고상법에 의한 100 nm BaTiO₃ 분말의 합성

김정환,정한승,조준엽,홍정오,김영태,허강헌,Kim, Jung-Hwan,Jung, Han-Seong,Cho, Joon-Yeob,Hong, Jeong-Oh,Kim, Young-Tae,Hur, Kang-Heon 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.2

$BaTiO_3$ powder was synthesized by the solid-state reaction of fine $BaTiO_3$ and $TiO_2$ raw materials. Fine grinding media of 50 and 300 microns were used for obtaining fine particulate mixture of $BaTiO_3$ and $TiO_2$ with high homogeneity. Effect of the size of grinding media on the synthesis mechanism of $BaTiO_3$ was discussed on the basis of the particulate morphology and thermogravimetry data for the mixture powders. By using the finer grinding media, $BaTiO_3$ was formed at the lower temperature and the particle size with the relatively narrower distribution could be obtained. $BaTiO_3$ powder with the average size of 100 nm was synthesized by the solid reaction in vacuum atmosphere.

구강병소에서 분리된 포도상구균의 약제 내성 및 내성 유형에 관한 연구

김정환,신형식,Kim, Jung-Hwan,Shin, Hyoung-Shik 대한치주과학회 1988 Journal of Periodontal & Implant Science Vol.18 No.2

새로운 2-Quinazolylacetonitrile 유도체들의 합성

김정환,민경수,Kim, Jung Hwan,Min, Kyung Su 대한화학회 2001 대한화학회지 Vol.45 No.6

H-chelate형태의 2-Quinazolylacetonitrile유도체들은 2-cyanomethylquinazoline에 여러가지 친전자체들, 즉, 4-chloroquinazoline, 4-chloro-2-phenylquinazoline, 4,6-dichloropyrinidine, 4,6-dichloro-2-phenylpyrimidine, 4,6-dichloro-5-phenylpyrimidine, 2-chloroauinoxaline,1,3- dichloroisoquinoline, 2,6-dichloropyrazine, 2-chloropyrazine, 4,6-dichloro-2,5-diphenylpyrimidine 등을 반응시켜 얻을 수 있었다. 합성된 H-chelate화합물들은 polymethine계의 발색단 구조를 가지게 된다. 이들 화합물에 대한 구조는 분광학적인 방법으로 분석 확인 하였다. 2-Quinazolylacetonitrile derivatives containing H-chelate have been synthesized from 2-cyanomethylquinazoline using electrophiles such as 4-chloroquinazoline, 4-chloro-2-phenylquinazoline, 4,6-dichloropyrimidine, 4,6-dichloro-2-phenylpyrimidine, 4,6-dichloro-5-phenylpyrimidine, 2-chloroquinoxaline, 1,3-dichloroisoquinoline, 2,6-dichloropyrazine, 2-chloropyrazine and 4,6-dichloro-2,5-diphenylpyrimidine. These H-chelates may serve as a polymethine chromophore system. Structures of the target molecules were identified by spectral methods.

원형 쉬프트 통신의 중첩 효과 분석

김정환,노정규,송하윤,Kim, Jung-Hwan,Rho, Jung-Kyu,Song, Ha-Yoon 한국정보처리학회 2002 정보처리학회논문지 A Vol.9 No.2

