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한철희,김충기,서광석,Han, Cheol-Hui,Kim, Chung-Gi,Seo, Gwang-Seok 대한전자공학회 1981 전자공학회지 Vol.18 No.1
양호한 특성의 I2L 구조를 구현하기 위한 새로운 공정을 제안하였다. 이 구조에서는, extrinsic base 의 불순물 농도가 높으며, 또한 collector는 불순물 농도가 낮은 intrinsic base와 self align된다. 제안한 공정에서는 spin-on source를 확산원으로 사용하였고, mask 단계를 줄이기 위하여 열처리로 단단해진 spin-on source를 확산 mask로 사용하였다. 이 공정에 의하여 13단 ring oscil-lator를 포함한 시험소자를 6.5μm의 epi 충을 갖는 n/n+ silicon wafer 상에 제작하였다. 제작한 시험소자의 특성은, collector가 세 개인 I2L의 경우 npn transistor의 상향 전류이득은 최대치가 8이었으며, collector가 하나인 I2L의 속도전력적과 최소 전달 지연시간은 각각3.5 pJ과 50ns 이었다. A new I2L process for a high performance I2L structure is proposed. The modifiedstructure consists of a heavily doped extrinsic base and lowly doped intrinsic base where the collector regions are self-alignment with the intrinsic base regions. The proposed process untilizes spin-on sources as the diffusion sources and the self-alignment of collectors is achieved by using the hardened spin-on source as a diffusion mask. Test devices including a 13-stage ring oscillator have been fabricated by the proposed process on n/n+ silicon wafers with 6.5$\mu$m epitaxial layer. The maximum upward current gain of npn transistors is 8 for a three collector I2L cell. The speed-power product and minimum propagation delay for a one collector structure are 3.5 pJ and 50 ns, respectively.
채널 내를 비행하는 가변스팬 날개 공력특성 II (비대칭 날개 펼침)
한철희,Han, Cheolheui 항공우주시스템공학회 2016 항공우주시스템공학회지 Vol.10 No.3
In this paper, a wind-tunnel test is accomplished to investigate the roll characteristics of a variable-span wing flying inside a channel. The factors that affect the roll characteristics of the wing were identified by analyzing the measured data; accordingly, when the wing is flying without both the ground and sidewall effects, the asymmetric wing extension causes the roll moment. Both the ground and the sidewall can increase the roll moment, but when the wing is affected by both the ground and the sidewall, the roll moment does not increase as much as the case where the wing is only affected by the ground. Also, the aerodynamic characteristics of the flying wing inside a channel are the nonlinear function of the wing height and the gap between the wingtip and the sidewall, both of which should be considered in a study of the stability and the flight control of the wing-in-ground effect of the vehicle flying inside a channel.
미래 수직이착륙 항공기로서의 UFO형 항공기 공기역학 추정
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2015 융ㆍ복합기술연구소 논문집 Vol.5 No.2
Flying Saucer(flying disk type UFO) is a rotating disk that flies through the air. Thus, the aerodynamical features of the Flying Saucer can be estimated by taking a close look on the aerodynamics of the rotating disk. In the present paper, the aerodynamics of the rotating disk are reviewed focusing on the their application to the possibility of the UFO type VTOL aircraft. Finally, a combination of Avro Aircraft and Frisbee concepts is suggested as a possible new UFO type VTOL aircraft.
한철희,전문수,Han, Cheolheui,Chon, Munsoo 한국교통대학교 융복합기술연구소 2013 융ㆍ복합기술연구소 논문집 Vol.3 No.1
Unsteady fluid dynamics analysis of flow characteristics inside a Metal DPF system is done using a commercial CAE software, CFD-ACE+. The time profiles of both temperature and pressure of exhaust gas are given as initial conditions. It was found that the position of connecting pipes and the numbering of exhaust gases did not affect the flow uniformity. The presence of a DPF resulted in the significant flow nonuniformity effect on the flow characteristics at the inlet of the DPF. Present results can be applied to the selection of optimal geometry that produces uniform flow characteristics inside a DPF system.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2011 융ㆍ복합기술연구소 논문집 Vol.1 No.1
Thermal analysis of a cooling module using Peltier elements are performed using a commercial software, CFD-ACE+. A standard k-e two-equation turbulent model is applied in order to represent the turbulent shear stress. Computed values are compared with the theoretical values for the validation. The effect of mass flow rates and transferred heat amounts on the temperature distributions inside the cooling system is analyzed. It was found that the increase in the mass flow rates causes the exit temperature rise. The increase in the absorbed heat amount diminished the overall temperature on the fin surfaces. In the present analysis, the material characteristics of the Peltier element itself are not considered. In the future, the effect of the turbulence models and material characteristics will be studied in detail.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2014 융ㆍ복합기술연구소 논문집 Vol.4 No.1
Investigation of flow characteristics behind a edged backward facing step is important for selecting appropriate positions of building constructions in the desert area. In the present study, the effect of edge angles on the flow characteristics is investigated using a commercial software CFD-ACE+. When the edge angle is less than 30 degree, reattachment length decreases, whereas when the edge angle is larger than 30 degrees, reattachment angle increases. It can be concluded that the flow patterns behind an edged backward facing step is classified as the two, streamlined and bluffed bodies. Appropriate edge angles have an effect of increasing the momentum toward the wall, which can reduce the reattachment length. It can be said that present results can be utilized for diverse industrial applications that includes the backward facing step.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2016 융ㆍ복합기술연구소 논문집 Vol.6 No.2
Accurate simulation of wakeshapes behind a wing is important for the performance prediction of the aircraft and the wake hazard problem in the airport. In the present study, wakeshapes behind a wing inside tunnels are simulated in regard to the development of wing-in-ground effect vehicles. A discrete vortex method with a nonplanar ground modelling is used for the simulation. It was found that the wingtip vortices move toward outboard directions when the wing is in ground effect. When the wing is placed inside tunnels, the wingtip vortices move along the tunnel wall with counter clockwise direction. As the gap between the wingtip and the tunnel decreases, the wingtip vortices move further along the tunnel wall. Both vortices from bothsides of the wing will murge, which will be studied in future using a viscous computation.