Application of Wuhan Ionospheric Oblique Backscattering Sounding System (WIOBSS) for the investigation of midlatitude ionospheric irregularities

An upgrade of Wuhan Ionospheric Backscattering Sounding System (WIOBSS) was developed in 2015. Based on the Universal Serial Bus (USB), and a high performance FPGA, the newly designed WIOBSS has a completely digital structure, which makes it portable and flexible. Two identical WIOBSSs, which were situated at Mile (24.31°N, 103.39°E) and Puer (22.74°N, 101.05°E) respectively, were used to investigate the ionospheric irregularities. The comparisons of group distance, Doppler shift and width between Mile-Puer and Puer-Mile VHF ionospheric propagation paths indicate that the reciprocity of the irregularities is satisfied at midlatitude region. The WIOBSS is robust in the detection of ionospheric irregularities.     

Inverse identification of constitutive parameters of Ti2AlNb intermetallic alloys based on cooperative particle swarm optimization

Ti₂AlNb intermetallic alloy is a relatively newly developed high-temperature-resistant structural material, which is expected to replace nickel-based super alloys for thermally and mechanically stressed components in aeronautic and automotive engines due to its excellent mechanical properties and high strength retention at elevated temperature. The aim of this work is to present a fast and reliable methodology of inverse identification of constitutive model parameters directly from cutting experiments. FE-machining simulations implemented with a modified Johnson-Cook (TANH) constitutive model are performed to establish the robust link between observables and constitutive parameters. A series of orthogonal cutting experiments with varied cutting parameters is carried out to allow an exact comparison to the 2D FE-simulations. A cooperative particle swarm optimization algorithm is developed and implemented into the Matlab programs to identify the enormous constitutive parameters. Results show that the simulation observables (i.e., cutting forces, chip morphologies, cutting temperature) implemented with the identified optimal material constants have high consistency with those obtained from experiments, which illustrates that the FE-machining models using the identified parameters obtained from the proposed methodology could be predicted in a close agreement to the experiments. Considering the wide range of the applied unknown parameters number, the proposed inverse methodology of identifying constitutive equations shows excellent prospect, and it can be used for other newly developed metal materials.     

Orbit determination and prediction of GEO satellite of BeiDou during repositioning maneuver

In order to establish a continuous GEO satellite orbit during repositioning maneuvers, a suitable maneuver force model has been established associated with an optimal orbit determination method and strategy. A continuous increasing acceleration is established by constructing a constant force that is equivalent to the pulse force, with the mass of the satellite decreasing throughout maneuver. This acceleration can be added to other accelerations, such as solar radiation, to obtain the continuous acceleration of the satellite. The orbit determination method and strategy are illuminated, with subsequent assessment of the orbit being determined and predicted accordingly. The orbit of the GEO satellite during repositioning maneuver can be determined and predicted by using C-Band pseudo-range observations of the BeiDou GEO satellite with COSPAR ID 2010-001A in 2011 and 2012. The results indicate that observations before maneuver do affect orbit determination and prediction, and should therefore be selected appropriately. A more precise orbit and prediction can be obtained compared to common short arc methods when observations starting 1 day prior the maneuver and 2 h after the maneuver are adopted in POD (Precise Orbit Determination). The achieved URE (User Range Error) under non-consideration of satellite clock errors is better than 2 m within the first 2 h after maneuver, and less than 3 m for further 2 h of orbit prediction.     

机载系统NANDFlash存储技术

为了发挥NANDFlash在机载环境中非易失性、体积小、固态性、重量轻、低功耗、抗震动等特点,介绍了NANDFlash的存储特性,对NANDFlash存储的关键技术进行了改进,提出了基于域机制的地址映射方式和基于阈值的损耗均衡方法,为机载系统能够更加可靠、实时和安全地进行数据存储提供了选择。     

一种用于飞机试验台的三分力传感器

多分力载荷传感器是一种常用的传感器,但通常当各分力的量程相差太大时难以取得良好的效果。提出了一种新型传感器结构形式,减少了各分力之间的耦合,使得在各分力量程不匹配的情况下亦可获得较高的测量精度。     

计算机生成兵力

介绍分布交互仿真（ＤＩＳ）环境中计算机生成兵力（ＣＧＦ）的概念,分析ＣＧＦ系统的原理、结构、特点和主要研究内容。介绍现有的ＣＧＦ系统,分析ＣＧＦ系统与人工智能以及ＣＧＦ实体与ＤＩＳ的３种仿真类型之间的关系。     

VHF/UHF振幅闪烁和VHF快速法拉弟旋转起伏

本文利用1988年9月至1989年5月在武昌(114.4°E,30.6°N)同时接收日本ETS-Ⅱ卫星(130.0°E)发出的VHF(136MHz)信标信号和苏联静止站-T卫星(99.0°E)发出的UHP(714MHz)广播电视信号时获得的观测记录,对夜间出现的双频(VHF/UHF)闪烁和VHF快速(每分钟大于5次的起伏)法拉弟旋转起伏(以下用FRF表示法拉弟旋转起伏)进行了统计分析,结果发现在临近太阳黑子最大年份观测到的双频夜间闪烁主要为急始型,呈赤道特性,且在临近二分点的月份里有最大出现率,秋季更为明显;伴随VHF振幅闪烁出现的快速FRF常与UHF振幅闪烁共存,以及产生这种现象的不规则体由西向东漂移,东-西向的漂移速度分量,在子夜前为140m/s,在子夜后为90m/s。      

载人航天器的发射窗口及太阳能帆板的最佳受晒

首先根据载人航天器轨道运行段的基本特征,利用球面三角公式推导了：①阳光方向与载人航天器太阳能帆板法向的最佳夹角公式;②圆轨道的受晒因子公式。然后根据理论分析,引入帆板的效率系数。最后借助于计算机代数ｍａｔｈｅｍａｔｉｃａ系统,建立了一种分析帆板最佳受晒的直观、清晰、简便的方法。所得的结论为确定载人航天器的发射窗口提供了依据。