Sample records for reliability fault trees

  1. DFTCalc: Reliability centered maintenance via fault tree analysis (tool paper)

    Guck, Dennis; Spel, Jip; Stoelinga, Mariëlle Ida Antoinette; Butler, Michael; Conchon, Sylvain; Zaïdi, Fatiha


    Reliability, availability, maintenance and safety (RAMS) analysis is essential in the evaluation of safety critical systems like nuclear power plants and the railway infrastructure. A widely used methodology within RAMS analysis are fault trees, representing failure propagations throughout a system.

  2. DFTCalc: reliability centered maintenance via fault tree analysis (tool paper)

    Guck, Dennis; Spel, Jip; Stoelinga, Mariëlle; Butler, Michael; Conchon, Sylvain; Zaïdi, Fatiha


    Reliability, availability, maintenance and safety (RAMS) analysis is essential in the evaluation of safety critical systems like nuclear power plants and the railway infrastructure. A widely used methodology within RAMS analysis are fault trees, representing failure propagations throughout a system.

  3. Fault-Tree Compiler

    Butler, Ricky W.; Boerschlein, David P.


    Fault-Tree Compiler (FTC) program, is software tool used to calculate probability of top event in fault tree. Gates of five different types allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language easy to understand and use. In addition, program supports hierarchical fault-tree definition feature, which simplifies tree-description process and reduces execution time. Set of programs created forming basis for reliability-analysis workstation: SURE, ASSIST, PAWS/STEM, and FTC fault-tree tool (LAR-14586). Written in PASCAL, ANSI-compliant C language, and FORTRAN 77. Other versions available upon request.

  4. Reliability database development for use with an object-oriented fault tree evaluation program

    Heger, A. Sharif; Harringtton, Robert J.; Koen, Billy V.; Patterson-Hine, F. Ann


    A description is given of the development of a fault-tree analysis method using object-oriented programming. In addition, the authors discuss the programs that have been developed or are under development to connect a fault-tree analysis routine to a reliability database. To assess the performance of the routines, a relational database simulating one of the nuclear power industry databases has been constructed. For a realistic assessment of the results of this project, the use of one of existing nuclear power reliability databases is planned.

  5. Methodology for reliability allocation based on fault tree analysis and dualistic contrast

    TONG Lili; CAO Xuewu


    Reliability allocation is a difficult multi-objective optimization problem.This paper presents a methodology for reliability allocation that can be applied to determine the reliability characteristics of reactor systems or subsystems.The dualistic contrast,known as one of the most powerful tools for optimization problems,is applied to the reliability allocation model of a typical system in this article.And the fault tree analysis,deemed to be one of the effective methods of reliability analysis,is also adopted.Thus a failure rate allocation model based on the fault tree analysis and dualistic contrast is achieved.An application on the emergency diesel generator in the nuclear power plant is given to illustrate the proposed method.

  6. Fault maintenance trees: reliability centered maintenance via statistical model checking

    Ruijters, Enno; Guck, Dennis; Drolenga, Peter; Stoelinga, Mariëlle


    The current trend in infrastructural asset management is towards risk-based (a.k.a. reliability centered) maintenance, promising better performance at lower cost. By maintaining crucial components more intensively than less important ones, dependability increases while costs decrease. This requires

  7. Fault maintenance trees: reliability centered maintenance via statistical model checking

    Ruijters, Enno Jozef Johannes; Guck, Dennis; Drolenga, Peter; Stoelinga, Mariëlle Ida Antoinette

    The current trend in infrastructural asset management is towards risk-based (a.k.a. reliability centered) maintenance, promising better performance at lower cost. By maintaining crucial components more intensively than less important ones, dependability increases while costs decrease. This requires

  8. Use of Fault Tree Analysis for Automotive Reliability and Safety Analysis

    Lambert, H


    Fault tree analysis (FTA) evolved from the aerospace industry in the 1960's. A fault tree is deductive logic model that is generated with a top undesired event in mind. FTA answers the question, ''how can something occur?'' as opposed to failure modes and effects analysis (FMEA) that is inductive and answers the question, ''what if?'' FTA is used in risk, reliability and safety assessments. FTA is currently being used by several industries such as nuclear power and chemical processing. Typically the automotive industries uses failure modes and effects analysis (FMEA) such as design FMEAs and process FMEAs. The use of FTA has spread to the automotive industry. This paper discusses the use of FTA for automotive applications. With the addition automotive electronics for various applications in systems such as engine/power control, cruise control and braking/traction, FTA is well suited to address failure modes within these systems. FTA can determine the importance of these failure modes from various perspectives such as cost, reliability and safety. A fault tree analysis of a car starting system is presented as an example.

  9. Reliability analysis of a wastewater treatment plant using fault tree analysis and Monte Carlo simulation.

    Taheriyoun, Masoud; Moradinejad, Saber


    The reliability of a wastewater treatment plant is a critical issue when the effluent is reused or discharged to water resources. Main factors affecting the performance of the wastewater treatment plant are the variation of the influent, inherent variability in the treatment processes, deficiencies in design, mechanical equipment, and operational failures. Thus, meeting the established reuse/discharge criteria requires assessment of plant reliability. Among many techniques developed in system reliability analysis, fault tree analysis (FTA) is one of the popular and efficient methods. FTA is a top down, deductive failure analysis in which an undesired state of a system is analyzed. In this study, the problem of reliability was studied on Tehran West Town wastewater treatment plant. This plant is a conventional activated sludge process, and the effluent is reused in landscape irrigation. The fault tree diagram was established with the violation of allowable effluent BOD as the top event in the diagram, and the deficiencies of the system were identified based on the developed model. Some basic events are operator's mistake, physical damage, and design problems. The analytical method is minimal cut sets (based on numerical probability) and Monte Carlo simulation. Basic event probabilities were calculated according to available data and experts' opinions. The results showed that human factors, especially human error had a great effect on top event occurrence. The mechanical, climate, and sewer system factors were in subsequent tier. Literature shows applying FTA has been seldom used in the past wastewater treatment plant (WWTP) risk analysis studies. Thus, the developed FTA model in this study considerably improves the insight into causal failure analysis of a WWTP. It provides an efficient tool for WWTP operators and decision makers to achieve the standard limits in wastewater reuse and discharge to the environment.

  10. Fault-Tree Compiler Program

    Butler, Ricky W.; Martensen, Anna L.


    FTC, Fault-Tree Compiler program, is reliability-analysis software tool used to calculate probability of top event of fault tree. Five different types of gates allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language of FTC easy to understand and use. Program supports hierarchical fault-tree-definition feature simplifying process of description of tree and reduces execution time. Solution technique implemented in FORTRAN, and user interface in Pascal. Written to run on DEC VAX computer operating under VMS operating system.

  11. The fault-tree compiler

    Martensen, Anna L.; Butler, Ricky W.


    The Fault Tree Compiler Program is a new reliability tool used to predict the top event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N gates. The high level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precise (within the limits of double precision floating point arithmetic) to the five digits in the answer. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Corporation VAX with the VMS operation system.

  12. Fault Tree Handbook


    to be Evaluated Manufacturer Location Seismic Susceptibility Flood Susceptibility Temperature Humidity Radiation Wear-out Susceptibility Test...For the category " Seismic Susceptibility," we might define several sensitivity levels ranging from no sensitivity to extreme sensitivity, and for more... Hanford Company, Richland, Wash- ington, ARH-ST-l 12, July 1975. 40. W.E. Vesely, "Analysis of Fault Trees by Kinetic Tree Theory," Idaho Nuclear

  13. Rare event simulation for dynamic fault trees

    Ruijters, Enno Jozef Johannes; Reijsbergen, D.P.; de Boer, Pieter-Tjerk; Stoelinga, Mariëlle Ida Antoinette


    Fault trees (FT) are a popular industrial method for reliability engineering, for which Monte Carlo simulation is an important technique to estimate common dependability metrics, such as the system reliability and availability. A severe drawback of Monte Carlo simulation is that the number of

  14. Assessment Method for the Reliability of Power Transformer Based on Fault-tree Analysis%基于粒子群优化支持向量机的变压器故障诊断

    费胜巍; 苗玉彬; 刘成良


    Accurate assessment of system reliability with limited or insufficient statistical data is difficult. At present, to assess the reliability of the transformers primarily depend on the statistics data, and the result of the assessment does not accurately reflect the reliability of a transformer. Fault tree is a powerful tool for depicting the logical relationships between the faults system. However, for a sophisticated reliability system, like power transformer,fault analysis is hard or infeasible because of the complexities of the equipment configuration and its faults. This paper presents a method which overcomes the drawbacks of traditional fault-tree analysis (FTA) by using FTA based on fault probability and equivalent calculation of each failure mode. Based on the further analysis of typical failure modes and influences of power transformer, the fault-tree of transformer is set up by using FTA techniques and the assessment method for the reliability of transformer is put forward, combined with the index of the importance and the method of improved analytic hierarchy process(IAHP). The assessment examples show the method can deduct the failure modes of transformer clearly, meanwhile, find out the weaknesses in time during the operation and get better assessment results. The method is helpful for the reliability analysis of a sophisticated system.

  15. Guideliness for system modeling: fault tree [analysis

    Lee, Yoon Hwan; Yang, Joon Eon; Kang, Dae Il; Hwang, Mee Jeong


    This document, the guidelines for system modeling related to Fault Tree Analysis(FTA), is intended to provide the guidelines with the analyzer to construct the fault trees in the level of the capability category II of ASME PRA standard. Especially, they are to provide the essential and basic guidelines and the related contents to be used in support of revising the Ulchin 3 and 4 PSA model for risk monitor within the capability category II of ASME PRA standard. Normally the main objective of system analysis is to assess the reliability of system modeled by Event Tree Analysis (ETA). A variety of analytical techniques can be used for the system analysis, however, FTA method is used in this procedures guide. FTA is the method used for representing the failure logic of plant systems deductively using AND, OR or NOT gates. The fault tree should reflect all possible failure modes that may contribute to the system unavailability. This should include contributions due to the mechanical failures of the components, Common Cause Failures (CCFs), human errors and outages for testing and maintenance. This document identifies and describes the definitions and the general procedures of FTA and the essential and basic guidelines for reving the fault trees. Accordingly, the guidelines for FTA will be capable to guide the FTA to the level of the capability category II of ASME PRA standard.


    Dobrivoje Catic


    Full Text Available In the introductory part, the history development is presented, and it points out the importance of using the Fault Tree Analysis - FTA method for analysis of the reliability and safety of technical systems. By analyzing a number of references related to the FTA method, the FTA methodology is established, and explanation of some steps by this method is given in this paper. As an example of the practical application of methods, the failure of the solar concentrators is analyzed.For the failure analysis of the considered device, it is necessary to know the structure, functioning, working conditions and all factors that have a greater or less influence on its reliability. Along with an explanation of certain parts of the fault tree, the estimation of the significance of certain events is done, and it is considered to be able to eliminate causes of failure or to minimize the consequences of failure.

  17. The Fault Tree Compiler (FTC): Program and mathematics

    Butler, Ricky W.; Martensen, Anna L.


    The Fault Tree Compiler Program is a new reliability tool used to predict the top-event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, AND m OF n gates. The high-level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precisely (within the limits of double precision floating point arithmetic) within a user specified number of digits accuracy. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Equipment Corporation (DEC) VAX computer with the VMS operation system.

  18. Object-oriented fault tree evaluation program for quantitative analyses

    Patterson-Hine, F. A.; Koen, B. V.


    Object-oriented programming can be combined with fault free techniques to give a significantly improved environment for evaluating the safety and reliability of large complex systems for space missions. Deep knowledge about system components and interactions, available from reliability studies and other sources, can be described using objects that make up a knowledge base. This knowledge base can be interrogated throughout the design process, during system testing, and during operation, and can be easily modified to reflect design changes in order to maintain a consistent information source. An object-oriented environment for reliability assessment has been developed on a Texas Instrument (TI) Explorer LISP workstation. The program, which directly evaluates system fault trees, utilizes the object-oriented extension to LISP called Flavors that is available on the Explorer. The object representation of a fault tree facilitates the storage and retrieval of information associated with each event in the tree, including tree structural information and intermediate results obtained during the tree reduction process. Reliability data associated with each basic event are stored in the fault tree objects. The object-oriented environment on the Explorer also includes a graphical tree editor which was modified to display and edit the fault trees.

  19. Analytical Model and Algorithm of Fuzzy Fault Tree

    杨艺; 何学秋; 王恩元; 刘贞堂


    In the past, the probabilities of basic events were described as triangular or trapezoidal fuzzy number that cannot characterize the common distribution of the primary events in engineering, and the fault tree analyzed by fuzzy set theory did not include repeated basic events. This paper presents a new method to a nalyze the fault tree by using normal fuzzy number to describe the fuzzy probability of each basic event which is more suitably used to analyze the reliability in safety systems, and then the formulae of computing the fuzzy probability of the top event of the fault tree which includes repeated events are derived. Finally, an example is given.

  20. Method for software reliability assessment based on fuzzy fault tree analysis%软件可靠度的模糊故障树评定方法

    刘博宁; 张鹏; 张建业; 马秋芝


    软件可靠性的定量评价是软件可靠性工程的关键问题之一,采用故障树方法对软件进行定性和定量分析,提出了两类情况下对影响软件可靠性的主次因素划分及其模糊权重的计算方法.在此基础上,建立多级模糊评价模型,提出了增广和聚合算法,并给出了软件可靠度算式.选择某型航空装备软件进行了测试实例分析,实验结果表明了该方法评价结构的合理性与评价算法的有效性,适用于软件质量及开发过程控制的工程实践.%The quantitative assessment of software reliability is one of the most important problem for software reliability project, this paper used firstly the qualitative and quantitative analyzing based on fault tree analysis of software, it proposed the method for fuzzy weight calculating and the primary and secondary ingredients compartmentalizing. It established the multi-grade fuzzy assessment model, discussed the enhanced and converging arithmetic, and proposed the expressions of reliability. This method presented its rationality of assessment configuration and validity of assessment arithmetic through testing and analyzing of an aero equipment' s software, it could be used on quality and exploitation control engineering for software.

  1. Modeling and Analysis of Component Faults and Reliability

    Le Guilly, Thibaut; Olsen, Petur; Ravn, Anders Peter;


    that are automatically generated. The stochastic information on the faults is used to estimate the reliability of the fault affected system. The reliability is given with respect to properties of the system state space. We illustrate the process on a concrete example using the Uppaal model checker for validating...... the ideal system model and the fault modeling. Then the statistical version of the tool, UppaalSMC, is used to find reliability estimates.......This chapter presents a process to design and validate models of reactive systems in the form of communicating timed automata. The models are extended with faults associated with probabilities of occurrence. This enables a fault tree analysis of the system using minimal cut sets...

  2. Evidential Networks for Fault Tree Analysis with Imprecise Knowledge

    Yang, Jianping; Huang, Hong-Zhong; Liu, Yu; Li, Yan-Feng


    Fault tree analysis (FTA), as one of the powerful tools in reliability engineering, has been widely used to enhance system quality attributes. In most fault tree analyses, precise values are adopted to represent the probabilities of occurrence of those events. Due to the lack of sufficient data or imprecision of existing data at the early stage of product design, it is often difficult to accurately estimate the failure rates of individual events or the probabilities of occurrence of the events. Therefore, such imprecision and uncertainty need to be taken into account in reliability analysis. In this paper, the evidential networks (EN) are employed to quantify and propagate the aforementioned uncertainty and imprecision in fault tree analysis. The detailed conversion processes of some logic gates to EN are described in fault tree (FT). The figures of the logic gates and the converted equivalent EN, together with the associated truth tables and the conditional belief mass tables, are also presented in this work. The new epistemic importance is proposed to describe the effect of ignorance degree of event. The fault tree of an aircraft engine damaged by oil filter plugs is presented to demonstrate the proposed method.

  3. Workflow Fault Tree Generation Through Model Checking

    Herbert, Luke Thomas; Sharp, Robin


    We present a framework for the automated generation of fault trees from models of realworld process workflows, expressed in a formalised subset of the popular Business Process Modelling and Notation (BPMN) language. To capture uncertainty and unreliability in workflows, we extend this formalism...... of the system being modelled. From these calculations, a comprehensive fault tree is generated. Further, we show that annotating the model with rewards (data) allows the expected mean values of reward structures to be calculated at points of failure....


    陈涛; 孙伟; 张旭


    In order to increase the accuracy of fault tree analysis and improve the predictive viaracity of reliability analysis, the transmission qear box of wind power was provided as study case. Fault tree model was divided into several sub-units and grey relation theory was used to establish the reliability links between various units. In the base unit, basic feature events were defined to generalize the probability characteristics of similar basic events. In addition, rftliability of each basic feature events was calculated by stress-strength interference model and Monte Carlo method. Based on these work, reliability of whole transmission can be solved. The results indicate that the method an improve the objectivity of reliability analysis, and the system reliability can be predicted fleetly if the design parameters are known.%为提高故障树分析在可靠性预测过程中的准确性,以风电齿轮箱传动系统为研究对象,将故障树模型划分为若干子单元,利用灰色关联度理论建立各单元之间的可靠度联系;对于基准单元,定义基本特征事件表征同类底事件的概率特征,利用应力-强度干涉模型及蒙特卡罗数值法模拟各基本特征事件的可靠度,在此基础上求解整个传动系统的可靠度.结果表明:该方法不仅可提高可靠度计算的客观性,且能够在设计参数已知的前提下对系统可靠度进行快速预测.

  5. A Novel Framework for Real-Time Fault Diagnosis Based on Dynamic Fault Tree Analysis

    Rongxing Duan


    Full Text Available To meet the real-time diagnosis requirements of the complex system, this study proposes a novel framework for real-time fault diagnosis using dynamic fault tree analysis. It pays special attention to meeting two challenges: model development and real-time reasoning. In terms of the challenge of model development, we use a dynamic fault tree model to capture the dynamic behavior of system failure mechanisms and calculate some reliability results by mapping a dynamic fault tree into an equivalent Bayesian Network (BN in order to avoid the infamous state space explosion problem. In terms of the real-time reasoning challenge, we adopt a logic compilation based inference algorithm, which compiles the BN into an arithmetic circuit and retrieves answers to probabilistic queries by evaluating and differentiating the arithmetic circuit. Furthermore, we incorporate sensors data into fault diagnosis, cope with the sensors reliability and propose the schemes on how to update the Diagnostic Importance Factor (DIF and the minimal cut sets. Finally, a case study is given to validate the efficiency of this method.

  6. An Algorithm for Fault-Tree Construction

    Taylor, J. R.


    An algorithm for performing certain parts of the fault tree construction process is described. Its input is a flow sheet of the plant, a piping and instrumentation diagram, or a wiring diagram of the circuits, to be analysed, together with a standard library of component functional and failure...... models. A systematic approach to component model construction is also presented....

  7. Fault tree analysis for urban flooding

    Ten Veldhuis, J.A.E.; Clemens, F.H.L.R.; Van Gelder, P.H.A.J.M.


    Traditional methods to evaluate flood risk mostly focus on storm events as the main cause of flooding. Fault tree analysis is a technique that is able to model all potential causes of flooding and to quantify both the overall probability of flooding and the contributions of all causes of flooding to

  8. Fuzzy fault tree analysis of roller oscillating tooth gear drive

    李瑰贤; 杨伟君; 张欣; 李笑; 刘福利


    Conventional fault tree and reliability analysis do not reflect the characteristics of basic events asnon-stationary and ergodic process. To overcome these drawbacks, theory of fuzzy sets is employed to run faulttree analysis(FTA) of roller oscillating tooth gear drive( ROTGD), the relative frequencies of basic events areconsidered as symmetrical normal fuzzy numbers, from the logical relationship between different events in thefault tree and fuzzy operators AND and OR, fuzzy probability of top event is solved. Finally, an example is giv-en to demonstrate a real ROTGD system.

  9. A Simple Method to Derive Minimal Cut Sets for a Non-coherent Fault Tree

    Takehisa Kohda


    Minimal cut sets (or prime implicants: minimal combinations of basic event conditions leading to system failure)are important information for reliability/safety analysis and design. To obtain minimal cut sets for general non-coherent fault trees, including negative basic events or multi-valued basic events, a special procedure such as the consensus rule must be applied to the results obtained by logical operations for coherent fault trees, which will require more steps and time.This paper proposes a simple method for a non-coherent fault tree, whose top event is represented as an AND combination of monotonic sub-trees. A "monotonic" sub-tree means that it does not have both positive and negative representations for each basic event. It is proven that minimal cut sets can be obtained by a conventional method for coherent fault trees. An illustrative example of a simple event tree analysis shows the detail and characteristics of the proposed method.

  10. Reliability Analysis for Electric Multiple Units Based on Fault Tree Monte Carlo Method%基于故障树—蒙特卡洛方法的动车组可靠性分析

    胡川; 姚建伟


    建立CRH2型动车组系统及其走行子系统、牵引传动子系统、制动子系统、高压电器子系统、辅助供电子系统以及网络控制子系统的故障树,在此基础上运用蒙特卡洛方法和MATLAB软件,对动车组的可靠性进行仿真分析.结果表明:基于故障树分析的蒙特卡洛仿真方法能快速、准确地计算动车组整车的可靠性;当动车组各基本部件发生故障的概率服从指数分布时,整个动车组系统发生故障的概率也服从指数分布;动车组最重要的3个分系统依次为空气供给分系统、接地保护开关和高压设备箱分系统以及牵引传动分系统.%The fault trees of the CRH2 EMU system as well as its subsystems of running, traction drive, braking, high voltage apparatus, auxiliary power supply and network control were established. On that basis, Monte Carlo method and MATLAB software were applied to simulate and analyze the reliability of the EMU. The results indicate that, Monte Carlo simulation method which is based on fault tree analysis, can rapidly and accurately calculate the reliability of the whole EMU. If the fault probabilities of EMU various basic components obey exponential distribution, then does the fault probability of the whole EMU system. The three most important partial systems of the EMU are, in order, the air supply partial system, the grounding protection switch and high voltage equipment box partial system and traction drive partial system.

  11. Fuzzy Uncertainty Evaluation for Fault Tree Analysis

    Kim, Ki Beom; Shim, Hyung Jin [Seoul National University, Seoul (Korea, Republic of); Jae, Moo Sung [Hanyang University, Seoul (Korea, Republic of)


    This traditional probabilistic approach can calculate relatively accurate results. However it requires a long time because of repetitive computation due to the MC method. In addition, when informative data for statistical analysis are not sufficient or some events are mainly caused by human error, the probabilistic approach may not be possible because uncertainties of these events are difficult to be expressed by probabilistic distributions. In order to reduce the computation time and quantify uncertainties of top events when basic events whose uncertainties are difficult to be expressed by probabilistic distributions exist, the fuzzy uncertainty propagation based on fuzzy set theory can be applied. In this paper, we develop a fuzzy uncertainty propagation code and apply the fault tree of the core damage accident after the large loss of coolant accident (LLOCA). The fuzzy uncertainty propagation code is implemented and tested for the fault tree of the radiation release accident. We apply this code to the fault tree of the core damage accident after the LLOCA in three cases and compare the results with those computed by the probabilistic uncertainty propagation using the MC method. The results obtained by the fuzzy uncertainty propagation can be calculated in relatively short time, covering the results obtained by the probabilistic uncertainty propagation.

  12. Fault tree analysis for urban flooding.

    ten Veldhuis, J A E; Clemens, F H L R; van Gelder, P H A J M


    Traditional methods to evaluate flood risk generally focus on heavy storm events as the principal cause of flooding. Conversely, fault tree analysis is a technique that aims at modelling all potential causes of flooding. It quantifies both overall flood probability and relative contributions of individual causes of flooding. This paper presents a fault model for urban flooding and an application to the case of Haarlem, a city of 147,000 inhabitants. Data from a complaint register, rainfall gauges and hydrodynamic model calculations are used to quantify probabilities of basic events in the fault tree. This results in a flood probability of 0.78/week for Haarlem. It is shown that gully pot blockages contribute to 79% of flood incidents, whereas storm events contribute only 5%. This implies that for this case more efficient gully pot cleaning is a more effective strategy to reduce flood probability than enlarging drainage system capacity. Whether this is also the most cost-effective strategy can only be decided after risk assessment has been complemented with a quantification of consequences of both types of events. To do this will be the next step in this study.

  13. Building and Analysis of Computer Aided Fuze Fault Tree

    王亚斌; 刘明杰; 谭惠民


    A common software to analyze fuze fault tree is developed to simplify the trivialness in generating the fuze fault tree and reduce the manual calculation work. The overall structure, function and implementation of the system are introduced. The software based on Windows platform is used to generate the fuze fault tree in graphics mode. A quantitative analysis of fuze fault tree can be obtained by the method of minimum cut sets. A calculation example is used to verify the function of the software. Consequently, the expected requirements of this software system are achieved to a certain level.

  14. Fault tolerant highly reliable inertial navigation system

    Jeerage, Mahesh; Boettcher, Kevin

    This paper describes a development of failure detection and isolation (FDI) strategies for highly reliable inertial navigation systems. FDI strategies are developed based on the generalized likelihood ratio test (GLRT). A relationship between detection threshold and false alarm rate is developed in terms of the sensor parameters. A new method for correct isolation of failed sensors is presented. Evaluation of FDI performance parameters, such as false alarm rate, wrong isolation probability, and correct isolation probability, are presented. Finally a fault recovery scheme capable of correcting false isolation of good sensors is presented.

  15. Combination of Fault Tree and Neural Networks in Excavator Diagnosis

    Li Guoping; Zhang Qingwei; Ma Xiao


    By using the theory of artificial intelligence fault diagnosis of hydraulic excavator of several basic problems are discussed in this paper, the artificial intelligence neural network model is established for the fault diagnosis of hydraulic system; the combined application of fault diagnosis analysis (FTA) and artificial neural network is evaluated. In view of the hydraulic excavator failure symptom of dispersion and fuzziness, the fault diagnosis method was presented based on the fault tree...

  16. Fault tree analysis of KNICS RPS software

    Park, Gee Yong; Kwon, Kee Choon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Koh, Kwang Yong; Jee, Eun Kyoung; Seong, Poong Hyun [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Lee, Dae Hyung [Doosan Heavy Industries and Construction, Yongin (Korea, Republic of)


    This paper describes the application of a software Fault Tree Analysis (FTA) as one of the analysis techniques for a Software Safety Analysis (SSA) at the design phase and its analysis results for the safety-critical software of a digital reactor protection system, which is called the KNICS RPS, being developed in the KNICS (Korea Nuclear Instrumentation and Control Systems) project. The software modules in the design description were represented by Function Blocks (FBs), and the software FTA was performed based on the well-defined fault tree templates for the FBs. The SSA, which is part of the verification and validation (V and V) activities, was activated at each phase of the software lifecycle for the KNICS RPS. At the design phase, the software HAZOP (Hazard and Operability) and the software FTA were employed in the SSA in such a way that the software HAZOP was performed first and then the software FTA was applied. The software FTA was applied to some critical modules selected from the software HAZOP analysis.

  17. Efficient Fault Tree Analysis of Complex Fault Tolerant Multiple-Phased Systems

    MO Yuchang; LIU Hongwei; YANG Xiaozong


    Fault tolerant multiple phased systems (FTMPS), i.e., systems whose critical components are independently replicated and whose operational life can be partitioned in a set of disjoint periods, are called "phases". Because of their deployment in critical applications, their reliability analysis is a task of primary relevance to validate the designs. Fault tree analysis based on binary decision diagram (BDD) is one of the most commonly used techniques for FTMPS reliability analysis. To utilize the technique the fault tree structure of FTMPS needs to be converted into the corresponding BDD format. Our research work shows that the system BDD generation algorithms presented in the literature are too inefficient to be used for industrial complex FTPMS because of the problems, such as variable ordering and combination of large BDDs. This paper presents a more efficient approach consisting of a flatting pre-processing technique, a proved efficient ordering heuristic and a bottom-up generation algorithm. The approach tries to combine share-variable BDDs by complex combination operation firstly and then combine no-share-variable BDDs using simple combination operation, thus to alvoid the intensive computations caused by large BDD combination operations. An example FTMPS is analyzed to illustrate the advantages of our approach.

  18. Fault recovery in the reliable multicast protocol

    Callahan, John R.; Montgomery, Todd L.; Whetten, Brian


    The Reliable Multicast Protocol (RMP) provides a unique, group-based model for distributed programs that need to handle reconfiguration events at the application layer. This model, called membership views, provides an abstraction in which events such as site failures, network partitions, and normal join-leave events are viewed as group reformations. RMP provides access to this model through an application programming interface (API) that notifies an application when a group is reformed as the result of a some event. RMP provides applications with reliable delivery of messages using an underlying IP Multicast (12, 5) media to other group members in a distributed environment even in the case of reformations. A distributed application can use various Quality of Service (QoS) levels provided by RMP to tolerate group reformations. This paper explores the implementation details of the mechanisms in RMP that provide distributed applications with membership view information and fault recovery capabilities.

  19. Naive Fault Trees for Safety Evaluations in Early Project Phase

    Rajabali Nejad, Mohammadreza


    Naive Fault Trees (NFT) aim to extend the application of Fault Trees (FT) and make them appealing for system designers in the early project life cycle. NFT use input intervals and values to estimate the frequency of a top event. This extension facilitates the assignment of failure probability to

  20. Sensitivity Investigation of Fault Tree Analysis with Matrix-Algebraic Method

    Pokorádi László


    Full Text Available The Fault Tree Analysis (FTA is a systematic, deductive (top-down type and probabilistic risk assessment tool which shows the causal relations leading to a given undesired event, referred to as the “Top Event” (TE. The events, which cannot be subdivided, are called the Basic Events. Fault Tree diagram displays the undesired state of the investigated system (top event in terms of the states of its components (basic events. The Fault Tree Analysis is a graphical design technique main result of which is a tree, a dendritic graph. Probabilistic Fault Tree Analysis (PFTA is a quantitative analysis method used to calculate the probability of Top Event from given failure probabilities of system components. The objective of the sensitivity analysis is to show how the change in any system parameter influences the resultant reliability value of the whole system. The main aim of this study is to elaborate an easy-used algorithm for setting-up of Linear Fault Tree Sensitivity Model (LFTSM. This modular approach process uses matrix-algebraic method based upon the mathematical diagnostic modeling of aircraft systems and gas turbine engines. The paper shows the adaptation of linear mathematical diagnostic modeling methodology for setting-up of LFTSM and its possibility of use to investigate Fault Tree sensitivity by a demonstrative example.



    Based on the fuzzy set theory and the expand principle, using fuzzy number as the boundary condition of fault tree analysis, a new method of analyzing fuzzy fault probability of the top event is developed. Fuzzy importance analysis of the basic event is proposed as well. A practical example is given. This method is a new way to solve the obscure problems of fault tree analysis and has great value in engineering practice.

  2. Using Reliability Block Diagrams and Fault Tree circuits, to develop a Condition Based Maintenance Model for a Vessel’s Main Propulsion System and Related Subsystems

    Mohan Anantharaman


    Full Text Available Merchant shipping has undergone a great transformation over the past three decades. The shipping market is highly competitive, which coupled with high crewing and fuel costs, leads to high operational costs. One of the paramount factor involved in vessel operation is the Maintenance cost and there is a dire need to keep this cost to a minimum. Fortunately the earlier policy of repair only maintenance in commercial shipping has been done away with, and was replaced by the policy of preventive maintenance. Planned Maintenance System was introduced by ship management companies in the early 90’s. Planned Maintenance offered benefits over the repair only policy, but has its own demerits. Many a time machinery equipment is opened up for routine maintenance after a specified time interval, irrespective of the need. This could lead to potential failures, which is explained by the fact that preventive maintenance resulted in meddling of a well set piece of machinery equipment, leading to its subsequent failure. This is where Condition based maintenance or CBM steps into prominence. CBM monitors the health of the machinery equipment, analyses the condition and helps you in decision making. The Main Propulsion system forms the heart of a vessel and we need to ensure its reliability, together with the reliability of its associated sub-systems. The entire system can be represented by reliability block diagrams, to show the interdependence of various components comprising the system. This helps in the decision making process of CBM whereby ship’s engineer may decide to stop the running machinery equipment, open and overhaul the same, else postpone the overhaul for a later safe date.

  3. GRAFTED - GRAphical Fault Tree EDitor: A Fault Tree Description Program For Target Vulnerability/Survivability Analysis. User Manual


    9: Fault Tree Description of Generic Missile With Power Module. 3.4 Summary The remainder of the Generic Missile model will not be described in full...if the changes should be saved, and the Fault Tree Description files re-compiled. The next time GRAFTED is run from this directory, the Generic Missile model will

  4. [The Application of the Fault Tree Analysis Method in Medical Equipment Maintenance].

    Liu, Hongbin


    In this paper, the traditional fault tree analysis method is presented, detailed instructions for its application characteristics in medical instrument maintenance is made. It is made significant changes when the traditional fault tree analysis method is introduced into the medical instrument maintenance: gave up the logic symbolic, logic analysis and calculation, gave up its complicated programs, and only keep its image and practical fault tree diagram, and the fault tree diagram there are also differences: the fault tree is no longer a logical tree but the thinking tree in troubleshooting, the definition of the fault tree's nodes is different, the composition of the fault tree's branches is also different.

  5. Combination of Fault Tree and Neural Networks in Excavator Diagnosis

    Li Guoping


    Full Text Available By using the theory of artificial intelligence fault diagnosis of hydraulic excavator of several basic problems are discussed in this paper, the artificial intelligence neural network model is established for the fault diagnosis of hydraulic system; the combined application of fault diagnosis analysis (FTA and artificial neural network is evaluated. In view of the hydraulic excavator failure symptom of dispersion and fuzziness, the fault diagnosis method was presented based on the fault tree and fuzzy neural network. On the basis of analysis of the hydraulic excavator system works, the fault tree model of hydraulic excavator was built by using fault diagnosis tree. And then, utilizing the example of hydraulic excavator fault diagnosis, the method of building neural network, obtaining training samples and neural network learning in the process of intelligent fault diagnosis are expounded. And the status monitoring data of hydraulic excavator was used as the sample data source. Using fuzzy logic methods the samples were blurred. The fault diagnosis of hydraulic excavator was achieved with BP neural network. The experimental result demonstrated that the information of sign failure was fully used through the algorithm. The algorithm was feasible and effective to fault diagnosis of hydraulic excavator. A new diagnosis method was proposed for fault diagnosis of other similar device.

  6. Fault tree analysis of most common rolling bearing tribological failures

    Vencl, Aleksandar; Gašić, Vlada; Stojanović, Blaža


    Wear as a tribological process has a major influence on the reliability and life of rolling bearings. Field examinations of bearing failures due to wear indicate possible causes and point to the necessary measurements for wear reduction or elimination. Wear itself is a very complex process initiated by the action of different mechanisms, and can be manifested by different wear types which are often related. However, the dominant type of wear can be approximately determined. The paper presents the classification of most common bearing damages according to the dominant wear type, i.e. abrasive wear, adhesive wear, surface fatigue wear, erosive wear, fretting wear and corrosive wear. The wear types are correlated with the terms used in ISO 15243 standard. Each wear type is illustrated with an appropriate photograph, and for each wear type, appropriate description of causes and manifestations is presented. Possible causes of rolling bearing failure are used for the fault tree analysis (FTA). It was performed to determine the root causes for bearing failures. The constructed fault tree diagram for rolling bearing failure can be useful tool for maintenance engineers.

  7. Fault Tree Analysis for an Inspection Robot in a Nuclear Power Plant

    Ferguson, Thomas A.; Lu, Lixuan


    The life extension of current nuclear reactors has led to an increasing demand on inspection and maintenance of critical reactor components that are too expensive to replace. To reduce the exposure dosage to workers, robotics have become an attractive alternative as a preventative safety tool in nuclear power plants. It is crucial to understand the reliability of these robots in order to increase the veracity and confidence of their results. This study presents the Fault Tree (FT) analysis to a coolant outlet piper snake-arm inspection robot in a nuclear power plant. Fault trees were constructed for a qualitative analysis to determine the reliability of the robot. Insight on the applicability of fault tree methods for inspection robotics in the nuclear industry is gained through this investigation.

  8. Sequence Algebra, Sequence Decision Diagrams and Dynamic Fault Trees

    Rauzy, Antoine B., E-mail: Antoine.Rauzy@lix.polytechnique.f [LIX-CNRS, Computer Science, Ecole Polytechnique, 91128 Palaiseau Cedex (France)


    A large attention has been focused on the Dynamic Fault Trees in the past few years. By adding new gates to static (regular) Fault Trees, Dynamic Fault Trees aim to take into account dependencies among events. Merle et al. proposed recently an algebraic framework to give a formal interpretation to these gates. In this article, we extend Merle et al.'s work by adopting a slightly different perspective. We introduce Sequence Algebras that can be seen as Algebras of Basic Events, representing failures of non-repairable components. We show how to interpret Dynamic Fault Trees within this framework. Finally, we propose a new data structure to encode sets of sequences of Basic Events: Sequence Decision Diagrams. Sequence Decision Diagrams are very much inspired from Minato's Zero-Suppressed Binary Decision Diagrams. We show that all operations of Sequence Algebras can be performed on this data structure.

  9. Fuzzy set theoretic approach to fault tree analysis


    Research in conventional fault tree analysis (FTA) is based mainly on failure ... Thus for a very complex system having large number of components, the ..... Smaller, the triangular fuzzy number B-Ai, will result in the best approximation for B.

  10. The Fault tree analysis of the lead acid battery’s degradation

    K. BRIK


    Full Text Available In this paper the authors present an approach of reliability to analyze lead-acid battery’s degradation. The construction of causal tree analysis offers a framework privileged to the deductive analysis which consists in seeking the various possible combinations of events leading to the loss of batteries capacity. The description of the causality chain is completed by a fault tree analysis (FTA established from the equivalent electric circuit of battery.

  11. The Fault tree analysis of the lead acid battery’s degradation



    In this paper the authors present an approach of reliability to analyze lead-acid battery’s degradation. The construction of causal tree analysis offers a framework privileged to the deductive analysis which consists in seeking the various possible combinations of events leading to the loss of batteries capacity. The description of the causality chain is completed by a fault tree analysis (FTA) established from the equivalent electric circuit of battery.

  12. Microcomputer applications of, and modifications to, the modular fault trees

    Zimmerman, T.L.; Graves, N.L.; Payne, A.C. Jr.; Whitehead, D.W. [Sandia National Labs., Albuquerque, NM (United States)


    The LaSalle Probabilistic Risk Assessment was the first major application of the modular logic fault trees after the IREP program. In the process of performing the analysis, many errors were discovered in the fault tree modules that led to difficulties in combining the modules to form the final system fault trees. These errors are corrected in the revised modules listed in this report. In addition, the application of the modules in terms of editing them and forming them into the system fault trees was inefficient. Originally, the editing had to be done line by line and no error checking was performed by the computer. This led to many typos and other logic errors in the construction of the modular fault tree files. Two programs were written to help alleviate this problem: (1) MODEDIT - This program allows an operator to retrieve a file for editing, edit the file for the plant specific application, perform some general error checking while the file is being modified, and store the file for later use, and (2) INDEX - This program checks that the modules that are supposed to form one fault tree all link up appropriately before the files are,loaded onto the mainframe computer. Lastly, the modules were not designed for relay type logic common in BWR designs but for solid state type logic. Some additional modules were defined for modeling relay logic, and an explanation and example of their use are included in this report.

  13. Fault tolerance and reliability in integrated ship control

    Nielsen, Jens Frederik Dalsgaard; Izadi-Zamanabadi, Roozbeh; Schiøler, Henrik


    Various strategies for achieving fault tolerance in large scale control systems are discussed. The positive and negative impacts of distribution through network communication are presented. The ATOMOS framework for standardized reliable marine automation is presented along with the corresponding...

  14. Fault tolerance and reliability in integrated ship control

    Nielsen, Jens Frederik Dalsgaard; Izadi-Zamanabadi, Roozbeh; Schiøler, Henrik


    Various strategies for achieving fault tolerance in large scale control systems are discussed. The positive and negative impacts of distribution through network communication are presented. The ATOMOS framework for standardized reliable marine automation is presented along with the corresponding...

  15. Parallel Processing for Large-scale Fault Tree in Wireless Sensor Networks

    Xinyan Wang


    Full Text Available Wireless sensor networks (WSN covers many kinds of technologies, such as technology of sensor, embedded system, wireless communication, etc. WSN is different from the traditional networks in size, communication distance and energy-constrained so as to develop new topology, protocol, quality of service (QoS, and so on. In order to solve the problem of self-organizing in the topology, this paper proposes a novel strategy which is based on communication delay between sensors. Firstly, the gateway selects some boundary nodes to connect. Secondly, the boundary nodes choose inner nodes. The rest may be deduced by analogy. Finally, a net-tree topology with multi-path routing is developed. The analyses of the topology show that net-tree has strong ability in self-organizing and extensible. However, the scale of system is usually very large and complexity so that it is hard to detect the failure nodes when the nodes fail. To solve the greater challenge, the paper proposes to adopt fault tree analysis. Fault tree is a commonly used method to analyze the reliability of a network or system. Based on the fault tree analysis, a parallel computing algorithm is represented to these faults in the net-tree. Firstly, two models for parallel processing are came up and we focus on the parallel processing algorithm based on the cut sets. Then, the speedup ratio is studied. Compare with the serial algorithm, the results of the experiment shows that the efficiency has been greatly improved.

  16. Study of the reliability of the Auxiliary Feedwater System of a LWR nuclear power plant through the Fault Tree and Bayesian Network; Estudo de confiabilidade do Sistema Auxiliar de Agua de Alimentacao de uma central nuclear a agua leve por arvore de falhas e rede Bayesiana

    Lava, Deise Diana


    This paper aims to present a study of the reliability of the Auxiliary Feedwater System (AFWS) through the methods of Fault Tree and Bayesian Network. Therefore, the paper consists of a literature review of the history of nuclear energy and the methodologies used. The AFWS is responsible for providing water system to cool the secondary circuit of nuclear reactors of the PWR type when normal feeding water system failure. How this system operates only when the primary system fails, it is expected that the AFWS failure probability is very low. The AFWS failure probability is divided into two cases: the first is the probability of failure in the first eight hours of operation and the second is the probability of failure after eight hours of operation, considering that the system has not failed within the first eight hours. The calculation of the probability of failure of the second case was made through the use of Fault Tree and Bayesian Network, that it was constructed from the Fault Tree. The results of the failure probability obtained were very close, on the order of 10{sup -3}. (author)

  17. Accident Fault Trees for Defense Waste Processing Facility

    Sarrack, A.G.


    The purpose of this report is to document fault tree analyses which have been completed for the Defense Waste Processing Facility (DWPF) safety analysis. Logic models for equipment failures and human error combinations that could lead to flammable gas explosions in various process tanks, or failure of critical support systems were developed for internal initiating events and for earthquakes. These fault trees provide frequency estimates for support systems failures and accidents that could lead to radioactive and hazardous chemical releases both on-site and off-site. Top event frequency results from these fault trees will be used in further APET analyses to calculate accident risk associated with DWPF facility operations. This report lists and explains important underlying assumptions, provides references for failure data sources, and briefly describes the fault tree method used. Specific commitments from DWPF to provide new procedural/administrative controls or system design changes are listed in the ''Facility Commitments'' section. The purpose of the ''Assumptions'' section is to clarify the basis for fault tree modeling, and is not necessarily a list of items required to be protected by Technical Safety Requirements (TSRs).

  18. Fault Tree Generation and Augmentation Project

    National Aeronautics and Space Administration — Fault Management (FM) is one of the key components of system autonomy. In order to guarantee FM effectiveness and control the cost, tools are required to automate...

  19. Analysis of superheater's pipe wall overtemperature by fault tree diagnose

    盛德仁; 任浩仁; 陈坚红; 李蔚


    After research on a 2000t/h subcritical forced-circulation balanced v entilation were applied boiler and the structure and operation of its auxiliary system builds up this heat transfer model of a superheater's pipe wall and analy ze the effect of primary factors on the overtemperature of the pipe wall. Fault tree structure was used to uncover the multiplayer logic between the overtempera ture of the superheater's pipe wall and the faults.

  20. Parameter estimation and reliable fault detection of electric motors

    Dusan PROGOVAC; Le Yi WANG; George YIN


    Accurate model identification and fault detection are necessary for reliable motor control. Motor-characterizing parameters experience substantial changes due to aging, motor operating conditions, and faults. Consequently, motor parameters must be estimated accurately and reliably during operation. Based on enhanced model structures of electric motors that accommodate both normal and faulty modes, this paper introduces bias-corrected least-squares (LS) estimation algorithms that incorporate functions for correcting estimation bias, forgetting factors for capturing sudden faults, and recursive structures for efficient real-time implementation. Permanent magnet motors are used as a benchmark type for concrete algorithm development and evaluation. Algorithms are presented, their properties are established, and their accuracy and robustness are evaluated by simulation case studies under both normal operations and inter-turn winding faults. Implementation issues from different motor control schemes are also discussed.

  1. Fault Diagnosis of Machine Based on Fuzzy Reliability Theory


    According to life analysis in reliability theory, certain diagnosis rules can be used to diagnose machines' faults. On this basis, considering the indefiniteness in machine working states, the accurate diagnosis rule was extended to fuzzy diagnosis rule by using basic concepts and methods of fuzzy mathematics. The formulas of fault probability under different conditions were deduced. In the end, an example is given and the results of two methods were compared.

  2. Fault Diagnosis and Reliability Analysis Using Fuzzy Logic Method

    Miao Zhinong; Xu Yang; Zhao Xiangyu


    A new fuzzy logic fault diagnosis method is proposed. In this method, fuzzy equations are employed to estimate the component state of a system based on the measured system performance and the relationship between component state and system performance which is called as "performance-parameter" knowledge base and constructed by expert. Compared with the traditional fault diagnosis method, this fuzzy logic method can use humans intuitive knowledge and dose not need a precise mapping between system performance and component state. Simulation proves its effectiveness in fault diagnosis. Then, the reliability analysis is performed based on the fuzzy logic method.

  3. Design of Reliable Adaptive Filter with Fault Tolerance Using DSP

    Ryoo, D. W.; Lee, J. W. [Electronics and Telecommunications Research Institute, Taejon (Korea); Seo, B. H. [Kyungbok National University, Taegu (Korea)


    LSM algorithm has been used for plant identifier and noise cancellation. This algorithm has been researched for performance enhancement of filtering. The design and development of a reliable system has been becoming a key issue in industry field because the reliability of a system is considered as an important factor to perform the system's function successfully. And the computing with reliability and fault tolerance is a important factor in the case of aviation, system communication, and nuclear plant. This paper presents design of reliable adaptive filter with fault tolerance. Generally, redundancy is used for reliability. In this case it needs computing or circuit for voting mechanism or computing for fault detection or switching part. But this presented Filter is not in need of computing for voting mechanism, or fault detection. Therefore it has simple computing , and practicality for application. And in this paper, reliability of adaptive filter is analyzed. The effectiveness of the proposed adaptive filter is demonstrated to the case studies of plant identifier and noise cancellation by using DSP. (author). 9 refs., 18 figs.

  4. Modeling Sensor Reliability in Fault Diagnosis Based on Evidence Theory.

    Yuan, Kaijuan; Xiao, Fuyuan; Fei, Liguo; Kang, Bingyi; Deng, Yong


    Sensor data fusion plays an important role in fault diagnosis. Dempster-Shafer (D-R) evidence theory is widely used in fault diagnosis, since it is efficient to combine evidence from different sensors. However, under the situation where the evidence highly conflicts, it may obtain a counterintuitive result. To address the issue, a new method is proposed in this paper. Not only the statistic sensor reliability, but also the dynamic sensor reliability are taken into consideration. The evidence distance function and the belief entropy are combined to obtain the dynamic reliability of each sensor report. A weighted averaging method is adopted to modify the conflict evidence by assigning different weights to evidence according to sensor reliability. The proposed method has better performance in conflict management and fault diagnosis due to the fact that the information volume of each sensor report is taken into consideration. An application in fault diagnosis based on sensor fusion is illustrated to show the efficiency of the proposed method. The results show that the proposed method improves the accuracy of fault diagnosis from 81.19% to 89.48% compared to the existing methods.

  5. An Integrated Approach of Model checking and Temporal Fault Tree for System Safety Analysis

    Koh, Kwang Yong; Seong, Poong Hyun [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)


    Digitalization of instruments and control systems in nuclear power plants offers the potential to improve plant safety and reliability through features such as increased hardware reliability and stability, and improved failure detection capability. It however makes the systems and their safety analysis more complex. Originally, safety analysis was applied to hardware system components and formal methods mainly to software. For software-controlled or digitalized systems, it is necessary to integrate both. Fault tree analysis (FTA) which has been one of the most widely used safety analysis technique in nuclear industry suffers from several drawbacks as described in. In this work, to resolve the problems, FTA and model checking are integrated to provide formal, automated and qualitative assistance to informal and/or quantitative safety analysis. Our approach proposes to build a formal model of the system together with fault trees. We introduce several temporal gates based on timed computational tree logic (TCTL) to capture absolute time behaviors of the system and to give concrete semantics to fault tree gates to reduce errors during the analysis, and use model checking technique to automate the reasoning process of FTA.

  6. Spanning Trees and bootstrap reliability estimation in correlation based networks

    Tumminello, M; Lillo, F; Micciché, S; Mantegna, R N


    We introduce a new technique to associate a spanning tree to the average linkage cluster analysis. We term this tree as the Average Linkage Minimum Spanning Tree. We also introduce a technique to associate a value of reliability to links of correlation based graphs by using bootstrap replicas of data. Both techniques are applied to the portfolio of the 300 most capitalized stocks traded at New York Stock Exchange during the time period 2001-2003. We show that the Average Linkage Minimum Spanning Tree recognizes economic sectors and sub-sectors as communities in the network slightly better than the Minimum Spanning Tree does. We also show that the average reliability of links in the Minimum Spanning Tree is slightly greater than the average reliability of links in the Average Linkage Minimum Spanning Tree.

  7. Fault-Tolerant Tree-Based Multicasting in Mesh Multicomputers

    WU Jie; CHEN Xiao


    We propose a fault-tolerant tree-based multicast algorithm for 2-dimensional (2-D) meshes based on the concept of the extended safety level which is a vector associated with each node to capture fault information in the neighborhood. In this approach each destination is reached through a minimum number of hops. In order to minimize the total number of traffic steps, three heuristic strategies are proposed. This approach can be easily implemented by pipelined circuit switching (PCS). A simulation study is conducted to measure the total number of traffic steps under different strategies. Our approach is the first attempt to address the faulttolerant tree-based multicast problem in 2-D meshes based on limited global information with a simple model and succinct information.

  8. A Study on Landslide Risk Management by Applying Fault Tree Logics

    Kazmi Danish


    Full Text Available Slope stability is one of the focal areas of curiosity to geotechnical designers and also appears logical for the application of probabilistic approaches since the analysis lead to a “probability of failure”. Assessment of the existing slopes in relation with risks seems to be more meaningful when concerning with landslides. Probabilistic slope stability analysis (PSSA is the best option in covering the landslides events. The intent here is to bid a probabilistic framework for quantified risk analysis with human uncertainties. In this regard, Fault Tree Analysis is utilized and for prediction of risk levels, consequences of the failures of the reference landslides have been taken. It is concluded that logics of fault trees is best fit, to clinch additional categories of uncertainty; like human, organizational, and knowledge related. In actual, the approach has been used in bringing together engineering and management performances and personnel, to produce reliability in slope engineering practices.


    Cai Jiakun; Chen Jinshui


    On the base of study of the correlation of fault tree's main data-minimum cut sets, minimum path sets, non-intersect minimum cut sets and non-intersect minimum path sets, transformation method among main data are found, i.e. the transformation can be realized by the operation of cut sets matrixes. This method provides a new way to reduce "NP" difficulty and simplify FTA.

  10. New algorithm to detect modules in a fault tree for a PSA

    Jung, Woo Sik [Sejong University, Seoul (Korea, Republic of)


    A module or independent subtree is a part of a fault tree whose child gates or basic events are not repeated in the remaining part of the fault tree. Modules are necessarily employed in order to reduce the computational costs of fault tree quantification. This paper presents a new linear time algorithm to detect modules of large fault trees. The size of cut sets can be substantially reduced by replacing independent subtrees in a fault tree with super-components. Chatterjee and Birnbaum developed properties of modules, and demonstrated their use in the fault tree analysis. Locks expanded the concept of modules to non-coherent fault trees. Independent subtrees were manually identified while coding a fault tree for computer analysis. However, nowadays, the independent subtrees are automatically identified by the fault tree solver. A Dutuit and Rauzy (DR) algorithm to detect modules of a fault tree for coherent or non-coherent fault tree was proposed in 1996. It has been well known that this algorithm quickly detects modules since it is a linear time algorithm. The new algorithm minimizes computational memory and quickly detects modules. Furthermore, it can be easily implemented into industry fault tree solvers that are based on traditional Boolean algebra, binary decision diagrams (BDDs), or Zero-suppressed BDDs. The new algorithm employs only two scalar variables in Eqs. to that are volatile information. After finishing the traversal and module detection of each node, the volatile information is destroyed. Thus, the new algorithm does not employ any other additional computational memory and operations. It is recommended that this method be implemented into fault tree solvers for efficient probabilistic safety assessment (PSA) of nuclear power plants.

  11. A testing-coverage software reliability model considering fault removal efficiency and error generation.

    Li, Qiuying; Pham, Hoang


    In this paper, we propose a software reliability model that considers not only error generation but also fault removal efficiency combined with testing coverage information based on a nonhomogeneous Poisson process (NHPP). During the past four decades, many software reliability growth models (SRGMs) based on NHPP have been proposed to estimate the software reliability measures, most of which have the same following agreements: 1) it is a common phenomenon that during the testing phase, the fault detection rate always changes; 2) as a result of imperfect debugging, fault removal has been related to a fault re-introduction rate. But there are few SRGMs in the literature that differentiate between fault detection and fault removal, i.e. they seldom consider the imperfect fault removal efficiency. But in practical software developing process, fault removal efficiency cannot always be perfect, i.e. the failures detected might not be removed completely and the original faults might still exist and new faults might be introduced meanwhile, which is referred to as imperfect debugging phenomenon. In this study, a model aiming to incorporate fault introduction rate, fault removal efficiency and testing coverage into software reliability evaluation is developed, using testing coverage to express the fault detection rate and using fault removal efficiency to consider the fault repair. We compare the performance of the proposed model with several existing NHPP SRGMs using three sets of real failure data based on five criteria. The results exhibit that the model can give a better fitting and predictive performance.

