• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.19-25
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• 2000

배수성과 인장강성을 가지는 복합 보강재를 사용하여 보강한 포화점성토의 거동에 선행하중이 미치는 영향을 조사하기위하여 평면변형을 시험을 수행하였다. 보강하지 않은 공시체와 보강한 공시체에 대하여 이방압밀(K=0.3, σ3'=50kPa)을 실시하고 비배수 및 배수전단시험을 일정변형율 속도를 실시하였다. 선행하중을 가한 시험의 경우는 이방압밀후 소정의 선행하중을 가하여 크리이프, 제하, 에이징 후에 비배수 전단시험을 실시하였다. 시험결과 분석한 결과 포화전성성토와 같이 연약한 토질이라도 다짐을 잘하고 보강토의 큰 배수압툭강도를 이용하여 큰 배수압축강도를 이용하여 큰 선행하중을 가하여 과압밀 상태로 함으로써 비배수 전단시에 큰 초기강성을 가지는 것을 알수 있었다. 즉, 점성토의 보강토의 경우 보강에 의한 배수강도의 증가는 큰 선행하중을 가하기 위하여 사용하는 것이 가장 효율적인 것으로 판단된다.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.193-201
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• 2000

교란상태개념(Disturbed State Concept;DSA)모델릉 이용하여 포화사질토의 동역학적 거동을 모사하는 예측기법을 개발하였다. 실내진동전단시험 자료로부터 DSC모델 매개변수를 찾고, DSC 모델을 이용하여 전개한 응력중분과 변형률중분의 관계를 표현하는 탄소성구성방정식으로부터 진동하중을 받는 지반재료의 간극수압 및 유효응력 변화, 그리고 축자응력-축방향변형률 거동을 예측하였다. 압축 및 인장 재하시에는 DSC모델을 사용하여 변형률 경화(strain-hardening)및 진동하중에 의한 변형률 연화(cyclic-softening)현상을 모사하고, 제하(unloading)시에는 선형탄성모델을 사용하여 근사화하였다. 예측 결과를 실내전단시럼 결과와 비교하여 예측기법을 검증하였다.

• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.41-45
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• 1993

To study the prevention of mycotoxin contamination, a large number of sample sources were collected, and Penicilliurn sp. were isolated. TLC and HPLC methods were applied to confirm the patulin producing abilities of isolated strains. From 321 sample sources such as fruit (46), rice (31), corn (19), barley (22) and soil (38), 203 strains of Penicilliurn sp. were isolated. By the result of TLC, 21 strains were assumed to be patulin producing strains, but as a result of HPLC, only 17 strains produced patulin. Among them, E-219 strain showed highest patulin level as 0.12 mg/ml broth.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.33-38
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• 1997

Four bacterial strains able to degrade dichlorobenzene as the sole source of carbon and energy were isolated from soil by selective enrichment culture, and among them, one isolation was the best in the cell growth and identified as Pseudomonas sp. DCB3 by its morphology and physiological properties. Cell growth dramatically increased in a minimal medium containing 500ppm of dichlorobenzene was not detected any more at 72 hours after cultivation. The optimal temperature and initial pH for the growth of the isolated strain were 30$\circ$C and 7.0, respectively. Cell growth was increased by supplementing $(NH_2)_2CO$ and 50 ppm yeast extract as additional nutrients. Therefore, it was suggested that Pseudomonas sp. DCB3 could be effectively used for the biological treatment of wastewater containing dichlorobenzene.

• Microbiology and Biotechnology Letters
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• v.25 no.3
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• pp.322-327
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• 1997

Photosynthetic bacterium strain N-1 was isolated from the eutrophic wet soil and identified as Rhodospirillum rubrum. The optimum conditions for the cultivation of R. rubrum N-1 were estimated as 0.2% (w/v) of sodium acetate, 0.2% (w/v) of sodium propionate, 0.2% (w/v) of sodium butyrate in the Lasscelles basal medium at 30$circ$C, pH 7.0 under 4000 lux of the illumination. The removal efficiencies of total organic acid and chemical oxygen demand (COD$_{Cr}$) in swine wastewater were 80% and 87%, respectively, when 10% (v/v) of R. rubrum N-1 was inoculated.

