• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.88-97
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• 2016

A closed loop thermal control system simulates space thermal environment to verify the satellites' functionality in extremely cold/hot temperature. It is composed of a cryogenic blower, thermal shroud, heater, cryogenic valves. This paper presents an overview of closed loop thermal control system's design parameter and test results for control parameter. A capacity of blower is calculated through energy balance equation and an advantage/disadvantage for a shroud material and a type was analysed. The thermal control system is controlled by a constant density of fluid in the system. A requested performance of closed loop thermal control system was verified by measuring a homogeneity and stability of shroud through control parameter such as density and RPM of blower.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.39 no.3
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• pp.40-42
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• 2010

벽 스위치를 경유하여 구성되는 조명회로와 같이 폐회로에서만 동작하는 폐회로 전력선통신을 근간으로 하여 매우 저가로 구현이 가능하고, 에너지 절전효과가 큰 조명제어 시스템에 대하여 기술한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.129-132
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• 2008

For the development of the 30tonf level LOx/kerosene liquid rocket engine, turbopump-gas generator closed-loop coupled tests are performed. To simulate engine operation conditions, combustion chamber was substituted by flow control orifices. In simulated engine system operation environment, chill-down procedure, startup characteristics, nominal operability of turbopump+gas generator coupled Test Plant are confirmed. Turbopump and gas generator are confirmed to operate well in simulated engine environment. The control system for regulating power and mixture ratio of Test Plant are also successfully confirmed.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.4
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• pp.457-463
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• 2002

The closed cycle diesel engine is used in a closed circuit system which has no air breathing. The working fluid as intake mixture are consisted of oxygen, argon and recirculated exhaust gas in order to obtain underwater or underground power sources. In the present study, the high pressure diesel engine which can be operated by the closed cycle system with high intake pressure for increasing the net power rate is designed. It has been carried out to investigate the combustion characteristics of high pressure diesel engine according to the power rate. The maximum cylinder pressure and heat release rate were investigated. Also, major experimental data such as specific fuel consumption rate, oxygen concentrations, fuel conversion efficiency, polytropic exponent, and IMEP were compared with low pressure diesel engine experimental data.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.65-72
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• 2002

The closed cycle diesel system is operated in closed circuit system where there is non air breathing with working fluid consists of combination of oxygen, argon and recycled exhaust gas far obtaining underwater or underground power sources. Experimental apparatus using the MTU8V183SE92 high pressurized engine adapted for closed cycle running, capable of operating at the system pressure of maximum 5 bar is constructed with ACAP as data acquisition system in order to operate equally in the open cycle in surface or the closed cycle in submerged conditions. The general features and the characteristics of combustion of HP(high pressure) diesel engine, specially designed and manufactured only for CCDE, are investigated. The test results of performance of HP diesel engine in closed cycle system are presented with respect to power and boost pressure and compared with those of low pressure diesel engine. The oxygen concentration and specific heat ratio are investigated with its deviation

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.379-382
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• 2009

본 논문에서는 폐회로 다중 안테나 송수신 (closed-loop multiple-input multiple-output) 기법을 사용하는 적응형 협동 다중 홉 중계 시스템을 제안한다. 중계기와 기지국 사이의 이동성이 낮기 때문에, 폐회로 다중 안테나 송수신 기법은 개회로 다중 안테나 송수신 기법보다 높은 다이버시티 이득을 얻을 수 있다. 이 때, 한 개 이상의 중계 터미널들은 기지국으로 전송을 공유하고 프리코딩 가중치벡터를 피드백하기 위해 하나의 협동 그룹에 포함되어야 한다. 피드백 비트의 증가로 인한 전송량 감소를 최소화 하기 위해 코드북 기반의 최대비 전송 기법을 사용하여 비트백 비트수를 제한한다. 기지국은 협동 중계 그룹 중에서 채널 상태가 가장 좋은 중계기를 선택하고, 프리코딩을 위한 인덱스 값을 중계기에 피드백한다. 이러한 중계 시스템을 위해 피드백 형태와 선택 프로토콜 시나리오를 제안하고, 모의실험을 통해 중계기 선택에 따른 성능을 확인한다.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.446-453
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• 2000

The closed cycle diesel system is operated in closed circuit system where there is non air breathing with working fluid consisted of the combination of oxygen, argon and recycled exhaust gas for obtaining underwater or underground power sources. this study has been carried out to analysis the performance of closed cycle system by means of investigation on the combustion characteristics of diesel engine MTU8V183TE52 operating in open, semi-closed, and closed cycle modes. The combustion in closed mode starts a little bit earlier than in open cycle mode. The oxygen concentration and fuel consumption at 240kW closed cycle running are 21∼24% by volume and 77∼79kg/h, respectively. The maximum cylinder pressure and ignition delay time are investigated 110bar and 8.9degree. Also, The combustion simulation program has been studied to predict whether or not combustion. The results from numerical prediction for the basic, cylinder averaged quantities such as the cylinder pressure and the heat release showed excellent with the experimental data.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.120.1-120.1
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• 2013

우주 궤도환경은 $10^{-5}$ torr 이하의 고진공 및 $100^{\circ}C$의 고온과 $150^{\circ}C$이하의 극저온 환경으로 특징지어지며, 위성체 및 위성체 부품은 이와 같은 우주 궤도환경에서의 성능검증이 필수적이다. 지상에서 이와 같은 환경을 모사하기 위해서는 열진공챔버가 사용되며, 열진공 챔버는 진공배기계와 열제어 시스템으로 구성된다. 특히 위성체 또는 위성부품의 열환경을 모사하기 위해 기체 질소를 이용한 폐회로 열제어 시스템이 사용된다. 폐회로 열제어 시스템은 슈라우드, 극저온 블로워, 히터 등으로 구성이 된다. 열제어 시스템의 신뢰성을 높이기 위해서는 핵심 부품인 극저온 블로워의 이중화가 필요하다. 본 논문에서는 위성체 및 위성체 부품의 열진공 시험에 사용되는 열진공 챔버 열제어 시스템의 핵심인 극저온 블로워의 이중화를 위한 기구 설계 및 제어로직 설계 등이 포함되어 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.38-41
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• 2009

For the technology development of LOx/kerosene liquid rocket engine, turbopump-gas generator closed-loop coupled tests using 30tonf main engine components such as turbopump and gas generator except combustion chamber are performed. In the engine system operation environment, simulating combustion chamber by flow control units, the chill-down procedure, startup characteristics, nominal operability and smooth shutdown of turbopump+gas generator closed-loop coupled Test Plant are successfully confirmed. The serviceability of the turbopump and gas generator are evaluated. The feed-back control system for the turbopump rotational speed and gas generator mixture ratio are also verified. The results of closed-loop coupled test will be used as the technology development for the liquid rocket engine.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.157-162
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• 2010

In this paper, We propose that the adaptive cooperative relay transmission technique using closed-loop MIMO scheme for duplex communication system. As the mobility between relay and base station is little, closed-loop MIMO is better diversity gain than open-loop MIMO. At this time, more than one relaying terminals are included in one cooperative group to share their transmission and take precoding weight feedback. For minimization of throughput reduction caused by increasing feedback bits, we use codebook-based MRT that limit the number of feedback bits. Among the cooperative relay group, the best relays are selected from the base stataion and get the feedback. A protocol senarios are also proposed for this relay system.