A comparative reliability analysis of free-piston Stirling machines
Schreiber, Jeffrey G.
2001-02-01
A free-piston Stirling power convertor is being developed for use in an advanced radioisotope power system to provide electric power for NASA deep space missions. These missions are typically long lived, lasting for up to 14 years. The Department of Energy (DOE) is responsible for providing the radioisotope power system for the NASA missions, and has managed the development of the free-piston power convertor for this application. The NASA Glenn Research Center has been involved in the development of Stirling power conversion technology for over 25 years and is currently providing support to DOE. Due to the nature of the potential missions, long life and high reliability are important features for the power system. Substantial resources have been spent on the development of long life Stirling cryocoolers for space applications. As a very general statement, free-piston Stirling power convertors have many features in common with free-piston Stirling cryocoolers, however there are also significant differences. For example, designs exist for both power convertors and cryocoolers that use the flexure bearing support system to provide noncontacting operation of the close-clearance moving parts. This technology and the operating experience derived from one application may be readily applied to the other application. This similarity does not pertain in the case of outgassing and contamination. In the cryocooler, the contaminants normally condense in the critical heat exchangers and foul the performance. In the Stirling power convertor just the opposite is true as contaminants condense on non-critical surfaces. A methodology was recently published that provides a relative comparison of reliability, and is applicable to systems. The methodology has been applied to compare the reliability of a Stirling cryocooler relative to that of a free-piston Stirling power convertor. The reliability analysis indicates that the power convertor should be able to have superior reliability
Namkoong, Sun; Hong, Seung Phil; Kim, Myung Hwa; Park, Byung Cheol
2013-01-01
Background Nowadays, although its clinical value remains controversial institutions utilize hair mineral analysis. Arguments about the reliability of hair mineral analysis persist, and there have been evaluations of commercial laboratories performing hair mineral analysis. Objective The objective of this study was to assess the reliability of intra-laboratory and inter-laboratory data at three commercial laboratories conducting hair mineral analysis, compared to serum mineral analysis. Method...
Small nuclear power reactor emergency electric power supply system reliability comparative analysis
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)
The results of a comparative analysis of the fuel reliability indicator on NPPs with WWER and PWR reactors are presented in this report. As an exponent for a comparative reliability analysis of the WANO fuel reliability indicator is used. The fuel reliability indicator provides a general measure of the extent to which the reactor coolant activity is increased as a result of fuel damage. The analysis of fuel reliability indicator values during 1991-2001 at NPPs with WWER-1000 and WWER-440 reactors (Russia, Ukraine, Bulgaria, Czech Republic, Slovakia, Hungary, Finland) is carried out. The high level of WWER fuel reliability is scored except for cases of fuel failures in separate operating periods of some units. (author)
Power electronics reliability analysis.
Smith, Mark A.; Atcitty, Stanley
2009-12-01
This report provides the DOE and industry with a general process for analyzing power electronics reliability. The analysis can help with understanding the main causes of failures, downtime, and cost and how to reduce them. One approach is to collect field maintenance data and use it directly to calculate reliability metrics related to each cause. Another approach is to model the functional structure of the equipment using a fault tree to derive system reliability from component reliability. Analysis of a fictitious device demonstrates the latter process. Optimization can use the resulting baseline model to decide how to improve reliability and/or lower costs. It is recommended that both electric utilities and equipment manufacturers make provisions to collect and share data in order to lay the groundwork for improving reliability into the future. Reliability analysis helps guide reliability improvements in hardware and software technology including condition monitoring and prognostics and health management.
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
Comparative Study on Response Surfaces for Reliability Analysis of Spatially Variable Soil Slope
李亮; 褚雪松
2015-01-01
This paper focuses on the performance of the second-order polynomial-based response surfaces on the reliability of spatially variable soil slope. A single response surface constructed to approximate the slope system failure performance functionG(X) (called single RS) and multiple response surfaces constructed on finite number of slip surfaces (called multiple RS) are developed, respectively. Single RS and multiple RS are applied to evaluate the system failure probability pf for a cohesive soil slope together with Monte Carlo simulation (MCS). It is found thatpf calculated by single RS deviates significantly from that obtained by searching a large number of potential slip surfaces, and this deviation becomes insignificant with the decrease of the number of random variables or the increase of the scale of fluctuation. In other words, single RS cannot approximateG(X) with reasonable accuracy. The value ofpf from multiple response surfaces fits well with that obtained by searching a large number of potential slip surfaces. That is, multiple RS can estimateG(X) with reasonable accuracy.
Introduction to reliability analysis
Reliability analysis is concerned with the analysis of devices and systems whose individual components are prone to failure. This textbook presents an introduction to reliability analysis of repairable and nonrepairable systems. It is based on courses given to both undergraduate and graduate students of engineering and statistics as well as in workshops for professional engineers and scientists. The book concentrates on the methodology of the subject and on understanding theoretical results rather than on its theoretical development. An intrinsic aspect of reliability analysis is that the failure of components is best modelled using techniques drawn from probability and statistics. The author covers all the basic concepts required from these subjects and covers the main modern reliability analysis techniques thoroughly. These include: the graphical analysis of life data, maximum likelihood estimation, and Bayesian estimation. Throughout, the emphsis is on the practicalities of the subject with numerous examples drawn from industrial and engineering settings. (orig.) With 50 figs
The use of expert systems can be helpful to improve the transparency and repeatability of assessments in areas of risk analysis with limited data available. In this field, human reliability analysis (HRA) is no exception, and, in particular, dependence analysis is an HRA task strongly based on analyst judgement. The analysis of dependence among Human Failure Events refers to the assessment of the effect of an earlier human failure on the probability of the subsequent ones. This paper analyses and compares two expert systems, based on Bayesian Belief Networks and Fuzzy Logic (a Fuzzy Expert System, FES), respectively. The comparison shows that a BBN approach should be preferred in all the cases characterized by quantifiable uncertainty in the input (i.e. when probability distributions can be assigned to describe the input parameters uncertainty), since it provides a satisfactory representation of the uncertainty and its output is directly interpretable for use within PSA. On the other hand, in cases characterized by very limited knowledge, an analyst may feel constrained by the probabilistic framework, which requires assigning probability distributions for describing uncertainty. In these cases, the FES seems to lead to a more transparent representation of the input and output uncertainty. - Highlights: • We analyse treatment of uncertainty in two expert systems. • We compare a Bayesian Belief Network (BBN) and a Fuzzy Expert System (FES). • We focus on the input assessment, inference engines and output assessment. • We focus on an application problem of interest for human reliability analysis. • We emphasize the application rather than math to reach non-BBN or FES specialists
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
Discourse Analysis Procedures: Reliability Issues.
Hux, Karen; And Others
1997-01-01
A study evaluated and compared four methods of assessing reliability on one discourse analysis procedure--a modified version of Damico's Clinical Discourse Analysis. The methods were Pearson product-moment correlations; interobserver agreement; Cohen's kappa; and generalizability coefficients. The strengths and weaknesses of the methods are…
Kettaneh, Adrien; Heude, Barbara; Lommez, Agnès; Borys, Jean-Michel; Ducimetière, Pierre; Charles, Marie-Aline
2005-01-01
OBJECTIVE: To evaluate the reproducibility of the measurement of% body fat by bipedal biometrical impedance analysis (BIA) compared with anthropometric measurements of adiposity in children and the correlations between these methods in children and adults.METHODS: A cross-sectional study in a total of 1080 adults and children enrolled in 1999 in the Fleurbaix-Laventie Ville Sant?I (FLVS II) population-based study in northern France. The reproducibility of anthropometrical and BIA methods was ...
Failure Analysis for Improved Reliability
Sood, Bhanu
2016-01-01
Outline: Section 1 - What is reliability and root cause? Section 2 - Overview of failure mechanisms. Section 3 - Failure analysis techniques (1. Non destructive analysis techniques, 2. Destructive Analysis, 3. Materials Characterization). Section 4 - Summary and Closure
Integrating reliability analysis and design
This report describes the Interactive Reliability Analysis Project and demonstrates the advantages of using computer-aided design systems (CADS) in reliability analysis. Common cause failure problems require presentations of systems, analysis of fault trees, and evaluation of solutions to these. Results have to be communicated between the reliability analyst and the system designer. Using a computer-aided design system saves time and money in the analysis of design. Computer-aided design systems lend themselves to cable routing, valve and switch lists, pipe routing, and other component studies. At EG and G Idaho, Inc., the Applicon CADS is being applied to the study of water reactor safety systems
Reliability analysis of interdependent lattices
Limiao, Zhang; Daqing, Li; Pengju, Qin; Bowen, Fu; Yinan, Jiang; Zio, Enrico; Rui, Kang
2016-06-01
Network reliability analysis has drawn much attention recently due to the risks of catastrophic damage in networked infrastructures. These infrastructures are dependent on each other as a result of various interactions. However, most of the reliability analyses of these interdependent networks do not consider spatial constraints, which are found important for robustness of infrastructures including power grid and transport systems. Here we study the reliability properties of interdependent lattices with different ranges of spatial constraints. Our study shows that interdependent lattices with strong spatial constraints are more resilient than interdependent Erdös-Rényi networks. There exists an intermediate range of spatial constraints, at which the interdependent lattices have minimal resilience.
Reliability Analysis of Wind Turbines
Toft, Henrik Stensgaard; Sørensen, John Dalsgaard
2008-01-01
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...
Computational methods for efficient structural reliability and reliability sensitivity analysis
Wu, Y.-T.
1993-01-01
This paper presents recent developments in efficient structural reliability analysis methods. The paper proposes an efficient, adaptive importance sampling (AIS) method that can be used to compute reliability and reliability sensitivities. The AIS approach uses a sampling density that is proportional to the joint PDF of the random variables. Starting from an initial approximate failure domain, sampling proceeds adaptively and incrementally with the goal of reaching a sampling domain that is slightly greater than the failure domain to minimize over-sampling in the safe region. Several reliability sensitivity coefficients are proposed that can be computed directly and easily from the above AIS-based failure points. These probability sensitivities can be used for identifying key random variables and for adjusting design to achieve reliability-based objectives. The proposed AIS methodology is demonstrated using a turbine blade reliability analysis problem.
Integration of reliability and tolerance effect analysis
Brombacher, A.C.; Boer; Loo, van 't, J.
1989-01-01
The authors focus on the development of systems with online optimized reliability. They argue that in the case of online analysis, reliability analysis should have the same importance as functional analysis currently has, and that reliability should be integrated in a design. Further the function of a quality assurance team is only to check this built-in reliability, not to make a functional correct design also reliable. Therefore the designer (or design team) should be able to perform reliab...
Integration of reliability and tolerance effect analysis
Brombacher, A.C.; Boer, de H.A.; Loo, van 't J.
1989-01-01
The authors focus on the development of systems with online optimized reliability. They argue that in the case of online analysis, reliability analysis should have the same importance as functional analysis currently has, and that reliability should be integrated in a design. Further the function of
Software reliability analysis in probabilistic risk analysis
Probabilistic Risk Analysis (PRA) is a tool which can reveal shortcomings of the NPP design in general. PRA analysts have not had sufficient guiding principles in modelling particular digital components malfunctions. Digital I and C systems are mostly analysed simply and the software reliability estimates are engineering judgments often lacking a proper justification. The OECD/NEA Working Group RISK's task DIGREL develops a taxonomy of failure modes of digital I and C systems. The EU FP7 project HARMONICS develops software reliability estimation method based on an analytic approach and Bayesian belief network. (author)
Gate-Level Circuit Reliability Analysis: A Survey
Ran Xiao
2014-01-01
Full Text Available Circuit reliability has become a growing concern in today’s nanoelectronics, which motivates strong research interest over the years in reliability analysis and reliability-oriented circuit design. While quite a few approaches for circuit reliability analysis have been reported, there is a lack of comparative studies on their pros and cons in terms of both accuracy and efficiency. This paper provides an overview of some typical methods for reliability analysis with focus on gate-level circuits, large or small, with or without reconvergent fanouts. It is intended to help the readers gain an insight into the reliability issues, and their complexity as well as optional solutions. Understanding the reliability analysis is also a first step towards advanced circuit designs for improved reliability in the future research.
An accuracy analysis of Army Material System Analysis Activity discrete reliability growth model
Thalieb, Rio M.
1988-01-01
The accuracy of the discrete reliability growth model developed by Army Material System Analysis Activity (AMSAA) is analysed. The mean, standard deviation, and 95 precent confidence interval of the estimate of reliability resulting from simulating the AMSAA discrete reliability growth model are computed. The mean of the estimate of reliability from the AMSAA discrete reliability growth model is compared with the mean of the reliability estimate using the Exponential discrete reliability grow...
On Bayesian System Reliability Analysis
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
Reliability Analysis of Money Habitudes
Delgadillo, Lucy M.; Bushman, Brittani S.
2015-01-01
Use of the Money Habitudes exercise has gained popularity among various financial professionals. This article reports on the reliability of this resource. A survey administered to young adults at a western state university was conducted, and each Habitude or "domain" was analyzed using Cronbach's alpha procedures. Results showed all six…
Reliability analysis of software based safety functions
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.)
MargaritaStolarova
2014-06-01
Full Text Available This report has two main purposes. First, we combine well-known analytical approaches to conduct a comprehensive assessment of agreement and correlation of rating-pairs and to dis-entangle these often confused concepts, providing a best-practice example on concrete data and a tutorial for future reference. Second, we explore whether a screening questionnaire deve-loped for use with parents can be reliably employed with daycare teachers when assessing early expressive vocabulary. A total of 53 vocabulary rating pairs (34 parent-teacher and 19 mother-father pairs collected for two-year-old children (12 bilingual are evaluated. First, inter-rater reliability both within and across subgroups is assessed using the intra-class correlation coefficient (ICC. Next, based on this analysis of reliability and on the test-retest reliability of the employed tool, inter-rater agreement is analyzed, magnitude and direction of rating differences are considered. Finally, Pearson correlation coefficients of standardized vocabulary scores are calculated and compared across subgroups. The results underline the necessity to distinguish between reliability measures, agreement and correlation. They also demonstrate the impact of the employed reliability on agreement evaluations. This study provides evidence that parent-teacher ratings of children’s early vocabulary can achieve agreement and correlation comparable to those of mother-father ratings on the assessed vocabulary scale. Bilingualism of the evaluated child decreased the likelihood of raters’ agreement. We conclude that future reports of agree-ment, correlation and reliability of ratings will benefit from better definition of terms and stricter methodological approaches. The methodological tutorial provided here holds the potential to increase comparability across empirical reports and can help improve research practices and knowledge transfer to educational and therapeutic settings.
A comparative method for improving the reliability of brittle components
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
Combination of structural reliability and interval analysis
Zhiping Qiu; Di Yang; saac Elishakoff
2008-01-01
In engineering applications,probabilistic reliability theory appears to be presently the most important method,however,in many cases precise probabilistic reliability theory cannot be considered as adequate and credible model of the real state of actual affairs.In this paper,we developed a hybrid of probabilistic and non-probabilistic reliability theory,which describes the structural uncertain parameters as interval variables when statistical data are found insufficient.By using the interval analysis,a new method for calculating the interval of the structural reliability as well as the reliability index is introduced in this paper,and the traditional probabilistic theory is incorporated with the interval analysis.Moreover,the new method preserves the useful part of the traditional probabilistic reliability theory,but removes the restriction of its strict requirement on data acquisition.Example is presented to demonstrate the feasibility and validity of the proposed theory.
Integrated Methodology for Software Reliability Analysis
Marian Pompiliu CRISTESCU
2012-01-01
Full Text Available The most used techniques to ensure safety and reliability of the systems are applied together as a whole, and in most cases, the software components are usually overlooked or to little analyzed. The present paper describes the applicability of fault trees analysis software system, analysis defined as Software Fault Tree Analysis (SFTA, fault trees are evaluated using binary decision diagrams, all of these being integrated and used with help from Java library reliability.
Reliability analysis of continuous fiber composite laminates
Thomas, David J.; Wetherhold, Robert C.
1991-01-01
This paper describes two methods, the maximum distortion energy (MDE) and the principle of independent action (PIA), developed for the analysis of the reliability of a single continuous composite lamina. It is shown that, for the typical laminated plate structure, the individual lamina reliabilities can be combined in order to produce the upper and the lower bounds of reliability for the laminate, similar in nature to the bounds on properties produced from variational elastic methods. These limits were derived for both the interactive and the model failure considerations. Analytical expressions were also derived for the sensitivity of the reliability limits with respect to changes in the Weibull parameters and in loading conditions.
Analysis of information security reliability: A tutorial
This article presents a concise reliability analysis of network security abstracted from stochastic modeling, reliability, and queuing theories. Network security analysis is composed of threats, their impacts, and recovery of the failed systems. A unique framework with a collection of the key reliability models is presented here to guide the determination of the system reliability based on the strength of malicious acts and performance of the recovery processes. A unique model, called Attack-obstacle model, is also proposed here for analyzing systems with immunity growth features. Most computer science curricula do not contain courses in reliability modeling applicable to different areas of computer engineering. Hence, the topic of reliability analysis is often too diffuse to most computer engineers and researchers dealing with network security. This work is thus aimed at shedding some light on this issue, which can be useful in identifying models, their assumptions and practical parameters for estimating the reliability of threatened systems and for assessing the performance of recovery facilities. It can also be useful for the classification of processes and states regarding the reliability of information systems. Systems with stochastic behaviors undergoing queue operations and random state transitions can also benefit from the approaches presented here. - Highlights: • A concise survey and tutorial in model-based reliability analysis applicable to information security. • A framework of key modeling approaches for assessing reliability of networked systems. • The framework facilitates quantitative risk assessment tasks guided by stochastic modeling and queuing theory. • Evaluation of approaches and models for modeling threats, failures, impacts, and recovery analysis of information systems
Space Mission Human Reliability Analysis (HRA) Project
National Aeronautics and Space Administration — The purpose of this project is to extend current ground-based Human Reliability Analysis (HRA) techniques to a long-duration, space-based tool to more effectively...
Production Facility System Reliability Analysis Report
Dale, Crystal Buchanan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Klein, Steven Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-10-06
This document describes the reliability, maintainability, and availability (RMA) modeling of the Los Alamos National Laboratory (LANL) design for the Closed Loop Helium Cooling System (CLHCS) planned for the NorthStar accelerator-based ^{99}Mo production facility. The current analysis incorporates a conceptual helium recovery system, beam diagnostics, and prototype control system into the reliability analysis. The results from the 1000 hr blower test are addressed.
Huggel, C.; Raissig, A.; Rohrer, M.; Romero, G.; Diaz, A.; Salzmann, N.
2015-03-01
Damage caused by weather- and climate-related disasters have increased over the past decades, and growing exposure and wealth have been identified as main drivers of this increase. Disaster databases are a primary tool for the analysis of disaster characteristics and trends at global or national scales, and they support disaster risk reduction and climate change adaptation. However, the quality, consistency and completeness of different disaster databases are highly variable. Even though such variation critically influences the outcome of any study, comparative analyses of different databases are still rare to date. Furthermore, there is an unequal geographic distribution of current disaster trend studies, with developing countries being underrepresented. Here, we analyze three different disaster databases in the developing-country context of Peru: a global database (Emergency Events Database: EM-DAT), a multinational Latin American database (DesInventar) and a national database (Peruvian National Information System for the Prevention of Disasters: SINPAD). The analysis is performed across three dimensions: (1) spatial scales, from local to regional (provincial) and national scale; (2) timescales, from single events to decadal trends; and (3) disaster categories and metrics, including the number of single disaster event occurrence, or people killed and affected. Results show limited changes in disaster occurrence in the Cusco and ApurÍmac regions in southern Peru over the past four decades but strong positive trends in people affected at the national scale. We furthermore found large variations of the disaster metrics studied over different spatial and temporal scales, depending on the disaster database analyzed. We conclude and recommend that the type, method and source of documentation should be carefully evaluated for any analysis of disaster databases; reporting criteria should be improved and documentation efforts strengthened.
C. Huggel
2014-06-01
Full Text Available Loss and damage caused by weather and climate related disasters have increased over the past decades, and growing exposure and wealth have been identified as main drivers of this increase. Disaster databases are a primary tool for the analysis of disaster characteristics and trends at global or national scales, and support disaster risk reduction and climate change adaptation. However, the quality, consistency and completeness of different disaster databases are highly variable. Even though such variation critically influences the outcome of any study, comparative analyses of different disaster databases are still rare to date. Furthermore, there is an unequal geographic distribution of current disaster trend studies, with developing countries being under-represented. Here, we analyze three different disaster databases for the developing country context of Peru; a global database (EM-DAT, a regional Latin American (DesInventar and a national database (SINPAD. The analysis is performed across three dimensions, (1 spatial scales, from local to regional (provincial and national scale; (2 time scales, from single events to decadal trends; and (3 disaster categories and metrics, including the number of disaster occurrence, and damage metrics such as people killed and affected. Results show limited changes in disaster occurrence in the Cusco and Apurímac regions in southern Peru over the past four decades, but strong trends in people affected at the national scale. We furthermore found large variations of the disaster parameters studied over different spatial and temporal scales, depending on the disaster database analyzed. We conclude and recommend that the type, method and source of documentation should be carefully evaluated for any analysis of disaster databases; reporting criteria should be improved and documentation efforts strengthened.
Logic reliability analysis of adaptive control strategies
An approach is developed for the evaluation of the reliability of logic of adaptive control strategies, taking into account logic structural complexity and potential failure of programming modules. Flaws in the control system algorithm may not be discovered during debugging or initial testing and may only affect the performance under abnormal situations although the system may appear reliable in normal operations. Considering an adaptive control system designed for use in control of equipment employed in nuclear power stations, logic reliability evaluation is demonstrated. The approach given is applicable to any other designs and may be used to compare different control system logic structures from the reliability viewpoint. Evaluation of the reliability of control systems is essential to automated operation of equipment used in nuclear power plants. (author)
Reliability graph with general gates (RGGG). A novel method for reliability analysis
There are several methods for system reliability analysis such as reliability graphs, fault tree analyses, Markov chains, and Monte Carlo simulations. Among the existing methods, the reliability graphs are the most intuitive modeling method, but they are not widely used due to their limited expression power. In this paper, an intuitive and practical method for system reliability analysis named the reliability graph with general gates (RGGG) is reviewed. The proposed method introduces general gates to the conventional reliability graph method, which creates a one-to-one match from the actual structure of the system to the reliability graph of the system. A quantitative evaluation method is proposed by transforming the RGGG to an equivalent Bayesian network without losing the intuitiveness of the model. In addition, a method of analyzing the dynamic systems and repairable systems which uses the RGGG is introduced, and appropriate algorithms for the quantitative analyses are explained. It is concluded that the RGGG method is intuitive and easy-to-use in the analyses of static, dynamic, and repairable systems compared with other methods while its analysis results are the same as those of other methods. (author)
Reliability Analysis of Adhesive Bonded Scarf Joints
Kimiaeifar, Amin; Toft, Henrik Stensgaard; Lund, Erik;
2012-01-01
element analysis (FEA). For the reliability analysis a design equation is considered which is related to a deterministic code-based design equation where reliability is secured by partial safety factors together with characteristic values for the material properties and loads. The failure criteria are...... the FEA model, and a sensitivity analysis on the influence of various geometrical parameters and material properties on the maximum stress is conducted. Because the yield behavior of many polymeric structural adhesives is dependent on both deviatoric and hydrostatic stress components, different ratios...
A comparative study on the HW reliability assessment methods for digital I and C equipment
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
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)
RHR system reliability analysis of Krsko NPP
In this paper Systems reliability analysis is applied to residual heat Removal System in Krsko NPP. Fault tree method is used. Qualitative analysis of the fault tree was made using FTAP-2 computer code, and quantitative using IMPORT code. results are evaluated and their possible application is given. (author)
Reliability analysis on marine reactor systems
Reliability analysis was performed on the electric power supply system and residual heat removal systems of a marine reactor. Fault trees were constructed considering the functions of systems, and cumulative failure probability or unavailability was calculated by means of analytical method and/or Monte Carlo simulation. For the analysis of stand-by sub-systems, state transition method as well as Monte Carlo method were applied successfully. Sensitivity analysis was carried out to identify key components and to investigate the effect of variation of the failure rate to the system reliability. And also, the effectiveness of redundancy, maintenance and repair to the subsystem or component was investigated in detail. The results obtained here will be applicable for the decision making in design for the improvement of system reliability. (auth.)
Culture Representation in Human Reliability Analysis
David Gertman; Julie Marble; Steven Novack
2006-12-01
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.
Discrete event simulation versus conventional system reliability analysis approaches
Kozine, Igor
2010-01-01
Discrete Event Simulation (DES) environments are rapidly developing and appear to be promising tools for building reliability and risk analysis models of safety-critical systems and human operators. If properly developed, they are an alternative to the conventional human reliability analysis models...... and systems analysis methods such as fault and event trees and Bayesian networks. As one part, the paper describes briefly the author’s experience in applying DES models to the analysis of safety-critical systems in different domains. The other part of the paper is devoted to comparing conventional...
Representative Sampling for reliable data analysis
Petersen, Lars; Esbensen, Kim Harry
2005-01-01
regime in order to secure the necessary reliability of: samples (which must be representative, from the primary sampling onwards), analysis (which will not mean anything outside the miniscule analytical volume without representativity ruling all mass reductions involved, also in the laboratory) and data...
Event/Time/Availability/Reliability-Analysis Program
Viterna, L. A.; Hoffman, D. J.; Carr, Thomas
1994-01-01
ETARA is interactive, menu-driven program that performs simulations for analysis of reliability, availability, and maintainability. Written to evaluate performance of electrical power system of Space Station Freedom, but methodology and software applied to any system represented by block diagram. Program written in IBM APL.
Huggel, C.; A. Raissig; M. Rohrer; Romero, G.; Diaz, A.; Salzmann, N.
2015-01-01
Damage caused by weather- and climate-related disasters have increased over the past decades, and growing exposure and wealth have been identified as main drivers of this increase. Disaster databases are a primary tool for the analysis of disaster characteristics and trends at global or national scales, and they support disaster risk reduction and climate change adaptation. However, the quality, consistency and completeness of different disaster databases are highly variable...
Huggel, Christian; Raissig, Annik; Rohrer, Mario; Romero, Gilberto; Diaz, Alfonso; Salzmann, Nadine
2014-01-01
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 s...
Huggel, Christian; Raissig, Annik; Rohrer, Mario; Romero, Gilberto; Diaz, A; Salzmann, Nadine
2015-01-01
Damage caused by weather- and climate-related disasters have increased over the past decades, and growing exposure and wealth have been identified as main drivers of this increase. Disaster databases are a primary tool for the analysis of disaster characteristics and trends at global or national scales, and they support disaster risk reduction and climate change adaptation. However, the quality, consistency and completeness of different disaster databases are highly variable. Even though such...
Reliability Analysis of High Temperature Reactor Fuels
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)
Multiphase reliability analysis of complex systems
Azam, Mohammad S.; Tu, Fang; Pattipati, Krishna R.
2003-08-01
Modern industrial systems assume different configurations to accomplish multiple objectives during different phases of operation, and the component parameters may also vary from one phase to the next. Consequently, reliability evaluation of complex multi-phased systems is a vital and challenging issue. Maximization of mission reliability of a multi-phase system via optimal asset selection is another key demand; incorporation of optimization issues adds to the complexities of reliability evaluation processes. Introduction of components having self-diagnostics and self-recovery capabilities, along with increased complexity and phase-dependent configuration variations in network architectures, requires new approaches for reliability evaluation. This paper considers the problem of evaluating the reliability of a complex multi-phased system with self-recovery/fault-protection options. The reliability analysis is based on a colored digraph (i.e., multi-functional) model that subsumes fault trees and digraphs as special cases. These models enable system designers to decide on system architecture modifications and to determine the optimum levels of redundancy. A sum of disjoint products (SDP) approach is employed to compute system reliability. We also formulated the problem of optimal asset selection in a multi-phase system as one of maximizing the probability of mission success under random load profiles on components. Different methods (e.g., ordinal optimization, robust design, and nonparametric statistical testing) are explored to solve the problem. The resulting analytical expressions and the software tool are demonstrated on a generic programmable software-controlled switchgear, a data bus controller system and a multi-phase mission involving helicopters.
Reliability and risk analysis methods research plan
This document presents a plan for reliability and risk analysis methods research to be performed mainly by the Reactor Risk Branch (RRB), Division of Risk Analysis and Operations (DRAO), Office of Nuclear Regulatory Research. It includes those activities of other DRAO branches which are very closely related to those of the RRB. Related or interfacing programs of other divisions, offices and organizations are merely indicated. The primary use of this document is envisioned as an NRC working document, covering about a 3-year period, to foster better coordination in reliability and risk analysis methods development between the offices of Nuclear Regulatory Research and Nuclear Reactor Regulation. It will also serve as an information source for contractors and others to more clearly understand the objectives, needs, programmatic activities and interfaces together with the overall logical structure of the program
Human reliability analysis of control room operators
Santos, Isaac J.A.L.; Carvalho, Paulo Victor R.; Grecco, Claudio H.S. [Instituto de Engenharia Nuclear (IEN), Rio de Janeiro, RJ (Brazil)
2005-07-01
Human reliability is the probability that a person correctly performs some system required action in a required time period and performs no extraneous action that can degrade the system Human reliability analysis (HRA) is the analysis, prediction and evaluation of work-oriented human performance using some indices as human error likelihood and probability of task accomplishment. Significant progress has been made in the HRA field during the last years, mainly in nuclear area. Some first-generation HRA methods were developed, as THERP (Technique for human error rate prediction). Now, an array of called second-generation methods are emerging as alternatives, for instance ATHEANA (A Technique for human event analysis). The ergonomics approach has as tool the ergonomic work analysis. It focus on the study of operator's activities in physical and mental form, considering at the same time the observed characteristics of operator and the elements of the work environment as they are presented to and perceived by the operators. The aim of this paper is to propose a methodology to analyze the human reliability of the operators of industrial plant control room, using a framework that includes the approach used by ATHEANA, THERP and the work ergonomics analysis. (author)
Comparative reliability of cheiloscopy and palatoscopy in human identification
Sharma Preeti
2009-01-01
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.
Advances in human reliability analysis in Mexico
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
A comparative evaluation of five human reliability assessment techniques
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)
Sensitivity analysis in a structural reliability context
This thesis' subject is sensitivity analysis in a structural reliability context. The general framework is the study of a deterministic numerical model that allows to reproduce a complex physical phenomenon. The aim of a reliability study is to estimate the failure probability of the system from the numerical model and the uncertainties of the inputs. In this context, the quantification of the impact of the uncertainty of each input parameter on the output might be of interest. This step is called sensitivity analysis. Many scientific works deal with this topic but not in the reliability scope. This thesis' aim is to test existing sensitivity analysis methods, and to propose more efficient original methods. A bibliographical step on sensitivity analysis on one hand and on the estimation of small failure probabilities on the other hand is first proposed. This step raises the need to develop appropriate techniques. Two variables ranking methods are then explored. The first one proposes to make use of binary classifiers (random forests). The second one measures the departure, at each step of a subset method, between each input original density and the density given the subset reached. A more general and original methodology reflecting the impact of the input density modification on the failure probability is then explored. The proposed methods are then applied on the CWNR case, which motivates this thesis. (author)
Importance and difficulties of comparing reliability criteria and the assessment of reliability
Heylen, Evelyn; Van Hertem, Dirk
2014-01-01
Due to the importance of reliable electricity supply and the evolutions in the electrical grid, it can be expected that the way in which we assess reliability need to be adapted. At this moment, reliability is commonly assessed deterministically based on an N-1 criterion, while risk-based reliability assessment is widely available in academic works and is used in other industries. However, because of the years of successful use as well as the straightforward and transparent character of the c...
Reliability Analysis of Concurrent Systems using LTSA
G.N. Rodrigues; Rosenblum, D S; Wolf, J
2007-01-01
The analysis for software dependability is considered an important task within the software engineering life cycle. However, it is often impossible to carry out this task due to the complexity of available tools, lack of expert personnel and time-to-market pressures. As a result, released software versions may present unverified dependability properties subjecting customers to blind software reliability assessment. In particular, concurrent systems present certain behaviour that require a mor...
Bonfietti, Gerson
2003-07-01
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)
The quantitative failure of human reliability analysis
Bennett, C.T.
1995-07-01
This philosophical treatise argues the merits of Human Reliability Analysis (HRA) in the context of the nuclear power industry. Actually, the author attacks historic and current HRA as having failed in informing policy makers who make decisions based on risk that humans contribute to systems performance. He argues for an HRA based on Bayesian (fact-based) inferential statistics, which advocates a systems analysis process that employs cogent heuristics when using opinion, and tempers itself with a rational debate over the weight given subjective and empirical probabilities.
Sensitivity analysis in optimization and reliability problems
The paper starts giving the main results that allow a sensitivity analysis to be performed in a general optimization problem, including sensitivities of the objective function, the primal and the dual variables with respect to data. In particular, general results are given for non-linear programming, and closed formulas for linear programming problems are supplied. Next, the methods are applied to a collection of civil engineering reliability problems, which includes a bridge crane, a retaining wall and a composite breakwater. Finally, the sensitivity analysis formulas are extended to calculus of variations problems and a slope stability problem is used to illustrate the methods
System reliability analysis with natural language and expert's subjectivity
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
Reliability testing and reliability analysis of the over-load protective relay
ZHAO Jing-ying; CHEN Hong-jian; LIU Guo-jin; ZHANG Yong; WU Pin-hua
2007-01-01
The over-load protective relay is widely used for motor protection. The reliability of the over-load protective relay directly affects the safe running of a motor. The reliability testing and reliability analysis of the over-load protective relay is an important way to improve the reliability of products. In this paper, the reliability test method of the over-load protective relay is studied, and the reliability tests of the typical products are carried out on a reliability tester developed by authors. In terms of the testing results, the reliability analysis is finished. The failure reasons are found and the measures are put forward to improve the reliability of the products.
Reliability analysis of containment isolation systems
This report summarizes the results of the Reliability Analysis of Containment Isolation System Project. Work was performed in five basic areas: design review, operating experience review, related research review, generic analysis and plant specific analysis. Licensee Event Reports (LERs) and Integrated Leak Rate Test (ILRT) reports provided the major sources of containment performance information used in this study. Data extracted from LERs were assembled into a computer data base. Qualitative and quantitative information developed for containment performance under normal operating conditions and design basis accidents indicate that there is room for improvement. A rough estimate of overall containment unavailability for relatively small leaks which violate plant technical specifications is 0.3. An estimate of containment unavailability due to large leakage events is in the range of 0.001 to 0.01. These estimates are dependent on several assumptions (particularly on event duration times) which are documented in the report
Human reliability analysis under fire condition
It is identified in the fire probabilistic safety assessment (PSA) of nuclear power plants that human action has important effect on the risk of plant under fire condition. So it's necessary to assess human error probability under fire condition by the systemic methodology. The HCR/ORE and CBDTM models and specific considerations under fire condition were described in this paper. The combination of HCR/ORE, CBDTM and THERP was applied to human reliability analysis (HRA) under fire condition with an example given for demonstration. The basement of setting up the more practical fire PSA models for engineering is established. (authors)
Bayesian networks with applications in reliability analysis
Langseth, Helge
2002-01-01
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 ...
Reliability of the Emergency Severity Index: Meta-analysis
Amir Mirhaghi
2015-01-01
Full Text Available Objectives: Although triage systems based on the Emergency Severity Index (ESI have many advantages in terms of simplicity and clarity, previous research has questioned their reliability in practice. Therefore, the aim of this meta-analysis was to determine the reliability of ESI triage scales. Methods: This metaanalysis was performed in March 2014. Electronic research databases were searched and articles conforming to the Guidelines for Reporting Reliability and Agreement Studies were selected. Two researchers independently examined selected abstracts. Data were extracted in the following categories: version of scale (latest/older, participants (adult/paediatric, raters (nurse, physician or expert, method of reliability (intra/inter-rater, reliability statistics (weighted/unweighted kappa and the origin and publication year of the study. The effect size was obtained by the Z-transformation of reliability coefficients. Data were pooled with random-effects models and a meta-regression was performed based on the method of moments estimator. Results: A total of 19 studies from six countries were included in the analysis. The pooled coefficient for the ESI triage scales was substantial at 0.791 (95% confidence interval: 0.787‒0.795. Agreement was higher with the latest and adult versions of the scale and among expert raters, compared to agreement with older and paediatric versions of the scales and with other groups of raters, respectively. Conclusion: ESI triage scales showed an acceptable level of overall reliability. However, ESI scales require more development in order to see full agreement from all rater groups. Further studies concentrating on other aspects of reliability assessment are needed.
Integrated Reliability and Risk Analysis System (IRRAS)
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
Integrated Reliability and Risk Analysis System (IRRAS)
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
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.
Estimating Reliability of Power Factor Correction Circuits: A Comparative Study
P.Srinivas
2015-04-01
Full Text Available Reliability plays an important role in power supplies, as every power supply is the very heart of every electronics equipment. For other electronic equipment, a certain failure mode, at least for a part of the total system, can often be tolerated without serious (critical after effects. However, for the power supply no such condition can be accepted, since very high demands on the reliability must be achieved. At higher power levels, the CCM boost converter is preferred topology for implementation a front end with PFC. As a result significant efforts have been made to improve the performance of high boost converter. This paper is one the effort for improving the performance of the converter from the reliability point of view. In this paper a boost power factor correction converter is simulated with single switch and interleaving technique in CCM, DCM and CRM modes under different output power ratings and the reliability. Results of the converter are explored from reliability point of view.
Reliability Analysis Techniques for Communication Networks in Nuclear Power Plant
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
Structural reliability analysis based on the cokriging technique
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.
Reliability Analysis of a Green Roof Under Different Storm Scenarios
William, R. K.; Stillwell, A. S.
2015-12-01
Urban environments continue to face the challenges of localized flooding and decreased water quality brought on by the increasing amount of impervious area in the built environment. Green infrastructure provides an alternative to conventional storm sewer design by using natural processes to filter and store stormwater at its source. However, there are currently few consistent standards available in North America to ensure that installed green infrastructure is performing as expected. This analysis offers a method for characterizing green roof failure using a visual aid commonly used in earthquake engineering: fragility curves. We adapted the concept of the fragility curve based on the efficiency in runoff reduction provided by a green roof compared to a conventional roof under different storm scenarios. We then used the 2D distributed surface water-groundwater coupled model MIKE SHE to model the impact that a real green roof might have on runoff in different storm events. We then employed a multiple regression analysis to generate an algebraic demand model that was input into the Matlab-based reliability analysis model FERUM, which was then used to calculate the probability of failure. The use of reliability analysis as a part of green infrastructure design code can provide insights into green roof weaknesses and areas for improvement. It also supports the design of code that is more resilient than current standards and is easily testable for failure. Finally, the understanding of reliability of a single green roof module under different scenarios can support holistic testing of system reliability.
