Numerical simulations of spicule driving mechanisms

Spicules are known as one of the most prevalent small-scale dynamic phenomena on the sun, which are likely to give considerable contribution to coronal heating and mass supply. We discuss a model of the spicules driven by a train of slow MHD shock waves propagating along a vertical expanding magnetic flux tube. The shocks are initiated due to compression of the tube by the increasing external pressure in the lower chromosphere. Downflow of spicular material depends on radiative cooling and other dissipative processes.     

Grinding behavior and surface appearance of（TiC_p＋ TiB_w）/Ti-6Al-4V titanium matrix composites

（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.     

耐低温无石棉绝热层研制

通过添加含卤-锑的阻燃剂、芳纶纤维和增塑剂,研制了一种耐低温无石棉的丁腈绝热层配方 (TI506)。研究了芳纶纤维和增塑剂对绝热层静态烧蚀性能和Tg 的影响,对绝热层材料力学性能、比热容、热 导率等性能进行了测试。结果表明:芳纶纤维浆粕用量为10 ~15 份、芳纶短纤维用量为4 ~6 份时,绝热层烧 蚀性能最佳,线烧蚀率达到45 μm/ s,所选增塑剂DOS 用量为10 份、DBP 或ATBC 用量为20 份时,Tg 可达- 40℃,芳纶纤维制备的丁腈绝热层力学性能及烧蚀性能优良,并满足固体火箭发动机耐-40 ~60℃的环境。     

Possible consequences of a disk around B0656+14 on e–e and near-1 Hz gravitational wave production

Nearby pulsars B0656+14 and Geminga were proposed in the literature as the main sources of cosmic-ray positrons observed near Earth above 10 GeV. B0656+14 has comparable distance from Earth, similar magnetic field and period of Geminga. However, observations in the R and I bands indicate the presence of a disk of approximately 10⁻⁴ M_⊙ around B0656+14. Radio and pulsed γ-ray flux observations from this pulsar are also consistent with supernova fallback material and disk entering the light cylinder and partially quenching the development of electromagnetic showers in the magnetosphere. If this is the case, B0656+14 has unlikely given any contribution to e⁺ and e⁻ observed near Earth. Absolute flux measurements and the level of anisotropy in the high energy electron and positron arrival directions above 50 GeV will help in revealing if none, one of both nearby pulsars are sources of these particles observed near Earth.     

非定常N－S方程的线化及其差分求解

在微幅简谐振荡的假设下，对计算平面内非定常Ｎ－Ｓ方程进行了线比，并在ＭａｃＣｏｒｍａｒｋ于１９８０年提出的半隐格式的基础上，发展了一种适用于求解计算平面内线化Ｎ－Ｓ方程的差分格式．用该差分格式求解计算平面内的线化Ｎ－Ｓ方程时，可以避免求解五对角方程；且时间步长可以取得较大，计算效率高．     

基于蒙特卡洛树搜索的机载雷达编队策略优化

多机雷达协同探测是飞机协同作战研究的重要内容,编队策略影响着多机雷达协同探测的探测效能针对机载雷达编队策略的优化,基于部分可观察马尔可夫决策过程(POMDP)模型描述了编队策略优化问题,提出了一种基于蒙特卡洛树搜索(MCTS)的最优策略求解方法。以对敌方目标的探测性能为指标,将该方法与多种其他编队方法的结果进行了比较。试验结果表明,该方法很好地平衡了 MCTS 中利用与探索的关系,可以在规模较大的搜索空间内有效完成编队策略优化,在编队探测能力提升方面展示出了比其它方法更加优越的性能。     

航空复杂产品的 CATIA 结构稳健建模方法研究

针对现有建模方法无法有效对航空产品 CATIA 模型进行快速修改与重用的问题,提出了以曲面分割为建模策略的结构稳健性建模方法。该方法通过对父子关系关联传播路径进行分析,找出影响 CATIA 特征模型结果稳健性的因素,即几何元素方向、几何拓扑元素、建模策略。通过研究特征构建时,输人元素的性质和基于此性质的操作方法,实现结构稳健性建模,即通过对外部输人和建模过程中的关键几何元素进行方向控制、创建显式参考代替几何拓扑元素、禁止使用复杂草图、采用基于曲面分割的设计特征模块化建模策略等方式,实现特征模型的快速修改与重用。工程实例证明了所提方法的实用性和可靠性。     

关于军用航空认知战的顶层思考

军用航空认知战已成为现代战争的重要组成部分。随着科技的发展和战争形态的变化,认知战已经从传统战争策略中脱颖而出,成为一种具有重要战略意义的武器。旨在探讨军用航空认知战的概念内涵、基本原理、策略、技术,探讨了应对军用航空认知战的策略和措施,包括加强情报收集和分析、提高欺骗识别能力等。最后,总结了军用航空认知战的重要性和挑战性,并提出了未来研究和发展的建议和前景展望。     

三维空间拦截的前置追踪变结构制导律(英文)

This article aims to develop a head pursuit （HP） guidance law for three-dimensional hypervelocity interception, so that the effect of the perturbation induced by seeker detection can be reduced. On the basis of a novel HP three-dimensional guidance model, a nonlinear variable structure guidance law is presented by using Lyapunov stability theory. The guidance law positions the interceptor ahead of the target on its tlight trajectory, and the speed of the interceptor is required to be lower than that of the target, A numerical example of maneuvering ballistic target interception verifies the rightness of the guidance model and the effectiveness of the proposed method.