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1

A Comparative Analysis of Open Source Software Reliability  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this study is to compare the fitting (goodness-of-fit and prediction capabilities of three reliability models using the failure data of five popular open source software (OSS products. The failure data are modeled by Weibull and two other Non Homogenous Poisson Process (NHPP models (Yamada S-Shaped and Schneidewind. The OSS products considered are Eclipse, Apache HTTP Server 2, Firefox, MPlayer OS X, and ClamWin Free Antivirus. Weibull is chosen due to its popularity in lifetime and its flexibility in modeling various distributions. On the other hand, among many software reliability models, the NHPP models are prevalent. The goodness-of-fit is based on the entire failure data collected. Prediction is accomplished by estimating the models parameters based on partial failure history and then applying the estimates to the entire time span for which failure data is collected.  The outcomes show that a reliability model that fits the failure data well may not necessarily be a decent forecaster of future failure patterns.

Cobra Rahmani

2010-12-01

2

A Comparative Analysis of Methods of Polynomial Coefficients Determination for Reliability Indices of Ilorin Distribution Systems  

Directory of Open Access Journals (Sweden)

Full Text Available Distribution system delivers the transmitted energy to the end users which are customers. This paper develops a generalized polynomial model and compares the coefficients for the assessment of reliability indices of Ilorin distribution system feeders. The results of the coefficients obtained were validated by subjecting the polynomial model to three methods namely: Lagrange Polynomial, Newton and Chebychev Polynomial function methods. The results of the work showed that average values of -7x10-4 , 0.00212, -0.0256, 0.1549, - 0.4865 and 0.7049 were obtained as the coefficient values from the Lagrange, Newton and Chebychev polynomial function methods which compare favourably well with the coefficient values of -7x10-4 , 0.0021, -0.0257, 0.1549, -0.4865 and 0.7048 obtained from the simulation results. The knowledge of these coefficients will form a basis for adequate planning and management of power distribution systems.

Ganiyu A. Ajenikoko,

2014-01-01

3

Parametric statistical techniques for the comparative analysis of censored reliability data: a review  

International Nuclear Information System (INIS)

This paper summarizes part of the work carried out to date on seeking analytical solutions to the two-sample problem with censored data in the context of reliability and maintenance optimization applications. For this purpose, parametric two-sample tests for failure and censored reliability data are introduced and their applicability/effectiveness in common engineering problems is reviewed

4

Power electronics reliability analysis.  

Energy Technology Data Exchange (ETDEWEB)

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

Smith, Mark A.; Atcitty, Stanley

2009-12-01

5

Human reliability analysis  

International Nuclear Information System (INIS)

The authors present a treatment of human reliability analysis incorporating an introduction to probabilistic risk assessment for nuclear power generating stations. They treat the subject according to the framework established for general systems theory. Draws upon reliability analysis, psychology, human factors engineering, and statistics, integrating elements of these fields within a systems framework. Provides a history of human reliability analysis, and includes examples of the application of the systems approach

6

Reliability and Regression Analysis  

Science.gov (United States)

This applet, by David M. Lane of Rice University, demonstrates how the reliability of X and Y affect various aspects of the regression of Y on X. Java 1.1 is required and a full set of instructions is given in order to get the full value from the applet. Exercises and definitions to key terms are also given to help students understand reliability and regression analysis.

Lane, David M.

2009-02-17

7

Waste package reliability analysis  

International Nuclear Information System (INIS)

Proof of future performance of a complex system such as a high-level nuclear waste package over a period of hundreds to thousands of years cannot be had in the ordinary sense of the word. The general method of probabilistic reliability analysis could provide an acceptable framework to identify, organize, and convey the information necessary to satisfy the criterion of reasonable assurance of waste package performance according to the regulatory requirements set forth in 10 CFR 60. General principles which may be used to evaluate the qualitative and quantitative reliability of a waste package design are indicated and illustrated with a sample calculation of a repository concept in basalt. 8 references, 1 table

8

Risk analysis and reliability  

International Nuclear Information System (INIS)

Mathematical foundations of risk analysis are addressed. The importance of having the same probability space in order to compare different experiments is pointed out. Then the following topics are discussed: consequences as random variables with infinite expectations; the phenomenon of rare events; series-parallel systems and different kinds of randomness that could be imposed on such systems; and the problem of consensus of estimates of expert opinion

9

Reliability Analysis of Wind Turbines  

DEFF Research Database (Denmark)

In order to minimise the total expected life-cycle costs of a wind turbine it is important to estimate the reliability level for all components in the wind turbine. This paper deals with reliability analysis for the tower and blades of onshore wind turbines placed in a wind farm. The limit states consideres are in the ultimate limit state (ULS) extreme conditions in the standstill position and extreme conditions during operating. For wind turbines, where the magnitude of the loads is influenced by the control system, the ultimate limit state can occur in both cases. In the fatigue limit state (FLS) the reliability level for a wind turbine placed in a wind farm is considered, and wake effects from neighbouring wind turbines is taken into account. An illustrative example with calculation of the reliability for mudline bending of the tower is considered. In the example the design is determined according to the wind turbine standard IEC 61400-1 "Wind turbines - Design requirements" and different stochastic modelsfor the uncertainties are compared.

Toft, Henrik Stensgaard; SØrensen, John Dalsgaard

2008-01-01

10

IREP human reliability analysis  

International Nuclear Information System (INIS)

Human reliability analyses were performed as part of the several probabilistic risk assessments of the Interim Reliability Evaluation Program. The relationship of these human reliability analyses to other elements of the risk assessments is discussed here, along with a description of the modeling of the effects of human error into the system fault trees. The initial screening of the system for sites of inclusion in the system models of estimates of the effects of human errors are made by the system analysts. They then pinpoint specific components or specific plant procedural steps for which human errors would result in system degradation. The human reliability analysts then identify and quantify the effects of possible human errors for inclusion in the human error contribution blocks of the system fault trees

11

A reliability simulation language for reliability analysis  

International Nuclear Information System (INIS)

The results of work being undertaken to develop a Reliability Description Language (RDL) which will enable reliability analysts to describe complex reliability problems in a simple, clear and unambiguous way are described. Component and system features can be stated in a formal manner and subsequently used, along with control statements to form a structured program. The program can be compiled and executed on a general-purpose computer or special-purpose simulator. (DG)

12

Scyllac equipment reliability analysis  

International Nuclear Information System (INIS)

Most of the failures in Scyllac can be related to crowbar trigger cable faults. A new cable has been designed, procured, and is currently undergoing evaluation. When the new cable has been proven, it will be worked into the system as quickly as possible without causing too much additional down time. The cable-tip problem may not be easy or even desirable to solve. A tightly fastened permanent connection that maximizes contact area would be more reliable than the plug-in type of connection in use now, but it would make system changes and repairs much more difficult. The balance of the failures have such a low occurrence rate that they do not cause much down time and no major effort is underway to eliminate them. Even though Scyllac was built as an experimental system and has many thousands of components, its reliability is very good. Because of this the experiment has been able to progress at a reasonable pace

13

Integrating reliability analysis and design  

International Nuclear Information System (INIS)

This report describes the Interactive Reliability Analysis Project and demonstrates the advantages of using computer-aided design systems (CADS) in reliability analysis. Common cause failure problems require presentations of systems, analysis of fault trees, and evaluation of solutions to these. Results have to be communicated between the reliability analyst and the system designer. Using a computer-aided design system saves time and money in the analysis of design. Computer-aided design systems lend themselves to cable routing, valve and switch lists, pipe routing, and other component studies. At EG and G Idaho, Inc., the Applicon CADS is being applied to the study of water reactor safety systems

14

Reliability analysis of shutdown system  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the results of reliability analysis of Shutdown System (SDS) of Indian Prototype Fast Breeder Reactor. Reliability analysis carried out using Fault Tree Analysis predicts a value of 3.5 x 10{sup -8}/de for failure of shutdown function in case of global faults and 4.4 x 10{sup -8}/de for local faults. Based on 20 de/y, the frequency of shutdown function failure is 0.7 x 10{sup -6}/ry, which meets the reliability target, set by the Indian Atomic Energy Regulatory Board. The reliability is limited by Common Cause Failure (CCF) of actuation part of SDS and to a lesser extent CCF of electronic components. The failure frequency of individual systems is <1 x 10{sup -3}/ry, which also meets the safety criteria. Uncertainty analysis indicates a maximum error factor of 5 for the top event unavailability.

Kumar, C. Senthil [Aerb-Safety Research Institute, IGCAR Campus, Kalpakkam 603102 (India)]. E-mail: cskumar@igcar.ernet.in; John Arul, A. [Indira Gandhi Centre For Atomic Research, Kalpakkam 603102 (India); Pal Singh, Om [Atomic Energy Regulatory Board, Niyamak Bhavan, Anushaktinagar, Mumbai 400094 (India); Suryaprakasa Rao, K. [Industrial Engineering Division, Anna University, Chennai 60025 (India)

2005-01-01

15

Reliability analysis and operator modelling  

International Nuclear Information System (INIS)

The paper considers the state of operator modelling in reliability analysis. Operator models are needed in reliability analysis because operators are needed in process control systems. HRA methods must therefore be able to account both for human performance variability and for the dynamics of the interaction. A selected set of first generation HRA approaches is briefly described in terms of the operator model they use, their classification principle, and the actual method they propose. In addition, two examples of second generation methods are also considered. It is concluded that first generation HRA methods generally have very simplistic operator models, either referring to the time-reliability relationship or to elementary information processing concepts. It is argued that second generation HRA methods must recognise that cognition is embedded in a context, and be able to account for that in the way human reliability is analysed and assessed

16

Applications of reliability degradation analysis  

International Nuclear Information System (INIS)

Reliability degradation analysis is the analysis of the occurrences of degradations and the times of maintenance to determine their reliability and risk implications. A program is presented for applying reliability degradation analyses to maintenance data collected at nuclear power plants. As a specific part of the program, time trending of maintenance data is illustrated. Maintenance data on residual heat removal (RHR) pumps and service water (SW) pumps at selected boiling water reactor (BWR) plants are evaluated to show how trends in maintenance data, which generally do not involve failures, can be used to understand effectiveness of maintenance. These trends also are translated to specific impacts on pump unavailability and on core-damage frequency (assuming that the trends in failure rate are the same as those observed for degradation rate). The second application shows the use of reliability degradation analysis to quantitatively evaluate the effect of maintenance, i.e., the quantitative change in component unavailability when no maintenance is performed. Assessment of these impacts are important since they measure the reliability and risk impacts of maintenance and can be fed back to the maintenance program to improve its effectiveness

17

Reliability analysis of phased missions  

International Nuclear Information System (INIS)

In a phased mission the relevant system configuration (block diagram or fault tree) changes during consecutive time periods (phases). Many systems are required to perform phased missions. A classic example is a space vehicle. A reliability analysis for a phased mission encounters complexities not present with just one phase, but can be transformed into an analysis of a synthetic single phase case. The transformation has a potential for direct application, or can be used to study various computational algorithms and approximations

18

Solving reliability analysis problems in the polar space  

Directory of Open Access Journals (Sweden)

Full Text Available An optimization model that is widely used in engineering problems is Reliability-Based Design Optimization (RBDO. Input data of the RBDO is non-deterministic and constraints are probabilistic. The RBDO aims at minimizing cost ensuring that reliability is at least an accepted level. Reliability analysis is an important step in two-level RBDO approaches. Although many methods have been introduced to apply in reliability analysis loop of the RBDO, there are still many drawbacks in their efficiencies and stabilities. This paper proposes a novel method that converts the constrained reliability analysis problem to an unconstrained minimization problem in order to improve efficiency of the solution. Number of numerical experiments is conducted and then performance of the proposed method is compared with the existing reliability analysis methods.Keywords: Polar space, Reliability analysis, Reliability-based design optimization.

Ghasem Ezzati

2014-09-01

19

Human Reliability Analysis: session summary  

International Nuclear Information System (INIS)

The use of Human Reliability Analysis (HRA) to identify and resolve human factors issues has significantly increased over the past two years. Today, utilities, research institutions, consulting firms, and the regulatory agency have found a common application of HRA tools and Probabilistic Risk Assessment (PRA). The ''1985 IEEE Third Conference on Human Factors and Power Plants'' devoted three sessions to the discussion of these applications and a review of the insights so gained. This paper summarizes the three sessions and presents those common conclusions that were discussed during the meeting. The paper concludes that session participants supported the use of an adequately documented ''living PRA'' to address human factors issues in design and procedural changes, regulatory compliance, and training and that the techniques can produce cost effective qualitative results that are complementary to more classical human factors methods

20

Reliability Analysis and Reliability-Based Design Optimization of Circular Composite Cylinders Under Axial Compression  

Science.gov (United States)

This report describes the preliminary results of an investigation on component reliability analysis and reliability-based design optimization of thin-walled circular composite cylinders with average diameter and average length of 15 inches. Structural reliability is based on axial buckling strength of the cylinder. Both Monte Carlo simulation and First Order Reliability Method are considered for reliability analysis with the latter incorporated into the reliability-based structural optimization problem. To improve the efficiency of reliability sensitivity analysis and design optimization solution, the buckling strength of the cylinder is estimated using a second-order response surface model. The sensitivity of the reliability index with respect to the mean and standard deviation of each random variable is calculated and compared. The reliability index is found to be extremely sensitive to the applied load and elastic modulus of the material in the fiber direction. The cylinder diameter was found to have the third highest impact on the reliability index. Also the uncertainty in the applied load, captured by examining different values for its coefficient of variation, is found to have a large influence on cylinder reliability. The optimization problem for minimum weight is solved subject to a design constraint on element reliability index. The methodology, solution procedure and optimization results are included in this report.

Rais-Rohani, Masoud

2001-01-01

 
 
 
 
21

Creep-rupture reliability analysis  

Science.gov (United States)

A probabilistic approach to the correlation and extrapolation of creep-rupture data is presented. Time temperature parameters (TTP) are used to correlate the data, and an analytical expression for the master curve is developed. The expression provides a simple model for the statistical distribution of strength and fits neatly into a probabilistic design format. The analysis focuses on the Larson-Miller and on the Manson-Haferd parameters, but it can be applied to any of the TTP's. A method is developed for evaluating material dependent constants for TTP's. It is shown that optimized constants can provide a significant improvement in the correlation of the data, thereby reducing modelling error. Attempts were made to quantify the performance of the proposed method in predicting long term behavior. Uncertainty in predicting long term behavior from short term tests was derived for several sets of data. Examples are presented which illustrate the theory and demonstrate the application of state of the art reliability methods to the design of components under creep.

Peralta-Duran, A.; Wirsching, P. H.

1985-01-01

22

Reliable statistical fuel rod analysis  

International Nuclear Information System (INIS)

In the fuel rod design process it must be shown that the fuel rod response to the physical processes occurring in the rod during irradiation is limited to allowable values. The design can either be performed in a deterministic, and hence conservative way, or with statistical methods. Using the former way the permissible operation time may be underestimated impeding a full exploitation of the burn up capability of the fuel rod. In contrast, by adequately heeding the scattering of the parameters influencing the fuel rod response . or reactions . the statistical method allows a margin for extending the operation period. A special variant of the statistical methods is described and validated. The method is called semi statistical as it encompasses a statistical and a deterministic branch. It starts with computing rank correlation coefficients from Monte Carlo simulations, proceeds with converting them into quantiles and extracting specific design input values from the parameter distributions and eventually terminates by applying the sets of parameter values to deterministic fuel rod computations. The benefits of this reliable and straightforward analysis procedure are demonstrated

23

On Bayesian System Reliability Analysis  

International Nuclear Information System (INIS)

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

24

On Bayesian System Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

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.

Soerensen Ringi, M.

1995-05-01

25

How to assess and compare inter-rater reliability, agreement and correlation of ratings: an exemplary analysis of mother-father and parent-teacher expressive vocabulary rating pairs.  

Science.gov (United States)

This report has two main purposes. First, we combine well-known analytical approaches to conduct a comprehensive assessment of agreement and correlation of rating-pairs and to dis-entangle these often confused concepts, providing a best-practice example on concrete data and a tutorial for future reference. Second, we explore whether a screening questionnaire developed for use with parents can be reliably employed with daycare teachers when assessing early expressive vocabulary. A total of 53 vocabulary rating pairs (34 parent-teacher and 19 mother-father pairs) collected for two-year-old children (12 bilingual) are evaluated. First, inter-rater reliability both within and across subgroups is assessed using the intra-class correlation coefficient (ICC). Next, based on this analysis of reliability and on the test-retest reliability of the employed tool, inter-rater agreement is analyzed, magnitude and direction of rating differences are considered. Finally, Pearson correlation coefficients of standardized vocabulary scores are calculated and compared across subgroups. The results underline the necessity to distinguish between reliability measures, agreement and correlation. They also demonstrate the impact of the employed reliability on agreement evaluations. This study provides evidence that parent-teacher ratings of children's early vocabulary can achieve agreement and correlation comparable to those of mother-father ratings on the assessed vocabulary scale. Bilingualism of the evaluated child decreased the likelihood of raters' agreement. We conclude that future reports of agreement, correlation and reliability of ratings will benefit from better definition of terms and stricter methodological approaches. The methodological tutorial provided here holds the potential to increase comparability across empirical reports and can help improve research practices and knowledge transfer to educational and therapeutic settings. PMID:24994985

Stolarova, Margarita; Wolf, Corinna; Rinker, Tanja; Brielmann, Aenne

2014-01-01

26

How to assess and compare inter-rater reliability, agreement and correlation of ratings: an exemplary analysis of mother-father and parent-teacher expressive vocabulary rating pairs  

Directory of Open Access Journals (Sweden)

Full Text Available This report has two main purposes. First, we combine well-known analytical approaches to conduct a comprehensive assessment of agreement and correlation of rating-pairs and to dis-entangle these often confused concepts, providing a best-practice example on concrete data and a tutorial for future reference. Second, we explore whether a screening questionnaire deve-loped for use with parents can be reliably employed with daycare teachers when assessing early expressive vocabulary. A total of 53 vocabulary rating pairs (34 parent-teacher and 19 mother-father pairs collected for two-year-old children (12 bilingual are evaluated. First, inter-rater reliability both within and across subgroups is assessed using the intra-class correlation coefficient (ICC. Next, based on this analysis of reliability and on the test-retest reliability of the employed tool, inter-rater agreement is analyzed, magnitude and direction of rating differences are considered. Finally, Pearson correlation coefficients of standardized vocabulary scores are calculated and compared across subgroups. The results underline the necessity to distinguish between reliability measures, agreement and correlation. They also demonstrate the impact of the employed reliability on agreement evaluations. This study provides evidence that parent-teacher ratings of children’s early vocabulary can achieve agreement and correlation comparable to those of mother-father ratings on the assessed vocabulary scale. Bilingualism of the evaluated child decreased the likelihood of raters’ agreement. We conclude that future reports of agree-ment, correlation and reliability of ratings will benefit from better definition of terms and stricter methodological approaches. The methodological tutorial provided here holds the potential to increase comparability across empirical reports and can help improve research practices and knowledge transfer to educational and therapeutic settings.

MargaritaStolarova

2014-06-01

27

Satellite and satellite subsystems reliability: Statistical data analysis and modeling  

International Nuclear Information System (INIS)

Reliability has long been recognized as a critical attribute for space systems. Unfortunately, limited on-orbit failure data and statistical analyses of satellite reliability exist in the literature. To fill this gap, we recently conducted a nonparametric analysis of satellite reliability for 1584 Earth-orbiting satellites launched between January 1990 and October 2008. In this paper, we extend our statistical analysis of satellite reliability and investigate satellite subsystems reliability. Because our dataset is censored, we make extensive use of the Kaplan-Meier estimator for calculating the reliability functions. We derive confidence intervals for the nonparametric reliability results for each subsystem and conduct parametric fits with Weibull distributions using the maximum likelihood estimation (MLE) approach. We finally conduct a comparative analysis of subsystems failure, identifying the 'culprit subsystems' that drive satellite unreliability. The results here presented should prove particularly useful to the space industry for example in redesigning subsystem test and screening programs, or providing an empirical basis for redundancy allocation.

28

A Comparative Overview of Software Reliability Growth Models  

Directory of Open Access Journals (Sweden)

Full Text Available A software reliability growth model is one of the fundamental technique to assess software reliability quantitatively. The software reliability growth model is required to have a good performance in terms of goodness-of-fit, predictability, and so forth. In this paper, we will summarize some existing Software Reliability Growth Models (SRGM’s. Our main focus in this paper will be to provide a comparative overview of the various SRGM’s in general. The comparison will mainly be on the basis of what type of Testing-Effort Function (TEF is used by which type of probability distribution function, to describe Testing-Effort curve. First, we provide overview of Software Reliability and Software Reliability Growth Model. Next, with the intention of comparing various SRGMs we provide the Testing Effort Functions (TEFs given by various researchers. Then actual software data from the software projects have been used to demonstrate the comparison of SRGMs. The evaluation results from the various SRGMs are analyzed and compared to show which SRGM has fairly better prediction in estimating number of remaining faults, expected number of errors, future failure behavior from present and past failures, optimal release time and which SRGM comparatively describes the actual expenditure pattern more faithfully during software development process.

Razeef Mohd

2011-02-01

29

Reliability analysis of software based safety functions  

International Nuclear Information System (INIS)

The methods applicable in the reliability analysis of software based safety functions are described in the report. Although the safety functions also include other components, the main emphasis in the report is on the reliability analysis of software. The check list type qualitative reliability analysis methods, such as failure mode and effects analysis (FMEA), are described, as well as the software fault tree analysis. The safety analysis based on the Petri nets is discussed. The most essential concepts and models of quantitative software reliability analysis are described. The most common software metrics and their combined use with software reliability models are discussed. The application of software reliability models in PSA is evaluated; it is observed that the recent software reliability models do not produce the estimates needed in PSA directly. As a result from the study some recommendations and conclusions are drawn. The need of formal methods in the analysis and development of software based systems, the applicability of qualitative reliability engineering methods in connection to PSA and the need to make more precise the requirements for software based systems and their analyses in the regulatory guides should be mentioned. (orig.). (46 refs., 13 figs., 1 tab.)

30

LIFETIME ESTIMATION FROM ACCELERATED RELIABILITY TESTING USING FINITE ELEMENTS ANALYSIS  

Directory of Open Access Journals (Sweden)

Full Text Available The paper is focused at the study of the reliability and of the lifetime of ball bearings,using reliability accelerated testing. The main objectives of this paper are: the estimation of thelifetime and reliability of ball bearings. Taking into account the aspects regarding the statisticalprocessing of experimental data, we determined the main reliability parameters, which in turndetermine the main characteristics regarding the performance and the warranty period of the ballbearings. In this paper, the analysis with finite elements was used to validate and to compare thedata resulted from the accelerated reliability tests of the ball bearings

Sebastian Marian ZAHARIA

2013-05-01

31

Discrete event simulation versus conventional system reliability analysis approaches  

DEFF Research Database (Denmark)

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 to system reliability analysis with DES.

Kozine, Igor

2010-01-01

32

Reliability analysis of reactor pressure vessel intensity  

International Nuclear Information System (INIS)

This paper performs the reliability analysis of reactor pressure vessel (RPV) with ANSYS. The analysis method include direct Monte Carlo Simulation method, Latin Hypercube Sampling, central composite design and Box-Behnken Matrix design. The RPV integrity reliability under given input condition is proposed. The result shows that the effects on the RPV base material reliability are internal press, allowable basic stress and elasticity modulus of base material in descending order, and the effects on the bolt reliability are allowable basic stress of bolt material, preload of bolt and internal press in descending order. (authors)

33

Reliability analysis for wind turbines.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Modern wind turbines are complex aerodynamic, mechanical and electrical machines incorporating sophisticated control systems. Wind turbines have been erected in increasing numbers in Europe, the USA and elsewhere. In Europe, Germany and Denmark have played a particularly prominent part in developing the technology, and both countries have installed large numbers of turbines. This article is concerned with understanding the historic reliability of modern wind turbines. The prime objective of t...

Tavner, P. J.; Xiang, J.; Spinato, F.

2006-01-01

34

Simulation and reliability analysis of probabilistic dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The current probabilistic safety analysis is not capable of estimating the reliability of the complex dynamic systems where the interactions occur between hardware, software and human actions. In the safety analysis of these systems the time factor is as much important as it joins an evolution of physical variables and stochastic events. In this master thesis the simulation and reliability analysis of the probabilistic dynamics are considered. The new approach of stimulus based probabilistic ...

Eimontas, Tadas

2007-01-01

35

Reliability analysis for data management systems  

Science.gov (United States)

Report describes approach that uses computer model and can determine configurations with optimum reliability and least cost. Approach in application to modelling computer-controlled data management systems differs from conventional reliability analysis in that it considers systems organized around data base and looks at systems from equipment level rather than from component level.

Huang, Y.

1977-01-01

36

Comparability and Reliability Considerations of Adequate Yearly Progress  

Science.gov (United States)

The purpose of this study is to develop an estimate of Adequate Yearly Progress (AYP) that will allow for reliable and valid comparisons among student subgroups, schools, and districts. A shrinkage-type estimator of AYP using the Bayesian framework is described. Using simulated data, the performance of the Bayes estimator will be compared to…

Maier, Kimberly S.; Maiti, Tapabrata; Dass, Sarat C.; Lim, Chae Young

2012-01-01

37

Software reliability modeling and analysis  

Science.gov (United States)

A discrete and, as approximation to it, a continuous model for the software reliability growth process are examined. The discrete model is based on independent multinomial trials and concerns itself with the joint distribution of the first occurrence time of its underlying events (bugs). The continuous model is based on the order statistics of N independent nonidentically distributed exponential random variables. It is shown that the spacings between bugs are not necessarily independent or exponentially (geometrically) distributed. However, there is a statistical rationale for viewing them so conditionally. Some identifiability problems are pointed out and resolved. In particular, it appears that the number of bugs in a program is not identifiable. Estimated upper bounds and confidence bounds for the residual program eror content are given based on the spacings of the first k bugs removed.

Scholz, F.-W.

1986-01-01

38

Reliability Generalization (RG) Analysis: The Test Is Not Reliable  

Science.gov (United States)

Literature shows that most researchers are unaware of some of the characteristics of reliability. This paper clarifies some misconceptions by describing the procedures, benefits, and limitations of reliability generalization while using it to illustrate the nature of score reliability. Reliability generalization (RG) is a meta-analytic method…

Warne, Russell

2008-01-01

39

Reliability analysis of Angra I safety systems  

International Nuclear Information System (INIS)

A group of individuals formed at COPPE (Coordenacao dos Programas de Pos-graduacao em Engenharia) for reliability studies in nuclear power plants, are presented. The techniques used in that analysis and some examples are presented. (E.G.)

40

How useful and reliable are disaster databases in the context of climate and global change? A comparative case study analysis in Peru  

Science.gov (United States)

Loss and damage caused by weather and climate related disasters have increased over the past decades, and growing exposure and wealth have been identified as main drivers of this increase. Disaster databases are a primary tool for the analysis of disaster characteristics and trends at global or national scales, and support disaster risk reduction and climate change adaptation. However, the quality, consistency and completeness of different disaster databases are highly variable. Even though such variation critically influences the outcome of any study, comparative analyses of different disaster databases are still rare to date. Furthermore, there is an unequal geographic distribution of current disaster trend studies, with developing countries being under-represented. Here, we analyze three different disaster databases for the developing country context of Peru; a global database (EM-DAT), a regional Latin American (DesInventar) and a national database (SINPAD). The analysis is performed across three dimensions, (1) spatial scales, from local to regional (provincial) and national scale; (2) time scales, from single events to decadal trends; and (3) disaster categories and metrics, including the number of disaster occurrence, and damage metrics such as people killed and affected. Results show limited changes in disaster occurrence in the Cusco and Apurímac regions in southern Peru over the past four decades, but strong trends in people affected at the national scale. We furthermore found large variations of the disaster parameters studied over different spatial and temporal scales, depending on the disaster database analyzed. We conclude and recommend that the type, method and source of documentation should be carefully evaluated for any analysis of disaster databases; reporting criteria should be improved and documentation efforts strengthened.

Huggel, C.; Raissig, A.; Rohrer, M.; Romero, G.; Diaz, A.; Salzmann, N.

2014-06-01

 
 
 
 
41

Reliability analysis using network simulation  

International Nuclear Information System (INIS)

The models that can be used to provide estimates of the reliability of nuclear power systems operate at many different levels of sophistication. The least-sophisticated models treat failure processes that entail only time-independent phenomena (such as demand failure). More advanced models treat processes that also include time-dependent phenomena such as run failure and possibly repair. However, many of these dynamic models are deficient in some respects because they either disregard the time-dependent phenomena that cannot be expressed in closed-form analytic terms or because they treat these phenomena in quasi-static terms. The next level of modeling requires a dynamic approach that incorporates not only procedures for treating all significant time-dependent phenomena but also procedures for treating these phenomena when they are conditionally linked or characterized by arbitrarily selected probability distributions. The level of sophistication that is required is provided by a dynamic, Monte Carlo modeling approach. A computer code that uses a dynamic, Monte Carlo modeling approach is Q-GERT (Graphical Evaluation and Review Technique - with Queueing), and the present study had demonstrated the feasibility of using Q-GERT for modeling time-dependent, unconditionally and conditionally linked phenomena that are characterized by arbitrarily selected probability distributions

42

Software reliability experiments data analysis and investigation  

Science.gov (United States)

The objectives are to investigate the fundamental reasons which cause independently developed software programs to fail dependently, and to examine fault tolerant software structures which maximize reliability gain in the presence of such dependent failure behavior. The authors used 20 redundant programs from a software reliability experiment to analyze the software errors causing coincident failures, to compare the reliability of N-version and recovery block structures composed of these programs, and to examine the impact of diversity on software reliability using subpopulations of these programs. The results indicate that both conceptually related and unrelated errors can cause coincident failures and that recovery block structures offer more reliability gain than N-version structures if acceptance checks that fail independently from the software components are available. The authors present a theory of general program checkers that have potential application for acceptance tests.

Walker, J. Leslie; Caglayan, Alper K.

1991-01-01

43

A comparative study on the HW reliability assessment methods for digital I and C equipment  

Energy Technology Data Exchange (ETDEWEB)

It is necessary to predict or to evaluate the reliability of electronic equipment for the probabilistic safety analysis of digital instrument and control equipment. But most databases for the reliability prediction have no data for the up-to-date equipment and the failure modes are not classified. The prediction results for the specific component show different values according to the methods and databases. For boards and systems each method shows different values than others also. This study is for reliability prediction of PDC system for Wolsong NPP1 as a digital I and C equipment. Various reliability prediction methods and failure databases are used in calculation of the reliability to compare the effects of sensitivity and accuracy of each model and database. Many considerations for the reliability assessment of digital systems are derived with the results of this study. 14 refs., 19 figs., 15 tabs. (Author)

Jung, Hoan Sung; Sung, T. Y.; Eom, H. S.; Park, J. K.; Kang, H. G.; Lee, G. Y. [Korea Atomic Energy Research Institute, Taejeon (Korea); Kim, M. C. [Korea Advanced Institute of Science and Technology, Taejeon (Korea); Jun, S. T. [KHNP, Taejeon (Korea)

2002-03-01

44

Comparing two reliable multicast protocols for mobile computing  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english As networks with mobile devices becorne commonplace, many new applications for those networks arisc, including some that require coordination among groups of mobile clients. One basic tool for implementing coordination is reliable multicast, where delivery of a multicast message is atomic, i.e. cith [...] er all or none of the group members deliver the message. While several multicast protocols have been proposed for mobile networks, only a few works have considered reliable multicats. In this paper we present and compare two protocols based on Two-Phase-Commit that implement reliable multicast for structured mobile networks. Protocol iAM²C is a variant of protocol AM2C that employs a two-level hierarchical location management scheme to locate and route messages to the mobile hosts addressed by a multicast. Although hierarchical location management is not new in the context of mobile and cellular networks, we are unaware of any other work which combines hierarchical location management with protocols for reliable multicast. We have prototyped, simulated and evaluated both protocols using the MobiCS simulation enviromment. Our experiments indicate that despite some overhead incurred by the location management and the additional level of message redirection, iAM2C is more efficient than the AM² C protocol and scales well with the size of the wired network infra-structure.

Mateus de Freitas, Ribeiro; Markus, Endler.

45

Reliability analysis techniques for the design engineer  

International Nuclear Information System (INIS)

This paper describes a fault tree analysis package that eliminates most of the housekeeping tasks involved in proceeding from the initial construction of a fault tree to the final stage of presenting a reliability analysis in a safety report. It is suitable for designers with relatively little training in reliability analysis and computer operation. Users can rapidly investigate the reliability implications of various options at the design stage and evolve a system which meets specified reliability objectives. Later independent review is thus unlikely to reveal major shortcomings necessitating modification and project delays. The package operates interactively, allowing the user to concentrate on the creative task of developing the system fault tree, which may be modified and displayed graphically. For preliminary analysis, system data can be derived automatically from a generic data bank. As the analysis proceeds, improved estimates of critical failure rates and test and maintenance schedules can be inserted. The technique is applied to the reliability analysis of the recently upgraded HIFAR Containment Isolation System. (author)

46

Reliability Analysis of Data Storage Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Modern data storage systems are extremely large and consist of several tens or hundreds of nodes. In such systems, node failures are daily events, and safeguarding data from them poses a serious design challenge. The focus of this thesis is on the data reliability analysis of storage systems and, in particular, on the effect of different design choices and parameters on the system reliability. Data redundancy, in the form of replication or advanced erasure codes, is used to protect data from ...

Venkatesan, Vinodh

2012-01-01

47

Swimming pool reactor reliability and safety analysis  

International Nuclear Information System (INIS)

A reliability and safety analysis of Swimming Pool Reactor in China Institute of Atomic Energy is done by use of event/fault tree technique. The paper briefly describes the analysis model, analysis code and main results. Meanwhile it also describes the impact of unassigned operation status on safety, the estimation of effectiveness of defense tactics in maintenance against common cause failure, the effectiveness of recovering actions on the system reliability, the comparison of occurrence frequencies of the core damage by use of generic and specific data

48

Reliability analysis techniques for the design engineer  

International Nuclear Information System (INIS)

A fault tree analysis package is described that eliminates most of the housekeeping tasks involved in proceeding from the initial construction of a fault tree to the final stage of presenting a reliability analysis in a safety report. It is suitable for designers with relatively little training in reliability analysis and computer operation. Users can rapidly investigate the reliability implications of various options at the design stage, and evolve a system which meets specified reliability objectives. Later independent review is thus unlikely to reveal major shortcomings necessitating modification and projects delays. The package operates interactively allowing the user to concentrate on the creative task of developing the system fault tree, which may be modified and displayed graphically. For preliminary analysis system data can be derived automatically from a generic data bank. As the analysis procedes improved estimates of critical failure rates and test and maintenance schedules can be inserted. The computations are standard, - identification of minimal cut-sets, estimation of reliability parameters, and ranking of the effect of the individual component failure modes and system failure modes on these parameters. The user can vary the fault trees and data on-line, and print selected data for preferred systems in a form suitable for inclusion in safety reports. A case history is given - that of HIFAR containment isolation system. (author)system. (author)

49

Reliability Analysis of Aircraft Equipment Based on FMECA Method  

Science.gov (United States)

It is well known that reliability of aircraft equipment is very important to aircraft during the flight because performance of aircraft product can affect flight safe directly. In order to make the equipment work normally, FMECA is applied in an aircraft equipment to analyze its reliability and improve operational reliability of the product. Through its reliability mathematical model, average of operational time is predicted based on calculating failure probability of all electrical components. According to the process of reliability theory FMECA, all kinds of the failure mode, reasons, effects and criticality of the products can be determined completely. By comparing these criticality data as shown, the paper analyses adopted method by that the contents, accents and operating process of maintenance may be instituted finally. FMECA-based method for reliability analysis of the equipment and the equipment maintenance performs well. The results indicate that application of FMECA method can analyze reliability in detail and improve operational reliability of the equipment. Therefore this will supply theoretical bases and concrete measures of maintenance of the products to improve operational reliability of products. FMECA can be feasible and effective for improving operational reliability of all aircraft equipments.

Jun, Li; Huibin, Xu

50

Travel time Reliability Analysis Using Entropy  

Directory of Open Access Journals (Sweden)

Full Text Available Travel time reliability is a measure that is commonly extracted from travel time measurements. It has served as a vital indicator of the transportation system’s performance making the concept of obtaining reliability from travel time data very useful. Travel time is a good indicator of the performance of a particular highway segment. However, it does not convey all aspects of the overall performance of the transportation system. Travel Time Reliability is defined as the consistency of traffic conditions on a given link. Predictability is desired since travelers tend to give a higher value to consistency of travel times rather than the pure travel time data. Previous studies have explored various analysis approaches for this purpose. Most commonly used methods are the traditional statistical methods demonstrating variability. A vital question to ask is how adequate these standard statistical quantities are. There are numerous measures of travel time reliability that look at how reliable the travel time measurements are from different perspectives. This paper presents an overview of the current methods of calculating travel time reliability and introduces a new approach by using the concept of entropy from information theory. The information theory based approach is demonstrated through failure analysis.

Neveen Shlayan

2013-10-01

51

Reliability modelling and analysis of thermal MEMS  

Science.gov (United States)

This paper presents a MEMS reliability study methodology based on the novel concept of 'virtual prototyping'. This methodology can be used for the development of reliable sensors or actuators and also to characterize their behaviour in specific use conditions and applications. The methodology is demonstrated on the U-shaped micro electro thermal actuator used as test vehicle. To demonstrate this approach, a 'virtual prototype' has been developed with the modeling tools MatLab and VHDL-AMS. A best practice FMEA (Failure Mode and Effect Analysis) is applied on the thermal MEMS to investigate and assess the failure mechanisms. Reliability study is performed by injecting the identified defaults into the 'virtual prototype'. The reliability characterization methodology predicts the evolution of the behavior of these MEMS as a function of the number of cycles of operation and specific operational conditions.

Muratet, Sylvaine; Lavu, Srikanth; Fourniols, Jean-Yves; Bell, George; Desmulliez, Marc P. Y.

2006-04-01

52

Reliability modelling and analysis of thermal MEMS  

International Nuclear Information System (INIS)

This paper presents a MEMS reliability study methodology based on the novel concept of 'virtual prototyping'. This methodology can be used for the development of reliable sensors or actuators and also to characterize their behaviour in specific use conditions and applications. The methodology is demonstrated on the U-shaped micro electro thermal actuator used as test vehicle. To demonstrate this approach, a 'virtual prototype' has been developed with the modeling tools MatLab and VHDL-AMS. A best practice FMEA (Failure Mode and Effect Analysis) is applied on the thermal MEMS to investigate and assess the failure mechanisms. Reliability study is performed by injecting the identified defaults into the 'virtual prototype'. The reliability characterization methodology predicts the evolution of the behavior of these MEMS as a function of the number of cycles of operation and specific operational conditions

53

RAS. Reliability Analysis for Phased Missions  

Energy Technology Data Exchange (ETDEWEB)

The Reliability Analysis System, RAS, is an integrated package of computer programs for the quantification of fault trees. In particular, RAS has the capability of performing phased mission analysis. A phased mission is a task to be performed by a system during which the logic model and/or the component failure mode characteristics change at predetermined times. RAS is capable of finding minimal cut sets from fault trees and of calculating reliability characteristics for the basic events, the minimal cut sets, and the top event of a fault tree. In addition, mission cut set cancellation and four methods of bounding mission unreliability have been incorporated into RAS.

Rasmuson, D.; Marshall, N.H.; Burdick, G.R. [E G and G Idaho, Inc., Idaho Falls, ID (United States)

1981-05-01

54

Culture Representation in Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

Understanding human-system response is critical to being able to plan and predict mission success in the modern battlespace. Commonly, human reliability analysis has been used to predict failures of human performance in complex, critical systems. However, most human reliability methods fail to take culture into account. This paper takes an easily understood state of the art human reliability analysis method and extends that method to account for the influence of culture, including acceptance of new technology, upon performance. The cultural parameters used to modify the human reliability analysis were determined from two standard industry approaches to cultural assessment: Hofstede’s (1991) cultural factors and Davis’ (1989) technology acceptance model (TAM). The result is called the Culture Adjustment Method (CAM). An example is presented that (1) reviews human reliability assessment with and without cultural attributes for a Supervisory Control and Data Acquisition (SCADA) system attack, (2) demonstrates how country specific information can be used to increase the realism of HRA modeling, and (3) discusses the differences in human error probability estimates arising from cultural differences.

David Gertman; Julie Marble; Steven Novack

2006-12-01

55

Reliability Analysis of a Steel Frame  

Directory of Open Access Journals (Sweden)

Full Text Available A steel frame with haunches is designed according to Eurocodes. The frame is exposed to self-weight, snow, and wind actions. Lateral-torsional buckling appears to represent the most critical criterion, which is considered as a basis for the limit state function. In the reliability analysis, the probabilistic models proposed by the Joint Committee for Structural Safety (JCSS are used for basic variables. The uncertainty model coefficients take into account the inaccuracy of the resistance model for the haunched girder and the inaccuracy of the action effect model. The time invariant reliability analysis is based on Turkstra's rule for combinations of snow and wind actions. The time variant analysis describes snow and wind actions by jump processes with intermittencies. Assuming a 50-year lifetime, the obtained values of the reliability index b vary within the range from 3.95 up to 5.56. The cross-profile IPE 330 designed according to Eurocodes seems to be adequate. It appears that the time invariant reliability analysis based on Turkstra's rule provides considerably lower values of b than those obtained by the time variant analysis.

M. Sýkora

2002-01-01

56

Large-scale reliability analysis by decomposition and integration  

International Nuclear Information System (INIS)

In this decade, the risk analysis for light water reactor nuclear power plants and other related facilities has become of remarkable importance. However, the plants or facilities to be analyzed are, in most cases, large-scale and complicated. Fault tree analysis for such a large-scale and complicated system often requires extremely time- and cost-consuming works. In this paper, a new method for the reliability analysis of the large-scale and complicated system (large-scale reliability analysis, hereinafter) is presented. The method enables the large-scale reliability analysis to be carried out practically and efficiently by decomposing the system into several subsystems and integrating the results obtained through reliability analyses for subsystems. For the demonstration of the methodology, a reliability analysis for a safety-related system of BWR nuclear power plants is provided. The merits of the method are confirmed by this application and the validity is shown by comparing the result with that of Interim Reliability Evaluation Program

57

NASA program decisions using reliability analysis.  

Science.gov (United States)

NASA made use of the analytical outputs of reliability people to make management decisions on the Apollo program. Such decisions affected the amount of the incentive fees, how much acceptance testing was necessary, how to optimize development testing, whether to approve engineering changes, and certification of flight readiness. Examples of such analysis are discussed and related to programmatic decisions.-

Steinberg, A.

