1,720,990 research outputs found
Calibration of micromechanical parameters to reproduce a frictional cohesive continuum by the distinct element method
No full textA new contact bond model based on the Mohr-Coulomb failure criterion has been implemented in PFC2D to reproduce the behaviour of frictional cohesive (c, φ) geomaterials. According to this model, the bond
strength can be clearly divided into two distinct micromechanical contributions: an intergranular friction angle and a cohesive bond force. A parametric analysis has been run to validate the proposed model and to calibrate the micromechanical parameters. Simple relationships between the macromechanical strength parameters (c, φ) and the corresponding micromechanical quantities have been obtained so that they can be used to model geotechnical boundary value problems with the DEM without need of further calibration
DEM analysis of bonded granular geomaterials
No full textIn this paper, the application of the distinct element method (DEM) to frictional cohesive (c, ϕ) geomaterials is described. A new contact bond model based on the Mohr–Coulomb failure criterion has been implemented in PFC2D. According to this model, the bond strength can be clearly divided into two distinct micromechanical contributions: an intergranular friction angle and a cohesive bond force. A parametric analysis, based on several biaxial tests, has been run to validate the proposed model and to calibrate the micromechanical parameters. Simple relationships between the macromechanical strength parameters (c, ϕ) and the corresponding micromechanical quantities have been obtained so that they can be used to model boundary value problems with the DEM without need of further calibration.
As an example application, the evolution of natural cliffs subject to weathering has been studied. Different weathering scenarios have been considered for an initially vertical cliff. Firstly, the case of uniform weathering has been studied. Although unrealistic, this case has been considered in order to validate the DEM approach by comparison against analytical predictions available from limit analysis. Secondly, non-uniform weathering has been studied. The results obtained clearly show that with the DEM it is possible to realistically model boundary value problems of bonded geomaterials, which would be overwhelmingly difficult to do with other numerical techniques
On the optimal profile of a slope
No full textThe problem of determining the best profile for a c, φ soil slope is tackled, with reference to rigid rotational failure mechanisms. By means of limit analysis, upper bound values of collapse load are determined. A new mathematical function is derived to compute the external work made by the weight of a double spiral shaped soil region sliding away. It is found that a log spiral front is associated with a larger safety factor than a planar one. The obtained results may also explain the log-spiral shape of perimeter walls of some typical Japanese castles
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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