• Korean Journal of Human Ecology
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• v.7 no.2
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• pp.81-91
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• 1998

The subjects in this research were 368 girls in high school for survey, and wearing sensation and physiological responses were investigated through wearing trials on human body in climatic chamber based on these results from the survey. The results are as follows : 1. They enjoyed wearing t-shirts, jackets, vests, and blouses in order for the upper clothes, and they preferred t-shirts to blouses. For the lower clothes, they enjoyed slacks much more than skirts. The weight of clothes was significantly heavier in the group where they wore the uniforms(U-group) than in the group where they wore the free styles(F-group). When they chose the school wear, activity was the most important of all, and the maintenance was the least. 2. As the classes were a little cool and dry, most of them dissatisfied the environment. The degree of the satisfaction of the class environment and properties to it were higher in the U-group than in F-group. 3. In the textiles, colors, styles, activity, static electricity, seasonal property, and easiness of putting on and taking off the clothes, F-group was more satisfied than U-group. U-group was more satisfied than F-group in the soil of the clothes. 4. The thermal comfort, thickness, and tightness of the clothes were not significantly different between the groups. The clothes of U-group was heavier than those of F-group, and the tactile sensation in U-group was worse than F-group. In U-group the students felt the skirts very inconvenient when they acted. 5. The weight of the clothes influenced the wearing sensation, therefore the heavier the clothes were the less satisfied they felt. 6. The inside temperature of clothes was significantly higher in U-group than in F-group. The skin temperatures of abdomen and arm were significantly higher in U-group than in F-group, while the skin temperatures of thighs and legs were significantly lower in U-group than in F-group. U-group felt heavier than F-group in wearing the clothes. Therefore the improvement of the clothes weight is needed.

• Elastomers and Composites
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• v.47 no.4
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• pp.341-346
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• 2012

Injection molding is one of the widely used polymer processing operations. It is being used for not only conventional injection molding but gas injection molding, water injection molding, and injection compression molding. Injection compression molding involves injection and compression operation, and it gives uniform physical property and high dimensional quality of product. In this study, injection compression characteristics for various product shapes have been investigated by computer simulation. Product containing side wall showed not much effective in injection compression molding since wall thickness direction was perpendicular to the compression direction. Uniform and low shrinkage was observed in injection compression molding comparing conventional injection molding. Subsequently injection compression molding can be used for molding precise product. Optimal injection compression molding condition was obtained using design of experiment for plastic lens and the results were compared with conventional injection molding.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.29-34
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• 2012

Investigating safer ways to design and use to prevent a loss of life and property by failure of the structures are necessary and assessing total fatigue life with initiation and propagation of fatigue crack accurately through fatigue analysis is very important. The object of this study is to examine the initial life and propagation life when the fatigue crack is introduced from the root which is likely to appear in LOP(Lack of Penetration) cruciform fillet welded structure including bridges, ships and gas storage facilities which are impossible to be fully penetrated and to measure the rate of fatigue life until the final cleavage failure. As the result, each rate of fatigue life for fatigue failure is somewhat different in the range of 5% according to the thickness of material, however, the overall rate of initial life is in the range of 34~39% and propagation life showed the range of 61~66%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.8-9
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• 2006

Hafnium oxide ($HfO_2$) thin films were deposited on p-type (100) silicon wafers by atomic layer deposition (ALD) using TEMAHf and $O_3$. Prior to the deposition of $HfO_2$ films, a thin Hf ($10\;{\AA}$) metal layer was deposited. Deposition temperature of $HfO_2$ thin film was $350^{\circ}C$ and its thickness was $150\;{\AA}$. Samples were then annealed using furnace heating to temperature ranges from 500 to $900^{\circ}C$. The MOS capacitor of round-type was fabricated on Si substrates. Thermally evaporated $3000\;{\AA}$-thick AI was used as top electrode. In this work, We study the interface characterization of $HfO_2$/Hf/Si MOS capacitor depending on annealing temperature. Through AES(Auger Electron Spectroscopy), capacitance-voltage (C-V) and current-voltage (I-V) analysis, the role of Hf layer for the better $HfO_2$/Si interface property was investigated. We found that Hf meta1 layer in our structure effective1y suppressed the generation of interfacial $SiO_2$ layer between $HfO_2$ film and silicon substrate.

