WorldWideScience
 
 
1

A comparative reliability analysis of computer-generated bitemark overlays.  

Science.gov (United States)

This study compared the reliability of two methods used to produce computer-generated bitemark overlays with Adobe Photoshop (Adobe Systems Inc., San Jose, CA). Scanned images of twelve dental casts were sent to 30 examiners with different experience levels. Examiners were instructed to produce an overlay for each cast image based on the instructions provided for the two techniques. Measurements of the area and the x-y coordinate position of the biting edges of the anterior teeth were obtained using Scion Image software program (Scion Corporation, Frederick, MD) for each overlay. The inter- and intra-reliability assessment of the measurements was performed using an analysis of variance and calculation of reliability coefficients. The assessment of the area measurements showed significant variances seen in the examiner variable for both techniques resulting in low reliability coefficients. Conversely, the results for the positional measurements showed no significant differences in the variances between examiners with exceptionally high reliability coefficients. It was concluded that both techniques were reliable methods to produce bitemark overlays in assessing tooth position. PMID:15818864

McNamee, Anne H; Sweet, David; Pretty, Iain

2005-03-01

2

Comparative Study of Reliability Analysis Methods for Discrete Bimodal Information  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-07-15

3

A Comparative Analysis of Open Source Software Reliability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study is to compare the fitting (goodness-of-fit) and prediction capabilities of three reliability models using the failure data of five popular open source software (OSS) products. The failure data are modeled by Weibull and two other Non Homogenous Poisson Process (NHPP) models (Yamada S-Shaped and Schneidewind). The OSS prod...

Cobra Rahmani; Azad Azadmanesh; Lotfi Najjar

2010-01-01

4

A Comparative Analysis of Open Source Software Reliability  

Directory of Open Access Journals (Sweden)

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

Azad Azadmanesh

2010-12-01

5

Analysis of reliability AAN laboratory with comparative method  

International Nuclear Information System (INIS)

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

2001-02-01

6

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.

Chong Leong, Gan; Uda, Hashim

2013-01-01

7

Human reliability analysis  

International Nuclear Information System (INIS)

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

1988-01-01

8

FPSO reliability analysis example  

Energy Technology Data Exchange (ETDEWEB)

The objective of this report is to present a practical example of the application of structural reliability techniques to the analysis of an FPSO hull structure. The emphasis of the report is on how to set up a reliability analysis, the input data required, and how to interpret the results. The methodology is demonstrated with applications to a fictional FPSO vessel, using 'realistic' (but not actual) input data. The examples demonstrate a number of aspects of a reliability analysis, but they are not intended to cover all of the steps in the detail required for a rigorous analysis of an actual FPSO. Due to the complex structural form, the stochastic nature of the loading and nonlinear response of the vessel, the reliability analysis of FPSOs is challenging. A number of applications of reliability analysis are considered in the report which demonstrate methods to address some of the difficulties in the analysis of an example FPSO. (author)

NONE

2000-03-01

9

Comparative analysis of reliability of emergency power system of Bushehr nuclear power plant using PSA and Markov method  

International Nuclear Information System (INIS)

Design of emergency power system of a nuclear power plant is important considering reliability and redundancy of systems, due to its share in the risk of the plant. Reliability of emergency power system of Bushehr nuclear power plant is evaluated and compared for both KWU and WWER design using fault tree/event tree and also Markov

1998-01-01

10

Reliability and Regression Analysis  

Science.gov (United States)

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

Lane, David M.

2009-02-17

11

Comparative analysis of some reliability characteristics between two dissimilar redundant systems with replacement at common cause failure  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, probabilistic models for two dissimilar redundant systems with replacement at each common cause failure have been developed to analyze and compare some reliability characteristics. Two configurations are studied under the assumption that each system is replaced at the occurrence of common cause failure. Configuration I is a 3-out-of-4 cold standby system, while configuration II is 3-out-of-5 cold standby system. Explicit expressions for mean time to system failure (MTSF, steady-state availability, busy period and profit function for the three models are analyzed using Kolmogorov’s forward equations method. Comparisons are performed for specific values of system parameters. Furthermore, we compare these reliability characteristics for the two configurations and find that configuration II is more reliable and efficient than configuration I.   Keywords: Redundancy, replacement, Common cause failure.

Ibrahim Yusuf

2013-12-01

12

ATLAS reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

Key elements of the 36 MJ ATLAS capacitor bank have been evaluated for individual probabilities of failure. These have been combined to estimate system reliability which is to be greater than 95% on each experimental shot. This analysis utilizes Weibull or Weibull-like distributions with increasing probability of failure with the number of shots. For transmission line insulation, a minimum thickness is obtained and for the railgaps, a method for obtaining a maintenance interval from forthcoming life tests is suggested.

Bartsch, R.R.

1995-09-01

13

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

1983-11-14

14

Reliability analysis for wind turbines  

Energy Technology Data Exchange (ETDEWEB)

Modern wind turbines are complex aerodynamic, mechanical and electrical machines incorporating sophisticated control systems. Wind turbines have been erected in increasing numbers in Europe, the USA and elsewhere. In Europe, Germany and Denmark have played a particularly prominent part in developing the technology, and both countries have installed large numbers of turbines. This article is concerned with understanding the historic reliability of modern wind turbines. The prime objective of the work is to extract information from existing data so that the reliability of large wind turbines can be predicted, particularly when installed offshore in the future. The article uses data collected from the Windstats survey to analyse the reliability of wind turbine components from historic German and Danish data. Windstats data have characteristics common to practical reliability surveys; for example, the number of failures is collected for each interval but the number of turbines varies in each interval. In this article, the authors use reliability analysis methods which are not only applicable to wind turbines but relate to any repairable system. Particular care is taken to compare results from the two populations to consider the validity of the data. The main purpose of the article is to discuss the practical methods of predicting large-wind-turbine reliability using grouped survey data from Windstats and to show how turbine design, turbine configuration, time, weather and possibly maintenance can affect the extracted results. (Author).

Tavner, P. J. [New and Renewable Energy Group, School of Engineering, Durham University, Durham DH1 4RL, (United Kingdom); Xiang, J. [CREST, Loughborough University, Loughborough, (United Kingdom); Spinato, F. [New and Renewable Energy Group, School of Engineering, Durham University, Durham DH1 4RL, (United Kingdom)

2006-07-12

15

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

16

A reliability simulation language for reliability analysis  

International Nuclear Information System (INIS)

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

1986-01-01

17

Scyllac equipment reliability analysis  

International Nuclear Information System (INIS)

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

1975-11-17

18

Reliability Data Analysis Procedures for Comparing Failure Rates of the System Using Optimal Truncation of Short Tests  

Directory of Open Access Journals (Sweden)

Full Text Available A test was described for two systems, long term and short term with an exponentially distributed time between failures. The test is intended for checking the ratio MTBFl /MTBFs exceeds or equals a prescribed value, versus one that it is less than the prescribed value, by means of long term tests with large average sample number in the earlier system. Our proposed system focus on improving test by using low average sample number in short term which is having the advantage of economy in time requirement and cost. It produces optimum truncated test called binomial Sequential Probability Ratio Test. Criteria are proposed for determining the characteristics of truncated test followed with the discretizing effect of truncation on error probabilities with a view to optimization of its parameters. The search algorithm for truncation apex used in this system achieves closeness to the optimum which depends on successful choice of the initial approximation, search boundaries and on the search step. The enhanced reliability of modern technological systems, combined with the reduced time quotas allotted for creating new system is capable of yielding a highly efficacious test which increases reliability and feasibility of decisions.

Sangeetha.M

2012-03-01

19

Reliability analysis in intelligent machines  

Science.gov (United States)

Given an explicit task to be executed, an intelligent machine must be able to find the probability of success, or reliability, of alternative control and sensing strategies. By using concepts for information theory and reliability theory, new techniques for finding the reliability corresponding to alternative subsets of control and sensing strategies are proposed such that a desired set of specifications can be satisfied. The analysis is straightforward, provided that a set of Gaussian random state variables is available. An example problem illustrates the technique, and general reliability results are presented for visual servoing with a computed torque-control algorithm. Moreover, the example illustrates the principle of increasing precision with decreasing intelligence at the execution level of an intelligent machine.

Mcinroy, John E.; Saridis, George N.

1990-01-01

20

Reliability analysis techniques in power plant design  

International Nuclear Information System (INIS)

An overview of reliability analysis techniques is presented as applied to power plant design. The key terms, power plant performance, reliability, availability and maintainability are defined. Reliability modeling, methods of analysis and component reliability data are briefly reviewed. Application of reliability analysis techniques from a design engineering approach to improving power plant productivity is discussed. (author)

1981-05-01

 
 
 
 
21

Applications of reliability degradation analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Vesely, W.E. [Science Applications International Corp., Dublin, OH (United States); Samanta, P.K. [Brookhaven National Lab., Upton, NY (United States)

1996-02-01

22

Applications of reliability degradation analysis  

International Nuclear Information System (INIS)

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

1996-01-01

23

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, 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

1996-01-01

24

Human Reliability Analysis: session summary  

Energy Technology Data Exchange (ETDEWEB)

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.

Hall, R.E.

1985-01-01

25

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

26

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

Science.gov (United States)

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

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

2014-01-01

27

Power system reliability analysis using fault trees  

International Nuclear Information System (INIS)

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

2006-09-18

28

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

29

Reliability analysis of software based safety functions  

International Nuclear Information System (INIS)

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

1993-01-01

30

Simulation and reliability analysis of probabilistic dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2007-01-01

31

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

Science.gov (United States)

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

Warne, Russell

2008-01-01

32

System Cost Reliability Analysis Program (SCRAP) Documentation.  

Science.gov (United States)

This document presents documentation necessary to use the System Cost Reliability Analysis Program (SCRAP). This program, developed by OOAMA/MMERR, was established to realistically determine, in real time, the Total Annual Logistic cost of an aircraft wea...

W. F. Pytlik

1973-01-01

33

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

34

Reliability analysis of stiff versus flexible piping  

International Nuclear Information System (INIS)

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

1985-01-01

35

Reliability analysis for stiff versus flexible piping  

International Nuclear Information System (INIS)

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

1985-11-01

36

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-03-01

37

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.

38

Reliability Analysis of Aircraft Equipment Based on FMECA Method  

Science.gov (United States)

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

Jun, Li; Huibin, Xu

39

Travel time Reliability Analysis Using Entropy  

Directory of Open Access Journals (Sweden)

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

Neveen Shlayan

2013-10-01

40

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

 
 
 
 
41

Reliability analysis of HVDC grid combined with power flow simulations  

Energy Technology Data Exchange (ETDEWEB)

Based on a DC grid power flow solver and the proposed GEIR, we carried out reliability analysis for a HVDC grid test system proposed by CIGRE working group B4-58, where the failure statistics are collected from literature survey. The proposed methodology is used to evaluate the impact of converter configuration on the overall reliability performance of the HVDC grid, where the symmetrical monopole configuration is compared with the bipole with metallic return wire configuration. The results quantify the improvement on reliability by using the later alternative. (orig.)

Yang, Yongtao; Langeland, Tore; Solvik, Johan [DNV AS, Hoevik (Norway); Stewart, Emma [DNV KEMA, Camino Ramon, CA (United States)

2012-07-01

42

Reliability and Quantile Analysis of Pareto Distribution  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the reliability and Quantile analysis of the Pareto distribution. The main interests are in the relationship between? and various percentiles lives that describe the spread of the values in a set of data. Here these quantiles models are presented graphically and mathematically.

M. Shuaib Khan

2009-01-01

43

Reliability analysis of airship remote sensing system  

Science.gov (United States)

Airship Remote Sensing System (ARSS) for obtain the dynamic or real time images in the remote sensing of the catastrophe and the environment, is a mixed complex system. Its sensor platform is a remote control airship. The achievement of a remote sensing mission depends on a series of factors. For this reason, it is very important for us to analyze reliability of ARSS. In first place, the system model was simplified form multi-stage system to two-state system on the basis of the result of the failure mode and effect analysis and the failure tree failure mode effect and criticality analysis. The failure tree was created after analyzing all factors and their interrelations. This failure tree includes four branches, e.g. engine subsystem, remote control subsystem, airship construction subsystem, flying metrology and climate subsystem. By way of failure tree analysis and basic-events classing, the weak links were discovered. The result of test running shown no difference in comparison with theory analysis. In accordance with the above conclusions, a plan of the reliability growth and reliability maintenance were posed. System's reliability are raised from 89 percent to 92 percent with the reformation of the man-machine interactive interface, the augmentation of the secondary better-groupie and the secondary remote control equipment.

Qin, Jun

1998-08-01

44

Probabilistic reliability analysis of multiprocessor architectures  

Energy Technology Data Exchange (ETDEWEB)

The reliability performance of gracefully degradable multiprocessor systems (MPSS) is studied in this paper. A formal multi-partite probabilistic graph is proposed to model the multiprocessor system architectures. Three categories of the multiprocessor systems-configurations with crossbar switching, time shared buses, and multiport memories-are investigated. The relative reliability performances of all three multiprocessor architectures are compared and discussed in detail. The comparisons indicate that the distributed-crossbar-structured multiprocessor system is better than the other two MPS architectures at both low and high multiprocessing levels. 8 references.

Tian-pong Chang; Yung-ming Yu

1983-01-01

45

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

46

Reflections on the perspectives of reliability analysis  

International Nuclear Information System (INIS)

Current reliability technology and availability of reliability data enable meaningful analyses to be carried out for the quantified reliability and safety values of many types of systems. This does not necessarily mean that precise numeric values can be obtained and interpreted. It rather means that answers can be produced within an acceptable degree of accuracy and used as a basis for decision making. Improvements in existing techniques and data are still required and further validation is necessary. However, there appears to be problems in the grey area between deterministic analysis and statistically meaningful probabilistic analysis. These problems relate to what may be described as 'rare' events. Such events may require important considerations both within and outside the practical systems being studied. Three main facets seem to need further attention: methods for recognizing rare events of significance, techniques for describing and enumerating the patterns of rare event occurrences and means for communicating the results of such enumerations. Even with current techniques it is often the lessons learnt about system behaviour which arise from the attempt to quantify reliability and the discipline of thought which comes out of the process of analysis which are more important than the attainment of a precise numeric answer at the end of the day

1976-06-08

47

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)

2000-11-01

48

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

49

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)

1988-01-01

50

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 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)

1988-01-01

51

Advances in human reliability analysis in Mexico  

Energy Technology Data Exchange (ETDEWEB)

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

NONE

2010-10-15

52

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

53

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

54

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

55

Reliability Analysis for Safety Grade PLC  

International Nuclear Information System (INIS)

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

2010-10-01

56

Reliability Analysis for Safety Grade PLC  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-10-15

57

Computing failure probabilities. Applications to reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

The paper presents one method for calculating failure probabilities with applications to reliability analysis. The method is based on transforming the initial set of variables to a n-dimensional uniform random variable in the unit hypercube, together with the limit condition set and calculating the associated probability using a recursive method based on the Gauss-Legendre quadrature formulas to calculate the resulting multiple integrals. An example of application is used to illustrate the proposed method.

