基于神经网络的飞行器总体优化设计

针对经验公式存在的精度低、适用范围受限的缺点,采用广义回归网络代替经验公式计算气动特性,并将其嵌入到优化设计流程之中,提出了一种基于神经网络的飞行器总体优化设计方法。神经网络的训练样本输入、输出数据通过试验设计和涡格法计算得到。以高空长航时无人机为例,选取航时与机翼结构重量系数作为目标函数,应用所提出的方法进行总体优化设计。计算结果表明,提出的方法是可行的,能够满足设计要求,同时降低优化过程的复杂程度,减少迭代次数。     

Analytical approach to cosmic ray ionization by nuclei with charge Z in the middle atmosphere – Distribution of galactic CR effects

The effects of galactic and solar cosmic rays (CR) in the middle atmosphere are considered in this work. A new analytical approach for CR ionization by protons and nuclei with charge Z in the lower ionosphere and middle atmosphere is developed in this paper. For this purpose the ionization losses (dE/dh) according to the Bohr–Bethe–Bloch formula for the energetic charged particles are approximated in three different energy intervals. More accurate expressions for energy decrease E(h) and electron production rate profiles q(h) are derived. The obtained formulas allow comparatively easy computer programming. The integrand in q(h) gives the possibility for application of adequate numerical methods – such as Romberg method or Gauss quadrature, for the solution of the mathematical problem. On this way the process of interaction of cosmic ray particles with the upper, middle and lower atmosphere will be described much more realistically. Computations for cosmic ray ionization in the middle atmosphere are made. The full CR composition is taken into account: protons, Helium (α-particles), light L, medium M, heavy H and very heavy VH group of nuclei.     

Mesospheric doppler wind measurements from Aura Microwave Limb Sounder (MLS)

This paper describes a microwave limb technique for measuring Doppler wind in the Earth’s mesosphere. The research algorithm has been applied to Aura Microwave Limb Sounder (MLS) 118.75 GHz measurements where the O₂ Zeeman lines are resolved by a digital autocorrelation spectrometer. A precision of ∼17 m/s for the line-of-sight (LOS) wind is achieved at 80–92 km, which corresponds to radiometric noise during 1/6 s integration time. The LOS winds from Aura MLS are mostly in the meridional direction at low- and mid-latitudes with vertical resolution of ∼8 km. This microwave Doppler technique has potential to obtain useful winds down to ∼40 km of the Earth’s atmosphere if measurements from other MLS frequencies (near H₂O, O₃, and CO lines) are used. Initial analyses show that the MLS winds from the 118.75 GHz measurements agree well with the TIDI (Thermosphere Ionosphere Mesosphere Energetics and Dynamics Doppler Interferometer) winds for the perturbations induced by a strong quasi 2-day wave (QTDW) in January 2005. Time series of MLS winds reveal many interesting climatological and planetary wave features, including the diurnal, semidiurnal tides, and the QTDW. Interactions between the tides and the QTDW are clearly evident, indicating possible large tidal structural changes after the QTDW events dissipate.     

Interstellar planetary protection

In the coming decades the detection of Earth-like extrasolar planets, either apparently lifeless or exhibiting spectral signatures of life, will encourage design studies for craft to visit them. These missions will require the elaboration of an interstellar planetary protection protocol. Given a specific dose required to sterilize microorganisms on a spacecraft, a critical mean velocity can be determined below which a craft becomes self-sterilizing. This velocity is calculated to be below velocities previously projected for interstellar missions, suggesting that an active sterilization protocol prior to launch might be required. Given uncertainties in the surface conditions of a destination extrasolar planet, particularly at microscopic scales, the potential for unknown biochemistries and biologies elsewhere, or the possible inoculation of a lifeless planet that is habitable, then both lander and orbiter interstellar missions should be completely free of all viable organisms, necessitating a planetary protection approach applied to orbiters and landers bound for star systems with unknown local conditions for habitability. I discuss the case of existing craft on interstellar trajectories – Pioneer 10, 11 and Voyager 1 and 2.     

飞机飞行控制律/操纵效率器多学科优化设计

基于近似模型和遗传算法,针对多操纵面布局飞机提出一种对全包线飞行控制律和操纵效率器几何形状与位置进行多学科优化的设计方法.该方法采用力矩控制方式进行控制,应用鲁棒增益调参方法设计全包线飞行控制系统,利用试验设计方法和径向基神经网络响应面获取近似的气动学科模型和控制学科模型,在近似模型基础上由遗传算法获得优化的设计参数并最终获得优化的控制律和操纵效率器.以某多操纵面布局无尾飞机为例进行计算机飞行仿真验证,结果表明该方法具有可行性.      

硅橡胶基防热涂层动态烧蚀行为及机理研究

针对两种典型硅橡胶基防热涂层开展高温燃气流烧蚀实验，通过对烧蚀后涂层的宏观及微观形貌分析，探讨了其防隔热机理及烧蚀模型。研究结果表明：烧蚀后两种涂层均存在液态层、陶瓷层、热解层以及原始层；烧蚀过程中甲基苯基硅橡胶涂层主要发生主链“回咬”成环反应，导致树脂基体交联密度降低，力学性能下降，涂层外表面发生开裂，甲基乙烯基硅橡胶涂层则主要发生侧基交联反应，使树脂基体交联密度上升，促进涂层发生陶瓷化转变；热辐射、热容吸热、热解反应吸热以及热阻塞效应为四种主要的热耗散机制，质量损失产生的原因主要包括反应气体释放以及气动剪切力导致的机械剥蚀。     

How far is far enough? Requirements derivation for planetary mobility systems

The origination of duration and distance requirements on planetary mobility systems (generally, rovers) are reviewed in detail. It is found that a ‘clean’ flow down from scientific objectives to requirement to capability is rarely presented. Rather, the historical record shows that the capability of emerging designs has been adopted post-hoc as a requirement, simple comparative superiority to predecessor missions has been invoked in competitive situations, or the requirement has been driven by capability of other elements of a mission architecture, such as delivery precision or astronaut life support. These deviations from the idealized systems engineering process have nonetheless resulted in missions that have generally been considered highly successful.     

大型民用飞机偏离特性与尾旋敏感性分析

为了研究某常规布局大型民用飞机的偏离特性与尾旋敏感性,在CARDC的FL-14水平风洞(Φ3. 2m)中进行了飞机模型的大迎角静态测力试验。通过对试验结果的充分挖掘,利用一系列的稳定性判据进行分析,获得了飞机的大致初始偏离迎角和偏离区间,并预测了飞机的尾旋敏感性。     

大气行星波影响低频电波吸收变化的机制

本文根据冬季中低纬低电离层中、低频（ＬＦ）电波振幅扰动与高纬平流层中大气行昨波活动密切相关的观测事实，分析研究了可能引起低电离层对ＬＦ电波吸收变化诸因素的作用后，提出了一种能较好地解释观测现象的物理机制，大气行星波可通过两种方式改变大气离化率ｑ，因而引起低电离层中电子密度Ｎ扰动，进而改变由Ｎ大小决定的电离层电波吸收值，结果导致ＬＦ电波振幅发生相应变化。文中给出了描述这一物理计算公式和某些计算结果。