1,720,976 research outputs found
Making Waves Round a Structured Cloak: Lattices, Negative Refraction and Fringes
Get PDFUsing the framework of transformation optics, this paper presents a detailed analysis of a non-singular square cloak for acoustic, out-of-plane shear elastic and electromagnetic waves. Analysis of wave propagation through the cloak is presented and accompanied by numerical illustrations. The efficacy of the regularized cloak is demonstrated and an objective numerical measure of the quality of the cloaking effect is provided. It is demonstrated that the cloaking effect persists over a wide range of frequencies. As a demonstration of the effectiveness of the regularized cloak, a Young's double slit experiment is presented. The stability of the interference pattern is examined when a cloaked and uncloaked obstacle are successively placed in front of one of the apertures. This novel link with a well-known quantum mechanical experiment provides an additional method through which the quality of cloaks may be examined. In the second half of the paper, it is shown that an approximate cloak may be constructed using a discrete lattice structure. The efficiency of the approximate lattice cloak is analysed and a series of illustrative simulations presented. It is demonstrated that effective cloaking may be obtained by using a relatively simple lattice structure, particularly, in the low-frequency regime
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
Mathematical modelling of the dynamic response of metamaterial structures
No full textThis thesis constitutes an exposition of the work carried out by the author whilst examining several physical problems under the broad theme of the dynamic response of metamaterial structures.
An outline of the thesis is provided in chapter one.
Chapter two introduces some notation and preliminary results on general lattice equations.
Chapter three examines the dispersive behaviour of non-classical discrete elastic lattice systems.
In particular, the effect of distributing the inertial properties of the lattice over the elastic rods, in addition to at the junctions, is considered.
It is demonstrated that the effective material properties in the long wavelength limit are not what one would expect from the static response of the lattice.
The effect of various interactions on the dispersive properties of the triangular cell lattice is considered, including so-called truss, frame, and micro-polar interactions.
Compact analytical estimates for the band widths are presented, allowing the design of metamaterial structures possessing pass and/or stop bands at specific frequencies and in specified directions.
The finite frequency response of several lattice structures is considered in chapter four.
In particular, the dynamic anisotropy of both scalar and elastic lattices is examined.
The resulting strongly anisotropic material response is linked, explicitly, to the dispersive properties of the lattice.
A novel application of dynamic anisotropy to the focusing, shielding, and negative refraction of elastic waves using a flat discrete "metamaterial lens'' is presented.
Chapter five is devoted to the analysis, using the dynamic Green's function, of a finite rectilinear inclusion in an infinite square lattice.
Several representations of the Green's function are presented, including expression in terms of hypergeometric functions, which are employed in deriving band edge expansions.
It is shown that localised defect modes, characterised by displacements which decay rapidly away from the defect, can be initiated by reducing the mass of one or more lattice nodes, whilst ensuring that the mass of the nodes remains positive.
For one- and three-dimensional multi-atomic lattices, there exists a bound on the contrast in mass between the defect and ambient lattice such that localised defect modes exist.
However, it is shown that for the two-dimensional lattice, no such bound exists, provided that the masses remain positive.
The analysis of a finite-sized defect region is accompanied by the waveguide modes that may exist in a lattice containing an infinite chain of point defects.
A numerical simulation illustrates that the solution of the problem for an infinite chain can be used to predict the range of eigenfrequencies of localised modes for a finite but, sufficiently long, array of masses representing a rectilinear defect in a square lattice.
Continuing with the theme of defects, chapter six examines response of a triangular thermoelastic lattice, with an edge crack under mode I loading.
The response of the triangular lattice is compared with that of the corresponding continuum.
The model is related to the phenomenon of thermal striping, which occurs when a structure is exposed to periodic variations in temperature.
In the thermal striping regime, crack propagation is a fatiguing processes with the rate of crack growth being proportional to some power of the peak-to-peak amplitude of the stress intensity factor.
An "effective stress intensity factor'' for the lattice is introduced and it is demonstrated that, in the homogenised limit, the "effective stress intensity factor'' is lower than the stress intensity factor of the continuum for sufficiently long cracks and low frequencies.
Finally, chapter seven presents a detailed analysis of a non-singular square cloak for acoustic, out-of-plane shear elastic, and electromagnetic waves.
The propagation of waves through the cloak is examined analytically and is complemented with a range of numerical illustrations.
The efficacy of the regularised cloak is demonstrated and an objective numerical measure of the quality of the cloaking effect is introduced.
The results presented show that the cloaking effect persists over a sufficiently wide range of frequencies.
To illustrate further the effectiveness of the regularised cloak, a Young's double slit experiment is presented.
The stability of the interference pattern is examined when a cloaked and uncloaked obstacle are successively placed in front of one of the apertures.
A significant advantage of this particular regularised square cloak is the straightforward connection with a discrete lattice.
It is shown that an approximate cloak can be constructed using a discrete lattice structure.
The efficiency of such a lattice cloak is analysed and several illustrative simulations are presented.
It is demonstrated that effective cloaking can be achieved by using a relatively simple lattice, particularly in the low frequency regime.
This discrete lattice structure provides a possible avenue toward the physical realisation of invisibility cloaks
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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