The thermally and wind-driven ocean circulation is a complicated natural phenomenon in the atmospheric physics. Hence we need to reduce it using basic models and solve the models using approximate methods. A non-linea...The thermally and wind-driven ocean circulation is a complicated natural phenomenon in the atmospheric physics. Hence we need to reduce it using basic models and solve the models using approximate methods. A non-linear model of the thermally and wind-driven ocean circulation is used in this paper. The results show that the zero solution of the linear equation is a stable focus point, which is the path curve trend origin point as time (t) trend to infinity. By using the homotopic mapping perturbation method, the exact solution of the model is obtained. The homotopic mapping perturbation method is an analytic solving method, so the obtained solution can be used for analytic operating sequentially. And then we can also obtain the diversified qualitative and quantitative behaviors for corresponding physical quantities.展开更多
A spherical robot based on a novel double ballast masses principle is developed for military reconnaissance and unknown environment exploration. The robot is driven by two DC motors, each of which drives one ballast m...A spherical robot based on a novel double ballast masses principle is developed for military reconnaissance and unknown environment exploration. The robot is driven by two DC motors, each of which drives one ballast mass, and the two ballast masses are placed symmetrically on the major axis. Compared with the traditional ballast mass principle, the robot has featured high speed, the ability of slope climbing and obstacle overcoming in linear motion. The robot has two inputs and three DOF, which is a nonholonomic and underactuated system. The dynamic model of the robot is constructed, and the linear motion performance of robot in theory is proved by Adams simulation. The control system is briefly introduced, and the performance of the prototype is tested by experiments at last.展开更多
The effect of plasma actuator that uses saw-tooth or sine-wave shape electrodes on boundary layer flows is experimentally investigated.The measurement results are compared with a corresponding standard configuration (...The effect of plasma actuator that uses saw-tooth or sine-wave shape electrodes on boundary layer flows is experimentally investigated.The measurement results are compared with a corresponding standard configuration (conventional design using two rectangular strip electrodes)-the actuator that produces a nearly two-dimensional horizontal wall jet upon actuation.PIV measurements are used to characterize the actuators in a quiescent chamber.Operating in a steady manner,the new actuators result in the formation of streamwise and spanwise vortices.That is to say,the new actuators render the plasma actuators inducing three-dimensional variations in the shear layer,offering significant flexibility in flow control.The affected flowfield with the new actuators is significantly larger than that with the conventional linear actuators.While the conventional linear actuators affect primarily the boundary layer flow on a scale of about 1 cm above the wall,the new actuators affect the near wall region at a significantly larger scale.This new design broadens the applicability and enhances the flow control effects and it is potentially a more efficient flow control device.展开更多
The current-driven domain wall motion was investigated on permalloy nanowires with different dimensions by micromagnetic simulations.The critical current density increased with the reduction in both the width and thic...The current-driven domain wall motion was investigated on permalloy nanowires with different dimensions by micromagnetic simulations.The critical current density increased with the reduction in both the width and thickness of nanowires because of the enhanced hard-axis anisotropy.At a thickness of 5 nm,the critical current density decreased with the reduction of the nanowire width because of the reduced domain wall width.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.40876010)Main Direction Program of Knowledge Innovation Programs of the Chinese Academy of Sciences(No.KZCX2-YW-Q03-08)+3 种基金R & D Special Fund for Public Welfare Industry(meteorology)(No.GYHY200806010)LASG State Key Laboratory Special FundFoundation of Shanghai Municipal Education Commission(No.E03004)Natural Science Foundation of Zhejiang Province(No.Y6090164)
文摘The thermally and wind-driven ocean circulation is a complicated natural phenomenon in the atmospheric physics. Hence we need to reduce it using basic models and solve the models using approximate methods. A non-linear model of the thermally and wind-driven ocean circulation is used in this paper. The results show that the zero solution of the linear equation is a stable focus point, which is the path curve trend origin point as time (t) trend to infinity. By using the homotopic mapping perturbation method, the exact solution of the model is obtained. The homotopic mapping perturbation method is an analytic solving method, so the obtained solution can be used for analytic operating sequentially. And then we can also obtain the diversified qualitative and quantitative behaviors for corresponding physical quantities.
文摘A spherical robot based on a novel double ballast masses principle is developed for military reconnaissance and unknown environment exploration. The robot is driven by two DC motors, each of which drives one ballast mass, and the two ballast masses are placed symmetrically on the major axis. Compared with the traditional ballast mass principle, the robot has featured high speed, the ability of slope climbing and obstacle overcoming in linear motion. The robot has two inputs and three DOF, which is a nonholonomic and underactuated system. The dynamic model of the robot is constructed, and the linear motion performance of robot in theory is proved by Adams simulation. The control system is briefly introduced, and the performance of the prototype is tested by experiments at last.
基金supported by the National Natural Science Foundation of China (Grant No. 20091310918)
文摘The effect of plasma actuator that uses saw-tooth or sine-wave shape electrodes on boundary layer flows is experimentally investigated.The measurement results are compared with a corresponding standard configuration (conventional design using two rectangular strip electrodes)-the actuator that produces a nearly two-dimensional horizontal wall jet upon actuation.PIV measurements are used to characterize the actuators in a quiescent chamber.Operating in a steady manner,the new actuators result in the formation of streamwise and spanwise vortices.That is to say,the new actuators render the plasma actuators inducing three-dimensional variations in the shear layer,offering significant flexibility in flow control.The affected flowfield with the new actuators is significantly larger than that with the conventional linear actuators.While the conventional linear actuators affect primarily the boundary layer flow on a scale of about 1 cm above the wall,the new actuators affect the near wall region at a significantly larger scale.This new design broadens the applicability and enhances the flow control effects and it is potentially a more efficient flow control device.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50831002,50971025,51071022 and 11174031)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. 2011031)+1 种基金Beijing Municipal Natural Science Foundation (Grant No. 2102032)the Fundamental Research Funds for Central Universities
文摘The current-driven domain wall motion was investigated on permalloy nanowires with different dimensions by micromagnetic simulations.The critical current density increased with the reduction in both the width and thickness of nanowires because of the enhanced hard-axis anisotropy.At a thickness of 5 nm,the critical current density decreased with the reduction of the nanowire width because of the reduced domain wall width.