HUMAN RELIABILITY ANALYSIS FOR COMPUTERIZED PROCEDURES
Ronald L. Boring; David I. Gertman; Katya Le Blanc
2011-09-01
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.
Improved reliability analysis method based on the failure assessment diagram
Zhou, Yu; Zhang, Zheng; Zhong, Qunpeng
2012-07-01
With the uncertainties related to operating conditions, in-service non-destructive testing (NDT) measurements and material properties considered in the structural integrity assessment, probabilistic analysis based on the failure assessment diagram (FAD) approach has recently become an important concern. However, the point density revealing the probabilistic distribution characteristics of the assessment points is usually ignored. To obtain more detailed and direct knowledge from the reliability analysis, an improved probabilistic fracture mechanics (PFM) assessment method is proposed. By integrating 2D kernel density estimation (KDE) technology into the traditional probabilistic assessment, the probabilistic density of the randomly distributed assessment points is visualized in the assessment diagram. Moreover, a modified interval sensitivity analysis is implemented and compared with probabilistic sensitivity analysis. The improved reliability analysis method is applied to the assessment of a high pressure pipe containing an axial internal semi-elliptical surface crack. The results indicate that these two methods can give consistent sensitivities of input parameters, but the interval sensitivity analysis is computationally more efficient. Meanwhile, the point density distribution and its contour are plotted in the FAD, thereby better revealing the characteristics of PFM assessment. This study provides a powerful tool for the reliability analysis of critical structures.
Human Reliability Analysis for Small Modular Reactors
Ronald L. Boring; David I. Gertman
2012-06-01
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.
Reliability of Bolton analysis evaluation in tridimensional virtual models
Marianna Mendonca Brandão; Marcio Costal Sobral; Carlos Jorge Vogel
2015-01-01
Objective: The present study aimed at evaluating the reliability of Bolton analysis in tridimensional virtual models, comparing it with the manual method carried out with dental casts. Methods: The present investigation was performed using 56 pairs of dental casts produced from the dental arches of patients in perfect conditions and randomly selected from Universidade Federal da Bahia, School of Dentistry, Orthodontics Postgraduate Program. Manual measurements were obtained with the aid of a ...
Task Decomposition in Human Reliability Analysis
Boring, Ronald Laurids [Idaho National Laboratory; Joe, Jeffrey Clark [Idaho National Laboratory
2014-06-01
In the probabilistic safety assessments (PSAs) used in the nuclear industry, human failure events (HFEs) are determined as a subset of hardware failures, namely those hardware failures that could be triggered by human action or inaction. This approach is top-down, starting with hardware faults and deducing human contributions to those faults. Elsewhere, more traditionally human factors driven approaches would tend to look at opportunities for human errors first in a task analysis and then identify which of those errors is risk significant. The intersection of top-down and bottom-up approaches to defining HFEs has not been carefully studied. Ideally, both approaches should arrive at the same set of HFEs. This question remains central as human reliability analysis (HRA) methods are generalized to new domains like oil and gas. The HFEs used in nuclear PSAs tend to be top-down— defined as a subset of the PSA—whereas the HFEs used in petroleum quantitative risk assessments (QRAs) are more likely to be bottom-up—derived from a task analysis conducted by human factors experts. The marriage of these approaches is necessary in order to ensure that HRA methods developed for top-down HFEs are also sufficient for bottom-up applications.
Methods for Comprehensive Analysis of Heat Supply Reliability
V. A. Stennikov; I. V. Postnikov
2013-01-01
The paper deals with the problem of comprehensive analysis of heat supply reliability for consumers. It implies a quantitative assessment of the impact of all stages of heat energy production and distribution on heat supply reliability for each consumer of the heat supply system. A short review of existing methods for the analysis of fuel and heat supply reliability is presented that substantiates the key approaches to solving the problem of comprehensive analysis of heat supply reliability. ...
Comparative reliability of cheiloscopy and palatoscopy in human identification
Sharma Preeti; Saxena Susmita; Rathod Vanita
2009-01-01
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 import...
Reliability analysis of digital reactor protection system
The reliability analysis of the digital reactor protection system (RPS) is an essential part in the probabilistic safety assessment (PSA) of the advanced boiling water reactor (ABWR). In this study, the reliability model and methodology were modified to evaluate the reliability of the digital RPS installed in the Japanese ABWR plant. The hardware failure rates in the foreign data source of digital components were applied, based on the similarity of the function of the digital components. The hardware failure rates of the digital components were estimated to range from 10-5 (/hr) to 10-7 (/hr), according to the types of the components. The software error events and their recovery factors in the design and fabrication stages were evaluated, considering the verification and validation process provided by the Japanese industry guideline. Then, the software failure probability of the programmable digital component was evaluated, utilizing the probability of software error events and their recovery factors. This probability was estimated to be 3.3 10-7 (/demand), which was about one order higher than that of our previous estimation. These models and results were applied to evaluate the reactor trip system (RTS) and the engineered safety feature (ESF) actuation system of the ABWR plant, both of which are the subsystems of the RPS. The unavailability of the digital RTS was estimated to be the mean value of 7.2 10-6 (/demand). If an alternate rod insertion (ARI) and a manual scram were considered, the unavailability was estimated to decrease to 1.6 10-9. The ECCS unavailability was estimated to be also nearly equal to the same values as the previous estimation, because the system unavailability was dominated by the unavailability of the mechanical components, such as pumps, valves, etc. The sensitivity analyses were conducted systematically, in order to evaluate the effect of the modeling uncertainty on the RTS unavailability. The results indicated that the unavailability
Modeling human reliability analysis using MIDAS
Boring, R. L. [Human Factors, Instrumentation and Control Systems Dept., Idaho National Laboratory, Idaho Falls, ID 83415 (United States)
2006-07-01
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)
Modeling human reliability analysis using MIDAS
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)
Reliability analysis of an associated system
陈长杰; 魏一鸣; 蔡嗣经
2002-01-01
Based on engineering reliability of large complex system and distinct characteristic of soft system, some new conception and theory on the medium elements and the associated system are created. At the same time, the reliability logic model of associated system is provided. In this paper, through the field investigation of the trial operation, the engineering reliability of the paste fill system in No.2 mine of Jinchuan Non-ferrous Metallic Corporation is analyzed by using the theory of associated system.
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
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)
Fatigue Reliability Analysis of Turbine Disk Alloy Using Saddlepoint Approximation
Gan, Luping; Huang, Hong-Zhong; Zhu, Shun-Peng; Li, Yan-Feng; Yang, Yuanjian
2013-09-01
In this paper, a new fatigue reliability analysis method based on saddlepoint approximation (SPA) was proposed for calculating the probability of failure of turbine disk alloy in a low cycle fatigue (LCF) regime. Firstly, two LCF life prediction models based on total strain energy density and Support Vector Regression (SVR) metamodel are presented for turbine disk alloy GH4133 under different loading conditions at 250 °C. Compared with the SWT model, modified Walker model and Response Surface (RS) model, the predicted lives by the proposed models are within a factor of ±2 and a factor of ±1.1 respectively. Secondly, based on the fatigue design criteria, the probabilities of failure are calculated using SPA for the explicit and implicit performance functions using two proposed LCF models and viscosity-based model. These three models have provided the reliability design rules for GH4133. Finally, the failure probabilities curves between SPA and the designed fatigue lives are achieved. The reliability analysis results were found to be in good agreement with the calculated results of test data. These results show that SPA is very apt for the fatigue reliability analysis of turbine disk under different loading conditions using only a small number of samples without any distribution assumptions for random variables. Moreover, it can be used to estimate the system's probability of failure with a large number of random variables or high nonlinearity of performance functions. The effectiveness and accuracy of the combination of the fatigue models and SPA for fatigue reliability analysis are verified using three examples.
On some comparisons of lifetimes for reliability analysis
Ordering of non-negative random variables (lifetimes) has been intensively studied in the literature. When comparing lifetimes in different applications such as reliability and risk analysis, it is often of interest to analyze also the distances between these lifetimes. In this paper, we define and discuss the stress–strength ordering and distance on the basis of the well-known stress–strength model that describes, e.g., the probability that the strength of a structure is larger than the external stress. We also compare this probability with the distance based on the difference between the means of random variables of interest and discuss several examples. The results can be useful, e.g., for analyzing reliability and safety requirements at the design stage for various engineering objects
STARS software tool for analysis of reliability and safety
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
Reliability test and failure analysis of high power LED packages*
Chen Zhaohui; Zhang Qin; Wang Kai; Luo Xiaobing; Liu Sheng
2011-01-01
A new type application specific light emitting diode (LED) package (ASLP) with freeform polycarbonate lens for street lighting is developed, whose manufacturing processes are compatible with a typical LED packaging process. The reliability test methods and failure criterions from different vendors are reviewed and compared. It is found that test methods and failure criterions are quite different. The rapid reliability assessment standards are urgently needed for the LED industry. 85 ℃/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h, showing no visible degradation in optical performance for our modules, with two other vendors showing significant degradation. Some failure analysis methods such as C-SAM, Nano X-ray CT and optical microscope are used for LED packages. Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing. The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging. One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing.
Reliability test and failure analysis of high power LED packages
Zhaohui, Chen; Qin, Zhang; Kai, Wang; Xiaobing, Luo; Sheng, Liu
2011-01-01
A new type application specific light emitting diode (LED) package (ASLP) with freeform polycarbonate lens for street lighting is developed, whose manufacturing processes are compatible with a typical LED packaging process. The reliability test methods and failure criterions from different vendors are reviewed and compared. It is found that test methods and failure criterions are quite different. The rapid reliability assessment standards are urgently needed for the LED industry. 85 °C/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h, showing no visible degradation in optical performance for our modules, with two other vendors showing significant degradation. Some failure analysis methods such as C-SAM, Nano X-ray CT and optical microscope are used for LED packages. Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing. The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging. One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing.
Reliability analysis applied to structural tests
Diamond, P.; Payne, A. O.
1972-01-01
The application of reliability theory to predict, from structural fatigue test data, the risk of failure of a structure under service conditions because its load-carrying capability is progressively reduced by the extension of a fatigue crack, is considered. The procedure is applicable to both safe-life and fail-safe structures and, for a prescribed safety level, it will enable an inspection procedure to be planned or, if inspection is not feasible, it will evaluate the life to replacement. The theory has been further developed to cope with the case of structures with initial cracks, such as can occur in modern high-strength materials which are susceptible to the formation of small flaws during the production process. The method has been applied to a structure of high-strength steel and the results are compared with those obtained by the current life estimation procedures. This has shown that the conventional methods can be unconservative in certain cases, depending on the characteristics of the structure and the design operating conditions. The suitability of the probabilistic approach to the interpretation of the results from full-scale fatigue testing of aircraft structures is discussed and the assumptions involved are examined.
PC-PRAISE, BWR Piping Reliability Analysis
1 - Description of program or function: PC-PRAISE is a probabilistic fracture mechanics computer code developed for IBM or IBM compatible personal computers to estimate probabilities of leak and break in nuclear power plant cooling piping. 2 - Method of solution: PC-PRAISE considers the initiation and/or growth of crack-like defects in piping weldments. The initiation analyses are based on the results of laboratory studies and field observations in austenitic piping material operating under boiling water reactor conditions. The considerable scatter in such results is quantified and incorporated into a probabilistic model. The crack growth analysis is based on (deterministic) fracture mechanics principles, in which some of the inputs (such as initial crack size) are considered to be random variables. Monte Carlo simulation, with stratified sampling on initial crack size, is used to generate weldment reliability results. 3 - Restrictions on the complexity of the problem: There is essentially no limitation with PC-PRAISE but for large number of replications used in the Monte Carlo simulation scheme, computation time may become prohibitive
Individual Differences in Human Reliability Analysis
Jeffrey C. Joe; Ronald L. Boring
2014-06-01
While human reliability analysis (HRA) methods include uncertainty in quantification, the nominal model of human error in HRA typically assumes that operator performance does not vary significantly when they are given the same initiating event, indicators, procedures, and training, and that any differences in operator performance are simply aleatory (i.e., random). While this assumption generally holds true when performing routine actions, variability in operator response has been observed in multiple studies, especially in complex situations that go beyond training and procedures. As such, complexity can lead to differences in operator performance (e.g., operator understanding and decision-making). Furthermore, psychological research has shown that there are a number of known antecedents (i.e., attributable causes) that consistently contribute to observable and systematically measurable (i.e., not random) differences in behavior. This paper reviews examples of individual differences taken from operational experience and the psychological literature. The impact of these differences in human behavior and their implications for HRA are then discussed. We propose that individual differences should not be treated as aleatory, but rather as epistemic. Ultimately, by understanding the sources of individual differences, it is possible to remove some epistemic uncertainty from analyses.
RELIABILITY ANALYSIS OF CRANE BRAKE PARAMETERS
无
2002-01-01
The high failure rate of crane brake results from improper choice of braking torque. The mathematical model of reliability for the crane brake parameters is introduced. Based on large amount of actual data the parameter reliabilities of 5~50 t general overhead travelling cranes are calculated,the probabilities that the braking torque is less than the static torque acting on the axle when the load moves down are obtained. Moreover,the ways to improve the reliability of brake parameters are discussed,the most reasonable values of braking safety coefficient are given.
Reliability analysis of the combined district heating systems
Sharapov, V. I.; Orlov, M. E.; Kunin, M. V.
2015-12-01
Technologies that improve the reliability and efficiency of the combined district heating systems in urban areas are considered. The calculation method of reliability of the CHP combined district heating systems is proposed. The comparative estimation of the reliability of traditional and combined district heating systems is performed.
Analysis on Some of Software Reliability Models
无
2001-01-01
Software reliability & maintainability evaluation tool (SRMET 3.0) is introducted in detail in this paper,which was developed by Software Evaluation and Test Center of China Aerospace Mechanical Corporation. SRMET 3.0is supported by seven soft ware reliability models and four software maintainability models. Numerical characteristicsfor all those models are deeply studied in this paper, and corresponding numerical algorithms for each model are alsogiven in the paper.
Reliability in perceptual analysis of voice quality.
Bele, Irene Velsvik
2005-12-01
This study focuses on speaking voice quality in male teachers (n = 35) and male actors (n = 36), who represent untrained and trained voice users, because we wanted to investigate normal and supranormal voices. In this study, both substantial and methodologic aspects were considered. It includes a method for perceptual voice evaluation, and a basic issue was rater reliability. A listening group of 10 listeners, 7 experienced speech-language therapists, and 3 speech-language therapist students evaluated the voices by 15 vocal characteristics using VA scales. Two sets of voice signals were investigated: text reading (2 loudness levels) and sustained vowel (3 levels). The results indicated a high interrater reliability for most perceptual characteristics. Connected speech was evaluated more reliably, especially at the normal level, but both types of voice signals were evaluated reliably, although the reliability for connected speech was somewhat higher than for vowels. Experienced listeners tended to be more consistent in their ratings than did the student raters. Some vocal characteristics achieved acceptable reliability even with a smaller panel of listeners. The perceptual characteristics grouped in 4 factors reflected perceptual dimensions. PMID:16301102
System reliability analysis for kinematic performance of planar mechanisms
ZHANG YiMin; HUANG XianZhen; ZHANG XuFang; HE XiangDong; WEN BangChun
2009-01-01
Based on the reliability and mechanism kinematic accuracy theories, we propose a general methodology for system reliability analysis of kinematic performance of planar mechanisms. The loop closure equations are used to estimate the kinematic performance errors of planar mechanisms. Reliability and system reliability theories are introduced to develop the limit state functions (LSF) for failure of kinematic performance qualities. The statistical fourth moment method and the Edgeworth series technique are used on system reliability analysis for kinematic performance of planar mechanisms, which relax the restrictions of probability distribution of design variables. Finally, the practicality, efficiency and accuracy of the proposed method are demonstrated by numerical examples.
Reliability analysis of pipe whip impacts
A probabilistic analysis of a group distribution header (GDH) guillotine break and the damage resulting from the failed GDH impacting against a neighbouring wall was carried out for the Ignalita RBMK-1500 reactor. The NEPTUNE software system was used for the deterministic transient analysis of a GDH guillotine break. Many deterministic analyses were performed using different values of the random variables that were specified by ProFES software. All the deterministic results were transferred to the ProFES system, which then performed probabilistic analyses of piping failure and wall damage. The Monte Carlo Simulation (MCS) method was used to study the sensitivity of the response variables and the effect of uncertainties of material properties and geometry parameters to the probability of limit states. The First Order Reliability Method (FORM) was used to study the probability of failure of the impacted-wall and the support-wall. The Response Surface (RS/MCS) method was used in order to express failure probability as function and to investigate the dependence between impact load and failure probability. The results of the probability analyses for a whipping GDH impacting onto an adjacent wall show that: (i) there is a 0.982 probability that after a GDH guillotine break contact between GDH and wall will occur; (ii) there is a probability of 0.013 that the ultimate tensile strength of concrete at the impact location will be reached, and a through-crack may open; (iii) there is a probability of 0.0126 that the ultimate compressive strength of concrete at the GDH support location will be reached, and the concrete may fail; (iv) at the impact location in the adjacent wall, there is a probability of 0.327 that the ultimate tensile strength of the rebars in the first layer will be reached and the rebars will fail; (v) at the GDH support location, there is a probability of 0.11 that the ultimate stress of the rebars in the first layer will be reached and the rebars will fail
Issues in benchmarking human reliability analysis methods : a literature review.
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
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.
Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon
Garion, Cédric
2014-01-01
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...
Issues in benchmarking human reliability analysis methods: A literature review
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.
Human Reliability Analysis for Design: Using Reliability Methods for Human Factors Issues
Ronald Laurids Boring
2010-11-01
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.
Human Reliability Analysis for Design: Using Reliability Methods for Human Factors Issues
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.
Reliability and availability analysis for robot subsystem in automotive assembly plant: a case study
Fudzin, A. F.; Majid, M. A. A.
2015-12-01
The automotive assembly plant in a manufacturing environment consists of conveying systems and robots. Robots with high reliability will ensure no interruption during production. This study is to analyze the individual robot reliability compared to reliability of robots subsystem in series configuration. Availability was computed based on individual robots breakdown data. Failures due to robots breakdown often occurred during the operations. Actual maintenance data for a period of seven years were used for the analysis. Incorporation of failures rate and mean time between failures yield the reliability computation with the assumption of constant failure rate. Result from the analysis based on 5000 operating hours indicated reliability of series configuration of robots in a subsystem decreased to 2.8% in comparison to 38% reliability of the individual robot with the lowest reliability. The calculated lowest availability of the robots is 99.41%. The robot with the lowest reliability and availability should be considered for replacement.
Probabilistic safety analysis and human reliability analysis. Proceedings. Working material
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
Wei, Wei; Larrey-Lassalle, Pyrène; Faure, Thierry; Dumoulin, Nicolas; Roux, Philippe; Mathias, Jean-Denis
2016-03-01
Comparative decision making process is widely used to identify which option (system, product, service, etc.) has smaller environmental footprints and for providing recommendations that help stakeholders take future decisions. However, the uncertainty problem complicates the comparison and the decision making. Probability-based decision support in LCA is a way to help stakeholders in their decision-making process. It calculates the decision confidence probability which expresses the probability of a option to have a smaller environmental impact than the one of another option. Here we apply the reliability theory to approximate the decision confidence probability. We compare the traditional Monte Carlo method with a reliability method called FORM method. The Monte Carlo method needs high computational time to calculate the decision confidence probability. The FORM method enables us to approximate the decision confidence probability with fewer simulations than the Monte Carlo method by approximating the response surface. Moreover, the FORM method calculates the associated importance factors that correspond to a sensitivity analysis in relation to the probability. The importance factors allow stakeholders to determine which factors influence their decision. Our results clearly show that the reliability method provides additional useful information to stakeholders as well as it reduces the computational time. PMID:26815724
Fault Diagnosis and Reliability Analysis Using Fuzzy Logic Method
Miao Zhinong; Xu Yang; Zhao Xiangyu
2006-01-01
A new fuzzy logic fault diagnosis method is proposed. In this method, fuzzy equations are employed to estimate the component state of a system based on the measured system performance and the relationship between component state and system performance which is called as "performance-parameter" knowledge base and constructed by expert. Compared with the traditional fault diagnosis method, this fuzzy logic method can use humans intuitive knowledge and dose not need a precise mapping between system performance and component state. Simulation proves its effectiveness in fault diagnosis. Then, the reliability analysis is performed based on the fuzzy logic method.
Analysis on testing and operational reliability of software
ZHAO Jing; LIU Hong-wei; CUI Gang; WANG Hui-qiang
2008-01-01
Software reliability was estimated based on NHPP software reliability growth models. Testing reliability and operational reliability may be essentially different. On the basis of analyzing similarities and differences of the testing phase and the operational phase, using the concept of operational reliability and the testing reliability, different forms of the comparison between the operational failure ratio and the predicted testing failure ratio were conducted, and the mathematical discussion and analysis were performed in detail. Finally, software optimal release was studied using software failure data. The results show that two kinds of conclusions can be derived by applying this method, one conclusion is to continue testing to meet the required reliability level of users, and the other is that testing stops when the required operational reliability is met, thus the testing cost can be reduced.
Reliability Analysis of an Offshore Structure
Sørensen, John Dalsgaard; Thoft-Christensen, Palle; Rackwitz, R.; Bryla, P.
A jacket type offshore structure from the North Sea is considered. The time variant reliability is estimated for failure defined as brittie fradure and crack through the tubular roerober walls. The stochastic modeiling is described. The hot spot stress speetral moments as fundion of the stochastic...
A methodology to incorporate organizational factors into human reliability analysis
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)
Reliability analysis of rc containment structures under combined loads
This paper discusses a reliability analysis method and load combination design criteria for reinforced concrete containment structures under combined loads. The probability based reliability analysis method is briefly described. For load combination design criteria, derivations of the load factors for accidental pressure due to a design basis accident and safe shutdown earthquake (SSE) for three target limit state probabilities are presented
Reliability Analysis of Existing Vertical Wall Breakwaters
Burcharth, H. F.; Sørensen, John Dalsgaard
1998-01-01
Vertical wall breakwaters are used under quite different conditions where failure of the breakwater or a part of it will have very different consequences. Further a number of existing vertical wall breakwaters have been subjected to significant wave loads which have caused partial failures of the...... structures. The main objective of this paper is to describe how the reliability of existing breakwater structures within the expected remaining lifetime can be estimated taking into account the available information....
Network reliability analysis based on percolation theory
In this paper, we propose a new way of looking at the reliability of a network using percolation theory. In this new view, a network failure can be regarded as a percolation process and the critical threshold of percolation can be used as network failure criterion linked to the operational settings under control. To demonstrate our approach, we consider both random network models and real networks with different nodes and/or edges lifetime distributions. We study numerically and theoretically the network reliability and find that the network reliability can be solved as a voting system with threshold given by percolation theory. Then we find that the average lifetime of random network increases linearly with the average lifetime of its nodes with uniform life distributions. Furthermore, the average lifetime of the network becomes saturated when system size is increased. Finally, we demonstrate our method on the transmission network system of IEEE 14 bus. - Highlights: • Based on percolation theory, we address questions of practical interest such as “how many failed nodes/edges will break down the whole network?” • The percolation threshold naturally gives a network failure criterion. • The approach based on percolation theory is suited for calculations of large-scale networks
POSSIBILITY AND EVIDENCE-BASED RELIABILITY ANALYSIS AND DESIGN OPTIMIZATION
Hong-Zhong Huang
2013-01-01
Full Text Available Engineering design under uncertainty has gained considerable attention in recent years. A great multitude of new design optimization methodologies and reliability analysis approaches are put forth with the aim of accommodating various uncertainties. Uncertainties in practical engineering applications are commonly classified into two categories, i.e., aleatory uncertainty and epistemic uncertainty. Aleatory uncertainty arises because of unpredictable variation in the performance and processes of systems, it is irreducible even adding more data or knowledge. On the other hand, epistemic uncertainty stems from lack of knowledge of the system due to limited data, measurement limitations, or simplified approximations in modeling system behavior and it can be reduced by obtaining more data or knowledge. More specifically, aleatory uncertainty is naturally represented by a statistical distribution and its associated parameters can be characterized by sufficient data. If, however, the data is limited and can be quantified in a statistical sense, epistemic uncertainty can be considered as an alternative tool in such a situation. Of the several optional treatments for epistemic uncertainty, possibility theory and evidence theory have proved to be the most computationally efficient and stable for reliability analysis and engineering design optimization. This study first attempts to provide a better understanding of uncertainty in engineering design by giving a comprehensive overview of its classifications, theories and design considerations. Then a review is conducted of general topics such as the foundations and applications of possibility theory and evidence theory. This overview includes the most recent results from theoretical research, computational developments and performance improvement of possibility theory and evidence theory with an emphasis on revealing the capability and characteristics of quantifying uncertainty from different perspectives
Reliability analysis of PLC safety equipment
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
Reliability analysis of reactor systems by applying probability method
Probability method was chosen for analysing the reactor system reliability is considered realistic since it is based on verified experimental data. In fact this is a statistical method. The probability method developed takes into account the probability distribution of permitted levels of relevant parameters and their particular influence on the reliability of the system as a whole. The proposed method is rather general, and was used for problem of thermal safety analysis of reactor system. This analysis enables to analyze basic properties of the system under different operation conditions, expressed in form of probability they show the reliability of the system on the whole as well as reliability of each component
Reliability Analysis of an Offshore Structure
Sørensen, John Dalsgaard; Rackwitz, R.; Thoft-Christensen, Palle; Lebas, G.
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...
Digital Processor Module Reliability Analysis of Nuclear Power Plant
The system used in plant, military equipment, satellite, etc. consists of many electronic parts as control module, which requires relatively high reliability than other commercial electronic products. Specially, Nuclear power plant related to the radiation safety requires high safety and reliability, so most parts apply to Military-Standard level. Reliability prediction method provides the rational basis of system designs and also provides the safety significance of system operations. Thus various reliability prediction tools have been developed in recent decades, among of them, the MI-HDBK-217 method has been widely used as a powerful tool for the prediction. In this work, It is explained that reliability analysis work for Digital Processor Module (DPM, control module of SMART) is performed by Parts Stress Method based on MIL-HDBK-217F NOTICE2. We are using the Relex 7.6 of Relex software corporation, because reliability analysis process requires enormous part libraries and data for failure rate calculation
Statistical analysis on reliability and serviceability of caterpillar tractor
WANG Jinwu; LIU Jiafu; XU Zhongxiang
2007-01-01
For further understanding reliability and serviceability of tractor and to furnish scientific and technical theories, based on the promotion and application of it, the following experiments and statistical analysis on reliability (reliability and MTBF) serviceability (service and MTTR) of Donfanghong-1002 and Dongfanghong-802 were conducted. The result showed that the intervals of average troubles of these two tractors were 182.62 h and 160.2 h, respectively, and the weakest assembly of them was engine part.
Reliability-Analysis of Offshore Structures using Directional Loads
Sørensen, John Dalsgaard; Bloch, Allan; Sterndorff, M. J.
2000-01-01
Reliability analyses of offshore structures such as steel jacket platforms are usually performed using stochastic models for the wave loads based on the omnidirectional wave height. However, reliability analyses with respect to structural failure modes such as total collapse of a structure...... heights from the central part of the North Sea. It is described how the stochastic model for the directional wave heights can be used in a reliability analysis where total collapse of offshore steel jacket platforms is considered....
Reliability Analysis Of Thin-Walled Cylindrical Shells
Kala Zdeněk
2015-01-01
The subject of the article is the verification of the reliability of thin-walled rotationally symmetric cylindrical shells, using probabilistic approaches. Internal forces and stress of the shell are analysed assuming a membrane action. Material and geometric characteristics of the steel shell are considered as random variables. The reliability index is evaluated using the Latin Hypercube Sampling method. The results of the reliability analysis are derived in a general form, so that they may ...
Design and Analysis for Reliability of Wireless Sensor Network
Yongxian Song
2012-12-01
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.
ETARA - EVENT TIME AVAILABILITY, RELIABILITY ANALYSIS
Viterna, L. A.
1994-01-01
The ETARA system was written to evaluate the performance of the Space Station Freedom Electrical Power System, but the methodology and software can be modified to simulate any system that can be represented by a block diagram. ETARA is an interactive, menu-driven reliability, availability, and maintainability (RAM) simulation program. Given a Reliability Block Diagram representation of a system, the program simulates the behavior of the system over a specified period of time using Monte Carlo methods to generate block failure and repair times as a function of exponential and/or Weibull distributions. ETARA can calculate availability parameters such as equivalent availability, state availability (percentage of time at a particular output state capability), continuous state duration and number of state occurrences. The program can simulate initial spares allotment and spares replenishment for a resupply cycle. The number of block failures are tabulated both individually and by block type. ETARA also records total downtime, repair time, and time waiting for spares. Maintenance man-hours per year and system reliability, with or without repair, at or above a particular output capability can also be calculated. The key to using ETARA is the development of a reliability or availability block diagram. The block diagram is a logical graphical illustration depicting the block configuration necessary for a function to be successfully accomplished. Each block can represent a component, a subsystem, or a system. The function attributed to each block is considered for modeling purposes to be either available or unavailable; there are no degraded modes of block performance. A block does not have to represent physically connected hardware in the actual system to be connected in the block diagram. The block needs only to have a role in contributing to an available system function. ETARA can model the RAM characteristics of systems represented by multilayered, nesting block diagrams
Structural reliability analysis applied to pipeline risk analysis
Gardiner, M. [GL Industrial Services, Loughborough (United Kingdom); Mendes, Renato F.; Donato, Guilherme V.P. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)
2009-07-01
Quantitative Risk Assessment (QRA) of pipelines requires two main components to be provided. These are models of the consequences that follow from some loss of containment incident, and models for the likelihood of such incidents occurring. This paper describes how PETROBRAS have used Structural Reliability Analysis for the second of these, to provide pipeline- and location-specific predictions of failure frequency for a number of pipeline assets. This paper presents an approach to estimating failure rates for liquid and gas pipelines, using Structural Reliability Analysis (SRA) to analyze the credible basic mechanisms of failure such as corrosion and mechanical damage. SRA is a probabilistic limit state method: for a given failure mechanism it quantifies the uncertainty in parameters to mathematical models of the load-resistance state of a structure and then evaluates the probability of load exceeding resistance. SRA can be used to benefit the pipeline risk management process by optimizing in-line inspection schedules, and as part of the design process for new construction in pipeline rights of way that already contain multiple lines. A case study is presented to show how the SRA approach has recently been used on PETROBRAS pipelines and the benefits obtained from it. (author)
Reliability and safety analysis of redundant vehicle management computer system
Shi Jian; Meng Yixuan; Wang Shaoping; Bian Mengmeng; Yan Dungong
2013-01-01
Redundant techniques are widely adopted in vehicle management computer (VMC) to ensure that VMC has high reliability and safety. At the same time, it makes VMC have special char-acteristics, e.g., failure correlation, event simultaneity, and failure self-recovery. Accordingly, the reliability and safety analysis to redundant VMC system (RVMCS) becomes more difficult. Aimed at the difficulties in RVMCS reliability modeling, this paper adopts generalized stochastic Petri nets to establish the reliability and safety models of RVMCS. Then this paper analyzes RVMCS oper-ating states and potential threats to flight control system. It is verified by simulation that the reli-ability of VMC is not the product of hardware reliability and software reliability, and the interactions between hardware and software faults can reduce the real reliability of VMC obviously. Furthermore, the failure undetected states and false alarming states inevitably exist in RVMCS due to the influences of limited fault monitoring coverage and false alarming probability of fault mon-itoring devices (FMD). RVMCS operating in some failure undetected states will produce fatal threats to the safety of flight control system. RVMCS operating in some false alarming states will reduce utility of RVMCS obviously. The results abstracted in this paper can guide reliable VMC and efficient FMD designs. The methods adopted in this paper can also be used to analyze other intelligent systems’ reliability.
Mass Flow Meter Analysis for Reliable Measuring
Kupanovac, Tihomir; Špoljarić, Željko; Valter, Zdravko
2012-01-01
The aim of this paper is to show how to analyze and correctly chose measuring device specially applied on mass flow meter based on Coriolis principle. In the beginning short description of Coriolis based mass flow meter is given. Furthermore, comparison analysis of two flow meters shows where are the problems of wrongly applied method in slurry fluid measurement in production of powder detergents plant. Analysis is made using RS Logix 500 program. In given diagrams which show causes of wrong ...
Simulation Approach to Mission Risk and Reliability Analysis Project
National Aeronautics and Space Administration — It is proposed to develop and demonstrate an integrated total-system risk and reliability analysis approach that is based on dynamic, probabilistic simulation. This...
Reliability analysis of digital I and C systems at KAERI
This paper provides an overview of the ongoing research activities on a reliability analysis of digital instrumentation and control (I and C) systems of nuclear power plants (NPPs) performed by the Korea Atomic Energy Research Institute (KAERI). The research activities include the development of a new safety-critical software reliability analysis method by integrating the advantages of existing software reliability analysis methods, a fault coverage estimation method based on fault injection experiments, and a new human reliability analysis method for computer-based main control rooms (MCRs) based on human performance data from the APR-1400 full-scope simulator. The research results are expected to be used to address various issues such as the licensing issues related to digital I and C probabilistic safety assessment (PSA) for advanced digital-based NPPs. (author)
An intelligent method for contact fatigue reliability analysis of spur gear under EHL
胡贇; 刘少军; 常继华; 张建阁
2015-01-01
To complete the contact fatigue reliability analysis of spur gear under elastohydrodynamic lubrication (EHL) efficiently and accurately, an intelligent method is proposed. Oil film pressure is approximated using quadratic polynomial with intercrossing term and then mapped into the Hertz contact zone. Considering the randomness of the EHL, material properties and fatigue strength correction factors, the probabilistic reliability analysis model is established using artificial neural network (ANN). Genetic algorithm (GA) is employed to search the minimum reliability index and the design point by introducing an adjusting factor in penalty function. Reliability sensitivity analysis is completed based on the advanced first order second moment (AFOSM). Numerical example shows that the established probabilistic reliability analysis model could correctly reflect the effect of EHL on contact fatigue of spur gear, and the proposed intelligent method has an excellent global search capability as well as a highly efficient computing performance compared with the traditional Monte Carlo method (MCM).
The Reliability of Content Analysis of Computer Conference Communication
Rattleff, Pernille
2007-01-01
The focus of this article is the reliability of content analysis of students' computer conference communication. Content analysis is often used when researching the relationship between learning and the use of information and communications technology in educational settings. A number of studies where content analysis is used and classification…
Fieldbuses targeted to highly dependable distributed embedded systems are shifting from bus to star topologies. Surprisingly, despite the efforts into this direction, engineers lack of analyses that quantitatively characterize the system reliability achievable by buses and stars. Thus, to guide engineers in developing adequate bus and star fieldbuses, this work models, quantifies and compares the system reliability provided by simplex buses and stars for the case of the Controller Area Network (CAN). It clarifies how relevant dependability-related aspects affect reliability, refuting some intuitive ideas, and revealing some previously unknown bus and star benefits. - Highlights: • SANs models that quantify the reliability of simplex buses/stars in fieldbuses. • Models cover system relevant dependability-related features abstracted in the literature. • Results refute intuitive ideas about buses and stars and show some unexpected effects. • Models and results can guide the design of reliable simplex bus/stars fieldbuses
Reliability analysis of nonlinear MDOF dynamic systems
This paper presents a simplified procedure to estimate the probability of failure for nonlinear MDOF shear-type systems optimally designed due to the seismic excitation. The excitation is idealized as a nonstationary stochastic process. With the aid of the response modification factor-ductility factor relationship established by the authors for these systems, 'an equivalent linear criteria' of such systems is introduced. Then, a linear response and the equivalent criteria can be used to evaluate the limit state probability as a solution to the classical first excursion probability problem at least in approximation. An example of a three-story building is demonstrated and the results are compared by using a simulation method. (orig.)
Seismic reliability analysis of urban water distribution network
Li Jie; Wei Shulin; Liu Wei
2006-01-01
An approach to analyze the seismic reliability of water distribution networks by combining a hydraulic analysis with a first-order reliability method (FORM), is proposed in this paper.The hydraulic analysis method for normal conditions is modified to accommodate the special conditions necessary to perform a seismic hydraulic analysis. In order to calculate the leakage area and leaking flow of the pipelines in the hydraulic analysis method, a new leakage model established from the seismic response analysis of buried pipelines is presented. To validate the proposed approach, a network with 17 nodes and 24 pipelines is investigated in detail. The approach is also applied to an actual project consisting of 463 nodes and 767pipelines. Thee results show that the proposed approach achieves satisfactory results in analyzing the seismic reliability of large-scale water distribution networks.
Framework for Evaluating and Comparing Performance of Power System Reliability Criteria
Heylen, Evelyn; Labeeuw, Wouter; Deconinck, Geert; van Hertem, Dirk
2016-01-01
Evolutions in the power system challenge the manner in which power system reliability is managed. In particular, currently used reliability criteria, typically the deterministic N-1 criterion, are increasingly inadequate. Moving to an alternative approach is difficult as quantifying benefits is hard in a multifaceted environment and system operators are reluctant to move away from the easy and transparent existing criterion. This paper presents a generic framework to evaluate and compare soci...
Reliability analysis of the bulk cargo loading system including dependent components
Blokus-Roszkowska, Agnieszka
2016-06-01
In the paper an innovative approach to the reliability analysis of multistate series-parallel systems assuming their components' dependency is presented. The reliability function of a multistate series system with components dependent according to the local load sharing rule is determined. Linking these results for series systems with results for parallel systems with independent components, we obtain the reliability function of a multistate series-parallel system assuming dependence of components' departures from the reliability states subsets in series subsystem and assuming independence between these subsystems. As a particular case, the reliability function of a multistate series-parallel system composed of dependent components having exponential reliability functions is fixed. Theoretical results are applied practically to the reliability evaluation of a bulk cargo transportation system, which main area is to load bulk cargo on board the ships. The reliability function and other reliability characteristics of the loading system are determined in case its components have exponential reliability functions with interdependent departures rates from the subsets of their reliability states. Finally, the obtained results are compared with results for the bulk cargo transportation system composed of independent components.
Reliability-based analysis of river dikes during flood waves
Pham Quang, T.; van Gelder, P. H. A. J. M.; J. K. Vrijling; Thu, T.M.
2012-01-01
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 ...
