载机平台光电转塔目标定位的仿真算法

目标定位是光电转塔典型功能和任务之一，对其定位精度的考量也是转塔作战技术指标之一，针对该问题，从理论和仿真角度进行了分析。分析目标定位中用到的坐标系及其相互转换关系，给出光电转塔视轴反演、有源目标定位、无源目标定位的算法流程，通过仿真实验加以验证，考虑了定位过程中可能的随机误差来源，并分析是否采用均值滤波及其对定位结果的影响，最后通过Monte-Carlo分析计算了定位精度。分析结果表明:1）有源定位比无源定位的精度高，在仿真假设条件下，精度约提高1倍；2）均值滤波后，定位精度有较大提升（约提高15倍）；3）18 km距离时典型无源定位精度在80%置信度条件下约为39.4 m；4）统计直方图反映出80%置信度CEP半径及最大误差距离随载机位置、姿态、转塔视轴等（体现在目标载机距离上）不同参数的变化结果。     

Calculation of Ionization,Excitation and Electron Capture Cross Sections for Be4++H(2s, 2p) Collisions

A computational study of Be⁴⁺+H(2s, 2p) collisions has been carried out employing the Classical Trajectory Monte Carlo (CTMC) method for the impact energy range from 20 keV/u to 1000 keV/u. The integral n partial cross sections for H(n) excitation and Be³⁺(n) electron capture and, the total ionization and electron capture cross sections are calculated and compared to recent semiclassical results. A general good agreement is observed for the n partial and total electron capture and ionization cross sections. The comparative study of the three inelastic processes show no significant differences between both excited targets.     

Convergence of a non-failable mean-field particle system

The existing literature contains many examples of mean-field particle systems converging to the distribution of a Markov process conditioned to not hit a given set. In many situations, these mean-field particle systems are failable, meaning that they are not well defined after a given random time. Our first aim is to introduce an original mean-field particle system, which is always well defined and whose large number particle limit is, in all generality, the distribution of a process conditioned to not hit a given set. Under natural conditions on the underlying process, we also prove that the convergence holds uniformly in time as the number of particles goes to infinity. As an illustration, we show that our assumptions are satisfied in the case of a piece-wise deterministic Markov process.     

腐蚀管道的可靠度分析方法研究

对腐蚀管道的模糊可靠度计算方法进行了深入研究，提出了确定性可靠度和模糊可靠度两个基本概念；提出了基于断裂失效判据、基于FAD失效评估图和基于剩余强度3种方法计算模糊可靠度的方法；提出了3种新的方法计算确定性可靠度，即改进的JC法、GA—JC法和改进的Monte-Carlo法．以胜利油田某试验区已加入缓蚀剂的注水管道为例，采用本文建立的计算模糊可靠度的3种计算方法和确定性可靠度的3种方法，分别计算注水管道可靠度随着时间的变化趋势．在模糊可靠度的3种计算方法中，基于剩余强度失效方法比较适中，是计算模糊可靠度较好的方法；在确定性可靠度的3种计算方法中，改进的Monte-Carlo法较好．     

Reconstruction and interpretation of photon Doppler velocimetry spectrum for ejecta particles from shock-loaded sample in vacuum

The photon Doppler velocimetry(PDV) spectrum is investigated in an attempt to reveal the particle parameters of ejecta from shock-loaded samples in a vacuum. A GPU-accelerated Monte–Carlo algorithm, which considers the multiplescattering effects of light, is applied to reconstruct the light field of the ejecta and simulate the corresponding PDV spectrum.The influence of the velocity profile, total area mass, and particle size of the ejecta on the simulated spectra is discussed qualitatively. To facilitate a quantitative discussion, a novel theoretical optical model is proposed in which the singlescattering assumption is applied. With this model, the relationships between the particle parameters of ejecta and the peak information of the PDV spectrum are derived, enabling direct extraction of the particle parameters from the PDV spectrum.The values of the ejecta parameters estimated from the experimental spectrum are in good agreement with those measured by a piezoelectric probe.     

