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Exploring Cage-warped Rotation Isomers of C20 Fullerene: MP2 and Density Functional Calculations
Jangwon Lee,Yongjae Cho,MinJeong Jang,GaYoung Kook,HeeSu Gho,이창훈,Geun C. Hoang,Kee Hag Lee 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.2
Using the density functional methods B3LYP, M06-2X, PBE1PBE, B3LYP D3, M06-2X D3, and PBE1PBE D3, and the ab initio MP2 calculations, the optimized atomic structures and energies of C20 cage rotation isomers without a constraint were obtained. The reaction path between the two rotational isomers was then studied, in which there are three local stable atomic structures. One is the most stable fullerene structure with the D2h point group staggered between the upper and bottom pentagons (ST) and the other is the second lowest energy rotational isomer with the Cs point group eclipsed between the upper and bottom pentagons (EC) with a torn fullerene structure (M1) between ST and EC. The first transition structure T1 between the ST and the M1, and the second transition structure T2 between the M1 and the EC were then obtained along the reaction coordinate between these three structures. Vibration analysis of all optimized structures including the transition structures without a constraint was carried out. For each of the rotational isomers obtained by our calculations, thermodynamic stability was explained with the relative energy difference, and then the kinetic stability was analyzed as the HOMO?LUMO energy difference.
이창훈(C. H. Lee),정성기(S. K. Jung),노국현(K. H. Rho),양영록(Y. R. Yang),명노신(R. S. Myong),조태환(T. H. Cho) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
The concept of truncated airfoil sections has been suggested in order to extend the operational range of icing tunnels. With proper deflection of the small trailing-edge flap on the truncated airfoil the local pressure distribution may remain very close to that of the full-chord airfoil. The truncated flapped airfoil shape is studied by applying optimization methods. To verify the optimized truncated flapped airfoils, air flow and collection efficiency over the truncated airfoil are compared with the results of the full-scale airfoil by a computational method.
Nb 첨가 열연 고강도강에서 미세조직 및 기계적 물성에 미치는 권취온도의 영향
이창훈(C. H. Lee) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
The influence of coiling temperature on the microstructure and mechanical properties of Nb-microalloyed hot strips was studied by varing the coiling temperature continuously lengthwise within a hot strip, that is, the possibility of another factors to affect precipitation of Nb were excluded such as deformation temperature, deformation rate, amount of deformation in austenite, etc. It has been found that both yield and tensile strength increased with decreasing coiling temperature of hot strip since a ferrite-pearlite mixed microstructure has changed into ferrite-bainite or ferrite-martensite microstructures. The precipitation behavior resulted from a final coiling temperature or cooling stop temperature was significantly different in the hot strip. Most of the fine precipitates found in a strip were Nb-carbides, their size was about 10nm or less. The fraction of precipitates in a part of hot strip with a low coiling temperature of 440℃ was very small, hard to find the precipitates. On the other hand, the fraction of precipitates in a part of hot strip with a high coiling temperature of 580℃ was relatively large. The study on precipitation with various coiling temperatures in a strip suggests that NbC precipitation occurs during or after coiling in Nb-microalloyed hot strips.
전극형상에 따른 제조공기(I-Air)의 절연파괴 특성에 관한 연구
이창훈(C.H. Lee),김도석(D.S. Kim),常超(C. Chang),이창욱(C.W. Lee),김영수(Y.S. Kim),方亞偉(Y.W. Fang),최은혁(E.H. Choi),임창호(C.H. Lim),김정배 (J.B. Kim),이광식(K.S. Lee) 한국조명·전기설비학회 2006 한국조명·전기설비학회 학술대회논문집 Vol.2006 No.11월
본 연구는 SF?를 대체하기 위한 제조공기(I-Air)의 특성을 연구할 목적으로 교류고전압 인가 시 압력(P)변화 및 갭 길이의 변화에 따른 절연파괴특성을 연구하였다. 본 연구를 통해 챔버 내의 P가 증가 할수록 절연파괴특성은 증가하는 것을 확인했다. 그리고 불평등전계 보다 평등전계에서 절연파괴특성이 더 증가하고 전극간거리(d)가 증가 할수록 절연파괴특성이 증가하는 것을 확인했다. 특히 평등전계에서 d 및 높은 P일수록 SF?의 절연파괴전압(V<SUB>B</SUB>)에 I-Air의 V<SUB>B</SUB>의 근접도가 큼을 알 수 있었다.