• Transactions of Materials Processing
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• v.8 no.2
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• pp.169-177
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• 1999

Different pass strains and rolling temperatures were applied to understand the effects of pass strain and rolling temperature on flow stress and flow strain of AA5083 alloy. The specimens were prepared by conventional casting process followed by hot rolling. Hot torsion tests were conducted at temperature ranges of 350 to 52$0^{\circ}C$ under a strain rate of 1.0/sec. During the process, hot-restoration mechanisms, dynamic recovery(DRV) or dynamic recrystallization (DRX), of the AA5083 alloy were analyzed from the flow curves and deformed microstructures. It was found that while the rolling strain per pass and rolling temperature have little effect on the folw stress, they have significant effect on the failure strain. The DRV was responsible for the hot restoration mechanism of the hot-rolled specimen. heavily elongated grains and small subgrains containing dislocations were obtaned during the hot deformation. This was due to the presence of Al6Mn precipitate in the alloy.

• Journal of Powder Materials
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• v.2 no.3
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• pp.208-215
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• 1995

The aging effects on the characteristics of the melt spun Cu based shape memory alloys have been investigated by the microhardness test, X-ray diffraction, differential scanning calorimetry, scanning electron microscopy and transmission electron microscopy. After aged for specific times, hardness of the ribbons began to increase and shape memory capacity diminished. At the initial stage of aging the austenitic transformation temperatures increased gradually, but at last became nearly constant: That is, the aging deteriorated the thermal stability. The increase in hardness was due to the formation of the $\gamma_2$ precipitates. The loss in the shape memory capacity was due to the decrement of solute atoms in the matrix by the formation of the $\gamma_2$ precipitates. In this study, it was confirmed that Mn is an effective element for Improving the thermal stability.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.146.2-146.2
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• 2011

In this study, we have derived the abundances of several elements ? Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni - for the six F G K type stars in IC 2391 and the seven stars in NGC 6475. The spectra of those stars are taken from UVES POP archive data, of which resolution is 80,000. To derive the abundances of those elements, TAME (Tools for Automatic Measurement of Equivalent-widths), Kurucz stellar atmospheric model, and MOOG code are used. The stellar parameters (effective temperature, log g, metallicity, microturbulent velocity) are determined from the iron lines. The results provide the abundance differences of chemical elements between two open clusters, IC 2391 (a member of Gould Belt) and NGC 6475 (non-member of it), which would lead to better understanding about Gould Belt.

• Journal of the Korean Ceramic Society
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• v.24 no.2
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• pp.139-146
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• 1987

${\beta}$-SiC powders were prepared by the simultaneous reduction and carbiding of Jecheon quartzite at 1400$^{\circ}C$ for 7 hours in hydrogen atmosphere, using graphite or carbon black as the reducing and carbiding reagent. The prepared SiC powder was acid-treated with the mixture of fluoric acid and hydrochloric acid at room temperature and also by heating on an alcohol lamp for one hour, respectively. The impurities were mostly eliminated and the purity of SiC became 98.5% after hot acid treatment. The specific surface area of SiC powder was also increased up to 115㎡/g by hot acid treatment. This pure and fine SiC powder was hot-pressed at 1900$^{\circ}C$ for 30min, using 5wt% Al2O3 as a sintering aid. The density, M.O.R., KIC and hardness of the hot-pressed SiC ceramics were 3.195g/㎤, 48.7Kgf/$\textrm{mm}^2$, 5.4MN/㎥/2 and 2,182Kgf/$\textrm{mm}^2$, respectively.

• Korean Journal of Plant Resources
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• v.3 no.2
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• pp.107-114
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• 1990

In view of the results to have measured metallic elements which is included in 45 sorts of herb medicines and surveyed their distribution, 8 kinds ofmetals including Co, Ge, Ga, TL, Cd, As, 8i, Pb, are never or little includedin almost herb medicines . Other twenty-five sorts of elements (Mo, Sc, Be, V,Ni, Sn, Se, Ba, Cr, Sb, Si, Ti, B, Li, Mg, Ca, Cr, Mn, Fe, Cu, Zn, p, Al, Na,K) are more or Less included in all herb Bedicines ana Na, Ca, p and K aremetals that are included in Large quentities in comrarison with others . Patri-uiae Radix Contains 7 kinds of metal lic elements more than other herb medicinesdoes .

