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Microwave Dielectric Characteristics of Aluminum Magnesium Tantalate Based High Q Ceramics
Ji-WonChoi,Hwack-JooLee,Seok-JinYoon,Hyun-JaiKim 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.4
The microwave dielectric characteristics of (1-x)(Al1/2Ta1/2)O2-x(Mg1/3Ta2/3)O2 (0 x 1.0) ceramics were investigated by crystal structure, variations of ionic polarizability, and microstructures. As x increased, (1-x)(Al1/2Ta1/2)O2-x(Mg1/3Ta2/3)O2 transformed to tetragonal structure. Because the ionic radius of [Mg1/3Ta2/3]4+ was slightly bigger than one of [Al1/2Ta1/2]4+, the cell parameters increased with increase of (Mg1/3Ta2/3)O2 concentration and coincided with prediction of the molecular additivity rule. As x increased, the compositions revealed ordered phase and were of single phase above 60 mol%. The increase of the ordered phase and grain size enhanced the Q and when ordering was completed at x over 0.6, the grain size was major factor for the increase in the Q. Though the grain size increased, however, the porosity deteriorated the Q. Therefore, the Q depended on the order/disorder, the porosity, and the grain size in regular order.
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정문현(JungMoon-hyun),진윤수(JinYoon-soo),박만석(ParkMan-seok) 한국체육학회 2017 한국체육학회지 Vol.56 No.1
본 연구의 목적은 체육고등학교의 실태와 발전 방안을 살펴보는 것으로 전국 체육고등학교의 실태를 알아보고 대전체육고등학교의 문제점을 파악하고 이의 개선을 통한 발전 방안을 제시하고자 한다. 본 연구의 목적을 달성하기 위하여 전국체육중고등학교 실태와 대전체육중고등학교를 대상으로 설문조사를 실시하였다. 실태조사 결과 전국 체육고등학교는 16개 교에 3,915명이 재학하고 있었으며, 학생 수는 서울이 392명으로 가장 많았고, 부산 291명, 광주 290명, 경기 286명 순으로 나타났다. 일반고와 혼합형인 제주가 113명으로 가장 적은 것으로 조사되었다. 두 번째로 대전체육중고등학교 학생 323명, 지도자 35명을 대상으로 한 설문조사 결과, 학생들은 학년이 높을수록 만족도가 낮으며, 종목과 따라 학교 시설 만족도에 차이가 있는 것으로 나타났다. 지도자들은 근무 경력이 높을수록 체육시설에 대한 만족도가 높은 것으로 나타났다. 체육고등학교의 발전 방안으로 실태 분석을 통해 시설현황과 만족도, 운영의 문제점 및 해소 방안, 우수 체육인재 양성을 위한 훈련장 설치를 제시하였다. The purpose of this study is to examine the present condition and advancement of Daejeon physical ed. High school & Middle School, and it aims to review the present condition of physical ed. High school across the country and identify the problems with their facilities to present a plan of improvement and advancement of physical ed. high schools. Accordingly, research on present condition of physical ed. high school and survey research were conducted. The research on present condition showed the result of 16 physical ed. high schools across of country with 3,915 enrolled students. The number of students was found to be the highest with 392 in Seoul, followed by 291 in Busan, 290 in Gwangju and 286 in Gyeonggi. The number of students was found to be the lowest with 113 in Jeju with its combined type with general high school. Survey research was conducted with 323 students and 35 instructors at D physical ed. high school in D Metropolitan City, and the result showed that students’ satisfaction level lowered among upper year students with differences in satisfaction level according to event and school facilities. In regards to instructors, their satisfaction level was found to be high among instructors with a high number of working experiences. Based on the analysis of present condition of physical ed. high school, this study suggested that it would be necessary to install training facilities as a way to solve the problem with present condition of facilities, satisfaction level and operation, as well as cultivate competent athletes.
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Min-ChulKim,Ji-WonChoi,Chong-YunKang,Seok-JinYoon,Hyun-JaiKim,KiHyunYoon 한국전기전자재료학회 2002 Transactions on Electrical and Electronic Material Vol.3 No.1
The effects of substrate temperatures and annealing temperatures on the microstructures and ferroelectric properties of PbZr0.52Ti0.48O3 (PZT) thin films prepared by pulsed laser deposition (PLD) were investigated. For this purpose, the PZT films were deposited at various substrate temperatures (400∼600℃) with post annealing process in oxygen atmosphere. The single perovskite phase was formed at the deposition temperature of 500 to 550℃ without post annealing and the PZT films deposited below 500℃ formed the single phase with post annealing at 650℃. The grain size of the films increased and the grain boundary of the films was clearly defined as the substrate temperature increased from 400 to 550℃. The remnant polarization (Pr) and the coercive field (Ec) of the films deposited at 550℃ and annealed at 650℃ were 34.3 μC/cm2 and 60.2 kV/cm, respectively.
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Bender Typed Piezoelectric Multilayer Actuator
Byung-GukAhn,Dong-KyunLee,Deuk-YoungHan,강종윤,Ji-WonChoi,Hyun-JaiKim,Seok-JinYoon 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.3
A bender typed multilayer actuator (BMA) for decreasing the depolarization effect was designed and fabricated. Unlike bimorph and multimorph actuators in which depolarization occurred, the BMA did not generate depolarization because the polarization and the electric field directions are the same. The simulated results indicate that higher displacement of the BMA can be achieved by increasing input voltage. Compared with the multimorph actuator, the proposed actuator is expected to extend a life time as well as acceptable voltage range.
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Seung Min Oh,강민규,Young Ho Do,강종윤,Seok-JinYoon,Sahn Nahm 한국전기전자재료학회 2011 Transactions on Electrical and Electronic Material Vol.12 No.5
Lead zirconate titanate (PZT) films were fabricated on Pt/Ti/SiO2/Si substrate by the sol-gel method using a sol containing poly(N-vinylpyrrolidone) (PVP). PVP in alkoxide solutions can suppress the condensation reaction in gel films during heat treatment, and increase the viscosity of alkoxide solutions. Single-phase PZT films as thick as 1 μm were deposited by repetitive coating with successive third-step heat treatments at 150℃, 350℃ and 650℃. After heat treatment, the films were crack free, and optically transparent. As a result, we demonstrated a PZT film with a PVP molar ratio of 0.5, which has a permittivity of 734, a dielectric loss of 0.042, a Pr of 40.5 μC/cm2 and an Ec of 156 kV/cm.
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