激光与近相对论临界密度薄层相互作用产生大电量高能电子束

研究了激光与近相对论临界密度等离子体薄层相互作用时所产生的高能电子束的主要特征,包括平均有效温度以及截止能量等.实验结果表明,电子束的电量超过nC量级,平均有效温度可达8 MeV以上.PIC数值模拟证明,近相对论临界密度等离子体内,相对论自透明效应和激光钻孔效应共同形成一条磁化等离子体通道,电子与激光将在角向磁场的协助下发生Betatron共振.激光可将电子直接加速到很高能量,因此电子束平均有效温度("斜坡温度")远远超过Wilks定标率预计的平均温度.该研究为产生高亮度X射线源提供了一种新的可能途径.     

Pervasive randomness in physics: an introduction to its modelling and spectral characterisation

An introduction to the modelling and spectral characterisation of random phenomena is detailed at a level consistent with a first exposure to the subject at an undergraduate level. A signal framework for defining a random process is provided and this underpins an introduction to common random processes including the Poisson point process, the random walk, the random telegraph signal, shot noise, information signalling random processes, jittered pulse trains, birth–death random processes and Markov chains. An introduction to the spectral characterisation of signals and random processes, via either an energy spectral density or a power spectral density, is detailed. The important case of defining a white noise random process concludes the paper.     

Theoretical studies on structure and performance of [1,2,5]‐oxadiazolo‐[3,4‐d]‐pyridazine‐based derivatives

Based on energetic compound [1,2,5]‐oxadiazolo‐[3,4‐d]‐pyridazine, a series of functionalized derivatives were designed and first reported. Afterwards, the relationship between their structure and performance was systematically explored by density functional theory at B3LYP/6‐311 g (d, p) level. Results show that the bond dissociation energies of the weakest bond (N–O bond) vary from 157.530 to 189.411 kJ · mol^?1. The bond dissociation energies of these compounds are superior to that of HMX (N–NO_2, 154.905 kJ · mol^?1). In addition, H1, H2, H4, I2, I3, C1, C2, and D1 possess high density (1.818–1.997 g · cm^?3) and good detonation performance (detonation velocities, 8.29–9.46 km · s^?1; detonation pressures, 30.87–42.12 GPa), which may be potential explosives compared with RDX (8.81 km · s^?1, 34.47 GPa ) and HMX (9.19 km · s^?1, 38.45 GPa). Finally, allowing for the explosive performance and molecular stability, three compounds may be suggested as good potential candidates for high‐energy density materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Strategy of improving the stability and detonation performance for energetic material by introducing the boron atoms

A novel stable energetic compound (E)‐1,2‐diamino‐1,2‐dinitrodiboron (DANB) was theoretically designed based on the structure of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7). Atomization method in combination with Hess' law was used to predict the heat of formation. The detonation velocity (D) and detonation pressure (P) of DANB were approximatively estimated by using Kamlet–Jacobs equations. As a result, DANB has huge heat of formation (2013.5 kJ/mol) and specific enthalpy of combustion (?26.4 kJ/g). Furthermore, DANB possesses high crystal density (1.85 g/cm³) and heat of detonation (5476.0 cal/g), which lead to surprising detonation performance (D = 10.72 km/s, P = 51.9 GPa) that is greater than those of FOX‐7 (D = 8.63 km/s, P = 34.0 GPa) and CL‐20 (D = 9.62 km/s, P = 44.1 GPa). More importantly, DANB is very stable because its bond dissociation energy of the weakest bond (BDE = 357.8 kJ/mol) is larger than those of the most common explosives, such as FOX‐7 (BDE = 200.4 kJ/mol), CL‐20(BDE = 209.2 kJ/mol), HMX(BDE = 165.7 kJ/mol), and RDX (BDE = 161.4 kJ/mol). Therefore, our results show that DANB is a promising candidate for stable and powerful energetic material.     

