• Journal of Surface Science and Engineering
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• v.54 no.2
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• pp.90-95
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• 2021

Surface modification technique enabling the control of condensation provides various benefit in various engineering systems, such as heat transfer, desalination, power plants, and so on. In this study, lubricant oil-impregnation into Teflon-coated nanoporous anodic oxide layer of aluminum to enhance a de-wetting and mobility of water droplet on surface. Due to the surface treatment improving water-repellency, the condensation mode is changed to dropwise, thus the frequency of sliding condensed water droplet on surface is increased. For these reasons, the surface of oil-impregnated Teflon-coated nanoporous anodic aluminum oxide shows significantly enhanced condensation heat transfer compared to bare aluminum surface. In addition, the porosity of anodic aluminum oxide affected the mobility of water droplet even with oil-impregnation and Teflon-coating, indicating that the optimization of porous structure of anodic oxide is required for maximizing the condensation heat transfer.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.4
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• pp.165-170
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• 2021

Zirconium has excellent mechanical strength and high heat resistance and excellent corrosion resistance, and it is very important to study zirconium's dissimilar welding properties since it can be used in various applications under harsh environments. Similar welding of pure zirconium and dissimilar metal welding of pure zirconium and pure titanium were performed by TIG welding, and the welding properties were studied in association with microstructural and mechanical properties. In the Zr/Zr welded specimen, sound FZ and HAZ regions showed a basketweave microstructure composed of plate α phase. FZ region of Zr/Ti dissimilar welded specimen exhibited a maximum hardness value of 354.8 Hv, which is about three times higher than that of Ti base metal, due to the precipitation of very fine metastable ω and α phases in the beta matrix. In addition, due to the microstructural continuity in the FZ and HAZ regions, excellent elongation property of 21% was exhibited.

• Journal of Powder Materials
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• v.30 no.3
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• pp.210-216
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• 2023

In this study, machine learning models are proposed to predict the Vickers hardness of AlSi10Mg alloys fabricated by laser powder bed fusion (LPBF). A total of 113 utilizable datasets were collected from the literature. The hyperparameters of the machine-learning models were adjusted to select an accurate predictive model. The random forest regression (RFR) model showed the best performance compared to support vector regression, artificial neural networks, and k-nearest neighbors. The variable importance and prediction mechanisms of the RFR were discussed by Shapley additive explanation (SHAP). Aging time had the greatest influence on the Vickers hardness, followed by solution time, solution temperature, layer thickness, scan speed, power, aging temperature, average particle size, and hatching distance. Detailed prediction mechanisms for RFR are analyzed using SHAP dependence plots.

• Journal of Korea Foundry Society
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• v.17 no.6
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• pp.538-544
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• 1997

• 한국전자현미경학회:학술대회논문집
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• 2002.11a
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• pp.56-57
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• 2002

• Proceedings of the Korean Vacuum Society Conference
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• 1995.02a
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• pp.31-31
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• 1995

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.112-116
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• 2002

• Proceedings of the Korean Magnestics Society Conference
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• 2014.05a
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• pp.82-83
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• 2014

• Journal of Korea Foundry Society
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• v.14 no.1
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• pp.35-44
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• 1994

Mechanical properties of austempered ductile iron can be guaranteed if a good knowledge of its metallugical structure is obtained. In this paper, the effects of small Mo additions to austempered ductile iron on its metallurgical structures as a function of section size are examined. From the results, it is found that ${\gamma}-pool$ region and segregation of Mo in ${\gamma}-pool$ region are increased with increase in the section size.

• Journal of Korea Foundry Society
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• v.27 no.1
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• pp.13-19
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• 2007