Contributions de Maurice Clerc dans l'Agri 2013

Maurice Clerc (2013): Biogaz et partage des digestats entre bio et PER. Agri, 20.12.2013, page 11 Maurice Clerc (2013): Engrais de ferme: échanges entre paysans bio et PER. Agri, 29.11.2013, page 18 Maurice Clerc (2013): Les collaborations entre agriculteurs bio et PER. Agri, 15.11.2013, page 8 Maurice Clerc (2013): Il faut vérifier la pression des pneus des tracteurs. Agri, 11.10.2013, page 23 Maurice Clerc (2013): Faites davantage de tests à la bêche! Agri, 20.09.2013, page 23 Maurice Clerc und Hansueli Dierauer (2013): Recommandations pour les semis des cultures associées de cet automne. Agri, 06.09.2013, page 21 Maurice Clerc (2013): Les avantages des cultures associées de légumineuses à graines et céréales. Agri, 24.05.2013, page 2

Microdroplet impact at very high velocity

Water microdroplet impact at velocities up to 100 m/s for droplet diameters from 12 to 100 um is studied. This parameter range covers the transition from capillary-limited to viscosity-limited spreading of the impacting droplet. Splashing is absent for all measurements; the droplets always gently spread over the surface. The maximum spreading radius is compared to several existing models. The model by Pasandideh-Fard et al. agrees well with the measured data, indicating the importance of a thin boundary layer just above the surface, in which most of the viscous dissipation in the spreading droplet takes place. As explained by the initial air layer under the impacting droplet, a contact angle of 180 degrees is used as model input

Zig-zag instability of an Ising wall in liquid crystals

We present a theoretical explanation for the interfacial zigzag instability that appears in anisotropic systems. Such an instability has been experimentally highlighted for an Ising wall formed in a nematic liquid crystal cell under homeotropic anchoring conditions. From an envelope equation, relevant close to the Freedericksz transition, we have derived an asymptotic equation describing the interface dynamics in the vicinity of its bifurcation. The asymptotic limit used accounts for a strong difference between two of the elastic constants. The model is characterized by a conservative order parameter which satisfies a Cahn-Hilliard equation. It provides a good qualitative understanding of the experiments.Comment: 4 pagess, 4 figures, lette

Entropy-driven formation of the gyroid cubic phase

We show, by computer simulation, that tapered or pear-shaped particles, interacting through purely repulsive interactions, can freely self-assemble to form the three-dimensionally periodic, gyroid cubic phase. The Ia3d gyroid cubic phase is formed by these particles both on compression of an isotropic configuration and on expansion of a smectic A bilayer arrangement. For the latter case, it is possible identify the steps by which the topological transformation from non-intersecting planes to fully interpenetrating, periodic networks takes place</p