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1

A Comparative Analysis of Open Source Software Reliability  

Directory of Open Access Journals (Sweden)

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

Cobra Rahmani; Azad Azadmanesh; Lotfi Najjar

2010-01-01

2

Analysis of reliability AAN laboratory with comparative method  

International Nuclear Information System (INIS)

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

2000-01-00

3

Sensitivity and reliability of objective image analysis compared to subjective grading of bulbar hyperaemia.  

UK PubMed Central (United Kingdom)

AIMS: To establish the sensitivity and reliability of objective image analysis in direct comparison with subjective grading of bulbar hyperaemia. METHODS: Images of the same eyes were captured with a range of bulbar hyperaemia caused by vasodilation. The progression was recorded and 45 images extracted. The images were objectively analysed on 14 occasions using previously validated edge-detection and colour-extraction techniques. They were also graded by 14 eye-care practitioners (ECPs) and 14 non-clinicians (NCLs) using the Efron scale. Six ECPs repeated the grading on three separate occasions RESULTS: Subjective grading was only able to differentiate images with differences in grade of 0.70-1.03 Efron units (sensitivity of 0.30-0.53), compared to 0.02-0.09 Efron units with objective techniques (sensitivity of 0.94-0.99). Significant differences were found between ECPs and individual repeats were also inconsistent (p<0.001). Objective analysis was 16x more reliable than subjective analysis. The NCLs used wider ranges of the scale but were more variable than ECPs, implying that training may have an effect on grading. CONCLUSIONS: Objective analysis may offer a new gold standard in anterior ocular examination, and should be developed further as a clinical research tool to allow more highly powered analysis, and to enhance the clinical monitoring of anterior eye disease.

Peterson RC; Wolffsohn JS

2007-11-01

4

Reliability on intra-laboratory and inter-laboratory data of hair mineral analysis comparing with blood analysis.  

UK PubMed Central (United Kingdom)

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. METHODS: Two divided hair samples taken from near the scalp were submitted for analysis at the same time, to all laboratories, from one healthy volunteer. Each laboratory sent a report consisting of quantitative results and their interpretation of health implications. Differences among intra-laboratory and interlaboratory data were analyzed using SPSS version 12.0 (SPSS Inc., USA). RESULTS: All the laboratories used identical methods for quantitative analysis, and they generated consistent numerical results according to Friedman analysis of variance. However, the normal reference ranges of each laboratory varied. As such, each laboratory interpreted the patient's health differently. On intra-laboratory data, Wilcoxon analysis suggested they generated relatively coherent data, but laboratory B could not in one element, so its reliability was doubtful. In comparison with the blood test, laboratory C generated identical results, but not laboratory A and B. CONCLUSION: Hair mineral analysis has its limitations, considering the reliability of inter and intra laboratory analysis comparing with blood analysis. As such, clinicians should be cautious when applying hair mineral analysis as an ancillary tool. Each laboratory included in this study requires continuous refinement from now on for inducing standardized normal reference levels.

Namkoong S; Hong SP; Kim MH; Park BC

2013-02-01

5

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

International Nuclear Information System (INIS)

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

2003-01-01

6

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

Directory of Open Access Journals (Sweden)

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

Asad Ali; Mohd Amin A. Majid; Masdi Muhammad

2012-01-01

7

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

International Nuclear Information System (INIS)

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

1998-01-01

8

A Novel Three-Dimensional Motion Analysis Method for Measuring the Lumbar Spine Range of Motion: Repeatability and Reliability Compared With an Electrogoniometer.  

UK PubMed Central (United Kingdom)

Study Design. Repeatability and reliability for measuring methods for real time lumbar range of motion.Objective. We established a novel set of marker positions for three-dimensional motion analysis (VICON) to precisely determine lumbar spine range of motion (LROM) and lumbar motion; we compared the repeatability and reliability of VICON with those of an electrogoniometer.Summary of Background Data. The assessment of the LROM using X-ray is still one of the most precise methods, despite the radiation exposure. To avoid this, alternative methods, like the VICON and electrogoniometer, have been widely used. No study has reported the repeatability and reliability of LROM measurements using a VICON and electrogoniometer.Methods. The VICON system and electrogoniometer measured LROM and lumbar motion in seven healthy males over seven days. Differences between both systems were analyzed using Bland-Altman plots. Repeatability and reliability of the LROM measurements was assessed using coefficients of multiple correlations (CMCs) and intraclass correlation coefficients (ICCs), respectively. Standard error of measurement was calculated to quantify the systematic error in LROM measurements.Results. The mean maximum LROM values using the VICON system / electrogoniometer were 42° / 52° for flexion, 17° / 24° for extension, 16° / 16° for lateral bending, and 8° / 2° for axial rotation, respectively. Between VICON and the electrogoniometer, Bland-Altman plots revealed no discrepancies in LROM values except for flexion.CMCs for LROM showed excellent repeatability. LROM measurements with VICON showed excellent reliability for flexion and extension and fair-to-good reliability for other motions. LROM measurements with the electrogoniometer showed excellent reliability for flexion and fair-to-good reliability for other motions. Except for axial rotation, maximum ICCs using VICON were more reliable than the electrogoniometer for measuring lumbar motion.Conclusion. VICON with our novel marker set allows practical and reliable longitudinal assessment of dynamic LROM.

Tojima M; Ogata N; Yozu A; Sumitani M; Haga N

2013-06-01

9

Network reliability analysis. II  

International Nuclear Information System (INIS)

Methods are given for relating the reliability of a network to the reliability of its randomly failing nodes and links. Networks are considered in which nodes can fail as well as links. Also, variations of the basic model are described which are useful in special situations

1974-09-03

10

Reliability Analysis of Wind Turbines  

DEFF Research Database (Denmark)

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

Toft, Henrik Stensgaard; SØrensen, John Dalsgaard

2008-01-01

11

Integrating reliability analysis and design  

International Nuclear Information System (INIS)

[en] 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

1980-01-01

12

Integrating reliability analysis and design  

Energy Technology Data Exchange (ETDEWEB)

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.

Rasmuson, D.M.

1980-10-01

13

Reliability analysis of shutdown system  

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-01-01

14

Cost analysis of reliability investigations  

Energy Technology Data Exchange (ETDEWEB)

Taking Epsteins testing theory as a basis, premises are formulated for the selection of cost-optimized reliability inspection plans. Using an example, the expected testing costs and inspection time periods of various inspection plan types, standardized on the basis of the exponential distribution, are compared. It can be shown that sequential reliability tests usually involve lower costs than failure or time-fixed tests. The most 'costly' test is to be expected with the inspection plan type NOt.

Schmidt, F.

1981-04-01

15

Applications of reliability degradation analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-02-01

16

Reliability Analysis of Adhesive Bonded Scarf Joints  

DEFF Research Database (Denmark)

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

Kimiaeifar, Amin; Toft, Henrik Stensgaard

2012-01-01

17

Human Reliability Analysis: session summary  

International Nuclear Information System (INIS)

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

1985-01-01

18

Human Reliability Analysis: session summary  

Energy Technology Data Exchange (ETDEWEB)

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

Hall, R.E.

1985-01-01

19

Analysis of ventilation assembly reliability  

Energy Technology Data Exchange (ETDEWEB)

Problems are discussed associated with investigations into reliability of main ventilation assemblies employing horizontal and vertical fans. Probability of no-failure operation over a predetermined period of time (1000 h) was used as reliability factor. Reliability of vertical and horizontal fans with back-up units and standby assemblies is analyzed on the basis of failure statistics from Kuzbass mine ventilation system units (statistical data on failure of mechanical, electrical and electronic elements). Block diagrams are examined of ventilation and change-over system reliability with radial, axial and vertical fans. Four different ventilation systems are discussed and relevant conclusions are derived. Intensity of unit failures, ventilation assembly flowsheets and block diagrams of ventilation and change-over systems are given. 12 refs.

Petrov, N.N.; Butorina, O.S.

1986-11-01

20

On Bayesian System Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

The view taken in this thesis is that reliability, the probability that a system will perform a required function for a stated period of time, depends on a person`s state of knowledge. Reliability changes as this state of knowledge changes, i.e. when new relevant information becomes available. Most existing models for system reliability prediction are developed in a classical framework of probability theory and they overlook some information that is always present. Probability is just an analytical tool to handle uncertainty, based on judgement and subjective opinions. It is argued that the Bayesian approach gives a much more comprehensive understanding of the foundations of probability than the so called frequentistic school. A new model for system reliability prediction is given in two papers. The model encloses the fact that component failures are dependent because of a shared operational environment. The suggested model also naturally permits learning from failure data of similar components in non identical environments. 85 refs.

Soerensen Ringi, M.

1995-05-01

 
 
 
 
21

On Bayesian System Reliability Analysis  

International Nuclear Information System (INIS)

The view taken in this thesis is that reliability, the probability that a system will perform a required function for a stated period of time, depends on a person's state of knowledge. Reliability changes as this state of knowledge changes, i.e. when new relevant information becomes available. Most existing models for system reliability prediction are developed in a classical framework of probability theory and they overlook some information that is always present. Probability is just an analytical tool to handle uncertainty, based on judgement and subjective opinions. It is argued that the Bayesian approach gives a much more comprehensive understanding of the foundations of probability than the so called frequentistic school. A new model for system reliability prediction is given in two papers. The model encloses the fact that component failures are dependent because of a shared operational environment. The suggested model also naturally permits learning from failure data of similar components in non identical environments. 85 refs

1995-01-01

22

Reliability analysis of software based safety functions  

International Nuclear Information System (INIS)

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

1993-01-01

23

Discrete event simulation versus conventional system reliability analysis approaches  

DEFF Research Database (Denmark)

Discrete Event Simulation (DES) environments are rapidly developing and appear to be promising tools for building reliability and risk analysis models of safety-critical systems and human operators. If properly developed, they are an alternative to the conventional human reliability analysis models and systems analysis methods such as fault and event trees and Bayesian networks. As one part, the paper describes briefly the author’s experience in applying DES models to the analysis of safety-critical systems in different domains. The other part of the paper is devoted to comparing conventional approaches to system reliability analysis with DES.

Kozine, Igor

2010-01-01

24

A comparative method for improving the reliability of brittle components  

International Nuclear Information System (INIS)

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

2009-01-01

25

Integrated Methodology for Software Reliability Analysis  

Directory of Open Access Journals (Sweden)

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

Marian Pompiliu CRISTESCU; Laurentiu CIOVICA; Liviu CIOVICA

2012-01-01

26

Reliability analysis for structural components  

International Nuclear Information System (INIS)

[en] The main objective of the project was to determined the reliability of the primary components of a nuclear power reactor (specifically the steel pressure vessel for a light water reactor). The method is based on first principles and is supposed to have the highest possible freedom in choosing parameters, probability density functions, failure criteria and the ability to calculate even very small failure probabilities. For a given failure mode and failure criteria the governing parameters are established and the failure probability is determined by the pdf/cdf for these parameters. The important part of these functions are of course the low probability tails as long as we are dealing with low failure probabilities. The Monte Carlo method has been selected to attain the highest possible freedom in choosing parameters, pdf/cdf and failure criteria. An analytical program based on numerical integration has also been developed. An example is given with a steel pressure vessel for a BWR

1976-01-01

27

Reliability analysis of Angra I safety systems  

International Nuclear Information System (INIS)

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

1980-06-20

28

Human Reliability Analysis Using Event Trees.  

Science.gov (United States)

Operator behavior in a technologically complex situation such as a nuclear power plant shutdown is analyzed by making a human reliability analysis event tree (HRA event tree) of each action, breaking down each action into small elementary steps. The appli...

G. Heslinga

1983-01-01

29

Logic reliability analysis of adaptive control strategies  

International Nuclear Information System (INIS)

[en] 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)

1989-01-01

30

RHR system reliability analysis of Krsko NPP  

International Nuclear Information System (INIS)

[en] 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)

1984-01-01

31

Reliability modelling and analysis of thermal MEMS  

Energy Technology Data Exchange (ETDEWEB)

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

Muratet, Sylvaine [LAAS-CNRS 7, avenue du Colonel Roche 31077 TOULOUSE Cedex (France); Lavu, Srikanth [MIcroSystems Engineering Centre, Heriot-Watt University, Edinburgh EH14 4AS, Scotland (United Kingdom); Fourniols, Jean-Yves [LAAS-CNRS 7, avenue du Colonel Roche 31077 TOULOUSE Cedex (France); Bell, George [Institute for System Level Integration, Alba Centre, Alba Campus, Livingston EH54 7EG, Scotland (United Kingdom); Desmulliez, Marc P Y [MIcroSystems Engineering Centre, Heriot-Watt University, Edinburgh EH14 4AS, Scotland (United Kingdom)

2006-04-01

32

Comparing two reliable multicast protocols for mobile computing  

Scientific Electronic Library Online (English)

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

Ribeiro, Mateus de Freitas; Endler, Markus

2003-04-01

33

Culture Representation in Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

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

David Gertman; Julie Marble; Steven Novack

2006-12-01

34

Reliability analysis of ship structure system with multi-defects  

Science.gov (United States)

This paper analyzes the influence of multi-defects including the initial distortions, welding residual stresses, cracks and local dents on the ultimate strength of the plate element, and has worked out expressions of reliability calculation and sensitivity analysis of the plate element. Reliability analysis is made for the system with multi-defects plate elements. Failure mechanism, failure paths and the calculating approach to global reliability index are also worked out. After plate elements with multi-defects fail, the formula of reverse node forces which affect the residual structure is deduced, so are the sensitivity expressions of the system reliability index. This ensures calculating accuracy and rationality for reliability analysis, and makes it convenient to find weakness plate elements which affect the reliability of the structure system. Finally, for the validity of the approach proposed, we take the numerical example of a ship cabin to compare and contrast the reliability and the sensitivity analysis of the structure system with multi-defects with those of the structure system with no defects. The approach has implications for the structure design, rational maintenance and renewing strategy.

An, Hai; An, Weigang; Zhao, Weitao

2010-11-01

35

Reliability and Quantile Analysis of Pareto Distribution  

Directory of Open Access Journals (Sweden)

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

M. Shuaib Khan; M. Aleem; Zafar Iqbal; A.T. Pasha

2009-01-01

36

Human Reliability and Fault-Tree Analysis  

Energy Technology Data Exchange (ETDEWEB)

A method was developed to collect data on Human Reliability as an adjunct to Fault Tree Analysis. The need for these data, the method used for data collection, and the utility of quantified data for Design Support are described. Recommendations are made for research to raise the sample size and validate the estimates.

Stewart, C.

1982-01-01

37

Reliability analysis of personal dose monitoring data  

International Nuclear Information System (INIS)

In accordance to the monitor data of personal on nuclear reactor's worker, the slope of does distribution during distinct operational period can be calculated. Using slope analysis method, the defects of dose parameters and linear interrelation about mean dose per worker with the total energy of nuclear power are analyzed, and then the macroscopic examine method of reliability on a large data is given

1999-01-01

38

Comparing measures of reliability for indices of gingivitis and plaque.  

Science.gov (United States)

The purpose of this methodological study was to compare methods used to assess reliability for gingival inflammation and plaque. Duplicate examinations were conducted by one examiner on 17 subjects (506 scoring sites), using the gingival index (GI), bleeding points index (BPI), and plaque index (PI). The percentage of agreement, the weighted and unweighted kappa coefficients, and Pearson correlation coefficients were calculated as statistics of reliability for mesial buccal site scores and whole mouth mean scores when appropriate. For mesial buccal sites the respective values of the GI, BPI, and PI for weighted kappas were: 0.47, 0.49, and 0.75; for the correlation coefficients: 0.47, 0.49, and 0.76; for unweighted kappas, 0.39, 0.49, and 0.39; and for percentage of agreement 66.2%, 76.1%, and 51.2%. For whole mouth means the correlation coefficients for the GI, BPI, and PI were 0.87, 0.59, and 0.87, respectively. In conclusion, the most useful statistics in assessing the intraexaminer reliability of a solo examiner in descending order were the weighted kappa coefficient, Pearson correlation coefficient, the unweighted kappa coefficient, and percentage of agreement. PMID:8884641

Spolsky, V W; Gornbein, J A

1996-09-01

39

Comparing measures of reliability for indices of gingivitis and plaque.  

UK PubMed Central (United Kingdom)

The purpose of this methodological study was to compare methods used to assess reliability for gingival inflammation and plaque. Duplicate examinations were conducted by one examiner on 17 subjects (506 scoring sites), using the gingival index (GI), bleeding points index (BPI), and plaque index (PI). The percentage of agreement, the weighted and unweighted kappa coefficients, and Pearson correlation coefficients were calculated as statistics of reliability for mesial buccal site scores and whole mouth mean scores when appropriate. For mesial buccal sites the respective values of the GI, BPI, and PI for weighted kappas were: 0.47, 0.49, and 0.75; for the correlation coefficients: 0.47, 0.49, and 0.76; for unweighted kappas, 0.39, 0.49, and 0.39; and for percentage of agreement 66.2%, 76.1%, and 51.2%. For whole mouth means the correlation coefficients for the GI, BPI, and PI were 0.87, 0.59, and 0.87, respectively. In conclusion, the most useful statistics in assessing the intraexaminer reliability of a solo examiner in descending order were the weighted kappa coefficient, Pearson correlation coefficient, the unweighted kappa coefficient, and percentage of agreement.

Spolsky VW; Gornbein JA

1996-09-01

40

Reliability Analysis of High Temperature Reactor Fuels  

International Nuclear Information System (INIS)

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

2000-11-22

 
 
 
 
41

Reliability Analysis of Structural Timber Systems  

DEFF Research Database (Denmark)

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

SØrensen, John Dalsgaard; Hoffmeyer, P.

2000-01-01

42

TRIGA - INR research reactor reliability analysis  

International Nuclear Information System (INIS)

For a better operation we have to find and use every day new methods and strategies, based on the newest scientific and technical discoveries. Among such new techniques we could quote the probabilistic assessments. Probabilistic safety and statistical analysis provided insights useful for the reactor operation. The TRIGA Materials Test and Research reactor was commissioned at the beginning of 1980. Since then there were made extended tests on CANDU type fuel and structural materials. During the reactor operations there were unexpected shutdowns and failures of diverse reactor components. The data collected were statistically processed in order to obtain a reliability data base. This paper tried, indifferently of the cause, to analyze thoroughly the events. The study emphasizes that the most reactor's scrams took place in the first year of operation. The scrams number began to diminish thereafter but in the end of eighties it began to increase again. The greatest number of scrams were caused by the reactor electrical control and instrumentation. An important number of scrams were caused by the irradiation devices. The main conclusion of this study is that the insights are very useful to our operational procedures, to improve the maintenance strategy and the logbook recording. The data collected are useful to be compared with similar data bases for other research reactors. (authors)

2008-01-01

43

Human reliability analysis of control room operators  

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-07-01

44

Analysis of the Reliability Disparity and Reliability Growth Analysis of a Combat System Using AMSAA Extended Reliability Growth Models  

Canada Institute for Scientific and Technical Information (Canada)

The first part of this thesis seeks to identify and analyze which aspects of the MIL-HDBK-217 prediction model are causing the large variation between prediction and field reliability. The key findings of a literature review suggest that the main reason for the inaccuracy in prediction is because the constant failure rate assumption used in MIL-HDBK-217 is usually not applicable. Secondly, even if the constant failure rate assumption is applicable, the disparity may still exist in the presence of design and quality-related problems in new systems. A possible solution is to apply reliability growth testing (RGT) to new systems during the development phase in an attempt to remove these design deficiencies so that the system's reliability will grow and approach the predicted value. In view of the importance of RGT in minimizing the disparity, this thesis provides a detailed application of the U.S. Army Materiel Systems Analysis Activity (AMSAA) Extended Reliability Growth Models to the reliability growth analysis of a 155 mm SPH artillery gun. It shows how program managers can analyze test data using commercial software to estimate the system-demonstrated reliability and the increase in reliability due to delayed fixes.

2005-01-01

45

Reliability analysis of tubular joints in offshore structures. Structural reliability theory, Paper No. 23  

Energy Technology Data Exchange (ETDEWEB)

Reliability analysis of single tubular joints and offsore platforms with tubular joints is presented. The failure modes considered are yielding, punching, buckling and fatigue failure. Element reliability as well as systems reliability approach are used and illustrated by several examples. Finally, optimal design of tubular joints with reliability constraints is discussed and illustrated by an example. 12 refs.

Thoft-Christensen, P.; Soerensen, J.D.

1986-12-01

46

Human reliability analysis using event trees  

Energy Technology Data Exchange (ETDEWEB)

The shut-down procedure of a technologically complex installation as a nuclear power plant consists of a lot of human actions, some of which have to be performed several times. The procedure is regarded as a chain of modules of specific actions, some of which are analyzed separately. The analysis is carried out by making a human reliability analysis event tree (HRA event tree) of each action, breaking down each action into small elementary steps. The application of event trees in human reliability analysis implies more difficulties than in the case of technical systems where event trees were mainly used until now. The most important reason is that the operator is able to recover a wrong performance; memory influences play a significant role. In this study these difficulties are dealt with theoretically. The following conclusions can be drawn: in principle event trees may be used in human reliability analysis; although in practice the operator will recover his fault partly, theoretically this can be described as starting the whole event tree again; compact formulas have been derived, by which the probability of reaching a specific failure consequence on passing through the HRA event tree after several times of recovery is to be calculated.

Heslinga, G.

