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고상법에 의한 100 nm BaTiO<sub>3</sub> 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.
노인 복지를 위한 응급 상황 호출 프로그램의 개발 및 구현
김정환,조면균,김식,Kim, Jung-Hwan,Cho, Myeon-Gyun,Kim, Shik 대한임베디드공학회 2013 대한임베디드공학회논문지 Vol.8 No.2
This paper proposes a system that utilizes USN(Ubiquitous Sensor Network), Bluetooth and smart phone to improve the function of senior houses. In typical approach, a system in a senior house either directly accesses the status of elderly people by its sensor or is alerted by elderly people who trigger an emergency bell, derive a decision and take an appropriate action. In addition, it is possible for a designated social worker to check the status of senior patients through monitoring system connected by UTP(Unshielded Uwisted Pair) cables, but the responsible person has to be present to monitor patients' status. However, the new system, suggested in this paper, embed Bluetooth function in a blood pressure gauge, thus the smart phone receives patients' health information such as blood pressure through Bluebooth, if any abnormal event occurs. Consequently, the smart phone sends SMS(Short Message Service) to a responsible social worker or a designated hospital. When this program in the paper becomes a reality, an unmanned system that is able to determine suitable actions for certain events will be established, even if a social worker were absence.
새로운 BF<sub>2</sub>-Chelate 화합물들의 합성
김정환,김영은,Kim, Jung-Hwan,Kim, Yeung-Eun 대한화학회 2004 대한화학회지 Vol.48 No.4
$BF_2$-chelate 형태의 4-pyrimidylideneacetonitrile 유도체들은 4-pyrimidylideneacetonitrile 유도체들의 H-chelate 화합물들과 boron trifluoride diethyl etherate를 반응시켜 얻을 수 있었다. 또 이들 H-chelate 화합물들은 2-cyanomethylpyridine 유도체들에 여러가지 친전자체들 즉 4,6-dichloropyrimidine, 4,6-dichloro-2-methylpyrimidine, 4,6-dichloro-2-heptadecylpyrimidine, 4,6-dichloro-2-phenylpyrimidine, 4,6-dichloro-5-phenylpyrimidine 그리고 4,6-dichloro-2,5-diphenylpyrimidine을 친전자성 치환반응시켜 만들었다. 화합물에 대한 구조는 분광학적인 방법으로 분석하였다. 4-pyrimidylideneacetonitrile derivatives containing $BF_2$-chelate have been synthesized from H-chelates of 4-pyrimidylideneacetonitrile derivatives and boron trifluoride diethyl etherate. These H-chelates were prepared by the electrophilic substitution of 2-cyanomethylpyridine derivatives with electrophiles such as 4,6-dichloropyrimidine, 4,6-dichloro-2-methylpyrimidine, 4,6-dichloro-2-heptadecylpyrimidine, 4,6-dichloro-2-phenylpyrimidine, 4,6-dichloro-5-phenylpyrimidine and 4,6-dichloro-2,5-diphenylpyrimidine. Structures of the target molecules were identified by spectra methods.
50μm급 이트리아 안정화 지르코니아 비드의 미세구조 및 마모 조건에 따른 마모율 분석
김정환,윤세중,한병동,안철우,윤운하,최종진,Kim, Jung-Hwan,Yoon, Sae-Jung,Hahn, Byung-Dong,Ahn, Cheol-Woo,Yoon, Woon-Ha,Choi, Jong-Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.4
This study analyzes the mechanical properties, including the attrition rate, of $50{\mu}m$ size yttria-stabilized zirconia (YSZ) beads with different microstructures and high-energy milling conditions. The yttria distribution in the grain and grain-boundary of the fully sintered beads relates closely to Vickers hardness and the attrition rate of the YSZ beads. Grain size, fractured surfaces, and yttrium distribution are analyzed by electronic microscopes. For standardization and a reliable comparison of the attrition rate of zirconia beads with different conditions, Zr content in milled ceramic powder is analyzed and calculated by X-ray Fluorescence Spectrometer(XRF) instead of directly measuring the weight change of milled YSZ beads. The beads with small grain sizes sintered at lower temperature exhibit a higher Vickers hardness and lower attrition rate. The attrition rate of $50{\mu}m$ YSZ beads is measured and compared with the various materials properties of ceramic powders used for high-energy milling. The attrition rate of beads appears to be closely related to the Vickers hardness of ceramic materials used for milling, and demonstrates more than a 10 times higher attrition rate with Alumina(Hv ~1650) powder than $BaTiO_3$ powder (Hv ~315).
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.
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 Cyanomethyl-1,3,5-triazine 유도체들의 합성
김정환,김은주,Kim, Jung Hwan,Kim, Un Ju 대한화학회 1996 대한화학회지 Vol.40 No.11
6-Cyanomethyl-1, 3, 5-triazine의 2번과 4번 위치에 amino, n-propylamino, isopropylamino, 및 anilino기가 도입된 새로운 유도체 4들의 합성은 6-chloro-1, 3, 5-triazine 유도체 2'들과 3들을 tert-butyl cyanoacetate로 반응시켜 얻었으며, 6-chloro-1, 3, 5-triazine의 2번과 4번 위치에 amino, n-propylamino, isopropylamino, 및 anilino기가 도입된 유도체 2'들과 3들은 2, 4, 6-trichloro-1, 3, 5-triazine 및 4, 6-dichloro-1, 3, 5-triazine 유도체 2들과 amine 유도체들로부터 합성되었다. New 6-cyanomethyl-1,3,5-triazine derivatives 4 containing amino, n-propylamino, isopropylamino and anilino groups at 2-and 4-position on the 6-cyanomethyl-1,3,5-triazine ring were prepared from 6-chloro-l,3,5-triazine derivatives 2' and 3 with tert-butyl cyanoacetate. The derivatives of 6-chloro-l,3,5-triazine 2' and 3 containing amino, n-propylamino, isopropylamino and anilino groups at 2- and 4-position on the 6-chloro-1,3,5-triazine ring were prepared from 2,4,6-trichloro-1,3,5-triazine as well as 4,6-dichloro-1,3,5-triazine derivatives 2 with amine derivatives.
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.