• 항공우주시스템공학회지
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• 제1권2호
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• pp.27-36
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• 2007

The Damage Tolerant Design is developed to help alleviate structural failure and cracking problems in aerospace structures. Recently, the Damage Tolerant Design is required and recommended for most of aircraft design. In this paper, the damage tolerant design is applied to tilt rotor UAV. First of all, the fatigue load spectrum for the tilt rotor UAV is developed and fatigue analysis is performed for the flaperon joint which has FCL (fatigue critical location). Tilt rotor UAV has two modes: helicopter mode when UAV is taking off and landing; fixed wing mode when the tilt rotor UAV is cruising. To make fatigue load spectrum, FELIX is used for helicopter mode. TWIST is used for fixed wing mode. Fatigue analysis of flaperon joint is performed using fatigue load spectrum. E-N curve approach is used for picking crack initiation point. The LEFM(Linear Elastic Fracture Method) is considered for analyzing crack growth or propagation. Finally, including the crack initiation and propagation, the fatigue life is evaluated. Therefore the Damage Tolerant Design can be done.

• 한국기계가공학회지
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• 제11권1호
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• pp.125-133
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• 2012

This study aims at structural analysis with fatigue on the shock absorber mount of automobile. Two kinds of mount as original model 1 and reinforced model 2 are applied. Among the cases of nonuniform fatigue loads at both models, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'SAE bracket history' or 'SAE transmission', the maximum fatigue life at model 2 is 5 to 6 times as much as model 1 and the minimum damage at model 2 is decreased 5 to 6 times as much as model 1. In case of 'Sample history' as slow fatigue loading history, the minimum damage at model 2 becomes same as model 1 but the maximum fatigue life at model 2 is decreased more than 17 times as much as model 1. In case of 'Sample History' with the average stress of -$10^4MPa$ to $10^4MPa$ and the amplitude stress of 0MPa to $10^4MPa$, the possibility of maximum damage becomes 3%. This stress state can be shown with 5 times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. Safe and durable design of shock absorber can be effectively improved by using this study result on mount frame.

• Animal cells and systems
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• 제6권3호
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• pp.263-269
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• 2002

The p53 tumor suppressor gene is among the most frequently mutated and studied genes in human cancer, but the mechanisms by which it sur presses tumor formation remain unclear. DNA damage regulates both the protein levels of p53 and its affinity for specific DNA sequences. Stabilization of p53 in response to DNA damage is caused by its dissociation from Mdm2, a downstream target gene of p53 and a protein that targets p53 for degradation in the proteosome. Recent studies have suggested that phosphorylation of human p53 at Ser20 is important for stabilizing p53 in response to DNA damage through disruption of the interaction between Mdm2 and p53. We generated mice with an allele encoding changes at Ser20, known to be essential for p53 accumulation following DNA damage, to enable analyses of p53 stabilization in vivo. Our data showed that the mutant p53 was clearly defective for full stabilization of p53 in response to DNA damage. We concluded that Ser20 phosphorylation is critical for modulating the negative regulation of p53 by Mdm2, probably through phosphorylation-dependent inhibition of p53-Mdm2 interaction in the physiological context.

• Archives of Pharmacal Research
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• 제29권3호
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• pp.213-217
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• 2006

The present study was undertaken to test the hypothesis that dietary antioxidants protect DNA damage induced by peroxynitrite, a potent physiological inorganic toxin. The present study showed that dietary antioxidants such as (-)-epigallocatechin gallate, quercerin, rutin, resveratrol, and ursolic acid inhibit single strand breaks in supercoiled plasmid DNA induced by 3-morpholinosydnomine N-ethylcarbamide (SIN-1), a generator of peroxynitrite through the reaction between nitric oxide and superoxide anion. The formation of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in calf thymus DNA by SIN-1 was also inhibited by dietary antioxidants. When U937 cells were incubated with 1 mM SIN-1 bolus, a significant increase of 8-OH-dG level was observed. However, oxidative DNA damage was significantly lower in the cells pre-treated with dietary antioxidants when cells were exposed to SIN-1.

