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Raw Force-Deformation and Volumetric data for paper "Influence of the Poisson effect on the stress dependence of the elastic moduli of soil"
No full textThis dataset includes the raw data for the isotropic sphere compressions as used in the paper "Influence of the Poisson effect on the stress dependence of the elastic moduli of soil" by Stephanos Constandinou and Kevin Hanley (https://doi.org/10.1680/jgele.21.00135). More information is included in the ReadMe.txt file
Contact models for discrete element method simulations of non-spherical particles
Get PDFComputational modelling of granular systems has increased significantly in recent years, particularly using the Discrete-Element Method (DEM), a simulation tool proposed by Cundall & Strack (1979). In the most common implementation of DEM, particles are modelled as rigid bodies, for which the deformations at the contact points are captured by permitting overlaps between the interacting particles. These correlations between force and overlap are referred to as 'contact models'.
Particles in 3D DEM simulations are generally modelled as spheres because of their computational simplicity. Particle shape though is an important factor, causing a major increase in scientific interest in DEM modelling of non-spherical particle systems. One of the greatest limitations of using non-spherical particles in DEM modelling is the lack of appropriate mathematical relationships between the contact force and interparticle overlap. For this reason, contact models suitable for spheres are usually adopted which is not physically justifiable.
One of the most common methods of emulating non-spherical granules is the Multi-Spherical (MS) approach, where a number of spheres are 'glued' together in a cluster in order to construct a more complex shaped granule. Such an approach, however, leads to two sources of errors: (i) the contact model error arising from adopting a contact model suitable for individual spheres and (ii) the shape approximation error arising from modelling a specific desired particle shape using a finite number of spheres. Taking spherocylinders as an exemplar shape, a Finite Element Analysis (FEA) study was conducted to quantify both sources of errors. The study focused on the force responses obtained from the uniaxial compression of spherocylinders and the collisions between two identical spherocylinders. It should be noted that only the normal contact forces are considered in this thesis and any tangential interactions were disregarded.
For the contact model error, the rods used in the tests consisted of three spheres and had a variable aspect ratio by adjusting the sphere overlaps between the constituent spheres. The force response comparison was performed between the FEA results of MS rods and the results that would have been obtained in a DEM setting when different contact models were applied. A number of contour plots were generated showcasing the errors of 3 different contact models: Hertz, Hooke, Tatara. For the shape approximation error all granules tested had a fixed aspect ratio of 3:1. The force response comparison was performed entirely using FEA where the force responses of MS rods with a variable number of spheres was compared against that of a perfect spherocylinder. A number of contour plots were generated showcasing the errors as the number of constituent spheres increases. The results indicate that the MS approach with spherical contact models should generally be avoided for contact overlaps exceeding 1.5% of the constituent spheres' diameters. Additionally, while greater sphere overlaps mean more accurate shape representation, sphere overlaps of 60% should not be exceeded if contact models designed for spheres are to be used.
Going beyond distance-overlap based contact models, two volume-overlap based contact models were evaluated by performing indentation tests on a spherical granule with different shaped indenters using FEA. The energy-conserving model proposed by Feng (2021c) [Feng, Y. T. (2021c). An energy-conserving contact theory for discrete element modelling of arbitrarily shaped particles: Contact volume based model and computational issues. Computer Methods in Applied Mechanics and Engineering 373, 113493, doi: 10.1016/j.cma.2020.113493] cannot be recommended for practicality reasons. A linear volume-based model though seems like a better alternative since the stiffness index constant k is independent of the contacting bodies' shapes according to the FEA conducted. However, both models rely on calculating an accurate contact volume overlap which is difficult to obtain for arbitrary shapes and not in good agreement with the deformed volume obtainable from FEM.
Finally, the influence of the Poisson effect on the stress dependence of the elastic moduli of soil was examined. Hertzian spheres neglect the Poisson effect, so it was examined whether this omission contributes to the inability of smooth-sphere DEM simulations to correctly capture the stress dependence of the elastic moduli of soil. This was done by isotropically compressing a spherical granule of silica sand using FEM. At low-to-moderate confining stresses the Poisson effect had a measurable but very limited influence. It was found that the Poisson effect became significant only at confining stresses on the order of 100 MPa. Thus, at lower stresses, rough-surface contact models remain the most justifiable way to match the stress–stiffness response measured in laboratory testing using DEM simulations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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