• Journal of the Korean earth science society
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• v.22 no.4
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• pp.278-291
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• 2001

Mesothermal gold vein minerals of the Seolhwa mine were deposited in a single stage of massive quartz veins which filled the mainly NE-trending fault shear zones exclusively in the granitoid of the Gyeonggi Massif. The Seolhwa mesothermal gold mineralization is spatially associated with the Jurassic granitoid of 161 Ma. The vein quartz contains three main types of fluid inclusions at 25$^{\circ}$C: 1) low-salinity (< 5 wt.% NaCl), liquid CO$_{2}$-bearing, type IV inclusion; 2) gas-rich (> 70 vol.%), aqueous type II inclusions; 3) aqueous type I inclusions (0${\sim}$15 wt.% NaCl) containing small amounts of CO$_{2}$. The H$_{2}$O-CO$_{2}-CH$_{4}$-N$_{2}$-NaCl inclusions represent immiscible fluids trapped earlier along the solvurs curve at temperatures from 430$^{\circ}$ to 250$^{\circ}$C and pressures of 1 kbars. Detailed fluid inclusion chronologies may suggest a progressive decrease in pressure during the auriferous mineralization. The aqueous inclusion fluids represent either later fluids evelved through extensive fluid unmixing (CO$_{2}-CH$_{4}$ effervescence) from a homogeneous H$_{2}$O-CO$_{2}-CH$_{4}$-N$_{2}$-NaCl fluid due to decreases in temperature and pressure, or the influence of deep circulated meteoric waters possibly related to uplift and unloading of the mineralizing suites. The initial fluids were homogeneous containing H$_{2}$O-CO$_{2}-CH$_{4}$-N$_{2}$-NaCl components and the following properties: the initital temperature of >250$^{\circ}$ to 430$^{\circ}$C, X$_{CO}\;_{2}$ of 0.16 to 0.62, 5 to 14 mole% CH$_{4}$, 0.06 to 0.3 mole% N$_{2}$ and salinities of 0.4 to 4.9 wt.% NaCl. The T-X data for the Seolhwa gold mine may suggest that the Seolhwa auriferous hydrothermal system has been probably originated from adjacent granitic melt which facilitated the CH$_{4}$ formation and resulted in a reduced fluid state evidenced by the predominance of pyrrhotite. The dominance of negative ${\delta}\;^{34}$S values of sulfides (-0.6 to 1.4$%_o$o) are consistent with their deep igneous source.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.281-282
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• 2014

본 연구는 공정시간에 따른 전해 플라즈마 공정(Electrolytic Plasma Processing, EPP) 공정에 의해 형성된 산화 코팅층의 특성 변화를 알아보고자 한다. 실험에 사용되는 전해용액은 $Na_2SiO_3$(12g/l) + $Na_2SiF_6$(0.3g/l)+NaOH(3g/l) 기본용액에 다양한 농도의 NaOH(0-5g/l) 첨가한 전해용액을 사용하였다. AZ61 마그네슘 합금을 모재($22{\Phi}{\times}10mm$)로 사용하였으며 실험은 5분-60분 동안 진행되었다. 공정시간에 변화에 따른 EPP 코팅층 특성을 측정한 결과 공정시간이 증가함에 따라 코팅층 표면의 기공 크기가 커지고 코팅층 내에 기공수가 즐어드는 것을 확인하였다. 또한 XRD 분석을 통하여 형성된 코팅층에서 MgO, Mg2SiO4 상이 나타난 것을 확인할 수 있었다.(No. 2011-0030058),(2012H1B8A2026212)

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.1
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• pp.37-44
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• 1995

Concentration of particulate nitrate classified by formation mechanism and particle diameter in ambient air was determined from Feb. to Oct. 1993. Sampling was carried out using a two-stage Andersen air sampler at the top of a five-story building located at Kon-Kuk University in seoul. Concentration of N $H_{4}$N $O_{3}$ in TSP was measured by pyrolysis of sample filters at 160.deg.C for 1hr. concentration of N $H_{4}$N $O_{3}$ was higher in winter time compared with that in summmer time. Also, concentration of N $H_{4}$N $O_{3}$ was higher in fine particles compared with that in coarse particle. The range of N $H_{4}$N $O_{3}$ concentration was between 2.9 and 9.9.mu.g/ $m^{3}$. Weight fraction of N $H_{4}$N $O_{3}$ in total particulate nitrate was 31.1 .sim. 59.5%, and weight fraction of N $H_{4}$N $O_{3}$ in TSP was 2.1 .sim. 11.2%. Concentration of NaN $O_{3}$, which originated from sea salt, was highest in spring time and lowest in summer time,and the concentration range was between 0.1 and 0.7.mu.g/ $m^{3}$. NaN $O_{3}$/TSP ratio was very low (0.1 .sim. 0.4%) indicating that the portion of NaN $O_{3}$in TSP was negligible. Concentration of particulate nitrate originated from soil was 2.4 .sim. 2.9.mu.g/ $m^{3}$. Weight fraction of that in total particulate nitrate was 14.0 .sim. 37.1%.

