1,720,983 research outputs found
Gravity currents interacting with slopes and overhangs
Full text linkWhen a gravity current interacts with a barrier the flow is reflected back in the form of a moving hydraulic jump or bore. This latter phenomenon has important implications for estuarine mixing and sediment reworking in the oceanographic context. In order to examine those reflection processes two-dimensional gravity currents interacting with slopes and overhanging barriers are examined by laboratory experiments and theoretical analysis. Relevant parameters such as the initial volume of the dense fluid, the opening of the fixed gate used for the dense fluid release and the angle of the slope or overhang positioned inside the tank, were varied. An image analysis technique based on light attenuation was applied to evaluate the instantaneous density fields. The theoretical predictions, based on shallow-water theory, give reasonable agreement compared with the laboratory experiments about the spatial position of the dense current and the definition of the point where the reflection process starts. Moreover, the analysis of the density fields highlights the presence of areas within the dense current characterized by a greater dilution due to the reflection of the current. Nevertheless, the bulk entrainment parameter is only slightly affected by the presence of a steep slope or overhang
Topographic and boundary effects on steady and unsteady flow through straits
No full textAn overview of topographic and boundary effects in flows through straits is presented. The emphasis is on the various types of interaction of uniform and stratified flow with the topography of straits, especially the interaction with sills. The interaction of a single-layer flow in a channel with a sill (obstacle) depends on the Froude number of the flow and the relative height of the sill. Two classification schemes (one steady and one pseudo-steady) are given. For single-layer flow in straits where the effects of rotation are important a further parameter, the ratio of the channel width to a Rossby radius, is needed and a similar classification scheme as for the non-rotating flows can be obtained. Unsteady flows often result in bores (for single-layer flows) and internal bores (in stratified flows) and the behaviour of these is discussed. The flow of stratified flow past sills may generate lee waves, while the increased flow speeds at the sill may allow deep water to be drawn up and over the sill (aspiration). Features of the strait topography away from the sill, including slopes at the side of the channel and also downstream of the sill, channel curvature and channel widening have important effects on the character of the flow and on mixing. © 2004 Elsevier Ltd. All rights reserved
Emptying non-adiabatic filling boxes: The effects of heat transfers on the fluid dynamics of natural ventilation
No full textA model for steady flow in a ventilated space containing a heat source is developed, taking account of the main heat transfers at the upper and lower boundaries. The space has an opening at low level, allowing cool ambient air to enter the space, and an opening near the ceiling, allowing warm air to leave the space. The flow is driven by the temperature contrast between the air inside and outside the space (natural ventilation). Conductive heat transfer through the ceiling and radiant heat transfer from the ceiling to the floor are incorporated into the model, to investigate how these heat transports affect the flow and temperature distribution within the space. In the steady state, a layer of warm air occupies the upper part of the space, with the lower part of the space filled with cooler air (although this is warmer than the ambient air when the radiant transfer from ceiling to floor is included). Suitable scales are derived for the heat transfers, so that their relative importance can be characterized. Explicit relationships are found between the height of the interface, the opening area and the relative size of the heat transfers. Increasing heat conduction leads to a lowering of the interface height, while the inclusion of the radiant transfer tends to increase the interface height. Both of these effects are relatively small, but the effect on the temperatures of the layers is significant. Conductive heat transfer through the upper boundary leads to a significant lowering of the temperature in the space as a proportion of the injected heat flux is taken out of the space by conduction rather than advection. Radiative transfer from the ceiling to floor results in the lower layer becoming warmer than the ambient air. The results of the model are compared with full-scale laboratory results and a more complex unsteady model, and are shown to give results that are much more accurate than models which ignore the heat transfers. © 2012 Cambridge University Press
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
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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