Application of system reliability analysis to plant status monitoring
This paper describes a practical software tool which utilizes system reliability analysis technique to assist nuclear power plant operators and maintenance staff in making timely decision and reducing routine work burden. Specifically, this software, plant status monitoring (PSM), determines plant and its system operability status, monitor technical specifications and action statements compliance, assess dynamic operational reliability at various power levels (plant health), and monitor and produce equipment outage tags in consultation with technical specification requirements and plant health implications
Reliability and safety analysis for systems of fusion device
Alzbutas, Robertas, E-mail: robertas.alzbutas@lei.lt; Voronov, Roman
2015-05-15
Highlights: • Reliability is very important from fusion devices efficiency perspective. • Rich experience of probabilistic safety analysis exists in nuclear industry. • Reliability and safety analysis was applied for systems of fusion device. • This enables to identify and prioritize availability improvement measures. • Recommendations are based on cost effectiveness for risk decrease options. - Abstract: Fusion energy or thermonuclear power is a promising, literally endless source of energy. Development of fusion power is still under investigation and experimental phase, and a number of fusion devices are under construction in Europe. Since fusion energy is innovative and fusion devices contain unique and expensive equipment, an issue of their reliability is very important from their efficiency perspective. A Reliability, Availability, Maintainability, Inspectability (RAMI) analysis is being performed or is going to be performed in the nearest future for such fusion devices as ITER and DEMO in order to ensure reliable and efficient operation for experiments (e.g., in ITER) or for energy production purposes (e.g., in DEMO). On the other hand, rich experience of the reliability and Probabilistic Safety Analysis (PSA) exists in nuclear industry for fission power plants and other nuclear installations. In this paper, the Wendelstein 7-X (W7-X) device is mainly considered. This stellarator device is in commissioning stage in the Max-Planck-Institut für Plasmaphysik, Greifswald, Germany (IPP). In the frame of cooperation between the IPP and the Lithuanian Energy Institute (LEI) under the European Fusion Development Agreement a pilot project of a reliability analysis of the W7-X systems was performed with a purpose to adopt Nuclear Power Plant (NPP) PSA experience for fusion device systems. During the project reliability and safety (risk) analysis of a Divertor Target Cooling Circuit, which is an important system for permanent and reliable operation of in
Reliability and safety analysis for systems of fusion device
Highlights: • Reliability is very important from fusion devices efficiency perspective. • Rich experience of probabilistic safety analysis exists in nuclear industry. • Reliability and safety analysis was applied for systems of fusion device. • This enables to identify and prioritize availability improvement measures. • Recommendations are based on cost effectiveness for risk decrease options. - Abstract: Fusion energy or thermonuclear power is a promising, literally endless source of energy. Development of fusion power is still under investigation and experimental phase, and a number of fusion devices are under construction in Europe. Since fusion energy is innovative and fusion devices contain unique and expensive equipment, an issue of their reliability is very important from their efficiency perspective. A Reliability, Availability, Maintainability, Inspectability (RAMI) analysis is being performed or is going to be performed in the nearest future for such fusion devices as ITER and DEMO in order to ensure reliable and efficient operation for experiments (e.g., in ITER) or for energy production purposes (e.g., in DEMO). On the other hand, rich experience of the reliability and Probabilistic Safety Analysis (PSA) exists in nuclear industry for fission power plants and other nuclear installations. In this paper, the Wendelstein 7-X (W7-X) device is mainly considered. This stellarator device is in commissioning stage in the Max-Planck-Institut für Plasmaphysik, Greifswald, Germany (IPP). In the frame of cooperation between the IPP and the Lithuanian Energy Institute (LEI) under the European Fusion Development Agreement a pilot project of a reliability analysis of the W7-X systems was performed with a purpose to adopt Nuclear Power Plant (NPP) PSA experience for fusion device systems. During the project reliability and safety (risk) analysis of a Divertor Target Cooling Circuit, which is an important system for permanent and reliable operation of in
Society depends on services provided by critical infrastructures, and hence it is important that they are reliable and robust. Two main approaches for gaining knowledge required for designing and improving critical infrastructures are reliability analysis and vulnerability analysis. The former analyses the ability of the system to perform its intended function; the latter analyses its inability to withstand strains and the effects of the consequent failures. The two approaches have similarities but also some differences with respect to what type of information they generate about the system. In this view, the main purpose of this paper is to discuss and contrast these approaches. To strengthen the discussion and exemplify its findings, a Monte Carlo-based reliability analysis and a vulnerability analysis are considered in their application to a relatively simple, but representative, system the IEEE RTS96 electric power test system. The exemplification reveals that reliability analysis provides a good picture of the system likely behaviour, but fails to capture a large portion of the high consequence scenarios, which are instead captured in the vulnerability analysis. Although these scenarios might be estimated to have small probabilities of occurrence, they should be identified, considered and treated cautiously, as probabilistic analyses should not be the only input to decision-making for the design and protection of critical infrastructures. The general conclusion that can be drawn from the findings of the example is that vulnerability analysis should be used to complement reliability studies, as well as other forms of probabilistic risk analysis. Measures should be sought for reducing both the vulnerability, i.e. improving the system ability to withstand strains and stresses, and the reliability, i.e. improving the likely behaviour
Coverage Modeling and Reliability Analysis Using Multi-state Function
无
2007-01-01
Fault tree analysis is an effective method for predicting the reliability of a system. It gives a pictorial representation and logical framework for analyzing the reliability. Also, it has been used for a long time as an effective method for the quantitative and qualitative analysis of the failure modes of critical systems. In this paper, we propose a new general coverage model (GCM) based on hardware independent faults. Using this model, an effective software tool can be constructed to detect, locate and recover fault from the faulty system. This model can be applied to identify the key component that can cause the failure of the system using failure mode effect analysis (FMEA).
Reliability analysis of repairable systems using system dynamics modeling and simulation
Srinivasa Rao, M.; Naikan, V. N. A.
2014-07-01
Repairable standby system's study and analysis is an important topic in reliability. Analytical techniques become very complicated and unrealistic especially for modern complex systems. There have been attempts in the literature to evolve more realistic techniques using simulation approach for reliability analysis of systems. This paper proposes a hybrid approach called as Markov system dynamics (MSD) approach which combines the Markov approach with system dynamics simulation approach for reliability analysis and to study the dynamic behavior of systems. This approach will have the advantages of both Markov as well as system dynamics methodologies. The proposed framework is illustrated for a standby system with repair. The results of the simulation when compared with that obtained by traditional Markov analysis clearly validate the MSD approach as an alternative approach for reliability analysis.
Reliability analysis framework for computer-assisted medical decision systems
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
The decay heat removal in the Phenix Reactor has been designed with high level of safety and redundancy so that it should exist at least one way of removal whatever incident would be generated. In the following paragraph, we indicate the principal criteria used in the design, the different ways of operating and the global and qualitative reliability analysis in order to show the high degree of safety
RELIABILITY ANALYSIS OF RING, AGENT AND CLUSTER BASED DISTRIBUTED SYSTEMS
R.SEETHALAKSHMI
2011-08-01
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.
Recent advances in computational structural reliability analysis methods
Thacker, Ben H.; Wu, Y.-T.; Millwater, Harry R.; Torng, Tony Y.; Riha, David S.
1993-01-01
The goal of structural reliability analysis is to determine the probability that the structure will adequately perform its intended function when operating under the given environmental conditions. Thus, the notion of reliability admits the possibility of failure. Given the fact that many different modes of failure are usually possible, achievement of this goal is a formidable task, especially for large, complex structural systems. The traditional (deterministic) design methodology attempts to assure reliability by the application of safety factors and conservative assumptions. However, the safety factor approach lacks a quantitative basis in that the level of reliability is never known and usually results in overly conservative designs because of compounding conservatisms. Furthermore, problem parameters that control the reliability are not identified, nor their importance evaluated. A summary of recent advances in computational structural reliability assessment is presented. A significant level of activity in the research and development community was seen recently, much of which was directed towards the prediction of failure probabilities for single mode failures. The focus is to present some early results and demonstrations of advanced reliability methods applied to structural system problems. This includes structures that can fail as a result of multiple component failures (e.g., a redundant truss), or structural components that may fail due to multiple interacting failure modes (e.g., excessive deflection, resonate vibration, or creep rupture). From these results, some observations and recommendations are made with regard to future research needs.
Human reliability analysis methods for probabilistic safety assessment
Human reliability analysis (HRA) of a probabilistic safety assessment (PSA) includes identifying human actions from safety point of view, modelling the most important of them in PSA models, and assessing their probabilities. As manifested by many incidents and studies, human actions may have both positive and negative effect on safety and economy. Human reliability analysis is one of the areas of probabilistic safety assessment (PSA) that has direct applications outside the nuclear industry. The thesis focuses upon developments in human reliability analysis methods and data. The aim is to support PSA by extending the applicability of HRA. The thesis consists of six publications and a summary. The summary includes general considerations and a discussion about human actions in the nuclear power plant (NPP) environment. A condensed discussion about the results of the attached publications is then given, including new development in methods and data. At the end of the summary part, the contribution of the publications to good practice in HRA is presented. In the publications, studies based on the collection of data on maintenance-related failures, simulator runs and expert judgement are presented in order to extend the human reliability analysis database. Furthermore, methodological frameworks are presented to perform a comprehensive HRA, including shutdown conditions, to study reliability of decision making, and to study the effects of wrong human actions. In the last publication, an interdisciplinary approach to analysing human decision making is presented. The publications also include practical applications of the presented methodological frameworks. (orig.)
National Launch System comparative economic analysis
Prince, A.
1992-01-01
Results are presented from an analysis of economic benefits (or losses), in the form of the life cycle cost savings, resulting from the development of the National Launch System (NLS) family of launch vehicles. The analysis was carried out by comparing various NLS-based architectures with the current Shuttle/Titan IV fleet. The basic methodology behind this NLS analysis was to develop a set of annual payload requirements for the Space Station Freedom and LEO, to design launch vehicle architectures around these requirements, and to perform life-cycle cost analyses on all of the architectures. A SEI requirement was included. Launch failure costs were estimated and combined with the relative reliability assumptions to measure the effects of losses. Based on the analysis, a Shuttle/NLS architecture evolving into a pressurized-logistics-carrier/NLS architecture appears to offer the best long-term cost benefit.
Reliability Analysis of Wireless Sensor Networks Using Markovian Model
Jin Zhu
2012-01-01
Full Text Available This paper investigates reliability analysis of wireless sensor networks whose topology is switching among possible connections which are governed by a Markovian chain. We give the quantized relations between network topology, data acquisition rate, nodes' calculation ability, and network reliability. By applying Lyapunov method, sufficient conditions of network reliability are proposed for such topology switching networks with constant or varying data acquisition rate. With the conditions satisfied, the quantity of data transported over wireless network node will not exceed node capacity such that reliability is ensured. Our theoretical work helps to provide a deeper understanding of real-world wireless sensor networks, which may find its application in the fields of network design and topology control.
Reliability analysis of reactor inspection robot(RIROB)
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)
Bayesian Inference for NASA Probabilistic Risk and Reliability Analysis
Dezfuli, Homayoon; Kelly, Dana; Smith, Curtis; Vedros, Kurt; Galyean, William
2009-01-01
This document, Bayesian Inference for NASA Probabilistic Risk and Reliability Analysis, is intended to provide guidelines for the collection and evaluation of risk and reliability-related data. It is aimed at scientists and engineers familiar with risk and reliability methods and provides a hands-on approach to the investigation and application of a variety of risk and reliability data assessment methods, tools, and techniques. This document provides both: A broad perspective on data analysis collection and evaluation issues. A narrow focus on the methods to implement a comprehensive information repository. The topics addressed herein cover the fundamentals of how data and information are to be used in risk and reliability analysis models and their potential role in decision making. Understanding these topics is essential to attaining a risk informed decision making environment that is being sought by NASA requirements and procedures such as 8000.4 (Agency Risk Management Procedural Requirements), NPR 8705.05 (Probabilistic Risk Assessment Procedures for NASA Programs and Projects), and the System Safety requirements of NPR 8715.3 (NASA General Safety Program Requirements).
The comparability and reliability of five health-state valuation methods
Krabbe, P F; Essink-Bot, M L; Bonsel, G J
1997-01-01
The objective of the study was to consider five methods for valuing health states with respect to their comparability (convergent validity, value functions) and reliability. Valuation tasks were performed by 104 student volunteers using five frequently used valuation methods: standard gamble (SG), t
Distribution System Reliability Analysis for Smart Grid Applications
Aljohani, Tawfiq Masad
Reliability of power systems is a key aspect in modern power system planning, design, and operation. The ascendance of the smart grid concept has provided high hopes of developing an intelligent network that is capable of being a self-healing grid, offering the ability to overcome the interruption problems that face the utility and cost it tens of millions in repair and loss. To address its reliability concerns, the power utilities and interested parties have spent extensive amount of time and effort to analyze and study the reliability of the generation and transmission sectors of the power grid. Only recently has attention shifted to be focused on improving the reliability of the distribution network, the connection joint between the power providers and the consumers where most of the electricity problems occur. In this work, we will examine the effect of the smart grid applications in improving the reliability of the power distribution networks. The test system used in conducting this thesis is the IEEE 34 node test feeder, released in 2003 by the Distribution System Analysis Subcommittee of the IEEE Power Engineering Society. The objective is to analyze the feeder for the optimal placement of the automatic switching devices and quantify their proper installation based on the performance of the distribution system. The measures will be the changes in the reliability system indices including SAIDI, SAIFI, and EUE. The goal is to design and simulate the effect of the installation of the Distributed Generators (DGs) on the utility's distribution system and measure the potential improvement of its reliability. The software used in this work is DISREL, which is intelligent power distribution software that is developed by General Reliability Co.
Human reliability analysis of Lingao Nuclear Power Station
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
Behaviour State Analysis in Rett Syndrome: Continuous Data Reliability Measurement
Woodyatt, Gail; Marinac, Julie; Darnell, Ross; Sigafoos, Jeff; Halle, James
2004-01-01
Awareness of optimal behaviour states of children with profound intellectual disability has been reported in the literature as a potentially useful tool for planning intervention within this population. Some arguments have been raised, however, which question the reliability and validity of previously published work on behaviour state analysis.…
Reliability-Based Robustness Analysis for a Croatian Sports Hall
Čizmar, Dean; Kirkegaard, Poul Henning; Sørensen, John Dalsgaard;
2011-01-01
complex timber structure with a large number of failure modes is modelled with only a few dominant failure modes. First, a component based robustness analysis is performed based on the reliability indices of the remaining elements after the removal of selected critical elements. The robustness is...
Reliability Analysis of a Mono-Tower Platform
Kirkegaard, Poul Henning; Enevoldsen, I.; Sørensen, John Dalsgaard;
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...
Reliability Analysis of a Mono-Tower Platform
Kirkegaard, Poul Henning; Enevoldsen, I.; Sørensen, John Dalsgaard;
1990-01-01
In this paper, a reliability analysis of a Mono-tower platform is presented. Te failure modes considered are yielding in the tube cross sections and fatigue failure in the butts welds. The fatigue failrue mode is investigated with a fatigue model, where the fatigue strength is expressed through SN...
Analysis on Operation Reliability of Generating Units in 2005
Zuo Xiaowen; Chu Xue
2007-01-01
@@ The weighted average equivalent availability factor of thermal power units in 2005 was 92.34%, an increase of 0.64 percentage points as compared to that in 2004. The average equivalent availability factor in 2005 was 92.22%, a decrease of 0.95 percentage points as compared to that in 2004. The nationwide operation reliability of generating units in 2005 was analyzed completely in this paper.
Reliable analysis for pressure vessel based on ANSYS
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)
Modelling application for cognitive reliability and error analysis method
Fabio De Felice
2013-10-01
Full Text Available The automation of production systems has delegated to machines the execution of highly repetitive and standardized tasks. In the last decade, however, the failure of the automatic factory model has led to partially automated configurations of production systems. Therefore, in this scenario, centrality and responsibility of the role entrusted to the human operators are exalted because it requires problem solving and decision making ability. Thus, human operator is the core of a cognitive process that leads to decisions, influencing the safety of the whole system in function of their reliability. The aim of this paper is to propose a modelling application for cognitive reliability and error analysis method.
Human Reliability Analysis for Digital Human-Machine Interfaces
Ronald L. Boring
2014-06-01
This paper addresses the fact that existing human reliability analysis (HRA) methods do not provide guidance on digital human-machine interfaces (HMIs). Digital HMIs are becoming ubiquitous in nuclear power operations, whether through control room modernization or new-build control rooms. Legacy analog technologies like instrumentation and control (I&C) systems are costly to support, and vendors no longer develop or support analog technology, which is considered technologically obsolete. Yet, despite the inevitability of digital HMI, no current HRA method provides guidance on how to treat human reliability considerations for digital technologies.
Classification using least squares support vector machine for reliability analysis
Zhi-wei GUO; Guang-chen BAI
2009-01-01
In order to improve the efficiency of the support vector machine (SVM) for classification to deal with a large amount of samples,the least squares support vector machine (LSSVM) for classification methods is introduced into the reliability analysis.To reduce the computational cost,the solution of the SVM is transformed from a quadratic programming to a group of linear equations.The numerical results indicate that the reliability method based on the LSSVM for classification has higher accuracy and requires less computational cost than the SVM method.
Reliability of videotaped observational gait analysis in patients with orthopedic impairments
van Uden Caro JT
2005-03-01
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.
Nuclear power ecology: comparative analysis
Ecological effects of different energy sources are compared. Main actions for further nuclear power development - safety increase and waste management, are noted. Reasons of restrained public position to nuclear power and role of social and political factors in it are analyzed. An attempt is undertaken to separate real difficulties of nuclear power from imaginary ones that appear in some mass media. International actions of environment protection are noted. Risk factors at different energy source using are compared. The results of analysis indicate that ecological influence and risk for nuclear power are of minimum
Accident Sequence Evaluation Program: Human reliability analysis procedure
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
Reliability analysis of rotor blades of tidal stream turbines
Tidal stream turbines are used for converting kinetic energy of tidal currents into electricity. There are a number of uncertainties involved in the design of such devices and their components. To ensure safety of the turbines these uncertainties must be taken into account. The paper shows how this may be achieved for the design of rotor blades of horizontal-axis tidal stream turbines in the context of bending failure due to extreme loading. Initially, basic characteristics of such turbines in general and their blades in particular are briefly described. A probabilistic model of tidal current velocity fluctuations, which are the main source of load uncertainty, is then presented. This is followed by the description of reliability analysis of the blades, which takes into account uncertainties associated with tidal current speed, the blade resistance and the model used to calculate bending moments in the blades. Finally, the paper demonstrates how results of the reliability analysis can be applied to set values of the partial factors for the blade design. - Highlights: • A probabilistic model of the maximum of tidal current velocity fluctuations is proposed. • Reliability analysis of rotor blades of a tidal stream turbine is described. • Influence of pitch control system on the blade reliability is investigated. • Partial safety factors for the design of tidal turbine rotor blades are calibrated
Accident Sequence Evaluation Program: Human reliability analysis procedure
Swain, A.D.
1987-02-01
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.
Strength Reliability Analysis of Turbine Blade Using Surrogate Models
Wei Duan
2014-05-01
Full Text Available There are many stochastic parameters that have an effect on the reliability of steam turbine blades performance in practical operation. In order to improve the reliability of blade design, it is necessary to take these stochastic parameters into account. In this study, a variable cross-section twisted blade is investigated and geometrical parameters, material parameters and load parameters are considered as random variables. A reliability analysis method as a combination of a Finite Element Method (FEM, a surrogate model and Monte Carlo Simulation (MCS, is applied to solve the blade reliability analysis. Based on the blade finite element parametrical model and the experimental design, two kinds of surrogate models, Polynomial Response Surface (PRS and Artificial Neural Network (ANN, are applied to construct the approximation analytical expressions between the blade responses (including maximum stress and deflection and random input variables, which act as a surrogate of finite element solver to drastically reduce the number of simulations required. Then the surrogate is used for most of the samples needed in the Monte Carlo method and the statistical parameters and cumulative distribution functions of the maximum stress and deflection are obtained by Monte Carlo simulation. Finally, the probabilistic sensitivities analysis, which combines the magnitude of the gradient and the width of the scatter range of the random input variables, is applied to evaluate how much the maximum stress and deflection of the blade are influenced by the random nature of input parameters.
Reliability analysis for inspections of CANDU components and systems
Condition assessment of complex systems requires more than inspection data for the individual elements of the system. At the component level, knowledge of the probability of detection (POD) and sizing accuracy for defects is needed to properly interpret results. At the system level, probabilistic and deterministic methods guide safety assessments and life management strategies. The field of reliability analysis provides a framework for quantitative application of inspection results to both levels. Quantitative knowledge of inspection reliability can reduce the requirement to use conservative values for every quantity. A sound analysis of inspection reliability can produce a more targeted inspection scope, leading to fewer but more effective inspections and, consequently, lower radiation dose. Restart cases can be based on correct detection probability distributions rather than worst-case scenarios, and inspection intervals and expected life estimates can be optimized based on measured sizing uncertainties. This paper illustrates applications of inspection reliability analysis to optimize the inspect-repair-operate cycle for major CANDU primary heat transport elements, such as steam generator tubing, feeder piping, and fuel channels. (author)
Generating function approach to reliability analysis of structural systems
无
2009-01-01
The generating function approach is an important tool for performance assessment in multi-state systems. Aiming at strength reliability analysis of structural systems, generating function approach is introduced and developed. Static reliability models of statically determinate, indeterminate systems and fatigue reliability models are built by constructing special generating functions, which are used to describe probability distributions of strength (resistance), stress (load) and fatigue life, by defining composite operators of generating functions and performance structure functions thereof. When composition operators are executed, computational costs can be reduced by a big margin by means of collecting like terms. The results of theoretical analysis and numerical simulation show that the generating function approach can be widely used for probability modeling of large complex systems with hierarchical structures due to the unified form, compact expression, computer program realizability and high universality. Because the new method considers twin loads giving rise to component failure dependency, it can provide a theoretical reference and act as a powerful tool for static, dynamic reliability analysis in civil engineering structures and mechanical equipment systems with multi-mode damage coupling.
Fuzzy sensitivity analysis for reliability assessment of building structures
Kala, Zdeněk
2016-06-01
The mathematical concept of fuzzy sensitivity analysis, which studies the effects of the fuzziness of input fuzzy numbers on the fuzziness of the output fuzzy number, is described in the article. The output fuzzy number is evaluated using Zadeh's general extension principle. The contribution of stochastic and fuzzy uncertainty in reliability analysis tasks of building structures is discussed. The algorithm of fuzzy sensitivity analysis is an alternative to stochastic sensitivity analysis in tasks in which input and output variables are considered as fuzzy numbers.
Maintenance management of railway infrastructures based on reliability analysis
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.
Reliability Analysis of Free Jet Scour Below Dams
Chuanqi Li
2012-12-01
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.
Souza, Arlindo Antonio de; Polillo Filho, Adolfo; Santos, Otto Luiz Alcantara [PETROBRAS, Rio de Janeiro, RJ (Brazil)
2004-07-01
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)
BANK RATING. A COMPARATIVE ANALYSIS
Batrancea Ioan
2015-07-01
Full Text Available Banks in Romania offers its customers a wide range of products but which involves both risk taking. Therefore researchers seek to build rating models to help managers of banks to risk of non-recovery of loans and interest. In the following we highlight rating Raiffeisen Bank, BCR-ERSTE Bank and Transilvania Bank, based on the models CAAMPL and Stickney making a comparative analysis of the two rating models.
Reliability and maintainability analysis of electrical system of drum shearers
SEYED Hadi Hoseinie; MOHAMMAD Ataei; REZA Khalokakaie; UDAY Kumar
2011-01-01
The reliability and maintainability of electrical system of drum shearer at Parvade.l Coal Mine in central Iran was analyzed. The maintenance and failure data were collected during 19 months of shearer operation. According to trend and serial correlation tests, the data were independent and identically distributed (iid) and therefore the statistical techniques were used for modeling. The data analysis show that the time between failures (TBF) and time to repair (TTR) data obey the lognormal and Weibull 3 parameters distribution respectively. Reliability-based preventive maintenance time intervals for electrical system of the drum shearer were calculated with regard to reliability plot. The reliability-based maintenance intervals for 90%, 80%, 70% and 50% reliability level are respectively 9.91, 17.96, 27.56 and 56.1 h. Also the calculations show that time to repair (TTR) of this system varies in range 0.17-4 h with 1.002 h as mean time to repair (MTTR). There is a 80% chance that the electrical system of shearer of Parvade.l mine repair will be accomplished within 1.45 h.
A framework for intelligent reliability centered maintenance analysis
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
Reliability analysis of service water system under earthquake
Service water system is one of the important safety systems in nuclear power plant, whose failure probability is always gained by system reliability analysis. The probability of equipment failure under the earthquake is the function of the peak acceleration of earthquake motion, while the occurrence of earthquake is of randomicity, thus the traditional fault tree method in current probability safety assessment is not powerful enough to deal with such case of conditional probability problem. An analysis frame was put forward for system reliability evaluation in seismic condition in this paper, in which Monte Carlo simulation was used to deal with conditional probability problem. Annual failure probability of service water system was calculated, and failure probability of 1.46X10-4 per year was obtained. The analysis result is in accordance with the data which indicate equipment seismic resistance capability, and the rationality of the model is validated. (authors)
Virtual stress amplitude-based low cycle fatigue reliability analysis
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-ε-σ 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
Asymptotic Sampling for Reliability Analysis of Adhesive Bonded Stepped Lap Composite Joints
Kimiaeifar, Amin; Lund, Erik; Thomsen, Ole Thybo;
2013-01-01
is a promising and time efficient tool to calculate the probability of failure, is utilized, and a probabilistic model for the reliability analysis of adhesive bonded stepped lap composite joints, representative for the main laminate in a wind turbine blade subjected to static flapwise bending load......Reliability analysis coupled with finite element analysis (FEA) of composite structures is computationally very demanding and requires a large number of simulations to achieve an accurate prediction of the probability of failure with a small standard error. In this paper Asymptotic Sampling, which...... used to predict failure in the composite and adhesive layers, respectively, and the results are compared with the target reliability level implicitly used in the wind turbine standard IEC 61400-1. The accuracy and efficiency of Asymptotic Sampling is investigated by comparing the results with...
Brazilian gas network computational model for reliability analysis
Carvalho, Thomaz; Bilhim, Thiago; Ferreira, Gustavo P. D.; Pires, Luis F. G. [Dept. Eng. Mecanica, PUC-Rio (Brazil); Faertes, Denise; Saker, Leonardo [PETROBRAS Gas and Energia (Brazil)
2010-07-01
Pipeline thermo-hydraulic simulation is useful to support operation, design development and reliability analysis. PETROBRAS carried reliability programs in the last years. These studies are developed to evaluate gas chain security of supply, pointing out vulnerable points and proposing optimization measures to adopt. Previously, the Brazilian gas network could be modeled using sub-networks because of the physical separation between the Northeast and the Southeast networks, but in 2010 the new GASCAC pipeline will start up and change this. The new simulation models will have to handle this new configuration. The simulations developed by the Pontifice Catholic University of Rio de Janeiro deal with steady state and transient scenarios provided by a PETROBRAS group of experts. This paper discusses the alternatives and strategies used in the thermo-hydraulic simulation of the Brazilian gas pipeline network and analyses the advantages and disadvantages of each approach and the option used to meet the demands of the reliability analysis of the PETROBRAS gas reliability management sector.
S.A. Mohammadi
2011-10-01
Full Text Available Mean shift algorithms are among the most functional tracking methods which are accurate and havealmost simple computation. Different versions of this algorithm are developed which are differ in templateupdating and their window sizes. To measure the reliability and accuracy of these methods one shouldnormally rely on visual results or number of iteration. In this paper we introduce two new parameterswhich can be used to compare the algorithms especially when their results are close to each other.
Analysis of Gumbel Model for Software Reliability Using Bayesian Paradigm
Raj Kumar
2012-12-01
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.
Reliability analysis of maintenance operations for railway tracks
Railway engineering is confronted with problems due to degradation of the railway network that requires important and costly maintenance work. However, because of the lack of knowledge on the geometrical and mechanical parameters of the track, it is difficult to optimize the maintenance management. In this context, this paper presents a new methodology to analyze the behavior of railway tracks. It combines new diagnostic devices which permit to obtain an important amount of data and thus to make statistics on the geometric and mechanical parameters and a non-intrusive stochastic approach which can be coupled with any mechanical model. Numerical results show the possibilities of this methodology for reliability analysis of different maintenance operations. In the future this approach will give important informations to railway managers to optimize maintenance operations using a reliability analysis
Reliability analysis using an enhanced response surface moment method
Moment methods, which are powerful and simple techniques for analyzing the reliability of a system, evaluate the statistical moments of a system response function and use information from the probability distribution in the analysis. The full factorial moment method (FFMM) performs reliability analysis by using a 3n full factorial design of experiments (DOE) and the Pearson system for random variables. To overcome the inefficiency of FFMM, the response surface moment method (RSMM) has been proposed, which is based on a response surface model (RSM) that is updated by adding cross product terms into the simple quadratic model. In this paper, we propose the enhanced RSMM (RSMM+) that modifies the procedure of selecting a cross product term in the RSMM and adds a process of judging whether the response surface model can be established before performing an additional experiment. We apply the proposed method to several examples and show that it gives better results in efficiency
THE INVESTMENT RELIABILITY ANALYSIS FOR A SURFACE MINE
彭世济; 卢明银; 张达贤
1990-01-01
It is stipulated in the China national document, named"The Economical Appraisal Methods for Construction Projects" that dynamic analysis should dominate the project economical appraisal methods.This paper has set up a dynamic investment forecast model for Yuanbaoshan Surface Coal Mine. Based on this model, the investment reliability using simulation and analytic methods has been analysed, anti the probability that the designed internal rate of return can reach 8.4%, from economic points of view, have been also studied.
Reliability analysis based on the losses from failures.
Todinov, M T
2006-04-01
The conventional reliability analysis is based on the premise that increasing the reliability of a system will decrease the losses from failures. On the basis of counterexamples, it is demonstrated that this is valid only if all failures are associated with the same losses. In case of failures associated with different losses, a system with larger reliability is not necessarily characterized by smaller losses from failures. Consequently, a theoretical framework and models are proposed for a reliability analysis, linking reliability and the losses from failures. Equations related to the distributions of the potential losses from failure have been derived. It is argued that the classical risk equation only estimates the average value of the potential losses from failure and does not provide insight into the variability associated with the potential losses. Equations have also been derived for determining the potential and the expected losses from failures for nonrepairable and repairable systems with components arranged in series, with arbitrary life distributions. The equations are also valid for systems/components with multiple mutually exclusive failure modes. The expected losses given failure is a linear combination of the expected losses from failure associated with the separate failure modes scaled by the conditional probabilities with which the failure modes initiate failure. On this basis, an efficient method for simplifying complex reliability block diagrams has been developed. Branches of components arranged in series whose failures are mutually exclusive can be reduced to single components with equivalent hazard rate, downtime, and expected costs associated with intervention and repair. A model for estimating the expected losses from early-life failures has also been developed. For a specified time interval, the expected losses from early-life failures are a sum of the products of the expected number of failures in the specified time intervals covering the
Inclusion of task dependence in human reliability analysis
Dependence assessment among human errors in human reliability analysis (HRA) is an important issue, which includes the evaluation of the dependence among human tasks and the effect of the dependence on the final human error probability (HEP). This paper represents a computational model to handle dependence in human reliability analysis. The aim of the study is to automatically provide conclusions on the overall degree of dependence and calculate the conditional human error probability (CHEP) once the judgments of the input factors are given. The dependence influencing factors are first identified by the experts and the priorities of these factors are also taken into consideration. Anchors and qualitative labels are provided as guidance for the HRA analyst's judgment of the input factors. The overall degree of dependence between human failure events is calculated based on the input values and the weights of the input factors. Finally, the CHEP is obtained according to a computing formula derived from the technique for human error rate prediction (THERP) method. The proposed method is able to quantify the subjective judgment from the experts and improve the transparency in the HEP evaluation process. Two examples are illustrated to show the effectiveness and the flexibility of the proposed method. - Highlights: • We propose a computational model to handle dependence in human reliability analysis. • The priorities of the dependence influencing factors are taken into consideration. • The overall dependence degree is determined by input judgments and the weights of factors. • The CHEP is obtained according to a computing formula derived from THERP
Reliability analysis of crack propagation behavior of reactor components
A reliability analysis was carried out on a circumferential weld in the main coolant loop of a PWR with the aim of estimating the probability of a leak or break occurring in the planned life cycle of the plant. To get a basis for the reliability analysis the following influence factors were more closely examined: initial crack extent, load spectrum including the emergency 'earthquake' situation and crack growth characteristics. For the actual reliability analysis a computer program was developed, which took the individual input data, in accordance with their statistical parameter, into account in a simulation calculation in line with the Monte Carlo Method. The Forman Formula was used to estimate the fatigue crack growth caused by the sequence of load events. The result was, that the fatigue crack growth, even in the case of large initial cracks, was negligibly small. The probability, that, in the case of very deep initial cracks, one-off high quasi-static load, e.g. during an earthquake, could cause a locally limited crack-through, was estimated to be about 5x10-6 in forty years. (orig./HP)
Reliability engineering analysis of ATLAS data reprocessing campaigns
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.
Maximizing personnel performance in plantwide reliability-centered maintenance analysis
Techniques have been developed and proven effective that can be used to reduce the staffing requirements for implementation of a full-scale plantwide reliability-centered maintenance (RCM) program. The multiphase projects discussed in this paper integrate RCM into a broad-based preventive maintenance program concept that includes several programmatic functions, such as system reliability modeling, computerized RCM data bases, and quantitative and qualitative cost/benefit analyses. Through the use of computerized data bases, system models, equipment failure tracking, and preventive maintenance program effectiveness evaluations, the RCM programs can create a living reliability-based preventive maintenance program. The completed RCM data can be maintained and updated with current plant design and equipment performance history without large staffs of RCM analysts. The goal of any RCM project is the development of a structures and well-justified preventive maintenance program that ensures the reliability of plant components is maximized to the extent that an appropriate cost/benefit is achieved in return for the maintenance dollars expended. The methods discussed were developed for two full-scale RCM projects that are useful when implementing the program on a plantwide basis. The typical approach to RCM has been to establish a process on one pilot system and then continue the RCM process on selected systems periodically. By implementing an RCM program on a plantwide basis, benefits can be realized from and economy of scale and through the implementation of labor-saving analysis aids
High-Reliable PLC RTOS Development and RPS Structure Analysis
One of the KNICS objectives is to develop a platform for Nuclear Power Plant(NPP) I and C(Instrumentation and Control) system, especially plant protection system. The developed platform is POSAFE-Q and this work supports the development of POSAFE-Q with the development of high-reliable real-time operating system(RTOS) and programmable logic device(PLD) software. Another KNICS objective is to develop safety I and C systems, such as Reactor Protection System(RPS) and Engineered Safety Feature-Component Control System(ESF-CCS). This work plays an important role in the structure analysis for RPS. Validation and verification(V and V) of the safety critical software is an essential work to make digital plant protection system highly reliable and safe. Generally, the reliability and safety of software based system can be improved by strict quality assurance framework including the software development itself. In other words, through V and V, the reliability and safety of a system can be improved and the development activities like software requirement specification, software design specification, component tests, integration tests, and system tests shall be appropriately documented for V and V.
A semi-Markov reliability analysis of alternating systems
Current nuclear power plants must be highly reliable with respect to safety and economy. Consequently, development of a new safety evaluation methodology is desired for the accurate evaluation of safety and economy. A nuclear power plant consists of many systems. This paper is concerned with the reliability evaluation of alternating systems. An alternating system usually consists of multitrains, and its operation alternates from one train to another. Examples of these are the nuclear service cooling water system, the component cooling water system, and the chemical and volume control system. The alternating systems exhibit strong dynamic time-dependent reliability characteristics because of the alternating operational mode and the technical specification requirements that are particularly difficult to analyze by static fault-tree techniques. The method used in this paper is based on the semi-Markov reliability analysis. The system performance measures evaluated are its contribution to the total risk of the plant (e.g., core damage probability) and to plant unavailability (reactor downtime). It is concluded that the methodology developed in this study can be applied to existing alternating systems for plant-specific evaluation of the various alternatives in technical specifications
Domain of electronic systems is increasing day by day. To use them in safety critical applications, such as safety function of nuclear reactor, high reliability of these systems need to be ensured. As reliability measurement is costly and time consuming, models are the only solution. Various methods and models exist for reliability prediction, applicable at different stages. In this paper, a unified approach by integrating different methods to estimate system reliability from its basic components is presented. Techniques to increase the reliability of the system such as redundancy and repair are discussed. A method to determine number of spares, required for a given replaceable module for the mission time is presented. An example is taken to show the effect of redundancy and repair on the system reliability. Paper also discussed the effect of depletion of spare inventory and proposed method to incorporate this in system reliability estimation. (author)
Thompson, Bruce; Cook, Collen
2002-01-01
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)
An improved radial basis function network for structural reliability analysis
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
Mutation Analysis Approach to Develop Reliable Object-Oriented Software
Monalisa Sarma
2014-01-01
Full Text Available In general, modern programs are large and complex and it is essential that they should be highly reliable in applications. In order to develop highly reliable software, Java programming language developer provides a rich set of exceptions and exception handling mechanisms. Exception handling mechanisms are intended to help developers build robust programs. Given a program with exception handling constructs, for an effective testing, we are to detect whether all possible exceptions are raised and caught or not. However, complex exception handling constructs make it tedious to trace which exceptions are handled and where and which exceptions are passed on. In this paper, we address this problem and propose a mutation analysis approach to develop reliable object-oriented programs. We have applied a number of mutation operators to create a large set of mutant programs with different type of faults. We then generate test cases and test data to uncover exception related faults. The test suite so obtained is applied to the mutant programs measuring the mutation score and hence verifying whether mutant programs are effective or not. We have tested our approach with a number of case studies to substantiate the efficacy of the proposed mutation analysis technique.
Modeling of seismic hazards for dynamic reliability analysis
This paper investigates the appropriate indices of seismic hazard curves (SHCs) for seismic reliability analysis. In the most seismic reliability analyses of structures, the seismic hazards are defined in the form of the SHCs of peak ground accelerations (PGAs). Usually PGAs play a significant role in characterizing ground motions. However, PGA is not always a suitable index of seismic motions. When random vibration theory developed in the frequency domain is employed to obtain statistics of responses, it is more convenient for the implementation of dynamic reliability analysis (DRA) to utilize an index which can be determined in the frequency domain. In this paper, we summarize relationships among the indices which characterize ground motions. The relationships between the indices and the magnitude M are arranged as well. In this consideration, duration time plays an important role in relating two distinct class, i.e. energy class and power class. Fourier and energy spectra are involved in the energy class, and power and response spectra and PGAs are involved in the power class. These relationships are also investigated by using ground motion records. Through these investigations, we have shown the efficiency of employing the total energy as an index of SHCs, which can be determined in the time and frequency domains and has less variance than the other indices. In addition, we have proposed the procedure of DRA based on total energy. (author)
Strength Reliability Analysis of Stiffened Cylindrical Shells Considering Failure Correlation
Xu Bai; Liping Sun; Wei Qin; Yongkun Lv
2014-01-01
The stiffened cylindrical shell is commonly used for the pressure hull of submersibles and the legs of offshore platforms. There are various failure modes because of uncertainty with the structural size and material properties, uncertainty of the calculation model and machining errors. Correlations among failure modes must be considered with the structural reliability of stiffened cylindrical shells. However, the traditional method cannot consider the correlations effectively. The aim of this study is to present a method of reliability analysis for stiffened cylindrical shells which considers the correlations among failure modes. Firstly, the joint failure probability calculation formula of two related failure modes is derived through use of the 2D joint probability density function. Secondly, the full probability formula of the tandem structural system is given with consideration to the correlations among failure modes. At last, the accuracy of the system reliability calculation is verified through use of the Monte Carlo simulation. Result of the analysis shows the failure probability of stiffened cylindrical shells can be gained through adding the failure probability of each mode.
