Traitement des incertitudes des avis à dire d'expert pour l'évaluation de la sûreté des digues

3rd European Conference on Flood Risk Management FLOODrisk 2016, Lyon, FRA, 17-/10/2016 - 21/10/2016International audienceIn France, levees remain most of the time badly maintained; these long linear structures show signs of weaknesses on numerous occasions. Only incomplete information is usually available. The general lack of data describing the behaviour of the infrastructure during unwanted events led to estimate their safety mainly from expert judgement. Thus the ability of the expert to predict the level of functioning of an infrastructure for a type of hazard and its intensity is crucial. An error of judgement can have very serious consequences and the production of reliable information requires the ability of the expert to report accurately the uncertainties in its estimations, as well as associated confidence. In order to meet this need, our research within Incertu project (French Ministry of Ecology funding) aims to produce relevant scientific approaches and tools for the collection and processing reliable experts'statements or combined with a confidence level in the context of uncertain information and input data

Biological and Health-promoting Activity of Vinification Byproducts Produced in Spanish Vineyards

Several by-products are produced in the Spanish agricultural system. Among them, fresh and vinifiedgrape skins represent an abundant source of phenols with a potential nutraceutical value. Fresh grape skinextracts (FGSE) and vinification of grape skin extracts (VGSE) obtained by a microwave-assisted methodhave been chemically and biologically characterised. Their role in the maintenance of genetic stabilitywas stated by in vivo genotoxic and antigenotoxic evaluations (Drosophilla melanogaster wing spot test), aswell as by their potential chemopreventive effect (in an HL60 in vitro model). Total phenolic, anthocyaninand resveratrol contents were chemically characterised in the two extracts, showing some qualitativedifferences. Both extracts and resveratrol were not mutagenic in the Drosophila somatic mutation andrecombination tests, and exerted antigenotoxic activities against hydrogen peroxide. They also showedcytotoxic activity to HL60 leukaemia cells, with an IC50 of 4.5μL/mL, 4.6μL/mL and 98μM respectively andinduced apoptotic internucleosomic fragmentation in the HL60 cell line

Symbolic optimal expected time reachability computation and controller synthesis for probabilistic timed automata

In this paper we consider the problem of computing the optimal (minimum or maximum) expected time to reach a target and the synthesis of an optimal controller for a probabilistic timed automaton (PTA). Although this problem admits solutions that employ the digital clocks abstraction or statistical model checking, symbolic methods based on zones and priced zones fail due to the difficulty of incorporating probabilistic branching in the context of dense time. We work in a generalisation of the setting introduced by Asarin and Maler for the corresponding problem for timed automata, where simple and nice functions are introduced to ensure finiteness of the dense-time representation. We find restrictions sufficient for value iteration to converge to the optimal expected time on the uncountable Markov decision process representing the semantics of a PTA. We formulate Bellman operators on the backwards zone graph of a PTA and prove that value iteration using these operators equals that computed over the PTA’s semantics. This enables us to extract an ε-optimal controller from value iteration in the standard way

Application des probabilités subjectives pour la prise en compte des incertitudes issues de dires experts en analyse de risques

National audienceIn risk analysis, the engineer should continuously deal with uncertainty. These uncertainties can have different natures and they can be presented systematically or residually. We present an original approach based on subjective probabilities for the consideration of uncertainties associated with expert statements in functional models used in risk analysis. Implementation of Monte-Carlo simulations and sensitivity coefficients allows exploiting these uncertainties for decision support.En analyse de risque l’ingénieur doit faire face quotidiennement à de l’incertitude. Ces incertitudes peuvent être de natures diverses et présentes de manière résiduelle ou systématique. Nous présentons une démarche originale basée sur les probabilités subjectives pour la prise en compte des incertitudes liées aux dires experts dans les modèles fonctionnels utilisés en analyse de risque. La mise en oeuvre de simulations de Monte-Carlo et de coefficients de sensibilité permet d’exploiter ces incertitudes pour l’aide à la décision

