• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.1
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• pp.23-29
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• 1997

Effects of Co thickness on the formation of epitaxial $CoSi_2$ from the Co/Ti bilayer have been investigated. Ti and Co were sequentially deposited with the Ti thickness fixed at 5 or 10nm, while the Co thickness was varied from 5 to 30nm. The metal-deposited samples were then rapidly thermal-annealed in $N_2$ at $900^{\circ}C$ for 20 sec. Material properties of $CoSi_2$ thin films were analyzed by the 4-point probe, XRD, AES, andXTEM. When the as-deposited Co thickness was below 15nm, the $CoSi_2$ with high resistivity and rough interface was formed. On the other hand, when the Co thickness was above 15 nm, the epitaxial $CoSi_2$ with the resistivity of about 16 ~ 19 $\mu\Omega.cm$, uniform composition and thickness and flat interface was formed. Initial Ti thickness has sizable effect on the formation of $CoSi_2$, when the Co layer was very thin (~ 5 nm). But there was no significant effect of the Ti thickness for the initial Co thickness of above 15 nm.

• Composites Research
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• v.30 no.1
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• pp.26-34
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• 2017

This research presents studies on an improved method to predict the thermal conductivity of woven fabric composites, the effects of geometric structures of woven fabric composites on thermal conductivity, and structural optimization to improve the thermal conductivity using a genetic algorithm. The geometric structures of woven fabric composites were constructed numerically using the information generated on waviness, thickness, and width of fill and warp tows. Thermal conductivities of the composites were obtained using a thermal-electrical analogy. In the genetic algorithm, the chromosome string consisted of thickness and width of the fill and warp tows, and the objective function was the maximum thermal conductivity of woven fabric composites. The results confirmed that an improved method to predict the thermal conductivity was built successfully, and the inter-tow gap effect on the composite's thermal conductivity was analyzed suggesting that thermal conductivity of woven fabric composites was reduced as the gap between tows increased. For structural design, optimized structures for improving the thermal conductivity were analyzed and proposed. Generally, axial thermal conductivity of the fiber tow contributed more to thermal conductivity of woven fabric composites than transverse thermal conductivity of the tows.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.91-98
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• 2010

The increasing of power and processing speed and miniaturization of central processor unit (CPU) used in electronics equipment requires better performing thermal management systems. A typical thermal management package consists of thermal interfaces, heat dissipaters, and external cooling systems. There have been a number of experimental techniques and procedures for estimating thermal conductivity of thin, compressible thermal interface material (TIM). The TIM performance is affected by many factors and thus TIM should be evaluated under specified application conditions. In compact packaging of electronic equipment the chip is interfaced with a thin heat spreader. As the package is made thinner, the coupling between heat flow through TIM and that in the heat spreader becomes stronger. Thus, a TIM characterization system for considering the heat spreader effect is proposed and demonstrated in detail in this paper. The TIM test apparatus developed based on ASTM D-5470 standard for thermal interface resistance measurement of high performance TIM, including the precise measurement of changes in in-situ materials thickness. Thermal impedances are measured and compared for different directions of heat dissipation. The measurement of the TIM under the practical conditions can thus be used as the thermal criteria for the TIM selection.

• Journal of Korea Foundry Society
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• v.11 no.3
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• pp.245-253
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• 1991

It is known that the analysis of thermal stresses is substantially important in optimal design of casting mould. In this paper unsteady state thermal stresses generated in ingot and mould during the solidification process are analyzed by the two dimensional thermal elasto-plastic analysis. Distribution of temperature and stress of the mould is calculated using the finite element method and compared with experimental result. The significant results obtained in this study are as follows. At the early stage of the casting process, abrupt temperature change was shown in the vicinity of the inner surface of the mould. The largest temperature gradient is occurred at the corner of the mould. In the thermal stress analysis, compressible stress occurred in the inside wall of the mould where as tensile stress on outside wall. Smaller thermal stress is observed at the rounded corner. It is also observed that the shown is influenced by the thickness of the wall. A fairly good coincidence is found between analytical and experimental results, showing that the proposed analytical methodology is reliable.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2534-2539
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• 2007

