• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2061-2078
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• 2006

The main purpose of this paper is to establish the high temperature structural integrity evaluating procedures for the next generation reactors, which are to be operated at over 500$^{\circ}C$ and for 60 years. To do this, comparison studies of the high temperature structural design codes and assessment procedures such as the ASME-NH (USA), RCC-MR (France), DDS (Japan), and R5 (UK) are carried out in view of the accumulated inelastic strain and the creep-fatigue damage evaluations. Also the application procedures of the ASME-NH rules with the actual thermal and structural analysis results are described in detail. To overcome the complexity and the engineering costs arising from a real application of the ASME-NH rules by hand, all the procedures established in this study such as the time-dependent primary stress limits, total accumulated creep ratcheting strain limits, and the creep-fatigue damage limits are computerized and implemented into the SIE ASME-NH program. Using this program, the selected high temperature structures subjected to two cycle types are evaluated and the parametric studies for the effects of the time step size, primary load, number of cycles, normal temperature for the creep damage evaluations and the effects of the load history on the creep ratcheting strain calculations are investigated.

• Journal of Microbiology and Biotechnology
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• 제13권1호
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• pp.85-89
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• 2003

The difference in the thermotolerance between Saccharomyces cerevisiae KNU5377 and ATCC24858 was compared by assaying the amounts of trehalose accumulated under growth and heat shock conditions. Both strains exhibited similar trehalose accumulation during the growth period, but an intrinsic thermotolerance was much higher in KNU5377 than in the control strain. This result implied that some strain-specific characteristics of KNU5377, other than trehalose accumulation, primarily were responsible fur its higher intrinsic thermotolerance. Heat shock at $43^{\circ}C$ for 90 min to the exponentially growing cells resulted in the maximum level of trehalose In both strains. Trehalose accumulated at least twice more in KNU5377 by the heat shock than in the control, due to the maintenance of its neutral trehalase activity even after the heat shock. Consequently, the Increase of acquired thermotolerance in both strains correlated with an increase in the trehalose content in each strain. In conclusion, KNU5377 exhibited a well-modulated trehalose-related mechanism to accumulate more trehalose by means of maintaining neutral trehalase activity after heat shock than the control strain, thereby contributing to its acquired thermotolerance.

• Geomechanics and Engineering
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• 제34권5호
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• pp.577-595
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• 2023

A dynamic triaxial discrete element numerical model of lightweight soil was established using the discrete element method to study the microscopic mechanism of expanded polystyrene (EPS) particles in the soil under cyclic loading. The microscopic parameters of the discrete element model of the lightweight soil were calibrated depending on the dynamic triaxial test hysteresis curves. Based on the calibration results, the effects of the EPS particles volume ratio and amplitude on the contact force, displacement field, and velocity field of the lightweight soil under different accumulated strains were studied. The results showed that the hysteresis curves of lightweight soil exhibit nonlinearity, hysteresis, and strain accumulation. The strain accumulated in remolded soil is mainly tensile strain, and that in lightweight soil is mainly compressive strain. As the volume ratio of EPS particles increased, the contact force first increased and then decreased, and the displacement and velocity of the particles increased accordingly. With an increase in amplitude, the dynamic stress of the particle system increased, and the accumulation rate of the dynamic strain of the samples also increased. At 5% compressive strain, the contact force of the particles changed significantly and the number of particles deflected in the direction of velocity also increased considerably. These results indicated that the cemented structure of the lightweight soil began to fail at a compressive strain of 5%. Thus, a compressive strain of 5% is more reasonable than the dynamic strength failure standard of lightweight soil.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1592-1597
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• 2009

Ratcheting is a cyclic accumulation of strain under a cyclic loading. It is a kind of mechanisms which generate cracks in rail steels. Though some experimental and numerical study has been performed, modeling of ratcheting is still a challenging problem. In this study, an elastic-plastic constitutive equation considering non-linear kinematic hardening and isotropic hardening was applied. Under the tangential stress of the contact stresses, a cyclic stress-strain relation was obtained by using the model. Strain under repeated cycles was accumulated.

