733 research outputs found
Calculation of the separation streamlines of barchans and transverse dunes
We use FLUENT to calculate the wind profile over barchans and transverse
dunes. The form of the streamlines of flow separation at the lee side of the
dunes is determined for a symmetric barchan dune in three dimensions, and for
the height profile of a measured transverse dune field in the Len\c{c}\'ois
Maranhenses.Comment: 6 pages including 5 figures. Proceedings of PSIS 200
Traveling length and minimal traveling time for flow through percolation networks with long-range spatial correlations
We study the distributions of traveling length l and minimal traveling time t
through two-dimensional percolation porous media characterized by long-range
spatial correlations. We model the dynamics of fluid displacement by the
convective movement of tracer particles driven by a pressure difference between
two fixed sites (''wells'') separated by Euclidean distance r. For strongly
correlated pore networks at criticality, we find that the probability
distribution functions P(l) and P(t) follow the same scaling Ansatz originally
proposed for the uncorrelated case, but with quite different scaling exponents.
We relate these changes in dynamical behavior to the main morphological
difference between correlated and uncorrelated clusters, namely, the
compactness of their backbones. Our simulations reveal that the dynamical
scaling exponents for correlated geometries take values intermediate between
the uncorrelated and homogeneous limiting cases
Brazilian elections: voting for a scaling democracy
The proportional elections held in Brazil in 1998 and 2002 display identical
statistical signatures. In particular, the distribution of votes among
candidates includes a power-law regimen. We suggest that the rationale behind
this robust scaling invariance is a multiplicative process in which the voter's
choice for a candidate is governed by a product of probabilities.Comment: 4 pages, 2 figure
Heat Transport through Rough Channels
We investigate the two-dimensional transport of heat through viscous flow
between two parallel rough interfaces with a given fractal geometry. The flow
and heat transport equations are solved through direct numerical simulations,
and for different conduction-convection conditions. Compared with the behavior
of a channel with smooth interfaces, the results for the rough channel at low
and moderate values of the Peclet number indicate that the effect of roughness
is almost negligible on the efficiency of the heat transport system. This is
explained here in terms of the Makarov's theorem, using the notion of active
zone in Laplacian transport. At sufficiently high Peclet numbers, where
convection becomes the dominant mechanism of heat transport, the role of the
interface roughness is to generally increase both the heat flux across the wall
as well as the active length of heat exchange, when compared with the smooth
channel. Finally, we show that this last behavior is closely related with the
presence of recirculation zones in the reentrant regions of the fractal
geometry.Comment: 12 pages, 8 figure
Selection of strawberry cultivars with tolerance to Tetranychus urticae (Acari: Tetranychidae) and high yield under different managements.
Tetranychus urticae Koch (Acari: Tetranychidae) is considered the main pest of strawberry. Several factors can favor its development, among them the genotype susceptibility and cropping system. The aims of this study were to evaluate the agronomic performance of strawberry cultivars under different managements and to identify strawberry cultivars that meet tolerance to T. urticae and high fruit yield. Thirteen cultivars of strawberry ('Albion', 'Aleluia', 'Aromas', 'Camarosa', 'Camino Real', 'Campinas', 'Diamante', 'Dover', 'Festival', 'Seascape', 'Toyonoka', 'Tudla', and 'Ventana') under three managements (open field, low tunnel, and high tunnel) were evaluated. The T. urticae attack to different cultivars was influenced by managements, being low tunnel the one that provided higher infestations in the most evaluated cultivars. 'Camarosa' was the cultivar with the lower incidence of pest and 'Dover' had the higher infestation. The genotype most suitable for growing under different managements is the 'Festival' genotype, since it meets tolerance to T. urticae, high fruit yield, and phenotypic stability
The Complex Topology of Chemical Plants
We show that flowsheets of oil refineries can be associated to complex
network topologies that are scale-free, display small-world effect and possess
hierarchical organization. The emergence of these properties from such man-made
networks is explained as a consequence of the currently used principles for
process design, which include heuristics as well as algorithmic techniques. We
expect these results to be valid for chemical plants of different types and
capacities.Comment: 7 pages, 5 figures and 1 tabl
Transition from Knudsen to molecular diffusion in activity of absorbing irregular interfaces
We investigate through molecular dynamics the transition from Knudsen to
molecular diffusion transport towards 2d absorbing interfaces with irregular
geometry. Our results indicate that the length of the active zone decreases
continuously with density from the Knudsen to the molecular diffusion regime.
