• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.280-285
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• 1992

Enantiomeric separation of free amino acids has been achieved by a reversed phase liquid chromatography with addition of a Cu(Ⅱ) complex of N-alkyl-L-proline (alkyl: propyl, pentyl or octyl) to the mobile phase. The amino acids eluted were detected by a postcolumn OPA system. N-alkyl-L-proline was prepared and used as a chiral ligand of Cu(Ⅱ) chelate for the enantiomeric separation. The concentration of the Cu(Ⅱ) chelate, the organic modifier and pH affect the enantiomeric separation of free amino acids. The retention behaviour, varied with change in pH and the concentration of the Cu(Ⅱ) chelate, was different compared with those of the derivatized amino acids. The elution orders between D- and L-forms were consistent except histidine showing that L-forms elute earlier than D-forms. The retention mechanism for the enantiomeric separation can be illustrated by the stereospecificity of the ligand exchange reaction and the hydrophobic interaction between the substituent of amino acids and reversed phase, $C_18$.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.263-269
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• 1992

Low-firing dielectric materials with negative small temperature coefficients were investigated. The newly developed materials are based on Ti$O_2$(100-x)/ CuOx(X=1~5wt%) with small amount of Mn$O_2$ additive. The sample without CuO was not sintered at 90$0^{\circ}C$. As CuO content was increased the sample could be sintered at low temperature. However, the dielectric constant was decreased and the dielectric loss was increased. In the case of adding 3wt% CuO and 0.6wt% Mn$O_2$, the dielectric constant and the Q values appeared very high.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.60-65
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• 2004

[ $MoS_2S$ ] is a well-known metal sulfide applied as solid lubricants and an additive to prolong the life of sintered bearings under severe conditions. However, the high price of $MoS_2S$ limited its wide application. This study is aimed to investigated the possibility for application to solid lubricants for $Cu_2S$ as a substitute of v. Bronzes added $Cu_2S$ and $MoS_2S$ are produced by powder metallurgy in this study, and then evaluated their friction and wear properties. The sliding wear test using pin-on-disc type machine, was conducted at several sliding speeds for three type test pieces, bronze and bronzes added $Cu_2S/MoS_2$. Addition of $Cu_2S$ to bronze leads to relatively good friction and wear properties, although it is not so good as addition of $MoS_2S$. But the properties of bronze added $Cu_2S/MoS_2$ would be not suitable for the condition under the high sliding speed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.260-261
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• 2005

$YBa_2Cu_3O_{7-\delta}$ superconductor films have been prepared on silver substrates by electrophoretic deposition. As silver does not react with $YBa_2Cu_3O_{7-\delta}$ compound and has little influence on its superconductivity, it is usually doped in $YBa_2Cu_3O_7$ to improve the strength of the material and eliminate micro-cracks. It has been proved that Ag additive can lower the melting temperature of $YBa_2Cu_3O_{7-\delta}$ and act as linking bridge among $YBa_2Cu_3O_{7-\delta}$ particles, thus in this paper Ag doped $YBa_2Cu_3O_{7-\delta}$ thick films are prepared by electrophoretic co-deposition. As there are only some referenced experience formula and models for co-electrophoretic deposition and does not exist unified explanation, the behavior of Ag particles during co-electrophoretic deposition is also studied.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.125-133
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• 2016

With the aim of using a filler material in a conductive paste, fine Cu nanoparticles were synthesized through the high-speed chemical reaction between cuprous oxide ($Cu_2O$) powder and sulfuric acid in distilled water. Under external temperature of $7^{\circ}C$, sulfuric acid concentration of 48%, and $Cu_2O$ amount of 30 g, the $Cu_2O$ particles were eliminated and slightly aggregated Cu nanoparticles were synthesized. Futhermore, Cu nanoparticles of 224 nm, in which the aggregation between particles was obviousiy much suppressed, were synthesized with the choice of an additive. In the particle sample, occasionally there are coarse particles formed by the aggregation of fine nanoparticles and weak linkages between the nanoparticles. However, the coarse particles were destroyed and the linkages were broken after mixing with a resin formulation, indicating the behavior of untangling the aggregation between nanoparticles.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.62-66
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• 1998