Castillo, Enrique; Fernandez-Canteli, Alfonso; Minguez, Roberto

2002-08-01

58

Reliability analysis of wastewater treatment plants.  

Science.gov (United States)

This article presents a reliability analysis of 166 full-scale wastewater treatment plants operating in Brazil. Six different processes have been investigated, comprising septic tank+anaerobic filter, facultative pond, anaerobic pond+facultative pond, activated sludge, upflow anaerobic sludge blanket (UASB) reactors alone and UASB reactors followed by post-treatment. A methodology developed by Niku et al. [1979. Performance of activated sludge process and reliability-based design. J. Water Pollut. Control Assoc., 51(12), 2841-2857] is used for determining the coefficients of reliability (COR), in terms of the compliance of effluent biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP) and fecal or thermotolerant coliforms (FC) with discharge standards. The design concentrations necessary to meet the prevailing discharge standards and the expected compliance percentages have been calculated from the COR obtained. The results showed that few plants, under the observed operating conditions, would be able to present reliable performances considering the compliance with the analyzed standards. The article also discusses the importance of understanding the lognormal behavior of the data in setting up discharge standards, in interpreting monitoring results and compliance with the legislation. PMID:17897694

Oliveira, Sílvia C; Von Sperling, Marcos

2008-02-01

59

Subset simulation for structural reliability sensitivity analysis  

International Nuclear Information System (INIS)

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

2009-02-01

60

System reliability analysis with natural language and expert's subjectivity  

International Nuclear Information System (INIS)

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

1996-09-25

 
 
 
 
61

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)

1992-01-01

62

A taxonomy for human reliability analysis  

International Nuclear Information System (INIS)

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

1984-01-01

63

Bayesian networks with applications in reliability analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A common goal of the papers in this thesis is to propose, formalize and exemplify the use of Bayesian networks as a modelling tool in reliability analysis. The papers span work in which Bayesian networks are merely used as a modelling tool (Paper I), work where models are specially designed to utilize the inference algorithms of Bayesian networks (Paper II and Paper III), and work where the focus has been on extending the applicability of Bayesian networks to very large domains (Paper IV and ...

Langseth, Helge

2002-01-01

64

Reliability Analysis Techniques for Communication Networks in Nuclear Power Plant  

International Nuclear Information System (INIS)

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

2006-01-01

65

Appraisal on flight reliability on system level gray correlation analysis  

Energy Technology Data Exchange (ETDEWEB)

In order to resolve a flight conveyer's many appraisal factors, the system level gray correlation analysis theory was applied to the reliability appraisal of the flight link and then an appraisal index system of the colliery machine components reliability was established. Three flight chains were appraised using the system level gray correlation analysis model and the appraisal results are given for the reliability, inherent reliability and synthesis reliability. 4 refs., 3 tabs.

Wei Xiao-ling [Hebei University of Engineering, Handan (China). School of Mechanical and Electrical Engineering

2007-12-15

66

Integrated Reliability and Risk Analysis System (IRRAS)  

Energy Technology Data Exchange (ETDEWEB)

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

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

1992-01-01

67

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.

2010-06-01

68

Development of design framework based on reliability analysis using MATLAB  

Energy Technology Data Exchange (ETDEWEB)

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

Sung, Young Hwa; Kwak, Byung Man [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Maute, Kurt [University of Colorado at Boulder, Colorado (United States)

2007-07-01

69

Flaw Detection Reliability Assessment and Analysis.  

Science.gov (United States)

The assessment of nondestructive flaw detection reliability is complex in character due to the varied engineering and scientific disciplines involved. The evolution of nondestructive flaw detection reliability demonstration and assessment has involved var...

W. D. Rummel R. A. Rathke

1982-01-01

70

Standardizing the practice of human reliability analysis  

International Nuclear Information System (INIS)

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

1993-06-20

71

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.

2011-09-19

72

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

73

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)

2007-09-10

74

Comparative reliability of cheiloscopy and palatoscopy in human identification  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Sharma Preeti; Saxena Susmita; Rathod Vanita

2009-01-01

75

Reliability Analysis of Elasto-Plastic Structures  

DEFF Research Database (Denmark)

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

Thoft-Christensen, Palle; Sørensen, John Dalsgaard

1984-01-01

76

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

77

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

1989-08-14

78

Analysis of Sodium Valve Reliability Data at CREDO.  

Science.gov (United States)

The Centralized Reliability Data Organization (CREDO) has been established at Oak Ridge National Laboratory (ORNL) by the Department of Energy to provide a centralized source of data for reliability/maintainabilty analysis of advanced reactor systems. The...

T. F. Bott P. M. Haas

1979-01-01

79

Analysis of thermal reliability of the RA reactor  

International Nuclear Information System (INIS)

In the first part the basic elements of mathematical method used in further analysis are presented. The method offers the possibility for performance of an analysis of one or more quantities that are essential for thermic reliability on the basis of statistical data from reactor exploitation. This method could be used to determine the character of their behaviour, to analyze fluctuation around the mean and nominal values, to determine the probabilities of attaining and exceeding certain limits etc., these values being then compared with calculation and critical. In the second part of the paper the method is applied to the analysis of the fuel can temperature of reactor RA in Vinca. Two-year exploitation period has been observed at nominal power of 6,5 MW. The actual state of temperature compared with the values from the project indicates certain deviations which expressed over the probability give a factor of reliability in work of some fuel channels and zones. In the conclusion it is pointed out the possibility of application of the described methods in the safety analyses of reactor systems, and the purpose of application is realization of a more real solution, also obtaining of a more real picture regarding thermal reliability state (author)

1969-01-01

80

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

1985-01-01

 
 
 
 
81

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

1989-04-02

82

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)

2006-11-12

83

Combinatorial reliability analysis of multiprocessor computers  

Energy Technology Data Exchange (ETDEWEB)

The authors propose a combinatorial method to evaluate the reliability of multiprocessor computers. Multiprocessor structures are classified as crossbar switch, time-shared buses, and multiport memories. Closed-form reliability expressions are derived via combinatorial path enumeration on the probabilistic-graph representation of a multiprocessor system. The method can analyze the reliability performance of real systems like C.mmp, Tandem 16, and Univac 1100/80. User-oriented performance levels are defined for measuring the performability of degradable multiprocessor systems. For a regularly structured multiprocessor system, it is fast and easy to use this technique for evaluating system reliability with statistically independent component reliabilities. System availability can be also evaluated by this reliability study. 6 references.

Hwang, K.; Tian-Pong Chang

1982-12-01

84

Reliability Analysis in Wireless Sensor Networks  

Directory of Open Access Journals (Sweden)

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

Vijay Kumar,

2011-04-01

85

Techniques of quantitative reliability analysis for control rod drive systems  

International Nuclear Information System (INIS)

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

1980-01-01

86

Validation of Methodology for Reliability Analysis of Passive Safety Systems  

International Nuclear Information System (INIS)

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

2012-06-03

87

Reliability analysis and reliability-based optimization of composite laminated plate subject to buckling  

Science.gov (United States)

The purpose of this thesis is to investigate the effects of variations in design parameters on reliability of a composite plate subject to buckling. Then, the reliability-based design which maximize the reliability in terms of ply orientation angles of individual layers is obtained. It is illustrated the importance of considering the structural reliability in designing the composite plate subject to buckling. The composite material is known to have more uncertainties than a conventional material due to the fabrication process. It has been known that a deterministic optimum design is strongly anisotropic and very sensitive to the change in loading conditions. Therefore, it is necessary to consider the effect of variations in design parameters by applying the structural reliability theory. The reliability is evaluated by modeling the buckling failure as a series system consisting of potential eigenmodes. The mode reliability is obtained by the first-order reliability theory (FORM), where material constants, ply orientation angles and the applied loads are considered as random variables. In order to keep track of the intended buckling mode during the reliability analysis, the mode tracking method is utilized. Then, the failure probability of the series system is approximated by Ditlevsen's upper bound. The reliability-based optimization is formulated to find a laminate construction which maximize the system reliability. The problem is formulated as a nested problem with two levels of optimization; the reliability analysis and the reliability-based design. Through numerical calculation, the laminate construction of the reliability-based design is shown to be much different from that of the deterministic one. The deterministic buckling maximum design have more than two critical buckling modes. However, the reliability-based design has close mode reliabilies for the critical mode. The well balanced mode reliabilities in the latter lead to a higher system reliability. Finally, effects of the correlation between the random variables are investigated. It is clarified that the reliability-based design changes significantly in terms of the correlation coefficients. It is also shown that the reliability-based design ignoring correlation is sometimes less safe than even a deterministic buckling load maximization design when the random variables are correlated.

Kogiso, Nozomu

88

Reliability Analysis of A System Using Intuitionstic Fuzzy Sets  

Directory of Open Access Journals (Sweden)

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

M.K.Sharma

2012-07-01

89

Space Mission Human Reliability Analysis (HRA) Project  

Science.gov (United States)

The purpose of the Space Mission Human Reliability Analysis (HRA) Project is to extend current ground-based HRA risk prediction techniques to a long-duration, space-based tool. Ground-based HRA methodology has been shown to be a reasonable tool for short-duration space missions, such as Space Shuttle and lunar fly-bys. However, longer-duration deep-space missions, such as asteroid and Mars missions, will require the crew to be in space for as long as 400 to 900 day missions with periods of extended autonomy and self-sufficiency. Current indications show higher risk due to fatigue, physiological effects due to extended low gravity environments, and others, may impact HRA predictions. For this project, Safety & Mission Assurance (S&MA) will work with Human Health & Performance (HH&P) to establish what is currently used to assess human reliabiilty for human space programs, identify human performance factors that may be sensitive to long duration space flight, collect available historical data, and update current tools to account for performance shaping factors believed to be important to such missions. This effort will also contribute data to the Human Performance Data Repository and influence the Space Human Factors Engineering research risks and gaps (part of the HRP Program). An accurate risk predictor mitigates Loss of Crew (LOC) and Loss of Mission (LOM).The end result will be an updated HRA model that can effectively predict risk on long-duration missions.

Boyer, Roger

2014-01-01

90

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

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 analysis for components using Fuzzy Membership functions  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents reliability analysis for components using fuzzy operations. Probabilityassumption and Fuzzy State assumption (PROFUST reliability theory is used to find out the reliability ofeach system component. Here, the reliability of each system component is presented by trapezoidal fuzzynumber. The proposed method is used to simplify fuzzy arithmetic operations of fuzzy numbers. Finally, anumerical example is illustrated to verify the efficiency of used operations in the functions.

Chavan P.R.

2009-12-01

93

Reliability Analysis of a Mono-Tower Platform  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1988-01-01

94

Reliability Analysis of a Mono-Tower Platform  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

95

Reliability Analysis Techniques for Communication Networks in Nuclear Power Plant  

Energy Technology Data Exchange (ETDEWEB)

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

Lim, T. J. [Soongsil Univ., Seoul (Korea, Republic of); Jang, S. C.; Kang, H. G.; Kim, M. C.; Eom, H. S.; Lee, H. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2006-09-15

96

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)

2012-05-14

97

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

98

Reliability Analysis of Surface Mount Technology (SMT).  

Science.gov (United States)

This report indoctrinates the reader with the understanding of what is involved and necessary in designing and assessing the reliability of surface mount products. Deterministic methods were used to identify the primary design and environmental drivers an...

C. A. Myers K. K. Chakrabarti D. H. Merlino E. G. Palmer E. F. Pello

1993-01-01

99

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

100

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

 
 
 
 
101

Issues in benchmarking human reliability analysis methods: A literature review  

International Nuclear Information System (INIS)

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

2010-06-01

102

Security versus Reliability Analysis of Opportunistic Relaying  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Physical-layer security is emerging as a promising paradigm of securing wireless communications against eavesdropping between legitimate users, when the main link spanning from source to destination has better propagation conditions than the wiretap link from source to eavesdropper. In this paper, we identify and analyze the tradeoffs between the security and reliability of wireless communications in the presence of eavesdropping attacks. Typically, the reliability of the ma...

Zou, Yulong; Wang, Xianbin; Shen, Weiming; Hanzo, Lajos

2013-01-01

103

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

International Nuclear Information System (INIS)

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

2010-11-07

104

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

105

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

1994-11-21

106

Reliability evaluation for radionuclide transport analysis code MATRICS  

International Nuclear Information System (INIS)

A reliability evaluation for radionuclide transport analysis code, MATRICS, used in radionuclide transport analysis in the natural barrier system PA in H12 report has been carried out. Sensitivity analysis to radionuclide transport parameter in MATRICS and analytical solution has been performed, and the results of each analysis have been compared. Additionally sensitivity analysis using Talbot Method, Crump method and Hosono method has been carried out, and the results of each inverse Laplace transform method has been compared. The conclusions obtained from the results of the evaluation are summarized as follows. In case of the infinite matrix diffusion distance, an error among the results of each calculation is maximum about 0.4% in the range of Pe number from 1.0 to 100. And, an error among the results of each calculation is maximum about 5.5% in the range of transmissivity from 1.0x10-10 to 1.0x10-5 (m2/s). In case of the finite matrix diffusion distance (0.03-1.0(m)), an error among the results of each calculation is maximum about 0.7% in the range of Pe number from 1.0 to 100. And, an error among the results of each calculation is maximum about 2.4% in the range of transmissivity from 1.0x10-10 to 1.0x10-5 (m2/s). By comparing Talbot method with other inverse Laplace transform method, Talbot method is confirmed to give similar results with other inverse Laplace transform method in the range of Pe number from 5.0x10-1 to 2.0x103, and that of transmissivity below 1.0x10-7(m2/s). Therefore, it is concluded that the reliability of MATRICS are confirmed by conducting sensitivity analysis in the range of Pe number and transmissivity coefficient used in H12 report. (author)

2000-01-01

107

A methodology to incorporate organizational factors into human reliability analysis  

International Nuclear Information System (INIS)

A new holistic methodology for Human Reliability Analysis (HRA) is proposed to model the effects of the organizational factors on the human reliability. Firstly, a conceptual framework is built, which is used to analyze the causal relationships between the organizational factors and human reliability. Then, the inference model for Human Reliability Analysis is built by combining the conceptual framework with Bayesian networks, which is used to execute the causal inference and diagnostic inference of human reliability. Finally, a case example is presented to demonstrate the specific application of the proposed methodology. The results show that the proposed methodology of combining the conceptual model with Bayesian Networks can not only easily model the causal relationship between organizational factors and human reliability, but in a given context, people can quantitatively measure the human operational reliability, and identify the most likely root causes or the prioritization of root causes caused human error. (authors)

2010-08-01

108

Overview of a procedure for human reliability analysis  

International Nuclear Information System (INIS)

A human reliability analysis should be performed as an integral part of a probabilistic risk assessment. The methodology for conducting a human reliability analysis is described fully in NUREG/CR-1278, and a procedure for same in NUREG/CR-2254. This paper presents an overview of the procedure as used in the Interim Reliability Evaluation Program and described in Chapter 4 of the Probabilistic Risk Assessment Procedures Guide

1982-01-01

109

Reliability  

Science.gov (United States)

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

Christmann, Edwin P.; Badgett, John L.

