1,720,987 research outputs found
Matrix converter based voltage regulator for managing smart microgrid with high renewable energy penetrations
No full textThis thesis examines the use of matrix converter (MC) in voltage regulators intended for use in the low voltage (LV) distribution network. Voltage balance and voltage regulation can be controlled by adding a series compensation voltage with a transformer. The MC supplies the
injection transformer with an appropriate voltage which may be significantly unbalanced.
Prior-art MCs have been predominantly applied in motor drives which have relatively balanced
voltages and currents. This thesis shows the existing methods are not ideal for very unbalanced situations. It is shown that a traditional MC supplying an unbalanced load develops current harmonics at its input terminal. This thesis provides an improved MC modulation method that
can eliminate input harmonics. This result is confirmed by simulation and experimental work.
The thesis extends the traditional 3× 3 matrix into four wire compatible MC topologies including 3×4, 4×3 and 4×4 converters. For these cases, and generalised cases, solutions are presented for switch commutation. These are implemented with a field programmable gate array (FPGA). An experimental study is made of switch commutation for silicon and silicon carbide metal oxide semiconductor field-effect transistors (MOSFETs).</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
A matrix converter based voltage regulator for MV rural feeders
No full textIn this paper a Matrix Converter (MC) has been used with a series voltage injection transformer to regulate the voltages on a Medium-Voltage (MV) rural distribution feeder. This approach is well suited to pole top regulator applications as DC bus capacitors are avoided. The MC is controlled using a space vector modulation (SVM) method that is capable of regulating the positive-sequence voltage on a feeder while simultaneously cancelling negative sequence voltages produced by high levels of load or distributed generation unbalance or by the use of non-transposed lines. The study of the MC modulation processes is undertaken with an exact switching model for the higher frequency behaviours of the converter while a small signal Instantaneous Reactive Power (IRP) based average signal model is used to study the multi-cycle dynamic regulatory performances
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
An improved modulation method for matrix converters with unbalanced output loading
No full textIn this paper Instantaneous Reactive Power (IRP) theory is applied to develop an improved modulation method for Matrix Converters (MCs) operating with unbalanced loads. IRP theory shows that, for unbalanced loading conditions, the instantaneous power contains a constant component and a component that fluctuates at twice the fundamental frequency. In conventional modulation schemes the power fluctuation results in input current harmonics. The new method removes the harmonic distortion by synthesizing an input current vector that contains positive and negative sequence components that satisfy the power balance requirements but have only fundamental frequency components. The paper shows that the conventional modulation method may be converted to produce the required input current vector by phase modulation of the input current vector
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