• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.44-49
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• 2009

In this study, we performed urrban climate simulation how both the factor of environmental land and artificial factors influence on the formation of urban temperature. With deducing quantitative data, this study could get more accurate results of the urban temperature using urban climate simulation system. In the case of natural land cover, it appeared that there are effects on the lowering temperature and the lower temperature rate appeared in the water land cover on the whole. This is considered as temperature in water land was low because of the characteristics of water land having evaporation latent heat was high and convective sensible heat was low. In case of building which has building coverage ratio, 5% with 10 floors and building coverage ratio, 15 % with 6 floors, it appears that the temperature in the water land is $33.6^{\circ}C$. In case of building coverage ratio 5%, temperature dropped when buildings has more than 4 stories. This is regarded as the size of building is bigger, the temperature dropped in relatively because of the fluctuation of the rate of solar heat from the land. At the present time, the urban temperature are higher because of various artificial factors in the city. With these results, this study supposed to be a basies of the future studies for considering both the composition of building coverate ratio and floor plan.

• Journal of Biosystems Engineering
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• 제2권2호
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• pp.37-45
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• 1977

Solar energy is a potential source of power that offers much promise being used for low-temperature applications like drying farm crops, space heating, and water heating for domestic uses. Already much of it are being used for those purpose in foreign countries. However, very little research has been done to determine the possibility of using the solar energy in Korea. This study was conducted to develop the general prediction equation of the total radiation on a horizontal surface in Daejeon area based on 5 years 91972, Jun.1-1976. Dec.31) meteorological data (bright sunshine hours, average total horizontal radiation), and to obtain experimentally the thermal efficiency of solar air and water collectors, which will be used as a basic data of designing flat-plate solar collector system.In addition to the thermal efficiency of the collectorsthe relationship among those factors affecting it such as weather condition, orientation factor, and tilted angle of collector was analyzed. The results of this study were as follows. 1. The general predicted equation of the total radiation on a horizontal surface in Daejeon area based on bright sunshine hours was developed as $H_{av} =(1.546\frac{n}{N}-0.582)H_o$. Predicting the total radiation on a horizontal surface by the above equation was thought to be possible because to values of 0.882 was smaller than any t values at above 0.05 level on the basis of two tailed test of the difference between the calculated and the recorded values. 2.It was observed that optimum tilt angle of the collector in the summer and the autumn drying season was 13 degrees and 51 degrees respectively, these values could be obtained by adding or substracting approximately 25 degrees from the latitude of this area $(36.3^{\circ}N)$ .The relationship between orientation factor and declination of sun at suitable tilt angle of 33 degrees $(s=0.9\O)$ was shown at Fig.4. 3.The thermal efficiency of solar wdter collector was shown 13.4-51. 6% on Aug. 15 (the minimum radiation recorded) and 43.8 ~537% Aug.20 (the maximum radiation recorded), and 13.8~ 46.6 and 44.3~ 49.7 were shown on each corresponding day. 4.The thermal efficiency of the collectors according to the weather condition was shown a big difference of about 10% between the day of the maximum radiation recorded and the minimum, but the differen of efficiency between the air and the water collector was at most 2 ~ 3%. 5. Even if the efficiency of the solar water collector was a little higher than the solar air collector, for drying farm products, the solar air collector was thought to be more effective because the air heated by collector could be directly used for drying them.

• Current Photovoltaic Research
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• 제1권2호
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• pp.115-121
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• 2013

ZnO film has been used for CIGS solar cells as a buffer layer as itself or by doping Mg and Sn; ZnO film also has been used as a transparent conducting layer by doping Al or B for solar cells. Since ZnO itself is a host material for many applications it is necessary to understand the electrical and optical properties of ZnO film itself with various preparation conditions. We prepared ZnO films by converting ZnS precursor into ZnO film by thermal annealing. ZnO film was formed at low temperature as low as $500^{\circ}C$ by annealing a ZnS precursor layer in air. In the air annealing, the electrical resistivity decreased monotonically with increasing annealing temperature; the intensity of the green photoluminescence at 505 nm increased up to $750^{\circ}C$ annealing. The electrical resistivity further decreased and the intensity of green emission also increased in reducing atmospheres. The results suggest that deep-level defects originated by oxygen vacancy enhanced green emission, which reduce light transmittance and enhance the recombination of electrons in conduction band and holes in valence. More oxidizing environment is necessary to obtain defect-free ZnO film for higher transparency.

