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1

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

2

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)

3

Comparative Study Between Degradation Analysis and API 510 Remaining Life Evaluation Method for Feed Gas Filter Vessel Reliability Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study is to use the wall thickness data for degradation analysis of feed gas filter vessel and compare the results with remaining life evaluation method provided in API 510. The exponential model for degradation fitted best to the degradation (wall thickness data. Extrapolation of model gave the failure time for each thickness measurement location, thus providing a failure data set to be analyzed for the reliability function. The results obtained show that the degradation model is more optimistic than API 510 methods and thus it gives a failure free period of 690.33 years which is higher in comparison to life evaluated by using API 510 short term and long term corrosion rates which were calculated to be 510.43 and 628.75 years, respectively. These results can be used as a good starting point for Risk Based Inspection studies by estimating the probability of failure based on Weibull analysis.

Masdi Muhammad

2012-01-01

4

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

5

Comparative reliability studies and analysis of Au, Pd-coated Cu and Pd-doped Cu wire in microelectronics packaging.  

Science.gov (United States)

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 wire. Au bonds were identified to have faster IMC formation, compared to slower IMC growth of Cu. The obtained weibull slope, ? of three bonding wires are greater than 1.0 and belong to wearout reliability data point. Pd-doped Cu wire exhibits larger time-to-failure and cycles-to-failure in both wearout reliability tests in Highly Accelerated Temperature and Humidity (HAST) and Temperature Cycling (TC) tests. This proves Pd-doped Cu wire has a greater potential and higher reliability margin compared to Au and Pd-coated Cu wires. PMID:24244344

Chong Leong, Gan; Uda, Hashim

2013-01-01

6

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

7

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

8

A Comparative Analysis of Software Reliability Growth Models using defects data of Closed and Open Source Software  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study is to compare the fitting (goodness of fit) and prediction capability of eight Software Reliability Growth Models (SRGM) using fifty different failure Data sets. These data sets contain defect data collected from system test phase, operational phase (field defects) and Open Source Software (OSS) projects. The failure data are modelled by eight SRGM (Musa Okumoto, Inflection S-Shaped, Goel Okumoto, Delayed S-Shaped, Logistic, Gompertz, Yamada Exponential, and Generali...

Morisio, Maurizio; Vetro, Antonio; Ullah, Najeeb

2013-01-01

9

Waste package reliability analysis  

International Nuclear Information System (INIS)

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

10

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

11

Reliability Analysis of Wind Turbines  

DEFF Research Database (Denmark)

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

Toft, Henrik Stensgaard; SØrensen, John Dalsgaard

2008-01-01

12

Reliability analysis of structures  

Directory of Open Access Journals (Sweden)

Full Text Available The process of building an object consists of planning, design, construction, use and eventual demolition [1]. In each of these components in the process of building uncertainties occurs, which can be caused by human or natural effect. Human cause of uncertainties includes intentional and unintentional deviation from the optimal realization, the use of inappropriate materials, unverified construction methods, poor quality of connections between elements, changes to the building design without the consent of all parties. Natural effects are often unpredictable. Reliability is the ability of the structure to meet the construction requirements set out under specific conditions during the service life, according which it is designed to [2]. It refers to the carrying capacity, serviceability and durability of construction and according to them different degrees of reliability can be defined. One of the best ways of presenting the size of the uncertainty in the theory of reliability is the reliability index ?.

Stanojev Milovan

2014-01-01

13

Reliability analysis for radiographic measures of lumbar lordosis in adult scoliosis: a case–control study comparing 6 methods  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several methods are used to measure lumbar lordosis. In adult scoliosis patients, the measurement is difficult due to degenerative changes in the vertebral endplate as well as the coronal and sagittal deformity. We did the observational study with three examiners to determine the reliability of six methods for measuring the global lumbar lordosis in adult scoliosis patients. Ninety lateral lumbar radiographs were collected for the study. The radiographs were divided into normal (Cobb < 10°...

Hong, Jae Young; Suh, Seung Woo; Modi, Hitesh N.; Hur, Chang Yong; Song, Hae Ryong; Park, Jong Hoon

2010-01-01

14

Reliability of the electric power supply in the safety apparatus of nuclear power plants: a comparative analysis  

International Nuclear Information System (INIS)

This paper discusses the risk of total loss of electric power supply to the Class 1E system. Two alternatives are focused: a system with two off-site and two onsite power supplies emergency power supply, as recommended by the American Regulations, and a system with only one off-site and four on-site power supplies, applicable when two off-site are not available. To allow the fact that the equipment can be repaired, the method proper involves use of the Markov model, with which one can find, for each configuration of the system, the change over time of the probability of a simultaneous failure of all power sources. The sensitivity of each parameter is studied in each case and, on the basis of the results of the study, the author conclude that the system with two off-site power supplies is preferable in all alternatives analysed, although the system with one off-site power supply can be adopted with high reliability diesel-generators. (author)

15

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.)

16

Reliability analysis of phased missions  

International Nuclear Information System (INIS)

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

17

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

18

Analysis tools for reliability databases  

International Nuclear Information System (INIS)

This report outlines the work performed at Risoe, under contract with the Swedish Nuclear Power Inspectorate, with the goal to develop analysis tools for reliability databases, that can suit the information needs of the users of the TUD (Reliability/Maintenance/Operation) database, used at 12 nuclear power plants in Sweden and 2 in Finland. The TUD database stores operating experience data from the failure reports, that describe failures and repair on a large part of the equipment of the plants. Furthermore, the TUD contains background data on operating conditions, design, maintenance and test programs on the equipment and registers the changes in operating modes of each plant. Since 1993 the TUD is structured as a multi-user relational database. The analysis tools developed in this work are the result of the following analysis steps: 1. Investigate and select data 2. Make simple plots of the data 3. Analyze the data with statistical methods, including analysis of trend and dependency 4. Combine and implement these three steps in a prototype RDB with a simple user-interface. The resulting user-interface of the prototype RDB developed in the work, guides the user through the following steps: 4a. Build a population of sockets (sub-components or component level), 4b. Select the time-window and the failure events, 4c. Select the analysis tools to be incorporated in the report, 4d. Adjust the default report and print the report. The prototype RDB developed in this work, she prototype RDB developed in this work, shows that when the proper analysis tool is installed, the TUD database can help its users in identifying possible common cause failures and trends in reliability and costs of a population of component sockets

19

Software Architecture Reliability Analysis using Failure Scenarios  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose a Software Architecture Reliability Analysis (SARA) approach that benefits from both reliability engineering and scenario-based software architecture analysis to provide an early reliability analysis of the software architecture. SARA makes use of failure scenarios that are prioritized with respect to the user-perception in order to provide a severity analysis for the software architecture and the individual components.

Tekinerdogan, Bedir; So?zer, Hasan; Aksit, Mehmet

2005-01-01

20

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

 
 
 
 
21

Satellite and satellite subsystems reliability: Statistical data analysis and modeling  

International Nuclear Information System (INIS)

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

22

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

23

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.)

24

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

25

Integrated Methodology for Software Reliability Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

Cristescu, Marian Pompiliu; Ciovica, Laurentiu; Ciovica, Liviu

2012-01-01

26

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

27

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

Science.gov (United States)

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

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

2014-06-01

28

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

Directory of Open Access Journals (Sweden)

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

C. Huggel

2014-06-01

29

Reliability analysis using network simulation  

International Nuclear Information System (INIS)

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

30

Comparing two reliable multicast protocols for mobile computing  

Scientific Electronic Library Online (English)

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

Mateus de Freitas, Ribeiro; Markus, Endler.

2003-04-01

31

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)

32

Swimming pool reactor reliability and safety analysis  

International Nuclear Information System (INIS)

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

33

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)

34

Reliability modelling and analysis of thermal MEMS  

International Nuclear Information System (INIS)

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

35

Reliability modelling and analysis of thermal MEMS  

Science.gov (United States)

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

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

2006-04-01

36

Failure data and system reliability analysis  

International Nuclear Information System (INIS)

Discussions are given for the meanings of risk and safety assessment. Handling of data is important in the quest to perform probabilistic safety assessments (PSAs). Distribution functions of failure data and related statistical quantities are explained in details. Some topics regarding reliability analysis are also introduced in this lecture note. They include maintenance activity, matrix expressions of maintained systems, Boolean expression of a system reliability and analysis method for loop structures. Finally, dependent failure and common cause failure are discussed, paying much attention to the models of common cause failure (CCF). (author)

37

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

38

Reliability Analysis of a Steel Frame  

Directory of Open Access Journals (Sweden)

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

M. Sýkora

2002-01-01

39

Reliability Analysis of Structural Timber Systems  

DEFF Research Database (Denmark)

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

SØrensen, John Dalsgaard; Hoffmeyer, P.

2000-01-01

40

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)

 
 
 
 
41

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)

42

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

43

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

44

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

45

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

46

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

47

A comparative evaluation of five human reliability assessment techniques  

International Nuclear Information System (INIS)

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

48

Structural reliability analysis and seismic risk assessment  

Energy Technology Data Exchange (ETDEWEB)

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

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

1984-01-01

49

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

50

Structural reliability analysis and seismic risk assessment  

International Nuclear Information System (INIS)

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

51

Reliability Analysis of a Steel Frame  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A steel frame with haunches is designed according to Eurocodes. The frame is exposed to self-weight, snow, and wind actions. Lateral-torsional buckling appears to represent the most critical criterion, which is considered as a basis for the limit state function. In the reliability analysis, the probabilistic models proposed by the Joint Committee for Structural Safety (JCSS) are used for basic variables. The uncertainty model coefficients take into account the inaccuracy of the resistance mod...

Sy?kora, M.

2002-01-01

52

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)

53

Comparative availability and reliability assessment of design options for the secondary sodium loops of the EFR  

International Nuclear Information System (INIS)

The EFR (European Fast Reactor) project has entered a conceptual study period where different design alternatives are compared concerning feasibility, safety and economic aspects. This paper describes a comparative probabilistic availability and reliability assessment of alternative design options for the secondary sodium loops. These loops will provide heat transfer from the reactor pool to the water-steam (power generating) side. So a high operational availability of the secondary loops during plant lifetime is essential for economic power generation. Additionally a high reliability is required to fulfill the operational decay heat removal function in case of a reactor trip. Availabilities and reliabilities of the different options were assessed using failure mode and effect analysis and the fault tree method. (orig.)

54

The quantitative failure of human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Bennett, C.T.

1995-07-01

55

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

56

Reliability analysis of the diesel generators  

International Nuclear Information System (INIS)

The Operating Experience of the Diesel generators of the Italian Nuclear Power Plants has been analysed, in order to evaluate their quality level in comparison with the requirements defined in the design and to identify possible improving measures to be implemented both on operating and under construction plants. The collected data have been classified and elaborated, with the purpose to evaluate availability on demand and reliability in operation for each diesel. A comparison between the calculated reliability parameters and the corresponding international ones was also performed. Recurring failure modes were specifically analysed. In addition, an analysis of homogeneity for the diesels of the same plant and of all the plants is reported as well. In such a way, some critical subsystems of DGs has been identified. Moreover hardware modifications and surveillance program improvements have been found out, such to ensure better performance of the on-site electric power system

57

Advances in human reliability analysis in Mexico  

International Nuclear Information System (INIS)

Human Reliability Analysis (HRA) is a very important part of Probabilistic Risk Analysis (PRA), and constant work is dedicated to improving methods, guidance and data in order to approach realism in the results as well as looking for ways to use these to reduce accident frequency at plants. Further, in order to advance in these areas, several HRA studies are being performed globally. Mexico has participated in the International HRA Empirical study with the objective of -benchmarking- HRA methods by comparing HRA predictions to actual crew performance in a simulator, as well as in the empirical study on a US nuclear power plant currently in progress. The focus of the first study was the development of an understanding of how methods are applied by various analysts, and characterize the methods for their capability to guide the analysts to identify potential human failures, and associated causes and performance shaping factors. The HRA benchmarking study has been performed by using the Halden simulator, 14 European crews, and 15 HRA equipment s (NRC, EPRI, and foreign HRA equipment s using different HRA methods). This effort in Mexico is reflected through the work being performed on updating the Laguna Verde PRA to comply with the ASME PRA standard. In order to be considered an HRA with technical adequacy, that is, be considered as a capability category II, for risk-informed applications, the methodology used for the HRA in the original PRA is not considered sufficientloriginal 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)

58

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

59

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

60

Structural reliability analysis based on the cokriging technique  

International Nuclear Information System (INIS)

Approximation methods are widely used in structural reliability analysis because they are simple to create and provide explicit functional relationships between the responses and variables in stead of the implicit limit state function. Recently, the kriging method which is a semi-parameter interpolation technique that can be used for deterministic optimization and structural reliability has gained popularity. However, to fully exploit the kriging method, especially in high-dimensional problems, a large number of sample points should be generated to fill the design space and this can be very expensive and even impractical in practical engineering analysis. Therefore, in this paper, a new method-the cokriging method, which is an extension of kriging, is proposed to calculate the structural reliability. cokriging approximation incorporates secondary information such as the values of the gradients of the function being approximated. This paper explores the use of the cokriging method for structural reliability problems by comparing it with the Kriging method based on some numerical examples. The results indicate that the cokriging procedure described in this work can generate approximation models to improve on the accuracy and efficiency for structural reliability problems and is a viable alternative to the kriging.

 
 
 
 
61

CRAX/Cassandra Reliability Analysis Software  

Energy Technology Data Exchange (ETDEWEB)

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

Robinson, D.

1999-02-10

62

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

International Nuclear Information System (INIS)

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

63

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

64

Advancing Usability Evaluation through Human Reliability Analysis  

International Nuclear Information System (INIS)

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

65

Models of network reliability analysis, combinatorics, and Monte Carlo  

CERN Document Server

Unique in its approach, Models of Network Reliability: Analysis, Combinatorics, and Monte Carlo provides a brief introduction to Monte Carlo methods along with a concise exposition of reliability theory ideas. From there, the text investigates a collection of principal network reliability models, such as terminal connectivity for networks with unreliable edges and/or nodes, network lifetime distribution in the process of its destruction, network stationary behavior for renewable components, importance measures of network elements, reliability gradient, and network optimal reliability synthesis

Gertsbakh, Ilya B

2009-01-01

66

Reliability analysis of pipe whip impacts  

International Nuclear Information System (INIS)

A probability-based approach is presented as the integration of probabilistic methods and deterministic modelling based on the finite element method. An existing finite element software package was linked to an existing probabilistic package to analyse the complex mechanics that occur during the transient non-linear analysis of impact problems. This methodology is applied to a pipe whip analysis of a group-distribution-header, which results from a guillotine break, and subsequent impact with the adjacent building wall; this is a postulated accident for the Ignalina Nuclear Power Plant RBMK-1500 reactors. The uncertainties of material properties, component geometry data and loads were taken into consideration. The probabilities of failure of the impacted header and of the header support-wall were estimated given uncertainties in material properties, geometrical parameters and loading. The software ProFES was used for the probabilistic analysis and the finite element software NEPTUNE for deterministic structural integrity evaluation. The Monte Carlo Simulation, First Order Reliability method and Response Surface method were used in the probabilistic analysis

67

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

68

Human Reliability Analysis For Computerized Procedures  

International Nuclear Information System (INIS)

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

69

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

70

Structural reliability analysis of spillway gates  

International Nuclear Information System (INIS)

Concerns regarding the deterioration and the need to rehabilitate several of the major components of aging concrete dams in southern Quebec are discussed. Most of the dams were built before 1960 and are reaching their design life. This paper described an analytical procedure for determining if spillway gates need to be replaced or how much longer they can be expected to last. The procedure is based on reliability analysis and incorporates a model to predict the rate of corrosion of the gates. The procedure accounts for the variability in loads, deterioration processes and the geometrical and mechanical properties of the gates. Bayesian statistics are included to allow the model to be adjusted as new data becomes available. 16 refs., 2 tabs., 7 figs

71

Structural reliability analysis of spillway gates  

Energy Technology Data Exchange (ETDEWEB)

Concerns regarding the deterioration and the need to rehabilitate several of the major components of aging concrete dams in southern Quebec are discussed. Most of the dams were built before 1960 and are reaching their design life. This paper described an analytical procedure for determining if spillway gates need to be replaced or how much longer they can be expected to last. The procedure is based on reliability analysis and incorporates a model to predict the rate of corrosion of the gates. The procedure accounts for the variability in loads, deterioration processes and the geometrical and mechanical properties of the gates. Bayesian statistics are included to allow the model to be adjusted as new data becomes available. 16 refs., 2 tabs., 7 figs.

