• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.175-179
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• 2007

This experimental demonstration has successfully shown that it is possible to use direct sunlight for the illumination of deeper building zones using the material for light path system(light duct). Three kinds of reflectors which were 95% Silver vaporizing fixed, 85% Anodized and 85% Hot melted applied to evaluate and compare their performances each others. Also, these three kind of reflectors were compared in view point of economics. The most high performance was obtained in 95% Silver vaporizing fixed reflector hater than another reflectors of 85% Anodized reflector and 85% Hot melted reflector even though more high production cost in 95% Silver vaporizing fixed reflector. The rest two reflectors of 85% Anodized and 85% Hot melted $10{sim}15%$ less performance than 95% Silver vaporizing fixed reflector but their production cost were low than the production cost of 95% Silver vaporizing fixed reflector which identified very weak and light yellow color in the light.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.898-906
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• 2017

This paper discusses the efficient high fidelity calculation of external thermal loads of a spacecraft on its orbit. Thermal loads to a spacecraft consist of three major components, direct solar radiation, earth reflection of solar rays, and earth irradiation. With the assumption that both earth reflection and earth emission are diffuse, thermal loads from earth surface divided into pieces of segments to satellite surfaces are individually calculated and summed over. By using analytical integration of both reflected and emitted heat load by earth, high rate of numerical convergence is achieved and the results are even exactly calculated in special cases. Moreover, KD tree ray tracing is employed in the calculation of thermal load to determine whether the radiated ray is obstructed or not by satellite structure.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.154-156
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• 2008

A prototype of the desiccant cooling system with a regenerative evaporative cooler was built and tested for the performance evaluation. The regenerative evaporative cooler is to cool a stream of air using evaporative cooling effect without an inc6rease in the humidity ratio. It is comprised of multiple pairs of dry and wet channels and the evaporation water is supplied only to the wet channels. By redirecting a portion of the air flown out of the dry channel into the wet channel, the air can be cooled down to a temperature lower than its inlet wet-bulb temperature at the outlet end of the dry channels. Incorporating a regenerative evaporative cooler eliminates the need for deep dehumidification in the desiccant rotor that is necessary to achieve low air temperature in the system with a direct evaporative cooler. Subsequently, the regenerative evaporative cooler enables the use of low temperature heat source to regenerate the dehumidifier permitting the desiccant cooling system more beneficial compared with other thermal driven air conditioners. At the ARI condition with the regeneration temperature of $60^{\circ}C$, the prototype showed the cooling capacity of 4.4 kW and COP of 0.75.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.698-701
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• 2007

DAHAN, the first 1 MWe Solar Power Tower system locates north to Beijing where nearby The Great Wall is now under construction with cooperation between China and Korea. Results in predicting the preliminary performance of this central receiver system are presented in this paper. Operating cycles under some typical weather condition days are simulated and commented. These results can be used to assess the impact of alternative plant designs or operating strategies on annual energy production, with the final objective being to optimize the design of central receiver power plants. Two subsystems are considered in the system simulation: the solar field and the power block. Mathematic models are used to represent physical phenomena and relationships so that the characteristics of physical processes involving these phenomena can be predicted. Decisions regarding the best position for locating heliostats relative to the receiver and how high to place the receiver above the field constitute a multifaceted problem. Four different kinds of field layout are designed and analyzed by the use of ray tracing and mathematical simulation techniques to determine the overall optical performance ${\eta}_{field}$ and the spillage ${\eta}_{spill}$.The power block including a Rankine cycle is analyzed by conventional energy balance methods.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.190-195
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• 2008

The objective of this research is to determine overall heat transfer coefficients (K-value) of exterior wall, floor, and roof of Nakseonjae, a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope component. Heat flow sensors and T-type thermocouple were attached on the internal and the external surface of each building component, and real-time measurement data were collected for the three consecutive summer days. The K-values determined in this research showed good agreement with other results from open literature. Peak and annual thermal loads of the traditional residence estimated by a commercial energy simulation program were compared with those for a current apartment house. The traditional house showed lower annual cooling load than that of the current building. It may caused by the fact that the traditional building has less air-tight envelopes and no fenestration passing direct solar radiation into the space.

