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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.
산 완충능력과 토양 성분이 동전기-펜톤 공정에 의한 phenanthrene 오염토양 정화에 미치는 영향
김정환,나소정,박주양,변영덕,Kim, Jung Hwan,Na, So Jeong,Park, Joo Yang,Byun, Young Deog 한국지하수토양환경학회 2013 지하수토양환경 Vol.18 No.1
This research was conducted to investigate effects of acid buffering capacity and soil component in treatment of phenanthrene using electrokinetic-Fenton process. In Hadong clay of high acid buffering and low iron oxide content, it was difficult to oxidize phenanthrene due to shortage of iron catalyst and scavenger effect of carbonate minerals. The desorbed phenanthrene conductive to Fenton oxidation was transported toward cathode by electroosmotic flow. However, in Youngdong illitic clay, oxidation of phenanthrene near anode readily occurred compared to Hadong clay due to high iron content and low acid buffering capacity.
대기 플라즈마 용사공정을 이용한 Cu계 벌크 비정질 금속 코팅의 미세조직 분석과 나노 압입시험을 이용한 상 분석
김정환,강기철,윤상훈,나현택,이창희,Kim, Jung-Hwan,Kang, Ki-Cheol,Yoon, Sang-Hoon,Na, Hyun-Taek,Lee, Chang-Hee 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
In this study, Cu-based bulk metallic glass (BMG) coatings were deposited by atmospheric plasma spraying (APS) process with different process conditions (with- and without hydrogen gas). As adding the hydrogen gas, thermal energy in the plasma flame increased and induced difference in the melting state of the Cu-based BMG particles. The microstructure and mechanical properties of the coatings were analyzed using a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) and nano-indentation tester in the light of phase analysis. It was elucidated by the nano-indentation tests that un-melted region was a mainly amorphous phase which showed discrete plasticity observed as the flow serrations on the load.displacement (P - h) curves, and the curves of solidified region showed lower flow serrations as amorphous phase mingled with crystalline phase. Oxides produced during the spraying process had the highest hardness value among the phases and were well mixed with other phases resulted from the increase in melting degree.
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.
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.
한글 문자 입력 인터페이스 개발을 위한 눈-손 Coordination에 대한 연구
김정환,홍승권,명노해,Kim, Jung-Hwan,Hong, Seung-Kweon,Myung, Ro-Hae 대한인간공학회 2007 大韓人間工學會誌 Vol.26 No.2
Recently, various devices requiring text input such as mobile phone IPTV, PDA and UMPC are emerging. The frequency of text entry for them is also increasing. This study was focused on the evaluation of Korean text entry interface. Various models to evaluate text entry interfaces have been proposed. Most of models were based on human cognitive process for text input. The cognitive process was divided into two components; visual scanning process and finger movement process. The time spent for visual scanning process was modeled as Hick-Hyman law, while the time for finger movement was determined as Fitts' law. There are three questions on the model-based evaluation of text entry interface. Firstly, are human cognitive processes (visual scanning and finger movement) during the entry of text sequentially occurring as the models. Secondly, is it possible to predict real text input time by previous models. Thirdly, does the human cognitive process for text input vary according to users' text entry speed. There was time gap between the real measured text input time and predicted time. The time gap was larger in the case of participants with high speed to enter text. The reason was found out investigating Eye-Hand Coordination during text input process. Differently from an assumption that visual scan on the keyboard is followed by a finger movement, the experienced group performed both visual scanning and finger movement simultaneously. Arrival Lead Time was investigated to measure the extent of time overlapping between two processes. 'Arrival Lead Time' is the interval between the eye fixation on the target button and the button click. In addition to the arrival lead time, it was revealed that the experienced group uses the less number of fixations during text entry than the novice group. This result will contribute to the improvement of evaluation model for text entry interface.
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.