2008-11-01

110

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.

2011-11-01

111

Reliability analysis of tube hydroforming process  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we propose a reliability-mechanical study combination to treat the tube hydroforming process (THP). This process consists to apply an inner pressure combined to an axial displacement to manufacture the part. Our goal is the computation of the failure probability of the hydroforming process. Normally, this process is particularly complex and have to be solved numerically. There are several numerical techniques available to compute the solution. However, some design parameters ar...

2013-01-01

112

Analysis of MAC Protocol for Reliable Broadcast  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In wireless communication It is important to find a reliable broadcasting protocol that is especially designed for an optimum performance of public-safety and data travelling related applications. Using RSU and OBU, there are four novel ideas presented in this research work, namely choosing the nearest following node as the network probe node, headway-based segmentation, non-uniform segmentation and application adaptive. The integration of these ideas results in a protocol that possesses m...

Savita Savita; Anjali Anjali; Gurpal Singh

2013-01-01

113

Design and analysis of reliable interconection networks  

Energy Technology Data Exchange (ETDEWEB)

This dissertation addresses techniques for the design of reliable and fault-tolerant multistage interconnection networks used in large multiprocessor systems. Methods for the construction of fault-tolerant interconnection networks are described and their characteristics pertaining to performance and reliability are analyzed using theoretical models. The techniques used to achieve fault-tolerance are the provision of parallel layers of subnetworks, addition of extra switching stages, use of multiple passes, and addition of redundant switching elements and links. Graph-theoretic techniques are used to study the routing of permutations in several redundant-path networks. A class of fault-tolerant networks called Generalized Indra Networks are designed and analyzed. These networks can be designed for a broad range of reliability and performance. The problem of routing permutations in these networks is modeled as a vertex-coloring problem in graph theory and algorithms for the optimal routing of certain classes of permutations are developed. The theoretical results are also applied to the problem of performing permutations on extra-stage networks in multiple passes, each pass realizing a submap of the permutation.

Varma, A.M.

1986-01-01

114

Application of Support Vector Machine to Reliability Analysis of Engine Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 pr...

Zhang Xinfeng; Zhao Yan

2013-01-01

115

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

2006-01-01

116

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

117

Design and Analysis for Reliability of Wireless Sensor Network  

Directory of Open Access Journals (Sweden)

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

Yongxian Song

2012-12-01

118

A software tool for advanced reliability and safety analysis  

International Nuclear Information System (INIS)

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

1987-10-05

119

Systems reliability analysis for the national ignition facility  

International Nuclear Information System (INIS)

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

1996-10-03

120

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.

2009-09-01

 
 
 
 
121

Interactive reliability analysis project. FY 80 progress report  

International Nuclear Information System (INIS)

This report summarizes the progress to date in the interactive reliability analysis project. Purpose is to develop and demonstrate a reliability and safety technique that can be incorporated early in the design process. Details are illustrated in a simple example of a reactor safety system

1981-01-01

122

Evaluating some Reliability Analysis Methodologies in Seismic Design  

Directory of Open Access Journals (Sweden)

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

A. E. Ghoulbzouri

2011-01-01

123

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...

2014-01-01

124

Comparative Analysis of University Sports  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2012-01-01

125

Analysis of Computer Network Reliability and Criticality: Technique and Features  

Directory of Open Access Journals (Sweden)

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

Iraj Elyasi-Komari

2011-10-01

126

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1997-10-01

127

Human Reliability Analysis: A Case Study.  

Science.gov (United States)

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 evalua...

B. J. Bell

1982-01-01

128

Reliability methods of nuclear power plant safety analysis  

International Nuclear Information System (INIS)

The application of reliability methods in the quantification of the frequency of occurrence of accident chains is described. This is a part of a study concerned with the reliability analysis of the safety of unit 1 of the Dukovany nuclear power plant. Methods of event trees and failure trees are used, employing the TREE MASTER computer code. By way of example, the system of hydroaccumulators serving the emergency aftercooling of the reactor in a LOCA is described in detail. An example of reliability analysis of the human factor is also briefly outlined. (Z.M.). 6 figs., 3 tabs., 4 refs

1990-01-01

129

Analysis of MAC Protocol for Reliable Broadcast  

Directory of Open Access Journals (Sweden)

Full Text Available In wireless communication It is important to find a reliable broadcasting protocol that is especially designed for an optimum performance of public-safety and data travelling related applications. Using RSU and OBU, there are four novel ideas presented in this research work, namely choosing the nearest following node as the network probe node, headway-based segmentation, non-uniform segmentation and application adaptive. The integration of these ideas results in a protocol that possesses minimum latency, minimum probability of collision in the acknowledgment messages and unique robustness at different speeds and traffic volumes. Wireless communications are becoming the dominant form of transferring information,and the most active research field. In this dissertation, we will present one of the most applicable forms of Ad-Hoc networks; the Vehicular Ad-Hoc Networks (VANETs. VANET is the technology of building a robust Ad-Hoc network between mobile vehicles and each other, besides, between mobile vehicles and roadside units.

Savita Savita

2013-02-01

130

SPAR-H Human Reliability Analysis Method.  

Science.gov (United States)

In support of the Accident Sequence Precursor Program (ASP), the U.S. Nuclear Regulatory Commission (NRC), in conjunction with the Idaho National Laboratory (INL), in 1994 developed the Accident Sequence Precursor Standardized Plant Analysis Risk Model (A...

C. Smith D. Gertman H. Blackman J. Byers J. Marble

2005-01-01

131

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

1982-07-17

132

Analysis of component reliability of Korean standard nuclear power plants  

Energy Technology Data Exchange (ETDEWEB)

A study was performed to construct the component reliability database for Korean Standard Nuclear Power Plants (KSNPP). The component reliability data was gathered for YGN 3 and 4 and UCN 3 and 4. About 22000 components from 24 systems were selected, for which about 6300 maintenance records were gathered and analyzed. Based on those data, statistical analysis and Bayesian analysis were performed to produce the reliability data for each component group. In the analysis, three kinds of data were calculated that are the failure rate per plant operation time, the failure rate per component operation time, and the failure probability per demand. A sensitivity study were done using the KSNPP PSA to review the effect of the analyzed component reliability data on PSAs. 3 refs., 4 figs., 7 tabs. (Author)

Han, Sang Hoon; Choi, Sun Young; Lee, Soo Cheol; Lee, Yoon Hwan; Kim, Seung Hwan [Korea Atomic Energy Research Institute, Taejeon (Korea)

2002-03-01

133

Human reliability analysis in Loviisa probabilistic safety analysis  

International Nuclear Information System (INIS)

The human reliability analysis in the Loviisa PSA project is carried out for three major groups of errors in human actions: (A) errors made before an initiating event, (B) errors that initiate a transient and (C) errors made during transients. Recovery possibilities are also included in each group. The methods used or planned for each group are described. A simplified THERP approach is used for group A, with emphasis on test and maintenance error recovery aspects and dependencies between redundancies. For group B, task analyses and human factors assessments are made for startup, shutdown and operational transients, with emphasis on potential common cause initiators. For group C, both misdiagnosis and slow decision making are analyzed, as well as errors made in carrying out necessary or backup actions. New or advanced features of the methodology are described

1986-10-01

134

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

135

Density modification based reliability sensitivity analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

136

Application of system reliability analysis feedback to improve system availability  

International Nuclear Information System (INIS)

Though all the perceived operational and maintenance requirement are normally well taken care-of at design stage itself, still the scope for improvement either in system design or in operational/maintenance practices, never ends in order to further improve the system's performance/reliability. This paper brings out a case study as to how Reliability Analysis feedback has been gainfully utilized in identification of and reduction of individual component maintenance down time, which was indirectly degrading the reliability of one of the Reactor Shutdown system (namely Secondary Shutdown System-Sass), at KAPS. (author)

2005-12-01

137

Analysis of sodium valve reliability data at CREDO  

International Nuclear Information System (INIS)

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

1979-08-23

138

Analysis of sodium valve reliability data at CREDO. [LMFBR  

Energy Technology Data Exchange (ETDEWEB)

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

Bott, T F; Haas, P M

1979-01-01

139

Reliability-based analysis of river dikes during flood waves:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reliability and risk analyses are basic approaches, nowadays, for flood risk assessments in European countries such as the Netherlands, German, United Kingdom, etc. The methods also receive a lot of interest in developing countries. By considering uncertainties for both load and strength variables, the probability of failure for each element of the flood defence system can be formulated. This paper focuses on the reliability analysis of the Red river dike during a typical flood wave of 1/500 ...

Pham Quang, T.; Gelder, P. H. A. J. M.; Vrijling, J. K.; Thu, T. M.

2012-01-01

140

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 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

2007-02-01

 
 
 
 
141

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

142

RELIABILITY ANALYSIS OF RING, AGENT AND CLUSTER BASED DISTRIBUTED SYSTEMS  

Directory of Open Access Journals (Sweden)

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

R.SEETHALAKSHMI

2011-08-01

143

The development of a reliable amateur boxing performance analysis template.  

Science.gov (United States)

The aim of this study was to devise a valid performance analysis system for the assessment of the movement characteristics associated with competitive amateur boxing and assess its reliability using analysts of varying experience of the sport and performance analysis. Key performance indicators to characterise the demands of an amateur contest (offensive, defensive and feinting) were developed and notated using a computerised notational analysis system. Data were subjected to intra- and inter-observer reliability assessment using median sign tests and calculating the proportion of agreement within predetermined limits of error. For all performance indicators, intra-observer reliability revealed non-significant differences between observations (P > 0.05) and high agreement was established (80-100%) regardless of whether exact or the reference value of ±1 was applied. Inter-observer reliability was less impressive for both analysts (amateur boxer and experienced analyst), with the proportion of agreement ranging from 33-100%. Nonetheless, there was no systematic bias between observations for any indicator (P > 0.05), and the proportion of agreement within the reference range (±1) was 100%. A reliable performance analysis template has been developed for the assessment of amateur boxing performance and is available for use by researchers, coaches and athletes to classify and quantify the movement characteristics of amateur boxing. PMID:23121380

Thomson, Edward; Lamb, Kevin; Nicholas, Ceri

2013-01-01

144

IEEE guide for the analysis of human reliability  

International Nuclear Information System (INIS)

The Institute of Electrical and Electronics Engineers (IEEE) working group 7.4 of the Human Factors and Control Facilities Subcommittee of the Nuclear Power Engineering Committee (NPEC) has released its fifth draft of a Guide for General Principles of Human Action Reliability Analysis for Nuclear Power Generating Stations, for approval of NPEC. A guide is the least mandating in the IEEE hierarchy of standards. The purpose is to enhance the performance of an human reliability analysis (HRA) as a part of a probabilistic risk assessment (PRA), to assure reproducible results, and to standardize documentation. The guide does not recommend or even discuss specific techniques, which are too rapidly evolving today. Considerable maturation in the analysis of human reliability in a PRA context has taken place in recent years. The IEEE guide on this subject is an initial step toward bringing HRA out of the research and development arena into the toolbox of standard engineering practices

1987-11-15

145

Distribution-level electricity reliability: Temporal trends using statistical analysis  

International Nuclear Information System (INIS)

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

2012-10-01

146

Wind farm layout : a reliability and investment analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Investment and maintenance costs are higher for offshore wind power compared to onshore. Also, wind turbine components offshore are subjected to higher physical stresses compared to components onshore, due to harder winds. These strong winds often lead to longer outage times of failed offshore components compared to onshore. The reliability of the Swedish offshore wind farm Lillgrund is analysed in this report. The consequence of a component failure might be a smaller energy production than e...

Eriksson, Emil

2008-01-01

147

Reliability analysis of reactor inspection robot(RIROB)  

International Nuclear Information System (INIS)

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

2002-01-01

148

Six Single-Administration Reliability Coefficients for Criterion-Referenced Tests: A Comparative Study.  

Science.gov (United States)

Four criterion-referenced reliability coefficicents were compared to the Kuder-Richardson estimates and to each other. The Kuder-Richardson formulas 20 and 21, the Livingston, the Subkoviak and two Huynh coefficients were computed for a random sample of 33 criterion-referenced tests. The Subkoviak coefficient yielded the highest mean value;…

Downing, Steven M.; Mehrens, William A.

149

Accuracy Analysis of Army Material System Analysis Activity Discrete Reliability Growth Model.  

Science.gov (United States)

The accuracy of the discrete reliability growth model developed by Army Material System Analysis Activity (AMSAA) is analyzed. The mean, standard deviation, and 95 precent confidence interval of the estimate of reliability resulting from simulating the AM...

