588 research outputs found
Further evidence of the link between activity and metallicity using the flaring properties of stars in the Kepler field
The magnetic activity level of low-mass stars is known to vary as a function
of the physical properties of the star. Many studies have shown that the
stellar mass and rotation are both important parameters that determine magnetic
activity levels. In contrast, the impact of a star's chemical composition on
magnetic activity has received comparatively little attention. Data sets for
traditional activity proxies, e.g. X-ray emission or calcium emission, are not
large enough to search for metallicity trends in a statistically meaningful
way. Recently, studies have used the photometric variability amplitude as a
proxy for magnetic activity to investigate the role of metallicity because it
can be relatively easily measured for large samples of stars. These studies
find that magnetic activity and metallicity are positively correlated. In this
work, we investigate the link between activity and metallicity further by
studying the flaring properties of stars in the Kepler field. Similar to the
photometric variability, we find that flaring activity is stronger in more
metal-rich stars for a fixed mass and rotation period. This result adds to a
growing body of evidence that magnetic field generation is correlated with
metallicity.Comment: 6 pages, 5 figures, accepted for publication in MNRA
Cosmic censorship and spherical gravitational collapse with tangential pressure
We study the spherical gravitational collapse of a compact object under the
approximation that the radial pressure is identically zero, and the tangential
pressure is related to the density by a linear equation of state. It turns out
that the Einstein equations can be reduced to the solution of an integral for
the evolution of the area radius. We show that for positive pressure there is a
finite region near the center which necessarily expands outwards, if collapse
begins from rest. This region could be surrounded by an inward moving one which
could collapse to a singularity - any such singularity will necessarily be
covered by a horizon. For negative pressure the entire object collapses
inwards, but any singularities that could arise are not naked. Thus the nature
of the evolution is very different from that of dust, even when the ratio of
pressure to density is infinitesimally small.Comment: 16 pages, Latex file, two figures, uses epsf.st
Historical ‘signposts’ and other temporal indicators in the Czech lexicon
This article posits that the Czechs employ a great many historical markers, previously applied to other events of national importance, which help to shape collective memory and right the ‘wrongs’ of the past. It is argued that these temporal indicators share a number of clearly defined characteristics, and that their use is too systematic and calculated to be merely a function of the constraints of the lexicon. The first part of the study considers in detail questions of semantics (especially the distinction between denotation and connotation), the lexicographical sources available to the researcher, and the lexical ‘signpost’ in context, while the second part focuses on practical examples of lexical re-appropriation since 1918, with particular reference to dictionaries and the Czech National Corpus.University of Wolverhampto
Siamese hierarchical attention networks for extractive summarization
[EN] In this paper, we present an extractive approach to document summarization based on Siamese Neural Networks. Specifically, we propose the use of Hierarchical Attention Networks to select the most relevant sentences of a text to make its summary. We train Siamese Neural Networks using document-summary pairs to determine whether the summary is appropriated for the document or not. By means of a sentence-level attention mechanism the most relevant sentences in the document can be identified. Hence, once the network is trained, it can be used to generate extractive summaries. The experimentation carried out using the CNN/DailyMail summarization corpus shows the adequacy of the proposal. In summary, we propose a novel end-to-end neural network to address extractive summarization as a binary classification problem which obtains promising results in-line with the state-of-the-art on the CNN/DailyMail corpus.This work has been partially supported by the Spanish MINECO and FEDER founds under project AMIC (TIN2017-85854-C4-2-R). Work of Jose-Angel Gonzalez is also financed by Universitat Politecnica de Valencia under grant PAID-01-17.González-Barba, JÁ.; Segarra Soriano, E.; García-Granada, F.; Sanchís Arnal, E.; Hurtado Oliver, LF. (2019). Siamese hierarchical attention networks for extractive summarization. Journal of Intelligent & Fuzzy Systems. 