  12. TU-AB-BRD-03: Fault Tree Analysis

    Dunscombe, P. [University of Calgary (Canada)


    Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before a failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to

  13. Trees as indicators of past movements on the San Andreas Fault

    Wallace, R.E.; LaMarche, Valmore C.


    Trees are sources of information about fault movements that have occurred before the earliest historical reports. This kind of evidence can be used to improve estimates of when earthquakes will recur on faults known to be seismically active and to identify active faults that have no record of movement during recent history.

  14. Diagnosis of Constant Faults in Read-Once Contact Networks over Finite Bases using Decision Trees

    Busbait, Monther I.


    We study the depth of decision trees for diagnosis of constant faults in read-once contact networks over finite bases. This includes diagnosis of 0-1 faults, 0 faults and 1 faults. For any finite basis, we prove a linear upper bound on the minimum depth of decision tree for diagnosis of constant faults depending on the number of edges in a contact network over that basis. Also, we obtain asymptotic bounds on the depth of decision trees for diagnosis of each type of constant faults depending on the number of edges in contact networks in the worst case per basis. We study the set of indecomposable contact networks with up to 10 edges and obtain sharp coefficients for the linear upper bound for diagnosis of constant faults in contact networks over bases of these indecomposable contact networks. We use a set of algorithms, including one that we create, to obtain the sharp coefficients.

  15. Enterprise architecture availability analysis using fault trees and stakeholder interviews

    Närman, Per; Franke, Ulrik; König, Johan; Buschle, Markus; Ekstedt, Mathias


    The availability of enterprise information systems is a key concern for many organisations. This article describes a method for availability analysis based on Fault Tree Analysis and constructs from the ArchiMate enterprise architecture (EA) language. To test the quality of the method, several case-studies within the banking and electrical utility industries were performed. Input data were collected through stakeholder interviews. The results from the case studies were compared with availability of log data to determine the accuracy of the method's predictions. In the five cases where accurate log data were available, the yearly downtime estimates were within eight hours from the actual downtimes. The cost of performing the analysis was low; no case study required more than 20 man-hours of work, making the method ideal for practitioners with an interest in obtaining rapid availability estimates of their enterprise information systems.

  16. Fault Tree Based Diagnosis with Optimal Test Sequencing for Field Service Engineers

    Iverson, David L.; George, Laurence L.; Patterson-Hine, F. A.; Lum, Henry, Jr. (Technical Monitor)


    When field service engineers go to customer sites to service equipment, they want to diagnose and repair failures quickly and cost effectively. Symptoms exhibited by failed equipment frequently suggest several possible causes which require different approaches to diagnosis. This can lead the engineer to follow several fruitless paths in the diagnostic process before they find the actual failure. To assist in this situation, we have developed the Fault Tree Diagnosis and Optimal Test Sequence (FTDOTS) software system that performs automated diagnosis and ranks diagnostic hypotheses based on failure probability and the time or cost required to isolate and repair each failure. FTDOTS first finds a set of possible failures that explain exhibited symptoms by using a fault tree reliability model as a diagnostic knowledge to rank the hypothesized failures based on how likely they are and how long it would take or how much it would cost to isolate and repair them. This ordering suggests an optimal sequence for the field service engineer to investigate the hypothesized failures in order to minimize the time or cost required to accomplish the repair task. Previously, field service personnel would arrive at the customer site and choose which components to investigate based on past experience and service manuals. Using FTDOTS running on a portable computer, they can now enter a set of symptoms and get a list of possible failures ordered in an optimal test sequence to help them in their decisions. If facilities are available, the field engineer can connect the portable computer to the malfunctioning device for automated data gathering. FTDOTS is currently being applied to field service of medical test equipment. The techniques are flexible enough to use for many different types of devices. If a fault tree model of the equipment and information about component failure probabilities and isolation times or costs are available, a diagnostic knowledge base for that device can be

  17. PV Systems Reliability Final Technical Report: Ground Fault Detection

    Lavrova, Olga [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Flicker, Jack David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Johnson, Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    We have examined ground faults in PhotoVoltaic (PV) arrays and the efficacy of fuse, current detection (RCD), current sense monitoring/relays (CSM), isolation/insulation (Riso) monitoring, and Ground Fault Detection and Isolation (GFID) using simulations based on a Simulation Program with Integrated Circuit Emphasis SPICE ground fault circuit model, experimental ground faults installed on real arrays, and theoretical equations.

  18. Application of Fault Tree Analysis and Fuzzy Neural Networks to Fault Diagnosis in the Internet of Things (IoT for Aquaculture

    Yingyi Chen


    Full Text Available In the Internet of Things (IoT equipment used for aquaculture is often deployed in outdoor ponds located in remote areas. Faults occur frequently in these tough environments and the staff generally lack professional knowledge and pay a low degree of attention in these areas. Once faults happen, expert personnel must carry out maintenance outdoors. Therefore, this study presents an intelligent method for fault diagnosis based on fault tree analysis and a fuzzy neural network. In the proposed method, first, the fault tree presents a logic structure of fault symptoms and faults. Second, rules extracted from the fault trees avoid duplicate and redundancy. Third, the fuzzy neural network is applied to train the relationship mapping between fault symptoms and faults. In the aquaculture IoT, one fault can cause various fault symptoms, and one symptom can be caused by a variety of faults. Four fault relationships are obtained. Results show that one symptom-to-one fault, two symptoms-to-two faults, and two symptoms-to-one fault relationships can be rapidly diagnosed with high precision, while one symptom-to-two faults patterns perform not so well, but are still worth researching. This model implements diagnosis for most kinds of faults in the aquaculture IoT.

  19. Application of Fault Tree Analysis and Fuzzy Neural Networks to Fault Diagnosis in the Internet of Things (IoT) for Aquaculture.

    Chen, Yingyi; Zhen, Zhumi; Yu, Huihui; Xu, Jing


    In the Internet of Things (IoT) equipment used for aquaculture is often deployed in outdoor ponds located in remote areas. Faults occur frequently in these tough environments and the staff generally lack professional knowledge and pay a low degree of attention in these areas. Once faults happen, expert personnel must carry out maintenance outdoors. Therefore, this study presents an intelligent method for fault diagnosis based on fault tree analysis and a fuzzy neural network. In the proposed method, first, the fault tree presents a logic structure of fault symptoms and faults. Second, rules extracted from the fault trees avoid duplicate and redundancy. Third, the fuzzy neural network is applied to train the relationship mapping between fault symptoms and faults. In the aquaculture IoT, one fault can cause various fault symptoms, and one symptom can be caused by a variety of faults. Four fault relationships are obtained. Results show that one symptom-to-one fault, two symptoms-to-two faults, and two symptoms-to-one fault relationships can be rapidly diagnosed with high precision, while one symptom-to-two faults patterns perform not so well, but are still worth researching. This model implements diagnosis for most kinds of faults in the aquaculture IoT.

  20. Mines Systems Safety Improvement Using an Integrated Event Tree and Fault Tree Analysis

    Kumar, Ranjan; Ghosh, Achyuta Krishna


    Mines systems such as ventilation system, strata support system, flame proof safety equipment, are exposed to dynamic operational conditions such as stress, humidity, dust, temperature, etc., and safety improvement of such systems can be done preferably during planning and design stage. However, the existing safety analysis methods do not handle the accident initiation and progression of mine systems explicitly. To bridge this gap, this paper presents an integrated Event Tree (ET) and Fault Tree (FT) approach for safety analysis and improvement of mine systems design. This approach includes ET and FT modeling coupled with redundancy allocation technique. In this method, a concept of top hazard probability is introduced for identifying system failure probability and redundancy is allocated to the system either at component or system level. A case study on mine methane explosion safety with two initiating events is performed. The results demonstrate that the presented method can reveal the accident scenarios and improve the safety of complex mine systems simultaneously.

  1. Improvement of Matrix Converter Drive Reliability by Online Fault Detection and a Fault-Tolerant Switching Strategy

    Nguyen-Duy, Khiem; Liu, Tian-Hua; Chen, Der-Fa


    The matrix converter system is becoming a very promising candidate to replace the conventional two-stage ac/dc/ac converter, but system reliability remains an open issue. The most common reliability problem is that a bidirectional switch has an open-switch fault during operation. In this paper, a...

  2. A fault tree model to assess probability of contaminant discharge from shipwrecks.

    Landquist, H; Rosén, L; Lindhe, A; Norberg, T; Hassellöv, I-M; Lindgren, J F; Dahllöf, I


    Shipwrecks on the sea floor around the world may contain hazardous substances that can cause harm to the marine environment. Today there are no comprehensive methods for environmental risk assessment of shipwrecks, and thus there is poor support for decision-making on prioritization of mitigation measures. The purpose of this study was to develop a tool for quantitative risk estimation of potentially polluting shipwrecks, and in particular an estimation of the annual probability of hazardous substance discharge. The assessment of the probability of discharge is performed using fault tree analysis, facilitating quantification of the probability with respect to a set of identified hazardous events. This approach enables a structured assessment providing transparent uncertainty and sensitivity analyses. The model facilitates quantification of risk, quantification of the uncertainties in the risk calculation and identification of parameters to be investigated further in order to obtain a more reliable risk calculation.

  3. Compositional Analysis of Dynamic Fault Trees using Input/Output Interactive Markov Chains

    Crouzen, P.


    Dynamic fault trees (DFT) are widely used to analyze the fault-tolerance of computer systems. The syntax and semantics of DFT, however, lack formal definitions which has lead to vagueness in the interpretation of DFT. Existing analysis techniques also suffer from the statespace explosion problem. Th

  4. Review: Evaluation of Foot-and-Mouth Disease Control Using Fault Tree Analysis.

    Isoda, N; Kadohira, M; Sekiguchi, S; Schuppers, M; Stärk, K D C


    An outbreak of foot-and-mouth disease (FMD) causes huge economic losses and animal welfare problems. Although much can be learnt from past FMD outbreaks, several countries are not satisfied with their degree of contingency planning and aiming at more assurance that their control measures will be effective. The purpose of the present article was to develop a generic fault tree framework for the control of an FMD outbreak as a basis for systematic improvement and refinement of control activities and general preparedness. Fault trees are typically used in engineering to document pathways that can lead to an undesired event, that is, ineffective FMD control. The fault tree method allows risk managers to identify immature parts of the control system and to analyse the events or steps that will most probably delay rapid and effective disease control during a real outbreak. The present developed fault tree is generic and can be tailored to fit the specific needs of countries. For instance, the specific fault tree for the 2001 FMD outbreak in the UK was refined based on control weaknesses discussed in peer-reviewed articles. Furthermore, the specific fault tree based on the 2001 outbreak was applied to the subsequent FMD outbreak in 2007 to assess the refinement of control measures following the earlier, major outbreak. The FMD fault tree can assist risk managers to develop more refined and adequate control activities against FMD outbreaks and to find optimum strategies for rapid control. Further application using the current tree will be one of the basic measures for FMD control worldwide.

  5. Reliable systems - Fault tree analysis via Markov reward automata

    Guck, Dennis


    Today’s society is characterised by the ubiquitousness of hardware and software systems on which we rely on day in, day out. They reach from transportation systems like cars, trains and planes over medical devices at a hospital to nuclear power plants. Moreover, we can observe a trend of automation

  6. Reliable systems: fault tree analysis via Markov reward automata

    Guck, Dennis


    Today's society is characterised by the ubiquitousness of hardware and software systems on which we rely on day in, day out. They reach from transportation systems like cars, trains and planes over medical devices at a hospital to nuclear power plants. Moreover, we can observe a trend of automation

  7. Reliable systems: fault tree analysis via Markov reward automata

    Guck, Dennis


    Today's society is characterised by the ubiquitousness of hardware and software systems on which we rely on day in, day out. They reach from transportation systems like cars, trains and planes over medical devices at a hospital to nuclear power plants. Moreover, we can observe a trend of automation

  8. Integrating Insults: Using Fault Tree Analysis to Guide Schizophrenia Research across Levels of Analysis

    Angus W MacDonald


    Full Text Available The grand challenges of schizophrenia research are linking the causes of the disorder to its symptoms and finding ways to overcome those symptoms. We argue that the field will be unable to address these challenges within psychiatry’s standard neo-Kraepelinian (DSM perspective. At the same time the current corrective, based in molecular genetics and cognitive neuroscience, is also likely to flounder due to its neglect for psychiatry’s syndromal structure. We suggest adopting a new approach long used in reliability engineering, which also serves as a synthesis of these approaches. This approach, known as fault tree analysis, can be combined with extant neuroscientific data collection and computational modeling efforts to uncover the causal structures underlying the cognitive and affective failures in people with schizophrenia as well as other complex psychiatric phenomena. By making explicit how causes combine from basic faults to downstream failures, this approach makes affordances for 1 causes that are neither necessary nor sufficient in and of themselves, 2 within-diagnosis heterogeneity, and 3 between diagnosis co-morbidity.

  9. UML Statechart Fault Tree Generation By Model Checking

    Herbert, Luke Thomas; Herbert-Hansen, Zaza Nadja Lee

    Creating fault tolerant and efficient process work-flows poses a significant challenge. Individual faults, defined as an abnormal conditions or defects in a component, equipment, or sub-process, must be handled so that the system may continue to operate, and are typically addressed by implementin...

  10. Fault-tolerant search algorithms reliable computation with unreliable information

    Cicalese, Ferdinando


    Why a book on fault-tolerant search algorithms? Searching is one of the fundamental problems in computer science. Time and again algorithmic and combinatorial issues originally studied in the context of search find application in the most diverse areas of computer science and discrete mathematics. On the other hand, fault-tolerance is a necessary ingredient of computing. Due to their inherent complexity, information systems are naturally prone to errors, which may appear at any level - as imprecisions in the data, bugs in the software, or transient or permanent hardware failures. This book pr

  11. A New Fault-tolerant Switched Reluctance Motor with reliable fault detection capability

    Lu, Kaiyuan


    while no extra search coil is actually needed. The motor itself is able to continue to work under any faulted conditions, providing fault-tolerant features. The working principle, performance evaluation of this motor will be demonstrated in this paper and Finite Element Analysis results are provided....

  12. ACORN: a computer program for plotting fault trees. [In FORTRAN for CDC Cyber 74

    Carter, J.L.


    A description and user instructions are presented for ACORN, a FORTRAN computer program for drawing fault trees. ACORN analyzes the input logical structure of a fault tree and provides data for CalComp plot of the tree. AND, OR, and INHIBIT gates are permitted, and basic events are drawn as diamonds, circles, or houses. Each component (gate or basic event) can have a descriptive label within a rectangle attached to the top of its respective symbol. Tree logic is input as a set of FORTRAN statements, each defining a gate in terms of logical operations of the components input to it. ACORN develops the logical structure of the tree from the input statements. The tree's physical structure is developed by assigning relative spatial coordinates to the logical relationships between a gate and its inputs. ACORN provides input data checking, a printer plot of the fault tree, and plotting data for a CalComp model 763 plotter. The program is operational on a CONTROL DATA CYBER 74 computer. 2 figures, 1 table.

  13. Transforming incomplete fault tree to Ishikawa diagram as an alternative method for technology transfer

    Batzias, Dimitris F.


    Fault Tree Analysis (FTA) can be used for technology transfer when the relevant problem (called 'top even' in FTA) is solved in a technology centre and the results are diffused to interested parties (usually Small Medium Enterprises - SMEs) that have not the proper equipment and the required know-how to solve the problem by their own. Nevertheless, there is a significant drawback in this procedure: the information usually provided by the SMEs to the technology centre, about production conditions and corresponding quality characteristics of the product, and (sometimes) the relevant expertise in the Knowledge Base of this centre may be inadequate to form a complete fault tree. Since such cases are quite frequent in practice, we have developed a methodology for transforming incomplete fault tree to Ishikawa diagram, which is more flexible and less strict in establishing causal chains, because it uses a surface phenomenological level with a limited number of categories of faults. On the other hand, such an Ishikawa diagram can be extended to simulate a fault tree as relevant knowledge increases. An implementation of this transformation, referring to anodization of aluminium, is presented.

  14. The Reliability and Stability of an Inferred Phylogenetic Tree from Empirical Data.

    Katsura, Yukako; Stanley, Craig E; Kumar, Sudhir; Nei, Masatoshi


    The reliability of a phylogenetic tree obtained from empirical data is usually measured by the bootstrap probability (Pb) of interior branches of the tree. If the bootstrap probability is high for most branches, the tree is considered to be reliable. If some interior branches show relatively low bootstrap probabilities, we are not sure that the inferred tree is really reliable. Here, we propose another quantity measuring the reliability of the tree called the stability of a subtree. This quantity refers to the probability of obtaining a subtree (Ps) of an inferred tree obtained. We then show that if the tree is to be reliable, both Pb and Ps must be high. We also show that Ps is given by a bootstrap probability of the subtree with the closest outgroup sequence, and computer program RESTA for computing the Pb and Ps values will be presented.

  15. Designing Fault-Injection Experiments for the Reliability of Embedded Systems

    White, Allan L.


    This paper considers the long-standing problem of conducting fault-injections experiments to establish the ultra-reliability of embedded systems. There have been extensive efforts in fault injection, and this paper offers a partial summary of the efforts, but these previous efforts have focused on realism and efficiency. Fault injections have been used to examine diagnostics and to test algorithms, but the literature does not contain any framework that says how to conduct fault-injection experiments to establish ultra-reliability. A solution to this problem integrates field-data, arguments-from-design, and fault-injection into a seamless whole. The solution in this paper is to derive a model reduction theorem for a class of semi-Markov models suitable for describing ultra-reliable embedded systems. The derivation shows that a tight upper bound on the probability of system failure can be obtained using only the means of system-recovery times, thus reducing the experimental effort to estimating a reasonable number of easily-observed parameters. The paper includes an example of a system subject to both permanent and transient faults. There is a discussion of integrating fault-injection with field-data and arguments-from-design.

  16. Direct evaluation of fault trees using object-oriented programming techniques

    Patterson-Hine, F. A.; Koen, B. V.


    Object-oriented programming techniques are used in an algorithm for the direct evaluation of fault trees. The algorithm combines a simple bottom-up procedure for trees without repeated events with a top-down recursive procedure for trees with repeated events. The object-oriented approach results in a dynamic modularization of the tree at each step in the reduction process. The algorithm reduces the number of recursive calls required to solve trees with repeated events and calculates intermediate results as well as the solution of the top event. The intermediate results can be reused if part of the tree is modified. An example is presented in which the results of the algorithm implemented with conventional techniques are compared to those of the object-oriented approach.

  17. Graphical fault tree analysis for fatal falls in the construction industry.

    Chi, Chia-Fen; Lin, Syuan-Zih; Dewi, Ratna Sari


    The current study applied a fault tree analysis to represent the causal relationships among events and causes that contributed to fatal falls in the construction industry. Four hundred and eleven work-related fatalities in the Taiwanese construction industry were analyzed in terms of age, gender, experience, falling site, falling height, company size, and the causes for each fatality. Given that most fatal accidents involve multiple events, the current study coded up to a maximum of three causes for each fall fatality. After the Boolean algebra and minimal cut set analyses, accident causes associated with each falling site can be presented as a fault tree to provide an overview of the basic causes, which could trigger fall fatalities in the construction industry. Graphical icons were designed for each falling site along with the associated accident causes to illustrate the fault tree in a graphical manner. A graphical fault tree can improve inter-disciplinary discussion of risk management and the communication of accident causation to first line supervisors. Copyright © 2014 Elsevier Ltd. All rights reserved.



    A new fault tree analysis (FTA) computation method is put forth by using modularization technique in FTA with cut sets matrix, and can reduce NP (Nondeterministic polynomial) difficulty effectively. This software can run in IBM-PC and DOS 3.0 and up. The method provides theoretical basis and computation tool for application of FTA technique in the common engineering system

  19. Fault Injection Software Tools and Robust Design Principles for Reliability and Safety in Measurement Science Education

    Faller, Lisa-Marie; Zangl, Hubert; Leitzke, Juliana P.


    In the design of measurement systems we face the fact that parameters are subject to (measurement-) uncertainties. Additionally, components may behave entirely different from what is specified, which is then considered a fault. Consequently, both uncertainty as well as probability of failure should be considered in education on robust design and reliability. In this paper we present a teaching concept based on hardware fault injection using a simple level sensor system as an example. Learning objectives are faults, errors, failures, false alarms versus misses as well as advantages and disadvantages of redundancy.

  20. Possibilistic entropy-based measure of importance in fault tree analysis

    He Liping; Qu Fuzheng


    With respect to the subjective factors and nonlinear characteristics inherent in the important identifi-cation of fault tree analysis (FTA), a new important measure of FTA is proposed based on pcesibilistic information entropy. After investigating possibilistic information semantics, measure-theoretic terms, and entropy-like models, a two-dimensional framework has been constructed by combining both the set theory and the measure theory. By adopting the possibilistic assumption in place of the probabilistic one, an axiomatic index of importance is defined in the possibility space and then the modelling principles are presented. An example of the fault tree is thus provided, along with the concordance analysis and other discussions. The more conservative numerical results of importance rankings, which involve the more choices can be viewed as "soft" fault identification under a certain expected value. In the end, extension to evidence space and further research perspectives are discussed.

  1. Frontiers of reliability

    Basu, Asit P; Basu, Sujit K


    This volume presents recent results in reliability theory by leading experts in the world. It will prove valuable for researchers, and users of reliability theory. It consists of refereed invited papers on a broad spectrum of topics in reliability. The subjects covered include Bayesian reliability, Bayesian reliability modeling, confounding in a series system, DF tests, Edgeworth approximation to reliability, estimation under random censoring, fault tree reduction for reliability, inference about changes in hazard rates, information theory and reliability, mixture experiment, mixture of Weibul

  2. Integrated Methodology for Software Reliability Analysis

    Marian Pompiliu CRISTESCU


    Full Text Available The most used techniques to ensure safety and reliability of the systems are applied together as a whole, and in most cases, the software components are usually overlooked or to little analyzed. The present paper describes the applicability of fault trees analysis software system, analysis defined as Software Fault Tree Analysis (SFTA, fault trees are evaluated using binary decision diagrams, all of these being integrated and used with help from Java library reliability.

  3. Reliability of Coulomb stress changes inferred from correlated uncertainties of finite-fault source models

    Woessner, J.


    Static stress transfer is one physical mechanism to explain triggered seismicity. Coseismic stress-change calculations strongly depend on the parameterization of the causative finite-fault source model. These models are uncertain due to uncertainties in input data, model assumptions, and modeling procedures. However, fault model uncertainties have usually been ignored in stress-triggering studies and have not been propagated to assess the reliability of Coulomb failure stress change (ΔCFS) calculations. We show how these uncertainties can be used to provide confidence intervals for co-seismic ΔCFS-values. We demonstrate this for the MW = 5.9 June 2000 Kleifarvatn earthquake in southwest Iceland and systematically map these uncertainties. A set of 2500 candidate source models from the full posterior fault-parameter distribution was used to compute 2500 ΔCFS maps. We assess the reliability of the ΔCFS-values from the coefficient of variation (CV) and deem ΔCFS-values to be reliable where they are at least twice as large as the standard deviation (CV ≤ 0.5). Unreliable ΔCFS-values are found near the causative fault and between lobes of positive and negative stress change, where a small change in fault strike causes ΔCFS-values to change sign. The most reliable ΔCFS-values are found away from the source fault in the middle of positive and negative ΔCFS-lobes, a likely general pattern. Using the reliability criterion, our results support the static stress-triggering hypothesis. Nevertheless, our analysis also suggests that results from previous stress-triggering studies not considering source model uncertainties may have lead to a biased interpretation of the importance of static stress-triggering.

  4. An Integrated Fault Tolerant Robotic Controller System for High Reliability and Safety

    Marzwell, Neville I.; Tso, Kam S.; Hecht, Myron


    This paper describes the concepts and features of a fault-tolerant intelligent robotic control system being developed for applications that require high dependability (reliability, availability, and safety). The system consists of two major elements: a fault-tolerant controller and an operator workstation. The fault-tolerant controller uses a strategy which allows for detection and recovery of hardware, operating system, and application software failures.The fault-tolerant controller can be used by itself in a wide variety of applications in industry, process control, and communications. The controller in combination with the operator workstation can be applied to robotic applications such as spaceborne extravehicular activities, hazardous materials handling, inspection and maintenance of high value items (e.g., space vehicles, reactor internals, or aircraft), medicine, and other tasks where a robot system failure poses a significant risk to life or property.

  5. Realization of Fault Diagnosis for ATS Based on Fault Tree Analysis%ATS故障树法故障诊断功能的实现

    任献彬; 姜志森


    In absence of the transcendental experience of fault diagnosis,fault tree is an effective method which can be easily realized in engineering.With analyzing and inducing the association relationship between test items and SRUs,the expressing method of fault diagnosis information in fault tree database is obtained.The structure of fault tree,the data format of database,and fault diagnosis reasoning procedure are proposed,and the fault diagnosis system for ATS is designed.In this method,fault tree database can be designed easily,fault diagnosis procedure can be expressed definitely.This method has been applied in two types of ATS,both fault isolation rate and false alarm rate all meet the system needs.%当缺乏故障诊断先验知识时,故障树法是工程上易于实现的一种有效的故障诊断方法.通过分析、归纳测试项目与SRU的关联关系,得出了故障树模型中故障诊断知识的表达方式.以Access数据库为基础,提出了故障树的结构、数据组织形式及故障诊断的推理方法,并设计了适用于自动测试系统的故障诊断系统.该方法具有故障诊断推理过程表达明确、树模型易于建立等优点,已应用到两型机载电子设备的故障诊断中,故障隔离率和虚警率都达到了设计要求.

  6. Computer aided reliability, availability, and safety modeling for fault-tolerant computer systems with commentary on the HARP program

    Shooman, Martin L.


    Many of the most challenging reliability problems of our present decade involve complex distributed systems such as interconnected telephone switching computers, air traffic control centers, aircraft and space vehicles, and local area and wide area computer networks. In addition to the challenge of complexity, modern fault-tolerant computer systems require very high levels of reliability, e.g., avionic computers with MTTF goals of one billion hours. Most analysts find that it is too difficult to model such complex systems without computer aided design programs. In response to this need, NASA has developed a suite of computer aided reliability modeling programs beginning with CARE 3 and including a group of new programs such as: HARP, HARP-PC, Reliability Analysts Workbench (Combination of model solvers SURE, STEM, PAWS, and common front-end model ASSIST), and the Fault Tree Compiler. The HARP program is studied and how well the user can model systems using this program is investigated. One of the important objectives will be to study how user friendly this program is, e.g., how easy it is to model the system, provide the input information, and interpret the results. The experiences of the author and his graduate students who used HARP in two graduate courses are described. Some brief comparisons were made with the ARIES program which the students also used. Theoretical studies of the modeling techniques used in HARP are also included. Of course no answer can be any more accurate than the fidelity of the model, thus an Appendix is included which discusses modeling accuracy. A broad viewpoint is taken and all problems which occurred in the use of HARP are discussed. Such problems include: computer system problems, installation manual problems, user manual problems, program inconsistencies, program limitations, confusing notation, long run times, accuracy problems, etc.

  7. Fault Tree Analysis of Fire and Explosion Accidents for Dual Fuel (Diesel/Natural Gas) Ship Engine Rooms

    Yifeng Guan; Jie Zhao; Tengfei Shiand Peipei Zhu


    In recent years, China’s increased interest in environmental protection has led to a promotion of energy-efficient dual fuel (diesel/natural gas) ships in Chinese inland rivers. A natural gas as ship fuel may pose dangers of fire and explosion if a gas leak occurs. If explosions or fires occur in the engine rooms of a ship, heavy damage and losses will be incurred. In this paper, a fault tree model is presented that considers both fires and explosions in a dual fuel ship;in this model, dual fuel engine rooms are the top events. All the basic events along with the minimum cut sets are obtained through the analysis.The primary factors that affect accidents involving fires and explosions are determined by calculating the degree of structure importance of the basic events.According to these results, corresponding measures are proposed to ensure and improve the safety and reliability of Chinese inland dual fuel ships.

  8. Fault tree analysis of fire and explosion accidents for dual fuel (diesel/natural gas) ship engine rooms

    Guan, Yifeng; Zhao, Jie; Shi, Tengfei; Zhu, Peipei


    In recent years, China's increased interest in environmental protection has led to a promotion of energy-efficient dual fuel (diesel/natural gas) ships in Chinese inland rivers. A natural gas as ship fuel may pose dangers of fire and explosion if a gas leak occurs. If explosions or fires occur in the engine rooms of a ship, heavy damage and losses will be incurred. In this paper, a fault tree model is presented that considers both fires and explosions in a dual fuel ship; in this model, dual fuel engine rooms are the top events. All the basic events along with the minimum cut sets are obtained through the analysis. The primary factors that affect accidents involving fires and explosions are determined by calculating the degree of structure importance of the basic events. According to these results, corresponding measures are proposed to ensure and improve the safety and reliability of Chinese inland dual fuel ships.

  9. Fault Tree Model for Failure Path Prediction of Bolted Steel Tension Member in a Structural System

    Biswajit Som


    Full Text Available Fault tree is a graphical representation of various sequential combinations of events which leads to the failure of any system, such as a structural system. In this paper it is shown that a fault tree model is also applicable to a critical element of a complex structural system. This will help to identify the different failure mode of a particular structural element which might eventually triggered a progressive collapse of the whole structural system. Non-redundant tension member generally regarded as a Fracture Critical Member (FCM in a complex structural system, especially in bridge, failure of which may lead to immediate collapse of the structure. Limit state design is governed by the failure behavior of a structural element at its ultimate state. Globally, condition assessment of an existing structural system, particularly for bridges, Fracture Critical Inspection becomes very effective and mandatory in some countries. Fault tree model of tension member, presented in this paper can be conveniently used to identify the flaws in FCM if any, in an existing structural system and also as a check list for new design of tension member.

  10. Fuzzy fault tree analysis of nuclear-class butterfly valve%核级蝶阀的模糊故障树分析

    安宗文; 祝红林; 张鹏; 黄建龙; 邵兵


    为提高核级蝶阀的可靠性,引进模糊故障树的分析方法.建立核级蝶阀失效故障树,得到其最小割集,确定核级蝶阀在设计和运行阶段的薄弱环节,以采取提高可靠性的措施.提出可引用模糊故障树计算方法,对所建故障树进行定量计算,为核级蝶阀的合理维护提供参考依据.以密封圈损坏为例,得到密封圈损坏的概率为[0.005,0.024 9].%To improve the reliability of the nuclear-class butterfly valve, an analysis method of fuzzy fault tree was introduced. On the basis of the basic theory and procedure of fuzzy fault tree analysis, a failure fault tree of nuclear-class valve was established, the minimum cut set was obtained, and the weak links of nuclear-class valve during its design and operation period was determined, so that the measures could be taken to improve reliability. Besides, a calculation method based on the fuzzy fault tree was proposed for its quantitative evaluation, providing thus a reference for nuclear-class butterfly valve maintenance. A damaged sealing ring was taken to as an example obtain the probability being between 0. 005 and 0. 024 9.

  11. Effective confidence interval estimation of fault-detection process of software reliability growth models

    Fang, Chih-Chiang; Yeh, Chun-Wu


    The quantitative evaluation of software reliability growth model is frequently accompanied by its confidence interval of fault detection. It provides helpful information to software developers and testers when undertaking software development and software quality control. However, the explanation of the variance estimation of software fault detection is not transparent in previous studies, and it influences the deduction of confidence interval about the mean value function that the current study addresses. Software engineers in such a case cannot evaluate the potential hazard based on the stochasticity of mean value function, and this might reduce the practicability of the estimation. Hence, stochastic differential equations are utilised for confidence interval estimation of the software fault-detection process. The proposed model is estimated and validated using real data-sets to show its flexibility.

  12. Reliability modeling of digital RPS with consideration of undetected software faults

    Khalaquzzaman, M.; Lee, Seung Jun; Jung, Won Dea [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Man Cheol [Chung Ang Univ., Seoul (Korea, Republic of)


    This paper provides overview of different software reliability methodologies and proposes a technic for estimating the reliability of RPS with consideration of undetected software faults. Software reliability analysis of safety critical software has been challenging despite spending a huge effort for developing large number of software reliability models, and no consensus yet to attain on an appropriate modeling methodology. However, it is realized that the combined application of BBN based SDLC fault prediction method and random black-box testing of software would provide better ground for reliability estimation of safety critical software. Digitalizing the reactor protection system of nuclear power plant has been initiated several decades ago and now full digitalization has been adopted in the new generation of NPPs around the world because digital I and C systems have many better technical features like easier configurability and maintainability over analog I and C systems. Digital I and C systems are also drift-free and incorporation of new features is much easier. Rules and regulation for safe operation of NPPs are established and has been being practiced by the operators as well as regulators of NPPs to ensure safety. The failure mechanism of hardware and analog systems well understood and the risk analysis methods for these components and systems are well established. However, digitalization of I and C system in NPP introduces some crisis and uncertainty in reliability analysis methods of the digital systems/components because software failure mechanisms are still unclear.

  13. Reliable Fault Classification of Induction Motors Using Texture Feature Extraction and a Multiclass Support Vector Machine

    Jia Uddin


    Full Text Available This paper proposes a method for the reliable fault detection and classification of induction motors using two-dimensional (2D texture features and a multiclass support vector machine (MCSVM. The proposed model first converts time-domain vibration signals to 2D gray images, resulting in texture patterns (or repetitive patterns, and extracts these texture features by generating the dominant neighborhood structure (DNS map. The principal component analysis (PCA is then used for the purpose of dimensionality reduction of the high-dimensional feature vector including the extracted texture features due to the fact that the high-dimensional feature vector can degrade classification performance, and this paper configures an effective feature vector including discriminative fault features for diagnosis. Finally, the proposed approach utilizes the one-against-all (OAA multiclass support vector machines (MCSVMs to identify induction motor failures. In this study, the Gaussian radial basis function kernel cooperates with OAA MCSVMs to deal with nonlinear fault features. Experimental results demonstrate that the proposed approach outperforms three state-of-the-art fault diagnosis algorithms in terms of fault classification accuracy, yielding an average classification accuracy of 100% even in noisy environments.

  14. Fault and Defect Tolerant Computer Architectures: Reliable Computing with Unreliable Devices


    and polished using chemical- mechanical polishing ( CMP ) (Diagram 3). 5. Wet etching is done using hot H3PO4, then chemical dry etching is used to...modelled as a diode with a switchable threshold (i.e., turn-on) voltage. The switches are set or reset by electrochemical reduction or oxidation of the... characterizing the reliability of the overall system are examined. Key Definitions. Error is a manifestation of a fault in the system, in

  15. 基于条件规则与故障树法的燃气轮机故障诊断%Gas turbine engine fault diagnosis based on conditions of rule-based and fault tree

    尚文; 王维民; 齐鹏逸; 崔津; 曾咏奎


    Aiming at all kinds of the gas turbine fault diagnosis problems ,a comprehensive technology of the rule-based and fault tree method was investigated in the gas turbine fault diagnosis research. On the base of the established fault tree of gas turbine, the typical fault cases and maintenance experience were summarized, the based on condition the rules of logic reasoning model was established, the fault analysis principle of gas turbine based on signal processing was utilized, the certain conditions rules were increased in the middle of the fault tree events and bottom events, the physical and logical judge were judged to determine the fault tree on each branch diagnosis choice, thus every step of the fault diagnosis analysis were clear ,the accurate fault causes and failure parts were concluded in the end. For the gas turbine generating unit rotor vibration fault example of an offshore oil operation area, the rapid and accurate the root causes were analyzed by the based on rules conditiongs of fault tree method on the foundation of online monitoring ,The results indicate that the method is convenient in maintenance and technical staff to grasp, it can be widely used in gas turbine generating unit reliability maintenance field.%针对燃气轮机各类故障的诊断问题,将条件规则与故障树法相综合的诊断技术应用到燃气轮机的故障诊断研究中.在建立燃气轮机失效故障树的基础上,通过归纳总结典型的故障案例和维修经验,构建了基于条件规则的逻辑推理模型,利用基于信号处理技术的燃气轮机故障分析原理,在故障树的中间事件和底端事件上,增加了具体故障分析的条件规则,并进行了物理和逻辑判断,以确定故障树每个分支的诊断选择,从而明确了每一步的故障诊断分析,最终得出了精确的故障原因和故障部位.结合某海上石油作业区燃气轮机发电机组的转子振动故障实例,在进行燃气轮

  16. The research of mine rock burst hazard identification based on fault tree analysis

    LI Wen; JI Hong-guang; CHENG Jiu-long; CAI Si-jing


    In order to identify the rock burst hazard in coalmine and thus to give a credible forecast, firstly, analyzed such effect factors as natural geological factors and mining technological conditions based on the investigation of more than one hundred mine rock burst cases. Secondly, adopted the fault tree analysis (FTA) technology to the mine rock burst hazard identification for the first time and confirmed twelve kinds of basic events,that is, the large mining depth, the burst-orientation coal seams, the solid strata of roof and bottom, near the faults with bigger fall, the folds, the change of seam thickness, other regional tectonics transformation or stress strip, the drilling, blasting and extracting operation,the unscientific extracting methods, the illogical extracting sequence, the residual pillars and the too close distance between the working face and the residual areas or the stopping extracting lines. Moreover, worked out the fault tree of mine rock burst. At last, it made qualitative analysis and quantitative analysis and forecasted the rock burst hazard according to the characteristic of geologic structure and exploitation technology conditions in certain mine of Shandong Province, China, the rock burst accidents happened in the following exploitation validated that it is of feasibility and veracity adopting FTA to identify the mine rock burst hazard.

  17. Optimizing the Reliability and Performance of Service Composition Applications with Fault Tolerance in Wireless Sensor Networks.

    Wu, Zhao; Xiong, Naixue; Huang, Yannong; Xu, Degang; Hu, Chunyang


    The services composition technology provides flexible methods for building service composition applications (SCAs) in wireless sensor networks (WSNs). The high reliability and high performance of SCAs help services composition technology promote the practical application of WSNs. The optimization methods for reliability and performance used for traditional software systems are mostly based on the instantiations of software components, which are inapplicable and inefficient in the ever-changing SCAs in WSNs. In this paper, we consider the SCAs with fault tolerance in WSNs. Based on a Universal Generating Function (UGF) we propose a reliability and performance model of SCAs in WSNs, which generalizes a redundancy optimization problem to a multi-state system. Based on this model, an efficient optimization algorithm for reliability and performance of SCAs in WSNs is developed based on a Genetic Algorithm (GA) to find the optimal structure of SCAs with fault-tolerance in WSNs. In order to examine the feasibility of our algorithm, we have evaluated the performance. Furthermore, the interrelationships between the reliability, performance and cost are investigated. In addition, a distinct approach to determine the most suitable parameters in the suggested algorithm is proposed.

  18. Reliability Evaluation of Service-Oriented Architecture Systems Considering Fault-Tolerance Designs

    Kuan-Li Peng


    strategies. Sensitivity analysis of SOA at both coarse and fine grain levels is also studied, which can be used to efficiently identify the critical parts within the system. Two SOA system scenarios based on real industrial practices are studied. Experimental results show that the proposed SOA model can be used to accurately depict the behavior of SOA systems. Additionally, a sensitivity analysis that quantizes the effects of system structure as well as fault tolerance on the overall reliability is also studied. On the whole, the proposed reliability modeling and analysis framework may help the SOA system service provider to evaluate the overall system reliability effectively and also make smarter improvement plans by focusing resources on enhancing reliability-sensitive parts within the system.


    P.V. Srihari


    Full Text Available Fault diagnosis of gearboxes plays an important role in increasing the availability of machinery in condition monitoring. An effort has been made in this work to develop an artificial neural networks (ANN based fault detection system to increase reliability. Two prominent fault conditions in gears, worn-out and broken teeth, are simulated and five feature parameters are extracted based on vibration signals which are used as input features to the ANN based fault detection system developed in MATLAB, a three layered feed forward network using a back propagation algorithm. This ANN system has been trained with 30 sets of data and tested with 10 sets of data. The learning rate and number of hidden layer neurons are varied individually and the optimal training parameters are found based on the number of epochs. Among the five different learning rates used the 0.15 is deduced to be optimal one and at that learning rate the number of hidden layer neurons of 9 was the optimal one out of the three values considered. Then keeping the training parameters fixed, the number of hidden layers is varied by comparing the performance of the networks and results show the two and three hidden layers have the best detection accuracy.


    Roland Iosif MORARU


    Full Text Available Fault tree analysis is useful both in designing new products/services or in dealing with identified problems in existing ones. In the quality planning process, the analysis can be used to optimize process features and goals and to design for critical factors and human error. As part of safety process improvement, as it is emphasized in the present paper, it can be used to help identify root causes of undesired events such as occupational injuries and illnesses. A case study of application in industrial safety systems illustrates the aim, principle and structure of the technique, allowing better prevention measures selection and implementation.


    Annisa Sholikhatul Addawiyah


    Full Text Available Fault tree analysis adalah suatu penilaian risiko yang mampu mengidentifikasi potensi bahaya secara spesifik, fokus, rinci pada satu kejadian yang tidak diinginkan, dan mengetahui penyebab kejadian tersebut beserta angka probabilitasnya. Tercatat mulai tanggal 1 Januari – 30 April 2014 terjadi kebakaran sebanyak 10 kali di divisi spinning PT. Apac Inti Corpora dengan kasus tertinggi di unit spinning V (50% kejadian.Tujuan penelitian ini adalah mengetahui faktor penyebab kebakaran, mengembangkan penilaian risiko, dan mengetahui gambaran umum sistem manajemen penanggulangan kebakaran di unit spinning V PT. AIC. Desain penelitian ini adalah kualitatif eksplanatoris. Hasil pengembangan bagan fault tree analysis didapatkan 41 basic event, 24 intermediate event, 1 conditioning event, dan 1 undeveloped event yang secara matematis melalui persamaan aljabar boolean akan menghasilkan 35 single minimum cut sets dan 5 double component cut sets, dengan perhitungan angka probabilitas sebesar 0,3552. Hasil kesesuaian sistem manajemen penanggulangan kebakaran didapatkan 76 poin dari 81 poin standar regulasi yang berlaku di Indonesia. Simpulan penelitian ini adalah kemungkinan terjadinya kebakaran di spinning V sebesar 35,52%. Saran dari penelitian ini adalah dilakukannya evaluasi terhadap kegagalan deteksi dini dan kegagalan teknis. Fault tree analysis has advantages in identifying potential hazards in specifics, focus, detail on a potential undesirable event that called top event, and was able to find out the causes with the value of probability. Recorded at January 1th – April 30th, 2014, there had been 10 cases of fires in the spinning PT. Apac Inti Corpora with the highest cases at spinning V (50% event. The purpose of this research was find out the cause of fires, develop a risk assessment, and learn an overview of fires countermeasures management system in spinning V. This research was a qualitative – explanatory design. Result of development fault

  2. Fault tree modeling of AAC power source in multi-unit nuclear power plants PSA

    Han, Sang Hoon; Lim, Ho-Gon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)


    Dependencies between units are important to estimate a risk of a multi-unit site. One of dependencies is a shared system such as an alternating AC (AAC) power source. Because one AAC can support a single unit, it is necessary to appropriately treat such behavior of the AAC in multi-unit probabilistic safety assessment (PSA). The behavior of AAC in multi-unit site would show dynamic characteristics. For example, several units require the AAC at the same time. It is hard to decide which unit the AAC is connected to. It can vary depending on timing of station blackout (SBO), with time delay when emergency diesel generators fail while running. It is not easy to handle dynamic behavior using the static fault tree methodology. Typical way of estimating risk for multi-unit regarding to AAC is to assume that only one unit has AAC and the others does not. KIM calculates the risk for each unit and uses the average value from the results. Jung derives an equation to calculate the SBO frequency by considering all the combination of loss of offsite power and failure of emergency diesel generators in multi-unit site. It is also assumed that the AAC is connected to a pre-decided unit. We are developing a PSA model for multi-unit site for internal and external events. An extreme external hazard may result in loss of all offsite power in a site, where the appropriate modeling of an AAC becomes important. The static fault tree methodology is not good for dynamic situation. But, it can turn into a simple problem if an assumption is made: - The connecting order of AAC is pre-decided. This study provides an idea how to model AAC for each unit in the form of a fault tree, assuming the connecting order of AAC is given. This study illustrates how to model a fault tree for AAC in a multi-unit site. It provides an idea how to handle a shared system in multi-unit PSA, for such a case as loss of all offsite power in a site due to an extreme external hazard.

  3. APU Fault Diagnosis Research Based on Fault Tree Analysis Method%基于故障树分析法的APU故障诊断研究



    Fault tree analysis (FTA) is a widely -used method for failure analysis and fault diagnosis. Combining with APU' s working characters, the author analyzes the causes of starting difficukies, builds APU starting difficulty fault tree, and also gives a qualitative and quantitative analysis of basic causes of fault tree. It finally points out the APU fault suggestions to predict and prevent failure occurring.%故障树分析(FTA)是故障分析和故障诊断中广泛应用的一种方法。结合APU的工作特性,对APU启动困难的原因进行了分析,建立APU启动困难故障树,并对故障树的基本原因事件进行了定性、定量分析,进而提出了排除APU故障的方法,以达到预测与预防故障发生的目的。

  4. Fault-tree Models of Accident Scenarios of RoPax Vessels

    Pedro Ant(a)o; C. Guedes Soares


    Ro-Ro vessels for cargo and passengers (RoPax) are a relatively new concept that has proven to be popular in the Mediterranean region and is becoming more widespread in Northern Europe. Due to its design characteristics and amount of passengers, although less than a regular passenger liner, accidents with RoPax vessels have far reaching consequences both for economical and for human life. The objective of this paper is to identify hazards related to casualties of RoPax vessels. The terminal casualty events chosen are related to accident and incident statistics for this type of vessel. This paper focuses on the identification of the basic events that can lead to an accident and the performance requirements. The hazard identification is carried out as the first step of a Formal Safety Assessment (FSA) and the modelling of the relation between the relevant events is made using Fault Tree Analysis (FTA). The conclusions of this study are recommendations to the later steps of FSA rather than for decision making (Step 5 of FSA). These recommendations will be focused on the possible design shortcomings identified during the analysis by fault trees throughout cut sets. Also the role that human factors have is analysed through a sensitivity analysis where it is shown that their influence is higher for groundings and collisions where an increase of the initial probability leads to the change of almost 90% of the accident occurrence.

  5. The integration methods of fuzzy fault mode and effect analysis and fault tree analysis for risk analysis of yogurt production

    Aprilia, Ayu Rizky; Santoso, Imam; Ekasari, Dhita Murita


    Yogurt is a product based on milk, which has beneficial effects for health. The process for the production of yogurt is very susceptible to failure because it involves bacteria and fermentation. For an industry, the risks may cause harm and have a negative impact. In order for a product to be successful and profitable, it requires the analysis of risks that may occur during the production process. Risk analysis can identify the risks in detail and prevent as well as determine its handling, so that the risks can be minimized. Therefore, this study will analyze the risks of the production process with a case study in CV.XYZ. The method used in this research is the Fuzzy Failure Mode and Effect Analysis (fuzzy FMEA) and Fault Tree Analysis (FTA). The results showed that there are 6 risks from equipment variables, raw material variables, and process variables. Those risks include the critical risk, which is the risk of a lack of an aseptic process, more specifically if starter yogurt is damaged due to contamination by fungus or other bacteria and a lack of sanitation equipment. The results of quantitative analysis of FTA showed that the highest probability is the probability of the lack of an aseptic process, with a risk of 3.902%. The recommendations for improvement include establishing SOPs (Standard Operating Procedures), which include the process, workers, and environment, controlling the starter of yogurt and improving the production planning and sanitation equipment using hot water immersion.

  6. Improved Multispanning Tree Routing Using Efficient and Reliable Routing Algorithm for Irregular Networks

    L. Keerthana


    Full Text Available A Strategy of Multispanning Tree Zone Ordered Label Based routing is improved with Efficient and Reliable (EAR routing for irregular networks is presented and analyzed in this work. Most existing deadlock free routing methods for irregular topologies impose several limitations on node and channel labeling in an irregular network is based on a pre-defined spanning tree.It is not possible to form a deadlock free zone of three or four channel labels for two spanning tree. So this existing Multispanning Tree Zone Ordered Label Based routing is modified with Efficient and Reliable (EAR routing. EAR is based on four parameters length of the path,distance traversed,transmission of link and energy levels to dynamically determine and maintain the best routes.. The simulation results have shown highest packet delivery ratio, minimum latency, and energy consumption.

  7. 小水电电气设备安全性分析%Security Evaluation of Electrical Equipment Failure of Small Hydropower Station by Fault Tree Analysis

    白雪; 袁越; 吴博文; 傅质馨; 徐锦才


    The overall reliability of electrical equipment of small hydropower station is analysed in this paper. Fault tree model of components' failure rate is established. With dam top as the the fault tree top events, Minimum cut set and solution of the fault tree are presented in the Paper. Through the calculation of the electrical equipment failure probability of a small hydropower station in Zhejiang province, the safe influence degree of the electrical equipment failure to the top events is obtained. The results show the switch equipment on the key circuits is the important e-quipment component,which causes the top event and impacts the overall safety and reliability of the power supply system directly.%对我国小水电的电气设备进行安全性分析,建立了电气设备故障率的故障树模型,选择坝顶配电室为故障树的顶事件,并用下行法求出了该故障树的最小割集,通过对浙江省某小水电站进行电气设备故障概率计算,获得电气设备故障对顶事件造成的故障安全影响程度,结果表明线路上的开关设备是导致故障树顶事件发生的重要设备元件,直接影响着整体供电系统的安全可靠性.

  8. Fuzzy fault tree analysis on hoist disc brake%提升机盘式制动器的模糊故障树分析

    晋民杰; 郭空斐; 张帅; 杨明星


    In view of insufficiencies such as data lacking,environmental fuzziness and inaccurate data at analyzing the reliability of the hoist disc braking system at present,the fuzzy set theory was introduced into the fault tree analysis of the hoist disc brake.In addition,triangular fuzzy numbers were applied to characterize the fault occurrence probability of the hoist disc brake,and fuzzy fault tree was set up,which solved the inaccurate probability excellently.%针对目前提升机盘式制动系统进行可靠性分析时存在的数据不足和环境模糊性及数据的不精确性的问题,将模糊集合理论引入到提升机盘式制动器的故障树分析中,用三角模糊数刻画提升机盘式制动系统事件发生的概率,建立了模糊故障树,较好地解决了事件概率值不精确的问题.

  9. Bypassing BDD Construction for Reliability Analysis

    Williams, Poul Frederick; Nikolskaia, Macha; Rauzy, Antoine


    In this note, we propose a Boolean Expression Diagram (BED)-based algorithm to compute the minimal p-cuts of boolean reliability models such as fault trees. BEDs make it possible to bypass the Binary Decision Diagram (BDD) construction, which is the main cost of fault tree assessment....

  10. Faults

    National Oceanic and Atmospheric Administration, Department of Commerce — Through the study of faults and their effects, much can be learned about the size and recurrence intervals of earthquakes. Faults also teach us about crustal...

  11. Reliable Finite Frequency Filter Design for Networked Control Systems with Sensor Faults

    He-Hua Ju


    Full Text Available This paper is concerned with the reliable finite frequency filter design for networked control systems (NCSs subject to quantization and data missing. Taking into account quantization, possible data missing and sensor stuck faults, NCSs are modeled in the framework of discrete time-delay switched systems, and the finite frequency l2 gain is adopted for the filter design of discrete time-delay switched systems, which is converted into a set of linear matrix inequality (LMI conditions. By the virtues of the derived conditions, a procedure of reliable filter synthesis is presented. Further, the filter gains are characterized in terms of solutions to a convex optimization problem which can be solved by using the semi-definite programme method. Finally, an example is given to illustrate the effectiveness of the proposed method.

  12. Specification and Design of a Fault Recovery Model for the Reliable Multicast Protocol

    Montgomery, Todd; Callahan, John R.; Whetten, Brian


    The Reliable Multicast Protocol (RMP) provides a unique, group-based model for distributed programs that need to handle reconfiguration events at the application layer. This model, called membership views, provides an abstraction in which events such as site failures, network partitions, and normal join-leave events are viewed as group reformations. RMP provides access to this model through an application programming interface (API) that notifies an application when a group is reformed as the result of a some event. RMP provides applications with reliable delivery of messages using an underlying IP Multicast media to other group members in a distributed environment even in the case of reformations. A distributed application can use various Quality of Service (QoS) levels provided by RMP to tolerate group reformations. This paper explores the implementation details of the mechanisms in RMP that provide distributed applications with membership view information and fault recovery capabilities.

  13. Reliable and Fault-Tolerant Software-Defined Network Operations Scheme for Remote 3D Printing

    Kim, Dongkyun; Gil, Joon-Min


    The recent wide expansion of applicable three-dimensional (3D) printing and software-defined networking (SDN) technologies has led to a great deal of attention being focused on efficient remote control of manufacturing processes. SDN is a renowned paradigm for network softwarization, which has helped facilitate remote manufacturing in association with high network performance, since SDN is designed to control network paths and traffic flows, guaranteeing improved quality of services by obtaining network requests from end-applications on demand through the separated SDN controller or control plane. However, current SDN approaches are generally focused on the controls and automation of the networks, which indicates that there is a lack of management plane development designed for a reliable and fault-tolerant SDN environment. Therefore, in addition to the inherent advantage of SDN, this paper proposes a new software-defined network operations center (SD-NOC) architecture to strengthen the reliability and fault-tolerance of SDN in terms of network operations and management in particular. The cooperation and orchestration between SDN and SD-NOC are also introduced for the SDN failover processes based on four principal SDN breakdown scenarios derived from the failures of the controller, SDN nodes, and connected links. The abovementioned SDN troubles significantly reduce the network reachability to remote devices (e.g., 3D printers, super high-definition cameras, etc.) and the reliability of relevant control processes. Our performance consideration and analysis results show that the proposed scheme can shrink operations and management overheads of SDN, which leads to the enhancement of responsiveness and reliability of SDN for remote 3D printing and control processes.

  14. Reliability Improvement of a T-Type Three-Level Inverter With Fault-Tolerant Control Strategy

    Choi, Uimin; Blaabjerg, Frede; Lee, Kyo-Beum


    in a neutral-point switch, two methods will be proposed and compared based on thermal analysis and neutral-point voltage oscillation. The reliability of T-type inverter systems is improved considerably by the proposed algorithm when a switch fails. The proposed method does not require any additional components......This paper proposes a fault-tolerant control strategy for a T-type three-level inverter when an open-circuit fault occurs. The proposed method is explained by dividing fault into two cases: the faulty condition of half-bridge switches and neutral-point switches. In case of the open-circuit fault....... Simulation and experimental results verify the validity and feasibility of the proposed fault-tolerant control strategy....