R. M. Thalieb

1988-01-01

150

Architecture based Reliability Analysis of Continuously Running Concurrent Software Applications  

Directory of Open Access Journals (Sweden)

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

Rehab A. El Kharboutly

2008-01-01

151

Evaluation of the reliability of computerized profile cephalometric analysis  

Directory of Open Access Journals (Sweden)

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

Ferreira José Tarcísio Lima

2002-01-01

152

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

DEFF Research Database (Denmark)

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

Cecilio, Sergio Labeage; Gutierrez Lopez, Jose Manuel

2009-01-01

153

Reliability of videotaped observational gait analysis in patients with orthopedic impairments  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In clinical practice, visual gait observation is often used to determine gait disorders and to evaluate treatment. Several reliability studies on observational gait analysis have been described in the literature and generally showed moderate reliability. However, patients with orthopedic disorders have received little attention. The objective of this study is to determine the reliability levels of visual observation of gait in patients with orthopedic disorders. Methods The gait of thirty patients referred to a physical therapist for gait treatment was videotaped. Ten raters, 4 experienced, 4 inexperienced and 2 experts, individually evaluated these videotaped gait patterns of the patients twice, by using a structured gait analysis form. Reliability levels were established by calculating the Intraclass Correlation Coefficient (ICC, using a two-way random design and based on absolute agreement. Results The inter-rater reliability among experienced raters (ICC = 0.42; 95%CI: 0.38–0.46 was comparable to that of the inexperienced raters (ICC = 0.40; 95%CI: 0.36–0.44. The expert raters reached a higher inter-rater reliability level (ICC = 0.54; 95%CI: 0.48–0.60. The average intra-rater reliability of the experienced raters was 0.63 (ICCs ranging from 0.57 to 0.70. The inexperienced raters reached an average intra-rater reliability of 0.57 (ICCs ranging from 0.52 to 0.62. The two expert raters attained ICC values of 0.70 and 0.74 respectively. Conclusion Structured visual gait observation by use of a gait analysis form as described in this study was found to be moderately reliable. Clinical experience appears to increase the reliability of visual gait analysis.

van Uden Caro JT

2005-03-01

154

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

155

Failures Analysis and Reliability Calculation for Power Transformers  

Directory of Open Access Journals (Sweden)

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

M. Mirzai

2006-03-01

156

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

157

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

158

Intra-rater reliability of the posture analysis tool kit  

Scientific Electronic Library Online (English)

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

Ronette, Hough; Riette, Nel.

159

Analysis of reliability parameters of conveyor belt joints  

Directory of Open Access Journals (Sweden)

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

Adil TEMERZHANOV

2012-01-01

160

POSSIBILITY AND EVIDENCE-BASED RELIABILITY ANALYSIS AND DESIGN OPTIMIZATION  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Hong-Zhong Huang; Liping He; Yu Liu; Ning-Cong Xiao; Yan-Feng Li; Zhonglai Wang

2013-01-01

 
 
 
 
161

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

2001-04-01

162

Safety and reliability analysis of R-5 safety logic  

International Nuclear Information System (INIS)

Safety and reliability analysis of the R-5 reactor safety logic is presented. The analysis is based on fault free method. The index for reliability is shut down rate/year based on spurious (safe) failure rate of a channel. For R-5 it comes to 0.5/year. Fractional Dead Time (FDT) represents the fraction of operating time that the safety logic is unavailable and hence unable to protect. FDT is based on unsafe failure rate of a channel. FDTs of ET (poison injection trip), and the signal processing part (SP) of XT (neutronic and coolant pressure trips) and AT (absolute and conditioning trips) for R-5 come to 4x10"-"1"0, 4x10"-"4 and 4x10"-"5 respectively. Assumptions made in the analysis of safety logic are mentioned, however common made failure (CMF) analysis is not included. (M.G.B.)

1979-01-19

163

Reliability analysis of protection system using fault tree methods  

International Nuclear Information System (INIS)

This paper describes the use of the fault tree analysis as a method for analyzing the reliability of protection systems, and especially the unit protection systems. This analysis can be used for comparison between different configurations of a relay protection system and for estimating the influence of the availability of a single component on the availability of a complex structure. For the plant unit this component can be a primary one - for instance circuit breaker, or secondary - protection device, ect

2000-09-17

164

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)

2009-02-01

165

Quantification of Reliability Performance: Analysis Methods for Safety Instrumented System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Jigar, Abraham Almaw

2013-01-01

166

Reliability analysis of stiff versus flexible piping. Status report  

International Nuclear Information System (INIS)

Conservative design procedures adopted for nuclear piping systems usually result in stiff piping designs that use excessive support devices such as rigid supports and snubbers. Use of these piping support devices has created safety concerns. This report describes the interim result for a piping research project conducted at Lawrence Livermore National Laboratory (LLNL) for the US Nuclear Regulatory Commission (NRC). The overall objective of this research project is to develop modified design requirements and criteria which will improve piping reliability and minimize the use of pipe supports, snubbers, and pipe whip restraints. The current study was conducted to establish the necessary groundwork for this work based on the piping reliability analysis

1984-01-01

167

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

1987-01-01

168

Accident Sequence Evaluation Program: Human reliability analysis procedure  

Energy Technology Data Exchange (ETDEWEB)

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

Swain, A.D.

1987-02-01

169

On Reliability Analysis of Fault-tolerant Multistage Interconnection Networks  

Directory of Open Access Journals (Sweden)

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

Rinkle Aggarwal

2008-11-01

170

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.

2012-08-01

171

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

172

A framework for intelligent reliability centered maintenance analysis  

Energy Technology Data Exchange (ETDEWEB)

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.

Cheng Zhonghua [Department of Industrial Engineering, Tsinghua University, Beijing (China); Department of Management Engineering, Mechanical Engineering College, Shijiazhuang (China)], E-mail: chengzhonghua@mail.tsinghua.edu.cn; Jia Xisheng [Department of Management Engineering, Mechanical Engineering College, Shijiazhuang (China); Gao Ping; Wu Su; Wang Jianzhao [Department of Industrial Engineering, Tsinghua University, Beijing (China)

2008-06-15

173

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

2008-06-01

174

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 for minimizing impact of material defects and age-related degradation on valve reliability

1991-06-01

175

Virtual stress amplitude-based low cycle fatigue reliability analysis  

International Nuclear Information System (INIS)

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

2000-02-01

176

Comparative analysis of collaboration networks  

International Nuclear Information System (INIS)

In this paper we carry out a comparative analysis of the word network as the collaboration network based on the novel by M. Bulgakov 'Master and Margarita', the synonym network of the Russian language as well as the Russian movie actor network. We have constructed one-mode projections of these networks, defined degree distributions for them and have calculated main characteristics. In the paper a generation algorithm of collaboration networks has been offered which allows one to generate networks statistically equivalent to the studied ones. It lets us reveal a structural correlation between word network, synonym network and movie actor network. We show that the degree distributions of all analyzable networks are described by the distribution of q-type.

2011-03-14

177

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

International Nuclear Information System (INIS)

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

2010-04-01

178

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

Energy Technology Data Exchange (ETDEWEB)

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

Castet, Jean-Francois [School of Aerospace Engineering, Georgia Institute of Technology, 270 Ferst Drive, Atlanta, GA 30332-0150 (United States); Saleh, Joseph H., E-mail: jsaleh@gatech.ed [School of Aerospace Engineering, Georgia Institute of Technology, 270 Ferst Drive, Atlanta, GA 30332-0150 (United States)

2010-04-15

179

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

180

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

Directory of Open Access Journals (Sweden)

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

Wang Yufei

2013-10-01

 
 
 
 
181

A probabilistic analysis of dose assessment model using First-Order Reliability Method (FORM)  

Energy Technology Data Exchange (ETDEWEB)

As a part of safety assessment, the dose due to the normal evolution of repository was calculated. For reliable prediction of dose, the uncertainties in model parameters were considered. Compared to other uncertainty analysis methodologies, the FORM was used because of its simplicity and efficiency.

Song, Jongsoon [Chosun Univ., Kwangju (Korea, Republic of)

1996-12-31

182

Reliability analysis for nonnormal distributions using multi-level DOE  

International Nuclear Information System (INIS)

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

2004-11-03

183

Analysis of Gumbel Model for Software Reliability Using Bayesian Paradigm  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we have illustrated the suitability of Gumbel Model for software reliability data. The model parameters are estimated using likelihood based inferential procedure: classical as well as Bayesian. The quasi Newton-Raphson algorithm is applied to obtain the maximum likelihood estimates and associated probability intervals. The Bayesian estimates of the parameters of Gumbel model are obtained using Markov Chain Monte Carlo(MCMC simulation method in OpenBUGS(established software for Bayesian analysis using Markov Chain Monte Carlo methods. The R functions are developed to study the statistical properties, model validation and comparison tools of the model and the output analysis of MCMC samples generated from OpenBUGS. Details of applying MCMC to parameter estimation for the Gumbel model are elaborated and a real software reliability data set is considered to illustrate the methods of inference discussed in this paper.

Raj Kumar

2012-12-01

184

Reliability Engineering Analysis of ATLAS Data Reprocessing Campaigns  

Science.gov (United States)

During three years of LHC data taking, the ATLAS collaboration completed three petascale data reprocessing campaigns on the Grid, with up to 2 PB of data being reprocessed every year. In reprocessing on the Grid, failures can occur for a variety of reasons, while Grid heterogeneity makes failures hard to diagnose and repair quickly. As a result, Big Data processing on the Grid must tolerate a continuous stream of failures, errors and faults. While ATLAS fault-tolerance mechanisms improve the reliability of Big Data processing in the Grid, their benefits come at costs and result in delays making the performance prediction difficult. Reliability Engineering provides a framework for fundamental understanding of the Big Data processing on the Grid, which is not a desirable enhancement but a necessary requirement. In ATLAS, cost monitoring and performance prediction became critical for the success of the reprocessing campaigns conducted in preparation for the major physics conferences. In addition, our Reliability Engineering approach supported continuous improvements in data reprocessing throughput during LHC data taking. The throughput doubled in 2011 vs. 2010 reprocessing, then quadrupled in 2012 vs. 2011 reprocessing. We present the Reliability Engineering analysis of ATLAS data reprocessing campaigns providing the foundation needed to scale up the Big Data processing technologies beyond the petascale.

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

2014-06-01

185

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.

2009-12-01

186

Integrated design environment for human performance and human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

Work over the last few years at the Idaho National Engineering and Environmental Laboratory (INEEL) has included a major focus on applying human performance and human reliability knowledge and methods as an integral element of system design and development. This work has been pursued in programs in a wide variety of technical domains, beginning with nuclear power plant operations. Since the mid-1980`s the laboratory has transferred the methods and tools developed in the nuclear domain to military weapons systems and aircraft, offshore oil and shipping operations, and commercial aviation operations and aircraft design. Through these diverse applications the laboratory has developed an integrated approach and framework for application of human performance analysis, human reliability analysis (HRA), operational data analysis, and simulation studies of human performance to the design and development of complex systems. This approach was recently tested in the NASA Advanced Concepts Program {open_quotes}Structured Human Error Analysis for Aircraft Design.{close_quotes} This program resulted in the prototype software tool THEA (Tool for Human Error Analysis) for incorporating human error analysis in the design of commercial aircraft, focusing on airplane maintenance tasks. Current effort is directed toward applying this framework to the development of advanced Air Traffic Management (ATM) systems as part of NASA`s Advanced Air Transportation Technologies (AATT) program. This paper summarizes the approach, describes recent and current applications in commercial aviation, and provides perspectives on how the approach could be utilized in the nuclear power industry.

Nelson, W.R.

1997-05-01

187

The role of data analysis and surveillance in reliability analysis  

International Nuclear Information System (INIS)

As an introduction the data problem is illustrated by discussing failure modes and the question of random versus systematic failures. Structural failures are addressed briefly, while system failures are treated wih reference to control and instrumentation. The relevant German standards are investigated regarding probabilistic requirements. It is concluded, that reliability and risk assessments are still directed towards comparison, which on the other hand provide a powerful tool for a well balanced system design. Finally some examples are given on updating of literature data by experience. (orig.)

1982-08-01

188

Stability of the Reliability of LibQUAL+ (tm) Scores: A Reliability Generalization Meta-Analysis Study.  

Science.gov (United States)

Conducted a reliability generalization meta-analysis of subscale and total scale scores on the Web-administered LibQUAL+ (tm) (Cook and others, 2002), a measure of library service quality. Data for 18,161 participants from 43 universities show that score reliabilities are remarkably invariant across campuses and different over groups. (SLD)

Thompson, Bruce; Cook, Collen

2002-01-01

189

Reliability analysis of R-5 auxiliary core cooling system  

International Nuclear Information System (INIS)

The reliability analysis of the Auxiliary Core Cooling System (ACCS) of the R-5 reactor being set up at Trombay, from the point of view of its availability on demand is presented. Fault tree method has been used in the analysis. Failure data used and assumptions made in the analysis are given. The failure of the system to come into operation on demand turns out to be 6.4x10-3 (median value) for the system. The analysis also indicates that a screening of the components of the system is necessary. Critical components are pointed out. Based on the analysis, changes made in the design are mentioned. After incorporation of these changes, the unavailability of the system to come into operation on demand turns out to be 2x10-4. (auth.)

1979-01-19

190

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

1993-04-13

191

Some developments in human reliability analysis approaches and tools  

International Nuclear Information System (INIS)

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

1987-08-24

192

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

193

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

2011-09-01

194

Probabilistic Life and Reliability Analysis of Model Gas Turbine Disk  

Science.gov (United States)

In 1939, W. Weibull developed what is now commonly known as the "Weibull Distribution Function" primarily to determine the cumulative strength distribution of small sample sizes of elemental fracture specimens. In 1947, G. Lundberg and A. Palmgren, using the Weibull Distribution Function developed a probabilistic lifing protocol for ball and roller bearings. In 1987, E. V. Zaretsky using the Weibull Distribution Function modified the Lundberg and Palmgren approach to life prediction. His method incorporates the results of coupon fatigue testing to compute the life of elemental stress volumes of a complex machine element to predict system life and reliability. This paper examines the Zaretsky method to determine the probabilistic life and reliability of a model gas turbine disk using experimental data from coupon specimens. The predicted results are compared to experimental disk endurance data.

Holland, Frederic A.; Melis, Matthew E.; Zaretsky, Erwin V.

2002-01-01

195

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

International Nuclear Information System (INIS)

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

1989-01-01

196

Dynamic scapular movement analysis: is it feasible and reliable in stroke patients during arm elevation?  

