1,721,734 research outputs found
Recent advances in self-consistent RF sheath modeling and relatedphysical properties: Application to Tore Supra IC antennae
No full textNon-linear wave-plasma interactions in the plasma edge often set the operational limits for radio-frequency (RF) heating systems. Some peripheral Ion Cyclotron (IC) wave energy loss is attributed to a net direct current (DC) biasing of the edge plasma by RF-sheath rectification. In order to understand the underlying mechanisms driving these interactions, SSWICH (Selfconsistent Sheath and Wave for IC Heating) models self-consistently the interplay between RF wave propagation and edge plasma biasing, using a two-field fluid approach. RF and DC parts are coupled through non-linear RF and DC sheath boundary conditions (SBC). The iterative resolution of the coupled RF+DC model experiences convergence issues in the wide sheaths regime, i.e. large DC biasing relevant in the vicinity of high-power RF launchers. In order to overcome this difficulty and provide a first guess of the solution, the self-consistent RF+DC system was solved explicitly for the first time in this asymptotic wide sheaths limit, while keeping the possibility to excite the system by any realistic RF field map. Several original physical properties were observed. The radial penetration of the RF sheaths along lateral walls at both ends of the open magnetic field lines can be far deeper than the skin depth characteristic of the slow wave (SW) evanescence. This is interpreted invoking the Sheath-Plasma Wave, only appearing in the presence of sheaths and carrying them along material boundaries up to their leading edge. The RF voltages driving sheaths were shown to scale as the square root of the input RF power, consistent with some experimental observations and valuable for antenna design. This is illustrated in the case of Tore Supra antennae by the comparison of two Faraday screens with different electrical design that were experimented upon last year simultaneously. Since only the edge plasma is actually meshed, another issue is the emulation of radiating conditions in order to avoid reflections at the inner boundary of the domain. A versatile perfectly matched layer (PML) adapted to any medium was thus developed and extensively tested as an artificial dielectric material. As tokamak magnetized plasmas present two wave eigenmodes with opposite group velocities, simultaneous adaptation is impossible. The PML is accordingly adapted only for the fast wave if the plasma domain is far thicker than the SW skin depth. The PML should also be placed beyond the coupling zone of the fast wave
Estimated RF sheath power fluxes on ITER plasma facing components
No full textUsing numerical simulation, a first estimate is made of power fluxes caused by radio-frequency sheaths on plasma facing components surrounding the ITER Ion Cyclotron Range of Frequencies wave launcher. Three toroidal strap phasings were considered, and four plasma scenarios covering a broad range of Scrape-Off Layer densities. Parallel heat fluxes up to ∼16 MW/m2 are obtained, localized in poloidal peaks whose radial extension (initially 4–35 mm) increases when nearby flux tubes are coupled by exchanging RF currents. Quantitative results strongly depend on the local density, both via the unperturbed input profiles and via subsequent RF-induced modifications by E × B0 convection. Sources of uncertainty and aspects requiring further validation are identified
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
Lower hybrid current drive at high density on Tore Supra
No full textLower hybrid current drive (LHCD) experiments with line-averaged density varying between 1.5 × 1019 and 6 × 1019 m -3 are performed on the Tore Supra tokamak under quasi-steady-state conditions with respect to the fast electron dynamics. The LHCD efficiency is analysed from the fast electron bremsstrahlung (FEB) and electron cyclotron emission (ECE). The effect of plasma equilibrium and particle fuelling is documented. It is concluded that the fast decay of FEB with plasma density could be consistent with simple scaling of the current drive efficiency and FEB. Plasma edge measurements are presented looking for the effect on fast electron emission. In a specific case of particle fuelling, an anomalous decay of the hard x-ray and ECE signals suggests deleterious interaction of the wave with edge plasma. © 2013 IAEA, Vienna.Andrews V., 1985, PHYS FLUIDS, V28, P1148; Cesario R, 2006, NUCL FUSION, V46, P462, DOI 10.1088-0029-5515-46-4-007; Cesario R, 2010, NAT COMMUN, V1, DOI 10.1038-ncomms1052; Clairet F, 2004, PLASMA PHYS CONTR F, V46, P1567, DOI 10.1088-0741-3335-46-10-003; Decker J, 2011, NUCL FUSION, V51, DOI 10.1088-0029-5515-51-7-073025; Delpech L, 2011, FUSION ENG DES, V86, P815, DOI 10.1016-j.fusengdes.2010.12.062; FISCH NJ, 1978, PHYS REV LETT, V41, P873, DOI 10.1103-PhysRevLett.41.873; Fuchs V, 1996, PHYS PLASMAS, V3, P4023, DOI 10.1063-1.871536; Goniche M., 2010, P 19 TOP C RAD FREQ; Goniche M., 2010, AIP C P, V1406, P407; Goniche M, 2005, AIP CONF PROC, V787, P307; Hillairet J, 2010, NUCL FUSION, V50, DOI 10.1088-0029-5515-50-12-125010; Hoang G.T., 2009, NUCL FUSION, V49, P07500; Ikeda Y., 1995, PLASMA PHYS CONTROLL, V1, P415; Kirov KK, 2010, NUCL FUSION, V50, DOI 10.1088-0029-5515-50-7-075003; LIU CS, 1984, PHYS FLUIDS, V27, P1709, DOI 10.1063-1.864826; Ridolfini VP, 2011, NUCL FUSION, V51, DOI 10.1088-0029-5515-51-11-113023; Peysson Y, 1999, REV SCI INSTRUM, V70, P3987, DOI 10.1063-1.1150025; Peysson Y, 2012, PLASMA PHYS CONTR F, V54, DOI 10.1088-0741-3335-54-4-045003; Peysson Y, 2011, PLASMA PHYS CONTR F, V53, DOI 10.1088-0741-3335-53-12-124028; Peysson Y, 2007, AIP CONF PROC, V933, P293; Peyssona Y, 2008, PHYS PLASMAS, V15, DOI 10.1063-1.2981391; Peysson Y, 2000, PLASMA PHYS CONTR F, V42, pB87, DOI 10.1088-0741-3335-42-12B-308; Platania P., 2010, 37 C PLASM PHYS DUBL, P128; PORKOLAB M, 1978, NUCL FUSION, V18, P367, DOI 10.1088-0029-5515-18-3-008; Segui JL, 2005, REV SCI INSTRUM, V76, DOI 10.1063-1.2140225; USHIGUSA K, 1989, NUCL FUSION, V29, P1052, DOI 10.1088-0029-5515-29-6-015; van Houtte D, 2004, NUCL FUSION, V44, pL11, DOI 10.1088-0029-5515-44-5-L01; Wallace GM, 2011, NUCL FUSION, V51, DOI 10.1088-0029-5515-51-8-083032; Wallace GM, 2010, PHYS PLASMAS, V17, DOI 10.1063-1.346566256
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
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
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