Evolution of the charged grains in a two-dimensional dusty plasma under a spatially harmonic external force,in particular,their long-time behaviors after the force has been withdrawn,is studied by using molecular dyna...Evolution of the charged grains in a two-dimensional dusty plasma under a spatially harmonic external force,in particular,their long-time behaviors after the force has been withdrawn,is studied by using molecular dynamics simulation.Under an external force and a grain–grain interaction force,initially homogeneously distributed grains can reach a quasistationary state in the form of a disk crystal.After the external force is withdrawn,the disk moves initially with its size and shape nearly unchanged until it rapidly stops moving,and eventually the disk grain rotates like a vortex.The time needed to reach the final state increases with the strength of the initial external force increasing.展开更多
Prostatic hyperplasia and tumor are common diseases,and the minimally invasive surgery inserting the instruments through the urethra into the prostate is commonly conducted.Taking the robotic manipulator for such surg...Prostatic hyperplasia and tumor are common diseases,and the minimally invasive surgery inserting the instruments through the urethra into the prostate is commonly conducted.Taking the robotic manipulator for such surgery into consideration,this paper analyses the workspace of the end effector,and proposes the distribution error of the fixed point and the tracking error of manipulator end effector on the cone bottom surface of the workspace as the basis for control implementation of the manipulator.The D-H coordinate system of the manipulator is established and the trajectory planning of the end effector in the Cartesian space is carried out.The digital model was established,and dynamics simulation was performed in Solidworks and Matlab/Simulink environment to guide the manipulator design.Trajectory mapping and synchronization control between virtual model and the actual manipulator are realized based on digital twin technique.The virtual manipulator can reflect the real-time state of the manipulator with data interaction by comparing the dynamics simulation results with the motor current values obtained by experiment.Experiment was carried out with PD feedback control and Newton-Euler dynamics based feedforward control to get the trajectory tracking characteristic of each motor,errors of the fixed point and tracking performance of the end effector of the manipulator.The results show that compared with PD feedback control,feed forward control implementation can achieve a reduction of 30.0%in the average error of the fixed point of the manipulator and a reduction of 33.3%in the maximum error.展开更多
In this paper,a high-accuracy numerical scheme is developed for long-time dynamic simulations of 2D and 3D wave propagation phenomena.In the derivation of the present approach,the second order time derivative of the p...In this paper,a high-accuracy numerical scheme is developed for long-time dynamic simulations of 2D and 3D wave propagation phenomena.In the derivation of the present approach,the second order time derivative of the physical quantity in the wave equation is treated as a substitution variable.Based on the temporal discretization with the Krylov deferred correction(KDC)technique,the original wave problem is then converted into the modified Helmholtz equation.The transformed boundary value problem(BVP)in space is efficiently simulated by using the meshless generalized finite difference method(GFDM)with Taylor series after truncating the second and fourth order approximations.The developed scheme is finally verified by four numerical experiments including cases with complicated domains or the temporally piecewise defined source function.Numerical results match with the analytical solutions and results by the COMSOL software,which demonstrates that the developed KDC-GFDM can allow large time-step sizes for wave propagation problems in longtime intervals.展开更多
To increase launching frequency and decrease drag force of underwater projectiles,a serial multiprojectiles structure based on the principle of supercavitation is proposed in this paper.The drag reduction and supercav...To increase launching frequency and decrease drag force of underwater projectiles,a serial multiprojectiles structure based on the principle of supercavitation is proposed in this paper.The drag reduction and supercavitation characteristics of the underwater serial multi-projectiles are studied with computational fluid dynamics(CFD)and machine learning.Firstly,the numerical simulation model for the underwater supercavitating projectile is established and verified by experimental data.Then the evolution of the supercavitation for the serial multi-projectiles is described.In addition,the effects of different cavitation numbers and different distances between projectiles are investigated to demonstrate the supercavitation and drag reduction performance.Finally,the artificial neural network(ANN)model is established to predict the evolution of drag coefficient based on the data obtained by CFD,and the results predicted by ANN are in good agreement with the data obtained by CFD.The finding provides a useful guidance for the research of drag reduction characteristics of underwater serial projectiles.展开更多
Basin simulation can quantitatively rebuild the histories of structural development,sedimentary en-tombment,thermal regime,hydrocarbon generation,migration and accumulation in time and space with 3D date.Thus the way ...Basin simulation can quantitatively rebuild the histories of structural development,sedimentary en-tombment,thermal regime,hydrocarbon generation,migration and accumulation in time and space with 3D date.Thus the way by which the hydrocarbon generated,migrated and accumulated can be recog-nized.展开更多
The mathematical models of electro-hydraulic speed control system using series of pipesis presented. The principle of pipe effection on dynamics of the system is developed. Computersimulation and physical experiment a...The mathematical models of electro-hydraulic speed control system using series of pipesis presented. The principle of pipe effection on dynamics of the system is developed. Computersimulation and physical experiment are also carried out. The experimental results show that a rightchoosing of serial pipe for electro-hydraulic system enables the dynamic response of the system tobe improved effectively.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11975088 and 11705041)the Natural Science Foundation of Zhejiang Province,China(Grant No.LY15A050001)。
文摘Evolution of the charged grains in a two-dimensional dusty plasma under a spatially harmonic external force,in particular,their long-time behaviors after the force has been withdrawn,is studied by using molecular dynamics simulation.Under an external force and a grain–grain interaction force,initially homogeneously distributed grains can reach a quasistationary state in the form of a disk crystal.After the external force is withdrawn,the disk moves initially with its size and shape nearly unchanged until it rapidly stops moving,and eventually the disk grain rotates like a vortex.The time needed to reach the final state increases with the strength of the initial external force increasing.
