• 한국의류학회지
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• 제13권3호
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• pp.295-303
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• 1989

This study is to measure the thermal resistance of 7 types of Parka of different materials with thermal manikin and to compare their effects on physiological responses & subjective wear sensations. Following are the results obtained from the experiments 1) From the thermal manikin experiment, i) As an outer layer, although not significant, water proof fabric was warmer than water proof-vapor permeable fabric. ii) In case of insulating material, down was better for thermal resistance than polyester wadding of the same thickness. Moreover, as the down was thicker, it had more efficiency in thermal resistance. However, the marginal efficiency of thickness was found to be decreasing. 2) From the male-subject experiments, i) Chest temperature, mean skin temperature & microclimate temperature showed the same results on thermal resistance as those of the thermal manikin experiment. ii) Only during rest periods, there was a significant difference among 5 insulating materials in the sense of microclimate humidity. The almost same conclusion was obtained from the above experiments. Even the outer layer did not significantly affect thermal resistance & subjective wear sensation, insulating materials had a significant influence upon them. But in case of 3.5 cm down, it gave less comfortable than that of the thinner. Therefore the optional one for the best comfort & thermal resistance among 7 combinatins is the outer layer of water proff-vapor permeable & insulating material of 2.1 cm down.

• 한국의류학회지
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• 제22권5호
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• pp.565-574
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• 1998

The purpose of the study was to determine the effect of air velocity on the thermal resistance of wool ensembles. Three suits for men with different weaving structure and density were made with the same design and size for the study. In addition, Y-shirt, underwear, and socks were prepared for constructing the ensembles. Thermal insulation of air layer and 3 ensembles were measured by using thermal manikin in environmental chamber controlled at 2$0^{\circ}C$ and 65% RH with various air velocity. The results were as follows: 1. Thermal resistance of air layer was 0.079 m2.$^{\circ}C$/W with no air velocity(less than 0.2m/sec). 2. Thermal resistance of air layer decreased with increasing the air velocity rapidly. When the air velocity was 0.25 and 2.89 m/sec, the decreasing rate was 15% and 61%, respectively compared with no air velocity. 3. While there was little difference among the effective thermal insulation of 3 ensembles having different weaving structure and density with no air velocity, there was sharp difference among them when the air velocity increased. That is, the decreasing rate of effective thermal insulation of the ensemble which has higher air permeability was higher. 4. The decreasing rates of the effective thermal resistances of plain, twill and satin ensemble were 61, 54, and 49%, respectively when the air velocity was 2.89 m/sec which was a maximum air velocity in this study.

• 한국포장학회지
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• 제12권1호
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• pp.45-53
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• 2006

Thermal insulation is used in a variety of applications to protect temperature sensitive products from thermal damage. Several factors affect the performance of insulation packages. Among these factors, the thermal resistance of the insulating wall is the most important factor to determine the performance of the insulating package. In many cases, insulating wall consists of multi-layered structure and the heat transfer through this structure is a very complex process. In this study, an one-dimensional mathematical model, which includes all of the heat transfer principles covering conduction, convection and radiation in multi-layered structure, were developed. Based on this model, several heat transfer phenomena occurred in the air space between the layer of the insulating wall were investigated. From the simulation results, it was observed that the heat transfer through the air space between the layer were dominated by conduction and radiation and the low emissivity of the surface of each solid layer of the wall can dramatically increase the thermal resistance of the wall. For practical use, an equation was derived for the calculation of the thermal resistance of a multi-layered wall.

• 한국표면공학회지
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• 제31권1호
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• pp.12-23
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• 1998

The Thermal Barrier Coating(TBC) has been used to improve the heat barrier and tribological properties of the aircraft engine and the automobile engine in high temperature. Especially, the high temperature tribological propertied of the cylinder haed and the piston crown of diesel engine was emphasized. Therefore, the purpose of this work was to evaluate the microstructure, tribological propeer in high tempearmal shock resistance and bonding strength of five layer functionally gradient TBC for the applications. The five layerwere composed with 100% ceramic insulating later, 75(ceramic):25 (metal) layer, 50:50 layer, 25:75 layer and 100% metal bonding layer to redude the thermal stress. the YSL and MSL poweders were the insulation ceramics powers. The NiCrAly, Inconel625 and SUS powders were the bonding and mixingg powders for plasma spray process. According to the result of high temperature wear test, the wera resistance of YSZ/NiCrAlY siytem was most out standing at 600 and $800^{\circ}C$. At $400^{\circ}C$, the wear resistance of YSZ/Inconel system was better than others. Wear volume at other temperature because of the low temperature degration of zirconia. The thermal shock mechanism of 5 later is the vertical crack gegration in insulating layer. this means that the initial cracks were generated in the top layer, and then developed into the composite layers during thermal shock test. Finally, these cracks werereached to the interface of coating and substrate and also, these vertioal cracks join with the horizontal cracks of the each layers. The bonding strength of YSZ/NiCrAlY and YSZ/Inconel 5 layer system is better than other 5layer systems. The theramal shock resistance of thermal barrier coating s with 5 layer system is better than that of 3 layers and 2 layers.

