Hybridization of Bayesian networks and belief functions to assess risk. Application to aircraft deconstruction

This paper aims to present a study on knowledge management for the disassembly of end-of-life aircraft. We propose a model using Bayesian networks to assess risk and present three approaches to integrate the belief functions standing for the representation of fuzzy and uncertain knowledge

Couplage des réseaux bayésiens et des fonctions de croyance pour l'évaluation du risque.Application à la déconstruction d'avion

Cette communication a pour objectif de présenter des travaux sur la gestion des connaissances appliqués à la déconstruction des avions en fin de vie. Nous proposons un modèle utilisant les réseaux bayésiens pour évaluer les risques et nous présentons trois approches destinées à intégrer les fonctions de croyance dans le modèle d'évaluation des risques proposé

Consolidation des données statistiques par expertise et similarité pour la prévision des ventes

Cette communication a pour objectif de présenter des travaux sur des méthodes de prévisions de vente utilisant des données statistiques consolidées par des avis d'experts et des statistiques issues de cas similaires afin de piloter l'activité commerciale d'une entreprise disposant de plusieurs points de vente. Nous proposons un modèle de prévision intégrant les connaissances statistiques et expertes ainsi que les mesures de similarité pour affiner la prévision. Nous proposons également une méthode d’élicitation des avis d’experts sous forme de fonctions de croyance

Multi-temporal airborne structure-from-motion on caldera rim: Hazard, visitor exposure and origins of instabilities at Piton de la Fournaise

International audiencePiton de la Fournaise is one of the world's most active and visited volcanoes. Its summit crater (Cratère Dolomieu), the main tourist attraction, underwent a major caldera collapse in 2007 and its rim is not yet stabilized. In order to assess the caldera rim instability risk for visitors, we followed its structural evolution from 2007 to 2015. Using aerial photogrammetry campaigns, we mapped the unstable sites very precisely, carried out a quantitative analysis of the temporal evolution of these instabilities, and assessed the risks for visitors. Considering the 2008-2015 period, four sites close to the crater's edge showed significant horizontal ground motion (0.5-2 m), fracture widening (average of 0.3-0.56 m) and large-scale mass wasting volumes (total of 1.8+0.1 Â 10 6 m 3). We infer two different processes at work: (1) to the west and north, toppling of the basalt units occurs after periods of fracture widening due to the combined effect of magmatic intrusions and long-term inflation/deflation cycles; (2) to the south and east, parts of the caldera rim slowly slide towards the caldera centre, with significant accelerations during periods of enhanced volcanic activity (in 2008-2010 and 2014-2015). The official observation platform is the most stable zone to overlook the Cratère Dolomieu. By contrast, the most frequently visited area of the rim (northwest) outside the official platform is also the most unstable

How summit calderas collapse on basaltic volcanoes: New insights from the April 2007 caldera collapse of Piton de la Fournaise volcano

International audienceIn April 2007, Piton de la Fournaise volcano experienced a caldera collapse during its largest historical eruption. We present here a structural analysis both of the caldera and the surrounding area, and precise GPS data recorded with a dense GPS network specifically dedicated to the analysis of deformation related to the summit collapse structures. Despite a collapse of more than 300 m in the central zone, the geometry of the new caldera is similar in map view to that of the pre-existing collapsed structure, which was formed from the coalescence of several pit craters. The caldera shows an asymmetric inner geometry with sub-vertical walls in the NW quadrant and steep scarps composed of inward tilted blocks in the southern half. The presence of preserved polished surfaces on the lower part of the sub-vertical scarp indicates that it corresponds to the caldera north-western ring fault. The April 2007 caldera collapse led to the development and the reactivation of concentric fractures on the caldera rim, mostly along the southern limit of the caldera. GPS data show that fractures result from radial extensional stresses that are restricted within the first tens of meters of the caldera edge. GPS data also reveal that the caldera collapse was coeval with a centripetal deflation, whose magnitude is largest along the southern half of the caldera. The displacements recorded by GPS result from both a general deflation, due to magma withdrawal from Piton de la Fournaise's summit magma chamber, and additional local effects related to the caldera collapse. Comparison of the caldera collapses at Piton de la Fournaise, Miyakejima and Fernandina reveals striking similarities, with cyclic seismic signals accompanying small-scale deflation–inflation cycles. This strongly suggests a common mode of collapse. Hence, we propose a unifying model of caldera collapse in basaltic setting, in which the inward deflation due to magma withdrawal from the magma chamber prevents the collapse of the caldera roof until the gravitational stress acting on the rock column above the magma chamber exceeds the shear strength along pre-existing ring faults. The downward displacement stops when the pressure increase into the magma chamber is able to again sustain the rock column. The succession of (1) inward deflation that prevents the collapse, (2) collapse due to gravitational stress and (3) stopping of the downward motion is repeated many times. The frequency of the cycles is influenced by the rate of magma withdrawal and by the amount of intrusion of magma along the ring faults

Quantitative technology model : a statistical analysis

The problem -- The model -- Identification of the relations between variables -- Regrouping of similar cases -- Comparaison of two populations