Tensor-based multiscale method for diffusion problems in quasi-periodic heterogeneous media

This paper proposes to address the issue of complexity reduction for the numerical simulation of multiscale media in a quasi-periodic setting. We consider a stationary elliptic diffusion equation defined on a domain $D$ such that $\overline{D}$ is the union of cells $\{\overline{D_i}\}_{i\in I}$ and we introduce a two-scale representation by identifying any function $v(x)$ defined on $D$ with a bi-variate function $v(i,y)$, where $i \in I$ relates to the index of the cell containing the point $x$ and $y \in Y$ relates to a local coordinate in a reference cell $Y$. We introduce a weak formulation of the problem in a broken Sobolev space $V(D)$ using a discontinuous Galerkin framework. The problem is then interpreted as a tensor-structured equation by identifying $V(D)$ with a tensor product space $\mathbb{R}^I \otimes V(Y)$ of functions defined over the product set $I\times Y$. Tensor numerical methods are then used in order to exploit approximability properties of quasi-periodic solutions by low-rank tensors.Comment: Changed the choice of test spaces V(D) and X (with regard to regularity) and the argumentation thereof. Corrected proof of proposition 3. Corrected wrong multiplicative factor in proposition 4 and its proof (was 2 instead of 1). Added remark 6 at the end of section 2. Extended remark 7. Added references. Some minor improvements (typos, typesetting

Modeling of Heat Transfer and Unsaturated Flow in Woven Fiber Reinforcements during Direct Injection-Pultrusion Process of Thermoplastic Composites

International audienceThis paper provides a methodology for the modeling of heat transfer and polymer flow during direct thermoplastic injection pultrusion process. Pultrusion was initially developed with thermosets which have low viscosity. But the impregnation becomes a critical point with thermoplastics which exhibit higher viscosity. There are very few reported works on direct thermoplastic impregnation with injection within the die. In addition, the rare studies have not adequately addressed the issue of unsaturated flow in woven fiber reinforcements. The solution proposed here, models the polymer flow through dual-scale porous media. A heat transfer model is coupled to a flow model enriched with a sink term. Specific changes of variables are made so as to model the steady state solution of unsaturation along a continuous process. The sink term, added to the continuity equation, represents the absorption rate of polymer by the bundles. Data were measured on a pultrusion line and micrographs confirmed the modeling strategy with an unsaturated flow approach. The flow modeling coupled to heat transfer of the thermoplastic pultrusion process aims at determining the saturation evolution through the die so as to manufacture pultruded profiles with the lowest residual porosity

Ein neues Markenzeichen der Universität : Das Zentrum für Medien und Interaktivität (ZMI)

Das Zentrum für Medien und Interaktivität (ZMI) der Justus-Liebig-Universität Gießen ist eine in dieser Form neuartige Einrichtung, die anwendungsorientierte und praxisnahe Grundlagenforschung zu medienbezogenen Fragestellungen betreibt. Vor gut drei Jahren trafen sich Lehrende der Gießener Universität aus verschiedenen Fachbereichen, die in der einen oder anderen Form mit kommunikations- und medienwissenschaftlichen Fragen befasst sind. Aus dem universitären Alltag heraus entstand die Idee, diese Aktivitäten zu bündeln, und die Leitung der Justus-Liebig-Universität hat diese Initiative gerne aufgegriffen und sich zu eigen gemacht. Nach knapp zweijährigem Planungsvorlauf wurde das ZMI am 1. April 2001 gegründet. Es bündelt medienbezogene und mediengestützte Lehrangebote und bietet Dienstleistungen und Beratung im Bereich Online-Medien an. Partner des ZMI sind universitäre und außeruniversitäre Forschungs- und Bildungseinrichtungen, politische und administrative Institutionen, Medien- und andere Unternehmen

Data-Driven Identification for Linear-Viscoelastic Materials

Data-driven Identification (DDI) is a technique that allows to estimate the stresses of a sample and the behavior of the material solely by the use of strain information, avoiding the bias imposed by an empirical constitutive model. In this work, we extend the applicability of DDI from elasticity to linear-viscoelastic materials by extending the dimensionality of the problem. Rather than estimating the state of the elements considering an instantaneous value of strain-stress, we include the strain history of the sample in order to account for the viscosity effect. We also combine the method with data analysis techniques such as Kernel Principal Component Analysis to improve the estimation of stresses. Preliminary results in modeled samples show a clear improvement on the estimation of stresses when compared against the original formulation of the algorithm, allowing us to obtain results in cases where the original DDI fails to do so

NSUSY fits

We perform a global fit to Higgs signal-strength data in the context of light stops in Natural SUSY. In this case, the Wilson coefficients of the higher dimensional operators mediating g g -> h and h -> \gamma \gamma, given by c_g, c_\gamma, are related by c_g = 3 (1 + 3 \alpha_s/(2 \pi)) c_\gamma/8. We examine this predictive scenario in detail, combining Higgs signal-strength constraints with recent precision measurements of m_W, b-> s \gamma constraints and direct collider bounds on weak scale SUSY, finding regions of parameter space that are consistent with all of these constraints. However it is challenging for the allowed parameter space to reproduce the observed Higgs mass value with sub-TeV stops. We discuss some of the direct stop discovery prospects and show how global Higgs fits can be used to exclude light stop parameter space difficult to probe by direct collider searches. We determine the current status of such indirect exclusions and estimate their reach by the end of the 8 TeV LHC run.Comment: 41 pages, 13 figures. v3: final JHEP version, b to s gamma updated to latest data and typos correcte

Business/Human Capital : Heads of laboratory must meet economic expectations

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Les composites dans le ferroviaire : Sécurité et intelligence, les derniers développements

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Compression des renforts dans les procédés LCM : 2. Modélisation de la perméabilité

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