定数截尾有缺失场合反延时电路可靠性分析

在定数截尾数据有缺失的情形下,对单个电子元器件寿命服从单参数指数分布的反延时电路系统进行了可靠性分析。应用Bayes方法并结合矩估计法,得到了单个电子元器件的失效率、系统可靠度及系统平均寿命3个可靠性指标的Bayes估计。数值模拟算例表明,所得可靠性指标的Bayes估计的精度高于可靠性指标的极大似然估计(MLE),Bayes估计和极大似然估计的估计效果均随着数据缺失个数的增加而变差,并且Bayes估计受数据缺失个数的影响小于极大似然估计。     

基于性能退化分析的电连接器可靠性评估

某型电连接器具有寿命长、可靠性高的特点,传统的基于失效寿命数据的可靠性评估方法行不通。提出了基于性能退化分析的可靠性评估方法,给出了进行评估的一般步骤,并以温度为加速应力设计了该型电连接器的加速退化试验。分析了电连接器的接触失效机理,进而推导出退化模型,估计出了样品的伪寿命值。利用Anderson-Darling统计量确定寿命分布类型为对数正态分布,对寿命分布函数和Arrhenius加速方程的参数值进行了极大似然估计,推导出了该型电连接器在工作温度下的可靠度函数,得出t0.9为244 240h。     

屏蔽数据下并联系统广义指数部件的可靠性估计

针对具有屏蔽寿命数据的并联系统,研究了广义指数部件的可靠性估计问题.利用极大似然方法和贝叶斯理论给出了部件未知参数和可靠度函数的极大似然估计及贝叶斯估计.最后通过随机模拟对两种估计的效果进行了比较,并研究了样本量和屏蔽水平对估计精度的影响.     

一类动态系统的可靠性实时预测方法研究

研究了一类带有某种隐含的性能退化过程的动态系统的实时可靠性预测问题。在初始性能变量值不确定的情况下,首先基于粒子滤波算法和迭代极大似然估计方法,利用系统的输出信息辨识了性能退化轨道函数中的未知参数,并实时估计性能变量值。然后根据性能退化过程辨识结果实时地预测系统在未来一段时间内的可靠性指标。基于三容水箱的仿真实验结果验证了方法的有效性。     

一种新的时变参数递推估计方法

本文在极大似然估计与检测方法的基础上提出了一种新的时变参数推估计方法，该方法能快速跟踪参数的突变，仿真结果表明用该方法来估时时变参数能得到较好的的结果。     

一种基于团队的P2P信誉机制设计

在极大似然估计方法基础上,提出一种新的基于团队的信誉机制FTrust。FTrust通过P2P路由协议Kademlia传播信誉值,具有很强的可靠性。通过仿真结果分析,对比单纯极大似然估计,可以得出FYrust的显著优点。     

一种大尺度Gauss模糊的快速采样算法

针对大模板Gauss模糊的传统算法计算复杂度较高的缺点,提出了一种基于快速采样的新算法,将计算复杂度从O(N2)降到O(N)级别.利用极大似然估计理论,对传统Gauss模板和采样模板进行分析,给出了采样算法和传统算法的联系与区别.实验表明,新算法在极大的提高算法的速度的同时,可以将两者之间的能量误差控制在1%左右,当采样点等于10N时,人眼基本无法察觉两种算法的差异.     

并联监控电路可靠性分析及设计

分析了嵌入式系统死机的症状,并对现有的一系列死机恢复技术进行了介绍.为了提高嵌入式系统运行的可靠性,设计了由三个相同类型的监控电路并联所构成的监控系统,先在理论上对其可靠性进行了分析,然后从硬件和软件上分别进行了具体设计.并联监控电路相对于单个监控电路来说,其可靠性可极大地提高.     

一种基于迭代PTM模型的电路可靠性评估方法

纳米工艺的快速发展既给电路设计创造了新的机会,同时也带来了新的挑战,基于纳米器件的电路可靠性设计便是主要挑战之一,因此有必要研究在设计的早期阶段便能准确地评估电路可靠性的方法.考虑到经典的概率转移矩阵方法在电路可靠性计算中的优势与不足,文中提出了宏门的概念和以宏门为单位的迭代概率转移矩阵模型,并设计了相应的电路可靠性评估算法,可计算从原始输入到任意引线位置的电路可靠度,该算法的复杂性与宏门的数目成线性关系.理论分析与在74系列电路和ISCAS85基准电路上的实验结果证明了文中所提方法的准确性、有效性及潜在的应用价值.     

软件可靠性评估理论与实例研究

研究了软件可靠性评估的特点。采用Goal OkumotoNHPP软件可靠性评估模型和极大似然估计 ,计算了智能电磁流量变送器可靠性水平 ,得到了较为实用的结果     

一种无信标无线传感器网络中的目标定位策略

无信标无线传感器网络的传感器节点通常是按照一定的概率,以分组形式部署，为实现其定位和动态节点跟踪，提出了的无信标定位发现策略，在已有的部署之上,建立模型去反映目标位置和监测传感器探测信息之间的内在关系，同时还建立了预测模型来对目标移动方式进行推断。利用贝叶斯理论构造了一个条件概率分布,将以上两种模型相关参数归并起来,并在这个分布上应用最大似然估计(MLE)方法来估测目标的位置。实验结果表明此目标定位策略取得了较好的效果。     

基于统计理论的电台数目估计方法

针对对方电台发送信号的概率与我方接收到信号数目均为随机数目的情况,考虑基于统计方法的电台数目建模问题,提出基于贝塔二项泊松模型的建模方法,解决信源数目的估计问题。通过对参数的再参数化处理,给出相应的参数极大似然估计方法,并通过计算机仿真比较不同模型下的参数估计效果,说明该方法的有效性。     

