WorldWideScience

Sample records for system reliability assessments

  1. Operator reliability assessment system (OPERAS)

    International Nuclear Information System (INIS)

    Spurgin, A.J.; Hallam, J.W.; Spurgin, J.P.; Singh, A.

    1991-01-01

    The paper gives an overview of the OPERAS project. It discusses the background which led to the design of the PC-based data collection and analysis system connected to plant training simulators including those used for nuclear power plants. The usefulness of a system like OPERAS was perceived during an earlier EPRI project, the Operator Reliability Experiments project, by EPRI and PG and E. The data collection and analysis approaches used in OPERAS were developed during the ORE project. The paper not only discusses the design of OPERAS but discusses the functions performed and the current experiences with the two prototype systems. Also listed are potential uses of OPERAS by utility personnel in Operations, Training and PRA groups

  2. System Reliability Assessment of Offshore Pipelines

    NARCIS (Netherlands)

    Mustaffa, Z.

    2011-01-01

    The title of this thesis, System Reliability Assessment of Offshore Pipelines, portrays the application of probabilistic methods in assessing the reliability of these structures. The main intention of this thesis is to identify, apply and judge the suitability of the probabilistic methods in

  3. Reliability analysis and assessment of structural systems

    International Nuclear Information System (INIS)

    Yao, J.T.P.; Anderson, C.A.

    1977-01-01

    The study of structural reliability deals with the probability of having satisfactory performance of the structure under consideration within any specific time period. To pursue this study, it is necessary to apply available knowledge and methodology in structural analysis (including dynamics) and design, behavior of materials and structures, experimental mechanics, and the theory of probability and statistics. In addition, various severe loading phenomena such as strong motion earthquakes and wind storms are important considerations. For three decades now, much work has been done on reliability analysis of structures, and during this past decade, certain so-called 'Level I' reliability-based design codes have been proposed and are in various stages of implementation. These contributions will be critically reviewed and summarized in this paper. Because of the undesirable consequences resulting from the failure of nuclear structures, it is important and desirable to consider the structural reliability in the analysis and design of these structures. Moreover, after these nuclear structures are constructed, it is desirable for engineers to be able to assess the structural reliability periodically as well as immediately following the occurrence of severe loading conditions such as a strong-motion earthquake. During this past decade, increasing use has been made of techniques of system identification in structural engineering. On the basis of non-destructive test results, various methods have been developed to obtain an adequate mathematical model (such as the equations of motion with more realistic parameters) to represent the structural system

  4. Reliability assessment of nuclear structural systems

    International Nuclear Information System (INIS)

    Reich, M.; Hwang, H.

    1983-01-01

    Reliability assessment of nuclear structural systems has been receiving more emphasis over the last few years. This paper deals with the recent progress made by the Structural Analysis Division of Brookhaven National Laboratory (BNL), in the development of a probability-based reliability analysis methodology for safety evaluation of reactor containments and other seismic category I structures. An important feature of this methodology is the incorporation of finite element analysis and random vibration theory. By utilizing this method, it is possible to evaluate the safety of nuclear structures under various static and dynamic loads in terms of limit state probability. Progress in other related areas, such as the establishment of probabilistic characteristics for various loads and structural resistance, are also described. Results of an application of the methodology to a realistic reinforced concrete containment subjected to dead and live loads, accidental internal pressures and earthquake ground accelerations are presented

  5. A computational Bayesian approach to dependency assessment in system reliability

    International Nuclear Information System (INIS)

    Yontay, Petek; Pan, Rong

    2016-01-01

    Due to the increasing complexity of engineered products, it is of great importance to develop a tool to assess reliability dependencies among components and systems under the uncertainty of system reliability structure. In this paper, a Bayesian network approach is proposed for evaluating the conditional probability of failure within a complex system, using a multilevel system configuration. Coupling with Bayesian inference, the posterior distributions of these conditional probabilities can be estimated by combining failure information and expert opinions at both system and component levels. Three data scenarios are considered in this study, and they demonstrate that, with the quantification of the stochastic relationship of reliability within a system, the dependency structure in system reliability can be gradually revealed by the data collected at different system levels. - Highlights: • A Bayesian network representation of system reliability is presented. • Bayesian inference methods for assessing dependencies in system reliability are developed. • Complete and incomplete data scenarios are discussed. • The proposed approach is able to integrate reliability information from multiple sources at multiple levels of the system.

  6. An approach for assessing ALWR passive safety system reliability

    International Nuclear Information System (INIS)

    Hake, T.M.

    1991-01-01

    Many of the advanced light water reactor (ALWR) concepts proposed for the next generation of nuclear power plants rely on passive rather than active systems to perform safety functions. Despite the reduced redundancy of the passive systems as compared to active systems in current plants, the assertion is that the overall safety of the plant is enhanced due to the much higher expected reliability of the passive systems. In order to investigate this assertion, a study is being conducted at Sandia National Laboratories to evaluate the reliability of ALWR passive safety features in the context of probabilistic risk assessment (PRA). The purpose of this paper is to provide a brief overview of the approach to this study. The quantification of passive system reliability is not as straightforward as for active systems, due to the lack of operating experience, and to the greater uncertainty in the governing physical phenomena. Thus, the adequacy of current methods for evaluating system reliability must be assessed, and alternatives proposed if necessary. For this study, the Westinghouse Advanced Passive 600 MWe reactor (AP600) was chosen as the advanced reactor for analysis, because of the availability of AP600 design information. This study compares the reliability of AP600 emergency cooling system with that of corresponding systems in a current generation reactor

  7. Windfarm generation assessment for reliability analysis of power systems

    DEFF Research Database (Denmark)

    Negra, N.B.; Holmstrøm, O.; Bak-Jensen, B.

    2007-01-01

    Due to the fast development of wind generation in the past ten years, increasing interest has been paid to techniques for assessing different aspects of power systems with a large amount of installed wind generation. One of these aspects concerns power system reliability. Windfarm modelling plays...... in a reliability model and the generation of a windfarm is evaluated by means of sequential Monte Carlo simulation. Results are used to analyse how each mentioned Factor influences the assessment, and why and when they should be included in the model....

  8. Windfarm Generation Assessment for Reliability Analysis of Power Systems

    DEFF Research Database (Denmark)

    Barberis Negra, Nicola; Bak-Jensen, Birgitte; Holmstrøm, O.

    2007-01-01

    Due to the fast development of wind generation in the past ten years, increasing interest has been paid to techniques for assessing different aspects of power systems with a large amount of installed wind generation. One of these aspects concerns power system reliability. Windfarm modelling plays...... in a reliability model and the generation of a windfarm is evaluated by means of sequential Monte Carlo simulation. Results are used to analyse how each mentioned Factor influences the assessment, and why and when they should be included in the model....

  9. Windfarm Generation Assessment for ReliabilityAnalysis of Power Systems

    DEFF Research Database (Denmark)

    Negra, Nicola Barberis; Holmstrøm, Ole; Bak-Jensen, Birgitte

    2007-01-01

    Due to the fast development of wind generation in the past ten years, increasing interest has been paid to techniques for assessing different aspects of power systems with a large amount of installed wind generation. One of these aspects concerns power system reliability. Windfarm modelling plays...... in a reliability model and the generation of a windfarm is evaluated by means of sequential Monte Carlo simulation. Results are used to analyse how each mentioned Factor influences the assessment, and why and when they should be included in the model....

  10. Reliability assessment for safety critical systems by statistical random testing

    International Nuclear Information System (INIS)

    Mills, S.E.

    1995-11-01

    In this report we present an overview of reliability assessment for software and focus on some basic aspects of assessing reliability for safety critical systems by statistical random testing. We also discuss possible deviations from some essential assumptions on which the general methodology is based. These deviations appear quite likely in practical applications. We present and discuss possible remedies and adjustments and then undertake applying this methodology to a portion of the SDS1 software. We also indicate shortcomings of the methodology and possible avenues to address to follow to address these problems. (author). 128 refs., 11 tabs., 31 figs

  11. Statistical reliability assessment of software-based systems

    Energy Technology Data Exchange (ETDEWEB)

    Korhonen, J. [VTT Electronics, Espoo (Finland); Pulkkinen, U.; Haapanen, P. [VTT Automation, Espoo (Finland)

    1997-01-01

    Plant vendors nowadays propose software-based systems even for the most critical safety functions. The reliability estimation of safety critical software-based systems is difficult since the conventional modeling techniques do not necessarily apply to the analysis of these systems, and the quantification seems to be impossible. Due to lack of operational experience and due to the nature of software faults, the conventional reliability estimation methods can not be applied. New methods are therefore needed for the safety assessment of software-based systems. In the research project Programmable automation systems in nuclear power plants (OHA), financed together by the Finnish Centre for Radiation and Nuclear Safety (STUK), the Ministry of Trade and Industry and the Technical Research Centre of Finland (VTT), various safety assessment methods and tools for software based systems are developed and evaluated. This volume in the OHA-report series deals with the statistical reliability assessment of software based systems on the basis of dynamic test results and qualitative evidence from the system design process. Other reports to be published later on in OHA-report series will handle the diversity requirements in safety critical software-based systems, generation of test data from operational profiles and handling of programmable automation in plant PSA-studies. (orig.) (25 refs.).

  12. Statistical reliability assessment of software-based systems

    International Nuclear Information System (INIS)

    Korhonen, J.; Pulkkinen, U.; Haapanen, P.

    1997-01-01

    Plant vendors nowadays propose software-based systems even for the most critical safety functions. The reliability estimation of safety critical software-based systems is difficult since the conventional modeling techniques do not necessarily apply to the analysis of these systems, and the quantification seems to be impossible. Due to lack of operational experience and due to the nature of software faults, the conventional reliability estimation methods can not be applied. New methods are therefore needed for the safety assessment of software-based systems. In the research project Programmable automation systems in nuclear power plants (OHA), financed together by the Finnish Centre for Radiation and Nuclear Safety (STUK), the Ministry of Trade and Industry and the Technical Research Centre of Finland (VTT), various safety assessment methods and tools for software based systems are developed and evaluated. This volume in the OHA-report series deals with the statistical reliability assessment of software based systems on the basis of dynamic test results and qualitative evidence from the system design process. Other reports to be published later on in OHA-report series will handle the diversity requirements in safety critical software-based systems, generation of test data from operational profiles and handling of programmable automation in plant PSA-studies. (orig.) (25 refs.)

  13. The DYLAM approach to systems safety and reliability assessment

    International Nuclear Information System (INIS)

    Amendola, A.

    1988-01-01

    A survey of the principal features and applications of DYLAM (Dynamic Logical Analytical Methodology) is presented, whose basic principles can be summarized as follows: after a particular modelling of the component states, computerized heuristical procedures generate stochastic configurations of the system, whereas the resulting physical processes are simultaneously simulated to give account of the possible interactions between physics and states and, on the other hand, to search for system dangerous configurations and related probabilities. The association of probabilistic techniques for describing the states with physical equations for describing the process results in a very powerful tool for safety and reliability assessment of systems potentially subjected to dangerous incidental transients. A comprehensive picture of DYLAM capability for manifold applications can be obtained by the review of the study cases analyzed (LMFBR core accident, systems reliability assessment, accident simulation, man-machine interaction analysis, chemical reactors safety, etc.)

  14. The Development of a Demonstration Passive System Reliability Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Bucknor, Matthew; Grabaskas, David; Brunett, Acacia

    2014-06-22

    In this paper, the details of the development of a demonstration problem to assess the reliability of a passive safety system are presented. An advanced small modular reactor (advSMR) design, which is a pool-type sodium fast reactor (SFR) coupled with a passive reactor cavity cooling system (RCCS) is described. The RELAP5-3D models of the advSMR and RCCS that will be used to simulate a long-term station blackout (SBO) accident scenario are presented. Proposed benchmarking techniques for both the reactor and the RCCS are discussed, which includes utilization of experimental results from the Natural convection Shutdown heat removal Test Facility (NSTF) at the Argonne National Laboratory. Details of how mechanistic methods, specifically the Reliability Method for Passive Systems (RMPS) approach, will be utilized to determine passive system reliability are presented. The results of this mechanistic analysis will ultimately be compared to results from dynamic methods in future work. This work is part of an ongoing project at Argonne to demonstrate methodologies for assessing passive system reliability.

  15. A reliability assessment methodology for the VHTR passive safety system

    International Nuclear Information System (INIS)

    Lee, Hyungsuk; Jae, Moosung

    2014-01-01

    The passive safety system of a VHTR (Very High Temperature Reactor), which has recently attracted worldwide attention, is currently being considered for the design of safety improvements for the next generation of nuclear power plants in Korea. The functionality of the passive system does not rely on an external source of an electrical support system, but on the intelligent use of natural phenomena. Its function involves an ultimate heat sink for a passive secondary auxiliary cooling system, especially during a station blackout such as the case of the Fukushima Daiichi reactor accidents. However, it is not easy to quantitatively evaluate the reliability of passive safety for the purpose of risk analysis, considering the existing active system failure since the classical reliability assessment method cannot be applied. Therefore, we present a new methodology to quantify the reliability based on reliability physics models. This evaluation framework is then applied to of the conceptually designed VHTR in Korea. The Response Surface Method (RSM) is also utilized for evaluating the uncertainty of the maximum temperature of nuclear fuel. The proposed method could contribute to evaluating accident sequence frequency and designing new innovative nuclear systems, such as the reactor cavity cooling system (RCCS) in VHTR to be designed and constructed in Korea.

  16. An approach for assessing ALWR passive safety system reliability

    International Nuclear Information System (INIS)

    Hake, T.M.

    1991-01-01

    Many advanced light water reactor designs incorporate passive rather than active safety features for front-line accident response. A method for evaluating the reliability of these passive systems in the context of probabilistic risk assessment has been developed at Sandia National Laboratories. This method addresses both the component (e.g. valve) failure aspect of passive system failure, and uncertainties in system success criteria arising from uncertainties in the system's underlying physical processes. These processes provide the system's driving force; examples are natural circulation and gravity-induced injection. This paper describes the method, and provides some preliminary results of application of the approach to the Westinghouse AP600 design

  17. Quantitative reliability assessment for safety critical system software

    International Nuclear Information System (INIS)

    Chung, Dae Won; Kwon, Soon Man

    2005-01-01

    An essential issue in the replacement of the old analogue I and C to computer-based digital systems in nuclear power plants is the quantitative software reliability assessment. Software reliability models have been successfully applied to many industrial applications, but have the unfortunate drawback of requiring data from which one can formulate a model. Software which is developed for safety critical applications is frequently unable to produce such data for at least two reasons. First, the software is frequently one-of-a-kind, and second, it rarely fails. Safety critical software is normally expected to pass every unit test producing precious little failure data. The basic premise of the rare events approach is that well-tested software does not fail under normal routine and input signals, which means that failures must be triggered by unusual input data and computer states. The failure data found under the reasonable testing cases and testing time for these conditions should be considered for the quantitative reliability assessment. We will present the quantitative reliability assessment methodology of safety critical software for rare failure cases in this paper

  18. Reliability assessment of distribution power systems including distributed generations

    International Nuclear Information System (INIS)

    Megdiche, M.

    2004-12-01

    Nowadays, power systems have reached a good level of reliability. Nevertheless, considering the modifications induced by the connections of small independent producers to distribution networks, there's a need to assess the reliability of these new systems. Distribution networks present several functional characteristics, highlighted by the qualitative study of the failures, as dispersed loads at several places, variable topology and some electrotechnical phenomena which must be taken into account to model the events that can occur. The adopted reliability calculations method is Monte Carlo simulations, the probabilistic method most powerful and most flexible to model complex operating of the distribution system. We devoted a first part on the case of a 20 kV feeder to which a cogeneration unit is connected. The method was applied to a software of stochastic Petri nets simulations. Then a second part related to the study of a low voltage power system supplied by dispersed generations. Here, the complexity of the events required to code the method in an environment of programming allowing the use of power system calculations (load flow, short-circuit, load shedding, management of units powers) in order to analyse the system state for each new event. (author)

  19. Results of a Demonstration Assessment of Passive System Reliability Utilizing the Reliability Method for Passive Systems (RMPS)

    Energy Technology Data Exchange (ETDEWEB)

    Bucknor, Matthew; Grabaskas, David; Brunett, Acacia; Grelle, Austin

    2015-04-26

    Advanced small modular reactor designs include many advantageous design features such as passively driven safety systems that are arguably more reliable and cost effective relative to conventional active systems. Despite their attractiveness, a reliability assessment of passive systems can be difficult using conventional reliability methods due to the nature of passive systems. Simple deviations in boundary conditions can induce functional failures in a passive system, and intermediate or unexpected operating modes can also occur. As part of an ongoing project, Argonne National Laboratory is investigating various methodologies to address passive system reliability. The Reliability Method for Passive Systems (RMPS), a systematic approach for examining reliability, is one technique chosen for this analysis. This methodology is combined with the Risk-Informed Safety Margin Characterization (RISMC) approach to assess the reliability of a passive system and the impact of its associated uncertainties. For this demonstration problem, an integrated plant model of an advanced small modular pool-type sodium fast reactor with a passive reactor cavity cooling system is subjected to a station blackout using RELAP5-3D. This paper discusses important aspects of the reliability assessment, including deployment of the methodology, the uncertainty identification and quantification process, and identification of key risk metrics.

  20. Usage models in reliability assessment of software-based systems

    International Nuclear Information System (INIS)

    Haapanen, P.; Pulkkinen, U.; Korhonen, J.

    1997-04-01

    This volume in the OHA-project report series deals with the statistical reliability assessment of software based systems on the basis of dynamic test results and qualitative evidence from the system design process. Other reports to be published later on in the OHA-project report series will handle the diversity requirements in safety critical software-based systems, generation of test data from operational profiles and handling of programmable automation in plant PSA-studies. In this report the issues related to the statistical testing and especially automated test case generation are considered. The goal is to find an efficient method for building usage models for the generation of statistically significant set of test cases and to gather practical experiences from this method by applying it in a case study. The scope of the study also includes the tool support for the method, as the models may grow quite large and complex. (32 refs., 30 figs.)

  1. High reliability flow system - an assessment of pump reliability and optimisation of the number of pumps

    International Nuclear Information System (INIS)

    Butterfield, J.M.

    1981-01-01

    A system is considered where a number of pumps operate in parallel. Normally, all pumps operate, driven by main motors fed from the grid. Each pump has a pony motor fed from an individual battery supply. Each pony motor is normally running, but not engaged to the pump shaft. On demand, e.g. failure of grid supplies, each pony motor is designed to clutch-in automatically when the pump speed falls to a specified value. The probability of all the pony motors failing to clutch-in on demand must be demonstrated with 95% confidence to be less than 10 -8 per demand. This assessment considers how the required reliability of pony motor drives might be demonstrated in practice and the implications on choice of the number of pumps at the design stage. The assessment recognises that not only must the system prove to be extremely reliable, but that demonstration that reliability is adequate must be done during plant commissioning, with practical limits on the amount of testing performed. It is concluded that a minimum of eight pony motors should be provided, eight pumps each with one pony motor (preferred) or five pumps each with two independent pony motors. A minimum of two diverse pony motor systems should be provided. (author)

  2. Reliability assessment of redundant safety systems with degradation

    NARCIS (Netherlands)

    Rogova, E.S.

    2017-01-01

    Reliability of transport equipment plays a crucial role in providing safety for passengers. Safety systems of transport equipment perform safety functions with assigned safety integrity levels (SIL). If the reliability of a safety system is not sufficient, it has to be improved till the required

  3. Significant Inter-Test Reliability Across Approximate Number System Assessments

    Directory of Open Access Journals (Sweden)

    Nicholas Kurshan Dewind

    2016-03-01

    Full Text Available The approximate number system (ANS is the hypothesized cognitive mechanism that allows adults, infants, and animals to enumerate large sets of items approximately. Researchers usually assess the ANS by having subjects compare two sets and indicate which is larger. Accuracy or Weber fraction is taken as an index of the acuity of the system. However, as Clayton et al., (2015 have highlighted, the stimulus parameters used when assessing the ANS vary widely. In particular, the numerical ratio between the pairs, and the way in which non-numerical features are varied often differ radically between studies. Recently, Clayton et al. (2015 found that accuracy measures derived from two commonly used stimulus sets are not significantly correlated. They argue that a lack of inter-test reliability threatens the validity of the ANS construct. Here we apply a recently developed modeling technique to the same data set. The model, by explicitly accounting for the effect of numerical ratio and non-numerical features, produces dependent measures that are less perturbed by stimulus protocol. Contrary to their conclusion we find a significant correlation in Weber fraction across the two stimulus sets. Nevertheless, in agreement with Clayton et al., we find that different protocols do indeed induce differences in numerical acuity and the degree of influence of non-numerical stimulus features. These findings highlight the need for a systematic investigation of how protocol idiosyncrasies affect ANS assessments.

  4. Significant Inter-Test Reliability across Approximate Number System Assessments.

    Science.gov (United States)

    DeWind, Nicholas K; Brannon, Elizabeth M

    2016-01-01

    The approximate number system (ANS) is the hypothesized cognitive mechanism that allows adults, infants, and animals to enumerate large sets of items approximately. Researchers usually assess the ANS by having subjects compare two sets and indicate which is larger. Accuracy or Weber fraction is taken as an index of the acuity of the system. However, as Clayton et al. (2015) have highlighted, the stimulus parameters used when assessing the ANS vary widely. In particular, the numerical ratio between the pairs, and the way in which non-numerical features are varied often differ radically between studies. Recently, Clayton et al. (2015) found that accuracy measures derived from two commonly used stimulus sets are not significantly correlated. They argue that a lack of inter-test reliability threatens the validity of the ANS construct. Here we apply a recently developed modeling technique to the same data set. The model, by explicitly accounting for the effect of numerical ratio and non-numerical features, produces dependent measures that are less perturbed by stimulus protocol. Contrary to their conclusion we find a significant correlation in Weber fraction across the two stimulus sets. Nevertheless, in agreement with Clayton et al. (2015) we find that different protocols do indeed induce differences in numerical acuity and the degree of influence of non-numerical stimulus features. These findings highlight the need for a systematic investigation of how protocol idiosyncrasies affect ANS assessments.

  5. A computer aided reliability and risk assessment system

    International Nuclear Information System (INIS)

    Leicht, R.; Hecke, R. van; Wingender, H.J.

    1991-01-01

    Activities in the fields of reliability and risk analysis have led to the development of particular software tools which are now combined in the PC-based integrated CARARA system. The options available in this system cover a wide range of reliability-oriented tasks, e.g. organising raw failure data in the component/event data bank FDB, performing statistical analysis of those data with the program FDA, managing the resulting parameters in the reliability data bank RDB, and performing fault tree analysis with the fault tree code FTL or evaluating the risk of toxic or radioactive material release with the STAR code. (orig.)

  6. A Reliability Assessment Method for the VHTR Safety Systems

    International Nuclear Information System (INIS)

    Lee, Hyung Sok; Jae, Moo Sung; Kim, Yong Wan

    2011-01-01

    The Passive safety system by very high temperature reactor which has attracted worldwide attention in the last century is the reliability safety system introduced for the improvement in the safety of the next generation nuclear power plant design. The Passive system functionality does not rely on an external source of energy, but on an intelligent use of the natural phenomena, such as gravity, conduction and radiation, which are always present. Because of these features, it is difficult to evaluate the passive safety on the risk analysis methodology having considered the existing active system failure. Therefore new reliability methodology has to be considered. In this study, the preliminary evaluation and conceptualization are tried, applying the concept of the load and capacity from the reliability physics model, designing the new passive system analysis methodology, and the trial applying to paper plant.

  7. Complex method to calculate objective assessments of information systems protection to improve expert assessments reliability

    Science.gov (United States)

    Abdenov, A. Zh; Trushin, V. A.; Abdenova, G. A.

    2018-01-01

    The paper considers the questions of filling the relevant SIEM nodes based on calculations of objective assessments in order to improve the reliability of subjective expert assessments. The proposed methodology is necessary for the most accurate security risk assessment of information systems. This technique is also intended for the purpose of establishing real-time operational information protection in the enterprise information systems. Risk calculations are based on objective estimates of the adverse events implementation probabilities, predictions of the damage magnitude from information security violations. Calculations of objective assessments are necessary to increase the reliability of the proposed expert assessments.

  8. Reliability assessment of restructured power systems using reliability network equivalent and pseudo-sequential simulation techniques

    International Nuclear Information System (INIS)

    Ding, Yi; Wang, Peng; Goel, Lalit; Billinton, Roy; Karki, Rajesh

    2007-01-01

    This paper presents a technique to evaluate reliability of a restructured power system with a bilateral market. The proposed technique is based on the combination of the reliability network equivalent and pseudo-sequential simulation approaches. The reliability network equivalent techniques have been implemented in the Monte Carlo simulation procedure to reduce the computational burden of the analysis. Pseudo-sequential simulation has been used to increase the computational efficiency of the non-sequential simulation method and to model the chronological aspects of market trading and system operation. Multi-state Markov models for generation and transmission systems are proposed and implemented in the simulation. A new load shedding scheme is proposed during generation inadequacy and network congestion to minimize the load curtailment. The IEEE reliability test system (RTS) is used to illustrate the technique. (author)

  9. Structural Reliability Methods for Wind Power Converter System Component Reliability Assessment

    DEFF Research Database (Denmark)

    Kostandyan, Erik; Sørensen, John Dalsgaard

    2012-01-01

    reliability methods and simulation are implemented for the power converter system and results are compared. Based on an illustrative example, it is shown that structural reliability methods are appropriate techniques to use for further convertor system reliability estimation studies.......Wind power converter systems are essential subsystems in both off-shore and on-shore wind turbines. It is the main interface between generator and grid connection. This system is affected by numerous stresses where the main contributors might be defined as vibration and temperature loadings....... The temperature variations induce time-varying stresses and thereby fatigue loads. A probabilistic model is used to model fatigue failure for an electrical component in the power converter system. This model is based on a linear damage accumulation and physics of failure approaches, where a failure criterion...

  10. Integrated system reliability analysis

    DEFF Research Database (Denmark)

    Gintautas, Tomas; Sørensen, John Dalsgaard

    Specific targets: 1) The report shall describe the state of the art of reliability and risk-based assessment of wind turbine components. 2) Development of methodology for reliability and risk-based assessment of the wind turbine at system level. 3) Describe quantitative and qualitative measures...... (indicators) that can be used to assess the reliability of innovations and new technologies....

  11. Reliability assessment of Port Harcourt 33/11kv Distribution System ...

    African Journals Online (AJOL)

    Consumers of electrical energy expect a network to support their apparatuses with continuous and reliable supply.This makes reliability studies an important task besides all the other analyses required for assessing the system performance. The paper presents an analytical approach in the reliability assessment of the Port ...

  12. Approach to reliability assessment

    International Nuclear Information System (INIS)

    Green, A.E.; Bourne, A.J.

    1975-01-01

    Experience has shown that reliability assessments can play an important role in the early design and subsequent operation of technological systems where reliability is at a premium. The approaches to and techniques for such assessments, which have been outlined in the paper, have been successfully applied in variety of applications ranging from individual equipments to large and complex systems. The general approach involves the logical and systematic establishment of the purpose, performance requirements and reliability criteria of systems. This is followed by an appraisal of likely system achievment based on the understanding of different types of variational behavior. A fundamental reliability model emerges from the correlation between the appropriate Q and H functions for performance requirement and achievement. This model may cover the complete spectrum of performance behavior in all the system dimensions

  13. Reliability of system identification techniques to assess standing balance in healthy elderly

    NARCIS (Netherlands)

    Pasma, Jantsje H.; Engelhart, Denise; Maier, Andrea B.; Aarts, Ronald G.K.M.; Van Gerven, Joop M.A.; Arendzen, J. Hans; Schouten, Alfred C.; Meskers, Carel G.M.; Van Kooij, Herman Der

    2016-01-01

    Objectives System identification techniques have the potential to assess the contribution of the underlying systems involved in standing balance by applying well-known disturbances. We investigated the reliability of standing balance parameters obtained with multivariate closed loop system

  14. Reliability of System Identification Techniques to Assess Standing Balance in Healthy Elderly

    NARCIS (Netherlands)

    Pasma, J.H.; Engelhart, D.; Maier, A.B.; Aarts, R.G.K.M.; Van Gerven, J.M.A.; Arendzen, J.H.; Schouten, A.C.; Meskers, C.G.M.; Van der Kooij, H.

    2016-01-01

    Objectives System identification techniques have the potential to assess the contribution of the underlying systems involved in standing balance by applying well-known disturbances. We investigated the reliability of standing balance parameters obtained with multivariate closed loop system

  15. System reliability assessment with an approximate reasoning model

    Energy Technology Data Exchange (ETDEWEB)

    Eisenhawer, S.W.; Bott, T.F.; Helm, T.M.; Boerigter, S.T.

    1998-12-31

    The projected service life of weapons in the US nuclear stockpile will exceed the original design life of their critical components. Interim metrics are needed to describe weapon states for use in simulation models of the nuclear weapons complex. The authors present an approach to this problem based upon the theory of approximate reasoning (AR) that allows meaningful assessments to be made in an environment where reliability models are incomplete. AR models are designed to emulate the inference process used by subject matter experts. The emulation is based upon a formal logic structure that relates evidence about components. This evidence is translated using natural language expressions into linguistic variables that describe membership in fuzzy sets. The authors introduce a metric that measures the acceptability of a weapon to nuclear deterrence planners. Implication rule bases are used to draw a series of forward chaining inferences about the acceptability of components, subsystems and individual weapons. They describe each component in the AR model in some detail and illustrate its behavior with a small example. The integration of the acceptability metric into a prototype model to simulate the weapons complex is also described.

  16. Reliability Assessment for Tie Line Capacity Assistance of Power Systems Based On Multi-Agent System

    OpenAIRE

    Nadheer A. Shalash; Abu Zaharin Bin Ahmad

    2014-01-01

    Technological developments in industrial innovations have currently been related to interconnected system assistance and distribution networks. This important in order to enable an electrical load to continue receive power in the event of disconnection of load from the main power grid. This paper represents a method for reliability assessment of interconnected power systems based. The multi-agent system consists of four agents. The first agent was the generator agent to using as connected the...

  17. Uncertainty propagation and sensitivity analysis in system reliability assessment via unscented transformation

    International Nuclear Information System (INIS)

    Rocco Sanseverino, Claudio M.; Ramirez-Marquez, José Emmanuel

    2014-01-01

    The reliability of a system, notwithstanding it intended function, can be significantly affected by the uncertainty in the reliability estimate of the components that define the system. This paper implements the Unscented Transformation to quantify the effects of the uncertainty of component reliability through two approaches. The first approach is based on the concept of uncertainty propagation, which is the assessment of the effect that the variability of the component reliabilities produces on the variance of the system reliability. This assessment based on UT has been previously considered in the literature but only for system represented through series/parallel configuration. In this paper the assessment is extended to systems whose reliability cannot be represented through analytical expressions and require, for example, Monte Carlo Simulation. The second approach consists on the evaluation of the importance of components, i.e., the evaluation of the components that most contribute to the variance of the system reliability. An extension of the UT is proposed to evaluate the so called “main effects” of each component, as well to assess high order component interaction. Several examples with excellent results illustrate the proposed approach. - Highlights: • Simulation based approach for computing reliability estimates. • Computation of reliability variance via 2n+1 points. • Immediate computation of component importance. • Application to network systems

  18. Advanced Reactor PSA Methodologies for System Reliability Analysis and Source Term Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Grabaskas, D.; Brunett, A.; Passerini, S.; Grelle, A.; Bucknor, M.

    2017-06-26

    Beginning in 2015, a project was initiated to update and modernize the probabilistic safety assessment (PSA) of the GE-Hitachi PRISM sodium fast reactor. This project is a collaboration between GE-Hitachi and Argonne National Laboratory (Argonne), and funded in part by the U.S. Department of Energy. Specifically, the role of Argonne is to assess the reliability of passive safety systems, complete a mechanistic source term calculation, and provide component reliability estimates. The assessment of passive system reliability focused on the performance of the Reactor Vessel Auxiliary Cooling System (RVACS) and the inherent reactivity feedback mechanisms of the metal fuel core. The mechanistic source term assessment attempted to provide a sequence specific source term evaluation to quantify offsite consequences. Lastly, the reliability assessment focused on components specific to the sodium fast reactor, including electromagnetic pumps, intermediate heat exchangers, the steam generator, and sodium valves and piping.

  19. Reliability Assessment of Power Generation Systems Using Intelligent Search Based on Disparity Theory

    Directory of Open Access Journals (Sweden)

    Athraa Ali Kadhem

    2017-03-01

    Full Text Available The reliability of the generating system adequacy is evaluated based on the ability of the system to satisfy the load demand. In this paper, a novel optimization technique named the disparity evolution genetic algorithm (DEGA is proposed for reliability assessment of power generation. Disparity evolution is used to enhance the performance of the probability of mutation in a genetic algorithm (GA by incorporating features from the paradigm into the disparity theory. The DEGA is based on metaheuristic searching for the truncated sampling of state-space for the reliability assessment of power generation system adequacy. Two reliability test systems (IEEE-RTS-79 and (IEEE-RTS-96 are used to demonstrate the effectiveness of the proposed algorithm. The simulation result shows the DEGA can generate a larger variety of the individuals in an early stage of the next population generation. It is also able to estimate the reliability indices accurately.

  20. Performance and Risk Assessment of Soil-Structure Interaction Systems Based on Finite Element Reliability Methods

    Directory of Open Access Journals (Sweden)

    Quan Gu

    2014-01-01

    Full Text Available In the context of performance-based earthquake engineering, reliability method has been of significant importance in performance and risk assessment of structures or soil-structure interaction (SSI systems. The finite element (FE reliability method combines FE analysis with state-of-the-art methods in reliability analysis and has been employed increasingly to estimate the probability of occurrence of failure events corresponding to various hazard levels (e.g., earthquakes with various intensity. In this paper, crucial components for FE reliability analysis are reviewed and summarized. Furthermore, recent advances in both time invariant and time variant reliability analysis methods for realistic nonlinear SSI systems are presented and applied to a two-dimensional two story building on layered soil. Various time invariant reliability analysis methods are applied, including the first-order reliability method (FORM, importance sampling method, and orthogonal plane sampling (OPS method. For time variant reliability analysis, an upper bound of the failure probability is obtained from numerical integration of the mean outcrossing rate (MOCR. The MOCR is computed by using FORM analysis and OPS analysis. Results by different FE reliability methods are compared in terms of accuracy and computational cost. This paper provides valuable insights for reliability based probabilistic performance and risk assessment of SSI systems.

  1. Reliability of fluid systems

    Directory of Open Access Journals (Sweden)

    Kopáček Jaroslav

    2016-01-01

    Full Text Available This paper focuses on the importance of detection reliability, especially in complex fluid systems for demanding production technology. The initial criterion for assessing the reliability is the failure of object (element, which is seen as a random variable and their data (values can be processed using by the mathematical methods of theory probability and statistics. They are defined the basic indicators of reliability and their applications in calculations of serial, parallel and backed-up systems. For illustration, there are calculation examples of indicators of reliability for various elements of the system and for the selected pneumatic circuit.

  2. Reliability Assessment of Wind Farm Electrical System Based on a Probability Transfer Technique

    Directory of Open Access Journals (Sweden)

    Hejun Yang

    2018-03-01

    Full Text Available The electrical system of a wind farm has a significant influence on the wind farm reliability and electrical energy yield. The disconnect switch installed in an electrical system cannot only improve the operating flexibility, but also enhance the reliability for a wind farm. Therefore, this paper develops a probabilistic transfer technique for integrating the electrical topology structure, the isolation operation of disconnect switch, and stochastic failure of electrical equipment into the reliability assessment of wind farm electrical system. Firstly, as the traditional two-state reliability model of electrical equipment cannot consider the isolation operation, so the paper develops a three-state reliability model to replace the two-state model for incorporating the isolation operation. In addition, a proportion apportion technique is presented to evaluate the state probability. Secondly, this paper develops a probabilistic transfer technique based on the thoughts that through transfer the unreliability of electrical system to the energy transmission interruption of wind turbine generators (WTGs. Finally, some novel indices for describing the reliability of wind farm electrical system are designed, and the variance coefficient of the designed indices is used as a convergence criterion to determine the termination of the assessment process. The proposed technique is applied to the reliability assessment of a wind farm with the different topologies. The simulation results show that the proposed techniques are effective in practical applications.

  3. An introduction to the assessment of reliability of the heat supply systems

    International Nuclear Information System (INIS)

    Babiarz, Bozena

    2006-01-01

    The considering of the issue of heat supply system reliability requires taking into consideration their complexity and the extent of realization. Two approaches to reliability assessment for heat supply systems are possible: a simple global approach and universal system approach. The global approach is based on analysis of information related to system operation as a whole. The system approach induces system decomposition and combining partial models fro-selected components. This approach considers specific features and structure of heat supply system and diversified reliability criteria for selected subsystems. Methods for system evaluation of heat supply system reliability depend on number of parameters used for system description. The one-parameter assessment is based on so called stationary readiness coefficient for the whole system. In two-parameter method an additional parameter is added, named as mean failure period or as mean system capacity period. In three-parameter method, the generalized reliability characteristic based on mean heat shortage is added to give more information about the system

  4. Safety and reliability assessment

    International Nuclear Information System (INIS)

    1979-01-01

    This report contains the papers delivered at the course on safety and reliability assessment held at the CSIR Conference Centre, Scientia, Pretoria. The following topics were discussed: safety standards; licensing; biological effects of radiation; what is a PWR; safety principles in the design of a nuclear reactor; radio-release analysis; quality assurance; the staffing, organisation and training for a nuclear power plant project; event trees, fault trees and probability; Automatic Protective Systems; sources of failure-rate data; interpretation of failure data; synthesis and reliability; quantification of human error in man-machine systems; dispersion of noxious substances through the atmosphere; criticality aspects of enrichment and recovery plants; and risk and hazard analysis. Extensive examples are given as well as case studies

  5. Time-Tagged Risk/Reliability Assessment Program for Development and Operation of Space System

    Science.gov (United States)

    Kubota, Yuki; Takegahara, Haruki; Aoyagi, Junichiro

    We have investigated a new method of risk/reliability assessment for development and operation of space system. It is difficult to evaluate risk of spacecraft, because of long time operation, maintenance free and difficulty of test under the ground condition. Conventional methods are FMECA, FTA, ETA and miscellaneous. These are not enough to assess chronological anomaly and there is a problem to share information during R&D. A new method of risk and reliability assessment, T-TRAP (Time-tagged Risk/Reliability Assessment Program) is proposed as a management tool for the development and operation of space system. T-TRAP consisting of time-resolved Fault Tree and Criticality Analyses, upon occurrence of anomaly in the system, facilitates the responsible personnel to quickly identify the failure cause and decide corrective actions. This paper describes T-TRAP method and its availability.

  6. Reliability assessment of distribution system with the integration of renewable distributed generation

    International Nuclear Information System (INIS)

    Adefarati, T.; Bansal, R.C.

    2017-01-01

    Highlights: • Addresses impacts of renewable DG on the reliability of the distribution system. • Multi-objective formulation for maximizing the cost saving with integration of DG. • Uses Markov model to study the stochastic characteristics of the major components. • The investigation is done using modified RBTS bus test distribution system. • Proposed approach is useful for electric utilities to enhance the reliability. - Abstract: Recent studies have shown that renewable energy resources will contribute substantially to future energy generation owing to the rapid depletion of fossil fuels. Wind and solar energy resources are major sources of renewable energy that have the ability to reduce the energy crisis and the greenhouse gases emitted by the conventional power plants. Reliability assessment is one of the key indicators to measure the impact of the renewable distributed generation (DG) units in the distribution networks and to minimize the cost that is associated with power outage. This paper presents a comprehensive reliability assessment of the distribution system that satisfies the consumer load requirements with the penetration of wind turbine generator (WTG), electric storage system (ESS) and photovoltaic (PV). A Markov model is proposed to access the stochastic characteristics of the major components of the renewable DG resources as well as their influence on the reliability of a conventional distribution system. The results obtained from the case studies have demonstrated the effectiveness of using WTG, ESS and PV to enhance the reliability of the conventional distribution system.

  7. OSS reliability measurement and assessment

    CERN Document Server

    Yamada, Shigeru

    2016-01-01

    This book analyses quantitative open source software (OSS) reliability assessment and its applications, focusing on three major topic areas: the Fundamentals of OSS Quality/Reliability Measurement and Assessment; the Practical Applications of OSS Reliability Modelling; and Recent Developments in OSS Reliability Modelling. Offering an ideal reference guide for graduate students and researchers in reliability for open source software (OSS) and modelling, the book introduces several methods of reliability assessment for OSS including component-oriented reliability analysis based on analytic hierarchy process (AHP), analytic network process (ANP), and non-homogeneous Poisson process (NHPP) models, the stochastic differential equation models and hazard rate models. These measurement and management technologies are essential to producing and maintaining quality/reliable systems using OSS.

  8. Reliability assessment of Passive Containment Cooling System of an Advanced Reactor using APSRA methodology

    International Nuclear Information System (INIS)

    Kumar, Mukesh; Chakravarty, Aranyak; Nayak, A.K.; Prasad, Hari; Gopika, V.

    2014-01-01

    Highlights: • The paper deals with the reliability assessment of Passive Containment Cooling System of Advanced Heavy Water Reactor. • Assessment of Passive System ReliAbility (APSRA) methodology is used for reliability assessment. • Performance assessment of the PCCS is initially performed during a postulated design basis LOCA. • The parameters affecting the system performance are then identified and considered for further analysis. • The failure probabilities of the various components are assessed through a classical PSA treatment using generic data. - Abstract: Passive Systems are increasingly playing a prominent role in the advanced nuclear reactor systems and are being utilised in normal operations as well as safety systems of the reactors following an accident. The Passive Containment Cooling System (PCCS) is one of the several passive safety features in an Advanced Reactor (AHWR). In this paper, the APSRA methodology has been employed for reliability evaluation of the PCCS of AHWR. Performance assessment of the PCCS is initially performed during a postulated design basis LOCA using the best-estimate code RELAP5/Mod 3.2. The parameters affecting the system performance are then identified and considered for further analysis. Based on some pre-determined failure criterion, the failure surface for the system is predicted using the best-estimate code taking into account the deviations of the identified parameters from their nominal states as well as the model uncertainties inherent to the best estimate code. Root diagnosis is then carried out to determine the various failure causes, which occurs mainly due to malfunctioning of mechanical components. The failure probabilities of the various components are assessed through a classical PSA treatment using generic data. The reliability of the PCCS is then evaluated from the probability of availability of these components

  9. Reliability Assessment of a Single-Shot System by Use of Screen Test Results

    Science.gov (United States)

    2018-02-01

    unlimited. NUWC Keyport #17-002. Reliability Assessment of a Single-Shot System by Use of Screen Test Results Abstract: Field reliability prediction...approach described here assumes that the defect density during testing takes the form of an exponential decay, although other mathematical functions can...be substituted for the exponential. In order to apply the decay rate function to a discrete pass/fail test scheme, the approach provides for

  10. Reliability assessment on decay heat removal system of a fast reactor

    International Nuclear Information System (INIS)

    Hioki, Kazumasa

    1991-01-01

    The reliability of a decay heat removal system (DHRS) is influenced by the success criteria, the components which constitute the system, the support systems configuration, and the mission time. Assessments were performed to investigate quantitatively the effects of these items. Failure probabilities of DHRS under forced or natural circulation modes were calculated and then components and systems of large importance for each mode were identified. (author)

  11. Reliability Assessment Method of Reactor Protection System Software by Using V and Vbased Bayesian Nets

    International Nuclear Information System (INIS)

    Eom, H. S.; Park, G. Y.; Kang, H. G.; Son, H. S.

    2010-07-01

    Developed a methodology which can be practically used in quantitative reliability assessment of a safety c ritical software for a protection system of nuclear power plants. The base of the proposed methodology is V and V being used in the nuclear industry, which means that it is not affected with specific software development environments or parameters that are necessary for the reliability calculation. Modular and formal sub-BNs in the proposed methodology is useful tool to constitute the whole BN model for reliability assessment of a target software. The proposed V and V based BN model estimates the defects in the software according to the performance of V and V results and then calculate reliability of the software. A case study was carried out to validate the proposed methodology. The target software is the RPS SW which was developed by KNICS project

  12. Reliability of System Identification Techniques to Assess Standing Balance in Healthy Elderly.

    Science.gov (United States)

    Pasma, Jantsje H; Engelhart, Denise; Maier, Andrea B; Aarts, Ronald G K M; van Gerven, Joop M A; Arendzen, J Hans; Schouten, Alfred C; Meskers, Carel G M; van der Kooij, Herman

    2016-01-01

    System identification techniques have the potential to assess the contribution of the underlying systems involved in standing balance by applying well-known disturbances. We investigated the reliability of standing balance parameters obtained with multivariate closed loop system identification techniques. In twelve healthy elderly balance tests were performed twice a day during three days. Body sway was measured during two minutes of standing with eyes closed and the Balance test Room (BalRoom) was used to apply four disturbances simultaneously: two sensory disturbances, to the proprioceptive and the visual system, and two mechanical disturbances applied at the leg and trunk segment. Using system identification techniques, sensitivity functions of the sensory disturbances and the neuromuscular controller were estimated. Based on the generalizability theory (G theory), systematic errors and sources of variability were assessed using linear mixed models and reliability was assessed by computing indexes of dependability (ID), standard error of measurement (SEM) and minimal detectable change (MDC). A systematic error was found between the first and second trial in the sensitivity functions. No systematic error was found in the neuromuscular controller and body sway. The reliability of 15 of 25 parameters and body sway were moderate to excellent when the results of two trials on three days were averaged. To reach an excellent reliability on one day in 7 out of 25 parameters, it was predicted that at least seven trials must be averaged. This study shows that system identification techniques are a promising method to assess the underlying systems involved in standing balance in elderly. However, most of the parameters do not appear to be reliable unless a large number of trials are collected across multiple days. To reach an excellent reliability in one third of the parameters, a training session for participants is needed and at least seven trials of two minutes must be

  13. Reliability of System Identification Techniques to Assess Standing Balance in Healthy Elderly.

    Directory of Open Access Journals (Sweden)

    Jantsje H Pasma

    Full Text Available System identification techniques have the potential to assess the contribution of the underlying systems involved in standing balance by applying well-known disturbances. We investigated the reliability of standing balance parameters obtained with multivariate closed loop system identification techniques.In twelve healthy elderly balance tests were performed twice a day during three days. Body sway was measured during two minutes of standing with eyes closed and the Balance test Room (BalRoom was used to apply four disturbances simultaneously: two sensory disturbances, to the proprioceptive and the visual system, and two mechanical disturbances applied at the leg and trunk segment. Using system identification techniques, sensitivity functions of the sensory disturbances and the neuromuscular controller were estimated. Based on the generalizability theory (G theory, systematic errors and sources of variability were assessed using linear mixed models and reliability was assessed by computing indexes of dependability (ID, standard error of measurement (SEM and minimal detectable change (MDC.A systematic error was found between the first and second trial in the sensitivity functions. No systematic error was found in the neuromuscular controller and body sway. The reliability of 15 of 25 parameters and body sway were moderate to excellent when the results of two trials on three days were averaged. To reach an excellent reliability on one day in 7 out of 25 parameters, it was predicted that at least seven trials must be averaged.This study shows that system identification techniques are a promising method to assess the underlying systems involved in standing balance in elderly. However, most of the parameters do not appear to be reliable unless a large number of trials are collected across multiple days. To reach an excellent reliability in one third of the parameters, a training session for participants is needed and at least seven trials of two

  14. Balance Assessment in Sports-Related Concussion: Evaluating Test-Retest Reliability of the Equilibrate System.

    Science.gov (United States)

    Odom, Mitchell J; Lee, Young M; Zuckerman, Scott L; Apple, Rachel P; Germanos, Theodore; Solomon, Gary S; Sills, Allen K

    2016-01-01

    This study evaluated the test-retest reliability of a novel computer-based, portable balance assessment tool, the Equilibrate System (ES), used to diagnose sports-related concussion. Twenty-seven students participated in ES testing consisting of three sessions over 4 weeks. The modified Balance Error Scoring System was performed. For each participant, test-retest reliability was established using the intraclass correlation coefficient (ICC). The ES test-retest reliability from baseline to week 2 produced an ICC value of 0.495 (95% CI, 0.123-0.745). Week 2 testing produced ICC values of 0.602 (95% CI, 0.279-0.803) and 0.610 (95% CI, 0.299-0.804), respectively. All other single measures test-retest reliability values produced poor ICC values. Same-day ES testing showed fair to good test-retest reliability while interweek measures displayed poor to fair test-retest reliability. Testing conditions should be controlled when using computerized balance assessment methods. ES testing should only be used as a part of a comprehensive assessment.

  15. Department of Defense need for a micro-electromechanical systems (MEMS) reliability assessment program

    Science.gov (United States)

    Zunino, James L., III; Skelton, Donald

    2005-01-01

    As the United States (U.S.) Army transforms into a lighter, more lethal, and more agile force, the technologies that support both legacy and emerging weapon systems must decrease in size while increasing in intelligence. Micro-electromechanical systems (MEMS) are one such technology that the Army as well as entire DOD will heavily rely on in achieving these objectives. Current and future military applications of MEMS devices include safety and arming devices, guidance systems, sensors/detectors, inertial measurement units, tracking devices, radio frequency devices, wireless radio frequency identification (RFID), etc. Even though the reliance on MEMS devices has been increasing, there have been no studies performed to determine their reliability and failure mechanisms. Furthermore, no standardized test protocols exist for assessing reliability. Accordingly, the U.S. Army Corrosion Office at Picatinny, NJ has initiated the MEMS Reliability Assessment Program to address this issue.

  16. Reliability Assessment of IGBT Modules Modeled as Systems with Correlated Components

    DEFF Research Database (Denmark)

    Kostandyan, Erik; Sørensen, John Dalsgaard

    2013-01-01

    configuration. The estimated system reliability by the proposed method is a conservative estimate. Application of the suggested method could be extended for reliability estimation of systems composing of welding joints, bolts, bearings, etc. The reliability model incorporates the correlation between...

  17. Reliability Assessment of Active Distribution System Using Monte Carlo Simulation Method

    Directory of Open Access Journals (Sweden)

    Shaoyun Ge

    2014-01-01

    Full Text Available In this paper we have treated the reliability assessment problem of low and high DG penetration level of active distribution system using the Monte Carlo simulation method. The problem is formulated as a two-case program, the program of low penetration simulation and the program of high penetration simulation. The load shedding strategy and the simulation process were introduced in detail during each FMEA process. Results indicate that the integration of DG can improve the reliability of the system if the system was operated actively.

  18. Method for assessing software reliability of the document management system using the RFID technology

    Directory of Open Access Journals (Sweden)

    Kiedrowicz Maciej

    2016-01-01

    Full Text Available The deliberations presented in this study refer to the method for assessing software reliability of the docu-ment management system, using the RFID technology. A method for determining the reliability structure of the dis-cussed software, understood as the index vector for assessing reliability of its components, was proposed. The model of the analyzed software is the control transfer graph, in which the probability of activating individual components during the system's operation results from the so-called operational profile, which characterizes the actual working environment. The reliability structure is established as a result of the solution of a specific mathematical software task. The knowledge of the reliability structure of the software makes it possible to properly plan the time and finan-cial expenses necessary to build the software, which would meet the reliability requirements. The application of the presented method is illustrated by the number example, corresponding to the software reality of the RFID document management system.

  19. Interobserver Reliability of Three Validated Scoring Systems in the Assessment of Diabetic Foot Ulcers.

    Science.gov (United States)

    Forsythe, Rachael O; Ozdemir, Baris Ata; Chemla, Eric S; Jones, Keith G; Hinchliffe, Robert J

    2016-09-01

    Scoring systems for diabetic foot ulcers may be used for clinical purposes, research or audit, to help assess disease severity, plan management, and even predict outcomes. While many have been validated in study populations, little is known about their interobserver reliability. This prospective study aimed to evaluate interobserver reliability of 3 scoring systems for diabetic foot ulceration. After sharp debridement, diabetic foot ulcers were classified by a multidisciplinary pool of trained observers, using the PEDIS (Perfusion, Extent, Depth, Infection, Sensation), SINBAD (Site, Ischemia, Neuropathy, Bacterial infection, Depth), and University of Texas (UT) wound classification systems. Interobserver reliability was assessed using intraclass correlations (0 = no agreement; 1 = complete agreement). Thirty-seven patients (78.4% male) were assessed by a pool of 12 observers. Single observer reliability was slight to moderate for all scoring systems (UT 0.53; SINBAD 0.44; PEDIS 0.23-0.42), but multiple observer reliability was almost perfect (UT 0.94; SINBAD 0.91; PEDIS 0.80-0.90). The worst agreement for single observers was when scoring infection (SINBAD 0.28; PEDIS 0.28), ischemia (SINBAD 0.26; PEDIS 0.23), or both (UT 0.25); however, this improved to almost perfect agreement for multiple observers (infection: 0.83; ischemia: 0.80-0.82; both: 0.81). These classification systems may be reliably used by multiple observers, for example, when conducting research and audit. However, they demonstrate only slight to moderate reliability when used by a single observer on an individual subject and may therefore be less helpful in the clinical setting, when documenting ulcer characteristics or communicating between colleagues. © The Author(s) 2016.

  20. Assessing Changes in the Reliability of the U.S. Electric Power System

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, Peter H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Stanford Univ., CA (United States). Dept. of Physics; LaCommare, Kristina H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Eto, Joseph H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sweeney, James L. [Stanford Univ., CA (United States)

    2015-08-01

    Over the past 15 years, the most well-publicized efforts to assess trends in U.S. electric power system reliability have focused only on a subset of all power interruption events (see, for example, Amin 2008 and Campbell 2012)—namely, only the very largest events, which trigger immediate emergency reporting to federal agencies and industry regulators. Anecdotally, these events are thought by many to represent no more than 10% of the power interruptions experienced annually by electricity consumers. Moreover, a review of these emergency reports has identified shortcomings in relying on these data as reliable sources for assessing trends, even with the reliability events they report (Fisher et al. 2012). Recent work has begun to address these limitations by examining trends in reliability data collected annually by electricity distribution companies (Eto et al. 2012). In principle, all power interruptions experienced by electricity customers, regardless of size, are recorded by the distribution utility. Moreover, distribution utilities have a long history of recording this information, often in response to mandates from state public utility commissions (Eto et al. 2006). Thus, studies that rely on reliability data collected by distribution utilities can, in principle, provide a more complete basis upon which to assess trends or changes in reliability over time.

