1,721,026 research outputs found
Unblinded Data for PLAsTiCC Classification Challenge
No full textFor classification challenge (https://plasticc.org), the unblinded data files are included here. See PDF note above for more information. The original challenge (Sep 28, 2018 - Dec 17, 2018) was hosted at https://www.kaggle.com/c/PLAsTiCC-2018 .</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Machine learning applications in astrophysics: Reduced-order modelling for chemical kinetics and galaxy merger reconstruction with graph neural network
Full text linkThis thesis explores the application of deep learning techniques to two astrophysical problems: simplifying chemical kinetics calculations and reconstructing galaxy merger histories. A framework called Dengo is presented that can automatically generate chemical kinetics solvers from user-specified networks, enabling simplified integration of customized chemistry in simulations. The combination of neural ordinary differential equations and autoencoders is shown to be a promising approach for reducing the complexity of chemical kinetics simulations. Specifically, autoencoders identify the reduced reaction subspace while the neural ODE learn the latent space dynamics. This demonstrates the potential of using deep learning for reduced order modeling of complex chemical networks in astrophysics. For studying galaxy evolution, a conditional graph generative model is developed that can reconstruct the merger histories of observed galaxies from cosmological simulations. This allows identifying progenitors and formation pathways of galaxies across cosmic time. The model captures statistical properties of high-redshift progenitors and enables outlier detection and correlation identification. An overview of deep learning methods with a focus on techniques used in this thesis is also provided. The works demonstrate the potential of using deep learning for the selected problems in computational astrophysics and cosmic structure formation.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2024-09-16 without embargo termsThe student, Kwok Sun Tang, accepted the attached license on 2024-04-24 at 11:35.The student, Kwok Sun Tang, submitted this Dissertation for approval on 2024-04-24 at 11:42.This Dissertation was approved for publication on 2024-04-26 at 12:54.DSpace SAF Submission Ingestion Package generated from Vireo submission #20608 on 2024-09-16 at 00:36:0
Fundamental physics in extreme-gravity environments
Full text linkSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-10-20 without embargo termsThe student, Yiqi Xie, accepted the attached license on 2025-07-07 at 13:20.The student, Yiqi Xie, submitted this Dissertation for approval on 2025-07-11 at 15:50.This Dissertation was approved for publication on 2025-07-16 at 08:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #22430 on 2025-10-20 at 16:57:30Extreme gravity sourced by compact objects and their coalescences is a great avenue for testing Einstein’s general relativity and is deeply interconnected with fundamental physics. In this dissertation, we discuss three topics on the interplay between extreme gravity and fundamental physics driven by recent observational advancements. The first topic concerns making predictions about black holes in modified gravity. We prove that the spacetimes of isolated black holes in a broad class of modified gravity theories must be circular, justifying the long-existing use of a circular ansatz to simplify black hole solutions in these theories. We then analytically calculate the observables of the Blandford–Znajek process around a supermassive black hole in quadratic gravity. The calculation reveals a degeneracy between the black hole’s spin and the quadratic coupling, which hinders such an effect from constraining quadratic gravity unless the black hole is fast-spinning. The second topic concerns deciphering fundamental physics implications in gravitational-wave data from observations of compact binary coalescences. We search over the current gravitational-wave transient catalog for activated dipolar emission from massive scalar fields nonminimally coupled to gravity. Our Bayesian analysis suggests no evidence for these fields and places the most stringent upper-bound constraints on their coupling strengths. We then generalize the above search and combine it with the LIGO-Virgo-KAGRA parametrized inspiral tests of general relativity. This is achieved by extending the parametrized post-Einsteinian framework behind these tests using neural networks. We find that the resulting new framework leads to more theory-agnostic and more efficient tests of general relativity using gravitational waves. The third topic concerns improving gravitational-wave measurements of compact binary coalescences using domain knowledge from nuclear astrophysics. We show that modeling binary neutron star signals with binary Love relations breaks the distance-inclination degeneracy and improves the measurement of the neutron star masses. We forecast the decrease in the measurement error in the era of third-generation detectors, and we relax the assumptions behind our approach to prove the robustness of our forecasts
Experimental gravity with electromagnetic and gravitational waves
Full text linkElectromagnetic and gravitational observations can be used to elucidate the nature of compact objects and the fundamental properties of the material in their vicinity. Our ability to extract information about the underlying physics from observations of both electromagnetic and gravitational spectra depends on our understanding of the gravity theory that describes the geometry around these compact objects. For electromagnetic observations, we must also understand the complex astrophysics that produces the observed radiation. In this dissertation, we describe our efforts to constrain and detect deviations from general relativity using: the electromagnetic radiation emitted by an accretion disk around a black hole; the gravitational waves produced when comparable-mass black holes collide; and we have also studied chaotic signatures that could appear when a small compact object falls into a supermassive object during an extreme mass-ratio inspiral. Our analyses combined relativistic ray-tracing and Markov Chain Monte Carlo sampling techniques, as well as analytical and numerical calculations of the motion of particles. We found that even when a simple astrophysical model for the accretion disk is assumed a priori, the uncertainties and covariances between the parameters of the model and the parameters that control a deviation from general relativity make tests of general relativity very challenging when applied to accretion disk spectrum observations. We also found that current gravitational wave observations place constraints on metric deformation parameters that are more stringent than what can be achieved with current X-ray instruments. Based on our numerical findings when studying extreme mass-ratio inspirals, we conjecture that the geodesics of the as-of-yet unknown exact solution for spinning black holes in a dynamical Chern-Simons theory is integrable. Consequently, we predict the existence a fourth integral of motion associated with the exact solution. The work presented in this thesis advances the development of both analytic calculations and computational simulations to test our understanding of gravity’s fundamental properties with electromagnetic and gravitational waves.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2021-09-16 without embargo termsThe student, Alejandro Cardenas-Avendano, accepted the attached license on 2021-04-18 at 13:31.The student, Alejandro Cardenas-Avendano, submitted this Dissertation for approval on 2021-04-18 at 13:52.This Dissertation was approved for publication on 2021-04-19 at 16:56.DSpace SAF Submission Ingestion Package generated from Vireo submission #16393 on 2021-09-16 at 16:42:34Made available in DSpace on 2021-09-17T01:11:02Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-04-1
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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