4,406 research outputs found
From fracture to fragmentation: discrete element modeling -- Complexity of crackling noise and fragmentation phenomena revealed by discrete element simulations
Discrete element modelling (DEM) is one of the most efficient computational
approaches to the fracture processes of heterogeneous materials on mesoscopic
scales. From the dynamics of single crack propagation through the statistics of
crack ensembles to the rapid fragmentation of materials DEM had a substantial
contribution to our understanding over the past decades. Recently, the
combination of DEM with other simulation techniques like Finite Element
Modelling further extended the field of applicability. In this paper we briefly
review the motivations and basic idea behind the DEM approach to cohesive
particulate matter and then we give an overview of on-going developments and
applications of the method focusing on two fields where recent success has been
achieved. We discuss current challenges of this rapidly evolving field and
outline possible future perspectives and debates
Large deviations for clocks of self-similar processes
The Lamperti correspondence gives a prominent role to two random time
changes: the exponential functional of a L\'evy process drifting to
and its inverse, the clock of the corresponding positive self-similar process.
We describe here asymptotical properties of these clocks in large time,
extending the results of Yor and Zani
Poles and zeros of the scattering matrix associated to defect modes
We analyze electromagnetic waves propagation in one-dimensional periodic
media with single or periodic defects. The study is made both from the point of
view of the modes and of the diffraction problem. We provide an explicit
dispersion equation for the numerical calculation of the modes, and we
establish a connection between modes and poles and zeros of the scattering
matrix.Comment: 6 pages (Revtex), no figure
Discovery of 36 eclipsing EL CVn binaries found by the Palomar Transient Factory
We report the discovery and analysis of 36 new eclipsing EL CVn-type
binaries, consisting of a core helium-composition pre-white dwarf and an
early-type main-sequence companion, more than doubling the known population of
these systems. We have used supervised machine learning methods to search 0.8
million lightcurves from the Palomar Transient Factory, combined with SDSS,
Pan-STARRS and 2MASS colours. The new systems range in orbital periods from
0.46-3.8 d and in apparent brightness from ~14-16 mag in the PTF or
filters. For twelve of the systems, we obtained radial velocity
curves with the Intermediate Dispersion Spectrograph at the Isaac Newton
Telescope. We modelled the lightcurves, radial velocity curves and spectral
energy distributions to determine the system parameters. The radii (0.3-0.7
) and effective temperatures (8000-17000 K) of the
pre-He-WDs are consistent with stellar evolution models, but the masses
(0.12-0.28 ) show more variance than models predicted. This
study shows that using machine learning techniques on large synoptic survey
data is a powerful way to discover substantial samples of binary systems in
short-lived evolutionary stages
Caloric Curves for small systems in the Nuclear Lattice Gas Model
For pedagogical reasons we compute the caloric curve for 11 particles in a
lattice. Monte-Carlo simulation can be avoided and exact results are
obtained. There is no back-bending in the caloric curve and negative specific
heat does not appear. We point out that the introduction of kinetic energy in
the nuclear Lattice Gas Model modifies the results of the standard Lattice Gas
Model in a profound way.Comment: 12 pages, Revtex, including 4 postscript figure
TERC polymorphisms are associated both with susceptibility to colorectal cancer and with longer telomeres.
Shorter telomeres have been associated with increased risk of malignancy, including colorectal cancer (CRC). Telomere length is heritable and may be an intermediate phenotype linked to genetic susceptibility to CRC
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The influence of vegetation, fire spread and fire behaviour on biomass burning and trace gas emissions: Results from a process-based model
A process-based fire regime model (SPITFIRE) has been developed, coupled with ecosystem dynamics in the LPJ Dynamic Global Vegetation Model, and used to explore fire regimes and the current impact of fire on the terrestrial carbon cycle and associated emissions of trace atmospheric constituents. The model estimates an average release of 2.24 Pg C yrâ1 as CO2 from biomass burning during the 1980s and 1990s. Comparison with observed active fire counts shows that the model reproduces where fire occurs and can mimic broad geographic patterns in the peak fire season, although the predicted peak is 1â2 months late in some regions. Modelled fire season length is generally overestimated by about one month, but shows a realistic pattern of differences among biomes. Comparisons with remotely sensed burnt-area products indicate that the model reproduces broad geographic patterns of annual fractional burnt area over most regions, including the boreal forest, although interannual variability in the boreal zone is underestimated
Transient backbending behavior in the Ising model with fixed magnetization
The physical origin of the backbendings in the equations of state of finite
but not necessarily small systems is studied in the Ising model with fixed
magnetization (IMFM) by means of the topological properties of the observable
distributions and the analysis of the largest cluster with increasing lattice
size. Looking at the convexity anomalies of the IMFM thermodynamic potential,
it is shown that the order of the transition at the thermodynamic limit can be
recognized in finite systems independently of the lattice size. General
statistical mechanics arguments and analytical calculations suggest that the
backbending in the caloric curve is a transient behaviour which should not
converge to a plateau in the thermodynamic limit, while the first order
transition is signalled by a discontinuity in other observables.Comment: 24 pages, 11 figure
First results from the LUX dark matter experiment at the Sanford Underground Research Facility
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