• Resources Recycling
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• v.29 no.5
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• pp.28-37
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• 2020

In this study, the effect of precipitation temperature, ammonium chloride amount and addition method, vanadium and sodium hydroxide content of the solution on the precipitation of ammonium metavanadate were examined by using the sodium vanadate(NaVO₃) solution in alkali region as a starting material. As the pH of solution decreased, the addition amount of ammonium chloride and the vanadium content of the solution increased, the precipitation rate of ammonium metavanadate increased. In this research condition, the basic conditions for obtaining more than 90% of precipitation yield were 10,000mg/L of vanadium content, 2equivalents of ammonium chloride addition, room temperature, and 2 hours of precipitation time. The size of precipitated particles decreased with increasing precipitation rate. Especially when liquid ammonium chloride was injected into the solution, the precipitation rate was the slowest and the particle size of the precipitate was the largest. After the primary precipitation by adding ammonium chloride as a solid, the secondary precipitation was carried out by adding new reactants. At this time, the precipitation with added ammonium chloride solid was not affected by the precipitates present in the solution. However, when liquid ammonium chloride was added, new precipitate was deposited on the surface of the precipitate present in the solution, increasing its size. Due to the difference in ammonium metavanadate solubility to temperature, the precipitation temperature at the vanadium content of 10,000mg/L in the solution affected the precipitation rate of ammonium metavanadate and the precipitation temperature did not affect the precipitation rate at a high concentration of more than 30,000mg/L vanadium content in the solution.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.1
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• pp.37-41
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• 1991

In this study, the effect of solution treatment temperature on the tensile property in intermediate thermo-mechanical treated Al-Li alloys are investigated. After the intermediate thermo-mechanical treated Al-Li, Al-Li-Mg and Al-Li-Mg-Zr alloys were solution treated at various temperatures (500, 520 and $540^{\circ}C$), these were aged at $190^{\circ}C$, $240^{\circ}C$ and tested tensile properties. The results obtained from the experiment are as follows ; 1) The optimum solution heat-treatment temperature is $540^{\circ}C$ for a Al-Li alloy, and the recrystallized grain size is about $70{\mu}m$. 2) The optimum solution heat-treatment temperature is $500^{\circ}C$ for a Al-Li-Mg alloy, and the recrystallized grain size is the most coarse in all alloys. 3) The tensile property is independent of the solution treatment temperature in a Al-Li-Mg-Zr alloy, and the recrystallized grain size is the finest owing to addition of Zr.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.491-496
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• 2000

Single phae Pb(Mg1/3Nb2/3)O3-based solid solutions, the Mg2+ of which are replaced by 20mol% of Ni2+, Zn2+, Cd2+, and the Pb2+ of which are replaced by 0∼20 mol% of La3+, were synthesized and their ordering structures of B-site cations were investigated by XRD and TEM. The B'-site cations (Mg2+, Ni2+, Zn2+, Cd2+) are disordered while these B'-site cations and the B"-site cations (Nb5+) are nonstoichiometrically 1:1 ordered within the ordered nano-domains dispersed in the Nb5+-rich disordered matrix. The charge imbalance between the B'-rich ordered nano-domains and the B"-rich disordered matrix are compensated by the doping of electron donor such as La3+, which enhances the degree of nonstoichiometric 1:1 ordering. For a given La3+ content, the degree of nonstoichiometric 1:1 ordering increases as the average ionic size difference between the B'-and B"-site cations increases, Ni2+

• Environmental Engineering Research
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• v.11 no.1
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• pp.14-27
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• 2006

The proper management of discarded electronic devices (often called electronic-waste) is an emerging issue for solid waste professionals throughout the world because of the large growth of the waste stream, and the content of toxic metals in them, most notably heavy metals such as lead. Notebook computers are becoming one of the major components of discarded computer devices and will continue to increase in the waste stream in the future. While the computers hold great promise for recycling, a substantial amount of this waste is often disposed in municipal solid waste (MSW) landfills. The toxicity characteristic leaching procedure (TCLP) is commonly used to simulate worse case leaching conditions where a potentially hazardous waste is assumed to be disposed along with municipal solid waste in a landfill with actively decomposing materials overlying an aquifer. The objective of this study was to examine leaching potential of lead from discarded notebook computers using the scale-up TCLP, other standard leaching tests such as California waste extraction test (Cal WET), and the synthetic precipitation leaching procedure (SPLP) and actual landfill leachates as leaching solution. The scale-up TCLP is a modified TCLP (where the device was disassembled and leached in or near entirety) to meet the intent of the TCLP. The results showed that the scale-up TCLP resulted in relatively high lead found in the leachate with an average of 23.3 mg/L. The average level was less than those by the standard TCLP and WET (37.0 mg/L and 86.0 mg/L, respectively), but much greater than those by the SPLP and the extractions with the landfill leachates (0.55 mg/L and 1.47 mg/L, respectively). The pH of the leaching solution and the ability of the organic acids in the TCLP and WET to complex with the lead were identified as major factors that controlled the amount of lead leached from notebook computers. Based on the results obtained by a number of leaching tests in this study, notebook computers may present a potential leaching risk to the environment and human health upon land disposal. However, further investigation is still needed to assess the true risk posed by the land disposal of discarded notebook computers.

