1,720,971 research outputs found
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
Experimental Study of Air-Water Flow Properties on Low-Gradient Stepped Cascades
Full text linkStepped cascades are recognised for both aeration potential and energy dissipation, and have been employed in hydraulic structures for over 3,500 years. Yet little detailed information exists on their performance, especially pertaining to low-gradient cascades. This study presents a detailed investigation of both the macro and micro-scale flow properties on a low-gradient cascade (3.4 degree slope). Research is conducted on two large-size physical models: a 24m long multi-step cascade (10-2.4m long steps), and a single-step model with identical step height and length. The large size of the model allows near full-scale data acquisition under controlled flow conditions, minimising potential scale effects. The study comprises three distinct components: 1. A global investigation of the general flow properties of nappe flow on a low-gradient, multi-step cascade. Unforeseen three-dimensional characteristics of the flow, including supercritical shockwaves and sidewall standing-waves downstream of nappe impact, are identified and examined by the study. Although comparable to similar phenomena at channel bends and expansions, these have not been previously described on stepped cascades. Energy dissipation on the cascade is investigated, and is found to be over twice that observed for a smooth chute of similar gradient. 2. A complete characterisation of the air-water structure of flow in a nappe regime. Significant outcomes of the analysis include: - Air-concentration Distribution: The air-concentration distribution at the lower nappe of the free-falling jet shows good agreement with an analytical solution of the diffusion equation. The experimental results from the study, and a reanalysis of existing data, indicate a distinct relationship between the turbulent diffusivity in the shear layer and distance from the step brink. This contradicts earlier investigations that assumed constant diffusivity. Strong aeration of the flow, with a large volume of spray, occurs downstream of the nappe impact. Depth-averaged air concentrations of 40% to 50% are observed within the spray region, decreasing towards the downstream end of the step. -Velocity Distribution: A theoretical analysis of the momentum transfer process imparts an improved understanding of the momentum transfer and velocity redistribution within the free-falling jet. An analytical solution based on twodimensional wake flow is developed, superseding existing solutions based upon a monophase free-mixing layer. - Bubble-frequency Distribution: A quasi-parabolic relationship between bubble frequency and time-average air concentration across a cross-section is observed. A theoretical explanation for the parabolic relationship is developed, and two correction factors are introduced to provide a better representation of the experimental data. - Air-bubble and Water-droplet Size Distributions: Chord-length distributions are compared with standard probability distributions, showing good agreement with standard Weibull, gamma and log-normal probability distributions within various regions of the flow on the step. A computer model is developed to model interaction between a bubbly transition from water to air and fluctuations of the free surface. 3. A parallel investigation of the oxygen aeration efficiency of a stepped cascade. Measured air-water property data is used to calculate the air-water interface area in bubbly flow, and to estimate the theoretical aeration efficiency of the stepped cascade based upon the integration of the mass transfer equation. The aeration performance of the stepped cascade model is also measured experimentally in terms of dissolved oxygen content. This analysis allows a unique, successful comparison of experimental dissolved oxygen measurements with the numerical integration of the mass transfer equation
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
Stream Reaeration in Nonuniform Flow: Macroroughness Enhancement
Full text linkThe authors presented two papers that are a welcome addition to the topic of water quality and stream reaeration. The renewal theory and small eddy model provide interesting results for smooth and small-roughness channels. The discussers feel, however, that the second paper highlights some limits of the method, particularly when free-surface aeration takes place. The present discussion provides additional material on the problem of stream reaeration in the presence of 'whitewater' (i.e., air bubble entrainment). It complements the original paper, and some references are added, including large-scale data
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
Interfacial Aeration and Bubble Count Rate Distributions in a Supercritical Flow Past a Backward-Facing Step
Full text linkAn example of high-velocity open channel flows is a supercritical flow past an abrupt drop. In such a geometry, the basic air-water flow properties were measured, including distributions of void fraction and bubble count rate, and local air and water chord size distributions, at and downstream of the backward-facing step. The bubble count rate distributions were compared with a conceptual model of streamwise distribution of air and water chords which yields a quasi-parabolic relationship between bubble count rate and void fraction. The proposed model was an attempt to explain the experimental relationship between bubble count rate and void fraction, rather a meticulous breakdown of the complex air-water structure
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