Chouinard, L.E.; Laberge, E. [McGill Univ., Montreal, PQ (Canada). Dept. of Civil Engineering and Applied Mechanics; Gocevski, V. [Hydro-Quebec, Montreal, PQ (Canada)

1998-12-31

72

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

73

On some comparisons of lifetimes for reliability analysis  

International Nuclear Information System (INIS)

Ordering of non-negative random variables (lifetimes) has been intensively studied in the literature. When comparing lifetimes in different applications such as reliability and risk analysis, it is often of interest to analyze also the distances between these lifetimes. In this paper, we define and discuss the stress–strength ordering and distance on the basis of the well-known stress–strength model that describes, e.g., the probability that the strength of a structure is larger than the external stress. We also compare this probability with the distance based on the difference between the means of random variables of interest and discuss several examples. The results can be useful, e.g., for analyzing reliability and safety requirements at the design stage for various engineering objects

74

Reliability analysis of nonlinear MDOF dynamic systems  

International Nuclear Information System (INIS)

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

75

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

76

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

International Nuclear Information System (INIS)

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

77

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)

78

Travel time Reliability Analysis Using Entropy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Travel time reliability is a measure that is commonly extracted from travel time measurements. It has served as a vital indicator of the transportation system’s performance making the concept of obtaining reliability from travel time data very useful. Travel time is a good indicator of the performance of a particular highway segment. However, it does not convey all aspects of the overall performance of the transportation system. Travel Time Reliability is defined as the consistency of traff...

Neveen Shlayan; Vidhya Kumaresan; Pushkin Kachroo; Brian Hoeft

2013-01-01

79

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

80

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

 
 
 
 
81

Mathematical Methods in Survival Analysis, Reliability and Quality of Life  

CERN Document Server

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

Huber, Catherine; Mesbah, Mounir

2008-01-01

82

Discrete Event Simulation and Petri net Modeling for Reliability Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 modifi...

Behrooz Safarinejadian 1

2012-01-01

83

Examining Reliability and Validity of Job Analysis Survey Data.  

Science.gov (United States)

Job analysis has played a fundamental role in developing and validating licensure and certification examinations, but research on what constitutes reliable and valid job analysis data is lacking. This paper examines the reliability and validity of job analysis survey results. Generalizability theory and the multi-facet Rasch item response theory…

Wang, Ning; Wiser, Randall F.; Newman, Larry S.

84

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)

85

PC-PRAISE, BWR Piping Reliability Analysis  

International Nuclear Information System (INIS)

1 - Description of program or function: PC-PRAISE is a probabilistic fracture mechanics computer code developed for IBM or IBM compatible personal computers to estimate probabilities of leak and break in nuclear power plant cooling piping. 2 - Method of solution: PC-PRAISE considers the initiation and/or growth of crack-like defects in piping weldments. The initiation analyses are based on the results of laboratory studies and field observations in austenitic piping material operating under boiling water reactor conditions. The considerable scatter in such results is quantified and incorporated into a probabilistic model. The crack growth analysis is based on (deterministic) fracture mechanics principles, in which some of the inputs (such as initial crack size) are considered to be random variables. Monte Carlo simulation, with stratified sampling on initial crack size, is used to generate weldment reliability results. 3 - Restrictions on the complexity of the problem: There is essentially no limitation with PC-PRAISE but for large number of replications used in the Monte Carlo simulation scheme, computation time may become prohibitive

86

The NRC Human Reliability Analysis Research Program  

International Nuclear Information System (INIS)

The U.S. Nuclear Regulatory Commission's (NRC's) Human Reliability Analysis (HRA) Research Program is aimed at: (1) developing improved HRA methods, tools, and data; (2) developing HRA results and insights; and (3) providing HRA support to other NRC programs. The Fiscal Year 2001-2005 technical tasks include the development of improved methods and data for HRA quantification, the performance of a number of technical analyses supporting probabilistic risk assessment studies of various engineering issues (e.g., pressurised thermal shock risk), the development of improved methods for specific HRA problems (e.g., the treatment of latent errors), and the development of HRA guidance for a variety of user audiences. A program plan has been developed to support the execution of the research program. This paper summarises the HRA Research Program Plan. The plan is aimed at addressing key technical issues in HRA identified by the staff and by the Advisory Committee on Reactor Safeguards (ACRS) in its reviews of NRC's HRA activities [15-16]. Additional details can be found in the full report documenting the plan [17]. (authors)

87

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

88

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

89

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

90

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

91

RELIABILITY ANALYSIS OF PISTON MANUFACTURING SYSTEM  

Directory of Open Access Journals (Sweden)

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

Amit Kumar

2011-01-01

92

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

93

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

94

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

95

RELIABILITY ANALYSIS OF PISTON MANUFACTURING SYSTEM  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Amit Kumar; Sneh Lata

2011-01-01

96

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

97

POSSIBILITY AND EVIDENCE-BASED RELIABILITY ANALYSIS AND DESIGN OPTIMIZATION  

Directory of Open Access Journals (Sweden)

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

Hong-Zhong Huang

2013-01-01

98

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.

99

Advances in methods and applications of reliability and safety analysis  

International Nuclear Information System (INIS)

The know-how of the reliability and safety design and analysis techniques of Vtt has been established over several years in analyzing the reliability in the Finnish nuclear power plants Loviisa and Olkiluoto. This experience has been later on applied and developed to be used in the process industry, conventional power industry, automation and electronics. VTT develops and transfers methods and tools for reliability and safety analysis to the private and public sectors. The technology transfer takes place in joint development projects with potential users. Several computer-aided methods, such as RELVEC for reliability modelling and analysis, have been developed. The tool developed are today used by major Finnish companies in the fields of automation, nuclear power, shipbuilding and electronics. Development of computer-aided and other methods needed in analysis of operating experience, reliability or safety is further going on in a number of research and development projects

100

Reliability analysis of self-actuated shutdown system  

International Nuclear Information System (INIS)

An analytical study was performed for the reliability of a self-actuated shutdown system (SASS) under the unprotected loss of flow (ULOF) event in a typical loop-type liquid metal fast breeder reactor (LMFBR) by the use of the response surface Monte Carlo analysis method. Dominant parameters for the SASS, such as Curie point characteristics, subassembly outlet coolant temperature, electromagnetic surface condition, etc., were selected and their probability density functions (PDFs) were determined by the design study information and experimental data. To get the response surface function (RSF) for the maximum coolant temperature, transient analyses of ULOF were performed by utilizing the experimental design method in the determination of analytical cases. Then, the RSF was derived by the multi-variable regression analysis. The unreliability of the SASS was evaluated as a probability that the maximum coolant temperature exceeded an acceptable level, employing the Monte Carlo calculation using the above PDFs and RSF. In this study, sensitivities to the dominant parameter were compared. The dispersion of subassembly outlet coolant temperature near the SASS-was found to be one of the most sensitive parameters. Fault tree analysis was performed using this value for the SASS in order to evaluate the shutdown system reliability. As a result of this study, the effectiveness of the SASS on the reliability improvement in the LMFBR shutdown system was analytically confirmed. This study has been performed as a part of joint research and development projects for DFBR under the sponsorship of the nine Japanese electric power companies, Electric Power Development Company and the Japan Atomic Power Company. (author)

 
 
 
 
101

Strength Reliability Analysis of Turbine Blade Using Surrogate Models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

102

Reliability analysis of large, complex systems using ASSIST  

Science.gov (United States)

The SURE reliability analysis program is discussed as well as the ASSIST model generation program. It is found that semi-Markov modeling using model reduction strategies with the ASSIST program can be used to accurately solve problems at least as complex as other reliability analysis tools can solve. Moreover, semi-Markov analysis provides the flexibility needed for modeling realistic fault-tolerant systems.

Johnson, Sally C.

1988-01-01

103

Reliability analysis for power electronics modules  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper discusses the reliability of power electronics modules. The approach taken combines numerical modeling techniques with experimentation and accelerated testing to identify failure modes and mechanisms for the power module structure and most importantly the root cause of a potential failure. The paper details results for two types of failure (i) wire bond fatigue and (ii) substrate delamination. Finite element method modeling techniques have been used to predict the stress distributi...

Bailey, Christopher; Tilford, Tim; Lu, Hua

2007-01-01

104

Reliability analysis of PLC safety equipment  

Energy Technology Data Exchange (ETDEWEB)

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.

Yu, J.; Kim, J. Y. [Chungnam Nat. Univ., Daejeon (Korea, Republic of)

2006-06-15

105

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

106

Semantic compared cross impact analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Thorleuchter, Dirk; Den Poel, Dirk

2014-01-01

107

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

108

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

109

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.

110

Passive system reliability analysis challenges and a step towards resolution  

International Nuclear Information System (INIS)

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

111

The PAWS and STEM reliability analysis programs  

Science.gov (United States)

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

Butler, Ricky W.; Stevenson, Philip H.

1988-01-01

112

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

113

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

114

Human reliability analysis: a case study  

International Nuclear Information System (INIS)

This paper describes method using the Technique for Human Error Rate Prediction (THERP) as presented in NUREG/CR-2254. The entire analysis is documented, including the assumptions made based on a task analysis of the plant and of the accident being evaluated, the estimates of human error probabilities (HEPs) found in NUREG/CR-1278, the levels of dependence assigned, and the recovery factors analyzed. The case cited involves the establishment of feed and bleed following a loss of steam generator feed

115

Application of DFM in human reliability analysis  

International Nuclear Information System (INIS)

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

116

Reliability Analysis of a Mono-Tower Platform  

DEFF Research Database (Denmark)

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). The sensitivity of the systems reliability to various parameters is investigated. It is shown for the fatigue limit state is a significant failure mode for the Mono.tower platform. Further, it is shown for the fatigue failure mode the 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.

1988-01-01

117

Comparative analysis of biological networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent developments in molecular biology have resulted in experimental data that entails the relationships and interactions between biomolecules. Biomolecular interaction data, generally referred to as biological or cellular networks, are frequently abstracted using graph models. In systems biology, comparative analysis of these networks provides understanding of functional modularity in the cell by integrating cellular organization, functional hierarchy, and evolutionary conservation. In thi...

Koyuturk, Mehmet

2006-01-01

118

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

Directory of Open Access Journals (Sweden)

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

Marko ?epin

2008-07-01

119

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

Directory of Open Access Journals (Sweden)

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

André T. Beck

2008-06-01

120

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

 
 
 
 
121

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

122

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

123

Reliability Analysis of Repair Hours of RTPS through Weibull Model  

Directory of Open Access Journals (Sweden)

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

Dr. C.P.S. Hungund

2014-08-01

124

Research on Law’s Mask Texture Analysis System Reliability  

Directory of Open Access Journals (Sweden)

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

Gan Hong Seng

2014-05-01

125

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.

126

Nuclear power ecology: comparative analysis  

International Nuclear Information System (INIS)

Ecological effects of different energy sources are compared. Main actions for further nuclear power development - safety increase and waste management, are noted. Reasons of restrained public position to nuclear power and role of social and political factors in it are analyzed. An attempt is undertaken to separate real difficulties of nuclear power from imaginary ones that appear in some mass media. International actions of environment protection are noted. Risk factors at different energy source using are compared. The results of analysis indicate that ecological influence and risk for nuclear power are of minimum

127

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.)

128

State of the art report on aging reliability analysis  

International Nuclear Information System (INIS)

The goal of this report is to describe the state of the art on aging analysis methods to calculate the effects of component aging quantitatively. In this report, we described some aging analysis methods which calculate the increase of Core Damage Frequency (CDF) due to aging by including the influence of aging into PSA. We also described several research topics required for aging analysis for components of domestic NPPs. We have described a statistical model and reliability physics model which calculate the effect of aging quantitatively by using PSA method. It is expected that the practical use of the reliability-physics model will be increased though the process with the reliability-physics model is more complicated than statistical model

129

1991 comparative analysis of tritium in water  

International Nuclear Information System (INIS)

For environmental monitoring of radioactive materials, the competent authorities of the States and Federal Government of Germany continuously perform measurements and make their results accessible to the public in an appropriate way. In order to guarantee the comparability of measured values and a high degree of reliability of the applied methods, the authorities in charge of carrying out such tasks are obliged to take part in the comparative analyses (ring tests) organized by the central offices of the Federal Government. Therefore, the aim of this comparative analysis performed by order of the Federal Ministry of the Environment, Nature Protection and Reactor Safety consists mainly in providing the measuring offices in charge of monitoring waters, with samples with known tritium contents in order to get an overview of the accuracy of currently used processes; check the accuracy of the determinations performed, and, if necessary, detect and eliminate systematic errors; check, in particular by means of the samples T2 and T3, the calibration of the measuring devices and, if necessary, make corrections. To this effect, the comparative analysis fulfills the function of quality control of the processes used in environmental monitoring. (orig./BBR)

130

Distribution-level electricity reliability: Temporal trends using statistical analysis  

International Nuclear Information System (INIS)

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

131

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)

132

Reactor protection system reliability analysis of Daya Bay NPP  

International Nuclear Information System (INIS)

Based on the reliability analysis methods of FMEA and FTA, according to the result of ETA of PRA in Daya by NPP, the top events of the fault trees of reactor protection system and the success criteria were established. By using RISK-SPECTRUM procedure, the unavailability and the minimal cut-sets (MCS) of the fault trees were obtained. The results of analysis was put into the visual risk analysis software of Daya bay NPP as the support of data

133

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

134

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

135

Simplified plant analysis risk (SPAR) human reliability analysis (HRA) methodology: Comparisons with other HRA methods  

Energy Technology Data Exchange (ETDEWEB)

The 1994 Accident Sequence Precursor (ASP) human reliability analysis (HRA) methodology was developed for the U.S. Nuclear Regulatory Commission (USNRC) in 1994 by the Idaho National Engineering and Environmental Laboratory (INEEL). It was decided to revise that methodology for use by the Simplified Plant Analysis Risk (SPAR) program. The 1994 ASP HRA methodology was compared, by a team of analysts, on a point-by-point basis to a variety of other HRA methods and sources. This paper briefly discusses how the comparisons were made and how the 1994 ASP HRA methodology was revised to incorporate desirable aspects of other methods. The revised methodology was renamed the SPAR HRA methodology.

J. C. Byers; D. I. Gertman; S. G. Hill; H. S. Blackman; C. D. Gentillon; B. P. Hallbert; L. N. Haney

2000-07-31

136

Simplified Plant Analysis Risk (SPAR) Human Reliability Analysis (HRA) Methodology: Comparisons with other HRA Methods  

Energy Technology Data Exchange (ETDEWEB)

The 1994 Accident Sequence Precursor (ASP) human reliability analysis (HRA) methodology was developed for the U.S. Nuclear Regulatory Commission (USNRC) in 1994 by the Idaho National Engineering and Environmental Laboratory (INEEL). It was decided to revise that methodology for use by the Simplified Plant Analysis Risk (SPAR) program. The 1994 ASP HRA methodology was compared, by a team of analysts, on a point-by-point basis to a variety of other HRA methods and sources. This paper briefly discusses how the comparisons were made and how the 1994 ASP HRA methodology was revised to incorporate desirable aspects of other methods. The revised methodology was renamed the SPAR HRA methodology.