Towared an Experts Biases Treatment for Reliability assessment of River Levees

Dans un contexte incertain, lorsque les données issues des retours d’expérience, de statistiques ou de mesures physiques sont faiblement disponibles, l’utilisation du jugement expert demeure la seule source d’informations pertinente. Ces derniers sont sujets à des incertitudes et très susceptibles d’être entachées par des biais. Notre contexte de recherche vise à développer une méthode pour le recueil des avis des experts et le traitement des biais. Cette méthode contient trois phases principales : l’élicitation, la calibration et le dé-biasage. Dans cette communication nous nous focalisons sur la phase de calibration des avis des experts incertains.In an uncertain environment, when the data from the feedback, statistics or physical measures are poorly available, the use of expert judgment remains the only source of pertinent information. The latter are subject to uncertainty and very likely to be tainted by bias. Our context of research aims to develop a method for collecting expert opinion and the Treatment of bias. This method has three main phases: Elicitation, Calibration and Debiasing. In this paper we focus on phase of uncertain opinions experts’ calibration

Démarche d'Élicitation, Calibration, Agrégation et Dé-biaisage « EiCAD » du jugement d'expert pour l'évaluation probabiliste de la fiabilité structurelle des digues fluviales

10èmes journées Fiabilité des Matériaux et des Structures, Bordeaux, FRA, 27-/03/2018 - 28/03/2018National audienceIn civil engineering, utilization and exploitation of the expert judgment is an important issue in evaluating the structural reliability of civil works whose failure behaviour is poorly known and difficult to quantify. In this communication, the application of the elicitation, calibration, aggregation and debiasing steps of expert judgement to evaluate the reliability of river Levees is studied. These steps are been little exploited in the field of civil engineering while their implementation in other domains such as statistics, economics and psychology has witnessed a growing interest. The communication proposes a quantitative methodology of exploitation and treatment of the expert judgement for evaluating of probabilities of failure of the river levees. An application of this methodology in the case of an existing river levee is presented.En génie civil, l'utilisation et l'exploitation du jugement d'expert est un sujet important pour l'évaluation de la fiabilité structurelle des ouvrages dont le comportement de défaillance est mal connu et difficilement quantifiable. Dans cette communication l'application des démarches d'élicitation, de calibration, d'agrégation et de dé-biaisage des avis experts pour évaluer la fiabilité des digues fluviales est étudiée. Ces démarches sont peu exploitées dans le domaine du génie civil alors que leur mise en oeuvre dans d'autres domaines comme la statistique, l'économie et la psychologie a été témoin d'un intérêt croissant. La communication propose une démarche quantitative d'exploitation et de traitement du jugement d'expert pour l'évaluation des probabilités de défaillance des digues fluviales. Une application au cas d'une digue fluviale existante est présentée

Preliminary use of induced polarization measurement to study tree roots growing in earth dikes

International audienceRoots are recognized as an environmental hazard when growing in hydraulic earth structures, especially dikes. This study had two main purposes: first we tried to link the polarizations effects with each parameter such as root properties (type, diameter, function, decay state…), of the soil (type, water content) and seasonal variations of the tree (sap activity)

Decision-making method for assessing performance of large levee alignment

International audienceLevees are large alignment civil engineering works with a performance that is assessed with great difficulty due to its longitudinal variability. We hereby suggest that a decision-making support procedure should be identified, built and implemented so as to split levee alignments into homogeneous sections and identify them according to their performance level. Our work is focused on defining actions for the purpose of solving the decision-making problem with regard to large alignment works. In order to select a suitable decision-making method, we suggest a formulation and a comparison between two types of multi-criteria methods: the ELECTRE TRI outranking method and a unicriterion method. The relevance of building a unicriterion for the purpose of our study is investigated considering the existing operational interconnections between the levee evaluation criteria

Subjective Probabilities to Integrate Uncertainties in Levee Performance Assessment

International audienc

Traitement des biais heuristiques pour l’évaluation probabiliste de la sûreté des digues fluviales

National audienceEn France, la réglementation concernant l’évaluation du niveau de sécurité des linéaires de digues a été renforcée. Elle nécessite l’évaluation probabiliste du risque de défaillance des ouvrages. Or ceux-ci et leurs mécanismes de défaillances demeurent dans une large mesure mal connus, conduisant à une prédominance de l’exploitation du jugement expert dans les études de diagnostic. Ainsi une erreur de jugement peut avoir des conséquences catastrophiques et la production d’une information fiable induit que l’ingénieur est capable de décrire fidèlement ses évaluations ainsi que l’incertitude qui s’y rattache. Répondant à ce besoin, notre recherche vise à produire des approches et des outils scientifiques pertinents pour la collecte et le traitement des déclarations d'experts fiables ou assorties d’un degré de vraisemblance. Nous présentons ici nos recherches concernant l’identification et le traitement des biais susceptibles d’entacher les évaluations expertes