高度-速度剖面内再入轨迹快速规划

提出一种升力式再入航天器进入稠密大气后的轨迹规划方法。在预先设定攻角剖面的前提下，利用路径约束(驻点热流、动压和过载)在高度-速度(H-V)剖面内直接获得轨迹下边界；利用终端约束确定以轨迹下边界为基准的高度增量，进而通过下边界与高度增量的加和形成满足要求的再入轨迹。其中，增量的形式选取为分段二次型函数，其大小可通过割线法快速获得。倾斜角大小可根据纵向动力学方程反解得到，其方向依据航向误差角走廊确定。通过对典型工况的仿真，结果表明所提方法能够快速规划出再入轨迹，且适应性好。     

Experimental investigation on silica dust lofting due to charging within micro-cavities and surface electric field in the vacuum chamber

The charged dust particles can be mobilized electrostatically by the repulsion between the adjacent grains and the surface electric field due to the incoming electron current and the charge accumulation within the micro-cavities. In this study, the experimental results of the initial vertical launching velocities and the maximum dust heights are compared with the estimated values for the lofted spherical dust grains by the patch surface charging equations. Silica particles with the sizes between <6 and 45?µm in radius are loaded on a graphite plate, and they are exposed to the electron beam with 450?eV energy under 4?×?10^?3?Pa vacuum chamber pressure. During the first set of the experiments, the dust samples are tested without an initial compression process and an additional horizontal electric field. Second, the dust samples are compressed by two different weights in order to increase the packing density under approximately 780.7?Pa and 3780?Pa. Finally, the dust grains are placed between the two parallel aluminum plates to apply approximately 2000?V/m and 4800?V/m horizontal electric field. A high-speed camera is used to record the transportation of the dust grains together with a microscopic telescope, and the results point out that the patch surface dust-charging model estimations are in agreement with the first experiments. On the other hand, the dust particles from the compressed samples are lofted with higher velocities than the estimations, and the number of the dust lofting observations decreases significantly, which demonstrates the importance of the micro-cavities and the increased charging requirement to overcome the contact forces. When the horizontal electric field is present, the initial vertical launching velocities are measured to be lower than the other experiments, which can be attributed to the decreased charging requirement for the dust lofting as a result of inter-particle collisions and rolling motion. According to the experimental results, the electrostatic dust transportation can be controlled not only by the ambient plasma and the solar irradiation on the airless planetary bodies, but also by the surface properties such as the contact surfaces between the dust grains, the number of the micro-cavities related to the packing density, and the presence of the horizontal electric field contributing to the external forces by other particle motions.     

基于嵌入式FPGA加速ORB算法的遥感影像配准方法

卫星上计算资源有限，星载嵌入式处理器处理遥感影像的配准时通常需要很长的时间。可编程逻辑门阵列（FPGA）利用其内部可编程器件可用于加速图像处理。提出了一种基于Xilinx公司的ZYNQ芯片加速ORB算法的遥感影像配准方法，可用于3000×3000像素尺寸的卫星图像配准，缩短了计算耗时，提升了ORB算法的计算能效比。利用FPGA能够实现真正的并行计算电路，实现ORB算法多支路单层流水线的并行计算结构。采用软硬件结合的方法实现架构，能够处理不同分辨率的图像，可灵活配置特征点的数量。基于设计的加速ORB配准方法，获得了较高准确率。与软件实现相比,OVS-1A遥感影像偏移精度损失低于0.05个像元;GF.4遥感影像偏移精度损失小于0.9个像元。将ORB配准算法流程应用在ZYNQ7020上，耗时减少了57.50%。     

A general calculation method to specify center-of-buoyancy for the stratospheric airship with multiple gas cells

As the lighter-than-air (LTA) flight vehicle, the stratospheric airship is a desirable platform to provide communication and surveillance services. During the ascent from sea-level to the mission altitude, the volume of the lifting gas may change significantly, which will result in the change of the center-of-buoyancy (CB). A general calculation method is developed to specify CB for the stratospheric airship with a double-ellipsoid hull and an arbitrary number of the gas cells. The cross-section-integral (CSI) method is used as a basic calculation scenario to specify CB. Considering the complexity in determining the boundary between the helium and air in the gas cell, a searching algorithm is put forward and the specification of CB can be conducted by the iterative calculation. As an important application, the stable condition of the pitch angle is analyzed when the change of CB is involved. Under different initial configurations, the stable pitch angle of the stratospheric airship during the ascent is specified and compared, which shows the advantages of the multi-gas-cell configuration. The results of this paper may provide an important reference for the engineering application of the stratospheric airship.     

