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

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

Spatial synchrony in stream fish populations: influence of species traits

Spatial synchrony in population dynamics has been identified in most taxonomic groups. Numerous studies have reported varying levels of spatial synchrony among closely-related species, suggesting that species' characteristics may play a role in determining the level of synchrony. However, few studies have attempted to relate this synchrony to the ecological characteristics and/or life-history traits of species. Yet, as to some extent the extinction risk may be related to synchrony patterns, identifying a link between species' characteristics and spatial synchrony is crucial, and would help us to define effective conservation planning. Here, we investigated whether species attributes and temperature synchrony (i.e. a proxy of the Moran effect) account for the differences in spatial population synchrony observed in 27 stream fish species in France. After measuring and testing the level of synchrony for each species, we performed a comparative analysis to detect the phylogenetic signal of these levels, and to construct various multi-predictor models with species traits and temperature synchrony as covariates, while taking phylogenetic relatedness into account. We then performed model averaging on selected models to take model uncertainty into account in our parameter estimates. Fifteen of the 27 species displayed a significant level of synchrony. Synchrony was weak, but highly variable between species, and was not conserved across the phylogeny. We found that some species' characteristics significantly influenced synchrony levels. Indeed, the average model indicated that species associated with greater dispersal abilities, lower thermal tolerance, and opportunistic strategy displayed a higher degree of synchrony. These findings indicate that phylogeny and spatial temperature synchrony do not provide information pertinent for explaining the variations in species' synchrony levels, whereas the dispersal abilities, the life-history strategies and the upper thermal tolerance limits of species do appear to be quite reliable predictors of synchrony levels

Using a robust multi‐settings inference framework on published datasets still reveals limited support for the abundant centre hypothesis: More testing needed on other datasets

Aim: The abundant centre hypothesis (ACH) predicts a negative relationship between species abundance and the distance to the geographical range centre. Since its formulation, empirical tests of the ACH have involved different settings (e.g. the distance to the ecological niche or to the geographical range centre), but studies found contrasting support for this hypothesis. Here, we evaluate whether these discrepancies might stem from differences regarding the context in which the ACH is tested (geographical or environmental), how distances are measured, how species envelopes are delineated, how the relationship is evaluated and which data are used. Location: The Americas. Time period: 1800–2017. Major taxa studied: Mammals, birds, fish, and tree seedlings. Methods: Using published abundance data for 801 species, together with species range maps, we tested the ACH using three distance metrics in both environmental and geographical spaces with range and niche envelopes delineated using two different algorithms, totalling 12 different settings. We then evaluated the distance–abundance relationship using correlation coefficients (traditional approach) and mixed-effect models to reduce the effect of sampling noise on parameter estimates. Results: Similar to previous studies, correlation coefficients indicated an absence of effect of distance on abundance for all taxonomic groups and settings. In contrast, mixed-effect models highlighted relationships of various strengths and shapes, with a tendency for more theoretically supported settings to provide stronger support for the ACH. The relationships were however not consistent across taxonomic groups and settings, and were sometimes even opposite to ACH expectations. Main conclusions: We found mixed and inconclusive results regarding the ACH. These results corroborate recent findings, and suggest either that our ability to predict abundances from the location of populations within geographical or environmental spaces is low, or that the data used here have a poor signal-to-noise-ratio. The latter calls for further testing on other datasets using the same range of settings and methodological framework

Vieillisement hygrothermique d'assemblages structuraux polyepoxy : analyse de la mobilité moléculaire par spectroscopie diélectrique dynamique

Ce travail de thèse a consisté à étudier le vieillissement hygrothermique d'assemblages collés aluminium epoxy utilisés dans le secteur spatial. L'évolution des propriétés physiques, mécaniques et de la dynamique relaxationnelle dans cette configuration opérationnelle a été étudiée au cours d'un vieillissement réel en salle blanche et au cours de vieillissements accélérés. L'évolution de la contrainte à la rupture, des faciès de rupture, des transitions thermodynamiques et de la mobilité des entités associées aux modes de relaxation a été suivie au cours du vieillissement. A l'échelle macroscopique, une diminution de la contrainte à la rupture a été relevée au cours du stockage et des essais de vieillissement simulé. Une diminution de la zone de rupture cohésive a été observée. Le modèle phénoménologique de Hallberg-Peck a permis d'établir une corrélation entre les deux types de vieillissement à cette échelle. La dynamique relaxationnelle a mis en évidence des interactions physiques entre l'eau et la matrice à des niveaux localisés et délocalisé. La plastification du réseau par l'eau a été observée ainsi que des interactions locales. L'état du réseau, i.e. vitreux ou caoutchoutique, a révélé deux types de modifications suite au vieillissement. A l'échelle locale, une description analytique a permis d'établir une corrélation entre la durée du stockage et la température des essais de vieillissement simulé.During spacecraft integration - in clean room - materials are used under humid and thermal controlled conditions. The characterisation and the simulation of ageing phenomena in bonding assemblies are a challenge to improve their conception and their durability. One alternative is to use accelerated testing but the link between accelerated testing and true ageing is unknown. The aim of this study was to shed some light on this correlation. This study concerned a room temperature curing epoxy-amine adhesive used in aluminium assemblies. We focused on ground ageing (also called humid ageing). The experimental protocol consisted in taking samples at different ageing times in satellite integration room. The results were compared with those obtained after 7 days of accelerated testing with different hydrothermal conditions. Dielectrical, thermal and mechanical experiments were carried out. Broadband dielectric spectroscopy gave information about molecular mobility in wide temperature and frequency range. Relaxation times and activation energy associated with molecular mobility were studied. Physicochemical processes that occur into the adhesive like the glassy transition temperature Tg were studied by differential scanning calorimetry. Mechanical test was single lap shear test. The results obtained were related to the macroscopic behaviour of assemblies as a function of accelerated testing conditions or real-time ageing. Correlation of experiments data obtained for different ageing conditions - real-time ageing, accelerated testing ageing – allowed us to understand the evolution of the studied adhesive at different scale i.e. an interpretation at a molecular level was proposed

