1,720,957 research outputs found
Generalized Multicarrier PWM Technique for Two-Level Voltage Source Inverters
No full textTwo-level voltage source inverters are the mainstream solution for many power applications. The conventional modulation method of such inverters is the single-carrier pulsewidth modulation (PWM) technique. In this article, the usage of a generalized PWM method with three independent carriers is analyzed. The carrier phase-displacement angles are evaluated in order to reduce the common-mode voltage (CMV) total harmonic distortion (THD), the dc-link capacitor current THD, and the phase currents THD. These targets are difficult to be met at the same time and a cost function is deployed in order to look for a suitable solution that develops a tradeoff between all the targets. The proposed method has been tested in a laboratory prototype demonstrating its superior performance
Capacitor Lifetime Extension of Interleaved DC–DC Converters for Multistring PV Systems
No full textInterleaved dc–dc converters are being vastly applied for a wide range of applications. Inherent power sharing between the power modules and reduction of the output waveforms ripple are the main advantages of these power systems. However, in some cases, such as the multistring photovoltaic converters, each power module manages different power, leading to an unbalanced operation of the interleaved converters. In this case, the harmonic response of the conventional interleaving operation is degraded. This fact affects directly the expected lifetime of the dc-link capacitor of the power converter, which is one critical components of the system. In this article, a variable-angle phase displacement angle is proposed in order to mitigate this problem, achieving an extension of the converter lifetime
Common-Mode Voltage Harmonic Reduction in Variable Speed Drives Applying a Variable-Angle Carrier Phase-Displacement PWM Method
Full text linkArticle number 2929Electric variable speed drives (VSD) have been replacing mechanic and hydraulic systems
in many sectors of industry and transportation because of their better performance and reduced cost.
However, the electric systems still face the issue of being considered less reliable than the mechanical
ones. For this reason, researchers have been actively investigating effective ways to increase the
reliability of such systems. This paper is focused on the analysis of the common-mode voltage (CMV)
generated by the operation of the VSDs which directly affects to the lifetime and reliability of the
complete system. The method is based on the mathematical description of the harmonic spectrum of
the CMV depending on the PWM method implementation. A generalized PWM method where the
carriers present a variable phase-displacement is developed. As a result of the presented analysis, the
CMV reduction is achieved by applying the PWM method with optimal carrier phase-displacement
angles without any external component and/or passive filtering technique. The optimal values of
the carrier phase-displacement angles are obtained considering the minimization of the CMV total
harmonic distortion. The resulting method is easily implementable on mostly off-the-shelf mid-range
micro-controller control platforms. The strategy has been evaluated in a scaled-down experimental
setup proving its good performance.Junta de Andalucía P18-RT-1340Unión Europea SPARTAN-82138
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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