1,720,972 research outputs found
Hardware Dead Time Compensation for VSI Based Electrical Drives
No full textA full hardware modulator board for space vector modulation which allows the dead time effects compensation is presented in this paper. It consists of a
fully integrated digital set-up implemented on a programmable logic device. It is based on an adequate modification of the switching sequence generation on the base of the phase stator current signs and of the power modules status. In the paper, a detailed description of the modulator set-up will be provided together with some experimental results
Stereoselective halogenations of alkenes and alkynes in ionic liquids
No full text[GRAPHICS] Room-temperature ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium chloride, are used as "green" recyclable alternative to chlorinated solvents for the stereoselective halogenation of alkenes and alkynes
High Efficiency SVM Technique for VSI
No full textA space vector modulation technique for voltage source inverter which takes into account the power modules switching losses is presented in the paper. It is based on three digital separate circuits, which generate the modulation switching pattern by using a clock unit with three separate programmable frequency divisors. In particular, for each leg of the inverter, the switching frequency can be selected on the base of the instantaneous value of the corresponding
phase current. In this way, a modulation technique can be carried out in such a was as to keep the power modules losses lower than a maximum value and to reduce the current harmonic content
A Variable Frequency Space Vector Modulator for VSI Fed Induction Motor Drives
No full textA space vector modulator with variable clock frequency is presented in the paper. It is based on the selection of the appropriate modulator clock frequency according to the minimum value of the switching states duration. The purpose is to reduce at the same time the dead time effect on the voltage inverter output waveform, the harmonic content and switching losses. The proposed techniques has been implemented by means of a digital modulator realized by using programmable logic devices. Several tests have been performed and the results compared with the fixed frequency modulation techniques
A Low Cost Digital SVM Modulator with Dead Time Compensation
No full textA low cost digital modulator for SVM which allows the hardware compensation of the dead time effects is presented. It consists of a fully integrated digital set-up implemented on a programmable logic device. It is based on an adequate modification of the switching sequence generation on the base of the phase stator current signs and of the power modules status
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
Low Power Losses Configuration for DC/AC Converters
No full textA high efficiency converter topology is proposed in this paper. It has been designed and implemented for a particular application, in which the converter has to work in very critical external condition, such as anti-fire systems. The features to be achieved are the following: dc/ac conversion from a low voltage input source and a minimization of the conversion losses. A prototype has been manufactured and tested in laboratory, for validation and performances evaluation
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