Using Expert Models in Human Reliability Analysis - A Dependence Assessment Method Based on Fuzzy Logic

International audienceIn human reliability analysis (HRA), dependence analysis refers to assessing the influence of the failure of the operators to perform one task on the failure probabilities of subsequent tasks. A commonly used approach is the technique for human error rate prediction (THERP). The assessment of the dependence level in THERP is a highly subjective judgment based on general rules for the influence of five main factors. A frequently used alternative method extends the THERP model with decision trees. Such trees should increase the repeatability of the assessments but they simplify the relationships among the factors and the dependence level. Moreover, the basis for these simplifications and the resulting tree is difficult to trace. The aim of this work is a method for dependence assessment in HRA that captures the rules used by experts to assess dependence levels and incorporates this knowledge into an algorithm and software tool to be used by HRA analysts. A fuzzy expert system (FES) underlies the method. The method and the associated expert elicitation process are demonstrated with a working model. The expert rules are elicited systematically and converted into a traceable, explicit, and computable model. Anchor situations are provided as guidance for the HRA analyst's judgment of the input factors. The expert model and the FES-based dependence assessment method make the expert rules accessible to the analyst in a usable and repeatable way, with an explicit and traceable basis

Bayesian Networks from Scarce Data and Expert Judgment: A Human Reliability Analysis Application

This work addresses the development of Bayesian Belief Network (BBNs) for cases of small datasets available, emphasizing the need for a traceable development process. The application relates to a specific area of Human Reliability Analysis: the quantification of aggravating actions, as outcomes of inappropriate decisions (i.e., the so-called errors of commission, EOCs). The available data constitutes of two set of analyses of operational events (about thirty events in total) involving EOCs, in the form of patterns of analyst ratings on EOC-influencing factors and corresponding error-forcing impact (in the analysis framework of the CESA-Q method, the Quantification module of the Commission Error Search and Assessment method, developed by the authors’ research Group). This work presents a novel process for the quantification of the BBN parameters (the Conditional Probability Distributions, CPDs), combining an interpolation algorithm for populating the CPDs from part of the available evidence and Bayesian updates to adjust the BBN response to the rest of the available evidence. A first, prior BBN is developed, then sequentially updated to adjust to the two data sets. This allows some intermediate validation and puts forwards the steps for future BBN updates as new EOC events (or new analyst assessments) become available. Traceability in the BBN development comes from avoiding to elicit CPDs directly from expects, whereas, much of the judgment is constrained to the operational event analyses and to a set of anchor assessments required as input to the interpolation algorithm. These can be subject to review and, eventually, be defined such to reflect different beliefs. Once the set of inputs is given, the rest of the BBN development is performed by the algorithm, based on its pre-defined CPD filling rules and following a traceable and repeatable process

SHORT AND LONG-TERM EFFECTS OF VARIATION IN THE BREEDINGENVIRONMENT ON BEHAVIOUR AND FITNESS TRAITS IN ACOLONIAL, CAVITY NESTING RAPTOR

