• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.647-652
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• 2004

In aqueous tape casting of alumina slurry systems, the relationships between the suspension compositions and the defects of the dried tapes were discussed. The suspensions compositions were controlled with the ratios of the solids, water and organics binder contents. The effects of the thickness of dried tape and kinds of binder system were also examined. In the defect free region, the apparent viscosity showed nearly same value due to the count balancing effect of solid and organic binder content on the apparent viscosity. When water content was constant, increasing solid led to decrease of organic binder content. The defect free region was narrowed with increasing of casting thickness. When linear type acrylic emulsion binders system (D1000 and D 1035) were used, defect free zone formed the belt type in the triangle of solid, water and organic binder content according to the line of constant water contents. However the defect free region was not found in the cross-link type emulsion binder system (D 1050).

• Journal of the Korean Chemical Society
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• v.14 no.2
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• pp.169-177
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• 1970

A study was made on the radioiodination of organic compounds in presence of hydrogen peroxide both in aqueous and organic solvent systems. In case of the reaction of rosebengal, Hippuran, and 5-iodo-uracil the aqueous reaction system could give high labelling yield within a relatively short reaction time. Labelling yield of average 50% could be obtained within 30 minutes of reaction sequence. In cases of organic solvent systems (D.M.S.O., D.M.F., and Dioxane) the solvent system of D.M.S.O. could give better yield for neutral organic compounds, where as D.M.F. and Dioxane gave better labelling result for acidic materials. Especially, o-iodobenzoic acid, o-iodotoluene, and pentachlorophenol could be labelled better in organic solvent system.

• Korean Journal of Clinical Laboratory Science
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• v.40 no.1
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• pp.18-25
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• 2008

In classical titrimetric analyses, the major concern is the concentration of titrant, usually the aqueous solution of hydrochloric acid or sodium hydroxide, that could be changed as time goes by and it is accompanied with the inaccuracy of the resulting data. And the statistical approach, the nonlinear regression analysis, which is a well-known statistical method, was introduced to determine the accurate concentration of the titrant and the exact value of parameters, $K_a$, r, $C_a$, $C_b$, for 0.01 M aqueous solutions of analytes, sodium pyruvate, sodium acetate, sodium bicarbonate, ammonium hydroxide, ammonium chloride and acetic acid at $25^{\circ}C$. We used Gauss-Newton method for the linearlization of the nonlinear titration system and the two-parameter fitting showed appreciable convergent data for the parameters of the analytes set with the various range of $K_a$ value.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.649-655
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• 2001

The kinetics of the thermolysin-catalyzed synthesis of N-(benzyloxycarbonyl)-L-phenylalanyl-L-leucine ethyl ester (Z-Phe-LeuOEt) from N-(benzyloxycarbonyl)-L-phyenylalanine (Z-Phe) and L-leucine ethyl ester (LeuOEt) in an ethyl acetate saturated aqueous system in a batch operation were studied. The kinetics for the synthesis of Z-Phe-LeuOEt were expressed using a rate equation for the rapid equilibrium random bireactant mechanism. The four kinetic constants involved in the rate equation were determined numerically by the quasi-Newton method so as to fit the calculated results with the experimental data. Within the pH and temperature range examined, the $K_{cat}$ value for the synthesis of Z-Phe-LeuOEt reached a maximum at pH 7.0 and $45^{\circ}C$, whereas the affinity between Z-Phe and thermolysin reached a maximum at pH 6.0 adn $40^{\circ}C$. The inhibitory effect of Z-Phe on the condensation reaction decreased as the pH and temperature decreased. In contrast, they affinity between LeuOEt and thermolysin remained unchanged within the pH and temperature range examined. Therefore, it was concluded that the protonation state of the carboxyl groups. of Z-Phe was more imprtant than that of the amono groups of LeuOEt for the synthesis of Z-Phe-LeuOEt in the present solvent system. The equilibrium yield at pH 6.0 and $30^{\circ}C$ was 8% higher than that at pH 7.0 and $40^{\circ}C$, although the rate was much slower. This result suggested that the affinity between the enzyme and the substrate rather than the overall rate was a more important factor affecting the equilibrium yield, when the peptide synthesis was carried out in a product-precipitation system.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.11
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• pp.1886-1891
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• 2013

