• Analytical Science and Technology
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• v.11 no.4
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• pp.305-310
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• 1998

A reactive dye synthesized with an amine containing Eriochrome Black T derivative and cynauric chloride was immobilized on a cellulose membrane to construct an optical sensor for the detection of divalent transition metal ions in aqueous solution. The response of this reactive dye-based optical sensor was as sensitive as that of Eriochrome Black T in solution phase. Its typical detection limits for $Zn^{2+}$ and $Co^{2+}$ were $6.3{\times}10^{-5}mol/l$ and $2.5{\times}10^{-4}mol/l$, respectively. No loss in the sensitivity of reactive dye-based sensor was observed even the pH of flowing solutions continually varied for an extended period of time.

• Resources Recycling
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• v.15 no.2 s.70
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• pp.32-36
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• 2006

Magnesium has been used as light and functional material, and its demand is increasing as a material for automobile engine and for mobile phone or notebook PC case. Fused salt electrolysis and thermal reduction are regarded as main methods for the extraction of magnesium, and choice for the method is firstly according to raw material. In this study, magnesium metal is obtained by an electrolysis of magnesium chloride. Two types of fused salt mixtures were used as electrolyte and electrolyzed at 7V with a graphite anode having the same depth, and their results were compared with each other. A mixed salt of $KCl/NaCl/MgCl_2$ was the more effective than $KCl/NaCl/CaCl_2/CaF_2/MgCl_2$ in current efficiency through the experiments at $760^{\circ}C$. Purity of the prepared magnesium metal was above 98%. Some basic data for scale-up of the magnesium electrolysis equipment, which would be necessary for a commercialization, could be obtained.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.1
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• pp.48-57
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• 2016

Objectives: This study was conducted to evaluate the accuracy and precision of airborne metal analysis using polyvinyl chloride(PVC) membrane filter by pretreatment methods. Methods: A total of 75 spiked PVC samples for Cr, Fe and Mn ranged from 6 ug/sample to 40 ug/sample were used to evaluate recovery rates for three pretreatment methods: acid extraction, hot plate ashing and microwave digestion. For Mn, an additional 75 spiked mixed cellulose ester(MCE) membrane filters were analysed to compare the recovery rates of PVC samples. All samples were analysed with an inductively coupled plasma optical emission spectrometer(ICP-OES) and manganese samples were additionally analyzed by atomic absorption spectrometer(AAS). Results: The overall mean recovery rates of PVC samples for Cr, Fe and Mn were 90% or higher regardless of pretreatment methods, but there were statistically significant differences in recovery rates for Cr(p<0.05) and Mn(p<0.01) samples by pretreatment methods. The biases and the coefficient variations of PVC samples for three metals pretreated with three kinds of pretreatment methods ranged from 1.7% to 4.7% and from 1.6% to 6.5%, respectively. The manganese PVC samples pretreated by microwave digestion and analyzed with ICP-OES had the lowest bias at 1.9% and also showed lower bias than the bias for MCE samples, 2.7%. Conclusions: In order to accurately analyze the metals sampled with PVC membrane filters, microwave digestion and ICP-OES can be recommended.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3601-3606
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• 2012

Structural properties of a small hexapeptide molecule modeled after metal-binding siderochrome immersed in a room-temperature ionic liquid (RTIL) are studied via molecular dynamics simulations. We consider two different RTILs, each of which is made up of the same cationic species, 1-butyl-3-methylimidazolium ($BMI^+$), but different anions, hexafluorophosphate ($PF_6{^-}$) and chloride ($Cl^-$). We investigate how anionic properties such as hydrophobicity/hydrophilicity or hydrogen bonding capability affect the stabilization of the peptide in RTILs. To examine the effect of peptide-RTIL electrostatic interactions on solvation, we also consider a hypothetical solvent $BMI^0Cl^0$, a non-ionic counter-part of $BMI^+Cl^-$. For reference, we investigate solvation structures in common polar solvents, water and dimethylsulfoxide (DMSO). Comparison of $BMI^+Cl^-$ and $BMI^0Cl^0$ shows that electrostatic interactions of the peptide and RTIL play a significant role in the conformational fluctuation of the peptide. For example, strong electrostatic interactions between the two favor an extended conformation of the peptide by reducing its structural fluctuations. The hydrophobicity/hydrophilicity of RTIL anions also exerts a notable influence; specifically, structural fluctuations of the peptide become reduced in more hydrophilic $BMI^+Cl^-$, compared with those in more hydrophobic $BMI^+PF_6{^-}$. This is ascribed to the good hydrogen-bond accepting power of chloride anions, which enables them to bind strongly to hydroxyl groups of the peptide and to stabilize its structure. Transport properties of the peptide are examined briefly. Translations of the peptide significantly slow down in highly viscous RTILs.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2867-2872
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• 2010