Science.gov (United States)

Knowledge of three-dimensional scapular movements is essential to understand post-stroke shoulder pain. The goal of the present work is to determine the feasibility and the within and between session reliability of a movement protocol for three-dimensional scapular movement analysis in stroke patients with mild to moderate impairment, using an optoelectronic measurement system. Scapular kinematics of 10 stroke patients and 10 healthy controls was recorded on two occasions during active anteflexion and abduction from 0° to 60° and from 0° to 120°. All tasks were executed unilaterally and bilaterally. The protocol's feasibility was first assessed, followed by within and between session reliability of scapular total range of motion (ROM), joint angles at start position and of angular waveforms. Additionally, measurement errors were calculated for all parameters. Results indicated that the protocol was generally feasible for this group of patients and assessors. Within session reliability was very good for all tasks. Between sessions, scapular angles at start position were measured reliably for most tasks, while scapular ROM was more reliable during the 120° tasks. In general, scapular angles showed higher reliability during anteflexion compared to abduction, especially for protraction. Scapular lateral rotations resulted in smallest measurement errors. This study indicates that scapular kinematics can be measured reliably and with precision within one measurement session. In case of multiple test sessions, further methodological optimization is required for this protocol to be suitable for clinical decision-making and evaluation of treatment efficacy. PMID:24244414

De Baets, Liesbet; Van Deun, Sara; Desloovere, Kaat; Jaspers, Ellen

2013-01-01

197

Limits of reliability of optical properties of commercial glass in Mexico, a comparative analysis with experimental results; Limites de confiabilidad de propiedades opticas de vidrios comerciales en mexico, analisis comparativo con resultados experimentales  

Energy Technology Data Exchange (ETDEWEB)

The heat transfer through the buildings has been increased by the intensive use of glass in the building's covering; this situation has demanded more electrical energy for compensate the heat's gain or loss. Energy use in buildings is responsible for some 50% of CO{sub 2} emissions in many countries, so it's necessary a building's thermal design for a rational use of energy. The glass is an important material in the building's encircling, so it's essential to count on precise values of the glass's properties for design building's covering. Experimental evaluation on optical properties in some building's glasses to compare the experimental values with manufacturer's reported values inside tolerance limits. [Spanish] La ganancia de calor solar al interior de las edificaciones se ha visto incrementada por la tendencia actual en el uso intensivo y extensivo del vidrio en la envolvente, lo que ha aumentado la necesidad del uso de energia electrica para compensar con climatizacion artificial las ganancias y/o perdidas termicas en los espacios interiores de las edificaciones. El gasto energetico en edificios es responsable de cerca del 50% de emision de CO{sub 2} en varios paises, por lo que es necesario un diseno termico de la envolvente que contempla un uso racional de la energia. Por la importancia termica que el vidrio tiene en la envolvente de las edificaciones y la necesidad de contar con el valor de las propiedades lo mas preciso posible para su diseno, se planteo evaluar en forma experimental el comportamiento termico de algunos vidrios que tuviesen uso tanto real como potencial en las edificaciones de nuestro pais y comparar los valores obtenidos con los valores reportados por los fabricantes dentro de limites de tolerancia o confiabilidad.

Barrios Rodriguez, Pilar; Dorantes Rodriguez, Ruben J. [Universidad Autonoma Metropolitana Azcapotzalco, Mexico, D.F. (Mexico)

2000-07-01

198

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)

2010-02-01

199

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ep...

2008-01-01

200

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

International Nuclear Information System (INIS)

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

1989-06-12

 
 
 
 
201

Reliability analysis for stiff versus flexible piping systems  

International Nuclear Information System (INIS)

This paper describes the program plan and progress to date on a research program entitled, 'Reliability Analysis for Stiff Versus Flexible Piping Systems.' This two and one-half year program was undertaken by the Lawrence Livermore National Laboratory (LLNL) for the U.S. Nuclear Regulatory Commission (NRC) to develop improved requirements for nuclear piping system design. These improvements may involve NRC requirements, industry practice, as well as ASME code specifications. The overall approach to this problem is probabilistic, wherein the reliability of a piping system is evaluated, subject to daily events, transient loads, and postulated seismic events. The reliability model is capable of computing the failure probability of a complete piping system including piping, on-line components, and support devices. The total program is divided into three steps: the first step is to confirm safety concerns introduced by the stiff piping system design; the second step is to develop optimum, or near optimum, piping designs; and the third step is to perform a value impact study and propose changes. (orig.)

1983-01-01

202

Reliability and risk analysis using artificial neural networks  

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-12-31

203

Limitations in simulator time-based human reliability analysis methods  

International Nuclear Information System (INIS)

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

1989-11-26

204

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.)

1997-11-18

205

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

206

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)

2001-12-05

207

Method for reliability analysis of complex reactor systems  

International Nuclear Information System (INIS)

A method and a computer code for efficient and accurate reliability analyses of complex reactor systems are described and illustrated through an example. The method permits realistic analyses through its ability to accurately model and evaluate instantaneous and average unavailabilities for large systems with dependencies. The component models can include continuously monitored, non-repairable, and periodically tested components which are subject to failures resulting from components which are subject to failures resulting from component demands, stand-by conditions, human errors associated with testing and repair, as well as failures during actual operation. The numerical process used is efficient and allows analysis of general system configurations with arbitrary scheduling of maintenance operations

1982-07-19

208

Method for reliability analysis of complex reactor systems. [LMFBR  

Energy Technology Data Exchange (ETDEWEB)

A method and a computer code for efficient and accurate reliability analyses of complex reactor systems are described and illustrated through an example. The method permits realistic analyses through its ability to accurately model and evaluate instantaneous and average unavailabilities for large systems with dependencies. The component models can include continuously monitored, non-repairable, and periodically tested components which are subject to failures resulting from components which are subject to failures resulting from component demands, stand-by conditions, human errors associated with testing and repair, as well as failures during actual operation. The numerical process used is efficient and allows analysis of general system configurations with arbitrary scheduling of maintenance operations.

Elerath, J.G.; Vaurio, J.K.; Wood, A.P.

1982-01-01

209

Reliability Analysis of Systems Subject to First-Passage Failure  

Science.gov (United States)

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

Lutes, Loren D.; Sarkani, Shahram

2009-01-01

210

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

Directory of Open Access Journals (Sweden)

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

Zhifeng Liu

2011-07-01

211

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

Science.gov (United States)

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

Guthlin, Denise; Storch, Ilse; Kuchenhoff, Helmut

2014-01-01

212

A methodology for strain-based fatigue reliability analysis  

International Nuclear Information System (INIS)

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

2000-11-01

213

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.

2011-11-01

214

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

215

Reliability analysis of operating indicators of nuclear power plants  

International Nuclear Information System (INIS)

The results are given of the statistical analysis of indicators - the coefficients of availability obtained by the method of regression analysis. The basic methodological instrument was the regression of data by the increasing number of years from the start of commercial operation. Also monitored was the effect of the serial number of the unit on the site of the nuclear power plant on its reliability. The dependence was monitored of the coefficient of availability on the reactor manufacturer. A high dependence of the coefficient of availability was observed on the performance of the unit and on the reactor manufacturer. The time course over a period of 15 - 20 years of the availability coefficient was parabolic. (J.P.)

1983-10-25

216

Current Human Reliability Analysis Methods Applied to Computerized Procedures  

Energy Technology Data Exchange (ETDEWEB)

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

Ronald L. Boring

2012-06-01

217

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

Directory of Open Access Journals (Sweden)

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

Mohamed Oukili

2013-07-01

218

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Foli? Radomir; Laban Mirjana; Milanko Verica

2011-01-01

219

Deductive tree analysis for evaluating the reliability of construction operations  

International Nuclear Information System (INIS)

The importance of structural and construction safety is associated with the adverse consequences that may result from a structural failure and a construction accident. One of the most important objectives of any construction team is to minimize and control the risk levels of failure and accident of construction operations, as well as to determine the various critical factors which might lead to the increase of the probability of failure and accident of the operations. There are several uncertainty events and factors that contribute to the failure and accident of construction operations. The factors are associated with random, human-based or system uncertainty. Some of these factors include the level of engineering knowledge and experience, level of workmanship and attitude, level of communication procedures, methods and sequence of construction. Most of these factors are subjective, vague, and imprecisely defined, and therefore, they are expressed in semantic terms rather than mathematical measures. The subjectivity of the factors needs to be incorporated into the reliability estimation processes. The objective of this paper is to present a reliability evaluation methodology for construction operations that considers the effect of the factors and their uncertainties on the estimation of the risk measures for construction operations. The methodology is based on a deductive tree analysis approach which involves identifying a possible condition of the construction system and determining the various events and combination of the factors that contribute to the occurrence of that condition

1989-08-14

220

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)

1987-01-01

 
 
 
 
221

Application of human reliability analysis methodology of second generation  

International Nuclear Information System (INIS)

The human reliability analysis (HRA) is a very important part of probabilistic safety analysis. The main contribution of HRA in nuclear power plants is the identification and characterization of the issues that are brought together for an error occurring in the human tasks that occur under normal operation conditions and those made after abnormal event. Additionally, the analysis of various accidents in history, it was found that the human component has been a contributing factor in the cause. Because of need to understand the forms and probability of human error in the 60 decade begins with the collection of generic data that result in the development of the first generation of HRA methodologies. Subsequently develop methods to include in their models additional performance shaping factors and the interaction between them. So by the 90 mid, comes what is considered the second generation methodologies. Among these is the methodology A Technique for Human Event Analysis (ATHEANA). The application of this method in a generic human failure event, it is interesting because it includes in its modeling commission error, the additional deviations quantification to nominal scenario considered in the accident sequence of probabilistic safety analysis and, for this event the dependency actions evaluation. That is, the generic human failure event was required first independent evaluation of the two related human failure events . So the gathering of the new human error probabilities involves the nominal scenario quantification and cases of significant deviations considered by the potential impact on analyzed human failure events. Like probabilistic safety analysis, with the analysis of the sequences were extracted factors more specific with the highest contribution in the human error probabilities. (Author)

2009-07-05

222

Explicit time-dependent analysis in Monte Carlo reliability simulations  

Energy Technology Data Exchange (ETDEWEB)

Markov Monte Carlo methods have been employed for estimating reliability and availability of highly redundant systems with complex dependencies between component failure rates. There is, however, a major drawback with such Monte Carlo simulation when compared with analytical solutions or the numerical integration of the Markov equations. The result of a Monte Carlo simulation is a single number, the mission unreliability or unavailability (and an associated confidence interval). In contrast, deterministic methods provide curves of unreliability or unavailability versus time, allowing time-dependent trends to be observed and permitting a better and more general picture of system behavior to be obtained. To alleviate this drawback the authors have developed graphic algorithms that allow one to plot system unreliability and/or unavailability and the associated confidence intervals versus mission time. The procedures, moreover, add < 10% to the computation time required for a single Monte Carlo simulation to the maximum mission time to be considered.

Lewis, E.E.; Tu, Z.; Hald, U.P.; Boehm, F.

1987-01-01

223

Towards a non-wired simulator for reliability analysis  

International Nuclear Information System (INIS)

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

1991-06-10

224

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

225

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

1992-12-09

226

Events analysis of the main generator using reliability block diagram  

International Nuclear Information System (INIS)

Generator failure events at overseas and Japanese nuclear power plants were analyzed in detail through a reliability block diagram. This analysis not only took note of the total number of component failure and part failures but also focused on age-related degradation phenomena. Components or parts that were found to have failed most frequently included stator cooling system pipes, stator cooling system valves, automatic voltage regulators, and alternating-current exciters. Event reports on these components or parts were reexamined one by one. Because these components or parts have been adequately inspected, it was confirmed that there are no additional maintenance measures that should be reflected in Japanese pressurized water reactor (PWR) power plants. A comparison of the frequency of failures between Japanese and American power plants revealed that Japanese power plants suffered approximately one-tenth of the frequency of failures experienced in American plants, suggesting that higher levels of maintenance work are achieved at Japanese plants. (author)

2006-10-01

227

Application of the integrated reliability analysis system (IRAS)  

Energy Technology Data Exchange (ETDEWEB)

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

Kocza, Gabor; Bossche, Andre

1999-04-01

228

Application of the integrated reliability analysis system (IRAS)  

International Nuclear Information System (INIS)

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

1999-04-01

229

UPS reliability analysis with non-exponential duration distribution  

International Nuclear Information System (INIS)

In this paper, the reliability performance of uninterruptible power systems is studied. After the description of the protection system against anomalous conditions, a brief failure mode analysis is performed in order to define the fault tree referring to compensator output voltage. An analytical model able to deal with non-exponential life and repair time distributions is developed, using semi-Markov processes and assuming stochastic independence for the components of the system under study. The mean time between failure (MTBF) and the mean time to restoration of the compensator output voltage are then calculated exactly. Finally a mechanical bypass switch, which connects the load to the mains directly during long failures, is taken into account in the MTBF calculation via a simple approximation. Monte Carlo simulations are performed to validate the results of the analytical model and of the approximation

2003-08-01

230

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

231

Diagnosis based on reliability analysis using monitors and sensors  

International Nuclear Information System (INIS)

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

2008-04-01

232

Method for solving logical loops in system reliability analysis  

International Nuclear Information System (INIS)

The procedure for solving Boolean equations with unknown element(s) is presented. Discussions are made for operation of typical engineering systems with loop structure. It is revealed that components are necessary to be classified into three types. Time-dependent expression of a component's state is given and operating states of loop structures are identified by Boolean algebraic procedure. The procedure proposed in this paper is applicable to the condition that components can start at any time in system operational sequence, and each component has multiple chances to be started. A sample system was analyzed and the result was confirmed by a step by step analysis. The procedure shown in this paper is very useful in evaluating engineering systems which have logical loop structure(s), and also useful in effectively designing high reliable systems. (author)

2010-12-01

233

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

234

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

235

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.

236

Noncoding RNA gene detection using comparative sequence analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Noncoding RNA genes produce transcripts that exert their function without ever producing proteins. Noncoding RNA gene sequences do not have strong statistical signals, unlike protein coding genes. A reliable general purpose computational genefinder for noncoding RNA genes has been elusive. Results We describe a comparative sequence analysis algorithm for detecting novel structural RNA genes. The key idea is to test the pattern of substitution...

Rivas Elena; Eddy Sean R

2001-01-01

237

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 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

1992-10-01

238

A Simulation Methodology for Reliability Analysis in Multi-Core SoCs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reliability has become a significant challenge for system design in new process technologies. Higher integration levels dramatically increase power densities, which leads to higher temperature and adverse effects on reliability. In this paper, we introduce a simulation methodology to analyze reliability of multi-core SoCs. The proposed simulator is the first to provide system-on-chip level fine-grained reliability analysis. We use our simulation methodology to study the reliability effects of...

