• Journal of The Korean Society of Grassland and Forage Science
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• 제17권3호
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• pp.257-264
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• 1997

This study was conducted to assess present situiatioq of oversowing grassland yield and vegetational succession of abondoned since 6 years passed grassland in Wonju. The highest annual h s h weight yield was 28ton/ ha and the lowest was I lton/ha and the grass rate of investigated oversowing grasslands were range from 19.5% to 9lS%. The soil properties of abandoned oversowing grassland, such as soil pH content of organic matter, available phosphorus, exchangeable potasium, calcium, and magnesium were 5.7, 3.88%, 3lppm, O.lme1100g 4.9meI 100g and 2.3me/100g, respectively. The floristic composition of abandoned grassland were composed 26 species of vascular plants. The dominant species based on SDR, of grassland were Miscanthus sinensis var. purpurascens(56.32%). Artemisia feddei(48.62%) and Dactylis glomerata(43.85%). The biological spectra showed the H-$D_1$-$R_5$-e type.

• KSBB Journal
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• 제13권4호
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• pp.438-443
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• 1998

Effects of various environmental factors on cell size index(FCW/DCW) in Thalictrum rugosum. Lithospermum erythrorhizon and Taxus cuspidata plant cell suspension cultures were investigated. Time course change of cell size index were also observed. In batch cultures, FCW/DCW increased according to the decrease of sugar concentration. For short-term experiment within 24 hr, FCW/DCW value could be reduced significantly by increasing sugar concentration. When an osmoticum such as mannitol was added, FCW/DCW converged to a low value. Therefore, it was confirmed that osmolality of the medium was important in determining cell size or water content of the cells. Inorganic salts or treatment with organic solvent also exhibited some effect on the cell size index. However, pH and centrifugal force did not show any influences. On the other hand, it was found that the addition of Pluronic F-68 reduced FCW/DCW. By combining these results effectively, it may be possible to increase the cell concentration in high density culture to a higher extent.

• Journal of Environmental Health Sciences
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• 제23권4호
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• pp.97-103
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• 1997

Carbofuran was incubated for four weeks in three differenf types of paddy soil samples at 25$\circ$C. The soil samples prepared in the present study were as follows: control soil, 3% cellulose added soil and 10% cellulose added soil. The degradation rate of carbofuran significantly decreased by the addition of cellulose to soil(p<0.05). The initial pH of soils was 5.0. After incubation for four weeks, the pH of 10% cellulose added soil sample was lower than those of control soil and 3% cellulose added soil. According to increased organic carbon content of the soil, redox potentials of soils decreased. The decreased degradation rate of carbofuran in 10% cellulose added soil was related to the highly negative redox potentials in contrast with the oxidised conditions of control soil and 3% cellulose added soil.

• Journal of Environmental Health Sciences
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• 제23권4호
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• pp.121-126
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• 1997

Peroxidase as one of the organic enzyme catalyst is useful for the oxidation treatment of various aromatic compounds such as phenols. The peroxidase content of Oenanthe javanica was 24.85 unit/g-fw in leaf, 5.74 unit/g-fw in stem, and 34.69 unit/g-fw in root respectively. The crude peroxidase extracted from Oenanthe javanka can be kept under low temperature (-70$\circ$C) condition for 6 months with the maximum 1% activity reduction. The optimum conditions of removal for 100 ppm phenol was pH 6, hydrogen peroxide 3.5 mM, peroxidase activity 8 unit/ml, temperature 20$\circ$C respectively. In the wide range of concentration from 50 ppm to 750 ppm phenol reveals average 54% removal rate under the same peroxidase activity (8 unit/ml) and different amount of hydrogen peroxide proportional to phenol concentration. Especially at the concentration of 100 ppm the maximum phenol removal rate was 72%.

