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최윤호,강현덕,김도영,이재호,박윤옥,Choi, Y.H.,Kang, H.D.,Kim, D.Y.,Lee, J.H.,Park, Y.O. 한국전자통신연구원 2018 전자통신동향분석 Vol.33 No.2
The fundamental problem of communication is that of transmitting a message from a source to a destination over a channel through the use of a transmitter and receiver. To derive a theoretically optimal solution, the transmitter and receiver can be divided into several processing blocks, with each component analyzed and optimized. The idea of machine learning (or deep learning) communications systems goes back to the original definition of the communi-cation problem, and optimizes the transmitter and receiver jointly. Although today's systems have been optimized over the last decades, and it seems difficult to compete with their performance, deep learning based communication is attractive owing to its simplicity and the fact that it can learn to communicate over any type of channel without the need for mathematical modeling or analysis.
최윤호,정형석,Y.H. Choi,H.S. Chung 한국전자통신연구원 2023 전자통신동향분석 Vol.38 No.5
Recently, with the trend of information technology convergence and electrification, batteries are being widely used in fields such as industry, transportation, and specific applications. By 2030, the secondary battery market is expected to grow explosively by more than eight times compared with 2020 to $351.7 billion owing to the expanding adoption of electric vehicles. Depending on the electrochemical reactions in the electrode, a primary battery can only discharge through an irreversible reaction, while a secondary battery can be repeatedly charged and discharged using reversible reactions. According to the type of charge carrier ions, secondary batteries may be classified into those made of lithium, sodium, potassium, magnesium, and aluminum ions. We analyze the current status and technological issues of lithium-ion batteries, lithium-sulfur batteries, and solid-state batteries, which are representative examples of lithium secondary batteries. In addition, research trends in lithium secondary batteries are discussed.
최윤호,정형석,Y.H. Choi,H.S. Chung 한국전자통신연구원 2023 전자통신동향분석 Vol.38 No.6
Lithium accounts for only 0.0017% of the earth crust, and it is produced in geographically limited regions such as South America, the United States, and China. Since the first half of 2017, the price of lithium has been continuously increasing, and with the rapid adoption of electric vehicles, lithium resources are expected to be depleted in the near future. In addition, economic blocs worldwide face intensifying scenarios such as competition for technological supremacy and protectionism of domestic industries. Consequently, Korea is deepening its dependence on China for core materials and is vulnerable to the influence of the United States Inflation Reduction Act. We analyze post-lithium secondary battery technologies that rely on more earth-abundant elements to replace lithium, whose production is limited to specific regions. Specifically, we focus on the technological status and issues of sodium-ion, zinc-air, and redox-flow batteries. In addition, research trends in post-lithium secondary batteries are examined. Post-lithium secondary batteries seem promising for large-capacity energy storage systems while reducing the costs of raw materials compared with existing lithium-based technologies.
Vortex Tube 성능 개선을 위한 절두체의 형상 매개변수에 대한 연구
구한범(H.B. Koo),박준용(J.Y. Park),손덕영(D.Y. Sohn),최윤호(Y.H. Choi) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.4
Vortex tube is a thermal static device that separates compressed air into hot and cold streams. In general, the cooling efficiency of vortex tubes is lower than that of traditional air conditioning equipment and vortex tubes are mainly used for industrial spot cooling applications because of their quick responses. In this study, conical frustums are employed in the nozzle chamber to improve the cooling performance. Conical frustums can be used to decrease the ineffective mass fraction that directly passes through the cold exit without energy separation. The shape optimization of conical frustums has been performed using full factorial design. It is found that the height of frustums has the largest main effects on the cooling performance. Computational results show that the cooling performance can be increased by about 10% within the considered range of the design parameters. This is because the ineffective mass fraction toward the cold exit is decreased by about 20%.
자동차용 공기청정기의 성능 평가 및 설치 조건 도출을 위한 수치해석적 연구
이용훈(Y.H. Lee),서진원(J.W. Seo),박재홍(J.H. Park),최윤호(Y.H. Choi) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
In this study, an air cleaner is considered to improve comfort, safety, and health of automobile passengers. The performance and installation conditions of the air cleaner have been studied to investigate their effects on the air quality in the cabin room using numerical analysis. A five-passenger sedan and a seven-passenger minivan that have comparatively large indoor volume have been considered. The distributions of the local mean age and the volume averaged age of indoor air are calculated according to the variation of the placement and the air flow of the air cleaner. In addition, a decrease of contamination concentration, especially VOCs(volatile organic compounds), by the air cleaner is numerically analyzed with time-accurate unsteady calculation to quantify the effect of the air cleaner on the indoor air quality. As a result, the effective installation and operation conditions of the air cleaner for the automobile cabin room could be suggested.
공조 시스템이 후드겸용 전자레인지 포집효율에 미치는 영향에 관한 수치해석적 연구
권용민(Y.M. Gwon),손덕영(D.Y. Sohn),최윤호(Y.H. Choi),정희수(H.S. Jung),홍석만(S.M. Hong) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
The Over-The-Range(OTR) which is a microwave-hood combination includes a ventilation and cooking system. The ventilation system removes fumes and moisture generated in the main cooking device during the cooking process. However, the OTR has a low capture efficiency for a variety of reasons. The room ventilation system is one of the main effects to decrease the capture efficiency. In this paper, the performance and installation conditions of the OTR has been studied to investigate the effect of room ventilation system on the capture efficiency using numerical analysis.
예조건화된 압축성유동 수치기법에서의 풍상차분법의 수치특성 검토
길재흥(J. H. Gill),이두환(D. H. Lee),최윤호(Y. H. Choi),권장혁(J. H. Kwon),이승수(S. S. Lee) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
Studies of the numerical characteristics of implicit upwind. schemes, such as upwind ADI, Line Gauss-Seidel(LGS) and Point Gauss-Seidel(LU) algorithms, for preconditioned Navier-Stokes equations are performed. All the algorithms are expressed in approximate factorization form and Van Neumann stability analysis and convergence studies are made. Preconditioning is applied for efficient convergence at low Mach numbers and low Reynolds numbers. For high aspect ratio computations, the ADI and LGS algorithms show efficient and uniform convergence up to moderate aspect ratio if we adopt viscous preconditioning based on min-CFL/max-VNN time-step definition. The LU algorithm, on the other hand, shows serious deterioration in convergence rate as the grid aspect ratio increases. Computations for practical applications also verify these results.
자동차용 HVAC 시스템의 air-vent 고려 여부에 따른 차 실내 온열쾌적성 평가에 관한 연구
윤성현(S.H. Yoon),서진원(J.W. Seo),최윤호(Y.H. Choi),송봉하(B.H. Song),김용석(Y.S. Kim) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
The automotive HVAC system plays various roles such as car indoor heating, cooling and air quality control. This HVAC system consists of air-vents, ducts, heater, evaporator, HVAC module, etc. Recently, the research related with this is being performed through numerical analysis as well as experiments. A large amount of computation time is required when considering all parts of complicated HVAC system including an air-vent because the number of grid would be increased. Also, the working time will be increased if you perform the parametric analysis about the directions of an air-vent which decides an air discharge angle because CAD(modifying the geometry) and grid regeneration tasks are required. In this study, we removed the HVAC system including the air-vent from the computational domain and imposed the direction of the flow by using vector in order to shorten the working time according to the modification of the air-vent geometry. Also, it is expected that there will be a change in the car interior flow depending on consideration of air vent, so we performed various parametric study in order to set the flow without HVAC system to be the same flow considered the real geometry of air-vent.