Дисертації з теми "Reliability of model"
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1
Young, Robert Benjamin. "Reliability Transform Method." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/33824.
Повний текст джерелаАнотація:
Since the end of the cold war the United States is the single dominant naval power in the world. The emphasis of the last decade has been to reduce cost while maintaining this status. As the Navyâ s infrastructure decreases, so too does its ability to be an active participant in all aspects of ship operations and design. One way that the navy has achieved large savings is by using the Military Sealift Command to manage day to day operations of the Navyâ s auxiliary and underway replenishment ships. While these ships are an active part of the Navyâ s fighting force, they infrequently are put into harmâ s way. The natural progression in the design of these ships is to have them fully classified under current American Bureau of Shipping (ABS) rules, as they closely resemble commercial ships. The first new design to be fully classed under ABS is the T-AKE. The Navy and ABS consider the T-AKE program a trial to determine if a partnership between the two organizations can extend into the classification of all new naval ships. A major difficulty in this venture is how to translate the knowledge base which led to the development of current military specifications into rules that ABS can use for future ships.
The specific task required by the Navy in this project is to predict the inherent availability of the new T-AKE class ship. To accomplish this task, the reliability of T-AKE equipment and machinery must be known. Under normal conditions reliability data would be obtained from past ships with similar mission, equipment and machinery. Due to the unique nature of the T-AKE acquisition, this is not possible. Because of the use of commercial off the shelf (COTS) equipment and machinery, military equipment and machinery reliability data can not be used directly to predict T-AKE availability. This problem is compounded by the fact that existing COTS equipment and machinery reliability data developed in commercial applications may not be applicable to a military application. A method for deriving reliability data for commercial equipment and machinery adapted or used in military applications is required.
A Reliability Transform Method is developed that allows the interpolation of reliability data between commercial equipment and machinery operating in a commercial environment, commercial equipment and machinery operating in a military environment, and military equipment and machinery operating in a military environment. The reliability data for T-AKE is created using this Reliability Transform Method and the commercial reliability data. The reliability data is then used to calculate the inherent availability of T-AKE.Master of Science
2
Williamson, Jamie D. "Reliability of the Brief Assessment Model." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1101994832.
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3
Wan, Bo. "Improved Usage Model for Web Application Reliability Testing." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23135.
Повний текст джерелаАнотація:
Testing the reliability of an application usually requires a good usage model that accurately captures the likely sequences of inputs that the application will receive from the environment. The models being used in the literature are mostly based on Markov chains. They are used to generate test cases that are statistically close to what the applica-tion is expected to receive when in production. In this thesis, we propose a model for reli-ability testing that is created directly from the log file of a web application. Our proposed model is also based on Markov chains and has two components: one component, based on a modified tree, captures the most frequent behaviors, while the other component is another Markov chain that captures infrequent behaviors. The result is a statistically cor-rect model that shows clearly what most users do on the site.
The thesis also presents an evaluation method for estimating the accuracy of vari-ous reliability-testing usage models. The method is based on comparison between ob-served users’ traces and traces inferred from the usage model. Our method gauges the accuracy of the reliability-testing usage model by calculating the sum of goodness-of-fit values of each traces and scaling the result between 0 and 1. Finally, we present an experimental study on the log of a real web site and discuss the way to use proposed usage model to generate test sequences, as well as strength and weakness of the model for reliability testing.
4
Stockwell, Kathryn S. "Automatic phased mission system reliability model generation." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13583.
Повний текст джерелаАнотація:
There are many methods for modelling the reliability of systems based on component failure data. This task becomes more complex as systems increase in size, or undertake missions that comprise multiple discrete modes of operation, or phases. Existing techniques require certain levels of expertise in the model generation and calculation processes, meaning that risk and reliability assessments of systems can often be expensive and time-consuming. This is exacerbated as system complexity increases. This thesis presents a novel method which generates reliability models for phasedmission systems, based on Petri nets, from simple input files. The process has been automated with a piece of software designed for engineers with little or no experience in the field of risk and reliability. The software can generate models for both repairable and non-repairable systems, allowing redundant components and maintenance cycles to be included in the model. Further, the software includes a simulator for the generated models. This allows a user with simple input files to perform automatic model generation and simulation with a single piece of software, yielding detailed failure data on components, phases, missions and the overall system. A system can also be simulated across multiple consecutive missions. To assess performance, the software is compared with an analytical approach and found to match within 5% in both the repairable and non-repairable cases. The software documented in this thesis could serve as an aid to engineers designing new systems to validate the reliability of the system. This would not require specialist consultants or additional software, ensuring that the analysis provides results in a timely and cost-effective manner.
5
Kallan, Michael A. "Characterizing reliability for a Faculty Climate Survey: Estimation model dependencies and reliability generalization." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280288.
Повний текст джерелаАнотація:
Methods. Four reliability estimation models were employed to obtain estimates for faculty appointment and gender group measures derived from four questionnaire scales of a Faculty Climate Survey. Faculty responses were analyzed via (a) coefficient alpha, (b) IRT-Rasch, (c) IRT-Unfolding, and (d) CFA methods. Estimates and their components were compared across-groups within scale and within-group across scales to determine differences among estimation models and to uniquely characterize those differences. Scale dimensionality was assessed per-scale per-group using CFA. Secondary analyses included: (a) independent and dependent-group tests to determine the statistical significance of coefficient alpha differences; (b) bootstrapping simulation to determine the effect of sample size on estimates; and (c) analysis of variance to determine whether attitudinal differences existed between appointment, gender, or appointment-by-gender groups. Results. (1) Reliability estimation models identified important differences between appointment and gender group estimates for scale measures and among scale estimates for each group's set of scale measures. (2) Models were not equally sensitive to detecting differences, either between groups or among scales per group. (3) Alpha and CFA estimates did not always function as lower- and upper-bounds of an expected estimate range: 30% of alpha-CFA range "endpoints" were underestimates of observed ranges. (4) IRT-based estimates were generally located between alpha and CFA estimates, closer to alpha than to CFA estimates. (5) IRT-Unfolding estimates were frequently but not always greater than IRT-Rasch estimates: 30% were less. (6) Alpha and CFA estimation components did not provide comparable item-level information; thus, alpha and CFA plans for characterizing and improving scales differed. (7) IRT-Rasch and IRT-Unfolding estimation components did not provide comparable person-measure information, thereby informing observed differences in IRT-based estimates. (8) Sample size had an effect on CFA estimation: samples of N = 50 achieved highest estimates; samples of N = 500 best reproduced original estimates and components. (9) Modeling error via CFA made meaningful contributions to understanding scale functioning. (10) ANOVA findings were potentially modifiable (e.g., effect sizes), considering obtained reliability estimates. Conclusion. Reliability estimates have group, measure, and model-dependencies that influence the size and nature of obtained estimates and must be accounted for when estimates are interpreted.
