2,915 research outputs found
A fully semi-Lagrangian discretization for the 2D Navier--Stokes equations in the vorticity--streamfunction formulation
A numerical method for the two-dimensional, incompressible Navier--Stokes
equations in vorticity--streamfunction form is proposed, which employs
semi-Lagrangian discretizations for both the advection and diffusion terms,
thus achieving unconditional stability without the need to solve linear systems
beyond that required by the Poisson solver for the reconstruction of the
streamfunction. A description of the discretization of Dirichlet boundary
conditions for the semi-Lagrangian approach to diffusion terms is also
presented. Numerical experiments on classical benchmarks for incompressible
flow in simple geometries validate the proposed method
Fault-Tolerant Adaptive Parallel and Distributed Simulation
Discrete Event Simulation is a widely used technique that is used to model
and analyze complex systems in many fields of science and engineering. The
increasingly large size of simulation models poses a serious computational
challenge, since the time needed to run a simulation can be prohibitively
large. For this reason, Parallel and Distributes Simulation techniques have
been proposed to take advantage of multiple execution units which are found in
multicore processors, cluster of workstations or HPC systems. The current
generation of HPC systems includes hundreds of thousands of computing nodes and
a vast amount of ancillary components. Despite improvements in manufacturing
processes, failures of some components are frequent, and the situation will get
worse as larger systems are built. In this paper we describe FT-GAIA, a
software-based fault-tolerant extension of the GAIA/ART\`IS parallel simulation
middleware. FT-GAIA transparently replicates simulation entities and
distributes them on multiple execution nodes. This allows the simulation to
tolerate crash-failures of computing nodes; furthermore, FT-GAIA offers some
protection against byzantine failures since synchronization messages are
replicated as well, so that the receiving entity can identify and discard
corrupted messages. We provide an experimental evaluation of FT-GAIA on a
running prototype. Results show that a high degree of fault tolerance can be
achieved, at the cost of a moderate increase in the computational load of the
execution units.Comment: Proceedings of the IEEE/ACM International Symposium on Distributed
Simulation and Real Time Applications (DS-RT 2016
Weak nodes detection in urban transport systems: Planning for resilience in Singapore
The availability of massive data-sets describing human mobility offers the
possibility to design simulation tools to monitor and improve the resilience of
transport systems in response to traumatic events such as natural and man-made
disasters (e.g. floods terroristic attacks, etc...). In this perspective, we
propose ACHILLES, an application to model people's movements in a given
transport system mode through a multiplex network representation based on
mobility data. ACHILLES is a web-based application which provides an
easy-to-use interface to explore the mobility fluxes and the connectivity of
every urban zone in a city, as well as to visualize changes in the transport
system resulting from the addition or removal of transport modes, urban zones,
and single stops. Notably, our application allows the user to assess the
overall resilience of the transport network by identifying its weakest node,
i.e. Urban Achilles Heel, with reference to the ancient Greek mythology. To
demonstrate the impact of ACHILLES for humanitarian aid we consider its
application to a real-world scenario by exploring human mobility in Singapore
in response to flood prevention.Comment: 9 pages, 6 figures, IEEE Data Science and Advanced Analytic
Ab initio electronic transport and thermoelectric properties of solids from full and range-separated hybrid functionals
Spatio-temporal patterns of the European wildcat in a Mediterranean coastal area
