• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.437-442
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• 1996

High quality $YBa_2Cu_3O_y$(YBCO) thin films for directly coupled dc superconducting quantum interference device (SQUID) were fabricated by pulsed laser deposition. Several critical parameters have been optimized through systematic studies. Thus, the films showing the $T_c$ of above 91K and $J_c$ of above$2\times10^6A/cm^2$ at 77K were routinely obtained. Extensive AFM and X-ray diffraction studies have been conducted for morphological and structural analyses. The directly coupled DC-SQUIDs were fabricated from the YBCO thin films deposited on $SrTiO_3$ bicrystals under the optimized conditions. The measurement on $2I_c$ and swing voltage give 200$\mu$A and 17$\mu$V at 77K, respectively.

• Metals and materials international
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• v.24 no.6
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• pp.1432-1437
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• 2018

This work investigated edge-cracking behavior of equiatomic CoCrFeMnNi high-entropy alloy during hot rolling at rolling temperatures $500{\leq}T_R{\leq}1000^{\circ}C$. Edge cracks did not form in the material rolled at $500^{\circ}C$, but widened and deepened into the inside of plate as $T_R$ increased from $500^{\circ}C$. Edge cracks were most severe in the material rolled at $1000^{\circ}C$. Mn-Cr-O type non-metallic inclusion and oxidation were identified as major factors that caused edge cracking. The inclusions near edge region acted as preferential sites for crack formation. Connection between inclusion cracks and surface cracks induced edge cracking. Rolling at $T_R{\geq}600^{\circ}C$ generated distinct inclusion cracks whereas they were not serious at $T_R=500^{\circ}C$, so noticeable edge cracks formed at $T_R{\geq}600^{\circ}C$. At $T_R=1000^{\circ}C$, significant oxidation occurred at the crack surface. This accelerated edge crack penetration by embrittling the crack tip, so severe edge cracking occurred at $T_R=1000^{\circ}C$.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.80-88
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• 1997

The attempt to enhance the strength of materials has been an important subject for materials engineering and scientists. The strength of materials is termed as the ability to support high load without excessive deformation and without breaking catastrophically. The control of dislocation densities and barriers to the movement of dislocations have been considered to be the important methods for the strengthening materials. One of the approaches is mechanical blocking of dislocations by alternately depositing material layers. The typical structure of materials is multilayered and laminated composites. The thickness of each layer is typically in the range of nanometer. Ton avoid confusion with other terminology they may be defined as microlaminate composite materials. The manufacturing process of multilayered laminate structure will be introduced. And the current theoretical theories will be reviewed in view of strengthening of microlaminte composite materials.

• Proceedings of the Korean Magnestics Society Conference
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• 2015.05a
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• pp.46-46
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• 2015

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1625-1627
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• 2009

• Proceedings of the Korean Magnestics Society Conference
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• 2014.11a
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• pp.124-124
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• 2014

• Proceedings of the Korean Magnestics Society Conference
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• 2016.05a
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• pp.137-137
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• 2016

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.981-988
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• 2010

The effects of Cr and Al contents in Fe-Al and Fe-Cr alloys on oxidation resistance, hardness, and the thermal expansion coefficient were investigated. Fe-Al and Fe-Cr alloys above 10wt.%Al and 20wt.%Cr contents have a high oxidation resistance. The hardness of the Fe-Al and Fe-Cr alloys increased with an increase in Al and Cr contents due to solid solution or formation of an intermetallic compound. The coefficients of thermal expansion of the Fe-Al alloys were higher than those of the Fe-Cr alloys because the coefficient of thermal expansion of Al was higher than that of Fe and Cr.

• Journal of People, Plants, and Environment
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• v.24 no.6
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• pp.685-691
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• 2021

Background and objective: Understanding abstract art as an art form requires depth of thought. Moreover, understanding land art as abstract art is challenging, given its focus on the minimalism and abstract concepts. Much focus, research, and work were actively conducted in the 1970s, as it represented an abstract expression of minimalism. The characteristics of minimalism connote abstract meanings in the use of materials. Nevertheless, the original research of works or artists has often been mentioned, but few studies have analyzed the abstract language of land art materials. The aim of this study is to thus determine the abstract meanings of materials in land art from the 1970s to the 2010s. Methods: Art-based research was employed to address the aim. This study classified the land art materials into intangible and tangible materials, where intangible materials focused on lines, circles, and labyrinths, and tangible materials focused on the earth, stones, wood, and snow. Results: Intangible and tangible materials of land art conveyed various abstract meanings. Intangible materials were reflective of connection and symbiosis with nature, delivering abstract languages of 'take-nothing,' 'reflection' and 'opportunity.' Tangible materials reflected the abstract concepts of 'intervention,' 'resistance,' 'unliving,' and 'change,' and conveyed caveats. In other words, taken together, intangible and tangible materials were presented in symbiosis-and with caveats-and delivered messages for the present and the future. Interestingly, intangible materials inherently reflect symbiosis and communicate caveats in works based on a non-contextualized present and future. Conclusion: Interpretation of the abstract languages derived from intangible and tangible materials could imply a symbiosis between humans and nature, while conveying the message that caveats, to humans, are still ongoing. This relationship plays a significant role in an artist's selection of a medium, which is reflective of abstract beliefs reflected in contemporary, nature-based works created on Earth.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.285-291
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• 2012

Hydroxyapatite (HA) is well known as a biocompatible and bioactive material. HA has been practically applied as bone graft materials in a range of medical and dental fields. In this study, two types of dense hydroxyapatite ceramics were prepared from natural bones and synthetic materials. The biocompatibility of HA ceramics for supporting osteoblast cell growth and cytotoxicity using an in vitro MG-63 cell line model were respectively evaluated. Artificial hydroxyapatite shows relative density of 93% with 1-2 ${\mu}m$ after sintering, but a hydroxyapatite compact derived from bovine bone has low sintered density of 85% with a small content of MgO. Irrespective of the starting raw materials, both types of sintered hydroxyapatite displayed similar biocompatibility in the tests. FE-SEM observations showed that most MG-63 cells had a stellar shape and formed an intercellular matrix containing fibers on sintered HA. The cells were well attached and grown over the HA surface, indicating that there was no toxicity.