6
Askvid, Per. "A Model-Based Approach for Reliability Prediction." Thesis, Linköping University, Department of Computer and Information Science, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54323.
Повний текст джерелаАнотація:
When developing products, reliability is an important factor that has to be considered. For safety critical systems it is important to know the probability that an item will perform a required function without failure under stated conditions for a stated period of time. The main goal of a reliability prediction analysis is to predict the rate at which the product of a system will fail. To perform this prediction there are a number of methodologies available.
This Master Thesis proposes a model-based approach for reliability prediction calculations based on the physics of failure and supported by analysis of test-data field returns and physical models provided by the FIDES methodology. FIDES based reliability models have been integrated into a model-based diagnosis environment for seamless integration with other safety assessment analysis.
The model-based diagnosis environment used in this thesis is model-based reasoner RODON developed by Uptime Solutions AB. Components that uses the FIDES methodology have been developed in RODON, where components can be combined to systems by drag and drop method. Usage profiles that are defined according to the FIDES methodology in RODON are not system specific, which makes them reusable in other systems. The developed library of components and usage profiles makes it easy to model complex systems and perform reliability predictions according to the FIDES methodology.
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Jiang, Zhihua. "A reliability model for systems undergoing remanufacture." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/MQ45429.pdf.
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Yerneni, Ashok. "A reliability model incorporating software quality metrics." Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/50098.
Повний текст джерелаАнотація:
Large scale software development efforts in the past decade have posed a problem in terms of the reliability of the software. The size and complexity of software that is being developed is growing rapidly and integrating diverse pieces of software in the operational environment also poses severe reliability issues, resulting in increased development and operational costs. A number of reliability models have been defined in the literature to deal with problems of this kind. However, most of these models treat the system as a "black box" and do not consider the complexity of the software in its reliability predictions. Also, reliability is predicted after the system had been completely developed leaving little scope for any major design changes to improve system reliability.
This thesis reports on an effort to develop a reliability model based on complexity metrics which characterize a software system and runtime metrics which reflect the degree of testing of the system. A complete development of the reliability model is presented here. The model is simple and reflects on our intuition of the software development process and our understanding of the significance of the complexity metrics. Credibility analysis is done on the model by simulating a number of systems and applying the model. Data collected from three FORTRAN coded systems developed for NASA Goddard was used as representative of the actual software systems. An analysis of the results is finally presented.Master of Science
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9
Rodrigues, Genaina Nunes. "A model driven approach for software reliability prediction." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1446004/.
Повний текст джерелаАнотація:
Software reliability, one of the major software quality attributes, quantitatively expresses the continuity of correct service delivery. In current practice, reliability models are typically measurement-based models, and mostly employed in isolation at the later stage of the soft ware development process, after architectural decisions have been made that cannot easily be reversed early software reliability prediction models are often insufficiently formal to be ana- lyzable and not usually connected to the target system. We postulate it is possible to overcome these issues by supporting software reliability engineering from requirements to deployment using scenario specifications. We contribute a novel reliability prediction technique that takes into account the component structure exhibited in the scenarios and the concurrent nature of component-based systems by extending scenario specifications to model (1) the probability of component failure, and (2) scenario transition probabilities. Those scenarios are subsequently transformed into enhanced behaviour models to compute the system reliability. Additionally we enable the integration between reliability and development models through profiles that extend the core Unified Modelling Language (UML). By means of a reli ability profile, the architecture of a component-based system can express both method invoca tions and deployment relationships between the application components in one environment. To facilitate reliability prediction, and determine the impact of concurrency on systems reliability, we have extended the Label Transition System Analyser Tool (LTSA), implementing a plugin for reliability analysis. Finally, we evaluate our analysis technique with a case study focusing on Condor, a dis tributed job scheduler and resource management system. The purpose of the case study is to evaluate the efficacy of our analysis technique and to compare it with other reliability tech niques.
10
Kim, Injoong. "Development of a knowledge model for the computer-aided design for reliability of electronic packaging systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22708.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Co-Chair: Peak, Russell; Committee Co-Chair: Sitaraman, Suresh; Committee Member: Paredis, Christiaan; Committee Member: Pucha, Raghuram; Committee Member: Wong, C.
11
Moon, Min-Yeong. "Confidence-based model validation for reliability assessment and its integration with reliability-based design optimization." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5816.
Повний текст джерелаАнотація:
Conventional reliability analysis methods assume that a simulation model is able to represent the real physics accurately. However, this assumption may not always hold as the simulation model could be biased due to simplifications and idealizations. Simulation models are approximate mathematical representations of real-world systems and thus cannot exactly imitate the real-world systems. The accuracy of a simulation model is especially critical when it is used for the reliability calculation. Therefore, a simulation model should be validated using prototype testing results for reliability analysis. However, in practical engineering situation, experimental output data for the purpose of model validation is limited due to the significant cost of a large number of physical testing. Thus, the model validation needs to be carried out to account for the uncertainty induced by insufficient experimental output data as well as the inherent variability existing in the physical system and hence in the experimental test results. Therefore, in this study, a confidence-based model validation method that captures the variability and the uncertainty, and that corrects model bias at a user-specified target confidence level, has been developed. Reliability assessment using the confidence-based model validation can provide conservative estimation of the reliability of a system with confidence when only insufficient experimental output data are available.
Without confidence-based model validation, the designed product obtained using the conventional reliability-based design optimization (RBDO) optimum could either not satisfy the target reliability or be overly conservative. Therefore, simulation model validation is necessary to obtain a reliable optimum product using the RBDO process. In this study, the developed confidence-based model validation is integrated in the RBDO process to provide truly confident RBDO optimum design. The developed confidence-based model validation will provide a conservative RBDO optimum design at the target confidence level. However, it is challenging to obtain steady convergence in the RBDO process with confidence-based model validation because the feasible domain changes as the design moves (i.e., a moving-target problem). To resolve this issue, a practical optimization procedure, which terminates the RBDO process once the target reliability is satisfied, is proposed. In addition, the efficiency is achieved by carrying out deterministic design optimization (DDO) and RBDO without model validation, followed by RBDO with the confidence-based model validation. Numerical examples are presented to demonstrate that the proposed RBDO approach obtains a conservative and practical optimum design that satisfies the target reliability of designed product given a limited number of experimental output data.