  1. A reliability assessment and optimization for a passive system of the very high temperature reactor

    International Nuclear Information System (INIS)

    Lee, Chan Suh; Lee, Hyung Suk; Jae, Moo Sung

    2012-01-01

    Most modern engineering systems are multidisciplinary and their analysis is very complex. This makes it difficult for users to make a decision optimization. Optimization is powerful design improvement tool that is available nowadays. There are many optimization programs in modern society and it is used in various fields. Recently, a response surface was used to perform reliability analysis of a passive cooling system. In this study, PIAnO (Process Integration, Automation and Optimization) is used for assessing a reliability and optimizing a reference gas cooled reactor

  2. A reliability assessment and optimization for a passive system of the very high temperature reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chan Suh; Lee, Hyung Suk; Jae, Moo Sung [Hanyang University, Seoul (Korea, Republic of)

    2012-05-15

    Most modern engineering systems are multidisciplinary and their analysis is very complex. This makes it difficult for users to make a decision optimization. Optimization is powerful design improvement tool that is available nowadays. There are many optimization programs in modern society and it is used in various fields. Recently, a response surface was used to perform reliability analysis of a passive cooling system. In this study, PIAnO (Process Integration, Automation and Optimization) is used for assessing a reliability and optimizing a reference gas cooled reactor

  3. A study on a reliability assessment methodology for the VHTR safety systems

    International Nuclear Information System (INIS)

    Lee, Hyung Sok

    2012-02-01

    The passive safety system of a 300MWt VHTR (Very High Temperature Reactor)which has attracted worldwide attention recently is actively considered for designing the improvement in the safety of the next generation nuclear power plant. The passive system functionality does not rely on an external source of the electrical support system,but on an intelligent use of the natural phenomena, such as convection, conduction, radiation, and gravity. It is not easy to evaluate quantitatively the reliability of the passive safety for the risk analysis considering the existing active system failure since the classical reliability assessment method could not be applicable. Therefore a new reliability methodology needs to be developed and applied for evaluating the reliability of the conceptual designed VHTR in this study. The preliminary evaluation and conceptualization are performed using the concept of the load and capacity theory related to the reliability physics model. The method of response surface method (RSM) is also utilized for evaluating the maximum temperature of nuclear fuel in this study. The significant variables and their correlation are considered for utilizing the GAMMA+ code. The proposed method might contribute to designing the new passive system of the VHTR

  4. Nuclear computerized library for assessing reactor reliability (NUCLARR): User's guide: Part 3, NUCLARR system description

    International Nuclear Information System (INIS)

    Gilmore, W.E.; Gentillon, C.D.; Gertman, D.I.; Beers, G.H.; Galyean, W.J.; Gilbert, B.G.

    1988-06-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) is an automated data base management system for processing and storing human error probability and hardware component failure data. The NUCLARR system software resides on an IBM (or compatible) personal micro-computer. NUCLARR can be used by the end user to furnish data inputs for both human and hardware reliability analysis in support of a variety of risk assessment activities. The NUCLARR system is documented in a five-volume series of reports. Volume IV of this series is the User's Guide for operating the NUCLARR software and is presented in three parts. This document, Part 3: NUCLARR System Description, provides an in-depth discussion of the design characteristics and special features of the NUCLARR software. Part 3 also presents the organization of the data base structures and techniques used to manipulate the data

  5. Intraobserver and interobserver reliability assessment of tibial plateau fracture classification systems.

    Science.gov (United States)

    Taşkesen, Anıl; Demirkale, İsmail; Okkaoğlu, Mustafa Caner; Özdemir, Mahmut; Bilgili, Mustafa Gökhan; Altay, Murat

    2017-12-01

    This study aims to assess the intra- and interobserver reliability of commonly used tibial plateau fracture classification systems. This retrospective cohort study included computed tomography (CT) and plain radiographic images (lateral and anteroposterior X-rays) of 60 patients (40 males, 20 females; mean age 45.9 years; range 18 to 80 years) who presented to two orthopaedic clinics between January 2011 and January 2015 with unilateral tibial plateau fractures. All plain X-rays (XR) and CT images were evaluated by four observers on two separate occasions, 1.5 months apart. All fractures were classified according to the Arbeitsgemeinschaft für Osteosynthesefragen-Orthopaedic Trauma Association (AO-OTA), Schatzker, Hohl and Moore, Luo and revised Duparc systems. Intraobserver reliability was measured with Cohen's kappa (κ) coefficient and interobserver reliability with Fleiss' kappa coefficient. When Schatzker classification was performed, interobserver reliability was in moderate level for (κ=0.51) for XR and in substantial level for CT (κ=0.61). When AO/OTA classification was used, interobserver reliability was in moderate level for both methods of diagnosis (κXR=0.43 and κCT=0.54, respectively). In the Hohl and Moore classification, the interobserver reliability was also moderate for both methods of diagnosis (κXR=0.45 and κCT=0.51, respectively). Revised Duparc classification showed the lowest interobserver reliability ranging from fair to moderate level (κXR=0.27-0.55 and κCT=0.44-0.61). Interobserver reliability for Luo classification was κCT=0.47. Intraobserver reliability for CT in Luo classification was in substantial level for observers 1, 2 and 3 (κCT=0.67-0.71) and in perfect level for observer 4 (κCT=0.84). Intraobserver reliability was in substantial level in Schatzker classification and in moderate level at the other classifications. Among the classification systems compared in this study, Schatzker was the most reliable particularly when

  6. Dynamic reliability assessment and prediction for repairable systems with interval-censored data

    International Nuclear Information System (INIS)

    Peng, Yizhen; Wang, Yu; Zi, YanYang; Tsui, Kwok-Leung; Zhang, Chuhua

    2017-01-01

    The ‘Test, Analyze and Fix’ process is widely applied to improve the reliability of a repairable system. In this process, dynamic reliability assessment for the system has been paid a great deal of attention. Due to instrument malfunctions, staff omissions and imperfect inspection strategies, field reliability data are often subject to interval censoring, making dynamic reliability assessment become a difficult task. Most traditional methods assume this kind of data as multiple normal distributed variables or the missing mechanism as missing at random, which may cause a large bias in parameter estimation. This paper proposes a novel method to evaluate and predict the dynamic reliability of a repairable system subject to interval-censored problem. First, a multiple imputation strategy based on the assumption that the reliability growth trend follows a nonhomogeneous Poisson process is developed to derive the distributions of missing data. Second, a new order statistic model that can transfer the dependent variables into independent variables is developed to simplify the imputation procedure. The unknown parameters of the model are iteratively inferred by the Monte Carlo expectation maximization (MCEM) algorithm. Finally, to verify the effectiveness of the proposed method, a simulation and a real case study for gas pipeline compressor system are implemented. - Highlights: • A new multiple imputation strategy was developed to derive the PDF of missing data. • A new order statistic model was developed to simplify the imputation procedure. • The parameters of the order statistic model were iteratively inferred by MCEM. • A real cases study was conducted to verify the effectiveness of the proposed method.

  7. System Reliability Engineering

    International Nuclear Information System (INIS)

    Lim, Tae Jin

    2005-02-01

    This book tells of reliability engineering, which includes quality and reliability, reliability data, importance of reliability engineering, reliability and measure, the poisson process like goodness of fit test and the poisson arrival model, reliability estimation like exponential distribution, reliability of systems, availability, preventive maintenance such as replacement policies, minimal repair policy, shock models, spares, group maintenance and periodic inspection, analysis of common cause failure, and analysis model of repair effect.

  8. Reliability Assessment Of Wind Turbines

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2014-01-01

    Reduction of cost of energy for wind turbines are very important in order to make wind energy competitive compared to other energy sources. Therefore the turbine components should be designed to have sufficient reliability but also not be too costly (and safe). This paper presents models...... for uncertainty modeling and reliability assessment of especially the structural components such as tower, blades, substructure and foundation. But since the function of a wind turbine is highly dependent on many electrical and mechanical components as well as a control system also reliability aspects...... of these components are discussed and it is described how there reliability influences the reliability of the structural components. Two illustrative examples are presented considering uncertainty modeling, reliability assessment and calibration of partial safety factors for structural wind turbine components exposed...

  9. Addressing culture and management aspects of human reliability in system safety assessment

    Energy Technology Data Exchange (ETDEWEB)

    Embrey, David [Human Reliability Associates Ltd., Lancashire (United Kingdom)

    2005-07-01

    In this paper, an approach will be described, called IDEAS (Influence Diagram Evaluation and Assessment System) that can achieve this objective. This approach has been applied to a number of industrial domains including chemical processing, railways, nuclear power generation, aviation and marine transport. IDEAS has a number of important applications in improving the safety and reliability of operations and maintenance. Firstly, it provides an explicit and easily understandable model of both the direct and indirect factors that influence the reliability of task performance. This model is based upon a combination of information from all available sources, including research studies, incident reports and the insights of personnel actually engaged in maintenance operations at the 'harp end' This provides comprehensive and practical insights into the factors that influence maintenance reliability. (author)

  10. Validity and reliability of the Myotest accelerometric system for the assessment of vertical jump height.

    Science.gov (United States)

    Casartelli, Nicola; Müller, Roland; Maffiuletti, Nicola A

    2010-11-01

    The aim of the present study was to verify the validity and reliability of the Myotest accelerometric system (Myotest SA, Sion, Switzerland) for the assessment of vertical jump height. Forty-four male basketball players (age range: 9-25 years) performed series of squat, countermovement and repeated jumps during 2 identical test sessions separated by 2-15 days. Flight height was simultaneously quantified with the Myotest system and validated photoelectric cells (Optojump). Two calculation methods were used to estimate the jump height from Myotest recordings: flight time (Myotest-T) and vertical takeoff velocity (Myotest-V). Concurrent validity was investigated comparing Myotest-T and Myotest-V to the criterion method (Optojump), and test-retest reliability was also examined. As regards validity, Myotest-T overestimated jumping height compared to Optojump (p 0.98), that is, excellent validity. Myotest-V overestimated jumping height compared to Optojump (p 12 cm), high limits of agreement ratios (>36%), and low ICCs (9 cm). In conclusion, Myotest-T is a valid and reliable method for the assessment of vertical jump height, and its use is legitimate for field-based evaluations, whereas Myotest-V is neither valid nor reliable.

  11. Assessment of ALWR passive safety system reliability. Phase 1: Methodology development and component failure quantification

    International Nuclear Information System (INIS)

    Hake, T.M.; Heger, A.S.

    1995-04-01

    Many advanced light water reactor (ALWR) concepts proposed for the next generation of nuclear power plants rely on passive systems to perform safety functions, rather than active systems as in current reactor designs. These passive systems depend to a great extent on physical processes such as natural circulation for their driving force, and not on active components, such as pumps. An NRC-sponsored study was begun at Sandia National Laboratories to develop and implement a methodology for evaluating ALWR passive system reliability in the context of probabilistic risk assessment (PRA). This report documents the first of three phases of this study, including methodology development, system-level qualitative analysis, and sequence-level component failure quantification. The methodology developed addresses both the component (e.g. valve) failure aspect of passive system failure, and uncertainties in system success criteria arising from uncertainties in the system's underlying physical processes. Traditional PRA methods, such as fault and event tree modeling, are applied to the component failure aspect. Thermal-hydraulic calculations are incorporated into a formal expert judgment process to address uncertainties in selected natural processes and success criteria. The first phase of the program has emphasized the component failure element of passive system reliability, rather than the natural process uncertainties. Although cursory evaluation of the natural processes has been performed as part of Phase 1, detailed assessment of these processes will take place during Phases 2 and 3 of the program

  12. Energy Storage System Sizing Based on a Reliability Assessment of Power Systems Integrated with Wind Power

    Directory of Open Access Journals (Sweden)

    Nian Shi

    2017-03-01

    Full Text Available The available capacity is a major factor that influences the reliability contribution of energy storage in power systems integrated with wind power. This paper presents the capacity value of the energy storage metrics to quantitatively estimate the contribution of energy storage to the generation adequacy. A method in accordance with EFC approach has been introduced to model the capacity value of energy storage. The adequacy-oriented model of the energy storage available capacity is proposed for the energy storage system, regarding the roles of the key parameters for the CVES analysis. The case study results indicate that the capacity value of energy storage quantitatively weigh the contribution of the energy storage to system reliability. The sensitivity analysis of the impact factors for the CVES is conducted.

  13. New Approaches to Reliability Assessment

    DEFF Research Database (Denmark)

    Ma, Ke; Wang, Huai; Blaabjerg, Frede

    2016-01-01

    of energy. New approaches for reliability assessment are being taken in the design phase of power electronics systems based on the physics-of-failure in components. In this approach, many new methods, such as multidisciplinary simulation tools, strength testing of components, translation of mission profiles......, and statistical analysis, are involved to enable better prediction and design of reliability for products. This article gives an overview of the new design flow in the reliability engineering of power electronics from the system-level point of view and discusses some of the emerging needs for the technology...

  14. Reliability assessment of complex mechatronic systems using a modified nonparametric belief propagation algorithm

    International Nuclear Information System (INIS)

    Zhong, X.; Ichchou, M.; Saidi, A.

    2010-01-01

    Various parametric skewed distributions are widely used to model the time-to-failure (TTF) in the reliability analysis of mechatronic systems, where many items are unobservable due to the high cost of testing. Estimating the parameters of those distributions becomes a challenge. Previous research has failed to consider this problem due to the difficulty of dependency modeling. Recently the methodology of Bayesian networks (BNs) has greatly contributed to the reliability analysis of complex systems. In this paper, the problem of system reliability assessment (SRA) is formulated as a BN considering the parameter uncertainty. As the quantitative specification of BN, a normal distribution representing the stochastic nature of TTF distribution is learned to capture the interactions between the basic items and their output items. The approximation inference of our continuous BN model is performed by a modified version of nonparametric belief propagation (NBP) which can avoid using a junction tree that is inefficient for the mechatronic case because of the large treewidth. After reasoning, we obtain the marginal posterior density of each TTF model parameter. Other information from diverse sources and expert priors can be easily incorporated in this SRA model to achieve more accurate results. Simulation in simple and complex cases of mechatronic systems demonstrates that the posterior of the parameter network fits the data well and the uncertainty passes effectively through our BN based SRA model by using the modified NBP.

  15. Reliable computer systems.

    Science.gov (United States)

    Wear, L L; Pinkert, J R

    1993-11-01

    In this article, we looked at some decisions that apply to the design of reliable computer systems. We began with a discussion of several terms such as testability, then described some systems that call for highly reliable hardware and software. The article concluded with a discussion of methods that can be used to achieve higher reliability in computer systems. Reliability and fault tolerance in computers probably will continue to grow in importance. As more and more systems are computerized, people will want assurances about the reliability of these systems, and their ability to work properly even when sub-systems fail.

  16. A Reliability and Validity of an Instrument to Evaluate the School-Based Assessment System: A Pilot Study

    Science.gov (United States)

    Ghazali, Nor Hasnida Md

    2016-01-01

    A valid, reliable and practical instrument is needed to evaluate the implementation of the school-based assessment (SBA) system. The aim of this study is to develop and assess the validity and reliability of an instrument to measure the perception of teachers towards the SBA implementation in schools. The instrument is developed based on a…

  17. Algorithms for Bayesian network modeling and reliability assessment of infrastructure systems

    International Nuclear Information System (INIS)

    Tien, Iris; Der Kiureghian, Armen

    2016-01-01

    Novel algorithms are developed to enable the modeling of large, complex infrastructure systems as Bayesian networks (BNs). These include a compression algorithm that significantly reduces the memory storage required to construct the BN model, and an updating algorithm that performs inference on compressed matrices. These algorithms address one of the major obstacles to widespread use of BNs for system reliability assessment, namely the exponentially increasing amount of information that needs to be stored as the number of components in the system increases. The proposed compression and inference algorithms are described and applied to example systems to investigate their performance compared to that of existing algorithms. Orders of magnitude savings in memory storage requirement are demonstrated using the new algorithms, enabling BN modeling and reliability analysis of larger infrastructure systems. - Highlights: • Novel algorithms developed for Bayesian network modeling of infrastructure systems. • Algorithm presented to compress information in conditional probability tables. • Updating algorithm presented to perform inference on compressed matrices. • Algorithms applied to example systems to investigate their performance. • Orders of magnitude savings in memory storage requirement demonstrated.

  18. Automatic creation of Markov models for reliability assessment of safety instrumented systems

    International Nuclear Information System (INIS)

    Guo Haitao; Yang Xianhui

    2008-01-01

    After the release of new international functional safety standards like IEC 61508, people care more for the safety and availability of safety instrumented systems. Markov analysis is a powerful and flexible technique to assess the reliability measurements of safety instrumented systems, but it is fallible and time-consuming to create Markov models manually. This paper presents a new technique to automatically create Markov models for reliability assessment of safety instrumented systems. Many safety related factors, such as failure modes, self-diagnostic, restorations, common cause and voting, are included in Markov models. A framework is generated first based on voting, failure modes and self-diagnostic. Then, repairs and common-cause failures are incorporated into the framework to build a complete Markov model. Eventual simplification of Markov models can be done by state merging. Examples given in this paper show how explosively the size of Markov model increases as the system becomes a little more complicated as well as the advancement of automatic creation of Markov models

  19. Reliability assessment of emergency exhaust system in a pool-type research reactor

    International Nuclear Information System (INIS)

    Khan, S.A.

    1991-01-01

    The reliability of an extract system in a swimming-pool-type research reactor has been assessed. A global fault-tree analysis technique has been utilized. The basic event reliability data is based on both generic and reactor specific informations. The unavailability of the extract system is quantified in terms of the unavailability of the various functional requirements of the system. The unavailability is expressed as the probability of failure on demand. The computer system unavailability is determined from the minimal cutsets of the system. It is found that only three events have a major contribution to the top event, i.e., failures of compressed air supply, electric power supply and solenoid valve. A sensitivity analysis is performed to show the effects of variations in the data values of the dominant cutsets. An uncertainty analysis was also performend on the fault tree. The evaluations show that the reactor extract system lacks diversity and redundance in most of its components. It is tolerant of most minor degradations, as these are taken care of by the operating policies and procedures. However, it can not tolerate common cause failures, e.g. simultaneous compressed air and electric power supply failure. Based upon the results obtained, some recommendations are made. (orig.)

  20. Load Control System Reliability

    Energy Technology Data Exchange (ETDEWEB)

    Trudnowski, Daniel [Montana Tech of the Univ. of Montana, Butte, MT (United States)

    2015-04-03

    This report summarizes the results of the Load Control System Reliability project (DOE Award DE-FC26-06NT42750). The original grant was awarded to Montana Tech April 2006. Follow-on DOE awards and expansions to the project scope occurred August 2007, January 2009, April 2011, and April 2013. In addition to the DOE monies, the project also consisted of matching funds from the states of Montana and Wyoming. Project participants included Montana Tech; the University of Wyoming; Montana State University; NorthWestern Energy, Inc., and MSE. Research focused on two areas: real-time power-system load control methodologies; and, power-system measurement-based stability-assessment operation and control tools. The majority of effort was focused on area 2. Results from the research includes: development of fundamental power-system dynamic concepts, control schemes, and signal-processing algorithms; many papers (including two prize papers) in leading journals and conferences and leadership of IEEE activities; one patent; participation in major actual-system testing in the western North American power system; prototype power-system operation and control software installed and tested at three major North American control centers; and, the incubation of a new commercial-grade operation and control software tool. Work under this grant certainly supported the DOE-OE goals in the area of “Real Time Grid Reliability Management.”

  1. Distribution power system reliability assessment using Monte Carlo simulation: optimal maintenance strategy application

    International Nuclear Information System (INIS)

    Ocnasu, A.B.

    2008-10-01

    Today, the electricity sector is confronted with new challenges imposed by the deregulation of the electricity market, the international desire to reduce the greenhouse gases emissions, the development of new technologies. There is an increasing need to assess the reliability of the distribution systems. We can see a migration of methods specially used at transmission level to the distribution level. In a previous PhD, a method based on a sequential Monte Carlo simulation has been developed. The first part of this thesis deals with the study of acceleration methods. Two methods were tested, Antithetic Variates and Stratification. The best acceleration was achieved by a combination of these two methods. Then, we discussed the feasibility study of an optimization method based on reliability criteria. The chosen application was the preventive maintenance strategies optimization. We looked for the optimal number of preventive maintenance and the maximum value of failure rate when maintenance is carried out, minimising the total cost (cost of preventive maintenance, corrective maintenance and the cost of interruptions). In the end, a series of reflections related to the future development of a reliability analysis tool were presented. A modular structure of the tool is proposed to facilitate its use, and the possibility of parallel calculations for a better efficiency. (author)

  2. Probabilistic risk assessment course documentation. Volume 5. System reliability and analysis techniques Session D - quantification

    International Nuclear Information System (INIS)

    Lofgren, E.V.

    1985-08-01

    This course in System Reliability and Analysis Techniques focuses on the probabilistic quantification of accident sequences and the link between accident sequences and consequences. Other sessions in this series focus on the quantification of system reliability and the development of event trees and fault trees. This course takes the viewpoint that event tree sequences or combinations of system failures and success are available and that Boolean equations for system fault trees have been developed and are available. 93 figs., 11 tabs

  3. A Bayesian approach for integrating multilevel priors and data for aerospace system reliability assessment

    Directory of Open Access Journals (Sweden)

    Jian GUO

    2018-01-01

    Full Text Available This paper investigates Bayesian methods for aerospace system reliability analysis using various sources of test data and expert knowledge at both subsystem and system levels. Four scenarios based on available information for the priors and test data of a system and/or subsystems are studied using specific Bayesian inference techniques. This paper proposes the Bayesian melding method for integrating subsystem-level priors with system-level priors for both system- and subsystem-level reliability analysis. System and subsystem reliability outcomes are compared under different scenarios. Computational challenges for posterior inferences using the sophisticated Bayesian melding method are addressed using Markov Chain Monte Carlo (MCMC and adaptive Sampling Importance Re-sampling (SIR methods. A case study with simulation results illustrates the applications of the proposed methods and provides insights for aerospace system reliability analysis using available multilevel information.

  4. Assessment of the reliability of neutronic parameters of Ghana Research Reactor-1 control systems

    Energy Technology Data Exchange (ETDEWEB)

    Amponsah-Abu, E.O., E-mail: edwardabu2002@yahoo.com [National Nuclear Research Institute, Ghana Atomic Energy Commission, P.O. Box LG. 80, Legon-Accra (Ghana); Gbadago, J.K. [National Nuclear Research Institute, Ghana Atomic Energy Commission, P.O. Box LG. 80, Legon-Accra (Ghana); Akaho, E.H.K.; Akoto-Bamford, S. [School of Nuclear and Allied Sciences, University of Ghana (Ghana); Gyamfi, K.; Asamoah, M.; Baidoo, I.K. [National Nuclear Research Institute, Ghana Atomic Energy Commission, P.O. Box LG. 80, Legon-Accra (Ghana)

    2015-01-15

    Highlights: • The reliability of neutronics parameters of GHARR-I was assessed. • The reactor was operated at different power levels of 5–30 kW. • The pre-set flux was compared with the flux in the inner irradiation site. • Decrease in the core reactivity caused difference in flux on the meters and site. • Neutronic parameters become reliable when operation is done at reactivity of 4 mk. - Abstract: The Ghana Research Reactor-1 (GHARR-1) has been in operation for the past 19 years using a Micro-Computer Closed Loop System (MCCLS) and Control Console (CC) as the control systems. The two control systems were each coupled separately with a micro-fission chamber to measure the current pulses of the neutron fluxes in the core at excess reactivity of 4 mk. The MCCLS and CC meter readings at a pre-set flux of 5.0 × 10{sup 11} n/cm{sup 2} s were 6.42 × 10{sup 11} n/cm{sup 2} s and 5.0 × 10{sup 11} n/cm{sup 2} s respectively. Due to ageing and obsolescence, the MCCLS and some components that control the sensitivity and the reading mechanism of the meters were replaced. One of the fission chambers was also removed and the two control systems were coupled to one fission chamber. The reliability of the neutronic parameters of the control systems was assessed after the replacement. The results showed that when the reactor is operated at different power levels of 5–30 kW using one micro-fission chamber, the pre-set neutron fluxes at the control systems is 1.6 times the neutron fluxes obtained using a flux monitor at the inner irradiation site two of the reactor. The average percentage deviations of the obtained fluxes from the pre-set values of 1.67 × 10{sup 11}–1.0 × 10{sup 12} n/cm{sup 2} s were 36.5%. This compares very well with the decrease in core excess reactivity of 36.3% of the nominal value of 4 mk, after operating the reactor at critical neutron flux of 1.0 × 10{sup 9} n/cm{sup 2} s.

  5. RELIABILITY AND VALIDITY OF AN ACCELEROMETRIC SYSTEM FOR ASSESSING VERTICAL JUMPING PERFORMANCE

    Directory of Open Access Journals (Sweden)

    M.-A. Choukou

    2014-07-01

    Full Text Available The validity of an accelerometric system (Myotest© for assessing vertical jump height, vertical force and power, leg stiffness and reactivity index was examined. 20 healthy males performed 3ד5 hops in place”, 3ד1 squat jump” and 3× “1 countermovement jump” during 2 test-retest sessions. The variables were simultaneously assessed using an accelerometer and a force platform at a frequency of 0.5 and 1 kHz, respectively. Both reliability and validity of the accelerometric system were studied. No significant differences between test and retest data were found (p<0.05, showing a high level of reliability. Besides, moderate to high intraclass correlation coefficients (ICCs (from 0.74 to 0.96 were obtained for all variables whereas weak to moderate ICCs (from 0.29 to 0.79 were obtained for force and power during the countermovement jump. With regards to validity, the difference between the two devices was not significant for 5 hops in place height (1.8 cm, force during squat (-1.4 N · kg-1 and countermovement (0.1 N · kg-1 jumps, leg stiffness (7.8 kN · m-1 and reactivity index (0.4. So, the measurements of these variables with this accelerometer are valid, which is not the case for the other variables. The main causes of non-validity for velocity, power and contact time assessment are temporal biases of the takeoff and touchdown moments detection.

  6. First Assessment of Reliability Data for the LHC Accelerator and Detector Cryogenic System Components

    CERN Document Server

    Perinic, G; Alonso-Canella, I; Balle, C; Barth, K; Bel, J F; Benda, V; Bremer, J; Brodzinski, K; Casas-Cubillos, J; Cuccuru, G; Cugnet, M; Delikaris, D; Delruelle, N; Dufay-Chanat, L; Fabre, C; Ferlin, G; Fluder, C; Gavard, E; Girardot, R; Haug, F; Herblin, L; Junker, S; Klabi , T; Knoops, S; Lamboy, J P; Legrand, D; Metselaar, J; Park, A; Perin, A; Pezzetti, M; Penacoba-Fernandez, G; Pirotte, O; Rogez, E; Suraci, A; Stewart, L; Tavian, L J; Tovar-Gonzalez, A; Van Weelderen, R; Vauthier, N; Vullierme, B; Wagner, U

    2012-01-01

    The Large Hadron Collider (LHC) cryogenic system comprises eight independent refrigeration and distribution systems that supply the eight 3.3 km long accelerator sectors with cryogenic refrigeration power as well as four refrigeration systems for the needs of the detectors ATLAS and CMS. In order to ensure the highest possible reliability of the installations, it is important to apply a reliability centred approach for the maintenance. Even though large scale cryogenic refrigeration exists since the mid 20th century, very little third party reliability data is available today. CERN has started to collect data with its computer aided maintenance management system (CAMMS) in 2009, when the accelerator has gone into normal operation. This paper presents the reliability observations from the operation and the maintenance side, as well as statistical data collected by the means of the CAMMS system.

  7. Software reliability assessment

    International Nuclear Information System (INIS)

    Barnes, M.; Bradley, P.A.; Brewer, M.A.

    1994-01-01

    The increased usage and sophistication of computers applied to real time safety-related systems in the United Kingdom has spurred on the desire to provide a standard framework within which to assess dependable computing systems. Recent accidents and ensuing legislation have acted as a catalyst in this area. One particular aspect of dependable computing systems is that of software, which is usually designed to reduce risk at the system level, but which can increase risk if it is unreliable. Various organizations have recognized the problem of assessing the risk imposed to the system by unreliable software, and have taken initial steps to develop and use such assessment frameworks. This paper relates the approach of Consultancy Services of AEA Technology in developing a framework to assess the risk imposed by unreliable software. In addition, the paper discusses the experiences gained by Consultancy Services in applying the assessment framework to commercial and research projects. The framework is applicable to software used in safety applications, including proprietary software. Although the paper is written with Nuclear Reactor Safety applications in mind, the principles discussed can be applied to safety applications in all industries

  8. Application of fault tree analysis for customer reliability assessment of a distribution power system

    International Nuclear Information System (INIS)

    Abdul Rahman, Fariz; Varuttamaseni, Athi; Kintner-Meyer, Michael; Lee, John C.

    2013-01-01

    A new method is developed for predicting customer reliability of a distribution power system using the fault tree approach with customer weighted values of component failure frequencies and downtimes. Conventional customer reliability prediction of the electric grid employs the system average (SA) component failure frequency and downtime that are weighted by only the quantity of the components in the system. These SA parameters are then used to calculate the reliability and availability of components in the system, and eventually to find the effect on customer reliability. Although this approach is intuitive, information is lost regarding customer disturbance experiences when customer information is not utilized in the SA parameter calculations, contributing to inaccuracies when predicting customer reliability indices in our study. Hence our new approach directly incorporates customer disturbance information in component failure frequency and downtime calculations by weighting these parameters with information of customer interruptions. This customer weighted (CW) approach significantly improves the prediction of customer reliability indices when applied to our reliability model with fault tree and two-state Markov chain formulations. Our method has been successfully applied to an actual distribution power system that serves over 2.1 million customers. Our results show an improved benchmarking performance on the system average interruption frequency index (SAIFI) by 26% between the SA-based and CW-based reliability calculations. - Highlights: ► We model the reliability of a power system with fault tree and two-state Markov chain. ► We propose using customer weighted component failure frequencies and downtimes. ► Results show customer weighted values perform superior to component average values. ► This method successfully incorporates customer disturbance information into the model.

  9. Hawaii electric system reliability.

    Energy Technology Data Exchange (ETDEWEB)

    Silva Monroy, Cesar Augusto; Loose, Verne William

    2012-09-01

    This report addresses Hawaii electric system reliability issues; greater emphasis is placed on short-term reliability but resource adequacy is reviewed in reference to electric consumers' views of reliability %E2%80%9Cworth%E2%80%9D and the reserve capacity required to deliver that value. The report begins with a description of the Hawaii electric system to the extent permitted by publicly available data. Electrical engineering literature in the area of electric reliability is researched and briefly reviewed. North American Electric Reliability Corporation standards and measures for generation and transmission are reviewed and identified as to their appropriateness for various portions of the electric grid and for application in Hawaii. Analysis of frequency data supplied by the State of Hawaii Public Utilities Commission is presented together with comparison and contrast of performance of each of the systems for two years, 2010 and 2011. Literature tracing the development of reliability economics is reviewed and referenced. A method is explained for integrating system cost with outage cost to determine the optimal resource adequacy given customers' views of the value contributed by reliable electric supply. The report concludes with findings and recommendations for reliability in the State of Hawaii.

  10. Hawaii Electric System Reliability

    Energy Technology Data Exchange (ETDEWEB)

    Loose, Verne William [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Silva Monroy, Cesar Augusto [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2012-08-01

    This report addresses Hawaii electric system reliability issues; greater emphasis is placed on short-term reliability but resource adequacy is reviewed in reference to electric consumers’ views of reliability “worth” and the reserve capacity required to deliver that value. The report begins with a description of the Hawaii electric system to the extent permitted by publicly available data. Electrical engineering literature in the area of electric reliability is researched and briefly reviewed. North American Electric Reliability Corporation standards and measures for generation and transmission are reviewed and identified as to their appropriateness for various portions of the electric grid and for application in Hawaii. Analysis of frequency data supplied by the State of Hawaii Public Utilities Commission is presented together with comparison and contrast of performance of each of the systems for two years, 2010 and 2011. Literature tracing the development of reliability economics is reviewed and referenced. A method is explained for integrating system cost with outage cost to determine the optimal resource adequacy given customers’ views of the value contributed by reliable electric supply. The report concludes with findings and recommendations for reliability in the State of Hawaii.

  11. Reliability assessment of Wind turbines

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2015-01-01

    Wind turbines can be considered as structures that are in between civil engineering structures and machines since they consist of structural components and many electrical and machine components together with a control system. Further, a wind turbine is not a one-of-a-kind structure...... but manufactured in series production based on many component tests, some prototype tests and zeroseries wind turbines. These characteristics influence the reliability assessment where focus in this paper is on the structural components. Levelized Cost Of Energy is very important for wind energy, especially when...... comparing to other energy sources. Therefore much focus is on cost reductions and improved reliability both for offshore and onshore wind turbines. The wind turbine components should be designed to have sufficient reliability level with respect to both extreme and fatigue loads but also not be too costly...

  12. A METHOD BASED ON FUZZY SYSTEM FOR ASSESSING THE RELIABILITY OF SOFTWARE BASED ASPECTS

    Directory of Open Access Journals (Sweden)

    Mohammad Zavvar

    2015-08-01

    Full Text Available In fact, reliability as the qualities metric is the probability success or the probability that a system or a set of tasks will work without failure for a specified constraints of time and space, as specified in the design and operating conditions specified temperature, humidity, vibration and action. A relatively new methodologies for developing complex software systems engineering is an aspect oriented software systems, that provides the new methods for the separation of concerns multiple module configuration or intervention and automatic integration them with a system. In this paper, a method using fuzzy logic to measure software reliability based on the above aspects is presented. The proposed approach regarding the use of appropriate metrics and low errors in the estimation of reliability has a better performance than other methods.

  13. Reliability Assessment and Energy Loss Evaluation for Modern Wind Turbine Systems

    DEFF Research Database (Denmark)

    Zhou, Dao

    With a steady increase of the wind power penetration, the demands to the wind power technology are becoming the same as those to the conventional energy sources. In order to fulfill the requirements, power electronics technology is the key for the modern wind turbine systems – both the Doubly...... are explored in Chapter 6. The main contribution of this project is in developing a universal approach to evaluate and estimate the reliability and the cost of energy for modern wind turbine systems. Furthermore, simulation and experimental results validates the feasibility of an enhanced lifespan of the power...... to explore the reliability and cost of energy in the modern wind turbine systems. Moreover, advanced control strategies have been proposed and developed for an efficient and reliable operation during the normal condition as well as under grid faults. The documented thesis starts with the descriptions...

  14. Reliability assessment of embedded digital system using multi-state function

    International Nuclear Information System (INIS)

    Choi, Jong Gyun; Seong, Poong Hyun

    2006-01-01

    This work describes a combinatorial model for estimating the reliability of the embedded digital system by means of multi-state function. This model includes a coverage model for fault-handling techniques implemented in digital systems. The fault-handling techniques make it difficult for many types of components in digital system to be treated as binary state, good or bad. The multi-state function provides a complete analysis of multi-state systems as which the digital systems can be regarded. Through adaptation of software operational profile flow to multi-state function, the HW/SW interaction is also considered for estimation of the reliability of digital system. Using this model, we evaluate the reliability of one board controller in a digital system, Interposing Logic System (ILS), which is installed in YGN nuclear power units 3 and 4. Since the proposed model is a generalized combinatorial model, the simplification of this model becomes the conventional model that treats the system as binary state. This modeling method is particularly attractive for embedded systems in which small sized application software is implemented since it will require very laborious work for this method to be applied to systems with large software

  15. Lz-transform and inverse Lz-transform application to dynamic reliability assessment for multi-state system

    DEFF Research Database (Denmark)

    Lisnianski, A.; Ding, Y.

    2014-01-01

    of the system model with great number of states and solving a corresponding system of differential equations. Lz-transform method, which is used for reliability assessment drastically simplified the solution. Instead of straightforward finding of the resulting output stochastic process for entire MSS...

  16. System reliability assessment via sensitivity analysis in the Markov chain scheme

    International Nuclear Information System (INIS)

    Gandini, A.

    1988-01-01

    Methods for reliability sensitivity analysis in the Markov chain scheme are presented, together with a new formulation which makes use of Generalized Perturbation Theory (GPT) methods. As well known, sensitivity methods are fundamental in system risk analysis, since they allow to identify important components, so to assist the analyst in finding weaknesses in design and operation and in suggesting optimal modifications for system upgrade. The relationship between the GPT sensitivity expression and the Birnbaum importance is also given [fr

  17. An independent assessment of reliability of the Melbourne Cerebral Palsy Hip Classification System.

    Science.gov (United States)

    Shrader, M W; Koenig, A L; Falk, M; Belthur, M; Boan, C

    2017-10-01

    Neuromuscular (NM) hip dysplasia is common in patients with cerebral palsy (CP). Traditionally, migration percentage (MP) has been used to measure the severity of NM hip dysplasia; however, the MP has some limitations. The purpose of this study is to determine the intra- and inter-reliability of the Melbourne Cerebral Palsy Hip Classification System in the typical paediatric population of patients with CP. A total of 65 anteroposterior pelvis radiographs in patients (age range 12 years to 21 years) with CP spanning all grades (I to VI) of the classification system were identified and collected for analysis in this institutional review board approved study. Four paediatric orthopaedic surgeons and one orthopaedic surgical resident classified each radiograph according to the Melbourne system. Then, at least four weeks later, the raters repeated the process with a re-randomised order of radiographs. Statistical analysis was performed using the intraclass correlation coefficient (ICC) where 0.8 indicates almost perfect agreement. The interobserver reliability was found to be excellent with the ICC of 0.853 (0.813 to 0.887) and 0.839 (0.795 to 0.877). The intraobserver reliability was also found to be excellent with the ICC in the range of 0.838 to 0.933 among the raters. Subgroup analysis indicated no differences in the reliability of observers based on clinical experience. This study independently demonstrates that the Melbourne Cerebral Palsy Hip Classification System for NM hip dysplasia in patients with CP can be reliably used for communication among various healthcare providers and research and epidemiological purposes.

  18. Assessment of system reliability for a stochastic-flow distribution network with the spoilage property

    Science.gov (United States)

    Lin, Yi-Kuei; Huang, Cheng-Fu; Yeh, Cheng-Ta

    2016-04-01

    In supply chain management, satisfying customer demand is the most concerned for the manager. However, the goods may rot or be spoilt during delivery owing to natural disasters, inclement weather, traffic accidents, collisions, and so on, such that the intact goods may not meet market demand. This paper concentrates on a stochastic-flow distribution network (SFDN), in which a node denotes a supplier, a transfer station, or a market, while a route denotes a carrier providing the delivery service for a pair of nodes. The available capacity of the carrier is stochastic because the capacity may be partially reserved by other customers. The addressed problem is to evaluate the system reliability, the probability that the SFDN can satisfy the market demand with the spoilage rate under the budget constraint from multiple suppliers to the customer. An algorithm is developed in terms of minimal paths to evaluate the system reliability along with a numerical example to illustrate the solution procedure. A practical case of fruit distribution is presented accordingly to emphasise the management implication of the system reliability.

  19. Assessing the reliability of components with micro- and nano-structures when they are part a multi-scale system

    International Nuclear Information System (INIS)

    Ebrahimi, Nader; Shehadeh, Mahmoud

    2015-01-01

    Products with macro- and meso-scales components have grown into multi-scale systems where some of their components have shrunk to a smaller scale such as micro- and nano-structures. In practice, engineers may be unable to accurately assess their designs to improve the reliability of components in multi-scale systems, because component parts with micro- and nano-structures cannot be realized directly in system design phase. Thus, all kinds of design processes such as engineering verifications for physics or functions become increasingly complex in a muti-scale system. For this shortcoming, we present a parametric Bayesian method that enables engineers to assess indirectly the reliability and the quality of a component with either a micro-structure or a nano-structure using experimental data on failure time of the multi-scale system. Our proposed Bayesian approach is flexible in allowing a general model for distributions of failure times of a multi-scale system and its components. Our method is applied to a simulated data set. - Highlights: • A framework for assessment of reliability of components from a multi-scale system lifetime is presented here. • A Bayesian model is used, allowing instantaneous propagation of knowledge. • A set of analytical and numerical methods is used to make statistical inference about unknown parameters in the model

  20. Using wavefront coding technique as an optical encryption system: reliability analysis and vulnerabilities assessment

    Science.gov (United States)

    Konnik, Mikhail V.

    2012-04-01

    Wavefront coding paradigm can be used not only for compensation of aberrations and depth-of-field improvement but also for an optical encryption. An optical convolution of the image with the PSF occurs when a diffractive optical element (DOE) with a known point spread function (PSF) is placed in the optical path. In this case, an optically encoded image is registered instead of the true image. Decoding of the registered image can be performed using standard digital deconvolution methods. In such class of optical-digital systems, the PSF of the DOE is used as an encryption key. Therefore, a reliability and cryptographic resistance of such an encryption method depends on the size and complexity of the PSF used for optical encoding. This paper gives a preliminary analysis on reliability and possible vulnerabilities of such an encryption method. Experimental results on brute-force attack on the optically encrypted images are presented. Reliability estimation of optical coding based on wavefront coding paradigm is evaluated. An analysis of possible vulnerabilities is provided.

  1. Natural Circulation in Water Cooled Nuclear Power Plants Phenomena, models, and methodology for system reliability assessments

    Energy Technology Data Exchange (ETDEWEB)

    Jose Reyes

    2005-02-14

    In recent years it has been recognized that the application of passive safety systems (i.e., those whose operation takes advantage of natural forces such as convection and gravity), can contribute to simplification and potentially to improved economics of new nuclear power plant designs. In 1991 the IAEA Conference on ''The Safety of Nuclear Power: Strategy for the Future'' noted that for new plants the use of passive safety features is a desirable method of achieving simplification and increasing the reliability of the performance of essential safety functions, and should be used wherever appropriate''.

  2. Natural Circulation in Water Cooled Nuclear Power Plants Phenomena, models, and methodology for system reliability assessments

    International Nuclear Information System (INIS)

    Jose Reyes

    2005-01-01

    In recent years it has been recognized that the application of passive safety systems (i.e., those whose operation takes advantage of natural forces such as convection and gravity), can contribute to simplification and potentially to improved economics of new nuclear power plant designs. In 1991 the IAEA Conference on ''The Safety of Nuclear Power: Strategy for the Future'' noted that for new plants the use of passive safety features is a desirable method of achieving simplification and increasing the reliability of the performance of essential safety functions, and should be used wherever appropriate''

  3. Probabilistic safety assessment of Tehran Research Reactor using systems analysis programs for hands-on integrated reliability evaluations

    International Nuclear Information System (INIS)

    Hosseini, M.H.; Nematollahi, M.R.; Sepanloo, K.

    2004-01-01

    Probabilistic safety assessment application is found to be a practical tool for research reactor safety due to intense involvement of human interactions in an experimental facility. In this document the application of the probabilistic safety assessment to the Tehran Research Reactor is presented. The level 1 practicabilities safety assessment application involved: Familiarization with the plant, selection of accident initiators, mitigating functions and system definitions, event tree constructions and quantifications, fault tree constructions and quantification, human reliability, component failure data base development and dependent failure analysis. Each of the steps of the analysis given above is discussed with highlights from the selected results. Quantification of the constructed models is done using systems analysis programs for hands-on integrated reliability evaluations software

  4. Advances in reliability and system engineering

    CERN Document Server

    Davim, J

    2017-01-01

    This book presents original studies describing the latest research and developments in the area of reliability and systems engineering. It helps the reader identifying gaps in the current knowledge and presents fruitful areas for further research in the field. Among others, this book covers reliability measures, reliability assessment of multi-state systems, optimization of multi-state systems, continuous multi-state systems, new computational techniques applied to multi-state systems and probabilistic and non-probabilistic safety assessment.

  5. Reliability of subjective wound assessment

    NARCIS (Netherlands)

    Bloemen, M.C.T.; van Zuijlen, P.P.M.; Middelkoop, E.

    2011-01-01

    Introduction: Assessment of the take of split-skin graft and the rate of epithelialisation are important parameters in burn surgery. Such parameters are normally estimated by the clinician in a bedside procedure. This study investigates whether this subjective assessment is reliable for graft take

  6. Reliability of subjective wound assessment

    NARCIS (Netherlands)

    Bloemen, M. C. T.; van Zuijlen, P. P. M.; Middelkoop, E.

    2011-01-01

    Assessment of the take of split-skin graft and the rate of epithelialisation are important parameters in burn surgery. Such parameters are normally estimated by the clinician in a bedside procedure. This study investigates whether this subjective assessment is reliable for graft take and wound

  7. Numerical methods for reliability and safety assessment multiscale and multiphysics systems

    CERN Document Server

    Hami, Abdelkhalak

    2015-01-01

    This book offers unique insight on structural safety and reliability by combining computational methods that address multiphysics problems, involving multiple equations describing different physical phenomena, and multiscale problems, involving discrete sub-problems that together  describe important aspects of a system at multiple scales. The book examines a range of engineering domains and problems using dynamic analysis, nonlinear methods, error estimation, finite element analysis, and other computational techniques. This book also: ·       Introduces novel numerical methods ·       Illustrates new practical applications ·       Examines recent engineering applications ·       Presents up-to-date theoretical results ·       Offers perspective relevant to a wide audience, including teaching faculty/graduate students, researchers, and practicing engineers

  8. Reliability assessment of Wind turbines

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2015-01-01

    but manufactured in series production based on many component tests, some prototype tests and zeroseries wind turbines. These characteristics influence the reliability assessment where focus in this paper is on the structural components. Levelized Cost Of Energy is very important for wind energy, especially when...... comparing to other energy sources. Therefore much focus is on cost reductions and improved reliability both for offshore and onshore wind turbines. The wind turbine components should be designed to have sufficient reliability level with respect to both extreme and fatigue loads but also not be too costly...... (and safe). In probabilistic design the single components are designed to a level of reliability, which accounts for an optimal balance between failure consequences, cost of operation & maintenance, material costs and the probability of failure. Furthermore, using a probabilistic design basis...

  9. System-level Reliability Assessment of Power Stage in Fuel Cell Application

    DEFF Research Database (Denmark)

    Zhou, Dao; Wang, Huai; Blaabjerg, Frede

    2016-01-01

    High efficient and less pollutant fuel cell stacks are emerging and strong candidates of the power solution used for mobile base stations. In the application of the backup power, the availability and reliability hold the highest priority. This paper considers the reliability metrics from...

  10. Space Shuttle Propulsion System Reliability

    Science.gov (United States)

    Welzyn, Ken; VanHooser, Katherine; Moore, Dennis; Wood, David

    2011-01-01

    This session includes the following sessions: (1) External Tank (ET) System Reliability and Lessons, (2) Space Shuttle Main Engine (SSME), Reliability Validated by a Million Seconds of Testing, (3) Reusable Solid Rocket Motor (RSRM) Reliability via Process Control, and (4) Solid Rocket Booster (SRB) Reliability via Acceptance and Testing.

  11. Reliable Fluid Power Pitch Systems

    DEFF Research Database (Denmark)

    Liniger, Jesper; Pedersen, Henrik Clemmensen; Soltani, Mohsen

    2015-01-01

    The key objectives of wind turbine manufactures and buyers are to reduce the Total Cost of Ownership and Total Cost of Energy. Among others, low downtime of a wind turbine is important to increase the amount of energy produced during its lifetime. Historical data indicate that pitch systems...... accounts for a substantial part of the downtime of wind turbines. With a focus on fluid power pitch systems; this paper presents an overview of methods relevant to assessing and increasing the reliability and availability of such systems. Four major areas are identified and covered; failure analysis...

  12. A multi-state model for the reliability assessment of a distributed generation system via universal generating function

    International Nuclear Information System (INIS)

    Li, Yan-Fu; Zio, Enrico

    2012-01-01

    The current and future developments of electric power systems are pushing the boundaries of reliability assessment to consider distribution networks with renewable generators. Given the stochastic features of these elements, most modeling approaches rely on Monte Carlo simulation. The computational costs associated to the simulation approach force to treating mostly small-sized systems, i.e. with a limited number of lumped components of a given renewable technology (e.g. wind or solar, etc.) whose behavior is described by a binary state, working or failed. In this paper, we propose an analytical multi-state modeling approach for the reliability assessment of distributed generation (DG). The approach allows looking to a number of diverse energy generation technologies distributed on the system. Multiple states are used to describe the randomness in the generation units, due to the stochastic nature of the generation sources and of the mechanical degradation/failure behavior of the generation systems. The universal generating function (UGF) technique is used for the individual component multi-state modeling. A multiplication-type composition operator is introduced to combine the UGFs for the mechanical degradation and renewable generation source states into the UGF of the renewable generator power output. The overall multi-state DG system UGF is then constructed and classical reliability indices (e.g. loss of load expectation (LOLE), expected energy not supplied (EENS)) are computed from the DG system generation and load UGFs. An application of the model is shown on a DG system adapted from the IEEE 34 nodes distribution test feeder.

  13. Reliability Assessment of Concrete Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Middleton, C. R.

    This paper is partly based on research performed for the Highways Agency, London, UK under the project DPU/9/44 "Revision of Bridge Assessment Rules Based on Whole Life Performance: concrete bridges". It contains the details of a methodology which can be used to generate Whole Life (WL) reliability...... profiles. These WL reliability profiles may be used to establish revised rules for concrete bridges. This paper is to some extend based on Thoft-Christensen et. al. [1996], Thoft-Christensen [1996] et. al. and Thoft-Christensen [1996]....

  14. Concept of Korean reliability qualification system

    International Nuclear Information System (INIS)

    Kim, Hyoung Eui

    2008-01-01

    It has been passed eight years since Reliability Assessment Centers of 18 fields including machinery and electronic field were established in 2000 to enhance the reliability of components and materials which are foundation of domestic industry. When Reliability Assessment Center were established in 2000, many questions and issues have been headed. Those questions and issues were how reliability and quality are different, how the reliability measurement can be expressed, how the reliability requirements can be made, how the reliability of components can be tested and evaluated and etc. Currently it is the state that the controversy and improvement methods about reliability qualification, no failure test and one failure acceptance test were issued. This paper investigates the problems toward test and evaluation methods to certificate R-Mark and presents the direction of Korean Reliability Certification System

  15. Space Station Freedom power - A reliability, availability, and maintainability assessment of the proposed Space Station Freedom electric power system

    Science.gov (United States)

    Turnquist, S. R.; Twombly, M.; Hoffman, D.

    1989-01-01

    A preliminary reliability, availability, and maintainability (RAM) analysis of the proposed Space Station Freedom electric power system (EPS) was performed using the unit reliability, availability, and maintainability (UNIRAM) analysis methodology. Orbital replacement units (ORUs) having the most significant impact on EPS availability measures were identified. Also, the sensitivity of the EPS to variations in ORU RAM data was evaluated for each ORU. Estimates were made of average EPS power output levels and availability of power to the core area of the space station. The results of assessments of the availability of EPS power and power to load distribution points in the space stations are given. Some highlights of continuing studies being performed to understand EPS availability considerations are presented.

  16. Reliability assessment of home health care services.

    Science.gov (United States)

    Spyrou, Stergiani; Bamidis, Panagiotis; Kilintzis, Vassilis; Lekka, Irini; Maglaveras, Nicos; Pappas, Costas

    2007-01-01

    In this paper, a model of reliability assessment of services in Home Health Care Delivery is presented. Reliability is an important quality dimension for services and is included in non-functional requirements of a system. A stochastic Markov model for reliability assessment is applied to patient communication services, in the field of home health care delivery. The methodology includes the specification of scenarios, the definition of failures in scenarios as well as the application of the analytical model. The results of the methodology reveal the critical states of the Home Health Care System and recommendations for improvement of the services are proposed. The model gives valuable results in predicting service reliability and, independently of the error types, it can be applied to all fields of Regional Health Network (RHN).

  17. Concurrent Validity and Test-retest Reliability of the OPTOGait Photoelectric Cell System for the Assessment of Spatio-temporal Parameters of the Gait of Young Adults

    OpenAIRE

    Lee, Myung Mo; Song, Chang Ho; Lee, Kyoung Jin; Jung, Sang Woo; Shin, Doo Chul; Shin, Seung Ho

    2014-01-01

    [Purpose] The purpose of this study was to investigate the concurrent validity and test-retest reliability of the recently introduced OPTOGait Photoelectric Cell System for the assessment of spatio-temporal parameters of gait. [Subjects] Twenty healthy young adults (mean age = 27.35, SD = 7.4) were asked to walk 3 times on walkway at a comfortable speed. [Methods] Concurrent validity was assessed by comparing data obtained using the OPTOGait and GAITRite systems, and reliability was assessed ...

  18. Structural systems reliability analysis

    International Nuclear Information System (INIS)

    Frangopol, D.

    1975-01-01

    For an exact evaluation of the reliability of a structure it appears necessary to determine the distribution densities of the loads and resistances and to calculate the correlation coefficients between loads and between resistances. These statistical characteristics can be obtained only on the basis of a long activity period. In case that such studies are missing the statistical properties formulated here give upper and lower bounds of the reliability. (orig./HP) [de

  19. Systems reliability in high risk situations

    International Nuclear Information System (INIS)

    Hunns, D.M.

    1974-12-01

    A summary is given of five papers and the discussion of a seminar promoted by the newly-formed National Centre of Systems Reliability. The topics covered include hazard analysis, reliability assessment, and risk assessment in both nuclear and non-nuclear industries. (U.K.)

  20. Fundamentals and applications of systems reliability analysis

    International Nuclear Information System (INIS)

    Boesebeck, K.; Heuser, F.W.; Kotthoff, K.

    1976-01-01

    The lecture gives a survey on the application of methods of reliability analysis to assess the safety of nuclear power plants. Possible statements of reliability analysis in connection with specifications of the atomic licensing procedure are especially dealt with. Existing specifications of safety criteria are additionally discussed with the help of reliability analysis by the example of the reliability analysis of a reactor protection system. Beyond the limited application to single safety systems, the significance of reliability analysis for a closed risk concept is explained in the last part of the lecture. (orig./LH) [de

  1. Frequent sampling by clear venipuncture in unstable angina is a reliable method to assess haemostatic system activity

    NARCIS (Netherlands)

    Biasucci, L.M.; Liuzzo, G.; Caligiuri, G.; Monaco, C.; Quaranta, G.; Sperti, G.; Greef, W. van de; Maseri, A.; Kluft, C.

    1994-01-01

    Sudden limitations in coronary flow account for the majority of cases of UA. Measurement of TAT in peripheral blood represent a reliable marker of an ongoing thrombotic process. The aim of the study was to assess the reliability of frequent blood sampling (Phase A) and to correlate TAT fluctuation

  2. Power system reliability analysis using fault trees

    International Nuclear Information System (INIS)

    Volkanovski, A.; Cepin, M.; Mavko, B.

    2006-01-01

    The power system reliability analysis method is developed from the aspect of reliable delivery of electrical energy to customers. The method is developed based on the fault tree analysis, which is widely applied in the Probabilistic Safety Assessment (PSA). The method is adapted for the power system reliability analysis. The method is developed in a way that only the basic reliability parameters of the analysed power system are necessary as an input for the calculation of reliability indices of the system. The modeling and analysis was performed on an example power system consisting of eight substations. The results include the level of reliability of current power system configuration, the combinations of component failures resulting in a failed power delivery to loads, and the importance factors for components and subsystems. (author)

  3. Study on a System Reliability Calculation Method Using Failure Enumeration of Reliability Path

    International Nuclear Information System (INIS)

    Lee, Jang Il; Chun, Hwan Kyu; Jeong, Choong Min; Shin, Dong Jun; Suh, Myung Won; Park, Kee Jun

    2011-01-01

    Recently, systems such as aircraft, trains and ships have become larger more complex. Therefore, the reliability calculation of these systems is more difficult. This paper presents a reliability calculation algorithm for a complex system with a solution that is difficult to analyze. When the system has a very complex structure, it is very difficult to find an analytical solution. In this case, we can assess system reliability using the failure enumeration method of the reliability path. In this research, we represent the reliability block diagram by an adjacent matrix and define the reliability path. We can find any system status by the failure enumeration of the reliability path, and thus we can calculate any kind of system reliability through this process. This result can be applied to RCM (Reliability-Centered Maintenance) and reliability information-management systems, in which the system reliability is composed of the reliabilities of individual parts

  4. Reliability data collection and use in risk and availability assessment

    International Nuclear Information System (INIS)

    Colombari, V.

