• 한국국방경영분석학회지
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• 제35권3호
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• pp.1-15
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• 2009

현재 공군은 중앙창에서 국내 조달물자와 해외 도입물자를 공급받아 보관하고 전국 각 기지로 수송하여 기지별로 필요한 물자를 공급하고 있다. 이러한 물자를 중앙물자라고 부르며 항공, 철도, 육로 등 다양한 방편을 이용하여 수송한다. 이 중 항공이 차지하는 비중은 전체 물자의 10% 정도이며, 그 물량이 날로 증가하고 있다. 이렇듯 군에서 항공수송의 비중이 점점 커져가고 있지만, 항공수송을 활성화시키기 위한 수요예측이나 노선설계와 같은 연구는 매우 미흡한 실정이다. 본 연구는 회귀분석을 통하여 항공수송에 미치는 주요 요인과 영향력을 검증하였고 산출된 회귀모형식은 군 항공화물수요 예측에 있어 유용한 자료가 될 것이다.

• KIEAE Journal
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• 제10권3호
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• pp.89-96
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• 2010

In comparison with ordinary or heavy-weight concrete, light-weight air void concrete has the good aspects in optimizing super tall structure systems for the process of design considering wind load and seismic load by lightening total dead load of buildings and reducing natural resources used. Light-weight air void concrete has excellent properties of heat and sound insulating due to its high amount porosity of air voids. So, it has been used as partition walls and the floor of Ondol which is the traditional Korean floor heating system. Under the condition of which the supply of light-weight aggregates are limited, the development of light-weight concrete using air voids is highly required in the aspects of reduced manufacturing prices and mass production. In this study, we investigated the physical properties and thermal behaviors of specimens that applied different mixing ratios of foaming agent to evaluate the possibility of use in the structural elements. We proposed the estimating equation for compressive strength of each mix having different ratio of foaming agent. We also confirmed that the density of cement matrix is decreased as the mixing amount of foaming agent increase up to 0.6% of foaming agent mixing ratio which was observed by SEM. Based on porosity and compressive strength of control mortar without foaming agent, we built the estimating equations of compressive strength for mortars with foaming agent. The upper limit of use in foaming agent is about 0.6% of the binder amount. Each air void is independent, and size of voids range from 50 to $100{\mu}m$.

• Journal of Biosystems Engineering
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• 제3권1호
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• pp.64-76
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• 1978

A dimensional supply of petroleum fuels and increased competition for petroleum products has made the conservation of energy in grain drying an important cost and management factor. Research on solar grain drying is directed toward utilization of a renewable energy source as an alternative to petroleum fuels for drying. There are many technical and economic problems in accepting and adopting solor energy as a new energy source for grain drying. The purpose of this study are to assess the state of the art of solar grain drying and to find out the problems by reviewing literatures available. The results obtained may be summarized as follows; 1.It may be considered that the weather conditions in October of Korea was satisfactory for the forced natural air and solar heated air drying. 2. Solar energy is considered more applicable to low-temperature, In-storage drying systems than to high-temperature, high-speed drying systems. In-storage drying systems require low levels of heat input. The costs of collector systems to provide low temperature are considerably cheaper than for high-temperature systems. 3. Tubular type collector made of polyvinyle film seems to be the most practical at this stage of development and black-painted bare-plate collectors mounted on the outside of a typical, round, low-temperature drying bin can supply an appreciable amount of the energy efficiently needed for low-temperature grain drying at a lower cost. 4. All of the grains in solar drying tests was successfully dried up to safe storaged moisture levels without significant spoilage. Drying rates with solar system were faster than natural air drying systems, and usually a little slower than similar low-temperature electric drying systems. 5. Final grain moisture levels were lower in solar tests than in natural air tests, and generally higher than in tests with continuous heated air. 6. Savings of energy by use of solar collectors ranged from 23% to 55%, compared to the natural and electric ileated air drying systems. However, total drying cost effectiteness tvas not significant. Therefore, it is desirable that solar grain dry-ing sIFstems tvhich could be suitable for multiple heating purposes on farms shouldbe developed. 7. Supplemental heat with solar radiation did little to reduce air flow requirementsbut refuced drying time and increased the p\ulcornerobability of successful drying duringdrying poriod.

• 한국산학기술학회논문지
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• 제14권4호
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• pp.1568-1575
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• 2013

자동차의 유지보수 및 수리를 위한 장비에서 환경오염에 대한 관심이 증대되고 있음에도 불구하고, 국내 자동차 공조시스템에 대한 대부분의 이러한 장비는 환경오염에 대해 무관심뿐만 아니라 그 기능도 뒤떨어진 것이 사실이다. 이 논문에서는 자동차 공조시스템의 냉매의 회수 및 재충전을 위한 모니터링 기술과 진단 시스템을 개발하였다. 이러한 개발된 기술과 시스템은 냉매상태의 정확한 진단과 모니터링을 통하여 자동차 공조시스템에 정확한 냉매량을 충전가능하게 해준다. 또한 이러한 기술은 주변 온도에 따라서 냉매의 회수압력을 조절함으로서 냉매의 회수와 충전에 대한 정확한 제어를 가능하게 해준다.