Thus far, while the simulation model might be biased, it is assumed that we have correct distribution models for input variables and parameters. However, in real practical applications, only limited numbers of test data are available (parameter uncertainty) for modeling input distributions of material properties, manufacturing tolerances, operational loads, etc. Also, as before, only a limited number of output test data is used. Therefore, a reliability needs to be estimated by considering parameter uncertainty as well as biased simulation model. Computational methods and a process are developed to obtain confidence-based reliability assessment. The insufficient input and output test data induce uncertainties in input distribution models and output distributions, respectively. These uncertainties, which arise from lack of knowledge – the insufficient test data, are different from the inherent input distributions and corresponding output variabilities, which are natural randomness of the physical system.
12
Yim, Ka-wing. "A reliability-based land use and transportation optimization model." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B34618879.
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Yim, Ka-wing, and 嚴家榮. "A reliability-based land use and transportation optimization model." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B34618879.
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14
Dennison, Thomas E. "Fitting and prediction uncertainty for a software reliability model." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23678.
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15
Jenkins, Stewart A. 1974. "Rotary compressor model for investigating compressor performance and reliability." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9912.
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16
Yasuda, Hiroshi. "Improvement of model reliability in a soil-plant system." Kyoto University, 1995. http://hdl.handle.net/2433/160779.
Повний текст джерелаАнотація:
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・論文博士
博士(工学)
乙第8985号
論工博第3012号
新制||工||1006(附属図書館)
UT51-95-V472
(主査)教授 井上 頼輝, 教授 寺島 泰, 教授 松井 三郎
学位規則第4条第2項該当
17
Advani, Gurmukh Hiro. "Solder Joint Reliability: A Unified Thermo-Mechanical Model Approach." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27256.
Повний текст джерелаАнотація:
Due to an unprecedented pervasiveness of electronics in high performance applications, the dependability of mission critical equipment and systems, often solely depends on the reliability of underlying embedded electronic sub-systems. This includes reliability of the solder joints which are subject to fatigue failure over time in harsh operating environments replete with thermo-mechanical stresses.
Fatigue behavior of the solder joints has been previously studied under the separate domains of microstructure evolution and non-linear plastic deformations. The proposed study captures the underlying physics of failure mechanisms to model the failure initiation and degradation phases to obtain a unified model characterizing the overall fatigue behavior over the two phases.
The model development is followed by reliability analysis which takes into account the individual phases to establish the conditional relationship for a unified reliability model. The reliability analysis has been attempted using both the failure time and the damage accumulation approaches.
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Cheng, Nan. "Bayesian Nonparametric Reliability Analysis Using Dirichlet Process Mixture Model." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1307988021.
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Rutaganda, Remmy. "Automated Model-Based Reliability Prediction and Fault Tree Analysis." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-67240.
Повний текст джерелаАнотація:
This work was undertaken as a final year project in Computer Engineering, within the Department of Computer and Information Science at Linköping University. At the Department of Computer and Information Science, work oriented at testing and analyzing applications is developed to provide solution approaches to problems that arise in system product development. One of the current applications being developed is the ‘Systemics Analyst’. The purpose of the application is to facilitate for system developers with an analysis tool permitting insights on system reliability, system critical components, how to improve the system and the consequences as well as risks of a system failure. The purpose of the present thesis was to enhance the ‘Systemics Analyst application’ by incorporating an ‘automated model-based reliability prediction’ and ‘fault tree analysis’ modules. This enables reliability prediction and fault tree analysis diagrams to be generated automatically from the data files and relieves the system developer from manual creation of the diagrams. The enhanced Systemics Analyst application managed to present the results in respective models using the new incorporated functionality. To accomplish the above tasks, ‘Systemics Analyst application’ was integrated with a library that handles automated model-based reliability prediction and fault tree analysis, which is described in this thesis. The reader will be guided through the steps that are performed to accomplish the tasks with illustrating figures, methods and code examples in order to provide a closer vision of the work performed.
20
Qiu, Simon S. "A More General Markov Reliability Model for Computer Systems." NSUWorks, 1998. http://nsuworks.nova.edu/gscis_etd/782.
Повний текст джерелаАнотація:
This study will establish a new Markov reliability model using a more generalized approach in the development of an analytical estimation for the reliability of a large repairable computer system. The developed methods will present a precise way to establish reliability for computer systems' use which consist of hardware and software. This generic model, the N-channel and M-voter reliability model, is suitable for analyzing multiprocessor systems, array redundant systems, and larger repairable networked systems. All results are verified through use of currently published reliability models. The first part of the study introduces a general outline for computer hardware and software reliability, goal statement and barriers issues. A review of current literature on Markov system reliability models linked to the research is noted in the second part. The third section deploys new model methodology and solutions. The fourth reveals significant results, analysis and applications.
The conclusions and summary are presented in the final chapter. Discussions and recommendations are also presented in the last chapter.
21
Han, Yan, and Chi Pak Chan. "Modeling System Reliability For Digital Preservation: Model Modification and Four-Copy Model Study." British Library, 2008. http://hdl.handle.net/10150/105968.
Повний текст джерелаАнотація:
Research has been studied to evaluate the reliability of storage media and the reliability of a computer backup system. In this paper, we use the Continuous Time Markov Chain to model and analyze the reliability of a computer backup system. We propose a modified model from that of the Constantopoulos, Doerr and Petraki [1]. We analyze the difference, show computational results, and propose new input parameters (e.g. time to repair) for the model from our experience. Further we developed a four-copy data model to test if it fulfills the sample reliability rate set by the RLG-NARA. The modeling process can be applied to construct models for computer preservation systems using different storage media. The reliability of constructed models can be calculated so that preservation institutions can have quantitative data to decide their preservation strategies.
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Wang, Rong-Tsorng. "Reliability with multivariate dependency, Markov dependence and Martingales." Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322905.
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Vasudev, R. Sashin, and Ashok Reddy Vanga. "Accuracy of Software Reliability Prediction from Different Approaches." Thesis, Blekinge Tekniska Högskola, Avdelningen för för interaktion och systemdesign, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-1298.
Повний текст джерелаАнотація:
Many models have been proposed for software reliability prediction, but none of these models could capture a necessary amount of software characteristic. We have proposed a mixed approach using both analytical and data driven models for finding the accuracy in reliability prediction involving case study. This report includes qualitative research strategy. Data is collected from the case study conducted on three different companies. Based on the case study an analysis will be made on the approaches used by the companies and also by using some other data related to the organizations Software Quality Assurance (SQA) team. Out of the three organizations, the first two organizations used for the case study are working on reliability prediction and the third company is a growing company developing a product with less focus on quality. Data collection was by the means of interviewing an employee of the organization who leads a team and is in the managing position for at least last 2 years.svra06@student.bth.se
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Mikler, Jerzy. "On Improvement Of Maintenance Function : A Reference Model And Improvement Methodology." Doctoral thesis, KTH, Industriell produktion, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177188.
