Sorption,diffusion and permeation properties of oxygen and water in copolymer of ethylene and polar monomers

Asymmetric membranes, based on Poly[ethylene-co-(vinyl acetate)] (EVA) containing 70 wt.% of vinyl acetate, were prepared by a treatment of unilateral hydrolysis using solutions of sodium hydroxide dissolved in a mixture of water and methanol. The depth of hydrolyzed layers and the concentration of hydroxyl groups in the membranes were controlled by the reaction time. The oxygen permeability, P_O2, of these membranes decrease with the reaction time while the water permeability, P_H2O, reaches maximum at 30 min. The ideal separation factors of P_H2O to P_O2 of the EVA membranes treated for 1h to 4h are in the range of 3840 to 13500, and are greater than that of the EVA membranes. The plasticization effect of the membrane depends on the depth and concentration of hydroxyl groups and the concentration gradient of water in the membranes.     

Experimental investigation on longitudinal vortex control over a dihedral bluff body

The present paper addresses an experimental investigation of the dynamic and the control of a longitudinal vortex emanating from the front pillar of a dihedral bluff body corresponding to a simplified geometry of an automotive vehicle. The control system is based on a thin rectangular slot located along the lateral edge of the windscreen and provides steady suction or blowing normal to the lateral face of the geometry. Qualitative results obtained with dye visualizations and Schlieren photos provide an overview of the impact of the control on the topology of the vortex flow. Quantitative Stereo-PIV measurements and unsteady forces measurements are used to characterize the interaction between the control and the longitudinal vortex. Controls that change significantly the topology of the vortex core and reduce aerodynamic drag are identified.     

The 2D-Ising model near criticality: a FK-percolation analysis

We study the 2D-Ising model defined on finite boxes at temperatures that are below but very close from the critical point. When the temperature approaches the critical point and the size of the box grows fast enough, we establish large deviations estimates on FK-percolation events that concern the phenomenon of phase coexistence.