The Equivalence of Reliability Diagrams and Fault-Tree Analysis

Many practicing engineers model their systems using reliability diagrams, while others use fault-tree analysis. The theoretical equivalence of the two techniques is described. System reliability can be expressed in two ways: probability of success and probability of failure approach, in terms of the tie-sets (forward paths) of a reliability diagram. Similarly, one can write two other expressions in terms of the cut-sets of the system reliability diagram. If one uses the fault-tree analysis approach, the probability of failure is written in terms of element failures by applying the rules of symbolic logic (union and intersection). This equation is identical with the tie-set probability of failure equation. Also by applying DeMorgan's logic theorem to the fault-tree probability of the failure equation, one obtains the tie-set probability of success equation. Thus the two techniques are shown to be identical. The choice between the techniques is a matter of convenience and familiarity.     

Analysis of Reliability Block Diagrams by Boolean Techniques

A reliability block diagram for complex systems is often analyzed by applying the series/parallel product laws or, where this is not possible, by using a conditional probability result (Bayes theorem). In both cases, the analysis is conducted in the probabilistic domain and, for complex systems, is lengthy. An alternative method is to consider the component reliability parameters to be Boolean variables rather than probabilistic variables and to treat the whole problem as if it were Boolean. This has the advantage of allowing the use of powerful Boolean reduction theorems to contain the size of the problem. Unfortunately, much of this advantage is lost when conversion back into the probabilistic domain takes place. This paper presents a technique for overcoming this disadvantage; the technique is based on analysing and modifying the Boolean expression prior to the conversion process. The technique was originally developed as an aid to fault-tree analysis but it applies to general problems of reliability assessment. I claim no originality for the procedure. The motivation to write the paper is quite simple: the procedure is not as well-known as it should be either amongst practising reliability engineers or amongst those who teach the subject. The purpose of the paper is therefore tutorial.     

Reliability Analysis of Computer Systems Using Dataflow Graph Models

We use dataflow graphs to represent the computational structure, analogous to Petri nets and Turing machines, and have developed a method for analyzing the reliability of computer systems modeled as dataflow graphs. Because of the hierarchical nature of dataflow graphs, systems can be analyzed at several levels of abstraction. Reliabilities of subgraphs can be calculated using either traditional techniques or dataflow approach presented here (recursively). The reliabilities of subgraphs can then be combined leading to decomposition-aggregation approach. The time needed for an actor to complete its operation is not included in our analysis of dataflow graphs. Incorporation of the time element compounds the problem and we have not studied it yet.     

K-Terminal Network Reliability Measures With Binary Decision Diagrams

We present a network decomposition method using binary decision diagrams (BDD), a state-of-the-art data structure to encode, and manipulate Boolean functions, for computing the reliability of networks such as computer, communication, or power networks. We consider the K-terminal reliability measure R_K, which is defined as the probability that a subset K of nodes can communicate with each other, taking into account the possible failures of the network links. We present an exact algorithm for computing the if-terminal reliability of a network with perfect vertices in O(m^.F_max ^.2^Fmax.B_Fmax), where B_Fmax is the Bell number of the maximum boundary set of vertices F_max, and m is the number of network links. Several examples, and experiments show the effectiveness of this approach.     

基于信号流图的多通道测向雷达天馈系统误差分析

在多通道测向雷达天馈系统中,我们需要对系统进行校准来判断通道间信号相位和幅度的一致性、稳定性。为了有效判断系统校准数据中的误差值,找出引起系统误差的主要误差源,本文给出了一种基于信号流图的分析方法。该方法可根据流图相关法则直接得出精确结果并分析出主要误差源的位置,比传统的基于传输矩阵的分析方法更直观、更快捷。     

Reliability Analysis of Redundant Networks Using Flow Graphs

A flow graph approach for reliability analysis is applied to redundancy with elements in the simple series-parallel networks and to the more general case with elements in non-series-parallel combinations. The reliability of networks for elements with open or short failures is analyzed with flow graphs. Typical examples are shown.     

UPS系统可靠性分析

介绍了常见的UPS系统模型结构,详细分析了各种系统的可靠度计算方法。在此基础上推导出UPS串联热备份系统以及并联冗余系统的可靠度,并做了比较。     

系统数据库可靠性分析

近年来,随着计算机技术的发展和应用,数据库技术取得了迅速的发展,其可靠性也引起了人们越来越多的关注.首先,简单地介绍了数据库技术;然后,对导致数据库失效的主要原因进行了归纳总结;其次,对数据库的可靠性进行了分析,通过分析发现,将并联系统设计的思想融入到系统数据库的设计中,可以大大地提高系统数据库的可靠性;最后,对提高系统建设中数据库的可靠性的常见方法和技术进行了阐述和分析.     

