火星大气环境模拟装置设计及仿真分析研究

对火星表面大气环境特性进行了研究,通过选取合适的计算方法并结合FLUENT流体有限元计算软件对火星表面稀薄气体内部环流进行了模拟仿真分析,提出了以动量源模拟风扇段内流的仿真方法,并进行了可行性讨论。进一步实现了针对圆柱形模拟装置多工况下的内部气体流场稳态和非稳态计算仿真,并对计算结果进行了分析讨论,为火星大气环境模拟装置的设计提供了技术支持和参考。     

Gravity wave propagation studies using the Indian MST radar observations

The Indian MST radar facility at Gadanki (13.5°N, 79.2°E) has been utilised to study the propagation of gravity waves from the troposphere/lower stratosphere to the mesosphere and their interaction with the radar backscattered signal variations. The main objective is to correlate vertically propagating gravity waves derived from the tropospheric velocity fields with the dynamics of mesospheric scattering centres. The tropospheric wind velocities and signal strengths over the entire height range have been subjected to power spectral and wavelet analysis to determine the predominant wave periods/amplitudes and the coupling between the lower atmosphere and mesosphere. Results show that (a) the gravity waves are clearly detectable near tropopause heights, (b) while relatively higher period gravity waves (20–50 min) interact with mesospheric scattering centres, the lower period waves (<20 min) are absorbed in the troposphere itself, (c) the mesospheric scattering layers are affected by gravity waves of complementary periods.     

在轨航天器地气光环境分析

为得出定量化的遥感观测地气光环境数据,建立了简化的航天器地气光分布计算模型,首先将航天器及其各类运行轨道归纳到统一的照明模式中,地气光的分布主要考察航天器轨道面与地球晨昏面的夹角,然后考察航天器在每轨中的具体相位,以建立照度的几何传递关系;随后考察太阳辐照经地表后,最终到达航天器遥感观测载荷的光照度.计算结果能反映地气光在载荷观测方向2π半球视场内的分布情况,根据分布随空间变化的具体量级,对不同的离轴角进行照度积分,可转化为对观测仪器的地气光抑制能力要求.      

高空长航时无人机高精度自主定位方法

针对传统基于轨道动力学模型及非线性滤波进行间接敏感地平天文导航定位方法在实际应用中的局限性,提出了一种适用于高空长航时无人机自主导航定位的快速间接敏感地平天文解析定位新方法。分析了星光折射视高度天文量测的机理,导出天文三维定位的解析表达式,详细阐述了利用最小二乘微分校正法代替非线性滤波的天文定位方法,通过直接求解非线性量测方程组即可得到飞行器的精确位置信息,并对这种定位方法的定位精度进行了理论分析。该天文定位方法利用了星光折射间接敏感地平精度高的特点,又不需要飞行器动力学模型也不需要任何先验知识,算法简单可靠,计算量小,而定位精度与传统方法相当。最后,通过计算机仿真,验证了这种天文定位方法的有效性。     

Semi-empirical model of middle atmosphere wind from the ground to the lower thermosphere

During recent years, special attention has been paid to understanding the background circulation of the middle atmosphere. Particularly in the mesosphere/lower thermosphere (MLT) region, this has involved including data from a range of new radar measurements. It has also involved the comparison of existing empirical middle atmosphere wind models, such as CIRA-86 and HWM-93 to the new data. This has led to the construction of empirical models of MLT winds such as the Global Empirical Wind Model (GEWM). Further investigations are aimed at the construction of new empirical and semi-empirical wind models of the entire middle atmosphere including these new experimental results. The results of a new wind climatology (0–100 km) are presented here, based upon the GEWM, a reanalysis of stratospheric data, and a numerical model which is used to fill the gap between data from the stratospheric and MLT regions.     

A numerical model approximating extreme energetic electron events involved in the physical and chemical processes of the middle atmosphere

Relativistic electrons (with energies >150 keV) which originate in the outer radiation belt and detected by the Russian ‘Meteor’ series of satellites have been correlated with the atmospheric total ozone data compiled by almost 90 stations located around the world within the latitude zone 40°–70°N. In more than 60% of the stations examined we have detected a clear decrease of the ozone 3–5 days after the electron flux excess. A numerical model has been applied to approximate this effect based on relativistic electron initiated nitric oxides creation in the upper mesosphere with subsequent atmospheric transport (both vertical and horizontal) towards the upper stratosphere. A first attempt of local and temporal prediction of ozone depletion because of energetic electrons impact in the middle atmosphere has been illustrated.     

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.     

基于微波辐射测量的电波折射修正技术

针对电波折射修正精度直接影响无线电系统的探测和定位精度这一问题,提出了利用微波辐射计反演大气折射率剖面进行电波折射修正的解决方法,并引入RBF（Radial Basis Function,径向基）神经网络算法反演大气折射率.在青岛市气象局架设MP-3000A型多通道微波辐射计,开展了长达1个月的与探空数据的联合观测比对实验,对输出的大气折射率剖面进行了详细的分析.实验结果表明：RBF神经网络算法与MP-3000A自带的神经网络算法相比,反演大气折射率剖面的精度提高了30％以上,同时,电波折射修正的精度也得以提高.因此,利用微波辐射计反演大气折射率剖面进行电波折射修正方法可行.     

H-450 X射线参考辐射质的研建及验证

根据PTB和ISO 4037-1:2019要求,关于高空气比释动能系列（H系列）X射线参考辐射质的推荐数据,外推得出H-450的附加过滤为6.24 mm Cu,第一半值层（HVL_1st）为(5.39~5.52)mm Cu,平均光子能量为(214.25~214.78)keV,剂量率为11.51 Gy/h（距离焦斑为1 m处,管电流为10 mA）。随后,使用PTW32005电离室作为测量器具,采用半值层法建立H-450 X射线参考辐射质,得出HVL_1st为5.37 mm Cu,第二半值层（HVL_2nd）为5.97 mm Cu,同质系数为0.9。最后,使用PTW30013次级标准电离室测量得出H-450 X射线参考辐射质下距离焦斑1 m,管电流为10 mA时的剂量率值为11.98 Gy/h,与理论值的相对误差为4.07 %。采用MCNP 5软件对H-450 X射线参考辐射质进行能谱模拟并计算得出其平均光子能量为200.4 keV。     

直升机可计量性设计流程分析及参考模型构建

随着用户任务需求的增多,现代直升机功能日趋复杂并且长期处于复杂的使用环境中,机上所装载的大量测试类设备的精度会逐渐下降,计量保障人员必须定期检查上述关键测试类机载设备的精度指标,保证其处于完好状态.基于长期的直升机设计工作实践,本文总结了现有直升机计量保障中存在的问题,在现有可计量性及可计量性设计相关研究的基础上,明确...