Soft Cache Hits and the Impact of Alternative Content Recommendations on Mobile Edge Caching

Caching popular content at the edge of future mobile networks has been widely considered in order to alleviate the impact of the data tsunami on both the access and backhaul networks. A number of interesting techniques have been proposed, including femto-caching and "delayed" or opportunistic cache access. Nevertheless, the majority of these approaches suffer from the rather limited storage capacity of the edge caches, compared to the tremendous and rapidly increasing size of the Internet content catalog. We propose to depart from the assumption of hard cache misses, common in most existing works, and consider "soft" cache misses, where if the original content is not available, an alternative content that is locally cached can be recommended. Given that Internet content consumption is increasingly entertainment-oriented, we believe that a related content could often lead to complete or at least partial user satisfaction, without the need to retrieve the original content over expensive links. In this paper, we formulate the problem of optimal edge caching with soft cache hits, in the context of delayed access, and analyze the expected gains. We then show using synthetic and real datasets of related video contents that promising caching gains could be achieved in practice

3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability and habitability

The inner edge of the classical habitable zone is often defined by the critical flux needed to trigger the runaway greenhouse instability. This 1D notion of a critical flux, however, may not be so relevant for inhomogeneously irradiated planets, or when the water content is limited (land planets). Here, based on results from our 3D global climate model, we find that the circulation pattern can shift from super-rotation to stellar/anti stellar circulation when the equatorial Rossby deformation radius significantly exceeds the planetary radius. Using analytical and numerical arguments, we also demonstrate the presence of systematic biases between mean surface temperatures or temperature profiles predicted from either 1D or 3D simulations. Including a complete modeling of the water cycle, we further demonstrate that for land planets closer than the inner edge of the classical habitable zone, two stable climate regimes can exist. One is the classical runaway state, and the other is a collapsed state where water is captured in permanent cold traps. We identify this "moist" bistability as the result of a competition between the greenhouse effect of water vapor and its condensation. We also present synthetic spectra showing the observable signature of these two states. Taking the example of two prototype planets in this regime, namely Gl581c and HD85512b, we argue that they could accumulate a significant amount of water ice at their surface. If such a thick ice cap is present, gravity driven ice flows and geothermal flux should come into play to produce long-lived liquid water at the edge and/or bottom of the ice cap. Consequently, the habitability of planets at smaller orbital distance than the inner edge of the classical habitable zone cannot be ruled out. Transiting planets in this regime represent promising targets for upcoming observatories like EChO and JWST.Comment: Accepted for publication in Astronomy and Astrophysics, complete abstract in the pdf, 18 pages, 18 figure

The effect of rotation and tidal heating on the thermal lightcurves of Super Mercuries

Short period (<50 days) low-mass (<10Mearth) exoplanets are abundant and the few of them whose radius and mass have been measured already reveal a diversity in composition. Some of these exoplanets are found on eccentric orbits and are subjected to strong tides affecting their rotation and resulting in significant tidal heating. Within this population, some planets are likely to be depleted in volatiles and have no atmosphere. We model the thermal emission of these "Super Mercuries" to study the signatures of rotation and tidal dissipation on their infrared light curve. We compute the time-dependent temperature map at the surface and in the subsurface of the planet and the resulting disk-integrated emission spectrum received by a distant observer for any observation geometry. We calculate the illumination of the planetary surface for any Keplerian orbit and rotation. We include the internal tidal heat flow, vertical heat diffusion in the subsurface and generate synthetic light curves. We show that the different rotation periods predicted by tidal models (spin-orbit resonances, pseudo-synchronization) produce different photometric signatures, which are observable provided that the thermal inertia of the surface is high, like that of solid or melted rocks (but not regolith). Tidal dissipation can also directly affect the light curves and make the inference of the rotation more difficult or easier depending on the existence of hot spots on the surface. Infrared light curve measurement with the James Webb Space Telescope and EChO can be used to infer exoplanets' rotation periods and dissipation rates and thus to test tidal models. This data will also constrain the nature of the (sub)surface by constraining the thermal inertia.Comment: 15 pages, 13 figures, accepted for publication in Astronomy & Astrophysic

Multi-state and non-volatile control of graphene conductivity with surface electric fields

Planar electrodes patterned on a ferroelectric substrate are shown to provide lateral control of the conductive state of a two-terminal graphene stripe. A multi-level and on-demand memory control of the graphene resistance state is demonstrated under low sub-coercive electric fields, with a susceptibility exceeding by more than two orders of magnitude those reported in a vertical gating geometry. Our example of reversible and low-power lateral control over 11 memory states in the graphene conductivity illustrates the possibility of multimemory and multifunctional applications, as top and bottom inputs remain accessible.Comment: Graphene ferroelectric lateral structure for multi-state and non-volatile conductivity control, 4 pages, 4 figure

EVAA: A platform for experimental virtual archeological-acoustics to study the influence of performance space

International audienceResearch in historical musical acoustics has for several decades focused significantly on instrument fabrication. Such research has been able to highlight the acoustical impact of material and construction choices. Musicolog-ical studies have concentrated in parallel on understanding historical notation, playing styles, and even changes in musician posture over the centuries. In studying player and listener conditions in these historical studies, little attention has been given to the acoustical conditions of the performance, aside from extreme cases such as cathedral acoustic conditions. Extending the methodologies of experimental archaeology, recent advances in computational accuracy of acoustic virtual reality simulations offer the possibility to create ecologically valid reconstructions of historic sites. We present the development of an interactive immersive real-time simulator allowing musicians to perform "live" within virtual reconstructions of historic venues, comprising real-time adaptation of source directives with performer movements, rendered in Higher Order Ambisonics. Observations of the impact of acoustic variations on player performance, and the comparisons of the resulting performance between historically suitable venues and modern performance spaces from an audience perspective will complete the feedback loop between performer and listener necessary for a full understanding of the historical musical context

