Дисертації: "Model of reliability assessment"

1

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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2

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.

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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.

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3

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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4

Zhao, Liang. "Reliability-based design optimization using surrogate model with assessment of confidence level." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1194.

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The objective of this study is to develop an accurate surrogate modeling method for construction of the surrogate model to represent the performance measures of the compute-intensive simulation model in reliability-based design optimization (RBDO). In addition, an assessment method for the confidence level of the surrogate model and a conservative surrogate model to account the uncertainty of the prediction on the untested design domain when the number of samples are limited, are developed and integrated into the RBDO process to ensure the confidence of satisfying the probabilistic constraints at the optimal design. The effort involves: (1) developing a new surrogate modeling method that can outperform the existing surrogate modeling methods in terms of accuracy for reliability analysis in RBDO; (2) developing a sampling method that efficiently and effectively inserts samples into the design domain for accurate surrogate modeling; (3) generating a surrogate model to approximate the probabilistic constraint and the sensitivity of the probabilistic constraint with respect to the design variables in most-probable-point-based RBDO; (4) using the sampling method with the surrogate model to approximate the performance function in sampling-based RBDO; (5) generating a conservative surrogate model to conservatively approximate the performance function in sampling-based RBDO and assure the obtained optimum satisfy the probabilistic constraints. In applying RBDO to a large-scale complex engineering application, the surrogate model is commonly used to represent the compute-intensive simulation model of the performance function. However, the accuracy of the surrogate model is still challenging for highly nonlinear and large dimension applications. In this work, a new method, the Dynamic Kriging (DKG) method is proposed to construct the surrogate model accurately. In this DKG method, a generalized pattern search algorithm is used to find the accurate optimum for the correlation parameter, and the optimal mean structure is set using the basis functions that are selected by a genetic algorithm from the candidate basis functions based on a new accuracy criterion. Plus, a sequential sampling strategy based on the confidence interval of the surrogate model from the DKG method, is proposed. By combining the sampling method with the DKG method, the efficiency and accuracy can be rapidly achieved. Using the accurate surrogate model, the most-probable-point (MPP)-based RBDO and the sampling-based RBDO can be carried out. In applying the surrogate models to MPP-based RBDO and sampling-based RBDO, several efficiency strategies, which include: (1) using local window for surrogate modeling; (2) adaptive window size for different design candidates; (3) reusing samples in the local window; (4) using violated constraints for surrogate model accuracy check; (3) adaptive initial point for correlation parameter estimation, are proposed. To assure the accuracy of the surrogate model when the number of samples is limited, and to assure the obtained optimum design can satisfy the probabilistic constraints, a conservative surrogate model, using the weighted Kriging variance, is developed, and implemented for sampling-based RBDO.

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5

Lyons, Melinda. "Evaluation of a task performance resource constraint model to assess the impact of offshore emergency management on risk reduction." Thesis, Cranfield University, 2000. http://dspace.lib.cranfield.ac.uk/handle/1826/4056.

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In this age of safety awareness, technological emergencies still happen, occasionally with catastrophic results. Often human intervention is the only way of averting disaster. Ensuring that the chosen emergency managers are competent requires a combination of training and assessment. However, assessment currently relies on expert judgement of behaviour as opposed to its impact on outcome, therefore it would be difficult to incorporate such data into formal Quantitative Risk Assessments (QRA). Although there is, as yet, no suitable alternative to expert judgement, there is a need for methods of quantifying the impact of emergency management on risk reduction in accident and incidents. The Task Performance Resource Constraint (TPRC) model is capable of representing the critical factors. It calculates probability of task success with respect to time based on uncertainties associated with the task and resource variables. The results can then be used to assess the management performance based on the physical outcome in the emergency, thereby providing a measure of the impact of emergency management on risk with a high degree of objectivity. Data obtained from training exercises for offshore and onshore emergency management were measured and successfully used with the TPRC model. The resulting probability of success functions also demonstrated a high level of external validity when used with improvements in emergency management or design changes or real data from the Piper Alpha disaster. It also appeared to have more external validity than other HRQ/QRA techniques as it uses physical data that are a greater influence on outcome than psychological changes - though this could be because the current HRA/QRA techniques view human unreliability as probability of error rather than probability of failure. The simulation data were also used to build up distributions of timings for simple emergency management tasks. Using additional theoretical data, this demonstrated the model's potential for assessing the probability of successf or novel situations and future designs.

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6

Zhuang, Xing. "A New Reliability Assessment Model for Power Electronic Modules Considering Failure Mechanism Interaction." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27615.

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A reliability prediction method is proposed to determine the lifetime of IGBTs (Insulated Gate Bipolar Transistors) under power cycling test based on the performance of solder joint and wire bond. The failure characteristics of solder joint and wire bond are captured via selected PoF model respectively. To provide precise reliability prediction, PoF models are converted into probabilistic models. In addition, the failure interaction between wire bond and solder joint is studied. Wire bond lift-off is treated as the predominant failure mode based upon experiments from literature and solder joint degradation process is triggered by wire bond degradation process. Increased junction temperature is captured as it is affected by the degradation process of both components. In the end, the system reliability is computed in a series system configuration.

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7

Gil, Sagás Esteban Manuel. "Integrated network flow model for a reliability assessment of the national electric energy system." [Ames, Iowa : Iowa State University], 2007.

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8

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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9

Buhari, Muhammad. "Reliability assessment of ageing distribution cable for replacement in 'smart' distribution systems." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/reliability-assessment-of-ageing-distribution-cable-for-replacement-in-smart-distribution-systems(e253c774-b5e3-4872-9139-894e7df553f0).html.

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Majority of electricity networks have growing number of ageing elements. Critical network components, such as ageing underground cables, are very expensive to install and disruptive to replace. On the other hand, global climate changes have made connection of new low carbon technologies (LCT) into the grids increasingly necessary. These factors are contributing to the increasing complexity of the planning and management of power systems. Numerous techniques published on this subject tend to ignore the impact of LCT integration and the anchoring ꞌSmartꞌ solutions on ageing network assets, such as underground cables and transformers. This thesis presents the development procedures of an ageing underground cable reliability model (IEC-Arrhenius-Weibull model) and cable ranking models for replacement based on system wide effects and thermal loss-of-life metrics. In addition, a new concept of LCT integration and distribution network management was proposed using two optimization models. The first optimizes connection of new wind sources by minimizing the connection cost and the cost of cable thermal loss-of-lives in the planning period. In the second stage, the network is optimally reconfigured in such a way to minimize thermal-loss-of-life of ageing cable. Both optimization models are formulated as mixed integer non-linear programming (MINLP) problems applicable to radially operated medium voltage networks. To quantify the reliability benefits of the proposed approach, Sequential Monte Carlo Simulation (SMCS) procedure was formulated. Some of the main features of the SMCS procedure are the IEC-Arrhenius-Weibull model for ageing cable, optimal network reconfiguration, wind generation modelling using ARMA models and real time thermal ratings. The final outputs are reliability metrics, cable ranking lists for replacement, savings due to 'non-spend' cable thermal lives, etc. These studies have proven to be important in formulating an effective strategy for extending the lives of network cables, managing overall network reliability and planning cables replacement in power distribution networks.

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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.

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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
Dependability 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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11

Smith, William B. "Early component-based reliability assessment using UML based software models." Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2634.

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Thesis (M.S.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains vii, 62 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 26-27).

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12

Ha, Taesung Garland W. J. "Probabilistic risk assessment for a loss of coolant accident in McMaster Nuclear Reactor and application of reliability physics model for modeling human reliability." *McMaster only, 2006.

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13

Yang, Fang. "A Comprehensive Approach for Bulk Power System Reliability Assessment." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14488.

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Abstract The goal of this research is to advance the state of the art in bulk power system reliability assessment. Bulk power system reliability assessment is an important procedure at both power system planning and operating stages to assure reliable and acceptable electricity service to customers. With the increase in the complexity of modern power systems and advances in the power industry toward restructuring, the system models and algorithms of traditional reliability assessment techniques are becoming obsolete as they suffer from nonrealistic system models and slow convergence (even non-convergence) when multi-level contingencies are considered and the system is overstressed. To allow more rigor in system modeling and higher computational efficiency in reliability evaluation procedures, this research proposes an analytically-based security-constrained adequacy evaluation (SCAE) methodology that performs bulk power system reliability assessment. The SCAE methodology adopts a single-phase quadratized power flow (SPQPF) model as a basis and encompasses three main steps: (1) critical contingency selection, (2) effects analysis, and (3) reliability index computations. In the critical contingency selection, an improved contingency selection method is developed using a wind-chime contingency enumeration scheme and a performance index approach based on the system state linearization technique, which can rank critical contingencies with high accuracy and efficiency. In the effects analysis for selected critical contingencies, a non-divergent optimal quadratized power flow (NDOQPF) algorithm is developed to (1) incorporate major system operating practices, security constraints, and remedial actions in a constrained optimization problem and (2) guarantee convergence and provide a solution under all conditions. This algorithm is also capable of efficiently solving the ISO/RTO operational mode in deregulated power systems. Based on the results of the effects analysis, reliability indices that provide a quantitative indication of the system reliability level are computed. In addition, this research extends the proposed SCAE framework to include the effects of protection system hidden failures on bulk power system reliability. The overall SCAE methodology is implemented and applied to IEEE reliability test systems, and evaluation results demonstrate the expected features of proposed advanced techniques. Finally, the contributions of this research are summarized and recommendations for future research are proposed.