1983-01-01

47

Human reliability analysis using event trees  

Energy Technology Data Exchange (ETDEWEB)

The shut-down procedure of a technologically complex installation as a nuclear power plant consists of a lot of human actions, some of which have to be performed several times. The procedure is regarded as a chain of modules of specific actions, some of which are analyzed separately. The analysis is carried out by making a Human Reliability Analysis event tree (HRA event tree) of each action, breaking down each action into small elementary steps. The application of event trees in human reliability analysis implies more difficulties than in the case of technical systems where event trees were mainly used until now. The most important reason is that the operator is able to recover a wrong performance; memory influences play a significant role. In this study these difficulties are dealt with theoretically. The following conclusions can be drawn: in principle event trees may be used in human reliability analysis; although in practice the operator will recover his fault partly, theoretically this can be described as starting the whole event tree again; compact formulas have been derived, by which the probability of reaching a specific failure consequence on passing through the HRA event tree after several times of recovery is to be calculated.

Heslinga, G.

1983-01-01

48

Reliability Analysis for Safety Grade PLC  

International Nuclear Information System (INIS)

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

2010-01-01

49

Reliability Analysis for Safety Grade PLC  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-10-15

50

Comparative reliability of cheiloscopy and palatoscopy in human identification.  

UK PubMed Central (United Kingdom)

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

Sharma P; Saxena S; Rathod V

2009-10-01

51

Comparative reliability of cheiloscopy and palatoscopy in human identification  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Establishing a person?s identity in postmortem scenarios can be a very difficult process. Dental records, fingerprint and DNA comparisons are probably the most common techniques used in this context, allowing fast and reliable identification processes. However, under certain circumstances they cannot always be used; sometimes it is necessary to apply different and less known techniques. In forensic identification, lip prints and palatal rugae patterns can lead us to important information and help in a person?s identification. This study aims to ascertain the use of lip prints and palatal rugae pattern in identification and sex differentiation. Materials and Methods: A total of 100 subjects, 50 males and 50 females were selected from among the students of Subharti Dental College, Meerut. The materials used to record lip prints were lipstick, bond paper, cellophane tape, a brush for applying the lipstick, and a magnifying lens. To study palatal rugae, alginate impressions were taken and the dental casts analyzed for their various patterns. Results: Statistical analysis (applying Z-test for proportion) showed significant difference for type I, I?, IV and V lip patterns (P 0.05). Conclusion: This study not only showed that palatal rugae and lip prints are unique to an individual, but also that lip prints is more reliable for recognition of the sex of an individual.

Sharma Preeti; Saxena Susmita; Rathod Vanita

2009-01-01

52

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

Energy Technology Data Exchange (ETDEWEB)

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

Bonfietti, Gerson

2003-07-01

53

Sensitivity analysis in optimization and reliability problems  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-12-15

54

The quantitative failure of human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Bennett, C.T.

1995-07-01

55

Sensitivity analysis in optimization and reliability problems  

International Nuclear Information System (INIS)

[en] 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

2008-01-01

56

Comparing safety analysis techniques  

International Nuclear Information System (INIS)

In process industry Safety Instrumented Systems (SIS) and Emergency Shutdown Systems (ESD) are very important for the management/reduction of risk. In new standards (e.g. Ref. ) on functional safety of electrical/electronic/programmable electronic safety-related systems a quantification of the achieved safety is often required. These new standards do not prescribe how to calculate the achieved safety. Only guidelines and recommendations are given. The problem with this approach is that all kinds of different analysis techniques will be used and in industry the results of the analysis will be compared. These different analysis techniques all use different methodologies and assumptions, which implies that the results may not be comparable. In this paper an approach for comparing different analysis techniques and the qualitative and quantitative results from this comparison are described. The author suggests that, because of the differences in the analysis techniques, one analysis technique is to be preferred. The Enhanced Markov Analysis technique, described in this paper, could be used for this purpose because it covers most aspects relevant for quantification of safety.

2002-01-01

57

Reliability Analysis of Brittle, Thin Walled Structures  

Energy Technology Data Exchange (ETDEWEB)

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

Jonathan A Salem and Lynn Powers

2007-02-09

58

ZERBERUS - the code for reliability analysis of crack containing structures  

International Nuclear Information System (INIS)

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

1992-01-01

59

Reliability analysis of containment isolation systems  

Energy Technology Data Exchange (ETDEWEB)

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

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

1985-06-01

60

Reliability analysis of containment isolation systems  

International Nuclear Information System (INIS)

[en] 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

1985-01-01

 
 
 
 
61

Multiaxial fatigue reliability analysis of railroad wheels  

International Nuclear Information System (INIS)

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

2008-01-01

62

Appraisal on flight reliability on system level gray correlation analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-12-15

63

Reliability Analysis Techniques for Communication Networks in Nuclear Power Plant  

International Nuclear Information System (INIS)

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

2006-01-01

64

A comparative study on the reliability criteria determination  

International Nuclear Information System (INIS)

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

2009-01-01

65

CRAX/Cassandra Reliability Analysis Software  

Energy Technology Data Exchange (ETDEWEB)

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

Robinson, D.

1999-02-10

66

Advancing Usability Evaluation through Human Reliability Analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Ronald L. Boring; David I. Gertman

2005-07-01

67

Reliability Analysis of Tubular Joints in Offshore Structures  

DEFF Research Database (Denmark)

Reliability analysis of single tubular joints and offshore platforms with tubular joints is" presented. The failure modes considered are yielding, punching, buckling and fatigue failure. Element reliability as well as systems reliability approaches are used and illustrated by several examples. Finally, optimal design of tubular.joints with reliability constraints is discussed and illustrated by an example.

Thoft-Christensen, Palle; SØrensen, John Dalsgaard

1987-01-01

68

Development of design framework based on reliability analysis using MATLAB  

International Nuclear Information System (INIS)

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

2007-06-01

69

Reliability analysis of MURR safety functions  

Energy Technology Data Exchange (ETDEWEB)

This study investigated use of improved methods of reliability analysis (over those used in the WASH-1400 report) in reactor safety studies. The methods of event and fault trees that are used to analyze the accident sequences and the safety functions are described. Most importantly, an improvement over the current methods is used to construct the correct mathematical relationship between a system and its components a more advanced method of estimating failure rates and failure probabilities is presented, and a methodology is introduced solving existing problems in past studies (that had employed subjective probabilities). These methods are investigated in the framework of the University of Missouri Research Reactor (MURR) safety functions. Two significant classes of accidents (Loss of Flow and Loss of Coolant) are analyzed in this research project. Examples are presented showing the difference in the results from using the WASH.

Malliakos, A.

1980-01-01

70

HUMAN RELIABILITY ANALYSIS FOR COMPUTERIZED PROCEDURES  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-09-01

71

Structural reliability analysis of spillway gates  

International Nuclear Information System (INIS)

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

1998-10-01

72

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

International Nuclear Information System (INIS)

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

2007-01-01

73

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

International Nuclear Information System (INIS)

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

2008-01-01

74

Analysis of reliability parameters for complicated information measurement systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method of analysis of reliability parameters for complicated systems by means of generating functions is developed taking account of aging of the systems output elements. Main reliability parameters of complicated information measurement systems are examined in this paper.

Sydor, Andriy

75

Comparative assessment of selected PWR auxiliary feedwater system reliability analyses  

International Nuclear Information System (INIS)

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

1985-03-01

76

Modeling human reliability analysis using MIDAS  

International Nuclear Information System (INIS)

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

2006-01-01

77

Modeling human reliability analysis using MIDAS  

Energy Technology Data Exchange (ETDEWEB)

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)

Boring, R. L. [Human Factors, Instrumentation and Control Systems Dept., Idaho National Laboratory, Idaho Falls, ID 83415 (United States)

2006-07-01

78

Finite element reliability analysis of fatigue life  

International Nuclear Information System (INIS)

[en] Fatigue reliability is addressed by the first-order reliability method combined with a finite element method. Two-dimensional finite element models of components with cracks in mode I are considered with crack growth treated by the Paris law. Probability density functions of the variables affecting fatigue are proposed to reflect a setting where nondestructive evaluation is used, and the Rosenblatt transformation is employed to treat non-Gaussian random variables. Comparisons of the first-order reliability results and Monte Carlo simulations suggest that the accuracy of the first-order reliability method is quite good in this setting. Results show that the upper portion of the initial crack length probability density function is crucial to reliability, which suggests that if nondestructive evaluation is used, the probability of detection curve plays a key role in reliability. (orig.)

1992-01-01

79

Combinatorial reliability analysis of multiprocessor computers  

Energy Technology Data Exchange (ETDEWEB)

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

Hwang, K.; Tian-Pong Chang

1982-12-01

80

Reliability test and failure analysis of high power LED packages  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-01-15

 
 
 
 
81

Techniques of quantitative reliability analysis for control rod drive systems  

International Nuclear Information System (INIS)

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

1980-01-01

82

PC-PRAISE, BWR Piping Reliability Analysis  

International Nuclear Information System (INIS)

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

1997-01-01

83

Reliability Analysis of A System Using Intuitionstic Fuzzy Sets  

Directory of Open Access Journals (Sweden)

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

M.K.Sharma; Vintesh Sharma; Rajesh Dangwal

2012-01-01

84

Comparing the reliability of a trigonometric technique to goniometry and inclinometry in measuring ankle dorsiflexion.  

UK PubMed Central (United Kingdom)

OBJECTIVES: The purpose of this study was to compare the reliability of three previously used techniques for the measurement of ankle dorsiflexion ROM, open-chained goniometry, closed-chained goniometry, and inclinometry, to a novel trigonometric technique. METHODS: Twenty-one physiotherapy students used four techniques (open-chained goniometry, closed-chained goniometry, inclinometry, and trigonometry) to assess dorsiflexion range of motion in 24 healthy volunteers. All student raters underwent training to establish competence in the four techniques. Raters then measured dorsiflexion with a randomly assigned measuring technique four times over two sessions, one week apart. Data were analyzed using a technique by session analysis of variance, technique measurement variability being the primary index of reliability. Comparisons were also made between the measurements derived from the four techniques and those obtained from a computerized video analysis system. RESULTS: Analysis of the rater measurement variability around the technique means revealed significant differences between techniques with the least variation being found in the trigonometric technique. Significant differences were also found between the technique means but no differences between sessions were evident. The trigonometric technique produced mean ROMs closest in value to those derived from computer analysis. CONCLUSIONS: Application of the trigonometric technique resulted in the least variability in measurement across raters and consequently should be considered for use when changes in dorsiflexion ROM need to be reliably assessed.

Sidaway B; Euloth T; Caron H; Piskura M; Clancy J; Aide A

2012-07-01

85

RELIABILITY ANALYSIS OF PISTON MANUFACTURING SYSTEM  

Directory of Open Access Journals (Sweden)

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

Amit Kumar; Sneh Lata

2011-01-01

86

Issues in benchmarking human reliability analysis methods: A literature review  

Energy Technology Data Exchange (ETDEWEB)

There is a diversity of human reliability analysis (HRA) methods available for use in assessing human performance within probabilistic risk 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.

Boring, Ronald L.; Hendrickson, Stacey M.L. [Risk and Reliability Analysis Department, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-0748 (United States); Forester, John A., E-mail: jafores@sandia.go [Risk and Reliability Analysis Department, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-0748 (United States); Tran, Tuan Q. [Human Factors and Instrumentation and Control Systems Department, Idaho National Laboratory, PO Box 1624, MS 3605, Idaho Falls, ID 83404-3605 (United States); Lois, Erasmia [Human Factors and Reliability Branch, US Nuclear Regulatory Commission, Mail Stop C4A07M, Washington, DC 20555-0001 (United States)

2010-06-15

87

Issues in Benchmarking Human Reliability Analysis Methods: A Literature Review  

Energy Technology Data Exchange (ETDEWEB)

There is a diversity of human reliability analysis (HRA) methods available for use in assessing human performance within probabilistic risk 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 are presented in order to aid in the design of future HRA benchmarking endeavors.

Ronald L. Boring; Stacey M. L. Hendrickson; John A. Forester; Tuan Q. Tran; Erasmia Lois

2010-06-01

88

Issues in benchmarking human reliability analysis methods: A literature review  

International Nuclear Information System (INIS)

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

1624-01-00

89

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-04-01

90

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

International Nuclear Information System (INIS)

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

1996-01-01

91

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

Energy Technology Data Exchange (ETDEWEB)

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

Ronald Laurids Boring

2010-11-01

92

Reliability analysis of RC containment structures under combined loads  

International Nuclear Information System (INIS)

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

1984-01-01

93

Bypassing BDD Construction for Reliability Analysis  

DEFF Research Database (Denmark)

In this note, we propose a Boolean Expression Diagram (BED)-based algorithm to compute the minimal p-cuts of boolean reliability models such as fault trees. BEDs make it possible to bypass the Binary Decision Diagram (BDD) construction, which is the main cost of fault tree assessment.

Williams, Poul Frederick; Nikolskaia, Macha

2000-01-01

94

Reliability analysis of redundant disk arrays ?????? ??????????? ?????????? ?????????? ???????? ????????  

Directory of Open Access Journals (Sweden)

Full Text Available Redundant disk arrays for fault-tolerant data storages and reliability models of repairable systems are discussed. Simplified formulas for mean time to data loss (MTTDL) assessment with taking into consideration fault and repair specificity and calculation examples are also provided.??????????????? ??????????? ?????????? ???????? ???????, ?????????????? ???????????????? ???????? ??????, ? ????? ?????? ?????????? ????????????????? ?????? ? ??????? ?????????? ?????? ??? ??????? ???????? ??????? ????????? ?? ?????????? ????????? ??????? ? ??????? ?????? ? ?????? ????????? ??????? ? ?????????????? ?????????? ?? ????????? ?????? ? ???????.

?. ?. ??????; ?. ?. ??????; ?. ?. ???????

2013-01-01

95

POSSIBILITY AND EVIDENCE-BASED RELIABILITY ANALYSIS AND DESIGN OPTIMIZATION  

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

96

Gas and oil reliability engineering modeling and analysis  

CERN Multimedia

The advent of reliability engineering tools coupled with the cost of oil and gas operations has changed the paradigm of maintenance technology. A simple strategy of efficient replacement of failed equipment/component has been transformed into a more complex but proactive approach for keeping equipment running at peak efficiency concept of ""total process"" reliability engineering and maintenance. Applied Oil and Gas Reliability Engineering: Modeling and Analysis is the first book to apply reliability value improvement practices and process enterprises lifecycle analysis to the Oil and gas I

Calixto, Eduardo

2012-01-01

97

Design and analysis of reliable interconection networks  

Energy Technology Data Exchange (ETDEWEB)

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

Varma, A.M.

1986-01-01

98

Reliability analysis of PLC safety equipment  

International Nuclear Information System (INIS)

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

2006-01-01

99

Reliability Analysis Using Fault Tree Analysis: A Review  

Directory of Open Access Journals (Sweden)

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

Ahmed Ali Baig; Risza Ruzli; Azizul B. Buang

2013-01-01

100

Reliability analysis of grid connected small wind turbine power electronics  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-09-15

 
 
 
 
101

Reliability analysis of grid connected small wind turbine power electronics  

International Nuclear Information System (INIS)

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

2009-01-01

102

Human reliability considerations in the analysis of mechanical failures  

Energy Technology Data Exchange (ETDEWEB)

Inclusion of human reliability consideration in the analysis of equipment failures is shown to produce pragmatic results while avoiding negative results often associated with human error and its connotation of placing blame. Human error is considered a subset of human reliability. Situational and human factors, including support systems, are the root cause of many failures which may otherwise appear to result from human error.

Smith, J.B.

1985-02-01

103

System reliability: an example of nuclear reactor system analysis  

Energy Technology Data Exchange (ETDEWEB)

This paper presents an overview of the three reliability investigations of a 900 MWe reactor residual heat removal system. Following a description of the system and its functions, the main procedures used in operational reliability analysis, based on the analysis of occurrence records, are covered. The second part of the investigations covers predicted reliability, involving the use of the Markov method. It will be noted that the two types of analysis are in good agreement, the probability of system loss after two months' operation being of the order of 10/sup -1/. Additional investigation data are also given.

Coudray, R. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Dept. d' Etudes Mecaniques et Thermiques); Mattei, J.M. (CEA Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France). Dept. de Surete Nucleaire)

1984-01-01

104

Evaluating some Reliability Analysis Methodologies in Seismic Design  

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

105

Structural reliability analysis applied to pipeline risk analysis  

Energy Technology Data Exchange (ETDEWEB)

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)

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

106

Reliability analysis of an offshore structure  

Energy Technology Data Exchange (ETDEWEB)

For an offshore structure in the North Sea it is assumed that information from measurements and inspections is available. As illustrations measurements of the significant wave height and the marine growth and different inspection and repair results are considered. It is shown how the reliability estimates of the structure can be updated using Bayesian techniques. By minimizing the total expected costs including inspection, repair and failure costs during the lifetime an optimal inspection and repair strategy can be determined. The decision variables are the number of inspections, the time intervals between inspections and the inspection qualities. A parameter study is performed and an updated inspection plan is determined after the first inspection has taken place. (au) (12 refs.).

Soerensen, J.D.; Faber, M.H. (University of Aalborg, Aalborg (Denmark)); Rackwitz, R. (Technical University of Munich, Munich (Germany)); Thoft-Christensen, P. (CSR, Aalborg (Denmark)); Lebas, G. (ELF Aquitaine, Pau Cedex (France))

1992-12-01

107

Summary of component reliability data for probabilistic safety analysis of Korean standard nuclear power plant  

International Nuclear Information System (INIS)

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

2004-01-01

108

Applications of reliability analysis methods for wind turbines  

Energy Technology Data Exchange (ETDEWEB)

Since 1991 the Netherlands Energy Research Foundation ECN and Stork Product Engineering (SPE) are developing a methodology for reliability and safety assessment of wind turbines. In the first project 'Probabilistic Safety Assessment for Wind Turbines' a procedure has been established for a more structured evaluation of wind turbine safety, making use of reliability analysis techniques which have proven their benefits for many years in other branches of industry. A set of reliability analysis techniques like thorough system description, Failure Mode and Effect Analysis (FMEA), Event Tree Analysis (ETA) and Fault Tree Analysis (FTA) was selected. Its applicability for wind turbine engineering was evaluated by means of a case study of the Lagerwey LW 15/75 design. It was concluded that besides safety, the techniques are very useful towards availability and reliability and to improve procedures for testing, inspection and maintenance. From an economic point of view, the latter objectives are most beneficial for wind turbine designers and manufacturers. Therefore it was decided to carry out a second project 'Reliability Analysis and Design Review of the NEWECS-45' with the objective to improve the procedures for reliability analysis. The project has focused on establishing procedures for collection and feedback of operational and failure data with the aim to make an inventory of critical items. In this paper, the various aspects of reliability analysis techniques in wind turbine engineering will be discussed and illustrated with case studies. Three aspects are of special relevance for the wind turbine engineering community: procedures for evaluating wind turbine safety; reliability analysis methods in the design and development phase of a wind turbine; and data collection and feedback of operational experience. 3 figs., 3 tabs., 14 refs.

Rademakers, L.; Seebregts, A.; Verbruggen, T.

1994-10-01

109

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

International Nuclear Information System (INIS)

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

1997-10-01

110

Processing and analysis of reliability data on stator cooling pump  

International Nuclear Information System (INIS)

Based on actual failure data, reliability analysis of the nuclear power plant generator stator cooling water pump was given in this paper. The data were processed by statistical mathematics methods including empirical analysis, exponential and Weibull distribution fitting,and fitting results were verified. Finally, the comparison of reliability curves of exponential distribution and Weibull distribution of a component of generator stator cooling water pump was performed, and a practical equipment maintenance management was given. (authors)

2009-01-01

111

Analysis of human reliability on performing a specific action  

International Nuclear Information System (INIS)

To analyse human reliability on performing a specific action, human reliability analysis event trees are used involving the breakdown of an action into small elementary steps (events). An example of a specific action, the adjustment of a two-position switch, is analysed and the theory of event trees is explained briefly. The application of event trees in human reliability analysis involves more difficulties than in the case of technical systems, where event trees have been mainly used up until now. The main problem is that the operator is able to rectify his incorrect action, where memory effects play a significant role. In this study these difficulties are dealt with theoretically. (author).

1985-01-01

112

Analysis of human reliability on performing a specific action  

Energy Technology Data Exchange (ETDEWEB)

To analyse human reliability on performing a specific action, human reliability analysis event trees are used involving the breakdown of an action into small elementary steps (events). An example of a specific action, the adjustment of a two-position switch, is analysed and the theory of event trees is explained briefly. The application of event trees in human reliability analysis involves more difficulties than in the case of technical systems, where event trees have been mainly used up until now. The main problem is that the operator is able to rectify his incorrect action, where memory effects play a significant role. In this study these difficulties are dealt with theoretically.

Heslinga, G. (Technische Hogeschool Delft (Netherlands))

1985-01-01

113

Energy investment cost benefit analysis reliability  

International Nuclear Information System (INIS)

Much accuracy is required in methods to find out the profitability and choice of an energy investment. Beginning from a conventional cost-benefit analysis, this article discusses both profitability and other related problems

1993-01-01

114

Discrete Event Simulation and Petri net Modeling for Reliability Analysis  

Directory of Open Access Journals (Sweden)

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

Behrooz Safarinejadian 1

2012-01-01

115

Reliability analysis of fatigue sensitive joints in FPSO  

Energy Technology Data Exchange (ETDEWEB)

This paper contains a general description and the results of a reliability analysis made for fatigue sensitive joints in an FPSO. The main aim of the analysis was to demonstrate that the inspection program, which was specified based on the IMO resolution, will guarantee an acceptable probability level of fatigue and fracture failure during 20 years of service of the unit. Three approaches have been followed: the SN-approach and the fracture mechanics approach with and without allowance for fracture. The planned inspection program has been taken into account in the third approach. The stress assessment has been based on the spectral analysis corrected for the intermittent wetting effect. A short description of the deterministic analyses which preceded the reliability analysis has been included. It has been demonstrated in the paper that the probability of fatigue and fracture failure in an inspected structure can be assessed and judged by use of the reliability analysis.