Byers, James Clifford; Gertman, David Ira; Hill, Susan Gardiner; Blackman, Harold Stabler; Gentillon, Cynthia Ann; Hallbert, Bruce Perry; Haney, Lon Nolan

2000-08-01

137

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

138

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

139

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

140

Human reliability analysis of Lingao Nuclear Power Station  

International Nuclear Information System (INIS)

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

 
 
 
 
141

Reliable analysis for pressure vessel based on ANSYS  

International Nuclear Information System (INIS)

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

142

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

143

Reliability based analysis and design of anchor retrofitted concrete gravity dams  

Energy Technology Data Exchange (ETDEWEB)

This paper demonstrates that reliability based analysis and design of stabilized concrete gravity dams provides a consistent level of structural reliability, particularly where remedial design is necessary. An applied reliability based model in estimating the safety of concrete gravity dam monoliths was presented. As an example, traditional safety methods and sliding stability of the Pine Flat Dam were compared with results obtained from 2-dimensional finite element and reliability analyses. A comparison of sliding stability analysis results revealed that traditional measurement methods produced safety factor value that is 25 per cent below acceptable levels. Time history dependant reliability based design approaches produced a safety index at 10 per cent below acceptable limits. Considerations included the fact that a high number of random variables define a typical structural problem and that the joint probability density of all involved variables was difficult to model. It was concluded that reliability based design and finite element analysis were recommended for safety evaluation and design of concrete dams, with the same methods being applicable to stability analysis and design of arch dams. 13 refs., 3 tabs., 6 figs.

Kazemi, M.R. [Hannah Kazemi and Company Ltd., Vancouver, BC (Canada)

2004-07-01

144

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

145

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

146

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

147

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

148

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.

149

Reliability Analysis of Free Jet Scour Below Dams  

Directory of Open Access Journals (Sweden)

Full Text Available Current formulas for calculating scour depth below of a free over fall are mostly deterministic in nature and do not adequately consider the uncertainties of various scouring parameters. A reliability-based assessment of scour, taking into account uncertainties of parameters and coefficients involved, should be performed. This paper studies the reliability of a dam foundation under the threat of scour. A model for calculating the reliability of scour and estimating the probability of failure of the dam foundation subjected to scour is presented. The Maximum Entropy Method is applied to construct the probability density function (PDF of the performance function subject to the moment constraints. Monte Carlo simulation (MCS is applied for uncertainty analysis. An example is considered, and there liability of its scour is computed, the influence of various random variables on the probability failure is analyzed.

Chuanqi Li

2012-12-01

150

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

151

Comparative Analysis of Classifier Fusers  

Directory of Open Access Journals (Sweden)

Full Text Available There are many methods of decision making by an ensemble of classifiers. The most popular are methods that have their origin in voting method, where the decision of the common classifier is a combination of individual classifiers’ outputs. This work presents comparative analysis of some classifier fusion methods based on weighted voting of classifiers’ responses and combination of classifiers’ discriminant functions. We discus different methods of producing combined classifiers based on weights. We show that it is notpossible to obtain classifier better than an abstract model of committee known as an Oracle if it is based only on weighted voting but models based on discriminant function or classifier using feature values and class numbers could outperform the Oracle as well. Delivered conclusions are confirmed by the results of computer experiments carried out on benchmark and computer generated data.

Marcin Zmyslony

2012-06-01

152

Improvement in check valve reliability by integrity analysis of internals  

International Nuclear Information System (INIS)

The Electric Power Research Institute (EPRI) reports that valve unreliability is a major cause of plant downtime. The Institute of Nuclear Power Operations (INPO) issued a Significant Operating Experience Report (SOER) No. 86-03 that provides the plant owner guidance on check valve surveillance (inspection and testing) to improve reliability. The material condition of internal parts plays a key role in assuring reliability. The Service Water System at Comanche Peak operated to meet system functional needs for approximately seven years before the plant received an operating license. The failure of a cast 17-4 PH stainless steel disc pin hinge (swing arm) in a valve installed in this system resulted in recently issued NRC Information Notice 90-03. This paper summarizes work completed to assure the reliability of similar swing check valves at TU Electric's Comanche Peak Steam Electric Station (CPSES). Suitability for corrosive service was evaluated. Linear elastic fracture mechanics established acceptance criteria, surface inspection and in-place metallography were employed to screen defective cast material. Retrospective statistical analysis of inspection results was used to quantify success of the inspection and estimate improvement in valve reliability. Check valves having the same material with similar operating conditions have been installed at other plants. Other components having sand cast 17-4 PH stainless steel parts also may be affected. A strategy is proposed o may be affected. A strategy is proposed for minimizing impact of material defects and age-related degradation on valve reliability

153

Development of a human reliability analysis methodology during PHWR outages  

International Nuclear Information System (INIS)

The quality of probabilistic safety assessment (PSA) has become more important with emphasis on risk-informed regulation and application (RIR and A) in nuclear power industry. Human reliability analysis is definitely related to the quality of PSA because human errors have been identified as major contributors to PSA. According to NRC's 'Office of analysis and evaluation of operational data (AEOD)', 82% of the reactor trips and accident during outage is caused by the events related to human errors. There is, however, no one HRA method universally accepted. Furthermore, HRA during PHWR outage has not been performed around the world. Therefore, it is necessary to perform HRA during PHWR outage for the purpose of increasing the quality of PHWR PSA. In this study, Event Trees during PHWR outage were developed, and 10 human actions which should be quantified were derived from the Event Trees. A new HRA model during PHWR outage was also developed, the human actions were quantified with this model. The quantified values were compared with the values from 'Generic CANDU Probabilistic Safety Assessment' and the values estimated using ASEP. Core Damage Frequency was estimated of 6.96 x 10-5 using the Event Trees and the HRA model. It was 17 % higher value than CDF estimated using AECL data. It was considered the differences between the HEPs for OPHTS make CDF higher. Therefore, complementary study of reestimating HEP for OPHTS in detail is required for increasing the in detail is required for increasing the qualities of HRA and PSA. It is considered the Event Trees and the HRA model developed in this study can be important references when performing PSA during PHWR outage in the future

154

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

Directory of Open Access Journals (Sweden)

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

Mark Glaister

2009-03-01

155

SARA - SURE/ASSIST RELIABILITY ANALYSIS WORKSTATION (VAX VMS VERSION)  

Science.gov (United States)

SARA, the SURE/ASSIST Reliability Analysis Workstation, is a bundle of programs used to solve reliability problems. The mathematical approach chosen to solve a reliability problem may vary with the size and nature of the problem. The Systems Validation Methods group at NASA Langley Research Center has created a set of four software packages that form the basis for a reliability analysis workstation, including three for use in analyzing reconfigurable, fault-tolerant systems and one for analyzing non-reconfigurable systems. The SARA bundle includes the three for reconfigurable, fault-tolerant systems: SURE reliability analysis program (COSMIC program LAR-13789, LAR-14921); the ASSIST specification interface program (LAR-14193, LAR-14923), and PAWS/STEM reliability analysis programs (LAR-14165, LAR-14920). As indicated by the program numbers in parentheses, each of these three packages is also available separately in two machine versions. The fourth package, which is only available separately, is FTC, the Fault Tree Compiler (LAR-14586, LAR-14922). FTC is used to calculate the top-event probability for a fault tree which describes a non-reconfigurable system. PAWS/STEM and SURE are analysis programs which utilize different solution methods, but have a common input language, the SURE language. ASSIST is a preprocessor that generates SURE language from a more abstract definition. ASSIST, SURE, and PAWS/STEM are described briefly in the following paragraphs. For additional details about the individual packages, including pricing, please refer to their respective abstracts. ASSIST, the Abstract Semi-Markov Specification Interface to the SURE Tool program, allows a reliability engineer to describe the failure behavior of a fault-tolerant computer system in an abstract, high-level language. The ASSIST program then automatically generates a corresponding semi-Markov model. A one-page ASSIST-language description may result in a semi-Markov model with thousands of states and transitions. The ASSIST program also includes model-reduction techniques to facilitate efficient modeling of large systems. The semi-Markov model generated by ASSIST is in the format needed for input to SURE and PAWS/STEM. The Semi-Markov Unreliability Range Evaluator, SURE, is an analysis tool for reconfigurable, fault-tolerant systems. SURE provides an efficient means for calculating accurate upper and lower bounds for the death state probabilities for a large class of semi-Markov models, not just those which can be reduced to critical-pair architectures. The calculated bounds are close enough (usually within 5 percent of each other) for use in reliability studies of ultra-reliable computer systems. The SURE bounding theorems have algebraic solutions and are consequently computationally efficient even for large and complex systems. SURE can optionally regard a specified parameter as a variable over a range of values, enabling an automatic sensitivity analysis. SURE output is tabular. The PAWS/STEM package includes two programs for the creation and evaluation of pure Markov models describing the behavior of fault-tolerant reconfigurable computer systems: the Pade Approximation with Scaling (PAWS) and Scaled Taylor Exponential Matrix (STEM) programs. PAWS and STEM produce exact solutions for the probability of system failure and provide a conservative estimate of the number of significant digits in the solution. Markov models of fault-tolerant architectures inevitably lead to numerically stiff differential equations. Both PAWS and STEM have the capability to solve numerically stiff models. These complementary programs use separate methods to determine the matrix exponential in the solution of the model's system of differential equations. In general, PAWS is better suited to evaluate small and dense models. STEM operates at lower precision, but works faster than PAWS for larger models. The programs that comprise the SARA package were originally developed for use on DEC VAX series computers running VMS and were later ported for use on Sun series computers running

Butler, R. W.

1994-01-01

156

Adjoint operator approach to functional reliability analysis of passive fluid dynamical systems  

International Nuclear Information System (INIS)

Reliability analysis of passive systems mainly involves quantification of the margin to safety limits in probabilistic terms. For systems represented by complex models, propagating input uncertainty to get the response uncertainty and hence probability information requires intensive computational effort. Here a computationally efficient method for the functional reliability analysis of passive fluid dynamical systems is presented. The approach is based on continuous adjoint operator technique to generate a response surface approximating the given system model from the sensitivity coefficients. A numerical application of this method to the reliability analysis of heat transport in an asymmetrical natural convection loop is demonstrated. Computational efficiency and accuracy compared with the direct Monte-Carlo and forward response surface methods.

157

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

158

Reliability analysis (hardware) of a core temperature safety system  

International Nuclear Information System (INIS)

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

159

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

160

PRISM: probabilistic model checking for performance and reliability analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Probabilistic model checking is a formal verification technique for the modelling and analysis of stochastic systems. It has proved to be useful for studying a wide range of quantitative properties of models taken from many diffierent application domains. This includes, for example, performance and reliability properties of computer and communication systems. In this paper, we give an overview of the probabilistic model checking tool PRISM, focusing in particular on its support for continuous...

Kwiatkowska, Marta; Norman, Gethin; Parker, David

2009-01-01

 
 
 
 
161

Reliability analysis based on non-dimensional parameters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

162

Site-specific Probabilistic Load Modelling for Bridge Reliability Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reliability assessment of a short span beam-slab reinforced concrete bridge in Vienna is proposed using site-specific traffic data recorded using the Slovenian Weigh in Motion (SiWIM) system. An initial evaluation of the bridge using a determinintic approach shows that the critical limit state is bending. This paper describes the statistical analysis of the SiWIM data and the traffic flow simulations performed to predict the characteristic extreme load effects to which the bridge may be subje...

Caprani, Colin C.; Belay, A.; O Connor, A. J.

2003-01-01

163

Solid Rocket Booster Large Main and Drogue Parachute Reliability Analysis  

Science.gov (United States)

The parachutes on the Space Transportation System (STS) Solid Rocket Booster (SRB) are the means for decelerating the SRB and allowing it to impact the water at a nominal vertical velocity of 75 feet per second. Each SRB has one pilot, one drogue, and three main parachutes. About four minutes after SRB separation, the SRB nose cap is jettisoned, deploying the pilot parachute. The pilot chute then deploys the drogue parachute. The drogue chute provides initial deceleration and proper SRB orientation prior to frustum separation. At frustum separation, the drogue pulls the frustum from the SRB and allows the main parachutes that are mounted in the frustum to unpack and inflate. These chutes are retrieved, inspected, cleaned, repaired as needed, and returned to the flight inventory and reused. Over the course of the Shuttle Program, several improvements have been introduced to the SRB main parachutes. A major change was the replacement of the small (115 ft. diameter) main parachutes with the larger (136 ft. diameter) main parachutes. Other modifications were made to the main parachutes, main parachute support structure, and SRB frustum to eliminate failure mechanisms, improve damage tolerance, and improve deployment and inflation characteristics. This reliability analysis is limited to the examination of the SRB Large Main Parachute (LMP) and drogue parachute failure history to assess the reliability of these chutes. From the inventory analysis, 68 Large Main Parachutes were used in 651 deployments, and 7 chute failures occurred in the 651 deployments. Logistic regression was used to analyze the LMP failure history, and it showed that reliability growth has occurred over the period of use resulting in a current chute reliability of R = .9983. This result was then used to determine the reliability of the 3 LMPs on the SRB, when all must function. There are 29 drogue parachutes that were used in 244 deployments, and no in-flight failures have occurred. Since there are no observed drogue chute failures, Jeffreys Prior was used to calculate a reliability of R =.998. Based on these results, it is concluded that the LMP and drogue parachutes on the Shuttle SRB are suited to their mission and changes made over their life have improved the reliability of the parachute.

Clifford, Courtenay B.; Hengel, John E.

2009-01-01

164

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

Jinying Yang; Congzhi Wang; Weibao Qiu; Hairong Zheng

2014-08-01

165

A semi-Markov reliability analysis of alternating systems  

International Nuclear Information System (INIS)

Current nuclear power plants must be highly reliable with respect to safety and economy. Consequently, development of a new safety evaluation methodology is desired for the accurate evaluation of safety and economy. A nuclear power plant consists of many systems. This paper is concerned with the reliability evaluation of alternating systems. An alternating system usually consists of multitrains, and its operation alternates from one train to another. Examples of these are the nuclear service cooling water system, the component cooling water system, and the chemical and volume control system. The alternating systems exhibit strong dynamic time-dependent reliability characteristics because of the alternating operational mode and the technical specification requirements that are particularly difficult to analyze by static fault-tree techniques. The method used in this paper is based on the semi-Markov reliability analysis. The system performance measures evaluated are its contribution to the total risk of the plant (e.g., core damage probability) and to plant unavailability (reactor downtime). It is concluded that the methodology developed in this study can be applied to existing alternating systems for plant-specific evaluation of the various alternatives in technical specifications

166

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

167

Analysis of emergency diesel generators for improved reliability  

International Nuclear Information System (INIS)

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

168

Human reliability analysis in healthcare: A review of techniques  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Whilst Human Reliability Analysis (HRA) has been well-accepted and integrated into the safety management process in other industries, the application of such error analysis techniques to the problem of complication and reaction to treatment and the associated risks in healthcare is rare. Though the scarcity of HRA techniques in health-care is likely to be due in some part to the safety culture, much is likely to be due to a lack of awareness of the usefulness of the techniques and their appli...

Lyons, M.; Adams, S.; Woloshynowych, M.; Vincent, C.

2004-01-01

169

[Reliability of the novel gait analysis system RehaWatch].  

Science.gov (United States)

Quantitative gait analysis plays an important role in neurological and orthopedic rehabilitation regarding the evaluation of rehabilitation progress. However, most of the currently available gait analysis systems share the disadvantage of being expensive, time-consuming, and complex. A promising alternative is the portable gait analysis system RehaWatch. It is based on inertial sensors that allow the quantitative measurement of the important kinemetric variables acceleration and angular velocity. The associated software analyzes the sensor signals and calculates temporal (e.g., stride duration, gait phases) and spatial (e.g., stride length, foot angle) parameters on this basis. The aim of this study was to investigate the intraobserver reliability of RehaWatch. A total of 44 healthy subjects (age: 27.7±4.2 years) were included in the study. Each participant underwent three measurements (walking distance: 20 m) for each of the three sessions with a time interval of 48 h in-between. Variance analysis (General Linear Model) revealed no significant differences between gait parameters at different measuring points. ICCs (Average Measure Intraclass Correlations) were between 0.691 and 0.959. In addition to the results of the variance and correlation analysis the Bland-Altman plots suggest high reliability. PMID:20367327

Schwesig, René; Kauert, Ralf; Wust, Sylvia; Becker, Stephan; Leuchte, Siegfried

2010-04-01

170

Modeling of seismic hazards for dynamic reliability analysis  

International Nuclear Information System (INIS)

This paper investigates the appropriate indices of seismic hazard curves (SHCs) for seismic reliability analysis. In the most seismic reliability analyses of structures, the seismic hazards are defined in the form of the SHCs of peak ground accelerations (PGAs). Usually PGAs play a significant role in characterizing ground motions. However, PGA is not always a suitable index of seismic motions. When random vibration theory developed in the frequency domain is employed to obtain statistics of responses, it is more convenient for the implementation of dynamic reliability analysis (DRA) to utilize an index which can be determined in the frequency domain. In this paper, we summarize relationships among the indices which characterize ground motions. The relationships between the indices and the magnitude M are arranged as well. In this consideration, duration time plays an important role in relating two distinct class, i.e. energy class and power class. Fourier and energy spectra are involved in the energy class, and power and response spectra and PGAs are involved in the power class. These relationships are also investigated by using ground motion records. Through these investigations, we have shown the efficiency of employing the total energy as an index of SHCs, which can be determined in the time and frequency domains and has less variance than the other indices. In addition, we have proposed the procedure of DRA based on total energy. (author) energy. (author)

171

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

172

An improved radial basis function network for structural reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

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.

