• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.145-151
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• 2014

The antibacterial effect of Quercus salicina Blume extract was investigated and then the stability of a cream containing it best performing fraction, the ethyl acetate fraction, was evaluated. The antibacterial effect was evaluated on the skin microorganisms Staphylococcus aureus, Bacillus subtilis, Propionibacterium acnes, Escherichia coli, and Pseudomonas aeruginosa. Among the Q. salicina Blume extract fractions, the ethyl acetate fraction demonstrated the lowest minimum inhibitory concentration against S. aureus (1,200 ${\mu}g/ml$), B. subtilis (2,500 ${\mu}g/ml$), P. acnes (1,200 ${\mu}g/ml$) and P. aeruginosa (312 ${\mu}g/ml$). Therefore, a cream containing 0.25% ethyl acetate fraction of Q. salicina Blume extract was prepared and evaluated for stability. The pH, viscosity, and absorbance of the cream were measured under various temperatures (4, 20, 37, $45^{\circ}C$) and sun light during a 12 week period. The changes in viscosity, absorbance and pH of the cream did not change significantly during the term of the experiment when compared with a placebo cream. In addition, any change in color or odor of the cream was not observed during the 12 weeks. These results indicate that the ethyl acetate fraction of Q. salicina Blume extract has a high antibacterial effect and is stable as a cream. There is therefore some potential for its use in cosmetic materials.

• Polymer(Korea)
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• v.26 no.5
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• pp.644-652
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• 2002

This study aims at developing the conductive pastes consisting of room temperature vulcanizing (RTV) silicone and metal powder as matrix and filler, respectively. Electrical and rheological properties of metal - filled polymer composites are in general strongly affected by particle shape, side and dispersion state of the filler. In highly filled systems, particles tend to form very complex agglomerated structure which is easily changed when subjected to shear deformation. And the breakdown of agglomerated particles due to shear usually leads to the change of electrical conductivity of the composite. In this study, the effect of particle size and dispersion state of filler on the electrical conductivity of the composites are investigated to offer the selection criteria of conductive filler by measuring the rheological properties of uncured composites and the electrical conductivity of the cured composites. It was found that the type of metal filler systematically affected the rheological property, the susceptibility to shear and the degree of change of electrical conductivity of the composite. The effect of shear on the properties is more conspicuous in the composites containing large particle, indicating that both rheological and electrical properties can be improved by controlling the dispersion state at a given filler content.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.81-86
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• 1996

The physical properties of epoxy molding compound (EMC) according to the change of softening point of epoxy resin have been investigated in order to study the relationship between the properties of o-cresol novolac epoxy resin, which is main component of EMC for semiconductor encapsulation, and EMC. The softening points of used epoxy resin are 65.1 $^{\circ}C$, 72.2 $^{\circ}C$, and 83.0 $^{\circ}C$, respectively. The flexural strength and flexural modulus as mechanical properties were measured, and thermal expansion coefficient, thermal conductivity and glass transition temperature (Tg) as thermal properties, and spiral flow as moldability have been investigated to see the change of physical properties of EMC. The flexural modulus, thermal expansion coefficients in the glass state (${\alpha}_1$), and thermal conductivity of EMC were found to be keep constant value irrespective of the change of softening point, but Tg increased with softening point of epoxy resin, and the spiral flow decreased with that. It can be considered that these phenomena are due to the increase of crosslinking density of EMC according to the increase of softening point. The transition points were found out in the thermal expansion coefficient data in the rubbery state (${\alpha}_2$) and the flexural strength data. These can show the decrease of filler dispersion according to increase of epoxy resin viscosity.

