• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.498-503
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• 2006

A gas turbine blade with thermal barrier ceramic coating is operated at high temperature to increase engine efficiency. Recently, thermal barrier characteristics have been improved by advanced coating technology through microstructure control and increase of adhesion force of the coating layer. More advanced coating materials, rare earth zircon ate ceramics have been studied for replacing YSZ coatings as thermal barrier coatings. In this study, $La_2O_3,\;HfO_2,\;CeO_2,\;Gd_2O_3$ and pure or yttria stabilized zirconia were prepared. Microstructure analysis and the evaluation of mechanical properties such as Hertzian indentation and hardness test were performed.

• Nutrition Research and Practice
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• v.10 no.5
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• pp.487-493
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• 2016

BACKGROUND/OBJECTIVES: Turmeric (Curcuma longa L.) has been reported to have many biological functions including anti-obesity. Leptin, peptide hormone produced by adipocytes and its concentration is increased in proportion to the amount of the adipocytes. In the present study, we examined the effects of Korean turmeric on the regulation of adiposity and leptin levels in 3T3-L1 adipocytes and rats fed a high-fat and high-cholesterol diet. MATERIALS/METHODS: Leptin secretion, free fatty acid and glycerol contents in 3T3-L1 adipocytes were measured after incubation of cells with turmeric for 24 hours. Rats were divided into four experimental groups: a normal diet group (N), a high-fat and high-cholesterol diet group (HF), a high-fat and high-cholesterol diet group supplemented with 2.5% turmeric extracts (TPA group) and a high-fat and high-cholesterol diet group supplemented with 5% turmeric extracts (TPB group). Serum samples were used for the measurement of leptin concentration. RESULTS: Contents of free fatty acid and glycerol showed concentration dependent increase in response to turmeric extracts. Effects of turmeric extracts on reduction of lipid accumulation in 3T3-L1 cells were examined by Oil Red O staining. Treatment with turmeric extracts resulted in increased expression levels of adipose triglyceride lipase and hormone-sensitive lipase mRNA. The concentration of leptin from 3T3-L1 adipocytes was significantly decreased by turmeric. Proportional abdominal and epididymal fats weights of the turmeric 5% supplemented group, TPB has significantly decreased compared to the HF group. The serum levels of leptin in the TPA and TPB groups were significantly lower than those of the HF group. CONCLUSIONS: Based on these results, we suggested that Korean turmeric may contribute to the decreasing of body fat and regulating leptin secretion.

• Electrical & Electronic Materials
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• v.7 no.4
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• pp.294-299
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• 1994

CHF$_{3}$/CH$_{4}$Ar 플라즈마에 의해 형성된 산화막 식각 잔류물의 화학구조와 이 잔류물의 제거를 위한 세정방법을 x-ray photoelectron spectroscopy를 이용하여 조사하였다. 잔류무르이 구조는 CF$_{x}$-polymer와 Si-C, Si-O 결합으로 이루어진 SiO$_{y}$ C$_{z}$ 이었다. CF$_{4}$O$_{2}$ 플라즈마에 의한 silicon light etch는 산화막 식각 잔류물인 SiO$_{y}$ C$_{z}$ 층과 손상된 실리콘 표면을 제거하엿으며 NH$_{4}$OH-H$_{2}$O$_{2}$과 HF용액으로 완전히 제거되는 CF$_{x}$-polymer/SiO$_{x}$층을 남겼다. 100.angs.정도의 silicon light etch는 minority carrier life time과 thermal wave signal값을 초기 웨이퍼 수준까지 회복시켰으며 접합누설 전류도 거의 습식 식각 공정수준까지 감소시켰다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.387.2-387.2
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• 2016

Glass texturing is a sufficient method for changing the surface morphology to enhance the light trapping. In this study, glass texturing was applied to the perovskite solar cell for improving the current density. Glass substrates (back-side glass of FTO coated glass substrate) were textured by randomly structure assisted wet etching process using diluted HF solution at a constant concentration of etchants (HF:H2O=1:1). Then, the light trapping properties of suitable films were controlled over a wide range by varying the etching time (1, 2, 3, 4 and 5 min.). The surface texturing changed the reflected light in an angle that it can be reflected by substrate glass surface. As a result, Current density and cell efficiency were affected by light trapping layer using glass texturing method in perovskite solar cells.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1067-1072
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• 2002

A new polystyrene-divinylbenzene resin containing 2-(2-thiazolylazo)-5-dimethylamino-phenol (TAM) functional groups has been synthesized and its sorption behavior for nineteen metal ions, including Zr(Ⅳ),Hf(Ⅳ) and U(Ⅵ) has been investigated by batch and column methods. The chelating resin showed high sorption affinity for Zr(Ⅳ) at pH 1-5 and U(Ⅵ) at pH 4. Some parameters affecting the sorption of the metal ions have been detailed. The breakthrough and overall capacities were measured under optimized conditions. The overall capacities of Zr(Ⅳ), Th(Ⅳ) and U(Ⅵ), which showed higher than the other metal ions, were 0.90,0.84 and 0.80 mmol/g, respectively. The elution order of metal ions at pH 4 was evaluated as Zr(Ⅳ) > Th(Ⅳ) > U(Ⅵ) > Cu(Ⅱ) > Hf(Ⅳ) > W(Ⅵ) > Mo(Ⅵ) > In(Ⅲ) > Sn(Ⅳ) > Cr(Ⅲ) > V(Ⅴ) > Fe(Ⅲ). Quantitative recovery of most metal ions except Zr(Ⅳ) was achieved using 2M HNO3. Desorption and recovery of Zr(Ⅳ) was successfully performed with 2 M HClO4 and 2 M HCl.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1290-1295
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• 1988

