• Elastomers and Composites
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• v.43 no.2
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• pp.88-103
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• 2008

This study was purposed to investigate the effects of surfactants and fillers on physical properties of hydrophilic polyvinylsiloxane dental impression materials (PVS). Incorporation of surfactants enhanced the hydrophilicity of the PVS, however, it induced increased viscosity and permanent deformation ratio, delayed setting, and decreased tensile strength. At high concentrations of surfactant, the tensile strength was observed to decrease significantly due to the internal pore formation. Especially, the hydrophilicity of the PVS was significantly enhanced with the addition of Silwet L-77. However, the viscosity, strain in compression, pore formation, and setting time increased whereas the elastic recovery rate and strength remarkably decreased. The PVS dental materials containing Span 20 showed the lowest degree of viscosity increase, delayed setting, pore formation, and hydrophilicity. The delayed setting, pore formation, and strength decrease caused by the incorporation of surfactant were improved by substituting the crystalline quartz filler with diatomaceous earth while the contact angle of PVS dental materials increased.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.43-50
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• 2016

A reinforcement is required to ensure the structural safety in case of railway embankment excavation under railway load. A large diameter soil nailing with concrete wall is applied as the reinforcement method instead of the conventional soil nailing system. In this study, a series of 3 dimensional numerical analyses are performed to investigate the optimum reinforcement considering 15 different conditions based on the length, lateral spacing, diameter, and inclination of the reinforcement. The interface between soil nail and perimetric grout is considered by means of cohesion, stiffness and perimeter of the grout. 0.3 m of reinforcement diameter is assessed as the most appropriate based on the economical viewpoint though ground displacement decreases with the increase of diameter, however the difference of displacement is negligible between 0.4 m and 0.3 m of diameter. Surface settlement, lateral displacement of wall, and stress of reinforcement are calculated and economic viewpoint to reinforce embankment considered. Consequently, the optimum reinforcement conditions considering those factors are evaluated as 3 m in length, 0.3 m in diameter, 1.5 m in lateral spacing, and 10 degree of inclination angle in the case of 3 m of excavation depth. Additionally, inclined potential failure surface occurs with approximately 60 degrees from the end of nails and the surface settlement and wall lateral displacement are restrained successfully by the large diameter soil nailing, based on the result of shear strain rate.

• Korean Journal of Food Science and Technology
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• v.12 no.2
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• pp.103-108
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• 1980

To study the effects of diets containing red Ginseng, rats were fed diets containing various amounts of red Ginseng for 10 weeks. The Ginseng diets were 600 mg of red Ginseng extract concentration, 1,200 mg of red Ginseng powder, 6,000 mg of red Ginseng tea, 3,000 mg of red Ginseng extract concentration, 6,000 mg of red Ginseng extract concentration, 12,000 mg of red Ginseng extract concentration per Kg of diet, and control. As results, growth rate, feed efficiency ratio, organ weight, and hematocrit value showed no statistically significant differences between red Ginseng fed animals and the controls. Serum cholesterol level and GPT were slightly lower in the experimental animals than those in the controls. These differences, however, were not statistically significant. Serum GOT activities for all experimental animals showed no statistically significant except for Group fed with 6,000 mg of red Ginseng extract concentration per Kg diet. This Group revealed significantly lower GOT activities than those of the controls statistically. No abnormalities of liver, spleen, and kidney were observed in the experimental animals.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.3
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• pp.135-149
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• 2017

In order to obtain promising rice growth-promoting microbial strains that can be used as substitutes for chemical fertilizers, 172 bacterial strains were isolated from rice roots grown in Korean and Russian soils. Out of them, the strains KR076, KR083, KR181 and RRj228 showed plant growth-promoting activities on maize seedlings. Bacillus megaterium KR076 and Bacillus sp. KR083 showed both nitrogen-fixing and plant growth-promoting activities, while Rhizobium sp. KR181 and Pseudomonas sp. RRj228 appeared to support only plant growth-promotion, but not $N_2$ fixation. Especially, RRj228 showed high growth promoting activity at low concentrations. Inoculation studies with KR083 and RRj228 revealed a high affinity to the Japonica rice variety such as Junambyeo than the Korean Tongil type variety such as Arumbyeo. Both KR083 and RRj228 strains showed rhizoplane and/or endophytic colonization in Japonica and Tongil types rice when soaked with the bacterial suspension of $1.1{\times}10^5cfu\;ml^{-1}$ for six and twelve hours. However, the total bacterial cell numbers were higher in the roots of Japonica variety than in the Tongil type. In inoculation trials with Daesanbyeo rice variety, the seedlings inoculated with KR181 and RRj228 at the rate of $2.0{\times}10^6cfu\;ml^{-1}$ showed yield increment of 35% and 33% (p < 0.01), respectively, so that they contributed to the replacement of chemical fertilizer at half doses of N, $P_2O_5$, and $K_2O$ in pots. In Junambyeo rice seedlings, the strain RRj228, when inoculated with a cell suspension of $1.8{\times}10^6cfu\;ml^{-1}$, promoted 3.4% higher yield at 70% dose than at a full dose level of N $110kg\;ha^{-1}$ in field. These results suggest that the rhizobacteria KR181 and RRj228 are prospective strains for enhancing rice performance.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.333-352
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• 2017

