• 한국농공학회지
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• 제32권E호
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• pp.80-87
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• 1990

Energy balance equations Were developed to describe the heat transfer mechanisms in a double layer plastic greenhouse with a water curtain system. Heat transfer variables were determined by using various temperature data measured in a conventional prototype semicircular cross-section greenhouse over a range of water temperatures and water flow rates. The heat transfer coefficient between flowing water and greenhouse air was independent of water flow rates. But the heat transfer coefficient between water surface and the stagnant air space within the double plastic layer was dependent on water flow rates. Substituting the heat transfer coefficients, determined from the energy balance equations in the heat transfer equations, demonstrated various relationships among ambient air temperature, greenhouse air temperature, water temperature, and water flow rates. The heating benefits were linearly related to not only the inside and outside air temperatures but also to the water temperature. The energy conservation effects of the water curtain system were found even initial water temperatures were considerably lower than the greenhouse setting temperatures. Sensitivity analysis for heat transfer coefficients demonstrated that the heat transfer coefficient between greenhouse air and the stagnant air within the plastic layers was the most significant coefficient in the estimation of heating effects.

• 한국수정란이식학회지
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• 제13권1호
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• pp.69-76
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• 1998

This study was carried out to establish an effective system for embryo transfer techniques by analyzing several factors affecting in-vivo embryo transfer in Korean cattle Embryos were transferred into a toral of 301 recipients. The results obtained in studies on the factors affecting pregnancy rate after embryo transfer by condition of transfer time were as follows ; 1. The pregnancy rate by the seasons of transferred fresh and frozen embryos were not different, but the pregnancy rate was slightly higher in summer(80.8%). 2. The pregnancy rate by the days of embryo transfer after estrus were not different when fresh embryos were transferred, but the pregnancy rate was highest at 8 days when frozen embryos were transferred(P<0.01, 40.0%). 3. The pregnancy rate at estrus synchronization was remarkably higher with PGF$_2$$\alpha$ treated than natural (P<0.05, 70.4%, 43.4%). 4. The pragnancy rate by the degree of estrus synchronization was best when the estrus was synchronized in both fresh and frozen embryos (83.3% and 29.7%, respectively), but the pregnancy rate was not different among $\pm$2 days. But the pregnancy rate of frozen embryos were slightly higher when the recipients exhibited estrus earlier than donors.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1154-1161
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• 2016

The heat transfer characteristics between liquid lead bismuth eutectic (LBE) and helium are of great significance for the two-loop cooling system based on an accelerator-driven system (ADS). This paper presents an experimental study on the resistance characteristics and heat transfer performance in a LBE-helium experimental loop of ADS. Pressure drops in the LBE loop, the main heat transfer, and the coupled heat transfer characteristics between LBE and helium are investigated experimentally. The temperature of LBE has a significant effect on the LBE thermo-physical properties, and is therefore considered in the prediction of pressure drops. The results show that the overall heat transfer coefficient increases with the increasing helium flow rate and the decreasing inlet temperature of helium. Increasing the LBE Reynolds number and LBE inlet temperature promotes the heat transfer performance of main heat transfer and thus the overall heat transfer coefficient. The experimental results give an insight into the flow and heat transfer properties in a LBE-helium heat exchanger and are helpful for the optimization of an ADS system design.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1617-1628
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• 2017

In the passive residual heat removal system of a molten salt reactor, one of the residual heat removal methods is to use the thimble-type heat transfer elements of the drain salt tank to remove the residual heat of fuel salts. An experimental loop is designed and built with a single heat transfer element to analyze the heat transfer and flow characteristics. In this research, the influence of the size of a three-layer thimble-type heat transfer element on the heat transfer rate is analyzed. Two methods are used to obtain the heat transfer rate, and a difference of results between methods is approximately 5%. The gas gap width between the thimble and the bayonet has a large effect on the heat transfer rate. As the gas gap width increases from 1.0 mm to 11.0 mm, the heat transfer rate decreases from 5.2 kW to 1.6 kW. In addition, a natural circulation startup process is described in this paper. Finally, flashing natural circulation instability has been observed in this thimble-type heat transfer element.