    1989-01-01

    For EuReDatA it is a prevailing objective to initiate and support contact between experts, companies and institutions active in reliability engineering and research. Main topics of this 6th EuReDatA Conference are: Reliability data banks; incidents data banks; common cause data; source and propagation of uncertainties; computer aided risk analysis; reliability and incidents data acquisition and processing; human reliability; probabilistic safety and availability assessment; feedback of reliability into system design; data fusion; reliability modeling and techniques; structural and mechanical reliability; consequence modeling; software and electronic reliability; reliability tests. Some conference papers are separately indexed in the database. (HP)

  5. Failure Modes Taxonomy for Reliability Assessment of Digital Instrumentation and Control Systems for Probabilistic Risk Analysis - Failure modes taxonomy for reliability assessment of digital I and C systems for PRA

    International Nuclear Information System (INIS)

    Amri, A.; Blundell, N.; ); Authen, S.; Betancourt, L.; Coyne, K.; Halverson, D.; Li, M.; Taylor, G.; Bjoerkman, K.; Brinkman, H.; Postma, W.; Bruneliere, H.; Chirila, M.; Gheorge, R.; Chu, L.; Yue, M.; Delache, J.; Georgescu, G.; Deleuze, G.; Quatrain, R.; Thuy, N.; Holmberg, J.-E.; Kim, M.C.; Kondo, K.; Mancini, F.; Piljugin, E.; Stiller, J.; Sedlak, J.; Smidts, C.; Sopira, V.

    2015-01-01

    Digital protection and control systems appear as upgrades in older nuclear power plants (NPP), and are commonplace in new NPPs. To assess the risk of NPP operation and to determine the risk impact of digital systems, there is a need to quantitatively assess the reliability of the digital systems in a justifiable manner. Due to the many unique attributes of digital systems (e.g., functions are implemented by software, units of the system interact in a communication network, faults can be identified and handled online), a number of modelling and data collection challenges exist, and international consensus on the reliability modelling has not yet been reached. The objective of the task group called DIGREL has been to develop a taxonomy of failure modes of digital components for the purposes of probabilistic risk analysis (PRA). An activity focused on the development of a common taxonomy of failure modes is seen as an important step towards standardised digital instrumentation and control (I and C) reliability assessment techniques for PRA. Needs from PRA has guided the work, meaning, e.g., that the I and C system and its failures are studied from the point of view of their functional significance point of view. The taxonomy will be the basis of future modelling and quantification efforts. It will also help to define a structure for data collection and to review PRA studies. The proposed failure modes taxonomy has been developed by first collecting examples of taxonomies provided by the task group organisations. This material showed some variety in the handling of I and C hardware failure modes, depending on the context where the failure modes have been defined. Regarding the software part of I and C, failure modes defined in NPP PRAs have been simple - typically a software CCF failing identical processing units. The DIGREL task group has defined a new failure modes taxonomy based on a hierarchical definition of five levels of abstraction: 1. system level (complete

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

    DEFF Research Database (Denmark)

    Lee, Shinae; Zhou, Dao; Wang, Huai

    2016-01-01

    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...

  7. Expert system for the reliability assessment of hydro-carbon transporting pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Lukacs, J.; Nagy, G.; Toeroek, I. [Department of Mechanical Technology, University of Miskolc, Miskolc-Egyetemvaros (Hungary)

    1998-12-31

    Safety operation, condition monitoring, periodical inspection and rehabilitation of high-pressure hydro-carbon transporting pipelines are a complex problem. To answer arising questions is inconceivable without technical-critical evaluation of defects - originated during manufacturing or operation - can be found on the pipeline. This evaluation must be in line with requirements of our age, i.e. it has to assert such concept of which basis is not the `possible worst` but the `just happening wrong`. Solving these problems without application of computer resources is inconceivable in our time. The final purpose of the solution is the expert system and among the components of the expert system primarily the development of the knowledge base is needed. The paper demonstrates a possible structure of the knowledge base, furthermore its fundamental elements and their contents (defect types, evaluation possibilities of defects, categorisation of pipelines) and summaries the prospective advantages of its application. (orig.) 27 refs.

  8. French power system reliability report 2008

    International Nuclear Information System (INIS)

    Tesseron, J.M.

    2009-06-01

    The reliability of the French power system was fully under control in 2008, despite the power outage in the eastern part of the Provence-Alpes-Cote d'Azur region on November 3, which had been dreaded for several years, since it had not been possible to set up a structurally adequate network. Pursuant to a consultation meeting, the reinforcement solution proposed by RTE was approved by the Minister of Energy, boding well for greater reliability in future. Based on the observations presented in this 2008 Report, RTE's Power System Reliability Audit Mission considers that no new recommendations are needed beyond those expressed in previous reliability reports and during reliability audits. The publication of this yearly report is in keeping with RTE's goal to promote the follow-up over time of the evolution of reliability in its various aspects. RTE thus aims to contribute to the development of reliability culture, by encouraging an improved assessment by the different players (both RTE and network users) of the role they play in building reliability, and by advocating the taking into account of reliability and benchmarking in the European organisations of Transmission System Operators. Contents: 1 - Brief overview of the evolution of the internal and external environment; 2 - Operating situations encountered: climatic conditions, supply / demand balance management, operation of interconnections, management of internal congestion, contingencies affecting the transmission facilities; 3 - Evolution of the reliability reference guide: external reference guide: directives, laws, decrees, etc, ETSO, UCTE, ENTSO-E, contracting contributing to reliability, RTE internal reference guide; 4 - Evolution of measures contributing to reliability in the equipment field: intrinsic performances of components (generating sets, protection systems, operation PLC's, instrumentation and control, automatic frequency and voltage controls, transmission facilities, control systems, load

  9. Human reliability assessment in context

    International Nuclear Information System (INIS)

    Hollnagel, Erik

    2005-01-01

    Human Reliability Assessment (HRA) is conducted on the unspoken premise that 'human error' is a meaningful concept and that it can be associated with individual actions. The basis for this assumption it found in the origin of HRA, as a necessary extension of PSA to account for the impact of failures emanating from human actions. Although it was natural to model HRA on PSA, a large number of studies have shown that the premises are wrong, specifically that human and technological functions cannot be decomposed in the same manner. The general experience from accident studies also indicates that action failures are a function of the context, and that it is the variability of the context rather than the 'human error probability' that is the much sought for signal. Accepting this will have significant consequences for the way in which HRA, and ultimately also PSA, should be pursued

  10. An assessment of the reliability of the Ontario electricity system : 18-month outlook from April 2004 to September 2005

    International Nuclear Information System (INIS)

    2004-01-01

    This report presents a resource assessment by the Independent Electricity Market Operator (IMO) for the 18-month period from April 2004 to September 2005. It is based on the IMO's forecast of electricity demand. The information was provided by power generators in Ontario. The outlook for the electricity system has improved due to the return to service of 3 nuclear units and the addition of more than 700 MW of generation. The return to service of the nuclear units has decreased Ontario's reliance on imports to help meet energy demand in the province. The shutdown of 1150 MW of coal-fired generation at Lakeview Thermal Generating Station in Mississauga emphasizes the importance of improving transmission and generation capacity in the Toronto area. This report also includes updated values for existing resource scenarios and planned resource scenarios. The reliability of Ontario's transmission system was also assessed along with the adequacy of the existing resource to meet the forecast demand. The existing installed generation resources include 5 nuclear stations generating 10,831 MW of electricity, 5 coal stations generating 7,564 MW of electricity, 22 oil and gas fired stations generating 4,364 MW of electricity, 61 hydroelectric stations generating 7,676 MW of electricity, and 2 other stations generating 66 MW of electricity. Although the existing resource scenario is better than in previous reports, imports will be required under extreme weather conditions to help meet electricity demand in Ontario during peak periods. 21 tabs., 10 figs

  11. Reliable inverter systems

    Science.gov (United States)

    Nagano, S.

    1979-01-01

    Base driver with common-load-current feedback protects paralleled inverter systems from open or short circuits. Circuit eliminates total system oscillation that can occur in conventional inverters because of open circuit in primary transformer winding. Common feedback signal produced by functioning modules forces operating frequency of failed module to coincide with clock drive so module resumes normal operating frequency in spite of open circuit.

  12. Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE), Version 5.0. Volume 5, Systems Analysis and Risk Assessment (SARA) tutorial manual

    International Nuclear Information System (INIS)

    Sattison, M.B.; Russell, K.D.; Skinner, N.L.

    1994-07-01

    The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) refers to a set of several microcomputer programs that were developed to create and analyze probabilistic risk assessments (PRAs) primarily for nuclear power plants. This volume is the tutorial manual for the Systems Analysis and Risk Assessment (SARA) System Version 5.0, a microcomputer-based system used to analyze the safety issues of a open-quotes familyclose quotes [i.e., a power plant, a manufacturing facility, any facility on which a probabilistic risk assessment (PRA) might be performed]. A series of lessons is provided that guides the user through some basic steps common to most analyses performed with SARA. The example problems presented in the lessons build on one another, and in combination, lead the user through all aspects of SARA sensitivity analysis capabilities

  13. Innovations in power systems reliability

    CERN Document Server

    Santora, Albert H; Vaccaro, Alfredo

    2011-01-01

    Electrical grids are among the world's most reliable systems, yet they still face a host of issues, from aging infrastructure to questions of resource distribution. Here is a comprehensive and systematic approach to tackling these contemporary challenges.

  14. On Bayesian System Reliability Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen Ringi, M.

    1995-05-01

    The view taken in this thesis is that reliability, the probability that a system will perform a required function for a stated period of time, depends on a person`s state of knowledge. Reliability changes as this state of knowledge changes, i.e. when new relevant information becomes available. Most existing models for system reliability prediction are developed in a classical framework of probability theory and they overlook some information that is always present. Probability is just an analytical tool to handle uncertainty, based on judgement and subjective opinions. It is argued that the Bayesian approach gives a much more comprehensive understanding of the foundations of probability than the so called frequentistic school. A new model for system reliability prediction is given in two papers. The model encloses the fact that component failures are dependent because of a shared operational environment. The suggested model also naturally permits learning from failure data of similar components in non identical environments. 85 refs.

  15. On Bayesian System Reliability Analysis

    International Nuclear Information System (INIS)

    Soerensen Ringi, M.

    1995-01-01

    The view taken in this thesis is that reliability, the probability that a system will perform a required function for a stated period of time, depends on a person's state of knowledge. Reliability changes as this state of knowledge changes, i.e. when new relevant information becomes available. Most existing models for system reliability prediction are developed in a classical framework of probability theory and they overlook some information that is always present. Probability is just an analytical tool to handle uncertainty, based on judgement and subjective opinions. It is argued that the Bayesian approach gives a much more comprehensive understanding of the foundations of probability than the so called frequentistic school. A new model for system reliability prediction is given in two papers. The model encloses the fact that component failures are dependent because of a shared operational environment. The suggested model also naturally permits learning from failure data of similar components in non identical environments. 85 refs

  16. Concurrent validity and test-retest reliability of a global positioning system (GPS) and timing gates to assess sprint performance variables.

    Science.gov (United States)

    Waldron, Mark; Worsfold, Paul; Twist, Craig; Lamb, Kevin

    2011-12-01

    There has been no previous investigation of the concurrent validity and reliability of the current 5 Hz global positioning system (GPS) to assess sprinting speed or the reliability of integrated GPS-accelerometer technology. In the present study, we wished to determine: (1) the concurrent validity and reliability of a GPS and timing gates to measure sprinting speed or distance, and (2) the reliability of proper accelerations recorded via GPS-accelerometer integration. Nineteen elite youth rugby league players performed two over-ground sprints and were simultaneously assessed using GPS and timing gates. The GPS measurements systematically underestimated both distance and timing gate speed. The GPS measurements were reliable for all variables of distance and speed (coefficient of variation [CV] = 1.62% to 2.3%), particularly peak speed (95% limits of agreement [LOA] = 0.00 ± 0.8 km · h(-1); CV = 0.78%). Timing gates were more reliable (CV = 1% to 1.54%) than equivalent GPS measurements. Accelerometer measurements were least reliable (CV = 4.69% to 5.16%), particularly for the frequency of proper accelerations (95% LOA = 1.00 ± 5.43; CV = 14.12%). Timing gates and GPS were found to reliably assess speed and distance, although the validity of the GPS remains questionable. The error found in accelerometer measurements indicates the limits of this device for detecting changes in performance.

  17. The Reliability of Classification Decisions for the Furtado-Gallagher Computerized Observational Movement Pattern Assessment System--FG-COMPASS

    Science.gov (United States)

    Furtado, Ovande, Jr.; Gallagher, Jere D.

    2012-01-01

    Mastery of fundamental movement skills (FMS) is an important factor in preventing weight gain and increasing physical activity. To master FMS, performance evaluation is necessary. In this study, we investigated the reliability of a new observational assessment tool. In Phase I, 110 video clips of children performing five locomotor, and six…

  18. Automated reliability assessment for spectroscopic redshift measurements

    Science.gov (United States)

    Jamal, S.; Le Brun, V.; Le Fèvre, O.; Vibert, D.; Schmitt, A.; Surace, C.; Copin, Y.; Garilli, B.; Moresco, M.; Pozzetti, L.

    2018-03-01

    Context. Future large-scale surveys, such as the ESA Euclid mission, will produce a large set of galaxy redshifts (≥106) that will require fully automated data-processing pipelines to analyze the data, extract crucial information and ensure that all requirements are met. A fundamental element in these pipelines is to associate to each galaxy redshift measurement a quality, or reliability, estimate. Aim. In this work, we introduce a new approach to automate the spectroscopic redshift reliability assessment based on machine learning (ML) and characteristics of the redshift probability density function. Methods: We propose to rephrase the spectroscopic redshift estimation into a Bayesian framework, in order to incorporate all sources of information and uncertainties related to the redshift estimation process and produce a redshift posterior probability density function (PDF). To automate the assessment of a reliability flag, we exploit key features in the redshift posterior PDF and machine learning algorithms. Results: As a working example, public data from the VIMOS VLT Deep Survey is exploited to present and test this new methodology. We first tried to reproduce the existing reliability flags using supervised classification in order to describe different types of redshift PDFs, but due to the subjective definition of these flags (classification accuracy 58%), we soon opted for a new homogeneous partitioning of the data into distinct clusters via unsupervised classification. After assessing the accuracy of the new clusters via resubstitution and test predictions (classification accuracy 98%), we projected unlabeled data from preliminary mock simulations for the Euclid space mission into this mapping to predict their redshift reliability labels. Conclusions: Through the development of a methodology in which a system can build its own experience to assess the quality of a parameter, we are able to set a preliminary basis of an automated reliability assessment for

  19. Component reliability for electronic systems

    CERN Document Server

    Bajenescu, Titu-Marius I

    2010-01-01

    The main reason for the premature breakdown of today's electronic products (computers, cars, tools, appliances, etc.) is the failure of the components used to build these products. Today professionals are looking for effective ways to minimize the degradation of electronic components to help ensure longer-lasting, more technically sound products and systems. This practical book offers engineers specific guidance on how to design more reliable components and build more reliable electronic systems. Professionals learn how to optimize a virtual component prototype, accurately monitor product reliability during the entire production process, and add the burn-in and selection procedures that are the most appropriate for the intended applications. Moreover, the book helps system designers ensure that all components are correctly applied, margins are adequate, wear-out failure modes are prevented during the expected duration of life, and system interfaces cannot lead to failure.

  20. System Reliability of Timber Structures

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard

    2010-01-01

    For reduction of the risk of collapse in the event of loss of structural element(s), a structural engineer may take necessary steps to design a collapse-resistant structure that is insensitive to accidental circumstances e.g. by incorporating characteristics like redundancy, ties, ductility, key ...... elements, alternate load path(s) etc. in the structural design. In general these characteristics can have a positive influence on system reliability of a structure however, in Eurocodes ductility is only awarded for concrete and steel structures but not for timber structures. It is well......-called statical system effect, will usually increase the reliability of the whole structural system and give an extra safety margin compared to the deterministic code results. The aim of this fact sheet is to outline the relationship between system reliability and the characteristics ductility and redundancy....

  1. Reliability Assessment of an Innovative Wound Score.

    Science.gov (United States)

    Strauss, Michael B; Moon, Hojin; Busch, Jeremy A; Jones, Christopher K; Nhan, Lisa; Miller, Stuart; Le, Phi-Nga Jeannie

    2016-06-01

    The authors describe an innovative wound score and demonstrate its versatility for scoring a variety of wound types in addition to diabetic foot ulcers (DFUs). To further test its merits, they determined its interobserver reliability in a prospective series of patients. The Wound Score system the authors created integrates the most important features of 4 predominantly used wound scoring systems. It utilizes a logical 0 to 10 format based on 5 assessments each graded from 2 (best) to 0 (worst). The versatility and reliability of the Wound Score were studied in a prospective series of 94 patients with lower extremity wounds. The Wound Score was quick to determine, applicable to a variety of wound types and locations, and highly objective for grading the severity of each of the 5 assessments. The Wound Score categorized wound types as "healthy," "problem," or "futile" for evaluation and management. Diabetes was present in 75.9%, with 70% of the DFUs scoring in the "problem" wound range. Interobserver reli- ability was high (r = 0.81). The objectivity, versatility, and reliability of the Wound Score system facilitates making decisions about the management of wounds, whether DFUs or not, and provides quantification for compara- tive effectiveness research for wound management.

  2. Methodology for reliability based condition assessment

    International Nuclear Information System (INIS)

    Mori, Y.; Ellingwood, B.

    1993-08-01

    Structures in nuclear power plants may be exposed to aggressive environmental effects that cause their strength to decrease over an extended period of service. A major concern in evaluating the continued service for such structures is to ensure that in their current condition they are able to withstand future extreme load events during the intended service life with a level of reliability sufficient for public safety. This report describes a methodology to facilitate quantitative assessments of current and future structural reliability and performance of structures in nuclear power plants. This methodology takes into account the nature of past and future loads, and randomness in strength and in degradation resulting from environmental factors. An adaptive Monte Carlo simulation procedure is used to evaluate time-dependent system reliability. The time-dependent reliability is sensitive to the time-varying load characteristics and to the choice of initial strength and strength degradation models but not to correlation in component strengths within a system. Inspection/maintenance strategies are identified that minimize the expected future costs of keeping the failure probability of a structure at or below an established target failure probability during its anticipated service period

  3. Concurrent Validity and Test-retest Reliability of the OPTOGait Photoelectric Cell System for the Assessment of Spatio-temporal Parameters of the Gait of Young Adults.

    Science.gov (United States)

    Lee, Myung Mo; Song, Chang Ho; Lee, Kyoung Jin; Jung, Sang Woo; Shin, Doo Chul; Shin, Seung Ho

    2014-01-01

    [Purpose] The purpose of this study was to investigate the concurrent validity and test-retest reliability of the recently introduced OPTOGait Photoelectric Cell System for the assessment of spatio-temporal parameters of gait. [Subjects] Twenty healthy young adults (mean age = 27.35, SD = 7.4) were asked to walk 3 times on walkway at a comfortable speed. [Methods] Concurrent validity was assessed by comparing data obtained using the OPTOGait and GAITRite systems, and reliability was assessed by comparing data from the first and third OPTOGait sessions. [Results] Concurrent validity, as identified by intra-class correlation coefficients (ICC (2, 1) = 0.929-0.998), coefficients of variation (CVME = 0.32-11.30%), and 95% limits of agreement, showed high levels of correlation. In addition, the test-retest reliability of the OPTOGait Photoelectric Cell System was demonstrated as showing a high level of correlation with all spatio-temporal parameters by intra-class correlation coefficients (ICC (3, 1) = 0.785-0.952), coefficients of variation (CVME = 1.66-4.06%), 95% limits of agreement, standard error of measurement (SEM = 2.17-5.96%), and minimum detectable change (MDC95% = 6.01-16.52%). [Conclusion] The OPTOGait Photoelectric Cell System has strong concurrent validity along with relative and absolute test-retest reliabilities. This portable system with easy-to-use features can be used for clinical assessments or research purposes as an objective means of assessing gait.

  4. On Component Reliability and System Reliability for Space Missions

    Science.gov (United States)

    Chen, Yuan; Gillespie, Amanda M.; Monaghan, Mark W.; Sampson, Michael J.; Hodson, Robert F.

    2012-01-01

    This paper is to address the basics, the limitations and the relationship between component reliability and system reliability through a study of flight computing architectures and related avionics components for NASA future missions. Component reliability analysis and system reliability analysis need to be evaluated at the same time, and the limitations of each analysis and the relationship between the two analyses need to be understood.

  5. Random Fuzzy Extension of the Universal Generating Function Approach for the Reliability Assessment of Multi-State Systems Under Aleatory and Epistemic Uncertainties

    DEFF Research Database (Denmark)

    Li, Yan-Fu; Ding, Yi; Zio, Enrico

    2014-01-01

    . In this work, we extend the traditional universal generating function (UGF) approach for multi-state system (MSS) availability and reliability assessment to account for both aleatory and epistemic uncertainties. First, a theoretical extension, named hybrid UGF (HUGF), is made to introduce the use of random...... allow quantifying different levels of imprecision in system availability and reliability estimation. The HUGF approach is demonstrated with a numerical example, and applied to study a distributed generation system, with a comparison to the widely used Monte Carlo simulation method....

  6. System reliability of corroding pipelines

    International Nuclear Information System (INIS)

    Zhou Wenxing

    2010-01-01

    A methodology is presented in this paper to evaluate the time-dependent system reliability of a pipeline segment that contains multiple active corrosion defects and is subjected to stochastic internal pressure loading. The pipeline segment is modeled as a series system with three distinctive failure modes due to corrosion, namely small leak, large leak and rupture. The internal pressure is characterized as a simple discrete stochastic process that consists of a sequence of independent and identically distributed random variables each acting over a period of one year. The magnitude of a given sequence follows the annual maximum pressure distribution. The methodology is illustrated through a hypothetical example. Furthermore, the impact of the spatial variability of the pressure loading and pipe resistances associated with different defects on the system reliability is investigated. The analysis results suggest that the spatial variability of pipe properties has a negligible impact on the system reliability. On the other hand, the spatial variability of the internal pressure, initial defect sizes and defect growth rates can have a significant impact on the system reliability.

  7. Operational human performance reliability assessment (OHPRA)

    International Nuclear Information System (INIS)

    Haas, P.M.; Swanson, P.J.; Connelly, E.M.

    1993-01-01

    Operational Human Performance Reliability Assessment (OHPRA) is an approach for assessing human performance that is being developed in response to demands from modern process industries for practical and effective tools to assess and improve human performance, and therefore overall system performance and safety. The single most distinguishing feature of the approach is that is defines human performance in open-quotes operationalclose quotes terms. OHPRA is focused not on generation of human error probabilities, but on practical analysis of human performance to aid management in (1) identifying open-quotes fixableclose quotes problems and (2) providing input on the importance and nature of potential improvements. Development of the model in progress uses a unique approach for eliciting expert strategies for assessing performance. A PC-based model incorporating this expertise is planned. A preliminary version of the approach has already been used successfully to identify practical human performance problems in reactor and chemical process plant operations

  8. Progress in Methodologies for the Assessment of Passive Safety System Reliability in Advanced Reactors. Results from the Coordinated Research Project on Development of Advanced Methodologies for the Assessment of Passive Safety Systems Performance in Advanced Reactors

    International Nuclear Information System (INIS)

    2014-09-01

    Strong reliance on inherent and passive design features has become a hallmark of many advanced reactor designs, including several evolutionary designs and nearly all advanced small and medium sized reactor (SMR) designs. Advanced nuclear reactor designs incorporate several passive systems in addition to active ones — not only to enhance the operational safety of the reactors but also to eliminate the possibility of serious accidents. Accordingly, the assessment of the reliability of passive safety systems is a crucial issue to be resolved before their extensive use in future nuclear power plants. Several physical parameters affect the performance of a passive safety system, and their values at the time of operation are unknown a priori. The functions of passive systems are based on basic physical laws and thermodynamic principals, and they may not experience the same kind of failures as active systems. Hence, consistent efforts are required to qualify the reliability of passive systems. To support the development of advanced nuclear reactor designs with passive systems, investigations into their reliability using various methodologies are being conducted in several Member States with advanced reactor development programmes. These efforts include reliability methods for passive systems by the French Atomic Energy and Alternative Energies Commission, reliability evaluation of passive safety system by the University of Pisa, Italy, and assessment of passive system reliability by the Bhabha Atomic Research Centre, India. These different approaches seem to demonstrate a consensus on some aspects. However, the developers of the approaches have been unable to agree on the definition of reliability in a passive system. Based on these developments and in order to foster collaboration, the IAEA initiated the Coordinated Research Project (CRP) on Development of Advanced Methodologies for the Assessment of Passive Safety Systems Performance in Advanced Reactors in 2008. The

  9. Reliability demonstration of imaging surveillance systems

    International Nuclear Information System (INIS)

    Sheridan, T.F.; Henderson, J.T.; MacDiarmid, P.R.

    1979-01-01

    Security surveillance systems which employ closed circuit television are being deployed with increasing frequency for the protection of property and other valuable assets. A need exists to demonstrate the reliability of such systems before their installation to assure that the deployed systems will operate when needed with only the scheduled amount of maintenance and support costs. An approach to the reliability demonstration of imaging surveillance systems which employ closed circuit television is described. Failure definitions based on industry television standards and imaging alarm assessment criteria for surveillance systems are discussed. Test methods which allow 24 hour a day operation without the need for numerous test scenarios, test personnel and elaborate test facilities are presented. Existing reliability demonstration standards are shown to apply which obviate the need for elaborate statistical tests. The demonstration methods employed are shown to have applications in other types of imaging surveillance systems besides closed circuit television

  10. Reliability Assessment of Wave Energy Devices

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten; Kofoed, Jens Peter

    2012-01-01

    This paper focuses on reliability assessment of Wave Energy Device (WED) substructures with respect to fatigue loading. Failure due to fatigue is an important failure mode of most offshore structures. The focus of the fatigue reliability assessment is in this paper on welded details in steel...

  11. Quantitative assessment of probability of failing safely for the safety instrumented system using reliability block diagram method

    International Nuclear Information System (INIS)

    Jin, Jianghong; Pang, Lei; Zhao, Shoutang; Hu, Bin

    2015-01-01

    Highlights: • Models of PFS for SIS were established by using the reliability block diagram. • The more accurate calculation of PFS for SIS can be acquired by using SL. • Degraded operation of complex SIS does not affect the availability of SIS. • The safe undetected failure is the largest contribution to the PFS of SIS. - Abstract: The spurious trip of safety instrumented system (SIS) brings great economic losses to production. How to ensure the safety instrumented system is reliable and available has been put on the schedule. But the existing models on spurious trip rate (STR) or probability of failing safely (PFS) are too simplified and not accurate, in-depth studies of availability to obtain more accurate PFS for SIS are required. Based on the analysis of factors that influence the PFS for the SIS, using reliability block diagram method (RBD), the quantitative study of PFS for the SIS is carried out, and gives some application examples. The results show that, the common cause failure will increase the PFS; degraded operation does not affect the availability of the SIS; if the equipment was tested and repaired one by one, the unavailability of the SIS can be ignored; the corresponding occurrence time of independent safe undetected failure should be the system lifecycle (SL) rather than the proof test interval and the independent safe undetected failure is the largest contribution to the PFS for the SIS

  12. Dependent systems reliability estimation by structural reliability approach

    DEFF Research Database (Denmark)

    Kostandyan, Erik; Sørensen, John Dalsgaard

    2014-01-01

    Estimation of system reliability by classical system reliability methods generally assumes that the components are statistically independent, thus limiting its applicability in many practical situations. A method is proposed for estimation of the system reliability with dependent components, where...... the leading failure mechanism(s) is described by physics of failure model(s). The proposed method is based on structural reliability techniques and accounts for both statistical and failure effect correlations. It is assumed that failure of any component is due to increasing damage (fatigue phenomena...... identification. Application of the proposed method can be found in many real world systems....

  13. Designing magnetic systems for reliability

    International Nuclear Information System (INIS)

    Heitzenroeder, P.J.

    1991-01-01

    Designing magnetic system is an iterative process in which the requirements are set, a design is developed, materials and manufacturing processes are defined, interrelationships with the various elements of the system are established, engineering analyses are performed, and fault modes and effects are studied. Reliability requires that all elements of the design process, from the seemingly most straightforward such as utilities connection design and implementation, to the most sophisticated such as advanced finite element analyses, receives a balanced and appropriate level of attention. D.B. Montgomery's study of magnet failures has shown that the predominance of magnet failures tend not to be in the most intensively engineered areas, but are associated with insulation, leads, ad unanticipated conditions. TFTR, JET, JT-60, and PBX are all major tokamaks which have suffered loss of reliability due to water leaks. Similarly the majority of causes of loss of magnet reliability at PPPL has not been in the sophisticated areas of the design but are due to difficulties associated with coolant connections, bus connections, and external structural connections. Looking towards the future, the major next-devices such as BPX and ITER are most costly and complex than any of their predecessors and are pressing the bounds of operating levels, materials, and fabrication. Emphasis on reliability is a must as the fusion program enters a phase where there are fewer, but very costly devices with the goal of reaching a reactor prototype stage in the next two or three decades. This paper reviews some of the magnet reliability issues which PPPL has faced over the years the lessons learned from them, and magnet design and fabrication practices which have been found to contribute to magnet reliability

  14. Functional Gait Assessment and Balance Evaluation System Test: Reliability, Validity, Sensitivity, and Specificity for Identifying Individuals With Parkinson Disease Who Fall

    Science.gov (United States)

    Leddy, Abigail L.; Crowner, Beth E.

    2011-01-01

    Background Gait impairments, balance impairments, and falls are prevalent in individuals with Parkinson disease (PD). Although the Berg Balance Scale (BBS) can be considered the reference standard for the determination of fall risk, it has a noted ceiling effect. Development of ceiling-free measures that can assess balance and are good at discriminating “fallers” from “nonfallers” is needed. Objective The purpose of this study was to compare the Functional Gait Assessment (FGA) and the Balance Evaluation Systems Test (BESTest) with the BBS among individuals with PD and evaluate the tests' reliability, validity, and discriminatory sensitivity and specificity for fallers versus nonfallers. Design This was an observational study of community-dwelling individuals with idiopathic PD. Methods The BBS, FGA, and BESTest were administered to 80 individuals with PD. Interrater reliability (n=15) was assessed by 3 raters. Test-retest reliability was based on 2 tests of participants (n=24), 2 weeks apart. Intraclass correlation coefficients (2,1) were used to calculate reliability, and Spearman correlation coefficients were used to assess validity. Cutoff points, sensitivity, and specificity were based on receiver operating characteristic plots. Results Test-retest reliability was .80 for the BBS, .91 for the FGA, and .88 for the BESTest. Interrater reliability was greater than .93 for all 3 tests. The FGA and BESTest were correlated with the BBS (r=.78 and r=.87, respectively). Cutoff scores to identify fallers were 47/56 for the BBS, 15/30 for the FGA, and 69% for the BESTest. The overall accuracy (area under the curve) for the BBS, FGA, and BESTest was .79, .80, and .85, respectively. Limitations Fall reports were retrospective. Conclusion Both the FGA and the BESTest have reliability and validity for assessing balance in individuals with PD. The BESTest is most sensitive for identifying fallers. PMID:21071506

  15. Human reliability in probabilistic safety assessments

    International Nuclear Information System (INIS)

    Nunez Mendez, J.

    1989-01-01

    Nowadays a growing interest in medioambiental aspects is detected in our country. It implies an assessment of the risk involved in the industrial processess and installations in order to determine if those are into the acceptable limits. In these safety assessments, among which PSA (Probabilistic Safety Assessments), can be pointed out the role played by the human being in the system is one of the more relevant subjects. (This relevance has been demostrated in the accidents happenned). However in Spain there aren't manuals specifically dedicated to asses the human contribution to risk in the frame of PSAs. This report aims to improve this situation providing: a) a theoretical background to help the reader in the understanding of the nature of the human error, b) a guide to carry out a Human Reliability Analysis and c) a selected overwiev of the techniques and methodologies currently applied in this area. (Author)

  16. Human Reliability in Probabilistic Safety Assessments

    International Nuclear Information System (INIS)

    Nunez Mendez, J.

    1989-01-01

    Nowadays a growing interest in environmental aspects is detected in our country. It implies an assessment of the risk involved in the industrial processes and installations in order to determine if those are into the acceptable limits. In these safety assessments, among which PSA (Probabilistic Safety Assessments), can be pointed out the role played by the human being in the system is one of the more relevant subjects (This relevance has been demonstrated in the accidents happened) . However, in Spain there aren't manuals specifically dedicated to asses the human contribution to risk in the frame of PSAs. This report aims to improve this situation providing: a) a theoretical background to help the reader in the understanding of the nature of the human error, b) a quid to carry out a Human Reliability Analysis and c) a selected overview of the techniques and methodologies currently applied in this area. (Author) 20 refs

  17. Modification of risk assessment value to test industry reliability

    Science.gov (United States)

    Sorooshian, Shahryar

    2015-05-01

    This paper is in a form of a technical note, in which modified method of industry reliability analysis is reviewed. This paper introduces a multi-expert approach group decision making analysis for Risk Assessment Value (RAV), which directly tests the reliability of the system (industry). A case of construction industry has been studied for verification of the method. Reviewed RAV modified technique helps to assess the value of industry reliability; and brings contribution to the body of risk management knowledge.

  18. Reliability: on the reproducibility of assessment data.

    Science.gov (United States)

    Downing, Steven M

    2004-09-01

    All assessment data, like other scientific experimental data, must be reproducible in order to be meaningfully interpreted. The purpose of this paper is to discuss applications of reliability to the most common assessment methods in medical education. Typical methods of estimating reliability are discussed intuitively and non-mathematically. Reliability refers to the consistency of assessment outcomes. The exact type of consistency of greatest interest depends on the type of assessment, its purpose and the consequential use of the data. Written tests of cognitive achievement look to internal test consistency, using estimation methods derived from the test-retest design. Rater-based assessment data, such as ratings of clinical performance on the wards, require interrater consistency or agreement. Objective structured clinical examinations, simulated patient examinations and other performance-type assessments generally require generalisability theory analysis to account for various sources of measurement error in complex designs and to estimate the consistency of the generalisations to a universe or domain of skills. Reliability is a major source of validity evidence for assessments. Low reliability indicates that large variations in scores can be expected upon retesting. Inconsistent assessment scores are difficult or impossible to interpret meaningfully and thus reduce validity evidence. Reliability coefficients allow the quantification and estimation of the random errors of measurement in assessments, such that overall assessment can be improved.

  19. PWR system reliability improvement activities

    International Nuclear Information System (INIS)

    Yoshikawa, Yuichiro

    1985-01-01

    In Japan lacking in energy resources, it is our basic energy policy to accelerate the development program of nuclear power, thereby reducing our dependence. As referred to in the foregoing, every effort has been exerted on our part to improve the PWR system reliability by dint of the so-called 'HOMEMADE' TQC activities, which is our brain-child as a result of applying to the energy industry the quality control philosophy developed in the field of manufacturing industry

  20. Reliability analysis and updating of deteriorating systems with subset simulation

    DEFF Research Database (Denmark)

    Schneider, Ronald; Thöns, Sebastian; Straub, Daniel

    2017-01-01

    An efficient approach to reliability analysis of deteriorating structural systems is presented, which considers stochastic dependence among element deterioration. Information on a deteriorating structure obtained through inspection or monitoring is included in the reliability assessment through B...

  1. Immodest Witnesses: Reliability and Writing Assessment

    Science.gov (United States)

    Gallagher, Chris W.

    2014-01-01

    This article offers a survey of three reliability theories in writing assessment: positivist, hermeneutic, and rhetorical. Drawing on an interdisciplinary investigation of the notion of "witnessing," this survey emphasizes the kinds of readers and readings each theory of reliability produces and the epistemological grounds on which it…

  2. Reliability evaluation of a natural circulation system

    International Nuclear Information System (INIS)

    Jafari, Jalil; D'Auria, Francesco; Kazeminejad, Hossein; Davilu, Hadi

    2003-01-01

    This paper discusses a reliability study performed with reference to a passive thermohydraulic natural circulation (NC) system, named TTL-1. A methodology based on probabilistic techniques has been applied with the main purpose to optimize the system design. The obtained results have been adopted to estimate the thermal-hydraulic reliability (TH-R) of the same system. A total of 29 relevant parameters (including nominal values and plausible ranges of variations) affecting the design and the NC performance of the TTL-1 loop are identified and a probability of occurrence is assigned for each value based on expert judgment. Following procedures established for the uncertainty evaluation of thermal-hydraulic system codes results, 137 system configurations have been selected and each configuration has been analyzed via the Relap5 best-estimate code. The reference system configuration and the failure criteria derived from the 'mission' of the passive system are adopted for the evaluation of the system TH-R. Four different definitions of a less-than-unity 'reliability-values' (where unity represents the maximum achievable reliability) are proposed for the performance of the selected passive system. This is normally considered fully reliable, i.e. reliability-value equal one, in typical Probabilistic Safety Assessment (PSA) applications in nuclear reactor safety. The two 'point' TH-R values for the considered NC system were found equal to 0.70 and 0.85, i.e. values comparable with the reliability of a pump installed in an 'equivalent' forced circulation (active) system having the same 'mission'. The design optimization study was completed by a regression analysis addressing the output of the 137 calculations: heat losses, undetected leakage, loop length, riser diameter, and equivalent diameter of the test section have been found as the most important parameters bringing to the optimal system design and affecting the TH-R. As added values for this work, the comparison has

  3. Model of reliability assessment in ultrasonic nondestructive inspection

    International Nuclear Information System (INIS)

    Park, Ik Keun; Park, Un Su; Kim, Hyun Mook; Park, Yoon Won; Kang, Suk Chull; Choi, Young Hwan; Lee, Jin Ho

    2001-01-01

    Ultrasonic inspection system is consisted of the operator, equipment and procedure. The reliability of results in ultrasonic inspection is affected by its ability. Furthermore, the reliability of nondestructive testing is influenced by the inspection environment, other materials and types of defect. Therefore, it is very difficult to estimate the reliability of NDT due to various factors. In this study, the probability of detection, used logistic probability model and Monte Carlo simulation, estimated the reliability of ultrasonic inspection. The utility of the NDT reliability assessment is verified by the analysis of the data from round robin test applied these models

  4. Assessing software quality at each step of its life-cycle to enhance reliability of control systems

    International Nuclear Information System (INIS)

    Hardion, V.; Buteau, A.; Leclercq, N.; Abeille, G.; Pierre-Joseph, Z.; Le, S.

    2012-01-01

    A distributed software control system aims to enhance the upgrade ability and reliability by sharing responsibility between several components. The disadvantage is that it makes it harder to detect problems on a significant number of modules. With Kaizen in mind we have chosen to continuously invest in automation to obtain a complete overview of software quality despite the growth of legacy code. The development process has already been mastered by staging each life-cycle step thanks to a continuous integration server based on JENKINS and MAVEN. We enhanced this process, focusing on 3 objectives: Automatic Test, Static Code Analysis and Post-Mortem Supervision. Now, the build process automatically includes a test section to detect regressions, incorrect behaviour and integration incompatibility. The in-house TANGOUNIT project satisfies the difficulties of testing distributed components such as Tango Devices. In the next step, the programming code has to pass a complete code quality check-up. The SONAR quality server has been integrated in the process, to collect each static code analysis and display the hot topics on summary web pages. Finally, the integration of Google BREAKPAD in every TANGO Devices gives us essential statistics from crash reports and enables us to replay the crash scenarios at any time. We have already gained greater visibility on current developments. Some concrete results will be presented including reliability enhancement, better management of subcontracted software development, quicker adoption of coding standards by new developers and understanding of impacts when moving to a new technology. (authors)

  5. Jet reliability study Survey and Risk Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Esteban, G.

    2015-07-01

    Culham Center for Fusion Energy (CCFE) in UK has been contracted to undertake a second Deuterium-Tritium Experiment (DTE2) using Join European Torus (JET) in 2017, in support of technical developments for the ITER project. In order to manage risks of delay or early project termination CCFE has adopted a risk based inspection (RBI) process to identify the systems which could influence the successful delivery of DTE2 and in turn to identify by a basic risk assessment process those systems or components which require mitigating action in order to minimize risk. In this context, the primary purpose of the RBI is to address issues of reliability and satisfactory functionality in a similar way to that which a power plant operator would take to address its commercial risks in the event of loss of generating capacity. The objective of this presentation is describe the activities developed for Idom to deliver the survey, interviews and risk assessment of different systems of JET with the aim to identify the critical components and system that could affect the operation of JET during the DTE2 experiment. (Author)

  6. Hot Spot Temperature and Grey Target Theory-Based Dynamic Modelling for Reliability Assessment of Transformer Oil-Paper Insulation Systems: A Practical Case Study

    Directory of Open Access Journals (Sweden)

    Lefeng Cheng

    2018-01-01

    Full Text Available This paper develops a novel dynamic correction method for the reliability assessment of large oil-immersed power transformers. First, with the transformer oil-paper insulation system (TOPIS as the target of evaluation and the winding hot spot temperature (HST as the core point, an HST-based static ageing failure model is built according to the Weibull distribution and Arrhenius reaction law, in order to describe the transformer ageing process and calculate the winding HST for obtaining the failure rate and life expectancy of TOPIS. A grey target theory based dynamic correction model is then developed, combined with the data of Dissolved Gas Analysis (DGA in power transformer oil, in order to dynamically modify the life expectancy calculated by the built static model, such that the corresponding relationship between the state grade and life expectancy correction coefficient of TOPIS can be built. Furthermore, the life expectancy loss recovery factor is introduced to correct the life expectancy of TOPIS again. Lastly, a practical case study of an operating transformer has been undertaken, in which the failure rate curve after introducing dynamic corrections can be obtained for the reliability assessment of this transformer. The curve shows a better ability of tracking the actual reliability level of transformer, thus verifying the validity of the proposed method and providing a new way for transformer reliability assessment. This contribution presents a novel model for the reliability assessment of TOPIS, in which the DGA data, as a source of information for the dynamic correction, is processed based on the grey target theory, thus the internal faults of power transformer can be diagnosed accurately as well as its life expectancy updated in time, ensuring that the dynamic assessment values can commendably track and reflect the actual operation state of the power transformers.

  7. Reliability of Power Electronic Converter Systems

    DEFF Research Database (Denmark)

    for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power......-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....

  8. An approach for assessing human decision reliability

    International Nuclear Information System (INIS)

    Pyy, P.

    2000-01-01

    This paper presents a method to study human reliability in decision situations related to nuclear power plant disturbances. Decisions often play a significant role in handling of emergency situations. The method may be applied to probabilistic safety assessments (PSAs) in cases where decision making is an important dimension of an accident sequence. Such situations are frequent e.g. in accident management. In this paper, a modelling approach for decision reliability studies is first proposed. Then, a case study with two decision situations with relatively different characteristics is presented. Qualitative and quantitative findings of the study are discussed. In very simple decision cases with time pressure, time reliability correlation proved out to be a feasible reliability modelling method. In all other decision situations, more advanced probabilistic decision models have to be used. Finally, decision probability assessment by using simulator run results and expert judgement is presented

  9. Reliability assessment based on subjective inferences

    International Nuclear Information System (INIS)

    Ma Zhibo; Zhu Jianshi; Xu Naixin

    2003-01-01

    The reliability information which comes from subjective analysis is often incomplete prior. This information can be generally assumed to exist in the form of either a stated prior mean of R (reliability) or a stated prior credibility interval on R. An efficient approach is developed to determine a complete beta prior distribution from the subjective information according to the principle of maximum entropy, and the the reliability of survival/failure product is assessed via Bayes theorem. Numerical examples are presented to illustrate the methods

  10. Reliability models for Space Station power system

    Science.gov (United States)

    Singh, C.; Patton, A. D.; Kim, Y.; Wagner, H.

    1987-01-01

    This paper presents a methodology for the reliability evaluation of Space Station power system. The two options considered are the photovoltaic system and the solar dynamic system. Reliability models for both of these options are described along with the methodology for calculating the reliability indices.

  11. Reliability and protection against failure in computer systems

    International Nuclear Information System (INIS)

    Daniels, B.K.

    1979-01-01

    Computers are being increasingly integrated into the control and safety systems of large and potentially hazardous industrial processes. This development introduces problems which are particular to computer systems and opens the way to new techniques of solving conventional reliability and availability problems. References to the developing fields of software reliability, human factors and software design are given, and these subjects are related, where possible, to the quantified assessment of reliability. Original material is presented in the areas of reliability growth and computer hardware failure data. The report draws on the experience of the National Centre of Systems Reliability in assessing the capability and reliability of computer systems both within the nuclear industry, and from the work carried out in other industries by the Systems Reliability Service. (author)

  12. Reliability engineering for nuclear and other high technology systems

    International Nuclear Information System (INIS)

    Lakner, A.A.; Anderson, R.T.

    1985-01-01

    This book is written for the reliability instructor, program manager, system engineer, design engineer, reliability engineer, nuclear regulator, probability risk assessment (PRA) analyst, general manager and others who are involved in system hardware acquisition, design and operation and are concerned with plant safety and operational cost-effectiveness. It provides criteria, guidelines and comprehensive engineering data affecting reliability; it covers the key aspects of system reliability as it relates to conceptual planning, cost tradeoff decisions, specification, contractor selection, design, test and plant acceptance and operation. It treats reliability as an integrated methodology, explicitly describing life cycle management techniques as well as the basic elements of a total hardware development program, including: reliability parameters and design improvement attributes, reliability testing, reliability engineering and control. It describes how these elements can be defined during procurement, and implemented during design and development to yield reliable equipment. (author)

  13. Human reliability. Is probabilistic human reliability assessment possible?

    International Nuclear Information System (INIS)

    Mosneron Dupin, F.

    1996-01-01

    The possibility of carrying out Probabilistic Human Reliability Assessments (PHRA) is often doubted. Basing ourselves on the experience Electricite de France (EDF) has acquired in Probabilistic Safety Assessments for nuclear power plants, we show why the uncertainty of PHRA is very high. We then specify the limits of generic data and models for PHRA: very important factors are often poorly taken into account. To account for them, you need to have proper understanding of the actual context in which operators work. This demands surveys on the field (power plant and simulator) all of which must be carried out with behaviours science skills. The idea of estimating the probabilities of operator failure must not be abandoned, but probabilities must be given less importance, for they are only approximate indications. The qualitative aspects of PHRA should be given greater value (analysis process and qualitative insights). That is why the description (illustrated by case histories) of the main mechanisms of human behaviour, and of their manifestations in the nuclear power plant context (in terms of habits, attitudes, and informal methods and organization in particular) should be an important part of PHRA handbooks. These handbooks should also insist more on methods for gathering information on the actual context of the work of operators. Under these conditions, the PHRA should be possible and even desirable as a process for systematic analysis and assessment of human intervention. (author). 24 refs, 2 figs, 1 tab

  14. Passive System Reliability Towards Efficient Methodology

    International Nuclear Information System (INIS)

    Sarathy, U. Partha; Arul, A. John; Ramakrishnan, M.

    2011-01-01

    Passive System Reliability-Features/Methods: ♦ Passive System: No pumps, no valves, no human intervention, no signals. Passive System Reliability: ♦ Depends only on functionality or inherent robustness of the process and design. ♦ Since active equipment is absent, reliability of functionality is the dominant factor. ♦ Various causes like uncertainty in design and critical parameters, design process, environment etc. needs to be accounted. ♦ Quantification methodology is uncertainty propagation and estimation of nominal failure probability (as in structural reliability studies)

  15. Reliability and Assessment Techniques on Ground Excavation

    Directory of Open Access Journals (Sweden)

    Sanga Tangchawal

    2009-05-01

    Full Text Available Planning and assessment on the excavation of the brittle materials (soil or rock can be done by using the machinery and/or explosives. The reliability assessment has been proposed to predict the failure of ground during excavation process. The stability planning on cutting soil (rock face by machinery can be compared between the deterministic and the statistical method. The risk of using explosives for rock excavation has to concern on the damage and environmental impacts after blasting events.

  16. Reliability of Power Electronic Converter Systems

    DEFF Research Database (Denmark)

    for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power...... electronic converter systems; anomaly detection and remaining-life prediction for power electronics; reliability of DC-link capacitors in power electronic converters; reliability of power electronics packaging; modeling for life-time prediction of power semiconductor modules; minimization of DC......-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...

  17. Sequential decision reliability concept and failure rate assessment

    International Nuclear Information System (INIS)

    Ciftcioglu, O.

    1990-11-01

    Conventionally, a reliability concept is considered together with both each basic unit and their integration in a complicated large scale system such as a nuclear power plant (NPP). Basically, as the plant's operational status is determined by the information obtained from various sensors, the plant's reliability and the risk assessment is closely related to the reliability of the sensory information and hence the sensor components. However, considering the relevant information-processing systems, e.g. fault detection processors, there exists a further question about the reliability of such systems, specifically the reliability of the systems' decision-based outcomes by means of which the further actions are performed. To this end, a general sequential decision reliability concept and the failure rate assessment methodology is introduced. The implications of the methodology are investigated and the importance of the decision reliability concept in system operation is demonstrated by means of sensory signals in real-time from the Borssele NPP in the Netherlands. (author). 21 refs.; 8 figs

  18. Lz-transform and inverse Lz-transform application to dynamic reliability assessment for multi-state system

    DEFF Research Database (Denmark)

    Lisnianski, A.; Ding, Y.

    2014-01-01

    in the paper proposed finding Lztransform of this output process, which is essentially simpler because of using Ushakov's universal generating operator. Some reliability indices such as availability, expected performance, etc. may be found from the expression of this Lztransform. In order to find other indices...

  19. Assessment of Accuracy and Reliability in Acetabular Cup Placement Using an iPhone/iPad System.

    Science.gov (United States)

    Kurosaka, Kenji; Fukunishi, Shigeo; Fukui, Tomokazu; Nishio, Shoji; Fujihara, Yuki; Okahisa, Shohei; Takeda, Yu; Daimon, Takashi; Yoshiya, Shinichi

    2016-07-01

    Implant positioning is one of the critical factors that influences postoperative outcome of total hip arthroplasty (THA). Malpositioning of the implant may lead to an increased risk of postoperative complications such as prosthetic impingement, dislocation, restricted range of motion, polyethylene wear, and loosening. In 2012, the intraoperative use of smartphone technology in THA for improved accuracy of acetabular cup placement was reported. The purpose of this study was to examine the accuracy of an iPhone/iPad-guided technique in positioning the acetabular cup in THA compared with the reference values obtained from the image-free navigation system in a cadaveric experiment. Five hips of 5 embalmed whole-body cadavers were used in the study. Seven orthopedic surgeons (4 residents and 3 senior hip surgeons) participated in the study. All of the surgeons examined each of the 5 hips 3 times. The target angle was 38°/19° for operative inclination/anteversion angles, which corresponded to radiographic inclination/anteversion angles of 40°/15°. The simultaneous assessment using the navigation system showed mean±SD radiographic alignment angles of 39.4°±2.6° and 16.4°±2.6° for inclination and anteversion, respectively. Assessment of cup positioning based on Lewinnek's safe zone criteria showed all of the procedures (n=105) achieved acceptable alignment within the safe zone. A comparison of the performances by resident and senior hip surgeons showed no significant difference between the groups (P=.74 for inclination and P=.81 for anteversion). The iPhone/iPad technique examined in this study could achieve acceptable performance in determining cup alignment in THA regardless of the surgeon's expertise. [Orthopedics. 2016; 39(4):e621-e626.]. Copyright 2016, SLACK Incorporated.

  20. The contribution of instrumentation and control software to system reliability

    International Nuclear Information System (INIS)

    Fryer, M.O.

    1984-01-01

    Advanced instrumentation and control systems are usually implemented using computers that monitor the instrumentation and issue commands to control elements. The control commands are based on instrument readings and software control logic. The reliability of the total system will be affected by the software design. When comparing software designs, an evaluation of how each design can contribute to the reliability of the system is desirable. Unfortunately, the science of reliability assessment of combined hardware and software systems is in its infancy. Reliability assessment of combined hardware/software systems is often based on over-simplified assumptions about software behavior. A new method of reliability assessment of combined software/hardware systems is presented. The method is based on a procedure called fault tree analysis which determines how component failures can contribute to system failure. Fault tree analysis is a well developed method for reliability assessment of hardware systems and produces quantitative estimates of failure probability based on component failure rates. It is shown how software control logic can be mapped into a fault tree that depicts both software and hardware contributions to system failure. The new method is important because it provides a way for quantitatively evaluating the reliability contribution of software designs. In many applications, this can help guide designers in producing safer and more reliable systems. An application to the nuclear power research industry is discussed

  1. Valid, Reliable, and Appropriate Assessments for Adult English Language Learners

    Science.gov (United States)

    Kenyon, Dorry; Van Duzer, Carol

    2003-01-01

    Ensuring that language tests for adult English language learners are appropriate, valid, and reliable is a challenge. Performance-based assessments are complex to develop and implement. Yet, because the focus of assessment, both in the National Reporting System for Adult Education (NRS) descriptors and in the Department of Education's definition…

  2. Reliability

    OpenAIRE

    Condon, David; Revelle, William

    2017-01-01

    Separating the signal in a test from the irrelevant noise is a challenge for all measurement. Low test reliability limits test validity, attenuates important relationships, and can lead to regression artifacts. Multiple approaches to the assessment and improvement of reliability are discussed. The advantages and disadvantages of several different approaches to reliability are considered. Practical advice on how to assess reliability using open source software is provided.

  3. The Reliability of Parkour Skills Assessment

    Directory of Open Access Journals (Sweden)

    Martin Dvořák

    2018-01-01

    Full Text Available The aim of the study was to determine the reliability of parkour skills assessment in field conditions. Twenty young men completed three trials of a parkour obstacle course on two separate days. The tested group consisted of 10 beginners (age 16 ± 1 years, body mass = 65 ± 12 kg, height = 177 ± 7 cm and 10 advanced traceurs (age 18 ± 2 years, body mass = 68 ± 14 kg, height = 178 ± 6 cm. The performance was video-recorded and subsequently analyzed by three raters (total score 0–45. Median and percentiles were used to characterize results from all sessions by all raters. Inter-rater, intra-session and inter-session reliability were assessed using Krippendorff’s α for ordinal data. The Mann-Whitney test was used to assess the differences between beginners and advanced traceurs. Advanced traceurs obtained a total score from 41 to 44 whilst beginners achieved 27 to 33 points. Krippendorff’s α for total score ranged from 0.910 to 0.916 between raters, 0.828 to 0.874 between trials, and from 0.839 to 0.924 between days. The proposed parkour course differentiated two different ability levels and the skills assessment demonstrated excellent reliability between raters, trials, and days.

  4. System Reliability Analysis Considering Correlation of Performances

    International Nuclear Information System (INIS)

    Kim, Saekyeol; Lee, Tae Hee; Lim, Woochul

    2017-01-01

    Reliability analysis of a mechanical system has been developed in order to consider the uncertainties in the product design that may occur from the tolerance of design variables, uncertainties of noise, environmental factors, and material properties. In most of the previous studies, the reliability was calculated independently for each performance of the system. However, the conventional methods cannot consider the correlation between the performances of the system that may lead to a difference between the reliability of the entire system and the reliability of the individual performance. In this paper, the joint probability density function (PDF) of the performances is modeled using a copula which takes into account the correlation between performances of the system. The system reliability is proposed as the integral of joint PDF of performances and is compared with the individual reliability of each performance by mathematical examples and two-bar truss example.

  5. Reliability assessment using the concept of possibility

    International Nuclear Information System (INIS)

    Ping, R.; Zhao, G.

    1994-01-01

    The role of the possibility theory in the quantitative approach to the reliability of large scale systems, in particular man-machine systems, is discussed. According to the original idea due to professor L.A. Zadeh, an error rate may be associated with a possibility distribution and a probability distribution. They describe the potentiallity and the actuality for error. This is especially important for the analysis of big accidents

  6. System reliability effects in wind turbine blades

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Friis-Hansen, Peter; Berggreen, Christian

    2012-01-01

    from reliability point of view. The present paper discusses the specifics of system reliability behavior of laminated composite sandwich panels, and solves an example system reliability problem for a glass fiber-reinforced composite sandwich structure subjected to in-plane compression.......Laminated composite sandwich panels have a layered structure, where individual layers have randomly varying stiffness and strength properties. The presence of multiple failure modes and load redistribution following partial failures are the reason for laminated composites to exhibit system behavior...