Dai, H. Z.; Zhao, W.; Wang, W.; Cao, Z. G. [Harbin Institute of Technology, Harbin (China)

2011-09-15

173

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

174

Reliability analysis of Indian pressurized heavy water reactor piping  

International Nuclear Information System (INIS)

In this paper, a probabilistic analysis of primary heat transport of Indian Pressurized Heavy Water reactor is presented. The probability of failure of the straight pipes with through wall circumferential flaws subjected to bending moment is calculated. The failure criteria considered is net section collapse and R6 method. Probability of failure is obtained with crack growth initiation as the limiting condition. The variability in the crack size and material properties (tensile and fracture) is considered. The probability of failure is calculated at different levels of applied load. Various methods of probability estimation are presented and their equivalence is demonstrated. The probability of failure is obtained using classical Monte Carlo method, Monte Carlo with importance sampling, First Order Reliability Method (FORM), Second Order Reliability Method (SORM) and by numerical integration of the failure integral using Lepage's VEGAS algorithm. The results are utilized for demonstrating that for the leakage size crack, the pipe design has high probability for leak before break. (orig.)

175

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

International Nuclear Information System (INIS)

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

176

Reliability analysis of neutron flux monitoring system for PFBR  

International Nuclear Information System (INIS)

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

177

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

178

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.)

179

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)

180

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)

 
 
 
 
181

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

Science.gov (United States)

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.; Singh, S. S. K.; Alebrahim, R.; Azizi, M. A.; K, Elwaleed A.; Noorani, M. S. M.

2014-06-01

182

The Reliability of an Instrumented Start Block Analysis System.  

Science.gov (United States)

The swimming start is highly influential to overall competition performance. Therefore, it is paramount to develop reliable methods to perform accurate biomechanical analysis of start performance for training and research. The Wetplate Analysis System is a custom-made force plate system developed by the Australian Institute of Sport - Aquatic Testing, Training and Research Unit (AIS ATTRU). This sophisticated system combines both force data and 2D digitisation to measure 43 kinetic and kinematic parameter values in an attempt to evaluate start performance. Fourteen elite swimmers performed two maximal effort dives (performance was defined as time from start signal to 15 m) over two separate testing sessions. Intra-class correlation coefficients (ICC) were used to determine each parameter's reliability. The kinetic parameters all had ICC greater than 0.9 except the time of peak vertical force (0.742). This may have been due to variations in movement initiation after the starting signal between trials. The kinematic and time parameters also had ICC greater than 0.9 apart from for the time of maximum depth (0.719). This parameter was lower due to the swimmers varying their depth between trials. Based on the high ICC scores for 43 parameters, the Wetplate Analysis System is suitable for biomechanical analysis of swimming starts. PMID:25268512

Tor, Elaine; Pease, David L; Ball, Kevin A

2014-09-30

183

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

184

Comparative analysis of metal samples  

International Nuclear Information System (INIS)

Metal wastes were analysed to establish its origin with respect to a set of pieces. The elemental analysis was realized using the PIXE technique (Proton induced X-ray emission). Results are presented. (Author)

185

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

186

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

187

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

188

Reliability analysis of a utility-scale solar power plant  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the results of a reliability analysis for a solar central receiver power plant that employs a salt-in-tube receiver. Because reliability data for a number of critical plant components have only recently been collected, this is the first time a credible analysis can be performed. This type of power plant will be built by a consortium of western US utilities led by the Southern California Edison Company. The 10 MW plant is known as Solar Two and is scheduled to be on-line in 1994. It is a prototype which should lead to the construction of 100 MW commercial-scale plants by the year 2000. The availability calculation was performed with the UNIRAM computer code. The analysis predicted a forced outage rate of 5.4% and an overall plant availability, including scheduled outages, of 91%. The code also identified the most important contributors to plant unavailability. Control system failures were identified as the most important cause of forced outages. Receiver problems were rated second with turbine outages third. The overall plant availability of 91% exceeds the goal identified by the US utility study. This paper discuses the availability calculation and presents evidence why the 91% availability is a credible estimate. 16 refs.

Kolb, G.J.

1992-01-01

189

Reliability analysis of a utility-scale solar power plant  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the results of a reliability analysis for a solar central receiver power plant that employs a salt-in-tube receiver. Because reliability data for a number of critical plant components have only recently been collected, this is the first time a credible analysis can be performed. This type of power plant will be built by a consortium of western US utilities led by the Southern California Edison Company. The 10 MW plant is known as Solar Two and is scheduled to be on-line in 1994. It is a prototype which should lead to the construction of 100 MW commercial-scale plants by the year 2000. The availability calculation was performed with the UNIRAM computer code. The analysis predicted a forced outage rate of 5.4% and an overall plant availability, including scheduled outages, of 91%. The code also identified the most important contributors to plant unavailability. Control system failures were identified as the most important cause of forced outages. Receiver problems were rated second with turbine outages third. The overall plant availability of 91% exceeds the goal identified by the US utility study. This paper discuses the availability calculation and presents evidence why the 91% availability is a credible estimate. 16 refs.

Kolb, G.J.

1992-08-01

190

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

191

Enrichment reliability of solid polymer electrolysis for tritium water analysis  

International Nuclear Information System (INIS)

We have developed a novel advanced enrichment apparatus for environmental tritium analysis called SPET (Solid Polymer Electrolysis for Tritium Water). It generates no explosive gas, requires no aqueous electrolyte, terminates enrichment rapidly, and the volume reduction is infinite. It has an automatic shutdown system which gives uniform conditions on every run, making the handling and determination of tritium concentrations very easy. The reliability of SPET was studied using environmental concentration standard water and the reproducibility error was found to be within 4%, which is sufficient for environmental measurements.(author)

192

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

193

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)

194

Reliability and validity of goniometric turnout measurements compared with MRI and retro-reflective markers.  

Science.gov (United States)

There is no consensus on a valid and reliable method of measuring turnout. However, there is a building awareness that such measures need to exist. Total turnout is the sum of hip rotation, tibial torsion, and contributions from the foot. To our knowledge, there has been no research that directly measures and then sums each individual component of turnout to verify a total turnout value. Furthermore, the tibial torsion component has not previously been confirmed by an imaging study. The purpose of this study was to test the validity and reliability of a single total passive turnout (TPT) test taken with a goniometer by comparing it with the sum of the individual components. Fourteen female dancers were recruited as participants. Measurements of the subjects' right and left legs were gathered for the components of turnout. Tibial torsion was measured using Magnetic Resonance Imaging (MRI). Retro-reflective marker assisted measurements were used to calculate the static components of TPT. Hip external rotation, TPT, and total active turnout (TAT) were measured by goniometer. Additional standing turnout values were collected on rotational disks. Tibial torsion and hip rotation were summed and compared with three whole-leg turnout values using Two-Tailed T-Tests and Pearson product-moment correlation coefficients. Tibial torsion measurements in dancers were found to demonstrate substantial variation between subjects and between legs in the same subject. The range on the right leg was 16 degrees to 60 degrees, and the range on the left leg was 16 degrees to 52 degrees. Retro-reflective markers and biomechanical theory demonstrated that when the knee is extended and locked, "screwed home," it will not factor into a whole-leg turnout value. TAT and turnout on the disks were not statistically significant when compared with the summed total. Statistical significance was achieved in four of the eight measurement series comparing TPT with the summed value of tibial torsion and hip rotation. The advantages of a standard, valid, and reliable method of measuring turnout are many, and the risks are few. Some advantages include improved training techniques, mastery of the use of turnout at an earlier age, better dancer and teacher compliance with suggested turnout rates, understanding the use of parallel position, understanding the etiology of many dance-related injuries, and possible development of preventative measures. PMID:19618571

Grossman, Gayanne; Waninger, Kevin N; Voloshin, Arkady; Reinus, William R; Ross, Rachael; Stoltzfus, Jill; Bibalo, Kathleen

2008-01-01

195

Evaluation of Reliability Coefficients for Two-Level Models via Latent Variable Analysis  

Science.gov (United States)

A latent variable analysis procedure for evaluation of reliability coefficients for 2-level models is outlined. The method provides point and interval estimates of group means' reliability, overall reliability of means, and conditional reliability. In addition, the approach can be used to test simple hypotheses about these parameters. The…

Raykov, Tenko; Penev, Spiridon

2010-01-01

196

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

International Nuclear Information System (INIS)

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

197

Reliability analysis of single crystal NiAl turbine blades  

Science.gov (United States)

As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

1995-01-01

198

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.

199

Standardization of domestic human reliability analysis and experience of human reliability analysis in probabilistic safety assessment for NPPs under design  

International Nuclear Information System (INIS)

This paper introduces the background and development activities of domestic standardization of procedure and method for Human Reliability Analysis (HRA) to avoid the intervention of subjectivity by HRA analyst in Probabilistic Safety Assessment (PSA) as possible, and the review of the HRA results for domestic nuclear power plants under design studied by Korea Atomic Energy Research Institute. We identify the HRA methods used for PSA for domestic NPPs and discuss the subjectivity of HRA analyst shown in performing a HRA. Also, we introduce the PSA guidelines published in USA and review the HRA results based on them. We propose the system of a standard procedure and method for HRA to be developed

200

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

 
 
 
 
201

CARES - CERAMICS ANALYSIS AND RELIABILITY EVALUATION OF STRUCTURES  

Science.gov (United States)

The beneficial properties of structural ceramics include their high-temperature strength, light weight, hardness, and corrosion and oxidation resistance. For advanced heat engines, ceramics have demonstrated functional abilities at temperatures well beyond the operational limits of metals. This is offset by the fact that ceramic materials tend to be brittle. When a load is applied, their lack of significant plastic deformation causes the material to crack at microscopic flaws, destroying the component. CARES calculates the fast-fracture reliability or failure probability of macroscopically isotropic ceramic components. These components may be subjected to complex thermomechanical loadings. The program uses results from a commercial structural analysis program (MSC/NASTRAN or ANSYS) to evaluate component reliability due to inherent surface and/or volume type flaws. A multiple material capability allows the finite element model reliability to be a function of many different ceramic material statistical characterizations. The reliability analysis uses element stress, temperature, area, and volume output, which are obtained from two dimensional shell and three dimensional solid isoparametric or axisymmetric finite elements. CARES utilizes the Batdorf model and the two-parameter Weibull cumulative distribution function to describe the effects of multi-axial stress states on material strength. The shear-sensitive Batdorf model requires a user-selected flaw geometry and a mixed-mode fracture criterion. Flaws intersecting the surface and imperfections embedded in the volume can be modeled. The total strain energy release rate theory is used as a mixed mode fracture criterion for co-planar crack extension. Out-of-plane crack extension criteria are approximated by a simple equation with a semi-empirical constant that can model the maximum tangential stress theory, the minimum strain energy density criterion, the maximum strain energy release rate theory, or experimental results. For comparison, Griffith's maximum tensile stress theory, the principle of independent action, and the Weibull normal stress averaging models are also included. Weibull material strength parameters, the Batdorf crack density coefficient, and other related statistical quantities are estimated from four-point bend bar or uniform uniaxial tensile specimen fracture strength data. Parameter estimation can be performed for single or multiple failure modes by using the least-squares analysis or the maximum likelihood method. A more limited program, CARES/PC (COSMIC number LEW-15248) runs on a personal computer and estimates ceramic material properties from three-point bend bar data. CARES/PC does not perform fast fracture reliability estimation. CARES is written in FORTRAN 77 and has been implemented on DEC VAX series computers under VMS and on IBM 370 series computers under VM/CMS. On a VAX, CARES requires 10Mb of main memory. Five MSC/NASTRAN example problems and two ANSYS example problems are provided. There are two versions of CARES supplied on the distribution tape, CARES1 and CARES2. CARES2 contains sub-elements and CARES1 does not. CARES is available on a 9-track 1600 BPI VAX FILES-11 format magnetic tape (standard media) or in VAX BACKUP format on a TK50 tape cartridge. The program requires a FORTRAN 77 compiler and about 12Mb memory. CARES was developed in 1990. DEC, VAX and VMS are trademarks of Digital Equipment Corporation. IBM 370 is a trademark of International Business Machines. MSC/NASTRAN is a trademark of MacNeal-Schwendler Corporation. ANSYS is a trademark of Swanson Analysis Systems, Inc.

Nemeth, N. N.

1994-01-01

202

Reliability and accuracy in three-dimensional gait analysis: a comparison of two lower body protocols.  

Science.gov (United States)

The standard Plug-in-Gait (PiG) protocol used in three-dimensional gait analysis is prone to errors arising from inconsistent anatomical landmark identification and knee axis malalignment. The purpose of this study was to estimate the reliability and accuracy of a custom made lower body protocol (MA) compared with the PiG protocol. Twenty-five subjects volunteered to evaluate the intertrial reliability. In addition, intersession reliability was examined in 10 participants. An indirect indicator of accuracy according to the knee varus/valgus and flexion/extension range of motion (ROM) was used. Regarding frontal plane knee angles and moments as well as transverse plane motions in the knee and hip joint, the intersession errors were lower for the MA compared with the standard approach. In reference to the knee joint angle cross-talk, the MA produced 4.7° more knee flexion/extension ROM and resulted in 6.5° less knee varus/valgus ROM in the frontal plane. Therefore, the MA tested in this study produced a more accurate and reliable knee joint axis compared with the PiG protocol. These results are especially important for measuring frontal and transverse plane gait parameters. PMID:22813723

Stief, Felix; Böhm, Harald; Michel, Katja; Schwirtz, Ansgar; Döderlein, Leonhard

2013-02-01

203

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

International Nuclear Information System (INIS)

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

204

Comparative kinetic analysis of two fungal ?-glucosidases  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The enzymatic hydrolysis of cellulose is still considered as one of the main limiting steps of the biological production of biofuels from lignocellulosic biomass. It is a complex multistep process, and various kinetic models have been proposed. The cellulase enzymatic cocktail secreted by Trichoderma reesei has been intensively investigated. ?-glucosidases are one of a number of cellulolytic enzymes, and catalyze the last step releasing glucose from the inhibitory cellobiose. ?-glucosidase (BGL1 is very poorly secreted by Trichoderma reesei strains, and complete hydrolysis of cellulose often requires supplementation with a commercial ?-glucosidase preparation such as that from Aspergillus niger (Novozymes SP188. Surprisingly, kinetic modeling of ?-glucosidases lacks reliable data, and the possible differences between native T. reesei and supplemented ?-glucosidases are not taken into consideration, possibly because of the difficulty of purifying BGL1. Results A comparative kinetic analysis of ?-glucosidase from Aspergillus niger and BGL1 from Trichoderma reesei, purified using a new and efficient fast protein liquid chromatography protocol, was performed. This purification is characterized by two major steps, including the adsorption of the major cellulases onto crystalline cellulose, and a final purification factor of 53. Quantitative analysis of the resulting ?-glucosidase fraction from T. reesei showed it to be 95% pure. Kinetic parameters were determined using cellobiose and a chromogenic artificial substrate. A new method allowing easy and rapid determination of the kinetic parameters was also developed. ?-Glucosidase SP188 (Km = 0.57 mM; Kp = 2.70 mM has a lower specific activity than BGL1 (Km = 0.38 mM; Kp = 3.25 mM and is also more sensitive to glucose inhibition. A Michaelis-Menten model integrating competitive inhibition by the product (glucose has been validated and is able to predict the ?-glucosidase activity of both enzymes. Conclusions This article provides a useful comparison between the activity of ?-glucosidases from two different fungi, and shows the importance of fully characterizing both enzymes. A Michaelis-Menten model was developed, including glucose inhibition and kinetic parameters, which were accurately determined and compared. This model can be further integrated into a cellulose hydrolysis model dissociating ?-glucosidase activity from that of other cellulases. It can also help to define the optimal enzymatic cocktails for new ?-glucosidase activities.

