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Czochralski법에 의한 $Bi_{12}SiO_{20}$ 단결정 성장
정광철,오근호 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.5
The necessary conditions for the growth of high quality Bi12SiO20 single crystals by the Czochralski method have been determined. The interface of melt and crystal was transformed convex to concave above 7 rpm. For growth <001> and <111> directions, facet morphology exhibited 4-fold and 6-fold symmetry. When the crystal of <001> growth direction was broadened, minor facet {110} was developed outstandingly.
정광철,주경,전윤석,오근호,김의훈,이석근,Chung, K.C.,Joo, K.,Chun, Y.S.,Orr, K.K.,Kim, E.H.,Lee, S.K. 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.2
Al2O3/SiC composite-material was synthesized by the birth-spread mechanism through the carbothermal reduction reaction of SiO2 in Ha-Dong Kaolin with carbon powder under H2 gas atmosphere at 1300~140$0^{\circ}C$. Average diameter of synthesized SiC whiskers were 1${\mu}{\textrm}{m}$ and aspect ratio (c/a) was 10~100. Al2O3 particles and SiC whiskers were mixed homogeneously in the reacted pellet.
Floating Zone법에 의한 올리빈 $[(Mg_{1-x}Fe}_{x})_2SiO_4]$단결정 성장
정광철,강승민,신재혁,한종원,최종건,오근호,박한수,문종수 한국결정성장학회 1993 한국결정성장학회지 Vol.3 No.1
커다란 olivine 단결정을 image furnace(floating zone furnace)를 사용하여 산소분압의 조절하에서 성장시켰다. 결정은 투명하였으며 길이가 65mm, 직경이 8mm였다. 산소분압이 감소할 때 결정내 제2상이 증가하여 결정을 엷은 갈색에서 짙은 갈색으로 변화시켰다. 이 제2상은 EPMA결과 Mg가 기저를 이룬 것에 Si와 Fe가 solid solution을 형성한 것이었다. Large single crystals of olivine were grown by using image furnace(floating zone furnace)under controlled partial pressure of oxygen. The transparent crystals have maximum sizes 65mm in length by 7mm in diameter. When partial pressure of oxygen was decreased, the portion of secondary phases in crystals were increased so that it made crystals dark brown. The secondary phases were proved to be solid solution of Mg, Si, and Fe by electron microprobe analysis. Mg was major portion and the rest was minor.
고성능 고가용성을 위한 ALTIBASE(TM) 자료저장 관리기의 설계
정광철,이규웅,배해영,Jeong, Gwang-Cheol,Lee, Gyu-Ung,Bae, Hae-Yeong 한국정보처리학회 2003 정보처리학회논문지D Vol.10 No.6
기존 디스크 기반 데이터베이스 관리 디스트를 주저장 장치로 활용하는 특징적 환경 때문에 주기억 상주 데이터베이스 관리 시스템의 메모리 관리, 인덱스 관리, 자료저장 관리 기능 등에 대한 설계 및 구현 기술이 기본적으로 다르다. 본 논문에서는 현재 상용 시스템으로 사용되고 있는 $ALTIBASE^{TM}$ 주기억 상주 DBMS 의 설계 및 구현 내용을 기술한다. 특히 자료저장 관리기의 세부 구성요소에 대한 구조적 특징가 주요 기능인 트랜잭션 처리 기법과 회복 관리 기법에 대하여 기존 DBMS 의 기능가 비교 설명하며, 고가용성을 위한 데이터베이스 이중화 기능 및 이중화 작업 시 발생하는 트랜잭션 충돌 해결 방법에 대하여 설명한다. 또한 $ALTIBASE^{TM}$ 시스템의 성능을 측정하기 위하여 다양한 환경에서 실험된 TPS 결과를 보인다. Main memory database systems use the different implementation techniques to sturucture and organize the user dta and system catalogs, since traditional database systems are optimized for the characteristics of disk storage environment. We present, in this paper, the design considerations for our main memory database system $ALTIBASE^{TM}$ that is currently applied to the time-critical applications. We focus on the design issues of storage manager in $ALTIBASE^{TM}$. The major components are introduced, and features and characteristics of transaction management and recovery method are described. We also present the database replication mechanism and its conflict resolution mechanism for high availability and performance. In order to evaluate our transaction performance, we show various experimental reports as measured by the TPS.
쥐 뇌 myelin 의 인지질 메칠기 전달 효소의 식별과 특성
정광철,유병설,최명언 ( Kwang Chul Chung,Byung Sul Yu,Myung Un Choi ) 생화학분자생물학회 1990 BMB Reports Vol.23 No.1
In this paper we described the presence of phospholipid-N-methyltransferase (PMT) in rat brain myelin and characterized the general properties of the enzyme. The methylation of phospholipids was measured by the incorportion of the [^(14)C]-methyl group from S-adenosyl-L-methionine into lipids and the final phospholipid was analyzed by TLC. The myelin was purified by subcellular fractionation followed by two consecutive discontinuous sucrose density gradient centrifugations and three times of osmotic shock. This highly purified myelin contained the transferase activity and the specific activity was found to be 13 pmol/mg protein/h. This myelin-localized activity was about 3-fold higher than that of the whole brain homogenate. The general properties of myelin enzyme were examined including effects of pH and exogenuous phospholipids, variations of substrates concentrations, dependence of Mg^(++) ion, washing conditions of various aqueous media, and effects of treatments of trypsin and N-ethylmaleimide. Overall results suggested that the basic properties of myelin localized PMT showed similarity to the known PMT. However some characteristics such as pH optima and effect of lipid were distinct from the PMT of other subcellular fractions.
정광철,오근호,최종건 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.4
Single crystals of YBa2Cu3O7-x have been grown in BaCuO2 flux at temperature of 125$0^{\circ}C$ and examined using XRD, EDAX and light microscopy. The YBCO crystals were grown in a cavity which was formed by the reduction of CuO and became large by the directional solidification in the crucible. The observed crystal growth habit is square planar with the c-axis normal to the plane. The surface morphology of grown crystals were growth ledges and growth sprial paterns on a (001) face.