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

2006-01-01

239

Human reliability analysis for advanced control room of KNGR  

International Nuclear Information System (INIS)

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

2000-12-01

240

Human reliability analysis for advanced control room of KNGR  

Energy Technology Data Exchange (ETDEWEB)

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

Kim, Myung-Ro; Park, Seong-Kyu [Korea Power Engineering Co., Inc., Yongin (Korea)

2000-07-01

 
 
 
 
241

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

1987-12-07

242

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.

243

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

244

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

1973-01-01

245

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.)

1980-09-01

246

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

247

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

1983-01-01

248

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

249

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 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)

2006-11-12

250

Analysis of Computer Network Reliability and Criticality: Technique and Features  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper describes modern technologies of Computer Network Reliability. Software tool is developed to estimate of the CCN critical failure probability (construction of a criticality matrix) by results of the FME(C)A-technique. The internal information factors, such as collisions and congestion of switchboards, routers and servers, influence on a network reliability and safety (besides of hardware and software reliability and external extreme factors). The means and features of Failures Modes...

Iraj Elyasi-Komari; Anatoliy Gorbenko; Vyacheclav Kharchenko; Athanasios Mamalis

2011-01-01

251

Analysis and Optimization of MPSoC Reliability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2006-01-01

252

Reliability Modeling and Analysis of SCI Topological Network  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Hongzhe Xu; Jun Huang; Yaoming Zhou

2012-01-01

253

Reliability Analysis of Free Jet Scour Below Dams  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Chuanqi Li; Shuai Wang; Wei Wang

2012-01-01

254

Prediction Capability Analysis of Two and Three Parameters Software Reliability Growth Models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study aims to analyze the predict capability of some of the popular Software Reliability growth models to understand the potential of having two or three parameters to facilitate the estimation process. The predict validity analysis will be on two key factors, one pertaining to the degree of fitment on available failure data and the other for its prediction capability. The validity analysis will be to arrive at a trade-off in choosing a simple model as compared to a complex model by dete...

Prince Williams, D. R.

2006-01-01

255

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 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. Trans. Reliab., 42 (1993) 542-546 Wat son,

1996-02-01

256

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

257

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

2000-01-01

258

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

259

Reliability Analysis and Modeling of ZigBee Networks  

Science.gov (United States)

The architecture of ZigBee networks focuses on developing low-cost, low-speed ubiquitous communication between devices. The ZigBee technique is based on IEEE 802.15.4, which specifies the physical layer and medium access control (MAC) for a low rate wireless personal area network (LR-WPAN). Currently, numerous wireless sensor networks have adapted the ZigBee open standard to develop various services to promote improved communication quality in our daily lives. The problem of system and network reliability in providing stable services has become more important because these services will be stopped if the system and network reliability is unstable. The ZigBee standard has three kinds of networks; star, tree and mesh. The paper models the ZigBee protocol stack from the physical layer to the application layer and analyzes these layer reliability and mean time to failure (MTTF). Channel resource usage, device role, network topology and application objects are used to evaluate reliability in the physical, medium access control, network, and application layers, respectively. In the star or tree networks, a series system and the reliability block diagram (RBD) technique can be used to solve their reliability problem. However, a division technology is applied here to overcome the problem because the network complexity is higher than that of the others. A mesh network using division technology is classified into several non-reducible series systems and edge parallel systems. Hence, the reliability of mesh networks is easily solved using series-parallel systems through our proposed scheme. The numerical results demonstrate that the reliability will increase for mesh networks when the number of edges in parallel systems increases while the reliability quickly drops when the number of edges and the number of nodes increase for all three networks. More use of resources is another factor impact on reliability decreasing. However, lower network reliability will occur due to network complexity, more resource usage and complex object relationship.

Lin, Cheng-Min

260

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)

 
 
 
 
261

Operator reliability analysis during NPP small break LOCA  

International Nuclear Information System (INIS)

To assess the human factor characteristic of a NPP main control room (MCR) design, the MCR operator reliability during a small break LOCA is analyzed, and some approaches for improving the MCR operator reliability are proposed based on the analyzing results

1990-01-01

262

Wind turbine reliability : a database and analysis approach.  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-02-01

263

Reliability and availability studies for industrial power system analysis  

Energy Technology Data Exchange (ETDEWEB)

Reliability and availability (R and A) studies have been made a part of the IEEE Recommended Practice For Industrial and Commercial Power System Analysis (IEEE Standard 399-1980). R and A studies should improve the selection of system configurations and components by basing decisions on quantitative information rather than on intuitive and qualitative decisions. The RandA indices for any electric power system design can be computed from knowledge of the statistical performance of individual components within the system. One of the important indices is the system overall downtime, which has a direct cost impact due to plant process interruption. In addition to RandA computation of electrical components in simple series or parallel configurations, other commonly encountered electrical power systems situations are considered such as a) scheduled maintenance of system components, b) manual switching of system components, c) transformer overloading practices, d) parallel redundant connections within a system, e) spare components available on short notice, and f) local generator units. These situations will be discussed, and the methods of calculation required to include them in RandA studies will be presented.

Yu, L.; Beck, R.T.

1983-11-01

264

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)

2003-01-13

265

A new human reliability analysis method using dynamics concept  

Energy Technology Data Exchange (ETDEWEB)

Operational nuclear power plants in Korea have been subject to routine periodic reviews of plant operational and special safety review. In this periodic safety reviews (PSRs), human factors are one of eleven important safety factors. This paper presents a new dynamic human reliability analysis method and its application for quantifying the human error probabilities in implementing PSRs. For comparisons of current HRA methods with the new method, the characteristics of THERP, HCR, and SLIM-MAUD, which are most frequency used method in PSAs, are discussed. The action associated with implementation of the cavity flooding during a station blackout sequence is considered for its application. This method is based on the concepts of the quantified correlation between the performance requirement and performance achievement. The MAAP 3.0B code and Latin Hypercube sampling technique are used to determine the uncertainty of the performance achievement parameter. Meanwhile, the value of the performance requirement parameter is obtained from interviews. Based on these stochastic obtained, human error probabilities are calculated with respect to the various means and variances of the things. It is shown that this method is very flexible in that it can be applied to any kind of the operator actions, including the actions associated with the implementation of accident management strategies. (author)

Jae, M. [Hanyan Univ., Dept. of Nuclear Engineering, Seoul (Korea, Republic of)

2002-07-01

266

Requalification of offshore structures. Reliability analysis of pipelines  

Energy Technology Data Exchange (ETDEWEB)

The objectives of this study may be divided into three parts. Part 1: Selection of failure modes. Select failure modes for offshore pipelines, which from a client point of view are relevant. The following failure modes referring to yielding, buckling, bursting, accidental and corrosion design criteria were considered: Hoop stress design criteria; Local buckling criteria; static on-bottom stability criteria; Excessive buckling criteria; Upheaval buckling criteria; Fatigue design criteria; Pressure containment (bursting) design criteria; Trawling gear impact design criteria; Pitting corrosion design criteria; Longitudinal grooving of corrosion design criteria; Free span criteria. Part 2: Review of background for probabilistic analysis methods. The fundamental theoretical background has been available for several decades, however, it is within the last two decades a practical approach has been presented. This implies commercial software products such as PROBAN (PROBabilistic ANalysis), which has been released by DnV. Part 3: Detailed studies of the failure modes: Hoop Stress Design Criteria Upheaval Buckling. Instead of studying all failure modes to a general level, it has been decided to study two failure modes in detail, namely Structural Analysis (Hoop Stress Design Criteria) and Buckling Design Criteria (Upheaval Buckling). Hoop Stress Design Criteria: The actual safety level for a 10 inch. submarine pipeline, is estimated. Furthermore a sensitivity analysis of the safety level by varying the internal pressure, P{sub i} and the wall thickness, t. Upheaval Buckling: The main objective of this study is to improve the state of the art tools for evaluating the safety level regarding the failure mode for upheaval buckling. The state of the art calculation tools are not actually estimating a safety level. Instead by giving information on imperfection length, imperfection height, functional loading conditions, outer diameter of pipe, minimum height of the cover soil in which the pipeline is buried, these tools will return an answer saying the safety level comply with requirements, or safety level does not comply with requirements. However, the tools do not give a quantitative evaluation. The safety level might be conservative. The idea of using probabilistic methods is to apply the inspection data, which are collected currently anyway to calculate an actual reliability index, {beta}. This might be related to a probability of failure, P{sub f}. DnV has then related this probability to the conventional safety classes (low, normal or high safety classes). This procedure might be followed not only when designing the pipelines, but also for updating the safety levels for nearly outdated pipelines, in order to receive requalification. Again actual inspection data are applied to estimate the reliability. This approach gives an actual safety level, and measured to improve this if necessary might be carried out, e.g. to increase the cover of soil. (au)

NONE

1999-04-01

267

An efficient phased mission reliability analysis for autonomous vehicles  

International Nuclear Information System (INIS)

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

2010-03-01

268

A comparative analysis of aircraft noise performances  

Directory of Open Access Journals (Sweden)

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

Nicola Gualandi

2009-09-01

269

EPRI/NRC-RES fire human reliability analysis guidelines  

International Nuclear Information System (INIS)

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

2010-06-07

270

EPRI/NRC-RES fire human reliability analysis guidelines.  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-03-01

271

Reliability and Security Analysis on Two-Cell Dynamic Redundant System  

Directory of Open Access Journals (Sweden)

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

Hongsheng Su

2013-05-01

272

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Barati Ramin; Setayeshi Saeed

2012-01-01

273

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

274

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

275

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

276

The Transferable Belief Model for reliability analysis of systems with data uncertainties and failure dependencies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dealing with uncertainty adds a further level of complexity to problems of reliability analysis. The uncertainties which impact reliability studies usually involve incomplete or imprecise reliability data and complex failure dependencies. This paper proposes an original methodology based on the Transferable Belief Model (TBM) to include failure dependencies between components in the evaluation of the reliability of the whole system, given both epistemic and aleatory uncertainties. First, base...

Sallak, Mohamed; Scho?n, Walter; Aguirre, Felipe

2010-01-01

277

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

International Nuclear Information System (INIS)

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

1996-11-01

278

Reliability analysis of stiff versus flexible piping. Final project report  

International Nuclear Information System (INIS)

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

1985-01-01

279

Good Practices for Implementing Human Reliability Analysis (HRA).  

Science.gov (United States)

The U.S. Nuclear Regulatory Commission is establishing good practices for performing human reliability analyses (HRAs) and reviewing HRAs to assess the quality of those analyses. The good practices were developed as part of the NRC's activities to address...

A. Kolaczkowski J. Forester E. Lois S. Cooper

2005-01-01

280

Reliability analysis based on losses from failure Modelling  

Directory of Open Access Journals (Sweden)

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

Dr. Amit Gupta , Renu Garg

2013-06-01

 
 
 
 
281

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

1996-06-01

282

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

Energy Technology Data Exchange (ETDEWEB)

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.

Montani, S. [Dipartimento di Informatica, Universita del Piemonte Orientale, Via Bellini 25g, 15100 Alessandria (Italy)], E-mail: stefania@mfn.unipmn.it; Portinale, L. [Dipartimento di Informatica, Universita del Piemonte Orientale, Via Bellini 25g, 15100 Alessandria (Italy)], E-mail: portinal@mfn.unipmn.it; Bobbio, A. [Dipartimento di Informatica, Universita del Piemonte Orientale, Via Bellini 25g, 15100 Alessandria (Italy)], E-mail: bobbio@mfn.unipmn.it; Codetta-Raiteri, D. [Dipartimento di Informatica, Universita del Piemonte Orientale, Via Bellini 25g, 15100 Alessandria (Italy)], E-mail: raiteri@mfn.unipmn.it

2008-07-15

283

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

Energy Technology Data Exchange (ETDEWEB)

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.

Balakrishnan, Meera; Trivedi, Kishor S

1996-06-01

284

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)

1981-01-01

285

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

286

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

287

Reliability and risk analysis data base development: an historical perspective  

Energy Technology Data Exchange (ETDEWEB)

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 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. Tr

Fragola, Joseph R

1996-02-01

288

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

International Nuclear Information System (INIS)

Common cause failures (CCFs) have long been recognized as an important issue in the probabilistic safety assessment (PSA) for nuclear power plants. Uncertainty ranges of system failure probabilities are important information for the evaluation of system reliability. The function of CCF analysis together with uncertainty analysis has been provided to the GO-FLOW methodology. Overview of the GO-FLOW methodology, the method to treat the CCFs in the GO-FLOW, the procedure of CCF analysis together with uncertainty are described. As the sample system, PWR auxiliary feedwater system has been taken and an analysis has been performed by the proposed analysis framework. (orig.)

1997-11-01

289

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

Energy Technology Data Exchange (ETDEWEB)

Common cause failures (CCFs) have long been recognized as an important issue in the probabilistic safety assessment (PSA) for nuclear power plants. Uncertainty ranges of system failure probabilities are important information for the evaluation of system reliability. The function of CCF analysis together with uncertainty analysis has been provided to the GO-FLOW methodology. Overview of the GO-FLOW methodology, the method to treat the CCFs in the GO-FLOW, the procedure of CCF analysis together with uncertainty are described. As the sample system, PWR auxiliary feedwater system has been taken and an analysis has been performed by the proposed analysis framework. (orig.) 15 refs.

Matsuoka, T.; Obayashi, M. [Ministry of Transportation, Tokyo (Japan). Ship Research Inst.

1997-11-01

290

Review of the Byron/Braidwood Units 1 and 2 auxiliary feedwater system reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

This report presents the results of a review of the Auxiliary Feedwater System Reliability Analysis for Byron Units 1 and 2/Braidwood Units 1 and 2. The objective of this report is to estimate the probability that the Auxiliary Feedwater System will fail to perform its mission for each of three different initiators: (1) loss of main feedwater with offsite power available, (2) loss of offsite power, (3) loss of all 460 VAC power. The scope, methodology, and failure data are prescribed by NUREG-0611, Appendix III. The results are compared with those obtained in NUREG-0611 for other Westinghouse plants.

Youngblood, R.; Papazoglou, I.A.