  15. Goal-Function Tree Modeling for Systems Engineering and Fault Management

    Johnson, Stephen B.; Breckenridge, Jonathan T.


    This paper describes a new representation that enables rigorous definition and decomposition of both nominal and off-nominal system goals and functions: the Goal-Function Tree (GFT). GFTs extend the concept and process of functional decomposition, utilizing state variables as a key mechanism to ensure physical and logical consistency and completeness of the decomposition of goals (requirements) and functions, and enabling full and complete traceabilitiy to the design. The GFT also provides for means to define and represent off-nominal goals and functions that are activated when the system's nominal goals are not met. The physical accuracy of the GFT, and its ability to represent both nominal and off-nominal goals enable the GFT to be used for various analyses of the system, including assessments of the completeness and traceability of system goals and functions, the coverage of fault management failure detections, and definition of system failure scenarios.

  16. Risk assessment for enterprise resource planning (ERP) system implementations: a fault tree analysis approach

    Zeng, Yajun; Skibniewski, Miroslaw J.


    Enterprise resource planning (ERP) system implementations are often characterised with large capital outlay, long implementation duration, and high risk of failure. In order to avoid ERP implementation failure and realise the benefits of the system, sound risk management is the key. This paper proposes a probabilistic risk assessment approach for ERP system implementation projects based on fault tree analysis, which models the relationship between ERP system components and specific risk factors. Unlike traditional risk management approaches that have been mostly focused on meeting project budget and schedule objectives, the proposed approach intends to address the risks that may cause ERP system usage failure. The approach can be used to identify the root causes of ERP system implementation usage failure and quantify the impact of critical component failures or critical risk events in the implementation process.

  17. Risk management of PPP project in the preparation stage based on Fault Tree Analysis

    Xing, Yuanzhi; Guan, Qiuling


    The risk management of PPP(Public Private Partnership) project can improve the level of risk control between government departments and private investors, so as to make more beneficial decisions, reduce investment losses and achieve mutual benefit as well. Therefore, this paper takes the PPP project preparation stage venture as the research object to identify and confirm four types of risks. At the same time, fault tree analysis(FTA) is used to evaluate the risk factors that belong to different parts, and quantify the influencing degree of risk impact on the basis of risk identification. In addition, it determines the importance order of risk factors by calculating unit structure importance on PPP project preparation stage. The result shows that accuracy of government decision-making, rationality of private investors funds allocation and instability of market returns are the main factors to generate the shared risk on the project.

  18. Fault Tree Analysis: A survey of the state-of-the-art in modeling, analysis and tools

    Ruijters, Enno Jozef Johannes; Stoelinga, Mariëlle Ida Antoinette


    Fault tree analysis (FTA) is a very prominent method to analyze the risks related to safety and economically critical assets, like power plants, airplanes, data centers and web shops. FTA methods comprise of a wide variety of modelling and analysis techniques, supported by a wide range of software

  19. Fault tree analysis: A survey of the state-of-the-art in modeling, analysis and tools

    Ruijters, Enno Jozef Johannes; Stoelinga, Mariëlle Ida Antoinette


    Fault tree analysis (FTA) is a very prominent method to analyze the risks related to safety and economically critical assets, like power plants, airplanes, data centers and web shops. FTA methods comprise of a wide variety of modelling and analysis techniques, supported by a wide range of software

  20. Fault tree analysis for integrated and probabilistic risk analysis of drinking water systems.

    Lindhe, Andreas; Rosén, Lars; Norberg, Tommy; Bergstedt, Olof


    Drinking water systems are vulnerable and subject to a wide range of risks. To avoid sub-optimisation of risk-reduction options, risk analyses need to include the entire drinking water system, from source to tap. Such an integrated approach demands tools that are able to model interactions between different events. Fault tree analysis is a risk estimation tool with the ability to model interactions between events. Using fault tree analysis on an integrated level, a probabilistic risk analysis of a large drinking water system in Sweden was carried out. The primary aims of the study were: (1) to develop a method for integrated and probabilistic risk analysis of entire drinking water systems; and (2) to evaluate the applicability of Customer Minutes Lost (CML) as a measure of risk. The analysis included situations where no water is delivered to the consumer (quantity failure) and situations where water is delivered but does not comply with water quality standards (quality failure). Hard data as well as expert judgements were used to estimate probabilities of events and uncertainties in the estimates. The calculations were performed using Monte Carlo simulations. CML is shown to be a useful measure of risks associated with drinking water systems. The method presented provides information on risk levels, probabilities of failure, failure rates and downtimes of the system. This information is available for the entire system as well as its different sub-systems. Furthermore, the method enables comparison of the results with performance targets and acceptable levels of risk. The method thus facilitates integrated risk analysis and consequently helps decision-makers to minimise sub-optimisation of risk-reduction options.

  1. Fault Tree Analysis for Safety/Security Verification in Aviation Software

    Andrew J. Kornecki


    Full Text Available The Next Generation Air Traffic Management system (NextGen is a blueprint of the future National Airspace System. Supporting NextGen is a nation-wide Aviation Simulation Network (ASN, which allows integration of a variety of real-time simulations to facilitate development and validation of the NextGen software by simulating a wide range of operational scenarios. The ASN system is an environment, including both simulated and human-in-the-loop real-life components (pilots and air traffic controllers. Real Time Distributed Simulation (RTDS developed at Embry Riddle Aeronautical University, a suite of applications providing low and medium fidelity en-route simulation capabilities, is one of the simulations contributing to the ASN. To support the interconnectivity with the ASN, we designed and implemented a dedicated gateway acting as an intermediary, providing logic for two-way communication and transfer messages between RTDS and ASN and storage for the exchanged data. It has been necessary to develop and analyze safety/security requirements for the gateway software based on analysis of system assets, hazards, threats and attacks related to ultimate real-life future implementation. Due to the nature of the system, the focus was placed on communication security and the related safety of the impacted aircraft in the simulation scenario. To support development of safety/security requirements, a well-established fault tree analysis technique was used. This fault tree model-based analysis, supported by a commercial tool, was a foundation to propose mitigations assuring the gateway system safety and security. 

  2. An Overview of Risk Quantification Issues for Digitalized Nuclear Power Plants using a Static Fault Tree

    Kang, Hyun Gook; Kim, Man Cheol; Lee, Seung Jun; Lee, Ho Jung; Eom, Heung Seop; Chol, Jong Gyun; Jang, Seung Cheol [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)


    Risk caused by safety-critical instrumentation and control (I and C) systems considerably affects overall plant risk. As digitalization of safety-critical systems in nuclear power plants progresses, a risk model of a digitalized safety system is required and must be included in a plant safety model in order to assess this risk effect on the plant. Unique features of a digital system cause some challenges in risk modeling. This article aims at providing an overview of the issues related to the development of a static fault-tree-based risk model. We categorize the complicated issues of digital system probabilistic risk assessment (PRA) into four groups based on their characteristics: hardware module issues, software issues, system issues, and safety function issues. Quantification of the effect of these issues dominates the quality of a developed risk model. Recent research activities for addressing various issues, such as the modeling framework of a software-based system, the software failure probability and the fault coverage of a self monitoring mechanism, are discussed. Although these issues are interrelated and affect each other, the categorized and systematic approach suggested here will provide a proper insight for analyzing risk from a digital system

  3. An improved IEEE 802.11 protocol for reliable data transmission in power distribution fault diagnosis

    Campoccia, F.; Di Silvestre, M.L.; Sanseverino, E.R.; Zizzo, G. [Palermo Univ., Palermo (Italy)


    In power systems, on-line transmission between local units and the central unit can be done by means of power line communications or wireless technology. During an electrical fault, the reliability of the distribution system depends on the security of the timely protective and restorative actions on the network. This paper focused on the WiFi system because of its economy and ease of installation. However, WiFi systems are typically managed by the IEEE 802.11 protocol, which is not reliable in terms of security in data communication. In WiFi networks, data is divided into packets and sent in succession to reduce errors within the radio channel. The IEEE 802.11 protocol has high probability for loss of packets or delay in their transmission. In order to ensure the reliability of data transmission times between two terminal units connected by WiFi stations, a new protocol was derived by modifying the IEEE 802.11. The improvements of the new protocol were highlighted and its capability for the diagnostic service was verified. The modified protocol eliminates the danger of collisions between packets and optimizes the transmission time for sending information. 6 refs., 7 tabs., 8 figs.

  4. Fault analysis of chemical oxygen iodine laser based on fault tree%基于故障树的氧碘化学激光器故障分析

    张政; 曹益平; 沈志康; 关小伟


    The paper establishes a fault tree model for chemical oxygen iodine laser(COIL) considering power abnormity as its peak affair of fault, and then makes down-way qualitative analysis and quantitative analysis with the minimum cut-set theory. It is indicated that the reliability of iodine supply subsystem is minimum, followed by the chlorine supply subsystem, in the seven subsystems of COIL. The probability at which the power of COIL is abnormal is 3. 99%, that is, the reliability of laser is 96.01%.%为方便快捷地查找出氧碘化学激光器故障发生的原因,以氧碘化学激光器常见故障为例,建立了其功率失常的故障树模型,用最小割集理论按下行法对模型进行了定性分析和定量分析.分析表明:氧碘化学激光器7个子系统中,碘供给子系统的可靠性最低,氯气供给子系统次之,这与实际情况相符.计算出的氧碘化学激光器出光不正常发生概率为3.99%,其可靠度为96.01%.

  5. Considering the Fault Dependency Concept with Debugging Time Lag in Software Reliability Growth Modeling Using a Power Function of Testing Time


    Since the early 1970s tremendous growth has been seen in the research of software reliability growth modeling. In general, software reliability growth models (SRGMs) are applicable to the late stages of testing in software development and they can provide useful information about how to improve the reliability of software products. A number of SRGMs have been proposed in the literature to represent time-dependent fault identification / removal phenomenon; still new models are being proposed that could fit a greater number of reliability growth curves. Often, it is assumed that detected faults are immediately corrected when mathematical models are developed. This assumption may not be realistic in practice because the time to remove a detected fault depends on the complexity of the fault, the skill and experience of the personnel, the size of the debugging team, the technique, and so on. Thus, the detected fault need not be immediately removed, and it may lag the fault detection process by a delay effect factor. In this paper, we first review how different software reliability growth models have been developed, where fault detection process is dependent not only on the number of residual fault content but also on the testing time, and see how these models can be reinterpreted as the delayed fault detection model by using a delay effect factor. Based on the power function of the testing time concept, we propose four new SRGMs that assume the presence of two types of faults in the software: leading and dependent faults. Leading faults are those that can be removed upon a failure being observed. However, dependent faults are masked by leading faults and can only be removed after the corresponding leading fault has been removed with a debugging time lag. These models have been tested on real software error data to show its goodness of fit, predictive validity and applicability.

  6. Reliable H∞ control of discrete-time systems against random intermittent faults

    Tao, Yuan; Shen, Dong; Fang, Mengqi; Wang, Youqing


    A passive fault-tolerant control strategy is proposed for systems subject to a novel kind of intermittent fault, which is described by a Bernoulli distributed random variable. Three cases of fault location are considered, namely, sensor fault, actuator fault, and both sensor and actuator faults. The dynamic feedback controllers are designed not only to stabilise the fault-free system, but also to guarantee an acceptable performance of the faulty system. The robust H∞ performance index is used to evaluate the effectiveness of the proposed control scheme. In terms of linear matrix inequality, the sufficient conditions of the existence of controllers are given. An illustrative example indicates the effectiveness of the proposed fault-tolerant control method.

  7. 大功率风电机用变桨距减速器的故障树分析%Fault Tree Analysis for Reducer of Variable Pitch System in High Power Wind Turbine

    何卫东; 郭洪亮; 李永华


    The fault tree simulation technology is proposed high-power wind turbine with the variable propeller pitch gear fault tree analysis. This method adopts stochastic simulation method for solving engineering problems to obtain approximate values and reliability parameters. It can find out the strong and weak links of the gear system and,improve the accuracy of reliability analysis. Which has engineering application with great promotional value.%提出利用故障树模拟技术进行大功率风电机用变桨距减速器的故障树分析(Fault Tree Analysis,FTA).这种方法采用随机模拟方法为分析手段,模拟求解工程技术问题的近似数值,从而获得系统的可靠性参数.利用CAFTA分析软件找出了影响大功率风电机用变桨距减速器系统及子系统可靠性的关键件及薄弱环节,提高系统可靠性分析精度.这种方法具有很大的工程实际应用推广价值.

  8. Reliability Growth Modeling and Optimal Release Policy Under Fuzzy Environment of an N-version Programming System Incorporating the Effect of Fault Removal Efficiency


    Failure of a safety critical system can lead to big losses. Very high software reliability is required for automating the working of systems such as aircraft controller and nuclear reactor controller software systems. Fault-tolerant softwares are used to increase the overall reliability of software systems. Fault tolerance is achieved using the fault-tolerant schemes such as fault recovery (recovery block scheme), fault masking (N-version programming (NVP)) or a combination of both (Hybrid scheme). These softwares incorporate the ability of system survival even on a failure. Many researchers in the field of software engineering have done excellent work to study the reliability of fault-tolerant systems. Most of them consider the stable system reliability. Few attempts have been made in reliability modeling to study the reliability growth for an NVP system. Recently, a model was proposed to analyze the reliability growth of an NVP system incorporating the effect of fault removal efficiency. In this model, a proportion of the number of failures is assumed to be a measure of fault generation while an appropriate measure of fault generation should be the proportion of faults removed. In this paper, we first propose a testing efficiency model incorporating the effect of imperfect fault debugging and error generation. Using this model, a software reliability growth model (SRGM) is developed to model the reliability growth of an NVP system. The proposed model is useful for practical applications and can provide the measures of debugging effectiveness and additional workload or skilled professional required. It is very important for a developer to determine the optimal release time of the software to improve its performance in terms of competition and cost. In this paper, we also formulate the optimal software release time problem for a 3VP system under fuzzy environment and discuss a the fuzzy optimization technique for solving the problem with a numerical illustration.

  9. Comparison of various methods to quantify a fault tree for Seismic PSA

    Han, Sang Hoon; Park, Jin Hee; Kim, Dong San; Lim, Ho-Gon; Jang, Seung Cheol [KAERI, Daejeon (Korea, Republic of)


    Typically, quantification (evaluation of frequency) of a sequence in a PSA is performed by generating minimal cut sets and quantifying it using REA (Rare event approximation) or MCUB (Minimal cut upper bound) method. MCUB gives more exact value than REA. But, it is known that REA and MCUB method may produce very conservative value when a probability of each event is larger than 0.1 such as in seismic PSA. The PSA software AIMS-PSA and FTREX developed in KAERI use REA and MCUB method to quantify a PSA model. Thus, it is necessary to verify the quantification result for seismic PSA. There are several method/software available for the verification. ACUBE developed by EPRI quantifies the pre-generated minimal cut sets using BDD (binary decision diagram) method. FTeMC developed by KAERI is based on Monte Carlo method. FtBdd developed by KAERI is based on BDD, but it can be applied for small fault trees. In section 2, a simple example is provided to characterize various methods. The results of those methods are compared for a seismic PSA model. REA and MCUB may produce very conservative value for a seismic PSA model which includes events whose probabilities are large. It is not easy to get the exact value for every case. We should recognize the limitation of each method/software when analyzing the quantification results for PSA. To verify the results, a supporting analysis can be used using other software such as Monte Carlo method.

  10. Causation mechanism analysis for haze pollution related to vehicle emission in Guangzhou, China by employing the fault tree approach.

    Huang, Weiqing; Fan, Hongbo; Qiu, Yongfu; Cheng, Zhiyu; Xu, Pingru; Qian, Yu


    Recently, China has frequently experienced large-scale, severe and persistent haze pollution due to surging urbanization and industrialization and a rapid growth in the number of motor vehicles and energy consumption. The vehicle emission due to the consumption of a large number of fossil fuels is no doubt a critical factor of the haze pollution. This work is focused on the causation mechanism of haze pollution related to the vehicle emission for Guangzhou city by employing the Fault Tree Analysis (FTA) method for the first time. With the establishment of the fault tree system of "Haze weather-Vehicle exhausts explosive emission", all of the important risk factors are discussed and identified by using this deductive FTA method. The qualitative and quantitative assessments of the fault tree system are carried out based on the structure, probability and critical importance degree analysis of the risk factors. The study may provide a new simple and effective tool/strategy for the causation mechanism analysis and risk management of haze pollution in China.

  11. A new formalism that combines advantages of fault-trees and Markov models: Boolean logic driven Markov processes

    Bouissou, Marc; Bon, Jean-Louis


    This paper introduces a modeling formalism that enables the analyst to combine concepts inherited from fault trees and Markov models in a new way. We call this formalism Boolean logic Driven Markov Processes (BDMP). It has two advantages over conventional models used in dependability assessment: it allows the definition of complex dynamic models while remaining nearly as readable and easy to build as fault-trees, and it offers interesting mathematical properties, which enable an efficient processing for BDMP that are equivalent to Markov processes with huge state spaces. We give a mathematical definition of BDMP, the demonstration of their properties, and several examples to illustrate how powerful and easy to use they are. From a mathematical point of view, a BDMP is nothing more than a certain way to define a global Markov process, as the result of several elementary processes which can interact in a given manner. An extreme case is when the processes are independent. Then we simply have a fault-tree, the leaves of which are associated to independent Markov processes.

  12. Fuzzy fault tree assessment based on improved AHP for fire and explosion accidents for steel oil storage tanks.

    Shi, Lei; Shuai, Jian; Xu, Kui


    Fire and explosion accidents of steel oil storage tanks (FEASOST) occur occasionally during the petroleum and chemical industry production and storage processes and often have devastating impact on lives, the environment and property. To contribute towards the development of a quantitative approach for assessing the occurrence probability of FEASOST, a fault tree of FEASOST is constructed that identifies various potential causes. Traditional fault tree analysis (FTA) can achieve quantitative evaluation if the failure data of all of the basic events (BEs) are available, which is almost impossible due to the lack of detailed data, as well as other uncertainties. This paper makes an attempt to perform FTA of FEASOST by a hybrid application between an expert elicitation based improved analysis hierarchy process (AHP) and fuzzy set theory, and the occurrence possibility of FEASOST is estimated for an oil depot in China. A comparison between statistical data and calculated data using fuzzy fault tree analysis (FFTA) based on traditional and improved AHP is also made. Sensitivity and importance analysis has been performed to identify the most crucial BEs leading to FEASOST that will provide insights into how managers should focus effective mitigation.

  13. Study of Fault Diagnosis of De-airing Pug Mill Based on Fuzzy Fault Tree%基于模糊故障树的真空练泥机故障诊断研究

    周明康; 陆新


    采用了模糊故障树分析法来研究真空练泥机的主要故障,通过建立故障树模型,对故障树进行定性分析;定量分析则应用模糊数来确定故障概率,为维修策略提供参考.此方法具有较大的灵活性和适应性.%This article uses the fuzzy fault tree analytic method to study the main fault of the de-airing pug mill and through the established fault tree model .carries out the qualitative analysis of the fault tree. It also uses the fuzzy number in the quantitative analysis to confirm the failure probability and provides a reference for the maintenance strategy. This method has the great flexibility and the compatibility.

  14. A failure analysis of drill string based on fault tree%基于事故树的钻柱失效分析方法

    臧艳彬; 王瑞和; 张锐; 王子振


    针对复杂地质条件下钻柱失效事故频发、防控措施效果不理想的现状,应用图论中的事故树分析方法,在演绎钻柱失效诱因与防控措施逻辑关系的基础上,建立了钻柱失效事故树模型.运用最小割集与径集分析了钻柱失效的路径和最优防控途径,并以川东北地区钻柱失效为例进行了实例分析.结果表明,该地区钻柱失效概率为56.81%,事故树定量计算结果与实际统计值相符合,证明基于事故树的钻柱失效分析方法切实可行,事故树结构合理,计算结果真实、可靠.同时,通过计算事故树基本事件的3个重要度,为制定钻柱失效防控对策提供了理论依据,增强了防控措施的针对性和实用性.%In view of frequent occurrences of drill-string failure under complicated geological conditions and the less effectiveness of preventive measures,the present paper applied the fault tree analysis (FTA) of the graph theory to interpret the logical relationship of an inducement of drill-string failure and related control measures,established a fault tree model for drill-string failure,and analyzed paths of drill-string failure and the optimal prevention ways by using the least cut-set and the least path-set.The drill-string failure analysis in the northeastern Sichuan exploration area was taken as a case study.The results indicated that the probability of drill-string failure in the study area obtained by quantitative analysis of fault tree was 56.81%, consistent with the actual statistics.The case study proved that the drill-string failure analysis based on FTA was feasible,the structure of the fault tree involved was reasonable and the calculation results were truthful and reliable.Meanwhile, the calculation of importance magnitude by fault tree for basic events provided the drill-string failure prevention and control with a theoretical basis,which enhanced the pertinence and practicality of prevention and control measures.

  15. Goal-Function Tree Modeling for Systems Engineering and Fault Management

    Patterson, Jonathan D.; Johnson, Stephen B.


    The draft NASA Fault Management (FM) Handbook (2012) states that Fault Management (FM) is a "part of systems engineering", and that it "demands a system-level perspective" (NASAHDBK- 1002, 7). What, exactly, is the relationship between systems engineering and FM? To NASA, systems engineering (SE) is "the art and science of developing an operable system capable of meeting requirements within often opposed constraints" (NASA/SP-2007-6105, 3). Systems engineering starts with the elucidation and development of requirements, which set the goals that the system is to achieve. To achieve these goals, the systems engineer typically defines functions, and the functions in turn are the basis for design trades to determine the best means to perform the functions. System Health Management (SHM), by contrast, defines "the capabilities of a system that preserve the system's ability to function as intended" (Johnson et al., 2011, 3). Fault Management, in turn, is the operational subset of SHM, which detects current or future failures, and takes operational measures to prevent or respond to these failures. Failure, in turn, is the "unacceptable performance of intended function." (Johnson 2011, 605) Thus the relationship of SE to FM is that SE defines the functions and the design to perform those functions to meet system goals and requirements, while FM detects the inability to perform those functions and takes action. SHM and FM are in essence "the dark side" of SE. For every function to be performed (SE), there is the possibility that it is not successfully performed (SHM); FM defines the means to operationally detect and respond to this lack of success. We can also describe this in terms of goals: for every goal to be achieved, there is the possibility that it is not achieved; FM defines the means to operationally detect and respond to this inability to achieve the goal. This brief description of relationships between SE, SHM, and FM provide hints to a modeling approach to

  16. Dynamic fault trees resolution: A conscious trade-off between analytical and simulative approaches

    Chiacchio, F., E-mail: [Dipartimento di Matematica e Informatica-DMI, Universita degli Studi di Catania (Italy); Compagno, L., E-mail: [Dipartimento di Ingegneria Industriale e Meccanica-DIIM, Universita degli Studi di Catania (Italy); D' Urso, D., E-mail: [Dipartimento di Ingegneria Industriale e Meccanica-DIIM, Universita degli Studi di Catania (Italy); Manno, G., E-mail: [Dipartimento di Matematica e Informatica-DMI, Universita degli Studi di Catania (Italy); Trapani, N., E-mail: [Dipartimento di Ingegneria Industriale e Meccanica-DIIM, Universita degli Studi di Catania (Italy)


    Safety assessment in industrial plants with 'major hazards' requires a rigorous combination of both qualitative and quantitative techniques of RAMS. Quantitative assessment can be executed by static or dynamic tools of dependability but, while the former are not sufficient to model exhaustively time-dependent activities, the latter are still too complex to be used with success by the operators of the industrial field. In this paper we present a review of the procedures that can be used to solve quite general dynamic fault trees (DFT) that present a combination of the following characteristics: time dependencies, repeated events and generalized probability failure. Theoretical foundations of the DFT theory are discussed and the limits of the most known DFT tools are presented. Introducing the concept of weak and strong hierarchy, the well-known modular approach is adapted to study a more generic class of DFT. In order to quantify the approximations introduced, an ad-hoc simulative environment is used as benchmark. In the end, a DFT of an accidental scenario is analyzed with both analytical and simulative approaches. Final results are in good agreement and prove how it is possible to implement a suitable Monte Carlo simulation with the features of a spreadsheet environment, able to overcome the limits of the analytical tools, thus encouraging further researches along this direction. - Highlights: > Theoretical foundations of the DFT are reviewed and the limits of the analytical techniques are assessed. > Hierarchical technique is discussed, introducing the concepts of weak and strong equivalence. > Simulative environment developed with a spreadsheet electronic document is tested. > Comparison between the simulative and the analytical results is performed. > Classification of which technique is more suitable is provided, depending on the complexity of the DFT.

  17. Bayesian updating in a fault tree model for shipwreck risk assessment.

    Landquist, H; Rosén, L; Lindhe, A; Norberg, T; Hassellöv, I-M


    Shipwrecks containing oil and other hazardous substances have been deteriorating on the seabeds of the world for many years and are threatening to pollute the marine environment. The status of the wrecks and the potential volume of harmful substances present in the wrecks are affected by a multitude of uncertainties. Each shipwreck poses a unique threat, the nature of which is determined by the structural status of the wreck and possible damage resulting from hazardous activities that could potentially cause a discharge. Decision support is required to ensure the efficiency of the prioritisation process and the allocation of resources required to carry out risk mitigation measures. Whilst risk assessments can provide the requisite decision support, comprehensive methods that take into account key uncertainties related to shipwrecks are limited. The aim of this paper was to develop a method for estimating the probability of discharge of hazardous substances from shipwrecks. The method is based on Bayesian updating of generic information on the hazards posed by different activities in the surroundings of the wreck, with information on site-specific and wreck-specific conditions in a fault tree model. Bayesian updating is performed using Monte Carlo simulations for estimating the probability of a discharge of hazardous substances and formal handling of intrinsic uncertainties. An example application involving two wrecks located off the Swedish coast is presented. Results show the estimated probability of opening, discharge and volume of the discharge for the two wrecks and illustrate the capability of the model to provide decision support. Together with consequence estimations of a discharge of hazardous substances, the suggested model enables comprehensive and probabilistic risk assessments of shipwrecks to be made.

  18. Reliable fault detection and diagnosis of photovoltaic systems based on statistical monitoring approaches

    Harrou, Fouzi


    This study reports the development of an innovative fault detection and diagnosis scheme to monitor the direct current (DC) side of photovoltaic (PV) systems. Towards this end, we propose a statistical approach that exploits the advantages of one-diode model and those of the univariate and multivariate exponentially weighted moving average (EWMA) charts to better detect faults. Specifically, we generate array\\'s residuals of current, voltage and power using measured temperature and irradiance. These residuals capture the difference between the measurements and the predictions MPP for the current, voltage and power from the one-diode model, and use them as fault indicators. Then, we apply the multivariate EWMA (MEWMA) monitoring chart to the residuals to detect faults. However, a MEWMA scheme cannot identify the type of fault. Once a fault is detected in MEWMA chart, the univariate EWMA chart based on current and voltage indicators is used to identify the type of fault (e.g., short-circuit, open-circuit and shading faults). We applied this strategy to real data from the grid-connected PV system installed at the Renewable Energy Development Center, Algeria. Results show the capacity of the proposed strategy to monitors the DC side of PV systems and detects partial shading.

  19. Application of FTA Method to Reliability Analysis of Vacuum Resin Shot Dosing Equipment


    Faults of vacuum resin shot dosing equipment are studied systematically and the fault tree of the system is constructed by using the fault tree analysis(FTA) method. Then the qualitative and quantitative analysis of the tree is carried out, respectively, and according to the results of the analysis, the measures to improve the system are worked out and implemented. As a result, the reliability of the equipment is enhanced greatly.

  20. Fault Severity Evaluation and Improvement Design for Mechanical Systems Using the Fault Injection Technique and Gini Concordance Measure

    Jianing Wu


    Full Text Available A new fault injection and Gini concordance based method has been developed for fault severity analysis for multibody mechanical systems concerning their dynamic properties. The fault tree analysis (FTA is employed to roughly identify the faults needed to be considered. According to constitution of the mechanical system, the dynamic properties can be achieved by solving the equations that include many types of faults which are injected by using the fault injection technique. Then, the Gini concordance is used to measure the correspondence between the performance with faults and under normal operation thereby providing useful hints of severity ranking in subsystems for reliability design. One numerical example and a series of experiments are provided to illustrate the application of the new method. The results indicate that the proposed method can accurately model the faults and receive the correct information of fault severity. Some strategies are also proposed for reliability improvement of the spacecraft solar array.

  1. The Reliability of Classification of Terminal Nodes in GUIDE Decision Tree to Predict the Nonalcoholic Fatty Liver Disease

    Mehdi Birjandi


    Full Text Available Tree structured modeling is a data mining technique used to recursively partition a dataset into relatively homogeneous subgroups in order to make more accurate predictions on generated classes. One of the classification tree induction algorithms, GUIDE, is a nonparametric method with suitable accuracy and low bias selection, which is used for predicting binary classes based on many predictors. In this tree, evaluating the accuracy of predicted classes (terminal nodes is clinically of special importance. For this purpose, we used GUIDE classification tree in two statuses of equal and unequal misclassification cost in order to predict nonalcoholic fatty liver disease (NAFLD, considering 30 predictors. Then, to evaluate the accuracy of predicted classes by using bootstrap method, first the classification reliability in which individuals are assigned to a unique class and next the prediction probability reliability as support for that are considered.

  2. A coupled Bayesian and fault tree methodology to assess future groundwater conditions in light of climate change

    J. J. Huang


    Full Text Available Maintaining acceptable groundwater levels, particularly in arid areas, while protecting ecosystems, are key measures against desertification. Due to complicated hydrological processes and their inherent uncertainties, investigations of groundwater recharge conditions are challenging, particularly in arid areas under climate changing conditions. To assist planning to protect against desertification, a fault tree methodology, in conjunction with fuzzy logic and Bayesian data mining, are applied to Minqin Oasis, a highly vulnerable regime in northern China. A set of risk factors is employed within the fault tree framework, with fuzzy logic translating qualitative risk data into probabilities. Bayesian data mining is used to quantify the contribution of each risk factor to the final aggregated risk. The implications of both historical and future climate trends are employed for temperature, precipitation and potential evapotranspiration (PET to assess water table changes under various future scenarios. The findings indicate that water table levels will continue to drop at the rate of 0.6 m yr−1 in the future when climatic effects alone are considered, if agricultural and industrial production capacity remain at 2004 levels.

  3. Risk-Control Approach for a Bottleneck Spanning Tree Problem with the Total Network Reliability under Uncertainty

    Takashi Hasuike


    parameters to edge costs is introduced as objective functions in the risk-control. Furthermore, in order to maintain the constructing spanning tree network entirely, the reliability for each edge is introduced, and maximizing the total reliability of spanning tree is assumed as the third objective function. The proposed model is a multiobjective programming problem, and hence, it is difficult to solve it directly without setting some optimal criterion. Therefore, satisfaction functions for each object and the integrated function are introduced, and the exact solution algorithm is developed by performing deterministic equivalent transformations. A numerical example is provided by comparing our proposed model with previous standard models.

  4. Scheduling and Voltage Scaling for Energy/Reliability Trade-offs in Fault-Tolerant Time-Triggered Embedded Systems

    Pop, Paul; Poulsen, Kåre Harbo; Izosimov, Viacheslav;


    In this paper we present an approach to the scheduling and voltage scaling of low-power fault-tolerant hard real-time applications mapped on distributed heterogeneous embedded systems. Processes and messages are statically scheduled, and we use process re-execution for recovering from multiple tr...... are satisfied and the energy is minimized. We present a constraint logic programming- based approach which is able to find reliable and schedulable implementations within limited energy and hardware resources. The developed algorithms have been evaluated using extensive experiments....

  5. Lithium battery safety and reliability

    Levy, Samuel C.

    Lithium batteries have been used in a variety of applications for a number of years. As their use continues to grow, particularly in the consumer market, a greater emphasis needs to be placed on safety and reliability. There is a useful technique which can help to design cells and batteries having a greater degree of safety and higher reliability. This technique, known as fault tree analysis, can also be useful in determining the cause of unsafe behavior and poor reliability in existing designs.

  6. Energy/Reliability Trade-offs in Fault-Tolerant Event-Triggered Distributed Embedded Systems

    Gan, Junhe; Gruian, Flavius; Pop, Paul;


    This paper presents an approach to the synthesis of low-power fault-tolerant hard real-time applications mapped on distributed heterogeneous embedded systems. Our synthesis approach decides the mapping of tasks to processing elements, as well as the voltage and frequency levels for executing each...

  7. Fault tree analysis for CNC hydraulic system based on fuzzy theory%基于模糊理论的数控机床液压系统故障树分析

    米金华; 李彦锋; 李海庆; 黄洪钟


    以某数控机床液压系统为研究对象,针对其故障发生概率具有模糊性和不确定性的特点,将模糊理论引入故障树分析中,采用三角型模糊数来描述底事件发生概率.通过分析该系统故障发生的机理,建立了该系统的模糊故障树,在定性分析的基础上进行定量计算,得到了基本事件的模糊重要度这项可靠性指标,为系统的可靠性评估、故障诊断以及维修决策提供了理论依据.%In this paper, fuzzy theory is introduced into the fault tree analysis for machine hydraulic systems to characterize the fuzziness and uncertainty of occurrence probability.The triangular fuzzy numbers are utilized to qualify the probability of basic events.The fuzzy fault tree can be constructed according to failure modes of systems.In addition, quantitative computing can be performed based on qualitative analysis subsequently.Fuzzy importance measure of each basic event can be further computed which can provide a theoretical basis for system reliability assessment, fault diagnosis and maintenance.

  8. A Generic Algorithm for Dynamic Fault Tree in Spacecraft with Repeated Events%含共因事件航天系统的通用动态故障树方法

    刘涛; 季振洲; 王庆; 朱素霞


    Dynamic fault tree approaches are generally used to address repeated dynamic events such as component dependence and order of input in space complex systems, but its solving process often lead to ultra high computational complexity. An accurate GDFTA ( Generic Dynamic Fault-Tree Algorithm) method based on system definition assumptions is used to analyze the type of failure. This method begins with the probability distribution of basic events and takes into account the logical time sequence and the connection style of the dynamic gates. The GDFTA outperform the Markov method in solving the universal dynamic fault trees for avoiding the Markov state space crisis. In experiments, several dynamic tree examples are used to test its feasibility. Then, experiments using the standard dynamic tree benchmark set show high accuracy of reliability test results of four types of systems. Moreover, the computational time is much less than a Mante Carlo simulated method.%为了表示航天复杂系统中组件依赖关系和输入次序等动态事件与共因事件,动态故障树的求解过程通常会面临很高的计算复杂度与时间开销.基于系统定义假设,由基本事件的概率分布入手,根据动态门的时序逻辑定义和关联方式,给出系统故障事件的准确通用计算方法GDFTA(Generic Dynamic Fault-Tree Algorithm).GDFTA方法实现了通用的动态树求解,避免了Markov方法的状态空间爆炸问题,并取得了较理想的计算准确性.通过对动态树实例的可靠性评估证明该方法可行.在标准动态故障树测试集中,四类不同系统的可靠性结果精度优于Monte Carlo方法,计算效率也有显著提高.

  9. Pyrometamorphism of Fault Zone Rocks Induced by Frictional Heating in High-velocity Friction Tests: Reliable Records of Seismic Slip?

    Ree, J.; Ando, J.; Kim, J.; Han, R.; Shimamoto, T.


    Recognition of seismic slip zone is important for a better understanding of earthquake generation processes in fault zones and paleoseismology. However, there has been no reliable record of ancient seismic slip except pseudotachylyte. Recently, it has been suggested that decomposition (dehydration or decarbonation) products due to frictional heating can be used as a seismic slip record. The decomposition products, however, can be easily rehydrated or recarbonated with pervasive fluid migration in the fault zone after seismic slip, raising some question about their stability as a seismic slip record. Here, we review microstructural and mineralogical changes of the simulated fault zones induced by frictional heating (pyrometamorphism) from high-velocity friction tests (HVFT) on siltstone, sandstone and carbonates at seismic slip rates, and discuss on their stability after seismic slip. HVFT on siltstone generates pseuodotachylyte in the principal slip zone (0.30-0.75 mm thick) with 'damage' layer (0.1-0.2 mm thick) along its margins. Chlorite in the damage layer suffers an incipient dehydration with many voids (0.2-1.0 μm in diameter) in transmission electron microscopy (TEM), appearing as dark tiny spots both in plane-polarized light and back-scattered electron (BSE) photomicrographs. HVFT on brown sandstone induces a color change of wall rocks adjacent to the principal slip zone (brown to red) due to the dehydration of iron hydroxides with frictional heating. These dehydration products in siltstone and sandstone due to frictional heating may be unstable since they would be easily rehydrated with fluid infiltration after a seismic slip. HVFT on carbonates including Carrara marble and siderite-bearing gouges produces decarbonation products of nano-scale lime (CaO) and magnetite (Fe3O4), respectively. Lime is a very unstable phase whereas magnetite is a stable and thus may be used as an indicator of seismic slip. The simulated fault zones of Carrara marble contain

  10. Fault Diagnosis Expert System of Diesel Engine Based on Fault Tree%基于层次分析法的发动机故障诊断专家系统

    崔中清; 薛金红; 杨小强


    运用故障树分析法进行康明斯发动机的故障分析,建立了发动机常见故障的层次树模型,并将其转化成二叉故障树以构建专家系统的知识库;研究了系统的推理诊断流程:采用层次分析法设计了故障诊断专家系统.基于Windows平台和Delphi7.0语言开发了故障诊断专家系统.提供了一套简单、实用的故障诊断工具,给装备的故障诊断带来了极大的方便.%The fault analysis of Cummins engine is demonstrated with the fault tree analytical method. The common fault's analytic hierarchy tree is constructed and turned into binary fault trees. Meanwhile,the knowledge base is set up with the method of production rule and frame experss. Then Cummins engine fault diagnosis system is designed on the thought of analytical hierarchy process. The software application is developed using Delphi 7.0 language. This software offers a simple and practical tool for users and brings great convenience to engineering corps.

  11. Impact of deep coalescence on the reliability of species tree inference from different types of DNA markers in mammals.

    Alejandro Sánchez-Gracia

    Full Text Available An important challenge for phylogenetic studies of closely related species is the existence of deep coalescence and gene tree heterogeneity. However, their effects can vary between species and they are often neglected in phylogenetic analyses. In addition, a practical problem in the reconstruction of shallow phylogenies is to determine the most efficient set of DNA markers for a reliable estimation. To address these questions, we conducted a multilocus simulation study using empirical values of nucleotide diversity and substitution rates obtained from a wide range of mammals and evaluated the performance of both gene tree and species tree approaches to recover the known speciation times and topological relationships. We first show that deep coalescence can be a serious problem, more than usually assumed, for the estimation of speciation times in mammals using traditional gene trees. Furthermore, we tested the performance of different sets of DNA markers in the determination of species trees using a coalescent approach. Although the best estimates of speciation times were obtained, as expected, with the use of an increasing number of nuclear loci, our results show that similar estimations can be obtained with a much lower number of genes and the incorporation of a mitochondrial marker, with its high information content. Thus, the use of the combined information of both nuclear and mitochondrial markers in a species tree framework is the most efficient option to estimate recent speciation times and, consequently, the underlying species tree.

  12. SCAP: a new methodology for safety management based on feedback from credible accident-probabilistic fault tree analysis system.

    Khan, F I; Iqbal, A; Ramesh, N; Abbasi, S A


    As it is conventionally done, strategies for incorporating accident--prevention measures in any hazardous chemical process industry are developed on the basis of input from risk assessment. However, the two steps-- risk assessment and hazard reduction (or safety) measures--are not linked interactively in the existing methodologies. This prevents a quantitative assessment of the impacts of safety measures on risk control. We have made an attempt to develop a methodology in which risk assessment steps are interactively linked with implementation of safety measures. The resultant system tells us the extent of reduction of risk by each successive safety measure. It also tells based on sophisticated maximum credible accident analysis (MCAA) and probabilistic fault tree analysis (PFTA) whether a given unit can ever be made 'safe'. The application of the methodology has been illustrated with a case study.

  13. Power electronics reliability analysis.

    Smith, Mark A.; Atcitty, Stanley


    This report provides the DOE and industry with a general process for analyzing power electronics reliability. The analysis can help with understanding the main causes of failures, downtime, and cost and how to reduce them. One approach is to collect field maintenance data and use it directly to calculate reliability metrics related to each cause. Another approach is to model the functional structure of the equipment using a fault tree to derive system reliability from component reliability. Analysis of a fictitious device demonstrates the latter process. Optimization can use the resulting baseline model to decide how to improve reliability and/or lower costs. It is recommended that both electric utilities and equipment manufacturers make provisions to collect and share data in order to lay the groundwork for improving reliability into the future. Reliability analysis helps guide reliability improvements in hardware and software technology including condition monitoring and prognostics and health management.

  14. Reliability Assessment of Offshore Wind Turbines Considering Faults of Electrical / Mechanical Components

    Kostandyan, Erik; Sørensen, John Dalsgaard


    of structural, mechanical and electrical components are important, in order to optimally plan Operation & Maintenance strategies. A general model for reliability estimation of structural, mechanical or electrical components is described. For a representative failure mode a corresponding limit state...

  15. Design of a Programmable System for Failure Modes and Effect Analysis of Steam-Power Plant Based on the Fault Tree Analysis

    Dr. Zuhair I. Ahmad Al- Dauod


    Full Text Available In this paper, the system of the power plant has been investigated as a special type of industrial systems, which has a significant role in improving societies since the electrical energy has entered all kinds of industries, and it is considered as the artery of modern life. The aim of this research is to construct a programming system, which could be used to identify the most important failure modes that are occur in a steam type of power plants. Also the effects and reasons of each failure mode could be analyzed through the usage of this programming system reaching to the basic events (main reasons that causing each failure mode. The construction of this system for FMEA is depending on the logical relationships of the fault tree analysis for the systems that contained in the power station. The designing of such system could be used as an assistance tool for the specialist user (the power engineer in identifying of all reasons and effects for any type of failures. So this is help to fastening the repairing operation of the identified failure mode to improve the efficiency of operating system as represented by the maintainability, which is a function of system reliability. The selection of the steam type of power generation systems for the application of this study, because this type is the most common type of Iraqi power plants. While such the designed system could be programmed to be use in another types of industrial systems.

  16. Observer-based reliable stabilization of uncertain linear systems subject to actuator faults, saturation, and bounded system disturbances.

    Fan, Jinhua; Zhang, Youmin; Zheng, Zhiqiang


    A matrix inequality approach is proposed to reliably stabilize a class of uncertain linear systems subject to actuator faults, saturation, and bounded system disturbances. The system states are assumed immeasurable, and a classical observer is incorporated for observation to enable state-based feedback control. Both the stability and stabilization of the closed-loop system are discussed and the closed-loop domain of attraction is estimated by an ellipsoidal invariant set. The resultant stabilization conditions in the form of matrix inequalities enable simultaneous optimization of both the observer gain and the feedback controller gain, which is realized by converting the non-convex optimization problem to an unconstrained nonlinear programming problem. The effectiveness of proposed design techniques is demonstrated through a linearized model of F-18 HARV around an operating point.

  17. Reliability study of the Controls Interlocks Beam Dumping System CIBDS V5

    Blumenschein, Miriam Ruth


    The CIBDS V5 reliability study includes a failure mode and effect analysis, a failure rate prediction and a fault tree analysis. The different steps of these analyses, the assumptions as well as the results are summarised in this note.

  18. Non-binary decomposition trees - a method of reliability computation for systems with known minimal paths/cuts

    Malinowski, Jacek


    A coherent system with independent components and known minimal paths (cuts) is considered. In order to compute its reliability, a tree structure T is constructed whose nodes contain the modified minimal paths (cuts) and numerical values. The value of a non-leaf node is a function of its child nodes' values. The values of leaf nodes are calculated from a simple formula. The value of the root node is the system's failure probability (reliability). Subsequently, an algorithm computing the system's failure probability (reliability) is constructed. The algorithm scans all nodes of T using a stack structure for this purpose. The nodes of T are alternately put on and removed from the stack, their data being modified in the process. Once the algorithm has terminated, the stack contains only the final modification of the root node of T, and its value is equal to the system's failure probability (reliability)

  19. Re-examining the reliability of tree-ring isotope ratio as a his- torical CO2 proxy


    To examine the reliability of using tree ring d 13C and the modelof isotopic fractionation in reconstructing atmospheric CO2 levels, we studied the variations of some important parameters of several subtropical species under natural field conditions. It was found that, different from other researchers' results, leaf conductance to CO2 transfer, g, did not change in proportion to the change in rate of CO2 assimilation, A, with the result that intercellular concen- tration of CO2, Ci, could not keep constant. Thus, we con-clude that the use of tree-ring isotope ratios in the recon-struction of atmospheric CO2 variation based on the presup-position that Ci keeps constant during assimilation is not reliable under current circumstances.

  20. Production of Reliable Flight Crucial Software: Validation Methods Research for Fault Tolerant Avionics and Control Systems Sub-Working Group Meeting

    Dunham, J. R. (Editor); Knight, J. C. (Editor)


    The state of the art in the production of crucial software for flight control applications was addressed. The association between reliability metrics and software is considered. Thirteen software development projects are discussed. A short term need for research in the areas of tool development and software fault tolerance was indicated. For the long term, research in format verification or proof methods was recommended. Formal specification and software reliability modeling, were recommended as topics for both short and long term research.

  1. Probabilistic Risk Analysis and Fault Trees as Tools in Improving the Delineation of Wellhead Protection Areas: An Initial Discussion

    Rodak, C. M.; Silliman, S. E.


    Delineation of a wellhead protection area (WHPA) is a critical component of managing / protecting the aquifer(s) supplying potable water to a public water-supply well. While a number of previous authors have addressed questions related to uncertainties in advective capture zones, methods for assessing WHPAs in the presence of uncertainty in the chemistry of groundwater contaminants, the relationship between land-use and contaminant sources, and the impact on health risk within the receiving population are more limited. Probabilistic risk analysis (PRA) combined with fault trees (FT) addresses this latter challenge by providing a structure whereby four key WHPA issues may be addressed: (i) uncertainty in land-use practices and chemical release, (ii) uncertainty in groundwater flow, (iii) variability in natural attenuation properties (and/or remediation) of the contaminants, and (iv) estimated health risk from contaminant arrival at a well. The potential utility of PRA-FT in this application is considered through a simplified case study involving management decisions related both to regional land use planning and local land-use zoning regulation. An application-specific fault tree is constructed to visualize and identify the events required for health risk failure at the well and a Monte Carlo approach is used to create multiple realizations of groundwater flow and chemical transport to a well in a model of a simple, unconfined aquifer. Model parameters allowed to vary during this simplified case study include hydraulic conductivity, probability of a chemical spill (related to land use variation in space), and natural attenuation through variation in rate of decay of the contaminant. Numerical results are interpreted in association with multiple land-use management scenarios as well as multiple cancer risk assumptions regarding the contaminant arriving at the well. This case study shows significant variability of health risk at the well, however general trends were

  2. Source Data Impacts on Epistemic Uncertainty for Launch Vehicle Fault Tree Models

    Al Hassan, Mohammad; Novack, Steven; Ring, Robert


    Launch vehicle systems are designed and developed using both heritage and new hardware. Design modifications to the heritage hardware to fit new functional system requirements can impact the applicability of heritage reliability data. Risk estimates for newly designed systems must be developed from generic data sources such as commercially available reliability databases using reliability prediction methodologies, such as those addressed in MIL-HDBK-217F. Failure estimates must be converted from the generic environment to the specific operating environment of the system in which it is used. In addition, some qualification of applicability for the data source to the current system should be made. Characterizing data applicability under these circumstances is crucial to developing model estimations that support confident decisions on design changes and trade studies. This paper will demonstrate a data-source applicability classification method for suggesting epistemic component uncertainty to a target vehicle based on the source and operating environment of the originating data. The source applicability is determined using heuristic guidelines while translation of operating environments is accomplished by applying statistical methods to MIL-HDK-217F tables. The paper will provide one example for assigning environmental factors uncertainty when translating between operating environments for the microelectronic part-type components. The heuristic guidelines will be followed by uncertainty-importance routines to assess the need for more applicable data to reduce model uncertainty.

  3. Trees

    Al-Khaja, Nawal


    This is a thematic lesson plan for young learners about palm trees and the importance of taking care of them. The two part lesson teaches listening, reading and speaking skills. The lesson includes parts of a tree; the modal auxiliary, can; dialogues and a role play activity.

  4. Fault Tree Analysis of Urban Traffic Congestion Causes%大城市交通拥堵致因的故障树分析

    王潇; 王武宏; 毛琰; 郭宏伟; 郭伟伟; 金晶


    The reasons for traffic congestion in different cities, regions or road networks are varied. In order to take effective measures to solve the congestion problems, an application of FT A (Fault Tree Analysis) in analyzing causes of urban traffic congestion was proposed. It analyzed the related instructions of Fault Tree of congestion and took Guangan Road in Beijing as an example and established a fault tree model of road congestion to analyze the basic causes, and identified major causes through qualitative and quantitative analysis. The results provide the solutions of road congestion to improving traffic condition.%为解决拥堵问题,提出将故障树分析法引入道路交通拥堵中.对道路拥堵故障树进行了相关说明,以北京丰台区广安路为例,构建道路拥堵的故障树模型,分析引起拥堵的所有可能原因,并通过定性和定量分析找出了主要拥堵原因,给出了解决道路拥堵的方案.

  5. 螺杆钻具万向轴故障树模型及花瓣强度分析%Model of the Fault Tree of Screwdrill Cardan Shaft and Petal Strength Analysis

    韩传军; 黄显萍; 王玮; 刘洋; 张杰


    The cardan shaft of screwdrill tends to fail. Therefore, the fault tree analysis method was applied to study its reliability. The fault tree model was established with the cardan shaft assembly failure as the top event. The ascending method was used to make a qualitative analysis of 14 minimal cut sets of the tree. The finite element method was used to conduct a strength analysis of petal-type cardan shaft under the combined action of compression and torsion. The findings show that the petal root and the minimum cross-section are of high stress zone and they are subject to fracture failure most easily. The preciseness of the finite element analysis was verified through comparison with the field failure example.%针对螺杆钻具中易发生失效的万向轴部分,应用故障树分析方法对其可靠性进行了研究.建立以万向轴总成失效为顶事件的故障树模型,采用“上行法”定性分析了故障树的14个最小割集.利用有限元法对压扭组合作用下的花瓣式万向轴进行了强度分析,分析结果表明,花瓣的根部和最小截面处为高应力区,最易发生断裂失效.通过与现场失效实例对比,验证了有限元分析方法的正确性.

  6. Fault tree analysis of the F&H Canyon Exhaust Systems at the Savannah River Site

    Low, J.M.; Marshall, K.M.


    The Canyon Exhaust System (CES) for the F&H Canyon chemical Separations Facilities are considered safety class items (SCIs). SCIs are defined in DOE Order 6430.1A as systems, components, and structures, including portions of process systems, whose failure could adversely affect the environment or safety and health of the public. As such, any modification to SCIs must be carefully reviewed for impact to safety. During the last year, the Savannah River Technology Center of WSRC has been requested to perform two major evolutions on the Canyon Exhaust Systems. These evaluations include an Upgrade to Canyon Exhaust System (UCES) Project for both F&H Areas and a Backfit analysis for a standby diesel generator in F-Area. The purpose of the first evaluation was to evaluate the impact of cost reduction options on the UCES reliability. The purpose of the second analysis was to provide justification for not upgrading an existing standby diesel generator to meet current safety class standards.

  7. 高温气冷堆示范工程反应堆保护系统故障树模型的建立和分析%Development and Analysis of Fault Tree Model of HTR-PM Reactor Protection System

    郭超; 李铎; 熊华胜


    数字化保护系统正逐步取代模拟系统,应用于新建和升级的核电厂中,数字化保护系统的可靠性分析已成为仪控领域的热点研究课题。本工作以高温气冷堆示范工程(H T R-PM )的反应堆保护系统为研究对象,研究数字化保护系统故障树模型的建立和分析方法,主要研究内容包括:故障树顶事件的选取;基于失效模式与影响分析(FM EA )的故障树搭建方法,重点研究保护系统冗余通道的“2/4”表决逻辑以及通道旁通的处理方法;对故障树模型进行定性分析,并根据故障树的最小割集讨论保护系统的薄弱环节。该研究对于分析数字化保护系统的可靠性并改进系统设计具有重要意义。%Digital reactor protection system ( RPS ) is gradually replacing analog counterparts and being applied in newly-built and upgraded nuclear power plant (NPP) , and the analysis of digital RPS reliability is one of the hot topics in the research field of NPP I&C .Based on RPS of high temperature gas-cooled reactor pebble bed module (HTR-PM ) ,the research of this paper focused on development and analysis of digital RPS fault tree model ,which was outlined as following :The top event for a fault tree was chosen ;the method to build a fault tree model based on failure modes and effects analysis (FMEA) was studied ,specially focusing on the sub-tree of redundant channel“2-out-of-4” logic and the fault tree under one channel bypass ;the qualitative analysis of fault tree ,such as RPS weakness according to minimal cut sets was summarized .The research is important to analyze digital RPS reliability and to improve its design .

  8. Software reliability

    Bendell, A


    Software Reliability reviews some fundamental issues of software reliability as well as the techniques, models, and metrics used to predict the reliability of software. Topics covered include fault avoidance, fault removal, and fault tolerance, along with statistical methods for the objective assessment of predictive accuracy. Development cost models and life-cycle cost models are also discussed. This book is divided into eight sections and begins with a chapter on adaptive modeling used to predict software reliability, followed by a discussion on failure rate in software reliability growth mo

  9. A methodological combined framework for roadmapping biosensor research: a fault tree analysis approach within a strategic technology evaluation frame.