A comparison study is made between the dynamic properties of an argillaceous siltstone and its grouting-reinforced body. The purpose is to investigate how grout injection can help repair broken soft rocks. A slightly weathered argillaceous siltstone is selected, and part of the siltstone is mechanically crushed and cemented with Portland cement to simulate the grouting-reinforced body. Core specimens with the size of $50mm{\times}38mm$ are prepared from the original rock and the grouting-reinforced body. Impact tests on these samples are then carried out using a Split Hopkinson Pressure Bar (SHPB) apparatus. Failure patterns are analyzed and geotechnical parameters of the specimens are estimated. Based on the experimental results, for the grouting-reinforced body, its shock resistance is poorer than that of the original rock, and most cracks happen in the cementation boundaries between the cement mortar and the original rock particles. It was observed that the grouting-reinforced body ends up with more fragmented residues, most of them have larger fractal dimensions, and its dynamic strength is generally lower. The mass ratio of broken rocks to cement has a significant effect on its dynamic properties and there is an optimal ratio that the maximum dynamic peak strength can be achieved. The dynamic strain-softening behavior of the grouting-reinforced body is more significant compared with that of the original rock. Both the time dependent damage model and the modified overstress damage model are equally applicable to the original rock, but the former performs much better compared with the latter for the grouting-reinforced body. In addition, it was also shown that water content and impact velocity both have significant effect on dynamic properties of the original rock and its grouting-reinforced body. Higher water content leads to more small broken rock pieces, larger fractal dimensions, lower dynamic peak strength and smaller elastic modulus. However, the water content plays a minor role in fractal dimensions when the impact velocity is beyond a certain value. Higher impact loading rate leads to higher degree of fragmentation and larger fractal dimensions both in argillaceous siltstone and its grouting-reinforced body. These results provide a sound basis for the quantitative evaluation on how cement grouting can contribute to the repair of broken soft rocks.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.9-15
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• 2004

The cracking resistance of asphalt mixtures is generally evaluated by measuring a single parameter (i.e., Tensile strength, Stiffness). However, the use of a single parameter has been questioned in the evaluation of asphalt mixture cracking performance. The focus of this study was to clearly identify the key properties and characteristics associated with the cracking resistance of asphalt mixtures. Results of fracture, creep, and strength tests at multiple loading rates performed on the modified and unmodified mixtures showed that the mixture cracking resistance was primarily affected by the rate of micro-damage accumulation. This was reflected in the m-value, without affecting the fracture energy limit. It was also observed that the short loading time (elastic) stiffness alone could not differentiate the mixture cracking resistance of the mixtures. It was concluded that the key to characterize the cracking resistance of asphalt mixture is in the evaluation of the combined effects of creep and failure limits. It was also found that a residual dissipated energy parameter measured from Superpave IDT strength test gave the quick and useful way to distinguish the difference of cracking resistance of asphalt mixtures. Failure strain in the longer-term creep test appeared to be a useful parameter for evaluating the combined effects of creep and failure limits of asphalt mixtures.

• Food Science of Animal Resources
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• v.30 no.4
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• pp.609-616
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• 2010

