1,720,963 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
Random walk models of turbulent dispersion
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.An understanding of the dispersion of contaminants in turbulent flows is important in many fields ranging from air pollution to chemical engineering, and random walk models provide one approach to understanding and calculating aspects of dispersion. Two types of random walk model are investigated in this thesis. The first type, so-called "one-particle models", are capable of predicting only mean concentrations while the second type, "two-particle models", are able to give some information on the fluctuations in concentration as well. Many different one-particle random walk models have been proposed previously and several criteria have emerged to distinguish good models from bad. In this thesis, the relationships between the various criteria are examined and it is shown that most of the criteria are equivalent. It is also shown how a model can be designed to (i) satisfy the criteria exactly and (ii) be consistent with inertial subrange theory. Some examples of models which obey the criteria are described. The theory developed for one-particle models is then extended to the two-particle case and used to design a two-particle model suitable for modelling dispersion in high Reynolds number isotropic turbulence. The properties of this model are investigated in detail and compared with previous models. In contrast to most previous models, the new model is three-dimensional and leads to a prediction for the particle separation probability density function which is in agreement with inertial subrange theory. The values of concentration variance from the new model are compared with experimental data and show encouraging agreement.Meteorological Offic
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
Scalar transport in turbulent shear flows
No full textTurbulent diffusion can be defined as the study of how a fluid in turbulent motion transports foreign substances that it contains. There are many examples, including smoke, acid rain, and other pollution in the atmosphere, salt in the sea and estuaries, and hot water in factory cooling systems. The foreign substance may have properties (especially its density and overall volume) that affect the motion of the ambient fluid, but it is often the case that the contaminant (as the foreign substance will be called in these lectures) is passive, i.e. the motion of the ambient fluid is the same as it would be in the absence of the contaminant. In practice nearly all cases of atmospheric dispersion fall into this category, as do many industrial applications. On the other hand the presence of dissolved salt has a profound effect on the behaviour of estuaries. These lectures will deal primarily with passive contaminants, although much of what is said applies qualitatively or, sometimes with minor modifications, even quantitatively to non-passive diffusion.
Host fluid flows are, in practice, incompressible, i.e. the density of each fluid element is invariant during the motion (or can be regarded as invariant for all practical purposes). Variations of density from fluid element to fluid element are, of course, quite consistent with incompressible behaviour (e.g. in the atmosphere), but they will not be relevant in these lectures. The ambient fluid will therefore be taken as having constant uniform density p. The velocity field at position x and time t in the ambient fluid will be denoted by T(x,t), where (by incompressibility).........
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
Air pollution modelling for environmental impact assessment
No full textThe aims of the lectures are:
(i) to explain what concentration fluctuations are;
(ii) to illustrate their importance in environmental impact assessment;
(iii) to discuss some factors relevant to the quantitative description of concentration fluctuations;
(iv) to describe a framework for this description.
It will be clear from the lectures, and from others later in the Workshop that there is rapidly increasing awareness of the importance of concentration fluctuations and, consequently, much research activity into their properties. Not surprisingly there are still many unsolved problems, and a by-product of the lectures will be to highlight one or two of the most important
- …
