1,723,481 research outputs found
NDT for the diagnosis of modern, historical and archaeological structures
Full text linkThis thesis has been developed with the aim to explore thoroughly potential and limit of the GPR and ERT methods for monitoring heterogeneous structures where different construction materials are combined together.
Firstly we analysed the GPR response, in various construction materials related to different modern, historical or archaeological structures. In particular, three real examples were investigated during the thesis, namely: the Pyramid of Caius Cestius, the Passage of Commodus and the Colle Oppio Ninpheum, all in Rome. According to the different types of material and frequency antennas, different GPR responses and therefore dissimilar degree of resolution and of attenuation was obtained.
In light of this, the interposition between the surface of the investigated medium and the GPR antenna of a dielectric material (e.g. Plexiglas) was performed in order to improve the resolution.
Furthermore, an application of the GPR and ERT methods for monitoring a load test executed on masonry samples was presented. This panels were built up in the laboratory controlled conditions using tuff and bricks (widespread materials employed in Italy for decades for masonry buildings) and also were reproduced in the phase of theoretical modeling. The laboratory samples are reinforced with a conductive fibre fabric, where a high-conductive material (steel wires) is combined together with a dielectric material (basalt fibre).
In order to improve the sample-antenna coupling in the presence of conductive reinforcements, a Plexiglas (polimetilmetacrilato - PMMA) plate was added underneath a 2 GHz antenna. GPR data were acquired along profiles spaced 0.1 m apart and ERT measurements were executed on a 0.1 m regular spaced grid with a dipole-dipole array operating in a three-dimensional configuration. GPR datasets were also analysed in non-conventional mode, by means of the picking of the reflection time of the EM wave from the rear face of the wall samples.
Results show that GPR and electrical resistivity tomography were both able to detect fractures and weakness zones caused by the load application, even though with a higher resolution for the georadar with respect to the geoelectrical method. Moreover, mapping the GPR data in terms of the dielectric constant and mean absolute amplitude is particularly diagnostic to detect the effective fracturing pattern, after the application of the diagonal load. Therefore, GPR and ERT methods can reduce the degree of uncertainty in the detection of fractures, voids or cavities, with respect to the standard processing, by the combined analysis of radargrams, time-slices and resistivity ERT models.
Furthermore, for the GPR laboratory data acquired directly on the reinforced face of samples, it is demonstrated how interposing a layer of dielectric material between the antenna and the structure can substantially improve the antenna coupling and consequently the capability to detect fractures and to reach the rear face of the sample, despite losing resolution in the case of shallow high-conductive layers.
Finally, three-dimensional synthetic simulations on the same samples validate the experimental evidences. Therefore, we demonstrate that this approach can be a reliable tool to monitor static load tests and it can be further extended to the whole load cycle (before, during and after the experiment)
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
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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