• Korean Journal of Materials Research
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• v.7 no.4
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• pp.276-286
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• 1997

SOFC용 L $a_{0.68}$Ca/ sub 0.32/C $r_{0.97}$ $O_{3}$분말은 수산염법에 의해 제조되었고, 이 합성된 분말을 이용한 슬러리의 최적제조조건과 그린 필름의 최적 소성조건을 얻었으며,이 제조 조건에서 소결 시간과 온도에 따라 제조된 연결재료의 결정구조, 미세구조 및 소결거동을 각각X-선 회절, 주사전자현미경 그리고 에너지 분산 분광계를 이용하여 조사하였다. L $a_{0.68}$C $a_{0.32}$C $r_{0.97}$ $O_{3}$의 저온소결은 $Ca_{m}$ (Cr $O_{4}$)$_{n}$에 의해 이루어졌음이 관찰되었고, 이때 $Ca_{m}$ (Cr $O_{4}$)$_{n}$은 불규칙하게 녹아서 L $a_{1-x}$C $a_{x}$Cr $O_{3-}$$\delta$/와 반응하고 이 현상이 질량 이동을 증가시켜 시편의 급격한 결정립 성장과 조밀화를 야기시켰다. 이러한 결정립 성장과 조밀화는 소결온도 140$0^{\circ}C$부터 일어났다.X>부터 일어났다.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.21-21
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• 1996

• Journal of Nutrition and Health
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• v.29 no.9
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• pp.1013-1020
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• 1996

The purpose of this study was to investigate nutrient intake and bone status in rural postmenopausal women in Korea. Ten postmenopausal women in An-Sung area participated in this study and they were divided into two groups ; women in group I had been postmenopausal for 4 years or less and those in group II had been postmenopausal for 5 years or more before the present study began. Their environmental factors and dietary intakes were surveyed through the personal interviews. Serum levels of calcium, phosphorus, parathyroid hormone(PTH), estradiol and urinary Ca, P, creatinine, hydroxyproline levels were measured from December 4 to December 27 in 1993. The reults of this study are summarized as follows : Average ages of group I and II were 54.8 and 57.2 years. Average menopausal ages of group I and II were 50.8 and 47.3 years. The nutrient intakes of subjects were higher than recommended dietary allowances(RDA) except calorie, protein, calcium, and vitamin A. The nutrient status did not show any significant difference between group I and II. Serum levels of Ca, P, PTH, estradiol and urinary P, creatinine excretion did not show any significant difference between group I and II, and all levels were in normal range. Urinary Ca excretion(p<0.05) and hydroxyproline excretion(p<0.01) were significantly lower in group I than in group II. Urinary Ca/creatinine(Ca/cr) and hydroxyproline/creatinine(Hpr/cr) rations were significantly higher in group II than in group I(p<0.01. And Hpr/cr levels of group I were in normal range, but most of subjects in group II were higher than 0.017 indicating sign of osteoporosis. Correlations between parameters showed that serum PTH adn urinary Ca, Ca/cr levels were positive related (p<0.01), and the years of the after menopausal year and urinary Hpr/cr was also positive related(p<0.05). The present results suggests that it is difficult to protect postmenopausal women's bone destruction having Korean usual diets. Therefore, to prevent osteoporosis with aging, minimizing the hormonal changes in postmenopausal women is needed as well as Ca supplementation and proper exercise before menopause begins.

• Journal of Powder Materials
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• v.28 no.1
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• pp.31-37
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• 2021

This study explores reducing the oxygen content of a commercial Ti-48Al-2Cr-2Nb powder to less than 400 ppm by deoxidation in the solid state (DOSS) using Ca vapor, and investigates the effect of Ca vapor on the surface chemical state. As the deoxidation temperature increases, the oxygen concentration of the Ti-48Al-2Cr-2Nb powder decreases, achieving a low value of 745 ppm at 1100℃. When the deoxidation time is increased to 2 h, the oxygen concentration decreases to 320ppm at 1100℃, and the oxygen reduction rate is approximately 78% compared to that of the raw material. The deoxidized Ti-48Al-2Cr-2nb powder maintains a spherical shape, but the surface shape changes slightly owing to the reaction of Ca and Al. The oxidation state of Ti and Al on the surface of the Ti-48Al-2Cr-2Nb powder corresponds to a mixture of TiO2 and Al2O3. As a result, the peaks of metallic Ti and Ti suboxide intensify as TiO2 and Al2O3 in the surface oxide layer are reduced by Ca vapor deposition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.169-175
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• 2014