Kaminski, M.L. [Nevesbu, The Hague (Netherlands); Krekel, M. [Bluewater, Hoofddorp (Netherlands)

1995-12-31

116

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

Directory of Open Access Journals (Sweden)

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

Nir Kshetri

2013-01-01

117

Analysis of sodium valve reliability data at CREDO  

International Nuclear Information System (INIS)

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

1979-08-23

118

Simulation and reliability analysis of sequential complex systems with S.ESCAF  

International Nuclear Information System (INIS)

ESCAF is a standalone, desk-top unit for simple and low-cost reliability analysis of even the most complex systems. This paper presents the S.ESCAF add-on option, which greatly increases the possibilities available to researchers and reliability engineers in the analysis of sequential systems, as compared with conventional methods. Examples are given to illustrate the power and performances of S.ESCAF, due largely to electronic simulation of the studied system, and its ease-of-use. In particular, users do not need highly specialized knowledge in reliability, computer science, or electronics. (author).

1985-01-01

119

Comparative Analysis of University Sports  

Directory of Open Access Journals (Sweden)

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

?. ?sra ?rturan; Natasha Brison; Tiffany Allen

2012-01-01

120

The weakest t-norm based intuitionistic fuzzy fault-tree analysis to evaluate system reliability.  

UK PubMed Central (United Kingdom)

In this paper, a new approach of intuitionistic fuzzy fault-tree analysis is proposed to evaluate system reliability and to find the most critical system component that affects the system reliability. Here weakest t-norm based intuitionistic fuzzy fault tree analysis is presented to calculate fault interval of system components from integrating expert's knowledge and experience in terms of providing the possibility of failure of bottom events. It applies fault-tree analysis, ?-cut of intuitionistic fuzzy set and T(?) (the weakest t-norm) based arithmetic operations on triangular intuitionistic fuzzy sets to obtain fault interval and reliability interval of the system. This paper also modifies Tanaka et al.'s fuzzy fault-tree definition. In numerical verification, a malfunction of weapon system "automatic gun" is presented as a numerical example. The result of the proposed method is compared with the listing approaches of reliability analysis methods.

Kumar M; Yadav SP

2012-07-01

 
 
 
 
121

RELIABILITY ANALYSIS OF RING, AGENT AND CLUSTER BASED DISTRIBUTED SYSTEMS  

Directory of Open Access Journals (Sweden)

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

R.SEETHALAKSHMI; K.S.RAVICHANDRAN

2011-01-01

122

Reliability Analysis of Dynamic Stability in Waves  

DEFF Research Database (Denmark)

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

SØborg, Anders Veldt

2004-01-01

123

IEEE guide for the analysis of human reliability  

International Nuclear Information System (INIS)

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

1987-01-01

124

State of the art report on aging reliability analysis  

International Nuclear Information System (INIS)

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

2002-01-01

125

Reliability analysis of cluster-based ad-hoc networks  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-10-15

126

Reliability analysis of cluster-based ad-hoc networks  

International Nuclear Information System (INIS)

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

2008-01-01

127

The Reliability of Content Analysis of Computer Conference Communication  

DEFF Research Database (Denmark)

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

Rattleff, Pernille

2007-01-01

128

Reliability estimation of steam turbine blade considering a dynamic analysis  

International Nuclear Information System (INIS)

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

2002-01-01

129

Reliability analysis of TLP tethers under impulsive loading  

International Nuclear Information System (INIS)

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

2020-01-00

130

Reliability analysis of the emergency power supply system of the STARFIRE tokamak  

Energy Technology Data Exchange (ETDEWEB)

Early attention to safety will ensure that the potential safety advantages of fusion are realized. Reliability analysis techniques are applied to a major safety system, the emergency power supply system, using the STARFIRE design as an example. The median failure probability of this system is found to be 2 X 10/sup -6/ at shutdown, with an error factor of 5. This is comparable with the reliability of similar systems in existing fission power stations.

Gierszewski, P.J.; Heising, C.D.

1984-01-01

131

Reliability analysis of the emergency power supply system of the STARFIRE tokamak  

International Nuclear Information System (INIS)

Early attention to safety will ensure that the potential safety advantages of fusion are realized. Reliability analysis techniques are applied to a major safety system, the emergency power supply system, using the STARFIRE design as an example. The median failure probability of this system is found to be 2 X 10-6 at shutdown, with an error factor of 5. This is comparable with the reliability of similar systems in existing fission power stations

1984-01-01

132

Reliability analysis of contaminant transport in saturated porous media  

Energy Technology Data Exchange (ETDEWEB)

An approach to probabilistic analysis of contaminant transport based on first- and second-order reliability methods (FORM and SORM) is presented. In addition, system reliability methodology is introduced for the analysis of problems with more than one limit state function. Conventional one-dimensional finite difference and two-dimensional finite element models are coupled with the FORM and SORM algorithms to perform reliability analyses of advection-dominated contaminant transport. A comparison of the results of FORM and SORM analyses with the results of Monte Carlo simulations shows that FORM tends to overestimate the probability of exceedence in spatially variable domains. However, SORM accounts for the nonlinearity of the limit state surface and remains accurate, giving results consistent with Monte Carlo simulation. Finally, while the analyses presented here considered relatively simple problems, the methodology is shown to have the necessary flexibility for application to problems of practical interest.

Jang, Yeon-Soo; Sitar, N.; Der Kiureghian, A. (Univ. of California, Berkeley, CA (United States))

1994-08-01

133

Reliability-Based Robustness Analysis for a Croatian Sports Hall  

DEFF Research Database (Denmark)

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

?izmar, Dean; Kirkegaard, Poul Henning

2011-01-01

134

Evaluation of the reliability of computerized profile cephalometric analysis  

Directory of Open Access Journals (Sweden)

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

Ferreira José Tarcísio Lima; Telles Carlos de Souza

2002-01-01

135

Architecture based Reliability Analysis of Continuously Running Concurrent Software Applications  

Directory of Open Access Journals (Sweden)

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

Rehab A. El Kharboutly; Reda Ammar; Swapna S. Gokhale

2008-01-01

136

Reliability of videotaped observational gait analysis in patients with orthopedic impairments  

Directory of Open Access Journals (Sweden)

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

Brunnekreef Jaap J; van Uden Caro JT; van Moorsel Steven; Kooloos Jan GM

2005-01-01

137

Failures Analysis and Reliability Calculation for Power Transformers  

Directory of Open Access Journals (Sweden)

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

M. Mirzai; A. Gholami; F. Aminifar

2006-01-01

138

Human reliability analysis of Lingao Nuclear Power Station  

International Nuclear Information System (INIS)

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

2001-01-01

139

Analysis of Computer Network Reliability and Criticality: Technique and Features  

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

140

Relay aging and reliability analysis of nuclear power station  

International Nuclear Information System (INIS)

Based on the analysis and test of the aging failure and reliability of LEACH relays produced in 1999, it was realized that the failure is due to the resistance decrement and heat generation caused by insulation material degradation. Measuring the outer shell temperature can monitor the aging process. For the unreliable batch, it is necessary to start the batch replacement program. (authors)

2006-01-01

 
 
 
 
141

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-07-31

142

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-08-01

143

Spinal appearance questionnaire: factor analysis, scoring, reliability, and validity testing.  

UK PubMed Central (United Kingdom)

STUDY DESIGN: Cross sectional. OBJECTIVE: This study presents the factor analysis of the Spinal Appearance Questionnaire (SAQ) and its psychometric properties. SUMMARY OF BACKGROUND DATA: Although the SAQ has been administered to a large sample of patients with adolescent idiopathic scoliosis (AIS) treated surgically, its psychometric properties have not been fully evaluated. This study presents the factor analysis and scoring of the SAQ and evaluates its psychometric properties. METHODS: The SAQ and the Scoliosis Research Society-22 (SRS-22) were administered to AIS patients who were being observed, braced or scheduled for surgery. Standard demographic data and radiographic measures including Lenke type and curve magnitude were also collected. RESULTS: Of the 1802 patients, 83% were female; with a mean age of 14.8 years and mean initial Cobb angle of 55.8° (range, 0°-123°). From the 32 items of the SAQ, 15 loaded on two factors with consistent and significant correlations across all Lenke types. There is an Appearance (items 1-10) and an Expectations factor (items 12-15). Responses are summed giving a range of 5 to 50 for the Appearance domain and 5 to 20 for the Expectations domain. The Cronbach's ? was 0.88 for both domains and Total score with a test-retest reliability of 0.81 for Appearance and 0.91 for Expectations. Correlations with major curve magnitude were higher for the SAQ Appearance and SAQ Total scores compared to correlations between the SRS Appearance and SRS Total scores. The SAQ and SRS-22 Scores were statistically significantly different in patients who were scheduled for surgery compared to those who were observed or braced. CONCLUSION: The SAQ is a valid measure of self-image in patients with AIS with greater correlation to curve magnitude than SRS Appearance and Total score. It also discriminates between patients who require surgery from those who do not.

Carreon LY; Sanders JO; Polly DW; Sucato DJ; Parent S; Roy-Beaudry M; Hopkins J; McClung A; Bratcher KR; Diamond BE

2011-08-01

144

Reliability analysis of an advanced water treatment facility  

Energy Technology Data Exchange (ETDEWEB)

The evaluation of wastewater treatment plant reliability is an important component in the assessment of potential impacts associated with any wastewater discharge of water reuse project. The reliability of the San Diego Aqua III Advanced Water Treatment (AWT) facility is probabilistically analyzed using data collected between October 1994 and September 1995. Reliability is evaluated in terms of the facility's ability produce a consistent effluent quality and the probability of failure of mechanical components. The analysis includes characterizing the effluent from individual unit processes in terms of magnitude and variability of concentration of a number of pollutants, and expressing the mechanical reliability of the system in terms of equipment availability. Pollutants used to characterize treatment performance include physical parameters, nitrogen compounds, anions, trace and major metals, organic compounds, and bacteriological indicators. The results show that the Aqua III AWT produced a highly consistent effluent with minimal variation, and that the mechanical systems were available nearly 100% of the time. It is demonstrated that mechanical failures did not significantly affect effluent quality. The methodology that was used for this analysis is applicable to any continuous treatment or production process in which the effectiveness of individual process units can be determined by direct measurements or by analysis of specific or indicator constituents.

Eisenberg, D.; Olivieri, A.; Soller, J.; Gagliardo, P.

1998-07-01

145

Accident Sequence Evaluation Program: Human reliability analysis procedure  

Energy Technology Data Exchange (ETDEWEB)

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

Swain, A.D.

1987-02-01

146

On Reliability Analysis of Fault-tolerant Multistage Interconnection Networks  

Directory of Open Access Journals (Sweden)

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

Rinkle Aggarwal; Dr. Lakhwinder Kaur

2008-01-01

147

Identifying Sources of Difference in Reliability in Content Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available This paper reports on a case study which identifies and illustrates sources of difference in agreement in relation to reliability in a context of quantitative content analysis of a transcript of an online asynchronous discussion (OAD). Transcripts of 10 students in a month-long online asynchronous discussion were coded by two coders using an instrument with two categories, five processes, and 19 indicators of Problem Formulation and Resolution (PFR). Sources of difference were identified in relation to: coders; tasks; and students. Reliability values were calculated at the levels of categories, processes, and indicators. At the most detailed level of coding on the basis of the indicator, findings revealed that the overall level of reliability between coders was .591 when measured with Cohen’s kappa. The difference between tasks at the same level ranged from .349 to .664, and the difference between participants ranged from .390 to .907. Implications for training and research are discussed.

Elizabeth Murphy; Justyna Ciszewska-Carr

2005-01-01

148

Analysis of Software Reliability Data using Exponential Power Model  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, Exponential Power (EP) model is proposed to analyze the software reliability data and the present work is an attempt to represent that the model is as software reliability model. The approximate MLE using Artificial Neural Network (ANN) method and the Markov chain Monte Carlo (MCMC) methods are used to estimate the parameters of the EP model. A procedure is developed to estimate the parameters of the EP model using MCMC simulation method in OpenBUGS by incorporating a module into OpenBUGS. The R functions are developed to study the various statistical properties of the proposed model and the output analysis of MCMC samples generated from OpenBUGS. A real software reliability data set is considered for illustration of the proposed methodology under informative set of priors.

Ashwini Kumar Srivastava; Vijay Kumar

2011-01-01

149

Reliability Analysis of Free Jet Scour Below Dams  

Directory of Open Access Journals (Sweden)

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

Chuanqi Li; Shuai Wang; Wei Wang

2012-01-01

150

Measuring Upper Airway Volume: Accuracy and Reliability of Dolphin 3D Software Compared to Manual Segmentation in Craniosynostosis Patients.  

UK PubMed Central (United Kingdom)

CONCLUSION: The airway analysis tool of Dolphin 3D is not accurate or reliable enough to use in a Le Fort III osteotomy evaluation. When scanning properties are conditioned and measurements are standardized, accuracy and reliability may increase.

de Water VR; Saridin JK; Bouw F; Murawska MM; Koudstaal MJ

2013-10-01

151

A review of structural system reliability analysis for offshore structures  

Energy Technology Data Exchange (ETDEWEB)

Structural reliability assessment (SRA) can be carried out at both component and system levels. Component level analysis can be applied to individual structural components and there has been significant progress in the applications of SRA for structural integrity assessment and modern design code formulation (both at component level). On the other hand, analysis at system level, which deals with the reliability of complete structures and assemblies in multiple failure modes, has not yet made a significant impact on offshore structural engineering. One of the main problems with complete system level analysis is the large demand on computational power due to the complexity of offshore structures. The demand is large because the number of possible failure paths increases exponentially (in fact, factorially) with the number of components (members and joints) in the structure. In order to reduce the demand on computational power, several search algorithms have been developed. One such algorithm is based on the deterministic reserve strength ratio (RSR) analysis and is gaining popularity. This paper will briefly outline the current understanding in structural system reliability analysis and the basic principles of various search algorithms. Some examples will be referred to in the discussion of the advantages and limitations of various approaches. Finally, the implications of the current state of the art to structural risk management will also be discussed.

Kam, J.C.P.; Snell, R.O.; Shetty, N.K.

1995-12-31

152

Virtual stress amplitude-based low cycle fatigue reliability analysis  

International Nuclear Information System (INIS)

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

2000-01-01

153

Informatics Security Metrics Comparative Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The informatics security concept is defined. For informatics applications which have a classical structure, the development, current use, maintenance, and reengineering particularities are described for distributed systems and m-applications. Metrics are built for the security of open informatics applications and a method for their validation is proposed. To see when a metric is adequate a comparative analysis is made for each indicator using a representative diversity of data sets for the test.

Ion IVAN; Luckacs BREDA

2007-01-01

154

Fault tree - a method for reliability analysis of power systems  

Energy Technology Data Exchange (ETDEWEB)

During the past decades great efforts have been made in several countries to develop effective and practical methods to analyse the safety of power systems. Most of the work has been related to major risks that are relevant e.g. to power system reliability. Several alternative and complementary methods have been developed to identify potential risks and to assess their significance. The reliability of power systems must maintain an acceptable level. This level is monitored by reliability analysis, which in this report is studied by using the fault tree method. Fault tree analysis is a technique of system reliability and safety analysis and it has been widely applied in several industrial branches. It has been developed to identify factors leading to a defined undesired event, i.e. an accident. The method can be used both qualitatively and quantitatively. Fault-tree analysis can be a most simple or a most sophisticated analytic reliability tool depending on the needs of the analyst. For the system-safety analyst, fault trees provide an objective basis for analysing failure modes and probability. The simple logic applies to both systems and subsystems, and is an effective visualisation tool for management as well as engineering. The main problems with fault tree analysis are that the method is time consuming and needs good expertise. However, regardless of their expertise two different persons can seldom construct similar fault trees on the same system. These factors have given the incentive to start the research on automation of the fault tree construction especially for process systems. Considerable efforts have been made in several countries to develop suitable algorithms for this purpose. The scope of this report is to introduce the fault tree method, describe its structure and explain how it is constructed. The aim is also to examine the possibilities of the fault tree method in reliability analysis of power systems. Connections between the concepts are proposed. Material has been collected from various sources. In order to obtain the relevant and accurate publications internet-based databases have been used, for instance IEEExplore and Inspec. Material has also been gathered from the databases of the HUT library. (orig.)

Riikonen, J.; Lammintausta, M.

2002-07-01

155

Reliability based analysis and design of anchor retrofitted concrete gravity dams  

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

156

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

Directory of Open Access Journals (Sweden)

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

Wang Yufei; Qian Qiuye; Weixia Luan; Wang Guizhou

2013-01-01

157

RELIABILITY AND SAFETY ANALYSIS OF THE PROCESS PLANT  

Directory of Open Access Journals (Sweden)

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

Jelenka B. Savkovic-Stevanovic

2010-01-01

158

Reliability analysis of crack propagation behavior of reactor components  

International Nuclear Information System (INIS)

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

1984-01-01

159

High-Reliable PLC RTOS Development and RPS Structure Analysis  

International Nuclear Information System (INIS)

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

2008-01-01

160

High-Reliable PLC RTOS Development and RPS Structure Analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-04-15

 
 
 
 
161

Reliability Analysis of Shoulder Balance Measures: Comparison of the Four Available Methods.  

UK PubMed Central (United Kingdom)

Study Design. Observational study with three examinersObjectives. To compare the reliability of shoulder balance measurement methodsSummary of Background Data. There are several measurement methods for shoulder balance. No reliability analysis has been performed, despite the clinical importance of this measurement.Methods. Whole spine postero-anterior radiographs (n = 270) were collected to compare the reliability of the four shoulder balance measures in adolescent idiopathic scoliosis patients. Each radiograph was measured twice by each of the three examiners using the four measurement methods. The data was analyzed statistically to determine the inter- and intraobserver reliability.Result. Overall, the four radiographic methods showed an excellent intraclass correlation coefficient (ICC) regardless of severity in intraobserver comparisons (>0.904). In addition, the mean absolute difference (MAD) values in all methods were low and were comparatively similar (<1.73?). However, in interobserver comparisons, reliabilities were significantly decreased in the less severe radiographs, firstly on radiographic shoulder height measures (ICCs>0.445, MAD<3.91?). However, the ICCs in the coracoid height difference and clavicular angle methods were in the excellent range (>0.810 and >0.787, respectively) regardless of severity. In addition, the MAD values in the clavicular angle method were lower (<0.62?) than others.Conclusions. The higher reliability of the clavicular angle and coracoids height difference methods indicate the clinical usefulness of these methods. Physicians should selectively use the shoulder balance measurement method clinically.

Hong JY; Suh SW; Yang JH; Park SY; Han JH

2013-06-01

162

Comparative analysis of Bragg fibers.  

Science.gov (United States)

In this paper, we compare three analysis methods for Bragg fibers, viz. the transfer matrix method, the asymptotic method and the Galerkin method. We also show that with minor modifications, the transfer matrix method is able to calculate exactly the leakage loss of Bragg fibers due to a finite number of H/L layers. This approach is more straightforward than the commonly used Chew's method. It is shown that the asymptotic approximation condition should be satisfied in order to get accurate results. The TE and TM modes, and the band gap structures are analyzed using Galerkin method. PMID:19471526

Guo, Shangping; Albin, Sacharia; Rogowski, Robert

2004-01-12

163

Comparative analysis of Bragg fibers.  

UK PubMed Central (United Kingdom)

In this paper, we compare three analysis methods for Bragg fibers, viz. the transfer matrix method, the asymptotic method and the Galerkin method. We also show that with minor modifications, the transfer matrix method is able to calculate exactly the leakage loss of Bragg fibers due to a finite number of H/L layers. This approach is more straightforward than the commonly used Chew's method. It is shown that the asymptotic approximation condition should be satisfied in order to get accurate results. The TE and TM modes, and the band gap structures are analyzed using Galerkin method.

Guo S; Albin S; Rogowski R

2004-01-01

164

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

Directory of Open Access Journals (Sweden)

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

Mark Glaister; Hanna Hauck; Corinne S. Abraham; Kevin L. Merry; Dean Beaver; Bernadette Woods; Gillian McInnes

2009-01-01

165

Integrated design environment for human performance and human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Nelson, W.R.

1997-05-01

166

Reliability data collection and analysis for Korean standard nuclear power plants  

International Nuclear Information System (INIS)

[en] We have been developed component reliability database for Korea standard nuclear power plants which has their own characteristics. The purpose of the reliability DB is to supply domestic reliability data for PSA, RIR and A, PSR etc instead of generic data. We structured the reliability DB framework and guideline for standardized Data collecting and analysis. Based on them, we collected and analyzed the component failure data from TR and daily operation reports and made a data collection rule for the component operating data such as the number of demand and operating hour. Some failure rates of failure modes of YGN 4 are compared with the generic data. 60% of the 56 failure rates don't a large difference from the generic data. And 62% have lower failure rates and 38% have higher failure rates than generic data. There are 11 failure modes of which failure rates are zero. It is resulted from short plant operating year

2001-01-01

167

Some developments in human reliability analysis approaches and tools  

International Nuclear Information System (INIS)

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

1988-01-01

168

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

Directory of Open Access Journals (Sweden)

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.