Launch vehicles are exposed to aerodynamic heating conditions while flying at high Mach numbers in the atmosphere. In this study aerodynamic heating test for fairing nose-cone was done using ATSF(Aerodynamic Thermal Simulation Facility) and Engineering Model for fairing. ATSF is a facility that can simulate given temperature profile using about 4,000 halogen heaters on fairing model. Aerodynamic heating profile is got from result of thermal analysis using MINIVER, Thermal Desktop and SINDA/FLUINT. After aerodynamic heat test, it is found that initial temperature of fairing inner surface and thickness of BMS has important effects on temperature of fairing inner surface. Also it is confirmed that maximum temperature of fairing nose-cone inner surface during flight is lower than allowable temperature limit. Later, thermal correlation between thermal analysis and experimental results will be done using aerodynamic heating test result

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.363-368
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• 2001

Studies on brake system recently are focused on braking performance, especially the consideration on safety of braking system in an extreme situation and reduction of vibration and noise during braking operation. The thermal crack and Judder from the friction between brake disc and pad can bring the threaten of passengers' safety in the end. Braking force comes from the change of kinetic energy to friction energy. Since heat energy is developed from here, the analysis on thermal stress and thermal strain can be the good data when selecting the material of brake pad and designing heat radiation holes on the disc and it will also be the data when designing the thickness of the disc. This paper is intended to show a creative design method by suggesting the thermal analysis data through FEM study and using shape design parameters.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1205-1210
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• 2004

Cracks in the underground structures are mainly observed due to internal ununiformity of thermal stresses or restraint of structural movement in associate with rapid temperature gradient. Especially, thermal cracks are known to occur easily in a massive structure, but possibility of these depend on the amount of cement applied and ratio of span to height of the structure even though the thickness is less than specification‘s. Thus, this study aims at how to control thermal cracks in a massive subway structure and figures out an optimized construction method and procedure. As results of parametric study for length, height and outer temperature for concrete placement, it is found that hydration heats were not affected by both length and height of concrete placement but thermal stresses were greatly dependent. Most effective ways of controling thermal cracks were to fit a proper ratio of length to height of concrete placement and to decrease temperature of concrete placement as much as possible.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.1-4
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• 2003

Recently, a structure has been larger and higher under the improvement of construction technique. So, a concrete constructions that a mat foundation thickness of structure is over 80cm have been many. Also, because of the reason high strength concrete, the matter of thermal crack have become an important task to be solved absolutely. In a cause a thermal crack occurrence, there used, mixture of concrete, construction and so forth. In this study, we executed temperature and stress analysis of mat foundation to know the effect the construction condition a thermal crack of mat foundation. And we evaluated quantitatively about the occurrence possibility of thermal crack using the hydration heat analysis program. By using of this analysis technique, will can control skilfully the quality of a mat foundation in advance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.1-4
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• 2003

Recently, a structure has been larger and higher under the improvement of construction technique. So, a mass concrete constructions that a mat foundation thickness of structure is over 80cm have been many. Also, because of the reason of high strength of concrete, the matter of thermal crack have become an important task to be solved absolutely. tn a cause of a thermal crack occurrence, there are material used, mixture of concrete, construction condition and so forth. In this study, we executed temperature and stress analysis of mat foundation to know the effect of the construction condition on a thermal crack of mat foundation. And we evaluated quantitatively about the occurrence possibility of thermal crack using the hydration heat analysis program. By using of this analysis technique, we will can control skilfully the quality of a mat foundation in advance.

• Solar Energy
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• v.8 no.1
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• pp.22-32
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• 1988

It is known that the energy consumption and indoor thermal comfort in residential buildings are affected by the thermal performance of building envelopes. The thermal performance of building envelopes varies with their design methods. In this study, the thermal performance changes by the insulating construction types of exterior walls were analyzed, 1) by varing the thickness of the insulation 2) by varing the location of the insulation 3) by varing the location of the plane airspace The analyzed results are presented and the thermal performance evaluating factors were compared and discussed.