    Siontorou, Christina G; Batzias, Fragiskos A


    Biosensor technology began in the 1960s to revolutionize instrumentation and measurement. Despite the glucose sensor market success that revolutionized medical diagnostics, and artificial pancreas promise currently the approval stage, the industry is reluctant to capitalize on other relevant university-produced knowledge and innovation. On the other hand, the scientific literature is extensive and persisting, while the number of university-hosted biosensor groups is growing. Considering the limited marketability of biosensors compared to the available research output, the biosensor field has been used by the present authors as a suitable paradigm for developing a methodological combined framework for "roadmapping" university research output in this discipline. This framework adopts the basic principles of the Analytic Hierarchy Process (AHP), replacing the lower level of technology alternatives with internal barriers (drawbacks, limitations, disadvantages), modeled through fault tree analysis (FTA) relying on fuzzy reasoning to count for uncertainty. The proposed methodology is validated retrospectively using ion selective field effect transistor (ISFET) - based biosensors as a case example, and then implemented prospectively membrane biosensors, putting an emphasis on the manufacturability issues. The analysis performed the trajectory of membrane platforms differently than the available market roadmaps that, considering the vast industrial experience in tailoring and handling crystallic forms, suggest the technology path of biomimetic and synthetic materials. The results presented herein indicate that future trajectories lie along with nanotechnology, and especially nanofabrication and nano-bioinformatics, and focused, more on the science-path, that is, on controlling the natural process of self-assembly and the thermodynamics of bioelement-lipid interaction. This retained the nature-derived sensitivity of the biosensor platform, pointing out the differences

  10. Reliability of measured data for pH sensor arrays with fault diagnosis and data fusion based on LabVIEW.

    Liao, Yi-Hung; Chou, Jung-Chuan; Lin, Chin-Yi


    Fault diagnosis (FD) and data fusion (DF) technologies implemented in the LabVIEW program were used for a ruthenium dioxide pH sensor array. The purpose of the fault diagnosis and data fusion technologies is to increase the reliability of measured data. Data fusion is a very useful statistical method used for sensor arrays in many fields. Fault diagnosis is used to avoid sensor faults and to measure errors in the electrochemical measurement system, therefore, in this study, we use fault diagnosis to remove any faulty sensors in advance, and then proceed with data fusion in the sensor array. The average, self-adaptive and coefficient of variance data fusion methods are used in this study. The pH electrode is fabricated with ruthenium dioxide (RuO2) sensing membrane using a sputtering system to deposit it onto a silicon substrate, and eight RuO2 pH electrodes are fabricated to form a sensor array for this study.

  11. Reliability of Measured Data for pH Sensor Arrays with Fault Diagnosis and Data Fusion Based on LabVIEW

    Yi-Hung Liao


    Full Text Available Fault diagnosis (FD and data fusion (DF technologies implemented in the LabVIEW program were used for a ruthenium dioxide pH sensor array. The purpose of the fault diagnosis and data fusion technologies is to increase the reliability of measured data. Data fusion is a very useful statistical method used for sensor arrays in many fields. Fault diagnosis is used to avoid sensor faults and to measure errors in the electrochemical measurement system, therefore, in this study, we use fault diagnosis to remove any faulty sensors in advance, and then proceed with data fusion in the sensor array. The average, self-adaptive and coefficient of variance data fusion methods are used in this study. The pH electrode is fabricated with ruthenium dioxide (RuO2 sensing membrane using a sputtering system to deposit it onto a silicon substrate, and eight RuO2 pH electrodes are fabricated to form a sensor array for this study.

  12. A Systematic Approach to Sensitivity Analysis of Fault Tolerant Systems in NMR Architecture

    Kourosh Aslansefat


    Full Text Available A fault tree illustrates the ways through which a system fails. It states different ways in which combination of faulty components result in an undesired event in the system. Being used in phases such as designing and exploiting industrial systems, and the designers able to evaluate the dependability attributes such as reliability, MTTF and sensitivity. In addition, in the mentioned ability, the fault tree is a systematic method for finding systems bottlenecks and weakness point. In spite of its extensive use in evaluating the reliability of systems, fault tree is rarely used in calculating sensitivity. In the last decade, few researches has been conducted in this field, however these methods are not applicable to large scale systems and are not systematic. This paper provides a systematic method for evaluating system sensitivity through fault tree. Then, it introduces sensitivity of NMR architecture as one of the common structures of fault tolerance which is used for enhancing systems’ reliability, safety and availability in industry. This article presents a comprehensive and parameterized formula for NMR structure's sensitivity. The presented method can be a great help for designing and exploiting reliable systems engineers in systematic and instant calculation of sensitivity by means of fault tree.

  13. Analytical solutions of linked fault tree probabilistic risk assessments using binary decision diagrams with emphasis on nuclear safety applications[Dissertation 17286

    Nusbaumer, O. P. M


    This study is concerned with the quantification of Probabilistic Risk Assessment (PRA) using linked Fault Tree (FT) models. Probabilistic Risk assessment (PRA) of Nuclear Power Plants (NPPs) complements traditional deterministic analysis; it is widely recognized as a comprehensive and structured approach to identify accident scenarios and to derive numerical estimates of the associated risk levels. PRA models as found in the nuclear industry have evolved rapidly. Increasingly, they have been broadly applied to support numerous applications on various operational and regulatory matters. Regulatory bodies in many countries require that a PRA be performed for licensing purposes. PRA has reached the point where it can considerably influence the design and operation of nuclear power plants. However, most of the tools available for quantifying large PRA models are unable to produce analytically correct results. The algorithms of such quantifiers are designed to neglect sequences when their likelihood decreases below a predefined cutoff limit. In addition, the rare event approximation (e.g. Moivre's equation) is typically implemented for the first order, ignoring the success paths and the possibility that two or more events can occur simultaneously. This is only justified in assessments where the probabilities of the basic events are low. When the events in question are failures, the first order rare event approximation is always conservative, resulting in wrong interpretation of risk importance measures. Advanced NPP PRA models typically include human errors, common cause failure groups, seismic and phenomenological basic events, where the failure probabilities may approach unity, leading to questionable results. It is accepted that current quantification tools have reached their limits, and that new quantification techniques should be investigated. A novel approach using the mathematical concept of Binary Decision Diagram (BDD) is proposed to overcome these

  14. Analytical solutions of linked fault tree probabilistic risk assessments using binary decision diagrams with emphasis on nuclear safety applications[Dissertation 17286

    Nusbaumer, O. P. M


    This study is concerned with the quantification of Probabilistic Risk Assessment (PRA) using linked Fault Tree (FT) models. Probabilistic Risk assessment (PRA) of Nuclear Power Plants (NPPs) complements traditional deterministic analysis; it is widely recognized as a comprehensive and structured approach to identify accident scenarios and to derive numerical estimates of the associated risk levels. PRA models as found in the nuclear industry have evolved rapidly. Increasingly, they have been broadly applied to support numerous applications on various operational and regulatory matters. Regulatory bodies in many countries require that a PRA be performed for licensing purposes. PRA has reached the point where it can considerably influence the design and operation of nuclear power plants. However, most of the tools available for quantifying large PRA models are unable to produce analytically correct results. The algorithms of such quantifiers are designed to neglect sequences when their likelihood decreases below a predefined cutoff limit. In addition, the rare event approximation (e.g. Moivre's equation) is typically implemented for the first order, ignoring the success paths and the possibility that two or more events can occur simultaneously. This is only justified in assessments where the probabilities of the basic events are low. When the events in question are failures, the first order rare event approximation is always conservative, resulting in wrong interpretation of risk importance measures. Advanced NPP PRA models typically include human errors, common cause failure groups, seismic and phenomenological basic events, where the failure probabilities may approach unity, leading to questionable results. It is accepted that current quantification tools have reached their limits, and that new quantification techniques should be investigated. A novel approach using the mathematical concept of Binary Decision Diagram (BDD) is proposed to overcome these

  15. Trees

    Henri Epstein


    An algebraic formalism, developed with V. Glaser and R. Stora for the study of the generalized retarded functions of quantum field theory, is used to prove a factorization theorem which provides a complete description of the generalized retarded functions associated with any tree graph. Integrating over the variables associated to internal vertices to obtain the perturbative generalized retarded functions for interacting fields arising from such graphs is shown to be possible for a large cate...

  16. Trees

    Epstein, Henri


    An algebraic formalism, developped with V. Glaser and R. Stora for the study of the generalized retarded functions of quantum field theory, is used to prove a factorization theorem which provides a complete description of the generalized retarded functions associated with any tree graph. Integrating over the variables associated to internal vertices to obtain the perturbative generalized retarded functions for interacting fields arising from such graphs is shown to be possible for a large cat...

  17. Trees

    Epstein, Henri


    An algebraic formalism, developped with V.~Glaser and R.~Stora for the study of the generalized retarded functions of quantum field theory, is used to prove a factorization theorem which provides a complete description of the generalized retarded functions associated with any tree graph. Integrating over the variables associated to internal vertices to obtain the perturbative generalized retarded functions for interacting fields arising from such graphs is shown to be possible for a large category of space-times.

  18. Fault Diagnosis Approach of Local Ventilation System in Coal Mines Based on Multidisciplinary Technology

    GONG Xiao-yan; XUE He; TAO Xin-li; HU Ning


    In order to reduce the probability of fault occurrence of local ventilation system in coal mine and prevent gas from exceeding the standard limit, an approach incorporating the reliability analysis, rough set theory, genetic algorithm (GA), and intelligent decision support system (IDSS) was used to establish and develop a fault diagnosis system of local ventilation in coal mine. Fault tree model was established and its reliability analysis was performed. The algorithms and software of key fault symptom and fault diagnosis rule acquiring were also analyzed and developed. Finally, a prototype system was developed and demonstrated by a mine instance. The research results indicate that the proposed approach in this paper can accurately and quickly find the fault reason in a local ventilation system of coal mines and can reduce difficulty of the fault diagnosis of the local ventilation system, which is significant to decrease gas exploding accidents in coal mines.

  19. Coverage Modeling and Reliability Analysis Using Multi-state Function


    Fault tree analysis is an effective method for predicting the reliability of a system. It gives a pictorial representation and logical framework for analyzing the reliability. Also, it has been used for a long time as an effective method for the quantitative and qualitative analysis of the failure modes of critical systems. In this paper, we propose a new general coverage model (GCM) based on hardware independent faults. Using this model, an effective software tool can be constructed to detect, locate and recover fault from the faulty system. This model can be applied to identify the key component that can cause the failure of the system using failure mode effect analysis (FMEA).

  20. Fault Tree Analysis of Mortar Shell Exploding Nearby%迫击炮弹近弹原因的故障树分析

    刘超; 田晓丽; 梁东晨; 黄德雨; 秦伟


    Based on the factors contributing to the problem of mortar shell exploding nearby ,the fault tree is set up .According to the procedure of fault tree analysis ,the impacts of these important events at all levels on the top event are analyzed .Special attention should be taken to avoid these factors in product design and use ,in order to avoid the occurrence of the bomb exploding near the mor‐tar .%通过对造成迫击炮弹近弹问题的因素进行故障树分析,按照建立故障树、故障树的定性分析和故障树的定量计算的步骤分析出这些影响顶事件各级事件的重要程度,从而在产品设计及使用过程中应当特别注意避开这些因素,以免发生近弹。

  1. Application of fault tree approach for the causation mechanism of urban haze in Beijing--Considering the risk events related with exhausts of coal combustion.

    Huang, Weiqing; Fan, Hongbo; Qiu, Yongfu; Cheng, Zhiyu; Qian, Yu


    Haze weather has become a serious environmental pollution problem which occurs in many Chinese cities. One of the most critical factors for the formation of haze weather is the exhausts of coal combustion, thus it is meaningful to figure out the causation mechanism between urban haze and the exhausts of coal combustion. Based on above considerations, the fault tree analysis (FAT) approach was employed for the causation mechanism of urban haze in Beijing by considering the risk events related with the exhausts of coal combustion for the first time. Using this approach, firstly the fault tree of the urban haze causation system connecting with coal combustion exhausts was established; consequently the risk events were discussed and identified; then, the minimal cut sets were successfully determined using Boolean algebra; finally, the structure, probability and critical importance degree analysis of the risk events were completed for the qualitative and quantitative assessment. The study results proved that the FTA was an effective and simple tool for the causation mechanism analysis and risk management of urban haze in China.

  2. 非二态故障树分析发展动态%Development trend of no-binary state fault tree analysis

    翁肖力; 李锦飞; 陈静


    Fault Tree Analysis(FTA) is widely used for its desirabl e quality which apply for qualitative and quantitative research of complex syste m.In general,this technique is used in the condition which is supposed that compone nts have dependent and definite distribution.However,in fact,no-binary state fau lt pattern often appear in variable systems.The research of mulistate fault tree analysis become an important subject at present.%故障树分析技术,因 其在复杂系统可靠性的定性、定量研究中所表现出的优势而被广泛应用。但是,一般情况下 的故障树分析都是事先假定元部件具有相互独立,确定分布的状态下使用,而在现实中,往 往会出现非二态的系统失效模式。因此,对非二态情况的故障树的研究已成为当前的重要课题。

  3. Application of fuzzy grey relational analysis in fault tree analysis%模糊灰关联分析方法在故障树分析中的应用

    周真; 马德仲; 于晓洋; 樊尚春


    针对传统的故障树分析方法在分析具有模糊性、灰色性特点的多状态不确定性复杂系统时存在的不足,提出利用模糊灰关联分析方法对传统的故障树分析方法进行改进:用三角模糊数来表示基本事件的模糊概率;计算顶上事件模糊概率和基本事件的模糊重要度;以基本事件模糊重要度作为参考列,以最小割集组成的特征矩阵作为比较列,通过计算关联系数进而求出最小割集所代表的故障模式与顶上事件之间的灰色关联度.应用该方法对风力发电机系统中风轮叶片故障树进行分析,找出了系统的薄弱环节,为预防事故的发生,改进系统可靠性和安全性提供了理论依据.%It is unsatisfactory to apply the classical fault tree analysis (FTA) to the multi-state uncertainty complex system with fuzzy and grey characteristics. So the method, fuzzy grey relational analysis, was applied to improve the FTA. The triangular fuzzy number was used to denote the fuzzy probability of the basic event. The fuzzy probability of the top event and fuzzy significances of basic events were calculated. Then, the set made up of fuzzy significances of basic events was taken as a reference sequence and the characteristic matrix made up of minimal cut sets was taken as a comparative sequence, grey relation degrees between the top event and minimal cut sets were computed after getting incidence coefficients between them. The fault tree of rotor blades in the wind power generation was analyzed by this method. The results can provide theoretical bases for finding out weaknesses, preventing faults, improving reliability and safety of the system.

  4. A Novel Method of Fault Diagnosis for Rolling Bearing Based on Dual Tree Complex Wavelet Packet Transform and Improved Multiscale Permutation Entropy

    Guiji Tang


    Full Text Available A novel method of fault diagnosis for rolling bearing, which combines the dual tree complex wavelet packet transform (DTCWPT, the improved multiscale permutation entropy (IMPE, and the linear local tangent space alignment (LLTSA with the extreme learning machine (ELM, is put forward in this paper. In this method, in order to effectively discover the underlying feature information, DTCWPT, which has the attractive properties as nearly shift invariance and reduced aliasing, is firstly utilized to decompose the original signal into a set of subband signals. Then, IMPE, which is designed to reduce the variability of entropy measures, is applied to characterize the properties of each obtained subband signal at different scales. Furthermore, the feature vectors are constructed by combining IMPE of each subband signal. After the feature vectors construction, LLTSA is employed to compress the high dimensional vectors of the training and the testing samples into the low dimensional vectors with better distinguishability. Finally, the ELM classifier is used to automatically accomplish the condition identification with the low dimensional feature vectors. The experimental data analysis results validate the effectiveness of the presented diagnosis method and demonstrate that this method can be applied to distinguish the different fault types and fault degrees of rolling bearings.

  5. Auto-OBSD: Automatic parameter selection for reliable Oscillatory Behavior-based Signal Decomposition with an application to bearing fault signature extraction

    Huang, Huan; Baddour, Natalie; Liang, Ming


    Bearing signals are often contaminated by in-band interferences and random noise. Oscillatory Behavior-based Signal Decomposition (OBSD) is a new technique which decomposes a signal according to its oscillatory behavior, rather than frequency or scale. Due to the low oscillatory transients of bearing fault-induced signals, the OBSD can be used to effectively extract bearing fault signatures from a blurred signal. However, the quality of the result highly relies on the selection of method-related parameters. Such parameters are often subjectively selected and a systematic approach has not been reported in the literature. As such, this paper proposes a systematic approach to automatic selection of OBSD parameters for reliable extraction of bearing fault signatures. The OBSD utilizes the idea of Morphological Component Analysis (MCA) that optimally projects the original signal to low oscillatory wavelets and high oscillatory wavelets established via the Tunable Q-factor Wavelet Transform (TQWT). In this paper, the effects of the selection of each parameter on the performance of the OBSD for bearing fault signature extraction are investigated. It is found that some method-related parameters can be fixed at certain values due to the nature of bearing fault-induced impulses. To adaptively tune the remaining parameters, index-guided parameter selection algorithms are proposed. A Convergence Index (CI) is proposed and a CI-guided self-tuning algorithm is developed to tune the convergence-related parameters, namely, penalty factor and number of iterations. Furthermore, a Smoothness Index (SI) is employed to measure the effectiveness of the extracted low oscillatory component (i.e. bearing fault signature). It is shown that a minimum SI implies an optimal result with respect to the adjustment of relevant parameters. Thus, two SI-guided automatic parameter selection algorithms are also developed to specify two other parameters, i.e., Q-factor of high-oscillatory wavelets and

  6. 应用马尔科夫状态图法进行可靠性评估%Evaluation of Reliability of a Fault-tolerance Computer System by Markov Status Graph Evaluation of Reliability of a Fault-tolerance Computer System by Markov Status Graph



    应用马尔科夫状态图法,对一个实际的硬件式可修容错计算机系统进行了可靠性评估。并针对两种容错方式分别得出各自的评估数据,通过实际的数据分析了其优缺点及最佳适用范围。%In this paper, the reliability of a fault-tolerance computer system is evaluated by Markov status graph. Majority voting method and single store method are used to evaluate the reliability and usability of the fault-tolerance system. Through practical computation, the comparison data are also given.

  7. The Climatic Role in Formation of Fault-Offset Geomorphic Features: Reliable Measurements for Slip-Per-Event Studies

    Salisbury, J. B.; Arrowsmith, J. R.; Rockwell, T. K.; Haddad, D.; Zielke, O.; Maddugo, C.


    Analyses of active fault zones have burgeoned with the availability of high-resolution topographic data. Airborne and terrestrial light detection and ranging (LiDAR) datasets are now publicly available via web-based repositories such as and provide a means to remotely analyze fault-offset geomorphic features. Because these features (e.g., stream channels and alluvial bars) can be preserved in a landscape for centuries or more, it is important to understand the frequencies and conditions under which they form and to determine whether these conditions are the result of a localized storm event or a more widespread climate signal. Typically, slip-per-event studies in southern California along the San Andreas and San Jacinto Faults have assumed that channels form locally and more frequently than the surface-rupturing earthquakes that offset them; clusters of similarly displaced stream channels are attributed to the number of earthquakes that have occurred since channel formation. In an effort to test this widely accepted hypothesis, we present new measurements of fault-offset stream channels for the creeping section of the central San Andreas fault (SAF) where large ground rupturing earthquakes are not expected. Analysis of Northern California EarthScope LiDAR Project data for small-scale fault-offset geomorphic features has initially revealed 41 offset stream channels with a minimum offset magnitude of ~5 m, however, several 2-3 m offsets are present. However, in an area with steady aseismic creep, one would expect a completely random distribution of offset channel magnitudes if channel formation is localized and random. The noticeable 5 m minimum-offset cluster throughout the creeping SAF suggests that for this entire area, channel formation is systematic. We suggest that widespread, climate-driven channel incision events control channel formation in central and southern California and that they are manifest as clusters of offset magnitudes in

  8. BRAM存储器EDAC容错技术可靠性分析%The BRAM Reliability Analysis with EDAC Fault-Tolerant Technology

    伊小素; 邓燕; 潘雄; 江云天; 张家铭


    In space flight, the embedded high-density BlockRAM memories are susceptible to single-event upsets {SEUa) as the user storage resource in SRAM-6ased FPGA, which result in failure of the user data. Thus the EDAC technology is widely used as fault-tolerant method. In the development of commercial SRAM-FPGA, the validity of EDAC is affected by the encoding and decoding module. The commercial SRAM-FPGA BRAM memory reliability model with EDAC fault-tolerant technology is proposed, while taking into account the reliability q/"EDAC encoding and decoding module. The reliability parameters boundary condition of encoding and decoding module is obtained for improving the BRAM reliability. Finally, the simulation shows a reasonable approximation of the relation and the correctness of the boundary condition, which provides a reference for the project feasibility analysis by the use of BRAM memory with EDAC fault-tolerant technology.%SRAM型FPGA内部高密度BRAM存储模块作为用户存储资源,在空间运行中易受单粒子翻转效应影响,造成用户数据失效,EDAC技术被广泛采用作为其容错手段.对于商用型SRAM - FPGA,编码/解码模块可靠性对EDAC容错技术有效性具有很大影响,因此本文在考虑编码/解码模块可靠性影响情况下,对商用SRAM - FPGA内嵌BRAM存储器进行EDAC容错技术可靠性建模,并得到提高BRAM可靠性需满足的编码/解码模块的可靠生参数限制条件关系式,最后通过仿真验证其模型的合理性及限制条件关系式的正确性,为相关工程设计中SRAM型FPGA的BRAM存储器EDAC容错技术的可行性设计提供指导

  9. Improvement of the reliability graph with general gates to analyze the reliability of dynamic systems that have various operation modes

    Shin, Seung Ki [Div. of Research Reactor System Design, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); No, Young Gyu; Seong, Poong Hyun [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)


    The safety of nuclear power plants is analyzed by a probabilistic risk assessment, and the fault tree analysis is the most widely used method for a risk assessment with the event tree analysis. One of the well-known disadvantages of the fault tree is that drawing a fault tree for a complex system is a very cumbersome task. Thus, several graphical modeling methods have been proposed for the convenient and intuitive modeling of complex systems. In this paper, the reliability graph with general gates (RGGG) method, one of the intuitive graphical modeling methods based on Bayesian networks, is improved for the reliability analyses of dynamic systems that have various operation modes with time. A reliability matrix is proposed and it is explained how to utilize the reliability matrix in the RGGG for various cases of operation mode changes. The proposed RGGG with a reliability matrix provides a convenient and intuitive modeling of various operation modes of complex systems, and can also be utilized with dynamic nodes that analyze the failure sequences of subcomponents. The combinatorial use of a reliability matrix with dynamic nodes is illustrated through an application to a shutdown cooling system in a nuclear power plant.

  10. Fault Management for Efficient Data Gathering in Wireless Sensor Networks

    M.Y. Mohamed Yacoab


    Full Text Available Wireless Sensor Networks (WSNs are naturally fault-prone owing to the common wireless communication medium, severe developed environments and resources limitation. In data gathering, node and network failures are common in WSNs. It is also essential for the WSN to be able to detect faults early and establish revival actions in order to avoid ruin of service due to faults. In this study we propose a fault management scheme which can efficiently gather data in wireless sensor networks. Our fault management scheme is capable of detecting network faults and node faults along with fault recovery. Initially, we assign some nodes as Reliable nodes (R nodes in the data aggregation tree, to perform accurate fault discovery and recovery. These R nodes collects the details of residual battery power and signal strength of all intermediate nodes. Node faults are detected by comparing the data values of each node with its neighbor and link failure are detected by estimating the Signal to Noise Ratio (SNR and Link Quality Indicator (LQI. In case of any link failure in the network, the succeeding R node will send a failure warning message to the previous R node and will then try to forward the packet to the next R node via an alternate path. By simulation results, we show that our proposed technique achieves good packet delivery ratio with reduced energy consumption and delay.

  11. Some fundamental aspects of fault-tree and digraph-matrix relationships for a systems-interaction evaluation procedure

    Alesso, H.P.


    Recent events, such as Three Mile Island-2, Brown's Ferry-3, and Crystal River-3, have demonstrated that complex accidents can occur as a result of dependent (common-cause/mode) failures. These events are now being called Systems Interactions. A procedure for the identification and evaluation of Systems Interactions is being developed by the NRC. Several national laboratories and utilities have contributed preliminary procedures. As a result, there are several important views of the Systems Interaction problem. This report reviews some fundamental mathematical background of both fault-oriented and success-oriented risk analyses in order to bring out the advantages and disadvantages of each. In addition, it outlines several fault-oriented/dependency analysis approaches and several success-oriented/digraph-matrix approaches. The objective is to obtain a broad perspective of present options for solving the Systems Interaction problem.

  12. Fault tolerant computing systems

    Randell, B


    Fault tolerance involves the provision of strategies for error detection, damage assessment, fault treatment and error recovery. A survey is given of the different sorts of strategies used in highly reliable computing systems, together with an outline of recent research on the problems of providing fault tolerance in parallel and distributed computing systems. (15 refs).

  13. 镁铝粉尘爆炸事故树分析与控制措施%Fault Tree Analysis and Control on Magnesium-Aluminum-Dust-Explosion

    周德红; 李文; 冯豪; 张飞; 王倩; 赵栋


    镁铝粉尘爆炸事故是典型的金属粉尘爆炸事故,也是造成二次爆炸事故威力最大的伤亡损失事故之一。在基于分析镁铝粉尘燃烧爆炸机理的基础上,运用事故树分析法对镁铝粉尘爆炸的原因事件进行分析。通过镁铝金属粉尘爆炸事故树的最小径(割)集和结构重要度分析,主要从防止金属粉尘积聚到爆炸极限和防止金属粉尘遇到点火源两处方面提出了预防镁铝金属粉尘爆炸事故的对策措施,为了更好地预防镁铝金属粉尘爆炸事故地发生、实施安全生产管理提供技术支持和参考依据。%Magnesium-aluminum-dust-explosion accident mainly refers to metal dust explosion accident and is one of the powerful accidents causing casualties when the secondary explosion occurs. Based on the analysis of magnesium-aluminum-dust-explosion combustion mechanism, this paper analyzs the causes of the acciddents of magnesium-aluminium-dust-explosions via fault tree analysis. According to the analysis of minimal path sets and structure importance of magnesium aluminum dust explosion fault tree,countermeasures to prevent dust explosion are presented concerning prevention of dust accumulation to explosion limit and preventing dust from contacting ignition source. The concrete prevention measures are also presented.

  14. The reliability model of the fault-tolerant computing system with triple-modular redundancy based on the independent nodes

    Rahman, P. A.; Bobkova, E. Yu


    This paper deals with a reliability model of the restorable non-stop computing system with triple-modular redundancy based on independent computing nodes, taking into consideration the finite time for node activation and different node failure rates in the active and passive states. The obtained by authors generalized reliability model and calculation formulas for reliability indices for the system based on identical and independent computing nodes with the given threshold for quantity of active nodes, at which system is considered as operable, are also discussed. Finally, the application of the generalized model to the particular case of the non-stop restorable computing system with triple-modular redundancy based on independent nodes and calculation examples for reliability indices are also provided.

  15. Research on the Diagnosis Decision-making of Key Units Based on Ontology and Fault Tree%基于本体故障树的关键机组诊断决策研究

    于德介; 赵丹; 周安美


    In order to meet the requirements of locating fault causes of continuous work equipments or units in petrochemical enterprise quickly,an ontology based fault tree construction method was proposed.In the proposed method,the fault tree is generated from domain ontology,and then the ratio of efficiency to time for fault diagnosis is obtained through the quantitative analysis of the fault tree.At last,the optimal fault diagnosis path can be obtained according to the descending order of the ratio of efficiency to time for fault diagnosis.This method combines the advantages of ontology and fault tree,and it realizes rapid fault causes locating based on knowledge sharing and reuse.Application example shows that the efficiency of fault diagnosis can be increased and the costs of enterprise's maintenance can be reduced by using the proposed method.%为了满足石化企业连续性工作设备或机组在发生故障后对故障原因进行快速定位的要求,将本体先进的知识表示方法引入到成熟的故障树研究中,提出了基于本体的故障树构建方法,并通过对生成的故障树进行定量分析,计算出故障判明效时比,以其从大到小的顺序为依据找到故障诊断最优路径,实现了本体和故障树的优势结合.该方法在知识共享和重用的基础上,实现对故障的快速诊断定位,从而提高了故障诊断效率,减少了企业的生产维护成本.

  16. Application of fault tree analysis on fire and blast accidents of LPG tank%事故树分析法在LPG储罐火灾爆炸事故中的应用

    郝彩霞; 许彦; 龚声武


    LPG (liquefied petroleum gas) is one of the usual dangerous chemicals. Contrast to the common chemical container, the chance of fire and blast accidents caused by LPG tank are larger, which means accidents caused by LPG tank will give rise to great losses and severe damages. So the study on the fire and blast accidents of LPG tank has a great significance. In view of the causation, the LPG tank accident can be classify into two different models, one is destruction of the chemical, the other is physical fire and explosion. In this paper the two types of accident of the LPG tank were analyzed, whick focused on the factors that cause fire and blast accident and physical blast accident of the LPG tank. The fault trees model was established with fire and blast accident and physical blast accident of the LPG tank as the top event. Through the qualitative analysis of these fault trees, all the minimum cut-sets affecting the top event were obtained. By calculating structure importance degree of the basic event, the primary factors which affect the accident of the LPG storage tank were confirmed. According to these results, corresponding measures were put forward so that the safety and reliability of LPG tanks could be ensured and improved.%LPG(液化石油气)属于危险化学品之一,LPG储罐发生火灾爆炸的机率大,造成的损失比较严重,故对其火灾爆炸事故进行研究具有重要意义.LPG储罐爆炸根据其发生机理分为化学爆炸(燃爆)和物理爆炸两种模式.本文通过对LPG储罐燃爆、物理爆炸两类事故进行系统分析,建立了以LPG储罐燃爆、物理爆炸为顶事件的事故树.通过对其事故树的定性分析,得到了影响顶事件的各个最小割(径)集.通过计算底事件的结构重要度,确定了影响LPG储罐火灾爆炸事故的主要因素,并提出了相应的改进措施,进而提高LPG储罐的安全性和运行可靠性.

  17. 防空导弹飞行中其安全系统失效的故障树分析%Fault Tree Analysis of the Safe-arming of an Air-faced Missile in Flight

    高培旺; 马晓青


    建立了防空导弹在飞行过程中其安全系统失效故障树的一般模型,由此分析和确定引起安全系统故障的各种因素及模式,给出系统故障概率的近似计算公式。%This paper establishes a generic model of fault tree of the safe-arming of an air-faced missile in flight, by which we finds out various fault factors and fault modes, and gives an approximate formula of the fault prlbability of the safearming in flight.

  18. Reliability modelling of repairable systems using Petri nets and fuzzy Lambda-Tau methodology

    Knezevic, J.; Odoom, E.R


    A methodology is developed which uses Petri nets instead of the fault tree methodology and solves for reliability indices utilising fuzzy Lambda-Tau method. Fuzzy set theory is used for representing the failure rate and repair time instead of the classical (crisp) set theory because fuzzy numbers allow expert opinions, linguistic variables, operating conditions, uncertainty and imprecision in reliability information to be incorporated into the system model. Petri nets are used because unlike the fault tree methodology, the use of Petri nets allows efficient simultaneous generation of minimal cut and path sets.

  19. Fault locator of an allyl chloride plant

    Savković-Stevanović Jelenka B.


    Full Text Available Process safety analysis, which includes qualitative fault event identification, the relative frequency and event probability functions, as well as consequence analysis, was performed on an allye chloride plant. An event tree for fault diagnosis and cognitive reliability analysis, as well as a troubleshooting system, were developed. Fuzzy inductive reasoning illustrated the advantages compared to crisp inductive reasoning. A qualitative model forecast the future behavior of the system in the case of accident detection and then compared it with the actual measured data. A cognitive model including qualitative and quantitative information by fuzzy logic of the incident scenario was derived as a fault locator for an ally! chloride plant. The obtained results showed the successful application of cognitive dispersion modeling to process safety analysis. A fuzzy inductive reasoner illustrated good performance to discriminate between different types of malfunctions. This fault locator allowed risk analysis and the construction of a fault tolerant system. This study is the first report in the literature showing the cognitive reliability analysis method.

  20. Fault Analysis of Online Commodity Shopping Service Based on Fault Tree Analysis%基于故障树方法的在线购物服务失误分析



    提升顾客满意度一直是电商们的主要改进目标。为了提升顾客满意度,就必须先明确为什么服务会失误,得出影响服务失误的关键因素。从而去更好的改进服务水平。文中应用故障树方法对在线购物服务失效进行分析,并得出服务失效的关键因素,同时通过仿真进行了验证该方法的有效性和可行性。%It's a long time that E -business man take to improve the Customer Satisfaction Index as the major problem.In order improve Customer Satisfaction Index.The reason why service is failed and get the key point influence the problem.Then to get a better service quality.This paper choice Fault Tree Analysis to online shopping service failure,and get the key factory, through simulation verified the effectiveness and feasibility of the method.

  1. 基于智能容错技术的雷达软件可靠性研究%A Study on Radar Software Reliability Based on Intelligent Fault-tolerating

    刘旭; 胡未琼; 戴伟


    In order to ensure the radar works stably in fighting against the enemies, the software reliability of the radar embedded data processing system must be improved and the ability of fault-tolerating must be enhanced. In this paper which based on the deep research of software reliability, a variety of methods in the aspect of software framework designing and software design processing at the stage of fault-avoiding is offered, and a design of intelligent monitoring software which uses the key techniques of fault detecting, fault restoring and fault isolating at the stage of fault-tolerating is put forward and also the detailed exposition on the softwares structure and fault-tolerating processing is made. These techniques of software reliability ensure that the radar system works stably.%为保障雷达能够在对敌作战中持久稳定地工作,必须提高雷达嵌入式数据处理软件的可靠性,加强软件系统的容错能力.通过对软件可靠性技术领域的深入研究,文中在软件避错阶段针对软件架构设计以及软件开发过程方面提出一系列方法;同时在软件容错阶段利用故障检测、故障恢复及故障隔离等关键技术设计出智能监控软件方案,并对其软件结构和容错处理流程进行详细阐述.采用上述可靠性措施可以保障系统健壮稳定地运行.

  2. Fault Tree Analysis for Red Oil Explosion in Reprocessing Facility%后处理设施的红油爆炸故障树分析

    王任泽; 王学新; 庄大杰; 曹芳芳


    Almost all spent fuel reprocessing facilities have adopted Purex process .T he red oil explosion is a great concern in safety study of spent fuel reprocessing facilities adopting Purex process .The event tree and fault tree analysis was performed for the red oil explosion of a medium level radioactive waste liquid evaporator for the collective decontamination and separation cycle segment in a representative reprocessing facility in this paper . The results show that the occurrence frequency of a red oil explosion is extremely low ,and human errors and common cause failures are major causes to a red oil explosion . Therefore , some relevant measures should be taken to prevent such accidents .%目前世界上几乎所有的乏燃料后处理设施均选用 Purex流程。红油爆炸事故是 Purex流程后处理设施安全研究的焦点问题之一。本文对典型后处理设施共去污分离循环工段的中放废液蒸发器的红油爆炸事故进行了事件树-故障树分析。结果显示,红油爆炸事故的发生频率极低;人因失误和共因失效对整个红油爆炸事故的贡献很大。应采取相应措施,以预防事故的发生。

  3. Tools for developing a quality management program: proactive tools (process mapping, value stream mapping, fault tree analysis, and failure mode and effects analysis).

    Rath, Frank


    This article examines the concepts of quality management (QM) and quality assurance (QA), as well as the current state of QM and QA practices in radiotherapy. A systematic approach incorporating a series of industrial engineering-based tools is proposed, which can be applied in health care organizations proactively to improve process outcomes, reduce risk and/or improve patient safety, improve through-put, and reduce cost. This tool set includes process mapping and process flowcharting, failure modes and effects analysis (FMEA), value stream mapping, and fault tree analysis (FTA). Many health care organizations do not have experience in applying these tools and therefore do not understand how and when to use them. As a result there are many misconceptions about how to use these tools, and they are often incorrectly applied. This article describes these industrial engineering-based tools and also how to use them, when they should be used (and not used), and the intended purposes for their use. In addition the strengths and weaknesses of each of these tools are described, and examples are given to demonstrate the application of these tools in health care settings.

  4. 中波HgCdTe光导探测器组件的故障树和失效研究%Study on HgCdTe Detector Assemble Fault Tree and Failure Analysis

    王韡; 许金通; 周青; 张立瑶; 李向阳


    Discussed are the reliability problems of HgCdTe(MCT) infrared photoconductive detectors working at near room temperature,including package failure,chip bonding failure and performance attenuation.Based on collecting the failure data of the detectors,fault tree analysis(FTA) was built by analyzing the failure mechanism of physics and chemistry,manufacturing process and parameters of the detectors.Minimal cut sets of FTA were obtained from qualitative analysis and the failure probability of top event was calculated.The failure modes in detectors,structures and process were analyzed.%讨论了近室温工作的HgCdTe中波光导探测器组件的可靠性问题,包括组件封装失效、引线键合失效和探测器的性能衰减等。通过收集探测器组件的失效信息,对其失效物理化学机制、制造工艺和探测器参数进行了分析,建立了组件的故障树(FTA),为探测器组件的失效分析提供了理论依据。由FTA定性分析得出探测器组件FTA的最小割集;计算了顶事件的失效几率。通过计算底事件概率重要度,得出组件封装失效是探测器组件失效的主要故障途径;同时实验发现,失效组件探测器的少子寿命值有较大的衰减,这可能起源于失效探测器的表面钝化层退化。

  5. Warranty Cost Analysis for Product Family Based on Fault Tree Mapping%基于故障树映射的产品族保证成本分析

    刘一骝; 刘子先


    针对当前制造企业的产品通常以产品族而不是单一产品的形式存在的现实,对现有的基于单一产品的保证成本计算模型进行了改进,并指出产品族保证成本计算取决于配置产品的元件的可靠性.通过逆向搜索的方法,元件可靠性可以根据故障树模型向BOM模型映射得到.作者通过一个笔记本电脑的案例说明文中方法的操作过程,并比较了企业采用FRW和PRW两种策略时保证成本的差异.%Currently, product warranty cost is calculated based on individual products. However, today, warranty is always offered with respect to product family rather than individual products. Thus, new method is necessary for product warranty cost calculation. In this paper, the existing models for individual products are modified to adapt to product family. In the new model, module reliability is defined through the mapping from the fault tree model to the bill of material (BOM) model by using inverse search. The warranty cost calculation for laptop computer is used to show the application of the proposed method. The results are compared with the existing method such as free replacement warranty (FRW) and pro-rata warranty ( PRW). It shows that the proposed method is effective.

  6. Fault tree analysis on decreases of desalination rate and permeate flow rate of seawater reverse osmosis desalination system%反渗透海水淡化系统“脱盐率与产水量下降”故障树分析

    姜周曙; 翁翔彬; 王剑; 雷淳正


    故障树分析是一种逻辑演绎的故障诊断方法,在核反应堆和航天器可靠性等领域已得到成功应用。反渗透法是目前应用最广泛的海水淡化方法。“脱盐率与产水量下降”是反渗透海水淡化系统中最为典型且损失重大的故障类型。基于对反渗透海水淡化膜组件结构和系统工作流程与机理的深入分析,给出了“脱盐率与产水量下降”的故障树;利用布尔代数求出最小割集及最小径集,完成了对故障基本事件的结构重要度分析,对故障基本事件进行了危险等级划分并提出了上述故障的处理方法。研究工作为超大规模反渗透海水淡化故障诊断专家系统中知识库的构建提供了一套科学实用的方法。%Fault tree analysis (FTA) is a deductive fault diagnosis, which has been successfully applied in such areas as the assessment of reliability of nuclear reactors and spacecrafts. Currently reverse osmosis (RO) is the most widely used seawater desalination methodology. The decline of both desalination rate and permeate flow rate is considered the most typical type of fault which causes significant loss in the seawater reverse osmosis (SWRO) system. Based on an in-depth analysis of the component structure and operational principle of the seawater reverse osmosis membrane, this paper manages to work out the fault tree of the decline of desalination rate and permeate flow rate. With the help of Boolean algebra, the minimal cut sets and minimal path sets were successfully established, and the analysis of the importance of basic events structure was finally completed. This research provides a set of scientific and practical methods for the construction of the knowledge base in the SWRO fault diagnosis expert system.

  7. Integrated Reliability and Risk Analysis System (IRRAS)

    Russell, K D; McKay, M K; Sattison, M.B. Skinner, N.L.; Wood, S T [EG and G Idaho, Inc., Idaho Falls, ID (United States); Rasmuson, D M [Nuclear Regulatory Commission, Washington, DC (United States)


    The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a microcomputer. This program provides functions that range from graphical fault tree construction to cut set generation and quantification. Version 1.0 of the IRRAS program was released in February of 1987. Since that time, many user comments and enhancements have been incorporated into the program providing a much more powerful and user-friendly system. This version has been designated IRRAS 4.0 and is the subject of this Reference Manual. Version 4.0 of IRRAS provides the same capabilities as Version 1.0 and adds a relational data base facility for managing the data, improved functionality, and improved algorithm performance.

  8. Reliability Assessment of Fuel Cell System - A Framework for Quantitative Approach

    Lee, Shinae; Zhou, Dao; Wang, Huai


    such as component failures, the system architecture, and operational strategies. This paper suggests an approach that includes Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA), and Reliability Block Diagram (RBD). For a case study, and the service lifetime of a commercial 5 kW Proton Exchange...

  9. Extending Failure Modes and Effects Analysis Approach for Reliability Analysis at the Software Architecture Design Level

    Sozer, Hasan; Tekinerdogan, Bedir; Aksit, Mehmet; Lemos, de Rogerio; Gacek, Cristina


    Several reliability engineering approaches have been proposed to identify and recover from failures. A well-known and mature approach is the Failure Mode and Effect Analysis (FMEA) method that is usually utilized together with Fault Tree Analysis (FTA) to analyze and diagnose the causes of failures.

  10. Validation of Land Cover Products Using Reliability Evaluation Methods

    Wenzhong Shi


    Full Text Available Validation of land cover products is a fundamental task prior to data applications. Current validation schemes and methods are, however, suited only for assessing classification accuracy and disregard the reliability of land cover products. The reliability evaluation of land cover products should be undertaken to provide reliable land cover information. In addition, the lack of high-quality reference data often constrains validation and affects the reliability results of land cover products. This study proposes a validation schema to evaluate the reliability of land cover products, including two methods, namely, result reliability evaluation and process reliability evaluation. Result reliability evaluation computes the reliability of land cover products using seven reliability indicators. Process reliability evaluation analyzes the reliability propagation in the data production process to obtain the reliability of land cover products. Fuzzy fault tree analysis is introduced and improved in the reliability analysis of a data production process. Research results show that the proposed reliability evaluation scheme is reasonable and can be applied to validate land cover products. Through the analysis of the seven indicators of result reliability evaluation, more information on land cover can be obtained for strategic decision-making and planning, compared with traditional accuracy assessment methods. Process reliability evaluation without the need for reference data can facilitate the validation and reflect the change trends of reliabilities to some extent.


    Kuznetsov Dmitriy Viktorovich


    Full Text Available The scenario of a hydrodynamic accident of water flow over a crest of a soil dam is considered by the method of fault tree analysis, for which the basic reasons and controlled diagnostic indicators of an accident have been defined. Logical operators “AND”/”OR” were used for creation of a sequence of logically connected events, leading to an undesired event in the scenario of accident. The scenario of the accident was plotted in case of three basic reasons - an excessive settling of a dam crest, an excess flood, an inoperable spillway, taking into account the sequence of the events’ development and with observance of the necessary conditions leading to an accident. “Technical” reasons were observed in the present scenario, force majeure events were not considered. The provided scenario of the accident consists of two branches of events’ development: the left one that depends on an upstream level, and the right one that depends on settling of a dam crest. In each of the considered events an accident “the water spill over a crest of a soil dam” is possible only in case of execution of two different conditions at the same time, i.e. in case of an appropriate upstream level and the appropriate mark of a crest of a soil dam. The conditions of the accident are defined by diagnostic indices - the upstream level and settling of a dam crest, which at the same time are safety criteria of the hydraulic structure for soil dams. They allow defining the technical condition of the construction. Four possible technical conditions are suggested for the definition of technical statuses - normative, operable, limited operable, abnormal. Criteria of safety are the boundaries of the state: for loading and impact - it is the upstream level, for geometrical compliance of the construction - it is a dam crest mark.

  12. Design and Implementation of a Fault Injection Mechanism for Software Reliability Evaluation%一种面向软件可靠性评估的故障注入机制的设计与实现

    胡嘉伟; 江建慧


    To improve the accuracy of the software reliability evaluation, more failure data of programs under evaluation are needed. This paper presents a fault injection mechanism for software reliability evaluation. The program fault type distribution, fault location distribution, fault occurring time distribution and inputs of the program are considered during the fault injection scheme generation. Therefore, the proposed mechanism can reasonably emulate the program failure. A fault injection scheme generator is implemented and integrated into an in-house PIN-based dynamic software fault injection system. The TINY compiler, LZ77 and CRC32 programs are chosen as target applications to verify the efficiency and reasonability of the proposed fault injection mechanism. Two groups of failure data are collected by testing and fault injection, respectively, and the Jelinski-Moranda model is used to get two sets of reliability attributes. The experimental results show that the fault injection based software reliability evaluation method is at least as efficient and reasonable as the conventional test based methods. It is more suitable for large scale programs, and the exponential distribution assumption is better for fault occurring time distribution.%为了获取更加全面的程序失效数据以提高软件可靠性评估的准确性,提出一种面向软件可靠性评估的故障注入机制.该机制在生成故障注入方案时充分考虑了程序故障类型分布、故障空间分布、故障发生时间分布及程序输入等因素,从而能够合理地反映程序真实的失效情况.实现了故障注入方案生成器,并集成到自行开发的基于Intel PIN框架的动态软件故障注入工具软件中.为了验证所提出的故障注入机制的合理性和有效性,以TINY语言编译器、LZ77压缩程序、CRC32程序为例,分别通过测试和故障注入实验的方式收集了相应的失效数据,然后用Jelinski-Moranda模型计算得到了2组

  13. Design of TV Fault Repair Model Based on Decision Tree Algorithm%基于决策树算法的电视机故障维修模型设计

    武彤; 程辉


    Before a television set comes into market,it is required to undergo a series of examination to guarantee its quality. Once a flaw is found,it will go to back shop to be doubly checked and repaired. The fault reason and fault component located are usually determined by their own working experience. It places very strict requirements on the workers,and cannot improve the repair efficiency. TV produc-tion line fault repair model based on the decision tree algorithm is researched which is able to accurately and quickly find out the relation-ship among the fault type,fault reason and product type. So it saves the time of looking for the fault reason and type,considerably eleva-ting the productivity of repairing.%在电视机生产线中,有许多产品质量控制检查点。产品在某个检查点查出存在质量问题,将进入返修线进行修理。在返修点由修理工人凭经验来确定故障原因及定位故障元器件类型,这样就对修理工有很高的要求,而且不能有效地提高维修工作效率。文中研究的基于决策树算法的电视机生产线故障维修模型,能够通过模型找出产品类型、故障现象与故障原因之间的关系,从而快速地确定故障类型,这样节省了查找故障原因及类型的时间,提高了维修效率。

  14. A Bypass-Ring Scheme for a Fault Tolerant Multicast

    V. Dynda


    Full Text Available We present a fault tolerant scheme for recovery from single or multiple node failures in multi-directional multicast trees. The scheme is based on cyclic structures providing alternative paths to eliminate faulty nodes and reroute the traffic. Our scheme is independent of message source and direction in the tree, provides a basis for on-the-fly repair and can be used as a platform for various strategies for reconnecting tree partitions. It only requires an underlying infrastructure to provide a reliable routing service. Although it is described in the context of a message multicast, the scheme can be used universally in all systems using tree-based overlay networks for communication among components.

  15. Application of Gray Correlation Fault Tree on Risks of Green Building Design%基于灰色关联故障树的绿色建筑设计风险研究

    刘静乐; 王恩茂


    绿色建筑的设计阶段决定了绿色建筑的功能,为了保证绿色建筑功能的实现,必须对绿色建筑的设计风险进行有效的管理。用故障树对绿色建筑的设计风险进行分析,找出易使设计方案出现问题的基本因素作为故障树的底事件。利用灰色关联进行分析,对故障树的底事件按照关联度的大小进行排序。再根据关联度找出最需要重视的底事件,并对其提出管理意见,以便在实际项目中进行管理与控制,保证设计的顺利进行。%The design of green building determines its function. Therefore,in order to ensure the implementation of green building features,risk of green building design must be effectively managed. Firstly,using fault tree, risks of green building design are analyzed to identify fundamental factors as the bottom of the fault tree events. Secondly,using gray correlation analysis,the bottom of the fault tree events are sorted in accordance with the degree of correlation. Finally,according to relevancy,the most important basic events is identified. Some suggestions are proposed to carry out the actual project management and control and to ensure the smooth progress of the design.

  16. 基于双树复小波变换的轴承故障诊断研究%Research on Bearing Fault Diagnosis Based on Dual--tree Complex Wavelet Transform



    提出了一种基于双树复小波变换解调技术的轴承故障诊断新方法。该方法利用双树复小波变换具有近似平移不变性、避免频率混叠和有效降噪的优点,首先对轴承故障振动信号进行双树复小波分解和重构,将振动信号分解成实部和虚部,然后计算振动信号的双树复小波幅值包络和包络谱。齿轮箱轴承故障振动实验信号的分析表明,该方法能在强噪声环境下准确提取轴承故障产生的周期性瞬态冲击信号,能有效消除频率混叠现象和强噪声的影响,能有效识别轴承内圈和外圈故障。%A novel method of bearing fault diagnosis based on demodulation technique of DTCWT. It is demonstrated that the proposed dual-tree complex wavelet transform has better shift invariance, reduced frequency aliasing effect and de-noising ability. The bearing fault vibration signals were firstly decomposed and recostructed using dual-tree complex wavelet transform. Then the real and i maginary parts were obtained and the vibration signals were amplitude demodulated. In the end, the amplitude envelope and wavelet envelope spectrum were computed. Therefore, the characteristics of the bearing faults can be recognized according to the wavelet envelope spectrum. The experimental resuits show that fault diagnosis based on dual-tree complex wavelet transform can diagnose bearing faults effectively under strong noise conditions and reduce spectral aliasing.

  17. Fault Tree Analysis of Fire and Explosion in Oil Storage Tank%油库储油罐火灾爆炸事故树分析



    Large quantity of oil in oil storage tank is highly flammable and explosive.If any accident happens,consequences are beyond measure.According to characteristics of broad area of the security management in oil storage tank,and by analysis of the influencing factors and conditions related to fire and explosion accident in the oil storage tank,integrated fault tree model is established.The logical relationship between the accident and the basic events is clarified by carrying out qualitative analysis,while the structure importance factors of the basic events are ranked by carrying out quantitative analysis.Therefore the emphasis part in which there is potential of fire and explosion is found,and reasonable strategy for setting the security monitoring points is worked out.The results can provide basic for decision-marking of informational application in security management.%油库储油罐储存的油料具有易燃易爆性且存储量大,一旦发生事故后果严重.针对油库储油罐安全管理点多面广的特点,分析储油罐火灾爆炸事故的相关影响因素和条件,建立完善的事故树模型.通过定性分析理清火灾爆炸事故与基本事件的逻辑关系,定量分析获得顶上事件发生的概率和各基本事件的结构重要度顺序,找出储油罐存在火灾爆炸事故隐患的重点部位,制订科学合理的安全信息监控点策略,为油库安全管理手段向信息化迈进,预防事故的发生提供决策依据.

  18. 一种状态事件故障树的定量分析方法%A Method for Quantitative Analysis of State/Event Fault Tree

    徐丙凤; 黄志球; 胡军; 魏欧; 肖芳雄


    State/Event Fault Tree (SEFT) is a modeling technique for describing the causal chains which lead to failure in complex systems .One important way for capturing the safety parameters of systems is quantitatively analyzing the probabilistic char-acteristic of system failures .As lack of precise semantics ,SEFT can only be quantitatively analyzed after its semantics being precise-ly described .In this paper ,we present a quantitative analysis method of SEFT based on Interactive Markov Chain (IMC) .Firstly ,In-terface Interactive Markov Chain (Interface-IMC) is proposed based on refining the interactive action of IMC into input and output actions .Secondly ,the precise semantics of SEFT is described based on Interface-IMC .Thirdly ,a quantitative analysis method is pre-sented based on formal semantic model of SEFT .Finally ,the method in this paper is illustrated by modeling and quantitatively ana-lyzing SEFT of aircraft landing gear system .%状态事件故障树是一种适合于描述复杂系统中失效因果链的建模技术,对系统失效结果的概率特性进行定量分析是获得系统安全性参数的一种重要途径。由于状态事件故障树是半形式化模型,需先精确描述其语义才能进行定量分析。为此,本文提出一种基于交互马尔可夫链的状态事件故障树定量分析方法。首先,通过将交互马尔可夫链的交互动作精化为输入和输出动作,提出接口交互马尔可夫链模型用于状态事件故障树的形式语义描述。然后,在此形式语义的基础上设计了一种状态事件故障树定量分析方法。最后给出了一个飞机起落架收放系统的状态事件故障树建模及概率特性定量分析的实例研究。

  19. A Novel Method for Detection and Classification of Covered Conductor Faults

    Stanislav Misak


    Full Text Available Medium-Voltage (MV overhead lines with Covered Conductors (CCs are increasingly being used around the world primarily in forested or dissected terrain areas or in urban areas where it is not possible to utilize MV cable lines. The CC is specific in high operational reliability provided by the conductor core insulation compared to Aluminium-Conductor Steel-Reinforced (ACSR overhead lines. The only disadvantage of the CC is rather the problematic detection of faults compared to the ACSR. In this work, we consider the following faults: the contact of a tree branch with a CC and the fall of a conductor on the ground. The standard protection relays are unable to detect the faults and so the faults pose a risk for individuals in the vicinity of the conductor as well as it compromises the overall safety and reliability of the MV distribution system. In this article, we continue with our previous work aimed at the method enabling detection of the faults and we introduce a method enabling a classification of the fault type. Such a classification is especially important for an operator of an MV distribution system to plan the optimal maintenance or repair the faulty conductors since the fall of a tree branch can be solved later whereas the breakdown of a conductor means an immediate action of the operator.

