260 research outputs found
Resurrecting the alien director: Jean-Pierre Jeunet in Hollywood
This essay examines the critical reception of Jean-Pierre Jeunet's Alien Resurrection in the popular Anglo-American press, where the film was often discussed in terms that highlighted the director's status as an 'outsider'. The anxiety that the film elicits among critics, it is argued, is a function of the very abjection that is depicted graphically within the film: a fear of the unclassifiable and of the crossing of boundaries
Dynamic Modeling and Simulation of a Real World Billiard
Gravitational billiards provide an experimentally accessible arena for
testing formulations of nonlinear dynamics. We present a mathematical model
that captures the essential dynamics required for describing the motion of a
realistic billiard for arbitrary boundaries. Simulations of the model are
applied to parabolic, wedge and hyperbolic billiards that are driven
sinusoidally. Direct comparisons are made between the model's predictions and
previously published experimental data. It is shown that the data can be
successfully modeled with a simple set of parameters without an assumption of
exotic energy dependence.Comment: 10 pages, 3 figure
Velocity distribution of fluidized granular gases in presence of gravity
The velocity distribution of a fluidized dilute granular gas in the direction
perpendicular to the gravitational field is investigated by means of Molecular
Dynamics simulations. The results indicate that the velocity distribution can
be exactly described neither by a Gaussian nor by a stretched exponential law.
Moreover, it does not exhibit any kind of scaling. In fact, the actual shape of
the distribution depends on the number of monolayers at rest, on the
restitution coefficient and on the height at what it is measured. The role
played by the number of particle-particle collisions as compared with the
number of particle-wall collisions is discussed
Energy fluctuations in vibrated and driven granular gases
We investigate the behavior of energy fluctuations in several models of
granular gases maintained in a non-equilibrium steady state. In the case of a
gas heated from a boundary, the inhomogeneities of the system play a
predominant role. Interpreting the total kinetic energy as a sum of independent
but not identically distributed random variables, it is possible to compute the
probability density function (pdf) of the total energy. Neglecting correlations
and using the analytical expression for the inhomogeneous temperature profile
obtained from the granular hydrodynamic equations, we recover results which
have been previously observed numerically and which had been attributed to the
presence of correlations. In order to separate the effects of spatial
inhomogeneities from those ascribable to velocity correlations, we have also
considered two models of homogeneously thermostated gases: in this framework it
is possible to reveal the presence of non-trivial effects due to velocity
correlations between particles. Such correlations stem from the inelasticity of
collisions. Moreover, the observation that the pdf of the total energy tends to
a Gaussian in the large system limit, suggests that they are also due to the
finite size of the system.Comment: 13 pages, 10 figure
An elastic, plastic, viscous model for slow shear of a liquid foam
We suggest a scalar model for deformation and flow of an amorphous material
such as a foam or an emulsion. To describe elastic, plastic and viscous
behaviours, we use three scalar variables: elastic deformation, plastic
deformation rate and total deformation rate; and three material specific
parameters: shear modulus, yield deformation and viscosity. We obtain equations
valid for different types of deformations and flows slower than the relaxation
rate towards mechanical equilibrium. In particular, they are valid both in
transient or steady flow regimes, even at large elastic deformation. We discuss
why viscosity can be relevant even in this slow shear (often called
"quasi-static") limit. Predictions of the storage and loss moduli agree with
the experimental literature, and explain with simple arguments the non-linear
large amplitude trends
2022 Proposed base case model for eastern Atlantic and Mediterranean bluefin tuna assessment using stock synthesis.
This document presents the proposed base case for the assessment of Eastern Atlantic and Mediterranean population of bluefin tuna using Stock Synthesis in 2022. The model runs from 1950 to 2020 and was fitted to length composition data, conditional age-at-length (otolith and spines–length-age pairs), 16 fishing fleets and 11 indices of abundance. Growth is modeled by a Richards function with Linf fixed at 271 cm, K fixed at 0.23387, and the shape parameter is estimated by the model. A Beverton-Holt stock recruitment relationship was estimated in the model with the steepness and sigmaR fixed at 0.9 and 0.6, respectively. R0 is freely estimated. Although the diagnostics indicate an acceptable stability of the model, there are important conflicts between the catch information, length composition and index data. The model fits to length compositions were not good, but the model followed most of the indices fairly fine. The model results showed that the SSB decreased since 1950 until 1970s, remaining relatively stable at low values during the 1980-2009 period, and showing a sharp and steady increased since 2010. Model diagnostics indicated that the different source of data provides contradicting information about the stock, resulting in biases in the results
Non-Gaussian Velocity Distribution Function in a Vibrating Granular Bed
The simulation of granular particles in a quasi two-dimensional container
under the vertical vibration as an experimental accessible model for granular
gases is performed. The velocity distribution function obeys an
exponential-like function during the vibration and deviates from the
exponential function in free-cooling states. It is confirmed that this
exponential-like distribution function is produced by Coulomb's friction force.
A Langevin equation with Coulomb's friction is proposed to describe the motion
of such the system.Comment: 4 pages, 4 figures. to be published in Journal of Physical Society of
Japan Vol.73 No.
Dynamics of electrostatically-driven granular media. Effects of Humidity
We performed experimental studies of the effect of humidity on the dynamics
of electrostatically-driven granular materials. Both conducting and dielectric
particles undergo a phase transition from an immobile state (granular solid) to
a fluidized state (granular gas) with increasing applied field. Spontaneous
precipitation of solid clusters from the gas phase occurs as the external
driving is decreased. The clustering dynamics in conducting particles is
primarily controlled by screening of the electric field but is aided by
cohesion due to humidity. It is shown that humidity effects dominate the
clustering process with dielectric particles.Comment: 4 pages, 4 fig
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