• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.254-261
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• 2004

Until now, there are different kinds of design and evaluation method criteria for ship hulls and ship strength based on allowable stress design using past experiences. But for many sinking accidents of large ships in operation, it has also a doubt about allowable stress design. It is recognized that structural plastic collapse caused by large external force is a main cause of that accidents. Therefore, there is the need for new design criteria based on ultimate limit state with a consideration about progressive collapse behavior as a safety assessment of ship hulls. Also many aluminum alloy ships is built for the purposes of lightweight of ship hulls, with that, a developing of criteria based on ultimate limit state should be made. In this study, the ultimate strength characteristics of aluminum ship hull are investigated by the ALPS/USAS program using already developed design formula for aluminum plate and stiffened panel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.655-659
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• 1997

The analysis of cracks at the interface between dissimilar materilar has received a great deal of attention in recent years. In this paper we conducted the static tensile test for the aluminum bonded single lap-joint with the interface edge crack. Comparing this results, that is ultimate load and strain value of aluminum adherend by strain gauge with the fracture mechanics parameters, compliance and stress intensity factors acquied from the boundary element analysis, we concluded that there are critical value of crack length to provoke the interface fracture.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.574-580
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• 2006

Anisotropy has an important effect on the strain distribution in aluminum alloy sheet forming, and it is closely related to the thinning and formability of sheet metals. Thus, the anisotropy of the material should be properly considered for the realistic analyses of aluminum sheet forming processes. For this, anisotropy can be approached in two different scales: phenomenological and microstructural (polycrystal) models. Recent anisotropic models (Yld2000-2d; Barlat et al.[1] 2003, Cuitino et al.[2] 1992) were employed in this work. For the simulation using shell element, the method which can impose plane stress condition in the polycrystal model is developed. Lankford values and yield stress ratios are calculated along various directions. As planar anisotropic behavior, a circular cup deep drawing simulation was carried out to compare the phenomenological and microstructure models in terms of earing profile.

• Transactions of Materials Processing
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• v.18 no.5
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• pp.422-427
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• 2009

Computed tomography(CT) has been applied to measure micro-defects in the aluminum knuckle parts manufactured by the thixoforming process. 6061 aluminum alloys were used to form knuckle samples in the semi-solid temperature after the SIMA processing of billets. Tensile specimens were cut from the different locations in a thixoformed knuckle. The size and the distribution of forming defects in tensile specimens were analyzed using CT scanning and image analysis technology before tensile tests. It has been qualitatively shown that the stress-strain curves were significantly affected by the size and the distribution of forming defects although the defect sizes lie in the range of micro-meters.

• Transactions of Materials Processing
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• v.6 no.4
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• pp.338-345
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• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress stage and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for material behaviour for variation of strain rate. Therefore, to investigate the effect of compression speed on deformation of aluminum alloy with globular microstructure, the compression test for semi-solid aluminum alloy with controlled solid fraction is perform by material test system which is attracted with furance. The behavior of semi-solid aluminum alloy were discussed for the various solid fraction and die speed. The material constants in stress-strain were are also proposed.

• Toxicological Research
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• v.20 no.3
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• pp.213-223
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• 2004

This work aimed to study the effectiveness of cellular oxidative parameter (malondial-dehyde, protein carbonyl, and 8-hydroxy-2'deoxyguanosine). The experimental groups were aluminum treated rats and control rats. Aluminum treatd rats were given intraperitoneally aluminum nitrate nonahydrate ($Al^{3+}$, 0.2 mmol/kg) daily for 30 days except Sunday. Control rats were injected 1 ml of saline. After the dose, rats were decapitated and hippocampus and cerebral cortex were removed. The measured parameters were tissue malondialdehyde (MDA, index of lipid peroxidation), protein carbonyl (index of protein oxidation), 8-hydroxy-2'-deoxy-guanosine (8-OHdG, index of DNA oxidation), reduced glutathione (GSH) levels as well as glutathione reductase (GR) and catalase. AI concentrations in the tissues were also measured. All results were corrected by tissue protein levels. The results were as followed; 1. The concentrations of AI in the cortex and hippocampus were significantly higher in the AI-treated rats than in the control rats. 2. Antioxidative enzyme's activity, catalase and GR, were significantly higher in the AI-treated rats than the control rats. GSH levels were also higher in the AI-treated rats. 3. MDA, protein carbonyl, and 8-OHdG concentration of AI-treated rats were significantly higher than those of control rats. 4. The concentrations of antioxidants, and oxidative stress parameter were correlated with the concentrations of AI in hippocampus and cerebral cortex. Catalase and GR activity were also correlated with the concentration of AI. Based on these results, it can be suggested that intraperitoneally injected AI was accumulated in the brain and induced the increase of antioxidant levels and antioxidative enzyme activity. Also, the oxidative products of cellular macromolecules are significantly related to tissue AI concentration. Therefore MDA, protein carbonyl, and 8-OHdG are useful markers for oxidative stress on cellular macromolecules.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.172-176
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• 2013

