RESUMO
As a key component of a sediment sampler designed for ultra-high pressures, the sealing structure determines whether pressure retention can be reliably achieved. This study constructed a finite element model to study sealing performance and reveal the sealing mechanism. The effects of the hardness and compression rate of O-ring as well as seawater pressure on the sealing performance were studied. The study showed that a self-tightening seal can be formed when the coefficient of friction on the sealing surface is less than or equal to 0.25. In addition, the maximum contact stress of the O-ring increased nearly linearly with increasing pressure, and it was larger than the corresponding pressure. However, with increasing pressure, the maximum Von-Mises stress initially increased rapidly, then tended to stabilize, and then continued to increase. Although increasing the hardness reduced the principal strain, the stress increased correspondingly. Within the compression rate range from 10 to 25%, the hardness of the O-ring had a greater impact on the contact pressure than the compression rate. In order to further verify that the finite element analysis was accurate, the sealing performance was tested, and the results showed that the seal was reliable and capable of sealing a deep-sea sampler.
RESUMO
PURPOSE: The study aimed to investigate the prognosis and safety of perioperative chemotherapy (PC) compared with adjuvant chemotherapy (AC). METHODS: We systematically searched and assessed studies in PubMed, Embase, and the Cochrane Library from inception to 1st September 2022. RESULTS: Eighteen studies were eligible for the analysis, including 4686 patients in total. Our study found that patients with resectable gastric cancer undergoing PC had favorable prognosis on OS (HR 0.77; 95% CI 0.69 to 0.87) and DFS (HR 0.76; 95% CI 0.69 to 0.84) than those who undergoing AC. Addition of neoadjuvant chemotherapy (NAC) to AC provided higher R0 resection rate but did not increase the risk of postoperative complication rate and most of the adverse event rates. CONCLUSION: Our study demonstrated that PC shows better OS and DFS in Asians with resectable gastric cancer compared with AC. PC should be preferred because of its favorable prognosis and similar safety.