1983-11-01

291

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

Energy Technology Data Exchange (ETDEWEB)

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

Anderson-cooke, Christine M [Los Alamos National Laboratory

2010-01-01

292

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

Directory of Open Access Journals (Sweden)

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

Mohd Iqbal Ridwan

2013-05-01

293

Reliability Analysis Study of Digital Reactor Protection System in Nuclear Power Plant  

Energy Technology Data Exchange (ETDEWEB)

The Digital I and C systems are believed to improve a plants safety and reliability generally. The reliability analysis of digital I and C system has become one research hotspot. Traditional fault tree method is one of means to quantify the digital I and C system reliability. Review of advanced nuclear power plant AP1000 digital protection system evaluation makes clear both the fault tree application and analysis process to the digital system reliability. One typical digital protection system special for advanced reactor has been developed, which reliability evaluation is necessary for design demonstration. The typical digital protection system construction is introduced in the paper, and the process of FMEA and fault tree application to the digital protection system reliability evaluation are described. Reliability data and bypass logic modeling are two points giving special attention in the paper. Because the factors about time sequence and feedback not exist in reactor protection system obviously, the dynamic feature of digital system is not discussed.

Guo, Xiao Ming; Liu, Tao; Tong, Jie Juan; Zhao, Jun [Tsinghua University, Beijing (China)

2011-08-15

294

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...

2008-01-01

295

Reliability and Validity of Learning Behaviors Scale (LBS) Scores with Academically Talented Students: A Comparative Perspective  

Science.gov (United States)

In this study, teacher ratings of academically talented (AT) students on the Learning Behaviors Scale (LBS) were examined for evidence of reliability and validity in two cohorts attending a summer program. The LBS is a 29-item rating scale assessing learning behaviors related to academic success, Cohort 1 consisted of 387 students and Cohort 2…

Worrell, Frank C.; Schaefer, Barbara A.

2004-01-01

296

A study of annunciator response model application in human reliability analysis  

International Nuclear Information System (INIS)

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

2010-11-01

297

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

298

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

299

A Reliable Method for Rhythm Analysis during Cardiopulmonary Resuscitation  

Science.gov (United States)

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

Ayala, U.; Irusta, U.; Ruiz, J.; Eftest?l, T.; Kramer-Johansen, J.; Alonso-Atienza, F.; Alonso, E.; Gonzalez-Otero, D.

2014-01-01

300

Application of reliability analysis method to fusion component testing  

International Nuclear Information System (INIS)

The term reliability here implies that a component satisfies a set of performance criteria while under specified conditions of use over a specified period of time. For fusion nuclear technology, the reliability goal to be pursued is the development of a mean time between failures (MTBF) for a component which is longer than its lifetime goal. While the component lifetime is mainly determined by the fluence limitation (i.e., damage level) which leads to performance degradation or failure, the MTBF represents an arithmetic average life of all units in a population. One method of assessing the reliability goal involves determining component availability needs to meet the goal plant availability, defining a test-analyze-fix development program to improve component reliability, and quantifying both test times and the number of test articles that would be required to ensure that a specified target MTBF is met. Statistically, constant failure rates and exponential life distributions are assumed for analyses and blanket component development is used as an example. However, as data are collected the probability distribution of the parameter of interest can be updated in a Bayesian fashion. The nuclear component testing program will be structured such that reliability requirements for DEMO can be achieved. The program shall not exclude the practice of a good design (such as reducing the complexity of the system to the minimum essential for the required operation), the execution of high quality manufacturing and inspection processes, and the implication of quality assurance and control for component development. In fact, the assurance of a high quality testing/development program is essential so that there is no question left for reliability

1994-07-01

 
 
 
 
301

Multi-element analysis of Japanese tea leaves by neutron activation analysis and the single comparator method  

International Nuclear Information System (INIS)

The reliability of the single comparator method in neutron activation analysis has been studied by comparing the calculated and experimental k values and by determining the concentration of trace elements in iron. The method has been applied to the analysis of tea leaves for thirteen elements; their concentrations varied over five orders of magnitude. (Auth.)

1979-10-01

302

Reliability modeling and analysis of smart power systems  

CERN Document Server

The volume presents the research work in understanding, modeling and quantifying the risks associated with different ways of implementing smart grid technology in power systems in order to plan and operate a modern power system with an acceptable level of reliability. Power systems throughout the world are undergoing significant changes creating new challenges to system planning and operation in order to provide reliable and efficient use of electrical energy. The appropriate use of smart grid technology is an important drive in mitigating these problems and requires considerable research acti

Karki, Rajesh; Verma, Ajit Kumar

2014-01-01

303

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

304

Reliability analysis of semicoherent systems through their lattice polynomial descriptions  

CERN Document Server

A semicoherent system can be described by its structure function or, equivalently, by a lattice polynomial function expressing the system lifetime in terms of the component lifetimes. In this paper we point out the parallelism between the two descriptions and use the natural connection of lattice polynomial functions and relevant random events to collect exact formulas for the system reliability. We also discuss the equivalence between calculating the reliability of semicoherent systems and calculating the distribution function of a lattice polynomial function of random variables.

Dukhovny, Alexander

2008-01-01

305

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

1995-01-01

306

Screening, sensitivity, and uncertainty for the CREAM method of Human Reliability Analysis  

International Nuclear Information System (INIS)

This paper reports a sensitivity analysis of the Cognitive Reliability and Error Analysis Method for Human Reliability Analysis. We consider three different aspects: the difference between the outputs of the Basic and Extended methods, on the same HRA scenario; the variability in outputs through the choices made for common performance conditions (CPCs); and the variability in outputs through the assignment of choices for cognitive function failures (CFFs). We discuss the problem of interpreting categories when applying the method, compare its quantitative structure to that of first generation methods and discuss also how dependence is modelled with the approach. We show that the control mode intervals used in the Basic method are too narrow to be consistent with the Extended method. This motivates a new screening method that gives improved accuracy with respect to the Basic method, in the sense that (on average) halves the uncertainty associated with the Basic method. We make some observations on the design of a screening method that are generally applicable in Risk Analysis. Finally, we propose a new method of combining CPC weights with nominal probabilities so that the calculated probabilities are always in range (i.e. between 0 and 1), while satisfying sensible properties that are consistent with the overall CREAM method

2013-07-01

307

Reliability analysis of common hazardous waste treatment processes  

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-05-01

308

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

1993-01-01

309

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)

1996-01-01

310

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

311

Comparative analysis of Carnaval II Library  

International Nuclear Information System (INIS)

The Carnaval II cross sections library from the french fast reactor calculation system is evaluated in two ways: 1"0) a comparative analysis of the calculations system for fast reactors at IEN (Instituto de Engenharia Nuclear) using a 'benchmark' model is done; 2"0) a comparative analysis in relation to the french system itself is also done, using calculations realized with two versions of the french library: the SETR-II and the CARNAVAL IV, the first one being anterior and the second one posterior to the Carnaval II version, the one used by IEN. (Author)

1981-04-15

312

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

Energy Technology Data Exchange (ETDEWEB)

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

Peters, Valerie A.; Ogilvie, Alistair B.

2012-01-01

313

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

314

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

Directory of Open Access Journals (Sweden)

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

Lei Nie

2013-05-01

315

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

International Nuclear Information System (INIS)

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

2000-01-01

316

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

317

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

318

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

319

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

Energy Technology Data Exchange (ETDEWEB)

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

Choi, Sun Yeong; Han, Sang Hoon

2005-04-01

320

Reliability analysis of shear strengthening EBR FRP models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work presents a statistically oriented study aiming to assess the reliability of some of the most well known design models available for the prediction of the contribution of fiber reinforced polymer (FRP) systems applied according to the externally bonded reinforcing (EBR) technique for the shear strengthening of reinforced concrete (RC) beams. Relevant data was collected from experimental programs carried out in recent years in the context of the shear strengthening with FR...

Lima, Joa?o L. T.; Barros, Joaquim A. O.

2011-01-01

 
 
 
 
321

Reliability analysis of bonded joints with variations in adhesive thickness  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Bonded joints are used in several industrial applications as a surrogate of more expensive repairs, but their reliability must be ascertained. Failure in a bonded joint mainly occurs in the adhesive due to stress concentrations that directly depend on the adhesive thickness. In practice, it is difficult to ensure a good accuracy of the final adhesive thickness, leading to uncertainty to its spatial variability. This uncertainty greatly influences the strength of the bonded joint. This work de...

2013-01-01

322

Intrinsic Geometric Analysis of the Network Reliability and Voltage Stability  

CERN Multimedia

This paper presents the intrinsic geometric model for the solution of power system planning and its operation. This problem is large-scale and nonlinear, in general. Thus, we have developed the intrinsic geometric model for the network reliability and voltage stability, and examined it for the IEEE 5 bus system. The robustness of the proposed model is illustrated by introducing variations of the network parameters. Exact analytical results show the accuracy as well as the efficiency of the proposed solution technique.

Gupta, N; Bellucci, S

2010-01-01

323

Diagnosing MOV problems using comparative trace analysis  

International Nuclear Information System (INIS)

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

1992-07-01

324

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

325

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The photovoltaic sector in Morocco is a serious option for the future. The integration of this type of energy into the grid has a considerable effect on the adequacy of the grid. The objective of this work is to assess the reliability of the Moroccan power grid at the hierarchical level I (HLI: load coverage under the assumption of infinite node) using a non-sequential Monte Carlo simulation in which photovoltaic generation is introduced. In order to lead such a study, a model was used in ord...

Mohamed Oukili; Smail Zouggar; Mohamed Seddik; Taoufik Ouchbel; François Vallée; Mohamed El Hafiani

2013-01-01

326

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

1982-01-01

327

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

Energy Technology Data Exchange (ETDEWEB)

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.

Cepin, Marko [Jozef Stefan Institute, Ljubljana (Slovenia)], E-mail: marko.cepin@ijs.si

2008-10-15

328

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

329

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

International Nuclear Information System (INIS)

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

1985-02-01

330

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

331

Image analysis in comparative genomic hybridization  

Energy Technology Data Exchange (ETDEWEB)

Comparative genomic hybridization (CGH) is a new technique by which genomic imbalances can be detected by combining in situ suppression hybridization of whole genomic DNA and image analysis. We have developed software for rapid, quantitative CGH image analysis by a modification and extension of the standard software used for routine karyotyping of G-banded metaphase spreads in the Magiscan chromosome analysis system. The DAPI-counterstained metaphase spread is karyotyped interactively. Corrections for image shifts between the DAPI, FITC, and TRITC images are done manually by moving the three images relative to each other. The fluorescence background is subtracted. A mean filter is applied to smooth the FITC and TRITC images before the fluorescence ratio between the individual FITC and TRITC-stained chromosomes is computed pixel by pixel inside the area of the chromosomes determined by the DAPI boundaries. Fluorescence intensity ratio profiles are generated, and peaks and valleys indicating possible gains and losses of test DNA are marked if they exceed ratios below 0.75 and above 1.25. By combining the analysis of several metaphase spreads, consistent findings of gains and losses in all or almost all spreads indicate chromosomal imbalance. Chromosomal imbalances are detected either by visual inspection of fluorescence ratio (FR) profiles or by a statistical approach that compares FR measurements of the individual case with measurements of normal chromosomes. The complete analysis of one metaphase can be carried out in approximately 10 minutes. 8 refs., 7 figs., 1 tab.

Lundsteen, C.; Maahr, J.; Christensen, B. [and others

1995-01-01

332

Comparative Analysis on Constitutional Supervision Modes  

Directory of Open Access Journals (Sweden)

Full Text Available

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

Key words: Constitutional supervision modes; Comparative study

Wenjing WANG

2012-11-01

333

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

International Nuclear Information System (INIS)

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

2011-10-01

334

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

335

Reliability analysis of digital instrumentation and control systems  

Energy Technology Data Exchange (ETDEWEB)

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)

Veeramany, A.; Pandey, M.D., E-mail: aveerama@uwaterloo.ca [Univ. of Waterloo, Dept. of Civil and Environmental Engineering, Waterloo, Ontario (Canada)

2011-07-01

336

Reliability and maintenance analysis of the CERN PS booster  

CERN Document Server

The PS Booster Synchrotron being a complex accelerator with four superposed rings and substantial additional equipment for beam splitting and recombination, doubts were expressed at the time of project authorization as to its likely operational reliability. For 1975 and 1976, the average down time was 3.2% (at least one ring off) or 1.5% (all four rings off). The items analysed are: operational record, design features, maintenance, spare parts policy, operating temperature, effects of thunderstorms, fault diagnostics, role of operations staff and action by experts. (15 refs).

Staff, P S B

1977-01-01

337

Reliability and maintenance analysis of the CERN PS booster  

International Nuclear Information System (INIS)

The PS Booster Synchrotron (PSB) is a complex accelerator with four superposed rings and substantial additional equipment for beam splitting and recombination. Doubts were expressed at the time of project authorization as to its likely operational reliability. For 1975 and 1976, the average down time was 3.2% (at least one ring off) or 1.5% (all four rings off). The items analyzed are: operational record, design features, maintenance, spare parts policy, operating temperature, effects of thunderstorms, fault diagnostics, role of operations staff and action by experts

1977-06-01

338

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

339

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

2000-06-28

340

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.

2008-01-01

 
 
 
 
341

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

342

Development of an analysis rule of diagnosis error for standard method of human reliability analysis  

International Nuclear Information System (INIS)

This paper presents the status of development of Korea standard method for Human Reliability Analysis (HRA), and proposed a standard procedure and rules for the evaluation of diagnosis error probability. The quality of KSNP HRA was evaluated using the requirement of ASME PRA standard guideline, and the design requirement for the standard HRA method was defined. Analysis procedure and rules, developed so far, to analyze diagnosis error probability was suggested as a part of the standard method. And also a study of comprehensive application was performed to evaluate the suitability of the proposed rules

2003-10-01

343

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

344

Comparative Analysis on Constitutional Supervision Modes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Wang, Wenjing; Wang, Xiaorui

2012-01-01

345

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...

Premzl Marko; Gamulin Vera

2007-01-01

346

Comparative Analysis: A Feasible Software Engineering Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The reasonable choice is a critical success factor for decision- making in the field of software engineering (SE). A case-driven comparative analysis has been introduced and a procedure for its systematic application has been suggested. The paper describes how the proposed method can be built in a general framework for SE activities. Some examples of experimental versions of the framework are brie y presented.

Maneva, Nelly

2007-01-01

347

Reliability analysis of event-related brain potentials to olfactory stimuli.  