Discharge characteristic of very high frequency capacitively coupled argon plasma

The discharge characteristics of capacitively coupled argon plasmas driven by very high frequency discharge are studied. The mean electron temperature and electron density are calculated by using the Ar spectral lines at different values of power(20 W–70 W) and four different frequencies(13.56 MHz, 40.68 MHz, 94.92 MHz, and 100 MHz). The mean electron temperature decreases with the increase of power at a fixed frequency. The mean electron temperature varies nonlinearly with frequency increasing at constant power. At 40.68 MHz, the mean electron temperature is the largest. The electron density increases with the increase of power at a fixed frequency. In the cases of driving frequencies of 94.92 MHz and 100 MHz, the obtained electron temperatures are almost the same, so are the electron densities. Particle-in-cell/MonteCarlo collision(PIC/MCC) method developed within the Vsim 8.0 simulation package is used to simulate the electron density, the potential distribution, and the electron energy probability function(EEPF) under the experimental condition.The sheath width increases with the power increasing. The EEPF of 13.56 MHz and 40.68 MHz are both bi-Maxwellian with a large population of low-energy electrons. The EEPF of 94.92 MHz and 100 MHz are almost the same and both are nearly Maxwellian.     

Water mist attenuates guided laser based on Monte Carlo method

The round-trip attenuating process of lasers used for guiding in artificial water mists is studied with the Monte-Carlo method. A new way for confirming the scattering directions of photons is established based on calculating Mie cumulative probability distribution function of the polydisperse mist and user defined function fitting by Matlab. Two Monte-Carlo methods for photons tracking are mentioned and their efficiencies are discussed and balanced in this paper. A conclusion is come to that the Wight method is evidently more efficiency than the Event method, and the former is adopted in this paper. The radiuses of frequently-used water mists are usually in the range of 10¹–10² μm which are found to be suited to attenuate the 10.6 μm laser and can be used for laser stealth. But the effect is worse for 1.06 μm laser.     

Influence of the Coulomb forces on the thermodynamic and transport properties of non stoichiometric cerium dioxide

Abstract

In this study, it is demonstrated that the Coulomb interactions explains the essential of experimental thermodynamic and transport thermodynamic results.     

Particle methods for PDEs arising in financial modeling

We numerically study convection–diffusion equations arising in financial modeling. We focus on the convection-dominated cases, in which the diffusion coefficients are relatively small. Both finite-difference and Monte-Carlo methods which are widely used in the problems of this kind might be inefficient due to severe restrictions on the meshsize and the number of realizations needed to achieve high resolution.We propose an alternative approach based on particle methods which have extremely low numerical diffusion and thus do not have the aforementioned restrictions. Our approach is based on the operator splitting: The hyperbolic steps are made using the method of characteristics, while the parabolic steps are performed using either a special discretization of the integral representation of the solution (which leads to a deterministic particle method) or a stochastic random walk approach.We apply the designed particle methods to a variety of test problems and the numerical results indicate high accuracy, efficiency and robustness of both the deterministic and stochastic methods. In addition, our numerical experiments clearly demonstrate that the deterministic particle method outperforms its stochastic counterpart.     

电子束放射照相的特性与参数优化

短脉冲强激光产生的电子束具有源尺寸小、脉宽窄、准单能谱等特点, 在放射照相诊断中具有独特作用. 本文通过分析电子在材料中散射并采用蒙特卡罗方法数值模拟, 研究了100 keV到几百MeV能量电子束对有厚度起伏或存在界面的靶的透视, 并与质子、X射线束透视结果比较, 给出了电子束放射照相的特性与参数优化: 基于电子在材料中非弹性散射或能量损失, 选用能量使其射程与靶厚度接近的电子束来诊断靶厚度不均匀性; 基于电子在材料中的弹性散射, 选用射程超过靶厚度的电子束来诊断靶界面.