Martingale relations for the M⧸GI⧸1 queue with Markov modulated Poisson input

AbstractThis paper is concerned with single server queueing systems with renewal service process and Poisson arrivals modulated by a finite-state Markov chain. Exponential martingales are associated with a chain embedded at service completion epochs in the stochastic process describing the joint evolution of the number of customers in the queue and the state of the environment. The analysis of these martingales leads to a new and unified treatment of various known results concerning the stability condition and the steady state statistics, as well as to several new properties. Noteworthy among them are a conservation law that relates the duration of the busy period to the state of the environment at the end of the busy period, and some absolute continuity properties with respect to other queues of the same type

Estimating a CBRN atmospheric release in a complex environment using Gaussian Processes

International audienceIn this paper, we present a new methodology for the estimation and the prediction of the concentration of pollutant in a complex environment. We take benefit of a semi-parametric formulation of the problem to perform a faster and more efficient estimation of the pollutant cloud. In a first part, we present how we use the Gaussian process to model the interactions between position and time given the observations. Then, we introduce the expansion as a function of the observations through the time, and we construct an estimator of the time of release from it within change-point detection framework. Then, we use this time estimate to obtain the position (or more likely, a confidence region of the position) of the source. Several simulations are provided in a complex city scenario that demonstrate the accuracy of the proposed technique

Slow flows of yield stress fluids: complex spatio-temporal behaviour within a simple elasto-plastic model

A minimal athermal model for the flow of dense disordered materials is proposed, based on two generic ingredients: local plastic events occuring above a microscopic yield stress, and the non-local elastic release of the stress these events induce in the material. A complex spatio-temporal rheological behaviour results, with features in line with recent experimental observations. At low shear rates, macroscopic flow actually originates from collective correlated bursts of plastic events, taking place in dynamically generated fragile zones. The related correlation length diverges algebraically at small shear rates. In confined geometries bursts occur preferentially close to the walls yielding an intermittent form of flow localization.Comment: 4 pages, 4 figure

Automating the Porting of Linux to the VirtualLogix Hypervisor using Semantic Patches

International audienceVirtualization is a promising technology for running multiple operating systems (OS’s) on a single processor. Preparing an OS for use with virtualization, however, involves making some changes to the OS code, which must be repeated for each version, whether a new release or a client customization. Typically such changes are expressed as patches, but patches are often not portable from one version to another, and thus manual adjustments are needed as well. In this paper, we consider the use of the automated transformation system Coccinelle to perform the changes required to port several versions of Linux to the VLX hypervisor. Coccinelle provides a notion of semantic patches, which are more abstract than standard patches, and thus are potentially applicable to a wider range of OS versions. We have applied this approach in the context of Linux versions 2.6.13, 2.6.14, and 2.6.15, for the ARM architecture