28,229 research outputs found
Improving information filtering via network manipulation
Recommender system is a very promising way to address the problem of
overabundant information for online users. Though the information filtering for
the online commercial systems received much attention recently, almost all of
the previous works are dedicated to design new algorithms and consider the
user-item bipartite networks as given and constant information. However, many
problems for recommender systems such as the cold-start problem (i.e. low
recommendation accuracy for the small degree items) are actually due to the
limitation of the underlying user-item bipartite networks. In this letter, we
propose a strategy to enhance the performance of the already existing
recommendation algorithms by directly manipulating the user-item bipartite
networks, namely adding some virtual connections to the networks. Numerical
analyses on two benchmark data sets, MovieLens and Netflix, show that our
method can remarkably improve the recommendation performance. Specifically, it
not only improve the recommendations accuracy (especially for the small degree
items), but also help the recommender systems generate more diverse and novel
recommendations.Comment: 6 pages, 5 figure
The Degasperis-Procesi equation with self-consistent sources
The Degasperis-Procesi equation with self-consistent sources(DPESCS) is
derived. The Lax representation and the conservation laws for DPESCS are
constructed. The peakon solution of DPESCS is obtained.Comment: 15 page
Microwave-induced nonequilibrium temperature in a suspended carbon nanotube
Antenna-coupled suspended single carbon nanotubes exposed to 108 GHz
microwave radiation are shown to be selectively heated with respect to their
metal contacts. This leads to an increase in the conductance as well as to the
development of a power-dependent DC voltage. The increased conductance stems
from the temperature dependence of tunneling into a one-dimensional electron
system. The DC voltage is interpreted as a thermovoltage, due to the increased
temperature of the electron liquid compared to the equilibrium temperature in
the leads
Coherent control at its most fundamental: CEP-dependent electron localization in photodissoziation of a H2+ molecular ion beam target
Measurements and calculations of the absolute carrier-envelope phase (CEP)
effects in the photodissociation of the simplest molecule, H2+, with a 4.5-fs
Ti:Sapphire laser pulse at intensities up to (4 +- 2)x10^14 Watt/cm^2 are
presented. Localization of the electron with respect to the two nuclei (during
the dissociation process) is controlled via the CEP of the ultra-short laser
pulses. In contrast to previous CEP-dependent experiments with neutral
molecules, the dissociation of the molecular ions is not preceded by a
photoionization process, which strongly influences the CEP dependence.
Kinematically complete data is obtained by time- and position-resolved
coincidence detection. The phase dependence is determined by a single-shot
phase measurement correlated to the detection of the dissoziation fragments.
The experimental results show quantitative agreement with ab inito 3D-TDSE
calculations that include nuclear vibration and rotation.Comment: new version includes minore changes and adding the supp_material.pd
Terahertz dynamics of a topologically protected state: quantum Hall effect plateaus near cyclotron resonance in a GaAs/AlGaAs heterojunction
We measure the Hall conductivity of a two-dimensional electron gas formed at
a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron
resonance frequency by employing a highly sensitive Faraday rotation method
coupled with electrical gating of the sample to change the electron density. We
observe clear plateau-and step-like features in the Faraday rotation angle vs.
electron density and magnetic field (Landau-level filling factor), which are
the high frequency manifestation of quantum Hall plateaus - a signature of
topologically protected edge states. The results are compared to a recent
dynamical scaling theory.Comment: 18 pages, 3 figure
Hole Doping Dependence of the Coherence Length in Thin Films
By measuring the field and temperature dependence of magnetization on
systematically doped thin films, the critical current
density and the collective pinning energy are determined in
single vortex creep regime. Together with the published data of superfluid
density, condensation energy and anisotropy, for the first time we derive the
doping dependence of the coherence length or vortex core size in wide doping
regime directly from the low temperature data. It is found that the coherence
length drops in the underdoped region and increases in the overdoped side with
the increase of hole concentration. The result in underdoped region clearly
deviates from what expected by the pre-formed pairing model if one simply
associates the pseudogap with the upper-critical field.Comment: 4 pages, 4 figure
Statistical Topography of Glassy Interfaces
Statistical topography of two-dimensional interfaces in the presence of
quenched disorder is studied utilizing combinatorial optimization algorithms.
Finite-size scaling is used to measure geometrical exponents associated with
contour loops and fully packed loops. We find that contour-loop exponents
depend on the type of disorder (periodic ``vs'' non-periodic) and they satisfy
scaling relations characteristic of self-affine rough surfaces. Fully packed
loops on the other hand are unaffected by disorder with geometrical exponents
that take on their pure values.Comment: 4 pages, REVTEX, 4 figures included. Further information can be
obtained from [email protected]
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