• Korean Journal of Soil Science and Fertilizer
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• v.16 no.1
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• pp.20-27
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• 1983

A series of laboratory experiment was conducted to find out the chemical composition, characterization of humic substances by physical and chemical methods and reaction of Na-pyrophosphate, $Ca(OH)_2$ and rice straw with albumin on the degradation of soil organic matter in the volcanic ask soils of the Jeju Island. Results obtained were summarized as follows: 1. The contents of organic matter, available silicon, active iron and aluminum concentration in volcanic ash the soils were remarkably higher but available phosphorous was comparatively lower than the mineral soils. In volcanic ash soil, the contents of potassium, calcium and magnessium were higher in upland soil than that of forest soil. The ratios of active $Al^{{+}{+}{+}}/Fe^{{+}{+}}$, C/P and $K/Ca^+$ Mg were apparently high in volcanic ash soils while that of $SiO_2$/O.M. was high in mineral soil. 2. The carbon/nitrogen ratio in humin, humic acid content in organic matter, and carbon contents of humin in total carbon of soil organic matter were apparently higher in the volcanic ash soils than in the mineral soils, The total nitrogen and fractions of acid or alkali soluble nitrogen were remarkably high in volcanic ash soils while mineralizable nitrogen ($NH_4$-N and $NO_3$) contents were high in mineral soils. 3. The values of K600, RF and log K were also higher in volcanic ash soils than those in mineral soils, and the absorbance in the visible range were high and color was dark in the soil of which humification was progressed Extracted humic acid from volcanic ash soil was less reactive to the oxidizing chemical reagent and was persistance to the acid or alkali hydrolysises. 4. The major oxygen-containing functional groups in humic substances of volcanic ash soils were phenolic-OH alcoholic-OH and carboxyl groups while those in mineral soil were methoxyl and carbonyl groups. 5. Absorption spectra of alkaline solution of humic acid ranged from 200 nm to maxima 500 nm. Visible spectra peaks of from humic substances in the visible region were recognized at 350, 420, 450 and 480 nm. Only one single absorbance peak was observed in the visible region at 362 nm for Heugag series and two absorbance Peak were also at 360 nm and 390 nm for Yeungrag series. 6. Evolution of carbon as $Co_2$ was increased with addition of Na-pyrophosphate in Namweon and Heugag series, and "priming effects" took place on the soil organic matter decomposition by addition of rice straw with albumin in Ido series.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.298-305
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• 1992

The carbonization behaviors of CFRP fabricated with 2D-woven fabric and matrix phenolic resin have been studied. The changes in dimension were observed in the temperature range of 365-37$0^{\circ}C$ in the thickness direction, 118-12$0^{\circ}C$ in the normal direction each other by TMA analysis. Observation with the optical microscope shows that the formed cracks and pores during the fabrication of CFRP were propagated with the increase of pyrolysis temperaure. New cracks and pores were formed in the pyrolysis temperature range of 400-50$0^{\circ}C$ In line with the formation and propagation of cracks, porosity was increased and density was decreased rapidly in the pyrolysis temperature range of from 40$0^{\circ}C$ to 70$0^{\circ}C$. Therefore heating rate in the carbonization process need to be controlled carefully by intervals.

• Biomedical Science Letters
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• v.9 no.4
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• pp.195-201
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• 2003