1972-01-01

58

Reliability analysis of the auxiliary feedwater system  

International Nuclear Information System (INIS)

The reliability of a NPP auxiliary feedwater system is evaluated using the fault tree analysis. The system is analyzed during the time interval 0 to 6 hours with the computer package program PREP/KITT which is described in more detail. (author)

59

Reliability analysis based on operational success criteria  

Science.gov (United States)

Failure Modes, Effects, and Criticality Analysis Model disregards failures of insignificant components. Assumptions used to establish baselines for reliability prediction and analytical method are listed. Techniques are applicable to any commercial design and can be extended into software or management systems.

Esmond, F. G.; Johnson, M. D.

1972-01-01

60

Reliability Analysis of Structural Timber Systems  

DEFF Research Database (Denmark)

Structural systems like timber trussed rafters and roof elements made of timber can be expected to have some degree of redundancy and nonlinear/plastic behaviour when the loading consists of for example snow or imposed load. In this paper this system effect is modelled and the statistic characteristics of the load-bearing capacity is estimated in the form of a characteristic value and a coefficient of variation. These two values are of primary importance for codes of practice based on the partial safety factor format since the partial safety factor is closely related to the coefficient of variation. In the paper a stochastic model is described for the strength of a single piece of timber taking into account the stochastic variation of the strength and stiffness with length. Also stochastic models for different types of loads are formulated. First, simple representative systems with different types of redundancy and non-linearity are considered. The statistical characteristics of the load bearing capacity aredetermined 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 the above stochastic models, statistical characteristics (distribution function, 5% quantile and coefficient of variation) are determined. Generally, the results show that taking the system effects into account the characteristic load bearing capacity can be increased and the partial safety factor decreased compared to the values obtained if the system effects are not considered.

SØrensen, John Dalsgaard; Hoffmeyer, P.

2000-01-01

 
 
 
 
61

Comparative risk analysis  

International Nuclear Information System (INIS)

In this paper, the risks of various energy systems are discussed considering severe accidents analysis, particularly the probabilistic safety analysis, and probabilistic safety criteria, and the applications of these criteria and analysis. The comparative risk analysis has demonstrated that the largest source of risk in every society is from daily small accidents. Nevertheless, we have to be more concerned about severe accidents. The comparative risk analysis of five different energy systems (coal, oil, gas, LWR and STEC (Solar)) for the public has shown that the main sources of risks are coal and oil. The latest comparative risk study of various energy has been conducted in the USA and has revealed that the number of victims from coal is 42 as many than victims from nuclear. A study for severe accidents from hydro-dams in United States has estimated the probability of dam failures at 1 in 10,000 years and the number of victims between 11,000 and 260,000. The average occupational risk from coal is one fatal accident in 1,000 workers/year. The probabilistic safety analysis is a method that can be used to assess nuclear energy risks, and to analyze the severe accidents, and to model all possible accident sequences and consequences. The 'Fault tree' analysis is used to know the probability of failure of the different systems at each point of accident sequences and to calculate the probability of risks. After calculating the probability of failure, the criteria for judginbility of failure, the criteria for judging the numerical results have to be developed, that is the quantitative and qualitative goals. To achieve these goals, several systems have been devised by various countries members of AIEA. The probabilistic safety ana-lysis method has been developed by establishing a computer program permit-ting to know different categories of safety related information. 19 tabs. (author)

62

Comparative reliability of cheiloscopy and palatoscopy in human identification  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Establishing a person?s identity in postmortem scenarios can be a very difficult process. Dental records, fingerprint and DNA comparisons are probably the most common techniques used in this context, allowing fast and reliable identification processes. However, under certain circumstances they cannot always be used; sometimes it is necessary to apply different and less known techniques. In forensic identification, lip prints and palatal rugae patterns can lead us to important information and help in a person?s identification. This study aims to ascertain the use of lip prints and palatal rugae pattern in identification and sex differentiation. Materials and Methods: A total of 100 subjects, 50 males and 50 females were selected from among the students of Subharti Dental College, Meerut. The materials used to record lip prints were lipstick, bond paper, cellophane tape, a brush for applying the lipstick, and a magnifying lens. To study palatal rugae, alginate impressions were taken and the dental casts analyzed for their various patterns. Results: Statistical analysis (applying Z-test for proportion showed significant difference for type I, I?, IV and V lip patterns (P < 0.05 in males and females, while no significant difference was observed for the same in the palatal rugae patterns (P > 0.05. Conclusion: This study not only showed that palatal rugae and lip prints are unique to an individual, but also that lip prints is more reliable for recognition of the sex of an individual.

Sharma Preeti

2009-01-01

63

Advances in human reliability analysis in Mexico  

International Nuclear Information System (INIS)

Human Reliability Analysis (HRA) is a very important part of Probabilistic Risk Analysis (PRA), and constant work is dedicated to improving methods, guidance and data in order to approach realism in the results as well as looking for ways to use these to reduce accident frequency at plants. Further, in order to advance in these areas, several HRA studies are being performed globally. Mexico has participated in the International HRA Empirical study with the objective of -benchmarking- HRA methods by comparing HRA predictions to actual crew performance in a simulator, as well as in the empirical study on a US nuclear power plant currently in progress. The focus of the first study was the development of an understanding of how methods are applied by various analysts, and characterize the methods for their capability to guide the analysts to identify potential human failures, and associated causes and performance shaping factors. The HRA benchmarking study has been performed by using the Halden simulator, 14 European crews, and 15 HRA equipment s (NRC, EPRI, and foreign HRA equipment s using different HRA methods). This effort in Mexico is reflected through the work being performed on updating the Laguna Verde PRA to comply with the ASME PRA standard. In order to be considered an HRA with technical adequacy, that is, be considered as a capability category II, for risk-informed applications, the methodology used for the HRA in the original PRA is not considered sufficiently detailed, and the methodology had to upgraded. The HCR/CBDT/THERP method was chosen, since this is used in many nuclear plants with similar design. The HRA update includes identification and evaluation of human errors that can occur during testing and maintenance, as well as human errors that can occur during an accident using the Emergency Operating Procedures. The review of procedures for maintenance, surveillance and operation is a necessary step in HRA and provides insight into the possible mechanisms for human error at the plant. (Author)

64

Advances in human reliability analysis in Mexico  

Energy Technology Data Exchange (ETDEWEB)

Human Reliability Analysis (HRA) is a very important part of Probabilistic Risk Analysis (PRA), and constant work is dedicated to improving methods, guidance and data in order to approach realism in the results as well as looking for ways to use these to reduce accident frequency at plants. Further, in order to advance in these areas, several HRA studies are being performed globally. Mexico has participated in the International HRA Empirical study with the objective of -benchmarking- HRA methods by comparing HRA predictions to actual crew performance in a simulator, as well as in the empirical study on a US nuclear power plant currently in progress. The focus of the first study was the development of an understanding of how methods are applied by various analysts, and characterize the methods for their capability to guide the analysts to identify potential human failures, and associated causes and performance shaping factors. The HRA benchmarking study has been performed by using the Halden simulator, 14 European crews, and 15 HRA equipment s (NRC, EPRI, and foreign HRA equipment s using different HRA methods). This effort in Mexico is reflected through the work being performed on updating the Laguna Verde PRA to comply with the ASME PRA standard. In order to be considered an HRA with technical adequacy, that is, be considered as a capability category II, for risk-informed applications, the methodology used for the HRA in the original PRA is not considered sufficiently detailed, and the methodology had to upgraded. The HCR/CBDT/THERP method was chosen, since this is used in many nuclear plants with similar design. The HRA update includes identification and evaluation of human errors that can occur during testing and maintenance, as well as human errors that can occur during an accident using the Emergency Operating Procedures. The review of procedures for maintenance, surveillance and operation is a necessary step in HRA and provides insight into the possible mechanisms for human error at the plant. (Author)

NONE

2010-10-15

65

Bridging Resilience Engineering and Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

There has been strong interest in the new and emerging field called resilience engineering. This field has been quick to align itself with many existing safety disciplines, but it has also distanced itself from the field of human reliability analysis. To date, the discussion has been somewhat one-sided, with much discussion about the new insights afforded by resilience engineering. This paper presents an attempt to address resilience engineering from the perspective of human reliability analysis (HRA). It is argued that HRA shares much in common with resilience engineering and that, in fact, it can help strengthen nascent ideas in resilience engineering. This paper seeks to clarify and ultimately refute the arguments that have served to divide HRA and resilience engineering.

Ronald L. Boring

2010-06-01

66

Reliability Analysis for Safety Grade PLC  

Energy Technology Data Exchange (ETDEWEB)

In this paper, describe reliability analysis for digital safety grade PLC which developed with the aim to use the operating nuclear power plants and new plants by POSCO ICT co., POSAFE-Q consist of the Sub Rack, power modules, processor modules, communication modules, digital input / output module (DI / DO), analog input / output modules (AI / AO), pulse counter module, TC (Thermocouple), RTD (Resistance Temperature Detector), Local Repeater

Choi, Kyung Chul; Hwang, Sung Jae; Jung, Tae Hyok; Kim, Tae Hee; Song, Seung Whan [POSCO ICT Co., Seoul (Korea, Republic of)

2010-10-15

67

Reliability Analysis for Safety Grade PLC  

International Nuclear Information System (INIS)

In this paper, describe reliability analysis for digital safety grade PLC which developed with the aim to use the operating nuclear power plants and new plants by POSCO ICT co., POSAFE-Q consist of the Sub Rack, power modules, processor modules, communication modules, digital input / output module (DI / DO), analog input / output modules (AI / AO), pulse counter module, TC (Thermocouple), RTD (Resistance Temperature Detector), Local Repeater

68

Second generation methods for human reliability analysis. ATHEANA analysis  

International Nuclear Information System (INIS)

The paper describes the principles and status of development of 2nd generation methods for human reliability analysis, which concentrate on the contextual elements that can trigger cognitive mechanisms of error resulting in hazardous operator interventions. The ATHEANA (A Technique for Human Error ANAlysis) model of 1996 was the outcome of the first major efforts. CREAM (Cognitive Reliability and Error Analysis Method), developed by Hollnagel, is another important tool. The paper describes both the first and revised versions of ATHEANA. (author)

69

The quantitative failure of human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

This philosophical treatise argues the merits of Human Reliability Analysis (HRA) in the context of the nuclear power industry. Actually, the author attacks historic and current HRA as having failed in informing policy makers who make decisions based on risk that humans contribute to systems performance. He argues for an HRA based on Bayesian (fact-based) inferential statistics, which advocates a systems analysis process that employs cogent heuristics when using opinion, and tempers itself with a rational debate over the weight given subjective and empirical probabilities.

Bennett, C.T.

1995-07-01

70

Sensitivity analysis in optimization and reliability problems  

Energy Technology Data Exchange (ETDEWEB)

The paper starts giving the main results that allow a sensitivity analysis to be performed in a general optimization problem, including sensitivities of the objective function, the primal and the dual variables with respect to data. In particular, general results are given for non-linear programming, and closed formulas for linear programming problems are supplied. Next, the methods are applied to a collection of civil engineering reliability problems, which includes a bridge crane, a retaining wall and a composite breakwater. Finally, the sensitivity analysis formulas are extended to calculus of variations problems and a slope stability problem is used to illustrate the methods.

Castillo, Enrique [Department of Applied Mathematics and Computational Sciences, University of Cantabria, Avda. Castros s/n., 39005 Santander (Spain)], E-mail: castie@unican.es; Minguez, Roberto [Department of Applied Mathematics, University of Castilla-La Mancha, 13071 Ciudad Real (Spain)], E-mail: roberto.minguez@uclm.es; Castillo, Carmen [Department of Civil Engineering, University of Castilla-La Mancha, 13071 Ciudad Real (Spain)], E-mail: mariacarmen.castillo@uclm.es

2008-12-15

71

Sensitivity analysis in optimization and reliability problems  

International Nuclear Information System (INIS)

The paper starts giving the main results that allow a sensitivity analysis to be performed in a general optimization problem, including sensitivities of the objective function, the primal and the dual variables with respect to data. In particular, general results are given for non-linear programming, and closed formulas for linear programming problems are supplied. Next, the methods are applied to a collection of civil engineering reliability problems, which includes a bridge crane, a retaining wall and a composite breakwater. Finally, the sensitivity analysis formulas are extended to calculus of variations problems and a slope stability problem is used to illustrate the methods

72

Reliability Analysis of Brittle, Thin Walled Structures  

Energy Technology Data Exchange (ETDEWEB)

One emerging application for ceramics is diesel particulate filters being used order to meet EPA regulations going into effect in 2008. Diesel particulates are known to be carcinogenic and thus need to be minimized. Current systems use filters made from ceramics such as mullite and corderite. The filters are brittle and must operate at very high temperatures during a burn out cycle used to remove the soot buildup. Thus the filters are subjected to thermal shock stresses and life time reliability analysis is required. NASA GRC has developed reliability based design methods and test methods for such applications, such as CARES/Life and American Society for Testing and Materials (ASTM) C1499 “Standard Test Method for Equibiaxial Strength of Ceramics.”

Jonathan A Salem and Lynn Powers

2007-02-09

73

Probability techniques for reliability analysis of composite materials  

Science.gov (United States)

Traditional design approaches for composite materials have employed deterministic criteria for failure analysis. New approaches are required to predict the reliability of composite structures since strengths and stresses may be random variables. This report will examine and compare methods used to evaluate the reliability of composite laminae. The two types of methods that will be evaluated are fast probability integration (FPI) methods and Monte Carlo methods. In these methods, reliability is formulated as the probability that an explicit function of random variables is less than a given constant. Using failure criteria developed for composite materials, a function of design variables can be generated which defines a 'failure surface' in probability space. A number of methods are available to evaluate the integration over the probability space bounded by this surface; this integration delivers the required reliability. The methods which will be evaluated are: the first order, second moment FPI methods; second order, second moment FPI methods; the simple Monte Carlo; and an advanced Monte Carlo technique which utilizes importance sampling. The methods are compared for accuracy, efficiency, and for the conservativism of the reliability estimation. The methodology involved in determining the sensitivity of the reliability estimate to the design variables (strength distributions) and importance factors is also presented.

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

74

A taxonomy for human reliability analysis  

International Nuclear Information System (INIS)

A human interaction taxonomy (classification scheme) was developed to facilitate human reliability analysis in a probabilistic safety evaluation of a nuclear power plant, being performed at Ontario Hydro. A human interaction occurs, by definition, when operators or maintainers manipulate, or respond to indication from, a plant component or system. The taxonomy aids the fault tree analyst by acting as a heuristic device. It helps define the range and type of human errors to be identified in the construction of fault trees, while keeping the identification by different analysts consistent. It decreases the workload associated with preliminary quantification of the large number of identified interactions by including a category called 'simple interactions'. Fault tree analysts quantify these according to a procedure developed by a team of human reliability specialists. The interactions which do not fit into this category are called 'complex' and are quantified by the human reliability team. The taxonomy is currently being used in fault tree construction in a probabilistic safety evaluation. As far as can be determined at this early stage, the potential benefits of consistency and completeness in identifying human interactions and streamlining the initial quantification are being realized

75

Reliability analysis of containment isolation systems  

International Nuclear Information System (INIS)

This report summarizes the results of the Reliability Analysis of Containment Isolation System Project. Work was performed in five basic areas: design review, operating experience review, related research review, generic analysis and plant specific analysis. Licensee Event Reports (LERs) and Integrated Leak Rate Test (ILRT) reports provided the major sources of containment performance information used in this study. Data extracted from LERs were assembled into a computer data base. Qualitative and quantitative information developed for containment performance under normal operating conditions and design basis accidents indicate that there is room for improvement. A rough estimate of overall containment unavailability for relatively small leaks which violate plant technical specifications is 0.3. An estimate of containment unavailability due to large leakage events is in the range of 0.001 to 0.01. These estimates are dependent on several assumptions (particularly on event duration times) which are documented in the report

76

Reliability Analysis Techniques for Communication Networks in Nuclear Power Plant  

International Nuclear Information System (INIS)

The objectives of this project is to investigate and study existing reliability analysis techniques for communication networks in order to develop reliability analysis models for nuclear power plant's safety-critical networks. It is necessary to make a comprehensive survey of current methodologies for communication network reliability. Major outputs of this study are design characteristics of safety-critical communication networks, efficient algorithms for quantifying reliability of communication networks, and preliminary models for assessing reliability of safety-critical communication networks

77

CRAX/Cassandra Reliability Analysis Software  

Energy Technology Data Exchange (ETDEWEB)

Over the past few years Sandia National Laboratories has been moving toward an increased dependence on model- or physics-based analyses as a means to assess the impact of long-term storage on the nuclear weapons stockpile. These deterministic models have also been used to evaluate replacements for aging systems, often involving commercial off-the-shelf components (COTS). In addition, the models have been used to assess the performance of replacement components manufactured via unique, small-lot production runs. In either case, the limited amount of available test data dictates that the only logical course of action to characterize the reliability of these components is to specifically consider the uncertainties in material properties, operating environment etc. within the physics-based (deterministic) model. This not only provides the ability to statistically characterize the expected performance of the component or system, but also provides direction regarding the benefits of additional testing on specific components within the system. An effort was therefore initiated to evaluate the capabilities of existing probabilistic methods and, if required, to develop new analysis methods to support the inclusion of uncertainty in the classical design tools used by analysts and design engineers at Sandia. The primary result of this effort is the CMX (Cassandra Exoskeleton) reliability analysis software.

Robinson, D.

1999-02-10

78

Advancing Usability Evaluation through Human Reliability Analysis  

International Nuclear Information System (INIS)

This paper introduces a novel augmentation to the current heuristic usability evaluation methodology. The SPAR-H human reliability analysis method was developed for categorizing human performance in nuclear power plants. Despite the specialized use of SPAR-H for safety critical scenarios, the method also holds promise for use in commercial off-the-shelf software usability evaluations. The SPAR-H method shares task analysis underpinnings with human-computer interaction, and it can be easily adapted to incorporate usability heuristics as performance shaping factors. By assigning probabilistic modifiers to heuristics, it is possible to arrive at the usability error probability (UEP). This UEP is not a literal probability of error but nonetheless provides a quantitative basis to heuristic evaluation. When combined with a consequence matrix for usability errors, this method affords ready prioritization of usability issues

79

SURE reliability analysis: Program and mathematics  

Science.gov (United States)

The SURE program is a new reliability analysis tool for ultrareliable computer system architectures. The computational methods on which the program is based provide an efficient means for computing accurate upper and lower bounds for the death state probabilities of a large class of semi-Markov models. Once a semi-Markov model is described using a simple input language, the SURE program automatically computes the upper and lower bounds on the probability of system failure. A parameter of the model can be specified as a variable over a range of values directing the SURE program to perform a sensitivity analysis automatically. This feature, along with the speed of the program, makes it especially useful as a design tool.

Butler, Ricky W.; White, Allan L.

1988-01-01

80

Advancing Usability Evaluation through Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

This paper introduces a novel augmentation to the current heuristic usability evaluation methodology. The SPAR-H human reliability analysis method was developed for categorizing human performance in nuclear power plants. Despite the specialized use of SPAR-H for safety critical scenarios, the method also holds promise for use in commercial off-the-shelf software usability evaluations. The SPAR-H method shares task analysis underpinnings with human-computer interaction, and it can be easily adapted to incorporate usability heuristics as performance shaping factors. By assigning probabilistic modifiers to heuristics, it is possible to arrive at the usability error probability (UEP). This UEP is not a literal probability of error but nonetheless provides a quantitative basis to heuristic evaluation. When combined with a consequence matrix for usability errors, this method affords ready prioritization of usability issues.

Ronald L. Boring; David I. Gertman

2005-07-01

 
 
 
 
81

Development of design framework based on reliability analysis using MATLAB  

International Nuclear Information System (INIS)

The aim of this research is to implement a design framework based on reliability analysis and make it possibly used for a reliable and robust design under uncertainties. Different types of reliability methods and algorithms are programmed to explore their characteristics. In our work, RIA and the PMA are employed for formulating the reliability analysis problems. A number of reliability methods are introduced in this program such as FORM, AMV/AMV+ and MCS. Reliability analysis can be easily performed with this tool box only if a drive file is ready to run. Users need to select random design variables and define their distributions and correlation

82

Standardizing the practice of human reliability analysis  

International Nuclear Information System (INIS)

The practice of human reliability analysis (HRA) within the nuclear industry varies greatly in terms of posited mechanisms that shape human performance, methods of characterizing and analytically modeling human behavior, and the techniques that are employed to estimate the frequency with which human error occurs. This variation has been a source of contention among HRA practitioners regarding the validity of results obtained from different HRA methods. It has also resulted in attempts to develop standard methods and procedures for conducting HRAs. For many of the same reasons, the practice of HRA has not been standardized or has been standardized only to the extent that individual analysts have developed heuristics and consistent approaches in their practice of HRA. From the standpoint of consumers and regulators, this has resulted in a lack of clear acceptance criteria for the assumptions, modeling, and quantification of human errors in probabilistic risk assessments

83

Human Reliability Analysis For Computerized Procedures  

International Nuclear Information System (INIS)

This paper provides a characterization of human reliability analysis (HRA) issues for computerized procedures in nuclear power plant control rooms. It is beyond the scope of this paper to propose a new HRA approach or to recommend specific methods or refinements to those methods. Rather, this paper provides a review of HRA as applied to traditional paper-based procedures, followed by a discussion of what specific factors should additionally be considered in HRAs for computerized procedures. Performance shaping factors and failure modes unique to computerized procedures are highlighted. Since there is no definitive guide to HRA for paper-based procedures, this paper also serves to clarify the existing guidance on paper-based procedures before delving into the unique aspects of computerized procedures.

84

HUMAN RELIABILITY ANALYSIS FOR COMPUTERIZED PROCEDURES  

Energy Technology Data Exchange (ETDEWEB)

This paper provides a characterization of human reliability analysis (HRA) issues for computerized procedures in nuclear power plant control rooms. It is beyond the scope of this paper to propose a new HRA approach or to recommend specific methods or refinements to those methods. Rather, this paper provides a review of HRA as applied to traditional paper-based procedures, followed by a discussion of what specific factors should additionally be considered in HRAs for computerized procedures. Performance shaping factors and failure modes unique to computerized procedures are highlighted. Since there is no definitive guide to HRA for paper-based procedures, this paper also serves to clarify the existing guidance on paper-based procedures before delving into the unique aspects of computerized procedures.

Ronald L. Boring; David I. Gertman; Katya Le Blanc

2011-09-01

85

Reliability Analysis of Elasto-Plastic Structures  

DEFF Research Database (Denmark)

This paper only deals with framed and trussed structures which can be modelled as systems with ductile elements. The elements are all assumed to be linear-elastic perfectly plastic. The loading is assumed to be concentrated and time-independent. The strength of the elements and the loads are modelled by normally distributed stochastic variables. This last assumption is not essential, since non-normally distributed variables can be approximated by equivalent normally distributed variables by well-known methods. All geometrical dimensions and stiffness quantities are assumed to be deterministic. Failure of this type of system is defined either as formation of a mechanism or by failure of a prescribed number of elements. In the first case failure is independent of the order in which the elements fail, but this is not so by the second definition. The reliability analysis consists of two parts. In the first part significant failure modes are determined. Nonsignificant failure modes are those that only contribute negligibly to the failure probability of the structure. Significant failure modes are determined by the (l-unzipping method by Thoft-Christensen [1]. Two different formulations of this method are described and the two definitions of failure can be used by the first formulation, but only the failure definition based on formation of a mechanism by the second formulation. The second part of the reliability analysis is an estimate of the failure probability for the structure on the basis of the significant failure modes. The significant failure modes are as usual modelled as elements in a series system (see e.g. Thoft-Christensen & Baker [2)). Several methods to perform this estimate are presented including upper- and lower-bound estimates. Upper bounds for the failure probability estimate are obtained if the failure mechanisms are used. Lower bounds can be calculated on the basis of series systems where the elements are the non-failed elements in a non-failed structure (see Augusti & Baratta [3]).

Thoft-Christensen, Palle; SØrensen, John Dalsgaard

1984-01-01

86

Human Reliability Analysis for Small Modular Reactors  

Energy Technology Data Exchange (ETDEWEB)

Because no human reliability analysis (HRA) method was specifically developed for small modular reactors (SMRs), the application of any current HRA method to SMRs represents tradeoffs. A first- generation HRA method like THERP provides clearly defined activity types, but these activity types do not map to the human-system interface or concept of operations confronting SMR operators. A second- generation HRA method like ATHEANA is flexible enough to be used for SMR applications, but there is currently insufficient guidance for the analyst, requiring considerably more first-of-a-kind analyses and extensive SMR expertise in order to complete a quality HRA. Although no current HRA method is optimized to SMRs, it is possible to use existing HRA methods to identify errors, incorporate them as human failure events in the probabilistic risk assessment (PRA), and quantify them. In this paper, we provided preliminary guidance to assist the human reliability analyst and reviewer in understanding how to apply current HRA methods to the domain of SMRs. While it is possible to perform a satisfactory HRA using existing HRA methods, ultimately it is desirable to formally incorporate SMR considerations into the methods. This may require the development of new HRA methods. More practicably, existing methods need to be adapted to incorporate SMRs. Such adaptations may take the form of guidance on the complex mapping between conventional light water reactors and small modular reactors. While many behaviors and activities are shared between current plants and SMRs, the methods must adapt if they are to perform a valid and accurate analysis of plant personnel performance in SMRs.

Ronald L. Boring; David I. Gertman

2012-06-01

87

Comparison of methods for dependency determination between human failure events within human reliability analysis  

International Nuclear Information System (INIS)

The Human Reliability Analysis (HRA) is a highly subjective evaluation of human performance, which is an input for probabilistic safety assessment, which deals with many parameters of high uncertainty. The objective of this paper is to show that subjectivism can have a large impact on human reliability results and consequently on probabilistic safety assessment results and applications. The objective is to identify the key features, which may decrease of subjectivity of human reliability analysis. Human reliability methods are compared with focus on dependency comparison between Institute Jozef Stefan - Human Reliability Analysis (IJS-HRA) and Standardized Plant Analysis Risk Human Reliability Analysis (SPAR-H). Results show large differences in the calculated human error probabilities for the same events within the same probabilistic safety assessment, which are the consequence of subjectivity. The subjectivity can be reduced by development of more detailed guidelines for human reliability analysis with many practical examples for all steps of the process of evaluation of human performance. (author)

88

Reliability analysis of nonlinear MDOF dynamic systems  

International Nuclear Information System (INIS)

One of the more practical approximations that are currently used by the nuclear power profession for the purpose of design s well as analysis consists of utilizing the response modification factor (RMF). This factor was originally developed for single-degree-of-freedom systems for their nonlinear response analysis and design. Use of RMF is not effective, however, for multiple-degree-of-freedom (MDOF) systems because the nonlinear deformation usually concentrates at certain part of the systems. In this context, the present authors recently developed a method of optimum design which minimizes the spatial concentration of nonlinear deformation within each building, regardless of its specific dynamic characteristics. This paper demonstrates a method of reliability analysis for MDOF buildings thus optimally designed. In this paper, nonlinear MDOF shear-type systems designed optimally are subjected to seismic motions idealized as a nonstationary stochastic process. With the aids of the established RMF-ductility factor relationship for the optimum system, RMF can be used to develop the limit state in the equivalent linear systems

89

STARS software tool for analysis of reliability and safety  

International Nuclear Information System (INIS)

This paper reports on the STARS (Software Tool for the Analysis of Reliability and Safety) project aims at developing an integrated set of Computer Aided Reliability Analysis tools for the various tasks involved in systems safety and reliability analysis including hazard identification, qualitative analysis, logic model construction and evaluation. The expert system technology offers the most promising perspective for developing a Computer Aided Reliability Analysis tool. Combined with graphics and analysis capabilities, it can provide a natural engineering oriented environment for computer assisted reliability and safety modelling and analysis. For hazard identification and fault tree construction, a frame/rule based expert system is used, in which the deductive (goal driven) reasoning and the heuristic, applied during manual fault tree construction, is modelled. Expert system can explain their reasoning so that the analyst can become aware of the why and the how results are being obtained. Hence, the learning aspect involved in manual reliability and safety analysis can be maintained and improved

90

Probabilistic risk assessment course documentation. Volume 3. System reliability and analysis techniques, Session A - reliability  

International Nuclear Information System (INIS)

This course in System Reliability and Analysis Techniques focuses on the quantitative estimation of reliability at the systems level. Various methods are reviewed, but the structure provided by the fault tree method is used as the basis for system reliability estimates. The principles of fault tree analysis are briefly reviewed. Contributors to system unreliability and unavailability are reviewed, models are given for quantitative evaluation, and the requirements for both generic and plant-specific data are discussed. Also covered are issues of quantifying component faults that relate to the systems context in which the components are embedded. All reliability terms are carefully defined. 44 figs., 22 tabs

91

Reliability Analysis in Wireless Sensor Networks  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a Markov model for reliability using different types of Sensors and spares that replace sensors in case failure occurs. The primary idea in this paper is to address and analyze the reliability issues to device a reliable and fault tolerance model for a sensor network system. We analyzed the model in terms of reliability and MTTF (Mean-Time-To-Failure. Our research work focus on the mechanism for providing an alternative of a redundant network by replacing the faulty sensor with the available spares.

Vijay Kumar,

2011-04-01

92

Techniques of quantitative reliability analysis for control rod drive systems  

International Nuclear Information System (INIS)

Reliability analysis is a method by which the degree of successful performance of a system, under certain stipulated conditions, may be expressed in quantitative terms. Techniques of quantitative reliability analysis for control rod drive systems, which are presented, consist in: drawing up of system block diagrams as basis for the reliability analysis for normal and scram operation; estimation of possible fault rates (''mean rates'') of system components; reliability analysis of the complete control systems (total number of control rod drive mechanisms) on the basis of the analysis of the indjvidual rod drives. (author)

93

Individual Differences in Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

While human reliability analysis (HRA) methods include uncertainty in quantification, the nominal model of human error in HRA typically assumes that operator performance does not vary significantly when they are given the same initiating event, indicators, procedures, and training, and that any differences in operator performance are simply aleatory (i.e., random). While this assumption generally holds true when performing routine actions, variability in operator response has been observed in multiple studies, especially in complex situations that go beyond training and procedures. As such, complexity can lead to differences in operator performance (e.g., operator understanding and decision-making). Furthermore, psychological research has shown that there are a number of known antecedents (i.e., attributable causes) that consistently contribute to observable and systematically measurable (i.e., not random) differences in behavior. This paper reviews examples of individual differences taken from operational experience and the psychological literature. The impact of these differences in human behavior and their implications for HRA are then discussed. We propose that individual differences should not be treated as aleatory, but rather as epistemic. Ultimately, by understanding the sources of individual differences, it is possible to remove some epistemic uncertainty from analyses.

Jeffrey C. Joe; Ronald L. Boring

2014-06-01

94

Reliability Analysis of A System Using Intuitionstic Fuzzy Sets  

Directory of Open Access Journals (Sweden)

Full Text Available In General fuzzy sets are used to analyze the system Reliability. Present paper attempts to review the fuzzy/possibility tools when dealing with reliability of series-parallel network systems. Various issues of reasoning-based approaches in this framework are reviewed, discussed and compared with the standard approaches of reliability. To analyze the fuzzy system reliability, the reliability of each component of the system is considered as a trapezoidal intuitionstic fuzzy number. Trapezoidal intuitionstic fuzzy number arithmetic operations are also performed to evaluate the fuzzy reliability of the system. A numerical example is also given to illustrate the method.

M.K.Sharma

2012-07-01

95

Mathematical Methods in Survival Analysis, Reliability and Quality of Life  

CERN Document Server

Reliability and survival analysis are important applications of stochastic mathematics (probability, statistics and stochastic processes) that are usually covered separately in spite of the similarity of the involved mathematical theory. This title aims to redress this situation: it includes 21 chapters divided into four parts: Survival analysis, Reliability, Quality of life, and Related topics. Many of these chapters were presented at the European Seminar on Mathematical Methods for Survival Analysis, Reliability and Quality of Life in 2006.

Huber, Catherine; Mesbah, Mounir

2008-01-01

96

Combinatorial methods in netwotk reliability analysis  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a stochastic network is an undirected graph with unreliable edges and absolutely reliable nodes. Its connectedness probability is determined by reliability preserving network reduction. The principle of this method consists in splitting the underlying deterministic graph of the stochastic network into two edge-disjoint subgraphs via a separating node set. One of the subgraphs is replaced with a simpler structured graph (replacement graph in such a way that the interesting reliability criterion of the original stochastic network is retained. Special attention is given to the construction of suitable replacement graphs. The case of a 3-point separating node set is considered in more detail.

F. Beichelt

2014-01-01

97

RELIABILITY ANALYSIS OF PISTON MANUFACTURING SYSTEM  

Directory of Open Access Journals (Sweden)

Full Text Available Now days, internal combustion engines are used in most of the automobiles andmechanical machineries. The piston is a part without which no internal combustion engine canwork i.e., piston plays a vital role in almost all types of vehicles. So, the reliability of pistonmanufacturing system is most essential for the proper functioning of vehicles. In this paper, faulttree method is used to analyze the reliability of piston manufacturing system. Also, risk reductionworth is adopted as a measure of importance for identifying the crucial element that hassignificant impact on the reliability.

Amit Kumar

2011-01-01

98

Towards the Formal Reliability Analysis of Oil and Gas Pipelines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is customary to assess the reliability of underground oil and gas pipelines in the presence of excessive loading and corrosion effects to ensure a leak-free transport of hazardous materials. The main idea behind this reliability analysis is to model the given pipeline system as a Reliability Block Diagram (RBD) of segments such that the reliability of an individual pipeline segment can be represented by a random variable. Traditionally, computer simulation is used to perf...

Ahmed, Waqar; Hasan, Osman; Tahar, Sofiene; Hamdi, Mohammad Salah

2014-01-01

99

Reliability Analysis of a Mono-Tower Platform  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper a reliability analysis of a Mono-tower platform is presented. The failure modes, considered, are yelding in the tube cross-sections, and fatigue failure in the butt welds. The fatigue failure mode is investigated with a fatigue model, where the fatigue strength is expressed through SN relations. In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability as well as systems reliability is estimated using first-order reliability methods(FORM...

Kirkegaard, Poul Henning; Enevoldsen, I.; Sørensen, John Dalsgaard; Brincker, Rune

1988-01-01

100

Reliability Analysis of a Mono-Tower Platform  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper a reliability analysis of a Mono-tower platform is presented. The failure modes, considered, are yelding in the tube cross-sections, and fatigue failure in the butt welds. The fatigue failure mode is investigated with a fatigue model, where the fatigue strength is expressed through SN relations. In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability as well as systems reliability is estimated using first-order reliability methods(FORM...

Kirkegaard, Poul Henning; Enevoldsen, I.; Sørensen, John Dalsgaard; Brincker, Rune

2010-01-01

 
 
 
 
101

Reliability Analysis for Safety Grade PLC(POSAFE-Q)  

International Nuclear Information System (INIS)

Safety Grade PLC(Programmable Logic Controller), POSAFE-Q, was developed recently in accordance with nuclear regulatory and requirements. In this paper, describe reliability analysis for digital safety grade PLC (especially POSAFE-Q). Reliability analysis scope is Prediction, Calculation of MTBF (Mean Time Between Failure), FMEA (Failure Mode Effect Analysis), PFD (Probability of Failure on Demand). (author)

102

Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon  

CERN Document Server

Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] [2]. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in gl...

Garion, Cédric

2014-01-01

103

Issues in benchmarking human reliability analysis methods : a literature review.  

Energy Technology Data Exchange (ETDEWEB)

There is a diversity of human reliability analysis (HRA) methods available for use in assessing human performance within probabilistic risk assessment (PRA). Due to the significant differences in the methods, including the scope, approach, and underlying models, there is a need for an empirical comparison investigating the validity and reliability of the methods. To accomplish this empirical comparison, a benchmarking study is currently underway that compares HRA methods with each other and against operator performance in simulator studies. In order to account for as many effects as possible in the construction of this benchmarking study, a literature review was conducted, reviewing past benchmarking studies in the areas of psychology and risk assessment. A number of lessons learned through these studies are presented in order to aid in the design of future HRA benchmarking endeavors.

Lois, Erasmia (US Nuclear Regulatory Commission); Forester, John Alan; Tran, Tuan Q. (Idaho National Laboratory, Idaho Falls, ID); Hendrickson, Stacey M. Langfitt; Boring, Ronald L. (Idaho National Laboratory, Idaho Falls, ID)

2008-04-01

104

Probabilistic safety analysis and human reliability analysis. Proceedings. Working material  

International Nuclear Information System (INIS)

An international meeting on Probabilistic Safety Assessment (PSA) and Human Reliability Analysis (HRA) was jointly organized by Electricite de France - Research and Development (EDF DER) and SRI International in co-ordination with the International Atomic Energy Agency. The meeting was held in Paris 21-23 November 1994. A group of international and French specialists in PSA and HRA participated at the meeting and discussed the state of the art and current trends in the following six topics: PSA Methodology; PSA Applications; From PSA to Dependability; Incident Analysis; Safety Indicators; Human Reliability. For each topic a background paper was prepared by EDF/DER and reviewed by the international group of specialists who attended the meeting. The results of this meeting provide a comprehensive overview of the most important questions related to the readiness of PSA for specific uses and areas where further research and development is required. Refs, figs, tabs

105

Software For Analysis Of Reliability, Redundancy, And Cost  

Science.gov (United States)

CARRAC is software tool for combined analysis of reliability, redundancy, and cost of alternative choices of subsystem that is part of larger system. Uses various parameters entered from computer keyboard to determine subsystem and redundancy method (if any) that minimizes cost. Also, calculation selected from five different mathematical models that enable application of CARRAC to wide variety of cases. Uses parameters to calculate and compare total expected cost for alternatives of a chosen subsystem. Written in Microsoft Quick-Basic v4.5.

Patterson, R. L.; Suich, R. C.

1995-01-01

106

Human Reliability Analysis for Design: Using Reliability Methods for Human Factors Issues  

Energy Technology Data Exchange (ETDEWEB)

This paper reviews the application of human reliability analysis methods to human factors design issues. An application framework is sketched in which aspects of modeling typically found in human reliability analysis are used in a complementary fashion to the existing human factors phases of design and testing. The paper provides best achievable practices for design, testing, and modeling. Such best achievable practices may be used to evaluate and human system interface in the context of design safety certifications.

Ronald Laurids Boring

2010-11-01

107

Human Reliability Analysis for Design: Using Reliability Methods for Human Factors Issues  

International Nuclear Information System (INIS)

This paper reviews the application of human reliability analysis methods to human factors design issues. An application framework is sketched in which aspects of modeling typically found in human reliability analysis are used in a complementary fashion to the existing human factors phases of design and testing. The paper provides best achievable practices for design, testing, and modeling. Such best achievable practices may be used to evaluate and human system interface in the context of design safety certifications.

108

Design Parameters Influencing Reliability of CCGA Assembly: A Sensitivity Analysis  

Science.gov (United States)

Area Array microelectronic packages with small pitch and large I/O counts are now widely used in microelectronics packaging. The impact of various package design and materials/process parameters on reliability has been studied through extensive literature review. Reliability of Ceramic Column Grid Array (CCGA) package assemblies has been evaluated using JPL thermal cycle test results (-50(deg)/75(deg)C, -55(deg)/100(deg)C, and -55(deg)/125(deg)C), as well as those reported by other investigators. A sensitivity analysis has been performed using the literature da to study the impact of design parameters and global/local stress conditions on assembly reliability. The applicability of various life-prediction models for CCGA design has been investigated by comparing model's predictions with the experimental thermal cycling data. Finite Element Method (FEM) analysis has been conducted to assess the state of the stress/strain in CCGA assembly under different thermal cycling, and to explain the different failure modes and locations observed in JPL test assemblies.

Tasooji, Amaneh; Ghaffarian, Reza; Rinaldi, Antonio

2006-01-01

109

Suicide reporting content analysis: abstract development and reliability.  

Science.gov (United States)

Despite substantial research on media influences and the development of media guidelines on suicide reporting, research on the specifics of media stories that facilitate suicide contagion has been limited. The goal of the present study was to develop a content analytic strategy to code features in media suicide reports presumed to be influential in suicide contagion and determine the interrater reliability of the qualitative characteristics abstracted from newspaper stories. A random subset of 151 articles from a database of 1851 newspaper suicide stories published during 1988 through 1996, which were collected as part of a national study in the United States to identify factors associated with the initiation of youth suicide clusters, were evaluated. Using a well-defined content-analysis procedure, the agreement between raters in scoring key concepts of suicide reports from the headline, the pictorial presentation, and the text were evaluated. The results show that while the majority of variables in the content analysis were very reliable, assessed using the kappa statistic, and obtained excellent percentages of agreement, the reliability of complicated constructs, such as sensationalizing, glorifying, or romanticizing the suicide, was comparatively low. The data emphasize that before effective guidelines and responsible suicide reporting can ensue, further explication of suicide story constructs is necessary to ensure the implementation and compliance of responsible reporting on behalf of the media. PMID:18265736

Gould, Madelyn S; Midle, Jennifer Bassett; Insel, Beverly; Kleinman, Marjorie

2007-01-01

110

Reliability analysis of RC containment structures under combined loads  

International Nuclear Information System (INIS)

This paper discusses a reliability analysis method and load combination design criteria for reinforced concrete containment structures under combined loads. The probability based reliability analysis method is briefly described. For load combination design criteria, derivations of the load factors for accidental pressure due to a design basis accident and safe shutdown earthquake (SSE) for three target limit state probabilities are presented

111

POSSIBILITY AND EVIDENCE-BASED RELIABILITY ANALYSIS AND DESIGN OPTIMIZATION  

Directory of Open Access Journals (Sweden)

Full Text Available Engineering design under uncertainty has gained considerable attention in recent years. A great multitude of new design optimization methodologies and reliability analysis approaches are put forth with the aim of accommodating various uncertainties. Uncertainties in practical engineering applications are commonly classified into two categories, i.e., aleatory uncertainty and epistemic uncertainty. Aleatory uncertainty arises because of unpredictable variation in the performance and processes of systems, it is irreducible even adding more data or knowledge. On the other hand, epistemic uncertainty stems from lack of knowledge of the system due to limited data, measurement limitations, or simplified approximations in modeling system behavior and it can be reduced by obtaining more data or knowledge. More specifically, aleatory uncertainty is naturally represented by a statistical distribution and its associated parameters can be characterized by sufficient data. If, however, the data is limited and can be quantified in a statistical sense, epistemic uncertainty can be considered as an alternative tool in such a situation. Of the several optional treatments for epistemic uncertainty, possibility theory and evidence theory have proved to be the most computationally efficient and stable for reliability analysis and engineering design optimization. This study first attempts to provide a better understanding of uncertainty in engineering design by giving a comprehensive overview of its classifications, theories and design considerations. Then a review is conducted of general topics such as the foundations and applications of possibility theory and evidence theory. This overview includes the most recent results from theoretical research, computational developments and performance improvement of possibility theory and evidence theory with an emphasis on revealing the capability and characteristics of quantifying uncertainty from different perspectives. Possibility and evidence theory-based reliability methods have many advantages for practical engineering when compared with traditional probability-based reliability methods. They can work well under limited data while the latter need large amounts of information, more than possible in engineering practice due to aleatory and epistemic uncertainties. The possible directions for future work are summarized.