Casanave Dominique

2010-02-01

205

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)

206

Current situation and development on reliability analysis of operation process in the nuclear power plant  

International Nuclear Information System (INIS)

Reliability analysis on operation process in nuclear power plant is the key basis of ensuring safety and the requirement to improve the effectiveness of plant. Taking the background of operation process reliability as a starting point in consideration, the adaptability of reliability analysis method was reviewed and technical ways of analyzing related problems were discussed

207

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

208

Rent control: a comparative analysis  

Scientific Electronic Library Online (English)

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

S, Maass.

209

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

210

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

211

A Fault Analysis based Model for Software Reliability Estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Garima Chawla,; Santosh Kr Thakur,

2013-01-01

212

Performance Analysis of Reliability in Wireless Sensor Network  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nowadays Wireless Sensor Network (WSN) is top rising field .It is broadly used in lots of application areas since previous few years. Sensor is the mainly significant and fundamental part in WSN. Reliability is one of the key aspects of WSN. Reliability is nothing but the consistency in measuring the results. It is necessary for efficient and reliable data transmission process. Congestion control is required for increasing reliability of network. In this paper, we are discussing the effects o...

Maktedar, Praful P.; Deshpande, Asso Prof Vivek S.; Helonde, Dr J. B.; Wadhai, Dr V. M.

2013-01-01

213

A Fault Analysis based Model for Software Reliability Estimation  

Directory of Open Access Journals (Sweden)

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

Garima Chawla,

2013-07-01

214

Reliability analysis of diesel generators of Wolsung Unit 1  

International Nuclear Information System (INIS)

As a maintenance optimization project to improve the safety of Wolsung NPP (Nuclear Power Plant), reliability of diesel generators are estimated based on the operating experience, and improvement options are suggested. A reliability measure is suggested for the estimation of reliability for standby safety systems to reflect availability. It is assessed that the reliability of diesel generators can be much improved if the suggested improvement options are implemented

215

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

216

Reliability Analysis of Metro Door System Based on FMECA  

Directory of Open Access Journals (Sweden)

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

Xiaoqing Cheng

2013-11-01

217

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

218

Time-dependent reliability analysis and condition assessment of structures  

International Nuclear Information System (INIS)

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

219

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

220

Reliability analysis of the service water system of Angra 1 reactor  

International Nuclear Information System (INIS)

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

 
 
 
 
221

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

222

Study on the Reliability Data Analysis Method for Electric Fuze  

Science.gov (United States)

Some key points of reliable data collection and analytic technology of the electric fuze are discussed in this paper. The produce, collection methods, note proceedings of the reliable data of the electric fuze are also discussed, so reliable database of every component in the electric fuzes should be established, the primary and secondary method - - an analytical method which uses the reliable data of the electric fuze with the application of the fuze products, then the key components which have influences on the reliability can be found.

Xu, Jianjun; Wang, Zhijun

223

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

224

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

225

Application of Support Vector Machine to Reliability Analysis of Engine Systems  

Directory of Open Access Journals (Sweden)

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

Zhang Xinfeng

2013-07-01

226

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

Science.gov (United States)

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

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

2014-10-01

227

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)

228

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1983-05-01

229

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

230

Reliability Analysis For Substation Employing B. F. Technique  

Directory of Open Access Journals (Sweden)

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

MOHIT KUMAR, RAM AVTAR JASWAL

2013-06-01

231

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

232

De-aggregated reliability analysis of freezing rain hazard  

Science.gov (United States)

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

Erfani, Reza

233

The reliability of mercury analysis in environmental materials  

International Nuclear Information System (INIS)

Mercury occurs in nature in its native elemental as well as in different mineral forms. It has been mined for centuries and is used in many branches of industry, agriculture and medicine. Mercury is very toxic to man and reports of poisoning due to the presence of the element in fish and shellfish caught at Minamata and Niigata, Japan have led not only to local investigations but to multi-national research into the sources and the levels of mercury in the environment. The concentrations at which the element has to be determined in these studies are extremely small, usually of the order of a few parts in 109 parts of environmental material. Few analytical techniques provide the required sensitivity for analysis at such low concentrations, and only two are normally used for mercury: neutron activation analysis and atomic absorption photometry. They are also the most convenient end points of various separation schemes for different organic mercury compounds. Mercury analysis at the ppb-level is beset with many problems: volatility of the metal and its compounds, impurity of reagents, interference by other elements and many other analytical difficulties may influence the results. To be able to draw valid conclusions from the analyses it is necessary to know the reliability attached to the values obtained. To assist laboratories in the evaluation of their analytical performance, the International Atomic Energy Agency through its own laboratory at Seibersdorf already organised in 1967 an intercomparison of mercury analysis in flour. Based on the results obtained at that time, a whole series of intercomparisons of mercury determinations in nine different environmental materials was undertaken in 1971. The materials investigated included corn and wheat flour, spray-dried animal blood serum, fish solubles, milk powder, saw dust, cellulose, lacquer paint and coloric material

234

Inservice data reporting standards for engineering reliability and risk analysis  

International Nuclear Information System (INIS)

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

235

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

236

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)

237

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)

238

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)

239

The effect of loss functions on empirical Bayes reliability analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 propose...

Camara, Vincent A. R.; Tsokos, Chris P.

1999-01-01

240

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.

 
 
 
 
241

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

242

Performance Analysis of Reliability in Wireless Sensor Network  

Directory of Open Access Journals (Sweden)

Full Text Available Nowadays Wireless Sensor Network (WSN is top rising field .It is broadly used in lots of application areas since previous few years. Sensor is the mainly significant and fundamental part in WSN. Reliability is one of the key aspects of WSN. Reliability is nothing but the consistency in measuring the results. It is necessary for efficient and reliable data transmission process. Congestion control is required for increasing reliability of network. In this paper, we are discussing the effects of node density and reporting rate on the network performance.

Mr. Praful P. Maktedar

2013-03-01

243

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

244

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

International Nuclear Information System (INIS)

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

245

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-02-01

246

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

247

Monte Carlo methods for the reliability analysis of Markov systems  

International Nuclear Information System (INIS)

This paper presents Monte Carlo methods for the reliability analysis of Markov systems. Markov models are useful in treating dependencies between components. The present paper shows how the adjoint Monte Carlo method for the continuous time Markov process can be derived from the method for the discrete-time Markov process by a limiting process. The straightforward extensions to the treatment of mean unavailability (over a time interval) are given. System unavailabilities can also be estimated; this is done by making the system failed states absorbing, and not permitting repair from them. A forward Monte Carlo method is presented in which the weighting functions are related to the adjoint function. In particular, if the exact adjoint function is known then weighting factors can be constructed such that the exact answer can be obtained with a single Monte Carlo trial. Of course, if the exact adjoint function is known, there is no need to perform the Monte Carlo calculation. However, the formulation is useful since it gives insight into choices of the weight factors which will reduce the variance of the estimator

248

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)

249

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

250

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

251

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

International Nuclear Information System (INIS)

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

252

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

International Nuclear Information System (INIS)

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

253

Comparative analysis of seismic risk assessment methodology  

Energy Technology Data Exchange (ETDEWEB)

SRA methodologies are separated into SPSA and SMM. SPSA methodology that has been widely used for seismic risk analysis has two kinds of methodologies such as Zion method and SSMRP method. SPSA methodology is suitable to interfacing with the analysis of internal event. However, the results of SPSA have uncertainties because of uncertainties in seismic hazard analysis and subjective judgement. Zion method specially developed for commercial use is less expensive and less time consuming but more uncertain than SSMRP method, since the former performs the fragility analysis less in detail than the latter. SMM is impossible to interface with the analysis of internal event but the uncertainties that are occurred during seismic hazard analysis is reduced because of the screening using RLE (review level earthquake). Therefore, if SPSA-based SMM methodology is chosen to be developed, the results of SRA will be more reliable and it requires low costs and time. In addition, the new methodology will require the development of a new evaluating code for SRA. (Author) 26 refs., 25 figs., 16 tabs.

Park, Chang Kyoo; Kim, Tae Woon; Hwang, Mi Jung [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1994-07-01

254

Comparative analysis of seismic risk assessment methodology  

International Nuclear Information System (INIS)

SRA methodologies are separated into SPSA and SMM. SPSA methodology that has been widely used for seismic risk analysis has two kinds of methodologies such as Zion method and SSMRP method. SPSA methodology is suitable to interfacing with the analysis of internal event. However, the results of SPSA have uncertainties because of uncertainties in seismic hazard analysis and subjective judgement. Zion method specially developed for commercial use is less expensive and less time consuming but more uncertain than SSMRP method, since the former performs the fragility analysis less in detail than the latter. SMM is impossible to interface with the analysis of internal event but the uncertainties that are occurred during seismic hazard analysis is reduced because of the screening using RLE (review level earthquake). Therefore, if SPSA-based SMM methodology is chosen to be developed, the results of SRA will be more reliable and it requires low costs and time. In addition, the new methodology will require the development of a new evaluating code for SRA. (Author) 26 refs., 25 figs., 16 tabs

255

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.

256

Simple method for comparing reliability of two serum tumour markers in breast carcinoma.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

AIMS--To compare the two breast tumour markers, CA15-3 and mucinous-like carcinoma associated antigen (MCA), using Receiver Operating Characteristic (ROC) curve analysis. METHODS--One hundred and ninety six patients "presenting" with breast carcinoma had serum CA15-3 and MCA concentrations measured. RESULTS--Using these markers as indicators of stage IV disease at the recommended laboratory level, true positive rates (TPR) and false positive rates (FPR) were obtained as follows: CA15-3 TPR = ...

O Brien, D. P.; Gough, D. B.; Skehill, R.; Grimes, H.; Given, H. F.

1994-01-01

257

Comparative analysis of methods of hardness assessment  

Directory of Open Access Journals (Sweden)

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

A. Czarski

2009-12-01

258

Reliability Analysis of Distribution Automation on Different Feeders  

Directory of Open Access Journals (Sweden)

Full Text Available Automating a distribution system is an effective means to provide a more reliable and economical system in the fast growing technological world. This paper delivers into automating a system using two- stage restoration (partial automation and put forward a feeder automation system based on substation automation platform that can be applied to electrical distribution systems for high economic-technical efficiency. Improved reliability is evaluated when feeder automation is applied to distribution. This paper studies three different feeders and decides on the most probable reliable feeder among them.

V. Krishna Murthy

2011-12-01

259

Reliability improvement of robotics systems: Analysis, design and real time supervision  

International Nuclear Information System (INIS)

Reliability improvement of Robotics Systems is a key issue in automation and autonomy in maintenance and intervention tasks in Hostile Environment. Constraints in hostile environment require different way of using and programming of robots when compared with industrial application. To take maximum benefit of robot technology, the level of Confidence in the robotics tool must be much higher than in classical production world. To increase this level of confidence, application of Reliability Engineering in combination with strong knowledge of robot technology leads to such an objective. In this paper, three different aspects are considered and developed as tools to be used in different stage of this improvement. The first one is the Analysis of reliability of robotics and in remote handling systems in general to identify failure modes, effects on the system, sensitive components and needs of redundancy. Tools as the Failure Modes, Effects and Criticality Analysis are presented as well as the Fault Tree Analysis. The second one deals with design criteria for new robot systems or improvement of existing one using reliability and safety driven design concepts. Such concepts are applicable on mechanical design, electrical design and electronic design including the computer controller of the robot. The last aspect is the control in real time of availability of functions, safety level as well as failure detection in the various subsystems composing a robot device. Techniques oems composing a robot device. Techniques of supervision by use of safety check subroutines are considered. Experiences of such improvement process of robotics for maintenance of Fusion machines is discussed. (author). Figs

260

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

 
 
 
 
261

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

262

Analysis of the Component-Based Reliability in Computer Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 failure of a computer network to the system parameters.Desempeño en términos de fiabilidad de redes de computador notiva este artículo. Teoremas límite sobre la duración extrema de cola y el ti...

Img Jpg Gt Ius, Saulius Minkevi Lt Img Width Height Src Http Fbpe Img Cubo V. N.

2010-01-01

263

Reliability Analysis in Parallel and Distributed Systems with Network Contention  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

El, Hussein Ghor; Rafic Hage Chehade; Tamim Fliti

2012-01-01

264

Time-dependent reliability analysis of nuclear reactor operators using probabilistic network models  

International Nuclear Information System (INIS)

Human factors are very important for the reliability of a nuclear power plant. Human behavior has essentially a time-dependent nature. The details of thinking and decision making processes are important for detailed analysis of human reliability. They have, however, not been well considered by the conventional methods of human reliability analysis. The present paper describes the models for the time-dependent and detailed human reliability analysis. Recovery by an operator is taken into account and two-operators models are also presented

265

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

266

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The human reliability analysis (HRA) is a highly subjective evaluation of human performance, which is an input for probabilistic safety assessment, which deals with many parameters of high uncertainty. The objective of this paper is to show that subjectivism can have a large impact on human reliability results and consequently on probabilistic safety assessment results and applications. The objective is to identify the key features, which may decrease subjectivity of human reliability analysi...

Marko ?epin

2008-01-01

267

Comparative analysis of radionuclide inventory in sediment 1995  

International Nuclear Information System (INIS)

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

268

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

269

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Sozer, Hasan; Tekinerdogan, Bedir; Aksit, Mehmet

2007-01-01

270

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

271

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

272

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

273

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

274

A comparative analysis of aircraft noise performances  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a comparative analysis of aircraft acoustical performance based on the definition of a noise performance indicator called ENSA (equivalent number of standard aircraft). ENSA methodology is based on the choice of a standard aircraft, then ENSA’s values are obtained by comparing the generic aircraft’s performances with the standard aircraft’s performances. The performance evaluation is performed by analysing for each aircraft the equivalent number of standard aircrafts...

Nicola Gualandi; Luca Mantecchini

2009-01-01

275

Comparative analysis of rigidity across protein families  

International Nuclear Information System (INIS)

We present a comparative study in which 'pebble game' rigidity analysis is applied to multiple protein crystal structures, for each of six different protein families. We find that the main-chain rigidity of a protein structure at a given hydrogen bond energy cutoff is quite sensitive to small structural variations, and conclude that the hydrogen bond constraints in rigidity analysis should be chosen so as to form and test specific hypotheses about the rigidity of a particular protein. Our comparative approach highlights two different characteristic patterns ('sudden' or 'gradual') for protein rigidity loss as constraints are removed, in line with recent results on the rigidity transitions of glassy networks

276

Highly comparative fetal heart rate analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A database of fetal heart rate (FHR) time series measured from 7221 patients during labor is analyzed with the aim of learning the types of features of these recordings that are informative of low cord pH. Our 'highly comparative' analysis involves extracting over 9000 time-series analysis features from each FHR time series, including measures of autocorrelation, entropy, distribution, and various model fits. This diverse collection of features was developed in previous work...

Fulcher, B. D.; Georgieva, A. E.; Redman, C. W. G.; Jones, Nick S.

2014-01-01

277

Comparative analysis of methods of hardness assessment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: The aim of this paper is to show how it could utilize the statistical methods for the process management.Design/methodology/approach: The research methodology bases on a theoretical analysis and empirical researches. A practical solution is presented to compare measurements methods of hardness and to estimate capability indices of measurement system.Findings: Measurement system analysis (MSA), particularly theory of statistical tests brings correct results for the analysed case.Resea...

Czarski, A.

2009-01-01

278

System Analysis of International Relations: Concepts’ Comparability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The article is devoted to analysis upon comparison of international relations concepts which were formed in the environment of existence of various political regimes. First of all we mean concepts of such periods: soviet totalitarianism (USSR), post soviet authoritarianism (Russia) and democratic transformation (Ukraine). The very basis of research method which contains comparative analysis of international relations can be presented in the form of the following components. First. The m...

