2,511 research outputs found
Nonlocality-controlled interaction of spatial solitons in nematic liquid crystals
We demonstrate experimentally that the interactions between a pair of
nonlocal spatial optical solitons in a nematic liquid crystal (NLC) can be
controlled by the degree of nonlocality. For a given beam width, the degree of
nonlocality can be modulated by varying the pretilt angle of NLC molecules via
the change of the bias. When the pretilt angle is smaller than pi/4, the
nonlocality is strong enough to guarantee the independence of the interactions
on the phase difference of the solitons. As the pretilt angle increases, the
degree of nonlocality decreases. When the degree is below its critical value,
the two solitons behavior in the way like their local counterpart: the two
in-phase solitons attract and the two out-of-phase solitons repulse.Comment: 3 pages, 4 figure
O(\alpha_s) QCD Corrections to Spin Correlations in process at the NLC
Using a Generic spin basis, we present a general formalism of one-loop
radiative corrections to the spin correlations in the top quark pair production
at the Next Linear Collider, and calculate the O(\alpha_s) QCD corrections
under the soft gluon approximation. We find that: (a) in Off-diagonal basis,
the QCD corrections to () scattering
process increase the differential cross sections of the dominant spin component
() by
and depending on the scattering angle for
and 1 TeV, respectively; (b) in {Off-diagonal basis}
(Helicity basis), the dominant spin component makes up 99.8% () of
the total cross section at both tree and one-loop level for ,
and the Off-diagonal basis therefore remains to be the optimal spin basis after
the inclusion of QCD corrections.Comment: 12 pages, 4 figures, revised version (a few print mistakes are
corrected, some numerical results are modified, and Fig.4 is added
A Survey on Backdoor Attack and Defense in Natural Language Processing
Deep learning is becoming increasingly popular in real-life applications,
especially in natural language processing (NLP). Users often choose training
outsourcing or adopt third-party data and models due to data and computation
resources being limited. In such a situation, training data and models are
exposed to the public. As a result, attackers can manipulate the training
process to inject some triggers into the model, which is called backdoor
attack. Backdoor attack is quite stealthy and difficult to be detected because
it has little inferior influence on the model's performance for the clean
samples. To get a precise grasp and understanding of this problem, in this
paper, we conduct a comprehensive review of backdoor attacks and defenses in
the field of NLP. Besides, we summarize benchmark datasets and point out the
open issues to design credible systems to defend against backdoor attacks.Comment: 12 pages, QRS202
A Leaf Recognition Algorithm for Plant Classification Using Probabilistic Neural Network
In this paper, we employ Probabilistic Neural Network (PNN) with image and
data processing techniques to implement a general purpose automated leaf
recognition algorithm. 12 leaf features are extracted and orthogonalized into 5
principal variables which consist the input vector of the PNN. The PNN is
trained by 1800 leaves to classify 32 kinds of plants with an accuracy greater
than 90%. Compared with other approaches, our algorithm is an accurate
artificial intelligence approach which is fast in execution and easy in
implementation.Comment: 6 pages, 3 figures, 2 table
Seed-Guided Topic Discovery with Out-of-Vocabulary Seeds
Discovering latent topics from text corpora has been studied for decades.
Many existing topic models adopt a fully unsupervised setting, and their
discovered topics may not cater to users' particular interests due to their
inability of leveraging user guidance. Although there exist seed-guided topic
discovery approaches that leverage user-provided seeds to discover
topic-representative terms, they are less concerned with two factors: (1) the
existence of out-of-vocabulary seeds and (2) the power of pre-trained language
models (PLMs). In this paper, we generalize the task of seed-guided topic
discovery to allow out-of-vocabulary seeds. We propose a novel framework, named
SeeTopic, wherein the general knowledge of PLMs and the local semantics learned
from the input corpus can mutually benefit each other. Experiments on three
real datasets from different domains demonstrate the effectiveness of SeeTopic
in terms of topic coherence, accuracy, and diversity.Comment: 12 pages; Accepted to NAACL 202
Some field experience with subsynchronous vibration of centrifugal compressors
A lot of large chemical fertilizer plants producing 1000 ton NH3/day and 1700 ton urea/day were constructed in the 1970's in China. During operation, subsynchronous vibration takes place occasionally in some of the large turbine-compressor sets and has resulted in heavy economic losses. Two cases of subsynchronous vibration are described: Self-excited vibration of the low-pressure (LP) cylinder of one kind of N2-H2 multistage compressor; and Forced subsynchronous vibration of the high-pressure (HP) cylinder of the CO2 compressor
Magmatic record of India-Asia collision
This work was financially co-supported by Chinese Academy of Sciences (XDB03010301) and other Chinese funding agencies (Project 973: 2011CB403102 and 2015CB452604; NSFC projects: 41225006, 41273044, and 41472061).New geochronological and geochemical data on magmatic activity from the India-Asia collision zone enables recognition of a distinct magmatic flare-up event that we ascribe to slab breakoff. This tie-point in the collisional record can be used to back-date to the time of initial impingement of the Indian continent with the Asian margin. Continental arc magmatism in southern Tibet during 80-40 Ma migrated from south to north and then back to south with significant mantle input at 70-43 Ma. A pronounced flare up in magmatic intensity (including ignimbrite and mafic rock) at ca. 52-51 Ma corresponds to a sudden decrease in the India-Asia convergence rate. Geological and geochemical data are consistent with mantle input controlled by slab rollback from ca. 70 Ma and slab breakoff at ca. 53 Ma. We propose that the slowdown of the Indian plate at ca. 51 Ma is largely the consequence of slab breakoff of the subducting Neo-Tethyan oceanic lithosphere, rather than the onset of the India-Asia collision as traditionally interpreted, implying that the initial India-Asia collision commenced earlier, likely at ca. 55 Ma.Publisher PDFPeer reviewe
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