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AZ31 마그네슘합금 레이저 용접부의 미세조직 및 미소경도의 분포에 관한 연구
최영환(Y.H. Choi),이목영(M.Y. Lee),최시훈(S.-H. Choi) 한국레이저가공학회 2012 한국레이저가공학회지 Vol.15 No.3
The laser weld of AZ31 magnesium alloy was characterized with OM, EBSD and micros vickers hardness tester in experiment. EBSD analysis and micro-hardness measurements were carried out at the three regions (Equiaxed Zone, Columnar Dendrite Zone, Base Metal) of the welded AZ31Mg alloy sheets. The magnesium alloy show the rectangular shape bead in laser weld. EBSD analysis revealed that the three regions show the heterogeneous distribution of grain size and microtexture. Micro-hardness measurement also revealed that the heterogeneous distribution of microstructure contributed to the heterogeneous micro-hardness distribution in the three regions.
캡플레이트를 이용한 장스팬용 춤이 깊은 데크의 휨성능 개선
박기연,남윤선,최영환,김영호,최성모,Park, K.Y.,Nam, Y.S.,Choi, Y.H.,Kim, Y.H.,Choi, S.M. 한국강구조학회 2013 韓國鋼構造學會 論文集 Vol.25 No.5
철골구조의 층고를 절감을 위해 유럽을 중심으로 춤이 깊은 데크를 사용한 슬림플로어 공법이 개발되어 적용되고 있다. 국내에서도 장스팬과 층고절감을 요구하는 건물이 증가하고 있지만 7m이상 장스팬에 춤이 깊은 데크를 적용 시 과도한 처짐에 의한 사용성 문제를 초래한다. 따라서 본 연구는 장스팬에 적용되는 춤이 깊은 데크의 콘크리트 타설시 처짐의 사용성 및 개방형 단면의 불안정성에 의한 휨비틀림 등의 문제를 개선하는 방안으로 Cap형태의 plate(이하 '캡 플레이트')를 두가지 형태(Flat, Hat)로 개발하고 보강 길이와 위치의 최적화를 이론적 계산을 통해 도출하였다. 이 캡플레이트를 춤이 깊은 데크의 골상부에 일정 간격으로 설치하여 상부 개방형 불안전성을 극복하고 단면의 강성을 증대시켜 중앙부 처짐을 제어하고자 한다. 캡 플레이트의 설치위치와 보강길이에 따른 휨서능 개선의 효과를 해석과 실험을 통해 검증하고자 한다. Slim floor system using deep decks has been developed and employed in Europe to reduce the floor height of steel structures. Although long span buildings involving the issue of reducing floor height are being increasingly built in Korea, employing deep decks in more than 7m long span structures is likely to cause problems associated with excessive deflection. This study is applied to the long-span concrete casting of the deep deck plate usability of deflection due to bending and torsional instability of open cross-section, as a way to improve the problem of cap plates are suggested, and the optimum length of reinforcement and location are derived from theoretic estimation. The cap plates are placed on the deep decks with regular intervals to overcome the instability of open sections, improve the stiffness of the sections and control the deflection at the centers. The improvement in flexural capacity associated with the location of the cap plates and the length of reinforcement are verified through analysis and test.
차홍기,이원석,최영환,이주철,이강찬,Cha, H.,Lee, W.,Choi, Y.,Lee, J.,Lee, K. 한국전자통신연구원 2019 전자통신동향분석 Vol.34 No.2
Blockchain enables encrypted, definitive, and immutable records of transactions to be shared and maintained across distributed nodes in peerto-peer networks. Since the establishment of the ISO/TC 307 (Blockchain and distributed ledger technologies (DLT)), Blockchain and DLT have been actively standardized. In this paper, we introduce the international standardization activities and deliverables carried out by ISO, ITU-T, and W3C.
조일준,이진,최영환,김성환,Cho, I. J.,Lee, J.,Choi, Y. H.,Kim, S. H. 대한의용생체공학회 1988 의공학회지 Vol.9 No.2
As a muscular contraction is sustained, the power spectrum of the myoelectric signal is compressed into lower frequencies. The median frequency appears to be the prefered parameters to monitor this compression. This paper describes a technique and a device which provide an estimate of the median frequency using a TMS32020 DSP chip and IBM PC for tracking of this parameter. Results obtained from myoelectric signal are presented and discussed.
신호상,홍진기,김진수,정연기,정명조,정해동,최영환,Shin, H.S.,Hong, J.K.,Kim, J.S.,Chung, Y.K.,Jhung, M.J.,Chung, H.D.,Choi, Y.H. 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.4
The renewed global interest in nuclear power has arisen from the need to reduce greenhouse gas emissions and to provide sufficient electricity for a growing global population. Many countries with nuclear power plants (NPPs) are still implementing license extensions of 10~20 years, and even consideration is being given to the concept of life-beyond-60, a further period of license extension from 60 to 80 years. To solve the materials aging problem is integral to its success. A foundation for effective aging management of nuclear power plants is that aging is properly taken into account at each stage of a plant's lifetime, i.e. in design, manufacture, construction and operation including long term operation and decommissioning. To evaluate the plant aging phenomena, a lot of background information such as materials and environment of the parts of the reactor and plant systems is needed by the experts. Information on degradation mechanisms is also used. In this paper, a regulation on the integrated materials aging management for nuclear facilities is proposed. The proposed regulation identifies key elements of effective aging management for nuclear power plants and provides the requirements on aging management for nuclear facilities throughout all stages of the lifetime of the plant.