33,318 research outputs found
Activation thresholds in epidemic spreading with motile infectious agents on scale-free networks
We investigate a fermionic susceptible-infected-susceptible model with
mobility of infected individuals on uncorrelated scale-free networks with
power-law degree distributions of exponents
. Two diffusive processes with diffusion rate of an infected
vertex are considered. In the \textit{standard diffusion}, one of the
nearest-neighbors is chosen with equal chance while in the \textit{biased
diffusion} this choice happens with probability proportional to the neighbor's
degree. A non-monotonic dependence of the epidemic threshold on with an
optimum diffusion rate , for which the epidemic spreading is more
efficient, is found for standard diffusion while monotonic decays are observed
in the biased case. The epidemic thresholds go to zero as the network size is
increased and the form that this happens depends on the diffusion rule and
degree exponent. We analytically investigated the dynamics using quenched and
heterogeneous mean-field theories. The former presents, in general, a better
performance for standard and the latter for biased diffusion models, indicating
different activation mechanisms of the epidemic phases that are rationalized in
terms of hubs or max -core subgraphs.Comment: 9 pages, 4 figure
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Hybrid Prototypes to Assist Modeling Automotive Seats
The development of new modular seats is an important issue in the automotive industry.
However, is very time consuming and costly. Virtual models and hybrid prototypes could
accelerate the car seats development process. The hybrid prototypes are mainly manufactured by
rapid prototyping with multi materials. The objective of this paper is to establish a methodology
to develop innovative lightweight multi-functional, modular car seats to be used in Multi-Purpose
Vehicles (MPV), by means of FEA simulation and rapid prototyping additive/subtractive
technologies utilizing multi materials. A case study is presented to validate the developed
methodology. The manufactured hybrid prototype’s reproduces the main functionalities of the
MPV modular seat, namely its three key positions: normal, stored and table.Mechanical Engineerin
Are Magnetic Wind-Driving Disks Inherently Unstable?
There have been claims in the literature that accretion disks in which a
centrifugally driven wind is the dominant mode of angular momentum transport
are inherently unstable. This issue is considered here by applying an
equilibrium-curve analysis to the wind-driving, ambipolar diffusion-dominated,
magnetic disk model of Wardle & Konigl (1993). The equilibrium solution curves
for this class of models typically exhibit two distinct branches. It is argued
that only one of these branches represents unstable equilibria and that a real
disk/wind system likely corresponds to a stable solution.Comment: 5 pages, 2 figures, to be published in ApJ, vol. 617 (2004 Dec 20).
Uses emulateapj.cl
The structures underlying soliton solutions in integrable hierarchies
We point out that a common feature of integrable hierarchies presenting
soliton solutions is the existence of some special ``vacuum solutions'' such
that the Lax operators evaluated on them, lie in some abelian subalgebra of the
associated Kac-Moody algebra. The soliton solutions are constructed out of
those ``vacuum solitons'' by the dressing transformation procedure.Comment: Talk given at the I Latin American Symposium on High Energy Physics,
I SILAFAE, Merida, Mexico, November/96, 5 pages, LaTeX, needs aipproc.tex,
aipproc.sty, aipproc.cls, available from
ftp://ftp.aip.org/ems/tex/macros/proceedings/6x9
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