空时二维线性预测谱估计算法

线性预测是时间序列分析中常用方法,针对传统一维线性预测谱估计算法只能估计信号源角度或信号频率问题,提出空时二维线性预测算法。采取对空时二维阵列接收到的数据进行数据抽取和排列,和对数据协方差矩阵进行重新构造的方法,求取空时二维线性预测权值并进行谱峰搜索。重点分析了空时二维的前向预测、后向预测和双向预测算法的原理,着重研究了构造的空时二维线性预测协方差矩阵的数据结构,讨论了前向、后向和双向预测的相互关系以及二维与一维的关系,并与空时二维最小方差算法、空时二维多重信号分类(multiple signal classification, MUSIC)算法进行了对比与分析。理论分析与仿真表明,一维空域、一维时域算法的前向、后向和双向预测为空时二维预测算法的特例,同时空时二维预测算法不仅克服了空时二维最小方差算法、空时二维MUSIC算法不能解相干信号源的缺点,还具有很好的测向测频能力。     

Multi-target tracking algorithm of boost-phase ballistic missile defense

Considering the problem of multiple ballistic missiles tracking of boost-phase ballistic missile defense,a boost-phase tracking algorithm based on multiple hypotheses tracking(MHT) concept is proposed.This paper focuses on the tracking algorithm for hypothesis generation,hypothesis probability calculation, hypotheses reduction and pruning and other sectors.From an engineering point of view,a technique called the linear assignment problem(LAP) used in the implementation of M-best feasible hypotheses generation,the number of the hypotheses is relatively small compared with the total number that may exist in each scan, also the iV-scan back pruning is used,the algorithm’s efficiency and practicality have been improved.Monte Carlo simulation results show that the proposed algorithm can track the boost phase of multiple ballistic missiles and it has a good tracking performance compared with joint probability data association(JPDA).     

Method of target tracking with Doppler blind zone constraint

Doppler blind zone （DBZ） has a bad influence on the airborne early warning radar, although it has good detection performance for low altitude targets with pulse Doppler （PD） technology. In target tracking, the blind zone can cause target tracking breakage easily. In order to solve this problem, a parallel particle filter （PF） algorithm based on multi-hypothesis motion models （MHMMs） is proposed. The algorithm produces multiple possible target motion models according to the DBZ constraint. Particles are updated with the constraint in each motion model. Once the first measurement from the target which reappears from DBZ falls into the particle cloud formed by any model, the measurementtrack association succeeds and track breakage is avoided. The simulation results show that on the condition of different DBZ ranges, a high association ratio can be got for targets with different maneuverability levels, which accordingly improves the tracking quality.     

Cued search algorithm with uncertain detection performance for phased array radars

A cued search algorithm with uncertain detection performance is proposed for phased array radars. Firstly, a target search model based on the information gain criterion is presented with known detection performance, and the statistical characteristic of the detection probability is calculated by using the fluctuant model of the target radar cross section （RCS）. Secondly, when the detection probability is completely unknown, its probability density function is modeled with a beta distribution, and its posterior probability distribution with the radar observation is derived based on the Bayesian theory. Finally simulation results show that the cued search algorithm with a known RCS fluctuant model can achieve the best performance, and the algorithm with the detection probability modeled as a beta distribution is better than that with a random selected detection probability because the model parameters can be updated by the radar observation to approach to the real value of the detection probability.     

英语幽默会话中歧义现象的语义解析

从语义的角度对英语幽默会话中的歧义现象进行了分析和总结。通过解释语音引起的歧义、词汇引起的歧义和句法引起的歧义，阐明了歧义在英语会话中的幽默效果。     

基于主特征矢量的相干信号DOA估计算法

为了进一步提高相干信号DOA估计的精度,提出了一种基于主特征矢量的相干信号DOA估计改进算法。算法选取了信号子空间对应的主特征向量,将其进行反向共轭变换得到增广主特征矢量,再构造线性预测方程,利用加权最小二乘法求解预测方程中的多项式系数,最后求根得到信号的DOA估计。改进算法克服了PUMA算法在信号完全相干条件下性能恶化的缺陷,当信号完全相干以及部分相干时都具有良好的性能,并且提高了最大可分辨信号数,当信噪比较低、快拍数较少时仍保持较高精度。相比于PUMA算法,当信号部分相干时,文中算法的均方根误差约降低了0.2°;当信号完全相干时,均方根误差约降低了0.8°。通过与多种解相干算法进行比较,算法性能得到了验证。     

3N+1猜想中同汇性研究和超级压缩迭代

给出了关于3N 1猜想中的同汇概念，建立了相关的几个定义及定理，这些定理的建立在对研究奇数2a 1(a∈Nd)的压缩迭代时可以转化为研究奇数a的首席叙拉古阶，从而在研究这一类奇数的压缩迭代时起到简化作用．另外对3a(a∈Nd)型奇数，构造出与3a同汇的无穷数列．并给出超级压缩迭代概念及超级压缩迭代下的x的项公式。     

一些大损耗介质填充圆柱双站RCS的矩量法分析

用矩量法对一些用于雷达隐身技术和微波暗室设计的大损耗介电材料填充的无限长介质圆柱在TM波照射下的双站RCS进行了数值计算.仿真结果表明，大介电常数低损耗材料散射较弱.当ka0较小时，填充介质的电参数对散射的影响较明显，且随双站角增大缓慢减少；当ka0较大时，填充介质的电参数对散射的影响不明显，且散射能量集中于反射方向.     

3N+1猜想中周期数的研究

给出了关于3N 1猜想中周期数存在的一个必要条件：S^l(mxi)=nxi，并在此基础上推广为S^l(σbxi=n^b 1xi，且给出周期数x1的具体表达式x1=r1／(1-3^l／2^k)。证明了圈长为2和3的周期数不存在。     

一种改进不等间距灰色预测模型

传统不等间距灰色模型UGM(1,1)及其改进型都是基于指数模型建立的,仅对指数变化规律序列有较好的预测精度,而对于常见的线性变化序列则预测误差较大。针对该问题,通过模型拓展,在现有文献模型的基础上增加线性因素,并采用新陈代谢的思想,提出一种改进不等间距灰色预测模型AUGM(1,1),并进行实例仿真比较分析。结果表明:改进模型在预测精度和实用性上均有较大改善,且克服了传统灰色预测模型不适用于线性变化序列预测的局限,拓宽了灰色预测模型的适用范围。