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Your search keyword '"Millán, Emmanuel N."' showing total 26 results
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26 results on '"Millán, Emmanuel N."'

3. Evaluating the importance of environmental factors on the spatial distribution of livestock settlements in the Monte desert with a Monte Carlo based model: Settlement Dynamics in Drylands (SeDD)

Author

Millán, Emmanuel N., Goirán, Silvana, Aranibar, Julieta N., Forconesi, Leonardo, Garino, Carlos García, and Bringa, Eduardo M.

Subjects
Quantitative Biology - Populations and Evolution
Abstract

In the Monte desert, increasing population density, changing land rights and infrastructure may encourage livestock activity, with unknown consequences on ecosystems. Factors that influence livestock settlement distribution may affect ecosystem degradation. We hypothesize that surface and groundwater availability influence livestock settlements distribution. We evaluated this hypothesis with a Monte Carlo based model to simulate Settlement Dynamics in Drylands (SeDD), which calculates probabilities on a gridded region based on six environmental factors: groundwater depth, vegetation type, proximity to rivers, paved roads, old river beds, and existing settlements. A parameter sweep, including millions of simulations, was run with combinations of parameters related to these factors. The sets of parameter values that minimized the residuals between simulations and observations indicated the relative importance of each factors on settlement distribution. Distances to rivers and old river beds were critical to explain the current distribution of settlements, while vegetation, paved roads, and water table depths were not important. Spatial distribution of simulated vegetation, which included degradation around livestock settlements, generally agreed with remotely sensed vegetation classes. The model could be a useful tool to evaluate the effects of land use changes (water provision, river flows), on settlement distribution and vegetation degradation in arid environments.

Published
2015

14. A Monte Carlo code for the collisional evolution of porous aggregates (CPA).

Author

Millán, Emmanuel N., Planes, María Belén, Urbassek, Herbert M., and Bringa, Eduardo M.

Subjects
*POROUS silica, *RANDOM sets, *PROTOPLANETARY disks, *MONOMERS, *POROSITY, *DUST
Abstract

Context. The collisional evolution of submillimeter-sized porous dust aggregates is important in many astrophysical fields. Aims. We have developed a Monte Carlo code to study the processes of collision between mass-asymmetric, spherical, micron-sized porous silica aggregates that belong to a dust population. Methods. The Collision of Porous Aggregates (CPA) code simulates collision chains in a population of dust aggregates that have different sizes, masses, and porosities. We start from an initial distribution of granular aggregate sizes and assume some collision velocity distribution. In particular, for this study we used a random size distribution and a Maxwell-Boltzmann velocity distribution. A set of successive random collisions between pairs of aggregates form a single collision chain. The mass ratio, filling factor, and impact velocity influence the outcome of the collision between two aggregates. We averaged hundreds of thousands of independent collision chains to obtain the final, average distributions of aggregates. Results. We generated and studied four final distributions (F), for size (n), radius (R), porosity, and mass-porosity distributions, for a relatively low number of collisions. In general, there is a profuse generation of monomers and small clusters, with a distribution F(R) R-6 for small aggregates. Collisional growth of a few very large clusters is also observed. Collisions lead to a significant compaction of the dust population, as expected. Conclusions. The CPA code models the collisional evolution of a dust population and incorporates some novel features, such as the inclusion of mass-asymmetric aggregates (covering a wide range of aggregate radii), inter-granular friction, and the influence of porosity. [ABSTRACT FROM AUTHOR]

Published
2023
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