  20. 基于双树复小波包变换的滚动轴承故障诊断%Fault diagnosis of rolling bearing based on dual-tree complex wavelet packet transform

    胥永刚; 孟志鹏; 陆明


    The operation states of rolling bearings which are the most common and important parts in the mechanical equipment, will affect the whole machine operation condition directly. Due to the working environment of rolling, bearing is complicated, the fault vibration signal of rolling bearing is usually non-stationary, and the strong noise interference is contained in the vibration signal at the same time. So it is important to eliminate the noise interference and extract fault feature information effectively for the rolling bearing. Dual-tree complex wavelet packet transform is a new method of signal processing. Dual-tree complex wavelet packet transform has many good characteristics, for example, approximate shift invariance, good directional selectivity、perfect reconstruction, limited data redundancy, efficient computational efficiency and so on. The high frequency part of dual-tree complex wavelet transform that is not decomposed, is further decomposed by dual-tree complex wavelet packet transform, so as to improve the whole frequency band signal frequency resolution and reduce the loss of information. In view of the above situation, a new fault diagnosis method is proposed based on dual-tree complex wavelet packet transform and threshold de-noising. Firstly, the non-stationary fault signal is decomposed into several different frequency band components through dual-tree complex wavelet packet decomposition. Secondly, Kurtosis and the cross-correlation coefficient of each component are obtained and compared. Due to the kurtosis reflecting the signal variations, if the kurtosis value is bigger, the degree of the change of signal is bigger too. The correlation coefficient can reflect the proximity between the component and the original signal at the same time, the correlation coefficient is bigger, the more similar with the original signal. Finally, the components that have a bigger value are chosen to be de-noised by a soft threshold and reconstructed by dual-tree

  1. Suitability review of FMEA and reliability analysis for digital plant protection system and digital engineered safety features actuation system

    Kim, I. S.; Kim, T. K.; Kim, M. C.; Kim, B. S.; Hwang, S. W.; Ryu, K. C. [Hanyang Univ., Seoul (Korea, Republic of)


    Of the many items that should be checked out during a review stage of the licensing application for the I and C system of Ulchin 5 and 6 units, this report relates to a suitability review of the reliability analysis of Digital Plant Protection System (DPPS) and Digital Engineered Safety Features Actuation System (DESFAS). In the reliability analysis performed by the system designer, ABB-CE, fault tree analysis was used as the main methods along with Failure Modes and Effect Analysis (FMEA). However, the present regulatory technique dose not allow the system reliability analysis and its results to be appropriately evaluated. Hence, this study was carried out focusing on the following four items ; development of general review items by which to check the validity of a reliability analysis, and the subsequent review of suitability of the reliability analysis for Ulchin 5 and 6 DPPS and DESFAS L development of detailed review items by which to check the validity of an FMEA, and the subsequent review of suitability of the FMEA for Ulchin 5 and 6 DPPS and DESFAS ; development of detailed review items by which to check the validity of a fault tree analysis, and the subsequent review of suitability of the fault tree for Ulchin 5 and 6 DPPS and DESFAS ; an integrated review of the safety and reliability of the Ulchin 5 and 6 DPPS and DESFAS based on the results of the various reviews above and also of a reliability comparison between the digital systems and the comparable analog systems, i.e., and analog Plant Protection System (PPS) and and analog Engineered Safety Features Actuation System (ESFAS). According to the review mentioned above, the reliability analysis of Ulchin 5 and 6 DPPS and DESFAS generally satisfies the review requirements. However, some shortcomings of the analysis were identified in our review such that the assumed test periods for several equipment were not properly incorporated in the analysis, and failures of some equipment were not included in the

  2. Faults Discovery By Using Mined Data

    Lee, Charles


    Fault discovery in the complex systems consist of model based reasoning, fault tree analysis, rule based inference methods, and other approaches. Model based reasoning builds models for the systems either by mathematic formulations or by experiment model. Fault Tree Analysis shows the possible causes of a system malfunction by enumerating the suspect components and their respective failure modes that may have induced the problem. The rule based inference build the model based on the expert knowledge. Those models and methods have one thing in common; they have presumed some prior-conditions. Complex systems often use fault trees to analyze the faults. Fault diagnosis, when error occurs, is performed by engineers and analysts performing extensive examination of all data gathered during the mission. International Space Station (ISS) control center operates on the data feedback from the system and decisions are made based on threshold values by using fault trees. Since those decision-making tasks are safety critical and must be done promptly, the engineers who manually analyze the data are facing time challenge. To automate this process, this paper present an approach that uses decision trees to discover fault from data in real-time and capture the contents of fault trees as the initial state of the trees.

  3. Analysis of Syetem Reliability in Manufacturing Cell Based on Triangular Fuzzy Number

    ZHANG Caibo; HAN Botang; SUN Changsen; XU Chunjie


    Due to lacking of test-data and field-data in reliability research during the design stage of manufacturing cell system. The degree of manufacturing cell system reliability research is increased. In order to deal with the deficient data and the uncertainty occurred from analysis and judgment, the paper discussed a method for studying reliability of manufacturing cell system through the analysis of fuzzy fault tree, which was based on triangular fuzzy number. At last, calculation case indicated that it would have great significance for ascertaining reliability index, maintenance and establishing keeping strategy towards manufacturing cell system.

  4. Experimental Study of Water Tree Affecting the Reliability of XLPE Cable Insulation%水树枝影响交联聚乙烯电缆绝缘可靠性的试验研究

    沈庆河; 郑晓泉; 刘嵘; 王金锋; 刘辉


    水树枝生长速度较慢,主要影响聚烯烃绝缘电力电缆的寿命;电树枝生长速度较快,主要影响电缆的可靠性。在高频恒定电压(15kV、20kV)下研究交联聚乙烯电缆中水树枝的生长规律,发现聚烯烃绝缘中的水树枝或电树枝存在相互转化的可能性。试验结果表明:干燥的水树枝引发电树枝的几率最高,湿润水树枝引发电树枝的几率最低,水树枝会影响电缆绝缘的可靠性。%Water trees grow very slowly and mainly affect the life of polyolefin insulation power cable. Electrical trees grow very fast and mainly affect the reliability of cable. The growth rule of water tree in XLPE cable under high frequency and constant voltage was studied, and the possibility of mutual transformation between water tree and electrical tree in the polyolefin insulation was found. The results show that the probability of electrical tree intiated by dry water tree and wet water tree is the highest and lowest respectively, and the water tree would affect the reliability of cable insulation.

  5. Discrete event simulation versus conventional system reliability analysis approaches

    Kozine, Igor


    Discrete Event Simulation (DES) environments are rapidly developing and appear to be promising tools for building reliability and risk analysis models of safety-critical systems and human operators. If properly developed, they are an alternative to the conventional human reliability analysis models...... and systems analysis methods such as fault and event trees and Bayesian networks. As one part, the paper describes briefly the author’s experience in applying DES models to the analysis of safety-critical systems in different domains. The other part of the paper is devoted to comparing conventional approaches...

  6. 基于故障树的应急预案诊断方法研究%Research on a Diagnostic Method for Emergency Plans Based on Fault Tree

    荣莉莉; 鲁荣辉


    对应急预案进行诊断有利于对预案的修订与完善.从故障诊断角度提出一种预案评估方法.根据预案文本中出现的主、谓、宾等语义故障,建立预案标准故障树;然后依据应急过程将待诊断预案分解成四部分,表示成句子集合的形式;依据故障树,用逻辑推理诊断法对这些句子进行诊断,从而确定预案的具体缺陷.最后采用一个实际的地震预案进行了实例研究,确定其需要加强和完善的方面,并量化地得到该预案的故障率,为修订和完善应急预案提供有针对性的参考依据.%Diagnosing released emergency plans benefits a lot for the revision and improvement of emergency plans. From the perspective of fault diagnosis, this paper proposed a method of evaluating emergency plans. According to the common semantic "failures" , such as ' subject failure" , " object failure" , " predicate failure" occurred in emergency plans, a standard fault tree of emergency plans was established; Then breaking the diagnosed plan down into four parts in line with the contingency task, each part was further broke down into sentences; Afterwards, using logical reasoning diagnosis method to diagnose these sentences based on the standard fault tree in order to find the specific defects of the plan. Finally, a case study was conducted taking an actual earthquake emergency plan as an example. Some aspects needing to be strengthened were found and the fault rate was quantified, which provided specific reference to revise and improve the emergency plan.

  7. FIPES: A new fault injection method for wireless sensor network reliability evaluation%FIPES:一种新的故障注入评测无线传感器网络及其可靠性方法

    黄旭; 陈冬岩; 李会; 邵珠瑜; 于磊磊


    In wireless sensor networks (WSNs), reliability and fault tolerance are the important specifications to evaluate the performance of WSNs. Although many WSNs protocols have achieved a good performance under laboratory and simulation circumstances, however in actual deployment, complex environment can lead to some problems, such as system abnormal, communication interruption, packet loss, reliability decline and etc. Because of the restrictions of application environment, it is difficult to carry out system debugging and failure analysis. In this paper we present a new method of injecting faults into WSNs artificially. Through simulating the scene interference and observing the change of the network, we can evaluate the reliability and fault tolerance of the network. We can find a way to improve the network performance through analyzing the change of the network after injecting faults. Using pairs of WSNs node and FIPES node, we evaluated this system in a five-storey office. Experimental results show that the FIPES can inject various kinds of fault into WSNs effectively, and PIPES can evaluate WSNs performance specifications such as reliability, packet loss rate and etc.%在无线传感器网络(wireless sensor networks,WSNs)中,可靠性和容错性是评价WSNs性能的重要指标.尽管在实验室和仿真环境中很多WSNs协议均可取得良好的性能,但是在实际部署后,复杂的现场环境常会导致网络出现系统异常、通信中断、数据包丢失、可靠性下降等问题.由于现场环境限制,进行系统调试和故障分析变得非常复杂.提出一种在实验环境中向WSNs网络人为注入模拟现场干扰的故障,并通过观察注入故障后网络的反应以评价网络的可靠性和容错性的系统结构和实现方法.通过分析故障注入(fault injection,FI)后的网络性能,可以有针对性地对网络机制作出改进来提高网络的可靠性和稳定性.在一栋办公楼内分别用WSNs节点和故

  8. Fault Estimation

    Stoustrup, Jakob; Niemann, H.


    This paper presents a range of optimization based approaches to fault diagnosis. A variety of fault diagnosis prob-lems are reformulated in the so-called standard problem setup introduced in the literature on robust control. Once the standard problem formulations are given, the fault diagnosis pr...... problems can be solved by standard optimization tech-niques. The proposed methods include: (1) fault diagnosis (fault estimation, (FE)) for systems with model uncertainties; (2) FE for systems with parametric faults, and (3) FE for a class of nonlinear systems.......This paper presents a range of optimization based approaches to fault diagnosis. A variety of fault diagnosis prob-lems are reformulated in the so-called standard problem setup introduced in the literature on robust control. Once the standard problem formulations are given, the fault diagnosis...

  9. Reliable control using the primary and dual Youla parameterizations

    Niemann, Hans Henrik; Stoustrup, J.


    in connection with reliable control and feedback control with fault rejection. The main emphasis is on fault modeling. A number of fault diagnosis problems, reliable control problems, and feedback control with fault rejection problems are formulated/considered, again, mainly from a fault modeling point of view......Different aspects of modeling faults in dynamic systems are considered in connection with reliable control (RC). The fault models include models with additive faults, multiplicative faults and structural changes in the models due to faults in the systems. These descriptions are considered....... Reliability is introduced by means of the (primary) Youla parameterization of all stabilizing controllers, where an additional loop is closed around a diagnostic signal. In order to quantify the level of reliability, the dual Youla parameterization is introduced which can be used to analyze how large faults...

  10. 故障容错光交叉通道数据链路的可靠性%Reliability of a Fault Tolerant Optical Cross-channel Data Link

    王新华; 甄子洋; 龚华军; 杨一栋


    Optical cross-channel data link (OCCDL) Is an important part for data exchange among the fly-by-light redundancy flight control computers. In order to improve the reliability of OCCDL system, a new OCCDL system with multi-link fault tolerant capability is designed. The structure of the OCCDL is given and the workflows of the OCCDL system under the conditions of normal operation and fault operation are analyzed. The fault-tolerant logical algorithms of its main component parts such as optical switch and optical link are designed. A Markov chain-based stability model of OCCDL system is established, and the fault probability calculations of optical link, optical switch, field programmable gate array(FPGA) and double-ports random access memory(RAM) are analyzed. The numerical simulation results show that the reliability and stability of OCCDL system are significantly improved. Moreover, the OCCDL system has the traits of real-time and practicality.%光交叉通道数据链路(OCCDL)是光传飞行控制系统余度计算机之间进行数据交换的重要途径.为了提高OCCDL系统的可靠性,提出一种新的具有多链路故障容错能力的OCCDL系统.给出了该OCCDL系统的结构配置,分析了系统正常工作和故障工作情况下的工作流程,设计了系统光开关故障、光链路等关键部分的故障容错逻辑,建立了基于马尔可夫链的OCCDL系统可靠性模型,分析了光链路、光开关、现场可编程门阵列(FPGA)和双口随机存取存储器(RAM)等组成部分的故障概率计算问题.数值仿真结果表明,与传统数据链路系统相比,该OCCDL系统的可靠度和稳定度均得到了显著提高,并且具有良好的实时性和工程实用性等特点.

  11. Fault-tolerant design

    Dubrova, Elena


    This textbook serves as an introduction to fault-tolerance, intended for upper-division undergraduate students, graduate-level students and practicing engineers in need of an overview of the field.  Readers will develop skills in modeling and evaluating fault-tolerant architectures in terms of reliability, availability and safety.  They will gain a thorough understanding of fault tolerant computers, including both the theory of how to design and evaluate them and the practical knowledge of achieving fault-tolerance in electronic, communication and software systems.  Coverage includes fault-tolerance techniques through hardware, software, information and time redundancy.  The content is designed to be highly accessible, including numerous examples and exercises.  Solutions and powerpoint slides are available for instructors.   ·         Provides textbook coverage of the fundamental concepts of fault-tolerance; ·         Describes a variety of basic techniques for achieving fault-toleran...

  12. Use of Sequent Peak Algorithm Drought Severity Index and Hydroclimatic Reconstructions from Tree-Rings to Inform Water Supply Reliability Planning

    Bray, B. S.; Palhegyi, G.


    California is in the midst of a severe drought with below average runoff since WY 2012. Within this context, many water resource managers are scrutinizing water supply reliability assumptions for planning studies. Severe droughts represent a relatively rare phenomenon, occurring only a handful of times within our limited 100-year period of watershed runoff records. Furthermore, droughts may have different runoff magnitudes and durations that inherently present a challenge for direct comparisons of one drought with another. We use the sequent peak algorithm as a drought severity index (SPADSI) that accounts for both drought magnitude and duration relative to an assumed minimum release policy and fixed level-of-development (LOD) demand modeling framework. The SPADSI allows direct, quantitative evaluation of different policy options for lessening drought severity where, for example, layering a customer rationing policy onto model results reduced the SPADSI for the historical 1976-77 drought from 520 to 450 thousand acre-feet (TAF) and 1987-92 drought from 650 to 415 TAF for 2015 LOD. A strong correlation (R2 = 0.96) between Mokelumne River watershed runoff and tree-ring hydroclimate reconstructions for neighboring American and Stanislaus watersheds from Meko et al. (2014) was the basis for an extended 1100-year historical reconstruction of Mokelumne Watershed annual runoff. The reconstructed runoff timeseries is used to investigate extended historical drought durations for the Mokelumne Watershed where shorter one- to three-year droughts are most probable durations (>90%) whereas longer duration droughts lasting as long as 10 years such as occurred in 1776-85 are also possible, though much less likely. Applying the SPADSI to the reconstructed runoff timeseries showed that recent droughts e.g. 1929-34, 1976-77, and 1987-92 are all relatively severe within this millennial context, falling on the distribution tail of the extended SPADSI dataset. These findings are

  13. Reliability analysis and initial requirements for FC systems and stacks

    Åström, K.; Fontell, E.; Virtanen, S.

    In the year 2000 Wärtsilä Corporation started an R&D program to develop SOFC systems for CHP applications. The program aims to bring to the market highly efficient, clean and cost competitive fuel cell systems with rated power output in the range of 50-250 kW for distributed generation and marine applications. In the program Wärtsilä focuses on system integration and development. System reliability and availability are key issues determining the competitiveness of the SOFC technology. In Wärtsilä, methods have been implemented for analysing the system in respect to reliability and safety as well as for defining reliability requirements for system components. A fault tree representation is used as the basis for reliability prediction analysis. A dynamic simulation technique has been developed to allow for non-static properties in the fault tree logic modelling. Special emphasis has been placed on reliability analysis of the fuel cell stacks in the system. A method for assessing reliability and critical failure predictability requirements for fuel cell stacks in a system consisting of several stacks has been developed. The method is based on a qualitative model of the stack configuration where each stack can be in a functional, partially failed or critically failed state, each of the states having different failure rates and effects on the system behaviour. The main purpose of the method is to understand the effect of stack reliability, critical failure predictability and operating strategy on the system reliability and availability. An example configuration, consisting of 5 × 5 stacks (series of 5 sets of 5 parallel stacks) is analysed in respect to stack reliability requirements as a function of predictability of critical failures and Weibull shape factor of failure rate distributions.

  14. Fault tolerant software modules for SIFT

    Hecht, M.; Hecht, H.


    The implementation of software fault tolerance is investigated for critical modules of the Software Implemented Fault Tolerance (SIFT) operating system to support the computational and reliability requirements of advanced fly by wire transport aircraft. Fault tolerant designs generated for the error reported and global executive are examined. A description of the alternate routines, implementation requirements, and software validation are included.

  15. Reliability analysis for new technology-based transmitters

    Brissaud, Florent, E-mail: florent.brissaud.2007@utt.f [Institut National de l' Environnement Industriel et des Risques (INERIS), Parc Technologique Alata, BP 2, 60550 Verneuil-en-Halatte (France); Universite de Technologie de Troyes (UTT), Institut Charles Delaunay (ICD) and STMR UMR CNRS 6279, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Barros, Anne; Berenguer, Christophe [Universite de Technologie de Troyes (UTT), Institut Charles Delaunay (ICD) and STMR UMR CNRS 6279, 12 rue Marie Curie, BP 2060, 10010 Troyes cedex (France); Charpentier, Dominique [Institut National de l' Environnement Industriel et des Risques (INERIS), Parc Technologique Alata, BP 2, 60550 Verneuil-en-Halatte (France)


    The reliability analysis of new technology-based transmitters has to deal with specific issues: various interactions between both material elements and functions, undefined behaviours under faulty conditions, several transmitted data, and little reliability feedback. To handle these particularities, a '3-step' model is proposed, based on goal tree-success tree (GTST) approaches to represent both the functional and material aspects, and includes the faults and failures as a third part for supporting reliability analyses. The behavioural aspects are provided by relationship matrices, also denoted master logic diagrams (MLD), with stochastic values which represent direct relationships between system elements. Relationship analyses are then proposed to assess the effect of any fault or failure on any material element or function. Taking these relationships into account, the probabilities of malfunction and failure modes are evaluated according to time. Furthermore, uncertainty analyses tend to show that even if the input data and system behaviour are not well known, these previous results can be obtained in a relatively precise way. An illustration is provided by a case study on an infrared gas transmitter. These properties make the proposed model and corresponding reliability analyses especially suitable for intelligent transmitters (or 'smart sensors').

  16. New Mathematical Derivations Applicable to Safety and Reliability Analysis

    Cooper, J.A.; Ferson, S.


    Boolean logic expressions are often derived in safety and reliability analysis. Since the values of the operands are rarely exact, accounting for uncertainty with the tightest justifiable bounds is important. Accurate determination of result bounds is difficult when the inputs have constraints. One example of a constraint is that an uncertain variable that appears multiple times in a Boolean expression must always have the same value, although the value cannot be exactly specified. A solution for this repeated variable problem is demonstrated for two Boolean classes. The classes, termed functions with unate variables (including, but not limited to unate functions), and exclusive-or functions, frequently appear in Boolean equations for uncertain outcomes portrayed by logic trees (event trees and fault trees).

  17. Assessment of Network and Data Communication Reliability for Lungmen NPS

    Hsu, Teng Chieh; Chou, Hwai Pwu [National Tsing Hua University, Hsinchu (China); Chao, Chun Chang [The Institute of Nuclear Energy Research, Taoyuan (China)


    The Lungmen nuclear power station (NPS) is an advanced boiling water reactor (ABWR) with fully digitized instrumentation and control (I and C) system. The present work is to use the probabilistic risk assessment (PRA) technique to investigate the concerns about network reliability and data communication errors for Lungmen NPS. The reactor protection system (RPS) has chosen as the target to investigate the network and data communication reliability. A fault tree based on the RPS configuration has been modeled to evaluate the weak point in the digital logic part. A Lungmen NPS event tree model has also built to calculate the core damage frequency (CDF). Sensitivity studies were performed by assuming various data communication delays and errors and to evaluate the network affect and the influence on the CDF.

  18. Handling Software Faults with Redundancy

    Carzaniga, Antonio; Gorla, Alessandra; Pezzè, Mauro

    Software engineering methods can increase the dependability of software systems, and yet some faults escape even the most rigorous and methodical development process. Therefore, to guarantee high levels of reliability in the presence of faults, software systems must be designed to reduce the impact of the failures caused by such faults, for example by deploying techniques to detect and compensate for erroneous runtime conditions. In this chapter, we focus on software techniques to handle software faults, and we survey several such techniques developed in the area of fault tolerance and more recently in the area of autonomic computing. Since practically all techniques exploit some form of redundancy, we consider the impact of redundancy on the software architecture, and we propose a taxonomy centered on the nature and use of redundancy in software systems. The primary utility of this taxonomy is to classify and compare techniques to handle software faults.

  19. Embedding Binary Tree in VLSI/WSI Processor Array



    Many reconfiguration schemes for fault-tolerant binary tree architectures have been proposed in the literature[1-6].The VLSI layouts of most previous studies are based on the classical H-tree layout,resulting in low area utilization and likely an unnecessarily high maufacturing cost simply due to the waste of a significant portion of silicon area. In this paper,we present an area-efficient approach to the reconfigurable binary tree architecture.Area utilization and interconnection complexity of our design compare favorably with the other known approaches.In the reliability analysis,we take into account the fact that accepted chips(after fabrication)are with different degrees of redundancy initially,so as to obtain results which better reflect real situations.

  20. Study on Knowledge -based Intelligent Fault Diagnosis of Hydraulic System

    Xuexia Liu


    Full Text Available A general framework of hydraulic fault diagnosis system was studied. It consisted of equipment knowledge bases, real-time databases, fusion reasoning module, knowledge acquisition module and so on. A tree-structure model of fault knowledge was established. Fault nodes knowledge was encapsulated by object-oriented technique. Complete knowledge bases were made including fault bases and diagnosis bases. It could describe the fault positions, the structure of fault, cause-symptom relationships, diagnosis principles and other knowledge. Taking the fault of left and right lifting oil cylinder out of sync for example, the diagnostic results show that the methods were effective.

  1. Reliability and availability evaluation of Wireless Sensor Networks for industrial applications.

    Silva, Ivanovitch; Guedes, Luiz Affonso; Portugal, Paulo; Vasques, Francisco


    Wireless Sensor Networks (WSN) currently represent the best candidate to be adopted as the communication solution for the last mile connection in process control and monitoring applications in industrial environments. Most of these applications have stringent dependability (reliability and availability) requirements, as a system failure may result in economic losses, put people in danger or lead to environmental damages. Among the different type of faults that can lead to a system failure, permanent faults on network devices have a major impact. They can hamper communications over long periods of time and consequently disturb, or even disable, control algorithms. The lack of a structured approach enabling the evaluation of permanent faults, prevents system designers to optimize decisions that minimize these occurrences. In this work we propose a methodology based on an automatic generation of a fault tree to evaluate the reliability and availability of Wireless Sensor Networks, when permanent faults occur on network devices. The proposal supports any topology, different levels of redundancy, network reconfigurations, criticality of devices and arbitrary failure conditions. The proposed methodology is particularly suitable for the design and validation of Wireless Sensor Networks when trying to optimize its reliability and availability requirements.

  2. Reliability of Arctic offshore installations

    Bercha, F.G. [Bercha Group, Calgary, AB (Canada); Gudmestad, O.T. [Stavanger Univ., Stavanger (Norway)]|[Statoil, Stavanger (Norway)]|[Norwegian Univ. of Technology, Stavanger (Norway); Foschi, R. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Civil Engineering; Sliggers, F. [Shell International Exploration and Production, Rijswijk (Netherlands); Nikitina, N. [VNIIG, St. Petersburg (Russian Federation); Nevel, D.


    Life threatening and fatal failures of offshore structures can be attributed to a broad range of causes such as fires and explosions, buoyancy losses, and structural overloads. This paper addressed the different severities of failure types, categorized as catastrophic failure, local failure or serviceability failure. Offshore tragedies were also highlighted, namely the failures of P-36, the Ocean Ranger, the Piper Alpha, and the Alexander Kieland which all resulted in losses of human life. P-36 and the Ocean Ranger both failed ultimately due to a loss of buoyancy. The Piper Alpha was destroyed by a natural gas fire, while the Alexander Kieland failed due to fatigue induced structural failure. The mode of failure was described as being the specific way in which a failure occurs from a given cause. Current reliability measures in the context of offshore installations only consider the limited number of causes such as environmental loads. However, it was emphasized that a realistic value of the catastrophic failure probability should consider all credible causes of failure. This paper presented a general method for evaluating all credible causes of failure of an installation. The approach to calculating integrated reliability involves the use of network methods such as fault trees to combine the probabilities of all factors that can cause a catastrophic failure, as well as those which can cause a local failure with the potential to escalate to a catastrophic failure. This paper also proposed a protocol for setting credible reliability targets such as the consideration of life safety targets and escape, evacuation, and rescue (EER) success probabilities. A set of realistic reliability targets for both catastrophic and local failures for representative safety and consequence categories associated with offshore installations was also presented. The reliability targets were expressed as maximum average annual failure probabilities. The method for converting these annual

  3. Analysis of the Rural Residents' Health Risk: Based on Fault Tree Analysis%我国农村居民健康风险分析:基于故障树分析法

    张芳洁; 张吉龙


    The level of rural health services and health status of rural residents are the very important indicator of rural development. Health risks, in rural households, especially in disadvantaged families are one of the important economic risks, and are the important factors impacting on the living standards of rural residents and rural social stability. Fault tree analysis as a common risk analysis method, by which logical relationship with chart analysis by the main risk to the accident and a combination of individual events will be formed. This thesis, based on the construction of the tree of health risks, analyzes the health risks the rural residents facing, and gives the appropriate methods of risks assessment and risk management strategies.%农村医疗卫生服务水平和农村居民健康状况是衡量农村社会发展水平的重要指标.健康风险是农村居民家庭尤其是贫困家庭面临的重要经济风险之一,是影响农村居民生活水平和农村社会稳定的重要因素.故障树法作为一种常用的风险分析方法,能够通过树形的逻辑关系图表分析引起主要风险事故发生的原因,揭示个别事件组合可能会形成的风险状况.文章通过对农村居民健康风险故障树的构建,分析农村居民面临的健康风险,并简要介绍相应的风险评价方法和风险管理策略.

  4. Skewed Binary Search Trees

    Brodal, Gerth Stølting; Moruz, Gabriel


    It is well-known that to minimize the number of comparisons a binary search tree should be perfectly balanced. Previous work has shown that a dominating factor over the running time for a search is the number of cache faults performed, and that an appropriate memory layout of a binary search tree...... can reduce the number of cache faults by several hundred percent. Motivated by the fact that during a search branching to the left or right at a node does not necessarily have the same cost, e.g. because of branch prediction schemes, we in this paper study the class of skewed binary search trees....... For all nodes in a skewed binary search tree the ratio between the size of the left subtree and the size of the tree is a fixed constant (a ratio of 1/2 gives perfect balanced trees). In this paper we present an experimental study of various memory layouts of static skewed binary search trees, where each...

  5. Design and implementation of an expert system for remote fault diagnosis in ship lift


    In this paper an expert system for remote fault diagnosis in the ship lift was developed by analysis of the fault tree and combination with VPN. The fault tree was constructed based on the operation condition of the ship lift. The diagnosis model was constructed by hierarchical classification of the fault tree structure, and the inference mechanism was given. Logical structure of the fault diagnosis in the ship lift was proposed. The implementation of the expert system for remote fault diagnosis in the ship lift was discussed, and the expert system developed was realized on the VPN virtual network. The system was applied to the Gaobaozhou ship lift project, and it ran successfully.

  6. Design and implementation of an expert system for remote fault diagnosis in ship lift


    In this paper an expert system for remote fault diagnosis in the ship lift was developed by analysis of the fault tree and combination with VPN. The fault tree was constructed based on the operation condition of the ship lift. The diagnosis model was constructed by hierarchical classification of the fault tree structure, and the inference mechanism was given. Logical structure of the fault diagnosis in the ship lift was proposed. The implementation of the expert system for remote fault diagnosis in the ship...

  7. The sharing risk assessment to hydraulic public private partnership project during implementation based on fault tree analysis%基于FTA的水电公私合营项目实施阶段共担风险评价

    严斌; 陈达; 刘小敏


    以水电公私合营(public private partnership,PPP)项目实施阶段风险为研究对象,进行了共担风险的识别,确认了3种类型的共担风险,在风险识别的基础上利用故障树分析(fault tree analysis,FTA)方法对分属不同主体的风险因素进行评价,通过计算单元的结构重要度确定出影响项目实施风险因素的重要性排序.分析结果表明:私人部门的管理水平低、项目外部环境复杂性和公共部门过多的行政干预等几个方面是产生项目共担风险的主要因素.

  8. 列车追尾事故的故障树分析兼谈复杂系统安全%Fault Tree Analysis of Train Crash Accident and Discussion on Safety of Complex Systems



    The train crash accident at Wenzhou city was rated as an especially serious accident which happened at the rapid development stage of train transportation in China. Taking train crash accident as the top event, fault tree analysis was conducted to depict the possible reasons and accident modes. The events contributing to train crash accident are discussed from the their nature to preventive measures. From a broader viewpoint, safety issues of the three elements of a complex safety-critical system (hardware, software and human) are addressed along with technological and management strategies and suggestions.%温州动车组追尾事故是我国铁路大发展时期发生的特别重大事故.为更深入了解事故的可能原因,以列车追尾事故为顶事件,开展故障树分析,探讨事故的各种发生模式,剖析造成事故的各种事件,并从宏观的角度讨论了复杂安全关键系统的安全要素和策略,给出了一些建议.

  9. Fault Tree Analysis of Power Distribution Vehicle Started Stop in Low Temperature%电源配电车低温启动后停机的故障树分析

    倪峰; 李锐敏; 杨淑霞


    某型号电源配电车做环境试验,低温环境启动成功后停机。更换手打输油泵后,启动成功,工作正常。针对这种现象,根据低温启动的技术要求和原理、发电机组低温启动成功后停机故障树,分析原因,现场采取措施有效,实施效果良好,得到了同行的认可及推广。%The type power distribution vehicle for environmental testing , low temperature environment stop after a successful started .After change hands oil transfer pump , start the success , working properly .In this paper , ac-cording to this phenomenon , the technology requirements of the low temperature start and principle , generating set after the success of the low-temperature start stop the fault tree , analysis the reason , the measures to effectively , implementing effect is very good and get the approvl .

  10. Fault diagnosis

    Abbott, Kathy


    The objective of the research in this area of fault management is to develop and implement a decision aiding concept for diagnosing faults, especially faults which are difficult for pilots to identify, and to develop methods for presenting the diagnosis information to the flight crew in a timely and comprehensible manner. The requirements for the diagnosis concept were identified by interviewing pilots, analyzing actual incident and accident cases, and examining psychology literature on how humans perform diagnosis. The diagnosis decision aiding concept developed based on those requirements takes abnormal sensor readings as input, as identified by a fault monitor. Based on these abnormal sensor readings, the diagnosis concept identifies the cause or source of the fault and all components affected by the fault. This concept was implemented for diagnosis of aircraft propulsion and hydraulic subsystems in a computer program called Draphys (Diagnostic Reasoning About Physical Systems). Draphys is unique in two important ways. First, it uses models of both functional and physical relationships in the subsystems. Using both models enables the diagnostic reasoning to identify the fault propagation as the faulted system continues to operate, and to diagnose physical damage. Draphys also reasons about behavior of the faulted system over time, to eliminate possibilities as more information becomes available, and to update the system status as more components are affected by the fault. The crew interface research is examining display issues associated with presenting diagnosis information to the flight crew. One study examined issues for presenting system status information. One lesson learned from that study was that pilots found fault situations to be more complex if they involved multiple subsystems. Another was pilots could identify the faulted systems more quickly if the system status was presented in pictorial or text format. Another study is currently under way to

  11. Circuit design for reliability

    Cao, Yu; Wirth, Gilson


    This book presents physical understanding, modeling and simulation, on-chip characterization, layout solutions, and design techniques that are effective to enhance the reliability of various circuit units.  The authors provide readers with techniques for state of the art and future technologies, ranging from technology modeling, fault detection and analysis, circuit hardening, and reliability management. Provides comprehensive review on various reliability mechanisms at sub-45nm nodes; Describes practical modeling and characterization techniques for reliability; Includes thorough presentation of robust design techniques for major VLSI design units; Promotes physical understanding with first-principle simulations.


    谢开贵; 周平; 周家启; 孙渝江; 龙小平


    提出一种中压配电系统可靠性评估算法。该算法对复杂的中压配电系统(带子馈线)有较强的处理能力,利用前向搜索算法确定断路器动作影响范围,用故障扩散方法确定故障隔离的范围,从而确定节点的故障类型。根据故障的类型,便可形成相应的节点、馈线以及系统的可靠性指标。以RBTS—Bus6,RBTS—Bus2等配电网络和大量实际运行网络验证了该方法的有效性和实用性。%A reliability evaluation algorithm for medium voltage radial distribution network is proposed. The algorithm is suitable for evaluating the relatively complex systems which consist of many sub-feeders. It employes ahead-searching-method to determine the influencing area of breaker, applies fault-spreading-method to determine disconnection area, based on which the failure types of nodes can be determined. Then the reliability indices of nodes, feeders and system can be calculated. The RBTS-Bus6, RBTS-Bus2 and other medium voltage radial distribution networks are evaluated by using the algorithm, which verifies the effectiveness of the proposed algorithm.

  13. The role of reliability graph models in assuring dependable operation of complex hardware/software systems

    Patterson-Hine, F. A.; Davis, Gloria J.; Pedar, A.


    The complexity of computer systems currently being designed for critical applications in the scientific, commercial, and military arenas requires the development of new techniques for utilizing models of system behavior in order to assure 'ultra-dependability'. The complexity of these systems, such as Space Station Freedom and the Air Traffic Control System, stems from their highly integrated designs containing both hardware and software as critical components. Reliability graph models, such as fault trees and digraphs, are used frequently to model hardware systems. Their applicability for software systems has also been demonstrated for software safety analysis and the analysis of software fault tolerance. This paper discusses further uses of graph models in the design and implementation of fault management systems for safety critical applications.

  14. Integrated Approach To Design And Analysis Of Systems

    Patterson-Hine, F. A.; Iverson, David L.


    Object-oriented fault-tree representation unifies evaluation of reliability and diagnosis of faults. Programming/fault tree described more fully in "Object-Oriented Algorithm For Evaluation Of Fault Trees" (ARC-12731). Augmented fault tree object contains more information than fault tree object used in quantitative analysis of reliability. Additional information needed to diagnose faults in system represented by fault tree.

  15. Coordination Control Strategy for Compound Fault of MMC-HVDC

    Zhang Ming Guang; Zhang Zhao Yu; Qiu Li Jie; Chen Xi


    Single-line to ground fault of DC side and sub-module fault are typical faults of MMC-HVDC. When each of the above faults occurs, the system will give a signal for circuit-breaker releasing, this will result in interruption of power delivery, the stability of the system is greatly reduced. When these two faults occur simultaneously, research on control strategy for compound fault will help to improve the reliability of the system. While single-line to ground fault of DC side happens, only the...

  16. FTA法在提高冷轧板喷涂表面质量中的应用%The application of fault tree analysis to improveing the sheet steel surface quality of powder coating

    刘莉; 贾文友


    冷轧板喷涂表面在生产过程中有许多表面质量缺陷,如表面缩孔缺陷,严重制约冷轧板喷涂的品质和制造成本.为了是提高冷轧板喷涂表面质量,本文运用FTA方法(故障树分析方法),分析某家电外箱体冷轧板喷涂生产过程中形成表面缩孔缺陷的原因,绘制故障树,进行布尔代数计算求出最小割集,提出部分优化措施,最终提升该系列产品的市场竞争力,并为进一步研究提供帮助.%During the sheet steel powder coating process,there are many surface quality defects,such as the surface of shrinkage cavity problem,which seriously affect the sheet steel surface quality of powder coating and manufacturing costs.The study aims to improve the sheet steel surface quality of powder coating.This paper employs FTA method to analyze the causes of the surface of shrinkage cavity problem about a household appliance sheet steel box,to draw fault tree,to compute the minimal cut-sets by Boolean algebra and to propose some optimized measures.Finally,the conclusions can be applied to enhance the products market competition,and to expand this future research.

  17. Analysis of the reliabilities of maglev train power system with FTA method

    Long, Zhiqiang; Lu, Zhiquo; Chen, Huixing; Liu, Shaoke


    As to the high safeties and reliabilities of the magnetic suspension train, the most fundamental rule is that under all supposed running disturbances, faults, and other urgent conditions, and at any time, the running train can all stop at any given point, where the passengers can get off the train completely and can all find a safe stopping place. The object studied in this paper is the CMS-3 type electromagnetic suspension sample train developed in the National University of Defense Technology. Based on the method of fault tree analysis, the safeties and the reliabilities of the key part (the power system) of the train are analyzed systematically. And the instructive viewpoints and the improving measures are put forward.

  18. The Comprehensive Study of Electrical Faults in PV Arrays

    M. Sabbaghpur Arani


    Full Text Available The rapid growth of the solar industry over the past several years has expanded the significance of photovoltaic (PV systems. Fault analysis in solar photovoltaic (PV arrays is a fundamental task to increase reliability, efficiency, and safety in PV systems and, if not detected, may not only reduce power generation and accelerated system aging but also threaten the availability of the whole system. Due to the current-limiting nature and nonlinear output characteristics of PV arrays, faults in PV arrays may not be detected. In this paper, all possible faults that happen in the PV system have been classified and six common faults (shading condition, open-circuit fault, degradation fault, line-to-line fault, bypass diode fault, and bridging fault have been implemented in 7.5 KW PV farm. Based on the simulation results, both normal operational curves and fault curves have been compared.

  19. Fault tolerant operation of switched reluctance machine

    Wang, Wei

    The energy crisis and environmental challenges have driven industry towards more energy efficient solutions. With nearly 60% of electricity consumed by various electric machines in industry sector, advancement in the efficiency of the electric drive system is of vital importance. Adjustable speed drive system (ASDS) provides excellent speed regulation and dynamic performance as well as dramatically improved system efficiency compared with conventional motors without electronics drives. Industry has witnessed tremendous grow in ASDS applications not only as a driving force but also as an electric auxiliary system for replacing bulky and low efficiency auxiliary hydraulic and mechanical systems. With the vast penetration of ASDS, its fault tolerant operation capability is more widely recognized as an important feature of drive performance especially for aerospace, automotive applications and other industrial drive applications demanding high reliability. The Switched Reluctance Machine (SRM), a low cost, highly reliable electric machine with fault tolerant operation capability, has drawn substantial attention in the past three decades. Nevertheless, SRM is not free of fault. Certain faults such as converter faults, sensor faults, winding shorts, eccentricity and position sensor faults are commonly shared among all ASDS. In this dissertation, a thorough understanding of various faults and their influence on transient and steady state performance of SRM is developed via simulation and experimental study, providing necessary knowledge for fault detection and post fault management. Lumped parameter models are established for fast real time simulation and drive control. Based on the behavior of the faults, a fault detection scheme is developed for the purpose of fast and reliable fault diagnosis. In order to improve the SRM power and torque capacity under faults, the maximum torque per ampere excitation are conceptualized and validated through theoretical analysis and

  20. Reliability of emergency ac power systems at nuclear power plants

    Battle, R E; Campbell, D J


    Reliability of emergency onsite ac power systems at nuclear power plants has been questioned within the Nuclear Regulatory Commission (NRC) because of the number of diesel generator failures reported by nuclear plant licensees and the reactor core damage that could result from diesel failure during an emergency. This report contains the results of a reliability analysis of the onsite ac power system, and it uses the results of a separate analysis of offsite power systems to calculate the expected frequency of station blackout. Included is a design and operating experience review. Eighteen plants representative of typical onsite ac power systems and ten generic designs were selected to be modeled by fault trees. Operating experience data were collected from the NRC files and from nuclear plant licensee responses to a questionnaire sent out for this project.

  1. Research on the Fault Coefficient in Complex Electrical Engineering

    Yi Sun


    Full Text Available Fault detection and isolation in a complex system are research hotspots and frontier problems in the reliability engineering field. Fault identification can be regarded as a procedure of excavating key characteristics from massive failure data, then classifying and identifying fault samples. In this paper, based on the fundamental of feature extraction about the fault coefficient, we will discuss the fault coefficient feature in complex electrical engineering in detail. For general fault types in a complex power system, even if there is a strong white Gaussian stochastic interference, the fault coefficient feature is still accurate and reliable. The results about comparative analysis of noise influence will also demonstrate the strong anti-interference ability and great redundancy of the fault coefficient feature in complex electrical engineering.

  2. Lifeline system network reliability calculation based on GIS and FTA

    TANG Ai-ping; OU Jin-ping; LU Qin-nian; ZHANG Ke-xu


    Lifelines, such as pipeline, transportation, communication, electric transmission and medical rescue systems, are complicated networks that always distribute spatially over large geological and geographic units.The quantification of their reliability under an earthquake occurrence should be highly regarded, because the performance of these systems during a destructive earthquake is vital in order to estimate direct and indirect economic losses from lifeline failures, and is also related to laying out a rescue plan. The research in this paper aims to develop a new earthquake reliability calculation methodology for lifeline systems. The methodology of the network reliability for lifeline systems is based on fault tree analysis (FTA) and geological information system(GIS). The interactions existing in a lifeline system are considered herein. The lifeline systems are idealized as equivalent networks, consisting of nodes and links, and are described by network analysis in GIS. Firstly, the node is divided into two types: simple node and complicated node, where the reliability of the complicated node is calculated by FTA and interaction is regarded as one factor to affect performance of the nodes. The reliability of simple node and link is evaluated by code. Then, the reliability of the entire network is assessed based on GIS and FTA. Lastly, an illustration is given to show the methodology.

  3. 基于故障树分析的区域粮食安全风险因子识别和分类%Identification and classification of risk factors of regional grain security based on fault tree analysis

    起晓星; 刘黎明; 刘亚彬; 王莉


    区域粮食安全是国家宏观粮食安全的基础.该文运用故障树法对影响中国粮食供需安全的风险因子进行了定性识别,建立了粮食安全风险因子识别的指标体系;在此基础上,提出风险系数法对区域粮食安全风险因子进行定量识别.该文以湖南省洞庭湖区为例进行了实证分析,并依据各风险因子风险来源的不同对它们进行分类,建立了风险因子的分类体系.结果表明:自然灾害、耕地资源约束、水资源约束、劳动力短缺、农药和化肥投入成本约束、人均粮食消费量变化、收入水平变化、人口数量变化是影响该区域粮食安全的主要风险因子.研究的结果可以为相关部门的政策制定提供客观依据,也能为讲一步开展粮食安全风险评估奠定基础.%Regional food security is the basis of national general food security. In this paper, risk factors of food supply and demand in China were qualitatively identified by using fault tree method, and after that the identification indexes system of risk factors of food security was established. Based on the qualitative identification, was risk coefficient method to quantitatively identify risk factors of regional food security was. Meanwhile, a case study was carried out in Dongting Lake area in Hunan Province, and the risk factors were classified according to their different risk sources. The results showed that: natural disasters, farmland resource constraints, water constraints, labor shortage, input cost constraints of fertilizers and pesticides, food consumption changes per capita, income changes, population change were the risk factors of food security in Dongting Lake area. The result can provide strong and relevant evidence for regional policy makers. Based on the results, risk assessment for food security also can be carried out.

  4. Application of HAZOP and fault tree analysis (FTA) in hazard identification of ammonia synthesis plant%HAZOP研究与故障树分析在合成氨装置危险辨识中的应用

    马志刚; 靳明程; 陈衍涛; 高小呐; 佟淑娇


    The feedstock, intermediate product and product of ammonia synthesis plant possess the properties of explosion, burning and poison; meanwhile the process and equipments of ammonia synthesis plant are very complex. So, various hazardous factors are prone to cause fires, explosion, poisoning breakout and other accidents, which may result in production breakdown, devices damage, and even lead to great casualties and huge property losses. In this paper, comprehensive analytical method, HAZOP study and fault tree analysis (FTA) , were applied in hazad identification of ammonia synthesis plant. According to HAZOP result of ammonia synthesis plant, 23 potential hazards were found. HAZOP study result indicated that the gas compress part was major hazard. So, FTA was applied in hazard identification of gas compress part. FTA result indicated that breakdown of compressor exit pressure detector (PIA3-2) have significant influence to fire and explosion hazards of compressor, so it should be strictly prevented in producing. FTA and HAZOP have complementary advantages, which not only more fully and reasonably help to find out unsafe factors causing accidents, but also provide a new approach for the system safety a-nalysis, which make the risk analysis of system more scientific, complete and reasonable, and provide theoretical support for accident prevention and accidents reduction.%合成氨装置的原料、产品危险性高,并且生产过程复杂,因此在运行过程中可能导致火灾、爆炸、中毒等事故,有些事故甚至给社会和环境造成严重破坏.对HAZOP研究与故障树分析进行组合,应用在合成氨装置的危险辨识中.通过HAZOP研究,合成氨主体装置共发现风险因素23项,其中合成氨装置的合成气压缩单元安全隐患较多,因此对其进行故障树分析,合成气压缩机单元火灾、爆炸故障树的最小割集为72个,最小径集为6个.从基本事件结构重要度结果来看,压缩

  5. 基于事故树和贝叶斯的军民航飞行冲突风险研究%Risk Analysis of Civil Aviation and Military Flight Conflict Based on Fault Tree and Bayesian

    朱磊; 梁晓龙; 张佳强


    In order to fully understand the causes of the civil aviation and military flight conflict and near-miss potential accident,and its causes are focused prevention and probability of accurate prediction of events.first,a fault tree model has been set up to analyze the likely causes that may lead to the civil aviation and military flight conflict and near-miss potential accident,summarized the basic events which lead to the top events.The minimum cut sets and structure importance of basic events have been worked out.Then,the basic events probability assignment reasonably.It is concluded that the structure of the basic events importance,based on this,the probability of such basic events affect the occurrence probability of the top event hace been pointed out.In the end,the Bayesian Network diagram is also mapped out,the probability and the probability of the top middle events are calanlated,as well compared with monitoring results,it has proved the feasibility of the method.%为充分了解当前军民航飞行冲突、危险接近事故征候的成因,并对其发生原因进行有重点的预防和对事件发生概率的精确预测,首先建立事故树模型,对其原因进行分析;总结导致其发生的基本事件,计算事故树模型的最小割集和各个基本事件的结构重要度;其次对军民航飞行冲突、危险接近事故征候的发生概率进行合理的取值,得出基本事件的概率重要度,指出基本事件发生概率对顶事件发生概率的影响;最后构建军民航飞行冲突、危险接近事故征候贝叶斯网络模型,计算中间事件的条件概率和顶事件发生概率,并与实际结果进行对比,验证方法可行性。



    Fault tolerance in microprocessor systems has become a popular topic of architecture research.Much work has been done at different levels to accomplish reliability against soft errors, and some fault tolerance architectures have been proposed. But little attention is paid to the thread level superscalar fault tolerance.This letter introduces microthread concept into superscalar processor fault tolerance domain, and puts forward a novel fault tolerance architecture, namely, MicroThread Based (MTB) coarse grained transient fault tolerance superscalar processor architecture, then discusses some detailed implementations.

  7. Optimizing solution of fault location using single terminal quantities

    DONG XinZhou; SHI ShenXing; CUI Tao; LU Qiang


    This paper firstly evaluated the impedance method and traveling waves method for fault location, and studied the robustness of fault location method based on im-pedance. Then it proposed an assembled fault location method for a transmission line based on single-terminal electrical quantities, in which the fault zone was firstly determined by impedance method with robustness then the accurate fault position was pinpointed by traveling waves method. EMTP (Electromagnetic Transient Pro-gram) simulations showed that the proposed method can overcome the drawbacks of impedance method and traveling waves method when either one is used alone, and improve both the accuracy and the reliability of fault location.

  8. Reliability assessment for components of large scale photovoltaic systems

    Ahadi, Amir; Ghadimi, Noradin; Mirabbasi, Davar


    Photovoltaic (PV) systems have significantly shifted from independent power generation systems to a large-scale grid-connected generation systems in recent years. The power output of PV systems is affected by the reliability of various components in the system. This study proposes an analytical approach to evaluate the reliability of large-scale, grid-connected PV systems. The fault tree method with an exponential probability distribution function is used to analyze the components of large-scale PV systems. The system is considered in the various sequential and parallel fault combinations in order to find all realistic ways in which the top or undesired events can occur. Additionally, it can identify areas that the planned maintenance should focus on. By monitoring the critical components of a PV system, it is possible not only to improve the reliability of the system, but also to optimize the maintenance costs. The latter is achieved by informing the operators about the system component's status. This approach can be used to ensure secure operation of the system by its flexibility in monitoring system applications. The implementation demonstrates that the proposed method is effective and efficient and can conveniently incorporate more system maintenance plans and diagnostic strategies.

  9. Analysis of energy leakage characteristics of dual-tree complex wavelet packet transform and its application on gear fault diagnosis%基于双树复小波包变换能量泄漏特性分析的齿轮故障诊断

    胥永刚; 孟志鹏; 赵国亮; 付胜


    为有效利用双树复小波包变换提取齿轮故障特征信息,提出基于双树复小波包能量泄漏特性分析的故障诊断方法。首先根据高斯白噪声频率充满整个频带的特性,通过双树复小波包变换对高斯白噪声进行分解,利用频带能量泄漏的定量分析方法,验证了双树复小波包变换具有较低的频带能量泄漏特性;其次利用双树复小波包变换逐层分解信号,对每层分解所得分量求其FFT谱的峭度,得到基于双树复小波包变换的谱峭度图,根据图中峭度最大的原则,可以自动准确的选择信号分解最佳层数和最佳分量;最后将基于双树复小波包变换的谱峭度图的故障诊断方法应用于实际工程中,对齿轮故障振动信号进行分析,选择最佳分解层数和分量后利用希尔伯特包络解调,有效准确地提取了故障特征信息,验证了方法的可行性和有效性。该研究可为旋转机械设备中齿轮箱故障诊断的故障特征提取提供参考。%The gear is the key component of rotating machinery, so a fault in the gear will directly affect the condition of the whole machine’s operation. It was difficult to extract the fault feature information effectively from the vibration signals of a faulty gear. In the field of fault diagnosis, envelope demodulation was one of the most common signal processing methods. However, a filtering process was required before envelope demodulation. The parameters of a filter were determined by experience, and that has a great influence on the results of signal processing. The discrete wavelet packet transform has a larger energy leakage of frequency band, which obviously affected the results of the envelope demodulation. It is necessary to have a method with a lower energy leakage of the frequency band before envelope demodulation. The dual tree complex wavelet packet transform (DT-CWPT) was a new signal processing method that had many

  10. An effort allocation model considering different budgetary constraint on fault detection process and fault correction process

    Vijay Kumar


    Full Text Available Fault detection process (FDP and Fault correction process (FCP are important phases of software development life cycle (SDLC. It is essential for software to undergo a testing phase, during which faults are detected and corrected. The main goal of this article is to allocate the testing resources in an optimal manner to minimize the cost during testing phase using FDP and FCP under dynamic environment. In this paper, we first assume there is a time lag between fault detection and fault correction. Thus, removal of a fault is performed after a fault is detected. In addition, detection process and correction process are taken to be independent simultaneous activities with different budgetary constraints. A structured optimal policy based on optimal control theory is proposed for software managers to optimize the allocation of the limited resources with the reliability criteria. Furthermore, release policy for the proposed model is also discussed. Numerical example is given in support of the theoretical results.

  11. Faults and Diagnosis Systems in Power Converters

    Lee, Kyo-Beum; Choi, Uimin


    efforts have been put into making these systems better in terms of reliability in order to achieve high power source availability, reduce the cost of energy and also increase the reliability of overall systems. Among the components used in power converters, a power device and a capacitor fault occurs most......A power converter is needed in almost all kinds of renewable energy systems and drive systems. It is used both for controlling the renewable source and for interfacing with the load, which can be grid-connected or working in standalone mode. Further, it drives the motors efficiently. Increasing...... frequently. Therefore, it is important to monitor the power device and capacitor fault to increase the reliability of power electronics. In this chapter, the diagnosis methods for power device fault will be discussed by dividing into open- and short-circuit faults. Then, the condition monitoring methods...

  12. Faults in Linux

    Palix, Nicolas Jean-Michel; Thomas, Gaël; Saha, Suman


    In 2001, Chou et al. published a study of faults found by applying a static analyzer to Linux versions 1.0 through 2.4.1. A major result of their work was that the drivers directory contained up to 7 times more of certain kinds of faults than other directories. This result inspired a number...... of development and research efforts on improving the reliability of driver code. Today Linux is used in a much wider range of environments, provides a much wider range of services, and has adopted a new development and release model. What has been the impact of these changes on code quality? Are drivers still...... a major problem? To answer these questions, we have transported the experiments of Chou et al. to Linux versions 2.6.0 to 2.6.33, released between late 2003 and early 2010. We find that Linux has more than doubled in size during this period, but that the number of faults per line of code has been...

