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저 순도 BaCO<sub>3</sub> 분말을 사용한 Yba<sub>2</sub>Cu<sub>3</sub>O<sub>7-y</sub> 초전도체의 합성
김찬중,박순동,최정숙,전병혁,문종백,이상헌,성태현,Kim, Chan-Joong,Park, Soon-Dong,Choi, Jung-Suk,Jun, Byung-Hyuk,Moon, Jong-Baik,Lee, Sang-Heon,Sung, Tae-Hyun 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1
[ $YBa_2Cu_3O_{7-y}$ ](123) powders were synthesized by the solid state reaction method using two different purity $BaCO_3$ powders (99.75% and 99.7% purity) and $Y_2O_3$ (99.9%) and CuO (99.9%) powders. The effect of $BaCO_3$ purity on the formation of a 123 phase and the superconducting properties were investigated. The mixtures of raw powders were calcined at temperature ranges of $800^{\circ}C-880^{\circ}C$ in air and finally made into a single grain samples by a melt processing with top seeding. It was found that a 123 phase was well formed at temperature above $870^{\circ}C$, but the purity effect on the 123 formation was negligible. The single-grain 123 samples prepared from the different $BaCO_3$ powders showed the same $T_c$ value of 90.5 K and similar $J_c$ values about $10^4\;A/cm^2$ at 0 T and 77 K, and $10^3\;A/cm^2$ at 2 T and 77 K. This result indicates that the low purity, cheap price $BaCO_3$ powder can be used as a raw material for the fabrication of single-grain, high-$J_c$ superconducting levitator.
당뇨병 환자에서 백내장 수술 후 수정체유화술 시간에 따른 각막내피세포의 변화
김찬중,최상경,Chan Joong Kim,Sang Kyung Choi 대한안과학회 2007 대한안과학회지 Vol.48 No.11
Purpose: To investigate the difference in corneal endothelial cell loss between diabetic and non-diabetic patients who were divided by the degree of phacoemulsification time after phacoemulsification with intraocular lens implantation. Methods: Forty eyes of 30 patients with diabetes and 47 eyes of 36 patients without diabetes were divided by phacoemulsification time into 3 groups: less than 40 seconds, from 40 to 80 seconds and over 80 seconds. The corneal endothelial cell density was compared before and 1, 4 and 16 weeks after phacoemulsification by one-way ANOVA. Bivariate correlation analysis was used to identify the correlation between phacoemulsification time and the endothelial density before and 1, 4 and 16 weeks after phcoemulsification. Results: The endothelial cell densities in diabetic and non-diabetic patients with different phacoemulsification time were not significantly different when compared before and 1, 4 and 16 weeks after phacoemulsification (P>0.05). Phacoemulsificaiton time and endothelial cell loss at 1, 4 and 16 weeks also showed no significant correlation. Conclusions: Diabetes and differences in phacoemulsification time had no significant influence on corneal endothelial cell loss. This result suggests uncomplicated phacoemulsificaion is a safe method for cataract extraction in patients with or without diabetes.