• Journal of Periodontal and Implant Science
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• 제47권1호
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• pp.41-50
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• 2017

Purpose: The aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging. Methods: We evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically. Results: The detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than $100{\mu}m$. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform. Conclusions: We were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.

• 폴리머
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• 제31권2호
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• pp.123-129
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• 2007

세 종류의 폴리올레핀 복합재료의 기계적인 특성과 파괴인성 메커니즘이 연구되었다. 기계적 특성을 조사하기 위해 인장 시험 및 아이조드 충격 시험이 수행되었다. 균열 선단 주위의 파손 메커니즘을 정확히 조사하기 위해 2노치-4점 굽힘 기법이 도입/적용되었다. 광학현미경과 투과형 전자현미경을 이용하여, 폴리올레핀 복합재료의 균열 선단 주변 국부적인 파괴인성 특성들이 관찰되었다. 이를 통한 구체적인 관찰은, 폴리올레핀 복합재료의 균열선단 주변에 전단밴딩, 크레이즈, 입자-수지간 분리, 고무입자의 캐비테이션, 크랙 휭 및 크랙 분기 등과 같은 다양한 파괴인성 메커니즘들이 존재함을 보여주었다. 이러한 파괴인성 메커니즘들은 아이조드 충격 시험에서 보여진 파괴인성 값의 증가에 대한 실질적인 원인으로 보여진다. 본 연구를 바탕으로, 2노치-4점 굽힘 기법은 폴리올레핀 복합재료의 파괴 거동과 그와 관련된 파괴인성 메커니즘을 기술할 수 있는 충분한 정보를 제공하였다.

• 대한기계학회논문집A
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• 제31권7호
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• pp.732-738
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• 2007

Effects of melt-mixing conditions on fracture properties of hydroxyapatite filled bioabsorbable poly(L-lactic acid)(HA/PLLA) composites was investigated by measuring the firacture toughness value of HA/PLLA composites prepared under different mixing time and rotor speed. The fracture surface morphology was also examined by profile measurement and scanning electron microscopies. It was found that the fracture toughness of HA/PLLA composites decreases due to decrease of ductile deformation of PLLA matrix and debonding of interfaces with increase of the rotor speed and mixing time. Effect of mixing process on neat PLLA was also assessed, and it was found that the fracture toughness of PLLA decreases due to disappearance of multiple craze formation and increase of defects. Such thermal and shear-stress degradation were found to be the primary mechanisms of the degradation of HA/PLLA composites during melt-mixing process.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.121-121
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• 1992

Deformation behavior of compatible polymer blends was studied using scanning electron, optical, and transmission electron microscopies. Four different compatible systems were employed and charaterized in this investigation : polystyrene(PS) and polyphenylene oxide(PPO), polystyrene(PS) and polyvinlmethylether(PVME), polystyrene(PS) and poly $\alpha$-methylstyrene(P$\alpha$MS). Individual craze and shear deformation zone microstructures were examined by transmission microscopy (TEM). For TEM observations, specimens deformed in-situ on a TEM grid were utilized. Quantiative analysis of these crazes and shear deformation zones was obtained from the nicrodensitometry of the TEM negatives in the manner developed by Lauterwasser and Kramer. Microdensitometry resulys showed that the fibril extension ratio decreased as the PPO content increased in the PS/PPO blends, and finally, for 100% PPO, only shear deformation zones were observed. For the PS/PVME blends, the ribril extension ratio also decreased as the VME content increased. For the PS/P$\alpha$MS blends, the fibril extension ratio increased as the P$\alpha$MS content increased, For the PPO/P$\alpha$MS blends, the fibril extension ratio increased as the P$\alpha$MS content increased.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1056-1061
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• 2003

CD-R disc drive is one of the basic options of personal computer today. In this trend, various CD-R discs can be purchased in every market. Even very low quality discs are in market too. Today's CD-R disc drive is being operated over 10,000 RPM. So the possibility of the disc fracture is growing faster. Sometimes, during the test of a new disc drive by various methods to confirm the quality of it, fracture of the disc happens. And it happens in end user's personal computer scarcely. In this reason, new methods to confirm the quality and the failure mechanism of the optical disc are studied in this paper.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.150-155
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• 2004