Hong-Zhong Huang

2013-01-01

112

Reliability  

Science.gov (United States)

In essence, reliability is the consistency of test results. To understand the meaning of reliability and how it relates to validity, imagine going to an airport to take flight #007 from Pittsburgh to San Diego. If, every time the airplane makes the flight

Christmann, Edwin P.; Badgett, John L.

2008-11-01

113

Reliability analysis of reactor systems by applying probability method  

International Nuclear Information System (INIS)

Probability method was chosen for analysing the reactor system reliability is considered realistic since it is based on verified experimental data. In fact this is a statistical method. The probability method developed takes into account the probability distribution of permitted levels of relevant parameters and their particular influence on the reliability of the system as a whole. The proposed method is rather general, and was used for problem of thermal safety analysis of reactor system. This analysis enables to analyze basic properties of the system under different operation conditions, expressed in form of probability they show the reliability of the system on the whole as well as reliability of each component

114

Reliability Analysis of Existing Vertical Wall Breakwaters  

DEFF Research Database (Denmark)

Vertical wall breakwaters are used under quite different conditions where failure of the breakwater or a part of it will have very different consequences. Further a number of existing vertical wall breakwaters have been subjected to significant wave loads which have caused partial failures of the structures. The main objective of this paper is to describe how the reliability of existing breakwater structures within the expected remaining lifetime can be estimated taking into account the available information.

Burcharth, H. F.; SØrensen, John Dalsgaard

1998-01-01

115

Communications reliability analysis in networked embedded systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a novel method to obtain an analytical expression of the reliability of a data transmission between two terminals of a networked system where components may fail in different manners, e.g. silent or babbling, and some failures may propagate to the adjacent components. This method is exemplified on a typical architecture for critical networked systems; comparison to a common approach which does not consider multiple failure modes and propagating failures shows the benefits ...

Aza-vallina, Damien; Denis, Bruno; Faure, Jean-marc

2011-01-01

116

Development of Reliability Analysis Toolkit for Analysing Plant Maintenance Data  

Directory of Open Access Journals (Sweden)

Full Text Available Plant failure and maintenance data can be found in abundance, however, their utilization as a basis for improvement action is not fully optimized. This happens because many reliability analyses based on plant data are tedious and time consuming due to non-standardized nature of the data being recorded. To overcome this issue, this study aims to develop a computer based reliability analysis toolkit to facilitate proper analysis of plant data. The toolkit can be used to perform both exploratory and inferential analysis. The developed toolkit has been demonstrated capable of assisting data gathering and analysis as well producing estimation of reliability measures.

Hussin Hilmi

2014-07-01

117

Reliability analysis of PLC safety equipment  

International Nuclear Information System (INIS)

FMEA analysis for Nuclear Safety Grade PLC, failure rate prediction for nuclear safety grade PLC, sensitivity analysis for components failure rate of nuclear safety grade PLC, unavailability analysis support for nuclear safety system

118

Uncertainty analysis of system reliability and availability for nuclear power generation stations  

International Nuclear Information System (INIS)

Uncertainty analysis of systems' reliability assessments with particular emphasis on commercial nuclear power generation stations has been investigated. A thorough review of reliability theory concepts which pertain to assessments of uncertainty is presented. Sources of uncertainty in reliability assessments are identified, and methods to account for their existence are discussed. Available methods for determining uncertainties in system characteristics (such as unavailability) by synthesizing the known or assumed uncertainties in component characteristics (propagation of errors) are presented and compared

119

Reliability Analysis Using Fault Tree Analysis: A Review  

Directory of Open Access Journals (Sweden)

Full Text Available This paper reviews the literature published on the recent modifications made in the field of risk assessment using Fault Tree Analysis (FTAin the last decade. This method was developed in 1960’s for the evaluation and estimation of system reliability and safety. In this paper we have presented the general procedure for FTA, its application in various fields and the modifications that have been made through the time to overcome the inadequacies of the method. In the last section some of the future wok is also discussed with a simplified methodology.

Ahmed Ali Baig

2013-06-01

120

Design and Analysis for Reliability of Wireless Sensor Network  

Directory of Open Access Journals (Sweden)

Full Text Available Reliability is an important performance indicator of wireless sensor network, to some application fields, which have high demands in terms of reliability, it is particularly important to ensure reliability of network. At present, the reliability research findings of wireless sensor network are much more at home and abroad, but they mainly improve network reliability from the networks topology, reliable protocol and application layer fault correction and so on, and reliability of network is comprehensive considered from hardware and software aspects is much less. This paper adopts bionic hardware to implement bionic reconfigurable of wireless sensor network nodes, so as to the nodes have able to change their structure and behavior autonomously and dynamically, in the cases of the part hardware are failure, and the nodes can realize bionic self-healing. Secondly, Markov state diagram and probability analysis method are adopted to realize solution of functional model for reliability, establish the relationship between reliability and characteristic parameters for sink nodes, analyze sink nodes reliability model, so as to determine the reasonable parameters of the model and ensure reliability of sink nodes.

Yongxian Song

2012-12-01

 
 
 
 
121

Systems reliability analysis for the national ignition facility  

International Nuclear Information System (INIS)

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

122

Semantic compared cross impact analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of cross impact analysis (CIA) is to predict the impact of a first event on a second. For organizations strategic planning, it is helpful to identify the impacts among organizations internal events and to compare these impacts to the corresponding impacts of external events from organizations competitors. For this, literature has introduced compared cross impact analysis (CCIA) that depicts advantages and disadvantages of the relationships between organizations events to the relations...

Thorleuchter, Dirk; Den Poel, Dirk

2014-01-01

123

Reliability Analysis of an Offshore Structure : A Case Study I  

DEFF Research Database (Denmark)

A jacket type offshore structure from the North Sea is considered. The time variant reliability is estimated for failure defined as brittie fradure and crack through the tubular roerober walls. The stochastic modeiling is described. The hot spot stress speetral moments as fundion of the stochastic variables are desenbed using spline fundion response surfaces. A Laplace integral expansion is used to estimate the time variant reliability. Parameter studies are performed for the reliability estimates and the results of the time variant and the time invariant reliability analyses are compared.

SØrensen, John Dalsgaard; Thoft-Christensen, Palle

1992-01-01

124

Reliability analysis of grid connected small wind turbine power electronics  

Energy Technology Data Exchange (ETDEWEB)

Grid connection of small permanent magnet generator (PMG) based wind turbines requires a power conditioning system comprising a bridge rectifier, a dc-dc converter and a grid-tie inverter. This work presents a reliability analysis and an identification of the least reliable component of the power conditioning system of such grid connection arrangements. Reliability of the configuration is analyzed for the worst case scenario of maximum conversion losses at a particular wind speed. The analysis reveals that the reliability of the power conditioning system of such PMG based wind turbines is fairly low and it reduces to 84% of initial value within one year. The investigation is further enhanced by identifying the least reliable component within the power conditioning system and found that the inverter has the dominant effect on the system reliability, while the dc-dc converter has the least significant effect. The reliability analysis demonstrates that a permanent magnet generator based wind energy conversion system is not the best option from the point of view of power conditioning system reliability. The analysis also reveals that new research is required to determine a robust power electronics configuration for small wind turbine conversion systems. (author)

Arifujjaman, Md.; Iqbal, M.T.; Quaicoe, J.E. [Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John' s, NL (Canada)

2009-09-15

125

Evaluating some Reliability Analysis Methodologies in Seismic Design  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Accounting for uncertainties that are present in geometric and material data of reinforced concrete buildings is performed in this study within the context of performance based seismic engineering design. Approach: Reliability of the expected performance state is assessed by using various methodologies based on finite element nonlinear static pushover analysis and specialized reliability software package. Reliability approaches that were considered included full coupling with an external finite element code and surface response based methods in conjunction with either first order reliability method or importance sampling method. Various types of probability distribution functions that model parameters uncertainties were introduced. Results: The probability of failure according to the used reliability analysis method and to the selected distribution of probabilities was obtained. Convergence analysis of the importance sampling method was performed. The required duration of analysis as function of the used reliability method was evaluated. Conclusion/Recommendations: It was found that reliability results are sensitive to the used reliability analysis method and to the selected distribution of probabilities. Durations of analysis for coupling methods were found to be higher than those associated to surface response based methods; one should however include time needed to derive these lasts. For the reinforced concrete building considered in this study, it was found that significant variations exist between all the considered reliability methodologies. The full coupled importance sampling method is recommended, but the first order reliability method applied on a surface response model can be used with good accuracy. Finally, the distributions of probabilities should be carefully identified since giving the mean and the standard deviation were found to be insufficient.

A. E. Ghoulbzouri

2011-01-01

126

Comparative Analysis of University Sports  

Directory of Open Access Journals (Sweden)

Full Text Available The authors compare collegiate sports governance in Turkey and the United States using comparative analysis techniques. Using the U.S. National Collegiate Athletic Association as a model, the authors evaluate structural and political aspects of the Turkish University Sports Federation to identify new potentialities for its growth and for the support of collegiate sports within Turkey.

Tiffany Allen

2012-01-01

127

Passive system reliability analysis challenges and a step towards resolution  

International Nuclear Information System (INIS)

In recent years, there have been a lot of efforts to quantify reliability of passive systems of type B. Some of such methodologies proposed are REPAS, RMPS and APSRA. These methods have uncovered some of the very important aspects related to passive system performance and reliability. However they lack to explain the important issues in model uncertainties, dynamic reliability and time dependence and variation of process parameters. This paper presents an improved methodology 'APSRA+' which will overcome the issue of process parameter deviations and their interdependencies. This APSRA+ also features a Monte Carlo simulation based dynamic reliability analysis, which will take care of dynamic failure characteristics of components used in passive systems. (author)

128

Reliability analysis framework for computer-assisted medical decision systems  

International Nuclear Information System (INIS)

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 training nor building multiple decision models to assess the case-specific CAD accuracy

129

The PAWS and STEM reliability analysis programs  

Science.gov (United States)

The PAWS and STEM programs are new design/validation tools. These programs provide a flexible, user-friendly, language-based interface for the input of Markov models describing the behavior of fault-tolerant computer systems. These programs produce exact solutions of the probability of system failure and provide a conservative estimate of the number of significant digits in the solution. PAWS uses a Pade approximation as a solution technique; STEM uses a Taylor series as a solution technique. Both programs have the capability to solve numerically stiff models. PAWS and STEM possess complementary properties with regard to their input space; and, an additional strength of these programs is that they accept input compatible with the SURE program. If used in conjunction with SURE, PAWS and STEM provide a powerful suite of programs to analyze the reliability of fault-tolerant computer systems.

Butler, Ricky W.; Stevenson, Philip H.

1988-01-01

130

Analysis of Computer Network Reliability and Criticality: Technique and Features  

Directory of Open Access Journals (Sweden)

Full Text Available The paper describes modern technologies of Computer Network Reliability. Software tool is developed to estimate of the CCN critical failure probability (construction of a criticality matrix by results of the FME(CA-technique. The internal information factors, such as collisions and congestion of switchboards, routers and servers, influence on a network reliability and safety (besides of hardware and software reliability and external extreme factors. The means and features of Failures Modes and Effects (Critical Analysis (FME(CA for reliability and criticality analysis of corporate computer networks (CCN are considered. The examples of FME(CA-Technique for structured cable system (SCS is given. We also discuss measures that can be used for criticality analysis and possible means of criticality reduction. Finally, we describe a technique and basic principles of dependable development and deployment of computer networks that are based on results of FMECA analysis and procedures of optimization choice of means for fault-tolerance ensuring.

Iraj Elyasi-Komari

2011-10-01

131

PSA applications and piping reliability analysis: where do we stand?  

Energy Technology Data Exchange (ETDEWEB)

This reviews a recently proposed framework for piping reliability analysis. The framework was developed to promote critical interpretations of operational data on pipe failures, and to support application-specific-parameter estimation.

Lydell, B.O.Y. [RSA Technologies, San Diego, CA (United States)

1997-10-01

132

A history and analysis of hydrogen maser reliability  

Science.gov (United States)

Hydrogen masers an integral part of the Deep Space Network, provide extremely accurate navigation about the outer planets, as well as precise location of tracking stations. Reliability of equipment over extended periods of time was considered. The Deep Space Network has a number of hydrogen masers deployed and in the test cycle, which enabled an analysis of reliability of several generations and breeds of construction. A history and analysis of hydrogen maser reliability over a three-year period was compiled several types of masers.

Curtright, J. B.

1982-01-01

133

A foundation for reliable spatial proteomics data analysis.  

Science.gov (United States)

Quantitative mass-spectrometry-based spatial proteomics involves elaborate, expensive, and time-consuming experimental procedures, and considerable effort is invested in the generation of such data. Multiple research groups have described a variety of approaches for establishing high-quality proteome-wide datasets. However, data analysis is as critical as data production for reliable and insightful biological interpretation, and no consistent and robust solutions have been offered to the community so far. Here, we introduce the requirements for rigorous spatial proteomics data analysis, as well as the statistical machine learning methodologies needed to address them, including supervised and semi-supervised machine learning, clustering, and novelty detection. We present freely available software solutions that implement innovative state-of-the-art analysis pipelines and illustrate the use of these tools through several case studies involving multiple organisms, experimental designs, mass spectrometry platforms, and quantitation techniques. We also propose sound analysis strategies for identifying dynamic changes in subcellular localization by comparing and contrasting data describing different biological conditions. We conclude by discussing future needs and developments in spatial proteomics data analysis. PMID:24846987

Gatto, Laurent; Breckels, Lisa M; Burger, Thomas; Nightingale, Daniel J H; Groen, Arnoud J; Campbell, Callum; Nikolovski, Nino; Mulvey, Claire M; Christoforou, Andy; Ferro, Myriam; Lilley, Kathryn S

2014-08-01

134

Reliability, Validity, Comparability and Practical Utility of Cybercrime-Related Data, Metrics, and Information  

Directory of Open Access Journals (Sweden)

Full Text Available With an increasing pervasiveness, prevalence and severity of cybercrimes, various metrics, measures and statistics have been developed and used to measure various aspects of this phenomenon. Cybercrime-related data, metrics, and information, however, pose important and difficult dilemmas regarding the issues of reliability, validity, comparability and practical utility. While many of the issues of the cybercrime economy are similar to other underground and underworld industries, this economy also has various unique aspects. For one thing, this industry also suffers from a problem partly rooted in the incredibly broad definition of the term “cybercrime”. This article seeks to provide insights and analysis into this phenomenon, which is expected to advance our understanding into cybercrime-related information.

Nir Kshetri

2013-02-01

135

Application of DFM in human reliability analysis  

International Nuclear Information System (INIS)

Combining with ATHEANA, the possible to identify EFCs and UAs using DFM is studied; and then Steam Generator Tube Rupture (SGTR) accident is modeled and solved. Through inductive analysis, 26 Prime Implicants (PIs) are obtained and the meaning of results is interpreted; and one of PIs is similar to the accident scenario of human failure event in one nuclear power plant. Finally, this paper discusses the methods of quantifying PIs, analysis of Error of commission (EOC) and so on. (authors)

136

Software reliability: Application of a reliability model to requirements error analysis  

Science.gov (United States)

The application of a software reliability model having a well defined correspondence of computer program properties to requirements error analysis is described. Requirements error categories which can be related to program structural elements are identified and their effect on program execution considered. The model is applied to a hypothetical B-5 requirement specification for a program module.

Logan, J.

1980-01-01

137

The effect of loss functions on empirical Bayes reliability analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the present study is to investigate the sensitivity of empirical Bayes estimates of the reliability function with respect to changing of the loss function. In addition to applying some of the basic analytical results on empirical Bayes reliability obtained with the use of the “popular” squared error loss function, we shall derive some expressions corresponding to empirical Bayes reliability estimates obtained with the Higgins–Tsokos, the Harris and our proposed logarithmic loss functions. The concept of efficiency, along with the notion of integrated mean square error, will be used as a criterion to numerically compare our results. It is shown that empirical Bayes reliability functions are in general sensitive to the choice of the loss function, and that the squared error loss does not always yield the best empirical Bayes reliability estimate.

Camara Vincent A. R.

1998-01-01

138

Phased-mission system reliability analysis. Volume 1: methodology  

Energy Technology Data Exchange (ETDEWEB)

Phased missions analysis is a method for reliability analysis of dyanmic engineered systems such as those found in the nuclear power industry. This report presents new, practical methods for analysis of phased missions. Specifically, techniques for calculating system reliability, availability, and expected number of failures are given. Demonstration of the methods is carried out through an analysis of an Emergency Core Cooling System of a Pressurized Water Reactor during a loss of coolant accident. While this example problem is realistically modelled, the input failure and repair data are hypothetical.

Fussell, J.B.

1981-07-01

139

Phased-mission system reliability analysis. Volume 1: methodology  

International Nuclear Information System (INIS)

Phased missions analysis is a method for reliability analysis of dyanmic engineered systems such as those found in the nuclear power industry. This report presents new, practical methods for analysis of phased missions. Specifically, techniques for calculating system reliability, availability, and expected number of failures are given. Demonstration of the methods is carried out through an analysis of an Emergency Core Cooling System of a Pressurized Water Reactor during a loss of coolant accident. While this example problem is realistically modelled, the input failure and repair data are hypothetical

140

Reliability Analysis of a Mono-Tower Platform  

DEFF Research Database (Denmark)

In this paper, a reliability analysis of a Mono-tower platform is presented. Te failure modes considered are yielding in the tube cross sections and fatigue failure in the butts welds. The fatigue failrue mode is investigated with a fatigue model, where the fatigue strength is expressed through SN relations. In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability as well as systems reliability, is estimated using first-order reliability methods(FORM). The sensitivity of the systems reliability to various parameters is investigated. It is shown that the fatigue limit state is a significant failure mode for the Mono-tower platform. Further, it is shown for the fatigue failure mode that the largest contributions to the overall uncertainty are due to the damping ratio, the inertia coefficient, the stress concentration factor, the model uncertainties, and the parameters describing the fatigue strength.

Kirkegaard, Poul Henning; Enevoldsen, I.

1990-01-01

 
 
 
 
141

Reliability analysis of repairable systems using system dynamics modeling and simulation  

Science.gov (United States)

Repairable standby system's study and analysis is an important topic in reliability. Analytical techniques become very complicated and unrealistic especially for modern complex systems. There have been attempts in the literature to evolve more realistic techniques using simulation approach for reliability analysis of systems. This paper proposes a hybrid approach called as Markov system dynamics (MSD) approach which combines the Markov approach with system dynamics simulation approach for reliability analysis and to study the dynamic behavior of systems. This approach will have the advantages of both Markov as well as system dynamics methodologies. The proposed framework is illustrated for a standby system with repair. The results of the simulation when compared with that obtained by traditional Markov analysis clearly validate the MSD approach as an alternative approach for reliability analysis.

Srinivasa Rao, M.; Naikan, V. N. A.

2014-07-01

142

Fatigue Reliability Analysis of a Mono-Tower Platform  

DEFF Research Database (Denmark)

In this paper, a fatigue reliability analysis of a Mono-tower platform is presented. The failure mode, fatigue failure in the butt welds, is investigated with two different models. The one with the fatigue strength expressed through SN relations, the other with the fatigue strength expressed through linear-elastic fracture mechanics (LEFM). In determining the cumulative fatigue damage, Palmgren-Miner's rule is applied. Element reliability, as well as systems reliability, is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters is investigated. The systems reliability index, estimated by using the fatigue elements with the fatigue strength expressed through SN relations, is found to be smaller than the systems reliability index estimated by using LEFM. It is shown that the systems reliability index is very sensitive to variations of the natural period, damping ratio, current, stress spectrum and parameters describing the fatigue strength. Further, soil damping is shown to be significant for the Mono-tower.

Kirkegaard, Poul Henning; SØrensen, John Dalsgaard

1991-01-01

143

Network reliability analysis for 3G cellular topology design  

Directory of Open Access Journals (Sweden)

Full Text Available Network reliability is an important issue in the topological design of the 3G cellular networks in order to guaranteeconsistent services. This paper aims to present network reliability analysis of various network topologies, including spanning tree, single ring, multiring, and two versions of hybrid ring-and-tree. We derived reliability analysis models for the hybrid ring-and-tree topologies in terms of the operational probability of the network links. The preliminary results show that the network reliability of the hybrid multiring-and-tree topologies is 116.78% and 13.78% higher than that of the spanning tree and the single ring topology, respectively, while it is only about 37.3% less than that of the pure multiring topologies.

Chutima Prommak

2010-07-01

144

Reliability Analysis of Repair Hours of RTPS through Weibull Model  

Directory of Open Access Journals (Sweden)

Full Text Available In our earlier paper Hungund CPS and Shrikant Patil [3], the suitability of the Weibull distribution for repair hours of seven units of Raichur Thermal Power Station (RTPS was tested using Chi-square test of Goodness of Fit (GoF. It was found that the Weibull Model best suites to the repair hours data of RTPS. In order to identify the best performing units of RTPS, further the results are need to be analyzed using Reliability theory. Hence in this paper, reliability analysis is studied using Weibull Model to identify the efficiencies of seven units of TPP. Based on reliability analysis, reliability rankings are computed to identify best performing units. Conclusions are drawn based on the results obtained.

Dr. C.P.S. Hungund

2014-08-01

145

Research on Law’s Mask Texture Analysis System Reliability  

Directory of Open Access Journals (Sweden)

Full Text Available Texture analysis of X-ray bone image using Laws’ mask for direct evaluation of the bone quality has been popular. Nevertheless, detailed reliability evaluation of the system classification has been relatively unknown. In this study, we will examine the reliability of the Laws’ mask system classification by using the confusion matrix approach. The precise detection system by using standard deviation statistical descriptor is supported by the true positive of 87.5% and true negative of 83.33%. In conclusion, the statistical analysis of the texture based osteoporosis detection system’s reliability discloses a true potential in this detection technique. Nevertheless, future researches should include a larger image database to enhance the reliability of the results.

Gan Hong Seng

2014-05-01

146

Reliability and comparability of the accelerometer and the linear position measuring device in resistance training.  

Science.gov (United States)

The purpose of this study was to determine the intermachine reliability attained from devices used to measure the common variables in sports performance. Repeatability conditions were established by creating a similar set of conditions under which the measurements were taken from both devices. The objectives of this research were to demonstrate the reliability between two devices in a bench press movement--the linear position measuring device (LPM) isoinertial dynamometer (T-Force) and the 3D (Myotest) accelerometer (AC)--and to compare the existing correlations between maximum velocity, maximum estimated strength, and peak power estimate variables in the bench press exercise. Forty bench press exercise trials were analyzed simultaneously, performed by 3 different subjects (age: 26.74 ± 1.2 years, height: 175.74 ± 4.04 cm, weight: 78.7 ± 3.35 kg) at maximum velocity (25 kg additional load). Three simple linear regression models were developed, supplied by the LPM on the basis of the AC data. The assumption of independence of errors was compared by means of the Durban-Watson test, and partial autocorrelation coefficients were established at an overall p < 0.05 significance level. It has not been possible to confirm the presence of a general correlation between the measurements of both devices. Regarding the assumption of independence of errors, the presence of generalized autocorrelation was confirmed. Linear regression analysis revealed an intermachine correlation in one of the nonconclusive cases, (peak power) variable and subject 1, r (10) = 0.640, p = 0.024. No partial autocorrelation was found. The devices should not be used interchangeably as instruments. PMID:22847523

Gomez-Piriz, Pedro T; Sanchez, Eva T; Manrique, David C; Gonzalez, Esther P

2013-06-01

147

Reliability analysis of nonlinear MDOF dynamic systems  

International Nuclear Information System (INIS)

This paper presents a simplified procedure to estimate the probability of failure for nonlinear MDOF shear-type systems optimally designed due to the seismic excitation. The excitation is idealized as a nonstationary stochastic process. With the aid of the response modification factor-ductility factor relationship established by the authors for these systems, 'an equivalent linear criteria' of such systems is introduced. Then, a linear response and the equivalent criteria can be used to evaluate the limit state probability as a solution to the classical first excursion probability problem at least in approximation. An example of a three-story building is demonstrated and the results are compared by using a simulation method. (orig.)

148

Use of COMCAN III in system design and reliability analysis  

International Nuclear Information System (INIS)

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

149

14 CFR Appendix N to Part 25 - Fuel Tank Flammability Exposure and Reliability Analysis  

Science.gov (United States)

... Fuel Tank Flammability Exposure and Reliability Analysis N Appendix N TO Part 25...Fuel Tank Flammability Exposure and Reliability Analysis N25.1General. ...requested, the time period assumed in the reliability analysis (60 flight hours must be...

2010-01-01

150

Comparison of Methods for Dependency Determination between Human Failure Events within Human Reliability Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The human reliability analysis (HRA is a highly subjective evaluation of human performance, which is an input for probabilistic safety assessment, which deals with many parameters of high uncertainty. The objective of this paper is to show that subjectivism can have a large impact on human reliability results and consequently on probabilistic safety assessment results and applications. The objective is to identify the key features, which may decrease subjectivity of human reliability analysis. Human reliability methods are compared with focus on dependency comparison between Institute Jožef Stefan human reliability analysis (IJS-HRA and standardized plant analysis risk human reliability analysis (SPAR-H. Results show large differences in the calculated human error probabilities for the same events within the same probabilistic safety assessment, which are the consequence of subjectivity. The subjectivity can be reduced by development of more detailed guidelines for human reliability analysis with many practical examples for all steps of the process of evaluation of human performance.

Marko ?epin

2008-07-01

151

Revisiting Methodological Issues in Transcript Analysis: Negotiated Coding and Reliability  

Science.gov (United States)

Transcript analysis is an important methodology to study asynchronous online educational discourse. The purpose of this study is to revisit reliability and validity issues associated with transcript analysis. The goal is to provide researchers with guidance in coding transcripts. For validity reasons, it is suggested that the first step is to…

Garrison, D. R.; Cleveland-Innes, M.; Koole, Marguerite; Kappelman, James

2006-01-01

152

Reliability analysis of I-section steel columns designed according to new Brazilian building codes  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents an evaluation of the safety of I-section steel columns designed according to the new revision of the Brazilian code for design of steel buildings (NBR8800 and to the code for loads and safety of structures (NBR8681. The safety evaluation is based on structural reliability analysis of columns designed to comply with these codes, and on advanced (FE-based analysis of actual column resistance. The effects of geometrical imperfections and residual stresses in column resistance are taken into account. The uncertainty in yield stress, elasticity modulus, geometrical imperfections and dead and live loads are considered in the reliability evaluation. Reliability indexes are obtained for several column configurations. These indexes reflect the safety of the columns designed according to the two building codes. Reliability indexes are compared with target reliability indexes used in calibration of the ANSI code and with indexes proposed in the new EUROCODE.

André T. Beck

2008-06-01

153

Reliability Analysis of Dynamic Stability in Waves  

DEFF Research Database (Denmark)

The assessment of a ship's intact stability is traditionally based on a semi-empirical deterministic concept that evaluates the characteristics of ship's calm water restoring leverarm curves. Today the ship is considered safe with respect to dynamic stability if its calm water leverarm curves exhibit sufficient characteristics with respect to slope at zero heel (GM value), maximum leverarm, positive range of stability and area below the leverarm curve. The rule-based requirements to calm water leverarm curves are entirely based on experience obtained from vessels in operation and recorded accidents in the past. The rules therefore only leaves little room for evaluation and improvement of safety of a ship's dynamic stability. A few studies have evaluated the probability of ship stability loss in waves using Monte Carlo simulations. However, since this probability may be in the order of 10-4 per ship year such brute force Monte-Carlo simulations are not always feasible due to the required computational resources. Previous studies of dynamic stability of ships in waves typically focused on the capsizing event. In this study the objective is to establish a procedure that can identify "critical wave patterns" that most likely will lead to the occurrence of a considered adverse event. Examples of such adverse events are stability loss, loss of maneuverability, cargo damage, and seasickness. The adverse events related to dynamic stability are considered as a function of the roll angle, the roll velocity, and the roll acceleration. This study will therefore describe how considered adverse events can be combined into a single utility function that in its scale expresses different magnitudes of the criticality (or assessed consequences) of the adverse events. It will be illustrated how the distribution of the exceedance probability may be established by an estimation of the out-crossing rate of the "safe set" defined by the utility function. This out-crossing rate will be established using the so-called Madsen's Formula.A bi-product of this analysis is a set of short wave time series that at different exceedance levels may be used in a codified evaluation of a vessels intact stability in waves.

SØborg, Anders Veldt

2004-01-01

154

Reliability of the Decay Heat Removal System of Phenix, Concepts and Qualitative Reliability Analysis  

International Nuclear Information System (INIS)

The decay heat removal in the Phenix Reactor has been designed with high level of safety and redundancy so that it should exist at least one way of removal whatever incident would be generated. In the following paragraph, we indicate the principal criteria used in the design, the different ways of operating and the global and qualitative reliability analysis in order to show the high degree of safety

155

Reliability analysis for Atucha II reactor protection system signals  

International Nuclear Information System (INIS)

Atucha II is a 745 MW Argentine Power Nuclear Reactor constructed by ENACE SA, Nuclear Argentine Company for Electrical Power Generation and SIEMENS AG KWU, Erlangen, Germany. A preliminary modular logic analysis of RPS (Reactor Protection System) signals was performed by means of the well known Swedish professional risk and reliability software named Risk-Spectrum taking as a basis a reference signal coded as JR17ER003 which command the two moderator loops valves. From the reliability and behavior knowledge for this reference signal follows an estimation of the reliability for the other 97 RPS signals. Because the preliminary character of this analysis Main Important Measures are not performed at this stage. Reliability is by the statistic value named unavailability predicted. The scope of this analysis is restricted from the measurement elements to the RPS buffer outputs. In the present context only one redundancy is analyzed so in the Instrumentation and Control area there no CCF (Common Cause Failures) present for signals. Finally those unavailability values could be introduced in the failure domain for the posterior complete Atucha II reliability analysis which includes all mechanical and electromechanical features. Also an estimation of the spurious frequency of RPS signals defined as faulty by no trip is performed

156

Reliability analysis of cluster-based ad-hoc networks  

Energy Technology Data Exchange (ETDEWEB)

The mobile ad-hoc wireless network (MAWN) is a new and emerging network scheme that is being employed in a variety of applications. The MAWN varies from traditional networks because it is a self-forming and dynamic network. The MAWN is free of infrastructure and, as such, only the mobile nodes comprise the network. Pairs of nodes communicate either directly or through other nodes. To do so, each node acts, in turn, as a source, destination, and relay of messages. The virtue of a MAWN is the flexibility this provides; however, the challenge for reliability analyses is also brought about by this unique feature. The variability and volatility of the MAWN configuration makes typical reliability methods (e.g. reliability block diagram) inappropriate because no single structure or configuration represents all manifestations of a MAWN. For this reason, new methods are being developed to analyze the reliability of this new networking technology. New published methods adapt to this feature by treating the configuration probabilistically or by inclusion of embedded mobility models. This paper joins both methods together and expands upon these works by modifying the problem formulation to address the reliability analysis of a cluster-based MAWN. The cluster-based MAWN is deployed in applications with constraints on networking resources such as bandwidth and energy. This paper presents the problem's formulation, a discussion of applicable reliability metrics for the MAWN, and illustration of a Monte Carlo simulation method through the analysis of several example networks.

Cook, Jason L. [Quality Engineering and System Assurance, Armament Research Development Engineering Center, Picatinny Arsenal, NJ (United States); Ramirez-Marquez, Jose Emmanuel [School of Systems and Enterprises, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ 07030 (United States)], E-mail: Jose.Ramirez-Marquez@stevens.edu

2008-10-15

157

Distribution-level electricity reliability: Temporal trends using statistical analysis  

International Nuclear Information System (INIS)

This paper helps to address the lack of comprehensive, national-scale information on the reliability of the U.S. electric power system by assessing trends in U.S. electricity reliability based on the information reported by the electric utilities on power interruptions experienced by their customers. The research analyzes up to 10 years of electricity reliability information collected from 155 U.S. electric utilities, which together account for roughly 50% of total U.S. electricity sales. We find that reported annual average duration and annual average frequency of power interruptions have been increasing over time at a rate of approximately 2% annually. We find that, independent of this trend, installation or upgrade of an automated outage management system is correlated with an increase in the reported annual average duration of power interruptions. We also find that reliance on IEEE Standard 1366-2003 is correlated with higher reported reliability compared to reported reliability not using the IEEE standard. However, we caution that we cannot attribute reliance on the IEEE standard as having caused or led to higher reported reliability because we could not separate the effect of reliance on the IEEE standard from other utility-specific factors that may be correlated with reliance on the IEEE standard. - Highlights: ? We assess trends in electricity reliability based on the information reported by the electric utilities. ? We use rigorous statistical techniques to account for utility-specific differences. ? We find modest declines in reliability analyzing interruption duration and frequency experienced by utility customers. ? Installation or upgrade of an OMS is correlated to an increase in reported duration of power interruptions. ? We find reliance in IEEE Standard 1366 is correlated with higher reported reliability.

158

The Reliability of Content Analysis of Computer Conference Communication  

DEFF Research Database (Denmark)

The focus of this article is the reliability of content analysis of students' computer conference communication. Content analysis is often used when researching the relationship between learning and the use of information and communications technology in educational settings. A number of studies where content analysis is used and classification systems are developed are presented and discussed along with the author's own development and use of a classification system. However, the question of the reliability of content analysis is not often addressed or discussed in the literature. On examining the reliability of classifications in an empirical study of study groups' academic discussions in computer conferences in a distance education course, the present author found the reliability to be extraordinarily low. For some classifications the deviation was as high as 13% when the same person (coder) classified the same computer conference message at two different times. When two different coders classified the same computer conference messages, the deviation was as high as 27%. This low reliability-and the lack of discussion of this crucial matter in the literature-has profound implications. Not just for the author's own research but for all studies and results based upon content analysis of computer conference communication. Therefore, this issue needs to be addressed. A possible solution-where each computer conference message can be classified as having both one and/or other kinds of information-is proposed. This might not be a solution to the problem of low reliability of content analysis and the use of classification systems, but it does shed light on the problem and goes some way towards reducing it.

Rattleff, Pernille

2007-01-01

159

Reliability design analysis on electric double layer capacitor: Supercap  

Science.gov (United States)

An electric double layer capacitor, SUPERCAP, providing up to one million microfarad capacitance in less than one cubic inch was developed. Because of its ultra high capacitance and very low leakage current, the SUPERCAP can be used as the standby power source to power CMOS RAMs and microcomputers during undesirable primary power interruptions. The reliability design analysis on SUPERCAPs by means of failure mode and effects analysis is described together with the product structure, manufacturing process, and the reliability test results of the finished SUPERCAPs.

Watanabe, N.

1982-09-01

160

Notes on numerical reliability of several statistical analysis programs  

Science.gov (United States)

This report presents a benchmark analysis of several statistical analysis programs currently in use in the USGS. The benchmark consists of a comparison between the values provided by a statistical analysis program for variables in the reference data set ANASTY and their known or calculated theoretical values. The ANASTY data set is an amendment of the Wilkinson NASTY data set that has been used in the statistical literature to assess the reliability (computational correctness) of calculated analytical results.

Landwehr, J. M.; Tasker, G. D.

1999-01-01

 
 
 
 
161

Reliability analysis of TLP tethers under impulsive loading  

International Nuclear Information System (INIS)

In the present study, reliability assessment of Tension Leg Platform (TLP) tethers against maximum tension (i.e. tension exceeding yield) has been carried out under combined action of extreme wave and impulsive forces. For this purpose, a nonlinear dynamic analysis of TLP has been carried out in time domain. A limit state function for maximum tension (i.e. tension exceeding yield) has been derived employing Von-Mises theory of failure. Using this derived limit state function and responses obtained after dynamic analysis under sinusoidal, half-triangular and triangular impulsive forces, reliability assessment of the TLP tethers has been carried out. Design point, important for probabilistic design of tethers, has been located on the failure surface after solving a constrained optimization problem. To study the influence of various random variables on tether reliability, sensitivity analysis has been carried out. Effects of angle of impact; effect of variable submergence; and effect of material yield strength on tether reliability have also been studied on parametric basis. Effect of uncertainty on overall tether reliability has also been discussed to show the importance of quality control in the various design parameters

162

Reliability analysis of reactor inspection robot(RIROB)  

International Nuclear Information System (INIS)

This report describes the method and the result of the reliability analysis of RIROB developed in Korea Atomic Energy Research Institute. There are many classic techniques and models for the reliability analysis. These techniques and models have been used widely and approved in other industries such as aviation and nuclear industry. Though these techniques and models have been approved in real fields they are still insufficient for the complicated systems such RIROB which are composed of computer, networks, electronic parts, mechanical parts, and software. Particularly the application of these analysis techniques to digital and software parts of complicated systems is immature at this time thus expert judgement plays important role in evaluating the reliability of the systems at these days. In this report we proposed a method which combines diverse evidences relevant to the reliability to evaluate the reliability of complicated systems such as RIROB. The proposed method combines diverse evidences and performs inference in formal and in quantitative way by using the benefits of Bayesian Belief Nets (BBN)

163

Evaluation of the reliability of computerized profile cephalometric analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The use of computers as an auxiliary instrument for case evaluation and procedures in health sciences is not new, and their advantages are well known. A growing number of orthodontists are using computerized systems for cephalometric analysis. Thus, this study evaluated the reliability of both computerized and manual methods used for creating profile cephalograms. Fifty profile radiographs were selected from the files of the Post-Graduate Course in Orthodontics at the Dental School of the Federal University of Rio de Janeiro. The good quality of the material was the only necessary requirement for selection. Results were submitted to the interclass correlation coefficient and a reliable similarity between cephalometric data obtained through both evaluated methods was found. However, the clinical utilization of computerized cephalometric analysis is not absolutely reliable.

Ferreira José Tarcísio Lima

2002-01-01

164

Architecture based Reliability Analysis of Continuously Running Concurrent Software Applications  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this paper is to describe a reliability and availability analysis methodology for a continuously running, concurrent application. We propose a state space approach to epresent the architecture of a concurrent application, which is then mapped to an irreducible discrete time Markov chain (DTMC to obtain architectural statistics. We discuss how the application architecture can be extracted from profile data to facilitate the use of our methodology to analyze the reliability of practical software applications. We illustrate the methodology using a case study of a MRSS news ticker application. The state space explosion issue which may arise in the practical application of the methodology is then discussed and methods to alleviate the issue are suggested. To the best of our nowledge, this research is one of the first steps in pushing the state of the art in architecturebased software reliability analysis from sequential to concurrent software applications.

Rehab A. El Kharboutly

2008-01-01

165

Distribution System Reliability Analysis for Smart Grid Applications  

Science.gov (United States)

Reliability of power systems is a key aspect in modern power system planning, design, and operation. The ascendance of the smart grid concept has provided high hopes of developing an intelligent network that is capable of being a self-healing grid, offering the ability to overcome the interruption problems that face the utility and cost it tens of millions in repair and loss. To address its reliability concerns, the power utilities and interested parties have spent extensive amount of time and effort to analyze and study the reliability of the generation and transmission sectors of the power grid. Only recently has attention shifted to be focused on improving the reliability of the distribution network, the connection joint between the power providers and the consumers where most of the electricity problems occur. In this work, we will examine the effect of the smart grid applications in improving the reliability of the power distribution networks. The test system used in conducting this thesis is the IEEE 34 node test feeder, released in 2003 by the Distribution System Analysis Subcommittee of the IEEE Power Engineering Society. The objective is to analyze the feeder for the optimal placement of the automatic switching devices and quantify their proper installation based on the performance of the distribution system. The measures will be the changes in the reliability system indices including SAIDI, SAIFI, and EUE. The goal is to design and simulate the effect of the installation of the Distributed Generators (DGs) on the utility's distribution system and measure the potential improvement of its reliability. The software used in this work is DISREL, which is intelligent power distribution software that is developed by General Reliability Co.

Aljohani, Tawfiq Masad

166

GO-FLOW; A new reliability analysis methodology  

Energy Technology Data Exchange (ETDEWEB)

In this paper a new reliability analysis methodology, GO-FLOW, is presented. Detailed explanations and two examples of GO-GLOW analysis are given. The GO-FLOW is a success-oriented system analysis technique. The modeling technique produces the GO-FLOW chart, which is composed of operators and signal lines and represents a function of the system. The examples of analysis show the applicability of the GO-FLOW method to a phased mission problem and to a time-dependent unavailability analysis.

Matsuoka, T.; Kobayashi, M. (Ship Research Inst., Tokyo (Japan))

1988-01-01

167

Intra-rater reliability of the posture analysis tool kit  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english BACKGROUND: Health care professionals mainly assess posture through qualitative observation of the relationship between a plumb line and specified anatomical landmarks. However, quantitative assessments of spinal alignment are mostly done by biophotogrammetry and are limited to laboratory environmen [...] ts. The Posture Analysis Toolkit (PAT), a photogrammetric measurement instrument was developed in 2009 to assess standing posture. AIM: The aim of this study was to test the intra-rater reliability of the Posture Analysis Toolkit. METHODOLOGY: A prospective, cross-sectional study design was conducted. Fourteen participants were required to do three measurements of the posture of a single subject using the PAT. Photographs of the anterior and left lateral upright standing posture were taken once, and imported three times for computerised analysis. Reliability was determined using descriptive statistics per session, confidence interval for the median difference between sessions, 95% limits of agreement and Spearman correlations. RESULTS: In this study the intra-rater reliability of PAT between sessions was good. CONCLUSION: The Posture Analysis Toolkit was tested and proved to be reliable for use as an instrument for the assessment of standing postural alignment. Recommendations are suggested for the development of the PAT.

Ronette, Hough; Riette, Nel.

2013-04-01

168

Analysis of reliability parameters of conveyor belt joints  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the article was found the causes defects vulcanized joints based on analysis of operating of conveyor belts, given the physical and mathematical model of failure joints. Measures have been developed to improve the reliability of the joints of conveyor belts.

