1,721,149 research outputs found
Physical and numerical modelling of air-water flows: An Introductory Overview
No full textIn free-surface turbulent flows, large amount of air may be entrapped and advected in the water current. The resulting air-water flows are frequently observed in natural water systems, where they are also relevant to water quality, ecological sustainability and integrated assessment within such systems. Herein, a review of physical and numerical modelling of air-water flows is developed, providing some fundamentals towards a consistent modelling of such flows to graduate and Ph.D. level students as well as young researchers in environmental sciences and engineering, with pre-requisite knowledge in basic fluid mechanics. After some theoretical and metrology considerations, the main criteria for the design of physical models and the current literature on the numerical studies are discussed. Two case-studies, the hydraulic jump and the dropshaft, are used to show the application of such criteria and methods. Overall, the paper presents current knowledges/challenges on physical and numerical modelling of self-aerated free-surface flows
Human body stability in floodwaters: the 2011 flood in Brisbane CBD
Full text linkThe flooding of urbanised areas constitutes a hazard to the population and infrastructure. Floods through inundated urban environments have been studied recently and the potential impact of flowing waters on pedestrians is not well known. Herein the stability of individuals in floodwaters is reviewed based upon the re-analysis of detailed field measurements in an inundated section of the central business district of the City of Brisbane (Australia) during the 2011 flood. Detailed water elevation and velocity data were recorded. On-site observations showed some hydrodynamic instability linked to local topographic effects, in the form of a combination of fast turbulent fluctuations and (very) slow fluctuations of water level and velocity associated with surges. The flow conditions in Gardens Point Road was unsafe for individuals and a review of past guidelines suggests that many previous recommendations are over-optimistic and unsafe in real floodwaters
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
Tailwater Level Effects on Flow Conditions at an Abrupt Drop
Full text linkThis paper presents an experimental study of the transition from supercritical to subcritical flow at an abrupt drop. The paper reports a wide range of experimental conditions and the relevant regime charts. Long-term experimental results show that some flow configurations tend to behave quasiperiodically (i.e. oscillating flow patterns). The experimental results have direct implications on the design and construction of spillway stilling basins where abrupt drops may be used to stabilise the position of the jump. The present study proposes design guidelines taking into account the different flow types, for a range of tailwater flow conditions. These guidelines are essential for a safe and proper operation of stilling basins with abrupt drop
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
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