Background: This preliminary study examined the effects of an 8-week supervised reactive balance training program on reaction time (RT) and foot speed, static balance and balance confidence in healthy older adults ...Background: This preliminary study examined the effects of an 8-week supervised reactive balance training program on reaction time (RT) and foot speed, static balance and balance confidence in healthy older adults compared to an exercise control group. Methods: Twenty-five older adults were randomly assigned to a reactive balance training group (QuickBoard; n = 12; 71.0 ± 8.6 years) or a stationary cycling group (control; n = 13; 70.2 ± 6.0 years). Both groups were tested for foot RT foot speed, static balance, and balance confidence at baseline, 4-week, 8-week, and 4-week follow-up. Results: Results indicated significant improvements in QuickBoard foot RT and speed in both groups with greater improvements in the QuickBoard group. However, no group difference was found in static balance performance. Conclusion: Although the improvements in RT and foot speed may be beneficial for fall and trip prevention, the implications of the current findings for trio avoidance and oerformance of daily tasks are unclear.展开更多
Buckling could be induced when shallow arches were subjected to vertical step loads. In-plane static and dynamic buckling of shallow pin-ended parabolic arches with a horizontal cable was investigated. Based on the eq...Buckling could be induced when shallow arches were subjected to vertical step loads. In-plane static and dynamic buckling of shallow pin-ended parabolic arches with a horizontal cable was investigated. Based on the equations of motion derived from Hamilton's principle, nonlinear equilibrium equations and static buckling equilibrium equations were deduced. Through the pseudo-static analysis, approximate solutions to the lower and upper dynamic buckling loads under step loads were obtained, for shallow parabolic arches. The results show that dynamic buckling and snap-through buckling are impossible when modified slenderness ratio λ<λc and λ>λs, where λc and λs denote critical slenderness ratios of bucking and snap-through buckling, respectively; effects of the stiffness of the horizontal cable on the dynamic buckling are significant; and the dynamic buckling loads under a equivalent central concentrated step load are lower than the loads under a distributed load appreciably.展开更多
In this paper,we investigate the stability of quark stars with four different types of inner matter configurations;isotropic,charged isotropic,anisotropic and charged anisotropic by using the concept of cracking.For t...In this paper,we investigate the stability of quark stars with four different types of inner matter configurations;isotropic,charged isotropic,anisotropic and charged anisotropic by using the concept of cracking.For this purpose,we have applied local density perturbations technique to the hydrostatic equilibrium equation as well as on physical parameters involved in the model.We conclude that quark stars become potentially unstable when inner matter configuration is changed and electromagnetic field is applied.展开更多
文摘Background: This preliminary study examined the effects of an 8-week supervised reactive balance training program on reaction time (RT) and foot speed, static balance and balance confidence in healthy older adults compared to an exercise control group. Methods: Twenty-five older adults were randomly assigned to a reactive balance training group (QuickBoard; n = 12; 71.0 ± 8.6 years) or a stationary cycling group (control; n = 13; 70.2 ± 6.0 years). Both groups were tested for foot RT foot speed, static balance, and balance confidence at baseline, 4-week, 8-week, and 4-week follow-up. Results: Results indicated significant improvements in QuickBoard foot RT and speed in both groups with greater improvements in the QuickBoard group. However, no group difference was found in static balance performance. Conclusion: Although the improvements in RT and foot speed may be beneficial for fall and trip prevention, the implications of the current findings for trio avoidance and oerformance of daily tasks are unclear.
基金Project (50478075) supported by the National Natural Science Foundation of China
文摘Buckling could be induced when shallow arches were subjected to vertical step loads. In-plane static and dynamic buckling of shallow pin-ended parabolic arches with a horizontal cable was investigated. Based on the equations of motion derived from Hamilton's principle, nonlinear equilibrium equations and static buckling equilibrium equations were deduced. Through the pseudo-static analysis, approximate solutions to the lower and upper dynamic buckling loads under step loads were obtained, for shallow parabolic arches. The results show that dynamic buckling and snap-through buckling are impossible when modified slenderness ratio λ<λc and λ>λs, where λc and λs denote critical slenderness ratios of bucking and snap-through buckling, respectively; effects of the stiffness of the horizontal cable on the dynamic buckling are significant; and the dynamic buckling loads under a equivalent central concentrated step load are lower than the loads under a distributed load appreciably.
文摘In this paper,we investigate the stability of quark stars with four different types of inner matter configurations;isotropic,charged isotropic,anisotropic and charged anisotropic by using the concept of cracking.For this purpose,we have applied local density perturbations technique to the hydrostatic equilibrium equation as well as on physical parameters involved in the model.We conclude that quark stars become potentially unstable when inner matter configuration is changed and electromagnetic field is applied.