• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.866-870
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• 2008

In this study, we designed cold gas propulsion system with minimum 0.25 mm nozzle and micro-thrust measurement system to analyze flow characteristic of micro propulsion system in ambient and vacuum condition. Argon and Nitrogen are used for propellant and the result of experiments is compared with CFD analysis and theory. But there is a point where reduced scale versions of conventional propulsion systems will no longer be practical. Therefore, a fundamentally different approach to propulsion systems was taken. That is thermal transpiration based micro propulsion system. It has no moving parts such as lubricants, pressurizing system and can pump the gaseous propellant by temperature gradient only(cold to hot). We are advancing basic research of propulsion system based on thermal transpiration in vacuum conditions and had tried experiment process and theoretical access in advance. To characterize membrane of Knudsen pump, we select Polyimide material that has low thermal conductivity(0.29 W/mK) and can stand high temperature($300^{\circ}C$) for long time. And we fabricated hole diameter 1, 0.5, 0.2, 0.1 mm using precision manufacturing. Experimental results show that pressure gradient efficiency of Knudsen pump is increased to maximum 82% according to Knudsen number and thick membranes are more effective than thin membranes in transition flow regime.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.98-104
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• 2005

Saw dust concrete f3r finding out insulation characteristic was tested using test plate $30cm{\times}30cm{\times}5cm$. basically, molds f3r the test of compressive, tensile, normal without sawdust, $0.05\%,\;0.1\%,\;0.2\%,\; 0.4\%,\;0.6\%,\;0.8\%,\;1.0\%,\;1.2\%,\;1.4\%,\;1.6\%,\;1.5\%,\;2.0\%$, mixing proportion. heat conductivity of the saw dust concrete mixed with the above proportion was taken in this study. Thermal conduction of normal concrete depends on mixing proportion strength aggregate character, water content. all these items are specified here in fables. $1.8\%\~2.0\%$ saw-dust mising concrete shows as the faction as normal insulation material has its function. and the higher saw-dust mixing rate becomes, the thermal conduction becomes the less Then, the conclusions are that saw-dust using concrete has better insulation function than normal concrete.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.714-716
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• 2001

This paper is about the characteristic analysis of a heater-trigger HTS switch. It is composed of a BSCCO tape wire and a heater as a thermal quench source. To minimize the heat flow to the liquid nitrigen, the epoxy was used around them. The heater-trigger switch operates in the process that the HTS tape is thermally quenched by the current flowing through the heater. Since the switch works in coolant, it needs to be designed by the accurate thermal characteristic analysis. Here, we focus on FEM for it.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.407-412
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• 2012

This study investigated the process of thermal-induced growth of micro-crack developed at the crystalline solar cell using EL image, determined the output characteristic according to the pattern of micro-crack, analyzed the I-V characteristic according to the pattern of crack growth, and predicted the output value using simulation. The purpose of this study was, therefore, to investigate the process of thermal-induced growth of micro-crack developed at the early stage of PV module completion using EL image, to analyze the resulting decrement of output and predict the output value using simulation. It was observed that the crack grew increasingly by the thermal condition, and accordingly the lowering of output was accelerated. The output values of crack patterns with various direction were predicted using simulation, resulting in close I-V curve with only around 4% of error rate. It is considered that it is possible to predict the electric characteristic of solar cell module using only pattern of micro-crack occurred at solar cell based on our results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.287-288
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• 2005

In this study, we have investigated electro-optical characteristics of thermal and UV stressed TN cells on the rubbed polyimide surface. Mono-domain alignments of thermal stressed TN cells over temperature of liquid crystal isotropic phase were almost same that of no thermal stressed TN cells. Also, threshold voltage and response time of thermal stressed TN cells were same that of no thermal stressed TN cells. Finally, the residual DC voltage of the thermal stressed TN cell on the polyimide surface show decrease of characteristics as increasing thermal stress time. Therefore, thermal stability of TN cell was decreased by high thermal stress for the long times.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.101-106
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• 2005