Damage tolerance reliability analysis of automotive spot-welded joints
Mahadevan, Sankaran; Ni Kan
2003-07-01
This paper develops a damage tolerance reliability analysis methodology for automotive spot-welded joints under multi-axial and variable amplitude loading history. The total fatigue life of a spot weld is divided into two parts, crack initiation and crack propagation. The multi-axial loading history is obtained from transient response finite element analysis of a vehicle model. A three-dimensional finite element model of a simplified joint with four spot welds is developed for static stress/strain analysis. A probabilistic Miner's rule is combined with a randomized strain-life curve family and the stress/strain analysis result to develop a strain-based probabilistic fatigue crack initiation life prediction for spot welds. Afterwards, the fatigue crack inside the base material sheet is modeled as a surface crack. Then a probabilistic crack growth model is combined with the stress analysis result to develop a probabilistic fatigue crack growth life prediction for spot welds. Both methods are implemented with MSC/NASTRAN and MSC/FATIGUE software, and are useful for reliability assessment of automotive spot-welded joints against fatigue and fracture.
Reliability analysis of Indian pressurized heavy water reactor piping
In this paper, a probabilistic analysis of primary heat transport of Indian Pressurized Heavy Water reactor is presented. The probability of failure of the straight pipes with through wall circumferential flaws subjected to bending moment is calculated. The failure criteria considered is net section collapse and R6 method. Probability of failure is obtained with crack growth initiation as the limiting condition. The variability in the crack size and material properties (tensile and fracture) is considered. The probability of failure is calculated at different levels of applied load. Various methods of probability estimation are presented and their equivalence is demonstrated. The probability of failure is obtained using classical Monte Carlo method, Monte Carlo with importance sampling, First Order Reliability Method (FORM), Second Order Reliability Method (SORM) and by numerical integration of the failure integral using Lepage's VEGAS algorithm. The results are utilized for demonstrating that for the leakage size crack, the pipe design has high probability for leak before break. (orig.)
User's manual of a support system for human reliability analysis
Many kinds of human reliability analysis (HRA) methods have been developed. However, users are required to be skillful so as to use them, and also required complicated works such as drawing event tree (ET) and calculation of uncertainty bounds. Moreover, each method is not so complete that only one method of them is not enough to evaluate human reliability. Therefore, a personal computer (PC) based support system for HRA has been developed to execute HRA practically and efficiently. The system consists of two methods, namely, simple method and detailed one. The former uses ASEP that is a simplified THERP-technique, and combined method of OAT and HRA-ET/DeBDA is used for the latter. Users can select a suitable method for their purpose. Human error probability (HEP) data were collected and a database of them was built to use for the support system. This paper describes outline of the HRA methods, support functions and user's guide of the system. (author)
Review of the treat upgrade reactor scram system reliability analysis
In order to resolve some key LMFBR safety issues, ANL personnel are modifying the TREAT reactor to handle much larger experiments. As a result of these modifications, the upgraded Treat reactor will not always operate in a self-limited mode. During certain experiments in the upgraded TREAT reactor, it is possible that the fuel could be damaged by overheating if, once the computer systems fail, the reactor scram system (RSS) fails on demand. To help ensure that the upgraded TREAT reactor is shut down when required, ANL personnel have designed a triply redundant RSS for the facility. The RSS is designed to meet three reliability goals: (1) a loss of capability failure probability of 10-9/demand (independent failures only); (2) an inadvertent shutdown probability of 10-3/experiment; and (3) protection agaist any known potential common cause failures. According to ANL's reliability analysis of the RSS, this system substantially meets these goals
Comparative Analysis of Classifier Fusers
Marcin Zmyslony
2012-06-01
Full Text Available There are many methods of decision making by an ensemble of classifiers. The most popular are methods that have their origin in voting method, where the decision of the common classifier is a combination of individual classifiers’ outputs. This work presents comparative analysis of some classifier fusion methods based on weighted voting of classifiers’ responses and combination of classifiers’ discriminant functions. We discus different methods of producing combined classifiers based on weights. We show that it is notpossible to obtain classifier better than an abstract model of committee known as an Oracle if it is based only on weighted voting but models based on discriminant function or classifier using feature values and class numbers could outperform the Oracle as well. Delivered conclusions are confirmed by the results of computer experiments carried out on benchmark and computer generated data.
Comparative Analysis of Classifier Fusers
Marcin Zmyslony
2012-05-01
Full Text Available There are many methods of decision making by an ensemble of classifiers. The most popular are methods that have their origin in voting method, where the decision of the common classifier is a combination of individual classifiers’ outputs. This work presents comparative analysis of some classifier fusion methods based on weighted voting of classifiers’ responses and combination of classifiers’ discriminant functions. We discus different methods of producing combined classifiers based on weights. We show that it is not possible to obtain classifier better than an abstract model of committee known as an Oracle if it is based only on weighted voting but models based on discriminant function or classifier using feature values and class numbers could outperform the Oracle as well. Delivered conclusions are confirmed by the results of computer experiments carried out on benchmark and computer generated data.
Comparative analysis of collaboration networks
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.
Human reliability analysis for accident sequences in NPP
The purpose of this paper is to perform a human performance analysis in accident conditions for the operating NPP. This analysis is realized using Human Reliability Analysis (HRA) methods. HRA methods have necessary tools to analyze the human actions, to estimate the human error probabilities and to identify the major factors which could have a negative influence on the mitigating of the consequences of the abnormal events in NPP. The analyzed events are from CANDU 600 NPP. In order to achieve the analysis of these events the THEP and SPAR-H methods were used. After analyzing the results the actuated equipment, the negative influence factors on the human performance and the dependence levels between the human actions and between the human actions and diagnosis were established. In addition, some recommendations were formulated which could influence positive the human performance on the mitigating of the consequences of the accident sequences in NPP. (authors)
Barrios Rodriguez, Pilar; Dorantes Rodriguez, Ruben J. [Universidad Autonoma Metropolitana Azcapotzalco, Mexico, D.F. (Mexico)
2000-07-01
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.
Improvement of human reliability analysis method for PRA
It is required to refine human reliability analysis (HRA) method by, for example, incorporating consideration for the cognitive process of operator into the evaluation of diagnosis errors and decision-making errors, as a part of the development and improvement of methods used in probabilistic risk assessments (PRAs). JNES has been developed a HRA method based on ATHENA which is suitable to handle the structured relationship among diagnosis errors, decision-making errors and operator cognition process. This report summarizes outcomes obtained from the improvement of HRA method, in which enhancement to evaluate how the plant degraded condition affects operator cognitive process and to evaluate human error probabilities (HEPs) which correspond to the contents of operator tasks is made. In addition, this report describes the results of case studies on the representative accident sequences to investigate the applicability of HRA method developed. HEPs of the same accident sequences are also estimated using THERP method, which is most popularly used HRA method, and comparisons of the results obtained using these two methods are made to depict the differences of these methods and issues to be solved. Important conclusions obtained are as follows: (1) Improvement of HRA method using operator cognitive action model. Clarification of factors to be considered in the evaluation of human errors, incorporation of degraded plant safety condition into HRA and investigation of HEPs which are affected by the contents of operator tasks were made to improve the HRA method which can integrate operator cognitive action model into ATHENA method. In addition, the detail of procedures of the improved method was delineated in the form of flowchart. (2) Case studies and comparison with the results evaluated by THERP method. Four operator actions modeled in the PRAs of representative BWR5 and 4-loop PWR plants were selected and evaluated as case studies. These cases were also evaluated using
Decision theory, the context for risk and reliability analysis
According to this model of the decision process then, the optimum decision is that option having the largest expected utility. This is the fundamental model of a decision situation. It is necessary to remark that in order for the model to represent a real-life decision situation, it must include all the options present in that situation, including, for example, the option of not deciding--which is itself a decision, although usually not the optimum one. Similarly, it should include the option of delaying the decision while the authors gather further information. Both of these options have probabilities, outcomes, impacts, and utilities like any option and should be included explicitly in the decision diagram. The reason for doing a quantitative risk or reliability analysis is always that, somewhere underlying there is a decision to be made. The decision analysis therefore always forms the context for the risk or reliability analysis, and this context shapes the form and language of that analysis. Therefore, they give in this section a brief review of the well-known decision theory diagram
Reliability and risk analysis data base development: an historical perspective
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
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
Reliability and risk analysis using artificial neural networks
Robinson, D.G. [Sandia National Labs., Albuquerque, NM (United States)
1995-12-31
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.
A Research Roadmap for Computation-Based Human Reliability Analysis
Boring, Ronald [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mandelli, Diego [Idaho National Lab. (INL), Idaho Falls, ID (United States); Joe, Jeffrey [Idaho National Lab. (INL), Idaho Falls, ID (United States); Smith, Curtis [Idaho National Lab. (INL), Idaho Falls, ID (United States); Groth, Katrina [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-08-01
The United States (U.S.) Department of Energy (DOE) is sponsoring research through the Light Water Reactor Sustainability (LWRS) program to extend the life of the currently operating fleet of commercial nuclear power plants. The Risk Informed Safety Margin Characterization (RISMC) research pathway within LWRS looks at ways to maintain and improve the safety margins of these plants. The RISMC pathway includes significant developments in the area of thermalhydraulics code modeling and the development of tools to facilitate dynamic probabilistic risk assessment (PRA). PRA is primarily concerned with the risk of hardware systems at the plant; yet, hardware reliability is often secondary in overall risk significance to human errors that can trigger or compound undesirable events at the plant. This report highlights ongoing efforts to develop a computation-based approach to human reliability analysis (HRA). This computation-based approach differs from existing static and dynamic HRA approaches in that it: (i) interfaces with a dynamic computation engine that includes a full scope plant model, and (ii) interfaces with a PRA software toolset. The computation-based HRA approach presented in this report is called the Human Unimodels for Nuclear Technology to Enhance Reliability (HUNTER) and incorporates in a hybrid fashion elements of existing HRA methods to interface with new computational tools developed under the RISMC pathway. The goal of this research effort is to model human performance more accurately than existing approaches, thereby minimizing modeling uncertainty found in current plant risk models.
Limitations in simulator time-based human reliability analysis methods
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
Failure and Reliability Analysis for the Master Pump Shutdown System
BEVINS, R.R.
2000-09-05
The Master Pump Shutdown System (MPSS) will be installed in the 200 Areas of the Hanford Site to monitor and control the transfer of liquid waste between tank farms and between the 200 West and 200 East areas through the Cross-Site Transfer Line. The Safety Function provided by the MPSS is to shutdown any waste transfer process within or between tank farms if a waste leak should occur along the selected transfer route. The MPSS, which provides this Safety Class Function, is composed of Programmable Logic Controllers (PLCs), interconnecting wires, relays, Human to Machine Interfaces (HMI), and software. These components are defined as providing a Safety Class Function and will be designated in this report as MPSS/PLC. Input signals to the MPSS/PLC are provided by leak detection systems from each of the tank farm leak detector locations along the waste transfer route. The combination of the MPSS/PLC, leak detection system, and transfer pump controller system will be referred to as MPSS/SYS. The components addressed in this analysis are associated with the MPSS/SYS. The purpose of this failure and reliability analysis is to address the following design issues of the Project Development Specification (PDS) for the MPSS/SYS (HNF 2000a): (1) Single Component Failure Criterion, (2) System Status Upon Loss of Electrical Power, (3) Physical Separation of Safety Class cables, (4) Physical Isolation of Safety Class Wiring from General Service Wiring, and (5) Meeting the MPSS/PLC Option 1b (RPP 1999) Reliability estimate. The failure and reliability analysis examined the system on a component level basis and identified any hardware or software elements that could fail and/or prevent the system from performing its intended safety function.
Fifty Years of THERP and Human Reliability Analysis
Ronald L. Boring
2012-06-01
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.
Passive system reliability analysis using the APSRA methodology
In this paper, we present a methodology known as APSRA (Assessment of Passive System ReliAbility) for evaluation of reliability of passive systems. The methodology has been applied to the boiling natural circulation system in the Main Heat Transport System of the Indian AHWR concept. In the APSRA methodology, the passive system reliability is evaluated from the evaluation of the failure probability of the system to carryout the desired function. The methodology first determines the operational characteristics of the system and the failure conditions by assigning a predetermined failure criteria. The failure surface is predicted using a best estimate code considering deviations of the operating parameters from their nominal states, which affect the natural circulation performance. Since applicability of the best estimate codes to passive systems are neither proven nor understood enough, APSRA relies more on experimental data for various aspects of natural circulation such as steady-state natural circulation, flow instabilities, CHF under oscillatory condition, etc. APSRA proposes to compare the code predictions with the test data to generate the uncertainties on the failure parameter prediction, which is later considered in the code for accurate prediction of failure surface of the system. Once the failure surface of the system is predicted, the cause of failure is examined through root diagnosis, which occurs mainly due to failure of mechanical components. The failure probability of these components are evaluated through a classical PSA treatment using the generic data. Reliability of the natural circulation system is evaluated from the probability of availability of the components for the success of natural circulation in the system
IDHEAS – A NEW APPROACH FOR HUMAN RELIABILITY ANALYSIS
G. W. Parry; J.A Forester; V.N. Dang; S. M. L. Hendrickson; M. Presley; E. Lois; J. Xing
2013-09-01
This paper describes a method, IDHEAS (Integrated Decision-Tree Human Event Analysis System) that has been developed jointly by the US NRC and EPRI as an improved approach to Human Reliability Analysis (HRA) that is based on an understanding of the cognitive mechanisms and performance influencing factors (PIFs) that affect operator responses. The paper describes the various elements of the method, namely the performance of a detailed cognitive task analysis that is documented in a crew response tree (CRT), and the development of the associated time-line to identify the critical tasks, i.e. those whose failure results in a human failure event (HFE), and an approach to quantification that is based on explanations of why the HFE might occur.
Reliability analysis of structures under periodic proof tests in service
Yang, J.-N.
1976-01-01
A reliability analysis of structures subjected to random service loads and periodic proof tests treats gust loads and maneuver loads as random processes. Crack initiation, crack propagation, and strength degradation are treated as the fatigue process. The time to fatigue crack initiation and ultimate strength are random variables. Residual strength decreases during crack propagation, so that failure rate increases with time. When a structure fails under periodic proof testing, a new structure is built and proof-tested. The probability of structural failure in service is derived from treatment of all the random variables, strength degradations, service loads, proof tests, and the renewal of failed structures. Some numerical examples are worked out.
Reliability analysis of selected systems of nuclear power unit
The reliability analysis is discussed of selected facilities of the 440 MW nuclear power unit using the failure tree method. The first part of the paper deals with the primary circuit and analyses the possibility of a dangerous failure arising of the system of accident alarm of the first order of the WWER 440 nuclear reactor during the event of the ''outage of four and more circulating pumps''. The second part of the paper is related to the secondary circuit. It studies the causes and probabilities of the failures of functions of condensate flow pumping and control with regard to the event the ''turbogenerator failure''. (author)
Human Performance Modeling for Dynamic Human Reliability Analysis
Boring, Ronald Laurids [Idaho National Laboratory; Joe, Jeffrey Clark [Idaho National Laboratory; Mandelli, Diego [Idaho National Laboratory
2015-08-01
Part of the U.S. Department of Energy’s (DOE’s) Light Water Reac- tor Sustainability (LWRS) Program, the Risk-Informed Safety Margin Charac- terization (RISMC) Pathway develops approaches to estimating and managing safety margins. RISMC simulations pair deterministic plant physics models with probabilistic risk models. As human interactions are an essential element of plant risk, it is necessary to integrate human actions into the RISMC risk framework. In this paper, we review simulation based and non simulation based human reliability analysis (HRA) methods. This paper summarizes the founda- tional information needed to develop a feasible approach to modeling human in- teractions in RISMC simulations.
COMPARATIVE ANALYSIS OF CELEBRITY AND NON-CELEBRITY ADVERTISEMENT
Ammar Asad; Muhammad Naseem Hayat; Shafaqat Mehmood
2013-01-01
This study is undertaken to make a comparative analysis of celebrity advertisement and non-celebrity advertisement with respect to attitude toward advertisement, attitude toward brand, purchase intentions, and advertising attributes. For this purpose, a simple random sample of 200 students studying four different disciplines was taken from the Private University in Lahore. For econometric proof, reliability analysis, descriptive analysis, and independent sample T-test was used to interpret th...
Development of distribution system reliability and risk analysis models
Northcote-Green, J. E. D.; Vismor, T. D.; Brooks, C. L.
1981-08-01
The overall objectives of a research project were to: determine distribution reliability assessment methods currently used by the industry; develop a general outage reporting scheme suitable for a wide variety of distributing utilities (reliability model); develop a model for predicting the reliability of future system configurations (risk model); and compile a handbook of reliability assessment methods designed specifically for use by the practicing distribution engineer. Emphasis was placed on compiling and organizing reliability assessment techniques presently used by the industry. The project examined reliability evaluation from two perspectives: historical and predictive assessment. Two reliability assessment models, HISRAM - the historical reliability assessment model and PRAM - the predictive reliability assessment model were developed. Each model was tested in a utility environment by the Duquesne Light Company and the Public Service Electric and Gas Company of New Jersey. A survey of 56 diverse utilities served as a basis for examining current distribution reliability assessment practices in the electric power industry.
Tailoring a Human Reliability Analysis to Your Industry Needs
DeMott, D. L.
2016-01-01
Companies at risk of accidents caused by human error that result in catastrophic consequences include: airline industry mishaps, medical malpractice, medication mistakes, aerospace failures, major oil spills, transportation mishaps, power production failures and manufacturing facility incidents. Human Reliability Assessment (HRA) is used to analyze the inherent risk of human behavior or actions introducing errors into the operation of a system or process. These assessments can be used to identify where errors are most likely to arise and the potential risks involved if they do occur. Using the basic concepts of HRA, an evolving group of methodologies are used to meet various industry needs. Determining which methodology or combination of techniques will provide a quality human reliability assessment is a key element to developing effective strategies for understanding and dealing with risks caused by human errors. There are a number of concerns and difficulties in "tailoring" a Human Reliability Assessment (HRA) for different industries. Although a variety of HRA methodologies are available to analyze human error events, determining the most appropriate tools to provide the most useful results can depend on industry specific cultures and requirements. Methodology selection may be based on a variety of factors that include: 1) how people act and react in different industries, 2) expectations based on industry standards, 3) factors that influence how the human errors could occur such as tasks, tools, environment, workplace, support, training and procedure, 4) type and availability of data, 5) how the industry views risk & reliability, and 6) types of emergencies, contingencies and routine tasks. Other considerations for methodology selection should be based on what information is needed from the assessment. If the principal concern is determination of the primary risk factors contributing to the potential human error, a more detailed analysis method may be employed
Inclusion of fatigue effects in human reliability analysis
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.
Inclusion of fatigue effects in human reliability analysis
Griffith, Candice D. [Vanderbilt University, Nashville, TN (United States); Mahadevan, Sankaran, E-mail: sankaran.mahadevan@vanderbilt.edu [Vanderbilt University, Nashville, TN (United States)
2011-11-15
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.
Reliability analysis and prediction of mixed mode load using Markov Chain Model
The aim of this paper is to present the reliability analysis and prediction of mixed mode loading by using a simple two state Markov Chain Model for an automotive crankshaft. The reliability analysis and prediction for any automotive component or structure is important for analyzing and measuring the failure to increase the design life, eliminate or reduce the likelihood of failures and safety risk. The mechanical failures of the crankshaft are due of high bending and torsion stress concentration from high cycle and low rotating bending and torsional stress. The Markov Chain was used to model the two states based on the probability of failure due to bending and torsion stress. In most investigations it revealed that bending stress is much serve than torsional stress, therefore the probability criteria for the bending state would be higher compared to the torsion state. A statistical comparison between the developed Markov Chain Model and field data was done to observe the percentage of error. The reliability analysis and prediction was derived and illustrated from the Markov Chain Model were shown in the Weibull probability and cumulative distribution function, hazard rate and reliability curve and the bathtub curve. It can be concluded that Markov Chain Model has the ability to generate near similar data with minimal percentage of error and for a practical application; the proposed model provides a good accuracy in determining the reliability for the crankshaft under mixed mode loading
Reliability analysis and prediction of mixed mode load using Markov Chain Model
Nikabdullah, N. [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia and Institute of Space Science (ANGKASA), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (Malaysia); Singh, S. S. K.; Alebrahim, R.; Azizi, M. A. [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (Malaysia); K, Elwaleed A. [Institute of Space Science (ANGKASA), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (Malaysia); Noorani, M. S. M. [School of Mathematical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (Malaysia)
2014-06-19
The aim of this paper is to present the reliability analysis and prediction of mixed mode loading by using a simple two state Markov Chain Model for an automotive crankshaft. The reliability analysis and prediction for any automotive component or structure is important for analyzing and measuring the failure to increase the design life, eliminate or reduce the likelihood of failures and safety risk. The mechanical failures of the crankshaft are due of high bending and torsion stress concentration from high cycle and low rotating bending and torsional stress. The Markov Chain was used to model the two states based on the probability of failure due to bending and torsion stress. In most investigations it revealed that bending stress is much serve than torsional stress, therefore the probability criteria for the bending state would be higher compared to the torsion state. A statistical comparison between the developed Markov Chain Model and field data was done to observe the percentage of error. The reliability analysis and prediction was derived and illustrated from the Markov Chain Model were shown in the Weibull probability and cumulative distribution function, hazard rate and reliability curve and the bathtub curve. It can be concluded that Markov Chain Model has the ability to generate near similar data with minimal percentage of error and for a practical application; the proposed model provides a good accuracy in determining the reliability for the crankshaft under mixed mode loading.
Reliability analysis and prediction of mixed mode load using Markov Chain Model
Nikabdullah, N.; Singh, S. S. K.; Alebrahim, R.; Azizi, M. A.; K, Elwaleed A.; Noorani, M. S. M.
2014-06-01
The aim of this paper is to present the reliability analysis and prediction of mixed mode loading by using a simple two state Markov Chain Model for an automotive crankshaft. The reliability analysis and prediction for any automotive component or structure is important for analyzing and measuring the failure to increase the design life, eliminate or reduce the likelihood of failures and safety risk. The mechanical failures of the crankshaft are due of high bending and torsion stress concentration from high cycle and low rotating bending and torsional stress. The Markov Chain was used to model the two states based on the probability of failure due to bending and torsion stress. In most investigations it revealed that bending stress is much serve than torsional stress, therefore the probability criteria for the bending state would be higher compared to the torsion state. A statistical comparison between the developed Markov Chain Model and field data was done to observe the percentage of error. The reliability analysis and prediction was derived and illustrated from the Markov Chain Model were shown in the Weibull probability and cumulative distribution function, hazard rate and reliability curve and the bathtub curve. It can be concluded that Markov Chain Model has the ability to generate near similar data with minimal percentage of error and for a practical application; the proposed model provides a good accuracy in determining the reliability for the crankshaft under mixed mode loading.
Current Human Reliability Analysis Methods Applied to Computerized Procedures
Ronald L. Boring
2012-06-01
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.
This paper introduces the background and development activities of domestic standardization of procedure and method for Human Reliability Analysis (HRA) to avoid the intervention of subjectivity by HRA analyst in Probabilistic Safety Assessment (PSA) as possible, and the review of the HRA results for domestic nuclear power plants under design studied by Korea Atomic Energy Research Institute. We identify the HRA methods used for PSA for domestic NPPs and discuss the subjectivity of HRA analyst shown in performing a HRA. Also, we introduce the PSA guidelines published in USA and review the HRA results based on them. We propose the system of a standard procedure and method for HRA to be developed
Productivity enhancement and reliability through AutoAnalysis
Garetto, Anthony; Rademacher, Thomas; Schulz, Kristian
2015-09-01
The decreasing size and increasing complexity of photomask features, driven by the push to ever smaller technology nodes, places more and more challenges on the mask house, particularly in terms of yield management and cost reduction. Particularly challenging for mask shops is the inspection, repair and review cycle which requires more time and skill from operators due to the higher number of masks required per technology node and larger nuisance defect counts. While the measurement throughput of the AIMS™ platform has been improved in order to keep pace with these trends, the analysis of aerial images has seen little advancement and remains largely a manual process. This manual analysis of aerial images is time consuming, dependent on the skill level of the operator and significantly contributes to the overall mask manufacturing process flow. AutoAnalysis, the first application available for the FAVOR® platform, offers a solution to these problems by providing fully automated analysis of AIMS™ aerial images. Direct communication with the AIMS™ system allows automated data transfer and analysis parallel to the measurements. User defined report templates allow the relevant data to be output in a manner that can be tailored to various internal needs and support the requests of your customers. Productivity is significantly improved due to the fast analysis, operator time is saved and made available for other tasks and reliability is no longer a concern as the most defective region is always and consistently captured. In this paper the concept and approach of AutoAnalysis will be presented as well as an update to the status of the project. The benefits arising from the use of AutoAnalysis will be discussed in more detail and a study will be performed in order to demonstrate.
Step-stress analysis for predicting dental ceramic reliability
Borba, Márcia; Cesar, Paulo F.; Griggs, Jason A.; Bona, Álvaro Della
2013-01-01
Objective To test the hypothesis that step-stress analysis is effective to predict the reliability of an alumina-based dental ceramic (VITA In-Ceram AL blocks) subjected to a mechanical aging test. Methods Bar-shaped ceramic specimens were fabricated, polished to 1µm finish and divided into 3 groups (n=10): (1) step-stress accelerating test; (2) flexural strength- control; (3) flexural strength- mechanical aging. Specimens from group 1 were tested in an electromagnetic actuator (MTS Evolution) using a three-point flexure fixture (frequency: 2Hz; R=0.1) in 37°C water bath. Each specimen was subjected to an individual stress profile, and the number of cycles to failure was recorded. A cumulative damage model with an inverse power law lifetime-stress relation and Weibull lifetime distribution were used to fit the fatigue data. The data were used to predict the stress level and number of cycles for mechanical aging (group 3). Groups 2 and 3 were tested for three-point flexural strength (σ) in a universal testing machine with 1.0 s in 37°C water. Data were statistically analyzed using Mann-Whitney Rank Sum test. Results Step-stress data analysis showed that the profile most likely to weaken the specimens without causing fracture during aging (95% CI: 0–14% failures) was: 80 MPa stress amplitude and 105 cycles. The median σ values (MPa) for groups 2 (493±54) and 3 (423±103) were statistically different (p=0.009). Significance The aging profile determined by step-stress analysis was effective to reduce alumina ceramic strength as predicted by the reliability estimate, confirming the study hypothesis. PMID:23827018
Reliability and availability requirements analysis for DEMO: fuel cycle system
The Demonstration Power Plant (DEMO) will be a fusion reactor prototype designed to demonstrate the capability to produce electrical power in a commercially acceptable way. Two of the key elements of the engineering development of the DEMO reactor are the definitions of reliability and availability requirements (or targets). The availability target for a hypothesized Fuel Cycle has been analysed as a test case. The analysis has been done on the basis of the experience gained in operating existing tokamak fusion reactors and developing the ITER design. Plant Breakdown Structure (PBS) and Functional Breakdown Structure (FBS) related to the DEMO Fuel Cycle and correlations between PBS and FBS have been identified. At first, a set of availability targets has been allocated to the various systems on the basis of their operating, protection and safety functions. 75% and 85% of availability has been allocated to the operating functions of fuelling system and tritium plant respectively. 99% of availability has been allocated to the overall systems in executing their safety functions. The chances of the systems to achieve the allocated targets have then been investigated through a Failure Mode and Effect Analysis and Reliability Block Diagram analysis. The following results have been obtained: 1) the target of 75% for the operations of the fuelling system looks reasonable, while the target of 85% for the operations of the whole tritium plant should be reduced to 80%, even though all the tritium plant systems can individually reach quite high availability targets, over 90% - 95%; 2) all the DEMO Fuel Cycle systems can reach the target of 99% in accomplishing their safety functions. (authors)
Reliability analysis on a shell and tube heat exchanger
Lingeswara, S.; Omar, R.; Mohd Ghazi, T. I.
2016-06-01
A shell and tube heat exchanger reliability was done in this study using past history data from a carbon black manufacturing plant. The heat exchanger reliability study is vital in all related industries as inappropriate maintenance and operation of the heat exchanger will lead to major Process Safety Events (PSE) and loss of production. The overall heat exchanger coefficient/effectiveness (Uo) and Mean Time between Failures (MTBF) were analyzed and calculated. The Aspen and down time data was taken from a typical carbon black shell and tube heat exchanger manufacturing plant. As a result of the Uo calculated and analyzed, it was observed that the Uo declined over a period caused by severe fouling and heat exchanger limitation. This limitation also requires further burn out period which leads to loss of production. The MTBF calculated is 649.35 hours which is very low compared to the standard 6000 hours for the good operation of shell and tube heat exchanger. The guidelines on heat exchanger repair, preventive and predictive maintenance was identified and highlighted for better heat exchanger inspection and repair in the future. The fouling of heat exchanger and the production loss will be continuous if proper heat exchanger operation and repair using standard operating procedure is not followed.
Deductive tree analysis for evaluating the reliability of construction operations
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
Probabilistic structural analysis methods for improving Space Shuttle engine reliability
Boyce, L.
1989-01-01
Probabilistic structural analysis methods are particularly useful in the design and analysis of critical structural components and systems that operate in very severe and uncertain environments. These methods have recently found application in space propulsion systems to improve the structural reliability of Space Shuttle Main Engine (SSME) components. A computer program, NESSUS, based on a deterministic finite-element program and a method of probabilistic analysis (fast probability integration) provides probabilistic structural analysis for selected SSME components. While computationally efficient, it considers both correlated and nonnormal random variables as well as an implicit functional relationship between independent and dependent variables. The program is used to determine the response of a nickel-based superalloy SSME turbopump blade. Results include blade tip displacement statistics due to the variability in blade thickness, modulus of elasticity, Poisson's ratio or density. Modulus of elasticity significantly contributed to blade tip variability while Poisson's ratio did not. Thus, a rational method for choosing parameters to be modeled as random is provided.
Application of human reliability analysis methodology of second generation
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)
Reliability Analysis of a Glacier Lake Warning System Using a Bayesian Net
Sturny, Rouven A.; Bründl, Michael
2013-04-01
Beside structural mitigation measures like avalanche defense structures, dams and galleries, warning and alarm systems have become important measures for dealing with Alpine natural hazards. Integrating them into risk mitigation strategies and comparing their effectiveness with structural measures requires quantification of the reliability of these systems. However, little is known about how reliability of warning systems can be quantified and which methods are suitable for comparing their contribution to risk reduction with that of structural mitigation measures. We present a reliability analysis of a warning system located in Grindelwald, Switzerland. The warning system was built for warning and protecting residents and tourists from glacier outburst floods as consequence of a rapid drain of the glacier lake. We have set up a Bayesian Net (BN, BPN) that allowed for a qualitative and quantitative reliability analysis. The Conditional Probability Tables (CPT) of the BN were determined according to manufacturer's reliability data for each component of the system as well as by assigning weights for specific BN nodes accounting for information flows and decision-making processes of the local safety service. The presented results focus on the two alerting units 'visual acoustic signal' (VAS) and 'alerting of the intervention entities' (AIE). For the summer of 2009, the reliability was determined to be 94 % for the VAS and 83 % for the AEI. The probability of occurrence of a major event was calculated as 0.55 % per day resulting in an overall reliability of 99.967 % for the VAS and 99.906 % for the AEI. We concluded that a failure of the VAS alerting unit would be the consequence of a simultaneous failure of the four probes located in the lake and the gorge. Similarly, we deduced that the AEI would fail either if there were a simultaneous connectivity loss of the mobile and fixed network in Grindelwald, an Internet access loss or a failure of the regional operations
Folić Radomir
2011-01-01
Full Text Available Large panel residential buildings, dating from second half of 20 Century, are to be found in almost every urban settlement across Europe. Within the context of three case studies of urban blocks in Bulgaria (Mladost - Sofia, Macedonia (Karpos III - Skopje and Serbia (Detelinara - Novi Sad, comparative analysis and evaluation of technical and structural characteristics according to reliability (seismic resistance and fire safety and sustainability (energy efficiency, internal air quality, accessibility criteria has been conducted. Additionally, previous experiences from individual renewal projects are reviewed. Previous experiences and comparative analysis results, could contribute to formulation of wider applicable solutions and development of new urban renewal strategies.
Reliability analysis of repairable system based on GO-FLOW methodology
A quantitative analysis method named GO-FLOW is introduced to analyze the reliability of system with priority in maintenance and the amount of repairman limited. Approximate formulas model that can be applied to the GO-FLOW calculation is derived for the reliability parameters of repairable assembly. Then the model's feasibility is validated, and its error is analyzed. An example of redundancy pump component is presented, and the result achieved by GO-FLOW is compared with that by GO methodology. The results show that GO-FLOW Methodology can be used for quantitative analysis of this sort of repairable system; The model of GO-FLOW is effective and the algorithm is more convenient compared with GO methodology. (authors)
Basic aspects of stochastic reliability analysis for redundancy systems
Much confusion has been created by trying to establish common cause failure (CCF) as an extra phenomenon which has to be treated with extra methods in reliability and data analysis. This paper takes another approach which can be roughly described by the statement that dependent failure is the basic phenomenon, while 'independent failure' refers to a special limiting case, namely the perfectly homogeneous population. This approach is motivated by examples demonstrating that common causes do not lead to dependent failure, so far as physical dependencies like shared components are excluded, and that stochastic dependencies are not related to common causes. The possibility to select more than one failure behaviour from an inhomogeneous population is identified as an additional random process which creates stochastic dependence. However, this source of randomness is usually treated in the deterministic limit, which destroys dependence and hence yields incorrect multiple failure frequencies for redundancy structures, thus creating the need for applying corrective CCF models. (author)
Time-dependent reliability analysis and condition assessment of structures
Ellingwood, B.R. [Johns Hopkins Univ., Baltimore, MD (United States)
1997-01-01
Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process.
Steps of the reliability analysis of NPP-piping
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
Reliability Analysis Using Dimension Reduction Method with Variable Sampling Points
This study provides how the Dimension Reduction (DR) method as an efficient technique for reliability analysis can acquire its increased efficiency when it is applied to highly nonlinear problems. In the highly nonlinear engineering systems, 4N+1 (N: number of random variables) sampling is generally recognized to be appropriate. However, there exists uncertainty concerning the standard for judgment of non-linearity of the system as well as possibility of diverse degrees of non-linearity according to each of the random variables. In this regard, this study judged the linearity individually on each random variable after 2N+1 sampling. If high non-linearity appeared, 2 additional sampling was administered on each random variable to apply the DR method. The applications of the proposed sampling to the examples produced the constant results with increased efficiency
Analogical reasoning for reliability analysis based on generic data
Kozin, Igor O
1996-10-01
The paper suggests using the systemic concept 'analogy' for the foundation of an approach to analyze system reliability on the basis of generic data, describing the method of structuring the set that defines analogical models, an approach of transition from the analogical model to a reliability model and a way of obtaining reliability intervals of analogous objects.
Sociological analysis and comparative education
Woock, Roger R.
1981-12-01
It is argued that comparative education is essentially a derivative field of study, in that it borrows theories and methods from academic disciplines. After a brief humanistic phase, in which history and philosophy were central for comparative education, sociology became an important source. In the mid-50's and 60's, sociology in the United States was characterised by Structural Functionalism as a theory, and Social Survey as a dominant methodology. Both were incorporated into the development of comparative education. Increasingly in the 70's, and certainly today, the new developments in sociology are characterised by an attack on Positivism, which is seen as the philosophical position underlying both functionalism and survey methods. New or re-discovered theories with their attendant methodologies included Marxism, Phenomenological Sociology, Critical Theory, and Historical Social Science. The current relationship between comparative education and social science is one of uncertainty, but since social science is seen to be returning to its European roots, the hope is held out for the development of an integrated social theory and method which will provide a much stronger basis for developments in comparative education.
Folić Radomir; Laban Mirjana; Milanko Verica
2011-01-01
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, ...
A reliability analysis of the revised competitiveness index.
Harris, Paul B; Houston, John M
2010-06-01
This study examined the reliability of the Revised Competitiveness Index by investigating the test-retest reliability, interitem reliability, and factor structure of the measure based on a sample of 280 undergraduates (200 women, 80 men) ranging in age from 18 to 28 years (M = 20.1, SD = 2.1). The findings indicate that the Revised Competitiveness Index has high test-retest reliability, high inter-item reliability, and a stable factor structure. The results support the assertion that the Revised Competitiveness Index assesses competitiveness as a stable trait rather than a dynamic state. PMID:20712175
Models and data requirements for human reliability analysis
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
Bayesian networks inference algorithm to implement Dempster Shafer theory in reliability analysis
This paper deals with the use of Bayesian networks to compute system reliability. The reliability analysis problem is described and the usual methods for quantitative reliability analysis are presented within a case study. Some drawbacks that justify the use of Bayesian networks are identified. The basic concepts of the Bayesian networks application to reliability analysis are introduced and a model to compute the reliability for the case study is presented. Dempster Shafer theory to treat epistemic uncertainty in reliability analysis is then discussed and its basic concepts that can be applied thanks to the Bayesian network inference algorithm are introduced. Finally, it is shown, with a numerical example, how Bayesian networks' inference algorithms compute complex system reliability and what the Dempster Shafer theory can provide to reliability analysis
Reliability improvement of robotics systems: Analysis, design and real time supervision
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
In Part II of this work, the adjoint sensitivity analysis procedure developed in Part I is applied to perform sensitivity analysis of several dynamic reliability models of systems of increasing complexity, culminating with the consideration of the International Fusion Materials Irradiation Facility (IFMIF) accelerator system. Section II presents the main steps of a procedure for the automated generation of Markov chains for reliability analysis, including the abstraction of the physical system, construction of the Markov chain, and the generation and solution of the ensuing set of differential equations; all of these steps have been implemented in a stand-alone computer code system called QUEFT/MARKOMAG-S/MCADJSEN. This code system has been applied to sensitivity analysis of dynamic reliability measures for a paradigm '2-out-of-3' system comprising five components and also to a comprehensive dynamic reliability analysis of the IFMIF accelerator system facilities for the average availability and, respectively, the system's availability at the final mission time. The QUEFT/MARKOMAG-S/MCADJSEN has been used to efficiently compute sensitivities to 186 failure and repair rates characterizing components and subsystems of the first-level fault tree of the IFMIF accelerator system. (authors)
The reliability of mercury analysis in environmental materials
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
Peters, Valerie A.; Ogilvie, Alistair; Veers, Paul S.
