A separable ternary decision diagram based analysis of generalized phased-mission reliability

This paper considers the reliability analysis of a generalized phased-mission system (GPMS) with two-level modular imperfect coverage. Due to the dynamic behavior & the statistical dependencies, generalized phased-mission systems offer big challenges in reliability modeling & analysis. A new family of decision diagrams called ternary decision diagrams (TDD) is proposed for use in the resulting separable approach to the GPMS reliability evaluation. Compared with existing methods, the accuracy of our solution increases due to the consideration of modular imperfect coverage; the computational complexity decreases due to the nature of the TDD, and the separation of mission imperfect coverage from the solution combinatorics. In this paper, the TDD-based separable approach is presented, and compared with existing methods for analyzing the GPMS reliability. An example generalized phased-mission system is analyzed to illustrate the advantages of our approach.     

基于二元决策图的事件树分析

通过分析传统事件树分析法在求解复杂系统可靠性时的不足,提出了一种基于二元决策图的事件树分析方法,主要讨论了各支点事件之间存在相关性的异常情况。二元决策图给出了故障树结构的二叉树的逻辑形式,用于描述系统失效的原因,并对系统顶事件进行分析。在对系统进行可靠性分析的过程中,由于不需要将最小割集和质蕴涵项作为中间步骤,从而提高了系统可靠性分析的效率和精度,为大型复杂系统的可靠性分析提供了一条新途径。     

面向决策支持的数据智能系统研究

为了从自动监控系统的海量数据中准确及时地得到所需的信息,并以直观明晰的图表形式表示出来,以便决策者能够作出快速而正确的判断和决策,给出了数据智能系统(DIS)的构成和定义,分析了DIS的主要研究内容,总结了DIS的企业级应用和研究从MIS到ERP再到业务智能的逐步发展过程,为构建先进的面向决策支持的数据智能系统提供了一种可行的思路。     

Determination of combinational logic circuit reliability through generation of fault diagnosis tests

This paper investigates the relationships between a given set of excitation vectors and the test sets for faults occuring in combinational circuits, in order to obtain new conditions for determining the redundant cubes of terminal states. The analysis presented is concluded with two new algorithms for the evaluation of combinational logic circuit reliability.     

Reliability block diagram analysis

The fundamental principles and techniques employed in the analysis of complex reliability block diagrams are described, together with a systematic method of translating reliability block diagrams into probability state diagrams. The techniques of simplifying probability state diagrams by combining parallel transitions, combining states and approximating the diagrams are discussed in depth.     

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.     

An efficient method for terminal and multiterminal pathset enumeration

The literature is abundant with algorithms for determining separately the paths for the single terminal pair, paths for multiterminal pairs and cuts for a specified terminal pair of any network, from knowledge of the reliability logic diagram (RLD). However, very few methods are available as efficient algorithms for enumerating simultaneously the paths between any single terminal pair, paths for multiterminal pairs and cuts for the specified terminal pair.The present paper provides a conceptually simple and computationally efficient algorithm to obtain simultaneously the paths between any single pair of terminals, paths for multiterminal pairs and the cuts for the specified terminal pair of interest of any complex network. The algorithm is easy and computationally economical and also applicable to graphs having both nodes and branches of finite non-zero failure probability.An illustrative example is provided to demonstrate the effectiveness of the proposed algorithm.     

Mathematical foundations of minimal cutsets

Since their introduction in the reliability field, binary decision diagrams have proved to be the most efficient tool to assess Boolean models such as fault trees. Their success increases the need of sound mathematical foundations for the notions that are involved in reliability and dependability studies. This paper clarifies the mathematical status of the notion of minimal cutsets which have a central role in fault-tree assessment. Algorithmic issues are discussed. Minimal cutsets are distinct from prime implicants and they have a great interest from both a computation complexity and practical viewpoint. Implementation of BDD algorithms is explained. All of these algorithms are implemented in the Aralia software, which is widely used. These algorithms and their mathematical foundations were designed to assess efficiently a very large noncoherent fault tree that models the emergency shutdown system of a nuclear reactor     

A new methodology to handle Boolean models with loops

It is often convenient, in reliability analyses, to describe the system under study by means of a set of Boolean equations. Fault trees can be seen as hierarchical sets of Boolean equations. In some cases, the model contains loops, because the system embeds at least two components whose states depend on one another. Reliability networks are a typical example of looped models. Classical fault tree assessment methods fail to assess this kind of model. This paper proposes a logical framework to clarify the meaning of looped sets of Boolean equations; and a binary decision diagrams based method is proposed to assess them. This approach is illustrated with experimental results on a benchmark of reliability networks.     

Variable Ordering to Improve BDD Analysis of Phased-Mission Systems With Multimode Failures

Recently, Z. Tang, and J. B. Dugan proposed a new algorithm (DEP-BDD) based on binary decision diagrams (BDD) for reliability analysis of phased-mission systems (PMS) with multimode failures. Although the variable ordering is very important from a practical point of view, it has not been treated directly. This paper develops four ordering heuristics for DEP-BDD based on two ordinary schemes, and evaluates these schemes & heuristics with hundreds of randomly generated fault trees having different sizes and structure properties. As a synthesis of the obtained performance results, we propose a heuristic selection strategy.      