  7. Mass and Reliability System (MaRS)

    Science.gov (United States)

    Barnes, Sarah

    2016-01-01

    The Safety and Mission Assurance (S&MA) Directorate is responsible for mitigating risk, providing system safety, and lowering risk for space programs from ground to space. The S&MA is divided into 4 divisions: The Space Exploration Division (NC), the International Space Station Division (NE), the Safety & Test Operations Division (NS), and the Quality and Flight Equipment Division (NT). The interns, myself and Arun Aruljothi, will be working with the Risk & Reliability Analysis Branch under the NC Division's. The mission of this division is to identify, characterize, diminish, and communicate risk by implementing an efficient and effective assurance model. The team utilizes Reliability and Maintainability (R&M) and Probabilistic Risk Assessment (PRA) to ensure decisions concerning risks are informed, vehicles are safe and reliable, and program/project requirements are realistic and realized. This project pertains to the Orion mission, so it is geared toward a long duration Human Space Flight Program(s). For space missions, payload is a critical concept; balancing what hardware can be replaced by components verse by Orbital Replacement Units (ORU) or subassemblies is key. For this effort a database was created that combines mass and reliability data, called Mass and Reliability System or MaRS. The U.S. International Space Station (ISS) components are used as reference parts in the MaRS database. Using ISS components as a platform is beneficial because of the historical context and the environment similarities to a space flight mission. MaRS uses a combination of systems: International Space Station PART for failure data, Vehicle Master Database (VMDB) for ORU & components, Maintenance & Analysis Data Set (MADS) for operation hours and other pertinent data, & Hardware History Retrieval System (HHRS) for unit weights. MaRS is populated using a Visual Basic Application. Once populated, the excel spreadsheet is comprised of information on ISS components including

  8. Towards Reliable Integrated Services for Dependable Systems

    DEFF Research Database (Denmark)

    Schiøler, Henrik; Ravn, Anders Peter; Izadi-Zamanabadi, Roozbeh

    2003-01-01

    Reliability issues for various technical systems are discussed and focus is directed towards distributed systems, where communication facilities are vital to maintain system functionality. Reliability in communication subsystems is considered as a resource to be shared among a number of logical c...

  9. [Analysis of validity and reliability of three radiographic classification systems for preoperative assessment of bone stock loss in revision total hip arthroplasty].

    Science.gov (United States)

    Käfer, W; Fraitzl, C R; Kinkel, S; Puhl, W; Kessler, S

    2004-01-01

    It was the purpose of this prospective study to analyze validity and reliability of three different radiographic classification systems, which are used to assess bone stock loss prior to revision total hip arthroplasty. Investigation was performed using the classification systems according to 1) Paprosky et al., 2) Hungerford et al., and 3) the German Society of Orthopaedics and Traumatology (DGOT). Twenty-eight consecutive patients with diagnosis of aseptic failure of total hip arthroplasty were enrolled in the study. Interrater agreement was analyzed by evaluating the classifications preoperatively by three investigators with different level of clinical experience using a blinded observer technique. Validity was analyzed by comparison of preoperative radiographic findings (n = 3) and an intraoperative control by visualization and palpation (n = 1). Spearman coefficient of correlation (r(s)) was used to establish levels of agreement among multiple ordinal variables. Interrater reliability testing using paired comparison between the three investigators revealed non-homogeneous coefficients of correlation (r(s): Paprosky femur: 0.45 - 0.67, acetabulum: 0.38 - 0.63; Hungerford: 0.46 - 0.66; DGOT femur: 0.38 - 0.59, acetabulum: 0.42 - 0.76). Paired analysis of correlation between preoperative and intraoperative findings again showed non-homogeneous coefficients of correlation (r(s): Paprosky femur: 0.59 - 0.68, acetabulum: 0.39 - 0.70; Hungerford: 0.39 - 0.74; DGOT femur: 0.44 - 0.60, acetabulum: 0.36 - 0.76). In general, defects were grossly underestimated preoperatively. The level of experience did not influence the validity of measurements. Our results indicate that these classifications do not provide valid and reliable assessment of femoral and acetabular bone stock loss prior to revision total hip arthroplasty.

  10. PV Systems Reliability Final Technical Report.

    Energy Technology Data Exchange (ETDEWEB)

    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)

    2015-12-01

    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.

  11. Solid State Lighting Reliability Components to Systems

    CERN Document Server

    Fan, XJ

    2013-01-01

    Solid State Lighting Reliability: Components to Systems begins with an explanation of the major benefits of solid state lighting (SSL) when compared to conventional lighting systems including but not limited to long useful lifetimes of 50,000 (or more) hours and high efficacy. When designing effective devices that take advantage of SSL capabilities the reliability of internal components (optics, drive electronics, controls, thermal design) take on critical importance. As such a detailed discussion of reliability from performance at the device level to sub components is included as well as the integrated systems of SSL modules, lamps and luminaires including various failure modes, reliability testing and reliability performance. This book also: Covers the essential reliability theories and practices for current and future development of Solid State Lighting components and systems Provides a systematic overview for not only the state-of-the-art, but also future roadmap and perspectives of Solid State Lighting r...

  12. RELIABILITY ASSESSMENT OF A SUBSEA HIPPS

    OpenAIRE

    Stølen, Ellen Margrete

    2014-01-01

    Safety instrumented systems are vital in the oil and gas industry. A SIS consists of input elements, a logic solver and final elements. A High Integrity Pressure Protection System is an example of such a system. HIPPS is installed to protect a platform from too high pressure by shutting off the source before exceeding the design pressure. The IEC 61508 and IEC 61511 are used in the oil and gas industry during all phases of a SIS lifecycle. As a measure of SIS reliability, both standards use s...

  13. Reliability of large and complex systems

    CERN Document Server

    Kolowrocki, Krzysztof

    2014-01-01

    Reliability of Large and Complex Systems, previously titled Reliability of Large Systems, is an innovative guide to the current state and reliability of large and complex systems. In addition to revised and updated content on the complexity and safety of large and complex mechanisms, this new edition looks at the reliability of nanosystems, a key research topic in nanotechnology science. The author discusses the importance of safety investigation of critical infrastructures that have aged or have been exposed to varying operational conditions. This reference provides an asympt

  14. Are subjective assessments of snoring sounds reliable?

    Science.gov (United States)

    Rohrmeier, Christian; Fischer, René; Merz, Anne-Kathrin; Ettl, Tobias; Herzog, Michael; Kuehnel, Thomas S

    2015-01-01

    The aim of this study is to investigate whether snoring sounds can be reliably, i.e. reproducibly and comparably, assessed by the listener. This is an absolute prerequisite if an objective method is to provide a valid representation of subjective assessments of snoring sounds. Fifty-three subjects, both men and women, from different age categories assessed snoring sequences in terms of their annoyance level. This was done using a paired comparison model with ten sequences, once at original volume and once at adjusted peak level. In addition, assessments of 50 sequences were made using a visual analog scale (VAS). In the first paired comparison the assessments displayed very high consistency (K = 0.94) and high concordance (W = 0.83). The results showed very good agreement between the sexes (r s = 0.98), between different levels of snoring-related experience (r s = 0.99) and between different ages (r s = 0.98). At adjusted peak level there was also very high consistency (K = 0.91) although concordance was clearly lower (W = 0.50). The rankings in the two paired comparisons showed a high degree of correlation (r s = 0.81). The assessments on the VAS revealed good inter-rater reliability (α = 0.73) and a high degree of correlation with the result of the first paired comparison (r s = 0.93). Snoring sounds can be assessed in a reproducible and comparable manner in terms of their annoyance level. There are no gender-specific differences, and age-specific and experience-specific differences also appear to be negligible. While volume plays a dominant role, other characteristics of the sounds are also sufficient to permit an assessment.

  15. RELIABILITY ANALYSIS OF POWER DISTRIBUTION SYSTEMS

    Directory of Open Access Journals (Sweden)

    Popescu V.S.

    2012-04-01

    Full Text Available Power distribution systems are basic parts of power systems and reliability of these systems at present is a key issue for power engineering development and requires special attention. Operation of distribution systems is accompanied by a number of factors that produce random data a large number of unplanned interruptions. Research has shown that the predominant factors that have a significant influence on the reliability of distribution systems are: weather conditions (39.7%, defects in equipment(25% and unknown random factors (20.1%. In the article is studied the influence of random behavior and are presented estimations of reliability of predominantly rural electrical distribution systems.

  16. Reliability of Power Electronic Converter Systems

    DEFF Research Database (Denmark)

    The main aims of power electronic converter systems (PECS) are to control, convert, and condition electrical power flow from one form to another through the use of solid-state electronics. This book outlines current research into the scientific modeling, experimentation, and remedial measures......-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...... for advancing the reliability, availability, system robustness, and maintainability of PECS at different levels of complexity. Drawing on the experience of an international team of experts, this book explores the reliability of PECS covering topics including an introduction to reliability engineering in power...

  17. Reliability of Power Electronic Converter Systems

    DEFF Research Database (Denmark)

    electronic converter systems; anomaly detection and remaining-life prediction for power electronics; reliability of DC-link capacitors in power electronic converters; reliability of power electronics packaging; modeling for life-time prediction of power semiconductor modules; minimization of DC......-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......The main aims of power electronic converter systems (PECS) are to control, convert, and condition electrical power flow from one form to another through the use of solid-state electronics. This book outlines current research into the scientific modeling, experimentation, and remedial measures...

  18. Design for Reliability of Power Electronic Systems

    DEFF Research Database (Denmark)

    Wang, Huai; Ma, Ke; Blaabjerg, Frede

    2012-01-01

    Advances in power electronics enable efficient and flexible processing of electric power in the application of renewable energy sources, electric vehicles, adjustable-speed drives, etc. More and more efforts are devoted to better power electronic systems in terms of reliability to ensure high...... on a 2.3 MW wind power converter is discussed with emphasis on the reliability critical components IGBTs. Different aspects of improving the reliability of the power converter are mapped. Finally, the challenges and opportunities to achieve more reliable power electronic systems are addressed.......). A collection of methodologies based on Physics-of-Failure (PoF) approach and mission profile analysis are presented in this paper to perform reliability-oriented design of power electronic systems. The corresponding design procedures and reliability prediction models are provided. Further on, a case study...

  19. Reliability Based Optimization of Structural Systems

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    1987-01-01

    The optimization problem to design structural systems such that the reliability is satisfactory during the whole lifetime of the structure is considered in this paper. Some of the quantities modelling the loads and the strength of the structure are modelled as random variables. The reliability...... is estimated using first. order reliability methods ( FORM ). The design problem is formulated as the optimization problem to minimize a given cost function such that the reliability of the single elements satisfies given requirements or such that the systems reliability satisfies a given requirement....... For these optimization problems it is described how a sensitivity analysis can be performed. Next, new optimization procedures to solve the optimization problems are presented. Two of these procedures solve the system reliability based optimization problem sequentially using quasi-analytical derivatives. Finally...

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

    Science.gov (United States)

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

    2015-01-01

    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. Diakoptical reliability analysis of transistorized systems

    International Nuclear Information System (INIS)

    Kontoleon, J.M.; Lynn, J.W.; Green, A.E.

    1975-01-01

    Limitations both on high-speed core availability and computation time required for assessing the reliability of large-sized and complex electronic systems, such as used for the protection of nuclear reactors, are very serious restrictions which continuously confront the reliability analyst. Diakoptic methods simplify the solution of the electrical-network problem by subdividing a given network into a number of independent subnetworks and then interconnecting the solutions of these smaller parts by a systematic process involving transformations based on connection-matrix elements associated with the interconnecting links. However, the interconnection process is very complicated and it may be used only if the original system has been cut in such a manner that a relation can be established between the constraints appearing at both sides of the cut. Also, in dealing with transistorized systems, one of the difficulties encountered is that of modelling adequately their performance under various operating conditions, since their parameters are strongly affected by the imposed voltage and current levels. In this paper a new interconnection approach is presented which may be of use in the reliability analysis of large-sized transistorized systems. This is based on the partial optimization of the subdivisions of the torn network as well as on the optimization of the torn paths. The solution of the subdivisions is based on the principles of algebraic topology, with an algebraic structure relating the physical variables in a topological structure which defines the interconnection of the discrete elements. Transistors, and other nonlinear devices, are modelled using their actual characteristics, under normal and abnormal operating conditions. Use of so-called k factors is made to facilitate accounting for use of electrical stresses. The approach is demonstrated by way of an example. (author)

  2. Student Precision and Reliability of the Team Sport Assessment in ...

    African Journals Online (AJOL)

    TSAP) and formative assessment of invasion sport. The specific objectives were to determine the degree of agreement among expert observers, inter-observer reliability (internal consistency), and intra observer reliability (temporal reliability).

  3. Computer system reliability safety and usability

    CERN Document Server

    Dhillon, BS

    2013-01-01

    Computer systems have become an important element of the world economy, with billions of dollars spent each year on development, manufacture, operation, and maintenance. Combining coverage of computer system reliability, safety, usability, and other related topics into a single volume, Computer System Reliability: Safety and Usability eliminates the need to consult many different and diverse sources in the hunt for the information required to design better computer systems.After presenting introductory aspects of computer system reliability such as safety, usability-related facts and figures,

  4. Reliability of power electronic converter systems

    CERN Document Server

    Chung, Henry Shu-hung; Blaabjerg, Frede; Pecht, Michael

    2016-01-01

    This book outlines current research into the scientific modeling, experimentation, and remedial measures for advancing the reliability, availability, system robustness, and maintainability of Power Electronic Converter Systems (PECS) at different levels of complexity.

  5. Time-variant reliability assessment through equivalent stochastic process transformation

    International Nuclear Information System (INIS)

    Wang, Zequn; Chen, Wei

    2016-01-01

    Time-variant reliability measures the probability that an engineering system successfully performs intended functions over a certain period of time under various sources of uncertainty. In practice, it is computationally prohibitive to propagate uncertainty in time-variant reliability assessment based on expensive or complex numerical models. This paper presents an equivalent stochastic process transformation approach for cost-effective prediction of reliability deterioration over the life cycle of an engineering system. To reduce the high dimensionality, a time-independent reliability model is developed by translating random processes and time parameters into random parameters in order to equivalently cover all potential failures that may occur during the time interval of interest. With the time-independent reliability model, an instantaneous failure surface is attained by using a Kriging-based surrogate model to identify all potential failure events. To enhance the efficacy of failure surface identification, a maximum confidence enhancement method is utilized to update the Kriging model sequentially. Then, the time-variant reliability is approximated using Monte Carlo simulations of the Kriging model where system failures over a time interval are predicted by the instantaneous failure surface. The results of two case studies demonstrate that the proposed approach is able to accurately predict the time evolution of system reliability while requiring much less computational efforts compared with the existing analytical approach. - Highlights: • Developed a new approach for time-variant reliability analysis. • Proposed a novel stochastic process transformation procedure to reduce the dimensionality. • Employed Kriging models with confidence-based adaptive sampling scheme to enhance computational efficiency. • The approach is effective for handling random process in time-variant reliability analysis. • Two case studies are used to demonstrate the efficacy

  6. Safety instrumented systems in the oil and gas industry : Concepts and methods for safety and reliability assessments in design and operation

    Energy Technology Data Exchange (ETDEWEB)

    Lundteigen, Mary Ann

    2009-07-01

    This thesis proposes new methods and gives new insight to safety and reliability assessments of safety instrumented systems (SISs). These systems play an important role in many industry sectors and are used to detect the onset of hazardous events and mitigate their consequences to humans, the environment, and material assets. The thesis focuses on SIS applications in the oil and gas industry. Here, the SIS must respond to hazardous events such as gas leakages, fires, and over pressurization. Because there are personnel onboard the oil and gas installations, the operations take place in a vulnerable marine environment, and substantial values are associated with the offshore facilities, the reliability of SIS is of great concern to the public, the authorities, and the plant owners. The objective of this project has been to identify some of the key factors that influence the SIS reliability, clarify their effects on reliability, and suggest means to improve the treatment of these factors in safety and reliability assessments in design and operation. The project builds on concepts, methods, and definitions in two key standards for SIS design, construction, and operation: IEC 61508 and IEC 61511. The main contributions from this project are: A product development model that integrates reliability, availability, maintainability, and safety (RAMS) requirements with product development. The contributions have been presented in ten articles, five published in international journals, two submitted for publication, and three presented at conferences and in conference proceedings. The contributions are also directed to the industry and the actors that are involved in SIS design, construction, and operation. Even if the oil and gas industry is the main focus area, the results may be relevant for other industry sectors as well. SIS manufacturers and SIS designers face a large number of requirements from authorities, oil companies, international standards, and so on. At the same

  7. Assessment of the Reliability of Concrete Bridges

    DEFF Research Database (Denmark)

    Middleton, C. R.; Thoft-Christensen, Palle

    a significant shift in emphasis for the highways authorities around the world away from the design of new structures over to maintaining the existing infrastructure. As a result, bridge owners are seeking improved ways of inspecting, assessing, maintaining and repairing their existing stock of bridges...... in the wake of ever increasing traffic loads and volumes, and an ageing population of bridges subject to various mechanisms of deterioration. The goal is to optimise the allocation of limited resources whilst maintaining their bridges in a safe and serviceable condition. Reliability analysis is one tool being...

  8. Reliability of dynamic systems under limited information.

    Energy Technology Data Exchange (ETDEWEB)

    Field, Richard V., Jr. (.,; .); Grigoriu, Mircea

    2006-09-01

    A method is developed for reliability analysis of dynamic systems under limited information. The available information includes one or more samples of the system output; any known information on features of the output can be used if available. The method is based on the theory of non-Gaussian translation processes and is shown to be particularly suitable for problems of practical interest. For illustration, we apply the proposed method to a series of simple example problems and compare with results given by traditional statistical estimators in order to establish the accuracy of the method. It is demonstrated that the method delivers accurate results for the case of linear and nonlinear dynamic systems, and can be applied to analyze experimental data and/or mathematical model outputs. Two complex applications of direct interest to Sandia are also considered. First, we apply the proposed method to assess design reliability of a MEMS inertial switch. Second, we consider re-entry body (RB) component vibration response during normal re-entry, where the objective is to estimate the time-dependent probability of component failure. This last application is directly relevant to re-entry random vibration analysis at Sandia, and may provide insights on test-based and/or model-based qualification of weapon components for random vibration environments.

  9. Reliability Growth in Space Life Support Systems

    Science.gov (United States)

    Jones, Harry W.

    2014-01-01

    A hardware system's failure rate often increases over time due to wear and aging, but not always. Some systems instead show reliability growth, a decreasing failure rate with time, due to effective failure analysis and remedial hardware upgrades. Reliability grows when failure causes are removed by improved design. A mathematical reliability growth model allows the reliability growth rate to be computed from the failure data. The space shuttle was extensively maintained, refurbished, and upgraded after each flight and it experienced significant reliability growth during its operational life. In contrast, the International Space Station (ISS) is much more difficult to maintain and upgrade and its failure rate has been constant over time. The ISS Carbon Dioxide Removal Assembly (CDRA) reliability has slightly decreased. Failures on ISS and with the ISS CDRA continue to be a challenge.

  10. Telecommunications system reliability engineering theory and practice

    CERN Document Server

    Ayers, Mark L

    2012-01-01

    "Increasing system complexity require new, more sophisticated tools for system modeling and metric calculation. Bringing the field up to date, this book provides telecommunications engineers with practical tools for analyzing, calculating, and reporting availability, reliability, and maintainability metrics. It gives the background in system reliability theory and covers in-depth applications in fiber optic networks, microwave networks, satellite networks, power systems, and facilities management. Computer programming tools for simulating the approaches presented, using the Matlab software suite, are also provided"

  11. Integrated Reliability and Risk Analysis System (IRRAS)

    International Nuclear Information System (INIS)

    Russell, K.D.; McKay, M.K.; Sattison, M.B.; Skinner, N.L.; Wood, S.T.; Rasmuson, D.M.

    1992-01-01

    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

  12. Reliability of histologic assessment in patients with eosinophilic oesophagitis.

    Science.gov (United States)

    Warners, M J; Ambarus, C A; Bredenoord, A J; Verheij, J; Lauwers, G Y; Walsh, J C; Katzka, D A; Nelson, S; van Viegen, T; Furuta, G T; Gupta, S K; Stitt, L; Zou, G; Parker, C E; Shackelton, L M; D Haens, G R; Sandborn, W J; Dellon, E S; Feagan, B G; Collins, M H; Jairath, V; Pai, R K

    2018-04-01

    The validity of the eosinophilic oesophagitis (EoE) histologic scoring system (EoEHSS) has been demonstrated, but only preliminary reliability data exist. Formally assess the reliability of the EoEHSS and additional histologic features. Four expert gastrointestinal pathologists independently reviewed slides from adult patients with EoE (N = 45) twice, in random order, using standardised training materials and scoring conventions for the EoEHSS and additional histologic features agreed upon during a modified Delphi process. Intra- and inter-rater reliability for scoring the EoEHSS, a visual analogue scale (VAS) of overall histopathologic disease severity, and additional histologic features were assessed using intra-class correlation coefficients (ICCs). Almost perfect intra-rater reliability was observed for the composite EoEHSS scores and the VAS. Inter-rater reliability was also almost perfect for the composite EoEHSS scores and substantial for the VAS. Of the EoEHSS items, eosinophilic inflammation was associated with the highest ICC estimates and consistent with almost perfect intra- and inter-rater reliability. With the exception of dyskeratotic epithelial cells and surface epithelial alteration, ICC estimates for the remaining EoEHSS items were above the benchmarks for substantial intra-rater, and moderate inter-rater reliability. Estimation of peak eosinophil count and number of lamina propria eosinophils were associated with the highest ICC estimates among the exploratory items. The composite EoEHSS and most component items are associated with substantial reliability when assessed by central pathologists. Future studies should assess responsiveness of the score to change after a therapeutic intervention to facilitate its use in clinical trials. © 2018 John Wiley & Sons Ltd.

  13. Technical reliability of geological disposal for high-level radioactive wastes in Japan. The second progress report. Part 3. Safety assessment for geological disposal systems

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-11-01

    Based on the Advisory Committee Report on Nuclear Fuel Cycle Backend Policy submitted to the Japanese Government in 1997, JNC documents the progress of research and development program in the form of the second progress report (the first one published in 1992). It summarizes an evaluation of the technical reliability and safety of the geological disposal concept for high-level radioactive wastes (HLW) in Japan. The present document, the part 3 of the progress report, concerns safety assessment for geological disposal systems definitely introduced in part 1 and 2 of this series and consists of 9 chapters. Chapter I concerns the methodology for safety assessment while Chapter II deals with diversity and uncertainty about the scenario, the adequate model and the required data of the systems above. Chapter III summarizes the components of the geological disposal system. Chapter IV refers to the relationship between radioactive wastes and human life through groundwater, i.e. nuclide migration. In Chapter V is made a reference case which characterizes the geological environmental data using artificial barrier specifications. (Ohno. S.)

  14. Fatigue Reliability of Offshore Wind Turbine Systems

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2012-01-01

    Optimization of the design of offshore wind turbine substructures with respect to fatigue loads is an important issue in offshore wind energy. A stochastic model is developed for assessing the fatigue failure reliability. This model can be used for direct probabilistic design and for calibration...... of appropriate partial safety factors / fatigue design factors (FDF) for steel substructures of offshore wind turbines (OWTs). The fatigue life is modeled by the SN approach. Design and limit state equations are established based on the accumulated fatigue damage. The acceptable reliability level for optimal...... fatigue design of OWTs is discussed and results for reliability assessment of typical fatigue critical design of offshore steel support structures are presented....

  15. Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR): Data manual

    International Nuclear Information System (INIS)

    Gilbert, B.G.; Reece, W.J.; Gertman, D.I.; Gilmore, W.E.; Galyean, W.J.

    1990-12-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) is an automated data base management system for processing and storing human error probability and hardware component failure data. The NUCLARR system software resides on an IBM (or compatible) personal computer. NUCLARR can furnish the end user with data inputs for both human and hardware reliability analysis in support of a variety of risk assessment activities. The NUCLARR system is documented is a five-volume series of reports. Volume V: Data Manual provides a hard-copy representation of all data and related information available within the NUCLARR system software. This document is organized in three sections. Part 1 is the summary description, which presents an overview of the NUCLARR system and data processing procedures. Part 2 contains all data and information relevant to the human error probability (HEP) data side of NUCLARR. Data and information for the hardware component failure data (HCFD) side are presented in Part 3. 7 refs

  16. Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR)

    International Nuclear Information System (INIS)

    Gilbert, B.G.; Reece, W.J.; Gertman, D.I.; Gilmore, W.E.; Galyean, W.J.

    1990-12-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) is an automated data base management system for processing and storing human error probability and hardware component failure data. The NUCLARR system software resides on an IBM (or compatible) personal computer. NUCLARR can furnish the end user with data inputs for both human and hardware reliability analysis in support of a variety of risk assessment activities. The NUCLARR system is documented in a five-volume series of reports. Volume 5: Data Manual provides a hard-copy representation of all data and related information available within the NUCLARR system software. This document is organized in three sections. Part 1 is the summary description, which presents an overview of the NUCLARR system and data processing procedures. Part 2 contains all data and information relevant to the human error probability (HEP) data side of NUCLARR. Data and information for the hardware component failure data (HCFD) side are presented in Part 3. 7 refs

  17. Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR): Data manual

    International Nuclear Information System (INIS)

    Gilbert, B.G.; Reece, W.J.; Gertman, D.I.; Gilmore, W.E.; Galyean, W.J.

    1990-12-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) is an automated data base management system for processing and storing human error probability and hardware component failure data. The NUCLARR system software resides on an IBM (or compatible) personal computer. NUCLARR can furnish the end user with data inputs for both human and hardware reliability analysis in support of a variety of risk assessment activities. The NUCLARR system is documented in a five-volume series of reports. Volume V: Data Manual provides a hard-copy representation of all data and related information available within the NUCLARR system software. This document is organized in three sections. Part 1 is the summary description, which presents an overview of the NUCLARR system and data processing procedures. Part 2 contains all data and information relevant to the human error probability (HEP) side of NUCLARR. Data and information for the hardware component failure data (HCFD) side are presented in Part 3. 7 refs., 1 fig

  18. System reliability time-dependent models

    International Nuclear Information System (INIS)

    Debernardo, H.D.

    1991-06-01

    A probabilistic methodology for safety system technical specification evaluation was developed. The method for Surveillance Test Interval (S.T.I.) evaluation basically means an optimization of S.T.I. of most important system's periodically tested components. For Allowed Outage Time (A.O.T.) calculations, the method uses system reliability time-dependent models (A computer code called FRANTIC III). A new approximation, which was called Independent Minimal Cut Sets (A.C.I.), to compute system unavailability was also developed. This approximation is better than Rare Event Approximation (A.E.R.) and the extra computing cost is neglectible. A.C.I. was joined to FRANTIC III to replace A.E.R. on future applications. The case study evaluations verified that this methodology provides a useful probabilistic assessment of surveillance test intervals and allowed outage times for many plant components. The studied system is a typical configuration of nuclear power plant safety systems (two of three logic). Because of the good results, these procedures will be used by the Argentine nuclear regulatory authorities in evaluation of technical specification of Atucha I and Embalse nuclear power plant safety systems. (Author) [es

  19. An artificial intelligence system for reliability studies

    International Nuclear Information System (INIS)

    Llory, M.; Ancelin, C.; Bannelier, M.; Bouhadana, H.; Bouissou, M.; Lucas, J.Y.; Magne, L.; Villate, N.

    1990-01-01

    The EDF (French Electricity Company) software developed for computer aided reliability studies is considered. Such software tools were applied in the study of the safety requirements of the Paluel nuclear power plant. The reliability models, based on IF-THEN type rules, and the generation of models by the expert system are described. The models are then processed applying algorithm structures [fr

  20. Downhole telemetry system reliability calculation and improvement

    Science.gov (United States)

    Trofimova, E. S.; Rubtsova, O. O.; Ishchenko, A. V.; Danilov, V. Yu.

    2017-09-01

    The article gives an estimation and a calculation of the reliability indexes for the downhole telemetry system downhole unit under severe operating conditions of high temperature environment. The reliability-growth methods are suggested. It is shown that the use of redundancy significantly extends mean time to failure even in high temperature environment.

  1. Reliable computer systems design and evaluatuion

    CERN Document Server

    Siewiorek, Daniel

    2014-01-01

    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.

  2. B-52 stability augmentation system reliability

    Science.gov (United States)

    Bowling, T. C.; Key, L. W.

    1976-01-01

    The B-52 SAS (Stability Augmentation System) was developed and retrofitted to nearly 300 aircraft. It actively controls B-52 structural bending, provides improved yaw and pitch damping through sensors and electronic control channels, and puts complete reliance on hydraulic control power for rudder and elevators. The system has experienced over 300,000 flight hours and has exhibited service reliability comparable to the results of the reliability test program. Development experience points out numerous lessons with potential application in the mechanization and development of advanced technology control systems of high reliability.

  3. Reliability Results of NERSC Systems

    Energy Technology Data Exchange (ETDEWEB)

    Petascale Data Storage Institute (PDSI); Mokhtarani, Akbar; Mokhtarani, Akbar; Kramer, William; Hick, Jason

    2008-05-27

    In order to address the needs of future scientific applications for storing and accessing large amounts of data in an efficient way, one needs to understand the limitations of current technologies and how they may cause systeminstability or unavailability. A number of factors can impact system availability ranging from facility-wide power outage to a single point of failure such as network switches or global file systems. In addition, individual component failure in a system can degrade the performance of that system. This paper focuses on analyzing both of these factors and their impacts on the computational and storage systems at NERSC. Component failure data presented in this report primarily focuses on disk drive in on of the computational system and tape drive failure in HPSS. NERSC collected available component failure data and system-wide outages for its computational and storage systems over a six-year period and made them available to the HPC community through the Petascale Data Storage Institute.

  4. Reliability modeling of Clinch River breeder reactor electrical shutdown systems

    International Nuclear Information System (INIS)

    Schatz, R.A.; Duetsch, K.L.

    1974-01-01

    The initial simulation of the probabilistic properties of the Clinch River Breeder Reactor Plant (CRBRP) electrical shutdown systems is described. A model of the reliability (and availability) of the systems is presented utilizing Success State and continuous-time, discrete state Markov modeling techniques as significant elements of an overall reliability assessment process capable of demonstrating the achievement of program goals. This model is examined for its sensitivity to safe/unsafe failure rates, sybsystem redundant configurations, test and repair intervals, monitoring by reactor operators; and the control exercised over system reliability by design modifications and the selection of system operating characteristics. (U.S.)

  5. Probabilistic simulation applications to reliability assessments

    International Nuclear Information System (INIS)

    Miller, Ian; Nutt, Mark W.; Hill, Ralph S. III

    2003-01-01

    Probabilistic risk/reliability (PRA) analyses for engineered systems are conventionally based on fault-tree methods. These methods are mature and efficient, and are well suited to systems consisting of interacting components with known, low probabilities of failure. Even complex systems, such as nuclear power plants or aircraft, are modeled by the careful application of these approaches. However, for systems that may evolve in complex and nonlinear ways, and where the performance of components may be a sensitive function of the history of their working environments, fault-tree methods can be very demanding. This paper proposes an alternative method of evaluating such systems, based on probabilistic simulation using intelligent software objects to represent the components of such systems. Using a Monte Carlo approach, simulation models can be constructed from relatively simple interacting objects that capture the essential behavior of the components that they represent. Such models are capable of reflecting the complex behaviors of the systems that they represent in a natural and realistic way. (author)

  6. Reliability of power system with open access

    International Nuclear Information System (INIS)

    Ehsani, A.; Ranjbar, A. M.; Fotuhi Firuzabad, M.; Ehsani, M.

    2003-01-01

    Recently, in many countries, electric utility industry is undergoing considerable changes in regard to its structure and regulation. It can be clearly seen that the thrust towards privatization and deregulation or re regulation of the electric utility industry will introduce numerous reliability problems that will require new criteria and analytical tools that recognize the residual uncertainties in the new environment. In this paper, different risks and uncertainties in competitive electricity markets are briefly introduced; the approach of customers, operators, planners, generation bodies and network providers to the reliability of deregulated system is studied; the impact of dispersed generation on system reliability is evaluated; and finally, the reliability cost/reliability worth issues in the new competitive environment are considered

  7. Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR): Summary description

    International Nuclear Information System (INIS)

    Gertman, D.I.; Gilmore, W.E.; Galyean, W.J.; Groh, M.R.; Gentillon, C.D.; Gilbert, B.G.; Reece, W.J.

    1990-05-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) is an automate data base management system for storing and processing human error probability and hardware component failure rate data. The NUCLARR system software resides on an IBM (or compatible) personal microcomputer. NUCLARR can be accessed by the end user to furnish data suitable for input in human and/or hardware reliability analysis to support a variety of risk assessment activities. The NUCLARR system is documented in a five-volume series of reports. This document Volume 1, of this series is the Summary Description, which presents an overview of the data management system, including a description of data collection, data qualification, data structure, and taxonomies. Programming activities, procedures for processing data, a user's guide, and hard copy data manual are presented in Volumes 2 through 5, NUREG/CR-4639

  8. Reliability Evaluation of Distribution System with Distributed Generation

    Science.gov (United States)

    Chen, Guoyan; Zhang, Feng; You, Dahai; Wang, Yong; Lu, Guojun; Zou, Qi; Liu, Hengwei; Qian, Junjie; Xu, Heng

    2017-07-01

    Distribution system reliability assessment is an important part of power system reliability assessment. In recent years, distributed generations (DG) are more and more connected to distribution system because of its flexible and friendly environment features, which imposes a great influence on distribution system reliability. Hence, a reliability evaluation method suitable for distribution system with DG is imperative, which is proposed in this paper. First, a probabilistic model of DG output is established based on the generation characteristics of DG. Second, the island operation mode of distribution system with DG is researched, subsequently, the calculation method of the probability of island successful operation is put forward on the basis of DG model and the load model. Third, a reliability assessment methodology of distribution system with DG is proposed by improving the traditional minimal path algorithm for reliability evaluation of distribution system. Finally, some results are obtained by applying the proposed method to the IEEE-RBTS Bus6 system, which are consistent with the well-known facts. In this way, the proposed method is proved to be reasonable and effective.

  9. Design for Reliability of Power Electronic Systems

    DEFF Research Database (Denmark)

    Yang, Yongheng; Wang, Huai; Sangwongwanich, Ariya

    2018-01-01

    Power density, efficiency, cost, and reliability are the major challenges when designing a power electronic system. Latest advancements in power semiconductor devices (e.g., silicon carbide devices) and topological innovations have vital contributions to power density and efficiency. Nevertheless.......e., mission profiles) is usually harsh, where the input power can change quickly and randomly, resulting in considerable temperature swings in the power electronics. This may induce failures to the power electronic systems. If remain untreated (i.e., ill-designed system without considering reliability......), the cost for maintenance will increase, thus affecting the reputation for the manufacturers and, more important, the cost of energy in renewables. Hence, it calls for highly reliable power electronic systems, where the reliability together with various common design parameters should be taken into account...

  10. Reliability of microtechnology interconnects, devices and systems

    CERN Document Server

    Liu, Johan; Sarkka, Jussi; Tegehall, Per-Erik; Andersson, Cristina

    2011-01-01

    This text discusses the reliability of microtechnology products from the bottom up, beginning with devices and extending to systems. It covers many topics, and it addresses specific failure modes in solder and conductive adhesives at great length.

  11. Nanoscale deformation measurements for reliability assessment of material interfaces

    Science.gov (United States)

    Keller, Jürgen; Gollhardt, Astrid; Vogel, Dietmar; Michel, Bernd

    2006-03-01

    With the development and application of micro/nano electronic mechanical systems (MEMS, NEMS) for a variety of market segments new reliability issues will arise. The understanding of material interfaces is the key for a successful design for reliability of MEMS/NEMS and sensor systems. Furthermore in the field of BIOMEMS newly developed advanced materials and well known engineering materials are combined despite of fully developed reliability concepts for such devices and components. In addition the increasing interface-to volume ratio in highly integrated systems and nanoparticle filled materials are challenges for experimental reliability evaluation. New strategies for reliability assessment on the submicron scale are essential to fulfil the needs of future devices. In this paper a nanoscale resolution experimental method for the measurement of thermo-mechanical deformation at material interfaces is introduced. The determination of displacement fields is based on scanning probe microscopy (SPM) data. In-situ SPM scans of the analyzed object (i.e. material interface) are carried out at different thermo-mechanical load states. The obtained images are compared by grayscale cross correlation algorithms. This allows the tracking of local image patterns of the analyzed surface structure. The measurement results are full-field displacement fields with nanometer resolution. With the obtained data the mixed mode type of loading at material interfaces can be analyzed with highest resolution for future needs in micro system and nanotechnology.

  12. Design for Reliability in Renewable Energy Systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Zhou, Dao; Sangwongwanich, Ariya

    2017-01-01

    Power electronics are widely used in renewable energy systems to achieve lower cost of energy, higher efficiency and high power density. At the same time, the high reliability of the power electronics products is demanded, in order to reduce the failure rates and ensure cost-effective operation...... of the renewable energy systems. This paper thus describes the basic concepts used in reliability engineering, and presents the status and future trends of Design for Reliability (DfR) in power electronics, which is currently undergoing a paradigm shift to a physics-of-failure approach. Two case studies of a 2 MW...

  13. Reliability assessment using Bayesian networks. Case study on quantative reliability estimation of a software-based motor protection relay

    International Nuclear Information System (INIS)

    Helminen, A.; Pulkkinen, U.

    2003-06-01

    In this report a quantitative reliability assessment of motor protection relay SPAM 150 C has been carried out. The assessment focuses to the methodological analysis of the quantitative reliability assessment using the software-based motor protection relay as a case study. The assessment method is based on Bayesian networks and tries to take the full advantage of the previous work done in a project called Programmable Automation System Safety Integrity assessment (PASSI). From the results and experiences achieved during the work it is justified to claim that the assessment method presented in the work enables a flexible use of qualitative and quantitative elements of reliability related evidence in a single reliability assessment. At the same time the assessment method is a concurrent way of reasoning one's beliefs and references about the reliability of the system. Full advantage of the assessment method is taken when using the method as a way to cultivate the information related to the reliability of software-based systems. The method can also be used as a communicational instrument in a licensing process of software-based systems. (orig.)

  14. Reliability and diagnostic of modular systems

    Directory of Open Access Journals (Sweden)

    J. Kohlas

    2014-01-01

    Full Text Available Reliability and diagnostic are in general two problems discussed separately. Yet the two problems are in fact closely related to each other. Here, this relation is considered in the simple case of modular systems. We show, how the computation of reliability and diagnostic can efficiently be done within the same Bayesian network induced by the modularity of the structure function of the system.

  15. Use of COMCAN III in system design and reliability analysis

    International Nuclear Information System (INIS)

    Rasmuson, D.M.; Shepherd, J.C.; Marshall, N.H.; Fitch, L.R.

    1982-03-01

    This manual describes the COMCAN III computer program and its use. COMCAN III is a tool that can be used by the reliability analyst performing a probabilistic risk assessment or by the designer of a system desiring improved performance and efficiency. COMCAN III can be used to determine minimal cut sets of a fault tree, to calculate system reliability characteristics, and to perform qualitative common cause failure analysis

  16. Safety and reliability assessment by using dynamic reliability analysis method

    International Nuclear Information System (INIS)

    Lee, Sook Hyung; Oh, Se Ki

    1997-01-01

    DYLAM and its related applications are reviewed in detail and found to have many favorable characteristics. Concerning human factor analysis, the study demonstrates that DYLAM methodology represents and appropriate tool to study man-machine behavior provided that DYLAM is used to model machine behavior and an appropriate operator interface human factor model is included. A hybrid model which is a synthesis of the DYLAM model, a system thermodynamic simulation model and a neutral network predicative model, is implemented and used to analyze dynamically the CANDU pressurizer system

  17. Reliability modelling and simulation of switched linear system ...

    African Journals Online (AJOL)

    Thus, constructing a subsystem Markov model and matching its parameters with the specified safety factors provides the basis for the entire system analysis. For the system simulation, temporal databases and predictive control algorithm are designed. The simulation results are analyzed to assess the reliability of the system ...

  18. Advanced Reconnaissance System Component Reliability Study

    Science.gov (United States)

    1956-07-31

    or chemical interaction of the air atoms and molecules.on the vehicle skin or lens and window materials. The quantity of molecules present is very low...I Mill -• •ri... ": :’s t:.... 111 . . . orIII. i...1 MINI . • ; . . .1...!.... : . •..1 • . , , BIM El MIMIIMO= .. insma’ • • . wart...Reliability were discussed. "Some Reliability Aspects of Systems Design", Moskowitz, Fred and * Lean , John’, RADC Technical Note 55-4 "Reliability is

  19. A Passive System Reliability Analysis for a Station Blackout

    Energy Technology Data Exchange (ETDEWEB)

    Brunett, Acacia; Bucknor, Matthew; Grabaskas, David; Sofu, Tanju; Grelle, Austin

    2015-05-03

    The latest iterations of advanced reactor designs have included increased reliance on passive safety systems to maintain plant integrity during unplanned sequences. While these systems are advantageous in reducing the reliance on human intervention and availability of power, the phenomenological foundations on which these systems are built require a novel approach to a reliability assessment. Passive systems possess the unique ability to fail functionally without failing physically, a result of their explicit dependency on existing boundary conditions that drive their operating mode and capacity. Argonne National Laboratory is performing ongoing analyses that demonstrate various methodologies for the characterization of passive system reliability within a probabilistic framework. Two reliability analysis techniques are utilized in this work. The first approach, the Reliability Method for Passive Systems, provides a mechanistic technique employing deterministic models and conventional static event trees. The second approach, a simulation-based technique, utilizes discrete dynamic event trees to treat time- dependent phenomena during scenario evolution. For this demonstration analysis, both reliability assessment techniques are used to analyze an extended station blackout in a pool-type sodium fast reactor (SFR) coupled with a reactor cavity cooling system (RCCS). This work demonstrates the entire process of a passive system reliability analysis, including identification of important parameters and failure metrics, treatment of uncertainties and analysis of results.

  20. The validity and reliability of a global positioning satellite system device to assess speed and repeated sprint ability (RSA) in athletes.

    Science.gov (United States)

    Barbero-Alvarez, José C; Coutts, Aaron; Granda, Juan; Barbero-Alvarez, Verónica; Castagna, Carlo

    2010-03-01

    There is a limited understanding of the validity and reliability of commercially available global positioning satellite (GPS) devices for assessing repeated sprint performance in athletes. The aims of this study were to assess the convergent validity and the test-retest reliability of a GPS device for measuring repeated sprint ability test (RSAT) variables. Two groups participated in this study, a group of 21 physical education students (age: 20.2+/-2.3 years, stature: 1.75+/-0.42 m, body mass: 68.0+/-6.8kg) and a second group 14 elite junior soccer players (age: 14.5+/-1.2 years, stature: 1.60+/-0.09 m, body mass: 57.7+/-3.8kg) volunteered to participate in this study. Convergent validity was assessed as the correlation between sprint performance (15 and 30-m) using both timing lights and a portable GPS device during a RSAT (7 x 30-m sprints with 30-s of active recovery). The 7 x 30-m RSAT test-retest reliability using GPS device was assessed in elite junior soccer players repeating the test 1 week apart and expressing reliability as a coefficient of variation. Results showed a strong correlation between peak speed measures with the GPS device and RSAT performance measured with timing lights for the 15-m (r(2)=0.87, p<0.001, N=147) and 30-m (r(2)=0.94, p<0.001, N=147) splits, respectively. There was a low coefficient of variation for summated maximal speed (1.7%) and peak speed (1.2%) during the 7 x 30-m RSAT, but high variation for the percentage decrement score (36.2%). These results provide evidence to support the use of the GPS device as an alternative measure to assess repeated sprint performance but suggest a percentage decrement score is not a reliable measure of RSAT performance. Copyright 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  1. System Reliability for LED-Based Products

    Energy Technology Data Exchange (ETDEWEB)

    Davis, J Lynn; Mills, Karmann; Lamvik, Michael; Yaga, Robert; Shepherd, Sarah D; Bittle, James; Baldasaro, Nick; Solano, Eric; Bobashev, Georgiy; Johnson, Cortina; Evans, Amy

    2014-04-07

    Results from accelerated life tests (ALT) on mass-produced commercially available 6” downlights are reported along with results from commercial LEDs. The luminaires capture many of the design features found in modern luminaires. In general, a systems perspective is required to understand the reliability of these devices since LED failure is rare. In contrast, components such as drivers, lenses, and reflector are more likely to impact luminaire reliability than LEDs.

  2. Reliability analysis framework for computer-assisted medical decision systems

    International Nuclear Information System (INIS)

    Habas, Piotr A.; Zurada, Jacek M.; Elmaghraby, Adel S.; Tourassi, Georgia D.

    2007-01-01

    We present a technique that enhances computer-assisted decision (CAD) systems with the ability to assess the reliability of each individual decision they make. Reliability assessment is achieved by measuring the accuracy of a CAD system with known cases similar to the one in question. The proposed technique analyzes the feature space neighborhood of the query case to dynamically select an input-dependent set of known cases relevant to the query. This set is used to assess the local (query-specific) accuracy of the CAD system. The estimated local accuracy is utilized as a reliability measure of the CAD response to the query case. The underlying hypothesis of the study is that CAD decisions with higher reliability are more accurate. The above hypothesis was tested using a mammographic database of 1337 regions of interest (ROIs) with biopsy-proven ground truth (681 with masses, 656 with normal parenchyma). Three types of decision models, (i) a back-propagation neural network (BPNN), (ii) a generalized regression neural network (GRNN), and (iii) a support vector machine (SVM), were developed to detect masses based on eight morphological features automatically extracted from each ROI. The performance of all decision models was evaluated using the Receiver Operating Characteristic (ROC) analysis. The study showed that the proposed reliability measure is a strong predictor of the CAD system's case-specific accuracy. Specifically, the ROC area index for CAD predictions with high reliability was significantly better than for those with low reliability values. This result was consistent across all decision models investigated in the study. The proposed case-specific reliability analysis technique could be used to alert the CAD user when an opinion that is unlikely to be reliable is offered. The technique can be easily deployed in the clinical environment because it is applicable with a wide range of classifiers regardless of their structure and it requires neither additional

  3. Software engineering practices for control system reliability

    International Nuclear Information System (INIS)

    S. K. Schaffner; K. S White

    1999-01-01

    This paper will discuss software engineering practices used to improve Control System reliability. The authors begin with a brief discussion of the Software Engineering Institute's Capability Maturity Model (CMM) which is a framework for evaluating and improving key practices used to enhance software development and maintenance capabilities. The software engineering processes developed and used by the Controls Group at the Thomas Jefferson National Accelerator Facility (Jefferson Lab), using the Experimental Physics and Industrial Control System (EPICS) for accelerator control, are described. Examples are given of how their procedures have been used to minimized control system downtime and improve reliability. While their examples are primarily drawn from their experience with EPICS, these practices are equally applicable to any control system. Specific issues addressed include resource allocation, developing reliable software lifecycle processes and risk management

  4. Reliability-based assessment of polyethylene pipe creep lifetime

    Energy Technology Data Exchange (ETDEWEB)

    Khelif, Rabia [LaMI-UBP and IFMA, Campus de Clermont-Fd, Les Cezeaux, BP 265, 63175 Aubiere Cedex (France); LR3MI, Departement de Genie Mecanique, Universite Badji Mokhtar, BP 12, Annaba 23000 (Algeria)], E-mail: rabia.khelif@ifma.fr; Chateauneuf, Alaa [LGC-University Blaise Pascal, Campus des Cezeaux, BP 206, 63174 Aubiere Cedex (France)], E-mail: alaa.chateauneuf@polytech.univ-bpclermont.fr; Chaoui, Kamel [LR3MI, Departement de Genie Mecanique, Universite Badji Mokhtar, BP 12, Annaba 23000 (Algeria)], E-mail: chaoui@univ-annaba.org

    2007-12-15

    Lifetime management of underground pipelines is mandatory for safe hydrocarbon transmission and distribution systems. The use of high-density polyethylene tubes subjected to internal pressure, external loading and environmental variations requires a reliability study in order to define the service limits and the optimal operating conditions. In service, the time-dependent phenomena, especially creep, take place during the pipe lifetime, leading to significant strength reduction. In this work, the reliability-based assessment of pipe lifetime models is carried out, in order to propose a probabilistic methodology for lifetime model selection and to determine the pipe safety levels as well as the most important parameters for pipeline reliability. This study is enhanced by parametric analysis on pipe configuration, gas pressure and operating temperature.

  5. Reliability-based assessment of polyethylene pipe creep lifetime

    International Nuclear Information System (INIS)

    Khelif, Rabia; Chateauneuf, Alaa; Chaoui, Kamel

    2007-01-01

    Lifetime management of underground pipelines is mandatory for safe hydrocarbon transmission and distribution systems. The use of high-density polyethylene tubes subjected to internal pressure, external loading and environmental variations requires a reliability study in order to define the service limits and the optimal operating conditions. In service, the time-dependent phenomena, especially creep, take place during the pipe lifetime, leading to significant strength reduction. In this work, the reliability-based assessment of pipe lifetime models is carried out, in order to propose a probabilistic methodology for lifetime model selection and to determine the pipe safety levels as well as the most important parameters for pipeline reliability. This study is enhanced by parametric analysis on pipe configuration, gas pressure and operating temperature

  6. Heroic Reliability Improvement in Manned Space Systems

    Science.gov (United States)

    Jones, Harry W.

    2017-01-01

    System reliability can be significantly improved by a strong continued effort to identify and remove all the causes of actual failures. Newly designed systems often have unexpected high failure rates which can be reduced by successive design improvements until the final operational system has an acceptable failure rate. There are many causes of failures and many ways to remove them. New systems may have poor specifications, design errors, or mistaken operations concepts. Correcting unexpected problems as they occur can produce large early gains in reliability. Improved technology in materials, components, and design approaches can increase reliability. The reliability growth is achieved by repeatedly operating the system until it fails, identifying the failure cause, and fixing the problem. The failure rate reduction that can be obtained depends on the number and the failure rates of the correctable failures. Under the strong assumption that the failure causes can be removed, the decline in overall failure rate can be predicted. If a failure occurs at the rate of lambda per unit time, the expected time before the failure occurs and can be corrected is 1/lambda, the Mean Time Before Failure (MTBF). Finding and fixing a less frequent failure with the rate of lambda/2 per unit time requires twice as long, time of 1/(2 lambda). Cutting the failure rate in half requires doubling the test and redesign time and finding and eliminating the failure causes.Reducing the failure rate significantly requires a heroic reliability improvement effort.

  7. Reliability analysis of flood defence systems

    NARCIS (Netherlands)

    Steenbergen, H.M.G.M.; Lassing, B.L.; Vrouwenvelder, A.C.W.M.; Waarts, P.H.

    2004-01-01

    In recent years an advanced program for the reliability analysis of flood defence systems has been under development. This paper describes the global data requirements for the application and the setup of the models. The analysis generates the probability of system failure and the contribution of

  8. Lifetime Reliability Assessment of Concrete Slab Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    A procedure for lifetime assesment of the reliability of short concrete slab bridges is presented in the paper. Corrosion of the reinforcement is the deterioration mechanism used for estimating the reliability profiles for such bridges. The importance of using sensitivity measures is stressed...

  9. Reliability-Based Optimization of Series Systems of Parallel Systems

    DEFF Research Database (Denmark)

    Enevoldsen, I.; Sørensen, John Dalsgaard

    Reliability-based design of structural systems is considered. Especially systems where the reliability model is a series system of parallel systems are analysed. A sensitivity analysis for this class of problems is presented. Direct and sequential optimization procedures to solve the optimization...... problems are described. Numerical tests indicate that a sequential technique called the bounds iteration method (BIM) is particularly fast and stable....

  10. Theory of reliable systems. [reliability analysis and on-line fault diagnosis

    Science.gov (United States)

    Meyer, J. F.

    1974-01-01

    Research is reported in the program to refine the current notion of system reliability by identifying and investigating attributes of a system which are important to reliability considerations, and to develop techniques which facilitate analysis of system reliability. Reliability analysis, and on-line fault diagnosis are discussed.

  11. Reliability-Based Optimization of Series Systems of Parallel Systems

    DEFF Research Database (Denmark)

    Enevoldsen, I.; Sørensen, John Dalsgaard

    1993-01-01

    Reliability-based design of structural systems is considered. In particular, systems where the reliability model is a series system of parallel systems are treated. A sensitivity analysis for this class of problems is presented. Optimization problems with series systems of parallel systems......) a sequential formulation based on optimality criteria; and (4) a sequential formulation including a new so-called bounds iteration method (BIM). Numerical tests indicate that the sequential technique including the BIM is particularly fast and stable. The B1M is not only effective in reliabilitybased...... optimization of series systems of parallel systems, but it is also efficient in reliability-based optimization of series systems in general....

  12. Investigation of the Validity and Reliability of Balance Evaluation Systems Test (BESTest in Assessment of Balance Disorders in People With Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Samira Kamalian Lari

    2018-01-01

    Conclusion  After changing and removing part of question 6 of the second domain, results demonstrated that the questionnaire BESTest is a valid and reliable test for assessing balance performance in multiple sclerosis patients. It can be used as an accurate tool, both in the areas of clinical (to evaluate the patients’ equilibrium status and purposeful therapy planning and to apply for scientific research in patients with multiple sclerosis.

  13. Power plant productivity and reliability information system

    Energy Technology Data Exchange (ETDEWEB)

    Pazos, R.; Lizarraga, E.

    1988-04-01

    This article describes an information system for handling equipment failure information of fossil fuel plants. This system produces 33 different reports, which contain failure statistics, plant availability, unavailability classified by cause, plant reliability indices, and maintenance productivity indices. Some of the innovations introduced by this system are: (1) event partition into any number of subevents for accurate description of event evolution, (2) separation of equipment and event cause for easy reporting, and (3) failure-mode information for better event description.

  14. Assessing the reliability of the Gambling Functional Assessment: Revised.

    Science.gov (United States)

    Weatherly, Jeffrey N; Miller, Joseph C; Montes, Kevin S; Rost, Chase

    2012-06-01

    Dixon and Johnson (Anal Gambl Behav 1: 44-49, 2007) proposed the Gambling Functional Assessment as a tool to identify the consequences maintaining the respondent's gambling behavior, but subsequent studies on its psychometric properties suggested that it could use improvement. The present study investigated the internal consistency of the Gambling Functional Assessment--Revised using the responses of 1,060 undergraduate students. Temporal reliability was assessed by a second administration of the measure four (n = 87) or twelve (n = 98) weeks after the first administration. Temporal reliability was also compared to the South Oaks Gambling Screen (Lesieur and Blume in Am J Psychiatry 144: 1184-1188, 1987), which was also administered at both time points. Internal consistency measures were good to excellent, even when potential non-gamblers were excluded from the analyses. Temporal stability was also very good, with the possible exception of the consequence of "escape" at 12 weeks. The Gambling Functional Assessment--Revised represents a potentially useful tool for researchers and therapists interested in why respondents are gambling.

  15. Sustainable, Reliable Mission-Systems Architecture

    Science.gov (United States)

    O'Neil, Graham; Orr, James K.; Watson, Steve

    2007-01-01

    A mission-systems architecture, based on a highly modular infrastructure utilizing: open-standards hardware and software interfaces as the enabling technology is essential for affordable and sustainable space exploration programs. This mission-systems architecture requires (a) robust communication between heterogeneous system, (b) high reliability, (c) minimal mission-to-mission reconfiguration, (d) affordable development, system integration, and verification of systems, and (e) minimal sustaining engineering. This paper proposes such an architecture. Lessons learned from the Space Shuttle program and Earthbound complex engineered system are applied to define the model. Technology projections reaching out 5 years are mde to refine model details.