• Journal of Pharmaceutical Investigation
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• v.27 no.4
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• pp.295-301
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• 1997

Nitrendipine, a slightly soluble calcium channel blocking agent forms a solid dispersion system with $hydroxypropyl-{\beta}-cyclodextrin$, which exhibits better dissolution characteristics than the uncomplexed drug. The dissolution rate of nitrendipine was markedly increased in solid dispersion system in pharmacopeial disintegration media at pH 1.2 and pH 6.8. Four different dosage forms of nitrendipine were administered to rats: (a) nitrendipine in the solution of PEG 400; (b) nitrendipine solid dispersion system with $hydroxypropyl-{\beta}-cyclodextrin$ in a molar ratio of 1:2 by solvent evaporation method and administered in capsule form; (c) physical mixture of nitrendipine with $hydroxypropyl-{\beta}-cyclodextrin$ in a molar ratio of 1:2 and administered in capsule form; (d) nitrendipine alone administered in capsule form. Relative bioavailability after the oral administration of various dosage forms to rats with a dose of 10 mg/kg equivalent to nitrendipine was compared with that of nitrendipine in the solution of PEG 400. The AUC of solid dispersion was significantly bigger than that of nitrendipine powder. $T_{max}$ of solid dispersion was significantly shorter and $C_{max}$ was higher than that of nitrendipine powder. These results indicate that the bioavailability of nitrendipine could be improved markedly by inclusion complexation. An interesting correlation also appears to exist between the in vitro dissolution data and the area under the plasma concentration-time curves.

• Journal of the Mineralogical Society of Korea
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• v.25 no.2
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• pp.117-122
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• 2012

The leaching of Li from fly ashes was studied. The fly ash produced from the Taean electric power plant of the Korea Western Power Co., Ltd. was used for this study. The Li leaching was observed according to the changes in solid:solution ratio, solution types (seawater or deionized water), and the $CO_2$ condition in the atmosphere. The results showed that the Li concentrations in the solution increased continuously as the solid:solution ratio increased. The Li leaching per unit mass of fly ash was greater when the deionized water was used for the experiment and when the $CO_2$ dissolution is limited during the reaction because the precipitation of $CaCO_3$ is suppressed under those conditions. At high solid:solution ratio, $Mg^{2+}$, the ion preventing the Li extraction from seawater by adsorption, was effectively removed from the seawater.

• Journal of Sensor Science and Technology
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• v.18 no.6
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• pp.441-448
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• 2009

Magnesia partially stabilized zirconia(Mg-PSZ) solid electrolytes for an improvement of thermal shock resistance, which is suitable for the measurement of oxygen activity in a molten steel, were prepared by post-thermal aging treatment. The steelmaking oxygen sensor elements were formed by an injection molding method, sintered at $1650^{\circ}C$, and then thermal aged ranged from 1250 to $1400^{\circ}C$. Sintered density and porosity were decreased as increasing the magnesia content in a zirconia-magnesia solid solution. Fractions of cubic phase to the synthesized Mg-PSZ solid electrolytes were ranged from 13.13 to 79.54.% after post-thermal aging treatment. Very dense microstructure without voids in the grains was obtained by the post-thermal aging process. Fine tetragonal phase crystallites precipitated on the cubic surface during post-thermal aging up to $1300^{\circ}C$ improve a thermal shock resistance and reappearance of electro motive force(EMF) curve.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.661-661
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• 2013