Theoretical considerations in the development of new cutting tool materials for high speed machining is presented. The progressive wear of cutting tools is assumed to consist of the abrasive and solution components as major modes. Theoretical calculations of relative wear rates between various tool materials based on the two modes are possible using their hardness and solubility data. Assuming cementite as the major hard particles in machining steels, relative wear rates of possible tool materials were calculated. The results indicate that $Al_{2}$O$_{3}$ in oxides, HfN in nitrides and HfC in carbides are the optimal tool materials from the view point of mechanical and thermochemical wear resistance. And several methods for improving the fracture toughness of the above tool materials are suggested.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.745-764
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• 2023

In the Republic of Congo, Banded iron formations (BIFs) occur in two areas: the Chaillu Massif and the Ivindo Basement Complex, which are segments of the Archean Congo craton outcropping in the northwestern and southwestern parts of the country. They show interesting potential with significant mineral resources reaching 2 Bt and grades up to 60% Fe. BIFs consist mostly of oxide-rich facies (hematite/magnetite), but carbonate-rich facies are also highlighted. They are found across the country within the similar geological sequences composed of amphibolites, gneisses and greenschists. The Post-Archean Australian Shale (PAAS)-normalized patterns of BIFs show enrichment in elements such as SiO₂, Fe₂O₃, CaO, P₂O₅, Cr, Cu, Zn, Nb, Hf, U and depletion in TiO₂, Al₂O₃, MgO, Na₂O, K₂O, Sc, Th, Ba, Zr, Rb, Ni, V. REE diagrams show slight light REEs (rare earth elements; LREEs) compared to heavy REEs (HREEs), and positive La and Eu anomalies. The lithological associations, as well as the very high (Eu/Eu^*)_SN ratios> 1.8 shown by the BIFs, suggest that they are related to Algoma-type BIFs. The positive correlations between Zr and TiO₂, Al₂O₃, Hf suggest that the contamination comes mainly from felsic rocks, while the absence of correlations between MgO and Cr, Ni argues for negligeable contributions from mafic sources. Pr/Pr^* vs. Ce/Ce^* diagram indicates that the Congolese BIFs were formed in basins with redox heterogeneity, which varies from suboxic to anoxic and from oxic to anoxic conditions. They were formed through hydrothermal vents in the seawater, with relatively low proportions of detrital inputs derived from igneous sources through continental weathering. Some Congolese BIFs show high contents in Cr, Ni and Cu, which suggest that iron (Fe) and silicon (Si) have been leached through hydrothermal processes associated with submarine volcanism. We discussed their tectonic setting and depositional environment and proposed that they were deposited in extensional back-arc basins, which also recorded hydrothermal vent fluids.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.783-786
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• 2009

Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and ion chromatography(IC) were employed to analyze the thermal behavior of $Li_xCoO_2$ cathode material of lithium ion battery. The mass loss peaks appearing between 60 and 125 ${^{\circ}C}$ in TGA and the exothermic peaks with 4.9 and 7.0 J/g in DSC around 75 and 85 ${^{\circ}C}$ for the $Li_xCoO_2$ cathodes of 4.20 and 4.35 V cells are explained based on disruption of solid electrolyte interphase (SEI) film. Low temperature induced HF formation through weak interaction between organic electrolyte and LiF is supposed to cause carbonate film disruption reaction, $Li_2CO_3\;+\;2HF{\rightarrow}\;2LiF\;+\;CO_2\;+\;H_2O$. The different spectral DSC/TGA pattern for the cathode of 4.5 V cell has also been explained. Presence of ionic carbonate in the cathode has been identified by ion chromatography and LiF reported by early researchers has been used for explaining the film SEI disruption process. The absence of mass loss peak for the cathode washed with dimethyl carbonate (DMC) implies ionic nature of the film. The thermal behavior above 150 ${^{\circ}C}$ has also been analyzed and presented.

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.95-95
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• 2009

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.57-61
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• 2009

$MnFe_2O_4$ nanoparticles have been prepared by a sol-gel method. The structural and magnetic properties have been investigated by XRD, SEM, and $M{\ddot{o}}ssbauer$ spectroscopy, VSM. $MnFe_2O_4$ powder that was annealed at $250^{\circ}C$ has spinel structure and behaved superparamagnetically at room temperature. $MnFe_2O_4$ annealed at 400 and $500^{\circ}C$ has a typical spinel structure and is ferrimagnetic in nature. The estimated size of superparammagnetic $MnFe_2O_4$ nanoparticle is around 17 nm. The hyperfine fields of the A and B patterns at 4.2 K were found to be 508 and 475 kOe, respectively. The blocking temperature ($T_B$) of superparammagnetic $MnFe_2O_4$ nanoparticle is about 120 K. The magnetic anisotropy constant and relaxation time constant of $MnFe_2O_4$ nanoparticle were calculated to be $4.9{\times}10^5erg/cm^3$.