  13. The inference of gene trees with species trees.

    Szöllősi, Gergely J; Tannier, Eric; Daubin, Vincent; Boussau, Bastien


    This article reviews the various models that have been used to describe the relationships between gene trees and species trees. Molecular phylogeny has focused mainly on improving models for the reconstruction of gene trees based on sequence alignments. Yet, most phylogeneticists seek to reveal the history of species. Although the histories of genes and species are tightly linked, they are seldom identical, because genes duplicate, are lost or horizontally transferred, and because alleles can coexist in populations for periods that may span several speciation events. Building models describing the relationship between gene and species trees can thus improve the reconstruction of gene trees when a species tree is known, and vice versa. Several approaches have been proposed to solve the problem in one direction or the other, but in general neither gene trees nor species trees are known. Only a few studies have attempted to jointly infer gene trees and species trees. These models account for gene duplication and loss, transfer or incomplete lineage sorting. Some of them consider several types of events together, but none exists currently that considers the full repertoire of processes that generate gene trees along the species tree. Simulations as well as empirical studies on genomic data show that combining gene tree-species tree models with models of sequence evolution improves gene tree reconstruction. In turn, these better gene trees provide a more reliable basis for studying genome evolution or reconstructing ancestral chromosomes and ancestral gene sequences. We predict that gene tree-species tree methods that can deal with genomic data sets will be instrumental to advancing our understanding of genomic evolution.

  14. Online fault location on crossbonded AC cables in underground transmission systems

    F. Jensen, Christian; Bak, Claus Leth; Gudmundsdottir, Unnur Stella


    system are identified. The fault locator system uses the Wavelet Transform both to create reliable triggers in the units and to estimate the fault location based on time domain signals obtained in the substations by two fault locator units. Field measurements of faults artificially created on a section...

  15. Machine Fault Signature Analysis

    Pratesh Jayaswal


    Full Text Available The objective of this paper is to present recent developments in the field of machine fault signature analysis with particular regard to vibration analysis. The different types of faults that can be identified from the vibration signature analysis are, for example, gear fault, rolling contact bearing fault, journal bearing fault, flexible coupling faults, and electrical machine fault. It is not the intention of the authors to attempt to provide a detailed coverage of all the faults while detailed consideration is given to the subject of the rolling element bearing fault signature analysis.

  16. Common-Cause Failure Analysis for Reactor Protection System Reliability Studies

    Gentillon, C.; Rasmuson, D.; Eide, S.; Wierman, T.


    Analyses were performed of the safety-related performance of the reactor protection system (RPS) at U.S. Westinghouse and General Electric commercial reactors during the period 1984 through 1995. RPS operational data from these reactors were collected from the Nuclear Plant Reliability Data System (NPRDS) and Licensee Event Reports (LER). The common-cause failure (CCF) modeling in the fault trees developed for these studies and the analysis and use of common-cause failure data were sophisticated, state-of-the-art efforts. The overall CCF effort helped to test and expand the limits of the U.S. Nuclear Regulatory Commission's CCF methodology.

  17. Reliability prediction techniques

    Whittaker, B.; Worthington, B.; Lord, J.F.; Pinkard, D.


    The paper demonstrates the feasibility of applying reliability assessment techniques to mining equipment. A number of techniques are identified and described and examples of their use in assessing mining equipment are given. These techniques include: reliability prediction; failure analysis; design audit; maintainability; availability and the life cycle costing. Specific conclusions regarding the usefulness of each technique are outlined. The choice of techniques depends upon both the type of equipment being assessed and its stage of development, with numerical prediction best suited for electronic equipment and fault analysis and design audit suited to mechanical equipment. Reliability assessments involve much detailed and time consuming work but it has been demonstrated that the resulting reliability improvements lead to savings in service costs which more than offset the cost of the evaluation.

  18. Passive Fault-tolerant Control of Discrete-time Piecewise Affine Systems against Actuator Faults

    Tabatabaeipour, Seyed Mojtaba; Izadi-Zamanabadi, Roozbeh; Bak, Thomas


    In this paper, we propose a new method for passive fault-tolerant control of discrete time piecewise affine systems. Actuator faults are considered. A reliable piecewise linear quadratic regulator (LQR) state feedback is designed such that it can tolerate actuator faults. A sufficient condition...... for the exis- tence of a passive fault-tolerant controller is derived and formulated as the feasibility of a set of linear matrix inequalities (LMIs). The upper bound on the performance cost can be minimized using a convex optimization problem with LMI constraints which can be solved efficiently. The approach...

  19. Time Property Analysis Method for State/Event Fault Tree%一种状态事件故障树的时间特性分析方法∗

    徐丙凤; 黄志球; 胡军; 魏欧; 李伟湋


    State/Event fault tree (SEFT) is a modeling technique for describing the causal chains which lead to failure in component- based embedded systems, and the top event of SEFT describes the result of the failure. One important way for capturing the mean time parameter of system failure is to quantitatively analyze the mean time of the top event occurrence, which provides support for system safety evaluation. However, it is necessary to formally describe SEFT semantics in order to quantitatively analyze the time property. In this paper, a time property analysis method for SEFT based on interactive Markov chain (IMC) is presented. Firstly, interface interactive Markov chain (Interface-IMC) is proposed based on refining the interactive action of IMC. Secondly, semantics of components and logic gates in SEFT are formally described by Interface-IMC. Thirdly, the semantics of SEFT is obtained by composing all the Interface-IMCs generated in the above steps. During this process, weak bisimilarity technique is applied to reduce state space. Then, a quantitative time analysis method is presented based on the formal semantic model of SEFT. Finally, the time analysis processes for the SEFT of aircraft radar landing control system and sprinkler system are illustrated by the proposed method. The method provides a new solution for analyzing time properties of component-based system failure.%状态事件故障树是一种适合于描述构件化嵌入式系统失效因果链的建模技术,其顶层事件描述失效发生的结果。对顶层事件发生的平均时间进行分析,是获得系统平均失效时间参数的一种有效方法,可为系统的安全性评估提供支持。由于状态事件故障树缺乏严格语义,使得必须先对其进行形式化描述才能进行定量分析。为此,提出了一种基于交互马尔可夫链的状态事件故障树时间特性分析方法。首先,精化交互马尔可夫链的交互动作,建立接口交互马

  20. Reliability and Probabilistic Risk Assessment - How They Play Together

    Safie, Fayssal M.; Stutts, Richard G.; Zhaofeng, Huang


    PRA methodology is one of the probabilistic analysis methods that NASA brought from the nuclear industry to assess the risk of LOM, LOV and LOC for launch vehicles. PRA is a system scenario based risk assessment that uses a combination of fault trees, event trees, event sequence diagrams, and probability and statistical data to analyze the risk of a system, a process, or an activity. It is a process designed to answer three basic questions: What can go wrong? How likely is it? What is the severity of the degradation? Since 1986, NASA, along with industry partners, has conducted a number of PRA studies to predict the overall launch vehicles risks. Planning Research Corporation conducted the first of these studies in 1988. In 1995, Science Applications International Corporation (SAIC) conducted a comprehensive PRA study. In July 1996, NASA conducted a two-year study (October 1996 - September 1998) to develop a model that provided the overall Space Shuttle risk and estimates of risk changes due to proposed Space Shuttle upgrades. After the Columbia accident, NASA conducted a PRA on the Shuttle External Tank (ET) foam. This study was the most focused and extensive risk assessment that NASA has conducted in recent years. It used a dynamic, physics-based, integrated system analysis approach to understand the integrated system risk due to ET foam loss in flight. Most recently, a PRA for Ares I launch vehicle has been performed in support of the Constellation program. Reliability, on the other hand, addresses the loss of functions. In a broader sense, reliability engineering is a discipline that involves the application of engineering principles to the design and processing of products, both hardware and software, for meeting product reliability requirements or goals. It is a very broad design-support discipline. It has important interfaces with many other engineering disciplines. Reliability as a figure of merit (i.e. the metric) is the probability that an item will

  1. Coordination Control Strategy for Compound Fault of MMC-HVDC

    Zhang Ming Guang


    Full Text Available Single-line to ground fault of DC side and sub-module fault are typical faults of MMC-HVDC. When each of the above faults occurs, the system will give a signal for circuit-breaker releasing, this will result in interruption of power delivery, the stability of the system is greatly reduced. When these two faults occur simultaneously, research on control strategy for compound fault will help to improve the reliability of the system. While single-line to ground fault of DC side happens, only the electric potential auxiliary point of DC side is changed, system’s power transport normally. When sub-module is fault, redundancy fault-tolerated control strategy is presented, which replace the failed sub-modules with equal number of redundant sub-modules, it can restrain the fluctuation of direct current. A double terminals and 21 voltage-level MMC-HVDC system simulation model is set up in PSCAD/EMTDC. From the computation and simulation results, it is concluded that the proposed control strategy is correct for above compound fault, it can achieve rapid recovery after faults, effectively improve fault tolerance of the system, develop the stability and reliability of the system.

  2. Distributed Fault-Tolerant Control of Networked Uncertain Euler-Lagrange Systems Under Actuator Faults.

    Chen, Gang; Song, Yongduan; Lewis, Frank L


    This paper investigates the distributed fault-tolerant control problem of networked Euler-Lagrange systems with actuator and communication link faults. An adaptive fault-tolerant cooperative control scheme is proposed to achieve the coordinated tracking control of networked uncertain Lagrange systems on a general directed communication topology, which contains a spanning tree with the root node being the active target system. The proposed algorithm is capable of compensating for the actuator bias fault, the partial loss of effectiveness actuation fault, the communication link fault, the model uncertainty, and the external disturbance simultaneously. The control scheme does not use any fault detection and isolation mechanism to detect, separate, and identify the actuator faults online, which largely reduces the online computation and expedites the responsiveness of the controller. To validate the effectiveness of the proposed method, a test-bed of multiple robot-arm cooperative control system is developed for real-time verification. Experiments on the networked robot-arms are conduced and the results confirm the benefits and the effectiveness of the proposed distributed fault-tolerant control algorithms.

  3. Data-driven design of fault diagnosis and fault-tolerant control systems

    Ding, Steven X


    Data-driven Design of Fault Diagnosis and Fault-tolerant Control Systems presents basic statistical process monitoring, fault diagnosis, and control methods, and introduces advanced data-driven schemes for the design of fault diagnosis and fault-tolerant control systems catering to the needs of dynamic industrial processes. With ever increasing demands for reliability, availability and safety in technical processes and assets, process monitoring and fault-tolerance have become important issues surrounding the design of automatic control systems. This text shows the reader how, thanks to the rapid development of information technology, key techniques of data-driven and statistical process monitoring and control can now become widely used in industrial practice to address these issues. To allow for self-contained study and facilitate implementation in real applications, important mathematical and control theoretical knowledge and tools are included in this book. Major schemes are presented in algorithm form and...


    N. Selvaganesan


    Full Text Available Faults in engineering systems are difficult to avoid and may result in serious consequences. Effective fault detection and diagnosis can improve system reliability and avoid expensive maintenance. In this paper fuzzy system based fault detection scheme for permanent magnet synchronous generator is proposed. The sequence current components like positive and negative sequence currents are used as fault indicators and given as inputs to fuzzy fault detector. Also, the fuzzy inference system is created and rule base is evaluated, relating the sequence current component to the type of faults. These rules are fired for specific changes in sequence current component and the faults are detected. The feasibility of the proposed scheme for permanent magnet synchronous generator is demonstrated for different types of fault under various operating conditions using MATLAB/Simulink.

  5. Mine-Hoist Active Fault Tolerant Control System and Strategy

    WANG Zhi-jie; WANG Yao-cai; MENG Jiang; ZHAO Peng-cheng; CHANG Yan-wei


    Based on fault diagnosis and fault tolerant technologies, the mine-hoist active fault-tolerant control system (MAFCS) is presented with corresponding strategies,, which includes the fault diagnosis module (FDM), the dynamic library (DL) and the fault-tolerant control module (FCM). When a fault is judged from some sensor by FDM, FCM reconfigure the state of MAFCS by calling the parameters from all sub libraries in DL, in order to ensure the reliability and safety of mine hoist. The simulating result shows that, MAFCS is of certain intelligence, which can adopt the corresponding control strategies according to different fault modes, even when there are quite difference between the real data and the prior fault modes.

  6. Solving fault diagnosis problems linear synthesis techniques

    Varga, Andreas


    This book addresses fault detection and isolation topics from a computational perspective. Unlike most existing literature, it bridges the gap between the existing well-developed theoretical results and the realm of reliable computational synthesis procedures. The model-based approach to fault detection and diagnosis has been the subject of ongoing research for the past few decades. While the theoretical aspects of fault diagnosis on the basis of linear models are well understood, most of the computational methods proposed for the synthesis of fault detection and isolation filters are not satisfactory from a numerical standpoint. Several features make this book unique in the fault detection literature: Solution of standard synthesis problems in the most general setting, for both continuous- and discrete-time systems, regardless of whether they are proper or not; consequently, the proposed synthesis procedures can solve a specific problem whenever a solution exists Emphasis on the best numerical algorithms to ...

  7. LMI approach to reliable H∞ control of linear systems

    Yao Bo; Wang Fuzhong


    The reliable design problem for linear systems is concerned with. A more practical model of actuator faults than outage is considered. An LMI approach of designing reliable controller is presented for the case of actuator faults that can be modeled by a scaling factor. The resulting control systems are reliable in that they provide guaranteed asymptotic stability and H∞ performance when some control component (actuator) faults occur. A numerical example is also given to illustrate the design procedure and their effectiveness. Furthermore, the optimal standard controller and the optimal reliable controller are compared to show the necessity of reliable control.

  8. 双树复小波和局部投影算法在齿轮故障诊断中的应用%Application of gear fault diagnosis method based on dual-tree complex wavelet transform and local projective method

    胥永刚; 赵国亮; 马朝永; 杨红玉


    齿轮故障振动信号往往表现为非线性非平稳特性,并且早期故障振动信号往往包含较强的背景噪声,不利于故障特征的提取。针对该问题,提出了基于双树复小波变换和局部投影算法的齿轮故障诊断方法。首先,对故障信号进行双树复小波变换,得到不同尺度下的小波系数和最后一层的尺度系数,并计算各层小波系数的模与相角。然后,选择模周期性较强的小波系数或尺度系数进行局部投影算法处理,得到周期性增强的系数的模,并选择合适的阈值进行软阈值处理。最后,利用处理后的系数进行双树复小波重构,从而提取出齿轮故障特征信号,进行希尔伯特包络解调分析便能准确地得到故障特征频率。仿真信号和工程应用表明,该方法能够有效地提取齿轮故障特征信息,提供了一种齿轮故障特征提取的新方法。%As gear fault vibration signal is always nonlinear and nonstationary and always with a strong background noise which result in difficulty of fault feature extraction ,a new method based on dual‐tree complex wavelet transform and local projective method is proposed .As a improved method of the conventional discrete wavelet transform (DWT ) ,dual‐tree complex wavelet transform has many advantages over DWT ,such as the improvement of frequency aliasing and oscillations of wavelet coeffi‐cients which is the key to the method proposed .Local projective method for nonlinear time series has a good ability of signal period strengthen and noise suppression ,which fits for wavelet coefficients denoising .Firstly ,the fault signal is decomposed by dual‐tree complex wavelet transform to obtain the coefficients of different layers .Secondly ,the nonlinear time series method is used to strengthen the periodicity of the coefficient whose amplitude is more periodic ,and then do soft‐threshold denoising . Finally ,the fault characteristic

  9. Energy-efficient fault-tolerant systems

    Mathew, Jimson; Pradhan, Dhiraj K


    This book describes the state-of-the-art in energy efficient, fault-tolerant embedded systems. It covers the entire product lifecycle of electronic systems design, analysis and testing and includes discussion of both circuit and system-level approaches. Readers will be enabled to meet the conflicting design objectives of energy efficiency and fault-tolerance for reliability, given the up-to-date techniques presented.

  10. A Primer on Architectural Level Fault Tolerance

    Butler, Ricky W.


    This paper introduces the fundamental concepts of fault tolerant computing. Key topics covered are voting, fault detection, clock synchronization, Byzantine Agreement, diagnosis, and reliability analysis. Low level mechanisms such as Hamming codes or low level communications protocols are not covered. The paper is tutorial in nature and does not cover any topic in detail. The focus is on rationale and approach rather than detailed exposition.

  11. Fault-tolerant control for current sensors of doubly fed induction generators based on an improved fault detection method

    Li, Hui; Yang, Chao; Hu, Yaogang


    Fault-tolerant control of current sensors is studied in this paper to improve the reliability of a doubly fed induction generator (DFIG). A fault-tolerant control system of current sensors is presented for the DFIG, which consists of a new current observer and an improved current sensor fault...... detection algorithm, and fault-tolerant control system are investigated by simulation. The results indicate that the outputs of the observer and the sensor are highly coherent. The fault detection algorithm can efficiently detect both soft and hard faults in current sensors, and the fault-tolerant control...... system can effectively tolerate both types of faults. © 2013 Published by Elsevier Ltd. All rights reserved....


    Yu. O. Kuzmin


    Full Text Available Recent deformation processes taking place in real time are analyzed on the basis of data on fault zones which were collected by long-term detailed geodetic survey studies with application of field methods and satellite monitoring.A new category of recent crustal movements is described and termed as parametrically induced tectonic strain in fault zones. It is shown that in the fault zones located in seismically active and aseismic regions, super intensive displacements of the crust (5 to 7 cm per year, i.e. (5 to 7·10–5 per year occur due to very small external impacts of natural or technogenic / industrial origin.The spatial discreteness of anomalous deformation processes is established along the strike of the regional Rechitsky fault in the Pripyat basin. It is concluded that recent anomalous activity of the fault zones needs to be taken into account in defining regional regularities of geodynamic processes on the basis of real-time measurements.The paper presents results of analyses of data collected by long-term (20 to 50 years geodetic surveys in highly seismically active regions of Kopetdag, Kamchatka and California. It is evidenced by instrumental geodetic measurements of recent vertical and horizontal displacements in fault zones that deformations are ‘paradoxically’ deviating from the inherited movements of the past geological periods.In terms of the recent geodynamics, the ‘paradoxes’ of high and low strain velocities are related to a reliable empirical fact of the presence of extremely high local velocities of deformations in the fault zones (about 10–5 per year and above, which take place at the background of slow regional deformations which velocities are lower by the order of 2 to 3. Very low average annual velocities of horizontal deformation are recorded in the seismic regions of Kopetdag and Kamchatka and in the San Andreas fault zone; they amount to only 3 to 5 amplitudes of the earth tidal deformations per year.A ‘fault

  13. Enumerating Trees

    Kucharczyk, Robert A


    In this note we discuss trees similar to the Calkin-Wilf tree, a binary tree that enumerates all positive rational numbers in a simple way. The original construction of Calkin and Wilf is reformulated in a more algebraic language, and an elementary application of methods from analytic number theory gives restrictions on possible analogues.

  14. Fault Management Design Strategies

    Day, John C.; Johnson, Stephen B.


    Development of dependable systems relies on the ability of the system to determine and respond to off-nominal system behavior. Specification and development of these fault management capabilities must be done in a structured and principled manner to improve our understanding of these systems, and to make significant gains in dependability (safety, reliability and availability). Prior work has described a fundamental taxonomy and theory of System Health Management (SHM), and of its operational subset, Fault Management (FM). This conceptual foundation provides a basis to develop framework to design and implement FM design strategies that protect mission objectives and account for system design limitations. Selection of an SHM strategy has implications for the functions required to perform the strategy, and it places constraints on the set of possible design solutions. The framework developed in this paper provides a rigorous and principled approach to classifying SHM strategies, as well as methods for determination and implementation of SHM strategies. An illustrative example is used to describe the application of the framework and the resulting benefits to system and FM design and dependability.

  15. Fault Management Design Strategies

    Day, John C.; Johnson, Stephen B.


    Development of dependable systems relies on the ability of the system to determine and respond to off-nominal system behavior. Specification and development of these fault management capabilities must be done in a structured and principled manner to improve our understanding of these systems, and to make significant gains in dependability (safety, reliability and availability). Prior work has described a fundamental taxonomy and theory of System Health Management (SHM), and of its operational subset, Fault Management (FM). This conceptual foundation provides a basis to develop framework to design and implement FM design strategies that protect mission objectives and account for system design limitations. Selection of an SHM strategy has implications for the functions required to perform the strategy, and it places constraints on the set of possible design solutions. The framework developed in this paper provides a rigorous and principled approach to classifying SHM strategies, as well as methods for determination and implementation of SHM strategies. An illustrative example is used to describe the application of the framework and the resulting benefits to system and FM design and dependability.


    M. Ahmed; V. Laxmi; M. S. Gaur


    Occurrence of faults in Network on Chip (NoC) is inevitable as the feature size is continuously decreasing and processing elements are increasing in numbers.Faults can be revocable if it is transient.Transient fault may occur inside router,or in the core or in communication wires.Examples of transient faults are overflow of buffers in router,clock skew,cross talk,etc..Revocation of transient faults can be done by retransmission of faulty packets using oblivious or adaptive routing algorithms.Irrevocable faults causes non-functionality of segment and mainly occurs during fabrication process.NoC reliability increases with the efficient routing algorithms,which can handle the maximum faults without deadlock in network.As transient faults are temporary and can be easily revoked using retransmission of packet,permanent faults require efficient routing to route the packet by bypassing the nonfunctional segments.Thus,our focus is on the analysis of adaptive minimal path fault tolerant routing to handle the permanent faults.Comparative analysis between partial adaptive fault tolerance routing West-First,North-Last,Negative-First,Odd Even,and Minimal path Fault Tolerant routing (MinFT) algorithms with the nodes and links failure is performed using NoC Interconnect RoutinG and Application Modeling simulator (NIRGAM) for the 2D Mesh topology.Result suggests that MinFT ensures data transmission under worst conditions as compared to other adaptive routing algorithms.

  17. A General Approach to Study the Reliability of Complex Systems

    G. M. Repici


    Full Text Available In recent years new complex systems have been developed in the automotive field to increase safety and comfort. These systems integrate hardware and software to guarantee the best results in vehicle handling and make products competitive on the market.However, the increase in technical details and the utilization and integration of these complicated systems require a high level of dynamic control system reliability. In order to improve this fundamental characteristic methods can be extracted from methods used in the aeronautical field to deal with reliability and these can be integrated into one simplified method for application in the automotive field.Firstly, as a case study, we decided to analyse VDC (the Vehicle Dynamics Control system by defining a possible approach to reliability techniques. A VDC Fault Tree Analysis represents the first step in this activity: FTA enables us to recognize the critical components in all possible working conditions of a car, including cranking, during 'key-on'-'key-off ' phases, which is particularly critical for the electrical on-board system (because of voltage reduction.By associating FA (Functional Analysis and FTA results with a good FFA (Functional Failure Analysis, it is possible to define the best architecture for the general system to achieve the aim of a high reliability structure.The paper will show some preliminary results from the application of this methodology, taken from various typical handling conditions from well established test procedures for vehicles.

  18. Tree compression with top trees

    Bille, Philip; Gørtz, Inge Li; Landau, Gad M.;


    We introduce a new compression scheme for labeled trees based on top trees. Our compression scheme is the first to simultaneously take advantage of internal repeats in the tree (as opposed to the classical DAG compression that only exploits rooted subtree repeats) while also supporting fast...

  19. Tree compression with top trees

    Bille, Philip; Gørtz, Inge Li; Landau, Gad M.


    We introduce a new compression scheme for labeled trees based on top trees [3]. Our compression scheme is the first to simultaneously take advantage of internal repeats in the tree (as opposed to the classical DAG compression that only exploits rooted subtree repeats) while also supporting fast...

  20. Tree compression with top trees

    Bille, Philip; Gørtz, Inge Li; Landau, Gad M.


    We introduce a new compression scheme for labeled trees based on top trees. Our compression scheme is the first to simultaneously take advantage of internal repeats in the tree (as opposed to the classical DAG compression that only exploits rooted subtree repeats) while also supporting fast...

  1. Large seismic faults in the Hellenic arc

    B. S. Papazachos


    Full Text Available Using information concerning reliable fault plane solutions, spatial distribution of strong earthquakes (Ms³ 6.0 as well as sea bottom and coastal topography, properties of the seismic faults (orientation, dimension, type of faulting were determined in seven shallow (h < 40 km seismogenic regions along the convex part of thc Hellenic arc (Hellenic trench and in four seismogenic regions of intermediate depth earthquakes (h = 40-100 km along the concave part of this arc. Except for the northwesternmost part of the Hellenic trench, where the strike-slip Cephalonia transform fault dominates, all other faults along this trench are low angle thrust faults. III thc western part of the trench (Zante-west Crete faults strike NW-SE and dip NE, while in its eastern part (east Crete-Rhodos faults strike WNW-ESE and dip NNE. Such system of faulting can be attributed to an overthrust of the Aegean lithosphere on the eastern Mediterranean lithosphere. The longest of these faults (L = 300 km is that which produced the largest known shallow earthquake in the Mediterranean area (21 July 365, Ms = 8.3 which is located near the southwestern coast of Crete. The second longest such fault (L = l 70 km is that which produced a large earthquake (December 1303, Ms = 8.0 in the easternmost part of the trench (east of Rhodos island. Both earthquakes were associated with gigantic tsunamis which caused extensive damage in the coast of many Eastern Mediterranean countries. Seismic faults of the intermediate depth earthquakes in the shallow part of the Benioff zone (h = 40- 100 km are of strike-slip type, with a thrust component. The orientations of these faults vary along the concave part of the arc in accordance with a subduction of remnants of all old lithospheric slab from the convex side (Mediterranean to the concave side (Aegean of thc Hellenic arc. The longest of these faults (L = 220 km is that which produced the largest known intermediate depth earthquake in the

  2. Data-Driven Adaptive Observer for Fault Diagnosis

    Shen Yin; Xuebo Yang; Hamid Reza Karimi


    This paper presents an approach for data-driven design of fault diagnosis system. The proposed fault diagnosis scheme consists of an adaptive residual generator and a bank of isolation observers, whose parameters are directly identified from the process data without identification of complete process model. To deal with normal variations in the process, the parameters of residual generator are online updated by standard adaptive technique to achieve reliable fault detection performance. After...

  3. Fault tolerant system design for uninterruptible power supplies

    B. Y. Volochiy; D. S. Kuznetsov


    The problem of design for reliability of a fault tolerant system for uninterruptible power supplies is considered. Configuration of a fault tolerant system determines the structure of an uninterruptible power supply: power supply built from modules of the same type, stand-by sliding reserve for them, twice total reserve of the power supply with two accumulator batteries, the controls and diagnostics means. The developed tool for automated analytical model of fault tolerant systems generation ...

  4. Fault Tolerant Homopolar Magnetic Bearings

    Li, Ming-Hsiu; Palazzolo, Alan; Kenny, Andrew; Provenza, Andrew; Beach, Raymond; Kascak, Albert


    Magnetic suspensions (MS) satisfy the long life and low loss conditions demanded by satellite and ISS based flywheels used for Energy Storage and Attitude Control (ACESE) service. This paper summarizes the development of a novel MS that improves reliability via fault tolerant operation. Specifically, flux coupling between poles of a homopolar magnetic bearing is shown to deliver desired forces even after termination of coil currents to a subset of failed poles . Linear, coordinate decoupled force-voltage relations are also maintained before and after failure by bias linearization. Current distribution matrices (CDM) which adjust the currents and fluxes following a pole set failure are determined for many faulted pole combinations. The CDM s and the system responses are obtained utilizing 1D magnetic circuit models with fringe and leakage factors derived from detailed, 3D, finite element field models. Reliability results are presented vs. detection/correction delay time and individual power amplifier reliability for 4, 6, and 7 pole configurations. Reliability is shown for two success criteria, i.e. (a) no catcher bearing contact following pole failures and (b) re-levitation off of the catcher bearings following pole failures. An advantage of the method presented over other redundant operation approaches is a significantly reduced requirement for backup hardware such as additional actuators or power amplifiers.

  5. Modelling tree biomasses in Finland

    Repola, J.


    Biomass equations for above- and below-ground tree components of Scots pine (Pinus sylvestris L), Norway spruce (Picea abies [L.] Karst) and birch (Betula pendula Roth and Betula pubescens Ehrh.) were compiled using empirical material from a total of 102 stands. These stands (44 Scots pine, 34 Norway spruce and 24 birch stands) were located mainly on mineral soil sites representing a large part of Finland. The biomass models were based on data measured from 1648 sample trees, comprising 908 pine, 613 spruce and 127 birch trees. Biomass equations were derived for the total above-ground biomass and for the individual tree components: stem wood, stem bark, living and dead branches, needles, stump, and roots, as dependent variables. Three multivariate models with different numbers of independent variables for above-ground biomass and one for below-ground biomass were constructed. Variables that are normally measured in forest inventories were used as independent variables. The simplest model formulations, multivariate models (1) were mainly based on tree diameter and height as independent variables. In more elaborated multivariate models, (2) and (3), additional commonly measured tree variables such as age, crown length, bark thickness and radial growth rate were added. Tree biomass modelling includes consecutive phases, which cause unreliability in the prediction of biomass. First, biomasses of sample trees should be determined reliably to decrease the statistical errors caused by sub-sampling. In this study, methods to improve the accuracy of stem biomass estimates of the sample trees were developed. In addition, the reliability of the method applied to estimate sample-tree crown biomass was tested, and no systematic error was detected. Second, the whole information content of data should be utilized in order to achieve reliable parameter estimates and applicable and flexible model structure. In the modelling approach, the basic assumption was that the biomasses of

  6. Absolute age determination of quaternary fault and formation

    Cheong, Chang Sik; Lee, Kwang Sik; Choi, Man Sik [Korea Basic Science Institute, Seoul (Korea, Republic of)] (and others)


    The annual ('01-'01) objective of this project is to data the fault activity for the presumed quaternary fault zones to the western part of the Ulsam fault system and southeastern coastal area near the Wolseong Nuclear Power Plant. Rb-Sr, K-Ar, OSL, C-14 and U-series disequilibrium methods were applied to the fault rocks, organic matter and quaternary formations collected from the Pyeonghae, Bogyeongsa, Yugyeri, Byegkye, Gacheon-1 and Joil outcrops of the Yangsan fault system, the Baenaegol outcrop of the Moryang fault system, the Susyongji(Madong-2), Singye, Hwalseongri, Ipsil and Wonwonsa outcrops of the Ulsan fault system and from quaternary marine terraces (Oryoo and Kwangseong sites) in the southeastern coastal area. The experimental procedure of the OSL SAR protocol was reexamined to get more reliable dating results.

  7. Decentralized Fault Management for Service Dependability in Ubiquitous Networks

    Grønbæk, Lars Jesper


    Obtaining reliable operation of end-user services in future ubiquitous networking environments is challenging. Faults occur and heterogeneous networks make it difficult to deploy network wide fault management mechanisms. This PhD lecture presents a study on the options an end-node has to mitigate...

  8. Control switching in high performance and fault tolerant control

    Niemann, Hans Henrik; Poulsen, Niels Kjølstad


    The problem of reliability in high performance control and in fault tolerant control is considered in this paper. A feedback controller architecture for high performance and fault tolerance is considered. The architecture is based on the Youla-Jabr-Bongiorno-Kucera (YJBK) parameterization. By usi...

  9. A Complete Analytic Model for Fault Diagnosis of Power Systems

    LIU Daobing; GU Xueping; LI Haipeng


    Interconnections of the modem bulk electric power systems, while contributing to the operating economy and reliability by means of mutual assistance between the subsystems, result in an increased complexity of fault diagnosis and a more serious consequence of misdiagnosis. The online fault diagnosis has become a more challenging problem for dispatchers to operate a power system securely,

  10. Fault Tolerant Feedback Control

    Stoustrup, Jakob; Niemann, H.


    An architecture for fault tolerant feedback controllers based on the Youla parameterization is suggested. It is shown that the Youla parameterization will give a residual vector directly in connection with the fault diagnosis part of the fault tolerant feedback controller. It turns out...... that there is a separation be-tween the feedback controller and the fault tolerant part. The closed loop feedback properties are handled by the nominal feedback controller and the fault tolerant part is handled by the design of the Youla parameter. The design of the fault tolerant part will not affect the design...... of the nominal feedback con-troller....

  11. Context trees

    Ganzinger, Harald; Nieuwenhuis, Robert; Nivela, Pilar


    Indexing data structures are well-known to be crucial for the efficiency of the current state-of-the-art theorem provers. Examples are \\emph{discrimination trees}, which are like tries where terms are seen as strings and common prefixes are shared, and \\emph{substitution trees}, where terms keep their tree structure and all common \\emph{contexts} can be shared. Here we describe a new indexing data structure, \\emph{context trees}, where, by means of a limited kind of conte...

  12. Two Trees

    Cochrane, John. H.; Longstaff, Francis A.; Santa-Clara, Pedro


    We solve a model with two “Lucas trees.†Each tree has i.i.d. dividend growth. The investor has log utility and consumes the sum of the two trees’ dividends. This model produces interesting asset-pricing dynamics, despite its simple ingredients. Investors want to rebalance their portfolios after any change in value. Since the size of the trees is fixed, however, prices must adjust to offset this desire. As a result, expected returns, excess returns, and return volatility all vary throug...

  13. MEMS reliability

    Hartzell, Allyson L; Shea, Herbert R


    This book focuses on the reliability and manufacturability of MEMS at a fundamental level. It demonstrates how to design MEMs for reliability and provides detailed information on the different types of failure modes and how to avoid them.

  14. Fault Tree Analysis of the Lack of Competency of Rural Doctors Under Essential Medicine System%基本药物制度背景下乡村医生胜任力不足的故障树分析

    贾海艺; 尹文强; 陈钟鸣; 朱丽丽; 郑骥飞; 秦晓强; 黄冬梅


    Objective To explore reasons for the lack of competency of rural doctors under essential medicine system. Methods We enrolled 621 rural doctors from 134 village health centers in Shandong Province from August to December, 2012 using multi - stage stratified random sampling method. We also enrolled 642 rural doctors form 225 village centers in Shandong province from December 2013 to March 2014 using complete random sampling method. Questionnaire survey, qualitative interview and literature analysis were conducted to collect relevant data,including general information,the influence of essential medicine system on rural doctors,the current status of life and work of rural doctors and the cognition of rural doctors on the occupation. We built fault tree analysis model,in which the lack of competency of rural doctors was set as the top event,to investigate reasons for the lack of competency of rural doctors. Results In two surveys, we distributed 621 and 642 questionnaires respectively,and all questionnaires were returned with an effective returning rate of 100. 0% . Among subjects, 81. 1% (499 / 615) graduated from technical secondary school or below that education level,57. 3% (335 / 585)hadn' t registered with any pension insurance,94. 2% (572 / 607)were unsatisfied with their income,55. 9% (356 / 637) were unsatisfied with their job,76. 3% (488 / 640)believed their contribution to the society was increasing,and 58. 1% (371 / 639) thought their living condition hadn't been improved;47. 6% (303 / 637)said that they always compared themselves with rural teachers,and 40. 0% (255 / 638) thought the best occupation in rural areas is teacher. The interviews and literature analysis showed the following results. With further implementation of essential medicine system in grass root level,the working volume and working pressure of rural doctors increased,while their income decreased,and the drop of medicine revenue further lowered their income. The trust of villagers in rural

  15. Reliability importance analysis of Markovian systems at steady state using perturbation analysis

    Phuc Do Van [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France); Barros, Anne [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France)], E-mail:; Berenguer, Christophe [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France)


    Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity analysis remains widely open. In this paper, the perturbation method is used to estimate an importance factor, called multi-directional sensitivity measure, in the framework of Markovian systems. Some numerical examples are introduced to show why this method offers a promising tool for steady-state sensitivity analysis of Markov processes in reliability studies.

  16. Reliability Assessment of Fuel Cell System - A Framework for Quantitative Approach

    Lee, Shinae; Zhou, Dao; Wang, Huai


    Hydrogen Fuel Cell (FC) technologies have been developed to overcome the operational and environmental challenges associated with using conventional power sources. Telecommunication industry, in particular, has implemented FC systems for the backup power function. The designers and manufacturers...... of such FC systems have great interest in verifying the performance and safety of their systems. Reliability assessment is designated to support decision-making about the optimal design and the operation strategies for FC systems to be commercial viable. This involves the properties of the system...... such as component failures, the system architecture, and operational strategies. This paper suggests an approach that includes Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA), and Reliability Block Diagram (RBD). For a case study, and the service lifetime of a commercial 5 kW Proton Exchange...

  17. Fault Diagnosis of Plunger Pump in Truck Crane Based on Relevance Vector Machine with Particle Swarm Optimization Algorithm

    Wenliao Du


    Full Text Available Promptly and accurately dealing with the equipment breakdown is very important in terms of enhancing reliability and decreasing downtime. A novel fault diagnosis method PSO-RVM based on relevance vector machines (RVM with particle swarm optimization (PSO algorithm for plunger pump in truck crane is proposed. The particle swarm optimization algorithm is utilized to determine the kernel width parameter of the kernel function in RVM, and the five two-class RVMs with binary tree architecture are trained to recognize the condition of mechanism. The proposed method is employed in the diagnosis of plunger pump in truck crane. The six states, including normal state, bearing inner race fault, bearing roller fault, plunger wear fault, thrust plate wear fault, and swash plate wear fault, are used to test the classification performance of the proposed PSO-RVM model, which compared with the classical models, such as back-propagation artificial neural network (BP-ANN, ant colony optimization artificial neural network (ANT-ANN, RVM, and support vectors, machines with particle swarm optimization (PSO-SVM, respectively. The experimental results show that the PSO-RVM is superior to the first three classical models, and has a comparative performance to the PSO-SVM, the corresponding diagnostic accuracy achieving as high as 99.17% and 99.58%, respectively. But the number of relevance vectors is far fewer than that of support vector, and the former is about 1/12–1/3 of the latter, which indicates that the proposed PSO-RVM model is more suitable for applications that require low complexity and real-time monitoring.

  18. Fault detection and isolation in systems with parametric faults

    Stoustrup, Jakob; Niemann, Hans Henrik


    The problem of fault detection and isolation of parametric faults is considered in this paper. A fault detection problem based on parametric faults are associated with internal parameter variations in the dynamical system. A fault detection and isolation method for parametric faults is formulated...

  19. Iowa Bedrock Faults

    Iowa State University GIS Support and Research Facility — This fault coverage locates and identifies all currently known/interpreted fault zones in Iowa, that demonstrate offset of geologic units in exposure or subsurface...

  20. null Faults, null Images

    National Oceanic and Atmospheric Administration, Department of Commerce — Through the study of faults and their effects, much can be learned about the size and recurrence intervals of earthquakes. Faults also teach us about crustal...

  1. Analysis of a hardware and software fault tolerant processor for critical applications

    Dugan, Joanne B.


    Computer systems for critical applications must be designed to tolerate software faults as well as hardware faults. A unified approach to tolerating hardware and software faults is characterized by classifying faults in terms of duration (transient or permanent) rather than source (hardware or software). Errors arising from transient faults can be handled through masking or voting, but errors arising from permanent faults require system reconfiguration to bypass the failed component. Most errors which are caused by software faults can be considered transient, in that they are input-dependent. Software faults are triggered by a particular set of inputs. Quantitative dependability analysis of systems which exhibit a unified approach to fault tolerance can be performed by a hierarchical combination of fault tree and Markov models. A methodology for analyzing hardware and software fault tolerant systems is applied to the analysis of a hypothetical system, loosely based on the Fault Tolerant Parallel Processor. The models consider both transient and permanent faults, hardware and software faults, independent and related software faults, automatic recovery, and reconfiguration.

  2. Talking Trees

    Tolman, Marvin


    Students love outdoor activities and will love them even more when they build confidence in their tree identification and measurement skills. Through these activities, students will learn to identify the major characteristics of trees and discover how the pace--a nonstandard measuring unit--can be used to estimate not only distances but also the…

  3. SIFT - Multiprocessor architecture for Software Implemented Fault Tolerance flight control and avionics computers

    Forman, P.; Moses, K.


    A brief description of a SIFT (Software Implemented Fault Tolerance) Flight Control Computer with emphasis on implementation is presented. A multiprocessor system that relies on software-implemented fault detection and reconfiguration algorithms is described. A high level reliability and fault tolerance is achieved by the replication of computing tasks among processing units.

  4. A Fault Diagnostic Method for Position Sensor of Switched Reluctance Wind Generator

    Wang, Chao; Liu, Xiao; Liu, Hui


    Fast and accurate fault diagnosis of the position sensor is of great significance to ensure the reliability as well as sensor fault tolerant operation of the Switched Reluctance Wind Generator (SRWG). This paper presents a fault diagnostic scheme for a SRWG based on the residual between the estim...

  5. Reliability Analysis of Distributed Grid-connected Photovoltaic System Monitoring Network

    Fu Zhixin


    Full Text Available A large amount of distributed grid-connected Photovoltaic systems have brought new challenges to the dispatching of power network. Real-time monitoring the PV system can efficiently help improve the ability of power network to accept and control the distributed PV systems, and thus mitigate the impulse on the power network imposed by the uncertainty of its power output. To study the reliability of distributed PV monitoring network, it is of great significance to look for a method to build a highly reliable monitoring system, analyze the weak links and key nodes of its monitoring performance in improving the performance of the monitoring network. Firstly a reliability model of PV system was constructed based on WSN technology. Then, in view of the dynamic characteristics of the network’s reliability, fault tree analysis was used to judge any possible reasons that cause the failure of the network and logical relationship between them. Finally, the reliability of the monitoring network was analyzed to figure out the weak links and key nodes. This paper provides guidance to build a stable and reliable monitoring network of a distributed PV system.

  6. Performance based fault diagnosis

    Niemann, Hans Henrik


    Different aspects of fault detection and fault isolation in closed-loop systems are considered. It is shown that using the standard setup known from feedback control, it is possible to formulate fault diagnosis problems based on a performance index in this general standard setup. It is also shown...

  7. Fault Tolerant Control Systems

    Bøgh, S. A.

    was to avoid a total close-down in case of the most likely faults. The second was a fault tolerant attitude control system for a micro satellite where the operation of the system is mission critical. The purpose was to avoid hazardous effects from faults and maintain operation if possible. A method...

  8. PV Systems Reliability Final Technical Report.

    Lavrova, Olga [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Flicker, Jack David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Johnson, Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Armijo, Kenneth Miguel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gonzalez, Sigifredo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schindelholz, Eric John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sorensen, Neil R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Yang, Benjamin Bing-Yeh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    The continued exponential growth of photovoltaic technologies paves a path to a solar-powered world, but requires continued progress toward low-cost, high-reliability, high-performance photovoltaic (PV) systems. High reliability is an essential element in achieving low-cost solar electricity by reducing operation and maintenance (O&M) costs and extending system lifetime and availability, but these attributes are difficult to verify at the time of installation. Utilities, financiers, homeowners, and planners are demanding this information in order to evaluate their financial risk as a prerequisite to large investments. Reliability research and development (R&D) is needed to build market confidence by improving product reliability and by improving predictions of system availability, O&M cost, and lifetime. This project is focused on understanding, predicting, and improving the reliability of PV systems. The two areas being pursued include PV arc-fault and ground fault issues, and inverter reliability.

  9. A Novel Protection Scheme against Fault Resistance for AC Microgrid

    Xinrui Liu


    Full Text Available The faults characteristics of the lines in AC microgrid are weakened due to the fault resistance, which may refuse protection action. To solve the problems caused by different types of the faults through fault resistance (FTFR, the faults where the fault point resistance is greater than zero in AC microgrid, a novel FTFR protection scheme based on the active power of 0-frame component or d-frame component consumed by fault resistance is proposed in this paper as the backup protection of FTFR. This proposed protection scheme utilizes the active power of 0-frame component or d-frame component consumed by fault resistance to identify internal FTFR and external faults. It performs well in grid-connected mode and islanded mode by adopting self-adaptive threshold and is not affected by the factors such as the fault position and the fault resistance value. The theoretical analysis and various simulations show that this protection scheme can identify and isolate different types of internal FTFR in AC microgrid with high reliability and high sensitivity.


    B.Anni Princy


    Full Text Available A software reliability exemplary projects snags the random process as disillusionments which were the culmination yield of two progressions: emerging faults and initial state values. The predominant classification uses the logistic analysis effort function mounting efficient software on the real time dataset. The detriments of the logistic testing were efficaciously overcome by Pareto distribution. The estimated outline ventures the resolved technique for analyzing the suitable communities and the preeminent of fit for a software reliability progress model. Its constraints are predictable to evaluate the reliability of a software system. The future process will permit for software reliability estimations that can be used both as prominence Indicator, but also for planning and controlling resources, the development times based on the onslaught assignments of the efficient computing and reliable measurement of a software system was competent.

  11. Model-Based Fault Tolerant Control for Hybrid Dynamic Systems with Sensor Faults%一类带有传染器故障的混合系统的容错控制

    杨浩; 冒泽慧; 姜斌


    A model-based fault tolerant control approach for hybrid linear dynamic systems is proposed in this paper. The proposed method, taking advantage of reliable control, can maintain the performance of the faulty system during the time delay of fault detection and diagnosis (FDD) and fault accommodation (FA), which can be regarded as the first line of defence against sensor faults.Simulation results of a three-tank system with sensor fault are given to show the efficiency of the method.

  12. Information Based Fault Diagnosis

    Niemann, Hans Henrik; Poulsen, Niels Kjølstad


    Fault detection and isolation, (FDI) of parametric faults in dynamic systems will be considered in this paper. An active fault diagnosis (AFD) approach is applied. The fault diagnosis will be investigated with respect to different information levels from the external inputs to the systems....... These inputs are disturbance inputs, reference inputs and auxilary inputs. The diagnosis of the system is derived by an evaluation of the signature from the inputs in the residual outputs. The changes of the signatures form the external inputs are used for detection and isolation of the parametric faults....

  13. Open-Switch Fault Diagnosis and Fault Tolerant for Matrix Converter with Finite Control Set-Model Predictive Control

    Peng, Tao; Dan, Hanbing; Yang, Jian


    To improve the reliability of the matrix converter (MC), a fault diagnosis method to identify single open-switch fault is proposed in this paper. The introduced fault diagnosis method is based on finite control set-model predictive control (FCS-MPC), which employs a time-discrete model of the MC...... topology and a cost function to select the best switching state for the next sampling period. The proposed fault diagnosis method is realized by monitoring the load currents and judging the switching state to locate the faulty switch. Compared to the conventional modulation strategies such as carrier...

  14. Phylogenetic trees

    Baños, Hector; Bushek, Nathaniel; Davidson, Ruth; Gross, Elizabeth; Harris, Pamela E.; Krone, Robert; Long, Colby; Stewart, Allen; WALKER, Robert


    We introduce the package PhylogeneticTrees for Macaulay2 which allows users to compute phylogenetic invariants for group-based tree models. We provide some background information on phylogenetic algebraic geometry and show how the package PhylogeneticTrees can be used to calculate a generating set for a phylogenetic ideal as well as a lower bound for its dimension. Finally, we show how methods within the package can be used to compute a generating set for the join of any two ideals.

  15. Earthquake fault superhighways

    Robinson, D. P.; Das, S.; Searle, M. P.


    Motivated by the observation that the rare earthquakes which propagated for significant distances at supershear speeds occurred on very long straight segments of faults, we examine every known major active strike-slip fault system on land worldwide and identify those with long (> 100 km) straight portions capable not only of sustained supershear rupture speeds but having the potential to reach compressional wave speeds over significant distances, and call them "fault superhighways". The criteria used for identifying these are discussed. These superhighways include portions of the 1000 km long Red River fault in China and Vietnam passing through Hanoi, the 1050 km long San Andreas fault in California passing close to Los Angeles, Santa Barbara and San Francisco, the 1100 km long Chaman fault system in Pakistan north of Karachi, the 700 km long Sagaing fault connecting the first and second cities of Burma, Rangoon and Mandalay, the 1600 km Great Sumatra fault, and the 1000 km Dead Sea fault. Of the 11 faults so classified, nine are in Asia and two in North America, with seven located near areas of very dense populations. Based on the current population distribution within 50 km of each fault superhighway, we find that more than 60 million people today have increased seismic hazards due to them.

  16. Analysis of fault using microcomputer protection by symmetrical component method

    Ashish Choubey


    Full Text Available To enhance power supply reliability for the user terminals in the case of the distribution system to avoid interference by the fault again, rapidly complete the automatic identification, positioning, automatic fault isolation, network reconfiguration until the resumption of supply of non-fault section, a microprocessor-based relay protection device has developed. As the fault component theory is widely used in microcomputer protection, and fault component exists in the network of fault component, it is necessary to build up the fault component network when short circuit fault emerging and to draw the current and voltage component phasor diagram at fault point. In order to understand microcomputer protection based on the symmetrical component principle, we obtained the sequence current and sequence voltage according to the concept of symmetrical component. Distribution line directly to user-oriented power supply, the reliability of its operation determines the quality and level of electricity supply. In recent decades, because of the general power of the tireless efforts of scientists and technicians, relay protection technology and equipment application level has been greatly improved, but the current domestic production of computer hardware, protection devices are still outdated systems. Software development has maintenance difficulties and short survival time. With the factory automation system interface functions weak points, the network communication cannot meet the actual requirements. Protection principle configuration and device manufacturing process to be improved and so on.

  17. Reliability of Power Electronic Converter Systems

    -link capacitance in power electronic converter systems; wind turbine systems; smart control strategies for improved reliability of power electronics system; lifetime modelling; power module lifetime test and state monitoring; tools for performance and reliability analysis of power electronics systems; fault......-tolerant adjustable speed drive systems; mission profile oriented reliability design in wind turbine and photovoltaic systems; reliability of power conversion systems in photovoltaic applications; power supplies for computers; and high-power converters. Reliability of Power Electronic Converter Systems is essential...... reading for researchers, professionals and students working with power electronics and their applications, particularly those specializing in the development and application of power electronic converters and systems....

  18. Game tree algorithms and solution trees

    W.H.L.M. Pijls (Wim); A. de Bruin (Arie)


    textabstractIn this paper, a theory of game tree algorithms is presented, entirely based upon the concept of solution tree. Two types of solution trees are distinguished: max and min trees. Every game tree algorithm tries to prune nodes as many as possible from the game tree. A cut-off criterion in

  19. Electron Tree

    Appelt, Ane L; Rønde, Heidi S


    The photo shows a close-up of a Lichtenberg figure – popularly called an “electron tree” – produced in a cylinder of polymethyl methacrylate (PMMA). Electron trees are created by irradiating a suitable insulating material, in this case PMMA, with an intense high energy electron beam. Upon discharge......, during dielectric breakdown in the material, the electrons generate branching chains of fractures on leaving the PMMA, producing the tree pattern seen. To be able to create electron trees with a clinical linear accelerator, one needs to access the primary electron beam used for photon treatments. We...... appropriated a linac that was being decommissioned in our department and dismantled the head to circumvent the target and ion chambers. This is one of 24 electron trees produced before we had to stop the fun and allow the rest of the accelerator to be disassembled....

  20. Electron Tree

    Appelt, Ane L; Rønde, Heidi S


    The photo shows a close-up of a Lichtenberg figure – popularly called an “electron tree” – produced in a cylinder of polymethyl methacrylate (PMMA). Electron trees are created by irradiating a suitable insulating material, in this case PMMA, with an intense high energy electron beam. Upon discharge......, during dielectric breakdown in the material, the electrons generate branching chains of fractures on leaving the PMMA, producing the tree pattern seen. To be able to create electron trees with a clinical linear accelerator, one needs to access the primary electron beam used for photon treatments. We...... appropriated a linac that was being decommissioned in our department and dismantled the head to circumvent the target and ion chambers. This is one of 24 electron trees produced before we had to stop the fun and allow the rest of the accelerator to be disassembled....

  1. Planetary Gearbox Fault Diagnosis Using Envelope Manifold Demodulation

    Weigang Wen


    Full Text Available The important issue in planetary gear fault diagnosis is to extract the dependable fault characteristics from the noisy vibration signal of planetary gearbox. To address this critical problem, an envelope manifold demodulation method is proposed for planetary gear fault detection in the paper. This method combines complex wavelet, manifold learning, and frequency spectrogram to implement planetary gear fault characteristic extraction. The vibration signal of planetary gear is demodulated by wavelet enveloping. The envelope energy is adopted as an indicator to select meshing frequency band. Manifold learning is utilized to reduce the effect of noise within meshing frequency band. The fault characteristic frequency of the planetary gear is shown by spectrogram. The planetary gearbox model and test rig are established and experiments with planet gear faults are conducted for verification. All results of experiment analysis demonstrate its effectiveness and reliability.

  2. Research on Transformer Fault Based on Probabilistic Neural Network

    Li Yingshun


    Full Text Available With the development of computer science and technology, and increasingly intelligent industrial production, the application of big data in industry also advances rapidly, and the development of artificial intelligence in the aspect of fault diagnosis is particularly prominent. On the basis of MATLAB platform, this paper constructs a fault diagnosis expert system of artificial intelligence machine based on the probabilistic neural network, and it also carries out a simulation of production process by the use of bionic algorithm. This paper makes a diagnosis of transformer fault by the use of an expert system developed by this paper, and verifies that the probabilistic neural network has a good convergence, fault-tolerant ability and big data handling capability in the fault diagnosis. It is suitable for industrial production, which can provide a reliable mathematical model for the construction of fault diagnosis expert system in the industrial production.

  3. A Fault-Tolerant Architecture for Parlay Application Server

    LI Yong-ping; CHEN Jun-liang


    As the value-added service providing system in the Next-Generation Networks (NGN), Application Servers (AS) are required to provide the carrier-class reliability. To increase the reliability of AS, the fault-tolerant technology is often adopted. This paper proposes a fault-tolerant architecture for AS against single-point faults. The result of analysis shows that the architecture has a good reliability and is easily extendable. Such an advantage is attributed to a kind of special fault-tolerant design, which is different from others in that two Service Logic Program (SLP) instances do not only provide backups to each other, but also share them in the service traffic.

  4. A novel 2-phase reliability improvement of digital circuits

    Shojaei, Maryam; Mahani, Ali


    Nowadays several methods based on modular redundancy are proposed to increase the reliability of digital circuits. Redundant fault tolerant techniques increase the consumed power and area overhead. So in this paper a two phase fault tolerant design is proposed to get the balance between reliability and area overhead. In the first phase, reliability optimization of digital circuits which utilizes the architecture with higher reliability as an objective function is considered. Then the automatic insertion of selective non-uniform redundancy is applied to improve the reliability of obtained circuit as second phase. To show the effectiveness of the proposed method, simulation results are compared with triple modular redundancy.

  5. Nerual Networks with Decision Trees for Diagnosis Issues

    Yahia Kourd


    Full Text Available This paper presents a new idea for fault detection and isolation (FDI technique which is applied to industrial system. This technique is bas ed on Neural Networks fault-free and Faulty behaviours Models (NNFMs. NNFMs are used for resid ual generation, while decision tree architecture is used for residual evaluation. The d ecision tree is realized with data collected from the NNFM’s outputs and is used to isolate dete ctable faults depending on computed threshold. Each part of the tree corresponds to spe cific residual. With the decision tree, it becomes possible to take the appropriate decision r egarding the actual process behaviour by evaluating few numbers of residuals. In comparison to usual systematic evaluation of all residuals, the proposed technique requires less com putational effort and can be used for on line diagnosis. An application example is presented to i llustrate and confirm the effectiveness and the accuracy of the proposed approach.