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.937-944
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• 2011

Studies have been carried out in order to reduce fuel-cladding chemical interaction (FCCI) behavior of metallic fuel in sodium-cooled fast reactors (SFR) using an electroplating technique. A $20{\mu}m$ thick Cr layer has been plated by the electrochemical method in the Sargent bath over the HT9 (12Cr-1Mo) clad material and diffusion couple tests of the U-10Zr metallic fuel as well as the rare earth alloy (70Ce-29La) have been conducted. The results show that the Cr plating can prevent FCCI behavior along the fuel-clad interface. However, cracks developed through the thickness during plating, which resulted in the migration of some fuel constituents. Variation of bath temperature, application of pulse current, and post heat treatment have been conducted to control such cracks. We found out that some conditions like the pulse current and the post heat treatment enhanced the layer property by reducing the internal cracks and improving the diffusion couple test.

• Korean Journal of Metals and Materials
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• v.47 no.3
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• pp.202-208
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• 2009

The effects of aging time on the microstructure and shear strength of the Low Temperature Co-fired Ceramic (LTCC)/Ag pad/Electroless Nickel Immersion Gold (ENIG)/BGA solder joints were investigated through isothermal aging at $150^{\circ}C$ for 1000 h with conventional Sn-37Pb and Sn-3Ag-0.5Cu. $Ni_3Sn_4$ intermetallic compound (IMC) layers was formed at the interface between Sn-37Pb solder and LTCC substrate as-reflowed state, while $(Ni,Cu)_3Sn_4$ IMC layer was formed between Sn-3Ag-0.5Cu solder and LTCC substrate. Additional $(Cu,Ni)_6Sn_5$ layer was found at the interface between the $(Ni,Cu)_3Sn_4$ layer and Sn-3Ag-0.5Cu solder after aging at $150^{\circ}C$ for 500 h. Thickness of the IMC layers increased and coarsened with increasing aging time. Shear strength of both solder joints increased with increasing aging time. Failure mode of BGA solder joints with LTCC substrate after shear testing revealed that shear strength of the joints depended on the adhesion between Ag metallization and LTCC. Fracture mechanism of Sn-37Pb solder joint was a mixture of ductile and pad lift, while that of Sn-3Ag-0.5Cu solder joint was a mixture of ductile and brittle $(Ni,Cu)_3Sn_4$ IMC fracture morphology. Failure mechanisms of LTCC/Ag pad/ENIG/BGA solder joints were also interpreted by finite element analyses.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.155-163
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• 2011

Carbon nanotubes (CNT) have been attracted much attention since they have been expected to be used in various areas by virtue of their outstanding physical, electrical, and chemical properties. In order to make full use of their prominent electric conductivity in some areas such as electron emission sources, device interconnects, and electrodes in energy storage devices, direct growth of CNT with vertical alignment is definitely beneficial issue because they can maintain mechanical stability and high conductivity at the interface between substrates. Here, we report direct growth of vertically aligned CNT (VCNT) on Cu foils using thermal chemical vapor deposition and characterize the field emission property of the VCNT. The VCNT's height was controlled by changing the growth temperature, growth time, and catalytic layer thickness. Optimum growth condition was found to be $800^{\circ}C$ for 20 min with acetylene and hydrogen mixtures on Fe catalytic layer of 1 nm thick. The diameter of VCNT grown was smaller than that of usual multi walled CNT. Based on the result of field emission characterization, we concluded that the VCNT on Cu foils can be useful in various potential applications where high conductivity through the interface between CNT and substrate is required.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.5
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• pp.669-683
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• 2012

The water supply pipes are buried across wide range of areas, so it is hard to spot them using excavation and takes a large amount of expense. Thus, there is a high risk for direct research and application, accompanying many difficulties in implementation of them. Therefore, it is more economical and convenient to use indirect evaluation variables than direct evaluation of the buried pipes in assessing the degree of pipe deterioration. To assess the degree of pipe deterioration using the indirect evaluation variables, it should be done first to identify how and to what extent they affect the degree of deterioration. This study measured the evaluation variables for pipe deterioration using the pipe endoscope and analyzed the measurement results and the degree of impact on the pipes. In addition, this study attempted to evaluate the adequateness of the pipe deterioration evaluation using the indirect variables based on the analysis results. The evaluation variables measured through the pipe endoscope were the thickness of sediments, size of scale, degree of desquamation and condition of connections. For the indirect evaluation variables, the data such as the property data from GIS pipe network map as well as the material, diameter, age and pipe lining material of the pipe, road type, leakage frequency, average water velocity and water pressure using the leakage repair records was collected. Using the collected data, this study comparatively analyzed the indirect evaluation variables for the degree of pipe deterioration and the results from the pipe endoscope to choose appropriate variables for pipe deterioration evaluation and calculated the weights of the indirect variables on the degree of deterioration. The results showed that the order of the impact of indirect variables on deterioration was pipe age > pipe lining material > road type > leakage frequency > average water velocity with their weights of 0.45, 0.20, 0.15, 0.10, and 0.10, respectively. Conclusively, the results suggest that the measures of sediment thickness, scale size, degree of desquamation and condition of connections are appropriate for the evaluation of pipe deterioration and sufficient for the analysis of the impact of the indirect variables on deterioration.

