An algorithm for detecting a change in a stochastic process

The problem of detecting a change from one given stationary and ergodic stochastic process to another such process is considered. It is assumed that both stochastic processes are processes with memory and that they are mutually independent. A sequential test is proposed and analyzed. It is proved that the proposed test is asymptotically optimal in a mathematically precise sense.     

An improved model for protective-system reliability

A Markov model extends and improves previous models for determining the unreadiness probability and unavailability of a protective system, such as those found on electric-power transmission and distribution systems. Improved definitions of unreadiness probability and other relevant measures are proposed, based on a new Markov model of the system. This new model provides a more direct and physically important definition of unreadiness, and can be computed based on typical system-transition rates. Using this model, it is possible to estimate the optimal value of the protection inspection interval, viz, the time between inspections of the protective system. The model accounts for the operation of backup protection, the removal of protection for inspection, the occurrence of common-cause failures, and the usual clearing of faults     

An S-shaped software reliability growth model with two types of errors

An S-shaped software reliability growth model (SRGM) based on a non-homogeneous Poisson process (NHPP) with two types of errors has been proposed. The errors have been classified depending upon their severity. We have estimated the model parameters and obtained the optimum release policies which minimize the cost subject to achieving a given level of reliability. Numerical results illustrating the applicability of the proposed model are also presented.     

Outlier-resistant algorithms for detecting a change in a stochasticprocess

Outlier-resistant algorithms that detect a change from a given nominal stationary process to another such process are given. The nominal processes are assumed to be mutually independent and to satisfy some general regularity conditions. The outlier sequences are assumed to be independently and identically distributed and independent of the nominal processes. The proposed algorithms are sequential and consist of uniformly bounded steps. The asymptotic performance of the algorithms is analyzed, both in the absence and the presence of outliers. Breakdown points and influence functions are defined and analyzed. The algorithms are studied in more detail for Gaussian autoregressive nominal processes     

Data stability in an application of a software reliability model

The Goel-Okumoto (1979) model of reliability growth is applied to the failure data for a large software development project. This is done by fitting the model parameters to the error counts and test times, which are periodically tabulated. In the early phases of system testing, the problem of inaccurate estimation due to insufficient reliability growth occurs. A simple test is devised to measure the stability of the data with respect to this problem. In practice, such a test on the data can be used to determine when system testing has sufficiently progressed to allow one to expect reasonable estimates from reliability growth models     

红外成像系统对点目标动态探测概率分析

检测概率、虚警概率和信噪比是红外点目标检测系统的3个核心指标,本文在恒虚警检测准则下,分析了红外点目标单帧检测（单一门限检测）的检测概率、虚警概率和信噪比三者之间的关系。重点分析计算了采用多帧累积检测的双门限检测方法时,第二门限的选取策略,实现了在不提高对系统信噪比要求的前提下,提高检测概率、降低虚警概率的目的,解决了威胁度大、误报和漏报代价高的高价值目标的检测问题。     

Software reliability growth model with error dependency

Generally, in a complex software system there may be errors, whose removal is dependent on the previously removed errors and may result in a slowing down of the removal process for a period time. This dependency can be described in different ways. In this paper, we develop an SRGM which takes care of the underlying error dependency in a software system. The SRGM has the built-in flexibility and has been tested on real software error data to show its applicability.     

An electromigration and thermal model of power wires for a priori high-level reliability prediction

In this paper, a simple power-distribution electrothermal model including the interconnect self-heating is used together with a statistical model of average and rms currents of functional blocks and a high-level model of fanout distribution and interconnect wirelength. Following the 2001 SIA roadmap projections, we are able to predict a priori that the minimum width that satisfies the electromigration constraints does not scale like the minimum metal pitch in future technology nodes. As a consequence, the percentage of chip area covered by power lines is expected to increase at the expense of wiring resources unless proper countermeasures are taken. Some possible solutions are proposed in the paper.     

An improved reliability model for Si and GaN power FET

The existing standard reliability models for power devices are not satisfactory and they fall short of predicting failure rates or wear-out lifetime of semiconductor products. This is mainly attributed to two reasons; the lack of a unified approach for predicting device failure rates and the fact that all commercial reliability evaluation methods relay on the acceleration of one dominant failure mechanism. Recently, device reliability research programs are aimed to develop new theoretical models and experimental methods that would result a better assessment of the device lifetime as well as point out on the dominating failure mechanism for particular operating conditions. A new model, named Multi failure mechanism, Overstress Life test (MOL) has been introduced and posed a better understanding of the dominating failure mechanisms under various stressed conditions in advanced FPGA devices (for 45 and 28 nm technologies). In this work we present, for the first time, the implementation of the MOL model to investigate the reliability of silicon power MOSFET and GaN power FET devices. Both, LTSpice simulation and experimental data are presented for a test circuit of a ring oscillator, based on CMOS-FET, NMOS-FET, PMOS-FET and N-channel e-GaN FET. The monitored data was acquired in-situ in form of the ring frequency or Vds values that enabled to assess the lifetime and determine the dominating mechanism during accelerated wearout by temperature, applied bias voltage, thermal cycling, gamma and electron irradiation. Moreover, in the case of GaN devices, RDS-On monitoring circuit has also been operated during thermal cycling of the tested component and the acceleration factor was derived for various operational parameters.     

