36,117 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
Intrinsic Percolative Superconductivity in KxFe2-ySe2 Single Crystals
Magnetic field penetration and magnetization hysteresis loops (MHLs) have
been measured in KxFe2-ySe2 single crystals. The magnetic field penetration
shows a two-step feature with a very small full-magnetic-penetration field
(Hp1= 300 Oe at 2 K), and accordingly the MHL exhibits an abnormal vanishing of
the central peak near zero field below 13 K. The width of the MHL in KxFe2-ySe2
at the same temperature is in general much smaller than that measured in the
relatives Ba0.6K0.4Fe2As2 and Ba(Fe0.92Co0.08)2As2, and the MHLs in the latter
two samples show the normal central peak near zero field. All these anomalies
found in KxFe2-ySe2 can be understood in the picture that the sample is
percolative with weakly coupled superconducting islands.Comment: 5 page, 4 figure
The complex multiferroic phase diagram of MnCoWO
The complete magnetic and multiferroic phase diagram of
MnCoWO single crystals is investigated by means of magnetic,
heat capacity, and polarization experiments. We show that the ferroelectric
polarization in the multiferroic state abruptly changes
its direction twice upon increasing Co content, x. At x=0.075,
rotates from the axis into the plane and at
x=0.15 it flips back to the axis. The origin of the multiple
polarization flops is identified as an effect of the Co anisotropy on the
orientation and shape of the spin helix leading to thermodynamic instabilities
caused by the decrease of the magnitude of the polarization in the
corresponding phases. A qualitative description of the ferroelectric
polarization is derived by taking into account the intrachain (axis) as
well as the interchain (axis) exchange pathways connecting the magnetic
ions. In a narrow Co concentration range (0.1x0.15), an
intermediate phase, sandwiched between the collinear high-temperature and the
helical low-temperature phases, is discovered. The new phase exhibits a
collinear and commensurate spin modulation similar to the low-temperature
magnetic structure of MnWO.Comment: 18 pages, 6 figure
Exact Diagonalisation of The XY-Hamiltonian of Open Linear Chains with Periodic Coupling Constants and Its Application to Dynamics of One-Dimensional Spin Systems
A new method of diagonalisation of the XY-Hamiltonian of inhomogeneous open
linear chains with periodic (in space) changing Larmor frequencies and coupling
constants is developed. As an example of application, multiple quantum dynamics
of an inhomogeneous chain consisting of 1001 spins is investigated. Intensities
of multiple quantum coherences are calculated for arbitrary inhomogeneous
chains in the approximation of the next nearest interactions.
{\it Key words:} linear spin chain, nearest--neighbour approximation,
three--diagonal matrices, diagonalisation, fermions, multiple--quantum NMR,
multiple--quantum coherence, intensities of multiple--quantum coherences.
{\it PACS numbers:} 05.30.-d; 76.20.+qComment: 21 pages + 1 figure (to download separately via ps-format
Hydroxyapatite Nanocrystal Deposition on Plasma Modified Titanium Surface
Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is materials mainly known for its special ability to contact
bone tissue. Nanostructures on implant surfaces, a coating composed of nano-HAp particles on Ti, have
aroused increasing research interest in the biomedical field. In this study, we prepared HAp nanocrystal
coated Ti surface by plasma surface modification and wet chemical method and then evaluated biological
behavior of MC3T3-E1 on the HAp coated on plasma modified Ti surface. Nano-size crystals of sintered
HAp were uniformly coated on polyacrylic acid (PAA) deposited Ti surface through the ionic interaction between
calcium ions on the HAp nanocrystal and carboxyl groups on the PAA/Ti. In vitro cell tests revealed
surface modification of Ti surface with HAp nanocrystal significantly improved the proliferation and
growth of the osteoblastic MC3T3-E1 cells and induced them to differentiate at an enhanced level.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3495
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Optimal gridding and degridding in radio interferometry imaging
In radio interferometry imaging, the gridding procedure of convolving
visibilities with a chosen gridding function is necessary to transform
visibility values into uniformly sampled grid points. We propose here a
parameterised family of "least-misfit gridding functions" which minimise an
upper bound on the difference between the DFT and FFT dirty images for a given
gridding support width and image cropping ratio. When compared with the widely
used spheroidal function with similar parameters, these provide more than 100
times better alias suppression and RMS misfit reduction over the usable dirty
map. We discuss how appropriate parameter selection and tabulation of these
functions allow for a balance between accuracy, computational cost and storage
size. Although it is possible to reduce the errors introduced in the gridding
or degridding process to the level of machine precision, accuracy comparable to
that achieved by CASA requires only a lookup table with 300 entries and a
support width of 3, allowing for a greatly reduced computation cost for a given
performance
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A review of net zero energy buildings in hot and humid climates: Experience learned from 34 case study buildings
Sustainable development in the building sector requires the integration of energy efficiency and renewable energy utilization in buildings. In recent years, the concept of net zero energy buildings (NZEBs) has become a potential plausible solution to improve efficiency and reduce energy consumption in buildings. To achieve an NZEB goal, building systems and design strategies must be integrated and optimized based on local climatic conditions. This paper provides a comprehensive review of NZEBs and their current development in hot and humid regions. Through investigating 34 NZEB cases around the world, this study summarized NZEB key design strategies, technology choices and energy performance. The study found that passive design and technologies such as daylighting and natural ventilation are often adopted for NZEBs in hot and humid climates, together with other energy efficient and renewable energy technologies. Most NZEB cases demonstrated site annual energy consumption intensity less than 100 kW-hours (kWh) per square meter of floor space, and some buildings even achieved “net-positive energy” (that is, they generate more energy locally than they consume). However, the analysis also shows that not all NZEBs are energy efficient buildings, and buildings with ample renewable energy adoption can still achieve NZEB status even with high energy use intensity. This paper provides in-depth case-study-driven analysis to evaluate NZEB energy performance and summarize best practices for high performance NZEBs. This review provides critical technical information as well as policy recommendations for net zero energy building development in hot and humid climates
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