WorldWideScience
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Comparative Study of Reliability Analysis Methods for Discrete Bimodal Information  

Energy Technology Data Exchange (ETDEWEB)

The distribution of a response usually depends on the distribution of a variable. When the distribution of a variable has two different modes, the response also follows a distribution with two different modes. In most reliability analysis methods, the number of modes is irrelevant, but not the type of distribution. However, in actual problems, because information is often provided with two or more modes, it is important to estimate the distributions with two or more modes. Recently, some reliability analysis methods have been suggested for bimodal distributions. In this paper, we review some methods such as the Akaike information criterion (Aic) and maximum entropy principle (Me) and compare them with the Monte Carlo simulation (MRCS) using mathematical examples with two different modes.

Lim, Woochul; Jang, Junyong; Lee, Taehee [Hanyang Univ., Seoul (Korea, Republic of)

2013-07-15

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Comparative Study of Reliability Analysis Methods for Discrete Bimodal Information  

International Nuclear Information System (INIS)

The distribution of a response usually depends on the distribution of a variable. When the distribution of a variable has two different modes, the response also follows a distribution with two different modes. In most reliability analysis methods, the number of modes is irrelevant, but not the type of distribution. However, in actual problems, because information is often provided with two or more modes, it is important to estimate the distributions with two or more modes. Recently, some reliability analysis methods have been suggested for bimodal distributions. In this paper, we review some methods such as the Akaike information criterion (Aic) and maximum entropy principle (Me) and compare them with the Monte Carlo simulation (MRCS) using mathematical examples with two different modes

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A Comparative Analysis of Open Source Software Reliability  

OpenAIRE

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 lif...

Cobra Rahmani; Azad Azadmanesh; Lotfi Najjar

2010-01-01

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Analysis of reliability AAN laboratory with comparative method  

International Nuclear Information System (INIS)

The AAN method is an analysis method which has good accuracy and precision. The samples of SRM 1646a Estuary sediment, SRM 1648 Urban particulate, SRM 1573 a Tomato leaves, and CRM No. 3 Chlorella was analyzed with AAN method in the AAN Laboratory at P2TRR. The analyzed method result show the 10 % relation of the element contain with long life time, if considered with certificate. These mean the result of the analysis done by the NAA in P2TRR is good

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Reliability analysis  

International Nuclear Information System (INIS)

The author summarizes points about reliability modeling. There are three aspects to reliability modeling. The first is the ''systems topology'' aspect. The purpose here is to express the reliability of a system in terms of the reliability of its components. This a true ''analysis'' approach, breaking big pieces into little pieces. The next is the issue of causes. What are the possible causes, or combinations of causes, that could cause reactor components to fail in such combinations that the system would fail as a result? Here, the author pursues a ''reductionist'' analytical approach, identifying a list or ''candidate'' causes that might result in system failure, and then, examining each one using the system logic function to see if it is, in fact, a cause of system failure. The third aspect of reliability modeling is to describe the time-dependent reliability behavior of the individual causes

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Small nuclear power reactor emergency electric power supply system reliability comparative analysis  

International Nuclear Information System (INIS)

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

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Probabilistic-statistical analysis of WWER fuel element leaking causes and comparative analysis of the fuel reliability indicator on NPPs with WWER and PWR reactors  

International Nuclear Information System (INIS)

The results of a comparative analysis of the fuel reliability indicator on NPPs with WWER and PWR reactors are presented in this report. As an exponent for a comparative reliability analysis of the WANO fuel reliability indicator is used. The fuel reliability indicator provides a general measure of the extent to which the reactor coolant activity is increased as a result of fuel damage. The analysis of fuel reliability indicator values during 1991-2001 at NPPs with WWER-1000 and WWER-440 reactors (Russia, Ukraine, Bulgaria, Czech Republic, Slovakia, Hungary, Finland) is carried out. The high level of WWER fuel reliability is scored except for cases of fuel failures in separate operating periods of some units. (author)

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Reliable Shapelet Image Analysis  

CERN Document Server

Aims: We discuss the applicability and reliability of the shapelet technique for scientific image analysis. Methods: We quantify the effects of non-orthogonality of sampled shapelet basis functions and misestimation of shapelet parameters. We perform the shapelet decomposition on artificial galaxy images with underlying shapelet models and galaxy images from the GOODS survey, comparing the publicly available IDL implementation with our new C++ implementation. Results: Non-orthogonality of the sampled basis functions and misestimation of the shapelet parameters can cause substantial misinterpretation of the physical properties of the decomposed objects. Additional constraints and image preprocessing have to be incorporated in order to achieve reliable decomposition results.

Melchior, P; Bartelmann, M

2006-01-01

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Reliable Shapelet Image Analysis  

OpenAIRE

Aims: We discuss the applicability and reliability of the shapelet technique for scientific image analysis. Methods: We quantify the effects of non-orthogonality of sampled shapelet basis functions and misestimation of shapelet parameters. We perform the shapelet decomposition on artificial galaxy images with underlying shapelet models and galaxy images from the GOODS survey, comparing the publicly available IDL implementation with our new C++ implementation. Results: Non-or...

Melchior, P.; Meneghetti, M.; Bartelmann, M.

2006-01-01

10

Reliability of bioimpedance analysis compared with other adiposity measurements in children: the FLVS II Study  

OpenAIRE

OBJECTIVE: To evaluate the reproducibility of the measurement of% body fat by bipedal biometrical impedance analysis (BIA) compared with anthropometric measurements of adiposity in children and the correlations between these methods in children and adults.METHODS: A cross-sectional study in a total of 1080 adults and children enrolled in 1999 in the Fleurbaix-Laventie Ville Sant?I (FLVS II) population-based study in northern France. The reproducibility of anthropometrical and BIA methods was ...

Kettaneh, Adrien; Heude, Barbara; Lommez, Agne?s; Borys, Jean-michel; Ducimetie?re, Pierre; Charles, Marie-aline

2005-01-01

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Reliability of bioimpedance analysis compared with other adiposity measurements in children: the FLVS II Study.  

OpenAIRE

OBJECTIVE: To evaluate the reproducibility of the measurement of% body fat by bipedal biometrical impedance analysis (BIA) compared with anthropometric measurements of adiposity in children and the correlations between these methods in children and adults.METHODS: A cross-sectional study in a total of 1080 adults and children enrolled in 1999 in the Fleurbaix-Laventie Ville Sant?I (FLVS II) population-based study in northern France. The reproducibility of anthropometrical and BIA methods was ...

Kettaneh, Adrien; Heude, Barbara; Lommez, Agne?s; Borys, Jean-michel; Ducimetie?re, Pierre; Charles, Marie-aline

2005-01-01

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Comparative Reliability Studies and Analysis of Au, Pd-Coated Cu and Pd-Doped Cu Wire in Microelectronics Packaging  

OpenAIRE

This paper compares and discusses the wearout reliability and analysis of Gold (Au), Palladium (Pd) coated Cu and Pd-doped Cu wires used in fineline Ball Grid Array (BGA) package. Intermetallic compound (IMC) thickness measurement has been carried out to estimate the coefficient of diffusion (Do) under various aging conditions of different bonding wires. Wire pull and ball bond shear strengths have been analyzed and we found smaller variation in Pd-doped Cu wire compared to Au and Pd-doped Cu...

Chong Leong, Gan; Uda, Hashim

2013-01-01

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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

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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

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Comparative study on response surfaces for reliability analysis of spatially variable soil slope  

Science.gov (United States)

This paper focuses on the performance of the second-order polynomial-based response surfaces on the reliability of spatially variable soil slope. A single response surface constructed to approximate the slope system failure performance function G( X) (called single RS) and multiple response surfaces constructed on finite number of slip surfaces (called multiple RS) are developed, respectively. Single RS and multiple RS are applied to evaluate the system failure probability p f for a cohesive soil slope together with Monte Carlo simulation (MCS). It is found that p f calculated by single RS deviates significantly from that obtained by searching a large number of potential slip surfaces, and this deviation becomes insignificant with the decrease of the number of random variables or the increase of the scale of fluctuation. In other words, single RS cannot approximate G( X) with reasonable accuracy. The value of p f from multiple response surfaces fits well with that obtained by searching a large number of potential slip surfaces. That is, multiple RS can estimate G( X) with reasonable accuracy.

Li, Liang; Chu, Xue-song

2015-03-01

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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.

17

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

18

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

19

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

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Reliability analysis of Angra I safety systems  

International Nuclear Information System (INIS)

An extensive reliability analysis of some safety systems of Angra I, are presented. The fault tree technique, which has been successfully used in most reliability studies of nuclear safety systems performed to date is employed. Results of a quantitative determination of the unvailability of the accumulator and the containment spray injection systems are presented. These results are also compared to those reported in WASH-1400. (E.G.)

21

Bound of the reliability perturbations for Markovian analysis under uncertainty  

Energy Technology Data Exchange (ETDEWEB)

Various bounds are given for the reliability for Markovian analysis under uncertainty, when the transition matrix perturbation is known through its bound. Estimations are given for the variance of the reliability and compared in a simple example.

Dengis, D.; Devooght, J.

1987-01-01

22

Reliability Analysis of Adhesive Bonded Scarf Joints  

DEFF Research Database (Denmark)

A probabilistic model for the reliability analysis of adhesive bonded scarfed lap joints subjected to static loading is developed. It is representative for the main laminate in a wind turbine blade subjected to flapwise bending. The structural analysis is based on a three dimensional (3D) finite element analysis (FEA). For the reliability analysis a design equation is considered which is related to a deterministic code-based design equation where reliability is secured by partial safety factors together with characteristic values for the material properties and loads. The failure criteria are formulated using a von Mises, a modified von Mises and a maximum stress failure criterion. The reliability level is estimated for the scarfed lap joint and this is compared with the target reliability level implicitly used in the wind turbine standard IEC 61400-1. A convergence study is performed to validate the FEA model, and a sensitivity analysis on the influence of various geometrical parameters and material properties on the maximum stress is conducted. Because the yield behavior of many polymeric structural adhesives is dependent on both deviatoric and hydrostatic stress components, different ratios of the compressive to tensile adhesive yield stresses in the failure criterion are considered. It is shown that the chosen failure criterion, the scarf angle and the load are significant for the assessment of the probability of failure.

Kimiaeifar, Amin; Toft, Henrik Stensgaard

2012-01-01

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RELIABILITY ANALYSIS USING SIMULATION MODELLING  

Directory of Open Access Journals (Sweden)

Full Text Available

ENGLISH ABSTRACT: The reliability analysis of complex systems may often become unmanageable. especially when state or time dependent failure rate~, repair facilities and standby operations are present in a system. This paper describes the possible use of a simulation approach and the development of a reliability. availability and maintainability simulator which may be used to alleviate some of the disadvantages inherent in the traditional analytical approach.

AFRIKAANSE OPSOMMING: Die analise van die betroubaarheid van 'n komplekse stelsel mag 50ms onhanteerbaar raak veral indien die stelsel toestand- of tydafhanklike falingsternpo's, herstelfasiliteite en bystandtoerusting insluit. Hierdieartikel beskryf die moontlike toepassing van 'n simulas.iebenadering asook die ontwikkeling van 'n betroubaarheid-. beskikbaarhe.id- en instandhoubaarheidsimulator wat gebruik mag word om sommige van die nadele, inherent aan die tradisionele analitiese benadering, te oorkern.

S.J. Claasen

2012-01-01

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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

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Reliability of Rapid Subtyping Tools Compared to That of Phylogenetic Analysis for Characterization of Human Immunodeficiency Virus Type 1 Non-B Subtypes and Recombinant Forms?  

OpenAIRE

Human immunodeficiency virus type 1 (HIV-1) subtyping is often estimated on the basis of pol sequences by using online websites instead of phylogenetic analysis (phy). We evaluated the reliability of distinct rapid subtyping tools versus phy with a large panel of HIV-1 non-B subtypes and circulating recombinant forms (CRF). pol sequences (277 protease [PR] and 171 reverse transcriptase [RT] sequences) previously assigned by phy to eight distinct HIV-1 non-B subtypes were obtained from 277 HIV...

Holgui?n, A?frica; Lo?pez, Marisa; Soriano, Vincent

2008-01-01

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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

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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

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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

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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

30

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

31

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.)

32

A comparative method for improving the reliability of brittle components  

International Nuclear Information System (INIS)

Calculating the absolute reliability built in a product is often an extremely difficult task because of the complexity of the physical processes and physical mechanisms underlying the failure modes, the complex influence of the environment and the operational loads, the variability associated with reliability-critical design parameters and the non-robustness of the prediction models. Predicting the probability of failure of loaded components with complex shape for example is associated with uncertainty related to: the type of existing flaws initiating fracture, the size distributions of the flaws, the locations and the orientations of the flaws and the microstructure and its local properties. Capturing these types of uncertainty, necessary for a correct prediction of the reliability of components is a formidable task which does not need to be addressed if a comparative reliability method is employed, especially if the focus is on reliability improvement. The new comparative method for improving the resistance to failure initiated by flaws proposed here is based on an assumed failure criterion, an equation linking the probability that a flaw will be critical with the probability of failure associated with the component and a finite element solution for the distribution of the principal stresses in the loaded component. The probability that a flaw will be critical is determined directly, after a finite number of steps equal to the number of finite elements into which thhe number of finite elements into which the component is divided. An advantage of the proposed comparative method for improving the resistance to failure initiated by flaws is that it does not rely on a Monte Carlo simulation and does not depend on knowledge of the size distribution of the flaws and the material properties. This essentially eliminates uncertainty associated with the material properties and the population of flaws. On the basis of a theoretical analysis we also show that, contrary to the common belief, in general, for non-interacting flaws randomly located in a stressed volume, the distribution of the minimum failure stress is not necessarily described by a Weibull distribution. For the simple case of a single group of flaws all of which become critical beyond a particular threshold value for example, the Weibull distribution fails to predict correctly the probability of failure. If in a particular load range, no new critical flaws are created by increasing the applied stress, the Weibull distribution also fails to predict correctly the probability of failure of the component. In these cases however, the probability of failure is correctly predicted by the suggested alternative equation. The suggested equation is the correct mathematical formulation of the weakest-link concept related to random flaws in a stressed volume. The equation does not require any assumption concerning the physical nature of the flaws and the physical mechanism of failure and can be applied in any situation of locally initiated failure by non-interacting entities

33

A comparative method for improving the reliability of brittle components  

Energy Technology Data Exchange (ETDEWEB)

Calculating the absolute reliability built in a product is often an extremely difficult task because of the complexity of the physical processes and physical mechanisms underlying the failure modes, the complex influence of the environment and the operational loads, the variability associated with reliability-critical design parameters and the non-robustness of the prediction models. Predicting the probability of failure of loaded components with complex shape for example is associated with uncertainty related to: the type of existing flaws initiating fracture, the size distributions of the flaws, the locations and the orientations of the flaws and the microstructure and its local properties. Capturing these types of uncertainty, necessary for a correct prediction of the reliability of components is a formidable task which does not need to be addressed if a comparative reliability method is employed, especially if the focus is on reliability improvement. The new comparative method for improving the resistance to failure initiated by flaws proposed here is based on an assumed failure criterion, an equation linking the probability that a flaw will be critical with the probability of failure associated with the component and a finite element solution for the distribution of the principal stresses in the loaded component. The probability that a flaw will be critical is determined directly, after a finite number of steps equal to the number of finite elements into which the component is divided. An advantage of the proposed comparative method for improving the resistance to failure initiated by flaws is that it does not rely on a Monte Carlo simulation and does not depend on knowledge of the size distribution of the flaws and the material properties. This essentially eliminates uncertainty associated with the material properties and the population of flaws. On the basis of a theoretical analysis we also show that, contrary to the common belief, in general, for non-interacting flaws randomly located in a stressed volume, the distribution of the minimum failure stress is not necessarily described by a Weibull distribution. For the simple case of a single group of flaws all of which become critical beyond a particular threshold value for example, the Weibull distribution fails to predict correctly the probability of failure. If in a particular load range, no new critical flaws are created by increasing the applied stress, the Weibull distribution also fails to predict correctly the probability of failure of the component. In these cases however, the probability of failure is correctly predicted by the suggested alternative equation. The suggested equation is the correct mathematical formulation of the weakest-link concept related to random flaws in a stressed volume. The equation does not require any assumption concerning the physical nature of the flaws and the physical mechanism of failure and can be applied in any situation of locally initiated failure by non-interacting entities.

Todinov, M.T. [Department of Mechanical Engineering and Mathematical Sciences, Oxford Brookes University, Oxford OX33 1HX (United Kingdom)], E-mail: mtodinov@brookes.ac.uk

2009-02-15

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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)

35

Integrated Methodology for Software Reliability Analysis  

Directory of Open Access Journals (Sweden)

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

Marian Pompiliu CRISTESCU

2012-01-01

36

Reliability analysis of stiff versus flexible piping  

International Nuclear Information System (INIS)

The overall objective of 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. The current study was conducted to establish the necessary groundwork based on the piping reliability analysis. A confirmatory piping reliability assessment indicated that removing rigid supports and snubbers tends to either improve or affect very little the piping reliability. The authors then investigated a couple of changes to be implemented in Regulatory Guide (RG) 1.61 and RG 1.122 aimed at more flexible piping design. They concluded that these changes substantially reduce calculated piping responses and allow piping redesigns with significant reduction in number of supports and snubbers without violating ASME code requirements. Furthermore, the more flexible piping redesigns are capable of exhibiting reliability levels equal to or higher than the original stiffer design. An investigation of the malfunction of pipe whip restraints confirmed that the malfunction introduced higher thermal stresses and tended to reduce the overall piping reliability. Finally, support and component reliabilities were evaluated based on available fragility data. Results indicated that the support reliability usually exhibits a moderate decrease as the piping flexibility increases. Most on-line pumps and valves showed an insignificant reduction in reliability for a moreficant reduction in reliability for a more flexible piping design

37

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

38

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)

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 they 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 databases are still rare to date. Furthermore, there is an unequal geographic distribution of current disaster trend studies, with developing countries being underrepresented. Here, we analyze three different disaster databases in the developing-country context of Peru: a global database (Emergency Events Database: EM-DAT), a multinational Latin American database (DesInventar) and a national database (Peruvian National Information System for the Prevention of Disasters: SINPAD). The analysis is performed across three dimensions: (1) spatial scales, from local to regional (provincial) and national scale; (2) timescales, from single events to decadal trends; and (3) disaster categories and metrics, including the number of single disaster event occurrence, or 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 positive trends in people affected at the national scale. We furthermore found large variations of the disaster metrics 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.

2015-03-01

39

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

40

Structural reliability analysis and reliability-based design optimization: Recent advances  

Science.gov (United States)

We review recent research activities on structural reliability analysis, reliability-based design optimization (RBDO) and applications in complex engineering structural design. Several novel uncertainty propagation methods and reliability models, which are the basis of the reliability assessment, are given. In addition, recent developments on reliability evaluation and sensitivity analysis are highlighted as well as implementation strategies for RBDO.

Qiu, ZhiPing; Huang, Ren; Wang, XiaoJun; Qi, WuChao

2013-09-01

41

Reliability analysis of redundant-path interconnection networks  

Energy Technology Data Exchange (ETDEWEB)

The reliability of some redundant-path multistage interconnection networks is characterized. The classes of networks are: the Generalized Indra Networks, Merged Delta Networks, and Augmented C-Networks. The reliability measures are: terminal reliability and broadcast reliability. Symbolic expressions are derived for these reliability measures in terms of component reliabilities. The results are useful in comparing network designs for a given reliability requirement.

Varma, A. (International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center); Raghavendra, C.S. (Univ. of Southern Calif., Los Angeles, CA (US))

1989-04-01

42

Reliability analysis for hazardous waste treatment processes.  

Science.gov (United States)

The reliability of a treatment process is addressed in terms of achieving a regulatory effluent concentration standard and the design safety factors associated with the treatment process. This methodology was then applied to two aqueous hazardous waste treatment processes: packed tower aeration and activated sludge (aerobic) biological treatment. The designs achieving 95 percent reliability were compared with those designs based on conventional practice to determine their patterns of conservatism. Scoping-level treatment costs were also related to reliability levels for these treatment processes. The results indicate that the reliability levels for the physical/chemical treatment process (packed tower aeration) based on the deterministic safety factors range from 80 percent to over 99 percent, whereas those for the biological treatment process range from near 0 percent to over 99 percent, depending on the compound evaluated. Increases in reliability per unit increase in treatment costs are most pronounced at lower reliability levels (less than about 80 percent) than at the higher reliability levels (greater than 90 percent, indicating a point of diminishing returns. Additional research focused on process parameters that presently contain large uncertainties may reduce those uncertainties, with attending increases in the reliability levels of the treatment processes. PMID:10765403

Waters, R D; Parker, F L

1999-04-01

43

Reliability analysis for hazardous waste treatment processes  

Energy Technology Data Exchange (ETDEWEB)

The reliability of a treatment process is addressed in terms of achieving a regulatory effluent concentration standard and the design safety factors associated with the treatment process. This methodology was then applied to two aqueous hazardous waste treatment processes: packed tower aeration and activated sludge (aerobic) biological treatment. The designs achieving 95% reliability were compared with those designs based on conventional practice to determine their patterns of conservatism. Scoping-level treatment costs were also related to reliability levels for these treatment processes. The results indicate that the reliability levels for the physical/chemical treatment process (packed tower aeration) based on the deterministic safety factors range from 80% to over 99%, whereas those for the biological treatment process range from near 0% to over 99%, depending on the compound evaluated. Increases in reliability per unit increase in treatment costs are most pronounced at lower reliability levels (less than about 80%) than at the higher reliability levels (greater than 90%), indicating a point of diminishing returns. Additional research focused on process parameters that presently contain large uncertainties may reduce those uncertainties, with attending increases in the reliability levels of the treatment processes.

Waters, R.D. (Sandia National Labs., Carlsbad, NM (United States)); Parker, F.L. (Vanderbilt Univ., Nashville, TN (United States))

1999-04-01

44

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)

45

Comparing two reliable multicast protocols for mobile computing  

Scientific Electronic Library Online (English)

Full Text Available 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.

2003-04-01

46

RHR system reliability analysis of Krsko NPP  

International Nuclear Information System (INIS)

In this paper Systems reliability analysis is applied to residual heat Removal System in Krsko NPP. Fault tree method is used. Qualitative analysis of the fault tree was made using FTAP-2 computer code, and quantitative using IMPORT code. results are evaluated and their possible application is given. (author)

47

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)

48

Reliability Analysis of Suspension Bridges against Flutter  

Science.gov (United States)

A reliability analysis of suspension bridges against flutter failure is presented using the basic theory of reliability. For the purpose of analysis, uncertainties considered are those arising from the variations in geometric and mechanical properties of bridge, modelling, damping and experimentally obtained flutter derivatives. These uncertainties are incorporated by multiplying the computed flutter wind speed with a number of independent factors, which are considered as random variables. Each factor is assumed to follow log-normal distribution. The wind environment at the site, which may cause flutter failure, is considered as the other uncertainty necessary for computing the reliability against flutter failure. The flutter wind speed for the bridge is determined using a finite element approach and a multimode analysis. The effect of some important parameters such as the mean wind speed at the site, coefficients of variation of the multiplying factors associated with damping, modelling and flutter derivatives on the reliability estimates is investigated. The results of the study show that the reliability against flutter failure is sensitive to the variation of the above parameters.

POURZEYNALI, S.; DATTA, T. K.

2002-06-01

49

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

50

A bound of the reliability perturbations for Markovian analysis under uncertainty  

International Nuclear Information System (INIS)

Various bounds are given for the reliability for Markovian analysis under uncertainty, when the transition matrix perturbation is known through its bound. Estimations are given for the variance of the reliability and compared in a simple example. (author)

51

Reliability analysis of prestressed concrete containment structures  

International Nuclear Information System (INIS)

The reliability analysis of prestressed concrete containment structures subjected to combinations of static and dynamic loads with consideration of uncertainties of structural and load parameters is presented. Limit state probabilities for given parameters are calculated using the procedure developed at BNL, while that with consideration of parameter uncertainties are calculated by a fast integration for time variant structural reliability. The limit state surface of the prestressed concrete containment is constructed directly incorporating the prestress. The sensitivities of the Choleskey decomposition matrix and the natural vibration character are calculated by simplified procedures. (author)

52

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)

53

Reliability Analysis of High Temperature Reactor Fuels  

International Nuclear Information System (INIS)

This paper presents the results of reliability analysis of the TRISO -coated fuel particles for the High Temperature Test Reactor (HTTR), Japan. The reliability of fuel particle was evaluated based on the failure probability of each coating layer, and only the failure due to internal gas pressure and shrinkage of pyrolytic carbon (PyC) layer was considered The analysis results show that, no significant failure occurs up to about 45 MWd/kgU for the first core fuel particle and up to about 75 MWd/kgU for the reload core fuel particle. The fuel particle is predicted to fail completely at about 50 MWd/kgU for the first core fuel particle and at about 85 MWd/kgU for the reload core fuel particle. This results show that the TRISO -coated fuel particle for the HTTR to have high reliability. No failure occurs up to the maximum burnup design level, i.e. 33 MWd/kgU for the first core fuel particle and 60 MWd/kgU for the reload core fuel particle. The analysis results show also that the fuel particle reliability (coating layers) depends on the irradiation temperature. The failure occurs at lower burnup if the irradiation temperature increases. (author)

54

Bayesian decision analysis and reliability certification  

International Nuclear Information System (INIS)

Reliability certification is set as a problem of Bayesian Decision Analysis. Uncertainties about the system reliability are quantified by assuming the parameters of the models describing the stochastic behavior of components as random variables. A utility function quantifies the relative value of each possible level of system reliability after having been accepted or the opportunity loss of the same level if the system has been rejected. A decision about accepting or rejecting the system can be made either on the basis of the existing prior assessment of uncertainties or after obtaining further information through testing of the components or the system at a cost. The concepts of value of perfect information, expected value of sample information and the expected net gain of sampling are specialized to the reliability of a multicomponent system to determine the optimum component testing scheme prior to deciding on the system's certification. A component importance ranking is proposed on the basis of the expected value of perfect information about the reliability of each component. The proposed approach is demonstrated on a single component system failing according to a Poisson random process and with natural conjugate prior probability density functions (pdf) for the failure rate and for a multicomponent system under general assumptions

55

Reliability and risk analysis methods research plan  

International Nuclear Information System (INIS)

This document presents a plan for reliability and risk analysis methods research to be performed mainly by the Reactor Risk Branch (RRB), Division of Risk Analysis and Operations (DRAO), Office of Nuclear Regulatory Research. It includes those activities of other DRAO branches which are very closely related to those of the RRB. Related or interfacing programs of other divisions, offices and organizations are merely indicated. The primary use of this document is envisioned as an NRC working document, covering about a 3-year period, to foster better coordination in reliability and risk analysis methods development between the offices of Nuclear Regulatory Research and Nuclear Reactor Regulation. It will also serve as an information source for contractors and others to more clearly understand the objectives, needs, programmatic activities and interfaces together with the overall logical structure of the program

56

Probabilistic Analysis on Network Reliability Problem  

CERN Document Server

The network reliability problem for evaluating the network failure probability has been extensively studied. For a given undirected graph $G$, the network failure probability is the probability such that edge failures make $G$ unconnected. It is assumed that edge failures occur independently with the same probability. In this paper, a probabilistic analysis on the network reliability problem will be shown. We assume a simple random graph model closely related to the Erd\\H{o}s-R\\'{e}nyi random graph. By using the fact that the cut-set space of $G$ is a linear space over $\\Bbb F_2$ spanned by the incident matrix of $G$, we have derived upper and lower bounds on expected network failure probability. The ensemble analysis used here is very similar to the analysis on the input-output weight distribution of a low-density generator matrix code with column weight 2.

