• Journal of the Mineralogical Society of Korea
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• v.20 no.1 s.51
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• pp.21-33
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• 2007

The dispersion/flocculation behavior of bentonite is a major concern in performance of drilling fluid. We studied the dispersion/flocculation characteristics of three commercial bentonites [two CMC (carboxymethyl cellulose) treated and one untreated] in waters of different pHs and salt concentrations. We also examined changes in the viscosity of bentonite suspensions in such waters as a major rheological property of drilling fluid. The dispersion/flocculation behaviors of bentonites were measured by two methods: colorimetric and light scattering method. Light scattering method allows estimating the floc diameter and flocculation rate. The dispersion and flocculation behaviors were diverse with the different bentonites and water qualities. In distilled water, all the bentonites were well dispersed up to first 10 minutes. After that, the CMC-bearing bentonites were flocculated. In salt waters, all the samples were flocculated and the flocculation rate is varied with salt concentration and polymer content. The volume of settled flocs decreased with increasing salt concentration. The flocculation rate and floc diameter increased with decreasing pH of solutions, whereas the volume of settled flocs increased with increasing pH of solutions. The bentonites of fast flocculation behavior had low viscosity. The results of the present study will be helpful in applying bentonites to drilling fluids in diverse environments.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.557-561
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• 2007

Polypropylene (PP)/corn starch master batch (starch-MB) blends with different PP compositions of 40, 50, 60, and 80 wt% were prepared by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The chemical structures and thermal properties of the PP/starch-MB blends were investigated by FT-IR, differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The chemical structure was confirmed by the existence of hydroxy group. There was no district change in melting temperature and melting enthalpy, and TGA curve indicated a decrease in degradation temperature with starch-MB content. The porosity change of blend was measured by scanning electron microscope (SEM), the degree of porosity on the blend surface increased with the starch-MB content. The rheological properties indicated an increase in complex viscosity, shear thinning tendency and elasticity with the starch-MB concentration. These effects were confirmed by an oscillatory viscometer at $200^{\circ}C$. From these results, it is found that 40 wt% is the optimum starch-MB concentration. The fiber was fabricated from PP60/MB40 with 40 wt% starch-MB and the porosity and tensile properties were investigated.

• Korean Journal of Environmental Agriculture
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• v.18 no.3
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• pp.292-297
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• 1999

This study was performed to estimate the possibility of use of plant materials as catalytic agents fur the decontamination of waste waters contaminated with organic pollutants by using 2,4-dichlorophenol(2,4-DCP) as a model pollutant. Plant materials containing high peroxidase activity were selected as catalysts for the removal of 2,4-DCP. Peroxidase activity, which plant materials were containing, was measured, and the greatest peroxidase activity was observed in shepherd's purse, followed by turnip, sweet potato, Chinese cabbage and white radish. The peroxidase activity in shepherd's purse was four times higher than that of horseradish purchased in U.S.A. Using shepherd' s purse and turnip, it was investigated the effect of various factors on the decontamination of 2,4-DCP through oxidative coupling. The removal of 2,4-DCP was extremely fast, and a maximal removal could be achieved within 3 min for shepherd' s purse and 15min for turnip. The pH range was from 3.0 to 8.0 and the amount of $H_2O_2$ added was 9mM when maximal removal was achieved(over 90%). No increasing removal of 2,4-DCP was observed due to increasing the amount of $H_2O_2$ added (over 9mM). The initial concentration affected the transformation of 2,4-DCP incubated with plant materials. When turnip was used as catalytic agent, it was observed decreasing transformation of 2,4-DCP due to increasing initial concentration.

