• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.556-560
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• 1996

In order to examine thd accuracy of intersection counting method, the fiber orientation distribution of simulation figure platted by PC is measured using image processing. The fiber orientation distribution obtained by an image processing method is compared with those by the intersection counting method. The result shows that the errors of the intersection counting method are large because its measurement is made by the cross point of the scanning line and the fiber.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.252-257
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• 2005

Injection molding is a very important industrial process for the manufacturing of plastics objects. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation' orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of weld-line in injection-molded products is assessed. And the effects of fiber content and injection mold-gate conditions on the fiber orientation are also discussed.

• 동력기계공학회지
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• 제10권4호
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• pp.99-104
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• 2006

Young's modulus of composite has been predicted by Eshelby's equivalent inclusion method modified with Mori-Tanaka's mean field theory, where short fibers of aspect ratio distribution are assumed to be aligned. Young's modulus of the composite is predicted with the smallest class interval for simulating the actual distribution of fiber aspect ratio, which is compared with that computed using different class intervals. Young's modulus of the composite predicted with mean aspect ratio or the largest class interval is overestimated by the maximum 10%. As the class interval of short fibers for predicting Young's modulus decreases, the predicted results show good agreements with those obtained using the actual distribution of fiber aspect ratio. It can be finally concluded from the study that if and only if the class interval of short fiber normalized by the maximum aspect ratio is smaller than 0.1, the predicted results are consistent with those obtained using the actual distribution of aspect ratio.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.434-439
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• 2013

PURPOSE. The aim of the present study was to evaluate the effects of posts with different morphologies on stress distribution in an endodontically treated mandibular premolar by using finite element models (FEMs). MATERIALS AND METHODS. A mandibular premolar was modeled using the ANSYS software program. Two models were created to represent circular and oval fiber posts in this tooth model. An oblique force of 300 N was applied at an angle of $45^{\circ}$ to the occlusal plane and oriented toward the buccal side. von Mises stress was measured in three regions each for oval and circular fiber posts. RESULTS. FEM analysis showed that the von Mises stress of the circular fiber post (426.81 MPa) was greater than that of the oval fiber post (346.34 MPa). The maximum distribution of von Mises stress was in the luting agent in both groups. Additionally, von Mises stresses accumulated in the coronal third of root dentin, close to the post space in both groups. CONCLUSION. Oval fiber posts are preferable to circular fiber posts in oval-shaped canals given the stress distribution at the postdentin interface.

• 동력기계공학회지
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• 제21권5호
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• pp.13-19
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• 2017

The effect of heat treatment temperature (HTT) on the mechanical properties of polyacrylonitrile (PAN)-based carbon fiber had been investigated. The heat treatment on the carbon fiber was conducted under high vacuum atmosphere of $10^{-6}mmHg$, and the range of temperature of $1,000^{\circ}C$ to $2,000^{\circ}C$. As a results, The tensile strength of carbon fiber and carbon fiber composites showed increasing tendency with the rise of heat treatment temperature. And, the shape parameter of Weibull distribution for the strength of carbon single fiber showed an increasing trend until $1,800^{\circ}C$. But the shape parameter of Weibull distribution for the strength of carbon fiber composites showed no clear tendency with the rise of heat treatment temperature. The cause of reinforcement effect of the carbon fiber by the heat treatment was regarded as the carbonization of carbon single fiber.

• 한국전산구조공학회논문집
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• 제22권6호
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• pp.587-596
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• 2009

섬유 가교 곡선은 섬유보강 시멘트 복합체의 인장 거동을 예측하고 분석하는데 중요한 요인이다. 이 연구의 목적은 ECC에서 섬유 배향각의 분포와 섬유 개수를 정량적으로 고려할 수 있는 섬유 가교 모델을 제시하는 것이다. 이를 위하여 먼저 섬유 배향각과 섬유 개수를 정량적으로 고려할 수 있는 섬유 가교 모델을 유도하였다. 섬유 배향각과 섬유 개수는 이미지 프로세싱 기법을 사용하여 계측하였다. 이미지 분석을 통하여 계측한 섬유 배향각에 대한 확률밀도함수와 섬유 개수는 섬유 배향각을 2차원이나 3차원에 무작위로 분포된 것으로 가정하는 것과 큰 차이를 보였다. 이는 타설방법이나 유동흐름에 따라 섬유 분포 특성이 영향을 받기 때문으로, 모델의 검증을 위해 정확한 섬유분포 특성을 파악할 필요가 있다. 따라서 이미지 프로세싱 방법으로 계측한 섬유 분포 특성을 근간으로 보강섬유의 배향각과 단면 내 섬유 개수를 고려하여 얻은 섬유 가교 곡선으로 1축 인장 거동을 모사하였다. 모사한 1축 인장 거동은 실험 결과와 유사하게 다중 균열과 변형률 경화 거동을 보이는 등 1축 인장 거동을 정확히 나타낼 수 있는 것으로 검증되었다.

