1,721,000 research outputs found
Synergistic interplay of thermodiffusive instability and turbulence in premixed flames
No full textIn this work, we experimentally analyze the interplay of thermo-diffusive (TD) intrinsic flame instabilities and
turbulence in premixed flame propagation. We utilize methane/hydrogen/air Bunsen flames at atmospheric
pressure and variable hydrogen content, and variable turbulence intensity. Experiments are designed to
maintain the laminar unstretched premixed flame speed constant by adjusting the equivalence ratio φ for each
flame. As the hydrogen content is increased and φ is decreased, thermo-diffusive intrinsic flame instabilities
are gradually promoted. We study the effect of thermo-diffusive instability on the global consumption speed
by analyzing the contribution of flame surface area increase and flame mean reactivity measured via a stretch
factor. We observe that the turbulence-instability interplay mainly occurs through an enhancement of flame
reactivity and not flame area. In addition, a power spectral density (PSD) analysis of the flame curvature reveals
that the spectra of unstable flames are consistently more energetic due to the wider range of linearly unstable
scales interacting with the turbulent integral scale. A forced weakly nonlinear numerical model is also utilized
to aid in the understanding of the experimental findings. The model exhibits a characteristic unforced PSD,
representing the energy content of the typical spatiotemporal chaotic TD-unstable solution. When forced, the
model exhibits PSD that emerge from the interplay of the turbulent spectrum and the characteristic TD-unstable
spectrum, and, as a result are consistently more energetic than the TD-stable spectra
Scaling transition of turbulent flame speed for thermodiffusively unstable flames
No full textThis work presents an experimental set of Bunsen flames characterized by a moderate Reynolds number and a variable turbulence intensity. Ten lean hydrogen-enriched methane-air mixtures at three turbulence levels are investigated, ranging from methane-air to hydrogen-air mixtures. Such mixtures are selected to have an almost constant laminar flame speed while inducing the onset of thermal-diffusive (TD) instability by gradually increasing the hydrogen content of the blend. The flames' global consumption speed, stretch factor, and flame surface area are investigated and discussed as functions of the effective Lewis number of the mixture. As the interplay between TD instability and turbulence enhances the overall flame propagation, below a transitional Lewis number, flames are observed to be particularly sensitive to external turbulent forcing. This synergistic interaction is discussed in terms of Karlovitz and Lewis numbers. A parameterization of the turbulent flame speed is thus proposed, based on a functional form depending, concurrently, on both Karlovitz and Lewis numbers. The proposed form is shown to fit the experimental results at different turbulence levels and to capture the flame speed enhancement across the transitional Lewis number
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
Aida
No full textDe cada obra s'ha digitalitzat un programa sencer. De la resta s'han digitalitzat les parts que són diferents.Direcció artística Empresa Juan Mestres CalvetIntèrprets : Serafina Di Leo ; Aurora Buades D'Alessio ; Francesco Merli ; Pablo Vidal ; Vincenzo BettoniÒpera de Giuseppe Verd
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
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