• The Korean Journal of Mycology
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• v.27 no.4 s.91
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• pp.304-311
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• 1999

Batch kinetics during the exo-polysaccharide (EPS) fermentation of Ganoderma lucidum was investigated as a function of different substrates (glucose and starch), substrate concentration $(1{\sim}7%,\;w/v)$ and subculture (3 times). Logistic model for mycelial growth fitted the experimental data better than Monod and two thirds power model. The Luedeking-Pirt equation was adequate to fit the kinetic data of product formation and substrate consumption. The EPS production was strongly non-growth associated, although it was mixed type. The product formation and sustrate consumption by growth associated mechanism decreased as the concentration of glucose increased, while those of the non-growth associated mechanism increased. However, starch medium increased the growth associated and non-growth associated substrate consumption indicating higher availability of substrate. Also, batch culture in starch medium showed the higher specific growth rate and stability during subculture than those in glucose medium. In conclusion, the enhanced EPS production and stability in the subculture was found to be remarkably improved by use of starch as sole carbon source in medium. The maximum mycelium dry weight and EPS production of 9.463 and 10.410 g/l, respectively, were obtained after shake culture of 7 days at $30^{\circ}C$ from the media containing 7% starch.

• Applied Chemistry for Engineering
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• v.29 no.6
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• pp.682-689
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• 2018

In this paper, the stability criteria of cosmeceuticals emulsion containing Broussonetia kazinoki extracts was established using the central composite design model. As optimization conditions of the emulsification using the central composite design model, concentrations of the emulsifier and emulsion stabilizer were used as a quantitative factor while emulsion stability index (ESI) and polydispersity index (PDI) were used as a reaction value. The targeted values of ESI and PDI were estimated as over 60% and the minimum number, respectively. Optimized concentrations of the emulsifier and emulsion stabilizer were 3.73 and 3.07 wt%, respectively, from the emulsification optimization based on ESI and PDI values. The estimated reaction values of ESI and PDI were 60% and 0.585, respectively. As concentrations of the emulsifier and emulsion stabilizer increased, the stability of the emulsion prepared tended to increase. The emulsifier was one of the most influential factors for ESI than the emulsion stabilizer. On the other hand, the PDI value was similarly affected by both the emulsion and emulsion stabilizer. The ESI of the cosmeceuticals emulsion prepared under experimental conditions deduced from the central synthesis planning model showed at least about 45% of the stability. However, all of the emulsions were separated after 4 weeks from the initial preparation. When the concentration of the emulsifier was more than 3.72 wt%, the ESI value was over 60%. Also the layer separation rate decreased with increasing the emulsion stabilizer concentration.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.453-459
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• 2019

In this study, the influence factors on the stability of the O/W (oil in water) emulsions prepared with coconut oil and the nonionic mixed surfactant (Tween 80-Span 80) were evaluated. The concentration and HLB value of the nonionic mixed surfactant, and the degree of agitation were used as manufacture factors. The stability of prepared O/W emulsions were measured with the mean droplet size, zeta-potential, emulsion stability index (ESI), and thermal instability index (TII). The mean droplet size of the prepared O/W emulsions was from 100 to 200 nm. As the concentration of mixed surfactant and the homogenization speed increased, the droplet sizes decreased, while the zeta-potential values increased. The effect of HLB values increased in the order of 6.0, 10.0 and 8.0, and at the HLB value of 8 the smallest mean droplet size as 120 nm was obtained whereas the largest value of the zeta-potential between 10 and 60 mV. From the results of ESI and TII, the stability of prepared O/W emulsions increased in order of 6.0, 10.0 and 8.0 of HLB values, and ESI and TII values were above 80% and below 20% respectively at HLB value of 8.0.

• Membrane Journal
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• v.28 no.6
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• pp.406-413
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• 2018

In OBIGGS, a small amount of ozone in the atmosphere damages the polymer membrane. Therefore, the ozone removal device is installed at the front end to prevent the damage of the membrane by reducing the concentration of ozone in the gas delivered to the membrane. In this study, two hollow fiber membranes, PI and PSf, used to fabrication hollow fiber module with an effective membrane area of $6.37cm^2$ for gas separation in OBIGGS. The ozone concentration in the chamber was maintained at 2-3 ppm. The gas was continuously supplied into the module by using a pump. The gas permeation characteristics and the tensile strength were evaluated as a function of ozone exposure time. The PI-based hollow fiber membrane showed only 20% reduction in the transmittance, and remained its original uniformity without any significant changes. However, when PSf type hollow fiber membranes were used, the permeability decreased by more than 80% and the tensile strength decreased by more than 70%.