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Allahvirdizadeh, Reza. "Reliability-Based Assessment and Optimization of High-Speed Railway Bridges." Licentiate thesis, KTH, Bro- och stålbyggnad, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-301318.

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Increasing the operational speed of trains has attracted a lot of interest in the last decades and has brought new challenges, especially in terms of infrastructure design methodology, as it may induce excessive vibrations. Such demands can damage bridges, which in turn increases maintenance costs, endangers the safety of passing trains and disrupts passenger comfort. Conventional design provisions should therefore be evaluated in the light of modern concerns; nevertheless, several previous studies have highlighted some of their shortcomings. It should be emphasized that most of these studies have neglected the uncertainties involved, which preventsthe reported results from representing a complete picture of the problem. In this respect, the present thesis is dedicated to evaluating the performance of conventional design methods, especially those related to running safety and passenger comfort, using probabilistic approaches. To achieve this objective, a preliminary study was carried out using the first-order reliability method for short/medium span bridges passed by trains at a wide range of operating speeds. Comparison of these results with the corresponding deterministic responses showed that applying a constant safety factor to the running safety threshold does not guarantee that the safety index will be identical for all bridges. It also shows that the conventional design approaches result in failure probabilities that are higher than the target values. This conclusion highlights the need to update the design methodology for running safety. However, it would be essential to determine whether running safety is the predominant design criterion before conducting further analysis. Therefore, a stochastic comparison between this criterion and passenger comfort was performed. Due to the significant computational cost of such investigations, subset simulation and crude Monte-Carlo (MC) simulation using meta-models based on polynomial chaos expansion were employed. Both methods were found to perform well, with running safety almost always dominating the passenger comfort limit state. Subsequently, classification-based meta-models, e.g. support vector machines, k-nearest neighbours and decision trees, were combined using ensemble techniques to investigate the influence of soil-structure interaction on the evaluated reliability of running safety. The obtained results showed a significant influence, highlighting the need for detailed investigations in further studies. Finally, a reliability-based design optimization was conducted to update the conventional design method of running safety by proposing minimum requirements for the mass per length and moment of inertia of bridges. It is worth mentioning that the inner loop of the method was solved by a crude MC simulation using adaptively trained Kriging meta-models.
Att öka tågens hastighet har väckt stort intresse under de senaste decennierna och har medfört nya utmaningar, särskilt när det gäller broanalyser, eftersom tågen inducerar stora vibrationer. Sådana vibrationer kan öka underhållskostnaderna, äventyra säkerheten för förbipasserande tåg och påverka passagerarkomforten. Konstruktionsbestämmelser bör därför utvärderas mot bakgrund av dessa problem; dock har flera tidigare studier belyst några av bristerna i dagens bestämmelser. Det bör understrykas att de flesta av dessa studier har försummat de osäkerheter som är involverade, vilket hindrar de rapporterade resultaten från att representera en fullständig bild av problemet. I detta avseende syftar denna avhandling till att utvärdera prestandan hos konventionella analysmetoder, särskilt de som rör körsäkerhet och passagerarkomfort, med hjälp av sannolikhetsmetoder. För att uppnå detta mål genomfördes en preliminär studie med första ordningens tillförlitlighetsnmetod för broar med kort/medellång spännvidd som passeras av tåg med ett brett hastighetsspektrum. Jämförelse av dessa resultat med motsvarande deterministiska respons visade att tillämpa en konstant säkerhetsfaktor för verifieringen av trafiksäkerhet inte garanterar att säkerhetsindexet kommer att vara identiskt för alla broar. Det visar också att de konventionella analysmetoderna resulterar i brottsannolikheter som är högre än målvärdena. Denna slutsats belyser behovet av att uppdatera analysmetoden för trafiksäkerhet. Det skulle emellertid vara viktigt att avgöra om trafiksäkerhet är det dominerande designkriteriet innan ytterligare analyser genomförs. Därför utfördes en stokastisk jämförelse mellan detta kriterium och kriteriet för passagerarkomfort. På grund av den betydande. analystiden för sådana beräkningar användes delmängdssimulering och Monte-Carlo (MC) simulering med metamodeller baserade på polynomisk kaosutvidgning. Båda metoderna visade sig fungera bra, med trafiksäkerhet som nästan alltid dominerade över gränsningstillståndet för passagerarkomfort. Därefter kombinerades klassificeringsbaserade metamodeller som stödvektormaskin och beslutsträd genom ensembletekniker, för att undersöka påverkan av jord-brointeraktion på den utvärderade tillförlitligheten gällande trafiksäkerhet. De erhållna resultaten visade en signifikant påverkan och betonade behovet av detaljerade undersökningar genom ytterligare studier. Slutligen genomfördes en tillförlitlighetsbaserad konstruktionsoptimering för att föreslå ett minimikrav på erforderlig bromassa per längdmeter och tröghetsmoment. Det är värt att nämna att metodens inre loop löstes med en MC-simulering med adaptivt tränade Kriging-metamodeller.

QC 20210910

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Crawley, P. D. "Risk and reliability assessment of multiple reservoir water supply headworks systems /." Title page, contents and synopsis only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phc911.pdf.

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16

Caycho-Rodríguez, Tomás, José M. Tomás, Miguel Barboza-Palomino, José Ventura-León, Miguel Gallegos, Mario Reyes-Bossio, and Lindsey W. Vilca. "Assessment of Fear of COVID-19 in Older Adults: Validation of the Fear of COVID-19 Scale." Springer, 2021. http://hdl.handle.net/10757/655711.

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There is no information in Peru on the prevalence of mental health problems associated with COVID-19 in older adults. In this sense, the aim of the study was to gather evidence on the factor structure, criterion-related validity, and reliability of the Spanish version of the Fear of COVID-19 Scale (FCV-19S) in this population. The participants were 400 older adults (mean age = 68.04, SD = 6.41), who were administered the Fear of COVID-19 Scale, Revised Mental Health Inventory-5, Patient Health Questionnaire-2 items, and Generalized Anxiety Disorder Scale 2 items. Structural equation models were estimated, specifically confirmatory factor analysis (CFA), bifactor CFA, and structural models with latent variables (SEM). Internal consistency was estimated with composite reliability indexes (CRI) and omega coefficients. A bifactor model with both a general factor underlying all items plus a specific factor underlying items 1, 2, 4, and 5 representing the emotional response to COVID better represents the factor structure of the scale. This structure had adequate fit and good reliability, and additionally fear of COVID had a large effect on mental health. In general, women had more fear than men, having more information on COVID was associated to more fear, while having family or friends affected by COVID did not related to fear of the virus. The Spanish version of the Fear of COVID-19 Scale presents evidence of validity and reliability to assess fear of COVID-19 in the Peruvian older adult population.

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Shmerling, Robert Zachary. "STRUCTURAL CONDITION ASSESSMENT OF PRESTRESSED CONCRETE TRANSIT GUIDEWAYS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3529.

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Objective condition assessment is essential to make better decisions for safety and serviceability of existing civil infrastructure systems. This study explores the condition of an existing transit guideway system that has been in service for thirty-five years. The structural system is composed of six-span continuous prestressed concrete bridge segments. The overall transit system incorporates a number of continuous bridges which share common design details, geometries, and loading conditions. The original analysis is based on certain simplifying assumptions such as rigid behavior over supports and simplified tendon/concrete/steel plate interaction. The current objective is to conduct a representative study for a more accurate understanding of the structural system and its behavior. The scope of the study is to generate finite element models (FEMs) to be used in static and dynamic parameter sensitivity studies, as well load rating and reliability analysis of the structure. The FEMs are used for eigenvalue analysis and simulations. Parameter sensitivity studies consider the effect of changing critical parameters, including material properties, prestress loss, and boundary and continuity conditions, on the static and dynamic structural response. Load ratings are developed using an American Association for State Highway Transportation Officials Load and Resistance Factor Rating (AASHTO LRFR) approach. The reliability of the structural system is evaluated based on the data obtained from various finite element models. Recommendations for experimental validation of the FEM are presented. This study is expected to provide information to make better decisions for operations, maintenance and safety requirements; to be a benchmark for future studies, to establish a procedure and methodology for structural condition assessment, and to contribute to the general research body of knowledge in condition assessment and structural health monitoring.
M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering

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18

Elerath, Jon Garrett. "Reliability model and assessment of redundant arrays of inexpensive disks (RAID) incorporating latent defects and non-homogeneous Poisson process events." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6733.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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19

Andrews, Curtis Kyo-shin. "Validity and Reliability of Peer Assessment Rating Index Scores of Digital and Plaster Models." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1208136018.

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20

Mukhametzianova, Leisan. "Vliv lidského činitele na bezpečnost průmyslových pecí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399208.

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The presented doctoral thesis is focused on assessment of human factor impact on safety of industrial furnaces. Industrial furnaces are classified as machinery and belong to a group of industrial thermal equipment. The operation of industrial furnaces is burdened with the risks which the manufacturers and the furnace operators realize. The first part of the thesis presents an analysis of the current situation of legislation and scientific knowledges in the field of assessment of human factor impact on safety of industrial furnaces. In this part of the thesis the issue of human factor in other industrial branches: chemical industry, aviation and nuclear industry is also described. On the basis of conducted research the main aim of the thesis was established: preparation of a methodology for assessment of human factor impact on safety of industrial furnaces. Secondary targets were also listed. The second part deals with the assessment of risks connected with the operation of industrial furnaces and the assessment of human factor impact on safety of industrial furnaces. The furnace safety requirements, the process of furnaces risk assessment, the methods used for risk assessment and problems connected with the risk assessment are described. This part of the thesis explains the concept of human factor, presents a classification and description of the methods used for human reliability assessment, as well as the factors influencing the reliability of the operator. The third part of the thesis contains a proposed methodology for assessment of human factor impact on safety of industrial furnaces. Within the methodology performance shaping factors are stated, qualitative and quantitative assessment of human factor impact on safety of industrial furnaces is made and the system integration of the knowledges into the developed methodology is proposed – qualitative model for improvement of system state. The methodology is further verified on a real equipment – a hardening furnace.

