1,721,105 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
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
Robustness for the Starting Point of Two Iterative Methods for Fitting Debye or Cole-Cole Models to a Dielectric Permittivity Spectrum
No full textCurve-fitting means the determination of the set of parameters that best fit the input data set as expressed by a given function that is usually non-linear. The paper addresses the curve fitting of Debye and Cole-Cole models to a dielectric permittivity spectrum. The success of a nonlinear curve fit heavily depends on the choice of the algorithm and how close the starting point is to the solution. For these reasons, two different algorithms, the Levenberg-Marquardt and the Variable Projection algorithms, were used for constrained optimization and compared, with particular reference to robustness with respect to the choice of the starting point of the reconstruction procedure. The dielectric spectrum of blood plasma with different glucose concentrations is taken as reference data and a Monte Carlo analysis was conducted to evaluate accuracy and precision in the two methods provided as the distance of the initial parameters from the true value's changes. In general, both algorithms with constraints on the parameters provide good results for practical situations, although the Variable Projection Algorithm has a greater computational burden for large data sets
Material Characterization via Microwave Spectroscopy: Singular Spectrum Analysis
No full textDetermining the characteristic of materials is of paramount importance in different branches of science since it provides information about the structure, chemical composition, and molecular processes in the matter. The problem consists in exploiting the dielectric spectrum to gain information about the dipolar strengths, the dielectric losses, and the correlation times of the relaxation processes present in the system. Looking for the DRT avoids drawbacks related to non-linear inversion, since the problem is linearly formulated, and does not require information about the model order. However, it entails to invert a Fredholm integral equation of first kind, a notoriously ill-posed problem. In this paper, by exploiting the dilationally-invariance nature of the operator, an appropriate transformation is used to obtain a convolutional-type operator. Analytical upper and lower bound of the SVD of the transformed operator are then established. This allows for an analytical prediction of how many singular values to maintain in the TSVD regularization, given a certain threshold
Inverse Scattering Problem with Multi-Frequency Data and Evanescent Wave as Incident Field
No full textThe inverse scattering problem is well known and studied in the literature, especially with far-zone data, i.e., with scatterers in the radiation zone. This paper addresses the near- zone inverse scattering problem with an evanescent wave as the illuminating field. In details, we studied the linearized near-field scattering operator for mono-dimensional inhomogeneous media from multi-frequency data in a 2D configuration. Using estab-lished mathematical results, the eigenspectrum of the operator is derived in closed form
Dielectric Models of Blood-Glucose Solutions: A Systematic Literature Review
No full textThe characterization of dielectric properties of blood-glucose (or similar) solutions is a tricky and critical element in the design, simulation, evaluation, and prototyping of microwave sensors for non-invasive glucose monitoring. Unfortunately, the extensive literature on dielectric properties of biological tissues—blood-glucose solutions in particular—is sometimes contradictory. The use of different materials, different frequency ranges, different glucose ranges, ad hoc assumptions, simplifications not always justified, different measurement techniques, different tissue models, different fitting algorithms often lead to divergent results and conclusions. This is confusing for those who do bibliographic research on the subject and are looking for experimental data to use in their projects and simulations. Therefore, we systematically reviewed, organized and presented the main knowledge available in the literature about blood-glucose models, to help researchers by providing them relevant information in one place. The systematic review of literature is conducted by applying the well-known and proven Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol, a trustworthy method for establishing the published state of the art of any given topic. After screening, ten models are selected and their main characteristics are summarized. The proposed research questions about the common trends in the results, the current gaps and the future directions of research are addressed. The main outcomes are the absence of any reference model shared by the scientific community and the need to deepen the physical and mathematical modeling of dielectric properties of biological tissues
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
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