Yano, Akiyuki

2011-01-01

57

Human reliability analysis of control room operators  

Energy Technology Data Exchange (ETDEWEB)

Human reliability is the probability that a person correctly performs some system required action in a required time period and performs no extraneous action that can degrade the system Human reliability analysis (HRA) is the analysis, prediction and evaluation of work-oriented human performance using some indices as human error likelihood and probability of task accomplishment. Significant progress has been made in the HRA field during the last years, mainly in nuclear area. Some first-generation HRA methods were developed, as THERP (Technique for human error rate prediction). Now, an array of called second-generation methods are emerging as alternatives, for instance ATHEANA (A Technique for human event analysis). The ergonomics approach has as tool the ergonomic work analysis. It focus on the study of operator's activities in physical and mental form, considering at the same time the observed characteristics of operator and the elements of the work environment as they are presented to and perceived by the operators. The aim of this paper is to propose a methodology to analyze the human reliability of the operators of industrial plant control room, using a framework that includes the approach used by ATHEANA, THERP and the work ergonomics analysis. (author)

Santos, Isaac J.A.L.; Carvalho, Paulo Victor R.; Grecco, Claudio H.S. [Instituto de Engenharia Nuclear (IEN), Rio de Janeiro, RJ (Brazil)

2005-07-01

58

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

59

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

Energy Technology Data Exchange (ETDEWEB)

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

Bonfietti, Gerson

2003-07-01

60

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

61

Sensitivity analysis in a structural reliability context  

International Nuclear Information System (INIS)

This thesis' subject is sensitivity analysis in a structural reliability context. The general framework is the study of a deterministic numerical model that allows to reproduce a complex physical phenomenon. The aim of a reliability study is to estimate the failure probability of the system from the numerical model and the uncertainties of the inputs. In this context, the quantification of the impact of the uncertainty of each input parameter on the output might be of interest. This step is called sensitivity analysis. Many scientific works deal with this topic but not in the reliability scope. This thesis' aim is to test existing sensitivity analysis methods, and to propose more efficient original methods. A bibliographical step on sensitivity analysis on one hand and on the estimation of small failure probabilities on the other hand is first proposed. This step raises the need to develop appropriate techniques. Two variables ranking methods are then explored. The first one proposes to make use of binary classifiers (random forests). The second one measures the departure, at each step of a subset method, between each input original density and the density given the subset reached. A more general and original methodology reflecting the impact of the input density modification on the failure probability is then explored. The proposed methods are then applied on the CWNR case, which motivates this thesis. (author)

62

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

63

Seismic reliability analysis of vertical pumps  

International Nuclear Information System (INIS)

This paper deals with the evaluation of the cumulative damage of a vertical pump's rotor shaft subjected to earthquake excitation. The equation of motion is derived, and the behavior of the rotor is calculated. The torsional moment due to the collision is calculated and used to evaluate the cumulative damage of the shaft. From this analysis, it is clear that the shaft of the vertical pump for a nuclear power plant has enough reliability to withstand earthquake excitation. (author)

64

ZERBERUS - the code for reliability analysis of crack containing structures  

International Nuclear Information System (INIS)

Brief description of the First- and Second Order Reliability Methods, being the theoretical background of the code, is given. The code structure is described in detail, with special emphasis to the new application fields. The numerical example investigates failure probability of steam generator tubing affected by stress corrosion cracking. The changes necessary to accommodate this analysis within the ZERBERUS code are explained. Analysis results are compared to different Monte Carlo techniques. (orig./HP)

65

Qualitative analysis in reliability and safety studies  

International Nuclear Information System (INIS)

The qualitative evaluation of system logic models is described as it pertains to assessing the reliability and safety characteristics of nuclear systems. Qualitative analysis of system logic models, i.e., models couched in an event (Boolean) algebra, is defined, and the advantages inherent in qualitative analysis are explained. Certain qualitative procedures that were developed as a part of fault-tree analysis are presented for illustration. Five fault-tree analysis computer-programs that contain a qualitative procedure for determining minimal cut sets are surveyed. For each program the minimal cut-set algorithm and limitations on its use are described. The recently developed common-cause analysis for studying the effect of common-causes of failure on system behavior is explained. This qualitative procedure does not require altering the fault tree, but does use minimal cut sets from the fault tree as part of its input. The method is applied using two different computer programs. 25 refs

66

Infusing Reliability Techniques into Software Safety Analysis  

Science.gov (United States)

Software safety analysis for a large software intensive system is always a challenge. Software safety practitioners need to ensure that software related hazards are completely identified, controlled, and tracked. This paper discusses in detail how to incorporate the traditional reliability techniques into the entire software safety analysis process. In addition, this paper addresses how information can be effectively shared between the various practitioners involved in the software safety analyses. The author has successfully applied the approach to several aerospace applications. Examples are provided to illustrate the key steps of the proposed approach.

Shi, Ying

2015-01-01

67

Subset simulation for structural reliability sensitivity analysis  

International Nuclear Information System (INIS)

Based on two procedures for efficiently generating conditional samples, i.e. Markov chain Monte Carlo (MCMC) simulation and importance sampling (IS), two reliability sensitivity (RS) algorithms are presented. On the basis of reliability analysis of Subset simulation (Subsim), the RS of the failure probability with respect to the distribution parameter of the basic variable is transformed as a set of RS of conditional failure probabilities with respect to the distribution parameter of the basic variable. By use of the conditional samples generated by MCMC simulation and IS, procedures are established to estimate the RS of the conditional failure probabilities. The formulae of the RS estimator, its variance and its coefficient of variation are derived in detail. The results of the illustrations show high efficiency and high precision of the presented algorithms, and it is suitable for highly nonlinear limit state equation and structural system with single and multiple failure modes

68

A comparative study on the reliability criteria determination  

International Nuclear Information System (INIS)

There are two methods to determine the reliability criteria for maintenance effectiveness monitoring; using the failure probability, and the importance from PRA. Comparisons of the results from these two methods provides an insight on the relevancy of setting the reliability criteria to improve the maintenance effectiveness. (author)

69

Multiaxial fatigue reliability analysis of railroad wheels  

International Nuclear Information System (INIS)

A general methodology for fatigue reliability degradation of railroad wheels is proposed in this paper. Both fatigue crack initiation and crack propagation life are included in the proposed methodology using previously developed multiaxial fatigue models by the same authors. A response surface method in conjunction with design of experiments is used to develop a closed form approximation of the fatigue damage accumulation with respect to the input random variables. The total fatigue life of railroad wheels under stochastic loading is simulated, accounting for the spatial and temporal randomness of the fatigue damage. The field observations of railroad wheel fatigue failures are compared with the numerical predictions using the proposed methodology

70

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

71

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

72

Reliability analysis of containment isolation systems  

Energy Technology Data Exchange (ETDEWEB)

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.

Pelto, P.J.; Ames, K.R.; Gallucci, R.H.

1985-06-01

73

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

74

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

75

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

76

The reliability analysis of reactor neutron flux (power) control  

International Nuclear Information System (INIS)

The results of a reliability analysis taking into consideration related failures and the effect of regular maintenance of control system components are described. The analysis is focused on the determination of the control system components reliability characteristics and on the algorithm computation. Modifications of the control system are recommended on the basis of the results to increase the system reliability

77

Comparative assessment of selected PWR auxiliary feedwater system reliability analyses  

International Nuclear Information System (INIS)

This paper presents a sample of results obtained in reviewing utility submittals of Auxiliary Feedwater System reliability studies. These results are then used to illustrate a few general points regarding such studies. The submittals and reviews for operating license applications are quite significant in that they represent an application of probabilistic risk assessment techniques in the licensing process

78

Reliability analysis of pressure vessels containing cracks  

Energy Technology Data Exchange (ETDEWEB)

Traditional analyses of cracked pressure vessels fail to consider the variability and uncertainty of material properties and working loads that demonstrate variations. This paper presented a probabilistic analysis model for predicting the reliability of cracked pressure vessels. The model used fracture mechanics to consider variabilities in material properties, uncertainty in operating loads, and degradation of structural residual strength resulting from crack initiation and propagation. Fracture mechanics were used to identify the probability of fracture failure at specific loading cycles. The Monte Carlo method was then used to calculate the probability of fracture failure at specified loadings cycles, as well as to calculate the allowable loading cycle for the required probability of fracture failure. The combined effects of existing cracks and newly initiating cracks were also investigated. The model was designed to incorporate data from inspections and non-destructive testing. 5 refs., 3 figs.

Xu, J.; Forcinito, M.; Alves, P. [AP Dynamics Inc., Calgary, AB (Canada)

2008-07-01

79

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

80

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

81

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

82

Reliability test and failure analysis of high power LED packages  

Energy Technology Data Exchange (ETDEWEB)

A new type application specific light emitting diode (LED) package (ASLP) with freeform polycarbonate lens for street lighting is developed, whose manufacturing processes are compatible with a typical LED packaging process. The reliability test methods and failure criterions from different vendors are reviewed and compared. It is found that test methods and failure criterions are quite different. The rapid reliability assessment standards are urgently needed for the LED industry. 85 {sup 0}C/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h, showing no visible degradation in optical performance for our modules, with two other vendors showing significant degradation. Some failure analysis methods such as C-SAM, Nano X-ray CT and optical microscope are used for LED packages. Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing. The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging. One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing. (semiconductor devices)

Chen Zhaohui [Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang Qin; Wang Kai; Luo Xiaobing; Liu Sheng, E-mail: victorliu63@126.com [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2011-01-15

83

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

84

Modeling human reliability analysis using MIDAS  

International Nuclear Information System (INIS)

This paper documents current efforts to infuse human reliability analysis (HRA) into human performance simulation. The Idaho National Laboratory is teamed with NASA Ames Research Center to bridge the SPAR-H HRA method with NASA's Man-machine Integration Design and Analysis System (MIDAS) for use in simulating and modeling the human contribution to risk in nuclear power plant control room operations. It is anticipated that the union of MIDAS and SPAR-H will pave the path for cost-effective, timely, and valid simulated control room operators for studying current and next generation control room configurations. This paper highlights considerations for creating the dynamic HRA framework necessary for simulation, including event dependency and granularity. This paper also highlights how the SPAR-H performance shaping factors can be modeled in MIDAS across static, dynamic, and initiator conditions common to control room scenarios. This paper concludes with a discussion of the relationship of the workload factors currently in MIDAS and the performance shaping factors in SPAR-H. (authors)

85

Validation of Methodology for Reliability Analysis of Passive Safety Systems  

International Nuclear Information System (INIS)

The passive safety systems base their operation on natural forces (e.g. gravity, gas expansion) that can be consider always reliable; anyway they may fail their mission because of the change of the boundary conditions (e.g. fouling in the pipes, presence of un-condensable gases etc.) that reduce their reliability value to less than one. The extensive use of passive safety systems, mainly in advanced reactors design, makes necessary to deeply study the approach to their reliability assessment, so to apply a structured methodology that, with statistical and physical consideration, tries to reproduce reality with an acceptable degree of approximation, but that has to be carefully validated as well. The classical risk assessment tools used to study reliability (e.g., Failure Mode and Effects Analysis (FMEA), FTA, Hazard Operational Analysis (HAZOP), etc.) are not adequate to solve this problem because these tools are devoted to the analysis of operation of physical component, while in our case the analysis is devoted to consider the deviation from expected system behavior due to ''alterations'' in the environmental conditions. Different methodologies have been proposed (e.g. REPAS/RMPS, APSRA) with the aim to evaluate the reliability of the passive systems based on the natural circulation phenomenon to be adopted in the PSA safety study of nuclear power plants. In this paper the result of the activity aimed at validating the calculation of the reliability applied to an experimental facility is described. The experimental facility is a simple vertical square shaped natural circulation loop, where the horizontal lower tube is heated and the upper horizontal tube is cooled. An experimental test matrix is setup where the power at the lower horizontal tube is fixed, while different temperatures at the heat sink are applied. The range of the temperatures at the heat sink is selected in order to have unstable natural circulation and at certain value stable. The natural circulation loop simulates a passive system with a fixed reliability experimentally obtained that has to be compared with the calculated one. This activity has been performed in the framework of the IAEA-CRPI31018 titled ''Development of Methodologies for the Assessment of Passive Safety System Performance in Advanced Reactors''.(author).

86

Statistical analysis and modelling of small satellite reliability  

Science.gov (United States)

This paper attempts to characterize failure behaviour of small satellites through statistical analysis of actual in-orbit failures. A unique Small Satellite Anomalies Database comprising empirical failure data of 222 small satellites has been developed. A nonparametric analysis of the failure data has been implemented by means of a Kaplan-Meier estimation. An innovative modelling method, i.e. Bayesian theory in combination with Markov Chain Monte Carlo (MCMC) simulations, has been proposed to model the reliability of small satellites. An extensive parametric analysis using the Bayesian/MCMC method has been performed to fit a Weibull distribution to the data. The influence of several characteristics such as the design lifetime, mass, launch year, mission type and the type of satellite developers on the reliability has been analyzed. The results clearly show the infant mortality of small satellites. Compared with the classical maximum-likelihood estimation methods, the proposed Bayesian/MCMC method results in better fitting Weibull models and is especially suitable for reliability modelling where only very limited failures are observed.

Guo, Jian; Monas, Liora; Gill, Eberhard

2014-05-01

87

Meta-Analysis of Scale Reliability Using Latent Variable Modeling  

Science.gov (United States)

A latent variable modeling approach is outlined that can be used for meta-analysis of reliability coefficients of multicomponent measuring instruments. Important limitations of efforts to combine composite reliability findings across multiple studies are initially pointed out. A reliability synthesis procedure is discussed that is based on…

Raykov, Tenko; Marcoulides, George A.

2013-01-01

88

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)

89

Failures Analysis and Reliability Calculation for Power Transformers  

OpenAIRE

Failures of transformers in sub-transmission systems not only reduce reliability of power system but also have significant effects on power quality since one of the important components of any system quality is reliability of that system. To enhance utility reliability, failure analysis and its rates, failure origin and physical damage causes must be studied. This paper describes a case study of the reliability of sub-transmission transformers (63/20 KV) installed in Mazandaran province, oper...

Mirzai, M.; Gholami, A.; Aminifar, F.

2006-01-01

90

Reliability Analysis of a Mono-Tower Platform  

OpenAIRE

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

91

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

92

Optimization Based Efficiencies in First Order Reliability Analysis  

Science.gov (United States)

This paper develops a method for updating the gradient vector of the limit state function in reliability analysis using Broyden's rank one updating technique. In problems that use commercial code as a black box, the gradient calculations are usually done using a finite difference approach, which becomes very expensive for large system models. The proposed method replaces the finite difference gradient calculations in a standard first order reliability method (FORM) with Broyden's Quasi-Newton technique. The resulting algorithm of Broyden updates within a FORM framework (BFORM) is used to run several example problems, and the results compared to standard FORM results. It is found that BFORM typically requires fewer functional evaluations that FORM to converge to the same answer.

Peck, Jeffrey A.; Mahadevan, Sankaran

2003-01-01

93

Issues in benchmarking human reliability analysis methods: A literature review  

International Nuclear Information System (INIS)

There is a diversity of human reliability analysis (HRA) methods available for use in assessing human performance within probabilistic risk assessments (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 comparing and evaluating HRA methods in assessing operator performance in simulator experiments is currently underway. 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 is presented in order to aid in the design of future HRA benchmarking endeavors.

94

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

95

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

96

Key Reliability Drivers of Liquid Propulsion Engines and A Reliability Model for Sensitivity Analysis  

Science.gov (United States)

This paper is to address the in-flight reliability of a liquid propulsion engine system for a launch vehicle. We first establish a comprehensive list of system and sub-system reliability drivers for any liquid propulsion engine system. We then build a reliability model to parametrically analyze the impact of some reliability parameters. We present sensitivity analysis results for a selected subset of the key reliability drivers using the model. Reliability drivers identified include: number of engines for the liquid propulsion stage, single engine total reliability, engine operation duration, engine thrust size, reusability, engine de-rating or up-rating, engine-out design (including engine-out switching reliability, catastrophic fraction, preventable failure fraction, unnecessary shutdown fraction), propellant specific hazards, engine start and cutoff transient hazards, engine combustion cycles, vehicle and engine interface and interaction hazards, engine health management system, engine modification, engine ground start hold down with launch commit criteria, engine altitude start (1 in. start), Multiple altitude restart (less than 1 restart), component, subsystem and system design, manufacturing/ground operation support/pre and post flight check outs and inspection, extensiveness of the development program. We present some sensitivity analysis results for the following subset of the drivers: number of engines for the propulsion stage, single engine total reliability, engine operation duration, engine de-rating or up-rating requirements, engine-out design, catastrophic fraction, preventable failure fraction, unnecessary shutdown fraction, and engine health management system implementation (basic redlines and more advanced health management systems).

Huang, Zhao-Feng; Fint, Jeffry A.; Kuck, Frederick M.

2005-01-01

97

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

98

Reliability estimation in a multilevel confirmatory factor analysis framework.  

Science.gov (United States)

Scales with varying degrees of measurement reliability are often used in the context of multistage sampling, where variance exists at multiple levels of analysis (e.g., individual and group). Because methodological guidance on assessing and reporting reliability at multiple levels of analysis is currently lacking, we discuss the importance of examining level-specific reliability. We present a simulation study and an applied example showing different methods for estimating multilevel reliability using multilevel confirmatory factor analysis and provide supporting Mplus program code. We conclude that (a) single-level estimates will not reflect a scale's actual reliability unless reliability is identical at each level of analysis, (b) 2-level alpha and composite reliability (omega) perform relatively well in most settings, (c) estimates of maximal reliability (H) were more biased when estimated using multilevel data than either alpha or omega, and (d) small cluster size can lead to overestimates of reliability at the between level of analysis. We also show that Monte Carlo confidence intervals and Bayesian credible intervals closely reflect the sampling distribution of reliability estimates under most conditions. We discuss the estimation of credible intervals using Mplus and provide R code for computing Monte Carlo confidence intervals. PMID:23646988

Geldhof, G John; Preacher, Kristopher J; Zyphur, Michael J

2014-03-01

99

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

100

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

101

Reliability analysis of pipe whip impacts  

International Nuclear Information System (INIS)

A probabilistic analysis of a group distribution header (GDH) guillotine break and the damage resulting from the failed GDH impacting against a neighbouring wall was carried out for the Ignalita RBMK-1500 reactor. The NEPTUNE software system was used for the deterministic transient analysis of a GDH guillotine break. Many deterministic analyses were performed using different values of the random variables that were specified by ProFES software. All the deterministic results were transferred to the ProFES system, which then performed probabilistic analyses of piping failure and wall damage. The Monte Carlo Simulation (MCS) method was used to study the sensitivity of the response variables and the effect of uncertainties of material properties and geometry parameters to the probability of limit states. The First Order Reliability Method (FORM) was used to study the probability of failure of the impacted-wall and the support-wall. The Response Surface (RS/MCS) method was used in order to express failure probability as function and to investigate the dependence between impact load and failure probability. The results of the probability analyses for a whipping GDH impacting onto an adjacent wall show that: (i) there is a 0.982 probability that after a GDH guillotine break contact between GDH and wall will occur; (ii) there is a probability of 0.013 that the ultimate tensile strength of concrete at the impact location will be reached, and a through-crack may open; (iii) there is a probability of 0.0126 that the ultimate compressive strength of concrete at the GDH support location will be reached, and the concrete may fail; (iv) at the impact location in the adjacent wall, there is a probability of 0.327 that the ultimate tensile strength of the rebars in the first layer will be reached and the rebars will fail; (v) at the GDH support location, there is a probability of 0.11 that the ultimate stress of the rebars in the first layer will be reached and the rebars will fail. It can be concluded that after a GDH guillotine break, the GDH reinforced concrete support-wall and the impacted wall will develop a through-crack or crush with a probability about 0.013. Only the first layer of rebars, however, will fail in either the impacted-wall or the support-wall with probabilities of 0.327 and 0.11, respectively

102

Reliability analysis of VVER-1000 information and control systems  

International Nuclear Information System (INIS)

The subject of the analysis is the reliability of the information and control systems for the Ukrainian nuclear power plants (NPP) with pressurized-water reactors type VVER-1000. The analysis had three directions. 1. The analysis of the reliability of the instruments. 2. The analysis of the reliability of the NPP systems in whole under the realization of the different functions. 3. The analysis of the accidents in the time of the NPP operation, which look place because of the control and information systems failures. The applications of the obtain results are described. (author)

103

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

104

Application of Support Vector Machine to Reliability Analysis of Engine Systems  

OpenAIRE

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...

Zhang Xinfeng; Zhao Yan

2013-01-01

105

Reliability block diagram with general gates and its application to system reliability analysis  

International Nuclear Information System (INIS)

Highlights: ? Conventional reliability block diagram is extended to enhance the expression power. ? The mathematical definition of the proposed method is provided. ? For quantitative analysis, how to develop an equivalent Bayesian network is provided. ? The usefulness of the proposed method is demonstrated with two examples. - Abstract: For those systems that can be modeled with perfect nodes and unreliable arcs such as communication systems, a reliability graph with general gates (RGGG) was developed. Similarly, for more efficient system reliability analysis of those systems that can be modeled with unreliable nodes and perfect arcs, a reliability block diagram with general gates (RBDGG) was developed as an intuitive and easy-to-use method for system reliability analysis. One of the unique characteristics of RBDGG is to allow node connection relations of general gates such as the AND gate and the k-out-of-n gate other than the OR gate connection relation of the conventional reliability block diagram (RBD). Mathematical formulations for RBDGG and a method of mapping a RBDGG model into an equivalent Bayesian network model without losing the one-to-one matching characteristic of the RBDGG for quantitative analysis is also provided. With the application to two example systems, the usefulness of the proposed RBDGG is demonstrated.

106

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

107

Reliability analysis of reactor protection systems  

International Nuclear Information System (INIS)

A theoretical mathematical study of reliability is presented and the concepts subsequently defined applied to the study of nuclear reactor safety systems. The theory is applied to investigations of the operational reliability of the Siloe reactor from the point of view of rod drop. A statistical study conducted between 1964 and 1971 demonstrated that most rod drop incidents arose from circumstances associated with experimental equipment (new set-ups). The reliability of the most suitable safety system for some recently developed experimental equipment is discussed. Calculations indicate that if all experimental equipment were equipped with these new systems, only 1.75 rod drop accidents would be expected to occur per year on average. It is suggested that all experimental equipment should be equipped with these new safety systems and tested every 21 days. The reliability of the new safety system currently being studied for the Siloe reactor was also investigated. The following results were obtained: definite failures must be detected immediately as a result of the disturbances produced; the repair time must not exceed a few hours; the equipment must be tested every week. Under such conditions, the rate of accidental rod drops is about 0.013 on average per year. The level of nondefinite failures is less than 10-6 per hour and the level of nonprotection 1 hour per year. (author)

108

Digital Processor Module Reliability Analysis of Nuclear Power Plant  

International Nuclear Information System (INIS)

The system used in plant, military equipment, satellite, etc. consists of many electronic parts as control module, which requires relatively high reliability than other commercial electronic products. Specially, Nuclear power plant related to the radiation safety requires high safety and reliability, so most parts apply to Military-Standard level. Reliability prediction method provides the rational basis of system designs and also provides the safety significance of system operations. Thus various reliability prediction tools have been developed in recent decades, among of them, the MI-HDBK-217 method has been widely used as a powerful tool for the prediction. In this work, It is explained that reliability analysis work for Digital Processor Module (DPM, control module of SMART) is performed by Parts Stress Method based on MIL-HDBK-217F NOTICE2. We are using the Relex 7.6 of Relex software corporation, because reliability analysis process requires enormous part libraries and data for failure rate calculation

109

Empirical Estimates of the Comparative Reliability of Matching Tests and Multiple-Choice Tests.  

Science.gov (United States)

Three types of test were compared: a completion test, a matching test, and a multiple-choice test. The completion test was more reliable than the matching test, and the matching test was more reliable than the multiple-choice test. (Author/BW)

Zimmerman, Donald W.; And Others

1984-01-01

110

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

Edwin P. Christmann

2008-11-01

111

Strength Reliability Analysis of Turbine Blade Using Surrogate Models  

OpenAIRE

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 M...

Wei Duan; Liqiang An; Zhangqi Wang

2014-01-01

112

Evaluating some Reliability Analysis Methodologies in Seismic Design  

OpenAIRE

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 wi...

Ghoulbzouri, A. E.; Khamlichi, A.; Almansa, F. L.; Vera, M. A. P.; Cintas, M. D. R.

2011-01-01

113

On reliability analysis of multi-categorical forecasts  

OpenAIRE

Reliability analysis of probabilistic forecasts, in particular through the rank histogram or Talagrand diagram, is revisited. Two shortcomings are pointed out: Firstly, a uniform rank histogram is but a necessary condition for reliability. Secondly, if the forecast is assumed to be reliable, an indication is needed how far a histogram is expected to deviate from uniformity merely due to randomness. Concerning the first shortcoming, it is suggested that forecasts be grouped or stratified along...

Bro?cker, J.

2008-01-01

114

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

115

A software tool for advanced reliability and safety analysis  

International Nuclear Information System (INIS)

A knowledge based approach to systems safety and reliability analysis to be implemented in an intelligent software bool (STARS: Software Tool for Advanced Reliability and Safety) is presented. The tool will offer intelligent and power ful support in performing qualitative hazard analysis, logic modelling (fault tree, event tree construction) and probabilistic analysis for large and complex systems as found in chemical process plant and nuclear industy. (author)

116

Semantic compared cross impact analysis  

OpenAIRE

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

117

Dispatcher reliability analysis : SPICA-Rail experiment.  

OpenAIRE

Although considered as not safety critical (safety function being performed by other sub-systems), railway supervision systems can contribute to hazardous scenarios. It is of primary importance to identify this type of scenarios and evaluate the behaviour of human operators. A state of the art in human reliability is presented. This article presents an experimental protocol based on an automatic train supervision system coupled to a traffic simulator. It allows to gather data for human reliab...

Belmonte, Fabien; Boulanger, Jean-louis; Scho?n, Walter

2008-01-01

118

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

119

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

120

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

121

Comparative Analysis of University Sports  

OpenAIRE

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; ?sra ?rturan, ?.; Natasha Brison

2012-01-01

122

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

123

Reliability analysis of grid connected small wind turbine power electronics  

International Nuclear Information System (INIS)

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.

124

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

125

System availability management technique for reliability and maintainability analysis  

Science.gov (United States)

Method for total system availability analysis is based on numerical prediction of the reliability, maintainability, and availability of each function system. It incorporates these functional-system estimates into an overall mathematical model.

