Analyzing and Modeling the Performance of the HemeLB Lattice-Boltzmann Simulation Environment

We investigate the performance of the HemeLB lattice-Boltzmann simulator for cerebrovascular blood flow, aimed at providing timely and clinically relevant assistance to neurosurgeons. HemeLB is optimised for sparse geometries, supports interactive use, and scales well to 32,768 cores for problems with ~81 million lattice sites. We obtain a maximum performance of 29.5 billion site updates per second, with only an 11% slowdown for highly sparse problems (5% fluid fraction). We present steering and visualisation performance measurements and provide a model which allows users to predict the performance, thereby determining how to run simulations with maximum accuracy within time constraints.Comment: Accepted by the Journal of Computational Science. 33 pages, 16 figures, 7 table

Dynamic selection of dispersal pathways for species persistence under climate change

Ongoing climate change is already affecting distributions of many species. Future impacts of climate change are expected to be even greater. Conservation planning methodologies are usually based on the assumption that species distributions change relatively slowly unless they are directly affected by human activities, but this assumption is inappropriate under climate change. To address this problem, we develop a model that, assuming a fixed budget limiting the selection of areas devoted to conservation, selects areas for each of different periods of time, and indicates how species disperse between selected areas on successive periods. These areas are termed dispersal pathways. Their effectiveness is assessed based on the performance to retain species suitable climates over time, and on the ability of species to disperse between the areas. The model identifies maximum effective dispersal pathways, limited to some given budget. We applied the model to nine Iberian species and considered four climate change and budgetary scenarios. Climate change scenarios assuming reductions of greenhouse gas emissions had relatively modest gains in species retention areas. But larger budgets for area selection translate in significantly better retention levels. Nevertheless, our model identified species that, regardless the high conservation investment attained with unlimited budget, have a very limited ability to disperse to climatically suitable areas. Connectivity enhancement and assisted colonization could be considered for such cases

Comparação de programas comerciais para dimensionamento de lajes em betão armado

Devido à evolução contínua de programas de cálculo, é impensável efectuar projectos de estabilidade nos dias de hoje sem o auxílio destas ferramentas. As dificuldades associadas à análise e dimensionamento automático de lajes em betão armado parecem representar um cenário de interesse significativo para a comunidade técnica. No presente trabalho comparam-se os resultados de três programas comerciais de cálculo de lajes em termos de deslocamentos, esforços e armadura. Para esse efeito são consideradas uma laje quadrada simplesmente apoiada, uma laje em L (descontinuidade geométrica) e uma laje fungiforme (descontinuidade de carga devido ao apoio isolado), apresentandose recomendações a adoptar na modelação. As possíveis estratégias de modelação para lajes contínuas fungiformes são discutidas, tendo em vista uniformizar os esforços associados a forças pontuais

Entangled networks, synchronization, and optimal network topology

A new family of graphs, {\it entangled networks}, with optimal properties in many respects, is introduced. By definition, their topology is such that optimizes synchronizability for many dynamical processes. These networks are shown to have an extremely homogeneous structure: degree, node-distance, betweenness, and loop distributions are all very narrow. Also, they are characterized by a very interwoven (entangled) structure with short average distances, large loops, and no well-defined community-structure. This family of nets exhibits an excellent performance with respect to other flow properties such as robustness against errors and attacks, minimal first-passage time of random walks, efficient communication, etc. These remarkable features convert entangled networks in a useful concept, optimal or almost-optimal in many senses, and with plenty of potential applications computer science or neuroscience.Comment: Slightly modified version, as accepted in Phys. Rev. Let

Flexural behaviour of an innovative connection for structural sandwich panels

This paper presents the results experimental work conducted with composite beam specimens that are part of a series of studies to determine the feasibility of using a new type of shear connector, called PERFOFRP, in Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) structural sandwich wall panels. The connector is consisted of a flat Glass Fiber Reinforced Polymer (GFRP) plate with aligned holes evenly distributed along its length. The perforated part of connector is embedded in the concrete layers and the connection is materialized by the combined effects of friction/adhesion and of the mechanical interlock between the perforated laminate and the concrete dowels formed by the concrete that pass through the holes. Previously, the authors of the present paper investigated the mechanical behaviour of connections made with PERFOFRP connectors under transversal loads. Nonetheless, up to now, no investigation was published on the flexural behaviour of sandwich panels produced with the PERFOFRP connectors. In the present paper, the overall mechanical behaviour of the connection under flexure was investigated, being reported: failure modes, stiffness and ultimate flexural capacities of composite beams. The impact of using connectors made with two different types of GFRP laminates were investigated on the mechanical behaviour of composite beams was investigated.BASF(undefined