통신과 계산 작업을 중첩 수행함으로써 통신 시간의 감춤 효과를 얻는 것은 일반적인 병렬 프로그램 최적화 방법 중의 하나이다. 본 논문에서는 데이타 병렬 프로그램에서 자주 사용되는 군집 통신(collective communication)의 하나인 원형 쉬프트(circular shift) 통신에 대해 중첩 효과를 실험하고 고찰하였다. 이더넷 스위치로 연결된 클러스터 시스템에서 원형 쉬프트 통신을 수행할 때, 중첩으로 얻을 수 있는 최대 이득과 중첩할 수 없는 시간을 측정하였다. 각 플랫폼 별로 이러한 측정값들을 얻어 퇴적화 컴파일러의 입력으로 활용할 수 있을 것이다. 한편 기존의 성능 모델을 통해 퇴적화하는 것은 크게 두가지 문제를 갖고 있다. 하나는 기본적인 점대점 통신에 입각한 모델을 제공하기 때문에 통신 라이브러리의 함수를 사용할 때의 종합적인 효과, 특히, 군집 통신과 같은 경우에는 적용하기 어렵다는 것이다. 다른 하나는 군집 통신의 성능은 분석은 가능하지만, 중첩 효과는 분석할 수 없다는 것이다. 본 논문에서는 이러한 기존 모델의 단점을 보완하여 확장하였다. 또한, 원형 쉬프트 통신에 대한 실험 결과를 토대로 확장된 모델의 매개 변수 값들을 추출하여 예제 프로그램을 통해 분석하였다. Many researchers have been interested in the optimization of parallel programs through the latency hiding by overlapping the communication with the computation. We ana1yzed overlapping effects in the circular shift communication which is one of the collective communications being frequently used In many data parallel programs. We measured the time which can be possibly overlapped and the time which cannot be overlapped in over all circular shift communication period on an Ethernet switch-based clustered system. The result from each platform nay be used for the input of optimizing compilers. The previous performance models usually have two kinds of drawbacks one is only based on point-to-point communication, so it is not appropriate for analyzing the overall effects of collective communications. The other provides the performance of collective communication, but no overlapping effect. In this paper we extended the previous models and analyzed the experimental results of the extended model.

새로운 5-Benzyl-4-cyanomethyl-2-methylpyrimidine 유도체들의 합성

김정환,한문수,Kim, Jung Hwan,Han, Mun Su 대한화학회 1996 대한화학회지 Vol.40 No.4

5-Benzyl-4-cyanomeygyl-2-methylpyrimidine의 6번 위치에 chloro, methoxy, ethoxy, phienoxy, 및 anilino기가 도입된 새로운 유도체(5)들의 합성은5-Benzyl-4-cyanomeygyl-2-methylpyrimidine 유도체(3)들과 tert-butylcyanoacetate로부터 합성되었으며, 5-Benzyl-4-cyanomeygyl-2-methylpyrimidine의 6번 위치에 chloro, methoxy, ethoxy, isopropoxy, 및 anilino기가 도입된 유도체(3)들은 5-Benzyl-4-cyanomeygyl-2-methylpyrimidine(2)로부터 합성되었다. The synthesis of new 5-benzyl-4-cyanomethyl-2-methylpyrimidine derivatives (5) containing chloro, methoxy, ethoxy, phenoxy and anilino groups at 6-position on the pyrimidine ring were prepared from 5-benzyl-4-chloro-2-methylpyrimidine derivatives (3) and tert-butylcyanoacetate. The derivatives of 5-benzyl-4-chloro-2-methylpyrimidine (3) containing chloro, methoxy, ethoxy, isopropoxy, phenoxy and anilino groups at 6-position on the pyrimidine ring were prepared from 5-benzyl-4,6-dichloro-2-methylpyrimidine (2).

새로운 2-Amino-4-methylcyano-5-methylsulfonylpyrimidine 유도체들의 합성

김정환,한문수,김은주,Kim, Jung-Hwan,Han, Mun-Su,Kim, Un-Ju 대한화학회 1995 대한화학회지 Vol.39 No.9

The derivatives of 2-amino-4-methylcyano-5-methylsulfonylpyrimidine 6 containing chloro, methoxy, ethoxy, phenoxy, amino and anilino groups at 6-position on the pyrimidine ring were prepared from 2-amino-4-chloro-5-methylsulfonylpyrimidine derivatives 4 and tert-butylcyanoacetate. The derivatives of 2-amino-4-chloro-5-methylsulfonylpyrimidine 4 containing methoxy, ethoxy, isopropoxy, phenoxy, amino and anilino groups at 6-position on the pyrimidine ring were prepared from 2-amino-4,6-dichloro-5-methylsulfonylpyrimidine 3. Pyrimidine의 6번위치에 chloro, methoxy, ethoxy, amino, 및 amino 기가 도입된 2-amino-4-methylcyano-5-methylsulfonylpyrimidine 유도체 6들은 2-Amino-4-methylcyano-5-methylsulfonylpyrimidine 유도체 4들과 tert-butylcyanoacetate로부터 합성되었으며 pyrimidine의 6번 위치에 methoxy, ethoxy, isopropoxy, phenoxy, amino 및 anilino기가 도입된 2-amino-4-methylcyano-5-methylsulfonylpyrimidine 유도체 4들은 2-amino-4-methylcyano-5-methylsulfonylpyrimidine 3으로부터 합성되었다.

