1,721,049 research outputs found
Numerical simulation of gravel unconstrained flow experiments: a comparison between DAN-3D and RASH-3D codes
No full textInfluence of bed curvature on the numerical modelling of unconstrained granular materials
No full textThis paper deals with the theoretical-numerical and experimental treatment of dry rock avalanches moving down a chute. Depth-averaged field equations of balance of mass and momentum as prescribed by Savage and Hutter (1991) are implemented in the RASH3D code. They describe the temporal evolution of the depth averaged velocity and the distributi0n of the avalanche depth. A Coulomb-type behavior of the mass is assumed. To incorporate the curvature effects of the bed, the centripetal acceleration term has been here implemented in the code.
Carried out experiments consist in the release of granular material on an inclined plane that is connected to a horizontal run-out zone through a sharp transition. Comparison of the experimental findings with the computational results proved that dropping the centripetal acceleration term can have the effect of leading to unverifiable error in the determination of the well fitted friction angle because the tuned parameter obtained for fitting a runout distance may be dependent on these local effects. In particular, an overestimation of the computed dynamic friction angle respect to its measured value is observed
Numerical modelling of a rock avalanche laboratory experiment in the framework of the "Rockslidetec" alpine project
No full textThis paper illustrates the results of a collaboration born among the authors, in the framework of the INTERREG IIIA ‘‘Rockslidetec’’ project, with the aim of studying rock avalanche propagation by means of physical and numerical modelling. The EPFL rock mechanics laboratory has carried out an experimental campaign. Tests consist in releasing unconstrained gravel flows on an inclined panel. One of the experiments has been simulated by the codes developed by the partners. The Cemagref code and RASH3D (Politecnico di Torino) are based on a continuum mechanics approach; EPAN3D (CETE) on a discrete approach. Cemagref results, although rather far from observations made on deposit morphology, reproduce quite well the travel distance, without any parameter calibration. RASH3D reproduces well the velocity of propagation of the rear and front of the mass, but less the final deposit shape. EPAN3D reproduces very well the final deposit but the calculations are based on the calibration of 11 parameters
Hollow cylinder tests on boom clay: Modelling of strain localization in the anisotropic excavation damaged zone
No full textBoom Clay is extensively studied as a potential candidate to host underground nuclear waste disposal in Belgium. To guarantee the safety of such a disposal, the mechanical behaviour of the clay during gallery excavation must be properly predicted. In that purpose, a hollow cylinder experiment on Boom Clay has been designed to reproduce, in a small-scale test, the Excavation Damaged Zone (EDZ) as experienced during the excavation of a disposal gallery in the underground. In this article, the focus is made on the hydro-mechanical constitutive interpretation of the displacement (experimentally obtained by medium resolution X-ray tomography scanning). The coupled hydromechanical response of Boom Clay in this experiment is addressed through finite element computations with a constitutive model including strain hardening/softening, elastic and plastic cross-anisotropy and a regularization method for the modelling of strain localization processes. The obtained results evidence the directional dependency of the mechanical response of the clay. The softening behaviour induces transient strain localization processes, addressed through a hydro-mechanical second grade model. The shape of the obtained damaged zone is clearly affected by the anisotropy of the materials, evidencing an eye-shaped EDZ. The modelling results agree with experiments not only qualitatively (in terms of the shape of the induced damaged zone), but also quantitatively (for the obtained displacement in three particular radial directions).© Springer-Verlag Wien 2012
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
In situ non conventional shear tests for the mechanical characterizationof a bimrock
No full textSix non conventional in situ shear tests were carried out in order to investigate the strength properties of the Shale Limestone Chaotic Complex bimrock at the Santa Barbara disused open-pit mine. The
testing procedure ensures that the failure surface is free to develop in a tortuous way along block/matrix contacts, thus allowing for the evaluation of the bimrock strength parameters by taking into account the influence of blocks, and ultimately to overcome the size limitation of laboratory specimens. The evaluated operative strength
parameters show an overall larger friction angle and a lower cohesion compared to that of the clayey matrix, in agreement with the common bimrock mechanical behaviour
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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