• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.75-87
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• 2007

Groundwater recharge rates were estimated and compared in a headwater catchment at the Gwangneung Supersite using three different methods: water-table fluctuation (WTF), mass balance, and hydrograph separation techniques. Data were obtained during the rainy season from June to September 2005. Two different WTF methods estimated the groundwater recharge rate as 25.9% and 23.6%. The mass balance calculation of chloride ions indicated recharge rates of 13.4% on average. Baseflow separation using chloride ion as a tracer from six storm hydrographs produced a 14.0% net baseflow rate on average. Because of the implicit assumption of a long-term steady state without storage change, recharge rates calculated by mass balance and hydrograph separation were smaller than those done with WTF methods, which include the amount of increased storage due to the water-level rise. Subsequently, the WTF method is superior to others in the estimation of groundwater recharge rate to comprehend the dynamic characteristics of the hydrologic cycle.

• Korean Journal of Food Science and Technology
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• v.33 no.2
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• pp.209-215
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• 2001

This study was conducted to examine the effects of 2,2,6,6-tetramethyl-1-piperidine oxoammonium ion(TEMPO) and sodium bromide(NaBr) for the selective oxidation on primary alcohol groups of rice starch molecules in rice flour and to use oxidized rice flour in Julpyun to extend its shelf life. Reaction time decreased with higher levels of TEMPO and NaBr. Yield and selectivity decreased with increased NaBr levels. TEMPO increased yield until certain levels, but decreased thereafter. The levels of TEMPO and NaBr for the preparation of oxidized rice flour were determined as 0.9 and 44 mM/100 mM anhydroglucose unit, respectively. Water and oil binding capacities, and viscosity increased significantly by the oxidation of rice flour. The partial replacement of rice flour with oxidized rice flour increased peak viscosity and decreased setback. Oxidized rice flour with the increased amount of water showed positive effect on the textural properties of Julpyun during storage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.17 no.3
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• pp.226-232
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• 1988

Non-enzymatic browning is a carbohydrate dehydration reaction, accelerated thorough the interaction of amino compounds. Reaction depends on several factors including temperature, reactant concentration, pH, water activity and specific ion concentrations, and result in progressive development of brown pigments in the affected food systems. The present study was designed to utilize a kinetic approach to analyze the effect of temperature and water activity on the browning development in green ten. The green tea was controlled at aw of 0.33, 0.44, 0.52 and 0.65 using saturated salt solutions and then stored at 35,45 and $55^{\circ}C$. Author portion of the sample of which the water activities were controlled in the same manner was stored at 35 and $55^{\circ}C$ alternately with 7 days interval. Simplified kinetic models were used to obtain the various kinetic parameters for browning development in green tea subjected to accelerated shelf-life tests(ASLT). The reaction of browning development was zero order. The activation energies calculated from Arrhenius plot ranged $1.5{\sim}2.4kcal/mole$ and $Q_{10}$ values were between 1.07 and 1.12. These kinetic parameters were then used to predict browning development under the nonsteady storage. Assessed from the parameters the shelf-lives at $25^{\circ}C$, the time to reach 1.02 O.D./g solid at which severe brown color change could be detectable, ranged 57 to 113 days and showed decrease with increase in aw. The predicted shelf-lives at different water activities were a little higher than actual values.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.162-168
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• 2013

$Li_2MnO_3-LiMO_2$(M=Ni, Co, Mn) nano-composite is a promising cathode material for xEV application due to its high theoretic capacity. However high voltage operating system of $Li_2MnO_3-LiMO_2$(M=Ni, Co, Mn) has worked as a hurdle in its application because of the inherent demerits, such as cycle life degradation and gas evolution. In order to enhance cell performance of $Li_2MnO_3-LiMO_2$(M=Ni, Co, Mn)/graphite cell, we examined electrolyte mainly composed of FEC, fluroalkyl ether and $LiPF_6$ (F-based EL). F-based EL showed much better discharging retention ratio than 1.3 M $LiPF_6$ EC/EMC/DMC (3/4/3, v/v/v) (STD). Furthermore gas evolution, especially CO and $CO_2$ during $60^{\circ}C$ storage for 30 days was dramatically reduced owing to thermal stable SEI formation effect of F-based EL.

• Journal of Chest Surgery
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• v.30 no.6
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• pp.553-558
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• 1997

Arterial allografts have known advantages over prosthetic vascular conduit for treatment of heart valvular disease, congenital heart disease and aortic disease. Cell viability may play a role in determining the longterm outcome of allografts. Endothelial cell is one important part in determining the allograft viability. To evaluate the viability of endothelial cells using current allograft preservation technique, porcine heart valve leaflets and arterial wall were subjected to collagenase digestion. Single endothelial cell suspension was labeled with GSA-PITC(Griffonia simplicifolia agglutininfluorescein isothiocyan te), a vascular, endothelial cell specific marker. The cell suspension was washed and incubated with Pl(Propidium iodide), which does not bind with viable cells, Endothelial cell viability was evaluated by calculating the percentage of GSA-FITC(+) and Pl(-) group using flowcytometric analysis. Allografts were treated with $4^{\circ}C$ antibiotic solo!ion for 24 hours for sterilization. After this, half of allografts were stored in $4^{\circ}C$ RPMI 1640 with HEPES buffer culture medium with 10% fetal bovine serum for 1 to 14 days(Group I). Another half of allografts were cryopreserved with a currently used technique (Group II). During the procurement and sterilization of arterial allografts, 22.8% and 24.4% of endothelial cell viability declined, respectively. In Group I, 11.9% of endothelial cell viability declined further steadily during 14 days of storage. In Group II, 13.7% of endothelial cell viability declined. These results show that largest loss of endothelial cell viability occurs during the nitial process. After 14 days of arterial allograft storage under $4^{\circ}C$ nutrient medium or cryopreservation, about 40% of endothelial cell viability is maintained. There were no differences between the endothelial cell viability from aortic valve leaflet, pulmonic valve leaflets, aortic wall and pulmonic wall.

