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Erratum: Loading-unloading hysteresis loop of randomly rough adhesive contacts (Physical Review E - Statistical, Nonlinear, and Soft Matter Physics (2015) 92 (062404))
No full textThis corrects the article DOI: 10.1103/PhysRevE.92.062404
Loading-unloading hysteresis loop of randomly rough adhesive contacts
Full text linkWe investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough
profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave vectors.
A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged,
and the calculated contact area and applied load are shown as a function of the penetration, for loading and
unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis
loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der
Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in
metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical
properties and the energy of adhesion on the hysteresis process
Strength of anisotropy in a granular material: Linear versus nonlinear contact model
No full textIn this paper, we deal with anisotropy in an idealized granular material made of a collection of frictional, elastic,
contacting particles. We present a theoretical analysis for an aggregate of particles isotropically compressed
and then sheared, in which two possible contacts laws between particles are considered: a linear contact law,
where the contact stiffness is constant; and a nonlinear contact law, where the contact stiffness depends on the
overlapping between particles. In the former case the anisotropy observed in the aggregate is associated with
particle arrangement. In fact, although the aggregate is initially characterized by an isotropic network of contacts,
during the loading, an anisotropic texture develops, which is measured by a fabric tensor.With a nonlinear contact
law it is possible to develop anisotropy because contacting stiffnesses are different, depending on the orientation
of the contact vectors with respect to the axis of the applied deformation. We find that before the peak load is
reached, an aggregate made of particles with a linear contact law develops a much smaller anisotropy compared
with that of an aggregate with a nonlinear law
DEM simulation of anisotropic granular materials:elastic and inelastic behavior
Full text linkIn this work, Discrete Elements Method simulations are carried out to investigate the effective stiffness of an assembly of frictional, elastic spheres under anisotropic loading. Strain probes, following both forward and backward paths, are performed at several anisotropic levels and the corresponding stress is measured. For very small strain perturbations, we retrieve the linear elastic regime where the same response is measured when incremental loading and unloading are applied. Differently, for a greater magnitude of the incremental strain a different stress is measured, depending on the direction of the perturbation. In the case of unloading probes, the behavior stays elastic until non-linearity is reached.Under forward perturbations, the aggregate shows an intermediate inelastic stiffness, in which the main contribution comes from the normal contact forces. That is, when forward incremental probes are applied the behavior of anisotropic aggregates is an incremental frictionless behavior. In this regime we show that contacts roll or slide so the incremental tangential contact forces are zero. Graphical Abstract: [Figure not available: see fulltext.].</p
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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