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Du, Plessis Minette. "The validity and reliability of the General Child Assessment model as pre-forensic screening instrument for children between three and five years old." Thesis, North-West University, 2012. http://hdl.handle.net/10394/9013.

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The forensic assessment of young children is a difficult and often daunting task for professionals working in the field of child sexual abuse. A forensic assessment with pre-school children requires that the professional have knowledge of various aspects of the children themselves and the disclosure of abuse, and remain as neutral and objective as possible while conducting the assessment. Literature indicates that the knowledge of the child’s social, behavioural and developmental level is essential in order to conduct a developmental sensitive forensic interview. Although the term “pre-forensic screening” is relatively new in the field of forensics, Hewitt (1999) and Carnes (2006) refer to “pre-screening” and “developmental, behavioural and social assessment”, respectively. The study examined the usefulness of the General Child Assessment Model as a pre-forensic screening technique specifically for children aged 3-5 years. The researcher adopted a qualitative approach to explore the usefulness of the General Child Assessment Model as a pre-forensic screening instrument with professionals working in the clinical as well as forensic field. Seven semi-structured interviews were conducted with professionals trained in the general child assessment model. The interviews focused on the professionals’ use of the model in general, the value they attached to the model, its usefulness as a pre-forensic screening instrument with children aged 3-5 years, strengths and limitations of the model as a pre-forensic screening instrument, and practical recommendations for using the model in the forensic context. The data from the semi-structured interviews was analysed and divided into themes and subthemes, which were further described and linked with relevant literature .It became clear that the use of this assessment model had value in the therapeutic as well as forensic context. The model was described as an important and valuable part of the forensic process as it provides a holistic view of the child in context. The strengths and limitations of the model as a pre-forensic screening instrument were also explored and the participants made practical recommendations to optimise the use of the model as a pre-forensic screening instrument. In addition, a case study was used to evaluate the model as a pre-forensic screening instrument.
Thesis (MSW (Forensic Practice))--North-West University, Potchefstroom Campus, 2013.

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Schaefer, Sandra M. "An Assessment of Methods for Testing the Reliability of Wildlife Occurrence Models Used in Gap Analysis." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/SchaeferSM2002.pdf.

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23

Zhao, Xiaoyun. "Road network and GPS tracking with data processing and quality assessment." Licentiate thesis, Högskolan Dalarna, Mikrodataanalys, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:du-17354.

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GPS technology has been embedded into portable, low-cost electronic devices nowadays to track the movements of mobile objects. This implication has greatly impacted the transportation field by creating a novel and rich source of traffic data on the road network. Although the promise offered by GPS devices to overcome problems like underreporting, respondent fatigue, inaccuracies and other human errors in data collection is significant; the technology is still relatively new that it raises many issues for potential users. These issues tend to revolve around the following areas: reliability, data processing and the related application. This thesis aims to study the GPS tracking form the methodological, technical and practical aspects. It first evaluates the reliability of GPS based traffic data based on data from an experiment containing three different traffic modes (car, bike and bus) traveling along the road network. It then outline the general procedure for processing GPS tracking data and discuss related issues that are uncovered by using real-world GPS tracking data of 316 cars. Thirdly, it investigates the influence of road network density in finding optimal location for enhancing travel efficiency and decreasing travel cost. The results show that the geographical positioning is reliable. Velocity is slightly underestimated, whereas altitude measurements are unreliable.Post processing techniques with auxiliary information is found necessary and important when solving the inaccuracy of GPS data. The densities of the road network influence the finding of optimal locations. The influence will stabilize at a certain level and do not deteriorate when the node density is higher.

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24

Sims, Maureen Estelle. "Rubric Rating with MFRM vs. Randomly Distributed Comparative Judgment: A Comparison of Two Approaches to Second-Language Writing Assessment." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7312.

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The purpose of this study is to explore a potentially more practical approach to direct writing assessment using computer algorithms. Traditional rubric rating (RR) is a common yet highly resource-intensive evaluation practice when performed reliably. This study compared the traditional rubric model of ESL writing assessment and many-facet Rasch modeling (MFRM) to comparative judgment (CJ), the new approach, which shows promising results in terms of reliability and validity. We employed two groups of raters<&hyphen>”novice and experienced<&hyphen>”and used essays that had been previously double-rated, analyzed with MFRM, and selected with fit statistics. We compared the results of the novice and experienced groups against the initial ratings using raw scores, MFRM, and a modern form of CJ<&hyphen>”randomly distributed comparative judgment (RDCJ). Results showed that the CJ approach, though not appropriate for all contexts, can be valid and as reliable as RR while requiring less time to generate procedures, train and norm raters, and rate the essays. Additionally, the CJ approach is more easily transferable to novel assessment tasks while still providing context-specific scores. Results from this study will not only inform future studies but can help guide ESL programs to determine which rating model best suits their specific needs.

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CALLOU, Gustavo Rau de Almeida. "Assessment to support the planning of sustainable data centers with high availability." Universidade Federal de Pernambuco, 2013. https://repositorio.ufpe.br/handle/123456789/12262.

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The advent of services such as cloud computing, social networks and e-commerce has led to an increased demand for computer resources from data centers. Prominent issues for data center designers are sustainability, cost, and dependability, which are significantly affected by the redundant architectures required to support these services. Within this context, models are important tools for designers when attempting to quantify these issues before implementing the final architecture. This thesis proposes a set of models for the integrated quantification of the sustainability impact, cost, and dependability of data center power and cooling infrastructures. This is achieved with the support of an evaluation environment which is composed of ASTRO, Mercury and Optimization tools. The approach taken to perform the system dependability evaluation employs a hybrid modeling strategy which recognizes the advantages of both stochastic Petri nets and reliability block diagrams. Besides that, a model is proposed to verify that the energy flow does not exceed the maximum power capacity that each component can provide (considering electrical devices) or extract (assuming cooling equipment). Additionally, an optimization method is proposed for improving the results obtained by Reliability Block Diagrams, Stochastic Petri nets and Energy Flow models through the automatic selection of the appropriate devices from a list of candidate components. This list corresponds to a set of alternative components that may compose the data center architecture. Several case studies are presented that analyze the environmental impact and dependability metrics as well as the operational energy cost of real-world data center power and cooling architectures.
Submitted by João Arthur Martins (joao.arthur@ufpe.br) on 2015-03-12T18:54:10Z No. of bitstreams: 2 Tese Gustavo Callou.pdf: 4626749 bytes, checksum: 336a34ffc39f6ac623fa1144de2a66bf (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5)
Made available in DSpace on 2015-03-12T18:54:10Z (GMT). No. of bitstreams: 2 Tese Gustavo Callou.pdf: 4626749 bytes, checksum: 336a34ffc39f6ac623fa1144de2a66bf (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013-11-12
O surgimento de servi¸cos como computa¸c˜ao nas nuvens, redes sociais e com´ercio eletrˆonico tem aumentado a demanda por recursos computacionais dos data centers. Preocupa¸c˜oes decorrentes para os projetistas de data center s˜ao sustentabilidade, custo, e dependabilidade, os quais s˜ao significativamente afetados pelas arquiteturas redundantes requeridas para suportar tais servi¸cos. Nesse contexto, modelos s˜ao ferramentas importantes para projetistas quanto a tentativa de quantificar esses problemas antes mesmo de implementar a arquitetura final. Nessa tese, um conjunto de modelos ´e proposto para a quantifica¸c˜ao integrada do impacto na sustentabilidade, custo e dependabilidade das infraestruturas de refrigeramento e potˆencia de data centers. Isso ´e obtido com o suporte do ambiente de avalia¸c˜ao que ´e composto pelas ferramentas ASTRO, Mercury e o m´odulo de otimiza¸c˜ao. A avalia¸c˜ao de dependabilidade faz uso de uma estrat´egia de modelagem h´ıbrida que usa as vantagens tanto das redes de Petri estoc´asticas como dos diagramas de blocos de confiabilidade. Al´em disso, um modelo ´e proposto para realizar a verifica¸c˜ao se fluxo de energia n˜ao excede a capacidade m´axima de potˆencia que cada equipamento pode prover (considerando dispositivos el´etricos) ou extrair (assumindo equipamentos de refrigera¸c˜ao). Adicionalmente, um m´etodo de otimiza¸c˜ao ´e proposto para melhorar os resultados obtidos atrav´es dos diagramas de blocos de confiabilidade, das redes de Petri estoc´asticas e do modelo de fluxo de energia pela sele¸c˜ao autom´atica dos dispositivos apropriados a partir da lista de componentes candidatos. Essa lista corrresponde a um conjunto de componentes que podem ser utilizados para compor a arquitetura de data center. V´arios estudos de casos s˜ao apresentados para analisar o impacto ambiental, a dependabilidade e o custo operacional de energia el´etrica de arquiteturas reais de potˆencia e refrigera¸c˜ao de data centers.

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Neluheni, Tshililo Sedney. "Exploring quality and assessment models for English first additional language in Grade 10." Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/27630.

