• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.87.2-87
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• 2003

Long-term repeated culturing of biocontrol agents on a certain medium often results in reduced biocontrol efficacy and altered physiology. Effect of culturing media on biocontrol ability and physiological state of Burkholderia gladioli strain B543 was investigated. Over 20 times repeated cultivation of B. giadioli strain B543 on Kings B medium or nutrient agar medium showed improved biological control of cucumber damping-off caused by Pythium ultimum, while one time cultivation on KB or NA did not. The repeated cultivation also induced the physiological changes of the biocontrol agent such as antifungal activity and the production of protease and siderophore. Our result indicates that adaptation to proper culturing medium can alter biocontrol ability and must consider in optimizing the use of biocontrol agents.

• Transactions of Materials Processing
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• v.15 no.7 s.88
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• pp.479-484
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• 2006

The evolution of strain states and textures during rolling with various conditions was investigated by finite element method (FEM) simulations and measurements of rolling textures. Symmetrical rolling with a high friction gives rise to a strong variation of shear strains in rolled sample leading to the formation of texture gradients throughout the thickness layers. A small variation of shear strains during rolling with a well lubrication condition leads to the formation of a fairly homogeneous rolling texture throughout the sheet thickness. During asymmetrical rolling, a proper control of rolling parameters provides the evolution of a fairly homogeneous shear texture throughout the whole sheet thickness.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.322-328
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• 1993

During the screening of antifungal compounds from microbial secondary metabolites to control phytophthora blight of red pepper caused by Phytophthora capsici, a soil isolate, strain 38D10 was selected. Based on taxonomic studies, this strain was identified as Streptomyces neyagawaensis. The antifungal compound was purified from culture broth by HP-20 column chromatography, ethyl acetate extraction, silica gel column chromatography, HPLC and identified as concanamycin B by UV. $^1H$-NMR, $^{13}C$-NMR, SIMS analysis. Concanamycin B has strong antifungal activity against some phytopathogenic fungi but not antivacterial activity and preventive value were 50% and 100% at 125ppm and 250ppm in pot assay.

• Korean Journal of Organic Agriculture
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• v.12 no.1
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• pp.101-114
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• 2004

This study was carried out to clarify the effects of antagonistic microorganism, Bacillus sp. JC181 isolated from the greenhouse soil grown cucumber plants on the growth inhibition of plant pathogen, fusarium wilt (Fusarium oxysporum) occurred in cucumber plants in greenhouse. Antagonistic bacterial strains were isolated and were investigated into the antifungal activity of the antagonistic microorganism against fusarium wilt. Screened fourteen bacterial strains which strongly inhibited F. oxysporum were isolated from thc greenhouse soil grown cucumber plants, and the best antagonistic bacterial strain designated as JC181, was finally selected. Antagonistic bacterial strain JC181 was identified to be the genus Bacillus sp. based on the morphological and biochemical characterization. Bacillus sp. JC181 showed 58.2% of antifungal activity against the plant pathogen growth of F. oxysporum. By the bacterialization of culture broth and heated filtrates of culture broth, Bacterial strain, Bacillus sp. JC181. showed 91.2% and 260% of antifungal activity against F. oxysporum, respectivrly.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.498-500
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• 2009

본 연구에서는 한국인 아동의 우식치아로부터 분리한 S. mutans K7으로부터 HtrA gene을 동정하고 HtrA expression이 산성환경하에서 S. mutans의 생육에 미치는 영향을 알아보았다. S. mutans K7의 HtrA mutant strain은 산성환경에서 parental strain과 비교하였을 때, 생육에 있어서 상당한 차이를 나타내었다. 또한 Biofilm formation에 관여하는 GtfB, 와 GtfC의 발현량도 현저히 줄어들었다. 그리고 HtrA mutant strain에 HtrA gene을 삽입하여 HtrA의 발현량을 회복하였을 경우에는 acid stress하에서 control과 같은 nomal growth phenotype을 회복하였다. 이러한 결과들은 S. mutans K7에서 HtrA가 acid stress동안에 중요한 역할을 담당함을 제시하고 있다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.47-52
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• 2004

Springback comes from the release of residual stress after forming. The control of phenomenon is especially important in the sheet metal forming since there are no other practical methods available to correct the dimensional inaccuracy from springback. Therefore the accurate predication before the die machining has been a long goal in the Held of sheet metal forming. The aim of the present study is to enhance the prediction capability of finite element(FE) analysis for the springback phenomenon. For this purpose FE analysis for V-bending has been carried out with the commercial programs, LS-DYNA. The FE analysis results have been validated through the comparison of experimental. The experimental results measured directly by the strain gauge have given the confidence to FEA.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.952-956
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• 1989

We experimentally investigated the mechanical and electrical characteristics of the poly vinyl alcohol(PVA) hydrogel which have attracted special interest as a mechanochemical material, and the applicability of the hydrogel membrane to a sensor for measuring large strain. As a result, the PVA hydrogel could be regarded as a Hookean elastic material and was treated as an electric resistance which was proportional to the tensile strain within a linearly elastic range.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1897-1904
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• 2002

Monotonic torsional and pure torsional low cycle fatigue(LCF) test with artificial degradation were performed on duplex stainless steel(CF8M). CF8M is used in pipes and valves in nuclear reactor coolant system. It was aged at 430$^{\circ}C$ for 3600hrs. Through the monotonic and LCF test, it is found that mechanical properties(i.e., yield strength, strain hardening exponent, strength coefficient etc.) increase and fatigue life(N$\sub$f/) decreases with degradation of material. The relationship between shear strain amplitude(${\gamma}$$\sub$a/)and N$\sub$f/ was proposed.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.41-54
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• 1991

Laser speckle photography-one of the Laser speckle measurement methods which, recently, are used widely in various science, and engineering applications are succesfully used in the non-contact measurement of In-plaane displacement. In this study, automated measurement and analysis are tried in the laser speckle photo- graphy method using a video camera, computer control and processing, and a X-Y positioning table driven by computer controlled stepping motor. The experiment was compared with the theorecial strain and stress data from finite element method. The result showed that displacement, strain and stress can be measured more accurately and conveniently by using this approach.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.344-349
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• 2008

Ratcheting behavior of IN 718 was investigated at $649^{\circ}C$ under various proportional and non-proportional loading conditions with stress control. The material response was initially elastic but substantial plastic strain was developed as the material softened cyclically. Ratcheting strain was measured to near fatigue life, and is found to have three stages of development - primary, secondary (steady-state) and tertiary. The secondary stage dominates for most cases. Under the same equivalent stress amplitude and mean stress, it was revealed that circular path loading gives higher ratcheting rates and shorter lives than linear paths and that the more ratcheting occurs when the cyclic load is in the same direction as the mean stress. The ratcheting strain at failure depends not only on its rate but also on fatigue life itself, and it is not a primary life-determining factor.