Satisfiability of General Intruder Constraints with and without a Set Constructor

Many decision problems on security protocols can be reduced to solving so-called intruder constraints in Dolev Yao model. Most constraint solving procedures for protocol security rely on two properties of constraint systems called monotonicity and variable origination. In this work we relax these restrictions by giving a decision procedure for solving general intruder constraints (that do not have these properties) that stays in NP. Our result extends a first work by L. Mazar\'e in several directions: we allow non-atomic keys, and an associative, commutative and idempotent symbol (for modeling sets). We also discuss several new applications of the results.Comment: Submitted to the Special issue of Information and Computation on Security and Rewriting Techniques (SecReT), 2011. 59 page

Pt-modified Ni aluminides, MCrAlY-base multilayer coatings and TBC systems fabricated by Spark Plasma Sintering for the protection of Ni-base superalloys

Pt-modified Ni aluminides and MCrAlY coatings (where M=Ni and/or Co) are widely used on turbine blades and vanes for protection against oxidation and corrosion and as bond coatings in thermal barrier coating (TBC) systems. The present work shows the ability of a new fabrication technique, the Spark Plasma Sintering, to develop rapidly new coating compositions and microstructures. This technique allows combining powders and metallic foils on a superalloy substrate in order to obtain multilayered coatings in a single short experiment. Fabrication of MCrAlY overlays with local Pt and/or Al enrichment is shown, as well as fabrication of coatings made of ζ-PtAl2, ε-PtAl, α-AlNiPt2, martensitic β- (Ni,Pt)Al or Pt-rich γ/γ′ phases. The realization of a complete TBC system with a porous and adherent Yttria Stabilized Zirconia (YSZ) layer on a γ/γ′ low mass bond coating is also demonstrated. Difficulties of fabrication are reviewed and discussed, such as Y segregation, risks of carburization, local overheating, or difficulty to coat complex shape parts. Finally, some first results of cyclic oxidation are given

Intruder deducibility constraints with negation. Decidability and application to secured service compositions

The problem of finding a mediator to compose secured services has been reduced in our former work to the problem of solving deducibility constraints similar to those employed for cryptographic protocol analysis. We extend in this paper the mediator synthesis procedure by a construction for expressing that some data is not accessible to the mediator. Then we give a decision procedure for verifying that a mediator satisfying this non-disclosure policy can be effectively synthesized. This procedure has been implemented in CL-AtSe, our protocol analysis tool. The procedure extends constraint solving for cryptographic protocol analysis in a significative way as it is able to handle negative deducibility constraints without restriction. In particular it applies to all subterm convergent theories and therefore covers several interesting theories in formal security analysis including encryption, hashing, signature and pairing.Comment: (2012

The Effects of Reduced Social Security Contributions on Employment: an Evaluation of the 2003 French Reform

In 2003, the French government decided to reform the system managing the different minimum wage regulations and the targeted reductions to employers' social security contributions. The main objective of the reform was to simplify the complex regulations that were created by the progressive introduction of the 35-hour week. The reform incidentally created large variations in labour costs, depending on the type of firm and the wage level within the firm. This paper presents an evaluation of the impact of this reform on employment using a balanced panel of firms with more than five employees, drawn from a matching between several administrative data sources from 2000 to 2005. In both types of firm, significant employment elasticities can be found with respect to labour costs that have the expected signs: a rise of 1% in average labour costs reduces employment by 0.4%. As the majority of firms that remained on the 39-hour week received greater reductions, the Fillon reform allowed them to raise their level of employment. Firms that adopted the 35-hour week experienced the opposite: the reform led to a fall in employment. Ultimately, the Fillon reform has had no clear effect on aggregate employment, measured either in job numbers or full-time equivalents (FTE)

Description of the unsteady flow pattern from peak efficiency to near surge in subsonic centrifugal compressor stage

This paper aims to describe the flow structure modifications when the operating point moves from peak efficiency to near stall condition in a moderate pressure ratio centrifugal compressor stage consisted of a splittered unshrouded impeller and a vaned diffuser. The investigations are based on three-dimensional U-RANS simulation results. The flow is described in the impeller and in the vaned diffuser through time-averaged flow quantities and unsteady fluctuations. Results show that at low mass flow rate, the effects of secondary flow in the impeller are more pronounced, inducing both, high time-averaged values and temporal fluctuations of the flow angle near the shroud at the diffuser inlet, leading to vane suction side boundary layer separation. Pressure waves due to impeller diffuser interaction spread through the vaned diffuser generating unsteadiness which intensifies at near surge condition

Les effets des aides publiques aux Hôtels Cafés Restaurants et leurs interactions

La Mission Animation de la Recherche DARES du Ministère du Travail, de l'Emploi et de la Santé (MAR-DARES) a lancé au cours de l'été 2009 un appel d'offre intitulé " Evaluation des effets de l'aide financière aux employeurs du secteur des Hôtels-cafés-restaurants dans le cadre de la loi du 9 août 2004 " dans le but de quantifier l'impact sur l'emploi et les salaires d'une politique sectorielle originale. L'équipe du Centre d'Etude de l'Emploi a été retenue pour évaluer les effets de cette politique sur les entreprises des différents secteurs des Hôtels-cafés-restaurants. L'objet de ce rapport est des présenter les résultats de ce travail d'évaluation.Évaluation politique publique, aide à l'emploi sectorielle, Hôtel-café-restaurant