2009-09-01
This report addresses the general data requirements for reliability analysis of fielded wind turbines and other wind plant equipment. The report provides a list of the data needed to support reliability and availability analysis, and gives specific recommendations for a Computerized Maintenance Management System (CMMS) to support automated analysis. This data collection recommendations report was written by Sandia National Laboratories to address the general data requirements for reliability analysis of fielded wind turbines. This report is intended to help the reader develop a basic understanding of what data are needed from a Computerized Maintenance Management System (CMMS) and other data systems, for reliability analysis. The report provides: (1) a list of the data needed to support reliability and availability analysis; and (2) specific recommendations for a CMMS to support automated analysis. Though written for reliability analysis of wind turbines, much of the information is applicable to a wider variety of equipment and a wider variety of analysis and reporting needs.
Reliability analysis of the service water system of Angra 1 reactor
A reliability analysis of the service water system is done aiming to use in the evaluation of the non reliability of the Component Cooling System (SRC) for great loss of cooling accidents in nuclear power plants. (E.G.)
An Intelligent Method for Structural Reliability Analysis Based on Response Surface
桂劲松; 刘红; 康海贵
2004-01-01
As water depth increases, the structural safety and reliability of a system become more and more important and challenging. Therefore, the structural reliability method must be applied in ocean engineering design such as offshore platform design. If the performance function is known in structural reliability analysis, the first-order second-moment method is often used. If the performance function could not be definitely expressed, the response surface method is always used because it has a very clear train of thought and simple programming. However, the traditional response surface method fits the response surface of quadratic polynomials where the problem of accuracy could not be solved, because the true limit state surface can be fitted well only in the area near the checking point. In this paper, an intelligent computing method based on the whole response surface is proposed, which can be used for the situation where the performance function could not be definitely expressed in structural reliability analysis. In this method, a response surface of the fuzzy neural network for the whole area should be constructed first, and then the structural reliability can be calculated by the genetic algorithm. In the proposed method, all the sample points for the training network come from the whole area, so the true limit state surface in the whole area can be fitted. Through calculational examples and comparative analysis, it can be known that the proposed method is much better than the traditional response surface method of quadratic polynomials, because, the amount of calculation of finite element analysis is largely reduced, the accuracy of calculation is improved,and the true limit state surface can be fitted very well in the whole area. So, the method proposed in this paper is suitable for engineering application.
RELIABILITY ANALYSIS OF BIDDERS AND THEIR TENDER OFFERS CONCERNING EXECUTION OF CONSTRUCTION WORKS
Galkina Elena Vladislavovna
2016-06-01
Full Text Available In the article the reliability analysis methods of bidders and their tenders offers for implementation of construction works are offered. The special attention is focused on the complexity of these processes and the necessity of participation of serious, professional and responsible executors. Application of the described methods leads to a conclusion on the decrease of risks related to selection of a participant of a construction pro-ject. In the article the main stages of the implementation procedure are defined. That allows considering the economic state of applicants, and both economic and technical indicators of tender offers’ reliability. The main characteristics to be considered on each stage are revealed. The author makes a conclusion that the reliability of bidders is determined by the comparison of their economic states with the capacities for implementation of the orders with the specified characteristics. According to the terminology of the article, the reliability of applicant’s of-fers is the ability to execute orders on the bidder’s own conditions. In addition the author states that determining the reliability is based on the comparison of tender offers and contender’s characteristics of objects. The rational methods to compare economic indicators are offered. Along with this, it was found out that at the current moment the method of comparing the technical indicators for the projects-analogues with the indicators of a bidder’s object is not formalized. It limits the application of this method. Finally, it was concluded that the development of the methods applied to technical indicators provided a coherent system for evaluating the reliability of the construction bidders and their offers. It allows creating the basis for the development of appropriate automated system that can be used both for selection of competitive organizations and for preparation of offers by the applicants.
Evaluation of ATHEANA methodology a second generation human reliability analysis
Incidents and accidents at nuclear power plants (NPP) have been and always will be considered as undesired occurrences. Human error (REASON, 1990) is probably the major contributor to serious accidents as those that occurred at Three Mile Island NPP, Unit 2 (TMI-2), in 1979, and Chernobyl, Unit 4, in 1986, and (AEOD/E95-01, 1995 at others NPPs. Reviews and analysis of those accidents and others near-misses have shown operators performing actions that are not required for the accident response and, in fact, worsen the plant's condition. This action, where a person does something that it's not supposed to do, believing that it was the right thing to do, resulting in changes in the plant that may be worse than if he had done nothing, is called Error of Commission (EOC). These inappropriate actions are rightly affected (NUREG-1624, Rev.1, 2000) by the off-normal context (i.e., the combination of plant conditions and performance shaping factors) of the event scenario that virtually forces the operator to fail. Considering that this kind of human intervention could be an important failure mode and precursor to more serious events, aggravated by the fact that actual probabilistic risk assessment (PRA), does not consider this kind of error, a new methodology (NUREG-1624, Rev.1, 2000) was developed of Human Reliability Analysis (HRA), called 'A Technique for Human Event Analysis' (ATHEANA). ATHEANA is a multidisciplinary second-generation HRA method and provides an HRA quantification process and PRA modeling interface that can accommodate and represent human performance in real nuclear power plant accidents. This paper presents this new methodology in order to identified its weak and strong points, to evaluate its advantages and disadvantages and its benefits to safety, and finally, to analyze its application to Angra NPP. (author)
Evaluation of pharmaceuticals in surface water: reliability of PECs compared to MECs.
Celle-Jeanton, Hélène; Schemberg, Dimitri; Mohammed, Nabaz; Huneau, Frédéric; Bertrand, Guillaume; Lavastre, Véronique; Le Coustumer, Philippe
2014-12-01
Due to the current analytical processes that are not able to measure all the pharmaceutical molecules and to the high costs and the consumption of time to sample and analyze PhACs, models to calculate Predicted Environmental Concentrations (PECs) have been developed. However a comparison between MECs and PECs, taking into account the methods of calculations and peculiarly the parameters included in the calculation (consumption data, pharmacokinetic parameters, elimination rate in STPs and in the environment), is necessary to assess the validity of PECs. MEC variations of sixteen target PhACs [acetaminophen (ACE), amlodipine (AML), atenolol (ATE), caffeine (CAF), carbamazepine (CAR), doxycycline (DOX), epoxycarbamazepine (EPO), fluvoxamine (FLU), furosemide (FUR), hydrochlorothiazide (HYD), ifosfamide (IFO), losartan (LOS), pravastatin (PRA), progesterone (PROG), ramipril (RAM), trimetazidine (TRI)] have been evaluated during one hydrological cycle, from October 2011 to October 2012 and compared to PECs calculated by using an adaptation of the models proposed by Heberer and Feldmann (2005) and EMEA (2006). Comparison of PECs and MECS has been achieved for six molecules: ATE, CAR, DOX, FUR, HYD and PRA. DOX, FUR and HYD present differences between PECs and MECs on an annual basis but their temporal evolutions follow the same trends. PEC evaluation for these PhACs could then be possible but need some adjustments of consumption patterns, pharmacokinetic parameters and/or mechanisms of (bio)degradation. ATE, CAR and PRA are well modeled; PECs can then be used as reliable estimation of concentrations without any reserve. PMID:25080069
Architecture for Interlock Systems Reliability Analysis with Regard to Safety and Availability
Wagner, S; Schmidt, R; Zerlauth, M; Vergara-Fernandez, A
2011-01-01
In the design of interlock loops for the signal exchange in machine protection systems, the choice of the hardware architecture impacts on machine safety and availability. The reliable performance of a machine stop (leaving the machine in a safe state) in case of an emergency, is an inherent requirement. The constraints in terms of machine availability on the other hand may differ from one facility to another. Spurious machine stops, lowering machine availability, may to a certain extent be tolerated in facilities where they do not cause undue equipment wearout. In order to compare various interlock loop architectures in terms of safety and availability, the occurrence frequencies of related scenarios have been calculated in a reliability analysis, using a generic analytical model. This paper presents the results and illustrates the potential of the analysis method for supporting the choice of interlock system architectures.
Procedure for conducting a human-reliability analysis for nuclear power plants. Final report
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
Wind turbine reliability : a database and analysis approach.
Linsday, James (ARES Corporation); Briand, Daniel; Hill, Roger Ray; Stinebaugh, Jennifer A.; Benjamin, Allan S. (ARES Corporation)
2008-02-01
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.
Potential Improvements in Human Reliability Analysis for Fire Risk Assessments
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)
Monte Carlo methods for the reliability analysis of Markov systems
This paper presents Monte Carlo methods for the reliability analysis of Markov systems. Markov models are useful in treating dependencies between components. The present paper shows how the adjoint Monte Carlo method for the continuous time Markov process can be derived from the method for the discrete-time Markov process by a limiting process. The straightforward extensions to the treatment of mean unavailability (over a time interval) are given. System unavailabilities can also be estimated; this is done by making the system failed states absorbing, and not permitting repair from them. A forward Monte Carlo method is presented in which the weighting functions are related to the adjoint function. In particular, if the exact adjoint function is known then weighting factors can be constructed such that the exact answer can be obtained with a single Monte Carlo trial. Of course, if the exact adjoint function is known, there is no need to perform the Monte Carlo calculation. However, the formulation is useful since it gives insight into choices of the weight factors which will reduce the variance of the estimator
Analysis of reliability centered maintenance for service water system in nuclear power plants
Reliability centered maintenance (RCM) methodology has been applied to a service water system in AP1000 nuclear power plant. Using the functional failure modes and effect analysis (FMEA) and logic tree analysis (LTA), the optimized maintenance strategy is established based on a better understanding of the relevant information on this system and related equipments (including the functional failures, failure modes and effects)conclude. Compared with the current maintenance strategy, this maintenance strategy optimized by RCM conducts the condition monitoring and periodical maintenance for dominant failures but conducts periodical test for the recessive failures. (authors)
RENT CONTROL: A COMPARATIVE ANALYSIS
Sue-Mari Maass
2012-11-01
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
Gernand, Jeffrey L.; Gillespie, Amanda M.; Monaghan, Mark W.; Cummings, Nicholas H.
2010-01-01
Success of the Constellation Program's lunar architecture requires successfully launching two vehicles, Ares I/Orion and Ares V/Altair, in a very limited time period. The reliability and maintainability of flight vehicles and ground systems must deliver a high probability of successfully launching the second vehicle in order to avoid wasting the on-orbit asset launched by the first vehicle. The Ground Operations Project determined which ground subsystems had the potential to affect the probability of the second launch and allocated quantitative availability requirements to these subsystems. The Ground Operations Project also developed a methodology to estimate subsystem reliability, availability and maintainability to ensure that ground subsystems complied with allocated launch availability and maintainability requirements. The verification analysis developed quantitative estimates of subsystem availability based on design documentation; testing results, and other information. Where appropriate, actual performance history was used for legacy subsystems or comparative components that will support Constellation. The results of the verification analysis will be used to verify compliance with requirements and to highlight design or performance shortcomings for further decision-making. This case study will discuss the subsystem requirements allocation process, describe the ground systems methodology for completing quantitative reliability, availability and maintainability analysis, and present findings and observation based on analysis leading to the Ground Systems Preliminary Design Review milestone.
An efficient phased mission reliability analysis for autonomous vehicles
Remenyte-Prescott, R., E-mail: R.Remenyte-Prescott@nottingham.ac.u [Nottingham Transportation Engineering Centre, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Andrews, J.D. [Nottingham Transportation Engineering Centre, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Chung, P.W.H. [Department of Computer Science, Loughborough University, Loughborough LE11 3TU (United Kingdom)
2010-03-15
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.
An efficient phased mission reliability analysis for autonomous vehicles
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.
Muhammad Hashim
2013-04-01
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.
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
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
Sardi, Adacilis Ramirez; Lamoureux, Julie A; Cohn, Tanya M; Phillip-Samuel, Shirley G
2016-01-01
Traditionally, troponin levels are measured in the blood using an automated laboratory protocol, but the use of a faster technology, the point-of-care (POC) testing of troponin levels, has shown promise in the effective differential diagnosis of cardiac injury. The purpose of this study was to compare the 2 methods. A total of 1567 patients were seen in the emergency department who were tested with both the POC iSTAT troponin and laboratory troponin from a secondary analysis of retrospective data collected between June 2012 and December 2012. The values for laboratory troponin varied between 0 and 30 with a mean and standard deviation of 0.060 ± 0.842 and the values for POC testing varied between 0 and 17.2 with a mean and standard deviation of 0.042 ± 0.492. The Bland-Altman analysis showed a systematic negative bias for the POC values compared with the laboratory troponin values. Lowering the POC cut-off value for troponin to 0.035 yielded 3 out of 4 better validity coefficients compared with those with the suggested manufacturer's cut-off value of 0.08 when predicting the gold standard. The POC troponin can be used to measure troponin level and similar diagnosis if the cut-off value for the POC troponin is lowered to 0.035 instead of the 0.08 suggested manufacturer's cut-off. PMID:27575797
Wind turbine reliability, how does it compare with other embedded generation sources.
Tavner, P.J.; Xiang, J. P.
2005-01-01
Wind turbines are being introduced into the distribution and transmission networks of Europe in increasing numbers. Their reliability has become a factor in network reliability. This has been exemplified by a report from Germany about the reserve necessary to maintain a secure supply with high levels of wind-powered generation in the system. Some difficulty arises because of the variable nature of the wind resource but some is attributable to the unreliability of wind turbines as power source...
Reliability model analysis and primary experimental evaluation of laser triggered pulse trigger
High performance pulse trigger can enhance performance and stability of the PPS. It is necessary to evaluate the reliability of the LTGS pulse trigger, so we establish the reliability analysis model of this pulse trigger based on CARMES software, the reliability evaluation is accord with the statistical results. (authors)
Reliability and Creep/Fatigue Analysis of a CMC Component
Murthy, Pappu L. N.; Mital, Subodh K.; Gyekenyesi, John Z.; Gyekenyesi, John P.
2007-01-01
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.
Mission reliability analysis of fault-tolerant multiple-phased systems
Fault-tolerant multiple-phased systems (FTMPS) are defined as systems whose critical components are independently replicated and whose operational life can be partitioned into a set of disjoint periods, called 'phases'. Because of their deployment in critical applications, their mission reliability analysis is a task of primary relevance to validate the designs. This paper is focused on the reliability analysis of FTMPS with random phase durations, non-exponentially distributed repair activities and different repair policies. For self-repairable FTMPS with a component-level reconfiguration architecture, we derive several efficient formulations from the underlying structure characteristics for their intraphase behavior analysis. We also present a uniform solution framework of the mission reliability for FTMPS with generally distributed phase durations. Compared with existing methods based on deterministic and stochastic Petri nets or Markov regenerative stochastic Petri nets, our approach is more simple in concept and powerful in computation. Two examples of FTMPS are analyzed to illustrate the advantages of our approach
Mission reliability analysis of fault-tolerant multiple-phased systems
Mo Yuchang [Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)], E-mail: myc@ftcl.hit.edu.cn; Siewiorek, Daniel [Department of Computer Science and Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Yang Xiaozong [Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)
2008-07-15
Fault-tolerant multiple-phased systems (FTMPS) are defined as systems whose critical components are independently replicated and whose operational life can be partitioned into a set of disjoint periods, called 'phases'. Because of their deployment in critical applications, their mission reliability analysis is a task of primary relevance to validate the designs. This paper is focused on the reliability analysis of FTMPS with random phase durations, non-exponentially distributed repair activities and different repair policies. For self-repairable FTMPS with a component-level reconfiguration architecture, we derive several efficient formulations from the underlying structure characteristics for their intraphase behavior analysis. We also present a uniform solution framework of the mission reliability for FTMPS with generally distributed phase durations. Compared with existing methods based on deterministic and stochastic Petri nets or Markov regenerative stochastic Petri nets, our approach is more simple in concept and powerful in computation. Two examples of FTMPS are analyzed to illustrate the advantages of our approach.
Automated migration analysis based on cell texture: method & reliability
Chittenden Thomas W
2005-03-01
Full Text Available 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 indicates the front lines of cell migration superimposed on each original image, with automated reporting of the distance traversed vs. time. Expert preference compares to manual placement of leading edge shows complete equivalence of automated vs. manual leading edge definition for cell migration measurement. Conclusion Our method is indistinguishable from careful manual determinations of cell front lines, with the advantages of full automation, objectivity, and speed.
Development of Markov model of emergency diesel generator for dynamic reliability analysis
Jin, Young Ho; Choi, Sun Yeong; Yang, Joon Eon [Korea Atomic Energy Research Institute, Taejon (Korea)
1999-02-01
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.
RELIABILITY ANALYSIS OF THE PRIMARY CYLINDER OF THE 10 MN HYDRAULIC PRESS
Zhao Jingyi; Zhuoru; Wang Yiqun
2000-01-01
According to the demand of high reliability of the primary cylinder of the hydraulic press,the reliability model of the primary cylinder is built after its reliability analysis.The stress of the primary cylinder is analyzed by finite element software-MARC,and the structure reliability of the cylinder based on stress-strength model is predicted,which would provide the reference to the design.
RELIABILITY ANALYSIS FOR AN AERO ENGINE TURBINE DISK UNDER LOW CYCLE FATIGUE CONDITION
C.L. Liu; Z.Z. Lü; Y.L. Xu
2004-01-01
Reliability analysis methods based on the linear damage accumulation law (LDAL) and load-life interference model are studied in this paper. According to the equal probability rule, the equivalent loads are derived, and the reliability analysis method based on load-life interference model and recurrence formula is constructed. In conjunction with finite element analysis (FEA) program, the reliability of an aero engine turbine disk under low cycle fatigue (LCF) condition has been analyzed. The results show the turbine disk is safety and the above reliability analysis methods are feasible.
Reliability analysis of the recirculation phase of the safety injection system of Angra-1
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)
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
NIMARA, S.
2016-02-01
Full Text Available This paper proposes data-dependent reliability evaluation methodology for digital systems described at Register Transfer Level (RTL. It uses a hybrid hierarchical approach, combining the accuracy provided by Gate Level (GL Simulated Fault Injection (SFI and the low simulation overhead required by RTL fault injection. The methodology comprises the following steps: the correct simulation of the RTL system, according to a set of input vectors, hierarchical decomposition of the system into basic RTL blocks, logic synthesis of basic RTL blocks, data-dependent SFI for the GL netlists, and RTL SFI. The proposed methodology has been validated in terms of accuracy on a medium sized circuit – the parallel comparator used in Check Node Unit (CNU of the Low-Density Parity-Check (LDPC decoders. The methodology has been applied for the reliability analysis of a 128-bit Advanced Encryption Standard (AES crypto-core, for which the GL simulation was prohibitive in terms of required computational resources.
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
Lee, Alice T.; Gunn, Todd; Pham, Tuan; Ricaldi, Ron
1994-01-01
This handbook documents the three software analysis processes the Space Station Software Analysis team uses to assess space station software, including their backgrounds, theories, tools, and analysis procedures. Potential applications of these analysis results are also presented. The first section describes how software complexity analysis provides quantitative information on code, such as code structure and risk areas, throughout the software life cycle. Software complexity analysis allows an analyst to understand the software structure, identify critical software components, assess risk areas within a software system, identify testing deficiencies, and recommend program improvements. Performing this type of analysis during the early design phases of software development can positively affect the process, and may prevent later, much larger, difficulties. The second section describes how software reliability estimation and prediction analysis, or software reliability, provides a quantitative means to measure the probability of failure-free operation of a computer program, and describes the two tools used by JSC to determine failure rates and design tradeoffs between reliability, costs, performance, and schedule.
Reliability Analysis Multiple Redundancy Controller for Nuclear Safety Systems
Son, Gwangseop; Kim, Donghoon; Son, Choulwoong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-05-15
This controller is configured for multiple modular redundancy (MMR) composed of dual modular redundancy (DMR) and triple modular redundancy (TMR). The architecture of MRC is briefly described, and the Markov model is developed. Based on the model, the reliability and Mean Time To Failure (MTTF) are analyzed. In this paper, the architecture of MRC for nuclear safety systems is described. The MRC is configured for multiple modular redundancy (MMR) composed of dual modular redundancy (DMR) and triple modular redundancy (TMR). Markov models for MRC architecture was developed, and then the reliability was analyzed by using the model. From the reliability analyses for the MRC, it is obtained that the failure rate of each module in the MRC should be less than 2 Χ 10{sup -4}/hour and the MTTF average increase rate depending on FCF increment, i. e. ΔMTTF/ΔFCF, is 4 months/0.1.
Embedded mechatronic systems 1 analysis of failures, predictive reliability
El Hami, Abdelkhalak
2015-01-01
In operation, mechatronics embedded systems are stressed by loads of different causes: climate (temperature, humidity), vibration, electrical and electromagnetic. These stresses in components which induce failure mechanisms should be identified and modeled for better control. AUDACE is a collaborative project of the cluster Mov'eo that address issues specific to mechatronic reliability embedded systems. AUDACE means analyzing the causes of failure of components of mechatronic systems onboard. The goal of the project is to optimize the design of mechatronic devices by reliability. The projec
Reliability modeling and analysis of smart power systems
Karki, Rajesh; Verma, Ajit Kumar
2014-01-01
The volume presents the research work in understanding, modeling and quantifying the risks associated with different ways of implementing smart grid technology in power systems in order to plan and operate a modern power system with an acceptable level of reliability. Power systems throughout the world are undergoing significant changes creating new challenges to system planning and operation in order to provide reliable and efficient use of electrical energy. The appropriate use of smart grid technology is an important drive in mitigating these problems and requires considerable research acti
Application of GO methodology for reliability analysis of repairable system
GO methodology is a method of system reliability with success-oriented, it has been applied in non-repairable system. The author studies application of GO methodology in repairable system. Considering dependence of components, the quantitative formulas of some GO operations for repairable system have been derived. According to this study, the GO program has been developed. Reliability parameters such as steady availability and failure number can be calculated directly from GO figure and a High Pressure Injection System of Nuclear Power Plant example is given. The study is available for developing and application of GO methodology in repairable system such as nuclear engineering pipeline systems or chemical process systems
Technical information report: Plasma melter operation, reliability, and maintenance analysis
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
Lund, Hans; Søndergaard, K; Zachariassen, T;
2005-01-01
The aim of this study was to examine the learning effect during a set of isokinetic measurements, to evaluate the reliability of the Biodex System 3 PRO dynamometer, and to compare the Biodex System 3 PRO and the Lido Active dynamometers on both extension and flexion over the elbow and the knee at...... interval. When comparing the first five measurements (Biodex), no systematic effect over time and an excellent reliability were found with respect to elbow and knee flexion and extension. No difference in muscle strength (Nm) between the Biodex and Lido was observed for knee flexion (P = 0.59), knee...... extension (P = 0.18) and elbow extension (P = 0.63). However, elbow flexion showed a 14.8% (95% CI: 11.2-18.4%; P = 0.0001) higher peak torque on Biodex. In conclusion, no learning effect was observed and the Biodex proved to be a highly reliable isokinetic dynamometer. A difference was observed when...
Brunham Robert C
2004-07-01
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 β 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.
Bruce Weaver
2014-09-01
Full Text Available Missing data is a frequent problem for researchers conducting exploratory factor analysis (EFA or reliability analysis. The SPSS FACTOR procedure allows users to select listwise deletion, pairwise deletion or mean substitution as a method for dealing with missing data. The shortcomings of these methods are well-known. Graham (2009 argues that a much better way to deal with missing data in this context is to use a matrix of expectation maximization (EM covariances(or correlations as input for the analysis. SPSS users who have the Missing Values Analysis add-on module can obtain vectors ofEM means and standard deviations plus EM correlation and covariance matrices via the MVA procedure. But unfortunately, MVA has no /MATRIX subcommand, and therefore cannot write the EM correlations directly to a matrix dataset of the type needed as input to the FACTOR and RELIABILITY procedures. We describe two macros that (in conjunction with an intervening MVA command carry out the data management steps needed to create two matrix datasets, one containing EM correlations and the other EM covariances. Either of those matrix datasets can then be used asinput to the FACTOR procedure, and the EM correlations can also be used as input to RELIABILITY. We provide an example that illustrates the use of the two macros to generate the matrix datasets and how to use those datasets as input to the FACTOR and RELIABILITY procedures. We hope that this simple method for handling missing data will prove useful to both students andresearchers who are conducting EFA or reliability analysis.
Reliability analysis of common hazardous waste treatment processes
Waters, R.D. [Vanderbilt Univ., Nashville, TN (United States)
1993-05-01
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.
Reliability Analysis of Timber Structures through NDT Data Upgrading
Sousa, Hélder; Sørensen, John Dalsgaard; Kirkegaard, Poul Henning
robustness are dealt in chapter 5. The second part of this document begins in chapter 6, where a practical application of the premise definitions and methodologies is given through the implementation of upgraded models with NDT and MDT data. Structural life-cycle is, therefore, assessed and reliability and...
Statistical Analysis of Human Reliability of Armored Equipment
LIU Wei-ping; CAO Wei-guo; REN Jing
2007-01-01
Human errors of seven types of armored equipment, which occur during the course of field test, are statistically analyzed. The human error-to-armored equipment failure ratio is obtained. The causes of human errors are analyzed. The distribution law of human errors is acquired. The ratio of human errors and human reliability index are also calculated.
Architecture-Based Reliability Analysis of Web Services
Rahmani, Cobra Mariam
2012-01-01
In a Service Oriented Architecture (SOA), the hierarchical complexity of Web Services (WS) and their interactions with the underlying Application Server (AS) create new challenges in providing a realistic estimate of WS performance and reliability. The current approaches often treat the entire WS environment as a black-box. Thus, the sensitivity…
Windfarm Generation Assessment for ReliabilityAnalysis of Power Systems
Negra, Nicola Barberis; Holmstrøm, Ole; Bak-Jensen, Birgitte; Sørensen, Poul
2007-01-01
Due to the fast development of wind generation in the past ten years, increasing interest has been paid to techniques for assessing different aspects of power systems with a large amount of installed wind generation. One of these aspects concerns power system reliability. Windfarm modelling plays a...
Windfarm Generation Assessment for Reliability Analysis of Power Systems
Barberis Negra, Nicola; Bak-Jensen, Birgitte; Holmstrøm, O.; Sørensen, P.
2007-01-01
Due to the fast development of wind generation in the past ten years, increasing interest has been paid to techniques for assessing different aspects of power systems with a large amount of installed wind generation. One of these aspects concerns power system reliability. Windfarm modelling plays a...
Windfarm generation assessment for reliability analysis of power systems
Negra, N.B.; Holmstrøm, O.; Bak-Jensen, B.; Sørensen, Poul Ejnar
2007-01-01
Due to the fast development of wind generation in the past ten years, increasing interest has been paid to techniques for assessing different aspects of power systems with a large amount of installed wind generation. One of these aspects concerns power system reliability. Windfarm modelling plays a...
Reliability analysis of common hazardous waste treatment processes
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
Megan E McCool
Full Text Available Patients actively seek information about how to cope with their health problems, but the quality of the information available varies. A number of instruments have been developed to assess the quality of patient information, primarily though in English. Little is known about the reliability of these instruments when applied to patient information in German. The objective of our study was to investigate and compare the reliability of two validated instruments, DISCERN and EQIP, in order to determine which of these instruments is better suited for a further study pertaining to the quality of information available to German patients with eczema. Two independent raters evaluated a random sample of 20 informational brochures in German. All the brochures addressed eczema as a disorder and/or therapy options and care. Intra-rater and inter-rater reliability were assessed by calculating intra-class correlation coefficients, agreement was tested with weighted kappas, and the correlation of the raters' scores for each instrument was measured with Pearson's correlation coefficient. DISCERN demonstrated substantial intra- and inter-rater reliability. It also showed slightly better agreement than EQIP. There was a strong correlation of the raters' scores for both instruments. The findings of this study support the reliability of both DISCERN and EQIP. However, based on the results of the inter-rater reliability, agreement and correlation analyses, we consider DISCERN to be the more precise tool for our project on patient information concerning the treatment and care of eczema.
Fazeli, Seyed Hossein
2010-01-01
The purpose of research described in the current study is the psychological reliability, its importance, application, and more to investigate on the impact analysis of psychological reliability of population pilot study for selection of particular reliable multi-choice item test in foreign language research work. The population for subject…
A study of annunciator response model application in human reliability analysis
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)
Hartigan, Irene
2011-02-01
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.
Reliability importance analysis of Markovian systems at steady state using perturbation analysis
Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity analysis remains widely open. In this paper, the perturbation method is used to estimate an importance factor, called multi-directional sensitivity measure, in the framework of Markovian systems. Some numerical examples are introduced to show why this method offers a promising tool for steady-state sensitivity analysis of Markov processes in reliability studies
Reliability Analysis and Standardization of Spacecraft Command Generation Processes
Meshkat, Leila; Grenander, Sven; Evensen, Ken
2011-01-01
center dot In order to reduce commanding errors that are caused by humans, we create an approach and corresponding artifacts for standardizing the command generation process and conducting risk management during the design and assurance of such processes. center dot The literature review conducted during the standardization process revealed that very few atomic level human activities are associated with even a broad set of missions. center dot Applicable human reliability metrics for performing these atomic level tasks are available. center dot The process for building a "Periodic Table" of Command and Control Functions as well as Probabilistic Risk Assessment (PRA) models is demonstrated. center dot The PRA models are executed using data from human reliability data banks. center dot The Periodic Table is related to the PRA models via Fault Links.
Reliability Analysis of Public Survey in Satisfaction with Nuclear Safety
Korea Institute of Nuclear Safety (KINS) carried out a questionnaire survey on public's understanding nuclear safety and regulation in order to grasp public acceptance for nuclear energy. The survey was planned to help to analyze public opinion on nuclear energy and provide basic data for advertising strategy and policy development. In this study, based on results of the survey, the reliability of the survey was evaluated according to each nuclear site
Intrinsic Geometric Analysis of the Network Reliability and Voltage Stability
Gupta, N.; Tiwari, B N; S. Bellucci
2010-01-01
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 pr...
Intrinsic Geometric Analysis of the Network Reliability and Voltage Stability
Gupta, N; Bellucci, S
2010-01-01
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.
ANALYSIS OF INDICATORS OF RELIABILITY OF ELECTRICAL NETWORKS
Popescu V.
2012-01-01
Problems of the optimization reliability in electrical networks of the different class of voltage have probabilistic nature, they discretely change and depend on the number of factors both definite and indefinite and have importance by selection of electric equipment, graph of development of electrical networks and voltage levels. The definition of the major factors, which have determining significance on their value and speed of their change allow to elaborate methods of their optimization a...
Reliability Analysis of Monopile Foundations for Offshore Wind Turbines
Depina, Ivan
2016-01-01
Initiated by the increasing energy demands and instabilities in oil and gas prices there is an ongoing transition from the conventional to the renewable energy sources across Europe. The goal is to satisfy 20% of the energy demands with the renewable energy sources by 2020. In order to achieve this goal there is a continuous development of reliable and cost-efficient renewable energy sources. One of the renewable energy sources with a considerable potential is the offshore wind energy. The of...
Analysis of Transmission Methods for Ultra-Reliable Communications
Shariatmadari, Hamidreza; Iraji, Sassan; Jäntti, Riku
2015-01-01
Fifth generation of cellular systems is expected to widely enable machine-type communications (MTC). The envisioned applications and services for MTC have diverse requirements which are not fully supported with current wireless systems. Ultra-reliable communications (URC) with low-latency is an essential feature for mission-critical applications, such asindustrial automation, public safety, and vehicular safety applications. This feature guarantees a communication service with a high level of...
ERP Software Evaluation and Comparative Analysis
Kalpic, Damir; Fertalj, Kresimir
2004-01-01
This paper presents the results of an investigation performed in 2001 under the title Comparative Analysis of Information Systems Software in Croatia. The focus was set on the comparative analysis of domestic and foreign Enterprise Resource Planning (ERP) software, which is present in Croatia. The investigation was performed from the standpoint of ERP applicability, regardless of the development methods and information technology. In other words, the evaluation was performed primarily from th...
FISCAL DISCIPLINE WITHIN THE EU: COMPARATIVE ANALYSIS
SORIN CELEA
2013-12-01
Full Text Available This paper focuses on the analysis of the convergence indicators relative to fiscal area in the EU; subsequent to a description of the main peculiarities of the convergence criteria, the reseach develops a critical analysis on a comparative perspective of the actual values of fiscal convergence indicators registered in EU countries compared with the reference values of the indicators, with emphasis on the differences between emerging and developed countries.
Assessment of modern methods of human factor reliability analysis in PSA studies
The report is structured as follows: Classical terms and objects (Probabilistic safety assessment as a framework for human reliability assessment; Human failure within the PSA model; Basic types of operator failure modelled in a PSA study and analyzed by HRA methods; Qualitative analysis of human reliability; Quantitative analysis of human reliability used; Process of analysis of nuclear reactor operator reliability in a PSA study); New terms and objects (Analysis of dependences; Errors of omission; Errors of commission; Error forcing context); and Overview and brief assessment of human reliability analysis (Basic characteristics of the methods; Assets and drawbacks of the use of each of HRA method; History and prospects of the use of the methods). (P.A.)
Mapping Green Spaces in Bishkek—How Reliable can Spatial Analysis Be?
Peter Hofmann
2011-05-01
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.
Peters, Valerie A.; Ogilvie, Alistair B.
2012-01-01
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.
Comparative Environmental Threat Analysis: Three Case Studies.
Latour, J. B.; Reiling, R.
1994-01-01
Reviews how carrying capacity for different environmental problems is operationalized. Discusses whether it is possible to compare threats, using the exceeding of carrying capacity as a yardstick. Points out problems in comparative threat analysis using three case studies: threats to European groundwater resources, threats to ecosystems in Europe,…
Analysis of Syetem Reliability in Manufacturing Cell Based on Triangular Fuzzy Number
ZHANG Caibo; HAN Botang; SUN Changsen; XU Chunjie
2006-01-01
Due to lacking of test-data and field-data in reliability research during the design stage of manufacturing cell system. The degree of manufacturing cell system reliability research is increased. In order to deal with the deficient data and the uncertainty occurred from analysis and judgment, the paper discussed a method for studying reliability of manufacturing cell system through the analysis of fuzzy fault tree, which was based on triangular fuzzy number. At last, calculation case indicated that it would have great significance for ascertaining reliability index, maintenance and establishing keeping strategy towards manufacturing cell system.
Morehouse, Dennis V.
2006-01-01
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.
Reliability and coverage analysis of non-repairable fault-tolerant memory systems
Cox, G. W.; Carroll, B. D.
1976-01-01
A method was developed for the construction of probabilistic state-space models for nonrepairable systems. Models were developed for several systems which achieved reliability improvement by means of error-coding, modularized sparing, massive replication and other fault-tolerant techniques. From the models developed, sets of reliability and coverage equations for the systems were developed. Comparative analyses of the systems were performed using these equation sets. In addition, the effects of varying subunit reliabilities on system reliability and coverage were described. The results of these analyses indicated that a significant gain in system reliability may be achieved by use of combinations of modularized sparing, error coding, and software error control. For sufficiently reliable system subunits, this gain may far exceed the reliability gain achieved by use of massive replication techniques, yet result in a considerable saving in system cost.
A survey on reliability and safety analysis techniques of robot systems in nuclear power plants
Eom, H.S.; Kim, J.H.; Lee, J.C.; Choi, Y.R.; Moon, S.S
2000-12-01
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.
A survey on reliability and safety analysis techniques of robot systems in nuclear power plants
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
Mathematical modeling and reliability analysis of a 3D Li-ion battery
RICHARD HONG PENG LIANG
2014-02-01
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.
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
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)
Reliability and Sensitivity Analysis of Cast Iron Water Pipes for Agricultural Food Irrigation
Yanling Ni
2014-07-01
Full Text Available This study aims to investigate the reliability and sensitivity of cast iron water pipes for agricultural food irrigation. The Monte Carlo simulation method is used for fracture assessment and reliability analysis of cast iron pipes for agricultural food irrigation. Fracture toughness is considered as a limit state function for corrosion affected cast iron pipes. Then the influence of failure mode on the probability of pipe failure has been discussed. Sensitivity analysis also is carried out to show the effect of changing basic parameters on the reliability and life time of the pipe. The analysis results show that the applied methodology can consider different random variables for estimating of life time of the pipe and it can also provide scientific guidance for rehabilitation and maintenance plans for agricultural food irrigation. In addition, the results of the failure and reliability analysis in this study can be useful for designing of more reliable new pipeline systems for agricultural food irrigation.
Development of Reliability Analysis Method for Nuclear Power Plant Protection System
The paper presents a method and procedures for the reliability analysis of safety related nuclear power plant systems. The analysis provides an appropriate model to represent the system that will facilitate the applications of reliability engineering techniques during the design, construction and operating stages of a plant's life. The analysis assists in selecting design alternatives with high reliability and high safety potential during early design phase. It also ensures that all conceivable failure modes and their effects on operational success of the system have been considered. The output of the analysis is to be used as inputs to determine and to update the test interval of the system
Reliability Analysis of Systems with Time-Varying Failure Rates
Moustafa Magdi S.
2001-01-01
A non-homogeneous Markov model is used to obtain closed form solutions of the state probabilities and the reliability of M modules in series where each module has N m components in parallel. The components have exponential time-varying failure rates which depend on the module. If the failure rates are independent of the modules the results are extended to a K-out-of-N:G system and series-parallel. Examples of assuming the Weibull distributions are presented to illustrate the results.
Reliability and maintenance analysis of the CERN PS booster
Staff, P S B
1977-01-01
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).
ANALYSIS OF INDICATORS OF RELIABILITY OF ELECTRICAL NETWORKS
Popescu V.
2012-12-01
Full Text Available Problems of the optimization reliability in electrical networks of the different class of voltage have probabilistic nature, they discretely change and depend on the number of factors both definite and indefinite and have importance by selection of electric equipment, graph of development of electrical networks and voltage levels. The definition of the major factors, which have determining significance on their value and speed of their change allow to elaborate methods of their optimization and to elaborate effective methods of their growth limitation in electrical networks with the different class of voltage.
