37,795 research outputs found
Detection of Review Abuse via Semi-Supervised Binary Multi-Target Tensor Decomposition
Product reviews and ratings on e-commerce websites provide customers with
detailed insights about various aspects of the product such as quality,
usefulness, etc. Since they influence customers' buying decisions, product
reviews have become a fertile ground for abuse by sellers (colluding with
reviewers) to promote their own products or to tarnish the reputation of
competitor's products. In this paper, our focus is on detecting such abusive
entities (both sellers and reviewers) by applying tensor decomposition on the
product reviews data. While tensor decomposition is mostly unsupervised, we
formulate our problem as a semi-supervised binary multi-target tensor
decomposition, to take advantage of currently known abusive entities. We
empirically show that our multi-target semi-supervised model achieves higher
precision and recall in detecting abusive entities as compared to unsupervised
techniques. Finally, we show that our proposed stochastic partial natural
gradient inference for our model empirically achieves faster convergence than
stochastic gradient and Online-EM with sufficient statistics.Comment: Accepted to the 25th ACM SIGKDD Conference on Knowledge Discovery and
Data Mining, 2019. Contains supplementary material. arXiv admin note: text
overlap with arXiv:1804.0383
An experimental approach to quantify strain transfer efficiency of fibre bragg grating sensors to host structures
This paper developed a method to evaluate the strain transfer efficiency of
fibre Bragg grating sensors to host structures. Various coatings were applied to
fibre Bragg grating sensors after being fabricated. They were epoxy, silane
agent and polypropylene, representing different surface properties. A neat epoxy
resin plate was used as the host in which the coated fibre sensors were embedded
in the central layer. The tensile strain output from the FBGs was compared with
that obtained from electrical strain gauges which were attached on the surface
of the specimen. A calculating method based on the measured strains was
developed to quantify the strain transfer function of different surface
coatings. The strain transfer coefficient obtained from the proposed method
provided a direct indicator to evaluate the strain transfer efficiency of
different coatings used on the FBG sensors, under either short or long-term
loading. The results demonstrated that the fibre sensor without any coating
possessed the best strain transfer, whereas, the worst strain transfer was
created by polypropylene coating. Coatings play a most influential role in
strain measurements using FBG sensors
Hofstadter-type energy spectra in lateral superlattices defined by periodic magnetic and electrostatic fields
We calculate the energy spectrum of an electron moving in a two-dimensional
lattice which is defined by an electric potential and an applied perpendicular
magnetic field modulated by a periodic surface magnetization. The spatial
direction of this magnetization introduces complex phases into the Fourier
coefficients of the magnetic field. We investigate the effect of the relative
phases between electric and magnetic modulation on band width and internal
structure of the Landau levels.Comment: 5 LaTeX pages with one gif figure to appear in Phys. Rev.
Strong coupling of a mechanical oscillator and a single atom
We propose and analyze a setup to achieve strong coupling between a single
trapped atom and a mechanical oscillator. The interaction between the motion of
the atom and the mechanical oscillator is mediated by a quantized light field
in a laser driven high-finesse cavity. In particular, we show that high
fidelity transfer of quantum states between the atom and the mechanical
oscillator is in reach for existing or near future experimental parameters. Our
setup provides the basic toolbox for coherent manipulation, preparation and
measurement of micro- and nanomechanical oscillators via the tools of atomic
physics.Comment: 4 pages, 2 figures, minro changes, accepted by PR
Expected Sensitivity to Galactic/Solar Axions and Bosonic Super-WIMPs based on the Axio-electric Effect in Liquid Xenon Dark Matter Detectors
We present systematic case studies to investigate the sensitivity of axion
searches by liquid xenon detectors, using the axio-electric effect (analogue of
the photoelectric effect) on xenon atoms. Liquid xenon is widely considered to
be one of the best target media for detection of WIMPs (Weakly Interacting
Massive Particles which may form the galactic dark matter) using nuclear
recoils. Since these detectors also provide an extremely low radioactivity
environment for electron recoils, very weakly-interacting low-mass particles (<
100 keV/c^2), such as the hypothetical axion, could be detected as well - in
this case using the axio-electric effect. Future ton-scale liquid Xe detectors
will be limited in sensitivity only by irreducible neutrino background
(pp-chain solar neutrino and the double beta decay of 136Xe) in the mass range
between 1 and 100 keV/c^2. Assuming one ton-year of exposure, galactic axions
(as non-relativistic dark matter) could be detected if the axio-electric
coupling g_Ae is greater than 10^-14 at 1 keV/c^2 (or $10^-13 at 100 keV/c^2).
Below a few keV/c^2, and independent of the mass, a solar axion search would be
sensitive to a coupling g_Ae ~ 10^-12. This limit will set a stringent upper
bound on axion mass for the DFSV and KSVZ models for the mass ranges m_A < 0.1
eV/c^2 and < 10 eV/c^2, respectively. Vector-boson dark matter could also be
detected for a coupling constant alpha'/alpha > 10^-33 (for mass 1 keV/c^2) or
> 10^-27 (for mass 100 keV/c^2).Comment: 17 pages, 10 figure
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