• Proceedings of the KWS Conference
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• 2009.11a
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• pp.221-225
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• 2009

A solar thermal collector is a solar collector specifically intended to collect heat: that is, to absorb sunlight to provide heat. A flat plate is the most common type of solar thermal collector, and is usually used as a solar hot water panel to generate solar hot water. A flat plate collector consists basically of an insulated metal box with a glass or a plastic cover and a dark-colored copper absorber plate. Solar radiation is absorbed by the copper absorber plate and transferred to water that circulates through the collector in copper tubes. Ultrasonic welding is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to work pieces being held together under pressure to create a solid-state weld. In this study, we developed solar collector ultrasonic welding machine with digital controlled power supply and tested various welding conditions such as welding pressure, welding amplitude, welding speed. Welding speed was considered in 2~12m/min. The width of ultrasonic welds was increased with welding amplitude by 2.2~2.5mm. The fracture load of ultrasonic welds showed 20% higher than domestic products.

• Journal of Biosystems Engineering
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• v.26 no.5
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• pp.441-448
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• 2001

Hot air heater with light oil combustion is used as the most common heater for greenhouse heating in the winter season. However, exhaust gas heat discharged to atmosphere through chimney reaches up to 10~20% of total heat capacity of the oil burred. In order to recover the heat of this exhaust gas and to use for greenhouse heating, the heat pipe type exhaust heat recovery system was manufactured and tested in this experiment. The system consisted of a heat exchanger made of heat pipes, ø15.88${\times}$600mm located in the rectangular box of 675(L)${\times}$425(W)${\times}$370(H)mm, an air suction fan and air ducts. The number of heat pipe was 60, calculated considering the heat exchange amount between exhaust gas and air and heat transfer capacity of a heat pipe. The working fluid of heat pipe was acetone because acetone is known for its excellent heat transfer capacity. The system was attached to the exhaust gas path. According to the performance test it could recover 53,809 to 74,613kJ/h depending on the inlet air temperature of 12 to -12˚at air flow rate of 1.100㎥/h. The temperature of the exhaust gas left the heat exchanger dropped to 100$^{\circ}C$ from 270$^{\circ}C$ after the heat exchange between the suction air and the exhaust gas.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2597-2602
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• 2007

In this paper, the performance analysis is experimentally carried out in order to select the best cooling fan and shroud considering both cooling performance and noise reduction. 4 cooling fans have been tested in the fan tester and the real excavator. In order to obtain the performance of the cooling fans, flow capacity has been estimated by measuring flow velocity using a hot wire anemometer, and noise radiation has been also measured to estimate the fan noise. Characteristics of a box-type and a streamlined shroud have been examined by changing the immersion depth of cooling fans. Based upon the results, the best cooling fan is selected. Finally, the criterion to select the best cooling fan has been set up.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.1
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• pp.54-60
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• 1994

In this paper, we present the analytical models for the change of the lateral electric field distribution and the velocity saturation region length with the electron trapping of stressed SC-PMOSFET in the saturation region. To derive the hot-electron-induced lateral electric field of stressed SC-PMOSFET. Ko's pseudo two dimensional box model in the saturation region which illustrates the analysis of the velocity saturation region is modified under the condition of electron trapping in the oxide near the drain region. From the results, we have the following lateral electric field in the y-direction, that is, E(y) ES1satT.cosh(y/l) qNS1tT.sinh(y/l)/lCox. It is shown that the trapped electrons influence the field in the drain region. decreasing the lateral electric field. Calculated velocity saturaion length increases with the trapped electrons. increasing the drain current of stressed SCPMOSFET. This results well explain the HEIP phenomenon of PMOSFET's.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.249-252
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• 1997

Mini-mill process which is one of the new steel making process to be able to produce the hot rolled strip by thin slab caster, was completed in the kwangyang steel work. The new process was constructed liquid core deduction, tandem reduction unit, induction heater, coil box and finishing mill to be varied width. Therefore, in oder to make sure of target strip width, analysis of actual plant data was done to fine out amount of width deviation. Finally, the predication system of width in the mini-mill process was developed to included temperature caculation model.

• Journal of Electrochemical Science and Technology
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• v.6 no.1
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• pp.26-33
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• 2015

In this study, cell performance and thermal stability of lithium-ion cells with a polyimide (PI) separator are investigated. In comparison to conventional polyethylene (PE) separator, the PI separator exhibits distinct advantage in microporous structure, leading to superior reliability of the cell. The cells with PI separator exhibit good cell performances as same as the cells with PE separator, but their reliability was superior to the cell with PE separator. Especially in the hot-box test at 150 and 180℃, PI separator showed a contraction percentage close to 0% at 150℃, while the PE separator showed a contraction percentage greater than 10% in both width and length. Therefore, the PI separator can be the promising candidate for separators of the next generation of lithium-ion battery.