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This research aimed at exploring the quality assurance and assessment models used for English First Additional language (EFAL) in the Further Education and Training (FET) band especially in Grade 10. It examined various quality assurance models used by grade 10 educators in designing the assessment tasks, with specific reference to EFAL. This study adopted the industry based SABS ISO 9004-2 conceptual framework. This conceptual framework ensures that the task to be performed and the objectives to be achieved are clearly spelt out, including how they affect quality. A qualitative research approach was used, specifically a case study. Convenient sampling was used to select the three participant of this study, namely; two EFAL educators and one Head of Department (HoD). Data was collected through semi-structured interviews, document analysis and research journal, and triangulated to support the conclusion and to make the findings more reliable. The main research question of the study was: To what extent do English First Additional Language (EFAL) educators employ quality assurance measures in their assessment. In order to fully explore the quality assurance measures employed in EFAL assessment tasks, four sub- research questions were envisaged in this study. The following themes emerged from the data collected: assessment of EFAL, quality of the assessment tasks, assessment challenges as well as internal moderation. With regard to assessment of EFAL the results of the study indicated that educators have minimal level of skill to construct high quality assessment tasks due to poor understanding of OBA and the terminology associated with OBA. As a result, they resorted to prescribed portfolio assessment tasks as dominant form of assessment. The study also found that the quality of such assessment tasks is below the expected standard as Learning Outcomes and Assessment Standards are the major quality assurance measures utilized. Furthermore the study revealed that challenges such as overcrowding and shortage of learner support material are the inhibiting factors towards development and implementation of quality assessment tasks. The study further revealed that moderation of those Grade 10 portfolio assessment tasks which occur at school level by the HoD, focused mainly on the accuracy of mark transfer from the learner’s script to the mark sheets rather than on the quality of the assessment task. The study further revealed a corroboration of concepts used in the conceptual framework based on the SABS ISO 9004-2, as educators do not have acceptable level of establishing quality structure or measures for effective control, evaluation and improvement of service quality throughout all stages of learning and assessment. The difficulty was attributed to educator’s lack of knowledge with regard quality assurance mechanisms, assessment and the terminology associated with Outcomes Based Assessment. Copyright
Dissertation (MEd)--University of Pretoria, 2011.
Science, Mathematics and Technology Education
unrestricted

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27

Xu, Changyi. "Operational dependability model generation." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI129.

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L'objectif à long terme des ingénieurs et des chercheurs est d'évaluer la fiabilité des systèmes industriels complexes. Les évaluations de la sécurité fondées sur des modèles effectuées ces dernières années, en particulier les études d'analyse structurelle et de modélisation des composants, fournissent des méthodes pratiques d'évaluation de la fiabilité,Toutefois, l'absence d'un cadre permettant d'évaluer simultanément la structure et les comportements des différents éléments d'un modèle unifié n'a pas permis d'obtenir d'excellentes évaluations. En outre, les opérations du système n'étant pas pris en compte dans le modèle, il n'est pas possible d'évaluer la qualité et la quantité du service en termes de fiabilité du opérations. Cette invention concerne un procédé de génération de modèle formalisé qui permet d 'évaluer la fiabilité du fonctionnement du système en tenant compte de sa structure, de ses divers comportements et de ses opérations. La composition du modèle de composant est introduite pour générer un modèle global du système. Afin de tenir pleinement compte de la structure du système, l 'état total de défaillance du système est déterminé sur la base de l' expression de défaillance obtenue. Sur le plan qualitatif, la fiabilité opérationnelle est encore renforcée par l'application des spécifications de trajectoire.Et, Sur le plan quantitif, il est renforcée par la mise au point d'une technique d'évaluation des coûts appelée arbre de calcul de capacité. Enfin, l'exemple d'un système industriel illustre l'énorme potentiel qu'offre l'étude pour garantir la fiabilité des services fournis par les systèmes industriels complexes
Assessing complex industrial systems to be on dependable service is what the engineers and researchers have long been aiming for. Recent advanced researches in the Model-based safety assessment, especially the Structre Analysis and Component Modeling, provide the practicable methodologies to assess the dependability, yet a lack of the framework which is able to assess both the structure and the various behaviors of the components in one uniformed model retains them to achieve the excellent assessment. Moreover, as the system’s operations are not considerable in the models, the service in the aspect of operational dependability is not able to be assessed both in quality and in quantity. Although several existing assessment tools have already show their potential to model the various behaviors in the form of n-state models or consider the operations as repair priority to be event sequence in the model, fusing ‘structure’, ‘various behaviors’ and ‘operations’ is still a challenge, highlighting a need for one viable framework that bridge the gap among them both by quality or quantity. In this research, a formal model generation approach is studied to bridge this gap, which is able to assess the system operatinal dependability by considering the system structure, various behaviors, and operations. Here, the composition of the component models is introduced in order to generate a global model of the system, the total breakdown states are identified according to the resulted failure expression for the purpose to fully consider the system’s structure, and the operational dependability is further realized by quality by applying the trajectory specifications, while by quantity by developing a cost evaluating technology termed Capacity Calculation Fault Tree. In the end, a demonstration of a miniplant system illustrates the wide potential of this research for guaranteeing the dependable service of complex industrial systems

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Yajima, Ayako. "Assessment of Soil Corrosion in Underground Pipelines via Statistical Inference." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1435602696.

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Wallnerström, Carl Johan. "On Risk Management of Electrical Distribution Systems and the Impact of Regulations." Licentiate thesis, KTH, Electromagnetic Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4717.

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The Swedish electricity market was de-regulated in 1996, followed by new laws and a new regulation applied to the natural monopolies of electrical distribution systems (EDS). These circumstances have motivated distribution systems operators (DSOs) to introduce more comprehensive analysis methods. The laws, the regulation and additional incentives have been investigated within this work and results from this study can be valuable when developing risk methods or other quantitative methods applied to EDS. This tendency is not unique for Sweden, the results from a comparative study of customer outage compensation laws between Sweden and UK is for example included.

As a part of investigating these incentives, studies of the Swedish regulation of customer network tariffs have been performed which provide valuable learning when developing regulation models in different countries. The Swedish regulatory model, referred to as the Network Performance Assessment Model (NPAM), was created for one of the first de-regulated electricity markets in the world and has a unique and novel approach. For the first time, an overall presentation of the NPAM has been performed including description of the underlying theory as a part of this work. However, the model has been met by difficulties and the future usage of the model is uncertain. Furthermore, the robustness of the NPAM has been evaluated in two studies with the main conclusion that the NPAM is sensitive toward small variations in input data. Results from these studies are explained theoretically investigating algorithms of the NPAM.

A pre-study of a project on developing international test systems is presented and this ongoing project aims to be a useful input when developing risk methods. An application study is included with the approach to systematically describe the overall risk management process at a DSO including an evaluation and ideas of future developments. The main objective is to support DSOs in the development of risk management, and to give academic reference material to utilize industry experience. An idea of a risk management classification has been concluded from this application study. The study provides an input to the final objective of a quantitative risk method.

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Cuxart, i. Jardí Anna. "Models estadístics en avaluació educativa: les proves d'accés a la universitat." Doctoral thesis, Universitat Politècnica de Catalunya, 1998. http://hdl.handle.net/10803/6528.

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La tesis se inscribe en un doble ámbito científico formado por la Estadística y la Pedagogía. El objetivo de la tesis es la investigación de modelos estadísticos y estrategias de análisis que puedan ser de utilidad en el seguimiento de sistemas de evaluación complejos. Su motivación se encuentra en la necesidad de analizar las Pruebas de Aptitud para el Acceso a la Universidad (PAAU), que regulan el acceso a la universidad en España, desde la perspectiva de la ciencia estadística. La validez y fiabilidad de los exámenes COU (Curso de Orientación Universitaria) y PAAU han merecido una atención especial a lo largo de la investigación. Asimismo, se analizan con detenimiento las principales fuentes de variación de dichas notas: las diferencias entre centros de secundaria y el proceso de corrección de las pruebas PAAU.
En la Introducción, una vez resumidas las características del sistema de evaluación de las pruebas PAAU y discutido el papel de la estadística en el tratamiento de datos en educación, se establecen los objetivos concretos de la tesis, a la luz de las necesidades existentes y de los trabajos de investigación realizados hasta el momento.
El Capítulo 1 ilustra las diferencias entre los exámenes COU y las pruebas PAAU. Se aborda el estudio de la asociación entre ambas puntuaciones. La modelización de la variación de la nota PAAU individual por medio de modelos de regresión coeficientes aleatorios permite evidenciar (y medir) las diferencias entre centros de secundaria en cuanto a los estándares utilizados en COU. Este primer capítulo contiene una detallada introducción a los modelos de coeficientes aleatorios, también llamados modelos de nivel múltiple, que posteriormente se aplicaran en los capítulos 2 y 4, en la versión de modelos multivariantes de componentes de la varianza. El segundo capitulo, en un enfoque que complementa el anterior, se centra en el estudio de las medias (de COU y de PAAU) de cada centro, en la estructura de covarianza entre ambas. Como resultado relevante cabe citar la aplicación a la selección de la combinación más eficiente.
El Capítulo 3 se ha dedicado enteramente a la calidad del sistema de corrección de los exámenes PAAU. La modelización presentada ha permitido evaluar el impacto de los correctores en términos de la varianza debida a las diferencias en el grado de severidad y a la varianza generada por la inconsistencia. Para la obtención de los datos se ha requerido del diseño de experimentos. Dichos experimentos, que han evidenciado una serie de puntos débiles del sistema, deberían ser realizados de manera sistemática cada año en una estrategia de mejora de la calidad del proceso.
El Capítulo 4 estudia la covarianza del conjunto de notas PAAU tanto a nivel estudiante como a nivel centro, ofreciendo nuevos elementos de reflexión para la validez de dichas pruebas.
El Capítulo 5 resume la aplicación de varias propuestas de la tesis a la primera convocatoria de las pruebas PAAU-LOGSE.
El Capítulo 6 incluye las conclusiones de la tesis así como una serie de propuestas de seguimiento y mejora de la calidad global del sistema.

