• Advances in materials Research
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• v.11 no.3
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• pp.191-209
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• 2022

Very slow degradation of synthetic based polymers has created a severe environmental issue that increased awareness towards research in polymers of biodegradable property. Soy protein isolate (SPI) is a natural biopolymer used as matrix in green composites but it has limitations of low mechanical properties and high water sensitivity. To enhance mechanical properties and reduce water sensitivity of Jute-SPI composites, SPI was modified with pine rosin which is also a natural cross-linking agent. 30% glycerol on the weight basis of a matrix was used as a plasticizer. The fibre volume fraction was kept constant at 0.2 whereas the pine rosin in SPI ranged from 5% to 30% of the matrix. The effects of pine rosin on mechanical, thermal, water sensitivity and surface morphology have been characterized using various techniques. The mechanical properties and water absorbency were found to be optimum for 15% pine rosin in Jute-SPI composite. Therefore, Jute-SPI composite without pine rosin and with 15% pine rosin were chosen for investigation through characterization by Fourier transforms infrared spectroscopy (FTIR), Thermo-gravimetric analysis (TGA), X-Ray diffraction (XRD) and Scanning electron microscope (SEM). The surface morphology of the composite was influenced by pine rosin which is shown in the SEM image. TGA measurement showed that the thermal properties improved due to the addition of pine rosin. Antimicrobial test showed antimicrobial property in the composite occurring 15% pine rosin. The research paper concludes that the modification of SPI resin with an optimum percentage of pine rosin enhanced mechanical, thermal as well as water-resistant properties of jute fibre reinforced composites.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.575-580
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• 2023

An electrode was prepared by dip-coating NiFe₂O₄ powder on stainless steel (SUS) support for the application in the alkaline water electrolysis. The prepared electrode was analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), and was evaluated for the voltage properties with the change of current density in oxygen evolution reaction (OER) and hydrgen evolution reaction (HER) using 1, 3 and 7 M KOH solution. From the SEM and EDXS analysis, it was confirmed that the prepared electrode had NiFe₂O₄ on the SUS support. In OER and HER, the voltage in the 7 M KOH solution had a value of 1.35 and -1.90 V at 0.2 and -0.2 A/cm² of the current density, respectively. It was considered that the prepared electrode could be use as an electrode in the alkaline water electrolysis from the experimental results.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.740-744
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• 1994

This study was undertaken to prove the suppressing effect of green tea on the intestinal absorption of heavy metals using in vitro membrane filtration system. From drinking water contaminated with 10 and 100 times level of water quality standard for heavy metals, the removal ratio of lead (Pb) was $50{\sim}70%$ by green and black teas, and $30{\sim}40%$ by roasted barley tea. The removal ratio of cadmium (Cd) was $30{\sim}40%$ by green tea and black teas, and $10{\sim}20%$ by roasted barley tea. The removal effect from drinking water contaminated with both lead and cadmium was lower than that from water contaminated singly with lead or cadmium. It appears that tea components and filter membrane compete toward the adsorption of two heavy metals. Among the extraction conditions of raw tea materials at $70^{\circ}C$, 2 minutes and $95^{\circ}C$ , 10 minutes, the removal ratios of heavy metals were similar.

• 한국해양학회지
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• v.20 no.3
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• pp.30-36
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• 1985

Water quality of seawater samples from ten stations was measured and analyzed to study the causes and the characteristics of the yellowish-green-colored zone in the Nakdong Estuary in February, May, August and October, 1984. The color of the yellowish-green-colored zone was equivalent to the grade 7 according to the Forel water-color meter and was observable throughout the year. The characteristics of the zone were low in transparency and high in the concentration of suspended solids, and about 52% of the suspended solids consisted of volatile substances. The chlorophyll a contents ranged from 0.4mg/$m^3$ to 51.0mg/$m^3$ and dissolved oxygen was in a state of supersaturation within the yellowish-green-colored zone. Nutrient concentrations were higher within the colored zone than the outside. Positive correlation was observed between tne concentrations of nutrients and chlorophyll a. Our results showed that the signficant portion of suspended solids sampled from the yellowish-green-colored zone consisted of phytoplanktons of which bloom was possibly induced by inflow of the nutrient-rich Nakdong River water.

• Journal of Food Hygiene and Safety
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• v.14 no.3
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• pp.238-243
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• 1999

The storage stability from powdered anchovy and its preparation cooperated with three additives (water extract from green tea and boxthorn and BHT) was studied. The results are as follows: 1. When the additives were added to powdered anchovy, the storage stability was improved. The antioxidative activities of water extract from green tea and boxthorn were considerably higher than BHT. The antioxidative activities were decreased in the rank order boxthorn > green tea> BHT. 2. The more the concentration of natural additives was increased, the more the storage stability was improved. The rank order was$60^{\circ}>40^{\circ}>20^{\circ}$ Bx. 3. The A V and POV of powdered anchovy were increased in the rank order to 6 < 12 < 18 < 24 < 30 months by storage term. 4. This clearly suggested that water extract at $20^{\circ}>$ Bx level from boxthorn was possible utilization as a new natural antioxidant for storage stability of powdered anchovy.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.531-538
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• 2012

