• KSBB Journal
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• v.26 no.1
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• pp.57-61
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• 2011

The principal objective of this study was to determine the optimal conditions for the production of biosurfactant by the indigenous bacterium, Pseudoalteromonas sp. HK-3, originating from oil-spilled areas. The relationship between total biosurfactant production and the factors affecting biosurfactant production were evaluated by statistical analysis using SPSS software. The effects of various supplemental carbon sources (e.g., glucose, dextrose, mannitol, citrate, acetate) on the maximal production of biosurfactant by the test culture of Pseudoalteromonas sp. HK-3 was then evaluated. As a result, mannitol was found in this study to be the best supplemental carbon source for the production of biosurfactant. A spot inoculation of crude cultural liquid containing the HK-3 cells generated the largest clear zone, whereas only small clear zones appeared around the spots inoculated with either supernatant only or cell pellets following centrifugation. Our results demonstrated that the HK-3 test culture supplemented with 2% mannitol at an initial pH of 6 generated the maximal amount of biosurfactant within 72 h of incubation.

• Journal of Technologic Dentistry
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• v.29 no.1
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• pp.49-57
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• 2007

This study was to add crushed frit with different grain sizes to 3Y-TZP so that it could determine the mechanical properties depending on sintering temperature. In this study, 3 types specimens were prepared in powder with respective additions of 20wt.% frit, which was sized through 24-, 48- and 72-hour ball milling with zirconia. Then, sintered pellets were tested in experiments under the temperature variations for different compositions. As a result, this study came to the following findings: 1. It was found that the higher sintering temperature and the longer ball milling time of frit led to the higher sintered density. 2. Bending strength tended to increase with higher sintering temperature and longer ball milling time of frit. 3. Hardness tended to increase with higher sintering temperature and longer ball milling time of frit. 4. However, it was found that fracture toughness didn't vary significantly depending on sintering temperature. From these findings, it was concluded that the smaller frit grain size and the narrower particle size distribution of frit lead to the better mechanical properties.

• KSBB Journal
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• v.18 no.2
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• pp.127-132
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• 2003

The effect of 4 kinds of alcohols was investigated on the production of bacterial cellulose (BC) by Gluconacetobacter hansenii PJK. The addition of alcohols and acetic acid to medium caused the pellets of bacterial cellulose to aggregate into a lump, which could be easily separated from the culture medium. The growth rate of cells and the production yield of BC increased in the medium containing ethanol. Other alcohols in the medium decreased cell growth and the cellulose production rate, because of their toxic effects. The addition of ethanol depressed the conversion of a $\textrm{Cel}^{+}$ cell to a $\textrm{Cel}^{-}$ mutant in shaking culture. Cells subcultured three in a medium containing ethanol produced BC without any loss of BC production yield.

• Electrical & Electronic Materials
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• v.10 no.3
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• pp.217-225
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• 1997

In this study, the PVDF organic thin film was fabricated by the physical vapor deposition method to be dry-process. The distance of heat source and substrate was 5[cm] and the temperature of substrate was 30[.deg. C], when the pressure had reached 2.0 x 10$^{-5}$ [Torr], the temperature of heat source was reached to 285[.deg. C] to heat at 6-8[.deg. C/min] rate, the shutter was opened and deposition was started. TG-DTA(Thermogravimetric-Differential Thermal Analysis) spectrum of PVDF pellets showed that endothermic peak arose at 170[.deg. C] and exothermic peak at 524[.deg. C], but that of thin PVDF film showed that endothermic peak arose at 145[.deg. C] and exothermic peak at 443[.deg C]. The current density was increased linearly with increasing voltage but increased nonlinearly with higher electric field than 250[kV/cm] and activation energy was about 0.667[eV] at the temperature of 30-90[.deg. C].

• Journal of Environmental Science International
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• v.29 no.2
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• pp.155-166
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• 2020

This study was conducted to analyze the current situation of the logging operation system and to suggest an effective policy plan to secure important raw materials for the use of forest biomass. The dissemination of forestry mechanization and the establishment of the logging operation are important tasks to establish a system and reduce costs of timber production by increasing the use of forest biomass; this includes increasing the supply of timber for domestic products and increasing the production of wood chips and wood pellets. In particular, the efficiency of steep-slopes catenary system machinery for yarding such as tower-yarder and swing-yarder should be urgently supplied to cope with forest production and supply of forest biomass energy resources. In addition, it is necessary to continuously promote the dissemination of high-performance forestry machinery as is being done in Japan. At the same time, instead of distributing or retaining the spread of forestry machinery to the state and local governments, it is necessary to distribute timber production work centered on forest cooperatives or private timber producers to be carried out by wood producers, forest cooperatives and individuals.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.815-824
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• 2015