• Resources Recycling
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• v.29 no.1
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• pp.25-34
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• 2020

Electrochemical Quartz Crystal microbalance is a tool that is capable of measuring nanogram-scale mass change on electrode surface. When applying alternating voltage to the quartz crystal with metal electrode formed on both sides, a resonant frequency by inverse piezoelectric effect depends on its thickness. The resonant frequency changes sensitively by mass change on its electrode surface; frequency increase with metal dissolution and decrease with metal deposition on the electrode surface. The relationship between resonant frequency and mass change is shown by Sauerbrey equation so that the mass change during metal dissolution can be measured in real time. Especially, it is effective in the case of reaction mechanism and rate studies accompanied by precipitation, volatilization, compound formation, etc. resulting in difficulties on ex-situ AA or ICP analysis. However, it should be carefully considered during EQCM experiments that temperature, viscosity, and hydraulic pressure of solution, and stress and surface roughness can affect on the resonant frequency. Application of EQCM was shown as a case study on leaching of platinum using aqueous chlorine for obtaining activation energy. A platinum electrode of quartz crystal oscillator with 1000 Å thickness exposed to solution was used as leaching sample. Electrogenerated chlorine as oxidant was purged and its concentration was controlled in hydrochloric acid solution. From the experimental results, platinum dissolution by chlorine is chemical reaction control with activation energy of 83.5 kJ/mol.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.463-473
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• 2017

Bentonite swells when it comes into contact with water and makes it a viscous fluid. Thus it is widely used in civil engineering works for waterproofing. Utilizing the properties of bentonite, the slurry shield TBM supports excavated face with pressurized slurry as well as transporting excavated muck. When bentonite is in contact with seawater, due to the change of double layer thickness, its expandability and viscosity are lowered. This may cause problems for excavation stability and muck discharge due to the increase of sea water inflow when Slurry TBM is used under sea water conditions. In this study, the change of slurry condition caused by the inflow of sea water during tunnel excavation with Slurry TBM was investigated and a slurry management guideline was proposed. For this purpose, a laboratory test was carried out based on the slurry management criterions applied in the field, and a method applicable to the field where sea water is affected has been proposed.

• Journal of Life Science
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• v.11 no.2
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• pp.144-152
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• 2001

In order to improve functionality of kochujang which is one of the traditional foods of Korea, sea tangle powder(2, 4, 6 and 8% sea tangle powder on the glutinous rice weight basis) was added to the raw material of kochujang and then investigated the change of physiochemical properties with control kochujang during the fermentation at 3$0^{\circ}C$ for 120 days. During 120 days fermentation, moisture and crude protein contents were gradually decreased with fermentation time, whereas crude fat content NaCl were slightly increased with fermentation time. The contents of reducing sugar of sea tangle kochujang was rapidly increased until 60 days of fermentation after that it was increased slightly up to 90 days of fermentation to the highest value and then reduced slightly or not changed approximately until 120 days. pH was reduced up to 60 days of fermentation after that it remained 4.63~4.91 in 90~120 days. Acidity was increased with fermentation time, and it was the highest value of 11.5~12.4$m\ell$ in 120 days of fermentation. Viscosity was increased with increased with fermentation time. Especially a case of additional sample of 8% sea tangle powder was highly increased until 60 days. A case of color difference value, in initial time of preparation of kochujang was distinct difference of value for additional samples respectively but as the fermentation progressed, among the samples not found consistent change of color difference value. L value was gradually decreased during fermentation. A value was decreased up to 30 days of fermentation and it was increased again totally at 60 days of fermentation. B value was decreased totally at initial time of fermentation and a case of control was increased again at 90 days of fermentation, the other samples increased again 60 days earlier than 30 days.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.299-308
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• 1976

