1,130 research outputs found
Marine Protected Areas and commercial fisheries: the existing fishery in potential protected areas, and a modelling study of the impact of protected areas on North Sea Plaice
Dit rapport presenteert resultaten van onderzoek, dat in 2005/2006 is uitgevoerd. In het kader van de Europese Vogel en Habitat Richtlijnen dienen lidstaten te beschermen gebieden op zee aan te wijzen, wat mogelijk zou leiden tot beperkingen van visserijactiviteiten in deze gebieden. De vraag was, welke invloed dit zou hebben op de vis en visserij. In dit onderzoek is enerzijds een statische beschrijving opgesteld van de visserijinspanning en de vangsten in de voorgestelde gebieden, en is anderzijds een eerste analyse (simulatie-model) opgezet van het lange-termijn effect op migrerende vis (schol). Dit onderzoek werd eind 2006 afgerond met een concept-rapport
Quasi-binary amorphous phase in a 3D system of particles with repulsive-shoulder interactions
We report a computer-simulation study of the equilibrium phase diagram of a
three-dimensional system of particles with a repulsive step potential. Using
free-energy calculations, we have determined the equilibrium phase diagram of
this system. At low temperatures, we observe a number of distinct crystal
phases. However, under certain conditions the system undergoes a glass
transition in a regime where the liquid appears thermodynamically stable. We
argue that the appearance of this amorphous low-temperature phase can be
understood by viewing this one-component system as a pseudo-binary mixture.Comment: 4 pages, 4 figure
Resolution of singularities by rational functions
Results on the rational approximation of functions containing singularities
are presented. We build further on the ''lightning method'', recently proposed
by Trefethen and collaborators, based on exponentially clustering poles close
to the singularities. Our results are obtained by augmenting the lightning
approximation set with either a low-degree polynomial basis or poles clustering
towards infinity, in order to obtain a robust approximation of the smooth
behaviour of the function. This leads to a significant increase in the
achievable accuracy as well as the convergence rate of the numerical scheme.
For the approximation of on , the optimal convergence rate as
shown by Stahl in 1993 is now achieved simply by least-squares fitting
Waterlike thermodynamic anomalies in a repulsive-step potential system
We report a computer-simulation study of the equilibrium phase diagram of a
three-dimensional system of particles with a repulsive step potential. The
phase diagram is obtained using free-energy calculations. At low temperatures,
we observe a number of distinct crystal phases. We show that at certain values
of the potential parameters the system exhibits the water-like thermodynamic
anomalies: density anomaly and diffusion anomaly. The anomalies disappear with
increasing the repulsive step width: their locations move to the region inside
the crystalline phase.Comment: 6 pages, 5 figure
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