Temerzhanov, Adil; Stolpovskikh, Ivan; S?adkowski, Aleksander

2012-01-01

169

Intra-rater reliability of the posture analysis tool kit  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english BACKGROUND: Health care professionals mainly assess posture through qualitative observation of the relationship between a plumb line and specified anatomical landmarks. However, quantitative assessments of spinal alignment are mostly done by biophotogrammetry and are limited to laboratory environmen [...] ts. The Posture Analysis Toolkit (PAT), a photogrammetric measurement instrument was developed in 2009 to assess standing posture. AIM: The aim of this study was to test the intra-rater reliability of the Posture Analysis Toolkit. METHODOLOGY: A prospective, cross-sectional study design was conducted. Fourteen participants were required to do three measurements of the posture of a single subject using the PAT. Photographs of the anterior and left lateral upright standing posture were taken once, and imported three times for computerised analysis. Reliability was determined using descriptive statistics per session, confidence interval for the median difference between sessions, 95% limits of agreement and Spearman correlations. RESULTS: In this study the intra-rater reliability of PAT between sessions was good. CONCLUSION: The Posture Analysis Toolkit was tested and proved to be reliable for use as an instrument for the assessment of standing postural alignment. Recommendations are suggested for the development of the PAT.

Ronette, Hough; Riette, Nel.

170

Human reliability analysis of Lingao Nuclear Power Station  

International Nuclear Information System (INIS)

The necessity of human reliability analysis (HRA) of Lingao Nuclear Power Station are analyzed, and the method and operation procedures of HRA is briefed. One of the human factors events (HFE) is analyzed in detail and some questions of HRA are discussed. The authors present the analytical results of 61 HFEs, and make a brief introduction of HRA contribution to Lingao Nuclear Power Station

171

Reliability analysis of the WWER-440 Type 213 safety systems  

International Nuclear Information System (INIS)

The design and function of two systems included in the localization of design basis accidents in the Czechoslovak nuclear power plant at Mochovce (four WWER-440 units of type 213) are described. These accidents are represented by LOCA (I.D. 500) with loss of in-site power and maximum rated earthquake (6 balls on the MSK-64 scale). The passive pressure accumulator system and the low pressure injection system of ECCS (LPIS) were chosen for the reliability analysis (fault tree); attention was centered primarily on the effect of human error. Uncertainty analysis of the two systems was carried out as the next step. The results of the reliability analysis are presented in graphical and tabulated forms. The analysis revealed a great importance of correct and verified selection of the top event of the fault tree (the passive system) and stressed the need for periodical testing during the refueling on the LPIS system. (author). 14 figs., 1 tab., 3 refs

172

Reliable analysis for pressure vessel based on ANSYS  

International Nuclear Information System (INIS)

With the PDS of ANSYS procedure, the ramdomicity of the actually structure design parameters is simulated, by taking the wall thickness, pressure load and elastic module as input random variables. Based on the reliability analysis of the pressure vessel by Monte-Carlo procedure, the stress probability distribution of this finite element analysis model and the sensitivity of the design parameters such as the pressure load and wall thickness to the stress distribution are obtained. (authors)

173

Modelling application for cognitive reliability and error analysis method  

Directory of Open Access Journals (Sweden)

Full Text Available The automation of production systems has delegated to machines the execution of highly repetitive and standardized tasks. In the last decade, however, the failure of the automatic factory model has led to partially automated configurations of production systems. Therefore, in this scenario, centrality and responsibility of the role entrusted to the human operators are exalted because it requires problem solving and decision making ability. Thus, human operator is the core of a cognitive process that leads to decisions, influencing the safety of the whole system in function of their reliability. The aim of this paper is to propose a modelling application for cognitive reliability and error analysis method.

Fabio De Felice

2013-10-01

174

A study of operational and testing reliability in software reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

Software reliability is an important aspect of any complex equipment today. Software reliability is usually estimated based on reliability models such as nonhomogeneous Poisson process (NHPP) models. Software systems are improving in testing phase, while it normally does not change in operational phase. Depending on whether the reliability is to be predicted for testing phase or operation phase, different measure should be used. In this paper, two different reliability concepts, namely, the operational reliability and the testing reliability, are clarified and studied in detail. These concepts have been mixed up or even misused in some existing literature. Using different reliability concept will lead to different reliability values obtained and it will further lead to different reliability-based decisions made. The difference of the estimated reliabilities is studied and the effect on the optimal release time is investigated.

Yang, B.; Xie, M

2000-12-01

175

On Reliability Analysis of Fault-tolerant Multistage Interconnection Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The design of a suitable interconnection network for inter-processor communication is one of the key issues of the system performance. The reliability of these networks and their ability to continue operating despite failures are major concerns in determining the overall system performance. In this paper a new irregular network IABN has been proposed modifying existing ABN network. ABN is a regular multipath network with limited fault tolerance. The reliabilities of the IABN and ABN multi-stage interconnection networks have been calculated and compared in terms of the Upper and Lower bounds of Mean time to failure (MTTF.The IABN is a network that provides much better fault-tolerance by providing three time more paths between any pair of source-destination and better reliability at the expanse of little more cost than ABN.

Rinkle Aggarwal

2008-11-01

176

Accident Sequence Evaluation Program: Human reliability analysis procedure  

Energy Technology Data Exchange (ETDEWEB)

This document presents a shortened version of the procedure, models, and data for human reliability analysis (HRA) which are presented in the Handbook of Human Reliability Analysis With emphasis on Nuclear Power Plant Applications (NUREG/CR-1278, August 1983). This shortened version was prepared and tried out as part of the Accident Sequence Evaluation Program (ASEP) funded by the US Nuclear Regulatory Commission and managed by Sandia National Laboratories. The intent of this new HRA procedure, called the ''ASEP HRA Procedure,'' is to enable systems analysts, with minimal support from experts in human reliability analysis, to make estimates of human error probabilities and other human performance characteristics which are sufficiently accurate for many probabilistic risk assessments. The ASEP HRA Procedure consists of a Pre-Accident Screening HRA, a Pre-Accident Nominal HRA, a Post-Accident Screening HRA, and a Post-Accident Nominal HRA. The procedure in this document includes changes made after tryout and evaluation of the procedure in four nuclear power plants by four different systems analysts and related personnel, including human reliability specialists. The changes consist of some additional explanatory material (including examples), and more detailed definitions of some of the terms. 42 refs.

Swain, A.D.

1987-02-01

177

Accident Sequence Evaluation Program: Human reliability analysis procedure  

International Nuclear Information System (INIS)

This document presents a shortened version of the procedure, models, and data for human reliability analysis (HRA) which are presented in the Handbook of Human Reliability Analysis With emphasis on Nuclear Power Plant Applications (NUREG/CR-1278, August 1983). This shortened version was prepared and tried out as part of the Accident Sequence Evaluation Program (ASEP) funded by the US Nuclear Regulatory Commission and managed by Sandia National Laboratories. The intent of this new HRA procedure, called the ''ASEP HRA Procedure,'' is to enable systems analysts, with minimal support from experts in human reliability analysis, to make estimates of human error probabilities and other human performance characteristics which are sufficiently accurate for many probabilistic risk assessments. The ASEP HRA Procedure consists of a Pre-Accident Screening HRA, a Pre-Accident Nominal HRA, a Post-Accident Screening HRA, and a Post-Accident Nominal HRA. The procedure in this document includes changes made after tryout and evaluation of the procedure in four nuclear power plants by four different systems analysts and related personnel, including human reliability specialists. The changes consist of some additional explanatory material (including examples), and more detailed definitions of some of the terms. 42 refs

178

Reliability analysis for inspections of CANDU components and systems  

International Nuclear Information System (INIS)

Condition assessment of complex systems requires more than inspection data for the individual elements of the system. At the component level, knowledge of the probability of detection (POD) and sizing accuracy for defects is needed to properly interpret results. At the system level, probabilistic and deterministic methods guide safety assessments and life management strategies. The field of reliability analysis provides a framework for quantitative application of inspection results to both levels. Quantitative knowledge of inspection reliability can reduce the requirement to use conservative values for every quantity. A sound analysis of inspection reliability can produce a more targeted inspection scope, leading to fewer but more effective inspections and, consequently, lower radiation dose. Restart cases can be based on correct detection probability distributions rather than worst-case scenarios, and inspection intervals and expected life estimates can be optimized based on measured sizing uncertainties. This paper illustrates applications of inspection reliability analysis to optimize the inspect-repair-operate cycle for major CANDU primary heat transport elements, such as steam generator tubing, feeder piping, and fuel channels. (author)

179

Strength Reliability Analysis of Turbine Blade Using Surrogate Models  

Directory of Open Access Journals (Sweden)

Full Text Available There are many stochastic parameters that have an effect on the reliability of steam turbine blades performance in practical operation. In order to improve the reliability of blade design, it is necessary to take these stochastic parameters into account. In this study, a variable cross-section twisted blade is investigated and geometrical parameters, material parameters and load parameters are considered as random variables. A reliability analysis method as a combination of a Finite Element Method (FEM, a surrogate model and Monte Carlo Simulation (MCS, is applied to solve the blade reliability analysis. Based on the blade finite element parametrical model and the experimental design, two kinds of surrogate models, Polynomial Response Surface (PRS and Artificial Neural Network (ANN, are applied to construct the approximation analytical expressions between the blade responses (including maximum stress and deflection and random input variables, which act as a surrogate of finite element solver to drastically reduce the number of simulations required. Then the surrogate is used for most of the samples needed in the Monte Carlo method and the statistical parameters and cumulative distribution functions of the maximum stress and deflection are obtained by Monte Carlo simulation. Finally, the probabilistic sensitivities analysis, which combines the magnitude of the gradient and the width of the scatter range of the random input variables, is applied to evaluate how much the maximum stress and deflection of the blade are influenced by the random nature of input parameters.

Wei Duan

2014-05-01

180

Maintenance management of railway infrastructures based on reliability analysis  

International Nuclear Information System (INIS)

Railway infrastructure maintenance plays a crucial role for rail transport. It aims at guaranteeing safety of operations and availability of railway tracks and related equipment for traffic regulation. Moreover, it is one major cost for rail transport operations. Thus, the increased competition in traffic market is asking for maintenance improvement, aiming at the reduction of maintenance expenditures while keeping the safety of operations. This issue is addressed by the methodology presented in the paper. The first step of the methodology consists of a family-based approach for the equipment reliability analysis; its purpose is the identification of families of railway items which can be given the same reliability targets. The second step builds the reliability model of the railway system for identifying the most critical items, given a required service level for the transportation system. The two methods have been implemented and tested in practical case studies, in the context of Rete Ferroviaria Italiana, the Italian public limited company for railway transportation.

 
 
 
 
181

Beyond reliability, multi-state failure analysis of satellite subsystems: A statistical approach  

International Nuclear Information System (INIS)

Reliability is widely recognized as a critical design attribute for space systems. In recent articles, we conducted nonparametric analyses and Weibull fits of satellite and satellite subsystems reliability for 1584 Earth-orbiting satellites launched between January 1990 and October 2008. In this paper, we extend our investigation of failures of satellites and satellite subsystems beyond the binary concept of reliability to the analysis of their anomalies and multi-state failures. In reliability analysis, the system or subsystem under study is considered to be either in an operational or failed state; multi-state failure analysis introduces 'degraded states' or partial failures, and thus provides more insights through finer resolution into the degradation behavior of an item and its progression towards complete failure. The database used for the statistical analysis in the present work identifies five states for each satellite subsystem: three degraded states, one fully operational state, and one failed state (complete failure). Because our dataset is right-censored, we calculate the nonparametric probability of transitioning between states for each satellite subsystem with the Kaplan-Meier estimator, and we derive confidence intervals for each probability of transitioning between states. We then conduct parametric Weibull fits of these probabilities using the Maximum Likelihood Estimation (MLE) approach. After validating the results, we compare the reliability versus multi-state failure analyses of three satellite subsystems: the thruster/fuel; the telemetry, tracking, and control (TTC); and the gyro/sensor/reaction wheel subsystems. The results are particularly revealing of the insights that can be gleaned from multi-state failure analysis and the deficiencies, or blind spots, of the traditional reliability analysis. In addition to the specific results provided here, which should prove particularly useful to the space industry, this work highlights the importance of conducting, beyond the traditional reliability analysis, multi-state failure analysis of any engineering system when seeking to understand its failure behavior.

182

Analysis on Reliability of Wine Tasters’ Evaluation Results Based on the Analysis of Variance  

Directory of Open Access Journals (Sweden)

Full Text Available Based on the data related to the evaluation score of wine taster provided in 2012 CUMCM, this study firstly adopts confidence interval method to eliminate the effect of wine tasters’ personal differences. Then, by using analysis of variance, we make a test of significance on evaluation results of wine tasters from Group A and B at the significance level of 0.05. Results show that there is no significant difference in the sensory evaluation results of wine tasters from the two groups. By comparing the variance of comprehensive scores given by wine tasters from the two groups, we confirm the evaluation results of wine tasters from which group are more reliable. Results of the model shows that variances of evaluation results given by wine tasters from Group B are all smaller than that of Group A, which prove that evaluation result of wine tasters from Group B is more reliable.

Wang Yufei

2013-10-01

183

FAMILIARIZATION, RELIABILITY, AND COMPARABILITY OF A 40-M MAXIMAL SHUTTLE RUN TEST  

Directory of Open Access Journals (Sweden)

Full Text Available The aims of this study were to examine familiarization and reliability associated with a 40-m maximal shuttle run test (40-m MST, and to compare performance measures from the test with those of a typical unidirectional multiple sprint running test (UMSRT. 12 men and 4 women completed four trials of the 40-m MST (8 × 40-m; 20 s rest periods followed by one trial of a UMSRT (12 × 30-m; repeated every 35 s; with seven days between trials. All trials were conducted indoors and performance times were recorded via twin-beam photocells. Significant between-trial differences in mean 40-m MST times were indicative of learning effects between trials 1 and 2. Test-retest reliability across the remaining trials as determined by coefficient of variation (CV and intraclass correlation coefficient (ICC revealed: a very good reliability for measures of fastest and mean shuttle time (CV = 1.1 - 1.3%; ICC = 0.91 - 0.92; b good reliability for measures of blood lactate (CV = 10.1 - 23.9%; ICC = 0.74 - 0.82 and ratings of perceived exertion (CV = 5.3 - 7.6%; ICC = 0.79 - 0.84; and c poor reliability for measures of fatigue (CV = 38.7%; ICC = 0.59. Comparisons between performance indices of the 40-m MST and the UMSRT revealed significant correlations between all measures, except pre-test blood lactate concentration (r = 0. 47. Whilst the 40-m MST does not appear to provide more information than can be gleaned from a typical UMSRT, following the completion of a familiarization trial, the 40-m MST provides an alternative and, except for fatigue measures, reliable means of evaluating repeated sprint ability

Mark Glaister

2009-03-01

184

RELIABILITY AND SAFETY ANALYSIS OF THE PROCESS PLANT  

Directory of Open Access Journals (Sweden)

Full Text Available A safety model involves qualitative and quantitative information processing was derived in thispaper. Process safety analysis which including qualitative fault event identification, relative frequenciesand event probability function as well as consequence analysis was provided. As a case study theammonia plant production was used. The obtained results have shown successful application cognitivemodelling to process reliability analysis. The highest possible uncertainty was obtained when allprobabilities are equal one, and zero entropy is ecountered for relationship that are totally deterministic. Foraccidents detection the model was forcasted the future behavior of the system and than comparedthis with the actual situation. The obtained results were illustrated useful estimation of the systembehaviour during abnormal situation.

Jelenka B. Savkovic-Stevanovic

2010-06-01

185

Reliability analysis (hardware) of a core temperature safety system  

International Nuclear Information System (INIS)

This paper deals with the evaluation of hardware reliability of a computerised safety system for the detection of core outlet temperature disturbances of a sodium cooled fast breeder reactor. The analysis, is carried out by the use of a complete Markov model of the system; it takes into account the different mission phases due to necessity of testing them during their operation time. The study is carried out in parametric form, in order to get a sensitivity analysis of the various influences of the parameters involved. The aim of the work is to demonstrate that it is possible to reach such a reliability figure by using standard computing units: the achievement is done by means of an opportune redundancy voting scheme and testing policy. Evaluations on ''fail to danger/fail to safe'' failure rate of the system units, are also shown. (author)

186

Reliability analysis for nonnormal distributions using multi-level DOE  

International Nuclear Information System (INIS)

The reliability analysis for nonnormal distributions using the three level DOE(Design Of Experiments) method was developed by Seo and Kwak in 2002. Although this method estimates only up to the first four moments(mean, standard deviation, skewness, and kurtosis) of the system response function, the result and the type of probability distribution determined by using the Pearson system are shown very good. However the accuracy is low in case of nonlinear performance function and sometimes, the level calculated is outside of the region in which the random variable is defined. In this article we suggest a modified three level DOE method to overcome these weaknesses and to obtain optimum choice for 3 levels and weights to handle nonnormal distributions. Furthermore we extend it to finding the optimum choice for 5 levels and weights to increase the accuracy in case of nonlinear performance function. A systematic procedure for reliability analysis is then proposed by using the Pearson system

187

Reliability analysis using an enhanced response surface moment method  

International Nuclear Information System (INIS)

Moment methods, which are powerful and simple techniques for analyzing the reliability of a system, evaluate the statistical moments of a system response function and use information from the probability distribution in the analysis. The full factorial moment method (FFMM) performs reliability analysis by using a 3n full factorial design of experiments (DOE) and the Pearson system for random variables. To overcome the inefficiency of FFMM, the response surface moment method (RSMM) has been proposed, which is based on a response surface model (RSM) that is updated by adding cross product terms into the simple quadratic model. In this paper, we propose the enhanced RSMM (RSMM+) that modifies the procedure of selecting a cross product term in the RSMM and adds a process of judging whether the response surface model can be established before performing an additional experiment. We apply the proposed method to several examples and show that it gives better results in efficiency

188

Reliability analysis of maintenance operations for railway tracks  

International Nuclear Information System (INIS)

Railway engineering is confronted with problems due to degradation of the railway network that requires important and costly maintenance work. However, because of the lack of knowledge on the geometrical and mechanical parameters of the track, it is difficult to optimize the maintenance management. In this context, this paper presents a new methodology to analyze the behavior of railway tracks. It combines new diagnostic devices which permit to obtain an important amount of data and thus to make statistics on the geometric and mechanical parameters and a non-intrusive stochastic approach which can be coupled with any mechanical model. Numerical results show the possibilities of this methodology for reliability analysis of different maintenance operations. In the future this approach will give important informations to railway managers to optimize maintenance operations using a reliability analysis

189

The application of two recently developed human reliability techniques to cognitive error analysis  

International Nuclear Information System (INIS)

Cognitive error can lead to catastrophic consequences for manned systems, including those whose design renders them immune to the effects of physical slips made by operators. Four such events, pressurized water and boiling water reactor accidents which occurred recently, were analysed. The analysis identifies the factors which contributed to the errors and suggests practical strategies for error recovery or prevention. Two types of analysis were conducted: an unstructured analysis based on the analyst's knowledge of psychological theory, and a structured analysis using two recently-developed human reliability analysis techniques. In general, the structured techniques required less effort to produce results and these were comparable to those of the unstructured analysis. (author)

190

Fiber Access Networks: Reliability Analysis and Swedish Broadband Market  

Science.gov (United States)

Fiber access network architectures such as active optical networks (AONs) and passive optical networks (PONs) have been developed to support the growing bandwidth demand. Whereas particularly Swedish operators prefer AON, this may not be the case for operators in other countries. The choice depends on a combination of technical requirements, practical constraints, business models, and cost. Due to the increasing importance of reliable access to the network services, connection availability is becoming one of the most crucial issues for access networks, which should be reflected in the network owner's architecture decision. In many cases protection against failures is realized by adding backup resources. However, there is a trade off between the cost of protection and the level of service reliability since improving reliability performance by duplication of network resources (and capital expenditures CAPEX) may be too expensive. In this paper we present the evolution of fiber access networks and compare reliability performance in relation to investment and management cost for some representative cases. We consider both standard and novel architectures for deployment in both sparsely and densely populated areas. While some recent works focused on PON protection schemes with reduced CAPEX the current and future effort should be put on minimizing the operational expenditures (OPEX) during the access network lifetime.

Wosinska, Lena; Chen, Jiajia; Larsen, Claus Popp

191

Reliability analysis of crack propagation behavior of reactor components  

International Nuclear Information System (INIS)

A reliability analysis was carried out on a circumferential weld in the main coolant loop of a PWR with the aim of estimating the probability of a leak or break occurring in the planned life cycle of the plant. To get a basis for the reliability analysis the following influence factors were more closely examined: initial crack extent, load spectrum including the emergency 'earthquake' situation and crack growth characteristics. For the actual reliability analysis a computer program was developed, which took the individual input data, in accordance with their statistical parameter, into account in a simulation calculation in line with the Monte Carlo Method. The Forman Formula was used to estimate the fatigue crack growth caused by the sequence of load events. The result was, that the fatigue crack growth, even in the case of large initial cracks, was negligibly small. The probability, that, in the case of very deep initial cracks, one-off high quasi-static load, e.g. during an earthquake, could cause a locally limited crack-through, was estimated to be about 5x10-6 in forty years. (orig./HP)

192

High-Reliable PLC RTOS Development and RPS Structure Analysis  

International Nuclear Information System (INIS)

One of the KNICS objectives is to develop a platform for Nuclear Power Plant(NPP) I and C(Instrumentation and Control) system, especially plant protection system. The developed platform is POSAFE-Q and this work supports the development of POSAFE-Q with the development of high-reliable real-time operating system(RTOS) and programmable logic device(PLD) software. Another KNICS objective is to develop safety I and C systems, such as Reactor Protection System(RPS) and Engineered Safety Feature-Component Control System(ESF-CCS). This work plays an important role in the structure analysis for RPS. Validation and verification(V and V) of the safety critical software is an essential work to make digital plant protection system highly reliable and safe. Generally, the reliability and safety of software based system can be improved by strict quality assurance framework including the software development itself. In other words, through V and V, the reliability and safety of a system can be improved and the development activities like software requirement specification, software design specification, component tests, integration tests, and system tests shall be appropriately documented for V and V.

193

High-Reliable PLC RTOS Development and RPS Structure Analysis  

Energy Technology Data Exchange (ETDEWEB)

One of the KNICS objectives is to develop a platform for Nuclear Power Plant(NPP) I and C(Instrumentation and Control) system, especially plant protection system. The developed platform is POSAFE-Q and this work supports the development of POSAFE-Q with the development of high-reliable real-time operating system(RTOS) and programmable logic device(PLD) software. Another KNICS objective is to develop safety I and C systems, such as Reactor Protection System(RPS) and Engineered Safety Feature-Component Control System(ESF-CCS). This work plays an important role in the structure analysis for RPS. Validation and verification(V and V) of the safety critical software is an essential work to make digital plant protection system highly reliable and safe. Generally, the reliability and safety of software based system can be improved by strict quality assurance framework including the software development itself. In other words, through V and V, the reliability and safety of a system can be improved and the development activities like software requirement specification, software design specification, component tests, integration tests, and system tests shall be appropriately documented for V and V.

Sohn, H. S.; Song, D. Y.; Sohn, D. S.; Kim, J. H. [Enersys Co., Daejeon (Korea, Republic of)

2008-04-15

194

Analysis of emergency diesel generators for improved reliability  

International Nuclear Information System (INIS)

Nuclear generating station emergency diesel generators are among the most critical safeguards systems because of their need to operate as designed in the event of a loss of off-site power and to be operational to permit nuclear unit operation. This paper will detail the need for analysis of diesel engines to ensure reliability, performance, and availability of the diesel generator and nuclear unit. The requirements for a state-of-the-art analysis program will be given, showing the benefits derived from digital data collection and computer aided diagnostics. These benefits include more frequent analysis, improved scheduling of tests and historical comparison and trending of data. Commonwealth Edison operates twenty-four emergency diesel generators at six nuclear generating stations. Case studies of actual malfunctions detected will be used to illustrate analysis methods and the capabilities of their engine analysis program

195

User's guide for the Reliability Analysis System (RAS)  

International Nuclear Information System (INIS)

The Reliability Analysis System (RAS) is an integrated package of computer programs for the quantification of fault trees. In particular, RAS has the capacity of performing phased mission analysis. RAS is based upon the MOCUS, POCUS, KITT-1, SRTPRN, and COMCAN programs. Mission cut set cancellation and four methods of bounding mission unreliability have been incorporated into RAS. A new cut set algorithm, FATRAM, is also included in RAS. RAS is written for the CDC Cyber-76 computer system and utilizes external storage devices. The program is available from the Argonne Code Center, 9700 South Cass Avenue, Argonne, Illinois 60439

196

Damage tolerance reliability analysis of automotive spot-welded joints  

Energy Technology Data Exchange (ETDEWEB)

This paper develops a damage tolerance reliability analysis methodology for automotive spot-welded joints under multi-axial and variable amplitude loading history. The total fatigue life of a spot weld is divided into two parts, crack initiation and crack propagation. The multi-axial loading history is obtained from transient response finite element analysis of a vehicle model. A three-dimensional finite element model of a simplified joint with four spot welds is developed for static stress/strain analysis. A probabilistic Miner's rule is combined with a randomized strain-life curve family and the stress/strain analysis result to develop a strain-based probabilistic fatigue crack initiation life prediction for spot welds. Afterwards, the fatigue crack inside the base material sheet is modeled as a surface crack. Then a probabilistic crack growth model is combined with the stress analysis result to develop a probabilistic fatigue crack growth life prediction for spot welds. Both methods are implemented with MSC/NASTRAN and MSC/FATIGUE software, and are useful for reliability assessment of automotive spot-welded joints against fatigue and fracture.

Mahadevan, Sankaran; Ni Kan

2003-07-01

197

Damage tolerance reliability analysis of automotive spot-welded joints  

International Nuclear Information System (INIS)

This paper develops a damage tolerance reliability analysis methodology for automotive spot-welded joints under multi-axial and variable amplitude loading history. The total fatigue life of a spot weld is divided into two parts, crack initiation and crack propagation. The multi-axial loading history is obtained from transient response finite element analysis of a vehicle model. A three-dimensional finite element model of a simplified joint with four spot welds is developed for static stress/strain analysis. A probabilistic Miner's rule is combined with a randomized strain-life curve family and the stress/strain analysis result to develop a strain-based probabilistic fatigue crack initiation life prediction for spot welds. Afterwards, the fatigue crack inside the base material sheet is modeled as a surface crack. Then a probabilistic crack growth model is combined with the stress analysis result to develop a probabilistic fatigue crack growth life prediction for spot welds. Both methods are implemented with MSC/NASTRAN and MSC/FATIGUE software, and are useful for reliability assessment of automotive spot-welded joints against fatigue and fracture

198

Reliability analysis of pipelines with corrosion defects using surrogate models  

Energy Technology Data Exchange (ETDEWEB)

The most adequate procedure for measuring the structural safety is through the quantification of its failure probability. The determination of this value can be made using the first order reliability method (FORM) that leads to an optimization problem to solve the structural reliability problem. Other alternative is to apply Monte Carlo simulation method. The present work has the aim to present a methodology for safety verification and optimum design of pipelines with defect caused by corrosion. The methods used here to verify the safety of pipelines with corrosion defects use information from the deterministic analysis in its calculations. The choice of the deterministic method directly affects the calculation of failure probability of the structure. To obtain the failure pressure load, the FEM is applied considering both physical and geometric nonlinearities. This is a costly simulation problem even for a single simulation. When, in a reliability analysis procedure using the FEM, many random variables and gradient evaluations are applied, the issued related to computational time becomes very critical, and could be even prohibitively, depending on the case of study. Surrogate models are here used to overcome the above mentioned problem. (author)

Torres, Juliana V.S. [Federal University of Pernambuco (UFPE), Recife, PE (Brazil); Afonso, Silvana M. Bastos [Federal University of Pernambuco (UFPE), Recife, PE (Brazil). Dept. of Civil Engineering; Vaz, Luiz Eloy [Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Dept. of Applied Mechanics and Structures

2009-07-01

199

Strength reliability analysis of stiffened cylindrical shells considering failure correlation  

Science.gov (United States)

The stiffened cylindrical shell is commonly used for the pressure hull of submersibles and the legs of offshore platforms. There are various failure modes because of uncertainty with the structural size and material properties, uncertainty of the calculation model and machining errors. Correlations among failure modes must be considered with the structural reliability of stiffened cylindrical shells. However, the traditional method cannot consider the correlations effectively. The aim of this study is to present a method of reliability analysis for stiffened cylindrical shells which considers the correlations among failure modes. Firstly, the joint failure probability calculation formula of two related failure modes is derived through use of the 2D joint probability density function. Secondly, the full probability formula of the tandem structural system is given with consideration to the correlations among failure modes. At last, the accuracy of the system reliability calculation is verified through use of the Monte Carlo simulation. Result of the analysis shows the failure probability of stiffened cylindrical shells can be gained through adding the failure probability of each mode.

Bai, Xu; Sun, Liping; Qin, Wei; Lv, Yongkun

2014-03-01

200

Reliability analysis of shuffle-exchange network systems  

International Nuclear Information System (INIS)

Shuffle-exchange networks (SENs) have been widely considered as practical interconnection systems due to their size of its switching elements (SEs) and uncomplicated configuration. SEN is a network among a large class of topologically equivalent multistage interconnection networks (MINs) that includes omega, indirect binary n-cube, baseline, and generalized cube. In this paper, SEN with additional stages that provide more redundant paths are analyzed. A common network topology with a 2x2 basic building block in a SEN and its variants in terms of extra-stages is investigated. As an illustration, three types of SENs are compared: SEN, SEN with an additional stage (SEN+), and SEN with two additional stages (SEN+2). Finally, three measures of reliability: terminal, broadcast, and network reliability for the three SEN systems are analyzed

 
 
 
 
201

User's manual of a support system for human reliability analysis  

International Nuclear Information System (INIS)

Many kinds of human reliability analysis (HRA) methods have been developed. However, users are required to be skillful so as to use them, and also required complicated works such as drawing event tree (ET) and calculation of uncertainty bounds. Moreover, each method is not so complete that only one method of them is not enough to evaluate human reliability. Therefore, a personal computer (PC) based support system for HRA has been developed to execute HRA practically and efficiently. The system consists of two methods, namely, simple method and detailed one. The former uses ASEP that is a simplified THERP-technique, and combined method of OAT and HRA-ET/DeBDA is used for the latter. Users can select a suitable method for their purpose. Human error probability (HEP) data were collected and a database of them was built to use for the support system. This paper describes outline of the HRA methods, support functions and user's guide of the system. (author)

202

Use of stochastic processes for mechanical reliability analysis and examples  

International Nuclear Information System (INIS)

The paper starts with a short reconsideration of foundations of reliability analysis as applied to mechanical components. A comprehensive approach for dealing with mechanical reliability problems seems to rely upon the use of stochastic processes. In complete generality, these processes would develop along space and time coordinates. Time refers to the life of interest to the component and space to its physical domain. However, stated in this form, the problem turns out to be almost unsolvable. To find answers one should look for simpler schemes. The investigation of practical cases leads to approximations which allow to infer the structure of the stochastic processes and to compute the corresponding probability of level crossing. To this purpose, two practical cases are considered for illustration purposes. The cases regard a nuclear reactor pressure-tube under loss-of-coolant accident and a pressure safety bursting diaphragm. (orig.)

203

Reliability analysis of neutron flux monitoring system for PFBR  

International Nuclear Information System (INIS)

The Neutron Flux Monitoring System (NFMS) measures reactor power, rate of change of power and reactivity changes in the core in all states of operation and shutdown. The system consists of instrument channels that are designed and built to have high reliability. All channels are required to have a Mean Time Between Failures (MTBF) of 150000 hours minimum. Failure Mode and Effects Analysis (FMEA) and failure rate estimation of NFMS channels has been carried out. FMEA is carried out in compliance with MIL-STD-338B. Reliability estimation of the channels is done according to MIL-HDBK-217FN2. Paper discusses the methodology followed for FMEA and failure rate estimation of two safety channels and results. (author)

204

Comparative study of three computer programs for rapid evaluation of reliability (EFICACE, LADIFISE, PEFAT)  

International Nuclear Information System (INIS)

This memorandum describes the results obtained from a comparative study of three computer programs in their simplified version for use in rapid reliability calculations. The three computer programs selected were: EFICACE of the SESA - LADIFISE of the CNET - PEFAT of the CISI. For each program, its purpose is defined, the manner in which the data is entered in the data cards is described, and the way the results are utilized in the computer printouts and listing is explained. Finally, the simplicity of the utilisation of each program is emphasized along with their respective advantages and disadvantages

205

Reliability of shoulder range of motion comparing a goniometer to a digital level.  

Science.gov (United States)

The clinical use of digital levels, for joint measurement, may be a viable alternative to standard goniometry. The purpose of this study was to determine the intra- and intertester reliability of a construction grade digital level compared to the standard universal goniometer for measurements for active assisted shoulder range of motion (ROM). Two experienced physical therapists measured shoulder flexion, external rotation (ER), and internal rotation (IR) ROM bilaterally, on two different occasions, in 20 patients (9 males, 11 females, 18-79 years old) with unilateral shoulder pathology, using a goniometer and a digital level. Relative reliability was assessed by using intraclass correlation coefficients (ICC), and absolute reliability was assessed by using 95% limits of agreement (LOA). Intratester ICCs ranged from 0.91 to 0.99, and LOA ranged from 3 degrees to 9 degrees for measurements made with the goniometer and digital level. Intertester ICCs ranged from 0.31 to 0.95, and LOA ranged from 6 degrees to 25 degrees . For the comparison of goniometric vs. digital level ROM, ICCs ranged from 0.71 to 0.98. ER and IR ROM were 3-5 degrees greater for the digital level than the goniometer (p basis of the average intratester LOA for the goniometer and the digital level, a change of 6-11 degrees is needed to be certain that true change has occurred. For comparison of measures made by two different therapists, a change is of 15 degrees is required to be certain a true change has occurred. A digital level can be used to reliably measure shoulder ROM but should not be used interchangeably with a standard goniometer. PMID:20557263

Mullaney, Michael J; McHugh, Malachy P; Johnson, Christopher P; Tyler, Timothy F

2010-07-01

206

Asymptotic Sampling for Reliability Analysis of Adhesive Bonded Stepped Lap Composite Joints  

DEFF Research Database (Denmark)

Reliability analysis coupled with finite element analysis (FEA) of composite structures is computationally very demanding and requires a large number of simulations to achieve an accurate prediction of the probability of failure with a small standard error. In this paper Asymptotic Sampling, which is a promising and time efficient tool to calculate the probability of failure, is utilized, and a probabilistic model for the reliability analysis of adhesive bonded stepped lap composite joints, representative for the main laminate in a wind turbine blade subjected to static flapwise bending load, is presented. Three dimensional (3D) FEA is used for the structural analysis together with a design equation that is associated with a deterministic code-based design equation where reliability is secured by partial safety factors. The Tsai-Wu and the maximum principal stress failure criteria are used to predict failure in the composite and adhesive layers, respectively, and the results are compared with the target reliability level implicitly used in the wind turbine standard IEC 61400-1. The accuracy and efficiency of Asymptotic Sampling is investigated by comparing the results with predictions obtained using the Monte Carlo simulation technique. Finally, the partial safety factors are calibrated, and it is shown that the methodology can be further applied to general calibration of partial safety factors to be used in deterministic design.

Kimiaeifar, Amin; Lund, Erik

2013-01-01

207

Reliability-Analysis of Offshore Structures using Directional Loads  

DEFF Research Database (Denmark)

Reliability analyses of offshore structures such as steel jacket platforms are usually performed using stochastic models for the wave loads based on the omnidirectional wave height. However, reliability analyses with respect to structural failure modes such as total collapse of a structure generally require that the directional dependence of the environmental loads (e.g. wave and wind actions) be taken into account. In the present paper a stochastic model for directional wave heights is presented. Stochastic dependence between extreme wave heights from different directions is taken into account. It is shown how the parameters in the stochastic model can be determined using a generalized Maximum Likelihood method such that the stochastic model becomes consistent with a stochastic model for the omnidirectional wave height. The calibration is illustrated by an example with hindcast wave heights from the central part of the North Sea. It is described how the stochastic model for the directional wave heights can be used in a reliability analysis where total collapse of offshore steel jacket platforms is considered.

SØrensen, John Dalsgaard; Bloch, Allan

2000-01-01

208

Reliability and risk analysis using artificial neural networks  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses preliminary research at Sandia National Laboratories into the application of artificial neural networks for reliability and risk analysis. The goal of this effort is to develop a reliability based methodology that captures the complex relationship between uncertainty in material properties and manufacturing processes and the resulting uncertainty in life prediction estimates. The inputs to the neural network model are probability density functions describing system characteristics and the output is a statistical description of system performance. The most recent application of this methodology involves the comparison of various low-residue, lead-free soldering processes with the desire to minimize the associated waste streams with no reduction in product reliability. Model inputs include statistical descriptions of various material properties such as the coefficients of thermal expansion of solder and substrate. Consideration is also given to stochastic variation in the operational environment to which the electronic components might be exposed. Model output includes a probabilistic characterization of the fatigue life of the surface mounted component.

Robinson, D.G. [Sandia National Labs., Albuquerque, NM (United States)

1995-12-31

209

Failure and Reliability Analysis for the Master Pump Shutdown System  

International Nuclear Information System (INIS)

The Master Pump Shutdown System (MPSS) will be installed in the 200 Areas of the Hanford Site to monitor and control the transfer of liquid waste between tank farms and between the 200 West and 200 East areas through the Cross-Site Transfer Line. The Safety Function provided by the MPSS is to shutdown any waste transfer process within or between tank farms if a waste leak should occur along the selected transfer route. The MPSS, which provides this Safety Class Function, is composed of Programmable Logic Controllers (PLCs), interconnecting wires, relays, Human to Machine Interfaces (HMI), and software. These components are defined as providing a Safety Class Function and will be designated in this report as MPSS/PLC. Input signals to the MPSS/PLC are provided by leak detection systems from each of the tank farm leak detector locations along the waste transfer route. The combination of the MPSS/PLC, leak detection system, and transfer pump controller system will be referred to as MPSS/SYS. The components addressed in this analysis are associated with the MPSS/SYS. The purpose of this failure and reliability analysis is to address the following design issues of the Project Development Specification (PDS) for the MPSS/SYS (HNF 2000a): (1) Single Component Failure Criterion, (2) System Status Upon Loss of Electrical Power, (3) Physical Separation of Safety Class cables, (4) Physical Isolation of Safety Class Wiring from General Service Wiring, and (5) Meeting the MPSS/PLC Option 1b (RPP 1999) Reliability estimate. The failure and reliability analysis examined the system on a component level basis and identified any hardware or software elements that could fail and/or prevent the system from performing its intended safety function

210

Fifty Years of THERP and Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

In 1962 at a Human Factors Society symposium, Alan Swain presented a paper introducing a Technique for Human Error Rate Prediction (THERP). This was followed in 1963 by a Sandia Laboratories monograph outlining basic human error quantification using THERP and, in 1964, by a special journal edition of Human Factors on quantification of human performance. Throughout the 1960s, Swain and his colleagues focused on collecting human performance data for the Sandia Human Error Rate Bank (SHERB), primarily in connection with supporting the reliability of nuclear weapons assembly in the US. In 1969, Swain met with Jens Rasmussen of Risø National Laboratory and discussed the applicability of THERP to nuclear power applications. By 1975, in WASH-1400, Swain had articulated the use of THERP for nuclear power applications, and the approach was finalized in the watershed publication of the NUREG/CR-1278 in 1983. THERP is now 50 years old, and remains the most well known and most widely used HRA method. In this paper, the author discusses the history of THERP, based on published reports and personal communication and interviews with Swain. The author also outlines the significance of THERP. The foundations of human reliability analysis are found in THERP: human failure events, task analysis, performance shaping factors, human error probabilities, dependence, event trees, recovery, and pre- and post-initiating events were all introduced in THERP. While THERP is not without its detractors, and it is showing signs of its age in the face of newer technological applications, the longevity of THERP is a testament of its tremendous significance. THERP started the field of human reliability analysis. This paper concludes with a discussion of THERP in the context of newer methods, which can be seen as extensions of or departures from Swain’s pioneering work.

Ronald L. Boring

2012-06-01

211

Sociological analysis and comparative education  

Science.gov (United States)

It is argued that comparative education is essentially a derivative field of study, in that it borrows theories and methods from academic disciplines. After a brief humanistic phase, in which history and philosophy were central for comparative education, sociology became an important source. In the mid-50's and 60's, sociology in the United States was characterised by Structural Functionalism as a theory, and Social Survey as a dominant methodology. Both were incorporated into the development of comparative education. Increasingly in the 70's, and certainly today, the new developments in sociology are characterised by an attack on Positivism, which is seen as the philosophical position underlying both functionalism and survey methods. New or re-discovered theories with their attendant methodologies included Marxism, Phenomenological Sociology, Critical Theory, and Historical Social Science. The current relationship between comparative education and social science is one of uncertainty, but since social science is seen to be returning to its European roots, the hope is held out for the development of an integrated social theory and method which will provide a much stronger basis for developments in comparative education.

Woock, Roger R.

1981-12-01

212

Reliability analysis of shearwall structure with soil structure interaction  

International Nuclear Information System (INIS)

The reliability assessment of a site-dependent structural system under seismic environment is studied in this report. The stiffness parameters of the system (soil as well as structure) are considered as random variable. The random distribution of modal frequencies are obtained. A new response spectral density function is defined which include the effect of randomness of the model frequencies. A stationary random process is used to simulate the seismic excitation load along with the random operational loads. The random vibration analysis in frequency domain is used to obtain the statistical properties of the dynamic response of structure to a stochastic ground excitation. A typical shear wall supporting the containment building of a hypothetical nuclear power plant located on uniform sand deposit is chosen for the numerical study. A sensitivity analysis is performed to evaluate the influence of various parameters on the reliability of the system, such as: the effect of soil-structure interaction, stiffnesses of soil, randomness of strength of materials (concrete, steel), distribution of reinforcement in concrete members, types of design spectral densities, and different level of Safe Shut down Earthquake acceleration and maximum possible acceleration, etc. A computer program is developed based on the method presented in this study to perform the numerical analysis

213

Reliability Analysis of Systems Subject to First-Passage Failure  

Science.gov (United States)

An obvious goal of reliability analysis is the avoidance of system failure. However, it is generally recognized that it is often not feasible to design a practical or useful system for which failure is impossible. Thus it is necessary to use techniques that estimate the likelihood of failure based on modeling the uncertainty about such items as the demands on and capacities of various elements in the system. This usually involves the use of probability theory, and a design is considered acceptable if it has a sufficiently small probability of failure. This report contains findings of analyses of systems subject to first-passage failure.

