17,618 research outputs found
Numerical modeling of surface runoff and erosion due to moving rainstorms at the drainage basin scale
A physically-based distributed erosion model (MEFIDIS) was applied to evaluate the consequences of storm movement on runoff and erosion from the Alenquer basin in Portugal. Controlled soil flume laboratory experiments were also used to test the model. Nine synthetic circular storms were used, combining three storm diameters (0.5, 1 and 2 times the Alenquer basin's axial length) with three speeds of storm movement (0.5, 1 and 2 m/s); storm intensities were synthesized in order to maintain a constant rainfall depth of 50 mm. The model was applied to storms moving downstream as well as upstream along the basin's axis. In all tests, downstream-moving storms caused significantly higher peak runoff (56.5%) and net erosion (9.1%) than did upstream-moving storms. The consequences for peak runoff were amplified as the storm intensity increased. The hydrograph shapes were also different: for downstream-moving storms, runoff started later and the rising limb was steeper, whereas for upstream moving storms, runoff started early and the rising limb was less steep. Both laboratory and model simulations on the Alenquer basin showed that the direction of storm movement, especially in case of extreme rainfall events, significantly affected runoff and soil loss.http://www.sciencedirect.com/science/article/B6V6C-4K7WTYF-3/1/05f00859098982a6ae43cfee9cc48fe
Monte Carlo Simulations of Some Dynamical Aspects of Drop Formation
In this work we present some results from computer simulations of dynamical
aspects of drop formation in a leaky faucet. Our results, which agree very well
with the experiments, suggest that only a few elements, at the microscopic
level, would be necessary to describe the most important features of the
system. We were able to set all parameters of the model in terms of real ones.
This is an additional advantage with respect to previous theoretical works.Comment: 7 pages (Latex), 6 figures (PS) Accepted to publication in Int. J.
Mod. Phys. C Source Codes at http://www.if.uff.br/~arlim
Sociabilidade das especies florestais da caatinga em Santa Maria da Boa Vista,PE.
O trabalho foi executado na Fazenda Canaa, municipio de Santa Maria da Boa Vista, PE, com o objetivo de determinar o grau de afinidade entre as especies da caatinga e a importancia das mesmas, para fornecer subsidios tecnicos e eventuais programas de manejo, de formacao de povoamentos heterogeneos e de enriquecimento da comunidade vegetal com essencias de maior valor economico madeireiro. Avaliou-se a composicao floristica quanto a frequencia, densidade e dominancia. A similaridade entre as parcelas e a associacao de especies foram analisadas pelo Coeficiente de Jaccard. Os resultados obtidos permitiram concluir que a vegetacao e caracterizada pela presenca do angico (Anademanthera macrocarpa), jurema-preta (Mimosa hostilis), jurema-vermelha (Mimosa sp), manicoba-brava (Manihot sp) e pau-piranha (Pisonia sp), sendo essas especies mais frequents; o angico e a especie dominante, sendo a mais explorada. Rama-de-boi (Acacia piauhiensis) e espinheiro (Pithecellobium viridiflorium) apresentam alto indice de associacao, permitindo portanto aventar a possiblidade do seu uso em consorcio
On the Temperley-Lieb reflection matrices
This work concerns the boundary integrability of the spin-s
Temperley-Lieb model. A systematic computation method is
used to constructed the solutions of the boundary Yang-Baxter equations. For
half-integer, a general free parameter solution is presented.
It turns that for integer, the general solution has free
parameters. Moreover, some particular solutions are discussed.Comment: LaTex 17 page
Cosmological constant constraints from observation-derived energy condition bounds and their application to bimetric massive gravity
Among the various possibilities to probe the theory behind the recent
accelerated expansion of the universe, the energy conditions (ECs) are of
particular interest, since it is possible to confront and constrain the many
models, including different theories of gravity, with observational data. In
this context, we use the ECs to probe any alternative theory whose extra term
acts as a cosmological constant. For this purpose, we apply a model-independent
approach to reconstruct the recent expansion of the universe. Using Type Ia
supernova, baryon acoustic oscillations and cosmic-chronometer data, we perform
a Markov Chain Monte Carlo analysis to put constraints on the effective
cosmological constant . By imposing that the cosmological
constant is the only component that possibly violates the ECs, we derive lower
and upper bounds for its value. For instance, we obtain that and within,
respectively, and confidence levels. In addition, about
30\% of the posterior distribution is incompatible with a cosmological
constant, showing that this method can potentially rule it out as a mechanism
for the accelerated expansion. We also study the consequence of these
constraints for two particular formulations of the bimetric massive gravity.
Namely, we consider the Visser's theory and the Hassan and Roses's massive
gravity by choosing a background metric such that both theories mimic General
Relativity with a cosmological constant. Using the
observational bounds along with the upper bounds on the graviton mass we obtain
constraints on the parameter spaces of both theories.Comment: 11 pages, 4 figures, 1 tabl
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