전역 이기종 환경에서의 정적 태스크 스케줄링의 비교 연구

김정환,Kim Jung-Hwan 한국정보처리학회 2006 정보처리학회논문지 A Vol.13 No.2

DAG(Directed Acyclic Graph) 기반의 스케줄링을 포함한 많은 스케줄링 문제들은 대부분 NP-Complete로 알려져 있으며, 따라서 휴리스틱에 기반한 많은 알고리즘 연구들이 진행되어 왔다. 이 중 HEFT와 CPOP은 이기종 환경에서 효과적인 알고리즘으로 알려져 있다. 본 논문의 이전 연구에서는 이기종 환경이 보다 현실성 있는 전역 네트워크로 구성된 경우에 대해 효과적인 3개의 알고리즘(CPOC, eCPOC, eCPOP)을 제안한 바 있다. 본 논문에서는 이들 총 5개의 알고리즘에서 사용하는 휴리스틱을 체계적으로 분석하고, 다양한 벤치마크를 사용한 실험을 통해 비교 분석하였다. 실험 결과 전역 이기종 환경에서 eCPOC이 가장 우수한 성능을 보여주었고, 또한 제안된 3개의 알고리즘에서 사용하는 휴리스틱들이 전역 이기종 환경에서 효과적임이 확인되었다. Most scheduling problems including DAG(Directed Acyclic Graph)-based are known to be NP-complete, so many heuristic-based scheduling algorithms have been researched. HEFT and CPOP are such algorithms which have been devised to be effective in heterogeneous environment. We proposed, in the previous research, three scheduling algorithms which are effective in realistic global heterogeneous environment: CPOC, eCPOPC and eCPOP. In this paper, the heuristics which are used in the above five algorithms will be systematically analyzed. Those algorithms will be also studied experimentally using various benchmarks. Experimental results show that the eCPOC generates better schedules than any other algorithms and the heuristics which are used in the proposed algorithms are effective in the global heterogeneous environment.

초등학교 수학과 ICT 활용 교육에서 스프레드시트를 활용한 교수-학습에 관한 연구

김정환,구정모,한병래,Kim, Jung-Hwan,Gu, Jung-Mo,Han, Byoung-Rae 한국정보교육학회 2009 정보교육학회논문지 Vol.13 No.3

Many current researches are limited in the statistics field, which is a part of mathematics class in the secondary school. Moreover, it's hard to apply to the elementary school since they are written in English. To overcome this limitations, the objectives from the unit that is suitable for using EXCEL in the elementary mathematics lessons are selected in this research. And a problem-based learning model for these lessons would be introduced that it can help students to focus on solving substances of the problems by reducing the time for arithmetic calculation.

새로운 Bichromophore 화합물들의 합성

김정환,김영은,Kim, Jung-Hwan,Kim , Yeung-Eun 대한화학회 2008 대한화학회지 Vol.52 No.5

PLD를 이용한 강유전체(PZT, PST, PT)/YBCO 박막 구조의 제작과 전기적인 특성에 관한 연구

김정환,이재형,문병무,Kim, Jung-Hwan,Lee, Jae-Hyung,Moon, Byung-Moo 한국전기전자재료학회 1998 전기전자재료학회논문지 Vol.11 No.7

(PZT, PST, PT)/ YBCO structured have been grown on single crystal $LaAlO_3$ using in-situ Nb:YAG pulsed laser deposition technique. The optimum conditions of fabrication for high quality films have been established under various oxygen pressure. TBCO was used as a metallic electrode for polarizing ferroelectric thin fillms. Lattice mismatch of these materials were found to be with in 3%. As a result XRD patterns and rocking curves, (PZT, PST, PT)/ YBCO multiayered thin films on $LaAlO_3$ substrates showed preferred orientation to c-axis. For invastigation on electrical properties of ferroelectric thin films, remanent polaiztion $P_r$ and coercive field $E_c$ were measured for three samples. At each optimum condition, they showed the values of P_r=60 \mu C/cm^2 and E_c=240kV/ cm for PT, 30\mu C/cm^2 and 105kV/cm for PZT, 1.5\mu C/cm^2$ and 15kV/cm for PST. Frequency dependence of dielectric properties of ferroelectric thin fillms was also investigated. As a result, it showed the frequency dependence was relatively small in the range of 10Hz~10kHz.