Davenport, G. K.

1970-01-01

126

Comparative analysis of diadochokinetic movements.  

Science.gov (United States)

Tests of diadochokinesia are an inherent part of a neurological examination. Various quantifying methods have been proposed to increase the objectivity, sensitivity, and reliability of such examinations. The methods used and analyses performed, however, differ substantially between tasks. We used a three-dimensional, ultrasound-based recording device to continuously record joint angles during three diadochokinetic movements, avoiding any external constraints of the movements. Alternate pronation and supination of the forearm, tapping with the whole hand and with the index finger in isolation were analyzed in a sample of 63 healthy control subjects. The most sensitive measure for capturing effects of gender, sex, and active hand was frequency. The right hand was faster than the left in all tasks, tapping performance declined with increasing age, and male subjects were faster than females in forearm diadochokinesia. Other measures that characterize speed of movement such as maximum angular velocities and accelerations did not yield comparable sensitivity in detecting the same statistical effects. However, angular velocity achieved the highest test-retest reliability for forearm diadochokinesia, while frequency was reproduced in the tapping tasks. Additional measures characterizing symmetry of the angular velocity profiles and intraindividual variability were shown to be largely independent of movement speed. Examples in neurological patients showed that the data define a valuable standard against which pathological performance can be precisely evaluated. In addition, the different measures captured dissociable aspects of motor performance that may further help to characterize the deficit and adjust therapy. PMID:10437981

Hermsdörfer, J; Marquardt, C; Wack, S; Mai, N

1999-08-01

127

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

128

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

129

Discrete Event Simulation and Petri net Modeling for Reliability Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Analytical methods in reliability analysis are useful for studying simple problems. For complex networks with cross-linked (non-series/parallel component configurations, it is difficult to use mathematical reliability analysis. Powerful methods for reliability analysis of such systems have been developed using discrete event simulation. The main drawback of these methods is that they are computer time intensive. In this paper, the main idea behind these methods is further explored and modified in order to reduce the computational loads. The modified approach presented here leads to a great time saving which is very important for reliability analysis of large scale systems. This modified method is then modeled by Petri net, which is a powerful modeling tool. The network reliability modeling technique developed in the paper has two main advantages. First, it can be easily implemented through a systematic and standard approach. Second, the developed model will greatly help solving the reliability analysis problem since it is simple and graphical.

Behrooz Safarinejadian 1

2012-05-01

130

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

131

Reliability and risk analysis of large systems with ageing components  

International Nuclear Information System (INIS)

Applications of limit reliability functions to the reliability evaluation of large multi-state systems composed of independent components are considered. The main emphasis is on multi-state systems with ageing components because of the importance of such an approach in safety analysis, assessment and prediction, and analysing the effectiveness of operation processes of real technical systems. The results concerned with multi-state series systems are applied to the reliability evaluation and risk function determination of a homogeneous bus transportation system. Results on limit reliability functions of a homogeneous multi-state 'm out of n' system are applied to durability evaluation of a steel rope. A non-homogeneous series-parallel pipeline systems composed of several lines of pipe segments is estimated as well. Moreover, the reliability evaluation of the model homogeneous parallel-series electrical energy distribution system is performed

132

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

133

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

134

Reliability analysis of cluster-based ad-hoc networks  

International Nuclear Information System (INIS)

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 ill reliability metrics for the MAWN, and illustration of a Monte Carlo simulation method through the analysis of several example networks

135

Reliability and vulnerability analyses of critical infrastructures: Comparing two approaches in the context of power systems  

International Nuclear Information System (INIS)

Society depends on services provided by critical infrastructures, and hence it is important that they are reliable and robust. Two main approaches for gaining knowledge required for designing and improving critical infrastructures are reliability analysis and vulnerability analysis. The former analyses the ability of the system to perform its intended function; the latter analyses its inability to withstand strains and the effects of the consequent failures. The two approaches have similarities but also some differences with respect to what type of information they generate about the system. In this view, the main purpose of this paper is to discuss and contrast these approaches. To strengthen the discussion and exemplify its findings, a Monte Carlo-based reliability analysis and a vulnerability analysis are considered in their application to a relatively simple, but representative, system the IEEE RTS96 electric power test system. The exemplification reveals that reliability analysis provides a good picture of the system likely behaviour, but fails to capture a large portion of the high consequence scenarios, which are instead captured in the vulnerability analysis. Although these scenarios might be estimated to have small probabilities of occurrence, they should be identified, considered and treated cautiously, as probabilistic analyses should not be the only input to decision-making for the design and protection of critical infrastructures. The general conclusion that can be drawn from the findings of the example is that vulnerability analysis should be used to complement reliability studies, as well as other forms of probabilistic risk analysis. Measures should be sought for reducing both the vulnerability, i.e. improving the system ability to withstand strains and stresses, and the reliability, i.e. improving the likely behaviour

136

Reliability analysis of a BWR decay heat removal system  

International Nuclear Information System (INIS)

The reliability of an additional low pressure heat removal system, installed in Leibstadt Nuclear Power Station, has been analysed using probabilistic risk analysis techniques. Leibstadt is a General Electric boiling water reactor of the BWR/6 product line with a Mark-III containment. The need for the additional system is discussed in terms of the Licensing Criteria applicable to nuclear power plants in Switzerland. As a result of the concern in the U.S. over the reliability of decay heat al capability of LWR's, further analyses have been undertaken to determine the effect of this additional system on the reliability of decay heat function of Leibstadt

137

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 esults, 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.

138

Application of Bayesian Methods for Age-dependent Reliability Analysis  

OpenAIRE

In this paper authors present a general methodology for age dependent reliability analysis of degrading or ageing systems, structures and components.The methodology is based on Bayesian methods and inference, its ability to incorporate prior information and on idea that ageing can be thought as age dependent change of believes about reliability parameters, when change of belief occurs not just due to new failure data or other information which becomes available in time, but ...

Alzbutas, Robertas; Ies?mantas, Tomas

2012-01-01

139

Analysis of sodium valve reliability data at CREDO  

International Nuclear Information System (INIS)

The Centralized Reliability Data Organization (CREDO) has been established at Oak Ridge National Laboratory (ORNL) by the Department of Energy to provide a centralized source of data for reliability/maintainabilty analysis of advanced reactor systems. The current schedule calls for develoment of the data system at a moderate pace, with the first major distribution of data in late FY-1980. Continuous long-term collection of engineering, operating, and event data has been initiated at EBR-II and FFTF

140

Density modification based reliability sensitivity analysis  

OpenAIRE

Sensitivity analysis of a numerical model, for instance simulating physical phenomena, is useful to quantify the influence of the inputs on the model responses. This paper proposes a new sensitivity index, based upon the modification of the probability density function (pdf) of the random inputs, when the quantity of interest is a failure probability (probability that a model output exceeds a given threshold). An input is considered influential if the input pdf modification ...

Lemai?tre, Paul; Sergienko, Ekatarina; Arnaud, Aure?lie; Bousquet, Nicolas; Gamboa, Fabrice; Iooss, Bertrand

2012-01-01

141

RELIABILITY ANALYSIS OF RING, AGENT AND CLUSTER BASED DISTRIBUTED SYSTEMS  

Directory of Open Access Journals (Sweden)

Full Text Available The introduction of pervasive devices and mobile devices has led to immense growth of real time distributed processing. In such context reliability of the computing environment is very important. Reliability is the probability that the devices, links, processes, programs and files work efficiently for the specified period of time and in the specified condition. Distributed systems are available as conventional ring networks, clusters and agent based systems. Reliability of such systems is focused. These networks are heterogeneous and scalable in nature. There are several factors, which are to be considered for reliability estimation. These include the application related factors like algorithms, data-set sizes, memory usage pattern, input-output, communication patterns, task granularity and load-balancing. It also includes the hardware related factors like processor architecture, memory hierarchy, input-output configuration and network. The software related factors concerning reliability are operating systems, compiler, communication protocols, libraries and preprocessor performance. In estimating the reliability of a system, the performance estimation is an important aspect. Reliability analysis is approached using probability.

R.SEETHALAKSHMI

2011-08-01

142

On reliability analysis of multi-categorical forecasts  

Directory of Open Access Journals (Sweden)

Full Text Available Reliability analysis of probabilistic forecasts, in particular through the rank histogram or Talagrand diagram, is revisited. Two shortcomings are pointed out: Firstly, a uniform rank histogram is but a necessary condition for reliability. Secondly, if the forecast is assumed to be reliable, an indication is needed how far a histogram is expected to deviate from uniformity merely due to randomness. Concerning the first shortcoming, it is suggested that forecasts be grouped or stratified along suitable criteria, and that reliability is analyzed individually for each forecast stratum. A reliable forecast should have uniform histograms for all individual forecast strata, not only for all forecasts as a whole. As to the second shortcoming, instead of the observed frequencies, the probability of the observed frequency is plotted, providing and indication of the likelihood of the result under the hypothesis that the forecast is reliable. Furthermore, a Goodness-Of-Fit statistic is discussed which is essentially the reliability term of the Ignorance score. The discussed tools are applied to medium range forecasts for 2 m-temperature anomalies at several locations and lead times. The forecasts are stratified along the expected ranked probability score. Those forecasts which feature a high expected score turn out to be particularly unreliable.

J. Bröcker

2008-08-01

143

Reliability analysis of dispersion nuclear fuel elements  

International Nuclear Information System (INIS)

Taking a dispersion fuel element as a special particle composite, the representative volume element is chosen to act as the research object. The fuel swelling is simulated through temperature increase. The large strain elastoplastic analysis is carried out for the mechanical behaviors using FEM. The results indicate that the fission swelling is simulated successfully; the thickness increments grow linearly with burnup; with increasing of burnup: (1) the first principal stresses at fuel particles change from tensile ones to compression ones, (2) the maximum Mises stresses at the particles transfer from the centers of fuel particles to the location close to the interfaces between the matrix and the particles, their values increase with burnup; the maximum Mises stresses at the matrix exist in the middle location between the two particles near the mid-plane along the length (or width) direction, and the maximum plastic strains are also at the above region

144

Human reliability analysis methods for probabilistic safety assessment  

International Nuclear Information System (INIS)

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

145

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

146

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

147

Reliability estimation of steam turbine blade considering a dynamic analysis  

International Nuclear Information System (INIS)

In this study, the probabilistic analysis to apply variation of applied stress and strength was performed in order to assure safety of the low pressure steam turbine blade. Applied stress history was evaluated using dynamic analysis in service condition. The fatigue strength under rotating-bending load was evaluated by staircase method at stress ratio R=-1. The most appropriate distribution for probabilistic characteristic of fatigue strength at 2x107 cycles was 3-parameter Weibull distribution. Reliability with variation of applied stress and strength was derived from First Order Reliability Method(FORM)

148

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

149

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

150

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)

151

Bayesian Inference for NASA Probabilistic Risk and Reliability Analysis  

Science.gov (United States)

This document, Bayesian Inference for NASA Probabilistic Risk and Reliability Analysis, is intended to provide guidelines for the collection and evaluation of risk and reliability-related data. It is aimed at scientists and engineers familiar with risk and reliability methods and provides a hands-on approach to the investigation and application of a variety of risk and reliability data assessment methods, tools, and techniques. This document provides both: A broad perspective on data analysis collection and evaluation issues. A narrow focus on the methods to implement a comprehensive information repository. The topics addressed herein cover the fundamentals of how data and information are to be used in risk and reliability analysis models and their potential role in decision making. Understanding these topics is essential to attaining a risk informed decision making environment that is being sought by NASA requirements and procedures such as 8000.4 (Agency Risk Management Procedural Requirements), NPR 8705.05 (Probabilistic Risk Assessment Procedures for NASA Programs and Projects), and the System Safety requirements of NPR 8715.3 (NASA General Safety Program Requirements).

Dezfuli, Homayoon; Kelly, Dana; Smith, Curtis; Vedros, Kurt; Galyean, William

2009-01-01

152

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

153

Reliability-Based Robustness Analysis for a Croatian Sports Hall  

DEFF Research Database (Denmark)

This paper presents a probabilistic approach for structural robustness assessment for a timber structure built a few years ago. The robustness analysis is based on a structural reliability based framework for robustness and a simplified mechanical system modelling of a timber truss system. A complex timber structure with a large number of failure modes is modelled with only a few dominant failure modes. First, a component based robustness analysis is performed based on the reliability indices of the remaining elements after the removal of selected critical elements. The robustness is expressed and evaluated by a robustness index. Next, the robustness is assessed using system reliability indices where the probabilistic failure model is modelled by a series system of parallel systems.

?izmar, Dean; Kirkegaard, Poul Henning

2011-01-01

154

Comparing the Reliability of Regular Topologies on a Backbone Network. A Case Study  

DEFF Research Database (Denmark)

The aim of this paper is to compare the reliability of regular topologies on a backbone network. The study is focused on a large-scale fiberoptic network. Different regular topological solutions as single ring, double ring or 4-Regular grid are applied to the case study, and compared in terms of degree, diameter, average distance, economical cost and availability. Furthermore, other non-quantitative parameters such as expandability, embeddability and algorithmic support are introduced.

Cecilio, Sergio Labeage; Gutierrez Lopez, Jose Manuel

2009-01-01

155

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

156

Failures Analysis and Reliability Calculation for Power Transformers  

Directory of Open Access Journals (Sweden)

Full Text Available Failures of transformers in sub-transmission systems not only reduce reliability of power system but also have significant effects on power quality since one of the important components of any system quality is reliability of that system. To enhance utility reliability, failure analysis and its rates, failure origin and physical damage causes must be studied. This paper describes a case study of the reliability of sub-transmission transformers (63/20 KV installed in Mazandaran province, operated in sub-transmission system. The information obtained from Meandering Regional Electric Company. The results of study and analysis on 60 substation including more than 110 transformers installed in sub-transmission system show that the failure modes of transformers can be represented by Weibull distribution. Weibull statistics have been widely used and accepted as a successful mathematical method to predict the remaining life time of any equipment. Useful conclusions are presented both for power systems operators and manufactures for improving the reliability of transformers.

M. Mirzai

2006-03-01

157

Reliability analysis - systematic approach based on limited data  

International Nuclear Information System (INIS)

The initial approaches required for reliability analysis are outlined. These approaches highlight the system boundaries, examine the conditions under which the system is required to operate, and define the overall performance requirements. The discussion is illustrated by a simple example of an automatic protective system for a nuclear reactor. It is then shown how the initial approach leads to a method of defining the system, establishing performance parameters of interest and determining the general form of reliability models to be used. The overall system model and the availability of reliability data at the system level are next examined. An iterative process is then described whereby the reliability model and data requirements are systematically refined at progressively lower hierarchic levels of the system. At each stage, the approach is illustrated with examples from the protective system previously described. The main advantages of the approach put forward are the systematic process of analysis, the concentration of assessment effort in the critical areas and the maximum use of limited reliability data. (author)

158

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

159

Reliability of spectral analysis of fetal heart rate variability.  

Science.gov (United States)

Spectral analysis of fetal heart rate variability could provide information on fetal wellbeing. Unfortunately, fetal heart rate recordings are often contaminated by artifacts. Correction of these artifacts affects the outcome of spectral analysis, but it is currently unclear what level of artifact correction facilitates reliable spectral analysis. In this study, a method is presented that estimates the error in spectral powers due to artifact correction, based on the properties of the Continuous Wavelet Transformation. The results show that it is possible to estimate the error in spectral powers. The information about this error makes it possible for clinicians to assess the reliability of spectral analysis of fetal heart rate recordings that are contaminated by artifacts. PMID:25570577

Warmerdam, G J J; Vullings, R; Bergmans, J W M; Oei, S G

2014-01-01

160

Safety and reliability analysis of R-5 safety logic  

International Nuclear Information System (INIS)

Safety and reliability analysis of the R-5 reactor safety logic is presented. The analysis is based on fault free method. The index for reliability is shut down rate/year based on spurious (safe) failure rate of a channel. For R-5 it comes to 0.5/year. Fractional Dead Time (FDT) represents the fraction of operating time that the safety logic is unavailable and hence unable to protect. FDT is based on unsafe failure rate of a channel. FDTs of ET (poison injection trip), and the signal processing part (SP) of XT (neutronic and coolant pressure trips) and AT (absolute and conditioning trips) for R-5 come to 4x10-10, 4x10-4 and 4x10-5 respectively. Assumptions made in the analysis of safety logic are mentioned, however common made failure (CMF) analysis is not included. (M.G.B.)

161

Quantification of Reliability Performance: Analysis Methods for Safety Instrumented System  

OpenAIRE

The reliability performance of a safety instrumented system (SIS) can be determined by severalanalytical methods, such as simplified formulas, fault tree analysis and Markov analysis. Thesemethods are mentioned in annex B of IEC 61508-6, but this part is not normative and the usermay choose which method to use based on the specific operational characteristics of the SIS.Moreover, since it does not provide detailed explanations, proofs and generalized formulas forkoon architecture, it is diffi...

Jigar, Abraham Almaw

2013-01-01

162

Human Reliability Analysis for Digital Human-Machine Interfaces  

Energy Technology Data Exchange (ETDEWEB)

This paper addresses the fact that existing human reliability analysis (HRA) methods do not provide guidance on digital human-machine interfaces (HMIs). Digital HMIs are becoming ubiquitous in nuclear power operations, whether through control room modernization or new-build control rooms. Legacy analog technologies like instrumentation and control (I&C) systems are costly to support, and vendors no longer develop or support analog technology, which is considered technologically obsolete. Yet, despite the inevitability of digital HMI, no current HRA method provides guidance on how to treat human reliability considerations for digital technologies.

Ronald L. Boring

2014-06-01

163

Reliability analysis of rotor blades of tidal stream turbines  

International Nuclear Information System (INIS)

Tidal stream turbines are used for converting kinetic energy of tidal currents into electricity. There are a number of uncertainties involved in the design of such devices and their components. To ensure safety of the turbines these uncertainties must be taken into account. The paper shows how this may be achieved for the design of rotor blades of horizontal-axis tidal stream turbines in the context of bending failure due to extreme loading. Initially, basic characteristics of such turbines in general and their blades in particular are briefly described. A probabilistic model of tidal current velocity fluctuations, which are the main source of load uncertainty, is then presented. This is followed by the description of reliability analysis of the blades, which takes into account uncertainties associated with tidal current speed, the blade resistance and the model used to calculate bending moments in the blades. Finally, the paper demonstrates how results of the reliability analysis can be applied to set values of the partial factors for the blade design. - Highlights: • A probabilistic model of the maximum of tidal current velocity fluctuations is proposed. • Reliability analysis of rotor blades of a tidal stream turbine is described. • Influence of pitch control system on the blade reliability is investigated. • Partial safety factors for the design of tidal turbine rotor blades are calibrated

164

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

165

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)

166

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

167

Reliability analysis framework for computer-assisted medical decision systems  

International Nuclear Information System (INIS)

We present a technique that enhances computer-assisted decision (CAD) systems with the ability to assess the reliability of each individual decision they make. Reliability assessment is achieved by measuring the accuracy of a CAD system with known cases similar to the one in question. The proposed technique analyzes the feature space neighborhood of the query case to dynamically select an input-dependent set of known cases relevant to the query. This set is used to assess the local (query-specific) accuracy of the CAD system. The estimated local accuracy is utilized as a reliability measure of the CAD response to the query case. The underlying hypothesis of the study is that CAD decisions with higher reliability are more accurate. The above hypothesis was tested using a mammographic database of 1337 regions of interest (ROIs) with biopsy-proven ground truth (681 with masses, 656 with normal parenchyma). Three types of decision models, (i) a back-propagation neural network (BPNN), (ii) a generalized regression neural network (GRNN), and (iii) a support vector machine (SVM), were developed to detect masses based on eight morphological features automatically extracted from each ROI. The performance of all decision models was evaluated using the Receiver Operating Characteristic (ROC) analysis. The study showed that the proposed reliability measure is a strong predictor of the CAD system's case-specific accuracy. Specifically, the ROC area index for CAD predictions with h 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

168

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.

169

Radioactivity Analysis for Reliability Assessment in the Environmental Samples  

International Nuclear Information System (INIS)

The objective of this research was to assess the reliability of data and to improve nuclear analytical techniques concerning the Domestic Radioactivity Intercomparison program for environmental radioactivity monitoring of Jeju from 1998 to 2006. Gross beta for filter papers and water samples was determined, and gamma nuclides for natural and artificial nuclides in soil and water samples were analyzed. The gross beta activity of all samples except for the water samples of 1998 and 1999 showed a good agreement within the confidence intervals. In gamma nuclides, and of soil samples and most nuclides in the water samples, with the exception of several nuclides, were evaluated to be reliable. Based on these results, it is considered that a reliable method for the analysis and monitoring of environmental radioactivity were established, which may play an important role in case of emergency radiation accident

170

A framework for intelligent reliability centered maintenance analysis  

International Nuclear Information System (INIS)

To improve the efficiency of reliability-centered maintenance (RCM) analysis, case-based reasoning (CBR), as a kind of artificial intelligence (AI) technology, was successfully introduced into RCM analysis process, and a framework for intelligent RCM analysis (IRCMA) was studied. The idea for IRCMA is based on the fact that the historical records of RCM analysis on similar items can be referenced and used for the current RCM analysis of a new item. Because many common or similar items may exist in the analyzed equipment, the repeated tasks of RCM analysis can be considerably simplified or avoided by revising the similar cases in conducting RCM analysis. Based on the previous theory studies, an intelligent RCM analysis system (IRCMAS) prototype was developed. This research has focused on the description of the definition, basic principles as well as a framework of IRCMA, and discussion of critical techniques in the IRCMA. Finally, IRCMAS prototype is presented based on a case study

171

A Most Probable Point-Based Method for Reliability Analysis, Sensitivity Analysis and Design Optimization  

Science.gov (United States)

A major step in a most probable point (MPP)-based method for reliability analysis is to determine the MPP. This is usually accomplished by using an optimization search algorithm. The optimal solutions associated with the MPP provide measurements related to safety probability. This study focuses on two commonly used approximate probability integration methods; i.e., the Reliability Index Approach (RIA) and the Performance Measurement Approach (PMA). Their reliability sensitivity equations are first derived in this paper, based on the derivatives of their respective optimal solutions. Examples are then provided to demonstrate the use of these derivatives for better reliability analysis and Reliability-Based Design Optimization (RBDO).

Hou, Gene J.-W.; Gumbert, Clyde R.; Newman, Perry A.

2004-01-01

172

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

173

Virtual stress amplitude-based low cycle fatigue reliability analysis  

International Nuclear Information System (INIS)

A method for virtual stress amplitude-based low cycle fatigue reliability analysis is developed. Different from existent methods, probability-based modified Ramberg-Osgood stress-strain relations (P-?-? curves) are newly introduced to take into account the scatter of stress-strain responses, where the metallurgical quality of material is not enough good i.e. weld metal to show a same stress-strain response for different specimens under same loading level. In addition, a virtual stress amplitude-based analysis is used to be in agreement with the existent codes for nuclear components. i.e. ASME section III. The analysis is performed by a principle of the stochastic analysis system in same safety level concurrently. Combined the probability-based modified Ramberg-Osgood stress-strain relations, the probability-based Langer S-N curves (P-S-N curves) and the Neuber's local stress-strain rule, the method can be applied to predict the fatigue life at specified reliability and loading history and to estimate the reliability at specified loading history and expectation fatigue life. Applicability of the method has been indicated by a test analysis of 1Cr18Ni9ti steel-weld metal, which was used for machining the pipes of some nuclear reactors, during low cycle fatigue

174

INTRODUCING NEW PARAMETERS TO COMPARE THE ACCURACY AND RELIABILITY OF MEAN-SHIFT BASED TRACKING ALGORITHMS  

OpenAIRE

Mean shift algorithms are among the most functional tracking methods which are accurate and havealmost simple computation. Different versions of this algorithm are developed which are differ in templateupdating and their window sizes. To measure the reliability and accuracy of these methods one shouldnormally rely on visual results or number of iteration. In this paper we introduce two new parameterswhich can be used to compare the algorithms especially when their results are close to each ot...

Mohammadi, S. A.; Mahzoun, M. R.

2011-01-01

175

Toward Reliable Estimates of Abundance: Comparing Index Methods to Assess the Abundance of a Mammalian Predator  

OpenAIRE

Due to time and financial constraints indices are often used to obtain landscape-scale estimates of relative species abundance. Using two different field methods and comparing the results can help to detect possible bias or a non monotonic relationship between the index and the true abundance, providing more reliable results. We used data obtained from camera traps and feces counts to independently estimate relative abundance of red foxes in the Black Forest, a forested landscape in southern ...

Gu?thlin, Denise; Storch, Ilse; Ku?chenhoff, Helmut

2014-01-01

176

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

177

Reliability analysis of the tunnel rack and dry well monitored retrievable storage concepts  

International Nuclear Information System (INIS)

This report presents the results of a reliability analysis of the preliminary designs of the tunnel rack and open field dry well monitored retrievable storage (MRS) concepts. The study investigates the qualitative reliability of both MRS concepts and establishes the basis for a quantitative reliability evaluation program. Failure modes that potentially impact material throughput were identified for each storage concept. No failure mode was identified that would preclude either concept from performing its intended function. Owing to the preliminary design status of each concept, many of the identified failure modes could be eliminated as each design progresses. For an equivalent throughput, the dry well concept requires less equipment than the tunnel rack concept but must perform a greater number of functions and will likely be required to meet comparatively higher levels of operational reliability. 7 references, 3 figures

178

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

179

Reliability Analysis of Metro Door System Based on FMECA  

OpenAIRE

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 ar...

Xiaoqing Cheng; Zongyi Xing; Yong Qin; Yuan Zhang; Shaohuang Pang; Jun Xia

2013-01-01

180

Reliability analysis based on non-dimensional parameters  

OpenAIRE

A reliability analysis method is proposed that starts with the identification of all variables involved. These are divided in three groups: (a) variables fixed by codes, as loads and strength project values, and their corresponding partial safety coefficients, (b) geometric variables defining the dimension of the main elements involved, (c) the cost variables, including the possible damages caused by failure, (d) the random variables as loads, strength, etc., and (e)the variables defining the...

