1,721,562 research outputs found
Efficient Calculation of PWM AC Losses in Hairpin Windings for Synchronous BPM Machines
No full textThis paper focuses on the alternative current (AC) losses in hairpin winding variation due to the skin and proximity effects in synchronous brushless permanent magnet machines when supplied from a pulse width modulation (PWM) inverter. Based on a motor used in a 200kW electrical drive unit, three main methodologies are investigated to demonstrate the importance of these additional losses and how it is possible to take them into account when modeling the electrical machine performance. A more rigorous approach and two more time-efficient ones are utilized for the purpose, showing powerful ways of taking into consideration the pulse width modulation induced eddy currents losses in stator conductors since the early stages of the design process. A reduction ratio of 30:1 in computation time gives the proposed methodologies great merit not only in modeling single operating points, but over the full torque-speed characteristic, efficiency maps, and drive/duty-cycles analyses
Eddy-Current Losses evaluation in hairpin wound motor fed by PWM Inverter
No full textThis paper presents different approaches proposed to evaluate eddy-current losses in hairpin wound motor fed by pulse width modulated inverter, underlining strengths and weaknesses of everyone and applying them, as test-case, to a 200kW induction motor designed for a premium electric vehicle. The first three approaches are based on the finite element analysis: the first, the more accurate one, use a transient analysis that request long execution time and high memory usage, the second is based on tool that permits rapidly to evaluate the steady state conditions imposing a sinewave current and the third uses a single-slot simplified model. The fourth approach proposes a rapid monodimensional analytic method based on hypotheses that permit to consider the superposition effects of the Eddy Current Losses of every current harmonic component. The fifth approach makes uses of the proposed analytic method by leveraging a rapid investigation of current harmonic content due to pulse width modulation based on a lumped parameter motor model.
In addition, the paper discusses important considerations about the use of the hairpin technology fed by pulse width modulation that can be drawn from the analysis of the obtained result
Color Sensors based on amorphous silicon
No full textStiebig H, Knipp D. Color Sensors based on amorphous silicon. In: Popescu M, ed. “Physics and Application of disordered materials. INOE; 2002: 323-348
Interferometric sensors based on amorphous silicon
No full textStiebig H, Bunte E, Jun KH. Interferometric sensors based on amorphous silicon. In: Lucovsky G, Popescu M, eds. Non-crystalline Materials for Optoelectronics. Optoelectronic materials and devices . Vol 1. Bucharest-Magurele: INOE; 2004: 417-440
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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