Metal enrichment in a semi-analytical model, fundamental scaling relations, and the case of Milky Way galaxies

Gas flows play a fundamental role in galaxy formation and evolution, providing the fuel for the star formation process. These mechanisms leave an imprint in the amount of heavy elements. Thus, the analysis of this metallicity signature provides additional constraint on the galaxy formation scenario. We aim to discriminate between four different galaxy formation models based on two accretion scenarios and two different star formation recipes. We address the impact of a bimodal accretion scenario and a strongly regulated star formation recipe. We present a new extension of the eGalICS model, which allows us to track the metal enrichment process. Our new chemodynamical model is applicable for situations ranging from metal-free primordial accretion to very enriched interstellar gas contents. We use this new tool to predict the metallicity evolution of both the stellar populations and gas phase. We also address the evolution of the gas metallicity with the star formation rate (SFR). We then focus on a sub-sample of Milky Way-like galaxies. We compare both the cosmic stellar mass assembly and the metal enrichment process of such galaxies with observations and detailed chemical evolution models. Our models, based on a strong star formation regulation, allow us to reproduce well the stellar mass to gas-phase metallicity relation observed in the local universe. However, we observe a systematic shift towards high masses. Our $Mstar-Zg-SFR relation is in good agreement with recent measurements: our best model predicts a clear dependence with the SFR. Both SFR and metal enrichment histories of our Milky Way-like galaxies are consistent with observational measurements and detailed chemical evolution models. We finally show that Milky Way progenitors start their evolution below the observed main sequence and progressively reach this observed relation at z = 0.Comment: 22 pages, 11 figure

LES DISCRIMINATIONS A L'EMBAUCHE DANS LA SPHERE PUBLIQUE : EFFETS RESPECTIFS DE L'ADRESSE ET DE L'ORIGINE

Cette étude évalue la discrimination dans l’accès à l’emploi dans trois professions présentes à la fois dans le secteur privé et dans la Fonction Publique. Deux dimensions sont examinées : l’effet de la réputation du lieu de résidence et l’effet de l’origine maghrébine. Elle est réalisée sur données expérimentales de testing réalisé dans trois professions en tension pour lesquelles la discrimination devrait a priori être très réduite : les responsables administratifs de catégorie A, les techniciens de maintenance de catégorie B et les aides soignantes de catégorie C. Pour chaque profession, nous avons construit 3 profils fictifs de candidats à l’emploi similaires en tout point à l’exception de la caractéristique testée (l’origine signalée par la consonance du prénom et du nom, ou la réputation du lieu de résidence). Entre octobre 2015 et avril 2016, nous avons envoyé 3258 candidatures en réponse à 1086 offres d’emploi. L’étude consiste en une exploitation statistique des résultats de ces envois.Nous mettons en avant trois principaux résultats, conditionnellement au fait que des données de testing ne fournissent qu’une mesure partielle, ponctuelle et localisée des discriminations à l’embauche. Premièrement, nous ne trouvons pas que les discriminations à l’embauche sont plus faibles dans la Fonction Publique que dans le secteur privé. Deuxièmement, nous ne sommes pas parvenus à mettre en évidence l’existence de discriminations qui seraient spécifiques à la Fonction Publique d’Etat ; en revanche, nous fournissons plusieurs preuves de l’existence d’une discrimination dans l’accès à l’emploi, selon l’origine et le lieu de résidence, pour les Fonctions Publiques Hospitalière et Territoriale.Troisièmement, le mode de recrutement par concours tel qu’il est organisé dans la Fonction Publique Territoriale ne permet pas de garantir un accès égal à l’emploi public : nous trouvons des discriminations à la fois pour les recrutements de contractuels et pour ceux de fonctionnaires titulaires après un concours

Estimation of relative position and coordination of mobile underwater robotic platforms through electric sensing.

International audienceIn the context of underwater robotics, positioning and coordination of mobile agents can prove a challenging problem. To address this issue, we propose the use of electric sensing, with a technique inspired by weakly electric fishes. In particular, the approach relies on one or several of the agents applying an electric field to their environment. Using electric measures, others agents are able to reconstruct their relative position with respect to the emitter, over a range that is function of the geometry of the emitting agent and of the power applied to the environment. Efficacy of the technique is illustrated using a number of numerical examples. The approach is shown to allow coordination of unmanned underwater vehicles, including that of bio-inspired swimming robotic platforms

Action-Perception Trade-Offs for Anguilliform Swimming Robotic Platforms with an Electric Sense

International audienceThe work presented addresses the combination of anguilliform swimming-based propulsion with the use of an electric sensing modality for a class of unmanned underwater vehicles, and in particular investigates the relative influence of adjustments to the swimming gait on the platform's displacement speed and on sensing performance. This influence is quantified, for a relevant range of swimming gaits, using experimental data recordings of displacement speeds, and a boundary element method-based numerical simulation tool allowing to reconstruct electric measures. Results show that swimming gaits providing greater movement speeds tend to degrade sensing performance. Conversely, gaits yielding accurate sensing tend to prove slower. To reconcile opposing tendencies, a simple action-perception cost function is designed, with the purpose of adjusting an anguilliform swimmer's gait shape, in accordance with respective importance afforded to action (i.e. movement speed) and perception