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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.
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 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.
The Optimized Detection Range of RFID-based Positioning System using k-Nearest Neighbor Algorithm
김정환(Kim Jung-Hwan),허준(Heo Joon),한수희(Han Soo-Hee),김상민(Kim Sang-Min) 대한공간정보학회 2008 한국지형공간정보학회 학술대회 Vol.2008 No.10
The positioning technology for a moving object is an important and essential component of ubiquitous communication computing environment and applications, for which Radio Frequency IDentification Identification (RFID) is has been considered as also a core technology for ubiquitous wireless communication. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor (k-nn) algorithm using detected k-tags which have known coordinates and k can be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in 1-Dimensional space, the square in 2-Dimensional space and the cubic in 3-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2- and 3-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space and 143% of the tag spacing distance in 3-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.
김정환 ( Jung Hwan Kim ),박한빈 ( Han Bin Park ),강태삼 ( Tae Sam Kang ),박정근 ( Jung Keun Park ) 한국센서학회 2014 센서학회지 Vol.23 No.1
We developed a low-cost automatic diagnosis system for water quality in cooling towers to measure the concentrations of key ingredients such as Ca2+, Cl-, PO4 3-, and Fe2+. Ca2+, and Cl- are the main factors that cause the generation of scale, corrosion, and sludge in water pipes. PO4 3- prevents corrosion, sludge and scale by inhibiting the ions (i.e., Ca2+, Cl-) from sticking to the pipes. Fe2+ is an indicator of pipe corrosion. The proposed system consists of a microprocessor, a specimen container and heater, a precision pump, relays and valves, LED optical sources, and photo detectors. It automatically collects water samples and carries out pretreatment for determining the concentration of each chemical, and then estimates the concentration of each ion using low-cost LED optical sources and detectors. Experimental results showed that the accuracy of the proposed system is sufficiently high for water quality diagnosis and management of cooling towers, demonstrating the possibility of the proposed system`s wide usage in real environments.
김정환(Kim Jung-Hwan),허요한(Heo Yo-Han),최정아(Choi Jung-Ah),김도현(Kim Do-Hyeun),변상용(Byun Sang-Yong),안기중(Ahn Khi-Jung) 한국콘텐츠학회 2005 한국콘텐츠학회 종합학술대회 논문집 Vol.3 No.2
최근 무선인터넷을 이용할 수 있는 환경이 많이 만들어지면서 PDA를 이용한 무선인터넷의 활용도가 점점 더 많아지고 있다. PDA를 이용한 무선인터넷의 인프라가 많이 구축되면서 사용자들은 점점 더 많은 서비스와 다양한 콘텐츠를 요구하게 되었고, 실제로 다양한 서비스가 PDA에서 이용되고 있다. 이러한 사회적 여건 변화에 따라 본 논문에서는 휴대가 간편하고 손쉽게 정보를 얻을 수 있는 무선 인터넷 기반의 PDA를 이용하여 작명서비스를 받을 수 있도록 작명에 필요한 법칙을 알고리즘화하고 서비스를 설계하고 구현한다. Recently, with the rise of wireless Internet, it is becoming popular to use PDA. Also, the more wireless Internet Infra increases, the more services and a variety of contents are needed. Actually, a number of services is being used for PDA. Accordingly, this paper designs and implements naming service based on wireless Internet which is portable and easy for information. We develope the algorithm, design and implement the service for naming service.
태양광 발전 시스템의 최적 설치 각도 예측에 관한 연구
김정환(Jung-Hwan Kim),유권종(Gwon-Jong Yu),소정훈(Jung-Hun So),차한주(Han-Ju Cha),유병규(Byung-Gyu Yu) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
The measured solar radiation on tilted surfaces by all directions has been widely used as important solar radiation data in installing photovoltaic system. The photovoltaic systems is much affected by angle and direction of incident rays. The results obtained in this research could be used in installing optimal photovoltaic systems.