1,720,969 research outputs found
A Review of Voltage-Clamping Methods for Solid-State Circuit Breakers
Get PDFIn recent years, the interest in DC systems has increased dramatically because of some key advantages, in terms of efficiency and reliability, that this technology can offer compared to AC systems in applications such as shipboard distribution, more electric aircrafts, DC microgrids, battery protection, and photovoltaics. In this context, DC circuit breakers based on power semiconductors, the so-called solid-state circuit breakers, are becoming a popular choice because of their fast intervention speed, which is typically on the order of microseconds. Unfortunately, power electronics are vulnerable to 'breakdown', which is a dangerous operating condition triggered by overvoltages. During current interruption, the energy stored in the inductive elements of the system must be dissipated, and this typically creates a very high voltage spike on the interrupting component, which is the breaker pole. This phenomenon, if not controlled, could lead to the premature failure of the semiconductor inside the solid-state circuit breaker. For this reason, suitable techniques aimed to control the voltage gradient and overshoot during interruption have been presented in the literature. This paper analyzes and compares the performances of the voltage-clamping solutions presented in the technical literature, which range from simple passive devices to more advanced solutions
Comment on: outpatient parenteral antibiotic therapy (OPAT) for bone and joint infections: experience from a UK teaching hospital-based service.
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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
Optimal flux reference to operate a five-phase induction machine under two open-phase fault condition
No full textElectrical drives are largely adopted in industry and in the last years, thanks to the increased awareness towards the environment, they are spreading as a means for transport. The most common electrical machines are three-phase and their construction is well known. However, for a three-phase machine the first fault on one phase of either the machine or the inverter implies the impossibility to develop a torque causing the stop of the machine. Multiphase machines among all the different advantages allow to keep operating until three phases are healthy. For this reason, these types of machines are spreading in all the applications for which the continuity of service is necessary. In this paper a five-phase induction machine is considered. In particular, for this machine, the working conditions with two faulted open phases is studied and the optimal reference for the machine flux is evaluated together with the maximum allowable torque. Both the cases of adjacent and non-Adjacent faulted phases are analyzed and the results are proven by means of numerical simulations
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
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
Mefloquine versus quinine plus sulphalene-pyrimethamine (metakelfin) for treatment of uncomplicated imported falciparum malaria acquired in Africa
No full textWe conducted a multicenter, randomized, open-label trial to compare mefloquine with a 3-day quinine plus sulphalene-pyrimethamine (SP) regimen for the treatment of imported uncomplicated malaria acquired in Africa. The end points of the study were efficacy, tolerability, and length of hospital stay. From July 1999 to February 2003, 187 patients were enrolled in five centers in Italy, of whom 93 were randomized to receive mefloquine (the M group) and 94 were randomized to receive quinine plus SP (the QSP group). Immigrants and visiting relatives and friends represented 90% of the cases and were mainly from western African countries. A slightly increased proportion of cases in the QSP group had abnormal alanine aminotransferase levels at the baseline. The early cure rate was similar in the two groups: 98.9% (confidence interval [CI] = 97 to 100%) in the M group and 96.8% (CI = 93 to 100%) in the QSP group. The extended follow-up was completed by 135 subjects (72.2%), and no case of recrudescence was detected. There were no differences in the parasite clearance time, but patients in the M group had shorter mean fever clearance time (35.9 h versus 44.4 h for the QSP group; P = 0.05) and a shorter mean hospital stay (3.9 days versus 4.6 days for the QSP group; P = 0.007). The overall proportions of reported side effects were similar in the two groups, but patients in the M group had a significantly higher rate of central nervous system disturbances (29.0% versus 9.6% for the QSP group; P < 0.001)
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