• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.183-188
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• 1998

Gas sensitizations of tin oxide film were investigated by measuring the change of film resistance in various gas atmospheres such as $N_2,\; O_2,\; H_2O$. The main test sample, polycrystalline $SnO_2$ film containing small Sb as a dopant was prepared by a sputtering technique and showed a long term stability in base resistance and thus, in gas sensitivity. The adsorption of oxygen on the film surface as a type of $(O_{ads})$ at the temperature of around $300^{\circ}C$ played important roles in sensor operating mechanism. The roles were ⅰ) the increase of base resistance in ambient air, which consequently lead to high sensitivity and ⅱ) the promotion of fast recovery. The reaction of hydrogen gas with the already adsorbed $(O_{ads})$ ions was considered as a decisive sensitization mechanism of tin oxide film. However, the dissociation of hydrogen molecules on film surface, by direct donation of electron to film also took a major part in the sensitization. The effect of humidity on gas sensitization was found to be negligible at the sensor operating temperature of around $300^{\circ}C$.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.899-917
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• 2017

Sixty four tests were performed in a steel tank to investigate the axial responses of piles driven into organic soil prepared at two different densities using a drop hammer. Four different pile materials were used: wood, steel, smooth concrete, and rough concrete, with different length to diameter ratios. The results of the load tests showed that the shaft load capacity of rough concrete piles continuously increased with pile settlement. In contrast, the others pile types reached the ultimate shaft resistance at a settlement equal to about 10% of the pile diameter. The ratios of base to shaft capacities of the piles were found to vary with the length to diameter ratio, surface roughness, and the density of the organic soil. The ultimate unit shaft resistance of the rough concrete pile was always greater than that of other piles irrespective of soil condition and pile length. However, the ultimate base resistance of all piles was approximately close to each other.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.124-133
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• 1997

Corrosion behavior of welded SWS400 steel used for bridges was studied in a range of the acid-rain environment using immersion, potentiodynamic polartization, polarization resistance, and galvanic corrosion tests. The SWS400 steel exhibited active corrosion behavior in the range of acid-rain environment, i.e. no passivation. As the results of immersion corrosion test, Tafel extrapolation method, and polarization resistance measurement, the average corrosion rats of the steels were 0.31-0.72 mm/year in the pH of 4-5, and 0.17 mm/yera in the pH 6, respectively. The steel showed a resistance to corrosion in the pH 6. The observed active behavior of SWS400 steel in chloride-containing environment indicated that the chloride ions exerts a detrimental influence on the formation of passive films. Galvanic corrosion was observed between the weld and the base metals because the weld is anodic to the base metal.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.4
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• pp.187-191
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• 2004

In this work, we used the PCID simulator for simulation of solar cell and examined the effect of front-back surface recombination velocity, minority carrier diffusion length, junction depth and emitter sheet-resistance. As the effect of base thickness, the efficiency decreased by the increase in series resistance with the increase of the thickness and found decrease in efficiency by decrease of the current as the effect of the recombination. Also, as the effect of base resistivity, the efficiency increased somewhat with the decrease in resistivity, but when the resistivity exceeded certain value, the efficiency decreased as a increase in the recombination ratio. The optimum efficiency was obtained at the resistivity 0.5 $\Omega$-cm, and thickness $100\mu\textrm{m}$. We have successfully achieved 10.8% and 13.7% efficiency large area($103mm{\times}103mm$) mono-crystalline silicon solar cells without and with PECVD silicon nitride antireflection coating.

• Laser Solutions
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• v.3 no.1
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• pp.38-45
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• 2000

A 4㎾ RS840 CO2 laser with a powder auto-feeding apparatus has been used to deposit multiple overlapping tracks of Ni-base superalloy on to low carbon steel. It was found that the surface roughness(turbulence) of an overlapped cladding layer decreased with the increase of the overlapping ratio in an oscillating manner. When the overlapping ratio had values of 0.62, the surface turbulence was lowest. Overlapping ratio offer significant potential for improvement of materials surface properties such as corrosion performance and wear resistance. This paper reports that the overlapping ratio shows best corrosion resistance. The tensile residual stresses generated at the higher overlapping ratio( ＞ 0.45) and the element concentration of Fe increased in the surface layer at the lower overlapping ratio( ＜ 0.45) may lead to worse corrosion resistance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.265-273
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• 2006

