Régime alimentaire de la Loutre, Lutra lutra, sur l'île de Noirmoutier (Vendée)

One of the remaining French otter populations lives on Noirmoutier island where the marine environment offers food resources. A study of the otters' diets will prove if these resources are used or not

Extended geometric processes: Semiparametric estimation and application to reliability

International audienceLam (2007) introduces a generalization of renewal processes named Geometric processes, where inter-arrival times are independent and identically distributed up to a multiplicative scale parameter, in a geometric fashion. We here envision a more general scaling, not necessarily geometric. The corresponding counting process is named Extended Geometric Process (EGP). Semiparametric estimates are provided and studied for an EGP, which includes consistency results and convergence rates. In a reliability context, arrivals of an EGP may stand for successive failure times of a system submitted to imperfect repairs. In this context, we study: 1) the mean number of failures on some finite horizon time; 2) a replacement policy assessed through a cost function on an infinite horizon time

Integrated System for students' Evaluation Using KM Approach

International audienceWith the number of international students increasing globally and the mobility of students is becoming a condition to secure a good job and to gain a shining career, evaluating candidates prerequisites is becoming challenging. This paper presents how knowledge management approach using AI techniques could help academic institutions in the evaluation of international students profiles by providing an adapted methodology. This methodology implemented in the proposed system will help institutions gain more time in processing students files, provide accurate evaluation of candidates by taking their cultural background into consideration and avoid human errors

Introducing QoS support in Bluetooth Piconetwith a Class-Based EDF Scheduling

In this paper, we focus on the Bluetooth wireless network, analyzing its ability to support Quality of Service (QoS) requirements defined by the application. In particular, we are interested in two QoS parameters: (i) an application constraint denoting the importance degree of a message, and (ii) its delivery deadline. The QoS perceived by the application depends on the efficiency of the scheduling schemes chosen at the medium access layer. We define the minimal knowledge level required by a scheduling scheme to support these QoS constraints. As an example of classical scheduling schemes, we analyze performances of One-Round Robin (1-RR) and show that it does not provide a sufficient service differentiation. To achieve better service differentiation, we first present enhancements accounting locally for the two QoS parameters. These enhancements are applied to 1-RR scheduling scheme and we then give a comparison between the two versions. These comparisons are done by evaluating in each class, the average message response time and the percentage of messages missing their deadline. We then introduce enhancements in the intra-piconet scheduling. So, we define a new Bluetooth global scheduling, called Class-Based Earliest Deadline First (CB-EDF) that takes into account both locally and globally these two QoS parameters. Simulation results show that CB-EDF achieves a good service differentiation and allows the coexistence of messages with different application constraints on the same ACL link. Moreover, CB-EDF is a flexible solution that adapts itself to the provided knowledge level

Estimation par assimilation de données variationnelle de champs de pluie à petite échelle à partir d'atténuations de micro-ondes de satellites TV

International audienceLes deux moyens principaux pour observer les précipitations sont les radars météorologiques et les réseaux de pluviomètres. Cependant les premiers sont chers et ne sont pas disponibles partout, et les seconds ne fournissent que des mesures ponctuelles. Or la pluie est un phénomène naturel présentant une forte variabilité spatio-temporelle. Nous présentons ici une méthode permettant de reconstituer des champs de pluie à petite échelle à partir de l'affaiblissement par la pluie des ondes radio en bande Ku (10-12 GHz) en provenance de satellites de télévision. les mesures d'affaiblissements sont couplées à un modèle numérique d'évolution des champs de pluie (advection) via un algorithme d'assimilation de données variationnelle (AD-VAR). cette méthode est appliquée sur des données enregistrées en 2013 dans l'Ardèche dans le cadre de la campagne européenne HyMeX (Hydrological cycle in mediterranean Experiment). Les cartes de précipitations obtenues à petite échelle (10s, 0,5 *0.5km2) sont comparées à des observations radar et pluviomètres colocalisées

Semiparametric estimate of the efficiency of imperfect maintenance actions for a gamma deteriorating system

International audienceA system is considered, which is deteriorating over time according to a non homogeneous gamma process with unknown parameters. The system is subject to periodic and instantaneous imperfect maintenance actions (repairs). Each imperfect repair removes a proportion ρ of the accumulated degradation since the previous repair. The parameter ρ hence appears as a measure for the maintenance efficiency. This model is called arithmetic reduction of degradation of order 1. The system is inspected right before each maintenance action, thus providing some multivariate measurement of the successively observed deterioration levels. Based on these data, a semiparametric estimator of ρ is proposed, considering the parameters of the underlying gamma process as nuisance parameters. This estimator is mainly based on the range of admissible ρ's, which depends on the data. Under technical assumptions, consistency results are obtained, with surprisingly high convergence rates (up to exponential). The case where several i.i.d. systems are observed is next envisioned. Consistency results are obtained for the efficiency estimator, as the number of systems tends to infinity, with a convergence rate that can be higher or lower than the classical square root rate. Finally, the performances of the estimators are illustrated on a few numerical examples

Observation of the shock wave propagation induced by a high-power laser irradiation into an epoxy material

The propagation of laser-induced shock waves in a transparent epoxy sample is investigated by optical shadowgraphy. The shock waves are generated by a focused laser (3 ns pulse duration—1.2 to 3.4TWcm−2) producing pressure from 44 to 98.9 GPa. It is observed that the shock wave and the release wave created by the shock reverberation at the rear face are both followed by a dark zone in the pictures. This corresponds to the creation of a tensile zone resulting from the crossing on the loading axis of the release waves coming from the edge of the impact area (2D effects). After the laser shock experiment, the residual stresses in the targets are identified and quantified through a photoelasticimetry analysis of the recovered samples. This work results in a new set of original data which can be directly used to validate numerical models implemented to reproduce the behaviour of epoxy under extreme strain rate loading. The residual stresses observed prove that the high-pressure shocks can modify the pure epoxy properties, which could have an influence on the use made of these materials