1,721,005 research outputs found
A hybrid microwave heterodyne receiver design for use in distributed fibre sensing of spontaneous Brillouin backscatter
No full textOptical fibre sensing has long made use of direct detection methods in order to detect a Brillouin backscatter signal which, due to its very nature, is able to divulge information pertaining to the temperature and strain being applied to an optical fibre over a distance of many tens of kilometres. As the resolution of both these measurands has improved, physical limits have been approached which have necessitated research into other forms of detection such as coherent detection. In this instance a weak backscatter signal is effectively amplified by an optical local oscillator signal generating a beat frequency at 11 GHz with all the information needed for temperature and strain sensing remaining ever present. This beat frequency is then detected before being subsequently analysed. At the University of Southampton previous work on this detection method has proved fruitful with the upshot being that research in this area is now being carried out both in an academic and industrial environment. The research conducted in this thesis takes what has been demonstrated in previous coherent detection of Brillouin backscatter at the University of Southampton and builds upon its weakest point, namely that of having a spatial resolution of only 20m as determined by the resolution bandwidth of the electronic spectrum analyser incorporated as the previous sensor's receiver. In order to improve this spatial resolution the electronic spectrum analyser has needed to be removed from the fibre sensor and to be replaced with purpose built microwave electronics in the form of a hybrid microwave heterodyne receiver. This has meant a stage of microwave heterodyning being incorporated via this new receiver in order to bring the 11GHz beat frequency down to a more amenable 1GHz second beat frequency, still with all the information necessary for temperature and strain sensing remaining on this signal. The subsequent incorporation of a bandwidth-tuneable bandpass filter centred at 1GHz has then allowed for improved spatial resolution to be observed. This 1GHz intermediate frequency was chosen as components at this frequency have better specifications in terms of noise figure and gain flatness than those at a higher frequency. Theoretical models have been developed for noise and signal to noise evaluation of this new optical fibre sensor both before and during construction. Results are highlighted in this thesis which demonstrate that the new hybrid receiver is efficient and powerful in its ability to improve the spatial resolution of the coherent optical fibre sensing technique. Simultaneous sensing of strain and temperature at a section 20km distant along a sensing fibre has demonstrated a temperature and strain resolution of <7.3K and <190µε when employing the sensor for 10m spatial resolution sensing together with <9.5K and <240µε when employing it for 4m spatial resolution sensing.</p
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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