No abstract

This paper presents a numerical study of the effect of fine content on the mechanical behavior of gap-graded granular materials using the discrete element method. Triaxial compression tests are performed on different samples with fine contents varied from 0% to 40%. It was found that, starting from 20%, fine content has a visible effect on the shear strength. The optimal fine content is about 30%, at which the shear strength is the best. An investigation into the granular micro-structure showed that the fine particles, on one hand, come into contact with coarse particles, but on the other hand, separate the latter ones as fine content increases beyond 20%. Consequently, the shear stress is transmitted more and more through the coarse-fine contacts but less and less through the coarse-coarse contacts. For fine content ≤ 30%, the coarse-coarse contacts primarily carry the shear stress. Above this optimal fine content, the fine-coarse contacts overtake the coarse-coarse ones. The fine-fine contacts have little contribution to supporting the shear stress. For the studied range of fine content, the coarse particles primarily carry the shear stress, leaving the fine particles under relatively low stresses. Moreover, the fine particles are greatly softened by the shear loading. A classification of binary mixtures depending on their micro-structure was also proposed.

Molecular dynamics was used to quantify the role of the size, charge and polarisability of F -, Cl -, Br -, I -and Na + ions in their distribution in the water/vapour interface system. Our results show that the larger polarizable anions I -and Br -is attracted to the surface which is traced back to surface-modified ion hydration, while the F -was repelled from the interface and the Cl -occupied the total volume of the water slab. Moreover, by artificially increasing the ions charge, anions were localized to the center of the water slab. These results demonstrate that the effect of polarizability cannot be neglected in the transport mechanism.

This study analyzes the effects of some important factors of champagne technology on the ellipticity and Brewster angle microscopy (BAM) of the air/champagne interface in view of using the optical properties of the adsorption layer of base wine to forecast the stability of the champagne bubble collar. Using standard, ultrafiltered, and ultraconcentrated wines it was observed that champagne can lose amphiphilic macromolecules which adsorb on the inner glass wall of the bottle during storage, particles such as dead yeasts can adhere to the adsorption layer, a weak increase of the ethanol content during bottle fermentation can reduce significantly the ellipticity of the adsorption layer, and CO2 has no significant effect on the properties of that layer. Surprisingly, no visible differences of the adsorption layer were noticed between the experimental champagnes of the 2004 vintage of three vine varieties (Chardonnay, Pinot noir, and Pinot meunier). From analysis of all samples it is proposed that the mean value and standard deviation of the ellipticity measured during 30 min after pouring the wine in a Petri dish are physical quantities which satisfactorily characterize the adsorption layer of champagne. When needed, further characterization of the adsorption layer may be obtained by a detailed analysis of the kinetics of ellipticity during the same period and inspection of the BAM images of the interface.