基于动态逆和神经网络的机动弹头姿态控制系统设计

机动弹头是复杂的非线性系统,它给姿态控制系统设计人员以极大的挑战。为了满足飞行稳定性要求,提高系统的适应性和鲁棒性,本文构造了动态逆神经网络姿态控制系统,设计了慢变量和快变量动态逆,引入了在线神经网络进行逆误差的补偿。实例仿真的结果表明:动态逆和在线神经网络的结合,能够实现弹头的稳定飞行。     

一种恒电长度干涉仪分析的新方法

对数周期天线的相位中心随频率呈线性变化,用2个对数周期天线可以构成具有恒电特性的干涉仪天线阵,在工程应用中,天线相位中心较大的测试误差会导致天线阵调试困难.通过对恒电长度干涉仪的分析,提出了利用相位扫频测试对天线阵进行调试分析的方法,避免了繁杂的相位中心测试,简化了天线阵的调试过程,测试数据可直接用于系统校正.     

重力空射稳定伞阻力特征自动化设计

为进行重力空射稳定伞的初步设计,文章以多体动力学软件(ADAMS)为二次开发平台,构建了重力空射箭-伞系统的动力学仿真模型;推导了火箭和稳定伞的气动模型,并利用动态链接子程序实现了气动力的加载;通过ADAMS命令语言建立了参数化模型和用户界面。在此基础上,自编可行方向优化算法实现了稳定伞阻力特征的自动化设计。最后,根据仿真计算结果对试验火箭出舱时间、安全通道、回收方式等问题进行了分析,为后续空射稳定伞的细节设计以及空射总体方案的确定提供了参考。     

Using the radial basis function neural network to predict ionospheric critical frequency of F2 layer over Wuhan

Neural networks (NNs) have been applied to ionospheric predictions recently. This paper uses radial basis function neural network (RBF-NN) to forecast hourly values of the ionospheric F₂ layer critical frequency(f_oF₂), over Wuhan (30.5N, 114.3E), China. The false nearest neighbor method is used to determine the embedding dimension, and the principal component analysis (PCA) is used to reduce noise and dimension. The whole study is based on a sample of about 26,000 observations of f_oF₂ with 1-h time resolution, derived during the period from January 1981 to December 1983. The performance of RBF-NN is estimated by calculating the normalized root-mean-squared (NRMSE) error, and its results show that short-term predictions of f_oF₂ are improved.     

拓扑数据分析在复杂脑网络分析中的应用

针对复杂脑网络分析中网络结构变化阈值选择中没有公认的标准确定合适阈值这一问题,基于拓扑分析中的持续同调性理论,本文提出一种多尺度大脑网络建模分析方法,该方法在大脑全尺度距离范围之内,通过不断增加阈值,运用Rips过滤算法捕获网络的动态持续拓扑特征,并用条形码和持续图对拓扑特征可视化,最后通过计算持续图之间的Bottleneck距离和Wasserstein距离分析持续特征的稳定性。实验结果表明,该方法能更准确地提取大脑网络的拓扑结构特征并提高诊断分类的准确性。     

气体自发光在高超声速流场显示中的应用

提出了利用高焓气体自发光作为高超声速流场显示的方法,介绍了在使用高焓运行的激波风洞中,对二维模型的高超声速绕流流场使用此种方法的初步结果,可观察到二维棱形柱的尾流和马赫波的相交。结果表明此种方法不需外加光源,对于结构限制无法设置透明部件的模型,无疑是简单可行的。     

A two-step weighted least-squares method for joint estimation of source and sensor locations: A general framework

It is well known that the Two-step Weighted Least-Squares(TWLS) is a widely used method for source localization and sensor position refinement. For this reason, we propose a unified framework of the TWLS method for joint estimation of multiple disjoint sources and sensor locations in this paper. Unlike some existing works, the presented method is based on more general measurement model, and therefore it can be applied to many different localization scenarios.Besides, it does not have the initialization and local convergence problem. The closed-form expression for the covariance matrix of the proposed TWLS estimator is also derived by exploiting the first-order perturbation analysis. Moreover, the estimation accuracy of the TWLS method is shown analytically to achieve the Cramér-Rao Bound(CRB) before the threshold effect takes place. The theoretical analysis is also performed in a common mathematical framework, rather than aiming at some specific signal metrics. Finally, two numerical experiments are performed to support the theoretical development in this paper.     

Very low frequency interferometry for the Chang’E-2 project

Very low frequency interferometry among two astronomical experiments has been proposed and accepted for further study for the second phase of China’s lunar exploration programme (the Chang’E Programme), which is envisaged to operate a lander and a rover on the surface of the moon. This experiment is an interferometer experiment in the very low frequency (VLF, f < 15 MHz) regime of radio frequencies with at least degree-level angular resolution. The goals include observing solar storm activities, Coronal Mass Ejections, Auroral Kilometric Radiation, and planetary radiation in the solar system, studying the origin of Cosmic Rays, spectral properties of pulsars, surveying ionized hydrogen in the Galaxy, and exploring coherent radio emissions.     

基于线性二次型的飞控参数故障渐近调节

 研究了含有参数故障的线性系统,提出了一种基于线性二次型的控制策略。采用该渐近调节反馈控制律,可以减小系统由于容错控制算法时延所致的性能下降。针对某飞机模型进行了仿真,结果验证了所提出策略的有效性。     

Coupled Stress-Electricity Model for Electromagnetic Emission Induced by Concrete Fracture

Electromagnetic emission induced during concrete fracturing is of great significance to health monitoring of concrete structures.A coupled stress-electricity model is established by analyzing the interaction between stress and electricity during concrete fracturing.And based on this model,the electromagnetic radiation parameters are calculated.The theoretical calculation is well coincident with experimental results.This work provides theoretical support for concrete testing system.