• Journal of Environmental Science International
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• v.20 no.8
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• pp.1061-1068
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• 2011

Evapotranspiration is one of the important elements related water cycle and there is many kind of measurement method of evapotranspiration today. This study developed mini lysimeter for the purpose of direct measurement of evapotranspiration and installed on 5th, July, 2010 at the field of MRI which located at Tsukuba, Ibaraki, Japan for continuous measurement and understand relation between evapotranspiration and meteorological elements expecially radiation elements. And compared the evapotranspiration data of lysimeter with Bowen Ratio Method. The result of this study is as follows; There is high related with solar radiation and evapotranspiration with $R^2$=0.947. and 46 % of solar radiation converted into evapotranspiration during clear 5 days. In net radiation also highly related with evapotranspiration, we can derive evapotranspiration is mainly controlled by radiation energy in clear days. From the 104 days data, there is only 9 % difference between Bowen Ratio Method and evapotranspiration of lysimeter which was developed from this study is very useful to estimate evapotranspiration at field site with simple and high accuracy. High accuracy and resolution measurement of evapotranspiration by lysimeter can give a chance further study of meteorological phenomena of on ground expecially in night time condensation which means abnormal energy flow.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.392-398
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• 2020

Producing solar grade silicon using an inexpensive method is a key factor in lowering silicon solar cell costs; the direct electrochemical reduction of SiO₂ in molten salt is one of the more promising candidates for manufacturing this silicon. In this study, SiO₂ granules were electrochemically reduced in molten CaCl₂ (850℃) using Ag-Si eutectic droplets that catalyze electrochemical reduction and purify the Si product. When Ag is used as the working electrode, the Ag-Si eutectic mixture is formed naturally during SiO₂ reduction. However, since the Ag-Si eutectic droplets are liquid at 850℃, they are easily lost during the reduction process. To minimize the loss of liquid Ag-Si eutectic droplets, a cylindrical graphite container working electrode was introduced and Ag was added separately to the working electrode along with the SiO₂ granules. The graphite container working electrode successfully prevented the loss of the Ag-Si eutectic droplets during reduction. As a result, the Ag-Si eutectic droplets acted as stable catalysts for the electrochemical reduction of SiO₂, thereby producing one-dimensional Si rods through a mechanism similar to that of vapor-liquid-solid growth.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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• pp.203-210
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• 2015

This paper investigates the failure of a car with a 2.5-liter CRDi engine of the Hyundai Company. The failure is caused by intermittent poor acceleration while driving. To analyze the cause, we investigated the air intake volume, the fuel injection, and the air-fuel ratio, which were determined to be normal. The brake switch signal error was discovered while analyzing the function that limits the output of the engine. While investigating the cause, we discovered the corrosion of the pins on the connector of the brake switch. We determined that it was generated by soapy water flowing in the solar film. Therefore, the cause of the failure was the brake switch signal errors. Additionally, we determined that ECM was the normal fail-safe mode that implemented the override device for safety during normal acceleration. Based on these results, further solar film experiments must be conducted to fully elucidate the causes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.253-253
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• 2011

ZnTe semiconductor is very attractive a material for optoelectronic devices in the visible green spectral region because of it has direct bandgap of 2.26 eV. The prototypes of ZnTe light emitting diodes (LEDs) have been reported [1], showing that their green emission peak closely matches the most sensitive region of the human eye. The optoelectronic properties of ZnTe:O film allow to expect a large optical gain in the intermediate emission band, which emission band lies about 0.4-0.6 eV below the conduction band of ZnTe [2]. So, the ZnTe system is useful for the production of high-efficiency multi-junction solar cells [2,3]. In this work, the ZnTe:O thin films were deposited on Al2O3 substrates by using the radio frequency magnetron sputtering system. Three sets of samples were prepared using argon and oxygen as the sputtering gas. The deposition chamber was pre-pumped down to a base pressure of 10-7 Torr before introducing gas. The deposition pressure was fixed at 10-3 Torr throughout this work. During the ZnTe deposition, the substrate temperature was 300 oC. The optical properties were also investigated by using the ultraviolte-visible (UV-Vis) spectrophotometer.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.401-401
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• 2011

In this work, we deposited Al2O3doped ZnO (AZO) thin films by direct current (DC) magnetron sputtering method with a $40^{\circ}$ tilted target, for application in the front layer of thin film solar cell. Wet chemical etching behavior of AZO films was also investigated. In order to optimize textured AZO films, oxalic acid ($C_2H_2O_4$)has been used as wet etchant of AZO film. In this experiment we used 0.001% concentration of oxalic acid various etching time, that showed an anisotropy in etching texture of AZO films. Electrical resistivity, Hall mobility and carrier concentration measurements are performed by using the Hall measurement, that are $6{\times}10^{-4}{\Omega}cm$, $20{\sim}25cm^2/V-s$ and $4{\sim}6{\times}10^{20}$, respectively.