Повний текст джерелаАнотація:
In order to produce products and services, companies are using various tangible assets such as production equipment and facilities. The goal of the maintenance function is to maintain these assets so they operate safely, efficiently and economically. This function includes technical, administrative and management activities, carried out in order to keep company’s assets in a state, or restore these to a state, in which they can perform the required functions. The activities should be planned and carried out in a way that allows for obtaining the required technical condition, availability, meets the safety requirements for humans and the environment, ensures quality of delivered products and services, and secures the anticipated service life of individual devices. Both effectiveness and efficiency of the maintenance function are very important to each company trying to operate with profit. As follows from the recent research, the performance of maintenance functions in most of the studied companies around the world is in general unsatisfactory, and the underlying reasons of the subnormal behavior are not sufficiently identified, understood and described. The result of research presented in this thesis is an improvement support system based on an explanatory model of the maintenance function. This model shows the mechanisms interconnecting the motivations, intents and rationale behind the involved actors, entities and maintenance activities, and in this way gains understanding of how, and in what way the total performance of the maintenance function is affected, thereby supporting improvement decisions. As maintenance cost is a sharply increasing part of the operational costs, it is an evident target for operational and managerial improvement. This research area is strongly encouraged by industry, and is becoming a topic of increasing interest in the academia.QC 20151117
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Arikan, Gokce. "Reliability-based Design Model For Rubble-mound Coastal Defense Structures." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611602/index.pdf.
Повний текст джерелаАнотація:
In this thesis, a new computer model (tool) for the reliability-based design of
rubble-mound coastal defense structures is developed in which design is
carried out in a user frienly way giving outputs on time variant reliability for
the predetermined lifetimes and damage levels. The model aims to perform the
following steps:
1. Determine the sources of uncertainties in design parameters
2. Evaluate the damage risk of coastal structures which are at design stage
and are recently constructed.
3. Study the sensitivity of limit state functions to the design parameters.
Different from other reliability studies on coastal projects, a new design
computer program is developed that can be easily used by everyone working in
coastal engineering field.
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Pedersen, Robert Fossmark. "Prospective and Efficient Techniques for Model Reduction in Reliability Calculations." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22881.
Повний текст джерелаАнотація:
A reliable electric power supply is essential for modern society. Recently, severe blackouts worldwide have attracted attention to reliability studies in power system planning and operation. The relevance of the traditional N-1 criterion has been discussed, and much focus has been directed towards developing satisfactory probability based reliability tools. Goodtech Project & Services has developed a methodology for calculation of online power delivery reliability for use in power system operation and planning. The method, based on Markov models, analyzes the entire network for a large number of fault combinations, a useful approach for relatively small networks. However, the computation time increases polynomial with increasing system size. Because the impact of an outage has a limited geographical extent, it is desirable to reduce the system to be simulated, so that it only includes the affected area. The objective of this project is to develop methods for identifying the components that can be considered influenced by a fault. The focus of the pre-study was to evaluate which post-processing method best suited for developing a reduced network system. In the pre-study, power flow results from the standard DC load flow were used. The main focus of this thesis has been on developing and implementing fast methods for obtaining the necessary power flow data needed in order to use the post-processing methods. Three approaches have been investigated and tested, namely AC load flow based on the fast decoupled load flow with compensation techniques for obtaining the post- contingency power flows, DC load flow with compensation techniques and the efficient bounding method. The key principle of the compensation methods is that the effect of outages can be calculated by introducing simple compensation terms, thus avoiding the need to rebuild and factorize the system matrices for every contingency case. The bounding method is based on the principle of sensitivity factors and the fact that given knowledge about changes inside a boundary certain conclusions can be made regarding the changes outside it, thus eliminating the need for studying the entire system. The method based on the fast decoupled load flow is the only method that gives the possibility to provide an exact solution, and is also the only method that includes reactive power and voltage magnitudes. It is therefore recommended used in cases where a high degree of accuracy is important, or if reactive power and voltages are of interest. Tests show that the DC load flow is fastest. The accuracy is assumed sufficient for most intended purposes, and should therefore the preferred choice in most cases. Bounding methods are especially useful in highly meshed grids, and if only the largest changes are of interest.
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Tiassou, Kossi. "Aircraft operational reliability - A Model-based approach and case studies." Phd thesis, INSA de Toulouse, 2013. http://tel.archives-ouvertes.fr/tel-00807442.
Повний текст джерелаАнотація:
Lors de la conception des avions, il est courant que les constructeurs évaluent la sûreté de fonctionnement en utilisant des modèles stochastiques, mais l'évaluation de la fiabilité opérationnelle à l'aide de modèles en ligne, pendant la réalisation des missions, reste rarement effectuée. Souvent, l'évaluation stochastique concerne la sécurité des avions. Cette thèse porte sur la modélisation de la fiabilité opérationnelle des avions, pour aider à la planification des activités de maintenance et des missions, ainsi qu'à la bonne réalisation de ces dernières. Nous avons développé une approche de modélisation, basée sur un méta-modèle qui sert de base i) de structuration des informations nécessaires à l'évaluation de la fiabilité opérationnelle d'un avion et ii) pour la construction de modèles stochastiques pouvant être mis à jour dynamiquement. La mise à jour concerne l'état courant des systèmes avion, un profil de mission et les moyens de maintenance disponibles dans les diverses escales incluses dans le profil de la mission. L'objectif est de permettre l'évaluation de la fiabilité opérationnelle en ligne. Deux cas d'études, basés sur des sous-systèmes avion, sont considérés à titre d'illustration. Nous présentons des exemples de résultats qui montrent le rôle important de l'évaluation de la fiabilité opérationnelle pendant une mission d'avion.
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Cassir, C. "A flow model for the analysis of transport network reliability." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364764.
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Tiassou, Kossi Blewoussi. "Aircraft operational reliability : A model-based approach and case studies." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0012/document.