• ALGAE
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• 제37권4호
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• pp.317-329
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• 2022

Carotenoids are effective antioxidants that are found in various photosynthetic organisms. Marine microalgae are an advantageous bioresource for carotenoid production because they do not compete with other crops for freshwater and arable land. This study reports a newly isolated Dunaliella strain from the Geumhong Saltpan on Yeongjong Island, West Sea, Korea. The new strain was isolated and classified as Dunaliella salina through phylogenetic analysis and was named the OH214 strain (Deposit ID: KCTC14434BP). The newly isolated strain can survive in a wide range of NaCl concentrations (0.3-5.0 M NaCl), but grows well in 0.6 to 1.5 M NaCl culture medium. Under high-light conditions (500 ± 10 μmol photons m^-2 s^-1), the cells accumulated three times more β-carotene than under low-light conditions (50 ± 5 μmol photons m^-2 s^-1). The cells accumulated 2.5-fold more β-carotene under nitrogen-deficient (1 mM KNO₃) conditions (3.24 ± 0.36 ㎍ 10⁶ cells^-1) than in nitrogen-sufficient conditions (>5 mM KNO₃). The lutein content under nitrogen-deficient conditions (1.73 ± 0.09 ㎍ 10⁶ cells^-1) was more than 24% higher than that under nitrogen-sufficient conditions. Under the optimized culture condition for carotenoid induction using natural seawater, D. salina OH214 strain produced 7.97 ± 0.09 mg g DCW^-1 of β-carotene and 4.65 ± 0.18 mg g DCW^-1 of lutein, respectively. We propose that this new microalga is a promising strain for the simultaneous production of β-carotene and lutein.

• 한국미생물·생명공학회지
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• 제4권3호
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• pp.111-115
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• 1976

자연계에서 카드뮴 내성균을 142주 분리하여 그 중 1,500 ppm의 카드뮴 함유배지에서 가장 잘 증식하는 1주를 선발하여 Enterobater cloacae로 동정하였다. 본균은 배지중 카드뮴의 농도가 높아질수록 생장이 억제되었으며 0.5ppm의 카드뮴 함유 배지에서 최고 59%의 카드뮴을 균체내에 축적하였다. 카드뮴의 축적량은 균체의 건물양에 비례하여 균체 건물 1g당 7.8 mg이었으며 균체내 축적된 카드뮴은 60-70%가 세포벽획분에 존재하였다.

• Journal of Microbiology and Biotechnology
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• 제13권2호
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• pp.182-190
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• 2003

A new phaC gene cluster encoding polyhydroxyalkanoate (PHA) synthase I PHA depolymerase, and PHA synthase II was cloned using the touchdown PCR method, from medium-chain length (mcl-) PHA-producing strain Pseudomonas putida KT2440. The molecular structure of the cloned phaCl gene was analyzed, and the phylogenic relationship was compared with other phaCl genes cloned from Pseudomonas species. The cloned phaCl gene was expressed in a recombinant E. coli to the similar level of PHA synthase in the parent strain P. putida KT2440, but no significant amount of mcl-PHA was accumulated. The isolated phaCl gene was re-introduced into the parent strain P. putida KT2440 to amplify the PHA synthase I activity, and the recombinant P. purida accumulated mcl-PHA more effectively, increasing from 26.6 to $43.5\%$. The monomer compositions of 3-hydroxylalkanoates in mcl-PHA were also modified significantly in the recombinant P. putida enforcing the cloned phaCl gene.

