No abstract

The purpose of this study is to gain better understanding of' flow patterns and mjxing conditions in a particular single-screw extruder: the Buss Cokneader. To this end, the residence time distribution IFWD) of the polymer was investigated experimentally for different combinations of the operating variables (i.e. feed rate, screw rotation speed). The measurement of RTD used a standard stimulus-response technique. Two kinds of tracer were used: h e anthracene and anthracene grafted on the polymer. It was shown that only the second could characterize the actual flow of the polymer in the extruder. It does not perturb the flow and has the same rheological behavior as the studied fluid. Thanks to the fiTD data, a model of the extruder based on the combination of ideal reactors, such as contiuous stirred tank reactors or plug flow reactors, was finally set up. The establishment of relationships between model parameters and extrusion conditions allowed the: prediction of RTD with good agreement.

No abstract

Contre la prolifération des paniques morales ou, au contraire, des discours enchantés à propos des « digital natives » , la génération née avec le numérique, un retour aux enquêtes – tant quantitatives que qualitatives – menées ces dernières années permet, à propos des pratiques culturelles des adolescent-e-s, de faire un point. Si le numérique est, en effet, porteur d''évolutions indéniables, celles-ci doivent cependant être recontextualisées dans le temps long des générations.