Lutes, Loren D.; Sarkani, Shahram

2009-01-01

214

Reliability analysis of selected systems of nuclear power unit  

International Nuclear Information System (INIS)

The reliability analysis is discussed of selected facilities of the 440 MW nuclear power unit using the failure tree method. The first part of the paper deals with the primary circuit and analyses the possibility of a dangerous failure arising of the system of accident alarm of the first order of the WWER 440 nuclear reactor during the event of the ''outage of four and more circulating pumps''. The second part of the paper is related to the secondary circuit. It studies the causes and probabilities of the failures of functions of condensate flow pumping and control with regard to the event the ''turbogenerator failure''. (author)

215

Analysis of Mobile Phone Reliability Based on Active Disassembly Using Smart Materials  

Directory of Open Access Journals (Sweden)

Full Text Available When using shape memory materials into active disassembly of actual electronic products, because the elastic modulus of shape memory materials is affected by the temperature is relatively large, therefore, the main difference of environmental reliability between active disassembly products and common products is the impact of collision and vibration under different temperature. Establishing three-dimensional analysis model, comparing the impact of collision and vibration of mobile phone shells which are made up of PVC materials after casting & radiation and PC/ABS materials under different temperature. Analyzing the reliability of mobile phone under different temperature and optimizing its structure according to data of testing.

Zhifeng Liu

2011-07-01

216

Integration of human reliability analysis into the high consequence process  

Energy Technology Data Exchange (ETDEWEB)

When performing a hazards analysis (HA) for a high consequence process, human error often plays a significant role in the hazards analysis. In order to integrate human error into the hazards analysis, a human reliability analysis (HRA) is performed. Human reliability is the probability that a person will correctly perform a system-required activity in a required time period and will perform no extraneous activity that will affect the correct performance. Even though human error is a very complex subject that can only approximately be addressed in risk assessment, an attempt must be made to estimate the effect of human errors. The HRA provides data that can be incorporated in the hazard analysis event. This paper will discuss the integration of HRA into a HA for the disassembly of a high explosive component. The process was designed to use a retaining fixture to hold the high explosive in place during a rotation of the component. This tool was designed as a redundant safety feature to help prevent a drop of the explosive. This paper will use the retaining fixture to demonstrate the following HRA methodology`s phases. The first phase is to perform a task analysis. The second phase is the identification of the potential human, both cognitive and psychomotor, functions performed by the worker. During the last phase the human errors are quantified. In reality, the HRA process is an iterative process in which the stages overlap and information gathered in one stage may be used to refine a previous stage. The rationale for the decision to use or not use the retaining fixture and the role the HRA played in the decision will be discussed.

Houghton, F.K.; Morzinski, J.

1998-12-01

217

Structural reliability codes for probabilistic design : - a debate paper based on elementary reliability and decision analysis concepts  

DEFF Research Database (Denmark)

For the practical applications of probabilistic reliability methods it is important to make decisions about the target reliability level. Presently calibration to existing design practice seems to be the only practicable and politically reasonable solution to this decision problem. However, several difficulties of ambiguity and definition show up when attempting to make the transition from a given authorized partial safety factor code to a superior probabilistic code. For any chosen probabilistic code format there is a considerable variation of the reliability level over the set of structures defined by the partial safety factor code. Thus, there is a problem about which of these levels to choose as target level. Moreover, if two different probabilistic code formats are considered, then a constant reliability level in the one code does not go together with a constant reliability level in the other code. The last problem must be accepted as the state of the matter and it seems that it can only be solved pragmatically by standardizing a specific code format as reference format for constant reliability. By an example this paper illustrates that a presently valid partial safety factor code imposes a quite considerable variation of the reliability measure as defined by a specific probabilistic code format. Decision theoretical principles are applied to get guidance about which of these different reliability levels of existing practice to choose as target reliability level. Moreover, it is shown that the chosen probabilistic code format has not only strong influence on the formal reliability measure, but also on the formal cost of failure to be associated if a design made to the target reliability level is considered to be optimal. In fact, the formal cost of failure can be different by several orders of size for two different, but by and large equally justifiable probabilistic code formats. Thus, the consequence is that a code format based on decision theoretical concepts and formulated as an extension of a probabilistic code format must specify formal values to be used as costs of failure. A principle of prudence is suggested for guiding the choice of the reference probabilistic code format for constant reliability. In the author's opinion there is an urgent need for establishing a standard probabilistic reliability code. This paper presents some considerations that may be debatable, but nevertheless point at a systematic way to choose such a code.Keywords: Code calibration, Structural reliability, Decision analysis, Reliability index, Partial safetyfactors, Target reliability.

Ditlevsen, Ove Dalager

1997-01-01

218

Forecasting methods: a comparative analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Forecasting is an important tool for management, planning and administration in various fields. In this paper forecasting performance of different methods is considered using time series data of Pakistan's export to United Sates and money supply. It is found that, like other studies of this nature, no single forecasting method provides better forecast for both the series. The techniques considered are ARIMA, Regression Analysis, Vector Autoregression (VAR), Error Correction Model ...

Iqbal, Javed

2001-01-01

219

Reliability Analysis for Adhesive Bonded Composite Stepped Lap Joints Loaded in Fatigue  

DEFF Research Database (Denmark)

This paper describes a probabilistic approach to calculate the reliability of adhesive bonded composite stepped lap joints loaded in fatigue using three- dimensional finite element analysis (FEA). A method for progressive damage modelling is used to assess fatigue damage accumulation and residual strength under fully reversed cyclic loading based on stiffness/strength degradation. The FEA simulations are conducted using the commercial FEA code ANSYS 12.1. A design equation for fatigue failure of wind turbine blades is chosen based on recommendations given in the wind turbine standard IEC 61400-1, where partial safety factors are introduced together with characteristic values. Asymptotic sampling is used to estimate the reliability with support points generated by randomized Sobol sequences. The predicted reliability level is compared with the implicitly required target reliability level defined by the wind turbine standard IEC 61400-1. Finally, an approach for the assessment of the reliability of adhesive bonded composite stepped lap joints loaded in fatigue is presented. The introduced methodology can be applied in the same way to calculate the reliability level of wind turbine blade components loaded in fatigue.

Kimiaeifar, Amin; SØrensen, John Dalsgaard

2012-01-01

220

Inclusion of fatigue effects in human reliability analysis  

International Nuclear Information System (INIS)

The effect of fatigue on human performance has been observed to be an important factor in many industrial accidents. However, defining and measuring fatigue is not easily accomplished. This creates difficulties in including fatigue effects in probabilistic risk assessments (PRA) of complex engineering systems that seek to include human reliability analysis (HRA). Thus the objectives of this paper are to discuss (1) the importance of the effects of fatigue on performance, (2) the difficulties associated with defining and measuring fatigue, (3) the current status of inclusion of fatigue in HRA methods, and (4) the future directions and challenges for the inclusion of fatigue, specifically sleep deprivation, in HRA. - Highlights: ?We highlight the need for fatigue and sleep deprivation effects on performance to be included in human reliability analysis (HRA) methods. Current methods do not explicitly include sleep deprivation effects. ? We discuss the difficulties in defining and measuring fatigue. ? We review sleep deprivation research, and discuss the limitations and future needs of the current HRA methods.

 
 
 
 
221

Inclusion of fatigue effects in human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

The effect of fatigue on human performance has been observed to be an important factor in many industrial accidents. However, defining and measuring fatigue is not easily accomplished. This creates difficulties in including fatigue effects in probabilistic risk assessments (PRA) of complex engineering systems that seek to include human reliability analysis (HRA). Thus the objectives of this paper are to discuss (1) the importance of the effects of fatigue on performance, (2) the difficulties associated with defining and measuring fatigue, (3) the current status of inclusion of fatigue in HRA methods, and (4) the future directions and challenges for the inclusion of fatigue, specifically sleep deprivation, in HRA. - Highlights: >We highlight the need for fatigue and sleep deprivation effects on performance to be included in human reliability analysis (HRA) methods. Current methods do not explicitly include sleep deprivation effects. > We discuss the difficulties in defining and measuring fatigue. > We review sleep deprivation research, and discuss the limitations and future needs of the current HRA methods.

Griffith, Candice D. [Vanderbilt University, Nashville, TN (United States); Mahadevan, Sankaran, E-mail: sankaran.mahadevan@vanderbilt.edu [Vanderbilt University, Nashville, TN (United States)

2011-11-15

222

Current Human Reliability Analysis Methods Applied to Computerized Procedures  

Energy Technology Data Exchange (ETDEWEB)

Computerized procedures (CPs) are an emerging technology within nuclear power plant control rooms. While CPs have been implemented internationally in advanced control rooms, to date no US nuclear power plant has implemented CPs in its main control room (Fink et al., 2009). Yet, CPs are a reality of new plant builds and are an area of considerable interest to existing plants, which see advantages in terms of enhanced ease of use and easier records management by omitting the need for updating hardcopy procedures. The overall intent of this paper is to provide a characterization of human reliability analysis (HRA) issues for computerized procedures. It is beyond the scope of this document to propose a new HRA approach or to recommend specific methods or refinements to those methods. Rather, this paper serves as a review of current HRA as it may be used for the analysis and review of computerized procedures.

Ronald L. Boring

2012-06-01

223

Model-based human reliability analysis: prospects and requirements  

International Nuclear Information System (INIS)

Major limitations of the conventional methods for human reliability analysis (HRA), particularly those developed for operator response analysis in probabilistic safety assessments (PSA) of nuclear power plants, are summarized as a motivation for the need and a basis for developing requirements for the next generation HRA methods. It is argued that a model-based approach that provides explicit cognitive causal links between operator behaviors and directly or indirectly measurable causal factors should be at the core of the advanced methods. An example of such causal model is briefly reviewed, where due to the model complexity and input requirements can only be currently implemented in a dynamic PSA environment. The computer simulation code developed for this purpose is also described briefly, together with current limitations in the models, data, and the computer implementation

224

Transient Reliability Analysis Capability Developed for CARES/Life  

Science.gov (United States)

The CARES/Life software developed at the NASA Glenn Research Center provides a general-purpose design tool that predicts the probability of the failure of a ceramic component as a function of its time in service. This award-winning software has been widely used by U.S. industry to establish the reliability and life of a brittle material (e.g., ceramic, intermetallic, and graphite) structures in a wide variety of 21st century applications.Present capabilities of the NASA CARES/Life code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code can compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth failure conditions CARES/Life can handle sustained and linearly increasing time-dependent loads, whereas in cyclic fatigue applications various types of repetitive constant-amplitude loads can be accounted for. However, in real applications applied loads are rarely that simple but vary with time in more complex ways such as engine startup, shutdown, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. A methodology has now been developed to allow the CARES/Life computer code to perform reliability analysis of ceramic components undergoing transient thermal and mechanical loading. This means that CARES/Life will be able to analyze finite element models of ceramic components that simulate dynamic engine operating conditions. The methodology developed is generalized to account for material property variation (on strength distribution and fatigue) as a function of temperature. This allows CARES/Life to analyze components undergoing rapid temperature change in other words, components undergoing thermal shock. In addition, the capability has been developed to perform reliability analysis for components that undergo proof testing involving transient loads. This methodology was developed for environmentally assisted crack growth (crack growth as a function of time and loading), but it will be extended to account for cyclic fatigue (crack growth as a function of load cycles) as well.

Nemeth, Noel N.

2001-01-01

225

Statistical Analysis of Reliability in edge detection techniques using Optical Coherent Tomography image  

Directory of Open Access Journals (Sweden)

Full Text Available Optical Coherence Tomography (OCT has many uses in medicine and engineering biology. It is a non-invasive technique where Edge detection in image processing playing a significant role in characterization of boundaries and identifying the structural properties in image. In this paper, Choroidal neovascularization – OCT image is comparatively analysis by various Edge Detection techniques. Statistical analysis of Mean Square Error (MSE is compared with multidimensional scaling methods. On the reliability of scaling, inter-correlation matrix in calculated from correction, dissimilarly and Euclidean distance model is evolved. Resultant graph described the characteristics of edge detection techniques.

G MOHANDASS

2013-04-01

226

Reliability and sustainability analysis of large panel residential buildings in Sofia, Skopje and Novi Sad  

Directory of Open Access Journals (Sweden)

Full Text Available Large panel residential buildings, dating from second half of 20 Century, are to be found in almost every urban settlement across Europe. Within the context of three case studies of urban blocks in Bulgaria (Mladost - Sofia, Macedonia (Karpos III - Skopje and Serbia (Detelinara - Novi Sad, comparative analysis and evaluation of technical and structural characteristics according to reliability (seismic resistance and fire safety and sustainability (energy efficiency, internal air quality, accessibility criteria has been conducted. Additionally, previous experiences from individual renewal projects are reviewed. Previous experiences and comparative analysis results, could contribute to formulation of wider applicable solutions and development of new urban renewal strategies.

Foli? Radomir

2011-01-01

227

Reliability analysis of repairable system based on GO-FLOW methodology  

International Nuclear Information System (INIS)

A quantitative analysis method named GO-FLOW is introduced to analyze the reliability of system with priority in maintenance and the amount of repairman limited. Approximate formulas model that can be applied to the GO-FLOW calculation is derived for the reliability parameters of repairable assembly. Then the model's feasibility is validated, and its error is analyzed. An example of redundancy pump component is presented, and the result achieved by GO-FLOW is compared with that by GO methodology. The results show that GO-FLOW Methodology can be used for quantitative analysis of this sort of repairable system; The model of GO-FLOW is effective and the algorithm is more convenient compared with GO methodology. (authors)

228

Reliability analysis and component functional allocations for the ESF multi-loop controller design  

International Nuclear Information System (INIS)

This paper deals with the reliability analysis and component functional allocations to ensure the enhanced system reliability and availability. In the Engineered Safety Features, functionally dependent components are controlled by a multi-loop controller. The system reliability of the Engineered Safety Features-Component Control System, especially, the multi-loop controller which is changed comparing to the conventional controllers is an important factor for the Probability Safety Assessment in the nuclear field. To evaluate the multi-loop controller's failure rate of the k-out-of-m redundant system, the binomial process is used. In addition, the component functional allocation is performed to tolerate a single multi-loop controller failure without the loss of vital operation within the constraints of the piping and component configuration, and ensure that mechanically redundant components remain functional. (author)

229

Reliability and sustainability analysis of large panel residential buildings in Sofia, Skopje and Novi Sad  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Large panel residential buildings, dating from second half of 20 Century, are to be found in almost every urban settlement across Europe. Within the context of three case studies of urban blocks in Bulgaria (Mladost - Sofia), Macedonia (Karpos III - Skopje) and Serbia (Detelinara - Novi Sad), comparative analysis and evaluation of technical and structural characteristics according to reliability (seismic resistance and fire safety) and sustainability (energy efficiency, internal air quality, ...

Foli? Radomir; Laban Mirjana; Milanko Verica

2011-01-01

230

Comparative Study of the Moroccan Power Grid Reliability in Presence of Photovoltaic and Wind Generation  

Directory of Open Access Journals (Sweden)

Full Text Available The photovoltaic sector in Morocco is a serious option for the future. The integration of this type of energy into the grid has a considerable effect on the adequacy of the grid. The objective of this work is to assess the reliability of the Moroccan power grid at the hierarchical level I (HLI: load coverage under the assumption of infinite node using a non-sequential Monte Carlo simulation in which photovoltaic generation is introduced. In order to lead such a study, a model was used in order to calculate the hourly solar radiation and to determine the time evolution of the electrical power produced by photovoltaic power plants. Finally, we also compared the impact of both PV and wind generations in terms of adequacy of the Moroccan electrical supply.

Mohamed Oukili

2013-07-01

231

Reliability analysis of large scaled structures by optimization technique  

International Nuclear Information System (INIS)

This paper presents a reliability analysis based on the optimization technique using PNET (Probabilistic Network Evaluation Technique) method for the highly redundant structures having a large number of collapse modes. This approach makes the best use of the merit of the optimization technique in which the idea of PNET method is used. The analytical process involves the minimization of safety index of the representative mode, subjected to satisfaction of the mechanism condition and of the positive external work. The procedure entails the sequential performance of a series of the NLP (Nonlinear Programming) problems, where the correlation condition as the idea of PNET method pertaining to the representative mode is taken as an additional constraint to the next analysis. Upon succeeding iterations, the final analysis is achieved when a collapse probability at the subsequent mode is extremely less than the value at the 1st mode. The approximate collapse probability of the structure is defined as the sum of the collapse probabilities of the representative modes classified by the extent of correlation. Then, in order to confirm the validity of the proposed method, the conventional Monte Carlo simulation is also revised by using the collapse load analysis. Finally, two fairly large structures were analyzed to illustrate the scope and application of the approach. (orig./HP)

232

Rent control: a comparative analysis  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Recent case law shows that vulnerable, previously disadvantaged private sector tenants are currently facing eviction orders - and consequential homelessness - on the basis that their leases have expired. In terms of the case law it is evident that once their leases have expired, these households do [...] not have access to alternative accommodation. In terms of the Constitution, this group of marginalised tenants have a constitutional right of access to adequate housing and a right to occupy land with legally secure tenure. The purpose of this article is to critically analyse a number of legislative interventions, and specifically rent control, that were imposed in various jurisdictions in order to provide strengthened tenure protection for tenants. The rationale for this analysis is to determine whether the current South African landlord-tenant regime is able to provide adequate tenure protection for vulnerable tenants and therefore in the process of transforming in line with the Constitution. The legal construction of rent control was adopted in pre-1994 South Africa, England and New York City to provide substantive tenure protection for tenants during housing shortages. These statutory interventions in the different private rental markets were justified on the basis that there was a general need to protect tenants against exploitation by landlords. However, the justification for the persistent imposition of rent control in New York City is different since it protects a minority group of financially weak tenants against homelessness. The English landlord-tenant regime highlights the importance of a well-structured social sector that can provide secure, long-term housing options for low-income households who are struggling to access the private rental sector. Additionally, the English rental housing framework shows that if the social sector is functioning as a "safety net" for low-income households, the private sector would be able to uphold deregulation. In light of these comparisons and the fact that the South African social sector is not functioning optimally yet, the question is whether the South African private sector is able to provide the required level of tenure protection for struggling tenants. Recent case law shows that tenants are at liberty to lodge unfair practice complaints with the Rental Housing Tribunals on the basis that the landlords' ground for termination of the lease constitutes an unfair practice. The Court defined an unfair practice as a practice that unreasonably prejudices the tenants' rights or interests. This judicial development signifies some transformation in the private sector since it allows the Tribunals to scrutinise landlords' reasons for termination of tenancies in light of tenants' personal and socioeconomic circumstances. The Tribunals are therefore empowered to weigh the interests of both parties and decide whether to confirm termination of the lease or set aside such termination. In light of this recent development, the Tribunals can provide strengthened tenure protection for destitute tenants on a case by case basis, which incorporates a flexible context-sensitive approach to the provision of secure housing rights in the landlord-tenant framework. This methodology is similar to the German approach. Even though this judicial development is welcomed, it raises some concerns with regard to landlords' property rights and specifically landlords' constitutional property rights since Tribunals are now at liberty to set aside contractually agreed grounds for termination of leases without any statutory guidance. The legislation fails to provide any information regarding legitimate grounds for termination, which might have to be rectified in future. The grounds listed in the rent control legislation should serve as a starting point to determine which grounds for termination of a lease should generally be upheld. However, German landlord-tenant law shows that a statutory ground for termination of a lease shoul

S, Maass.

233

Development the hybrid code metric for software reliability analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A hybrid code metric to evaluate the software reliability that takes into account the relative cost of software development at different stages of the lifecycle has been developed. This allows to analyse the software reliability at the early lifecycle stages.

Yakovyna, Vitaliy; Buta, Vasyl

2013-01-01

234

Towards a non-wired simulator for reliability analysis  

International Nuclear Information System (INIS)

This paper outlines the objectives and preliminary results of a research programme aiming to increase the advantages of electronic simulators used for reliability studies of complex systems. Research work has resulted in the design of a device based on an electronic simulator capable of carrying out all types of simulation without the drawback of wiring, as is currently the case. Its performance levels as regards speed are comparable to those of wired simulators and this is its main advantage over studies made on a computer. In addition, the simulator is connected to a computer which greatly increases system flexibility and user-friendliness. The first results obtained illustrate what characteristics can be expected of such a system, both as regards the anticipated computation time and the extended processing capabilities (such as the study of common cause failures). (author)

235

The GO-FLOW reliability analysis methodology - analysis of common cause failures with uncertainty  

International Nuclear Information System (INIS)

The Ship Research Institute has been developing a new reliability analysis methodology GO-FLOW which is a success-oriented system analysis technique. This paper describes a function of analyzing common cause failures together with uncertainty analysis in the GO-FLOW methodology. (author). 9 refs., 5 figs., 1 tab

236

A Fault Analysis based Model for Software Reliability Estimation  

Directory of Open Access Journals (Sweden)

Full Text Available When a software system is designed, the major concern is the software quality. The quality of software depends on different factors such as software reliability, efficiency, cost etc. In this paper, we have defined the software reliability as the measure of software quality. There are different available models that estimate the reliability of software based on type of faults, fault density etc. In this paper, a study on different aspects related to software reliability are discussed..

Garima Chawla,

2013-07-01

237

A Fault Analysis based Model for Software Reliability Estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

When a software system is designed, the major concern is the software quality. The quality of software depends on different factors such as software reliability, efficiency, cost etc. In this paper, we have defined the software reliability as the measure of software quality. There are different available models that estimate the reliability of software based on type of faults, fault density etc. In this paper, a study on different aspects related to software reliability are discussed..

Garima Chawla,; Santosh Kr Thakur,

2013-01-01

238

Diagnosis based on reliability analysis using monitors and sensors  

International Nuclear Information System (INIS)

We develop a process for using monitors or sensors to optimize diagnostic decision trees (DDTs) generated for large systems. We present algorithms for optimizing the diagnosis process, which combines evidence data captured from monitors or sensors into the diagnostic tree generation process to produce DDTs. Since evidence data can be extracted from monitors and sensors, we developed a method for sensor modeling. Our method allows modeling monitors or sensors as an abstract layer on top of a systems fault tree model. This method of modeling allows the designer to graphically link monitors or sensors to the components that they monitor, without impacting the reliability analysis. We use a real system from the industry to demonstrate the practicality and effectiveness of our algorithms and methods

239

Reliability Analysis of Metro Door System Based on FMECA  

Directory of Open Access Journals (Sweden)

Full Text Available The metro door system is one of the high failure rate subsystems of metro trains. The Failure Mode, Effects and Criticality Analysis (FMECA method is applied to analyze the reliability of metro door system in this paper. Firstly, failure components of the door are statistically analyzed, and the major failure components are determined. Secondly, failures are classified according to their impacts on operation, and methods of calculating failure mode criticality and the related coefficients are illustrated. Finally, the FMECA is detailed in the selected 12 failure modes, and the failure modes are discovered that they have the most significant effect on metro door system. The obtained results can be used for optimal design and maintenance of the metro door system.

Xiaoqing Cheng

2013-11-01

240

Time-dependent reliability analysis and condition assessment of structures  

Energy Technology Data Exchange (ETDEWEB)

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.

Ellingwood, B.R. [Johns Hopkins Univ., Baltimore, MD (United States)

1997-01-01

 
 
 
 
241

Bayesian networks inference algorithm to implement Dempster Shafer theory in reliability analysis  

International Nuclear Information System (INIS)

This paper deals with the use of Bayesian networks to compute system reliability. The reliability analysis problem is described and the usual methods for quantitative reliability analysis are presented within a case study. Some drawbacks that justify the use of Bayesian networks are identified. The basic concepts of the Bayesian networks application to reliability analysis are introduced and a model to compute the reliability for the case study is presented. Dempster Shafer theory to treat epistemic uncertainty in reliability analysis is then discussed and its basic concepts that can be applied thanks to the Bayesian network inference algorithm are introduced. Finally, it is shown, with a numerical example, how Bayesian networks' inference algorithms compute complex system reliability and what the Dempster Shafer theory can provide to reliability analysis

242

Bayesian networks inference algorithm to implement Dempster Shafer theory in reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with the use of Bayesian networks to compute system reliability. The reliability analysis problem is described and the usual methods for quantitative reliability analysis are presented within a case study. Some drawbacks that justify the use of Bayesian networks are identified. The basic concepts of the Bayesian networks application to reliability analysis are introduced and a model to compute the reliability for the case study is presented. Dempster Shafer theory to treat epistemic uncertainty in reliability analysis is then discussed and its basic concepts that can be applied thanks to the Bayesian network inference algorithm are introduced. Finally, it is shown, with a numerical example, how Bayesian networks' inference algorithms compute complex system reliability and what the Dempster Shafer theory can provide to reliability analysis.

Simon, C. [Centre de Recherche en Automatique de Nancy (CRAN-UMR 7039), Nancy University, CNRS, 2 Rue Jean Lamour, 54509 Vandoeuvre (France)], E-mail: christophe.simon@cran.uhp-nancy.fr; Weber, P. [Centre de Recherche en Automatique de Nancy (CRAN-UMR 7039), Nancy University, CNRS, 2 Rue Jean Lamour, 54509 Vandoeuvre (France)], E-mail: philippe.weber@cran.uhp-nancy.fr; Evsukoff, A. [COPPE/Universidade Federal do Rio de Janeiro, Rio de Janeiro RJ, Brazil, P.O. Box 68506, 21941-972 Rio de Janeiro, RJ (Brazil)], E-mail: alexandre.evsukoff@coc.ufrj.br

2008-07-15

243

Use of computer codes for system reliability analysis  

International Nuclear Information System (INIS)

This paper gives a collective summary of the studies performed at the JRC, ISPRA on the use of computer codes for complex systems analysis. The computer codes dealt with are: CAFTS-SALP software package, FRANTIC, FTAP, computer code package RALLY, and BOUNDS codes. Two reference study cases were executed by each code. The results obtained logic/probabilistic analysis as well as computation time are compared

244

Models and data requirements for human reliability analysis  

International Nuclear Information System (INIS)

It has been widely recognised for many years that the safety of the nuclear power generation depends heavily on the human factors related to plant operation. This has been confirmed by the accidents at Three Mile Island and Chernobyl. Both these cases revealed how human actions can defeat engineered safeguards and the need for special operator training to cover the possibility of unexpected plant conditions. The importance of the human factor also stands out in the analysis of abnormal events and insights from probabilistic safety assessments (PSA's), which reveal a large proportion of cases having their origin in faulty operator performance. A consultants' meeting, organized jointly by the International Atomic Energy Agency (IAEA) and the International Institute for Applied Systems Analysis (IIASA) was held at IIASA in Laxenburg, Austria, December 7-11, 1987, with the aim of reviewing existing models used in Probabilistic Safety Assessment (PSA) for Human Reliability Analysis (HRA) and of identifying the data required. The report collects both the contributions offered by the members of the Expert Task Force and the findings of the extensive discussions that took place during the meeting. Refs, figs and tabs

245

Reliability Analysis For Substation Employing B. F. Technique  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the object is to improve the reliability and overall performances of Rice Mill. When a more complexities increase in the system, the reliability evaluations become more difficult. Therefore, the derivation of symbolic reliability expression is simplified and a general system in compact form is helpful. Before this, the techniques executed earlier to solve such reliability models are very time consuming and very tedious calculations. Therefore, in this study Boolean function technique and algebra is used to evaluate systems, overall performance. Reliability of considered system has been computed by using Weibull and Exponential time distributions. M.T.T.F. of the considered system an important reliability parameter has been evaluated to develop practical utility of the model. A mathematical model has been developed with the help of Boolean function technique to measuring reliability.

MOHIT KUMAR, RAM AVTAR JASWAL

2013-06-01

246

Reliability analysis of I-section steel columns designed according to new Brazilian building codes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This paper presents an evaluation of the safety of I-section steel columns designed according to the new revision of the Brazilian code for design of steel buildings (NBR8800) and to the code for loads and safety of structures (NBR8681). The safety evaluation is based on structural reliability analy [...] sis of columns designed to comply with these codes, and on advanced (FE-based) analysis of actual column resistance. The effects of geometrical imperfections and residual stresses in column resistance are taken into account. The uncertainty in yield stress, elasticity modulus, geometrical imperfections and dead and live loads are considered in the reliability evaluation. Reliability indexes are obtained for several column configurations. These indexes reflect the safety of the columns designed according to the two building codes. Reliability indexes are compared with target reliability indexes used in calibration of the ANSI code and with indexes proposed in the new EUROCODE.

André T., Beck; André S., Dória.

2008-06-01

247

Reliability analysis and its application in the Loviisa nuclear power plant project  

International Nuclear Information System (INIS)

A reliability analysis was performed consisting of the following stages: the failure mode and effects analysis, the common mode failure analysis, reliability models and numerical calculations. The obtained results were applied in the LOVIISA reactor reliability analysis. A summary of analyses carried out until 1974 and the future stages of the research programme with regard to the selection of objects for the reliability analysis are given. The analysis of the reactor protection system, radiation monitoring system, after-heat removal system and a consequence diagram related to a loss of coolant accident are described as examples. In quantitative analysis, fault-tree techniques and Monte Carlo simulation were primarily used. (J.P.)

248

Novel shared-path protection algorithm and reliability analysis model based on Bayesian network for multilink failures  

Science.gov (United States)

For the multilink failure problem of wavelength division multiplexing (WDM) optical networks, we establish a reliability analysis model of shared-path protection strategy based on the Bayesian network and correlated link failure probability and analyze the reliability of light paths assigned by two shared-path protection algorithms. The new reliability model makes the reliability calculation of path subject to multilink failures possible, greatly simplifying the calculation of probabilistic reasoning. In addition, based on the new Bayesian network reliability analysis model, a novel differentiated shared-path protection (DSPP) algorithm is proposed to protect against multilink failures in WDM optical networks. Simulation experiments show that, compared with the two previous shared-path protection algorithms, the DSPP algorithm not only can satisfy the specific requirements of users but also has better survivability for multilink failures.

Xu, Jun; Chang, Huiyou; Xu, Chang; Yi, Yang

2009-12-01

249

Animal models are reliably mimicking human diseases? A morphological study that compares animal with human NAFLD.  

Science.gov (United States)

Non-alcoholic fatty liver disease (NAFLD) is a clinical-pathological syndrome that includes a wide spectrum of morphological alterations. In research, animal models are crucial in evaluating not only the pathogenesis of NAFLD and its progression, but also the therapeutic effects of various agents. Investigations on the ultrastructural features of NAFLD in humans are not copious, due to the difficulty to obtain human samples and to the long time of NAFLD to evolve. Translational comparative studies on the reliability of animal models in representing the histopathologic picture as seen in humans are missing. To overcome this lack of investigations, we compared the ultrastructural NAFLD features of an animal model versus human. Sprague-Dawley rats were fed with a high fat diet (HFD) for 1-4 weeks, while control rats were fed with a standard diet. Human specimens were collected from patients with diagnosed fatty liver disease, undergoing liver biopsies or surgery. Rat and human samples were examined by light microscopy and by transmission and high resolution scanning electron microscopy. The present work demonstrated that NAFLD in animal model and in human, share overlapping ultrastructural features. In conclusion, animal HFD represent an appropriate tool in studying the pathogenesis of NAFLD. Microsc. Res. Tech. 77:790-796, 2014. © 2014 Wiley Periodicals, Inc. PMID:25044260

Solinas, Paola; Isola, Michela; Lilliu, Maria Alberta; Conti, Gabriele; Civolani, Alberto; Demelia, Luigi; Loy, Francesco; Isola, Raffaella

2014-10-01

250

Reliability analysis of the service water system of Angra 1 reactor  

International Nuclear Information System (INIS)

A reliability analysis of the service water system is done aiming to use in the evaluation of the non reliability of the component cooling system (SRC) for great loss of cooling accidents in nuclear power plants. (E.G.)

251

De-aggregated reliability analysis of freezing rain hazard  

Science.gov (United States)

This work addresses issues for improving the estimation of the recurrence rate and the distribution in severity of extreme ice events in the Montreal area, which is required in order to determine design criteria for structures such as electric transmission lines. Some of the limitations of current methods for studying extreme freezing rain events are due to the relatively short data records. This results in variability of 'at site' data sets that have only a few large accumulations. The methods developed in this work address these issues. First, de-aggregated analysis is used to obtain better statistical fits by grouping storms according to physical variables that are correlated with the occurrence of ice storms (spatial patterns of sea level pressure (SLP) or 1000 to 500 hPa geopotential height anomalies). And second a procedure to decrease the uncertainty on estimates of the hazard function at high return periods based on solving the CRREL Simple icing model using reliability method is developed. In this procedure, uncertainty is propagated through the model by treating it as a function of random variables. Anomaly maps of several meteorological variables were investigated for the objective categorization of ice storms. The NCEP reanalysis data was used to compile spatial patterns for the analysis of the storms identified and categorized by Rauber et al (2001). Several multivariate statistical analysis procedures were used to investigate the effectiveness of sea level pressure, the 1000 to 500 hPa, and the 1000 to 925 hPa geopotential heights for clustering these storms. Results indicated that the k-means algorithm applied to principle component scores of the storm anomaly maps provided the best clustering results. The results indicated that storms with higher precipitations belong to a group associated with the phenomena of cold air damming as a result of the Appalachian Mountains. Environment Canada hourly data was used to identify freezing rain events and obtain measurements of wind speed and precipitation during the events that occurred over Ottawa, Montreal, and Quebec City. General Pareto or Generalized Extreme Value distributions are fitted to the data of total precipitation or total radial ice accumulation for each cluster using a peaks-over-threshold approach. Statistical tests indicate the resulting distributions for precipitation are significantly different from each cluster. This de-aggregated approach improves estimates of the icing hazard by improving statistical fits and by reducing the sensitivity of the results to the choice of threshold. The second approach used to improve the estimates of the icing hazard function, using reliability methods, considers total precipitation, freezing ratio, and wind speed as the random variables in solving the icing model. The most likely combination of variables associated with high ice accumulations was found to high total precipitation, high freezing ratios, but only slightly higher than average wind speed. The latter is useful for defining load combinations (wind speed and ice accumulation) for structural design purposes. Finally, the superstation approach of Jones and White (2002a) was investigated by combining Environment Canada data for Ottawa, Montreal and Quebec City. Monte Carlo simulations were performed on the regional set of data using 'at site' indexes. The reliability analysis of empirical icing equation produced results similar to Jones and White at quantiles associated with the 50 year return period. However there were greater differences at higher quantiles. The estimated return periods for radial ice accumulations of 45mm are 160, 210, and 85 years for Montreal, Ottawa, and Quebec City respectively.

Erfani, Reza

252

Inservice data reporting standards for engineering reliability and risk analysis  

International Nuclear Information System (INIS)

On two recent occasions, structural and mechanical engineers were challenged either to come up with a solution to the data base problem of the reliability analysis methodology or to avoid using the tool as a serious mathematical model to resolve issues of safety and productivity. The two occasions were: (1) The September 1978 publication of an assessment of the 1975 Reactor Safety Study (WASH-1400), by a review panel by H.W. Lewis. (2) The convening in December 1978 of an international symposium on inservice data reporting and analysis, sponsored by the American Society of Mechanical Engineers and held at San Francisco. This paper is a direct response to the challenge. The notion of an adequate data base is first defined in terms of three essential elements. It is then demonstrated via a medical analogy that an 'optimal' plan of data reporting and some national or international standards for such reporting are desirable. A formula for estimating variabilities based on a combination of inservice and failure data is proposed. (orig.)

253

Analysis of the reliability of a statistical oil spill response model.  

Science.gov (United States)

A statistical oil spill response model is developed and validated by means of actual oil slick observations reported during the Prestige accident and trajectories of drifter buoys. The model is based on the analysis of a database of hypothetical oil spill scenarios simulated by means of a Lagrangian transport model. To carry out the simulations, a re-analysis database consisting of 44-year hindcast dataset of wind and waves and climatologic daily mean surface currents is used. The number of scenarios required to obtain statistically reliable results is investigated, finding that 200 scenarios provide an optimal balance between the accuracy of the results and the computational effort. The reliability of the model was analyzed by comparing the actual data with the numerical results. The agreement found between actual and numerical data shows that the developed statistical oil spill model is a valuable tool to support spill response planning. PMID:20701930

Abascal, Ana J; Castanedo, Sonia; Medina, Raul; Liste, Maria

2010-11-01

254

Architecture for Interlock Systems Reliability Analysis with Regard to Safety and Availability  

CERN Document Server

In the design of interlock loops for the signal exchange in machine protection systems, the choice of the hardware architecture impacts on machine safety and availability. The reliable performance of a machine stop (leaving the machine in a safe state) in case of an emergency, is an inherent requirement. The constraints in terms of machine availability on the other hand may differ from one facility to another. Spurious machine stops, lowering machine availability, may to a certain extent be tolerated in facilities where they do not cause undue equipment wearout. In order to compare various interlock loop architectures in terms of safety and availability, the occurrence frequencies of related scenarios have been calculated in a reliability analysis, using a generic analytical model. This paper presents the results and illustrates the potential of the analysis method for supporting the choice of interlock system architectures.

Wagner, S; Schmidt, R; Zerlauth, M; Vergara-Fernandez, A

2011-01-01

255

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

Directory of Open Access Journals (Sweden)

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

Muhammad Hashim

2013-04-01

256

Application of Support Vector Machine to Reliability Analysis of Engine Systems  

Directory of Open Access Journals (Sweden)

Full Text Available Reliability analysis plays a very important role for assessing the performance and making maintenance plans of engine systems. This research presents a comparative study of the predictive performances of support vector machines (SVM , least square support vector machine (LSSVM and neural network time series models for forecasting failures and reliability in engine systems. Further, the reliability indexes of engine systems are computed by the weibull probability paper programmed with Matlab. The results shows that the probability distribution of the forecasting outcomes is consistent to the distribution of the actual data, which all follow weibull distribution and the predictions by SVM and LSSVM can provide accurate predictions of the characteristic life. So SVM and LSSVM are both another choice of engine system reliability analysis. Moreover, the predictive precise of the method based on LSSVM is higher than that of SVM. In small samples, the prediction by LSSVM will be more popular, because its compution cost is lower and the precise can be more satisfied.

Zhang Xinfeng

2013-07-01

257

Procedure for conducting a human-reliability analysis for nuclear power plants. Final report  

International Nuclear Information System (INIS)

This document describes in detail a procedure to be followed in conducting a human reliability analysis as part of a probabilistic risk assessment when such an analysis is performed according to the methods described in NUREG/CR-1278, Handbook for Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications. An overview of the procedure describing the major elements of a human reliability analysis is presented along with a detailed description of each element and an example of an actual analysis. An appendix consists of some sample human reliability analysis problems for further study

258

Procedure for conducting a human-reliability analysis for nuclear power plants. Final report  

Energy Technology Data Exchange (ETDEWEB)

This document describes in detail a procedure to be followed in conducting a human reliability analysis as part of a probabilistic risk assessment when such an analysis is performed according to the methods described in NUREG/CR-1278, Handbook for Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications. An overview of the procedure describing the major elements of a human reliability analysis is presented along with a detailed description of each element and an example of an actual analysis. An appendix consists of some sample human reliability analysis problems for further study.

Bell, B.J.; Swain, A.D.

1983-05-01

259

Analysis and Optimization of MPSoC Reliability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Advancements in technology enable integration of multiple devices on a single core, resulting in increased on chip power and temperature densities. Higher temperatures, in turn, present a significant challenge for reliability. In this work we propose a comprehensive framework for analyzing reliability of multi-core systems, considering permanent faults. We show that aggressive power management can have an impact on reliability due to temperature cycling. Our cycle-accurate simulation methodol...

Coskun, Ayse K.; Simunic Rosing, Tajana; Mihic, Kresimir; Micheli, Giovanni; Leblebici, Yusuf

2006-01-01

260

Analysis of reliability centered maintenance for service water system in nuclear power plants  

International Nuclear Information System (INIS)

Reliability centered maintenance (RCM) methodology has been applied to a service water system in AP1000 nuclear power plant. Using the functional failure modes and effect analysis (FMEA) and logic tree analysis (LTA), the optimized maintenance strategy is established based on a better understanding of the relevant information on this system and related equipments (including the functional failures, failure modes and effects)conclude. Compared with the current maintenance strategy, this maintenance strategy optimized by RCM conducts the condition monitoring and periodical maintenance for dominant failures but conducts periodical test for the recessive failures. (authors)

 
 
 
 
261

Reliability and risk analysis data base development: an historical perspective  

International Nuclear Information System (INIS)

Collection of empirical data and data base development for use in the prediction of the probability of future events has a long history. Dating back at least to the 17th century, safe passage events and mortality events were collected and analyzed to uncover prospective underlying classes and associated class attributes. Tabulations of these developed classes and associated attributes formed the underwriting basis for the fledgling insurance industry. Much earlier, master masons and architects used design rules of thumb to capture the experience of the ages and thereby produce structures of incredible longevity and reliability (Antona, E., Fragola, J. and Galvagni, R. Risk based decision analysis in design. Fourth SRA Europe Conference Proceedings, Rome, Italy, 18-20 October 1993). These rules served so well in producing robust designs that it was not until almost the 19th century that the analysis (Charlton, T.M., A History Of Theory Of Structures In The 19th Century, Cambridge University Press, Cambridge, UK, 1982) of masonry voussoir arches, begun by Galileo some two centuries earlier (Galilei, G. Discorsi e dimostrazioni mathematiche intorno a due nuove science, (Discourses and mathematical demonstrations concerning two new sciences, Leiden, The Netherlands, 1638), was placed on a sound scientific basis. Still, with the introduction of new materials (such as wrought iron and steel) and the lack of theoretical knowledge and computational facilities, approximate met computational facilities, approximate methods of structural design abounded well into the second half of the 20th century. To this day structural designers account for material variations and gaps in theoretical knowledge by employing factors of safety (Benvenuto, E., An Introduction to the History of Structural Mechanics, Part II: Vaulted Structures and Elastic Systems, Springer-Verlag, NY, 1991) or codes of practice (ASME Boiler and Pressure Vessel Code, ASME, New York) originally developed in the 19th century (Antona, E., Fragola, J. and Galvagni, R. Risk based decision analysis in design. Fourth SRA Europe Conference Proceedings, Rome, Italy, 18-20 October 1993). These factors, although they continue to be heuristically based, attempt to account for uncertainties in the design environment (e.g., the load spectra) and residual materials defects (Fragola, J.R. et al., Investigation of the risk implications of space shuttle solid rocket booster chamber pressure excursions. SAIC Document No. SAIC/NY 95-01-10, New York, NY). Although the approaches may appear different, at least at first glance, the intention in both the insurance and design arenas was to establish an 'infrastructure of confidence' to enable rational decision making for future endeavours. Maturity in the design process of conventional structures such as bridges, buildings, boilers, and highways has led to the loss of recognition of the role that robustness plays in these designs to qualify them against their normal failure environment. So routinely do we expect these designs to survive that we tend to think of the individual failures (which do occur on occasion) as isolated 'freak' accidents. Attempts to uncover potential underlying classes and document associated attributes are rare, and even when they are undertaken 'human error' or 'one-of-a-kind accidents' is often cited as the major cause which somehow seems to absolve the analyst from the responsibility of further data collection (Levy, M. and Salvadori, M., Why Buildings Fall Down, W.W. Norton and Co., New York, NY, 1992; Pecht, M., Nash, F.R. and Long, J.H., Understanding and solving the real reliability assurance problems. 1995 Proceedings of Annual RAMS Symposium, IEEE, New York, NY, 1995). The confusion has proliferated to the point where legitimate calls for scepticism regarding the scant data resources available (Evans, R.A., Bayes paradox. IEEE Trans. Reliab., R-31 (1982) 321) have given way to cries that some data sources be abandoned altogether (Cushing, M. et al., Comparison of electronics-reliability assessment approaches.