Cerium (Ⅳ) ion-initiated graft copolymerizations of acrylamide and of acrylonitirile to silk fibroins were investigated. When acrylamide was used, the change in ceric ammonium nitrate concentration exhibited a maximum in degree of grafting at 0.01 M. Also observed was that the change in acetic acid content in reaction media gave a maximum in degree of grafting at 7% acetic acid in water. Degree of grafting was increased generally with increase in acrylamide concentration reaction time and reaction temperature. When acrylonitrile monomer was used for grafting,different results were obtained. Addition of nitric acid was more effective in enhancing the degree of grafting than the addition of acetic acid.Generally the grafting of acrylonitrile to silk fibroins was less efficient than the grafting of acrylamide. The portion of grafted silk fibroins insoluble in Lowe's reagent exhibited the IR absorption bands characteristics to both vinyl polymers and silk fibroins, indicating the grafting of vinyl monomers to silk fibroins. To examine the molecular weight of graft vinyl polymer, a sample of grafted silk was hydrolyzed by 10% sodium hydroxide. Viscosity measurements indicated that the molecular weight of the graft polymer was in the range of 105.

• The Korean Journal of Food And Nutrition
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• v.31 no.6
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• pp.926-932
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• 2018

This research was conducted to investigate the changes in quality characteristics of cheonggukjang fermented with the addition of hazelnut (10, 20, 30 and 40%) including; water content, pH, hydrophilic and lipophilic substances, color, viscosity and angiotensin converting enzyme inhibition activity. There was no significant change in pH with the addition of hazelnut. The water content significantly decreased with the addition of hazelnut. Hazelnut was also found to brighten the color of cheonggukjang. L-value and b-value increased with the addition of cheonggjuang. There was an insignificant change in the a-value. There was a slight decrease in the content of hydrophilic with addition of hazelnuts. Where there was more than 20% addition of hazelnut to soybean, the viscous substance content in cheonggukjang decreased significantly. Angiotensin converting enzyme inhibitory activity increased proportionally to the amount of hazelnut added. It was identified that the addition of 40% of hazelnut made its angiotensin converting enzyme inhibitory activity 10% point higher than that of control. These results suggests that the addition of hazelnut makes it possible to produce cheongkukjang of excellent angiotensin converting enzyme inhibitory activity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.53-61
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• 2021

This paper is a preliminary study for the development of a drone for inspection inside a boiler in a thermal power plant, which is a high-temperature environment, and validated whether the drone can fly normally through a high-temperature environment simulation using AirSim. In a high-temperature flight environment, the aerodynamic characteristics of the air density and viscosity are different from room temperature, and the flight performance of the drone is also changed accordingly. Therefore, in order to confirm the change of the aerodynamic characteristics of the propeller according to the temperature change, the propeller analysis and thrust test through JBLADE, and the operation characteristics prediction through the electric propulsion system performance prediction model were performed. In addition, the analysis and performance prediction results were applied to AirSim for simulation, and the aircraft redesigned through the analysis of the results. As a result of the redesign, it was confirmed that about 65% of the maximum power used before the redesign was reduced to 52% to obtain the necessary thrust when hovering in an environment of 80℃.

• Journal of Physiology & Pathology in Korean Medicine
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• v.34 no.4
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• pp.191-200
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• 2020

The purpose of this pilot study was to examine the effect of tongue color change due to food ingestion on tongue diagnosis by both Korean Medicine doctors and digital tongue diagnosis system. In order to obtain objective and quantitative data, we used digital camera to collect the data. Prior to our investigation, we conducted a brief survey of 26 Korean Medicine doctors and found out that tongue diagnosis is frequently used and food-stained tongue could be commonly observed in clinics. Depending on their color, viscosity, and amount of intake, various foods caused stains with different colors and thicknesses. Also, duration and amount of food stain on tongue were different from person to person. Since coffee-stained tongue was the most frequently observed one in clinics according to the survey, we used coffee to evaluate the effect of food-stained tongue on tongue diagnosis. Korean Medicine doctors tended to interpret coffee-stained tongue as having yellow tongue coat but their judgement on tongue body color did not differ in spite of the coffee stains. Meanwhile, tongue diagnosis system algorithm tended to judge coffee-stained tongue as having normal but yellowish tongue coat and reddish tongue body. Altogether, food color on tongue can influence tongue diagnosis outcomes. Further research is needed in order to develop more efficient tongue diagnosis algorithm and digital medical service system.