1,721,075 research outputs found
X-rays from Compton scattering around accreting black holes
Get PDFCompton scattering is one of the most important radiation processes from accreting compact objects. Hard X-rays can be produced by Compton upscattering of soft seed photons from the accretion disk. Here we use both theoretical and observational methods to investigate the hard X-ray emission around accreting Black Holes. We attempt to observationally constrain the geometry of the accretion flow using the observed spectra from the outburst of a transient black hole. The rapid rise of the hard X-ray flux is almost certainly associated with most of the disk mass moving inwards, so the optically thick disk should not extend down to the last stable orbit until the outburst peak. The low/hard state is seen at the start of the rise showing that this is probably associated with a truncated disk. Attempts to derive the inner disk radius from reflection model parameters are inconclusive due to the effects of ionization. We describe a new approach to numerically modelling Compton scattering around accreting sources by solving the distribution functions. This approach (based on work by Guilbert 1981) involves breaking the scattering into individual segments of space and time. We show how a coarse angle grid can be adapted to mimic an arbitrarily fine grid with very little increase in run-time. The resulting code automatically includes time dependent behaviour. We extend the code to calculate the time dependent, self consistent electron distribution resulting from the Compton cooling. This can be used even where the Compton cooling time is shorter than the light crossing time. We show that any system in which the seed photons are dominated by reprocessing should produce soft lags of the order of the light crossing time. Future observations, with more sophisticated satellites, may be able to identify this lag
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Wave runup on atoll reefs
No full textThe aim of this research was to take the first step in understanding the wave runup process on an atoll reef using the XBeach model. Field data collected from 3 November 2013 to 13 April 2014 at Kwajalein Atoll in the Republic of the Marshall Islands was used. The dataset included data on bathymetry, waves, water levels and wave-induced runup. The data was analysed and subsequently used to model the hydrodynamics across the reef and the wave runup. The hydrostatic and non-hydrostatic XBeach models were used to capture both components of runup, infragravity and incident swash. Finally, a conceptual model was created to investigate the effect of variations in the atoll reef parameter space on the wave runup.Hydraulic EngineeringCivil Engineering and Geoscience
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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