AA 7055铝合金板材的微观组织与力学性能

研究AA 7055-T7751板材不同厚度层的力学性能,并采用电子背散射衍射(EBSD)、透射电子显微镜(TEM)、小角度X射线散射(SAXS)等分析技术研究板材不同厚度层的微观组织。结果表明:从板材表层到厚度中心,再结晶程度从69%下降到19.1%,亚晶粒尺寸从10μm减小到2μm;板材厚度中心主要为轧制型织构,远离中心层其含量逐渐减少,板材表层主要为剪切型织构;板材主要强化相为盘状η'相,其盘面半径为3.7 nm,厚度为1~3 nm,与基体的共格应变约为0.0133;板材不同厚度层沿轧制方向的拉伸屈服强度近似呈线性变化:σ_y=-38.7S+604.8(0≤S≤1)。     

过冷度对飞行器贮箱热力学排气系统性能的影响

为了研究低温推进剂贮箱的压力控制特性和热力学排气系统的运行特性,建立了耦合贮箱内流体流动相变过程与热力学排气系统(TVS)的数学模型,对TVS系统运行后贮箱的压力和温度变化进行了仿真计算。在以液氮为贮存工质的低温流体高效贮存平台上,进行了仿真模型的验证。分析了不同液体过冷度对低温贮箱温度和压力控制特性的影响。研究发现,在相同的在轨贮存周期内,对于饱和状态的液氢和液氧,TVS只有在排气模式下才能实现低温贮箱的压力控制,而对于过冷状态的液氢和液氧,TVS只需进行混合模式运行便可实现低温贮箱压力控制,且TVS混合运行时间随液体过冷度的增加而减少,16 K液氢时TVS的运行时间(546 s)相比于20 K液氢(663 s)减少了17.6%,78 K液氧时TVS的运行时间(2 760 s)相比于90 K液氧(16 469 s)减少了83.2%。过冷液体与气枕的混合可以实现低温流体在轨贮存过程中的零排放。     

微系统Interposer测试技术与发展趋势

随着微系统技术向三维立体集成不断发展,Interposer技术逐渐成为关注的焦点,是未来电子系统小型化和多功能化的重要技术途径,具有广阔的应用市场和发展前景。关于Interposer的测试技术研究也提上发展日程。对目前Interposer测试技术的研究现状和发展趋势进行了综述,重点总结了研究机构在Interposer测试技术领域的研究现状,并对技术发展趋势做了简单展望。     

隐身飞机战术干扰效能评估

从雷达距离公式和干扰方程出发,结合隐身飞机不同姿态角对应的RCS值,建立了隐身飞机战术干扰条件下的雷达探测距离模型.在考虑烧穿距离这一限制因素后,依据不同干扰模式设定了相应的干扰距离,仿真研究了雷达探测距离在不同干扰模式下的变化,并评估了隐身飞机的战术干扰性能.仿真结果表明,隐身飞机战术干扰方式灵活、干扰压制效能高,在一定程度上缩减了雷达探测距离.     

An optimization tool for satellite equipment layout

Selection of the satellite equipment layout with performance constraints is a complex task which can be viewed as a constrained multi-objective optimization and a multiple criteria decision making problem. The layout design of a satellite cabin involves the process of locating the required equipment in a limited space, thereby satisfying various behavioral constraints of the interior and exterior environments. The layout optimization of satellite cabin in this paper includes the C.G. offset, the moments of inertia and the space debris impact risk of the system, of which the impact risk index is developed to quantify the risk to a satellite cabin of coming into contact with space debris. In this paper an optimization tool for the integration of CAD software as well as the optimization algorithms is presented, which is developed to automatically find solutions for a three-dimensional layout of equipment in satellite. The effectiveness of the tool is also demonstrated by applying to the layout optimization of a satellite platform.     

