1,720,959 research outputs found
Flow Regulation of Low Head Hydraulic Propeller Turbines by Means of Variable Rotational Speed: Aerodynamic Motivations
No full textTo date, hydraulic energy is still, among the renewable ones, the most widespread and most exploited to produce electricity. With the current trend to exploit any renewable source available, the limits for the economic convenience of hydroelectric power plants have significantly changed, making it interesting and convenient to use even small heads and low flow rates. In the specific applications of hydraulic turbines operating with low heads, the Kaplan turbine plays the predominant role among the available machines, also given the possibility of carrying out an “on cam” regulation, acting simultaneously on the geometry of the rotor and distributor rows, thus allowing a wide flow rate adjustment range. However, for applications characterized by very low heads and low available powers, it may not be convenient to use complex regulating devices. For this reason, these plants usually use axial machines characterized by a partial regulation (of the distributor or of the rotor), significantly reducing the operating range of the machine compared to the case of double regulation. In the last decade, the development of reliable and less expensive permanent magnet generators and power electronic converters and related new control strategies has paved the way for the concept of regulating hydraulic turbines by means of variable rotational speed. This regulation principle is based on the possibility of acting in the case of using synchronous permanent magnets electric generators and electronic power converters and on the variation of the rotational speed of the machine while keeping the grid frequency constant. The concept can be applied both to pure propellers with fixed a rotor and fixed distributor and to hydraulic axial turbines with regulation based on the modification of the variable guide vane opening angle. Although this new regulation approach, even in the case of the combined guide vane and rotational speed regulation, does not allow to recover most of the energy losses due to the variation of the operating conditions as effectively as the Kaplan double regulation does, the variation of the rotation speed, coupled with the variation of the opening of the distributor row, allows to reduce the tangential kinetic energy losses generated at the turbine exit during the off-design operations of a fixed blade opening angle rotor. At the same time, this type of regulation offers a simple and thus low-cost solution. The present study develops the theory underlying this regulation concept, based on the use of the turbomachinery fundamental equations, and reports the results of the off-design CFD analysis carried out for different combinations of rotation speeds and openings of the distributor, showing the improvement of the hydraulic efficiency over a large range of operating conditions with respect to the single regulation approach
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
Advances in Image Processing, Artificial Intelligence and Intelligent Robotics
No full textThe aim of this reprint is to give researchers the opportunity to present new tendencies, the latest achievements and research directions, and their current work on important issues in image processing, deep learning, soft computing, sensor fusion, robotic vision, and applied industrial solutions in robotics
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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