Complex decision diagrams

Complex decision diagrams to represent integer-valued functions in the form of complex Hadamard transforms and spectra are introduced. With the distinctive and unique properties of the transform, the novel complex decision diagrams could be further simplified by reduction rules and a half-spectra theorem that will lead to a more compact representation     

Determining terminal-pair reliability based on edge expansiondiagrams using OBDD

For calculating terminal-pair reliability, most published algorithms are based on the sum of disjoint products. However, these tree-based partitions lack the capability to avoid redundant computation due to the isomorphic sub-problems. To overcome these problems, an efficient methodology to evaluate the terminal-pair reliability, based on edge expansion diagrams using OBDD (ordered binary decision diagram) is presented. First, the success path function of a given network is constructed based on OBDD by traversing the network with diagram-based edge expansion. Then the reliability of the network is obtained by directly evaluating on this OBDD recursively. The effectiveness of this approach is demonstrated by performing experiments on benchmarks collected by previous works including the larger networks (from 4 to 2 ⁹⁹ paths). A dramatic improvement, as demonstrated by the experimental results for a 2-by-n lattice network is that the number of OBDD nodes is only linearly proportional to the number of stages, and is much better than previous algorithms which have exponential complexity by using the sum of disjoint products. The CPU time of reliability calculation for a 100-stage lattice network is only about 2.5 seconds with 595 nodes generated on a SPARC 20 workstation with 128 MBytes of memory. Thus, with this approach, the terminal-pair reliability of large networks can be efficiently evaluated better than thought possible     

迅速发展的大规模光盘文件系统

本文叙述了一个大规模光盘文件数据系统以及它的结构，特点，终端检索方法，可靠性并指出存在的问题及今后研究的课题。     

激光照射指示器整机性能检测方法研究

根据激光末端制导的工作原理,分析了激光照射指示器的性能指标,提出了各性能指标的数字化检测方法。采用模拟回波和精密延时电路检测照射能力、用CCD采集激光光斑测试激光束散角,实现了整机性能的数字化检测。能够测量每个照射周期各激光脉冲的能量、脉冲间隔、频率精度等参数,并在同一脉冲序列图中绘出波形。给出了电路框图、光路图和数据处理的方法。采用的四通道结构和上位机与下位机串行通讯的措施,减小了仪器的体积,提高了硬件的模块化结构和软件的可靠性与可视化程度。     

Health assessment and management of wind turbine blade based on the fatigue test data

With the quality problem becoming increasingly prominent, it is necessary to assess and manage the health condition of the wind turbine blade. The health degree is defined and calculated by the Grey Relation (GR) model to assess the health condition of the wind turbine blade quantitatively. The availability, reliability and artificial test result are taken as three indexes of the health degree. The availability is defined according to the stiffness degradation affected by the environmental temperature. Based on the health assessment results, after determining the decision objectives and the management strategies, the weights of the decision objectives and the health management decision are determined by the Analytic Hierarchy Process and Fuzzy (AHP-Fuzzy) decision method. This process is shown in a practical example of the 3 MW wind turbine blade. As a result, an approach and a certain theoretical guidance for the health assessment and management of wind turbine blade are proposed.     

基于加权IFS证据合成的多源信息融合方法

为权衡信息融合系统对各条证据的可信程度,提出基于直觉模糊交叉熵的证据折扣方法,用于直觉模糊证据合成规则。并根据确定性理论,对直觉模糊决策中的记分函数进行改进,得到基于确定性因子的记分函数形式,用于直觉模糊证据合成结果判定。最后通过与其他算法的对比实验,验证算法在多传感器目标识别应用中是有效的,且具有较高的计算效率。     

OBDD-based evaluation of k-terminal network reliability

An efficient approach to determining the reliability of an undirected k-terminal network based on 2-terminal reliability functions is presented. First, a feasible set of (k-1) terminal-pairs is chosen, and the 2-terminal reliability functions of the (k-1) terminal-pairs are generated based on the edge expansion diagram using an OBDD (ordered binary decision diagram). Then the k-terminal reliability function can be efficiently constructed by combining these (k-1) reliability expressions with the Boolean and operation. Because building 2-terminal reliability functions and reducing redundant computations by merging reliability functions can be done very efficiently, the proposed approaches are much faster than those which directly expand the entire network or directly factor the k-terminal networks. The effectiveness of this approach is demonstrated by performing experiments on several large benchmark networks. An example of appreciable improvement is that the evaluation of the reliability of a source-terminal 3/spl times/10 all-terminal network took only 2.4 seconds on a SPARC 20 workstation. This is much faster than previous factoring-algorithms.     

Better graphs for dependability modeling

It is shown that fault trees (FTs) can be better understood, and more easily evaluated, if they are drawn more strictly as pictures of—at least partly minimized—switching functions of digital electronics. In this context a clearer graph theoretical interpretation of fault trees and reliability block diagrams is given. Both are best interpreted as marked directed acyclic graphs. The role of binary decision diagrams (BDDs) is reviewed in this context.As to Petri nets (PNs) of systems, it is shown first that FTs can be modeled more compactly as PNs, if on any path from input to output AND and OR gates appear alternatingly. Then a 3-phased design of PNs is introduced, including a very simple way of finding the places of the two binary system states (“good” and “bad”) via special FTs and success trees.In the Appendix it is shown why it is, in general, so hard to treat cases of s-dependent components via FTs.All of the above is discussed with many examples.     

Environment and Movement Model for Mobile Terminal Location Tracking

Mobile terminal position location, tracking and prediction are becomingimportant areas of research for advanced cellular communications.Methods for mobile terminal location are evaluated using simulations. To obtain accurate simulation results, the simulation environment and terminalmotion model must be as realistic as possible. This paper describes a simulation system for mobile terminals located within vehicles in dense urban environments. These are the mobiles with the greatest need for locationpredictions in the environments of greatest interest to network providers. Theradio propagation model is based on well known multipath radio propagationmodels. The motion model combines an accurate kinematic model for vehicular motion with a driver decision model to mimic human driving decisions.Simulatedmobile terminal motion tracks are presented, showing how realistic motionsare generated.