Science.gov (United States)

Olfactory event-related potentials (OERP) have been used to investigate olfactory processing in health and disease. However, the reliability of the OERP has yet to be established statistically. The present study examined test-retest reliability of the OERP over a 4-week interval. EEG was recorded from Fz, Cz, and Pz, using a single-stimulus paradigm with amyl acetate. Reliabilities for ERP component latencies and interpeak amplitudes were assessed as intraclass and Pearson product-moment correlation coefficients. Reliabilities were higher for latency than for amplitude. Highest correlation coefficients were observed for P2 latency, specifically at Cz and Pz P3 amplitude and latency exhibited high reliability at Cz and Pz. Fz demonstrated weakest correlation coefficients. The data suggest that OERP reliability is comparable to that of auditory and visual ERPs, supporting the use of OERPs in both basic research and clinical assessment. PMID:12462501

Thesen, Thomas; Murphy, Claire

2002-11-01

348

High throughput gene expression analysis identifies reliable expression markers of human corneal endothelial cells.  

Science.gov (United States)

Considerable interest has been generated for the development of suitable corneal endothelial graft alternatives through cell-tissue engineering, which can potentially alleviate the shortage of corneal transplant material. The advent of less invasive suture-less key-hole surgery options such as Descemet's Stripping Endothelial Keratoplasty (DSEK) and Descemet's Membrane Endothelial Keratoplasty (DMEK), which involve transplantation of solely the endothelial layer instead of full thickness cornea, provide further impetus for the development of alternative endothelial grafts for clinical applications. A major challenge for this endeavor is the lack of specific markers for this cell type. To identify genes that reliably mark corneal endothelial cells (CECs) in vivo and in vitro, we performed RNA-sequencing on freshly isolated human CECs (from both young and old donors), CEC cultures, and corneal stroma. Gene expression of these corneal cell types was also compared to that of other human tissue types. Based on high throughput comparative gene expression analysis, we identified a panel of markers that are: i) highly expressed in CECs from both young donors and old donors; ii) expressed in CECs in vivo and in vitro; and iii) not expressed in corneal stroma keratocytes and the activated corneal stroma fibroblasts. These were SLC4A11, COL8A2 and CYYR1. The use of this panel of genes in combination reliably ascertains the identity of the CEC cell type. PMID:23844023

Chng, Zhenzhi; Peh, Gary S L; Herath, Wishva B; Cheng, Terence Y D; Ang, Heng-Pei; Toh, Kah-Peng; Robson, Paul; Mehta, Jodhbir S; Colman, Alan

2013-01-01

349

Reliability analysis of discrete event dynamic systems with Petri nets  

International Nuclear Information System (INIS)

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

2009-11-01

350

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

351

The role of human reliability analysis for enhancing crew performance  

International Nuclear Information System (INIS)

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

1986-01-01

352

A knowledge based approach for systems safety and reliability analysis  

International Nuclear Information System (INIS)

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

1988-02-15

353

Availability analysis for high reliability computer systems in nuclear facilities  

International Nuclear Information System (INIS)

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

1977-07-01

354

Reliability Analysis of an Offshore Structure : A Case Study II  

DEFF Research Database (Denmark)

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

Sørensen, John Dalsgaard; Rackwitz, R.

1992-01-01

355

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

1993-08-15

356

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-03-15

357

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

358

Reliability analysis of a structural ceramic combustion chamber  

Science.gov (United States)

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

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

1991-01-01

359

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

360

A New-Generation Continuous Glucose Monitoring System: Improved Accuracy and Reliability Compared with a Previous-Generation System  

Science.gov (United States)

Abstract Background Use of continuous glucose monitoring (CGM) systems can improve glycemic control, but widespread adoption of CGM utilization has been limited, in part because of real and perceived problems with accuracy and reliability. This study compared accuracy and performance metrics for a new-generation CGM system with those of a previous-generation device. Subjects and Methods Subjects were enrolled in a 7-day, open-label, multicenter pivotal study. Sensor readings were compared with venous YSI measurements (blood glucose analyzer from YSI Inc., Yellow Springs, OH) every 15?min (±5?min) during in-clinic visits. The aggregate and individual sensor accuracy and reliability of a new CGM system, the Dexcom® (San Diego, CA) G4™ PLATINUM (DG4P), were compared with those of the previous CGM system, the Dexcom SEVEN® PLUS (DSP). Results Both study design and subject characteristics were similar. The aggregate mean absolute relative difference (MARD) for DG4P was 13% compared with 16% for DSP (P80?mg/dL) compared with 76% for DSP (P<0.001). Ninety percent of the DG4P sensors had an individual MARD ?20% compared with only 76% of DSP sensors (P=0.015). Half of DG4P sensors had a MARD less than 12.5% compared with 14% for the DSP sensors (P=0.028). The mean absolute difference for biochemical hypoglycemia (YSI <70?mg/dL) for DG4P was 11?mg/dL compared with 16?mg/dL for DSP (P<0.001). Conclusions The performance of DG4P was significantly improved compared with that of DSP, which may increase routine clinical use of CGM and improve patient outcomes.

Bailey, Timothy; Watkins, Elaine; Liljenquist, David; Price, David; Nakamura, Katherine; Boock, Robert; Peyser, Thomas

2013-01-01

 
 
 
 
361

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

362

Reliability-tools in geotechnical design, an approach for river dike analysis:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The application of reliability analysis in civil engineering is still an emerging technology, more so in geotechnical engineering and even more so in application to river dikes. However, much experience remains to be gained, recently, especially in European countries (the Netherlands, Germany, United Kingdom…) as well as in the United States of America. This paper focuses, only, on the general framework of reliability analysis in geotechnical engineering design and an example for river dike...

Pham Quang, T.; Vrijling, J. K.; Gelder, P. H. A. J. M.; Thu, T. M.

2010-01-01

363

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

364

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

365

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

Science.gov (United States)

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

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

2014-03-01

366

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)

1991-01-01

367

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

2007-03-01

368

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-03-15

369

Examination of Reliability Critical Items in Liquid Metal Reactors: An Analysis by the Centralized Reliability Data Organization (CREDO).  

Science.gov (United States)

The Centralized Reliability Data Organization (CREDO) is the largest repository of liquid metal reactor (LMR) component reliability data in the world. It is jointly sponsored by the US Department of Energy (DOE) and the Power Reactor and Nuclear Fuel Deve...

B. L. Humphrys M. J. Haire K. H. Koger J. F. Manneschmidt K. Setoguchi

1987-01-01

370

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

371

Automated migration analysis based on cell texture: method & reliability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background In this paper, we present and validate a way to measure automatically the extent of cell migration based on automated examination of a series of digital photographs. It was designed specifically to identify the impact of Second Hand Smoke (SHS) on endothelial cell migration but has broader applications. The analysis has two stages: (1) preprocessing of image texture, and (2) migration analysis. Results The output is a graphic overlay that ind...

Qin Jianfeng; Chittenden Thomas W; Gao Ling; Pearlman Justin D

2005-01-01

372

Analytical simulation of water system capacity reliability, 1. Modified frequency-duration analysis  

Science.gov (United States)

The problem addressed is the computation of the unavailability and expected unserved demand of a water supply system having random demand, finished water storage, and unreliable capacity components. Examples of such components include pumps, treatment plants, and aqueducts. Modified frequency-duration analysis estimates these reliability statistics by, first, calculating how often demand exceeds available capacity and, second, comparing the amount of water in storage with how long such capacity deficits last. This approach builds upon frequency-duration methods developed by the power industry for analyzing generation capacity deficits. Three versions of the frequency-duration approach are presented. Two yield bounds to system unavailability and unserved demand and the third gives an estimate of their true values between those bounds.

Hobbs, Benjamin F.; Beim, Gina K.

1988-09-01

373

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)

2000-12-01

374

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)

2007-06-01

375

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

376

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.

377

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

378

Comparative Transcriptome Analysis of Four Prymnesiophyte Algae  

Science.gov (United States)

Genomic studies of bacteria, archaea and viruses have provided insights into the microbial world by unveiling potential functional capabilities and molecular pathways. However, the rate of discovery has been slower among microbial eukaryotes, whose genomes are larger and more complex. Transcriptomic approaches provide a cost-effective alternative for examining genetic potential and physiological responses of microbial eukaryotes to environmental stimuli. In this study, we generated and compared the transcriptomes of four globally-distributed, bloom-forming prymnesiophyte algae: Prymnesium parvum, Chrysochromulina brevifilum, Chrysochromulina ericina and Phaeocystis antarctica. Our results revealed that the four transcriptomes possess a set of core genes that are similar in number and shared across all four organisms. The functional classifications of these core genes using the euKaryotic Orthologous Genes (KOG) database were also similar among the four study organisms. More broadly, when the frequencies of different cellular and physiological functions were compared with other protists, the species clustered by both phylogeny and nutritional modes. Thus, these clustering patterns provide insight into genomic factors relating to both evolutionary relationships as well as trophic ecology. This paper provides a novel comparative analysis of the transcriptomes of ecologically important and closely related prymnesiophyte protists and advances an emerging field of study that uses transcriptomics to reveal ecology and function in protists.

Koid, Amy E.; Liu, Zhenfeng; Terrado, Ramon; Jones, Adriane C.; Caron, David A.; Heidelberg, Karla B.

2014-01-01

379

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

380

Finite State Machine Based Evaluation Model for Web Service Reliability Analysis  

CERN Multimedia

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

 
 
 
 
381

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

Science.gov (United States)

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

Ang, Rebecca P.; Huan, Vivien S.

2006-01-01

382

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

1978-01-01

383

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

384

Reliability of contemporary data-acquisition techniques for LEED analysis  

Energy Technology Data Exchange (ETDEWEB)

It is becoming clear that one of the principal limitations in LEED structure analysis is the quality of the experimental I-V profiles. This limitation is discussed, and data acquisition procedures described, which for simple systems, seem to enhance the quality of agreement between the results of theoretical model calculations and experimental LEED spectra. By employing such procedures to obtain data from Cu(100), excellent agreement between computed and measured profiles has been achieved. 7 figures.

Noonan, J.R.; Davis, H.L.

1980-10-01

385

Reliability of contemporary data-acquisition techniques for LEED analysis  

International Nuclear Information System (INIS)

It is becoming clear that one of the principal limitations in LEED structure analysis is the quality of the experimental I-V profiles. This limitation is discussed, and data acquisition procedures described, which for simple systems, seem to enhance the quality of agreement between the results of theoretical model calculations and experimental LEED spectra. By employing such procedures to obtain data from Cu(100), excellent agreement between computed and measured profiles has been achieved. 7 figures

1980-06-20

386

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...

1989-01-01

387

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...

2011-01-01

388

Analysis of threaded connection reliability for compression applications  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-07-01

389

Noncoding RNA gene detection using comparative sequence analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Noncoding RNA genes produce transcripts that exert their function without ever producing proteins. Noncoding RNA gene sequences do not have strong statistical signals, unlike protein coding genes. A reliable general purpose computational genefinder for noncoding RNA genes has been elusive. Results We describe a comparative sequence analysis algorithm for detecting novel structural RNA genes. The key idea is to test the pattern of substitutions observed in a pairwise alignment of two homologous sequences. A conserved coding region tends to show a pattern of synonymous substitutions, whereas a conserved structural RNA tends to show a pattern of compensatory mutations consistent with some base-paired secondary structure. We formalize this intuition using three probabilistic "pair-grammars": a pair stochastic context free grammar modeling alignments constrained by structural RNA evolution, a pair hidden Markov model modeling alignments constrained by coding sequence evolution, and a pair hidden Markov model modeling a null hypothesis of position-independent evolution. Given an input pairwise sequence alignment (e.g. from a BLASTN comparison of two related genomes we classify the alignment into the coding, RNA, or null class according to the posterior probability of each class. Conclusions We have implemented this approach as a program, QRNA, which we consider to be a prototype structural noncoding RNA genefinder. Tests suggest that this approach detects noncoding RNA genes with a fair degree of reliability.

Eddy Sean R

2001-10-01

390

An advanced human reliability analysis methodology: analysis of cognitive errors focused on  

International Nuclear Information System (INIS)

The conventional Human Reliability Analysis (HRA) methods such as THERP/ASEP, HCR and SLIM has been criticised for their deficiency in analysing cognitive errors which occurs during operator's decision making process. In order to supplement the limitation of the conventional methods, an advanced HRA method, what is called the 2nd generation HRA method, including both qualitative analysis and quantitative assessment of cognitive errors has been being developed based on the state-of-the-art theory of cognitive systems engineering and error psychology. The method was developed on the basis of human decision-making model and the relation between the cognitive function and the performance influencing factors. The application of the proposed method to two emergency operation tasks is presented

2001-10-01

391

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

392

Hawaiian propolis: comparative analysis and botanical origin.  

Science.gov (United States)

Propolis is a resinous mixture of substances collected and processed from various botanical sources by honeybees (Apis mellifera). We recently obtained Hawaiian propolis, the study of which, to our knowledge, has not been reported. The purpose of this study was to analyze the composition of Hawaiian propolis and to identify its botanical origin. A comparative analysis of Hawaiian and Okinawan propolis and of the glandular trichomes on Macaranga tanarius fruit (the botanical origin of Okinawan propolis) was performed using reversed-phase high-performance liquid chromatography coupled with high resolution-electrospray mass spectrometry. Hawaiian propolis contained nine prenylflavonoids that were also isolated from Okinawan propolis. In conclusion, we suggest that the botanical origin of Hawaiian propolis is M. tanarius, the same as that of Okinawan propolis. PMID:24689281

Inui, Saori; Hosoya, Takahiro; Kumazaw, Shigenori

2014-02-01

393

Construction QA/QC systems: comparative analysis  

International Nuclear Information System (INIS)

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

1980-01-01

394

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

395

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

International Nuclear Information System (INIS)

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

2007-09-10

396

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

397

Comparative analysis of available life cycle inventories of cement in the EU  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Life cycle inventories are a prerequisite of life cycle assessments. This paper conducts a comparative analysis of inventories of several different types of cement produced in Europe. It considers the production of 1 kg of cement from cradle to gate and all results are based on this mass unit. The reliability of cement inventories is affected by inaccurate or non-representative data, and comparative analysis is difficult due to varying system boundary definitions. Only the four main emissions...

Josa Garcia-tornel, Alejandro; Aguado Cea, Antonio; Heino, Atte; Byars, Ewan; Cardim Carvalho Filho, Arnaldo

2004-01-01

398

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

International Nuclear Information System (INIS)

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

1981-09-23

399

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

1986-11-16

400

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

 
 
 
 
401

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

1985-01-01

402

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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