A disjoint algorithm for seismic reliability analysis of lifeline networks
无
2002-01-01
The algorithm is based on constructing a disjoin kg t set of the minimal paths in a network system. In this paper,cubic notation was used to describe the logic function of a network in a well-balanced state, and then the sharp-product operation was used to construct the disjoint minimal path set of the network. A computer program has been developed, and when combined with decomposition technology, the reliability of a general lifeline network can be effectively and automatically calculated.
Reliability analysis of digital instrumentation and control systems
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)
A New Method for System Reliability Analysis of Tailings Dam Stability
Liu, X.; Tang, H.; Xiong, C.; Ni, W.
2012-12-01
CSS was significant to system reliability analysis. Besides, the CSS was described with non-circular shape, which was much more superior to the circular one. Moreover, compare with the LEM, the numerical method has the ability to reflect the variability in a whole space of the dam. The second one is the orthogonal design modules aimed to generate high-quality training samples according to the variability of soil layers. The third one is the response surface model based on SVM, which was designed to obtain the explicit performance function through the well-prepared training samples. The fourth one is the MCS model, which can perform steady and effective reliability analysis through the explicit performance function. As a result, a new approach for reliability analysis of tailings dam stability was presented. As a case study, the Yong-ping Copper Mine Tailings Dam in Jiangxi Province of China was analyzed in detail by this new method. It was shown that the effectiveness of the new method is considerable. In sum, this research is geared towards providing new ideas and available examples for future reliability assessment of tailings dam stability.
Papazoglou, I A; Gyftopoulos, E P
1978-09-01
A methodology for the assessment of the uncertainties about the reliability of nuclear reactor systems described by Markov models is developed, and the uncertainties about the probability of loss of coolable core geometry (LCG) of the Clinch River Breeder Reactor (CRBR) due to shutdown system failures, are assessed. Uncertainties are expressed by assuming the failure rates, the repair rates and all other input variables of reliability analysis as random variables, distributed according to known probability density functions (pdf). The pdf of the reliability is then calculated by the moment matching technique. Two methods have been employed for the determination of the moments of the reliability: the Monte Carlo simulation; and the Taylor-series expansion. These methods are adopted to Markovian problems and compared for accuracy and efficiency.
A methodology for the assessment of the uncertainties about the reliability of nuclear reactor systems described by Markov models is developed, and the uncertainties about the probability of loss of coolable core geometry (LCG) of the Clinch River Breeder Reactor (CRBR) due to shutdown system failures, are assessed. Uncertainties are expressed by assuming the failure rates, the repair rates and all other input variables of reliability analysis as random variables, distributed according to known probability density functions (pdf). The pdf of the reliability is then calculated by the moment matching technique. Two methods have been employed for the determination of the moments of the reliability: the Monte Carlo simulation; and the Taylor-series expansion. These methods are adopted to Markovian problems and compared for accuracy and efficiency
Rajaguru, Pushparajah
2014-01-01
The principal aim of this PhD program is the development of an optimisation and risk based methodology for reliability and robustness predictions of packaged electronic components. Reliability based design optimisation involves the integration of reduced order modelling, risk analysis and optimisation. The increasing cost of physical prototyping and extensive qualification testing for reliability assessment is making virtual qualification a very attractive alternative for the electronics indu...
Reliability analysis of the solar array based on Fault Tree Analysis
The solar array is an important device used in the spacecraft, which influences the quality of in-orbit operation of the spacecraft and even the launches. This paper analyzes the reliability of the mechanical system and certifies the most vital subsystem of the solar array. The fault tree analysis (FTA) model is established according to the operating process of the mechanical system based on DFH-3 satellite; the logical expression of the top event is obtained by Boolean algebra and the reliability of the solar array is calculated. The conclusion shows that the hinges are the most vital links between the solar arrays. By analyzing the structure importance(SI) of the hinge's FTA model, some fatal causes, including faults of the seal, insufficient torque of the locking spring, temperature in space, and friction force, can be identified. Damage is the initial stage of the fault, so limiting damage is significant to prevent faults. Furthermore, recommendations for improving reliability associated with damage limitation are discussed, which can be used for the redesigning of the solar array and the reliability growth planning.
Seismic elastic-plastic time history analysis and reliability study of quayside container crane
Jin, Yulong; Li, Zengguang
2010-06-01
Quayside container crane is a kind of huge dimension steel structure, which is the major equipment used for handling container at modern ports. With the aim to validate the safety and reliability of the crane under seismic loads, besides conventional analysis, elastic-plastic time history analysis under rare seismic intensity is carried out. An ideal finite element (FEM) elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes. Furthermore, according to elastic-plastic time history analysis theory, deformation, stress and damage pattern of the structure under rare seismic intensity are investigated. Based on the above analysis, the established reliability model according to the reliability theory, together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis. The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity, and the structure needs to be reinforced.
Root cause analysis in support of reliability enhancement of engineering components
Reliability based methods have been widely used for the safety assessment of plant system, structures and components. These methods provide a quantitative estimation of system reliability but do not give insight into the failure mechanism. Understanding the failure mechanism is a must to avoid the recurrence of the events and enhancement of the system reliability. Root cause analysis provides a tool for gaining detailed insights into the causes of failure of component with particular attention to the identification of fault in component design, operation, surveillance, maintenance, training, procedures and policies which must be improved to prevent repetition of incidents. Root cause analysis also helps in developing Probabilistic Safety Analysis models. A probabilistic precursor study provides a complement to the root cause analysis approach in event analysis by focusing on how an event might have developed adversely. This paper discusses the root cause analysis methodologies and their application in the specific case studies for enhancement of system reliability. (author)
Fast neutron reactor safety. Reliability analysis of Phenix decay heat removal function
This paper presents a reliability analysis of the Phenix decay heat removal function. After summarizing analysis results of sequences leading to failure of this function, the main steps in a probabilistic risk assessment are described: computation of reliability and maintenance parameters for the various systems involved, followed by probabilistic analysis of failure sequences. The extent to which the various systems contribute to the total risk is analyzed. Certain maintenance recommendations were made accordingly
Methodology for reliability allocation based on fault tree analysis and dualistic contrast
TONG Lili; CAO Xuewu
2008-01-01
Reliability allocation is a difficult multi-objective optimization problem.This paper presents a methodology for reliability allocation that can be applied to determine the reliability characteristics of reactor systems or subsystems.The dualistic contrast,known as one of the most powerful tools for optimization problems,is applied to the reliability allocation model of a typical system in this article.And the fault tree analysis,deemed to be one of the effective methods of reliability analysis,is also adopted.Thus a failure rate allocation model based on the fault tree analysis and dualistic contrast is achieved.An application on the emergency diesel generator in the nuclear power plant is given to illustrate the proposed method.
A knowledge based approach for systems safety and reliability analysis
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
Reliability analysis of protection systems in NPP applying fault-tree analysis method
This paper demonstrates the applicability and limits of dependability analysis in nuclear power plants (NPPS) based on the reactor protection refurbishment project (RRP) in NPP Paks. This paper illustrates case studies from the reliability analysis for NPP Paks. It also investigates the solutions for the connection between the data acquisition and subsystem control units (TSs) and the voter units (VTs), it analyzes the influence of the voting in the VT computer level, it studies the effects of the testing procedures to the dependability parameters. (author)
Reliability of three-dimensional gait analysis in cervical spondylotic myelopathy.
McDermott, Ailish
2010-10-01
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.
Reliability analysis of K-out-of-N: G systems with dependent failures and imperfect coverage
Moustafa, Magdi S
1997-10-01
This paper presents a Markov model for reliability analysis of K-out-of-N: G systems subject to dependent failures with imperfect coverage. Closed form solutions of the probabilities are used to obtain the reliability and the mean time to failure (MTTF). A numerical example is provided to illustrate the results.
Smith, Jack E.; Hakel, Milton D.
1979-01-01
Examined are questions pertinent to the use of the Position Analysis Questionnaire: Who can use the PAQ reliably and validly? Must one rely on trained job analysts? Can people having no direct contact with the job use the PAQ reliably and validly? Do response biases influence PAQ responses? (Author/KC)
Application of factor analysis in evaluation of financial reliability of life insurance companies
Malynych, Anna Mykolayivna
2011-11-01
Full Text Available The article presents the results of factor analysis of the financial reliability of life insurance companies in Ukraine. It was found out the latent factors explaining the so called case and result the mechanism of forming of the financial reliability of the native life-insurance companies at different phases of functioning the life insurance market in Ukraine.
Nonlinear instability and reliability analysis of composite laminated beams
Fereidooni, Alireza
the beam subjected to substantial excitation loading parameters increases in a typical nonlinear manner and leads to the beats phenomena. The principal regions of dynamic instability are determined for various loading and boundary conditions using the Floquet's theory. The beam response in the regions of instability is investigated. Axially loaded beam may be unstable not just in load equal to critical load and/or loading frequency equal to beam natural frequency. In fact there are infinite points in region of instability in plane load vs. frequency that the beam can be unstable. The region of instability of the shear deformable beams is wider compare to the non-shear deformable beams. The lower bound of the instability region of the shear deformable beams changes faster than upper bound. Probabilistic stability analysis of the uncertain laminated beams subject to both conservative and nonconservative loads is studied. The effects of material and geometry uncertainties on dynamics instability of the beam, is investigated through a probabilistic finite element analysis and Monte Carlo Simulation methods. For non-conservative systems variations of uncertain material properties has a smaller influence than variations of geometric properties over the instability of the beam.
A double-loop adaptive sampling approach for sensitivity-free dynamic reliability analysis
Dynamic reliability measures reliability of an engineered system considering time-variant operation condition and component deterioration. Due to high computational costs, conducting dynamic reliability analysis at an early system design stage remains challenging. This paper presents a confidence-based meta-modeling approach, referred to as double-loop adaptive sampling (DLAS), for efficient sensitivity-free dynamic reliability analysis. The DLAS builds a Gaussian process (GP) model sequentially to approximate extreme system responses over time, so that Monte Carlo simulation (MCS) can be employed directly to estimate dynamic reliability. A generic confidence measure is developed to evaluate the accuracy of dynamic reliability estimation while using the MCS approach based on developed GP models. A double-loop adaptive sampling scheme is developed to efficiently update the GP model in a sequential manner, by considering system input variables and time concurrently in two sampling loops. The model updating process using the developed sampling scheme can be terminated once the user defined confidence target is satisfied. The developed DLAS approach eliminates computationally expensive sensitivity analysis process, thus substantially improves the efficiency of dynamic reliability analysis. Three case studies are used to demonstrate the efficacy of DLAS for dynamic reliability analysis. - Highlights: • Developed a novel adaptive sampling approach for dynamic reliability analysis. • POD Developed a new metric to quantify the accuracy of dynamic reliability estimation. • Developed a new sequential sampling scheme to efficiently update surrogate models. • Three case studies were used to demonstrate the efficacy of the new approach. • Case study results showed substantially enhanced efficiency with high accuracy
THE COMPARATIVE ANALYSIS OF ECOLOGICAL INDICATORS
Bikova E.V.
2006-04-01
Full Text Available The comparative analysis of ecological indicators designed and specified for Moldova and similar indicators of the countries of CIS is made in the work. Some general items of information about power systems of the countries of CIS (the established capacities, manufacture of the electric power are given, the analysis of dynamics of emissions GHG- СО2, NOx, SO2 in Moldova and comparison with the emissions level in other countries of CIS is made.
Comparative analysis of black carbon in soils
Schmidt, Michael W I; Skjemstad, Jan O.; Czimczik, Claudia I.; Glaser, Bruno; Prentice, Ken M; Gelinas, Yves; Thomas A.J. Kuhlbusch
2001-01-01
Black carbon (BC), produced by incomplete combustion of fossil fuels and vegetation, occurs ubiquitously in soils and sediments. BC exists as a continuum from partly charred material to highly graphitized soot particles, with no general agreement on clear-cut boundaries of definition or analysis. In a comparative analysis, we measured BC forms in eight soil samples by six established methods. All methods involved removal of the non-BC components from the sample by thermal or chemical means or...
Reliability analysis of protection system of advanced pressurized water reactor - APR 1400
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
Within the framework of the DEAB project sponsored by the BMFT, a reliability analysis program has been set up for the safety and reliability assessment of the required systems and components, which for the most part are new developments and therefore need reliability testing with the data available so far. The paper explains the application of the program to simulated transport in the shaft, and simulated materials handling and waste item deposition in the mine destined to serve as a repository. The systems data available are preliminary reliability data, which were used to assess the failure rates to be expected, and the non-availability periods of the various systems. (orig./DG)
Vibration reliability sensitivity analysis of general system with correlation failure modes
The vibration problem of the general system is the main object of research. The material properties and geometry of general system are random parameters because of the manufacturing environment, technical conditions, manufacturing and installation errors, multiphase materials, features and other factors. According to the relation criterion that the difference between the natural frequency and the driving frequency of general systems is not beyond a specific value, the vibration reliability mode and vibration reliability of general systems are defined considering the correlation of the multi-order natural frequency and the random characteristics of structure size and material, and the vibration reliability analysis method for avoiding the resonant is carried out. The second-order joint failure probability is obtained by using the numerical integration method. Based on the reliability design theory and sensitivity analysis method, the vibration reliability sensitivity of the general system with correlation failure modes is extensively discussed and a numerical method for vibration reliability sensitivity design is presented. The variation regularities of vibration reliability sensitivity are obtained and the effects of random parameters on vibration reliability of the general system are studied. The presented method provided the theoretic basis for the reliability design of the general system. A numerical example demonstrated that the proposed method is effective
Reliability analysis study of digital reactor protection system in nuclear power plant
The Digital I and C systems are believed to improve a plant's safety and reliability generally. The reliability analysis of digital I and C system has become one research hotspot. Traditional fault tree method is one of means to quantify the digital I and C system reliability. One typical digital protection system special for advanced reactor has been developed in this paper, which reliability evaluation is necessary for design demonstration. The typical digital protection system construction is introduced in the paper, and the process of FMEA and fault tree application to the digital protection system reliability evaluation are described. Reliability data and bypass logic modeling are two points giving special attention in the paper. Because the factors about time sequence and feedback not exist in reactor protection system obviously, the dynamic feature of digital system is not discussed. (authors)
RELIABILITY-BASED DESIGN AND ANALYSIS ON HYDRAULIC SYSTEM FOR SYNTHETIC RUBBER PRESS
Yao Chengyu; Zhao Jingyi
2005-01-01
To overcome the design limitations of traditional hydraulic control system for synthetic rubber press and such faults as high fault rate, low reliability, high energy-consuming and which always led to shutting down of post-treatment product line for synthetic rubber, brand-new hydraulic system combining with PC control and two-way cartridge valves for the press is developed, whose reliability is analyzed, reliability model of the hydraulic system for the press is established by analyzing processing steps, and reliability simulation of each step and the whole system is carried out by software MATLAB, which is verified through reliability test. The fixed time test has proved not that theory analysis is sound, but the system has characteristics of reasonable design and high reliability,and can lower the required power supply and operational energy cost.
The first Superphenix fuel load reliability analysis and validation
The excellent behavior of PHENIX driver fuel and the burnup values currently reached suggest that the first SUPERPHENIX fuel load will meet the design lifetime. However, to ensure the reliability of the entire load, all the parameters affecting fuel behavior in reactor must be analyzed. For that purpose, we have taken into account all the results of the examination and verifications during the fabrication process of the first load subassemblies. These data concern geometrical parameters or oxide composition as well as the cladding tube and plug weld soundness tests. The objective is to determine the actual dispersion of all the parameters to ensure the absence of failure due to fabrication defects with very high statistical confidence limits. The influence of all the parameters has been investigated for the situations which can occur during power-up, steady-state operation and transients. The fabrication quality allows us to demonstrate that in all cases good behavior criteria for fuel and structure will be maintained. This demonstration is based on calculation code results as well as on validation by specific experiments
Correlation analysis for screening key parameters for passive system reliability analysis
Highlights: • A method for screening key parameters used in passive system reliability analysis. • T–H model is a relationship between output and each input. • Correlation coefficient between output and input is influenced by T–H performance. • Correlation coefficient is also affected by uncertainty of input. - Abstract: Passive systems are widely used in new generation nuclear power plants to enhance their safety. Reliability of passive system operating based on natural circulation must be assessed in terms of functional failure. The functional failure probability evaluation requires repeatedly running the thermal–hydraulic (T–H) code which simulates the system responses under different values of the input parameters. In practice, repeated running of the code is quite costly in terms of running time and artificial neural network (ANN) has been proposed to replace the T–H model. However, the number of input parameters can be too large to satisfy the requirement of the ANN. In this paper we illustrate a systematic methodology to screen the key parameters for passive system operation based on correlation analysis for reducing the number of inputs. Correlation analysis is a well-known statistical method to assess the relationships among parameters. In the case of interest for passive system reliability, we consider the T–H model as a relationship between model inputs and outputs, which can be used in correlation analysis. With this method, key parameters can be screened with limited numbers of samples. The passive containment cooling system in AP1000 is analyzed and 4 parameters are identified as important ones from 47 inputs
COMPARATIVE ANALYSIS OF CELEBRITY AND NON-CELEBRITY ADVERTISEMENT
Ammar Asad
2013-12-01
Full Text Available This study is undertaken to make a comparative analysis of celebrity advertisement and non-celebrity advertisement with respect to attitude toward advertisement, attitude toward brand, purchase intentions, and advertising attributes. For this purpose, a simple random sample of 200 students studying four different disciplines was taken from the Private University in Lahore. For econometric proof, reliability analysis, descriptive analysis, and independent sample T-test was used to interpret the results. Our findings show that there is no significant difference between celebrity and non-celebrity advertisement with respect to attitude toward advertisement, attitude toward brand, purchasing intentions, and advertising attributes. The limitations and recommendations of this research are also given.
Fatigue reliability analysis on the interface of the plane head and the barrel
Background: There are many uncertainties in the fatigue design of the equipment, the probability method can be used to assign the fatigue design. Purpose: To provide the structure fatigue reliability of the area of the plane head interface. Methods: The fatigue reliability analysis has been done by using the reliability method which considering the geometry dimensions uncertainty and loads uncertainty. Results: The dimensions uncertainty has great effect on the uncertainty of the products' life. Meanwhile, this article provides one method, by using 6σ concept, to solve the fatigue reliability analysis considering the loads uncertainty. Conclusions: The loads uncertainty results can be combined with the dimensions results to get the overall reliability results. (authors)
Determination of Weibull Analysis of the Hypereutectic Silumins Reliability in Failure Time Respect
J. Szymszal
2009-07-01
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.
Task analysis and computer aid development for human reliability analysis in nuclear power plants
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
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)
Simulation and Non-Simulation Based Human Reliability Analysis Approaches
Boring, Ronald Laurids [Idaho National Lab. (INL), Idaho Falls, ID (United States); Shirley, Rachel Elizabeth [Idaho National Lab. (INL), Idaho Falls, ID (United States); Joe, Jeffrey Clark [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mandelli, Diego [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2014-12-01
Part of the U.S. Department of Energy’s Light Water Reactor Sustainability (LWRS) Program, the Risk-Informed Safety Margin Characterization (RISMC) Pathway develops approaches to estimating and managing safety margins. RISMC simulations pair deterministic plant physics models with probabilistic risk models. As human interactions are an essential element of plant risk, it is necessary to integrate human actions into the RISMC risk model. In this report, we review simulation-based and non-simulation-based human reliability assessment (HRA) methods. Chapter 2 surveys non-simulation-based HRA methods. Conventional HRA methods target static Probabilistic Risk Assessments for Level 1 events. These methods would require significant modification for use in dynamic simulation of Level 2 and Level 3 events. Chapter 3 is a review of human performance models. A variety of methods and models simulate dynamic human performance; however, most of these human performance models were developed outside the risk domain and have not been used for HRA. The exception is the ADS-IDAC model, which can be thought of as a virtual operator program. This model is resource-intensive but provides a detailed model of every operator action in a given scenario, along with models of numerous factors that can influence operator performance. Finally, Chapter 4 reviews the treatment of timing of operator actions in HRA methods. This chapter is an example of one of the critical gaps between existing HRA methods and the needs of dynamic HRA. This report summarizes the foundational information needed to develop a feasible approach to modeling human interactions in the RISMC simulations.
Nikulin, M; Mesbah, M; Limnios, N
2004-01-01
Parametric and semiparametric models are tools with a wide range of applications to reliability, survival analysis, and quality of life. This self-contained volume examines these tools in survey articles written by experts currently working on the development and evaluation of models and methods. While a number of chapters deal with general theory, several explore more specific connections and recent results in "real-world" reliability theory, survival analysis, and related fields.
Reliability-tools in geotechnical design, an approach for river dike analysis
Pham Quang, T.; J. K. Vrijling; Van Gelder, P.H.A.J.M.; Thu, T.M.
2010-01-01
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 r...
Li Wang; Zaiwen Liu; Chongchong Yu
2013-01-01
This paper proposes a reliability estimation method based on Step-Stress Accelerated Degradation Testing (SSADT) data analysis using unequal interval time series analysis. A Multi-Regression Time Varying Auto-Regressive (MRTVAR) degradation time series model is proposed. Product SSADT data are treated as unequal interval composite time series and described using MRTVAR time series model and utilized to predict long-term trend of degradation. By using the suggested method, product reliability ...
Academic Expectations Stress Inventory: Development, Factor Analysis, Reliability, and Validity
Ang, Rebecca P.; Huan, Vivien S.
2006-01-01
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…
Test-retest reliability of trunk accelerometric gait analysis
Henriksen, Marius; Lund, Hans; Moe-Nilssen, R;
2004-01-01
-57) underwent the same protocol on 2 consecutive days. The raw acceleration signals from six self-selected walking speeds were transformed into a horizontal-vertical coordinate system to remove unwanted variability caused by gravity. Acceleration root mean square values, cadences, step and stride lengths were...... may have a definite potential in clinical gait analysis....
Jung, Won Dea; Kim, Jae Whan; Park, Jin Kyun; Ha, Jae Joo [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-02-01
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)
Full-text: This project is to refurbish the Instrumental Delayed Neutron Activation Analysis System for Simultaneously Determination of Uranium and Thorium namely PAUTS. PAUTS use nuclear techniques for the quantitative determination of Uranium-235 (U-235) and Thorium-232 (Th-232)radionuclides contents in the samples. It consists of three main automation procedures namely Control sample handling, Data Acquisition for neutron counting, and data handling and analysis program. The automation control technology for this project is based on a personal computer (PC), Ethernet communication support, programmable automation control (PAC) module CFP 2220, infrared photo sensors and LabVIEW software package. The analysis samples capsule was placed in transfers containers or rabbit and will be transfer using fast pneumatic sample handling for activation by irradiate it to neutron in the reactor core. Both radionuclides as a fission product will decay and emit the delayed neutron which are count using the nuclear counting electronics module. Studies on the reliability of fast pneumatic sample handling using the statistical method shows that 95 % confidence level had been reach. Results shows the mean transfer time of the sample from the loader to the reactor core is 3251 ± 210 ms, while the mean transfer time of the samples from the core to the counter chamber is 3264 ± 407 ms. The overall system reliability has been verified using analysis of calibration standard material with known quantity of uranium and thorium IAEA-S17, the IAEA-ThO2 and the IAEA-S14 method. At the moment nuclear counting electronic based on 4 units neutron detector and the results were in line with the previous experiment. Results shows that the content of U and Th is in the average of 19:35 ppm and 432.25 ppm respectively compared with the known quantity of the sample is 29.0 ppm and 460 ppm. Studies on the effects pneumatic sample handling to the irradiation time parameter indicated that the previous
Uncertainty analysis of nonlinear systems employing the first-order reliability method
In most mechanical systems, properties of the system elements have uncertainties due to several reasons. For example, mass, stiffness coefficient of a spring, damping coefficient of a damper or friction coefficients have uncertain characteristics. The uncertain characteristics of the elements have a direct effect on the system performance uncertainty. It is very important to estimate the performance uncertainty since the performance uncertainty is directly related to manufacturing yield and consumer satisfaction. Due to this reason, the performance uncertainty should be estimated accurately and considered in the system design. In this paper, performance measures are defined for nonlinear vibration systems and the performance measure uncertainties are estimated employing the first order reliability method (FORM). It was found that the FORM could provide good results in spite of the system nonlinear characteristics. Comparing to the results obtained by Monte Carlo Simulation (MCS), the accuracy of the uncertainty analysis results obtained by the FORM is validated
Evaluation of reliability of Coats-Redfern method for kinetic analysis of non-isothermal TGA
R. Ebrahimi-Kahrizsangi; M. H. Abbasi
2008-01-01
A critical examination was made on the reliability of kinetic parameters of nonisothermal thermoanalytical rate measurement by the widely applied Coats-Redfern(CR) equation. For this purpose, simulated TGA curves were made for reactions with different kinetic models, including chemical, diffusion (Janders) and mixed mechanism at different heating rates. The results show that, for reactions controlled kinetically by one mechanism, all solid state reaction models show linear trends by use of CR method and this method can not distinct the correct reaction model. For reactions with mixed mechanism, the CR method shows nonlinear trends and the reaction models and kinetic parameters can not be extracted from CR curves. The overall conclusion from this comparative appraisal of the characteristics of the CR approach to kinetic analysis of TGA data is that the CR approach is generally unsuitable for determination of kinetic parameters.
Development of reliability analysis tools and database for Integrated Risk Management System (IRMS)
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)
Sensitivity analysis for reliable design verification of nuclear turbosets
In this paper, we present an application of sensitivity analysis for design verification of nuclear turbosets. Before the acquisition of a turbogenerator, energy power operators perform independent design assessment in order to assure safe operating conditions of the new machine in its environment. Variables of interest are related to the vibration behaviour of the machine: its eigenfrequencies and dynamic sensitivity to unbalance. In the framework of design verification, epistemic uncertainties are preponderant. This lack of knowledge is due to inexistent or imprecise information about the design as well as to interaction of the rotating machinery with supporting and sub-structures. Sensitivity analysis enables the analyst to rank sources of uncertainty with respect to their importance and, possibly, to screen out insignificant sources of uncertainty. Further studies, if necessary, can then focus on predominant parameters. In particular, the constructor can be asked for detailed information only about the most significant parameters.
Reliability Modeling and Analysis of Flexible Manufacturing Cells
Savsar, Mehmet
2010-01-01
The demand for customized products has been continuously increasing in recent years and a great deal of attention has been given to automation of manufacturing, specifically to flexible manufacturing systems (FMS) and flexible manufacturing cells (FMC). FMC are less costly, smaller, and less complex systems than FMS. In order to get full benefit from these systems, they have to be analyzed in detail before implementation as well as during their operations. While modeling and analysis of tradi...
Reliability analysis of structural stainless steel design provisions
Afshan, S; Francis, P.; Baddoo, NR; Gardner, L.
2015-01-01
Since the establishment of the Eurocode design provisions for structural stainless steel, a considerable amount of both statistical material data and experimental results on structural elements has been generated. In light of this, the current partial resistance factors recommended in EN 1993-1-4 for the design of stainless steel elements are re-evaluated. First, following an analysis of material data from key stainless steel producers, representative values of the over-strength and the coeff...
Analysis of threaded connection reliability for compression applications
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
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.
Analysis of complete logical structures in system reliability assessment
The application field of the fault-tree techniques has been explored in order to assess whether the AND-OR structures covered all possible actual binary systems. This resulted in the identification of various situations requiring the complete AND-OR-NOT structures for their analysis. We do not use the term non-coherent for such cases, since the monotonicity or not of a structure function is not a characteristic of a system, but of the particular top event being examined. The report presents different examples of complete fault-trees, which can be examined according to different degrees of approximation. In fact, the exact analysis for the determination of the smallest irredundant bases is very time consuming and actually necessary only in some particular cases (multi-state systems, incidental situations). Therefore, together with the exact procedure, the report shows two different methods of logical analysis that permit the reduction of complete fault-trees to AND-OR structures. Moreover, it discusses the problems concerning the evaluation of the probability distribution of the time to first top event occurrence, once the hypothesis of structure function monotonicity is removed
An improved rank assessment method for weibull analysis of reliability data
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)
Timander, Tobias; WESTERLUND, JIMMY
2012-01-01
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...
Being supported by scarce empirical data, most of the performance influencing factors in human reliability analysis (HRA) have to be assessed on the basis of the analyst's knowledge on the human performance in given tasks and their context. Therefore, the outcome of HRA may only be warranted by a proper application of their knowledge based on sufficient information about the tasks and situations. However, most of the HRA methodologies, including the newly developed ones, focus on the provision of cognitive models, error mechanisms, error types and analysis method while leaving the information collection mostly in the hands of the analyst. This paper suggests structured information analysis (SIA), which helps HRA analysts in collecting and structuring such information on tasks and contexts. The SIA consists of three parts: the scenario analysis, the goal-means analysis, and the cognitive function analysis. An expert evaluation showed that this three-part information analysis allowed more expressiveness and hence more confidence on the error prediction than ASEP HRA
A survey on the human reliability analysis methods for the design of Korean next generation reactor
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
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.
A survey on the human reliability analysis methods for the design of Korean next generation reactor
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
Xin-Jia Meng
2015-01-01
Full Text Available Multidisciplinary reliability is an important part of the reliability-based multidisciplinary design optimization (RBMDO. However, it usually has a considerable amount of calculation. The purpose of this paper is to improve the computational efficiency of multidisciplinary inverse reliability analysis. A multidisciplinary inverse reliability analysis method based on collaborative optimization with combination of linear approximations (CLA-CO is proposed in this paper. In the proposed method, the multidisciplinary reliability assessment problem is first transformed into a problem of most probable failure point (MPP search of inverse reliability, and then the process of searching for MPP of multidisciplinary inverse reliability is performed based on the framework of CLA-CO. This method improves the MPP searching process through two elements. One is treating the discipline analyses as the equality constraints in the subsystem optimization, and the other is using linear approximations corresponding to subsystem responses as the replacement of the consistency equality constraint in system optimization. With these two elements, the proposed method realizes the parallel analysis of each discipline, and it also has a higher computational efficiency. Additionally, there are no difficulties in applying the proposed method to problems with nonnormal distribution variables. One mathematical test problem and an electronic packaging problem are used to demonstrate the effectiveness of the proposed method.
Comparative analysis of twelve Dothideomycete plant pathogens
Ohm, Robin; Aerts, Andrea; Salamov, Asaf; Goodwin, Stephen B.; Grigoriev, Igor
2011-03-11
The Dothideomycetes are one of the largest and most diverse groups of fungi. Many are plant pathogens and pose a serious threat to agricultural crops grown for biofuel, food or feed. Most Dothideomycetes have only a single host and related Dothideomycete species can have very diverse host plants. Twelve Dothideomycete genomes have currently been sequenced by the Joint Genome Institute and other sequencing centers. They can be accessed via Mycocosm which has tools for comparative analysis
Comparative Analysis of Terrorists’ Communication Strategies
Denis Alexandrovich Zhuravliev
2015-01-01
There is a wide-spread approach in a research literature to regard terrorism as a communicative process. From this point of view, the author offers a comparative analysis of the three most common communication strategies of terrorist groups, including transforming the role of the mass media, the Internet and a combined approach. The author also argues that a particular communication strategy determines a structure of a terrorist organization.
Comparative Analysis of VNSA Complex Engineering Efforts
Gary Ackerman
2016-01-01
The case studies undertaken in this special issue demonstrate unequivocally that, despite being forced to operate clandestinely and facing the pressures of security forces seeking to hunt them down and neutralize them, at least a subset of violent non-state actors (VNSAs) are capable of some genuinely impressive feats of engineering. At the same time, success in such endeavours is not guaranteed and VNSAs will undoubtedly face a number of obstacles along the way. A comparative analysis of the...
ANALYSIS AND COMPARATIVE STUDY OF SEARCHING TECHNIQUES
Yuvraj Singh Chandrawat*
2015-01-01
We live in the age of technolgy and it is quiet obvious that it is increasing day-by-day endlessly. In this technical era researchers are focusing on the development of the existing technologies. Software engineering is the dominant branch of Computer Science that deals with the development and analysis of the software. The objective of this study is to analyze and compare the existing searching algorithms (linear search and binary search). In this paper, we will discuss both thes...
Comparative analysis of enterprise architecture frameworks
Oblak, Danica
2012-01-01
Today's enterprises are facing a competitive power in the dynamically changing business environment. With increasing complexity of enterprise, enterprise architecture have become an important field. Creating an enterprise architecture can be complex task, so enterprise architecture framework were created to simplify the process and guide an architect through all areas of architecture development. This study concentrates on the comparative analysis of enterprise architecture frameworks. T...
Fundus camera systems: a comparative analysis
DeHoog, Edward; Schwiegerling, James
2009-01-01
Retinal photography requires the use of a complex optical system, called a fundus camera, capable of illuminating and imaging the retina simultaneously. The patent literature shows two design forms but does not provide the specifics necessary for a thorough analysis of the designs to be performed. We have constructed our own designs based on the patent literature in optical design software and compared them for illumination efficiency, image quality, ability to accommodate for patient refract...
A method for reliability analysis of complex reactor systems
The method illustrated through an example permits realistic analyses through its availability 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 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
Finite State Machine Based Evaluation Model for Web Service Reliability Analysis
M, Thirumaran; Abarna, S; P, Lakshmi
2011-01-01
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...
As digital instrumentation and control systems are being progressively introduced into nuclear power plants, a growing number of related technical issues are coming to light needing to be resolved. As a result, an understanding of relevant terms and basic concepts becomes increasingly important. Under the framework of the OECD/NEA WGRISK DIGREL Task Group, the authors were involved in reviewing definitions of terms forming the supporting vocabulary for addressing issues related to the safety and reliability analysis of digital instrumentation and control (SRA of DI and C). These definitions were extracted from various standards regulating the disciplines that form the technical and scientific basis of SRA DI and C. The authors discovered that different definitions are provided by different standards within a common discipline and used differently across various disciplines. This paper raises the concern that a common understanding of terms and basic concepts has not yet been established to address the very specific technical issues facing SRA DI and C. Based on the lessons learned from the review of the definitions of interest and the analysis of dependency relationships existing between these definitions, this paper establishes a set of recommendations for the development of a consistent terminology for SRA DI and C. - Highlights: ●We reviewed definitions of terms used in reliability analysis of digital systems. ●Different definitions are provided by different standards within a common discipline. ●Acyclic and cyclic structures of dependency in defining terms are compared. ●Three recommendations for the development of a consistent terminology provided
Ken Hashimoto
2014-10-01
Full Text Available In this study, we developed a highly reliable CAE analysis model of the mechanisms that cause loosening of bolt fasteners, which has been a bottleneck in automobile development and design, using a technical element model for highly accurate CAE that we had previously developed, and verified its validity. Specifically, drawing on knowledge gained from our clarification of the mechanisms that cause loosening of bolt fasteners using actual machine tests, we conducted an accelerated bench test consisting of a threedimensional vibration load test of the loosening of bolt fasteners used in mounts and rear suspension arms, where interviews with personnel at an automaker indicated loosening was most pronounced, and reproduced actual machine tests with CAE analysis based on a technical element model for highly accurate CAE analysis. Based on these results, we were able to reproduce dynamic behavior in which larger screw pitches (lead angles lead to greater non-uniformity of surface pressure, particularly around the nut seating surface, causing loosening to occur in areas with the lowest surface pressure. Furthermore, we implemented highly accurate CAE analysis with no error (gap compared to actual machine tests.
Human Reliability Analysis in Frame of Probabilistic Safety Assessment Projects in Czech Republic
Human reliability analysis has proved to be a very important part of probabilistic safety analysis all over the world. It has been also an integral part of both Probabilistic Safety Level-1 studies developed in Czech Republic - Nuclear Power Plant Dukovany Probabilistic Safety Assessment and Nuclear Power Plant Temelin Probabilistic Safety Assessment and most of their consequent applications. The methodology used in human reliability analysis in frame of these studies is described in the first part of the paper. In general, the methodology is based on the well-known and most frequently used methods Technique for Human Error Rate Prediction and ASEP. The up-to-date decision tree method is used to address procedure-driven operator's interventions during plant response to initiating event. Some interesting results of human reliability analysis performed for Nuclear Power Plant Dukovany are described in the second part of the paper. The recommendations resulting from the analysis led to the standardization of some, up to that time, non-standard operator's actions and to the development of procedures for them. Generally, the procedures were found to be deficient from several points of view, what contributed to the decision to develop quite new emergency procedures for Nuclear Power Plant Dukovany. The human reliability analysis projects going on or planned for the very next future are described in the final part of the paper. safety analysis; risk assessment; reliability; nuclear power plants; human factors; errors; Czech Republic; operators; emergencies;
Perez-Padilla, Rogelio; Fernando C Wehrmeister; Celli, Bartolome R.; Lopez-Varela, Maria Victorina; Montes de Oca, Maria; Muiño, Adriana; Talamo, Carlos; Jardim, Jose R; Valdivia, Gonzalo; Lisboa, Carmen; Menezes, Ana Maria B.
2013-01-01
QUESTION A 6-second spirometry test is easier than full exhalations. We compared the reliability of the ratio of the Forced expiratory volume in 1 second/Forced expiratory volume in 6 seconds (FEV1/FEV6) to the ratio of the FEV1/Forced vital capacity (FEV1/FVC) for the detection of airway obstruction. METHODS The PLATINO population-based survey in individuals aged 40 years and over designed to estimate the prevalence of post-Bronchodilator airway obstruction repeated for the same study partic...
Reliability Analysis of Repairable Systems Using Stochastic Point Processes
TAN Fu-rong; JIANG Zhi-bin; BAI Tong-shuo
2008-01-01
In order to analyze the failure data from repairable systems, the homogeneous Poisson process(HPP) is usually used. In general, HPP cannot be applied to analyze the entire life cycle of a complex, re-pairable system because the rate of occurrence of failures (ROCOF) of the system changes over time rather thanremains stable. However, from a practical point of view, it is always preferred to apply the simplest methodto address problems and to obtain useful practical results. Therefore, we attempted to use the HPP model toanalyze the failure data from real repairable systems. A graphic method and the Laplace test were also usedin the analysis. Results of numerical applications show that the HPP model may be a useful tool for the entirelife cycle of repairable systems.
Reliability and life-cycle analysis of deteriorating systems
Sánchez-Silva, Mauricio
2016-01-01
This book compiles and critically discusses modern engineering system degradation models and their impact on engineering decisions. In particular, the authors focus on modeling the uncertain nature of degradation considering both conceptual discussions and formal mathematical formulations. It also describes the basics concepts and the various modeling aspects of life-cycle analysis (LCA). It highlights the role of degradation in LCA and defines optimum design and operation parameters. Given the relationship between operational decisions and the performance of the system’s condition over time, maintenance models are also discussed. The concepts and models presented have applications in a large variety of engineering fields such as Civil, Environmental, Industrial, Electrical and Mechanical engineering. However, special emphasis is given to problems related to large infrastructure systems. The book is intended to be used both as a reference resource for researchers and practitioners and as an academic text ...