This study was conducted to determine the effects of dietary low grade soybean, fermented with Aspergillus oryzae (FSB 1) or Bacillus subtilis var. natto (FSB 2), on egg production and quality, fat and cholesterol content, and the fatty acid (FA) profile of eggs by lipid layer. A total of 18 Hi-Line strain layers, 22 wk of age, were randomly assigned to three dietary treatments: no fermented soybean (control), control with 15% FSB 1 (C + FSB 1), and control with 15% FSB 2 (C + FSB 2). The rate of egg production and egg weight were evaluated between two periods: one was from the 1st to 4th wk and the other was from the 5th to 8th wk. At the 8th wk, a total of 30 eggs were randomly selected from each treatment group and analyzed for physical quality, fat content, fatty acid composition and cholesterol content. The results showed that egg production was increased in hens fed with diets containing fermented soybeans from the 5th to 8th wk period (p<0.01). A similar tendency was observed through eight weeks' cumulative egg production (p<0.05). There were no significant differences in egg production between the C + FSB 1 and C + FSB 2 treatment groups (p>0.05). Egg weight and other physical properties did not vary between treatment groups (p>0.05). Egg yolks among different treatment groups were similar in fat content, but egg yolks in the C + FSB 1 and C + FSB 2 groups had lower oleic acid (p<0.05), higher linoleic, ${\alpha}$-linolenic, and arachidonic acids (p<0.01), and lower cholesterol content (p<0.05) than those in the control group. In conclusion, supplementation of fermented low grade soybeans might be useful as a functional feedstuff to improve egg production and quality for a healthy human diet.

• Polymer(Korea)
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• v.25 no.1
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• pp.98-107
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• 2001

Dielectric properties and shape memory characteristics of SBS composites filled with carbon black as conductive filler and (Ba,Ca)$(Sn,Ti)O_3$ or $SrTiO_3$ as dielectrics were investigated for the development of phantom model. SBS/carbon black composite showed an increment of complex dielectric constant with increasing the content of carbon black and the frequency dependence that the dielectric constant decreases with the frequency. The complex dielectric constant and the conductivity of SBS/carbon black/dielectrics composites increased with the increase of dielectrics and the characteristics of the frequency dependence also occurred by the effect of carbon black. Phantom materials with the dielectric properties and the conductivity corresponding to human tissues for the measurement of specific absorption rate(SAR) within the frequency range of current mobile phones(775MHz~2GHz) could be developed by adjusting the composition ratios of carbon black, dielectrics and SBS and by controlling the characteristic of frequency dependence of composite. From thermomechanical cycling test good shape recoverability could be obtained in SBS composite even though the residual strain was increased by the effect of filler.

• Journal of Life Science
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• v.17 no.2 s.82
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• pp.272-278
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• 2007

Proteases are enzymes that break peptide bonds between amino acids of other proteins and occupy a crucial position with respect to their applications in both physiological and commercial fields. In order to screen new source of protease, bacteria producing extracellular proteases at low temperature were isolated from deep sea water of East Sea, Korea. A bacterium showing the best growth rate and production of an extracellular protease at low temperature was designated HJ 47. The DNA sequence analysis of the 16S rRNA gene, phenotypic tests and morphology led to the placement of this organism in the genus Pseudoalteromonas. Although maximal growth was observed at $37^{\circ}C$, enzyme production per culture time was maximum at $20^{\circ}C$. At this temperature, extracellluar protease production was detected from the end of the exponential phage to stationary phase, and maximal at 15 hours after initial production. The optimum temperature and pH of the protease were found to be $35^{\circ}C$ and 8.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.2
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• pp.322-328
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• 2002

This study was carried out to investigate antimutagenic and anticancer effects of ethanolic extract of Korean traditional doenjang added sea tangle. Most of the mineral content of doeniang was increased by addition of sea tangle. In the Ames test, the antimutagenic effect of ethanol extract of Korean traditional doenjang added 5% sea tangle was higher than that of control (no additive), 10%, and 15% sea tangle additions. The inhibition rate of ethanol extract (200$\mu\textrm{g}$/plate) of doenjang added 5% sea tangle in the S. typhimurium TA100 strain showed 97.0% inhibition against the mutagenesis induced by MNNG. In addition, the suppression of ethanol extract (200$\mu\textrm{g}$/plate) of doenjang added 5% sea tangle in the S. typhimurium TA98 and TA100 strains showed 60.2% and 69.1% inhibition respectively, against the mutagenesis induced by 4NQO. The suppressions under the same condition against B($\alpha$ )P and Trp-P-1 in the TA98 and TA100 strains were 71.7% and 87.3%, and 66.6% and 80.8%, respectively. In the anticancer effects, the cytotoxicity of doenjang added 5% sea tangle on the cell lines with human lung carcinoma (A549), human hepatocellular carcinoma (HepG2), and human gastric carcinoma (KATOIII) were inhibited with increasing the extract concentration. The treatment of 1.0 mg/mL Doenjang added 5% sea tangle showed strong cytotoxicity of 56.4%, 87.67%, and 89.5% against A549, HepG2, and KATOIII, respectively.