• Resources Recycling
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• v.14 no.6 s.68
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• pp.28-36
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• 2005

A hydrometallurgical process to leach cobalt from the waste cathodic active material, $LiCoO_{2}$, and subsequently to separate it by solvent extraction was developed. The optimum leaching conditions for high recovery of colbalt and lithium were obtained: 2.0 M sulfuric acid, 5 $vol.\%$ hydrogen peroxide, $75^{\circ}C$ leaching temperature, 30 minutes leaching time and an initial pulp density of 100 g/L. The respective leaching efficiencies for Co and Li were $93\%$ and $94.5\%$. About $85\%$ Co was extracted from the sulfuric acid leach liquor containing 44.72 g/L Co and 5.43 g/L Li, using 1.5 M Cyanex272 as an extractant at the initial pH 5.0 and in organic to aqueous phase ratio of 1.6:1 under the single stage extraction conditions. The Co in the raraffinate was completely extracted by 0.5 M Na-Cyanex272 at the inital pH 5.0, and an organic to aqueous phase ratio of 1;1. The cobalt sulfate solution of higher than $99.99\%$ purity could be recovered from waste $LiCoO_{2}$, using a series of hydrometallurgical processes: sulfuric acid leaching of waste $LiCoO_{2}$- solvent extraction of Co by Na-Cyanex 271 - scrubbing of Li by sodium carbonate solution - stripping of Co by sulfuric acid solution.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.1-5
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• 1999

The dispersing performance of oligomer-type anionic surfactants ($C_mD-Na$), cooligomers of diethylester maleate and alkylvinylether of different alkyl chain lengths or polymerization degree were studied on the aqueous suspension of iron dxide or titanium dioxide particles which are hydrophilic pigments. The dispersion behavior of oligomer-type surfactants for these dispersoids, although anion charges on the surface of pigments particles showed different dispersing properties, was dependent upon the side alkyl chain length. Oligomer-type surfactants having more than $C_8$ side alkyl chain exhibited large dispersing action for relatively hydrophobic ${\alpha}-Fe_2O_3$ and Anatase $TiO_2$ in the concentration range of more than 0.1% oligomer-type surfactant solutions.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.317-322
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• 2016

While PFOS sodium salt ($C_8F_{17}SO_3Na$) was not degraded by microorganisms for 28 days, the 4 alternatives were biodegraded at the rates of 21.6% for $C_{25}F_{17}H_{32}S_3O_{13}Na_3$, 20.5% for $C_{15}F_9H_{21}S_2O_8Na_2$, 15.8% for $C_{23}F_{18}H_{28}S_2O_8Na_2$ and 6.4% for $C_{17}F_9H_{25}S_2O_8Na_2$, respectively. The acute toxicity test using Daphnia magna was conducted for 48 hours, the half effective concentration ($EC_{50}$) of PFOS sodium salt ($C_8F_{17}SO_3Na$) was evaluated in 54.5 mg/L. While the 4 alternatives did not show any effect at 500.0 mg/L. The surface tension of the PFOS salt ($C_8F_{17}SO_3Na$) is 46.2 mN/m at a concentration of 500.0 mg/L. While the surface tension of the 4 alternatives was found to be superior to PFOS sodium salt ($C_8F_{17}SO_3Na$). The surface tension of $C_{23}F_{18}H_{28}S_2O_8Na_2$ (20.9 mN/m) has the lowest, followed by $C_{15}F_9H_{21}S_2O_8Na_2$ (23.4 mN/m), $C_{17}F_9H_{25}S_2O_8Na_2$ (27.3 mN/m), $C_{25}F_{17}H_{32}S_3O_{13}Na_3$ (28.2 mN/m). The four kinds of alternatives ($C_{15}F_9H_{21}S_2O_8Na_2$, $C_{17}F_9H_{25}S_2O_8Na_2$, $C_{23}F_{18}H_{28}S_2O_8Na_2$, $C_{25}F_{17}H_{32}S_3O_{13}Na_3$) were found to be superior to PFOS sodium salt ($C_8F_{17}SO_3Na$) in terms of biodegradation, Daphnia sp. acute toxicity and surface tension, and thus they were considered applicable as PFOS alternatives. Especially biodegradation rate of $C_{15}F_9H_{21}S_2O_8Na_2$, $C_{23}F_{18}H_{28}S_2O_8Na_2$ and $C_{25}F_{17}H_{32}S_3O_{13}Na_3$ was relatively high as 15.8~21.6%, and Daphnia sp. acute toxicity and surface tension were considerably superior (surface tension 39~55%) to PFOS sodium salt. Therefore, these alternatives are considered to be available as an alternative of PFOS.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.764-768
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• 2002