Nanofiltration of Cork Wastewaters and Their Possible Use in Leather Industry as Tanning Agents

Cork processing wastewater is a very complex mixture of vegetal extracts and has, among other natural compounds, a very high content of phenolic/tannic colloidal matter that is responsible for severe environmental problems. In the present work, the concentration of this wastewater by nanofiltration was investigated with the aim of producing a cork tannin concentrate to be utilized in tanning. Permeation results showed that the permeate fluxes are controlled by both osmotic pressure and fouling/gel layer phenomena, leading to a rapid decrease of permeate fluxes with the concentration factor. The rejection coefficients to organic matter were higher than 95%, indicating that nanofiltration has a very good ability to concentrate the tannins and produce a permeate stream depleted from organic matter. The cork tannin concentrate obtained by nanofiltration and evaporation had total solids concentration of 34.8 g/l. The skins tanned by this concentrate were effectively converted to leather with a shrinking temperature of 7 degrees C

Pull-out behaviour of Glass-Fibre Reinforced Polymer perforated plate connectors embedded in concrete. Part I: Experimental program

The Glass Fibre Reinforced Polymer (GFRP) connectors studied in this work were previously proposed by the authors for connecting the outer Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) layers of sandwich panels for prefabricated modular housing. In this building system, SFRSCC was used to totally eliminate the need for conventional reinforcement and to decrease the thickness of the panel's outer layers, with consequent reduction of the global self-weigh of the panels, while GFRP connectors aimed to significantly decrease thermal bridging effects. For a reliable design of the structural elements that make use of these connectors, the mechanical behaviour of this connection should be known and taken into account. The present paper summarizes the results obtained in an experimental research devoted to the assessment of the behaviour of GFRP-SFRSCC connection by performing pullout tests with specimens representative of the developed sandwich panel. The specimens were designed to examine the influence of the number and geometry of holes executed in the GFRP connector that assure the connection between these two materials.This work is part of the research project QREN number 5387, LEGOUSE, involving the companies Mota-Engil, CiviTest, the ISISE/University of Minho and PIEP. The first author would like to thank the financial support provided by PAIP/UNILA. The third author wish to acknowledge the grant SFRH/BSAB/114302/2016 provided by FCT.info:eu-repo/semantics/publishedVersio

A better characterization of the chemical composition of exoplanets atmospheres with ARIEL

Since the discovery of the first extrasolar planet more than twenty years ago, nearly four thousand planets orbiting stars other than the Sun (http://exoplanet.eu/) have been discovered. Current observational instruments (on board the Hubble Space Telescope, Spitzer, and on ground-based facilities) have allowed the scientific community to obtain important information on the physical and chemical properties of these planets. However, for a more in-depth characterisation of these worlds, more powerful telescopes are needed. Thanks to the high sensitivity of their instruments, the next generation of space observatories (e.g. JWST, ARIEL) will provide observations of unprecedented quality, allowing us to extract far more information than what was previously possible. Such high quality observations will provide constraints on theoretical models of exoplanet atmospheres and lead to a greater understanding of their physics and chemistry. Important modelling efforts have been carried out during the past few years, showing that numerous parameters and processes (such as the elemental abundances, temperature, mixing, etc.) are likely to affect the atmospheric composition of exoplanets and subsequently the observable spectra. In this manuscript, we review the different parameters that can influence the molecular composition of exoplanet atmospheres. We show that the high-precision of ARIEL observations will improve our view and characterisation of exoplanet atmospheres. We also consider future developments that are necessary to improve atmospheric models, driven by the need to interpret the available observations

Inverse lift: a signature of the elasticity of complex fluids?

To understand the mechanics of a complex fluid such as a foam we propose a model experiment (a bidimensional flow around an obstacle) for which an external sollicitation is applied, and a local response is measured, simultaneously. We observe that an asymmetric obstacle (cambered airfoil profile) experiences a downards lift, opposite to the lift usually known (in a different context) in aerodynamics. Correlations of velocity, deformations and pressure fields yield a clear explanation of this inverse lift, involving the elasticity of the foam. We argue that such an inverse lift is likely common to complex fluids with elasticity.Comment: 4 pages, 4 figures, revised version, submitted to PR