• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.1051-1059
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• 2004

Two phase thermosyphone loop for electronics cooling are designed and manufactured to test its performance under the partial load and low environment temperature conditions. The thermosyphone device has six evaporators connected parallel for the purpose of cooling six power amplifier units (PAU) independently. The heater modules for simulating PAUs are adhered with thermal pad to the evaporator plates to reduce the contact resistance. There are unbalanced distributions of liquid refrigerant in the differently heated evaporators due to the vapor pressure difference. To reduce the vapor pressure differences caused by partial heating, two evaporators are connected each other using the copper tube. The pressure regulation tube successfully reduces these unbalances and it is good candidates for a field distributed systems. Under the low environment temperature operating condition, such as $-30^{\circ}C$, there may be unexpected subcooling in condenser. It leads the very low saturation pressure, and under this condition there exists explosive boiling in evaporator. The abrupt pressure rise due to the explosive boiling inhibits the supplement of liquid refrigerant to the evaporator for continuous cooling. Finally the cooling cycle will be broken. For the normal circulation of refrigerant there may be an optimum cooling air flow rate in condenser to adjust the given heat load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.11
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• pp.760-766
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• 2008

The characteristics of heat transfer and pressure drop of several different porous materials which can be used as inserts inside solar volumetric air receivers were experimentally investigated. Generally, porous materials were inserted into solar volumetric air receivers to increase the thermal performance. In the present work, honeycomb (diameter: 100 mm, thickness: 30 mm), laminated mesh (diameter: 100 mm, thickness: 1 mm) are considered as the inserts for the experiment. The experimental apparatus consists mainly of a cylindrical ceramic duct as a receiver and an electric heater as an energy source. This system is an intake open loop, which used as air of working fluid. The temperatures inside the ceramic tube are measured by thermocouples, which are installed at each layer of the porous materials. The pressure-drop experimental apparatus is fabricated alike the above experimental equipment. An acrylic tube is used like as the ceramic tube, which has the same specifications of the ceramic tube. The pressure drop of porous materials inserted in the acrylic tube is measured between front and rear of those by transmitter. The results show that the laminated mesh surpasses the honeycomb of heat transfer and pressure drop increase as the porous material thickness and Reynolds number.

• Journal of the Korea Safety Management & Science
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• v.20 no.3
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• pp.27-36
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• 2018

The steel pipe manufacturing industry deals with facilities and materials. Especially thermal facilities are close to vapor cloud explosion (VCE) and may cause secondary damage to facilities because they deal with corrosive substances such as hydrofluoric acid, sulfuric acid and acid, fire, explosion, leakage etc. It is in danger. In this study, hazard identification method was conducted using HAZOP techniques and quantitative risk analysis was conducted using e-CA, a program that supports accident impact analysis. Equipment in the influence range of ERPG - 3 was determined to be a facility requiring replacement. It was decided that neutralization is necessary using slaked lime. Based on the cost of loss, We presented the proper replacement which is the timing of the dangerous facility. As a result, It was ideal to replace the facilities with 20 years of heat treatment facilities, one year of hydrofluoric acid storage tank, 20 years of sulfuric acid storage tank, and 5 years of hydrochloric acid storage tank.

• Journal of the Korean Society for Railway
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• v.14 no.2
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• pp.100-108
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• 2011

This paper investigates the structural stability and reliability on improving performance of flexible brake pad used in high speed train. To this end, an improved model of flexible pad was obtained through structural analysis. Brake pad specimens were subjected to modal, stroke and endurance tests to examine the dynamic characteristics and mechanical stability. The hot spot generation with increasing rotational speed was observed on chassis dynamometer equipment and then the structurally uniform contact between the disc and pad was achieved. The temperature distribution of flexible pad was measured using the infrared camcorder. Hence, the proposed flexible pad showed the better structural stability and thermal energy emission.

• Smart Structures and Systems
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• v.12 no.3_4
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• pp.415-426
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• 2013

Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. In monitoring, displacement measurement capability is important to keep track of performance of bridge, in part or as whole. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Though expansion joint is critical for bridge performance, its inspection and monitoring has not been considered significantly because the monitoring requires long-term data using cost intensive equipment. Recently, a wireless smart sensor network (WSSN) has drawn significant attention for transportation infrastructure monitoring because of its merits in low cost, easy installation, and versatile on-board computation capability. In this paper, a rapid wireless displacement monitoring system, wireless hybrid sensor (WHS), has been developed to monitor displacement of expansion joints of bridges. The WHS has been calibrated for both static and dynamic displacement measurement in laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been measured. The short-term displacement trend in terms of temperature is calculated. With the WHS system, approximately 6% of the time has been spent for installation, and 94% of time for the measurement showing strong potential of the developed system for rapid displacement monitoring.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.13-19
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• 2008