S.A. Mohammadi; M.R. Mahzoun

2011-01-01

169

Reliability analysis of pipelines with corrosion defects using surrogate models  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-01

170

Review of the treat upgrade reactor scram system reliability analysis  

International Nuclear Information System (INIS)

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

1984-01-01

171

Photovoltaic module reliability improvement through application testing and failure analysis  

Energy Technology Data Exchange (ETDEWEB)

During the first four years of the U.S. Department of Energy (DOE) National Photovoltatic Program, the Jet Propulsion Laboratory Low-Cost Solar Array (LSA) Project purchased about 400 kW of photovoltaic modules for test and experiments. In order to identify, report, and analyze test and operational problems with the Block Procurement modules, a problem/failure reporting and analysis system was implemented by the LSA Project with the main purpose of providing manufacturers with feedback from test and field experience needed for the improvement of product performance and reliability. A description of the more significant types of failures is presented, taking into account interconnects, cracked cells, dielectric breakdown, delamination, and corrosion. Current design practices and reliability evaluations are also discussed. The conducted evaluation indicates that current module designs incorporate damage-resistant and fault-tolerant features which address field failure mechanisms observed to date.

Dumas, L.N.; Shumka, A.

1982-08-01

172

Comparative reliability analyses of zirconium oxide and lithium disilicate restorations in vitro and in vivo.  

UK PubMed Central (United Kingdom)

BACKGROUND: The authors analyzed the in vitro and in vivo performance of lithium disilicate glass-ceramic (LDGC) restorations and yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) (that is, zirconium oxide) restorations with regard to reliability, clinical performance and abrasion resistance. METHODS: In the in vitro study, four authors subjected samples of LDGC, Y-TZP and metal-ceramic crowns to step-stress fatigue testing. Four investigators assessed the in vivo clinical performance of LDGC and zirconium oxide-based restorations at four and seven years, respectively. In addition, one author conducted a randomized, controlled clinical trial to analyze the volumetric loss of enamel and ceramic antagonist surfaces. RESULTS: The LDGC crowns exhibited the highest fatigue load-to-failure values in the in vitro analysis. The results of the in vivo assessment showed that the clinical performance of the LDGC restorations at four years was comparable to that of the zirconium oxide-based crowns at seven years. The results of the in vivo, randomized, controlled clinical trial showed that LDGC crowns were not only resistant to wear, but also were wear friendly to enamel antagonist surfaces. CONCLUSIONS: The LDGC crowns in the in vitro and in vivo studies exhibited high durability, and they were wear friendly to opposing natural dentition. CLINICAL IMPLICATIONS: LDGC and zirconium oxide-based crowns are a clinically acceptable means of treating teeth that require full-coverage restorations. In addition, LDGC materials exhibit excellent clinical performance, as well as demonstrate acceptable abrasion compatibility with the opposing natural dentition.

Silva NR; Thompson VP; Valverde GB; Coelho PG; Powers JM; Farah JW; Esquivel-Upshaw J

2011-04-01

173

Comparative analysis of collaboration networks  

International Nuclear Information System (INIS)

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

2011-03-14

174

Reliability and risk analysis using artificial neural networks  

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-12-31

175

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

DEFF Research Database (Denmark)

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

Kimiaeifar, Amin; Lund, Erik

2013-01-01

176

Failure and Reliability Analysis for the Master Pump Shutdown System  

International Nuclear Information System (INIS)

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

2000-01-01

177

Measuring Upper Airway Volume: Accuracy and Reliability of Dolphin 3D Software Compared to Manual Segmentation in Craniosynostosis Patients.  

UK PubMed Central (United Kingdom)

PURPOSE: To test the accuracy and reliability of Dolphin 3-dimensional (3D) software airway analysis compared with manual segmentation in patients who underwent a Le Fort III osteotomy. MATERIALS AND METHODS: Computed tomographic scans of 20 patients with syndromic craniosynostosis at Sophia's Children's Hospital (Rotterdam, The Netherlands) were used for airway volume measurements using Dolphin 3D. The same scans had been used for measurement using a manual segmentation method. The results of this previous study were reported in 2010. The manual segmentation measuring result was used as a gold standard. The airway was subdivided into the oropharynx and the nasal passage. A linear mixed effects statistical model was applied. RESULTS: Dolphin 3D measurements differed from manual segmentation by 9 to 43%, depending on the observer, the time at which the measured scan was acquired (pre- or postoperative), and the airway compartment being measured. The highest accuracy for Dolphin 3D was found for measurements from postoperative scans of the nasal passage. CONCLUSION: The airway analysis tool of Dolphin 3D is not accurate or reliable enough to use in a Le Fort III osteotomy evaluation. When scanning properties are conditioned and measurements are standardized, accuracy and reliability may increase.

de Water VR; Saridin JK; Bouw F; Murawska MM; Koudstaal MJ

2013-10-01

178

Boiler reliability  

International Nuclear Information System (INIS)

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

1997-11-18

179

Bayesian reliability analysis for the two-parameter exponential distribution  

Directory of Open Access Journals (Sweden)

Full Text Available This paper discusses the Bayesian reliability analysis for the two-parameter exponential distribution on the basis of the life tests that are terminated after a pre assigned number of failures, when the prior distribution of the location parameter, given the scale, is assumed to be exponential, while the scale parameter is assumed to have an inverse Gaussian prior distribution. The usual assumption of the squared error loss function is also made. A situation dealing with attribute life testing is also considered.

Samir K. Battacharya; Ravinder K. Tyagi

1992-01-01

180

Automating the Performance and Reliability Analysis of Enterprise Information Systems.  

UK PubMed Central (United Kingdom)

Good quality models for the analysis of complex enterpriseinformation systems (EIS) are hard to build and requirelots of experience and effort, which are not alwaysavailable. A possible solution to deal with the previous issueis to build automated procedures for quality model generation.Such procedures shall encapsulate previous existingknowledge on quality modeling and their use shall reducethe cost of developing quality models. In this paper, weconcentrate on the performance and reliability of EIS andwe investigate the automatic generation of quality modelsfrom EIS architectural descriptions comprising additionalinformation related to the aspects that affect the quality ofthe EIS.

Apostolos Zarras; Valerie Issarny; Inria Rocquencourt; Domaine De Voluceau

 
 
 
 
181

Reliability engineering  

Energy Technology Data Exchange (ETDEWEB)

Reliability is formally defined as the probability that an item will survive without failure for a stated period of time, under stated conditions of use; probability and statistics accordingly furnish the basis for much of reliability theory. The present conference gives attention to mathematical techniques, system reliability modeling and design, reliability in mechanical and electronic components and systems, reliability assessments for microelectronics, process plant reliability, the reliability analysis of distributed systems, a case history of weapon reliability, and the management of reliability.

O' connor, P.D.T.

1988-01-01

182

Reliability of 2 ultrasonic imaging analysis methods in quantifying lumbar multifidus thickness.  

UK PubMed Central (United Kingdom)

STUDY DESIGN: Reliability study. OBJECTIVES: To compare the within- and between-day intrarater reliability of rehabilitative ultrasound imaging (RUSI) using static images (static RUSI) and video clips (video RUSI) to quantify multifidus muscle thickness at rest and while contracted. Secondary objectives were to compare the measurement precision of averaging multiple measures and to estimate reliability in individuals with and without low back pain (LBP). BACKGROUND: Although intrarater reliability of static RUSI in measuring multifidus thickness has been established, using video RUSI may improve reliability estimates, as it allows examiners to select the optimal image from a video clip. Further, multiple measurements and LBP status may affect RUSI reliability estimates. METHODS: Static RUSI and video RUSI were used to quantify multifidus muscle thickness at rest and during contraction and percent thickness change in 27 volunteers (13 without LBP and 14 with LBP). Three static RUSI images and 3 video RUSI video clips were collected in each of 2 sessions 1 to 4 days apart. Reliability and precision were assessed using intraclass correlation coefficients, standard error of measurement, minimal detectable change, bias, and 95% limits of agreement. RESULTS: Using an average of 2 measures yielded optimal measurement precision for static RUSI and video RUSI. Based on the average of 2 measures obtained under the same circumstance, there was no significant difference in the reliability estimates between static RUSI and video RUSI across all testing conditions. Reliability point estimates (intraclass correlation coefficient model 3,2) of multifidus thickness were 0.99 for within-day comparisons and ranged from 0.93 to 0.98 for between-day comparisons. The within- and between-day intraclass correlation coefficients (model 3,2) of percent thickness change ranged from 0.97 to 0.99 and from 0.80 to 0.90, respectively. The exploratory analysis showed no significant difference in the reliability estimates between asymptomatic and LBP participants across most testing conditions. CONCLUSION: Both RUSI methods yielded high reliability estimates for multifidus muscle measurements. Using an average of 2 measures obtained optimal measurement precision. Overall, video RUSI is a reliable surrogate for static RUSI for multifidus muscle measurements and has the additional advantage of requiring shorter data collection time.

Wong AY; Parent EC; Kawchuk GN

2013-04-01

183

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

Directory of Open Access Journals (Sweden)

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

Zhifeng Liu; Liuxian Zhao; Jun Zhong; Xinyu Li; Huanbo Cheng

2011-01-01

184

Studies for further development of analysis methods for evaluation of the structure reliability of piping components  

International Nuclear Information System (INIS)

In the context of BMWi reactor safety research, GRS was to develop an analytical tool on a probabilistic basis for quantitative assessment of the structural reliability of defective pipeline components. The project is based on the probabilistic computer program PRAISE (Piping Reliability Analysis Including Seismic Events) which is available as source code. Preliminary findings showed that this program was not flexible enough, so that a new program was developed under the title PROST (Probabilistische Strukturberechnungen). The contribution describes the modifications made in PRAISE, the developments on PROST, and presents a comparative evaluation of the results obtained with the two programs so far.

2002-01-01

185

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-07-01

186

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

DEFF Research Database (Denmark)

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

Ditlevsen, Ove Dalager

1997-01-01

187

Objective structured assessment of technical skills and checklist scales reliability compared for high stakes assessments.  

UK PubMed Central (United Kingdom)

BACKGROUND: The establishment of assessment reliability at the level of the individual trainee is an important attribute of assessment methodologies, particularly for doctors who have been failed. This issue is of particular importance for the process of competence assessment in the USA, UK, Australia and New Zealand. METHODS: We use data from 19 applicants for higher surgical training in 2008 at the Royal College of Surgeons in Ireland to compare: (i) the objective structured assessment of technical skills (OSATS) method; and (ii) a procedure-specific checklist to assess surgical technical skills in the excision of a sebaceous cyst task by two experienced senior surgeons. RESULTS: The overall interrater reliability (IRR) of the OSATS assessment as determined by a correlation coefficient was 0.507 (P < 0.03) and 0.67 with coefficient alpha, considerably below the accepted 0.8 level of IRR. The checklist's overall IRR was 0.89. Individually, only five (26%) of the OSATS assessments reached the 0.8 level of IRR in contrast to 18 (95%) of the checklist assessments. DISCUSSION: We propose binary procedure-based assessment checklists as more reliable assessment instruments with more robust reproducibility.

Gallagher AG; O'Sullivan GC; Leonard G; Bunting BP; McGlade KJ

2012-09-01

188

Objective structured assessment of technical skills and checklist scales reliability compared for high stakes assessments.  

Science.gov (United States)

BACKGROUND: The establishment of assessment reliability at the level of the individual trainee is an important attribute of assessment methodologies, particularly for doctors who have been failed. This issue is of particular importance for the process of competence assessment in the USA, UK, Australia and New Zealand. METHODS: We use data from 19 applicants for higher surgical training in 2008 at the Royal College of Surgeons in Ireland to compare: (i) the objective structured assessment of technical skills (OSATS) method; and (ii) a procedure-specific checklist to assess surgical technical skills in the excision of a sebaceous cyst task by two experienced senior surgeons. RESULTS: The overall interrater reliability (IRR) of the OSATS assessment as determined by a correlation coefficient was 0.507 (P OSATS assessments reached the 0.8 level of IRR in contrast to 18 (95%) of the checklist assessments. DISCUSSION: We propose binary procedure-based assessment checklists as more reliable assessment instruments with more robust reproducibility. PMID:22943748

Gallagher, Anthony G; O'Sullivan, Gerald C; Leonard, Gerald; Bunting, Brendan P; McGlade, Kieran J

2012-09-01

189

Reliable circuit analysis and design using nanoscale devices  

Science.gov (United States)

The miniaturization of the devices into nanoscale has enabled ultra high density chips, but at the cost of increased defect density. In this manuscript, Markov Random Field (MRF) approach is used to evaluate the device reliability in the presence of high defect density. Both hard and soft errors have been considered. We have presented a NANOLAB based fault model of 8-bit full adder, basic building block being 2:1 multiplexer. At each level, a Triple Modular Redundancy (TMR) is employed to enhance reliability. The results are compared with another 8-bit full adder, designed using logic gates. Assuming defect rate up to 10%, the circuits are evaluated for stuck at faults. Further, we have augmented the NANOLAB tool to include a design library of various types of flip flops. A 4-bit SISO right shift register is used as vehicle for exemplifying our approach. The fault tolerant approach N-Modular Redundancy (NMR) is compared at different levels of granularity and for varying levels of N. It is observed that NMR fails to provide the device fault tolerance when defect rate is higher than a threshold value.

Kumawat, Renu; Sahula, Vineet; Gaur, M. S.

2013-01-01

190

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

DEFF Research Database (Denmark)

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

Kimiaeifar, Amin; SØrensen, John Dalsgaard

2012-01-01

191

Inclusion of fatigue effects in human reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-11-15

192

Inclusion of fatigue effects in human reliability analysis  

International Nuclear Information System (INIS)

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

2011-01-01

193

A methodology for strain-based fatigue reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

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

Zhao, Y.X

2000-11-01

194

Model-based human reliability analysis: prospects and requirements  

International Nuclear Information System (INIS)

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

2004-01-01

195

Reliability analysis of operating indicators of nuclear power plants  

International Nuclear Information System (INIS)

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

1983-01-01

196

A human reliability analysis of a nuclear explosives dismantlement  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the methodology used in a human reliability analysis (HRA) conducted during a quantitative hazard assessment of a nuclear weapon disassembly process performed at the Pantex plant. The probability of human errors during the disassembly process is an extremely important aspect of estimating accident-sequence frequency for nuclear weapons processing. The methods include the systematic identification of potential human-initiated or enabled accident sequences using an accident-sequence fault tree, the extensive use of walkthroughs and videotaping of the disassembly process, and hands-on testing of postulated human errors. THERP modeling of rule-based behavior and operational data analysis of errors in skill-based behavior are described. A simple method for evaluating the approximate likelihood of nonmalevolent violations of procedures was developed and used to examine the process. The HRA occurred concurrently with process design, so considerable interaction between the analysts and designers occurred and resulted in design changes that are discussed in the paper.

Bott, T.F.

1995-07-01

197

[Comparative analysis in artificial nutrition].  

UK PubMed Central (United Kingdom)

INTRODUCTION: It is well known to Hungarian experts in the field of nutrition that hospital inpatients in this country do not have the required nutrition. AIM: To compare data of intensive care national costing analysis from England and intensive care unit in County Hospital, Eger, Hungary in order to advise a cost effective nutrition protocol. METHOD: English data were extracted from the report of Intensive Care National Cost Block Programme, year 1999. The Hungarian data were obtained by top down method from annual costing report of the same year. The authors used Purchasing Power Parity to make international cost comparison between these countries. RESULTS: In proportion to Purchasing Power Parity, the hospital budget per patient for nutrition is more than double in England than in the studied intensive care unit in Hungary. Intensive care units in England spend 1% on nutrition, 13% on drugs and 10% on disposables. There is only 0.2% spent on nutrition, 29.8% on drugs and 8% on disposables in the studied intensive care unit in Hungary. Cost of nutrition per patient day is HUF 117 in Hungary, which is even lower than the hospital budget per patient day for nutrition. CONCLUSION: On the basis of the above findings and literature review as well, the authors set up a cost effective nutrition guideline: 1. Identify malnourished patient. 2. Nutrition can be delayed for 4-5 days in not malnourished patient. 3. Enteral nutrition should always be the first choice. 4. Total parenteral nutrition is beneficial only if given over at least 7 days. 5) It is cost effective to prevent nosocomial infections even at higher cost.

Csomós A; Okrös I

2003-03-01

198

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

Directory of Open Access Journals (Sweden)

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

G MOHANDASS; DR. R. ANANDA NATARAJAN

2013-01-01

199

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

International Nuclear Information System (INIS)

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

2006-01-01

200

Reliability analysis of a deep water flexible riser system  

Energy Technology Data Exchange (ETDEWEB)

Oil companies all over the world are increasingly looking towards developing deep water oil and gas fields. Floating systems offer an efficient alternative for deep water production. Flexible risers are an important part of the floating production systems. Presently, flexible risers are designed by allowing a utilization factor, which is based on experience from laboratory tests, theoretical pipe mechanics and engineering know-how, not based on reliability or risk assessment. Hence, it is very important to assess the safety level in current design practice and to aim at a rational and safe design procedure. In this paper, a reliability analysis procedure for flexible riser systems based on response surface and FORM/SORM methods is outlined and it is applied to a deep water riser system for ULS condition. A failure criterion at the top end only is considered; this location being critical for this riser in ULS. The results indicate a sufficient safety level in the design for the top end of the riser. However, it is emphasized that this is not a conclusive result with respect to riser safety. A more comprehensive study is required to assess the overall safety level for flexible riser systems. Such a study should include a number of different riser configurations and limit states, especially FLS criteria, to arrive at more general conclusions.

Karunakaran, D.; Leira, B.J. [SINTEF, Trondheim (Norway); Olufsen, A.; Nordsve, N.T. [Statoil, Trondheim (Norway)

1995-12-31

 
 
 
 
201

Reliability analysis of large scaled structures by optimization technique  

International Nuclear Information System (INIS)

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

1987-01-01

202

Application of human reliability analysis methodology of second generation  

International Nuclear Information System (INIS)

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

2009-01-01

203

A Fault Analysis based Model for Software Reliability Estimation  

Directory of Open Access Journals (Sweden)

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

Garima Chawla,; Santosh Kr Thakur,

2013-01-01

204

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

International Nuclear Information System (INIS)

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

2008-01-01

205

Quantitative analysis and evaluation on reliability of mine ventilation network  

Energy Technology Data Exchange (ETDEWEB)

Variation trend and distribution rule of air flow in the ventilation network system in Daliuta coal mine were analyzed and the density functions of air-quantity distribution in the airways were established based on the network flow theory and statistics principle. Rationality about the quantitative parameters of the functions was verified by using the maximum likelihood estimation (MLE). The reliability evaluation models of mine ventilation network were established based on the disjoint minimal path set algorithm and its modeling process was presented. All the calculation processes were realized by means of MATLAB6.X and VC++6.0. The results show that the quantitative analysis indexes reflect the practical situation of the ventilation network system in Daliuta coal mine. 9 refs., 1 fig., 2 tabs.

Wang Hong-de; Liu Zhen-tang [Dalian Jiaotong University, Dalian (China). Environment and Chemistry Engineering Institute

2007-07-01

206

Reliability Analysis Using Dimension Reduction Method with Variable Sampling Points  

International Nuclear Information System (INIS)

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

2009-01-01

207

Time-dependent reliability analysis and condition assessment of structures  

Energy Technology Data Exchange (ETDEWEB)

Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process.

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

1997-01-01

208

Diagnosis based on reliability analysis using monitors and sensors  

International Nuclear Information System (INIS)

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

2008-01-01

209

UPS reliability analysis with non-exponential duration distribution  

International Nuclear Information System (INIS)

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

2003-01-01

210

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

UK PubMed Central (United Kingdom)

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

Stief F; Böhm H; Michel K; Schwirtz A; Döderlein L

2013-02-01

211

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

Science.gov (United States)

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

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

2012-07-06

212

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

International Nuclear Information System (INIS)

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

1992-01-01

213

Comparative Analysis of Control Strategies  

CERN Document Server

Different ways of modelling quantum control systems, formulating control problems and solving the resulting problems are considered and compared. In particular, we compare the performance of geometric and optimal control, as well as iterative techniques for optimal control design versus local gradient optimization using a Lyapunov-type potential function for two problems of general interest: global control of qubits and entanglement generation in the form of Bell state preparation.

Schirmer, Sonia G; Wang, Xiaoting

2008-01-01

214

Models and data requirements for human reliability analysis  

International Nuclear Information System (INIS)

[en] 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

1989-01-01

215

CGAS: comparative genomic analysis server.  

UK PubMed Central (United Kingdom)

SUMMARY: Comparative approach is one of the most essential methods for extracting functional and evolutionary information from genomic sequences. So far, a number of sequence comparison tools have been developed, and most are either for on-site use, requiring program installation but providing a wide variety of analyses, or for the online search of user's sequences against given databases on a server. We newly devised an Asynchronous JavaScript and XML (Ajax)-based system for comparative genomic analyses, CGAS, with highly interactive interface within a browser, requiring no software installation. The current version, CGAS version 1, provides functionality for viewing similarity relationships between user's sequences, including a multiple dot plot between sequences with their annotation information. The scrollbar-less 'draggable' interface of CGAS is implemented with Google Maps API version 2. The annotation information associated with the genomic sequences compared is synchronously displayed with the comparison view. The multiple-comparison viewer is one of the unique functionalities of this system to allow the users to compare the differences between different pairs of sequences. In this viewer, the system tells orthologous correspondences between the sequences compared interactively. This web-based tool is platform-independent and will provide biologists having no computational skills with opportunities to analyze their own data without software installation and customization of the computer system. Availability and Implementation: CGAS is available at http://cgas.ist.hokudai.ac.jp/.

Itoh M; Watanabe H

2009-04-01

216

Sociological analysis and comparative education  

Science.gov (United States)

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

Woock, Roger R.

