• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.735-742
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• 2014

A self-piercing rivet (SPR) is a mechanical component for joining dissimilar material sheets such as those of aluminum alloy and steel. Unlike conventional rivets, the SPR directly pierces sheets without the need for drilling them beforehand. However, the regular SPR can undergo buckling when it pierces a high-strength steel sheet, warranting the design of a helical SPR. In this study, the joining and forging processes using the helical SPR were simulated using the commercial FEM code, DEFORM-3D. High-tensile-strength steel sheets of different strengths were joined with aluminum alloy sheets using the designed helical SPR. The simulation results were found to agree with the experimental results, validating the optimal design of a helical SPR that can pierce high-strength steel sheets.

• Journal of Pharmacopuncture
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• v.4 no.1
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• pp.123-124
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• 2001

Purpose. Free radicals are implicated in the pathophysiology of aging, ischemic injury and neurodegenerative disorders. To deform]no whether Hominis Placenta extract prevents $H_2O_2$-induced apoptosis, we have performed morphological and biochemical analyses for the detection of apoptotic phenomena in the pineal tumor cell line $PGT-{\beta}$ We have also peformed cytochemical and immunocytochemical analyses for the detection of changes in nitric oxide synthase (NOS) activity and estimated the expression . of apoptotic genes using reverse transcription-polymerase chain reaction (RT-PCR) Methods. $PGT-{\beta}\;cells$ were pretreated with Hominis Placenta extracts $(0,\;10^{-2}\;{\mu}g/ml)$ for 2 hours and then exposed to $H_2O_2\;(0,\;50\;{\mu}M)$ for 3 hours. Appearance of apoptotic characteristics were monitored using 4, 6-diamidino-2-phenylindole dihydrochloride (DAPI) staining assay, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay and flow cytometric analysis. NOS activity was measured by NADPH-diaphorase cytochemistry. Expression of inducible NOS (iNOS) and nuclear factor kappa B (NF k B) was assessed via immunocytochemistry. The expression of apoptotic genes was examined by RT-PCR. Results. After 3 flours of exposure to $H_2O_2$, it was shown that $PGT-{\beta}\;cells$ treated with $H_2O_2(50\;{\mu}M)$ exhibit classical apoptotic features and increases in NOS activity and caspase-3 expression. Treatment with Hominis Placenta extract resulted in a reduced occurrence of apoptotic features. DAPI staining, TUNEL and flow cytometric assays revealed decreases in the occurrence of nuclear fragmentation and in the sub-Gl fraction in the $PGT-{\beta}\;cells$ treated with Hominis Placenta extract. Cells treated with Hominis Placenta extract also showed lower activity of NADPH-diaphorase and immunoreactivities of both iNOS and NF k B than those of $H_2O_2$-treated cells which were not treated with Hominis Placenta extract. By RT-PCR, it was shown that the level of caspase-3 mRNA was derreased In the cells treated with Hominis Placenta . extract. Conclusions. This study shows that Hominis Placenta extract prevents $H_2O_2$-induced apoptosis in $PGT-{\beta}\;cells$; inhibitions of iNOS and caspnse-3 are possible mechanisms of the protection against apoptosis.