On the influence that the ground electrode diameter has in the propulsion efficiency of an asymmetric capacitor in nitrogen gas

In this work the propulsion force developed in an asymmetric capacitor will be calculated for three different diameters of the ground electrode. The used ion source is a small diameter wire, which generates a positive corona discharge in nitrogen gas directed to the ground electrode. By applying the fluid dynamic and electrostatic theories all hydrodynamic and electrostatic forces that act on the considered geometries will be computed in an attempt to provide a physical insight on the force mechanism that acts on the asymmetrical capacitors, and also to understand how to increase the efficiency of propulsion.Comment: 13 pages, 8 figures, Accepted for publication in "Physics of Plasmas

Biofouling in tubes: some trends and perspectives

A significant increase in the literature concerning the formation of biological deposits in tubes has been noticed in the last few years. Yet, the scope of the majority of the reports is limited to the study of a single operating parameter. Besides, the operating conditions differ significantly from case to case, renderino difficult the absortion of the available information. In this work, a survey of the most recent publications on the subject of tube biofouling is undertaken, as a means of clarifying further research proprams. Emphasis is placed on the systems used, experimental equipments adopted and, essentially on the parameters studied. Of these, specially attention is qiven to the influence of tube material and roughness, foulant type and concentration, fluid velocity and temperature field