Castillo Ron, Enrique; Fraile Lerma, Alberto; Alarco?n A?lvarez, Enrique; Ferna?ndez-canteli, Alfonso

2000-01-01

181

Inclusion of task dependence in human reliability analysis  

International Nuclear Information System (INIS)

Dependence assessment among human errors in human reliability analysis (HRA) is an important issue, which includes the evaluation of the dependence among human tasks and the effect of the dependence on the final human error probability (HEP). This paper represents a computational model to handle dependence in human reliability analysis. The aim of the study is to automatically provide conclusions on the overall degree of dependence and calculate the conditional human error probability (CHEP) once the judgments of the input factors are given. The dependence influencing factors are first identified by the experts and the priorities of these factors are also taken into consideration. Anchors and qualitative labels are provided as guidance for the HRA analyst's judgment of the input factors. The overall degree of dependence between human failure events is calculated based on the input values and the weights of the input factors. Finally, the CHEP is obtained according to a computing formula derived from the technique for human error rate prediction (THERP) method. The proposed method is able to quantify the subjective judgment from the experts and improve the transparency in the HEP evaluation process. Two examples are illustrated to show the effectiveness and the flexibility of the proposed method. - Highlights: • We propose a computational model to handle dependence in human reliability analysis. • The priorities of the dependence influencing factors are taken into consideration. • The overall dependence degree is determined by input judgments and the weights of factors. • The CHEP is obtained according to a computing formula derived from THERP

182

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)

183

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

184

Reliability and availability analysis of two alternative evacuation systems designed for the Next European Torus (NET)  

International Nuclear Information System (INIS)

This paper discusses the reliability and availability issues in case of two different evacuation system designs which have been proposed for the Next European Torus (NET). One of these designs uses turbo molecular pumps while the other employs cryogenic pumps to evacuate waste products from the torus after every fusion cycle. The aim of this paper is to assess and compare the feasibility of the above two designs form the reliability and availability point of view. A detailed failure mode analysis has been carried out for these two systems and appropriate mathematical mdoels have been developed to calculate their respective reliabilities. Using these mathematical models an extensive parameter study of the system reliability has been carried out over a given range of the component reliabilities. This parameter study shows that the maximum value of the turbo molecular pump system reliability is 96% while the corresponding value for the cryogenic pump system is only 81.6%. The target value for the system availability is 99.9%. This requires that the system mean repair time should be 48 h, appropriate modifications must be made to the turbo pump system design to increase its reliabilump system design to increase its reliability accordingly. (author). 4 refs.; 10 figs

185

Comparative study on shear wave speed estimation algorithms in ARFI for improving its reliability.  

Science.gov (United States)

Quantitatively assessing the tissue stiffness with acoustic radiation force impulse (ARFI) method has proved its worth in clinical trials. Much attention has been focused on the research of the displacement estimation algorithm in ARFI. However, the subsequent shear wave speed estimation part can also affect the accuracy and reliability of the results. In this study, several algorithms for shear wave speed estimation were designed and compared using the ultrasound radio-frequency data collected from a self-developed ARFI system. These RT based algorithms were classified as two types: the transformation being performed on the time-location displacement matrix or on the time-depth displacement matrix. The algorithms in Type I attempt to find the best trajectory of the shear wave propagation in one depth, while those in Type II try to directly find the time points when the wavefront passed each lateral location in the whole depth range. Experiments were performed on soft tissue mimicking phantom and ex vivo pork tissue sample. The reliability of repeated measurements and the computation time of these algorithms were compared to find the most stable and time-saving one for ARFI. The results can give us inspiration on how to design a better algorithm for shear wave speed estimation and help to improve the measurement reliability of ARFI. PMID:25569938

Yang, Jinying; Wang, Congzhi; Qiu, Weibao; Zheng, Hairong

2014-01-01

186

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.

187

Analysis and Reliability Performance Comparison of Different Facial Image Features  

Directory of Open Access Journals (Sweden)

Full Text Available This study performs reliability analysis on the different facial features with weighted retrieval accuracy on increasing facial database images. There are many methods analyzed in the existing papers with constant facial databases mentioned in the literature review. There were not much work carried out to study the performance in terms of reliability and also how the method will perform on increasing the size of the database. In this study certain feature extraction methods were analyzed on the regular performance measure and also the performance measures are modified to fit the real time requirements by giving weight ages for the closer matches. In this study four facial feature extraction methods are performed, they are DWT with PCA, LWT with PCA, HMM with SVD and Gabor wavelet with HMM. Reliability of these methods are analyzed and reported. Among all these methods Gabor wavelet with HMM gives more reliability than other three methods performed. Experiments are carried out to evaluate the proposed approach on the Olivetti Research Laboratory (ORL face database.

J. Madhavan

2014-11-01

188

Reliability Engineering Analysis of ATLAS Data Reprocessing Campaigns  

Science.gov (United States)

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 Engineering approach supported continuous improvements in data reprocessing throughput during LHC data taking. The throughput doubled in 2011 vs. 2010 reprocessing, then quadrupled in 2012 vs. 2011 reprocessing. We present the Reliability Engineering analysis of ATLAS data reprocessing campaigns providing the foundation needed to scale up the Big Data processing technologies beyond the petascale.

Vaniachine, A.; Golubkov, D.; Karpenko, D.; Atlas Collaboration

2014-06-01

189

Maximizing personnel performance in plantwide reliability-centered maintenance analysis  

International Nuclear Information System (INIS)

Techniques have been developed and proven effective that can be used to reduce the staffing requirements for implementation of a full-scale plantwide reliability-centered maintenance (RCM) program. The multiphase projects discussed in this paper integrate RCM into a broad-based preventive maintenance program concept that includes several programmatic functions, such as system reliability modeling, computerized RCM data bases, and quantitative and qualitative cost/benefit analyses. Through the use of computerized data bases, system models, equipment failure tracking, and preventive maintenance program effectiveness evaluations, the RCM programs can create a living reliability-based preventive maintenance program. The completed RCM data can be maintained and updated with current plant design and equipment performance history without large staffs of RCM analysts. The goal of any RCM project is the development of a structures and well-justified preventive maintenance program that ensures the reliability of plant components is maximized to the extent that an appropriate cost/benefit is achieved in return for the maintenance dollars expended. The methods discussed were developed for two full-scale RCM projects that are useful when implementing the program on a plantwide basis. The typical approach to RCM has been to establish a process on one pilot system and then continue the RCM process on selected systems periodically. By implementing an RCM program on a plantwide basis,nting an RCM program on a plantwide basis, benefits can be realized from and economy of scale and through the implementation of labor-saving analysis aids

190

Some developments in human reliability analysis approaches and tools  

International Nuclear Information System (INIS)

Since human actions have been recognized as an important contributor to safety of operating plants in most industries, research has been performed to better understand and account for the way operators interact during accidents through the control room and equipment interface. This paper describes the integration of a series of research projects sponsored by the Electric Power Research Institute to strengthen the methods for performing the human reliability analysis portion of the probabilistic safety studies. It focuses on the analytical framework used to guide the analysis, the development of the models for quantifying time-dependent actions, and simulator experiments used to validate the models. (author)

191

Reliability assessment of a Qualisys 3D gait analysis system  

OpenAIRE

To evaluate the reliability of the Qualisys 3D motion analysis system, one test subject’s gait was recorded (Ntotal=24) by eight high-speed cameras. Markers were used for tracking the movements (TrackManager by Qualisys) and together with force plate data was analyzed with 3D-analysis software (Visual 3D basic by C-Motion). Examined parameters were joint angles for both legs, and moments and powers for the right leg. These parameters were examined in the sagittal (X), frontal (Y) and the tr...

Eigster, Michael

2010-01-01

192

Design and Analysis for Reliability of Wireless Sensor Network  

OpenAIRE

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 co...

Yongxian Song; Ting Chen; Juanli Ma; Yuan Feng; Xianjin Zhang

2012-01-01

193

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

194

An improved radial basis function network for structural reliability analysis  

International Nuclear Information System (INIS)

Approximation methods such as response surface method and artificial neural network (ANN) method are widely used to alleviate the computation costs in structural reliability analysis. However most of the ANN methods proposed in the literature suffer various drawbacks such as poor choice of parameter setting, poor generalization and local minimum. In this study, a support vector machine-based radial basis function (RBF) network method is proposed, in which the improved RBF model is used to approximate the limit state function and then is connected to a reliability method to estimate failure probability. Since the learning algorithm of RBF network is replaced by the support vector algorithm, the advantage of the latter, such as good generalization ability and global optimization are propagated to the former, thus the inherent drawback of RBF network can be defeated. Numerical examples are given to demonstrate the applicability of the improved RBF network method in structural reliability analysis, as well as to illustrate the validity and effectiveness of the proposed method

195

Review of the treat upgrade reactor scram system reliability analysis  

International Nuclear Information System (INIS)

In order to resolve some key LMFBR safety issues, ANL personnel are modifying the TREAT reactor to handle much larger experiments. As a result of these modifications, the upgraded Treat reactor will not always operate in a self-limited mode. During certain experiments in the upgraded TREAT reactor, it is possible that the fuel could be damaged by overheating if, once the computer systems fail, the reactor scram system (RSS) fails on demand. To help ensure that the upgraded TREAT reactor is shut down when required, ANL personnel have designed a triply redundant RSS for the facility. The RSS is designed to meet three reliability goals: (1) a loss of capability failure probability of 10-9/demand (independent failures only); (2) an inadvertent shutdown probability of 10-3/experiment; and (3) protection agaist any known potential common cause failures. According to ANL's reliability analysis of the RSS, this system substantially meets these goals

196

Boiler reliability  

International Nuclear Information System (INIS)

Reliability is an important factor when investors evaluate economics for power plant and boiler proposals. Consequently, more advanced methods are needed for analyzing and reporting boiler reliability. Availability analysis methods need proper initial data in order to attain the objectives of analysis. Possible data sources are international databases and plant operation feedback data but for CFB boilers general databases do not exist and plant's records on operating experience are in many cases incomplete. FWE Oy has developed an internal system to collect, report and analyze the reliability of CFB boilers. The retrieved data is further analyzed for marketing and sales purposes. The idea is to be able to determine the reliability of a new plant on the basis of operating disturbances experienced in existing power plants. The data will also be used in product development and in preparing comparative and follow-up reports for the power plants participating in the reliability monitoring. (orig.)

197

Human reliability analysis for accident sequences in NPP  

International Nuclear Information System (INIS)

The purpose of this paper is to perform a human performance analysis in accident conditions for the operating NPP. This analysis is realized using Human Reliability Analysis (HRA) methods. HRA methods have necessary tools to analyze the human actions, to estimate the human error probabilities and to identify the major factors which could have a negative influence on the mitigating of the consequences of the abnormal events in NPP. The analyzed events are from CANDU 600 NPP. In order to achieve the analysis of these events the THEP and SPAR-H methods were used. After analyzing the results the actuated equipment, the negative influence factors on the human performance and the dependence levels between the human actions and between the human actions and diagnosis were established. In addition, some recommendations were formulated which could influence positive the human performance on the mitigating of the consequences of the accident sequences in NPP. (authors)

198

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

199

Improvement of human reliability analysis method for PRA  

International Nuclear Information System (INIS)

It is required to refine human reliability analysis (HRA) method by, for example, incorporating consideration for the cognitive process of operator into the evaluation of diagnosis errors and decision-making errors, as a part of the development and improvement of methods used in probabilistic risk assessments (PRAs). JNES has been developed a HRA method based on ATHENA which is suitable to handle the structured relationship among diagnosis errors, decision-making errors and operator cognition process. This report summarizes outcomes obtained from the improvement of HRA method, in which enhancement to evaluate how the plant degraded condition affects operator cognitive process and to evaluate human error probabilities (HEPs) which correspond to the contents of operator tasks is made. In addition, this report describes the results of case studies on the representative accident sequences to investigate the applicability of HRA method developed. HEPs of the same accident sequences are also estimated using THERP method, which is most popularly used HRA method, and comparisons of the results obtained using these two methods are made to depict the differences of these methods and issues to be solved. Important conclusions obtained are as follows: (1) Improvement of HRA method using operator cognitive action model. Clarification of factors to be considered in the evaluation of human errors, incorporation of degraded plant safety condition into HRA and investigation of HEPs which are affected by the contents of operator tasks were made to improve the HRA method which can integrate operator cognitive action model into ATHENA method. In addition, the detail of procedures of the improved method was delineated in the form of flowchart. (2) Case studies and comparison with the results evaluated by THERP method. Four operator actions modeled in the PRAs of representative BWR5 and 4-loop PWR plants were selected and evaluated as case studies. These cases were also evaluated using THERP method to compare the results with the improved method. In general, HEPs evaluated by the improved method are greater than HEPs evaluated by THERP method. (3) Characteristics of the improved HRA method. As many reference tables which can be applied for various cases are prepared in the improved HRA method, the prospect of realization of reproducibility, i.e. similar results are obtained independently to analysis, and traceability, i.e. process to the final results is clear and is also to be shared among analysts, can be said to be achieved. (author)

200

Reliability analysis and prediction of mixed mode load using Markov Chain Model  

International Nuclear Information System (INIS)

The aim of this paper is to present the reliability analysis and prediction of mixed mode loading by using a simple two state Markov Chain Model for an automotive crankshaft. The reliability analysis and prediction for any automotive component or structure is important for analyzing and measuring the failure to increase the design life, eliminate or reduce the likelihood of failures and safety risk. The mechanical failures of the crankshaft are due of high bending and torsion stress concentration from high cycle and low rotating bending and torsional stress. The Markov Chain was used to model the two states based on the probability of failure due to bending and torsion stress. In most investigations it revealed that bending stress is much serve than torsional stress, therefore the probability criteria for the bending state would be higher compared to the torsion state. A statistical comparison between the developed Markov Chain Model and field data was done to observe the percentage of error. The reliability analysis and prediction was derived and illustrated from the Markov Chain Model were shown in the Weibull probability and cumulative distribution function, hazard rate and reliability curve and the bathtub curve. It can be concluded that Markov Chain Model has the ability to generate near similar data with minimal percentage of error and for a practical application; the proposed model provides a good accuracy in determining the reliability for the crankshaft under mixed mode loading

201

Reliability analysis and prediction of mixed mode load using Markov Chain Model  

Energy Technology Data Exchange (ETDEWEB)

The aim of this paper is to present the reliability analysis and prediction of mixed mode loading by using a simple two state Markov Chain Model for an automotive crankshaft. The reliability analysis and prediction for any automotive component or structure is important for analyzing and measuring the failure to increase the design life, eliminate or reduce the likelihood of failures and safety risk. The mechanical failures of the crankshaft are due of high bending and torsion stress concentration from high cycle and low rotating bending and torsional stress. The Markov Chain was used to model the two states based on the probability of failure due to bending and torsion stress. In most investigations it revealed that bending stress is much serve than torsional stress, therefore the probability criteria for the bending state would be higher compared to the torsion state. A statistical comparison between the developed Markov Chain Model and field data was done to observe the percentage of error. The reliability analysis and prediction was derived and illustrated from the Markov Chain Model were shown in the Weibull probability and cumulative distribution function, hazard rate and reliability curve and the bathtub curve. It can be concluded that Markov Chain Model has the ability to generate near similar data with minimal percentage of error and for a practical application; the proposed model provides a good accuracy in determining the reliability for the crankshaft under mixed mode loading.

Nikabdullah, N. [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia and Institute of Space Science (ANGKASA), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (Malaysia); Singh, S. S. K.; Alebrahim, R.; Azizi, M. A. [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (Malaysia); K, Elwaleed A. [Institute of Space Science (ANGKASA), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (Malaysia); Noorani, M. S. M. [School of Mathematical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (Malaysia)

2014-06-19

202

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

203

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

204

The DYLAM approach for the dynamic reliability analysis of systems  

International Nuclear Information System (INIS)

In many real systems, failures occurring to the components, control failures and human interventions often interact with the physical system evolution in such a way that a simple reliability analysis, de-coupled from process dynamics, is very difficult or even impossible. In the last ten years many dynamic reliability approaches have been proposed to properly assess the reliability of these systems characterized by dynamic interactions. The DYLAM methodology, now implemented in its latest version, DYLAM-3, offers a powerful tool for integrating deterministic and failure events. This paper describes the main features of the DYLAM-3 code with reference to the classic fault-tree and event-tree techniques. Some aspects connected to the practical problems underlying dynamic event-trees are also discussed. A simple system, already analyzed with other dynamic methods is used as a reference for the numerical applications. The same system is also studied with a time-dependent fault-tree approach in order to show some features of dynamic methods vs classical techniques. Examples including stochastic failures, without and with repair, failures on demand and time dependent failure rates give an extensive overview of DYLAM-3 capabilities

205

Limitations in simulator time-based human reliability analysis methods  

International Nuclear Information System (INIS)

Developments in human reliability analysis (HRA) methods have evolved slowly. Current methods are little changed from those of almost a decade ago, particularly in the use of time-reliability relationships. While these methods were suitable as an interim step, the time (and the need) has come to specify the next evolution of HRA methods. As with any performance-oriented data source, power plant simulator data have no direct connection to HRA models. Errors reported in data are normal deficiencies observed in human performance; failures are events modeled in probabilistic risk assessments (PRAs). Not all errors cause failures; not all failures are caused by errors. Second, the times at which actions are taken provide no measure of the likelihood of failures to act correctly within an accident scenario. Inferences can be made about human reliability, but they must be made with great care. Specific limitations are discussed. Simulator performance data are useful in providing qualitative evidence of the variety of error types and their potential influences on operating systems. More work is required to combine recent developments in the psychology of error with the qualitative data collected at stimulators. Until data become openly available, however, such an advance will not be practical

206

A Bayesian Framework for Reliability Analysis of Spacecraft Deployments  

Science.gov (United States)

Deployable subsystems are essential to mission success of most spacecraft. These subsystems enable critical functions including power, communications and thermal control. The loss of any of these functions will generally result in loss of the mission. These subsystems and their components often consist of unique designs and applications for which various standardized data sources are not applicable for estimating reliability and for assessing risks. In this study, a two stage sequential Bayesian framework for reliability estimation of spacecraft deployment was developed for this purpose. This process was then applied to the James Webb Space Telescope (JWST) Sunshield subsystem, a unique design intended for thermal control of the Optical Telescope Element. Initially, detailed studies of NASA deployment history, "heritage information", were conducted, extending over 45 years of spacecraft launches. This information was then coupled to a non-informative prior and a binomial likelihood function to create a posterior distribution for deployments of various subsystems uSing Monte Carlo Markov Chain sampling. Select distributions were then coupled to a subsequent analysis, using test data and anomaly occurrences on successive ground test deployments of scale model test articles of JWST hardware, to update the NASA heritage data. This allowed for a realistic prediction for the reliability of the complex Sunshield deployment, with credibility limits, within this two stage Bayesian framework.

Evans, John W.; Gallo, Luis; Kaminsky, Mark

2012-01-01

207

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

208

Failure and Reliability Analysis for the Master Pump Shutdown System  

Energy Technology Data Exchange (ETDEWEB)

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.

BEVINS, R.R.

2000-09-05

209

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

210

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

211

IDHEAS – A NEW APPROACH FOR HUMAN RELIABILITY ANALYSIS  

Energy Technology Data Exchange (ETDEWEB)

This paper describes a method, IDHEAS (Integrated Decision-Tree Human Event Analysis System) that has been developed jointly by the US NRC and EPRI as an improved approach to Human Reliability Analysis (HRA) that is based on an understanding of the cognitive mechanisms and performance influencing factors (PIFs) that affect operator responses. The paper describes the various elements of the method, namely the performance of a detailed cognitive task analysis that is documented in a crew response tree (CRT), and the development of the associated time-line to identify the critical tasks, i.e. those whose failure results in a human failure event (HFE), and an approach to quantification that is based on explanations of why the HFE might occur.

G. W. Parry; J.A Forester; V.N. Dang; S. M. L. Hendrickson; M. Presley; E. Lois; J. Xing

2013-09-01

212

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

213

Reliability Analysis of Consensus in Cooperative Transport Systems  

OpenAIRE

Our work is concerned with the reliability analysis of a 1-of-n selection algorithm with the aim of solving the problem of reaching to an agreement among n processes in presence of unrestricted communication failures. We show the use of probabilistic model checking as a technique to calculate the probability of reaching to an outcome (e.g., disagreement). We describe how we used PRISM model checker to build and verify a model of a 1-of-n selection algorithm. We also discuss how the performanc...

Villani, Emilia; Fathollahnejad, Negin; Pathan, Risat; Barbosa, Raul; Karlsson, Johan

2013-01-01

214

Application of CBDTM and AP1000 human reliability analysis  

International Nuclear Information System (INIS)

To carry out the AP1000 post-accident Human Reliability Analysis (HRA) and model the operator performance shaping factors (PSF) in a proper way, the Cause-based Decision Tree Method (CBDTM) is selected as one of the methods to calculate the probability of diagnostic errors in the AP1000 HRA. The PSFs related to the working load, signal displays, operation procedures and panel design are considered in the CBDTM model, thus the relation among the plant information, operators and procedures can be properly addressed to obtain more reasonable results of AP1000 HRA. (authors)

215

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

216

Toward reliable estimates of abundance: comparing index methods to assess the abundance of a Mammalian predator.  

Science.gov (United States)

Due to time and financial constraints indices are often used to obtain landscape-scale estimates of relative species abundance. Using two different field methods and comparing the results can help to detect possible bias or a non monotonic relationship between the index and the true abundance, providing more reliable results. We used data obtained from camera traps and feces counts to independently estimate relative abundance of red foxes in the Black Forest, a forested landscape in southern Germany. Applying negative binomial regression models, we identified landscape parameters that influence red fox abundance, which we then used to predict relative red fox abundance. We compared the estimated regression coefficients of the landscape parameters and the predicted abundance of the two methods. Further, we compared the costs and the precision of the two field methods. The predicted relative abundances were similar between the two methods, suggesting that the two indices were closely related to the true abundance of red foxes. For both methods, landscape diversity and edge density best described differences in the indices and had positive estimated effects on the relative fox abundance. In our study the costs of each method were of similar magnitude, but the sample size obtained from the feces counts (262 transects) was larger than the camera trap sample size (88 camera locations). The precision of the camera traps was lower than the precision of the feces counts. The approach we applied can be used as a framework to compare and combine the results of two or more different field methods to estimate abundance and by this enhance the reliability of the result. PMID:24743565

Güthlin, Denise; Storch, Ilse; Küchenhoff, Helmut

2014-01-01

217

On the use of uncertainty importance measures in reliability and risk analysis  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses the use of uncertainty importance measures in reliability and risk analysis. Such measures are used to rank the importance of components (activities) of complex systems. The measures reflect to what degree the uncertainties on the component level influence the uncertainties on the system level. An example of such a measure is the change in the variance of the reliability of the system when ignoring the uncertainties in the component reliability. The measures are traditionally based on a Bayesian perspective as knowledge-based (subjective) probabilities express the epistemic uncertainties about the reliability and risk parameters introduced. In this paper we carry out a rethinking of the rationale for such measures. What information do they provide compared to the traditional importance measures such as the improvement potential and the Birnbaum measure? To discuss these issues we distinguish between two situations: (A) the key quantities of interest are observable quantities such as the occurrence of a system failure and the number of failures and (B) the key quantities of interest are fictional parameters constructed to reflect the aleatory uncertainties. A new type of combined sets of measures are introduced based on an integration of a traditional measure and a related uncertainty importance measure. A simple reliability example is used to illustrate the analysis and findings.

Aven, T., E-mail: terje.aven@uis.n [University of Stavanger (Norway); Nokland, T.E. [University of Stavanger and IRIS - International Research Institute of Stavanger (Norway)

2010-02-15

218

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)

219

A methodology for strain-based fatigue reliability analysis  

International Nuclear Information System (INIS)

A significant scatter of the cyclic stress-strain (CSS) responses should be noted for a nuclear reactor material, 1Cr18Ni9Ti pipe-weld metal. Existence of the scatter implies that a random cyclic strain applied history will be introduced under any of the loading modes even a deterministic loading history. A non-conservative evaluation might be given in the practice without considering the scatter. A methodology for strain-based fatigue reliability analysis, which has taken into account the scatter, is developed. The responses are approximately modeled by probability-based CSS curves of Ramberg-Osgood relation. The strain-life data are modeled, similarly, by probability-based strain-life curves of Coffin-Manson law. The reliability assessment is constructed by considering interference of the random fatigue strain applied and capacity histories. Probability density functions of the applied and capacity histories are analytically given. The methodology could be conveniently extrapolated to the case of deterministic CSS relation as the existent methods did. Non-conservative evaluation of the deterministic CSS relation and availability of present methodology have been indicated by an analysis of the material test results

220

Reliability and maintainability analysis of bread production line.  

Science.gov (United States)

The statistical analysis of the bread production line of the failure and repair data at machine and line levels was displayed. The experiment covers a period of twenty-five months. The best fit of the failure data between the common theoretical distributions was found and its parameters were computed. The reliability and hazard rate modes for all machines and the entire production line were calculated as well. The models could prove to be a useful tool to assess the current conditions, and to predict the reliability for upgrading the maintenance policy of the production line. It was pointed out that (a) the availability of the bread production line is 90.74% and went down to 86.76% because the equipment's failures cause an additional production gap in the line, (b) the 53.5% of all failures occurred at the bread machine, cooling tower machine, and volumetric-divider machine, and (c) the machines of the bread production line that displayed increasing hazard rate functions were identified. This analysis will be very useful in terms of identifying the occurring and latent problems in manufacturing process of bread and improve it. PMID:20301018

Tsarouhas, Panagiotis H; Arvanitoyannis, Ioannis S

2010-04-01

221

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.

222

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

223

Systems reliability analysis of mechanical and hydraulic drive systems  

International Nuclear Information System (INIS)

This article presents a new method for systems reliability analysis of mechanical and hydraulic systems. The method is based on finite element equations, which describe motion and equilibrium between internal and external loads for structures and mechanisms. This approach is different from the well-known application of the finite element method in structural reliability analysis . A detailed description shows how the finite element equations can be adapted to analyse mechanical and hydraulic systems. Quite common is the finite element description of structures of solid materials. The theory has been extended to describe the simple flow of fluids. Due to the similarity in the approach, it is possible to describe systems containing solid and fluidic components with a single set of equations. This article also covers physically non-linear behaviour of complex components, which asks for a special treatment. Therefore, two strategies to solve the systems of equations are discussed. It is shown how the theory can be implemented in software to be used by design engineers

224

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

225

Analysis of dependent failures in risk assessment and reliability evaluation  

International Nuclear Information System (INIS)

The ability to estimate the risk of potential reactor accidents is largely determined by the ability to analyze statistically dependent multiple failures. The importance of dependent failures has been indicated in recent probabilistic risk assessment (PRA) studies as well as in reports of reactor operating experiences. This article highlights the importance of several different types of dependent failures from the perspective of the risk and reliability analyst and provides references to the methods and data available for their analysis. In addition to describing the current state of the art, some recent advances, pitfalls, misconceptions, and limitations of some approaches to dependent failure analysis are addressed. A summary is included of the discourse on this subject, which is presented in the Institute of Electrical and Electronics Engineers/American Nuclear Society PRA Procedures Guide

226

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)

227

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

228

Rent control: a comparative analysis  

Scientific Electronic Library Online (English)

Full Text Available 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 should not be imposed in an absolutist fashion but rather place a

S, Maass.

229

RENT CONTROL: A COMPARATIVE ANALYSIS  

Directory of Open Access Journals (Sweden)

Full Text Available 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 socio-economic 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 should not be imposed in an absolutist fashion but rather place a

Sue-Mari Maass

2012-11-01

230

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 list of the data needed to support reliability and availability analysis, and gives specific 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 fielded wind turbines. This report is intended to help the reader develop a basic understanding of what data are needed from a Computerized Maintenance Management System (CMMS) and other data systems, for reliability analysis. The report provides: (1) a list of the data needed to support reliability and availability analysis; and (2) 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 a wider variety of analysis and reporting needs.

Peters, Valerie A.; Ogilvie, Alistair; Veers, Paul S.