Повний текст джерелаАнотація:
Lors de la conception des avions, il est courant que les constructeurs évaluent la sûreté de fonctionnement en utilisant des modèles stochastiques, mais l'évaluation de la fiabilité opérationnelle à l’aide de modèles en ligne, pendant la réalisation des missions, reste rarement effectuée. Souvent, l'évaluation stochastique concerne la sécurité des avions. Cette thèse porte sur la modélisation de la fiabilité opérationnelle des avions, pour aider à la planification des activités de maintenance et des missions, ainsi qu’à la bonne réalisation de ces dernières. Nous avons développé une approche de modélisation, basée sur un méta-modèle qui sert de base i) de structuration des informations nécessaires à l’évaluation de la fiabilité opérationnelle d’un avion et ii) pour la construction de modèles stochastiques pouvant être mis à jour dynamiquement. La mise à jour concerne l'état courant des systèmes avion, un profil de mission et les moyens de maintenance disponibles dans les diverses escales incluses dans le profil de la mission. L'objectif est de permettre l'évaluation de la fiabilité opérationnelle en ligne. Deux cas d’études, basés sur des sous-systèmes avion, sont considérés à titre d'illustration. Nous présentons des exemples de résultats qui montrent le rôle important de l’évaluation de la fiabilité opérationnelle pendant une mission d’avionDependability assessment, by system manufacturer, during aircraft design, based on stochastic modeling, is of common practice, but model based operational dependability assessment online, during missions' achievement, is seldom done. Usually, the stochastic assessment addresses aircraft safety.This thesis addresses aircraft operational dependability modeling to support mission and maintenance planning, as well as the achievement of the missions. We develop a modeling approach, based on a meta-model that is used as a basis i) to structure the information needed to assess aircraft operational reliability and ii) to build a stochastic model that can be updated dynamically. The update concerns the current state of the aircraft system, a mission profile and the maintenance facilities available at the flight stop locations involved in the mission. The aim is to enable operational reliability assessment online. Two case studies, based on aircraft subsystems, are considered for illustration. We present examples of evaluation results that show the valuable role of operational dependability assessment during aircraft mission
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Yang, Shu, and Shu Yang. "Estimating Freeway Travel Time Reliability for Traffic Operations and Planning." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/623003.
Повний текст джерелаАнотація:
Travel time reliability (TTR) has attracted increasing attention in recent years, and is often listed as one of the major roadway performance and service quality measures for both traffic engineers and travelers. Measuring travel time reliability is the first step towards improving travel time reliability, ensuring on-time arrivals, and reducing travel costs. Four components may be primarily considered, including travel time estimation/collection, quantity of travel time selection, probability distribution selection, and TTR measure selection. Travel time is a key transportation performance measure because of its diverse applications and it also serves the foundation of estimating travel time reliability. Various modelling approaches to estimating freeway travel time have been well developed due to widespread installation of intelligent transportation system sensors. However, estimating accurate travel time using existing freeway travel time models is still challenging under congested conditions. Therefore, this study aimed to develop an innovative freeway travel time estimation model based on the General Motors (GM) car-following model. Since the GM model is usually used in a micro-simulation environment, the concepts of virtual leading and virtual following vehicles are proposed to allow the GM model to be used in macro-scale environments using aggregated traffic sensor data. Travel time data collected from three study corridors on I-270 in St. Louis, Missouri was used to verify the estimated travel times produced by the proposed General Motors Travel Time Estimation (GMTTE) model and two existing models, the instantaneous model and the time-slice model. The results showed that the GMTTE model outperformed the two existing models due to lower mean average percentage errors of 1.62% in free-flow conditions and 6.66% in two congested conditions. Overall, the GMTTE model demonstrated its robustness and accuracy for estimating freeway travel times. Most travel time reliability measures are derived directly from continuous probability distributions and applied to the traffic data directly. However, little previous research shows a consensus of probability distribution family selection for travel time reliability. Different probability distribution families could yield different values for the same travel time reliability measure (e.g. standard deviation). It is believe that the specific selection of probability distribution families has few effects on measuring travel time reliability. Therefore, two hypotheses are proposed in hope of accurately measuring travel time reliability. An experiment is designed to prove the two hypotheses. The first hypothesis is proven by conducting the Kolmogorov–Smirnov test and checking log-likelihoods, and Akaike information criterion with a correction for finite sample sizes (AICc) and Bayesian information criterion (BIC) convergences; and the second hypothesis is proven by examining both moment-based and percentile-based travel time reliability measures. The results from the two hypotheses testing suggest that 1) underfitting may cause disagreement in distribution selection, 2) travel time can be precisely fitted using mixture models with higher value of the number of mixture distributions (K), regardless of the distribution family, and 3) the travel time reliability measures are insensitive to the selection of distribution family. Findings of this research allows researchers and practitioners to avoid the work of testing various distributions, and travel time reliability can be more accurately measured using mixture models due to higher value of log-likelihoods. As with travel time collection, the accuracy of the observed travel time and the optimal travel time data quantity should be determined before using the TTR data. The statistical accuracy of TTR measures should be evaluated so that the statistical behavior and belief can be fully understood. More specifically, this issue can be formulated as a question: using a certain amount of travel time data, how accurate is the travel time reliability for a specific freeway corridor, time of day (TOD), and day of week (DOW)? A framework for answering this question has not been proposed in the past. Our study proposes a framework based on bootstrapping to evaluate the accuracy of TTR measures and answer the question. Bootstrapping is a computer-based method for assigning measures of accuracy to multiple types of statistical estimators without requiring a specific probability distribution. Three scenarios representing three traffic flow conditions (free-flow, congestion, and transition) were used to fully understand the accuracy of TTR measures under different traffic conditions. The results of the accuracy measurements primarily showed that: 1) the proposed framework can facilitate assessment of the accuracy of TTR, and 2) stabilization of the TTR measures did not necessarily correspond to statistical accuracy. The findings in our study also suggested that moment-based TTR measures may not be statistically sufficient for measuring freeway TTR. Additionally, our study suggested that 4 or 5 weeks of travel time data is enough for measuring freeway TTR under free-flow conditions, 40 weeks for congested conditions, and 35 weeks for transition conditions. A considerable number of studies have contributed to measuring travel time reliability. Travel time distribution estimation is considered as an important starting input of measuring travel time reliability. Kernel density estimation (KDE) is used to estimate travel time distribution, instead of parametric probability distributions, e.g. Lognormal distribution, the two state models. The Hasofer Lind - Rackwitz Fiessler (HL-RF) algorithm, widely used in the field of reliability engineering, is applied to this work. It is used to compute the reliability index of a system based on its previous performance. The computing procedure for travel time reliability of corridors on a freeway is first introduced. Network travel time reliability is developed afterwards. Given probability distributions estimated by the KDE technique, and an anticipated travel time from travelers, the two equations of the corridor and network travel time reliability can be used to address the question, "How reliable is my perceived travel time?" The definition of travel time reliability is in the sense of "on time performance", and it is conducted inherently from the perspective of travelers. Further, the major advantages of the proposed method are: 1) The proposed method demonstrates an alternative way to estimate travel time distributions when the choice of probability distribution family is still uncertain; 2) the proposed method shows its flexibility for being applied onto different levels of roadways (e.g. individual roadway segment or network). A user-defined anticipated travel time can be input, and travelers can utilize the computed travel time reliability information to plan their trips in advance, in order to better manage trip time, reduce cost, and avoid frustration.
