• Journal of Environmental Science International
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• v.12 no.12
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• pp.1321-1327
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• 2003

Two different kinds of cases, with and without addition of noncrystalline silica to the Hadong kaolin were studied to obtain useful information on the synthesis of zeolite. The research was carried out to investigate the formation area and the crystalized degree of zeolite according to a synthetic time, the water content of raw material mixture, KOH concentration, and stirring intensity. In the case of without addition of noncrystalline silica to the Hadong kaolin and the low concentration range of KOH, the structure of the kaolin was not changed. However, when the mole ratio of K2O/SiO$_2$ in natural kaolin was increased, Linde-L zeolite and unknown structure of kaolins, U-1 and U-2 were produced. While in the high concentration range of KOH, the unknown structure of kaolins, U-6 and U-2, were produced and the production rate of U-6 was increased with the increased of K2O/SiO$_2$ mole ratio. In the case of with addition of noncrystalline silica to the Hadong kaolin and treatment with KOH hydrothermal processing, ZSM-5, ZSM-35, and Linde-L zeolites and the mixture of unknown structure of zeolites, U-1, U-2, U-3, and U-4, were obtained. Both cases demonstrated that the synthesis of zeolite from the Hadong kaolin was highly influenced by KOH concentration of raw material mixture.

• Journal of the Korean Chemical Society
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• v.42 no.2
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• pp.220-227
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• 1998

Homogeneous precipitation of $Y^{3+}$ with urea has been studied in order to investigate the effect of urea concentration on the preparation of monodispersed colloidal "Yttrium Hydroxycarbonate $(Y(OH)CO_3 \cdot nH_2O)$". As the initial concentration of urea increased, the mean size of colloidal precipitates decreased, and the rate of precipitation of $Y^{3+}$ increased. When the initial concentration of urea was higher than $4.0 \sim 7.0 M$, precipitates obtained were no more monodispersed colloidal particles, but coagulated big particles; and, although the initial concentration of urea increased over 4.0 M, the rate of precipitation did not increased. It is important to decide the proper initial concentration of urea, because excessive urea can cause the environmental problems such as water pollution.

• Journal of Environmental Science International
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• v.17 no.6
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• pp.581-589
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• 2008

This study was carried out to evaluate the effect of water quality of cooling tower on Legionella pneumophila disinfection using Ru/Ti electrode. The influences of parameters such as pH, turbidity, $CaCO_3$ and TOC were investigated using laboratory scale batch reactor. Oxidants such as free Cl, $ClO_2,\;H_2O_2\;and\;O_3$ were measured. The results showed that all of the water quality parameters of cooling tower had deteriorated disinfection of Legionella pneumophila. When the turbidity, $CaCO_3$ and TOC was increased, oxidants which was generated during electrolysis was decreased. pH, free Cl, $ClO_2\;and\;H_2O_2$ concentration were decreased with the increase of pH, whereas $O_3$ concentration was increased with the increase of pH. The order of effect of water quality on the disinfection performance for Legionella pneumophila was turbidity > $CaCO_3$ > TOC > pH. To obtain the safety standard (1000 CFU/L), the simultaneous increase current and NaCl dosage was needed.

• Bulletin of the Korean Chemical Society
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• v.13 no.4
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• pp.425-428
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• 1992

Sodium substituted samples of $Y_{1-x}Na_xBa_2Cu_3O_{7-y}$ for $0.00{\leq}x{\leq}0.16$ were prepared and characterized by X-ray powder pattern, electrical resistivity and magnetic susceptibility measurements, Raman spectroscopy, and idometric titration. The Na substituted compounds have narrow solid solution limits where $0.00{\leq}x{\leq}0.16.$ As the Na concentration increases, the parent orthorhombic structure tends to gradually change to tetragonal. Small changes in the superconducting transition temperature, Tc, are observed in this solid solution region. Raman spectra for the Na phases are virtually identical with that of $YBa_2Cu_3O_7$ except that the Cu(1)-O(4) stretching mode at 504 $cm^{-1}$ and the Cu(2)-O(2,3) bending mode at 340 $cm^{-1}$ for x = 0.16 are slightly shifted. The hole concentrations of the sodium substituted compounds ranged from 0.31 to 0.33 per Cu site are increased with Na content. The substitution of $Na^+$ for $Y^{3+}$ site appears to create oxygen vacancies in the Cu-O chains, causes structural change from orthorhombic to tetragonal, and increases hole concentration in the substituted system.

