An internal ballistic model of electromagnetic railgun based on PFN coupled with multi-physical field and experimental validation

To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.

A SIMULATION STUDY OF DEPOSITION UNDER TWO TYPES OF IMPINGING TRAJECTORIES

A model coupling particle aggregation and randomwalk surface diffusion has been developed for 2D simulation of depositional growth, in which impinging particles follow either a straight-line trajectory of cosine distribution, representing typically sputter deposition, or a scattered trajectory, representing typically electrochemical deposition. Simulations of the growth under various impinging conditions and effective surface diffusivity have been carried out. Pattern and defect development in deposition on flat, trenched and ridged substrates have been investigated. We found that on flat and ridged substrates, both types of trajectories yield similar features, including formation of cone-like defects on surface ridges. While on trenched substrate, the straight-line impingement yielded more uniform step coverage than the scattered impingement.

Allowed Spatial Transitions and Cancellation of the Richard­son-Langmuir Ban

The ancient emission formulas of Langmuir and Richardson entered the calculations of subtle effects in semiconductor devices as basic ones.But,in the physics of semiconductor devices,these models have long played a purely decorative role,since they can describe in the most rough approximation only individual sections of the I-V characteristic.But it is precisely the fact that these formulas are basic when describing the barrier current-voltage characteristics(CVC)and prevented the consideration and use of thermoelectric effects in materials on a nano-scale.Thus,as these basic emission models actually imposed a ban on the MEASURABILITY of local thermoelectric effects,the existence of which has already been proven both phenomenologically and experimentally.The quantum transition technique is based on classical models.But it can also be used to correct these classic formulas.The calculation of the spatial transition of electrons over the potential barrier,taking into account the polarity of the kinetic energy,gives currents that are significantly higher than the currents of Langmuir and Richardson,including in the initial section of the I-V characteristic.Moreover,ballistic currents are concentrated at energy levels close to the threshold.This effect of condensation of electrons flowing down the barrier transforms the"anomalous"Seebeck coefficients into normal MEASURABLE Local Thermal EMF,including in p-n junctions.

Scaling relation of domain competition on(2+1)-dimensional ballistic deposition model with surface diffusion

During heteroepitaxial overlayer growth multiple crystal domains nucleated on a substrate surface compete with each other in such a manner that a domain covered by neighboring ones stops growing.The number density of active domains ρ decreases as the height h increases.A simple scaling argument leads to a scaling law of ρ~ h^（-γ） with a coarsening exponent γ=d/z,where d is the dimension of the substrate surface and z the dynamic exponent of a growth front.This scaling relation is confirmed by performing kinetic Monte Carlo simulations of the ballistic deposition model on a two-dimensional（d=2） surface,even when an isolated deposited particle diffuses on a crystal surface.

基于Chebyshev外弹道多项式的坦克弹丸落点跟踪控制:一种自适应鲁棒反馈方法

本文研究了运动坦克弹丸落点的跟踪控制问题.首先建立稳定系统的多体动力学模型.其次建立塔身指向系统的非线性櫚合动力学方程.随后建立6自由度外弹道弹丸的弹道方程,通过坐标变换将瞄准问题转化为落点跟踪问题,提出一种自适应鲁棒反馈控制方法,使预测落点精确跟踪期望位置.最后采用Chebyshev代理模型代替EB微分方程,有效减少协同仿真所需的时间.本文将电子束过程与跟踪控制问题相结合,有效地保证了坦克炮的首轮命中率.