• Journal of the Korean institute of surface engineering
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• v.52 no.6
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• pp.283-288
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• 2019

MCrAlY overaly coatings are used as oxidation barrier coatings to prevent degradation of the underlying substrate in high temperature and oxidizing environment of the hot section of gas turbines. Therefore, oxidation resistance in high temperature is important property of MCrAlY coatings. Also, coefficients of thermal expansion (CTE) of MCrAlY have middle value of that of Ni-based superalloys and oxides, which have the effect of preventing the delamination of the surface oxides. Cyclic oxidation test is one of the most useful methods for evaluating the high temperature durability of coatings used in gas turbines. In this study, NiCoCrAlY overlay coatings were formed on Inconel 792(IN 792) substrates by vacuum plasma spraying process. Vacuum plasma sprayed NiCoCrAlY coatings and IN 792 susbstrates were exposed to 1000℃ one-hour cyclic oxidation environment. NiCoCrAlY coatings showed lower weight gain in short-term oxidation. In long-term oxidation, IN 792 substrates showed higher weight loss due to delamination of surface oxide but NiCoCrAlY coatings showed lower weight loss. X-ray diffraction (XRD) analysis showed α-Al2O3 and NiCr₂O₄ was formed during the cyclic oxidation test. Through cross-section observation using scanning electron microscopy (SEM) and electron back scatter diffraction (EBSD) analysis, thermally grown oxide (TGO) layer composed of α-Al₂O₃ and NiCr₂O₄ was formed and the thickness of TGO increased during 1000℃ cyclic oxidation test. β phase in upper side of NiCoCrAlY coating was depleted due to oxidation of Al and outer beta depletion zone thickness also increased as the cyclic oxidation time increased.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.322-329
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• 2009

60 nm- and 20 nm-thick hydrogenated amorphous silicon (a-Si:H) layers were deposited on 200 nm $SiO_2/Si$ substrates using ICP-CVD (inductively coupled plasma chemical vapor deposition). A 10 nm-Ni layer was then deposited by e-beam evaporation. Finally, 10 nm-Ni/60 nm a-Si:H/200 nm-$SiO_2/Si$ and 10 nm-Ni/20 nm a-Si:H/200 nm-$SiO_2/Si$ structures were prepared. The samples were annealed by rapid thermal annealing for 40 seconds at $200{\sim}500^{\circ}C$ to produce $NiSi_x$. The resulting changes in sheet resistance, microstructure, phase, chemical composition and surface roughness were examined. The nickel silicide on a 60 nm a-Si:H substrate showed a low sheet resistance at T (temperatures) >$450^{\circ}C$. The nickel silicide on the 20 nm a-Si:H substrate showed a low sheet resistance at T > $300^{\circ}C$. HRXRD analysis revealed a phase transformation of the nickel silicide on a 60 nm a-Si:H substrate (${\delta}-Ni_2Si{\rightarrow}{\zeta}-Ni_2Si{\rightarrow}(NiSi+{\zeta}-Ni_2Si)$) at annealing temperatures of $300^{\circ}C{\rightarrow}400^{\circ}C{\rightarrow}500^{\circ}C$. The nickel silicide on the 20 nm a-Si:H substrate had a composition of ${\delta}-Ni_2Si$ with no secondary phases. Through FE-SEM and TEM analysis, the nickel silicide layer on the 60 nm a-Si:H substrate showed a 60 nm-thick silicide layer with a columnar shape, which contained both residual a-Si:H and $Ni_2Si$ layers, regardless of annealing temperatures. The nickel silicide on the 20 nm a-Si:H substrate had a uniform thickness of 40 nm with a columnar shape and no residual silicon. SPM analysis shows that the surface roughness was < 1.8 nm regardless of the a-Si:H-thickness. It was confirmed that the low temperature silicide process using a 20 nm a-Si:H substrate is more suitable for thin film transistor (TFT) active layer applications.