Among the various prime movers for combined heat and power (CHP) system, the CNG engine is the most commonly used power generation equipment of which power is less than 1MW. The 300 kW class CNG engine for CHP can meet stringent emission regulations with the adoption of stoichiometric air-fuel ratio control and three way catalyst. As the thermal efficiency of the stoichiometric ratio engine is lower than that of lean burn engine, it is necessary to operate the stoichiometric engine at its minimum spark advance for the best torque (MBT). However, knock control should be introduced for the engine under high intake air temperature conditions because MBT operating conditions are generally very close to those of knock occurrence. In this study, engine performances and knocking characteristics were experimentally investigated for the CNG engine that needs to be operated at higher intake air temperature conditions than normal conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.82-88
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• 2008

This paper describes the influence of the bridge formed between electrodes by electrolyte for tracking process. Electrolytes is made by IEC(International Electrotechnical Commission) 60589, NaCl added to deionized water as each 1, 3, 5[wt%]. The used test equipment is made according to KS(Korean Industrial Standard) C IEC 00112. It is investigated voltage, current, value of resistance and thermal image when bridge formed between electrodes on tracking process. As a result, as conductivity of electrolyte gets bigger as Joule's heat on bridge also gets bigger. But It is not over electrolyte's boiling point due to evaporation heat of electrolyte. However as conductivity of electrolyte gets bigger as the necessary time of dry band gets shorter. So dry band is existed more long time between ahead of droplet to next droplet and discharge chance at dry band gets much. Therefore tracking process gets faster.

• Science of Emotion and Sensibility
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• v.17 no.3
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• pp.75-82
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• 2014

This study investigated the physical properties of aramid/nylon ATY and aramid ATY for protective garments according to the aramid and nylon characteristics fed on the core and effect components of air jet texturing equipment. Tenacity decrease of aramid ATY was much more higher than that of nylon ATY because of slick of aramid filament surface. Tenacity of aramid/nylon ATY was most affected by the tenacity of nylon on the effect component of ATY. Breaking strain of nylon ATY was two times higher than that of nylon before air jet texturing, then, in case of aramid ATY and aramid/nylon ATY, were 5.9-6.7 times higher than those before air jet texturing. Initial modulus decrease of aramid ATY showed 86.5% of initial modulus of aramid before air jet texturing, then aramid/nylon hibrid ATY showed arithmetic average value of initial modulus of aramid and nylon ATY. Wet and dry thermal shrinkages of aramid/nylon hybrid ATY were dominated by those of nylon filament on the effect component of ATY.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.363-368
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• 2007

Lithium-ion batteries providing high gravimetric energy density are rapidly replacing Ni-Cd and Ni-H2 in aerospace applications. The main advantage is the weight reduction of the battery system. Weight is a major concern in aerospace applications. Also, lithium-ion offer low thermal dissipation, high energy efficiency, and low cell cost. The Onboard battery module for KSLV-I(Korea Space Launch Vehicle) contains 80 Sony US18650 cells configured as 10 strings in parallel, with each string containing 8 series connected cells. This allows to meet voltage and capacity requirements specified for the mission. In this paper design description and specifications of lithium-ion battery developed are presented. Qualification test flow is also shown to make sure the performance in the predicted space environment. Electrical performance was simulated by dedicated program, and verified with electronic load. Lastly, the capacity was proven on real equipment load assembly.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.257-263
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• 2013

In case of image observation equipments, CCTV for short distance visual field is usually installed and operated mostly as the means of crime-prevention. However, the extensive demand for monitoring problems in case of the increase in intelligent crimes and disasters has led to the necessity of the development of long-distance observation equipments embedded with Night View functions. In case of the Night View equipments, the relevant market is set up to be focused mostly on Thermal Observation Device(hereinafter, TOD), but some shortcomings such as the limitation of image visibility and excessive maintenance cost, etc. have actually caused the necessity of new long distance Night View equipment. Moreover there might follow lots of difficulties in long-distance visualization in the event that irregular reflection is generated by minute particles in the atmosphere such as fog, smog, and dust, etc. These factors are motivate the work presented in this study. Our study is aimed at the realization of Pulsed Laser Illuminator and newly proposed Range-Gated image acquisition technology. And also the implementation of Tracker for continuous trace of the objects of interest from the obtained sequence images.