The base material of optical disc is the amorphous polymer, polycarbonate. So crack growth on the rotating optical disc could happen by the static centrifugal force. This phenomenon is called static fatigue. Today's CD-R disc drive is being operated over 10,000 RPM. This is increasing the possibility of the disc fracture when operating. In this reason, new method to measure the static fatigue threshold quality and the way to calculate the threshold J-integral value and the safe crack length of the optical disc are studied. Finally the environmental effect to optical disc is also studied in this paper.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.45-49
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• 2008

The monorail system as new transportation system mostly has being constructed as an elevated construction. In particular, in case of construction to elevated structure in the center of a city, it is important to decision for a monorail station to be considered the minimization. We must purchase the required lands prior to design the monorail stations because of separation of a platform and a waiting room. So We can exclude the problem that it have too close between a monorail station and the other building. Therefore the standard width and elevation of the monorail station shall be considered the efficient execution, economic and transportation. We have many thing to resolve as the plan of minimization to the station of monorail. But we know the ultimate in environmentally friendly transportation, of course, is our monorail system and we are positive as to a popular transportation craze.

• 한국멀티미디어학회논문지
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• 제24권5호
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• pp.709-716
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• 2021

The current trend of entertainment programs is an "Sub-character." This study is to find out which strategies were chosen, considering the entertainment program "Hang Out With Yoo" as the beginning and front-runner of craze for Sub-characters. The following results were deduced: implementation of trendy characters, aggressive acceptance of growth narrative and expansion of episodes. The success or failure of an entertainment program depends on the implementation method of differentiated characters. At this point in time when Sub-characters are continuously developed, this program is meaningful in that it has presented the strategies for Sub-characters reflecting the demand of audience.

• 한국전자거래학회지
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• 제26권3호
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• pp.155-174
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• 2021

본 연구는 새롭게 떠오르는 재테크 방법 중 아이템의 희귀성을 이용하여 출시가보다 비싼 가격에 재판매하는 리셀(Resell) 재테크에 주목하였다. 리셀 시장은 패션 분야를 중심으로 세계적으로 시장 규모가 급격히 성장하고 있을 뿐만 아니라 국내에도 열풍이 불고 있으나 아직까지 체계적인 리셀 시장에 대한 실증적인 분석은 부족하다. 이에 본 연구는 리셀의 대표적 사이트인 StockX의 스니커즈 데이터를 활용하여 리셀 시장에 관심 있는 사용자들에게 기본적인 가이드라인을 제시하고 리셀 시장의 진입장벽을 해소하고자 한다. 약 150만 개의 데이터를 수집하여 XGBoost 알고리즘과 Prophet 모형을 통하여 분석을 진행하였다. 분석 결과 리셀 거래에 유효한 영향을 미치는 요인들을 각 변수 별로 파악할 수 있었고 어떤 종류의 스니커즈가 리셀 거래를 하기에 적합한지 확인할 수 있었다. 또한 스니커즈들의 과거데이터를 통해 미래의 가격을 예측하여 추후의 수익성을 예상할 수 있었다. 본 연구는 아직 시작 단계인 리셀 분야에 대한 실증 분석을 기반으로 시장 진입 및 활용에 대한 가이드라인을 제시하고 더 나아가 마니아층 위주로 점유되던 리셀 시장을 활성화할 수 있을 것으로 기대한다.

• 한국패션뷰티학회지
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• 제3권1호
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• pp.39-49
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• 2005

The purpose of this study is to analyze the consumption value and characteristic of content in cosmetics & perfume advertisement in men's fashion magazines in order to understand the changes of men's cosmetics market which is recently getting great attention along with the craze for 'florally handsome men', and 'eolzzang'(=gorgeous face), and examine the changes of the culture of men's make-up. I selected Esquire which had firstly produced men's fashion magazine in Korea, and implemented the content analysis, the quantitative analysis method, by separating linguistic elements ken visual elements. The results are as follows: In the analysis of consumption value revealed in the linguistic elements of cosmetics advertisement, emotion value was the highest in both cosmetics and perfume, while function value was the second highest in cosmetics and rarity value was the second highest in perfume. About the changes of content characteristics of visual elements, in both cosmetics and perfume advertisement, there were a lot of visual advertisements focused on figures without the mixture of linguistic expressions. Between advertisement in 1990s and that in 2000s, there were meaningful differences only in types and object of meaning of used symbols.