一种改进型免疫算法在TDOA定位中的应用

为解决传统TDOA定位估计所带来的非线性优化问题,首先通过最大似然估计将其转换为峰值搜索优化问题,再提出一种基于克隆选择思想的改进型免疫算法对其进行求解。该算法采用浮点数编码方式,提高了运算效率;引入高斯变异算子和变异控制变量,加强了局部搜索能力。仿真实验表明,在保证一定抗体数目的前提下,该算法适应性强,性能稳定,能快速逼近全局最优的解,且算法定位精度更高。     

基于小波域广义高斯分布的SAR图像分割算法

针对利用灰度共生矩阵作为纹理特征的传统方法不能够有效表征图像的边缘高频信息的问题,结合小波的多分辨率分析,提出了一种基于小波变换域统计特性的合成孔径雷达（SAR）图像分割算法。图像经过小波变换后,其统计特性服从广义高斯分布（GGD）,利用最大似然（ML）估计,推导出GGD的两个参数[α]、[β],提出了利用Newton-Raphson法对[β]进行快速迭代求解。并将[α]、[β]作为SAR图像的纹理特征,利用K-Means对其进行分割。通过对典型的SAR图像结果分析,表明了该算法的有效性。     

Probabilistic fault detector for Wireless Sensor Network

This paper proposed a novel centralized hardware fault detection approach for a structured Wireless Sensor Network (WSN) based on Naïve Bayes framework. For most WSNs, power supply is the main constraint of the network because most applications are in severe situation and the sensors are equipped with battery only. In other words, the battery’s life is the network’s life. To maximize the network’s life, the proposed method, Centralized Naïve Bayes Detector (CNBD) analyzes the end-to-end transmission time collected at the sink. Thus all the computation will not be performed in individual sensor node that poses no additional power burden to the battery of each sensor node. We have conducted thorough performance evaluation. The obtained results showed better performance can be obtained under a network size of 100-node WSN simulations at various network traffic conditions and different number of faulty nodes.     

Coherent summation of multiple short-time signals for direct positioning of a wideband source based on delay and Doppler

We consider identifying the source position directly from the received source signals. This direct position determination (DPD) approach has been shown to be superior in terms of better estimation accuracy and improved robustness to low signal-to-noise ratios (SNRs) to the conventional two-step localization technique, where signal measurements are extracted first and the source position is then estimated from them. The localization of a wideband source such as a communication transmitter or a radar whose signal should be considered deterministic is investigated in this paper. Both passive and active localization scenarios, which correspond to the source signal waveform being unknown and being known respectively, are studied. In both cases, the source signal received at each receiver is partitioned into multiple non-overlapping short-time signal segments for the DPD task. This paper proposes the use of coherent summation that takes into account the coherency among the short-time signals received at the same receiver. The study begins with deriving the Cramér–Rao lower bounds (CRLBs) of the source position under coherent summation-based and non-coherent summation-based DPDs. Interestingly, we show analytically that with coherent summation, the localization accuracy of the DPD improves as the time interval between two short-time signals increases. This paper also develops approximate maximum likelihood (ML) estimators for DPDs with coherent and non-coherent summations. The CRLB results and the performance of the proposed source position estimators are illustrated via simulations.     

Synthesis of frequency‐independent phase shifters using negative group delay active circuit

This article describes a synthesis method dedicated to the design of frequency‐independent phase shifters (PSs). This innovative PS structure consists in a transmission line cascaded with a negative group delay (NGD) active circuit so that the absolute constant group delays generated by both of them are identical but of opposite signs. So, in principle, it exhibits a constant overall phase and a group delay close to zero. Broadband linear positive phase slopes are obtained through use of an NGD active circuit whose characteristics are recalled prior to the extraction of the PS synthesis relations. The design and simulations of a PS of compact size are reported. The experimental results confirm the expected frequency‐independent transmission‐phase value of 145° ± 10° with an insertion gain of 2 ± 2 dB over a 160% relative frequency band. At last, future prospects allowed by the specific properties of this PS are presented. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2010.     

Flexible Distribution-Based Regression Models for Count Data: Application to Medical Diagnosis

Abstract

Data mining techniques have been successfully utilized in different applications of significant fields, including medical research. With the wealth of data available within the health-care systems, there is a lack of practical analysis tools to discover hidden relationships and trends in data. The complexity of medical data that is unfavorable for most models is a considerable challenge in prediction. The ability of a model to perform accurately and efficiently in disease diagnosis is extremely significant. Thus, the model must be selected to fit the data better, such that the learning from previous data is most efficient, and the diagnosis of the disease is highly accurate. This work is motivated by the limited number of regression analysis tools for multivariate counts in the literature. We propose two regression models for count data based on flexible distributions, namely, the multinomial Beta-Liouville and multinomial scaled Dirichlet, and evaluated the proposed models in the problem of disease diagnosis. The performance is evaluated based on the accuracy of the prediction which depends on the nature and complexity of the dataset. Our results show the efficiency of the two proposed regression models where the prediction performance of both models is competitive to other previously used regression models for count data and to the best results in the literature.     

基于Chan氏算法和文化算法的协同定位

提出一种到达时间差(TDOA)定位方法,利用Chan氏算法进行初始定位估计,将估计结果作为经验知识存储于信念空间中,采用文化算法求解定位估计中的最大似然函数,获得最佳估计坐标值,从而实现对移动台的最终定位估计。历史知识的引入能有效避免陷入局部最优值,并改善算法的定位精度。仿真实验结果表明,该方法性能稳定、定位精度高、收敛速度快。