  16. Reliability centered operational performance measure for computer systems in NPPs

    International Nuclear Information System (INIS)

    Khobare, S.K.; Chandra, Umesh; Govindarajan, G.

    1992-01-01

    There could be arguments in favour and against the application of digital computers in highly safety critical plants like nuclear power plants (NPPs). The unfavourable arguments arise mainly due to grey areas in accurate assessment, demonstration of the required reliability and availability of computer systems. This requirement is important particularly for computer applications in control and protection logic systems of the NPPs. Systematic performance comparison study is required to be made for these applications against the conventional hard wired logic systems. The present paper discusses reliability centered system and plant performance measures to analyse the gains of computer applications in the NPPs. (author). 5 refs. 2 tabs

  17. Reliability assessment of AOSpine thoracolumbar spine injury classification system and Thoracolumbar Injury Classification and Severity Score (TLICS) for thoracolumbar spine injuries: results of a multicentre study.

    Science.gov (United States)

    Kaul, Rahul; Chhabra, Harvinder Singh; Vaccaro, Alexander R; Abel, Rainer; Tuli, Sagun; Shetty, Ajoy Prasad; Das, Kali Dutta; Mohapatra, Bibhudendu; Nanda, Ankur; Sangondimath, Gururaj M; Bansal, Murari Lal; Patel, Nishit

    2017-05-01

    The aim of this multicentre study was to determine whether the recently introduced AOSpine Classification and Injury Severity System has better interrater and intrarater reliability than the already existing Thoracolumbar Injury Classification and Severity Score (TLICS) for thoracolumbar spine injuries. Clinical and radiological data of 50 consecutive patients admitted at a single centre with a diagnosis of an acute traumatic thoracolumbar spine injury were distributed to eleven attending spine surgeons from six different institutions in the form of PowerPoint presentation, who classified them according to both classifications. After time span of 6 weeks, cases were randomly rearranged and sent again to same surgeons for re-classification. Interobserver and intraobserver reliability for each component of TLICS and new AOSpine classification were evaluated using Fleiss Kappa coefficient (k value) and Spearman rank order correlation. Moderate interrater and intrarater reliability was seen for grading fracture type and integrity of posterior ligamentous complex (Fracture type: k = 0.43 ± 0.01 and 0.59 ± 0.16, respectively, PLC: k = 0.47 ± 0.01 and 0.55 ± 0.15, respectively), and fair to moderate reliability (k = 0.29 ± 0.01 interobserver and 0.44+/0.10 intraobserver, respectively) for total score according to TLICS. Moderate interrater (k = 0.59 ± 0.01) and substantial intrarater reliability (k = 0.68 ± 0.13) was seen for grading fracture type regardless of subtype according to AOSpine classification. Near perfect interrater and intrarater agreement was seen concerning neurological status for both the classification systems. Recently proposed AOSpine classification has better reliability for identifying fracture morphology than the existing TLICS. Additional studies are clearly necessary concerning the application of these classification systems across multiple physicians at different level of training and trauma centers to evaluate not

  18. Mammography image assessment; validity and reliability of current scheme

    International Nuclear Information System (INIS)

    Hill, C.; Robinson, L.

    2015-01-01

    Mammographers currently score their own images according to criteria set out by Regional Quality Assurance. The criteria used are based on the ‘Perfect, Good, Moderate, Inadequate’ (PGMI) marking criteria established by the National Health Service Breast Screening Programme (NHSBSP) in their Quality Assurance Guidelines of 2006 1 . This document discusses the validity and reliability of the current mammography image assessment scheme. Commencing with a critical review of the literature this document sets out to highlight problems with the national approach to the use of marking schemes. The findings suggest that ‘PGMI’ scheme is flawed in terms of reliability and validity and is not universally applied across the UK. There also appear to be differences in schemes used by trainees and qualified mammographers. Initial recommendations are to be made in collaboration with colleagues within the National Health Service Breast Screening Programme (NHSBSP), Higher Education Centres, College of Radiographers and the Royal College of Radiologists in order to identify a mammography image appraisal scheme that is fit for purpose. - Highlights: • Currently no robust evidence based marking tools in use for the assessment of images in mammography. • Is current system valid, reliable and robust? • How can the current image assessment tool be improved? • Should students and qualified mammographers use the same tool? • What marking criteria are available for image assessment?

  19. Reliability Issues in Distributed Operating Systems

    NARCIS (Netherlands)

    Tanenbaum, A.S.; van Renesse, R.

    1987-01-01

    The authors examine the various kinds of distributed systems and discuss some of the reliability issues involved. They first concentrate on the causes of unreliability, illustrating these with some general solutions and examples. Among the issues treated are interprocess communication, machine

  20. Reliability achievement in high technology space systems

    Science.gov (United States)

    Lindstrom, D. L.

    1981-01-01

    The production of failure-free hardware is discussed. The elements required to achieve such hardware are: technical expertise to design, analyze, and fully understand the design; use of high reliability parts and materials control in the manufacturing process; and testing to understand the system and weed out defects. The durability of the Hughes family of satellites is highlighted.

  1. Reliability Analysis of Structural Timber Systems

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Hoffmeyer, P.

    2000-01-01

    types of redundancy and non-linearity are considered. The statistical characteristics of the load bearing capacity are determined by reliability analysis. Next, more complex systems are considered modelling the mechanical behaviour of timber roof elements I stressed skin panels made of timber. Using...

  2. System-Reliability Cumulative-Binomial Program

    Science.gov (United States)

    Scheuer, Ernest M.; Bowerman, Paul N.

    1989-01-01

    Cumulative-binomial computer program, NEWTONP, one of set of three programs, calculates cumulative binomial probability distributions for arbitrary inputs. NEWTONP, CUMBIN (NPO-17555), and CROSSER (NPO-17557), used independently of one another. Program finds probability required to yield given system reliability. Used by statisticians and users of statistical procedures, test planners, designers, and numerical analysts. Program written in C.

  3. Reliability modeling of an engineered barrier system

    International Nuclear Information System (INIS)

    Ananda, M.M.A.; Singh, A.K.; Flueck, J.A.

    1993-01-01

    The Weibull distribution is widely used in reliability literature as a distribution of time to failure, as it allows for both increasing failure rate (IFR) and decreasing failure rate (DFR) models. It has also been used to develop models for an engineered barrier system (EBS), which is known to be one of the key components in a deep geological repository for high level radioactive waste (HLW). The EBS failure time can more realistically be modelled by an IFR distribution, since the failure rate for the EBS is not expected to decrease with time. In this paper, we use an IFR distribution to develop a reliability model for the EBS

  4. Assessment of the reliability of an on-site MBR system for greywater treatment and the associated aesthetic and health risks.

    Science.gov (United States)

    Friedler, E; Shwartzman, Z; Ostfeld, A

    2008-01-01

    This study analyses the reliability of an on-site MBR system for greywater treatment and reuse. To achieve this goal simulation was performed based on the IWA ASM1 model which was adapted to describe biological and physical mechanisms for MBR greywater treatment based systems. Model results were found to agree well with experimental data from an on site pilot greywater treatment plant, after which the calibrated model was used in a Monte Carlo mode for generating statistical data on the MBR system performance under different scenarios of failures and inflow loads variations. Effluents quality and their associated risks were successfully estimated. Copyright IWA Publishing 2008.

  5. Reliability systems for implantable cardiac defibrillator batteries

    Science.gov (United States)

    Takeuchi, Esther S.

    The reliability of the power sources used in implantable cardiac defibrillators is critical due to the life-saving nature of the device. Achieving a high reliability power source depends on several systems functioning together. Appropriate cell design is the first step in assuring a reliable product. Qualification of critical components and of the cells using those components is done prior to their designation as implantable grade. Product consistency is assured by control of manufacturing practices and verified by sampling plans using both accelerated and real-time testing. Results to date show that lithium/silver vanadium oxide cells used for implantable cardiac defibrillators have a calculated maximum random failure rate of 0.005% per test month.

  6. Reliability Standards of Complex Engineering Systems

    Science.gov (United States)

    Galperin, E. M.; Zayko, V. A.; Gorshkalev, P. A.

    2017-11-01

    Production and manufacture play an important role in today’s modern society. Industrial production is nowadays characterized by increased and complex communications between its parts. The problem of preventing accidents in a large industrial enterprise becomes especially relevant. In these circumstances, the reliability of enterprise functioning is of particular importance. Potential damage caused by an accident at such enterprise may lead to substantial material losses and, in some cases, can even cause a loss of human lives. That is why industrial enterprise functioning reliability is immensely important. In terms of their reliability, industrial facilities (objects) are divided into simple and complex. Simple objects are characterized by only two conditions: operable and non-operable. A complex object exists in more than two conditions. The main characteristic here is the stability of its operation. This paper develops the reliability indicator combining the set theory methodology and a state space method. Both are widely used to analyze dynamically developing probability processes. The research also introduces a set of reliability indicators for complex technical systems.

  7. System ergonomics as an approach to improve human reliability

    International Nuclear Information System (INIS)

    Bubb, H.

    1988-01-01

    The application of system technics on ergonomical problems is called system ergonomics. This enables improvements of human reliability by design measures. The precondition for this is the knowledge of how information processing is performed by man and machine. By a separate consideration of sensory processing, cognitive processing, and motory processing it is possible to have a more exact idea of the system element 'man'. The system element 'machine' is well described by differential equations which allow an ergonomical assessment of the manouverability. The knowledge of information processing of man and machine enables a task analysis. This makes appear on one hand the human boundaries depending on the different properties of the task and on the other hand suitable ergonomical solution proposals which improve the reliability of the total system. It is a disadvantage, however, that the change of human reliability by such measures may not be quoted numerically at the moment. (orig.)

  8. The analytic hierarchy process as a systematic approach to the identification of important parameters for the reliability assessment of passive systems

    International Nuclear Information System (INIS)

    Zio, E.; Cantarella, M.; Cammi, A.

    2003-01-01

    Passive systems play a crucial role in the development of future solutions for nuclear plant technology. A fundamental issue still to be resolved is the quantification of the reliability of such systems. In this paper, we firstly illustrate a systematic methodology to guide the definition of the failure criteria of a passive system and the evaluation of its probability of occurrence, through the identification of the relevant system parameters and the propagation of their associated uncertainties. Within this methodology, we propose the use of the analytic hierarchy process as a structured and reproducible tool for the decomposition of the problem and the identification of the dominant system parameters. An example of its application to a real passive system is illustrated in details

  9. Reliability-based condition assessment of steel containment and liners

    International Nuclear Information System (INIS)

    Ellingwood, B.; Bhattacharya, B.; Zheng, R.

    1996-11-01

    Steel containments and liners in nuclear power plants may be exposed to aggressive environments that may cause their strength and stiffness to decrease during the plant service life. Among the factors recognized as having the potential to cause structural deterioration are uniform, pitting or crevice corrosion; fatigue, including crack initiation and propagation to fracture; elevated temperature; and irradiation. The evaluation of steel containments and liners for continued service must provide assurance that they are able to withstand future extreme loads during the service period with a level of reliability that is sufficient for public safety. Rational methodologies to provide such assurances can be developed using modern structural reliability analysis principles that take uncertainties in loading, strength, and degradation resulting from environmental factors into account. The research described in this report is in support of the Steel Containments and Liners Program being conducted for the US Nuclear Regulatory Commission by the Oak Ridge National Laboratory. The research demonstrates the feasibility of using reliability analysis as a tool for performing condition assessments and service life predictions of steel containments and liners. Mathematical models that describe time-dependent changes in steel due to aggressive environmental factors are identified, and statistical data supporting the use of these models in time-dependent reliability analysis are summarized. The analysis of steel containment fragility is described, and simple illustrations of the impact on reliability of structural degradation are provided. The role of nondestructive evaluation in time-dependent reliability analysis, both in terms of defect detection and sizing, is examined. A Markov model provides a tool for accounting for time-dependent changes in damage condition of a structural component or system. 151 refs

  10. Nuclear plant reliability data system. 1979 annual reports of cumulative system and component reliability

    International Nuclear Information System (INIS)

    1979-01-01

    The primary purposes of the information in these reports are the following: to provide operating statistics of safety-related systems within a unit which may be used to compare and evaluate reliability performance and to provide failure mode and failure rate statistics on components which may be used in failure mode effects analysis, fault hazard analysis, probabilistic reliability analysis, and so forth

  11. Structural reliability analysis and seismic risk assessment

    International Nuclear Information System (INIS)

    Hwang, H.; Reich, M.; Shinozuka, M.

    1984-01-01

    This paper presents a reliability analysis method for safety evaluation of nuclear structures. By utilizing this method, it is possible to estimate the limit state probability in the lifetime of structures and to generate analytically the fragility curves for PRA studies. The earthquake ground acceleration, in this approach, is represented by a segment of stationary Gaussian process with a zero mean and a Kanai-Tajimi Spectrum. All possible seismic hazard at a site represented by a hazard curve is also taken into consideration. Furthermore, the limit state of a structure is analytically defined and the corresponding limit state surface is then established. Finally, the fragility curve is generated and the limit state probability is evaluated. In this paper, using a realistic reinforced concrete containment as an example, results of the reliability analysis of the containment subjected to dead load, live load and ground earthquake acceleration are presented and a fragility curve for PRA studies is also constructed

  12. Risk and reliability assessment for telecommunications networks

    Energy Technology Data Exchange (ETDEWEB)

    Wyss, G.D.; Schriner, H.K.; Gaylor, T.R.

    1996-08-01

    Sandia National Laboratories has assembled an interdisciplinary team to explore the applicability of probabilistic logic modeling (PLM) techniques to model network reliability for a wide variety of communications network architectures. The authors have found that the reliability and failure modes of current generation network technologies can be effectively modeled using fault tree PLM techniques. They have developed a ``plug-and-play`` fault tree analysis methodology that can be used to model connectivity and the provision of network services in a wide variety of current generation network architectures. They have also developed an efficient search algorithm that can be used to determine the minimal cut sets of an arbitrarily-interconnected (non-hierarchical) network without the construction of a fault tree model. This paper provides an overview of these modeling techniques and describes how they are applied to networks that exhibit hybrid network structures (i.e., a network in which some areas are hierarchical and some areas are not hierarchical).

  13. Reliability of assessment of adherence to an antimicrobial treatment guideline

    NARCIS (Netherlands)

    Mol, PGM; Gans, ROB; Panday, PVN; Degener, JE; Laseur, M; Haaijer-Ruskamp, FM

    Assessment procedures for adherence to a guideline must be reliable and credible. The aim of this study was to explore the reliability of assessment of adherence, taking account of the professional backgrounds of the observers. A secondary analysis explored the impact of case characteristics on

  14. Different Reliability Assessment Approaches for Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten Mejlhede; Sørensen, John Dalsgaard

    2015-01-01

    Reliability assessments are of importance for wave energy converters (WECs) due to the fact that accessibility might be limited in case of failure and maintenance. These failure rates can be adapted by reliability considerations. There are two different approaches to how reliability can be estima......Reliability assessments are of importance for wave energy converters (WECs) due to the fact that accessibility might be limited in case of failure and maintenance. These failure rates can be adapted by reliability considerations. There are two different approaches to how reliability can...... be estimated: the so-called classical reliability theory and the probabilistic reliability theory. The classical reliability theory is often used for failure rate estimations of mechanical and electrical components, whereas the probabilistic reliability theory is commonly used for structural components....... For WECs, mechanical/electrical components as well as structural components are of importance. Therefore, both reliability theories need to be incorporated in WEC designs, WEC developments and improvements of WECs. This paper gives an overview of the two reliability theories and how they can be combined...

  15. 76 FR 16250 - Planning Resource Adequacy Assessment Reliability Standard

    Science.gov (United States)

    2011-03-23

    ... planning, horizon. The Commission agrees with Borlick's comment, and emphasizes that any type of demand...; Order No. 747] Planning Resource Adequacy Assessment Reliability Standard AGENCY: Federal Energy... (Planning Resource Adequacy Analysis, Assessment and [[Page 16251

  16. 76 FR 42534 - Mandatory Reliability Standards for Interconnection Reliability Operating Limits; System...

    Science.gov (United States)

    2011-07-19

    ... Reliability Operating Limits; System Restoration Reliability Standards AGENCY: Federal Energy Regulatory... data necessary to analyze and monitor Interconnection Reliability Operating Limits (IROL) within its... Interconnection Reliability Operating Limits, Order No. 748, 134 FERC ] 61,213 (2011). \\2\\ The term ``Wide-Area...

  17. Systems reliability Benchmark exercise part 1-Description and results

    International Nuclear Information System (INIS)

    Amendola, A.

    1986-01-01

    The report describes aims, rules and results of the Systems Reliability Benchmark Exercise, which has been performed in order to assess methods and procedures for reliability analysis of complex systems and involved a large number of European organizations active in NPP safety evaluation. The exercise included both qualitative and quantitative methods and was structured in such a way that separation of the effects of uncertainties in modelling and in data on the overall spread was made possible. Part I describes the way in which RBE has been performed, its main results and conclusions

  18. Reliable and Valid Assessment of Clinical Bronchoscopy Performance

    DEFF Research Database (Denmark)

    Konge, Lars; Larsen, Klaus Richter; Clementsen, Paul

    2012-01-01

    Background: There have been several attempts to systematically assess performance in bronchoscopy. Earlier validation studies have used bronchoscopy simulators, not real-life performance in patients. Objectives: The aim of this study was to explore the reliability and validity of an assessment tool...... aspects of the assessment, but post hoc tests showed different discriminative abilities. Conclusions: This new tool for assessing clinical bronchoscopy performance has a high interrater reliability. One rater assessing performance of 3 bronchoscopies ensures sufficient reliability. The assessment tool......: The interrater reliability was high, with Cronbach's a = 0.86. Assessment of 3 bronchoscopies by a single rater had a generalizability coefficient of 0.84. The correlation between experience and performance was good (Pearson correlation = 0.76). There were significant differences between the groups for all...

  19. Reliability analysis of digital I and C systems at KAERI

    International Nuclear Information System (INIS)

    Kim, Man Cheol

    2013-01-01

    This paper provides an overview of the ongoing research activities on a reliability analysis of digital instrumentation and control (I and C) systems of nuclear power plants (NPPs) performed by the Korea Atomic Energy Research Institute (KAERI). The research activities include the development of a new safety-critical software reliability analysis method by integrating the advantages of existing software reliability analysis methods, a fault coverage estimation method based on fault injection experiments, and a new human reliability analysis method for computer-based main control rooms (MCRs) based on human performance data from the APR-1400 full-scope simulator. The research results are expected to be used to address various issues such as the licensing issues related to digital I and C probabilistic safety assessment (PSA) for advanced digital-based NPPs. (author)

  20. Reliability and Validity Assessment of a Linear Position Transducer

    Directory of Open Access Journals (Sweden)

    Manuel V. Garnacho-Castaño

    2015-03-01

    Full Text Available The objectives of the study were to determine the validity and reliability of peak velocity (PV, average velocity (AV, peak power (PP and average power (AP measurements were made using a linear position transducer. Validity was assessed by comparing measurements simultaneously obtained using the Tendo Weightlifting Analyzer Systemi and T-Force Dynamic Measurement Systemr (Ergotech, Murcia, Spain during two resistance exercises, bench press (BP and full back squat (BS, performed by 71 trained male subjects. For the reliability study, a further 32 men completed both lifts using the Tendo Weightlifting Analyzer Systemz in two identical testing sessions one week apart (session 1 vs. session 2. Intraclass correlation coefficients (ICCs indicating the validity of the Tendo Weightlifting Analyzer Systemi were high, with values ranging from 0.853 to 0.989. Systematic biases and random errors were low to moderate for almost all variables, being higher in the case of PP (bias ±157.56 W; error ±131.84 W. Proportional biases were identified for almost all variables. Test-retest reliability was strong with ICCs ranging from 0.922 to 0.988. Reliability results also showed minimal systematic biases and random errors, which were only significant for PP (bias -19.19 W; error ±67.57 W. Only PV recorded in the BS showed no significant proportional bias. The Tendo Weightlifting Analyzer Systemi emerged as a reliable system for measuring movement velocity and estimating power in resistance exercises. The low biases and random errors observed here (mainly AV, AP make this device a useful tool for monitoring resistance training.

  1. Fast Reliability Assessing Method for Distribution Network with Distributed Renewable Energy Generation

    Science.gov (United States)

    Chen, Fan; Huang, Shaoxiong; Ding, Jinjin; Ding, Jinjin; Gao, Bo; Xie, Yuguang; Wang, Xiaoming

    2018-01-01

    This paper proposes a fast reliability assessing method for distribution grid with distributed renewable energy generation. First, the Weibull distribution and the Beta distribution are used to describe the probability distribution characteristics of wind speed and solar irradiance respectively, and the models of wind farm, solar park and local load are built for reliability assessment. Then based on power system production cost simulation probability discretization and linearization power flow, a optimal power flow objected with minimum cost of conventional power generation is to be resolved. Thus a reliability assessment for distribution grid is implemented fast and accurately. The Loss Of Load Probability (LOLP) and Expected Energy Not Supplied (EENS) are selected as the reliability index, a simulation for IEEE RBTS BUS6 system in MATLAB indicates that the fast reliability assessing method calculates the reliability index much faster with the accuracy ensured when compared with Monte Carlo method.

  2. Procedures for controlling the risks of reliability, safety, and availability of technical systems

    International Nuclear Information System (INIS)

    1987-01-01

    The reference book covers four sections. Apart from the fundamental aspects of the reliability problem, of risk and safety and the relevant criteria with regard to reliability, the material presented explains reliability in terms of maintenance, logistics and availability, and presents procedures for reliability assessment and determination of factors influencing the reliability, together with suggestions for systems technical integration. The reliability assessment consists of diagnostic and prognostic analyses. The section on factors influencing reliability discusses aspects of organisational structures, programme planning and control, and critical activities. (DG) [de

  3. Nuclear power plant emergency core cooling system reliability analysis - reliability estimation for small LOCA

    International Nuclear Information System (INIS)

    Vojnovic, Dj.

    1989-01-01

    System performance reliability depends not only on its own availability but also on requirements which are placed the system. This paper shows a way of system performance reliability estimation for a NPP Emergency Core Cooling System in case of small LOCA. The event scenario and requirements for systems are determined with event tree. Finally, the ECCS reliability estimation is performed on the basis of system requirements. (author)

  4. Generation reliability assessment in oligopoly power market using Monte Carlo simulation

    International Nuclear Information System (INIS)

    Haroonabadi, H.; Haghifam, M.R.

    2007-01-01

    This paper addressed issues regarding power generation reliability assessment (HLI) in deregulated power pool markets. Most HLI reliability evaluation methods are based on the loss of load (LOLE) approach which is among the most suitable indices to describe the level of generation reliability. LOLE refers to the time in which load is greater than the amount of available generation. While most reliability assessments deal only with power system constraints, this study considered HLI reliability assessment in an oligopoly power market using Monte Carlo simulation (MCS). It evaluated the sensitivity of the reliability index to different reserve margins and future margins. The reliability index was determined by intersecting the offer and demand curves of power plants and comparing them to other parameters. The paper described the fundamentals of an oligopoly power pool market and proposed an algorithm for HLI reliability assessment for such a market. The proposed method was assessed on the IEEE-Reliability Test System with satisfactory results. In all cases, generation reliability indices were evaluated with different reserve margins and various load levels. 19 refs., 7 figs., 1 appendix

  5. Generation reliability assessment in oligopoly power market using Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Haroonabadi, H. [Islamic Azad Univ., Islamshahr (Iran, Islamic Republic of). Dept. of Electrical Engineering; Haghifam, M.R. [Tarbiat Modares Univ., Tehran (Iran, Islamic Republic of). Dept. of Electrical and Computer Engineering

    2007-07-01

    This paper addressed issues regarding power generation reliability assessment (HLI) in deregulated power pool markets. Most HLI reliability evaluation methods are based on the loss of load (LOLE) approach which is among the most suitable indices to describe the level of generation reliability. LOLE refers to the time in which load is greater than the amount of available generation. While most reliability assessments deal only with power system constraints, this study considered HLI reliability assessment in an oligopoly power market using Monte Carlo simulation (MCS). It evaluated the sensitivity of the reliability index to different reserve margins and future margins. The reliability index was determined by intersecting the offer and demand curves of power plants and comparing them to other parameters. The paper described the fundamentals of an oligopoly power pool market and proposed an algorithm for HLI reliability assessment for such a market. The proposed method was assessed on the IEEE-Reliability Test System with satisfactory results. In all cases, generation reliability indices were evaluated with different reserve margins and various load levels. 19 refs., 7 figs., 1 appendix.

  6. Analysis of reliability parameters for complicated information measurement systems

    OpenAIRE

    Sydor, Andriy

    2012-01-01

    A method of analysis of reliability parameters for complicated systems by means of generating functions is developed taking account of aging of the systems output elements. Main reliability parameters of complicated information measurement systems are examined in this paper.

  7. Reliability and validity of subjective assessment of lumbar lordosis in ...

    African Journals Online (AJOL)

    Background: Reliability and validity studies of different lumbar curvature analysis and measurement techniques have been documented however there is limited literature on the reliability and validity of subjective visual analysis. Radiological assessment of lumbar lordotic curve aids in early diagnosis of conditions even ...

  8. System reliability analysis with natural language and expert's subjectivity

    International Nuclear Information System (INIS)

    Onisawa, T.

    1996-01-01

    This paper introduces natural language expressions and expert's subjectivity to system reliability analysis. To this end, this paper defines a subjective measure of reliability and presents the method of the system reliability analysis using the measure. The subjective measure of reliability corresponds to natural language expressions of reliability estimation, which is represented by a fuzzy set defined on [0,1]. The presented method deals with the dependence among subsystems and employs parametrized operations of subjective measures of reliability which can reflect expert 's subjectivity towards the analyzed system. The analysis results are also expressed by linguistic terms. Finally this paper gives an example of the system reliability analysis by the presented method

  9. Reliable neuronal systems: the importance of heterogeneity.

    Directory of Open Access Journals (Sweden)

    Johannes Lengler

    Full Text Available For every engineer it goes without saying: in order to build a reliable system we need components that consistently behave precisely as they should. It is also well known that neurons, the building blocks of brains, do not satisfy this constraint. Even neurons of the same type come with huge variances in their properties and these properties also vary over time. Synapses, the connections between neurons, are highly unreliable in forwarding signals. In this paper we argue that both these fact add variance to neuronal processes, and that this variance is not a handicap of neural systems, but that instead predictable and reliable functional behavior of neural systems depends crucially on this variability. In particular, we show that higher variance allows a recurrently connected neural population to react more sensitively to incoming signals, and processes them faster and more energy efficient. This, for example, challenges the general assumption that the intrinsic variability of neurons in the brain is a defect that has to be overcome by synaptic plasticity in the process of learning.

  10. Control system reliability at Jefferson Lab

    International Nuclear Information System (INIS)

    At Thomas Jefferson National Accelerator Facility (Jefferson Lab), the availability of the control system is crucial to the operation of the accelerator for experimental programs. Jefferson Lab's control system, uses 68040 based microprocessors running VxWorks, Unix workstations, and a variety of VME, CAMAC. GPIB, and serial devices. The software consists of control system toolkit software, commercial packages, and over 200 custom and generic applications, some of which are highly complex. The challenge is to keep this highly diverse and still growing system, with over 162,000 control points, operating reliably, while managing changes and upgrades to both the hardware and software. Downtime attributable to the control system includes the time to troubleshoot and repair problems and the time to restore the machine to operation of the scheduled program. This paper describes the availability of the control system during the last year, the heaviest contributors to downtime and the response to problems. Strategies for improving the robustness of the control system am detailed and include changes in hardware, software, procedures and processes. The improvements range from the routine preventive hardware maintenance, to improving their ability to detect, predict and prevent problems. This paper also describes the software tools used to assist in control system troubleshooting, maintenance and failure recovery processes

  11. Control system reliability at Jefferson Lab

    International Nuclear Information System (INIS)

    White, K.S.; Areti, H.; Garza, O.

    1997-01-01

    At Thomas Jefferson National Accelerator Facility (Jefferson Lab), the availability of the control system is crucial to the operation of the accelerator for experimental programs. Jefferson Lab's control system, uses 68040 based microprocessors running VxWorks, Unix workstations, and a variety of VME, CAMAC. GPIB, and serial devices. The software consists of control system toolkit software, commercial packages, and over 200 custom and generic applications, some of which are highly complex. The challenge is to keep this highly diverse and still growing system, with over 162,000 control points, operating reliably, while managing changes and upgrades to both the hardware and software. Downtime attributable to the control system includes the time to troubleshoot and repair problems and the time to restore the machine to operation of the scheduled program. This paper describes the availability of the control system during the last year, the heaviest contributors to downtime and the response to problems. Strategies for improving the robustness of the control system am detailed and include changes in hardware, software, procedures and processes. The improvements range from the routine preventive hardware maintenance, to improving their ability to detect, predict and prevent problems. This paper also describes the software tools used to assist in control system troubleshooting, maintenance and failure recovery processes

  12. Study on Assembly Precision Reliability Assessment for Industrial Sensing Devices

    Directory of Open Access Journals (Sweden)

    Fan Tian

    2017-01-01

    Full Text Available This paper investigates the method of assembly precision reliability assessment for industrial sensing devices. The part variation is formulated by small displacement torsor. The assembly error model is developed through the approach of pose transformation matrix, then the error transfer between the parts is analyzed and the assembly error is calculated. The concept of assembly precision reliability is proposed. Monte Carlo simulation is adopted to calculate the reliability, after that the procedure of assembly precision reliability is determined. Case study of a laser sensor is provided therefore the effectiveness of the proposed models is verified.

  13. Reliability analysis of service water system under earthquake

    International Nuclear Information System (INIS)

    Yu Yu; Qian Xiaoming; Lu Xuefeng; Wang Shengfei; Niu Fenglei

    2013-01-01

    Service water system is one of the important safety systems in nuclear power plant, whose failure probability is always gained by system reliability analysis. The probability of equipment failure under the earthquake is the function of the peak acceleration of earthquake motion, while the occurrence of earthquake is of randomicity, thus the traditional fault tree method in current probability safety assessment is not powerful enough to deal with such case of conditional probability problem. An analysis frame was put forward for system reliability evaluation in seismic condition in this paper, in which Monte Carlo simulation was used to deal with conditional probability problem. Annual failure probability of service water system was calculated, and failure probability of 1.46X10 -4 per year was obtained. The analysis result is in accordance with the data which indicate equipment seismic resistance capability, and the rationality of the model is validated. (authors)

  14. Learning Analytics for Peer-assessment: (Disadvantages, Reliability and Implementation

    Directory of Open Access Journals (Sweden)

    Blaženka Divjak

    2017-01-01

    Full Text Available Learning analytics deals with the data that occurs from students' interaction with ICT: collecting data, analyzing and reporting that can influence learning and teaching. Analysis of validity and reliability of assessment lags behind other applications of learning analytics. We present here mathematical modeling of learning analytics for assessment, especially for peer-assessment. In addition, we analyze and categorize students' recognition of advantages and disadvantages of peer-assessment. Finally implementations of reliability check of peer-assessment in Moodle Workshop module are explained.

  15. Reliable control system for nuclear power plant

    International Nuclear Information System (INIS)

    Okamoto, Tetsuo; Miyazaki, Shiro

    1980-01-01

    The System 1100 for nuclear power plants is the measuring and control system which utilizes the features of the System 1100 for electric power market in addition to the results of nuclear instrumentation with EBS-ZN series, and it has the following features. The maintenance and inspection in operation are easy. The construction of control loops is made flexibly by the combination of modules. The construction of multi-variable control system using mainly feed forward control is easy. Such functions as the automatic switching of control modes can be included. The switching of manual and automatic operations is easy, and if some trouble occurred in a module, the manual operation can be made. The aseismatic ability is improved by rigid structure cubicles. Nonflammable materials are used for wires, multi-core cables, paints and printed boards. The anti-noise characteristics are improved, and the reliability is high. The policy of developing the System 1100 for nuclear power plants, the type approval tests on modules and units and the type approval test on the system are described. The items of the system type approval test were standard performance test, earthquake test, noise isolation test, temperature and humidity test, and drift test. The aseismatic cubicle showed good endurance in its vibration test. (Kako, I.)

  16. Demand Response as a System Reliability Resource

    Energy Technology Data Exchange (ETDEWEB)

    Eto, Joseph H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Energy Technologies Division; Lewis, Nancy Jo [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Energy Technologies Division; Watson, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Energy Technologies Division; Kiliccote, Sila [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Energy Technologies Division; Auslander, David [Univ. of California, Berkeley, CA (United States); Paprotny, Igor [Univ. of California, Berkeley, CA (United States); Makarov, Yuri [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2012-12-31

    The Demand Response as a System Reliability Resource project consists of six technical tasks: • Task 2.1. Test Plan and Conduct Tests: Contingency Reserves Demand Response (DR) Demonstration—a pioneering demonstration of how existing utility load-management assets can provide an important electricity system reliability resource known as contingency reserve. • Task 2.2. Participation in Electric Power Research Institute (EPRI) IntelliGrid—technical assistance to the EPRI IntelliGrid team in developing use cases and other high-level requirements for the architecture. • Task 2.3. Research, Development, and Demonstration (RD&D) Planning for Demand Response Technology Development—technical support to the Public Interest Energy Research (PIER) Program on five topics: Sub-task 1. PIER Smart Grid RD&D Planning Document; Sub-task 2. System Dynamics of Programmable Controllable Thermostats; Sub-task 3. California Independent System Operator (California ISO) DR Use Cases; Sub-task 4. California ISO Telemetry Requirements; and Sub-task 5. Design of a Building Load Data Storage Platform. • Task 2.4. Time Value of Demand Response—research that will enable California ISO to take better account of the speed of the resources that it deploys to ensure compliance with reliability rules for frequency control. • Task 2.5. System Integration and Market Research: Southern California Edison (SCE)—research and technical support for efforts led by SCE to conduct demand response pilot demonstrations to provide a contingency reserve service (known as non-spinning reserve) through a targeted sub-population of aggregated residential and small commercial customers enrolled in SCE’s traditional air conditioning (AC) load cycling program, the Summer Discount Plan. • Task 2.6. Demonstrate Demand Response Technologies: Pacific Gas and Electric (PG&E)—research and technical support for efforts led by PG&E to conduct a demand response pilot demonstration to provide non

  17. A high reliability oxygen deficiency monitoring system

    International Nuclear Information System (INIS)

    Parry, R.; Claborn, G.; Haas, A.; Landis, R.; Page, W.; Smith, J.

    1993-05-01

    The escalating use of cryogens at national laboratories in general and accelerators in particular, along with the increased emphasis placed on personnel safety, mandates the development and installation of oxygen monitoring systems to insure personnel safety in the event of a cryogenic leak. Numerous vendors offer oxygen deficiency monitoring systems but fail to provide important features and/or flexibility. This paper describes a unique oxygen monitoring system developed for the Magnet Test Laboratory (MTL) at the Superconducting Super Collider Laboratory (SSCL). Features include: high reliability, oxygen cell redundancy, sensor longevity, simple calibration, multiple trip points, offending sensor audio and visual indication, global alarms for building evacuation, local and remote analog readout, event and analog data logging, EMAIL event notification, phone line voice status system, and multi-drop communications network capability for reduced cable runs. Of particular importance is the distributed topology of the system which allows it to operate in a stand-alone configuration or to communicate with a host computer. This flexibility makes it ideal for small applications such as a small room containing a cryogenic dewar, as well as larger systems which monitor many offices and labs in several buildings

  18. Automated cephalometry: system performance reliability using landmark-dependent criteria.

    Science.gov (United States)

    Tanikawa, Chihiro; Yagi, Masakazu; Takada, Kenji

    2009-11-01

    The purpose of the present study was to evaluate reliability of a system that performs automatic recognition of anatomic landmarks and adjacent structures on lateral cephalograms using landmark-dependent criteria unique to each landmark. To evaluate the reliability of the system, the system was used to examine 65 lateral cephalograms. The area of each system-identified anatomic structure surrounding the landmark and the position of each system-identified landmark were compared with norms using confidence ellipses with alpha = .01, which were derived from the scattergrams of 100 estimates obtained according to the method reported by Baumrind and Frantz. When the system-identified area overlapped with the norm area, anatomic structure recognition was considered successful. In addition, when the system-identified point was located within the norm area, landmark identification was considered successful. Based on these judgment criteria, success rates were calculated for all landmarks. The system successfully identified all specified anatomic structures in all the images and determined the positions of the landmarks with a mean success rate of 88% (range, 77%- 100%). With the incorporation of the rational assessment criteria provided by confidence ellipses, the proposed system was confirmed to be reliable.

  19. Assessment of power reliability and improvement potential by using ...

    African Journals Online (AJOL)

    This paper presents the use of smart reclosers for improving reliability of a distribution system of one of the major cities of Ethiopia. As frequent power interruptions are posing a huge problem to the life of the people and the economy, finding a solution to the problem is very essential. Electric reliability has affected social well ...

  20. System safety and reliability using object-oriented programming techniques

    International Nuclear Information System (INIS)

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

    1987-01-01

    Direct evaluation fault tree codes have been written in recursive, list-processing computer languages such as PL/1 (PATREC-I) and LISP (PATREC-L). The pattern-matching strategy implemented in these codes has been used extensively in France to evaluate system reliability. Recent reviews of the risk management process suggest that a data base containing plant-specific information be integrated with a package of codes used for probabilistic risk assessment (PRA) to alleviate some of the difficulties that make a PRA so costly and time-intensive. A new programming paradigm, object-oriented programming, is uniquely suited for the development of such a software system. A knowledge base and fault tree evaluation algorithm, based on previous experience with PATREC-L, have been implemented using object-oriented techniques, resulting in a reliability assessment environment that is easy to develop, modify, and extend

  1. Diagnostics and reliability of pipeline systems

    CERN Document Server

    Timashev, Sviatoslav

    2016-01-01

    The book contains solutions to fundamental problems which arise due to the logic of development of specific branches of science, which are related to pipeline safety, but mainly are subordinate to the needs of pipeline transportation.          The book deploys important but not yet solved aspects of reliability and safety assurance of pipeline systems, which are vital aspects not only for the oil and gas industry and, in general, fuel and energy industries , but also to virtually all contemporary industries and technologies. The volume will be useful to specialists and experts in the field of diagnostics/ inspection, monitoring, reliability and safety of critical infrastructures. First and foremost, it will be useful to the decision making persons —operators of different types of pipelines, pipeline diagnostics/inspection vendors, and designers of in-line –inspection (ILI) tools, industrial and ecological safety specialists, as well as to researchers and graduate students.

  2. Towards Reliable Integrated Services for Dependable Systems

    DEFF Research Database (Denmark)

    Schiøler, Henrik; Ravn, Anders Peter; Izadi-Zamanabadi, Roozbeh

    connections and a reliability management framework is suggested. We suggest a network layer level reliability management protocol RRSVP (Reliability Resource Reservation Protocol) as a counterpart of the RSVP for bandwidth and time resource management. Active and passive standby redundancy by background...... applications residing on alternative routes. Details are provided for the operation of RRRSVP based on reliability slack calculus. Conclusions summarize the considerations and give directions for future research....

  3. Exploitation examination of reliability of coal dust systems

    International Nuclear Information System (INIS)

    Dojchinovski, Ilija; Trajkovski, Kole

    1997-01-01

    Designers and operators wish is, long, failure free operation at designed parameters of every system. Always we know the system start up time, but we don't know how long this system will operate successfully. Because of that in this article is given a method how, step by step, to determine the reliability of the system. Reliability parameters are obtained from experimental and operational data. When reliability parameters are determined then it is very easy to compare reliability of similar systems, for example excavators, or different systems, such as truck and rubber band transport system. Practical use of the theory of reliability is by purchasing of the systems when manufacturers have to have and present reliability parameters and on this way we can decide which system satisfies our needs regarding the quality-price-reliability. Reliability can be practically used in system operation where: 1) system reliability is maintained with proper start, use and shutdown of the system; 2) a system reliability is maintained with good maintenance organization; 3) a system reliability is maintained with innovations and improvements with final purpose removing of the imperfections experienced through the operation. Reliability is very important parameter in power generation plants. (Author)

  4. Reliability and comparison of acromion assessment techniques on x-ray and magnetic resonance imaging (reliability of acromion assessment techniques)

    International Nuclear Information System (INIS)

    Viskontas, D.G.; MacDermid, J.C.; Drosdowech, D.S.; Garvin, G.J.; Romano, W.M.; Faber, K.J.

    2005-01-01

    To determine the reliability and correlation of plain radiography and magnetic resonance imaging (MRI) in the assessment of acromion morphology. Materials and Methods: Acromion morphology was assessed using the lateral acromion angle (LAA) and the acromion-humeral interval (AHI). Thirty patients who had x-rays and MRI for impingement syndrome were included. Six blinded observers assessed the acromion morphology subjectively and objectively. Results: Neither acromion assessment technique demonstrated a positive correlation (kappa and intraclass coefficient 0.55) when measured objectively by experienced observers. Conclusion: The LAA and the AHI are both reliable acromion assessment techniques on X-ray and MRI when measured objectively and by experienced observers. (author)

  5. Practice of value-based distribution reliability assessment (VBDRA) at Scarborough Public Utilities

    International Nuclear Information System (INIS)

    Chen, R-L.

    1995-01-01

    The development of value-based distribution reliability assessment (VBDRA) at Scarborough Public Utilities was described. Load point reliability indices, customer interruption costs (CIC), continuity and service reliability, accuracy of CIC, and the aspects of application of VBDRA were addressed. The application of VBDRA to a long-term rebuild plan for 4.16 kV distribution system was described. The importance of a cost-benefit analysis for implementation of VBDRA was emphasized. In the case of the Scarborough Public Utilities Commission the enhanced feeder reliability assessment was found to influence the allocation of funding to where it provided the most value to customers. 14 refs., 3 tabs., 3 figs

  6. Using the Hemophilia Joint Health Score for assessment of children: Reliability of the Spanish version.

    Science.gov (United States)

    R, Cuesta-Barriuso; A, Torres-Ortuño; S, Pérez-Alenda; J, Carrasco Juan; F, Querol; J, Nieto-Munuera; Ja, López-Pina

    2018-02-27

    Numerous measuring instruments for the evaluation of hemophilic arthropathy have been developed. One of the most used systems is the Hemophilia Joint Health Score (HJHS) given its sensitivity to clinical changes appearing in the joints because of recurrent hemarthrosis. Assessing the interrater reliability, using the Spanish version of the HJHS (version 2.1) in children with hemophilia. Reliability study to assess the interrater reliability of the Spanish version of HJHS. A sample of 36 children aged 7-13 years diagnosed with hemophilia A or B was used. Two physiotherapists performed physical assessments with the Spanish version of the HJHS. Descriptive statistics (range, mean, standard deviation) and the analysis of interrater reliability were calculated. The interrater reliability was heterogeneous since the Kappa coefficient range (ĸ), although significant (p reliability of the Spanish population version of the HJHS is high. This scale should be used generically in evaluating musculoskeletal pediatric patients with hemophilia.

  7. Mechanical system reliability for long life space systems

    Science.gov (United States)

    Kowal, Michael T.

    1994-01-01

    The creation of a compendium of mechanical limit states was undertaken in order to provide a reference base for the application of first-order reliability methods to mechanical systems in the context of the development of a system level design methodology. The compendium was conceived as a reference source specific to the problem of developing the noted design methodology, and not an exhaustive or exclusive compilation of mechanical limit states. The compendium is not intended to be a handbook of mechanical limit states for general use. The compendium provides a diverse set of limit-state relationships for use in demonstrating the application of probabilistic reliability methods to mechanical systems. The compendium is to be used in the reliability analysis of moderately complex mechanical systems.

  8. Pump system characterization and reliability enhancement

    International Nuclear Information System (INIS)

    Staunton, R.H.

    1998-01-01

    Pump characterization studies were performed at the Oak Ridge National Laboratory (ORNL) to review and analyze six years (1990-1995) of data from pump systems at domestic nuclear plants. The studies considered not only pumps and pump motors but also pump-related circuit breakers and turbine drives (i.e., the pump system). One significant finding was that the number of 'significant' failures of the pump circuit breaker exceeds the number of significant failures of the pump itself. The study also shows how regulatory code testing was designed for the pump only and therefore did not lead to the discovery of other significant pump system failures. Potential diagnostic technologies, both experimental and mature, suitable for on-line and off-line pump testing were identified. The study does not select or recommend technologies but proposes diagnostic technologies and monitoring techniques that should be further evaluated/developed for making meaningful and critically-needed improvements in the reliability of the pump system. (author)

  9. Multi Anode Photomultiplier Tube Reliability Assessment for the JEM-EUSO Space Mission

    OpenAIRE

    Prieto-Alfonso, H.; del Peral, L.; Casolino, M.; Tsuno, K.; Ebisuzaki, T.; Frías, M. D. Rodríguez; Collaboration, JEM-EUSO

    2015-01-01

    Reliability assessment in concerned with the analysis of devices and systems whose individual components are prone to fail. This reliability analysis documents the process and results of reliability determination of the JEM-EUSO photomultiplier tube component using the methods 217 Plus. Quantum efficiency degradation and radiation hardness assurance. In conclussion, the levels of damage suffered by the PMTs which comprise the focal surface of JEM-EUSO Space Telescope, are acceptable. The resu...

  10. Human reliability in complex systems: an overview

    International Nuclear Information System (INIS)

    Embrey, D.E.

    1976-07-01

    A detailed analysis is presented of the main conceptual background underlying the areas of human reliability and human error. The concept of error is examined and generalized to that of human reliability, and some of the practical and methodological difficulties of reconciling the different standpoints of the human factors specialist and the engineer discussed. Following a survey of general reviews available on human reliability, quantitative techniques for prediction of human reliability are considered. An in-depth critical analysis of the various quantitative methods is then presented, together with the data bank requirements for human reliability prediction. Reliability considerations in process control and nuclear plant, and also areas of design, maintenance, testing and emergency situations are discussed. The effects of stress on human reliability are analysed and methods of minimizing these effects discussed. Finally, a summary is presented and proposals for further research are set out. (author)

  11. Reliable and valid assessment of Lichtenstein hernia repair skills

    DEFF Research Database (Denmark)

    Carlsen, C G; Lindorff Larsen, Karen; Funch-Jensen, P

    2014-01-01

    of an assessment tool designed to measure surgical skills in Lichtenstein hernia repair. METHODS: Key issues were identified through a focus group interview. On this basis, an assessment tool with eight items was designed. Ten surgeons and surgical trainees were video recorded while performing Lichtenstein hernia...... repair, (four experts, three intermediates, and three novices). The videos were blindly and individually assessed by three raters (surgical consultants) using the assessment tool. Based on these assessments, validity and reliability were explored. RESULTS: The internal consistency of the items was high...... a significant difference between the three groups which indicates construct validity, p skills can be assessed blindly by a single rater in a reliable and valid fashion with the new procedure-specific assessment tool. We recommend this tool for future assessment...

  12. Iterative Development and Reliability of the OMERACT Hand Osteoarthritis MRI Scoring System

    DEFF Research Database (Denmark)

    Haugen, Ida K; Østergaard, Mikkel; Eshed, Iris

    2014-01-01

    To develop and test the interreader reliability of the OMERACT Hand Osteoarthritis Magnetic Resonance Scoring System (HOAMRIS) for assessment of structural and inflammatory hand OA features in the interphalangeal joints.......To develop and test the interreader reliability of the OMERACT Hand Osteoarthritis Magnetic Resonance Scoring System (HOAMRIS) for assessment of structural and inflammatory hand OA features in the interphalangeal joints....

  13. Time-dependent reliability analysis and condition assessment of structures

    International Nuclear Information System (INIS)

    Ellingwood, B.R.

    1997-01-01

    Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process

  14. A computer system for the analysis of integrated circuit reliability

    Science.gov (United States)

    Mauri, P.

    1989-12-01

    The formulation of total reliability assessment of integrated circuits involves an increasing amount of knowledge and data and hence it requires increasing computerized assistance. To perform this an information system has been designed and implemented. Following engineering practice, the key features of the system are (1) the collection of different types of data, e.g. electrical parameter measurements and qualitative description of the mode and the mechanism of failure and (2) the implementation of procedures coming from methods often applied, e.g. statistical or new approaches, such as formalization of cause-effect chains as studied for artificial intelligence applications. The system architecture has been designed so as to allow direct user maintenance, and hence a quick updating of reliability knowledge and information. Furthermore, its modularity eases the implementation of new procedures. Computer support improves the quality of data analysis and allows for the application of new methods and models.

  15. System reliability evaluation of a touch panel manufacturing system with defect rate and reworking

    International Nuclear Information System (INIS)

    Lin, Yi-Kuei; Huang, Cheng-Fu; Chang, Ping-Chen

    2013-01-01

    In recent years, portable consumer electronic products, such as cell phone, GPS, digital camera, tablet PC, and notebook are using touch panel as interface. With the demand of touch panel increases, performance assessment is essential for touch panel production. This paper develops a method to evaluate system reliability of a touch panel manufacturing system (TPMS) with defect rate of each workstation and takes reworking actions into account. The system reliability which evaluates the possibility of demand satisfaction can provide to managers with an understanding of the system capability and can indicate possible improvements. First, we construct a capacitated manufacturing network (CMN) for a TPMS. Second, a decomposition technique is developed to determine the input flow of each workstation based on the CMN. Finally, we generate the minimal capacity vectors that should be provided to satisfy the demand. The system reliability is subsequently evaluated in terms of the minimal capacity vectors. A further decision making issue is discussed to decide a reliable production strategy. -- Graphical abstract: The proposed procedure to evaluate system reliability of the touch panel manufacturing system (TPMS). Highlights: • The system reliability of a touch panel manufacturing system (TPMS) is evaluated. • The reworking actions are taken into account in the TPMS. • A capacitated manufacturing network is constructed for the TPMS. • A procedure is proposed to evaluate system reliability of TPMS

  16. Assessment of microelectronics packaging for high temperature, high reliability applications

    Energy Technology Data Exchange (ETDEWEB)

    Uribe, F.

    1997-04-01

    This report details characterization and development activities in electronic packaging for high temperature applications. This project was conducted through a Department of Energy sponsored Cooperative Research and Development Agreement between Sandia National Laboratories and General Motors. Even though the target application of this collaborative effort is an automotive electronic throttle control system which would be located in the engine compartment, results of this work are directly applicable to Sandia`s national security mission. The component count associated with the throttle control dictates the use of high density packaging not offered by conventional surface mount. An enabling packaging technology was selected and thermal models defined which characterized the thermal and mechanical response of the throttle control module. These models were used to optimize thick film multichip module design, characterize the thermal signatures of the electronic components inside the module, and to determine the temperature field and resulting thermal stresses under conditions that may be encountered during the operational life of the throttle control module. Because the need to use unpackaged devices limits the level of testing that can be performed either at the wafer level or as individual dice, an approach to assure a high level of reliability of the unpackaged components was formulated. Component assembly and interconnect technologies were also evaluated and characterized for high temperature applications. Electrical, mechanical and chemical characterizations of enabling die and component attach technologies were performed. Additionally, studies were conducted to assess the performance and reliability of gold and aluminum wire bonding to thick film conductor inks. Kinetic models were developed and validated to estimate wire bond reliability.

  17. System reliability, performance and trust in adaptable automation.

    Science.gov (United States)

    Chavaillaz, Alain; Wastell, David; Sauer, Jürgen

    2016-01-01

    The present study examined the effects of reduced system reliability on operator performance and automation management in an adaptable automation environment. 39 operators were randomly assigned to one of three experimental groups: low (60%), medium (80%), and high (100%) reliability of automation support. The support system provided five incremental levels of automation which operators could freely select according to their needs. After 3 h of training on a simulated process control task (AutoCAMS) in which the automation worked infallibly, operator performance and automation management were measured during a 2.5-h testing session. Trust and workload were also assessed through questionnaires. Results showed that although reduced system reliability resulted in lower levels of trust towards automation, there were no corresponding differences in the operators' reliance on automation. While operators showed overall a noteworthy ability to cope with automation failure, there were, however, decrements in diagnostic speed and prospective memory with lower reliability. Copyright © 2015. Published by Elsevier Ltd.

  18. Photographic assessment of burn size and depth: reliability and validity

    NARCIS (Netherlands)

    Hop, M.; Moues, C.; Bogomolova, K.; Nieuwenhuis, M.; Oen, I.; Middelkoop, E.; Breederveld, R.; de Baar, M.

    2014-01-01

    Objective: The aim of this study was to examine the reliability and validity of using photographs of burns to assess both burn size and depth. Method: Fifty randomly selected photographs taken on day 0-1 post burn were assessed by seven burn experts and eight referring physicians. Inter-rater

  19. The advantages of reliability centered maintenance for standby safety systems

    International Nuclear Information System (INIS)

    Dam, R.F.; Ayazzudin, S.; Nickerson, J.H.; DeLong, A.I.

    2002-01-01

    Full text: On standby safety systems, nuclear plants have to balance the requirements of demonstrating the reliability of each system, while maintaining the system and plant availability. With the goal of demonstrating statistical reliability, these systems have extensive testing programs, which often makes the system unavailable and this can impact the plant capacity. The inputs to the process are often safety and regulatory related, resulting in programs that provide a high level of scrutiny on the systems being considered. In such cases, the value of the application of a maintenance optimization strategy, such as Reliability Centered Maintenance (RCM), is questioned. Part of the question stems from the use of the word 'Reliability' in RCM, which implies a level of redundancy when applied to a system maintenance program driven by reliability requirements. A deeper look at the RCM process, however, shows that RCM has the goal of ensuring that the system operates 'reliably' through the application of an integrated maintenance strategy. This is a subtle, but important distinction. Although the system reliability requirements are an important part of the strategy evaluation, RCM provides a broader context where testing is only one part of an overall strategy focused on ensuring that component function is maintained through a combination of monitoring technologies (including testing), predictive techniques, and intrusive maintenance strategies. Each strategy is targeted to identify known component degradation mechanisms. The conclusion is that a maintenance program driven by reliability requirements will tend to have testing defined at a frequency intended to support the needed statistics. The testing demonstrates that the desired function is available today. Maintenance driven by functional requirements and known failure causes, as developed through an RCM assessment, will have frequencies tied to industry experience with components and rely on a higher degree of

  20. ASSESSMENT OF ORGANIZATIONAL AND TECHNOLOGICAL RELIABILITY OF INDUSTRIAL CONSTRUCTION ENTERPRISES

    Directory of Open Access Journals (Sweden)

    Gazaryan Robert Kamoevich

    2012-10-01

    Full Text Available In this article, the procedure of identification of organizational and technological reliability is described. This methodology is applicable both to separate functional areas and to all industrial enterprises. Its objective is to assess the expediency of reorganization. The objective of this scientific research is the substantiation of reorganization of an industrial enterprise. Multivariable models, or convolutions, were used as research methods. According to the RF law, industrial enterprises are divided into four functional areas, each of which is assessed on the basis of multiple criteria. Assessment of organizational and technological reliability requires a multi-parameter model. Its axes correspond to the number of evaluation criteria. The set of criteria designated for the assessment of organizational and technological reliability is identified on the basis of the homogeneity of trend indicators designated for centripetal and centrifugal models. The axes of a multi-parameter model represent real and benchmark values. The unit serves as the benchmark value; it is the maximal value of this parameter. The formula based on average values shall be used to determine the total value of the above parameters. The authors have also generated a model of organizational and technological reliability of industrial enterprises. It is noteworthy that assessment of organizational and technological reliability of an industrial enterprise requires a concentric multi-layer model developed through the application of the convolution method.