• Journal of information and communication convergence engineering
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• 제8권4호
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• pp.355-364
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• 2010

A session transfer method, referred to as a Recipient Serving-call session control function (S-CSCF) Assured (RSA), is proposed in order to support both session mobility and consistency in IP multimedia subsystem (IMS) based next generation network (NGN). RSA session transfer simplifies a basic session transfer operation specified in [1] by using the user agent client (UAC) like characteristics of an S-CSCF. To show its efficiency, the session transfer delay and the traffic cost of RSA session transfer are investigated and compared with those of existing session transfer applications, including Assured and Consultative session transfers, by practically considering multiple session transfer failures. It is shown that RSA session transfer can further improve user experience by reducing session transfer delay as well as traffic cost than Assured and Consultative session transfers.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.138-143
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• 2005

Finite Element analysis is widely applied to elevated temperature forging processes and shows a lot of information of plastic deformation such as strain, stress, defects, damages and temperature distributions. In highly elevated temperature deformation processes, temperature of material and tool have significant influence on tool life, deformation conditions and productivities. To predict temperature related properties accurately, adequate coefficients of not only contact heat transfer between material and dies but also convection heat transfer due to coolants are required. In most F.E analysis, too higher value of contact heat transfer coefficient is usually applied to get acceptable temperature distribution of tool. For contact heat transfer coefficients between die and workpiece, accurate values were evaluated with different pressure and lubricants conditions. But convection heat transfer coefficients have not been investigated for forging lubricants. In this research, convection heat transfer coefficients for cooling by emulsion lubricants are suggested by experiment and Inverse method. To verify acquired convection and contact heat transfer coefficients, tool temperature was measured for the comparison between measured tool temperature and analysis results. To increase analysis accuracy, repeated analysis scheme was applied till temperature of the tool got to be in the steady-state conditions. Verification of heat transfer coefficients both contact and convection heat transfer coefficients was proven with good accordance between measurement and analysis.

• 대한기계학회논문집B
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• 제20권2호
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• pp.720-729
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• 1996

An analysis of convective boiling heat transfer for refrigerant mixtures is performed for an annular flow to investigate the degradation of the heat transfer rate. Annular flow is selected in this study because a great portion of the evaporator in the refrigeration and air conditioning system is known to be in the annular flow regime. Mass transfer effect due to composition difference between liquid and vapor is included in this analysis, which is considered to be one of driving forces for the mass transfer at the interface. Due to the concentration gradient at the interface the mass transfer is interfered, so is the evaporative heat transfer at the interface. The mass transfer resistance makes the interface temperature slightly higher and, as a result, the heat transfer coefficients decrease compared with those without mass transfer effects. The degradatioin of the heat transfer rate reaches its maximum at a certain composition. The composition difference between vapor core and vapor at the interface has a direct effect on the temperature difference between the vapor core and the interface and the degradation of the heat transfer rate. Correction factor $C_{F}$ for the mixture effects is added to the correlation for pure substances and the flow boiling heat transfer coefficients can be calculated using the modified equation.n.

• 에너지공학
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• 제24권2호
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• pp.103-109
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• 2015

배열회수 보일러는 입구 확관 덕트와 전열관군으로 이루어져 있는데 전열관군에서 열전달 효율을 향상하기 위해서는 전열관군 전에서 배기가스 유동이 균일하게 되어야 한다. 본 연구에서는 전열관군 전의 배열회수 보일러 입구 덕트에서 유동 특성을 살펴보았고 전열관군의 열전달 메커니즘을 지금까지 다른 연구들에서 적용하였던 일정한 열전달 량으로 한 경우와 전열관군 배관의 내부와 외부의 대류열전달을 고려한 열전달 메커니즘을 적용한 경우의 해석에서 온도 분포를 비교하여 배열회수 보일러의 전열관군에서 실제 현상에 보다 적합한 열전달 메커니즘을 정립하는 것을 목적으로 하였다. 본 연구를 통하여 전열관군 배관의 내부와 외부의 대류열전달을 고려한 열전달 메커니즘을 적용한 해석이 일정한 열전달 량을 적용한 경우보다 온도 분포가 타당한 결과를 도출하였고 이렇게 적용한 경우는 배열회수 보일러 탈질설비 전단에서 온도 분포가 설계 기준 ${\pm}10^{\circ}C$에 만족함을 알 수 있었다.