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Pllana, Drilon, and Fredrik Lohman. "Självutvärderingsverktyget språngbrädan : En mixad studie om verktygets aktualitet inom offensiv kvalitetsutveckling." Thesis, Mittuniversitetet, Institutionen för kvalitets- och maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-38811.

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Det primära syftet med studien var att undersöka hur ett medelstort företag upplever självutvärderingsverktyget språngbrädan. Syftet var också att bidra med kunskap om forskningsläget kring språngbrädan. En mixad metod användes där datainsamlingen genomfördes genom en enkät på ett urval av företaget. Första delen av enkäten utgjorde en lättversion av språngbrädan som användes för självutvärdering av verksamheten, därigenom fick respondenterna uppleva verktyget. Andra delen av enkäten utgjorde en utvärdering av hur språngbrädan upplevs, med både skalfrågor och öppna frågor. Resultatet visar att en övervägande del är positiva till språngbrädan och kan tänka sig fortsätta använda verktyget. En övervägande del är neutrala i frågan huruvida språngbrädan behöver utvecklas och anpassas efter den egna verksamheten, och huruvida det finns fördelar och nackdelar. Resultatet visar också att språngbrädan är väldigt outforskat där endast en vetenskaplig artikel identifierades. Slutsatsen är att det behövs fler studier där deltagarna informeras om arbetssättet självutvärdering
The primary purpose of the study was to investigate how a medium-sized company experiences the self-assessment tool - the springboard. The purpose was also to contribute with knowledge about the research that has been conducted on the springboard. A mixed method was used where the data collection was conducted on a sample of the company's operations through a survey. The first part of the survey constituted a light version of the springboard that was used for self-assessment of the business, thereby letting the respondents experience the tool. The second part of the survey was an evaluation of how the tool is experienced, with both rating questions and open questions. The result shows that the majority is positive to the springboard and can imagine continuing to use the tool. A majority is neutral to the question of whether the springboard needs to be developed and adapted to its own business, and whether there are advantages and disadvantages. The result also shows that the springboard is very unexplored where only one scientific article was identified. The conclusion is that more studies are needed, where the participants are informed about the method of self-assessment and about the tool prior to the study, in order to obtain more comprehensive data.

2019-06-27

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32

Cross, Richard J. (Richard John). "Inference and Updating of Probabilistic Structural Life Prediction Models." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19828.

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Aerospace design requirements mandate acceptable levels of structural failure risk. Probabilistic fatigue models enable estimation of the likelihood of fatigue failure. A key step in the development of these models is the accurate inference of the probability distributions for dominant parameters. Since data sets for these inferences are of limited size, the fatigue model parameter distributions are themselves uncertain. A hierarchical Bayesian approach is adopted to account for the uncertainties in both the parameters and their distribution. Variables specifying the distribution of the fatigue model parameters are cast as hyperparameters whose uncertainty is modeled with a hyperprior distribution. Bayes' rule is used to determine the posterior hyperparameter distribution, given available data, thus specifying the probabilistic model. The Bayesian formulation provides an additional advantage by allowing the posterior distribution to be updated as new data becomes available through inspections. By updating the probabilistic model, uncertainty in the hyperparameters can be reduced, and the appropriate level of conservatism can be achieved. In this work, techniques for Bayesian inference and updating of probabilistic fatigue models for metallic components are developed. Both safe-life and damage-tolerant methods are considered. Uncertainty in damage rates, crack growth behavior, damage, and initial flaws are quantified. Efficient computational techniques are developed to perform the inference and updating analyses. The developed capabilities are demonstrated through a series of case studies.

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Silva, Monia Aparecida da. "Construção e estudo de evidências de validade e fidedignidade do inventário dimensional de avaliação do desenvolvimento infantil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/173315.

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Анотація:

A prevalência de crianças com atrasos no desenvolvimento em um ou mais domínios varia entre 16 e 18% na literatura, mas estima-se que apenas 30% dos casos são detectados pelos profissionais de saúde. Em parte, este déficit na detecção se deve à falta de utilização de instrumentos de avaliação ou rastreio. No contexto brasileiro são poucos os instrumentos disponíveis para avaliar desenvolvimento infantil e, além disso, os que existem apresentam limitações. A presente tese teve como objetivo construir o Inventário Dimensional de Avaliação do Desenvolvimento Infantil (IDADI) para avaliação de crianças de zero a 72 meses com base no relato parental. Para a construção do IDADI, foram realizados três estudos. O Estudo I consistiu em uma revisão sistemática da literatura para identificar os instrumentos mais utilizados na avaliação dos marcos do desenvolvimento infantil e suas propriedades psicométricas. Ele forneceu as bases para a seleção dos domínios que integram o IDADI e para a construção de itens. O Estudo II realizou os procedimentos teóricos e metodológicos de construção do IDADI e a análise de evidências de validade de conteúdo. O Estudo III analisou as evidências de validade da estrutura interna do IDADI, a fidedignidade e as evidências de validade baseadas na relação com variáveis critério. Foram utilizados pressupostos da Teoria Clássica dos Testes e da psicometria moderna com a aplicação do modelo de Rasch. O processo de construção foi guiado com o rigor teórico e metodológico indicado pela literatura e apresentou evidências favoráveis de validade de conteúdo. Também foram comprovadas evidências de validade baseadas na estrutura interna, na relação com variáveis critério e de fidedignidade. Estes resultados fortalecem o potencial do IDADI para avaliação multidimensional do desenvolvimento infantil no contexto brasileiro, tanto na clínica como na pesquisa. Estudos futuros serão realizados para elaboração de normas de interpretação, de um inventário breve para utilização em programas de atenção infantil e de uma versão de tarefas para avaliação direta da criança.
The prevalence of children with developmental delays in one or more domains varies between 16 and 18% according to the literature, but it is estimated that only 30% of cases are detected by health professionals. In part, this deficit in detection is due to the lack of use of assessment or screening instruments. In the Brazilian context, there are few instruments available to evaluate child development, and, in addition, those that exist have some limitations. The purpose of this dissertation was to construct the Dimensional Inventory of Child Development Assessment (IDADI) to evaluate children from zero to 72 months based on parental report. For the construction of IDADI, three studies were carried out. Study I consisted of a systematic review of the literature to identify the most used instruments in assessing child developmental milestones and their psychometric properties. It has provided the basis for the selection of the domains that integrate IDADI and for the items construction. Study II have performed the theoretical and methodological procedures for the construction of IDADI and the analysis of content validity evidences. Study III have analyzed the evidences of validity for the internal structure of IDADI, reliability and validity evidences based on the relation with criterion variables. We used the assumptions of the Classical Test Theory and modern psychometric methods with the application of the Rasch model. The construction process was guided with theoretical and methodological rigor indicated by the literature and has demonstrated favorable evidences of content validity. Evidences of validity based on internal structure, criterion-related validity and reliability were established. These results reinforce the potential of IDADI for multidimensional assessment of child development in the Brazilian context, both in clinical and research contexts. Future studies will be conducted to stablish norms for interpretation, to create a short version for use in child care programs and a child direct assessment version including developmental tasks.

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34

Kaya, Deniz. "Software Reliability Assessment." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606466/index.pdf.

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Анотація:

In spite of the fact that software reliability studies have attracted great deal of attention from different disciplines in 1970s, applications of the subject have rarely been involved in the software industry. With the rise of technological advances especially in the military electronics field, reliability of software systems gained importance. In this study, a company in the defense industries is inspected for their abilities and needs regarding software reliability, and an improvement proposal with metrics measurement system is formed. A computer tool is developed for the evaluation of the performance of the improvement proposal. Results obtained via this tool indicate improved abilities in the development of reliable software products.

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35

Руденко, Александр Антонович. "Вероятностные модели и методы оценивания надежности программных средств с учетом вторичных дефектов". Thesis, Полтавский национальный технический университет им. Ю. Кондратюка, 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/19065.