Troyan, Sergey

2009-01-01

279

A comparative analysis of frog early development  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The current understanding of Xenopus laevis development provides a comparative background for the analysis of frog developmental modes. Our analysis of development in various frogs reveals that the mode of gastrulation is associated with developmental rate and is unrelated to egg size. In the gastrula of the rapidly developing embryos of the foam-nesting frogs Engystomops coloradorum and Engystomops randi, archenteron and notochord elongation overlapped with involution at the blastopore lip, ...

Del Pino, Eugenia M.; Venegas-ferri?n, Michael; Romero-carvajal, Andre?s; Montenegro-larrea, Paola; Sa?enz-ponce, Natalia; Moya, Iva?n M.; Alarco?n, Ingrid; Sudou, Norihiro; Yamamoto, Shinji; Taira, Masanori

2007-01-01

280

Mapping Green Spaces in Bishkek—How Reliable can Spatial Analysis Be?  

Directory of Open Access Journals (Sweden)

Full Text Available Within urban areas, green spaces play a critically important role in the quality of life. They have remarkable impact on the local microclimate and the regional climate of the city. Quantifying the ‘greenness’ of urban areas allows comparing urban areas at several levels, as well as monitoring the evolution of green spaces in urban areas, thus serving as a tool for urban and developmental planning. Different categories of vegetation have different impacts on recreation potential and microclimate, as well as on the individual perception of green spaces. However, when quantifying the ‘greenness’ of urban areas the reliability of the underlying information is important in order to qualify analysis results. The reliability of geo-information derived from remote sensing data is usually assessed by ground truth validation or by comparison with other reference data. When applying methods of object based image analysis (OBIA and fuzzy classification, the degrees of fuzzy membership per object in general describe to what degree an object fits (prototypical class descriptions. Thus, analyzing the fuzzy membership degrees can contribute to the estimation of reliability and stability of classification results, even when no reference data are available. This paper presents an object based method using fuzzy class assignments to outline and classify three different classes of vegetation from GeoEye imagery. The classification result, its reliability and stability are evaluated using the reference-free parameters Best Classification Result and Classification Stability as introduced by Benz et al. in 2004 and implemented in the software package eCognition (www.ecognition.com. To demonstrate the application potentials of results a scenario for quantifying urban ‘greenness’ is presented.

Peter Hofmann

2011-05-01

 
 
 
 
281

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

282

Reliability Engineering Analysis of ATLAS Data Reprocessing Campaigns  

CERN Document Server

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

Vaniachine, A; The ATLAS collaboration; Karpenko, D

2013-01-01

283

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

284

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

285

Reliability analysis for LEB ring magnet power system in SSC  

International Nuclear Information System (INIS)

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

286

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

287

Teacher Policy: A Framework for Comparative Analysis  

Science.gov (United States)

This article outlines a framework for analysis of teacher focused policy studies within an international and comparative perspective. Using the notion of the professional life cycle of teachers, the article examines examples of key empirical studies that illustrate the impact of policy on addressing such issues as teacher recruitment, education,…

Tatto, Maria Teresa

2008-01-01

288

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

289

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-04-01

290

Reliability Analysis in Parallel and Distributed Systems with Network Contention  

Directory of Open Access Journals (Sweden)

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

Hussein EL Ghor

2012-11-01

291

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

292

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

293

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

294

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

International Nuclear Information System (INIS)

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

295

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

296

An Empirical Analysis of the Effect of Criticality, Complexity and Organisational Influence on Software Reliability  

Directory of Open Access Journals (Sweden)

Full Text Available This paper is motivated by a desire to improve software reliability, in particular, the reliability of software that impacts the operational and financial viability of organisations. We examine the effects of Criticality, Complexity, and Organisational Influence on information systems reliability. Questionnaires were used to gather quantitative data for statistical analysis. Post-hoc in-depth interviews were used to help explain results of the statistical analysis. Surprisingly, no associations were observed between Reliability and Criticality or between Reliability and Complexity. A positive relationship was found, however, between system Reliability and Organisational Influence. The interviews indicated that organisations mitigated the potential negative effects of Complexity through additional planning, and achieved more reliable software by assigning more competent project managers They managed Criticality by assigning more competent project managers to more critical systems. The significant relationship between system Reliability and Organisational Influence indicates that IS managers respond to internal political pressures. This result implies that senior management should take steps to ensure that excessive Organisational Influence does not cause IS managers to misallocate resources. For example, for each major project, the IS steering committee can determine the desired level of reliability, appoint project mangers with the appropriate skill set, and periodically communicate with these project managers about the activities used to achieve each system's desired level of reliability.

Paul Bowen

2000-11-01

297

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)

298

Predicting Rainfall Using the Principles of Fuzzy Set Theory and Reliability Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents occurrence of rainfall using principles of fuzzy set theory and principles of reliability analysis. Both the abstract and the rest of the paper are discussed from these two points of view. First, a fuzzy inference model for predicting rainfall using scan data from the USDA Soil Climate Analysis Network Station at Alabama Agricultural and Mechanical University (AAMU campus for the year 2004 is presented. The model further reflects how an expert would perceive weather conditions and apply this knowledge before inferring a rainfall. Fuzzy variables were selected based on judging patterns in individual monthly graphs for 2003 and 2004 and the influence of different variables that caused rainfall. A decrease in temperature (TP and an increase in wind speed (WS when compared between the ith and (i ? 1th day were found to have a positive relation with a rainfall (RF occurrence in most cases. Therefore, TP and WS were used in the antecedent part of the production rules to predict rainfall (RF. Results of the model showed better performance when threshold values for 1 Relative Humidity (RH of ith day; 2 Humidity Increase (HI between the ith and (i ? 1th day; and 3 Product (P of decrease in temperature (TP and an increase in wind speed (WS were introduced. The percentage of error was 12.35 when compared the calculated amount of rainfall with actual amount of rainfall. This is followed by prediction of rainfall using principles of reliability analysis. This is done by comparing theoretical probabilities with experimental probabilities for the occurrence of two main events, namely, Relative Humidity (RH and Humidity Increase (HI being in between specified threshold values. The experimental values of probability are falling in between ? ? ? and ? + ? for both RH and HI parameters, where ? is the mean value and ? is the standard deviation.

Mahbub Hasan

2013-11-01

299

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.

300

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

International Nuclear Information System (INIS)

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

 
 
 
 
301

Reliability analysis of Airbus A-330 computer flight management system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Diploma thesis deals with digitized, computerized flight control system »Fly-by-wire« and security aspects of the computer system of an aircraft Airbus A330. As for space and military aircraft structures is also in commercial airplanes, much of the financial contribution devoted to reliability. Conventional aircraft control systems have, and some are still, to rely on mechanical and hydraulic connections between the controls on aircraft operated by the pilot and control surfaces. But newer...

Fajmut, Metod

2010-01-01

302

Modified generalized linear failure rate distribution: Properties and reliability analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

303

Seismic reliability analysis of nuclear power plant piping system  

International Nuclear Information System (INIS)

The objective of the study presented was to develop a method for analyzing stochastic seismic stress of piping system subjected to multiple support excitations specified in terms of different response spectrum at all supports. Simultaneously, the cross-correlation of the modal response with close frequency is considered. Using the second moment method, the failure probability of the piping element can be given, further, the reliability of the piping system can be also found

304

Launch and Assembly Reliability Analysis for Human Space Exploration Missions  

Science.gov (United States)

NASA's future human space exploration strategy includes single and multi-launch missions to various destinations including cis-lunar space, near Earth objects such as asteroids, and ultimately Mars. Each campaign is being defined by Design Reference Missions (DRMs). Many of these missions are complex, requiring multiple launches and assembly of vehicles in orbit. Certain missions also have constrained departure windows to the destination. These factors raise concerns regarding the reliability of launching and assembling all required elements in time to support planned departure. This paper describes an integrated methodology for analyzing launch and assembly reliability in any single DRM or set of DRMs starting with flight hardware manufacturing and ending with final departure to the destination. A discrete event simulation is built for each DRM that includes the pertinent risk factors including, but not limited to: manufacturing completion; ground transportation; ground processing; launch countdown; ascent; rendezvous and docking, assembly, and orbital operations leading up to trans-destination-injection. Each reliability factor can be selectively activated or deactivated so that the most critical risk factors can be identified. This enables NASA to prioritize mitigation actions so as to improve mission success.

Cates, Grant; Gelito, Justin; Stromgren, Chel; Cirillo, William; Goodliff, Kandyce

2012-01-01

305

Significance Test of Reliability Evaluation with Three-parameter Weibull Distribution Based on Grey Relational Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available With the aid of the grey system theory, the grey relational analysis of the reliability with the three-parameter Weibull distribution is made for the Weibull parameter evaluation and its significance test. Via the theoretical value set and the experimental value set of the reliability relied on the lifetime data of a product, the model of the constrained optimization of the Weibull parameter evaluation based on the maximum grey relational grade. The grey significance of the reliability function with the three-parameter Weibull distribution is tested by means of the proposed criterion of the grey significance analysis of the reliability evaluation at the given grey confidence level. The cases of the helicopter component, the specimen and the ceramic material show that the grey relational analysis of the reliability is effective in the Weibull parameter evaluation and its significance test.

Xintao Xia

2013-06-01

306

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

International Nuclear Information System (INIS)

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

307

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

308

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)

309

COMPARATIVE ANALYSIS OF STRESS OF COMPETITIVE ORGANIZATIONS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Kolic?, Marina

2012-01-01

310

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

311

Comparative genomic analysis of prion genes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Gamulin Vera; Premzl Marko

2007-01-01

312

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)

313

Reliability analysis of K-out-of-N: G systems with dependent failures and imperfect coverage  

International Nuclear Information System (INIS)

This paper presents a Markov model for reliability analysis of K-out-of-N: G systems subject to dependent failures with imperfect coverage. Closed form solutions of the probabilities are used to obtain the reliability and the mean time to failure (MTTF). A numerical example is provided to illustrate the results

314

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

315

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

316

Analysis of nickel-cadmium battery reliability data containing zero failures  

Science.gov (United States)

An analysis of reliability data on Nickel-Cadmium (NiCd) batteries (for use in spacecraft) is presented. The data were collected by Gates Aerospace and represent a substantial reliability database. The data were taken from the performance of 183 satellites which were in operation from between .1 and 22 years, for a total of 278 million cell-hours of operation.

Denson, William K.; Klein, Glenn C.

1992-01-01

317

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

318

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

319

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

320

The reliability analysis of the diversity structure of for integral reactor  

International Nuclear Information System (INIS)

It is commonly recognized that system reliability and functionality of digital system are better than those of analog system in general cases. Moreover, the digital system is superior in system operation and maintenance compared to the existing analog system. However, in spite of these advantages, there are also negative factors in the application of this new technology to the safety system design since there exists a potential in common mode failure of system operations. Generally, the diversity is adopted to prevent Common Mode Failure(CMF) of the Instrumentation and Control System (I and C) using digital technology in the nuclear fields. We implemented the diversity within a channel to prevent CMF of the Plant Protection System (PPS) using digital technology for integral reactor. Each PPS channel has two sets of different hardware. The purpose of this paper is to evaluate the effects on the reliability of PPS adopting the diverse mean and to assure the integrity of PPS. This paper shows that the result of reactor trip success probability of PPS is higher than the value of the analog system. Finally we demonstrate the integrity of PPS design in SMART Pilot Plant through the comparative analysis of results of the reactor trip success probability for PPS and that of existing analog one

 
 
 
 
321

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 metabolic rates (drifts 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

322

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

International Nuclear Information System (INIS)

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

323

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.

324

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

325

Reliability analysis of digital instrumentation and control systems  

International Nuclear Information System (INIS)

The NUREG-CR/6942 technical report proposed a Markov state transition model for the main feedwater valve (MFV) controller system as part of a Probabilistic Risk Assessment (PRA) of Digital Feedwater Control System (DFWCS). The proposed model extends the Markov model to allow the use of non-exponential distribution in the time to next output of the controller system responsible for maintaining the water level. This case study demonstrates the general application of semi-Markov process model for digital instrumentation and control systems. System failure probability and mission reliability measures are determined. (author)

326

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

327

Preliminary analysis of the impact of power cycling on CTA-21 equipment reliability  

Science.gov (United States)

The effects of power turn-off on Deep Space Station control room equipment were considered. Reliability analysis indicated that there may be some correlation between an observed increase in failure rate and cycling equipment power.

Cole, E. R.

1978-01-01

328

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 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

329

Highly comparative fetal heart rate analysis.  

Science.gov (United States)

A database of fetal heart rate (FHR) time series measured from 7 221 patients during labor is analyzed with the aim of learning the types of features of these recordings that are informative of low cord pH. Our 'highly comparative' analysis involves extracting over 9 000 time-series analysis features from each FHR time series, including measures of autocorrelation, entropy, distribution, and various model fits. This diverse collection of features was developed in previous work [1]. We describe five features that most accurately classify a balanced training set of 59 'low pH' and 59 'normal pH' FHR recordings. We then describe five of the features with the strongest linear correlation to cord pH across the full dataset of FHR time series. The features identified in this work may be used as part of a system for guiding intervention during labor in future. This work successfully demonstrates the utility of comparing across a large, interdisciplinary literature on time-series analysis to automatically contribute new scientific results for specific biomedical signal processing challenges. PMID:23366590

Fulcher, B D; Georgieva, A E; Redman, C W G; Jones, N S

2012-01-01

330

Use of Fault Tree Analysis for Automotive Reliability and Safety Analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Lambert, H

2003-09-24

331

Reliability of three-dimensional gait analysis in adults with acquired incomplete spinal cord injury  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background: Incomplete spinal cord injury (SCI) results in varying degrees of gait impairments. Three-dimensional (3D) gait analysis has been recommended as part of a standardised gait assessment for individuals with incomplete SCI. However, reliability of 3D gait analysis has not been established for this population. The aim of the present study was to investigate intra- and inter-session reliability of gait kinematics in a group of individuals with incomplete SCI. We also sought to estimate...

Wedege, Pia

2013-01-01

332

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

International Nuclear Information System (INIS)

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

333

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

334

Emergency diesel generator reliability analysis high flux isotope reactor  

International Nuclear Information System (INIS)

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

335

Reliability analysis of discrete event dynamic systems with Petri nets  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-11-15

336

Comparative analysis of protein interaction networks.  

Science.gov (United States)

Recent advances in proteomics and computational biology have lead to a flood of protein interaction data and resulting interaction networks (e.g. (Gavin et al., 2002)). Here I first analyse the status and quality of parts lists (genes and proteins), then comparatively assess large-scale protein interaction data (von Mering et al., 2002) and finally try to identify biological meaningful units (e.g. pathways, cellular processes) within interaction networks that are derived from the conservation of gene neighborhood (Snel et al., 2002). Possible extensions of gene neighborhood analysis to eukaryotes (von Mering and Bork, 2002) will be discussed. PMID:12385984

Bork, Peer

2002-01-01

337

Update of the human reliability analysis for a nuclear power plant  

International Nuclear Information System (INIS)

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

338

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

International Nuclear Information System (INIS)

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

339

Summary of the preparation of methodology for digital system reliability analysis for PSA purposes  

International Nuclear Information System (INIS)

The report is structured as follows: Specific features of and requirements for the digital part of NPP Instrumentation and Control (I and C) systems (Computer-controlled digital technologies and systems of the NPP I and C system; Specific types of digital technology failures and preventive provisions; Reliability requirements for the digital parts of I and C systems; Safety requirements for the digital parts of I and C systems; Defence-in-depth). Qualitative analyses of NPP I and C system reliability and safety (Introductory system analysis; Qualitative requirements for and proof of NPP I and C system reliability and safety). Quantitative reliability analyses of the digital parts of I and C systems (Selection of a suitable quantitative measure of digital system reliability; Selected qualitative and quantitative findings regarding digital system reliability; Use of relations among the occurrences of the various types of failure). Mathematical section in support of the calculation of the various types of indices (Boolean reliability models, Markovian reliability models). Example of digital system analysis (Description of a selected protective function and the relevant digital part of the I and C system; Functional chain examined, its components and fault tree). (P.A.)