• Journal of the Korean Electrochemical Society
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• v.26 no.4
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• pp.71-79
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• 2023

In this study, we employed anionic, cationic, and nonionic surfactants for the hydrophilization of porous substrates used in the fabrication of pore-filling membranes. We investigated the extent of hydrophilization based on the type of surfactant, its concentration, and immersion time. Furthermore, we used the hydrophilized substrates to produce pore-filling anion exchange membranes and compared their ion conductivity to determine the optimal hydrophilization conditions. For the ionic surfactants used in this study, we observed that hydrophilization progressed rapidly from the beginning of immersion when the applied concentration was 3.0 wt%, compared to lower concentrations (0.05, 0.5, and 1.0 wt%). In contrast, for the relatively larger molecular weight non-ionic surfactants, smooth hydrophilization was not observed. There was no apparent correlation between the degree of hydrophilization and the ion conductivity of the anion exchange membrane. This discrepancy suggests that an excessive hydrophilization process during the treatment of porous substrates leads to excessive adsorption of the surfactant on the sparse surfaces of the porous substrate, resulting in a significant reduction in porosity and subsequently decreasing the content of polymer electrolyte capable of ion exchange, thereby greatly increasing the electrical resistance of the membrane.

• Polymer(Korea)
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• v.24 no.4
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• pp.505-512
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• 2000

The mixture density data for poly(lactide-co-glycolide) [PLGA] with supercritical $CO_2$, CHF$_3$ and CHClF$_2$ were obtained in the temperature range of 27 to 10$0^{\circ}C$ and at pressures as high as 3000 bar (PLGA$_{x}$, Where the molar concentration of glycolide in the backbone, x, range from 0 to 50 mol%). The PLA-$CO_2$, PLA-CHF$_3$, and PLA-CHClF$_2$ systems dissolve in the pressure less than 1430 below 700, and below 100 bar, respectively. The mixture density shows from 1.084 to 1.334 g/cm$^3$ at temperatures from 27 to 93$^{\circ}C$. The PLGA$_{15}$ -$CO_2$ mixture dissolves at pressures of below 1900 bar and the mixture density is in the range of 1.158 to 1.247 g/cm$^3$ at temperatures between 37 and 92$^{\circ}C$. The solubilities of the PLGA$_{25}$ for $CO_2$, CHF$_3$, and CHClF$_2$ are shown to pressure as high as 2390, 1470, and 118 bar, respectively, and the mixture density exhibits iron 1.154 to 1.535 g/cm$^3$ at temperatures from 29 to 81$^{\circ}C$. The PLGA$_{50}$-$CO_2$ system does not dissolve at 24$0^{\circ}C$ and 3000 bar while the PLGA$_{50}$-CHCIF$_2$ does easily at 5$0^{\circ}C$ and 100 bar. The mixture density for the PLGA-CHClF$_2$ system increases even at low pressures as the glycolide molar concentration increases.es.es.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.2
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• pp.108-113
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• 1997

A field experiment was conducted to evaluate effect of phosphate coated slow release fertilizer on the directly seeded rice. Odae byeo was seeded by drill under dry condition. The soil was a sandy clay loam soil located in the Experimental Farm of the Kangweon National University, Chuncheon, Kangweon-Do. The yield of rice from the urea applicated directly seeded field was 84.9% of the yield from the transplanted field, and showed no difference between split application treatments. The yield from the phosphate coated slow release fertilizer was the highest showing 110.7% of the yield from the urea application. The yield from the polymer coated slow release fertilizer was 90.4%. The yield from the organic fertilizer 400kg/10a treatment was 81.8% and was 94.8% from the organic fertilizer 600kg/10a treatment. In 1996 experiment, the yield from the phosphate coated slow release fertilizer was higher than the yield from the transplanted field. The $NO_3-N$ and $NH_4-N$ concentrations in soil solution at the depth of 15cm revealed that nitrogen leaching was the highest from the urea N40-0-30-30 treatment, and the lowest from the phosphate coated slow release fertilizer. The phosphorus concentration showed similar pattern. Therefore, use of phosphate coated slow release fertilizer increased rice yield and decreased loss of nitrogen and phosphorus loss.