  6. Statistical fault detection in photovoltaic systems

    Garoudja, Elyes


    Faults in photovoltaic (PV) systems, which can result in energy loss, system shutdown or even serious safety breaches, are often difficult to avoid. Fault detection in such systems is imperative to improve their reliability, productivity, safety and efficiency. Here, an innovative model-based fault-detection approach for early detection of shading of PV modules and faults on the direct current (DC) side of PV systems is proposed. This approach combines the flexibility, and simplicity of a one-diode model with the extended capacity of an exponentially weighted moving average (EWMA) control chart to detect incipient changes in a PV system. The one-diode model, which is easily calibrated due to its limited calibration parameters, is used to predict the healthy PV array\\'s maximum power coordinates of current, voltage and power using measured temperatures and irradiances. Residuals, which capture the difference between the measurements and the predictions of the one-diode model, are generated and used as fault indicators. Then, the EWMA monitoring chart is applied on the uncorrelated residuals obtained from the one-diode model to detect and identify the type of fault. Actual data from the grid-connected PV system installed at the Renewable Energy Development Center, Algeria, are used to assess the performance of the proposed approach. Results show that the proposed approach successfully monitors the DC side of PV systems and detects temporary shading.

  7. Fault Detection and Control of Process Systems

    Vu Trieu Minh


    Full Text Available This paper develops a stochastic hybrid model-based control system that can determine online the optimal control actions, detect faults quickly in the control process, and reconfigure the controller accordingly using interacting multiple-model (IMM estimator and generalized predictive control (GPC algorithm. A fault detection and control system consists of two main parts: the first is the fault detector and the second is the controller reconfiguration. This work deals with three main challenging issues: design of fault model set, estimation of stochastic hybrid multiple models, and stochastic model predictive control of hybrid multiple models. For the first issue, we propose a simple scheme for designing faults for discrete and continuous random variables. For the second issue, we consider and select a fast and reliable fault detection system applied to the stochastic hybrid system. Finally, we develop a stochastic GPC algorithm for hybrid multiple-models controller reconfiguration with soft switching signals based on weighted probabilities. Simulations for the proposed system are illustrated and analyzed.

  8. Comparison between open phase fault of arc suppression coil and single phase to earth fault in coal mine distribution network

    LI Xiao-bo; WANG Chong-lin


    When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and reliable run of the network.We first introduce a three-phase five-column arc suppression coil (TPFCASC) and discuss its autotracking compensation theory.Then we compare the single phase to ground fault of the coal mine distribution network with an open phase fault at the TPFCASC using the Thévenin theory, the symmetrical-component method and the complex sequence network respectively. The results show that, in both types of faults, zero-sequence voltage of the network will appear and the maximum magnitude of this zero-sequence voltage is different in both faults. Based on this situation, a protection for the open phase fault at the TPFCASC should be estab-lished.

  9. Layered clustering multi-fault diagnosis for hydraulic piston pump

    Du, Jun; Wang, Shaoping; Zhang, Haiyan


    Efficient diagnosis is very important for improving reliability and performance of aircraft hydraulic piston pump, and it is one of the key technologies in prognostic and health management system. In practice, due to harsh working environment and heavy working loads, multiple faults of an aircraft hydraulic pump may occur simultaneously after long time operations. However, most existing diagnosis methods can only distinguish pump faults that occur individually. Therefore, new method needs to be developed to realize effective diagnosis of simultaneous multiple faults on aircraft hydraulic pump. In this paper, a new method based on the layered clustering algorithm is proposed to diagnose multiple faults of an aircraft hydraulic pump that occur simultaneously. The intensive failure mechanism analyses of the five main types of faults are carried out, and based on these analyses the optimal combination and layout of diagnostic sensors is attained. The three layered diagnosis reasoning engine is designed according to the faults' risk priority number and the characteristics of different fault feature extraction methods. The most serious failures are first distinguished with the individual signal processing. To the desultory faults, i.e., swash plate eccentricity and incremental clearance increases between piston and slipper, the clustering diagnosis algorithm based on the statistical average relative power difference (ARPD) is proposed. By effectively enhancing the fault features of these two faults, the ARPDs calculated from vibration signals are employed to complete the hypothesis testing. The ARPDs of the different faults follow different probability distributions. Compared with the classical fast Fourier transform-based spectrum diagnosis method, the experimental results demonstrate that the proposed algorithm can diagnose the multiple faults, which occur synchronously, with higher precision and reliability.

  10. A comparative analysis of reliability, maintainability and availability for two alternatives of the production submarine systems: ANM and submarine ducts versus BOP and a subsea well testing tree; Analise comparativa da confiabilidade, mantenabilidade e disponibilidade para duas alternativas de sistemas submarino de producao: ANM e dutos submarinos versus BOP e arvore submarina de teste

    Souza, Arlindo Antonio de; Polillo Filho, Adolfo; Santos, Otto Luiz Alcantara [PETROBRAS, Rio de Janeiro, RJ (Brazil)


    This technical article presents a study using the concepts of the Engineering of the Reliability and Risk Analysis with the objective of doing a comparative evaluation of the reliability of two alternative production systems for a marine well: one composed by a wet christmas tree (ANM) producing through underwater ducts (flow lines) and other, usually used in tests of long duration, using a subsea BOP and a subsea well testing tree (AST). The central point of the work was the evaluation of the probability of happening an event considered as critic, denominated 'critical flaw', during the well production life. The work uses one of the procedures and methodologies adopted in the Well Construction Engineering, GERISK, together with four computer applications for data treatment, generation of flaw distribution curves and times of repair, modelling and Monte Carlo simulations. The adopted strategy was the one of starting from the existent report, to assume an interval for the possible real value of the relevant parameters and then to establish the scenarios (more probable, optimist and pessimist). Based on those sceneries, the considered premises, the modelling and the reliabilities obtained for each one of the variables, the simulations have been made. As results, are presented the medium readiness, MTTFF (Mean Time To First Failure), the number of flaws and the expected costs. The work also displays the sensibility analysis in respect to the time of production of the well. (author)

  11. Diagnosis of three types of constant faults in read-once contact networks over finite bases

    Busbait, Monther I.


    We study the depth of decision trees for diagnosis of three types of constant faults in read-once contact networks over finite bases containing only indecomposable networks. For each basis and each type of faults, we obtain a linear upper bound on the minimum depth of decision trees depending on the number of edges in networks. For bases containing networks with at most 10 edges, we find sharp coefficients for linear bounds.

  12. Locating hardware faults in a parallel computer

    Archer, Charles J.; Megerian, Mark G.; Ratterman, Joseph D.; Smith, Brian E.


    Locating hardware faults in a parallel computer, including defining within a tree network of the parallel computer two or more sets of non-overlapping test levels of compute nodes of the network that together include all the data communications links of the network, each non-overlapping test level comprising two or more adjacent tiers of the tree; defining test cells within each non-overlapping test level, each test cell comprising a subtree of the tree including a subtree root compute node and all descendant compute nodes of the subtree root compute node within a non-overlapping test level; performing, separately on each set of non-overlapping test levels, an uplink test on all test cells in a set of non-overlapping test levels; and performing, separately from the uplink tests and separately on each set of non-overlapping test levels, a downlink test on all test cells in a set of non-overlapping test levels.

  13. Systems Analysis Programs for Hands-On Integrated Reliability Evaluations (SAPHIRE) Technical Reference

    C. L. Smith; W. J. Galyean; S. T. Beck


    The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) is a software application developed for performing a complete probabilistic risk assessment (PRA) using a personal computer (PC) running the Microsoft Windows? operating system. Herein information is provided on the principles used in the construction and operation of Version 6.0 and 7.0 of the SAPHIRE system. This report summarizes the fundamental mathematical concepts of sets and logic, fault trees, and probability. This volume then describes the algorithms used to construct a fault tree and to obtain the minimal cut sets. It gives the formulas used to obtain the probability of the top event from the minimal cut sets, and the formulas for probabilities that apply for various assumptions concerning reparability and mission time. It defines the measures of basic event importance that SAPHIRE can calculate. This volume gives an overview of uncertainty analysis using simple Monte Carlo sampling or Latin Hypercube sampling, and states the algorithms used by this program to generate random basic event probabilities from various distributions. Also covered are enhance capabilities such as seismic analysis, cut set "recovery," end state manipulation, and use of "compound events."

  14. Systems Analysis Programs for Hands-On Integrated Reliability Evaluations (SAPHIRE) Technical Reference Manual

    C. L. Smith; W. J. Galyean; S. T. Beck


    The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) is a software application developed for performing a complete probabilistic risk assessment (PRA) using a personal computer (PC) running the Microsoft Windows? operating system. Herein information is provided on the principles used in the construction and operation of Version 6.0 and 7.0 of the SAPHIRE system. This report summarizes the fundamental mathematical concepts of sets and logic, fault trees, and probability. This volume then describes the algorithms used to construct a fault tree and to obtain the minimal cut sets. It gives the formulas used to obtain the probability of the top event from the minimal cut sets, and the formulas for probabilities that apply for various assumptions concerning reparability and mission time. It defines the measures of basic event importance that SAPHIRE can calculate. This volume gives an overview of uncertainty analysis using simple Monte Carlo sampling or Latin Hypercube sampling, and states the algorithms used by this program to generate random basic event probabilities from various distributions. Also covered are enhance capabilities such as seismic analysis, cut set "recovery," end state manipulation, and use of "compound events."

  15. Locating hardware faults in a data communications network of a parallel computer

    Archer, Charles J.; Megerian, Mark G.; Ratterman, Joseph D.; Smith, Brian E.


    Hardware faults location in a data communications network of a parallel computer. Such a parallel computer includes a plurality of compute nodes and a data communications network that couples the compute nodes for data communications and organizes the compute node as a tree. Locating hardware faults includes identifying a next compute node as a parent node and a root of a parent test tree, identifying for each child compute node of the parent node a child test tree having the child compute node as root, running a same test suite on the parent test tree and each child test tree, and identifying the parent compute node as having a defective link connected from the parent compute node to a child compute node if the test suite fails on the parent test tree and succeeds on all the child test trees.

  16. Cross-fault pressure depletion, Zechstein carbonate reservoir, Weser-Ems area, Northern German Gas Basin

    Corona, F.V.; Brauckmann, F.; Beckmann, H.; Gobi, A.; Grassmann, S.; Neble, J.; Roettgen, K. [ExxonMobil Production Deutschland GmbH (EMPG), Hannover (Germany)


    A cross-fault pressure depletion study in Upper Permian Zechstein Ca2 carbonate reservoir was undertaken in the Weser-Ems area of the Northern German Gas Basin. The primary objectives are to develop a practical workflow to define cross-fault pressures scenarios for Zechstein Ca2 reservoir drillwells, to determine the key factors of cross-fault pressure behavior in this platform carbonate reservoir, and to translate the observed cross-fault pressure depletion to fault transmissibility for reservoir simulation models. Analysis of Zechstein Ca2 cross-fault pressures indicates that most Zechstein-cutting faults appear to act as fluid-flow baffles with some local occurrences of fault seal. Moreover, there appears to be distinct cross-fault baffling or pressure depletion trends that may be related to the extent of the separating fault or fault system, degree of reservoir flow-path tortuosity, and quality of reservoir juxtaposition. Based on the above observations, a three-part workflow was developed consisting of (1) careful interpretation and mapping of faults and fault networks, (2) analysis of reservoir juxtaposition and reservoir juxtaposition quality, and (3) application of the observed cross-fault pressure depletion trends. This approach is field-analog based, is practical, and is being used currently to provide reliable and supportable pressure prediction scenarios for subsequent Zechstein fault-bounded drill-well opportunities.

  17. Reliability Engineering

    Lazzaroni, Massimo


    This book gives a practical guide for designers and users in Information and Communication Technology context. In particular, in the first Section, the definition of the fundamental terms according to the international standards are given. Then, some theoretical concepts and reliability models are presented in Chapters 2 and 3: the aim is to evaluate performance for components and systems and reliability growth. Chapter 4, by introducing the laboratory tests, puts in evidence the reliability concept from the experimental point of view. In ICT context, the failure rate for a given system can be


    Han Yilun


    Fault diagnosis expert system for hydraulic support is studied.The system is achieved by Turbo-prolong Language, it summaries the experience of the domain expert and sets up a fault tree, knowledge base is developed by a productive rule.According to the feature of diagnosis, the system selects forward non-determination inferring and limited depth-first search strategy.It can accomplish expert diagnosis of more than 50 kinds faults in hydraulic support.

  19. Reliability Modeling of Wind Turbines

    Kostandyan, Erik

    and uncertainties are quantified. Further, estimation of annual failure probability for structural components taking into account possible faults in electrical or mechanical systems is considered. For a representative structural failure mode, a probabilistic model is developed that incorporates grid loss failures...... components. Thus, models of reliability should be developed and applied in order to quantify the residual life of the components. Damage models based on physics of failure combined with stochastic models describing the uncertain parameters are imperative for development of cost-optimal decision tools...... for Operation & Maintenance planning. Concentrating efforts on development of such models, this research is focused on reliability modeling of Wind Turbine critical subsystems (especially the power converter system). For reliability assessment of these components, structural reliability methods are applied...

  20. Sliding mode fault detection and fault-tolerant control of smart dampers in semi-active control of building structures

    Yeganeh Fallah, Arash; Taghikhany, Touraj


    Recent decades have witnessed much interest in the application of active and semi-active control strategies for seismic protection of civil infrastructures. However, the reliability of these systems is still in doubt as there remains the possibility of malfunctioning of their critical components (i.e. actuators and sensors) during an earthquake. This paper focuses on the application of the sliding mode method due to the inherent robustness of its fault detection observer and fault-tolerant control. The robust sliding mode observer estimates the state of the system and reconstructs the actuators’ faults which are used for calculating a fault distribution matrix. Then the fault-tolerant sliding mode controller reconfigures itself by the fault distribution matrix and accommodates the fault effect on the system. Numerical simulation of a three-story structure with magneto-rheological dampers demonstrates the effectiveness of the proposed fault-tolerant control system. It was shown that the fault-tolerant control system maintains the performance of the structure at an acceptable level in the post-fault case.

  1. Interpreting Tree Ensembles with inTrees

    Deng, Houtao


    Tree ensembles such as random forests and boosted trees are accurate but difficult to understand, debug and deploy. In this work, we provide the inTrees (interpretable trees) framework that extracts, measures, prunes and selects rules from a tree ensemble, and calculates frequent variable interactions. An rule-based learner, referred to as the simplified tree ensemble learner (STEL), can also be formed and used for future prediction. The inTrees framework can applied to both classification an...

  2. Analysis on reliability of ZPW-2000A track circuit based on FMEA and FTA%基于FMEA和FTA的ZPW-2000A轨道电路可靠性分析

    王文斌; 苏宏升


    According to the reliability issues of ZPW-2000A type jointless audio frequency-shift modulated track circuit system, the method of combining Failure Modes and Effect Analysis(FMEA)and Fault Tree Analysis(FTA)is proposed for research and analysis of the system reliability. The system is analyzed and defined, and the FMEA table is completed. All possible failure modes, failure effects, fault detection methods and remedial measures are obtained. The fault tree is built. The minimal cut sets of the fault tree are got, and the qualitative and quantitative analyses of the fault tree are conducted. The weak links of the sys-tem are located by qualitative analysis. The fail probability of roof events, important degree of each minimal cut sets and reliabil-ity index are gained through the quantitative analysis. The validity of the reliability analysis method is verified by comparison with the relevant technical requirements.%针对ZPW-2000A型无绝缘移频轨道电路系统的可靠性问题,提出采用故障模式影响分析(FMEA)和故障树分析(FTA)相结合的方法,对系统进行可靠性研究和分析。通过对系统分析和定义,建立故障模式影响分析表,找出所有可能的故障模式、故障后果、故障检测方法和补救措施等,在此基础上建立系统故障树,求取最小割集,进行定性和定量分析。定性分析判定系统的薄弱环节,定量分析计算顶事件的故障概率、各最小割集的重要度及系统的可靠性指标,通过与相关技术规定比较,验证了该可靠性分析方法的有效性。

  3. Detecting intermittent resistive faults in digital CMOS circuits

    Ebrahimi, Hassan; Kerkhoff, Hans G.; Rohani, A.


    Interconnection reliability threats dependability of highly critical electronic systems. One of most challenging interconnection-induced reliability threats are intermittent resistive faults (IRFs). The occurrence rate of this kind of defects can take e.g. one month, and the duration of defects can

  4. Spatio-temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch: A dendrogeomorphic approach using broad-leaved trees

    Šilhán, Karel; Pánek, Tomáš; Turský, Ondřej; Brázdil, Rudolf; Klimeš, Jan; Kašičková, Lucie


    The undercut slope of the Skalická Strážnice/Vrchy hill situated in the piedmont of the Carpathian Mountains (Czech Republic) is a regional landslide "hotspot", notorious for its repeated recent and historical sliding reactivations. We performed tree-ring analysis of a large number (n = 274) of broad-leaved trees to reconstruct the spatio-temporal patterns of landslide reactivation for a period spanning more than one hundred years (1884-2011). Although tree rings of broad-leaved trees are less-reliable archives of landslide activity than those of conifers, the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock. Although some known landslide years could not be found (or were expressed by only weak signals) in the reconstructed dataset, the majority of landslide events reconstructed from the tree-ring series coincide with hydrometeorological data, revealing a correlation with heavy summer rainfalls lasting from two to ten days. The spatial distribution of landslide recurrence derived from the tree-ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock.

  5. Audubon Tree Study Program.

    National Audubon Society, New York, NY.

    Included are an illustrated student reader, "The Story of Trees," a leaders' guide, and a large tree chart with 37 colored pictures. The student reader reviews several aspects of trees: a definition of a tree; where and how trees grow; flowers, pollination and seed production; how trees make their food; how to recognize trees; seasonal changes;…

  6. Small nuclear power reactor emergency electric power supply system reliability comparative analysis; Analise da confiabilidade do sistema de suprimento de energia eletrica de emergencia de um reator nuclear de pequeno porte

    Bonfietti, Gerson


    This work presents an analysis of the reliability of the emergency power supply system, of a small size nuclear power reactor. Three different configurations are investigated and their reliability analyzed. The fault tree method is used as the main tool of analysis. The work includes a bibliographic review of emergency diesel generator reliability and a discussion of the design requirements applicable to emergency electrical systems. The influence of common cause failure influences is considered using the beta factor model. The operator action is considered using human failure probabilities. A parametric analysis shows the strong dependence between the reactor safety and the loss of offsite electric power supply. It is also shown that common cause failures can be a major contributor to the system reliability. (author)

  7. Enhanced Reliability MEMS Deformable Mirrors for Space Imaging Applications Project

    National Aeronautics and Space Administration — The goal of this project is to develop and demonstrate a reliable, fault-tolerant wavefront control system that will fill a critical technology gap in NASA's vision...

  8. Fault Detection and Isolation in Centrifugal Pumps

    Kallesøe, Carsten

    Centrifugal pumps are used in a variety of different applications, such as water supply, wastewater, and different industrial applications. Some pump installations are crucial for the applications to work. Failures can lead to substantial economic losses and can influence the life of many people...... when they occur. Therefore, detection of faults, if possible in an early stage, and isolation of their causes are of great interest. Especially fault detection, which can be used for predictive maintenance, can decrease working expenses and increase the reliability of the application in which the pump...... is placed. The topic of this work is Fault Detection and Identification in centrifugal pumps. Different approaches are developed with special focus on robustness. Robustness with respect to disturbances, unknown parts of the system, and parameter variations are considered. All developed algorithms...

  9. Fault Detection under Fuzzy Model Uncertainty

    Marek Kowal; Józef Korbicz


    The paper tackles the problem of robust fault detection using Takagi-Sugeno fuzzy models. A model-based strategy is employed to generate residuals in order to make a decision about the state of the process. Unfortunately, such a method is corrupted by model uncertainty due to the fact that in real applications there exists a model-reality mismatch. In order to ensure reliable fault detection the adaptive threshold technique is used to deal with the mentioned problem. The paper focuses also on fuzzy model design procedure. The bounded-error approach is applied to generating the rules for the model using available measurements. The proposed approach is applied to fault detection in the DC laboratory engine.

  10. Aspen Trees.

    Canfield, Elaine


    Describes a fifth-grade art activity that offers a new approach to creating pictures of Aspen trees. Explains that the students learned about art concepts, such as line and balance, in this lesson. Discusses the process in detail for creating the pictures. (CMK)

  11. Assessing sensitivity of Probabilistic Seismic Hazard Analysis (PSHA) to fault parameters: Sumatra case study

    Omang, A.; Cummins, P. R.; Horspool, N.; Hidayati, S.


    Slip rate data and fault geometry are two important inputs in determining seismic hazard, because they are used to estimate earthquake recurrence intervals which strongly influence the hazard level in an area. However, the uncertainty of slip-rates and geometry of the fault are rarely considered in any probabilistic seismic hazard analysis (PSHA), which is surprising given the estimates of slip-rates can vary significantly from different data sources (e.g. geological vs. Geodetic). We use the PSHA method to assess the sensitivity of seismic hazard to fault slip-rates along the Great Sumatran Fault in Sumatra, Indonesia. We will consider the epistemic uncertainty of fault slip rate by employing logic trees to include alternative slip rate models. The weighting of the logic tree is determined by the probability density function of the slip rate estimates using the approach of Zechar and Frankel (2009). We consider how the PSHA result accounting for slip rate uncertainty differs from that for a specific slip rate by examining hazard values as a function of return period and distance from the fault. We also consider the geometry of the fault, especially the top and the bottom of the rupture area within a fault, to study the effect from different depths. Based on the results of this study, in some cases the uncertainty in fault slip-rates, fault geometry and maximum magnitude have a significant effect on hazard level and area impacted by earthquakes and should be considered in PSHA studies.

  12. Reliability Analysis of Phased Mission Systems by the Considering the Sensitivity Analysis, Uncertainty and Common Cause Failure Analysis using the GO-FLOW Methodology

    Muhammad Hashim


    Full Text Available The reliability is the probability that a device will perform its required function under stated conditions for a specified period of time. The Common Cause Failure (CCFs is the multiple failures and has long been recognized (U.S. NRC, 1975 as an important issue in the Probabilistic Safety Assessment (PSA and uncertainty and sensitivity analysis has the important information for the evaluation of system reliability. In this study, two cases has been considered, in the first case, author have made the analysis of reliability of PWR safety system by GO-FLOW methodology alternatively to Fault Tree Analysis and Even Tree because it is success-oriented system analysis technique and comparatively easy to conduct the reliability analysis of the complex system. In the second case, sensitivity analysis has been made in order to prioritize the important parameters which have largest contribution to system reliability and also for common cause failure analysis and uncertainty analysis. For an example of phased mission system, PWR containment spray system has been considered.

  13. Morphostructural study of the Belledonne faults system (French Alps).

    Billant, Jérémy; Bellier, Olivier; Hippolyte, Jean-Claude; Godard, Vincent; Manchuel, Kevin


    topographic data that we obtained using photogrammetry. Fault slip rates cannot be reliably assessed because of the lack of morphologic features that can be dated. For the Arcalod and Brion faults, when considering that the observed offset are inherited from Würm, the calculated fault slip rates are much larger than those deduced for other faults in France suggesting that the studied morphologic markers are older than the Würm. For the Jasneuf fault, assuming a constant long term (since Messinian) fault slip rate, the comparison of the long term offset (measured using cliff offsets) and short term offset (measured using stream offsets and fault scarps) yields a fault slip rate which is of 0.13±0.03 mm/yr. The extension of the fault is poorly constrained and we can not ascertain the prolongation of the Jasneuf fault outside of the Vercors plateau nor in depth. Nevertheless, if this fault is limited to the sedimentary cover and do not extend outside of the Vercors plateau, it could generate Mw 5.7 earthquakes each ~500 years. On the other hand we can not exclude that a large part of the deformation could be accommodated by aseismic creep as indicated by pressure solution features (Gratier et al.,2003).

  14. Iterative learning based fault diagnosis for discrete linear uncer tain systems

    Wei Cao; Ming Sun


    In order to detect and estimate faults in discrete lin-ear time-varying uncertain systems, the discrete iterative learning strategy is applied in fault diagnosis, and a novel fault detection and estimation algorithm is proposed. And the threshold limited tech-nology is adopted in the proposed algorithm. Within the chosen optimal time region, residual signals are used in the proposed algo-rithm to correct the introduced virtual faults with iterative learning rules, making the virtual faults close to these occurred in practical systems. And the same method is repeated in the rest optimal time regions, thereby reaching the aim of fault diagnosis. The proposed algorithm not only completes fault detection and estimation for dis-crete linear time-varying uncertain systems, but also improves the reliability of fault detection and decreases the false alarm rate. The final simulation results verify the validity of the proposed algorithm.

  15. Measurement and analysis of workload effects on fault latency in real-time systems

    Woodbury, Michael H.; Shin, Kang G.


    The authors demonstrate the need to address fault latency in highly reliable real-time control computer systems. It is noted that the effectiveness of all known recovery mechanisms is greatly reduced in the presence of multiple latent faults. The presence of multiple latent faults increases the possibility of multiple errors, which could result in coverage failure. The authors present experimental evidence indicating that the duration of fault latency is dependent on workload. A synthetic workload generator is used to vary the workload, and a hardware fault injector is applied to inject transient faults of varying durations. This method makes it possible to derive the distribution of fault latency duration. Experimental results obtained from the fault-tolerant multiprocessor at the NASA Airlab are presented and discussed.

  16. Satellite Fault Diagnosis Using Support Vector Machines Based on a Hybrid Voting Mechanism

    Hong Yin


    Full Text Available The satellite fault diagnosis has an important role in enhancing the safety, reliability, and availability of the satellite system. However, the problem of enormous parameters and multiple faults makes a challenge to the satellite fault diagnosis. The interactions between parameters and misclassifications from multiple faults will increase the false alarm rate and the false negative rate. On the other hand, for each satellite fault, there is not enough fault data for training. To most of the classification algorithms, it will degrade the performance of model. In this paper, we proposed an improving SVM based on a hybrid voting mechanism (HVM-SVM to deal with the problem of enormous parameters, multiple faults, and small samples. Many experimental results show that the accuracy of fault diagnosis using HVM-SVM is improved.

  17. Fault Risk Assessment of Underwater Vehicle Steering System Based on Virtual Prototyping and Monte Carlo Simulation

    He Deyu


    Full Text Available Assessing the risks of steering system faults in underwater vehicles is a human-machine-environment (HME systematic safety field that studies faults in the steering system itself, the driver’s human reliability (HR and various environmental conditions. This paper proposed a fault risk assessment method for an underwater vehicle steering system based on virtual prototyping and Monte Carlo simulation. A virtual steering system prototype was established and validated to rectify a lack of historic fault data. Fault injection and simulation were conducted to acquire fault simulation data. A Monte Carlo simulation was adopted that integrated randomness due to the human operator and environment. Randomness and uncertainty of the human, machine and environment were integrated in the method to obtain a probabilistic risk indicator. To verify the proposed method, a case of stuck rudder fault (SRF risk assessment was studied. This method may provide a novel solution for fault risk assessment of a vehicle or other general HME system.

  18. Software reliability models for critical applications

    Pham, H.; Pham, M.


    This report presents the results of the first phase of the ongoing EG&G Idaho, Inc. Software Reliability Research Program. The program is studying the existing software reliability models and proposes a state-of-the-art software reliability model that is relevant to the nuclear reactor control environment. This report consists of three parts: (1) summaries of the literature review of existing software reliability and fault tolerant software reliability models and their related issues, (2) proposed technique for software reliability enhancement, and (3) general discussion and future research. The development of this proposed state-of-the-art software reliability model will be performed in the second place. 407 refs., 4 figs., 2 tabs.

  19. Software reliability models for critical applications

    Pham, H.; Pham, M.


    This report presents the results of the first phase of the ongoing EG G Idaho, Inc. Software Reliability Research Program. The program is studying the existing software reliability models and proposes a state-of-the-art software reliability model that is relevant to the nuclear reactor control environment. This report consists of three parts: (1) summaries of the literature review of existing software reliability and fault tolerant software reliability models and their related issues, (2) proposed technique for software reliability enhancement, and (3) general discussion and future research. The development of this proposed state-of-the-art software reliability model will be performed in the second place. 407 refs., 4 figs., 2 tabs.

  20. Reliable computer systems design and evaluatuion

    Siewiorek, Daniel


    Enhance your hardware/software reliabilityEnhancement of system reliability has been a major concern of computer users and designers ¦ and this major revision of the 1982 classic meets users' continuing need for practical information on this pressing topic. Included are case studies of reliablesystems from manufacturers such as Tandem, Stratus, IBM, and Digital, as well as coverage of special systems such as the Galileo Orbiter fault protection system and AT&T telephone switching processors.

  1. Unimodular trees versus Einstein trees

    Alvarez, Enrique; Gonzalez-Martin, Sergio [Universidad Autonoma, Instituto de Fisica Teorica, IFT-UAM/CSIC, Madrid (Spain); Universidad Autonoma de Madrid, Departamento de Fisica Teorica, Madrid (Spain); Martin, Carmelo P. [Universidad Complutense de Madrid (UCM), Departamento de Fisica Teorica I Facultad de Ciencias Fisicas, Madrid (Spain)


    The maximally helicity violating tree-level scattering amplitudes involving three, four or five gravitons are worked out in Unimodular Gravity. They are found to coincide with the corresponding amplitudes in General Relativity. This a remarkable result, insofar as both the propagators and the vertices are quite different in the two theories. (orig.)

  2. Unimodular Trees versus Einstein Trees

    Alvarez, Enrique; Martin, Carmelo P


    The maximally helicity violating (MHV) tree level scattering amplitudes involving three, four or five gravitons are worked out in Unimodular Gravity. They are found to coincide with the corresponding amplitudes in General Relativity. This a remarkable result, insofar as both the propagators and the vertices are quite different in both theories.

  3. Unimodular trees versus Einstein trees

    Álvarez, Enrique; González-Martín, Sergio; Martín, Carmelo P.


    The maximally helicity violating tree-level scattering amplitudes involving three, four or five gravitons are worked out in Unimodular Gravity. They are found to coincide with the corresponding amplitudes in General Relativity. This a remarkable result, insofar as both the propagators and the vertices are quite different in the two theories.

  4. Optimal Sensor Allocation for Fault Detection and Isolation

    Azam, Mohammad; Pattipati, Krishna; Patterson-Hine, Ann


    Automatic fault diagnostic schemes rely on various types of sensors (e.g., temperature, pressure, vibration, etc) to measure the system parameters. Efficacy of a diagnostic scheme is largely dependent on the amount and quality of information available from these sensors. The reliability of sensors, as well as the weight, volume, power, and cost constraints, often makes it impractical to monitor a large number of system parameters. An optimized sensor allocation that maximizes the fault diagnosibility, subject to specified weight, volume, power, and cost constraints is required. Use of optimal sensor allocation strategies during the design phase can ensure better diagnostics at a reduced cost for a system incorporating a high degree of built-in testing. In this paper, we propose an approach that employs multiple fault diagnosis (MFD) and optimization techniques for optimal sensor placement for fault detection and isolation (FDI) in complex systems. Keywords: sensor allocation, multiple fault diagnosis, Lagrangian relaxation, approximate belief revision, multidimensional knapsack problem.

  5. A New Method of Improving Transformer Restricted Earth Fault Protection



    Full Text Available A new method of avoiding malfunctioning of the transformer restricted earth fault (REF protection is presented. Application of the proposed method would eliminate unnecessary operation of REF protection in the cases of faults outside protected zone of a transformer or a magnetizing inrush accompanied by current transformer (CT saturation. On the basis of laboratory measurements and simulations the paper presents a detailed performance assessment of the proposed method which is based on digital phase comparator. The obtained results show that the new method was stable and precise for all tested faults and that its application would allow making a clear and precise difference between an internal fault and: (i external fault or (ii magnetizing inrush. The proposed method would improve performance of REF protection and reduce probability of maloperation due to CT saturation. The new method is robust and characterized by high speed of operation and high reliability and security.

  6. A Novel Approach for Core Selection in Shared Tree Multicasting

    Bidyut Gupta


    Full Text Available Multicasting is preferred over multiple unicasts from the viewpoint of better utilization of network bandwidth. Multicasting can be done in two different ways: source based tree approach and shared tree approach. Protocols such as Core Based Tree (CBT, Protocol Independent Multicasting Sparse Mode (PIM-SM use shared treeapproach. Shared tree approach is preferred over source-based tree approach because in the later construction of minimum cost treeper source is needed unlike a single shared tree in the former approach.The work presented in this paper provides an efficient core selection method for shared tree multicasting. In this work, we have used a new concept known as pseudo diameter for core selection. The presented methodselects more than one core to achieve fault tolerance

  7. Fault location method for transmission line based on traveling waves

    ZHENG Na; ZHAO Yulin


    The single phase grounding fault location is the focus which researchers pay attention to and study in power system. The accurate fault location can lighten the patrolling burden, and enhance the reliability of the power network. It adopts A/D which has high speed, and uses TMS320VC5402 DSP chip as the system core. This paper presented theory of operation based on traveling waves and achieved software and hardware in detail.

  8. Analytical Approaches to Guide SLS Fault Management (FM) Development

    Patterson, Jonathan D.


    Extensive analysis is needed to determine the right set of FM capabilities to provide the most coverage without significantly increasing the cost, reliability (FP/FN), and complexity of the overall vehicle systems. Strong collaboration with the stakeholders is required to support the determination of the best triggers and response options. The SLS Fault Management process has been documented in the Space Launch System Program (SLSP) Fault Management Plan (SLS-PLAN-085).

  9. A model for reliability analysis and calculation applied in an example from chemical industry

    Pejović Branko B.


    Full Text Available The subject of the paper is reliability design in polymerization processes that occur in reactors of a chemical industry. The designed model is used to determine the characteristics and indicators of reliability, which enabled the determination of basic factors that result in a poor development of a process. This would reduce the anticipated losses through the ability to control them, as well as enabling the improvement of the quality of production, which is the major goal of the paper. The reliability analysis and calculation uses the deductive method based on designing of a scheme for fault tree analysis of a system based on inductive conclusions. It involves the use standard logical symbols and rules of Boolean algebra and mathematical logic. The paper eventually gives the results of the work in the form of quantitative and qualitative reliability analysis of the observed process, which served to obtain complete information on the probability of top event in the process, as well as objective decision making and alternative solutions.

  10. Development of Markov model of emergency diesel generator for dynamic reliability analysis

    Jin, Young Ho; Choi, Sun Yeong; Yang, Joon Eon [Korea Atomic Energy Research Institute, Taejon (Korea)


    The EDG (Emergency Diesal Generator) of nuclear power plant is one of the most important equipments in mitigating accidents. The FT (Fault Tree) method is widely used to assess the reliability of safety systems like an EDG in nuclear power plant. This method, however, has limitations in modeling dynamic features of safety systems exactly. We, hence, have developed a Markov model to represent the stochastic process of dynamic systems whose states change as time moves on. The Markov model enables us to develop a dynamic reliability model of EDG. This model can represent all possible states of EDG comparing to the FRANTIC code developed by U.S. NRC for the reliability analysis of standby systems. to access the regulation policy for test interval, we performed two simulations based on the generic data and plant specific data of YGN 3, respectively by using the developed model. We also estimate the effects of various repair rates and the fractions of starting failures by demand shock to the reliability of EDG. And finally, Aging effect is analyzed. (author). 23 refs., 19 figs., 9 tabs.

  11. Reliability with imperfect diagnostics. [flight-maintenance sequence

    White, A. L.


    A reliability estimation method for systems that continually accumulate faults because of imperfect diagnostics is developed and an application for redundant digital avionics is presented. The present method assumes that if a fault does not appear in a short period of time, it will remain hidden until a majority of components are faulty and the system fails. A certain proportion of a component's faults are detected in a short period of time, and a description of their detection is included in the reliability model. A Markov model of failure during flight for a nonreconfigurable five-plex is presented for a sequence of one-hour flights followed by maintenance.

  12. Analysis and prevention of accident-caused faults in power cable lines

    Susakova Tatyana V.


    Full Text Available To ensure fault-free operation of power cable lines it is essential to make a thorough analysis of the type of faults and their location. The paper considers the most common type of faults and main reasons for cable damage. The case study of cable faults at an urban network (Zabaikalsky Krai shows that the root cause is insulation deterioration, especially with the cables reaching the end of their 35 year lifetime. Therefore, to prevent faults and mitigate the threats it is necessary to increase surveillance of cable systems and use cables with higher reliability and functionality, e.g., XLPE cables.

  13. Insurance Applications of Active Fault Maps Showing Epistemic Uncertainty

    Woo, G.


    Insurance loss modeling for earthquakes utilizes available maps of active faulting produced by geoscientists. All such maps are subject to uncertainty, arising from lack of knowledge of fault geometry and rupture history. Field work to undertake geological fault investigations drains human and monetary resources, and this inevitably limits the resolution of fault parameters. Some areas are more accessible than others; some may be of greater social or economic importance than others; some areas may be investigated more rapidly or diligently than others; or funding restrictions may have curtailed the extent of the fault mapping program. In contrast with the aleatory uncertainty associated with the inherent variability in the dynamics of earthquake fault rupture, uncertainty associated with lack of knowledge of fault geometry and rupture history is epistemic. The extent of this epistemic uncertainty may vary substantially from one regional or national fault map to another. However aware the local cartographer may be, this uncertainty is generally not conveyed in detail to the international map user. For example, an area may be left blank for a variety of reasons, ranging from lack of sufficient investigation of a fault to lack of convincing evidence of activity. Epistemic uncertainty in fault parameters is of concern in any probabilistic assessment of seismic hazard, not least in insurance earthquake risk applications. A logic-tree framework is appropriate for incorporating epistemic uncertainty. Some insurance contracts cover specific high-value properties or transport infrastructure, and therefore are extremely sensitive to the geometry of active faulting. Alternative Risk Transfer (ART) to the capital markets may also be considered. In order for such insurance or ART contracts to be properly priced, uncertainty should be taken into account. Accordingly, an estimate is needed for the likelihood of surface rupture capable of causing severe damage. Especially where a

  14. Fast Tree: Computing Large Minimum-Evolution Trees with Profiles instead of a Distance Matrix

    N. Price, Morgan; S. Dehal, Paramvir; P. Arkin, Adam


    Gene families are growing rapidly, but standard methods for inferring phylogenies do not scale to alignments with over 10,000 sequences. We present FastTree, a method for constructing large phylogenies and for estimating their reliability. Instead of storing a distance matrix, FastTree stores sequence profiles of internal nodes in the tree. FastTree uses these profiles to implement neighbor-joining and uses heuristics to quickly identify candidate joins. FastTree then uses nearest-neighbor interchanges to reduce the length of the tree. For an alignment with N sequences, L sites, and a different characters, a distance matrix requires O(N^2) space and O(N^2 L) time, but FastTree requires just O( NLa + N sqrt(N) ) memory and O( N sqrt(N) log(N) L a ) time. To estimate the tree's reliability, FastTree uses local bootstrapping, which gives another 100-fold speedup over a distance matrix. For example, FastTree computed a tree and support values for 158,022 distinct 16S ribosomal RNAs in 17 hours and 2.4 gigabytes of memory. Just computing pairwise Jukes-Cantor distances and storing them, without inferring a tree or bootstrapping, would require 17 hours and 50 gigabytes of memory. In simulations, FastTree was slightly more accurate than neighbor joining, BIONJ, or FastME; on genuine alignments, FastTree's topologies had higher likelihoods. FastTree is available at

  15. Fault Monitoring and Fault Recovery Control for Position Moored Tanker

    Fang, Shaoji; Blanke, Mogens


    This paper addresses fault tolerant control for position mooring of a shuttle tanker operating in the North Sea. A complete framework for fault diagnosis is presented but the loss of a sub-sea mooring line buoyancy element is given particular attention, since this fault could lead to mooring line....... Properties of detection and fault-tolerant control are demonstrated by high fidelity simulations....

  16. Fault tolerant control for uncertain systems with parametric faults

    Niemann, Hans Henrik; Poulsen, Niels Kjølstad


    A fault tolerant control (FTC) architecture based on active fault diagnosis (AFD) and the YJBK (Youla, Jarb, Bongiorno and Kucera)parameterization is applied in this paper. Based on the FTC architecture, fault tolerant control of uncertain systems with slowly varying parametric faults...

  17. Fault isolability conditions for linear systems with additive faults

    Niemann, Hans Henrik; Stoustrup, Jakob


    In this paper, we shall show that an unlimited number of additive single faults can be isolated under mild conditions if a general isolation scheme is applied. Multiple faults are also covered. The approach is algebraic and is based on a set representation of faults, where all faults within a set...

  18. FaultBuster: data driven fault detection and diagnosis for industrial systems

    Bergantino, Nicola; Caponetti, Fabio; Longhi, Sauro


    Efficient and reliable monitoring systems are mandatory to assure the required security standards in industrial complexes. This paper describes the recent developments of FaultBuster, a purely data-driven diagnostic system. It is designed so to be easily scalable to different monitor tasks....... Multivariate statistical models based on principal components are used to detect abnormal situations. Tailored to alarms, a probabilistic inference engine process the fault evidences to output the most probable diagnosis. Results from the DX 09 Diagnostic Challenge shown strong detection properties, while...

  19. Fault-tolerant and Diagnostic Methods for Navigation

    Blanke, Mogens


    Precise and reliable navigation is crucial, and for reasons of safety, essential navigation instruments are often duplicated. Hardware redundancy is mostly used to manually switch between instruments should faults occur. In contrast, diagnostic methods are available that can use analytic redundancy...... to diagnose faults and autonomously provide valid navigation data, disregarding any faulty sensor data and use sensor fusion to obtain a best estimate for users. This paper discusses how diagnostic and fault-tolerant methods are applicable in marine systems. An example chosen is sensor fusion for navigation...

  20. Fault tolerant system design for uninterruptible power supplies

    B. Y. Volochiy


    Full Text Available The problem of design for reliability of a fault tolerant system for uninterruptible power supplies is considered. Configuration of a fault tolerant system determines the structure of an uninterruptible power supply: power supply built from modules of the same type, stand-by sliding reserve for them, twice total reserve of the power supply with two accumulator batteries, the controls and diagnostics means. The developed tool for automated analytical model of fault tolerant systems generation and illustration of its capabilities in determination of requirements for repair service and accumulator batteries are given.

  1. Fault Analysis in Cryptography

    Joye, Marc


    In the 1970s researchers noticed that radioactive particles produced by elements naturally present in packaging material could cause bits to flip in sensitive areas of electronic chips. Research into the effect of cosmic rays on semiconductors, an area of particular interest in the aerospace industry, led to methods of hardening electronic devices designed for harsh environments. Ultimately various mechanisms for fault creation and propagation were discovered, and in particular it was noted that many cryptographic algorithms succumb to so-called fault attacks. Preventing fault attacks without

  2. SABRE: a bio-inspired fault-tolerant electronic architecture.

    Bremner, P; Liu, Y; Samie, M; Dragffy, G; Pipe, A G; Tempesti, G; Timmis, J; Tyrrell, A M


    As electronic devices become increasingly complex, ensuring their reliable, fault-free operation is becoming correspondingly more challenging. It can be observed that, in spite of their complexity, biological systems are highly reliable and fault tolerant. Hence, we are motivated to take inspiration for biological systems in the design of electronic ones. In SABRE (self-healing cellular architectures for biologically inspired highly reliable electronic systems), we have designed a bio-inspired fault-tolerant hierarchical architecture for this purpose. As in biology, the foundation for the whole system is cellular in nature, with each cell able to detect faults in its operation and trigger intra-cellular or extra-cellular repair as required. At the next level in the hierarchy, arrays of cells are configured and controlled as function units in a transport triggered architecture (TTA), which is able to perform partial-dynamic reconfiguration to rectify problems that cannot be solved at the cellular level. Each TTA is, in turn, part of a larger multi-processor system which employs coarser grain reconfiguration to tolerate faults that cause a processor to fail. In this paper, we describe the details of operation of each layer of the SABRE hierarchy, and how these layers interact to provide a high systemic level of fault tolerance.

  3. Microelectronics Reliability


    convey any rights or permission to manufacture, use, or sell any patented invention that may relate to them. This report was cleared for public release...testing for reliability prediction of devices exhibiting multiple failure mechanisms. Also presented was an integrated accelerating and measuring ...13  Table 2  T, V, F and matrix versus  measured  FIT

  4. Fault-tolerant quantum computation

    Preskill, J


    The discovery of quantum error correction has greatly improved the long-term prospects for quantum computing technology. Encoded quantum information can be protected from errors that arise due to uncontrolled interactions with the environment, or due to imperfect implementations of quantum logical operations. Recovery from errors can work effectively even if occasional mistakes occur during the recovery procedure. Furthermore, encoded quantum information can be processed without serious propagation of errors. In principle, an arbitrarily long quantum computation can be performed reliably, provided that the average probability of error per gate is less than a certain critical value, the accuracy threshold. It may be possible to incorporate intrinsic fault tolerance into the design of quantum computing hardware, perhaps by invoking topological Aharonov-Bohm interactions to process quantum information.



    Based on radial basis function (RBF) neural networks, the healthy working model of each sub-system of robot in FMS is established. A new approach to fault on-line detection and diagnosis according to neural networks model is presented. Fault double detection based on neural network model and threshold judgement and quick fault identification based on multi-layer feedforward neural networks are applied, which can meet quickness and reliability of fault detection and diagnosis for robot in FMS.

  6. 基于Petri网模型的铁路快捷货运产品可靠性评价%Railway Express Freight Product Reliability Evaluation Based on Petri Net Model

    王丹竹; 郎茂祥; 孙岩


    为准确评价及预测铁路快捷货运产品的可靠性,在全面分析铁路快捷货运产品可靠性影响因素的基础上,建立用于产品可靠性评价的故障树模型,并采用下行法求取故障树的最小割集;结合Petri网建模方法与故障树基本理论,将产品故障树转化为Petri网仿真模型,并证明两者的等价性;利用Matlab仿真软件进行基于关联矩阵的Petri网模型求解,并以北京—上海间特快货物班列为例,得到该产品的可靠度及故障因素重要度排序.实证结果显示,应用Petri网模型来求解产品可靠性评价问题,不仅能够有效提升求解过程的效率,而且准确易行.研究成果可以为提高铁路快捷货运产品可靠性和市场竞争力提供科学依据和必要支撑.%To accurately evaluate the reliability of railway express freight product, on the basis of analysis on reliability influence factors of it, a fault tree is built, and the minimal cut sets of the fault tree is given. Combined with the basic theory of Petri net and fault tree analysis, the fault tree of railway express freight product is transformed into Petri net simulation model, and this transformation is proved to be an equivalent transformation. Using Matlab simulation software, the reliability and the importance of failure factors of railway express freight product between Beijing and Shanghai are obtained. Empirical results indicate the Petri net can solve the problem efficiently and effectively, which demonstrates feasibility of the method in addressing this problem. Research results of this paper will provide a scientific basis and necessary support in improving the reliability and market competitiveness of railway express freight product.

  7. Quaternary Fault Lines

    Department of Homeland Security — This data set contains locations and information on faults and associated folds in the United States that are believed to be sources of M>6 earthquakes during the...

  8. Review of Dynamic Reliability Methodology in Probabilistic Safety Assessments of Nuclear Power Plants%核电厂概率安全分析中动态可靠性方法综述

    张永发; 童节娟; 周羽; 蔡琦


    Dynamic reliability method can make up the shortage of traditional Event Tree/Fault Tree method. It can be used to complete the current reliability and safety assessment methods of nuclear power plants. In recent 30 years, a relatively perfect theory foundation (probabilistic dynamics) has been developed. On this basis? Monte Carlo simulation and discrete dynamic event tree were formed. The research situation and technical characteristics of the dynamic reliability theory and method were introduced. And the future trend of dynamic reliability was also discussed.%用动态可靠性方法弥补传统事件树/故障树方法的不足,补充和完善现有核电厂的可靠性与安全性评估,已成为核电厂概率安全研究的一新发展点.近30年来,动态可靠性已具有相对成熟的理论基础——概率动力学,并形成了蒙特卡罗(MC)模拟和离散动态事件树(DDET)两类主要方法.本文简要介绍动态可靠性理论和方法的研究现状与技术特点,并对未来趋势进行分析.

  9. Modeling and Fault Simulation of Propellant Filling System

    Jiang, Yunchun; Liu, Weidong; Hou, Xiaobo


    Propellant filling system is one of the key ground plants in launching site of rocket that use liquid propellant. There is an urgent demand for ensuring and improving its reliability and safety, and there is no doubt that Failure Mode Effect Analysis (FMEA) is a good approach to meet it. Driven by the request to get more fault information for FMEA, and because of the high expense of propellant filling, in this paper, the working process of the propellant filling system in fault condition was studied by simulating based on AMESim. Firstly, based on analyzing its structure and function, the filling system was modular decomposed, and the mathematic models of every module were given, based on which the whole filling system was modeled in AMESim. Secondly, a general method of fault injecting into dynamic system was proposed, and as an example, two typical faults - leakage and blockage - were injected into the model of filling system, based on which one can get two fault models in AMESim. After that, fault simulation was processed and the dynamic characteristics of several key parameters were analyzed under fault conditions. The results show that the model can simulate effectively the two faults, and can be used to provide guidance for the filling system maintain and amelioration.

  10. Finite Sholander Trees, Trees, and their Betweenness

    Chvátal, Vašek; Schäfer, Philipp Matthias


    We provide a proof of Sholander's claim (Trees, lattices, order, and betweenness, Proc. Amer. Math. Soc. 3, 369-381 (1952)) concerning the representability of collections of so-called segments by trees, which yields a characterization of the interval function of a tree. Furthermore, we streamline Burigana's characterization (Tree representations of betweenness relations defined by intersection and inclusion, Mathematics and Social Sciences 185, 5-36 (2009)) of tree betweenness and provide a relatively short proof.


    Deepika Chawla


    Full Text Available Software faults are one of major criteria to estimate the software quality or the software reliability. There are number of matrices defined that uses the software faults to estimate the software quality. But when we have a large software system with thousands of class modules, in such case it is not easy to apply the software matrices on each module of software system. The present work isthe solution of the defined problem. In this work software quality is estimated by using the rejection method on software faults. The rejection method is applied on the basis on Fuzzy Logic in a softwaresystem. To perform the analysis in an effective way the weightage approach is used on the software faults. In this work we have assigned different weightage on software faults to categorize the faults respective to fault criticality and the frequency. Once the faults are categorized the next work is the implementation of proposed work software fault to represents the accepted and rejectedmodules from the software system. The obtained result shows the better visualization of software quality in case of software fault analysis.

  12. Assessment of student conceptions of evolutionary trees

    Blacquiere, Luke

    Biologists use evolutionary trees to depict hypotheses about the relationships among taxa. Trees possess lines that represent lineages, internal nodes that represent where lineages become evolutionarily isolated from one another and terminal nodes that represent the taxa under consideration. Interpreting a tree (i.e., "tree-thinking") is an important skill for biologists yet many students struggle when reading evolutionary trees. Common documented misconceptions include using morphological similarity, internal node counting or terminal node proximity, instead of identifying the internal node that represents a most recent common ancestor (MRCA), to determine relationships among taxa. I developed an instrument to assess whether students were using common ancestry or another, non-scientific, strategy to determine relationships among taxa. The study is the first to explicitly test hypotheses about how students approach reading evolutionary trees. To test the hypotheses an instrument was developed. The instrument is the first reliable and valid assessment testing student understanding of how to use most recent common ancestor to interpret evolutionary relationships in tree diagrams. Instructors can use the instrument as a diagnostic tool enabling them to help students learn this challenging concept. This study shows that, contrary to the assertion that students hold misconceptions about evolutionary trees made in the literature, students do not consistently use erroneous strategies when interpreting trees. This study suggests that a constructivist perspective of cognitive structure describes students' conception of evolutionary trees more closely than a misconception perspective.

  13. A Benchmark Evaluation of Fault Tolerant Wind Turbine Control Concepts

    Odgaard, Peter Fogh; Stoustrup, Jakob


    As the world’s power supply to a larger and larger degree depends on wind turbines, it is consequently and increasingly important that these are as reliable and available as possible. Modern fault tolerant control (FTC) could play a substantial part in increasing reliability of modern wind turbin...... accommodation is handled in software sensor and actuator blocks. This means that the wind turbine controller can continue operation as in the fault free case. The other two evaluated solutions show some potential but probably need improvements before industrial applications....

  14. Application of the fault diagnosis strategy based on hierarchical information fusion in motors fault diagnosis


    This paper has analyzed merits and demerits of both neural network technique and of the information fusion methods based on the D-S (dempster-shafer evidence) Theory as well as their complementarity, proposed the hierarchical information fusion fault diagnosis strategy by combining the neural network technique and the fused decision diagnosis based on D-S Theory, and established a corresponding functional model. Thus, we can not only solve a series of problems caused by rapid growth in size and complexity of neural network structure with diagnosis parameters increasing, but also can provide effective method for basic probability assignment in D-S Theory. The application of the strategy to diagnosing faults of motor bearings has proved that this method is of fairly high accuracy and reliability in fault diagnosis.

  15. Fault-diagnosis applications. Model-based condition monitoring. Acutators, drives, machinery, plants, sensors, and fault-tolerant systems

    Isermann, Rolf [Technische Univ. Darmstadt (DE). Inst. fuer Automatisierungstechnik (IAT)


    Supervision, condition-monitoring, fault detection, fault diagnosis and fault management play an increasing role for technical processes and vehicles in order to improve reliability, availability, maintenance and lifetime. For safety-related processes fault-tolerant systems with redundancy are required in order to reach comprehensive system integrity. This book is a sequel of the book ''Fault-Diagnosis Systems'' published in 2006, where the basic methods were described. After a short introduction into fault-detection and fault-diagnosis methods the book shows how these methods can be applied for a selection of 20 real technical components and processes as examples, such as: Electrical drives (DC, AC) Electrical actuators Fluidic actuators (hydraulic, pneumatic) Centrifugal and reciprocating pumps Pipelines (leak detection) Industrial robots Machine tools (main and feed drive, drilling, milling, grinding) Heat exchangers Also realized fault-tolerant systems for electrical drives, actuators and sensors are presented. The book describes why and how the various signal-model-based and process-model-based methods were applied and which experimental results could be achieved. In several cases a combination of different methods was most successful. The book is dedicated to graduate students of electrical, mechanical, chemical engineering and computer science and for engineers. (orig.)

