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PZT 세라믹스의 전기기계결합계수 온도 안정성에 관한 연구
이개명,Lee, Gae-Myoung 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.1
In this paper, PZT piezoelectric ceramic specimens with 4 compositions (Zr/Ti=50/50, 53/47, 56/44, 58/42) in $Pb(Zr,Ti)O_3$ system were fabricated. We studied effects of poling strength and thermal aging on the temperature characteristics of eletromechanical coupling factor k31 of the specimens, which were poled with the DC electric fields, 1.5, 2.5 and 3.5 kV/mm respectively and thermally aged for an hour at $200^{\circ}C$. The eletromechanical coupling factor k31 of the specimen with the composition Zr/Ti= 53/47, nearest to the morphotropic phase boundary decreased the most greatly, irrelevant to the intensity of poling field, due to 1st thermal aging. And the temperature coefficient of eletromechanical coupling factor k31 was (-) in the tetragonal phase composition and (+) in the rhombohedral phase composition, which is reverse in the temperature coefficient of resonance frequency. It is interesting that eletromechanical coupling factor k31 of PZT ceramics is shown to be able to increase as temperature increase in the interval $-20{\sim}80^{\circ}C$.
이개명(Gae-Myoung Lee),황충구(Choong-Gu Hwang) 대한전기학회 2015 전기학회논문지 Vol.64 No.5
An 1 MW PV plant constructed at the Ara campus of Jeju National University in May 2012, which was the biggest roof-top PV plant in Korea and the biggest PV plant in Jeju Island at the time. In this paper the generation characteristics of the plant was analyzed on the basis of the data obtained during 2 years. The amount of electrical energy generated by the plant in July was less than those by the PV plants of the other regions except Jeju Island in Korea, which might be due to the long rainy season started in June earlier than the other regions. But those generated by the plant during summer season was more than those during autumn, which was different trend from the other regions in Korea. And the yearly capacity factor of the pant was 12.7% which is low relatively in Korea. The loss of the transformer in the plant, as expected, was shown to increase according to increasing the electrical energy generated by the plant. Summer"s transformer loss was greater than spring"s one in spite of summer"s generated electrical energy less than spring"s one, which tells that the transformer have the need to strengthen its cooling in summer.
이개명(Lee, Gae-Myoung),오성보(Oh, Seong-Bo) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.2
보안구역 내의 외곽울타리지역의 경비체제를 인적경비에서 과학화경비로 전환함에 따라 안정된 보안설비의 적정관 리를 위한 조명개선이 요구되어진다. 본 논문에서는 효율적인 외곽 감시를 수행할 수 있도록 경비과학화시스템에 적합한 등기구 선정과 균일한 조도환경을 조성하기 위하여 조명설비의 부적절한 적용으로 모니터에 눈부심이 심한 울타리 지역을 선정하여 LED 등의 용량을 변화시키며 등기구의 각도, 등주간의 거리, 등기구의 취부높이 등의 조정에 따른 현장 모의실험 으로 감시모니터에 발생하는 눈부심을 해소시키고자 하였다. 또한 모의실험 조건에 따른 CCTV 화면분석과 조도값을 바탕으 로 공항 외곽지역과 유사한 조건으로 조명 모델링하고 소비전력이 다른 LED 광원을 이용한 시뮬레이션 실시로 공항 외곽 보안설비의 적정운영 위한 조명설계안을 제시하고자 한다. Lighting improvements are needed for adequate operation of security installations according to the turn of scientific policing instead of human policing. The basic principles of security lighting is to provide sufficient lighting over a specific area so that anyone moving in or around can be seen easily. Also, in security lighting, illuminance and uniformity are to be considered for clearing of CCTV screen through the lighting improvement. To achieve such goals, each pole is to be considered of the height and the space of luminaries as well as the wattage and the type of lamps. In this paper, the lighting designs show the adequate operations of fence security systems through the actual measurement of illuminance by mock-up and the illuminance analyses for obtaining proper illuminance and uniformity value to keep brightness of CCTV screen able to confirm objects considering characteristics of CCTV monitor by simulations.