During braking at a train, thermal energy is generated due to the frictions between disk and lining and wheel and shoe. In general, the braking transfers the kinetic energy into thermal energy. Therefore. the frictional characteristics are varied according to the braking force, the thermal resistance, and the thermostable, etc. Using a Dynamo testing we have studied the frictional characteristics and the thermal distribution to investigate a stable speed and to improve the testing method through comparing and analysing in the measurement or the thermocouple temperature and infrared camera.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.244-246
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• 1996

In an controlled electric machine, the variations of motor parameters such as stator and rotor time constant are caused by the temperature rise, thus it is needed to calculate the accurate parameter through the dynamic characteristic analysis considering the temperature variation. In this paper, the dynamic characteristic analysis method of vector controlled LIM is proposed using coupled magnetic & thermal 2D FEM taking into account the movement.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1502-1509
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• 2011

This Paper presents characteristic analysis in terms of interior permanent magnet synchronous motor for electric vehicle propulsion using numerical analysis. Torque ripple analysis, thermal analysis, demagnetization analysis of permanent magnet and mechanical stress analysis with variable operating condition are presented. According to these characteristic analysis, both the performance of motor and possible problems during the operation are examined thoroughly in advance.

• Elastomers and Composites
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• v.51 no.2
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• pp.138-146
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• 2016

It is an inconvenience for silica nano-particles to dry again when using it in that they cohere each other through moisture in the air. Acrylamide groups were introduced to improve such inconvenience and copolymerized with silica nano-particles and then we copolymerized again with polyamic acid in order to increase thermal characteristic. Amide block copolymers were prepared using silica and (3-mercaptopropyl) trimethoxysilane (MPTMS) with a siloxane group, using 2,6-Lutidine as a catalyst. Amide block polymers and copolymers were synthesized via ATRP after brominating pyromellitic dianhydride (PMDA) and polyamic acid of methylene diphenyl diamine (MDA), using ${\alpha}$-bromo isobutyryl bromide. Characteristic peaks of copolymer with amide and imide groups and patterns of amorphous polymers were researched by FT-IR and XRD analyses and the analysis of surface characteristic groups was conducted via XPS. A change in thermal properties was examined through DSC and TGA and solubility for solvents was also researched.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.8
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• pp.169-176
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• 2019

The purpose of this study was to analyze outdoor thermal comfort of apartments planning characteristic of pedestrian height in Beijing, China. Selecting 322 apartment complexes with more than 1000 households and more than 10 buildings(including 10 buildings), mainly in Chaoyang District and Tongzhou District to select 32 basic layout types and then 12 typical layout types were select in 32 basic layout types. Finally, the simulation was conducted for the 12 typical layout types using the micro-climate model ENVI-met to evaluate the wind environment, the thermal environment and the comfort. The results of this study as follows: In the parallel arrangement, it has the best outdoor thermal comfort of Slab-East-Parallel(S/E/P). Next is Slab-South-Parallel(S/S/P), Tower-South-Parallel(T/S/P) in turn. In the stagger arrangement, Mixture-South-North and South Stagger-1(M/S/NSS-1) has the best outdoor thermal comfort and Slab-South-North and South Stagger(S/S/NSS), Tower-South-North and South Stagger(T/S/NSS), Mixture-South-North and South Stagger-3(M/S/NSS-3), Mixture-South-North and South Stagger-4(M/S/NSS-4), Mixture-South-North and South Stagger-2(M/S/NSS-2) in turn. In the cluster arrangement, Mixture-Mixture-Cluster-2(M/M/C-2) has the best outdoor thermal comfort and Mixture-Mixture-Cluster-3(M/M/C-3), Mixture-Mixture-Cluster-1(M/M/C-1) in turn. Due to the low wind speed and high air temperature, it is necessary to consider the layout types that can form the wind road at first, such as Mixture-South-North and South Stagger-1(M/S/NSS-1), Slab-South-North and South Stagger(S/S/NSS) and so on.