The supercavitation has attracted a growing interest because of its potential for high-speed vehicle maneuvering and drag reduction. To better understand the reverse flow characteristics of a water-vapor mixture in su...The supercavitation has attracted a growing interest because of its potential for high-speed vehicle maneuvering and drag reduction. To better understand the reverse flow characteristics of a water-vapor mixture in supercavitating flows around a hydrofoil, a numerical simulation is conducted using a unified supercavitation model, which combines a modified RNG k-~ turbulence model and a cavitation one. By comparing the related experimental results, the reverse motion of the water-vapor mixture is found in the cavitation area in all supercavitation stages. The inverse pressure gradient leads to reverse pressure fluctuations in the cavity, followed by the reverse motion of the water-vapor two-phase interface. Compared with the water-vapor mixture area at the back of the cavity, the pressure in the vapor area is inversely and slowly reduced, a higher-pressure gradient occurs near the cavity boundary.展开更多
Conventional rotary actuators mainly rely on electric or hydraulic/pneumatic motors to convert energy into mechanical motion,making them one of the most widely used actuation methods in industrial manufacturing,roboti...Conventional rotary actuators mainly rely on electric or hydraulic/pneumatic motors to convert energy into mechanical motion,making them one of the most widely used actuation methods in industrial manufacturing,robotics,and automation control.However,these traditional actuators often suffer from limitations in operability and applicability due to their complex structures,bulky systems,high energy consumption,and severe mechanical wear.Liquid crystal elastomers(LCEs)have been increasingly used for programmable actuation applications,owing to their ability to undergo large,reversible,and anisotropic deformations in response to external stimuli.In this work,we propose a compact flexible rotary joint(FRJ)based on LCEs.To describe the thermo-mechanical coupled behaviors,a constitutive model is developed and further implemented for finite element analysis(FEA).Through combining experiments and simulations,we quantify the dynamic rotational behavior of the rotor rotating relative to the base driven by the induced strain of the FRJ under cyclic thermal stimuli.The proposed rotary joint features a simple structure,lightweight design,low energy consumption,and easy control.These characteristics endow it with significant potential for miniaturization and integration in the field of soft actuation and robotics.展开更多
The current-induced magnetic switching is studied in Co/Cu/Co nanopillar with an in-plane magnetization traversed under the perpendicular-to-plane external field.Magnetization switching is found to take place when the...The current-induced magnetic switching is studied in Co/Cu/Co nanopillar with an in-plane magnetization traversed under the perpendicular-to-plane external field.Magnetization switching is found to take place when the current density exceeds a threshold.By analyzing precessional trajectories,evolutions of domain walls and magnetization switching times under the perpendicular magnetic field,there are two different magnetization switching modes:nucleation and domain wall motion reversal;uniform magnetization reversal.The first mode occurs at lower current density,which is realized by the formation of the reversal nucleus and domain wall motion;while the second mode occurs through complete magnetization reversal at higher current density.Furthermore,the switching time reduces as the spin-polarized current density increases,which can also be grouped into two reversal modes.展开更多
基金Project supported by the National Natural Science Foun-dation of China(Grant No.50679001)
文摘The supercavitation has attracted a growing interest because of its potential for high-speed vehicle maneuvering and drag reduction. To better understand the reverse flow characteristics of a water-vapor mixture in supercavitating flows around a hydrofoil, a numerical simulation is conducted using a unified supercavitation model, which combines a modified RNG k-~ turbulence model and a cavitation one. By comparing the related experimental results, the reverse motion of the water-vapor mixture is found in the cavitation area in all supercavitation stages. The inverse pressure gradient leads to reverse pressure fluctuations in the cavity, followed by the reverse motion of the water-vapor two-phase interface. Compared with the water-vapor mixture area at the back of the cavity, the pressure in the vapor area is inversely and slowly reduced, a higher-pressure gradient occurs near the cavity boundary.
基金Project supported by the National Natural Science Foundation of China(Nos.12125205,12321002,12132014,and 12072316)the Key Research and Development Program of Zhejiang Province of China(No.2021C01183)。
文摘Conventional rotary actuators mainly rely on electric or hydraulic/pneumatic motors to convert energy into mechanical motion,making them one of the most widely used actuation methods in industrial manufacturing,robotics,and automation control.However,these traditional actuators often suffer from limitations in operability and applicability due to their complex structures,bulky systems,high energy consumption,and severe mechanical wear.Liquid crystal elastomers(LCEs)have been increasingly used for programmable actuation applications,owing to their ability to undergo large,reversible,and anisotropic deformations in response to external stimuli.In this work,we propose a compact flexible rotary joint(FRJ)based on LCEs.To describe the thermo-mechanical coupled behaviors,a constitutive model is developed and further implemented for finite element analysis(FEA).Through combining experiments and simulations,we quantify the dynamic rotational behavior of the rotor rotating relative to the base driven by the induced strain of the FRJ under cyclic thermal stimuli.The proposed rotary joint features a simple structure,lightweight design,low energy consumption,and easy control.These characteristics endow it with significant potential for miniaturization and integration in the field of soft actuation and robotics.
基金supported by the National Natural Science Foundation of China (Grant No. 5042810)
文摘The current-induced magnetic switching is studied in Co/Cu/Co nanopillar with an in-plane magnetization traversed under the perpendicular-to-plane external field.Magnetization switching is found to take place when the current density exceeds a threshold.By analyzing precessional trajectories,evolutions of domain walls and magnetization switching times under the perpendicular magnetic field,there are two different magnetization switching modes:nucleation and domain wall motion reversal;uniform magnetization reversal.The first mode occurs at lower current density,which is realized by the formation of the reversal nucleus and domain wall motion;while the second mode occurs through complete magnetization reversal at higher current density.Furthermore,the switching time reduces as the spin-polarized current density increases,which can also be grouped into two reversal modes.
