1,720,968 research outputs found
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
High Repetition-Rate Laser-Driven Particle Generation – Towards High Flux Fast Neutron Sources
Get PDFHigh-flux, high repetition-rate pulsed neutron sources are of interest for probing studies such as neutron-induced damage processes in materials employed and considered for shielding purposes in fusion reactors.
Simulating the effect an intense neutron flux has on such materials will ultimately guide designs for future fusion reactors. Laser-driven neutron sources employing petawatt laser systems show great potential to fulfill the need for such a neutron source. One of the most common approaches for neutron generation utilizing lasers as drivers is the pitcher–catcher geometry in which a directional ion beam is generated from a pitcher target and impinges on a catcher target producing neutrons through nuclear reactions within the catcher material. Despite the fact that neutron generation using such setups have only recently gained attention, it has so far shown the highest neutron yields using short-pulse lasers. To date, experiments predominantly studied neutron generation on a single shot basis, especially since the development of a high repetition-rate laser-driven neutron source faces a variety of challenges.
In this thesis, the individual components of a successful high repetition-rate laser-driven neutron source were investigated and developed. The focus of this work was especially the development of a stable target
system compatible with high repetition-rate laser operations, the development of a design for the catcher target, allowing for optimization of ion beam-catcher overlap, and an efficient ion and neutron beam detection platform.
For this work, a robust version of the SLAC-developed converging liquid microjet target delivery systems was designed and fielded. This system was successfully implemented at two different laser facilities, surviving
more than 1000 shots on target with no apparent damage to the nozzle or degradation of the liquid target. The liquid microjet system was implemented to study high repetition-rate deuteron acceleration from heavy water microjet targets at the ALEPH laser facility reaching average fluxes of 1×10^12 deuterons/sr/min at a repetition rate of 0.5 Hz. Stable deuteron acceleration over 60 shots was observed at varying laser energies on target, suggesting a more favorable scaling of the ion beam cut-off energy than currently established in the literature.
A flexible, repetition-rate compatible neutron generation platform was designed around a stackable catcher target, which can be adjusted based on laser parameters and experimental conditions. This specific design aims at enhancing the generation of high-flux, directional neutron beams. A flexible detector setup simultaneously monitors the ion and neutron beam emission characteristics to study their individual shot-to-shot parameter changes and the correlations between them. Employing cryogenic or ambient-temperature liquid jet targets as a pitcher enables high-repetition-rate operation.
This novel platform was successfully tested using cryogenic liquid deuterium jet targets at the Texas Petawatt laser facility demonstrating efficient generation of forward directed neutron beams with fluxes reaching 7.2×10^9 neutrons/sr within a narrow divergence angle of ±20◦. As such, this work lays the foundation for future high-repetition-rate experiments towards pulsed, high-flux, fast neutron sources for radiation-induced effect studies relevant for fusion science and applications that require neutron beams with short pulse duration for the probing of fast evolving processes complementary to X-rays
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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