To inactivate the microorganisms on the surface of blueberries after harvest and to secure microbial safety, a bubble-aqueous chlorine dioxide washing system was developed. After treating the freshly prepared blueberries with the bubble-aqueous chlorine dioxide washing system, the changes in the microbial populations and quality of the blueberries were determined during storage $4{\pm}1^{\circ}C$. Microbiological data indicated that the populations of total aerobic bacteria, yeast and mold decreased by 1.4 and 1.3 log CFU/g at the treatment of 20 ppm aqueous chlorine dioxide with the system, respectively. There was no significant difference in color change and weight loss during storage among treatments. In addition, this washing system could handle approximately 60 kg of blueberry per hour, resulting in labor-saving. Therefore, these results clearly suggest that the bubble-aqueous chlorine dioxide washing system could be useful in improving the microbiological safety of fresh blueberries after harvest.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.18.2-18.2
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• 2010

For the past a few years, we have intensively researched the printable inorganic conductors and ZnO-based amorphous oxide semiconductors (AOSs) for thin-film transistors. For printable conductor materials, we have focused on the aqueous Ag and Cu ink which possess a variety of advantages, comparing with the conventional metal inks based on organic solvent system. The aqueous Ag ink was designed to achieve the long-term dispersion stability using a specific polymer which can act as a dispersant and capping agent, and the aqueous Cu ink was carefully formulated to endow the oxidation stability in air and even aqueous solvent system. The both inks were successfully printed onto either polymer or glass substrate, exhibiting the superior conductivity comparable to that of bulk one. For printable ZnO-based AOSs, we have researched the noble way to resolve the critical problem, a high processing-temperature above $400^{\circ}C$, and recently discovered that Ga doping in ZnO-based AOSs promotes the formation of oxide lattice structures with oxygen vacancies at low annealing-temperatures, which is essential for acceptable thin-film transistor performance. The mobility dependence on annealing temperature and AOS composition was analyzed, and the chemical role of Ga are clarified, as are requirements for solution-processed, low-temperature annealed AOSs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.805-815
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• 2001

Glaucoma is an eye disease which is caused by abnormal high IOP (Intra Ocular Pressure). High IOP is caused by the aqueous humor which is produced consistently but not drained due to malfunction of the trabecular system which has a role of draining the aqueous humor into the venous system. Currently, there are three methods to treat glaucoma-using medicines, surgical operation, and using implant device. The first and second methods are not long acting, so the use of implants is increasing in these days in order to drain out the aqueous humor compulsory. However, though conventional implants have a capability of pressure regulation, they cannot maintain IOPs desired for different patients, and too much aqueous humor are usually drained, to cause hypotony. To solve these problems, it is needed to develop a new implant which is capable of controling the IOP actively and copes with personal difference of patients. An active glaucoma implant consists of the valve actuator, pressure sensor, controller, and power supply. In this paper, firstly, we make an analysis of the operation of a conventional implant using a bond graph and show defects and limitations of the conventional valve analytically. Secondly, we design and analyze a valve actuator considering actuation principles, resistance elements, control methods, and energy sources focused on power saving problem. Finally, using simulations the possibility of the proposed valve actuator is investigated.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.387-389
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• 2001

• Clean Technology
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• v.20 no.4
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• pp.349-353
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• 2014

Succinic acid is an important precursor in industries producing biopolymers, pharmaceutical and food additives and green solvents. However, due to the high price of petroleum and the global $CO_2$ emission, the biological production of succinic acid from renewable biomass is a novel process due to the fixation of $CO_2$ into succinate during fermentation. In this study, aqueous two phase systems based on imidazolium ionic liquids/$K_2HPO_4$ were used as an effective separation and concentration process for succinic acid. Experimental results show that aqueous two phase systems can be formed by adding appropriate amount of imidazolium ionic liquids to aqueous $K_2HPO_4$ solutions in the presence of succinic acid. It can be found that the ability of imidazolium ionic liquids for phase separation followed the order [HMIm][Br]${\fallingdotseq}$[OMIm][Br]>[BMIm][Br]>[EMIm][Br]. The maximum value of extraction efficiency for succinic acid was about 90% and the amount of coextracted water into top phase is proportional to the chain length of cation in imidazolium ionic liquids. It was concluded that the aqueous two phase systems composed of imidazolium ionic liquids/$K_2HPO_4$ was effective for the selective extraction and concentration of succinic acid.

• Journal of Powder Materials
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• v.12 no.1
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• pp.56-63
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• 2005

Ag powder was prepared from $AgNO_3$ by wet chemical reduction method using various reduction agent system involving $AgNO_3$, $AgNO_2$(AgCl) and Ag complex ion aqueous solution. The pure Ag powder could be prepared regardless of reaction system but the particle shape and distribution were affected very much according to the kind of reduction agents and reaction systems. The optimum reaction system for the preparation of the silver powder having the uniform particle shape and size distribution was Ag complex ion aqueous solution-reduction agent system and in particular, $H_2O_2$ and $C_6H_8O_6$as a reduction agent leaded the more uniform particle shape and size distribution.