  1. Composite system reliability evaluation by stochastic calculation of system operation

    Energy Technology Data Exchange (ETDEWEB)

    Haubrick, H.-J.; Hinz, H.-J.; Landeck, E. [Dept. of Power Systems and Power Economics (Germany)

    1994-12-31

    This report describes a new developed probabilistic approach for steady-state composite system reliability evaluation and its exemplary application to a bulk power test system. The new computer program called PHOENIX takes into consideration transmission limitations, outages of lines and power stations and, as a central element, a highly sophisticated model to the dispatcher performing remedial actions after disturbances. The kernel of the new method is a procedure for optimal power flow calculation that has been specially adapted for the use in reliability evaluations under the above mentioned conditions. (author) 11 refs., 8 figs., 1 tab.

  2. Reliability of decision-support systems for nuclear emergency management

    International Nuclear Information System (INIS)

    Ionescu, Tudor B.

    2013-08-01

    Decision support systems for nuclear emergency management (DSNE) are currently used worldwide to assist decision makers in taking emergency response countermeasures in case of accidental releases of radioactive materials from nuclear facilities. The present work has been motivated by the fact that, up until now, DSNE systems have not been regarded as safetycritical software systems, such as embedded software currently being used in vehicles and aircraft. The core of any DSNE system is represented by the different simulation codes linked together to form the dispersion simulation workflow. These codes require input emission and meteorological data to produce forecasts of the atmospheric dispersion of radioactive pollutants and other substances. However, the reliability of the system not only depends on the trustworthiness of the measured (or generated) input data but also on the reliability of the simulation codes used. The main goal of this work is to improve the reliability of DSNE systems by adapting current state of the art methods from the domain of software reliability engineering to the case of atmospheric dispersion simulation codes. The current approach is based on the design by diversity principle for improving the reliability of codes and the trustworthiness of results as well as on a flexible fault-tolerant workflow scheduling algorithm for ensuring the maximum availability of the system. The author's contribution is represented by (i) an acceptance test for dispersion simulation results, (ii) an adjudication algorithm (voter) based on comparing taxonomies of dispersion simulation results, and (iii) a feedback-control based fault-tolerant workflow scheduling algorithm. These tools provide means for the continuous verification of dispersion simulation codes while tolerating timing faults caused by disturbances in the underlying computational environment and will thus help increase the reliability and trustworthiness of DSNE systems in missioncritical

  3. Reliability of decision-support systems for nuclear emergency management

    Energy Technology Data Exchange (ETDEWEB)

    Ionescu, Tudor B.

    2013-08-15

    Decision support systems for nuclear emergency management (DSNE) are currently used worldwide to assist decision makers in taking emergency response countermeasures in case of accidental releases of radioactive materials from nuclear facilities. The present work has been motivated by the fact that, up until now, DSNE systems have not been regarded as safetycritical software systems, such as embedded software currently being used in vehicles and aircraft. The core of any DSNE system is represented by the different simulation codes linked together to form the dispersion simulation workflow. These codes require input emission and meteorological data to produce forecasts of the atmospheric dispersion of radioactive pollutants and other substances. However, the reliability of the system not only depends on the trustworthiness of the measured (or generated) input data but also on the reliability of the simulation codes used. The main goal of this work is to improve the reliability of DSNE systems by adapting current state of the art methods from the domain of software reliability engineering to the case of atmospheric dispersion simulation codes. The current approach is based on the design by diversity principle for improving the reliability of codes and the trustworthiness of results as well as on a flexible fault-tolerant workflow scheduling algorithm for ensuring the maximum availability of the system. The author's contribution is represented by (i) an acceptance test for dispersion simulation results, (ii) an adjudication algorithm (voter) based on comparing taxonomies of dispersion simulation results, and (iii) a feedback-control based fault-tolerant workflow scheduling algorithm. These tools provide means for the continuous verification of dispersion simulation codes while tolerating timing faults caused by disturbances in the underlying computational environment and will thus help increase the reliability and trustworthiness of DSNE systems in missioncritical

  4. Improvement of the Reliability Graph with General Gates to Analyze the Reliability of Dynamic Systems That Have Various Operation Modes

    Directory of Open Access Journals (Sweden)

    Seung Ki Shin

    2016-04-01

    Full Text Available 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.

  5. Reliability and Maintainability Data for Liquid Metal Cooling Systems

    Energy Technology Data Exchange (ETDEWEB)

    Cadwallader, Lee Charles [Idaho National Laboratory

    2015-05-01

    One of the coolants of interest for future fusion breeding blankets is lead-lithium. As a liquid metal it offers the advantages of high temperature operation for good station efficiency, low pressure, and moderate flow rate. This coolant is also under examination for use in test blanket modules to be used in the ITER international project. To perform reliability, availability, maintainability and inspectability (RAMI) assessment as well as probabilistic safety assessment (PSA) of lead-lithium cooling systems, component failure rate data are needed to quantify the system models. RAMI assessment also requires repair time data and inspection time data. This paper presents a new survey of the data sets that are available at present to support RAMI and PSA quantification. Recommendations are given for the best data values to use when quantifying system models.

  6. Response and Reliability Problems of Dynamic Systems

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present thesis consists of selected parts of the work performed by the author on stochastic dynamics and reliability theory of dynamically excited structures primarily during the period 1986-1996.......The present thesis consists of selected parts of the work performed by the author on stochastic dynamics and reliability theory of dynamically excited structures primarily during the period 1986-1996....

  7. Reliability program requirements for aeronautical and space system contractors

    Science.gov (United States)

    1987-01-01

    General reliability program requirements for NASA contracts involving the design, development, fabrication, test, and/or use of aeronautical and space systems including critical ground support equipment are prescribed. The reliability program requirements require (1) thorough planning and effective management of the reliability effort; (2) definition of the major reliability tasks and their place as an integral part of the design and development process; (3) planning and evaluating the reliability of the system and its elements (including effects of software interfaces) through a program of analysis, review, and test; and (4) timely status indication by formal documentation and other reporting to facilitate control of the reliability program.

  8. Brake System Analysis, Reliability Testing And Control Using Bench Experiments

    OpenAIRE

    Xu, Z.; Yang, B.

    1997-01-01

    In this project, the authors investigated the dynamics and reliability of a brake control system using a test bench which is a Lincoln Town Car brake system. The objectives of the project are to: 1) experimentally characterize the brake system; 2) obtain good nonlinear models of the brake system; 3) perform reliability analysis of the brake control system; and, 4) develop algorithms for brake malfunction detection and brake reliability enhancement. By using the brake test bench, the dynamic c...

  9. Assessment of the reliability of ultrasonic inspection methods

    International Nuclear Information System (INIS)

    Haines, N.F.; Langston, D.B.; Green, A.J.; Wilson, R.

    1982-01-01

    The reliability of NDT techniques has remained an open question for many years. A reliable technique may be defined as one that, when rigorously applied by a number of inspection teams, consistently finds then correctly sizes all defects of concern. In this paper we report an assessment of the reliability of defect detection by manual ultrasonic methods applied to the inspection of thick section pressure vessel weldments. Initially we consider the available data relating to the inherent physical capabilities of ultrasonic techniques to detect cracks in weldment and then, independently, we assess the likely variability in team to team performance when several teams are asked to follow the same specified test procedure. The two aspects of 'capability' and 'variability' are brought together to provide quantitative estimates of the overall reliability of ultrasonic inspection of thick section pressure vessel weldments based on currently existing data. The final section of the paper considers current research programmes on reliability and presents a view on how these will help to further improve NDT reliability. (author)

  10. CADRIGS--computer aided design reliability interactive graphics system

    International Nuclear Information System (INIS)

    Kwik, R.J.; Polizzi, L.M.; Sticco, S.; Gerrard, P.B.; Yeater, M.L.; Hockenbury, R.W.; Phillips, M.A.

    1982-01-01

    An integrated reliability analysis program combining graphic representation of fault trees, automated data base loadings and reference, and automated construction of reliability code input files was developed. The functional specifications for CADRIGS, the computer aided design reliability interactive graphics system, are presented. Previously developed fault tree segments used in auxiliary feedwater system safety analysis were constructed on CADRIGS and, when combined, yielded results identical to those resulting from manual input to the same reliability codes

  11. Insights from a reliability review of digital plant protection system

    International Nuclear Information System (INIS)

    Kim, I.S.; Hwang, S.W.; Kim, B.S.; Jeong, C.H.; Oh, S.H.

    2001-01-01

    The full text follows: As part of the design efforts for Ulchin nuclear power plant units 5 and 6 of Korea, a reliability analysis of digital plant protection system (DPPS) was performed by ABB-CE. An independent review of the DPPS reliability analysis was undertaken by Hanyang University to assist Korea Institute of Nuclear Safety (KINS), the nuclear regulatory body of Korea, in evaluating the design acceptability of the digital system. The DPPS is designed to encompass both reactor trip function and ESFAS (engineered safety feature actuation system) initiation function. The major methods used by the ABB-CE to assess the Ulchin 5-6 DPPS reliability are failure mode and effect analysis (FMEA) and fault tree analysis. Hence, our independent review was conducted focusing on: -) the establishment of review criteria based on various sources, such as the standard review plan of KINS, 10CFR50 Appendix A, IEEE standards 279, 577, and 603; -) the suitability of the FMEA and fault tree analysis for the Ulchin 5-6 DPPS, including the specific methods used (e.g., for human reliability analysis and common-cause failure analysis), the assumptions made (e.g., with respect to test frequency and watchdog timer coverage), and the data employed (e.g., CCF parameter, human error probability, and processor failure rate); and -) the design acceptability of the DPPS especially as compared to the analog plant protection system from a reliability and safety perspective. The paper shall also discuss key issues requiring further in-depth investigation, such as reliability of programmable logic controllers (PLCs), coverage factor of watchdog timers, and susceptibility of redundant digital units to common cause failure. Sensitivity analyses were carried out to investigate the impact of several parameters of special interest, like the coverage factor of watchdog timer and human error probability (e.g. an operator error to manually trip the reactor, or to mis-calibrate the trip parameters) on

  12. Reliable and valid assessment of performance in thoracoscopy

    DEFF Research Database (Denmark)

    Konge, Lars; Lehnert, Per; Hansen, Henrik Jessen

    2012-01-01

    BACKGROUND: As we move toward competency-based education in medicine, we have lagged in developing competency-based evaluation methods. In the era of minimally invasive surgery, there is a need for a reliable and valid tool dedicated to measure competence in video-assisted thoracoscopic surgery....... The purpose of this study is to create such an assessment tool, and to explore its reliability and validity. METHODS: An expert group of physicians created an assessment tool consisting of 10 items rated on a five-point rating scale. The following factors were included: economy and confidence of movement...

  13. An analytical framework for reliability growth of one-shot systems

    International Nuclear Information System (INIS)

    Hall, J. Brian; Mosleh, Ali

    2008-01-01

    In this paper, we introduce a new reliability growth methodology for one-shot systems that is applicable to the case where all corrective actions are implemented at the end of the current test phase. The methodology consists of four model equations for assessing: expected reliability, the expected number of failure modes observed in testing, the expected probability of discovering new failure modes, and the expected portion of system unreliability associated with repeat failure modes. These model equations provide an analytical framework for which reliability practitioners can estimate reliability improvement, address goodness-of-fit concerns, quantify programmatic risk, and assess reliability maturity of one-shot systems. A numerical example is given to illustrate the value and utility of the presented approach. This methodology is useful to program managers and reliability practitioners interested in applying the techniques above in their reliability growth program

  14. Human reliability analysis methods for probabilistic safety assessment

    International Nuclear Information System (INIS)

    Pyy, P.

    2000-11-01

    Human reliability analysis (HRA) of a probabilistic safety assessment (PSA) includes identifying human actions from safety point of view, modelling the most important of them in PSA models, and assessing their probabilities. As manifested by many incidents and studies, human actions may have both positive and negative effect on safety and economy. Human reliability analysis is one of the areas of probabilistic safety assessment (PSA) that has direct applications outside the nuclear industry. The thesis focuses upon developments in human reliability analysis methods and data. The aim is to support PSA by extending the applicability of HRA. The thesis consists of six publications and a summary. The summary includes general considerations and a discussion about human actions in the nuclear power plant (NPP) environment. A condensed discussion about the results of the attached publications is then given, including new development in methods and data. At the end of the summary part, the contribution of the publications to good practice in HRA is presented. In the publications, studies based on the collection of data on maintenance-related failures, simulator runs and expert judgement are presented in order to extend the human reliability analysis database. Furthermore, methodological frameworks are presented to perform a comprehensive HRA, including shutdown conditions, to study reliability of decision making, and to study the effects of wrong human actions. In the last publication, an interdisciplinary approach to analysing human decision making is presented. The publications also include practical applications of the presented methodological frameworks. (orig.)

  15. Bayesian assessment of the variability of reliability measures

    Directory of Open Access Journals (Sweden)

    Enrique López Droguett

    2006-04-01

    Full Text Available Population variability analysis, also known as the first stage in two-stage Bayesian updating, is an estimation procedure for the assessment of the variability of reliability measures among a group of sub-populations of similar systems. The estimated variability distributions are used as prior distributions in system-specific Bayesian updates. In this paper we present a Bayesian approach for population variability analysis involving the use of non-conjugate variability models that works over a continuous, rather than the discretized, variability model parameter space. The cases to be discussed are the ones typically encountered by the reliability practitioner: run-time data for failure rate assessment, demand-based data for failure probability assessment, and expert-based evidence for failure rate and failure probability analysis. We outline the estimation procedure itself as well as its link with conventional Bayesian updating procedures, describe the results generated by the procedures and their behavior under various data conditions, and provide numerical examples.Análise de variabilidade populacional, também conhecida como o primeiro estágio no processo de atualização Bayesiana em dois estágios, é um procedimento de estimação utilizado para a quantificação da variabilidade de métricas de confiabilidade num conjunto de sub-populações de sistemas similares. As distribuições de variabilidade obtidas são usadas como distribuições a priori em atualizações Bayesianas específicas para um sistema. Neste artigo, apresenta-se um procedimento Bayesiano para a análise da variabilidade populacional envolvendo o uso de modelos de variabilidade não-conjugados que utilizam um espaço contínuo, ao invés de discreto, dos parâmetros do modelo de variabilidade. Discutem-se casos tipicamente encontrados na prática: dados de falha no tempo, dados de falha sob demanda e opiniões de especialistas para a estimação da taxa e

  16. Modified Tuck Jump Assessment: Reliability and Training of Raters

    Directory of Open Access Journals (Sweden)

    Craig A. Smith, Nicole J. Chimera, Monica R. Lininger, Meghan Warren

    2017-09-01

    Full Text Available We are writing with regard to “Intra- and inter-rater reliability of the modified tuck jump assessment,” by Fort-Vanmeerhaeghe et al. (2017 published in the Journal of Sports Science & Medicine. The authors reported on the reliability of the modified Tuck Jump Assessment (TJA. The purpose of the article was twofold: to introduce a new scoring methodology and to report on the interrater and intrarater reliability. The authors found the modified TJA to have excellent interrater reliability (ICC = 0.94, 95% CI = 0.88-0.97 and intrarater reliability (rater 1 ICC = 0.94, 95% CI = 0.88-0.9; rater 2 ICC = 0.96, 95% CI = 0.92-0.98 with experienced raters (n = 2 in a sample of 24 elite volleyball athletes. Overall, we found the study to be well conducted and valuable to the field of injury screening; however, the study did not adequately explain how the raters were trained in the modified TJA to improve consistency of scoring, or the modifications of the individual flaw “excessive contact noise at landing.” This information is necessary to improve the clinical utility of the TJA and direct future reliability studies. The TJA has been changed at least three times in the literature: from the initial introduction (Myer et al., 2006 to the most referenced and detailed protocol (Myer et al., 2011 to the publication under discussion (Fort-Vanmeerhaeghe et al., 2017. The initial test protocol was based upon clinical expertise and has evolved over time as new research emerged and problems arose with the original TJA. Initially, the TJA was scored on a visual analog scale (Myer et al., 2006, changed to a dichotomous scale (0 for no flaw or 1 for flaw present (Myer et al., 2011 and most recently modified using an ordinal scale (Fort-Vanmeerhaeghe et al., 2017. A significant disparity in the reported interrater and intrarater reliability arose with the dichotomously scored TJA, between those involved in the development of the TJA (Herrington et al., 2013

  17. Integrating software reliability concepts into risk and reliability modeling of digital instrumentation and control systems used in nuclear power plants

    International Nuclear Information System (INIS)

    Arndt, S. A.

    2006-01-01

    As software-based digital systems are becoming more and more common in all aspects of industrial process control, including the nuclear power industry, it is vital that the current state of the art in quality, reliability, and safety analysis be advanced to support the quantitative review of these systems. Several research groups throughout the world are working on the development and assessment of software-based digital system reliability methods and their applications in the nuclear power, aerospace, transportation, and defense industries. However, these groups are hampered by the fact that software experts and probabilistic safety assessment experts view reliability engineering very differently. This paper discusses the characteristics of a common vocabulary and modeling framework. (authors)

  18. An integrated reliability management system for nuclear power plants

    International Nuclear Information System (INIS)

    Kimura, T.; Shimokawa, H.; Matsushima, H.

    1998-01-01

    The responsibility in the nuclear field of the Government, utilities and manufactures has increased in the past years due to the need of stable operation and great reliability of nuclear power plants. The need to improve the reliability is not only for the new plants but also for those now running. So, several measures have been taken to improve reliability. In particular, the plant manufactures have developed a reliability management system for each phase (planning, construction, maintenance and operation) and these have been integrated as a unified system. This integrated reliability management system for nuclear power plants contains information about plant performance, failures and incidents which have occurred in the plants. (author)

  19. High Reliability Oscillators for Terahertz Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To develop reliable THz sources with high power and high DC-RF efficiency, Virginia Diodes, Inc. will develop a thorough understanding of the complex interactions...

  20. Apples to Apples: Equivalent-Reliability Power Systems Across Diverse Resource Mix Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Stephen, Gordon W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Frew, Bethany A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sigler, Devon [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jones, Wesley B [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-03-28

    Electricity market research is highly price sensitive, and prices are strongly influenced by balance of supply and demand. This work looks at how to combine capacity expansion models and reliability assessment tools to assess equivalent-reliability power systems across diverse resource mix scenarios.

  1. Expert System for UNIX System Reliability and Availability Enhancement

    Science.gov (United States)

    Xu, Catherine Q.

    1993-01-01

    Highly reliable and available systems are critical to the airline industry. However, most off-the-shelf computer operating systems and hardware do not have built-in fault tolerant mechanisms, the UNIX workstation is one example. In this research effort, we have developed a rule-based Expert System (ES) to monitor, command, and control a UNIX workstation system with hot-standby redundancy. The ES on each workstation acts as an on-line system administrator to diagnose, report, correct, and prevent certain types of hardware and software failures. If a primary station is approaching failure, the ES coordinates the switch-over to a hot-standby secondary workstation. The goal is to discover and solve certain fatal problems early enough to prevent complete system failure from occurring and therefore to enhance system reliability and availability. Test results show that the ES can diagnose all targeted faulty scenarios and take desired actions in a consistent manner regardless of the sequence of the faults. The ES can perform designated system administration tasks about ten times faster than an experienced human operator. Compared with a single workstation system, our hot-standby redundancy system downtime is predicted to be reduced by more than 50 percent by using the ES to command and control the system.

  2. Reliability Estimation for Digital Instrument/Control System

    International Nuclear Information System (INIS)

    Yang, Yaguang; Sydnor, Russell

    2011-01-01

    Digital instrumentation and controls (DI and C) systems are widely adopted in various industries because of their flexibility and ability to implement various functions that can be used to automatically monitor, analyze, and control complicated systems. It is anticipated that the DI and C will replace the traditional analog instrumentation and controls (AI and C) systems in all future nuclear reactor designs. There is an increasing interest for reliability and risk analyses for safety critical DI and C systems in regulatory organizations, such as The United States Nuclear Regulatory Commission. Developing reliability models and reliability estimation methods for digital reactor control and protection systems will involve every part of the DI and C system, such as sensors, signal conditioning and processing components, transmission lines and digital communication systems, D/A and A/D converters, computer system, signal processing software, control and protection software, power supply system, and actuators. Some of these components are hardware, such as sensors and actuators, their failure mechanisms are well understood, and the traditional reliability model and estimation methods can be directly applied. But many of these components are firmware which has software embedded in the hardware, and software needs special consideration because its failure mechanism is unique, and the reliability estimation method for a software system will be different from the ones used for hardware systems. In this paper, we will propose a reliability estimation method for the entire DI and C system reliability using a recently developed software reliability estimation method and a traditional hardware reliability estimation method

  3. Assessment of the Reliability of Concrete Slab Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Jensen, F. M.; Middleton, C. R.

    This paper is based on research performed for the Highways Agency, London, UK under the project DPU/9/44 "Revision of Bridge Assessment Rules Based on Whole Life Performance: Concrete Bridges". It contains details of a methodology which can be used to generate Whole Life (WL) reliability profiles....

  4. Reliable and Valid Assessment of Point-of-care Ultrasonography

    DEFF Research Database (Denmark)

    Todsen, Tobias; Tolsgaard, Martin Grønnebæk; Olsen, Beth Härstedt

    2015-01-01

    OBJECTIVE: To explore the reliability and validity of the Objective Structured Assessment of Ultrasound Skills (OSAUS) scale for point-of-care ultrasonography (POC US) performance. BACKGROUND: POC US is increasingly used by clinicians and is an essential part of the management of acute surgical...

  5. Problems in Estimating Composite Reliability of "Unitised" Assessments

    Science.gov (United States)

    Bramley, Tom; Dhawan, Vikas

    2013-01-01

    This paper discusses the issues involved in calculating indices of composite reliability for "modular" or "unitised" assessments of the kind used in GCSEs, AS and A level examinations in England. The increasingly widespread use of on-screen marking has meant that the item-level data required for calculating indices of…

  6. 75 FR 66038 - Planning Resource Adequacy Assessment Reliability Standard

    Science.gov (United States)

    2010-10-27

    ... adequacy of specific loads (customer demand and energy requirements) within a Planning Authority Area... risks regarding the capability to balance resources and demand in a planning timeframe. Acknowledging...] Planning Resource Adequacy Assessment Reliability Standard Issued October 21, 2010. AGENCY: Federal Energy...

  7. Qualification Users' Perceptions and Experiences of Assessment Reliability

    Science.gov (United States)

    Chamberlain, Suzanne

    2013-01-01

    This paper presents the findings of a study designed to explore qualification users' perceptions and experiences of reliability in the context of national assessment outcomes in England. The study consisted of 17 focus groups conducted across six sectors of qualification users: students, teachers, trainee teachers, job-seekers, employers and…

  8. Assessment of reliability of Greulich and Pyle (gp) method for ...

    African Journals Online (AJOL)

    Background: Greulich and Pyle standards are the most widely used age estimation standards all over the world. The applicability of the Greulich and Pyle standards to populations which differ from their reference population is often questioned. This study aimed to assess the reliability of Greulich and Pyle (GP) method for ...

  9. Reliability of scored patient generated subjective global assessment ...

    African Journals Online (AJOL)

    Objective: Establish the reliability of the scored Patient Generated-Subjective Global Assessment (PG-SGA) in determining nutritional status among Antiretroviral Therapy (ART) naive HIV-infected adults. Methods: A descriptive, cross sectional study among outpatient medical clinics, in The AIDS Support Organization ...

  10. Reliability of medical audit in quality assessment of medical care

    Directory of Open Access Journals (Sweden)

    Camacho Luiz Antonio Bastos

    1996-01-01

    Full Text Available Medical audit of hospital records has been a major component of quality of care assessment, although physician judgment is known to have low reliability. We estimated interrater agreement of quality assessment in a sample of patients with cardiac conditions admitted to an American teaching hospital. Physician-reviewers used structured review methods designed to improve quality assessment based on judgment. Chance-corrected agreement for the items considered more relevant to process and outcome of care ranged from low to moderate (0.2 to 0.6, depending on the review item and the principal diagnoses and procedures the patients underwent. Results from several studies seem to converge on this point. Comparisons among different settings should be made with caution, given the sensitivity of agreement measurements to prevalence rates. Reliability of review methods in their current stage could be improved by combining the assessment of two or more reviewers, and by emphasizing outcome-oriented events.

  11. Condition-based Human Reliability Assessment for digitalized control room

    International Nuclear Information System (INIS)

    Kang, H. G.; Jang, S. C.; Eom, H. S.; Ha, J. J.

    2005-04-01

    In safety-critical systems, the generation failure of an actuation signal is caused by the concurrent failures of the automated systems and an operator action. These two sources of safety signals are complicatedly correlated. The failures of sensors or automated systems will cause a lack of necessary information for a human operator and result in error-forcing contexts such as the loss of corresponding alarms and indications. In the conventional analysis, the Human Error Probabilities (HEP) are estimated based on the assumption of 'normal condition of indications and alarms'. In order to construct a more realistic signal-generation failure model, we have to consider more complicated conditions in a more realistic manner. In this study, we performed two kinds of investigation for addressing this issue. We performed the analytic calculations for estimating the effect of sensors failures on the system unavailability and plant risk. For the single-parameter safety signals, the analysis result reveals that the quantification of the HEP should be performed by focusing on the 'no alarm from the automatic system and corresponding indications unavailable' situation. This study also proposes a Condition-Based Human Reliability Assessment (CBHRA) method in order to address these complicated conditions in a practical way. We apply the CBHRA method to the manual actuation of the safety features such as a reactor trip and auxiliary feedwater actuation in Korean Standard Nuclear Power Plants. In the case of conventional single HEP method, it is very hard to consider the multiple HE conditions. The merit of CBHRA is clearly shown in the application to the AFAS generation where no dominating HE condition exits. In this case, even if the HE conditions are carefully investigated, the single HEP method cannot accommodate the multiple conditions in a fault tree. On the other hand, the application result of the reactor trip in SLOCA shows that if there is a dominating condition, the use

  12. Nonspecialist Raters Can Provide Reliable Assessments of Procedural Skills

    DEFF Research Database (Denmark)

    Mahmood, Oria; Dagnæs, Julia; Bube, Sarah

    2018-01-01

    BACKGROUND: Competency-based learning has become a crucial component in medical education. Despite the advantages of competency-based learning, there are still challenges that need to be addressed. Currently, the common perception is that specialist assessment is needed for evaluating procedural ...... study suggests that nonspecialist raters can provide reliable and valid assessments of video recorded cystoscopies. This could make mastery learning and competency-based education more feasible....

  13. User's guide to the Reliability Estimation System Testbed (REST)

    Science.gov (United States)

    Nicol, David M.; Palumbo, Daniel L.; Rifkin, Adam

    1992-01-01

    The Reliability Estimation System Testbed is an X-window based reliability modeling tool that was created to explore the use of the Reliability Modeling Language (RML). RML was defined to support several reliability analysis techniques including modularization, graphical representation, Failure Mode Effects Simulation (FMES), and parallel processing. These techniques are most useful in modeling large systems. Using modularization, an analyst can create reliability models for individual system components. The modules can be tested separately and then combined to compute the total system reliability. Because a one-to-one relationship can be established between system components and the reliability modules, a graphical user interface may be used to describe the system model. RML was designed to permit message passing between modules. This feature enables reliability modeling based on a run time simulation of the system wide effects of a component's failure modes. The use of failure modes effects simulation enhances the analyst's ability to correctly express system behavior when using the modularization approach to reliability modeling. To alleviate the computation bottleneck often found in large reliability models, REST was designed to take advantage of parallel processing on hypercube processors.

  14. Reliability of the hazelbaker assessment tool for lingual frenulum function.

    Science.gov (United States)

    Amir, Lisa H; James, Jennifer P; Donath, Susan M

    2006-03-09

    About 3% of infants are born with a tongue-tie which may lead to breastfeeding problems such as ineffective latch, painful attachment or poor weight gain. The Hazelbaker Assessment Tool for Lingual Frenulum Function (HATLFF) has been developed to give a quantitative assessment of the tongue-tie and recommendation about frenotomy (release of the frenulum). The aim of this study was to assess the inter-rater reliability of the HATLFF. Fifty-eight infants referred to the Breastfeeding Education and Support Services (BESS) at The Royal Women's Hospital for assessment of tongue-tie and 25 control infants were assessed by two clinicians independently. The Appearance items received kappas between about 0.4 to 0.6, which represents "moderate" reliability. The first three Function items (lateralization, lift and extension of tongue) had kappa values over 0.65 which indicates "substantial" agreement. The four Function items relating to infant sucking (spread, cupping, peristalsis and snapback) received low kappa values with insignificant p values. There was 96% agreement between the two assessors on the recommendation for frenotomy (kappa 0.92, excellent agreement). The study found that the Function Score can be more simply assessed using only the first three function items (ie not scoring the sucking items), with a cut-off of frenotomy. We found that the HATLFF has a high reliability in a study of infants with tongue-tie and control infants.

  15. Reliability of the Hazelbaker Assessment Tool for Lingual Frenulum Function

    Directory of Open Access Journals (Sweden)

    James Jennifer P

    2006-03-01

    Full Text Available Abstract Background About 3% of infants are born with a tongue-tie which may lead to breastfeeding problems such as ineffective latch, painful attachment or poor weight gain. The Hazelbaker Assessment Tool for Lingual Frenulum Function (HATLFF has been developed to give a quantitative assessment of the tongue-tie and recommendation about frenotomy (release of the frenulum. The aim of this study was to assess the inter-rater reliability of the HATLFF. Methods Fifty-eight infants referred to the Breastfeeding Education and Support Services (BESS at The Royal Women's Hospital for assessment of tongue-tie and 25 control infants were assessed by two clinicians independently. Results The Appearance items received kappas between about 0.4 to 0.6, which represents "moderate" reliability. The first three Function items (lateralization, lift and extension of tongue had kappa values over 0.65 which indicates "substantial" agreement. The four Function items relating to infant sucking (spread, cupping, peristalsis and snapback received low kappa values with insignificant p values. There was 96% agreement between the two assessors on the recommendation for frenotomy (kappa 0.92, excellent agreement. The study found that the Function Score can be more simply assessed using only the first three function items (ie not scoring the sucking items, with a cut-off of ≤4 for recommendation of frenotomy. Conclusion We found that the HATLFF has a high reliability in a study of infants with tongue-tie and control infants

  16. Assessing and updating the reliability of concrete bridges subjected to spatial deterioration - principles and software implementation

    DEFF Research Database (Denmark)

    Schneider, Ronald; Fischer, Johannes; Bügler, Maximilian

    2015-01-01

    Inspection and maintenance of concrete bridges is a major cost factor in transportation infrastructure, and there is significant potential for using information gained during inspection to update predictive models of the performance and reliability of such structures. In this context, this paper ...... is a step towards developing a software tool that can be used by engineering practitioners to perform reliability assessments of ageing concrete bridges and update their reliability with inspection and monitoring data.......Inspection and maintenance of concrete bridges is a major cost factor in transportation infrastructure, and there is significant potential for using information gained during inspection to update predictive models of the performance and reliability of such structures. In this context, this paper...... presents an approach for assessing and updating the reliability of prestressed concrete bridges subjected to chloride-induced reinforcement corrosion. The system deterioration state is determined based on a Dynamic Bayesian Network (DBN) model that considers the spatial variability of the corrosion process...

  17. Reliability of the Spinal Cord Assessment Tool for Spastic Reflexes.

    Science.gov (United States)

    Akpinar, Pinar; Atici, Arzu; Ozkan, Feyza U; Aktas, Ilknur; Kulcu, Duygu G; Kurt, Kubra Neslihan

    2017-06-01

    To assess the reliability of the Spinal Cord Assessment Tool for Spastic Reflexes (SCATS). Observational reliability study of the SCATS. Inpatient rehabilitation unit at an education and research hospital. Subjects (N=47) between the ages of 18 and 88 years with spinal cord injury (SCI) and with American Spinal Injury Association Impairment Scale grades from A to D with spasticity, who were at least 6 months postinjury. Not applicable. Interrater and test-retest reliability of the SCATS. The SCATS had substantial to almost perfect interrater agreement (κ=.669-1.000) between the 2 physiatrists. Test-retest agreement of the SCATS was also substantial to almost perfect (κ=.614-1.000) as well. There was a significant correlation between the SCATS clonus scores and the Modified Ashworth scores of the hip, knee, and ankle. No correlation was found between SCATS extensor spasm scores and Modified Ashworth scores. The SCATS flexor spasm scores were only correlated significantly with the ankle plantar flexor Modified Ashworth scores (P<.05). The SCATS is a reliable tool for assessing spasm activity and spastic hypertonia in patients with SCI. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  18. Time domain series system definition and gear set reliability modeling

    International Nuclear Information System (INIS)

    Xie, Liyang; Wu, Ningxiang; Qian, Wenxue

    2016-01-01

    Time-dependent multi-configuration is a typical feature for mechanical systems such as gear trains and chain drives. As a series system, a gear train is distinct from a traditional series system, such as a chain, in load transmission path, system-component relationship, system functioning manner, as well as time-dependent system configuration. Firstly, the present paper defines time-domain series system to which the traditional series system reliability model is not adequate. Then, system specific reliability modeling technique is proposed for gear sets, including component (tooth) and subsystem (tooth-pair) load history description, material priori/posterior strength expression, time-dependent and system specific load-strength interference analysis, as well as statistically dependent failure events treatment. Consequently, several system reliability models are developed for gear sets with different tooth numbers in the scenario of tooth root material ultimate tensile strength failure. The application of the models is discussed in the last part, and the differences between the system specific reliability model and the traditional series system reliability model are illustrated by virtue of several numerical examples. - Highlights: • A new type of series system, i.e. time-domain multi-configuration series system is defined, that is of great significance to reliability modeling. • Multi-level statistical analysis based reliability modeling method is presented for gear transmission system. • Several system specific reliability models are established for gear set reliability estimation. • The differences between the traditional series system reliability model and the new model are illustrated.

  19. Reliability analysis of wind embedded power generation system for ...

    African Journals Online (AJOL)

    This paper presents a method for Reliability Analysis of wind energy embedded in power generation system for Indian scenario. This is done by evaluating the reliability index, loss of load expectation, for the power generation system with and without integration of wind energy sources in the overall electric power system.

  20. Distribution power system reliability assessment using Monte Carlo simulation: optimal maintenance strategy application; Evaluation de la surete de fonctionnement des reseaux de distribution par la simulation Monte Carlo: application a des strategies de maintenance optimales

    Energy Technology Data Exchange (ETDEWEB)

    Ocnasu, A.B.

    2008-10-15

    Today, the electricity sector is confronted with new challenges imposed by the deregulation of the electricity market, the international desire to reduce the greenhouse gases emissions, the development of new technologies. There is an increasing need to assess the reliability of the distribution systems. We can see a migration of methods specially used at transmission level to the distribution level. In a previous PhD, a method based on a sequential Monte Carlo simulation has been developed. The first part of this thesis deals with the study of acceleration methods. Two methods were tested, Antithetic Variates and Stratification. The best acceleration was achieved by a combination of these two methods. Then, we discussed the feasibility study of an optimization method based on reliability criteria. The chosen application was the preventive maintenance strategies optimization. We looked for the optimal number of preventive maintenance and the maximum value of failure rate when maintenance is carried out, minimising the total cost (cost of preventive maintenance, corrective maintenance and the cost of interruptions). In the end, a series of reflections related to the future development of a reliability analysis tool were presented. A modular structure of the tool is proposed to facilitate its use, and the possibility of parallel calculations for a better efficiency. (author)

  1. Valid, Reliable, and Appropriate Assessments for Adult English Language Learners. ERIC Q & A.

    Science.gov (United States)

    Kenyon, Dorry; Van Duzer, Carol

    This document examines the concepts of validity, reliability, and appropriateness from a language testing perspective as they apply to the following four assessment issues raised by the National Reporting System (NRS): (1) What type of language assessment seems to be required by the NRS: proficiency or achievement?; (2) Knowing that the NRS…

  2. Advanced reactor instrumentation and control reliability and risk assessment

    International Nuclear Information System (INIS)

    Fullwood, R.; Gunther, W.; Valente, J.; Azarm, M.A.

    1991-01-01

    Advanced nuclear power reactors will used different approaches to achieving a higher level of safety than the first generation. One approach used the technological developments in computation and electronics in the form of digital instrumentation and control (I ampersand C) to enhance the reliability, and accuracy of information for plant control, responding to the information, and controlling the plant and its systems under normal and upset environments in various states of degradation. Evaluating the reliability and safety of advanced I ampersand C systems requires determining the reliability of the I ampersand C used in the advanced reactors which involves distributed processing, data pile-up, interactive systems, the man-machine interface, various forms of automatic control, and systems interactions. From these analyses will come an understanding of the potential of the new I ampersand C, and protection from its vulnerabilities to enhance the safe operation of the new plants. Technological, safety, reliability, and regulatory issues associated with advanced I ampersand C for the new reactors are discussed herein. The issues are presented followed by suggested approaches to their resolution

  3. Reading and writing assessment scales: preliminary reliability evidences.

    Science.gov (United States)

    Kida, Adriana de Souza Batista; Chiari, Brasília Maria; Avila, Clara Regina Brandão de

    2010-01-01

    Reliability of Reading and Writing Assessment Instruments. To investigate the reliability of two scales created to evaluate both reading and writing of children with ages between 8:0 and 11:11 years. Two scales were created: a reading scale, composed of 12 testing items organized into four competency fields (letter knowledge and phonographemic relation, decoding of isolated items, reading fluency, reading comprehension), and a writing scale, with five items organized into three fields (letter writing and graphophonemic relation, codification of isolated items, writing construction). One hundred students (64 girls) from Public Schools, with ages raging between 8:0 and 11:11 years, were selected. Twenty students (12 girls) participated in the applicability study, resulting in the study version of the Scales. These scales were later applied to the remaining 80 students (52 girls). The obtained responses were assessed and computed for score assignment: item scores, competence field score (CFS) and raw scale score (RSS). Data were submitted to statistical analysis: the Cronbach's alpha coefficient was calculated and correlations between items (Pearson's correlation coefficient) were verified. A significance level of 0.05 was used. a = 0.866 and a = 0.461 were obtained for the Reading and Writing Scales, respectively. Correlations between the items were observed, ranging from weak to strong, and confirmed the alpha values. The Reading Scale was proven reliable, achieving acceptable levels for diagnostic instruments; the Writing Scale did not present an acceptable reliability level to measure the performance of the tested children.

  4. Thermal environment assessment reliability using temperature--humidity indices.

    Science.gov (United States)

    d'Ambrosio Alfano, Francesca Romana; Palella, Boris Igor; Riccio, Giuseppe

    2011-01-01

    A reliable assessment of the thermal environment should take into account the whole of the six parameters affecting the thermal sensation (air temperature, air velocity, humidity, mean radiant temperature, metabolic rate and thermo-physical properties of clothing). Anyway, the need of a quick evaluation based on few measurements and calculations has leaded to like best temperature-humidity indices instead of rational methods based on the heat balance on the human body. Among these, Canadian Humidex, preliminarily used only for weather forecasts, is becoming more and more widespread for a generalized assessment of both outdoor and indoor thermal environments. This custom arouses great controversies since using an index validated in outdoor conditions does not assure its indoor reliability. Moreover is it really possible to carry out the thermal environment assessment ignoring some of variables involved in the physiological response of the human body? Aiming to give a clear answer to these questions, this paper deals with a comparison between the assessment carried out according to the rational methods suggested by International Standards in force and the Humidex index. This combined analysis under hot stress situations (indoor and outdoor) has been preliminarily carried out; in a second phase the study deals with the indoor comfort prediction. Obtained results show that Humidex index very often leads to the underestimation of the workplace dangerousness and a poor reliability of comfort prediction when it is used in indoor situations.

  5. Conceptual Software Reliability Prediction Models for Nuclear Power Plant Safety Systems

    International Nuclear Information System (INIS)

    Johnson, G.; Lawrence, D.; Yu, H.

    2000-01-01

    The objective of this project is to develop a method to predict the potential reliability of software to be used in a digital system instrumentation and control system. The reliability prediction is to make use of existing measures of software reliability such as those described in IEEE Std 982 and 982.2. This prediction must be of sufficient accuracy to provide a value for uncertainty that could be used in a nuclear power plant probabilistic risk assessment (PRA). For the purposes of the project, reliability was defined to be the probability that the digital system will successfully perform its intended safety function (for the distribution of conditions under which it is expected to respond) upon demand with no unintended functions that might affect system safety. The ultimate objective is to use the identified measures to develop a method for predicting the potential quantitative reliability of a digital system. The reliability prediction models proposed in this report are conceptual in nature. That is, possible prediction techniques are proposed and trial models are built, but in order to become a useful tool for predicting reliability, the models must be tested, modified according to the results, and validated. Using methods outlined by this project, models could be constructed to develop reliability estimates for elements of software systems. This would require careful review and refinement of the models, development of model parameters from actual experience data or expert elicitation, and careful validation. By combining these reliability estimates (generated from the validated models for the constituent parts) in structural software models, the reliability of the software system could then be predicted. Modeling digital system reliability will also require that methods be developed for combining reliability estimates for hardware and software. System structural models must also be developed in order to predict system reliability based upon the reliability

  6. Reliable data acquisition for inspection systems

    Science.gov (United States)

    Silva, V. P.; Silva, D. S.; Boccardo, D. R.; Machado, R. C. S.; Carmo, L. F. R. C.

    2015-01-01

    In Brazil, the road transportation of dangerous goods is subject to regulatory control, which is conducted by Inmetro, the National Institute of Metrology, Quality and Technology. Currently, the process of monitoring such inspections is done manually, leaving the possibility of some inconsistencies: inspections held outside the authorized local inspection, incorrectly, incompletely, or even be held. Thus, in order to increase the reliability of such inspections, it is needed a closer monitoring by the regulatory agency. One approach towards that, is the implementation of an automated process in which evidences are collected in a reliable way during the inspections, enabling further analyses. This work employs security mechanisms on a portable device to ensure the confidence of the evidences collected during an inspection, paving the way for later more robust analyzes.

  7. Validity and reliability of balance assessment software using the Nintendo Wii balance board: usability and validation.

    Science.gov (United States)

    Park, Dae-Sung; Lee, GyuChang

    2014-06-10

    A balance test provides important information such as the standard to judge an individual's functional recovery or make the prediction of falls. The development of a tool for a balance test that is inexpensive and widely available is needed, especially in clinical settings. The Wii Balance Board (WBB) is designed to test balance, but there is little software used in balance tests, and there are few studies on reliability and validity. Thus, we developed a balance assessment software using the Nintendo Wii Balance Board, investigated its reliability and validity, and compared it with a laboratory-grade force platform. Twenty healthy adults participated in our study. The participants participated in the test for inter-rater reliability, intra-rater reliability, and concurrent validity. The tests were performed with balance assessment software using the Nintendo Wii balance board and a laboratory-grade force platform. Data such as Center of Pressure (COP) path length and COP velocity were acquired from the assessment systems. The inter-rater reliability, the intra-rater reliability, and concurrent validity were analyzed by an intraclass correlation coefficient (ICC) value and a standard error of measurement (SEM). The inter-rater reliability (ICC: 0.89-0.79, SEM in path length: 7.14-1.90, SEM in velocity: 0.74-0.07), intra-rater reliability (ICC: 0.92-0.70, SEM in path length: 7.59-2.04, SEM in velocity: 0.80-0.07), and concurrent validity (ICC: 0.87-0.73, SEM in path length: 5.94-0.32, SEM in velocity: 0.62-0.08) were high in terms of COP path length and COP velocity. The balance assessment software incorporating the Nintendo Wii balance board was used in our study and was found to be a reliable assessment device. In clinical settings, the device can be remarkably inexpensive, portable, and convenient for the balance assessment.

  8. Research on reliability management systems for Nuclear Power Plant

    International Nuclear Information System (INIS)

    Maki, Nobuo

    2000-01-01

    Investigation on a reliability management system for Nuclear Power Plants (NPPs) has been performed on national and international archived documents as well as on current status of studies at Idaho National Engineering and Environmental Laboratory (INEEL), US NPPs (McGuire, Seabrook), a French NPP (St. Laurent-des-Eaux), Japan Atomic Energy Research Institute (JAERI), Central Research Institute of Electric Power Industries (CRIEPI), and power plant manufacturers in Japan. As a result of the investigation, the following points were identified: (i) A reliability management system is composed of a maintenance management system to inclusively manage maintenance data, and an anomalies information and reliability data management system to extract data from maintenance results stored in the maintenance management system and construct a reliability database. (ii) The maintenance management system, which is widely-used among NPPs in the US and Europe, is an indispensable system for the increase of maintenance reliability. (iii) Maintenance management methods utilizing reliability data like Reliability Centered Maintenance are applied for NPP maintenance in the US and Europe, and contributing to cost saving. Maintenance templates are effective in the application process. In addition, the following points were proposed on the design of the system: (i) A detailed database on specifications of facilities and components is necessary for the effective use of the system. (ii) A demand database is indispensable for the application of the methods. (iii) Full-time database managers are important to maintain the quality of the reliability data. (author)

  9. Suprahyoid Muscle Complex: A Reliable Neural Assessment Tool For Dysphagia?

    DEFF Research Database (Denmark)

    Kothari, Mohit; Stubbs, Peter William; Pedersen, Asger Roer

    be a non-invasive reliable neural assessment tool for patients with dysphagia. Objective: To investigate the possibility of using the suprahyoid muscle complex (SMC) using surface electromyography (sEMG) to assess changes to neural pathways by determining the reliability of measurements in healthy...... participants over days. Methods: Seventeen healthy participants were recruited. Measurements were performed twice with one week between sessions. Single pulse (at 120% and 140% of the resting motor threshold (rMT)) and paired pulse (2 ms and 15 ms paired pulse) transcranial magnetic stimulation (TMS) were used...... to elicit MEPs in the SMC which were recorded using sEMG. Results: ≈50% of participants (range: 42%-58%; depending on stimulus type/intensity) had significantly different MEP values between day 1 and day 2 for single pulse and paired pulse TMS. A large stimulus artefact resulted in MEP responses that could...

  10. Improving the reliability of stator insulation system in rotating machines

    International Nuclear Information System (INIS)

    Gupta, G.K.; Sedding, H.G.; Culbert, I.M.

    1997-01-01

    Reliable performance of rotating machines, especially generators and primary heat transport pump motors, is critical to the efficient operation on nuclear stations. A significant number of premature machine failures have been attributed to the stator insulation problems. Ontario Hydro has attempted to assure the long term reliability of the insulation system in critical rotating machines through proper specifications and quality assurance tests for new machines and periodic on-line and off-line diagnostic tests on machines in service. The experience gained over the last twenty years is presented in this paper. Functional specifications have been developed for the insulation system in critical rotating machines based on engineering considerations and our past experience. These specifications include insulation stress, insulation resistance and polarization index, partial discharge levels, dissipation factor and tip up, AC and DC hipot tests. Voltage endurance tests are specified for groundwall insulation system of full size production coils and bars. For machines with multi-turn coils, turn insulation strength for fast fronted surges in specified and verified through tests on all coils in the factory and on samples of finished coils in the laboratory. Periodic on-line and off-line diagnostic tests were performed to assess the condition of the stator insulation system in machines in service. Partial discharges are measured on-line using several techniques to detect any excessive degradation of the insulation system in critical machines. Novel sensors have been developed and installed in several machines to facilitate measurements of partial discharges on operating machines. Several off-line tests are performed either to confirm the problems indicated by the on-line test or to assess the insulation system in machines which cannot be easily tested on-line. Experience with these tests, including their capabilities and limitations, are presented. (author)

  11. A model for assessing human cognitive reliability in PRA studies

    International Nuclear Information System (INIS)

    Hannaman, G.W.; Spurgin, A.J.; Lukic, Y.

    1985-01-01

    This paper summarizes the status of a research project sponsored by EPRI as part of the Probabilistic Risk Assessment (PRA) technology improvement program and conducted by NUS Corporation to develop a model of Human Cognitive Reliability (HCR). The model was synthesized from features identified in a review of existing models. The model development was based on the hypothesis that the key factors affecting crew response times are separable. The inputs to the model consist of key parameters the values of which can be determined by PRA analysts for each accident situation being assessed. The output is a set of curves which represent the probability of control room crew non-response as a function of time for different conditions affecting their performance. The non-response probability is then a contributor to the overall non-success of operating crews to achieve a functional objective identified in the PRA study. Simulator data and some small scale tests were utilized to illustrate the calibration of interim HCR model coefficients for different types of cognitive processing since the data were sparse. The model can potentially help PRA analysts make human reliability assessments more explicit. The model incorporates concepts from psychological models of human cognitive behavior, information from current collections of human reliability data sources and crew response time data from simulator training exercises

  12. MRI interrReader and intra-reader reliabilities for assessing injury morphology and posterior ligamentous complex integrity of the spine according to the thoracolumbar injury classification system and severity score

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Guen Young; Lee, Joon Woo; Choi, Seung Woo; Lim, Hyun Jin; Sun, Hye Young; Kang, Yu Suhn; Kang, Heung Sik [Dept. of Radiology, Seoul National University Bundang Hospital, Seongnam (Korea, Republic of); Chai, Jee Won; Kim, Su Jin [Dept. of Radiology, SMG-SNU Boramae Medical Center, Seoul (Korea, Republic of)

    2015-08-15

    To evaluate spine magnetic resonance imaging (MRI) inter-reader and intra-reader reliabilities using the thoracolumbar injury classification system and severity score (TLICS) and to analyze the effects of reader experience on reliability and the possible reasons for discordant interpretations. Six radiologists (two senior, two junior radiologists, and two residents) independently scored 100 MRI examinations of thoracolumbar spine injuries to assess injury morphology and posterior ligamentous complex (PLC) integrity according to the TLICS. Inter-reader and intra-reader agreements were determined and analyzed according to the number of years of radiologist experience. Inter-reader agreement between the six readers was moderate (k = 0.538 for the first and 0.537 for the second review) for injury morphology and fair to moderate (k = 0.440 for the first and 0.389 for the second review) for PLC integrity. No significant difference in inter-reader agreement was observed according to the number of years of radiologist experience. Intra-reader agreements showed a wide range (k = 0.538-0.822 for injury morphology and 0.423-0.616 for PLC integrity). Agreement was achieved in 44 for the first and 45 for the second review about injury morphology, as well as in 41 for the first and 38 for the second review of PLC integrity. A positive correlation was detected between injury morphology score and PLC integrity. The reliability of MRI for assessing thoracolumbar spinal injuries according to the TLICS was moderate for injury morphology and fair to moderate for PLC integrity, which may not be influenced by radiologist' experience.

  13. Development of Probabilistic Reliability Models of Photovoltaic System Topologies for System Adequacy Evaluation

    Directory of Open Access Journals (Sweden)

    Ahmad Alferidi

    2017-02-01

    Full Text Available The contribution of solar power in electric power systems has been increasing rapidly due to its environmentally friendly nature. Photovoltaic (PV systems contain solar cell panels, power electronic converters, high power switching and often transformers. These components collectively play an important role in shaping the reliability of PV systems. Moreover, the power output of PV systems is variable, so it cannot be controlled as easily as conventional generation due to the unpredictable nature of weather conditions. Therefore, solar power has a different influence on generating system reliability compared to conventional power sources. Recently, different PV system designs have been constructed to maximize the output power of PV systems. These different designs are commonly adopted based on the scale of a PV system. Large-scale grid-connected PV systems are generally connected in a centralized or a string structure. Central and string PV schemes are different in terms of connecting the inverter to PV arrays. Micro-inverter systems are recognized as a third PV system topology. It is therefore important to evaluate the reliability contribution of PV systems under these topologies. This work utilizes a probabilistic technique to develop a power output model for a PV generation system. A reliability model is then developed for a PV integrated power system in order to assess the reliability and energy contribution of the solar system to meet overall system demand. The developed model is applied to a small isolated power unit to evaluate system adequacy and capacity level of a PV system considering the three topologies.

  14. Systems reliability analysis for the national ignition facility

    International Nuclear Information System (INIS)

    Majumdar, K.C.; Annese, C.E.; MacIntyre, A.T.; Sicherman, A.

    1996-01-01

    A Reliability, Availability and Maintainability (RAM) analysis was initiated for the National Ignition Facility (NIF). The NIF is an inertial confinement fusion research facility designed to achieve controlled thermonuclear reaction; the preferred site for the NIF is the Lawrence Livermore National Laboratory (LLNL). The NIF RAM analysis has three purposes: (1) to allocate top level reliability and availability goals for the systems, (2) to develop an operability model for optimum maintainability, and (3) to determine the achievability of the allocated goals of the RAM parameters for the NIF systems and the facility operation as a whole. An allocation model assigns the reliability and availability goals for front line and support systems by a top-down approach; reliability analysis uses a bottom-up approach to determine the system reliability and availability from component level to system level

  15. The reliability of nuclear power plant safety systems

    International Nuclear Information System (INIS)

    Susnik, J.

    1978-01-01

    A criterion was established concerning the protection that nuclear power plant (NPP) safety systems should afford. An estimate of the necessary or adequate reliability of the total complex of safety systems was derived. The acceptable unreliability of auxiliary safety systems is given, provided the reliability built into the specific NPP safety systems (ECCS, Containment) is to be fully utilized. A criterion for the acceptable unreliability of safety (sub)systems which occur in minimum cut sets having three or more components of the analysed fault tree was proposed. A set of input MTBF or MTTF values which fulfil all the set criteria and attain the appropriate overall reliability was derived. The sensitivity of results to input reliability data values was estimated. Numerical reliability evaluations were evaluated by the programs POTI, KOMBI and particularly URSULA, the last being based on Vesely's kinetic fault tree theory. (author)

  16. Assessing the coding reliability of work accidents statistical data: How coders make a difference.

    Science.gov (United States)

    Jacinto, Celeste; Santos, Fernando P; Guedes Soares, Carlos; Silva, Sílvia A

    2016-12-01

    This study assesses the reliability of the coding procedure for a set of variables belonging to the European Statistics of Accidents at Work (ESAW). The work focused on the Portuguese data and experience with the system. In Portugal, this task has been systematically carried out by GEP (the governmental Cabinet for Strategy and Planning), here defined as the "reference group" or "expert group." However, it is anticipated that this coding task will be performed by non-expert people, since paper-forms will be replaced by e-forms, similarly to what happened in a few EU countries. This study aims to: (a) assess the current situation, that is, to quantify reliability of data coded by GEP (reference group), and (b) assess the impact on the reliability level when the coding is carried out by non-experts (two different groups of coders). The study comprises the estimation of both intercoder and intracoder reliability for a set of 8 nominal variables. The assessment applies 3 reliability coefficients calculated by 3 software packages. The results reveal that the expert group (GEP) holds good to excellent reliability (inter- and intracoder agreements), between 68-98%, while there is a considerable "loss of reliability" (-5% to -39%) when the coding process is transferred to other people, without special training or knowledge in this task. This work gives quantified evidence that reliability of coding accident data is substantially affected by the coders' profile. Moreover, certain variables, regardless of the coder, systematically hold a higher level of coding reliability than others, suggesting that certain codes may need improvement. Future studies should assess coding quality across the EU countries using the ESAW protocol. Directions for improving the quality of accident data and related statistics; data that is used by researchers and governmental decision-makers to derive prevention strategies. Copyright © 2016 Elsevier Ltd and National Safety Council. All rights

  17. System Reliability of Timber Structures with Ductile Behaviour

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Čizmar, Dean

    2011-01-01

    . An evaluation method of the ductile behaviour is introduced. For different ductile behaviours, the system reliability is estimated based on Monte Carlo simulation. A correlation between the strength of the structural elements is introduced. The results indicate that the reliability of a structural timber system......The present paper considers the evaluation of timber structures with the focus on robustness due to connection ductility. The robustness analysis is based on the structural reliability framework applied to a simplified mechanical system. The structural timber system is depicted as a parallel system...... can be significantly increased due to the ductile behavior....

