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합성가스 충돌제트화염에서 충돌거리에 따른 열전달 특성에 관한 연구
정병규(Byeonggyu Jeong),김동찬(Dongchan Kim),최종민(Jongmin Choi),이기만(Keeman Lee) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
An experimental study has been conducted to investigate the thermal behavior of laminar syngas/air mixture with 10% hydrogen content impinging normally to a flat plate of cylinder. Effects of impinging distance(H/d=0.8, 1.2, 1.6, 2.0, 3.0) as major parameters on surface temperature of radial direction were examined experimentally by the direct photos and data acquisitions from impinging plate. There were 1 times and 2 times of maximum peak point of radial direction with respect to the impinging distance for the investigation. Maximum temperature of stagnation point was investigated in H/d=0.8. As H/d is increased, the maximum peak point was moved in to the radial direction.
Ductilization of Nanoporous Ceramics by Crystallinity Control
Kim, Jung Woo,Shin, Dahye,Park, Yang Jeong,Jang, Dongchan,Cho, Sung Oh American Chemical Society 2019 NANO LETTERS Vol.19 No.12
<P>Synthesizing ceramic materials with a significant amount of deformability is one of the most important engineering pursuits. In this study, we demonstrate the emergence of metal-like plasticity through the crystallinity control in the monolithic zirconia with the vertically aligned honeycomb-like periodic nanopore structures fabricated using the anodizing technique. The crystalline orders of the nanoporous zirconia films vary between monoclinic, tetragonal, and amorphous phases after the heat treatment and/or proton irradiation, whereas the vertical pore structures are maintained. The micropillar compression tests on those samples reveal a large amount of plasticity, more than 20% of total stains, in the as-anodized and proton-irradiated samples, both of which contain the amorphous phase. In contrast, the fully crystallized zirconia that resulted from annealing at 500 °C shows the brittle failure, the typical characteristic of conventional ceramic foams. These results offer a new opportunity for the nanoporous ceramic materials to be used in various applications, benefited from the tunable structural stability.</P> [FIG OMISSION]</BR>
Hippocampal Subfields Volume Reduction in High Schoolers with Previous Verbal Abuse Experiences
Sangwon Lee,유재현,Ko Woon Kim,Dongchan Kim,HyunWook Park,Jee Wook Choi,Martin H. Teicher,Bumseok Jeong 대한정신약물학회 2018 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.16 No.1
Objective: Reduced hippocampal volume and alterations in white matter tracts have been frequently reported in adults having the history of emotional maltreatment. We investigated whether these structural change occur in adolescents with previous verbal abuse (VA) experiences. Methods: Hippocampal subfield volume and white matter structural connectivity measures were assessed in 31 first year male high school students with various degrees of exposure to parental and peer VA. Results: The high VA group showed significant volume reduction in the left cornu ammonis (CA) 1 and left subiculum compared to the low VA group (p<0.05). Volumes of left hippocampal subfields CA1 and subiculum were negatively correlated with previous VA experiences (p<0.05). Increased mean diffusivity (MD) of the splenium of the corpus callosum was related to high VA score across all subjects (p<0.05). There was an inverse relationship between volume of the CA1 and subiculum and MD of the splenium (p<0.05). Conclusion: Exposure to parental and peer VA may affect development of the left hippocampal subfields and the splenium of corpus callosum. These structural alterations can be discernible during adolescence.