1981-12-01

217

Reliability Analysis For Substation Employing B. F. Technique  

Directory of Open Access Journals (Sweden)

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

MOHIT KUMAR, RAM AVTAR JASWAL

2013-01-01

218

Reliability analysis of the service water system of Angra 1 reactor  

International Nuclear Information System (INIS)

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

1983-01-01

219

Reliability analysis of the service water system of Angra 1 reactor  

International Nuclear Information System (INIS)

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

1984-01-01

220

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

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

 
 
 
 
221

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1983-05-01

222

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

International Nuclear Information System (INIS)

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

1983-01-01

223

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

CERN Document Server

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

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

2011-01-01

224

Qualitative human reliability analysis for spent fuel handling  

International Nuclear Information System (INIS)

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

2006-01-01

225

Reliability analysis and optimization in the design of distributed systems  

Energy Technology Data Exchange (ETDEWEB)

Reliability measures and efficient evaluation algorithms are presented to aid in designing reliable distributed systems. The terminal reliability between a pair of computers is a good measure in computer networks. For distributed systems, to capture more effectively the redundancy in resources, such as programs and files, two new reliability measures are introduced. These measures are Distributed Program Reliability (DPR) and Distributed System Reliability (DSR). A simple and efficient algorithm, SYREL, is developed to evaluate the reliability between two computing centers. This algorithm incorporates conditional probability, set theory, and Boolean algebra in a distinct approach to achieve fast execution times and obtain compact expressions. An elegant and unified approach based on graph-theoretic techniques is used in developing algorithms to evaluate DPR and DSR measures. It performs a breadth-first search on the graph representing a given distributed system to enumerate all the subgraphs that guarantee the proper accessibility for executing the given tasks(s). These subgraphs are then used to evaluate the desired reliabilities. Several optimization algorithms are developed for designing reliable systems under a cost constraint.

Hariri, S.

1986-01-01

226

Reliability and risk analysis data base development: an historical perspective  

International Nuclear Information System (INIS)

Collection of empirical data and data base development for use in the prediction of the probability of future events has a long history. Dating back at least to the 17th century, safe passage events and mortality events were collected and analyzed to uncover prospective underlying classes and associated class attributes. Tabulations of these developed classes and associated attributes formed the underwriting basis for the fledgling insurance industry. Much earlier, master masons and architects used design rules of thumb to capture the experience of the ages and thereby produce structures of incredible longevity and reliability (Antona, E., Fragola, J. and Galvagni, R. Risk based decision analysis in design. Fourth SRA Europe Conference Proceedings, Rome, Italy, 18-20 October 1993). These rules served so well in producing robust designs that it was not until almost the 19th century that the analysis (Charlton, T.M., A History Of Theory Of Structures In The 19th Century, Cambridge University Press, Cambridge, UK, 1982) of masonry voussoir arches, begun by Galileo some two centuries earlier (Galilei, G. Discorsi e dimostrazioni mathematiche intorno a due nuove science, (Discourses and mathematical demonstrations concerning two new sciences, Leiden, The Netherlands, 1638), was placed on a sound scientific basis. Still, with the introduction of new materials (such as wrought iron and steel) and the lack of theoretical knowledge and computational facilities, approximate methods of structural design abounded well into the second half of the 20th century. To this day structural designers account for material variations and gaps in theoretical knowledge by employing factors of safety (Benvenuto, E., An Introduction to the History of Structural Mechanics, Part II: Vaulted Structures and Elastic Systems, Springer-Verlag, NY, 1991) or codes of practice (ASME Boiler and Pressure Vessel Code, ASME, New York) originally developed in the 19th century (Antona, E., Fragola, J. and Galvagni, R. Risk based decision analysis in design. Fourth SRA Europe Conference Proceedings, Rome, Italy, 18-20 October 1993). These factors, although they continue to be heuristically based, attempt to account for uncertainties in the design environment (e.g., the load spectra) and residual materials defects (Fragola, J.R. et al., Investigation of the risk implications of space shuttle solid rocket booster chamber pressure excursions. SAIC Document No. SAIC/NY 95-01-10, New York, NY). Although the approaches may appear different, at least at first glance, the intention in both the insurance and design arenas was to establish an 'infrastructure of confidence' to enable rational decision making for future endeavours. Maturity in the design process of conventional structures such as bridges, buildings, boilers, and highways has led to the loss of recognition of the role that robustness plays in these designs to qualify them against their normal failure environment. So routinely do we expect these designs to survive that we tend to think of the individual failures (which do occur on occasion) as isolated 'freak' accidents. Attempts to uncover potential underlying classes and document associated attributes are rare, and even when they are undertaken 'human error' or 'one-of-a-kind accidents' is often cited as the major cause which somehow seems to absolve the analyst from the responsibility of further data collection (Levy, M. and Salvadori, M., Why Buildings Fall Down, W.W. Norton and Co., New York, NY, 1992; Pecht, M., Nash, F.R. and Long, J.H., Understanding and solving the real reliability assurance problems. 1995 Proceedings of Annual RAMS Symposium, IEEE, New York, NY, 1995). The confusion has proliferated to the point where legitimate calls for scepticism regarding the scant data resources available (Evans, R.A., Bayes paradox. IEEE Trans. Reliab., R-31 (1982) 321) have given way to cries that some data sources be abandoned altogether (Cushing, M. et al., Comparison of electronics-reliability assessment approaches. Trans. Reliab., 42 (1993) 542-546 Wat son,

1996-01-01

227

Using financial ratio analysis to compare hospitals' performance.  

UK PubMed Central (United Kingdom)

Financial ratio analysis allows a hospital to evaluate its own performance over time and to compare itself with other hospitals. Through reclassification procedures, potential distortions are reduced, and administrative decisions can be based on more reliable rations. Step 1 reclassifies financial statements for analysis, step 2 computes and explains ratios, and step 3 combines ratios into patterns for interpretations. Step 4 describes the 209-hospital sample, step 5 compares three individual hospitals' ratios to industry ratios, and step 6 discusses behavior of two hospitals' ratios and industry ratios over time.

Choate GM; Tanaka K

1979-12-01

228

ITER [International Thermonuclear Experimental Reactor] guide for reliability analysis  

International Nuclear Information System (INIS)

Demanding reliability and availability (R and A) goals have been established for the International Thermonuclear Experimental Reactor (ITER). The credibility that such goals can be achieved depends on the implementation of a dedicated R and A assurance program from the outset of the design efforts. A guide for ITER reliability analyses has been prepared and preliminary results have been obtained. 6 figs

1989-01-01

229

Potential Improvements in Human Reliability Analysis for Fire Risk Assessments  

International Nuclear Information System (INIS)

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

2003-01-13

230

A new human reliability analysis method using dynamics concept  

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-07-01

231

A new human reliability analysis method using dynamics concept  

International Nuclear Information System (INIS)

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

2002-01-01

232

Towards a non-wired simulator for reliability analysis  

International Nuclear Information System (INIS)

[en] This paper outlines the objectives and preliminary results of a research programme aiming to increase the advantages of electronic simulators used for reliability studies of complex systems. Research work has resulted in the design of a device based on an electronic simulator capable of carrying out all types of simulation without the drawback of wiring, as is currently the case. Its performance levels as regards speed are comparable to those of wired simulators and this is its main advantage over studies made on a computer. In addition, the simulator is connected to a computer which greatly increases system flexibility and user-friendliness. The first results obtained illustrate what characteristics can be expected of such a system, both as regards the anticipated computation time and the extended processing capabilities (such as the study of common cause failures). (author)[fr] Ce papier presente les objectifs et les premiers resultats d'une recherche concernant lesavantages et les inconvenients des simulateurs electroniques cables pour les etudes de fiabilite de systemes complexes. Cette recherche a conduit a la conception d'un appareil constitue a la base d'un simulateur electronique capable de supporter toute simulation sans avoir de cablage a realiser. Ce systeme a des performances de vitesse comparables a celles des simulateurs cables, ce qui constitue son principal interet par rapport aux etudes realisees sur ordinateur. De plus, le simulateur est etroitement associe a un ordinateur qui ameliore considerablement la souplesse et la convivialite de l'ensemble. Les premiers resultats obtenus montrent quelles caracteristiques on peut attendre d'un tel systeme ausi bien au niveau des temps de calcul qu'au niveau des possibilites etendues de traitement qui ont ete prevues (telles que l'etude des defaillances de cause commune). (author)

1991-01-01

233

Comparative kinetic analysis of two fungal ?-glucosidases  

Directory of Open Access Journals (Sweden)

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

Chauve Marie; Mathis Hugues; Huc Delphine; Casanave Dominique; Monot Frédéric; Ferreira Nicolas

2010-01-01

234

An efficient phased mission reliability analysis for autonomous vehicles  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-03-15

235

An efficient phased mission reliability analysis for autonomous vehicles  

International Nuclear Information System (INIS)

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

2010-01-01

236

RENT CONTROL: A COMPARATIVE ANALYSIS  

Directory of Open Access Journals (Sweden)

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

Sue-Mari Maass

2012-01-01

237

Rent control: a comparative analysis  

Scientific Electronic Library Online (English)

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

Maass, S

2012-01-01

238

Reliability and Security Analysis on Two-Cell Dynamic Redundant System  

Directory of Open Access Journals (Sweden)

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

Hongsheng Su

2013-01-01

239

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

International Nuclear Information System (INIS)

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

2005-01-01

240

Reliability Analysis of Distribution Automation on Different Feeders  

Directory of Open Access Journals (Sweden)

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

C. Bhargava; P.S.R. Murthy; V. Krishna Murthy

2011-01-01

 
 
 
 
241

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

International Nuclear Information System (INIS)

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

1996-11-01

242

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-02-01

243

Application of Metric-based Software Reliability Analysis to Example Software  

International Nuclear Information System (INIS)

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

2008-01-01

244

Reliability analysis based on losses from failure Modelling  

Directory of Open Access Journals (Sweden)

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

Dr. Amit Gupta , Renu Garg

2013-01-01

245

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-07-15

246

The reliability analysis of cutting tools in the HSM processes  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: This article mainly describe the reliability of the cutting tools in the high speed turning by normaldistribution model.Design/methodology/approach: A series of experimental tests have been done to evaluate the reliabilityvariation of the cutting tools. From experimental results, the tool wear distribution and the tool life are determined,and the tool life distribution and the reliability function of cutting tools are derived. Further, the reliability ofcutting tools at anytime for high speed machining (HSM) is easily calculated from cutting parameters and toolwear limit from the derived reliability function.Findings: The higher the cutting speed, the sooner the tool flank wear, and the faster the degrade speed of thereliability curve. It means that the sooner the tool flank wear rate, the shorter the tool life, and it is the time tochange the cutting tool.Practical implications: This paper shows that the tool flank wear rate can be described by the reliabilitydegrade rate, the higher the flank wear rate, the steeper the tool reliability degrade rate.Originality/value: This article is discussing about the tool wear variation of the cutting tool from the point ofreliability. From the reliability variation of the cutting tool, we can further predict the tool life, in order to decidethe tool replacement time.

W.S. Lin

2008-01-01

247

Reliability and risk analysis data base development: an historical perspective  

Energy Technology Data Exchange (ETDEWEB)

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

Fragola, Joseph R

1996-02-01

248

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

Energy Technology Data Exchange (ETDEWEB)

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

Anderson-cooke, Christine M [Los Alamos National Laboratory

2010-01-01

249

Reliability Engineering Analysis of ATLAS Data Reprocessing Campaigns  

CERN Document Server

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

Vaniachine, A; The ATLAS collaboration; Karpenko, D

2013-01-01

250

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

International Nuclear Information System (INIS)

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

1995-01-01

251

Long term reliability analysis of standby diesel generators  

International Nuclear Information System (INIS)

[en] The long term reliability of 11 diesel generators of 125 to 250 kV A size has been analysed from 26 years of data base information on individual diesel service as standby power supplies for the Chalk River research reactor facilities. Failure to start on demand and failure to run data is presented and failure by diesel subsystem and multiple failures are also analysed. A brief comparison is made with reliability studies of larger diesel generator units used for standby power service in nuclear power plants. (author)

1988-01-01

252

Linear-time computer network reliability analysis algorithm  

Energy Technology Data Exchange (ETDEWEB)

The best-known solution methods for network reliability problems are of exponential time-complexity. This exponential behavior can render even moderately sized problems computationally intractable due to the enormous amount of time required to generate a solution. To render such problems solvable, an approximation algorithm was developed that accurately estimates the source-to-terminal reliability of an arbitrary network. Linear time-complexity is a unique feature of this estimation algorithm, as is the fact that upper and lower bounds are also generated.

Belovich, S.

1987-01-01

253

Reliability analysis of common hazardous waste treatment processes  

International Nuclear Information System (INIS)

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

1993-01-01

254

Reliability Analysis in Parallel and Distributed Systems with Network Contention  

Directory of Open Access Journals (Sweden)

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

Hussein EL Ghor; Rafic Hage Chehade; Tamim Fliti

2012-01-01

255

Reliability analysis of common hazardous waste treatment processes  

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-05-01

256

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

Energy Technology Data Exchange (ETDEWEB)

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

Peters, Valerie A.; Ogilvie, Alistair B.

2012-01-01

257

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

Directory of Open Access Journals (Sweden)

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

Peter Hofmann; Josef Strobl; Ainura Nazarkulova

2011-01-01

258

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

Directory of Open Access Journals (Sweden)

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

Lei Nie; Yuan Guo; Lina Xu

2013-01-01

259

Comparative analysis of seismic risk assessment methodology  

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-07-01

260

Comparative analysis of seismic risk assessment methodology  

International Nuclear Information System (INIS)

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

1994-01-01

 
 
 
 
261

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-12-01

262

[Angiographic assessment of functionally insignificant left main coronary artery stenoses: reliability compared to intracoronary pressure measurement  

UK PubMed Central (United Kingdom)

BACKGROUND AND OBJECTIVE: Left main coronary artery disease (LMCA) is still a widely accepted indication for coronary artery bypass surgery. Intermediate LMCA disease, however, often cannot be evaluated reliably on the basis of clinical and angiographic information alone. The deferral of surgical revascularization based on fractional flow reserve (FFR) measurements has been shown to be safe and feasible when taking an FFR value of (3) 0.75 as cutoff. This study was performed to compare the accuracy of visual angiographic assessment of intermediate LMCA stenoses by experienced interventional cardiologists with functional assessment by FFR in a patient population with excellent long-term outcome after deferral of surgery on the basis of FFR measurements. PATIENTS AND METHODS: 24 of 51 consecutive patients with intermediate LMCA disease were deferred from surgery based on an FFR value of > or = 0.75. Each angiogram was retrospectively reviewed independently by three experienced interventional cardiologists. Reviewers were blinded to initial FFR results, clinical data, and clinical outcome and asked to classify each lesion as SIGNIFICANT (FFR < 0.75), NOT SIGNIFICANT (FFR > or = 0.75), or UNSURE if the observer was unable to make a decision based on the angiogram. RESULTS: Mean follow-up was 29 +/- 13.6 months. No death or myocardial infarction was observed, event-free survival was 69 %. When taking the "unsure" classifications into consideration the individual reviewers achieved correct lesion classification with respect to FFR results on average in 58 % to 82 % of cases. Interobserver variability resulted in only 46 % of cases in concordant lesion classification (3 agreements or 2 agreements and 1 "unsure" evaluation). The number of concordant agreements between the individual pairs of reviewers did not exceed the rate of coincidental agreements that could be expected to result from simple guessing (mean KAPPA coefficient 0.04). More than 50 % of patients with excellent long-term outcome after deferral of surgery would potentially have undergone operative revascularization if consensual decision making had been solely based on angiographic lesion assessment. CONCLUSION: The functional significance of intermediate or equivocal LMCA lesions should not be based on visual assessment alone, even when performed by experienced interventional cardiologists.

Lindstaedt M; Spiecker M; Lawo T; Yazar A; Mügge A; Bojara W; Germing A

2006-09-01

263

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-04-01

264

Analysis of the Component-Based Reliability in Computer Networks  

Scientific Electronic Library Online (English)

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

Minkeviius, Saulius

2010-01-01

265

A methodology for photovoltaic system reliability and economic analysis  

Energy Technology Data Exchange (ETDEWEB)

It is pointed out that the operation of large terrestrial photovoltaic (PV) power systems (over 50 peak kilowatts) is a fairly recent event. The present investigation provides a review of the characteristics of current and future PV systems and selects a methodology to allow the system designer to consider system reliability and maintenance parameters early in the design. The goal is to minimize the cost of system output energy over system life. Thus, cost per kW-hour is the objective function which PV system designers should minimize. Attention is given to an integrated reliability, availability, maintainability (RAM) model, which represents failure and repair, and provides the corrective maintenance portion of the yearly maintenance cost. The RAM model and a life-cycle energy cost model are combined to provide the information the designer needs for system optimization.

Stember, L.H.; Huss, W.R.; Bridgman, M.S.

1982-08-01

266

Development of Reliability Analysis Method for Nuclear Power Plant Protection System  

International Nuclear Information System (INIS)

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

2009-01-01

267

Comparing Criteria for Attachment Disorders: Establishing Reliability and Validity in High-Risk Samples.  

Science.gov (United States)

Objective: To determine whether published subtypes of attachment disorder can be reliably identified by trained clinicians reviewing data from high-risk populations and to investigate the relationship between disorder classification and standardized measures of attachment behavior. Method: Twenty or more children aged 18 to 48 months and their…

Boris, Neil W.; Hinshaw-Fuselier, Sarah S.; Smyke, Anna T.; Scheeringa, Michael S.; Heller, Sherryl S.; Zeanah, Charles H.

2004-01-01

268

Reliability analysis of a dual-redundant engine controller  

Energy Technology Data Exchange (ETDEWEB)

A Markov model is developed to predict the reliability of a full-authority, dual-redundant aircraft engine controller. The effects of failures of any of the controllers sensors, electronic interface modules, processors and actuators, as well as the consequences of redundancy management decisions are modeled. The model issued to study parameter sensitivity and to develop quantitative data in support of design tradeoffs. The effects of scheduled maintenance of the inflight shutdown rate of the engine are determined.

Gai, E.; Harrison, J.V.; Luppold, R.H.

1983-04-01

269

Reliability Analysis of Public Survey in Satisfaction with Nuclear Safety  

International Nuclear Information System (INIS)

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.

2005-01-01

270

Comparative analysis of peat gasification reactor configuration  

Energy Technology Data Exchange (ETDEWEB)

A comparative analysis of two generic (fluidized and entrained beds) and two specific (PEATGAS and the Rockwell International) hydrogasifiers involved data-base assessment, regression analysis, a chemical-engineering evaluation of down- and upstream equipment needs, and computer simulation. The study concluded that the PEATGAS reactor is closer to commercialization than the Rockwell.

1981-07-01

271

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

International Nuclear Information System (INIS)

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

1983-01-01

272

Application of reliability analysis methods to the comparison of two safety circuits  

International Nuclear Information System (INIS)

Two circuits of different design, intended for assuming the ''Low Pressure Safety Injection'' function in PWR reactors are analyzed using reliability methods. The reliability analysis of these circuits allows the failure trees to be established and the failure probability derived. The dependence of these results on test use and maintenance is emphasized as well as critical paths. The great number of results obtained may allow a well-informed choice taking account of the reliability wanted for the type of circuits.

1975-06-09

273

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

International Nuclear Information System (INIS)

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

1982-01-01

274

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

International Nuclear Information System (INIS)

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

2008-01-01

275

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-10-15

276

Comparative analysis of methods of hardness assessment  

Directory of Open Access Journals (Sweden)

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

A. Czarski

2009-01-01

277

Reliability analysis of the solar array based on Fault Tree Analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-07-19

278

NREL Gearbox Reliability Collaborative Experimental Data Overview and Analysis: Preprint  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-05-01

279

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

International Nuclear Information System (INIS)

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

2008-01-01

280

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

Directory of Open Access Journals (Sweden)

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

Xintao Xia; Yantao Shang; Yinping Jin; Long Chen

2013-01-01

 
 
 
 
281

Reliability analysis of a dual-redundant engine controller  

Energy Technology Data Exchange (ETDEWEB)

A Markov model is developed to predict the reliability of a full-authority, dual-redundant aircraft engine controller. The effects of failures of any of the controller's sensors, electronic interface modules, processors and actuators, as well as the consequences of redundancy management decisions are modeled. The use of the model to perform parameter sensitivity studies and to develop quantitative data in support of design tradeoffs is described. The effects of scheduled maintenance on the inflight shutdown rate of the engine are determined. 6 refs.

Gai, E.; Harrison, J.V.; Luppold, R.H.

1981-01-01

282

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

Directory of Open Access Journals (Sweden)

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

R.K. Agnihotri; Ajit Khare; Sanjay Jain

2008-01-01

283

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

International Nuclear Information System (INIS)

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

2000-06-28

284

Analysis of Statistical Distributions Used for Modeling Reliability and Failure Rate of Temperature Alarm Circuit  

International Nuclear Information System (INIS)

[en] Several statistical distributions are used to model various reliability and maintainability parameters. The applied distribution depends on the' nature of the data being analyzed. The presented paper deals with analysis of some statistical distributions used in reliability to reach the best fit of distribution analysis. The calculations rely on circuit quantity parameters obtained by using Relex 2009 computer program. The statistical analysis of ten different distributions indicated that Weibull distribution gives the best fit distribution for modeling the reliability of the data set of Temperature Alarm Circuit (TAC). However, the Exponential distribution is found to be the best fit distribution for modeling the failure rate

2011-01-01

285

Estimating and comparing the reliability of a suite of workplace-based assessments: an obstetrics and gynaecology setting.  

