The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impac...The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impact system. To design anti-impact structures of the thin-wall cylindrical tubes with this new method, the cost of the experiment can be considerably reduced. The feasibility and validity of this method are demonstrated by a dropping hammer experiment. In addition, this paper deals with the influence of constrained damping layers on the anti-impact capability and energy-absorption of thin-wall cylindrical tubes. Results show that the constrained damping layers make the energy-absorption and the anti-impact capability increased comparing with the naked tubes; the thickness of the damping layer should be restricted in a range, or else the anti-impact capability will decrease with the increase of the damping layer thickness; for the constrained layer, the anti-impact capability will increase with the augment of its thickness.展开更多
Fragment mass distributions of quasifission induced by 238U on 160, 26Mg, 32S, 35C1, 40Ca and 65Zn targets at several bombarding energies have been calculated with the two-step model. The experimental data are reprodu...Fragment mass distributions of quasifission induced by 238U on 160, 26Mg, 32S, 35C1, 40Ca and 65Zn targets at several bombarding energies have been calculated with the two-step model. The experimental data are reproduced consistently, and the mechanism of the distribution shape is also analyzed by investigating the different incident channels.展开更多
Objective:To determine the association between tea consumption and the risk of stroke. Methods:We searched the PubMed database from January 1966 to March 2012 and reviewed reference lists of retrieved articles to iden...Objective:To determine the association between tea consumption and the risk of stroke. Methods:We searched the PubMed database from January 1966 to March 2012 and reviewed reference lists of retrieved articles to identify relevant studies. Studies were included if they reported relative risks (RRs) and corresponding 95% confidence intervals (CIs) of stroke with respect to three or more categories of tea consumption. A random-effects model was used to combine the study-specific risk estimates. Results:Fourteen studies, consisting of 513 804 participants with a median follow-up of 11.5 years, were included in this meta-analysis. We observed a modest but statistically significant inverse association between tea consumption and risk of stroke. An increase of three cups/d in tea consumption was associated with a 13% decreased risk of stroke (RR 0.87; 95% CI, 0.81-0.94). The decreased risk of stroke with tea consumption was consistent among most subgroups. Based on the three studies that provided results for stroke subtypes, tea consumption was also inversely associated with the risk of ischemic stroke (RR 0.76; 95% CI, 0.69-0.84), but not cerebral hemorrhage (RR 0.96; 95% CI, 0.82-1.11) or subarachnoid hemorrhage (RR 0.81; 95% CI, 0.57-1.16). Conclusions:Tea consumption is associated with a decreased risk of stroke, particularly ischemic stroke. More well-designed, rigorously conducted studies are needed in order to make confident conclusions about the association between tea consumption and stroke subtypes.展开更多
文摘The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impact system. To design anti-impact structures of the thin-wall cylindrical tubes with this new method, the cost of the experiment can be considerably reduced. The feasibility and validity of this method are demonstrated by a dropping hammer experiment. In addition, this paper deals with the influence of constrained damping layers on the anti-impact capability and energy-absorption of thin-wall cylindrical tubes. Results show that the constrained damping layers make the energy-absorption and the anti-impact capability increased comparing with the naked tubes; the thickness of the damping layer should be restricted in a range, or else the anti-impact capability will decrease with the increase of the damping layer thickness; for the constrained layer, the anti-impact capability will increase with the augment of its thickness.
基金supported by the National Natural Science Foundation of China(Grant Nos.11275068,11375062,11305059 and 10979024)the C3S2 Computing Center in Huzhou Teachers College
文摘Fragment mass distributions of quasifission induced by 238U on 160, 26Mg, 32S, 35C1, 40Ca and 65Zn targets at several bombarding energies have been calculated with the two-step model. The experimental data are reproduced consistently, and the mechanism of the distribution shape is also analyzed by investigating the different incident channels.
基金Project (No. 2007C13058) supported by the Science and Technology Key Project of Zhejiang Province, China
文摘Objective:To determine the association between tea consumption and the risk of stroke. Methods:We searched the PubMed database from January 1966 to March 2012 and reviewed reference lists of retrieved articles to identify relevant studies. Studies were included if they reported relative risks (RRs) and corresponding 95% confidence intervals (CIs) of stroke with respect to three or more categories of tea consumption. A random-effects model was used to combine the study-specific risk estimates. Results:Fourteen studies, consisting of 513 804 participants with a median follow-up of 11.5 years, were included in this meta-analysis. We observed a modest but statistically significant inverse association between tea consumption and risk of stroke. An increase of three cups/d in tea consumption was associated with a 13% decreased risk of stroke (RR 0.87; 95% CI, 0.81-0.94). The decreased risk of stroke with tea consumption was consistent among most subgroups. Based on the three studies that provided results for stroke subtypes, tea consumption was also inversely associated with the risk of ischemic stroke (RR 0.76; 95% CI, 0.69-0.84), but not cerebral hemorrhage (RR 0.96; 95% CI, 0.82-1.11) or subarachnoid hemorrhage (RR 0.81; 95% CI, 0.57-1.16). Conclusions:Tea consumption is associated with a decreased risk of stroke, particularly ischemic stroke. More well-designed, rigorously conducted studies are needed in order to make confident conclusions about the association between tea consumption and stroke subtypes.