Like most small felids, the European wildcat Felis silvestris is a rather elusive species, poorly detectable in the wild, due to several aspects of its biology. Camera trapping can represent a suitable tool to understand temporal activity patterns and habitat preferences of such elusive species. We used intensive camera trapping over two full years to investigate spatio-temporal patterns of the wildcat in a Mediterranean coastal protected area (Maremma Regional Park, central Italy). At the seasonal scale, the wildcat showed a marked twilight activity in summer and winter (mating period), and nocturnal activity in autumn. Conversely, a peak of activity during the day, i.e., in broad daylight, was reported in spring. Reproductive females may limit their nocturnal movements in spring to increase protection from predators to their kittens at the den, although further data are required to support this conclusion. At seasonal, semestral, and yearly temporal scales, the frequency of wildcat detections increased along with availability of shrubwood. These results emphasise the importance for this small felid of areas with dense vegetation cover (Mediterranean maquis and shrubwood, in our study area). Areas densely covered with shrubby vegetation are expected to provide benefits to this elusive small cat in terms of reduced human disturbance (included tourists), availability of prey (e.g., small mammals), as well as shelter, essential to ensure protection towards potential larger predators
Secondo contributo alla conoscenza della flora esotica dell'Arcipelago Toscano, Italia
Si presenta qui un secondo contributo per la realizzazione di una Checklist della flora esotica dell'Arcipelago Toscano. Per ogni taxon sono riportati lo status di naturalizzazione, sia per ciascuna isola che per l'intero Arcipelago, e i dati relativi alla distribuzione locale. Delle 31 specie elencate, 18 risultano nuove per il territorio dell'Arcipelago Toscano, tra le quali 4 nuove per l'intera Toscana; le restanti sono nuove per una o più isole
CHASMAPORTHETES MELEI N.SP., AN ENDEMIC HYAENID (CARNIVORA, MAMMALIA) FROM THE MONTE TUTTAVISTA FISSURE FILLINGS (LATE PLIOCENE TO EARLY PLEISTOCENE; SARDINIA, ITALY)
Occurrence of large carnivores in island ecosystems is unusual, especially in the case of top predators. Here, a new endemic hyaenid species, Chasmaporthetes melei, from the late Late Pliocene to earliest Pleistocene fissure fillings of Monte Tuttavista, Orosei, Sardinia, is described. Although smaller, C. melei is morphologically comparable with the Plio-Pleistocene Eurasian hunting-hyena Chasmaporthetes lunensis, a possible ancestor of the Sardinian species. C. melei displays all the characteristic feeding adaptations of Chasmaporthetes, including a derived enamel structure similar to the condition in extant bone-crushing hyaenas. C. melei was an active predator that nonetheless included a relatively large amount of bone in its diet.
SHORT NOTE
Dimenticare Firenze. La mostra La casa abitata del 1965 a Palazzo Strozzi. Forgetting Florence. The exhibition La casa abitata of 1965 at Palazzo Strozzi
Habitat use and home range traits of resident and relocated hares (Lepus europaeus, Pallas)
The aim of the study was to know the habitat preferences and home range of resident and relocated brown hares during the no hunting period. The trial was carried out in a protected area (PA) and in a free hunting territory (FHT), both located in Florence province. During captures 21 hares were equipped with a necklace radio tag: 7 hares, resident group, were released in the same area of capture and 14 hares, relocated group, were relocated in six different locations within the FHT. The effect of place of release was analyzed by ANOVA and/or non parametric methods. Results showed that the home ranges of the resident group were characterised by a greater presence of fallow land and shrub land than relocated group (P< 0.05). Home range sizes and Max distances from the releasing sites differed between the two groups. Resident hares preferred landscape characterized by a higher density of patches than the relocated hares (152 vs. 70 n/100ha, 43 vs. 12 n/100ha, 4703 vs. 8142 sq.m respectively; P<0.01). The landscape structure indexes, the home range sizes and the maximum distance from the releasing sites suggest that the relocated hares even if released in suited habitats, will move from their releasing point to look for better habitats. Landscape with most complexity are preferred from the resident hare, and this result should be consider when a project to reintroduction of this lagomorph in a territory is programmed, or when it is necessary to improve the dynamic of a natural population
MUSEO DEL CALCIO DI COVERCIANO. Il BIM E LA GESTIONE DEL PATRIMONIO CULTURALE ATTRAVERSO LA METODOLOGIA SCAN TO BIM COVERCIANO FOOTBALL MUSEUM. THE BIM AND THE MANAGEMENT OF CULTURAL HERITAGE WITH THE SCAN TO BIM METHODOLOGY
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