1,721,047 research outputs found
CONTROL OF NON-AXISYMMETRIC MAGNETIC FIELDS FOR PLASMA ENHANCED PERFORMANCES: THE RFX CONTRIBUTION
No full textActive control of non-axisymmetric magnetic fields has been developed to increase the plasma performances in Tokamaks and RFPs. In the past at RFX, the effect of non-axisymmetric fields, static and rotating, with m = 0, n > 0, was studied. Through a plasma non linear coupling, the internal tearing modes coupled with the external m = 0 fields are dragged into rotation. The results have encouraged to realize a dedicated system for the generation of non-axisymmetric magnetic field by using ad hoc saddle coil arrays. One hundred and Ninety-two uniformly distributed saddle coils, each fed through switching power supply have been installed for the generation of m = 0 and 1 magnetic fields in a range n = 1-24. Each coil will be operated in a frequency range from dc to 300 Hz and will produce a maximum field intensity of 50 mT dc at the plasma surface. The resulting configuration of coils, power supplies, measurements and real time control equipment gives nowadays the most versatile system for studies of non-axisymmetric field effect on plasma. The experiments will be focused to increase the present understanding in the control of Resistive Wall Modes (RWMs) and to analyse the resonant and non-resonant MHD mode interaction with external magnetic fields, common issues for present Tokamaks and RFPs.The paper reviews the state-of-art of MHD control performed with non-axisymmetric external magnetic fields on Tokamaks and RFPs, with reference to the RWMs and field errors. The RFX contribution to the MHD mode control by external fields is discussed
Study of the RFX circuits with a 0-dimensional plasma model
No full textThe poloidal and toroidal circuit performance of the Reversed Fiel Pinch experiment RFX is studied with a circuit plasma model which accounts for the coupling of the two circuits by constraining the evolution of the magnetic field distribution in the plasma. RFP configurations at 2 MA current and beta-theta = 0.1 can be produced with pulse length up to 250 ms
Fault analysis and special tests of thyristor for RFX AC/DC converters
No full textIn the RFX nuclear fusion experiment, 20 AC/DC converter units, for a total installed power of over 400 MVA, are used to feed the machine magnets. Due to the special characteristics of the load, and in particular to the expected fault conditions, the converter bridges must withstand a high number (approximately 2000) of severe overloads during the life of the machine; in particular, the thyristors must carry a current two or three times larger than the nominal current without any damage. In addition, the thyristors must not explode, even in the case of a slightly higher surge current than the previous one, when the fuse does not blow quickly. As the manufacturer's data did not cover the thyristor performance under these specific requirements, new tests on the thyristors had to be carried out, and the results are discusse
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
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