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Анотація:

Диссертация на соискание ученой степени кандидата технических наук по специальности 05.13.06 – информационные технологии – Национальный технический университет "Харьковский политехнический институт", Харьков, 2015. Диссертация посвящена разработке моделей, методов оценки надежности программно-технических комплексов, информационной технологии на основе учета внесения вторичных дефектов. Как показывает проведенный анализ, необходимость обеспечения точности оценки надежности программного обеспечения обуславливает актуальность научных исследований, посвященных разработке и совершенствованию методов и моделей оценки. В существующих моделях оценки надежности не учитывается фактор вторичных дефектов или этому аспекту не уделяется внимание вообще. Это может привести, с одной стороны, к неэффективному применению и распределению методов и средств повышения надежности, а с другой, к недооценке рисков, связанных с возникновением отказов. Усовершенствованы вероятностные модели оценки надежности программных средств на основе учета параметров вторичных дефектов, путем модификаций функций риска этих моделей, что позволяет адекватно отображать процессы тестирования и сопровождения программных средств. В рамках исследования был проведен анализ классификаций моделей, анализ вероятностных моделей повышения надежности на предмет возможности их модификаций с тем, чтобы учитывать вторичные дефекты. Наиболее целесообразно в контексте поставленной задачи использовать модель Джелински-Моранды. Разработан метод оценивания числа вторичных дефектов программных средств, основанный на анализе статистических данных проявления первичных дефектов программных средств, что позволяет повысить точность количественных оценок эксплуатационных показателей. Потребность в разработке метода вызвана трудностями аналитического нахождения вторичных дефектов на основе моделей оценки надежности программных средств. В методе оценивания числа вторичных дефектов по статистическим данным выявления дефектов учитываются факторы раннего и поздних этапов тестирования (эксплуатации), что соответствует реалиям соответствующих этапов жизненного цикла программ.
The dissertation on obtaining the scientific degree of candidate of technical sciences in the specialty 05.13.06 – information technologies – National technical University "Kharkiv Polytechnic Institute", Kharkov, 2015. The dissertation dedicated to the developing of models, methods of reliability estimation of software-technical complexes of information technology on the basis of making secondary defects. Scientific results are: improving probabilistic models of reliability estimation of software based on the parameters of secondary defects by modifying the risk function of these models that allows to reflect processes of testing and maintenance of software; method of estimating secondary defects of software tools that is based on the analysis of statistical data of manifestation of primary defects of software tools that allows to raise the accuracy of the quantitative assessment of performance indicators; the method of calculating the average intensity of manifestation of defects and the average change in the intensity of manifestation of defects with the help of modified model Jelinski-Moranda that, unlike existing, takes into account factor of secondary defects that allows to verify the reliability of software tools. Information technology of assessment the secure of software tools taking into account the secondary defects is devised basing on the method of estimating the number of secondary defects according to the statistics of defect detection and the method of calculating the average intensity of manifestation of defects and the average change in the intensity of manifestation of defects. The proposed models and methods allow to raise the accuracy of estimation of reliability of software and hardware complexes that is achieved by taking into account the factor of secondary defects.

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36

Mafu, Masakheke. "Reliability analysis: assessment of hardware and human reliability." Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/6280.

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Анотація:

Most reliability analyses involve the analysis of binary data. Practitioners in the field of reliability place great emphasis on analysing the time periods over which items or systems function (failure time analyses), which make use of different statistical models. This study intends to introduce, review and investigate four statistical models for modeling failure times of non-repairable items, and to utilise a Bayesian methodology to achieve this. The exponential, Rayleigh, gamma and Weibull distributions will be considered. The performance of the two non-informative priors will be investigated. An application of two failure time distributions will be carried out. To meet these objectives, the failure rate and the reliability functions of failure time distributions are calculated. Two non-informative priors, the Jeffreys prior and the general divergence prior, and the corresponding posteriors are derived for each distribution. Simulation studies for each distribution are carried out, where the coverage rates and credible intervals lengths are calculated and the results of these are discussed. The gamma distribution and the Weibull distribution are applied to failure time data.The Jeffreys prior is found to have better coverage rate than the general divergence prior. The general divergence shows undercoverage when used with the Rayleigh distribution. The Jeffreys prior produces coverage rates that are conservative when used with the exponential distribution. These priors give, on average, the same average interval lengths and increase as the value of the parameter increases. Both priors perform similar when used with the gamma distribution and the Weibull distribution. A thorough discussion and review of human reliability analysis (HRA) techniques will be considered. Twenty human reliability analysis (HRA) techniques are discussed; providing a background, description and advantages and disadvantages for each. Case studies in the nuclear industry, railway industry, and aviation industry are presented to show the importance and applications of HRA. Human error has been shown to be the major contributor to system failure.

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Руденко, Олександр Антонович. "Імовірнісні моделі та методи оцінювання надійності програмних засобів з урахуванням вторинних дефектів". Thesis, ТОВ "Фірма "Техсервіс", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/19064.

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Анотація:

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.06 – інформаційні технології – Національний технічний університет "Харківський політехнічний інститут", Харків, 2015. Дисертація присвячена розробці моделей, методів оцінювання надійності програмно-технічних комплексів, інформаційної технології на основі врахування внесення вторинних дефектів. Науковими результатами є: удосконалення імовірнісних моделей оцінки надійності програмних засобів на основі врахування параметрів вторинних дефектів шляхом модифікації функцій ризику цих моделей, що дозволяє адекватно відображати процеси тестування і супроводу програмних засобів; метод оцінювання числа вторинних дефектів програмних засобів, що ґрунтується на аналізі статистичних даних прояву первинних дефектів програмних засобів, що дозволяє підвищити точність оцінок кількісних експлуатаційних показників; метод обчислення середньої інтенсивності прояву дефектів і середньої зміни інтенсивності прояву дефектів за допомогою модифікованої моделі Джелінські-Моранди, у якому, на відміну від існуючих, враховується фактор вторинних дефектів, що дозволяє верифікувати показники надійності програмних засобів. На основі методу оцінювання числа вторинних дефектів за статистичними даними виявлення дефектів та методу обчислення середньої інтенсивності прояву дефектів і середньої зміни інтенсивності прояву дефектів розроблена інформаційна технологія оцінювання надійності програмних засобів з урахуванням вторинних дефектів. Запропоновані моделі і методи дозволяють підвищити точність оцінювання надійності програмно-технічних комплексів, що досягається за рахунок урахування фактора вторинних дефектів.
The dissertation on obtaining the scientific degree of candidate of technical sciences in the specialty 05.13.06 – information technologies – National technical University "Kharkiv Polytechnic Institute", Kharkov, 2015. The dissertation dedicated to the developing of models, methods of reliability estimation of software-technical complexes of information technology on the basis of making secondary defects. Scientific results are: improving probabilistic models of reliability estimation of software based on the parameters of secondary defects by modifying the risk function of these models that allows to reflect processes of testing and maintenance of software; method of estimating secondary defects of software tools that is based on the analysis of statistical data of manifestation of primary defects of software tools that allows to raise the accuracy of the quantitative assessment of performance indicators; the method of calculating the average intensity of manifestation of defects and the average change in the intensity of manifestation of defects with the help of modified model Jelinski-Moranda that, unlike existing, takes into account factor of secondary defects that allows to verify the reliability of software tools. Information technology of assessment the secure of software tools taking into account the secondary defects is devised basing on the method of estimating the number of secondary defects according to the statistics of defect detection and the method of calculating the average intensity of manifestation of defects and the average change in the intensity of manifestation of defects. The proposed models and methods allow to raise the accuracy of estimation of reliability of software and hardware complexes that is achieved by taking into account the factor of secondary defects.

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38

Kartali, Csaba. "Posouzeni spolehlivosti procesu výroby průmyslových bezpečnostních přileb." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-432518.

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Анотація:

The theoretical part of this master thesis lists all the necessary prerequisites which are needed in order to carry out a full and comprehensive reliability assessment of any given process. To do so it provides an overview of reliability in general, mathematical and statistical guidance together with a more detailed picture of the application and description of the process by quantifiable indicators. Furthermore it gives an overview of two important analysis tools, such as FTA and FMEA, accompanied by the basic principle and summary of the Six Sigma methodology and tools. The practical part of the thesis deals with the detailed description, quantification and goals of the process of safety helmet manufacturing and testing in order to be able to carry out a suitable assessment of the reliability by using the necessary set of tools and methods in order to identify the failures and their causes in the process by addressing them with suitable means of changes and corrective actions.

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39

Pizzo, Walter Nogueira. "Avaliação da disponibilidade de sistemas computacionais críticos para o controle do espaço aéreo por meio de modelo analítico da teoria de filas." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-02102008-174430/.

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Анотація:

O transporte aéreo e a indústria de sistemas de defesa foram setores pioneiros na utilização de sistemas computacionais críticos, incrementando os níveis de automação nas atividades de controle do espaço aéreo. Com o crescimento desses setores, verificado pela expansão dos números de vôos, volumes de cargas e usuários, assim como pela ampliação e diversidade das operações militares, os sistemas de controle têm assumido maior complexidade técnica, introduzindo novos recursos de automação ou facilidades adicionais de apoio para funções exercidas manualmente. Essa situação tem ampliado a dependência dos serviços prestados, relativamente à disponibilidade dos sistemas computacionais. Diretrizes de projeto e procedimentos operacionais são estabelecidos para manter os níveis de segurança nos casos de falha, no entanto a disponibilidade torna-se parâmetro crítico, na medida em que algumas falhas podem afetar a eficiência nominal da prestação dos serviços. Nesse cenário, este trabalho propõe um modelo para avaliação da disponibilidade de sistemas de controle do espaço aéreo, a partir de recursos de análises da teoria de filas. Inicialmente é citado um modelo geral para análise de disponibilidade de data centers. Em seguida, é apresentada uma extensão do modelo geral para análise da disponibilidade em sistemas de controle do espaço aéreo. Para isso, considerou-se a intervenção humana existente nessa atividade, cujas decisões de controle são exercidas por operadores qualificados (controladores), tanto nas atividades inerentes ao serviço de controle, quanto nos casos de degradação, nos quais os operadores ou técnicos de manutenção assumem alguma tarefa de reparo, decorrente da eventual indisponibilidade de funções do sistema.
Due to the growth in airspace utilization, which can be verified both in terms of the expansions in aerial movements, airports and volumes of transported passengers and cargo, as well as in terms of the expansion of military operations demands and diversity, airspace control activities have been increasing their technical complexity, introducing new features into the existent automation systems or creating additional resources for the automation of some functions previously performed by human operators. This situation has increased the dependence on the availability of the computer systems involved in the services provided by control centers. Project directives and operational procedures are established in order to maintain the safety integrity levels of the systems, in case any failure occurs. However, the availability becomes a critical parameter, once failure events can force an undesirable state of degraded operation, jeopardizing the nominal capacity of the services being performed through any controlled airspace. In this scenario, this work presents an availability model for the computer systems used in airspace control centers, based on analysis from queuing theory. A general model is first presented, referencing a case study that describes the use of queuing models to access the availability of generic data centers. Further considerations are introduced to extend this general model in order to propose its application for the specific computer systems used in airspace control centers, where operational control relies on human activities. In this case, system operation involves intensive use of human-machine interfaces (HMI), for the regular control services provided, and additional technical or operational maintenance activities, occasionally imposed to repair a momentary loss of any function of the system.