部分相干艾里光在大气湍流中的光束扩展与漂移

基于Andrews和Philips的经典漂移方差模型,结合部分相干艾里光的交叉谱密度函数和Tatarskii功率谱,推导出部分相干艾里光在大气中传输时的光束扩展和漂移解析式,对比分析了不同的衰减因子、湍流强度和相干度等参数对部分相干艾里光的光束扩展和漂移的影响,并与高斯光束所得结果进行了比较.研究表明:衰减因子、湍流强度和相干度等对光束漂移影响较大,当它们的取值增大时,漂移越严重;内尺度对光束漂移几乎没有影响;在相同的条件下,艾里光束的光束漂移要比高斯光束小两个数量级,且其本身具有自恢复特性和较强的抑制湍流特性.     

基于光纤光栅的冲击能检测

提出一种利用光纤光栅作为传感元构成传感阵列对冲击能进行检测的方法.通过搭建简易冲击系统装置,将光纤光栅应变传感器沿轴向对称粘贴于圆杆表面,对入射应力波能量进行检测.实验结果表明,两杆对心正冲击时入射应力波幅值最大,能量传递效率最高.通过分析频率域内的应力波信号可知,其能量主要集中在0~5 000Hz频率范围内.将入射应力波能量与冲杆动能进行对比,结果表明冲杆与圆杆传递能比在93%以上,基本满足冲击机械性能测试的需求.     

部分相干Airy光束在大气湍流中的光强演化

为了利用Airy光束的无衍射、自恢复和自弯曲特性抑制大气湍流效应,实现远距离无线光通信,对部分相Airy光束在大气湍流中传输时的光强演化进行了研究.利用高斯-谢尔模型的交叉谱密度函数、广义惠更斯-菲涅尔原理以及Rytov相位近似法,推导了部分相干Airy在湍流大气中平均光强的表达式.分别从传播距离、湍流强度等方面对光强分布的影响进行了模拟仿真,并对光束自身参数对光强分布的影响进行了相关实验验证.结果表明:随着传播距离的增加,部分相干Airy光束的旁瓣逐渐衰减,主瓣逐渐扩散;在传播足够远时,其旁瓣逐渐消失,主瓣逐渐演化为高斯分布.仿真和实验结果一致表明光束的截断因子越小、特征长度和相干长度越长,光束的光强分布保持越完整.     

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进行了介质阻挡放电低温等离子体脱除伴有SO2的烟气中NO的研究,分别进行了直接等离子体脱硫脱硝和间接等离子体脱硫脱硝实验.在直接等离子体脱硫脱硝中,模拟烟气等混合气直接通入等离子体发生器,在反应器中电离分解NO以及和生成的高能电子、离子和自由基等离子体相互反应而进行脱除NO;间接等离子体脱硫脱硝中,模拟烟气连接在等离子体发生器出口与从反应器中产生出的等离子体发生氧化反应而进行脱除NO.结果表明,无论直接形式还是间接形式,脱硝效率都要比脱硫效率高,间接脱硫脱硝能够大大降低功率输入,节省能耗,具有重要的实际应用价值和意义.氨气的加入,有利于脱除效率的提升.     

Multiplicative non-Gaussian noise and additive Gaussian white noise induced transition in a piecewise nonlinear model

We study the transition problems in a piecewise nonlinear model induced by correlated multiplicative non-Gaussian noise and additive Gaussian white noise. Firstly, applying the path integral approach, the unified colored noise approximation, the analytical expression of the steady-state probability density function (SPD) is derived. Then the change regulation of the SPD is analyzed with the change of the strength and relevance of multiplicative noise and additive noise. From numerical computations we obtain some new nonlinear phenomena: the transition can be induced by the cross-correlation strength between noises, the non-Gaussian noise intensity and the Gaussian noise intensity as well as the non-Gaussian noise deviation parameter. This indicates that the effect of the non-Gaussian noise intensity on SPD is the same as that of the Gaussian noise intensity. Moreover, we also find the correlation time of the non-Gaussian noise can not induce the transition.