The Output Pdf of a Polarity Coincidence Correlation Detector

A general expression is derived for the probability density function of the output of a cross correlator, the inputs of which are assumed to consist of clipped sine waves of similar frequency plus uncorrelated, stationary Gaussian noise. The correlator output is shown to be a piecewise linear function of the random phase difference between the two input processes; hence, the density function for the correlator output is obtained by a relatively simple transformationfrom the probability density function of the random phase difference.     

Signal Representation by Prolate Spheroidal Wave Functions

The efficiency for signal representation of the angular prolate spheroidal wave function, particularly the two sets Sol(1, t) and Sol(8, t) is discussed Six signal waveforms are considered: rectangular, triangular, trapezoidal, exponential, Gaussian, and cosine-squared. For each, a representation is made in terms of the two sets above and also the Fourier cosine functions. As the number of terms of the representation increases, the approximation gets better. A measure of the ?goodness? of the approximation is the percentage of the total signal energy represented by the finite expansion, over a fixed, finite time interval. The angular prolate spheroidal wave functions are a very efficient orthogonal set in this sense. Their principal advantage over Fourier cosine functions occurs for cases whereby only a very few terms of the expansion are to be used to approximate a signal shape.     

基于GRASP算法的 甲板航空保障作业流程优化

甲板航空保障作业流程是连接舰载机回收和出动的重要纽带,是舰载机机群作战能力生成的核心环节。面向航空保障作业部分流程的不确定性,以航空保障完工时间最小化为优化目标,考虑甲板作业过程所涉及的固定前后序流程约束、不可并行作业约束、保障人员约束、保障设备约束和资源供给能力约束等约束条件,构建了甲板航空保障作业流程优化的数学模型;在此基础上,针对问题的求解设计了相适应的GRASP算法,在初始解构造阶段引入了基于规则的生成策略,在邻域搜索阶段采用双向对齐机制进行局部优化。基于保障任务案例的仿真结果显示,该算法有效地解决了甲板航空保障作业流程优化且相对于其他经典算法更为高效和稳定。     

Effect of Vertical Deflections and Ocean Currents on a Maneuvering Ship

Vertical deflections and ocean currents introduce errors into ship's inertial navigation systems (SINS). In the absence of exact knowledge, these quantities may be treated as distance-dependent stationary random processes. However, these distance-dependent random processes enter SINS as time-dependent error sources. The autocorrelation functions of these time functions depend on the manner in which the ship maneuvers. An equation relating the time-dependent autocorrelation function to the distance-dependent autocorrelation function is derived. The time-dependent autocorrelation function is obtained for four different situations. The first two examples are ships steaming at constant heading and constant, but not necessarily known, velocity. The third example involves a ship tracking back and forth over the same path. The last example describes a ship that steams at a constant speed but changes heading in a random manner.     

基于边界的无人机主动SLAM算法

同步定位与地图构建技术是无人机实现真正自主导航的关键。为克服被动同步定位与地图构建算法的缺陷,研究了基于边界的无人机主动同步定位与地图构建算法。在无人机的探测区域周围产生候选边界点,通过建立合理的目标函数,从候选边界点中选择目标点,控制无人机朝该目标点方向运动,再运用扩展卡尔曼滤波算法更新无人机的运动状态。通过建立的无人机简化模型,对提出的算法和随机同步定位与地图构建算法进行对比研究,仿真结果表明该算法是有效可行的。     

The Circular Synthetic Radar

A new type of synthetic radar, the circular synthetic radar, uses a simple interferometer whose elements are mounted at the ends of a horizontal boom rotating about a vertical mast. Pulses are radiated alternately ?in-phase? and in ?phase-quadrature.? The returning echoes are also detected incoherently, both ?in-phase? and in ?phase-quadrature.? The four distinct outputs are fed into an on-line computer which, after a Fourier analysis, synthesizes a mapping function of the azimuthal distribution of targets.     

Output Probability Density Functions for Cross Correlators Utilizing Sampling Techniques

Sampling techniques provide a practical means of obtaining cross-correlation functions. In this paper, the correlation function is described by sums of the form Z = begin{equation*}Z = Sigma^{N}_{j=1}X_{j}Y_{j}end{equation*}. A general expression is derived for the probability density function of the random variable Z under the condition that Xj and Yj are stationary, jointly Gaussian random processes with nonzero means and unit variances.     

Measurement of Distributed Targets with the Random Signal Radar

A model of a distributed target as a collection of independent, Poisson distributed point scatterers or scattering centers in a range-velocity target space is introduced and is characterized by a deterministic function called the ?scatterer density function.? This function is the density of the point scatterers in the range-velocity space and can be estimated in a relatively straightforward manner by any radar having adequate resolution in both range and velocity and no ambiguities in the region occupied by the distributed target. The use of the random signal radar with a correlator receiver is considered here and the statistical properties of the correlator output, when the return signal is from a distributed target, are derived. It is shown that the spectral density is simply related to the scatterer density function. The technique is illustrated by an example in which the target is a tornado modeled as a cylinder with constant angular velocity. The example suggests that is a possible to remotely estimate the radar cross section per unit volume as a function of distance from the center of the tornado.     

