1,720,996 research outputs found
Flow Velocity Distribution in Rivers through Image-Based Technique Calibrated by ADCP Measurements
No full textIn the context of climate change, the knowledge of flow discharge is of crucial importance. Flow
discharge is not a direct measurement but is estimated on the basis of information of flow velocity
and cross-sectional flow area. Thus, accurate flow velocity measurements are critical for defining
early warning systems for flood management and for quick decision-making for emergency actions.
In recent years, the acoustic Doppler current profiler (ADCP) has been especially used to measure
flow velocity profiles and the flow discharge, in natural and man-made waterways[1]. During flood
events, because of continuously changing in flow velocities, water depths, and high sediment
concentrations, conditions is not safe for measurement operator. As consequence, in high flow
conditions, measurement equipment’s like current meters and/or more advanced instruments such as
ADCP cannot be used. For this reason, especially in the last decade, alternative approach based on
image processing techniques has been increasingly used to obtain the distribution of the surface
velocity, from which the flow discharge might be estimated. Several software tools have been also
implemented for the image-based technique application, enabling researchers and practitioners to
derive flow velocity data with high spatial and temporal resolution [2,3]. In comparison to the
traditional measurement methods, the image-based technique presents the advantage to be nonintrusive
allowing the safe estimation of surface velocity distribution also during floods. One of
challenges in the application of image techniques is determining the error in estimating surface
velocity, whose quantification depends on many factors characterizing not only the measurement
conditions but also the processing method used
Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory
No full textThe estimation of velocity profile in turbulent open channels is a difficult task due to the significant effects of the secondary flow. The present paper investigates the mechanism of the velocity-dip phenomenon, whereby the location of the maximum velocity appears to be below the free surface. Previous studies conducted in straight channels relate the mechanism of the velocity-dip phenomenon to secondary flow induced by anisotropy of turbulence. This work focuses on high-curved channels where the secondary motion, which is also induced by the channel’s curvature, evolves along the bend. The width-to-depth ratio, B/h, is one of the most important parameters that are affecting the secondary motion entity. In particular, the present study aims to investigatetheevolutionofthevelocity-dipalongthebendfortwovaluesofthewidth-to-depthratio andtheapplicabilityoftheentropicmodelforthedip-phenomenonestimation. Theresultsshowthat the velocity-dip is more accentuated for low values of the width-to-depth ratio, where the secondary motion plays a fundamental role in the distribution of the downstream flow velocity, although the velocity-dip is also present when the aspect ratio is higher than 10. Furthermore, the velocity profiles that were estimated by applying the entropic model are in good agreement with the measured ones, especially for B/h < 10
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
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