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Reduced electrical resistivity of reaction-sintered SiC by nitrogen doping
Jeon, Young-Sam,Shin, Hyunho,Lee, Young-Hyun,Kang, Sang-Won Cambridge University Press (Materials Research Soc 2008 Journal of materials research Vol.23 No.4
<P>A post heat treatment of reaction-sintered SiC at 1700 °C in nitrogen atmosphere significantly reduced electrical resistivity. A trace of insulating Si3N4 phase was detected via nitrogen heat treatment in high-resolution transmission electron microscopy observation; however, based on x-ray photoelectron spectroscopy, the evidence of nitrogen doping into SiC lattice has been claimed as the mechanism to the decreased resistivity. The increase of the total volume of SiC was apparent in x-ray diffraction during the nitrogen heat treatment, which was interpreted to stem from the growth of the nitrogen-doped intergranular SiC particles and surface doping of the primary SiC to reduce the contact resistance between the primary SiC particles.</P>
Effect of Surface Treatment on Fatigue Strength of SCM440H
Hyunho Yeom(염현호),Moon Gu Lee(이문구),Choon Man Lee(이춘만),Yongho Jeon(전용호) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.8
Increased efficiency and improved performance associated with light-weight materials were investigated in this study. Numerous studies have investigated surface treatments to improve the fatigue strength of metals. Laser heat treatment is a promising method because the power and spot size can be easily controlled, allowing a small heat affected zone (HAZ). However, changes in the material properties can result; in particular, the material can become more brittle. In this study, a combination of laser heat treatment and vibration peening was proposed to increase fatigue strength without changing the material characteristics. SCM440H was investigated experimentally, and specimens were tested using a giga-cycle ultrasonic fatigue tester. The results show that the combination of these two processes significantly increased the fatigue strength and, furthermore, different fracture types were observed after a small and large number of cycles.
모바일 콘텐츠의 수묵 담채 렌더링을 위한 프로세싱 기법
장현호(Hyunho Jang),전재웅(Jaewoong Jeon),최윤철(Yoon-Chul Choy) 한국콘텐츠학회 2011 한국콘텐츠학회논문지 Vol.11 No.3
스마트폰과 태블릿 PC 같은 모바일 기기의 보급과 콘텐츠 사용 증가로 모바일 환경에서의 컴퓨터 그래픽스 연구가 활발하게 진행되고 있다. 그러나 아직까지 수묵화 및 담채 렌더링 기법과 같은 비실사적 기법을 모바일 기기 상에서 효과적으로 구현하기 위한 연구는 부족한 편이다. 모바일 기기는 데스크 탑 환경에 비해 하드웨어적 한계를 가지고 있기 때문에 비실사적 렌더링 기법이 적용된 콘텐츠를 렌더링 하기 위해서는 단말기의 제약성을 고려한 특화된 렌더링 파이프 라인이 필요하다. 본 논문에서는 비실사적 기법 중에서도 수묵화 기법과 담채화 기법을 모바일 환경에서 구현하기 위한 3차원 그래픽스 렌더링 파이프 라인과 쉐이딩 파일 전처리 기법을 제안한다. 제안하는 기법을 이용하면 비사실적 렌더링이 적용된 다양한 3D 모바일 콘텐츠를 생성할 수 있고 사용자는 모바일 디스플레이 환경에서 실시간으로 수묵 담채 렌더링 된 콘텐츠를 볼 수 있을 것으로 기대한다. Development of mobile devices such as smart phones and tablet PC and increased usage for mobile contents make researches of mobile computer graphics noticeable. However, previous non-photorealistic renderings such as an ink-and-wash painting with thin colors are almost designed for desktop platform and not well-matched for mobile devices. In the result, mobile-specific rendering techniques are needed to create 3D mobile contents with non-photorealistic graphics. We introduce processing techniques that are especially ink-and-wash painting and oriental thin coloring in mobile devices. Through the result of this paper, it is expected that various 3D mobile contents with non-photorealistic styles are made. Proposed work also can allow mobile devices render it in realtime using proposed preprocessing techniques and rendering pipelines.
염현호(Hyunho Yeom),정용찬(Yongchan Jung),김차영(Chayeong Kim),강기영(Ki-Young Kangb),이문구(Moon Gu Lee),홍민성(Min-Sung Hong),전용호(Yongho Jeon) 한국생산제조학회 2015 한국생산제조학회지 Vol.24 No.6
The demand of high cycle fatigue behavior on plate material is increasing because of its various applications. However, the high-cycle fatigue life data of the plate material is very rare compared to the rod material. Thus, in this study, a plate specimen is designed for the ultrasonic fatigue test because it is time efficient as compared to the conventional fatigue test. To apply the ultrasonic fatigue test, the specimen design is required to resonate at 20 kHz. Therefore, the dynamic elastic modulus was determined by measuring the resonance frequency with a piezoelectric element and laser doppler vibrometer (LDV). As a result, the plate specimen is designed and demonstrated using the ultrasonic fatigue testing machine. The ultrasonic fatigue test results were compared with the hydraulic fatigue test results.