1,720,962 research outputs found
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
Models of flow and diffusion: I : Selective withdrawal from a stratified fluid II: Dispersal of hydrogen in the retina
Get PDFThis dissertation is divided into two parts. In the first part we investigate the withdrawal of fluid from a region of fluid with the outlet situated at an arbitrary location. A model for the dispersal of hydrogen released into the retina in an attempt to estimate blood flow in the eye is considered in the second part.
In the first part, the flow induced by a line sink at an arbitrary location in a fluid of finite depth with a free surface, relevant to flows in reservoirs, lakes and cooling ponds, is examined. A rigid-lid solution for small flow rates is obtained and a numerical method based on fundamental singularities techniques is applied to the full nonlinear problem. Both linear and numerical steady solutions are obtained for the shape of the free surface and show good agreement. The results suggest that steady non-linear solutions are limited to flow rates below some critical value that depends on the sink location, the surface tension and the strength of the flow. A theorem has been proven regarding the behaviour of the fluid surface and some interesting surface shapes are obtained.
The two-dimensional steady flow of an inviscid fluid induced by a line sink located at an arbitrary location in a region of infinite depth is computed. The solution in the limit of small Froude number is obtained analytically, and numerically for the nonlinear problem. The asymptotic solution is found to have a property that if the horizontal location of the sink, xs 1 a second stagnation point forms on the free surface. This has implications for the design of outlets in dams and reservoirs. Numerical solution for the nonlinear problem confirms these properties. The effect of moving the sink horizontally has also been considered. The maximum Froude numbers at which steady solutions exist are computed and compared with previous work and the effects of surface tension are investigated.
Finally in this part, we examine the unsteady flow due to a line sink in a fluid of finite depth with surface tension where the sink is situated at an arbitrary depth and location. Here we focus on critical values of flow rate that lead to steady or drawn down surfaces and the transitions between the different cases. A solution to the un-steady, linear problem is derived using an integral equation technique. The unsteady, nonlinear equation is then solved numerically using a novel fundamental singularities method. The shape of the free surface is computed for a range of parameter values where the effects of surface tension are taken into account. The linear solution is shown to be in a good agreement with the full nonlinear solution until the depth becomes significant, at which point the nonlinearities become apparent and the two solutions begin to differ slightly. We will examine the behaviour of the flow when the fluid is stagnant and the sink is turned on suddenly. Initially, the free surface is pulled down everywhere regardless of Froude number, F , and surface tension, β, firstly, either near the wall, if the sink is close to the wall, or above the sink, in cases where the sink is situated further from the origin. If the Froude number, F , is large enough the initial dip will keep going until drawdown occurs. However, if the Froude number, F , is smaller, the central region rebounds upward and that leads to a more complicated situation where there are several possible outcomes. There are three general states at the breakdown point of the simulations. These are, evolution to a steady state, drawdown of the surface and something in between which may include breaking waves or splashes. In particular, we obtained critical drawdown values of F for a range of values of β, sink location, xs, and different layer depths, H.
In the second major part of the thesis, two mathematical models of advection and diffusion of hydrogen within the retina are discussed to assist in interpretation of the “Hydrogen clearance technique” that is used to estimate blood flow. The first model assumes the retina consists of three, well-mixed layers with different thickness, and the second is a two-dimensional model consisting of three regions that represent the layers in the retina. Diffusion between the layers and leakage through the outer edges are considered. Solutions to the governing equations are obtained by employing Fourier series and finite difference methods for the two models, respectively. The effect of important parameters on the hydrogen concentration is examined and discussed, and a formula is derived for the speed of travel of the bolus of hydrogen. The results contribute to understanding the dispersal of hydrogen in the retina and in particular the effect of flow in the vascular retina. It is shown that the predominant features of the process are captured by the simpler model, meaning that the predictions in experiments can be interpreted without detailed simulation
Modelling of withdrawal of a stratified fluid from a porous medium
Get PDFThe problem of withdrawal of fluid from a porous medium has many applications in reservoir engineering and aquifer sustainability. The extraction from layers of fluid of different density is of particular interest. When pumping begins in a phreatic aquifer, the interface between layers may draw down leading to undesirable (non-potable) water entering the outlet, or water entering an oil pipeline. We investigate the flow into a line sink or circular drain in a saturated porous medium containing a stratified fluid with either an interface between layers of different density or a free surface. Analytical techniques, spectral methods and full numerical calculations are used. The conditions under which the interface may draw down are studied by considering when steady, sub-critical flows exist and then examining unsteady flows that lead to the drawdown of the interface. In two dimensions, the critical solutions that appear to be the limiting steady flow in any given situation have been computed with both hodograph methods and a spectral method, with good agreement. The spectral method is then modified to consider unsteady flows and in particular the approach to a steady state or the drawdown of the interface. Critical flow parameters have been obtained. In three dimensions, the axisymmetric flow into a circular well is considered by extending the spectral method. Again, steady and unsteady problems were solved to find the critical flow parameters. Results obtained were compared with full numerical simulations via the COMSOLTM package, again with good agreement. In all situations, a strong relationship was found between the limiting steady flows and the drawdown of the interface.
The understanding gained in this work is important to issues of water quality in stratified aquifers
Intrusion flow into a density stratified resevoir
Get PDFSteady two-dimensional flows from an angled structure into a lake or a reservoir where the interface between the intrusion and the ambient fluid separates from a solid wall is considered. The fluid is assumed to be of finite depth and the incoming channel makes an angle _ with the horizontal axis. The problem is formulated using conformal mapping and integral equation techniques and the resulting problem is solved using a surface angle approach. The shape of the interface is computed for a range of entry angle and flow rate. Exact solutions are presented at a high flow rate and compared with the solutions to nonlinear problem. Solutions with waves are shown to exist on the interface at small flow rate and these are computed at very small entry angles using a physical plane method. The case in which the lake or the reservoir is stratified in density is also considered and separation height is determined for different values of the stratification. In all cases, the parameter space in which steady solutions exist is studied and limiting solutions are obtained. The results have implications for the design of efficient inflow structures for reservoirs and for water quality management
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
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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