• Polymer(Korea)
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• v.25 no.1
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• pp.78-89
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• 2001

Morphological changes of unsaturated polyester/polyvinylacetate semi-IPN were studied while the phase separation and the cure reaction occurred in a competing fashion. The light scattering and thermal analysis techniques were used to investigate the phase separation rates and mechanical properties resultantly induced by molecular diffusion of thermoplastic polymer during the curing process of thermosetting polymer. The reaction activation energy was calculated by using Flynn-Wall method and the semi-IPN structure exhibited various phase-separation morphological characteristics. When PVAc composition was 10 wt%, the phase separation was not observed during the curing reaction, but the phase separation occurred in a similar fashion to nucleation and growth(NG) mechanism at room temperature. On the other hand, when PVAc composition was over 11.65 wt%, the phase separation was generated in the middle of the curing process. Consequently, the phase separation seemed to influence the curing reaction rate, which was also supported by the changing activation energy with conversion and PVAc composition. Finally, the total scattered intensity was measured at various temperature, and subsequently the diffusion rates of phase separation R(${\beta}m$) were evaluated.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.1
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• pp.78-86
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• 2012

In this study, dark fermentative hydrogen production (DFHP) from acid pretreated microalgal biomass was optimized with via statistical experimental design. Acid concentration and reaction time were varied from 0.1 to 3% (v/w) and 10 to 60 min with substrate concentration of 76 g dry cell weight (dcw)/L and initial pH of 7.4, respectively. During the fermentation, pH was not controlled. The optimal condition was found that at $H_{2}$ yield reached to 37.3 mL $H_{2}/g$ dcw at 1.2% HCl and 48 min. Through regression analysis, it was found that $H_{2}$ yield was well fitted by a quadratic polynomial equation ($R^{2}$=0.95). HCl concentration was the most significant factor influencing DFHP. The results of ANOVA verify that HCl concentration was the most significant factor influencing DFHP.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.361-365
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• 2007

The precipitation reaction of some rare earth chlorides ($Ce/Nd/GdCl_3$) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature ($450{\sim}750^{\circ}C$) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for $NdCl_3$ and $GdCl_3$, and an oxide ($REO_2$) for $CeCl_3$ are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (${\Delta}G_r$). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at $750^{\circ}C$ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of $CeCl_3$, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.387-393
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• 1995

Diffusion coefficients of moisture and solid, reaction rate constants of carotene destruction, and the fitness of drying models for moisture transfer were determined to study the characteristics of mass transfer during osmotic dehydration. Moisture loss and solid gain were increased with increase of temperature and concentration; temperature had higher osmotic effect than concentration. Diffusion coefficient showed similar trend with osmotic effect. Diffusion coefficients of solids were larger than those of moisture because the movement of solid was faster than that of moisture at the high temperature. Reaction rate constants were affected to the greater extent by concentration changes than by temperature changes. Arrhenius equation was applied to determine the effect of temperature on diffusion coefficients and reaction rate constants. Moisture diffusion required high activation energy in $20^{\circ}Brix$, while relatively low in $60^{\circ}Brix$. To predict the diffusion coefficients and reaction rate constants, a model was established by using the optimum functions of temperature and concentration. The model had high $R^2$ value when applied to diffusion coefficients, but low when applied to reaction rate constants. Quadratic drying model was most fittable to express moisture transfer during drying. In conclusion, moisture content of carrots could be predictable during the osmotic dehydration process, and thereby mass transfer characteristics could be determined by predicted moisture content and diffusion coefficient.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.622-630
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• 1998

Rotating Biological Contactor (RBC) was tested for the removal of total ammonia nitrogen (TAN) by using simulated aquaculture system. RBC performance was evaluated by controlling revolution rate of disk and hydraulic residence tile (HRT). The optimum revolution rate of disk was 4 rpm, As HRT of RBC was increased, TAN removal efficiency of RBC and TAN concentration of rearing water were increased. HRT for maintaining lowest TAN concentration of rearing water was 9.5 minutes and at that condition TAN concentration of rearing tank was $1.03 g/m^3$

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.3
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• pp.458-465
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• 2011

Response surface methodology (RSM) was applied to optimize substrate conditions of ribose and hydrolyzed wheat gluten solution for Maillard reaction. Independent variables were NaCl concentration of hydrolyzed wheat gluten ($X_1$), concentration of ribose ($X_2$) and concentration of hydrolyzed wheat gluten ($X_3$), while the dependent variables of the central composite design (CCD) were browning index (absorbance 420 nm), DPPH radical scavenging activity (DF) and sensory preference (score). Optimum substrate conditions at $140^{\circ}C$, 30 min reaction were 3% NaCl concentration of hydrolyzed wheat gluten, 6.2% concentration of ribose and 13.27% concentration of hydrolyzed wheat gluten. The coefficients of determination ($R^2$) were 0.975, 0.960 and 0.854, the model fit was very significant (p<0.001). DPPH radical scavenging activities and sensory preferences were predicted as 700 (DF) and 8.42 (score), respectively. The model solution increased more browning and DPPH radical scavenging activities with increasing ribose and hydrolyzed wheat gluten concentration. Especially hydrolyzed wheat gluten concentration was the most influential factor, while NaCl concentration of hydrolyzed wheat gluten hardly affected the responses. Sensory preference was increased with rising wheat gluten concentration and decreasing NaCl concentration of hydrolyzed wheat gluten.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.335-341
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• 2013

