非参量量化秩检测器的性能研究

 许多作者讨论过非参量秩检测器在雷达信号处理中的应用。秩检测器首先把接收波形样本转换为秩。如果检验单元和参考单元的噪声样本独立和分布,则无信号时检验单元的秩具有离散均匀分布,与输入噪声的分布无关。所以秩检测器可能提供分布自由的恒虚警率性能。量化秩检测器（QRD）只对二进量化秩进行积累,所以它实现起来很经济。本文分析QRD的检测性能。证明QRD有一最佳秩量化门限（ORQT）。确定高斯和韦伯噪声中的ORQT。另外,把QRD同高斯噪声中的局部最佳秩检测器和最佳参量检测器进行比较。     

现代飞机交流电源过电压保护问题探讨

本文在分析现代飞机电源系统所使用的几种过电压保护装置工作原理的基础上,着重对其反延时特性和动作电压进行计算,并就决定和影响过电压保护性能指标的电路参数的调整进行了计算和论述。     

关于刚体转动的角速度和角加速度的讨论

在理论力学教学中，平面运动刚体的转动与基点无关的证明过于简单，本利用矢量代数的知识，证明平面运动刚体的角度与角加速度与基点的选择无关。     

一种新的二维最大熵图象阈值分割方法

根据最大熵原理提出了一种用二维最大熵获取二值图象的新方法，介绍了用梯度－区域灰度均值二维最大熵求取阈值的原理和过程。计算机仿真结果表明，采用本文提出的阈值分割方法，对于直方图平坦的灰度图象处理效果尤为理想。     

Using gamma-ray burst prompt emission to probe relativistic shock acceleration

It is widely accepted that the prompt transient signal in the 10 keV–10 GeV band from gamma-ray bursts (GRBs) arises from multiple shocks internal to the ultra-relativistic expansion. The detailed understanding of the dissipation and accompanying acceleration at these shocks is a currently topical subject. This paper explores the relationship between GRB prompt emission spectra and the electron (or ion) acceleration properties at the relativistic shocks that pertain to GRB models. The focus is on the array of possible high-energy power-law indices in accelerated populations, highlighting how spectra above 1 MeV can probe the field obliquity in GRB internal shocks, and the character of hydromagnetic turbulence in their environs. It is emphasized that diffusive shock acceleration theory generates no canonical spectrum at relativistic MHD discontinuities. This diversity is commensurate with the significant range of spectral indices discerned in prompt burst emission. Such system diagnostics are now being enhanced by the broad-band spectral coverage of bursts by the Fermi Gamma-Ray Space Telescope; while the Gamma-Ray Burst Monitor (GBM) provides key diagnostics on the lower energy portions of the particle population, the focus here is on constraints in the non-thermal, power-law regime of the particle distribution that are provided by the Large Area Telescope (LAT).     

A simple control law for reducing the effective characteristic acceleration of a solar sail

The direction and magnitude of a solar sail acceleration are strongly related. For this reason, once the characteristic acceleration has been fixed, it is not possible to modulate the acceleration in a particular direction. In this work, a semi-analytical switching control law is derived, enabling a solar sail to emulate a smaller effective characteristic acceleration (without changes in geometry or optical properties); by periodically changing the pitch (cone) angle of the sail, in average over time, the acceleration produced by the sail matches exactly (in both direction and magnitude) that of a “smaller” sail. The range in which this is possible is determined, and the limitations on this range due to the size difference is computed. The method is validated on optimal Earth-Mars trajectories.     

Hexapod多自由度微激励系统的振动时域波形控制

摘要： Hexapod多自由度微激励系统常用于航天器有效载荷在轨微振动环境的模拟，但采用现有控制方法无法精确稳定跟踪低频正弦加速度，这是由于系统耦合度高、非线性在低频段较强，被控对象相位滞后过大造成的.针对此问题，基于传统离线迭代控制方法，提出一种复合超前校正、多倍频陷波滤波器的改进离线迭代控制方法.其中，离线迭代进行补偿控制，超前校正进一步补偿系统相位，多倍频陷波滤波器去除非线性干扰.跟踪低频定频正弦加速度的实验结果表明，对比传统离线迭代控制方法，改进方法收敛快、控制精度高；对比现有自适应正弦振动控制方法，改进方法将符合精度要求的加速度控制频带下限由14.5 Hz扩宽至8 Hz.实验结果验证了所提方法的有效性.     

基于最小一乘的跑道入口高度计算

跑道入口高度是关系着飞机能否安全着陆的关键参数,在其计算中需要采用曲线拟合预测的方法。目前大多是采用基于最小二乘准则的拟合方式。由于最小二乘准则的局限性,当下滑道随机误差不满足正态分布,在飞行数据中出现异常点时会给预测带来较大误差。将最小一乘方法引入到跑道入口高度计算问题中,提高了算法的稳健性,很好地克服了这一问题。     

Electric potential structures of auroral acceleration region border from multi-spacecraft Cluster data

This paper studies an auroral event using data from three spacecraft of the Cluster mission, one inside and two at the poleward edge of the bottom of the Auroral Acceleration Region (AAR). The study reveals the three-dimensional profile of the region’s poleward boundary, showing spatial segmentation of the electric potential structures and their decay in time. It also depicts localized magnetic field variations and field-aligned currents that appear to have remained stable for at least 80?s. Such observations became possible due to the fortuitous motion of the three spacecraft nearly parallel to each other and tangential to the AAR edge, so that the differences and variations can be seen when the spacecraft enter and exit the segmentations, hence revealing their position with respect to the AAR.     

小样本条件下多应力加速寿命试验预测方法

鉴于导弹中的电子设备价格昂贵、可用于试验的样本量少,在开展加速试验以及寿命预测的实际工作中通常为小样本的背景。文章研究探索小样本条件下多应力加速试验寿命预测方法,分别建立通用对数线性模型、 BAS-BP神经网络模型、灰色–支持向量回归模型,结合多应力加速试验数据在各应力条件下的样本容量分别为 56组、20组、10组、5组的情况下,比较 3种模型的预测效果,分析各模型的适用场合和时机,探索小样本条件下模型的选优问题,为小样本条件下多应力加速试验寿命预测提供有益的借鉴。