1,720,962 research outputs found
Design and experimental evaluation of a travelling-wave thermoacoustic refrigerator driven by a cascade thermoacoustic engine
No full textEffect of phase adjustment on the acoustic field of a cascade thermoacoustic engine
No full text This study set out to explore the influence of phase adjustment on the acoustic field of a cascade thermoacoustic engine. The system consists of one standing wave unit and one traveling wave unit arranged in series. The straight-line configuration allows suppressing a time-averaged mass flow or Gedeon streaming, which causes some unwanted convective heat transport and reduces the efficiency of the system. Theoretically, the regenerator of the traveling wave unit must be operated within the traveling wave phasing and high impedance region in order to achieve an efficient performance. The various techniques of phase adjustment by modifying the configurations and geometrical dimensions of the system are investigated both numerically and experimentally to adjust the position of the sweet spot as well as to achieve the high acoustic impedance in the regenerator. The effective tuning methods with less modification here are accomplished by changing the volume of the down-cavity and reducing the flow area of the down-resonator by inserting the pencil. However, the pencil insertion scheme causes an extra loss due to viscous dissipation that should be taken into account. The change of the down-resonator length has a strong effect on the acoustic field in the system. After the phase-adjustment schemes are completely implemented, the performance of the proposed system is significantly improved, in which the regenerator of the traveling wave unit operates within the traveling wave phase region with high acoustic impedance. This prototype operated with air at atmospheric pressure can supply acoustic power up to 33 W to the down-resonator, which is about 9.5% of Carnot efficiency. </jats:p
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
Evaluation of Random Stack Materials for Use in Thermoacoustic Refrigerators
No full textIn a thermoacoustic refrigerator, energy conversion between thermal and acoustic power is achieved by means of an oscillatory motion of a compressible fluid along a solid body referred to as “stack”. Traditionally, stacks have been most often made by arranging large number of thin plates at equal spacing to fill out the cross section of a thermoacoustic resonator. Other geometries such as circular pores, square or hexagonal pores (honeycombs) or pin-arrays can also be considered. Most common irregular geometry includes layers of woven wire mesh stacked along the resonator length. The advantages of thermoacoustic engines over other conventional energy conversion devices lie in their relatively simple hardware assembly, without the need for any dynamic sealing and lubrication. However, the fabrication of stacks, for example made out of very thin parallel plates, is usually costly and impractical, while using pre-fabricated stacks (e.g. ceramic catalytic converter substrates or honeycomb used in aerospace industry) has high materials costs, which limits the cost advantages of thermoacoustic engines. However, many of these problems could be avoided if irregular stack geometries made out of random (very often waste) materials could be used. There is a wide range of such candidate materials, including glass or steel wool, ceramic chippings, waste material from metal machining (swarf, Scourers), beds of glass or metal balls etc. However the main difficulty is the lack of experimental data characterising the performance of such stacks at the design stage. In this paper, the performance of a standing wave thermoacoustic refrigerator with a stack made of a few chosen random materials, is measured and compared to the one with a parallel plate stack. It is hoped that this work will be beneficial for developing low-cost thermoacoustic prime movers and heat pumps.</jats:p
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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