Distributed Algorithms for Stochastic Source Seeking With Mobile Robot Networks

Autonomous robot networks are an effective tool for monitoring large-scale environmental fields. This paper proposes distributed control strategies for localizing the source of a noisy signal, which could represent a physical quantity of interest such as magnetic force, heat, radio signal, or chemical concentration. We develop algorithms specific to two scenarios: one in which the sensors have a precise model of the signal formation process and one in which a signal model is not available. In the model-free scenario, a team of sensors is used to follow a stochastic gradient of the signal field. Our approach is distributed, robust to deformations in the group geometry, does not necessitate global localization, and is guaranteed to lead the sensors to a neighborhood of a local maximum of the field. In the model-based scenario, the sensors follow a stochastic gradient of the mutual information (MI) between their expected measurements and the expected source location in a distributed manner. The performance is demonstrated in simulation using a robot sensor network to localize the source of a wireless radio signal

Large deviation principle at fixed time in Glauber evolutions

Abstract: We consider the evolution of an asymptotically decoupled probability measure ν on Ising spin configurations under a Glauber dynamics. We prove that for any t > 0, ν t is asymptotically decoupled and hence satisfies a large deviation principle with the relative entropy density as rate function

Random walks on FKG-horizontally oriented lattices

Abstract: We study the asymptotic behavior of the simple random walk on oriented versions of Z2. The considered lattices are not directed on the vertical axis but unidirectional on the horizontal one, with centered random orientations which are positively correlated. We prove that the simple random walk is transient and also prove a functional limit theorem in the space V([O, 00[, JR2) of cadlag functions, with an unconventional normalization

Low-temperature dynamics of the Curie-Weiss Model: Periodic orbits, multiple histories, and loss of Gibbsianness

We consider the Curie-Weiss model at a given initial temperature in vanishing external field evolving under a Glauber spin-flip dynamics corresponding to a possibly different temperature. We study the limiting conditional probabilities and their continuity properties and discuss their set of points of discontinuity (bad points). We provide a complete analysis of the transition between Gibbsian and non-Gibbsian behavior as a function of time, extending earlier work for the case of independent spin-flip dynamics. For initial temperature bigger than one we prove that the time-evolved measure stays Gibbs forever, for any (possibly low) temperature of the dynamics. In the regime of heating to low-temperatures from even lower temperatures, when the initial temperature is smaller than the temperature of the dynamics, and smaller than 1, we prove that the time-evolved measure is Gibbs initially and becomes non-Gibbs after a sharp transition time. We find this regime is further divided into a region where only symmetric bad configurations exist, and a region where this symmetry is broken. In the regime of further cooling from low-temperatures there is always symmetry-breaking in the set of bad configurations. These bad configurations are created by a new mechanism which is related to the occurrence of periodic orbits for the vector field which describes the dynamics of Euler-Lagrange equations for the path large deviation functional for the order parameter. To our knowledge this is the first example of the rigorous study of non-Gibbsian phenomena related to cooling, albeit in a mean-field setup.Comment: 31 pages, 24 figure

Utilisation d’un site web intégré de webmapping et de gestion de contenus. L’exemple de recherches en cours en pétroarchéologie du silex appliquée au Paléolithique moyen

The nature of flints used in prehistory is essential information for increasing our knowledge of old settlements. The study of this raw material as well as the identification of its source, contribute to the evaluation of the mobility of prehistoric men and their behavior in relation to mineral resources, thus contributing to a better understanding of certain problems related to prehistoric economies. An innovative multi-field approach, based on a series of geological surveys of the siliceous formations of the French Massif Central, of Morocco and of northern Bulgaria, makes it possible today to better determine the limits of the areas exploited. The study is based on a complete examination of the evolution of flint on three scales (macroscopy, microscopy, ultramicroscopy) thus representing an improvement over petro-archaeology which traditionally uses the methods of petrography, mineralogy and micropaleontology. Moreover, the reconstitution of the initial shapes of material clarifies the technical procedures implemented for their exploitation. This methodological innovation, based on a rigorous sampling, makes it possible to present the results of an integrated analysis of the geological samples in their areas of natural diffusion. It proposes a refined paleogeographic vision of the removal made by men in these areas and of their anthropic and natural transformation at the archaeological site. The original diffusion of this scientific study, which is still in progress, is based on a platform of content management and groupware, called Map’N, which integrates access to cartographic webservices and online functions of geocoding of the iconographic and cartographic documents used or produced by these research projects

Gibbs-non-Gibbs transitions via large deviations: computable examples

We give new and explicitly computable examples of Gibbs-non-Gibbs transitions of mean-field type, using the large deviation approach introduced in [4]. These examples include Brownian motion with small variance and related diffusion processes, such as the Ornstein-Uhlenbeck process, as well as birth and death processes. We show for a large class of initial measures and diffusive dynamics both short-time conservation of Gibbsianness and dynamical Gibbs-non-Gibbs transitions

Continuous path planning for a data harvesting mobile server

Abstract—We consider a queueing system composed of queues distributed at fixed locations in a continuous envi-ronment and a mobile server serving the jobs in the queues with spatially varying rates. For a fluid model of this system, we provide a necessary and sufficient stabilizability condition. Then we briefly investigate the question of server trajectory optimization for the problem of draining the initial fluid in two queues when no further arrivals occur. I