• 한국표면공학회지
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• 제30권4호
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• pp.272-280
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• 1997

The Thermal Barrier Coation(TBC) to improve the that barrier and wear resistant propenrty in high temperature ofthe aircraftength between the accumlation of the aircraft engine and the automobile engine has usually the two layer structure. One is a creamic top layer for heat insulation and the other is a metal bond layer to facilitate the bond strength between the top ceramic layer and the substrate. But, the coated layers should be peeled off because of the accumulation of the thermal stress by the differance of the thermal expantion coefficient between metal and ceramics in a hrat cyclic environment. In this study, the intermediate layer by plasm spray process was introduced to reduce the thermal stress. The powders of plasm spray coating were the Yttria Stabilized Zirconia (YSZ), the Magnesia Stabillized Zirconia(MSZ) and NiCrAlY. the intermediate layer was sprayed with the powders of the bond cast for the purpose of test were executed. The high temperature wear resistance tends to decreasnceee wear and thermal shock test were exeucuted. The high temperature were resistance of the YSZ TBC is better that of the MSZ TBC. The wearrsistance tends to decrease accoring to incresing the temperature between $400^{\circ}C$to $600^{\circ}C$. The thermal shock life of the 3 layer TBC with YSZ top casting was the most outstanding thermal shock rsisstasnce. This means that the intermediate layer should play an importnat roll to alleviate the diffrerence of the thermal expansion coef frcients between metallic layer and cermics layer.

• Journal of Welding and Joining
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• 제10권4호
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• pp.181-189
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• 1992

The purpose of this investigation is to examine the effects of the strengthening treatments on the mechanical properties of the flame-sprayed titania ceramic coating layer. The strengthening treatments for flame sprayed specimens were carried out in 12 different conditions in vaccum furance. The mechanical properties such as microhardness, thermal shock resistance, adhesive strength and erosion resistance were tested for the sprayed specimens after strengthening treatments. And it was clear that the mechanical properties of coating layer were much improved by the strengthening treatments. The results obtained are summarized as follows; 1. It was shown that the metallurgical bond was formed between substrate and coating layer by the strengthening treatments and that thermal shock resistance and adhesive strength were remarkably raised. 2. Microhardness of coating lay was considerably increased by the strengthening treatments. 3. Erosion resistance and porosity of coating layer were slightly improved by the strengthening treatments.

• 한국세라믹학회지
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• 제54권6호
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• pp.525-529
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• 2017

To improve the thermal resistance of a porous borosilicate lining block, we prepared and applied polysiloxane-fumed silica-ethanol slurry on top of the block and fired the coating layer using a torch for 5 minutes at $800^{\circ}C$. We conducted magnified characterizations using a microscope and XRD analysis to observe phase transformations, and TGA-DTA analysis to determine the thermal resistance. Thermal characterizations showed improved heat resistance with relatively high polysiloxane content slurry. Cross-sectional optical microscope observation showed less melting near the surface and decreased pore formation area with higher polysiloxane content slurry. XRD analysis revealed that the block and coating layer were amorphous phases. TGA-DTA analysis showed an endothermic reaction at around $550^{\circ}C$ as the polysiloxane in the coating layer reacted to form SiOC. Therefore, coating polysiloxane on a borosilicate block contributes to preventing the melting of the block at temperatures above $800^{\circ}C$.

• 대한가정학회지
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• 제37권11호
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• pp.157-165
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• 1999

This study was carried out to examine the effect of clothing materials and multi-layered textiles on thermal resistance value. Cotton, polyester, wool, silk, rayon and acetate were selected for the specimens. Thermal resistance value was tested with 2 kinds of methods(thermo labo II and BK type tester). The results were as follows; 1. The effects of clothing materials for thermal resistance value were decreased by adding layers. 2. When the fabrics are measured with multiple layers, the fabric of the lowest thermal resistance value at single layer was showed the highest increasing tendency for all test methods.

• 한국표면공학회지
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• 제55권6호
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• pp.408-416
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• 2022

In this study, the effect of Au-Sn alloy coating on reliability of electrical contacts was investigated via comparison with Au-Co alloy coating. The results show that Au-Sn alloy exhibited lower contact resistance and higher solder spreadability than those of Au-Co alloy after thermal aging. In the case of Au-Co alloy plating, the underlying Ni element diffused into Au-Co layer to form Ni oxides on surface during thermal aging, leading to increased contact resistance and decreased solder spreadability. Meanwhile, for Au-Sn alloy plating, Au-Ni-Sn metallic compound was formed at the interface between Au-Sn layer and underlying Ni layer. This compound acted as a diffusion barrier, thereby inhibiting the diffusion of Ni to Au-Sn layer during thermal aging. Consequently, Au-Sn alloy layer showed better contact reliability than that of Au-Co alloy layer.

• 설비공학논문집
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• 제6권2호
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• pp.155-165
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• 1994

In this study, the following factors are investigated from experiments for a vertical parallel plate heat exchanger under the frosting condition ; the growth of frost layer, the characteristics of heat and mass transfer, the change of mass flow rate of the air passing through the heat exchanger, and the pressure drop of the air in the heat exchanger. The amount of heat and mass flux of water vapor transferred from the air stream to the heat exchanger surface is large at the early stage of frosting and then decreases dramatically, and the extent of decreasing rate becomes moderate with time. The frost layer formed near the inlet of the heat exchanger is thicker and denser than that formed near the outlet. It is found that the gradient of the amount of frost along the flow direction increases with time. In the early period of frost formation, the thermal resistance between the air and the cooling plate increases dramatically and then the extent of change decreases with time. Initially the convective thermal resistance is dominant. Then, while the convective thermal resistance decreases with time, the conductive thermal resistance continues to increase with time and finally the conductive thermal resistance becomes dominant.