The nanocrystalline $CeO_2$ was synthesized by mechanical milling and subsequent heat-treatment with the mixture of $Ce(OH)_4$ precursor and diluent, NaCl. Using deionized water, the diluent, NaCl, in the mixture has been easily dissolved out. Diffusion barrier was provided by the diluent during heat-treatment, which suppressed not only the coarsening of primary particle but also the agglormeration between the particles. Crystallite and aggregate size of $CeO_2$ depended on the concentration of diluent, temperature and time of heat-treatment; increased with the temperature and time increases. In case the mixture was heat-treated at high than $600^{\circ}C$, however, the crystallite size was saturated near 20 nm, which was supposed to be due to the densification of diluent.

• Food Science and Preservation
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• v.13 no.2
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• pp.192-197
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• 2006

The optimum cultural conditions for production of yellow pigment by Monascus purpureus MMK2 were investigated in liquid culture. Monascus purpureus MMK2 was shown to give the maximum production of yellow pigment in the medium containing of 3.0% wheat flour, 0.15% $NaNO_3$, 0.25% $Na_2HPO_4\;12H_2O\;and\;0.15%\;MgSO_4\;7H_2O$. The optimal culture conditions for temperature and initial pH were $30^{\circ}C$ and 6.5, respectively. The yellow pigment production reached a maximum level at the 7th day of cultivation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.5
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• pp.241-246
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• 2003

The transparent conducting thin film of ATO (antimony-doped tin oxide) was successfully fabricated on$SiO_2$/glass substrate by a sol-gel dip coating method. The crystalline phase of the ATO thin film was identified as SnO$_2$ major phase and the film thickness was about 100 nm/layer at the withdrawal speed of 50 mm/minute. Optical transmittance and electrical resistivity of the 400 nm-thick ATO thin film which was annealed under nitrogen atmosphere were 84% and $5.0\times 10^{-3}\Omega \textrm{cm}$, respectively. It was found that the $SiO_2$ layer inhibited Na ion diffusion and the formation of impurities like $Na_2SnO_3$ or SnO while increasing Sb ion concentration and higher ratio of $Sb^{5+}/Sb^{3+}$in the film. Annealing at nitrogen atmosphere leads to the reduction of $Sn^{4+}$ as well as $Sb^{5+}$ resulting in decrease of the electrical resistivity of the film.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.159-163
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• 2016

Up-conversion (UC) luminescence properties of polycrystalline $Er^{3+}/Yb^{3+}$ doped $NaGd(MoO_4)_2$ phosphors synthesized by a simple solid-state reaction method were investigated in detail. Used to 980 nm excitation (InfraRed area), $Er^{3+}/Yb^{3+}$ co-doped $NaGd(MoO_4)_2$ exhibited very weak red emissions near 650 and 670 nm, and very strong green UC emissions at 540 and 550 nm corresponding to the infra 4f transitions of $Er^{3+}(^4F_{9/2},\;^2H_{11/2},\;^4S_{3/2}){\rightarrow}Er^{3+}(^4I_{15/2})$. The optimum doping concentration of $Er^{3+}$, $Yb^{3+}$ for highest emission intensity was determined by XRD and PL analysis. The $Er^{3+}/Yb^{3+}$ (10.0/10.0 mol%) co-doped $NaGd(MoO_4)_2$ phosphor sample exhibited very strong shiny green emission. A possible UC mechanism for $Er^{3+}/Yb^{3+}$ co-doped $NaGd(MoO_4)_2$ depending on the pump power dependence was discussed.