1,720,992 research outputs found
Field Observations of the Onset of an Upwelling on the Western Coast of Sicily during september 1984
No full textApplication of the nonlocal Darcy law to the propagation of nonlinear thermoelastic waves in fluid saturated porous media
No full textIn the propagation of nonlinear waves in fluid saturated porous media, a key role is played by the Darcy law. In many cases one should take into account a realistic spatial or temporal variability of rock parameters, as permeability, porosity, diffusivity.To this purpose we here introduce a nonlocal Modified Darcy Law (MDL) by considering a fractional derivative generalization of the classical case. As an application we here study the effect of a generalized Darcy law on the propagation of nonlinear thermoelastic waves in porous media. In more details, we discuss an application of this MDL to an early Natale and Salusti model about quick and strong pressure and temperature waves in fluid saturated rocks. The original model leads to the Burgers equation, while with the MDL here we obtain a nonlocal formulation of the Burgers equation. We moreover find the analytic solution in the case that diffusion plays a secondary role. With this nonlocal model we obtain a richer analysis of realistic characteristic of such transient phenomena, in particular the spatial delays in wave propagation. © 2013 Elsevier B.V. All rights reserved
Analysis and modeling of contourite drifts and contour currents off promontories in the Italian Seas (Mediterranean Sea)
No full textThe complex relationship between currents flowing around capes and their related contourite deposits is still an interesting topic to confront, both from a sedimentologic and oceanographic perspective. We analyze here recent observations of contourite drifts, located at intermediate depths off promontories in the southern Tyrrhenian and in the southern Adriatic Sea. These contourites are located slightly upstream from the cape tip of Cape Vaticano, while they occur both upstream and downstream, in the lee wave region, of the Gargano Promontory. We therefore analyze and discuss tank and numerical simulations of contour-following flows, with particular attention to the presence of turbulent phenomena occurring in the lee region. Discussing the classical stream-tube model (i.e., a thin vein of dense water flowing around a cape) we moreover provide physical justification for some aspects we recognized in the study experiments. The comparison between bathymetric-stratigraphic data and numerical, tank and analytic results, allows investigation of the possible occurrence of sediment drifts around capes. We found that the presence of turbulence, and thus of erosive conditions for sediments in the lee of a cape, can be detected by using dimensionless numbers related to cape dimension and ocean current features. This work can be seen as a new approach to bridge the gap between marine sedimentology and physical oceanography
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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