• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.219-235
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• 2013

In order to investigate the changes in sea water characteristics and stratification due to operation of Shihwa tidal power plant, three dimensional numerical model is used. In summer, the density of inner part of Shihwa Lake is more affected by salinity than water temperature due to fresh water discharge. Before tidal power plant operation, the sea water characteristics in Shihwa Lake shows relatively high temperature and low salinity. After tidal power plant operation, water temperature decreases slightly and salinity tends to increase in Shihwa Lake. Also, density increases and stratification tends to weaken by mixing with sea water.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.258-263
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• 2006

ANAMMOX (Anaerobic ammonium oxidation) reactor, which was cultivated ANAMMOX bacteria in mesophilic condition ($35^{\circ}C$), was operated to investigate the effects of temperature. In $20{\sim}30^{\circ}C$ of operation condition, which was assumed as field-temperature, total N removal and $NH_4-N$ removal rate were declined from about 2.50 and $1.27kg\;N/{m^3}_{reactor}-day$ (0.06 and 0.03 kg N/kgVSS/day) to 1.62 and $0.41kg\;N/{m^3}_{reactor}-day$ (0.04 and 0.01 kg N/kgVSS/day), In this range of temperature, ANAMMOX had very low activities but acid fermentation bacteria and denitrifiers, which were competitors of substrates, had high activities relatively. Though operation temperature was higher than inhibition condition for two months, ANAMMOX activities could not been recovered once they were inhibited by low temperature. This fact was resulted from very slow doubling time of ANAMMOX bacteria. This study shows that maintenance device of optimal temperature is necessary required in field application of ANAMMOX.

• Journal of Conservation Science
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• v.29 no.4
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• pp.311-320
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• 2013

The showcase has insufficient temperature control, but it has excellent humidity control. The annual average temperature and relative humidity inside the showcase was $18.8^{\circ}C$ and 60.3%, respectively, and the showcase showed lower temperature and higher humidity than the exhibition room. The temperature inside the showcase appeared with high variation according to the seasons, while relative humidity was ranging from 59% to 61% regardless of the seasons. The showcase showed high temperature and humidity likewise the exhibition room in summer. In addition, lowering of temperature was elevated relative humidity according to the operation of air conditioner in summer. A moisture problem occurred because the temperature and humidity differences between the exhibition room and showcase were large according to the operation of air conditioner in winter. PI for temperature and relative humidity inside the showcase is 18.0%, and it means conservation environment for exhibition is unsuitable. In particular, continuous management of temperature and humidity inside the showcase is required because PI in the summer and winter is less than 1.0%.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.17-25
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• 2017

Recently, research and application for a power module have been actively studied according to the increasing demand for the production of vehicles, smartphones and semiconductor devices. The power modules based on the transient liquid phase (TLP) technology for bonding of power semiconductor devices have been introduced in this paper. The TLP bonding has been widely used in semiconductor packaging industry due to inhibiting conventional Pb-base solder by the regulation of end of life vehicle (ELV) and restriction of hazardous substances (RoHS). In TLP bonding, the melting temperature of a joint layer becomes higher than bonding temperature and it is cost-effective technology than conventional Ag sintering process. In this paper, a variety of TLP bonding technologies and their characteristics for bonding of power module have been described.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.70-75
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• 2008

This paper describes a tool-clamping/unclamping mechanism for application of a micro-spindle. The mechanism is based on one-way shape memory effect and interference-fit. The corresponding mathematical models and a few considerable design parameters are mentioned in this paper. Especially, necessary conditions for the clamping and unclamping operation are investigated through finite element analysis. The analysis results show that the differences between the diametral deformations of the tool holder in high temperature and that in low temperature are increased according to amounts of the interference. Thus the less interference between the tool-holder and the ring, the less tolerance to allow the clamping and unclamping operation because the inner diameter of the tool holder in high temperature should be smaller than the diameter of the tool shank, and that in low temperature should be larger than the diameter of the tool shank. In addition, the design for maximization of clamping force are investigated based on finite element analysis. The results show that the more amounts of the interference, the more clamping force. As the result, the interference should be considered as a important factor to maximize the tool clamping force.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.50-60
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• 2013