2009-09-01

231

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

232

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

233

Steps of the reliability analysis of NPP-piping  

International Nuclear Information System (INIS)

The various steps of the reliability analysis of nuclear power plant piping are: definition and classification of safety-related leakages, determination of damage mechanism, definition of leak classes, subdivision of the system, definition of relevant elements with respect to the damage mechanisms acting and their population by using general as well as special operating experience and by differentiating in pipe elements and connections, determination of the plants and systems which are relevant for the evaluation of operating experience, determination of leak areas and their frequencies by referring to the leak-related locations, and determination of the frequency for different leak areas in the systems under investigation. Examples are given. 4 figs., 3 tabs

234

An Application of Graph Theory in Markov Chains Reliability Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents reliability analysis which was realized for an industrial company. The aim of the paper is to present the usage of discrete time Markov chains and the flow in network approach. Discrete Markov chains a well-known method of stochastic modelling describes the issue. The method is suitable for many systems occurring in practice where we can easily distinguish various amount of states. Markov chains are used to describe transitions between the states of the process. The industrial process is described as a graph network. The maximal flow in the network corresponds to the production. The Ford-Fulkerson algorithm is used to quantify the production for each state. The combination of both methods are utilized to quantify the expected value of the amount of manufactured products for the given time period.

Pavel Skalny

2014-01-01

235

Application of the integrated reliability analysis system (IRAS)  

International Nuclear Information System (INIS)

This paper introduces a UNIX-based computer aided reliability assessment system, IRAS, which was developed in the Brite/Euram project BE-4250. It utilises fault propagation models for automatic generation of Fault Trees, Cause-Consequence Diagrams and FMECA. Therefore, it has the following features: a Model Builder which allows the creation of the fault propagation models in a hierarchical manner; a Fault Tree Analysis module that is able to generate Fault Trees on demand and to extract minimal cut sets; an FMECA module that is able to search for and group effects of basic events according to their criticality, severity and probability; a Real Time Fault Location (RTFL) module that enables the fast detection of the most probable cause(s) of system malfunction based on information available from sensors and/or operator. This paper describes the underlying ideas and procedures of IRAS and shows an example application to a Hot Strip Steel Mill

236

Reliability Analysis For Substation Employing B. F. Technique  

OpenAIRE

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 tec...

Mohit Kumar, Ram Avtar Jaswal

2013-01-01

237

Failure Analysis and Field Failures: a Real Shortcut to Reliability Improvement  

OpenAIRE

Starting from two case histories, where only after thorough Failure Analysis the suddenly appearance of a failure was linked to much earlier events, the possibility of improving the reliability and of adjusting the reliability prediction tools are discussed.

Mura, G.; Cassanelli, G.

2007-01-01

238

Reliability analysis based on losses from failure Modelling  

OpenAIRE

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...

Dr Amit Gupta, Renu Garg

2013-01-01

239

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

240

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

International Nuclear Information System (INIS)

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

241

Human reliability analysis for advanced control room of KNGR  

International Nuclear Information System (INIS)

There are two purposes in Human Reliability Analysis (HRA) which was performed during Korean Next Generation Reactor (KNGR) Phase 2 research project. One is to present the human error probability quantification results for Probabilistic Safety Assessment (PSA) and the other is to provide a list of the critical operator actions for Human Factor Engineering (HFE). Critical operator actions were identified from the KNGR HRA/RSA based on selection criteria and incorporated in the MMI Task Analysis, where they receive additional treatment. The use of HRA/PSA results in design, procedure development, and training was ensured by their incorporation in the MMI task analysis and MCR design such as fixed position alarms, displays and controls. Any dominant PSA sequence that takes credit for human performance to achieve acceptable results was incorporated in MMIS validation activities through the PSA-based critical operator actions. The integration of KNGR HRA into MMI design was sufficiently addressed all applicable review criteria of NUREG-0800, Chapter 18, Section 2 F and NUREG-0711. (S.Y.)

242

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

243

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)

244

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

245

Determining which primate audiograms are reliable for comparing sensitivity in different species  

Science.gov (United States)

This study investigated all known audiograms of nonhuman primates going back to the study by Elder in 1934. In total, audiograms have been published for 28 species of nonhuman primates, with macaques being the most intensively studied. The aim of this project was to determine which audiograms represent reliable measures of sensitivity by examining interlaboratory, intraspecific, and individual variability. Auditory thresholds were taken from the audiograms by digitally scanning each graph and then extracting amplitude and frequency data using SIGMASCAN PRO image measurement software. The precision of this method was verified by comparing extracted data with published threshold values from numerous studies. The results indicate that several patterns are consistently illustrated regardless of which techniques were used, although there is some degree of variability in audiograms produced in different laboratories. For example, several studies have found that anthropoids have better low-frequency hearing than prosimians, and nearly all monkeys show the 4-kHz dip. Another interesting finding was that a lack of low-frequency sensitivity in certain taxa (e.g., patas monkeys) cannot simply be explained as the result of using headphones instead of loudspeakers. With judicious usage, audiograms can be useful for comparing biologically meaningful differences in primate hearing patterns.

Coleman, Mark N.

2005-09-01

246

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

247

Failure Analysis towards Reliable Performance of Aero-Engines  

Directory of Open Access Journals (Sweden)

Full Text Available Aero-engines are critical components whose reliable performance decides the primary safety of anaircrafthelicopter. This is met by rigorous maintenance schedule with periodic inspection/nondestructive testingof various engine components. In spite of these measures, failure of areo-engines do occur rather frequentlyin comparison to failure of other components. Systematic failure analysis helps one to identify root causeof the failure, thus enabling remedial measures to prevent recurrence of such failures. Turbine blades madeof nickel or cobalt-based alloys are used in aero-engines. These blades are subjected to complex loadingconditions at elevated temperatures. The main causes of failure of blades are attributed to creep, thermalfatigue and hot corrosion. Premature failure of blades in the combustion zone was reported in one of theaero-engines. The engine had both the compressor and the free-turbine in a common shaft. Detailedfailure analysis revealed the presence of creep voids in the blades that failed. Failure of turbine bladeswas also detected in another aero-engine operating in a coastal environment. In this failure, the protectivecoating on the blades was cracked at many locations. Grain boundary spikes were observed on these locations.The primary cause of this failure was the hot corrosion followed by creep damage

T. Jayakumar

2013-04-01

248

Reliability Estimation of High Voltage Ceramic Capacitor by Failure Analysis  

International Nuclear Information System (INIS)

This paper presents a result of failure analysis and reliability evaluation for high voltage ceramic capacitors. The failure modes and failure mechanisms were studied in two ways in order to estimate component life and failure rate. The causes of failure mechanisms for zero resistance phenomena under withstanding voltage test in high voltage ceramic capacitors molded by epoxy resin were studied by establishing an effective root cause failure analysis. Particular emphasis was placed on breakdown phenomena at the ceramic-epoxy interface. The validity of the results in this study was confirmed by the results of accelerated testing. Thermal cycling test for high voltage ceramic capacitor mounted on a magnetron were implemented. Delamination between ceramic and epoxy, which might cause electrical short in underlying circuitry, can occur during curing or thermal cycle. The results can be conveniently used to quickly identify defective lots, determine B10 life estimation each lot at the level of inspection, and detect major changes in the vendors processes. Also, the condition for dielectric breakdown was investigated for the estimation of failure rate with load-strength interference model

249

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

250

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)

251

Radionuclides in sediments - a comparative analysis, 1981  

International Nuclear Information System (INIS)

On behalf of the BMI (Federal German Ministry of the Interior), the BfG in 1981 again started an interlaboratory comparison (among 42 measuring points) on the topic of radionuclides in sediments. The study was intended to test the reliability of G?, G?/R? measurements in sedimentary samples under practical conditions. The comparative analyses again revealed a number of error sources, and errors could be corrected. This was achieved not least by a good cooperation among the participating laboratories who contributed a.o. very useful information and ideas. (orig./HP)

252

Qualitative human reliability analysis for spent fuel handling  

International Nuclear Information System (INIS)

Human reliability analysis (HRA) methods have been developed primarily to provide information for use in probabilistic risk assessments (PRAs) that analyze nuclear power plant (NPP) operations. Given the original emphasis of these methods, it is understandable that many HRAs have not ventured far from NPP control room applications. Despite this historical focus on the control room, there has been growing interest and discussion regarding the application of HRA methods to other NPP activities such as spent fuel handling (SFH) or operations in different types of facilities. One recently developed HRA method, 'A Technique for Human Event Analysis' (ATHEANA) has been proposed as a promising candidate for diverse applications due to its particular approach for systematically uncovering the dynamic, contextual conditions influencing human performance. This paper describes one successful test of this proposition by presenting portions of a recently completed project in which a scoping study was performed to accomplish the following goals: (1) investigate what should be included in a qualitative HRA for spent fuel and cask handling operations; and (2) demonstrate that the ATHEANA HRA technique can be usefully applied to these operations. The preliminary, scoping qualitative HRA examined, in a generic manner, how human performance of SFH and dry cask storage operations (DCSOs) can plausibly lead to radiological consequences that impact the public and the environment. The study the public and the environment. The study involved the performance of typical, qualitative HRA tasks such as collecting relevant information and the preliminary identification of human failure events or unsafe actions, relevant influences (e.g., performance shaping factors, other contextual factors), event scenario development and categorization of human failure event (HFE) scenario groupings. Information from relevant literature sources was augmented with subject matter expert interviews and analysis of an edited video of selected operations. Elements of NUREG-1792, Good Practices for Implementing Human Reliability Analyses (HRA) and NUREG-1624, Rev. 1, Technical Basis and Implementation Guidelines for A Technique for Human Event Analysis (ATHEANA) formed critical parts of the technical basis for the preliminary analysis. Mis-loading of spent fuel into a cask and dropping of a loaded cask were the two human failure event groupings of primary interest, although all human performance aspects of DCSOs were considered to some extent. Of important note is that HRA is typically performed in the context of a plant-specific PRA study. This analysis was performed without the benefit of the context provided by a larger PRA study, nor was it plant specific, and so it investigated only generic HRA issues relevant to SFH. However, the improved understanding of human performance issues provided by the study will likely enhance the ability to carry out a detailed qualitative HRA for a specific NPP at some point in the future. Furthermore, support was obtained regarding the potential for applying ATHEANA beyond NPP settings. This paper provides a description of the process followed during the analysis, a description of the HFE scenario groupings, discussion regarding general human performance vulnerabilities, and a detailed examination of one HFE scenario developed in the study. (authors)

253

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.

254

The reliability analysis of cutting tools in the HSM processes  

OpenAIRE

Purpose: This article mainly describe the reliability of the cutting tools in the high speed turning by normaldistribution model.Design/methodology/approach: A series of experimental tests have been done to evaluate the reliabilityvariation of the cutting tools. From experimental results, the tool wear distribution and the tool life are determined,and the tool life distribution and the reliability function of cutting tools are derived. Further, the reliability ofcutting tools at anytime for h...

Lin, W. S.

2008-01-01

255

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

256

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

257

Reliability and Security Analysis on Two-Cell Dynamic Redundant System  

Directory of Open Access Journals (Sweden)

Full Text Available Based on analysis on reliability and security on three types of two-cell dynamic redundant systems which has been widely applied in modern railway signal system, whose isomorphic Markov model was established in this paper. During modeling several important factors, including common-cause failure, coverage of diagnostic systems, online maintainability, and periodic inspection maintenance, and as well as many failure modes, were considered, which made the established model more credible. Through analysis and calculation on reliability and security indexes of the three types of two-module dynamic redundant structures, the paper acquires a significant conclusion, i.e., the safety and reliability of the kind of structure possesses an upper limit, and can not be inordinately improved through the hardware and software comparison methods under the failure and repairing rate fixed. Finally, the paper performs the simulation investigations, and compares the calculation results of the three redundant systems, and analysis each advantages and disadvantages, and gives out each application scope, which provides a theoretical technical support for the railway signal equipments selection.

Hongsheng Su

2013-05-01

258

Application of Reliability Analysis for Optimal Design of Monolithic Vertical Wall Breakwaters  

DEFF Research Database (Denmark)

Reliability analysis and reliability-based design of monolithic vertical wall breakwaters are considered. Probabilistic models of some of the most important failure modes are described. The failures are sliding and slip surface failure of a rubble mound and a clay foundation. Relevant design variables are identified and a reliability-based design optimization procedure is formulated. Results from an illustrative example are given.

Burcharth, H. F.; SØrensen, John Dalsgaard

1995-01-01

259

Reliability model analysis and primary experimental evaluation of laser triggered pulse trigger  

International Nuclear Information System (INIS)

High performance pulse trigger can enhance performance and stability of the PPS. It is necessary to evaluate the reliability of the LTGS pulse trigger, so we establish the reliability analysis model of this pulse trigger based on CARMES software, the reliability evaluation is accord with the statistical results. (authors)

260

Human reliability analysis of the Tehran research reactor using the SPAR-H method  

OpenAIRE

The purpose of this paper is to cover human reliability analysis of the Tehran research reactor using an appropriate method for the representation of human failure probabilities. In the present work, the technique for human error rate prediction and standardized plant analysis risk-human reliability methods have been utilized to quantify different categories of human errors, applied extensively to nuclear power plants. Human reliability analysis is, indeed, an integral and significant p...

Barati Ramin; Setayeshi Saeed

2012-01-01

261

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

262

Probabilistic Analysis of Aircraft Gas Turbine Disk Life and Reliability  

Science.gov (United States)

Two series of low cycle fatigue (LCF) test data for two groups of different aircraft gas turbine engine compressor disk geometries were reanalyzed and compared using Weibull statistics. Both groups of disks were manufactured from titanium (Ti-6Al-4V) alloy. A NASA Glenn Research Center developed probabilistic computer code Probable Cause was used to predict disk life and reliability. A material-life factor A was determined for titanium (Ti-6Al-4V) alloy based upon fatigue disk data and successfully applied to predict the life of the disks as a function of speed. A comparison was made with the currently used life prediction method based upon crack growth rate. Applying an endurance limit to the computer code did not significantly affect the predicted lives under engine operating conditions. Failure location prediction correlates with those experimentally observed in the LCF tests. A reasonable correlation was obtained between the predicted disk lives using the Probable Cause code and a modified crack growth method for life prediction. Both methods slightly overpredict life for one disk group and significantly under predict it for the other.

Melis, Matthew E.; Zaretsky, Erwin V.; August, Richard

1999-01-01

263

Preliminary analysis of shutdown system reliability of a gas graphite type reactor  

International Nuclear Information System (INIS)

This work applies some Reliability Analysis tools the Failure Mode and Effects Analysis (FMEA), the Fault Tree, and the Reliability Block Diagram (RBD) - to study a shutdown system to a graphite reactor. The main goal of the present work is to provide means for identification of critical points of the system, and to enable a detailed study of safety analysis. (author)

264

A graph trace based reliability analysis of electric power systems with time-varying loads and dependent failures  

Energy Technology Data Exchange (ETDEWEB)

A new approach to the prediction of the reliability of electrical systems is presented. In this approach a graph trace based reliability analysis of electric transmission and/or distribution systems is used. The systems are modeled using containers with iterators, where the iterators manage graph edges and are used to process through the topology of the graph. The analysis provides a means of computationally handling dependent failure rates and cascading failures. The effects of weather, time-varying loads, equipment age, wetness, and dependent failures associated with repaired components are considered. A sequential Monte Carlo simulation is used to evaluate the reliability changes for different system configurations, including distributed generation and transmission lines. Historical weather records and loading are used to update the component failure rates on-the-fly. Simulation results are compared against historical reliability field measurements. (author)

Cheng, Danling; Broadwater, Robert P. [Department of Electrical and Computer Engineering, Virginia Tech, 1214 Univ. City Blvd, H-95, Blacksburg, VA 24060 (United States); Zhu, Dan [Electrical Distribution Inc., 311 Cherokee Drive, Blacksburg, VA 24060 (United States); Lee, Serena [Department of Research and Development, Con Edison, 4 Irving Place, New York, NY 10003 (United States)

2009-09-15

265

Structural characterization of genomes by large scale sequence-structure threading: application of reliability analysis in structural genomics  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background We establish that the occurrence of protein folds among genomes can be accurately described with a Weibull function. Systems which exhibit Weibull character can be interpreted with reliability theory commonly used in engineering analysis. For instance, Weibull distributions are widely used in reliability, maintainability and safety work to model time-to-failure of mechanical devices, mechanisms, building constructions and equipment. Results We have found that the Weibull function describes protein fold distribution within and among genomes more accurately than conventional power functions which have been used in a number of structural genomic studies reported to date. It has also been found that the Weibull reliability parameter ? for protein fold distributions varies between genomes and may reflect differences in rates of gene duplication in evolutionary history of organisms. Conclusions The results of this work demonstrate that reliability analysis can provide useful insights and testable predictions in the fields of comparative and structural genomics.

Brunham Robert C

2004-07-01

266

Application of Metric-based Software Reliability Analysis to Example Software  

International Nuclear Information System (INIS)

The software reliability of TELLERFAST ATM software is analyzed by using two metric-based software reliability analysis methods, a state transition diagram-based method and a test coverage-based method. The procedures for the software reliability analysis by using the two methods and the analysis results are provided in this report. It is found that the two methods have a relation of complementary cooperation, and therefore further researches on combining the two methods to reflect the benefit of the complementary cooperative effect to the software reliability analysis are recommended

267

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

268

Reliability analysis of water distribution systems under uncertainty  

International Nuclear Information System (INIS)

In most of the developing countries, the Water Distribution Networks (WDN) are of intermittent type because of the shortage of safe drinking water. Failure of a pipeline(s) in such cases will cause not only the fall in one or more nodal heads but also the poor connectivity of source with various demand nodes of the system. Most of the previous works have used the two-step algorithm based on pathset or cutset approach for connectivity analysis. The computations become more cumbersome when connectivity of all demand nodes taken together with that of supply is carried out. In the present paper, network connectivity based on the concept of Appended Spanning Tree (AST) is suggested to compute global network connectivity which is defined as the probability of the source node being connected with all the demand nodes simultaneously. The concept of AST has distinct advantages as it attacks the problem directly rather than in an indirect way as most of the studies so far have done. Since the water distribution system is a repairable one, a general expression for pipeline avialability using the failure/repair rate is considered. Furthermore, the sensitivity of global reliability estimates due to the likely error in the estimation of failure/repair rates of various pipelines is also studied

269

Potential Improvements in Human Reliability Analysis for Fire Risk Assessments  

International Nuclear Information System (INIS)

The results of numerous fire risk assessments (FRA) and the experience gained from actual fire events have shown that fire can be a significant contributor to nuclear power plant (NPP) risk. However, on the basis of reviews of the FRAs performed for the Individual Plant External Events Examination (IPEEE) program in the U.S. and on recent research performed by U.S. Nuclear Regulatory Commission (NRC) to support increased use of risk information in regulatory decision making [e.g., Ref. 1, 2], it has become clear that improved modelling and quantification of human performance during fire events requires a better treatment of the special environment and response context produced by fires. This paper describes fire-related factors that have been identified as potentially impacting human performance, discusses to what extent such factors were modelled in the IPEEE FRAs, discusses prioritization of the factors likely to be most important to a realistic assessment of plant safety, and discusses which factors are likely to need additional research and development in order to allow adequate modelling in the human reliability analysis (HRA) portions of FRAs. The determination of which factors need to be modelled and the improvement of HRA related approaches for modelling such factors are critical aspects of the NRC's plan to improve FRA methods, tools, and data and to update a number of existing FRAs. (authors)

270

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

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 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

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

273

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 computationalhat the method considered is computationally very efficient and provides consistent reliability estimates. (authors)

274

Prediction of Stress Induced Voiding Reliability in Cu Damascene Interconnect by Computer Aided Vacancy Migration Analysis  

Science.gov (United States)

The method of computer aided vacancy migration analysis has been developed to predict the stress induced voiding (SiV) reliability. In this method, distribution of hydrostatic stress was calculated by the finite element analysis (FEA), and vacancy concentration distribution was calculated by the finite difference analysis (FDA). In this paper, SiV acceleration tests were conducted in various widths of Cu lines in organic ultralow-k dielectric (Cu/Ta/ULK/SiCN) or silicon oxide dielectric (Cu/Ta/SiO2/SiCN) and these results were compared with the results of the vacancy migration analyses. The number of SiV failures increased in the line with width of 0.35 µm for Cu/Ta/SiO2/SiCN interconnects and 0.20 µm for Cu/Ta/ULK/SiCN interconnects, respectively, under SiV acceleration tests. The results obtained by vacancy migration analysis show similar behavior as the results of SiV acceleration tests. These results reveal that the vacancy migration analysis is useful to predict reliability of interconnects.

Shigeyama, Haruhisa; Nemoto, Takenao; Toshimitsu Yokobori, A., Jr.

2011-05-01

275

Evaluation and identification of reliable reference genes for pharmacogenomics, toxicogenomics, and small RNA expression analysis.  

Science.gov (United States)

Pharmacogenomics, toxicogenomics, and small RNA expression analysis are three of the most active research topics in the biological, biomedical, pharmaceutical, and toxicological fields. All of these studies are based on gene expression analysis, which requires reference genes to reduce the variations derived from different amounts of starting materials and different efficiencies of RNA extraction and cDNA synthesis. Thus, accurate normalization to one or several constitutively expressed reference genes is a prerequisite to valid gene expression studies. Although selection of reliable reference genes has been conducted in previous studies in several animals and plants, no research has been focused on pharmacological targets, and very few studies have had a toxicological context. More interestingly, no studies have been performed to identify reference genes for small RNA analysis although small RNA, particularly microRNA (miRNA)-related research is currently one of the fastest-moving topics. In this study, using MCF-7 breast cancer cells as a model, we employed quantitative real-time PCR (qRT-PCR), one of the most reliable methods for gene expression analysis in many research fields, to evaluate and to determine the most reliable reference genes for pharmacogenomics and toxicogenomics studies as well as for small RNA expression analysis. We tested the transcriptional expression of five protein-coding genes as well as five non-coding genes in MCF-7 cells treated with five different pharmaceuticals or toxicants [paclitaxel (PTX), gossypol (GOS), methyl jasmonate (JAS), L-nicotine (NIC), and melamine (mela)] and analyzed the stability of the selected reference genes by four different methods: geNorm, NormFinder, BestKeeper, and the comparative ?Ct method. According to our analysis, a protein-coding gene, hTBCA and four non-coding genes, hRNU44, hRNU48, hU6, and hRNU47, appear to be the most reliable reference genes for the five chemical treatments. Similar results were also obtained in dose-response and time-course assays with gossypol (GOS) treatment. Our results demonstrated that traditionally used reference genes, such as 18s RNA, ?-actin, and GAPDH, are not reliable reference genes for pharmacogenomics and toxicogenomics studies. In contrast, hTBCA and small RNAs are more stable during drug treatment, and they are better reference genes for pharmacogenomics and toxicogenomics studies. To widely use these genes as reference genes, these results should be corroborated by studies with other human cell lines and additional drugs classes and hormonal treatments. PMID:21412770

Chen, Dongliang; Pan, Xiaoping; Xiao, Peng; Farwell, Mary A; Zhang, Baohong

2011-10-01

276

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

277

Reliability analysis of reinforced concrete grids with nonlinear material behavior  

International Nuclear Information System (INIS)

Reinforced concrete grids are usually used to support large floor slabs. These grids are characterized by a great number of critical cross-sections, where the overall failure is usually sudden. However, nonlinear behavior of concrete leads to the redistribution of internal forces and accurate reliability assessment becomes mandatory. This paper presents a reliability study on reinforced concrete (RC) grids based on coupling Monte Carlo simulations with the response surface techniques. This approach allows us to analyze real RC grids with large number of failure components. The response surface is used to evaluate the structural safety by using first order reliability methods. The application to simple grids shows the interest of the proposed method and the role of moment redistribution in the reliability assessment

278

Reliability and Creep/Fatigue Analysis of a CMC Component  

Science.gov (United States)

High temperature ceramic matrix composites (CMC) are being explored as viable candidate materials for hot section gas turbine components. These advanced composites can potentially lead to reduced weight and enable higher operating temperatures requiring less cooling; thus leading to increased engine efficiencies. There is a need for convenient design tools that can accommodate various loading conditions and material data with their associated uncertainties to estimate the minimum predicted life as well as the failure probabilities of a structural component. This paper presents a review of the life prediction and probabilistic analyses performed for a CMC turbine stator vane. A computer code, NASALife, is used to predict the life of a 2-D woven silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) turbine stator vane due to a mission cycle which induces low cycle fatigue and creep. The output from this program includes damage from creep loading, damage due to cyclic loading and the combined damage due to the given loading cycle. Results indicate that the trends predicted by NASALife are as expected for the loading conditions used for this study. In addition, a combination of woven composite micromechanics, finite element structural analysis and Fast Probability Integration (FPI) techniques has been used to evaluate the maximum stress and its probabilistic distribution in a CMC turbine stator vane. Input variables causing scatter are identified and ranked based upon their sensitivity magnitude. Results indicate that reducing the scatter in proportional limit strength of the vane material has the greatest effect in improving the overall reliability of the CMC vane.

Murthy, Pappu L. N.; Mital, Subodh K.; Gyekenyesi, John Z.; Gyekenyesi, John P.

2007-01-01

279

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

280

Exploratory factor analysis and reliability analysis with missing data: A simple method for SPSS users  

Directory of Open Access Journals (Sweden)

Full Text Available Missing data is a frequent problem for researchers conducting exploratory factor analysis (EFA or reliability analysis. The SPSS FACTOR procedure allows users to select listwise deletion, pairwise deletion or mean substitution as a method for dealing with missing data. The shortcomings of these methods are well-known. Graham (2009 argues that a much better way to deal with missing data in this context is to use a matrix of expectation maximization (EM covariances(or correlations as input for the analysis. SPSS users who have the Missing Values Analysis add-on module can obtain vectors ofEM means and standard deviations plus EM correlation and covariance matrices via the MVA procedure. But unfortunately, MVA has no /MATRIX subcommand, and therefore cannot write the EM correlations directly to a matrix dataset of the type needed as input to the FACTOR and RELIABILITY procedures. We describe two macros that (in conjunction with an intervening MVA command carry out the data management steps needed to create two matrix datasets, one containing EM correlations and the other EM covariances. Either of those matrix datasets can then be used asinput to the FACTOR procedure, and the EM correlations can also be used as input to RELIABILITY. We provide an example that illustrates the use of the two macros to generate the matrix datasets and how to use those datasets as input to the FACTOR and RELIABILITY procedures. We hope that this simple method for handling missing data will prove useful to both students andresearchers who are conducting EFA or reliability analysis.