Microelectromechanical system switches are becoming more and more popular in the electronics industry; there is a need for careful selection of the materials in the design and fabrication of switches for reliability and performance issues. The membrane used for actuation to change the state of an RF switch is made mostly using gold or aluminum. Various designs of membranes have been proposed. Due to the flexure-type structures, the design complexity increases, which makes stress analysis mandatory to validate the reliability and performance of a switch. In this paper, the effective stress and actuation voltage required for different types of fixed-fixed membranes is analyzed using finite element modeling. Effective measures are presented to reduce the stress and voltage.

• Transactions of the Korean Society of Mechanical Engineers
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• v.4 no.2
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• pp.47-53
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• 1980

Kikukawa-Compliance method using a conventional clip-on gauge was employed to investigate fatigue crack growth and crack closure in 2017-T3 aluminum alloy. The crack growth rate plot against stress intensity range .DELTA.K on a log-log diagram exhibits a bilinear form with a transition at the growth rate of 10$\^$-4/ mm/cycle. The bilinear form appears still in the plot of growth rate versus effective stress intensity range .DELTA.K$\_$eff/. Fatigue crack growth rate could be well represented by .DELTA.K$\_$eff. The experimental results indicate that the effective stress intensity range ratio U depends on the maximum stress intensity factor K$\_$max/, but the stress ratio R does not affect U. The crack opening stress intensity factor K$\_$op/ tends to increase with increasing K$\_$max/ and decrease with increasing .DELTA.K.

• Journal of Crop Science and Biotechnology
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• v.10 no.2
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• pp.106-111
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• 2007

Increasing genetic variability with mutagenic agents has been broadly employed in plant breeding because it has the potential to alter one or more desirable traits. In this study, a molecular analysis assessed by Amplified Fragment Length Polymorphisms(AFLPs) and a morphological analysis based on seedlings subjected to aluminum stress were compared. Also, an analysis of allelic frequencies was performed to observe unique alleles present in the pool. Genetic distances ranging from 0.448 to 0.953 were observed, suggesting that mutation inducing was effective in generating variability. The genetic distances based on morphological data ranged from 0(genotypes 22 and 23) to 30.38(genotypes 15 and 29). In the analysis of allelic frequency, 13 genotypes presented unique alleles, suggesting that mutation inducing was also targeting unique sites. Mutants with good performance under aluminum stress(9, 15, 18 and 27) did not form the same clusters when morphological and molecular analyses were compared, suggesting that different genomic regions may be responsible for their better performance.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.4
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• pp.262-268
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• 2014

In order to reveal the aluminum (Al) stress tolerance mechanisms in alfalfa plant at low pH soil, a proteomic approach has been conducted. Alfalfa plants were exposed to Al stress for 5 days. The plant growth and total chlorophyll content are greatly affected by Al stress. The malondialdehyde (MDA) and $H_2O_2$ contents were increased in a low amount but free proline and soluble sugar contents, and the DPPH-radical scavenging activity were highly increased. These results indicate that antioxidant activity (DPPH activity) and osmoprotectants (proline and sugar) may involve in ROS ($H_2O_2$) homeostasis under Al stress. In proteomic analysis, over 500 protein spots were detected by 2-dimentional gel electrophoresis analysis. Total 17 Al stress-induced proteins were identified, of which 8 protein spots were up-regulated and 9 were down-regulated. The differential expression patterns of protein spots were selected and analyzed by the peptide mass fingerprinting (PMF) using MALDI-TOF MS analysis. Three protein spots corresponding to Rubisco were significantly down-regulated whereas peroxiredoxin and glutamine synthetase were up-regulated in response to Al stress. The different regulation patterns of identified proteins were involved in energy metabolism and antioxidant / ROS detoxification during Al stress in alfalfa. Taken together, these results provide new insight to understand the molecular mechanisms of alfalfa plant in terms of Al stress tolerance.