基于可靠性分析的立方星网络维护架构优化

立方星编队或星座构成分布式空间传感器网络，可提高立方星执行复杂空间任务的能力。然而立方星易发生故障，其故障时间不确定性也导致了传感器网络性能的不稳定，这凸显了对立方星网络进行在轨维护的重要性。考虑立方星传感器网络的功能维持问题，描述了一种网络维护架构，通过定期发射、在轨备份立方星以及时更换故障立方星，从而提高网络对单星随机失效事件的快速响应与恢复能力。建立了该架构的运行成本模型，包括固定成本、储存成本和短缺成本。收集整理了真实的立方星寿命数据，并使用最大化拟合优度参数估计方法得到最优立方星寿命的随机模型。采用基于蒙特卡罗仿真的遗传算法优化备用立方星的补给时刻和补给数量，在备份成本与系统性能下降所带来的损失之间进行权衡，使得系统的综合收益最优。     

基于ADS-B的飞机冲突探测

面对飞行流量持续快速增长、民航空域资源日益短缺的状况,对飞机间的潜在冲突进行有效探测,是避免飞机间危险接近或碰撞发生的关键.对飞机周围区域进行合理建模,给出了一种基于广播式自动相关监视(ADS-B)技术的确定型冲突探测算法,充分利用ADS-B报文提供的经度、纬度、速度和航向等信息及其报文高更新率等特点,预先排除无威胁飞机,然后分别从水平和垂直两个方向对飞机之间的冲突进行探测.运用Matlab进行功能仿真,结果表明该算法能有效排除无威胁的飞机,并且能够对有威胁的飞机及时给出告警.该算法对保证自由飞行条件下的飞行安全具有积极意义.     

空间引力波探测微牛电推进寿命评估研究现状

阐述了空间引力波探测任务中无拖曳控制技术对推进系统的特殊要求，介绍了目前主要的备选推进类型：冷气推进、离子电推进、会切型霍尔电推进、胶体电推进。针对面向空间引力波探测任务的电推进系统的寿命评估工作进行了任务分析，报告了目前微牛级电推进系统寿命试验研究现状，举例说明了目前主要应用的电推进装置寿命预测方式，包括半经验模型预测、数值模拟预测、基于数据驱动的预测以及系统层面的可靠性评估方法。对目前微牛级电推进系统的寿命评估研究现状进行总结，给出了发展思路。     

三种时频分析在复合材料无损检测中的应用

随着复合材料的广泛应用和现代信号处理技术的发展,时频分析方法已广泛应用于各类复合材料的损伤检测。将短时傅立叶变换、小波变换和黄氏变换三种时频分析技术经过Matlab编程,结合Lamb波应用于玻璃纤维增强的复合材料层合板的无损检测,并对三种时频结果进行比较与分析。结果表明：上述三种时频分析方法都能进行复合材料的损伤判定,但黄氏变换方法的分析精度更高。     

A novel signal processing approach for LEO space debris based on a fence-type space surveillance radar system

The increase in space debris can seriously threaten regular activities in the Low Earth Orbit (LEO) environment. Therefore, it is necessary to develop robust, efficient and reliable techniques to understand the potential motions of the LEO debris. In this paper, we propose a novel signal processing approach to detect and estimate the motions of LEO space debris that is based on a fence-type space surveillance radar system. Because of the sparse distribution of the orbiting debris through the fence in our observations, we formulate the signal detection and the motion parameter estimation as a sparse signal reconstruction problem with respect to an over-complete dictionary. Moreover, we propose a new scheme to reduce the size of the original over-complete dictionary without the loss of the important information. This new scheme is based on a careful analysis of the relations between the acceleration and the directions of arrival for the corresponding LEO space debris. Our simulation results show that the proposed approach can achieve extremely good performance in terms of the accuracy for detection and estimation. Furthermore, our simulation results demonstrate the robustness of the approach in scenarios with a low Signal-to-Noise Ratio (SNR) and the super-resolution properties. We hope our signal processing approach can stimulate further work on monitoring LEO space debris.     