Bruce Weaver

2014-09-01

281

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

282

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)

283

Transmission Line Fault Clearing System Reliability Assessment: Application of Life Data Analysis with Weibull Distribution and Reliability Block Diagram  

Directory of Open Access Journals (Sweden)

Full Text Available High voltage transmission lines are essential assets to electric utility companies as these lines transmit electricity generated by power stations to various regions throughout the country. Being exposed to the surrounding environments, transmission lines are susceptible to atmospheric conditions such as lightning strikes and flora and fauna encroachments. These conditions are called faults. Faults on transmission lines may cause disruption of electricity supply which will affect the overall power system and lead to a wide scale blackout. Therefore, fault clearing system is deployed to minimize the impact of the faults to the power system by disconnecting and isolating the affected transmission lines specifically. One of the main devices in fault  clearing system are the protective relays, which serve as the "brain" to provide the decision making element for correct protection and fault clearing operations. Without protective relays, fault clearing system is rendered useless. Hence, it is imperative for power utilities, such as Tenaga Nasional Berhad (TNB, which is an electric utility company in Malaysia, to assess the reliability of the protective relays. In this study, a statistical method called Life Data Analysis using Weibull Distribution is applied to assess the reliability of the protective relays.  Furthermore, the fault clearing system is modeled using Reliability Block Diagram to simulate the availability of the system and derive reliability indices which will assist TNB in managing the fault clearing system.

Mohd Iqbal Ridwan

2013-05-01

284

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

285

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

286

Assessment of modern methods of human factor reliability analysis in PSA studies  

International Nuclear Information System (INIS)

The report is structured as follows: Classical terms and objects (Probabilistic safety assessment as a framework for human reliability assessment; Human failure within the PSA model; Basic types of operator failure modelled in a PSA study and analyzed by HRA methods; Qualitative analysis of human reliability; Quantitative analysis of human reliability used; Process of analysis of nuclear reactor operator reliability in a PSA study); New terms and objects (Analysis of dependences; Errors of omission; Errors of commission; Error forcing context); and Overview and brief assessment of human reliability analysis (Basic characteristics of the methods; Assets and drawbacks of the use of each of HRA method; History and prospects of the use of the methods). (P.A.)

287

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

288

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

289

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

290

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

Energy Technology Data Exchange (ETDEWEB)

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.

Hendrickson, D.W. [ed.

1995-03-14

291

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

292

Reliability Analysis of Bearing Capacity of Large-Diameter Piles under Osterberg Test  

Directory of Open Access Journals (Sweden)

Full Text Available This study gives the reliability analysis of bearing capacity of large-diameter piles under osterberg test. The limit state equation of dimensionless random variables is utilized in the reliability analysis of vertical bearing capacity of large-diameter piles based on Osterberg loading tests. And the reliability index and the resistance partial coefficient under the current specifications are calculated using calibration method. The results show: the reliable index of large-diameter piles is correlated with the load effect ratio and is smaller than the ordinary piles; resistance partial coefficient of 1.53 is proper in design of large-diameter piles.

Lei Nie

2013-05-01

293

A survey on reliability and safety analysis techniques of robot systems in nuclear power plants  

Energy Technology Data Exchange (ETDEWEB)

The reliability and safety analysis techniques was surveyed for the purpose of overall quality improvement of reactor inspection system which is under development in our current project. The contents of this report are : 1. Reliability and safety analysis techniques suvey - Reviewed reliability and safety analysis techniques are generally accepted techniques in many industries including nuclear industry. And we selected a few techniques which are suitable for our robot system. They are falut tree analysis, failure mode and effect analysis, reliability block diagram, markov model, combinational method, and simulation method. 2. Survey on the characteristics of robot systems which are distinguished from other systems and which are important to the analysis. 3. Survey on the nuclear environmental factors which affect the reliability and safety analysis of robot system 4. Collection of the case studies of robot reliability and safety analysis which are performed in foreign countries. The analysis results of this survey will be applied to the improvement of reliability and safety of our robot system and also will be used for the formal qualification and certification of our reactor inspection system.

Eom, H.S.; Kim, J.H.; Lee, J.C.; Choi, Y.R.; Moon, S.S

2000-12-01

294

A survey on reliability and safety analysis techniques of robot systems in nuclear power plants  

International Nuclear Information System (INIS)

The reliability and safety analysis techniques was surveyed for the purpose of overall quality improvement of reactor inspection system which is under development in our current project. The contents of this report are : 1. Reliability and safety analysis techniques suvey - Reviewed reliability and safety analysis techniques are generally accepted techniques in many industries including nuclear industry. And we selected a few techniques which are suitable for our robot system. They are falut tree analysis, failure mode and effect analysis, reliability block diagram, markov model, combinational method, and simulation method. 2. Survey on the characteristics of robot systems which are distinguished from other systems and which are important to the analysis. 3. Survey on the nuclear environmental factors which affect the reliability and safety analysis of robot system 4. Collection of the case studies of robot reliability and safety analysis which are performed in foreign countries. The analysis results of this survey will be applied to the improvement of reliability and safety of our robot system and also will be used for the formal qualification and certification of our reactor inspection system

295

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

296

Diagnosing MOV problems using comparative trace analysis  

International Nuclear Information System (INIS)

The paper presents the concept of comparative trace analysis and shows it to be very effective in diagnosing motor operated valve (MOV) problems. Comparative trace analysis is simply the process of interpreting simultaneously gathered traces, each presenting a different perspective on the same series of events. The opening and closing of a motor operated valve is such a series of events. The simultaneous traces are obtained using Liberty Technologies' Valve Operation Test and Evaluation System (VOTES)reg-sign. The traces include stem thrust, motor current, motor power factor, motor power, switch actuations, vibration in three different frequency bands, spring pack displacement, and spring pack force. Spare and auxiliary channels enable additional key parameters to be measured, such as differential pressure and stem displacement. Though not specifically illustrated in this paper, the VOTES system also provides for FFT analysis on all traces except switches

297

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

298

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

299

Analysis of component reliability of Korean standard nuclear power plants (from commercial operation to 2002)  

International Nuclear Information System (INIS)

The reliability data of Korean NPP that reflects the plant specific characteristics is necessary for PSA of Korean standard nuclear power plants. We have performed a study to develop the component reliability DB and S/W for component reliability analysis. Based on the system, we had have collected the component operation data and failure/repair data during plant operation data to 1998/2000 for YGN 3,4/UCN 3,4 respectively. Recently, we have upgraded the database by collecting additional data by 2002 for Korean standard nuclear power plants and performed component reliability analysis and Bayesian analysis again. In this study, we supply the component reliability data for probabilistic safety analysis of Korean standard nuclear power

300

DEPEND-HRA-A method for consideration of dependency in human reliability analysis  

International Nuclear Information System (INIS)

A consideration of dependencies between human actions is an important issue within the human reliability analysis. A method was developed, which integrates the features of existing methods and the experience from a full scope plant simulator. The method is used on real plant-specific human reliability analysis as a part of the probabilistic safety assessment of a nuclear power plant. The method distinguishes dependency for pre-initiator events from dependency for initiator and post-initiator events. The method identifies dependencies based on scenarios, where consecutive human actions are modeled, and based on a list of minimal cut sets, which is obtained by running the minimal cut set analysis considering high values of human error probabilities in the evaluation. A large example study, which consisted of a large number of human failure events, demonstrated the applicability of the method. Comparative analyses that were performed show that both selection of dependency method and selection of dependency levels within the method largely impact the results of probabilistic safety assessment. If the core damage frequency is not impacted much, the listings of important basic events in terms of risk increase and risk decrease factors may change considerably. More efforts are needed on the subject, which will prepare the background for more detailed guidelines, which will remove the subjectivity from the evaluations as much as it is possible possible

301

Reliability analysis of common hazardous waste treatment processes  

Energy Technology Data Exchange (ETDEWEB)

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.

Waters, R.D. [Vanderbilt Univ., Nashville, TN (United States)

1993-05-01

302

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

303

Multicultural Competency Instrumentation: A Review and Analysis of Reliability Generalization  

Science.gov (United States)

This article reviews the internal consistency reliability of multicultural competency instrumentation. Additional psychometric properties are qualitatively reviewed for commonly used instruments and 5 other measures of multicultural competency that have not previously been reviewed in the literature. Results indicate that the most widely used…

Dunn, Todd W.; Smith, Timothy B.; Montoya, Jared A.

2006-01-01

304

Architecture-Based Reliability Analysis of Web Services  

Science.gov (United States)

In a Service Oriented Architecture (SOA), the hierarchical complexity of Web Services (WS) and their interactions with the underlying Application Server (AS) create new challenges in providing a realistic estimate of WS performance and reliability. The current approaches often treat the entire WS environment as a black-box. Thus, the sensitivity…

Rahmani, Cobra Mariam

2012-01-01

305

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

Science.gov (United States)

The reliability of a wastewater treatment plant is a critical issue when the effluent is reused or discharged to water resources. Main factors affecting the performance of the wastewater treatment plant are the variation of the influent, inherent variability in the treatment processes, deficiencies in design, mechanical equipment, and operational failures. Thus, meeting the established reuse/discharge criteria requires assessment of plant reliability. Among many techniques developed in system reliability analysis, fault tree analysis (FTA) is one of the popular and efficient methods. FTA is a top down, deductive failure analysis in which an undesired state of a system is analyzed. In this study, the problem of reliability was studied on Tehran West Town wastewater treatment plant. This plant is a conventional activated sludge process, and the effluent is reused in landscape irrigation. The fault tree diagram was established with the violation of allowable effluent BOD as the top event in the diagram, and the deficiencies of the system were identified based on the developed model. Some basic events are operator's mistake, physical damage, and design problems. The analytical method is minimal cut sets (based on numerical probability) and Monte Carlo simulation. Basic event probabilities were calculated according to available data and experts' opinions. The results showed that human factors, especially human error had a great effect on top event occurrence. The mechanical, climate, and sewer system factors were in subsequent tier. Literature shows applying FTA has been seldom used in the past wastewater treatment plant (WWTP) risk analysis studies. Thus, the developed FTA model in this study considerably improves the insight into causal failure analysis of a WWTP. It provides an efficient tool for WWTP operators and decision makers to achieve the standard limits in wastewater reuse and discharge to the environment. PMID:25487461

Taheriyoun, Masoud; Moradinejad, Saber

2015-01-01

306

Bayesian system reliability and availability analysis under the vague environment based on Exponential distribution  

OpenAIRE

Reliability modeling is the most important discipline of reliable engineering. The main purpose of this paper is to provide a methodology for discussing the vague environment. Actually we discuss on Bayesian system reliability and availability analysis on the vague environment based on Exponential distribution under squared error symmetric and precautionary asymmetric loss functions. In order to apply the Bayesian approach, model parameters are assumed to be vague random variables with vague...

Ramin Gholizadeh; Shirazi, Aliakbar M.; Maghdoode Hadian

2012-01-01

307

Root cause analysis in support of reliability enhancement of engineering components  

International Nuclear Information System (INIS)

Reliability based methods have been widely used for the safety assessment of plant system, structures and components. These methods provide a quantitative estimation of system reliability but do not give insight into the failure mechanism. Understanding the failure mechanism is a must to avoid the recurrence of the events and enhancement of the system reliability. Root cause analysis provides a tool for gaining detailed insights into the causes of failure of component with particular attention to the identification of fault in component design, operation, surveillance, maintenance, training, procedures and policies which must be improved to prevent repetition of incidents. Root cause analysis also helps in developing Probabilistic Safety Analysis models. A probabilistic precursor study provides a complement to the root cause analysis approach in event analysis by focusing on how an event might have developed adversely. This paper discusses the root cause analysis methodologies and their application in the specific case studies for enhancement of system reliability. (author)

308

Fast neutron reactor safety reliability analysis of Phenix decay heat removal function  

International Nuclear Information System (INIS)

A reliability analysis of the Phenix decay heat removal function is presented. 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

309

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

OpenAIRE

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

310

Reliability analysis of numerical simulation in near field behavior  

International Nuclear Information System (INIS)

The uncertainties of the boundary conditions, the elastic modulus and Poisson's ratio on the mechanical behavior at near field of high level radioactive waste repository were examined. The method used to examine the error propagation was the first order second moment method. The reliability of the maximum principal stress, maximum shear stress at crown of the tunnel and the minimum principal stress at spring line was examined for one million years. For elastic model, the reliability of the maximum shear stress gradually decreased while that of the maximum principle stress increased. That of the minimum principal stress was relatively low for one million years. This tendency was similar to that from the damage model. (author)

311

Reliability Analysis and Standardization of Spacecraft Command Generation Processes  

Science.gov (United States)

center dot In order to reduce commanding errors that are caused by humans, we create an approach and corresponding artifacts for standardizing the command generation process and conducting risk management during the design and assurance of such processes. center dot The literature review conducted during the standardization process revealed that very few atomic level human activities are associated with even a broad set of missions. center dot Applicable human reliability metrics for performing these atomic level tasks are available. center dot The process for building a "Periodic Table" of Command and Control Functions as well as Probabilistic Risk Assessment (PRA) models is demonstrated. center dot The PRA models are executed using data from human reliability data banks. center dot The Periodic Table is related to the PRA models via Fault Links.

Meshkat, Leila; Grenander, Sven; Evensen, Ken

2011-01-01

312

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.

313

Failure Analysis Methods for Reliability Improvement of Electronic Sensors  

OpenAIRE

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

314

Modified generalized linear failure rate distribution: Properties and reliability analysis  

OpenAIRE

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 reliabilit...

Ezzatallah Baloui Jamkhaneh

2014-01-01

315

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

316

Fundus camera systems: a comparative analysis  

OpenAIRE

Retinal photography requires the use of a complex optical system, called a fundus camera, capable of illuminating and imaging the retina simultaneously. The patent literature shows two design forms but does not provide the specifics necessary for a thorough analysis of the designs to be performed. We have constructed our own designs based on the patent literature in optical design software and compared them for illumination efficiency, image quality, ability to accommodate for patient refract...

Dehoog, Edward; Schwiegerling, James

2009-01-01

317

Comparative analysis of twelve Dothideomycete plant pathogens  

Energy Technology Data Exchange (ETDEWEB)

The Dothideomycetes are one of the largest and most diverse groups of fungi. Many are plant pathogens and pose a serious threat to agricultural crops grown for biofuel, food or feed. Most Dothideomycetes have only a single host and related Dothideomycete species can have very diverse host plants. Twelve Dothideomycete genomes have currently been sequenced by the Joint Genome Institute and other sequencing centers. They can be accessed via Mycocosm which has tools for comparative analysis

Ohm, Robin; Aerts, Andrea; Salamov, Asaf; Goodwin, Stephen B.; Grigoriev, Igor

2011-03-11

318

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)

319

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

320

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

321

Reliability analysis of the emergency power supply system for the 10 MW high temperature gas-cooled reactor  

International Nuclear Information System (INIS)

The features of the emergency power supply system of the 10 MW High Temperature Gas-cooled Reactor (HTR-10) are briefly introduced, and the reliability of the emergency power supply system of the HTR-10 is calculated using fault-tree analysis method. The calculating results are compared with those obtained using the standard nuclear power plant design method. All the results show that the emergency power supply system of the HTR-10 is not only with high reliability but also quite simple as well as economic

322

Convergence among Data Sources, Response Bias, and Reliability and Validity of a Structured Job Analysis Questionnaire.  

Science.gov (United States)

Examined are questions pertinent to the use of the Position Analysis Questionnaire: Who can use the PAQ reliably and validly? Must one rely on trained job analysts? Can people having no direct contact with the job use the PAQ reliably and validly? Do response biases influence PAQ responses? (Author/KC)

Smith, Jack E.; Hakel, Milton D.

1979-01-01

323

Reliability of three-dimensional gait analysis in cervical spondylotic myelopathy.  

LENUS (Irish Health Repository)

Gait impairment is one of the primary symptoms of cervical spondylotic myelopathy (CSM). Detailed assessment is possible using three-dimensional gait analysis (3DGA), however the reliability of 3DGA for this population has not been established. The aim of this study was to evaluate the test-retest reliability of temporal-spatial, kinematic and kinetic parameters in a CSM population.

McDermott, Ailish

2010-10-01

324

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)

325

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

OpenAIRE

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.

Agnihotri, R. K.; Ajit Khare; Sanjay Jain

2008-01-01

326

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

327

Application of factor analysis in evaluation of financial reliability of life insurance companies  

Directory of Open Access Journals (Sweden)

Full Text Available The article presents the results of factor analysis of the financial reliability of life insurance companies in Ukraine. It was found out the latent factors explaining the so called case and result the mechanism of forming of the financial reliability of the native life-insurance companies at different phases of functioning the life insurance market in Ukraine.

Malynych, Anna Mykolayivna

2011-11-01

328

Reliability analysis of protection system of advanced pressurized water reactor - APR 1400  

International Nuclear Information System (INIS)

Reliability analysis was carried out for the protection system of the Korean Advanced Pressurized Water Reactor - APR 1400. The main focus of this study was the reliability analysis of digital protection system, however, towards giving an integrated statement of complete protection reliability an attempt has been made to include the shutdown devices and other related aspects based on the information available to date. The sensitivity analysis has been carried out for the critical components / functions in the system. Other aspects like importance analysis and human error reliability for the critical human actions form part of this work. The framework provided by this study and the results obtained shows that this analysis has potential to be utilized as part of risk informed approach for future design / regulatory applications

329

Validity, reliability and stability of the portable Cortex Metamax 3B gas analysis system.  

Science.gov (United States)

This study investigated the performance of the portable Cortex Metamax 3B (MM3B) automated gas analysis system during both simulated and human exercise using adolescents. Repeated measures using a Gas Exchange System Validator (GESV) across a range of simulated metabolic rates, showed the MM3B to be adequately reliable (both percentage errors, and percentage technical error of measurements DBM) and a secondary criterion machine known to be accurate, the Jaeger Oxycon Pro system. No significant errors in V (E) were noted, yet the MM3B significantly overestimated both VO(2) and VCO(2) by approximately 10-17% at moderate and vigorous exercise as compared to the DBM and at all exercise levels compared to the Oxycon Pro. No significant differences were seen in any metabolic variable between the two criterion systems (DBM and Oxycon Pro). It is concluded the MM3B produces acceptably stable and reliable results, but is not adequately valid during moderate and vigorous exercise without some further correction of VO(2) and VCO(2). PMID:22075643

Macfarlane, D J; Wong, P

2012-07-01

330

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.

331

Human Reliability Analysis in Frame of Probabilistic Safety Assessment Projects in Czech Republic  

International Nuclear Information System (INIS)

Human reliability analysis has proved to be a very important part of probabilistic safety analysis all over the world. It has been also an integral part of both Probabilistic Safety Level-1 studies developed in Czech Republic - Nuclear Power Plant Dukovany Probabilistic Safety Assessment and Nuclear Power Plant Temelin Probabilistic Safety Assessment and most of their consequent applications. The methodology used in human reliability analysis in frame of these studies is described in the first part of the paper. In general, the methodology is based on the well-known and most frequently used methods Technique for Human Error Rate Prediction and ASEP. The up-to-date decision tree method is used to address procedure-driven operator's interventions during plant response to initiating event. Some interesting results of human reliability analysis performed for Nuclear Power Plant Dukovany are described in the second part of the paper. The recommendations resulting from the analysis led to the standardization of some, up to that time, non-standard operator's actions and to the development of procedures for them. Generally, the procedures were found to be deficient from several points of view, what contributed to the decision to develop quite new emergency procedures for Nuclear Power Plant Dukovany. The human reliability analysis projects going on or planned for the very next future are described in the final part of the paper. safety analysis; risk assessment; reliability; y analysis; risk assessment; reliability; nuclear power plants; human factors; errors; Czech Republic; operators; emergencies;

332

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

333

Vibration reliability sensitivity analysis of general system with correlation failure modes  

Energy Technology Data Exchange (ETDEWEB)

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.

Su, Changqing [Shenyang Aerospace University, Shenyang (China); Zhang, Yimin; Zhao, Qunchao [Northeastern University, Shenyang (China)

2011-12-15

334

Reliability analysis study of digital reactor protection system in nuclear power plant  

International Nuclear Information System (INIS)

The Digital I and C systems are believed to improve a plant's safety and reliability generally. The reliability analysis of digital I and C system has become one research hotspot. Traditional fault tree method is one of means to quantify the digital I and C system reliability. One typical digital protection system special for advanced reactor has been developed in this paper, which reliability evaluation is necessary for design demonstration. The typical digital protection system construction is introduced in the paper, and the process of FMEA and fault tree application to the digital protection system reliability evaluation are described. Reliability data and bypass logic modeling are two points giving special attention in the paper. Because the factors about time sequence and feedback not exist in reactor protection system obviously, the dynamic feature of digital system is not discussed. (authors)

335

Static response and reliability analysis of structural systems with random and interval properties  

Science.gov (United States)

This paper presents the displacement, stress and reliability analysis of structures with a mixture of random and interval parameters under uncertain static loads. The structural displacement and stress responses are random interval variables when some structural parameters/loads are modelled as random variables and others are considered as intervals. The random interval perturbation method and random interval moment method are employed to predict the random interval structural response. The structural reliability is not a deterministic value but an interval as the structural responses are random interval variables. The expressions for lower and upper bounds of reliability index, probability of failure and reliability of structural elements and systems are then developed by using the combination of the structural reliability theory and interval approach. Truss and frame structures are used as examples to demonstrate the validity and feasibility of the presented methods. The probabilistic and interval characteristics of structural static response and reliability are investigated and some useful conclusions are given.

Gao, Wei; Song, Chongmin; Tin-Loi, Francis

2010-06-01

336

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

337

Reliability analysis of fault-tolerant reconfigurable nano-architectures  

Energy Technology Data Exchange (ETDEWEB)

Manufacturing defects and transient errors will be abundant in high - density reconfigurable nano-scale designs. Recently, we have automated a computational scheme based on Markov Random Field (MRF) and Belief Propagation algorithms in a tool named NANOLAB to evaluate the reliability of nano architectures. In this paper, we show how our methodology can be exploited to design defect- and fault-tolerant programmable logic architectures. The effectiveness of such automation is illustrated by analyzing reconfigurable Boolean networks formed using different industry-based configurable logic blocks (CLBs), both in the presence of thermal perturbations and signal noise.

Bhaduri, D. (Debayan); Graham, P. S. (Paul S.); Shukla, S. K. (Sandeep K.)

2004-01-01

338

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

International Nuclear Information System (INIS)

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

339

Determination of Weibull Analysis of the Hypereutectic Silumins Reliability in Failure Time Respect  

Directory of Open Access Journals (Sweden)

Full Text Available The results of dynamic evaluation of the reliability of hypereutectic AlSi17Cu3NiMg silumin under the effect of symmetrical cyclic tensile-compressive stresses were presented. Studies were carried out on a normal-running fatigue testing machine, which was the mechanically driven resonant pulsator. For the needs of quantitative reliability evaluation and the time-to-failure evaluation, the procedures used in survival analysis, adapted to the analysis of failure-free operation with two- and three-parametric Weibull distributions, were applied. The values of the parameters were estimated using the method of maximum reliability and a rank-based non-parametric method. The results of the evaluation of the reliability and damage intensity are an important element in the determination of casting quality and enable a reliable estimation of the operational suitability time.

J. Szymszal

2009-07-01

340

A case study on effectiveness of structural reliability analysis in nuclear reactor safety assessment  

International Nuclear Information System (INIS)

The problems regarding the structural reliability of nuclear reactors occupy an important position in various aspects of nuclear reactor safety. In the present paper, descriptions are given of a new effective method for the quantitative evaluation of structural reliability based on ''stress strength model''. The developed method, which can take larger number of factors into consideraion than ever and can give results within moderate computing time, is applied to the reliability analysis of PWR pressure vessel. Although analysis is within the scope of linear elastic fracture mechanics (LEFM), the results show the relative importance of inspection as well as the parameter uncertainty for assuring the reliability of the structure. Furthermore the case study shows the effectiveness of this method for not only the evaluation of structrual reliability for safety assessment of nuclear power plants in general but also the improvements of the consistency in the design code

341

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.

342

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)

343

QuickView video preview software of colon capsule endoscopy: reliability in presenting colorectal polyps as compared to normal mode reading.  

Science.gov (United States)

OBJECTIVE. Colon capsule endoscopy (CCE) proved to be highly sensitive in detection of colorectal polyps (CP). Major limitation is the time-consuming video reading. The aim of this prospective, double-center study was to assess the theoretical time-saving potential and its possible impact on the reliability of "QuickView" (QV), in the presentation of CP as compared to normal mode (NM). METHODS. During NM reading of 65 CCE videos (mean patient´s age 56 years), all frames showing CPs were collected and compared to the number of frames presented by QV at increasing QV settings (10, 20, ... 80%). Reliability of QV in presenting polyps <6 mm and ?6 mm (significant polyp), and identifying patients for subsequent therapeutic colonoscopy, capsule egestion rate, cleansing level, and estimated time-saving potential were assessed. RESULTS. At a 30% QV setting, the QV video presented 89% of the significant polyps and 86% of any polyps with ?1 frame (per-polyp analysis) identified in NM before. At a 10% QV setting, 98% of the 52 patients with significant polyps could be identified (per-patient analysis) by QV video analysis. Capsule excretion rate was 74% and colon cleanliness was adequate in 85%. QV´s presentation rate correlates to the QV setting, the polyp size, and the number of frames per finding. CONCLUSIONS. Depending on its setting, the reliability of QV in presenting CP as compared to NM reading is notable. However, if no significant polyp is presented by QV, NM reading must be performed afterwards. The reduction of frames to be analyzed in QV might speed up identification of candidates for therapeutic colonoscopy. PMID:24325660

Farnbacher, Michael J; Krause, Horst H; Hagel, Alexander F; Raithel, Martin; Neurath, Markus F; Schneider, Thomas

2014-03-01

344

Comparative reliability of nasal pharyngoscopy and videofluorography in the assessment of velopharyngeal incompetence.  

Science.gov (United States)

A panel of three has reviewed a series of 100 videotape records of nasopharyngoscopy, basal fluorography and lateral fluorography made of patients being investigated for velopharyngeal incompetence. The quality of each record was assessed and estimates of movement made as a basis for comparison of the three methods. Nasopharyngoscopy and lateral fluorography provide a high proportion of material with good definition of the velopharyngeal isthmus (80%). Basal fluorography is less reliable (60%). Lateral fluorography was found to be unreliable as a measure of velopharyngeal incompetence, while estimates of movement from the other two were compatible. Basal fluorography is the procedure of choice in young children. Nasendoscopy provides good quality information more often than basal fluorography in patients over the age of eight and is markedly superior in the presence of a pharyngeal flap. PMID:7082883

Sinclair, S W; Davies, D M; Bracka, A

1982-04-01

345

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

OpenAIRE

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 recruitment was all under graduated students from second semester at large university in Iran (both male and female) that study English as a compulsory ...

Seyed Hossein Fazeli

2010-01-01

346

Reliability sensitivity analysis based on probability distribution perturbation with application to CO2 storage  

OpenAIRE

The objective of reliability sensitivity analysis is to determine input variables that mostly contribute to the variability of the failure probability. In this paper, we study a recently introduced method for the reliability sensitivity analysis based on a perturbation of the original probability distribution of the input variables. The objective is to determine the most influential input variables and to analyze their impact on the failure probability. We propose a moment i...

