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정우원,이임영,라경진 순천향대학교 부설 산업기술연구소 2019 순천향 산업기술연구소논문집 Vol.25 No.1
Today companies often are providing public vehicles to their employees improving work efficiency. Also Business Vehicle Intergrated Management System(BVIMS) provides that users can easily and quickly apply for dispatch and eliminate the hassle of manually operating the log records. However there are often people who manipulate or use their records for personal benefit. In this paper we propose BVIMS using blockchain technology. It improves the reliability of the system by preventing tampering with records. So from the viewpoint of business owners it is possible to operate efficiently and economically by operating the electronic processing through lack of time and manpower shortage caused by vehicle operation and to increase the reliability and integrity of stored data dramatically by using blockchain technology.
Effects of surface geometry and non-newtonian viscosity on the flow field in arterial stenoses
정우원,이계한 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9
Hemodynamics including flow pattern, shear stress, and blood viscosity characteristics has been believed to affect the development and progression of arterial stenosis, but previous studies lack of realistic physiological considerations such as irregular surface geometry, non-Newtonian viscosity characteristics and flow pulsatility. The effects of surface irregularities and non-Newtonian viscosity on flow fields were explored in this study using the arterial stenosis models with 48% arterial occlusions under physiological flow condition. Computational flow dynamics based on the finite volume method was employed for Newtonian and non-Newtonian fluid. The wall shear stresses (WSS) in the irregular surface model were higher compared to those in the smooth surface models. Also, non-Newtonian viscosity characteristics increase the peak WSS significantly. The dimensionless pressure drop and the time averaged WSS in pulsatile flow were higher than those in steady flow. But pulsatility effects on pressure and WSS were less significant compared to non-Newtonian viscosity effects. Therefore, irregular surface geometry and non-Newtonian viscosity characteristics should be considered in predicting pressure drop and WSS in stenotic arteries.
결정질 태양전지에서 니켈 전극 상요을 위한 열처리 방안
정우원(W.W. Jung),김성철(S.C. Kim),경도현(D.H. Kyung),권태영(T.Y. Kwon),이영석(Y.S. Lee),허윤성(Y.S. Heo),박승일(S.I. Park),이준신(J.S. Yi) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.4
고효율 태양전지를 위한 결정질 태양전지의 구조 중 UNSW에서 개발한 BCSC(buried contact solar cell)가 있는데, 이는 전면 전극을 laser 처리 후 무전해니켈 도금으로 형성한 것이다. 이같은 진면 전극을 형성하기 위해서는 무전해 nickel 도금 후 열처리가 필수적이다. 우리는 이 공정을 확립하기 위해 결정질 wafer에 후연을 PECVD로 SiNx막을 형성하여 30Ω/□로 도핑한 후 후면을 불산으로 제거한 상태에서 양면을 니켈 무전해 도금으로 전극을 형성하여 300℃, 350℃, 400℃에 서 각각 3,6,9분간 진행하였다. 그 결과 400℃에서 3분간 열처리된 sample이 상대적으로 가장 명확한 IV curve를 형성하였다. 이 실험의 결과는 PN 접합 구조에서 전극을 nickel로 사용할 때 유용하게 사용될 수 있다.
정우원(W. W. Jeong),이계한(K. H. Rhee),장안식(A. S. Jang),박경열(K. R. Park),전경진(K. J. Chun) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
When a water jet is injected on the body surface, the pressure and shear stress on the surface are important physical parameters in determining the body surface wash out and physical stimulus. We used the force plate in order to measure the surface average pressure for different nozzle types and distances between a nozzle and a plate. We used the nozzles with a hole dimeter of 1.8, 2.9, 3.2㎜, and the shower heads with 10 holes (hole diameter, 1㎜) and 20 holes (hole diameter, 1㎜). The distances between a nozzle and a plate was 10, 20, 30, 40㎝. The results showed that the surface forces were not affected by the distances between a nozzle and a plate. Further numerical studies will be performed to predict wall shear stress based on the measured pressure data.
유한요소/유한체적법 기반의 상용전산유체역학 프로그램의 유동장 변화에 대한 비교
정우원(W. Jeong),성재훈(J. Seong),이계한(K. Rhee),곽대순(Dai-Soon Kwak) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Recently, many studies for flow characteristics have used commercial computational fluid dynamics (CFD) software to simulate flow phenomena in various fields. The aim of this study is to contribute to the discussion on the efficiency of finite element (FE) and finite volume (FV) methods, which have mainly used as CFD solvers for situations with the same number of mesh elements and geometries. We compared the accuracy of the results and the flow patterns among three different commercial codes - Ansys CFX, Fluent and ADINA, which are used in many fields. We calculated threedimensional incompressible laminar flow problems with simple pipe and bifurcation models. Our results showed that FEM CFD codes (ADINA) were more influenced by the mesh type and quality compared to FVM CFD codes (Ansys CFX, Fluent). The computation time was found to be significantly shorter for the FVM compared to the FEM codes.