• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.197-202
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• 2021

Synthesis of Z-type hexaferrite Ba₃Co₂Fe₂₄O₄₁ (Ba₃Z) and Ba_1.5La_1.5Co₂Fe₂₄O₄₁ (Ba_1.5La_1.5Z) powders were tried using molten salt synthesis after primary calcination. Ba₃Z calcined at 1000℃ was formed with both M-type and Y-type hexaferrite, and then Z-type was obtained when sintered with molten salt at 1150℃ and 1200℃. In the case of Ba_1.5La_1.5Z calcined at 1000℃, however, M-type hexaferrite, CoFe₂O₄ (Spinel phase), and LaFeO₃ were synthesized. As a result, Z-type hexaferrite was not synthesized after sintering with molten salt. In addition, the aspect ratio of the particles decreased as the sintering temperature increased with molten salt synthesis. To obtain a single-phase Ba_1.5La_1.5Z with a high aspect ratio, it is expected the raw materials have to calcine below the temperature of a spinel phase formation before sintering with molten salt.

• Proceedings of the Korea Crystallographic Association Conference
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• 2000.05a
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• pp.20-20
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• 2000

• The Korean Journal of Mycology
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• v.21 no.1
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• pp.23-27
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• 1993

Ion effects on $11{\alpha}-hydroxylation$ of progesterone and $5{\alpha}-reduction\;of\;11{\alpha}-hydroxyprogesterone$ by Rhizopus nigricans were investigated. Metal ions such as $Cu^{2+},\;Cd^{2+},\;Co^{2+},\;Mn^{2+},\;Zn^{2+},\;Fe^{2+},\;Mg^{2+},\;Fe^{3+}\;and\;Na^+$ reduced the $11{\alpha}-hydroxylation$ activity, while $K^+$ stimulated the same reaction. Enzyme activity for the $5{\alpha}-reduction$ of $11{\alpha}-hydroxyprogesterone$ was increased in the presence of $Fe^{2+},\;Mn^{2+},\;Mg^{2+},\;Co^{2+},\;Zn^{2+},\;Fe^{3+},\;K^+\;and\;Na^+$, whereas it was decreased in the presence of $Cd^{2+}\;and\;Cu^{2+}$. Potassium ion of $10^{-3}\;M\;$ of concentration was found to be effective for the promotion of $11{\alpha}-hydroxylation$. On the other hand, cadmium ion of $10^{-4}\;M$ was proved to suppress the $5{\alpha}-reduction$ reaction. Progesterone is reported to be transformed into $11{\alpha}-hydroxyprogesterone$ which, in turn, is converted further into $11{\alpha}-hydroxy-allopregnane-3$, 20-dione by R. nigricans. From this point of view, the highest yield of $11{\alpha}-hydroxyprogesterone$ could be obtained when potassium ion of $10^{-3}\;M$ was given initially followed by addition of cadmium ion of $10^{-4}\;M$ to limit conversion of 11{\alpha}-hydroxyprogesterone into $11{\alpha}-hydroxy-allopregnane-\;3$, 20-dione.

• Resources Recycling
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• v.17 no.6
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• pp.17-23
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• 2008

In order to simulate the leaching solution of copper sulfide ore in $FeCl_3$ solutions, synthetic solutions with composition of $FeCl_3$-$FeCl_2$-$CuCl_2$-CuCl-NaCl-HCl-$H_2O$ were prepared. The concentration of iron and copper chloride was varied from 0.1 to 1 m in synthetic solutions. The effect of composition on the mixed solution pH and potential at $25^{\circ}C$ was measured. When HCl concentration was constant, the increase of CuCl concentration increased solution pH. The increase of other solutes excluding HCl and CuCl decreased solution pH owing to the increase of the activity coefficient of hydrogen ion. A high CuCl concentration favored the redox equilibrium in the direction of Cu(I), while $FeCl_3$ had the opposite effect.