262

Modified generalized linear failure rate distribution: Properties and reliability analysis  

Directory of Open Access Journals (Sweden)

Full Text Available This paper introduces a new comprehensive four-parameter distribution called the modified generalized linear failure rate (MGLFR distribution. The method generalizes some well-known and most commonly used distributions in reliability such as exponential, Rayleigh, linear failure rate, generalized linear failure rate and modified Weibull distribution. The study also investigates some essential properties of this new distribution and considers the problem of the evaluation of system reliability by describing the lifetimes of components based on a fuzzy MGLFR distribution and by developing fuzzy reliability characteristics. The results can be applied to determine the reliability of real objects where parameters of lifetime variable are subject to uncertainty.

Ezzatallah Baloui Jamkhaneh

2014-06-01

263

Constellation Ground Systems Launch Availability Analysis: Enhancing Highly Reliable Launch Systems Design  

Science.gov (United States)

Success of the Constellation Program's lunar architecture requires successfully launching two vehicles, Ares I/Orion and Ares V/Altair, in a very limited time period. The reliability and maintainability of flight vehicles and ground systems must deliver a high probability of successfully launching the second vehicle in order to avoid wasting the on-orbit asset launched by the first vehicle. The Ground Operations Project determined which ground subsystems had the potential to affect the probability of the second launch and allocated quantitative availability requirements to these subsystems. The Ground Operations Project also developed a methodology to estimate subsystem reliability, availability and maintainability to ensure that ground subsystems complied with allocated launch availability and maintainability requirements. The verification analysis developed quantitative estimates of subsystem availability based on design documentation; testing results, and other information. Where appropriate, actual performance history was used for legacy subsystems or comparative components that will support Constellation. The results of the verification analysis will be used to verify compliance with requirements and to highlight design or performance shortcomings for further decision-making. This case study will discuss the subsystem requirements allocation process, describe the ground systems methodology for completing quantitative reliability, availability and maintainability analysis, and present findings and observation based on analysis leading to the Ground Systems Preliminary Design Review milestone.

Gernand, Jeffrey L.; Gillespie, Amanda M.; Monaghan, Mark W.; Cummings, Nicholas H.

2010-01-01

264

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-11-15

265

Reliable Classification of Geologic Surfaces Using Texture Analysis  

Science.gov (United States)

Communication delays and bandwidth constraints are major obstacles for remote exploration spacecraft. Due to such restrictions, spacecraft could make use of onboard science data analysis to maximize scientific gain, through capabilities such as the generation of bandwidth-efficient representative maps of scenes, autonomous instrument targeting to exploit targets of opportunity between communications, and downlink prioritization to ensure fast delivery of tactically-important data. Of particular importance to remote exploration is the precision of such methods and their ability to reliably reproduce consistent results in novel environments. Spacecraft resources are highly oversubscribed, so any onboard data analysis must provide a high degree of confidence in its assessment. The TextureCam project is constructing a "smart camera" that can analyze surface images to autonomously identify scientifically interesting targets and direct narrow field-of-view instruments. The TextureCam instrument incorporates onboard scene interpretation and mapping to assist these autonomous science activities. Computer vision algorithms map scenes such as those encountered during rover traverses. The approach, based on a machine learning strategy, trains a statistical model to recognize different geologic surface types and then classifies every pixel in a new scene according to these categories. We describe three methods for increasing the precision of the TextureCam instrument. The first uses ancillary data to segment challenging scenes into smaller regions having homogeneous properties. These subproblems are individually easier to solve, preventing uncertainty in one region from contaminating those that can be confidently classified. The second involves a Bayesian approach that maximizes the likelihood of correct classifications by abstaining from ambiguous ones. We evaluate these two techniques on a set of images acquired during field expeditions in the Mojave Desert. Finally, the algorithm was expanded to perform robust texture classification across a wide range of lighting conditions. We characterize both the increase in precision achieved using different input data representations as well as the range of conditions under which reliable performance can be achieved. An ensemble learning approach is used to increase performance by leveraging the illumination-dependent statistics of an image. Our results show that the three algorithmic modifications lead to a significant increase in classification performance as well as an increase in precision using an adjustable and human-understandable metric of confidence.

Foil, G.; Howarth, D.; Abbey, W. J.; Bekker, D. L.; Castano, R.; Thompson, D. R.; Wagstaff, K.

2012-12-01

266

Evaluation of pharmaceuticals in surface water: Reliability of PECs compared to MECs.  

Science.gov (United States)

Due to the current analytical processes that are not able to measure all the pharmaceutical molecules and to the high costs and the consumption of time to sample and analyze PhACs, models to calculate Predicted Environmental Concentrations (PECs) have been developed. However a comparison between MECs and PECs, taking into account the methods of calculations and peculiarly the parameters included in the calculation (consumption data, pharmacokinetic parameters, elimination rate in STPs and in the environment), is necessary to assess the validity of PECs. MEC variations of sixteen target PhACs [acetaminophen (ACE), amlodipine (AML), atenolol (ATE), caffeine (CAF), carbamazepine (CAR), doxycycline (DOX), epoxycarbamazepine (EPO), fluvoxamine (FLU), furosemide (FUR), hydrochlorothiazide (HYD), ifosfamide (IFO), losartan (LOS), pravastatin (PRA), progesterone (PROG), ramipril (RAM), trimetazidine (TRI)] have been evaluated during one hydrological cycle, from October 2011 to October 2012 and compared to PECs calculated by using an adaptation of the models proposed by Heberer and Feldmann (2005) and EMEA (2006). Comparison of PECs and MECS has been achieved for six molecules: ATE, CAR, DOX, FUR, HYD and PRA. DOX, FUR and HYD present differences between PECs and MECs on an annual basis but their temporal evolutions follow the same trends. PEC evaluation for these PhACs could then be possible but need some adjustments of consumption patterns, pharmacokinetic parameters and/or mechanisms of (bio)degradation. ATE, CAR and PRA are well modeled; PECs can then be used as reliable estimation of concentrations without any reserve. PMID:25080069

Celle-Jeanton, Hélène; Schemberg, Dimitri; Mohammed, Nabaz; Huneau, Frédéric; Bertrand, Guillaume; Lavastre, Véronique; Le Coustumer, Philippe

2014-12-01

267

Method of reliability allocation based on fault tree analysis and fuzzy math in nuclear power plants  

International Nuclear Information System (INIS)

Reliability allocation is a kind of a difficult multi-objective optimization problem. It can not only be applied to determine the reliability characteristic of reactor systems, subsystem and main components but also be performed to improve the design, operation and maintenance of nuclear plants. The fuzzy math known as one of the powerful tools for fuzzy optimization and the fault analysis deemed to be one of the effective methods of reliability analysis can be applied to the reliability allocation model so as to work out the problems of fuzzy characteristic of some factors and subsystem's choice respectively in this paper. Thus we develop a failure rate allocation model on the basis of the fault tree analysis and fuzzy math. For the choice of the reliability constraint factors, we choose the six important ones according to practical need for conducting the reliability allocation. The subsystem selected by the top-level fault tree analysis is to avoid allocating reliability for all the equipment and components including the unnecessary parts. During the reliability process, some factors can be calculated or measured quantitatively while others only can be assessed qualitatively by the expert rating method. So we adopt fuzzy decision and dualistic contrast to realize the reliability allocation with the help of fault tree analysis. Finally the example of the emergency diesel generator's reliability allocation is used to illustrate reliability allocation model and improvte reliability allocation model and improve this model simple and applicable. (authors)

268

Wind turbine reliability : a database and analysis approach.  

Energy Technology Data Exchange (ETDEWEB)

The US wind Industry has experienced remarkable growth since the turn of the century. At the same time, the physical size and electrical generation capabilities of wind turbines has also experienced remarkable growth. As the market continues to expand, and as wind generation continues to gain a significant share of the generation portfolio, the reliability of wind turbine technology becomes increasingly important. This report addresses how operations and maintenance costs are related to unreliability - that is the failures experienced by systems and components. Reliability tools are demonstrated, data needed to understand and catalog failure events is described, and practical wind turbine reliability models are illustrated, including preliminary results. This report also presents a continuing process of how to proceed with controlling industry requirements, needs, and expectations related to Reliability, Availability, Maintainability, and Safety. A simply stated goal of this process is to better understand and to improve the operable reliability of wind turbine installations.

Linsday, James (ARES Corporation); Briand, Daniel; Hill, Roger Ray; Stinebaugh, Jennifer A.; Benjamin, Allan S. (ARES Corporation)

2008-02-01

269

Utilisation of principles from structural reliability in quantitative risk analysis: example from an offshore transport problem  

International Nuclear Information System (INIS)

The objective of this paper is to discuss the use of methods developed for calculation of the reliability of structures as a general tool for calculating probabilities within the context of quantitative risk analysis. By applying these methods the analyst is enabled to model the system, the uncertainties and the parameter correlations separately and systematically. This is ensured by flexible event and system modelling by logical combination of limit state functions and suitable uncertainty modelling by assigning marginal probability distributions and correlation measures. These properties might enable the analyst to include more knowledge in the analysis, compared to models traditionally applied in quantitative risk analysis. The subjectivistic theory of probability, which consistently allows subjective considerations to be included in the analysis, is adopted and provides the framework for the discussions. The paper concludes that methods of structural reliability represent a useful tool for calculating probabilities in a great number of situations in quantitative risk analysis. An example from an offshore towing operation sketches how these methods can open for stochastic modelling more in line with the characteristics of the actual system, compared to a typical event tree approach

270

A comparative analysis of aircraft noise performances  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a comparative analysis of aircraft acoustical performance based on the definition of a noise performance indicator called ENSA (equivalent number of standard aircraft. ENSA methodology is based on the choice of a standard aircraft, then ENSA’s values are obtained by comparing the generic aircraft’s performances with the standard aircraft’s performances. The performance evaluation is performed by analysing for each aircraft the equivalent number of standard aircrafts movements generating a noise level corresponding with one standard aircraft movement. This comparative analysis permits the evaluation of aircraft noise performance by comparing the ENSA values for different aircrafts.

Nicola Gualandi

2009-09-01

271

An efficient phased mission reliability analysis for autonomous vehicles  

International Nuclear Information System (INIS)

Autonomous systems are becoming more commonly used, especially in hazardous situations. Such systems are expected to make their own decisions about future actions when some capabilities degrade due to failures of their subsystems. Such decisions are made without human input, therefore they need to be well-informed in a short time when the situation is analysed and future consequences of the failure are estimated. The future planning of the mission should take account of the likelihood of mission failure. The reliability analysis for autonomous systems can be performed using the methodologies developed for phased mission analysis, where the causes of failure for each phase in the mission can be expressed by fault trees. Unmanned autonomous vehicles (UAVs) are of a particular interest in the aeronautical industry, where it is a long term ambition to operate them routinely in civil airspace. Safety is the main requirement for the UAV operation and the calculation of failure probability of each phase and the overall mission is the topic of this paper. When components or subsystems fail or environmental conditions throughout the mission change, these changes can affect the future mission. The new proposed methodology takes into account the available diagnostics data and is used to predict future capabilities of the UAV in real time. Since this methodology is based on the efficient BDD method, the quickly provided advice can be used in making decisions. When failures occur appropriate actions are required in order to preserve safety of the autonomous vehicle. The overall decision making strategy for autonomous vehicles is explained in this paper. Some limitations of the methodology are discussed and further improvements are presented based on experimental results.

272

An efficient phased mission reliability analysis for autonomous vehicles  

Energy Technology Data Exchange (ETDEWEB)

Autonomous systems are becoming more commonly used, especially in hazardous situations. Such systems are expected to make their own decisions about future actions when some capabilities degrade due to failures of their subsystems. Such decisions are made without human input, therefore they need to be well-informed in a short time when the situation is analysed and future consequences of the failure are estimated. The future planning of the mission should take account of the likelihood of mission failure. The reliability analysis for autonomous systems can be performed using the methodologies developed for phased mission analysis, where the causes of failure for each phase in the mission can be expressed by fault trees. Unmanned autonomous vehicles (UAVs) are of a particular interest in the aeronautical industry, where it is a long term ambition to operate them routinely in civil airspace. Safety is the main requirement for the UAV operation and the calculation of failure probability of each phase and the overall mission is the topic of this paper. When components or subsystems fail or environmental conditions throughout the mission change, these changes can affect the future mission. The new proposed methodology takes into account the available diagnostics data and is used to predict future capabilities of the UAV in real time. Since this methodology is based on the efficient BDD method, the quickly provided advice can be used in making decisions. When failures occur appropriate actions are required in order to preserve safety of the autonomous vehicle. The overall decision making strategy for autonomous vehicles is explained in this paper. Some limitations of the methodology are discussed and further improvements are presented based on experimental results.

Remenyte-Prescott, R., E-mail: R.Remenyte-Prescott@nottingham.ac.u [Nottingham Transportation Engineering Centre, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Andrews, J.D. [Nottingham Transportation Engineering Centre, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Chung, P.W.H. [Department of Computer Science, Loughborough University, Loughborough LE11 3TU (United Kingdom)

2010-03-15

273

Guidelines for reliability analysis of control elements and systems of nuclear power plants  

International Nuclear Information System (INIS)

The relationship is analysed between operating failures and the control system reliability. The procedure is defined of the reliability analysis of the control system for nuclear power plants from the qualitative and quantitative points of view. The preparation of input failure data for computations is assessed. Reliability computations for nuclear power plants in the Hungarian People's Republic are still in the initial stage. (Ha)

274

Psychometric Inferences from a Meta-Analysis of Reliability and Internal Consistency Coefficients  

Science.gov (United States)

A meta-analysis of the reliability of the scores from a specific test, also called reliability generalization, allows the quantitative synthesis of its properties from a set of studies. It is usually assumed that part of the variation in the reliability coefficients is due to some unknown and implicit mechanism that restricts and biases the…

Botella, Juan; Suero, Manuel; Gambara, Hilda

2010-01-01

275

EPRI/NRC-RES fire human reliability analysis guidelines  

International Nuclear Information System (INIS)

During the 1990s, the Electric Power Research Institute (EPRI) developed methods for fire risk analysis to support its utility members in the preparation of responses to Generic Letter 88-20, Supplement 4, 'Individual Plant Examination - External Events' (IPEEE). This effort produced a Fire Risk Assessment methodology for operations at power that was used by the majority of U.S. nuclear power plants (NPPs) in support of the IPEEE program and several NPPs overseas. Although these methods were acceptable for accomplishing the objectives of the IPEEE, EPRI and the U.S. Nuclear Regulatory Commission (NRC) recognized that they required upgrades to support current requirements for risk-informed, performance-based (RI/PB) applications. In 2001, EPRI and the USNRC's Office of Nuclear Regulatory Research (RES) embarked on a cooperative project to improve the state-of-the-art in fire risk assessment to support a new risk-informed environment in fire protection. This project produced a consensus document, NUREG/CR-6850 (EPRI 1011989), entitled 'Fire PRA Methodology for Nuclear Power Facilities' which addressed fire risk for at power operations. NUREG/CR-6850 developed high level guidance on the process for identification and inclusion of human failure events (HFEs) into the fire PRA (FPRA), and a methodology for assigning quantitative screening values to these HFEs. It outlined the initial considerations of performance shaping factors (PSFs) and related fire effects that may need to be addressed in developing best-estimate human error probabilities (HEPs). However, NUREG/CR-6850 did not describe a methodology to develop best-estimate HEPs given the PSFs and the fire-related effects. In 2007, EPRI and RES embarked on another cooperative project to develop explicit guidance for estimating HEPs for human failure events under fire generated conditions, building upon existing human reliability analysis (HRA) methods. This document provides a methodology and guidance for conducting a fire HRA. This process includes identification and definition of post-fire human failure events, qualitative analysis, quantification, recovery, dependency, and uncertainty. This document provides three approaches to quantification: screening, scoping, and detailed HRA. Screening is based on the guidance in NUREG/CR-6850, with some additional guidance for scenarios with long time windows. Scoping is a new approach to quantification developed specifically to support the iterative nature of fire PRA quantification. Scoping is intended to provide less conservative HEPs than screening, but requires fewer resources than a detailed HRA analysis. For detailed HRA quantification, guidance has been developed on how to apply existing methods to assess post-fire fire HEPs.

276

EPRI/NRC-RES fire human reliability analysis guidelines.  

Energy Technology Data Exchange (ETDEWEB)

During the 1990s, the Electric Power Research Institute (EPRI) developed methods for fire risk analysis to support its utility members in the preparation of responses to Generic Letter 88-20, Supplement 4, 'Individual Plant Examination - External Events' (IPEEE). This effort produced a Fire Risk Assessment methodology for operations at power that was used by the majority of U.S. nuclear power plants (NPPs) in support of the IPEEE program and several NPPs overseas. Although these methods were acceptable for accomplishing the objectives of the IPEEE, EPRI and the U.S. Nuclear Regulatory Commission (NRC) recognized that they required upgrades to support current requirements for risk-informed, performance-based (RI/PB) applications. In 2001, EPRI and the USNRC's Office of Nuclear Regulatory Research (RES) embarked on a cooperative project to improve the state-of-the-art in fire risk assessment to support a new risk-informed environment in fire protection. This project produced a consensus document, NUREG/CR-6850 (EPRI 1011989), entitled 'Fire PRA Methodology for Nuclear Power Facilities' which addressed fire risk for at power operations. NUREG/CR-6850 developed high level guidance on the process for identification and inclusion of human failure events (HFEs) into the fire PRA (FPRA), and a methodology for assigning quantitative screening values to these HFEs. It outlined the initial considerations of performance shaping factors (PSFs) and related fire effects that may need to be addressed in developing best-estimate human error probabilities (HEPs). However, NUREG/CR-6850 did not describe a methodology to develop best-estimate HEPs given the PSFs and the fire-related effects. In 2007, EPRI and RES embarked on another cooperative project to develop explicit guidance for estimating HEPs for human failure events under fire generated conditions, building upon existing human reliability analysis (HRA) methods. This document provides a methodology and guidance for conducting a fire HRA. This process includes identification and definition of post-fire human failure events, qualitative analysis, quantification, recovery, dependency, and uncertainty. This document provides three approaches to quantification: screening, scoping, and detailed HRA. Screening is based on the guidance in NUREG/CR-6850, with some additional guidance for scenarios with long time windows. Scoping is a new approach to quantification developed specifically to support the iterative nature of fire PRA quantification. Scoping is intended to provide less conservative HEPs than screening, but requires fewer resources than a detailed HRA analysis. For detailed HRA quantification, guidance has been developed on how to apply existing methods to assess post-fire fire HEPs.

Lewis, Stuart R. (Electric Power Research Institute, Charlotte, NC); Cooper, Susan E. (U.S. Nuclear Regulatory Commission, Rockville, MD); Najafi, Bijan (SAIC, Campbell, CA); Collins, Erin (SAIC, Campbell, CA); Hannaman, Bill (SAIC, Campbell, CA); Kohlhepp, Kaydee (Scientech, Tukwila, WA); Grobbelaar, Jan (Scientech, Tukwila, WA); Hill, Kendra (U.S. Nuclear Regulatory Commission, Rockville, MD); Hendrickson, Stacey M. Langfitt; Forester, John Alan; Julius, Jeff (Scientech, Tukwila, WA)

2010-03-01

277

Mission reliability analysis of fault-tolerant multiple-phased systems  

International Nuclear Information System (INIS)

Fault-tolerant multiple-phased systems (FTMPS) are defined as systems whose critical components are independently replicated and whose operational life can be partitioned into a set of disjoint periods, called 'phases'. Because of their deployment in critical applications, their mission reliability analysis is a task of primary relevance to validate the designs. This paper is focused on the reliability analysis of FTMPS with random phase durations, non-exponentially distributed repair activities and different repair policies. For self-repairable FTMPS with a component-level reconfiguration architecture, we derive several efficient formulations from the underlying structure characteristics for their intraphase behavior analysis. We also present a uniform solution framework of the mission reliability for FTMPS with generally distributed phase durations. Compared with existing methods based on deterministic and stochastic Petri nets or Markov regenerative stochastic Petri nets, our approach is more simple in concept and powerful in computation. Two examples of FTMPS are analyzed to illustrate the advantages of our approach

278

Mission reliability analysis of fault-tolerant multiple-phased systems  

Energy Technology Data Exchange (ETDEWEB)

Fault-tolerant multiple-phased systems (FTMPS) are defined as systems whose critical components are independently replicated and whose operational life can be partitioned into a set of disjoint periods, called 'phases'. Because of their deployment in critical applications, their mission reliability analysis is a task of primary relevance to validate the designs. This paper is focused on the reliability analysis of FTMPS with random phase durations, non-exponentially distributed repair activities and different repair policies. For self-repairable FTMPS with a component-level reconfiguration architecture, we derive several efficient formulations from the underlying structure characteristics for their intraphase behavior analysis. We also present a uniform solution framework of the mission reliability for FTMPS with generally distributed phase durations. Compared with existing methods based on deterministic and stochastic Petri nets or Markov regenerative stochastic Petri nets, our approach is more simple in concept and powerful in computation. Two examples of FTMPS are analyzed to illustrate the advantages of our approach.

Mo Yuchang [Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)], E-mail: myc@ftcl.hit.edu.cn; Siewiorek, Daniel [Department of Computer Science and Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Yang Xiaozong [Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)

2008-07-15

279

Reliability analysis for elastoplastic mechanical structures under stochastic uncertainty  

Energy Technology Data Exchange (ETDEWEB)

Problems from plastic limit load or shakedown analysis and optimal plastic design are based on the convex yield criterion and the linear equilibrium equation for the generic stress (state) vector {sigma}. Having to take into account, in practice, stochastic variations of the vector y = y({omega}) of model parameters, e.g. yield stresses, external loadings, cost coefficients, etc., the basic stochastic plastic analysis or optimal plastic design problem must be replaced - in order to get robust optimal designs/load factors - by an appropriate deterministic substitute problem. For this purpose, the existence of a statically admissible (safe) stress state vector is described first by means of an explicit scalar state function s{sup *} = s{sup *} (y,x) depending on the parameter vector y and the design vector x. The state or performance function s{sup *} (y,x) is defined by the minimum value function of a convex or linear program based on the basic safety conditions of plasticity theory: A safe (stress) state exists then if and only if s{sup *} < 0, and a safe stress state cannot be guaranteed if and only if s{sup *} {>=}0. Hence, the probability of survival can be represented by ps = P(s{sup *} (y({omega}),x)<0). Using FORM, the probability of survival is approximated then by the well-known formula p{sub s} {proportional_to} {phi} (parallel z{sup *}{sub x} parallel) where parallel z{sup *}{sub x} parallel denotes the length of a so-called {beta}-point, hence, a projection of the origin 0 to the failure domain (transformed to the space of normal distributed model parameters z({omega}) = T(y({omega}))). Moreover, {phi} = {phi}(t) denotes the distribution function of the standard N(0,1) normal distribution. Thus, the basic reliability condition, used e.g. in reliability-based optimal plastic design or in limit load analysis problems, reads parallel z{sup *}{sub x} parallel {>=} {phi}{sup -1}({alpha}{sub s}) with a prescribed minimum probability {alpha}{sub s}. In addition, several different response surface methods including the standard response surface method are also applied to compute a {beta}-point z{sup *}{sub x} in order to reduce the computational time as well as having more accurate results than the first order approximation methods by using the obtained response surface function with any simulation methods such as Monte Carlo Simulation. However, for the problems having a polygon type limit state function, the standard response surface methods can not approximate well enough. Thus, a response surface method based on the piecewise regression has been developed for such problems. Applications of the methods developed to several types of structures are presented for the examples given in this paper. (orig.)

Marti, K. [Federal Armed Forces Univ. Munich, Neubiberg (Germany). Aero-Space Engineering and Technology; Kaymaz, I. [Atatuerk Univ., Erzurum (Turkey). Dept. of Mechanical Engineering

2006-05-15

280

Reliability Modeling and Analysis of SCI Topological Network  

Directory of Open Access Journals (Sweden)

Full Text Available The problem of reliability modeling on the Scalable Coherent Interface (SCI rings and topological network is studied. The reliability models of three SCI rings are developed and the factors which influence the reliability of SCI rings are studied. By calculating the shortest path matrix and the path quantity matrix of different types SCI network topology, the communication characteristics of SCI network are obtained. For the situations of the node-damage and edge-damage, the survivability of SCI topological network is studied.

Hongzhe Xu

2012-03-01

 
 
 
 
281

Reliability analysis of an RC defense structure loaded by a dense snow avalanche pressure signal  

Science.gov (United States)

To protect humans, roads or houses against snow avalanches, civil engineering structures are widely used. Designing these structures is still a challenge especially due to the uncertainties related to the loading developed by a snow avalanche. The case of the avalanche of Taconnaz (France), which occurred in 1999 and where important parts of the RC defense structure were destroyed, underlines the necessary to consider reliability approaches for the design of such structures. This paper proposes a reliability analysis of an L-shaped reinforced concrete (RC) protective structure subjected to a dense snow avalanche. A deterministic mechanical model, based on the finite element method, has been developed and allows describing the behavior of the structure. Next, a reliable model allows propagating uncertainties through the mechanical model and assessing the failure probability of the structure. The choices of random variables (the inputs) and their distributions, the failure criteria and the reliability methods are presented and discussed. Two criteria are considered: on the one hand, a local criterion defined in term of stress exceedence within concrete and steel, and on the other hand a global criterion defined in term of maximal displacement of the structure. Moreover, Kernel Smoothing and Monte-Carlo methods are used and compared to assess the failure probability and to derive fragility curves. These latter describe the failure probability of the structure according to the loading magnitude.

Ousset, Isabelle; Bertrand, David; Limam, Ali; Naaïm, Mohamed

2014-05-01

282

Reliability and Comparability of Psychosis Patients' Retrospective Reports of Childhood Abuse  

Science.gov (United States)

An increasing number of studies are demonstrating an association between childhood abuse and psychosis. However, the majority of these rely on retrospective self-reports in adulthood that may be unduly influenced by current psychopathology. We therefore set out to explore the reliability and comparability of first-presentation psychosis patients’ reports of childhood abuse. Psychosis case subjects were drawn from the Aetiology and Ethnicity of Schizophrenia and Other Psychoses (ÆSOP) epidemiological study and completed the Childhood Experience of Care and Abuse Questionnaire to elicit abusive experiences that occurred prior to 16 years of age. High levels of concurrent validity were demonstrated with the Parental Bonding Instrument (antipathy: rs = 0.350–0.737, P < .001; neglect: rs = 0.688–0.715, P < .001), and good convergent validity was shown with clinical case notes (sexual abuse: ? = 0.526, P < .001; physical abuse: ? = 0.394, P < .001). Psychosis patients’ reports were also reasonably stable over a 7-year period (sexual abuse: ? = 0.590, P < .01; physical abuse: ? = 0.634, P < .001; antipathy: ? = 0.492, P < .01; neglect: ? = 0.432, P < .05). Additionally, their reports of childhood abuse were not associated with current severity of psychotic symptoms (sexual abuse: U = 1768.5, P = .998; physical abuse: U = 2167.5, P = .815; antipathy: U = 2216.5, P = .988; neglect: U = 1906.0, P = .835) or depressed mood (sexual abuse: ?2 = 0.634, P = .277; physical abuse: ?2 = 0.159, P = .419; antipathy: ?2 = 0.868, P = .229; neglect: ?2 = 0.639, P = .274). These findings provide justification for the use in future studies of retrospective reports of childhood abuse obtained from individuals with psychotic disorders. PMID:19776204

Fisher, Helen L.; Craig, Thomas K.; Fearon, Paul; Morgan, Kevin; Dazzan, Paola; Lappin, Julia; Hutchinson, Gerard; Doody, Gillian A.; Jones, Peter B.; McGuffin, Peter; Murray, Robin M.; Leff, Julian; Morgan, Craig

2011-01-01

283

Reliability analysis based on losses from failure Modelling  

Directory of Open Access Journals (Sweden)

Full Text Available As the cost of software application failures grows andas these failures increasingly impact business performance,software reliability will become progressively more important.Employing effective software reliability engineering techniquesto improve product and process reliability would be theindustry’s best interests as well as major challenges. As softwarecomplexity and software quality are highly related to softwarereliability, the measurements of software complexity and qualityattributes have been explored for early prediction of softwarereliability. Static as well as dynamic program complexitymeasurements have been collected, such as lines of code, numberof operators, relative program complexity, functional complexity,operational complexity, and so on. The complexity metrics can befurther included in software reliability models for earlyreliability prediction, for example, to predict the initial softwarefault density and failure rate.

Dr. Amit Gupta , Renu Garg

2013-06-01

284

Reliability analysis of stiff versus flexible piping. Final project report  

International Nuclear Information System (INIS)

This research project is to develop a technical basis for flexible piping designs which will improve piping reliability and minimize the use of pipe supports, snubbers, and pipe whip restraints. This study indicated that piping design can be made more reliable by some reduction of rigid supports and/or snubbers. This study also confirmed that the malfunction of pipe whip restraints introduced higher thermal stresses and tended to reduce the overall piping reliability. Finally, our results indicated that supports in a flexible piping design may need to be reevaluated and that the elimination of pipe supports which are close to components should be done with care in order to minimize the impact on the component reliability

285

Reliability analysis of the recirculation phase of the safety injection system of Angra-1  

International Nuclear Information System (INIS)

The calculation of several reliability parameters-failure probability, unavailability and unreliability - of the recirculation phase of the safety injection system of Angra-1, was done. This system has two distinct modes of operation (short term and long term) which were fault tree analysed both separately and as a whole. To obtain quantitative results the computer codes SAMPLE and PRET-KITT were utilized. The former was used to consider the uncertainties in the failure data (drawn integrally from WASH-1400) and the latter to obtain time dependent unreliability values. Hardware failures and common-mode failures were considered. Altough the analysis methods employed here differ somewhat from those used in WASH-1400, the results which could be compared were found to have the order of magnitude. A viability study of some suggestions of system's modifications was performed, and it has shown that some significant reliability improvements can be achieved with reasonably simple changes. (Author)

286

Stochastic Petri nets for the reliability analysis of communication network applications with alternate-routing  

International Nuclear Information System (INIS)

In this paper, we present a comparative reliability analysis of an application on a corporate B-ISDN network under various alternate-routing protocols. For simple cases, the reliability problem can be cast into fault-tree models and solved rapidly by means of known methods. For more complex scenarios, state space (Markov) models are required. However, generation of large state space models can get very labor intensive and error prone. We advocate the use of stochastic reward nets (a variant of stochastic Petri nets) for the concise specification, automated generation and solution of alternate-routing protocols in networks. This paper is written in a tutorial style so as to make it accessible to a large audience

287

RADYBAN: A tool for reliability analysis of dynamic fault trees through conversion into dynamic Bayesian networks  

International Nuclear Information System (INIS)

In this paper, we present RADYBAN (Reliability Analysis with DYnamic BAyesian Networks), a software tool which allows to analyze a dynamic fault tree relying on its conversion into a dynamic Bayesian network. The tool implements a modular algorithm for automatically translating a dynamic fault tree into the corresponding dynamic Bayesian network and exploits classical algorithms for the inference on dynamic Bayesian networks, in order to compute reliability measures. After having described the basic features of the tool, we show how it operates on a real world example and we compare the unreliability results it generates with those returned by other methodologies, in order to verify the correctness and the consistency of the results obtained

288

Reliability Analysis in Parallel and Distributed Systems with Network Contention  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper tackles the reliability problem of task allocation in heterogeneous distributed systems in the presence of network contention. A large number of scheduling heuristics has been presented in literature, but most of them target maximizing the system reliability without taking network contention delay into consideration. In this paper, we deal with a more realistic model for heterogeneous networks of workstations by taking network contention as an important factor in our study. Althoug...

El, Hussein Ghor; Rafic Hage Chehade; Tamim Fliti

2012-01-01

289

Software analysis handbook: Software complexity analysis and software reliability estimation and prediction  

Science.gov (United States)

This handbook documents the three software analysis processes the Space Station Software Analysis team uses to assess space station software, including their backgrounds, theories, tools, and analysis procedures. Potential applications of these analysis results are also presented. The first section describes how software complexity analysis provides quantitative information on code, such as code structure and risk areas, throughout the software life cycle. Software complexity analysis allows an analyst to understand the software structure, identify critical software components, assess risk areas within a software system, identify testing deficiencies, and recommend program improvements. Performing this type of analysis during the early design phases of software development can positively affect the process, and may prevent later, much larger, difficulties. The second section describes how software reliability estimation and prediction analysis, or software reliability, provides a quantitative means to measure the probability of failure-free operation of a computer program, and describes the two tools used by JSC to determine failure rates and design tradeoffs between reliability, costs, performance, and schedule.

Lee, Alice T.; Gunn, Todd; Pham, Tuan; Ricaldi, Ron

1994-01-01

290

Comparative analysis of methods of hardness assessment  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The aim of this paper is to show how it could utilize the statistical methods for the process management.Design/methodology/approach: The research methodology bases on a theoretical analysis and empirical researches. A practical solution is presented to compare measurements methods of hardness and to estimate capability indices of measurement system.Findings: Measurement system analysis (MSA, particularly theory of statistical tests brings correct results for the analysed case.Research limitations/implications: Comparative analysis of measurement methods – interlaboratory studies, delivery control etc. is necessary in the interpretation of results.Practical implications: Described methodology and results can be employed in the industrial practice.Originality/value: The complete statistical comparative analysis of methods of hardness measurement with the help of a stationary and mobile hardness tester.

A. Czarski

2009-12-01

291

Resource allocatiion: sequential data collection for reliability analysis involving systems and component level data  

Energy Technology Data Exchange (ETDEWEB)

In analyzing the reliability of complex systems, several types of data from full-system tests to component level tests are commonly available and are used. After a preliminary analysis, additional resources may be available to collect new data. The goal of resource allocation is to identify the best new data to collect to maximally improve the prediction of system reliability. While several possible definitions of 'maximally improve' are possible, we focus on reducing the uncertainty or the width of the uncertainty interval for the prediction of system reliability at a user-specified age(s). In this paper, we present an algorithm that allows us to estimate the anticipated improvement to the analysis with the addition of new data, based on current understanding of all of the statistical model parameters. This quantitative assessment of the anticipated improvement can be helpful to justify the benefits of collecting new data. Additionally by comparing different potential allocations, it is possible to determine what new data should be collected to improve our understanding of the response. This optimization takes into account the relative cost of different data types and can be based on flexible allocation options, or subject to logistical constraints.

Anderson-cooke, Christine M [Los Alamos National Laboratory

2010-01-01

292

Comparing Between Maximum Likelihood and Least Square Estimators for Gompertz Software Reliability Model  

Directory of Open Access Journals (Sweden)

Full Text Available Software reliability models (SRMs are very important for estimating and predicting software reliability in the testing/debugging phase. The contributions of this paper are as follows. First, a historical review of the Gompertz SRM is given. Based on several software failure data, the parameters of the Gompertz software reliability model are estimated using two estimation methods, the traditional maximum likelihood and the least square. The methods of estimation are evaluated using the MSE and R-squared criteria. The results show that the least square estimation is an attractive method in term of predictive performance and can be used when the maximum likelihood method fails to give good prediction results.

Lutfiah Ismail Al turk

2014-07-01

293

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several reliability engineering approaches have been proposed to identify and recover from failures. A well-known and mature approach is the Failure Mode and Effect Analysis (FMEA) method that is usually utilized together with Fault Tree Analysis (FTA) to analyze and diagnose the causes of failures. Unfortunately, both approaches seem to have primarily focused on failures of hardware components and less on software components. Moreover, for utilizing FMEA and FTA very often an existing implem...

Sozer, Hasan; Tekinerdogan, Bedir; Aksit, Mehmet

2007-01-01

294

The European COPHES/DEMOCOPHES project: towards transnational comparability and reliability of human biomonitoring results.  

Science.gov (United States)

COPHES/DEMOCOPHES has its origins in the European Environment and Health Action Plan of 2004 to "develop a coherent approach on human biomonitoring (HBM) in Europe". Within this twin-project it was targeted to collect specimens from 120 mother-child-pairs in each of the 17 participating European countries. These specimens were investigated for six biomarkers (mercury in hair; creatinine, cotinine, cadmium, phthalate metabolites and bisphenol A in urine). The results for mercury in hair are described in a separate paper. Each participating member state was requested to contract laboratories, for capacity building reasons ideally within its borders, carrying out the chemical analyses. To ensure comparability of analytical data a Quality Assurance Unit (QAU) was established which provided the participating laboratories with standard operating procedures (SOP) and with control material. This material was specially prepared from native, non-spiked, pooled urine samples and was tested for homogeneity and stability. Four external quality assessment exercises were carried out. Highly esteemed laboratories from all over the world served as reference laboratories. Web conferences after each external quality assessment exercise functioned as a new and effective tool to improve analytical performance, to build capacity and to educate less experienced laboratories. Of the 38 laboratories participating in the quality assurance exercises 14 laboratories qualified for cadmium, 14 for creatinine, 9 for cotinine, 7 for phthalate metabolites and 5 for bisphenol A in urine. In the last of the four external quality assessment exercises the laboratories that qualified for DEMOCOPHES performed the determinations in urine with relative standard deviations (low/high concentration) of 18.0/2.1% for cotinine, 14.8/5.1% for cadmium, 4.7/3.4% for creatinine. Relative standard deviations for the newly emerging biomarkers were higher, with values between 13.5 and 20.5% for bisphenol A and between 18.9 and 45.3% for the phthalate metabolites. Plausibility control of the HBM results of all participating countries disclosed analytical shortcomings in the determination of Cd when using certain ICP/MS methods. Results were corrected by reanalyzes. The COPHES/DEMOCOPHES project for the first time succeeded in performing a harmonized pan-European HBM project. All data raised have to be regarded as utmost reliable according to the highest international state of the art, since highly renowned laboratories functioned as reference laboratories. The procedure described here, that has shown its success, can be used as a blueprint for future transnational, multicentre HBM projects. PMID:24405937

Schindler, Birgit Karin; Esteban, Marta; Koch, Holger Martin; Castano, Argelia; Koslitz, Stephan; Cañas, Ana; Casteleyn, Ludwine; Kolossa-Gehring, Marike; Schwedler, Gerda; Schoeters, Greet; Hond, Elly Den; Sepai, Ovnair; Exley, Karen; Bloemen, Louis; Horvat, Milena; Knudsen, Lisbeth E; Joas, Anke; Joas, Reinhard; Biot, Pierre; Aerts, Dominique; Lopez, Ana; Huetos, Olga; Katsonouri, Andromachi; Maurer-Chronakis, Katja; Kasparova, Lucie; Vrbík, Karel; Rudnai, Peter; Naray, Miklos; Guignard, Cedric; Fischer, Marc E; Ligocka, Danuta; Janasik, Beata; Reis, M Fátima; Namorado, Sónia; Pop, Cristian; Dumitrascu, Irina; Halzlova, Katarina; Fabianova, Eleonora; Mazej, Darja; Tratnik, Janja Snoj; Berglund, Marika; Jönsson, Bo; Lehmann, Andrea; Crettaz, Pierre; Frederiksen, Hanne; Nielsen, Flemming; McGrath, Helena; Nesbitt, Ian; De Cremer, Koen; Vanermen, Guido; Koppen, Gudrun; Wilhelm, Michael; Becker, Kerstin; Angerer, Jürgen

2014-07-01

295

The European COPHES/DEMOCOPHES project : Towards transnational comparability and reliability of human biomonitoring results  

DEFF Research Database (Denmark)

COPHES/DEMOCOPHES has its origins in the European Environment and Health Action Plan of 2004 to "develop a coherent approach on human biomonitoring (HBM) in Europe". Within this twin-project it was targeted to collect specimens from 120 mother-child-pairs in each of the 17 participating European countries. These specimens were investigated for six biomarkers (mercury in hair; creatinine, cotinine, cadmium, phthalate metabolites and bisphenol A in urine). The results for mercury in hair are described in a separate paper. Each participating member state was requested to contract laboratories, for capacity building reasons ideally within its borders, carrying out the chemical analyses. To ensure comparability of analytical data a Quality Assurance Unit (QAU) was established which provided the participating laboratories with standard operating procedures (SOP) and with control material. This material was specially prepared from native, non-spiked, pooled urine samples and was tested for homogeneity and stability.Four external quality assessment exercises were carried out. Highly esteemed laboratories from all over the world served as reference laboratories. Web conferences after each external quality assessment exercise functioned as a new and effective tool to improve analytical performance, to build capacity and to educate less experienced laboratories. Of the 38 laboratories participating in the quality assurance exercises 14 laboratories qualified for cadmium, 14 for creatinine, 9 for cotinine, 7 for phthalate metabolites and 5 for bisphenol A in urine. In the last of the four external quality assessment exercises the laboratories that qualified for DEMOCOPHES performed the determinations in urine with relative standard deviations (low/high concentration) of 18.0/2.1% for cotinine, 14.8/5.1% for cadmium, 4.7/3.4% for creatinine. Relative standard deviations for the newly emerging biomarkers were higher, with values between 13.5 and 20.5% for bisphenol A and between 18.9 and 45.3% for the phthalate metabolites. Plausibility control of the HBM results of all participating countries disclosed analytical shortcomings in the determination of Cd when using certain ICP/MS methods. Results were corrected by reanalyzes. The COPHES/DEMOCOPHES project for the first time succeeded in performing a harmonized pan-European HBM project. All data raised have to be regarded as utmost reliable according to the highest international state of the art, since highly renowned laboratories functioned as reference laboratories. The procedure described here, that has shown its success, can be used as a blueprint for future transnational, multicentre HBM projects.

