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Steady state of solid-grain interfaces during simulated CPT

Butlanska J., Arroyo M., Gens A.

Studia Geotechnica et Mechanica

2013

Vol. 35, nr 4

13--22

It has recently been shown (Arroyo et al. [1]) that 3D DEM models are able to reproduce with reasonable accuracy the macroscopic response of CPT performed in calibration chambers filled with sand. However, the cost of each simulation is an important factor. Hence, to achieve manageable simulation times the discrete material representing the sand was scaled up to sizes that were more typical of gravel than sand. A side effect of the scaled-up discrete material size employed in the model was an increased fluctuation of the macro-response that can be filtered away to observe a macroscopic steady-state cone resistance. That observation is the starting point of this communication, where a series of simulations in which the size ratio between penetrometer and particles is varied are systematically analyzed. A micromechanical analysis of the penetrometer–particle interaction is performed. These curves reveal that a steady state is arrived also at the particle–cone contact level. The properties of this dynamic interface are independent of the initial density of the granular material.

Spatial distribution of scent marks in the Red Fox (Vulpes Vulpes L.) : do red foxes select certain plants as signal posts?

Miguel F., Valencia A. A., Arroyo M., Monclus R.

Polish Journal of Ecology

2009

Vol. 57, nr 3

605-609

Chemical signals are widely used in inter and intraspecific communication in many animals. The importance of scent marks in communication has led to a variety of strategies in animals to increase the detectability and persistence of their scent marks. We studied the scent marking of foxes in relation to the role of plants as scent posts in a suburban Mediterranean forest in Madrid. Twice a month, from October 2005 to April 2006, we prospected 16 fixed 50 x 50 m plots, randomly distributed along the study area. We registered all fox faeces and their association to different plants, as well as the potential availability of the different plant species in our study area. Our results indicate that faeces were associated with plants mainly in the clearings, foxes preferred wooden species to grasses as scent posts and holm oak shrubs and rockroses to other wooden species. These data suggest that red foxes select certain plants as substrates for their faeces and pose the possibility that they are guided by searching images when looking for scent posts.