• Analytical Science and Technology
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• v.14 no.2
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• pp.140-146
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• 2001

The study was carried out to analyze the pollutants, Fe, Cu, Cr, Zn, Cd for 3 sediments of 5 sites collected from lake in K river basin. 5cm sediment, which is nearly proximated to water from sediment of depth 30cm, showed higher Fe, Cu, Cr, Zn, Cd data than another 5-10cm and 10cm sediment, which is separated from sediment of depth 30cm. Also, 5cm sediment nearly proximated to water showed the following data: Fe, 34.9-39.8mg/L, Cu, 34.5-44.8mg/L, Cr, 68.0-79.2mg/L, Zn, 147.4-126.0mg/L, Cd, 2.2-1.0mg/L, respectively. From this results, we know the fact that the pollution degree of sediment has an effect on the water quality in like and stream.

• Analytical Science and Technology
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• v.23 no.3
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• pp.225-232
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• 2010

In present study, a conventional sol-gel method was used to prepare Fe-ACF/$TiO_2$ composites, a kind of composite photocatalysts, whose capability was evaluated by degrading methylene blue (MB) solution. The particle size, surface structure, crystal phase and elemental identification of the composites prepared were characterized by BET, SEM, XRD and EDX, respectively. The spectra of MB concentration degraded under visible light were obtained by UV/Vis spectrophotometer. These obtained spectra demonstrated the photocaltalytic activity from removal concentrations of MB. It was considered that these photonic activities are induced by a strong synergetic reaction among ACF, $TiO_2$ and Fe in the composite photocatalysts under visible light.

• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.121-126
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• 1999

This paper describes a fabrication of Fe-dispersed hydrophilic magnetic fluid and its application to oil seal in combination with the Nd-permanent magnet. The results are as follows; 1) Using silica coated iron particle of magnetization of 125.5 emu/g (at 10 kOe) and the mean particle size of 100 $\AA$, after multiple adsorption to the surface of silica coated iron particle with oleic acid ion, D.B.S. and T.M.A. ion, hydrophilic Fe-magnetic fluid [70 %(g/∝)Fe, magnetization of 52 emu/g and viscosity of 1450 cp] can be produced by dispersing the iron particle in ethylene glycol solution. 2) The oil seal apparatus consisting of six stages of Nd-permanent magnet (3200 Gauss) and Fe-magnetic fluid [70 %(g/∝) Fe] showed an excellent pressure resistance of 7400 g/$\textrm{cm}^2$ under the gap between shaft and oil seal was 0.2 mm.

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.31-35
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• 2014

The upper critical field ($H_{c2}$) was determined by applying a magnetic field along the ab plane and c axis for two single crystals of $BaFe_{2-x}Ru_xAs_2$ (x=0.48 and 0.75). The anisotropy of the $H_{c2}(0)$, ${\gamma}(0)=H_{c2}{^{ab}}(0)/H_{c2}{^c}(0)$, was ~1.6 for x=0.48 and ~2.3 for x=0.75. The angle-dependent resistance measured below $T_c$ allowed perfect scaling features based on anisotropic Ginzburg-Landau theory, leading to consistent anisotropy values. Because only one fitting parameter ${\gamma}$ is used in the scaling for each temperature, the validity of the ${\gamma}$ value was compared with that determined from ${\gamma}=H_{c2}{^{ab}}/H_{c2}{^c}$. The ${\gamma}$ obtained at a temperature close to $T_c$ was 3.0 and decreased to 2.0 at low temperatures. Comparing to the anisotropy determined for electron- or hole-doped $BaFe_2As_2$ using the same method, the present results point to consistent anisotropy in Ru-doped $BaFe_2As_2$ with other electron- or hole-doped $BaFe_2As_2$.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.63-67
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• 1997

환원확산법은 저렴한 Nd 산화물을 환원제를 이용하여 환원시키고 환원된 Nd가 Fe, FeB와 확산하여 주상인 Nd$_2$Fe14B가 만들어지는 공정으로 환원제로 사용된 CaO나 미반응 Ca 및 잔존 산소함량을 조절하는데 어려움이 있어 아직까지는 상업되지 못하고 있는 실정이다. 본 연구에서는 환원확산법을 이용하여 Nd-Fe-B계 영구자석에 사용될 미세분말을 제조하고 그 자기적 특성을 관찰하였다.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.35-36
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• 2006