Changements globaux et poissons d'eau douce : déterminants et implications de variations démographiques

Les changements climatiques on fait l'objet d'une attention grandissante, mais leurs influences sur les dynamiques de populations restent mal appréhendées. Nos résultats montrent que la température influence les dynamiques de populations de plusieurs espèces de poissons d'eau douce en France. Bien que des mécanismes communs aient été mis en évidence, les dynamiques de populations varient fortement en fonction des conditions environnementales locales. Les caractéristiques intrinsèques des espèces, au contraire de leur histoire évolutive, apparaissent comme des déterminants importants des dynamiques observées. Ces résultats pourraient permettre de mettre en place des mesures de gestion adaptées pour ces espèces, visant à réduire l'impact des changements environnementaux à venir.Climate change has been a subject of great interest across the past few years but its influence on population dynamics has seldom been considered. In this thesis, we demonstrate that climatic factors and in particular water temperatures have an influence on population dynamics of several freshwater fish species found in French rivers. Although common mechanisms acting at large spatial scales have been identified for the different species, considerable variations among populations have been revealed due to spatial heterogeneity of environmental conditions. Intrinsic characteristics of species appeared as important determinants of interspecific differences in population dynamics, contrary to their evolutionary history. Our results could be used to set up management conservation planning to limit the consequences of climate warming on freshwater fish species

New bonded assembly configuration for dynamic mechanical analysis of adhesives

A new sample configuration has been developed in order to study molecular mobility of an adhesive in a bonded assembly configuration by dynamic mechanical analysis. The torsional rectangular mode is used to provide a shear solicitation all along the adherend/adhesive interface. The initial mechanical properties of each assembly's constituent are first investigated as reference. The modulus of aluminum foils used as substrates exhibits a classic elastic component and a slight viscous part due to microstructural changes or stress relaxation. Four relaxation modes are highlighted and identified for epoxy adhesive tested as a bulk material. Its viscoelastic behavior is compared to the one of adhesive tested in assembly configuration. The relaxation modes of the adhesive remain visible in spite of the sample stiffening by aluminum foils. Relaxation modes comparison shows that the temperature of loss modulus associated with the mechanical manifestation of glass transition slightly increases for the assembly configuration. Energy losses during this relaxation are much higher in the assembly configuration. Influence of rigid aluminum substrates is discussed in terms of the adhesively bonded joint solicitation mode

Enthalpy relaxation phenomena of epoxy adhesive in operational configuration: Thermal, mechanical and dielectric analyses

Thermal cycling in space environment can cause physical aging of polymers used in structural adhesive bonded joint. Later, they can initiate failure. A methodology to follow physical aging effects on their thermal, mechanical and dielectric properties is applied to a commercial epoxy adhesive. The analytic description, using Tool, Narayanaswamy and Moynihan model gives a good description of the enthalpy relaxation. It is completed by a phenomenological analysis of the evolution of the adhesive thermal transitions, mechanical properties and molecular mobility. Testedsamples with bondedassembly are representative ofin service configurations. The influence of physical aging on the adhesive and the associated bonded assemblies is analyzed

A High Relative-Precision Color-Magnitude Diagram of M67

We have calibrated an extensive set of BVI observations of M67. We have selected stars that are most likely to be single-star members of the cluster using proper motion, radial velocity, and variability information from the literature, and an examination of the most probable color-magnitude diagram locations of unresolved stellar blends. Observations of M67 turnoff stars are a severe test of algorithms attempting to describe convective cores in the limit of small extent, and we find strong evidence of a ``hook'' just fainter than the turnoff gap. The stars in M67 support assertions that the degree of convective core overshooting decreases to zero for stars with masses in the range 1.0 < (M / M_sun) < 1.5, but that the degree of overshoot is smaller than currently used in published isochrones. We also verify that all current theoretical models for the lower main sequence (with the exception of Baraffe et al. 1998) are too blue for M_V >~ 6 even when the sequences are shifted to match M67 near the M_V of the Sun, probably due to a combination of problems with color-T_eff transformations and realistic surface boundary conditions for models. Finally, we identify a subset of cluster members with unusual photometry (candidate red giant binaries, blue straggler stars, and triple systems) deserving of further study.Comment: 25 pages, 15 figures, accepted for MNRA