Distributed precision jamming(DPJ)is a novel blanket jamming concept in electronic warfare,which delivers the jamming resource to the opponent equipment precisely and ensures that friendly devices are not affected.Rob...Distributed precision jamming(DPJ)is a novel blanket jamming concept in electronic warfare,which delivers the jamming resource to the opponent equipment precisely and ensures that friendly devices are not affected.Robust jamming performance and low hardware burden on the jammers are crucial for practical DPJ implementation.To achieve these goals,we study the robust design of wideband constant modulus(CM)discrete phase waveform for DPJ,where the worst-case combined power spectrum(CPS)of both the opponent and friendly devices is considered in the objective function,and the CM discrete phase constraints are used to design the wideband waveform.Specifically,the resultant mathematical model is a large-scale minimax multi-objective optimization problem(MOP)with CM and discrete phase constraints.To tackle the challenging MOP,we transform it into a single-objective minimization problem using the Lp-norm and Pareto framework.For the approximation problem,we propose the Riemannian conjugate gradient for CM discrete phase constraints(RCG-CMDPC)algorithm with low computational complexity,which leverages the complex circle manifold and a projection method to satisfy the CM discrete phase constraints within the RCG framework.Numerical examples demonstrate the superior robust DPJ effectiveness and computational efficiency compared to other competing algorithms.展开更多
The particle dynamics in an annular shear granular flow is studied using the discrete element method, and the influences of packing fraction, shear rate and friction coefficient are analyzed. We demonstrate the existe...The particle dynamics in an annular shear granular flow is studied using the discrete element method, and the influences of packing fraction, shear rate and friction coefficient are analyzed. We demonstrate the existence of a critical packing fraction exists in the shear granular flow. When the packing fraction is lower than this critical value, the mean tangential velocity profile exhibits a rate-independent feature. However, when the packing fraction exceeds this critical value, the tangential velocity profile becomes rate-dependent and varies gradually from linear to nonlinear with increasing shear rate. Furthermore, we find a continuous transition from the unjammed state to the jammed state in a shear granular flow as the packing fraction increases. In this transforming process, the force distribution varies distinctly and the contact force network also exhibits different features.展开更多
基金supported by the National Natural Science Foundation of China(No.62301581)the Postgraduate Scientific Research Innovation Project of Hunan Province,China(No.CX20230045)。
文摘Distributed precision jamming(DPJ)is a novel blanket jamming concept in electronic warfare,which delivers the jamming resource to the opponent equipment precisely and ensures that friendly devices are not affected.Robust jamming performance and low hardware burden on the jammers are crucial for practical DPJ implementation.To achieve these goals,we study the robust design of wideband constant modulus(CM)discrete phase waveform for DPJ,where the worst-case combined power spectrum(CPS)of both the opponent and friendly devices is considered in the objective function,and the CM discrete phase constraints are used to design the wideband waveform.Specifically,the resultant mathematical model is a large-scale minimax multi-objective optimization problem(MOP)with CM and discrete phase constraints.To tackle the challenging MOP,we transform it into a single-objective minimization problem using the Lp-norm and Pareto framework.For the approximation problem,we propose the Riemannian conjugate gradient for CM discrete phase constraints(RCG-CMDPC)algorithm with low computational complexity,which leverages the complex circle manifold and a projection method to satisfy the CM discrete phase constraints within the RCG framework.Numerical examples demonstrate the superior robust DPJ effectiveness and computational efficiency compared to other competing algorithms.
基金supported by the Key Project of the National Natural Science Foundation of China(10532040)the Programme of Changjiang Scholars and Innovative Research Team in University (IRT 0628)
文摘The particle dynamics in an annular shear granular flow is studied using the discrete element method, and the influences of packing fraction, shear rate and friction coefficient are analyzed. We demonstrate the existence of a critical packing fraction exists in the shear granular flow. When the packing fraction is lower than this critical value, the mean tangential velocity profile exhibits a rate-independent feature. However, when the packing fraction exceeds this critical value, the tangential velocity profile becomes rate-dependent and varies gradually from linear to nonlinear with increasing shear rate. Furthermore, we find a continuous transition from the unjammed state to the jammed state in a shear granular flow as the packing fraction increases. In this transforming process, the force distribution varies distinctly and the contact force network also exhibits different features.