A Flow Graph Analysis of 3--and 4-Port Junction Circulators

A simple theoretical model of a Iossless nonideal junction circulator is described. The model consists of a matched lossless n-port junction with a lossless two-port connected to each arm. The basic thought behind it is to separate the reflecting properties of the circulator from the other ones. For the case n=3, unsymmetrical as well as symmetrical junctions are treated. For a symmetrical three-port, the justification of the model has also been experimentally verified. In the case n=4, a symmetrical junction is treated. Flow graphs are used for visualizing the scattering matrices of combined networks and for calculating the coefficients of them.     

系统可靠性和可用性分析技术

随着科学技术的发展和社会的进步，系统可靠性和可用性分析成为一个越来越重要的研究领域。本文从可靠性的起源和发展出发进行论述，重点介绍了描述系统可靠性的参数以及两类系统可靠性和可用性的分析技术，对它们的模型、求解和各种分析方法之间的关系作了阐述，最后对存在的问题及解决的方法进行了归纳。     

Reliability Analysis for a Data Flow in Event-Driven Wireless Sensor Networks

For the purpose of designing more reliable networks, we extend the traditional reliability analysis from wired networks to wireless networks with imperfect components. This paper aims to study the reliability of a data flow in event-driven wireless sensor networks with acknowledgment-based transmission scheme. Initially, an event-driven wireless sensor network model is described in terms of limited node battery energy and shadowed fading channels. Then, in order to analyze the network reliability, wireless link reliability and node energy availability are investigated, respectively. Further the analytical expressions of the instantaneous network reliability and the mean time to failure are derived. Finally, the simulation results validate the correctness and accuracy of the analytical results.     

通信监测设备的可靠性分析与设计

仔细分析了信监测设备的结构特点和稳定运行的可靠性要求。在此基础上，系统的研究给出并实现了系统可靠性设计方案。理论分析和系统运行测试结果表明：设计分析了正确可靠。     

广播播控系统可靠性分析及解决方法

广播播控中心正逐步实现自动化和智能化,四川广播电视台从设备可靠性风险评估、系统运行状态预警到智能化故障处理三个方面构建智能系统,有效保障了广播播控系统稳定运行.     

有向矩阵的广义讯号流图

本文把讯号流图推广到有向矩阵系统，提出一种广义的讯号流图定义及其拓扑法则，并给出了复杂网络系统的若干应用实例。     

Analysis of Fourth-Order DC–DC Converters: A Flow Graph Approach

The signal flow graph (SFG) nonlinear modeling approach is well known for modeling DC-DC converters and it is a powerful analysis tool for higher order converter systems. Modeling of several specific fourth-order DC-DC converter circuits have been reported using conventional state-space averaging. Particular emphasis has been given, so far, only to arrive at any of the large, small-signal (SS) and steady-state models but not a generalized one. This paper gives the generalized SFG model of the fourth-order DC-DC converter topology that is useful for generating different types of fourth-order DC-DC converter circuits unified models. Further, it is shown that the deduction of large, SS and steady-state models from these unified SFGs is easy and straightforward. All possible fourth-order DC-DC converter circuits from its generalized topology have been identified and an analysis of a few converter circuits is given here for illustration of the proposed modeling method. Large-signal (LS) models are developed for different topology configurations and are programmed in SIMULINK simulator. LS responses against supply and load disturbances are obtained. Experimental observations are provided to validate the proposed modeling method.     

HS2000系统可靠性分析

对太原第一热电厂六期扩建工程15#机组热工控制系统HS2000的可靠性从设计、制造、应用三个方面进行了分析，并提出了进一步提高其可靠性的措施。     

弹载雷达系统的可靠性研究

弹载雷达系统作为一种成败型工作的复杂系统，具有故障后果严重及无事后维修性等特点，本文在对弹载雷达系统的储存可靠性进行计算机仿真的基础上，通过对其进行RCM分析，提出了周期可靠性思想，探讨了依靠该思想来维持弹载雷达系统结构定期高可靠性的方法及可靠性设计流程。     

MUDAS播音监控系统的可靠性分析

从定笥和定量的角度对ＭＵＤＡＳ（Ｍｕｌｔｉ－ｕｓｅｒ Ｄｉｇｉｔａｌ Ａｕｄｉｏ Ｓｅｒｖｅｒ）播音监控系统的可靠性进行了分析,从而得出对提高类似控制系统可靠性指标均有参考价值的几点建议。