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Origin of the ferromagnetism in ZnCoO from chemical reaction of Co<sub>3</sub>O<sub>4</sub>
Lee, S.,Kim, B.S.,Chan Cho, Y.,Shin, J.M.,Seo, S.W.,Cho, C.R.,Takeuchi, I.,Jeong, S.Y. Elsevier 2013 Current Applied Physics Vol.13 No.9
We investigated conversion of Co<SUB>3</SUB>O<SUB>4</SUB> to Co nanoclusters through hydrogen reduction. Quantitative analysis is performed on the conversion of Co<SUB>3</SUB>O<SUB>4</SUB> to Co metal as a function of hydrogen-injection conditions. Our results reveal that Co<SUB>3</SUB>O<SUB>4</SUB> must be completely eliminated to avoid formation of the metal phase in ZnCoO. We also propose a new M-T curve based method for detecting nano-sized Co clusters which are below the detection limit of diffraction techniques. It is also found that the Co phase can be transformed back to the Co<SUB>3</SUB>O<SUB>4</SUB> phase through oxygen annealing and that, as a result, the ferromagnetism can be eliminated. These findings are discussed in the context of the origin of ferromagnetism in ZnCoO.
편심하중이 작용하는 수평 곡선 I 형 거더의 휨·비틀림 상호작용
임정현(Lim, Jung-Hyun),이기세(Lee, Kee-Sei),김희수(Kim, Hee-Soo),최준호(Choi, Jun-Ho),강영종(Kang, Young Jong) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.9
수평 곡선 I-형 거더에는 초기곡률이라는 기하학적 특성으로 인해 휨 모멘트와 더불어 비틀림 모멘트가 작용하게 된다. 이러한 휨·비틀림 거동은 서로 상호 작용을 일으켜 약축방향으로 2차 휨거동을 유발하게 된다. 휨과 비틀림 간의 상호 작용은 곡선 거더를 조기에 비선형 상태 및 소성 상태로 유도하여 내하력의 저하를 야기하게 되고, 차량의 이동 위치에 따른 편심 하중은 비틀림을 더욱 증대시킬 수 있다. 그러나 기존에 연구되어왔던 직선 거더에 대한 휨·비틀림 상호관계식은 곡선 거더가 가지고 있는 거동 특성이 고려되지 않았기 때문에 수직하중을 받는 수평 곡선 I-형 거더의 극한 강도가 과대평가 될 수 있다. 따라서 이에 대한 보다 명확하고 합리적인 제안식의 적용이 곡선 거더의 설계 시에 필요하다. 본 연구에서는 유한요소해석을 통하여 편심하중이 작용하는 수평 곡선 I형 거더의 휨·비틀림 상호작용 특성을 파악하고 거동분석을 수행하였다. With bending moment, torsional moment due to geometric properties as “Initial curvature” acts in horizontally curved I-girder. These behavior causes the secondary effect of bending in minor-axis because of interaction between bending and torsion. The bending and torsion interaction cause a loss of load bearing capacity by induced the early inelastic or plasticity condition in curved girder. Also eccentric load by movements of traffic can increase torsion. However, Equation of interaction between bending and torsion for straight girder, not deal with characteristics of curved girder behavior in previous studies, can be overestimated for ultimate strength in horizontally curved I-girder acting vertical force. Therefore, using more rational, obvious suggestion is required when design curved girder. In this study, we identified the bending-torsional moment interaction for the horizontally curved I-girder of the eccentric load acting by FEM analysis.
Origin of the ferromagnetism in ZnCoO from chemical reaction of Co3O4
Seunghun Lee,Bum-Su Kim,조용찬,Jong-Moon Shin,Seung-Wan Seo,조채용,Ichiro Takeuchi,정세영 한국물리학회 2013 Current Applied Physics Vol.13 No.9
We investigated conversion of Co3O4 to Co nanoclusters through hydrogen reduction. Quantitativeanalysis is performed on the conversion of Co3O4 to Co metal as a function of hydrogen-injection conditions. Our results reveal that Co3O4 must be completely eliminated to avoid formation of the metalphase in ZnCoO. We also propose a new MeT curve based method for detecting nano-sized Co clusterswhich are below the detection limit of diffraction techniques. It is also found that the Co phase can betransformed back to the Co3O4 phase through oxygen annealing and that, as a result, the ferromagnetismcan be eliminated. These findings are discussed in the context of the origin of ferromagnetism in ZnCoO.