In the limit where molecular diffusion dominates, we find that this length
approaches a constant value of the order of the system size, in agreement with
theoretical predictions for Laplacian transport in irregular geometries.
Finally, we show that all these features can be qualitatively described in
terms of a simple random-walk model of the diffusion process.Comment: 4 pages, 4 figure
Composição E Diversidade De Anuros Na Restinga Do Município De Conde, Litoral Norte Do Estado Da Bahia, Nordeste Do Brasil
The Conde municipality is located in the northern coast of the state of Bahia (NC), northeastern Brazil, and is part of the Atlantic Tropical domain. The anuran fauna of the northern portion of the NC is still poorly known if compared to the southern portion. The Restinga is one of the predominant environments of the coastal plains of the NC and it is characterized essentially by presenting sandy soil covered by herbaceous and shrubby vegetation. The objective of this study was to determine the anuran species composition and diversity for the Restinga of the Conde municipality. Sampling was carried out at night by active search over four periods of five consecutive days each, two over the ‘main rainy season’ and two in a ‘lesser rainy season’, using 14 sample units (SUs) and five extra sample plots (EPs). We calculated dominance and species diversity using the Berger-Parker and Shannon-Wiener H’ indices, respectively. We used accumulation curves and the Jackknife 1 estimator to estimate anuran species richness, considering only the data obtained from the SUs. We recorded 713 anuran specimens distributed within 33 species, 13 genera and five families (Bufonidae, Craugastoridae, Hylidae, Leptodactylidae and Microhylidae). The Hylidae and Leptodactylidae families had the highest species richness. Considering only the SUs (Jackknife 1 estimator in brackets), we recorded 28 species in the study area (33.9 ± 2.3), 13 in Shrubby Vegetation Zones-SVZ (20.8 ± 2.9) and 25 in Freshwater Wetland Zones-FWZ (28.9 ± 1.9). The abundance and species diversity of the FWZ (n = 638 specimens; H’= 2.4) were higher than those recorded for the SVZ (n = 52 specimens; H’ = 1.9). The SVZ and FWZ showed distinct dominant species, wherein Pristimantis paulodutrai was the dominant species in SVZ and Scinax fuscomarginatus in FWZ. The Restinga of the Conde municipality stands out as the one with the highest anuran species richness already recorded considering only SVZ and FWZ. Moreover, its anuran species composition represented 55% of the anuran species known for the NC and included taxa common to three different morphoclimatic domains (Tropical Atlantic, Cerrado and Caatinga). © 2016, Universidade Estadual de Campinas UNICAMP. All rights reserved.16
On the synonymy of Stictocephala alta (Walker) and Thelia constans Walker (Hemiptera: Membracidae)
Black hole thermodynamical entropy
As early as 1902, Gibbs pointed out that systems whose partition function
diverges, e.g. gravitation, lie outside the validity of the Boltzmann-Gibbs
(BG) theory. Consistently, since the pioneering Bekenstein-Hawking results,
physically meaningful evidence (e.g., the holographic principle) has
accumulated that the BG entropy of a black hole is
proportional to its area ( being a characteristic linear length), and
not to its volume . Similarly it exists the \emph{area law}, so named
because, for a wide class of strongly quantum-entangled -dimensional
systems, is proportional to if , and to if
, instead of being proportional to (). These results
violate the extensivity of the thermodynamical entropy of a -dimensional
system. This thermodynamical inconsistency disappears if we realize that the
thermodynamical entropy of such nonstandard systems is \emph{not} to be
identified with the BG {\it additive} entropy but with appropriately
generalized {\it nonadditive} entropies. Indeed, the celebrated usefulness of
the BG entropy is founded on hypothesis such as relatively weak probabilistic
correlations (and their connections to ergodicity, which by no means can be
assumed as a general rule of nature). Here we introduce a generalized entropy
which, for the Schwarzschild black hole and the area law, can solve the
thermodynamic puzzle.Comment: 7 pages, 2 figures. Accepted for publication in EPJ
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