9,540 research outputs found
Choreographies in Practice
Choreographic Programming is a development methodology for concurrent
software that guarantees correctness by construction. The key to this paradigm
is to disallow mismatched I/O operations in programs, called choreographies,
and then mechanically synthesise distributed implementations in terms of
standard process models via a mechanism known as EndPoint Projection (EPP).
Despite the promise of choreographic programming, there is still a lack of
practical evaluations that illustrate the applicability of choreographies to
concrete computational problems with standard concurrent solutions. In this
work, we explore the potential of choreographies by using Procedural
Choreographies (PC), a model that we recently proposed, to write distributed
algorithms for sorting (Quicksort), solving linear equations (Gaussian
elimination), and computing Fast Fourier Transform. We discuss the lessons
learned from this experiment, giving possible directions for the usage and
future improvements of choreography languages
Quantifying signals with power-law correlations: A comparative study of detrended fluctuation analysis and detrended moving average techniques
Detrended fluctuation analysis (DFA) and detrended moving average (DMA) are
two scaling analysis methods designed to quantify correlations in noisy
non-stationary signals. We systematically study the performance of different
variants of the DMA method when applied to artificially generated long-range
power-law correlated signals with an {\it a-priori} known scaling exponent
and compare them with the DFA method. We find that the scaling
results obtained from different variants of the DMA method strongly depend on
the type of the moving average filter. Further, we investigate the optimal
scaling regime where the DFA and DMA methods accurately quantify the scaling
exponent , and how this regime depends on the correlations in the
signal. Finally, we develop a three-dimensional representation to determine how
the stability of the scaling curves obtained from the DFA and DMA methods
depends on the scale of analysis, the order of detrending, and the order of the
moving average we use, as well as on the type of correlations in the signal.Comment: 15 pages, 16 figure
Alignment transition in a nematic liquid crystal due to field-induced breaking of anchoring
We report on the alignment transition of a nematic liquid crystal from
initially homeotropic to quasi-planar due to field-induced anchoring breaking.
The initial homeotropic alignment is achieved by Langmuir-Blodgett monolayers.
In this geometry the anchoring strength can be evaluated by the Frederiks
transition technique. Applying an electric field above a certain threshold
provokes turbulent states denoted DSM1 and DSM2. While DSM1 does not affect the
anchoring, DSM2 breaks the coupling between the surface and the liquid crystal:
switching off the field from a DSM2 state does not immediately restore the
homeotropic alignment. Instead, we obtain a quasi-planar metastable alignment.
The cell thickness dependence for the transition is related to theComment: 7 pages, LaTeX2e article, 4 figures, 7 EPS files, added references,
accepted for publication in Europhysics Letter
Persistence of small-scale anisotropy of magnetic turbulence as observed in the solar wind
The anisotropy of magnetophydrodynamic turbulence is investigated by using
solar wind data from the Helios 2 spacecraft. We investigate the behaviour of
the complete high-order moment tensors of magnetic field increments and we
compare the usual longitudinal structure functions which have both isotropic
and anisotropic contributions, to the fully anisotropic contribution. Scaling
exponents have been extracted by an interpolation scaling function. Unlike the
usual turbulence in fluid flows, small-scale magnetic fluctuations remain
anisotropic. We discuss the radial dependence of both anisotropy and
intermittency and their relationship.Comment: 7 pages, 2 figures, in press on Europhys. Let
Intraband Optical Spectral Weight in the presence of a van Hove singularity: application to BiSrCaCuO
The Kubo single band sum rule is used to determine the optical spectral
weight of a tight binding band with further than nearest neighbour hopping. We
find for a wide range of parameters and doping concentrations that the change
due to superconductivity at low temperature can be either negative or positive.
In contrast, the kinetic energy change is always negative. We use an ARPES
determined tight binding parametrization of BiSrCaCuO
to investigate whether this can account for recent observations of a positive
change in the spectral weight due to the onset of superconductivity. With this
band structure we find that in the relevant doping regime a straightforward BCS
calculation of the optical spectral weight cannot account for the experimental
observations.Comment: 10 page 9 figure
Exploring the effect of geometric coupling on friction and energy dissipation in rough contacts of elastic and viscoelastic coatings
We study the frictional behavior of both elastic and viscoelastic thin
coatings bonded to a seemingly rigid substrate and sliding against a rough
profile in the presence of Coulomb friction at the interface. The aim is to
explore the effect of the coupling between the normal and tangential
displacement fields arising from the finiteness of the material thickness and
to quantify the contribution this can have on energy losses. We found that, due
to normal-tangential coupling, asymmetric contacts and consequently additional
friction are observed even for purely elastic layers, indeed associated with
zero bulk energy dissipation. Furthermore, enhanced viscoelastic friction is
reported in the case of viscoelastic coatings due to coupling, this time also
entailing larger bulk energy dissipation. Geometric coupling also introduces
additional interactions involving the larger scales normal displacements, which
leads to a significant increase of the contact area, under given normal load,
compared to the uncoupled contacts. These results show that, in the case of
contact interfaces involving thin deformable coating bonded to significantly
stiffer substrate, the effect of interfacial shear stresses on the frictional
and contact behavior cannot be neglected
The multiple V-shaped double peeling of elastic thin films from elastic soft substrates
M. P. is supported by the European Commission H2020 under Graphene Flagship Core 1 No. 696656 (WP14 “Polymer composites”) and FET Proactive “Neurofibres” Grant No. 732344
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