• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.202-207
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• 2004

An elastic-plastic finite element analysis of fatigue crack closure is performed for plane strain conditions. The stabilization behavior of crack opening level and the effect of mesh size on the crack opening stress are investigated. In order to obtain a stabilized crack opening level for plane strain conditions, the crack must be advanced through approximately four times the initial monotonic plastic zone. The crack opening load tends to increase with the decrease of mesh size. The mesh size nearly equal to the theoretical plane strain cyclic plastic zone size may provide reasonable numerical results comparable with experimental crack opening data. The crack opening behavior is influenced by the crack growth increment and discontinuous opening behavior is observed. A procedure to predict the most appropriate mesh size for different stress ratio is suggested. Crack opening loads predicted by the FE analysis based on the procedure suggested resulted in good agreement with experimental ones within the error of 5 %. Effect of the distance behind the crack tip on the crack opening load determined by the ASTM compliance offset method based on the load-displacement relation and by the rotational offset method based on the load-differential displacement relation is investigated. Optimal gage location and method to determine the crack opening load is suggested.

• 한국정밀공학회지
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• 제10권3호
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• pp.97-106
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• 1993

This is the study on fracture life under the interaction of creep and fatigue. It is difficult to explain the interaction of the creep and fatigue with indication of frequency but the dependency of the time should be considered. The formulation of material varieties causing by interaction of creep and fatigue is required in the accumulative damage method. The strain range partition method requires some of modification corresponding to the changes in temperature and load. All of other method also comprehended with above mentioned problems. Generally, in this field, the variety of stress-strain and suitable parameter is required and connective study between the macro and micro results seems to be insufficient. The linear damage rule is acquiring the support generally but it requires modification in the hgigh temperature instruments. The variety of stress effecting on crack and variety of stress on the metallurgical side are considered to be problems in the future days.

• 한국해양공학회지
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• 제9권2호
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• pp.112-122
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• 1995

In this work, prediction of fatigue life and fatigue crack growth are studied. 4th order polynominal function is presented to describe the crack growth behaviors from artifical pit of SM45C steel. Crack growth curves obtained from 4th order polyminal growth equations are in good agreement with experimental data The crack growth behaviors at arbitrary stress levels and investigated by the concept of elastic-plastic fracture mechanics using ${\Delta}J$. Fatigue life prediction are carried out by numerical integral method. Prediction lives obtained by proposed method in this study, is in good agreement with the experimental ones. Life prediction results calculated by using of ${\Delta}J$ better than those of ${\Delta}K$.

• 환경위생공학
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• 제23권4호
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• pp.23-29
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• 2008

This study was performed to develop mutant strain using a combination of UV irradiation procedures with protoplast mutagenesis in order to achieve an effective kasugamycin production from Streptomyceskasugaensis. Whenlessthan 1.0g/lof Linoleic acid was used, the cell growth was not inhibited. On the other hand, the cell growth was greatly inhibited when more than 1.6 g/l of linoleic acid was used. Among the various mutant strains, SK-12 was obtained in medium containing 1.6g/l of linoleic acid, showing the highest rate of both cell growth and kasugamycin production. In order to compare kasugamycin production with the SK-12 and the parent strain using soybean oil, cultures were performed in a flask. The production of kasugamycin was increased with the increase time. The maximum kasugamycin concentration was 1.2g/l after 6 days of culture. The product yield from soybean oil was 0.05g/l/g consumed carbon source, which was roughly 5.0 fold higher than the parent strain. These results show that it was effective method for obtaining a mutant resistant to linoleic acid for the effective production of kasugamycin from soybean oil.

• 한국전기전자재료학회논문지
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• 제30권12호
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• pp.757-761
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• 2017

The computational fourier-transform moire (CFTM) method has been briefly explained and this method was used to perform strain analysis of a misfit dislocation in a strained $Si/Si_{0.55}Ge_{0.45}$ layer. An essential advantage of the CFTM method is that it does not require unwrapping, such that errors due to improper unwrapping can be excluded. The analysis results revealed that the Si layer was grown with tensile stress on $Si_{0.55}Ge_{0.45}$ and lattice constant of the Si layer along the growth direction was 1.9% smaller than that of $Si_{0.55}Ge_{0.45}$. On the other hand, strain of the misfit dislocation in the strained $Si/Si_{0.55}Ge_{0.45}$ layer was maximum at the dislocation core due to an extra half-plane and the $e_{xx}$ and $e_{yy}$ values were positive and negative, respectively, along the direction of a burgers vector.

• 한국자동차공학회논문집
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• 제3권1호
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• pp.97-107
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• 1995

Global postbuckling analysis is accomplished for one-dimensional and two-dimensional delaminations. A new finite element model, which can be used to model the global postbuckling analysis of one-dimensional and two-dimensional delaminations, is presented. In order to calculate the strain energy release rate, geometrically nonlinear analysis is accomplished, and the incremental crack closure technique is introduced. To check the effectiveness of the finite element models and the incremental crack closure technique, the simplified closed-form sloution for a through-the-width delamination with plane strain condition is derived and compared with the finite element result. The finite element results show good agreement with the closed-foul1 solutions. The present method was extended to calculate the strain energy release rate for two-dimensional delamination. For a symmetric circular delamination, the strain energy release rate shows great variation along the delamination front. and the delamination growth appears to occur perpendicular to the loading direction.

