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논문 : 상변태 ; Fe-P 합금계의 열역학 성질과 상태도 계산
심재혁 ( Jae Hyeok Shim ),오창석 ( Chang Seok Oh ),이동녕 ( Dong Nyung Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 1996 대한금속·재료학회지 Vol.34 No.11
Thermodynamic and phase equilibrium data of the Fe-P system have been critically assessed by employing the CALPHAD method. The regular type solution model was applied to α(bcc), γ(fcc) and liquid Fe-P phases. The stoichiometric compound model was applied to the intermediate phases such as Fe3P, Fe2P and FeP. The parameters of the thermodynamic models have been evaluated from the thermodynamic and phase equilibrium data in the literature. Stable and metastable phase equilibria, To curves and thermodynamic properties have been calculated using the evaluated parameters. The calculated results are in fairly good agreement with the experimentally measured data.
심재동,심재혁,하헌필,Shim, Jae-Dong,Shim, Jae-Hyeok,Ha, Heon-Phil 한국재료학회 2012 한국재료학회지 Vol.22 No.3
Hydrogen is in the spotlight as an alternative next generation energy source for the replacement of fossil fuels because it has high specific energy density and emits almost no pollution, with zero $CO_2$ emission. In order to use hydrogen safely, reliable storage and transportation methods are required. Recently, solid hydrogen storage systems using metal hydrides have been under extensive development for application to fuel cell vehicles and fuel cells of MCFC and SOFC. For the practical use of hydrogen on a commercial basis, hydrogen storage materials should satisfy several requirements such as 1) hydrogen storage capacity of more than 6.5wt.% $H_2$, moderate hydrogen release temperature below $100^{\circ}C$, 3) cyclic reversibility of hydrogen absorption/desorption, 4) non toxicity and low price. Among the candidate materials, Li based metal hydrides are known to be promising materials with high practical potential in view of the above requirements. This paper reviews the characteristics and recent R&D trends of Li based complex hydrides, Li-alanates, Li-borohydrides, and Li-amides/imides.
최영석,심재혁,강신형,Choi, Young-Seok,Shim, Jae-Hyeok,Kang, Shin-Hyoung 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.1
In this study, the performance prediction programs for centrifugal pumps are developed. To estimate the losses in the centrifugal pump impellers, a two-zone model and TEIS(two elements in series) model are applied to the program. The basic concept of a two zone model considers the primary zone that is an isentropic core flow and the secondary zone that has a non-isentropic region at the impeller exit. The flow goes through two different zones and is mixed out at the impeller exit and the mixing process occurs with an increase in entropy, a decrease in total pressure. The level of the core flow diffusion in an impeller was calculated using TEIS(two elements in series) model. The effects of various parameters which are used in this program on the prediction of head and efficiency are discussed. The correlation curves used to select the effectiveness of the primitive TEIS model were suggested according to the specific speed of the centrifugal pumps.
이은재(Eun-Jae Lee),백승택(Seung-Taek Baek),최호석(Ho-Seok Choi),김영우(Young-Woo Kim),심재혁(Jae-Hyeok Shim),송상욱(Sang-Wook Song) 전력전자학회 2019 전력전자학술대회 논문집 Vol.2019 No.7
국내 전력 계통은 경제의 성장과 더불어 생활 수준의 향상에 따라 지속적인 증설과 발전이 이루어졌다. 전력설비의 밀도 측면에서 비추어보면 미국이나 일본 대비 적게는 2배에서 많게는 4배에 이르는 최고 수준의 설비 밀도를 보이고 있다. 또한 전체 전력 생산량의 40%이상이 수도권에서 소비되고 있지만 발전설비는 최대 전력 수요지인 수도권과 먼 해안에 인접한 지역에 편재되어 있기 때문에 발생하는 수요와 공급지의 불균형, 장거리 선로를 통한 전력 전송에서 야기되는 전력계통 운영 측면에서의 문제가 발생하게 된다. 최근 화두가 되고 있는 원전 축소, 노후 화력 발전소 정지, 송전선로 경과지에서의 건설 고압 송전선로 건설 반대 등의 요인으로 인하여 전력계통을 최대한 효율적이고 안정적으로 운영하여야 하는 대전제를 만족시키기 위한 방안으로 기존 AC 기반의 계통 설비에 전력변환기술을 기반으로 하는 DC 계통 및 FACTS 설비의 확대 적용하는 방안이 제시되고 있다. 본 논문에서는 다가올 MV급 이상의 전력변환설비의 개념 및 개발 현황에 대한 소개를 하고자 한다.
Mn 및 V 함량이 다른 페라이트-펄라이트 조직강의 강도와 변형능에 미치는 미세조직 인자의 영향
홍태운,이상인,심재혁,이준호,이명규,황병철,Hong, Tae-Woon,Lee, Sang-In,Shim, Jae-Hyeok,Lee, Junho,Lee, Myoung-Gyu,Hwang, Byoungchul 한국재료학회 2018 한국재료학회지 Vol.28 No.10
This study examines the effect of microstructural factors on the strength and deformability of ferrite-pearlite steels. Six kinds of ferrite-pearlite steel specimens are fabricated with the addition of different amounst of Mn and V and with varying the isothermal transformation temperature. The Mn steel specimen with a highest Mn content has the highest pearlite volume fraction because Mn addition inhibits the formation of ferrite. The V steel specimen with a highest V content has the finest ferrite grain size and lowest pearlite volume fraction because a large amount of ferrite forms in fine austenite grain boundaries that are generated by the pinning effect of many VC precipitates. On the other hand, the room-temperature tensile test results show that the V steel specimen has a longer yield point elongation than other specimens due to the highest ferrite volume fraction. The V specimen has the highest yield strength because of a larger amount of VC precipitates and grain refinement strengthening, while the Mn specimen has the highest tensile strength because the highest pearlite volume fraction largely enhances work hardening. Furthermore, the tensile strength increases with a higher transformation temperature because increasing the precipitate fraction with a higher transformation temperature improves work hardening. The results reveal that an increasing transformation temperature decreases the yield ratio. Meanwhile, the yield ratio decreases with an increasing ferrite grain size because ferrite grain size refinement largely increases the yield strength. However, the uniform elongation shows no significant changes of the microstructural factors.
기계화학반응에 의한 TiN/TiB<sub>2</sub>/Ti-silicides 나노복합분말의 합성과 반응기구
조영환,김지우,심재혁,안재평,오규환,Cho Young-Whan,Kim Ji-Woo,Shim Jae-Hyeok,Ahn Jae-Pyoung,Oh Kyu-Hwan 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.4
Nanostructured TiN/$TiB_2$/$TiSi_2$ and TiN/$TiB_2$/$Ti_5Si_2$ composite powders have been prepared by mechanochemical reaction from mixtures of Ti, BN, and $Si_3N_4$ powders. The raw materials have reacted to form a uniform mixture of TiN, $TiB_2$ and $TiSi_2$ or $Ti_5Si_3$ depending on the amount of $Si_3N_4$ used in the starting mixtures, and the reaction proceeded through so-called mechanically activated self-sustaining reaction (MSR). Fine TiN and $TiB_2$ crystallites less than a few tens of nanometer were homogeneously dispersed in the amorphous $TiSi_2$ or $Ti_5Si_3$ matrix after milling for 12 hours. These amorphous matrices became crystalline phases after annealing at high temperatures as expected, but the original microstructure did not change significantly.