• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.114-121
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• 2004

Thermal design changes and analysis on the engineering model of Command Telemetry Unit(CTU) for a geostationary communications satellite arc performed for the purpose of developing an engineering qualification model. A thermal model is developed by using power consumption measurement values of each functional board and thermal cycling test results. In modeling heat dissipated EEE parts, heat dissipation is imposed evenly on the EEE part footprint area which is projected to the printed circuit board. All the EEE parts of CTU meet the requirement of their allowable temperature range when placed on the engineering qualification level of thermal vacuum environments in accordance with the proposed thermal design changes.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.727-734
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• 2015

Currently, polyurethane (PU) foam is used in most refrigerators as a thermal insulator, whereby the material contributes to structural stiffness by joining the refrigerator cases; however, refrigerator PU foam induces a low thermal efficiency and results in environmental contamination. To resolve these issues, we applied the vacuum insulated panel (VIP) instead of PU form in the design of a new refrigerator type, whereby the VIP significantly contributes to the rectification of the previously mentioned issues. The VIP structure, however, cannot effectively hold refrigerator cases, so the present study investigated a new frame-structure concept by evaluating the stiffness using the topology optimization of refrigerator cases. Lastly, a refrigerator prototype comprising an optimal frame structure was built and subject to a stiffness test, and a comparison of the test results with those of a conventional refrigerator show that the structural stiffness of the prototype is sufficiently effective.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.200.1-200.1
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• 2016

Tungsten coatings on the graphite (CX-2320) were successfully deposited using the vacuum plasma spraying (VPS) method. An optimum coating procedure was developed and coating thicknesses of $409{\mu}m$ (without an interlayer) and $378{\mu}m$ (with an interlayer) were obtained with no cracks and no signs of delamination. The mechanical characteristics and microstructure of the tungsten coating layers were investigated using a Vickers hardness tester, FE-SEM, EDS, and XRD. The effect of a titanium interlayer on the properties of the tungsten coating was investigated. It was shown that the titanium interlayer prevented the diffusion of carbon to the tungsten layer, thereby suppressing the formation of tungsten carbide. Vickers hardness data yielded values that were 62.5 ~ 80.46% of those for bulk tungsten, indicating that tungsten coatings on graphite can be utilized as a plasma-facing material. High heat flux tests were performed by using thermal plasma with a maximum flux of $10MW/^2$. Vickers hardness after the heat flux test is performed to see a change in the mechanical properties. The formationof a tungsten carbide and the effect of the titanium interlayer for the diffusion barrier are investigated by using energy dispersion spectroscopy (EDS).

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.4
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• pp.542-550
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• 2010

Cooled infrared detector is widely used as the core part in a variety of the thermal imaging systems. For the selection of the highly reliable cooled infrared detector with good performance, it is necessary for us to possess the characterization methods of the well defined performance index of cooled infrared detector. In this paper, various performance index of the cooled infrared detector including reliability as well as the optical and cooling performance of cooled infrared detector are defined and their characterization methods will be investigated and implemented systematically.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.9
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• pp.814-824
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• 2016

The mission objective of STEP Cube Lab. (Cube Laboratory for Space Technology Experimental Project) classified as a pico-class satellite is to find space core technologies researched at domestic industry or university and to verify these technologies on mission orbit. To implement this objective, system level electrical integration and function test (EIT) by using developed flight software were performed in compliance with system requirements. And the effectiveness of the flight model (FM) was verified through launch and thermal vacuum test at acceptance level. This paper will introduce a series of process of electrical function tests for FM EIT, launch and thermal vacuum tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.921-930
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• 2013

Satrec Initiative successfully developed and verified a high-resolution electro-optical camera system, EOS-D Ver.1.0. We designed this system to give improved spatial and radiometric resolution compared with EOS-C series systems. The thermal control subsystem (TCS) of the EOS-D Ver.1.0 uses heaters to meet the opto-mechanical requirements during in-orbit operation and uses different thermal coatings and multi-layer insulation (MLI) blankets to minimize the heater power consumption. Also, we designed and verified a refocusing mechanism to compensate the misalignment caused by moisture desorption from the metering structure. We verified the design margin and workmanship by conducting the qualification level thermal vacuum test. We also performed the verification of thermal math model (TMM) by comparing with thermal balance test results. As a result, we concluded that it faithfully represents the thermal characteristics of the EOS-D Ver.1.0.

• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.182-185
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• 2006

In this work, we have constructed 3-axis flux-gate magnetometer for the attitude control of satellite. The constructed magnetometer shows uncertainty of ${\pm}1%$, noise level of $0.2nT/\sqrt{Hz}$ at 1 Hz under 1W power consumption. Environment test for satellite component, acceleration test and thermal cycle test were carried out. For the acceleration test, magnetometer was vibrated frequency ranging from 10 Hz to 1 kHz at 15 g (g : gravitational acceleration at earth), and for thermal cycle test, 4 times of thermal cycle were carried out temperature ranging from $-55^{\circ}C\;to\;+80^{\circ}C$ under vacuum of $1x10^{-6}Torr$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.96-102
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• 2003

The thermal design of MGSE(Mechanical Ground Support Equipment) panel is performed for thermal vacum thest of Ka-band EQM(Engineering Qualification Model) payload of communications and broadcasting satellite. The thermal environments are predicted to evaluate the performance of transponder equipments in the thermal vacum chamber. SINDA is used to verify the thermal design of the heat pipe layout. Embedded 16 heat pipes in the EQM payload developed for Ka-band trasponder equipments are designded properly. The heat fluz loaded on the external facesheet is 265W/㎡ for the hot platear function test of the traspinder equipments, and the zero heat flux for the cold plateau case. The maxium predicted heat transport capability is 2723 W-cm.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.195-199
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• 2007

In this study, bond strength tests were performed for the thermal barrier coating applied to the 1st stage turbine blade. After the tests, the specimens were cut and the locations of failure were observed by using optical microscope. The influence of heat treatment on bond strength of a bond coating and the difference among the three types of bond coatings are treated.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.345-350
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• 2014

The surface oxidation mechanism of lead-free solder alloys has been investigated with multiple reflow using X-ray photoelectron spectroscopy. It was found that the solder surface of Sn-Ag-Cu-In solder alloy is surrounded by a thin $InO_x$ layer after reflow process; this coating protects the metallic surface from thermal oxidation. Based on this result, we have performed a wetting balance test at various temperatures. The Sn-Ag-Cu-In solder alloy shows characteristics of both thermal oxidation and wetting balance better than those of Sn-Ag-Cu solder alloy. Therefore, Sn-Ag-Cu-In solder alloy is a good candidate to solve the two problems of easy oxidation and low wettability, which are the most critical problems of Pb-free solders.