http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
측정장치 압력손실과 면적평균 물리량 보정을 위한 다단 축류 팬과 압축기의 수치해석적 연구
최재호,김세미,이원석,최태우,김진욱,CHOI, JAEHO,KIM, SEMI,LEE, WONSUK,CHOI, TAEWOO,KIM, JINWOOK 한국수소및신에너지학회 2018 한국수소 및 신에너지학회논문집 Vol.29 No.4
A numerical investigation has been conducted to find the effects of pressure losses by struts and rakes, and averaging methods on the performance of a multi-stage axial fan and a multi-stage axial compressor. Struts and rakes which produce pressure losses are installed upstream of the aerodynamic inlet plane in the fan and the compressor rigs. Some of normal stator vanes are substituted with thick vanes with total pressure probes to measure total pressure between stages. Three-dimensional Reynolds-averaged Navier- Stokes equations with $k-{\omega}$ SST turbulence model were applied to analyze the pressure losses by the struts, inlet rakes, and thick instrumented vanes. The hexahedral grids were used to construct computational domain. Inlet pressure losses were evaluated for the compressor as a function of Mach number. The passage pressure losses due to the instrumented vanes were evaluated at the two speed lines in the fan. Total properties, such as pressure and temperature, were evaluated at the exit of the fan and the compressor with two different averaging methods which are area-averaging and mass-averaging, respectively.
박막형 기폭장치 내 이종금속 다층구조층의 화염전파 현상 해석연구
최재호(Jaeho Choi),김경진(Kyoungjin Kim) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
이 전산해석적 연구는 박막형 폭약 기폭장치의 성능 향상을 위해 나노 크기의 이종금속 다층구조를 박막 금속브릿지에 부착한 기폭장치 구조를 대상으로 한다. RC회로에 의한 브릿지 주울 발열 및 보론/티타늄 이종금속간 화학반응 모델링을 포함하여 3차원 다층구조 및 박막브릿지 복합구조에 대한 열 및 원자종 확산방정식 기반 3차원적 전산해석이 수행되었다. 전산해석 결과로 불균일한 브릿지 발열, 브릿지 열손실 등의 3차원적 효과가 예상보다 매우 크며, 이에 따라 1차원적 해석에 비교하여 점화시간 지연 및 더 전기에너지 요구사양 등에 큰 영향을 미침을 발견하였다. Ignition performance of thin film explosive initiators could be much improved by employing nanoscale intermetallic multilayers on top of metallic film bridge. This computational investigation carried out three-dimensional computations of thermal and atomic species diffusion for the microstructure of a thin film initiator with boron and titanium multilayers using the models of bridge joule heating by RC initiation circuit and intermetallic reaction propagation. The computational results found that the three-dimensional effects such as non-uniform bridge heating and bridge heat loss are quite significant, and they lead to longer delay of reaction ignition and higher energy requirement when compared to one-dimensional approximation.
이종금속 다층 박막구조 내 금속간 화학반응 전파 특성의 전산해석적 연구
최재호(Jaeho Choi),곽호상(Ho Sang Kwak),김경진(Kyoungjin Kim) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11
이 전산해석적 연구에서는 이종금속 박막으로 구성되는 다층구조에서 금속간 화학반응 전파현상을 열확산 및 화학종 확산방정식을 이용하여 모델링하였다. 금속간 화학반응은 Arrhenius 반응식을 따른다고 가정하였으며, 반응 점화는 열유속을 일정시간 동안 적용하는 것으로 모사하였다. 보론과 티타늄 층으로 이루어진 나노크기의 다층박막구조에 대한 전산해석 결과에서 높은 반응열을 동반하는 금속간 화학반응의 전파속도가 10m/s 정도로 상당히 높음을 확인하였다. In this numerical investigation, the propagation of intermetallic reaction through multilayers of two different metals has been modeled into governing equations of transient thermal and atomic species diffusion between binary metallic thin layers. The intermetallic reaction is assumed to follow the Arrhenius kinetics, while the reaction ignition is simulated by imposing heat flux for a certain amount of time. The computational results for nanoscale boron and titanium multilayers show high values of reaction propagation speed of approximately 10 m/s, which accompanies high rate of exothermic heat.
Laser Brazing 접합부 품질 주요 영향 인자 연구
최재호(Choi Jaeho),장인성(Chang Insung),권태용(Kwon Taeyong),김동명(Kim Dongmyung),도성섭(Do Sugnseop) 한국레이저가공학회 2008 한국레이저가공학회 학술대회 논문집 Vol.2008 No.-
The quality of laser brazed junction not only depends on the size of the gap between brazed metals but also affected by optimized parameters of laser source, pillar wire and robot. In this study, the result of laser brazing test and the relation between those parameters will be discussed.
외환 시장에서 마코브 체인을 활용한 포트폴리오 선정 모형과 투자 알고리즘 개발 및 성과평가
최재호(Jaeho Choi),정종빈(Jongbin Jung),김성문(Seongmoon Kim) 한국경영과학회 2015 한국경영과학회지 Vol.40 No.2
In this paper, we propose a portfolio selection model utilizing a Markov chain for investing in the foreign exchange market based on market forecasts and exchange rate movement predictions. The proposed model is utilized to compute optimum investment portfolio weights for investing in margin-based markets such as the FX margin market. We further present an objective investment algorithm for applying the proposed model in real-life investments. Empirical performance of the proposed model and investment algorithm is evaluated by conducting an experiment in the FX market consisting of the 7 most traded currency pairs, for a period of 9 years, from the beginning of 2005 to the end of 2013. We compare performance with 1) the Dollar Index, 2) a 1/N Portfolio that invests the equal amount in the N target assets, and 3) the Barclay BTOP FX Index. Performance is compared in terms of cumulated returns and Sharpe ratios. The results suggest that the proposed model outperforms all benchmarks during the period of our experiment, for both performance measures. Even when compared in terms of pre- and post-financial crisis, the proposed model outperformed all other benchmarks, showing that the model based on objective data and mathematical optimization achieves superior performance empirically.
최재호(Jaeho Choi),이청규(Chungkyu Lee),이재형(Jaehyoung Lee),김태섭(Taesub Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In the heavy diesel engine, the piston temperature distribution with the cooling gallery was experimentally investigated using the templug. As a result of the measurement, it is shown that the exhaust port side of the piston has the high temperature distribution compared to the intake port side of the piston because of the hot exhaust gas. With respect to the temperature around the combustion chamber, the temperature on the inside of the combustion chamber is lower than that on the top side of the piston. It is affected by the oil cooling through the cooling gallery under the combustion chamber. Also the temperature distribution of the piston ring region is decreased due to the oil cooling through the cooling gallery in the piston. The cooling effect of the piston ring region is larger than that of the combustion chamber.