34,639 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
Microstructure, magneto-transport and magnetic properties of Gd-doped magnetron-sputtered amorphous carbon
The magnetic rare earth element gadolinium (Gd) was doped into thin films of
amorphous carbon (hydrogenated \textit{a}-C:H, or hydrogen-free \textit{a}-C)
using magnetron co-sputtering. The Gd acted as a magnetic as well as an
electrical dopant, resulting in an enormous negative magnetoresistance below a
temperature (). Hydrogen was introduced to control the amorphous carbon
bonding structure. High-resolution electron microscopy, ion-beam analysis and
Raman spectroscopy were used to characterize the influence of Gd doping on the
\textit{a-}GdC(:H) film morphology, composition, density and
bonding. The films were largely amorphous and homogeneous up to =22.0 at.%.
As the Gd doping increased, the -bonded carbon atoms evolved from
carbon chains to 6-member graphitic rings. Incorporation of H opened up the
graphitic rings and stabilized a -rich carbon-chain random network. The
transport properties not only depended on Gd doping, but were also very
sensitive to the ordering. Magnetic properties, such as the spin-glass
freezing temperature and susceptibility, scaled with the Gd concentration.Comment: 9 figure
Integrable dispersionless KdV hierarchy with sources
An integrable dispersionless KdV hierarchy with sources (dKdVHWS) is derived.
Lax pair equations and bi-Hamiltonian formulation for dKdVHWS are formulated.
Hodograph solution for the dispersionless KdV equation with sources (dKdVWS) is
obtained via hodograph transformation. Furthermore, the dispersionless
Gelfand-Dickey hierarchy with sources (dGDHWS) is presented.Comment: 15 pages, to be published in J. Phys. A: Math. Ge
Morphology and thermal conductivity of model organic aerogels
The intersection volume of two independent 2-level cut Gaussian random fields
is proposed to model the open-cell microstructure of organic aerogels. The
experimentally measured X-ray scattering intensity, surface area and solid
thermal conductivity of both polymeric and colloidal organic aerogels can be
accounted for by the model.Comment: 5 pages. RevTex with 4 encapsulated figures. Higher resolution
figures have been submitted for publication. To be published in Phys. Rev. E
(Rapid Comm.). email, [email protected]
Deriving N-soliton solutions via constrained flows
The soliton equations can be factorized by two commuting x- and t-constrained
flows. We propose a method to derive N-soliton solutions of soliton equations
directly from the x- and t-constrained flows.Comment: 8 pages, AmsTex, no figures, to be published in Journal of Physics
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