A reliability analysis technique for object-oriented model using a reliability petri net

We propose a reliability analysis technique for the design specifications which are made by CRC methodology. We use a reliability Petri net as an analysis technique for CRC specification. The procedure of analyzing the system reliability is as follows: first, the collaboration graphs and message flow diagrams of CRC specification are transformed into an equivalent reliability Petri net which consists of places, transitions, input functions, output functions, failure rate of the input and output functions, and tokens. Secondly, we construct a reachability tree from a reliability Petri net, and establish the paths of all transitions for the reachability tree. These paths can be test cases. Finally, we calculate the values of reliability effect for all transitions in a reliability Petri net, select the transitions that have most effect on the system reliability, and search the messages and classes that are places of input and output fucntion in these transitions. Therefore, we can design these messages and classes very well for increasing the system reliability.     

Optimization of a reliability growth problem

A variation of the redundancy optimization problem of reliability has been considered here. Installation of a facility to any stage not only improves the reliability of that stage but the steadier output from this stage helps the other stages to function more reliably. Optimization of such facilities to various stages has to be made under Cost constraints. A pseudo-Boolean relation has been used to bring all these interactions in the formulation of the problem. The solution has been obtained by pseudo-Boolean programming also.     

Reliability growth plot - An underutilized tool in reliability analysis

System reliability and performance are improved by continuous improvement effort. The study of the increase in reliability as a function of time is the subject of reliability growth. Although the most well-known reliability growth model, the Duane model, is proposed more than thirty years ago, reliability growth analysis has attracted an increasing interest only recently because of the lack of time for testing and the high reliability of improved products leading to very few failures. In this paper we study a practical approach in reliability growth analysis. Based on the graphical plotting of failure data for some selected models, reliability can easily be estimated and predicted. This approach which is the original idea of the Duane model, overcomes the problem of parameter estimation and model validation that is usually complicated. It is especially useful when the model validation has to be done in order to select a suitable model. The approach, called the First-Model-Validation-Then-Parameter-Estimation approach, is simple and practical for the analysis of reliability growth data. We further develop some models and discuss their applicability in reliability engineering.     

Some criteria for reliability growth

The sequence of failures of a system is assumed to be modelled by a stochastic point process. Criteria for the reliability growth of such a system are introduced. The relationships between the criteria are deduced and preservation of the criteria under the formation of series systems is discussed.     

A testing-effort dependent software reliability model and its application

We discuss a software reliability growth model with testing-effort based on a nonhomogeneous Poisson process and its application to a testing-effort control problem. The time-dependent behaviour of testing-effort expenditures which is incorporated into software reliability growth is expressed by a Weibull curve due to the flexibility in describing a number of testing-effort expenditure patterns. Using several sets of actual software error data, the model fitting and examples of a testing-effort control problem are illustrated.     

Hypothesis-test for reliability in a stress-strength model, withprior information

The hypothesis for the reliability in a stress-strength model is considered under a Bayes perspective, where the parameter space is restricted to the nonnegative orthant. The critical region of the Bayes test is obtained. The results are illustrated by using real rocket motor experimental data     

Needed resources for software module test, using thehyper-geometric software reliability growth model

Considerable testing resources are required during software module testing. This paper, based on the `hyper-geometric distribution software reliability growth model' (HGDM) investigates two optimal resource allocation (OPT/RA) problems in software module testing: (1) minimization of the number of software faults (NSF) still undetected in the system after testing, given a fixed amount of testing resources; and (2) minimization of the total amount of testing resources required, given the NSF still undetected in the system after testing. Based on the concepts of average allocation and proportional allocation, two simple allocation methods are introduced. Experimental results show that the OPT/RA method can improve the quality and reliability of the software system much more than the simple allocation methods. Therefore, the OPT/RA method is very efficient for solving the `testing resource allocation' problem     

一种改进的可靠性分配方法及其应用验证

可靠性分配是系统设计中的重要工作,常用的可靠性分配方法如AGREE分配法、评分分配法对影响可靠性指标的因素考虑不全,并且都是针对串联系统的。利用贝叶斯网络在不确定性概率推理方面的优势,将传统的故障树转化为贝叶斯网络求解最小割集和底事件重要度。建立了改进的可靠性分配模型,首先将顶层可靠性指标在最小割集之间分配,然后根据底事件重要度和评分将最小割集对应的可靠性指标分配到底事件。以某型飞机电传操纵系统可靠性指标分配为例,仿真结果表明,贝叶斯网络相对于故障树分析计算底事件重要度更为简单、精度更高。改进的分配方法能够考虑影响可靠性指标的主要因素,实现指标的科学分配。     

An object-based approach for detecting small brain lesions: application to Virchow-Robin spaces

This paper is concerned with the detection of multiple small brain lesions from magnetic resonance imaging (MRI) data. A model based on the marked point process framework is designed to detect Virchow-Robin spaces (VRSs). These tubular shaped spaces are due to retraction of the brain parenchyma from its supplying arteries. VRS are described by simple geometrical objects that are introduced as small tubular structures. Their radiometric properties are embedded in a data term. A prior model includes interactions describing the clustering property of VRS. A Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC) optimizes the proposed model, obtained by multiplying the prior and the data model. Example results are shown on T1-weighted MRI datasets of elderly subjects.