• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.5
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• pp.690-695
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• 2016

This study was performed to evaluate the effect of alkaline treatment on Styela clava tunic (SCT). Considerable damage to the surface of alkali-treated SCT was observed by scanning electron microscopy (SEM) in a concentration-dependent manner upon alkaline treatment. The amount of crystalline region in SCT gradually increased with increasing NaOH concentration, which was analyzed by X-ray diffraction and thermogravimetric analysis. The initial enzymatic reaction of Celluclast toward SCT was elevated by treatment with NaOH up to 1.0 N concentration due to disruption of the SCT surface by promoting binding of enzymes with SCT. However, in the late stage of the enzyme reaction, hydrolysis rate decreased with elevation of NaOH concentration, thereby increasing the amount of non-reacted residuals. This result was due to the increase in the crystalline regions in SCT.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.255-260
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• 1998

Metal hydrides, $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$, were prepared using chemical synthetic method, and their physical properties were examined using various analytic techniques such as TGA, XRD, SEM and EDX. The activation of the chemically prepared $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$ was achieved by two hydriding/dehydriding cycles only. The miasurements of P-C-T curves revealed that 6 and 5.5 hydrogen atoms were stored in LaNi5and $LaNi_{4.5}Al_{0.5}$, respectively. The hydriding reaction rated for $LaNi_{4.5}Al_{0.5}$ were measured by the method of initial rates. It was found that the shrinking unreacted core model could be applied for the analysis of hydriding kinetics of $LaNi_5$. The rate controlling step of this reaction was the dissociative chemisorption of hydrogen molecules on the surface of $LaNi_5$. The activation energy was $9.506kcal/mol-H_2$. The rates measured in the temperature range from 273 to 343K and in pressure difference ($P_o-P_{eq}$) range form 0.25 to 0.66atm could be expressed as the following equation ; $\frac{dX}{dt}=4.636(P_o-P_{eq})$ exp($\frac{-9506}{RT}$).

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1825-1832
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• 2000

Column experiments were conducted by using soil columns, to investigate feasibility and efficiency of in-situ ozone enhanced remediation for diesel-contaminated soil. The injection of gaseous ozone into soil column revealed the enhanced decomposition of ozone due to the catalytic reaction between ozone and metal (e.g., Fe, Mn etc.) oxides as evidenced by as much as 25 times shorter half-life of ozone in a sand packed column than in a glass beads packed column. Substantial retardation in the transport of and the consumption of ozone were observed in the diesel contaminated field soil and sand packed columns. After 16 hrs ozonation, 80% of the initial mass of diesel (as diesel range organic) concentration of $800{\pm}50mg/kg$, was removed under the conditions of the flow rate of 50mL/min and $6mg-O_3/min$. Whereas, less than 30% of diesel was removed in the case of air injection. Analysis of the residual TPH(total petroleum hydrocarbon) and selected 8 aliphatics of diesel compounds in the inlet and the outlet of the column confirmed that diesel nonselectively reacted with ozone and then shifted to lower carbon numbered molecules. Water content also was found to be an important parameter in employing ozone to the hydrocarbon-contaminated soil.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.271-282
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• 1982

The browning development, mainly through the Maillard reaction, occurring in the dried fish meat products during storage causes reduction of the nutritional value due to the loss of the essential amino acid such as available lysine as well as off -flavor resulting in the deterioration of the food quality thus shortening the shelflife. In the work, the changes in the amount of available lysine, extractable nitrogenous compounds (nonprotein-N, amino-N, trimethylamine oxide, trimethylamine, and free lysine) and development of browning were measured to assess the relationship between the shelflife and the quality loss in dried filefish under the steady state conditions (35,45, and $55^{\circ}C;a_{w}'s$ of 0.44 0.52, 0.65 and 0.75 at each temperature) and fluctuating temperature condition of $35/55^{\circ}C$ will. alternating 7 day periods at each water activity. The results indicated that the amount of available lysine and extractable nitrogenous compounds except TMA decreased rapidly with increasing temperatures and water activities while the rate of available lysine and extractable nitrogenous compounds must be involved in the initial stage of brown pigment formation. The available lysine loss of the dried filefish products stored under the fluctuating temperature conditions was greater than that stored under its fixed mean temperature, $45^{\circ}C$. The activation energies for lysine loss obtained from the Arrhenius plot ranged 6.9 to 4.4 Kcal/mol and $Q_{10}$ values at $40^{\circ}C$ were 1.4 to 1.2. The values for browning were 15.7 to 14.4 Kcal/mol and 2.2 to 2.0 respectively. Shelf-life, defined as the time to reach 0.15 O. D./g solid or the limit of off-color deterioration by browning reaction, was extented longer than the halflife of Iysine loss, actually corresponding $75\%$ loss of available lysine. This suggested that the halflife of lysine loss might not be adequate to assess the shelf-life of the food system with high potential of protein, nonproteinous nitrogen compounds, and lipids.

• Polymer(Korea)
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• v.30 no.6
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• pp.478-485
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• 2006

Physical properties and flammability of polyhydroxyamides (PHAs) haying poly (ethylene-glycol) methyl ether (MPEG) and/or dimethylphenoxy pendants were studied by using DSC, TGA, FTIR, pyrolysis combustion flow calorimeter (PCFC), and X-ray diffractometer. The degradation temperatures of the polymers were recorded in the ranges of $276{\sim}396^{\circ}C$ in air. PCFC results showed that the heat release (HR) capacity and total heat release (total HR) values of the PHAs were increased with in-creasing molecular weight of MPEG. In case of M-PHA 2 annealed at $290^{\circ}C$, the values of HR capacity were siginificantly decreased from 253 to 42 J/gK, and 60% weight loss temperatures increased from 408 to $856^{\circ}C$ with an annealing temperature. The activation energy for the decomposition reaction of the PHAs showed in the range of $129.3{\sim}235.1kJ/mol$, which increased with increasing conversion. Tensile modulus of PHAs were decreased as increasing chain of MPEG, and showed an increase more than initial modulus after converted to PBOs.