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and $TiO_2$ for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the $TiO_2$ is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of $TiO_2$.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.163-174
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• 2021

Heatwaves are one of the most common phenomena originating from changes in the urban thermal environment. They are caused mainly by the evapotranspiration decrease of surface impermeable areas from increases in temperature and reflected heat, leading to a dry urban environment that can deteriorate aspects of everyday life. This study aimed to calculate daily maximum ground surface temperature affecting heatwaves, to quantify the effects of urban thermal environment control through water cycle restoration while validating its feasibility. The maximum surface temperature regression equation according to the impermeable area ratios of urban land cover types was derived. The estimated values from daily maximum ground surface temperature regression equation were compared with actual measured values to validate the calculation method's feasibility. The land cover classification and derivation of specific parameters were conducted by classifying land cover into buildings, roads, rivers, and lands. Detailed parameters were classified by the river area ratio, land impermeable area ratio, and green area ratio of each land-cover type, with the exception of the rivers, to derive the maximum surface temperature regression equation of each land cover type. The regression equation feasibility assessment showed that the estimated maximum surface temperature values were within the level of significance. The maximum surface temperature decreased by 0.0450℃ when the green area ratio increased by 1% and increased by 0.0321℃ when the impermeable area ratio increased by 1%. It was determined that the surface reduction effect through increases in the green area ratio was 29% higher than the increasing effect of surface temperature due to the impermeable land ratio.

• New & Renewable Energy
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• v.6 no.2
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• pp.27-32
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• 2010

Low Calorific Gas Turbine (LCGT) has been developed as a next generation power system using landfill gas (LFG) and biogas made from various organic wastes, food Waste, waste water and Livestock biogas. Low calorific fuel purification by pretreatment system and carbon dioxide fixation by green house system are very important design target for the optimum applications of LCGT. Main troubles of Low Calorific Gas Turbine system was derived from the impurities such as hydro sulfide, siloxane, water contained in biogas. Even if the quality of the bio fuel is not better than natural gas, LCGT may take low quality gas fuel and environmental friendly power system. The mechanical characterisitics of LCGT system is a high energy efficiency (>70%), wide range of output power (30 kW - 30 MW class) and very clean emission from power system (low NOx). A green house has been designed for four different carbon dioxide concentration from ambient air to 2000 ppm by utilizing the exhaust gas and hot water from LCGT system. LCGT is expected to contribute achieving the target of Renewable Portfolio Standards (RPS).

• Journal of Powder Materials
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• v.24 no.2
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• pp.147-152
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• 2017

Spherical-type zirconia granules are successfully fabricated by a spray-drying process using a water solvent slurry, and the change in the green density of the granule powder compacts is examined according to the organic polymers used. Two organic binders, polyvinyl alcohol (PVA) and 2-hydroxyethyl methacrylate (HEMA), which are dissolved in a water solvent and have different degrees of polymerization, are applied to the slurry with a plasticizer (polyethylene glycol). The granules employing a binder with a higher degree of polymerization (PVA) are not broken under a uniaxial press; consequently, they exhibit a poor green density of $2.4g/cm^3$. In contrast, the granule powder compacts employing a binder with a lower degree of polymerization (HEMA) show a higher density of $2.6g/cm^3$ with an increase in plasticizer content. The packing behavior of the granule powders for each organic polymer system is studied by examining the microstructure of the fracture surface at different applied pressures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.1
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• pp.100-106
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• 1999

Use of chemical preservative for controlling harmful microorganisms in food products has been debated due to public concerns about food quality because of perceived toxic and carcinogenic potential. Thus, use of non toxic natural antimicrobial agents has become essential. This study was investigated to determine the antimicrobial activity of water or ethanol extract of commercially available tea, and of solvent fractionated ethanol extracts obtained from steamed green tea. Both of water and ethanol extracts of green tea(steamed or roasted), oolong tea and black tea exhibited strong antimicrobial activity against gram positive and negative bacteria, but not effective against yeast and mold. Also, antimicrobial activity of ethanol extract of 4 different kinds of tea was stronger than that of water extract. Among 4 different tea, ethanol extract of steamed green tea was further fractionated. One thousand g/disk buthanol extract had the strongest antimicrobial activity against bacteria and mold. The concentration of the antimicrobial activity of buthanol extract in tested microorganisms ranged from 125~1000 g/disk except for Rhizopus javanicus. Antimicrobial activity of buthanol extract of steamed green tea was not destroyed by heating at 100oC for 60 min and at 121oC for 15 min, which is very stable over heat treatment. The inhibitory effect of the buthanol extract on the growth of Listeria monocytogenes and Staphylococcus aureus was investigated. Growth of both strains was started in the presence of 250 and 500 g/ml after 12 and 24 hour respectively, whereas complete inactivation of both strains was occurred in the presence of 1000 g/ml.