340

Development of reliability analysis tools and database for Integrated Risk Management System (IRMS)  

International Nuclear Information System (INIS)

The Korea Occupational Safety and Health Agency (KOSHA) is developing an Integrated Risk Management System (IRMS) to support the quantification and management of risk from chemical plants. The IRMS system includes the development of methodology, software tools and database necessary for quantitative risk assessment, which are consequence analysis software, graphical display of results on a geometric map, reliability analysis software, component reliability database, and equipment and hazardous material information databases. An overview of the IRMS will be presented in another paper, 'GIS-based IRMS.' The quantification of a risk consists of two major parts: one is a deterministic analysis, such as the consequence analysis of an explosion of flammable material, and the other is a probabilistic part such as the frequency analysis of and explosion or a reliability analysis of the protection system. This paper describes the development work in a probabilistic part of the IRMS. (author)

 
 
 
 
341

Structured information analysis for human reliability analysis of emergency tasks in nuclear power plants  

Energy Technology Data Exchange (ETDEWEB)

More than twenty HRA (Human Reliability Analysis) methodologies have been developed and used for the safety analysis in nuclear field during the past two decades. However, no methodology appears to have universally been accepted, as various limitations have been raised for more widely used ones. One of the most important limitations of conventional HRA is insufficient analysis of the task structure and problem space. To resolve this problem, we suggest SIA (Structured Information Analysis) for HRA. The proposed SIA consists of three parts. The first part is the scenario analysis that investigates the contextual information related to the given task on the basis of selected scenarios. The second is the goals-means analysis to define the relations between the cognitive goal and task steps. The third is the cognitive function analysis module that identifies the cognitive patterns and information flows involved in the task. Through the three-part analysis, systematic investigation is made possible from the macroscopic information on the tasks to the microscopic information on the specific cognitive processes. It is expected that analysts can attain a structured set of information that helps to predict the types and possibility of human error in the given task. 48 refs., 12 figs., 11 tabs. (Author)

Jung, Won Dea; Kim, Jae Whan; Park, Jin Kyun; Ha, Jae Joo [Korea Atomic Energy Research Institute, Taejeon (Korea)

2000-02-01

342

An improved rank assessment method for weibull analysis of reliability data  

International Nuclear Information System (INIS)

Weibull analysis has been applied widely in reliability data analysis. Rank assessment is one of the key steps in weibull analysis, which also induces the original errors. An improved median rank function obtained by genetic algorithms is presented to reduce the errors of rank assessment. (authors)

343

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)

344

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-03-01

345

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)

346

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

347

Comparative Analysis of Visco-elastic Models with Variable Parameters  

Directory of Open Access Journals (Sweden)

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

Silviu Nastac

2010-01-01

348

Markov Chains and reliability analysis for reinforced concrete structure service life  

Scientific Electronic Library Online (English)

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

Edna, Possan; Jairo José de Oliveira, Andrade.

349

Markov Chains and reliability analysis for reinforced concrete structure service life  

Scientific Electronic Library Online (English)

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

Edna, Possan; Jairo José de Oliveira, Andrade.

2014-06-01

350

Thermal characterization of compound semiconductor microwave devices for reliability analysis  

Science.gov (United States)

This dissertation shows that a new nondestructive technique has been developed which uses an atomic force microscope (AFM) to accurately determine the maximum temperature of devices under normal operating conditions at high resolution. This method is a novel and unique contribution to field of microscopic temperature measurement of electronic devices, in that it allows actual numbers corresponding to the temperature of the device to be measured using an AFM. This is in contrast to most published AFM thermal results, which have reported only qualitative and indirect semi-quantitative thermal information about the sample, and are unable to determine the temperature of the device. The technique combined with computer modeling is demonstrated for several compound semiconductor microwave devices that are used in commercial and military applications: Gallium Arsenide, Silicon Carbide (SiC), and Gallium Nitride (GaN). GaAs devices are currently used in the fields of radar and communications [1]. SiC and GaN devices, also called wide bandgap devices because of their electronic structure, are of particular importance in future applications in these fields [2,3]. The channel temperature of Gallium Arsenide (GaAs) devices was quantitatively measured using the quantitative scanning thermal microscopy (SThM) technique, which is a variation of AFM. The temperature of the devices was also characterized by infrared (IR) imaging and thermal modeling. It was found that the measured SThM temperature values were close to the calculated values from the model, and were higher than those found by IR, as predicted. These results are useful to the reliability community in that they help to predict a more accurate semiconductor device lifetime. The thermal characteristics of S-band silicon carbide monolithic microwave integrated circuits (MMICs) have also been investigated. It was found that high resolution atomic force thermal microscopy measurements and accurate finite element simulations show a much higher thermal response than that predicted by first order thermal calculations and infrared measurements. This difference may be explained by an increase in the lateral heat spreading on the device due to the improved thermal conductivity of the silicon carbide. These results can have a major effect on device reliability and packaging. To the author's knowledge, this is the first reported work which characterizes the thermal behavior of an actual silicon carbide MMIC device, and it does so at high resolution.

Mittereder, Jeffrey Andrew

351

DATA ANALYSIS METHODS AND THE RELIABILITY OF ANALYTIC EPIDEMIOLOGIC RESEARCH  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

352

Reactor scram experience for shutdown system reliability analysis  

International Nuclear Information System (INIS)

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

353

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

354

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

355

Analysis of structure reliability on beam using fuzzy finite element method  

Directory of Open Access Journals (Sweden)

Full Text Available The main requirement in designing a structure is to ensure the structure is reliable enough to withstand any loading. However, in the real world, for structural analysis, the presence of uncertainties in the input variable has reduced the accuracy of the calculated structural reliability. The purpose of this study is to determine the structural reliability with the consideration of uncertainties involved. The developed simulation method is the fuzzy set theory incorporating with the finite element methods followed with margin safety based on the yield strength of the structural reliability. This method is then used to analyze a given beam structure under loading for the material which are made from Aluminium 2024-T4. In this study, the modulus of section, s and loading, w are used as a fuzzy parameters. In conclusion, the combination of fuzzy set theory with the finite element method plays an important role in determining the structural reliability in the real world.

A. K. Ariffin

2013-03-01

356

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.

357

Analysis of set screw and side-lock connector reliability.  

Science.gov (United States)

A retrospective review of complications with connectors and lead-to-header interfaces was performed following 649 pacing procedures between 1980 and 1990. There were 88 lead revisions (13.6%), 81 device replacements or modifications (12.5%), and 480 new implants (74%) using devices of five manufacturers. Two basic connector types were studied, one utilizing a set screw and the other using a side-lock compression fitting. The set screw makes electrical contact and mechanically secures the lead connector pin with a set screw insulated by a self-sealing grommet or an integral or separate set screw cover. The side-lock makes electrical contact with an automatic spring mechanism while the plastic lead terminal is secured in the connector block of the pacemaker by a Delrin side-lock compression fitting. Four hundred fifty-nine set screw connector devices were followed for up to 12 years with 14 complications (3.1%) whereas 82 side-lock connector devices were followed for up to 5 years with one complication (1.2%). The set screw and side-lock connectors were reliable over the period of follow-up. Although the complication rate appeared lower with the side-lock, follow-up was shorter and the number of implants smaller. With the leads used in this study, the side-lock proved to be a desirable feature due to simplicity, speed, safety, and ease of use. One limitation is the requirement for a precise IS-1 connector terminal diameter. PMID:1279588

Tyers, G F; Sanders, R; Mills, P; Clark, J

1992-11-01

358

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

359

Rottlerin and curcumin: a comparative analysis.  

Science.gov (United States)

Rottlerin and curcumin are natural plant polyphenols with a long tradition in folk medicine. Over the past two decades, curcumin has been extensively investigated, while rottlerin has received much less attention, in part, as a consequence of its reputation as a selective PKC? inhibitor. A comparative analysis of genomic, proteomic, and cell signaling studies revealed that rottlerin and curcumin share a number of targets and have overlapping effects on many biological processes. Both molecules, indeed, modulate the activity and/or expression of several enzymes (PKC?, heme oxygenase, DNA methyltransferase, cyclooxygenase, lipoxygenase) and transcription factors (NF-?B, STAT), and prevent aggregation of different amyloid precursors (?-synuclein, amyloid A?, prion proteins, lysozyme), thereby exhibiting convergent antioxidant, anti-inflammatory, and antiamyloid actions. Like curcumin, rottlerin could be a promising candidate in the fight against a variety of human diseases. PMID:22758638

Maioli, Emanuela; Torricelli, Claudia; Valacchi, Giuseppe

2012-07-01

360

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

 
 
 
 
361

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

362

Compare containment subcompartment analysis code evaluation  

International Nuclear Information System (INIS)

Nuclear power plant subcompartment analyses are required to determine the containment pressure distribution that might result from a loss-of-coolant accident. The pressure distribution is used to calculate structural and mechanical design loads. The COMPARE code is used widely to perform subcompartment analysis. However, several simplifying assumptions are utilized to facilitate solution of the complex transient, two-phase, multidimensional flow problem. In particular, it is assumed that the flow is homogeneous, in thermodynamic equilibrium, and one-dimensional. In this study, these assumptions are evaluated by performing simplified transport and relaxation analyses. This results in definition of (a) geometric features and early-time periods that produce significant deviations from reality and (b) specific areas that require further study

363

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

364

Application of GO methodology in reliability analysis of offsite power supply of Daya Bay NPP  

International Nuclear Information System (INIS)

The author applies the GO methodology to reliability analysis of the offsite power supply system of Daya Bay NPP. The direct quantitative calculation formulas of the stable reliability target of the system with shared signals and the dynamic calculation formulas of the state probability for the unit with two states are derived. The method to solve the fault event sets of the system is also presented and all the fault event sets of the outer power supply system and their failure probability are obtained. The resumption reliability of the offsite power supply system after the stability failure of the power net is also calculated. The result shows that the GO methodology is very simple and useful in the stable and dynamic reliability analysis of the repairable system

365

Mechanical system reliability analysis using a combination of graph theory and Boolean function  

International Nuclear Information System (INIS)

A new method based on graph theory and Boolean function for assessing reliability of mechanical systems is proposed. The procedure for this approach consists of two parts. By using the graph theory, the formula for the reliability of a mechanical system that considers the interrelations of subsystems or components is generated. Use of the Boolean function to examine the failure interactions of two particular elements of the system, followed with demonstrations of how to incorporate such failure dependencies into the analysis of larger systems, a constructive algorithm for quantifying the genuine interconnections between the subsystems or components is provided. The combination of graph theory and Boolean function provides an effective way to evaluate the reliability of a large, complex mechanical system. A numerical example demonstrates that this method an effective approaches in system reliability analysis

366

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

367

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)

368

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

369

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

370

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

Energy Technology Data Exchange (ETDEWEB)

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

Namgung, Ihn [KEPCO International Nuclear Graduate School, Ulju (Korea, Republic of); Kang, H. G.; Chang, M. H.; Kim, C. H.; Yun, S. H.; Jung, K. J. [National Fusion Research Institute, Daejeon (Korea, Republic of)

2012-05-15

371

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

372

Reliability of a new biokinetic model of zirconium in internal dosimetry: part I, parameter uncertainty analysis.  

Science.gov (United States)

The reliability of biokinetic models is essential in internal dose assessments and radiation risk analysis for the public, occupational workers, and patients exposed to radionuclides. In this paper, a method for assessing the reliability of biokinetic models by means of uncertainty and sensitivity analysis was developed. The paper is divided into two parts. In the first part of the study published here, the uncertainty sources of the model parameters for zirconium (Zr), developed by the International Commission on Radiological Protection (ICRP), were identified and analyzed. Furthermore, the uncertainty of the biokinetic experimental measurement performed at the Helmholtz Zentrum München-German Research Center for Environmental Health (HMGU) for developing a new biokinetic model of Zr was analyzed according to the Guide to the Expression of Uncertainty in Measurement, published by the International Organization for Standardization. The confidence interval and distribution of model parameters of the ICRP and HMGU Zr biokinetic models were evaluated. As a result of computer biokinetic modelings, the mean, standard uncertainty, and confidence interval of model prediction calculated based on the model parameter uncertainty were presented and compared to the plasma clearance and urinary excretion measured after intravenous administration. It was shown that for the most important compartment, the plasma, the uncertainty evaluated for the HMGU model was much smaller than that for the ICRP model; that phenomenon was observed for other organs and tissues as well. The uncertainty of the integral of the radioactivity of Zr up to 50 y calculated by the HMGU model after ingestion by adult members of the public was shown to be smaller by a factor of two than that of the ICRP model. It was also shown that the distribution type of the model parameter strongly influences the model prediction, and the correlation of the model input parameters affects the model prediction to a certain extent depending on the strength of the correlation. In the case of model prediction, the qualitative comparison of the model predictions with the measured plasma and urinary data showed the HMGU model to be more reliable than the ICRP model; quantitatively, the uncertainty model prediction by the HMGU systemic biokinetic model is smaller than that of the ICRP model. The uncertainty information on the model parameters analyzed in this study was used in the second part of the paper regarding a sensitivity analysis of the Zr biokinetic models. PMID:22048485

Li, Wei Bo; Greiter, Matthias; Oeh, Uwe; Hoeschen, Christoph

2011-12-01

373

Analysis of whisker-toughened CMC structural components using an interactive reliability model  

Science.gov (United States)

Realizing wider utilization of ceramic matrix composites (CMC) requires the development of advanced structural analysis technologies. This article focuses on the use of interactive reliability models to predict component probability of failure. The deterministic William-Warnke failure criterion serves as theoretical basis for the reliability model presented here. The model has been implemented into a test-bed software program. This computer program has been coupled to a general-purpose finite element program. A simple structural problem is presented to illustrate the reliability model and the computer algorithm.

Duffy, Stephen F.; Palko, Joseph L.

1992-01-01

374

Reliability of wind farm design tools in complex terrain : A comparative study of commercial software  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A comparative study of two different approaches in wind energy simulations has been made where the aim was to investigate the performance of two commercially available tools. The study includes the linear model by WAsP and the computational fluid dynamic model of WindSim (also featuring an additional forest module). The case studied is a small wind farm located in the inland of Sweden featuring a fairly complex and forested terrain. The results showed similar estimations from both tools and i...

Timander, Tobias; Westerlund, Jimmy

2012-01-01

375

Comparative analysis of selected fuel cell vehicles  

Energy Technology Data Exchange (ETDEWEB)

Vehicles powered by fuel cells operate more efficiently, more quietly, and more cleanly than internal combustion engines (ICEs). Furthermore, methanol-fueled fuel cell vehicles (FCVs) can utilize major elements of the existing fueling infrastructure of present-day liquid-fueled ICE vehicles (ICEVs). DOE has maintained an active program to stimulate the development and demonstration o fuel cell technologies in conjunction with rechargeable batteries in road vehicles. The purpose of this study is to identify and assess the availability of data on FCVs, and to develop a vehicle subsystem structure that can be used to compare both FCVs and ICEV, from a number of perspectives--environmental impacts, energy utilization, materials usage, and life cycle costs. This report focuses on methanol-fueled FCVs fueled by gasoline, methanol, and diesel fuel that are likely to be demonstratable by the year 2000. The comparative analysis presented covers four vehicles--two passenger vehicles and two urban transit buses. The passenger vehicles include an ICEV using either gasoline or methanol and an FCV using methanol. The FCV uses a Proton Exchange Membrane (PEM) fuel cell, an on-board methanol reformer, mid-term batteries, and an AC motor. The transit bus ICEV was evaluated for both diesel and methanol fuels. The transit bus FCV runs on methanol and uses a Phosphoric Acid Fuel Cell (PAFC) fuel cell, near-term batteries, a DC motor, and an on-board methanol reformer. 75 refs.

NONE

1993-05-07

376

Comparative Analysis of Competitive Strategy Implementation  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents research findings on Competitive Strategy Implementation which compared the levels of strategy implementation achieved by different generic strategy groups, comprising firms inclined towards low cost leadership, differentiation or dual strategic advantage.  The study sought to determine the preferences for use of implementation armaments and compared how such armaments related to the level of implementation achieved.   Respondents comprised 71 top executives from 59 companies among the top 300 private sector firms in Kenya.  SPSS software was used to conduct t-test, ANOVA, and multiple linear regression analysis, to within 95% confidence interval or 5% statistical significance. The results indicated that there was no significant difference between the levels of strategy implementation achieved by any pair set of the three strategic groups.  The study revealed that the predictors of strategy implementation include the firm’s capacity to overcome resistance to change, having incentives based on meeting strictly quantitative targets, adopting a win-lose competitive posture, its effectiveness in strategy implementation, and the environmental rate of change.  The results also indicated that there was no significant difference between the preferences for use of either win-lose or win-win competition by any pair set of the strategic groups. 