36(5):4599-4607. https://doi.org/10.3233/JIFS-179011S45994607365N. Begum , M. Fattah , and F. Ren . Automatic text summarization using support vector machine 5(7) (2009), 1987–1996.J. Cheng and M. Lapata . Neural summarization by extracting sentences and words. In Proceedings of the 54th Annual Meeting of the Association for Computational Linguistics, ACL 2016, August 7-12, 2016, Berlin, Germany, Volume 1: Long Papers, 2016.K.M. Hermann , T. Kocisky , E. Grefenstette , L. Espeholt , W. Kay , M. Suleyman , and P. Blunsom . Teaching machines to read and comprehend, CoRR, abs/1506.03340, 2015.D.P. Kingma and J. Ba . Adam: A method for stochastic optimization. CoRR, abs/1412.6980, 2014.Lloret, E., & Palomar, M. (2011). Text summarisation in progress: a literature review. Artificial Intelligence Review, 37(1), 1-41. doi:10.1007/s10462-011-9216-zLouis, A., & Nenkova, A. (2013). Automatically Assessing Machine Summary Content Without a Gold Standard. Computational Linguistics, 39(2), 267-300. doi:10.1162/coli_a_00123Miao, Y., & Blunsom, P. (2016). Language as a Latent Variable: Discrete Generative Models for
Sentence Compression. Proceedings of the 2016 Conference on Empirical Methods in Natural
Language Processing. doi:10.18653/v1/d16-1031R. Mihalcea and P. Tarau . Textrank: Bringing order into text. In Proceedings of the 2004 Conference on Empirical Methods in Natural Language Processing, 2004.T. Mikolov , K. Chen , G. S. Corrado , and J. Dean . Efficient estimation of word representations in vector space, CoRR, abs/1301.3781, 2013.Minaee, S., & Liu, Z. (2017). Automatic question-answering using a deep similarity neural network. 2017 IEEE Global Conference on Signal and Information Processing (GlobalSIP). doi:10.1109/globalsip.2017.8309095R. Paulus , C. Xiong , and R. Socher , A deep reinforced model for abstractive summarization. CoRR, abs/1705.04304, 2017.Schuster, M., & Paliwal, K. K. (1997). Bidirectional recurrent neural networks. IEEE Transactions on Signal Processing, 45(11), 2673-2681. doi:10.1109/78.650093See, A., Liu, P. J., & Manning, C. D. (2017). Get To The Point: Summarization with Pointer-Generator Networks. Proceedings of the 55th Annual Meeting of the Association for
Computational Linguistics (Volume 1: Long Papers). doi:10.18653/v1/p17-1099Takase, S., Suzuki, J., Okazaki, N., Hirao, T., & Nagata, M. (2016). Neural Headline Generation on Abstract Meaning Representation. Proceedings of the 2016 Conference on Empirical Methods in Natural
Language Processing. doi:10.18653/v1/d16-1112G. Tur and R. De Mori . Spoken language understanding: Systems for extracting semantic information from speech, John Wiley & Sons, 2011
An integral equation approach to effective interactions between polymers in solution
We use the thread model for linear chains of interacting monomers, and the
``polymer reference interaction site model'' (PRISM) formalism to determine the
monomer-monomer pair correlation function for dilute and
semi-dilute polymer solutions, over a range of temperatures from very high
(where the chains behave as self-avoiding walks) to below the
temperature, where phase separation sets in. An inversion procedure, based on
the HNC integral equation, is used to extract the effective pair potential
between ``average'' monomers on different chains. An accurate relation between
, [the pair correlation function between the polymer
centers of mass (c.m.)], and the intramolecular form factors is then used to
determine , and subsequently extract the effective c.m.-c.m. pair
potential by a similar inversion procedure. depends on
temperature and polymer concentration, and the predicted variations are in
reasonable agreement with recent simulation data, except at very high
temperatures, and below the temperature.Comment: 13 pages, 13 figures, revtex ; revised versio
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