  16. Safety and reliability analysis in a polyvinyl chloride batch process using dynamic simulator-case study: Loss of containment incident.

    Rizal, Datu; Tani, Shinichi; Nishiyama, Kimitoshi; Suzuki, Kazuhiko


    In this paper, a novel methodology in batch plant safety and reliability analysis is proposed using a dynamic simulator. A batch process involving several safety objects (e.g. sensors, controller, valves, etc.) is activated during the operational stage. The performance of the safety objects is evaluated by the dynamic simulation and a fault propagation model is generated. By using the fault propagation model, an improved fault tree analysis (FTA) method using switching signal mode (SSM) is developed for estimating the probability of failures. The timely dependent failures can be considered as unavailability of safety objects that can cause the accidents in a plant. Finally, the rank of safety object is formulated as performance index (PI) and can be estimated using the importance measures. PI shows the prioritization of safety objects that should be investigated for safety improvement program in the plants. The output of this method can be used for optimal policy in safety object improvement and maintenance. The dynamic simulator was constructed using Visual Modeler (VM, the plant simulator, developed by Omega Simulation Corp., Japan). A case study is focused on the loss of containment (LOC) incident at polyvinyl chloride (PVC) batch process which is consumed the hazardous material, vinyl chloride monomer (VCM).

  17. Soft-Fault Detection Technologies Developed for Electrical Power Systems

    Button, Robert M.


    The NASA Glenn Research Center, partner universities, and defense contractors are working to develop intelligent power management and distribution (PMAD) technologies for future spacecraft and launch vehicles. The goals are to provide higher performance (efficiency, transient response, and stability), higher fault tolerance, and higher reliability through the application of digital control and communication technologies. It is also expected that these technologies will eventually reduce the design, development, manufacturing, and integration costs for large, electrical power systems for space vehicles. The main focus of this research has been to incorporate digital control, communications, and intelligent algorithms into power electronic devices such as direct-current to direct-current (dc-dc) converters and protective switchgear. These technologies, in turn, will enable revolutionary changes in the way electrical power systems are designed, developed, configured, and integrated in aerospace vehicles and satellites. Initial successes in integrating modern, digital controllers have proven that transient response performance can be improved using advanced nonlinear control algorithms. One technology being developed includes the detection of "soft faults," those not typically covered by current systems in use today. Soft faults include arcing faults, corona discharge faults, and undetected leakage currents. Using digital control and advanced signal analysis algorithms, we have shown that it is possible to reliably detect arcing faults in high-voltage dc power distribution systems (see the preceding photograph). Another research effort has shown that low-level leakage faults and cable degradation can be detected by analyzing power system parameters over time. This additional fault detection capability will result in higher reliability for long-lived power systems such as reusable launch vehicles and space exploration missions.

  18. A Practical approach for fault component network for Current and Voltage Phasor Diagram in Power Electronic Environment

    Mr. Ashish Choubey


    Full Text Available In many large-scale power plants, the structure of its auxiliary power system is complex, and the coordination of its relay protections is difficult. To enhance power supply reliability for the user terminals in the case of the distribution system to avoid interference by the fault again, rapidly complete the automatic identification, positioning, automatic fault isolation, network reconfiguration until the resumption of supply of non-fault section, a microprocessor-based relay protection device has developed. As the fault component theory is widely used in microcomputer protection, and fault component exists in the network of fault component, it is necessary to build up the fault component network when short circuit fault emerging and to draw the current and voltage component phasor diagram at fault point. We proposed a special phase sequence component based on the boundary condition. We analysis the velocity according to the relationship between analysis formula and phasor diagram and current in fault component boundary conditions and sequence voltage and current in boundary conditions. The negative and zero sequence component current and voltage at fault point are the same as fault component. The positive sequence component current and voltage at fault point are different from the fault component. So we consider the positive sequences according to that sequences we analyze the fault point

  19. A Practical approach for fault component network for Current and Voltage Phasor Diagram in Power Electronic Environment

    Ashish Choubey


    Full Text Available In many large-scale power plants, the structure of its auxiliary power system is complex, and the coordination of its relay protections is difficult. To enhance power supply reliability for the user terminals in the case of the distribution system to avoid interference by the fault again, rapidly complete the automatic identification, positioning, automatic fault isolation, network reconfiguration until the resumption of supply of non-fault section, a microprocessor-based relay protection device has developed. As the fault component theory is widely used in microcomputer protection, and fault component exists in the network of fault component, it is necessary to build up the fault component network when short circuit fault emerging and to draw the current and voltage component phasor diagram at fault point. We proposed a special phase sequence component based on the boundary condition. We analysis the velocity according to the relationship between analysis formula and phasor diagram and current in fault component boundary conditions and sequence voltage and current in boundary conditions. The negative and zero sequence component current and voltage at fault point are the same as fault component. The positive sequence component current and voltage at fault point are different from the fault component. So we consider the positive sequences according to that sequences we analyze the fault point.

  20. Active Fault Isolation in MIMO Systems

    Niemann, Hans Henrik; Poulsen, Niels Kjølstad


    Active fault isolation of parametric faults in closed-loop MIMO system s are considered in this paper. The fault isolation consists of two steps. T he first step is group- wise fault isolation. Here, a group of faults is isolated from other pos sible faults in the system. The group-wise fault iso...

  1. Research and Application of FTA and Petri Nets in Fault Diagnosis in the Pantograph-Type Current Collector on CRH EMU Trains

    Long-long Song


    Full Text Available A fault tree is established based on structural analysis, working principle analysis, and failure mode and effects analysis (FMEA of the pantograph-type current collector on the Chinese Rail High-Speed Electric Multiple Unit (CRH EMU train. To avoid the deficiencies of fault tree analysis (FTA, Petri nets modelling is used to address the problem of data explosion and carry out dynamic diagnosis. Relational matrix analysis is used to solve the minimal cut set equation of the fault tree. Based on the established state equation of the Petri nets, initial tokens and enable-transfer algorithms are used to express the fault transfer process mathematically and improve the efficiency of fault diagnosis inferences. Finally, using a practical fault diagnosis example for the pantographs on CRH EMU trains, the proposed method is proved to be reasonable and effective.

  2. Rough Faults, Distributed Weakening, and Off-Fault Deformation

    Griffith, W. A.; Nielsen, S. B.; di Toro, G.; Smith, S. A.; Niemeijer, A. R.


    We report systematic spatial variations of fault rocks along non-planar strike-slip faults cross-cutting the Lake Edison Granodiorite, Sierra Nevada, California (Sierran Wavy Fault) and the Lobbia outcrops of the Adamello Batholith in the Italian Alps (Lobbia Wavy Fault). In the case of the Sierran fault, pseudotachylyte formed at contractional fault bends, where it is found as thin (1-2 mm) fault-parallel veins. Epidote and chlorite developed in the same seismic context as the pseudotachylyte and are especially abundant in extensional fault bends. We argue that the presence of fluids, as illustrated by this example, does not necessarily preclude the development of frictional melt. In the case of the Lobbia fault, pseudotachylyte is present in variable thickness along the length of the fault, but the pseudotachylyte veins thicken and pool in extensional bends. The Lobbia fault surface is self-affine, and we conduct a quantitative analysis of microcrack distribution, stress, and friction along the fault. Numerical modeling results show that opening in extensional bends and localized thermal weakening in contractional bends counteract resistance encountered by fault waviness, resulting in an overall weaker fault than suggested by the corresponding static friction coefficient. Models also predict stress redistribution around bends in the faults which mirror microcrack distributions, indicating significant elastic and anelastic strain energy is dissipated into the wall rocks due to non-planar fault geometry. Together these observations suggest that, along non-planar faults, damage and energy dissipation occurs along the entire fault during slip, rather than being confined to the region close to the crack tip as predicted by classical fracture mechanics.


    Pan Zhongliang


    The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits with n primary inputs is not more than n + 1, for linear tree circuits is two, and for multiplication modulo circuits is two if n is an odd number or if n is an even number and m > 3, where the optimal test set of a circuit has minimal number of test vectors. Secondly,it is indicated that the cardinality of optimal multiple fault test set for linear tree circuits with n primary inputs is 1 + [n/(m - 1)], for multiplication modulo circuits is n+ 1, for fanout-free circuits that consist of 2-input linear tree circuits and 2-input multiplication modulo circuits is not greater than n+ 1, where [x] denotes the smallest integer greater than or equal to x. Finally,the single fault location approaches of linear tree circuits and multiplication modulo circuits are presented, and all faults in the two types of circuits can be located by using a test set with n + 1 vectors.

  4. Fault detection and identification based on combining logic and model in a wall-climbing robot

    Yong JIANG; Hongguang WANG; Lijin FANG; Mingyang ZHAO


    A combined logic- and model-based approach to fault detection and identification (FDI) in a suction foot control system of a wall-climbing robot is presented in this paper. For the control system, some fault models are derived by kinematics analysis. Moreover, the logic relations of the system states are known in advance. First, a fault tree is used to analyze the system by evaluating the basic events (elementary causes), which can lead to a root event (a particular fault). Then, a multiple-model adaptive estimation algorithm is used to detect and identify the model-known faults. Finally, based on the system states of the robot and the results of the estimation, the model-unknown faults are also identified using logical reasoning. Experiments show that the proposed approach based on the combination of logical reasoning and model estimating is efficient in the FDI of the robot.

  5. Mechanism of water-inrush from fault induced by mining near the working face

    WANG Lian-guo; WU Yu; MIAO Xie-xing; DONG Xu


    Adopted the fractal tree-like failure model, and established the renormalization group transform function of fractured fault, and investigated the mechanism of water-inrush from fault, and found out the critical probability of water-inrush from fault caused by fault fracture. The results indicate: when the failure rate P is less than the critical failure rate Pc=0.206 3, the failure of the system is just partial. When P is more than the critical failure rate Pc=0.206 3, the random distributed crannies concentrate to certain domain of attraction (such as the maximum shear stress face in the fault) gradually. The process will continue until the crannies run-through, forming conductivity channel, and cause water-inrush from fault.

  6. Fault diagnosis in neutral point indirectly grounded system based on information fusion

    于飞; 鞠丽叶; 刘喜梅; 崔平远; 钟秋海


    In neutral point indirectly grounded systems, phase-to-ground fault is putting new demands on fault diagnosis technology. Information fusion is applied to detect the phase-to-ground fault, which integrates several sources of information, including line current, line voltage, zero sequence current and voltage, and quintic harmonic wave component. This method is testified through the simulation of Matlab. Simulation results show that the precision and reliability of the detection has been greatly increased.

  7. A Fault Diagnostic Method for Position Sensor of Switched Reluctance Wind Generator

    Wang, Chao; Liu, Xiao; Liu, Hui;


    Fast and accurate fault diagnosis of the position sensor is of great significance to ensure the reliability as well as sensor fault tolerant operation of the Switched Reluctance Wind Generator (SRWG). This paper presents a fault diagnostic scheme for a SRWG based on the residual between the estim...... conditions. The results provide a feasible theoretical and technical basis for the effective condition monitoring and predictive maintenance of SRWG....

  8. Towards self-tuning residual generators for UAV control surface fault diagnosis

    Blanke, Mogens; Hansen, Søren


    Control surface fault diagnosis is essential for timely detection of manoeuvring and stability risks for an unmanned aircraft. Timely detection is crucial since control surface related faults impact stability of flight and safety. Reliable diagnosis require well fitting dynamical models but with ...... flights with different members of a population of UAVs that have inherent model uncertainty from one member to another and from one flight to another. Events with actual faults on control surfaces demonstrates the efficacy of the approach....

  9. Study on fault locating technology for satellite power system

    LONG Bing; JIANG Xing-wei; SONG Zheng-ji


    It is currently prevalent to locate faults for a satellite power system based on an expert system, not utilizing all the available information provided by tests. The casual network model for a satellite power system is presented. Considerations for failure probability of each component of the power system, the cost of applying each test, the influence of a precedent test result on the next test selection, and an optimal sequential testing algorithm for fault location is presented. This program is applied to locate the failure component of the power system of a satellite. The results show this program is very effective and it is very fast to generate an optimal diagnosis tree.

  10. Modular Tree Automata

    Bahr, Patrick


    Tree automata are traditionally used to study properties of tree languages and tree transformations. In this paper, we consider tree automata as the basis for modular and extensible recursion schemes. We show, using well-known techniques, how to derive from standard tree automata highly modular r...

  11. Simple street tree sampling

    David J. Nowak; Jeffrey T. Walton; James Baldwin; Jerry. Bond


    Information on street trees is critical for management of this important resource. Sampling of street tree populations provides an efficient means to obtain street tree population information. Long-term repeat measures of street tree samples supply additional information on street tree changes and can be used to report damages from catastrophic events. Analyses of...

  12. Modular tree automata

    Bahr, Patrick


    Tree automata are traditionally used to study properties of tree languages and tree transformations. In this paper, we consider tree automata as the basis for modular and extensible recursion schemes. We show, using well-known techniques, how to derive from standard tree automata highly modular...

  13. Fault Diagnosis Research for Metro Door Based on FTA%基于FTA的地铁车门故障诊断研究

    夏军; 邢宗义; 王晓浩


    Door system is a key subsystem of metro train, so the FTA method is applied to carry out the fault diagnosis research for reducing door maintenance time and improving door reliability. On the basis of analyzing the structure and working principle of metro door system, the disabled open fault of door system is selected as a top event to establish the fault tree. The minimum cut set is calculated by the Fussell-Vesely method, then the qualitative and quantitative analysis of FTA are carried out, so , so it can be concluded that EDCU , limit switch, nut component , screw and middle unlocking component have a great damage on door disabled open fault. The obtained results can be used for fault diagnosis of the metro door system.%车门系统是地铁列车的关键子系统,应用故障树分析FTA方法对地铁车门系统进行故障诊断研究有助于缩短车门检修时间和提高车门工作可靠性。在分析地铁车门系统结构和工作原理的基础之上,选取车门无法自动开门故障作为顶事件建立故障树,采用下行法求最小割集并进行定性与定量的综合分析,从而得出了EDCU、关闭行程开关、螺母组件、丝杆和中间解锁组件对车门无法自动开门故障的影响较大的诊断结果,为地铁车门系统的故障诊断提供辅助参考决策。

  14. Early Stage Software Reliability Estimation with Stochastic Reward Nets

    ZHAO Jing; LIU Hong-wei; CUI Gang; YANG Xiao-zong


    This paper presents software reliability modeling issues at the early stage of a software development for fault tolerant software management system. Based on Stochastic Reward Nets, an effective model of hierarchical view for a fault tolerant software management system is put forward, and an approach that consists of system transient performance analysis is adopted. A quantitative approach for software reliability analysis is given. The results show its usefulness for the design and evaluation of the early-stage software reliability modeling when failure data is not available.

  15. Reliability Evaluation of Metro Traction Power Supply System Based on FTA and FMEA Methods%基于FTA和FMEA法的地铁牵引供电系统可靠性评估

    胡海涛; 高朝晖; 何正友; 袁林


    The traction power supply system(TPSS)is the power source to guarantee safe and reliable operation of urban mass transit. Evaluation of the reliability of the system is critical to reliability research of the whole Metro power supply system. In this paper, fault tree analysis (FTA) and failure mode and effects analysis (FMEA) were used to evaluate the reliability of one typical Metro TPSS. Firstly, the system was defined and the FMEA table was consummated. Then,through grading the system voltages,the fault tree model was built up and the minimum cut sets of the fault tree were got. Finally,by using the self-developed reliability analysis software,the reliability of three cases of power supply "was evaluated. Compared with the actual project,the validity and practical applicability of the reliability analysis method were verified.%地铁牵引供电系统是保证地铁安全可靠运行的动力来源,其可靠性分析对整个地铁供电系统的可靠性研究至关重要.本文针对某一地铁典型牵引供电系统结构,利用故障树和故障模式与后果分析法对其进行可靠性评估.通过对系统进行定义及对系统电压等级的划分,建立故障模式和后果分析表格及供电系统的故障树模型.在此基础上,求取故障树的最小割集,并利用自主开发的可靠性分析软件对3种供电情况进行可靠性评估.最后与实际工程相比较,验证了该可靠性分析方法的有效性和实用性.

  16. Internal Leakage Fault Detection and Tolerant Control of Single-Rod Hydraulic Actuators

    Jianyong Yao


    Full Text Available The integration of internal leakage fault detection and tolerant control for single-rod hydraulic actuators is present in this paper. Fault detection is a potential technique to provide efficient condition monitoring and/or preventive maintenance, and fault tolerant control is a critical method to improve the safety and reliability of hydraulic servo systems. Based on quadratic Lyapunov functions, a performance-oriented fault detection method is proposed, which has a simple structure and is prone to implement in practice. The main feature is that, when a prescribed performance index is satisfied (even a slight fault has occurred, there is no fault alarmed; otherwise (i.e., a severe fault has occurred, the fault is detected and then a fault tolerant controller is activated. The proposed tolerant controller, which is based on the parameter adaptive methodology, is also prone to realize, and the learning mechanism is simple since only the internal leakage is considered in parameter adaptation and thus the persistent exciting (PE condition is easily satisfied. After the activation of the fault tolerant controller, the control performance is gradually recovered. Simulation results on a hydraulic servo system with both abrupt and incipient internal leakage fault demonstrate the effectiveness of the proposed fault detection and tolerant control method.

  17. Latest Progress of Fault Detection and Localization in Complex Electrical Engineering

    Zhao, Zheng; Wang, Can; Zhang, Yagang; Sun, Yi


    In the researches of complex electrical engineering, efficient fault detection and localization schemes are essential to quickly detect and locate faults so that appropriate and timely corrective mitigating and maintenance actions can be taken. In this paper, under the current measurement precision of PMU, we will put forward a new type of fault detection and localization technology based on fault factor feature extraction. Lots of simulating experiments indicate that, although there are disturbances of white Gaussian stochastic noise, based on fault factor feature extraction principal, the fault detection and localization results are still accurate and reliable, which also identifies that the fault detection and localization technology has strong anti-interference ability and great redundancy.

  18. Fault and meal detection by redundant continuous glucose monitors and the unscented Kalman filter

    Mahmoudi, Zeinab; Nørgaard, Kirsten; Poulsen, Niels Kjølstad


    The purpose of this study is to develop a method for detecting and compensating the anomalies of continuous glucose monitoring (CGM) sensors as well as detecting unannounced meals. Both features, sensor fault detection/correction and meal detection, are necessary to have a reliable artificial...... is in terms of a patient simulation model, where the model in the detector is the same as the patient simulation model used for evaluation of the detector. The detection module consists of two CGM sensors, two fault detectors, a fault isolator, and an adaptive unscented Kalman filter (UKF). Two types...... of sensor faults, i.e., drift and pressure induced sensor attenuation (PISA), are simulated by a Gaussian random walk model. Each of the fault detectors has a local UKF that receives the signal from the associated sensor, detects faults, and finally tunes the adaptive UKF. A fault isolator that accepts data...

  19. Fault Locating, Prediction and Protection (FLPPS)

    Yinger, Robert, J.; Venkata, S., S.; Centeno, Virgilio


    One of the main objectives of this DOE-sponsored project was to reduce customer outage time. Fault location, prediction, and protection are the most important aspects of fault management for the reduction of outage time. In the past most of the research and development on power system faults in these areas has focused on transmission systems, and it is not until recently with deregulation and competition that research on power system faults has begun to focus on the unique aspects of distribution systems. This project was planned with three Phases, approximately one year per phase. The first phase of the project involved an assessment of the state-of-the-art in fault location, prediction, and detection as well as the design, lab testing, and field installation of the advanced protection system on the SCE Circuit of the Future located north of San Bernardino, CA. The new feeder automation scheme, with vacuum fault interrupters, will limit the number of customers affected by the fault. Depending on the fault location, the substation breaker might not even trip. Through the use of fast communications (fiber) the fault locations can be determined and the proper fault interrupting switches opened automatically. With knowledge of circuit loadings at the time of the fault, ties to other circuits can be closed automatically to restore all customers except the faulted section. This new automation scheme limits outage time and increases reliability for customers. The second phase of the project involved the selection, modeling, testing and installation of a fault current limiter on the Circuit of the Future. While this project did not pay for the installation and testing of the fault current limiter, it did perform the evaluation of the fault current limiter and its impacts on the protection system of the Circuit of the Future. After investigation of several fault current limiters, the Zenergy superconducting, saturable core fault current limiter was selected for

  20. Fault Locating, Prediction and Protection (FLPPS)

    Yinger, Robert, J.; Venkata, S., S.; Centeno, Virgilio


    One of the main objectives of this DOE-sponsored project was to reduce customer outage time. Fault location, prediction, and protection are the most important aspects of fault management for the reduction of outage time. In the past most of the research and development on power system faults in these areas has focused on transmission systems, and it is not until recently with deregulation and competition that research on power system faults has begun to focus on the unique aspects of distribution systems. This project was planned with three Phases, approximately one year per phase. The first phase of the project involved an assessment of the state-of-the-art in fault location, prediction, and detection as well as the design, lab testing, and field installation of the advanced protection system on the SCE Circuit of the Future located north of San Bernardino, CA. The new feeder automation scheme, with vacuum fault interrupters, will limit the number of customers affected by the fault. Depending on the fault location, the substation breaker might not even trip. Through the use of fast communications (fiber) the fault locations can be determined and the proper fault interrupting switches opened automatically. With knowledge of circuit loadings at the time of the fault, ties to other circuits can be closed automatically to restore all customers except the faulted section. This new automation scheme limits outage time and increases reliability for customers. The second phase of the project involved the selection, modeling, testing and installation of a fault current limiter on the Circuit of the Future. While this project did not pay for the installation and testing of the fault current limiter, it did perform the evaluation of the fault current limiter and its impacts on the protection system of the Circuit of the Future. After investigation of several fault current limiters, the Zenergy superconducting, saturable core fault current limiter was selected for

  1. Sliding mode based fault detection, reconstruction and fault tolerant control scheme for motor systems.

    Mekki, Hemza; Benzineb, Omar; Boukhetala, Djamel; Tadjine, Mohamed; Benbouzid, Mohamed


    The fault-tolerant control problem belongs to the domain of complex control systems in which inter-control-disciplinary information and expertise are required. This paper proposes an improved faults detection, reconstruction and fault-tolerant control (FTC) scheme for motor systems (MS) with typical faults. For this purpose, a sliding mode controller (SMC) with an integral sliding surface is adopted. This controller can make the output of system to track the desired position reference signal in finite-time and obtain a better dynamic response and anti-disturbance performance. But this controller cannot deal directly with total system failures. However an appropriate combination of the adopted SMC and sliding mode observer (SMO), later it is designed to on-line detect and reconstruct the faults and also to give a sensorless control strategy which can achieve tolerance to a wide class of total additive failures. The closed-loop stability is proved, using the Lyapunov stability theory. Simulation results in healthy and faulty conditions confirm the reliability of the suggested framework.

  2. Guidelines for reliability analysis of digital systems in PSA context. Phase 1 status report

    Authen, S.; Larsson, J. (Risk Pilot AB, Stockholm (Sweden)); Bjoerkman, K.; Holmberg, J.-E. (VTT, Helsingfors (Finland))


    Digital protection and control systems are appearing as upgrades in older nuclear power plants (NPPs) and are commonplace in new NPPs. To assess the risk of NPP operation and to determine the risk impact of digital system upgrades on NPPs, quantitative reliability models are needed for digital systems. Due to the many unique attributes of these systems, challenges exist in systems analysis, modeling and in data collection. Currently there is no consensus on reliability analysis approaches. Traditional methods have clearly limitations, but more dynamic approaches are still in trial stage and can be difficult to apply in full scale probabilistic safety assessments (PSA). The number of PSAs worldwide including reliability models of digital I and C systems are few. A comparison of Nordic experiences and a literature review on main international references have been performed in this pre-study project. The study shows a wide range of approaches, and also indicates that no state-of-the-art currently exists. The study shows areas where the different PSAs agree and gives the basis for development of a common taxonomy for reliability analysis of digital systems. It is still an open matter whether software reliability needs to be explicitly modelled in the PSA. The most important issue concerning software reliability is proper descriptions of the impact that software-based systems has on the dependence between the safety functions and the structure of accident sequences. In general the conventional fault tree approach seems to be sufficient for modelling reactor protection system kind of functions. The following focus areas have been identified for further activities: 1. Common taxonomy of hardware and software failure modes of digital components for common use 2. Guidelines regarding level of detail in system analysis and screening of components, failure modes and dependencies 3. Approach for modelling of CCF between components (including software). (Author)

  3. Fault Tolerance, Reliability and Testability for Distributed Systems.


    A p;ocesso or all cncin hav 2ald* FIGURE2.1 A- 4 FAUL LOCTO AROC DUR OFSCIN 3.,PR _ _ __ol~ _ _ _ _ _ I , ,CD SUMAYOFAGNSTC Cseas Faile CopnnsTetdN.o... Journal , vol. 18, no. 2. p. 244, 1979 DAVI81 E. A. Davis and P. K. Giloth, "No. 4 ESS: performance objectives and service experience". Bell System...Technical Journal , vol. 60, no. 6, pp. 1203-1224, August, 1981 DlC179 V. DiCIcclo, C.A. Sunshine, J.A. Field, and E.G. Manning, "Alternatives for

  4. Energy-Aware Synthesis of Fault-Tolerant Schedules for Real-Time Distributed Embedded Systems

    Poulsen, Kåre Harbo; Pop, Paul; Izosimov, Viacheslav


    This paper presents a design optimisation tool for distributed embedded real-time systems that 1) decides mapping, fault-tolerance policy and generates a fault-tolerant schedule, 2) is targeted for hard real-time, 3) has hard reliability goal, 4) generates static schedule for processes and messages...

  5. Reliability and safety analysis of redundant vehicle management computer system

    Shi Jian; Meng Yixuan; Wang Shaoping; Bian Mengmeng; Yan Dungong


    Redundant techniques are widely adopted in vehicle management computer (VMC) to ensure that VMC has high reliability and safety. At the same time, it makes VMC have special char-acteristics, e.g., failure correlation, event simultaneity, and failure self-recovery. Accordingly, the reliability and safety analysis to redundant VMC system (RVMCS) becomes more difficult. Aimed at the difficulties in RVMCS reliability modeling, this paper adopts generalized stochastic Petri nets to establish the reliability and safety models of RVMCS. Then this paper analyzes RVMCS oper-ating states and potential threats to flight control system. It is verified by simulation that the reli-ability of VMC is not the product of hardware reliability and software reliability, and the interactions between hardware and software faults can reduce the real reliability of VMC obviously. Furthermore, the failure undetected states and false alarming states inevitably exist in RVMCS due to the influences of limited fault monitoring coverage and false alarming probability of fault mon-itoring devices (FMD). RVMCS operating in some failure undetected states will produce fatal threats to the safety of flight control system. RVMCS operating in some false alarming states will reduce utility of RVMCS obviously. The results abstracted in this paper can guide reliable VMC and efficient FMD designs. The methods adopted in this paper can also be used to analyze other intelligent systems’ reliability.

  6. Improving fault coverage and minimising the cost of fault identification when testing from finite state machines

    Guo, Qiang


    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Software needs to be adequately tested in order to increase the confidence that the system being developed is reliable. However, testing is a complicated and expensive process. Formal specification based models such as finite state machines have been widely used in system modelling and testing. In this PhD thesis, we primarily investigate fault detection and identification when testing from f...

  7. Investigation on design and reliability analysis of a new deployable and lockable mechanism

    Lin, Qing; Nie, Hong; Ren, Jie; Chen, Jinbao


    The traditional structure of the deployable and lockable mechanism on soft-landing gear system is complicated and unreliable. To overcome the defects, a new deployable and lockable mechanism for planetary probes is developed. The compression assembly shares a set of new mechanism with the deployment assembly and locking assembly. The new mechanism shows some advantages: more steady deployment, simpler mechanism and higher reliability. This paper presents an introduction of the deployment and locking theory of the new mechanism, and constitutes the fault tree, which would contribute to qualitative and quantitative analyses. In addition, probability importance and criticality importance of the new mechanism are derived and calculated. The reliability modeling and analysis of the mechanism are accomplished from static torque margin, torque and the work by torque. In investigation results, reliability rate that the new mechanism could deploy successfully is 0.999334. The crucial problems concentrate on the insufficiency of storage force torque of high strength spring, the lubrication failure between the inner cylinder and the outer cylinder of the strut and the stuck soft-landing gear system. And then, the paper presents some improvement approaches and suggestions according to the problems discussed above.

  8. Reliability and availability analysis of dependent-dynamic systems with DRBDs

    Distefano, Salvatore [University of Messina, Department of Mathematics, Engineering Faculty, Contrada di Dio, S. Agata, 98166 Messina (Italy)], E-mail:; Puliafito, Antonio [University of Messina, Department of Mathematics, Engineering Faculty, Contrada di Dio, S. Agata, 98166 Messina (Italy)], E-mail:


    Reliability/availability evaluation is an important, often indispensable, step in designing and analyzing (critical) systems, whose importance is constantly growing. When the complexity of a system is high, dynamic effects can arise or become significant. The system might be affected by dependent, cascade, on-demand and/or common cause failures, its units could interfere (load sharing, inter/sequence-dependency), and so on. It is also of great interest to evaluate redundancy and maintenance policies but, since dynamic behaviors usually do not satisfy the stochastic independence assumption, notations such as reliability block diagrams (RBDs), fault trees (FTs) or reliability graphs (RGs) become approximated/simplified techniques, unable to capture dynamic-dependent behaviors. To overcome such problem we developed a new formalism derived from RBDs: the dynamic RBDs (DRBDs). In this paper we explain how the DRBDs notation is able to adequately model and therefore analyze dynamic-dependent behaviors and complex systems. Particular emphasis is given to the modeling and the analysis phases, from both the theoretical and the practical point of views. Several case studies of dynamic-dependent systems, selected from literature and related to different application fields, are proposed. In this way we also compare the DRBDs approach with other methodologies, demonstrating its effectiveness.

  9. A method of multi-objective reliability tolerance design for electronic circuits

    Zhai Guofu; Zhou Yuege; Ye Xuerong; Hu Bo


    Tolerance design plays an important role in reliability design for electronic circuits.The traditional method only focuses on the consistency of output response.It is not able to meet the needs of increasing development of electronic products.This paper researches the state of related fields and proposes a method of multi-objective reliability tolerance design.The characteristics of output response and operating stresses on critical components are both defined as design objectives.Critical components and their operating stresses are determined by failure mode and effect analysis (FMEA) and fault tree analysis (FTA).Sensitivity analysis is carried out to determine sensitive parameters that affect the design objectives significantly.Monte Carlo and worst-case analysis are utilized to explore the tolerance levels of sensitive parameters.Design of experiment and regression analysis are applied in this method.The optimal tolerance levels are selected in accord with a quality-cost model to improve consistency of output response and reduce failure rates of critical components synchronously.The application in light-emitting diode (LED) drivers indicates details and potential.It shows that the proposed method provides a more effective way to improve performance and reliability of electronic circuits.

  10. A Fault Tolerant Resource Allocation Architecture for Mobile Grid

    P. T. Vanathi


    Full Text Available Problem statement: In order to achieve high level of reliability and availability, the grid infrastructure should be fault tolerant. Since the failure of resources affects job execution fatally, fault tolerance service is essential to satisfy QoS requirement in grid computing with respect to mobile nodes. Approach: We propose a fault tolerant technique for improving reliability in mobile grid environment considering the node mobility. The Cluster head and monitoring agent was designed in such a way it addresses both resource and network failure and present recovery techniques for overcoming the faults. Results: The proposed model achieves a identifiable performance when compared to the previous model (HRAA. By simulation results, we analyze the node and link failures on parameters such as delivery ratio, throughput and delay against the rate of success. Conclusion: The proposed fault tolerant approach checks for availability of the nodes with least work load for transferring the executed job to cluster head providing an alternate path in case of failure thereby enhancing the reliability of the grid environment.

  11. Tree of life and its applications

    Limin Lu


    Full Text Available The term “Tree of Life” was first used by Charles Darwin in 1859 as a metaphor for describing phylogenetic relationships among organisms. Over the past three decades, the recognized tree of life has improved considerably in overall size and reliability due to an increase in diversity of character resources, a dramatic growth in useable data, and the development of tree-reconstruction methods. As a bridge connecting phylogeny, evolution and related disciplines, such as molecular biology, ecology, genomics, bioinformatics and computer science, the tree of life is increasingly widely used. In this paper, we review the history and progress of tree of life studies and focus on its application in the following fields: (1 the reconstruction of phylogenetic trees at different taxonomic hierarchies to understand phylogenetic relationships among taxa; (2 investigation of the origins of taxa and biogeographic patterns based on dating estimation and biogeographic reconstruction; (3 examination of species’ diversification and its causes by integrating dated trees, ecological factors, environmental variation and key innovations; (4 the study of the origin and patterns of biodiversity, predating biodiversity dynamics, and development of conservation strategies. Finally, we evaluate the difficulties from matrix alignment, gene tree incongruence and “rogue taxa” distraction in tree reconstruction due to massive increases of useable data and in the context consider “supertree” building in the future.

  12. An Imperfect-debugging Fault-detection Dependent-parameter Software


    Software reliability growth models (SRGMs) incorporating the imperfect debugging and learning phenomenon of developers have recently been developed by many researchers to estimate software reliability measures such as the number of remaining faults and software reliability. However, the model parameters of both the fault content rate function and fault detection rate function of the SRGMs are often considered to be independent from each other. In practice, this assumption may not be the case and it is worth to investigate what if it is not. In this paper, we aim for such study and propose a software reliability model connecting the imperfect debugging and learning phenomenon by a common parameter among the two functions, called the imperfect-debugging fault-detection dependent-parameter model. Software testing data collected from real applications are utilized to illustrate the proposed model for both the descriptive and predictive power by determining the non-zero initial debugging process.

  13. Fault Monitooring and Fault Recovery Control for Position Moored Tanker

    Fang, Shaoji; Blanke, Mogens


    This paper addresses fault tolerant control for position mooring of a shuttle tanker operating in the North Sea. A complete framework for fault diagnosis is presented but the loss of a sub-sea mooring line buoyancy element is given particular attention, since this fault could lead to line breakage...... algorithm is proposed to accommodate buoyancy element failure and keep the mooring system in a safe state. Detection properties and fault-tolerant control are demonstrated by high delity simulations...

  14. Discriminating Fault Rate and Persistency to Improve Fault Treatment

    Bondavalli, Andrea; Chiaradonna, Silvano; Di Giandomenico,Felicita; Grandoni, Fabrizio


    In this paper the consolidate identification of faults, distinguished as transient or permanent/intermittent, is approached, through the definition of a fault identification mechanism, called a-count. The goal is to allow continued use of parts being hit by transient faults, which may lead to better overall system performance if proper handling is provided. Transient faults discrimination is especially important in all those dependability-qualified applications where replacing and repairing f...

  15. Study on Fault Current of DFIG during Slight Fault Condition

    Xiangping Kong; Zhe Zhang; Xianggen Yin; Zhenxing Li


    In order to ensure the safety of DFIG when severe fault happens, crowbar protection is adopted. But during slight fault condition, the crowbar protection will not trip, and the DFIG is still excited by AC-DC-AC converter. In this condition, operation characteristics of the converter have large influence on the fault current characteristics of DFIG. By theoretical analysis and digital simulation, the fault current characteristics of DFIG during slight voltage dips are studied. And the influenc...

  16. Grid reliability

    Saiz, P; Rocha, R; Andreeva, J


    We are offering a system to track the efficiency of different components of the GRID. We can study the performance of both the WMS and the data transfers At the moment, we have set different parts of the system for ALICE, ATLAS, CMS and LHCb. None of the components that we have developed are VO specific, therefore it would be very easy to deploy them for any other VO. Our main goal is basically to improve the reliability of the GRID. The main idea is to discover as soon as possible the different problems that have happened, and inform the responsible. Since we study the jobs and transfers issued by real users, we see the same problems that users see. As a matter of fact, we see even more problems than the end user does, since we are also interested in following up the errors that GRID components can overcome by themselves (like for instance, in case of a job failure, resubmitting the job to a different site). This kind of information is very useful to site and VO administrators. They can find out the efficien...

  17. Computer hardware fault administration

    Archer, Charles J.; Megerian, Mark G.; Ratterman, Joseph D.; Smith, Brian E.


    Computer hardware fault administration carried out in a parallel computer, where the parallel computer includes a plurality of compute nodes. The compute nodes are coupled for data communications by at least two independent data communications networks, where each data communications network includes data communications links connected to the compute nodes. Typical embodiments carry out hardware fault administration by identifying a location of a defective link in the first data communications network of the parallel computer and routing communications data around the defective link through the second data communications network of the parallel computer.

  18. Fault Tolerant Computer Architecture

    Sorin, Daniel


    For many years, most computer architects have pursued one primary goal: performance. Architects have translated the ever-increasing abundance of ever-faster transistors provided by Moore's law into remarkable increases in performance. Recently, however, the bounty provided by Moore's law has been accompanied by several challenges that have arisen as devices have become smaller, including a decrease in dependability due to physical faults. In this book, we focus on the dependability challenge and the fault tolerance solutions that architects are developing to overcome it. The two main purposes

  19. Fault tolerant linear actuator

    Tesar, Delbert


    In varying embodiments, the fault tolerant linear actuator of the present invention is a new and improved linear actuator with fault tolerance and positional control that may incorporate velocity summing, force summing, or a combination of the two. In one embodiment, the invention offers a velocity summing arrangement with a differential gear between two prime movers driving a cage, which then drives a linear spindle screw transmission. Other embodiments feature two prime movers driving separate linear spindle screw transmissions, one internal and one external, in a totally concentric and compact integrated module.

  20. Sensor fault diagnosis with a probabilistic decision process

    Sharifi, Reza; Langari, Reza


    In this paper a probabilistic approach to sensor fault diagnosis is presented. The proposed method is applicable to systems whose dynamic can be approximated with only few active states, especially in process control where we usually have a relatively slow dynamics. Unlike most existing probabilistic approaches to fault diagnosis, which are based on Bayesian Belief Networks, in this approach the probabilistic model is directly extracted from a parity equation. The relevant parity equation can be found using a model of the system or through principal component analysis of data measured from the system. In addition, a sensor detectability index is introduced that specifies the level of detectability of sensor faults in a set of analytically redundant sensors. This index depends only on the internal relationships of the variables of the system and noise level. The method is tested on a model of the Tennessee Eastman process and the result shows a fast and reliable prediction of fault in the detectable sensors.

  1. Concealed fault analysis based on the CT projection matrix

    Yang Zhen; Yao Wenli; Ma Liuzhu; Wise Lucas


    This paper proposes the concept of projection curves based on the theory of CT image reconstruction to probe the internal structure of the working panel prior to formal mining of the working panel. As well as reducing costs, this method provides safe and efficient excavation of the working panel. According to the results of the numerical model and the actual working panel, the new method has been proven to be accurate in detecting the location of the fault that extends into the face. Concealed faults of the internal working panel, as well as the start and end points of the fault, can be detected by this method. Engineering practice has proven that the method is highly reliable, has a highly decisive impact on faults for coal mining, and can be used to guide the safe mining of the working panel.

  2. Technologies for faults diagnosis of FPGA logic blocks

    C. U. Ngene


    Full Text Available The critical issues of testing field programmable gate arrays (FPGA with a view to diagnosing faults are an important step that ensures the reliability of FPGA designs. Correct diagnosis of faulty logic blocks of FPGAs guarantees restoration of functionality through replacement of faulty block with replacement units. This process can be done autonomously or without the intervention of an engineer depending on application area. This paper considers two methods for analysing test results of FPGA logic blocks with the purpose of localising and distinguishing faults. The algebraic logic and vector-logical methods are proposed for diagnosing faulty logic blocks in FPGA fabric. It is found that the algebraic logic method is more useful for processing of sparse faults tables when the number of coordinates with 1s values with respect to zero values ​​is not more than 20%, whereas the vector-logical method facilitates the analysis of faults table with predominance of 1s values.

  3. Research on fault mode and diagnosis of methane sensor

    WANG Qi-jun; CHENG Jiu-long


    To improve the reliability of coal mine safety monitoring systems we have analyzed the characteristics of a methane sensor, an important component of the monitoring system of production safety in a coal mine and studied the main type and mode of faults when the sensor was used on-line. We introduced a new method based on artificial neural network to detect faults of me-thane sensors. In addition, using the output information of a single methane sensor, we established a sensor output model of a dy-namic non-linear neural network for on-line fault detection. Finally, the fault of the heating wire of the sensor was simulated, indi-cating that, when the methane sensor had a fault, the predicted output of the neural network clearly deviated from the actual output,exceeding the pre-set threshold and showing that a fault had occurred in the methane sensor. The result shows that the model has good convergence and stability, and is quite capable of meeting the requirements for on-line fault detection of methane sensors.

  4. Research of Earthquake Potential from Active Fault Observation in Taiwan

    Chien-Liang, C.; Hu, J. C.; Liu, C. C.; En, C. K.; Cheng, T. C. T.


    We utilize GAMIT/GLOBK software to estimate the precise coordinates for continuous GPS (CGPS) data of Central Geological Survey (CGS, MOEA) in Taiwan. To promote the software estimation efficiency, 250 stations are divided by 8 subnets which have been considered by station numbers, network geometry and fault distributions. Each of subnets include around 50 CGPS and 10 international GNSS service (IGS) stations. After long period of data collection and estimation, a time series variation can be build up to study the effect of earthquakes and estimate the velocity of stations. After comparing the coordinates from campaign-mode GPS sites and precise leveling benchmarks with the time series from continuous GPS stations, the velocity field is consistent with previous measurement which show the reliability of observation. We evaluate the slip rate and slip deficit rate of active faults in Taiwan by 3D block model DEFNODE. First, to get the surface fault traces and the subsurface fault geometry parameters, and then establish the block boundary model of study area. By employing the DEFNODE technique, we invert the GPS velocities for the best-fit block rotate rates, long term slip rates and slip deficit rates. Finally, the probability analysis of active faults is to establish the flow chart of 33 active faults in Taiwan. In the past two years, 16 active faults in central and northern Taiwan have been assessed to get the recurrence interval and the probabilities for the characteristic earthquake occurred in 30, 50 and 100 years.

  5. Fault tolerant control based on active fault diagnosis

    Niemann, Hans Henrik


    An active fault diagnosis (AFD) method will be considered in this paper in connection with a Fault Tolerant Control (FTC) architecture based on the YJBK parameterization of all stabilizing controllers. The architecture consists of a fault diagnosis (FD) part and a controller reconfiguration (CR...

  6. Wind turbine fault detection and fault tolerant control

    Odgaard, Peter Fogh; Johnson, Kathryn


    In this updated edition of a previous wind turbine fault detection and fault tolerant control challenge, we present a more sophisticated wind turbine model and updated fault scenarios to enhance the realism of the challenge and therefore the value of the solutions. This paper describes the challe...

  7. Software reliability experiments data analysis and investigation

    Walker, J. Leslie; Caglayan, Alper K.


    The objectives are to investigate the fundamental reasons which cause independently developed software programs to fail dependently, and to examine fault tolerant software structures which maximize reliability gain in the presence of such dependent failure behavior. The authors used 20 redundant programs from a software reliability experiment to analyze the software errors causing coincident failures, to compare the reliability of N-version and recovery block structures composed of these programs, and to examine the impact of diversity on software reliability using subpopulations of these programs. The results indicate that both conceptually related and unrelated errors can cause coincident failures and that recovery block structures offer more reliability gain than N-version structures if acceptance checks that fail independently from the software components are available. The authors present a theory of general program checkers that have potential application for acceptance tests.

  8. Modeling and Simulation Reliable Spacecraft On-Board Computing

    Park, Nohpill


    The proposed project will investigate modeling and simulation-driven testing and fault tolerance schemes for Spacecraft On-Board Computing, thereby achieving reliable spacecraft telecommunication. A spacecraft communication system has inherent capabilities of providing multipoint and broadcast transmission, connectivity between any two distant nodes within a wide-area coverage, quick network configuration /reconfiguration, rapid allocation of space segment capacity, and distance-insensitive cost. To realize the capabilities above mentioned, both the size and cost of the ground-station terminals have to be reduced by using reliable, high-throughput, fast and cost-effective on-board computing system which has been known to be a critical contributor to the overall performance of space mission deployment. Controlled vulnerability of mission data (measured in sensitivity), improved performance (measured in throughput and delay) and fault tolerance (measured in reliability) are some of the most important features of these systems. The system should be thoroughly tested and diagnosed before employing a fault tolerance into the system. Testing and fault tolerance strategies should be driven by accurate performance models (i.e. throughput, delay, reliability and sensitivity) to find an optimal solution in terms of reliability and cost. The modeling and simulation tools will be integrated with a system architecture module, a testing module and a module for fault tolerance all of which interacting through a centered graphical user interface.

  9. Improving Multiple Fault Diagnosability using Possible Conflicts

    National Aeronautics and Space Administration — Multiple fault diagnosis is a difficult problem for dynamic systems. Due to fault masking, compensation, and relative time of fault occurrence, multiple faults can...

  10. BFTDT: Byzantine Fault Tolerance tryout for Dependable Transactions in Cloud

    Gayathri S


    Full Text Available Cloud Web Services (CWS is the technology used for business collaboration and integration among the web users. The Web Services Atomic Transactions (WS-AT have been used for the trusted distributed transaction processing over the web. The WS-AT in the distributed sense has byzantine faults to overcome that Byzantine Faults Techniques (BFT is used. The reliable coordinator provides the services that are Coordination services, Activation services, Registration Services and Completion services which make the transaction effective and reliable. In the trusted environment, to evade congestion of the resources, fair share bandwidth allocation scheme is used to allocate separate bandwidth for each web users and the transaction is processed Coordinator server and the Transaction Processing Monitor (TPM. The WS-AT for business applications analysis shows the high degree of dependability, security, trust, fault tolerance and fairness of the resources in the trusted environment.

  11. Fault Management Assistant (FMA) Project

    National Aeronautics and Space Administration — S&K Aerospace (SKA) proposes to develop the Fault Management Assistant (FMA) to aid project managers and fault management engineers in developing better and more...

  12. ESR dating of fault rocks

    Lee, Hee Kwon [Kangwon National Univ., Chuncheon (Korea, Republic of)


    Past movement on faults can be dated by measurement of the intensity of ESR signals in quartz. These signals are reset by local lattice deformation and local frictional heating on grain contacts at the time of fault movement. The ESR signals then trow back as a result of bombardment by ionizing radiation from surrounding rocks. The age is obtained from the ratio of the equivalent dose, needed to produce the observed signal, to the dose rate. Fine grains are more completely reset during faulting, and a plot of age vs grain size shows a plateau for grains below critical size : these grains are presumed to have been completely zeroed by the last fault activity. We carried out ESR dating of fault rocks collected from the Yangsan fault system. ESR dates from the this fault system range from 870 to 240 ka. Results of this research suggest that long-term cyclic fault activity continued into the pleistocene.

  13. Seismic fault zone trapped noise

    Hillers, G; Campillo, M; Ben‐Zion, Y; Roux, P


    Systematic velocity contrasts across and within fault zones can lead to head and trapped waves that provide direct information on structural units that are important for many aspects of earthquake and fault mechanics...

  14. Uniform analysis of fault trees through model transformations

    Ruijters, Enno Jozef Johannes; Schivo, Stefano; Stoelinga, Mariëlle Ida Antoinette; Rensink, Arend


    As the critical systems we rely on every day, such as nuclear power plants and airplanes, become ever more complex, the need to rigorously verify the safety and dependability of these systems is becoming very clear. Furthermore, deliberate attacks have become a prominent cause of concern for safety

  15. Waste Management facilities fault tree databank 1995 status report

    Minnick, W.V.; Wellmaker, K.A.


    The Safety Information Management and Analysis Group (SIMA) of the Safety Engineering Department (SED) maintains compilations of incidents that have occurred in the Separations and Process Control, Waste Management, Fuel Fabrication, Tritium and SRTC facilities. This report records the status of the Waste Management (WM) Databank at the end of CY-1994. The WM Databank contains more than 35,000 entries ranging from minor equipment malfunctions to incidents with significant potential for injury or contamination of personnel. This report documents the status of the WM Databank including the availability, training, sources of data, search options, Quality Assurance, and usage to which these data have been applied. Periodic updates to this memorandum are planned as additional data or applications are acquired.

  16. Software Fault Tree Analysis of Concurrent Ada Processes


    excerpt from the investigation into the Therac -25 accidents: It is clear from the AECL (Atomic Energy of Canada Limited) documentation on the...Publishing Co., Inc., New York, N.Y., 1988 25. Leveson, N.G and Turner, C.S., An Investigation of the Therac -25 Accidents, IEEE Computer, July 1993

  17. The property of fault zone and fault activity of Shionohira Fault, Fukushima, Japan

    Seshimo, K.; Aoki, K.; Tanaka, Y.; Niwa, M.; Kametaka, M.; Sakai, T.; Tanaka, Y.


    The April 11, 2011 Fukushima-ken Hamadori Earthquake (hereafter the 4.11 earthquake) formed co-seismic surface ruptures trending in the NNW-SSE direction in Iwaki City, Fukushima Prefecture, which were newly named as the Shionohira Fault by Ishiyama et al. (2011). This earthquake was characterized by a westward dipping normal slip faulting, with a maximum displacement of about 2 m (e.g., Kurosawa et al., 2012). To the south of the area, the same trending lineaments were recognized to exist even though no surface ruptures occurred by the earthquake. In an attempt to elucidate the differences of active and non-active segments of the fault, this report discusses the results of observation of fault outcrops along the Shionohira Fault as well as the Coulomb stress calculations. Only a few outcrops have basement rocks of both the hanging-wall and foot-wall of the fault plane. Three of these outcrops (Kyodo-gawa, Shionohira and Betto) were selected for investigation. In addition, a fault outcrop (Nameishi-minami) located about 300 m south of the southern tip of the surface ruptures was investigated. The authors carried out observations of outcrops, polished slabs and thin sections, and performed X-ray diffraction (XRD) to fault materials. As a result, the fault zones originating from schists were investigated at Kyodo-gawa and Betto. A thick fault gouge was cut by a fault plane of the 4.11 earthquake in each outcrop. The fault materials originating from schists were fault bounded with (possibly Neogene) weakly deformed sandstone at Shionohira. A thin fault gouge was found along the fault plane of 4.11 earthquake. A small-scale fault zone with thin fault gouge was observed in Nameishi-minami. According to XRD analysis, smectite was detected in the gouges from Kyodo-gawa, Shionohira and Betto, while not in the gouge from Nameishi-minami.

  18. Investigating fault coupling: Creep and microseismicity on the Hayward fault

    Evans, E. L.; Loveless, J. P.; Meade, B. J.; Burgmann, R.


    We seek to quantify the relationship between interseismic slip activity and microseismicity along the Hayward fault in the eastern San Francisco Bay Area. During the interseismic regime the Hayward fault is known to exhibit variable degrees of locking both along strike and down-dip. Background microseismicity on and near the fault has been suggested to provide independent information about the rates of interseismic creep and the boundaries of creeping regions. In particular, repeating earthquakes within the fault zone have been suggested as a proxy for fault creep rates. To investigate this relationship, we invert GPS data for microplate rotations, fault slip rates, and fault coupling using a block model that spans western United States and includes the San Andreas, Hayward, Calaveras, Rogers Creek, and Green Valley faults in the greater Bay area. The tectonic context provided by the regional scale model ensures that the slip budget across Bay Area faults is consistent with large scale tectonic motions and kinematically connected to the central San Andreas fault. We image the spatial distribution of interseismic slip on a triangulated mesh of the Hayward fault and compare the distribution of interseismic fault coupling with the number of earthquakes and the moment rate of all on-fault seismicity. We quantitatively test the hypothesis that microseismicity might define the transitions between locked and creeping regions. The calculated correlations are tested against a null hypothesis that microseismicity is randomly distributed. We further extend this investigation to the step over region between the Hayward and Calaveras faults to illuminate the interactions between linking faults.

  19. An Efficient Network Coding-Based Fault-Tolerant Mechanism in WBAN for Smart Healthcare Monitoring Systems

    Yuhuai Peng


    Full Text Available As a key technology in smart healthcare monitoring systems, wireless body area networks (WBANs can pre-embed sensors and sinks on body surface or inside bodies for collecting different vital signs parameters, such as human Electrocardiograph (ECG, Electroencephalograph (EEG, Electromyogram (EMG, body temperature, blood pressure, blood sugar, blood oxygen, etc. Using real-time online healthcare, patients can be tracked and monitored in normal or emergency conditions at their homes, hospital rooms, and in Intensive Care Units (ICUs. In particular, the reliability and effectiveness of the packets transmission will be directly related to the timely rescue of critically ill patients with life-threatening injuries. However, traditional fault-tolerant schemes either have the deficiency of underutilised resources or react too slowly to failures. In future healthcare systems, the medical Internet of Things (IoT for real-time monitoring can integrate sensor networks, cloud computing, and big data techniques to address these problems. It can collect and send patient’s vital parameter signal and safety monitoring information to intelligent terminals and enhance transmission reliability and efficiency. Therefore, this paper presents a design in healthcare monitoring systems for a proactive reliable data transmission mechanism with resilience requirements in a many-to-one stream model. This Network Coding-based Fault-tolerant Mechanism (NCFM first proposes a greedy grouping algorithm to divide the topology into small logical units; it then constructs a spanning tree based on random linear network coding to generate linearly independent coding combinations. Numerical results indicate that this transmission scheme works better than traditional methods in reducing the probability of packet loss, the resource redundant rate, and average delay, and can increase the effective throughput rate.

  20. Learning from examples - Generation and evaluation of decision trees for software resource analysis

    Selby, Richard W.; Porter, Adam A.


    A general solution method for the automatic generation of decision (or classification) trees is investigated. The approach is to provide insights through in-depth empirical characterization and evaluation of decision trees for software resource data analysis. The trees identify classes of objects (software modules) that had high development effort. Sixteen software systems ranging from 3,000 to 112,000 source lines were selected for analysis from a NASA production environment. The collection and analysis of 74 attributes (or metrics), for over 4,700 objects, captured information about the development effort, faults, changes, design style, and implementation style. A total of 9,600 decision trees were automatically generated and evaluated. The trees correctly identified 79.3 percent of the software modules that had high development effort or faults, and the trees generated from the best parameter combinations correctly identified 88.4 percent of the modules on the average.