• Korean Journal of Plant Resources
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• v.4 no.2
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• pp.39-45
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• 1991

Proximate compositions of the roots of cultured and wild Codonopsis lanceolata were examined as tile basic reasearch for the study of their source of processed foods.No significant difference in the contents was found between the wild root and thecultivated at 3$0^{\circ}C$ in biotronroom. In view of the results to have measured mineralswhich is included in 14 sorts of Codonopsis lanceolata and surveyed their distribution.12 kinds of minerals including T1, Co, Ge, Sm, Mo, Sc, Be, Cd, As, Ga, Bi, ph are ne-vel or little included in almost source. Other twenty-one sorts of minerals (Ni, Se,Ba, Sb, Si, Ti, B, Li, Ifs, Ca, Sr, Mn, Fe, Cu, Zn, p, Al, Na, V, Cr, K) are more or less in-cluded in all source and Ca, Mg, p, K, and Fe are metals that are included in large qu-entities in comparison with others. No minerals difference in the contents was foundbetween the cultivated temperature. The content of elements of inorganic metal differsaccording to the part of C. lanceolata.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.309-310
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• 2005

Some minor elements(Al, B, Ba, Ca, Cd, Co, Cr, Cu, Gd, Mg, Mn, Mo, Nd, Ni, P, Pb, Si, Sn, Sr, Ti, V, Yb, Zn and Zr) in iron compounds such as the S/G sludge of a power plant were separated from iron by anionic and cationic exchange methods. If a ICP-AES or AAS determination follows this method, minor elements of more than 2 or 20 ppm of Fe can be determined with an error less than 20% except Sn and Mo. Alkaline elements were excluded from this study since they can be easily recovered from an anionic exchange. Application to real sludge samples is ongoing.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_3
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• pp.127-137
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• 2001

The sonochemical Process has been applied as a treatment method and was investigated its effect on the decomposition of humic substances(HS). The reaction kinetics and mechanisms in the Process of sonochemical treatment for humic substances(HS) in wastewater have also been discussed. It was observed that the metal ions such as Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The mechanism of radical reaction is controlled by an oxidation process. The radicals are so reactive that most of them are consumed by HS radicals and hydroxyl radicals can be acted on organic solutes by hydroxyl addition, hydrogen abstraction, and electron transfer. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final steps of the reaction are the conversion of organic acids to carbon dioxide.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.697-699
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• 2009

Optical properties of white organic light-emitting devices (WOLEDs) fabricated utilizing a phosphor layer acting as a color conversion layer were investigated. The WOLEDs were achieved due to the enhancement in the color conversion efficiency of the phosphor layer, and the chromaticity coordinates of WOLEDs were (0.29, 0.33).

• Electrical & Electronic Materials
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• v.6 no.4
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• pp.311-317
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• 1993

발열체 소자에 있어서 발열체의 방사스펙트럼과 피가열체의 흡수스펙트럼을 일치시키는 문제는 효과적인 가열을 위하여 매우 중요한 연구과제이다. 본 연구는 재료의 합성기술과 열처리기술을 이용하여 PTC 서머스터의 R-T특성은 그대로 유지시키면서 원적외선 방사특성을 증대시키기 위한 것이다. 이를 위하여 BaTiO$_{3}$+1.67Al$_{2}$O$_{3}$+3.75SiO$_{2}$+1.25TiO$_{2}$을 기본조성으로 하고 여기에 첨가제로서 Sb$_{2}$O$_{3}$와 MnO$_{2}$를 선정하여 이의 첨가량과 소결온도 그리고 소결온도구배를 파라메터로한 시편을 제작하였으며 각 시편의 IR특성과 R-T특성등을 측정 검토한 결과 파장 4.5-14.5[.mu.m]범위에서 방사율 0.8이상의 고효율 원적외선 방사특성을 얻었다.