Two new energetic organic alkali metal salts, 1,1-diamino-2,2-dinitroethylene rubidium salt [Rb(FOX-7)${\cdot}H_2O$] and 1,1-diamino-2,2-dinitroethylene cesium salt [Cs(FOX-7)${\cdot}H_2O$], were synthesized by reacting of 1,1-diamino-2,2-dinitroethylene (FOX-7) and rubidium chloride or cesium chloride in alkali methanol aqueous solution, respectively. The thermal behaviors of Rb(FOX-7)${\cdot}H_2O$ and Cs(FOX-7)${\cdot}H_2O$ were studied with DSC and TG methods. The critical temperatures of thermal explosion of the two compounds are 216.22 and $223.73^{\circ}C$, respectively. Specific heat capacities of the two compounds were determined with a micro-DSC method, and the molar heat capacities are 217.46 and $199.47\;J\;mol^{-1}\;K^{-1}$ at 298.15 K, respectively. The adiabatic times-to-explosion were also calculated to be a certain value of 5.81 - 6.36 s for Rb(FOX-7)${\cdot}H_2O$, and 9.92 - 10.54 s for Cs(FOX-7)${\cdot}H_2O$. After FOX-7 becoming alkali metal salts, thermal decomposition temperatures of the compounds heighten with the rise of element period, but thermal decomposition processes become intense.

• The Journal of the Korean dental association
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• v.52 no.2
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• pp.96-104
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• 2014

The aim of this study was to investigate the frequency of positive patch test reaction to dental materials in patients with oral mucosal diseases. Epicutaneous patch test was performed in 110 patients with oral mucosal diseases; 41 patients with oral lichen planus(OLP), 44 patients with burning mouth syndrome(BMS), 25 patients with other oral mucosal diseases including recurrent aphthous ulcer and mucous membrane pemphigoid. The obtained results were as follows: Oral gold restorations were most common in patents with oral mucosal diseases and porcelain fused metal crown, implant appeared in the order. 33 of 110 patients did not appear skin reactions (negative, 30%) and 77 patients (positive, 70%) had skin reactions including redness, rash, blisters. Dental materials causing positive reaction to patch test were mainly as gold-sodium-thiosulfate (26.7%), nickel sulfate(Ni) (22.7%), cobalt chloride(Co) (14.7%), palladium chloride(Pd) (11.9%), potassium dichromate (10.7%) in order, respectively. In conclusion, old metal restorations could be the cause of oral mucosal diseases and epicutaneous patch test could be used as a tool to improve the oral conditions.

• Journal of the Korean institute of surface engineering
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• v.48 no.3
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• pp.73-81
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• 2015

Chloride plating solution was fabricated by dissolving metal Ni powders in solution with HCl and deionized water. Effects of deposition conditions on the properties of Ni films electrodeposited from chloride baths were studied. Current efficiency of Ni films electrodeposited from the baths containing saccharin was decreased with increasing the current density. Residual stress of Ni thin films ware measured to be about 230 ~ 435 MPa in the range of current density of $10{\sim}25mA/cm^2$. Cathode current efficiency in baths without saccharin was initially increased with increasing pH, while it was decreased with increasing pH further. Cathode current efficiency in baths with saccharin (except at pH 2) exhibited less 10 ~ 20% than that in baths without saccharin. Residual stress of Ni films electrodeposited from baths without saccharin was measured to be 388 ~ 473 MPa in the range of pH 2 ~ pH 5 and then was increased to 551 MPa at pH 6. On the other hand, residual stress of Ni films electrodeposited from baths with saccharin was increased with increasing pH. Surface morphology was strongly affected by the change of current density, but slightly by solution pH and addition of saccharin.