Maina A. S. Waweru

2011-09-01

377

Reliability and mass analysis of dynamic power conversion systems with parallel or standby redundancy  

International Nuclear Information System (INIS)

A combinatorial reliability approach was used to identify potential dynamic power conversion systems for space mission applications. A reliability and mass analysis was also performed, specifically for a 100-kWe nuclear Brayton power conversion system with parallel redundancy. Although this study was done for a reactor outlet temperature of 1100 K, preliminary system mass estimates are also included for reactor outlet temperatures ranging up to 1500 K

378

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

International Nuclear Information System (INIS)

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

379

Reliability and mass analysis of dynamic power conversion systems with parallel of standby redundancy  

International Nuclear Information System (INIS)

A combinatorial reliability approach is used to identify potential dynamic power conversion systems for space mission applications. A reliability and mass analysis is also performed, specifically for a 100 kWe nuclear Brayton power conversion system with parallel redundancy. Although this study is done for a reactor outlet temperature of 1100K, preliminary system mass estimates are also included for reactor outlet temperatures ranging up to 1500 K. 1 reference

380

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

 
 
 
 
381

Performance comparison of two methods for human reliability analysis  

International Nuclear Information System (INIS)

To minimize the human errors, three main items must be studied: (1) operator performance shaping factors; (2) the man-machine interface and (3) the man-man interface. This presentation concerns the second item and part of the third, i.e. the relationship between the NPP operation crew members, especially between the operator engineer and the assistant engineer and considers the technology for human error rate prediction and the detailed block diagram analysis. 2 refs, 3 figs

382

Stochastic Response and Reliability Analysis of Hysteretic Structures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 a...

Mørk, Kim Jørgensen

2011-01-01

383

Analysis of data reliability and stability in HR-SDN communication module  

Science.gov (United States)

Profibus is open industrial communication system for wide range of applications in manufacturing and process automation. In Profibus, FDL service use to need hard real-time system. In these systems required data reliability and stability and real-time feature. Profibus fieldbus networks used in many industrial fields because of it supports real-time industrial communication. So we analyze of data reliability and stabilization in profibus network. In this paper, there was to a station for communication which uses FDL from in the communication module which is used a data transfer possibility at once, and from communication period (ex. 10ms) it analyzed the system effect which it follows in transmission lag occurrence element and a data transfer error ratio it analyzed. Like this analytical result it led and there were from transmission for reliability and data stability they confirmed to HR-SDN communication modules and a guarantee yes or no. In this paper, we try to analysis of transmission delay ability for satisfaction data reliability and stability in specific system, which requested real-time feature. And, we analysis system reconstruction time and data delay time according to data/token packet loss. Packet-error occur physical layer in Profibus. As a result of above analysis, we propose method of enhancement of reliability in system which requested system reliability and stability. And, we confirm proposed method.

Choi, Dong-Hee; Shin, Jin-Chul; Park, Hong-Seong

2007-12-01

384

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)

385

[Reliability theory based on quality risk network analysis for Chinese medicine injection].  

Science.gov (United States)

A new risk analysis method based upon reliability theory was introduced in this paper for the quality risk management of Chinese medicine injection manufacturing plants. The risk events including both cause and effect ones were derived in the framework as nodes with a Bayesian network analysis approach. It thus transforms the risk analysis results from failure mode and effect analysis (FMEA) into a Bayesian network platform. With its structure and parameters determined, the network can be used to evaluate the system reliability quantitatively with probabilistic analytical appraoches. Using network analysis tools such as GeNie and AgenaRisk, we are able to find the nodes that are most critical to influence the system reliability. The importance of each node to the system can be quantitatively evaluated by calculating the effect of the node on the overall risk, and minimization plan can be determined accordingly to reduce their influences and improve the system reliability. Using the Shengmai injection manufacturing plant of SZYY Ltd as a user case, we analyzed the quality risk with both static FMEA analysis and dynamic Bayesian Network analysis. The potential risk factors for the quality of Shengmai injection manufacturing were identified with the network analysis platform. Quality assurance actions were further defined to reduce the risk and improve the product quality. PMID:25509315

Li, Zheng; Kang, Li-Yuan; Fan, Xiao-Hui

2014-08-01

386

Guidebook for reliability, availability, and maintainability analysis of NWTS repository equipment. Volume I. Technical report  

International Nuclear Information System (INIS)

The Guidebook, presented in two volumes, provides a methodology for applying reliability, availability and maintainability (RAM) evaluation techniques to the special needs of a nuclear waste repository. The qualitative and quantitative methods show how RAM considerations may be incorporated into equipment design documentation to improve the reliability and maintainability of repository equipment and systems. The qualitative techniques for applying RAM principles in the design process include the use and preparation of reliability block diagrams, failure modes and effects analysis, and an availability improvement list. The quantitative evaluation techniques involve allocation of availability goals, acquisition of reliability data, definition of data and modeling uncertainties, and quantification of system reliability or availability. Using the Conceptual Reference Repository Design (CRRD) as a basis, step-by-step instructions are provided for applying RAM tools such as systems modeling, failure modes and effects analysis, fault tree analysis, Markov model, maintainability task analysis, uncertainty analysis (Bayes' theorem), etc. The recommended computer programs that would facilitate application of the methodology are also discussed

387

Comparing reliability and validity of pediatric instruments for measuring health and well-being of children with spastic cerebral palsy.  

Science.gov (United States)

This study sought to examine the reliability and validity of three generic instruments for measuring the health of children with cerebral palsy (CP) and to compare them with a disease-specific measure, the Gross Motor Function Measure (GMFM). The Pediatric Evaluation and Disability Inventory (PEDI), the Pediatric Outcomes Data Collection Instrument (PODCI), and the Child Health Questionnaire (CHQ) were completed by the primary caregivers of 115 young children with spastic CP. The GMFM was administered to the children. The mean age of the sample was 5 years 8 months (range 3:1 to 10:4) and consisted of more males (58%) than females. The PEDI scales demonstrated higher internal consistency than the PODCI and CHQ scales. In comparison with the GMFM, the PODCI transfer and mobility scale (relative validity, 62%) and the PEDI mobility scale (relative validity, 53%) detected the most significant health differences between children with hemiplegia, diplegia, and quadriplegia. The PEDI social function scale detected the largest differences in cognitive function between children with an IQ of less than 70 compared with those with an IQ of 70 or greater. The reliability and validity of these different instruments varied significantly in this patient population. PMID:12162384

McCarthy, Melissa L; Silberstein, Charles E; Atkins, Eileen A; Harryman, Susan E; Sponseller, Paul D; Hadley-Miller, Nancy A

2002-07-01

388

Using Finite-Element Analysis In Estimating Reliability  

Science.gov (United States)

Method of estimating design survivability of structural component incorporates finite-element and probabilistic properties of materials. Involves evaluation of design parameters through direct comparisons of survivability of component expressed in terms of percentages of like components that survive at various lifetimes. Probabilistic properties of materials, given in terms of Weibull parameters, coupled with stress field computed by finite-element analysis to determine fatigue life based on initiation of cracks. Method applied to rotating disk containing bolt holes, representative of disks used in aerospace propulsion turbines. Also used in early stages of design process to optimize life-based designs, reducing testing of full-sized components needed to validate designs.

Zaretsky, Erwin V.; August, Richard

1994-01-01

389

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

390

Radionuclides in sediments - a comparative analysis 1983  

International Nuclear Information System (INIS)

On behalf of the BMI (Federal German Ministry of the Interior) the BfG in 1983 started another interlaboratory comparison (among 39 measuring points) on the topic of radionuclides in sediments, in order to test the reliability of G?, G?/R? measurements and individual nuclide measurements in sedimentary samples under practical conditions. The study again proved its usefulness in as much as some inadequacies were revealed, and error sources could be eliminated. (orig./HP)

391

Determination of Strength for Reliability Analysis of Multilayer Ceramic Capacitors  

International Nuclear Information System (INIS)

A NanoindenterTM equipped with a Vickers indenter was used to measure fracture toughness of Multilayer Capacitors (MLCs) and BaTiO3 blanks. Strength of blanks of 6.3 x 4.7 x 1.1 mm3 was measured by performing three-point flexure using a 4 mm support span. The size of the strength limiting pores in the flexure tests was compared to pore sizes measured on polished MLC cross sections, and it was found that much larger pores were present in the 3-point flexure specimens. Strength distributions for the MLCs were generated using the measured fracture toughness values, assuming the measured pores or second phase inclusions were strength limiting

392

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

393

Reliability reallocation models as a support tools in traffic safety analysis.  

Science.gov (United States)

One of the essential questions placed before a road authority is where to act first, i.e. which road sections should be treated in order to achieve the desired level of reliability of a particular road, while this is at the same time the subject of this research. The paper shows how the reliability reallocation theory can be applied in safety analysis of a road consisting of sections. The model has been successfully tested using two apportionment techniques - ARINC and the minimum effort algorithm. The given methods were applied in the traffic safety analysis as a basic step, for the purpose of achieving a higher level of reliability. The previous methods used for selecting hazardous locations do not provide precise values for the required frequency of accidents, i.e. the time period between the occurrences of two accidents. In other words, they do not allow for the establishment of a connection between a precise demand for increased reliability (expressed as a percentage) and the selection of particular road sections for further analysis. The paper shows that reallocation models can also be applied in road safety analysis, or more precisely, as part of the measures for increasing their level of safety. A tool has been developed for selecting road sections for treatment on the basis of a precisely defined increase in the level of reliability of a particular road, i.e. the mean time between the occurrences of two accidents. PMID:24434655

Ba?kali?, Svetlana; Jovanovi?, Dragan; Ba?kali?, Todor

2014-04-01

394

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

395

Analysis of the reliability of the active injection safety systems of Angra I  

International Nuclear Information System (INIS)

The reliability of the active emergency core cooling systems of Angra I nuclear power plant is evaluated. The fault tree analysis is employed. The unavailability of the above cited systems, is calculated. A parametric sensitivity analysis has been performed, due to the existing scattering in the failure and repair rate data of these system's components. The minimal cut sets were determined and, as a final step, a reliability importance analysis has been performed. This final step has required the development of a computer program. The methodology and data from the 'Reactor Safety Study' (Wash-1400) (in which the reliability of safety systems of a tipical PWR plant is calculated), is employed. The unavailability values for the safety systems analysed are too low, thus showing that in most cases the systems analysed are available to mitigate the effects of a loss-of-coolant accident. (Author)

396

Reliability analysis for structure strength of metal O-ring based on probability finite element method  

International Nuclear Information System (INIS)

Metal O-rings was required as a high reliability sealing element in the safety valve for the application in nuclear power plants. The finite element model for the metal O-rings was constructed with the method of elastoplastic contact analysis based on the ANSYS software. The deformation and equivalence stress distribution of the metal O-rings have been obtained. The Probabilistic Finite Element Analysis for the Structure Strength of Metal O-ring has been done with the ANSYS Probabilistic Design System (PDS). The analysis result indicates that the strength of the O-ring has high reliability. The strength limit of the material is the most important stochastic input parameter. The reliability of the O-ring can be improved by decreasing the dispersion of the property parameters of the material. (authors)

397

Piping-reliability analysis for pressurized-water-reactor feedwater lines  

International Nuclear Information System (INIS)

This paper presents a piping reliability analysis for feedwater lines at five PWR plants; the analysis is based on probabilistic fracture mechanics. On the basis of observed pipe cracks in these feedwater lines, the crack is modeled with an initial semi-elliptical shape along the pipe inner circumference. Initial crack samples are generated using the Monte Carlo technique in conjunction with an importance sampling scheme. The fatigue model for crack growth employs a Paris-type growth-rate equation. Leak probabilities for feedwater lines of five PWR plants are estimated through the first ten years of the design life. Comparison of estimated leak probabilities and leak data in the five PWR plants led to the conclusion that the piping reliability model used in the present analysis can provide a reasonable estimate of the reliability of PWR feedwater lines

398

Analysis of the reliability of the shutdown heat removal system for the CRBR  

International Nuclear Information System (INIS)

An analysis of the reliability of the Shutdown Heat Removal System (SHRS) for the Clinch River Breeder Reactor (CRBR) was performed using Markov analysis models. Seven initiating events were considered. The system description and the failure and repair data were based on the Preliminary Safety Analysis Report of the CRBR. The study identified several areas to which the reliability of the SHRS is sensitive. To achieve high reliability shutdown heat removal, improvements in these areas or verification of their adequacy is required. These areas included the availability of the Auxiliary Feedwater System, the capability of the SHRS to operate on one-loop natural-circulation and the low probability of the failure of two heat transport loops causing the reactor to shut down

399

The Monte Carlo Simulation Method for System Reliability and Risk Analysis  

CERN Document Server

Monte Carlo simulation is one of the best tools for performing realistic analysis of complex systems as it allows most of the limiting assumptions on system behavior to be relaxed. The Monte Carlo Simulation Method for System Reliability and Risk Analysis comprehensively illustrates the Monte Carlo simulation method and its application to reliability and system engineering. Readers are given a sound understanding of the fundamentals of Monte Carlo sampling and simulation and its application for realistic system modeling.   Whilst many of the topics rely on a high-level understanding of calculus, probability and statistics, simple academic examples will be provided in support to the explanation of the theoretical foundations to facilitate comprehension of the subject matter. Case studies will be introduced to provide the practical value of the most advanced techniques.   This detailed approach makes The Monte Carlo Simulation Method for System Reliability and Risk Analysis a key reference for senior undergra...

Zio, Enrico

2013-01-01

400

Comparative analysis of safety related site characteristics  

International Nuclear Information System (INIS)

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

 
 
 
 
401

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

402

A Comparative Analysis on Mining Frequent Itemsets  

Directory of Open Access Journals (Sweden)

Full Text Available Research on mining frequent itemsets is one of ` the emerging task in data mining.The purchasing of one product when another product is purchased represents an association rule. Association rules are useful for analyzing the customer behavior. It takes an important part in shopping basket data analysis, clustering. The FP-Growth and Apriori algorithm is the basic algorithm for mining association rules. This paper presents an efficient algorithm for mining frequent itemsets using Two Dimensional Transactions Reduction(TDTR approach which reduces the original database(D transactions to the reduced data base transactions D1 based on the min_sup count. Then for each item it finds the number of transactions that the item present and hence find the largest frequent itemset using the two dimensional approach. Using the largest item set property ,it finds the subset of frequent item sets. Thus TDTR approach reduces the number of scans in the database and hence improve the efficiency & accuracy by finding the number of association rules and reduces time to find the rules.This proposed approach compares the efficiency with traditional Apriori and FP-Growth algorithm.

D.Kerana Hanirex

2012-12-01

403

The Reliability and Maintainability Analysis of Pneumatic System of Rotary Drilling Machines  

Science.gov (United States)

In any blasthole drilling the bottom of the blasthole must be kept clean by evacuating drill cuttings or it flushing as soon as they appear to ensure efficient drilling. If it is not done well, a large quantity of energy will be consumed in regrinding with the consequent wear on drill bit and decrease penetration, apart from the risk of jamming. Therefore, research on reliability and probability of safe operation of pneumatic system of drilling machines is of prime importance to ensure safe drilling operations. In this paper, reliability of this system was modeled and analyzed. To doing this research, drilling machines in Sarcheshmeh Copper Mine in Iran have been selected for data collection and analysis. After reliability modeling of pneumatic system, maintenance scheduling has been presented based on different reliability levels. There were four rotary drilling machines in this mine (named A, B, C and D). Results showed that after about 7 h drilling of machines A and B, and after 103 and 44 h drilling of machines C and D respectively, noticeably the reliability of pneumatic system reached to 80 %. As a result, machines C and D have more reliable pneumatic systems in comparison to machines A and B and checking and servicing of pneumatic system before these time was essential. Also, maintainability analysis showed that more failures of pneumatic system of machines A, B, C and D will be noticeably repaired at about 28, 34, 6 and 9 h.

Rahimdel, Mohammad Javad; Hosienie, Seyed Hadi; Ataei, Mohammad; Khalokakaei, Reza

2013-10-01

404