基金Supported by National Natural Science Foundation of China(Grant No.51675400).
文摘Prostatic hyperplasia and tumor are common diseases,and the minimally invasive surgery inserting the instruments through the urethra into the prostate is commonly conducted.Taking the robotic manipulator for such surgery into consideration,this paper analyses the workspace of the end effector,and proposes the distribution error of the fixed point and the tracking error of manipulator end effector on the cone bottom surface of the workspace as the basis for control implementation of the manipulator.The D-H coordinate system of the manipulator is established and the trajectory planning of the end effector in the Cartesian space is carried out.The digital model was established,and dynamics simulation was performed in Solidworks and Matlab/Simulink environment to guide the manipulator design.Trajectory mapping and synchronization control between virtual model and the actual manipulator are realized based on digital twin technique.The virtual manipulator can reflect the real-time state of the manipulator with data interaction by comparing the dynamics simulation results with the motor current values obtained by experiment.Experiment was carried out with PD feedback control and Newton-Euler dynamics based feedforward control to get the trajectory tracking characteristic of each motor,errors of the fixed point and tracking performance of the end effector of the manipulator.The results show that compared with PD feedback control,feed forward control implementation can achieve a reduction of 30.0%in the average error of the fixed point of the manipulator and a reduction of 33.3%in the maximum error.
基金supported by the National Natural Science Foundation of China(Grant No.11802165)the Natural Science Foundation of Shandong Province of China(Grant No.ZR2017BA003)the China Postdoctoral Science Foundation(Grant No.2019M650158).
文摘In this paper,a high-accuracy numerical scheme is developed for long-time dynamic simulations of 2D and 3D wave propagation phenomena.In the derivation of the present approach,the second order time derivative of the physical quantity in the wave equation is treated as a substitution variable.Based on the temporal discretization with the Krylov deferred correction(KDC)technique,the original wave problem is then converted into the modified Helmholtz equation.The transformed boundary value problem(BVP)in space is efficiently simulated by using the meshless generalized finite difference method(GFDM)with Taylor series after truncating the second and fourth order approximations.The developed scheme is finally verified by four numerical experiments including cases with complicated domains or the temporally piecewise defined source function.Numerical results match with the analytical solutions and results by the COMSOL software,which demonstrates that the developed KDC-GFDM can allow large time-step sizes for wave propagation problems in longtime intervals.
基金supported by the National Natural Science Foun-dation of China(Grant No.11972194,12072160).
文摘To increase launching frequency and decrease drag force of underwater projectiles,a serial multiprojectiles structure based on the principle of supercavitation is proposed in this paper.The drag reduction and supercavitation characteristics of the underwater serial multi-projectiles are studied with computational fluid dynamics(CFD)and machine learning.Firstly,the numerical simulation model for the underwater supercavitating projectile is established and verified by experimental data.Then the evolution of the supercavitation for the serial multi-projectiles is described.In addition,the effects of different cavitation numbers and different distances between projectiles are investigated to demonstrate the supercavitation and drag reduction performance.Finally,the artificial neural network(ANN)model is established to predict the evolution of drag coefficient based on the data obtained by CFD,and the results predicted by ANN are in good agreement with the data obtained by CFD.The finding provides a useful guidance for the research of drag reduction characteristics of underwater serial projectiles.
文摘Basin simulation can quantitatively rebuild the histories of structural development,sedimentary en-tombment,thermal regime,hydrocarbon generation,migration and accumulation in time and space with 3D date.Thus the way by which the hydrocarbon generated,migrated and accumulated can be recog-nized.
文摘The mathematical models of electro-hydraulic speed control system using series of pipesis presented. The principle of pipe effection on dynamics of the system is developed. Computersimulation and physical experiment are also carried out. The experimental results show that a rightchoosing of serial pipe for electro-hydraulic system enables the dynamic response of the system tobe improved effectively.
