Non-adiabatic cluster expansion after ultrashort laser interaction

AbstractWe used X-ray spectroscopy as a diagnostic tool for investigating the properties of laser-cluster interactions at the stage in which non-adiabatic cluster expansion takes place and a quasi-homogeneous plasma is produced. The experiment was carried out with a 10 TW, 65 fs Ti:Sa laser focused on CO2 cluster jets. The effect of different laser-pulse contrast ratios and cluster concentrations was investigated. The X-ray emission associated to the Rydberg transitions allowed us to retrieve, through the density and temperature of the emitting plasma, the time after the beginning of the interaction at which the emission occurred. The comparison of this value with the estimated time for the "homogeneous" plasma formation shows that the degree of adiabaticity depends on both the cluster concentration and the pulse contrast. Interferometric measurements support the X-ray data concerning the plasma electron density

INFLUENCE OF RHEOLOGICAL PHENOMENA IN TIMBER-CONCRETE COMPOSITE BEAMS

In the paper, a new numerical program developed to model the long-term behaviour of timber-concrete composite beams is introduced. It allows taking into account in a rigorous way all rheological phenomena, such as creep, mechano-sorptive effect shrinkage and inelastic strains owing to variations of environmental temperature and relative humidity. The connection deformability is also considered By means of a comparison with an experimental test the capability of the program to predict the long-term behaviour is shown. The influence of different rheological phenomena on the total solution has been estimated. Timber mechano-sorptive effect, connection and timber creep affect very much the structural behaviour. Inelastic strains due to environmental condition changes (temperature and relative humidity) produce important effects as well