• Journal of the Korean Ceramic Society
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• 제28권8호
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• pp.635-639
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• 1991

Monolithic gels in the ZrO2-SiO2 system containing up to 30 mol% ZrO2 were prepared from the mixed solutions of Zr(O.nC3H7)4 and partially prehydrolyzed Si(OC2H5)4 (Tetraethyl orthosilicate) by the sol-gel method. The effect of parameters such as the hydrolysis temperature, the amount of water and HCl on the hydrolysis condensation process was investigated and the obtained gels were studied by the IR spectra and TG-DTA. The results showed that the gelation time becomes shorter with increasing content of HCl, H2O and gelation temperature, and that the polymerization was more easily completed with the higher water volume causing the elimination of unreacted organic groups.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.225-226
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• 2006

In this present investigation, Metal Injection Moulding (MIM) of M2 High Speed Steel (HSS) parts using a wax-High Density Polyethylene (HDPE) binder is shown. The elimination of organic binder was carried out by thermal debinding under inert atmosphere. In order to keep carbon in the sample that could improve the sintering process, incomplete debinding was performed between 450 and $600^{\circ}C$. The specimens were sintered at temperatures between 1210 and $1280^{\circ}C$ in high vacuum atmosphere, obtaining the 98% of the theoretical density. In the samples with higher residual carbon content, the sintering window was extended up to 20 degrees and the optimum temperature was lower.

• Journal of Sensor Science and Technology
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• 제24권2호
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• pp.88-92
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• 2015

In order to study the semi-conductive characteristics of carbon black-filled ethylene-propylene-diene monomer (EPDM) composite film, which is used for measuring occlusal force, composite samples with volume ratios of carbon black to EPDM ranging from 30% to 70% were prepared. The process of making a composite film consists of two steps, which involve the preparation of a slurry composition and the fabrication of a thin film using solution casting and a lamination process. To prepare the slurry composition, we dispersed carbon black nanoparticles into an organic solvent before mixing with an EPDM solution in toluene. The mechanical and electrical properties of the resulting carbon black-filled EPDM film were then investigated, and the results showed that the electrical resistance of a film decreases with the increase in the carbon black content. Furthermore, improved elastic recovery was observed after cross-linking the EPDM.

• Journal of the Mineralogical Society of Korea
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• 제10권1호
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• pp.45-49
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• 1997

Acid sulfate soils occur in the Gimhae plain where they have been formed from brackish alluvial sediments along the sea coast and river estuary. Acid sulfate soils suffer extremely acidity as a result of oxidation of pyrite. Total sulfur content of the soils was the highest in B horizon of Gimhae series and the lowest in A horizon of Deunggu series. The dominant fractions of sulfur in the soils were jarosite-S for Gimhae series, pyrite-S for Bongrim and Haecheog series, and organic-S for Deunggu series. The essential chemical processes of acid sulfate soils are, firstly, the formation of pyrite in waterlogged environment, and subsequently, the oxidation of this pyrite following natural or artificial drainage. Jarosite [K Fe3(SO4)2(OH)6] is a common sulfur mineral of the oxidation condition. Jarosite shows cubic particles with tetrahedral faces.

• Resources Recycling
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• 제13권4호
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• pp.17-22
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• 2004

This study was focused on the treatment of thickened sewage sludge. General bacteria and E. coli were disinfected over 99％ and organic compounds were decomposed after irradiation. It was suggested that this process can be an alternative for digestion Process. The moisture content in sludge was decreased over 10％ (w/w) and the coagulation of sludge particles was enhanced by irradiation at the dose of 15 kGy and addition of sea waste resource (star-fish) as a dewatering aid.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.705-708
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• 1991

Novel polysilamethylenosilanes (PSMS) were prepared by Wurtz type co-condensation of various mixtures of 2,4,4,6-tetrachloro-2,6-dimethyl-2,4,6-trisilahept ane (TSH) and dimethyldichlorosilane (D). When TSH was incorporated more than 25 mole%, PSMS polymers were soluble in common organic solvents probably due to the polycarbosilane linkage brought from TSH. The molecular weights of the polymer were measured by gel permeation chromatography and showed higher molecular weight with high TSH content. The thermal gravimetric residues increased as TSH contents increased. These properties suggested that PSMS polymers could be useful as ceramic precursors for silicon carbide.