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40

Da, Silva Maria da Guia. "Reliability assessment of meshed distribution systems." Thesis, Cardiff University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493157.

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41

Stølen, Ellen Margrete. "RELIABILITY ASSESSMENT OF A SUBSEA HIPPS." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produksjons- og kvalitetsteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24545.

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Анотація:

Safety instrumented systems are vital in the oil and gas industry. A SIS consists of input elements, a logic solver and final elements. A High Integrity Pressure Protection System is an example of such a system. HIPPS is installed to protect a platform from too high pressure by shutting off the source before exceeding the design pressure. The IEC 61508 and IEC 61511 are used in the oil and gas industry during all phases of a SIS lifecycle. As a measure of SIS reliability, both standards use safety integrity level. The standards lists several requirements for both hardware and software. Compliance to the SIL must be demonstrated by quantitative assessments including estimations to the SIS reliability. Several models for reliability assessments are demonstrated in IEC 61508.A HIPPS is installed to perform a safety instrumented function (SIF) that is operated in low-demand mode and its availability must be quantified by using the average probability of failure on demand, PFDavg. Some methods used to determine the reliability of a SIS are Reliability Block Diagrams, approximation formulas and Markov modeling.Proof testing a HIPPS is an expensive process due to downtime and availability of the system. It is therefore suggested to perform partial stroke testing (PST) on these systems. PST is performed while the operation is online, so there is no need to stop the production. This type of testing will reveal some of the dangerous failures on a system at a lower test interval than a full function test of the system.

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42

Alali, Dawood. "Probabilistic reliability assessment of transmission systems." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/88271/.

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Анотація:

Power system reliability is defined as the ability of a power system to perform its function of maintaining supply without allowing network variables (e.g. voltage, component loading and frequency) to stray too far from the standard ranges. Traditionally over many decades, reliability has been assessed using deterministic criteria, e.g., ‘N-1’ or ‘N-2’ standards under prescribed severe system demand levels. However, using the so-called worst-case deterministic approach does not provide explicitly an assessment of the probability of failure of the component or system, and the likelihood of the outages is treated equally. On the other hand, a probabilistic security assessment may offer advantages by considering (i) a statistical description of the performance of the system together with (ii) the application of historical fault statistics that provide a measure of the probability of faults leading to component or system outages. The electrical transmission system, like other systems, is concerned with reducing different risks and costs to within acceptable limits. Therefore, a more precise algorithm of a probabilistic reliability assessment of electrical transmission systems offers an opportunity to achieve such efficiency. This research work introduces the concept of applying the Line Overloading Risk Index (LORI) to assess one of the risks to transmission systems, namely, line overloading. Line failure or outage due to line overloading is catastrophic; they may lead to either load interruptions or system blackout. Some recent studies have focused on the assessment of the LORI; however, such research has been restricted to the analysis of system with very few intermediate demand levels and an assumed constant line thermal rating. This research work aims to extend the evaluation of the LORI through a comprehensive evaluation of transmission system performance under hour-by-hour system demand levels over a oneyear period, for intact systems, as well as ‘N-1’, ‘N-2’. In addition, probable hourly line thermal ratings have also been evaluated and considered over an annual cycle based on detailed meteorological data. In order to accomplish a detailed analysis of the system reliability, engineering data and historical line fault and maintenance data in real transmission systems were employed. The proposed improved probabilistic reliability assessment method was evaluated using a software package, namely, NEPLAN, thus making it possible to simulate different probable load flow cases instead of assuming a single ‘worst case scenario’. An automated process function in NEPLAN was developed using an extensive programming code in order to expedite the load flow modelling, simulation and result reporting. The successful use of the automation process to create multiple models and apply different contingencies, has made possible this probabilistic study which would not have been possible using a ‘manual’ simulation process. When calculating the LORI, the development of a Probabilistic Distribution Function (PDF) for line loading, line thermal rating and system demand was essential and useful. The developed algorithm takes into consideration the likelihood of events occurring in addition to severity, which offers opportunity for more efficient planning and operation of transmission systems. Study cases performed on real electric transmission systems in Dubai and the GB have demonstrated that the developed algorithm has potential as a useful tool in system planning and operation. The research presented in this thesis offers an improved algorithm of probabilistic reliability assessment for transmission systems. The selected index, along with the developed algorithm, can be used to rank the transmission lines based on the probabilistic line overloading risk. It provides valuable information on the degree of line overloading vulnerability for different uncertainties.

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Mason, Haley Alissa. "Determining Reliability Of The PEAK Assessment Tool Using Split Half Reliability." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1789.

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Анотація:

The present study looked at the internal reliability of the PEAK Relational Training Assessment, using a split-half method of measurement. The reliability of the assessment questions within each of the four factors, within the PEAK Relational Training Assessment was estimated through this process. Eighteen participants, between the ages of 26 months and ten years old were included in the study. All participants had been diagnosed with either a language based or developmental disability, including autism, seizure disorder, Down syndrome and related language disorders. The PEAK Relational Training Assessment (PEAK-D) was administered by a direct-care provider for each of the 18 participants and during standard instructional periods. Results indicate that for each of the 18 participants, there was a strong correlation between scores when one half of the items in each factor were compared to the remaining half. Results did show internal reliability for the PEAK-D when using split-half methodology.

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Ed-Daoui, Ilyas. "Towards systems-of-systems structural resilience assessment Resilience assessment as a foundation for systems-of-systems safety evaluation : application to an economic infrastructure An approach to systems-of-systems structural analysis through interoperability assessment : application on Moroccan Case A study of an adaptive approach for systems-of-systems integration A contribution to systems-of-systems concept standardization Unstructured peer-to-peer systems : towards swift Routing A deterministic approach for systems-of-systems resilience quantification Vers des systèmes de systèmes robustes Security enhancement architectural model for IMS based networks Towards reliable IMS-based networks." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR07.

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De nos jours, nous attendons des systèmes de systèmes d'être plus que simplement fonctionnel, mais aussi fiable, de préserver leurs performances, de mener les actions requises et, surtout, d'anticiper d'éventuelles défaillances. La résilience fait partie des nombreuses approches d'évaluation de la fiabilité. Elle est directement liée aux conséquences de perturbations et incertitudes. Il s'agit des conséquences en cas de perturbations et des incertitudes associées. La résilience est définie comme la capacité des systèmes à résister à une perturbation majeure selon paramètres de dégradation et à récupérer dans un délai, des coûts et des risques acceptables. Dans cette thèse, deux approches complémentaires sont proposées pour tenter d'analyser la résilience structurelle des systèmes de systèmes. La première est liée à l'extensibilité qui est une caractéristique des systèmes de systèmes puisqu'ils sont en continuelle évolution. L'un des principaux objectifs est d'évaluer la résilience structurelle en tenant compte de l'aspect dynamique et moyennant une évaluation de l'interopérabilité. D'autre part, un examen de la structure d'un système de systèmes et des flux internes représente la deuxième approche. Cela conduit à une évaluation de la résilience structurelle grâce à un ensemble d'indicateurs. Les deux approches proposées sont déterministes et peuvent être utilisées pour évaluer l'état courant de la structure du système de systèmes ou pour anticiper sa résilience dans des scénarios futurs. Un démonstrateur a été développé pour l'évaluation de la résilience structurelle. Dans la considération de territoires, il a servi à l'évaluation d'infrastructures industrielles réelles selon une approche systèmes de systèmes
Nowadays, we expect of SoS (systems-of-systems) more than just to be functional, but also to be reliable, to preserve their performance, to complete the required fonctions and rnost importantly to anticipate potential defects. The relationship with resilience is among the numerous perspectives tackling reliability in the context of SoS. It is about the consequences in case of disturbances and associated uncertainties. Resilience is defined as the ability of systems to withstand a major disruption within acceptable degradation parameters and to recover within an acceptable time, composite costs and risks. In this thesis, two complementary approaches are proposed in an attempt to analyze SoS structural resilience. First is related to extensibility which is a specific characteristic of SoS as they are in continuous evolvement and change. A major focus is to evaluate SoS structural resilience with regards to its dynamic aspect and through interoperability assessment. On the other hand, a consideration of the SoS structure and inner workflow pathways represents the second approach. This perspective leads to structural resilience assessment through a set of indicators. Both proposed approaches are deterministic and can be used to evaluate the current state of SoS structure or to anticipate its resilience in future scenarios. Futhermore, a prototype is designed in order to process the structural resilience assessment. Considering spatial objects, it has been used to conduct experiments on real-based industrial infrastructures approached as SoS

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Damani, Manoj Kumar. "Physics Based Reliability Assessment of Embedded Passives." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5095.

