1,720,955 research outputs found
Unsteady slot suction from a high-Reynolds-number cross-flow
No full textThe problem of unsteady suction from a high-Reynolds-number cross-flow into a slot is considered in the case where the suction is driven by a time-dependent slot pressure. The model uses linearised asymptotics based on a small parameter that defines the suction strength. An integro differential equation is derived for the mass flow into the slot and this is solved for various time-dependent slot pressures of practical interest. Closed-form expressions are also found for the shape of the shear layer dividing the external flow from the fluid in the slot. For a step function change in the slot pressure, a non-monotonic decay to the steady solution is observed, and for an oscillatory slot pressure there is a phase lag between the slot pressure and the mass flow. For rapidly changing slot pressures it is shown that slot injection can occur, even when the slot pressure remains below the free-stream pressure
A high-Reynolds-number cross-flow with injection and suction
No full textThe effect upon a high-Reynolds-number cross-flow of an upstream injection slot and a downstream suction slot of given geometries and strengths is examined. It is shown that the problem may be reduced to a single nonlinear singular integrodifferential equation. It transpires that, in the resulting flow, a total of five different regimes may be identified. For critical suction, the suction strength is just sufficient to reingest all of the previously injected flow. For weaker suctions, the flow is either subcritical, in which case the injected flow that cannot be reingested forms a layer downstream of the suction slot, or subsubcritical, in which case the lowpressure region produced by the injection is of sufficient strength that the ‘suction’ slot exhausts, rather than ingests, fluid. For suctions stronger than the critical value, the flow is supercritical, and the suction slot ingests some of the cross-flow as well as the previously injected flow, leading to an order-of-magnitude increase in the mass flow into the slot. Finally, for supersupercritical flow, when the suction strength is an order of magnitude larger than in cases previously considered, the injection slot is effectively absent and the mass flow into the slot once again jumps by an order of magnitude. In each case the equation governing the flow is solved asymptotically and numerically. Some limiting cases are also identified in which closed-form solutions may be determined
On the unsteady motion of two-dimensional sails
No full textAn equation is derived to describe the motion of a two-dimensional inextensible sail at a small, time-dependent, angle of incidence to a uniform two-dimensional flow. The equation derived is a singular partial integro-differential equation, which in the steady case reduces to the sail equation of Voelz. A number of limiting versions of the equation are derived and analysed for cases where the relative mass of the sail is large or small. For general unsteady sail motions the governing equation must be solved numerically. A scheme is proposed that employs Chebyshev polynomials to approximate the position of the sail; ordinary differential equations are derived to determine the relevant Chebyshev coefficients and a number of examples are illustrated and discussed. It is found that in some cases where the angle of attack changes sign the tension may become large; in these instances the underlying physical assumptions of the model may be violated
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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