We have studied on the magnetic properties of the specimen with additives Bi$_2$O$_3$and$V_2O_5$ that sintered at 900 $^{\circ}C$ for 4 hours for sybthesizing optimal Ni-Zn-Cu ferrite. Curie temperature rises from 240 $^{\circ}C$ to 270 $^{\circ}C$ as Ni contents increase. Magentic maximum induction$(B_m)$ increases from 2650 G to 3300 G, 3500 G in the specimens with $V_2O_5$ and Bi$_2$O$_3$resectively. On the contrary coercive force $(H_c)$ lowers to 2.05 Oe~1.05 Oe. Permeability all increase in the specimen with additives. In the specimen with additive Bi$_2$O$_3$, we have obtained the low relative loss factor of $6.3{\times}10^{-5}~7.84{\times}10^{-5}$ in the range of 1MHz due to increase of resistivity in grain boundary. In the specimen with additive $V_2O_5$ in spite of increase permeability relative loss factor increase of due to decrease of Q-value.

• Korean Journal of Environmental Agriculture
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• v.35 no.1
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• pp.79-86
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• 2016

BACKGROUND: This study was initiated to quantitatively evaluate the effects of five heavy metals on the growth and P removal efficiencies of Alcaligenes sp., known as the Phosphorus Accumulating Organisms (PAOs). It was cultivated in the batch system with five heavy metals, such as Cd, Cu, Zn, Pb and Ni, added in single and binary mixtures, respectively.METHODS AND RESULTS: IC₅₀ (half of inhibition concentration of bacterial growth) and EC₅₀ (half of effective concentration of phosphorus removal Efficiencies) were used to quantitatively evaluate the effects of heavy metals on the growth and phosphorus removal Efficiencies of Alcaligenes sp. In addition, Additive Index Value (A.I.V.) method was used to evaluate the interactive effects between Alcaligenes sp. and heavy metals. As a result, as the five heavy metals were singly added to Alcaligenes sp., the greatest inhibitory effects on the growth and P removal efficiencies of each bacteria was observed in the cadmium (Cd). In the binary mixture treatments of heavy metals, the treatments of lowest IC₅₀ and EC₅₀ were the Cd + Cu treatment. Based on the IC₅₀ and EC₅₀ of the binary mixtures of heavy metals treatments, most interactive effects between the heavy metals were found to be antagonistic.CONCLUSION: Based on the results obtained from this study, it appears that they could provide the basic information about the toxic effects of the respective treatments of single and binary mixtures of heavy metals on the growth and P removal efficiencies of Alcaligenes sp. through further study about the characterization of functional proteins involved in toxic effects of heavy metals.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.10a
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• pp.123-124
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• 2003

• Journal of the Korean Magnetics Society
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• v.18 no.2
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• pp.58-62
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• 2008

$Ni_{0.4}Zn_{0.4}Cu_{0.2}Fe_2O_4$ ferrite was fabricated by solid stat reaction method and sol-gel method. Because of the drawbacks of each method, we combined these two methods together. We proposed and experimentally verified that nanocrystalline ferrite additive was effective on improving the densification behavior and magnetic properties of NiZnCu ferrites for multilayer chip inductors. The initial permeability of the toroidal core Sample with 20 wt% nanocrystalline ferrite increased from 78.1 to 178.2 as annealing temperature is increased from $880^{\circ}C$ to $920^{\circ}C$. The density, shrinkage and saturation magnetization were increased with increasing annealing temperature, which was attributed to the decrease of additive grain size and increase of sintering density.

• Journal of the Korean Electrochemical Society
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• v.25 no.2
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• pp.81-87
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• 2022

In this study, the effect of alkylamine on copper electroplating was analyzed using cyclic voltammetry. When water-soluble alkylamines were added to the plating solution, the reduction reaction of Cu²⁺ was inhibited. The inhibition effect of 1,12-diaminododecane has been investigated at various concentrations and conditions of the plating solution. 1,12-diaminododecane was protonated in the acidic plating solution, and therefore, it did not act as a complexing agent for Cu²⁺. Accordingly, it was confirmed that the inhibiton effect of 1,12-diaminododecane was attributed to adsorption on the Cu surface. The adsorption of 1,12-diaminododecane exhibits two characteristics: (i) protonation and subsequent electrostatic attraction with anions pre-adsorbed on Cu surface, and (ii) direct adsorption on Cu surface via amine functional group. The adsorbed 1,12-diaminododecane caused three-dimensional growth and grain refining, as well as the inhibition effect, during Cu electroplating.