1,721,035 research outputs found
Experimental Characterization of FEEP Emitters
No full textThe FEEP thruster is presently considered for several scientific missions requiring micrnnewton-level thrust and very accurate thrust modulation capability. In particular, FEEP is baselined for the drag-free control of LISA, the multi-spacecraft gravitational wave antenna included as a Cornerstone mission in the ESA Horizon 2000 Plus Pmgramme. Recently, the performance of a family of FEEP emitters operating in the thrust range of the LISA drag-free control system (1-100 microN) was investigated at Centrospazio under ESA funding. Performed tests included a detailed analysis of the thruster dynamic response to voltage variations, together with stability and resolution investigations. These were the first tests of this kind ever made on FEEP thrusters. Several unforeseen features of FEEP operation were highlighted, most notably the fact that the thruster response presents considerable overshoot and settling time in the 1-20 microN lhrust range. This phenomenon is almost absent at higher thrust levels. As a result of this work, the first systematic collection of FEEP performance data was gathered. This is an important step towards the final development of an unique mlcronewton-level thruster
Experimental Performance of Field Emission Microthrusters
No full textThis paper presents the results of a series of tests performed on a set of field emission electric propulsion (FEEP) emitters, including recording of the current/voltage characteristic curves and ion beam scanning with electrostatic probes, This work was aimed at collecting reliable, systematic thruster performance data to be used as a basis for the definition of a reference thruster mathematical model (not reported here). Four FEEP emitters with three different slit height values were tested. Thrust produced covered the 1-170 uN range. Repeatability of thruster performance was found to depend on the degree of wetting of the emitter slit and on the presence of glow discharge between the electrodes. The latter represented an undesired effect and was therefore eliminated after the first series of experiments. Wetting, on the contrary, proved to be of the utmost importance. In some cases, thruster performance improved by up to as much as 150% within a few days of the beginning of the test, as a result of enhanced slit wetting
Capire il territorio: paesaggio, agricoltura e tutela ambientale in penisola sorrentina.
Get PDFAbstract.
The Lattari mountains and the territory of the Sorrento-Amalfi peninsula constitute a very steep mountain structure with a high hydrogeological risk. This physical structure was determinant for the genesis of the climate and the development of biotopes. In a similar way, it has conditioned the development of the human community by the affirmation of autarchic economies and a very varied and rich agriculture. Unfortunately, in recent times, the abandonment of niche agricultural practices risks not only causing the loss of a traditional economy but also damaging the landscape and geological stability. Only new policies for the protection of ancient crops will be able to guarantee a balanced and sustainable future for the peninsula
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
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
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