Projet de paysage participatif à Villandry

Cette recherche s’inscrit dans le cadre du projet intitulé « Participation des populations et renouvellement des pratiques paysagistes. Une approche par l’expérimentation et la comparaison des méthodes » au sein du programme « Paysage et Développement durable II », porté par le MEDDE. L’originalité de ce projet tient en partie à la collaboration entre des enseignants-chercheurs de trois écoles de paysage françaises (Angers, Versailles et Bordeaux) et des paysagistes, engagés ensemble dans deux démarches expérimentales. Nous revenons plus particulièrement dans cet article sur l’une des deux expérimentations, conduite sur la commune de Villandry dans le Val de Loire

Quantum Transport in Chemically-modified Two-Dimensional Graphene: From Minimal Conductivity to Anderson Localization

An efficient computational methodology is used to explore charge transport properties in chemically-modified (and randomly disordered) graphene-based materials. The Hamiltonians of various complex forms of graphene are constructed using tight-binding models enriched by first-principles calculations. These atomistic models are further implemented into a real-space order-N Kubo-Greenwood approach, giving access to the main transport length scales (mean free paths, localization lengths) as a function of defect density and charge carrier energy. An extensive investigation is performed for epoxide impurities with specific discussions on both the existence of a minimum semi-classical conductivity and a crossover between weak to strong localization regime. The 2D generalization of the Thouless relationship linking transport length scales is here illustrated based on a realistic disorder model.Comment: 14 pages, 18 figures, submitte

Increased insolation threshold for runaway greenhouse processes on Earth like planets

Because the solar luminosity increases over geological timescales, Earth climate is expected to warm, increasing water evaporation which, in turn, enhances the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can "runaway" until all the oceans are evaporated. Through increases in stratospheric humidity, warming may also cause oceans to escape to space before the runaway greenhouse occurs. The critical insolation thresholds for these processes, however, remain uncertain because they have so far been evaluated with unidimensional models that cannot account for the dynamical and cloud feedback effects that are key stabilizing features of Earth's climate. Here we use a 3D global climate model to show that the threshold for the runaway greenhouse is about 375 W/m$^2$, significantly higher than previously thought. Our model is specifically developed to quantify the climate response of Earth-like planets to increased insolation in hot and extremely moist atmospheres. In contrast with previous studies, we find that clouds have a destabilizing feedback on the long term warming. However, subsident, unsaturated regions created by the Hadley circulation have a stabilizing effect that is strong enough to defer the runaway greenhouse limit to higher insolation than inferred from 1D models. Furthermore, because of wavelength-dependent radiative effects, the stratosphere remains cold and dry enough to hamper atmospheric water escape, even at large fluxes. This has strong implications for Venus early water history and extends the size of the habitable zone around other stars.Comment: Published in Nature. Online publication date: December 12, 2013. Accepted version before journal editing and with Supplementary Informatio

Droit de la construction : de la jurisprudence à la pratique notariale

"Parce que le contentieux de la construction concerne les notaires à bien des égards, cette nouvelle chronique, rédigée par des universitaires et des praticiens, a pour objectif premier de brosser un panorama des décisions importantes rendues au cours de l\u27année 2012 en la matière. Les signataires de ces lignes ont ensuite cherché, dans le cadre de cette collaboration entre chercheurs et notaires, à enrichir leurs commentaires de conseils pratiques. Ainsi, au cours de l\u27année écoulée, la Cour de cassation s\u27est prononcée sur des questions générales d\u27organisation de l\u27immeuble, précisant la liberté de choix entre le statut de la copropriété et la division en volumes ou revenant sur les règles applicables aux travaux réalisés sur un mur mitoyen. Des précisions ont également été apportées sur le champ d\u27application de la responsabilité décennale des constructeurs, puisqu\u27il a été rappelé que le vendeur même non professionnel d\u27un immeuble rénové peut, à certaines conditions, engager sa responsabilité décennale, de même que cette cause de responsabilité est également susceptible de s\u27appliquer lorsque les dommages affectant un immeuble neuf causent des préjudices à des tiers ou se matérialisent par un simple risque d\u27écroulement, sans que la catastrophe ne soit encore survenue. Un arrêt important précise en outre, dans le domaine des assurances, la distinction entre la faute lourde, couverte, et celle intentionnelle, dont l\u27assureur ne répondra pas. On relèvera finalement trois décisions importantes en matière de vente d\u27immeubles à construire. Deux concernent la rédaction des actes, quant à la distinction entre les notions d\u27achèvement et de livraison d\u27une part, puis relativement aux clauses d\u27allongement de délai de livraison pour intempéries, d\u27autre part. Le dernier revient sur la question importante la rénovation en précisant l\u27étendue de la responsabilité du notaire dans le choix entre le modèle de la vente en l\u27état futur d\u27achèvement et celui de la vente d\u27immeuble à rénover." Gwenaëlle Durand-Pasquie