• 한국제4기학회지
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• 제24권2호
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• pp.1-11
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• 2010

지표 특성 차이에 따라 외부강제력에 대한 차별적인 반응을 보이는 지표 평형온도 분포를 실험하기 위해 에너지 균형 모형(Energy Balance Model, EBM)이 사용되었다. EBM은 입사되는 복사에너지가 각 위도별로 수송되는 에너지와 방출되는 복사에너지의 합과 균형을 이루었을 때의 온도를 산출한다. 지구의 에너지 원천인 태양복사에너지를 전지구 에너지 균형에 있어 중요하게 취급하기 위하여 위도별 알베도 변화뿐만 아니라 해륙의 분포 차이에 따른 에너지 균형을 고려한 지구 평형온도 분포에 관한 실험이 수행되었으며, 입사되는 태양복사에너지량을 강제력으로 하여 위도별 알베도의 선형적인 증감, 극지역 알베도의 5%, 10%, 15% 증감에 대한 반응, 극과 중위도 지역에서의 상반된 증감에 대한 반응을 실험하였다. 그리고 얼음-알베도 피드백의 유무에 대한 실험도 수행되었다. 극지역의 알베도를 증가시키면 입사되는 태양에너지를 차단시켜 위도별 열수송을 감소시키는데 이는 극지역을 저에너지 상태로 유지시킴으로써 저위도에서부터의 에너지 수송을 강화시킨다. 이러한 수송량의 차이로 인해 중위도 지역의 온도 변화는 극지역에 비해 크게 나타난다. 육지는 해양에 비해 열용량이 작기 때문에 평형온도에 도달하는 시간이 짧으며 알베도에 따른 온도변화에 민감하여 해양과의 온도차이를 유발시킨다. 따라서 평형온도는 지표가 가지는 특성인 알베도와 열용량의 차이에 따라 다르게 나타나며 알베도가 증가함에 따라 감소하고 열용량이 작을수록 변화율이 큰 특징이 있다. 얼음-알베도 피드백은 알베도의 선형적인 증가에 따른 지구 평형온도의 감소를 가속화시키지만 국지적으로는 비선형적인 감소를 보인다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.913-914
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• 2006

Amorphous diamond has a very low work function (1 eV) at modest temperature ($150^{\circ}C$). It has been coat coated on electron emitting electrodes. Such electrodes are used for cold cathode fluorescence lamps (CCFL) that illuminate liquid crystal displays (LCD) for rnote books and television sets. Amorphous diamond can dramatically reduce the turn-on voltage to lit CCFL so the lamp life can be greatly extended. Moreover, the electrical current can be increased to enhance the brightness of the light.

• 한국태양에너지학회 논문집
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• 제24권1호
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• pp.7-12
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• 2004

Mixtures type PCM, $H_2O$-NaOH that has relatively large capacity of the latent heat and long duration of phase change temperature was developed and experimentally analyzed for the low temperature storage of the food and medical products. The results could be summarized as follows; 1. Borax as nucleating agent and acrylic polymer as thickening agent were added to $H_2O$ to prevent the supercooling and phase separation. 2. Phase change (solid$\leftrightarrows$liquid) duration of $H_2O$ added with NaOH was prolonged longer 50% than that of pure $H_2O$. 3. Phase change temperature of the latent heat material, $H_2O$-NaOH was $1.5\sim2^{\circ}C$ the maximum latent Heat was 279 kJ/kg at the NaOH addition of 1.3 wt.%. 4. The specific heat of $H_2O$-NaOH at the solid and liquid state was increased in proportion to the wt.% of NaOH, when NaOH of $1.15\sim1.60$ wt.% was added to $H_2O$, the specific heat of the solid state was increased from 3.19 kJ/kg to 5.84 kJ/kg and that of liquid state from 7.8 kJ/kg to 10.28 kJ/kg. 5. When NaOH of $1.15\sim1.60$ wt.% was added to $H_2O$, the total heat storage capacity composed of sensible and latent heat was $313\sim331.3$ kJ/kg and the maximum heat storage capacity was occurred at NaOH addition of 1.30 wt. %.

