A congestion model for cell migration

This paper deals with a class of macroscopic models for cell migration in a saturated medium for two-species mixtures. Those species tend to achieve some motion according to a desired velocity, and congestion forces them to adapt their velocity. This adaptation is modelled by a correction velocity which is chosen minimal in a least-square sense. We are especially interested in two situations: a single active species moves in a passive matrix (cell migration) with a given desired velocity, and a closed-loop Keller-Segel type model, where the desired velocity is the gradient of a self-emitted chemoattractant. We propose a theoretical framework for the open-loop model (desired velocities are defined as gradients of given functions) based on a formulation in the form of a gradient flow in the Wasserstein space. We propose a numerical strategy to discretize the model, and illustrate its behaviour in the case of a prescribed velocity, and for the saturated Keller-Segel model

Historical collaborative geocoding

The latest developments in digital have provided large data sets that can increasingly easily be accessed and used. These data sets often contain indirect localisation information, such as historical addresses. Historical geocoding is the process of transforming the indirect localisation information to direct localisation that can be placed on a map, which enables spatial analysis and cross-referencing. Many efficient geocoders exist for current addresses, but they do not deal with the temporal aspect and are based on a strict hierarchy (..., city, street, house number) that is hard or impossible to use with historical data. Indeed historical data are full of uncertainties (temporal aspect, semantic aspect, spatial precision, confidence in historical source, ...) that can not be resolved, as there is no way to go back in time to check. We propose an open source, open data, extensible solution for geocoding that is based on the building of gazetteers composed of geohistorical objects extracted from historical topographical maps. Once the gazetteers are available, geocoding an historical address is a matter of finding the geohistorical object in the gazetteers that is the best match to the historical address. The matching criteriae are customisable and include several dimensions (fuzzy semantic, fuzzy temporal, scale, spatial precision ...). As the goal is to facilitate historical work, we also propose web-based user interfaces that help geocode (one address or batch mode) and display over current or historical topographical maps, so that they can be checked and collaboratively edited. The system is tested on Paris city for the 19-20th centuries, shows high returns rate and is fast enough to be used interactively.Comment: WORKING PAPE

Cooperative fault detection and isolation in a surveillance sensor network: a case study

International audienceThis work focuses on Fault Detection and Isolation (FDI) among sensors of a surveillance network. A review of the main characteristics of faults in sensor networks and the associated diagnosis techniques is first proposed. An extensive study has then been performed on the case study of the persistent monitoring of an area by a sensor network which provides binary measurements of the occurrence of events to be detected (intrusions). The performance of a reference FDI method with and without simultaneous intrusions has been quantified through Monte Carlo simulations. The combination of static and mobile sensors has also been considered and shows a significant performance improvement for the detection of faults and intrusions in this context

La fabrique des footballeurs

Les footballeurs professionnels sont devenus des figures médiatiques qui suscitent des réactions contradictoires. Objets d'identification, supports de célébrations des succès de " l'intégration " ou du triomphe du talent et de l'effort, ils font aussi l'objet de nombreuses critiques condamnant les attitudes et les revenus de footballeurs " pros " qui sont souvent taxés d'être des " mercenaires trop payés ". Derrière ces prises de positions contradictoires se cache une représentation très partagée selon laquelle on aurait à faire à des " enfants du peuple " touchés par la grâce d'un don, et que l'auteur propose de déconstruire. L'ouvrage invite ainsi à sortir de ces récits d'ascension quasi-miraculeux et explique de quelle manière on devient footballeur. En s'appuyant sur une enquête minutieuse étalée sur trois années à l'intérieur de l'école professionnelle d'un grand club français, l'auteur analyse des parcours de jeunes aspirants au football professionnel et l'étude de leur mode de formation entre 12 et 19 ans. Il montre comment cette formation, particulièrement intensive, incertaine, et englobante, " fabrique " les futurs footballeurs, en les enrôlant progressivement dans une course sportive qui exige investissements et renoncements. Malgré cet engagement, les pensionnaires restent cependant soumis à une concurrence sévère et à la forte incertitude de leurs chances de succès puisque le système de formation produit un grand nombre de laissés-pour-compte. Ce mode de formation concurrentiel façonne leur manière d'envisager le métier, et constitue un moteur de discipline, de fragilisation et d'individualisation