Motion of a single bubble rising in a countercurrent flow in a Hele-Shaw cell

We investigate experimentally the motion of isolated bubbles rising in a vertical Hele-Shaw cell in the presence of a downward flow. The bubbles are strongly flattened in the plane of the cell, their equivalent diameter d being large compared to the gap of the cell e . Furthermore, their dynamics is strongly influenced by the confinement which imposes thin liquid films between the bubble and the walls and strongly attenuates the flow perturbation in the liquid due to wall friction

Freshwaters: which NOM matters?

One of the difficulties encountered in the study of natural organic matter (NOM) in aquatic environments concerns terminology: a large number of different names and acronyms are used. In fact, this diversity merely reflects the variety of approaches applied to the study of NOM, leading to the definition and measurement of different operationally-defined fractions. As a result, the choice of the ‘best' method to use and of the ‘best' fraction to work on in a particular case is far from straightforward. This has as a consequence that often very simple methods for NOM characterisation are used in applied environmental studies and surveys. This study includes, first, a review of the most widely applied terminology, as described in over 500 articles, and, second, a first attempt at assessing how the panoply of methods available is really used in applied environmental studie

Processos de ramificació

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2016, Director: Carles Rovira EscofetIn this undergraduate thesis we will introduce the branching processes and one of their major applications, the neutron branching processes (one-group, isotropic case). First, in chapter I we begin with Galton-Watson processes and their properties. Chapter II deals with a generalization of branching processes introducing a parameter x (type) for each object of the processes that may represents, energy, position age etc. Finally in chapter III we apply this generalization into a real case, the neutron branching processes