996 research outputs found
Maxwell demon in Granular gas: a new kind of bifurcation? The hypercritical bifurcation
This paper starts with the investigation of the behaviour of a set of two
subsystems which are able to exchange some internal quantity according to a
given flux function. It is found that this sytem exhibit a bifurcation when the
flux passes through a maximum and that its kind (super-critical/sub-critical)
depends on the dissymmetry of the flux function near the maximum. It is also
found a new kind of bifurcation when the flux function is symmetric: we call it
hypercritical bifurcation because it generates much stronger fluctuations than
the super-critical one. The effect of a white noise is then investigated. We
show that an experimental set-up, leading to the Maxwell demon in granular gas,
displays all these kinds of bifurcation, just by changing the parameters of
excitation. It means that this system is much less simple as it was thought.Comment: 19 pages, 10 figure
Embedding ethics and ethical practice within and across the curriculum: emerging findings from a TQEF-funded project
Impact of Resonant Magnetic Perturbations on Zonal Modes, Drift-Wave Turbulence and the L-H Transition Threshold
We study the effects of Resonant Magnetic Perturbations (RMPs) on turbulence,
flows and confinement in the framework of resistive drift-wave turbulence. This
work was motivated, in parts, by experiments reported at the IAEA 2010
conference [Y. Xu {\it et al}, Nucl. Fusion \textbf{51}, 062030] which showed a
decrease of long-range correlations during the application of RMPs. We derive
and apply a zero-dimensional predator-prey model coupling the Drift-Wave Zonal
Mode system [M. Leconte and P.H. Diamond, Phys. Plasmas \textbf{19}, 055903] to
the evolution of mean quantities. This model has both density gradient drive
and RMP amplitude as control parameters and predicts a novel type of transport
bifurcation in the presence of RMPs. This model allows a description of the
full L-H transition evolution with RMPs, including the mean sheared flow
evolution. The key results are: i) The L-I and I-H power thresholds \emph{both}
increase with RMP amplitude |\bx|, the relative increase of the L-I threshold
scales as \Delta P_{\rm LI} \propto |\bx|^2 \nu_*^{-2} \gyro^{-2}, where
is edge collisionality and \gyro is the sound gyroradius. ii) RMPs
are predicted to \emph{decrease} the hysteresis between the forward and
back-transition. iii) Taking into account the mean density evolution, the
density profile - sustained by the particle source - has an increased turbulent
diffusion compared with the reference case without RMPs which provides one
possible explanation for the \emph{density pump-out} effect.Comment: 30 pages, IAEA-based articl
Soft Cache Hits and the Impact of Alternative Content Recommendations on Mobile Edge Caching
Caching popular content at the edge of future mobile networks has been widely
considered in order to alleviate the impact of the data tsunami on both the
access and backhaul networks. A number of interesting techniques have been
proposed, including femto-caching and "delayed" or opportunistic cache access.
Nevertheless, the majority of these approaches suffer from the rather limited
storage capacity of the edge caches, compared to the tremendous and rapidly
increasing size of the Internet content catalog. We propose to depart from the
assumption of hard cache misses, common in most existing works, and consider
"soft" cache misses, where if the original content is not available, an
alternative content that is locally cached can be recommended. Given that
Internet content consumption is increasingly entertainment-oriented, we believe
that a related content could often lead to complete or at least partial user
satisfaction, without the need to retrieve the original content over expensive
links. In this paper, we formulate the problem of optimal edge caching with
soft cache hits, in the context of delayed access, and analyze the expected
gains. We then show using synthetic and real datasets of related video contents
that promising caching gains could be achieved in practice
Letter from Helen M. LeConte to John Muir, 1912 Dec 31.
Berkeley, December 31st, 1912.Dear Mr. Muir:It argues that you are a fond Grandpapa as well as a writer of winder-books, when you remember the little children of your friends.They, through me, thank you so much for the lovely golden wheels that father and mother would not let them roll about.You will see that the good Scotch strain shows in the youngsters, inherited from both Grandmothers (Nisbet and Malcolm by name) when I tell you that they put the pretty playthings in their respective banks.We, the older ones, are very appreciative of the kind thought that comes with the valuable gift, and hope to use the gift for something permanent that the children in later years will be proud to connect with your name.A happy new year to you from the whole family, who join me in warmest greeting.sincerely,Helen M. LeConte[05336
Zonal profile corrugations and staircase formation: transport crossphase modulations
Recently, quasi-stationary structures called staircases were
observed in gyrokinetic simulations, in all transport channels [Dif-Pradalier
et al. Phys. Rev. Lett. 114, 085004 (2015)]. We present a novel analytical
theory - supported by plasma fluid simulations - for the generation of density
profile corrugations (staircase): Turbulent fluctuations self-organize to
generate quasi-stationary radial modulations of the
transport crossphase between density and electric potential
fluctuations. The radial modulations of the associated particle flux drive
zonal corrugations of the density profile, via a modulational instability. In
turn, zonal density corrugations regulate the turbulence via nonlinear damping
of the fluctuations.Comment: 22 pages, 11 figures. arXiv admin note: substantial text overlap with
arXiv:2111.0602
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