最大熵谱估计及其在电子战中的应用

介绍了最大熵谱估计的原理，与快速傅里叶变换相比，它有低的旁瓣和高的分辩力。同时讨论了在电子战方面的应用。     

一种基于协方差矩阵重构的相干信源DOA估计算法

针对空间相干信源的波达方向估计问题,提出了一种基于协方差矩阵重构的TSVD-ESPRIT算法。它利用包含所有信源信息的特征向量构造Toeplitz协方差矩阵,避免了阵列有效孔径的损失,分辨率高且稳定性好;并且利用ESPRIT算法代替MUSIC算法进行DOA估计,避免了谱峰搜索,大大降低了计算量。数据仿真和分析证明了该算法的正确性和有效性。     

Evaluation of Characteristics of Non-Metallic Inclusions in P/M Ni-Base Superalloy by Automatic Image Analysis

Non-metallic inclusions,especially the large ones,within P/M Ni-base superalloy have a major influence on fatigue characteristics,but are not directly measurable by routine inspection.In this paper,a method,automatic image analysis,is proposed for estimation of the content,size and amount of non-metallic inclusions in superalloy.The methodology for the practical application of this method is described and the factors affecting the precision of the estimation are discussed.In the experiment,the characteristics of the non-metallic inclusions in Ni-base P/M superalloy are analyzed.     

Navigation Accuracy Category-Position Models and Estimate Position Uncertainty Calculations for TIS-B System

Navigation accuracy category-position (NACp) is an important parameter for system accuracy of traffic information service-broadcast (TIS-B), which is determined by estimate position uncertainty (EPU). Centered about the problems that the existing EPU calculation based on noise measurement is low in accuracy and unfit for describing uncorrected biases in target reports, this article analyses the traditional NACp model, and uses the least square estimation (LSE) in EPU calculation. Furthermore, it proposes an extended NACp model, which considers both noise and biases and acquires EPU estimation with the help of approximate multiplex Taylor expression. Analysis and simulation show that the proposed method not only leads to significant improvement of the accuracy of EPU calculation, but is fit for EPU calculation with tracking biases in TIS-B system as well. As such it can find application in practice to depict different kinds of error models in TIS-B system.     

机载设备外场数据的可靠性增长分析

对我国航空机载设备外场数据的性质进行分析后,提出该种数据是变动母体混合数据,不同于通常用于可靠性估计的不变母体数据。提出外场数据中含有可靠性增长信息。 为利用外场数据来分析和评估航空机载设备的可靠性增长和可靠性状态,提出一个数学模型。模型的基本原理是最小二乘法。为说明模型的使用提供了一个实例。     

Assessment of the consequences of the Fengyun-1C breakup in low Earth orbit

On 11 January 2007, the People’s Republic of China conducted a successful anti-satellite test against one of their defunct polar-orbiting weather satellites. The target satellite, called Fengyun-1C, had a mass of 880 kg and was orbiting at an altitude of about 863 km when the collision occurred. Struck by a direct-ascent interceptor at a speed of 9.36 km/s, the satellite disintegrated, spreading the cataloged fragments between 200 and 4000 km, with the highest concentration near the breakup height. By the end of April 2008, 2377 pieces of debris, including the original payload remnant, had officially been cataloged by the US Space Surveillance Network. Of these, nearly 1% had reentered the Earth’s atmosphere. This deliberate act is the largest debris-generating event on record, and its consequences will adversely affect circumterrestrial space for many years.     

高动态下基于DMF的伪码捕获频差估计研究

基于数字匹配滤波器（DMF）的PN码捕获电路具有较快的捕获速度,但其输出主相关峰值对频差较为敏感。为了消除频差对捕获性能的影响,文章提出了一种基于FFT的频差估计算法。首先构造一个载波频差的希尔波特复矢量,然后对其进行快速傅里叶变换。该算法能够精确检测出载波频偏的绝对值大小和方向,可以有效地改善大频差下的伪码捕获性能。     

非线性时间序列在卫星通信网络数据预测中的研究

卫星通信网络数据预测在卫星通信系统中起着重要的作用,是系统建模的主要研究内容之一。由于卫星通信网络数据的非平稳性和不可预知因素的影响,决定了应采用非线性时间序列建模方法来分析、预测。在分析通信网络数据的基础上,建立卫星通信网络数据的ARIMA模型,在确定预测模型的阶和进行参数估计后,给出不同预测步数条件下的通信网络数据流量的预测,并进行了仿真对比实验。仿真结果表明,该模型在预测步数较小的情况下,预测误差在4％左右,具有良好的预测精度,为卫星通信网络数据流量的预测、异常检测和网络负载预测的应用奠定了坚实的基础。     

航空发动机鲁棒线性变参数滤波器设计

针对航空发动机线性变参数(LPV)模型部件性能参数估计问题,给出了一种新的鲁棒LPV滤波器设计方法。基于参数依赖的二次Lyapunov函数及仿射二次稳定性概念得到了稳定且满足H∞性能指标滤波器存在的充分条件,利用函数多凸性概念将其转化为线性矩阵不等式(LMI)约束下的常规凸优化问题,得到了滤波器的解。针对某型退化涡扇发动机部件性能参数估计的仿真结果表明,该滤波器的精度和鲁棒性满足设计要求。