Sergienko, Ekaterina; Lemai?tre, Paul; Arnaud, Aure?lie; Busby, Daniel; Gamboa, Fabrice

2013-01-01

347

Reliability and validity of match performance analysis in soccer :a multidimensional qualitative evaluation of opponent interaction  

OpenAIRE

Match performance analysis is widely used as a method for studying technical, tactical and physical aspects of player and team performance in a soccer match. Therefore, ensuring the validity and reliability of the collected data is important for match performance analysis to meet its intents and purposes effectively. However, most studies on soccer match performance use unidimensional frequency data based on analyses done in isolation from the match context. In addition, reliability studies r...

Tenga, Albin

2010-01-01

348

Reliability Assessment Based on Multivariate Degradation Measures and Competing Failure Analysis  

OpenAIRE

An reliability assessment model based on multivariate degradation measures and competing failure analysis is presented. The multi-dimensionality reduction processing has applied to multivariate degradation measures to extract the key features for ease of calculation. The cumulative distribution function of sudden failure is calculated in terms of degradation data rather than time domains, and the reliability assessment model based on competing failure analysis is established. An example of an...

Zhu Liang; Yan Jun; Haifeng Ling; Zhenglian Su

2011-01-01

349

Task analysis and computer aid development for human reliability analysis in nuclear power plants  

Energy Technology Data Exchange (ETDEWEB)

Importance of human reliability analysis (HRA) that predicts the error's occurrence possibility in a quantitative and qualitative manners is gradually increased by human errors' effects on the system's safety. HRA needs a task analysis as a virtue step, but extant task analysis techniques have the problem that a collection of information about the situation, which the human error occurs, depends entirely on HRA analyzers. The problem makes results of the task analysis inconsistent and unreliable. To complement such problem, KAERI developed the structural information analysis (SIA) that helps to analyze task's structure and situations systematically. In this study, the SIA method was evaluated by HRA experts, and a prototype computerized supporting system named CASIA (Computer Aid for SIA) was developed for the purpose of supporting to perform HRA using the SIA method. Additionally, through applying the SIA method to emergency operating procedures, we derived generic task types used in emergency and accumulated the analysis results in the database of the CASIA. The CASIA is expected to help HRA analyzers perform the analysis more easily and consistently. If more analyses will be performed and more data will be accumulated to the CASIA's database, HRA analyzers can share freely and spread smoothly his or her analysis experiences, and there by the quality of the HRA analysis will be improved. 35 refs., 38 figs., 25 tabs. (Author)

Yoon, W. C.; Kim, H.; Park, H. S.; Choi, H. H.; Moon, J. M.; Heo, J. Y.; Ham, D. H.; Lee, K. K.; Han, B. T. [Korea Advanced Institute of Science and Technology, Taejeon (Korea)

2001-04-01

350

Fundus camera systems: a comparative analysis.  

Science.gov (United States)

Retinal photography requires the use of a complex optical system, called a fundus camera, capable of illuminating and imaging the retina simultaneously. The patent literature shows two design forms but does not provide the specifics necessary for a thorough analysis of the designs to be performed. We have constructed our own designs based on the patent literature in optical design software and compared them for illumination efficiency, image quality, ability to accommodate for patient refractive error, and manufacturing tolerances, a comparison lacking in the existing literature. PMID:19137032

DeHoog, Edward; Schwiegerling, James

2009-01-10

351

Comparative Analysis of Virtual Education Applications  

OpenAIRE

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

352

Comparative Analysis of Hand Gesture Recognition Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available During past few years, human hand gesture for interaction with computing devices has continues to be active area of research. In this paper survey of hand gesture recognition is provided. Hand Gesture Recognition is contained three stages: Pre-processing, Feature Extraction or matching and Classification or recognition. Each stage contains different methods and techniques. In this paper define small description of different methods used for hand gesture recognition in existing system with comparative analysis of all method with its benefits and drawbacks are provided.

Arpana K. Patel

2015-03-01

353

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)

354

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

355

Availability analysis for high reliability computer systems in nuclear facilities  

International Nuclear Information System (INIS)

Availability, defined as the ratio of time a computer system is functioning normally to the total time it is in demand, is a measure of the overall accessibility to the system and its operational effectiveness. This ratio allows estimates of down time to be calculated for contingency planning. Single and multiple machine configurations are evaluated in terms of typical component values for mean time between failure (MTBF) and mean time to repair (MTTR), and the Availability of each configuration is computed. Through the use of interconnected, redundant processors with multiprogramming operating systems and all input data provided to each processor, down time for even failure prone units can be reduced from 781 to 32.3 hours per year. Several interconnection methods are shown with projected reliability data

356

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.

357

Reliablity analysis of gravity dams by response surface method  

Science.gov (United States)

A dam failure is one of the most important problems in dam industry. Since the mechanical behavior of dams is usually a complex phenomenon existing classical mathematical models are generally insufficient to adequately predict the dam failure and thus the safety of dams. Therefore, numerical reliability methods are often used to model such a complex mechanical phenomena. Thus, the main purpose of the present paper is to present the response surface method as a powerful mathematical tool used to study and foresee the dam safety considering a set of collected monitoring data. The derived mathematical model is applied to a case study, the Moste dam, which is the highest concrete gravity dam in Slovenia. Based on the derived model, the ambient/state variables are correlated with the dam deformation in order to gain a forecasting tool able to define the critical thresholds for dam management.

Humar, Nina; Kryžanowski, Andrej; Brilly, Mitja; Schnabl, Simon

2013-04-01

358

Reliability and replacement analysis of Great Lakes marine diesels  

Energy Technology Data Exchange (ETDEWEB)

A Colt-Pielstick PC2-400 series marine diesel engine has been used as a prototype for modeling. Parameters of Weibull and Exponential PDF's have been evaluated for seven vital system components: connecting rod bearing, cylinder head, cylinder jacket, cylinder liner and o-ring, cylinder piston, and fuel cam. Reliability and hazard functions for these itmes have been derived and discussed using both above PDF's. Reliability based models have bben developed and implemented to rationalize current winter layup replacement practices. Two systems have been considered: One for a ship equipped with one engine only and another for a two-engine ship. Howard's one-set competing process model has been implemented and extended to two sets of competing processes. A recursive iteration procedure has been used in the expected cost calculation. An efficient enumeration procedure has been presented to select the replacement policy which produces the minimum expected cost for an operating season. Computer codes have been developed using the above models, and several examples have been examined. The author has observed that current replacement practices are conservative. Results have also indicated that the total expected cost function changes almost linearly with time for these parameters. However, this linearity is very sensitive to the length of operating season. As far as replacement policies are concerned, there is a group of good replacement policies immediately following the best replacement policy; differences between the total expected costs resulting from these policies are not very significant for some cases within our parameter range.

Inoezue, B.

1990-01-01

359

Reliability analysis of a structural ceramic combustion chamber  

Science.gov (United States)

The Weibull modulus, fracture toughness and thermal properties of a silicon nitride material used to make a gas turbine combustor were experimentally measured. The location and nature of failure origins resulting from bend tests were determined with fractographic analysis. The measured Weibull parameters were used along with thermal and stress analysis to determine failure probabilities of the combustor with the CARES design code. The effect of data censoring, FEM mesh refinement, and fracture criterion were considered in the analysis.

Salem, Jonathan A.; Manderscheid, Jane M.; Freedman, Marc R.; Gyekenyesi, John P.

1991-01-01

360

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

361

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.

362

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

363

Inter comparison of REPAS and APSRA methodologies for passive system reliability analysis  

International Nuclear Information System (INIS)

The increasing use of passive systems in the innovative nuclear reactors puts demand on the estimation of the reliability assessment of these passive systems. The passive systems operate on the driving forces such as natural circulation, gravity, internal stored energy etc. which are moderately weaker than that of active components. Hence, phenomenological failures (virtual components) are equally important as that of equipment failures (real components) in the evaluation of passive systems reliability. The contribution of the mechanical components to the passive system reliability can be evaluated in a classical way using the available component reliability database and well known methods. On the other hand, different methods are required to evaluate the reliability of processes like thermohydraulics due to lack of adequate failure data. The research is ongoing worldwide on the reliability assessment of the passive systems and their integration into PSA, however consensus is not reached. Two of the most widely used methods are Reliability Evaluation of Passive Systems (REPAS) and Assessment of Passive System Reliability (APSRA). Both these methods characterize the uncertainties involved in the design and process parameters governing the function of the passive system. However, these methods differ in the quantification of passive system reliability. Inter comparison among different available methods provides useful insights into the strength and weakness of different methods. This paper highlights the results of the thermal hydraulic analysis of a typical passive isolation condenser system carried out using RELAP mode 3.2 computer code applying REPAS and APSRA methodologies. The failure surface is established for the passive system under consideration and system reliability has also been evaluated using these methods. Challenges involved in passive system reliabilities are identified, which require further attention in order to overcome the shortcomings of these methods. These procedures can then be applied for evaluating passive system reliability, which would be used in risk-informed decision-making. (author)

364

The Centralized Reliability Data Organization (CREDO); an advanced nuclear reactor reliability, availability, and maintainability data bank and data analysis center  

International Nuclear Information System (INIS)

The Centralized Reliability Data Organization (CREDO) is a data bank and data analysis center, which since 1985 has been jointly sponsored by the US Department of Energy's (US DOE's) Office of Technology Support Programs and Japan's Power Reactor and Nuclear Fuel Development Corporation (PNC). It focuses on reliability, availability and maintainability (RAM) data for components (e.g. valves, pumps, etc.) operating in advanced nuclear reactor facilities. As originally intended, the purpose of the CREDO system was to provide a centralized source of accurate, up-to-date data and information for use in RAM analyses necessary for meeting DOE's data needs in the areas of advanced reactor safety assessments, design and licensing. In particular, creation of the CREDO system was considered an essential element needed to fulfill the DOE Breeder Reactor Safety Program's commitment of 'identifying and exploiting areas in which probabilistic methods can be developed and used in making reactor safety Research and Development choices and optimizing designs of safety systems'. CREDO and its operation are explained. (author)

365

Markov Chains and reliability analysis for reinforced concrete structure service life  

Scientific Electronic Library Online (English)

Full Text Available 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

366

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

367

DATA ANALYSIS METHODS AND THE RELIABILITY OF ANALYTIC EPIDEMIOLOGIC RESEARCH  

OpenAIRE

Publications that compare randomized controlled trial and cohort study results on the effects of postmenopausal estrogen plus progestin therapy are reviewed. The 2 types of studies agree in identifying an early elevation in coronary heart disease (CHD) risk, and a later — developing elevation in breast cancer risk. Effects among women who begin hormone therapy within a few years following the menopause may be comparatively more favorable for CHD and less favorable for breast cancer. These a...

Prentice, Ross L.

2008-01-01

368

Finite State Machine Based Evaluation Model for Web Service Reliability Analysis  

CERN Document Server

Now-a-days they are very much considering about the changes to be done at shorter time since the reaction time needs are decreasing every moment. Business Logic Evaluation Model (BLEM) are the proposed solution targeting business logic automation and facilitating business experts to write sophisticated business rules and complex calculations without costly custom programming. BLEM is powerful enough to handle service manageability issues by analyzing and evaluating the computability and traceability and other criteria of modified business logic at run time. The web service and QOS grows expensively based on the reliability of the service. Hence the service provider of today things that reliability is the major factor and any problem in the reliability of the service should overcome then and there in order to achieve the expected level of reliability. In our paper we propose business logic evaluation model for web service reliability analysis using Finite State Machine (FSM) where FSM will be extended to analy...

M, Thirumaran; Abarna, S; P, Lakshmi

2011-01-01

369

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

370

Reliability analysis of microcomputer circuit modules and computer based control systems important to safety of nuclear power plants  

Energy Technology Data Exchange (ETDEWEB)

Computer based safety related control and instrumentation (C and I) systems are being employed in Indian Nuclear Power Plants (NPPs). These systems are designed around standardized family of microcomputer based circuit modules, which are qualified to the stringent requirements of the nuclear industry. Reliability analysis of standardized microcomputer circuit modules, used in the safety related C and I systems, were carried out using the analysis package based on the methodology and database of MIL-STD-217-F1. The circuit modules are the main building blocks of the safety related C and I systems in the forthcoming Indian NPPs. The article presents reliability analysis results of microcomputer and related circuit modules and a representative safety C and I system-Programmable Digital Comparator System (PDCS). Comparison of reliability values for prototype PDCS using commercial grade components, and for upgraded version PDCS using MIL grade or equivalent screened components was made. The estimated failure rate values of standardized microcomputer circuit modules will be useful, for reliability assessment of various other safety related C and I systems developed around these modules, for ongoing and future Indian NPPs.

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

1998-02-01

371

Measuring, using, and reducing experimental and computational uncertainty in reliability analysis of composite laminates  

Science.gov (United States)

The failure of the composite hydrogen tanks on the X-33 Reusable Launch Vehicle (RLV) from combined thermal and mechanical failure modes created a situation where the design weight was highly sensitive to uncertainties. Through previous research of sensitivity and reliability analysis on this problem, three areas of potential uncertainty reduction were recognized and became the focal points for this dissertation. The transverse elastic modulus and coefficient of thermal expansion were cited as being particularly sensitive input parameters with respect to weight. Measurement uncertainty analysis was performed on transverse modulus experiments, where the intermediate thickness measurements proved to be the greatest contributor to uncertainty. Data regarding correlations in the material properties of composite laminates is not always available, however the significance of correlated properties on probability of failure was detected. Therefore, a model was developed for correlations in composite properties based on micromechanics, specifically fiber volume fraction. The correlations from fiber volume fraction were combined with experimental data to give an estimate of the complete uncertainty, including material variability and measurement error. The probability of failure was compared for correlated material properties and independent random variables in an example pressure vessel problem. Including the correlations had a significant effect on the failure probability, however being unsafe or inefficient can depend on the material system. Reliability-based design simulations often use the traditional, crude Monte Carlo method as a sampling procedure for predicting failure. The combination of designing for very small failure probabilities and (˜10-8 - 10-6) and using computational expensive finite element models, makes traditional Monte Carlo very costly. The separable Monte Carlo method, which is an extension of conditional expectation, takes advantage of statistical independence of the limit state random variables of the response and capacity for improved accuracy in reliability calculations. The separation of response and capacity sampling enables flexible sample sizes, permitting low samples of the more expensive component (usually the response). In turn, this motivates the beneficial reallocation of uncertainty by reformulating the limit state. The variance estimator was derived for separable Monte Carlo and three example problems were used to compare the Monte Carlo methods. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

Smarslok, Benjamin P.

372

Construction QA/QC systems: comparative analysis  

International Nuclear Information System (INIS)

An analysis which compares the quality assurance/quality control (QA/QC) systems adopted in the highway, nuclear power plant, and U.S. Navy construction areas with the traditional quality control approach used in building construction is presented. Full participation and support by the owner as well as the contractor and AE firm are required if a QA/QC system is to succeed. Process quality control, acceptance testing and quality assurance responsibilities must be clearly defined in the contract documents. The owner must audit these responsibilities. A contractor quality control plan, indicating the tasks which will be performed and the fact that QA/QC personnel are independent of project time/cost pressures should be submitted for approval. The architect must develop realistic specifications which consider the natural variability of material. Acceptance criteria based on the random sampling technique should be used. 27 refs

373

Comparative Genome Analysis of Basidiomycete Fungi  

Energy Technology Data Exchange (ETDEWEB)

Fungi of the phylum Basidiomycota (basidiomycetes), make up some 37percent of the described fungi, and are important in forestry, agriculture, medicine, and bioenergy. This diverse phylum includes the mushrooms, wood rots, symbionts, and plant and animal pathogens. To better understand the diversity of phenotypes in basidiomycetes, we performed a comparative analysis of 35 basidiomycete fungi spanning the diversity of the phylum. Phylogenetic patterns of lignocellulose degrading genes suggest a continuum rather than a sharp dichotomy between the white rot and brown rot modes of wood decay. Patterns of secondary metabolic enzymes give additional insight into the broad array of phenotypes found in the basidiomycetes. We suggest that the profile of an organism in lignocellulose-targeting genes can be used to predict its nutritional mode, and predict Dacryopinax sp. as a brown rot; Botryobasidium botryosum and Jaapia argillacea as white rots.

Riley, Robert; Salamov, Asaf; Morin, Emmanuelle; Nagy, Laszlo; Manning, Gerard; Baker, Scott; Brown, Daren; Henrissat, Bernard; Levasseur, Anthony; Hibbett, David; Martin, Francis; Grigoriev, Igor

2012-03-19

374

Comparative Analysis on Visual Cryptographic Schemes?  

Directory of Open Access Journals (Sweden)

Full Text Available Visual cryptography is the techniques that deal with providing security to the multimedia data. The main concept behind this is, to encrypt a secret image into some shares. The secret can be revealed only when all the shares are combined. The central theme of visual cryptography is that it doesn’t require any manipulation or tough cryptographic knowledge and the decryption is done by human vision without the help of computers. Thus, visual cryptography is known for its least computational complexity yet much secure. In this work, we compared traditional visual cryptography, extended visual cryptography and colour extended cryptography with respect to PSNR, NCC and MSE. On analysis, it is found that the performance of colour extended visual cryptography is much better than the traditional visual cryptography and extended visual cryptography, in terms of Peak Signal to Noise Ratio (PSNR, Normalized Correlation Coefficient (NCC and Mean Square Error (MSE.

T. Anuradha

2014-09-01

375

Report on the analysis of field data relating to the reliability of solar hot water systems.  

Energy Technology Data Exchange (ETDEWEB)

Utilities are overseeing the installations of thousand of solar hot water (SHW) systems. Utility planners have begun to ask for quantitative measures of the expected lifetimes of these systems so that they can properly forecast their loads. This report, which augments a 2009 reliability analysis effort by Sandia National Laboratories (SNL), addresses this need. Additional reliability data have been collected, added to the existing database, and analyzed. The results are presented. Additionally, formal reliability theory is described, including the bathtub curve, which is the most common model to characterize the lifetime reliability character of systems, and for predicting failures in the field. Reliability theory is used to assess the SNL reliability database. This assessment shows that the database is heavily weighted with data that describe the reliability of SHW systems early in their lives, during the warranty period. But it contains few measured data to describe the ends of SHW systems lives. End-of-life data are the most critical ones to define sufficiently the reliability of SHW systems in order to answer the questions that the utilities pose. Several ideas are presented for collecting the required data, including photometric analysis of aerial photographs of installed collectors, statistical and neural network analysis of energy bills from solar homes, and the development of simple algorithms to allow conventional SHW controllers to announce system failures and record the details of the event, similar to how aircraft black box recorders perform. Some information is also presented about public expectations for the longevity of a SHW system, information that is useful in developing reliability goals.

Menicucci, David F. (Building Specialists, Inc., Albuquerque, NM)

2011-07-01

376

Reliability analysis of the shutdown heat removal system for the conceptual design study  

International Nuclear Information System (INIS)

The 1000 MW(e) LMFBR Development Plant Design is being developed under DOE sponsored Conceptual Design Studies (CDS). A reliability assessment of the CDS Shutdown Heat Removal System (SHRS) was performed. The assessment is an examination of the Normal Heat Removal System (NHRS) and two independent Dedicated Heat Removal Systems (DHRS) selected for use in CDS. By applying reliability concepts and methodology, the annual probability of SHRS failure was calculated and compared with established goals. 1 ref

377

Technology development of maintenance optimization and reliability analysis for safety features in nuclear power plants  

Energy Technology Data Exchange (ETDEWEB)

The reliability data management system (RDMS) for safety systems of PHWR type plants has been developed and utilized in the reliability analysis of the special safety systems of Wolsong Unit 1,2 with plant overhaul period lengthened. The RDMS is developed for the periodic efficient reliability analysis of the safety systems of Wolsong Unit 1,2. In addition, this system provides the function of analyzing the effects on safety system unavailability if the test period of a test procedure changes as well as the function of optimizing the test periods of safety-related test procedures. The RDMS can be utilized in handling the requests of the regulatory institute actively with regard to the reliability validation of safety systems. (author)

Kim, Tae Woon; Choi, Seong Soo; Lee, Dong Gue; Kim, Young Il

1999-12-01

378

An application of the fault tree analysis for the power system reliability estimation  

International Nuclear Information System (INIS)

The power system is a complex system with its main function to produce, transfer and provide consumers with electrical energy. Combinations of failures of components in the system can result in a failure of power delivery to certain load points and in some cases in a full blackout of power system. The power system reliability directly affects safe and reliable operation of nuclear power plants because the loss of offsite power is a significant contributor to the core damage frequency in probabilistic safety assessments of nuclear power plants. The method, which is based on the integration of the fault tree analysis with the analysis of the power flows in the power system, was developed and implemented for power system reliability assessment. The main contributors to the power system reliability are identified, both quantitatively and qualitatively. (author)

379

Model of the reliability analysis of the distributed computer systems with architecture "client-server"  

Science.gov (United States)

The paper considers the problem of the analysis of distributed computer systems reliability with client-server architecture. A distributed computer system is a set of hardware and software for implementing the following main functions: processing, storage, transmission and data protection. This paper discusses the distributed computer systems architecture "client-server". The paper presents the scheme of the distributed computer system functioning represented as a graph where vertices are the functional state of the system and arcs are transitions from one state to another depending on the prevailing conditions. In reliability analysis we consider such reliability indicators as the probability of the system transition in the stopping state and accidents, as well as the intensity of these transitions. The proposed model allows us to obtain correlations for the reliability parameters of the distributed computer system without any assumptions about the distribution laws of random variables and the elements number in the system.

Kovalev, I. V.; Zelenkov, P. V.; Karaseva, M. V.; Tsarev, M. Yu; Tsarev, R. Yu

2015-01-01

380

Technology development of maintenance optimization and reliability analysis for safety features in nuclear power plants  

International Nuclear Information System (INIS)

The reliability data management system (RDMS) for safety systems of PHWR type plants has been developed and utilized in the reliability analysis of the special safety systems of Wolsong Unit 1,2 with plant overhaul period lengthened. The RDMS is developed for the periodic efficient reliability analysis of the safety systems of Wolsong Unit 1,2. In addition, this system provides the function of analyzing the effects on safety system unavailability if the test period of a test procedure changes as well as the function of optimizing the test periods of safety-related test procedures. The RDMS can be utilized in handling the requests of the regulatory institute actively with regard to the reliability validation of safety systems. (author)

381

Reliability Analysis Modeling of ITER Tritium Storage and Delivery System at Conceptual Design Stage  

International Nuclear Information System (INIS)

ITER tokamak uses tritium and deuterium as fuel for nuclear fusion reaction, and handles largest amount tritium ever. For this reason, RAMI analysis of tritium storage and delivery system (SDS) design is important to review the reliability and availability of the system and improve design balance. The main purpose of SDS is to store and supply the gases needed for operation of ITER machine and to provide the necessary infrastructure for short and long term storage of large amounts of tritium. The SDS handles T2, D2(T), D2 and inactive gases in parallel independent to each gases. In this paper the reliability modeling of conceptual design of ITER SDS and consists of functional breakdown of Tritium SDS, reliability data base of tritium component/system and reliability block diagram and analysis model

382

Methodological Approach for Performing Human Reliability and Error Analysis in Railway Transportation System  

Directory of Open Access Journals (Sweden)

Full Text Available Today, billions of dollars are being spent annually world wide to develop, manufacture, and operate transportation system such trains, ships, aircraft, and motor vehicles. Around 70 to 90 percent oftransportation crashes are, directly or indirectly, the result of human error. In fact, with the development of technology, system reliability has increased dramatically during the past decades, while human reliability has remained unchanged over the same period. Accordingly, human error is now considered as the most significant source of accidents or incidents in safety-critical systems. The aim of the paper is the proposal of a methodological approach to improve the transportation system reliability and in particular railway transportation system. The methodology presented is based on Failure Modes, Effects and Criticality Analysis (FMECA and Human Reliability Analysis (HRA.

Fabio De Felice

2011-10-01

383

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

384

Reliability- and safety analysis of activity measuring systems  

International Nuclear Information System (INIS)

The monitoring system at the Forsmark reactor in Sweden is examined. The analysis shows that the probability of an inhibited function within a reactors life-time (30y) is 0.0113, if the demand for alarm is taken to be 0.1/y

385

Comprehensive reliability allocation method for CNC lathes based on cubic transformed functions of failure mode and effects analysis  

Science.gov (United States)

Reliability allocation of computerized numerical controlled(CNC) lathes is very important in industry. Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components, which is not applicable in some conditions. Aiming at solving the problem of CNC lathes reliability allocating, a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis(FMEA) is presented. Firstly, conventional reliability allocation methods are introduced. Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated. Subsequently, a cubic transformed function is established in order to overcome these limitations. Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence. Designers can choose appropriate transform amplitudes according to their requirements. Finally, a CNC lathe and a spindle system are used as an example to verify the new allocation method. Seven criteria are considered to compare the results of the new method with traditional methods. The allocation results indicate that the new method is more flexible than traditional methods. By employing the new cubic transformed function, the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.

Yang, Zhou; Zhu, Yunpeng; Ren, Hongrui; Zhang, Yimin

2015-02-01

386

Comprehensive reliability allocation method for CNC lathes based on cubic transformed functions of failure mode and effects analysis  

Science.gov (United States)

Reliability allocation of computerized numerical controlled(CNC) lathes is very important in industry. Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components, which is not applicable in some conditions. Aiming at solving the problem of CNC lathes reliability allocating, a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis(FMEA) is presented. Firstly, conventional reliability allocation methods are introduced. Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated. Subsequently, a cubic transformed function is established in order to overcome these limitations. Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence. Designers can choose appropriate transform amplitudes according to their requirements. Finally, a CNC lathe and a spindle system are used as an example to verify the new allocation method. Seven criteria are considered to compare the results of the new method with traditional methods. The allocation results indicate that the new method is more flexible than traditional methods. By employing the new cubic transformed function, the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.

Yang, Zhou; Zhu, Yunpeng; Ren, Hongrui; Zhang, Yimin

2015-03-01

387

Confirmatory Factor Analysis and Test-Retest Reliability of the Alcohol and Drug Confrontation Scale (ADCS)  

OpenAIRE

The addiction field lacks an accepted definition and reliable measure of confrontation. The Alcohol and Drug Confrontation Scale (ADCS) defines confrontation as warnings about the potential consequences of substance use. To assess psychometric properties, 323 individual entering recovery houses in U.S. urban and suburban areas were interviewed between 2003 and 2005 (20% women, 68% white). Analyses included test-retest reliability, confirmatory factor analysis, and measures of internal consist...

Polcin, Douglas L.; Galloway, Gantt P.; Bond, Jason; Korcha, Rachael; Greenfield, Thomas K.

