Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with...Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with nanosized Schwarz crystals exhibited high strength and excellent thermal stability.However,the grainsize effect and associated deformation mechanisms of Schwarz nanocrystals remain unknown.Here,we performed large-scale atomistic simulations to investigate the deformation behaviors and grain-size effect of nanocrystalline Cu with Schwarz crystals.Our simulations showed that similar to regular nanocrystals,Schwarz nanocrystals exhibit a strengthening-softening transition with decreasing grain size.The critical grain size in Schwarz nanocrystals is smaller than that in regular nanocrystals,leading to a maximum strength higher than that of regular nanocrystals.Our simulations revealed that the softening in Schwarz nanocrystals mainly originates from TB migration(or detwinning)and annihilation of GBs,rather than GB-mediated processes(including GB migration,sliding and diffusion)dominating the softening in regular nanocrystals.Quantitative analyses of simulation data further showed that compared with those in regular nanocrystals,the GB-mediated processes in Schwarz nanocrystals are suppressed,which is related to the low volume fraction of amorphous-like GBs and constraints of TB networks.The smaller critical grain size arises from the suppression of GB-mediated processes.展开更多
Maximum Voluntary Ventilation (MVV), one of the components of Pulmonary Function Testing (PFT), has multiple uses. Various factors including the inspiratory muscle strength (IMS) influence its magnitude. Our aim was t...Maximum Voluntary Ventilation (MVV), one of the components of Pulmonary Function Testing (PFT), has multiple uses. Various factors including the inspiratory muscle strength (IMS) influence its magnitude. Our aim was to quantify the IMS indirectly using an economical and non invasive bedside assessment tool, determine its association with MVV and then develop a predictive equation for MVV. 41 healthy non-athletic physical therapy students participated in the study. IMS measurement was performed with a sphygmomanometer. Average of the three net deflections in sphygmomanometer following deepest possible breaths was taken as indirect measurement of IMS in mm of Hg. MVV was measured according to ATS guidelines using a spirometer. Results from the data analysis revealed a significant correlation between IMS and MVV(r = 0.83, p < 0.001) and the coefficient of determination = 0.68. So, we developed a regression equation: Y = 1.9669(X) + 49.838 with SEE: 13.02L/min and ANOVA for the equation was (F=68.9, p < 0.001). Hence, it can be concluded that a strong correlation between the indirect IMS and MVV was established and a predictive equation to estimate MVV was developed. This equation proved to have a high predictive value with a small error of estimation. This indicates that the value of the indirect IMS measurement obtained using the sphygmomanometer can be used to estimate MVV in normal healthy individuals without the use of a conventional spirometer.展开更多
目的:系统评估可变阻力训练对运动员下肢爆发力表现的训练干预效果,为在训练实践中科学运用可变阻力训练提供证据支持。方法:通过中国知网(CNKI)、PubMed、Web of Science等数据库检索文献,利用Brughelli改进后的质量评分表评价文献质量...目的:系统评估可变阻力训练对运动员下肢爆发力表现的训练干预效果,为在训练实践中科学运用可变阻力训练提供证据支持。方法:通过中国知网(CNKI)、PubMed、Web of Science等数据库检索文献,利用Brughelli改进后的质量评分表评价文献质量,应用ReviewManager5.4软件分别进行数据合并、绘制森林图、异质分析以及Meta回归。结果:共纳入14篇文献,在最大力量(SMD=5.93,95%CI为[3.29,8.57])的提高上,可变阻力训练相比于传统抗阻训练能更显著地增强运动员的最大力量(P<0.0001);可变阻力训练对运动员的立定跳远能力(SMD=0.03,95%CI为[0.02,0.04])的影响也有非常显著的差异(P<0.0001);可变阻力训练对反向纵跳(SMD=3.58,95%CI为[1.89,5.27],P<0.0001)的提高差异同样非常显著,但对30 m冲刺跑成绩的提高(SMD=-0.02,95%CI为[-0.04,0.00])并无显著差异(P=0.08)。结论:相比于传统抗阻训练,6~12周的可变阻力训练能够更有效地提升运动员的下肢最大力量表现、立定跳远及反向纵跳成绩,且适宜的可变阻力负荷为20%~30%1RM。展开更多
