1,720,973 research outputs found
Characterization of damage evolution in non linear media by means of power law exponent: Modeling and experiments
No full textEffects of experimental configuration on the detection threshold of hysteretic elastic nonlinearity
No full textNonlinear elastic signature of granular consolidated or damaged media is often very small and might easily fall within the noise level. Therefore, it is important to determine an excitation amplitude threshold above which nonlinear measurements start to be meaningful. In this paper, we analyze the way this threshold is influenced by some parameters of the experimental configuration, such as the receiver position, and of the data analysis, such as the considered reference amplitude. Furthermore, this contribution shows that extracting absolute values of the nonlinear parameters often requires the a priori knowledge of the resonance structure of the mediu
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
Evidence of microstructure evolution in solid elastic media based on a power law analysis
No full textComplex and consolidated granular media or microcracked composites and metals usually exhibit a high level of nonlinearity in their elastic response already at low amplitudes of excitation. To quantify it, a proper nonlinear indicator y is introduced and its dependence on the excitation amplitude x is studied. The dependence of y on x is found in experiments to be a power law. Here we show that the different power law exponents measured for different materials could be predicted by proper classes of discrete models. An application is presented to link the exponent evolution and the changes of the microstructure due to the progression of damage mechanically induce
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
Edge detection combined with optical and infrared NDT techniques: an aid for wooden samples with complex surface and subsurface defects
No full textTo explore wood is to realize its complexity, its diversity, and its variability. The union of wood and paint is as
old as the human desire to protect an object, or simply to decorate a surface. The link between paint and wood is
therefore at the heart of any approach to conservation of these objects.
Panel paintings are increasingly being investigated using advanced non-destructive infrared and optical
measurement techniques. In the present work, a wooden sample having a complex surface and realized following
the Cennino Cennini rules, containing natural and fabricated defects (Mylar®
inserts), was investigated by
stimulated thermography, near-infrared reflectography, double-exposure (DE) and sandwich holographic (SH)
interferometry. The stimulated thermography technique consists in depositing energy, whatever be the means of
deposition and the type of energy (sun, flash lamp, laser, and hot air flow), into the observed system (in the
present case a wooden sample with complex surface and subsurface defects) and in monitoring the temporal
and/or local evolution of the surface temperature field of the system caused by this thermal stimulation. Infrared
reflectography is a non-destructive testing imaging technique based on the different optical behaviour of visible
and near-infrared (NIR) radiation through a thin pictorial layer. This effect is a consequence of both lower NIR
absorption and reduced NIR scattering due to the particle size smaller than the wavelength. The acquisition of
NIR images using LED lamps working at different wavelengths, seems a very promising method in this field.
However, NIR and DE are not dynamic techniques, while SH is a dynamic technique. In the latter, a number of
holograms can be made, each one recording a single state of the object, in a temporal sequence.
Since enhancing the edge of a detached area identified by SH, means improving the detection of the defect’s
position, this idea was applied in the present research. Instead, the defect’s depth was retrieved working with
phase analysis, i.e. using the pulsed phase thermography (PPT) technique.
Finally, the results coming from optical and infrared NDT techniques were compared each other in order to
explore the advantages and disadvantages of the methods used
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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