Using Information from Operating Experience to Inform Human Reliability Analysis
Bruce P. Hallbert; David I. Gertman; Julie Marble; Erasmia Lois; Nathan Siu
2004-06-01
This paper reports on efforts being sponsored by the U.S. NRC and performed by INEEL to develop a technical basis and perform work to extract information from sources for use in HRA. The objectives of this work are to: 1) develop a method for conducting risk-informed event analysis of human performance information that stems from operating experience at nuclear power plants and for compiling and documenting the results in a structured manner; 2) provide information from these analyses for use in risk-informed and performance-based regulatory activities; 3) create methods for information extraction and a repository for this information that, likewise, support HRA methods and their applications.
Using the HRA Calculator in Human Reliability Analysis done with Methodology Described in NUREG-1921
The HRA Calculator is a tool designed to help to the preparation and documentation of the analysis of human reliability in the probabilistic safety analysis (APS) of fire. Collect the tasks required to develop and quantify the probabilities of error in accordance with the methodology described in the NUREG-1921. The HRA Calculator is a database that includes the tasks indicated in the NUREG-1921 for the analysis of human reliability. For the task of quantitative analysis the HRA Calculator includes several methods of quantification for human actions that are performed before and after an accident, one of the main advantages of the HRA Calculator is the systematization and standardization of the analysis of human reliability of fire. It is also a tool that allows the use of criteria more objective to define and quantify human actions, so that models collected, to the extent possible, the reality of the plant as is as operated. (Author)
An advanced human reliability analysis methodology: analysis of cognitive errors focused on
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
A Vibration Reliability Analysis Method for the Uncertain Space Beam Structure
Yanyu Mo
2016-01-01
Full Text Available Considering that uncertainty is inherent and unavoidable in engineering practice and the available information about the uncertain parameters is always not sufficient, the paper tries to carry out the nonprobabilistic vibration reliability analysis so as to avoid resonance on uncertain structure with bounded parameters. The input uncertain-but-bounded parameters are treated as interval variables, and an interval model is adopted to describe bounded uncertainties. Then a theory of nonprobabilistic reliability is introduced, in which the dimensionless nonprobabilistic reliability index and system reliability index are defined. In order to investigate the resonance failure with reliability method, the resonance failure domains are stated according to the relationships between the natural frequencies and the excitation frequencies. Then the uncertain structure is modeled as a series system and a system reliability index is proposed to evaluate the safety of the structure. The paper also takes a frequency analysis on the uncertain space beam structure to get the resonance failure modes. A frequency analysis method based on the monotonicity discriminant of the frequency sensitivity is presented. Then an optimization algorithm is introduced to verify the validity of the former frequency analysis method. Two examples are provided to illustrate the effectiveness and feasibility of the presented method.
Report on the analysis of field data relating to the reliability of solar hot water systems.
Menicucci, David F. (Building Specialists, Inc., Albuquerque, NM)
2011-07-01
Utilities are overseeing the installations of thousand of solar hot water (SHW) systems. Utility planners have begun to ask for quantitative measures of the expected lifetimes of these systems so that they can properly forecast their loads. This report, which augments a 2009 reliability analysis effort by Sandia National Laboratories (SNL), addresses this need. Additional reliability data have been collected, added to the existing database, and analyzed. The results are presented. Additionally, formal reliability theory is described, including the bathtub curve, which is the most common model to characterize the lifetime reliability character of systems, and for predicting failures in the field. Reliability theory is used to assess the SNL reliability database. This assessment shows that the database is heavily weighted with data that describe the reliability of SHW systems early in their lives, during the warranty period. But it contains few measured data to describe the ends of SHW systems lives. End-of-life data are the most critical ones to define sufficiently the reliability of SHW systems in order to answer the questions that the utilities pose. Several ideas are presented for collecting the required data, including photometric analysis of aerial photographs of installed collectors, statistical and neural network analysis of energy bills from solar homes, and the development of simple algorithms to allow conventional SHW controllers to announce system failures and record the details of the event, similar to how aircraft black box recorders perform. Some information is also presented about public expectations for the longevity of a SHW system, information that is useful in developing reliability goals.
Implementation and Analysis of Probabilistic Methods for Gate-Level Circuit Reliability Estimation
WANG Zhen; JIANG Jianhui; YANG Guang
2007-01-01
The development of VLSI technology results in the dramatically improvement of the performance of integrated circuits. However, it brings more challenges to the aspect of reliability. Integrated circuits become more susceptible to soft errors. Therefore, it is imperative to study the reliability of circuits under the soft error. This paper implements three probabilistic methods (two pass, error propagation probability, and probabilistic transfer matrix) for estimating gate-level circuit reliability on PC. The functions and performance of these methods are compared by experiments using ISCAS85 and 74-series circuits.
Reliable survival analysis based on the Dirichlet process.
Mangili, Francesca; Benavoli, Alessio; de Campos, Cassio P; Zaffalon, Marco
2015-11-01
We present a robust Dirichlet process for estimating survival functions from samples with right-censored data. It adopts a prior near-ignorance approach to avoid almost any assumption about the distribution of the population lifetimes, as well as the need of eliciting an infinite dimensional parameter (in case of lack of prior information), as it happens with the usual Dirichlet process prior. We show how such model can be used to derive robust inferences from right-censored lifetime data. Robustness is due to the identification of the decisions that are prior-dependent, and can be interpreted as an analysis of sensitivity with respect to the hypothetical inclusion of fictitious new samples in the data. In particular, we derive a nonparametric estimator of the survival probability and a hypothesis test about the probability that the lifetime of an individual from one population is shorter than the lifetime of an individual from another. We evaluate these ideas on simulated data and on the Australian AIDS survival dataset. The methods are publicly available through an easy-to-use R package. PMID:26296502
First and second order approximate reliability analysis methods using evidence theory
The first order approximate reliability method (FARM) and second order approximate reliability method (SARM) are formulated based on evidence theory in this paper. The proposed methods can significantly improve the computational efficiency for evidence-theory-based reliability analysis, while generally provide sufficient precision. First, the most probable focal element (MPFE), an important concept as the most probable point (MPP) in probability-theory-based reliability analysis, is searched using a uniformity approach. Subsequently, FARM approximates the limit-state function around the MPFE using the linear Taylor series, while SARM approximates it using the quadratic Taylor series. With the first and second order approximations, the reliability interval composed of the belief measure and the plausibility measure is efficiently obtained for FARM and SARM, respectively. Two simple problems with explicit expressions and one engineering application of vehicle frontal impact are presented to demonstrate the effectiveness of the proposed methods. - Highlights: • The first order approximate reliability method using evidence theory is proposed. • The second order approximate reliability method using evidence theory is proposed. • The proposed methods can significantly improve the computational efficiency. • The proposed methods can provide sufficient accuracy for general engineering problems
Application of GO methodology in reliability analysis of offsite power supply of Daya Bay NPP
The author applies the GO methodology to reliability analysis of the offsite power supply system of Daya Bay NPP. The direct quantitative calculation formulas of the stable reliability target of the system with shared signals and the dynamic calculation formulas of the state probability for the unit with two states are derived. The method to solve the fault event sets of the system is also presented and all the fault event sets of the outer power supply system and their failure probability are obtained. The resumption reliability of the offsite power supply system after the stability failure of the power net is also calculated. The result shows that the GO methodology is very simple and useful in the stable and dynamic reliability analysis of the repairable system
Fabio De Felice
2011-10-01
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.
Tong-chun LI; Dan-dan LI; Zhi-qiang WANG
2010-01-01
In this study,the limit state equation for tensile reliability analysis of the foundation surface of a gravity dam was established.The possible crack length was set as the action effect and allowable crack length was set as the resistance in the limit state.The nonlinear FEM was used to obtain the crack length of the foundation surface of the gravity dam,and the linear response surface method based on the orthogonal test design method was used to calculate the reliability,providing a reasonable and simple method for calculating the reliability of the serviceability limit state.The Longtan RCC gravity dam was chosen as an example.An orthogonal test,including eleven factors and two levels,was conducted,and the tensile reliability was calculated.The analysis shows that this method is reasonable.
Kovalev, I. V.; Zelenkov, P. V.; Karaseva, M. V.; Tsarev, M. Yu; Tsarev, R. Yu
2015-01-01
The paper considers the problem of the analysis of distributed computer systems reliability with client-server architecture. A distributed computer system is a set of hardware and software for implementing the following main functions: processing, storage, transmission and data protection. This paper discusses the distributed computer systems architecture "client-server". The paper presents the scheme of the distributed computer system functioning represented as a graph where vertices are the functional state of the system and arcs are transitions from one state to another depending on the prevailing conditions. In reliability analysis we consider such reliability indicators as the probability of the system transition in the stopping state and accidents, as well as the intensity of these transitions. The proposed model allows us to obtain correlations for the reliability parameters of the distributed computer system without any assumptions about the distribution laws of random variables and the elements number in the system.
Reliability analysis of tunnel surrounding rock stability by Monte-Carlo method
XI Jia-mi; YANG Geng-she
2008-01-01
Discussed advantages of improved Monte-Carlo method and feasibility aboutproposed approach applying in reliability analysis for tunnel surrounding rock stability. Onthe basis of deterministic parsing for tunnel surrounding rock, reliability computing methodof surrounding rock stability was derived from improved Monte-Carlo method. The com-puting method considered random of related parameters, and therefore satisfies relativityamong parameters. The proposed method can reasonably determine reliability of sur-rounding rock stability. Calculation results show that this method is a scientific method indiscriminating and checking surrounding rock stability.
Implementation of an optimum algorithm for structural reliability analysis based on FEM
CHENG Ying; TU Hong-mao; FAN Hong-li
2006-01-01
To analyze structural reliability by the stochastic FE (finite element) method rapidly and efficiently,a method combined with the FE method and gradient optimum algorithm based on ANSYS was presented when referring to the geometric interpretation of structural reliability index.ANSYS-based development was adopted to implement it.Results of an example demonstrate that the method requires fewer FE calculations compared with the design point method and Monte-Carlo simulation,and achieves satisfactory accuracy.
Investigation of Common Symptoms of Cancer and Reliability Analysis
无
2007-01-01
Objective: To identify cancer distribution and treatment requirements, a questionnaire on cancer patients was conducted. It was our objective to validate a series of symptoms commonly used in traditional Chinese medicine (TCM). Methods: The M. D. Anderson Symptom Assessment Inventory (MDASI) was used with 10 more TCM items added. Questions regarding TCM application requested in cancer care were also asked. A multi-center, cross-sectional study was conducted in 340 patients from 4 hospitals in Beijing and Dalian. SPSS and Excel software were adopted for statistical analysis. The questionnaire was self-evaluated with the Cronbach's alpha score. Results: The most common symptoms were fatigue 89.4%, sleep disturbance 74.4%, dry mouth 72.9%, poor appetite 72.9%, and difficulty remembering 71.2%. These symptoms affected work (89.8%), mood (82.6%),and activity (76.8%), resulting in poor quality of life. Eighty percent of the patients wanted to regulate the body with TCM. Almost 100% of the patients were interested in acquiring knowledge regarding the integrated traditional Chinese medicine (TCM) and Western medicine (WM) in the treatment and rehabilitation of cancer. Cronbach's alpha score indicated that there was acceptable internal consistency within both the MDASI and TCM items, 0.86 for MDASI, 0.78 for TCM, and 0.90 for MDASI-TCM (23 items). Conclusions: Fatigue, sleep disturbance, dry mouth, poor appetite, and difficulty remembering are the most common symptoms in cancer patients. These greatly affect the quality of life for these patients. Patients expressed a strong desire for TCM holistic regulation. The MDASI and its TCM-adapted model could be a critical tool for the quantitative study of TCM symptoms.
Bertucci, W; Duc, S; Villerius, V; Pernin, J N; Grappe, F
2005-12-01
The SRM power measuring crank system is nowadays a popular device for cycling power output (PO) measurements in the field and in laboratories. The PowerTap (CycleOps, Madison, USA) is a more recent and less well-known device that allows mobile PO measurements of cycling via the rear wheel hub. The aim of this study is to test the validity and reliability of the PowerTap by comparing it with the most accurate (i.e. the scientific model) of the SRM system. The validity of the PowerTap is tested during i) sub-maximal incremental intensities (ranging from 100 to 420 W) on a treadmill with different pedalling cadences (45 to 120 rpm) and cycling positions (standing and seated) on different grades, ii) a continuous sub-maximal intensity lasting 30 min, iii) a maximal intensity (8-s sprint), and iiii) real road cycling. The reliability is assessed by repeating ten times the sub-maximal incremental and continuous tests. The results show a good validity of the PowerTap during sub-maximal intensities between 100 and 450 W (mean PO difference -1.2 +/- 1.3 %) when it is compared to the scientific SRM model, but less validity for the maximal PO during sprint exercise, where the validity appears to depend on the gear ratio. The reliability of the PowerTap during the sub-maximal intensities is similar to the scientific SRM model (the coefficient of variation is respectively 0.9 to 2.9 % and 0.7 to 2.1 % for PowerTap and SRM). The PowerTap must be considered as a suitable device for PO measurements during sub-maximal real road cycling and in sub-maximal laboratory tests. PMID:16320172
Reliability centered maintenance (RCM): quantitative analysis of an induction electric furnace
Diego Santos Cerveira; Miguel Afonso Sellitto
2015-01-01
The purpose of this article is to define a maintenance strategy for an electric induction furnace, installed on a special steels Foundry. The research method was the quantitative modeling. The proposed method is based on Reliability-Centered Maintenance (RCM), applied to industrial equipment. Quantitative analysis of reliability, availability and maintainability were used as support the definition of the maintenance strategy of the equipment. For research, historical data were collected from ...
Aiming the electrical system reliability improvement, the Angra-1 energy electric system has been modified. The two original Diesel generators were replaced by two new ones, and the former were configured as standby generators. The purpose of this work is to quantify the electric system reliability improvement under the mentioned modifications by using Markovian analysis. It was found that the new configuration for the emergency Diesel system improves significantly the power supply to the safety buses. (author). 8 refs., 3 figs., 5 tabs
MultiMetEval : Comparative and Multi-Objective Analysis of Genome-Scale Metabolic Models
Zakrzewski, Piotr; Medema, Marnix H.; Gevorgyan, Albert; Kierzek, Andrzej M.; Breitling, Rainer; Takano, Eriko; Fong, Stephen S.
2012-01-01
Comparative metabolic modelling is emerging as a novel field, supported by the development of reliable and standardized approaches for constructing genome-scale metabolic models in high throughput. New software solutions are needed to allow efficient comparative analysis of multiple models in the co
Adjoint sensitivity analysis of dynamic reliability models based on Markov chains - I: Theory
The development of the adjoint sensitivity analysis procedure (ASAP) for generic dynamic reliability models based on Markov chains is presented, together with applications of this procedure to the analysis of several systems of increasing complexity. The general theory is presented in Part I of this work and is accompanied by a paradigm application to the dynamic reliability analysis of a simple binary component, namely a pump functioning on an 'up/down' cycle until it fails irreparably. This paradigm example admits a closed form analytical solution, which permits a clear illustration of the main characteristics of the ASAP for Markov chains. In particular, it is shown that the ASAP for Markov chains presents outstanding computational advantages over other procedures currently in use for sensitivity and uncertainty analysis of the dynamic reliability of large-scale systems. This conclusion is further underscored by the large-scale applications presented in Part II. (authors)
Xin-dang He
2015-01-01
Full Text Available Using the convex model approach, the bounds of uncertain variables are only required rather than the precise probability distributions, based on which it can be made possible to conduct the reliability analysis for many complex engineering problems with limited information. In this paper, three types of convex model including interval, ellipsoid, and multiellipsoid convex uncertainty model are investigated, and a uniform model of nonprobabilistic reliability analysis is built. In the reliability analysis process, an effective space-filling design is introduced to generate representative samples of uncertainty space so as to reduce the computational cost and provide an accurate depiction of possible model outcome. Finally, Spearman’s rank correlation coefficient is used to perform parameters global sensitivity analysis. Three numerical examples are investigated to demonstrate the feasibility and accuracy of the presented method.
Analysis of strain gage reliability in F-100 jet engine testing at NASA Lewis Research Center
Holanda, R.
1983-01-01
A reliability analysis was performed on 64 strain gage systems mounted on the 3 rotor stages of the fan of a YF-100 engine. The strain gages were used in a 65 hour fan flutter research program which included about 5 hours of blade flutter. The analysis was part of a reliability improvement program. Eighty-four percent of the strain gages survived the test and performed satisfactorily. A post test analysis determined most failure causes. Five failures were caused by open circuits, three failed gages showed elevated circuit resistance, and one gage circuit was grounded. One failure was undetermined.
Problems Related to Use of Some Terms in System Reliability Analysis
Nadezda Hanusova
2004-01-01
Full Text Available The paper deals with problems of using dependability terms, defined in actual standard STN IEC 50 (191: International electrotechnical dictionary, chap. 191: Dependability and quality of service (1993, in a technical systems dependability analysis. The goal of the paper is to find a relation between terms introduced in the mentioned standard and used in the technical systems dependability analysis and rules and practices used in a system analysis of the system theory. Description of a part of the system life cycle related to reliability is used as a starting point. The part of a system life cycle is described by the state diagram and reliability relevant therms are assigned.
Inpatient care in Kazakhstan: A comparative analysis
Ainur B Kumar
2013-01-01
Full Text Available Background: Reforms in inpatient care are critical for the enhancement of the efficiency of health systems. It still remains the main costly sector of the health system, accounting for more than 60% of all expenditures. Inappropriate and ineffective use of the hospital infrastructure is also a big issue. We aimed to analyze statistical data on health indices and dynamics of the hospital stock in Kazakhstan in comparison with those of developed countries. Materials and Methods: Study design is comparative quantitative analysis of inpatient care indicators. We used information and analytical methods, content analysis, mathematical treatment, and comparative analysis of statistical data on health system and dynamics of hospital stock in Kazakhstan and some other countries of the world [Organization for Economic Cooperation and Development (OECD, USA, Canada, Russia, China, Japan, and Korea] over the period 2001-2011. Results : Despite substantial and continuous reductions over the past 10 years, hospitalization rates in Kazakhstan still remain high compared to some developed countries, including those of the OECD. In fact, the hospital stay length for all patients in Kazakhstan in 2011 is around 9.9 days, hospitalization ratio per 100 people is 16.3, and hospital beds capacity is 100 per 10,000 inhabitants. Conclusion: The decreased level of beds may adversely affect both medical organization and health system operations. Alternatives to the existing inpatient care are now being explored. The introduction of the unified national healthcare system allows shifting the primary focus on primary care organizations, which can decrease the demand on inpatient care as a result of improving the health status of people at the primary care level.
Comparative analysis of black carbon in soils
Schmidt, Michael W. I.; Skjemstad, Jan O.; Czimczik, Claudia I.; Glaser, Bruno; Prentice, Ken M.; Gelinas, Yves; Kuhlbusch, Thomas A. J.
2001-03-01
Black carbon (BC), produced by incomplete combustion of fossil fuels and vegetation, occurs ubiquitously in soils and sediments. BC exists as a continuum from partly charred material to highly graphitized soot particles, with no general agreement on clear-cut boundaries of definition or analysis. In a comparative analysis, we measured BC forms in eight soil samples by six established methods. All methods involved removal of the non-BC components from the sample by thermal or chemical means or a combination of both. The remaining carbon, operationally defined as BC, was quantified via mass balance, elemental composition or by exploiting benzenecarboxylic acids as molecular markers or applying 13C MAS NMR (magic angle spinning nuclear magnetic resonance) spectroscopy. BC concentrations measured for individual samples vary over 2 orders of magnitude (up to a factor of 571). One possible explanation for this wide range of results is that the individual BC methods rely on operational definitions with clear-cut but different boundaries and developed for specific scientific questions, whereas BC represents a continuum of materials with widely contrasting physicochemical properties. Thus the methods are inherently designed to analytically determine different parts of the continuum, and it is crucial to know how measurements made by different techniques relate to each other. It is clear from this preliminary comparative analysis that a collection of BC reference materials should be established as soon as possible 1 ) to ensure long-term intralaboratory and interlaboratory data quality and 2) to facilitate comparative analyses between different analytical techniques and scientific approaches
Analysis of data reliability and stability in HR-SDN communication module
Choi, Dong-Hee; Shin, Jin-Chul; Park, Hong-Seong
2007-12-01
Profibus is open industrial communication system for wide range of applications in manufacturing and process automation. In Profibus, FDL service use to need hard real-time system. In these systems required data reliability and stability and real-time feature. Profibus fieldbus networks used in many industrial fields because of it supports real-time industrial communication. So we analyze of data reliability and stabilization in profibus network. In this paper, there was to a station for communication which uses FDL from in the communication module which is used a data transfer possibility at once, and from communication period (ex. 10ms) it analyzed the system effect which it follows in transmission lag occurrence element and a data transfer error ratio it analyzed. Like this analytical result it led and there were from transmission for reliability and data stability they confirmed to HR-SDN communication modules and a guarantee yes or no. In this paper, we try to analysis of transmission delay ability for satisfaction data reliability and stability in specific system, which requested real-time feature. And, we analysis system reconstruction time and data delay time according to data/token packet loss. Packet-error occur physical layer in Profibus. As a result of above analysis, we propose method of enhancement of reliability in system which requested system reliability and stability. And, we confirm proposed method.
Reliability analysis of nuclear containment without metallic liners against jet aircraft crash
The present study presents a methodology for detailed reliability analysis of nuclear containment without metallic liners against aircraft crash. For this purpose, a nonlinear limit state function has been derived using violation of tolerable crack width as failure criterion. This criterion has been considered as failure criterion because radioactive radiations may come out if size of crack becomes more than the tolerable crack width. The derived limit state uses the response of containment that has been obtained from a detailed dynamic analysis of nuclear containment under an impact of a large size Boeing jet aircraft. Using this response in conjunction with limit state function, the reliabilities and probabilities of failures are obtained at a number of vulnerable locations employing an efficient first-order reliability method (FORM). These values of reliability and probability of failure at various vulnerable locations are then used for the estimation of conditional and annual reliabilities of nuclear containment as a function of its location from the airport. To study the influence of the various random variables on containment reliability the sensitivity analysis has been performed. Some parametric studies have also been included to obtain the results of field and academic interest.
A Comparative Study on Error Analysis
Wu, Xiaoli; Zhang, Chun
2015-01-01
of errors in the written and spoken production of L2 learners has a long tradition in L2 pedagogy. Yet, in teaching and learning Chinese as a foreign language (CFL), only handful studies have been made either to define the ‘error’ in a pedagogically insightful way or to empirically investigate the...... occurrence of errors either in linguistic or pedagogical terms. The purpose of the current study is to demonstrate the theoretical and practical relevance of error analysis approach in CFL by investigating two cases - (1) Belgian (L1) learners’ use of Chinese (L2) comparative sentences in written production...
Comparative Analysis of Virtual Education Applications
Kurt, Mehmet
2006-01-01
The research was conducted in order to make comparative analysis of virtual education applications. The research is conducted in survey model. The study group consists of total 300 institutes providing virtual education in the fall, spring and summer semesters of 2004; 246 in USA, 10 in Australia, 3 in South Africa, 10 in India, 21 in UK, 6 in Japan, 4 in Turkey. The information has been collected by online questionnaire sent to the target mass by e-mail. The questionnaire has been developed ...
Reliability analysis of digital reactor protection system of Tianwan nuclear power plant
In the paper the function and structure of digital reactor protection system of Tianwan NPP was analyzed and the top events of fault trees of digital reactor protection system were established based on the reliability analysis methods of FTA (Fault Tree Analysis). The unavailability and the Minimal Cut-Sets (MCS) of the fault trees were obtained by the analysis and calculation using RISK-SPECTRUM software. The result of the analysis contributes to the operation and maintenance of Tianwan NPP. (authors)
78 FR 45447 - Revisions to Modeling, Data, and Analysis Reliability Standard
2013-07-29
... Analysis Reliability Standard, Notice of Proposed Rulemaking, 78 FR 19,152 (Mar. 29, 2013), 142 FERC ] 61... Environmental Policy Act, Order No. 486, 52 FR 47897 (Dec. 17, 1987), FERC Stats. & Regs. Regulations Preambles... Energy Regulatory Commission 18 CFR Part 40 Revisions to Modeling, Data, and Analysis...
Content Analysis in Mass Communication: Assessment and Reporting of Intercoder Reliability.
Lombard, Matthew; Snyder-Duch, Jennifer; Bracken, Cheryl Campanella
2002-01-01
Reviews the importance of intercoder agreement for content analysis in mass communication research. Describes several indices for calculating this type of reliability (varying in appropriateness, complexity, and apparent prevalence of use). Presents a content analysis of content analyses reported in communication journals to establish how…
YANG Zhou; ZHU Yunpeng; REN Hongrui; ZHANG Yimin
2015-01-01
Reliability allocation of computerized numerical controlled(CNC) lathes is very important in industry. Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components, which is not applicable in some conditions. Aiming at solving the problem of CNC lathes reliability allocating, a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis(FMEA) is presented. Firstly, conventional reliability allocation methods are introduced. Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated. Subsequently, a cubic transformed function is established in order to overcome these limitations. Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence. Designers can choose appropriate transform amplitudes according to their requirements. Finally, a CNC lathe and a spindle system are used as an example to verify the new allocation method. Seven criteria are considered to compare the results of the new method with traditional methods. The allocation results indicate that the new method is more flexible than traditional methods. By employing the new cubic transformed function, the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.
Data collection on the unit control room simulator as a method of operator reliability analysis
The report consists of the following chapters: (1) Probabilistic assessment of nuclear power plant operation safety and human factor reliability analysis; (2) Simulators and simulations as human reliability analysis tools; (3) DOE project for using the collection and analysis of data from the unit control room simulator in human factor reliability analysis at the Paks nuclear power plant; (4) General requirements for the organization of the simulator data collection project; (5) Full-scale simulator at the Nuclear Power Plants Research Institute in Trnava, Slovakia, used as a training means for operators of the Dukovany NPP; (6) Assessment of the feasibility of quantification of important human actions modelled within a PSA study by employing simulator data analysis; (7) Assessment of the feasibility of using the various exercise topics for the quantification of the PSA model; (8) Assessment of the feasibility of employing the simulator in the analysis of the individual factors affecting the operator's activity; and (9) Examples of application of statistical methods in the analysis of the human reliability factor. (P.A.)
Estimating Reliability of Disturbances in Satellite Time Series Data Based on Statistical Analysis
Zhou, Z.-G.; Tang, P.; Zhou, M.
2016-06-01
Normally, the status of land cover is inherently dynamic and changing continuously on temporal scale. However, disturbances or abnormal changes of land cover — caused by such as forest fire, flood, deforestation, and plant diseases — occur worldwide at unknown times and locations. Timely detection and characterization of these disturbances is of importance for land cover monitoring. Recently, many time-series-analysis methods have been developed for near real-time or online disturbance detection, using satellite image time series. However, the detection results were only labelled with "Change/ No change" by most of the present methods, while few methods focus on estimating reliability (or confidence level) of the detected disturbances in image time series. To this end, this paper propose a statistical analysis method for estimating reliability of disturbances in new available remote sensing image time series, through analysis of full temporal information laid in time series data. The method consists of three main steps. (1) Segmenting and modelling of historical time series data based on Breaks for Additive Seasonal and Trend (BFAST). (2) Forecasting and detecting disturbances in new time series data. (3) Estimating reliability of each detected disturbance using statistical analysis based on Confidence Interval (CI) and Confidence Levels (CL). The method was validated by estimating reliability of disturbance regions caused by a recent severe flooding occurred around the border of Russia and China. Results demonstrated that the method can estimate reliability of disturbances detected in satellite image with estimation error less than 5% and overall accuracy up to 90%.
The design difference between Trillo NPP and other Spanish nuclear power plants (basic Westinghouse and General Electric designs) were made clear in the Human Reliability Analysis of the Probabilistic Safety Analysis (PSA) for Trillo NPP. The object of this paper is to describe the most significant characteristics of the Human Reliability Analysis carried out in the PSA, with special emphasis on the possible diagnostic errors and their consequences, based on the characteristics in the Emergency Operations Manual for Trillo NPP. - In the case of human errors before the initiating event (type 1), the existence of four redundancies in most of the plant safety systems, means that the impact of this type or error on the final results of the PSA is insignificant. However, in the case common cause errors, especially in certain calibration errors, some actions are significant in the final equation for core damage - The number of human actions that the operator has to carry out during the accidents (type 3) modelled, is relatively small in comparison with this value in other PSAs. This is basically due to the high level of automation at Rillo NPP - The Plant Operations Manual cannot be strictly considered to be a symptoms-based procedure. The operation Group must select the chapter from the Operations Manual to be followed, after having diagnosed the perturbing event, using for this purpose and Emergency and Anomaly Decision Tree (M.O.3.0.1) based on the different indications, alarms and symptoms present in the plant after the perturbing event. For this reason, it was decided to analyse the possible diagnosis errors. In the bibliography on diagnosis and commission errors available at the present time, there is no precise methodology for the analysis of this type of error and its incorporation into PSAs. The method used in the PSA for Trillo y NPP to evaluate this type of interaction, is to develop a Diagnosis Error Table, the object of which is to identify the situations in
Fault tree method is used for reliability analysis for reactor power control system, including uncertainty analysis and sensitive analysis. 'loss of regulation accident' top event and 'loss of effective control' top event are defined, corresponding fault tree are constructed, and contribution of hardware failure and software failure to system safety are calculated. It points out that common mode failures of software, actuator, sensor and operator's response have significant influence to system reliability in 'loss of regulation accident'; software common mode failure and operators' response have significant contribution to system reliability in 'loss of efficient control accident'. (authors)
Structure buckling and non-probabilistic reliability analysis of supercavitating vehicles
AN Wei-guang; ZHOU Ling; AN Hai
2009-01-01
To perform structure buckling and reliability analysis on supercavitating vehicles with high velocity in the submarine, supercavitating vehicles were simplified as variable cross section beam firstly. Then structural buckling analysis of supercavitating vehicles with or without engine thrust was conducted, and the structural buckling safety margin equation of supercavitating vehicles was established. The indefinite information was de-scribed by interval set and the structure reliability analysis was performed by using non-probabilistic reliability method. Considering interval variables as random variables which satisfy uniform distribution, the Monte-Carlo method was used to calculate the non-probabilistic failure degree. Numerical examples of supercavitating vehi-cles were presented. Under different ratios of base diameter to cavitator diameter, the change tendency of non-probabilistic failure degree of structural buckling of supereavitating vehicles with or without engine thrust was studied along with the variety of speed.
Analysis of the reliability of the active injection safety systems of Angra I
The reliability of the active emergency core cooling systems of Angra I nuclear power plant is evaluated. The fault tree analysis is employed. The unavailability of the above cited systems, is calculated. A parametric sensitivity analysis has been performed, due to the existing scattering in the failure and repair rate data of these system's components. The minimal cut sets were determined and, as a final step, a reliability importance analysis has been performed. This final step has required the development of a computer program. The methodology and data from the 'Reactor Safety Study' (Wash-1400) (in which the reliability of safety systems of a tipical PWR plant is calculated), is employed. The unavailability values for the safety systems analysed are too low, thus showing that in most cases the systems analysed are available to mitigate the effects of a loss-of-coolant accident. (Author)
Comparative genome analysis of Basidiomycete fungi
Riley, Robert; Salamov, Asaf; Henrissat, Bernard; Nagy, Laszlo; Brown, Daren; Held, Benjamin; Baker, Scott; Blanchette, Robert; Boussau, Bastien; Doty, Sharon L.; Fagnan, Kirsten; Floudas, Dimitris; Levasseur, Anthony; Manning, Gerard; Martin, Francis; Morin, Emmanuelle; Otillar, Robert; Pisabarro, Antonio; Walton, Jonathan; Wolfe, Ken; Hibbett, David; Grigoriev, Igor
2013-08-07
Fungi of the phylum Basidiomycota (basidiomycetes), make up some 37percent of the described fungi, and are important in forestry, agriculture, medicine, and bioenergy. This diverse phylum includes symbionts, pathogens, and saprotrophs including the majority of wood decaying and ectomycorrhizal species. To better understand the genetic diversity of this phylum we compared the genomes of 35 basidiomycetes including 6 newly sequenced genomes. These genomes span extremes of genome size, gene number, and repeat content. Analysis of core genes reveals that some 48percent of basidiomycete proteins are unique to the phylum with nearly half of those (22percent) found in only one organism. Correlations between lifestyle and certain gene families are evident. Phylogenetic patterns of plant biomass-degrading genes in Agaricomycotina suggest a continuum rather than a dichotomy between the white rot and brown rot modes of wood decay. Based on phylogenetically-informed PCA analysis of wood decay genes, we predict that that Botryobasidium botryosum and Jaapia argillacea have properties similar to white rot species, although neither has typical ligninolytic class II fungal peroxidases (PODs). This prediction is supported by growth assays in which both fungi exhibit wood decay with white rot-like characteristics. Based on this, we suggest that the white/brown rot dichotomy may be inadequate to describe the full range of wood decaying fungi. Analysis of the rate of discovery of proteins with no or few homologs suggests the value of continued sequencing of basidiomycete fungi.
The Reliability and Maintainability Analysis of Pneumatic System of Rotary Drilling Machines
Rahimdel, Mohammad Javad; Hosienie, Seyed Hadi; Ataei, Mohammad; Khalokakaei, Reza
2013-10-01
In any blasthole drilling the bottom of the blasthole must be kept clean by evacuating drill cuttings or it flushing as soon as they appear to ensure efficient drilling. If it is not done well, a large quantity of energy will be consumed in regrinding with the consequent wear on drill bit and decrease penetration, apart from the risk of jamming. Therefore, research on reliability and probability of safe operation of pneumatic system of drilling machines is of prime importance to ensure safe drilling operations. In this paper, reliability of this system was modeled and analyzed. To doing this research, drilling machines in Sarcheshmeh Copper Mine in Iran have been selected for data collection and analysis. After reliability modeling of pneumatic system, maintenance scheduling has been presented based on different reliability levels. There were four rotary drilling machines in this mine (named A, B, C and D). Results showed that after about 7 h drilling of machines A and B, and after 103 and 44 h drilling of machines C and D respectively, noticeably the reliability of pneumatic system reached to 80 %. As a result, machines C and D have more reliable pneumatic systems in comparison to machines A and B and checking and servicing of pneumatic system before these time was essential. Also, maintainability analysis showed that more failures of pneumatic system of machines A, B, C and D will be noticeably repaired at about 28, 34, 6 and 9 h.
An overview of digital I and C system reliability analysis in nuclear power plants
The transition from analog to digital technology has occurred in industry as a whole. This has left those who still use analog systems in a tough situation because the suppliers are decreasing the amount of service and spare parts that they have on hand for analog systems. Therefore, the transition from analog to digital for the Instrumentation and Control systems in nuclear power plants is of no exception. Since safety is of paramount importance for nuclear industry, the reliability and safety of digital systems should be demonstrated in a systematic manner before they are being adopted. For the simplest digital systems, the hardware reliability and software reliability are two fundamental components for digital system reliability analysis. This paper provides a literature survey on the work that has been performed in this field. (authors)
Migneault, Gerard E.
1987-01-01
Emulation techniques can be a solution to a difficulty that arises in the analysis of the reliability of guidance and control computer systems for future commercial aircraft. Described here is the difficulty, the lack of credibility of reliability estimates obtained by analytical modeling techniques. The difficulty is an unavoidable consequence of the following: (1) a reliability requirement so demanding as to make system evaluation by use testing infeasible; (2) a complex system design technique, fault tolerance; (3) system reliability dominated by errors due to flaws in the system definition; and (4) elaborate analytical modeling techniques whose precision outputs are quite sensitive to errors of approximation in their input data. Use of emulation techniques for pseudo-testing systems to evaluate bounds on the parameter values needed for the analytical techniques is then discussed. Finally several examples of the application of emulation techniques are described.
Reliability analysis using high dimensional model representation for mixed uncertain variables
The reliability estimation of a structural system depends on the type of uncertain parameters considered. If all the uncertain parameters are defined as random variables, then the reliability can be estimated by using probability theory. However, when modeling uncertain variables with limited information as intervals with upper and lower bounds, the entire range of these bounds should be explored. When dealing with the combination of both random and interval variables, as every combination of interval variables demands one probabilistic based analysis, the computational cost involved in estimating the reliability of the system increases exponentially. Therefore in this paper, high dimensional model representation (HDMR) is used to approximate the failure function accurately, and fast Fourier transform techniques are applied to solve the convolution integral. The proposed methodology demonstrates the improvement in computational efficiency and accuracy in the estimation of the reliability bounds using numerical examples.
RELIABILITY ANALYSIS OF THERMAL POWER GENERATING UNITS BASED ON WORKING HOURS
C.P.S. Hungund
2014-06-01
Full Text Available For any system reliability calculation, estimation plays a vital role and hence the analysis is to be diverted to calculate reliabilities of the units. To do this, we need to analyze failure rates or inter-failure time intervals or duration of the failure free operation of the units. This data is usually termed as Working Hours (successive failures. Working Hours implies that the gap between failure to failure which is directly linked with the reliability of the system. Hence in this paper, first we fit and test the suitability of the data using Exponential and Weibull distribution through chi-square Goodness of Fit (GoF test. In the later part, reliabilities of different units are calculated using the same distributions. Conclusions are drawn based on the results obtained.
Comparative Analysis of Visco-elastic Models with Variable Parameters
Silviu Nastac
2010-01-01
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.
Comparative analysis of heat transfer correlations for forced convection boiling
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
A passive system can fail either due to classical mechanical failure of components, referred to as hardware failure, or due to the failure of physical phenomena to fulfill the intended function, referred to as functional failure. In this paper a methodology is discussed for the integration of these two kinds of unreliability and applied to evaluate the integrated failure probability of the passive decay heat removal system of Indian 500 MWe prototype fast breeder reactor (PFBR). The probability of occurrence of various system hardware configurations is evaluated using the fault tree method and functional failure probabilities on the corresponding configurations are determined based on the overall approach reported in the reliability methods for passive system (RMPS) project. The variation of functional reliability with time, which is coupled to the probability of occurrence of various hardware system configurations is studied and incorporated in the integrated reliability analysis. It is observed that this consideration of the dependence of functional reliability on time will give significant advantages on system reliability. The integrated reliability analysis is also explained using an event tree. The impact of the provision for forced circulation in the primary circuit on functional reliability is also studied with this procedure and it is found that the forced circulation capability helps to bring down the total decay heat removal failure probability by lowering the peak temperatures after the reactor shut down.
