1,721,328 research outputs found
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
Simulation of entrained flow gasification with advanced coal conversion submodels. Part 1: Pyrolysis
No full textCFD modeling results for entrained flow coal gasification using advanced submodels for coal conversion are presented and compared to detailed experimental data. The focus of this investigation is on the accurate modeling of the pyrolysis process. An iterative procedure is proposed and validated to bridge the gap between detailed pyrolysis models such as CPD, FLASHCHAIN or FG-DVC and empirical models based on single- or multiple-step kinetic expressions, which are usually used in CFD. Multiple particle heating rates from the CFD solution are taken to perform detailed pyrolysis calculations and these results are used to find optimal kinetic parameters for the empirical models using an automated procedure. It is shown that the heating rate strongly influences the devolatilization process (rate and yield). CFD simulations are performed for the BYU entrained flow gasifier. Due to the high heating rate in entrained flow gasification, the volatile yield can differ significantly from the proximate analysis value. Accurate pyrolysis modeling is shown to be important to capture coal flame ignition, flame location, species distribution and outlet composition. Since the final volatile yield determines the split in carbon conversion between pyrolysis and the subsequent fast conversion in the gas phase and the heterogeneous char conversion, which is a comparatively slow process under gasification conditions, it also directly influences the overall carbon conversion. Overall, the application of the new comprehensive CFD model including the fitted kinetic rates is shown to give similar results to the full coupling of the CFD and pyrolysis software. The comparison between the simulations and the experiments shows very good agreement for three out of four coals. The fourth coal (lignite with high O/C ratio) is well outside the range for which the detailed models were developed, but reasonable agreement is still obtained
Bivariate extensions of the Extended Quadrature Method of Moments (EQMOM) to describe coupled droplet evaporation and heat-up
No full textIn this study, four Eulerian moment methods based on the
Extended Quadrature Method of
Moments
(EQMOM) (
Yuan, Laurent, & Fox, 2012
) are applied to model the evaporation of
droplets. EQMOM enables the number density function (NDF) to be reconstructed from a
set of moments of a droplet ensemble. Knowledge of the NDF allows us to describe the
disappearance
fl
ux of the smallest droplets accurately, which is a critical issue in moment
methods (
Fox, Laurent, & Massot, 2008
;
Yuan et al., 2012
). As EQMOM is restricted to
univariate distributions, initially only the droplet size is considered as an internal coor-
dinate. The description is then extended to the bivariate models
mono-thermal Extended
Conditional Quadrature Method of Moments
(mt-ECQMOM), whose formulation is based on
the semi-kinetic approach (
Vié, Laurent, & Massot, 2013
) and
Extended Conditional
Quadrature Method of Moments
(ECQMOM,
Marchisio & Fox, 2013
). Based on ECQMOM and
the general principle of a sectional method, a third bivariate approach is proposed, called
the
Extended Conditional Sectional Method of Moments
(ECSQMOM). The resulting three
bivariate approaches allow us to describe the coupling of heat-up and evaporation using
the internal coordinates droplet diameter and temperature.
The results based on EQMOM, mt-ECQMOM, ECQMOM and ECSQMOM are evaluated
against a direct numerical solution of the population balance equation (PBE) investigating
a test setup based on experimental studies for iso-octane sprays. Results indicate that in
the limiting case of a mono-thermal distribution, the ECQMOM model implementation
referenced above is not applicable to describe evaporating sprays accurately, whereas the
mt-ECQMOM leads to much better results. ECSQMOM is also found to yield good results,
even if the accuracy of mt-ECQMOM is not reached. However, since ECSQMOM offers the
potential to capture distributions with nonzero conditional variance, it can be considered
a suitable approach to describe the evolution of droplet distribution in sprays in future
applications
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
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
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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