面向战例知识图谱的本体构建

为构建合理的战例知识图谱,提出了一种面向领域知识图谱的工程化本体构建方法。基于该方法,构建了战例领域本体模型,建立了战例本体与实体的映射机制。检验实证,该方法构建的本体合理有效,能够为战例领域知识图谱构建提供有效的模型支撑。     

Recursive Computation of the Generalized Q Function

A recursive method of computing values of the generalized Q function is described. The Q function is also interpreted in terms of noncentral chi-square distributed random variables, and in terms of the difference between Poisson random variables.     

一种新的非扩张映像不动点的复合迭代算法

在Banach空间中．引进了一种新的逼近非扩张映像不动点的复合隐迭代格式。证明了一些弱收敛和强收敛定理。并给出了相对收敛率的估计。本研究结果改进了已有同类的结果。     

Statistical analysis of real clutter at different range resolutions

A statistical analysis is presented of real radar clutter data collected using the McMaster I FIX radar in 1998 and stored in the Grimsby database. We first show the deviations of the amplitude statistics from the Rayleigh model and the suitability of the K- and Weibull-distribution for the first-order amplitude statistical characterization. Thus we focus on the I and Q components of the available data and study their statistical compatibility with the compound Gaussian model. Towards this goal it has been necessary devising appropriate testing procedures; in particular, with reference to the higher order statistics agreement, we have designed a validation procedure involving the clutter representation into generalized spherical coordinates. Remarkably the results have confirmed the suitability of the spherically invariant random processes (SIRPs) for the correct modeling of the radar clutter. Finally we have performed a spectral analysis highlighting the close matching between the estimated clutter spectral density and the exponential model.     

随机振动载荷作用下的结构疲劳寿命估算

介绍了随机过程功率谱密度(PSD)函数的特性,讨论了在各种不同随机振动载荷下应用有限元分析(FEA)获得的应力响应功率谱密度(PSD)函数寿命预测的公式,并设计出具有实际应用价值的、可用于飞机研制工作的结构疲劳寿命估算计算机程序(FORTRAN程序)。为说明寿命预测的实际过程,文中最后对某型号飞机减速板进行了结构疲劳寿命的估算。     

随机运动目标区域持续探测概率的近似模型

研究了随机运动目标区域持续探测的探测概率描述和计算问题。定义了探测函数及目标存在和探测不成功的联合概率密度函数,推导了基于速度分布密度的搜索方程和基于特征迹线的方程的解。鉴于在搜索理论应用中难以获得时变的速度分布,以及搜索方程精确解的复杂性,提出了基于初始速度分布密度的对随机恒速运动目标的一个近似的搜索方程,给出了探测概率的解,并以直升机吊放声纳的一次探测过程,进行了算例仿真。     

Non-Gaussian random vector identification using sphericallyinvariant random processes

With the modeling of non-Gaussian radar clutter in mind, elegant and tractable techniques are presented for characterizing the probability density function (PDF) of a correlated non-Gaussian radar vector. The need for a library of multivariable correlated non-Gaussian PDFs in order to characterize various clutter scenarios is discussed. Specifically,. the theory of spherically invariant random processes (SIRPs) is examined in detail. Approaches based on the marginal envelope PDF and the marginal characteristic function have been used to obtain several multivariate non-Gaussian PDFs. An important result providing the PDF of the quadratic form of a spherically invariant random vector (SIRV) is presented. This result enables the problem of distributed identification of a SIRV to be addressed     

Transient Response of Tracking Filters with Randomly Interrupted Data

The transient responses during the initialization phase of a first-order ?-? tracking filter and a second-order Kalman filter are evaluated as a function of radar measurement accuracy and the probability of receiving valid data at the prescribed intervals. Monte Carlo simulation results are complemented by analysis of the filtering processes and curves are presented which clearly define the deterioration in filter performance attributable to reduced probabilities of data acquisition. In addition, the responses of ?-? and Kalman filters are shown to be identical when the ?, ? gains are selected optimally.     

基于UML图书馆管理信息系统的分析与设计

统一建模语言UML是一种面向对象的建模语言,支持面向对象的软件工程,以其强有力的表达能力而倍受人们关注。本文研究了图书馆组织结构、功能及其工作流程,运用UML对LMIS进行面向对象分析、设计,实现了对象模型向关系数据库模型的转换,对开发设计图书馆管理信息系统有一定的借鉴意义。     

飞机起落架滑行载荷识别

 在飞机滑行方向跑道路面不平度为平稳随机函数的假设下,采用滑行过程分段等速化、起落架动态特性分段线性化方法,把原非线性非平稳随机振动问题,简化为分段线性平稳随机振动问题。在频域中采用频响函数描述飞机动态特性,计及全机刚体平动和俯仰模态及结构前ｎ阶弹性模态,给出了从飞机重心处加速度观测值识别起落架接地点载荷自谱密度函数的方法。起落架当量线性参数采用迭代求解。算例表明,本方法和程序可行。     

On the Ambiguity Function of Random Binary-Phase-Coded Waveforms

The ambiguity function of truly random binary-phase-coded waveforms, as an approximation to those waveforms commonly employed in binary-modulated pseudonoise systems/encoded radar systems, is investigated. In a statistical sense, the ambiguity function is analytically derived in which the normally used deterministic cross-correlation process is replaced by its ensemble average. Various Doppler filter responses are presented and discussed. The results are compared with those obtained by transmitting an aperiodic maximum length pseudorandom sequence. It is shown that the ambiguity function of the latter case is closely represented by the ensemble-average response of the truly random binary signal.