1,720,955 research outputs found
Flow characteristics in gravel bed rivers: an experimental investigation
No full textThe characterization of the kinematic characteristics of flow in gravel-bed rivers is one of the most important problems. In the present paper the streamwise velocity and turbulence intensity profiles are investigated on the basis of data collected in a straight laboratory gravel-bed flume. In order to take into account spatial heterogeneities, the double-averaged velocities are considered for the anal-ysis. Results show that, because of the presence of gravels, all the streamwise velocity profiles show an inflection point. Thus, the experimental profiles can be interpreted by the mixing layer scheme and considered as a composition of two parts of constant velocity separated by a confined interme-diate region (mixing layer) containing the inflection point. The thickness of the mixing layer varies passing from the banks to the channel axis
Gravel-bed rivers: roughness surface identification and effect on flow characteristics
No full textRiverbeds are often covered with gravels. The characterization of the gravel bed is very complex, depending on many factors such as the gravels’ shape, morphology and spatial distribution. The presence of gravels determines a significant impact on flow field (Ferraro et al., 2016). The evaluation of flow velocity and turbulence characteristics in natural rough beds is a complex subject, still poorly understood despite the effort of several researchers, requiring both theoretical and experimental analyses. On one hand the bed roughness exhibits a significant spatial variability, on the other hand the presence of gravels determines a significant effect on flow velocity distribution, especially affecting it in the near-bed flow zone and determining the formation of coherent turbulence structures. How to reasonably quantify gravel bed surface roughness is still an open question and different methods have been proposed in literature (among others Nikora et al., 1998; Aberle and Nikora, 2006). It is important to understand the turbulent flow characteristics by resolving the spatial heterogeneities
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
Influence of Bed Roughness on Flow and Turbulence Structure Around a Partially-Buried, Isolated Freshwater Mussel
Get PDFThe present study uses eddy-resolving numerical simulations to investigate how bed roughness affects flow and turbulence structure around an isolated, partially-buried mussel (Unio elongatulus) aligned with the incoming flow. The rough-bed simulations resolve the flow past the exposed part of a gravel bed, whose surface is obtained from a laboratory experiment that also provides some additional data for validation of the numerical model. Results are also discussed for the limiting case of a horizontal smooth bed. Additionally, the effects of varying the level of burial of the mussel inside the substrate and the discharge through the two mussel siphons are investigated via a set of simulations in which the ratio between the median diameter of the (gravel) particles forming the rough bed, d50, and the height of the exposed part of the mussel, h, varies between 0.10 and 0.22. The increase of the bed roughness is associated with a strong amplification of the turbulence kinetic energy in the near-wake region. Increasing the bed roughness and/or reducing h intensifies the interactions of the eddies generated by the bed particles with the base and tip vortices induced by the active filtering and by the mussel shell, respectively, which, in turn, induces a more rapid dissipation of these vortices. Increasing the bed roughness also reduces the strength of the main downwelling flow region forming in the wake. The strong downwelling near the symmetry plane is the main reason why the symmetric wake shedding mode dominates in the smooth bed simulations with negligible active filtering. By contrast, the anti-symmetric wake shedding mode dominates in the simulations conduced with a high value of the bed roughness. The mean streamwise drag force coefficient for the emerged part of the shell and the dilution of the excurrent siphon jet increase with increasing bed roughness
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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