• 한국산업융합학회 논문집
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• 제18권1호
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• pp.18-29
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• 2015

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The system was introduced into a real building and was examined by the field measurement. Judging from the measurements during three years(1999~2001), the state of the system operation was very stable through this period and it was clear that the system contributes to reduction of energy consumption for air-conditioning. Futhermore, a simulation model used the simple heat diffusion equation was developed to simulate its thermal characteristics and performances. The simulations resulted in air temperature in good agreement with the measurements. Also, from the result of numerical analysis, it is clear that the amount of heat supply by using this system is more than the amount of energy loss to the room above it. Therefore, it is concluded that this systems is very useful and the proposed numerical model can be used for the prediction of system thermal performance.

• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.276-281
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• 2019

The process of separating oxygen and nitrogen from the air is mainly performed by electric liquefaction, which consumes a lot of electricity, resulting in higher operating costs. On the other hand, when used for cold energy of LNG, electric power can be reduced compared to the electric Linde cycle. Currently, LNG cold energy is used in the cold refrigeration warehouse, separation of air-liquefaction, and LNG cold energy generation in Japan. In this study, the system using LNG cold energy and the Linde cycle process system were simulated by PRO/II simulators, respectively, to cool the elevated air temperature from the compressor to about $-183^{\circ}C$ in the air liquefaction separation process. The required amount of electricity was compared with the latent heat utilization fraction of LNG, the LNG supply pressure, and the LNG cold energy usage. At the air flow rate of $17,600m^3/h$, the power source unit of the Linde cycle system was $0.77kWh/m^3$, compared with $0.3kWh/m^3$.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.106-114
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• 1999

Today, one of the most important objective in automobile development is to reduce the weight of automobile . The eventual depletion of petroleum and environmental regulations brought considerable emphasis to this area on increasing fuel efficiency. Conventional intake air-fuel system is very heavy because it is composed of numerous parts. The bulky size caused increase in the amount of metal being used to build automobile chassis and this became a serious weight problem. The size also caused difficulties in optimization of fuel supply system which in turn decreased engine efficiency. Currently , there are efforts to integrate several intake system modules into one. The purpose of this paper is to evaluate the directions of such development.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.333-339
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• 2000

This study was performed to investigate the performance of heat recovery device attached to exhaust gas funnel connected to combustion chamber of greenhouse heating system. The experiment heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas funnel, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amount by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air pipes and exhaust air passages crossing the pipes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through funnels.

• 대한기계학회논문집A
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• 제40권6호
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• pp.613-619
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• 2016

공기구동 제어밸브는 여러 유형의 발전소에서 유체계통의 유량을 제어하거나 탱크의 수위를 조절하는 중요한 기능을 수행하며 발전소 수명기간 동안 성능이 보장되어야 한다. 공기구동 제어밸브는 공기구동기에 공기를 공급하거나 배기하여 작동시키며, 다양한 기능을 하는 부속기기로 구성된 제어설비를 이용하여 공기량을 조절함으로서 밸브 위치를 제어한다. 본 논문에서는 2인치 공기구동기에 I/P 변환기, 포지셔너 등이 장착된 제어밸브 동작모사 실험 장치를 이용하여 공기공급배관에서의 공기누설, 밸브 패킹마찰력 변화, 포지셔너 설정 불량 등을 모사하고, 약 67% 개도에서 ${\pm}2%$ 이하 제어구간에서의 밸브-구동기 거동을 측정하여 비교하였다.

• 한국기계기술학회지
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• 제20권6호
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• pp.917-923
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• 2018

The drinking water supply system applicable to the laying hen consists of air-water heat pumps, drinking water tanks, heat stroage tank, circulation pumps, PE pipes, nipples, and control panels. When the heat pump system has power of 7.7 to 8.7 kW per hour, the performance coefficient is between 3.1 and 3.5. The supply temperature from the heat pump to the heat stroage tank was stabilized at about $12{\pm}1^{\circ}C$, but the return temperature showed a variation of from 8 to $14^{\circ}C$. Stratified temperature in the storage tank appeared at $12.^{\circ}C$, $13.5^{\circ}C$ and $14.4^{\circ}C$, respectively. The drinking water supply temperature remained set at $15^{\circ}C$ and $25^{\circ}C$, and the conventional tap water showed a variation for $23^{\circ}C$ to $30^{\circ}C$. As chickens grow older, the amount of food intake and drinking water increased. $y=-0.0563x^2+4.7383x+8.743$, $R^2=0.98$ and the feed intake showed $y=-0.1013x^2+8.5611x$. In the future, further studies will need to figure out the cooling effect on heat stress of livestock.