Electromagnetic armor is a new conceptual combat vehicle technology, which improves remarkably the defensive capability and maneuverability of vehicles. The authors present definitely to apply the electromagnetic theo...Electromagnetic armor is a new conceptual combat vehicle technology, which improves remarkably the defensive capability and maneuverability of vehicles. The authors present definitely to apply the electromagnetic theory to analyze the electromagnetic armor. Based on electromagnetics, the experienced expression of projectile and the physical model of PEMA (passive electromagnetic armor) are obtained when electric current flows through the system, and a computer simulation is given.展开更多
The rapid development of molecular dynamics(MD)simulations,as well as classical and reactive atomic potentials,has enabled tribologists to gain new insights into lubrication performance at the fundamental level.Howeve...The rapid development of molecular dynamics(MD)simulations,as well as classical and reactive atomic potentials,has enabled tribologists to gain new insights into lubrication performance at the fundamental level.However,the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately.This extensive study analyzed the effects of surface structure,applied load,and force field(FF)on the thin film lubrication of hexadecane.The lubricant film became more solid‐like as the applied load increased.In particular,with increasing applied load,there was an increase in the velocity slip,shear viscosity,and friction.The degree of ordering structure also changed with the applied load but rather insignificantly.It was also significantly dependent on the surface structure.The chosen FFs significantly influenced the lubrication performance,rheological properties,and molecular structure.The adaptive intermolecular reactive empirical bond order(AIREBO)potential resulted in more significant liquid‐like behaviors,and the smallest velocity slip,degree of ordering structure,and shear stress were compared using the optimized potential for liquid simulations of united atoms(OPLS‐UAs),condensed‐phase optimized molecular potential for atomic simulation studies(COMPASS),and ReaxFF.Generally,classical potentials,such as OPLS‐UA and COMPASS,exhibit more solid‐like behavior than reactive potentials do.Furthermore,owing to the solid‐like behavior,the lubricant temperatures obtained from OPLS‐UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF.The increase in shear stress,as well as the decrease in velocity slip with an increase in the surface potential parameterζ,remained conserved for all chosen FFs,thus indicating that the proposed surface potential parameterζfor the COMPASS FF can be verified for a wide range of atomic models.展开更多
The formula of the vibration response and power flow in beam-stiffened plate with force excitation applied on.the plate, have been obtained by using the Steepest Descent Integral method. The characteristics of the pow...The formula of the vibration response and power flow in beam-stiffened plate with force excitation applied on.the plate, have been obtained by using the Steepest Descent Integral method. The characteristics of the power flow have been studied through computer simulation.It is shown that the stiffener acts as an extra lineal excitation applied on the plate and changes the characteristics of the power flow of the infinite plate greatly The greater the stiffness and the smaller the distance between the exciting point and the stiffener is, the greater the induence is. Lastly, experiments have been carried out by using the dualaccelerometer measurement technique that based on cross spectrum, and the test data agree well with the theoretical results展开更多
There is growing interest in applying phase field methods as quantitative tools in materials discovery and development.However,large driving forces,common in many materials systems,lead to unstable phase field profile...There is growing interest in applying phase field methods as quantitative tools in materials discovery and development.However,large driving forces,common in many materials systems,lead to unstable phase field profiles,thus requiring fine spatial and temporal resolution.This demands more computational resources,limits the ability to simulate systems with a suitable size,and deteriorates the capability of quantitative prediction.Here,we develop a strategy to map the driving force to a constant perpendicular to the interface.Together with the third-order interpolation function,we find a stable phase field profile that is independent of the magnitude of the driving force.The power of this approach is illustrated using three models.We demonstrate that by using the driving force extension method,it is possible to employ a grid size orders of magnitude larger than traditional methods.This approach is general and should apply to many other phase field models.展开更多
Recently,Jia proposed a formalism to apply the variational principle to a coherent-pair condensate for a two-body Hamiltonian.The present study extends this formalism by including three-body forces.The result is the s...Recently,Jia proposed a formalism to apply the variational principle to a coherent-pair condensate for a two-body Hamiltonian.The present study extends this formalism by including three-body forces.The result is the same as the so-called variation after particle-number projection in the BCS case,but now,the particle number is always conserved,and the time-consuming projection is avoided.Specifically,analytical formulas of the average energy are derived along with its gradient for a three-body Hamiltonian in terms of the coherent-pair structure.Gradient vanishment is required to obtain analytical expressions for the pair structure at the energy minimum.The new algorithm iterates on these pair-structure expressions to minimize energy for a three-body Hamiltonian.The new code is numerically demonstrated when applied to realistic two-body forces and random three-body forces in large model spaces.The average energy can be minimized to practically any arbitrary precision.展开更多
文摘Electromagnetic armor is a new conceptual combat vehicle technology, which improves remarkably the defensive capability and maneuverability of vehicles. The authors present definitely to apply the electromagnetic theory to analyze the electromagnetic armor. Based on electromagnetics, the experienced expression of projectile and the physical model of PEMA (passive electromagnetic armor) are obtained when electric current flows through the system, and a computer simulation is given.
