We study the balance problem caused by forward leaning of the wearer's upper body during rehabilitation training with a lower limb rehabilitation exoskeleton. The instantaneous capture point is obtained by modelin...We study the balance problem caused by forward leaning of the wearer's upper body during rehabilitation training with a lower limb rehabilitation exoskeleton. The instantaneous capture point is obtained by modeling the human-exoskeleton system and using the capture point theory. By comparing the stability region with instantaneous capture points of different gait phases, the balancing characteristics of different gait phases and changes to the equilibrium state in the gait process are analyzed. Based on a model of the human-exoskeleton system and the condition of balance of different phases, a trajectory correction strategy is pro-posed for the instability of the human-exoskeleton system caused by forward leaning of the wearer's upper body. Finally, the reliability of the trajectory correction strategy is verified by carrying out experiments on the Zhejiang University Lower Extremity Exoskeleton. The proposed trajectory correction strategy can respond to forward leaning of the upper body in a timely manner. Additionally, in the process of the center of gravity transferred from a double-support phase to a single-support phase, the ratio of gait cycle to zero moment point transfer is reduced correspondingly, and the gait stability is improved.展开更多
Electron capture plays a pivotal role in the complex dynamics of supernova explosion.The electron capture rates on 55Co have been calculated by means of the proton-neutron quasiparticle random phase approximation (pn-...Electron capture plays a pivotal role in the complex dynamics of supernova explosion.The electron capture rates on 55Co have been calculated by means of the proton-neutron quasiparticle random phase approximation (pn-QRPA) theory. We have calculated these stellar electron capture rates for temperatures (in 109 K) 0. 01, 0. 1, 0. 2, 0.4, 0. 7, 1, 1.5, 2, 3, 5, 10, 30 and densities between 10 g · cm-3 and 1011 g · cm-3. Here we report the differences in electron capture rates with the rates of large shell model calculations.展开更多
Ideal proportional navigation （IPN） is a natural choice for exoatmospheric interception for its mighty capture capability and ease of implementation. The closed-form solution of two- dimensional ideal proportional n...Ideal proportional navigation （IPN） is a natural choice for exoatmospheric interception for its mighty capture capability and ease of implementation. The closed-form solution of two- dimensional ideal proportional navigation was conducted in previous public literature, whereas the practical interception happens in the three-dimensional space. A novel set of relative dynamic equations is adopted in this paper, which is with the advantage of decoupling relative motion in the instantaneous rotation plane of the line of sight from the rotation of this plane. The dimension-reduced IPN is constructed in this instantaneous plane, which functions as a three-dimensional guidance law. The trajectory features of dimension-reduced IPN are explored, and the capture regions of dimension-reduced IPN with limited acceleration against nonmaneuvering and maneuvering targets are analyzed by using phase plane method. It is proved that the capture capability of IPN is much stronger than true proportional navigation （TPN）, no matter the target maneuvers or not. Finally, simulation results indicate that IPN is more effective than TPN in exoatmospheric interception scenarios.展开更多
基金Project supported by the National Natural Science Foundation of China(No.51805469)。
文摘We study the balance problem caused by forward leaning of the wearer's upper body during rehabilitation training with a lower limb rehabilitation exoskeleton. The instantaneous capture point is obtained by modeling the human-exoskeleton system and using the capture point theory. By comparing the stability region with instantaneous capture points of different gait phases, the balancing characteristics of different gait phases and changes to the equilibrium state in the gait process are analyzed. Based on a model of the human-exoskeleton system and the condition of balance of different phases, a trajectory correction strategy is pro-posed for the instability of the human-exoskeleton system caused by forward leaning of the wearer's upper body. Finally, the reliability of the trajectory correction strategy is verified by carrying out experiments on the Zhejiang University Lower Extremity Exoskeleton. The proposed trajectory correction strategy can respond to forward leaning of the upper body in a timely manner. Additionally, in the process of the center of gravity transferred from a double-support phase to a single-support phase, the ratio of gait cycle to zero moment point transfer is reduced correspondingly, and the gait stability is improved.
文摘Electron capture plays a pivotal role in the complex dynamics of supernova explosion.The electron capture rates on 55Co have been calculated by means of the proton-neutron quasiparticle random phase approximation (pn-QRPA) theory. We have calculated these stellar electron capture rates for temperatures (in 109 K) 0. 01, 0. 1, 0. 2, 0.4, 0. 7, 1, 1.5, 2, 3, 5, 10, 30 and densities between 10 g · cm-3 and 1011 g · cm-3. Here we report the differences in electron capture rates with the rates of large shell model calculations.
基金co-supported by the National Science Foundation of China(No.11222215)the National Basic Research Program of China(No.2013CB733100)
文摘Ideal proportional navigation （IPN） is a natural choice for exoatmospheric interception for its mighty capture capability and ease of implementation. The closed-form solution of two- dimensional ideal proportional navigation was conducted in previous public literature, whereas the practical interception happens in the three-dimensional space. A novel set of relative dynamic equations is adopted in this paper, which is with the advantage of decoupling relative motion in the instantaneous rotation plane of the line of sight from the rotation of this plane. The dimension-reduced IPN is constructed in this instantaneous plane, which functions as a three-dimensional guidance law. The trajectory features of dimension-reduced IPN are explored, and the capture regions of dimension-reduced IPN with limited acceleration against nonmaneuvering and maneuvering targets are analyzed by using phase plane method. It is proved that the capture capability of IPN is much stronger than true proportional navigation （TPN）, no matter the target maneuvers or not. Finally, simulation results indicate that IPN is more effective than TPN in exoatmospheric interception scenarios.
