• 한국재료학회지
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• 제14권10호
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• pp.743-748
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• 2004

Modified Ni/YSZ cermets for high temperature electrolysis were synthesized by the direct ball milling of Ni and YSZ powder. The ball milling was carried out in dry process and in ethanol with varying milling time. While the dry-milling decreased the average size from 65 to $80{\mu}m$, the wet-milling decreased the average size down to $10{\mu}m$. In addition, very fine particles less than $0.1{\mu}m$ were observed in the wet-milling condition. The subsequent process of cold-pressing and sintering at $900^{\circ}C$ for 2 h did not affect the particle size of dry-milled powder. The electrical conductivity of the dry-milled Ni/YSZ cermet showed the value of $5{\times}10^{2}\;S/cm$ and this value was increased to $1.4{\times}10^{4}\;S/cm$ after the sintering at $900^{\circ}C$ for 2 h.

• 소성∙가공
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• 제22권3호
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• pp.123-132
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• 2013

Hot stamping, which is the hot pressing of special steel sheet using a cold die, can combine ease of shaping with high strength mechanical properties due to the hardening effect of rapid quenching. In this paper, a thermo-mechanical analysis of hot stamping using the finite element method in conjunction with phase transformations was performed in order to investigate the plastic deformation behavior, temperature history, and mechanical properties of the stamped car part. We also conducted a fully coupled thermo-mechanical analysis during the stamping and rapid quenching process to obtain the mechanical properties with the consideration of the effects of plastic deformation and phase transformation on the temperature histories at each point in the part. The finite element analysis could provide key information concerning the temperature histories and the sheet mechanical properties when the phase transformation is properly considered. Such an analysis can also be used to determine the effect of cyclic cooling on the tooling.

• 한국세라믹학회지
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• 제48권2호
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• pp.152-159
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• 2011

The green and hard machining characteristics of dental ceramics are of great interest to dental industry. The green bodies of TZP/$Al_2O_3$ composites were prepared by the cold isostatic pressing, and machined on the CNC lathe using PCD (polycrystalline diamond) insert under various machining conditions. With increasing nose radius of PCD insert, surface roughness initially increased due to increased cutting resistance, but decreased by the onset of sliding fracture. The lowest surface roughness was obtained at spindle speed of 1,300 rpm and lowest feed rate. Hard bodies were prepared by pressureless sintering the machined green bodies at several temperatures. The grinding test for sintered hard body was conducted using electroplated diamond bur with different grit sizes. During grinding, grain pull out in the composite was occurred due to thermal expansion mismatch between the alumina and zirconia. The strength of the composite decreased with alumina contents, due to increased surface roughness and high monoclinic phase transformed during grinding process. The final polished samples represented high strength by the elimination of a phase transformation layer.

• Preventive Nutrition and Food Science
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• 제13권4호
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• pp.292-298
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• 2008

The volatile composition of Kiyomi peel oil cultivated in Korea was studied by using gas chromatography and gas chromatography-mass spectrometry. The peel oil from the Kiyomi fruit was prepared by using a cold-pressing extraction method. Among the 65 components quantified in Kiyomi oil, 25 terpene hydrocarbons and 40 oxygenated compounds were identified, with peak weight percentages measuring 94.5% and 4.9%, respectively. Limonene was the predominant compound (87.5%), followed by myrcene (2.4%), sabinene (0.9%), $\alpha$-pinene (0.8%), $\beta$-sinensal (0.8%), (Z)-$\beta$-farnesene (0.7%), neryl acetate (0.6%), valencene (0.5%), $\alpha$-farnesene (0.5%), and $\alpha$-sinensal (0.5%). A unique characteristic of the volatile profile of the Kiyomi oil was the proportion of aldehydes (2.7%), which resulted from the relative abundance of $\alpha$- and $\beta$-sinensal. Another unique characteristic of the Korean Kiyomi oil was its relative abundance of $\beta$-sinensal, (Z)-$\beta$-farnesene, neryl acetate, valencene, $\alpha$-sinensal and nootkatone. Valencene and $\alpha$- and $\beta$-sinensal were regarded as the influential components of Korean Kiyomi peel oil.

• 중환자간호학회지
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• 제6권2호
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• pp.37-50
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• 2013

Purpose: The purpose of this study was to investigate the experience of horizontal violence in intensive care unit (ICU) nurses. Methods: This is a methodological triangulation study consists of quantitative and qualitative research methods. A total of 134 ICU nurses from 5 hospitals participated in a survey on nurse to nurse horizontal violence, and the qualitative data were collected through 3 focus group interviews. Results: 94.0% of the participants have experienced horizontal violence within the past 6 months. The question with the highest mean score was "dominating senior nurses mood", and the question with the lowest mean score was "physical assaults". The qualitative data analysis revealed 17 themes on the backgrounds, types, and influence of horizontal violence. Conclusion: The survey result shows that the problem of horizontal violence in ICU nurses is serious, and the focus group interview extracts additional types of horizontal violence such as "scolding in a wrong way", "pressing to resign", "leaving out in the cold", and "burning". Further research needs to be done to build a multidimensional model of horizontal violence in the nursing workplace.

