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무아레 간섭계 초정밀 변위 측정장치의 설계 및 PBGA 패키지 열변형 측정에의 응용
오기환,주진원,Oh, Ki-Hwan,Joo, Jin-Won 대한기계학회 2004 大韓機械學會論文集A Vol.28 No.11
A description of the basic principles of moire interferometry leads to the design of a eight-mirror four-beam interferometer for obtaining fringe patterns representing contour-maps of in-Plane displacements. The technique is implemented by the optical system using an environmental chamber for submicro-displacement mesurement. In order to estimate the reliability and applicabili쇼 of the system developed, the measurement of coefficient of thermal expansion (CTE) for a aluminium block is performed. Consequently, the system is applied to the measurement of thermal deformation of a WB-PBGA package assembly. Temperature dependent analyses of global and local deformations are presented to study the effect of the mismatch of CTE between materials composed of the package assemblies. Bending displacements of the packages and average strains of solder balls are documented. Thermal induced displacements calculated by FEM agree quantitatively with experimental results.
플래시 메모리 SSD를 이용한 알티베이스 확장 캐시의 구현
구동현(Koo Dong-hyun),오기환(Oh Gi-hwan),구슬기(Koo Seul-ki),강운학(Kang Woon-hak),이상원(Lee Sang-won) 한국정보과학회 2011 한국정보과학회 학술발표논문집 Vol.38 No.2C
DB에서 일반적인 연산 중 가장 큰 시간을 소모하는 부분은 I/O 시간이다. 이를 줄이기 위하여 여러 가지 연구가 진행되었는데 최근 플래시 메모리 SSD가 상용화 되면서 SSD를 이용하여 I/O시간을 줄이기 위한 연구가 진척 되었다. 본 논문에서는 메모리와 디스크로 구성된 기존 계층구조에 플래시 메모리 SSD를 추가해서 메모리 버퍼의 확장 캐시로 사용하는 기법을 국산 DBMS인 알티베이스에서 설계 구현 방안을 설명한다. 성능평가 수행 결과 DB사이즈 대비 10%의 SSD를 사용하여 최대 220%의 성능향상을 보였다.
굽힘시험시의 Mg/Al/STS 3층 클래드재의 변형 및 파단특성 분석
김인규 ( In Kyu Kim ),송준영 ( Jun Young Song ),오기환 ( Oh Ki Hwan ),홍순익 ( Sun Ig Hong ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.5
A three-point bending test was performed on roll-bonded Mg/Al/STS clad-metal plates under two different testing conditions (Mg layer in tension, or STS in tension) and their mechanical response and fracture behavior were investigated. Bending strength was found to be greater under the condition of Mg layer in tension. Heat treatment at 200℃ increased the bending formability, suggesting the interfacial strength increased at 200℃. Under the condition of Mg in tension, the clad heat-treated at 300℃ and 400℃ fractured in two steps, with the first step associated with the interfacial fracture between Mg and Al, and the second the fracture of the Mg layer. STS/Al layers were found to be bent without complete fracture. Under the condition of STS in tension, the clad heat-treated at 300℃ and 400℃ exhibited a very small load drop at the displacement, which is similar to that of the first load drop associated with the interfacial fracture under the condition of Mg in tension. In this case, no interfacial cracks were found and the complete cut-through fracture of clad was observed at low temperature heat treatment conditions, suggesting excellent interfacial strength. When the heat treatment temperature was higher than 300℃, interfacial cracks were observed. The local stress condition and the position of the interface with respect to the surface were found to have a great influence on the fracture behaviors of clad metals.
오기환,정한일,엄주태 대전대학교 산업기술연구소 1999 산업기술연구소 論文集 Vol.10 No.2
In recent, as the application domain of information system becomes large, the project management concept is applied to not only the large-scale construction projects but also the development of an information system. Most of the ERP vendors release methodologies and software for project management. The success stories of applying the project management concept to the large-scale construction projects and development of an information system have been reported. However a case study for applying the project management technology to small-scale projects was not reported yet. This paper is intended to show the case study for applying the project management technology to small-scale project using the project management software, NeX-Pert.