Stability of the essential spectrum for 2D--transport models with Maxwell boundary conditions

We discuss the spectral properties of collisional semigroups associated to various models from transport theory by exploiting the links between the so-called resolvent approach and the semigroup approach. Precisely, we show that the essential spectrum of the full transport semigroup coincides with that of the collisionless transport semigroup in any $L^p$--spaces $(1 <p < \infty)$ for three 2D--transport models with Maxwell--boundary conditions.Comment: 23 page

Exploring the Memory-Bandwidth Tradeoff in an Information-Centric Network

An information-centric network should realize significant economies by exploiting a favourable memory-bandwidth tradeoff: it is cheaper to store copies of popular content close to users than to fetch them repeatedly over the Internet. We evaluate this tradeoff for some simple cache network structures under realistic assumptions concerning the size of the content catalogue and its popularity distribution. Derived cost formulas reveal the relative impact of various cost, traffic and capacity parameters, allowing an appraisal of possible future network architectures. Our results suggest it probably makes more sense to envisage the future Internet as a loosely interconnected set of local data centers than a network like today's with routers augmented by limited capacity content stores.Comment: Proceedings of ITC 25 (International Teletraffic Congress), Shanghai, September, 201

Impact of traffic mix on caching performance in a content-centric network

For a realistic traffic mix, we evaluate the hit rates attained in a two-layer cache hierarchy designed to reduce Internet bandwidth requirements. The model identifies four main types of content, web, file sharing, user generated content and video on demand, distinguished in terms of their traffic shares, their population and object sizes and their popularity distributions. Results demonstrate that caching VoD in access routers offers a highly favorable bandwidth memory tradeoff but that the other types of content would likely be more efficiently handled in very large capacity storage devices in the core. Evaluations are based on a simple approximation for LRU cache performance that proves highly accurate in relevant configurations

A cooperative local search-based algorithm for the Multiple-Scenario Max-Min Knapsack Problem

8International audienceThe purpose of this article is to present a novel method to approximately solve the Multiple-Scenario Max-Min Knapsack Problem (MSM2KP). This problem models many real world situations, e.g. when for many scenarios noted $\pi \in \mathcal P=\{1,\ldots,P\}$, the aim is to identify the one offering a better alternative in term of maximizing the worst possible outcome. Herein is presented a cooperative approach based on two local search algorithms: (i) a limited-area local search applied in the elite neighborhood and which accepts the first solution with some deterioration threshold of the current solution, (ii) a wide range local search is applied to perform a sequence of paths exchange to improve the current solution. Results have been analyzed by means state-of-the art methods and via problem instances obtained by a generator code taken from the literature. The tests were executed in compeltely comparable scenarios to those of the literature. The results are promising and the efficiency of the proposed approach is also shown

LES OUTILS DU WEB 2.0 AU SERVICE DE L'ADMINISTRATION ÉLECTRONIQUE

De nos jours, l'Administration publique offre un nombre varié et important de services à ses usagers. Ces services souffrent généralement d’une lenteur souvent exagérée, d’une grande bureaucratie et, dans la plupart des cas, d’une rupture complète avec ses usagers. Afin de moderniser ses services et d'améliorer leur qualité, elle a utilisé, depuis des années déjà et d’une manière incrémentale, les TIC afin d'atteindre les objectifs fixés. Des gains importants en termes d'efficacité, de qualité de service, de productivité et de délai d'exécution se sont rapidement fait sentir auprès des usagers. Par ailleurs, avec la large utilisation et la diffusion des outils sociaux du web 2.0 souvent gratuits et leur adoption par les jeunes générations, il s'avère indispensable de les intégrer, en plus des TIC traditionnels, pour repenser les anciens services et en proposer de nouveaux pour répondre aux nouveaux besoins recensés. C’est dans ce contexte que se positionne notre article, qui a pour objectif de proposer une stratégie méthodologique basée sur les outils sociaux du web 2.0 permettant d'intégrer et de repositionner davantage les usagers dans la vie politique afin de garantir une bonne gouvernance dans le contexte national et d'atteindre les objectifs tracés par les politiques publiques

A characterization of the solutions of steady Hamilton-Jacobi equations

In this note, we propose to revisit the approximate stationary Hamilton-Jacobi equations and analyse the corresponding solutions following certain properties of the hamiltonian. This enables us to give a characterization of the zero set of the limiting solution. We also remark that the analysis can be applied for evolution equations with a time periodic source term

Well-posedness of general boundary-value problems for scalar conservation laws

International audienceIn this paper we investigate well-posedness for the problem u_t+ \div \ph(u)=f on (0,T)\!\times\!\Om, \Om \subset \R^N, with initial condition $u(0,\cdot)=u_0$ on \Om and with general dissipative boundary conditions $\varphi(u)\cdot \nu \in \beta_{(t,x)}(u)$ on (0,T)\!\times\!\ptl\Om. Here for a.e. (t,x)\in(0,T)\!\times\!\ptl\Om, $\beta_{(t,x)}(\cdot)$ is a maximal monotone graph on $\R$. This includes, as particular cases, Dirichlet, Neumann, Robin, obstacle boundary conditions and their piecewise combinations. As for the well-studied case of the Dirichlet condition, one has to interprete the {\it formal boundary condition} given by $\beta$ by replacing it with the adequate {\it effective boundary condition}. Such effective condition can be obtained through a study of the boundary layer appearing in approximation processes such as the vanishing viscosity approximation. We claim that the formal boundary condition given by $\beta$ should be interpreted as the effective boundary condition given by another monotone graph $\tilde \beta$, which is defined from $\beta$ by the projection procedure we describe. We give several equivalent definitions of entropy solutions associated with $\tilde \beta$ (and thus also with $\beta$). For the notion of solution defined in this way, we prove existence, uniqueness and $L^1$ contraction, monotone and continuous dependence on the graph $\beta$. Convergence of approximation procedures and stability of the notion of entropy solution are illustrated by several results

Single-machine scheduling with periodic and flexible periodic maintenance to minimize maximum tardiness.

International audienceThis paper considers a single machine scheduling problem with several maintenances periods. Specially, two situations are investigated. In the first one, maintenance periods are periodically fixed : maintenance is required after a periodic time interval. In the second one, the maintenance is not fixed but the maximum continuous working time of the machine which is allowed is determined. The objective is to minimize the maximum tardiness. These problems are known to be strongly NP-hard. We propose some dominance properties and an efficient heuristic. Branch-and-bound algorithms, in which the heuristics, the lower bounds and the dominance properties are incorporated, are proposed and tested computationally

Recognizing claw-free perfect graphs

AbstractWe present a polynomial-time algorithm to recognize claw-free perfect graphs. The algorithm is based on a decomposition theorem elucidating the structure of these graphs

Hard graphs for the maximum clique problem

The maximum clique problem is one of the NP-complete problems. There are graphs for which a reduction technique exists that transforms the problem for these graphs into one for graphs with specific properties in polynomial time. The resulting graphs do not grow exponentially in order and number. Graphs that allow such a reduction technique are called soft. Hard graphs are those graphs for which none of the reduction techniques can be applied. A list of properties of hard graphs is determined