1,721,773 research outputs found
Diagnostics and control of fusion-fission hybrid tokamak-based reactors: The technology for measurement systems
No full textA fusion-fission hybrid (FFH) reactor is a complex machine, which includes a tokamak fusion neutron source and two blankets: the tritium regeneration and the actinide burner zones. These three systems need their own diagnostics and controls. Problems associated with the implementation and integration of control systems call for a simplified technology. In this paper, the criteria determining the diagnostics needs of FFH reactors are reviewed bearing in mind the requirement that the measurements systems should be simple and robust, and their number be limited, considering the space occupied by the blankets. The diagnostics for the tokamak neutron source, including the machine protection and burn control are among the basic equipment. As the fusion and fission blankets can be integrated in a single subsystem their diagnostics must be conceived as an integrated package that includes the means for measuring isotope content, neutron multiplication and effective reactivity of the fission blanket, as well as tritium regeneration in the breeding blanket. The most recent technological developments the field of neutron spectroscopy for fusion and fission blankets are presented, including the diamond and self-powered neutron detectors technology
Photon detectors for epithermal neutron scattering at high-ω and low-q
No full textInelastic epithermal neutron scattering at high energy ((h) over bar
omega >= 1 eV) and low wave vector (q <= 10 angstrom(-1)) transfers is
the unique technique for the investigation of high-energy excitations in
a variety of systems, ranging from magnetic materials to semiconductors.
The key issue in order to make these measurements feasible on inverse
geometry spectrometers, is to develop suitable detection systems for
neutrons in the energy range 12100 eV: The Resonance Detector
Spectrometer configuration has to be considered as the most promising
approach for electron Volt neutron spectroscopy. This configuration will
be employed in the new low angle detector bank, VLAD, planned for
VESUVIO spectrometer operating at ISIS source. (C) 2004 Elsevier B.V.
All rights reserved
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
Comparison of Cadmium-Zinc-Telluride semiconductor and Yttriuim-Aluminum-Perovskite scintillator as photon detectors for epithermal neutron spectroscopy
Full text linkThe range of applications of epithermal neutron scattering experiments has been recently extended by the development of the Resonance Detector. In a Resonance Detector, resonant neutron absorption in an analyzer foil results in prompt emission of X- and grays which are detected by a photon counter. Several combinations of analyzer foils and photon detectors have been studied and tested over the years and best results have been obtained with the combination of a natural uranium and (i) Cadmium–Zinc–Telluride (CZT) semiconductor, (ii) Yttrium–Aluminum–Perovskite (YAP) scintillators. Here we compare the performance of the CZT semiconductor
and YAP scintillator as Resonance Detector units.
Two Resonance Detector prototypes made of natural uranium foil viewed by CZT and YAP were tested on the VESUVIO spectrometer at the ISIS spallation neutron source. The results show that both YAP and CZT can be used to detect epithermal neutrons in the energy range from 1 up to 66 eV. It was found that the signal-to-background ratio of the measurement can significantly be
improved by raising the lower level discrimination threshold on the g energy to about 600 keV. The advantages/disadvantages of the choice of a Resonance Detector based on YAP or CZT are discussed together with some potential applications
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
Development of resonant detectors for epithermal neutron spectroscopy at pulsed neutron sources
No full textNew perspectives for epithermal neutron spectroscopy are opened by the
development of new detectors for inverse Geometry time of flight
spectrometers at pulsed neutron sources. One example is the Very Low
Angle Detector (VLAD) bank planned to be delivered, within the next 4
years, within the eVERDI project, on the neutron spectrometer VESUVIO.
at the ISIS pulsed neutron source (UK). VLAD will extend the (q,omega)
kinematical region for neutron scattering to low wavefactor transfer (q
< 10Angstrom(-1)) still keeping energy transfer > 1 eV, thus allowing
the investigations of new experimental studies in condensed matter
systems. The technique being developed for detection of epithermal
neutrons, within this low q and high-energy transfer region, is the
Resonance Detection Technique. In this work, the state of the detector
development will be presented with special focus on the results obtained
with some prototype detectors. namely YAP scintillators and
cadmium-zinc-telluride semiconductors. (C) 2003 Elsevier B.V. All rights
reserved
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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