• Journal of Soil and Groundwater Environment
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• v.16 no.1
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• pp.82-90
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• 2011

Reactive reductants of cement/Fe(II) systems in dechlorinating chlorinated hydrocarbons have not been identified. The previous studies showed that a hematite/CaO/Fe(II) system had TCE degradation characteristics similar to those of cement/Fe(II) systems with regard to degradation kinetics and that lime (CaO) plays an important role in enhancing the reactivity for TCE dechlorination. The current study shows identified the formation of gypsum ($CaSO_4$) in the hematite/CaO/$FeSO_4$ system through the XRD analysis. The amounts of the gypsum increased with increment of the initial CaO dose. However, when CaO in the hematite/CaO/$FeSO_4$ system was replaced with gypsum, TCE degradation was not observed. Ca-removed Portland cement extracts (CPCX) in combination with $FeSO_4(CPCX/FeSO_4)$ showed no TCE degradation. On the other hands, the Portland cement extracts (PCX) in the presence of $FeSO_4(PCX/FeSO_4)$ and CPCX/CaO/$FeSO_4$ systems degraded 0.2 mM TCE within 5 days, indicating that CaO also played an important role dechlorination reactions in the systems. The pseudo-first-order rate constants (k) of the CPCX/CaO/$FeSO_4$ systems were 0.20, 0.24, and 0.72 $day^{-1}$, when the CaO dosages were 25, 50 and 75 g/L, respectively. The XRD analyses showed identified the common peaks having the d-values of 3.02, 2.27, and 1.87 in the reaction systems that showed TCE degradation. However, it was not possible to clearly identify the crystalline minerals having the three peaks from the references in JCPDS cards. This study reveals that the reactive agents in the cement/Fe(II) and the hematite/Fe(II) systems are likely to be those containing CaO and Fe(II).

• 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.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.240-246
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• 2023

This study was performed to convert NO_x in atmosphere by photochemical reaction utilizing the eco-friendly solar energy. The mortar specimen coated with photocatalyst was fabricated and the photochemical conversion efficiency of NO_x was analyzed. The photocatalyst coated concrete was fabricated by first adding TiO₂ photocatalyst on the bottom of mold first and next adding cement mortar and, then, curing the concrete mortar. The grease was sprayed on the bottom of mold in advance so that the concrete can be demolded easily after curing. The conversion efficiencies of NO_x by photochemical reactions were investigated systematically by changing the process variable conditions of amount of TiO₂ coating, UV-A light intensity, total gas flow rate, relative humidity and initial NO_x concentration. It was confirmed that the photocatalyst coated concrete fabricated in this study could convert NO_x successfully for various process conditions in atmosphere. In future, we believe this research result can be utilized as basic data to design the infrastructure of building, tunnel and road for controlling efficiently the air pollutants such as NO_x, SO_x, and VOCs.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.412-419
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• 2023

Anion exchange membrane electrolysis is considered a promising next-generation hydrogen production technology that can produce low-cost, clean hydrogen. However, anion exchange membrane electrolysis technology is in its early stages of development and requires intensive research on electrodes, which are a key component of the catalyst-system interface. In this study, we optimized the pressure conditions of the hot-pressing process to manufacture cobalt oxide electrodes for the development of a high uniformity and high adhesion electrode production process for the oxygen evolution reaction. As the pressure increased, the reduction of pores within the electrode and increased densification of catalytic particles led to the formation of a uniform electrode surface. The cobalt oxide electrode optimized for pressure conditions exhibited improved catalytic activity and durability. The optimized electrode was used as the anode in an AEMWE single cell, exhibiting a current density of 1.53 A cm^-2 at a cell voltage of 1.85 V. In a durability test conducted for 100 h at a constant current density of 500 mA cm^-2, it demonstrated excellent durability with a low degradation rate of 15.9 mV kh^-1, maintaining 99% of its initial performance.

• Korean Journal of Food Science and Technology
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• v.21 no.3
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• pp.351-359
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• 1989

This study was conducted to observe the physico-chemical exchange and effect of amino-carbonyl reaction between fructose and glycine . When various buffer solutions were added to equimolar mixture of fructose and glycine at pH 6.0 and $100^{\circ}C$, the browning effect was markedly observed by Mcllvaine buffer. Among the combinations of temperature and reaction time, the deep browning effect was obtained above $100^{\circ}C$, 3hr A marked browning effect obtained above pH 7.0 but little observed below pH 7.0. The browning effect was markedly increased at high fructose concentration. It required 4.0hrs and 32.9hrs to decrease 50% of initial concentration of fructose and glycine at $100^{\circ}C$ and pH 7 but 0.9hrs and 3.8hrs at $120^{\circ}C$, pH 7.0, respectively. The rate constant of fructose and glycine at $100^{\circ}C\;and\;120^{\circ}C$ were $1.78{\times}10^{-1},\;2.11{\times}10^{-2}\;and\;7.74{\times}10^{-1},\;1.83{\times}10^{-1}$, respectively. The formation of HMF was likely to follow the first order kinetics. The addition of 0.1M sodium sulfite, 0.1M sodium bisulfite and 0.1M calcium chloride to equimolar mixture (0.05M) surpressed the reaction up to 76.8%, 76.8% and 96.4%, respectively.