Some comparisons of residual life of coherent systems with exchangeable components

Most of the research, on the study of the reliability properties of technical systems, assume that the components of the system operate independently. However, in real life situation, it is more reasonable to assume that there is dependency among the components of the system. In this article, we give sufficient conditions based on the signature and the joint distribution of component lifetimes to obtain stochastic ordering results for coherent and mixed systems with exchangeable components. Some stochastic orders on dynamic (or conditional) signature of coherent systems are also provided. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 549–556, 2014     

高分辨率UAV SAR的三维运动误差分离与补偿

在基于SAR回波的数据处理中,多普勒调频率具有很高的估计精度且对场景的依赖性很小,可以更广泛地用于自聚焦处理。基于多普勒调频率参数估计,针对回波包络及相位分别提出了误差提取模型,并通过包络误差校正和相位误差补偿两个步骤实现了高精度的运动补偿处理。实测数据表明,本文方法可以在低精度导航信息情况下获取高分辨率雷达图像。     

Choosing arrival process models for service systems: Tests of a nonhomogeneous Poisson process

Service systems such as call centers and hospital emergency rooms typically have strongly time‐varying arrival rates. Thus, a nonhomogeneous Poisson process (NHPP) is a natural model for the arrival process in a queueing model for performance analysis. Nevertheless, it is important to perform statistical tests with service system data to confirm that an NHPP is actually appropriate, as emphasized by Brown et al. [8]. They suggested a specific statistical test based on the Kolmogorov–Smirnov (KS) statistic after exploiting the conditional‐uniform (CU) property to transform the NHPP into a sequence of i.i.d. random variables uniformly distributed on [0,1] and then performing a logarithmic transformation of the data. We investigate why it is important to perform the final data transformation and consider what form it should take. We conduct extensive simulation experiments to study the power of these alternative statistical tests. We conclude that the general approach of Brown et al. [8] is excellent, but that an alternative data transformation proposed by Lewis [22], drawing upon Durbin [10], produces a test of an NHPP test with consistently greater power. We also conclude that the KS test after the CU transformation, without any additional data transformation, tends to be best to test against alternative hypotheses that primarily differ from an NHPP only through stochastic and time dependence. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 66–90, 2014     

Some aging properties of parallel and series systems with a random number of components

In this article, we study aging properties of parallel and series systems with a random number of components. We show that the decreasing likelihood ratio property is closed under the formation of random minima. We also show, by counterexamples, that other aging properties are not closed under the formation of random minima or maxima. Some mistakes in the literature are corrected. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 238–243, 2014     

VFD滤波器的导航信道模拟器动态时延模拟方法

针对卫星导航信道模拟器信号仿真中,传统伪距多普勒模拟方法瞬时控制精度差、滤波器资源占用较大的不足,提出了基于拉格朗日插值延迟滤波器及Farrow结构实现的伪距多普勒模拟方法。在分析信道模拟器系统架构的基础上,建立了多普勒模拟方法的模型,包括延时计算模块和可变延迟滤波器两部分。与多速率采样数字延迟滤波器方法比较,该方法滤波器系数个数约为后者的0.2%,并且改变时延特性时,仅需更新1个参数。信道模拟器实测数据结果表明使用该方法伪码多普勒模拟精度可以达到0.1mHz。     

经典海浪谱下运动飞行器接收到的海浪磁场噪声

根据前人对海浪感应磁场研究的成果,在海浪是平稳正态随机过程的假设下,求出了飞行器接收的海浪感应磁场噪声功率谱的表达式.在讨论功率谱和飞行角度的关系时,发现海浪感应磁场随飞行角度变化,为低频、窄带大干扰或高频、宽带小干扰,并且在某些飞行角度会出现奇点.进行了仿真计算,结果符合理论表达式.     

正态总体下分布参数的Bayes序贯估计

论述正态总体分布参数的序贯估计和Bayes序贯估计问题。在Stein的双子样序贯估计的基础上 ,构造了Bayes双子样序贯估计 ,并作了剖析。此外 ,为了适应当前试验场地“试试看看 ,看看试试”的试验分析和鉴定的需要 ,给出了以序贯Bayes检验为基本出发点 ,使检验和序贯估计相联合的分析方法     

通气管暴露率检查曲线及使用对策

在建立蓄电池充放电模型的基础上,计算了常规潜艇的通气管暴露率,绘制了暴露率检查曲线,并给出了检查曲线的使用功能.     

线导鱼雷导引弹道的动力学分析

通过线导鱼雷常用导引方法—三点法、前置角法导引弹道的动力学分析 ,推导出不同方法下鱼雷旋回速率的解析表达式 ,并通过数字仿真对鱼雷线导导引弹道动力学特性进行探讨 ,明确了线导鱼雷导引弹道特性与导引方法之间的关系 .     

基于高性能DSP实现的多普勒波束锐化实时成像处理

在简要介绍多普勒波束锐化 (DBS)成像原理和TMS32 0C6 2 0 1芯片特点的基础上 ,着重讨论了DBS成像算法基于DSP的实现。在实现过程中充分考虑了通用DSP完成非线性运算、除法运算耗时大以及存贮I/O操作耗时不能忽略等特点。最后分析了算法性能并给出了实验结果