• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.109-115
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• 2020

Surfaces with various roughnesses were produced through laser processing, and the anisotropy and hydrophobicity of the surfaces were examined in the context of the microstructures. The fine particles transferred to the glass surface exhibited different sizes, and the roughness increased. Due to the change in the roughness, the liquid could not penetrate the space between the fine particles, and it was thus exposed to the air. We analyzed this phenomenon using the combined Wenzel and Cassie-Baxter models. Excessive fine particle formation on the substrate tended to increase the roughness and surface energy. The silver-glass-air contact analysis could clarify the mechanism of the reduction of the contact angle and differences in the metastable and stable states when the particles did not completely cover the glass substrate. The formation of microstructures with fine particles through the laser selective deposition led to the generation of an anisotropic surface as the water droplets diffused toward the glass substrate with a relatively high surface energy level.

• Computers and Concrete
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• v.12 no.5
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• pp.651-668
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• 2013

Concrete structures need repairing due to various reasons such as deteriorative effects, overloading, poor quality of workmanship and design failures. Cement based repair mortars are the most widely used solutions for concrete repair applications. Various factors may affect the bond strength between concrete substrate and repair mortars. In this paper, the effects of polymer additives, strength of the concrete substrate, surface roughness, surface wetness and aging on the bond between concrete substrate and repair mortar has been investigated. Full factorial experimental design is employed to investigate the main and interaction effects of these factors on the bond strength. Analysis of variance (ANOVA) under design of experiments (DOE) in Minitab 14 Statistical Software is used for the analysis. Results showed that the interaction bond strength is higher when the application surface is wet and strength of the concrete substrate is comparatively high. According to the results obtained from the analysis, the most effective repair mortar additive in terms of bonding efficiency was styrene butadiene rubber (SBR) within the investigated polymers and test conditions. This bonding ability improvement can be attributed to the self-flowing ability, high flexural strength and comparatively low air content of SBR modified repair mortars. On the other hand, styrene acrylate rubber (SAR) modified mortars was found incompatible with the concrete substrate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.859-863
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• 2010

Evolution of surface morphology of ${\alpha}-Al_2O_3$ substrate was investigated as a function of annealing temperature and time. Commercial (0001) ${\alpha}-Al_2O_3$ single crystal substrates were annealed in the range of $600-1000^{\circ}C$ in air. At $600^{\circ}C$, step-terrace structure started to be formed on the substrate. However, the surface roughness on the terrace was still considerable and a number of islands were observed on the step edges as well as the terraces. As the annealing temperature increased, the islands were absorbed into the step edges. Thus the terraces were smoother and the step edges were more straightened. Well-defined surface with a step height of 0.2 nm was formed above $900^{\circ}C$. On the other hand, when the substrate was annealed at a fixed temperature of $1000^{\circ}C$, the change of surface morphology was observed for the substrate annealed for 10 min. After the annealing for 30 min, the surface on which any islands could not survive was observed.

• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.796-801
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• 2008

$LaGaO_3$ thin film was prepared on Ni-Fe metal porous substrate by Pulsed Laser Deposition method. By the thermal reduction, the dense $NiO-{Fe_3}{O_4}$ substrate is changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate are controlled by the reduction temperature. It was found that a thermal expansion property of the Ni-Fe porous metal substrate is almost the same with that of $LaGaO_3$ based oxide. $LaGaO_3$ based electrolyte films are prepared by the pulsed laser deposition (PLD) method. The film composition is sensitively affected by the deposition temperature. The obtained film is amorphous state after deposition. After post annealing at 1073K in air, the single phase of $LaGaO_3$ perovskite was obtained. Since the thermal expansion coefficient of the film is almost the same with that of LSGM film, the obtained metal support LSGM film cell shows the high tolerance against a thermal shock and after 6 min startup from room temperature, the cell shows the almost theoretical open circuit potential.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.32-38
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• 1998