• 대한기계학회논문집A
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• 제22권4호
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• pp.953-959
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• 1998

To investigate accuracy of intensity method for measurement of the fiber orientation distribution, fiber orientation function is calculated by drawing simulation figures for the fiber orientation as varying fiber aspect ratio, fiber area ratio, and fiber orientation state, respectively. The values of fiber orientation function measured by intensity method are compared with the calculated values of fiber orientation function. The results show that measurement accuracy of the fiber orientation angle distribution by intensity method is affected by the fiber aspect ratio when the total length of oriented fiber is same. The average gradient of fiber orientation function is 0.94 for 1000mm of the total fiber length and is 0.93 for 2000 mm when the fiber aspect ratio is over 50. Measurement accuracy by intensity method is about 94% and the reliable data can be obtained by intensity method.

• Composites Research
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• 제16권6호
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• pp.1-9
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• 2003

본 논문에서는 웨이블 분포 함수를 이용한 확률 파손 해석을 통해 복합재 압력 용기의 섬유 강도를 예측하였다. 그리고 섬유 강도의 크기 효과를 확인하고 해석의 타당성을 입증하기 위하여 섬유 인장 시편, 한 방향 복합재 시편과 복합재 압력 용기를 이용만 강도 시험이 수행되었다. 해석적 방법으로 웨이블 최약 링크 파손 모델과 다단계 연속 파손 모델을 이용하였고, 해석 결과를 상호 비교하였다. 크기 효과에 의해, 시편의 부피가 증가함에 따라 섬유 인장 강도가 감소하는 경향을 나타내었다. 해석을 통해 예측한 한 방향 복합재 시편과 복합재 압력 용기의 후프 층 섬유 강도 분포는 시험 값과 좋은 일치를 보였다. 섬유 강도의 크기 효과는 소재와 제작 공정 변수의 함수로서, 다른 소재 및 제작 공정에 대해서는 다른 크기 효과를 보이게 된다.

• 한국정보기술학회 영문논문지
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• 제10권1호
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• pp.25-36
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• 2020

Motivation: Fibers as the extracellular filamentous structures determine the shape of the cytoskeletal structures. Their characterization and reconstruction from a 3D cellular image represent very useful quantitative information at the cellular level. In this paper, we presented a novel automatic method to extract fiber diameter distribution through a pipeline to reconstruct fibers from 3D fluorescence confocal images. The pipeline is composed of four steps: segmentation, skeletonization, template fitting and fiber tracking. Segmentation of fiber is achieved by defining an energy based on tensor voting framework. After skeletonizing segmented fibers, we fit a template for each seed point. Then, the fiber tracking step reconstructs fibers by finding the best match of the next fiber segment from the previous template. Thus, we define a fiber as a set of templates, based on which we calculate a diameter distribution of fibers.

• Composites Research
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• 제29권5호
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• pp.299-305
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• 2016

본 연구는 이변량 Gaussian 분포함수를 적용하여 CFRP 적층판의 섬유물성 변화를 추정하는 방법을 제안하였다. 섬유의 손상 분포를 규명하기 위하여 수정된 이변량 Gaussian 분포함수를 적용하여 5개의 미지 변수가 고려되었다. 조합된 컴퓨터 기법을 적용하여 역문제를 해결하기 위하여 본 연구에서는 몇 개의 고유진동수와 모드 정보를 입력데이터로 활용하였다. 수치해석 예제는 제안된 기법이 적층배열 변화에 따른 CFRP 판의 섬유 손상 분포 및 위치를 규명할 수 있는 적합하고 실용적은 방법임을 보여준다.