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Sproston, Jeremy James. "Model checking of probabilistic timed and hybrid systems." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391021.
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Qamber, I. S. H. "Markov modelling of equipment behaviour." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381011.
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Kim, Seong W. "Bayesian model selection using intrinsic priors for commonly used models in reliability and survival analysis /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841159.
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Thiruvengadachari, Sathish. "Experimental and neural network-based model for human-machine systems reliability." Diss., Online access via UMI:, 2006.
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Schreiber, Susanne. "Frequency preference and reliability of signal integration." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972577084.
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Ma, Li. "Web error classification and usage based model for Web reliability improvement." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258042.
Повний текст джерелаАнотація:
Thesis (Ph.D. in Computer Science)--S.M.U., 2007.Title from PDF title page (viewed Mar. 18, 2008). Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1731. Adviser: Jeff Tian. Includes bibliographical references.
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Dithinde, Mahongo. "Characterisation of model uncertainty for reliability-based design of pile foundations." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/21612.
Повний текст джерелаАнотація:
Dissertation (PhD)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: To keep pace with international trends, the introduction of geotechnical limit state design in South Africa is inevitable. To pave the way for implementation of limit state pile design in the country, the study quantifies model uncertainty in the classic static pile design formula under the Southern African geologic environment. The generated model uncertainty statistics are used to calibrate partial resistance factors in a reliability-based design framework. A series of pile performance predictions by the static formula are compared with measured performances. To capture the distinct soil types for the geologic region of Southern Africa as well as the local pile design and construction experience base, pile load tests and associated geotechnical data from the Southern African geologic environment are used. The methodology of collecting, compiling, and analyzing the pile load tests to derive the measured ultimate pile capacities is described. To facilitate the computation of the theoretical capacities, the site specific geotechnical data in the database are transformed to the desired engineering soil properties through well established empirical correlations. For a given pile test case, model uncertainty is presented in terms of a model factor computed as the ratio of the measured to the theoretical capacity, leading to n realisations of the model factor. To facilitate further interpretation and generalisation of the model factor realisation data, statistical analysis is carried out. The statistical analysis comprises of graphical representation by histograms, outliers detection and correction of erroneous values, and using the corrected data to compute the sample moments (mean, standard deviations, skewness and kurtosis) needed in reliability analysis. The analyses demonstrate that driven piles depict higher variability compared to bored piles irrespective of materials type. Furthermore, for a given pile installation method (driven or bored) the variability in non-cohesive materials is higher than that in cohesive materials. In addition to the above statistics, reliability analysis requires the theoretical probability distribution for the random variable under consideration. Accordingly it is demonstrated that the lognormal distribution is the most appropriate theoretical model for the model factor. Another key basis for reliability theory is the notion of randomness of the basic variables. To verify that the variation in the model factor is not explainable by deterministic variations in the database, an investigation of correlation of the model factor with underlying pile design parameters is carried out. It is shown that such correlation is generally weak. Correlation can have a significant impact on the calculated reliability index if not accounted for. Accordingly, the effects of the exhibited correlation is investigated through an approach based on regression theory in which systematic effects of design parameters are taken into account (generalised model factor). The model factor statistics from the conventional approach and those from the generalised model factor approach are used to determine reliability indexes implied by the current design practice. It is demonstrated that no significant improvement in values of the reliability indexes is gained by taking into account the effects of the weak correlation. The model factor statistics derived on the basis of the standard model factor approach are used to calibrate resistance factors. Four first order reliability methods are employed for the calibration of resistance factors. These include; the Mean Value First-Order Second Moment approach, an Approximate Mean Value First-Order Second Moment approach, the Advanced First-Order Second Moment approach using Excel spreadsheet, and the Advanced First-Order Second Moment approach (design point method). The resistance factors from the various calibration methods are presented for the target reliability index values of 2.0, 2.5, and 3.0. The analyses of the results demonstrate that for a given target reliability index, the resistance factors from the different methods are comparable. Furthermore, it is shown that for a given material type, the resistance factors are quite close irrespective of the pile installation method, suggesting differentiation of partial factors in terms of materials types only. Finally, resistance factors for use in probabilistic limit state pile design in South Africa are recommended.
