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유압관로에서 비정상유동의 압력측정부 주파수변화에 따른 응답특성
정지철,유영태 조선대학교 에너지.자원신기술연구소 1999 에너지·자원신기술연구소 논문지 Vol.21 No.1
The accurate control of dynamic power greatly influences on the efficiency, stability and economy of equipment, according as the mechanical facilities are becoming highly important in the industry fields. The pulsatory flow appears in the field of engineering, science and technology like pipe line. including power control system of machine equipment and blood flowing etc. The system can be modeled as a L-R-C series circuit with the resistance affected by signal frequency and amplitude. We compared the characteristics in theory with experiment, when a compressible fluid was transmitted by the regular ball valve which was connected by the speed controller that can change the frequency. According to increasing frequency in this paper amplitude of velocity in pulsating flow are dropped. Coefficient of viscosity become decrease so that impedance and resistance are increase. It is clarified that a smaller cavity volume and a larger sensing hole can realize a wider frequency band, a higher input impedance, and a smaller nonlinear.
정지철,신방웅,오세욱 한국지반환경공학회 2004 한국지반환경공학회논문집 Vol.5 No.2
During and after the construction of embankment on soft ground, consolidation settlements and lateral displacements develop. But generally it's very difficult to predict the magnitude of lateral deformations and the correct distribution of lateral displacements with depth under the toe of embankment because the consolidation and the shear deformations of soft ground occur simultaneously. This study shows that later displacements of ground surface arise by embankment loading act on soft clay hight water contents in laboratory model testing. The results of model test are observed settlement of embankment, amount of maximum rising and displacement of ground surface with loading velocity. The formula were proposed to predict lateral movement by test series 최근 연약지반상에 제체 등을 시공 중이나 시공 후에 압밀침하와 수평변위가 발생한다. 그러나 연약지반상의 압밀침하와 전단변위는 동시에 발생하므로 제체선단 아래 깊이에 따른 수평변위량과 수평변위 분포를 정확히 예측한다는 것은 매우 어려운 일이다. 본 연구에서는 고함수비 연약점토 지반에 성토 재하가 발생하는 경우 주변지반의 변위를 실내 모형 실험을 수행하여 연약토의 층후, 재하하중의 크기 및 재하속도 등이 성토본체의 침하량, 주변 지반의 변위, 지표면최대 융기량, 지표면변위 및 영향범위 등을 규명하고자 한다. 이러한 일련의 모형실험에 의하여 측방유동 예측식을 제안하였다.
금속 (Pt)과 4H-SiC의 계면상태에 따른 실리콘 카바이드 기반 고온 가스센서 특성 분석
정지철,구상모,Jung, Ji-Chul,Koo, Sang-Mo 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.4
Silicon carbide (SiC)-based gas sensors can be operated at very high temperatures. So far, catalytic metal-schottky diodes respond fast to a change between a reducing and an oxidizing atmosphere. Therefore SiC diodes have been suggested for high temperature gas sensor applications. In this work, the effect of reactivity of the catalytic surface on the 4H-SiC sensor-structures in 375 K~775 K have been studied and some fundamental simulations have also been performed.
Cr- 및 Ni- 소스/드레인 쇼트키 박막 트랜지스터의 장벽 특성에 대한 실험 및 모델링 연구
정지철,문경숙,구상모,Jung, Ji-Chul,Moon, Kyoung-Sook,Koo, Sang-Mo 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.10
By improving the conducting process of metal source/drain (S/D) in direct contact with the channel, schottky barrier metal-oxide-semiconductor field effect transistors (SB MOSFETs) reveal low extrinsic parasitic resistances, offer easy processing and allow for well-defined device geometries down to the smallest dimensions. In this work, we investigated the arrhenius plots of the SB MOSFETs with different S/D schottky barrier (SB) heights between simulated and experimental current-voltage characteristics. We fabricated SB MOSFETs using difference S/D metals such as Cr (${\Phi}_{Cr}$ ~4.5 eV) and Ni (${\Phi}_{Ni}$~5.2 eV), respectively. Schottky barrier height (${\Phi}_B$) of the fabricated devices were measured to be 0.25~0.31 eV (Cr-S/D device) and 0.16~0.18 eV (Ni-S/D device), respectively in the temperature range of 300 K and 475 K. The experimental results have been compared with 2-dimensional simulations, which allowed bandgap diagram analysis.