16,571 research outputs found
On the dynamics of social conflicts: looking for the Black Swan
This paper deals with the modeling of social competition, possibly resulting
in the onset of extreme conflicts. More precisely, we discuss models describing
the interplay between individual competition for wealth distribution that, when
coupled with political stances coming from support or opposition to a
government, may give rise to strongly self-enhanced effects. The latter may be
thought of as the early stages of massive, unpredictable events known as Black
Swans, although no analysis of any fully-developed Black Swan is provided here.
Our approach makes use of the framework of the kinetic theory for active
particles, where nonlinear interactions among subjects are modeled according to
game-theoretical tools.Comment: 26 pages, 7 figure
The XDEM Multi-physics and Multi-scale Simulation Technology: Review on DEM-CFD Coupling, Methodology and Engineering Applications
The XDEM multi-physics and multi-scale simulation platform roots in the Ex-
tended Discrete Element Method (XDEM) and is being developed at the In- stitute
of Computational Engineering at the University of Luxembourg. The platform is
an advanced multi- physics simulation technology that combines flexibility and
versatility to establish the next generation of multi-physics and multi-scale
simulation tools. For this purpose the simulation framework relies on coupling
various predictive tools based on both an Eulerian and Lagrangian approach.
Eulerian approaches represent the wide field of continuum models while the
Lagrange approach is perfectly suited to characterise discrete phases. Thus,
continuum models include classical simulation tools such as Computa- tional
Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended
configuration of the classical Discrete Element Method (DEM) addresses the
discrete e.g. particulate phase. Apart from predicting the trajectories of
individual particles, XDEM extends the application to estimating the thermo-
dynamic state of each particle by advanced and optimised algorithms. The
thermodynamic state may include temperature and species distributions due to
chemical reaction and external heat sources. Hence, coupling these extended
features with either CFD or FEA opens up a wide range of applications as
diverse as pharmaceutical industry e.g. drug production, agriculture food and
processing industry, mining, construction and agricultural machinery, metals
manufacturing, energy production and systems biology
Free Cooling Phase-Diagram of Hard-Spheres with Short- and Long-Range Interactions
We study the stability, the clustering and the phase-diagram of free cooling
granular gases. The systems consist of mono-disperse particles with additional
non-contact (long-range) interactions, and are simulated here by the
event-driven molecular dynamics algorithm with discrete (short-range shoulders
or wells) potentials (in both 2D and 3D). Astonishingly good agreement is found
with a mean field theory, where only the energy dissipation term is modified to
account for both repulsive or attractive non-contact interactions. Attractive
potentials enhance cooling and structure formation (clustering), whereas
repulsive potentials reduce it, as intuition suggests. The system evolution is
controlled by a single parameter: the non-contact potential strength scaled by
the fluctuation kinetic energy (granular temperature). When this is small, as
expected, the classical homogeneous cooling state is found. However, if the
effective dissipation is strong enough, structure formation proceeds, before
(in the repulsive case) non-contact forces get strong enough to undo the
clustering (due to the ongoing dissipation of granular temperature). For both
repulsive and attractive potentials, in the homogeneous regime, the cooling
shows a universal behaviour when the (inverse) control parameter is used as
evolution variable instead of time. The transition to a non-homogeneous regime,
as predicted by stability analysis, is affected by both dissipation and
potential strength. This can be cast into a phase diagram where the system
changes with time, which leaves open many challenges for future research.Comment: 22 pages, 15 figure
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