• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.39-45
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• 2024

Seismic safety of expansion joints for piping systems has been underscored by water pipe ruptures and leaks resulting from the Gyeongju and Pohang earthquakes. Metal bellows in piping systems are applied to prevent damage from earthquakes and road subsidence in soft ground. Designed with a series of corrugated segments called convolutions, metal bellows exhibit flexibility to accommodate displacements. Several studies have examined variations in convolution shapes and layers based on the intended performance to be evaluated. Nonetheless, the research on the seismic performance of complex bellows having multiple corrugation heights is limited. In this study, monotonic loading tests, cyclic loading tests, and fatigue tests were conducted to evaluate the shear performance in seismic conditions, of metal bellows with variable convolution heights. Single- and triple-layer bellows were considered for the experimentation. The results reveal that triple-layer bellows exhibit larger maximum deformation and fatigue life than single-layer bellows. However, the high stiffness of triple-layer bellows in resisting internal pressure poses certain disadvantages. The convolutions are less flexible at lower displacements and experience leakage at a rate related to the variable height of the convolutions in certain conditions. At lower deformation rates, the fatigue life is rated higher as the number of layers increase. It converges to a similar fatigue life at higher deformation rates.

• Clinical and Experimental Reproductive Medicine
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• v.33 no.1
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• pp.45-52
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• 2006

Objective: Our purpose was to investigate the relationship between the levels of IL-6 and tumor necrosis factor-${\alpha}$ in the peritoneal fluid of women with and without endometriosis and infertile women. Methods: This study is prospective and case-control study in University hospital, enrolled thirty-four women with laparoscopic findings of minimal to severe endometriosis, and thirty-seven women with no visual evidence of pelvic endometriosis and with benign gynecologic disease. IL-6 and tumor necrosis factor-${\alpha}$ levels in peritoneal fluid were determined using commercial ELISA. IL-6 and tumor necrosis factor-${\alpha}$ concentrations were compared among women with and without endometriosis, and with infertile and fertile women, and then also compared according the revised American Fertility Society classification. Results: IL-6 and tumor necrosis factor-${\alpha}$ concentrations were higher than in the peritoneal fluid of women with endometriosis than in matched normal controls. Cyclic variations in IL-6 concentrations were seen in peritoneal fluid from patients with endometriosis: the concentrations in the secretory phase were significantly higher than those in the proliferative phase. The concentrations were higher than among of infertile women than in fertile women. A significant correlation between IL-6 and tumor necrosis factor-${\alpha}$ concentrations and endometriosis stage III and IV was noted. Conclusion: Increased levels of IL-6 and tumor necrosis factor-${\alpha}$ in patients with endometriosis in the peritoneal fluid may be relate to the pathogenesis of endometriosis suggesting that partially contribute to the disturbed immune regulation observed in patients with endometriosis.