1,720,997 research outputs found
Turbidity current hydraulics and sediment deposition in erodible sinuous channels: Laboratory experiments and numerical simulations
No full textThis study explores the relationship between the hydraulics of turbidity currents in erodible sinuous channels and the resulting intra-channel sediment depocentres (channel bars). Four factors are considered to exert critical control on sedimentation in sinuous submarine channels: (1) the required equilibrium gradient of the flow versus the pre-existing channel gradient; (2) the wavelength of the flow rotation helicoid versus the channel curvature wavelength; (3) the degree of confinement of the channel-entering flow; and (4) the channel bank erodibility. The study verifies the role of these factors by testing a wide range of possible flow conditions and reveals the formative conditions for five types of intra-channel depocentres: point bars (meander bars), bars formed at the upslope or downslope bank in the channel-bend inflection zone, and the outer-bank bars formed directly upstream or downstream of the bend apex.
Channel meandering is caused by turbidity currents that deposit point bars and possibly bars at the upslope bank of the channel-bend inflection zone. These are currents that result in no significant aggradation or degradation of the channel, spill out moderately and have a rotation helicoid rising against the bend inner bank. Channel aggradation disfavours meandering, but an established meandering channel can maintain its behaviour when forced to aggrade at a modest rate. Currents forming outer-bank bars and possibly bars at the upslope bank of the bend inflection zone are approximately in equilibrium with the channel gradient, spill out moderately, have a rotation helicoid rising outwards at the bends, and result in an overall straightening of the sinuous channel. Channel-aggrading currents that form outer-bank bars and the bypass currents that form bars at the downslope bank of the bend inflection zone spill out excessively and have an intricate velocity structure due to interaction with re-entering overbank flow. These currents tend to fill up or strongly modify the pre-existing sinuous channel.
The study confirms and expounds on many previous laboratory inferences based on flows in solid-wall sinuous channels. It also demonstrates that numerical simulations can give considerable new insights into the sedimentation processes in submarine channels. The advantage of numerical simulations is that they allow monitoring of all crucial hydraulic parameters of the turbidity current and its responses to topography in three dimensions over full flow duration. Such simulations, when calibrated against laboratory experiments, can improve our understanding of both laboratory flows and natural turbidity currents
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
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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