6,645 research outputs found
Context-aware movie recommendations: An empirical comparison of pre-filtering, post-filtering and contextual modeling approaches
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-39878-0_13Proceedings of 14th International Conference, EC-Web 2013, Prague, Czech Republic, August 27-28, 2013.Context-aware recommender systems have been proven to improve the performance of recommendations in a wide array of domains and applications. Despite individual improvements, little work has been done on comparing different approaches, in order to determine which of them outperform the others, and under what circumstances. In this paper we address this issue by conducting an empirical comparison of several pre-filtering, post-filtering and contextual modeling approaches on the movie recommendation domain. To acquire confident contextual information, we performed a user study where participants were asked to rate movies, stating the time and social companion with which they preferred to watch the rated movies. The results of our evaluation show that there is neither a clear superior contextualization approach nor an always best contextual signal, and that achieved improvements depend on the recommendation algorithm used together with each contextualization approach. Nonetheless, we conclude with a number of cues and advices about which particular combinations of contextualization approaches and recommendation algorithms could be better suited for the movie recommendation domain.This work was supported by the Spanish Government
(TIN2011-28538-C02) and the Regional Government of Madrid (S2009TIC-1542
The Average Kinetic Energy of the Superconducting State
Isothermal magnetization curves are plotted as the magnetization times the
magnetic induction, , versus the applied field, H. We show
here that this new curve is the average kinetic energy of the superconducting
state versus the applied field, for type-II superconductors with a high
Ginzburg-Landau parameter . The maximum of occurs at
a field, , directly related to the upper critical field, ,
suggesting that may be extracted from such plots even in cases when
it is too high for direct measurement. We obtain these plots both
theoretically, from the Ginzburg-Landau theory, and experimentally, using a
Niobium sample with , and compare them.Comment: 11 pages, 9 postscript figure
Non-uniform Black Strings with Schwarzschild-(Anti-)de Sitter Foliation
We present some exact non-uniform black string solutions of 5-dimensional
pure Einstein gravity as well as Einstein-Maxwell-dilaton theory at arbitrary
dilaton coupling. The solutions share the common property that their
4-dimensional slices are Schwarzchild-(anti-)de Sitter spacetimes. The pure
gravity solution is also generalized to spacetimes of dimensions higher than 5
to get non-uniform black branes.Comment: LaTeX 14 pages, 3 eps figures. V2: version appeared in CQ
Edge and Bulk Transport in the Mixed State of a Type-II Superconductor
By comparing the voltage-current (V-I) curves obtained before and after
cutting a sample of 2H-NbSe2, we separate the bulk and edge contributions to
the transport current at various dissipation levels and derive their respective
V- I curves and critical currents. We find that the edge contribution is
thermally activated across a current dependent surface barrier. By contrast the
bulk V-I curves are linear, as expected from the free flux flow model. The
relative importance of bulk and edge contributions is found to depend on
dissipation level and sample dimensions. We further show that the peak effect
is a sharp bulk phenomenon and that it is broadened by the edge contribution
Stationary State Solutions of a Bond Diluted Kinetic Ising Model: An Effective-Field Theory Analysis
We have examined the stationary state solutions of a bond diluted kinetic
Ising model under a time dependent oscillating magnetic field within the
effective-field theory (EFT) for a honeycomb lattice . Time evolution of
the system has been modeled with a formalism of master equation. The effects of
the bond dilution, as well as the frequency and amplitude of
the external field on the dynamic phase diagrams have been discussed in detail.
We have found that the system exhibits the first order phase transition with a
dynamic tricritical point (DTCP) at low temperature and high amplitude regions,
in contrast to the previously published results for the pure case \cite{Ling}.
Bond dilution process on the kinetic Ising model gives rise to a number of
interesting and unusual phenomena such as reentrant phenomena and has a
tendency to destruct the first-order transitions and the DTCP. Moreover, we
have investigated the variation of the bond percolation threshold as functions
of the amplitude and frequency of the oscillating field.Comment: 8 pages, 4 figure
The Structure of Nanoscale Polaron Correlations in La1.2Sr1.8Mn2O7
A system of strongly-interacting electron-lattice polarons can exhibit charge
and orbital order at sufficiently high polaron concentrations. In this study,
the structure of short-range polaron correlations in the layered colossal
magnetoresistive perovskite manganite, La1.2Sr1.8Mn2O7, has been determined by
a crystallographic analysis of broad satellite maxima observed in diffuse X-ray
and neutron scattering data. The resulting q=(0.3,0,1) modulation is a
longitudinal octahedral-stretch mode, consistent with an incommensurate
Jahn-Teller-coupled charge-density-wave fluctuations, that implies an unusual
orbital-stripe pattern parallel to the directions.Comment: Reformatted with RevTe
Covariant anomaly and Hawking radiation from the modified black hole in the rainbow gravity theory
Recently, Banerjee and Kulkarni (R. Banerjee, S. Kulkarni, arXiv:0707.2449
[hep-th]) suggested that it is conceptually clean and economical to use only
the covariant anomaly to derive Hawking radiation from a black hole. Based upon
this simplified formalism, we apply the covariant anomaly cancellation method
to investigate Hawking radiation from a modified Schwarzschild black hole in
the theory of rainbow gravity. Hawking temperature of the gravity's rainbow
black hole is derived from the energy-momentum flux by requiring it to cancel
the covariant gravitational anomaly at the horizon. We stress that this
temperature is exactly the same as that calculated by the method of cancelling
the consistent anomaly.Comment: 5 page
Glass Transition in the Polaron Dynamics of CMR Manganites
Neutron scattering measurements on a bilayer manganite near optimal doping
show that the short-range polarons correlations are completely dynamic at high
T, but then freeze upon cooling to a temperature T* 310 K. This glass
transition suggests that the paramagnetic/insulating state arises from an
inherent orbital frustration that inhibits the formation of a long range
orbital- and charge-ordered state. Upon further cooling into the
ferromagnetic-metallic state (Tc=114 K), where the polarons melt, the diffuse
scattering quickly develops into a propagating, transverse optic phonon.Comment: 4 pages, 4 figures. Physical Review Letters (in Press
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