A multi-scale approach to determine the REV in complex carbonate rocks

Complex porous carbonates display heterogeneity at different scales, influencing their reservoir properties (e.g. porosity) especially since different porosity types may exist on different spatial scales. This requires a quantitative geometric description of the complex (micro)structure of the rocks. Modern computer tomography techniques permit acquiring detailed information concerning the porosity network at different scales. These datasets allow evolvement to a more objective pore classification based on mathematical parameters. However computational limitations in complex reservoir models do not allow incorporating heterogeneities on small scales (e.g. sub-meter scale) in full-field reservoir simulations [Nordahl and Ringrose, 2008]. The suggested workflow allows characterizing different porosity networks in travertine rocks as well as establishing confidence intervals regarding the Representative Elementary Volume (REV) of these samples. The results of this study prove that one has to be very critical when determining the REV of heterogeneous complex carbonate rocks, since they are influenced by both resolution and size of the dataset

Nonlinear evolution equations for degenerate transverse waves in anisotropic elastic solids

Transverse elastic waves behave differently in nonlinear isotropic and anisotropic media. Quadratically nonlinear coupling in the evolution equations for wave amplitudes is not possible in isotropic solids, but such a coupling may occur for certain directions in anisotropic materials. We identify the expression responsible for the coupling and we derive coupled canonical evolution equations for transverse wave amplitudes in the case of two-fold and three-fold symmetry acoustic axes. We illustrate our considerations by examples for a cubic crystal.Comment: 4 page

Bird's-eye view on Noise-Based Logic

Noise-based logic is a practically deterministic logic scheme inspired by the randomness of neural spikes and uses a system of uncorrelated stochastic processes and their superposition to represent the logic state. We briefly discuss various questions such as (i) What does practical determinism mean? (ii) Is noise-based logic a Turing machine? (iii) Is there hope to beat (the dreams of) quantum computation by a classical physical noise-based processor, and what are the minimum hardware requirements for that? Finally, (iv) we address the problem of random number generators and show that the common belief that quantum number generators are superior to classical (thermal) noise-based generators is nothing but a myth.Comment: paper in pres

AGROECOLOGIE : LE CHAINON MANQUANT ROLE DE CONSOMMATEURS ET D'ONG DANS LES PROCESSUS EMERGEANT D'APPRENTISSAGES

N° ISBN - 978-2-7380-1284-5International audienceAcademic texts on agro-ecology are often too limited to production systems. When notions of food systems and food value chains are described they introduce the consumer as a choice taker, reflecting neoclassical economic theory. The study of the emergence of two agroecological chains in Benin and Belgium explains how consumer demands are key learning resources for chain co-creation. In the case of the fair trade rice chain an NGO stimulates the cocreation process while in the beef chain in Gaume consumers who are directly involved in a deliberative process bring about this questioning. Agroecology, Food Systems, Participatory Research, Consumers, Learning process, Food Chain, Knowledge's, Biodiversity, Stock Farming, Rice Farmin