• 한국정밀공학회지
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• 제15권10호
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• pp.88-95
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• 1998

The purpose of this study is to predict the life of a Lug under the real service load history. The techniques of predicting a fatigue life under load spectrum are discussed and some are developed. The stress is calculated by multiplying the stress under unit force with the Finite Element Analysis. The cycles are counted by the Rainflow counting method and then the mean stress effect is considered by the suggested conversion function. The Manson's Double Linear Damage Rule is used as the cummulative damage method.

• 동아시아식생활학회지
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• 제18권4호
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• pp.608-617
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• 2008

This study examined the level of reaction towards damage related to health foods and the factors affecting this reaction among the elderly. Data were collected from 269 elderly individuals living in Seoul, Daejeon, Daegu, Gwangju and Busan. Frequencies, chi-square tests, and a multinomial logistic regression analysis were performed using the SPSS v. 14.0 program. When asked about their reaction towards damage related to health foods, approximately 48% of the respondents answered 'no response', 34% answered 'private response', and 18% answered 'public response'. Multinomial logistic regression analysis revealed that education level and awareness of health food price were significant factors influencing 'private response', and concerns about health foods and awareness of damage redemption were significant factors for 'public response'. These results imply that consumer education for elderly to prevent damage derived from the purchase and consumption of health foods is required.

• 한국정밀공학회지
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• 제16권7호
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• pp.168-177
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• 1999

Fatigue damage is the phenomena which is accumulated gradually with loading cycle in material. It is represented by fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$. Fracture mechanical parameters estimating large crack growth behavior can calculate quantitative amount of fatigue crack growth resistance in engineering material. But fatigue damage has influence on various load, material and environment. Therefore, In this study, we propose that artificial intelligent fatigue damage model can predicts fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$ simultaneously using fracture mechanical and nondestructive parameters.

• Ocean and Polar Research
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• 제25권spc3호
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• pp.417-421
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• 2003

In the reliability design of the breakwater armor layer, it is often necessary to calculate its damage accumulated over the life of the breakwater. In this paper comparison is made between the two methods proposed by Hanzawa et at. in 1996 and Melby and Kobayashi in 1998 to calculate the cumulative damage of the breakwater armor layer. Tn the case where a severe damage occurs at the beginning of the life or toe breakwater, the two methods do not show significant difference, but in general the farmer predicts a cumulative damage several times larger than the latter.

• Toxicological Research
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• 제17권4호
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• pp.249-253
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• 2001

Fumonisin B1, a mycotoxin, is thought to induce esophageal cancer in humans and apoptosis in animal cells by inhibiting ceramide synthase. Dumonisin Bl may also generate reactive oxygen species directly or indirectly, leading to DNA damage and lipid peroxidation. In this study, a DNA fragmentation assay, dichlorofluorescein (DCF) analysis, and single cell gel electrophoresis (SCGE) were used to investigate the involvement of cellular free radicals, specifically hydrogen peroxide, in the DNA damaging activity of fumonisin B1. From an in vitro DNA fragmentation assay, E. coli DNA, damage by fumonisin Bl was increased by the addition of superxide dismutase (SOD) and decreased by catalase. SCGE and DCF analysis in vivo showed that the nuclear DNA damage and intracellular free radicals in cultured rat hepatocytes treated with fumonisin B1 were increased with the concentration of fumonisin Bl . DNA damage and free radical generation were inhibited by the addition of catalase. Fumonisin Bl , in the presence of SOD, produces hydrogen peroxide causing oxidative DNA damage and protein malfunction, leading to genotoxicity and cytotoxicity of the toxin.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 단조 심포지엄
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• pp.141-146
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• 1999

In the stage of process design, many factors affecting tool life should be considered. Wear, Damage Accumulation and excessive die Stress are those. Most Engineer think wear and damage accumulation affection deeply to the cold forging dies and wear for the hot forging dies. In this report, the example that wear and stress distribution affect tool life in hot forging together will be introduced and the way to solve that problem using Finite Element Method.