• Food Science and Biotechnology
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• v.16 no.6
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• pp.999-1005
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• 2007

An oil-in-water (O/W) emulsion [20 wt% com oil, 0.5-6.0 wt% fish gelatin (FG), pH 3.0] was produced by high pressure homogenization, and the influence of pH, protein concentration, and homogenization condition on the formation of FG-stabilized emulsions was assessed by measuring particle size distribution, electrical charge, creaming stability, microstructure, and free FG concentration in the emulsions. Optical microscopy indicated that there were some large droplets ($d>10\;{\mu}m$) in all FG-emulsions, nevertheless, the amount of large droplets tended to decrease with increasing FG concentration. More than 90% of FG was present free in the continuous phase of the emulsions. To facilitate droplet disruption and prevent droplet coalescence within the homogenizer, homogenization time was adjusted in O/W emulsions stabilized by 2.0 or 4.0 wt% FG. However, the increase in the number of pass rather promoted droplet coalescence. This study has shown that the FG may have some limited use as a protein emulsifier in O/W emulsions.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.124-129
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• 2008

The objectives of this paper are to examine the effect of nano-particles on the pool type absorption heat transfer enhancement and to find the optimal conditions to design a highly effective compact absorber for $NH_3/H_2O$ absorption system. The effect of $Al_2O_3$ and CNT particles on the absorption performance is studied experimentally. The experimental ranges of the key parameters are 20% of $NH_3$ concentration, $0{\sim}0.08%$ (volume fraction) of CNT particles, and $0{\sim}0.06%$ (volume fraction) of $Al_2O_3$ nano-particles. For the $NH_3/H_2O$ nanofluids, the heat transfer rate and absorption rate with 0.02 vol% $Al_2O_3$ nano-particles were found to be 28.9% and 17.8% higher than those without nano-particles, respectively. It is recommended that the concentration of 0.02 vol% of $Al_2O_3$ nano-particles be the best candidate for $NH_3/H_2O$ absorption performance enhancement.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.11a
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• pp.118-118
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• 1994

Processings of the P $b_2$S $r_2$( $Y_{1-x}$ C $a_{x}$) C $u_3$ $O_{8+{\delta}}$ (2213)system for x=0.4-0.6 to control deleterious oxidative decomposition have been studied. Our results show that comounds are stable at both low p $O_2$ and high p $O_2$ if they are suitably oxidized. Various oxidation and deoxidation procedures have been investigated in order tp determine the optimum hole concentration in the Cu $O_2$layers for the maximum $T_{c}$. In cases x=0.5 and x=0.6, the optimum hole concentration in the 2213-phase is achieved, but with accelerated oxidative decomposition. Destite this, the maximum $T_{c}$~80-83K for the 2213-phase can be deduced when x=0.5 to 0.6 to 0.6

• Journal of Environmental Science International
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• v.13 no.3
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• pp.279-288
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• 2004

This study aimed at improving the $TiO_2$ photocatalytic degradation of HA. A set of tests was first conducted in the dark to study the adsorption of HA at different coexisting material concentration. Adsorption rate increased with adding cation ion but decreased with adding bicarbonate ion. The photodegradation of HA in the presence of UV irradiation was investigated as a function of different experimental condition: initial concentration of HA, $TiO_2$ weight, pH, air flow rate and coexisting material. It was increased either at low pH or by adding cation ion. The increase of cation strength in aqueous solution could provide a favorable condition for adsorption of HA on the $TiO_2$ surface and therefore enhance the photodegradation rate. It was found that bicarbonate ions slowed down the degradation rate by scavening the hydroxyl radicals.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.760-764
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• 2005

The influences of the oxidant($O_2\;and\;O_3$) on the FeOOH formation were studied with fixed $FeSO_4{\cdot}7H_2O$ concentration (0.5M) and NaOH equivalent ratio(0.5). The characteristics of the synthesized powders were evaluateed by XRD, and equantitative phase analysis. $\alpha-FeOOH$ (Geothite) and/or $\gamma-FeOOH$ was promoted when $O_3$ was used as a oxidant which is stronger oxidizing agent than $O_2$.

• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.174-180
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• 2002

In recent days, the study of a new phosphorescent phosphor has been performed in order to overcome the defect of sulfide phosphor and increase the brightness and long after-glow characteristic of phosphorescent phosphor. Particularly, sulfide phosphor usually used is so chemically unstable that the study of oxide phosphors are processing. $Eu^{2+}$, $Nd^{3+}$ doped Ba-Al-O phosphors sintered at $600{\sim}1500^{\circ}C$ for 2hours had the PL emission spectrum and after-glow over $1200^{\circ}C$. In this system, as the mole concentration of alumina increases, emission bands of phosphors moved from 500nm to 380nm. The optimum concentration of flux was 5wt% and after-glow characteristics of phosphors were found at the host material molar ratio ($BaCO_{3}:Al_{2}O_{3}$), 1:1 and 1:3.