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저온동시소성세라믹 기판 위에 제작된 PZT 박막의 증착조건이 박막의 구조적 특성에 미치는 영향
이경천,황현석,이태용,허원영,송준태,Lee, Kyung-Chun,Hwang, Hyun-Suk,Lee, Tae-Yong,Hur, Won-Young,Song, Joon-Tae 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.4
Recently, low temperature co-fired ceramic (LTCC) technology is widely used in sensors, actuators and microsystems fields because of its very good electrical and mechanical properties, high reliability and stability as well as possibility of making 3D micro structures. In this study, we investigated the effects of sputtering gas ratio and annealing temperature on the crystal structure of $Pb(ZrTi)O_3$ (PZT) thin films deposited on LTCC substrate. The LTCC substrate with thickness of $400\;{\mu}m$ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. The PZT thin films were deposited on Pt / Ti / LTCC substrates by RF magnetron sputtering method. The results showed that the crystallization of the films were enhanced as increasing $O_2$ mixing ratio. At about 25% $O_2$ mixing ratio, was well crystallized in the perovskite structure. PZT thin films was annealed at various temperatures. When the annealing temperature is lower, the PZT thin films become a phyrochlore phase. However, when the annealing temperature is higher than $600^{\circ}C$, the PZT thin films become a perovskite phase. At the annealing temperature of $700^{\circ}C$, perovskite PZT thin films with good quality structure was obtained.
이경천,이수진,장영진,김윤미,차한 대한마취통증의학회 2015 Anesthesia and pain medicine Vol.10 No.4
Background: The aim of this study was to investigate the efficacy of routine pre-anesthetic aspartate aminotransferase (AST) and alanine aminotransferase (ALT) tests for detection of hepatic abnormalities and usefulness in perioperative management. Methods: The laboratory findings of 14,185 pediatric patients younger than 18 years from October 2004 to December 2010 were investigated by retrospective review of medical records. All of the patients had undergone preoperative AST and ALT screening. Results: Among the 14,185 patients, 221 patients experienced elevation of both AST and ALT. However, only 21 patients were suspicious for hepatic disease defined as persistent elevation of AST and ALT preoperatively. Among the 221 patients with elevation of both AST and ALT, 20 patients were examined by additional abdominal ultrasonography and hepatic abnormalities were detected in 13 of these patients (65%) and 40 patients were consulted to the department of pediatrics or internal medicine. Conclusions: In this single-center, retrograde study, the usefulness of preoperative routine AST and ALT testing was shown to be limited for detection of hepatic abnormalities in pediatric patients undergoing general anesthesia. Further multi-center, large-scale investigation would be required.
이경천 부천대학 1992 論文集 Vol.13 No.-
This paper is concerned with a method to express shear strength of clay during onedimentional consolidation process. In order to know to relation between consolidation time and shear strength, a series of consolidation shear tests has been performed using a box shear apparatus with a single shear surface. The test results show that the degree of consolidation defined by means of the equivalent effective stress has a linear relationship to the shear strength, during primary and secondary consolidation.
이경천,김낙영 부천대학 2001 論文集 Vol.22 No.-
본 연구에서는 혹운모편마암과 화강편마암이 기반암으로 구성되어있고 지질적 조건이 유사한 도로터널 4개소유 선정, 실내·현장 시험 및 암반분류를 실시하였고 그 결과에 대한 회귀분석을 수행, 각각에 대한 상호관계를 분석하였다. 또한, 터널구간의 기반암이 흑운모편마암과 화강편마암으로 구성된 터널에서 실내시험결과를 활용하여 암반변형계수를 산정하기 위한 감쇠지수에 대한 식을 제시하였다. 본 연구대상 4개 도로터널에 대한 RMR과 Q, RMR과 Q, RMR과 RQD, Q와 RQD, 공내재하시험결과와 실내시험결과의 상관관계식에 대한 신뢰도 분석결과 Q와 RQD의 상관관계가 가장 밀접한 것으로 나타났다. Four road tunneis which the major part of bedrock consisted of biotite gneiss and granite gneiss and that geological conditions were similar were selected in the paper and laboratory and field test, rockmass rating of four tunnels were carried out. And the regression analysis was performed to find out correlation of results. It was proposed that the equation of reduction factor which could be assess deformation modulus through result of labortory test in biotite gneiss and granite gneiss. It was found that there was close correlation Q between RQD in four tunnels according to analysis of correlation of RMR between Q and RMR between RQD and Q between RQD and result of laboratory test between pressuremeter test.
지오셀 보강 층수에 따른 얕은 기초의 지지력에 관한 실험 및 해석적 연구
이경천,박영훈,김낙영 부천대학 2002 論文集 Vol.23 No.-
본 연구에서는 지반을 강화 할 수 있는 지오셀 시스템에 대한 지지력 메카니즘을 분석하고 다양한 평판재하시험을 실시하여 지지력 개선 효과를 평가하며, 모형토조 시험에 의한 지오셀 시스템의 지지력 실험에 의해 얕은 기초의 지지력 변화를 연구하였다. 연구 결과, 토조 실험 결과 상대밀도가 증가할수록 동일 위치의 수직 토압이 증가 하고 지오셀 보강실험에서는 상대밀도 증가에 의해 동일 작용하중에서 지오셀의 수직 ·수평 변형율이 상대적으로 감소하는 것으로 나타났다. 또한, 지오셀 시스템의 작용하중의 분산 효과에 의해 지오셀 시스템 아래의 수직 토압이 약 2배 정도 감소하는 것으로 분석되었으며, 이러한 현상이 지지력 증가에 직접적으로 영향을 미치는 것으로 연구되었다. The Geocell system is the advanced system of Geo-grids, and is one of geosynthetics used for earth reinforcement of construction structure on weak soil. It is the way to increase earth strength and bearing capacity by using three dimension type of geo-composite. This Paper analyzed the bearing capacity mechanism of Geocell system for earth reinforcement. Plate loading test using laboratory model study was performed, and bearing capacity increase and subsidence decrease of shallow foundation were evaluated. Also the effect of model test box and earth behavior was analyzed by finite element analysis. In the result of model test box experiment, vertical earth pressure in the same place increased, as relative density increased. Geocell system had effect on the decrease about 2 times of vertical earth pressure under the system, and it was analyzed to have direct influence on bearing capacity increase.