基于知识图谱和自动机器学习的软件缺陷预测

不稳定和召回率低效的软件缺陷预测模型难以在行业领域应用，为解决稳定和高效各项性能评价指标的软件缺陷预测模型在工程实践应用的问题，提出了一种基于知识图谱和自动化机器学习的软件缺陷预测方法AutoKGGAS，首先获取软件缺陷预测模型数据，对知识建模、知识获取、知识融合、知识储存与知识计算等知识图谱构建技术研究，实现知识图谱推荐优质软件缺陷预测模型作为自动化搜索的热启动输入条件，根据不同的软件缺陷预测评价指标，优化不同最佳的模型结构.其次实证研究采用NASA开源数据集实验对象和六种性能评价指标，实验结果表明， AutoKGGAS自动化软件缺陷预测模型在不同数据集不同评价指标方面，性能优于知识图谱推荐的传统经典软件缺陷预测模型.自动化软件缺陷预测模型为航天软件缺陷预测辅助代码审查测试提供了原型，在工程实践应用方面具有重要的意义.     

非恒定增压式微尺度拉瓦尔喷管流动特性

针对微尺度喷流在航天器运动状态切换时出现的非恒定增压变化,采用直接模拟蒙特卡洛(DSMC)方法对阶跃式增压和线性式增压两种模式下的微尺度拉瓦尔喷管流场进行了模拟,并对其变化过程中的流动特性进行了对比分析。结果显示：阶跃式增压会导致流动特性出现较大幅值的峰谷式波动,而线性式增压下的流动特性则呈现出线性变化的特点;黏性力对微尺度喷流的非恒定增压变化产生了重要的黏滞作用,在喉部扩张段至出口的流场中尤为明显;在设定的条件下,阶跃式增压过程中喷流产生的总冲量较线性式增压高59.5%,质量流量高74.7%,单位工质提供的冲量低约8.6%,波动性也高于线性式模型,阶跃式增压适用于系统需要较大推力改变运动状态且推进剂充足的情况,而线性式增压在系统精确微调或需要推进剂产生更高效能时具有明显的优势。     

一种利用ILSP的同步DS-CDMA信号快速盲解扩算法

针对同步DS-CDMA信号的盲解扩问题，本文提出了一种基于迭代最小二乘投影算法(ILSP)的快速盲解扩算法。本算法首先通过对截获信号的协方差矩阵进行特征分解，估计出由各用户扩频序列张成的信号子空间，然后结合扩频码序列的有限符号集特性，利用ILSP算法消除由特征分解产生的酉矩阵模糊问题，得到扩频序列的精确估计，最后利用估计得到的扩频序列对截获信号解扩得到信息码序列，完成DS-CDMA信号的盲解扩。仿真结果表明本算法在低信噪比条件下具有良好的盲解扩性能，且相较传统算法本文提出算法大大降低了计算复杂度 。     

等离子鞘套热力学波动对电磁波传播的影响

针对等离子鞘套热力学波动造成电磁波传播特性变化的问题，结合湍流理论、等离子理论和电磁波传播理论，得到了热力学参数波动与介电常数间的关系。计算了不同状态下热力学参数波动引起S和Ka波段电磁波透射和反射系数的变化。结果表明，当电子密度增大，S波段反射系数变化减小、透射系数变化增大；当Ka波段在碰撞频率10MHz时，反射系数变化增大、透射系数变化减小，在碰撞频率1GHz和50GHz时透射系数变化反射系数变化先增后减。不同高度下波动的影响也不同，S波段透射和反射系数变化随高度升高先减后增；Ka波段透射系数变化先减后增、反射系数变化先减后增而后再次减小。因此，应根据实际环境状态获得波动的包络范围，进而针对性开展测控通信系统设计。     

防风网对煤堆遮风效果的风洞实验研究

为了考察防风网对堆场煤堆的遮风效果,进行了防风网与煤堆之间区域的流场可视化实验。使用风洞模拟大气边界层条件,并将开孔率为38.5%的防风网模型布置在煤堆模型前方。实验中采用粒子成像测速(PIV)系统测量了防风网和堆场区域的平均风速分布,并且获得了煤堆表面的摩擦风速分布,进一步估算煤堆起尘量的变化情况。实验发现,防风网可有效降低煤堆表面迎风区域的摩擦风速,而对背风面的流场分布影响较小。研究结果可为防风网的遮护作用提供一定的实验支持。     

支线飞机综合飞行仿真平台设计

针对支线飞机机械操纵系统的特点,设计了由模块化的功能单元组成的综合飞行仿真平台,可以实现机械操纵系统数字仿真,在支线飞机的设计与制造中有着重要的应用价值,此平台通过改进还可用于支线飞机的试飞科目训练,从而降低试飞风险并缩短研制周期。