基金This project is supported by the Australian Research Council Discovery Projects DP170103173 and Linkage Project LP160101871.
文摘The rapid development of molecular dynamics(MD)simulations,as well as classical and reactive atomic potentials,has enabled tribologists to gain new insights into lubrication performance at the fundamental level.However,the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately.This extensive study analyzed the effects of surface structure,applied load,and force field(FF)on the thin film lubrication of hexadecane.The lubricant film became more solid‐like as the applied load increased.In particular,with increasing applied load,there was an increase in the velocity slip,shear viscosity,and friction.The degree of ordering structure also changed with the applied load but rather insignificantly.It was also significantly dependent on the surface structure.The chosen FFs significantly influenced the lubrication performance,rheological properties,and molecular structure.The adaptive intermolecular reactive empirical bond order(AIREBO)potential resulted in more significant liquid‐like behaviors,and the smallest velocity slip,degree of ordering structure,and shear stress were compared using the optimized potential for liquid simulations of united atoms(OPLS‐UAs),condensed‐phase optimized molecular potential for atomic simulation studies(COMPASS),and ReaxFF.Generally,classical potentials,such as OPLS‐UA and COMPASS,exhibit more solid‐like behavior than reactive potentials do.Furthermore,owing to the solid‐like behavior,the lubricant temperatures obtained from OPLS‐UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF.The increase in shear stress,as well as the decrease in velocity slip with an increase in the surface potential parameterζ,remained conserved for all chosen FFs,thus indicating that the proposed surface potential parameterζfor the COMPASS FF can be verified for a wide range of atomic models.
文摘The formula of the vibration response and power flow in beam-stiffened plate with force excitation applied on.the plate, have been obtained by using the Steepest Descent Integral method. The characteristics of the power flow have been studied through computer simulation.It is shown that the stiffener acts as an extra lineal excitation applied on the plate and changes the characteristics of the power flow of the infinite plate greatly The greater the stiffness and the smaller the distance between the exciting point and the stiffener is, the greater the induence is. Lastly, experiments have been carried out by using the dualaccelerometer measurement technique that based on cross spectrum, and the test data agree well with the theoretical results
基金This work is sponsored by the Office of Naval Research(ONR)under grant N00014-20-1-2327.Additional support is provided in part through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University which is jointly supported by the Office of the Provost,the Office for Research,and Northwestern University Information Technology.
文摘There is growing interest in applying phase field methods as quantitative tools in materials discovery and development.However,large driving forces,common in many materials systems,lead to unstable phase field profiles,thus requiring fine spatial and temporal resolution.This demands more computational resources,limits the ability to simulate systems with a suitable size,and deteriorates the capability of quantitative prediction.Here,we develop a strategy to map the driving force to a constant perpendicular to the interface.Together with the third-order interpolation function,we find a stable phase field profile that is independent of the magnitude of the driving force.The power of this approach is illustrated using three models.We demonstrate that by using the driving force extension method,it is possible to employ a grid size orders of magnitude larger than traditional methods.This approach is general and should apply to many other phase field models.
基金Supported by the National Natural Science Foundation of China(11405109)。
文摘Recently,Jia proposed a formalism to apply the variational principle to a coherent-pair condensate for a two-body Hamiltonian.The present study extends this formalism by including three-body forces.The result is the same as the so-called variation after particle-number projection in the BCS case,but now,the particle number is always conserved,and the time-consuming projection is avoided.Specifically,analytical formulas of the average energy are derived along with its gradient for a three-body Hamiltonian in terms of the coherent-pair structure.Gradient vanishment is required to obtain analytical expressions for the pair structure at the energy minimum.The new algorithm iterates on these pair-structure expressions to minimize energy for a three-body Hamiltonian.The new code is numerically demonstrated when applied to realistic two-body forces and random three-body forces in large model spaces.The average energy can be minimized to practically any arbitrary precision.