• 한국환경보건학회지
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• 제22권2호
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• pp.10-18
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• 1996

Experiments were carried out to find the possibility of an economic production of single cell protein(SCP) in mixed culture by Cellulomonas sp. KL-6 and a second organism. The second organism, strain LI-10, was isolated from the large intestines of a mouse. 1. When these strains were mixed, cell growth and carboxymethyl cellulase (CMCase) activity were increased to about 63% and 161%, respectively compared with that of single culture of strain KL-6. We found the mixed culture as a proper method of degradation of cellulose in our study. 2. Strain LI-10 was identified as E. coli. 3. This strain produced trace amounts of cellobiose, but glucose was not found in detectable amounts in the filter paper(FP) medium. 4. $CaCO_3$ injected in the medium at the ratio of 0.1% not only enhanced cell growth but also was effective as an acid neutralizing agent. 5. When this organism was cultured under the optimal medium (glucose 0.1%, $NH_4Cl$ 0.1%, yeast extract 2.0%, $KH_2PO_4$ 0.1%, KCl 0.05%, pH 7.2 and a temperature 30$\circ$C) for 5 days, a cell mass produced 1.18 g/l. The results showed the increase of cell mass up to 300% compared to 0.28 g/l produced in CMC medium.

• 미생물학회지
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• 제46권1호
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• pp.33-37
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• 2010

근권토양에서 분리한 세균 Bacillus subtilis RFO41은 인산 가용화능이 높고 auxin 등의 식물호르몬을 생산한다. 이 균주를 이용하여 가시도꼬마리(Xanthium italicum Moore)의 생장 촉진 실험을 화천군 파로호의 호안나대지에서 수행하였다. 19주 경과 후 자라난 가시도꼬마리를 채취하여 줄기와 뿌리 길이를 측정하고 식물을 건조시켜 중량을 측정하였다. 균주를 처리한 접종군이 미접종 대조군보다 가시도꼬마리의 건조중량이 67.7%나 높았으며 또한 가시도꼬마리의 줄기 길이도 균주를 처리한 접종군이 미접종 대조군보다 21.1% 길었는데 모두 통계적 유의성을 가졌다. 접종균주의 동태를 denaturing gradient gel electrophoresis 방법으로 조사하였는데 나대지 토양에서 접종균주가 유지되고 있으며 토양의 고유 세균군집에는 큰 영향을 미치지 않는 것을 확인하였다. 따라서 척박한 호안나대지 토양에서 B. subtilis RFO41의 인산가용화능과 식물호르몬의 생성능 등의 식물생장촉진 효과가 가시도꼬마리의 생장에 직접적인 영향을 미치는 것으로 판단할 수 있다. 이러한 식물 생장 촉진효과는 친환경적 미생물비료, 특히 민감한 호안나대지 등의 미생물학적 식생복원방법으로서의 가치를 뒷받침하는 것이라 할 수 있다.

• 상하수도학회지
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• 제23권2호
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• pp.175-180
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• 2009

This study was conducted to improve biological degradation efficiency of toluene as a model volatile organic compound (VOC) using yeast Candida tropicalis and to suggest an effective method for bioreactor operation. The yeast strain was immobilized with polyethylene glycol (PEG), alginate, and powdered activated carbon (PAC). The yeast-immobilized polymer media were used as fluidized materials in an airlift bioreactor. Polymer media without PAC were also made and operated in another airlift bioreactor. The two bioreactors showed toluene removal efficiencies ranging 80-96% at loading rates of $10-35 g/m^3-hr$, and the bioreactor containing the polymer media with PAC achieved higher removal efficiency. Protein contents in the liquid phase showed that the bioreactor using the yeast-immobilized polymer media with PAC had a higher rate of microbial growth initially than that without PAC. In addition, the microbial growth rate inside of the polymer media with PAC was five times higher than that without PAC. Consequently, the polymer media containing the yeast strain and PAC could enhance removal efficiencies for VOCs, and the immobilization method improve microbial activity and stability for a long-term operation of biological systems.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.178-178
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• 1999

Low temperature Si epitaxy can provide flexibility for a device designer to tailor or optimize the device performance. It is better method for controlling the doping thickness, concentration and profile than ion implantation and diffusion. But there is a limited growth thickness in this method. At a given temperature, the film grows epitaxially for a certain limiting thickness(hepi) and becomes amorphous. The transition from crystalline Si to amorphous Si is abrupt. In this study, Si film was deposited by ion beam sputter deposition on Si (0001) above a limiting thickness and measure the strain in the interface between crystalline Si and amorphous Si. The strain was compressive and the maximum value was about 2%.