• 한국유체기계학회 논문집
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• 제18권4호
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• pp.13-21
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• 2015

The system design of the Organic Rankine Cycle(ORC) is greatly influenced by the thermal properties such as the temperature or the thermal capacity of heat source. Typically waste heat, solar energy, geothermal energy, and so on are used as the heat source for the ORC. However, thermal energy supplying from these kinds of heat sources cannot be provided constantly. Hence, an experimental study was conducted to utilize fluctuating thermal energy efficiently. For this experiment, an impulse turbine and supersonic nozzles were applied and the supersonic nozzle was used to increase the velocity at the nozzle exit. In addition, these nozzles were used to adjust the mass flowrate depending on the amount of the supplied thermal energy. The experiment was conducted with maximum three nozzles due to the capacity of thermal energy. The experimented results were compared with the predicted results. The experiment showed that the useful output power could be producted from low-grade thermal energy as well as fluctuating thermal energy.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.402-408
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• 2011

Organic Rankine cycles (ORC) can be used to produce power from heat at different temperature levels available as geothermal heat, as biogenic heat from biomass, as solar or as waste heat. In ORC working fluids with relatively low critical temperatures and pressures can be compressed directly to their supercritical pressures and heated before expansion so as to obtain a better thermal match with their heat sources. In this work thermal performance of ORC with and without an internal heat exchanger is comparatively investigated in the range of subcritical and transcritical cycles. R134a is considered as working fluid and special attention is paid to the effect of turbine inlet pressure on the characteristics of the system. Results show that operation with supercritical cycles can provide better performance than subcritical cycles and the internal heat exchanger can improve the thermal efficiency when the temperature of heat source becomes higher.

• 한국태양에너지학회 논문집
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• 제34권5호
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• pp.43-52
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• 2014

A plant factory system is getting the spotlight as alternatives to cope with the weather anomaly and food crisis because of the global warming. A study on 'Plant Processing Factory System' has been proceeded to develope 'low-carbon green growth' since our government selected it as the green technologies in 2010. The plant factory has played a major role in growth industries connected to many other fields like low-carbon as well as lighting and automated system. This study is aimed to solve the problems on low productivity and health problem of plant workers caused by highly concentrated carbon dioxide and low temperature in each process in the plant factory. It is aimed to research data to understand the actual conditions of plant workers and improve the thermal environment.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.229-234
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• 2002

Under the hostile influence of the extreme space environmental conditions due to the deep space and direct solar flux, the thermal control in space applications is especially of major importance. There are tight temperature range restrictions for electro-optical elements while on the other hand there are low power consumption requirements due to the limited energy sources on the spacecraft. So, we usually have strong requirement of thermal and power control module in space applications. In this paper, the design concept of a thermal and power control module in the MSC(Multi-Spectral Camera) system which will be a payload on KOMPSATII is described in terms of H/W & S/W. This thermal and power control module, called THTM(Thermal and Telemetry Module) in MSC, resides inside the PMU(Payload Management Unit) which is responsible for the proper management of the MSC payload for controlling and monitoring the temperature insides the EOS(Electro-Optic System) and gathering all the analog telemetry from all the MSC sub-units, etc. Particularly, the designed heater controller has the special mode of "duty cycle" in addition to normal closed loop control mode as usual. THTM controls heaters in open loop according to on/off set time designed through analysis in duty cycle mode in case of all thermistor failure whereas it controls heaters by comparing the thermistor value to temperature based on closed loop in normal mode. And a designed THTM provides a checking and protection method against the failure in thermal control command using the test pulse in command itself.