In this study, we conducted the approximate multi-objective optimization of gap sizes of pressurized-water reactor (PWR) annular fuels. To determine the contacting tendency of the inner-outer gaps between the annular fuel pellets and cladding, thermoelastic-plastic-creep (TEPC)analysis of PWR annular fuels was performed, using in-house FE code. For the efficient heat transfer at certain levels of stress, we investigated the tensile, compressive hoop stress and temperature, and optimized the gap sizes using the non-dominant sorting genetic algorithm (NSGA-II). For this, response surface models of objective and constraint functions were generated, using central composite (CCD) and D-optimal design. The accuracy of approximate models was evaluated through $R^2$ value. The obtained optimal solutions by NSGA-II were verified through the TEPC analysis, and we compared the obtained optimum solutions and generated errors from the CCD and D-optimal design. We observed that optimum solutions differ, according to design of experiments (DOE) method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.407-412
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• 2014

A new apparatus for seawater desalination, based on the principle of gas hydrates, is suggested. The equipment continuously produces and pelletizes gas hydrates by a squeezing operation in a dual cylinder unit, which is able to extract pure hydrate pellets from the seawater-containing reactor. Desalination efficiency for each dissolved ion from seawater samples was tested by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC) analysis. This study demonstrates that the suggested method and the stated apparatus may solve the difficulty of separating hydrate crystals from concentrated brine solutions, and therefore may be applied to improve the efficiency of existing desalination processes.

• Natural Product Sciences
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• v.7 no.3
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• pp.76-82
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• 2001

The pharmacological activities of the acetonitrile (MeCN), hexane extracts and isolated pure terpenoidal compound Lupeol from the leaves of Teclea nobilis, Delile (TN), on inflammation induced by carrageenan an implantation of cotton pellets in rats; the nociceptive response using writhing and tail flick tests and the antipyretic activity in yeast-induced fever were examined in mice. Oral administration of TN extracts at doses of 150 and 300 mg/ks and lupeol 5 and 10 mg/kg showed a significant anti-inflammatory activity in rats. The extracts of TN and lupeol significantly decreased the number of contractions and stretchings induced by acetic acid and heat-induced pain in mice. The antipyretic effect of extracts and lupeol was also found to be significant. The behavioral observation of animals showed that the hexane extract and lupeol caused CNS depressant activity and did not produce any toxic or lethal effects in animals at various dose levels. The results suggest that the Teclea nobilis extracts and lupeol possesses anti-inflammatory, analgesic and antipyretic activities.

• Journal of the Korean Ceramic Society
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• v.27 no.4
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• pp.487-494
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• 1990

$Al_2O_3$-20w/o $ZrO_2$ composite powders were prepared by the emulsion-coprecipitation method and the effects of preparative conditions on powder characteristics were investigated. In the preparation of $Al_2O_3$-$ZrO_2$ composite powders, toluene was used instead of kerosene as the oil phase in emulsions. After coprecipitation, the emulsion was easily broken into a single liquid phase by adding methanol, and then precipitates could be effectively collected by filteration. The fact that all $ZrO_2$ phases present at room temperature in composite powders calcined at $1100^{\circ}C$ after washed by methanol had a tetragonal structure confirmed that methanol-washing enhanced the dispersibility of fine $ZrO_2$ particles in $Al_2O_3$ matrix. $Al_2O_3$-$ZrO_2$ composite powders were spherical particles of 0.2${\mu}{\textrm}{m}$ diameter. Pellets sintered at $1650^{\circ}C$ for 2hrs showed the relative theoretical density of 97.3% and the fracture toughness of 5.01MN/$m^{3/2}$.

• Composites Research
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• v.27 no.3
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• pp.83-89
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• 2014

The purpose of this study is to improve the strength and thermal conductivity of polybutylene terephthalate (PBT) by embedding various additives. Specimens were prepared using PBT pellets embedded with glass fibers (GF) and boron nitride (BN) powders. The test results showed that tensile strength decreased, and thermal conductivity increased with increasing BN contents. with thermal shock cycles conducted, unfilled PBT showed a considerable decrease in failure strain and strength, whereas strength and thermal conductivity of glass fiber and BN particle-embedded PBT had little differeces. With increasing BN, the thermal conductivity of PBT composites was highly improved.