• 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, $C_18$.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.2
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• pp.61-66
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• 2003

In order to prevent roll-over and a rapid boil-off of LNG in tanks, the phase equilibria of carbon dioxide in liquefied natural gas components as binary mixtures at cryogenic temperatures have been experimentally measured using Fourier transform infrared spectroscopy in conjunction with a specially designed variable pressure/temperature cryostat cell (pathlength 2 mm; pressures up to 30 bar). Solid carbon dioxide has been found to be comparatively soluble in liquid nitrogen (3.25$\times$${10}^{-6}$ mole fraction), liquid methane (1.04$\times$${10}^{-4}$ mole fraction), liquid ethane (3.1$\times$${10}^{-2}$ mole fraction) and liquid propane (6.11$\times$${10}^{-2}$ mole fraction) at their normal boiling temperatures. The solubilities of carbon dioxide in various cryogens, which increased with increasing temperature, are much lower than those obtained by others using gas chromatography. The differences are attributed to infrared spectroscopy selectively measuring dissolved solute in situ whereas gas chromatography measures microscopic particulate solid in addition to dissolved solute.

• Transactions on Electrical and Electronic Materials
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• v.7 no.1
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• pp.30-35
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• 2006

We have studied the motion of charged micro-particles that are immersed in a nematic liquid crystal (LC) and controlled by in-plane field. The LC is an anisotropic liquid such that the viscosity of the LC depends on flow direction, phase of the LC, and temperature, which affects the motion of the charged particles under the influence of electric field. This study shows that the motion of charged particles mainly depends on the applied voltage and the LC phase, but does not show any significant influence from the initial alignment of LC, although one may expect directional difference in drag force due to interaction between LC and particle. The viscosity changes due to temperature variations in nematic phase also show no signification influence on particle velocity when compared to the effect from varying in-plane field strength.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.588-595
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• 2009

The knowledge of grain growth of carbide particles is very important for manufacturing micrograined cemented carbides. In the present study, continuous and discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides is investigated using the Monte Carlo computer simulation technique. The Ostwald ripening process (solution/re-precipitation) and the grain boundary migration process are assumed in the simulation as the grain growth mechanism. The effects of liquid phase fraction, grain boundary energy and implanted coarse grain are examined. At higher liquid phase content, mass transfer via solid/liquid interfaces plays a major role in grain growth. Growth rate of the implanted grain was higher than that of the matrix grains through solution/re-precipitation and coalescence with neighboring grains. The results of these simulations qualitatively agree with experimental ones and suggest that distribution of liquid phase and carbide particle/carbide grain boundary energy as well as contamination by coarse grain are important factors controlling discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides. The contamination by coarse grains must by avoided in the manufacturing process of fine grain cemented carbides, especially with low Co.

• Applied Biological Chemistry
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• v.41 no.8
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• pp.595-599
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• 1998

An analytical method was developed to determine tricyclazole residues in rice grain, straw, and soil using high-performance liquid chromatography (HPLC) with ultraviolet absorption detection. Tricyclazole was extracted with methanol from moist rice grain, straw, and soil samples. n-Hexane washing was employed to remove nonpolar co-extractives during liquid-liquid partition. Tricyclazole was then extracted with dichloromethane from alkaline aqueous phase, while acidic interferences remained in the phase. Dichloromethane extract was further purified by silica gel column chromatography prior to HPLC determination. Reverse-phase HPLC using an octadecylsilyl column was successfully applied to separate and quantitate the tricyclazole residue in sample extracts monitored at ${\lambda}_{max}$ 225nm. Recoveries from fortified samples averaged $95.5{\pm}3.0%\;(n=6),\;87.5{\pm}20.%\;(n=6),\;and\;84.3{\pm}2.8%$ (n=12) for rice grain, straw, and soil, respectively. Detection limit of the method was 0.02 mg/kg for rice grain and soil samples while 0.05 mg/kg for rice straw samples. The proposed method was reproducible and sensitive enough to evaluate the safety of tricyclazole residues in rice grain, straw, and soil.

• Korean Journal of Materials Research
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• v.4 no.4
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• pp.393-400
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• 1994

A new process for uniform coating of copper to submicron tungsten powder has been developed. W-Cu alloy where copper can be uniformly distibuted has been made by the liquid phase sintering of thus prepared tungsten powder. It has been found that copper content can be lowered less than IOwt. % in our new process, maintaining the uniform distribution of copper in W-Cu alloy. Relative density above 96% was obtained after the liquid phase sintering when small amount of cobalt was added. It was revealed that the rapid increase of densification rate was due to the enhancement of wettability between tungsten particle and liquid copper.

• Journal of ILASS-Korea
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• v.12 no.2
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• pp.94-100
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• 2007

The liquid phase LPG injection (LPLi) system (the third generation technology) has been considered as one of the next generation fuel supply systems for LPG vehicles, since it has a very strong potential to accomplish the higher power, higher efficiency, and lower emission characteristics than the mixer type (the second generation technology) fuel supply system. To investigate the characteristics of LPG residue in liquid phase LPG injection system, various rubbers in LPG fuel system were reacted with LPG fuels during 3 months. The experimental results showed that the residue of a cover rubber in a fuel pump after test increased 10 times higher than that before test. Furthermore, the amount of sulfur, nitrogen species which are considered as main sources in deposit formation in the LPLi fuel injector were also found to be higher than that in original LPG fuel. And rubber properties of fuel pump cover were decreased after reaction test compared with those of the original rubber. Therefore, the rubber for fuel pump cover is not suitable for a proper material in LPLi fuel system. And these results can provide more information if a motor company shares the data of core rubber parts in field test LPLi vehicles.

• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.14-21
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• 1999

As an effective means to convey crushed materials from seabed to onboard ship and to raise hazardous or abrasive liquids, air-lift pump provides a reliable mechanism due to its simple configuration and easy-to-operate principle. The present study is focused on investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newtonian liquids. It is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates. The comparison between riser performance of the conveyed liquid flow rate calculated by the computer program and measured data with large scale air lift pump system constructed in 200 meter depth vertical tank reveals similar distribution.

• ETRI Journal
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• v.41 no.6
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• pp.820-828
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• 2019

A highly reliable conductive adhesive obtained by transient liquid-phase sintering (TLPS) technologies is studied for use in high-power device packaging. TLPS involves the low-temperature reaction of a low-melting metal or alloy with a high-melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag-coated Cu, a Sn96.5-Ag3.0-Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 ℃, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.27-36
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• 2000

In this study, spray characteristics of a dual airblast atomizer are addressed. Three dimensional characteristics of a dual airblast atomizer with air swirl are measured to provide the significant data. The liquid flow rate was fixed at 0.06 kg/min, and atomizing air was controlled at the liquid-air mass ratio of 4.0. The performance of the spray with co-swirl and counter-swirl flow was investigated at each point in the developed spray region using a three-component phase Doppler particle analyzer. This instrument was also used to evaluate the concentration profiles. The three dimensional mean velocity were investigated of present flow characteristics of the dual airblast atomizer. In addition, drop size distributions, mean droplet size profile, and droplet concentration were analyzed to understand atomization characteristics. This experimental results can be conveniently utilized for the preliminary design of gas turbine engines for aircraft.