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Multilayer embedded passives (resistors, inductors, and capacitors) on a printed wiring board can help to meet high performance requirements at a low cost and at a smaller size. Such an integration of embedded passives has new challenges with respect to design, materials, manufacturing, thermal management and reliability. As the area of integral passives on printed circuit boards is relatively new, there is inadequate literature on the thermo-mechanical reliability of integral passives. Therefore, there is a compelling need to understand the thermo-mechanical reliability of integral passives through the development of physics-based models as well as through experiments, and this thesis aims to develop such an experimental and theoretical program to study the thermo-mechanical reliability of integral passives.. As integral passives are often composite layers with dissimilar material properties compared to the other layers in the integral substrate, it is essential to ensure that RLC characteristics of the embedded passives do not deteriorate with thermal cycling due to thermo-mechanical deformations. This thesis aims to study the changes in the passive characteristics due to the thermally-induced deformations. Embedded capacitors and inductors have been looked at specifically in this research. Multi-field physics-based models have been constructed to determine the change in electrical parameters after thermal cycling. The thermo-mechanical models assume direction-dependent material properties for the board substrate and interconnect copper layers and temperature-dependent properties for interlayer dielectric and passive layers. Using the deformed geometry, the electrical characteristics have been determined at low frequency. In parallel to the models, test vehicle substrates have been subjected to 1000 thermal cycles between -55??o 125??nd high humidity and temperature conditions at 85??5RH for 500 hours, and it has been observed that there are significant changes in the electrical parameters. The results obtained from the physics-based simulations have been validated against the measured electrical characteristics from the fabricated functional test boards that have been thermal cycled.

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Gendron, Sylvie. "Development and reliability assessment of a questionnaire." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61345.

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This report describes a methodological study in which an interviewer-administered questionnaire was developed for use among incarcerated injection drug users (IDU) and assessed for reliability. A conceptual framework postulating psychosocio-behavioural determinants of condom use intention based on the Theory of Planned Behaviour (Ajzen, 1985) and the AIDS Risk Reduction Model (Catania et al., 1990) is presented first. This framework is specifically designed to include elements deemed relevant for the planning of HIV/AIDS preventive interventions targeted at incarcerated IDU. Questionnaire elaboration then involved a qualitative elicitation study, content validation, pilot testing, assessment of the internal consistency of eighteen additive scales defined a priori, and test-retest analyses. Results indicate that it is possible to obtain reliable data from incarcerated IDU. This sets the stage for eventual assessment of construct validity to assist in the choice of relevant measures and findings for consideration in the design of HIV/AIDS preventive public health interventions.

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Che, Yunxiang, and S3145469@student rmit edu au. "Aging structure life prediction and reliability assessment." RMIT University. SAMME, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091113.114541.

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Confront with the serious aging problem in aircraft structure field, the profession was tasked to unveil the mysterious in the mechanism of aging. In decades, many endeavours were put into different subjects such as, fatigue and crack calculation, corrosion analysis, reliability evaluation, life prediction, structure monitor and protection, structure repair, etc. In an effort of developing a reasonable model for life prediction and reliability evaluation, a wide range of topics in the field of aging structure reliability are reviewed. Many existing methods and tools are carefully studied to distinguish the advantages, disadvantages and the special application. With consideration of corrosion fatigue life, and based on the data obtained through investigating service status of the aging aircraft, a fuzzy reliability approach is proposed and presented. Initially, the thesis presents the literature review in the field, introducing the well-established theories and analysis tools of reliability and points out how such these methods can be used to assess the life and reliability of aging structure. Meanwhile, some characteristic parameters and distributions, as well as some crucial calculation formulations, procedures for aging aircraft reliability/risk analysis are given. Secondly, mathematical models are established to evaluate the initial crack size and to assess both randomness and fuzziness of the variables, which also successfully work out the probability of survival of existing structures over a time period and predict the operation time under specific reliability requirement. As a practical approach to the reliability of aging aircraft structure, example is presented and evaluated. While conduct the calculation, a few programs based on FORTRAN code are developed to solve the none-linear equation, to work out the multi dimension integration and to simulate the survival probability. The crack life prediction software AFGROW is selected for comparison of the calculation results, which also shows the appropriate accuracy of the established model. As conclusion, the effects of some variables including fuzzy factors on reliability and life of aging aircraft structure are finally discussed. It is apparent that the confines of the model are existing as fact because of the huge assumption of the parameters input and model uncertainties. Suggestions on further prospective research are proposed respectively.

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Jonnavithula, Satish. "Cost/benefit assessment of power system reliability." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23942.pdf.

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Camara, Louis Richard. "Statistical modeling and assessment of software reliability." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001699.

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Brand, W. W. (Willem Wouter). "Reliability assessment of a prestressed concrete member." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52430.

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Thesis (MScEng)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: First-order second-moment structural reliability methods are used to assess the reliability of a prestressed concrete beam. This beam was designed for imposed office floor loads and partitions following the limit states design method as provided for by the applicable South African structural codes, viz SABS 0100-1:1992 and SABS 0160:1989. The reliability is examined at two limit states. At the ultimate limit state of flexure the ultimate moment of resistance must exceed the applied external moment at the critical section, while at the serviceability limit state of deflection the deflection must satisfy the codespecified deflection criteria. Realistic theoretical models are selected to express the flexural strength and deflection of the prestressed concrete member, while appropriate probabilistic models are gathered from the literature for loading, resistance and modelling uncertainties. The calculated reliability index at the ultimate limit state of flexure (3.10) is lower than expected in view of the fact that this represents a non-critical limit state in the case of a Class 2 prestressed concrete member. This condition can be explained with reference to the relatively high uncertainty associated with the modelling error for flexural strength. The calculated reliability index at the serviceability limit state of deflection (l.67) compares well with acceptable practice. The study further focuses on the sensitivity of the reliability at the two limit states of interest to uncertainty in the various design parameters. The ultimate limit state of flexure is dominated by the uncertainty associated with the modelling error for flexural strength, while the contribution to the overall uncertainty of the ultimate strength and area of the prestressing steel and the effective depth is less significant. In comparison the reliability at the serviceability limit state of deflection is not dominated by the uncertainty associated with a single basic variable. Instead, the uncertainty associated with the modelling error, creep factor and prestress loss factor are all significant. It was also demonstrated that the variability in beam stiffness is not a major source of uncertainty in the case of a Class 2 prestressed concrete member. It is recommended that the present code provisions for ultimate strength and deflection should be reviewed to formulate theoretical models with reduced systematic and random errors. The effect of the uncertainty associated with the creep and prestressed loss factors should also be adressed by adjustment of the partial material factor for concrete at the serviceability limit state of deflection. Furthermore, research must be directed towards formulating an objective failure criterion for deflection. The uncertainty in the deflection limit must therefore be quantified with a probability distribution.
AFRIKAANSE OPSOMMING: Eerste-orde tweede-moment struktuur betroubaarheid metodes word ingespan om die betroubaarheid van 'n voorspanbeton balk te bereken. Hierdie balk is ontwerp vir opgelegte kantoor vloerbelasting en partisies volgens die grenstoestand ontwerp metode soos beskryf in die toepaslike Suid-Afrikaanse boukodes, naamlik SABS 0100-1: 1992 en SABS 0160: 1989. Die betroubaarheid word ondersoek by twee grenstoestande. By die swiglimiet van buiging moet die weerstandsmoment die eksterne aangewende moment oorskrei by die kritieke balksnit, terwyl die defleksie die kriteria soos voorgeskryf deur die kode moet bevredig by die dienslimiet van defleksie. Realistiese teoretiese modelle word gebruik om die buigsterkte en defleksie van die voorspanbeton balk te bereken. Verder is geskikte waarskynlikheid modelle uit die literatuur versamelom die belasting, weerstand en modelonsekerhede te karakteriseer. Die betroubaarheid indeks soos bereken vir die swiglimiet van buiging (3.10) is laer as wat verwag sou word in die lig van die feit dat hierdie nie 'n kritieke grenstoestand verteenwoordig in die geval van 'n Klas 2 voorspan element nie. Dit kan verklaar word met verwysing na die relatiewe groot onsekerheid wat geassosieer word met die modellering fout vir buigsterkte. Die berekende betroubaarheid indeks vir die dienslimiet van defleksie (1.67) vergelyk goed met aanvaarde praktyk. Die studie fokus verder op die sensitiwiteit van die betroubaarheid by die twee grenstoestande onder beskouing ten opsigte van die onsekerheid in die verskillende ontwerp parameters. By die swiglimiet van buiging word die onsekerheid oorheers deur die bydrae van die modelering fout vir buigsterkte. Die bydraes tot die totale onsekerheid deur die swigsterkte en area van die voorspanstaal sowel as die effektiewe diepte is minder belangrik. By die dienslimiet van defleksie word die betroubaarheid nie oorheers deur die onsekerheid van 'n enkele basiese veranderlike nie. In stede hiervan is die onsekerheid van die modellerings fout, kruipfaktor en voorspan verliesfaktor almal noemenswaardig. Daar word verder aangetoon dat die veranderlikheid in balkstyfheid nie 'n belangrike bron van onsekerheid in die geval van 'n Klas 2 voorspan element is nie. Daar word aanbeveel dat die bestaande voorskrifte in die kode vir buigsterkte en defleksie aangespreek moet word deur teoretiese modelle met klein modelonsekerhede te formuleer. Die uitwerking van die onsekerheid van die kruip- en voorspan verliesfaktore kan aangespreek word deur 'n aanpassing te maak in die parsiële materiaalfaktor vir beton in die geval van die dienslimiet van defleksie. Navorsing moet verder daarop gemik wees om 'n objektiewe falingskriterium vir defleksie te formuleer. Die onsekerheid van die toelaatbare defleksie moet dus gekwatifiseer word deur 'n waarskynlikheidsverdeling.

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