• Proceedings of the Safety Management and Science Conference
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• 2012.04a
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• pp.233-243
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• 2012

HBD(Hot Box Detector) is a device to monitor temperature rises to inappropriate lubricant use or mechanical defects. If a train operates without recognizing such an effect, it might result in bearing overheating due to defects and cause a dangerous situation that it could derail a train owing to the damage of axles. Now for the Gyeongbu HSL at 300km/h, the laws related to monitoring overheated axle bearings are notified in the Railway Safety Law and the Railway Construction Law. But in case of the conventional speed-up lines that a train operates at 180 to 230 km/h, the revised bill of relevant standards is ongoing. Therefore in this paper we present references and reviews investigated in order to use the optimal HBD in the conventional speed-up lines.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1193-1194
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• 2007

2004년 경부고속철도가 개통된 이후, 열차제어시스템에 있어서 크고 작은 여러 가지 문제점이 시스템의 안정화를 위한 초기 단계의 형태로서 발생되었다. 특히 국내에서 처음으로 열차가 300km/h로 운행됨에 따라, 열차의 고속 운행 환경에 대한 운영 및 유지보수의 어려움이 자주 유발되었다. 한 예로 2005년에는 서울에서 약 170km 남쪽에 위치한 칠곡 신호기계실(IEC) 지역에 설치된 선로변 설비인 HBD의 오동작이 발생됨에 따라 관련 설비에 대한 신뢰성은 물론 설비의 기능상의 문제점까지 전면적인 검토를 필요로 하였다. 본 논문에서는 고속선 운영 및 유지보수에 있어서 선로변 설비의 장애 원인을 조사, 분석, 검토함으로서 고속선 열차제어시스템 HBD에 대한 안정적인 운영 및 유지보수를 구현하기 위한 방안 제시를 주요 목적으로 한다.

• Journal of the Korean Society of Clothing and Textiles
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• v.36 no.1
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• pp.1-11
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• 2012

This paper reports on a prototype cooling garment applying a cooling module. The cooling module was composed of a Peltier device, a cold sink, a heat sink and two fans. A constant box was used to evaluate the cooling effect of the module. Two cooling modules were attached on each side of the garment. The wear trial was conducted using 10 male subjects in an environmental chamber maintained at $30{\pm}0.5^{\circ}C$, $50{\pm}5%$RH. Subjective sensations of thermal, humidity, and comfort were surveyed. Statistical package SPSS12.0 was used for the t-test and the Wilcoxon signed-rank test. The results showed that most effective cooling module decreased the temperature of the constant temperature box by $-4.9^{\circ}C$. The micro-temperature of the cooling garment with a Peltier device was lower than the control garment during the exercise. In particular, the chest skin temperature was $1.5^{\circ}C$ lower with the cooling garment than the control. The maximum temperature difference was $-2.57^{\circ}C$ on the sides of the $1^{st}$ layer. Subjective thermal sensation from wear trials of the Peltier device attached garment was lower than the control garment. Subjects felt more comfortable with the cooling garment in almost all the periods.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.111-119
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• 2007

The annual mean temperature of South Korea has risen by $1.3^{\circ}C$ for last 100 years by urbanization and industrialization. Especially, the frequency of unusual hot weather in summer increases for a long time and the frequency of unusual cold weather in winter clearly decreases. In recently, The considerable portion of curtain wall system is appled to building skin in domestic. As related to this, the Korea Institute of Construction Technology devised the box typed double skin facade(It is occasionally called as FDFS : Functional Double Facade System) as an alternative that reflects the distinctive local climate and saves cooling energy. Two mock-ups($49m^*4.9m$) applied to single skin(curtain wall) and double skin each were monitored under the outdoor condition. Therefore, the characteristics of natural ventilation and cooling energy consumption of each window had been analyzed in real time. The results of this study are summarized as follow, Analysis of the experiment on an air conditioner: the indoor temperature of the chamber with FDFS is lower than that of the chamber with single skin facades by $3{\sim}6$ degrees(C). A temperature variation of about $1{\sim}2$ degrees between the 0.2m and 1.7m height of the mock-up occurs in FDFS, while that of about maximum 7 degrees occurs in single skin facade at noon with abundant intensity of solar accident. Also, 67 percent of energy consumption for air conditioning has been saved.