Science.gov (United States)

This paper reports on a study that compares estimates of the reliability of a suite of workplace based assessment forms as employed to formatively assess the progress of trainee obstetricians and gynaecologists. The use of such forms of assessment is growing nationally and internationally in many specialties, but there is little research evidence on comparisons by procedure/competency and form-type across an entire specialty. Generalisability theory combined with a multilevel modelling approach is used to estimate variance components, G-coefficients and standard errors of measurement across 13 procedures and three form-types (mini-CEX, OSATS and CbD). The main finding is that there are wide variations in the estimates of reliability across the forms, and that therefore the guidance on assessment within the specialty does not always allow for enough forms per trainee to ensure that the levels of reliability of the process is adequate. There is, however, little evidence that reliability varies systematically by form-type. Methodologically, the problems of accurately estimating reliability in these contexts through the calculation of variance components and, crucially, their associated standard errors are considered. The importance of the use of appropriate methods in such calculations is emphasised, and the unavoidable limitations of research in naturalistic settings are discussed. PMID:23782043

Homer, Matt; Setna, Zeryab; Jha, Vikram; Higham, Jenny; Roberts, Trudie; Boursicot, Katherine

2013-06-19

286

Estimating and comparing the reliability of a suite of workplace-based assessments: an obstetrics and gynaecology setting.  

UK PubMed Central (United Kingdom)

This paper reports on a study that compares estimates of the reliability of a suite of workplace based assessment forms as employed to formatively assess the progress of trainee obstetricians and gynaecologists. The use of such forms of assessment is growing nationally and internationally in many specialties, but there is little research evidence on comparisons by procedure/competency and form-type across an entire specialty. Generalisability theory combined with a multilevel modelling approach is used to estimate variance components, G-coefficients and standard errors of measurement across 13 procedures and three form-types (mini-CEX, OSATS and CbD). The main finding is that there are wide variations in the estimates of reliability across the forms, and that therefore the guidance on assessment within the specialty does not always allow for enough forms per trainee to ensure that the levels of reliability of the process is adequate. There is, however, little evidence that reliability varies systematically by form-type. Methodologically, the problems of accurately estimating reliability in these contexts through the calculation of variance components and, crucially, their associated standard errors are considered. The importance of the use of appropriate methods in such calculations is emphasised, and the unavoidable limitations of research in naturalistic settings are discussed.

Homer M; Setna Z; Jha V; Higham J; Roberts T; Boursicot K

2013-08-01

287

Time-dependent reliability analysis of flood defences  

International Nuclear Information System (INIS)

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

2009-01-01

288

Trouble analysis for reliability evaluation of irradiation system in HIMAC  

International Nuclear Information System (INIS)

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

2009-01-01

289

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

International Nuclear Information System (INIS)

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

290

Architecture for interlock systems: reliability analysis with regard to safety and availability  

International Nuclear Information System (INIS)

For particle accelerators like LHC and other large experimental physics facilities like ITER, the machine protection relies on complex interlock systems. 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 wear-out. 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. The results show the advantages of a 2003 (3 redundant lines with 2-out-of-3 voting) over the 6 architectures under consideration for systems with high requirements in both safety and availability

2012-01-01

291

Comparative Analysis on Constitutional Supervision Modes  

Directory of Open Access Journals (Sweden)

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

Wenjing WANG; Xiaorui WANG

2012-01-01

292

Reliability analysis of an offshore structure. A case study - 2  

Energy Technology Data Exchange (ETDEWEB)

For an offshore structure in the North Sea it is assumed that information from measurements and inspections is available. As illustrations measurements of the significant wave height and the marine growth and different inspection and repair results are considered. It is shown how the reliability estimates of the structure can be updated using Bayesian techniques. By minimizing the total expected costs including inspection, repair and failure costs during the lifetime an optimal inspection and repair strategy can be determined. The decision variables are the number of inspections, the time intervals between inspections and the inspection qualities. A parameter study is performed and an updated inspection plan is determined after the first inspection has taken place. (au) (12 refs.).

Soerensen, J.D.; Faber, M.H. [University of Aalborg, Aalborg (Denmark); Rackwitz, R. [Technical University of Munich, Munich (Germany); Thoft-Christensen, P. [CSR, Aalborg (Denmark); Lebas, G. [ELF Aquitaine, Pau Cedex (France)

1992-12-01

293

Reliability Analysis of an Offshore Structure : A Case Study II  

DEFF Research Database (Denmark)

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

SØrensen, John Dalsgaard; Rackwitz, R.

1992-01-01

294

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

Science.gov (United States)

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

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

2012-03-08

295

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

UK PubMed Central (United Kingdom)

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

Nishiguchi S; Yamada M; Nagai K; Mori S; Kajiwara Y; Sonoda T; Yoshimura K; Yoshitomi H; Ito H; Okamoto K; Ito T; Muto S; Ishihara T; Aoyama T

2012-05-01

296

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

International Nuclear Information System (INIS)

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

1982-01-01

297

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

Directory of Open Access Journals (Sweden)

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

J. Szymszal; J. Pi?tkowski; T. Mikuszewski; M. Mali?ski

2009-01-01

298

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-09-15

299

DSM-III-R Axis IV: clinician reliability and comparability to patients' reports of stressor severity.  

UK PubMed Central (United Kingdom)

Stress has long been considered an important precipitant to the development or exacerbation of psychopathology (Selye 1980). However, it has been difficult to reach agreement on how to measure stressors reliably, and whether stressors should be assessed using an objective clinical rating or a subjective appraisal (Mazure and Druss 1995). When the DSM-III multiaxial diagnostic system was derived, Axis IV was designed to provide a mechanism for objectively rating the severity of psychosocial stressors that contributed to the development or exacerbation of psychiatric disorders (Williams 1985). With the continued use of this nosological system, DSM-III-R Axis IV has become the most commonly used assessment of stressors in clinical settings today. The current work focuses on whether DSM-III-R Axis IV can be used reliably by clinicians generating objective ratings, and on whether these objective ratings reflect patients' appraisals of the severity of their psychosocial stressors. Based on this work, options for future use of Axis IV are discussed.

Mazure CM; Kincare P; Schaffer CE

1995-02-01

300

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

Directory of Open Access Journals (Sweden)

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

Li Wang; Zaiwen Liu; Chongchong Yu

2013-01-01

 
 
 
 
301

NPP channel structure safety system reliability analysis. Methods and computer code SHARM-2  

International Nuclear Information System (INIS)

Special investigations on the methods for reliability assessment of safety related systems was performed in accordance with the development of general methodology for the NPP probabilistic safety analysis (PSA) in the USSR. The methods are based on the present-day advances in the field of NPP safety systems reliability and meet the main requirements placed on system analysis in performing the PSA. The methodical principles are implemented in SHARM-2 computer package used for the RBMK system reliability assessment. The main results of methodology and computer code development are given. (author). 3 refs, 1 fig., 3 tabs.

1991-01-01

302

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-03-15

303

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

International Nuclear Information System (INIS)

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

2007-01-01

304

Update of the human reliability analysis for a nuclear power plant  

International Nuclear Information System (INIS)

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

2006-01-01

305

Diagnosing MOV problems using comparative trace analysis  

International Nuclear Information System (INIS)

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

1992-01-01

306

Increasing the reliability of electricity production. A cost benefit analysis  

Energy Technology Data Exchange (ETDEWEB)

This report analyses three instruments aimed at increasing the reliability of electricity production. In the system of capacity markets, the transmission system operator (TSO) requires traders to back their own peak load plus a prescribed level of spare capacity with contracted capacity, the latter being tradable at secondary markets. With reserve contracts, the TSO contracts spare capacity from producers, holding it to be dispatched in case of a crisis. Capacity payments are a subsidy on capital costs, giving producers an incentive to build more capacity. These measures prove to be in efficient in preventing price spikes, as the welfare costs of price spikes are lower than the costs of the policy options, unless price spikes occur in an implausible high frequency. Capacity payments cannot prevent black-outs, as they do not induce enough investments in spare capacity. Black-outs can be prevented by capacity markets and reserve contracts, but at a high cost. Even if a 24-hour black-out of the Randstad area occurred every five years, it would be cheaper to accept the consequences of the black-out than to prevent it.

Lijesen, M.

2004-02-01

307

Reliability analysis of the rank transform for stereo matching.  

UK PubMed Central (United Kingdom)

The rank transform is a nonparametric technique which has been recently proposed for the stereo matching problem. The motivation behind its application to this problem is its invariance to certain types of image distortion and noise, as well as its amenability to real-time implementation. This paper derives one constraint which must be satisfied for a correct match. This has been termed the rank constraint. Experimental work has shown that this constraint is capable of resolving ambiguous matches, thereby improving matching reliability. A novel matching algorithm incorporating the rank constraint has also been proposed. This modified algorithm consistently resulted in an increased percentage of correct matches, for all test imagery used. Furthermore, the rank constraint has been used to devise a method of identifying regions of an image where the rank transform, and hence matching outcome, is more susceptible to noise. Experimental results have shown that the errors predicted using this technique are consistent with the actual errors which result when images are corrupted with noise. Such a method could be used to identify matches which are likely to be incorrect and/or provide a measure of confidence in a match.

Banks J; Bennamoun M

2001-01-01

308

Reliability analysis of the rank transform for stereo matching.  

Science.gov (United States)

The rank transform is a nonparametric technique which has been recently proposed for the stereo matching problem. The motivation behind its application to this problem is its invariance to certain types of image distortion and noise, as well as its amenability to real-time implementation. This paper derives one constraint which must be satisfied for a correct match. This has been termed the rank constraint. Experimental work has shown that this constraint is capable of resolving ambiguous matches, thereby improving matching reliability. A novel matching algorithm incorporating the rank constraint has also been proposed. This modified algorithm consistently resulted in an increased percentage of correct matches, for all test imagery used. Furthermore, the rank constraint has been used to devise a method of identifying regions of an image where the rank transform, and hence matching outcome, is more susceptible to noise. Experimental results have shown that the errors predicted using this technique are consistent with the actual errors which result when images are corrupted with noise. Such a method could be used to identify matches which are likely to be incorrect and/or provide a measure of confidence in a match. PMID:18244853

Banks, J; Bennamoun, M

2001-01-01

309

Analysis methods for structure reliability of piping components  

International Nuclear Information System (INIS)

In the frame of the German reactor safety research program of the Federal Ministry of Economics and Labour (BMWA) GRS has started to develop an analysis code named PROST (PRObabilistic STructure analysis) for estimating the leak and break probabilities of piping systems in nuclear power plants. The long-term objective of this development is to provide failure probabilities of passive components for probabilistic safety analysis of nuclear power plants. Up to now the code can be used for calculating fatigue problems. The paper mentions the main capabilities and theoretical background of the present PROST development and presents some of the results of a benchmark analysis in the frame of the European project NURBIM (Nuclear Risk Based Inspection Methodologies for Passive Components). (orig.)

2004-01-01

310

Analysis methods for structure reliability of piping components  

Energy Technology Data Exchange (ETDEWEB)

In the frame of the German reactor safety research program of the Federal Ministry of Economics and Labour (BMWA) GRS has started to develop an analysis code named PROST (PRObabilistic STructure analysis) for estimating the leak and break probabilities of piping systems in nuclear power plants. The long-term objective of this development is to provide failure probabilities of passive components for probabilistic safety analysis of nuclear power plants. Up to now the code can be used for calculating fatigue problems. The paper mentions the main capabilities and theoretical background of the present PROST development and presents some of the results of a benchmark analysis in the frame of the European project NURBIM (Nuclear Risk Based Inspection Methodologies for Passive Components). (orig.)

Schimpfke, T.; Grebner, H.; Sievers, J. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Koeln (Germany)

2004-07-01

311

An improved rank assessment method for weibull analysis of reliability data  

International Nuclear Information System (INIS)

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

2007-01-01

312

Sensitivity and reliability analysis on shear behavior of a discontinuity in uncertain underground structure considering multi-random variables  

International Nuclear Information System (INIS)

In this study, a sensitivity analysis on shear failure of a discontinuity adjacent to a circular opening has been performed based on a series system reliability analysis. To realize the failure surface of the system, Mohr-Coulomb yield criteria and other empirical models suggested by Jaeger, Ladanyi and Archambault, and Barton and Bandis have been adopted. Discontinuity direction, initial stress, pore water pressure and various physical properties obtainable from site investigation and Lab. test in discontinuous rock mass before the design stage are selected as multi-random variables, all of which could be simulated in terms of normal distribution, log-normal distribution, or beta distribution. In order to obtain generalized reliability index and failure probability, FORM(First-order reliability method) and PNET method have been adopted with modified HL-RF method as for an optimization scheme. A computer program has been developed and verified by comparing the analysis results by Monte Carlo simulation. The effect on probability of failure of cavern size, distance between a cavern and a discontinuity, and correlation coefficients have been reviewed through reliability analysis. The most sensitive parameter on system failure has been obtained through sensitivity study.

1998-01-01

313

Sensitivity and reliability analysis on shear behavior of a discontinuity in uncertain underground structure considering multi-random variables  

Energy Technology Data Exchange (ETDEWEB)

In this study, a sensitivity analysis on shear failure of a discontinuity adjacent to a circular opening has been performed based on a series system reliability analysis. To realize the failure surface of the system, Mohr-Coulomb yield criteria and other empirical models suggested by Jaeger, Ladanyi and Archambault, and Barton and Bandis have been adopted. Discontinuity direction, initial stress, pore water pressure and various physical properties obtainable from site investigation and Lab. test in discontinuous rock mass before the design stage are selected as multi-random variables, all of which could be simulated in terms of normal distribution, log-normal distribution, or beta distribution. In order to obtain generalized reliability index and failure probability, FORM(First-order reliability method) and PNET method have been adopted with modified HL-RF method as for an optimization scheme. A computer program has been developed and verified by comparing the analysis results by Monte Carlo simulation. The effect on probability of failure of cavern size, distance between a cavern and a discontinuity, and correlation coefficients have been reviewed through reliability analysis. The most sensitive parameter on system failure has been obtained through sensitivity study.

Choi, K. S.; Hwang, S. I. [KNETEC, Taejon (Korea, Republic of)

1998-10-01

314

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-03-01

315

Image analysis in comparative genomic hybridization  

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-01-01

316

Finite State Machine Based Evaluation Model for Web Service Reliability Analysis  

CERN Multimedia

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

M, Thirumaran; Abarna, S; P, Lakshmi

2011-01-01

317

Analysis of structure reliability on beam using fuzzy finite element method  

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

318

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

Science.gov (United States)

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

Ang, Rebecca P.; Huan, Vivien S.

2006-01-01

319

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

International Nuclear Information System (INIS)

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

1997-01-01

320

Comparative analysis of twelve Dothideomycete plant pathogens  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-03-11

 
 
 
 
321

Reliability of contemporary data-acquisition techniques for LEED analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

1980-10-01

322

Reliability of contemporary data-acquisition techniques for LEED analysis  

International Nuclear Information System (INIS)

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

1980-06-20

323

Embedded Hyperchaotic Generators: A Comparative Analysis  

Science.gov (United States)

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

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

324

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-07-01

325

Analysis of complete logical structures in system reliability assessment  

International Nuclear Information System (INIS)

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

1980-01-01

326

Validating Utility of TEIM: A Comparative Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Concrete efforts to integrate Software Engineering and Human Computer Interaction exist in the form of models by many researchers. An unconventional model called TEIM (The Evolved Integrated Model) of Software Engineering and Human Computer Interaction was proposed by us. There is a need to establish correlation with prior models as well validate utility of TEIM. In this paper product PS designed using SE-HCI integration model TEIM is evaluated by making a comparative analysis. For evaluation UGAM and IOI tools designed by DR.Anirudha Joshi are used. Our analysis showed that correlation of TEIM exists with prior models. Regression analysis showed that high correlation exists between TEIM and prior model.

Rajesh Kulkarni; P.Padmanabham

2013-01-01

327

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

International Nuclear Information System (INIS)

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

2001-01-01

328

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

Directory of Open Access Journals (Sweden)

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

Fabio De Felice; Antonella Petrillo

2011-01-01

329

Reliability analysis of emergency power system for 200 MW low temperature nuclear heating reactor  

International Nuclear Information System (INIS)

[en] The design features of the emergency power system for 200 MW Low Temperature Nuclear Heating Reactor were briefly introduced, and the reliability of the emergency power system was analyzed using fault tree analysis method. The results showed that the simplified emergency power system for 200 MW Low Temperature Nuclear Reactor has the same reliability index as the design method of the nuclear power plant. It also showed that the proposed design method of the emergency power system for 200 MW Low Temperature Nuclear Heating Reactor was not only reliable and safe but also very economic

1998-01-01

330

Systematic review of reliability and diagnostic validity of joint vibration analysis for diagnosis of temporomandibular disorders.  

UK PubMed Central (United Kingdom)

AIMS: To conduct a systematic review of papers reporting the reliability and diagnostic validity of the joint vibration analysis (JVA) for diagnosis of temporomandibular disorders (TMD). METHODS: A search of Pubmed identified English-language publications of the reliability and diagnostic validity of the JVA. Guidelines were adapted from applied STAndards for the Reporting of Diagnostic accuracy studies (STARD) to evaluate the publications. RESULTS: Fifteen publications were included in this review, each of which presented methodological limitations. CONCLUSION: This literature is unable to provide evidence to support the reliability and diagnostic validity of the JVA for diagnosis of TMD.

Sharma S; Crow HC; McCall WD Jr; Gonzalez YM

2013-01-01

331

System reliability analysis via generalized perturbation theory methods  

Energy Technology Data Exchange (ETDEWEB)

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

Gandini, A.

1986-01-01

332

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

International Nuclear Information System (INIS)

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

1985-01-01

333

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

International Nuclear Information System (INIS)

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

1985-01-01

334

Living PRAs [probabilistic risk analysis] made easier with IRRAS [Integrated Reliability and Risk Analysis System  

International Nuclear Information System (INIS)

The Integrated Reliability and Risk Analysis System (IRRAS) is an integrated PRA software tool that gives the user the ability to create and analyze fault trees and accident sequences using an IBM-compatible microcomputer. This program provides functions that range from graphical fault tree and event tree construction to cut set generation and quantification. IRRAS contains all the capabilities and functions required to create, modify, reduce, and analyze event tree and fault tree models used in the analysis of complex systems and processes. IRRAS uses advanced graphic and analytical techniques to achieve the greatest possible realization of the potential of the microcomputer. When the needs of the user exceed this potential, IRRAS can call upon the power of the mainframe computer. The role of the Idaho National Engineering Laboratory if the IRRAS program is that of software developer and interface to the user community. Version 1.0 of the IRRAS program was released in February 1987 to prove the concept of performing this kind of analysis on microcomputers. This version contained many of the basic features needed for fault tree analysis and was received very well by the PRA community. Since the release of Version 1.0, many user comments and enhancements have been incorporated into the program providing a much more powerful and user-friendly system. This version is designated ''IRRAS 2.0''. Version 3.0 will contain all of the features required for efficient event tree and fault tree construction and analysis. 5 refs., 26 figs

1989-01-01

335

Application of Fault Tree Analysis for Estimating Temperature Alarm Circuit Reliability  

International Nuclear Information System (INIS)

Fault Tree Analysis (FTA) is one of the most widely-used methods in system reliability analysis. It is a graphical technique that provides a systematic description of the combinations of possible occurrences in a system, which can result in an undesirable outcome. The presented paper deals with the application of FTA method in analyzing temperature alarm circuit. The criticality failure of this circuit comes from failing to alarm when temperature exceeds a certain limit. In order for a circuit to be safe, a detailed analysis of the faults causing circuit failure is performed by configuring fault tree diagram (qualitative analysis). Calculations of circuit quantitative reliability parameters such as Failure Rate (FR) and Mean Time between Failures (MTBF) are also done by using Relex 2009 computer program. Benefits of FTA are assessing system reliability or safety during operation, improving understanding of the system, and identifying root causes of equipment failures

2011-01-01

336

Application of human reliability analysis to nursing errors in hospitals.  

Science.gov (United States)

Adverse events in hospitals, such as in surgery, anesthesia, radiology, intensive care, internal medicine, and pharmacy, are of worldwide concern and it is important, therefore, to learn from such incidents. There are currently no appropriate tools based on state-of-the art models available for the analysis of large bodies of medical incident reports. In this study, a new model was developed to facilitate medical error analysis in combination with quantitative risk assessment. This model enables detection of the organizational factors that underlie medical errors, and the expedition of decision making in terms of necessary action. Furthermore, it determines medical tasks as module practices and uses a unique coding system to describe incidents. This coding system has seven vectors for error classification: patient category, working shift, module practice, linkage chain (error type, direct threat, and indirect threat), medication, severity, and potential hazard. Such mathematical formulation permitted us to derive two parameters: error rates for module practices and weights for the aforementioned seven elements. The error rate of each module practice was calculated by dividing the annual number of incident reports of each module practice by the annual number of the corresponding module practice. The weight of a given element was calculated by the summation of incident report error rates for an element of interest. This model was applied specifically to nursing practices in six hospitals over a year; 5,339 incident reports with a total of 63,294,144 module practices conducted were analyzed. Quality assurance (QA) of our model was introduced by checking the records of quantities of practices and reproducibility of analysis of medical incident reports. For both items, QA guaranteed legitimacy of our model. Error rates for all module practices were approximately of the order 10(-4) in all hospitals. Three major organizational factors were found to underlie medical errors: "violation of rules" with a weight of 826 x 10(-4), "failure of labor management" with a weight of 661 x 10(-4), and "defects in the standardization of nursing practices" with a weight of 495 x 10(-4). PMID:15660604

Inoue, Kayoko; Koizumi, Akio

2004-12-01

337

Application of human reliability analysis to nursing errors in hospitals.  