Schindler, Birgit Karin; Esteban, Marta

2014-01-01

296

Functional reliability analysis of safety grade decay heat removal system of PFBR by augmentation of approximate linear response surfaces - 143  

International Nuclear Information System (INIS)

Functional reliability analysis of passive safety systems is necessary to quantify the ability of the system to accomplish the intended function unaffected by the uncertainties pertained to the underlying physical processes. Functional reliability analysis includes Monte Carlo sampling of the uncertainties followed by computation of system response by a deterministic system code. For complex passive safety systems of small failure probability, Monte Carlo simulations using deterministic system codes are computationally expensive and often prohibitive. Functional failure analysis using computationally efficient approximate solutions like response surfaces has been quite popular. But in high dimensional problems, due to their approximate nature, response surfaces are not accurate enough. Nevertheless, approximate solutions provide a great source of insight for understanding system behavior. In this respect, the recently proposed Response Conditioning Method (RCM) based on Subset Simulation (SS) is considered in this paper to incorporate the knowledge obtained by approximate solutions in functional reliability analysis for obtaining consistent and computationally efficient reliability estimates. The method is applied to evaluate functional reliability of Passive Safety Grade Decay Heat removal system of Indian 500 MWe Prototype Fast Breeder Reactor (PFBR). The results are compared with direct Monte Carlo simulation and observed that the method considered is computationally very efficient and provides consistent reliability estimates. (authors)

297

A study of annunciator response model application in human reliability analysis  

International Nuclear Information System (INIS)

The Annunciator Response Model is a method introduced in 'Handbook of Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications'. It can be used to estimate the probability of noticing a particular annunciator or combination of annunciators and initiating action in response to them. No systematic study and application of the method has ever been performed in human reliability analysis (HRA) in China. In order to understand the method and its application effectively, first the basic theory of the Annunciator Response Model is described briefly, then some human error events presented in AP1000 HRA are analyzed with different HRA methods and the results are compared. Subsequently the applicability and comparability of the Annunciator Response Model in post-accident HRA are discussed. It is concluded that the Anunciator Response Model can preferably model the operators' responses to multiple annunciators, and the method can be applied to an engineering project in the case of diagnosis analysis of the post-accident events in responding to the cues without emphasis on excessive interpretation, judgment or decision-making. (authors)

298

A Reliable Method for Rhythm Analysis during Cardiopulmonary Resuscitation  

Science.gov (United States)

Interruptions in cardiopulmonary resuscitation (CPR) compromise defibrillation success. However, CPR must be interrupted to analyze the rhythm because although current methods for rhythm analysis during CPR have high sensitivity for shockable rhythms, the specificity for nonshockable rhythms is still too low. This paper introduces a new approach to rhythm analysis during CPR that combines two strategies: a state-of-the-art CPR artifact suppression filter and a shock advice algorithm (SAA) designed to optimally classify the filtered signal. Emphasis is on designing an algorithm with high specificity. The SAA includes a detector for low electrical activity rhythms to increase the specificity, and a shock/no-shock decision algorithm based on a support vector machine classifier using slope and frequency features. For this study, 1185 shockable and 6482 nonshockable 9-s segments corrupted by CPR artifacts were obtained from 247 patients suffering out-of-hospital cardiac arrest. The segments were split into a training and a test set. For the test set, the sensitivity and specificity for rhythm analysis during CPR were 91.0% and 96.6%, respectively. This new approach shows an important increase in specificity without compromising the sensitivity when compared to previous studies. PMID:24895621

Ayala, U.; Irusta, U.; Ruiz, J.; Eftestøl, T.; Kramer-Johansen, J.; Alonso-Atienza, F.; Alonso, E.; González-Otero, D.

2014-01-01

299

Probability maps as a measure of reliability for indivisibility analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Digital terrain models (DTMs represent segments of spatial data bases related to presentation of terrain features and landforms. Square grid elevation models (DEMs have emerged as the most widely used structure during the past decade because of their simplicity and simple computer implementation. They have become an important segment of Topographic Information Systems (TIS, storing natural and artificial landscape in forms of digital models. This kind of a data structure is especially suitable for morph metric terrain evaluation and analysis, which is very important in environmental and urban planning and Earth surface modeling applications. One of the most often used functionalities of Geographical information systems software packages is indivisibility or view shed analysis of terrain. Indivisibility determination from analog topographic maps may be very exhausting, because of the large number of profiles that have to be extracted and compared. Terrain representation in form of the DEMs databases facilitates this task. This paper describes simple algorithm for terrain view shed analysis by using DEMs database structures, taking into consideration the influence of uncertainties of such data to the results obtained thus far. The concept of probability maps is introduced as a mean for evaluation of results, and is presented as thematic display.

Joksi? Dušan

2005-01-01

300

Reliability Engineering Analysis of ATLAS Data Reprocessing Campaigns  

CERN Document Server

During three years of LHC data taking, the ATLAS collaboration completed three petascale data reprocessing campaigns on the Grid, with up to 2 PB of data being reprocessed every year. In reprocessing on the Grid, failures can occur for a variety of reasons, while Grid heterogeneity makes failures hard to diagnose and repair quickly. As a result, Big Data processing on the Grid must tolerate a continuous stream of failures, errors and faults. While ATLAS fault-tolerance mechanisms improve the reliability of Big Data processing in the Grid, their benefits come at costs and result in delays making the performance prediction difficult. Reliability Engineering provides a framework for fundamental understanding of the Big Data processing on the Grid, which is not a desirable enhancement but a necessary requirement. In ATLAS, cost monitoring and performance prediction became critical for the success of the reprocessing campaigns conducted in preparation for the major physics conferences. In addition, our Reliability...

Vaniachine, A; The ATLAS collaboration; Karpenko, D

2013-01-01

 
 
 
 
301

Comparative Analysis of Uncertainties in Urban Surface Runoff Modelling  

DEFF Research Database (Denmark)

In the present paper a comparison between three different surface runoff models, in the numerical urban drainage tool MOUSE, is conducted. Analysing parameter uncertainty, it is shown that the models are very sensitive with regards to the choice of hydrological parameters, when combined overflow volumes are compared - especially when the models are uncalibrated. The occurrences of flooding and surcharge are highly dependent on both hydrological and hydrodynamic parameters. Thus, the conclusion of the paper is that if the use of model simulations is to be a reliable tool for drainage system analysis, further research in improved parameter assessment for surface runoff models is needed.

Thorndahl, SØren; Schaarup-Jensen, Kjeld

2007-01-01

302

The Impact Analysis of Psychological Reliability of Population Pilot Study for Selection of Particular Reliable Multi-Choice Item Test in Foreign Language Research Work  

Science.gov (United States)

The purpose of research described in the current study is the psychological reliability, its importance, application, and more to investigate on the impact analysis of psychological reliability of population pilot study for selection of particular reliable multi-choice item test in foreign language research work. The population for subject…

Fazeli, Seyed Hossein

2010-01-01

303

Reliability modeling and analysis of smart power systems  

CERN Document Server

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

Karki, Rajesh; Verma, Ajit Kumar

2014-01-01

304

Reliability analysis for LEB ring magnet power system in SSC  

International Nuclear Information System (INIS)

The LEB ring magnet power system contains six subsystems, supervisory control, power supplies, regulation, DC bus, resonant cells, and fault sensing network. The system availability of the total LEB RMPS is required to be 0.999. The work in this paper is to allocate the overall LEB RMPS reliability requirement into reliability requirements for each of the subsystems and lower-tier items. The Feasibility-of-Objective technique combining with engineering experience is the key for the allocation. MIL-HDBK-217F is used to derate SCR components. 7 refs., 5 figs

305

Reliability modelling system for analysis of advanced battery technologies  

Science.gov (United States)

Key considerations in evaluating the reliability of advanced battery technologies include the impact of cell failures on battery performance and cost. Pacific Northwest Laboratory developed interactive microcomputer based simulation models to help battery developers use cell reliability data to calculate the expected performance of new battery technologies. Key benefits of this model include its capability to estimate the effect of cell failures upon: (1) battery system discharge performance, (2) system cycle life, and (3) system economic performance (tradeoffs between capital investment and lifetime operating costs).

Imhoff, C. H.; Hostick, C. J.; Nakaoka, R. K.

1985-05-01

306

Technical information report: Plasma melter operation, reliability, and maintenance analysis  

International Nuclear Information System (INIS)

This document provides a technical report of operability, reliability, and maintenance of a plasma melter for low-level waste vitrification, in support of the Hanford Tank Waste Remediation System (TWRS) Low-Level Waste (LLW) Vitrification Program. A process description is provided that minimizes maintenance and downtime and includes material and energy balances, equipment sizes and arrangement, startup/operation/maintence/shutdown cycle descriptions, and basis for scale-up to a 200 metric ton/day production facility. Operational requirements are provided including utilities, feeds, labor, and maintenance. Equipment reliability estimates and maintenance requirements are provided which includes a list of failure modes, responses, and consequences

307

The Barthel Index: comparing inter-rater reliability between nurses and doctors in an older adult rehabilitation unit.  

LENUS (Irish Health Repository)

To ensure accuracy in recording the Barthel Index (BI) in older people, it is essential to determine who is best placed to administer the index. The aim of this study was to compare doctors\\' and nurses\\' reliability in scoring the BI.

Hartigan, Irene

2011-02-01

308

Comparative analysis of Carnaval II Library  

International Nuclear Information System (INIS)

The Carnaval II cross sections library from the french fast reactor calculation system is evaluated in two ways: 10) a comparative analysis of the calculations system for fast reactors at IEN (Instituto de Engenharia Nuclear) using a 'benchmark' model is done; 20) a comparative analysis in relation to the french system itself is also done, using calculations realized with two versions of the french library: the SETR-II and the CARNAVAL IV, the first one being anterior and the second one posterior to the Carnaval II version, the one used by IEN. (Author)

309

14 CFR Appendix N to Part 25 - Fuel Tank Flammability Exposure and Reliability Analysis  

Science.gov (United States)

...Tank Flammability Exposure and Reliability Analysis N25.1General...altitude. (i) Inerting. A process where a noncombustible gas...inoperative under the Master Minimum Equipment List (MMEL) is requested, the time period assumed in the reliability analysis (60 flight...

2010-01-01

310

Comparative analysis of radionuclide inventory in sediment 1995  

International Nuclear Information System (INIS)

In order to test the reliability of methods used in environmental monitoring for radioactive substances, the Bundesanstalt fuer Gewaesserkunde in 1995 again carried out a comparative analysis ''Radionuclides in sediment'' with correspondingly labelled or conditioned samples. The primary aim of this project - independently of the method used in each instance and the measuring conditions observed - was to establish the extent to which the measuring results of the individual participants deviate from specified supposed values or likeliest contents, and also to valuate these deviations by means of illustrative quality parameters. In so far the aim of this comparative analysis differs from that of a so-called inter-laboratory experiment, where the primary objective is to obtain characteristic data for an analytical method (orig./SR)

311

Neutron activation analysis-comparative (NAAC)  

International Nuclear Information System (INIS)

A software system for the reduction of comparative neutron activation analysis data is presented. Libraries are constructed to contain the elemental composition and isotopic nuclear data of an unlimited number of standards. Ratios to unknown sample data are performed by standard calibrations. Interfering peak corrections, second-order activation-product corrections, and deconvolution of multiplets are applied automatically. Passive gamma-energy analysis can be performed with the same software. 3 figures

312

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

International Nuclear Information System (INIS)

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

313

Reliability Analysis in Parallel and Distributed Systems with Network Contention  

Directory of Open Access Journals (Sweden)

Full Text Available This paper tackles the reliability problem of task allocation in heterogeneous distributed systems in the presence of network contention. A large number of scheduling heuristics has been presented in literature, but most of them target maximizing the system reliability without taking network contention delay into consideration. In this paper, we deal with a more realistic model for heterogeneous networks of workstations by taking network contention as an important factor in our study. Although network contention is not considered in task scheduling, yet it has a great effect on the execution time of a parallel program. In our work, we rely on the hybrid algorithm investigated in [8] but with a new system model that allows us to capture network contention. We first develop a mathematical model for reliability based on the unreliability cost function caused by the execution of tasks on the system processors and by the inter-processor communication link where network contention caused by the inter-processor communication time in the link is considered as the main constraint. We then propose an evaluation function that approximates the total completion time of a given assignment by taking into account communication delays caused by network contention. In order to demonstrate the benefits of our model, we evaluate it by means of simulation. We show the significant improved accuracy and reliability of the produced schedules.

Hussein EL Ghor

2012-11-01

314

Prediction Analysis and the Reliability of a Mastery Test.  

Science.gov (United States)

The classical estimate of a binomial probability function is to estimate its mean in the usual manner and to substitute the results in the appropriate expression. Two alternative estimation procedures are described and examined. Emphasis is given to the single administration estimate of the mastery test reliability. (Author/CTM)

Wilcox, Rand R.

1979-01-01

315

Reliability analysis of common hazardous waste treatment processes  

International Nuclear Information System (INIS)

Five hazardous waste treatment processes are analyzed probabilistically using Monte Carlo simulation to elucidate the relationships between process safety factors and reliability levels. The treatment processes evaluated are packed tower aeration, reverse osmosis, activated sludge, upflow anaerobic sludge blanket, and activated carbon adsorption

316

Reliability Block Diagram (RBD) Analysis of NASA Dryden Flight Research Center (DFRC) Flight Termination System and Power Supply  

Science.gov (United States)

In order to perform public risk analyses for vehicles containing Flight Termination Systems (FTS), it is necessary for the analyst to know the reliability of each of the components of the FTS. These systems are typically divided into two segments; a transmitter system and associated equipment, typically in a ground station or on a support aircraft, and a receiver system and associated equipment on the target vehicle. This analysis attempts to analyze the reliability of the NASA DFRC flight termination system ground transmitter segment for use in the larger risk analysis and to compare the results against two established Department of Defense availability standards for such equipment.

Morehouse, Dennis V.

2006-01-01

317

Wind energy Computerized Maintenance Management System (CMMS) : data collection recommendations for reliability analysis.  

Energy Technology Data Exchange (ETDEWEB)

This report addresses the general data requirements for reliability analysis of fielded wind turbines and other wind plant equipment. The report provides a rationale for why this data should be collected, a list of the data needed to support reliability and availability analysis, and specific data recommendations for a Computerized Maintenance Management System (CMMS) to support automated analysis. This data collection recommendations report was written by Sandia National Laboratories to address the general data requirements for reliability analysis of operating wind turbines. This report is intended to help develop a basic understanding of the data needed for reliability analysis from a Computerized Maintenance Management System (CMMS) and other data systems. The report provides a rationale for why this data should be collected, a list of the data needed to support reliability and availability analysis, and specific recommendations for a CMMS to support automated analysis. Though written for reliability analysis of wind turbines, much of the information is applicable to a wider variety of equipment and analysis and reporting needs. The 'Motivation' section of this report provides a rationale for collecting and analyzing field data for reliability analysis. The benefits of this type of effort can include increased energy delivered, decreased operating costs, enhanced preventive maintenance schedules, solutions to issues with the largest payback, and identification of early failure indicators.

Peters, Valerie A.; Ogilvie, Alistair B.

2012-01-01

318

Reliability and availability analysis of dependent-dynamic systems with DRBDs  

International Nuclear Information System (INIS)

Reliability/availability evaluation is an important, often indispensable, step in designing and analyzing (critical) systems, whose importance is constantly growing. When the complexity of a system is high, dynamic effects can arise or become significant. The system might be affected by dependent, cascade, on-demand and/or common cause failures, its units could interfere (load sharing, inter/sequence-dependency), and so on. It is also of great interest to evaluate redundancy and maintenance policies but, since dynamic behaviors usually do not satisfy the stochastic independence assumption, notations such as reliability block diagrams (RBDs), fault trees (FTs) or reliability graphs (RGs) become approximated/simplified techniques, unable to capture dynamic-dependent behaviors. To overcome such problem we developed a new formalism derived from RBDs: the dynamic RBDs (DRBDs). In this paper we explain how the DRBDs notation is able to adequately model and therefore analyze dynamic-dependent behaviors and complex systems. Particular emphasis is given to the modeling and the analysis phases, from both the theoretical and the practical point of views. Several case studies of dynamic-dependent systems, selected from literature and related to different application fields, are proposed. In this way we also compare the DRBDs approach with other methodologies, demonstrating its effectiveness.

319

Mathematical modeling and reliability analysis of a 3D Li-ion battery  

Directory of Open Access Journals (Sweden)

Full Text Available The three-dimensional (3D Li-ion battery presents an effective solution to issues affecting its two-dimensional counterparts, as it is able to attain high energy capacities for the same areal footprint without sacrificing power density. A 3D battery has key structural features extending in and fully utilizing 3D space, allowing it to achieve greater reliability and longevity. This study applies an electrochemical-thermal coupled model to a checkerboard array of alternating positive and negative electrodes in a 3D architecture with either square or circular electrodes. The mathematical model comprises the transient conservation of charge, species, and energy together with electroneutrality, constitutive relations and relevant initial and boundary conditions. A reliability analysis carried out to simulate malfunctioning of either a positive or negative electrode reveals that although there are deviations in electrochemical and thermal behavior for electrodes adjacent to the malfunctioning electrode as compared to that in a fully-functioning array, there is little effect on electrodes further away, demonstrating the redundancy that a 3D electrode array provides. The results demonstrate that implementation of 3D batteries allow it to reliably and safely deliver power even if a component malfunctions, a strong advantage over conventional 2D batteries.

RICHARD HONG PENG LIANG

2014-02-01

320

Passive System Reliability Analysis: A Study on the Isolation Condenser  

International Nuclear Information System (INIS)

This paper deals with the reliability assessment of passive systems that have been developed in recent years by suppliers, industries, utilities, and research organizations, aimed at plant safety improvement and substantial simplification in its implementation. The present study concerns the passive decay heat removal systems that use, for the most part, a condenser immersed in a cooling pool. The focus of the paper is a reliability study of the isolation condenser system foreseen for advanced boiling water reactors (BWRs) for the removal of the excess sensible and core decay heat from the BWR by natural circulation. Furthermore, an approach aimed at the thermal-hydraulic performance assessment (i.e., the natural circulation failure evaluation) from the probability point of view is given. The study is not plant-specific-related but pertains to the conceptual design of the foregoing system

 
 
 
 
321

Windfarm Generation Assessment for ReliabilityAnalysis of Power Systems  

DEFF Research Database (Denmark)

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 a significant role in this assessment and different models have been created for it, but a representation which includes all of them has not been developed yet. This paper deals with this issue. First, a list of nine influencing Factors is presented and discussed. Secondly, these Factors are included 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.

Negra, Nicola Barberis; HolmstrØm, Ole

2007-01-01

322

Windfarm Generation Assessment for Reliability Analysis of Power Systems  

DEFF Research Database (Denmark)

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 a significant role in this assessment and different models have been created for it, but a representation which includes all of them has not been developed yet. This paper deals with this issue. First, a list of nine influencing Factors is presented and discussed. Secondly, these Factors are included 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. Udgivelsesdato: December

Barberis Negra, Nicola; Bak-Jensen, Birgitte

2007-01-01

323

Analysis of the Component-Based Reliability in Computer Networks  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Desempeño en términos de fiabilidad de redes de computador notiva este artículo. Teoremas límite sobre la duración extrema de cola y el tiempo de espera virtual extremo en redes de cola abierta en trafico pesado sao derivados y aplicados a un modelo de fiabilidad para redes de computador donde relac [...] ionamos el tiempo de falha de una red de computador al sistema de parámetros. Abstract in english Performance in terms of reliability of computer networks motivates this paper. Limit theorems on the extreme queue length and extreme virtual waiting time in open queueing networks in heavy traffic are derived and applied to a reliability model for computer networks where we relate the time of failu [...] re of a computer network to the system parameters.

Saulius, Minkevi< img width=12 height=19 src=" http:/fbpe/img/cubo/v12n1/img27.jpg" > ius.

324

Acquisition and statistical analysis of reliability data for I and C parts in plant protection system  

Energy Technology Data Exchange (ETDEWEB)

This project has been performed in order to construct I and C part reliability databases for detailed analysis of plant protection system and to develop a methodology for analysing trip set point drifts. Reliability database for the I and C parts of plant protection system is required to perform the detailed analysis. First, we have developed an electronic part reliability prediction code based on MIL-HDBK-217F. Then we have collected generic reliability data for the I and C parts in plant protection system. Statistical analysis procedure has been developed to process the data. Then the generic reliability database has been constructed. We have also collected plant specific reliability data for the I and C parts in plant protection system for YGN 3,4 and UCN 3,4 units. Plant specific reliability database for I and C parts has been developed by the Bayesian procedure. We have also developed an statistical analysis procedure for set point drift, and performed analysis of drift effects for trip set point. The basis for the detailed analysis can be provided from the reliability database for the PPS I and C parts. The safety of the KSNP and succeeding NPPs can be proved by reducing the uncertainty of PSA. Economic and efficient operation of NPP can be possible by optimizing the test period to reduce utility's burden. 14 refs., 215 figs., 137 tabs. (Author)

Lim, T. J.; Byun, S. S.; Han, S. H.; Lee, H. J.; Lim, J. S.; Oh, S. J.; Park, K. Y.; Song, H. S. [Soongsil Univ., Seoul (Korea)

2001-04-01

325

Failure Analysis Methods for Reliability Improvement of Electronic Sensors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper has documented the common failuremodes of electronic sensors. The effects of failure modes arestudied in detail and these are classified based on their criticalityand probability of occurrence. Methods for taking correctiveactions for eliminating the occurrence of various failure modesare also proposed. The paper also addresses FRACAS method andits effectiveness for reliability studies of sensors based on the realfailure modes observed in practice. It is understood that thedesigner...

Swajeeth Pilot. Panchangam; Naikan, V. N. A.

2012-01-01

326

Reliability and Sensitivity Analysis of Cast Iron Water Pipes for Agricultural Food Irrigation  

Directory of Open Access Journals (Sweden)

Full Text Available This study aims to investigate the reliability and sensitivity of cast iron water pipes for agricultural food irrigation. The Monte Carlo simulation method is used for fracture assessment and reliability analysis of cast iron pipes for agricultural food irrigation. Fracture toughness is considered as a limit state function for corrosion affected cast iron pipes. Then the influence of failure mode on the probability of pipe failure has been discussed. Sensitivity analysis also is carried out to show the effect of changing basic parameters on the reliability and life time of the pipe. The analysis results show that the applied methodology can consider different random variables for estimating of life time of the pipe and it can also provide scientific guidance for rehabilitation and maintenance plans for agricultural food irrigation. In addition, the results of the failure and reliability analysis in this study can be useful for designing of more reliable new pipeline systems for agricultural food irrigation.

Yanling Ni

2014-07-01

327

A New Method for System Reliability Analysis of Tailings Dam Stability  

Science.gov (United States)

For the purpose of stability evaluation, a tailings dam can be considered as an artificial slope made of special soil materials which mainly come from mine tailings. As a particular engineering project, a tailings dam generally has experienced multi-loop hydraulic sediments as well as a long-term consolidation in the process of construction. The characteristics of sediment and consolidation result in a unique distribution of the soil layers with significant uncertainties, which come from both nature development and various human activities, and thus cause the discrete and the variability of the physical-mechanical properties dramatically greater than the natural geo-materials. Therefore, the location of critical slip surface (CSS) of the dam usually presents a notable drift. So, it means that the reliability evaluation task for a tailings dam is a system reliability problem indeed. Unfortunately, the previous research of reliability of tailings dam was mainly confined to the limit equilibrium method (LEM), which has three obvious drawbacks. First, it just focused on the variability along the slip surface rather than the whole space of the dam. Second, a fixed CSS, instead of variable one, was concerned in most cases. Third, the shape of the CSS was usually simplified to a circular. The present paper tried to construct a new reliability analysis model combined with several advanced techniques involving finite difference method (FDM), Monte Carlo simulation (MCS), support vector machine (SVM) and particle swarm optimization (PSO). The new framework was consisted of four modules. The first one is the limit equilibrium finite difference mode, which employed the FLAC3D code to generate stress fields and then used PSO algorithm to search the location of CSS and corresponding minimum factor of safety (FOS). The most value of this module was that each realization of stress field would lead to a particular CSS and its FOS. In other words, the consideration of the drift of CSS was significant to system reliability analysis. Besides, the CSS was described with non-circular shape, which was much more superior to the circular one. Moreover, compare with the LEM, the numerical method has the ability to reflect the variability in a whole space of the dam. The second one is the orthogonal design modules aimed to generate high-quality training samples according to the variability of soil layers. The third one is the response surface model based on SVM, which was designed to obtain the explicit performance function through the well-prepared training samples. The fourth one is the MCS model, which can perform steady and effective reliability analysis through the explicit performance function. As a result, a new approach for reliability analysis of tailings dam stability was presented. As a case study, the Yong-ping Copper Mine Tailings Dam in Jiangxi Province of China was analyzed in detail by this new method. It was shown that the effectiveness of the new method is considerable. In sum, this research is geared towards providing new ideas and available examples for future reliability assessment of tailings dam stability.

Liu, X.; Tang, H.; Xiong, C.; Ni, W.

2012-12-01

328

Computationally-efficient phased-mission reliability analysis for systems with variable configurations  

Science.gov (United States)

Reliability analysis of ultra-reliable computer systems is an important tool for modeling and analyzing multi-phased mission systems and determining the final reliability. This paper describes the development of a new software tool for reliability analysis (HARP-PMS) through modification of the Hybrid Automated Reliablity Predictor (HARP). This tool may be used for fault-tolerant systems operating in phased-missions. Systems with variable configurations and changeable success-criteria are described. An efficient reconfiguration procedure is developed and mechanisms for modeling random phase-durations are discussed. The development of mechanisms for the computation of mean time between critical failures is given. The technique is described using an example with numerical results to show the effect of mission phases on system reliability.

Somani, Arun K.; Ritcey, James A.; Au, Stephen H. L.

1992-12-01

329

Diesel-generator reliability at nuclear power plants: data and preliminary analysis. Interim report  

International Nuclear Information System (INIS)

This report summarizes work performed under RP1233-1 relating to the collection and analysis of data pertaining to diesel generator reliability in nuclear power plants. Drawing from data collected on-site at plants, data supplied by utilites, and data from Licensee Event Reports (LERs), the report describes methods of deriving reliability estimates from data for use in probabilistic risk assessment and presents results when these methods are applied to data collected from 14 plants. Specifically, data are used to estimate diesel failure probabilities for failures to start and failure rates for failures to continue to run. A sampling theory approach and a Bayesian approach to failure probability estimation are compared. The data are used to derive estimates of diesel repair time for some plants, maintenance outages, and multiple diesel failure rates. In addition, a section is included that presents suggestions for failure-rate estimation when an accurate count of diesel start attempts at a plant is not available. The final section presents an analysis of diesel failures based on data from LERs, including a breakdown of failure event by subsystem, failure mode, and failure cause. Appendixes include detailed summaries of the data used in the analysis of previous sections

330

Sensitivity and importance analysis of Markov models using perturbation analysis: Applications in reliability studies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Sensitivity (or importance analysis) has been first defined for "static systems", i.e. systems described by combinatorial reliability models (fault or event trees) and several measures, both structural and probabilistic, have been proposed to assess component importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, ....), and described by Markov models or, more generally, by discrete events dynamic systems models (DEDS),...

Do, Phuc; Barros, Anne; Be?renguer, Christophe

2006-01-01

331

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including intercomponent and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity...

Do, Phuc; Barros, Anne; Berenguer, Christophe

2008-01-01

332

Extending the features of software for reliability analysis of fault-tolerant systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The developed software ASNA-2, which is an improved version of the software ASNA-1, is based on the technology of automated estimation of reliability indexes of fault-tolerant systems. This software is designed for automated evaluation of the reliability indexes of fault-tolerant hardware – software systems. This paper describes a software ASNA-2 with the peculiarities of procedures of reliability analysis of fault-tolerant systems. ? ?????? ???????????? ????...

Volochiy, Bohdan; Mandziy, Bohdan; Ozirkovskyi, Leonid

2012-01-01

333

Analysis of structure reliability on beam using fuzzy finite element method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main requirement in designing a structure is to ensure the structure is reliable enough to withstand any loading. However, in the real world, for structural analysis, the presence of uncertainties in the input variable has reduced the accuracy of the calculated structural reliability. The purpose of this study is to determine the structural reliability with the consideration of uncertainties involved. The developed simulation method is the fuzzy set theory incorporating with the finite el...

Ariffin, A. K.; Tan, S. C.; Ng, C. T.; Yusmye, A. Y. N.

2013-01-01

334

NREL Gearbox Reliability Collaborative Experimental Data Overview and Analysis: Preprint  

Energy Technology Data Exchange (ETDEWEB)

Most turbines in the market today follow a modular configuration comprised of a main shaft, gearbox, high speed shaft, and generator. The gearbox has the important task of increasing the slow rotor speeds to meet the electromechanical requirements of the electromechanical. These gearboxes are commonly composed of a planetary stage and several parallel shaft stages. The planetary, or epicyclical, design of the gearbox is a feature of the design that has many advantages compared to the traditional parallel shaft arrangement. Among these are that higher gear ratios can be achieved in a single stage, they are capable to carrying higher loads, and they require less space than the traditional parallel shaft arrangement. For this reason, planetary gearboxes they are commonly used in the first stage of the wind turbine gearboxes. However, planetary stages are more complex than the typical parallel shaft arrangement, and can be affected by deflection in the planet carrier, annulus deformations and bearing clearances. Unanticipated levels of these motions can reduce their life expectancy. This paper gives a brief overview of a subset of the experimental efforts, data, and analysis of the GRC project focusing on the planet carrier deformation.

Oyague, F.; Gorman, D.; Sheng, S.

2010-05-01

335

Comparative Analysis on Constitutional Supervision Modes  

Directory of Open Access Journals (Sweden)

Full Text Available

Constitution is the fundamental law of a nation and also the general regulations on administering state affairs and ensuring national security. This is why constitutional supervision is so important for a country. However, there are still many problems existing under the supervision mechanism regarding to its operability, materiality, and rationality. This paper tries to give proper suggestions on perfecting Chinese constitutional supervision through comparative analysis and other countries’ advanced experiences.

Key words: Constitutional supervision modes; Comparative study

Wenjing WANG

2012-11-01

336

Reliability analysis of the solar array based on Fault Tree Analysis  

Energy Technology Data Exchange (ETDEWEB)

The solar array is an important device used in the spacecraft, which influences the quality of in-orbit operation of the spacecraft and even the launches. This paper analyzes the reliability of the mechanical system and certifies the most vital subsystem of the solar array. The fault tree analysis (FTA) model is established according to the operating process of the mechanical system based on DFH-3 satellite; the logical expression of the top event is obtained by Boolean algebra and the reliability of the solar array is calculated. The conclusion shows that the hinges are the most vital links between the solar arrays. By analyzing the structure importance(SI) of the hinge's FTA model, some fatal causes, including faults of the seal, insufficient torque of the locking spring, temperature in space, and friction force, can be identified. Damage is the initial stage of the fault, so limiting damage is significant to prevent faults. Furthermore, recommendations for improving reliability associated with damage limitation are discussed, which can be used for the redesigning of the solar array and the reliability growth planning.

Wu Jianing; Yan Shaoze, E-mail: yansz@mail.tsinghua.edu.cn [State Key Laboratory of Tribology, Department of Precision Instruments and Mechanology, Tsinghua University,Beijing 100084 (China)

2011-07-19

337

Review of the human reliability analysis performed for Empire State Electric Energy Research Corporation  

International Nuclear Information System (INIS)

The Empire State Electric Energy Research Corporation (ESEERCO) commissioned Westinghouse to conduct a human reliability analysis to identify and quantify human error probabilities associated with operator actions for four specific events which may occur in light water reactors: loss of coolant accident, steam generator tube rupture, steam/feed line break, and stuck open pressurizer spray valve. Human Error Probabilities (HEPs) derived from Swain's Technique for Human Error Rate Prediction (THERP) were compared to data obtained from simulator exercises. A correlation was found between the HEPs derived from Swain and the results of the simulator data. The results of this study provide a unique insight into human factors analysis. The HEPs obtained from such probabilistic studies can be used to prioritize scenarios for operator training situations, and thus improve the correlation between simulator exercises and real control room experiences

338

Validity and reliability of 3D marker based scapular motion analysis: a systematic review.  

Science.gov (United States)

Methods based on cutaneous markers are the most popular for the recording of three dimensional scapular motion analysis. Numerous methods have been evaluated, each showing different levels of accuracy and reliability. The aim of this review was to report the metrological properties of 3D scapular kinematic measurements using cutaneous markers and to make recommendations based on metrological evidence. A database search was conducted using relevant keywords and inclusion/exclusion criteria in 5 databases. 19 articles were included and assessed using a quality score. Concurrent validity and reliability were analyzed for each method. Six different methods are reported in the literature, each based on different marker locations and post collection computations. The acromion marker cluster (AMC) method coupled with a calibration of the scapula with the arm at rest is the most studied method. Below 90-100° of humeral elevation, this method is accurate to about 5° during arm flexion and 7° during arm abduction compared to palpation (average of the 3 scapular rotation errors). Good to excellent within-session reliability and moderate to excellent between-session reliability have been reported. The AMC method can be improved using different or multiple calibrations. Other methods using different marker locations or more markers on the scapula blade have been described but are less accurate than AMC methods. Based on current metrological evidence we would recommend (1) the use of an AMC located at the junction of the scapular spine and the acromion, (2) the use of a single calibration at rest if the task does not reach 90° of humeral elevation, (3) the use of a second calibration (at 90° or 120° of humeral elevation), or multiple calibrations above 90° of humeral elevation. PMID:24856913

Lempereur, Mathieu; Brochard, Sylvain; Leboeuf, Fabien; Rémy-Néris, Olivier

2014-07-18

339

Reliability Analysis for the Fatigue Limit State of the ASTRID Offshore Platform:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A reliability analysis with respect to fatigue failure was performed for a concrete gravity platform designed for the Troll field. The reliability analysis was incorporated in the practical design-loop to gain more insight into the complex fatigue problem. In the analysis several parameters relating to wave excitation, structural response and material properties of the concrete were considered as being stochastic. From the work done it is concluded that designing a concrete platform for the T...

Vrouwenvelder, A. C. W. M.; Gostelie, E. M.

1986-01-01

340

IEEE guide for general principles of reliability analysis of nuclear power generating station protection systems  

International Nuclear Information System (INIS)

Presented is the Institute of Electrical and Electronics Engineers, Inc. (IEEE) guide for general principles of reliability analysis of nuclear power generating station protection systems. The document has been prepared to provide the basic principles needed to conduct a reliability analysis of protection systems. Included is information on qualitative and quantitative analysis, guides for failure data acquisition and use, and guide for establishment of intervals

 
 
 
 
341

Fast neutron reactor safety. Reliability analysis of Phenix decay heat removal function  

International Nuclear Information System (INIS)

This paper presents a reliability analysis of the Phenix decay heat removal function. After summarizing analysis results of sequences leading to failure of this function, the main steps in a probabilistic risk assessment are described: computation of reliability and maintenance parameters for the various systems involved, followed by probabilistic analysis of failure sequences. The extent to which the various systems contribute to the total risk is analyzed. Certain maintenance recommendations were made accordingly

342

Reliability analysis on eddy tube-defects quantitative detection in nuclear power plants  

International Nuclear Information System (INIS)

Finite element method is used in the reliability analysis on the quantitative detection of ECT (eddy current test), and based on the calculation and analysis of of the tube signals in nuclear power plants, the quantitative excursion of tube defects and qualitative relations under different depth and width conditions are obtained, which proved that reliability analysis is more practical when the width of the tube defects is very small, and the efficiency and precision of ECT can be improved. (authors)

343

Comparative performance analysis of mobile displays  

Science.gov (United States)

Cell-phone display performance (in terms of color quality and optical efficiency) has become a critical factor in creating a positive user experience. As a result, there is a significant amount of effort by cell-phone OEMs to provide a more competitive display solution. This effort is focused on using different display technologies (with significantly different color characteristics) and more sophisticated display processors. In this paper, the results of a mobile-display comparative performance analysis are presented. Three cell-phones from major OEMs are selected and their display performances are measured and quantified. Comparative performance analysis is done using display characteristics such as display color gamut size, RGB-channels crosstalk, RGB tone responses, gray tracking performance, color accuracy, and optical efficiency.

Safaee-Rad, Reza; Aleksic, Milivoje

2012-01-01

344

Failure Analysis Methods for Reliability Improvement of Electronic Sensors  

Directory of Open Access Journals (Sweden)

Full Text Available This paper has documented the common failuremodes of electronic sensors. The effects of failure modes arestudied in detail and these are classified based on their criticalityand probability of occurrence. Methods for taking correctiveactions for eliminating the occurrence of various failure modesare also proposed. The paper also addresses FRACAS method andits effectiveness for reliability studies of sensors based on the realfailure modes observed in practice. It is understood that thedesigner has an important role in elimination of the failure modesat the design stage itself. This is expected to result in reliabilitygrowth of sensor systems used in many critical systems such asspace applications, nuclear power plants, and chemical industriesetc.

Swajeeth Pilot. Panchangam

2012-08-01

345

Reliability of cyclin A assessment on tissue microarrays in breast cancer compared to conventional histological slides.  

Science.gov (United States)

Cyclin A has in some studies been associated with poor breast cancer survival, although all studies have not confirmed this. Its prognostic significance in breast cancer needs evaluation in larger studies. Tissue microarray (TMA) technique allows a simultaneous analysis of large amount of tumours on a single microscopic slide. This makes a rapid screening of molecular markers in large amount of tumours possible. Because only a small tissue sample of each tumour is punched on an array, the question has arisen about the representativeness of TMA when studying markers that are expressed in only a small proportion of cells. For this reason, we wanted to compare cyclin A expression on TMA and on traditional large sections. Two breast cancer TMAs were constructed of 200 breast tumours diagnosed between 1997-1998. TMA slides and traditional large section slides of these 200 tumours were stained with cyclin A antibody and analysed by two independent readers. The reproducibility of the two readers' results was good or even very good, with kappa values 0.71-0.87. The agreement of TMA and large section results was good with kappa value 0.62-0.75. Cyclin A overexpression was significantly (P<0.001) associated with oestrogen receptor and progesterone receptor negativity and high grade both on TMA and large sections. Cyclin A overexpression was significantly associated with poor metastasis-free survival both on TMA and large sections. The relative risks for metastasis were similar on TMA and large sections. This study suggests that TMA technique could be useful to study histological correlations and prognostic significance of cyclin A on breast cancer on a large scale. PMID:16670718

Aaltonen, K; Ahlin, C; Amini, R-M; Salonen, L; Fjällskog, M-L; Heikkilä, P; Nevanlinna, H; Blomqvist, C

2006-06-01

346

COMPARATIVE ANALYSIS OF STRESS OF COMPETITIVE ORGANIZATIONS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this thesis we examined the scope for coping with stress levels of the organization. We focused on the evaluation of stress in the Slovenian company A and consequently carried out a comparative analysis to model stress in relation to work with competing company in Italy. Initially, we presented the problem of stress, types of stress effects of stress, stres causes, consequences of stress, ways of management and accounting information relating to the work and stress. We have deepened th...

Kolic?, Marina

2012-01-01

347

Comparative analysis of the Borrelia garinii genome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Three members of the genus Borrelia (B.burgdorferi, B.garinii, B.afzelii) cause tick-borne borreliosis. Depending on the Borrelia species involved, the borreliosis differs in its clinical symptoms. Comparative genomics opens up a way to elucidate the underlying differences in Borrelia species. We analysed a low redundancy whole-genome shotgun (WGS) assembly of a B.garinii strain isolated from a patient with neuroborreliosis in comparison to the B.burgdorferi genome. This analysis reveals that...

Glo?ckner, G.; Lehmann, R.; Romualdi, A.; Pradella, S.; Schulte-spechtel, U.; Schilhabel, M.; Wilske, B.; Su?hnel, J.; Platzer, M.

2004-01-01

348

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

International Nuclear Information System (INIS)

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

349

Efficient surrogate models for reliability analysis of systems with multiple failure modes  

Energy Technology Data Exchange (ETDEWEB)

Despite many advances in the field of computational reliability analysis, the efficient estimation of the reliability of a system with multiple failure modes remains a persistent challenge. Various sampling and analytical methods are available, but they typically require accepting a tradeoff between accuracy and computational efficiency. In this work, a surrogate-based approach is presented that simultaneously addresses the issues of accuracy, efficiency, and unimportant failure modes. The method is based on the creation of Gaussian process surrogate models that are required to be locally accurate only in the regions of the component limit states that contribute to system failure. This approach to constructing surrogate models is demonstrated to be both an efficient and accurate method for system-level reliability analysis. - Highlights: > Extends efficient global reliability analysis to systems with multiple failure modes. > Constructs locally accurate Gaussian process models of each response. > Highly efficient and accurate method for assessing system reliability. > Effectiveness is demonstrated on several test problems from the literature.

Bichon, Barron J., E-mail: barron.bichon@swri.org [Southwest Research Institute, San Antonio, TX 78238 (United States); McFarland, John M., E-mail: john.mcfarland@swri.org [Southwest Research Institute, San Antonio, TX 78238 (United States); Mahadevan, Sankaran, E-mail: sankaran.mahadevan@vanderbilt.edu [Vanderbilt University, Nashville, TN 37235 (United States)

2011-10-15

350

Reliability analysis of protection systems in NPP applying fault-tree analysis method  

International Nuclear Information System (INIS)

This paper demonstrates the applicability and limits of dependability analysis in nuclear power plants (NPPS) based on the reactor protection refurbishment project (RRP) in NPP Paks. This paper illustrates case studies from the reliability analysis for NPP Paks. It also investigates the solutions for the connection between the data acquisition and subsystem control units (TSs) and the voter units (VTs), it analyzes the influence of the voting in the VT computer level, it studies the effects of the testing procedures to the dependability parameters. (author)

351

Embedded Hyperchaotic Generators: A Comparative Analysis  

Science.gov (United States)

In this paper, we present a comparative analysis of FPGA implementation performances, in terms of throughput and resources cost, of five well known autonomous continuous hyperchaotic systems. The goal of this analysis is to identify the embedded hyperchaotic generator which leads to designs with small logic area cost, satisfactory throughput rates, low power consumption and low latency required for embedded applications such as secure digital communications between embedded systems. To implement the four-dimensional (4D) chaotic systems, we use a new structural hardware architecture based on direct VHDL description of the forth order Runge-Kutta method (RK-4). The comparative analysis shows that the hyperchaotic Lorenz generator provides attractive performances compared to that of others. In fact, its hardware implementation requires only 2067 CLB-slices, 36 multipliers and no block RAMs, and achieves a throughput rate of 101.6 Mbps, at the output of the FPGA circuit, at a clock frequency of 25.315 MHz with a low latency time of 316 ns. Consequently, these good implementation performances offer to the embedded hyperchaotic Lorenz generator the advantage of being the best candidate for embedded communications applications.

Sadoudi, Said; Tanougast, Camel; Azzaz, Mohamad Salah; Dandache, Abbas

352

Time-dependent reliability analysis of flood defences  

International Nuclear Information System (INIS)

This paper describes the underlying theory and a practical process for establishing time-dependent reliability models for components in a realistic and complex flood defence system. Though time-dependent reliability models have been applied frequently in, for example, the offshore, structural safety and nuclear industry, application in the safety-critical field of flood defence has to date been limited. The modelling methodology involves identifying relevant variables and processes, characterisation of those processes in appropriate mathematical terms, numerical implementation, parameter estimation and prediction. A combination of stochastic, hierarchical and parametric processes is employed. The approach is demonstrated for selected deterioration mechanisms in the context of a flood defence system. The paper demonstrates that this structured methodology enables the definition of credible statistical models for time-dependence of flood defences in data scarce situations. In the application of those models one of the main findings is that the time variability in the deterioration process tends to be governed the time-dependence of one or a small number of critical attributes. It is demonstrated how the need for further data collection depends upon the relevance of the time-dependence in the performance of the flood defence system.