Aromatic hydrocarbons are of major concern among genotoxic chemicals due to their toxicity and persistence. Some microorganisms can utilize aromatic hydrocarbons as carbon and energy sources by inducing expression of catabolic operon(s). The XylR regulatory protein activates transcription of the catabolic enzymes to degrade BTEX (benzene, toluene, ethylbenzene, and xylene) from its cognate promoters, Pu and Ps upon exposure of the cells to the aromatic hydrocarbons. The activity of XylR on the promoters was previously monitored using luciferase luc reporter system. The xylR, its promoter Pr and the promoter Po for the phenolic compound catabolic operon were introduced upstream of firefly luciferase luc in the pGL3b vector to generate about 7.1 kb of pXRBTEX. Here E. coli harboring the plasmid was freeze-dried under various conditions to fin,d optimal conditions for storage and transport. The cell viability and luciferase activity were maintained better, when the cells were freeze-dried at -7$0^{\circ}C$ in the addition of the 10% skim milk or 12% sucrose. However, coaddition of protectants such as 10% skim milk plus 10% glucose or 12% sucrose plus 10% glucose, resulted in much better viability and bioluminescence activity compared with the effect of single addition of each protectant. In addition, it was shown that the freeze-dried cells maintained almost intact bioluminescent activities and cell viability for at least 1 week after freeze-drying. This work demonstrated that the properly freeze-dried recombinant bacterial cells could be utilized as a whole-cell biosensor for simple and rapid monitoring of BTEX in the environment.

• Microbiology and Biotechnology Letters
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• v.6 no.4
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• pp.155-159
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• 1978

Phenol utilizing yeast No. 558 isolated from soil sewage sediment was able to use substantial amount of phenol as the sole carbon source, and the biomass productivity by this organism was very excellent. This organism could grow well in 1000 ppm of phenol concentration, the maxim-um specific growth rate obtainable at pH 5.0, 3$0^{\circ}C$ was 0.27/hr., and the biomass yield coefficient Y vs. consumed phenol was 3.2. Maximum production rate of biomass was observed at 35$^{\circ}C$, pH 3.5 to pH 4.5, and the addition of the 0.005~0. 01% yeast extract was the most effective. Addition of HgCl$_2$ and phenyl hydrazine, inhibitors of oxide-reductase, in the phenol containing cultural liquid caused this organism no-growth at the concentration of 10$^{-5}$ M, 10$^{-3}$ M respectively. This organism could utilize not only phenol but catechol, resorcinol and benzidine.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.8
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• pp.597-604
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• 2013

A coupled thermomechanical analysis of composite structures in pyrolysis and ablation environments is performed. The pyrolysis and ablation models include the effects of mass loss, pore gas diffusion, endothermic reaction energy, surface recession, etc. The thermal and structural analysis interface is based upon a staggered coupling algorithm by using a commercial finite element code. The characteristics of the proposed method are investigated through numerical experiments with carbon/phenolic composites. The numerical studies are carried out to examine the surface recession rate by chemical and mechanical ablation. In addition, the effects of shrinkage or intumescence during the pyrolysis process are shown.

• Food Science and Preservation
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• v.13 no.3
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• pp.363-368
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• 2006

This study was performed to develop flavor materials from Elsholtzia ciliata Hylander with analyzing functionality and aroma profile and to optimize supercritical fluid extraction method and optimum condition. The qualities of water extracts such as total yield total phenolic compound electron donation ability, estragole and L-carvone, were affected by extraction pressure than time. The response variables had significant with pressure than with time and the established polynomial model was suitable(P>0.05) model by Lack-of-Fit analysis. The optimum extraction conditions which were limited of maximum value for dependent variables under experimental conditions based on central composite design were 238 bar and 42 min.

• Toxicological Research
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• v.31 no.1
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• pp.41-48
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• 2015