Ammonia circulation reactor (ACR) was devised for the effective pretreatment of corn stover. This method is designed to circulate aqueous ammonia continuously so that it can reduce the chemical and water consumption during pretreatment. In this study, ammonia pretreatment with various reaction conditions such as reaction time (4~12 hour), temperature ($60{\sim}80^{\circ}C$), and solid:liquid ratio (1:3~1:8) was tested. Chemical compositions including solid remaining after reaction, lignin and carbohydrates were analyzed and enzymatic digestibility was also measured. It was observed that as reaction conditions become more severe, lignin removal was significantly affected, which was in the range of 47.6~70.6%. On the other hands, glucan and xylan losses were not substantial as compared to that of lignin. At all tested conditions, the glucan loss was not changed substantially, which was between 4.7% and 15.2%, while the xylan loss varied, which was between 7.4% and 25.8%. With (15 FPU-GC220+30 CBU)/g-glucan of enzyme loading, corn stover treated using ammonia circulation reactor for 8~12 hours resulted in 90.1~94.5% of 72-h glucan digestibility, which was higher than 92.7% of $Avicel^{(R)}$-101. In addition, initial hydrolysis rate (at 24 hour) of this treated corn stover was 73.0~79.4%, which was shown to be much faster than 69.5% of $Avicel^{(R)}$-101. As reaction time increased, more lignin removal and it was assumed that the enhanced enzymatic digestibility of treated biomass was attributed to the lignin removal.

• Korean Journal of Food Science and Technology
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• v.30 no.6
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• pp.1273-1278
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• 1998

Conditions for enzyme-protein binding assay (EPBA) were established in order to detect biotin more rapidly and reproducibly than traditional microbiological assay (MBA). EPBA with streptavidin and biotin-KLH conjugate showed cross-reactivities on biocytin, a derivative with biotin activity, at the rate of 109% $(IC_{50}=0.3\;ppb)\;and\;197%\;(IC_{50}=0.8\;ppb)$, respectively, but not on other derivatives with no biotin activities, such as desthiobiotin, diaminobiotin and 2-iminobiotin. Detection ranges of biotin by EPBA with streptavidin and biotin-KLH conjugates were $0.01{\sim}30\;ng/mL\;and\;0.01{\sim}1.0\;ng/mL(ppb)$, respectively. In the spike test with milk, fruit flake and pine-carrot juice, the correlation coefficience between MBA and EPBA with biotin-KLH conjugates was r=0.994. But MBA showed cross-reactivities both on biocytin and desthiobiotin at the rate of 80.1% and 66.7%, respectively. Detection range of biotin by MBA was $0.1{\sim}0.5\;ng/mL(ppb)$. These results strongly suggest that EPBA is efficient for biotin detection in sensitivity, detection range, cross-reactivity and time consuming.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.991-1000
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• 2000

Methanotrophic consortium utilizing methane as the primary carbon source and secreting soluble methane monooxygenase (sMMO) was immobilized on celite R-635 to continuously treat a wastewater containing trichloroethylene (TCE). With influent 2 ppm of TCE. 80.4 and 84.5% of TCE was degraded in 6 and 20 hour of hydraulic retention time (HRT). respectively. and the removal efficiency of TCE was increased with an increase in HRT in methanotrophic consortium biofilm reactor (MCBR). With influent 5 ppm of TCE and 10 hour of HRT. average efficiency of TCE removal was decreased in initial stage. but gradually increased to 81%. TCE was degraded to 88.5 and 96.5% with 10 and 15 hour of HRT. respectively. when methane was supplied alternately with continuous oxygen supply at influent 5 ppm of TCE. The efficiency of TCE degradation was decreased probably because oxidation reaction of methane was proceeded slowly on MMO. when high concentration of methane was supplied with depletion of oxygen. As results of the pilot-scale study. biodegradation of TCE by MCBR system might be feasible at full-scale operation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.1
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• pp.45-55
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• 2015

Ultraviolet B (UVB) irradiation induces both production of reactive oxygen species (ROS) and glucocorticoids (GCs)-mediated stress responses such as an increase of $11{\beta}$-hydroxysteroid dehydrogenase type 1 ($11{\beta}$-HSD1) activity in skin. In addition, ROS-induced inflammatory mediators and proinflammatory cytokines trigger skin inflammation. In this study, as $11{\beta}$-HSD1 inhibitor recovered a decrease of catalase expression, we investigated whether Trapa japonica (TJ) extract and its fractions could inhibit $11{\beta}$-HSD1/ROS-induced skin inflammation in HaCaT keratinocytes. TJ extract and its fractions inhibited expressions of $11{\beta}$-HSD1 as well as the increase of ROS in UVB-exposed HaCaT keratinocytes. Moreover, proinflammatory cytokines such as interleukin (IL)- ${\alpha}$, - ${\beta}$ and tumor necrosis factor (TNF)-${\alpha}$, and cyclooxygenase (COX)-2 and inducible NO synthase (iNOS) as inflammatory mediators were also inhibited in both mRNA and protein levels. Finally, prostaglandin $E_2$ ($PGE_2$) produced by COX-2 was inhibited effectively by TJ extract and its fractions. Taken together, these results suggest that TJ extract could be a potential anti-inflammatory ingredient to inhibit UVB-induced inflammation in skin.