垂直相关仪测量高速目标深度的仿真分析

高速运动目标产生结构振动噪声,其多普勒效应对相关信号处理的参数估计造成影响。双阵元垂直相关仪主要测量目标俯仰角,并对目标深度进行估计。由带通型限带白噪声的相关特性分析,推导了多普勒容限的理论计算公式,在积分时间较短的条件下可避免互相关损失。浅海多途信道将导致相关峰出现多峰现象,沿深度方向高速运动目标有助于抑制交叉峰。仿真结果表明,信号多普勒容限与理论分析一致,垂直相关仪的时域相关峰结构与实际目标及其界面镜像空间分布规律一致,因而有利于识别直达声信号,且目标深度测量误差控制在10 m内。

一类多维指数分布的参数估计

考虑生存函数为-F（x1,x2,……xn）=P{X1＞x1…,Xn＞xn}=exp{-[n∑i=1（xi/θi）♂]δ}（0＜xi＜∞,0＜δ≤1,0＜θi＜∞,i=-↑1,n 的一类多维指数分布，给出了它的密度函数的表示式，并讨论了它的性质．提出了相关参数δ的估计δ，证明了δ有相合性和渐近正态性，得到了δ的渐近方差δ．最后还给出了若干随机模拟的结果．

基于滑窗置信传播算法的联合信源信道编码

针对联合信源信道编码中信源统计特性和信道噪声参数未知情况下,解码算法性能急剧下降的问题,提出一种基于滑窗置信传播算法(SWBP)的联合信源信道编码,简称滑窗算法。研究采用不规则重复累积(IRA)码来实现基于滑窗置信传播算法的联合信源信道编码,IRA码可以取得与低密度奇偶校验(LDPC)码同样优越的性能,但编码复杂度远远低于LDPC码。在解码端引入滑动窗口,通过实时地估计不断变化的信源统计特性和信道噪声参数,从而提高解码速率。实验结果表明该算法具有接近相关参数已知情况下的理想性能、不依赖于初始参数、复杂度低且易于实现等优点。

Sensitivity of Coupled Chaotic Dynamical System to Parameters in the Context of Data Assimilation

In this paper, a numerical modeling tool is described which can be used to explore various aspects of four dimensional variational data assimilation and parameter estimation arising in geophysical, environmental, biological and engineering sciences. A major component of this tool is a coupled chaotic dynamical system obtained by coupling two versions of the well-known Lorenz （1963） model with different time scales which differ by a certain time-scale factor. A tangent linear model and its adjoint are considered that correspond to a coupled chaotic system. The general idea of applying sensitivity measures （sensitivity functions） to coupled systems, emphasizing the data assimilation aspects, is explored as well by the forward sensitivity approach. For this purpose the set of sensitivity equations is derived from the nonlinear equations of the coupled dynamical system. To estimate the influence of model parameter uncertainties on the simulated state variables the relative error in the energy norm is used.