High temperature proton exchange membrane fuel cells (PEMFCs) using phosphoric acid (PA) doped polybenzimidazole (PBI) membranes have been concentrated as one of solutions to the limits with traditional low temperature PEMFCs. However, the amount of reported experimental data is not enough to catch the operational characteristics correlated with cell performance and durability. In this study, design of experiments (DOE) based operational optimization method for high temperature PEMFCs has been proposed. Response surface method (RSM) is very useful to effectively analyze target system's characteristics and to optimize operating conditions for a short time. Thus RSM using central composite design (CCD) as one of methodologies for design of experiments (DOE) was adopted. For this work, the statistic models which predict the performance and degradation rate with respect to the operating conditions have been developed. The developed performance and degradation models exhibit a good agreement with experimental data. Compared to the existing arbitrary operation, the expected cell lifetime and average cell performance during whole operation could be improved by optimizing operating conditions. Furthermore, the proposed optimization method could find different new optimal solutions for operating conditions if the target lifetime of the fuel cell system is changed. It is expected that the proposed method is very useful to find optimal operating conditions and enhance performance and durability for many other types of fuel cell systems.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1992.11a
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• pp.35-38
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• 1992

The feasibility of magnetohydrodynamic (MHD) Ship propulsion using superconduction magnets is reviewed in light of recent advances in high-temperature superconducting. The propulsion using a screw propeller in the noise reduction has it's own limitation. The epochal noiseless MHD propulsion method which does not have this disadvantage is studying nowadays. The subject of a marine MHD as propulsion has been examined before and was found to be interesting because of relatively low magnetic flux densities. It is demonstrated that the MHD propulsion is technically interesting with high magnetic flux density. The development of large-scale magnets using the high-temperature superconductors now under development could make it practical to construct submersibles for high-speed and silent operation.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.307-310
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• 2016

The operational cost for maintaining the superconductivity of high-temperature superconducting (HTS) cables needs to be reduced for feasible operation. It depends on factors such as AC loss and heat transfer from the outside. Effective operation requires design optimization and suitable operational conditions. Generally, it is known that critical currents increase and AC losses decrease as the operational temperature of liquid nitrogen ($LN_2$) is lowered. However, the cryo-cooler consumes more power to lower the temperature. To determine the effective operational temperature of the HTS cable while considering the critical current and AC loss, critical currents of the HTS cable conductor were measured under various temperature conditions using sub-cooled $LN_2$ by Stirling cryo-cooler. Next, AC losses were measured under the same conditions and their variations were analyzed. We used the results to select suitable operating conditions while considering the cryo-cooler's power consumption. We then recommended the effective operating temperature for the HTS cable system installed in an actual power grid in KEPCO's 154/22.9 kV transformer substation.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1515-1518
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• 2007

We demonstrate a high color gamut liquid crystal display (LCD) system (>100 %) by using a precompensated tri-chromatic LED-backlight module over a temperature range of (25 to $70^{\circ}C$), whose pre-compensated optical characteristic balances the spectral redshift and intensity decrease due to the temperature rising during operation.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.653-657
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• 2005

The commercial contract was made firstly in the world for one set of high temperature superconducting(HTS) cable system between buyer, Korea Electric Power Research Institute and seller, Sumitomo Electric Industries, Ltd. in August 2004. After fabrication, test and examination, the HTS cable system will be installed at the KEPRI's test field in Gochang, Jeonbuk province from the time of July 2005. KEPRI is preparing measurement and test facilities for field test of the HTS cable system and carrying out researches into the design and construction of superconducting cable test building, evaluation of cooling performance, measurement of AC loss, analysis of the quench phenomena due to excess current and means of linking the HTS cable system to the existing electric power supplying system. The constitution of, the method to install and the plan of test operation of the HTS cable system will be presented in this paper.