1,721,406 research outputs found
Effect of wind on precipitation intercepted by steep mountain slopes
No full textA simple and efficient formulation is developed to describe the effects of wind speed and directionon ground level precipitation intercepted by steep mountain slopes. A 3D rainfall field is reproduced frommeasurements of (vertical) precipitation intensity, wind speed, and wind direction. The Marshall-Palmer dropsize distribution is used to express the volumetric precipitation water content as a function of measured precipitationintensity, and raindrops are assumed to move horizontally with the measured wind speed and direction.Land topography is described using digital elevation model data, and local contributions to ground level precipitationare calculated as the interception of the obtained 3D rainfall field by horizontal and vertical surfacesthat constitute the elemental land surface systems. The developed formulation is tested at the Acquabona andFiames mountain slopes, located in the Northern Italian Dolomites, near the town of Cortina d’Ampezzo, wheredebris flow phenomena often occur. Simulation results are corroborated, although in an indirect and approximatemanner, by field estimates of debris flow volumes delivered by the considered mountain slopes in response tomonitored storm events. Although more accurate and comprehensive validation is needed, the developed formulationappears to constitute a useful diagnostic tool for providing interpretation of storm-flow hydrographsdelivered by steep mountain slopes in response to storm precipitations affected by wind
LAGRANGIAN NUMERICAL MODEL OF A BINARY MIXTURE AND SEGREGATION PROCESSES
No full textParticle size segregation is a quite evident phenomenon taking place when initially mixed particles with different size, mass density, shape, are subjected to shearing or to any body force such as gravity or centrifugal forces. In debris flows, segregation
moves big stones from the bank and the bed towards the free surface and the center of the stream and, by differential transport, to the front of the flood, with important effects on the flow resistance and on the stream evolution. In the present work a numerical model is developed in order to represent the simple particle movements in a binary mixture of spheres flowing over an inclined plane. The main aim is to · quantify the stresses and to model of the segregation phenomenon, andto relate the
forces acting on the different species to the gradient of concentration, the granular temperature, the tensor of the velocity deformation. It is assumed that the spheres are
infmitely stiff; the collisions take place in an infinitesimal time and are only binary. The statistic of particle movements and collisions allows the computation of the profiles of mean velocity, of concentration and of pseudo temperature. The results show a clear segregation of the small particles near the bottom, with big particles floating over them
Granular systems rheology and mechanics
No full textWe report on the experimental activity carried out on a rotating drum partially filled with grains or glass beads and a model of the grain stream
Granular shear flow in a rotating drum. New experiments.
No full textTechnical report on research activity, 2nd meeting Debris Flow Risk Project, Paris, France, December
Granular shear flow in a rotating drum. Kinetic stress tensor.
No full textTechnical report on research activity, 3rd meeting Debris Flow Risk Project, Cortina, Italy, June
Granular shear flow in a rotating drum.
No full textTechnical report on research activity, 1st meeting Debris Flow Risk Project, Grenoble, France, June
Lagrangian model of a binary mixture.
No full textTechnical report on research activity, 1st meeting Debris Flow Risk Project, Grenoble, France, June
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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