Owing to the increase in price of cigarettes in Korea, herbal cigarettes have received increasing attention as a non-smoking aid; however, its safety has hardly been studied. We analyzed some of the toxic components in the mainstream smoke of herbal cigarettes, performed a mutagenicity test on smoke condensates for safety assessment, and compared the results with the corresponding values of a general cigarette with the same tar content. Herbal cigarette "A" was smoked using automatic smoking machine under ISO conditions in a manner similar to general cigarette "T". The tar content measured was higher than that inscribed on the outside of a package. The mainstream smoke of herbal cigarette "A" did not contain detectable levels of tobacco-specific nitrosamines and nicotine. Carbon monoxide and benzo(${\alpha}$)pyrene contents in herbal cigarette "A" were higher than those in the general cigarette "T". The phenolic contents such as hydroquinone, resorcinol, and catechol in herbal cigarette "A" were higher than those in the general cigarette "T", but cresol contents in herbal cigarette "A" were lower than those in the general cigarette "T". The content of aromatic amines such as 4-aminobiphenyl in herbal cigarette "A" was higher than that in the general cigarette "T"; however, this difference was not statistically significant. On the other hand, 1-aminonaphthalene, 2-aminonaphthalene, and 3-aminobiphenyl contents in herbal cigarette "A" were lower than those in the general cigarette "T". The smoke condensates of herbal cigarette "A" exhibited a higher mutagenic potential than the condensates from the general cigarette "T" at the same concentration. We concluded that the mainstream smoke of herbal cigarette contains some toxic components, the smoke condensates of herbal cigarettes are mutagenic similar to general cigarette because of combustion products, and that the evaluation of the chemical and biological safety of all types of herbal cigarettes available on the market.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.1
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• pp.43-47
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• 2006

Ginseng (Panax ginseng CA. Meyer) hairy root cultures, which are established via the infection of ginseng root discs with Rhizobium rhizogenes, have been used to construct profiles of both biomass growth and nutrient consumption in flask cultures. In a 250 mL shake flask culture, the maximum biomass was observed on the 59th day of the culture period, at 216.8 g (fresh wt) per liter or 11.4 g (dry wt) per liter. The hairy roots were determined to have a growth rate of 0.355 g-DW/g cells/day during the exponential growth phase and a maximum specific growth rate on day 7. Total ginseng saponin and phenolic compound contents were noted to have increased within the latter portion of the culture period. Linear correlations between increases in biomass weight and nutrient uptake were used to imply the conductivity yield $2.60g-DW/(L{\cdot}mS)$ and carbon yield 0.45 g-DW/(g sugar) in the 250 mL flask cultures. The biomass yield when two different nitrogen sources were used (ammonia and nitrate) was shown to remain approximately constant. at $0.47g-DW/(L{\cdot}mM\;NH_4$) and $0.33g-DW/(L{\cdot}mM\;NO_3$); it remained at these levels for 16 days with the ammonia. and for 24 days with the nitrate. The biomass yield when a phosphate source was used was also shown to remain approximately constant for 9 days, at $3.17g-DW/(L{\cdot}mM\;PO_4$), with an $R^2$ of 0.99.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.107-115
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• 1998

This paper deals with the study on injection with EPDM(Ethylene propylene dien ter polymer) the gap which narrow, long, and tubular between an ablative composite tube and a steel motor case. Small size motor assembly was designed and manufactured for man-portable air defense propulsion system. Motor assembly is consisted with steel tube, ablative composite tube and insulation rubber. Ablative composite tube was made of carbon/phenolic prepreg by rolling process and insulation rubber was made of EPDM by TPM(Trans-power molding) process. To select the insulation rubber material, we tested ablative insulation property and degradation property at first and we tested fluidity, adhesive property and hardness of EPDM rubber. Finally we designed TPM process to manufacture motor case assembly and the motor case assembly was examined by non-destructive test(X-ray).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.735-741
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• 2018

In this paper, the surface recession of ablative materials was quantitatively analyzed using a high-speed camera and a three-dimensional profilometer. The ablation tests of the graphite and carbon/phenolic composite samples were performed using a 0.4 MW arc-heated wind tunnel for simulating the atmospheric re-entry environment. The real-time images during the ablation test were captured by the high-speed camera, and analyzed to calculate the surface recession and recession rate. Also, the surface data of samples were obtained using a three-dimensional profilometer, and the surface recession was precisely calculated from the difference of height between the surface data before and after the test. It is effective to complement the two measurement results in the comprehensive analysis of surface recession phenomena.