Pratical determination of the coordination number in granular media

International audienc

Pratical determination of the coordination number in granular media

International audienc

PRACTICAL DETERMINATION OF THE COORDINATION NUMBER IN GRANULAR MEDIA

In a random stacking of particles, the coordination number is defined as the mean number of particles touching a given one. A classical measurement by image analysis is directly based on this definition. It can be applied in the theoretical case of a global analysis but some problems occur for practical applications. We propose here a new measurement method based on the contribution to the Euler-Poincaré characteristic. A single measurement is performed both on the initial structure (particles linked by contacts) and on the segmented structure (isolated particles). The proposed method is robust w.r.t. the shape of the particles and their contacts

Percolation Transition and Topology

International audienceA number of bidimensional random structures with increasing densities are simulated to explore possible links between Euler-Poincaré characteristic (EPC), or connectivity, and percolation threshold. For each structure model, the percolation threshold is compared with a number of typical points (extrema, zero crossings...) of the EPC curve. From these exercises, it can be concluded that the percolation threshold cannot be generally predicted using the evolution of the EPC

Local contributions to the Euler-Poincare characteristic of a set

International audienceThe Euler–Poincaré characteristic (EPC) of a polyconvex subset X of Rd can be evaluated by covering the subset with an auxiliary tessellation, measuring its contribution within each cell of the tessellation and adding all contributions. Two different ways are proposed to define the contribution of a cell to the EPC of X. These contributions turn out to be related by duality formulae. Finally, three applications are given: the measurement of the EPC on adjacent fields, the measurement of the EPC on discretized images and the detection of defects in atomic structures

Local contributions to the Euler-Poincare characteristic of a set

International audienceThe Euler–Poincaré characteristic (EPC) of a polyconvex subset X of Rd can be evaluated by covering the subset with an auxiliary tessellation, measuring its contribution within each cell of the tessellation and adding all contributions. Two different ways are proposed to define the contribution of a cell to the EPC of X. These contributions turn out to be related by duality formulae. Finally, three applications are given: the measurement of the EPC on adjacent fields, the measurement of the EPC on discretized images and the detection of defects in atomic structures

Percolation Transition and Topology

International audienceA number of bidimensional random structures with increasing densities are simulated to explore possible links between Euler-Poincaré characteristic (EPC), or connectivity, and percolation threshold. For each structure model, the percolation threshold is compared with a number of typical points (extrema, zero crossings...) of the EPC curve. From these exercises, it can be concluded that the percolation threshold cannot be generally predicted using the evolution of the EPC

Choice between film or powder of PA11 for processing flax fiber-reinforced composites

International audienceThe biosourced Polyamide 11 (PA11) is envisaged as a matrix in structural ecocomposites in combination with long flax fibers. Herein we compare the thermal, rheological, physical, mechanical and hydrothermal behavior of PA11 available as film or powder. These data are used for choosing between the two forms of the PA11 and to determine the temperature, holding time and pressure ranges suited for the elaboration of biocomposites by induction heating. © Lavoisier 2016