6,744 research outputs found
An Assessment on the Use of Stationary Vehicles as a Support to Cooperative Positioning
In this paper, we consider the use of stationary vehicles as tools to enhance
the localisation capabilities of moving vehicles in a VANET. We examine the
idea in terms of its potential benefits, technical requirements, algorithmic
design and experimental evaluation. Simulation results are given to illustrate
the efficacy of the technique.Comment: This version of the paper is an updated version of the initial
submission, where some initial comments of reviewers have been taken into
accoun
A Distributed and Privacy-Aware Speed Advisory System for Optimising Conventional and Electric Vehicles Networks
One of the key ideas to make Intelligent Transportation Systems (ITS) work
effectively is to deploy advanced communication and cooperative control
technologies among the vehicles and road infrastructures. In this spirit, we
propose a consensus-based distributed speed advisory system that optimally
determines a recommended common speed for a given area in order that the group
emissions, or group battery consumptions, are minimised. Our algorithms achieve
this in a privacy-aware manner; namely, individual vehicles do not reveal
in-vehicle information to other vehicles or to infrastructure. A mobility
simulator is used to illustrate the efficacy of the algorithm, and
hardware-in-the-loop tests involving a real vehicle are given to illustrate
user acceptability and ease of the deployment.Comment: This is a journal paper based on the conference paper "Highway speed
limits, optimised consensus, and intelligent speed advisory systems"
presented at the 3rd International Conference on Connected Vehicles and Expo
(ICCVE 2014) in November 2014. This is the revised version of the paper
recently submitted to the IEEE Transactions on Intelligent Transportation
Systems for publicatio
Pattern formation in systems with competing interactions
There is a growing interest, inspired by advances in technology, in the low
temperature physics of thin films. These quasi-2D systems show a wide range of
ordering effects including formation of striped states, reorientation
transitions, bubble formation in strong magnetic fields, etc. The origins of
these phenomena are, in many cases, traced to competition between short ranged
exchange ferromagnetic interactions, favoring a homogeneous ordered state, and
the long ranged dipole-dipole interaction, which opposes such ordering on the
scale of the whole sample. The present theoretical understanding of these
phenomena is based on a combination of variational methods and a variety of
approximations, e.g., mean-field and spin-wave theory. The comparison between
the predictions of these approximate methods and the results of MonteCarlo
simulations are often difficult because of the slow relaxation dynamics
associated with the long-range nature of the dipole-dipole interactions. In
this note we will review recent work where we prove existence of periodic
structures in some lattice and continuum model systems with competing
interactions. The continuum models have also been used to describe
micromagnets, diblock polymers, etc.Comment: 11 pages, 1 figure, to appear in the AIP conference proceedings of
the 10th Granada Seminar on Computational Physics, Sept. 15-19, 2008. (v2)
Updated reference
Bistability patterns and nonlinear switching with very high contrast ratio in a 1550 nm quantum dash semiconductor laser
We report on the experimental observation of optical bistability (OB) and nonlinear switching (NS) in a nanostructure laser; specifically a 1550 nm quantum dash Fabry-Perot laser subject to external optical injection and operated in reflection. Different shapes of optical bistability and nonlinear switching, anticlockwise and clockwise, with very high on-off contrast ratio (up to 180:1) between output states were experimentally measured. These results added to the potential of nanostructure lasers for enhanced performance offer promise for use in fast all-optical signal processing applications in optical networks. © 2012 American Institute of Physics
Strong Shock Waves and Nonequilibrium Response in a One-dimensional Gas: a Boltzmann Equation Approach
We investigate the nonequilibrium behavior of a one-dimensional binary fluid
on the basis of Boltzmann equation, using an infinitely strong shock wave as
probe. Density, velocity and temperature profiles are obtained as a function of
the mixture mass ratio \mu. We show that temperature overshoots near the shock
layer, and that heavy particles are denser, slower and cooler than light
particles in the strong nonequilibrium region around the shock. The shock width
w(\mu), which characterizes the size of this region, decreases as w(\mu) ~
\mu^{1/3} for \mu-->0. In this limit, two very different length scales control
the fluid structure, with heavy particles equilibrating much faster than light
ones. Hydrodynamic fields relax exponentially toward equilibrium, \phi(x) ~
exp[-x/\lambda]. The scale separation is also apparent here, with two typical
scales, \lambda_1 and \lambda_2, such that \lambda_1 ~ \mu^{1/2} as \mu-->0$,
while \lambda_2, which is the slow scale controlling the fluid's asymptotic
relaxation, increases to a constant value in this limit. These results are
discussed at the light of recent numerical studies on the nonequilibrium
behavior of similar 1d binary fluids.Comment: 9 pages, 8 figs, published versio
The Simplest Piston Problem II: Inelastic Collisions
We study the dynamics of three particles in a finite interval, in which two
light particles are separated by a heavy ``piston'', with elastic collisions
between particles but inelastic collisions between the light particles and the
interval ends. A symmetry breaking occurs in which the piston migrates near one
end of the interval and performs small-amplitude periodic oscillations on a
logarithmic time scale. The properties of this dissipative limit cycle can be
understood simply in terms of an effective restitution coefficient picture.
Many dynamical features of the three-particle system closely resemble those of
the many-body inelastic piston problem.Comment: 8 pages, 7 figures, 2-column revtex4 forma
An assessment on the use of stationary vehicles to support cooperative positioning systems
In this paper, we evaluate the ability of stationary vehicles (e.g. parked or temporary stopped cars) as tools to enhance the capabilities of existing cooperative positioning algorithms in vehicular networks. First, some real-world facts are provided to support the feasibility of our ideas. Then, we examine the idea in greater details in terms of the technical requirements and methodological analysis, and provide a comprehensive experimental evaluation using dedicated simulations. The routing of a drone through an urban scenario is presented as a non-traditional application case, where the benefits of the proposed approach are reflected in a better utilisation of the flight time
Fluctuations of the heat flux of a one-dimensional hard particle gas
Momentum-conserving one-dimensional models are known to exhibit anomalous
Fourier's law, with a thermal conductivity varying as a power law of the system
size. Here we measure, by numerical simulations, several cumulants of the heat
flux of a one-dimensional hard particle gas. We find that the cumulants, like
the conductivity, vary as power laws of the system size. Our results also
indicate that cumulants higher than the second follow different power laws when
one compares the ring geometry at equilibrium and the linear case in contact
with two heat baths (at equal or unequal temperatures). keywords: current
fluctuations, anomalous Fourier law, hard particle gasComment: 5 figure
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