The heterogeneity of breeding environment leads the evolution of different behavioural strategies that individuals undertake to guarantee their fitness and survival. Moreover, the cyclic nature of animal life determines that each set of decision made by individuals during reproduction could severely affect behaviour and fitness traits during their successive stages of life cycle. Among different species that have been studied to investigate these relationships, migratory birds are optimal model species, since the rigid scheduling of their life cycle exacerbates the associations established among breeding environmental variations, fitness and behaviour. In the present thesis, I investigated the possible effects of variation in the breeding environment on fitness and behavioural traits of a colonial, migratory, avian species the lesser kestrel (Falco naumanni), assessing possible effects during two different temporal scales: in the current breeding season (short-term effects) and/or during successive life stages (long-term effects). In the first part, I analysed short-term effects of breeding environmental variations, observing whether nest-site quality and food resource abundancy and distribution could affect fitness and behaviour of lesser kestrel. Firstly, I have investigated the strategy implemented by lesser kestrel during nest-site selection, and whether individual differences in the nest-site preference could affect fitness. Secondly, I have assessed whether food resource abundancy could limit lesser kestrel\u2019s breeding performance and whether the patchy prey distribution in the breeding environment could negatively affect their foraging behaviour and fitness. In the second part, I have investigated whether variation in breeding environment could affect lesser kestrel during successive stages of the life cycle. I therefore analysed whether breeding area continental distribution affects migratory behaviour and strategy of five European populations of lesser kestrel. The overall results reported in this thesis suggested that lesser kestrel suffers variations in the breeding environment that occur during the current breeding season, indeed I have assessed that individuals rely on public information gathered from the environment to choose the most suitable nest-site and to identify optimal foraging areas. Foraging strategies adopted by lesser kestrel during the breeding season have evolved to cope with the heterogeneous prey distribution and to limit intraspecific competition among individuals of the same and different colonies. Moreover, food resource abundancy mediates individual fitness according to parent body condition. Finally, despite the absence of any direct effects of lesser kestrel migratory connectivity on individual fitness, I observed that the continental distribution of the breeding site reflects the location of the non-breeding areas in Africa. This evidence highlighted that European populations remain separated during the African stay and thus are subjected to different abiotic and biotic traits with possible profound effects on population dynamics

Home, dirty home: effect of old nest material on nest-site selection and breeding performance in a cavity-nesting raptor

The quality of a breeding site may have major fitness consequences. A fundamental step to understanding the process of nest-site selection is the identification of the information individuals use to choose high-quality nest sites. For secondary cavity-nesting bird species that do not add nest lining material, organic remains (faeces, pellets) accumulated inside nest cavities during previous breeding events may be a cue for high-quality nest-sites, as they contain information about past successful breeding and may improve thermal insulation of eggs during incubation. However, cavities in which breeding was successful might also contain more nest-dwelling ectoparasites than unoccupied cavities, offering an incentive for prospective parents to avoid them. We exposed breeding cavity-nesting lesser kestrels (Falco naumanni) to nestbox dyads consisting of a dirty (with a thick layer of organic substrate) and a clean nestbox (without organic material). Dirty nestboxes were strongly preferred, being occupied earlier and more frequently than clean ones. Hatching success in dirty nestboxes was significantly higher than in clean ones, suggesting a positive effect of organic nest material on incubation efficiency, while nestbox dirtiness did not significantly affect clutch and brood size. Nestlings from dirty nestboxes had significantly higher ectoparasite load than those from clean nestboxes soon after egg hatching, but this difference was not evident a few days later. Nest substrate did not significantly affect nestling growth. We concluded that nest substrate is a key driver of nest-site choice in lesser kestrels, although the adaptive value of such a strong preference appears elusive and may be context-dependent

Clock gene polymorphism and scheduling of migration : a geolocator study of the barn swallow Hirundo rustica

Circannual rhythms often rely on endogenous seasonal photoperiodic timers involving 'clock' genes, and Clock gene polymorphism has been associated to variation in phenology in some bird species. In the long-distance migratory barn swallow Hirundo rustica, individuals bearing the rare Clock allele with the largest number of C-terminal polyglutamine repeats found in this species (Q8) show a delayed reproduction and moult later. We explored the association between Clock polymorphism and migration scheduling, as gauged by light-level geolocators, in two barn swallow populations (Switzerland; Po Plain, Italy). Genetic polymorphism was low: 91% of the 64 individuals tracked year-round were Q7/Q7 homozygotes. We compared the phenology of the rare genotypes with the phenotypic distribution of Q7/Q7 homozygotes within each population. In Switzerland, compared to Q7/Q7, two Q6/Q7 males departed earlier from the wintering grounds and arrived earlier to their colony in spring, while a single Q7/Q8 female was delayed for both phenophases. On the other hand, in the Po Plain, three Q6/Q7 individuals had a similar phenology compared to Q7/Q7. The Swiss data are suggestive for a role of genetic polymorphism at a candidate phenological gene in shaping migration traits, and support the idea that Clock polymorphism underlies phenological variation in birds

A comparison of two Monte Carlo simulation approaches for the estimation of importance measures in multi-state systems

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