UK PubMed Central (United Kingdom)

Adverse events in hospitals, such as in surgery, anesthesia, radiology, intensive care, internal medicine, and pharmacy, are of worldwide concern and it is important, therefore, to learn from such incidents. There are currently no appropriate tools based on state-of-the art models available for the analysis of large bodies of medical incident reports. In this study, a new model was developed to facilitate medical error analysis in combination with quantitative risk assessment. This model enables detection of the organizational factors that underlie medical errors, and the expedition of decision making in terms of necessary action. Furthermore, it determines medical tasks as module practices and uses a unique coding system to describe incidents. This coding system has seven vectors for error classification: patient category, working shift, module practice, linkage chain (error type, direct threat, and indirect threat), medication, severity, and potential hazard. Such mathematical formulation permitted us to derive two parameters: error rates for module practices and weights for the aforementioned seven elements. The error rate of each module practice was calculated by dividing the annual number of incident reports of each module practice by the annual number of the corresponding module practice. The weight of a given element was calculated by the summation of incident report error rates for an element of interest. This model was applied specifically to nursing practices in six hospitals over a year; 5,339 incident reports with a total of 63,294,144 module practices conducted were analyzed. Quality assurance (QA) of our model was introduced by checking the records of quantities of practices and reproducibility of analysis of medical incident reports. For both items, QA guaranteed legitimacy of our model. Error rates for all module practices were approximately of the order 10(-4) in all hospitals. Three major organizational factors were found to underlie medical errors: "violation of rules" with a weight of 826 x 10(-4), "failure of labor management" with a weight of 661 x 10(-4), and "defects in the standardization of nursing practices" with a weight of 495 x 10(-4).

Inoue K; Koizumi A

2004-12-01

338

Problems Related to Use of Some Terms in System Reliability Analysis  

Directory of Open Access Journals (Sweden)

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

Nadezda Hanusova; Jiri Zahradnik

2004-01-01

339

A study on the reliability analysis of nuclear steel containment structures subject to internal pressure  

International Nuclear Information System (INIS)

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

1999-01-01

340

Reliability analysis of nuclear containment without metallic liners against jet aircraft crash  

International Nuclear Information System (INIS)

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.

2003-01-01

 
 
 
 
341

Determination of Strength for Reliability Analysis of Multilayer Ceramic Capacitors  

International Nuclear Information System (INIS)

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

1999-01-01

342

The fabrication reliability data analysis system DANTE-QC1  

International Nuclear Information System (INIS)

A sophisticated quality control system is needed to cut production costs and improve the quality of mixed oxide fuels. The system needs to extend the quality control from the characteristics of the product to the conditions of process to identify the abnormal parameter causing the below-quality product. The abnormal real-time of the product and process must be shown in graphical form by the data base, built up from fabrication knowledge gained over a number of years. DANTE-QC1 (Data Analysing Technology for Engineers) is a data analysis system for nuclear fuels with a relational data base management system developed to meet this need. The structure and operation of the DANTE data base system are described. (UK).

1991-01-01

343

Reliability Evaluation and Failure Analysis for NTC Thermistor  

Science.gov (United States)

Failures of NTC thermistor are analyzed. Visual inspection, electrical parameter test, non-destructive test, and destructive physical analysis were performed on the field samples to identify the root cause of failure. It was found that the predominant failure mechanism was the copper migration of dumet (copper-clad alloy) at glass-PVC interface for glass-coated chip type NTC thermistor molded with PVC. Next, an accelerated life test is designed to predict the lifetime. Temperature, voltage, and humidity are considered as accelerating variables. Under the assumptions of a general life-stress relationship and Weibull lifetime distribution, the parameters of life-stress relationship and acceleration factor for the migration are estimated by analyzing the test data.

Jung, Joon Sik; Kim, Jin Woo; Kim, Myung Soo; Jang, Joong Soon; Ryu, Dong Su

344

A theoretical analysis of the reliability of PWR pressure vessels  

International Nuclear Information System (INIS)

In a recent paper a simplified analysis of the probability of failure of a population of reactor vessels by the unstable extension of pre-existing cracks and flaws was proposed. The analysis, which is based on the methods of linear elastic fracture mechanics explicitly incorporates various effects, including (1) pre-service pressure tests, (2) the incidence and size distribution of cracks existing in vessels as they enter service, (3) the dispersion in material toughness and (4) crack growth in service by fatigue and corrosion-fatigue. In the present paper the sensitivity of the calculated failure rates throughout the life of the vessel to changes in certain of the basic assumptions is further examined. In particular, the variations coming from changes in mean toughness at both operating temperature and during the pre-service cold-hydro test, and in crack shape and size distribution are examined. The influence of ultrasonic examination during fabrication is also assessed. The numerical calculations have been made principally in the context of the conditions governing the manufacture and operation of pressurized water reactors (P.W.R.). Failure rates decrease the more the toughness at the operating temperature exceeds that pertaining during the cold-hydro test, although they are relatively insensitive to the absolute value of the toughness at operating temperatures. Failure rates directly reflect changes in the crack-size distribution function. They are also notably sensitive to crack growth rates, although only when every crack is assumed to grow by corrosion fatigue under 'wet' conditions do the failure rates enter the range of meaningful values. Repeated overpressurization of the vessel during the operation of the reactor to an extent not greater than that of the cold-hydro test can increase the failure rates by about an order of magnitude. (author).

1978-05-18

345

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

Energy Technology Data Exchange (ETDEWEB)

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

Orvis, D.D.; Frank, M.V.; Jacobsen, F.K.; Clarke, W.M.

1981-04-01

346

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

International Nuclear Information System (INIS)

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

1983-01-01

347

Reliability of the jones patellofemoral osteoarthritis score for radiological assessment of patellofemoral degenerative changes: comparing a physiotherapist to doctors.  

UK PubMed Central (United Kingdom)

Purpose: Radiological measurement scores are used by orthopaedic physiotherapists in triage and surveillance of patients with degenerative changes of the tibiofemoral and patellofemoral joints. The purpose of this study was to estimate the intra- and inter-observer reliability of a radiological measurement score to assess patellofemoral joint osteoarthritis, the Jones Patellofemoral Osteoarthritis Score (JPOS), with an orthopaedic physiotherapist and three grades of junior surgeons/doctors. Methods: A total of 390 skyline X-rays of the patellofemoral joint were reviewed on 2 occasions, 4 weeks apart, by an orthopaedic physiotherapist, 2 orthopaedic surgeons, and an orthopaedic doctor. Intra- and inter-observer reliability of the JPOS was calculated using a weighted kappa analysis. Results: The results indicated that while there was good overall intra-observer agreement for this measurement score for all assessors, inter-observer reliability was generally poor between the orthopaedic physiotherapist and the orthopaedic surgeons/doctor. Conclusion: Our findings call into question the use of the JPOS by orthopaedic physiotherapists working in triage or orthopaedic surveillance programmes with other orthopaedic clinicians.

Smith TO; Kang SN; De Sprenger Rover WB; Walton NP

2012-01-01

348

Reliability of the Jones Patellofemoral Osteoarthritis Score for Radiological Assessment of Patellofemoral Degenerative Changes: Comparing a Physiotherapist to Doctors  

Science.gov (United States)

ABSTRACT Purpose: Radiological measurement scores are used by orthopaedic physiotherapists in triage and surveillance of patients with degenerative changes of the tibiofemoral and patellofemoral joints. The purpose of this study was to estimate the intra- and inter-observer reliability of a radiological measurement score to assess patellofemoral joint osteoarthritis, the Jones Patellofemoral Osteoarthritis Score (JPOS), with an orthopaedic physiotherapist and three grades of junior surgeons/doctors. Methods: A total of 390 skyline X-rays of the patellofemoral joint were reviewed on 2 occasions, 4 weeks apart, by an orthopaedic physiotherapist, 2 orthopaedic surgeons, and an orthopaedic doctor. Intra- and inter-observer reliability of the JPOS was calculated using a weighted kappa analysis. Results: The results indicated that while there was good overall intra-observer agreement for this measurement score for all assessors, inter-observer reliability was generally poor between the orthopaedic physiotherapist and the orthopaedic surgeons/doctor. Conclusion: Our findings call into question the use of the JPOS by orthopaedic physiotherapists working in triage or orthopaedic surveillance programmes with other orthopaedic clinicians.

Kang, S.-N.; De Sprenger Rover, W.B.; Walton, N.P.

2012-01-01

349

Highly comparative fetal heart rate analysis.  

UK PubMed Central (United Kingdom)

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

Fulcher BD; Georgieva AE; Redman CW; Jones NS

2012-01-01

350

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

UK PubMed Central (United Kingdom)

This study investigated the performance of the portable Cortex Metamax 3B (MM3B) automated gas analysis system during both simulated and human exercise using adolescents. Repeated measures using a Gas Exchange System Validator (GESV) across a range of simulated metabolic rates, showed the MM3B to be adequately reliable (both percentage errors, and percentage technical error of measurements <2%) for measuring expired ventilation (V (E)), oxygen consumption (VO(2)), and carbon dioxide production (VCO(2)). Over a 3 h period, the MM3B was shown to be acceptably stable in measuring gas fractions, as well as V (E), VO(2), and VCO(2) generated by the GESV, especially at moderate and high metabolic rates (drifts <2% and of minor physiological significance). Using eight healthy adolescents during rest, moderate, and vigorous cycle ergometry, the validity of the MM3B was tested against the primary criterion Douglas bag method (DBM) and a secondary criterion machine known to be accurate, the Jaeger Oxycon Pro system. No significant errors in V (E) were noted, yet the MM3B significantly overestimated both VO(2) and VCO(2) by approximately 10-17% at moderate and vigorous exercise as compared to the DBM and at all exercise levels compared to the Oxycon Pro. No significant differences were seen in any metabolic variable between the two criterion systems (DBM and Oxycon Pro). It is concluded the MM3B produces acceptably stable and reliable results, but is not adequately valid during moderate and vigorous exercise without some further correction of VO(2) and VCO(2).

Macfarlane DJ; Wong P

2012-07-01

351

Asymptotic Analysis of Highly Reliable Retrial Systems with Finite Capacity  

UK PubMed Central (United Kingdom)

: An exponential approximation for a time of the 1st loss of a call and the behaviourof a flow of lost calls for a Markov retrial state-dependent queueing system with finite capacity,operating in Markov environment and in conditions of "fast" service, is studied. The methodof proof is based on the results about asymptotic behaviour of the 1st exit time from a fixedsubset of a semi-Markov process forming an S-set.1 IntroductionRetrial queues is comparatively a new direction in queueing models. Over recent years manypublications appeared concerning with the developing of approximating methods and analysisof a steady-state behaviour for different classes of retrial queueing models (see reviews of Yangand Templeton (1987), Falin (1990) and Kulkarni and Liang (1997), papers of Artalejo (1995),Artalejo and Falin (1995,1996), and a book of Falin and Templeton (1997)). Due to complexityof retrial models exact analytic solutions can be obtained only for special rare cases. Therefor...

Vladimir V. Anisimov

352

Reliability and error analysis on xenon/CT CBF  

International Nuclear Information System (INIS)

This article provides a quantitative error analysis of a simulation model of xenon/CT CBF in order to investigate the behavior and effect of different types of errors such as CT noise, motion artifacts, lower percentage of xenon supply, lower tissue enhancements, etc. A mathematical model is built to simulate these errors. By adjusting the initial parameters of the simulation model, we can scale the Gaussian noise, control the percentage of xenon supply, and change the tissue enhancement with different kVp settings. The motion artifact will be treated separately by geometrically shifting the sequential CT images. The input function is chosen from an end-tidal xenon curve of a practical study. Four kinds of cerebral blood flow, 10, 20, 50, and 80 cc/100 g/min, are examined under different error environments and the corresponding CT images are generated following the currently popular timing protocol. The simulated studies will be fed to a regular xenon/CT CBF system for calculation and evaluation. A quantitative comparison is given to reveal the behavior and effect of individual error resources. Mixed error testing is also provided to inspect the combination effect of errors. The experiment shows that CT noise is still a major error resource. The motion artifact affects the CBF results more geometrically than quantitatively. Lower xenon supply has a lesser effect on the results, but will reduce the signal/noise ratio. The lower xenon enhancement will lower the flow values in all areas of brain. (author)

2000-01-01

353

Comparative analysis of microbial DNA labeling methods  

Energy Technology Data Exchange (ETDEWEB)

A comparative analysis was conducted on several methods of radio-labeling microbial DNA, both plasmid and chromosomal molecules, using E. coli, B. subtilis, RI drd 19 and pBR 322 DNA. DNA-DNA hybridization and thermal stability of the duplexes was used to monitor labeling efficiency. Comparison of in vivo, nick-translation, and enzymatic methylation methods demonstrated that the in vivo radiolabeling approach yielded preparations with the lowest specific radioactivity, whereas that of the latter two methods was generally comparable and up to an order of magnitude greater (e.g., 10{sup 4} vs. 10{sup 5} or 10{sup 6} cpm/{mu}g). An advantage of the enzymatic methylation method over the nick-translation approach was the greater stability of the hybrid duplexes, as well as the fact that the reagents used are less expensive. 9 refs., 1 fig.

Svetlichkin, V.V.; Lysenko, A.M.; Ignashov, V.G.; Petrov., N.B.

1985-10-01

354

Comparative analysis of three thermal fatigue experiments  

International Nuclear Information System (INIS)

This paper presents an analysis of the ability of different criteria to predict fatigue crack initiation under thermal loading. More precisely the predictions of the number of cycles to crack initiation are compared with experimental results obtained using five different fatigue criteria in three types of thermal fatigue tests (namely the FAT3D, JRC and SPLASH test campaigns). This analysis has revealed that: The conventional criteria based on equivalent strain variation substantially overestimate the lifespan of a structure subjected to thermal loading. A criterion making account for loading multi-axiality is required to estimate thermal fatigue life. Three of the criteria studied give satisfactory results: the Zamrik criterion, the Park and Nelson criterion and a criterion taking hydrostatic pressure into consideration proposed by Amiable et al. The latter should be preferred for the accuracy of its results and the Zamrik criterion for its simplicity. (authors)

2008-01-01

355

Computer image analysis of comparative genomic hybridization  

Energy Technology Data Exchange (ETDEWEB)

We describe and evaluate the image-processing and analysis techniques we have developed for the quantitative analysis of comparative genomic hybridization. In a typical CGH application, two genomic DNA samples are simultaneously hybridized to metaphase chromosomes and detected with different fluorochromes. The primary data in CGH are contained in the intensity ratios of the fluorochromes as a function of position on the chromosomes, which reflect variation in DNA copy number ratio between the two DNA samples. Analysis involves chromosome segmentation, intensity normalization, background corrections, and calculation of the fluorescence intensity profiles and the ratio profile along the chromosome`s length. Profiles from several copies of the same chromosome in different metaphases are averaged to reduce the noise. Confidence intervals are calculated and displayed for the mean profiles. The techniques were evaluated by examining the variability found in comparisons of two normal genomic DNAs, where the ratio was expected to be constant, and by measuring the ratios obtained for cell lines with cytogenetically documented copy number changes involving several chromosomal segments. The limits of sensitivity of CGH analysis were investigated by simulation. Guidelines for the interpretation of CGH data and indications of areas for future development of the analytical techniques are also presented. 15 refs., 11 figs., 2 tabs.

Piper, J.; Sudar, D.; Pinkel, D. [Lawrence Berkeley Lab., CA (United States)] [and others

1995-01-01

356

Computer image analysis of comparative genomic hybridization.  

UK PubMed Central (United Kingdom)

We describe and evaluate the image-processing and analysis techniques we have developed for the quantitative analysis of comparative genomic hybridization (CGH; Science 258:818, 1992). In a typical CGH application, two genomic DNA samples are simultaneously hybridized to metaphase chromosomes and detected with different fluorochromes. The primary data in CGH are contained in the intensity ratios of the fluorochromes as a function of position on the chromosomes, which reflect variation in DNA copy number ratio between the two DNA samples. Analysis involves chromosome segmentation, intensity normalization, background corrections, and calculation of the fluorescence intensity profiles and the ratio profile along the chromosome's length. Profiles from several copies of the same chromosome in different metaphases are averaged to reduce the noise. Confidence intervals are calculated and displayed for the mean profiles. The techniques were evaluated by examining the variability found in comparisons of two normal genomic DNAs, where the ratio was expected to be constant, and by measuring the ratios obtained for cell lines with cytogenetically documented copy number changes involving several chromosomal segments. The limits of sensitivity of CGH analysis were investigated by simulation. Guidelines for the interpretation of CGH data and indications of areas for future development of the analytical techniques are also presented.

Piper J; Rutovitz D; Sudar D; Kallioniemi A; Kallioniemi OP; Waldman FM; Gray JW; Pinkel D

1995-01-01

357

Reliability Analysis of Safety Grade PLC(POSAFE-Q) for Nuclear Power Plants  

International Nuclear Information System (INIS)

[en] The Part Count Method of the military standard MILHDK- 217F has been used for the reliability prediction of the nuclear field. This handbook determines the Programmable Logic Controller (PLC) failure rate by summing the failure rates of the individual component included in the PLC. Normally it is easily predictable that the components added for the fault detection improve the reliability of the PLC. But the application of this handbook is estimated with poor reliability because of the increased component number for the fault detection. To compensate this discrepancy, the quantitative reliability analysis method is suggested using the functional separation model in this paper. And it is applied to the Reactor Protection System (RPS) being developed in Korea to identify any design weak points from a safety point of view

2006-01-01

358

Reliability Analysis of Safety Grade PLC(POSAFE-Q) for Nuclear Power Plants  

Energy Technology Data Exchange (ETDEWEB)

The Part Count Method of the military standard MILHDK- 217F has been used for the reliability prediction of the nuclear field. This handbook determines the Programmable Logic Controller (PLC) failure rate by summing the failure rates of the individual component included in the PLC. Normally it is easily predictable that the components added for the fault detection improve the reliability of the PLC. But the application of this handbook is estimated with poor reliability because of the increased component number for the fault detection. To compensate this discrepancy, the quantitative reliability analysis method is suggested using the functional separation model in this paper. And it is applied to the Reactor Protection System (RPS) being developed in Korea to identify any design weak points from a safety point of view.

Kim, J. Y.; Lyou, J. [Chungnam National University, Taejon (Korea, Republic of); Lee, D. Y.; Choi, J. G.; Park, W. M. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

2006-07-01

359

Reliability and sensitivity analysis for different photovoltaic remote area systems (Part One)  

Energy Technology Data Exchange (ETDEWEB)

Basic concepts of reliability of performance with respect to different remote area photovoltaic systems (PVRAS) are discussed. Characteristic equations of different PVRAS such as photovoltaic battery stand-alone system, photovoltaic battery-diesel generator hybrid system and diesel-battery hybrid systems are deduced as a function of operating hours and sun-availability hours per day, based on fault tree analysis technique for systems hardware reliability. Results of the study indicate that operating hours are a more significant factor in reliability than sun-hours availability for all three systems. Nevertheless, the photovoltaic battery-diesel hybrid system is the most reliable among the three alternatives studied. 7 refs., 1 tab., 4 figs.

Zahran, M.; El-Hefnawi, S. [National Research Center, Electronics Research Inst., Giza (Egypt); Hanafy, A.; Mahgoub, O. [Cairo Univ., Faculty of Engineering, Giza (Egypt); Kamel, M. [Benha Higher Inst. of Technology, Benha (Egypt)

1999-11-01

360

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

DEFF Research Database (Denmark)

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

Kamyod, Chayapol; Nielsen, Rasmus Hjorth

2012-01-01

 
 
 
 
361

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

Energy Technology Data Exchange (ETDEWEB)

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)

Lu, L. [School of Energy Systems and Nuclear Science, Univ. of Ontario, Inst. of Technology, 2000 Simcoe Street N., Oshawa, Ont. L1H 7K4 (Canada)

2006-07-01

362

Comparative Analysis of Visco-elastic Models with Variable Parameters  

Directory of Open Access Journals (Sweden)

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

Silviu Nastac; Adrian Leopa

2010-01-01

363

A comparative study of computed radiographic cephalometry and conventional cephalometry in reliability of head film measurements  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study was to compare and to find out the variability of head film measurements (landmarks identification) between Fuji computed radiographic cephalometry and conventional cephalometry. 28 Korean adults were selected. Lateral cephalometric FCR film and conventional cephalometric film of each subject was taken. Four investigators identified 24 cephalometric landmarks on lateral cephalometric FCR film and conventional cephalometric film were statistically analysed. The results were as follows : 1. In FCR film and conventional film, coefficient of variation (C.V.) of 24 landmarks was taken horizontally and vertically. 2. In comparison of significant differences of landmarks variability between FCR film and conventional film, horizontal l value of coefficient of variation showed significant differences in four landmarks among twenty-four landmarks, but vertical a value of coefficient of variation showed significant differences in sixteen landmarks among twenty-four landmarks. FCR film showed significantly less variability than conventional film in 17 subjects among 20 (4+16) subjects that sho wed significant difference.

Kim, Hyung Done; Kim, Kee Deog; Park, Chang Seo [Dept. of Dental Radiology, College of Dentistry, Yensei University, Seoul(Korea, Republic of)

1997-02-15

364

A comparative study of computed radiographic cephalometry and conventional cephalometry in reliability of head film measurements  

International Nuclear Information System (INIS)

The purpose of this study was to compare and to find out the variability of head film measurements (landmarks identification) between Fuji computed radiographic cephalometry and conventional cephalometry. 28 Korean adults were selected. Lateral cephalometric FCR film and conventional cephalometric film of each subject was taken. Four investigators identified 24 cephalometric landmarks on lateral cephalometric FCR film and conventional cephalometric film were statistically analysed. The results were as follows : 1. In FCR film and conventional film, coefficient of variation (C.V.) of 24 landmarks was taken horizontally and vertically. 2. In comparison of significant differences of landmarks variability between FCR film and conventional film, horizontal l value of coefficient of variation showed significant differences in four landmarks among twenty-four landmarks, but vertical a value of coefficient of variation showed significant differences in sixteen landmarks among twenty-four landmarks. FCR film showed significantly less variability than conventional film in 17 subjects among 20 (4+16) subjects that sho wed significant difference.

