• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1965-1971
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• 1997

The relaxation of stress concentration in notched members can be very significant in the improvement of notched strength and fatigue life. This paper investigated the relationship of stress concentration factor, and notched strength and fatigue life. The stress concentration factors were analyzed by FEM. Uniaxial tensile and fatigue tests were carried on plain woven composite specimens which have a main hole and two defence holes. From experimental results, the notched strength and the fatigue limit increased up to about 50% and 30% respectively due to the reduction in stress concentration. The fatigue lives predicted by Juvinall's approach were underestimated than test results and this trends were remarkable as nothed strength increased. This is because of the underestimation of a coefficient. A in S-N curve (.sigma.$_{ar}$ =A $N_{f}$ $^{B}$). Therefore, considering notched strength the coefficient A was modified. The fatigue lives by this process were agreed well with the experimental results.sults.

• Journal of Aerospace System Engineering
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• v.15 no.6
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• pp.19-25
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• 2021

This paper presents a method that uses the stress failure criteria to predict the tensile failure strength of open-hole laminates with stress concentrations. The composite material used in this study corresponds to a 177 ℃ cured, carbon/epoxy unidirectional tape prepreg. The results obtained by testing ten different laminates were compared and analyzed to verify the tensile strength of the open-hole laminates predicted using the proposed stress failure criteria. The findings of this study confirm that the tensile strength predictions performed using the proposed method are generally accurate, except in cases involving highly soft laminates (10% of 0° ply).

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.6
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• pp.1263-1269
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• 2014

Since the cyber defense has been dependent on commercial products and protection systems, in aspect of the recent trends, our cyber defence ecosystem can be more vulnerable. In case of general defense weapon companies, they have to be observed by the government such as certain proprietary technologies and products for the protection from the enemy. On the contrary, most cyber weapon companies have not been managed like that. For this reason, cyber attack can reach to the inside of our military through the security hole of commercial products. In this paper, we enhanced a military cyber protection ecosystems out of enemy attacks and analyze the hypothetical scenarios to evaluate and verify the vulnerability, and finally more securable ecosystem of military protection system is presented politically and technically.

• Research in Plant Disease
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• v.22 no.2
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• pp.81-93
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• 2016

Out of plant-associated bacteria, certain plant growth-promoting bacteria (PGPB) have been reported to increase plant growth and productivity and to elicit induced resistance against plant pathogens. In this study, our objective was to broaden the range of applications of leaf-colonizing PGPB for foliar parts of road tress and pepper. Total 1,056 isolates of endospore-forming bacteria from tree phylloplanes were collected and evaluated for the enzymatic activities including protease, lipase, and chitinase and antifungal capacities against two fungal pathogens, Colletotrichum graminicola and Botrytis cinerea. Fourteen isolates classified as members of the bacilli group displayed the capacity to colonize pepper leaves after spraying inoculation. Three strains, 5B6, 8D4, and 8G12, and the mixtures were employed to evaluate growth promotion, yield increase and defence responses under field condition. Additionally, foliar application of bacterial preparation was applied to the road tress in Yuseong, Daejeon, South Korea, resulted in increase of chlorophyll contents and leaf thickness, compared with non-treated control. The foliar application of microbial preparation reduced brown shot-hole disease of Prunus serrulata L. and advanced leaf abscission in Ginkgo biloba L. Collectively, our results suggest that leaf-colonizing bacteria provide potential microbial agents to increase the performance of woody plants such as tree and pepper through spray application.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.88-93
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• 1994

We fabricated a large-scale photovoltaic device for detecting-3-5$\mu$m IR, by forming of n$^{+}$-p junction in the $Hg_{1-x}Cd_{x}$Te (MCT) layer which was grown by LPE on CdTe substrate. The composition x of the MCT epitaxial layer was 0.295 and the hole concentration was 1.3${\times}10^{13}/cm^{4}$. The n$^{+}$-p junction was formed by B+ implantation at 100 keV with a does 3${\times}10^{11}/cm^{2}. The n$^{+}$ region has a circular shape with 2.68mm diameter. The vacuum-evaporated ZnS with resistivity of 2${\times}10^{4}{\Omega}$cm is used as an insulating layer over the epitaxial layer. ZnS plays the role of the anti-reflection coating transmitting more than 90% of 3~5$\mu$m IR. For ohmic contacts, gole was used for p-MCT and indium was used for n$^{+}$-MCT. The fabrication took 5 photolithographic masks and all the processing temperatures of the MCT wafer were below 90$^{\circ}C$. The R,A of the fabricated devices was 7500${\Omega}cm^{2}$. The carrier lifetime of the devices was estimated 2.5ns. The junction was linearly-graded and the concentration slope was measured to be 1.7${\times}10^{17}/{\mu}m$. the normalized detectivity in 3~5$\mu$m IR was 1${\times}10^{11}cmHz^{12}$/W, which is sufficient for real application.