Reliability analysis of production ships with emphasis on load combination and ultimate strength
Wang, Xiaozhi
1995-05-01
This thesis deals with ultimate strength and reliability analysis of offshore production ships, accounting for stochastic load combinations, using a typical North Sea production ship for reference. A review of methods for structural reliability analysis is presented. Probabilistic methods are established for the still water and vertical wave bending moments. Linear stress analysis of a midships transverse frame is carried out, four different finite element models are assessed. Upon verification of the general finite element code ABAQUS with a typical ship transverse girder example, for which test results are available, ultimate strength analysis of the reference transverse frame is made to obtain the ultimate load factors associated with the specified pressure loads in Det norske Veritas Classification rules for ships and rules for production vessels. Reliability analysis is performed to develop appropriate design criteria for the transverse structure. It is found that the transverse frame failure mode does not seem to contribute to the system collapse. Ultimate strength analysis of the longitudinally stiffened panels is performed, accounting for the combined biaxial and lateral loading. Reliability based design of the longitudinally stiffened bottom and deck panels is accomplished regarding the collapse mode under combined biaxial and lateral loads. 107 refs., 76 refs., 37 tabs.
Determination of Weibull Analysis of the Hypereutectic Silumins Reliability in Failure Time Respect
J. Szymszal; J. Piątkowski; T. Mikuszewski; M. Maliński
2009-01-01
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 thr...
This work presents the implementation of the Adjoint Sensitivity Analysis Procedure (ASAP) for the Continuous Time, Discrete Space Markov chains (CTMC), as an alternative to the other computational expensive methods. In order to develop this procedure as an end product in reliability studies, the reliability of the physical systems is analyzed using a coupled Fault-Tree - Markov chain technique, i.e. the abstraction of the physical system is performed using as the high level interface the Fault-Tree and afterwards this one is automatically converted into a Markov chain. The resulting differential equations based on the Markov chain model are solved in order to evaluate the system reliability. Further sensitivity analyses using ASAP applied to CTMC equations are performed to study the influence of uncertainties in input data to the reliability measures and to get the confidence in the final reliability results. The methods to generate the Markov chain and the ASAP for the Markov chain equations have been implemented into the new computer code system QUEFT/MARKOMAGS/MCADJSEN for reliability and sensitivity analysis of physical systems. The validation of this code system has been carried out by using simple problems for which analytical solutions can be obtained. Typical sensitivity results show that the numerical solution using ASAP is robust, stable and accurate. The method and the code system developed during this work can be used further as an efficient and flexible tool to evaluate the sensitivities of reliability measures for any physical system analyzed using the Markov chain. Reliability and sensitivity analyses using these methods have been performed during this work for the IFMIF Accelerator System Facilities. The reliability studies using Markov chain have been concentrated around the availability of the main subsystems of this complex physical system for a typical mission time. The sensitivity studies for two typical responses using ASAP have been
Lessons Learned on Benchmarking from the International Human Reliability Analysis Empirical Study
Ronald L. Boring; John A. Forester; Andreas Bye; Vinh N. Dang; Erasmia Lois
2010-06-01
The International Human Reliability Analysis (HRA) Empirical Study is a comparative benchmark of the prediction of HRA methods to the performance of nuclear power plant crews in a control room simulator. There are a number of unique aspects to the present study that distinguish it from previous HRA benchmarks, most notably the emphasis on a method-to-data comparison instead of a method-to-method comparison. This paper reviews seven lessons learned about HRA benchmarking from conducting the study: (1) the dual purposes of the study afforded by joining another HRA study; (2) the importance of comparing not only quantitative but also qualitative aspects of HRA; (3) consideration of both negative and positive drivers on crew performance; (4) a relatively large sample size of crews; (5) the use of multiple methods and scenarios to provide a well-rounded view of HRA performance; (6) the importance of clearly defined human failure events; and (7) the use of a common comparison language to “translate” the results of different HRA methods. These seven lessons learned highlight how the present study can serve as a useful template for future benchmarking studies.
Nigerian Power Sector: Comparative Analysis of Productivity
Iwuamadi ObiomaChidiebere
2015-06-01
Full Text Available Undoubtedly, power instability in the Nigerian Power Sector despite several mitigative measures by the government has created some chocks in the national socio-economic wheel of development. Unfortunately, the conceptual objective of the power reforms to remedy inadequate power generation capacity, inefficient usage of capacity, ineffective regulation and high technical losses is tardily being achieved. This research comparatively analyzed the rate of productivity change in Nigeria’s power sector from 2005 – 2013. The analysis reveals that privatization improved the productivity index by 89%. It is expected that this work may assist the power policy makers and regulators to come up with abetter framework for the full realization of the noble goals envisaged in this reform act.
Comparative Genome Analysis of Basidiomycete Fungi
Riley, Robert; Salamov, Asaf; Morin, Emmanuelle; Nagy, Laszlo; Manning, Gerard; Baker, Scott; Brown, Daren; Henrissat, Bernard; Levasseur, Anthony; Hibbett, David; Martin, Francis; Grigoriev, Igor
2012-03-19
Fungi of the phylum Basidiomycota (basidiomycetes), make up some 37percent of the described fungi, and are important in forestry, agriculture, medicine, and bioenergy. This diverse phylum includes the mushrooms, wood rots, symbionts, and plant and animal pathogens. To better understand the diversity of phenotypes in basidiomycetes, we performed a comparative analysis of 35 basidiomycete fungi spanning the diversity of the phylum. Phylogenetic patterns of lignocellulose degrading genes suggest a continuum rather than a sharp dichotomy between the white rot and brown rot modes of wood decay. Patterns of secondary metabolic enzymes give additional insight into the broad array of phenotypes found in the basidiomycetes. We suggest that the profile of an organism in lignocellulose-targeting genes can be used to predict its nutritional mode, and predict Dacryopinax sp. as a brown rot; Botryobasidium botryosum and Jaapia argillacea as white rots.
Reliability analysis and its applications in the design of the Loviisa nuclear power plant
The construction of Loviisa Nuclear Power Plant was started in 1970 as a cooperation between the Finnish utility company Imatran Voima Osakeyhtio and the USSR export organization V/O Atomenergoexport (formaerly V/O Technopromexport). Many domestic and foreign companies are participating in the project as subcontractors and consultants. The ordering of the plant gave rise to an extensive investigation on reliability engineering, which was mainly due to the following reasons. (1) The plant will provide, in due course, about 10% of Finland's electric power. (2) It is a requirement of the safety authorities that the conventional safety analysis be supplemented with a probabilistic analysis. (3) The plant is in some respect the first of its kind and the reliability analysis is considered to have a reviewing, unifying and coordinating influence on the non-turnkay delivery. In the report, the aims and organization of the reliability work are discussed in brief, while the methods and realization are discussed in greater detail. The practical tool of the reliability work consists of a systematic reliability analysis, made up of both qualitative and quantitative stages. In quantitative analysis, fault-tree techniques and Monte Carlo simulation are primarily used. Analytical calculation patterns are used for performing sensitivity analyses and, in particular, for the analysis of stand-by type safety systems. Applications have at first concentrated on safety-related systems. The analysis of the reactor protection system, radiation monitoring system, residula heat removal system and a consequence diagram related to a loss of coolant accident are described as examples. Principal problems such as data collection and common mode failure analysis are also discussed. (author)
Efficient surrogate models for reliability analysis of systems with multiple failure modes
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.
Comparative Analysis of Students’ Media Competences Levels
Alexander Fedorov
2015-08-01
Full Text Available This article analyzed the results of survey of university students’ media literacy competence (on the base of a classification of indicators of media literacy competence of the audience as an effective tool for comparative analysis of the levels of development of media competence of students of the control and experimental groups: the level of media competence of students who have a one-year training course in the framework of media literacy education courses four times higher than in similar indicators in the control group. Analysis of the results of this survey confirmed the general trend of media contacts of student audience – its orientation to entertainment genres of audiovisual media, visually appealing; positive, active, unmarried, childless, educated, highly qualified characters (primarily – male characters aged 19 to 35 years. These heroes are characteristic optimism, independence, intelligence, emotion. They have an excellent command of the life situation and have a positive impact on the development progress of the plot of a media text.
Comparation studies of uranium analysis method using spectrophotometer and voltammeter
Comparation studies of uranium analysis method by spectrophotometer and voltammeter had been done. The objective of experiment is to examine the reliability of analysis method and instrument performance by evaluate parameters; linearity, accuracy, precision and detection limit. Uranyl nitrate hexahydrate is used as standard, and the sample is solvent mixture of tributyl phosphate and kerosene containing uranium (from phosphoric acid purification unit Petrokimia Gresik). Uranium (U) stripping in the sample use HN03 0,5 N and then was analyzed by using of both instrument. Analysis of standard show that both methods give a good linearity by correlation coefficient > 0,999. Spectrophotometry give accuration 99,34 - 101,05 % with ratio standard deviation (RSD) 1,03 %; detection limit (DL) 0,05 ppm. Voltammetry give accuration 95,63 -101,49 % with RSD 3,91 %; detection limit (DL) 0,509 ppm. On the analysis of sludge samples were given the significantly different in result; spectrophotometry give U concentration 4,445 ppm by RSD 6,74 % and voltammetry give U concentration 7,693 by RSD 19,53%. (author)
In this paper, we describe a framework to efficiently assess the reliability of fault tolerant control systems on low-cost unmanned aerial vehicles. The analysis is developed for a system consisting of a fixed number of actuators. In addition, the system includes a scheme to detect failures in individual actuators and, as a consequence, switch between different control algorithms for automatic operation of the actuators. Existing dynamic reliability analysis methods are insufficient for this class of systems because the coverage parameters for different actuator failures can be time-varying, correlated, and difficult to obtain in practice. We address these issues by combining new fault detection performance metrics with pivotal decomposition. These new metrics capture the interactions in different fault detection channels, and can be computed from stochastic models of fault detection algorithms. Our approach also decouples the high dimensional analysis problem into low dimensional sub-problems, yielding a computationally efficient analysis. Finally, we demonstrate the proposed method on a numerical example. The analysis results are also verified by Monte Carlo simulations. - Highlights: • We study fault tolerant control (FTC) systems on low-cost unmanned aerial vehicles. • We build a reliability structure model for FTC systems. • New fault detection performance metrics are integrated via pivotal decomposition. • The fault detection metrics capture the interactions in fault detection channels. • Numerical results show that FTC techniques can improve system reliability
GAO Hai-feng; BAI Guang-chen
2015-01-01
To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method (SRSM) is proposed. SRSM integrates the advantages of support vector machine (SVM) and traditional response surface method (RSM), and utilizes experimental samples to construct a suitable response surface function (RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method (MCM); while SRSM (17.296 s) needs far less running time than MCM (10958 s) and RSM (9840 s). Therefore, under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.
Structural Reliability Assessment by Integrating Sensitivity Analysis and Support Vector Machine
Shao-Fei Jiang
2014-01-01
Full Text Available To reduce the runtime and ensure enough computation accuracy, this paper proposes a structural reliability assessment method by the use of sensitivity analysis (SA and support vector machine (SVM. The sensitivity analysis is firstly applied to assess the effect of random variables on the values of performance function, while the small-influence variables are rejected as input vectors of SVM. Then, the trained SVM is used to classify the input vectors, which are produced by sampling the residual variables based on their distributions. Finally, the reliability assessment is implemented with the aid of reliability theory. A 10-bar planar truss is used to validate the feasibility and efficiency of the proposed method, and a performance comparison is made with other existing methods. The results show that the proposed method can largely save the runtime with less reduction of the accuracy; furthermore, the accuracy using the proposed method is the highest among the methods employed.
Reliability assessment of generation and transmission systems using fault-tree analysis
This paper presents a method that integrates deterministic approach with fault-tree analysis for reliability assessment of a composite system (generation and transmission in power systems). The contingency screening is conducted in the first step. The results are further classified into three clusters in the second step: normal, local trouble and system trouble. The fault-tree analysis is used to assess the reliability of the composite system in the third step. Finally, Risk Reduction Worth is adopted as a measure of importance for identifying the crucial element that has significant impact on the reliability. In this paper, a composite system in Taiwan serves as an example for illustrating the simulation results attained by the proposed method. The simulation results, verified by Siemens PTI PSS/E TPLAN software package, show that the proposed method is applicable for large scale power systems.
Analysis of the Kinematic Accuracy Reliability of a 3-DOF Parallel Robot Manipulator
Guohua Cui
2015-02-01
Full Text Available Kinematic accuracy reliability is an important performance index in the evaluation of mechanism quality. By using a 3- DOF 3-PUU parallel robot manipulator as the research object, the position and orientation error model was derived by mapping the relation between the input and output of the mechanism. Three error sensitivity indexes that evaluate the kinematic accuracy of the parallel robot manipulator were obtained by adapting the singular value decomposition of the error translation matrix. Considering the influence of controllable and uncontrollable factors on the kinematic accuracy, the mathematical model of reliability based on random probability was employed. The measurement and calculation method for the evaluation of the mechanism’s kinematic reliability level was also provided. By analysing the mechanism’s errors and reliability, the law of surface error sensitivity for the location and structure parameters was obtained. The kinematic reliability of the parallel robot manipulator was statistically computed on the basis of the Monte Carlo simulation method. The reliability analysis of kinematic accuracy provides a theoretical basis for design optimization and error compensation.
Markov chain modelling of reliability analysis and prediction under mixed mode loading
Singh, Salvinder; Abdullah, Shahrum; Nik Mohamed, Nik Abdullah; Mohd Noorani, Mohd Salmi
2015-03-01
The reliability assessment for an automobile crankshaft provides an important understanding in dealing with the design life of the component in order to eliminate or reduce the likelihood of failure and safety risks. The failures of the crankshafts are considered as a catastrophic failure that leads towards a severe failure of the engine block and its other connecting subcomponents. The reliability of an automotive crankshaft under mixed mode loading using the Markov Chain Model is studied. The Markov Chain is modelled by using a two-state condition to represent the bending and torsion loads that would occur on the crankshaft. The automotive crankshaft represents a good case study of a component under mixed mode loading due to the rotating bending and torsion stresses. An estimation of the Weibull shape parameter is used to obtain the probability density function, cumulative distribution function, hazard and reliability rate functions, the bathtub curve and the mean time to failure. The various properties of the shape parameter is used to model the failure characteristic through the bathtub curve is shown. Likewise, an understanding of the patterns posed by the hazard rate onto the component can be used to improve the design and increase the life cycle based on the reliability and dependability of the component. The proposed reliability assessment provides an accurate, efficient, fast and cost effective reliability analysis in contrast to costly and lengthy experimental techniques.
Markov Chain Modelling of Reliability Analysis and Prediction under Mixed Mode Loading
SINGH Salvinder; ABDULLAH Shahrum; NIK MOHAMED Nik Abdullah; MOHD NOORANI Mohd Salmi
2015-01-01
The reliability assessment for an automobile crankshaft provides an important understanding in dealing with the design life of the component in order to eliminate or reduce the likelihood of failure and safety risks. The failures of the crankshafts are considered as a catastrophic failure that leads towards a severe failure of the engine block and its other connecting subcomponents. The reliability of an automotive crankshaft under mixed mode loading using the Markov Chain Model is studied. The Markov Chain is modelled by using a two-state condition to represent the bending and torsion loads that would occur on the crankshaft. The automotive crankshaft represents a good case study of a component under mixed mode loading due to the rotating bending and torsion stresses. An estimation of the Weibull shape parameter is used to obtain the probability density function, cumulative distribution function, hazard and reliability rate functions, the bathtub curve and the mean time to failure. The various properties of the shape parameter is used to model the failure characteristic through the bathtub curve is shown. Likewise, an understanding of the patterns posed by the hazard rate onto the component can be used to improve the design and increase the life cycle based on the reliability and dependability of the component. The proposed reliability assessment provides an accurate, efficient, fast and cost effective reliability analysis in contrast to costly and lengthy experimental techniques.
Guidelines for reliability analysis of digital systems in PSA context. Phase 1 status report
Digital protection and control systems are appearing as upgrades in older nuclear power plants (NPPs) and are commonplace in new NPPs. To assess the risk of NPP operation and to determine the risk impact of digital system upgrades on NPPs, quantitative reliability models are needed for digital systems. Due to the many unique attributes of these systems, challenges exist in systems analysis, modeling and in data collection. Currently there is no consensus on reliability analysis approaches. Traditional methods have clearly limitations, but more dynamic approaches are still in trial stage and can be difficult to apply in full scale probabilistic safety assessments (PSA). The number of PSAs worldwide including reliability models of digital I and C systems are few. A comparison of Nordic experiences and a literature review on main international references have been performed in this pre-study project. The study shows a wide range of approaches, and also indicates that no state-of-the-art currently exists. The study shows areas where the different PSAs agree and gives the basis for development of a common taxonomy for reliability analysis of digital systems. It is still an open matter whether software reliability needs to be explicitly modelled in the PSA. The most important issue concerning software reliability is proper descriptions of the impact that software-based systems has on the dependence between the safety functions and the structure of accident sequences. In general the conventional fault tree approach seems to be sufficient for modelling reactor protection system kind of functions. The following focus areas have been identified for further activities: 1. Common taxonomy of hardware and software failure modes of digital components for common use 2. Guidelines regarding level of detail in system analysis and screening of components, failure modes and dependencies 3. Approach for modelling of CCF between components (including software). (Author)
Guidelines for reliability analysis of digital systems in PSA context. Phase 1 status report
Authen, S.; Larsson, J. (Risk Pilot AB, Stockholm (Sweden)); Bjoerkman, K.; Holmberg, J.-E. (VTT, Helsingfors (Finland))
2010-12-15
Digital protection and control systems are appearing as upgrades in older nuclear power plants (NPPs) and are commonplace in new NPPs. To assess the risk of NPP operation and to determine the risk impact of digital system upgrades on NPPs, quantitative reliability models are needed for digital systems. Due to the many unique attributes of these systems, challenges exist in systems analysis, modeling and in data collection. Currently there is no consensus on reliability analysis approaches. Traditional methods have clearly limitations, but more dynamic approaches are still in trial stage and can be difficult to apply in full scale probabilistic safety assessments (PSA). The number of PSAs worldwide including reliability models of digital I and C systems are few. A comparison of Nordic experiences and a literature review on main international references have been performed in this pre-study project. The study shows a wide range of approaches, and also indicates that no state-of-the-art currently exists. The study shows areas where the different PSAs agree and gives the basis for development of a common taxonomy for reliability analysis of digital systems. It is still an open matter whether software reliability needs to be explicitly modelled in the PSA. The most important issue concerning software reliability is proper descriptions of the impact that software-based systems has on the dependence between the safety functions and the structure of accident sequences. In general the conventional fault tree approach seems to be sufficient for modelling reactor protection system kind of functions. The following focus areas have been identified for further activities: 1. Common taxonomy of hardware and software failure modes of digital components for common use 2. Guidelines regarding level of detail in system analysis and screening of components, failure modes and dependencies 3. Approach for modelling of CCF between components (including software). (Author)
Reliability analysis of nuclear piping system using semi-Markov process model
The paper presents a general model for evaluating the rupture frequencies and reliability of the piping system in nuclear power plant based on the theory of semi-Markov process. The proposed model is able to incorporate the effect of aging related degradation of pipes. Time dependent rupture frequencies are computed and compared against those obtained from the homogeneous Markov process model. (author)
Johnson Space Center's Risk and Reliability Analysis Group 2008 Annual Report
Valentine, Mark; Boyer, Roger; Cross, Bob; Hamlin, Teri; Roelant, Henk; Stewart, Mike; Bigler, Mark; Winter, Scott; Reistle, Bruce; Heydorn,Dick
2009-01-01
The Johnson Space Center (JSC) Safety & Mission Assurance (S&MA) Directorate s Risk and Reliability Analysis Group provides both mathematical and engineering analysis expertise in the areas of Probabilistic Risk Assessment (PRA), Reliability and Maintainability (R&M) analysis, and data collection and analysis. The fundamental goal of this group is to provide National Aeronautics and Space Administration (NASA) decisionmakers with the necessary information to make informed decisions when evaluating personnel, flight hardware, and public safety concerns associated with current operating systems as well as with any future systems. The Analysis Group includes a staff of statistical and reliability experts with valuable backgrounds in the statistical, reliability, and engineering fields. This group includes JSC S&MA Analysis Branch personnel as well as S&MA support services contractors, such as Science Applications International Corporation (SAIC) and SoHaR. The Analysis Group s experience base includes nuclear power (both commercial and navy), manufacturing, Department of Defense, chemical, and shipping industries, as well as significant aerospace experience specifically in the Shuttle, International Space Station (ISS), and Constellation Programs. The Analysis Group partners with project and program offices, other NASA centers, NASA contractors, and universities to provide additional resources or information to the group when performing various analysis tasks. The JSC S&MA Analysis Group is recognized as a leader in risk and reliability analysis within the NASA community. Therefore, the Analysis Group is in high demand to help the Space Shuttle Program (SSP) continue to fly safely, assist in designing the next generation spacecraft for the Constellation Program (CxP), and promote advanced analytical techniques. The Analysis Section s tasks include teaching classes and instituting personnel qualification processes to enhance the professional abilities of our analysts
Development of web-based reliability data analysis algorithm model and its application
For this study, a database model of plant reliability was developed for the effective acquisition and management of plant-specific data that can be used in various applications of plant programs as well as in Probabilistic Safety Assessment (PSA). Through the development of a web-based reliability data analysis algorithm, this approach systematically gathers specific plant data such as component failure history, maintenance history, and shift diary. First, for the application of the developed algorithm, this study reestablished the raw data types, data deposition procedures and features of the Enterprise Resource Planning (ERP) system process. The component codes and system codes were standardized to make statistical analysis between different types of plants possible. This standardization contributes to the establishment of a flexible database model that allows the customization of reliability data for the various applications depending on component types and systems. In addition, this approach makes it possible for users to perform trend analyses and data comparisons for the significant plant components and systems. The validation of the algorithm is performed through a comparison of the importance measure value (Fussel-Vesely) of the mathematical calculation and that of the algorithm application. The development of a reliability database algorithm is one of the best approaches for providing systemic management of plant-specific reliability data with transparency and continuity. This proposed algorithm reinforces the relationships between raw data and application results so that it can provide a comprehensive database that offers everything from basic plant-related data to final customized data.
Hierarchical modeling for reliability analysis using Markov models. B.S./M.S. Thesis - MIT
Fagundo, Arturo
1994-01-01
Markov models represent an extremely attractive tool for the reliability analysis of many systems. However, Markov model state space grows exponentially with the number of components in a given system. Thus, for very large systems Markov modeling techniques alone become intractable in both memory and CPU time. Often a particular subsystem can be found within some larger system where the dependence of the larger system on the subsystem is of a particularly simple form. This simple dependence can be used to decompose such a system into one or more subsystems. A hierarchical technique is presented which can be used to evaluate these subsystems in such a way that their reliabilities can be combined to obtain the reliability for the full system. This hierarchical approach is unique in that it allows the subsystem model to pass multiple aggregate state information to the higher level model, allowing more general systems to be evaluated. Guidelines are developed to assist in the system decomposition. An appropriate method for determining subsystem reliability is also developed. This method gives rise to some interesting numerical issues. Numerical error due to roundoff and integration are discussed at length. Once a decomposition is chosen, the remaining analysis is straightforward but tedious. However, an approach is developed for simplifying the recombination of subsystem reliabilities. Finally, a real world system is used to illustrate the use of this technique in a more practical context.
Gas turbine microprocessor control system: reliability test and analysis. Final report
Kunkel, R.G.; Rowen, W.I.; Withey, D.J.; Schaeffer, D.G.; Buckley, L.P.; Freeman, M.A.; MacFarland, W.J.; Norman, B.G.; Multhaup, H.A.; Roncevich, J.R.
1985-07-01
This report presents the results of a program conducted under EPRI Project RP2101-1, ''Gas Turbine Control System Reliability Analysis and Verification.'' This project articulates the operational capabilities of a new SPEEDTRONIC Mark IV gas turbine control system designed to improve reliability and availability of the system. The project was divided into three phases of study, including the Mark IV control system review, a study of reliability analysis and predictions, and a field verification test conducted at the Salt River Project Santan Generating Station, for a period of one year during which 2930 operating hours were logged on a preproduction Mark IV prototype unit. Improvements in the reliability and availability of the control system were demonstrated during this period. The Mark IV control system uses microprocessor technology where the control functions are distributed among four microcomputers. Three are identical and redundant control sections while the fourth handles communications. Powerful on-line diagnostics indicate the faulty section, which includes replaceable elements, and allows panel repair to be done while the gas turbine is operating, and therefore reduces the meantime to repair. Results of this project indicate that this new control system can upon reaching maturity attain established reliability objectives. Most importantly, design improvements were identified early in the program to enable adjustments to be made in the design, and to be checked out during the program. 3 refs., 88 figs., 44 tabs.
Sin, Gürkan; Meyer, Anne S.; Gernaey, Krist
2010-01-01
The reliability of cellulose hydrolysis models is studied using the NREL model. An identifiability analysis revealed that only 6 out of 26 parameters are identifiable from the available data (typical hydrolysis experiments). Attempting to identify a higher number of parameters (as done in the...
Reliability-tools in geotechnical design, an approach for river dike analysis
Pham Quang, T.; Vrijling, J.K.; van Gelder, P.H.A.J.M.; Thu, T.M.
2010-01-01
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, Unite
Shewan, Cynthia M.
1988-01-01
The study describes the Shewan Spontaneous Language Analysis (SSLA), establishes its reliability and validity, and reports on its use with 47 aphasic adults who had suffered a single unilateral occlusive cerebral vascular accident two to four weeks prior to testing and 30 normal adults. (Author/DB)
Onwuegbuzie, Anthony J.; Roberts, J. Kyle; Daniel, Larry G.
2005-01-01
In this article, the authors (a) illustrate how displaying disattenuated correlation coefficients alongside their unadjusted counterparts will allow researchers to assess the impact of unreliability on bivariate relationships and (b) demonstrate how a proposed new "what if reliability" analysis can complement null hypothesis significance tests of…
A new approach and software support to reliability analysis of repairable complex systems
A. Corlat
1995-02-01
Full Text Available A new method of reliability analysis of complex systems and software supporting is suggested. It is based on modelling of their evolution by means of semi- Markov processes. The results are obtained under general assumptions concerning the distributions of failure and repair times of the system's unit.
A new approach and software support to reliability analysis of repairable complex systems
A. Corlat; S. Corlat
1995-01-01
A new method of reliability analysis of complex systems and software supporting is suggested. It is based on modelling of their evolution by means of semi- Markov processes. The results are obtained under general assumptions concerning the distributions of failure and repair times of the system's unit.
The Lagrangian approach to Markov Monte Carlo methods for systems reliability analysis is generalized to include non-Markovian phenomena in which system components are replaced. The method is then employed to analyze the unreliability and unavailability of a number of redundant systems in which maintenance is carried out by batch or time replacement of aging components. (orig.)
Human reliability analysis of the Tehran research reactor using the SPAR-H method
Barati Ramin
2012-01-01
Full Text Available 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 part of probabilistic safety analysis studies, without it probabilistic safety analysis would not be a systematic and complete representation of actual plant risks. In addition, possible human errors in research reactors constitute a significant part of the associated risk of such installations and including them in a probabilistic safety analysis for such facilities is a complicated issue. Standardized plant analysis risk-human can be used to address these concerns; it is a well-documented and systematic human reliability analysis system with tables for human performance choices prepared in consultation with experts in the domain. In this method, performance shaping factors are selected via tables, human action dependencies are accounted for, and the method is well designed for the intended use. In this study, in consultations with reactor operators, human errors are identified and adequate performance shaping factors are assigned to produce proper human failure probabilities. Our importance analysis has revealed that human action contained in the possibility of an external object falling on the reactor core are the most significant human errors concerning the Tehran research reactor to be considered in reactor emergency operating procedures and operator training programs aimed at improving reactor safety.
Jones, Corinne A.; Hoffman, Matthew R.; Geng, Zhixian; Abdelhalim, Suzan M.; Jiang, Jack J.; McCulloch, Timothy M.
2014-01-01
Purpose: The purpose of this study was to investigate inter- and intrarater reliability among expert users, novice users, and speech-language pathologists with a semiautomated high-resolution manometry analysis program. We hypothesized that all users would have high intrarater reliability and high interrater reliability. Method: Three expert…
Stochastic analysis of radioactive waste package performance using first-order reliability method
In order to license an underground radioactive waste repository, it is important to demonstrate regulatory compliance with authoritative regulations. And it is evident from NRC's criteria for waste package performance that a stochastic analysis is necessary to provide that these criteria can be met with confidence. The first-order reliability method is an attractive approach to stochastic analysis and particularly useful when statistical information is incomplete, as is common for problems in the subsurface environment. Results from a first-order reliability analysis include an estimate of the probability of exceeding a specified performance criteria and measures of sensitivity of the stochastic solution to changes in random variables and their statistical moments. A method of stochastic analysis is illustrated by analyzing canister corrosion in a radioactive waste package
Gore, B.R.; Dukelow, J.S. Jr.; Mitts, T.M.; Nicholson, W.L. [Pacific Northwest Lab., Richland, WA (United States)
1995-10-01
This report presents a limited assessment of the conservatism of the Accident Sequence Evaluation Program (ASEP) human reliability analysis (HRA) procedure described in NUREG/CR-4772. In particular, the, ASEP post-accident, post-diagnosis, nominal HRA procedure is assessed within the context of an individual`s performance of critical tasks on the simulator portion of requalification examinations administered to nuclear power plant operators. An assessment of the degree to which operator perforn:Lance during simulator examinations is an accurate reflection of operator performance during actual accident conditions was outside the scope of work for this project; therefore, no direct inference can be made from this report about such performance. The data for this study are derived from simulator examination reports from the NRC requalification examination cycle. A total of 4071 critical tasks were identified, of which 45 had been failed. The ASEP procedure was used to estimate human error probability (HEP) values for critical tasks, and the HEP results were compared with the failure rates observed in the examinations. The ASEP procedure was applied by PNL operator license examiners who supplemented the limited information in the examination reports with expert judgment based upon their extensive simulator examination experience. ASEP analyses were performed for a sample of 162 critical tasks selected randomly from the 4071, and the results were used to characterize the entire population. ASEP analyses were also performed for all of the 45 failed critical tasks. Two tests were performed to assess the bias of the ASEP HEPs compared with the data from the requalification examinations. The first compared the average of the ASEP HEP values with the fraction of the population actually failed and it found a statistically significant factor of two bias on the average.
This report presents a limited assessment of the conservatism of the Accident Sequence Evaluation Program (ASEP) human reliability analysis (HRA) procedure described in NUREG/CR-4772. In particular, the, ASEP post-accident, post-diagnosis, nominal HRA procedure is assessed within the context of an individual's performance of critical tasks on the simulator portion of requalification examinations administered to nuclear power plant operators. An assessment of the degree to which operator perforn:Lance during simulator examinations is an accurate reflection of operator performance during actual accident conditions was outside the scope of work for this project; therefore, no direct inference can be made from this report about such performance. The data for this study are derived from simulator examination reports from the NRC requalification examination cycle. A total of 4071 critical tasks were identified, of which 45 had been failed. The ASEP procedure was used to estimate human error probability (HEP) values for critical tasks, and the HEP results were compared with the failure rates observed in the examinations. The ASEP procedure was applied by PNL operator license examiners who supplemented the limited information in the examination reports with expert judgment based upon their extensive simulator examination experience. ASEP analyses were performed for a sample of 162 critical tasks selected randomly from the 4071, and the results were used to characterize the entire population. ASEP analyses were also performed for all of the 45 failed critical tasks. Two tests were performed to assess the bias of the ASEP HEPs compared with the data from the requalification examinations. The first compared the average of the ASEP HEP values with the fraction of the population actually failed and it found a statistically significant factor of two bias on the average
Comparative analysis of safety related site characteristics
This document presents a comparative analysis of site characteristics related to long-term safety for the two candidate sites for a final repository for spent nuclear fuel in Forsmark (municipality of Oesthammar) and in Laxemar (municipality of Oskarshamn) from the point of view of site selection. The analyses are based on the updated site descriptions of Forsmark /SKB 2008a/ and Laxemar /SKB 2009a/, together with associated updated repository layouts and designs /SKB 2008b and SKB 2009b/. The basis for the comparison is thus two equally and thoroughly assessed sites. However, the analyses presented here are focussed on differences between the sites rather than evaluating them in absolute terms. The document serves as a basis for the site selection, from the perspective of long-term safety, in SKB's application for a final repository. A full evaluation of safety is made for a repository at the selected site in the safety assessment SR-Site /SKB 2011/, referred to as SR-Site main report in the following
Comparative analysis of safety related site characteristics
Andersson, Johan (ed.)
2010-12-15
This document presents a comparative analysis of site characteristics related to long-term safety for the two candidate sites for a final repository for spent nuclear fuel in Forsmark (municipality of Oesthammar) and in Laxemar (municipality of Oskarshamn) from the point of view of site selection. The analyses are based on the updated site descriptions of Forsmark /SKB 2008a/ and Laxemar /SKB 2009a/, together with associated updated repository layouts and designs /SKB 2008b and SKB 2009b/. The basis for the comparison is thus two equally and thoroughly assessed sites. However, the analyses presented here are focussed on differences between the sites rather than evaluating them in absolute terms. The document serves as a basis for the site selection, from the perspective of long-term safety, in SKB's application for a final repository. A full evaluation of safety is made for a repository at the selected site in the safety assessment SR-Site /SKB 2011/, referred to as SR-Site main report in the following
Yu, Taeho; Richardson, Jennifer C.
2015-01-01
The purpose of this study was to develop an effective instrument to measure student readiness in online learning with reliable predictors of online learning success factors such as learning outcomes and learner satisfaction. The validity and reliability of the Student Online Learning Readiness (SOLR) instrument were tested using exploratory factor…
System reliability assessment via sensitivity analysis in the Markov chain scheme
Methods for reliability sensitivity analysis in the Markov chain scheme are presented, together with a new formulation which makes use of Generalized Perturbation Theory (GPT) methods. As well known, sensitivity methods are fundamental in system risk analysis, since they allow to identify important components, so to assist the analyst in finding weaknesses in design and operation and in suggesting optimal modifications for system upgrade. The relationship between the GPT sensitivity expression and the Birnbaum importance is also given
Eldred, Michael Scott; Subia, Samuel Ramirez; Neckels, David; Hopkins, Matthew Morgan; Notz, Patrick K.; Adams, Brian M.; Carnes, Brian; Wittwer, Jonathan W.; Bichon, Barron J.; Copps, Kevin D.
2006-10-01
This report documents the results for an FY06 ASC Algorithms Level 2 milestone combining error estimation and adaptivity, uncertainty quantification, and probabilistic design capabilities applied to the analysis and design of bistable MEMS. Through the use of error estimation and adaptive mesh refinement, solution verification can be performed in an automated and parameter-adaptive manner. The resulting uncertainty analysis and probabilistic design studies are shown to be more accurate, efficient, reliable, and convenient.
Structural system reliability calculation using a probabilistic fault tree analysis method
Torng, T. Y.; Wu, Y.-T.; Millwater, H. R.
1992-01-01
The development of a new probabilistic fault tree analysis (PFTA) method for calculating structural system reliability is summarized. The proposed PFTA procedure includes: developing a fault tree to represent the complex structural system, constructing an approximation function for each bottom event, determining a dominant sampling sequence for all bottom events, and calculating the system reliability using an adaptive importance sampling method. PFTA is suitable for complicated structural problems that require computer-intensive computer calculations. A computer program has been developed to implement the PFTA.
Liu, Zengkai; Liu, Yonghong; Cai, Baoping
2014-01-01
Reliability analysis of the electrical control system of a subsea blowout preventer (BOP) stack is carried out based on Markov method. For the subsea BOP electrical control system used in the current work, the 3-2-1-0 and 3-2-0 input voting schemes are available. The effects of the voting schemes on system performance are evaluated based on Markov models. In addition, the effects of failure rates of the modules and repair time on system reliability indices are also investigated. PMID:25409010
A reliability model of a system which includes a protected object and a safety system has been proposed. The model allows taking into consideration the sequence of the system elements failures resulting in the system failure, as well as periodic serviceability testing of the elements. The described procedure of asymptotic estimations obtaining the mean time to failure and the failure probability depending on time is based in the renewal theory and considerably more simple than traditionally used Markov and semi-Markov models. The model application for rector control system sub-system reliability analysis was demonstrated
Fuzzy Fatigue Reliability Analysis of Offshore Platforms in Ice-Infested Waters
方华灿; 段梦兰; 贾星兰; 谢彬
2003-01-01
The calculation of fatigue stress ranges due to random waves and ice loads on offshore structures is discussed, and the corresponding accumulative fatigue damages of the structural members are evaluated. To evaluate the fatigue damage to the structures more accurately, the Miner rule is modified considering the fuzziness of the concerned parameters, and a new model for fuzzy fatigue reliability analysis of offshore structures members is developed. Furthermore, an assessment method for predicting the dynamics of the fuzzy fatigue reliability of structural members is provided.
Bayesian network (BN) is a powerful tool for human reliability analysis (HRA) as it can characterize the dependency among different human performance shaping factors (PSFs) and associated actions. It can also quantify the importance of different PSFs that may cause a human error. Data required to fully quantify BN for HRA in offshore emergency situations are not readily available. For many situations, there is little or no appropriate data. This presents significant challenges to assign the prior and conditional probabilities that are required by the BN approach. To handle the data scarcity problem, this paper presents a data collection methodology using a virtual environment for a simplified BN model of offshore emergency evacuation. A two-level, three-factor experiment is used to collect human performance data under different mustering conditions. Collected data are integrated in the BN model and results are compared with a previous study. The work demonstrates that the BN model can assess the human failure likelihood effectively. Besides, the BN model provides the opportunities to incorporate new evidence and handle complex interactions among PSFs and associated actions
On the resolution of ECG acquisition systems for the reliable analysis of the P-wave
The analysis of the P-wave on surface ECG is widely used to assess the risk of atrial arrhythmias. In order to provide reliable results, the automatic analysis of the P-wave must be precise and reliable and must take into account technical aspects, one of those being the resolution of the acquisition system. The aim of this note is to investigate the effects of the amplitude resolution of ECG acquisition systems on the P-wave analysis. Starting from ECG recorded by an acquisition system with a less significant bit (LSB) of 31 nV (24 bit on an input range of 524 mVpp), we reproduced an ECG signal as acquired by systems with lower resolution (16, 15, 14, 13 and 12 bit). We found that, when the LSB is of the order of 128 µV (12 bit), a single P-wave is not recognizable on ECG. However, when averaging is applied, a P-wave template can be extracted, apparently suitable for the P-wave analysis. Results obtained in terms of P-wave duration and morphology revealed that the analysis of ECG at lowest resolutions (from 12 to 14 bit, LSB higher than 30 µV) could lead to misleading results. However, the resolution used nowadays in modern electrocardiographs (15 and 16 bit, LSB <10 µV) is sufficient for the reliable analysis of the P-wave. (note)