353

Trouble analysis for reliability evaluation of irradiation system in HIMAC  

International Nuclear Information System (INIS)

In Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences (NIRS), the number of troubles in which failures, malfunctions, disorders, errors and human errors are included occurred in machines (hardware) and computers (software) of the irradiation system has increased year by year as the number of patient increases. We have started analyzing the events that have been recorded since 1999 to now so as to check reliability of the system and plan the program for maintaining the irradiation system. The occurrence history of the event roughly shows monotonous increase curve. The occurrence rate of the computer error has not varied so much since beginning. It means there are several latent bugs in the software. It should be noted that the hardware failures have been increasing. The system seems likely to come into the period of aging; particularly the event in which a cable breaks has begun to occur recently. The irradiation system is equipped with multifold safety interlock systems for protecting a patient from unwanted beam irradiations when a trouble occurs. For assurance of quality of the irradiation system, three kinds of maintenance are being performed. The maintenance program keeps the system highly reliable and there have been no serious damage on the treatments ever. (author)

354

Reliability Analysis Of Fire System On The Industry Facility By Use Fameca Method  

International Nuclear Information System (INIS)

FAMECA is one of the analysis method to determine system reliability on the industry facility. Analysis is done by some procedure that is identification of component function, determination of failure mode, severity level and effect of their failure. Reliability value is determined by three combinations that is severity level, component failure value and critical component. Reliability of analysis has been done for fire system on the industry by FAMECA method. Critical component which identified is pump, air release valve, check valve, manual test valve, isolation valve, control system etc

355

Reliability analysis of microcomputer boards and computer based systems important to safety of nuclear plants  

International Nuclear Information System (INIS)

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)

356

RELIABILITY ANALYSIS OF A SYSTEM OF BOILER USED IN READYMADE GARMENT INDUSTRY  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper deals with the reliability analysis of a system of boiler used in garment industry.The system consists of a single unit of boiler which plays an important role in garment industry. Usingregenerative point technique with Markov renewal process various reliability characteristics of interest areobtained.

R.K. Agnihotri

2008-01-01

357

Reliability analysis of in-service inspection for key components in nuclear power plants  

International Nuclear Information System (INIS)

The reliability of in-service inspection was calculated and analyzed based on the probability model and ultrasonic testing numerical model. The POD curve and its 95% lower bound of different defects in girth weld of RPV were calculated. The result indicated that the reliability analysis could give a quantitative evaluation for in-service inspection. (authors)

358

Weighted regression analysis for comparing varietal adaptation.  

Science.gov (United States)

The normally used joint linear regression analysis (OLS) is not appropriate for comparing estimates of stability parameters of varieties when the error variances of site means are heterogeneous. Weighted regression analysis (WLS), in these situations, yields more precise estimates of stability parameters. A comparison of the two analytical methods using the grain yield (kg ha(-1)) data of 12 varieties and one hybrid of pearl millet [Pennisetum typhoides (Burm.) S. & H.], tested at 26 sites in India, revealed that the weighted regression analysis yields more efficient estimates of regression coefficients (b i ) than the ordinary regression analysis, and that the standard errors of b i values were reduced by up to 43%. The estimated b i differed with the two procedures. The number of varieties with b i ssignificantly deviating from unity was not only more (five varieties) with weighted regression analysis than the ordinary regression analysis (one variety), but the classification of varieties as possessing general or specific adaptation differed with the two procedures. PMID:24221324

Virk, D S; Virk, P S; Mangat, B K; Harinarayana, G

1991-04-01

359

A data-informed PIF hierarchy for model-based Human Reliability Analysis  

International Nuclear Information System (INIS)

This paper addresses three problems associated with the use of Performance Shaping Factors in Human Reliability Analysis. (1) There are more than a dozen Human Reliability Analysis (HRA) methods that use Performance Influencing Factors (PIFs) or Performance Shaping Factors (PSFs) to model human performance, but there is not a standard set of PIFs used among the methods, nor is there a framework available to compare the PIFs used in various methods. (2) The PIFs currently in use are not defined specifically enough to ensure consistent interpretation of similar PIFs across methods. (3) There are few rules governing the creation, definition, and usage of PIF sets. This paper introduces a hierarchical set of PIFs that can be used for both qualitative and quantitative HRA. The proposed PIF set is arranged in a hierarchy that can be collapsed or expanded to meet multiple objectives. The PIF hierarchy has been developed with respect to a set fundamental principles necessary for PIF sets, which are also introduced in this paper. This paper includes definitions of the PIFs to allow analysts to map the proposed PIFs onto current and future HRA methods. The standardized PIF hierarchy will allow analysts to combine different types of data and will therefore make the best use of the limited data in HRA. The collapsible hierarchy provides the structure necessary to combine multiple types of information without reducing the quality of the information.formation.

360

Vibration reliability sensitivity analysis of general system with correlation failure modes  

International Nuclear Information System (INIS)

The vibration problem of the general system is the main object of research. The material properties and geometry of general system are random parameters because of the manufacturing environment, technical conditions, manufacturing and installation errors, multiphase materials, features and other factors. According to the relation criterion that the difference between the natural frequency and the driving frequency of general systems is not beyond a specific value, the vibration reliability mode and vibration reliability of general systems are defined considering the correlation of the multi-order natural frequency and the random characteristics of structure size and material, and the vibration reliability analysis method for avoiding the resonant is carried out. The second-order joint failure probability is obtained by using the numerical integration method. Based on the reliability design theory and sensitivity analysis method, the vibration reliability sensitivity of the general system with correlation failure modes is extensively discussed and a numerical method for vibration reliability sensitivity design is presented. The variation regularities of vibration reliability sensitivity are obtained and the effects of random parameters on vibration reliability of the general system are studied. The presented method provided the theoretic basis for the reliability design of the general system. A numerical example demonstrated that the proposed method is effective

 
 
 
 
361

Reliability and validity of gait analysis by android-based smartphone.  

Science.gov (United States)

Smartphones are very common devices in daily life that have a built-in tri-axial accelerometer. Similar to previously developed accelerometers, smartphones can be used to assess gait patterns. However, few gait analyses have been performed using smartphones, and their reliability and validity have not been evaluated yet. The purpose of this study was to evaluate the reliability and validity of a smartphone accelerometer. Thirty healthy young adults participated in this study. They walked 20 m at their preferred speeds, and their trunk accelerations were measured using a smartphone and a tri-axial accelerometer that was secured over the L3 spinous process. We developed a gait analysis application and installed it in the smartphone to measure the acceleration. After signal processing, we calculated the gait parameters of each measurement terminal: peak frequency (PF), root mean square (RMS), autocorrelation peak (AC), and coefficient of variance (CV) of the acceleration peak intervals. Remarkable consistency was observed in the test-retest reliability of all the gait parameter results obtained by the smartphone (p<0.001). All the gait parameter results obtained by the smartphone showed statistically significant and considerable correlations with the same parameter results obtained by the tri-axial accelerometer (PF r=0.99, RMS r=0.89, AC r=0.85, CV r=0.82; p<0.01). Our study indicates that the smartphone with gait analysis application used in this study has the capacity to quantify gait parameters with a degree of accuracy that is comparable to that of the tri-axial accelerometer. PMID:22400972

Nishiguchi, Shu; Yamada, Minoru; Nagai, Koutatsu; Mori, Shuhei; Kajiwara, Yuu; Sonoda, Takuya; Yoshimura, Kazuya; Yoshitomi, Hiroyuki; Ito, Hiromu; Okamoto, Kazuya; Ito, Tatsuaki; Muto, Shinyo; Ishihara, Tatsuya; Aoyama, Tomoki

2012-05-01

362

Reliability analysis of discrete event dynamic systems with Petri nets  

International Nuclear Information System (INIS)

This paper deals with dynamic reliability of embedded systems. It presents a method for deriving feared scenarios (which might lead the system to a critical situation) in Petri nets. A classical way to obtain scenarios in Petri nets is to generate the reachability graph. However, for complex systems, it leads to the state space explosion. To avoid this problem, in our approach, Petri net reachability is translated into provability of linear logic sequents. Linear logic bases are introduced and used to formally define scenarios and minimality of scenarios. These definitions allow the method to produce only pertinent scenarios. The steps of the method are described and illustrated through a landing-gear system example.

363

Reliability analysis of discrete event dynamic systems with Petri nets  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with dynamic reliability of embedded systems. It presents a method for deriving feared scenarios (which might lead the system to a critical situation) in Petri nets. A classical way to obtain scenarios in Petri nets is to generate the reachability graph. However, for complex systems, it leads to the state space explosion. To avoid this problem, in our approach, Petri net reachability is translated into provability of linear logic sequents. Linear logic bases are introduced and used to formally define scenarios and minimality of scenarios. These definitions allow the method to produce only pertinent scenarios. The steps of the method are described and illustrated through a landing-gear system example.

Sadou, Nabil [Supelec - IETR, Avenue de la Boulais, BP 81127, F35511 Cesson-Sevigne Cedex (France)], E-mail: nabil.sadou@supelec.fr; Demmou, Hamid [CNRS, LAAS, 7 Avenue du Colonel Roche, F-31077 Toulouse (France); Universite de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse (France)

2009-11-15

364

Emergency diesel generator reliability analysis high flux isotope reactor  

International Nuclear Information System (INIS)

A program to apply some of the techniques of reliability engineering to the High Flux Isotope Reactor (HFIR) was started on August 8, 1992. Part of the program was to track the conditional probabilities of the emergency diesel generators responding to a valid demand. This was done to determine if the performance of the emergency diesel generators (which are more than 25 years old) has deteriorated. The conditional probabilities of the diesel generators were computed and trended for the period from May 1990 to December 1992. The calculations indicate that the performance of the emergency diesel generators has not deteriorated in recent years, i.e., the conditional probabilities of the emergency diesel generators have been fairly stable over the last few years. This information will be one factor than may be considered in the decision to replace the emergency diesel generators

365

The role of human reliability analysis for enhancing crew performance  

International Nuclear Information System (INIS)

This paper summarizes some aspects of EPRI-sponsored research undertaken in support of improving the PRA technology. In particular, the consideration of how human actions that impact accident sequences can be analyzed in a systematic way to supplement the type of ergonomic studies normally carried out in support of control room design. The HRA/PRA approach described not only identifies the operator information and interface needs, but also helps to identify issues and areas for additional research. The process includes a link to data collections. Preliminary collections of data and analytical benchmark support the idea that such analytical frameworks and models provide support for ranking the importance of various human reliability issues

366

Reliability Analysis of an Offshore Structure : A Case Study II  

DEFF Research Database (Denmark)

For an offshore structure in the North Sea it is assumed that information from measurements and inspections is available. As illustrations measurements of the significant wave height and the marine growth and different inspection and repair results are considered. It is shown how the reliability estimates of the structure can be updated using Bayesian techniques. By minimizing the total expected costs including inspection, repair and failure costs during the lifetime an optimal inspection and repair strategy can be determined. The decision variables are the number of inspections, the time intervals between inspections and the inspection qualities. A parameter study is performed and an updated inspection plan is determined after the first inspection has taken place.

SØrensen, John Dalsgaard; Rackwitz, R.

1992-01-01

367

A knowledge based approach for systems safety and reliability analysis  

International Nuclear Information System (INIS)

The paper presents EXPRESS, an expert system developed for the automatization of reliability studies. The first part consists of the description of the method for static thermohydraulic systems. In this step, the knowledge representation based on two inference engines - ALOUETTE and LRC (developed by Electricite de France) is defined. The processes used to construct a fault tree from a topological and functional description of the system are described. Numerous examples are given. The lessons derived from the studies were validated on safety systems of the Paluel nuclear power plant. The development of the same approach for electric power systems is described, and the differences resulting from the sequential nature of these systems are emphasized. Finally, the main advantages of EXPRESS identified during the studies are shown. (author). Poster presentation. 4 refs, 1 fig

368

A study in the reliability analysis method for nuclear power plant structures (I)  

Energy Technology Data Exchange (ETDEWEB)

Nuclear power plant structures may be exposed to aggressive environmental effects that may cause their strength and stiffness to decrease over their service life. Although the physics of these damage mechanisms are reasonably well understood and quantitative evaluation of their effects on time-dependent structural behavior is possible in some instances, such evaluations are generally very difficult and remain novel. The assessment of existing steel containment in nuclear power plants for continued service must provide quantitative evidence that they are able to withstand future extreme loads during a service period with an acceptable level of reliability. Rational methodologies to perform the reliability assessment can be developed from mechanistic models of structural deterioration, using time-dependent structural reliability analysis to take loading and strength uncertainties into account. The final goal of this study is to develop the analysis method for the reliability of containment structures. The cause and mechanism of corrosion is first clarified and the reliability assessment method has been established. By introducing the equivalent normal distribution, the procedure of reliability analysis which can determine the failure probabilities has been established. The influence of design variables to reliability and the relation between the reliability and service life will be continued second year research.

Oh, Byung Hwan; Choi, Seong Cheol; Shin, Ho Sang; Yang, In Hwan; Kim, Yi Sung; Yu, Young; Kim, Se Hun [Seoul, Nationl Univ., Seoul (Korea, Republic of)

1999-03-15

369

Use of Fault Tree Analysis for Automotive Reliability and Safety Analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Lambert, H

2003-09-24

370

Functional reliability analysis of Safety Grade Decay Heat Removal System of Indian 500 MWe PFBR  

Energy Technology Data Exchange (ETDEWEB)

Passive systems are increasingly deployed in nuclear industry with an objective of increasing reliability and safety of operations with reduced cost. Methods for assessing the reliability of thermal-hydraulic passive systems, that is systems with moving working fluid, address the issues in natural buoyancy-driven flow that could result in a failure to meet the design safety limits under accident scenarios. This is referred as design functional reliability. This paper presents the results of functional reliability analysis carried out for the passive Safety Grade Decay Heat Removal System (SGDHRS) of Indian Prototype Fast Breeder Reactor (PFBR). The analysis is carried out based on the overall approach reported in the Reliability Methods for Passive System (RMPS, European Commission) project. Functional failure probability is calculated using Monte-Carlo method and also with method of moments.

Mathews, T. Sajith [AERB-Safety Research Institute, Kalpakkam 603102 (India); Ramakrishnan, M.; Parthasarathy, U. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Arul, A. John [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)], E-mail: arul@igcar.gov.in; Kumar, C. Senthil [AERB-Safety Research Institute, Kalpakkam 603102 (India)

2008-09-15

371

[Comparative analysis of Pleurotus ostreatus natural isolates].  

Science.gov (United States)

A comparative analysis is performed of the polymorphism of the Pleurotus ostreatus (Fr.) Kumm naturally occurring strains isolated from the natural substrates found in two geographically remote Russian natural preserves, the Central Arboreal Biosphere Tver State Preserve (CABTSP) and the Moscow State University Zvenigorod Biological Station (ZBS, Moscow oblast), and within the city of Moscow. The results of the frequency analysis for the isozyme loci alleles and for the sexual and vegetative incompatibility groups are presented; the genetic structure and the interpopulation relations among 58 P. ostreatus dikaryotic strains are estimated. The natural samples from the Moscow and Tver oblasts are shown to have a high degree of polymorphism with a genetic differentiation of 0.743; in spite of their territorial remoteness, they are, however, actively exchanging genetic material. The natural fungal isolates form two reproductively isolated groups. PMID:15938400

Shtaer, O V; Belokon', Iu S; Belokon', M M; Shnyreva, A V

2005-01-01

372

Comparative Analysis of Virtual Education Applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The research was conducted in order to make comparative analysis of virtual education applications. The research is conducted in survey model. The study group consists of total 300 institutes providing virtual education in the fall, spring and summer semesters of 2004; 246 in USA, 10 in Australia, 3 in South Africa, 10 in India, 21 in UK, 6 in Japan, 4 in Turkey. The information has been collected by online questionnaire sent to the target mass by e-mail. The questionnaire has been developed ...

Kurt, Mehmet

2006-01-01

373

A comparative dynamical analysis of Hebrew texts  

Directory of Open Access Journals (Sweden)

Full Text Available Three Hebrew texts, one of them the Hebrew bible, are investigated using dynamical analysis. First, the average mutual information for each of the texts is determined. The first minimum occurs at T=3 in all three cases, suggesting that 3-letter words are sufficient to study the dynamical properties of the texts. Using 3-letter words as the state space for each of the text, we construct a Markov chain model and compute the relative measure–theoretic entropy for each of the texts and use this tool as a means of comparing the information content of the three texts.

Pawel Góra

1999-01-01

374

Reliability analysis of the automatic control of the A-1 power plant coolant temperature  

International Nuclear Information System (INIS)

Reliability analysis of the automatic control of the A-1 reactor coolant temperature is performed taking into account the effect of both the dependent failures and the routine maintenance of control system components. In a separate supplement, reliability analysis is reported of coincidence systems of the A-1 power plant reactor. Both safe and unsafe failures are taken into consideration as well as the effect of maintenance of the respective branch elements

375

Reliability Estimation based on Step-Stress Accelerated Degradation Testing by Unequal Interval Time Series Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a reliability estimation method based on Step-Stress Accelerated Degradation Testing (SSADT data analysis using unequal interval time series analysis. A Multi-Regression Time Varying Auto-Regressive (MRTVAR degradation time series model is proposed. Product SSADT data are treated as unequal interval composite time series and described using MRTVAR time series model and utilized to predict long-term trend of degradation. By using the suggested method, product reliability is obtained. An example is presented as a verification of the modeling technique and estimation method. A reasonable estimation of lifetime and reliability of the product is obtained by employing the present method.  

Li Wang

2013-10-01

376

Reliability modelling of surface mining equipment: data gathering and analysis methodologies  

Energy Technology Data Exchange (ETDEWEB)

As the size and complexity of open pit mining equipment continue to increase, the implications of equipment failure become ever more critical. An unplanned failure can result in significantly higher repair costs than a planned maintenance or repair. Of even more importance is the loss of production associated with larger equipment failures. One method to mitigate the impact of failures is to improve the reliability of the equipment. A first step in reliability improvement is collection and analysis of the appropriate data. This paper will summarize relevant techniques for reliability analysis and identify data requirements and information sources.

Robert A. Hall; Laeeque K. Daneshmend

2003-09-01

377

An approach of HALT and Failure analysis for Product Reliability Improvement(An Application to controller for fan module)  

International Nuclear Information System (INIS)

HALT(Highly Accelerated Life Test) is the new technology for reliability assurance. The merit of HALT is a short period of the test time(about 3 to 7 days). This paper is an application of HALT and FA(Failure analysis) to improve the reliability of the fan module. Before HALT, some environmental test results were good. But we could not assure the reliability level of the test sample. So, we choose the technique of HALT to compare the test sample with a same product of the other leading company. After HALT, we found some defects(solder crack, cut of capacitor lead, varistor burning, etc) and we applied some FA technique to improve the reliability of fan module. After HALT and FA. We suggested some methods to improve the reliability of the module. So, the manufacturer applied design change and part replacement to the new fan module. After the last HALT about the new fan module, we prove the reliability growth

378

Applying reliability centered maintenance analysis principles to inservice testing  

International Nuclear Information System (INIS)

Federal regulations require nuclear power plants to use inservice test (IST) programs to ensure the operability of safety-related equipment. IST programs are based on American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code requirements. Many of these plants also use Reliability Centered Maintenance (RCM) to optimize system maintenance. ASME Code requirements are hard to change. The process for requesting authority to use an alternate strategy is long and expensive. The difficulties of obtaining this authority make the use of RCM method on safety-related systems not cost effective. An ASME research task force on Risk Based Inservice Testing is investigating changing the Code. The change will allow plants to apply RCM methods to the problem of maintenance strategy selection for safety-related systems. The research task force is working closely with the Codes and Standards sections to develop a process related to the RCM process. Some day plants will be able to use this process to develop more efficient and safer maintenance strategies

379

Optimizing quality assurance program benefits through performance and reliability analysis  

International Nuclear Information System (INIS)

Quality assurance (QA) principles have long been applied in part to many varied industrial enterprises. In general, the main emphasis in the past has been placed largely on standard management practices with the inclusion of quality control or inspection elements. The advent of commercial nuclear power brought the evolution of a more comprehensive approach to the applications of QA programs in this and related industries. However, the application philosophy was aimed almost totally at assuring the safety of the worker and the public. Recently, there has been a strong movement by industry and business in the United States and Europe to apply QA in a more general way to assure overall reliability as well as safety. The key to successfully accomplishing this is the determination of the degree of program intensity appropriate to the item or activity that is part of the total project or operation. This paper describes an approach to enable management to not only make initial determinations of how to apply the elements of a QA program, but how to continuously adjust the program to optimize the benefits that can be obtained

380

Reactor scram experience for shutdown system reliability analysis  

International Nuclear Information System (INIS)

Scram experience in a number of operating light water reactors has been reviewed. The date and reactor power of each scram was compiled from monthly operating reports and personal communications with the operating plant personnel. The average scram frequency from ''significant'' power (defined as P/sub trip//P/sub max greater than/ approximately 20 percent) was determined as a function of operating life. This relationship was then used to estimate the total number of reactor trips from above approximately 20 percent of full power expected to occur during the life of a nuclear power plant. The shape of the scram frequency vs. operating life curve resembles a typical reliability bathtub curve (failure rate vs. time), but without a rising ''wearout'' phase due to the lack of operating data near the end of plant design life. For this case the failures are represented by ''bugs'' in the plant system design, construction, and operation which lead to scram. The number of scrams would appear to level out at an average of around three per year; the standard deviations from the mean value indicate an uncertainty of about 50 percent. The total number of scrams from significant power that could be expected in a plant designed for a 40-year life would be about 130 if no wearout phase develops near the end of life

 
 
 
 
381

Reliability analysis of hierarchical computer-based systems subject to common-cause failures  

Energy Technology Data Exchange (ETDEWEB)

The results from reliability modeling and analysis are key contributors to design and tuning activities for computer-based systems. Each architecture style, however, poses different challenges for which analytical approaches must be developed or modified. The challenge we address in this paper is the reliability analysis of hierarchical computer-based systems (HS) with common-cause failures (CCF). The dependencies among components introduced by CCF complicate the reliability analysis of HS, especially when components affected by a common cause exist on different hierarchical levels. We propose an efficient decomposition and aggregation (EDA) approach for incorporating CCF into the reliability evaluation of HS. Our approach is to decompose an original HS reliability analysis problem with CCF into a number of reduced reliability problems freed from the CCF concerns. The approach is represented in a dynamic fault tree by a proposed CCF gate modeled after the functional dependency gate. We present the basics of the EDA approach by working through a hypothetical analysis of a HS subject to CCF and show how it can be extended to an analysis of a hierarchical phased-mission system subject to different CCF depending on mission phases.

Xing Liudong [Electrical and Computer Engineering Department, University of Massachusetts-Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747 (United States)]. E-mail: lxing@umassd.edu; Meshkat, Leila [Jet Propulsion Laboratory, California Institute of Technology, MS 301-180, Pasadena, CA 91109 (United States)]. E-mail: Leila.Meshkat@jpl.nasa.gov; Donohue, Susan K. [Department of Systems and Information Engineering, University of Virginia, 151 Engineers Way, P.O. Box 400747, Charlottesville, VA 22904 (United States)]. E-mail: SusanD@virginia.edu

2007-03-15

382

Reliability analysis of hierarchical computer-based systems subject to common-cause failures  

International Nuclear Information System (INIS)

The results from reliability modeling and analysis are key contributors to design and tuning activities for computer-based systems. Each architecture style, however, poses different challenges for which analytical approaches must be developed or modified. The challenge we address in this paper is the reliability analysis of hierarchical computer-based systems (HS) with common-cause failures (CCF). The dependencies among components introduced by CCF complicate the reliability analysis of HS, especially when components affected by a common cause exist on different hierarchical levels. We propose an efficient decomposition and aggregation (EDA) approach for incorporating CCF into the reliability evaluation of HS. Our approach is to decompose an original HS reliability analysis problem with CCF into a number of reduced reliability problems freed from the CCF concerns. The approach is represented in a dynamic fault tree by a proposed CCF gate modeled after the functional dependency gate. We present the basics of the EDA approach by working through a hypothetical analysis of a HS subject to CCF and show how it can be extended to an analysis of a hierarchical phased-mission system subject to different CCF depending on mission phases

383

Update of the human reliability analysis for a nuclear power plant  

International Nuclear Information System (INIS)

Human reliability analysis is a systematic framework, which includes the process of evaluation of human performance and associated impacts on structures, systems and components for a complex facility. The update of Human Reliability Analysis in Probabilistic Safety Assessment of a Nuclear Power Plant requires the development of an overall method for the human reliability analysis. The update is needed as the original human reliability analysis was performed years ago, as the methods have been improved, as the requirements for performing the analyses have changed and as the additional good practice was gained in the mean time. The method for update of human reliability analysis is developed with consideration of the current requirements and the good practice. The selected features of existing methods and the selected specific features are introduced into the method. The evaluation is performed and the preliminary results of human reliability analysis are introduced into the probabilistic safety assessment model. The preliminary results of evaluating the probabilistic safety assessment model identify the key risk contributors and the areas for possible improvement. (author)

384

Redevelopment and reliability study of simultaneously uranium and thorium analysis automation control system  

International Nuclear Information System (INIS)

Full-text: This project is to refurbish the Instrumental Delayed Neutron Activation Analysis System for Simultaneously Determination of Uranium and Thorium namely PAUTS. PAUTS use nuclear techniques for the quantitative determination of Uranium-235 (U-235) and Thorium-232 (Th-232)radionuclides contents in the samples. It consists of three main automation procedures namely Control sample handling, Data Acquisition for neutron counting, and data handling and analysis program. The automation control technology for this project is based on a personal computer (PC), Ethernet communication support, programmable automation control (PAC) module CFP 2220, infrared photo sensors and LabVIEW software package. The analysis samples capsule was placed in transfers containers or rabbit and will be transfer using fast pneumatic sample handling for activation by irradiate it to neutron in the reactor core. Both radionuclides as a fission product will decay and emit the delayed neutron which are count using the nuclear counting electronics module. Studies on the reliability of fast pneumatic sample handling using the statistical method shows that 95 % confidence level had been reach. Results shows the mean transfer time of the sample from the loader to the reactor core is 3251 ± 210 ms, while the mean transfer time of the samples from the core to the counter chamber is 3264 ± 407 ms. The overall system reliability has been verified using analysis of calibration standard material with known quantity of uranium and thorium IAEA-S17, the IAEA-ThO2 and the IAEA-S14 method. At the moment nuclear counting electronic based on 4 units neutron detector and the results were in line with the previous experiment. Results shows that the content of U and Th is in the average of 19:35 ppm and 432.25 ppm respectively compared with the known quantity of the sample is 29.0 ppm and 460 ppm. Studies on the effects pneumatic sample handling to the irradiation time parameter indicated that the previous experiments parameters produce optimal results of the IDNAA analysis using IAEA-S14. The results of this study show the overall reliability parameters of the PAUTs system. (author)

385

A GIS-based software for lifeline reliability analysis under seismic hazard  

Science.gov (United States)

Lifelines are vital networks, and it is important that those networks are still functional after major natural disasters such as earthquakes. Assessing reliability of lifelines requires spatial analysis of lifelines with respect to a given earthquake hazard map. In this paper, a GIS-based software for the spatial assessment of lifeline reliability which is developed by using GeoTools environment is presented. The developed GIS-based software imports seismic hazard and lifeline network layers and then creates a gridded network structure. Finally, it adopts a network reliability algorithm to calculate the upper and lower bounds for system reliability of the lifeline under seismic hazard. The software enables user visualizing the reliability values in graphical form as well as thematic lifeline reliability map with colors indicating reliability level along with the link and the overall network. It also provides functions for saving the analysis results in shape file format. The software is tested and validated for an application taken from literature which is a part of water distribution system of Bursa in Turkey. The developed GIS-based software module that creates GIS-based reliability map of the lifelines under seismic hazard is user friendly, modifiable, fast in execution time, illustrative and validated for the existing literature studies.

Sevtap Selcuk-Kestel, A.; Sebnem Duzgun, H.; Oduncuoglu, Lutfi

2012-05-01

386

Uncertainty analysis of nonlinear systems employing the first-order reliability method  

Energy Technology Data Exchange (ETDEWEB)

In most mechanical systems, properties of the system elements have uncertainties due to several reasons. For example, mass, stiffness coefficient of a spring, damping coefficient of a damper or friction coefficients have uncertain characteristics. The uncertain characteristics of the elements have a direct effect on the system performance uncertainty. It is very important to estimate the performance uncertainty since the performance uncertainty is directly related to manufacturing yield and consumer satisfaction. Due to this reason, the performance uncertainty should be estimated accurately and considered in the system design. In this paper, performance measures are defined for nonlinear vibration systems and the performance measure uncertainties are estimated employing the first order reliability method (FORM). It was found that the FORM could provide good results in spite of the system nonlinear characteristics. Comparing to the results obtained by Monte Carlo Simulation (MCS), the accuracy of the uncertainty analysis results obtained by the FORM is validated.

Choi, Chan Kyu; Yoo, Hong Hee [Hanyang University, Seoul (Korea, Republic of)

2012-01-15

387

Uncertainty analysis of nonlinear systems employing the first-order reliability method  

International Nuclear Information System (INIS)

In most mechanical systems, properties of the system elements have uncertainties due to several reasons. For example, mass, stiffness coefficient of a spring, damping coefficient of a damper or friction coefficients have uncertain characteristics. The uncertain characteristics of the elements have a direct effect on the system performance uncertainty. It is very important to estimate the performance uncertainty since the performance uncertainty is directly related to manufacturing yield and consumer satisfaction. Due to this reason, the performance uncertainty should be estimated accurately and considered in the system design. In this paper, performance measures are defined for nonlinear vibration systems and the performance measure uncertainties are estimated employing the first order reliability method (FORM). It was found that the FORM could provide good results in spite of the system nonlinear characteristics. Comparing to the results obtained by Monte Carlo Simulation (MCS), the accuracy of the uncertainty analysis results obtained by the FORM is validated

388

Reliability analysis of diverse safety logic systems of fast breeder reactor  

International Nuclear Information System (INIS)

Safety Logic for Fast Breeder Reactor (FBR) is designed to initiate safety action against Design Basis Events. Based on the outputs of various processing circuits, Safety logic system drives the control rods of the shutdown system. So, Safety Logic system is classified as safety critical system. Therefore, reliability analysis has to be performed. This paper discusses the Reliability analysis of Diverse Safety logic systems of FBRs. For this literature survey on safety critical systems, system reliability approach and standards to be followed like IEC-61508 are discussed in detail. For Programmable Logic device based systems, Hardware Description Languages (HDL) are used. So this paper also discusses the Verification and Validation for HDLs. Finally a case study for the Reliability analysis of Safety logic is discussed. (author)

389

A survey on the human reliability analysis methods for the design of Korean next generation reactor  

Energy Technology Data Exchange (ETDEWEB)

Enhanced features through applying recent domestic technologies may characterize the safety and efficiency of KNGR(Korea Next Generation Reactor). Human engineered interface and control room environment are expected to be beneficial to the human aspects of KNGR design. However, since the current method for human reliability analysis is not up to date after THERP/SHARP, it becomes hard to assess the potential of human errors due to both of the positive and negative effect of the design changes in KNGR. This is a state of the art report on the human reliability analysis methods that are potentially available for the application to the KNGR design. We surveyed every technical aspects of existing HRA methods, and compared them in order to obtain the requirements for the assessment of human error potentials within KNGR design. We categorized the more than 10 methods into the first and the second generation according to the suggestion of Dr. Hollnagel. THERP was revisited in detail. ATHEANA proposed by US NRC for an advanced design and CREAM proposed by Dr. Hollnagel were reviewed and compared. We conclude that the key requirements might include the enhancement in the early steps for human error identification and the quantification steps with considerations of more extended error shaping factors over PSFs(performance shaping factors). The utilization of the steps and approaches of ATHEANA and CREAM will be beneficial to the attainment of an appropriate HRA method for KNGR. However, the steps and data from THERP will be still maintained because of the continuity with previous PSA activities in KNGR design.

Lee, Yong Hee; Lee, J. W.; Park, J. C.; Kwack, H. Y.; Lee, K. Y.; Park, J. K.; Kim, I. S.; Jung, K. W

2000-03-01

390

A survey on the human reliability analysis methods for the design of Korean next generation reactor  

International Nuclear Information System (INIS)

Enhanced features through applying recent domestic technologies may characterize the safety and efficiency of KNGR(Korea Next Generation Reactor). Human engineered interface and control room environment are expected to be beneficial to the human aspects of KNGR design. However, since the current method for human reliability analysis is not up to date after THERP/SHARP, it becomes hard to assess the potential of human errors due to both of the positive and negative effect of the design changes in KNGR. This is a state of the art report on the human reliability analysis methods that are potentially available for the application to the KNGR design. We surveyed every technical aspects of existing HRA methods, and compared them in order to obtain the requirements for the assessment of human error potentials within KNGR design. We categorized the more than 10 methods into the first and the second generation according to the suggestion of Dr. Hollnagel. THERP was revisited in detail. ATHEANA proposed by US NRC for an advanced design and CREAM proposed by Dr. Hollnagel were reviewed and compared. We conclude that the key requirements might include the enhancement in the early steps for human error identification and the quantification steps with considerations of more extended error shaping factors over PSFs(performance shaping factors). The utilization of the steps and approaches of ATHEANA and CREAM will be beneficial to the attainment of an appropriate HRA method for KNGR. However, the steps and data from THERP will be still maintained because of the continuity with previous PSA activities in KNGR design

391

Reliability analysis of multi-trigger binary systems subject to competing failures  

International Nuclear Information System (INIS)

This paper suggests two combinatorial algorithms for the reliability analysis of multi-trigger binary systems subject to competing failure propagation and failure isolation effects. Propagated failure with global effect (PFGE) is referred to as a failure that not only causes outage to the component from which the failure originates, but also propagates through all other system components causing the entire system failure. However, the propagation effect from the PFGE can be isolated in systems with functional dependence (FDEP) behavior. This paper studies two distinct consequences of PFGE resulting from a competition in the time domain between the failure isolation and failure propagation effects. As compared to existing works on competing failures that are limited to systems with a single FDEP group, this paper considers more complicated cases where the systems have multiple dependent FDEP groups. Analysis of such systems is more challenging because both the occurrence order between the trigger failure event and PFGE from the dependent components and the occurrence order among the multiple trigger failure events have to be considered. Two combinatorial and analytical algorithms are proposed. Both of them have no limitation on the type of time-to-failure distributions for the system components. Their correctness is verified using a Markov-based method. An example of memory systems is analyzed to demonstrate and compare the applications and advantages of the two proposlications and advantages of the two proposed algorithms. - Highlights: ? Reliability of binary systems with multiple dependent functional dependence groups is analyzed. ? Competing failure propagation and failure isolation effect is considered. ? The proposed algorithms are combinatorial and applicable to any arbitrary type of time-to-failure distributions for system components.

392

Applicability Domain ANalysis (ADAN): a robust method for assessing the reliability of drug property predictions.  

Science.gov (United States)

We report a novel method called ADAN (Applicability Domain ANalysis) for assessing the reliability of drug property predictions obtained by in silico methods. The assessment provided by ADAN is based on the comparison of the query compound with the training set, using six diverse similarity criteria. For every criterion, the query compound is considered out of range when the similarity value obtained is larger than the 95th percentile of the values obtained for the training set. The final outcome is a number in the range of 0-6 that expresses the number of unmet similarity criteria and allows classifying the query compound within seven reliability categories. Such categories can be further exploited to assign simpler reliability classes using a traffic light schema, to assign approximate confidence intervals or to mark the predictions as unreliable. The entire methodology has been validated simulating realistic conditions, where query compounds are structurally diverse from those in the training set. The validation exercise involved the construction of more than 1000 models. These models were built using a combination of training set, molecular descriptors, and modeling methods representative of the real predictive tasks performed in the eTOX project (a project whose objective is to predict in vivo toxicological end points in drug development). Validation results confirm the robustness of the proposed assessment methodology, which compares favorably with other classical methods based solely on the structural similarity of the compounds. ADAN characteristics make the method well-suited for estimate the quality of drug predictions obtained in extremely unfavorable conditions, like the prediction of drug toxicity end points. PMID:24821140

Carrió, Pau; Pinto, Marta; Ecker, Gerhard; Sanz, Ferran; Pastor, Manuel

2014-05-27

393

A new approach for reliability analysis with time-variant performance characteristics  

International Nuclear Information System (INIS)

Reliability represents safety level in industry practice and may variant due to time-variant operation condition and components deterioration throughout a product life-cycle. Thus, the capability to perform time-variant reliability analysis is of vital importance in practical engineering applications. This paper presents a new approach, referred to as nested extreme response surface (NERS), that can efficiently tackle time dependency issue in time-variant reliability analysis and enable to solve such problem by easily integrating with advanced time-independent tools. The key of the NERS approach is to build a nested response surface of time corresponding to the extreme value of the limit state function by employing Kriging model. To obtain the data for the Kriging model, the efficient global optimization technique is integrated with the NERS to extract the extreme time responses of the limit state function for any given system input. An adaptive response prediction and model maturation mechanism is developed based on mean square error (MSE) to concurrently improve the accuracy and computational efficiency of the proposed approach. With the nested response surface of time, the time-variant reliability analysis can be converted into the time-independent reliability analysis and existing advanced reliability analysis methods can be used. Three case studies are used to demonstrate the efficiency and accuracy of NERS approach

394

Markov Chains and reliability analysis for reinforced concrete structure service life  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english From field studies and the literature, it was found that the degradation of concrete over time can be modelled probabilistically using homogeneous Markov Chains. To confirm this finding, this study presents an application of Markov Chains associated with the reliability analysis of experimental resu [...] lts of the degradation of concrete by chlorides. Experimental results were obtained for chloride penetration originating from non-accelerated tests in concretes in which the water/binder ratio was variable (0.40, 0.50 and 0.60) and that were produced with Pozzolanic Portland cement that was exposed for six months to the action of NaCl. Using a simulation process, the failure and safety probabilities were calculated by reliability and using Markov Chains, a service life project was estimated (a period of corrosion initiation). Compared to a concrete structure itself, the average error of service life predicted using Markov was approximately 14%. The results show a promissory methodology, in combination with the determination of concrete cover thickness, according to the required service life.

Edna, Possan; Jairo José de Oliveira, Andrade.

2014-06-01

395

Problems of reliability in layer-bylayer neutron activation analysis  

International Nuclear Information System (INIS)

The stages of analytical process, which are characteristic for layer-by-layer neutron activation analysis and at carring out of which the value of analytical signal can be istorted or the coordinate of the determined component can be changed are considered. Anomalous distribution of an impurity, determined by layer-by-layer neutron activation analysis, may be due to methodic reasons: action of high-energy gamma quanta, electrons, neutrons, and nuclear interactions during sample irradiation in nuclear reactor; transfer of the impurity from higher concentration to lower concentration layers (memory effect), contact of the etching solution With non-analysed areas of the semiconductor structure; different thickness of the film

396

Comparative Analysis of Visco-elastic Models with Variable Parameters  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents a theoretical comparative study for computational behaviour analysis of vibration isolation elements based on viscous and elastic models with variable parameters. The changing of elastic and viscous parameters can be produced by natural timed evolution demo-tion or by heating developed into the elements during their working cycle. It was supposed both linear and non-linear numerical viscous and elastic models, and their combinations. The results show the impor-tance of numerical model tuning with the real behaviour, as such the characteristics linearity, and the essential parameters for damping and rigidity. Multiple comparisons between linear and non-linear simulation cases dignify the basis of numerical model optimization regarding mathematical complexity vs. results reliability.

Silviu Nastac

2010-01-01

397

Comparative analysis of heat transfer correlations for forced convection boiling  

International Nuclear Information System (INIS)

A critical survey was conducted of the most relevant correlations of boiling heat transfer in forced convection flow. Most of the investigations carried out on partial nucleate boiling and fully developed nucleate boiling have led to the formulation of correlations that are not able to cover a wide range of operating conditions, due to the empirical approach of the problem. A comparative analysis is therefore required in order to delineate the relative accuracy of the proposed correlations, on the basis of the experimental data presently available. The survey performed allows the evaluation of the accuracy of the different calculating procedure; the results obtained, moreover, indicate the most reliable heat transfer correlations for the different operating conditions investigated. This survey was developed for five pressure range (up to 180bar) and for both saturation and subcooled boiling condition

398

Academic Expectations Stress Inventory: Development, Factor Analysis, Reliability, and Validity  

Science.gov (United States)

This article describes the development and initial validation of obtained scores from the Academic Expectations Stress Inventory (AESI), which measures expectations as a source of academic stress in middle and high school Asian students. In the first study, exploratory factor analysis results from 721 adolescents suggested a nine-item scale with…

Ang, Rebecca P.; Huan, Vivien S.

2006-01-01

399

Qualitative and quantitative reliability analysis of safety systems  

International Nuclear Information System (INIS)

A code has been developed for the comprehensive analysis of a fault tree. The code designated UNRAC (UNReliability Analysis Code) calculates the following characteristics of an input fault tree: (1) minimal cut sets; (2) top event unavailability as point estimate and/or in time dependent form; (3) quantitative importance of each component involved; and, (4) error bound on the top event unavailability. UNRAC can analyze fault trees, with any kind of gates (EOR, NAND, NOR, AND, OR), up to a maximum of 250 components and/or gates. The code is benchmarked against WAMCUT, MODCUT, KITT, BIT-FRANTIC, and PL-MODT. The results showed that UNRAC produces results more consistent with the KITT results than either BIT-FRANTIC or PL-MODT. Overall it is demonstrated that UNRAC is an efficient easy-to-use code and has the advantage of being able to do a complete fault tree analysis with this single code. Applications of fault tree analysis to safety studies of nuclear reactors are considered

400

Influence of sampling rate on accuracy and reliability of acoustic voice analysis.  

Science.gov (United States)

It is universally recognized that sampling rate (F(S)) influences the reliability and validity of acoustic voice measurements; however, an exact relationship has not been determined. The purpose of this experiment was to investigate the influence of F(S) on acoustic voice quality measurements, while considering the influences of gender, intra-subject variability, microphone, environmental noise, data acquisition hardware, and analysis software as balancing factors. The impact of F(S), from 44.1 kHz to 10 kHz, was explored by analyzing 864,000 measures of fundamental frequency, jitter, and shimmer, using three software analysis systems: MDVP, TF32, and PRAAT. Results suggest that the recommended, acceptable, and critical F(S) for acoustic voice analysis are above 26 kHz, above 19 kHz, and 12 kHz, respectively. Thus, voice samples captured above 26 kHz can be used for data analysis and compared without introducing error due to F(S). PMID:16147224

Deliyski, Dimitar D; Shaw, Heather S; Evans, Maegan K

2005-01-01