• 한국전기전자재료학회논문지
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• 제16권10호
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• pp.938-945
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• 2003

We fabricated Ni-substrate for YBCO coated conductors and evaluated the effects of pressing and annealing temperature and time on texture. Ni substrate was fabricated by powder metallurgy technique and compacts were prepared by applying uniaxial or isostatic pressure. The texture of substrate made by applying cold isostatic pressure (CIP) was stronger than that by uniaxial pressure which we attribute to the fact that the CIP method provided higher density and more uniform density distribution. It was observed that the substrate annealed at 400 C showed both retained texture and recrystallized texture. On the other hand, the texture of substrate significantly improved at annealing temperature above 500 C, forming strong 4-fold symmetry, [111] II ND texture, and FWHM of 9∼10 . It is to be noted that the degree of texture was almost independent of annealing temperature (500∼1000 C) and annealing time(1∼54 min, at 1000 C). EBSD and AFM analysis indicated that 99% of grain boundaries was low angle grain boundary and RMS was approximately 3 nm, respectively. Development of strong cube texture and high fraction of low angle grain boundary of Ni-substrate made by powder metallurgy technique in our study is considered to be suitable for the application of YBCO coated conductors.

• 한국정밀공학회지
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• 제34권2호
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• pp.77-81
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• 2017

CP (Commercially Pure) titanium has been widely used in various industries such as in energy plants and bio-materials because of an excellent corrosion resistance and its non-toxicity to the human body. But there are limitations for usage as structural materials due to low strength. The tensile properties of CP titanium could be improved by microstructure refinement such as in a SPD (Severe Plastic Deformation) process. However, high strengthening of CP titanium wire is impossible by SPD processes like ECAP (Equal Channel Angular Pressing), HPT (High-Pressure Torsion), and the ARB (Accumulative Roll Bonding) process. The study purposes are to increase the strength of CP titanium wire by optimization of the cold drawing process and the harmonization with mechanical properties by heat treatments for the next forming process. The optimization process was investigated with regard to the design of drawing dies and the reduction ratio of cross sections. The elongations of high strength CP titanium were controlled by heat treatment.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.68-71
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• 2003

We fabricated Ni-substrate for YBCO coated conductors and evaluated the effects of pressing and annealing time on texture. Ni substrate was fabricated by powder metallurgy technique and compacts were prepared by applying uniaxial or isostatic pressure. The texture of substrate made by applying cold isostatic pressure (CIP) was stronger than that by uniaxial pressure. The texture of substrate made by CIP had a strong 4-fold symmetry and [111] ∥ ND texture after annealing temperature of 100$0^{\circ}C$. It is to be noted that the degree of texture was almost independent of annealing time and the full-width at half-maximum (FWHM) of in-plane and out-of-plane was measured to be in the range of 9.55$^{\circ}$-10.53$^{\circ}$ and 8.57$^{\circ}$-9.85$^{\circ}$, respectively. Development of strong cube texture of Ni-substrate made by powder metallurgy technique in our study is considered to be suitable for the application of YBCO coated conductors.

• 한국세라믹학회지
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• 제55권4호
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• pp.337-343
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• 2018

The influence of solid loading in the slurry composition on the morphology of 3Y-TZP granules fabricated by two-fluid spray drying was investigated for solid contents varying between 30 wt% and 50 wt%. The resulting 3Y-TZP granules showed a sphere-like shape with diameters of $40-70{\mu}m$. However, a donut-like shape and a few cracks were observed on the granule surfaces fabricated using the slurry with 50 wt% solid content. The green density after cold isostatic pressing at 200 MPa was $2.1-2.2g/cm^3$, and a homogeneous fracture surface was obtained by complete destruction of granules. After sintering at $1500^{\circ}C$ for 2 h, all specimens had relative densities of 96.2 - 98.3%. With increasing solid content, the relative density decreased from 98.3% to 96.2%, but the grain size increased from $0.3{\mu}m$ to $0.6{\mu}m$. Highly sinterable zirconia granule powder could be obtained by controlling the slurry composition.

• Journal of Magnetics
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• 제11권3호
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• pp.126-129
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• 2006

The phosphate coating on the $(Fe_{0.97}Cr_{0.03})_{76}(Si_{0.5}B_{0.5})_{22}C_2$ amorphous powders with an average size of 10 ${\mu}m$ in diameter has been carried out in aqueous 1.0-2.0 wt% $H_3PO_4$ solutions, and the consolidation behavior and magnetic properties of their compressed powder cores has been investigated. The phosphate coating could provide efficient electrical insulation between amorphous powders and improved consolidation ability at room temperature. Especially when the powders were treated in more concentrated phosphoric acid solution, enhanced phosphate covering and higher frequency/dc-bias stability were achieved. The powder cores phosphate-coated in 2.0 wt% $H_3PO_4$ solution exhibited constant permeability of 21 up to 10 MHz, 110 of the quality factor at 0.9 MHz, 610 mW/cm3 core loss at 100 kHz/0.1 T and 89 of percent permeability at 100 kHz.