目的 探讨经颅直流电刺激(transcranial direct current stimulation, t DCS)对纵跳(counter movement jump, CMJ)能力的影响。方法 21名普通大学生(普通大学生组)和17名大学生运动员(运动员组)随机接受脑前额叶区2 m A、20 min的真刺激...目的 探讨经颅直流电刺激(transcranial direct current stimulation, t DCS)对纵跳(counter movement jump, CMJ)能力的影响。方法 21名普通大学生(普通大学生组)和17名大学生运动员(运动员组)随机接受脑前额叶区2 m A、20 min的真刺激(anodic t DCS,a-t DCS)或假刺激(sham t DCS,s-t DCS),采集刺激后即刻及10、20、30、40 min时间点的CMJ运动表现数据。对受试者不同时间点的跳跃高度、加速度、峰值功率、峰值垂直地面反作用力(vertical ground reaction force, v GRF)进行双因素重复测量方差分析(刺激类型×测试时间点)。结果 运动员组,受试者跳跃高度和峰值v GRF的刺激类型×测试时间点交互作用显著,简单效应分析发现a-t DCS后5个时间点的测试数据均显著优于基准值及s-t DCS后(P<0.05);加速度和峰值功率的刺激类型主效应显著。普通大学生组,受试者加速度、峰值功率、峰值v GRF的刺激类型×测试时间点交互作用显著,简单效应分析发现a-t DCS后5个时间点的测试数据均显著优于基准值及s-t DCS后(P<0.05);跳跃高度的刺激类型主效应显著。结论 脑前额叶区a-t DCS能显著改善CMJ完成过程中的多项指标且具有一定的持续性,可以考虑将其作为增强纵跳能力的一种手段。展开更多
Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given qua...Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given quadratic performance criteria. First, a control law is established for jump systems based on pontryagin’s minimum principle and it can be constructed through numerical solution of iterative equations. The aim of this control strategy is to obtain an optimal control which can minimize the cost function under the worst disturbance at every sampling time. Due to the difficulty of the assurance of stability, then the above mentioned approach is improved by determining terminal weighting matrix which satisfies cost monotonicity condition. The control move which is calculated by using this type of terminal weighting matrix as boundary condition naturally guarantees the mean square stability of the closed-loop system. A sufficient condition for the existence of the terminal weighting matrix is presented in linear matrix inequality （LMI） form which can be solved efficiently by available software toolbox. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.展开更多
Acoustic Doppler current profiles and water density profiles were measured over the 280 m deep continental slope of the Gulf of California to elucidate the bathymetric effect on zooplankton distribution. These measure...Acoustic Doppler current profiles and water density profiles were measured over the 280 m deep continental slope of the Gulf of California to elucidate the bathymetric effect on zooplankton distribution. These measurements were combined with water velocity and density simulations from the Regional Ocean Model System with and without the influence of Coriolis acceleration. The data revealed an acceleration of the near-bottom flow as it moved toward increasing depths. This acceleration was produced by the adjustment of the isopycnals to bathymetry (hydraulic jump). Zooplankton patches moved downward at the continental slope and then upward, thus exhibiting wave patterns. Model outputs without the effect of Coriolis acceleration also suggested that vertical zooplankton concentration followed a wave pattern. However, when Coriolis acceleration was added to the momentum equation, the horizontal zooplankton distribution was enhanced, which reduced the vertical zooplankton concentration observed over irregular bathymetries. Coriolis acceleration was responsible for horizontal dispersal of up to 20% of the total zooplankton concentration located over the wave trough.展开更多
文摘目的 探讨经颅直流电刺激(transcranial direct current stimulation, t DCS)对纵跳(counter movement jump, CMJ)能力的影响。方法 21名普通大学生(普通大学生组)和17名大学生运动员(运动员组)随机接受脑前额叶区2 m A、20 min的真刺激(anodic t DCS,a-t DCS)或假刺激(sham t DCS,s-t DCS),采集刺激后即刻及10、20、30、40 min时间点的CMJ运动表现数据。对受试者不同时间点的跳跃高度、加速度、峰值功率、峰值垂直地面反作用力(vertical ground reaction force, v GRF)进行双因素重复测量方差分析(刺激类型×测试时间点)。结果 运动员组,受试者跳跃高度和峰值v GRF的刺激类型×测试时间点交互作用显著,简单效应分析发现a-t DCS后5个时间点的测试数据均显著优于基准值及s-t DCS后(P<0.05);加速度和峰值功率的刺激类型主效应显著。普通大学生组,受试者加速度、峰值功率、峰值v GRF的刺激类型×测试时间点交互作用显著,简单效应分析发现a-t DCS后5个时间点的测试数据均显著优于基准值及s-t DCS后(P<0.05);跳跃高度的刺激类型主效应显著。结论 脑前额叶区a-t DCS能显著改善CMJ完成过程中的多项指标且具有一定的持续性,可以考虑将其作为增强纵跳能力的一种手段。
基金supported by the National Natural Science Foundation of China (60974001)Jiangsu "Six Personnel Peak" Talent-Funded Projects
文摘Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given quadratic performance criteria. First, a control law is established for jump systems based on pontryagin’s minimum principle and it can be constructed through numerical solution of iterative equations. The aim of this control strategy is to obtain an optimal control which can minimize the cost function under the worst disturbance at every sampling time. Due to the difficulty of the assurance of stability, then the above mentioned approach is improved by determining terminal weighting matrix which satisfies cost monotonicity condition. The control move which is calculated by using this type of terminal weighting matrix as boundary condition naturally guarantees the mean square stability of the closed-loop system. A sufficient condition for the existence of the terminal weighting matrix is presented in linear matrix inequality （LMI） form which can be solved efficiently by available software toolbox. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.
文摘Acoustic Doppler current profiles and water density profiles were measured over the 280 m deep continental slope of the Gulf of California to elucidate the bathymetric effect on zooplankton distribution. These measurements were combined with water velocity and density simulations from the Regional Ocean Model System with and without the influence of Coriolis acceleration. The data revealed an acceleration of the near-bottom flow as it moved toward increasing depths. This acceleration was produced by the adjustment of the isopycnals to bathymetry (hydraulic jump). Zooplankton patches moved downward at the continental slope and then upward, thus exhibiting wave patterns. Model outputs without the effect of Coriolis acceleration also suggested that vertical zooplankton concentration followed a wave pattern. However, when Coriolis acceleration was added to the momentum equation, the horizontal zooplankton distribution was enhanced, which reduced the vertical zooplankton concentration observed over irregular bathymetries. Coriolis acceleration was responsible for horizontal dispersal of up to 20% of the total zooplankton concentration located over the wave trough.
