Swimming microorganisms often have to propel in complex, non-Newtonian
fluids. We carry out experiments with self-propelling helical swimmers driven
by an externally rotating magnetic field in shear-thinning, inelastic fluids.
Similarly to swimming in a Newtonian fluid, we obtain for each fluid a
locomotion speed which scales linearly with the rotation frequency of the
swimmer, but with a prefactor which depends on the power index of the fluid.
The fluid is seen to always increase the swimming speed of the helix, up to 50%
faster and thus the strongest of such type reported to date. The maximum
relative increase for a fluid power index of around 0.6. Using simple scalings,
we argue that the speed increase is not due to the local decrease of the flow
viscosity around the helical filament but hypothesise instead that it
originates from confinement-like effect due to viscosity stratification around
the swimmer
Abstract:The noise maps that are currently proposed as part of the EU Directive are based on the calculation of the Lday, Levening and Lnight. These levels are calculated from emission and propagation models that are expensive in time. These noise maps are criticized for being distant from the perception of city users. Thus, calculation models of sound quality have been proposed, for being closer to city users' perception. They are either based on perceptual variables, or on acoustic measurements, or on georeferenced data, the latter being often already integrated into the Geographic Information Systems of most French metropolises. Considering 89 Parisian situations, this article proposes to compare the sound quality really perceived, with those from models using geo-referenced data. It also looks at the modeling of perceptual variables that influence the sound quality, such as perceived loudness, the perceived time ratio of traffic, voices and birds. To do this, such geo-referenced data as road traffic, the presence of gardens, food shops, restaurants, bars, schools, markets, are transformed into core densities. Being quick and easy to calculate, these densities predict effectively sound quality in the urban public space. Visualization of urban soundscape maps are proposed in this paper.
La Ciudad Blanca, o Ciudad Universitaria, como se la conoce desde tiempo atrás registra hechos de accidentalidad de transito que inquietan a su comunidad de estudiantes, docentes y empleados, dada las consecuencias que tales hechos acarrean a quienes en ella conviven a diario.
Este artículo considera en primer lugar la situación aludida atrás, a la luz de la información suministrada al respecto por la división de Vigilancia y Seguridad de la Universidad. A continuación se intenta una aproximación a la causalidad presente en dicha situación y, por último se presenta una propuesta de trabajo interfacultades, orientada a la pacificación del trafico dentro de la Ciudad Blanca.
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