• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.244-250
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• 2020

β-Tricalcium phosphate (β-TCP, Ca3(PO4)2) is a kind of biodegradable calcium phosphate ceramics with chemical and mineral compositions similar to those of bone. It is a potential candidate for bone repair surgery. To improve the bioactivity and osteoinductivity of β-TCP, various ions doped calcium phosphate have been studied. Among them, Iron is a trace element and its deficiency in the human body causes various problems. In this study, we investigated the effect of Fe ions on the structural variation, degradation behavior of β-TCP. Fe-doped β-TCP powders were synthesized by the coprecipitation method, and the heat treatment temperature was set at 925 and 1100℃. The structural analysis was carried out by Rietveld refinement using the X-ray diffraction results. Fe ions existed in a different state (Fe2+ or Fe3+) with different heat treatment temperatures, and the substitution sites (Ca-(4) and Ca-(5)) also changed with temperature. The degradation rate was fastest at Fe-doped β-TCP with heated at 1100℃. The cell viability behavior was also enhanced with the substitution of Fe ions. Therefore, the substitution of Fe ion has accelerated the degradation of β-TCP and improved the biocompatibility. It could be more utilized in biomedical devices.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.176-179
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• 2005

Spray casting of hypereutectic Al-Si based alloy has been reported to provide distinct advantages over ingot metallurgy (IM) or rapid solidification/powder metallurgy (RS/PM) process in terms of microstructure refinement. Hypereutectic Al-Si based alloys have been regarded attractive for automotive and aerospace application, due to high specific strength, good wear resistance, low coefficient of thermal expansion, high thermal stability, and good creep resistance. In this study, hypereutectic Al-25Si-2.0Cu-1.0Mg alloy was prepared by OSPREY spray casting process. High temperature deformation behavior of the hypereutectic Al-Si based alloy has been investigated by applying the internal variable theory proposed by Chang et al. The change of strain rate sensitivity and Creep transition were analyzed by using the load relaxation test and constant creep test.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.80-84
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• 2000

A mesh superposition technique is presented for an efficient analysis of structural behavior. Refined child mesh is superimposed over parent elements for the region of interest. It is a kind of adaptive mesh refinement, which allows locally refined mesh without introducing transition region or multipoint constraints. Proper boundary condition is necessary to avoid redundant rigid body motion and kinematic compatibility between neighbor elements. Delamination buckling analysis is conducted to demonstrate accuracy and efficiency of the present method.

• Bulletin of the Korean Mathematical Society
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• v.36 no.1
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• pp.33-45
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• 1999

In this paper, we are interested in studying weak covering properties in the presence of a countable compact condition. The purpose of this paper is to characterize an ideal weakly $\delta$$\theta$-refinable space and to show that every ideal weakly $\delta$$\theta$-refinable space is isocompact. Also, we consider the behavior under mappings of ideal weakly $\delta$$\theta$-refinable properties and productivity of ideal weakly $\delta$$\theta$-refinable properties.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.45-53
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• 2005

In this paper, we present a cross-layer analysis of wireless TCP systems over correlated channels. The effects of error correlation on the behavior of link retransmission strategy and the end-to-end throughput of TCP layer are investigated. Based on the cross-layer analysis, an efficient refinement of link layer protocol is proposed by consciously utilizing the information of channel correlations, which leads to the performance improvement of wireless TCP systems.

• International Journal of Costume and Fashion
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• v.4
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• pp.63-80
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• 2004

Elegance in dress has been mentioned as an important term for explaining a beauty of dress and a fashion image through the times in the history of dress. Nevertheless, it has been spoken indeterminately without analyzing the accurate meaning. In addition, almost all the scattered discourses of it were very limited to womenswear. The purpose of this study is to provide a framework for a better understanding of the concept of elegance and its aesthetic characteristics expressed visually on dress from the holistic viewpoint, focusing on male elegance in dress. To obtain the purpose, the documentary study and the practical analysis were carried out. Elegance in dress is based upon the idea of aristocratic taste cultivated by good breeding. It is expressed visually through not only the carefully contrived dress but also a sort of aura of dressed body with skillful ease. Its aesthetic values consist of luxury, nobility, refinement, femininity, harmony. Though male elegant styles had already existed throughout the history of dress, it was Mannerism in the 16th century which expressed ‘studied elegance’ for the first time. On the grounds of both the classification of periodic styles and the periodic values, they can be defined and categorized into Mannerism Elegance, Salon Elegance, Modern Elegance Since Dandyism, Aestheticism Elegance. In the late 20th century they can be recognised as Classic Dandyism Elegance, Soft Casual Elegance, Elaborate Heroic Elegance. Although male elegance in dress has been visualized in different ways depending on periodic values, it has essentially been a refined beauty of high class which was valued until recent years. Its common plastic features appear as soft shapes, subtle colors and delicate fabrics modulated with exquisiteness and well-adorned appearance, graceful behavior make elegant styles completed. All of elegant styles have m common with refinement, harmony as main aesthetic values.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.329-334
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• 2015

