1,720,960 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
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
Uncertainty quantification in RANS prediction of LOX cross-flow injection in methane
No full textThis work presents the numerical characterization under uncertainty of a pintle-injector liquid rocket engine thrust chamber, fueled with LOX-CH4 and operated at subcritical pressure. Being the design optimization the ultimate goal of this effort, the numerical characterization is carried out employing a Eulerian-Lagrangian Reynolds-averaged Navier Stokes equations approach. The numerical model of choice, as well as the rich variety of physical phenomena taking place in such a device, require the knowledge of a large number of model parameters, many of which are challenging to be calibrated under the severe thermophysical conditions of interest. A possible way to overcome this lack of knowledge is to resort to the Uncertainty Quantification (UQ) framework to estimate the effects of model and parameter uncertainties on the solution accuracy. In particular, this research aims at propagating the uncertainty associated with the most probable diameter which characterizes the injection Rosin-Rammler distribution for the liquid droplets, employing a Polynomial Chaos Expansion (PCE) representation of the uncertainty. The pintle configuration consists of a horizontal gaseous methane inflow and a vertical LOX spray injection. A set of RANS are conducted to generate the PCEs surrogate model for the estimation of the probability distribution of the quantities of interest, as well as the visualization of their credibility intervals. Lastly, to assess whether the uncertainty on the droplet diameter can overshadow the sensitivity to the pintle design, the same uncertainty quantification analysis is performed for two geometries, which differ in the distance between the annulus final section and the fuel-oxidizer impingement location
Large Eddy Simulations of Conventional and Alternative Aviation Fuel Spray Breakup
No full textMid-term climate neutrality cornerstone policies by international governments and institutions target a climate-neutral aviation system by 2050. In this context, sustainable aviation fuels (SAFs) represent a drop-in key enabling technology to foster an effective transition of the aviation sector towards net zero carbon. Nonetheless, peculiar and unexplored properties of unconventional fuel blends may profoundly impact the performance and safe operability of jet engines in terms of altitude relight, lean blow-out, and cold-start ignition, as well as emission levels of specific pollutants. In this regard, computational fluid dynamics (CFD) offers a pivotal active support tool, partially or entirely replacing vast, expensive, and practically difficult experimental campaigns. In the present research study, we first formulate a four-component and a five-component surrogate mixture describing the thermophysical properties of a petroleum-derived conventional aviation fuel, Jet A-2 POSF-10325, and a synthetic alcohol-to-jet (ATJ) fuel, Jet C-1 POSF-11498, leveraging Bayesian inference techniques provided by the BayeSAF algorithm. As a preliminary analysis, we investigate the effects of chemical composition on the fuel vaporization process by addressing zero-dimensional isolated droplet evaporation in a low-vaporization rate quiescent environment for Jet A-2 and Jet C-1 through an in-house MATLAB code. The outcome of this analysis highlights non-negligible differences in droplet diameter evolution due to preferential vaporization effects, remarking on the fundamental role of surrogate mixture formulation in the numerical characterization of both conventional and alternative jet fuels. Thereafter, we carry out non-reacting Eulerian-Lagrangian large eddy simulations (LES) of Jet A-2 and Jet C-1 spray breakup within a referee combustor test rig equipped with a realistic gas turbine injection system. Numerical simulations show that the liquid spray topology remains unaltered from a qualitative standpoint regardless of the jet fuel category, with Lagrangian parcels following a conical pattern downstream of the swirler exit plane as a result of the hollow-cone spray injection strategy and the radial advection due to the high centrifugal forces induced by the establishment of a conical-type vortex breakdown regime. As a result, both Jet A-2 and Jet C-1 test case configurations exhibit almost negligible liquid volume fraction levels within the breakdown-induced recirculation region. Nonetheless, relevant differences arise in the radial distribution of the droplet axial velocity and Sauter mean diameter within the near-injector region. Notably, liquid parcels describing Jet C-1 evolution in the computational domain exhibit overall lower values of the Sauter mean diameter compared with Jet A-2, indicating a more efficient spray breakup process
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
Aircraft Design with Well-to-Wake Optimization Under Uncertainty
No full textExploiting hybrid-electric propulsion in the aviation sector represents one of the possible strategies to tackle the challenging goals imposed by institutions on reducing anthropogenic climate impact. At the same time, Sustainable Aviation Fuels (SAFs) are regarded as the most viable short-term solution to address this requirement. We propose a general aircraft design framework that encompasses the combination of new solutions, i.e., alternative fuels and electric propulsion. The analysis is enriched by including the Well-to-Tank (WTT) processes that precede the aircraft operations, so that the entire fuel life cycle is taken into account. Given the rather unknown technological readiness of SAF production on the large scale, the effects of uncertainties that emerge during the WTT phase on the climate impact and aircraft energy requirement are evaluated by leveraging the potentiality of Uncertainty Quantification (UQ) techniques. The integration of uncertainty propagation with an optimization process enables the assessment of the impact of variance in the WTT chain on optimal design decisions. The presented methodology has been applied to a hybrid SAF/electric regional aircraft architecture with the aim of identifying the optimal hybridization strategy to minimize the overall Well- to-Wake (WTW) climate impact and energy consumption. Results show that the probability distributions of the selected observables are significantly influenced by the technology level of the battery pack. Furthermore, within a specified battery specific energy range, the optimal power management differs depending on the specific objective being pursued
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