2009-01-01

388

Adjoint sensitivity analysis of dynamic reliability models based on Markov chains - I: Theory  

International Nuclear Information System (INIS)

The development of the adjoint sensitivity analysis procedure (ASAP) for generic dynamic reliability models based on Markov chains is presented, together with applications of this procedure to the analysis of several systems of increasing complexity. The general theory is presented in Part I of this work and is accompanied by a paradigm application to the dynamic reliability analysis of a simple binary component, namely a pump functioning on an 'up/down' cycle until it fails irreparably. This paradigm example admits a closed form analytical solution, which permits a clear illustration of the main characteristics of the ASAP for Markov chains. In particular, it is shown that the ASAP for Markov chains presents outstanding computational advantages over other procedures currently in use for sensitivity and uncertainty analysis of the dynamic reliability of large-scale systems. This conclusion is further underscored by the large-scale applications presented in Part II. (authors)

389

Study on quantitative reliability analysis by multilevel flow models for nuclear power plants  

International Nuclear Information System (INIS)

Multilevel Flow Models (MFM) is a goal-oriented system modeling method. MFM explicitly describes how a system performs the required functions under stated conditions for a stated period of time. This paper presents a novel system reliability analysis method based on MFM (MRA). The proposed method allows describing the system knowledge at different levels of abstraction which makes the reliability model easy for understanding, establishing, modifying and extending. The success probabilities of all main goals and sub-goals can be available by only one-time quantitative analysis. The proposed method is suitable for the system analysis and scheme comparison for complex industrial systems such as nuclear power plants. (authors)

390

Problems Related to Use of Some Terms in System Reliability Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with problems of using dependability terms, defined in actual standard STN IEC 50 (191: International electrotechnical dictionary, chap. 191: Dependability and quality of service (1993, in a technical systems dependability analysis. The goal of the paper is to find a relation between terms introduced in the mentioned standard and used in the technical systems dependability analysis and rules and practices used in a system analysis of the system theory. Description of a part of the system life cycle related to reliability is used as a starting point. The part of a system life cycle is described by the state diagram and reliability relevant therms are assigned.

Nadezda Hanusova

2004-01-01

391

Analysis of strain gage reliability in F-100 jet engine testing at NASA Lewis Research Center  

Science.gov (United States)

A reliability analysis was performed on 64 strain gage systems mounted on the 3 rotor stages of the fan of a YF-100 engine. The strain gages were used in a 65 hour fan flutter research program which included about 5 hours of blade flutter. The analysis was part of a reliability improvement program. Eighty-four percent of the strain gages survived the test and performed satisfactorily. A post test analysis determined most failure causes. Five failures were caused by open circuits, three failed gages showed elevated circuit resistance, and one gage circuit was grounded. One failure was undetermined.

Holanda, R.

1983-01-01

392

Safe product design - the role of the NDE reliability analysis  

OpenAIRE

When pushed to the limits of their detection capability, NDE systems do not produce consistent hit/miss indications. Their capability of detecting small defects is therefore expressed in terms of POD. An adequate NDE system is required to ensure the structural integrity. In conventional signal response analysis, the POD is expressed as a function of the defect size, and its adequacy for the inspection task is tested against the maximum allowable defect size which will not undermine the struct...

Pavlovic, Mato; Ronneteg, Ulf; Mu?ller, Christina; Ewert, Uwe; Boller, Christian

2012-01-01

393

Analysis of threaded connection reliability for compression applications  

Energy Technology Data Exchange (ETDEWEB)

An investigation and evaluation of the performance and life expectancy of NPT threaded connections as applied to a particular type of reciprocating compressor unit was presented in this paper. The study provided an assessment of the levels of excitation forces acting on the threaded connections and the resulting stress that were determined from field vibration measurement results applied to a mechanical model of the system. The paper described several aspects of the study, including the literature survey; acoustical analysis; mechanical analysis; field measurements; and fatigue limit assessment. The paper also discussed the methodology that included concurrent streams of field measurements, engineering analysis and quality control assessment. Results and recommendations were also presented with reference to minor changes to the support design, improvements to the documentation, as well as the implementation of a quality control program. It was concluded that the recommendations were meant to ensure a consistent product by monitoring the threads on the piping system and its proper assembly. 10 refs., 6 figs.

Alves, P.; Forcinito, M.; Xu, J.; Ferguson, M. [AP Dynamics, Calgary, AB (Canada); Tardif, P. [BP America, Houston, TX (United States); Jensen, P. [BP Canada Energy Company, Calgary, AB (Canada)

2008-07-01

394

Analysis of complete logical structures in system reliability assessment  

International Nuclear Information System (INIS)

The application field of the fault-tree techniques has been explored in order to assess whether the AND-OR structures covered all possible actual binary systems. This resulted in the identification of various situations requiring the complete AND-OR-NOT structures for their analysis. We do not use the term non-coherent for such cases, since the monotonicity or not of a structure function is not a characteristic of a system, but of the particular top event being examined. The report presents different examples of complete fault-trees, which can be examined according to different degrees of approximation. In fact, the exact analysis for the determination of the smallest irredundant bases is very time consuming and actually necessary only in some particular cases (multi-state systems, incidental situations). Therefore, together with the exact procedure, the report shows two different methods of logical analysis that permit the reduction of complete fault-trees to AND-OR structures. Moreover, it discusses the problems concerning the evaluation of the probability distribution of the time to first top event occurrence, once the hypothesis of structure function monotonicity is removed

395

A review of the reliability analysis of LPRS including the components repairs  

International Nuclear Information System (INIS)

The reliability analysis of low pressure recirculation system in its long-term recicurlation phase before 24hs is presented. The possibility of repairing the components out of the containment is included. A general revision of analysis of the short-term recirculation phase is done. (author)

396

Reliability analysis of idealized tunnel support system using probability-based methods with case studies  

Science.gov (United States)

In order to determine the overall safety of a tunnel support lining, a reliability-based approach is presented in this paper. Support elements in jointed rock tunnels are provided to control the ground movement caused by stress redistribution during the tunnel drive. Main support elements contribute to stability of the tunnel structure are recognized owing to identify various aspects of reliability and sustainability in the system. The selection of efficient support methods for rock tunneling is a key factor in order to reduce the number of problems during construction and maintain the project cost and time within the limited budget and planned schedule. This paper introduces a smart approach by which decision-makers will be able to find the overall reliability of tunnel support system before selecting the final scheme of the lining system. Due to this research focus, engineering reliability which is a branch of statistics and probability is being appropriately applied to the field and much effort has been made to use it in tunneling while investigating the reliability of the lining support system for the tunnel structure. Therefore, reliability analysis for evaluating the tunnel support performance is the main idea used in this research. Decomposition approaches are used for producing system block diagram and determining the failure probability of the whole system. Effectiveness of the proposed reliability model of tunnel lining together with the recommended approaches is examined using several case studies and the final value of reliability obtained for different designing scenarios. Considering the idea of linear correlation between safety factors and reliability parameters, the values of isolated reliabilities determined for different structural components of tunnel support system. In order to determine individual safety factors, finite element modeling is employed for different structural subsystems and the results of numerical analyses are obtained in different design scenarios. Finally, the reliability index values are obtained for the entire support structure in different design scenarios. The results of the work demonstrates that proposed reliability evaluation method of tunnel support system is effective not only for investigating the reliability of individual elements in the structure, but also for building an overall estimation about reliability performance of the entire tunnel structure.

Gharouni-Nik, Morteza; Naeimi, Meysam; Ahadi, Sodayf; Alimoradi, Zahra

2014-06-01

397

System reliability analysis via generalized perturbation theory methods  

International Nuclear Information System (INIS)

In the probabilistic analysis of systems, a key point is identification of the important components. Such identification is in fact required in assisting the analyst to find weaknesses in design and operation and in suggesting optimal modifications for system upgrade. A number of methods have been suggested so far to evaluate the importance of basic components, generally based on the well-known Birnbaum's importance concept. A sensitivity methodology, mainly concerned with basic component parameters, is proposed here in relation to the Markov chain model and based on importance concepts widely used so far in nuclear reactor physics

398

Comparative performance analysis of agro-ecosystems  

OpenAIRE

Detailed and reliable information on land use systems, as needed for quantitative studies, is scarce and often of low quality. This calls for (guidelines on) data harmonization. Practical concepts to describe and study land use are discussed; the development of the Land Use Database software was instrumental in defining them. Required is that by plot, information on land use purpose(s), on operations and on observations as made by land users is put on record through interviews. To classify la...

Bie, C. A. J. M.

2000-01-01

399

Comparative metagenome analysis of an Alaskan glacier.  

Science.gov (United States)

The temperature in the Arctic region has been increasing in the recent past accompanied by melting of its glaciers. We took a snapshot of the current microbial inhabitation of an Alaskan glacier (which can be considered as one of the simplest possible ecosystems) by using metagenomic sequencing of 16S rRNA recovered from ice/snow samples. Somewhat contrary to our expectations and earlier estimates, a rich and diverse microbial population of more than 2,500 species was revealed including several species of Archaea that has been identified for the first time in the glaciers of the Northern hemisphere. The most prominent bacterial groups found were Proteobacteria, Bacteroidetes, and Firmicutes. Firmicutes were not reported in large numbers in a previously studied Alpine glacier but were dominant in an Antarctic subglacial lake. Representatives of Cyanobacteria, Actinobacteria and Planctomycetes were among the most numerous, likely reflecting the dependence of the ecosystem on the energy obtained through photosynthesis and close links with the microbial community of the soil. Principal component analysis (PCA) of nucleotide word frequency revealed distinct sequence clusters for different taxonomic groups in the Alaskan glacier community and separate clusters for the glacial communities from other regions of the world. Comparative analysis of the community composition and bacterial diversity present in the Byron glacier in Alaska with other environments showed larger overlap with an Arctic soil than with a high Arctic lake, indicating patterns of community exchange and suggesting that these bacteria may play an important role in soil development during glacial retreat. PMID:24712530

Choudhari, Sulbha; Lohia, Ruchi; Grigoriev, Andrey

2014-04-01

400

Comparative genomic analysis of prion genes  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The homologues of human disease genes are expected to contribute to better understanding of physiological and pathogenic processes. We made use of the present availability of vertebrate genomic sequences, and we have conducted the most comprehensive comparative genomic analysis of the prion protein gene PRNP and its homologues, shadow of prion protein gene SPRN and doppel gene PRND, and prion testis-specific gene PRNT so far. Results While the SPRN and PRNP homologues are present in all vertebrates, PRND is known in tetrapods, and PRNT is present in primates. PRNT could be viewed as a TE-associated gene. Using human as the base sequence for genomic sequence comparisons (VISTA, we annotated numerous potential cis-elements. The conserved regions in SPRNs harbour the potential Sp1 sites in promoters (mammals, birds, C-rich intron splicing enhancers and PTB intron splicing silencers in introns (mammals, birds, and hsa-miR-34a sites in 3'-UTRs (eutherians. We showed the conserved PRNP upstream regions, which may be potential enhancers or silencers (primates, dog. In the PRNP 3'-UTRs, there are conserved cytoplasmic polyadenylation element sites (mammals, birds. The PRND core promoters include highly conserved CCAAT, CArG and TATA boxes (mammals. We deduced 42 new protein primary structures, and performed the first phylogenetic analysis of all vertebrate prion genes. Using the protein alignment which included 122 sequences, we constructed the neighbour-joining tree which showed four major clusters, including shadoos, shadoo2s and prion protein-likes (cluster 1, fish prion proteins (cluster 2, tetrapode prion proteins (cluster 3 and doppels (cluster 4. We showed that the entire prion protein conformationally plastic region is well conserved between eutherian prion proteins and shadoos (18–25% identity and 28–34% similarity, and there could be a potential structural compatibility between shadoos and the left-handed parallel beta-helical fold. Conclusion It is likely that the conserved genomic elements identified in this analysis represent bona fide cis-elements. However, this idea needs to be confirmed by functional assays in transgenic systems.

Gamulin Vera

2007-01-01

401

Stochastic Response and Reliability Analysis of Hysteretic Structures  

DEFF Research Database (Denmark)

During the last 30 years response analysis of structures under random excitation has been studied in detail. These studies are motivated by the fact that most of natures excitations, such as earthquakes, wind and wave loads exhibit randomly fluctuating characters. For safety reasons this randomness must be considered by the designers of structures like tall buildings, off-shore structures,ships etc. The response of a structure is generally uncertain due to the uncertainty of the geometrical and physical parameters determining the system, the uncertainty of the excitation and the imperfections of the adapted mathematical model from which the structural response is determined. In general emphasis will be placed on applications of the various methods introduced rather on questions concerning the excistence and uniqueness of solutions.

MØrk, Kim JØrgensen

1989-01-01

402

Modelling of nuclear power plant control and instrumentation elements for automatic disturbance and reliability analysis  

International Nuclear Information System (INIS)

Present Final Report summarizes results of R/D work done within IAEA-VEIKI (Institute for Electrical Power Research, Budapest, Hungary) Research Contract No. 3210 during 3 years' period of 01.08.1982 - 31.08.1985. Chapter 1 lists main research objectives of the project. Main results obtained are summarized in Chapters 2 and 3. Outcomes from development of failure modelling methodologies and their application for C/I components of WWER-440 units are as follows (Chapter 2): improvement of available ''failure mode and effect analysis'' methods and mini-fault tree structures usable for automatic disturbance (DAS) and reliability (RAS) analysis; general classification and determination of functional failure modes of WWER-440 NPP C/I components; set up of logic models for motor operated control valves and rod control/drive mechanism. Results of development of methods and their application for reliability modelling of NPP components and systems cover (Chapter 3): development of an algorithm (computer code COMPREL) for component-related failure and reliability parameter calculation; reliability analysis of PAKS II NPP diesel system; definition of functional requirements for reliability data bank (RDB) in WWER-440 units. Determination of RDB input/output data structure and data manipulation services. Methods used are a-priori failure mode and effect analysis, combined fault tree/event tree modelling technique, structural computer programming, probability theory application to nuclear field

403

Comparative analysis of safety related site characteristics  

Energy Technology Data Exchange (ETDEWEB)

This document presents a comparative analysis of site characteristics related to long-term safety for the two candidate sites for a final repository for spent nuclear fuel in Forsmark (municipality of Oesthammar) and in Laxemar (municipality of Oskarshamn) from the point of view of site selection. The analyses are based on the updated site descriptions of Forsmark /SKB 2008a/ and Laxemar /SKB 2009a/, together with associated updated repository layouts and designs /SKB 2008b and SKB 2009b/. The basis for the comparison is thus two equally and thoroughly assessed sites. However, the analyses presented here are focussed on differences between the sites rather than evaluating them in absolute terms. The document serves as a basis for the site selection, from the perspective of long-term safety, in SKB's application for a final repository. A full evaluation of safety is made for a repository at the selected site in the safety assessment SR-Site /SKB 2011/, referred to as SR-Site main report in the following

Andersson, Johan (ed.)

2010-12-15

404

Analysis of the WWER-440 pressure control system and the core thermal reliability  

International Nuclear Information System (INIS)

Pressure deviations affect significanty the reactor core thermal reliability and it is of practical interest to analyze the reasons for these deviations. The paper presents a fault tree analysis of the pressurizer system during normal operation and a thermal reliability analysis of the reactor core. The TENAZ code is used for thermal reliability analysis assuming maximal deviation of 1% in the core inlet temperature, 4% in the local thermal power density, 20% in the reactor power output and 5% in the effect of corrosion products on the CHF ratio. Calculation results illustrate the dependence of the amplifying factors on the heat flux when various CHF correlations are used, and the fault probability vs the maximal heat flux at various deviations in the core inlet pressure

405

Reliability analysis of non-linear reinforced concrete frames using the response surface method  

International Nuclear Information System (INIS)

In this paper, a formulation to compute the reliability of reinforced concrete structures, in which physical and geometrical non-linearities are taken into account, is described. The adopted non-linear model allows the representation of the mechanical behaviour of concrete structures at the failure stage, which is governed by possible large displacement effects, softening behaviour of concrete and tension stiffening effects. On the other hand, the reliability model is based on adaptive failure surfaces representing the mechanical model responses. The failure surface is obtained by fitting the internal force ultimate state of the structure using a quadratic polynomial. The structural reliability index is estimated by the Rackwitz and Fiessler algorithm, which has shown to converge after a reduced amount of iterations. A parametric numerical analysis of columns and frames is presented for practical applications, where the partial safety factors proposed by international codes of practice are associated with reliability indexes

406

Resilience in IMS : End-to-End Reliability Analysis Via Markov Reward Models  

DEFF Research Database (Denmark)

Reliability evaluation of systems has been widely researched for improving system resilience especially in designing processes of a complex system. The convergence of different access networks is possible via IP Multimedia Subsystem (IMS) for development toward Next Generation Networks (NGNs) and supporting always on services. Therefore, not only Quality of Service (QoS) but also resilience is required. In this paper, we attempt to evaluate and analyze end-to-end reliability of the IMS system using a model proposed as a combination of Reliability Block Diagram (RBD) and Markov Reward Models (MRMs). The resilience of the IMS architecture is studied by applying 1:1 redundancy at different communication scenarios between end users within and across communication domains. The model analysis provides useful reliability characteristics of the system and can be further applied for system design processes.

Kamyod, Chayapol; Nielsen, Rasmus Hjorth

2012-01-01

407

An overview of digital I and C system reliability analysis in nuclear power plants  

International Nuclear Information System (INIS)

The transition from analog to digital technology has occurred in industry as a whole. This has left those who still use analog systems in a tough situation because the suppliers are decreasing the amount of service and spare parts that they have on hand for analog systems. Therefore, the transition from analog to digital for the Instrumentation and Control systems in nuclear power plants is of no exception. Since safety is of paramount importance for nuclear industry, the reliability and safety of digital systems should be demonstrated in a systematic manner before they are being adopted. For the simplest digital systems, the hardware reliability and software reliability are two fundamental components for digital system reliability analysis. This paper provides a literature survey on the work that has been performed in this field. (authors)

408

Lessons learned on benchmarking from the international human reliability analysis empirical study.  

Energy Technology Data Exchange (ETDEWEB)

The International Human Reliability Analysis (HRA) Empirical Study is a comparative benchmark of the prediction of HRA methods to the performance of nuclear power plant crews in a control room simulator. There are a number of unique aspects to the present study that distinguish it from previous HRA benchmarks, most notably the emphasis on a method-to-data comparison instead of a method-to-method comparison. This paper reviews seven lessons learned about HRA benchmarking from conducting the study: (1) the dual purposes of the study afforded by joining another HRA study; (2) the importance of comparing not only quantitative but also qualitative aspects of HRA; (3) consideration of both negative and positive drivers on crew performance; (4) a relatively large sample size of crews; (5) the use of multiple methods and scenarios to provide a well-rounded view of HRA performance; (6) the importance of clearly defined human failure events; and (7) the use of a common comparison language to 'translate' the results of different HRA methods. These seven lessons learned highlight how the present study can serve as a useful template for future benchmarking studies.

Lois, Erasmia (U.S. Nuclear Regulatory Commission, Washington, DC); Forester, John Alan; Dang, Vinh N. (Paul Scherrer Institute, Villigen PSI, Switzerland); Boring, Ronald L. (Idaho National Laboratory, Idaho Falls, ID); Bye, Andreas (OECD Halden Reactor Project, Halden, Norway)

2010-04-01

409

Lessons Learned on Benchmarking from the International Human Reliability Analysis Empirical Study  

Energy Technology Data Exchange (ETDEWEB)

The International Human Reliability Analysis (HRA) Empirical Study is a comparative benchmark of the prediction of HRA methods to the performance of nuclear power plant crews in a control room simulator. There are a number of unique aspects to the present study that distinguish it from previous HRA benchmarks, most notably the emphasis on a method-to-data comparison instead of a method-to-method comparison. This paper reviews seven lessons learned about HRA benchmarking from conducting the study: (1) the dual purposes of the study afforded by joining another HRA study; (2) the importance of comparing not only quantitative but also qualitative aspects of HRA; (3) consideration of both negative and positive drivers on crew performance; (4) a relatively large sample size of crews; (5) the use of multiple methods and scenarios to provide a well-rounded view of HRA performance; (6) the importance of clearly defined human failure events; and (7) the use of a common comparison language to “translate” the results of different HRA methods. These seven lessons learned highlight how the present study can serve as a useful template for future benchmarking studies.

Ronald L. Boring; John A. Forester; Andreas Bye; Vinh N. Dang; Erasmia Lois

2010-06-01

410

Application of response surfaces for reliability analysis of marine structures  

Energy Technology Data Exchange (ETDEWEB)

Marine structures subjected to multiple environmental loads (i.e. waves, current, wind) are considered. These loads are characterized by a set of corresponding parameters. The structural fatigue damage and long-term response are expressed in terms of these environmental parameters based on application of polynomial response surfaces. For both types of analysis, an integration across the range of variation for all the environmental parameters is required. The location of the intervals which give rise to the dominant contribution for these integrals depends on the relative magnitude of the coefficients defining the polynomials. The required degree of numerical subdivision in order to obtain accurate results is also of interest. These issues are studied on a non-dimensional form. The loss of accuracy which results when applying response surfaces of too low order is also investigated. Response surfaces with cut-off limits at specific lower-bound values for the environmental parameters are further investigated. Having obtained general expressions on non-dimensional form, examples which correspond to specific response quantities for marine structures are considered. Typical values for the polynomial coefficients, and for the statistical distributions representing the environmental parameters, are applied. Convergence studies are subsequently performed for the particular example response quantities in order to make comparison with the general formulation. For the extreme response, the application of 'extreme contours' obtained from the statistical distributions of the environmental parameters is explored.

Leira, Bernt J. [NTNU, Institute of Marine Technology, Trondheim 7491 (Norway); Holmas, Tore [Division of Structural Engineering, Marintek, SINTEF Group, Trondheim (Norway); Herfjord, Kjell [Norsk Hydro Research Center, Bergen (Norway)

2005-12-01

411

Application of response surfaces for reliability analysis of marine structures  

International Nuclear Information System (INIS)

Marine structures subjected to multiple environmental loads (i.e. waves, current, wind) are considered. These loads are characterized by a set of corresponding parameters. The structural fatigue damage and long-term response are expressed in terms of these environmental parameters based on application of polynomial response surfaces. For both types of analysis, an integration across the range of variation for all the environmental parameters is required. The location of the intervals which give rise to the dominant contribution for these integrals depends on the relative magnitude of the coefficients defining the polynomials. The required degree of numerical subdivision in order to obtain accurate results is also of interest. These issues are studied on a non-dimensional form. The loss of accuracy which results when applying response surfaces of too low order is also investigated. Response surfaces with cut-off limits at specific lower-bound values for the environmental parameters are further investigated. Having obtained general expressions on non-dimensional form, examples which correspond to specific response quantities for marine structures are considered. Typical values for the polynomial coefficients, and for the statistical distributions representing the environmental parameters, are applied. Convergence studies are subsequently performed for the particular example response quantities in order to make comparison with the general formulation. For the extreme rese general formulation. For the extreme response, the application of 'extreme contours' obtained from the statistical distributions of the environmental parameters is explored

412

[Failure analysis of medical linear accelerator with reliability analyses].  

Science.gov (United States)

We analyzed a number of cases about the Linac troubles in our hospital and have examined the effect of preventive maintenance with Weibull analysis and exponential distribution from April 2001 to March 2012. The total failure by irradiation disabled was 1, 192. (1) Medical linear accelerator (MLC) system was 24.0%, (2) radiation dosimetry system 13.1%, and the (3) cooling-water system was 26.5%. It accounts for 63.6% of the total number of failures. Each parameter value m, which means the shape parameter, and the failure period expectancy of parts ? were (1) 1.21, 1.46/3.9, 3.8 years. 3.7, 3.6 years. (2) 2.84, 1.59/6.6, 4.3 years. 6.7, 5.9 years. (3) 5.12, 4.16/6.1, 8.5 years. 6.1, 8.5 years. Each shape parameter was m>1. It is believed that they are in the worn-out failure period. To prevent failure, MLC performance should be overhauled once every 3 years and a cooling unit should be overhauled once every 7 years. Preventive maintenance is useful in assessing the failure of radiation therapy equipment. In a radiation dosimetry part, you can make a preemptive move before the failure by changing the monitor's dosimeter board with a new part from the repairs stockpiled every 6 months for maintenance. PMID:25672450

Zakimi, Ken; Watanabe, Hiroyuki; Ishida, Hideki; Take, Toshio; Kato, Mitsuyoshi; Iwai, Tsugunori; Nitta, Masaru; Kato, Kyouichi; Nakazawa, Yasuo

2014-12-01

413

Human reliability analysis during PSA at Trillo NPP: main characteristics and analysis of diagnostic errors  

International Nuclear Information System (INIS)

The design difference between Trillo NPP and other Spanish nuclear power plants (basic Westinghouse and General Electric designs) were made clear in the Human Reliability Analysis of the Probabilistic Safety Analysis (PSA) for Trillo NPP. The object of this paper is to describe the most significant characteristics of the Human Reliability Analysis carried out in the PSA, with special emphasis on the possible diagnostic errors and their consequences, based on the characteristics in the Emergency Operations Manual for Trillo NPP. - In the case of human errors before the initiating event (type 1), the existence of four redundancies in most of the plant safety systems, means that the impact of this type or error on the final results of the PSA is insignificant. However, in the case common cause errors, especially in certain calibration errors, some actions are significant in the final equation for core damage - The number of human actions that the operator has to carry out during the accidents (type 3) modelled, is relatively small in comparison with this value in other PSAs. This is basically due to the high level of automation at Rillo NPP - The Plant Operations Manual cannot be strictly considered to be a symptoms-based procedure. The operation Group must select the chapter from the Operations Manual to be followed, after having diagnosed the perturbing event, using for this purpose and Emergency and Anomaly Decision Tree (M.O.3.0.1) based on the different indications,3.0.1) based on the different indications, alarms and symptoms present in the plant after the perturbing event. For this reason, it was decided to analyse the possible diagnosis errors. In the bibliography on diagnosis and commission errors available at the present time, there is no precise methodology for the analysis of this type of error and its incorporation into PSAs. The method used in the PSA for Trillo y NPP to evaluate this type of interaction, is to develop a Diagnosis Error Table, the object of which is to identify the situations in which the mental picture of the plant which the operator had differs from the real state of the plant; if this were to occur, it could lead the group of operators to carry out actions which are not appropriate to the real accident situation. The method is based on the confusion matrix developed for the PSA at Oconee (NSAC-60). Probabilities based on the THERP method are assigned to the possible cases of erroneous diagnosis and to the recovery actions. This paper describe the hypotheses adopted for the analysis od the diagnosis errors and its integration into the PSA models. (Author) 4 refs

414

Reliability analysis of production ships with emphasis on load combination and ultimate strength  

Energy Technology Data Exchange (ETDEWEB)

This thesis deals with ultimate strength and reliability analysis of offshore production ships, accounting for stochastic load combinations, using a typical North Sea production ship for reference. A review of methods for structural reliability analysis is presented. Probabilistic methods are established for the still water and vertical wave bending moments. Linear stress analysis of a midships transverse frame is carried out, four different finite element models are assessed. Upon verification of the general finite element code ABAQUS with a typical ship transverse girder example, for which test results are available, ultimate strength analysis of the reference transverse frame is made to obtain the ultimate load factors associated with the specified pressure loads in Det norske Veritas Classification rules for ships and rules for production vessels. Reliability analysis is performed to develop appropriate design criteria for the transverse structure. It is found that the transverse frame failure mode does not seem to contribute to the system collapse. Ultimate strength analysis of the longitudinally stiffened panels is performed, accounting for the combined biaxial and lateral loading. Reliability based design of the longitudinally stiffened bottom and deck panels is accomplished regarding the collapse mode under combined biaxial and lateral loads. 107 refs., 76 refs., 37 tabs.

Wang, Xiaozhi

1995-05-01

415