用EA求解非固定时间轨道转移和拦截问题

随着航天任务需求的多样化 ,对航天器拦截和轨道转移问题不但提出了最省燃料的要求 ,而且提出了最小时间的要求。文中用EA算法解决了这一组合优化问题 ,仿真结果证明了算法的有效性     

GEO导航星广播星历拟合改进算法设计

设计了倾角较小的GEO导航星的广播星历拟合算法。该方法的核心思想是在常规拟合算法的基础上对位置观测量进行合理的坐标系参考平面旋转,特别是提出针对拟合迭代初值进行相应的坐标变换,从而既可以解决轨道参数拟合的相关性问题,使轨道参数拟合快速收敛,同时又兼顾了用户接收机的计算简便化。通过仿真验证,该方法简洁有效,拟合中误差RMS在厘米量级,能够保证拟合精度。     

Field test and probabilistic analysis of irregular steel debris casualty risks from a person-borne improvised explosive device

Person-borne improvised explosive devices (PBIEDs) are often used in terrorist attacks in Western countries. This study aims to predict the trajectories of PBIED fragments and the subsequent safety risks for people exposed to this hazard. An explosive field test with a typical PBIED composed of a plastic explosive charge and steel nut enhancements was performed to record initial fragment behaviour, including positions, velocity, and trajectory angles. These data were used to predict the full trajectory of PBIED fragments using a probabilistic analysis. In the probabilistic analyses a probability of fatality or serious injury was computed. Based on the results presented, many practical conclusions can be drawn, for instance, regarding safe evacuation distances if a person were exposed to a suspected PBIED.     

新型驱护舰编队舰空导弹防御体系射击效能研究

针对新型驱护舰编队舰空导弹防御体系射击效能评估这一难题,对其射击效能准则进行了确立,提出了基于排队论的射击效能评估模型,对体系射击效能进行仿真计算,总结出能对系统射击效能做出准确评估的方法,并利用实例对模型进行了验证。     

内编队地球重力场测量性能数值分析

内编队系统通过实现内卫星纯引力轨道环境和内卫星精密定轨,完成高精度地球重力场测量,实现了不依赖于加速度计的重力卫星实施新途径。针对内编队重力场测量性能难以解析分析的情况,基于MATLAB并行程序设计进行了重力场测量数值模拟,获得了内编队重力场测量的有效阶数及其精度。在内编队轨道高度为300km、内卫星干扰力为1.0×10-10m/s2、外卫星定轨精度为3cm、内外卫星相对状态测量精度为1mm的条件下,计算得到内编队测量重力场的有效阶数为72,相应的大地水准面累积误差为44cm,重力异常累积误差为4.5mGal,由此可知内编队测量重力场的有效阶数主要分布在低阶部分。     

SG高压水室在典型循环工况下的低周疲劳评估

本文应用有限元分析了ＳＧ高压水室在典型负荷波动下的热应力,根据所计算出的峰值应力循环幅,引用低周疲劳设计曲线,对结构的低周疲劳用ＡＳＭＥ规范进行了评估,发现ＳＧ在典型载荷循环下不产生显著的低周疲劳损伤。     

利用Roothaan-Hartree-Fock 原子波函数计算的低能电子被He和Ar原子弹性散射截面

利用原子的Roothaan-Hartree-Fock波函数计算了低能e~--He和e~--Ar弹性散射截面。计算采用模型势方法,其中包括静电势、交换势和极化势。计算结果和实验吻合较好。通过把我们的计算结果和其他作者利用不同原子波函数的计算结果进行比较,讨论了不同原子波函数之间的差别对计算结果的影响。     

关于地球坐标系中机械能守恒问题

在只考虑地球自转时，地球坐标系中质点和质点组的机械能守恒定律依然成立。     

Effect of welding processes and consumables on fatigue crack growth behaviour of armour grade quenched and tempered steel joints

Quenched and Tempered (Q&T) steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking (HIC) in the heat affected zone (HAZ) after welding. The use of austenitic stainless steel (ASS) consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel (LHF) consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. The use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. This microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&T steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&T Steel joints. Shielded metal arc welding (SMAW) and Flux cored arc welding (FCAW) were used for fabrication of joints using ASS and LHF consumables. The joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.     

天基光学短弧观测约束域的粒子群优化定轨方法

针对空间目标定轨问题,提出一种利用两段天基光学短弧观测数据的粒子群优化定轨新算法。在介绍天基光学短弧观测测量帧集、测量约束域及目标函数构造的基础上,为解决已有的基于网格搜索思想寻优的算法存在的多解、局部最优解及运算量过大等问题,提出了一种利用粒子群优化算法在约束域内对目标函数值寻优达到定轨目的的新算法。对算法的性能进行了仿真验证。多次仿真结果表明:该算法大大降低了计算量,且有效地解决了目标函数多解和局部最优解问题,对目标定轨的精度与定轨算法的克拉美罗下限接近。