833 research outputs found
A note on some critical thresholds of Bernoulli percolation
Consider Bernoulli bond percolation a locally finite, connected graph and
let be the threshold corresponding to a "first-moment
method" lower bound. Kahn (\textit{Electron.\ Comm.\ Probab.\ Volume 8,
184-187.} (2003)) constructed a counter-example to Lyons' conjecture of
and proposed a modification. Here we give a positive
answer to Kahn's modified question. The key observation is that in Kahn's
modification, the new expectation quantity also appears in the differential
inequality of one-arm events. This links the question to a lemma of
Duminil-Copin and Tassion (\textit{Comm. Math. Phys. Volume 343, 725-745.}
(2016)). We also study some applications for Bernoulli percolation on periodic
trees
A subperiodic tree whose intermediate branching number is strictly less than the intermediate growth rate
We construct an example of a subperiodic tree whose intermediate branching
number is strictly less than the intermediate growth rate. This answers a
question of Amir and Yang (2022) in the negative.Comment: 8 page
The wired minimal spanning forest on the Poisson-weighted infinite tree
We study the spectral and diffusive properties of the wired minimal spanning
forest (WMSF) on the Poisson-weighted infinite tree (PWIT). Let be the tree
containing the root in the WMSF on the PWIT and be a simple
random walk on starting from the root. We show that almost surely has
and
with high probability. That is, the
spectral dimension of is and its typical displacement
exponent is , almost surely. These confirm Addario-Berry's
predictions in arXiv:1301.1667.Comment: 35 page
Contextualized Non-local Neural Networks for Sequence Learning
Recently, a large number of neural mechanisms and models have been proposed
for sequence learning, of which self-attention, as exemplified by the
Transformer model, and graph neural networks (GNNs) have attracted much
attention. In this paper, we propose an approach that combines and draws on the
complementary strengths of these two methods. Specifically, we propose
contextualized non-local neural networks (CN), which can both
dynamically construct a task-specific structure of a sentence and leverage rich
local dependencies within a particular neighborhood.
Experimental results on ten NLP tasks in text classification, semantic
matching, and sequence labeling show that our proposed model outperforms
competitive baselines and discovers task-specific dependency structures, thus
providing better interpretability to users.Comment: Accepted by AAAI201
Time Reversal Method for Arch Bridge Cables Inspection using Longitudinal Guided Waves
Arch bridge cables consist of anchor heads, steel wires parallel arranged in an equilateral hexagon and hot-extruding PE sheathing layers outside the wires. The complex structure and contact force between wires aggravates the dispersion and attenuation of guided waves in steel wires. In order to reduce the attenuation of acoustical energy, below 80kHz low-frequency longitudinal guided waves is usually adopted. Low-frequency guided waves attenuate more slowly than high-frequency waves, but the received signal packets are wider and less recognizable. In this paper, the process of the time reversal method[1] is presented and the related parameters are calculated. Over a wide frequency range, using narrow-band pulse signals with different center-frequencies to drive comb-like magnetostrictive transducer array round the cable, extract the echo signals, which contains some feature information such as flaws, anchor heads, structural noise caused by contact force between wires. By taking advantage of the time-space compression characteristics of the method, the identification of anchor heads and flaws can be improved effectively and noise can also be decreased by driving the transducers again with the time reversed signal. Verification experiments show that the acoustical energy of guided waves can be focused on the position of flaws and the amplitude of flaws echo waves can be increased. At severe dispersion frequency, time reversal focusing process can improve the signal-noise ratio and suppress dispersion phenomenon caused by structural contact force
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