为了科学确定海洋油气井圈闭压力最大许可值,基于南海某海洋油气井固井工况,在研究API RP 90和ISO/TS 16530-2等国际标准的基础上,结合其井身结构、完井工具及水泥环封隔情况,建立了一套综合考虑井口装置、固完井工具、油套管强度及水...为了科学确定海洋油气井圈闭压力最大许可值,基于南海某海洋油气井固井工况,在研究API RP 90和ISO/TS 16530-2等国际标准的基础上,结合其井身结构、完井工具及水泥环封隔情况,建立了一套综合考虑井口装置、固完井工具、油套管强度及水泥环封隔能力的海洋油气井圈闭压力最大许可值确定方法,基于室内实验开展了某海洋油气井固井水泥环封隔能力测试,并结合实例井开展了环空圈闭压力最大许可值计算,分析了本方法的特点,为科学确定海洋油气井圈闭压力最大许可值及设计环空带压管控措施提供了依据。展开更多
基金the financial support from National Natural Science Foundation of China (Grants Nos.12325203,91963117,and 11921002)。
文摘Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with nanosized Schwarz crystals exhibited high strength and excellent thermal stability.However,the grainsize effect and associated deformation mechanisms of Schwarz nanocrystals remain unknown.Here,we performed large-scale atomistic simulations to investigate the deformation behaviors and grain-size effect of nanocrystalline Cu with Schwarz crystals.Our simulations showed that similar to regular nanocrystals,Schwarz nanocrystals exhibit a strengthening-softening transition with decreasing grain size.The critical grain size in Schwarz nanocrystals is smaller than that in regular nanocrystals,leading to a maximum strength higher than that of regular nanocrystals.Our simulations revealed that the softening in Schwarz nanocrystals mainly originates from TB migration(or detwinning)and annihilation of GBs,rather than GB-mediated processes(including GB migration,sliding and diffusion)dominating the softening in regular nanocrystals.Quantitative analyses of simulation data further showed that compared with those in regular nanocrystals,the GB-mediated processes in Schwarz nanocrystals are suppressed,which is related to the low volume fraction of amorphous-like GBs and constraints of TB networks.The smaller critical grain size arises from the suppression of GB-mediated processes.
文摘Maximum Voluntary Ventilation (MVV), one of the components of Pulmonary Function Testing (PFT), has multiple uses. Various factors including the inspiratory muscle strength (IMS) influence its magnitude. Our aim was to quantify the IMS indirectly using an economical and non invasive bedside assessment tool, determine its association with MVV and then develop a predictive equation for MVV. 41 healthy non-athletic physical therapy students participated in the study. IMS measurement was performed with a sphygmomanometer. Average of the three net deflections in sphygmomanometer following deepest possible breaths was taken as indirect measurement of IMS in mm of Hg. MVV was measured according to ATS guidelines using a spirometer. Results from the data analysis revealed a significant correlation between IMS and MVV(r = 0.83, p < 0.001) and the coefficient of determination = 0.68. So, we developed a regression equation: Y = 1.9669(X) + 49.838 with SEE: 13.02L/min and ANOVA for the equation was (F=68.9, p < 0.001). Hence, it can be concluded that a strong correlation between the indirect IMS and MVV was established and a predictive equation to estimate MVV was developed. This equation proved to have a high predictive value with a small error of estimation. This indicates that the value of the indirect IMS measurement obtained using the sphygmomanometer can be used to estimate MVV in normal healthy individuals without the use of a conventional spirometer.
文摘目的:系统评估可变阻力训练对运动员下肢爆发力表现的训练干预效果,为在训练实践中科学运用可变阻力训练提供证据支持。方法:通过中国知网(CNKI)、PubMed、Web of Science等数据库检索文献,利用Brughelli改进后的质量评分表评价文献质量,应用ReviewManager5.4软件分别进行数据合并、绘制森林图、异质分析以及Meta回归。结果:共纳入14篇文献,在最大力量(SMD=5.93,95%CI为[3.29,8.57])的提高上,可变阻力训练相比于传统抗阻训练能更显著地增强运动员的最大力量(P<0.0001);可变阻力训练对运动员的立定跳远能力(SMD=0.03,95%CI为[0.02,0.04])的影响也有非常显著的差异(P<0.0001);可变阻力训练对反向纵跳(SMD=3.58,95%CI为[1.89,5.27],P<0.0001)的提高差异同样非常显著,但对30 m冲刺跑成绩的提高(SMD=-0.02,95%CI为[-0.04,0.00])并无显著差异(P=0.08)。结论:相比于传统抗阻训练,6~12周的可变阻力训练能够更有效地提升运动员的下肢最大力量表现、立定跳远及反向纵跳成绩,且适宜的可变阻力负荷为20%~30%1RM。
文摘为了科学确定海洋油气井圈闭压力最大许可值,基于南海某海洋油气井固井工况,在研究API RP 90和ISO/TS 16530-2等国际标准的基础上,结合其井身结构、完井工具及水泥环封隔情况,建立了一套综合考虑井口装置、固完井工具、油套管强度及水泥环封隔能力的海洋油气井圈闭压力最大许可值确定方法,基于室内实验开展了某海洋油气井固井水泥环封隔能力测试,并结合实例井开展了环空圈闭压力最大许可值计算,分析了本方法的特点,为科学确定海洋油气井圈闭压力最大许可值及设计环空带压管控措施提供了依据。