  18. Bounds for the System Reliability Function.

    Science.gov (United States)

    1985-05-01

    RD-RIGS 529 SOUNDS FOR THE SYSTEN RELIABILITY FUNCTION(UD RIZONm i UNIV TUCSON DEPT OF MATHENATICS J 0 SNANTHIKUNAR NAY 85 AFOSR-AS RFOSR-84-6295... compute R. Except in some special cases [e.g. Agrawal and Satyanarayana (1984), Provan and Ball (1984), and Shanthikumar (1982, 1984)], the problem...bounds get tighter as m increases and give the exact unreallbility when m - n + 1. This allows one to progressively compute A,,At+I, ... , until a desired

  19. Reliability models applicable to space telescope solar array assembly system

    Science.gov (United States)

    Patil, S. A.

    1986-01-01

    A complex system may consist of a number of subsystems with several components in series, parallel, or combination of both series and parallel. In order to predict how well the system will perform, it is necessary to know the reliabilities of the subsystems and the reliability of the whole system. The objective of the present study is to develop mathematical models of the reliability which are applicable to complex systems. The models are determined by assuming k failures out of n components in a subsystem. By taking k = 1 and k = n, these models reduce to parallel and series models; hence, the models can be specialized to parallel, series combination systems. The models are developed by assuming the failure rates of the components as functions of time and as such, can be applied to processes with or without aging effects. The reliability models are further specialized to Space Telescope Solar Arrray (STSA) System. The STSA consists of 20 identical solar panel assemblies (SPA's). The reliabilities of the SPA's are determined by the reliabilities of solar cell strings, interconnects, and diodes. The estimates of the reliability of the system for one to five years are calculated by using the reliability estimates of solar cells and interconnects given n ESA documents. Aging effects in relation to breaks in interconnects are discussed.

  20. Reliability prediction for condition-based maintained systems

    Energy Technology Data Exchange (ETDEWEB)

    Saranga, H.; Knezevic, J

    2001-02-01

    The paper presents a methodology based on relevant condition predictor (RCP) for reliability prediction for systems under condition-based maintenance. By considering the event of not being able to recognise the fault initiation or the critical state in RCP-based maintenance, the methodology uses Markov models for reliability prediction. The cases of single and multiple relevant condition predictors are presented along with a numerical procedure to obtain the reliability functions for RCP-based maintained systems. Numerical examples are used to illustrate the methodology and the values of reliability are obtained at discrete time points using the numerical algorithm.

  1. System reliability analysis techniques and their relationship to mechanical/structural reliability problems

    International Nuclear Information System (INIS)

    Bourne, A.J.

    1980-01-01

    The paper gives a brief review of the techniques used in the reliability analysis of functional systems. It also considers some of the aspects arising in applying similar techniques to the reliability analysis of mechanical and structural components. The paper concludes that further data acquisition is of prime importance. Additionally, it is suggested that it may be worthwhile to pay increased attention to the on-line monitoring of deterioration in mechanical and structural elements. (orig.)

  2. Reliability of a Test Battery Designed for Quickly and Safely Assessing Diverse Indices of Neuromuscular Function

    Science.gov (United States)

    Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason, R.; Buxton, Roxanne E.; Lawrence, Emily L.; Sinka, Joseph; Guilliams, Mark E.; Ploutz-Snyder, Lori L.; Bloomberg, Jacob J.

    2010-01-01

    Spaceflight affects nearly every physiological system. Spaceflight-induced alterations in physiological function translate to decrements in functional performance. Purpose: To develop a test battery for quickly and safely assessing diverse indices of neuromuscular performance. I. Quickly: Battery of tests can be completed in approx.30-40 min. II. Safely: a) No eccentric muscle actions or impact forces. b) Tests present little challenge to postural stability. III. Diverse indices: a) Strength: Excellent reliability (ICC = 0.99) b) Central activation: Very good reliability (ICC = 0.87) c) Power: Excellent reliability (ICC = 0.99) d) Endurance: Total work has excellent reliability (ICC = 0.99) e) Force steadiness: Poor reliability (ICC = 0.20 - 0.60) National

  3. Reliability Architecture for Collaborative Robot Control Systems in Complex Environments

    Directory of Open Access Journals (Sweden)

    Liang Tang

    2016-02-01

    Full Text Available Many different kinds of robot systems have been successfully deployed in complex environments, while research into collaborative control systems between different robots, which can be seen as a hybrid internetware safety-critical system, has become essential. This paper discusses ways to construct robust and secure reliability architecture for collaborative robot control systems in complex environments. First, the indication system for evaluating the real-time reliability of hybrid internetware systems is established. Next, a dynamic collaborative reliability model for components of hybrid internetware systems is proposed. Then, a reliable, adaptive and evolutionary computation method for hybrid internetware systems is proposed, and a timing consistency verification solution for collaborative robot control internetware applications is studied. Finally, a multi-level security model supporting dynamic resource allocation is established.

  4. Review of Software Reliability Assessment Methodologies for Digital I and C Software of Nuclear Power Plants

    International Nuclear Information System (INIS)

    Cho, Jae Hyun; Lee, Seung Jun; Jung, Won Dea

    2014-01-01

    Digital instrumentation and control (I and C) systems are increasingly being applied to current nuclear power plants (NPPs) due to its advantages; zero drift, advanced data calculation capacity, and design flexibility. Accordingly, safety issues of software that is main part of the digital I and C system have been raised. As with hardware components, the software failure in NPPs could lead to a large disaster, therefore failure rate test and reliability assessment of software should be properly performed, and after that adopted in NPPs. However, the reliability assessment of the software is quite different with that of hardware, owing to the nature difference between software and hardware. The one of the most different thing is that the software failures arising from design faults as 'error crystal', whereas the hardware failures are caused by deficiencies in design, production, and maintenance. For this reason, software reliability assessment has been focused on the optimal release time considering the economy. However, the safety goal and public acceptance of the NPPs is so distinctive with other industries that the software in NPPs is dependent on reliability quantitative value rather than economy. The safety goal of NPPs compared to other industries is exceptionally high, so conventional methodologies on software reliability assessment already used in other industries could not adjust to safety goal of NPPs. Thus, the new reliability assessment methodology of the software of digital I and C on NPPs need to be developed. In this paper, existing software reliability assessment methodologies are reviewed to obtain the pros and cons of them, and then to assess the usefulness of each method to software of NPPs

  5. Reliability of Telemedicine in the Assessment of Seriously Ill Children.

    Science.gov (United States)

    Siew, Lawrence; Hsiao, Allen; McCarthy, Paul; Agarwal, Anup; Lee, Eric; Chen, Lei

    2016-03-01

    Data are limited that establish the clinical reliability of telemedicine in evaluating children who are seriously ill. Evaluation of a seriously ill child poses a challenge in that telemedicine is primarily visual, without the ability to perform a "hands-on" physical examination. Previous studies evaluating observation in assessing febrile children and children in respiratory distress have validated observation as both predictive and reliable in detecting underlying illness. The purpose of this study was to determine the interobserver reliability of telemedicine observations, compared with bedside observations, in assessing febrile children and children in respiratory distress. Children 2 to 36 months old presenting with a fever were evaluated by using the Yale Observation Scale; patients aged 2 months to 18 years presenting with respiratory symptoms were evaluated by using the Respiratory Observation Checklist, a list of observational signs of respiratory distress derived from validated studies and developed specifically for the present study by the authors. Telemedicine communication used commercially available tablet devices that provided 2-way, live-streamed images with audio. A total of 132 febrile subjects were evaluated by using the Yale Observation Scale. Strong agreement (Pearson's correlation coefficient, 0.81) was found between bedside and telemedicine observers. A total of 145 subjects were evaluated by using the Respiratory Observation Checklist. Excellent agreement between bedside and telemedicine observers was found for the impression of respiratory distress (κ = .85) and good agreement (κ > .6) for the majority of the remaining components of the checklist. Telemedicine, using commercially available telecommunications equipment, is reliable in the assessment of febrile children and children with respiratory distress. Copyright © 2016 by the American Academy of Pediatrics.

  6. Reliability of rubrics in the assessment of orthodontic oral presentation.

    Science.gov (United States)

    Bindayel, Naif A

    2017-10-01

    The aim of this study was to evaluate the reliability of using rubrics in dental education, specifically for undergraduate students' assessment in orthodontic oral presentation. A rubric-based case presentation assessment form was introduced to three contributing instructors. In each instructor's group, the course director, along with the assigned instructor, assessed 8 randomly selected fourth year male dental students utilizing the same assessment form (total of 24 students). The two final scorings made by the assigned instructor and the course director were then gathered for each student. The data of this prospective comparative study then was analyzed using paired t -test to look for any significant differences in the scoring of the course director and each instructor in each group. No significant statistical differences were detected in grading variables between the instructors and the course director. Furthermore, the data showed no significant correlations between the students' final course grade, and their case presentation grades scored by instructors'/course director. Despite the elaborate nature of the routine orthodontic case presentation, the use of rubrics was found to be a promising reliable assessment element.

  7. Design and reliability of a didactic inphographic rubric assessment

    Directory of Open Access Journals (Sweden)

    Yunuen Ixchel GUZMÁN-CEDILLO

    2017-12-01

    Full Text Available The objective of this study is to describe design, validity process and reliability of a rubric assessment to evaluate didactic infographics quality. Participants were fifteen judges who participate in different moments of elaboration rubric process; it was made in three process phases: design, settings and reliability determination. Content validity was obtained by percentage agreement between 3 judges by component of the rubric; likewise a Krippendorff’s alpha were applied (a = .710 in pilot assessment with 5 infographics in order to set possible writings contradictions between components and criteria of performance. The intern consistence was determined by Cronbach’s alpha (? = .806 in 22 infographics gradation. An Intraclass correlation coefficient icc (a = .909 was applied to 6 judges qualifications also a Krippendorff’s alpha (a = .538 both of them in ordinal levels. The rubric is composed by 9 components, 3 performance levels, definitions of each component and assignments how to use the rubric. Results suggest the rubric is valid and reliable to grade quality of didactic infographic.

  8. Reliability and validity of the Italian Eating Assessment Tool.

    Science.gov (United States)

    Schindler, Antonio; Mozzanica, Francesco; Monzani, Anna; Ceriani, Eleonora; Atac, Murat; Jukic-Peladic, Nikolina; Venturini, Claudia; Orlandoni, Paolo

    2013-11-01

    We sought to evaluate the reliability and validity of the Italian EAT-10 (Italian Eating Assessment Tool; I-EAT-10). The study consisted of 4 phases: item generation, internal consistency and reliability analysis, normative data generation, and validity analysis. Discussion of the EAT-10 with 30 patients and its back-translation were accomplished. The recruited population included 172 patients (40 with dysphonia and 132 with dysphagia) and 269 asymptomatic subjects for testing of internal consistency, and 94 patients with dysphagia and 158 asymptomatic subjects for test-retest reliability analysis. Normative data were gathered from the 269 subjects. The scores of patients and asymptomatic subjects were compared. The I-EAT-10 and flexible endoscopic evaluation of swallowing (FEES) scores in 94 patients were correlated. The I-EAT-10 scores made before and after successful swallowing rehabilitation in 38 patients were compared. Excellent internal consistency (Cronbach's alpha values of 0.90 and 0.93) and strong test-retest reliability (intraclass correlation coefficients of 0.95 and 0.98) were found in patients and asymptomatic subjects. The I-EAT-10 mean (+/- SD) score of the normal cohort was 0.6 +/- 1.1. The asymptomatic subjects and dysphonic patients scored lower than the dysphagic patients on the Kruskal-Wallis test (p = 0.001). The I-EAT-10 and FEES scores were mildly correlated. The mean I-EAT-10 score improved from 9.8 +/- 10.3 to 5.8 +/- 6.7 after swallowing rehabilitation (p = 0.04). The I-EAT-10 is a reliable, valid, symptom-specific outcome tool.

  9. Reliability assessment of germanium gate stacks with promising initial characteristics

    Science.gov (United States)

    Lu, Cimang; Lee, Choong Hyun; Nishimura, Tomonori; Nagashio, Kosuke; Toriumi, Akira

    2015-02-01

    This work reports on the reliability assessment of germanium (Ge) gate stacks with promising initial electrical properties, with focus on trap generation under a constant electric stress field (Estress). Initial Ge gate stack properties do not necessarily mean highly robust reliability when it is considered that traps are newly generated under high Estress. A small amount of yttrium- or scandium oxide-doped GeO2 (Y-GeO2 or Sc-GeO2, respectively) significantly reduces trap generation in Ge gate stacks without deterioration of the interface. This is explained by the increase in the average coordination number (Nav) of the modified GeO2 network that results from the doping.

  10. Reliability evaluation of deregulated electric power systems for planning applications

    International Nuclear Information System (INIS)

    Ehsani, A.; Ranjbar, A.M.; Jafari, A.; Fotuhi-Firuzabad, M.

    2008-01-01

    In a deregulated electric power utility industry in which a competitive electricity market can influence system reliability, market risks cannot be ignored. This paper (1) proposes an analytical probabilistic model for reliability evaluation of competitive electricity markets and (2) develops a methodology for incorporating the market reliability problem into HLII reliability studies. A Markov state space diagram is employed to evaluate the market reliability. Since the market is a continuously operated system, the concept of absorbing states is applied to it in order to evaluate the reliability. The market states are identified by using market performance indices and the transition rates are calculated by using historical data. The key point in the proposed method is the concept that the reliability level of a restructured electric power system can be calculated using the availability of the composite power system (HLII) and the reliability of the electricity market. Two case studies are carried out over Roy Billinton Test System (RBTS) to illustrate interesting features of the proposed methodology

  11. The constant failure rate model for fault tree evaluation as a tool for unit protection reliability assessment

    International Nuclear Information System (INIS)

    Vichev, S.; Bogdanov, D.

    2000-01-01

    The purpose of this paper is to introduce the fault tree analysis method as a tool for unit protection reliability estimation. The constant failure rate model applies for making reliability assessment, and especially availability assessment. For that purpose an example for unit primary equipment structure and fault tree example for simplified unit protection system is presented (author)

  12. The reliability of multistate, multioutput systems

    Science.gov (United States)

    Subelman, E. J.

    1981-01-01

    A system which can generate multiple signals such that each signal can have different quality states is modeled. A measure of the effectiveness of the system as a function of the status of its components is developed. Assuming only that the probability distribution of the status of each component is known, bounds on the probability distribution of the system's measure of effectiveness are developed.

  13. Research on Novel Algorithms for Smart Grid Reliability Assessment and Economic Dispatch

    Science.gov (United States)

    Luo, Wenjin

    In this dissertation, several studies of electric power system reliability and economy assessment methods are presented. To be more precise, several algorithms in evaluating power system reliability and economy are studied. Furthermore, two novel algorithms are applied to this field and their simulation results are compared with conventional results. As the electrical power system develops towards extra high voltage, remote distance, large capacity and regional networking, the application of a number of new technique equipments and the electric market system have be gradually established, and the results caused by power cut has become more and more serious. The electrical power system needs the highest possible reliability due to its complication and security. In this dissertation the Boolean logic Driven Markov Process (BDMP) method is studied and applied to evaluate power system reliability. This approach has several benefits. It allows complex dynamic models to be defined, while maintaining its easy readability as conventional methods. This method has been applied to evaluate IEEE reliability test system. The simulation results obtained are close to IEEE experimental data which means that it could be used for future study of the system reliability. Besides reliability, modern power system is expected to be more economic. This dissertation presents a novel evolutionary algorithm named as quantum evolutionary membrane algorithm (QEPS), which combines the concept and theory of quantum-inspired evolutionary algorithm and membrane computation, to solve the economic dispatch problem in renewable power system with on land and offshore wind farms. The case derived from real data is used for simulation tests. Another conventional evolutionary algorithm is also used to solve the same problem for comparison. The experimental results show that the proposed method is quick and accurate to obtain the optimal solution which is the minimum cost for electricity supplied by wind

  14. Issues and Methods for Assessing COTS Reliability, Maintainability, and Availability

    Science.gov (United States)

    Schneidewind, Norman F.; Nikora, Allen P.

    1998-01-01

    Many vendors produce products that are not domain specific (e.g., network server) and have limited functionality (e.g., mobile phone). In contrast, many customers of COTS develop systems that am domain specific (e.g., target tracking system) and have great variability in functionality (e.g., corporate information system). This discussion takes the viewpoint of how the customer can ensure the quality of COTS components. In evaluating the benefits and costs of using COTS, we must consider the environment in which COTS will operate. Thus we must distinguish between using a non-mission critical application like a spreadsheet program to produce a budget and a mission critical application like military strategic and tactical operations. Whereas customers will tolerate an occasional bug in the former, zero tolerance is the rule in the latter. We emphasize the latter because this is the arena where there are major unresolved problems in the application of COTS. Furthermore, COTS components may be embedded in the larger customer system. We refer to these as embedded systems. These components must be reliable, maintainable, and available, and must be with the larger system in order for the customer to benefit from the advertised advantages of lower development and maintenance costs. Interestingly, when the claims of COTS advantages are closely examined, one finds that to a great extent these COTS components consist of hardware and office products, not mission critical software [1]. Obviously, COTS components are different from custom components with respect to one or more of the following attributes: source, development paradigm, safety, reliability, maintainability, availability, security, and other attributes. However, the important question is whether they should be treated differently when deciding to deploy them for operational use; we suggest the answer is no. We use reliability as an example to justify our answer. In order to demonstrate its reliability, a COTS

  15. Examination of Web-Based PVGIS and SUNNY Design Web Photovoltaic System Simulation Programs and Assessment of Reliability of the Results

    OpenAIRE

    HAYDAROĞLU, Cem; Gümüş, Bilal

    2018-01-01

    Due to thepolluting effect of fossil fuels on environment and their exhaustible nature,investments in renewable energy resources continue to increase. In order tobenefit from solar energy which is one of these energy resources, 50 GW of new powerplants were installed only in 2015. Following the "regulation on unlicensedelectricity generation" issued to benefit from the renewable energypotential available in Turkey, the installation of systems that generateelectricity from solar ener...

  16. Discrete event simulation versus conventional system reliability analysis approaches

    DEFF Research Database (Denmark)

    Kozine, Igor

    2010-01-01

    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...

  17. thermal power stations' reliability evaluation in a hydrothermal system

    African Journals Online (AJOL)

    Dr Obe

    A quantitative tool for the evaluation of thermal power stations reliability in a hydrothermal system is presented. A reliable power station is one which would supply the required power within its installed capacity at any time within the specified voltage and frequency limits. Required for this evaluation are the station's installed ...

  18. thermal power stations' reliability evaluation in a hydrothermal system

    African Journals Online (AJOL)

    Dr Obe

    R. C. OKONKWO. Department of Electrical Engineering. UNIVERSITY OF NIGERIA. NSUKKA. ABSTRACT. A quantitative tool for the evaluation of thermal power stations reliability in a hydrothermal system is presented. A reliable power station is one which would supply the required power within its installed capacity at any ...

  19. A physical review on power system reliability factors

    International Nuclear Information System (INIS)

    Navid, Taghizadegan; Ahmad Reza, Zentabchi; Mohammad Ali, Tavakoli; Nader, Samsunchi; Mohammad Ali, Tavakoli

    2005-01-01

    Full text : Planning and design engineers and management must necessarily take into consideration the funds available, the requirements of regulatory agencies and other restrictions that may be imposed, as well as availability of equipment and supplies. A well-designed electrical power system strikes a reasonable between reliability and cost. A prime responsibility of power system operators is to operate their systems in such a way that will provide the maximum reliability of service possible with the facilities under their control

  20. A comparative evaluation of five human reliability assessment techniques

    International Nuclear Information System (INIS)

    Kirwan, B.

    1988-01-01

    A field experiment was undertaken to evaluate the accuracy, usefulness, and resources requirements of five human reliability quantification techniques (Techniques for Human Error Rate Prediction (THERP); Paired Comparisons, Human Error Assessment and Reduction Technique (HEART), Success Liklihood Index Method (SLIM)-Multi Attribute Utility Decomposition (MAUD), and Absolute Probability Judgement). This was achieved by assessing technique predictions against a set of known human error probabilities, and by comparing their predictions on a set of five realistic Probabilisitc Risk Assessment (PRA) human error. On a combined measure of accuracy THERP and Absolute Probability Judgement performed best, whilst HEART showed indications of accuracy and was lower in resources usage than other techniques. HEART and THERP both appear to benefit from using trained assessors in order to obtain the best results. SLIM and Paired Comparisons require further research on achieving a robust calibration relationship between their scale values and absolute probabilities. (author)

  1. Techniques for increasing the reliability of accelerator control system electronics

    International Nuclear Information System (INIS)

    Utterback, J.

    1993-09-01

    As the physical size of modern accelerators becomes larger and larger, the number of required control system circuit boards increases, and the probability of one of those circuit boards failing while in service also increases. In order to do physics, the experimenters need the accelerator to provide beam reliably with as little down time as possible. With the advent of colliding beams physics, reliability becomes even more important due to the fact that a control system failure can cause the loss of painstakingly produced antiprotons. These facts prove the importance of keeping reliability in mind when designing and maintaining accelerator control system electronics

  2. Ultra-Reliable Communication in 5G Wireless Systems

    DEFF Research Database (Denmark)

    Popovski, Petar

    2014-01-01

    —Wireless 5G systems will not only be “4G, but faster”. One of the novel features discussed in relation to 5G is Ultra-Reliable Communication (URC), an operation mode not present in today’s wireless systems. URC refers to provision of certain level of communication service almost 100 % of the time....... Example URC applications include reliable cloud connectivity, critical connections for industrial automation and reliable wireless coordination among vehicles. This paper puts forward a systematic view on URC in 5G wireless systems. It starts by analyzing the fundamental mechanisms that constitute...

  3. Nodal price volatility reduction and reliability enhancement of restructured power systems considering demand-price elasticity

    International Nuclear Information System (INIS)

    Goel, L.; Wu, Qiuwei; Wang, Peng

    2008-01-01

    With the development of restructured power systems, the conventional 'same for all customers' electricity price is getting replaced by nodal prices. Electricity prices will fluctuate with time and nodes. In restructured power systems, electricity demands will interact mutually with prices. Customers may shift some of their electricity consumption from time slots of high electricity prices to those of low electricity prices if there is a commensurate price incentive. The demand side load shift will influence nodal prices in return. This interaction between demand and price can be depicted using demand-price elasticity. This paper proposes an evaluation technique incorporating the impact of the demand-price elasticity on nodal prices, system reliability and nodal reliabilities of restructured power systems. In this technique, demand and price correlations are represented using the demand-price elasticity matrix which consists of self/cross-elasticity coefficients. Nodal prices are determined using optimal power flow (OPF). The OPF and customer damage functions (CDFs) are combined in the proposed reliability evaluation technique to assess the reliability enhancement of restructured power systems considering demand-price elasticity. The IEEE reliability test system (RTS) is simulated to illustrate the developed techniques. The simulation results show that demand-price elasticity reduces the nodal price volatility and improves both the system reliability and nodal reliabilities of restructured power systems. Demand-price elasticity can therefore be utilized as a possible efficient tool to reduce price volatility and to enhance the reliability of restructured power systems. (author)

  4. 76 FR 16277 - System Restoration Reliability Standards

    Science.gov (United States)

    2011-03-23

    ... Planning), EOP-005-2 (System Restoration from Blackstart Resources), and EOP-006-2 (System Restoration Coordination) as well as the definition of the term ``Blackstart Resource'' submitted to the Commission for..., generation operators, and certain transmission owners and distribution providers to ensure that plans...

  5. Reliability of Structural Systems with Correlated Elements

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Sørensen, John Dalsgaard

    1982-01-01

    Calculation of the probability of failure of a system with correlation members is usually a difficult and time-consuming numerical problem. However, for some types of systems with equally correlated elements this calculation can be performed in a simple way. This has suggested two new methods based...

  6. Assessing Reliability of Cold Spray Sputter Targets in Photovoltaic Manufacturing

    Science.gov (United States)

    Hardikar, Kedar; Vlcek, Johannes; Bheemreddy, Venkata; Juliano, Daniel

    2017-10-01

    Cold spray has been used to manufacture more than 800 Cu-In-Ga (CIG) sputter targets for deposition of high-efficiency photovoltaic thin films. It is a preferred technique since it enables high deposit purity and transfer of non-equilibrium alloy states to the target material. In this work, an integrated approach to reliability assessment of such targets with deposit weight in excess of 50 lb. is undertaken, involving thermal-mechanical characterization of the material in as-deposited condition, characterization of the interface adhesion on cylindrical substrate in as-deposited condition, and developing means to assess target integrity under thermal-mechanical loads during the physical vapor deposition (PVD) sputtering process. Mechanical characterization of cold spray deposited CIG alloy is accomplished through the use of indentation testing and adaptation of Brazilian disk test. A custom lever test was developed to characterize adhesion along the cylindrical interface between the CIG deposit and cylindrical substrate, overcoming limitations of current standards. A cohesive zone model for crack initiation and propagation at the deposit interface is developed and validated using the lever test and later used to simulate the potential catastrophic target failure in the PVD process. It is shown that this approach enables reliability assessment of sputter targets and improves robustness.

  7. Interrater reliability of the bedside shivering assessment scale.

    Science.gov (United States)

    Olson, DaiWai M; Grissom, Jana L; Williamson, Rachel A; Bennett, Stacey N; Bellows, Steven T; James, Michael L

    2013-01-01

    Since its early development, the Bedside Shivering Assessment Scale (BSAS) has had only initial psychometric testing. Before this instrument is incorporated into routine practice, its interrater reliability should be explored in a diverse group of practitioners. This prospective nonrandomized study used a panel of 5 observers who completed 100 paired assessments. Observers independently scored patients for shivering by using the BSAS. Kappa statistics were determined by using SAS version 9.4 with BSAS scores treated as ordinal data. A weighted kappa value of 0.48 from 100 paired observations of 22 patients indicates moderate agreement of the BSAS scores. Most of the BSAS scores were 0 or 1; dichotomizing shivering as little or no shivering versus significant shivering resulted in a kappa of 0.66 (substantial agreement). No relationship was found between timing of assessment or the role of the practitioner and the likelihood of both observers assigning the same BSAS score. The BSAS has adequate interrater reliability to be considered for use among a diverse group of practitioners.

  8. Integrated Markov-neural reliability computation method: A case for multiple automated guided vehicle system

    International Nuclear Information System (INIS)

    Fazlollahtabar, Hamed; Saidi-Mehrabad, Mohammad; Balakrishnan, Jaydeep

    2015-01-01

    This paper proposes an integrated Markovian and back propagation neural network approaches to compute reliability of a system. While states of failure occurrences are significant elements for accurate reliability computation, Markovian based reliability assessment method is designed. Due to drawbacks shown by Markovian model for steady state reliability computations and neural network for initial training pattern, integration being called Markov-neural is developed and evaluated. To show efficiency of the proposed approach comparative analyses are performed. Also, for managerial implication purpose an application case for multiple automated guided vehicles (AGVs) in manufacturing networks is conducted. - Highlights: • Integrated Markovian and back propagation neural network approach to compute reliability. • Markovian based reliability assessment method. • Managerial implication is shown in an application case for multiple automated guided vehicles (AGVs) in manufacturing networks

  9. Engineering systems reliability, safety, and maintenance an integrated approach

    CERN Document Server

    Dhillon, B S

    2017-01-01

    Today, engineering systems are an important element of the world economy and each year billions of dollars are spent to develop, manufacture, operate, and maintain various types of engineering systems around the globe. Many of these systems are highly sophisticated and contain millions of parts. For example, a Boeing jumbo 747 is made up of approximately 4.5 million parts including fasteners. Needless to say, reliability, safety, and maintenance of systems such as this have become more important than ever before.  Global competition and other factors are forcing manufacturers to produce highly reliable, safe, and maintainable engineering products. Therefore, there is a definite need for the reliability, safety, and maintenance professionals to work closely during design and other phases. Engineering Systems Reliability, Safety, and Maintenance: An Integrated Approach eliminates the need to consult many different and diverse sources in the hunt for the information required to design better engineering syste...

  10. A Mechanistic Reliability Assessment of RVACS and Metal Fuel Inherent Reactivity Feedbacks

    Energy Technology Data Exchange (ETDEWEB)

    Grabaskas, David; Brunett, Acacia J.; Passerini, Stefano; Grelle, Austin

    2017-09-24

    GE Hitachi Nuclear Energy (GEH) and Argonne National Laboratory (Argonne) participated in a two year collaboration to modernize and update the probabilistic risk assessment (PRA) for the PRISM sodium fast reactor. At a high level, the primary outcome of the project was the development of a next-generation PRA that is intended to enable risk-informed prioritization of safety- and reliability-focused research and development. A central Argonne task during this project was a reliability assessment of passive safety systems, which included the Reactor Vessel Auxiliary Cooling System (RVACS) and the inherent reactivity feedbacks of the metal fuel core. Both systems were examined utilizing a methodology derived from the Reliability Method for Passive Safety Functions (RMPS), with an emphasis on developing success criteria based on mechanistic system modeling while also maintaining consistency with the Fuel Damage Categories (FDCs) of the mechanistic source term assessment. This paper provides an overview of the reliability analyses of both systems, including highlights of the FMEAs, the construction of best-estimate models, uncertain parameter screening and propagation, and the quantification of system failure probability. In particular, special focus is given to the methodologies to perform the analysis of uncertainty propagation and the determination of the likelihood of violating FDC limits. Additionally, important lessons learned are also reviewed, such as optimal sampling methodologies for the discovery of low likelihood failure events and strategies for the combined treatment of aleatory and epistemic uncertainties.

  11. Seismic reliability assessment methodology for CANDU concrete containment structures

    International Nuclear Information System (INIS)

    Stephens, M.J.; Nessim, M.A.; Hong, H.P.

    1995-05-01

    A study was undertaken to develop a reliability-based methodology for the assessment of existing CANDU concrete containment structures with respect to seismic loading. The focus of the study was on defining appropriate specified values and partial safety factors for earthquake loading and resistance parameters. Key issues addressed in the work were the identification of an approach to select design earthquake spectra that satisfy consistent safety levels, and the use of structure-specific data in the evaluation of structural resistance. (author). 23 refs., 9 tabs., 15 figs

  12. HDMR methods to assess reliability in slope stability analyses

    Science.gov (United States)

    Kozubal, Janusz; Pula, Wojciech; Vessia, Giovanna

    2014-05-01

    -soil masses) resulting in sliding mechanisms have been investigated in this study. The reliability indices values drawn from the HDRM method have been compared with conventional approaches as neural networks: the efficiency of HDRM is shown in the case studied. References Chowdhury R., Rao B.N. and Prasad A.M. 2009. High-dimensional model representation for structural reliability analysis. Commun. Numer. Meth. Engng, 25: 301-337. Chowdhury R. and Rao B. 2010. Probabilistic Stability Assessment of Slopes Using High Dimensional Model Representation. Computers and Geotechnics, 37: 876-884.

  13. Human reliability

    International Nuclear Information System (INIS)

    Embrey, D.E.

    1987-01-01

    Concepts and techniques of human reliability have been developed and are used mostly in probabilistic risk assessment. For this, the major application of human reliability assessment has been to identify the human errors which have a significant effect on the overall safety of the system and to quantify the probability of their occurrence. Some of the major issues within human reliability studies are reviewed and it is shown how these are applied to the assessment of human failures in systems. This is done under the following headings; models of human performance used in human reliability assessment, the nature of human error, classification of errors in man-machine systems, practical aspects, human reliability modelling in complex situations, quantification and examination of human reliability, judgement based approaches, holistic techniques and decision analytic approaches. (UK)

  14. Software reliability growth model for safety systems of nuclear reactor

    International Nuclear Information System (INIS)

    Thirugnana Murthy, D.; Murali, N.; Sridevi, T.; Satya Murty, S.A.V.; Velusamy, K.

    2014-01-01

    The demand for complex software systems has increased more rapidly than the ability to design, implement, test, and maintain them, and the reliability of software systems has become a major concern for our, modern society.Software failures have impaired several high visibility programs in space, telecommunications, defense and health industries. Besides the costs involved, it setback the projects. The ways of quantifying it and using it for improvement and control of the software development and maintenance process. This paper discusses need for systematic approaches for measuring and assuring software reliability which is a major share of project development resources. It covers the reliability models with the concern on 'Reliability Growth'. It includes data collection on reliability, statistical estimation and prediction, metrics and attributes of product architecture, design, software development, and the operational environment. Besides its use for operational decisions like deployment, it includes guiding software architecture, development, testing and verification and validation. (author)

  15. Evaluating system reliability and targeted hardening strategies of power distribution systems subjected to hurricanes

    International Nuclear Information System (INIS)

    Salman, Abdullahi M.; Li, Yue; Stewart, Mark G.

    2015-01-01

    Over the years, power distribution systems have been vulnerable to extensive damage from hurricanes which can cause power outage resulting in millions of dollars of economic losses and restoration costs. Most of the outage is as a result of failure of distribution support structures. Over the years, various methods of strengthening distribution systems have been proposed and studied. Some of these methods, such as undergrounding of the system, have been shown to be unjustified from an economic point of view. A potential cost-effective strategy is targeted hardening of the system. This, however, requires a method of determining critical parts of a system that when strengthened, will have greater impact on reliability. This paper presents a framework for studying the effectiveness of targeted hardening strategies on power distribution systems subjected to hurricanes. The framework includes a methodology for evaluating system reliability that relates failure of poles and power delivery, determination of critical parts of a system, hurricane hazard analysis, and consideration of decay of distribution poles. The framework also incorporates cost analysis that considers economic losses due to power outage. A notional power distribution system is used to demonstrate the framework by evaluating and comparing the effectiveness of three hardening measures. - Highlight: • Risk assessment of power distribution systems subjected to hurricanes is carried out. • Framework for studying effectiveness of targeted hardening strategies is presented. • A system reliability method is proposed. • Targeted hardening is cost effective for existing systems. • Economic losses due to power outage should be considered for cost analysis.

  16. Statistical reliability assessment of UT round-robin test data for piping welds

    International Nuclear Information System (INIS)

    Kim, H.M.; Park, I.K.; Park, U.S.; Park, Y.W.; Kang, S.C.; Lee, J.H.

    2004-01-01

    Ultrasonic NDE is one of important technologies in the life-time maintenance of nuclear power plant. Ultrasonic inspection system is consisted of the operator, equipment and procedure. The reliability of ultrasonic inspection system is affected by its ability. The performance demonstration round robin was conducted to quantify the capability of ultrasonic inspection for in-service. Several teams employed procedures that met or exceeded with ASME sec. XI code requirements detected the piping of nuclear power plant with various cracks to evaluate the capability of detection and sizing. In this paper, the statistical reliability assessment of ultrasonic nondestructive inspection data using probability of detection (POD) is presented. The result of POD using logistic model was useful to the reliability assessment for the NDE hit or miss data. (orig.)

  17. Daya Bay Nuclear Power Station equipment reliability management system innovation

    International Nuclear Information System (INIS)

    Gao Ligang; Wang Zongjun

    2006-01-01

    Daya Bay Nuclear Power Station has achieved good performance since its commercial operation in 1994. The equipment reliability management system that features Daya Bay characteristics has been established through constant technology introduction, digestion and innovation. It is also based on the success of operational system, equipment maintenance system and technical support system. The system lays a solid foundation for the long-term safe operation of power station. This article emphasizes on the innovation part of equipment reliability management system in Daya Bay. (authors)

  18. Efficiency criteria for high reliability measured system structures

    International Nuclear Information System (INIS)

    Sal'nikov, N.L.

    2012-01-01

    The procedures of structural redundancy are usually used to develop high reliability measured systems. To estimate efficiency of such structures the criteria to compare different systems has been developed. So it is possible to develop more exact system by inspection of redundant system data unit stochastic characteristics in accordance with the developed criteria [ru

  19. Software reliability and safety in nuclear reactor protection systems

    International Nuclear Information System (INIS)

    Lawrence, J.D.

    1993-11-01

    Planning the development, use and regulation of computer systems in nuclear reactor protection systems in such a way as to enhance reliability and safety is a complex issue. This report is one of a series of reports from the Computer Safety and Reliability Group, Lawrence Livermore that investigates different aspects of computer software in reactor National Laboratory, that investigates different aspects of computer software in reactor protection systems. There are two central themes in the report, First, software considerations cannot be fully understood in isolation from computer hardware and application considerations. Second, the process of engineering reliability and safety into a computer system requires activities to be carried out throughout the software life cycle. The report discusses the many activities that can be carried out during the software life cycle to improve the safety and reliability of the resulting product. The viewpoint is primarily that of the assessor, or auditor

  20. Software reliability and safety in nuclear reactor protection systems

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, J.D. [Lawrence Livermore National Lab., CA (United States)

    1993-11-01

    Planning the development, use and regulation of computer systems in nuclear reactor protection systems in such a way as to enhance reliability and safety is a complex issue. This report is one of a series of reports from the Computer Safety and Reliability Group, Lawrence Livermore that investigates different aspects of computer software in reactor National Laboratory, that investigates different aspects of computer software in reactor protection systems. There are two central themes in the report, First, software considerations cannot be fully understood in isolation from computer hardware and application considerations. Second, the process of engineering reliability and safety into a computer system requires activities to be carried out throughout the software life cycle. The report discusses the many activities that can be carried out during the software life cycle to improve the safety and reliability of the resulting product. The viewpoint is primarily that of the assessor, or auditor.

  1. Quantifiable and Reliable Structural Health Management Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Major concerns for implementing a practical built-in structural health monitoring system are prediction accuracy and data reliability. It is proposed to develop...

  2. Automation of testing the metrological reliability of nondestructive control systems

    International Nuclear Information System (INIS)

    Zhukov, Yu.A.; Isakov, V.B.; Karlov, Yu.K.; Kovalevskij, Yu.A.

    1987-01-01

    Opportunities of microcomputers are used to solve the problem of testing control-measuring systems. Besides the main program the program of data processing when characterizing the nondestructive control systems is written in the microcomputer. The program includes two modules. The first module contains tests-programs, by which accuracy of functional elements of the microcomputer and interface elements with issuing a message to the operator on readiness of the elements for operation and failure of a certain element are determined. The second module includes: calculational programs when determining metrological reliability of measuring channel reliability, a calculational subprogram for random statistical measuring error, time instability and ''dead time''. Automation of testing metrological reliability of the nondestructive control systems increases reliability of determining metrological parameters and reduces time of system testing

  3. Some aspects of the interaction between systems- and structural reliability

    International Nuclear Information System (INIS)

    Schueller, G.K.; Schmitt, W.

    1979-01-01

    The purpose of this paper is to study the interaction between systems- and structural reliability analysis with reference to the design of structural components of LWR. Presently the evaluation of systems reliability is carried out apart from structural reliability analysis. Moreover, two basically different methodologies are used for analysis. While in systems analysis the simplified binary approach is still generally accepted, in structural reliability one has to resort to more sophisticated procedures to obtain realistic results. The interactive effect may be illustrated as follows: For example, the integrity of the primary circuit interacts with the integrity of the containment structure. This means that the probability of occurrence of the pipe rupture which may cause a LOCA and consequently leads to a build-up of temperature and pressure within the containment affects directly its structural reliability. The piping system, particularly the primary piping, in turn interacts with the protective system, which is part of the safety system. This piping structure is also subjected to various operational loading conditions. In a numerical example dealing with leakage probabilities of pipes it is shown how methods of structural reliability may be used to gain more insight in the estimation of failure rates of system components. (orig.)

  4. Reliability assessment of competing risks with generalized mixed shock models

    International Nuclear Information System (INIS)

    Rafiee, Koosha; Feng, Qianmei; Coit, David W.

    2017-01-01

    This paper investigates reliability modeling for systems subject to dependent competing risks considering the impact from a new generalized mixed shock model. Two dependent competing risks are soft failure due to a degradation process, and hard failure due to random shocks. The shock process contains fatal shocks that can cause hard failure instantaneously, and nonfatal shocks that impact the system in three different ways: 1) damaging the unit by immediately increasing the degradation level, 2) speeding up the deterioration by accelerating the degradation rate, and 3) weakening the unit strength by reducing the hard failure threshold. While the first impact from nonfatal shocks comes from each individual shock, the other two impacts are realized when the condition for a new generalized mixed shock model is satisfied. Unlike most existing mixed shock models that consider a combination of two shock patterns, our new generalized mixed shock model includes three classic shock patterns. According to the proposed generalized mixed shock model, the degradation rate and the hard failure threshold can simultaneously shift multiple times, whenever the condition for one of these three shock patterns is satisfied. An example using micro-electro-mechanical systems devices illustrates the effectiveness of the proposed approach with sensitivity analysis. - Highlights: • A rich reliability model for systems subject to dependent failures is proposed. • The degradation rate and the hard failure threshold can shift simultaneously. • The shift is triggered by a new generalized mixed shock model. • The shift can occur multiple times under the generalized mixed shock model.

  5. Use of reliability engineering tools in safety and risk assessment of nuclear facilities

    Energy Technology Data Exchange (ETDEWEB)

    Raso, Amanda Laureano; Vasconcelos, Vanderley de; Marques, Raíssa Oliveira; Soares, Wellington Antonio; Mesquita, Amir Zacarias, E-mail: amandaraso@hotmail.com, E-mail: vasconv@cdtn.br, E-mail: raissaomarques@gmail.com, E-mail: soaresw@cdtn.br, E-mail: amir@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Serviço de Tecnologia de Reatores

    2017-07-01

    Safety, reliability and availability are fundamental criteria in design, construction and operation of nuclear facilities, as nuclear power plants. Deterministic and probabilistic risk assessments of such facilities are required by regulatory authorities in order to meet licensing regulations, contributing to assure safety, as well as reduce costs and environmental impacts. Probabilistic Risk Assessment has become an important part of licensing requirements of the nuclear power plants in Brazil and in the world. Risk can be defined as a qualitative and/or quantitative assessment of accident sequence frequencies (or probabilities) and their consequences. Risk management is a systematic application of management policies, procedures and practices to identify, analyze, plan, implement, control, communicate and document risks. Several tools and computer codes must be combined, in order to estimate both probabilities and consequences of accidents. Event Tree Analysis (ETA), Fault Tree Analysis (FTA), Reliability Block Diagrams (RBD), and Markov models are examples of evaluation tools that can support the safety and risk assessment for analyzing process systems, identifying potential accidents, and estimating consequences. Because of complexity of such analyzes, specialized computer codes are required, such as the reliability engineering software develop by Reliasoft® Corporation. BlockSim (FTA, RBD and Markov models), RENO (ETA and consequence assessment), Weibull++ (life data and uncertainty analysis), and Xfmea (qualitative risk assessment) are some codes that can be highlighted. This work describes an integrated approach using these tools and software to carry out reliability, safety, and risk assessment of nuclear facilities, as well as, and application example. (author)

  6. Use of reliability engineering tools in safety and risk assessment of nuclear facilities

    International Nuclear Information System (INIS)

    Raso, Amanda Laureano; Vasconcelos, Vanderley de; Marques, Raíssa Oliveira; Soares, Wellington Antonio; Mesquita, Amir Zacarias

    2017-01-01

    Safety, reliability and availability are fundamental criteria in design, construction and operation of nuclear facilities, as nuclear power plants. Deterministic and probabilistic risk assessments of such facilities are required by regulatory authorities in order to meet licensing regulations, contributing to assure safety, as well as reduce costs and environmental impacts. Probabilistic Risk Assessment has become an important part of licensing requirements of the nuclear power plants in Brazil and in the world. Risk can be defined as a qualitative and/or quantitative assessment of accident sequence frequencies (or probabilities) and their consequences. Risk management is a systematic application of management policies, procedures and practices to identify, analyze, plan, implement, control, communicate and document risks. Several tools and computer codes must be combined, in order to estimate both probabilities and consequences of accidents. Event Tree Analysis (ETA), Fault Tree Analysis (FTA), Reliability Block Diagrams (RBD), and Markov models are examples of evaluation tools that can support the safety and risk assessment for analyzing process systems, identifying potential accidents, and estimating consequences. Because of complexity of such analyzes, specialized computer codes are required, such as the reliability engineering software develop by Reliasoft® Corporation. BlockSim (FTA, RBD and Markov models), RENO (ETA and consequence assessment), Weibull++ (life data and uncertainty analysis), and Xfmea (qualitative risk assessment) are some codes that can be highlighted. This work describes an integrated approach using these tools and software to carry out reliability, safety, and risk assessment of nuclear facilities, as well as, and application example. (author)

  7. Distribution system reliability evaluation using credibility theory

    African Journals Online (AJOL)

    Xufeng Xu, Joydeep Mitra

    switches, the distribution system can be divided into multiple SPSS, which are connected with tie switches. For example, SPSS corresponding to feeder F1 in Figure 2 is composed of {1, 2,…, 12}. Secondly, based on the definition of SPSS, the power supply area of each feeder is analyzed by depth-first search strategy. The.

  8. Validity and reliability of the Eating Assessment Tool (EAT-10).

    Science.gov (United States)

    Belafsky, Peter C; Mouadeb, Debbie A; Rees, Catherine J; Pryor, Jan C; Postma, Gregory N; Allen, Jacqueline; Leonard, Rebecca J

    2008-12-01

    The Eating Assessment Tool is a self-administered, symptom-specific outcome instrument for dysphagia. The purpose of this study was to assess the validity and reliability of the 10-item Eating Assessment Tool (EAT-10). The investigation consisted of 4 phases: 1) line-item generation, 2) line-item reduction and reliability, 3) normative data generation, and 4) validity analysis. All data were collected prospectively. Internal consistency was assessed with the Cronbach alpha. Test-retest reliability was evaluated with the Pearson product moment correlation coefficient. Normative data were obtained by administering the instrument to a community cohort of healthy volunteers. Validity was assessed by administering the instrument before and after dysphagia treatment and by evaluating survey differences between normal persons and those with known diagnoses. A total of 629 surveys were administered to 482 patients. The internal consistency (Cronbach alpha) of the final instrument was 0.960. The test-retest intra-item correlation coefficients ranged from 0.72 to 0.91. The mean (+/- SD) EAT-10 score of the normal cohort was 0.40 +/- 1.01. The mean EAT-10 score was 23.58 +/- 13.18 for patients with esophageal dysphagia, 23.10 +/- 12.22 for those with oropharyngeal dysphagia, 9.19 +/- 12.60 for those with voice disorders, 22.42 +/- 14.06 for those with head and neck cancer, and 11.71 +/- 9.61 for those with reflux. The patients with oropharyngeal and esophageal dysphagia and a history of head and neck cancer had a significantly higher EAT-10 score than did those with reflux or voice disorders (p EAT-10 score of the patients with dysphagia improved from 19.87 +/- 10.5 to 5.2 +/- 7.4 after treatment (p EAT-10 has displayed excellent internal consistency, test-retest reproducibility, and criterion-based validity. The normative data suggest that an EAT-10 score of 3 or higher is abnormal. The instrument may be utilized to document the initial dysphagia severity and monitor the

  9. [Reliability and applications of a grammar comprehension assessment test].

    Science.gov (United States)

    López-Higes, Ramón; Martín-Aragoneses, M Teresa; Rubio-Valdehita, Susana

    2010-04-01

    The sentence comprehension test from the sentence comprehension cognitive examination (ECCO) battery can be used to assess children and adults with grammar comprehension disorders by means of a simple verification procedure that requires few memory resources. AIM. To present a psychometric analysis of the sentence comprehension test based on the classical theory of tests and on item response theory, as well as several studies that show its usefulness for assessing grammar comprehension in different populations. The test was applied to 2238 subjects with ages ranging from 6 to 85 years. The analysis shows that the test has a high overall reliability and, through the age groups that were considered, it includes elements that are especially discriminating or informative (lexical and syntactic distractors) and is biased towards medium-low levels of the trait. In view of the results, the sentence comprehension test from the ECCO battery provides a reliable measure of grammar comprehension through a wide variety of constructions and has great potential value for use in the clinical and research domains.

  10. Reliability considerations of electronics components for the deep underwater muon and neutrino detection system

    International Nuclear Information System (INIS)

    Leskovar, B.

    1980-02-01

    The reliability of some electronics components for the Deep Underwater Muon and Neutrino Detection (DUMAND) System is discussed. An introductory overview of engineering concepts and technique for reliability assessment is given. Component reliability is discussed in the contest of major factors causing failures, particularly with respect to physical and chemical causes, process technology and testing, and screening procedures. Failure rates are presented for discrete devices and for integrated circuits as well as for basic electronics components. Furthermore, the military reliability specifications and standards for semiconductor devices are reviewed

  11. Reliability Modeling of Microelectromechanical Systems Using Neural Networks

    Science.gov (United States)

    Perera. J. Sebastian

    2000-01-01

    Microelectromechanical systems (MEMS) are a broad and rapidly expanding field that is currently receiving a great deal of attention because of the potential to significantly improve the ability to sense, analyze, and control a variety of processes, such as heating and ventilation systems, automobiles, medicine, aeronautical flight, military surveillance, weather forecasting, and space exploration. MEMS are very small and are a blend of electrical and mechanical components, with electrical and mechanical systems on one chip. This research establishes reliability estimation and prediction for MEMS devices at the conceptual design phase using neural networks. At the conceptual design phase, before devices are built and tested, traditional methods of quantifying reliability are inadequate because the device is not in existence and cannot be tested to establish the reliability distributions. A novel approach using neural networks is created to predict the overall reliability of a MEMS device based on its components and each component's attributes. The methodology begins with collecting attribute data (fabrication process, physical specifications, operating environment, property characteristics, packaging, etc.) and reliability data for many types of microengines. The data are partitioned into training data (the majority) and validation data (the remainder). A neural network is applied to the training data (both attribute and reliability); the attributes become the system inputs and reliability data (cycles to failure), the system output. After the neural network is trained with sufficient data. the validation data are used to verify the neural networks provided accurate reliability estimates. Now, the reliability of a new proposed MEMS device can be estimated by using the appropriate trained neural networks developed in this work.

  12. Feasibility and reliability of frailty assessment in the critically ill: a systematic review.

    Science.gov (United States)

    Pugh, Richard J; Ellison, Amy; Pye, Kate; Subbe, Christian P; Thorpe, Chris M; Lone, Nazir I; Clegg, Andrew

    2018-02-26

    For healthcare systems, an ageing population poses challenges in the delivery of equitable and effective care. Frailty assessment has the potential to improve care in the intensive care setting, but applying assessment tools in critical illness may be problematic. The aim of this systematic review was to evaluate evidence for the feasibility and reliability of frailty assessment in critical care. Our primary search was conducted in Medline, Medline In-process, EMBASE, CINAHL, PsycINFO, AMED, Cochrane Database of Systematic Reviews, and Web of Science (January 2001 to October 2017). We included observational studies reporting data on feasibility and reliability of frailty assessment in the critical care setting in patients 16 years and older. Feasibility was assessed in terms of timing of evaluation, the background, training and expertise required for assessors, and reliance upon proxy input. Reliability was assessed in terms of inter-rater reliability. Data from 11 study publications are included, representing 8 study cohorts and 7761 patients. Proxy involvement in frailty assessment ranged from 58 to 100%. Feasibility data were not well-reported overall, but the exclusion rate due to lack of proxy availability ranged from 0 to 45%, the highest rate observed where family involvement was mandatory and the assessment tool relatively complex (frailty index, FI). Conventional elements of frailty phenotype (FP) assessment required modification prior to use in two studies. Clinical staff tended to use a simple judgement-based tool, the clinical frailty scale (CFS). Inter-rater reliability was reported in one study using the CFS and although a good level of agreement was observed between clinician assessments, this was a small and single-centre study. Though of unproven reliability in the critically ill, CFS was the tool used most widely by critical care clinical staff. Conventional FP assessment required modification for general application in critical care, and an FI

  13. System Reliability for Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2013-01-01

    Deeper waters and harsher environments are the main factors that make the electricity generated by offshore wind turbines (OWTs) expensive due to high costs of the substructure, operation & maintenance and installation. The key goal of development is to decrease the cost of energy (CoE). In conse......Deeper waters and harsher environments are the main factors that make the electricity generated by offshore wind turbines (OWTs) expensive due to high costs of the substructure, operation & maintenance and installation. The key goal of development is to decrease the cost of energy (Co...... in inspections or measurements from condition monitoring systems. Finally, an example is established to illustrate the practical application of this framework for jacket type wind turbine substructure considering system effects....

  14. Final Report for the Virtual Reliability Realization System LDRD

    Energy Technology Data Exchange (ETDEWEB)

    DELLIN, THEODORE A.; HENDERSON, CHRISTOPHER L.; O' TOOLE, EDWARD J.

    2000-12-01

    Current approaches to reliability are not adequate to keep pace with the need for faster, better and cheaper products and systems. This is especially true in high consequence of failure applications. The original proposal for the LDRD was to look at this challenge and see if there was a new paradigm that could make reliability predictions, along with a quantitative estimate of the risk in that prediction, in a way that was faster, better and cheaper. Such an approach would be based on the underlying science models that are the backbone of reliability predictions. The new paradigm would be implemented in two software tools: the Virtual Reliability Realization System (VRRS) and the Reliability Expert System (REX). The three-year LDRD was funded at a reduced level for the first year ($120K vs. $250K) and not renewed. Because of the reduced funding, we concentrated on the initial development of the expertise system. We developed an interactive semiconductor calculation tool needed for reliability analyses. We also were able to generate a basic functional system using Microsoft Siteserver Commerce Edition and Microsoft Sequel Server. The base system has the capability to store Office documents from multiple authors, and has the ability to track and charge for usage. The full outline of the knowledge model has been incorporated as well as examples of various types of content.

  15. Assuring long-term reliability of concentrator PV systems

    Science.gov (United States)

    McConnell, R.; Garboushian, V.; Brown, J.; Crawford, C.; Darban, K.; Dutra, D.; Geer, S.; Ghassemian, V.; Gordon, R.; Kinsey, G.; Stone, K.; Turner, G.

    2009-08-01

    Concentrator PV (CPV) systems have attracted significant interest because these systems incorporate the world's highest efficiency solar cells and they are targeting the lowest cost production of solar electricity for the world's utility markets. Because these systems are just entering solar markets, manufacturers and customers need to assure their reliability for many years of operation. There are three general approaches for assuring CPV reliability: 1) field testing and development over many years leading to improved product designs, 2) testing to internationally accepted qualification standards (especially for new products) and 3) extended reliability tests to identify critical weaknesses in a new component or design. Amonix has been a pioneer in all three of these approaches. Amonix has an internal library of field failure data spanning over 15 years that serves as the basis for its seven generations of CPV systems. An Amonix product served as the test CPV module for the development of the world's first qualification standard completed in March 2001. Amonix staff has served on international standards development committees, such as the International Electrotechnical Commission (IEC), in support of developing CPV standards needed in today's rapidly expanding solar markets. Recently Amonix employed extended reliability test procedures to assure reliability of multijunction solar cell operation in its seventh generation high concentration PV system. This paper will discuss how these three approaches have all contributed to assuring reliability of the Amonix systems.

  16. Operator adaptation to changes in system reliability under adaptable automation.

    Science.gov (United States)

    Chavaillaz, Alain; Sauer, Juergen

    2017-09-01

    This experiment examined how operators coped with a change in system reliability between training and testing. Forty participants were trained for 3 h on a complex process control simulation modelling six levels of automation (LOA). In training, participants either experienced a high- (100%) or low-reliability system (50%). The impact of training experience on operator behaviour was examined during a 2.5 h testing session, in which participants either experienced a high- (100%) or low-reliability system (60%). The results showed that most operators did not often switch between LOA. Most chose an LOA that relieved them of most tasks but maintained their decision authority. Training experience did not have a strong impact on the outcome measures (e.g. performance, complacency). Low system reliability led to decreased performance and self-confidence. Furthermore, complacency was observed under high system reliability. Overall, the findings suggest benefits of adaptable automation because it accommodates different operator preferences for LOA. Practitioner Summary: The present research shows that operators can adapt to changes in system reliability between training and testing sessions. Furthermore, it provides evidence that each operator has his/her preferred automation level. Since this preference varies strongly between operators, adaptable automation seems to be suitable to accommodate these large differences.