• Journal of Ocean Engineering and Technology
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• v.18 no.4 s.59
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• pp.46-51
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• 2004

The surface layer in dredged and reclaimed marine clay is improved by mixing of shallow soils and hardening agents, which is made of cement, containing some other special admixtures. Tests in both laboratory and field settings are performed to investigate the improvement effect and strength properties of cement-stabilized soils. The test results show that the hardening agent sufficiently improves the soil properties of the surface layer, while increasing the load-carrying capacity. The strength of cement-stabilized soils depends, primarily, on water-to-cement ratio and curing temperature. That is, the higher curing temperature and the longer curing time, the higher the strength in cement-stabilized soils. The high ratio of water-ta-cement results in a lower strength.

• Microbiology and Biotechnology Letters
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• v.23 no.3
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• pp.322-328
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• 1995

A thermophilic bacteria showing proteolytic activity against defatted soybean was isolated from soil. It was identified as Bacillus amyloliquefaciens based on its morphological and physiological characteristics. The Bacillus amyloliquefaciens NS 15-4 was cultivated at 50$\circ$C by rotary shaking in a medium containing defatted soybean. An extracellular protease from this strain was purified to homogeneity by ammonium sulfate precipitation, ion exchange, and hydrophobic interaction chromatographies. The molecular weight of the enzyme was estimated to be approximately 30,000 by SDS-PAGE and the N-terminal amino acid sequence of the enzyme was turned out to be AQSVPYGISQIKAPA. The optimum temperature and pH for the enzyme reaction were 60$\circ$C and 11, respectively, and its thermostability was increased by the addition of calcium ion. The enzyme was inactivated by phenylmethylsulfonylfluoride, suggesting it be a serine protease. Comparing with other commercial proteases, the enzyme showed relatively high proteolytic activity against defatted soybean, a water-insoluble protein substrate.

• Korean Journal of Microbiology
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• v.23 no.4
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• pp.248-251
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• 1985

An imperfect fungus recognized as a dermatophyte was isolated from soil samples and the macroscopic, microscopic and physiological characteristics were examined. From the comparisons of this isolate with the known species, the strain belonged to the genus Microsporum. She showed mant different characteristics from the related species, including colony color and shape, or number in a cell of macrocondium. This isolate was considered to be a novel species in the genus Microsporum. Therefore the name was given to her as Microsporum nigricans Yeeh sp. nov. because of dark blackish color from the macroscopic observation.

• Korean Journal of Microbiology
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• v.24 no.1
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• pp.51-56
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• 1986

Eight strains of the bacteria capable of growing on salicylate as the sole carbon source were isolated form soil and river water. Three of these isolates were identified as Acinetobacter calcoaceticus (AcBl), Pseuomonas putida biotype B (PpB2), and P. putida biotype A (PpB3). Effects of temperature, pH and C source concentration on biodegradation of salicylate by PpB3 were wxamined. The optimum conditions were as follows; $30^{\circ}C$ for temperature, 7.0 for pH, and 10mM for C source concentration. Ultraviolet scanning spectrum of the salicylate was measured. The spectrum has two peaks at 225nm and 292nm. The spectra of the culture filtrates indicate that ring degradation of salicylate is accomplished.

• The Korean Journal of Food And Nutrition
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• v.7 no.2
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• pp.119-123
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• 1994

Aspergillus sp. BY-54 which produced a strong dextran hydrolyzing enzyme was isolated from soil. Using this strain, the optimal cultural conditions, enzyme purification and characterization were studied. The results are as follows : The optimal concentration of dextran as carbon source was l%. and the optimum temperature and the initial pH for enzyme production was 3$0^{\circ}C$, and 7.0, respectively. Dextranase was purified by DEAE-cellulose column chromatography with a linear gradient increase in NaCl. Km value of dextranase was 0.222%, and several glucans containing various types of glucosidic linkages such as DEAE-sephadex, CM-sephadex and sephadex G-100 were almost digested to a large extent with this dextranase. The enzyme was strongly inhibited by sodium fluoride, KMnO4 and p-CMB, while KCN caused 20% of activation.