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Effect of fly ash, basalt fibre and attapulgite nanoclay on the fresh properties, rheology and shrinkage behaviour of printable concrete
No full textInternational audienc
Convergence of higher derivatives of random polynomials with independent roots
No full textLet be a probability measure on , and let be the random polynomial whose zeros are sampled independently from . We study the asymptotic distribution of zeros of high-order derivatives of . We show that, for large classes of measures , the empirical distribution of zeros of the -th derivative converges back to for all derivative orders . This includes all discrete measures and a broad family of measures satisfying a mild dimension-nondegeneracy condition. We further establish a robustness result showing that, for arbitrary , even after adding a vanishing proportion of roots drawn from a dimension-nondegenerate perturbation, the derivative zero measures still converge back to . These results break the previously known logarithmic barrier on the order of differentiation and demonstrate that the limiting root distribution is preserved under differentiation of order growing nearly linearly with the degree
An experimental method for determining the in-plane shear modulus of carbon fibres
No full textInternational audienceThe performance of bituminous materials is often evaluated using rheological properties measured within the linear viscoelastic region. If there is a univocal temperature dependence of all the relaxation times, data obtained in different operating conditions can be translated onto a logarithmic scale where they partially overlap and merge into a single master curve. This is the well-known time–temperature superposition principle that has been successfully applied for decades. However, the empirical nature of the method has led to many different procedures being used for the graphical construction of the master curve. In addition, the continuously increasing calculating power has led to new approaches, such as the simultaneous modelling of the represented viscoelastic function. Losing track of the basic statements of the method is the hidden drawback of this wide range of available protocols with the risk of artefacts and incongruences being introduced in the construction of the master curves. This review summarizes these basic statements together with the empirical and phenomenological approaches developed over the years. The aim of this study is to help the reader in choosing the most appropriate method to build the master curves. Although the subject of the review is of general application, the field of bitumen is focused on
Foules d’Olivia Grandville. Un projet participatif aux confins des tensions du champ chorégraphique
No full textInternational audienceTandis que les projets participatifs se multiplient sur scène, la pièce Foules d’Olivia Grandville agit comme un révélateur des tensions qui traversent le monde artistique : entre ambition esthétique et bricolage organisationnel, promesse démocratique et risque d’inégalités, reconnaissance institutionnelle et possible instrumentalisation politique
A parsimonious tail compliant multiscale statistical model for aggregated rainfall
No full textInternational audienceModeling rainfall intensity distributions across aggregation scales (from sub-hourly to weekly) is essential for hydrological risk analysis and IDF curves. Aggregation naturally imposes mathematical constraints: return levels must be ordered by time scale, as daily accumulations necessarily exceed sub-daily ones. From a statistical perspective, each aggregation step should ideally not require additional parameters, yet parsimonious models describing the full distribution remain scarce, as most literature focuses on seasonal block maxima. In this study, we propose a parsimonious framework to model all rainfall intensities (low to large) across scales. We utilize the Extended Generalized Pareto Distribution (EGPD), which aligns with extreme value theory for both tails while remaining flexible for the bulk of the distribution. We establish a general result on the behavior of EGPD variables under various aggregation procedures. To overcome the difficulty of direct likelihood inference, we link the EGPD class to Poisson compound sums. This allows the use of the Panjer algorithm for efficient composite likelihood evaluation. Our approach ensures that return levels do not cross across scales and enables estimation for return periods below annual or seasonal levels. We demonstrate the method using sub-hourly series from six French stations with diverse climates. Only eight parameters are needed per station to capture scales from six minutes to three days. IDF curves above and below the annual scale are provided
Visualisation des ondes sonores dans l'eau par cymatique.: Cymaglyphes intégrés dans un film documentaire
No full textIntegrative assessment of biohydrogen and biomethane production from Brittany and Caribbean Sargassum (Ochrophyta, Fucales)
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Static bending of micromorphic Timoshenko beams
No full textInternational audienceAbstract This paper investigates statics and natural vibration of linear elastic cubic lattices, together with their continuum approximations. The lattice endowed with central and angular interactions, referred to as Gazis et al . ’s, is considered first: since the stiffness of each lattice phase must be positive, the equivalent macroscopic Poisson’s ratio must be lower than its central limit 1/4. A volumetric interaction based on a volume-dependent internal pressure is introduced as an additional non-central interaction for a complete calibration of the equivalent Poisson’s ratio up to its incompressibility limit 1/2. This volumetric interaction can also be classified as Fuchs-type, providing a potential energy that depends on the volume variation of each cell. The mixed differential-difference equations of the associated lattice derive from Hamilton’s principle applied to the discrete energies. The algebraic properties of the stiffness matrix of the discrete cell provide information on the positive definiteness of the potential energy, for each lattice with central and non-central interactions. The convergence of this finite lattice towards a linear elastic continuous right parallelepiped is shown in several static loading schemes. The discrete Lamé problem for the free vibration of this parallelepiped is solved for all the considered lattices. It is concluded that discrete and continuum elasticity can be connected by this cubic lattice within a complete range of elasticity parameters
Higher-order 2D lattices with long-range interactions and their nonlocal continua
No full textInternational audienceThis paper presents the formulation of two-dimensional (2D) square elastic lattices consisting of point-like material particles and incorporating central and angular (non-central) short- and long-range interactions of arbitrary order p . Each particle is assumed to interact with all other particles of the discrete medium along arbitrary directions. At the first-order asymptotic limit, these lattices converge to simple linear elastic continua. The lattice parameters are calibrated such that the asymptotic continuum behaves as a homogeneous, linear elastic, isotropic medium with a free Poisson’s ratio under both plane stress and plane strain conditions. When higher-order terms are retained in the asymptotic expansion, the discrete medium is shown to correspond to higher-order gradient elasticity or, equivalently, at the desired order, to a nonlocal elastic continuum. The exact wave dispersion properties of the generalized lattice with long-range interactions are investigated, with particular emphasis on the role of the discrete kernel. It is demonstrated that, for kernels with monotonically decreasing influence functions, the wave dispersion curves in the first Brillouin zone are monotonic for any interaction order p . We give a first proof from the analytical determination of the roots of the group velocity function, up to p = 5 interactions. Another proof is presented, whatever the number p of interactions, by expressing this gradient function through the Dirichlet kernel. Finally, the paper provides a calibration of nonlocal elasticity models to reproduce the wave dispersion characteristics of the higher-order lattice with long-range interactions. For both isotropic and anisotropic nonlocal models, the characteristic length scales are shown to depend on the interaction order and the shape of the discrete kernel