210 research outputs found
A posteriori agreement as a quality measure for readability prediction systems
All readability research is ultimately concerned with the research question whether it is possible for a prediction system to automatically determine the level of readability of an unseen text. A significant problem for such a system is that readability might depend in part on the reader. If different readers assess the readability of texts in fundamentally different ways, there is insufficient a priori agreement to justify the correctness of a readability prediction system based on the texts assessed by those readers. We built a data set of readability assessments by expert readers. We clustered the experts into groups with greater a priori agreement and then measured for each group whether classifiers trained only on data from this group exhibited a classification bias. As this was found to be the case, the classification mechanism cannot be unproblematically generalized to a different user group
Cosmological hydrogen recombination: Lyn line feedback and continuum escape
We compute the corrections to the cosmological hydrogen recombination history
due to delayed feedback of Lyman-series photons and the escape in the
Lyman-continuum. The former process is expected to slightly delay
recombination, while the latter should allow the medium to recombine a bit
faster. It is shown that the subsequent feedback of released Lyman-n photons on
the lower lying Lyman-(n-1) transitions yields a maximal correction of DN_e/N_e
0.22% at z~ 1050. Including only Lyman-\beta feedback onto the Lyman-\alpha
transition, accounts for most of the effect. We find corrections to the cosmic
microwave background TT and EE power spectra \change{with typical peak to peak
amplitude |DC^{TT}_l/C^{TT}_l|~0.15% and |\Delta C^{EE}_l/C^{EE}_l|~0.36% at
l<~3000. The escape in the Lyman-continuum and feedback of Lyman-\alpha photons
on the photoionization rate of the second shell lead to modifications of the
ionization history which are very small (less than |DN_e/N_e|~few x 10^{-6}).Comment: 5+epsilon pages, 7 figures, accepted versio
Back to the Roots: Predicting the Source Domain of Metaphors using Contrastive Learning
Metaphors frame a given target domain using concepts from another, usually more concrete, source domain. Previous research in NLP has focused on the identification of metaphors and the interpretation of their meaning. In contrast, this paper studies to what extent the source domain can be predicted computationally from a metaphorical text. Given a dataset with metaphorical texts from a finite set of source domains, we propose a contrastive learning approach that ranks source domains by their likelihood of being referred to in a metaphorical text. In experiments, it achieves reasonable performance even for rare source domains, clearly outperforming a classification baseline
The DEPOSIT computer code: calculations of electron-loss cross sections for complex ions colliding with neutral atoms
A description of the DEPOSIT computer code is presented. The code is intended
to calculate total and m-fold electron-loss cross sections (m is the number of
ionized electrons) and the energy T(b) deposited to the projectile (positive or
negative ion) during a collision with a neutral atom at low and intermediate
collision energies as a function of the impact parameter b. The deposited
energy is calculated as a 3D-integral over the projectile coordinate space in
the classical energy-deposition model. Examples of the calculated deposited
energies, ionization probabilities and electron-loss cross sections are given
as well as the description of the input and output data.Comment: 11 pages, 3 figure
Optical and near-infrared recombination lines of oxygen ions from Cassiopeia A knots
Context. Fast-moving knots (FMK) in the Galactic supernova remnant Cassiopeia
A consist mainly of metals and allow to study element production in supernovae
and shock physics in great detail. Aims. We work out theoretically and suggest
to observe previously unexplored class of spectral lines -- metal recombination
lines in optical and near-infrared bands -- emitted by the cold ionized and
cooling plasma in the fast-moving knots. Methods. By tracing ion radiative and
dielectronic recombination, collisional -redistribution and radiative
cascade processes, we compute resulting oxygen, silicon and sulphur
recombination line emissivities. It allows us to determine the oxygen
recombination line fluxes, based on the fast-moving knot model of Sutherland
and Dopita (1995b), that predicts existence of highly-ionized ions from
moderate to very low plasma temperatures. Results. The calculations predict
oxygen ion recombination line fluxes detectable on modern optical telescopes in
the wavelength range from 0.5 to 3 microns. Line ratios to
collisionally-excited lines will allow to probe in detail the process of rapid
cloud cooling after passage of a shock front, to test high abundances of O V
and O VI ions at low temperatures and measure them, to test existing
theoretical models of a FMK and to build more precise ones.Comment: 18 pages, 22 figures, version accepted by A&A. Electronic supplement
available at http://www.mpa-garching.mpg.de/~dima/CasA_ORL/e-sup
Ionization of highly charged relativistic ions by neutral atoms and ions
Ionization of highly charged relativistic ions by neutral atoms and ions is
considered. Numerical results of recently developed computer codes based on the
relativistic Born and the equivalent-photon approximations are presented. The
ionization of the outer shells dominate. For the outer projectile electron
shells, which give the main contribution to the process, the non-relativistic
Schr\"odinger wave functions can be used. The formulae for the non-relativistic
reduction of the Dirac matrix-elements are obtained for ionization of electrons
with arbitrary quantum numbers and .Comment: 7 pages, 3 figure
Cosmological recombination: feedback of helium photons and its effect on the recombination spectrum
In this paper we consider the re-processing of high frequency photons emitted
by HeII and HeI during the epoch of cosmological recombination by HeI and HI.
We demonstrate that, in comparison to computations which neglect all feedback
processes, the number of cosmological recombination photons that are related to
the presence of helium in the early Universe could be increased by ~40%-70%.
Our computations imply that per helium nucleus ~3-6 additional photons could be
produced. Therefore, a total of ~12-14 helium-related photons are emitted
during cosmological recombination. This is an important addition to
cosmological recombination spectrum which in the future may render it slightly
easier to determine the primordial abundance of helium using differential
measurements of the CMB energy spectrum. Also, since these photons are the only
witnesses of the feedback process at high redshift, observing them in principle
offers a way to check our understanding of the recombination physics. Here most
interestingly, the feedback of HeII photons on HeI leads to the appearance of
several additional, rather narrow spectral features in the HeI recombination
spectrum at low frequencies. Consequently, the signatures of helium-related
features in the CMB spectral distortion due to cosmological recombination at
some given frequency can exceed the average level of ~17% several times. We
find that in particular the bands around nu ~10GHz, ~35GHz, ~80GHz, and ~200GHz
seem to be affected strongly. In addition, we computed the changes in the
cosmological ionization history, finding that only the feedback of primary HeI
photons on the dynamics of HeII-->HeI recombination has an effect, producing a
change of DN_e/N_e ~+ 0.17% at z~2300. This result seems to be ~2-3 times
smaller than the one obtained in earlier computations for this process
(abridged).Comment: 28 pages, 24 figures, submitted to MNRA
Stance detection on social media: State of the art and trends
Stance detection on social media is an emerging opinion mining paradigm for
various social and political applications in which sentiment analysis may be
sub-optimal. There has been a growing research interest for developing
effective methods for stance detection methods varying among multiple
communities including natural language processing, web science, and social
computing. This paper surveys the work on stance detection within those
communities and situates its usage within current opinion mining techniques in
social media. It presents an exhaustive review of stance detection techniques
on social media, including the task definition, different types of targets in
stance detection, features set used, and various machine learning approaches
applied. The survey reports state-of-the-art results on the existing benchmark
datasets on stance detection, and discusses the most effective approaches. In
addition, this study explores the emerging trends and different applications of
stance detection on social media. The study concludes by discussing the gaps in
the current existing research and highlights the possible future directions for
stance detection on social media.Comment: We request withdrawal of this article sincerely. We will re-edit this
paper. Please withdraw this article before we finish the new versio
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