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MPCVD를 이용하여 밀리미터 길이로 수직 정렬된 탄소나노튜브의 합성
김유석,송우석,이승엽,최원철,박종윤,Kim, Y.S.,Song, W.S.,Lee, S.Y.,Choi, W.C.,Park, C.Y. 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.3
본 연구에서는 철(Fe)을 촉매금속으로 사용하고 마이크로웨이브 플라즈마 화학기상증착법(microwave plasma CVD)을 이용하여 얇은 다중벽 탄소나노튜브를 합성하였다. 촉매금속으로 사용된 철은 직류 마그네트론 스퍼터를 사용하여 증착하였으며, 탄소나노튜브의 합성에는 플라즈마 공급원인 수소($H_2$), 탄소 공급원인 메탄($CH_4$)과 함께 미량의 산소($O_2$) 또는 아르곤(Ar)과 함께 물을 수증기의 형태로 사용하였다. 산소 또는 수증기의 추가에 따른 탄소나노튜브의 성장률의 변화를 주사전자현미경으로 조사하였으며, 결정구조를 투과전자 현미경을 통해 관찰하였다. 또한 라만 분광법을 이용하여 추가 주입 기체의 종류에 따른 탄소나노튜브의 결정성의 변화를 분석하였다. 실험결과, 산소를 추가로 주입하였을 때 성장률이 가장 컸고 결정성도 개선되는 것을 확인하였다. 최종적으로 150 분 동안 합성하여 기판 위에 2.7 mm 이상의 수직 정렬된 얇은 다중벽 탄소나노튜브(thin-multiwalled CNTs)를 합성할 수 있었다. Millimeter-scale aligned arrays of thin-multiwalled carbon nanotube (t-MWCNT) on layered Si substrates have been synthesized by oxygen-assisted microwave plasma chemical vapor deposition (MPCVD). We have succeeded in growth of vertically aligned MWCNTs up to 2.7 mm in height for 150 min. The effect of $O_2$ and water vapour on growth rate was systematically investigated. In the case of $O_2$ gas, the growth rate was ${\sim}22{\mu}m/min$, which is outstanding growth rate comparing with those of conventional thermal CVD (TCVD). Scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and Raman spectroscopy were used to analyze the CNT morphology, composition and growth mechanism. The role of $O_2$ gas during the CNT growth was discussed on.
이중박동형 좌심실보조장치를 부착한 인체의 혈류 순환 모델
김유석(Y. S. Kim),임기무(K. M. Lim),김문수(M. S. Kim),심은보(E. B. Shim),최성욱(S. W. Choi) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
To develop VAD(Ventricular Assist Device) we prevent a numerical blood circulation model. Newly developed D-pulsatile VAD and, unlike conventional artificial heart blood flow can be inhaled by active, reducing the load of the heart in vivo to increase the amount of blood circulation can provide a variety of operating mode. In using VAD, it will change hemodynamic resistance at intra blood circulation by increasing blood pressure and blood circulation value quantities. A blood circulation or blood pressure changes depending on the model simulate characteristics of the public human condition. VAD numerical model is made to actual performance measurement for Twin Pulsatile Life Support System(T-PLS) that was developed by Kangwon National University Artificial Organ Center. We predicted and compared various operating condition using integrated model of VAD, Heart and circulatory system for increase of the blood circulation and minimize the load on the heart.
암의 비대칭적 성장, 혈관생성 및 혈류역학에 대한 수치적 연구
김유석(Y. S. Kim),심은보(E. B. Shim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Tumor hemodynamics in vascular state is numerically simulated using pressure node solution. The tumor angiogenesis pattern in our previous study is used for the geometry of vessel networks. For tumor angiogenesis, the equation that governed angiogenesis comprises a tumor angiogenesis factor (TAF) conservation equation in time and space, which is solved numerically using the Galerkin finite element method. A stochastic process model is used to simulate vessel formation and vessel. In this study, we use a two-dimensional model with planar vessel structure. Hemodynamics in vessel is assumed as incompressible steady flow with Newtonian fluid properties. In parent vessel, arterial pressure is assigned as a boundary condition whereas a constant terminal pressure is specified in tumor inside. Kirchhoff’s law is applied to each pressure node to simulate the pressure distribution in vessel networks. Transient pressure distribution along with angiogenesis pattern is presented to investigate the effect of tumor growth in tumor hemodynamics.