This study aims at evaluation of the fire resistance performance of cementitious materials for fire protection of tunnel. For this purpose, the research procedure was divided into three parts. First, base mix proportion with different material type were determined by fire test. Second, the fire test of cementitious materials for fire resistance were performed on base mix proportions to evaluated their performance. Third, the performance of cementitious materials for fire resistance compare to the target value and existing commercial products. If the performance of developed cemetitious materials for fire resistance were satisfied the target value, this studies were stopped. But, this research return to first process if the performance of cementitious materials for fire resistance are not satisfied the target value. As a result of this study, the spalling did not happen for develop and existing commercial product. Also, developed cementitious materials for fire resistance are shown with excellent compressive strength, flexural strength, and bond strength, because it used a height density aggregate. And developed cementitious materials has sufficient resistance for fire.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.181-189
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• 1998

In order to investigate the effect of base oil composition on the electronic insulating oil's performances, an experimental study has been conducted using different oils. Owing to their properties, like lower pour point and gas absorbing, naphthenic base oils are used more often than paraffmic base oils for the electronic insulating oil application. Naphthenic and paraffinic base oils are significantly different in their aromatic hydrocarbon content. In this paper, PXE(para xylyl ethane), LAB(linear alkylbenzene), C13 aromatic hydrocarbon mixture and C17 aromatic hydrocarbon mixture are investigated regarding their influence on insulating oil's performances. According to present study, breakdown voltage decreased with increasing aromatic lydrocarbon content in a deep dewaxed paraffmic base oil. However, any changing in the dissipation factor was not recognizable at small treated level. Furthermore, the volume resistance was not influenced by aromatic hydrocarbon content. The gassing tendency was found as a highly sensible property, changing with treating aromatic hydrocarbons. The higher benzene ring content in the hydrocarbon, the better gassing tendency.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.205-212
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• 1995

Effect of Mn addition on rolling contact fatigue of C-base induction hardened bearing steels has been investigated to develop inexpensive surface-hardened bearing steels with improved resistance to rolling contact fatigue. Fatigue tests were conducted in elasto-hydrodynamic lubricating conditions at a shaft speed of 5,000rpm, under max. Hertzian stress of $492kg/mm^2$. It was found in the C-Mn steels that effective depth of induction hardened layer and amount of retained austenite were slightly increased in comparison with those of C-base steels. finer interlamellar spacing of pearlite in the C-Mn steels was also observed using TEM. Decomposition of retained austenite during rolling contact fatigue was smaller in quantity in the C-Mn steels than C-base steels. This might be associated with enhanced mechanical stability of retained austenite with addition of Mn. Statistical analysis of fatigue life for C-Mn steels using Weibull distribution indicated that improved resistance to rolling contact fatigue was mainly attributed to transformation induced plasticity and mechanical stability of retained austenite.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.37 no.2 s.110
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• pp.70-77
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• 2005

For the purpose of developing liner board for water resistant corrugated board in the cold chain system, several types of base paper for corrugated board were purchased from the market and 6 different boards were produced in the mill by applying the chemicals, chosen in the previous studies, on the base paper. Then water-moisture resistance and physical properties of the boards were compared each other. The liner board which is dried at high temperature with pressure by Condebelt (CK paper) showed a superior performance in strength over common liner boards. Strength of the board increased by surface chemical treatment up to $60\%$ of compressive strength and $30\%$ of burst strength. Starch insolubilization with Ammonium Zirconium Carbonate and surface coating with a surface sizing agent and a moisture resistant chemical on CK paper showed the best result. Therefore this method was recommended to produce the outer liner board for water resistant corrugated board.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.33-37
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• 2003

The new textured surface epitaxial base(TSEB) cell as a high efficiency Si solar cell was fabricated and its eletro-optical characteristics were investigated. The fabricated device showed the open circuit voltage of 0.62 V, the short circuit current of 40 mA, the fill factor of 0.7, and the efficiency of 16% under the incident light of AM-1 100 mW/$cm^2$. The TSEB cell proposed in this paper has the structural superiority in the fabrication of high efficiency solar cell due to the carrier drift transport in the optical absorption region and the formation of back surface field by $P^-/P^+$ epitaxial base, and the low emitter series resistance by insertion of $n^+$ buried contact.