Digital ink-jet printing system has many advantages such as fast and fine printing of various images, high efficiency and low cost process. Generally digital ink-jet printing requires ceramic pigments of cyan, magenta, yellow and black with thermal and glaze stability above $1000^{\circ}C$ for the application of porcelain product design. In this study, pink-red colored $CaO-SnO_2-Cr_2O_3-SiO_2$ pigment was synthesized using solid state reaction. The synthesis conditions of $Ca(Cr,Sn)SiO_5$ pigment such as annealing temperature, amount of mineralizer and non-stoichiometric composition were optimized. Crystal structure and morphology of the obtained $Ca(Cr,Sn)SiO_5$ pigment were analyzed using XRD, SEM, PSA, FT-IR and effect of Cr substitution on the pigment color was analyzed using Uv-vis. spectrophotometer and CIE $L^*a^*b^*$ measurement.

• Journal of the Korean Ceramic Society
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• v.48 no.3
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• pp.246-250
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• 2011

Effects on sintering and electrical properties of $La_{0.7}Ca_{0.3}Cr_{0.9}Co_{0.1}O_{3-{\delta}}$ system, a interconnect material for cylindrical and flat tubular solid oxide fuel cells (SOFC), have been investigated by Ca-source when using $CaCO_3$ and $CaF_2$. When using $CaCO_3$ and $CaF_2$ was mixing as Ca-source, single phased perovskite solid solution was observed for each sample. The sintering temperature was decreased by $CaF_2$ contents was increased. When using 0.1 mole $CaF_2$ was densely sintered at $1400^{\circ}C$ and relative density was 93.8%. Also, electrical conductivity in oxidation and reducing atmosphere was 47, 4.3 S/cm, respectively, due to $F^-$ ion enhance the electrical conductivity in reducing atmosphere.

• 한국전기화학회:학술대회논문집
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• 2002.07a
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• pp.277-280
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• 2002

• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.255-258
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• 2001

• Journal of the Korean institute of surface engineering
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• v.34 no.1
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• pp.39-48
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• 2001

Fe-Cr-Al alloy has been studied for application in automobile muffler materials due to good corrosion and oxidation resistance. In order to develop the automobile muffler materials, corrosion behaviors of electron beam physical vapor deposition (EB-PVD) coated surface of muffler matericls of muffler materials were investigated using potentiostat. For 0.1M NaCl solution, corrosion potential and pitting potential of Fe-20Cr-10Al was higher than that of Fe-5Cr- 10Al samples. Especially, in the case of Ti and Nb coated samples, pitting potential increased remarkably compared with non-coated samples. For 0.1M $CaCl_2$ solution, Ti-coated Fe-20Cr-10Al showed remarkably improved pitting corrosion resistance in comparison with non-coated Fe-20Cr-10Al and Fe-5Cr-10Al. The number and size of pits were decreased in the case of Ti coated samples in the 0.1M NaCl and 0.1M $CaCl_2$ solution.

• International Journal of Oral Biology
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• v.39 no.1
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• pp.41-47
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• 2014

Streptococcus mutans (S. mutans) is a facultative anaerobic bacterium mainly found in the oral cavity and is known to contribute to tooth decay and gingivitis. Recent studies on intestinal microbiota have revealed that microorganisms forming a biofilm play important roles in maintaining tissue homeostasis through their own metabolism. However, the physiological roles of oral microorganisms such as S. mutans are still unclear. In our current study, we identified that constituents released from S. mutans (CR) reduce arecoline-mediated cytotoxicity without producing toxic effects themselves. Arecoline, as a major alkaloid of areca nut, is known to mediate cytotoxicity on oral epithelial cells and induces a sustained intracellular $Ca^{2+}$ ($[Ca^{2+}]_i$) increase that is cytotoxic. The exposure of human gingival fibroblast (HGF) cells to CR not only inhibited the sustained $[Ca^{2+}]_i$ increase but also the initial $[Ca^{2+}]_i$ elevation. In contrast, CR had no effects on the gene regulation mediated by arecoline. These results demonstrate that S. mutans has physiological role in reducing cytotoxicity in HGF cells and may be considered a novel pharmaceutical candidate.