25,298 research outputs found
Effects of energetic particles on zonal flow generation by toroidal Alfven eigenmode
Generation of zonal ow (ZF) by energetic particle (EP) driven toroidal Alfven
eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found
that, nonlinear resonant EP contri- bution dominates over the usual Reynolds
and Maxwell stresses due to thermal plasma nonlinear response. ZF can be forced
driven in the linear growth stage of TAE, with the growth rate being twice the
TAE growth rate. The ZF generation mechanism is shown to be related to
polarization induced by resonant EP nonlinearity. The generated ZF has both the
usual meso-scale and micro- scale radial structures. Possible consequences of
this forced driven ZF on the nonlinear dynamics of TAE are also discussed.Comment: To be submitted to Physics of Plasma
Holographic model for antiferromagnetic quantum phase transition induced by magnetic field
We propose a gravity dual of antiferromagnetic quantum phase transition (QPT)
induced by magnetic field and study the critical behavior around the quantum
critical point (QCP). It turns out that the boundary critical theory is a
strong coupling theory with dynamic exponent and that the hyperscaling
law is violated and logarithmic corrections appear near the QCP. Some novel
scaling relations are predicated, which can be tested by experiment data in
future. We also make some comparison with experimental data on low-dimensional
magnets BiCoPO and pyrochlores ErYTiO.Comment: published versions in PR
Summarisation & Visualisation of Large Volumes of Time-Series Sensor Data
a number of sensors, including an electricity usage
sensor supplied by Episensor. This poses our second
With the increasing ubiquity of sensor data, challenge, how to summarise an extended period of
presenting this data in a meaningful way to electrictiy usage data for a home user.
users is a challenge that must be addressed
before we can easily deploy real-world sensor
network interfaces in the home or workplace. In
this paper, we will present one solution to the
visualisation of large quantities of sensor data
that is easy to understand and yet provides
meaningful and intuitive information to a user,
even when examining many weeks or months of
historical data. We will illustrate this
visulalisation technique with two real-world
deployments of sensing the person and sensing
the home
Automatically detecting important moments from everyday life using a mobile device
This paper proposes a new method to detect important moments in our lives. Our work is motivated by the increase in the quantity of multimedia data, such as videos and photos, which are capturing life experiences into personal archives. Even though such media-rich data suggests visual processing to identify important moments, the oft-mentioned problem of the semantic gap means that users cannot automatically identify or retrieve important moments using visual processing techniques alone. Our approach utilises on-board sensors from mobile devices to automatically identify important moments, as they are happening
Mining user activity as a context source for search and retrieval
Nowadays in information retrieval it is generally accepted that if we can better
understand the context of users then this could help the search process, either at indexing time by including more metadata or at retrieval time by better modelling the user context. In this work we explore how activity recognition from tri-axial accelerometers can be employed to model a user's activity as a means of enabling context-aware information retrieval. In this paper we discuss how we can gather user activity automatically as a context source from a wearable mobile device and we evaluate the accuracy of our proposed user activity recognition algorithm. Our technique can recognise four kinds of activities which can be used to model part of an individual's current context. We discuss promising experimental results, possible approaches to improve our algorithms, and the impact of this work in modelling user context toward enhanced search and retrieval
On fast radial propagation of parametrically excited geodesic acoustic mode
The spatial and temporal evolution of parametrically excited geodesic
acoustic mode (GAM) initial pulse is investigated both analytically and
numerically. Our results show that the nonlinearly excited GAM propagates at a
group velocity which is, typically, much larger than that due to finite ion
Larmor radius as predicted by the linear theory. The nonlinear dispersion
relation of GAM driven by a finite amplitude drift wave pump is also derived,
showing a nonlinear frequency increment of GAM. Further implications of these
findings for interpreting experimental observations are also discussed
Drell-Yan Massive Lepton-Pair's Angular Distributions at Large
By measuring Drell-Yan massive lepton-pair's angular distributions, we can
identify the polarization of the virtual photon of invariant mass which
decays immediately into the lepton-pair. In terms of a modified QCD
factorization formula for Drell-Yan process, which is valid even if ,
we calculate the massive lepton-pair's angular distributions at large . We
find that the virtual photons produced at high are more likely to be
transversely polarized. We discuss the implications of this finding to the
J/ mesons' polarization measured recently at Fermilab.Comment: Latex, 10 pages including 4 figure
Model anisotropic quantum Hall states
Model quantum Hall states including Laughlin, Moore-Read and Read-Rezayi
states are generalized into appropriate anisotropic form. The generalized
states are exact zero-energy eigenstates of corresponding anisotropic two- or
multi-body Hamiltonians, and explicitly illustrate the existence of geometric
degrees of in the fractional quantum Hall effect. These generalized model
quantum Hall states can provide a good description of the quantum Hall system
with anisotropic interactions. Some numeric results of these anisotropic
quantum Hall states are also presented.Comment: 10 pages, 5 figure
Scheme for remote implementation of partially unknown quantum operation of two qubits in cavity QED
By constructing the recovery operations of the protocol of remote
implementation of partially unknown quantum operation of two qubits [An Min
Wang: PRA, \textbf{74}, 032317(2006)], we present a scheme to implement it in
cavity QED. Long-lived Rydberg atoms are used as qubits, and the interaction
between the atoms and the field of cavity is a nonresonant one. Finally, we
analyze the experimental feasibility of this scheme.Comment: 7 pages, 2 figure
- …