23,927 research outputs found
Probing viscoelastic properties of a thin polymer film sheared between a beads layer and quartz crystal resonator
We report measurements of viscoelastic properties of thin polymer films of
10-100 nm at the MHz range. These thin films are confined between a quartz
crystal resonator and a millimetric bead layer, producing an increase of both
resonance frequency and dissipation of the quartz resonator. The shear modulus
and dynamic viscosity of thin films extracted from these measurements are
consistent with the bulk values of the polymer. This modified quartz resonator
provides an easily realizable and effective tool for probing the rheological
properties of thin films at ambient environment.Comment: submitted to ap
The Meservey-Tedrov effect in FSF double tunneling junctions
Double tunneling junctions of ferromagnet-superconductor-ferromagnet
electrodes (FSF) show a jump in the conductance when a parallel magnetic field
reverses the magnetization of one of the ferromagnetic electrodes. This change
is generally attributed to the spin-valve effect or to pair breaking in the
superconductor because of spin accumulation. In this paper it is shown that the
Meservey-Tedrov effect causes a similar change in the conductance since the
magnetic field changes the energy spectrum of the quasi-particles in the
superconductor. A reversal of the bias reverses the sign in the conductance
jump
Gunrock: A High-Performance Graph Processing Library on the GPU
For large-scale graph analytics on the GPU, the irregularity of data access
and control flow, and the complexity of programming GPUs have been two
significant challenges for developing a programmable high-performance graph
library. "Gunrock", our graph-processing system designed specifically for the
GPU, uses a high-level, bulk-synchronous, data-centric abstraction focused on
operations on a vertex or edge frontier. Gunrock achieves a balance between
performance and expressiveness by coupling high performance GPU computing
primitives and optimization strategies with a high-level programming model that
allows programmers to quickly develop new graph primitives with small code size
and minimal GPU programming knowledge. We evaluate Gunrock on five key graph
primitives and show that Gunrock has on average at least an order of magnitude
speedup over Boost and PowerGraph, comparable performance to the fastest GPU
hardwired primitives, and better performance than any other GPU high-level
graph library.Comment: 14 pages, accepted by PPoPP'16 (removed the text repetition in the
previous version v5
Relaxed 2-D Principal Component Analysis by Norm for Face Recognition
A relaxed two dimensional principal component analysis (R2DPCA) approach is
proposed for face recognition. Different to the 2DPCA, 2DPCA- and G2DPCA,
the R2DPCA utilizes the label information (if known) of training samples to
calculate a relaxation vector and presents a weight to each subset of training
data. A new relaxed scatter matrix is defined and the computed projection axes
are able to increase the accuracy of face recognition. The optimal -norms
are selected in a reasonable range. Numerical experiments on practical face
databased indicate that the R2DPCA has high generalization ability and can
achieve a higher recognition rate than state-of-the-art methods.Comment: 19 pages, 11 figure
Rare case of magnetic Ag ion: double perovskite CsKAgF
Normally or transition metals are in a low-spin state. Here using
first-principles calculations, we report on a rare case of a high-spin =1
magnetic state for the Ag ion in the double perovskite
CsKAgF. We also explored a possibility of a conventional low-spin
=0 ground state and find an associated tetragonal distortion to be 0.29
{\AA}. However, the lattice elastic energy cost and the Hund exchange loss
exceed the e crystal-field energy gain, thus making the low-spin
tetragonal structure less favorable than the high-spin cubic structure. We
conclude that the compact perovskite structure of CsKAgF is an
important factor in stabilizing the unusual high-spin ground state of
Ag.Comment: 6 pages, 6 figures, accepted for publication in PR
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Application and research of wireless laser methane sensor in drainage pipeline monitoring
Laser methane sensor has been widely promoted and successfully applied in coal mines as a new and effective technology building on the approach of laser-based absorption detection. Compared with the traditional catalytic methane sensor, the laser methane sensor discussed offers the important advantages of a long calibration period, high detection precision, the absence of zero drift and low power consumption, all of which are significant advantages for use in coal mining applications. By compensating for the temperature and pressure of the gases present, the accuracy of the methane sensor is evident across a wide range of temperatures and pressures, making it suitable for gas detection, including methane, in pipelines as well. The wireless laser approach which is incorporated into the methane sensor allows wireless transmission and data uploading to a cloud server through NB-IoT. This tackles the problem in gas pipeline monitoring of the length of many pipelines and thus the wide distribution of the sensors, avoiding complicated wiring and thus high associated cost. Further, remote data management can then be achieved, all of which greatly improves the flexibility and security of the management of the pipeline and the data generated
Coulomb Screening of 2D Massive Dirac Fermions
A model of 2D massive Dirac fermions, interacting with a instantaneous
Coulomb interaction, is presented to mimic the physics of gapped graphene. The
static polarization function is calculated explicitly to analyze screening
effect at the finite temperature and density. Results are compared with the
massless case . We also show that various other works can be reproduced within
our model in a straightforward and unified manner
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