• The Korean Journal of Ecology
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• 제22권1호
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• pp.39-43
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• 1999

중금속에 대한 내성을 나타낸 Serratia marcescens를 이용하여 카드뮴 흡착 기작에 관하여 조사하였다. 먼저 카드뮴에 대하여 민감성을 나타내는 돌연변이 균주인 PM을 개발하였으며 PM균주는 50ppm 이상의 카드뮴 농도에서 성장하지 못하였다. 카드뮴을 50ppm 처리한 균주에서 10회 이상 계대 배양하여 카드뮴에 적응을 유도한 PA균주는 PC, PM균주에 비해 성장 속도가 증가하였으며 세포 내 카드뮴 축적량도 4∼5배 증가하였다. PA균주는 100 ppm 카드뮴 처리군에서 처리량 중 23%를 세포내에 축적하였으며 세포막 부위보다 세포질 부위에 더욱 많은 카드뮴을 축적하였다. 카드뮴 처리시, 전 세포 단백질 양상에서 28 KDa과 64 KDa의 2개의 유도 단백질과 45 KDa의 감소 유도 단백질을 확인하였으며 원자 흡광 분석을 통하여 각각의 유도 단백질에 결합된 카드뮴 양은 단백질 1 g당 318.25 ㎍, 325.37 ㎍이 검출되었다. 세포내에 축적된 카드뮴을 전자현미경을 이용하여 카드뮴 결합 물질을 확인한 결과, 세포질의 단백질 분획에서 28 KDa크기의 유도 단백질이 카드뮴과 흡착한 것으로 나타났다. 카드뮴 흡착에 대한 DNA조사 결과 20 Kb 크기의 plasmid가 존재하였으며, curing agent로 plasmid를 제거한 결과 카드뮴 내성을 상실하여 본 분리 균주의 카드뮴 내성 유전자는 plasmid상에 위치하는 것으로 확인하였다.

• 대한화장품학회지
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• 제11권1호
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• pp.1-12
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• 1985

A strain of Pseudomonas aeruginosa was isolated from the spoiled product and its characteristics on various formaldehyde-releasing preservatives were investigated. This strain, P. aeruginosa FR, could utilize 1.0% of imidazolidinyl urea and 0.2% of DMDM hydantoin as a sole carbon and nitrogen source in the minimal salts medium. With the growth of the strain in minimal salts medium containing imidazolidinyl urea, formic acid was initially accumulated according to the decrease of formaldehyde concentration. It was suggested that formaldehyde dehydrogenase was involved in this oxidation process and could catalyze formaldehyde, imidazolidinyl urea, DMDM hydantoin and quaternium-15, but not bronopol. MICs of this strain to each preservation were 0.03% in formaldehyde, 1.0% in imidazolidinyl urea, 0.2% in DMDM hydantoin, 0.2% in quaternium-15 and 0.1% of EDTA-2Na. But the MICs were diminished about ten times when 0.01% of EDTA-2Na was added to the preservative systems. In actual challenge test, the eyeliner and the pack which contained paraben and imidazolidinyl urea were not able to be protected from this strain, but when 0.05% EDTA-2Na was added the products were sufficiently preserved.

• Journal of Microbiology and Biotechnology
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• 제6권5호
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• pp.315-320
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• 1996

The role of glyoxylate bypass in a lysine-producing Corynebacterium lactofermentum strain was analyzed. Unlike the wild type, the strain expressed enzymes of glyoxylate bypass during growth in the fermentation broth containing glucose as the carbon source. To evaluate the importance of glyoxylate bypass in the strain, we disrupted chromosomal aceA by using a cloned fragment of the gene. Site-specific disruption of aceA which codes for the isocitrate lyase, the first enzyme of the bypass, was confirmed by Southern blot analysis. The aceA mutant strain completely lost isocitrate lyase activity and ability to grow in a minimal medium containing acetate as the sole carbon source. The mutant strain was similar to its parental strain in growth characteristics and produced comparable amounts of lysine in shake flasks containing glucose as the carbon source. The amount of oxaloacetate accumulated in the fermentation medium was similar for both strains, suggesting that expression of glyoxylate bypass does not necessarily lead to the increase in intracellular oxaloacetate. These data clearly demonstrate that glyoxylate bypass does not function as one of the routes of carbon supply for lysine production in the strain. It appears that the leakiness of the glyoxylate bypass in the strain might be the result of a secondary mutation which arose during previous strain development by random mutagenesis.