AFRIKAANSE OPSOMMING: Ten einde in pas te bly met internasionale neigings, is dit onafwendbaar dat geotegniese limietstaat-ontwerp in Suid Afrika ingevoer word. Ter voorbereiding vir die plaaslike toepassing van limietstaatontwerp op heipale, kwantifiseer hierdie ondersoek onsekerheid rondom die model vir klassieke statiese heipaalontwerpformules in die Suid Afrikaanse geologiese omgewing. Die statistiek van modelonsekerheid wat gegenereer is, word gebruik om parsiële weerstandsfaktore in ’n betoubaarheid-gebasseerde ontwerpraamwerk te kalibreer. ’n Reeks voorspellings van die gedrag van heipale volgens die statiese formules word vergelyk met die gemete gedrag. Om die kenmerkende grond-tipes in die geologiese gebied van Suidelike Afrika sowel as die plaaslike ondervinding met heipaalontwerp en - konstruksie vas te lê, word heipaaltoetse en die gassosieerde geotegniese data vanuit hierdie geologiese omgewing gebruik. Die metodiek vir die versameling, saamstelling en analise van heipaaltoetse om uiterste kapasiteite daarvan te bepaal, word beskryf. Terreinspesifieke geotegniese data in die databasis word getransformeer na die vereisde ingenieurseienskappe volgens gevestigde empiriese korrelasies. Vir ’n gegewe heipaaltoets word modelonsekerheid weergegee in terme van ’n modelfaktor wat bereken word as die verhouding van die gemete tot die teoretiese kapasiteit waaruit n uitkomstes van die modelfaktor dus gegenereer word. Om verdere interpretasie en veralgemening van die modelfaktordata te vergemaklik, word ’n statistiese analise daarop uitgevoer. Die statistiese analise bestaan uit grafiese voorstellings deur middel van histogramme, uitkenning van uitskieters en verbetering van foutiewe waardes, waarna die statistiese momente (gemiddeld, standaardafwyking, skeefheid en kurtose) vir gebruik in betroubaarheidsanalise bereken word. Volgens die analises toon ingedrewe heipale ’n groter veranderlikheid as geboorde pale, ongeag die grondtipe. Verder is die veranderlikheid van heipale in kohesielose materiale hoër as in kohesiewe materiale, ongeag die installasiemetode (ingedrewe of geboor). Bykomend tot bogemelde statistiek, vereis betroubaarheidsanalise die teoretiese waarskynlikheidsdistribusie van die ewekansige veranderlike onder beskouing. Ooreenkomstig word illustreer dat die log-normale verspreiding die mees toepaslike verspreiding vir die modelfaktor is. ’n Verdere sleutelvereiste vir betroubaarheidsteorie is die mate van ewekansigheid van die basiese veranderlikes. Om te bepaal of die variasie in die modelfaktor nie deur deterministiese veranderlikes in die databasis verduidelik kan word nie, word ’n ondersoek na die korrelasie van die modelfaktor met onderliggende heipaalontwerpfaktore uitgevoer. Sodanige korrelasie is in die algemeen as laag bevind. Korrelasie kan ’n belangrike invloed op die berekende betroubaarheidsindeks hê indien dit nie in ag geneem word nie. Dienooreenkomstig word die effek van die getoonde korrelasie ondersoek met behulp van die metode van regressie-analise waarin sistematiese effekte van ontwerpparameters in berekening gebring word (veralgemeende modelfaktor). Die modelfaktorstatistiek wat volg uit die konvensionele benadering en dié van die veralgemeende benadering word gebruik om betroubaarheidsindekse te bepaal wat deur die bestaande ontwerppraktyk geïmpliseer word. Die bevinding is dat daar nie ’n noemenswaardige verbetering in die waardes van die betroubaarheidsindekse is wanneer die effek van die swak korrelasie in berekening gebring word nie. Die statistiek van die modelfaktor wat afgelei is volgens die standaardbenadering word gebruik om die weerstandsfaktore te kalibreer. Vier eerste-orde betroubaarheidsmetodes word gebruik om die weerstandsfaktore te kalibreer, naamlik die Gemiddelde Waarde Eerste-Orde Tweede Moment benadering, die Benaderde Gemiddelde Waarde Eerste-Orde Tweede Moment benadering, die Gevorderde Eerste-Orde Tweede Moment benadering waarin ’n Excel sigblad gebruik word en die Gevorderde Eerste-Orde Tweede Moment benadering (die ontwerppuntmetode). Die weerstandsfaktore vanaf die verskillende kalibrasiemetodes word weergegee vir waardes van 2.0, 2.5 en 3.0 van die teikenbetroubaarheidsindeks. ’n Ontleding van die resultate toon dat vir ’n gegewe teiken betroubaarheidsindeks die weerstandsfaktore vanaf die verskillende metodes vergelykbaar is. Verder word getoon dat vir ’n gegewe grondsoort, die weerstandsfaktore vir verskillende metodes van installasie van die heipaal nie veel verskil nie. Dit wil dus voorkom asof parsiële faktore in terme van die grondsoort uitgedruk kan word. Ten slotte word weerstandsfaktore vir gebruik in plastiese limietstaatontwerp van heipale in Suid Afrika aanbeveel.
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Haywood, Alan M. "Evaluating general circulation climate model reliability with the Pliocene geological record." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271189.
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Lanford, Patricia. "A model for building trustworthiness in online stores." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Dissertations/LANFORD_PATRICIA_43.pdf.
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Trávníček, Jan. "Tvorba spolehlivostních modelů pro pokročilé číslicové systémy." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2013. http://www.nusl.cz/ntk/nusl-236226.
Повний текст джерелаАнотація:
This thesis deals with the systems reliability. At First, there is discussed the concept of reliability itself and its indicators, which can specifically express reliability. The second chapter describes the different kinds of reliability models for simple and complex systems. It further describes the basic methods for construction of reliability models. The fourth chapter is devoted to a very important Markov models. Markov models are very powerful and complex model for calculating the reliability of advanced systems. Their suitability is explained here for recovered systems, which may contain absorption states. The next chapter describes the standby redundancy. Discusses the advantages and disadvantages of static, dynamic and hybrid standby. There is described the influence of different load levels on the service life. The sixth chapter is devoted to the implementation, description of the application and description of the input file in XML format. There are discussed the results obtaining in experimental calculations.
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Dejan, Spasić. "Model pouzdanosti u procesu eksploatacije dizel motora." Phd thesis, Univerzitet u Novom Sadu, Tehnički fakultet Mihajlo Pupin u Zrenjaninu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110877&source=NDLTD&language=en.
Повний текст джерелаАнотація:
U okviru disertacije je na osnovu teorijske i empirijske analize i korišćenjem podataka izeksploatacije, formiran model pouzdanosti koji će doprineti povećanju pouzdanosti isigurnosti funkcionisanja dizel motora u procesu eksploatacije.Within this dissertation, on the basis of theoretical and empirical analysis and usage ofexploitation data, a reliability model was formed that will contribute to reliability increase and safety of diesel engine operation in the exploitation process.
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Bakouros, Y. L. "Offshore pipeline reliability prediction : An assessment of the breakdown characteristics of offshore pipelines and the development of a statistical technique to improve their reliability prediction with particular reference." Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233657.
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Naumann, Michael. "MEMS reliability in shock environments." Doctoral thesis, Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-117360.
Повний текст джерелаАнотація:
In der vorliegenden Arbeit wird eine Methode vorgestellt, mit welcher die Zuverlässigkeit mikroelektromechanischer Systeme (MEMS) bezüglich stoßinduzierter Fehlermechanismen bereits in der Entwurfsphase neuer Produkte abgeschätzt bzw. verbessert werden kann. Der Ansatz bezieht sich dabei auf bruch- sowie adhäsionsbedingte Ausfallmechanismen und erfordert zwei wesentliche Schritte. Zuerst werden Systemmodelle der jeweils zu untersuchenden mikromechanischen Systeme erstellt, welche die Berechnung der Stoßantwort wie auch der dabei auftretenden Belastungen in Sinne von Auslenkungen, Deformationen und Aufprallkräften ermöglichen. In einem zweiten Schritt wird die zur Fertigung vorgesehene Technologie bezüglich des Auftretens beider stoßbedingter Ausfallmechanismen sowie deren Abhängigkeit von verschiedenen Umgebungsbedingungen oder Betriebsparametern systematisch untersucht. Die aus der Prozesscharakterisierung resultierenden Daten dienen zur Ableitung prozessspezifischer Fehlerkriterien, welche die Einschätzung der zuvor berechneten Lasten ermöglichen. Auf diese Weise kann abgeschätzt werden, inwieweit die Zuverlässigkeit der betrachteten mikromechanischen Strukturen beeinflusst wird bzw. mit welchen Maßnahmen diese gesteigert werden kann.