• 벤처창업연구
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• 제7권1호
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• pp.165-175
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• 2012

최근 21세기 세계 경제가 지속적인 성장을 유지하기 위한 핵심요소로서 기술의 축적, 이전, 흡수, 상용화 등이 중요하게 인식되고 있으며, 정부는 공공연구기관에서 개발된 기술이 민간부문으로 이전되어 사업화되는 것을 촉진하고 민간부문에서 개발된 기술이 원활히 거래되고 사업화되는 것을 촉진하기 위해'기술의 이전 및 사업화 촉진에 관한 법률'을 마련했다. 또한 동 법률 제14조에서는 기술거래사의 등록 육성 및 지원에 관한 사항으로 '기술거래사' 자격제도를 도입하여 국가에서 등록, 운영, 관리하고 있으며 대부분의 선진국은 기술거래중개 기관을 민간에 이양하여 기술중개기관 또는 기술브러커로 지칭하고 있다. 국내에서는 이러한 자격제도 도입과 시장 활성화 촉진을 위한 다양한 조직과 기술중개시스템을 구축하였음에도 불구하고 기술거래사 등록제도와 사후관리에 대한 법률적 근거와 체계가 미흡하여 문제점이 발생되고 있다. 일례로 최근 기술거래관련 실적면제로 기술거래사 등록 활성화는 달성하였으나, 실적 검증을 통한 일정수준 이상의 전문가 선별에는 한계점이 나타나고 있다. 이에 경력증명서 기재 내용만으로 업무 경력 보유 여부를 판단하기에는 심사의 한계점이 드러나고 있어 이에 대한 대책이 시급하다. 또한 기술거래사 등록 시 의무적 교육이수제도가 2010년도에 법 개정 및 고시 개정으로 마련되었으나, 소양교육수준의 단기 교육과정 운영으로 신청자에게 다양한 전문지식 취득의 기회 제공이 어려움이 있는 것이다. 이에 본 연구에서는 한국과 중국의 기술거래사 제도 비교를 통해 기술거래사 제도개선에 대해 고찰해 보았다. 이를 통해 기술이전 사업화 시장 확대와 기술거래사 전문가의 업무영역 보장과 전문가로서의 입지확보 등 경쟁력을 강화하는데 활용될 수 있도록 개선안을 제시하였다.

• 한국도로학회논문집
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• 제3권3호
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• pp.147-158
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• 2001

콘크리트포장의 구조적 능력을 평가하는 가장 중요한 요소 중의 하나는 하중전달효과이다. 하중전달효과는 슬래브 상 하부 온도차, 다우월바 시공여부, 포장 노후도, 그리고 균열틈 등에 영향을 받는다. 본 연구의 목적은 콘크리트 포장의 하중전달효과 특성을 파악하고 하중전달효과에 영향을 주는 요소를 정량화하고 적절한 하중전달효과 조사방법을 제시하는 것이다. 연구결과 하중전달효과는 슬래브 표면온도가 아닌 슬래브 평균온도 영향을 받는 것으로 나타났다. 하중전달효과는 온도가 내려가고 균열틈이 벌어질수록 감소하는 것으로 나타났다. 다우월바를 시공한 구간의 경우 온도변화에 따라 하중전달효과는 큰 차이를 보이지 않은 반면, 다우월바를 시공하지 않은 구간에서는 온도가 내려갈수록 하중전달효과는 급격히 감소하였다. 다우월바를 시공한 구간이라도 포장이 노후화되면 하중전달효과는 온도가 하락함에 따라 감소하는 것으로 나타났다. 본 조사대상 구간에서는 슬래브 단위온도 하락시 하중전달효과는 1.4% 감소하는 것으로 나타났다.