  17. Reliability analysis of microcomputer boards and computer based systems important to safety of nuclear plants

    International Nuclear Information System (INIS)

    Shrikhande, S.V.; Patil, V.K.; Ganesh, G.; Biswas, B.; Patil, R.K.

    2010-01-01

    Computer Based Systems (CBS) are employed in Indian nuclear plants for protection, control and monitoring purpose. For forthcoming CBS, Reactor Control Division has designed and developed a new standardized family of microcomputer boards qualified to stringent requirements of nuclear industry. These boards form the basic building blocks of CBS. Reliability analysis of these boards is being carried out using analysis package based on MIL-STD-217Plus methodology. The estimated failure rate values of these standardized microcomputer boards will be useful for reliability assessment of these systems. The paper presents reliability analysis of microcomputer boards and case study of a CBS system built using these boards. (author)

  18. Influence Of Inspection Intervals On Mechanical System Reliability

    International Nuclear Information System (INIS)

    Zilberman, B.

    1998-01-01

    In this paper a methodology of reliability analysis of mechanical systems with latent failures is described. Reliability analysis of such systems must include appropriate usage of check intervals for latent failure detection. The methodology suggests, that based on system logic the analyst decides at the beginning if a system can fail actively or latently and propagates this approach through all system levels. All inspections are assumed to be perfect (all failures are detected and repaired and no new failures are introduced as a result of the maintenance). Additional assumptions are that mission time is much smaller, than check intervals and all components have constant failure rates. Analytical expressions for reliability calculates are provided, based on fault tree and Markov modeling techniques (for two and three redundant systems with inspection intervals). The proposed methodology yields more accurate results than are obtained by not using check intervals or using half check interval times. The conventional analysis assuming that at the beginning of each mission system is as new, give an optimistic prediction of system reliability. Some examples of reliability calculations of mechanical systems with latent failures and establishing optimum check intervals are provided

  19. SOFC Systems with Improved Reliability and Endurance

    Energy Technology Data Exchange (ETDEWEB)

    Ghezel-Ayagh, Hossein [Fuelcell Energy, Incorporated, Danbury, CT (United States)

    2015-12-31

    The overall goal of this U.S. Department of Energy (DOE) sponsored project was the development of Solid Oxide Fuel Cell (SOFC) technology suitable for ultra-efficient central power generation systems utilizing coal and natural gas fuels and featuring greater than 90% carbon dioxide capture. The specific technical objective of this project was to demonstrate, via analyses and testing, progress towards adequate stack life (≥ 4 years) and stack performance stability (degradation rate ≤ 0.2% per 1000 hours) in a low-cost SOFC stack design. This final technical report summarizes the progress made during the project period of 27 months. Significant progress was made in the areas of cell and stack technology development, stack module development, sub-scale module tests, and Proof-of-Concept Module unit design, fabrication and testing. The work focused on cell and stack materials and designs, balance-of-plant improvements, and performance evaluation covering operating conditions and fuel compositions anticipated for commercially-deployed systems. In support of performance evaluation under commercial conditions, this work included the design, fabrication, siting, commissioning, and operation of a ≥ 50 kWe proof-of-concept module (PCM) power plant, based upon SOFC cell and stack technology developed to date by FuelCell Energy, Inc. (FCE) under the Office of Fossil Energy’s Solid Oxide Fuel Cells program. The PCM system was operated for at least 1000 hours on natural gas fuel at FCE’s facility. The factory cost of the SOFC stack was estimated to be at or below the DOE’s high-volume production cost target (2011 $).

  20. Reliability and availability assessments for the next European Torus

    International Nuclear Information System (INIS)

    Bunde, R.

    1988-01-01

    To achieve its targets in reasonable time, the Next European Torus (NET) must be operated with considerable reliability and availability (R and A). Therefore, failure modes, effects, and criticality analysis (FMECA) of the overall plant and of its major components is already being performed as the design evolves. The present status of the R and A work is described in four steps: First, the R and A targets envisaged for the NET operation are discussed. Then an FMECA covering the overall plant is described, and a more detailed FMECA of major components is presented concerning the toroidal field coil systeml plasma heating systems; protection, instrumentation, and control systems; first wall and blanket, as well as the cooling system. Finally, the R and A results are compared with the targets, and measures for improvements are given

  1. Reliability assessment using degradation models: bayesian and classical approaches

    Directory of Open Access Journals (Sweden)

    Marta Afonso Freitas

    2010-04-01

    Full Text Available Traditionally, reliability assessment of devices has been based on (accelerated life tests. However, for highly reliable products, little information about reliability is provided by life tests in which few or no failures are typically observed. Since most failures arise from a degradation mechanism at work for which there are characteristics that degrade over time, one alternative is monitor the device for a period of time and assess its reliability from the changes in performance (degradation observed during that period. The goal of this article is to illustrate how degradation data can be modeled and analyzed by using "classical" and Bayesian approaches. Four methods of data analysis based on classical inference are presented. Next we show how Bayesian methods can also be used to provide a natural approach to analyzing degradation data. The approaches are applied to a real data set regarding train wheels degradation.Tradicionalmente, o acesso à confiabilidade de dispositivos tem sido baseado em testes de vida (acelerados. Entretanto, para produtos altamente confiáveis, pouca informação a respeito de sua confiabilidade é fornecida por testes de vida no quais poucas ou nenhumas falhas são observadas. Uma vez que boa parte das falhas é induzida por mecanismos de degradação, uma alternativa é monitorar o dispositivo por um período de tempo e acessar sua confiabilidade através das mudanças em desempenho (degradação observadas durante aquele período. O objetivo deste artigo é ilustrar como dados de degradação podem ser modelados e analisados utilizando-se abordagens "clássicas" e Bayesiana. Quatro métodos de análise de dados baseados em inferência clássica são apresentados. A seguir, mostramos como os métodos Bayesianos podem também ser aplicados para proporcionar uma abordagem natural à análise de dados de degradação. As abordagens são aplicadas a um banco de dados real relacionado à degradação de rodas de trens.

  2. Site reliability engineering how Google runs production systems

    CERN Document Server

    Petoff, Jennifer; Jones, Chris; Murphy, Niall Richard

    2016-01-01

    The overwhelming majority of a software system’s lifespan is spent in use, not in design or implementation. So, why does conventional wisdom insist that software engineers focus primarily on the design and development of large-scale computing systems? In this collection of essays and articles, key members of Google’s Site Reliability Team explain how and why their commitment to the entire lifecycle has enabled the company to successfully build, deploy, monitor, and maintain some of the largest software systems in the world. You’ll learn the principles and practices that enable Google engineers to make systems more scalable, reliable, and efficient—lessons directly applicable to your organization. This book is divided into four sections: Introduction—Learn what site reliability engineering is and why it differs from conventional IT industry practices Principles—Examine the patterns, behaviors, and areas of concern that influence the work of a site reliability engineer (SRE) Practices...

  3. Reliability-oriented energy storage sizing in wind power systems

    DEFF Research Database (Denmark)

    Qin, Zian; Liserre, Marco; Blaabjerg, Frede

    2014-01-01

    Energy storage can be used to suppress the power fluctuations in wind power systems, and thereby reduce the thermal excursion and improve the reliability. Since the cost of the energy storage in large power application is high, it is crucial to have a better understanding of the relationship...... between the size of the energy storage and the reliability benefit it can generate. Therefore, a reliability-oriented energy storage sizing approach is proposed for the wind power systems, where the power, energy, cost and the control strategy of the energy storage are all taken into account....... With the proposed approach, the computational effort is reduced and the impact of the energy storage system on the reliability of the wind power converter can be quantified....

  4. Extrapolation Method for System Reliability Assessment

    DEFF Research Database (Denmark)

    Qin, Jianjun; Nishijima, Kazuyoshi; Faber, Michael Havbro

    2012-01-01

    of integrals with scaled domains. The performance of this class of approximation depends on the approach applied for the scaling and the functional form utilized for the extrapolation. A scheme for this task is derived here taking basis in the theory of asymptotic solutions to multinormal probability integrals...

  5. Software Reliability Issues Concerning Large and Safety Critical Software Systems

    Science.gov (United States)

    Kamel, Khaled; Brown, Barbara

    1996-01-01

    This research was undertaken to provide NASA with a survey of state-of-the-art techniques using in industrial and academia to provide safe, reliable, and maintainable software to drive large systems. Such systems must match the complexity and strict safety requirements of NASA's shuttle system. In particular, the Launch Processing System (LPS) is being considered for replacement. The LPS is responsible for monitoring and commanding the shuttle during test, repair, and launch phases. NASA built this system in the 1970's using mostly hardware techniques to provide for increased reliability, but it did so often using custom-built equipment, which has not been able to keep up with current technologies. This report surveys the major techniques used in industry and academia to ensure reliability in large and critical computer systems.

  6. Designing incentive market mechanisms for improving restructured power system reliabilities

    DEFF Research Database (Denmark)

    Ding, Yi; Østergaard, Jacob; Wu, Qiuwei

    2011-01-01

    In a restructured power system, the monopoly generation utility is replaced by different electricity producers. There exists extreme price volatility caused by random failures by generation or/and transmission systems. In these cases, producers' profits can be much higher than those in the normal...... state. The reliability management of producers usually cannot be directly controlled by the system operators in a restructured power system. Producers may have no motivation to improve their reliabilities, which can result in serious system unreliability issues in the new environment. Incentive market...... mechanisms for improving the restructured power system reliabilities have been designed in this paper. In the proposed incentive mechanisms, penalty will be implemented on a producer if the failures of its generator(s) result in the variation of electricity prices. Incentive market mechanisms can motivate...

  7. Reliable Software Development for Machine Protection Systems

    CERN Document Server

    Anderson, D; Dragu, M; Fuchsberger, K; Garnier, JC; Gorzawski, AA; Koza, M; Krol, K; Misiowiec, K; Stamos, K; Zerlauth, M

    2014-01-01

    The Controls software for the Large Hadron Collider (LHC) at CERN, with more than 150 millions lines of code, resides amongst the largest known code bases in the world1. Industry has been applying Agile software engineering techniques for more than two decades now, and the advantages of these techniques can no longer be ignored to manage the code base for large projects within the accelerator community. Furthermore, CERN is a particular environment due to the high personnel turnover and manpower limitations, where applying Agile processes can improve both, the codebase management as well as its quality. This paper presents the successful application of the Agile software development process Scrum for machine protection systems at CERN, the quality standards and infrastructure introduced together with the Agile process as well as the challenges encountered to adapt it to the CERN environment.

  8. Electric Power quality Analysis in research reactor: Impacts on nuclear safety assessment and electrical distribution reliability

    International Nuclear Information System (INIS)

    Touati, Said; Chennai, Salim; Souli, Aissa

    2015-01-01

    The increased requirements on supervision, control, and performance in modern power systems make power quality monitoring a common practise for utilities. Large databases are created and automatic processing of the data is required for fast and effective use of the available information. Aim of the work presented in this paper is the development of tools for analysis of monitoring power quality data and in particular measurements of voltage and currents in various level of electrical power distribution. The study is extended to evaluate the reliability of the electrical system in nuclear plant. Power Quality is a measure of how well a system supports reliable operation of its loads. A power disturbance or event can involve voltage, current, or frequency. Power disturbances can originate in consumer power systems, consumer loads, or the utility. The effect of power quality problems is the loss power supply leading to severe damage to equipments. So, we try to track and improve system reliability. The assessment can be focused on the study of impact of short circuits on the system, harmonics distortion, power factor improvement and effects of transient disturbances on the Electrical System during motor starting and power system fault conditions. We focus also on the review of the Electrical System design against the Nuclear Directorate Safety Assessment principles, including those extended during the last Fukushima nuclear accident. The simplified configuration of the required system can be extended from this simple scheme. To achieve these studies, we have used a demo ETAP power station software for several simulations. (authors)

  9. Methodologies of the hardware reliability prediction for PSA of digital I and C systems

    International Nuclear Information System (INIS)

    Jung, H. S.; Sung, T. Y.; Eom, H. S.; Park, J. K.; Kang, H. G.; Park, J.

    2000-09-01

    Digital I and C systems are being used widely in the Non-safety systems of the NPP and they are expanding their applications to safety critical systems. The regulatory body shifts their policy to risk based and may require Probabilistic Safety Assessment for the digital I and C systems. But there is no established reliability prediction methodology for the digital I and C systems including both software and hardware yet. This survey report includes a lot of reliability prediction methods for electronic systems in view of hardware. Each method has both the strong and the weak points. This report provides the state-of-art of prediction methods and focus on Bellcore method and MIL-HDBK-217F method in deeply. The reliability analysis models are reviewed and discussed to help analysts. Also this report includes state-of-art of software tools that are supporting reliability prediction

  10. Mechanical system reliability analysis using a combination of graph theory and Boolean function

    International Nuclear Information System (INIS)

    Tang, J.

    2001-01-01

    A new method based on graph theory and Boolean function for assessing reliability of mechanical systems is proposed. The procedure for this approach consists of two parts. By using the graph theory, the formula for the reliability of a mechanical system that considers the interrelations of subsystems or components is generated. Use of the Boolean function to examine the failure interactions of two particular elements of the system, followed with demonstrations of how to incorporate such failure dependencies into the analysis of larger systems, a constructive algorithm for quantifying the genuine interconnections between the subsystems or components is provided. The combination of graph theory and Boolean function provides an effective way to evaluate the reliability of a large, complex mechanical system. A numerical example demonstrates that this method an effective approaches in system reliability analysis

  11. Reliable Integration of Terascale Systems with Nanoscale Devices

    Science.gov (United States)

    Naeimi, Helia

    Nanotechnology design has attracted considerable attention in recent years and seems to be the technology for the future generation of the electronic devices, either as scaled and more restricted conventional lithographic technology, or as emerging sublithographic technologies, such as nanowires, carbon nanotubes, NDR (Negative Differential Resistance) devices, or other nanotechnology devices. Each of these technologies provides one or more design benefits including feature-size scaling, high on-off ratios, and faster devices. However, all of these techniques share their most challenging design issue: reliability. Providing reliability is becoming constantly more challenging due to increases in both the device failure rate and system complexity. This work develops techniques that make achieving reliability in such systems feasible with practical area overhead and considerable improvement in area overhead and system reliability compared to related techniques. Conventional reliability techniques focus on low defect and fault rates, i.e., single event upset (SEU). These techniques cannot simply be scaled to larger systems with more unreliable devices. If these techniques are directly applied to the high defect and fault rate of the nanotechnology regime, they suffer impractically high overhead, or they may not achieve the desired reliability. Our approach in this thesis exploits the following design patterns to achieve a considerable area reduction compared to related works and achieve high reliability: (1) Fine-grained reliability: In this technique, the system is partitioned into fine-grained blocks, and the reliability is provided for each block. This technique is used to contain the area overhead and bound the impact on the throughput. (2) Using alternative resources: This technique improves the design quality by sparing other resources when system is tight on one resource. In our work we replace some of the spacial redundancies with temporal redundancy to limit

  12. Reliability of a semi-quantitative method for dermal exposure assessment (DREAM)

    NARCIS (Netherlands)

    Wendel de Joode, B. van; Hemmen, J.J. van; Meijster, T.; Major, V.; London, L.; Kromhout, H.

    2005-01-01

    Valid and reliable semi-quantitative dermal exposure assessment methods for epidemiological research and for occupational hygiene practice, applicable for different chemical agents, are practically nonexistent. The aim of this study was to assess the reliability of a recently developed

  13. Nuclear computerized library for assessing reactor reliability (NUCLARR): Part 2, Guide to operations: User's guide

    International Nuclear Information System (INIS)

    Gilmore, W.E.; Gentillon, C.D.; Gertman, D.I.; Beers, G.H.; Galyean, W.J.; Gilbert, B.G.

    1988-06-01

    The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) is an automated data base management system for processing and storing human error probability and hardware component failure data. The NUCLARR system software resides on an IBM (or compatible) personal micro-computer. NUCLARR can be used by the end user to furnish data inputs for both human and hardware reliability analysis in support of a variety of risk assessment activities. The NUCLARR system is documented in a five-volume series of reports. Volume IV of this series is the User's Guide for operating the NUCLARR software and is presented in three parts. This volume, Part 2: Guide to Operations, contains the instructions and basic procedures for using the NUCLARR software. Part 2 provides guidance and information for getting started, performing the desired functions, and making the most efficient use of the system's features

  14. The Assessment of Reliability Under Range Restriction: A Comparison of [Alpha], [Omega], and Test-Retest Reliability for Dichotomous Data

    Science.gov (United States)

    Fife, Dustin A.; Mendoza, Jorge L.; Terry, Robert

    2012-01-01

    Though much research and attention has been directed at assessing the correlation coefficient under range restriction, the assessment of reliability under range restriction has been largely ignored. This article uses item response theory to simulate dichotomous item-level data to assess the robustness of KR-20 ([alpha]), [omega], and test-retest…

  15. Reliability Performance Optimization of Meshed Electrical Distribution System Considering Customer and Energy based Reliability Indices

    Science.gov (United States)

    Arya, L. D.; Kela, K. B.

    2013-12-01

    This paper describes a methodology for determination of optimum failure rate and repair time for each component of a meshed distribution system. In this paper the reliability indices for a sample meshed network are optimized. An objective function incorporating customer and energy based reliability indices and their target values is formulated. These indices are function of failure rate and repair time of a section of a distribution network. Modification of failure rate and repair time modifies the cost attached to them. Hence the optimization of the objective function is achieved by modifying the failure rate and repair time of each section of the meshed distribution system accounting constraint on budget allocated. The problem has been solved using population based differential evolution and bare bones particle swarm optimization techniques and results have been compared for a sample meshed distribution system.

  16. Reliability modeling and analysis of smart power systems

    CERN Document Server

    Karki, Rajesh; Verma, Ajit Kumar

    2014-01-01

    The volume presents the research work in understanding, modeling and quantifying the risks associated with different ways of implementing smart grid technology in power systems in order to plan and operate a modern power system with an acceptable level of reliability. Power systems throughout the world are undergoing significant changes creating new challenges to system planning and operation in order to provide reliable and efficient use of electrical energy. The appropriate use of smart grid technology is an important drive in mitigating these problems and requires considerable research acti

  17. Incorporating Cyber Layer Failures in Composite Power System Reliability Evaluations

    Directory of Open Access Journals (Sweden)

    Yuqi Han

    2015-08-01

    Full Text Available This paper proposes a novel approach to analyze the impacts of cyber layer failures (i.e., protection failures and monitoring failures on the reliability evaluation of composite power systems. The reliability and availability of the cyber layer and its protection and monitoring functions with various topologies are derived based on a reliability block diagram method. The availability of the physical layer components are modified via a multi-state Markov chain model, in which the component protection and monitoring strategies, as well as the cyber layer topology, are simultaneously considered. Reliability indices of composite power systems are calculated through non-sequential Monte-Carlo simulation. Case studies demonstrate that operational reliability downgrades in cyber layer function failure situations. Moreover, protection function failures have more significant impact on the downgraded reliability than monitoring function failures do, and the reliability indices are especially sensitive to the change of the cyber layer function availability in the range from 0.95 to 1.

  18. Preparation of methodology for reliability analysis of selected digital segments of the instrumentation and control systems of NPPs. Pt. 1

    International Nuclear Information System (INIS)

    Hustak, S.; Patrik, M.; Babic, P.

    2000-12-01

    The report is structured as follows: (i) Introduction; (ii) Important notions relating to the safety and dependability of software systems for nuclear power plants (selected notions from IAEA Technical Report No. 397; safety aspects of software application; reliability/dependability aspects of digital systems); (iii) Peculiarities of digital systems and ways to a dependable performance of the required function (failures in the system and principles of defence against them; ensuring resistance of digital systems against failures at various hardware and software levels); (iv) The issue of analytical procedures to assess the safety and reliability of safety-related digital systems (safety and reliability assessment at an early stage of the project; general framework of reliability analysis of complex systems; choice of an appropriate quantitative measure of software reliability); (v) Selected qualitative and quantitative information about the reliability of digital systems; the use of relations between the incidence of various types of faults); and (vi) Conclusions and recommendations. (P.A.)

  19. Improving the Reliability of Case-Based Reasoning Systems

    Directory of Open Access Journals (Sweden)

    Xu Xu

    2010-09-01

    also discussed in this paper, especially the property that whether inter-feature of case exists redundancy. After that, the reliability of an individual suggested solution is studied. To illustrate these ideas, some experiments and their results are discussed in this paper. The results of experiments show a new route concerning on how to improve the reliability of a CBR system at an overall level.

  20. Reliability analysis of large, complex systems using ASSIST

    Science.gov (United States)

    Johnson, Sally C.

    1988-01-01

    The SURE reliability analysis program is discussed as well as the ASSIST model generation program. It is found that semi-Markov modeling using model reduction strategies with the ASSIST program can be used to accurately solve problems at least as complex as other reliability analysis tools can solve. Moreover, semi-Markov analysis provides the flexibility needed for modeling realistic fault-tolerant systems.

  1. Report on the analysis of field data relating to the reliability of solar hot water systems.

    Energy Technology Data Exchange (ETDEWEB)

    Menicucci, David F. (Building Specialists, Inc., Albuquerque, NM)

    2011-07-01

    Utilities are overseeing the installations of thousand of solar hot water (SHW) systems. Utility planners have begun to ask for quantitative measures of the expected lifetimes of these systems so that they can properly forecast their loads. This report, which augments a 2009 reliability analysis effort by Sandia National Laboratories (SNL), addresses this need. Additional reliability data have been collected, added to the existing database, and analyzed. The results are presented. Additionally, formal reliability theory is described, including the bathtub curve, which is the most common model to characterize the lifetime reliability character of systems, and for predicting failures in the field. Reliability theory is used to assess the SNL reliability database. This assessment shows that the database is heavily weighted with data that describe the reliability of SHW systems early in their lives, during the warranty period. But it contains few measured data to describe the ends of SHW systems lives. End-of-life data are the most critical ones to define sufficiently the reliability of SHW systems in order to answer the questions that the utilities pose. Several ideas are presented for collecting the required data, including photometric analysis of aerial photographs of installed collectors, statistical and neural network analysis of energy bills from solar homes, and the development of simple algorithms to allow conventional SHW controllers to announce system failures and record the details of the event, similar to how aircraft black box recorders perform. Some information is also presented about public expectations for the longevity of a SHW system, information that is useful in developing reliability goals.

  2. Reliability of Blotting Techniques to Assess Contact Lens Water Content.

    Science.gov (United States)

    Cañadas, Pilar; López-Miguel, Alberto; Gómez, Alba; López-de la Rosa, Alberto; Fernández, Itziar; González-García, María J

    2018-02-15

    To determine the reliability of wet and modified dry blotting techniques used in the gravimetric method to assess contact lens (CL) water content (WC), the accuracy of both techniques in comparison with the nominal WC, and also their agreement. We evaluated hydrated and dry CL mass values and WC using the gravimetric method in 440 daily disposable CLs. Samples assessed corresponded to Dailies Total 1, Dailies AquaComfort Plus, 1-Day Acuvue TruEye, and Biotrue ONEday. Back vertex power ranged from +3.00 diopters (D) to -6.00 D. Within-subject coefficient of variation (CVw) and intraclass correlation coefficients were calculated. Bland-Altman analysis was also performed. The modified dry blotting technique yielded significantly (P≤0.0001) higher hydrated CL mass values. The wet blotting technique provided significantly (P≤0.04) better consistency than the modified dry one. Values of CVw for wet and modified dry blotting techniques ranged from 1.2% to 2.1% and from 3.7% to 5.4%, respectively. As for dry CL mass values, CVw values were not significantly different (P≥0.05) between wet (range: 1.1%-1.9%) and dry (range: 1.0%-5.1%) blotting techniques, except for Dailies AquaComfort Plus (P=0.03). Bland-Altman analysis showed poor agreement between the techniques. The wet blotting technique yielded WC values close (around 1%) to nominal ones, in contrast to modified dry blotting technique (≥2.5%). The wet blotting technique is not only more reliable than the modified dry one when obtaining hydrated CL mass but also provides more accurate nominal WC measurements. Agreement between the techniques was poor.

  3. Reliability and safety analysis for systems of fusion device

    Energy Technology Data Exchange (ETDEWEB)

    Alzbutas, Robertas, E-mail: robertas.alzbutas@lei.lt; Voronov, Roman

    2015-05-15

    Highlights: • Reliability is very important from fusion devices efficiency perspective. • Rich experience of probabilistic safety analysis exists in nuclear industry. • Reliability and safety analysis was applied for systems of fusion device. • This enables to identify and prioritize availability improvement measures. • Recommendations are based on cost effectiveness for risk decrease options. - Abstract: Fusion energy or thermonuclear power is a promising, literally endless source of energy. Development of fusion power is still under investigation and experimental phase, and a number of fusion devices are under construction in Europe. Since fusion energy is innovative and fusion devices contain unique and expensive equipment, an issue of their reliability is very important from their efficiency perspective. A Reliability, Availability, Maintainability, Inspectability (RAMI) analysis is being performed or is going to be performed in the nearest future for such fusion devices as ITER and DEMO in order to ensure reliable and efficient operation for experiments (e.g., in ITER) or for energy production purposes (e.g., in DEMO). On the other hand, rich experience of the reliability and Probabilistic Safety Analysis (PSA) exists in nuclear industry for fission power plants and other nuclear installations. In this paper, the Wendelstein 7-X (W7-X) device is mainly considered. This stellarator device is in commissioning stage in the Max-Planck-Institut für Plasmaphysik, Greifswald, Germany (IPP). In the frame of cooperation between the IPP and the Lithuanian Energy Institute (LEI) under the European Fusion Development Agreement a pilot project of a reliability analysis of the W7-X systems was performed with a purpose to adopt Nuclear Power Plant (NPP) PSA experience for fusion device systems. During the project reliability and safety (risk) analysis of a Divertor Target Cooling Circuit, which is an important system for permanent and reliable operation of in

  4. Human reliability assessment on the basis of operating experience

    International Nuclear Information System (INIS)

    Straeter, O.

    1997-01-01

    For development of methodology, available models for qualitative assessment of human errors (e.g. by Swain, Hacker, Rasmussen) and a variety of known systematic approaches for quantitiative assessment of inadequate human action (e.g. THERP, ASEP, HCR, SLIM) were taken as a basis to establish a job specification, which in turn was used for developing a method for acquisition, characterisation and evaluation of errors. This method encompasses the two processes of event analysis and event evaluation: The first step comprises analysis of events by analysis of information describing the conditions and scenarios of relevance to the inadequate human action examined. In addition to the description of process sequences, information is taken into account on possible conditions that may bring about failure. As an assessment of human reliability requires manifold approaches for evaluation, a connectionistic procedure was developed for evaluation of the compilation of events based on a debate about various approaches from the domain of artificial intelligence (AI). This procedure yields both qualitative and quantitative information through a homogenous approach. (orig./GL) [de

  5. Assessment of Data Reliability of Wireless Sensor Network for Bioinformatics

    Directory of Open Access Journals (Sweden)

    Ting Dong

    2017-09-01

    Full Text Available As a focal point of biotechnology, bioinformatics integrates knowledge from biology, mathematics, physics, chemistry, computer science and information science. It generally deals with genome informatics, protein structure and drug design. However, the data or information thus acquired from the main areas of bioinformatics may not be effective. Some researchers combined bioinformatics with wireless sensor network (WSN into biosensor and other tools, and applied them to such areas as fermentation, environmental monitoring, food engineering, clinical medicine and military. In the combination, the WSN is used to collect data and information. The reliability of the WSN in bioinformatics is the prerequisite to effective utilization of information. It is greatly influenced by factors like quality, benefits, service, timeliness and stability, some of them are qualitative and some are quantitative. Hence, it is necessary to develop a method that can handle both qualitative and quantitative assessment of information. A viable option is the fuzzy linguistic method, especially 2-tuple linguistic model, which has been extensively used to cope with such issues. As a result, this paper introduces 2-tuple linguistic representation to assist experts in giving their opinions on different WSNs in bioinformatics that involve multiple factors. Moreover, the author proposes a novel way to determine attribute weights and uses the method to weigh the relative importance of different influencing factors which can be considered as attributes in the assessment of the WSN in bioinformatics. Finally, an illustrative example is given to provide a reasonable solution for the assessment.

  6. Improvement on reliability of control system in power plant

    International Nuclear Information System (INIS)

    Taguchi, S.; Mizumoto, T.; Hirose, Y.; Kashiwai, J.; Takami, I.; Shono, M.; Roji, Y.; Kizaki, S.

    1985-01-01

    Studies made of Japanese PWR operating experiences have revealed that failures in the control system are the primary causes of unscheduled shutdowns. An attempt has, therefore, been made to improve the reliability of the control system in order to raise the plant reliability. The following are the procedures applied to solve the issue; study of operating experiences, fault tree analysis and failure mode and effects analysis. Improvement measures are developed for the control system whose failure threatens to cause the plant trip during the plant life. These systems are the main feedwater control system, rod control system, pressurizer control system and main steam control system in the primary control system. As a result, the plant unavailability is expected to be reduced significantly by applying the improvements. The improvements are applied to the plants under construction and the operating plants in co-operation with utilities and vendors. (author)

  7. Impact of data source on travel time reliability assessment.

    Science.gov (United States)

    2014-08-01

    Travel time reliability measures are becoming an increasingly important input to the mobility and : congestion management studies. In the case of Maryland State Highway Administration, reliability : measures are key elements in the agencys Annual ...

  8. Selected Methods For Increases Reliability The Of Electronic Systems Security

    Directory of Open Access Journals (Sweden)

    Paś Jacek

    2015-11-01

    Full Text Available The article presents the issues related to the different methods to increase the reliability of electronic security systems (ESS for example, a fire alarm system (SSP. Reliability of the SSP in the descriptive sense is a property preservation capacity to implement the preset function (e.g. protection: fire airport, the port, logistics base, etc., at a certain time and under certain conditions, e.g. Environmental, despite the possible non-compliance by a specific subset of elements this system. Analyzing the available literature on the ESS-SSP is not available studies on methods to increase the reliability (several works similar topics but moving with respect to the burglary and robbery (Intrusion. Based on the analysis of the set of all paths in the system suitability of the SSP for the scenario mentioned elements fire events (device critical because of security.

  9. Reliability analysis of two unit parallel repairable industrial system

    Directory of Open Access Journals (Sweden)

    Mohit Kumar Kakkar

    2015-09-01

    Full Text Available The aim of this work is to present a reliability and profit analysis of a two-dissimilar parallel unit system under the assumption that operative unit cannot fail after post repair inspection and replacement and there is only one repair facility. Failure and repair times of each unit are assumed to be uncorrelated. Using regenerative point technique various reliability characteristics are obtained which are useful to system designers and industrial managers. Graphical behaviors of mean time to system failure (MTSF and profit function have also been studied. In this paper, some important measures of reliability characteristics of a two non-identical unit standby system model with repair, inspection and post repair are obtained using regenerative point technique.

  10. Comparing two reliability upper bounds for multistate systems

    International Nuclear Information System (INIS)

    Meng, Fan C.

    2005-01-01

    The path-cut reliability bound due to Esary and Proschan [J. Am. Stat. Assoc. 65 (1970) 329] and the minimax reliability bound due to Barlow and Proschan [Statistical Theory of Reliability and Life Testing: Probability Models, 1981] for binary systems have been generalized to multistate systems by Block and Savits [J. Appl. Probab. 19 (1982) 391]. Some comparison results concerning the two multistate lower bounds for various types of multistate systems are given by Meng [Probab. Eng. Inform. Sci. 16 (2002) 485]. In this note we compare the two multistate upper bounds and present results which generalize some previous ones obtained by Maymin [J. Stat. Plan. Inference 16 (1987) 337] for binary systems. Examples are given to illustrate our results

  11. Reliability and validity evidence of multiple balance assessments in athletes with a concussion.

    Science.gov (United States)

    Murray, Nicholas; Salvatore, Anthony; Powell, Douglas; Reed-Jones, Rebecca

    2014-01-01

    An estimated 300 000 sport-related concussion injuries occur in the United States annually. Approximately 30% of individuals with concussions experience balance disturbances. Common methods of balance assessment include the Clinical Test of Sensory Organization and Balance (CTSIB), the Sensory Organization Test (SOT), the Balance Error Scoring System (BESS), and the Romberg test; however, the National Collegiate Athletic Association recommended the Wii Fit as an alternative measure of balance in athletes with a concussion. A central concern regarding the implementation of the Wii Fit is whether it is reliable and valid for measuring balance disturbance in athletes with concussion. To examine the reliability and validity evidence for the CTSIB, SOT, BESS, Romberg test, and Wii Fit for detecting balance disturbance in athletes with a concussion. Literature considered for review included publications with reliability and validity data for the assessments of balance (CTSIB, SOT, BESS, Romberg test, and Wii Fit) from PubMed, PsycINFO, and CINAHL. We identified 63 relevant articles for consideration in the review. Of the 63 articles, 28 were considered appropriate for inclusion and 35 were excluded. No current reliability or validity information supports the use of the CTSIB, SOT, Romberg test, or Wii Fit for balance assessment in athletes with a concussion. The BESS demonstrated moderate to high reliability (interclass correlation coefficient = 0.87) and low to moderate validity (sensitivity = 34%, specificity = 87%). However, the Romberg test and Wii Fit have been shown to be reliable tools in the assessment of balance in Parkinson patients. The BESS can evaluate balance problems after a concussion. However, it lacks the ability to detect balance problems after the third day of recovery. Further investigation is needed to establish the use of the CTSIB, SOT, Romberg test, and Wii Fit for assessing balance in athletes with concussions.

  12. Embedded mechatronic systems 1 analysis of failures, predictive reliability

    CERN Document Server

    El Hami, Abdelkhalak

    2015-01-01

    In operation, mechatronics embedded systems are stressed by loads of different causes: climate (temperature, humidity), vibration, electrical and electromagnetic. These stresses in components which induce failure mechanisms should be identified and modeled for better control. AUDACE is a collaborative project of the cluster Mov'eo that address issues specific to mechatronic reliability embedded systems. AUDACE means analyzing the causes of failure of components of mechatronic systems onboard. The goal of the project is to optimize the design of mechatronic devices by reliability. The projec

  13. Discrete event simulation versus conventional system reliability analysis approaches

    DEFF Research Database (Denmark)

    Kozine, Igor

    2010-01-01

    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...

  14. Reliable sagittal plane kinematic gait assessments are feasible using low-cost webcam technology.

    Science.gov (United States)

    Saner, Robert J; Washabaugh, Edward P; Krishnan, Chandramouli

    2017-07-01

    Three-dimensional (3-D) motion capture systems are commonly used for gait analysis because they provide reliable and accurate measurements. However, the downside of this approach is that it is expensive and requires technical expertise; thus making it less feasible in the clinic. To address this limitation, we recently developed and validated (using a high-precision walking robot) a low-cost, two-dimensional (2-D) real-time motion tracking approach using a simple webcam and LabVIEW Vision Assistant. The purpose of this study was to establish the repeatability and minimal detectable change values of hip and knee sagittal plane gait kinematics recorded using this system. Twenty-one healthy subjects underwent two kinematic assessments while walking on a treadmill at a range of gait velocities. Intraclass correlation coefficients (ICC) and minimal detectable change (MDC) values were calculated for commonly used hip and knee kinematic parameters to demonstrate the reliability of the system. Additionally, Bland-Altman plots were generated to examine the agreement between the measurements recorded on two different days. The system demonstrated good to excellent reliability (ICC>0.75) for all the gait parameters tested on this study. The MDC values were typically low (gait assessments using webcam technology can be reliably used for clinical and research purposes. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Recent Advances in System Reliability Signatures, Multi-state Systems and Statistical Inference

    CERN Document Server

    Frenkel, Ilia

    2012-01-01

    Recent Advances in System Reliability discusses developments in modern reliability theory such as signatures, multi-state systems and statistical inference. It describes the latest achievements in these fields, and covers the application of these achievements to reliability engineering practice. The chapters cover a wide range of new theoretical subjects and have been written by leading experts in reliability theory and its applications.  The topics include: concepts and different definitions of signatures (D-spectra),  their  properties and applications  to  reliability of coherent systems and network-type structures; Lz-transform of Markov stochastic process and its application to multi-state system reliability analysis; methods for cost-reliability and cost-availability analysis of multi-state systems; optimal replacement and protection strategy; and statistical inference. Recent Advances in System Reliability presents many examples to illustrate the theoretical results. Real world multi-state systems...

  16. Portfolio assessment during medical internships: How to obtain a reliable and feasible assessment procedure?

    Science.gov (United States)

    Michels, Nele R M; Driessen, Erik W; Muijtjens, Arno M M; Van Gaal, Luc F; Bossaert, Leo L; De Winter, Benedicte Y

    2009-12-01

    A portfolio is used to mentor and assess students' clinical performance at the workplace. However, students and raters often perceive the portfolio as a time-consuming instrument. In this study, we investigated whether assessment during medical internship by a portfolio can combine reliability and feasibility. The domain-oriented reliability of 61 double-rated portfolios was measured, using a generalisability analysis with portfolio tasks and raters as sources of variation in measuring the performance of a student. We obtained reliability (Phi coefficient) of 0.87 with this internship portfolio containing 15 double-rated tasks. The generalisability analysis showed that an acceptable level of reliability (Phi = 0.80) was maintained when the amount of portfolio tasks was decreased to 13 or 9 using one and two raters, respectively. Our study shows that a portfolio can be a reliable method for the assessment of workplace learning. The possibility of reducing the amount of tasks or raters while maintaining a sufficient level of reliability suggests an increase in feasibility of portfolio use for both students and raters.

  17. Reliability and validity of emergency department triage systems

    NARCIS (Netherlands)

    van der Wulp, I.

    2010-01-01

    Reliability and validity of triage systems is important because this can affect patient safety. In this thesis, these aspects of two emergency department (ED) triage systems were studied as well as methodological aspects in these types of studies. The consistency, reproducibility, and criterion

  18. Improving Reliability, Security, and Efficiency of Reconfigurable Hardware Systems (Habilitation)

    NARCIS (Netherlands)

    Ziener, Daniel

    2017-01-01

    In this treatise,  my research on methods to improve efficiency, reliability, and security of reconfigurable hardware systems, i.e., FPGAs, through partial dynamic reconfiguration is outlined. The efficiency of reconfigurable systems can be improved by loading optimized data paths on-the-fly on an

  19. Bayesian approach in the power electric systems study of reliability ...

    African Journals Online (AJOL)

    This work aims to highlight prerogatives and advantages of the Bayesian approach in the reliability studies of the modern power electrical ... technological innovation make the data more uncertain related to the operation of the electric systems components, with the ...... Rocco S. C.M. & Klindt W., 1998. Distribution Systems ...

  20. An introduction to system reliability for solid-state lighting

    NARCIS (Netherlands)

    Driel, W.D. van; Evertz, F.E.; Zaal, J.J.M.; Morales Nápoles, O.; Yuan, C.A.

    2013-01-01

    Solid-State Lighting (SSL) applications are slowly but gradually pervading into our daily life. An SSL system is composed of an light-emitting diode (LED) engine with a microelectronic driver(s) in a housing that also supplies the optic design. Knowledge of system-level reliability is crucial for

  1. Reliability Analysis of a Two Dissimilar Unit Cold Standby System ...

    African Journals Online (AJOL)

    reliability and availability analysis are evaluated. This proposed system has been investigated under three modes: normal, partial failure, total failure. The failure and the repair time are assumed to have exponential distribution. The effect of failure rate on meantime to system failure ( MTSF ), steady state availability (. ( ). T.

  2. State distribution and reliability of some multi- state systems with ...

    African Journals Online (AJOL)

    mn : G series systems and second, the multi-state consecutive kn-out-of-mn : G parallel systems (see denitions 1 and 2).We begin by giving a non recursive formula which calculates the state distribution and the reliability of multi-state ...

  3. Improving Reliability and Durability of Efficient and Clean Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Prabhakar [Univ. of Connecticut, Storrs, CT (United States)

    2010-08-01

    Overall objective of the research program was to develop an in-depth understanding of the degradation processes in advanced electrochemical energy conversion systems. It was also the objective of the research program to transfer the technology to participating industries for implementation in manufacturing of cost effective and reliable integrated systems.

  4. Survey of bayesian belif nets for quantitative reliability assessment of safety critical software used in nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Eom, H.S.; Sung, T.Y.; Jeong, H.S.; Park, J.H.; Kang, H.G.; Lee, K

    2001-03-01

    As part of the Probabilistic Safety Assessment of safety grade digital systems used in Nuclear Power plants research, measures and methodologies applicable to quantitative reliability assessment of safety critical software were surveyed. Among the techniques proposed in the literature we selected those which are in use widely and investigated their limitations in quantitative software reliability assessment. One promising methodology from the survey is Bayesian Belief Nets (BBN) which has a formalism and can combine various disparate evidences relevant to reliability into final decision under uncertainty. Thus we analyzed BBN and its application cases in digital systems assessment area and finally studied the possibility of its application to the quantitative reliability assessment of safety critical software.

  5. Reliability of redundant structures of nuclear reactor protection systems

    International Nuclear Information System (INIS)

    Vojnovic, B.

    1983-01-01

    In this paper, reliability of various redundant structures of PWR protection systems has been analysed. Structures of reactor tip systems as well as the systems for activation of safety devices have been presented. In all those systems redundancy is achieved by means of so called majority voting logic ('r out of n' structures). Different redundant devices have been compared, concerning probability of occurrence of safe as well as unsafe failures. (author)

  6. Defect localization, characterization and reliability assessment in emerging photovoltaic devices.

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Benjamin Bing-Yeh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cruz-Campa, Jose Luis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Haase, Gad S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Tangyunyong, Paiboon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Colr, Edward Isaac [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Okandan, Murat [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nielson, Gregory N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-04-01

    Microsystems-enabled photovoltaics (MEPV) can potentially meet increasing demands for light-weight, portable, photovoltaic solutions with high power density and efficiency. The study in this report examines failure analysis techniques to perform defect localization and evaluate MEPV modules. CMOS failure analysis techniques, including electroluminescence, light-induced voltage alteration, thermally-induced voltage alteration, optical beam induced current, and Seabeck effect imaging were successfully adapted to characterize MEPV modules. The relative advantages of each approach are reported. In addition, the effects of exposure to reverse bias and light stress are explored. MEPV was found to have good resistance to both kinds of stressors. The results form a basis for further development of failure analysis techniques for MEPVs of different materials systems or multijunction MEPVs. The incorporation of additional stress factors could be used to develop a reliability model to generate lifetime predictions for MEPVs as well as uncover opportunities for future design improvements.

  7. Power system reliability memento; Memento de la surete du systeme electrique

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    The reliability memento of the French power system (national power transmission grid) is an educational document which purpose is to point out the role of each one as regards power system operating reliability. This memento was first published in 1999. Extensive changes have taken place since then. The new 2002 edition shows that system operating reliability is as an important subject as ever: 1 - foreword; 2 - system reliability: the basics; 3 - equipment measures taken in order to guarantee the reliability of the system; 4 - organisational and human measures taken to guarantee the reliability of the system; appendix 1 - system operation: basic concepts; appendix 2 - guiding principles governing the reliability of the power system; appendix 3 - international associations of transmission system operators; appendix 4 - description of major incidents.

  8. Some approaches to system reliability improvement in engineering design

    International Nuclear Information System (INIS)

    Shen, Kecheng.

    1990-01-01

    In this thesis some approaches to system reliability improvement in engineering design are studied. In particular, the thesis aims at developing alternative methodologies for ranking of component importance which are more related to the design practice and which are more useful in system synthesis than the existing ones. It also aims at developing component reliability models by means of stress-strength interference which will enable both component reliability prediction and design for reliability. A new methodology for ranking of component importance is first developed based on the notion of the increase of the expected system yield. This methodology allows for incorporation of different improvement actions at the component level such as parallel redundancy, standby redundancy, burn-in, minimal repair and perfect replacement. For each of these improvement actions, the increase of system reliability is studied and used as the component importance measure. A possible connection between the commonly known models of component lifetimes and the stress-strength interference models is suggested. Under some general conditions the relationship between component failure rate and the stress and strength distribution characteristics is studied. A heuristic approach for obtaining bounds on failure probability through stress-strength interference is also presented. A case study and a worked example are presented, which illustrate and verify the developed importance measures and their applications in the analytical as well as synthetical work of engineering design. (author)

  9. Reliability of redundant ductile structures with uncertain system ...

    Indian Academy of Sciences (India)

    Frangopol et al. 1997; Wen 2001) ..... limit chosen was 1/100th of the span length and was based on 'dangerously high levels' of deformation of ...... Enright M P, Frangopol D M 1999 Reliability-based condition assessment of deteriorating concrete.

  10. Aviation Fuel System Reliability and Fail-Safety Analysis. Promising Alternative Ways for Improving the Fuel System Reliability

    Directory of Open Access Journals (Sweden)

    I. S. Shumilov

    2017-01-01

    Full Text Available The paper deals with design requirements for an aviation fuel system (AFS, AFS basic design requirements, reliability, and design precautions to avoid AFS failure. Compares the reliability and fail-safety of AFS and aircraft hydraulic system (AHS, considers the promising alternative ways to raise reliability of fuel systems, as well as elaborates recommendations to improve reliability of the pipeline system components and pipeline systems, in general, based on the selection of design solutions.It is extremely advisable to design the AFS and AHS in accordance with Aviation Regulations АП25 and Accident Prevention Guidelines, ICAO (International Civil Aviation Association, which will reduce risk of emergency situations, and in some cases even avoid heavy disasters.ATS and AHS designs should be based on the uniform principles to ensure the highest reliability and safety. However, currently, this principle is not enough kept, and AFS looses in reliability and fail-safety as compared with AHS. When there are the examined failures (single and their combinations the guidelines to ensure the AFS efficiency should be the same as those of norm-adopted in the Regulations АП25 for AHS. This will significantly increase reliability and fail-safety of the fuel systems and aircraft flights, in general, despite a slight increase in AFS mass.The proposed improvements through the use of components redundancy of the fuel system will greatly raise reliability of the fuel system of a passenger aircraft, which will, without serious consequences for the flight, withstand up to 2 failures, its reliability and fail-safety design will be similar to those of the AHS, however, above improvement measures will lead to a slightly increasing total mass of the fuel system.It is advisable to set a second pump on the engine in parallel with the first one. It will run in case the first one fails for some reasons. The second pump, like the first pump, can be driven from the

  11. Power Electronics and Reliability in Renewable Energy Systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Ma, Ke; Zhou, Dao

    2012-01-01

    Power Electronics are needed in almost all kind of renewable energy systems. It is used both for controlling the renewable source and also for interfacing to the load, which can be grid-connected or working in stand-alone mode. More and more efforts are put into making renewable energy systems...... better in terms of reliability in order to ensure a high availability of the power sources, in this case the knowledge of mission profile of a certain application is crucial for the reliability evaluation/design of power electronics. In this paper an overview on the power electronic circuits behind...... the most common converter configurations for wind turbine and photovoltaic is done. Next different aspects of improving the system reliability are mapped. Further on examples of how to control the chip temperature in different power electronic configurations as well as operation modes for wind power...

  12. Reliability by design - a new approach to SAGD steam systems

    Energy Technology Data Exchange (ETDEWEB)

    Shook, Dave [KemeX Ltd (Canada)

    2011-07-01

    SAGD systems used in industry face a number of reliability issues. These issues are often the result of poor control and can impact production, safety, and lead to damaged equipment. This presentation discusses the importance of considering reliability issues for SAGD systems during the conceptual design phase to ensure that the equipment can be safely and effectively operated. Through the application of control theory and identification studies, it was found that disturbances are created by the OTSG. A thermo-hydraulic model of the OTSG was then completed to determine the different energy changes occurring in the system. The model shows how significant fluctuations in steam quality lead to drastic changes in wall temperature, which in turn impact tube reliability. The presentation shows that by applying control knowledge during the design phase and managing feed disturbances, bitumen production can be increased, damage to equipment can be decreased, and overall safety can be greatly improved.

  13. Feasibility study for the European Reliability Data System (ERDS)

    International Nuclear Information System (INIS)

    Mancini, G.

    1980-01-01

    In the framework of the Reactor Safety Programme of the Commission of the European Communities, the JRC - Ispra Establishment has performed a feasibility study for an integrated European Reliability Data System, the aim of which is the collection and organization of information related to the operation of LWRs with regard to component and systems behaviour, abnormal occurrences, outages, etc. Component Event Data Bank (CEGB), Abnormal Occurrences Reporting System, Generic Reliability Parameter Data Bank, Operating Unit Status Reports and the main activities carried out during the last two years are described. The most important achievements are briefly reported, such as: Reference Classification for Systems, Components and Failure Events, Informatic Structure of the Pilot Experiment of the CEDB, Information Retrieval System for Abnormal Occurrences Reports, Data Bank on Component Reliability Parameters, System on the Exchange of Operation Experience of LWRs, Statistical Data Treatment. Finally, the general conclusions of the feasibility study are summarized: the possibility and the usefulness for the creation of an integrated European Reliability Data System are outlined. (author)

  14. European Reliability Data System: main developments and use

    International Nuclear Information System (INIS)

    Amesz, J.; Capobianchi, S.; Kalfsbeek, H.W.; Mancini, G.

    1985-01-01

    The paper revises the aims and objectives of the European Reliability Data System (ERDS), a centralized system collecting and organizing information related to the operation of light water reactors. The paper first describes the recent developments of the four data banks constituting the system: Component Event Data Bank, Abnormal Occurrences Reporting System, Operating Unit Status Report and Reliability Parameters Data Bank. Then several issues are discussed referring mostly to the status of classification schemes and their use, to the operation of the banks (data input and transcoding) and to the retrieval and utilization of the information; in this latter case particularly the analysis potential of the data collection scheme of the AORS (Abnormal Occurrences Reporting System) is demonstrated. Finally, emphasis is given to the increasing role which artificial intelligence techniques such as natural language and expert systems and fuzzy logic may play in improving the future capabilities of the system

  15. A study of the reliability, validity and responsiveness of the HIV overview of problems evaluation system (HOPES) in assessing the quality of life of patients with AIDS and symptomatic HIV infection

    NARCIS (Netherlands)

    de Boer, J. B.; Sprangers, M. A.; Aaronson, N. K.; Lange, J. M.; van Dam, F. S.

    1996-01-01

    The objective of this study was to evaluate the feasibility, reliability, validity and responsiveness of the HIV Overview of Problems Evaluation System (HOPES) in a Dutch sample. The HOPES was administered three times in a one-year period to a sample of 106 outpatients with a symptomatic

  16. Laboratory Information Management System Chain of Custody: Reliability and Security

    Science.gov (United States)

    Tomlinson, J. J.; Elliott-Smith, W.; Radosta, T.

    2006-01-01

    A chain of custody (COC) is required in many laboratories that handle forensics, drugs of abuse, environmental, clinical, and DNA testing, as well as other laboratories that want to assure reliability of reported results. Maintaining a dependable COC can be laborious, but with the recent establishment of the criteria for electronic records and signatures by US regulatory agencies, laboratory information management systems (LIMSs) are now being developed to fully automate COCs. The extent of automation and of data reliability can vary, and FDA- and EPA-compliant electronic signatures and system security are rare. PMID:17671623

  17. Laboratory information management system chain of custody: reliability and security.

    Science.gov (United States)

    Tomlinson, J J; Elliott-Smith, W; Radosta, T

    2006-01-01

    A chain of custody (COC) is required in many laboratories that handle forensics, drugs of abuse, environmental, clinical, and DNA testing, as well as other laboratories that want to assure reliability of reported results. Maintaining a dependable COC can be laborious, but with the recent establishment of the criteria for electronic records and signatures by US regulatory agencies, laboratory information management systems (LIMSs) are now being developed to fully automate COCs. The extent of automation and of data reliability can vary, and FDA- and EPA-compliant electronic signatures and system security are rare.

  18. The reliability of structural systems operating at high temperature: Replacing engineering judgement with operational experience

    International Nuclear Information System (INIS)

    Chevalier, M.J.; Smith, D.J.; Dean, D.W.

    2012-01-01

    Deterministic assessments are used to assess the integrity of structural systems operating at high temperature by providing a lower bound lifetime prediction, requiring considerable engineering judgement. However such a result may not satisfy the structural integrity assessment purpose if the results are overly conservative or conversely plant observations (such as failures) could undermine the assessment result if observed before the lower bound lifetime. This paper develops a reliability methodology for high temperature assessments and illustrates the impact and importance of managing the uncertainties within such an analysis. This is done by separating uncertainties into three classifications; aleatory uncertainty, quantifiable epistemic uncertainty and unquantifiable epistemic uncertainty. The result is a reliability model that can predict the behaviour of a structural system based upon plant observations, including failure and survival data. This can be used to reduce the over reliance upon engineering judgement which is prevalent in deterministic assessments. Highlights: ► Deterministic assessments are shown to be heavily reliant upon engineering judgment. ► Based upon the R5 procedure, a reliability model for a structural system is developed. ► Variables must be classified as either aleatory or epistemic to model their impact on reliability. ► Operation experience is then used to reduce reliance upon engineering judgment. ► This results in a model which can predict system behaviour and learn from operational experience.

  19. Analysis of the Reliability of the "Alternator- Alternator Belt" System

    Directory of Open Access Journals (Sweden)

    Ivan Mavrin

    2012-10-01

    Full Text Available Before starting and also during the exploitation of va1ioussystems, it is vety imp011ant to know how the system and itsparts will behave during operation regarding breakdowns, i.e.failures. It is possible to predict the service behaviour of a systemby determining the functions of reliability, as well as frequencyand intensity of failures.The paper considers the theoretical basics of the functionsof reliability, frequency and intensity of failures for the twomain approaches. One includes 6 equal intetvals and the other13 unequal intetvals for the concrete case taken from practice.The reliability of the "alternator- alternator belt" system installedin the buses, has been analysed, according to the empiricaldata on failures.The empitical data on failures provide empirical functionsof reliability and frequency and intensity of failures, that arepresented in tables and graphically. The first analysis perfO!med by dividing the mean time between failures into 6 equaltime intervals has given the forms of empirical functions of fa ilurefrequency and intensity that approximately cotTespond totypical functions. By dividing the failure phase into 13 unequalintetvals with two failures in each interval, these functions indicateexplicit transitions from early failure inte1val into the randomfailure interval, i.e. into the ageing intetval. Functions thusobtained are more accurate and represent a better solution forthe given case.In order to estimate reliability of these systems with greateraccuracy, a greater number of failures needs to be analysed.

  20. Reliability allocation problem in a series-parallel system

    International Nuclear Information System (INIS)

    Yalaoui, Alice; Chu, Chengbin; Chatelet, Eric

    2005-01-01

    In order to improve system reliability, designers may introduce in a system different technologies in parallel. When each technology is composed of components in series, the configuration belongs to the series-parallel systems. This type of system has not been studied as much as the parallel-series architecture. There exist no methods dedicated to the reliability allocation in series-parallel systems with different technologies. We propose in this paper theoretical and practical results for the allocation problem in a series-parallel system. Two resolution approaches are developed. Firstly, a one stage problem is studied and the results are exploited for the multi-stages problem. A theoretical condition for obtaining the optimal allocation is developed. Since this condition is too restrictive, we secondly propose an alternative approach based on an approximated function and the results of the one-stage study. This second approach is applied to numerical examples