Frequency-amplitude behavior in the incipient movement of grains under vibration

The onset of the movement of particles placed on a horizontal rough surface subject to a vertical sinusoidal vibration is investigated through tracking experiments,theoretical analysis,and numerical simulations. The frequency of vibration needed to move particles decays exponentially with the amplitude of the oscillatory input.This behavior is explained through a simple mechanism in which a forced damped harmonic oscillator with a spring constant represents all the interactions between the particle and the surface.The numerical results compare well with experimental data,demonstrating that the forces included in the numerical calculations suitably account for the main particle response,even though the complexity of the surface is not fully taken into account.Describing the way in which frequency varies with amplitude could be relevant to technological applications such as cleaning of material surfaces.

Microphase separation of a miscible binary liquid mixture under confinement at the nanoscale

Recent experimental works suggested that the confinement into a cylindrical nanopore induced the microphase separation of a binary liquid,despite the miscible character of its bulk counterpart.A core–shell organization was evidenced such that one of the liquids was strongly anchored to the solid surface whereas the other was confined at the center of the pore.At the same time,a study based on atomistic simulations suggested a strong heterogeneity and the absence of a separation.In this work,by refining the solid–liquid interactions to qualitatively reproduce the experimental adsorption isotherms of both single liquids,the microphase separation and the core–shell structure are captured.By tuning the surface chemistry of the nanopore to mimic hydrophilic and hydrophobic confinement,we show that it is possible to control the structural characteristics of the core–shell structure.The molecular origin of the microphase separation is then ascribed to the strong hydrogen bonds and a commensurate arrangement between the confining material and both liquids.

Mechanical strength of soda-lime glass sandblasted by gravitation

Damage to a glass surface by sandblasting has a remarkable effect on its mechanical properties and strength.In this study,we analyze the superficial deterioration of soda-lime glass and its influence on the mechanical strength.Sandblasting by gravitation from a fixed height causes damages by the free fall of different quantities of sand,which we performed for a selected grain size and at different angles of inclination.To characterize the surface state,we used different roughness measures(the arithmetic mean value of the roughness Ra,the root mean square roughness Rq,and the maximum roughness Rmax)and measured the optical transmission(transmittance)at different points on the specimen surface using a profilometer.To determine the mechanical strength,we proceeded by two methods:first,by a shock ball(falling ball),and then by biaxial bending using circular supports.The effects of the surface damage on the optical transmission and the mechanical strength of the glass are graphically presented and discussed in this paper.