• Polymer(Korea)
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• v.32 no.4
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• pp.347-352
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• 2008

High impact polystyrene (HIPS) nanocomposites with organically modified montmorillonite (organoclay) via in situ polymerization were synthesized, and the effects of organoclay incorporation on material properties were investigated. Organoclays having a reactive group, vinylbenzyltrimethyl clay (VBC) and octadecylvinylbenzyldimethyl clay (ODVC), were prepared by the ion-exchange reactions of sodium montmorillonite with vinylbenzyltrimethyl ammonium chloride (VBTMAC) and octadecylvinylbenzyldimethyl ammonium bromide (ODVBDAB), respectively, and a commercial organoclay, $Cloisite^{(R)}$ 10A(C10A), was used for comparison. It was confirmed that the X-ray diffraction (XRD) peak of the nanocomposites prepared by ODVC disappeared, which indicates the exfoliation of silicate layers. On the contrary, the XRD peak of the nanocomposites prepared by C10A shifted to lower angle, indicative of the intercalation of polymer chains into silicate layers. Rheological properties such as storage modulus and complex viscosity increased with increasing organoclay.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• Journal of Ecology and Environment
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• v.37 no.3
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• pp.131-137
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• 2014

To investigate the solute pattern of salt marsh plants in Suncheon Bay in Korea, plants and soil samples were collected at three sites from July to September 2011. The soil pH around the investigated species was weakly alkaline, 6.9-8.1. The total ion and Cl- content of site 1 gradually increased, while those of site 2 and site 3 were lowest in August and highest in September. The exchangeable $Ca^{2+}$, $Mg^{2+}$ and $K^+$ in the soil were relatively constant during the study period, but the soil exchangeable $Na^+$ content was variable. Carex scabrifolia and Phragmites communis had constant leaf water content and very high concentrations of soluble carbohydrates during the study period. However, Suaeda malacosperma and S. japonica had high leaf water content and constant very low soluble carbohydrate concentrations. Carex scabrifolia accumulated similar amounts of $Na^+$ and $K^+$ ions in its leaves. Phragmites communis contained a high concentration of $K^+$ ions. Suada japonica and S. malacosperma had more $Na^+$ and $Cl^-$ ions than $K^+$ ions in their leaves. Suaeda japonica had higher levels of glycine betaine in its leaves under saline conditions than C. scabrifolia and P. communis. Consequently, the physiological characteristics of salt marsh chenopodiaceous plants (S. japonica and S. malacosperma) were the high storage capacity for inorganic ions (especially alkali cations and chloride) and accumulation of glycine betaine, but monocotyledonous plant species (C. scabrifolia and P. communis) showed high $K^+$concentrations, efficient regulation of ionic uptake, and accumulation of soluble carbohydrates. These characteristics might enable salt marsh plants to grow in saline habitats.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.171-180
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• 2013

Metal organic frameworks (MOFs) are a class of crystalline organic-inorganic hybrid compounds formed by coordination of metal clusters or ions with organic linkers. MOFs have recently attracted intense research interest due to their permanent porous structures, large surface areas and pore volume, high-dispersed metal species, and potential applications in gas adsorption, separation, and catalysis. $CO_2$ adsorption in MOFs has been investigated in two areas of $CO_2$ storage at high pressures and $CO_2$ adsorption at atmospheric pressure conditions. In this short review, $CO_2$ adsorption/separation results using MOFs conducted in our laboratory was explained in terms of four contributing effects; (1) coordinatively unsaturated open metal sites, (2) functionalization, (3) interpenetration/catenation, and (4) ion-exchange. Zeolitic imidazolate frameworks (ZIFs) and covalent organic frameworks (COFs) were also considered as a candidate material.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.305-311
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• 2010

The industrial by-product market has increased at a geometric rate worldwide with the rapid economic growth. At present time, conventional disposal methods of industrial by-products in Korea including landfill, incineration and storage already have reached their limits. In this study, the industrial by-products such as fly ash and silicafume were used as mineral admixtures, which are commonly added to concrete mix to inhance the economic efficiency, long-term strength and durability of concrete, to determine the optimized mix proportion of high performance shotcrete. Through the series of tests (compressive strength test, accelerated chloride ion penetration test, measurement of chloride diffusion coefficient). The results of the study showed that the proposed mix proportions satisfied the requirements of domestic as well as international guidelines for shotcrete, with a higher durability than the existing shotcrete.