1997-01-01

365

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

Energy Technology Data Exchange (ETDEWEB)

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

Wang, Xiaozhi

1995-05-01

366

Development of a Computerized Number Sense Scale for 3-rd Graders: Reliability and Validity Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available This study was to develop a computerized number sense scale (CNST) to assess the performance of students who had already completed the 3rd-grade mathematics curriculum. In total, 808 students from representative elementary schools, including cities, country and rural areas of Taiwan, participated in this study. The results of statistical analyses and content analysis indicated that this computerized number sense scale demonstrates good reliability and validity. Cronbach’s ? coefficient of the scale was .8526 and its construct reliability was .805. In addition, the 5-factor number sense model was empirically and theoretically supported via confirmatory factor analysis and literature review.

Der-Ching Yang; Mao-neng Fred Li; Wei-Jin Li

2008-01-01

367

Economic and reliability analysis for the technological renewal of gas networks  

International Nuclear Information System (INIS)

The effort made by Gas Distribution Companies to improve the quality of services rendered to its customers has resulted in their commitment to carry out feasibility studies, aiming at assessing both economic conditions and reliability of technical renewal programmes concerning gas networks. In this article are described: a) an analysis procedure on economic conditions and reliability, in order to detect and classify 'areas' where interventions take priority; b) the results of analyses carried out on a network prototype described and operated by a local computing system. In the above mentioned analysis reference was made both to test results and criteria currently adopted by international Companies with a long experience in a gas distribution.

1996-01-01

368

Integration of functional reliability analysis with hardware reliability: An application to safety grade decay heat removal system of Indian 500 MWe PFBR  

Energy Technology Data Exchange (ETDEWEB)

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.

Mathews, T. Sajith [AERB-Safety Research Institute, Kalpakkam 603 102, Tamilnadu (India)], E-mail: sajithmat@yahoo.com; Arul, A. John; Parthasarathy, U. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Kumar, C. Senthil [AERB-Safety Research Institute, Kalpakkam 603 102, Tamilnadu (India); Ramakrishnan, M. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Subbaiah, K.V. [AERB-Safety Research Institute, Kalpakkam 603 102, Tamilnadu (India)

2009-05-01

369

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

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of research described in the current study is the psychological reliability, its’ importance, application, and more to investigate on the impact analysis of psychological reliability of population pilot study for selection of particular reliable multi-choice item test in foreign language research work. The population for subject recruitment was all under graduated students from second semester at large university in Iran (both male and female) that study English as a compulsory paper. In Iran, English is taught as a foreign language.

Seyed Hossein Fazeli

2010-01-01

370

Living PRAs (probabilistic risk analysis) made easier with IRRAS (Integrated Reliability and Risk Analysis System)  

Energy Technology Data Exchange (ETDEWEB)

The Integrated Reliability and Risk Analysis System (IRRAS) is an integrated PRA software tool that gives the user the ability to create and analyze fault trees and accident sequences using an IBM-compatible microcomputer. This program provides functions that range from graphical fault tree and event tree construction to cut set generation and quantification. IRRAS contains all the capabilities and functions required to create, modify, reduce, and analyze event tree and fault tree models used in the analysis of complex systems and processes. IRRAS uses advanced graphic and analytical techniques to achieve the greatest possible realization of the potential of the microcomputer. When the needs of the user exceed this potential, IRRAS can call upon the power of the mainframe computer. The role of the Idaho National Engineering Laboratory if the IRRAS program is that of software developer and interface to the user community. Version 1.0 of the IRRAS program was released in February 1987 to prove the concept of performing this kind of analysis on microcomputers. This version contained many of the basic features needed for fault tree analysis and was received very well by the PRA community. Since the release of Version 1.0, many user comments and enhancements have been incorporated into the program providing a much more powerful and user-friendly system. This version is designated IRRAS 2.0''. Version 3.0 will contain all of the features required for efficient event tree and fault tree construction and analysis. 5 refs., 26 figs.

Russell, K.D.; Sattison, M.B. (EG and G Idaho, Inc., Idaho Falls, ID (USA)); Rasmuson, D.M. (Nuclear Regulatory Commission, Washington, DC (USA). Div. of Systems Research)

1989-01-01

371

Reliability and mass analysis of lunar-based reactor/stirling cycle power plants  

International Nuclear Information System (INIS)

The purpose of this analysis was to determine the mass and reliability characteristics of nuclear reactor/Stirling cycle power plant configurations that could provide 800 kW of electricity for a proposed National Aeronautics and Space Administration (NASA) lunar surface base. The specific goal of the work was to define and characterize minimum mass power plant configurations that could provide an acceptable system reliability risk. A generic power plant design concept that exhibited potential construction feasibility and met human-rated radiation dose criteria was developed to serve as the basis for the power plant configurations assessed in this study. A combinatorial reliability analysis model based on parallel, redundant, series, and r-out-of-n system and component configurations was used to improve system reliability to an acceptable risk level. As a result of this study, an increased awareness of the importance of reliability analyses on high-capacity space power system design configurations has evolved, and future NASA mission application studies requiring high power levels for electric propulsion and orbital or planetary surface operations will benefit from this type of analysis.

1989-01-01

372

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-06-01

373

A multi-point univariate decomposition method for structural reliability analysis  

International Nuclear Information System (INIS)

A new multi-point univariate decomposition method is presented for structural reliability analysis involving multiple most probable points (MPPs). The method involves a novel function decomposition at all MPPs that facilitates local univariate approximations of a performance function in the rotated Gaussian space, Lagrange interpolation for univariate component functions and return mapping to the standard Gaussian space, and Monte Carlo simulation. In addition to the effort in identifying all MPPs, the computational effort in the multi-point univariate method can be viewed as performing deterministic response analysis at user-selected input defined by sample points. Compared with the existing multi-point FORM/SORM, the multi-point univariate method developed provides a higher-order approximation of the boundary of the failure domain. Both the point-fitted SORM and the univariate method entail linearly varying cost with respect to the number of variables. However, the univariate method with less than nine sample points requires fewer calculations of the performance function than the point-fitted SORM. Numerical results indicate that the proposed method consistently generates an accurate and computationally efficient estimate of the probability of failure.

2010-01-01

374

A multi-point univariate decomposition method for structural reliability analysis  

Energy Technology Data Exchange (ETDEWEB)

A new multi-point univariate decomposition method is presented for structural reliability analysis involving multiple most probable points (MPPs). The method involves a novel function decomposition at all MPPs that facilitates local univariate approximations of a performance function in the rotated Gaussian space, Lagrange interpolation for univariate component functions and return mapping to the standard Gaussian space, and Monte Carlo simulation. In addition to the effort in identifying all MPPs, the computational effort in the multi-point univariate method can be viewed as performing deterministic response analysis at user-selected input defined by sample points. Compared with the existing multi-point FORM/SORM, the multi-point univariate method developed provides a higher-order approximation of the boundary of the failure domain. Both the point-fitted SORM and the univariate method entail linearly varying cost with respect to the number of variables. However, the univariate method with less than nine sample points requires fewer calculations of the performance function than the point-fitted SORM. Numerical results indicate that the proposed method consistently generates an accurate and computationally efficient estimate of the probability of failure.

Wei, D. [Caterpillar Technical Center, Mossville, IL 61552 (United States); Rahman, S., E-mail: rahman@engineering.uiowa.ed [Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242 (United States)

2010-05-15

375

Reliable evaluation of the quantal determinants of synaptic efficacy using Bayesian analysis.  

UK PubMed Central (United Kingdom)

Communication between neurones in the central nervous system depends on synaptic transmission. The efficacy of synapses is determined by pre- and postsynaptic factors that can be characterized using quantal parameters such as the probability of neurotransmitter release, number of release sites, and quantal size. Existing methods of estimating the quantal parameters based on multiple probability fluctuation analysis (MPFA) are limited by their requirement for long recordings to acquire substantial data sets. We therefore devised an algorithm, termed Bayesian Quantal Analysis (BQA), that can yield accurate estimates of the quantal parameters from data sets of as small a size as 60 observations for each of only 2 conditions of release probability. Computer simulations are used to compare its performance in accuracy with that of MPFA, while varying the number of observations and the simulated range in release probability. We challenge BQA with realistic complexities characteristic of complex synapses, such as increases in the intra- or intersite variances, and heterogeneity in release probabilities. Finally, we validate the method using experimental data obtained from electrophysiological recordings to show that the effect of an antagonist on postsynaptic receptors is correctly characterized by BQA by a specific reduction in the estimates of quantal size. Since BQA routinely yields reliable estimates of the quantal parameters from small data sets, it is ideally suited to identify the locus of synaptic plasticity for experiments in which repeated manipulations of the recording environment are unfeasible.

Bhumbra GS; Beato M

2013-01-01

376

Reliable evaluation of the quantal determinants of synaptic efficacy using Bayesian analysis.  

Science.gov (United States)

Communication between neurones in the central nervous system depends on synaptic transmission. The efficacy of synapses is determined by pre- and postsynaptic factors that can be characterized using quantal parameters such as the probability of neurotransmitter release, number of release sites, and quantal size. Existing methods of estimating the quantal parameters based on multiple probability fluctuation analysis (MPFA) are limited by their requirement for long recordings to acquire substantial data sets. We therefore devised an algorithm, termed Bayesian Quantal Analysis (BQA), that can yield accurate estimates of the quantal parameters from data sets of as small a size as 60 observations for each of only 2 conditions of release probability. Computer simulations are used to compare its performance in accuracy with that of MPFA, while varying the number of observations and the simulated range in release probability. We challenge BQA with realistic complexities characteristic of complex synapses, such as increases in the intra- or intersite variances, and heterogeneity in release probabilities. Finally, we validate the method using experimental data obtained from electrophysiological recordings to show that the effect of an antagonist on postsynaptic receptors is correctly characterized by BQA by a specific reduction in the estimates of quantal size. Since BQA routinely yields reliable estimates of the quantal parameters from small data sets, it is ideally suited to identify the locus of synaptic plasticity for experiments in which repeated manipulations of the recording environment are unfeasible. PMID:23076101

Bhumbra, G S; Beato, M

2012-10-17

377

Condition-based fault tree analysis (CBFTA): A new method for improved fault tree analysis (FTA), reliability and safety calculations  

International Nuclear Information System (INIS)

Condition-based maintenance methods have changed systems reliability in general and individual systems in particular. Yet, this change does not affect system reliability analysis. System fault tree analysis (FTA) is performed during the design phase. It uses components failure rates derived from available sources as handbooks, etc. Condition-based fault tree analysis (CBFTA) starts with the known FTA. Condition monitoring (CM) methods applied to systems (e.g. vibration analysis, oil analysis, electric current analysis, bearing CM, electric motor CM, and so forth) are used to determine updated failure rate values of sensitive components. The CBFTA method accepts updated failure rates and applies them to the FTA. The CBFTA recalculates periodically the top event (TE) failure rate (? TE) thus determining the probability of system failure and the probability of successful system operation-i.e. the system's reliability. FTA is a tool for enhancing system reliability during the design stages. But, it has disadvantages, mainly it does not relate to a specific system undergoing maintenance. CBFTA is tool for updating reliability values of a specific system and for calculating the residual life according to the system's monitored conditions. Using CBFTA, the original FTA is ameliorated to a practical tool for use during the system's field life phase, not just during system design phase. This paper describes the CBFTA method and its advantages are demonstrated by an example.

2007-01-01

378

Condition-based fault tree analysis (CBFTA): A new method for improved fault tree analysis (FTA), reliability and safety calculations  

Energy Technology Data Exchange (ETDEWEB)

Condition-based maintenance methods have changed systems reliability in general and individual systems in particular. Yet, this change does not affect system reliability analysis. System fault tree analysis (FTA) is performed during the design phase. It uses components failure rates derived from available sources as handbooks, etc. Condition-based fault tree analysis (CBFTA) starts with the known FTA. Condition monitoring (CM) methods applied to systems (e.g. vibration analysis, oil analysis, electric current analysis, bearing CM, electric motor CM, and so forth) are used to determine updated failure rate values of sensitive components. The CBFTA method accepts updated failure rates and applies them to the FTA. The CBFTA recalculates periodically the top event (TE) failure rate ({lambda} {sub TE}) thus determining the probability of system failure and the probability of successful system operation-i.e. the system's reliability. FTA is a tool for enhancing system reliability during the design stages. But, it has disadvantages, mainly it does not relate to a specific system undergoing maintenance. CBFTA is tool for updating reliability values of a specific system and for calculating the residual life according to the system's monitored conditions. Using CBFTA, the original FTA is ameliorated to a practical tool for use during the system's field life phase, not just during system design phase. This paper describes the CBFTA method and its advantages are demonstrated by an example.

Shalev, Dan M. [Unit for Management and Safety Engineering, Department of Industrial Engineering and Management, Ben-Gurion University (BGU) of the Negev, Beer Sheva (Israel); Israel Atomic Energy Commission, Nuclear Research Center Negev (NRCN) (Israel); Tiran, Joseph [Department of Mechanical Engineering, BGU of the Negev (Israel) and Pearlstone Center for Aeronautical Engineering Studies, BGU of the Negev (Israel)]. E-mail: tiran@bgu.ac.il

2007-09-15

379

Reliability assessment of generation and transmission systems using fault-tree analysis  

International Nuclear Information System (INIS)

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.

2009-01-01

380

Methodological Issues in the Content Analysis of Online Asynchronous Discussions: Unitizing, Reliability, and Latent Content  

Directory of Open Access Journals (Sweden)

Full Text Available This paper explores three methodological issues related to content analysis of online asynchronous discussions: unitizing, reliability, and manifest versus latent content. Unitizing involves balancing feasibility, reliability, identifiability, and discriminant capability of semantic versus syntactic units. Reliability is discussed in relation to differences between tasks, discussants, and number of coding decisions, as well as between coders. Manifest versus latent content contrasts observed versus intended behaviors in content analysis. For each of the three issues, the paper presents a brief theoretical overview. Each issue is subsequently contextualized and illustrated using empirical results. Finally, for each issue, the paper provides a discussion of lessons learned and implications. The paper concludes with suggestions for future studies.

Elizabeth Murphy; Justyna Ciszewska-Carr; Maria A Rodriguez Manzanares

2006-01-01

 
 
 
 
381

Operation safety of complex industrial systems. Forward-looking analysis and reliability databases  

International Nuclear Information System (INIS)

The forward-looking analysis of systems failure consists in identifying the conditions that may lead to failures and to foresee their consequences on the reliability, maintainability, availability and safety of systems at the design stage or at the operation stage. It is performed from various information, the selection and analysis of which allows to design a system model. The essential information is: a description of the real system (physical and functional structures), the characteristics of the system components and of the interactions between them (failure modes and their consequences), the relations between the system and its environment, and the consideration of human errors at the exploitation step. Content: 1 - steps of an operation safety analysis; 2 - functional analysis methods: FAST, RELIASEP, SADT, IDEFO, APTE and other methods; 3 - Forward-looking analysis methods: qualitative methods, mixed and quantitative methods, human factors; 4 - reliability databases. (J.S.)

2009-01-01

382

Blowfish Encryption: A Comparative Analysis using VHDL  

Directory of Open Access Journals (Sweden)

Full Text Available Data security has always been important in all aspects of life. Data may contain several form of information that we want to secure from any unauthorized access. It can be all the more important as technology continues to control various operations in our day to day life Reprogrammable devices are highly attractive options for hardware implementations of encryption algorithms as they provide cryptographic algorithm agility, physical security, and potentially much higher performance, therefore this paper investigates a hardware design to efficiently implement a special type block ciphers in VHDL and its comparative analysis in different parameter variation . This hardware design is applied to the new secret and variable size key block cipher called Blowfish designed to meet the requirements of the previous known standard and to increase security and to improve performance. The proposed algorithm will be used a variable key size.

Deepak Kumar Dakate; Pawan Dubey

2012-01-01

383

Reliability assessment of different plate theories for elastic wave propagation analysis in functionally graded plates.  

Science.gov (United States)

The importance of elastic wave propagation problem in plates arises from the application of ultrasonic elastic waves in non-destructive evaluation of plate-like structures. However, precise study and analysis of acoustic guided waves especially in non-homogeneous waveguides such as functionally graded plates are so complicated that exact elastodynamic methods are rarely employed in practical applications. Thus, the simple approximate plate theories have attracted much interest for the calculation of wave fields in FGM plates. Therefore, in the current research, the classical plate theory (CPT), first-order shear deformation theory (FSDT) and third-order shear deformation theory (TSDT) are used to obtain the transient responses of flexural waves in FGM plates subjected to transverse impulsive loadings. Moreover, comparing the results with those based on a well recognized hybrid numerical method (HNM), we examine the accuracy of the plate theories for several plates of various thicknesses under excitations of different frequencies. The material properties of the plate are assumed to vary across the plate thickness according to a simple power-law distribution in terms of volume fractions of constituents. In all analyses, spatial Fourier transform together with modal analysis are applied to compute displacement responses of the plates. A comparison of the results demonstrates the reliability ranges of the approximate plate theories for elastic wave propagation analysis in FGM plates. Furthermore, based on various examples, it is shown that whenever the plate theories are used within the appropriate ranges of plate thickness and frequency content, solution process in wave number-time domain based on modal analysis approach is not only sufficient but also efficient for finding the transient waveforms in FGM plates. PMID:23714123

Mehrkash, Milad; Azhari, Mojtaba; Mirdamadi, Hamid Reza

2013-05-09

384

Reliability assessment of different plate theories for elastic wave propagation analysis in functionally graded plates.  

UK PubMed Central (United Kingdom)

The importance of elastic wave propagation problem in plates arises from the application of ultrasonic elastic waves in non-destructive evaluation of plate-like structures. However, precise study and analysis of acoustic guided waves especially in non-homogeneous waveguides such as functionally graded plates are so complicated that exact elastodynamic methods are rarely employed in practical applications. Thus, the simple approximate plate theories have attracted much interest for the calculation of wave fields in FGM plates. Therefore, in the current research, the classical plate theory (CPT), first-order shear deformation theory (FSDT) and third-order shear deformation theory (TSDT) are used to obtain the transient responses of flexural waves in FGM plates subjected to transverse impulsive loadings. Moreover, comparing the results with those based on a well recognized hybrid numerical method (HNM), we examine the accuracy of the plate theories for several plates of various thicknesses under excitations of different frequencies. The material properties of the plate are assumed to vary across the plate thickness according to a simple power-law distribution in terms of volume fractions of constituents. In all analyses, spatial Fourier transform together with modal analysis are applied to compute displacement responses of the plates. A comparison of the results demonstrates the reliability ranges of the approximate plate theories for elastic wave propagation analysis in FGM plates. Furthermore, based on various examples, it is shown that whenever the plate theories are used within the appropriate ranges of plate thickness and frequency content, solution process in wave number-time domain based on modal analysis approach is not only sufficient but also efficient for finding the transient waveforms in FGM plates.

Mehrkash M; Azhari M; Mirdamadi HR

2014-01-01

385

Session 6: quantification of human error in LP/HC risk analysis. An overview of human-reliability analysis  

International Nuclear Information System (INIS)

[en] Human reliability analysis (HRA) is the general term to describe the quantification of human error and its effects on system reliability and safety. The three major papers that are reviewed provide information on three important aspects of HRA. The first paper, by Bell, deals with applications. Hall's paper discusses two sources of data for HRA. Meister's paper reviews some HRA methods which have been published for some time

1982-06-16

386

Guidelines for reliability analysis of digital systems in PSA context. Phase 1 status report  

International Nuclear Information System (INIS)

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)

2010-01-01

387

Guidelines for reliability analysis of digital systems in PSA context. Phase 1 status report  

Energy Technology Data Exchange (ETDEWEB)

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)

Authen, S.; Larsson, J. (Risk Pilot AB, Stockholm (Sweden)); Bjoerkman, K.; Holmberg, J.-E. (VTT, Helsingfors (Finland))

2010-12-15

388

Comparative Analysis of Competitive Strategy Implementation  

Directory of Open Access Journals (Sweden)

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

Maina A. S. Waweru

2011-01-01

389

Comparative analysis of selected fuel cell vehicles  

Energy Technology Data Exchange (ETDEWEB)

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

NONE

1993-05-07

390

COMPARATIVE ANALYSIS OF PTERYGIUM CLINICAL CHARACTERISTICS  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the research was to investigate the mutual relatedness of the clinical characteristics of pterygium (duration of the disease, size, grade, presence of Fuchs' patches and recurrence) and to point to the possibility of predicting the recurrence.For the purpose of research, a group of 55 patients with pterygium was recruited. The patients were operated using the technique by Arlt at the Ophthalmology Clinic in Nis, where a complete clinical examination was also performed. Anamnestic data were collected preoperatively. The size of external scum was measured with a millimeter scale ruler and Tan's biomicroscopic method was used to verify the grade. In order to observe the complications and recurrence, all patients were monitored postoperatively for one year.Pterygium represents a slow-growing formation which is confirmed by a high statistical significance (p < 0.001) of a correlation between its size and duration of development. Along with the growth of pterygium, its grade also increases. The reported difference in size between the two farthest grades – I and III has statistical significance (p < 0.001). Statistically, Fuchs' patches are more often present (p < 0.05) in larger pterygia. Compared to other factors, the presence of Fuchs' patches in pterygia increases the relative risk of recurrence by 6.62 times.A comparative analysis of clinical characteristics of pterygium is a good basis for predicting the recurrence, which represents the greatest problem in the treatment of this widespread disease.

Boban Dzunic; Predrag Jovanovic; Aleksandar Petrovic

2009-01-01