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김동국,지정범 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.12
A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. The main idea of this research is to provide a distinctive solution for the measurement and standardization of both the longitudinal and the transverse piezoelectric d-coefficients, d33 and d31, of ferroelectric thin films. In general, to get these two coefficients of thin films, two different measuring systems are required. Here, we propose the improved method for the evaluation of these two coefficients with single equipment and with the relatively convenient procedure. The two-step loading process of applying the both positive and the negative pressure has been introduced to acquire the piezoelectric coefficients. These results have been calibrated for both the longitudinal and 4he transverse piezoelectric d-coefficients, d33 and 431, of thin films by comparison with the virtual standard created from FEM. In this experiments, we have obtained d33 of 331pC/N and 031 of -92.2pC/N for the PZT thin films.
김동국,지정범 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.12
We have studied the effect of crystallization temperature, composition and film thickness, which are the fundamental processing parameters of lead zirconate titanate(PZT) thin film fabrication, in the respect of the piezoelectric properties by our pneumatic loading method(PLM). A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. Even though the piezoelectric properties of thin films are very critical factors in the micro-electro mechanical system(MEMS) and thin film sensor devices, a few reports for the piezoelectric characterization are provided for the last decade unlikely the bulk piezoelectric devices. We have found that the piezoelectric properties of thin films are improved as the increase of crystallization temperature up to 750$\^{C}$ and this behavior can be also explained by the analysis of dielectric polarization hysteresis loop, X-ray diffraction and scanning electron microscopy. The effect of Zr/Ti composition has been also studied. This gives us the fact that the maximum piezoelectricity is found near Morphotropic Phase Boundary(MPB) as bulk PZT system does.
서정범(Jung-Bum Seo),박성준(Sung-Jun Park),김지인(Jee-In Kim) 한국정보과학회 1997 한국정보과학회 학술발표논문집 Vol.24 No.2Ⅱ
가상환경기술이 과학, 공학, 예술, 오락등의 분야에서 활용되기 시작하면서 전문 VR(Virtual Reality)프로그래머가 아닌 사람들도 가상환경을 손쉽게 꾸밀수 있는 저작기술이 필요하게 되었다. 모델링 소프트웨어와 VR Toolkit을 이용하여 가상환경을 저작하는 기존의 기술은 “시각적 설계”에 초점을 맞추고 있으며, 전문 프로그래머가 아니면 가상환경 저작에 어려움이 있고, 가상 물체들 사이의 관계를 명시하는 방법이 쉽게 정의되어 있지 않다. 본 논문에서는 가상환경의 “시각적 설계”를 보완하는 “논리적 설계” 개념을 도입하고 시각언어(Visual Language)를 이용하여 가상환경 저착을 수행하는 기술을 제안한다. 가상환경 저작용 시각언어를 수학적으로 정의하는데 Unification을 근거로 한 문법을 사용하며, 작성된 가상환경을 대화형으로 분석할 수 있는 파싱 알고리즘을 제안한다.