This paper is to investigate of microhardness, adhesive strength, tensile strength, and fatigue strength of ceramic sprayed steel. Rotary bending fatigue tests have been conducted at room temperature in air and 3% NaCl solution using specimens of carbon steel(S45C) with sprayed coating layers of Ni-4.5% Al(under coating) and $TiO_2$ (top coating). The microhardness has been improved at $800^{\circ}C$ heat treatment and 150mm spraying distance. Tensile strength of the sprayed steel is dependent on the substrate strength. The fatigue strength of the sprayed steel is larger than that of substrate due to blasting and constraint surface of plastic deformation effect. In low stress level, the corrosion fatigue strength of the sprayed steel were lower than that of fatigue strength in air by corrosion.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.266-275
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• 1995

A numerical investigation on the conduction-natural convection-surface radiation conjugate heat transfer in the enclosure having substrate and chips has been performed. A 2-dimensional simulation model is developed by considering heat transfer by conduction, convection and radiation. The solutions to the equation of radiative transfer are obtained by the discrete ordinates method using S-4 quadrature. The effects of Rayleigh number and the substrate-fluid thermal conductivity ratio on the cooling of chip are analyzed. The result shows that radiation is the dominant heat transfer mode in the enclosure.

• Journal of Advanced Marine Engineering and Technology
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• v.13 no.2
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• pp.64-77
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• 1989

In this study, the experiments were carried out for the purpose of establishment of aluminium cementation to steel surface by diffusible heat treatment after making the coated film onto the substrate by arc spray method. Also, the microstructure and mechanical properties of the cementation layer produced by this study were inspected for various heat treatment and spraying conditions. Main results obtained are as follow ; 1. The coating film characteristics which have excellent errosion-resistance, high temperature oxidation-resistance are obtained by aluminium penetration heat treatment after making the sprayed aluminum coating film onto the steel substrate. 2. Aluminium diffusion penetration takes place at higher temperature than 660.deg.C, and the more heat treatment time and the higher heat treatment temperature adopted, the deeper diffusion layer obtained. 3. Insert gas arc spraying using argon gas as the carrier gas higher improvement of mechanical property than that of compressed air environment. 4. The coating film characteristics appeared to be improvement of adhesive property, porosity plugging effect by heat treatment in air environment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.82-83
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• 2008

AI doped ZnO (AZO) films, and intentionally Zn added AZO (ZAZO) films were prepared on Corning glass by rf magnetron sputtering, and the electrical, optical, and structural properties of the as-deposited films together with the air annealed films were investigated. The resistivity of the AZO films increased with increasing substrate temperature and having minimum resistivity at $150^{\circ}C$. At the high temperature, the ZAZO films showed improved electrical properties better than the AZO films due.to increase in both the carrier concentration and.the Hall mobility. Upon air annealing at $500^{\circ}C$, the resistivity of both AZO and ZAZO films increased substantially, but the relative amount of degradation was smaller for films deposited at $450^{\circ}C$ than the films deposited at $150^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.636-640
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• 1995

FeN thin films were deposited on glass by RF diode reactive sputtering. The films were annealed in the air and in vacuum. The film annealed in the air showed sharp decrease of saturation magnetization and change of easy axis direction to hard axis direction and vice versa after $300^{\circ}C$ anneal. The coercivity decreased down to 0.5 Oe after $400^{\circ}C$ anneal. After $450^{\circ}C$ anneal, the film showed ${\varepsilon}-Fe_{2-3}N$ phase. The films annealed in vacuum showed coercivity increase after $300^{\circ}C$ anneal for the film deposited with initial substrate temperature of $35^{\circ}C$ and after $400^{\circ}C$ anneal for the film deposited with initial substrate temperatue of $170^{\circ}C$. These films showed $Fe_{16}N_{2}$ X-ray peaks after $450^{\circ}C$ anneal.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.4
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• pp.40-46
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• 1995

The characteristics of the shielded suspended substrate coplanar waveguide(SSCPW) are analyzed by applying the point matchning method to the quasi-TEM mode approximation. The characteristic impedances and the effective dielectric constants are also calculated by changing the height of air and dielectric layer, and the strip width of SSCPW. Approaching the side strip width of SSCPW to zero, values of characteristic impedances and effective dielectric constants are agreed well with the results obtained by the variational method.