1,720,958 research outputs found
On the relation between surface waves on a bubble and the subharmonic combination-frequency emission
No full textThe characterisation of bubbles using a two-frequency excitation technique is known to accurately detect and size certain bubble samples. This is done through the generation of a signal at Wi ± Wp/2 when the bubble is insonified by a fixed MHz imaging signal Wi and a variable pumping frequency, Wp , tuned to the bubble's resonance. Recent work has suggested that the principal mechanism for the generation of the Wi ± Wp /2 signal is linked to the onset of surface waves on the bubble's surface This paper strengthens this argument through the comparison of published experimentally measured thresholds for the Wi ±Wp /2 signal with recent theoretical models which predict the driving sound field pressure amplitudes required for the onset of surface waves on a spherical surface
Acoustic detection of gas bubbles in a pipe
No full textThis report describes an acoustic system designed to detect gas bubbles in a pipe. The system makes simultaneous use of multiple techniques for detection and sizing; these include six resonance-based indicators, as well as off-resonance scattering. The abilities of these acoustic indicators to detect, size and count bubbles are compared. It was envisaged that using several simultaneous bubble detection techniques would compensate for restrictions inherent in the isolated use of individual techniques. For example, whilst geometric scattering tends to be more successful at locating bubbles than sizing them, the converse tends to hold for techniques which exploit the bubble resonance. In the latter case, the greater the tolerance allowed in the estimation of the bubble size from the measured resonance frequency, the more approximate may be the conversion algorithm. Single bubbles tethered to a wire in the pipe, and a freely rising stream of similar size bubbles, are examined. Results measured in these two cases are presented to indicate the potential of the location and sizing techniques. The effect on bubble resonance frequencies of confining the bubble in a pipe is considered in detail. Standard interpretations of bubble resonances in terms of bubble size assume free-field conditions, and require modification for the pipe environment. The necessary corrections are presented for the frequency range below the first transverse acoustic resonance of the pip
Comparison of the abilities of eight acoustic techniques to detect and size a single bubble
No full textThis paper details the preliminary results from the Characterisation Of Bubbles Using Simultaneous Techniques (COBUST). There are a range of acoustic techniques for characterising bubble populations within liquids. Each technique has limitations, and complete characterisation of a population requires the simultaneous use of several, so that the limitations of each find compensation in the others. Eight acoustic signals were scattered from a single bubble to determine how easily and accurately they can, individually or together, measure the bubble size
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
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