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기계적 합금화한 $\sigma$-VFe합금의 중성자 및 X선 회절에 의한 상분석
이충효,조재문,이상진,심해섭,이창희,Lee, Chung-Hyo,Jo, Jae-Mun,Lee, Sang-Jin,Sim, Hae-Seop,Lee, Chang-Hui 한국재료학회 2001 한국재료학회지 Vol.11 No.8
$\sigma$-VFe 금속간화합물에 대한 기계적 합금화(MA) 효과를 중성자 및 X선 회절법으로 조사하였다. MA 분말의 구조분석은 X선 회절(Cu-K$\alpha$) 린 중성자회절(HRPD, λ=1.835$\AA$)을 이용하여 행하였다. $\sigma$-VFe화합물의 MA시 큰 구조변화가 관찰되었으며, MA 60시간의 경우 Fe-Fe 훤자분포는 unit cell에 30개의 원자를 포함하고 있는 $\sigma$상의 tetragonal구조에서 $120^{\circ}C$이상에서 안정하게 존재하는 $\alpha$-(V,Fe) 고용체의 bcc 구조로 상변화함을 알 수 있었다. 또한 $\alpha$-VFe 화합물에 대한 중성자 및 X선 회절패턴의 비교분석을 행하였으며 그 결과 $\sigma$상이 가지는 화학적 규칙성에 기인하는 (101)과 (111) 회절 피크가 중성자 회절에서 뚜렷하게 관찰됨을 알 수 있었다. The mechanical alloying (MA) effect in $\sigma$-VFe intermetallic compound was studied by neutron and X-ray diffraction. The structure of MA $\sigma$-VFe powders were characterized by the X- ray diffraction with Cu- $K\alpha$ radiation and neutron diffraction with monochromatic neutrons of $1.835\AA$ using a high resolution powder diffractometer (HRPD). Mechanical alloying of $\sigma$-VFe compound gives rise to a dramatic structural change. After 60 hours of MA, the Fe-Fe distribution of the $\sigma$- phase VFe tetragonal structure with 30 atoms in a unit cell is found to change into that of the $\sigma$-(V,Fe) solid solution with bcc structure, which is a stable phase at elevated temperature above $1200^{\circ}C$. A comparison of X-ray diffraction data for the $\alpha$-phase has been also made with the corresponding neutron diffraction data. The (101) and (111) diffraction peaks of the $\sigma$-phase was clearly observed only in neutron diffraction pattern, which is believed to be a characteristic feature due to the chemical atomic ordering of $\sigma$- VFe phase.
이창희,민계료,Lee Chang-Hui,Min Gye-Ryo 한국국방경영분석학회 1992 한국국방경영분석학회지 Vol.18 No.2
In this paper in order to prevent break of operation of equipments resulted from the delay of parts supply, the continuous review(Q, r) inventory model with probabilistic lead time is developed. If the lead tire is random varivable, the cycle also is stochastic. Then it is not easy to obtain the total cost equation of this inventory model. Therefore it is assumed that one cycle is the interval of reorder points. When the lead time is assumed to have exponential probability distribution, the lot-size and reorder point which minimize total cost are obtained. And as the lead time increases, the order quantity and the total cost are greater, but the reorder point increases by a certain point of time and then decreases.
Studies of Porphyrin Synthesis through 3+1 Condensation
이창희,박주연,김한제,Lee, Chang Hui,Park, Ju Yeon,Kim, Han Je Korean Chemical Society 2000 Bulletin of the Korean Chemical Society Vol.21 No.1
Acid-catalyzed porphyrin formation from meso-aryltripyrromethanes and $25-bis({\alpha}$, - hydroxyl - $\alpha$ -phenyl) methylfuran is studied. The condensation resulted in selective scrambling of tripyrromethanes when the condensation was carried out with catalytic amounts of $BF_3$ in methylene chloride. But the reaction carried out with p-TsOH or $BEt_3$ catalysts in the presence of $NH_4Cl$ in acetonitrile, single porphyrin product was isolated without scrambling of starting tripyrromethane. The yields of porphyrin in these studies were somewhat lower than those of 2+2 condensations or aldehyde-pyrrole condensations.
이창희,조원섭,가재원,김한재,이필호,Lee, Chang Hui,Jo, Won Seop,Ga, Jae Won,Kim, Han Jae,Lee, Pil Ho Korean Chemical Society 2000 Bulletin of the Korean Chemical Society Vol.21 No.4
Corroles and oxacorroles were synthesized by acid-catalyzed, 2+2 condensation. The condensation afforded different corroles bearing core-heteroatoms at the predesignated locations. Regioselective a- a’ linkage be-tween pyrrole and furan or betwee n pyrrole and pyrrole was achieved by keeping the linking carbon at different position of starting dipyrromethanes. The condensation was only fruitful when furan-containing dipyrromethanes were condensed.