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800 V급 4H-SiC DMOSFET 전력 소자 구조 최적화 시뮬레이션
최창용,강민석,방욱,김상철,김남균,구상모,Choi, Chang-Yong,Kang, Min-Seok,Bahng, Wook,Kim, Sang-Cheol,Kim, Nam-Kyun,Koo, Sang-Mo 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8
In this work, we demonstrate 800 V 4H-SiC power DMOSFETs with several structural alterations to obtain a low threshold voltage ($V_{TH}$) and a high figure of merit ($V_B\;^2/R_{SP,ON}$), To optimize the device performance, we consider four design parameters; (a) the doping concentration ($N_{CSL}$) of current spreading layer (CSL) beneath the p-base region, (b) the thickness of p-base ($t_{BASE}$), (c) the doping concentration ($N_J$) and width ($W_J$) of a JFET region, (d) the doping concentration ($N_{EPI}$) and thickness ($t_{EPI}$) of epi-layer. These parameters are optimized using 2D numerical simulation and the 4H-SiC DMOSFET structure results in a threshold voltage ($V_{TH}$) below $^{\sim}$3.8 V, and high figure of merit ($V_B\;^2/R_{SP,ON}$>$^{\sim}$200 $MW/cm^2$) for a power MOSFET in $V_B\;^{\sim}$800 V range.
최창용,문경숙,구상모,Choi, Chang-Yong,Moon, Kyung-Sook,Koo, Sang-Mo 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.8
The substrate bias effect on the current level of SOI-MOSFETs for high temperature operation has been investigated. In this work, we demonstrate the current level of SOI-MOSFETs can be controlled at different temperatures by applying a control bias to the substrate, showing that all current levels below T=150$^{\circ}C$ can be adjusted to a constant current level. 2D numerical simulation results show that substrate bias effectively controls the current conduction; as the substrate bias effectively lower the potential of the channel, inversion carrier generation is effectively controlled and consequently a constant current conduction level is achieved up to T=150$^{\circ}C$. We also demonstrate that the device simulated in this work has same operation at any temperature below T=150$^{\circ}C$ through mixed mode simulation.
G 방정식을 이용한 실린더 챔버 내부 둔각물체 주위의 난류 예 혼합 화염 해석
최창용,박남섭,고상철,Choi Chang-Yong,Park Nam-Seob,Ko Sang-Cheol 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.4
In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.
원형 덕트유동에서의 Graetz 문제에 대한 이중교환 경계요소 해석
최창용,Choi, Chang Yong 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.2
The dual reciprocity boundary element method (DRBEM) is used to solve the Graetz problem of laminar flow inside circular duct. In this method the domain integral tenn of boundary integral equation resulting from source term of governing equation is transformed into equivalent boundary-only integrals by using the radial basis interpolation function, and therefore complicate domain discretization procedure Is completely removed. Velocity profile is obtained by solving the momentum equation first and then, using this velocities as Input data, energy equation Is solved to get the temperature profile by advancing from duct entrance through the axial direction marching scheme. DRBEM solution is tested for the uniform temperature and heat flux boundary condition cases. Local Nusselt number, mixed mean temperature and temperature profile inside duct at each dimensionless axial location are obtained and compared with exact solutions for the accuracy test Solutions arc in good agreement at the entry region as well as fully developed region of circular duct, and their accuracy are verified from error analysis.
크롬질화처리한 저탄소강의 고분자 전해질 연료전지 분리판으로서의 표면특성
최창용(Chang-Yong Choi),강남현(Nam-Hyun Kang),남대근(Dae-Geun Nam) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.5
Separator of stack in polymer electrolyte membrane fuel cell (PEMFC) is high cost and heavy. If we make it low cost and lighter, it will have a great ripple. In this study, low carbon steel is used as base metal of separator because the cost of low carbon steel is very cheaper commercial metal material than stainless steels, which is widely used as separator. Low carbon steel has not a good corrosion resistance. In order to improve the corrosion resistance and electrolytic conductivity, low carbon steel needs to be surface treated. We made Chromium electroplated layer of 5 μm, 10 μm thickness on the surface of low carbon steel and it was nitrided for 2 hours at 1000℃ in a furnace with 100 torr nitrogen gas pressure. Cross-sectional and surface microstructures of surface treated low carbon steel are investigated using SEM. And crystal structures are investigated by XRD. Interfacial contact resistance and corrosion tests were considered to simulate the internal operating conditions of PEMFC stack. The corrosion test was performed in 0.1 N H<sub>2</sub>SO<sub>4</sub> + 2 ppm F? solution at 80℃. Throughout this research, we try to know that low carbon steel can be replaced stainless steel in separator of PEMFC.
2차원 열전도 문제에 대한 Fast Multipole 경계요소법의 이론과 실행 알고리즘의 분석
최창용(Chang-Yong Choi) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.5
본 논문에서는 조밀한 계수행렬로 인해 경계요소 개수의 증가에 따른 계산 시간의 급격한 증가 때문에 대규모 문제를 쉽게 다룰 수 없는 기존 BEM 문제를 획기적으로 개선하는 새로운 BEM 해법인 FM-BEM을 소개한다. 단순한 2차원 정상상태 열전도문제를 통해서 FM-BEM과 기존 BEM의 계산시간과 정확도에 대한 해석 결과를 제시하였으며, 이로부터 FM-BEM 해법이 기존 BEM과 유사한 정확도를 유지하면서도 계산 속도를 획기적으로 높인다는 결과를 확인하였다. 결과적으로 본 연구에서는 FM-BEM의 적용 이론 및 관련 실행 알고리즘들을 고찰하고 이를 통해서 FM-BEM의 효용성을 검증하였으며, 향후 다양한 공학적 문제로의 적용 범위를 확대하고자 한다. This paper presents the fast multipole boundary element method (FM-BEM) as a new BEM solution methodology that overcomes many disadvantages of conventional BEM. In conventional BEM, large-scale problems cannot be treated easily because the computation time increases rapidly with an increase in the number of boundary elements owing to the dense coefficient matrix. Analysis results are obtained to compare FM-BEM with conventional BEM in terms of computation time and accuracy for a simple two-dimensional steady-state heat conduction problem. It is confirmed that the FM-BEM solution methodology greatly enhances the computation speed while maintaining solution accuracy similar to that of conventional BEM. As a result, the theory and implementation algorithm of FM-BEM are discussed in this study.
최창용(Choi Chang-Yong),조성환(Cho Sung-Hwan),곽희열(Kwak Hee-Youl),신우철(Shin U-Cheul) 한국태양에너지학회 2006 한국태양에너지학회 학술대회논문집 Vol.- No.-
This paper presents the simulation modeling and its results of the solar thermal driven absorption heating and cooling system for the library reading rooms of a cultural center building located in Gwangju Korea. In this study, single efficiency LiBr-H2O absorption chiller of the rated capacity 10 RT, and 0.7 COP with a evacuated tubular solar collector system is used for the solar cooling facility. A complete system composed of solar collectors, thermal storage tanks, absorption chiller, and auxiliary gas boiler is modelled, and the yearly solar energy supply rate of the system is predicted with the TRNSYS simulation results.