基于碱金属辅助电离的等离子鞘套模拟方法

为解决再入过程中通信黑障与探测异常问题，对等离子体鞘套地面模拟方法进行了研究。以RAM C-II 飞行试验为依据，计算了等离子体鞘套的参数范围。分析现有模拟设备，概括提出了高焓低速风洞的模拟方案，选取相适应的放电方式，并对流量功率进行了计算。针对高温环境对电磁设备造成损坏以及所需功率难以实现的问题，提出添加碱金属的解决方案，并进行了试验验证。试验结果表明，添加碱金属可以使电子密度提升约一个数量级。对方案效果进行评估，预期功率需求降至兆瓦量级。     

GNSS global real-time augmentation positioning: Real-time precise satellite clock estimation,prototype system construction and performance analysis

Lots of ambiguities in un-differenced (UD) model lead to lower calculation efficiency, which isn’t appropriate for the high-frequency real-time GNSS clock estimation, like 1 Hz. Mixed differenced model fusing UD pseudo-range and epoch-differenced (ED) phase observations has been introduced into real-time clock estimation. In this contribution, we extend the mixed differenced model for realizing multi-GNSS real-time clock high-frequency updating and a rigorous comparison and analysis on same conditions are performed to achieve the best real-time clock estimation performance taking the efficiency, accuracy, consistency and reliability into consideration. Based on the multi-GNSS real-time data streams provided by multi-GNSS Experiment (MGEX) and Wuhan University, GPS + BeiDou + Galileo global real-time augmentation positioning prototype system is designed and constructed, including real-time precise orbit determination, real-time precise clock estimation, real-time Precise Point Positioning (RT-PPP) and real-time Standard Point Positioning (RT-SPP). The statistical analysis of the 6 h-predicted real-time orbits shows that the root mean square (RMS) in radial direction is about 1–5 cm for GPS, Beidou MEO and Galileo satellites and about 10 cm for Beidou GEO and IGSO satellites. Using the mixed differenced estimation model, the prototype system can realize high-efficient real-time satellite absolute clock estimation with no constant clock-bias and can be used for high-frequency augmentation message updating (such as 1 Hz). The real-time augmentation message signal-in-space ranging error (SISRE), a comprehensive accuracy of orbit and clock and effecting the users’ actual positioning performance, is introduced to evaluate and analyze the performance of GPS + BeiDou + Galileo global real-time augmentation positioning system. The statistical analysis of real-time augmentation message SISRE is about 4–7 cm for GPS, whlile 10 cm for Beidou IGSO/MEO, Galileo and about 30 cm for BeiDou GEO satellites. The real-time positioning results prove that the GPS + BeiDou + Galileo RT-PPP comparing to GPS-only can effectively accelerate convergence time by about 60%, improve the positioning accuracy by about 30% and obtain averaged RMS 4 cm in horizontal and 6 cm in vertical; additionally RT-SPP accuracy in the prototype system can realize positioning accuracy with about averaged RMS 1 m in horizontal and 1.5–2 m in vertical, which are improved by 60% and 70% to SPP based on broadcast ephemeris, respectively.     

基于稀疏时频分解的空中目标微动特征分析

本文以直升机的RCS 信号为研究对象，利用Gabor 原子构造过完备时频原子库，在该库上实现基于匹配追踪（Matching Pursuit，MP）的信号分解，并结合遗传算法寻找最佳匹配原子。最后将每次分解得到的Gabor 原子进行Wigner-Ville 变换，利用结果叠加得到无交叉干扰项的信号的Wigner-Ville 分布（Wigner-VilleDistribution，WVD）。仿真结果表明，该方法能够提高稀疏分解的效率，并且用少量的Gabor 原子就能表示信号WVD。与直接进行Wigner-Ville 变换相比，本方法可以有效地抑制交叉干扰项，且保持高时频分辨率。     

交会对接光学成像敏感器中合作目标的分析与设计

交会对接技术是实现太空梭、太空平台和空间运输系统的装配、回收、补给、维修、太空人交换及营救等在轨服务的先决条件，交会对接光学成像敏感器是两航天器交会对接近距离平移靠拢段唯一能够提供六自由度相对导航信息的敏感器，由安装于追踪飞行器上的相机和安装于目标飞行器上的合作目标组成，采用角反射器作为合作目标标志，完成两飞行器间的相对位姿的解算.对其需求分析、设计方案、回光能量测试等进行了讨论，该方案已在神舟十一号载人飞船、天舟一号货运飞船与天宫二号的交会对接任务中成功验证，后续针对空间站及光学舱任务进行适应性修改.