基于运动特征和中心环绕模型的空对地车辆检测方法

平台的移动基于空基车辆检测以其视野广、速度快、适应性强等优点,近些年成为了智能交通和航空应急救援等领域内的一个热点课题。然而,在城市背景的交通环境下,由于复杂背景造成的干扰、车辆运动的不规律性以及光照等条件变化带来的噪声,有效地获取运动对象特征是空对地视觉监视方法面临的一个难题。为有效解决这一问题,提出了结合运动特征的中心环绕模型进行空对地车辆检测的算法。现有的空对地车辆检测算法,大多是针对固定的摄像头的情况下,基于运动特征进行检测,例如光流法、背景差法等。这些方法在对高速公路等背景相对较为简单的环境下获得了良好的检测结果,但当面对城市复杂背景条件或摄像头自身运动的状况时,难以有效地检测出运动目标。而在对颜色、强度等静态特征进行显著度分析的基础上,加入了对运动特征的分析,可以解决在复杂环境下准确提取车辆目标有效特征的问题。试验表明,相较于基于图像相减的检测算法和单一显著度算法,该算法可以获得更高的检测率与更低的误报率。     

BP网络在信号检测中的应用

本文对ＢＰ网络在信号的检测和处理方面的性能进行了分析，对该网络在信号检测中的应用进行了讨论并给出了计算机仿真结果。     

An Adaptive Network-based Fuzzy Inference System for the detection of thermal and TEC anomalies around the time of the Varzeghan,Iran, (Mw = 6.4) earthquake of 11 August 2012

Anomaly detection is extremely important for forecasting the date, location and magnitude of an impending earthquake. In this paper, an Adaptive Network-based Fuzzy Inference System (ANFIS) has been proposed to detect the thermal and Total Electron Content (TEC) anomalies around the time of the Varzeghan, Iran, (M_w = 6.4) earthquake jolted in 11 August 2012 NW Iran. ANFIS is the famous hybrid neuro-fuzzy network for modeling the non-linear complex systems. In this study, also the detected thermal and TEC anomalies using the proposed method are compared to the results dealing with the observed anomalies by applying the classical and intelligent methods including Interquartile, Auto-Regressive Integrated Moving Average (ARIMA), Artificial Neural Network (ANN) and Support Vector Machine (SVM) methods. The duration of the dataset which is comprised from Aqua-MODIS Land Surface Temperature (LST) night-time snapshot images and also Global Ionospheric Maps (GIM), is 62 days. It can be shown that, if the difference between the predicted value using the ANFIS method and the observed value, exceeds the pre-defined threshold value, then the observed precursor value in the absence of non seismic effective parameters could be regarded as precursory anomaly. For two precursors of LST and TEC, the ANFIS method shows very good agreement with the other implemented classical and intelligent methods and this indicates that ANFIS is capable of detecting earthquake anomalies. The applied methods detected anomalous occurrences 1 and 2 days before the earthquake. This paper indicates that the detection of the thermal and TEC anomalies derive their credibility from the overall efficiencies and potentialities of the five integrated methods.     

X-47B无人空战系统及其对抗途径分析

X-47B型无人空战系统是当今最先进的无人机系统之一,势必给现有电子对抗技术及装备带来严重冲击.从其任务使命、系统功能、特色技术入手,分析对其实施电子对抗的技术难点和可能的薄弱环节,探讨对X-47B进行侦察探测和电子对抗的技术途径.     

频率捷变时间精密测试系统

较详细地介绍了捷变时间的定义以及６种常用测量方法的原理、数据处理过程、及测量结果等内容。６种方法分别为检相－示波器法、鉴频－示波器法、检相－时间间隔计数器法、鉴频一时间间隔计数器法，ＨＰ５３７２Ａ测频和ＨＰ５３７２Ａ测相。给出了这几种测量方法的适用范围和优缺点。