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Hernandez, Hernandez Erika. "SEGMENT-BASED RELIABILITY ASSESSMENT FOR WATER DISTRIBUTION NETWORKS." UKnowledge, 2017. https://uknowledge.uky.edu/ce_etds/59.
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In recent years, water utilities have placed a greater emphasis on the reliability and resilience of their water distribution networks. This focus has increased due to the continuing aging of such infrastructure and the potential threat of natural or man-made disruptions. As a result, water utilities continue to look for ways to evaluate the resiliency of their systems with a goal of identifying critical elements that need to be reinforced or replaced. The simulation of pipe breaks in water reliability studies is traditionally modeled as the loss of a single pipe element. This assumes that each pipe has an isolation valve on both ends of the pipe that can be readily located and operated under emergency conditions. This is seldom the case. The proposed methodology takes into account that multiple pipes may be impacted during a single failure as a result of the necessity to close multiple isolation valves in order to isolate the “segment” of pipes necessary to contain the leak.
This document presents a simple graphical metric for use in evaluating the performance of a system in response to a pipe failure. The metrics are applied to three different water distribution systems in an attempt to illustrate the fact that different pipe segments may impact system performance in different ways. This information is critical for use by system managers in deciding which segments to prioritize for upgrades or replacement.
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Carey, Scott. "Estimating reliability of software systems : an evaluation of current methods /." Master's thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-10242009-020152/.
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Agarwal, Jitendra. "An interacting objects process model for the study of non-linear dynamics." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259475.
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AlKanhal, AbdulAziz A. "Novel cutaneous abscess model : model development and exploration of reliability and validity of detecting key diagnostic features." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54700.
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Introduction: The difficulty of differential diagnoses between cellulitis and occult cutaneous abscess remains the main issue in clinical practice. Educational efforts, however, have been invested into building simulation models directed toward the treatment of cutaneous abscesses. The discrepancy between the problem in clinical practice and educational efforts in this area requires simulation models that can provide an opportunity for trainees to practice their diagnostic skills.
Aims: The study focuses on creating a cutaneous abscess model that is detectable by ultrasound and evaluating the reliability and validity of detecting clinical and sonographic features of cutaneous abscess disease on the basis of the model.
Materials and methods: Six identical models were made, each consisting of a water balloon filled with mock abscess and two glue threads inside a pork belly, and radiologist standardized ultrasound images of the model. Reliability and validity of detecting key diagnostic features on the basis of the model by 24 judges were explored.
Results: Cronbach’s alpha across all models were 0.89 and 0.87 for clinical and sonographic features, respectively. The intraclass correlation coefficient was 0.71 for both clinical and sonographic features. The correlation between all clinical and sonographic features and corresponding construct were statistically significant (p < 0.01). Content validity indices were 0.90 for clinical features construct and 0.85 for the sonographic features construct.
Discussion: The model was constructed from simple, widely available and easy to assemble materials. It is a high fidelity, cost-effective model and can be used as a simulator for diagnosis of cutaneous abscess in medical education. Study data expressed excellent internal consistency and high agreement among judges. The clinical and sonographic features were significantly correlating to the overall corresponding construct. It also reveals strong content validity. The constructed cutaneous abscess model has reliable and valid ability in demonstrating both clinical and sonographic features. Further studies are needed to examine the efficacy of the model for training and correlations with the clinical outcomes in real practice.
Conclusion: The novel high fidelity cost-effective cutaneous abscess model allows for reliable and valid detection of the clinical and sonographic diagnostic features of the cutaneous abscess disease.Surgery, Department of
Medicine, Faculty of
Graduate
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Noh, Yoojeong Choi Kyung K. "Input model uncertainty and reliability-based design optimization with associated confidence level." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/412.
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Bund, Robert E. J. "Evaluation of a discrete modification of the continuous AMSAA reliability growth model." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27032.
Повний текст джерелаАнотація:
A new discrete reliability growth model is created by modifying the often used Army Material System Analysis Activity (AMSAA) continuous reliability growth model. The new model is labeled the AMSAA-D model. Its accuracy is evaluated and compared with three other existing discrete reliability growth models. In particular it is more accurate than an AMSAA discrete model which requires computer supported numerical methods to calculate the reliability estimates from test data. The AMSAA-D reliability estimates can be made with a hand-held calculator. Computer simulations were used to generate test data needed for the evaluation. The simulated test plan assumes that repeated tests on a system are performed until a predetermined number of failures occur, at which time a design change is made to the system to improve its reliability. Ten reliability values are specified to define a reliability growth pattern. Five hundred replications of each growth pattern are simulated. For each replication, reliability estimates are calculated for each of the ten sets of generated test data using equations from each of the ten sets of generated test data using equations from each of the four growth models. Averages and sample mean square error values across the 500 replications are used to determine accuracy. Sensitivity of the AMSAA-D model to the number of failures before system modification and to the number of possible failure causes is system modification and to the number of possible failure causes is also evaluated. Theses. (SDW)
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Lin, Jufei, and 林汝霏. "Reliability Study of DINA Model." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/34811686548869154208.
Повний текст джерелаАнотація:
碩士國立臺中教育大學
教育測驗統計研究所
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In recent years, there were many studies on DINA models. In this study, through the knowledge structure to understand the cognitive attributes of these items, and explore the impact of different variables on the reliability of the attributes in the DINA model. This study through a simulation study to explore a fixed item length, that in different item parameters, in different item measuring the average number of skills for attribute reliability; the same as item measuring the average number of skills, the different item parameters, and different item length that will affect attribute reliability; with the data to simulate the experimental properties, compare items of reliability and consistency of the attribute validity. The results of this study are found : 1. Fixed item length, in the same item measuring the average number of skills, when the item parameters increase over figures, their attribute reliability followed by lower; 2. Fixed item length, the same item parameters, with the increase of number of item measuring the average number of skills, that attribute reliability followed by increased; 3. The same item measuring the average number of skills, in the same item parameters, with the increase item length, that attribute reliability will be followed by increased; 4. The same item measuring the average number of skills, compare three different items length, item parameters with increase, that attribute reliability will be reduced; 5. The result of empirical data and simulation data are conformed; 6. To the simulation data, the estimation results of attribute reliability and estimation results of attribute validity are consistency in the item length and item parameters..