3,703 research outputs found
Synonymy of Rhamphidera Skelley with Bancous Pic, termitophilous fungus beetles (Coleoptera: Erotylidae).
ThegenusBancousPic, originally described in the Heteromera (Rhysopaussidae) and later transferred to Cucujiformia (incertae sedis), was found to be congeneric with Rhamphidera Skelley (Erotylidae). Bancous is here placed in the family Erotylidae (Erotylinae, Tritomini) and Rhamphidera is moved into synonymy. This synonymy creates two new combinations: Bancous perplexus (Skelley) and Bancous eureka (Skelley). Bancous is redescribed and a lectotype is designated for Bancous irregularis Pic
Universal, Unsupervised (Rule-Based), Uncovered Sentiment Analysis
We present a novel unsupervised approach for multilingual sentiment analysis
driven by compositional syntax-based rules. On the one hand, we exploit some of
the main advantages of unsupervised algorithms: (1) the interpretability of
their output, in contrast with most supervised models, which behave as a black
box and (2) their robustness across different corpora and domains. On the other
hand, by introducing the concept of compositional operations and exploiting
syntactic information in the form of universal dependencies, we tackle one of
their main drawbacks: their rigidity on data that are structured differently
depending on the language concerned. Experiments show an improvement both over
existing unsupervised methods, and over state-of-the-art supervised models when
evaluating outside their corpus of origin. Experiments also show how the same
compositional operations can be shared across languages. The system is
available at http://www.grupolys.org/software/UUUSA/Comment: 19 pages, 5 Tables, 6 Figures. This is the authors version of a work
that was accepted for publication in Knowledge-Based System
One model, two languages: training bilingual parsers with harmonized treebanks
We introduce an approach to train lexicalized parsers using bilingual corpora
obtained by merging harmonized treebanks of different languages, producing
parsers that can analyze sentences in either of the learned languages, or even
sentences that mix both. We test the approach on the Universal Dependency
Treebanks, training with MaltParser and MaltOptimizer. The results show that
these bilingual parsers are more than competitive, as most combinations not
only preserve accuracy, but some even achieve significant improvements over the
corresponding monolingual parsers. Preliminary experiments also show the
approach to be promising on texts with code-switching and when more languages
are added.Comment: 7 pages, 4 tables, 1 figur
Geometric descriptions for the polarization for nonparaxial optical fields: a tutorial
This article provides an overview of the local description of polarization
for nonparaxial fields, for which all Cartesian components of the vector field
are significant. The polarization of light at each point is characterized by a
polarization matrix, as opposed to the matrix used in the
study of polarization for paraxial light. For nonparaxial light, concepts like
the degree of polarization, the Stokes parameters and the Poincar\'e sphere
have generalizations that are either not unique or not trivial. This work aims
to clarify some of these discrepancies and provide a framework that highlights
the similarities and differences with the description for the paraxial regimes.
Particular emphasis is placed on geometric interpretations.Comment: 38 pages, 9 figure
Geometric phases in 2D and 3D polarized fields: geometrical, dynamical, and topological aspects
Geometric phases are a universal concept that underpins numerous phenomena
involving multi-component wave fields. These polarization-dependent phases are
inherent in interference effects, spin-orbit interaction phenomena, and
topological properties of vector wave fields. Geometric phases have been
thoroughly studied in two-component fields, such as two-level quantum systems
or paraxial optical waves. However, their description for fields with three or
more components, such as generic nonparaxial optical fields routinely used in
modern nano-optics, constitutes a nontrivial problem. Here we describe
geometric, dynamical, and total phases calculated along a closed spatial
contour in a multi-component complex field, with particular emphasis on 2D
(paraxial) and 3D (nonparaxial) optical fields. We present several equivalent
approaches: (i) an algebraic formalism, universal for any multi-component
field; (ii) a dynamical approach using the Coriolis coupling between the spin
angular momentum and reference-frame rotations; and (iii) a geometric
representation, which unifies the Pancharatnam-Berry phase for the 2D
polarization on the Poincar\'e sphere and the Majorana-sphere representation
for the 3D polarized fields. Most importantly, we reveal close connections
between geometric phases, angular-momentum properties of the field, and
topological properties of polarization singularities in 2D and 3D fields, such
as C-points and polarization M\"obius strips.Comment: 21 pages, 11 figures, to appear in Rep. Prog. Phy
Lorenz-Mie scattering of focused light via complex focus fields: an analytic treatment
The Lorenz-Mie scattering of a wide class of focused electromagnetic fields
off spherical particles is studied. The focused fields in question are
constructed through complex focal displacements, leading to closed-form
expressions that can exhibit several interesting physical properties, such as
orbital and/or spin angular momentum, spatially-varying polarization, and a
controllable degree of focusing. These fields constitute complete bases that
can be considered as nonparaxial extensions of the standard Laguerre-Gauss
beams and the recently proposed polynomials-of-Gaussians beams. Their analytic
form turns out to lead also to closed-form expressions for their multipolar
expansion. Such expansion can be used to compute the field scattered by a
spherical particle and the resulting forces and torques exerted on it, for any
relative position between the field's focus and the particle.Comment: 11 pages, 7 figure
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