• Resources Recycling
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• v.27 no.3
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• pp.8-15
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• 2018

Solvent extraction behavior of light rare earth elements (Pr, Nd) and medium rare erath elements (Tb, Dy) in the HCl-PC88A-kerosene extraction system was investigated in order to separate high-purity light rare earths (Pr, Nd) and medium rare earths (Tb, Dy) in the mixed rare earth chloride solution. In the batch test step, it was confirmed that the separation efficiency was good when the extractant concentration (PC88A) was 0.5 M, the equilibrium pH after extraction was 0.8 to 1.0 (initial pH 1.3 of the feed), the concentrations of hydrochloric acid in scrubbing solution was set as 0.1 M, the concentrations of hydrochloric acid in stripping solution was set as 2.0 M or more. Based on the experimental data obtained from the batch test, the mixer-settler was composed as follows; 4 stages of extraction, 8 stages of scrubbing, 4 stages of stripping, and 3 stages of pickling organic solution. The Mixer-settler was operated for 180 hours, and the operating conditions were continuously adjusted to obtain the high-purity light/medium rare earths. Finally, the purity of light (Pr, Nd) and medium rare earth elements (Tb, Dy) was reached as 3 N class.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.167-174
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• 2005

Smaller size and higher integration of electronic components make smaller gap between metal conducting layers in electronic package. Under harsh environmental conditions (high temperature/humidity), electronic component respond to applied voltages by electrochemically ionization of metal and metal filament formation, which lead to short failure and this phenomenon is termed electrochemical migration(ECM). In this work, printed circuit board(PCB) is used for determination of ECM characteristics. Copper leads of PCB are soldered by eutectic solder alloys. Insulation breakdown time is measured at $85^{\circ}C,\;85{\%}RH$. CAF is the main mechanism of ECM at PCB. Pb is more susceptible to CAF rather than Sn, which corresponds well to the corrosion resistance of solder materials in aqueous environment. Polarization tests in chloride or chloride-free solutions fur pure metal and eutectic solder alloys are performed to understand ECM characteristics. Lifetime results show well defined log-normal distribution which resulted in biased voltage factor(n=2) by voltage scaling. Details on migration mechanism and lifetime statistics will be presented and discussed.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.151-157
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• 2010

Purpose: The purposes of this study was to evaluates shear bond strength between zirconia core and veneer-ceramic in order to examine the clinical practice of colored zirconia block fabricated by infiltration method into the metal chloride solution. Material and methods: CNU block and $Everest{(R)}$ ZS blank were used. VITA In-$Ceram{(R)}$2000 YZ Coloring liquid (LL1) and 3 aqueous metal chloride solutions containing chromium and molybdenum ingredients were used. 40 zirconia specimens were prepared into cuboid shape ($5{\times}5{\times}10 mm$). All specimens were divided into 5 groups by infiltrating into the coloring liquids. After that, porcelain was build up into the shape of $5{\times}5{\times}4mm^3$, followed by sintering. The maximum loading and shear bond strength was measured. Failure patterns and failure sites were examined. Results: 1. There were no statistical differences in shear bond strength between zirconia blocks (P > .05). 2. There were no statistically significant differences in shear bond strength between non-colored and colored zirconia blocks, while shear bond strength of non-colored zirconia blocks is higher than that of colored specimen (P > .05). 3. In the comparison with shear bond strength among colored zirconia blocks, there were no statistical differences according to kinds of coloring liquid (P > .05). 4. Mixed failure patterns were mainly observed in the failure between zirconia and veneering ceramic. The veneering ceramic failure of all specimens was observed in either interface of zirconia or veneering ceramic. Conclusion: Shear bond strength between colored zirconia and veneering ceramic shows lower tendency than non-colored zirconia, but there was clinically allowable value.