예비력과 같은 생리적 정보들을 획득하는 연구들이 활발히 진행되고 있다. 본 논문에서는 혈관 영역화 과정에서 획득한 혈관 구조 정보를 입력 데이터로 사용하여 관상동맥의 삼차원 삼각 표면 메쉬 모델을 생성하는 방법을 제안한다. 관상동맥 영역화 결과로부터 삼각형 표면 메쉬 모델을 만드는 방법으로는 Marching cube 알고리즘에 기반한 방법들이 있지만 이산적인 영상 공간에서 수행되는 알고리즘으로 가늘고 다양한 굴곡을 갖는 혈관 경계를 표현하기 힘들다. 제안된 방법은 관상동맥 영역화 과정에서 추정한 혈관 중심좌표와 법선 벡터 그리고 직경 정보를 이용하여 기존 방법들보다 정교하게 단일 혈관 가닥들에 대한 삼각 표면 메쉬들을 생성하고 분기가 일어나 중첩되는 메쉬들은 메쉬 병합 기법을 사용하여 처리함으로써 통합된 관상동맥 메쉬를 생성한다.