열전재료는 열-전기가 상호 가역적으로 변하는 재료로서, 에너지 변환소재 분야에서 널리 각광받고 있다. 열전재료의 성능은 무차원 열전성능지수(dimensionless figure of merit, $ZT={\alpha}^2{\sigma}T/{\kappa}$)로 평가된다. 여기서 ${\alpha}$는 제벡계수(Seebeck coefficient), ${\sigma}$는 전기전도도(electrical conductivity), ${\kappa}$는 열전도도(thermal conductivity), T는 Kelvin 온도를 나타낸다. 500 K에서 800 K까지의 중온 영역에서 우수한 열전특성을 보이는 $Mg_2X$ (X=Si, Ge, Sn)와 이들의 고용체는 성분원소가 독성이 없고, 매장량이 많아 친환경 열전재료로 각광받고 있다. $Mg_2X$ 고용체 중 $Mg_2Si-Mg_2Sn$ 고용체는 Si와 Sn의 큰 원자량 차이로 인해 낮은 열전도도와 높은 성능지수(ZT)를 얻을 것이라 예상되며 열전발전 소자로서의 응용이 기대된다. Sb가 도핑된 $Mg_{2+x}Si_{0.7}Sn_{0.3}Sb_y$ (x=0, 0.1, 0.2, y=0, 0.01) 고용체를 고상합성과 기계적 합금화로 합성한 후, 진공 열간압축 성형을 통해 성공적으로 제조하였다. X선 회절분석으로 상합성과 고용체 형성 여부를 확인하였고, Mg의 과잉첨가와 Sb 도핑에 따른 열전특성의 변화를 조사하였다.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.66-70
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• 1985

This study was to investigate physical properties of the system $Ca(Mg_{1-x}Al_x) (Si_{2-x}Al_x)O_6$ by quenching method. This system $\chi$=0.1 to 0.3 had same crystal phase microstructure and similar properties. Bulk density microhardness thermal expansion coefficient and modulus of rupture of these solid solutions were 2.87~2.95g/cm3 850~900kg/$mm^2$, $7.5~7.8{\times}10^{-6}$/$^{\circ}C$ and 1950~1980kg/$cm^2$ respectively.

• Journal of Pharmaceutical Investigation
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• v.31 no.3
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• pp.151-160
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• 2001

The purpose of this study is to investigate the interaction of progesterone with various cyclodextrins (CDs) in the aqueous solution and in solid state, and finally to formulate a parenteral aqueous formulation. CDs used were ${\alpha}-$, ${\beta}-$, and ${\gamma}-CD$, $2-hydroxypropyl-{\beta}-CD$ (HPCD), sulfobutyl $ether-{\beta}-CD$ (SBCD), $dimethyl-{\beta}-CD$ (DMCD) and $trimethyl-{\beta}-CD$ (TMCD). The solubility studies of progesterone were performed in the presence of various CDs as a function of concentration or temperature. The solubility of progesterone increased in the rank order of ${\alpha}-CD$ < ${\beta}-CD$ < ${\gamma}-CD$ < TMCD$ < HPCD < DMCD < SBCD. Addition of SBCD (200 mg/ml) in water increased the aqueous solubility $(9.36\;{\mu}g/ml)$ about 3,200 times, and lowering the temperature facilitated the solubilization of progesterone. However, the addition of HPCD and SBCD in 20:80 (v/v) polyethylene glycol 300-water and propylene glycol-water cosolvents markedly decreased the solubility of progesterone, compared with solubilizing effects in water. Physical mixtures and solid dispersions of progesterone with HPCD or SBCD were prepared, and evaluated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), near IR spectroscopy and dissolution studies. By DSC and IR studies, it was found that progesterone was dispersed in HPCD in monotectic state and dissolved rapidly from both solid dispersions. Based on solubility studies, new aqueous progesterone fonnulations (5 mg/ml) containing SBCD (200 mg/ml) could be prepared and did not form precipitates even after 2 months at $4^{\circ}C$. The solution was transparent when mixed with normal saline and 5% dextrose injection at 1: 1, 1:10 and 1:20 (v/v) even after 7 days. Permeation rates of progesterone through a cellulose membrane from 20% PEG 300 solution $(50\;{\mu}g/ml)$ containing HPCD or SBCD were compared with oily formulation. Permeation of progesterone from oily formulation did not occur up to 8 hr, but aqueous formulations showed fast permeation rates from early stage of permeation study. The addition of HPCD or SBCD retarded the permeation rates of progesterone with the increase of CD concentrations, suggesting the possibility of a controlled absorption from the site administered intramuscularly. These results demonstrate that it is feasible to develop a new progesterone parenteral aqueous injection (5 mg/ml) using SBCD.