The aim of this paper is to determine the proper heat treatment temperature for SDSS tube production without ${\sigma}$-phase precipitation. When Mother steel tube was heat treated at $800^{\circ}C$ temperature, relatively a large amount of ${\sigma}$-phase precipitated and grain refinement of ferrite phase occurred simultaneously. However, in Pilgered and Drawn steel tubes, grain refinement of the ferrite phase did not occur and a small amount of ${\sigma}$-phase precipitated. For all three types of steel tubes, the pitting potential was reduced to 2/5 or less compared with the untreated one and corrosion also occurred in the salt spray test due to the precipitation of ${\sigma}$-phase. When heat treatment temperature was $900^{\circ}C$, grain refinement of the ferrite phase occurred and very little ${\sigma}$-phase precipitated in Pilgered and Drawn steel tubes. But when heat treatment was done at $1,000^{\circ}C$ temperature, all three types of steel tubes had a similar corrosion properties of that of untreated one and also corrosion did not occur in the salt spray test, as ${\sigma}$-phase did not precipitate. Therefore, the optimum heat treatment temperature range is determined to be more than $1000^{\circ}C$ for the SDSS at which corrosion does not occur.

• Journal of Powder Materials
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• v.19 no.1
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• pp.32-39
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• 2012

This study investigated refinement behaviors of TiC powders produced under different impact energy conditions using a mechanical milling process. The initial coarse TiC powders with an average diameter of 9.3 ${\mu}m$ were milled for 5, 20, 60 and 120 mins through the conventional low energy mechanical milling (LEMM, 22G) and specially designed high energy mechanical milling (HEMM, 65G). TiC powders with angular shape became spherical one and their sizes decreased as the milling time increased, irrespective of milling energy. Based upon the FE-SEM and BET results of milled powders, it was found initial coarse TiC powders readily became much finer near 100 nm within 60 min under HEMM, while their sizes were over 200 nm under LEMM, despite the long milling time of up to 120 min. Particularly, ultra-fine TiC powders with an average diameter of 77 nm were fabricated within 60 min in the presence of toluene under HEMM.

• The KIPS Transactions:PartD
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• v.18D no.6
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• pp.443-450
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• 2011

Model-based Component development methodologies consider the whole system as an component and develop physical components through recursive decomposition and refinements of components in a top-down manner. We developed a model translator that can be used to formally verify interaction consistency among components, especially the interaction behavior between before- and after- refinements of components. This translator can be used to identify potential problems in the refinement process so that problems can be addressed from the early stage of development. This paper introduces our translation approach and the organization of the translator. The translator has been applied to two case studies to show its usefulness.

• Journal of Powder Materials
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• v.14 no.1 s.60
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• pp.26-31
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• 2007

Manufacturing bulk nanostructured materials with least grain growth from initial powders is challenging because of the bottle neck of bottom-up methods using the conventional powder metallurgy of compaction and sintering. In this study, bottom-up type powder metallurgy processing and top-down type SPD (Severe Plastic Deformation) approaches were combined in order to achieve both real density and grain refinement of metallic powders. ECAP (Equal Channel Angular Pressing), one of the most promising processes in SPD, was used for the powder consolidation method. For understanding the ECAP process, investigating the powder density as well as internal stress, strain distribution is crucial. We investigated the consolidation and plastic deformation of the metallic powders during ECAP using the finite element simulations. Almost independent behavior of powder densification in the entry channel and shear deformation in the main deformation zone was found by the finite element method. Effects of processing parameters on densification and density distributions were investigated.