1,720,992 research outputs found
An elastic–viscoplastic model with non-affine deformation and rotation of a distribution of embedded fibres
No full textreinforced by a distribution of fibres has been formulated. The fibre distribution is a symmetric positive-definite tensor with unit trace that is determined by an evolution equation. This evolution equation includes a competition between tendencies for affine evolution of the distribution and non-affine evolution causing the distribution to align with the elastic distortional deformation tensor or to become isotropic. Two elastic deformation measures are introduced associated with the fibre distribution. Specifically, non-affine measures of elastic distribution stretch and non-coaxiality of the distribution cause anisotropic stress response. The resulting model describes a number of effects relevant to growth and remodelling of biological tissues as well as to additive manufacturing of artificial materials. For example, the equations model the smooth transition from isotropic to anisotropic response seen in many biological tissues
A continuum model for granular materials exhibiting a smooth transition between inelastic flow and elastic jamming
Full text linkA continuum model for granular materials, which transitions from an elastic jammed phase to rapid flows, is developed using a large deformation Eulerian formulation for compressible elastic-viscoplastic response. The model incorporates constitutive functions capturing mu(I) rheology, the value of the solid fraction developed for steady-state shearing, and the transient response for shear reversal based on experiments and simulations of interacting particles using the Discrete Element Method (DEM). The present model exhibits hyperelastic response with the stress determined by measures of elastic dilatation and elastic distortional deformations. This causes the stress to naturally have a direction different from the rate of deformation tensor for transient response. Examples examine pure dilation, steady-state simple shear, transient shearing with shear reversal for constant volume and constant non-shearing components of stress, and the transient transition to jamming
Assessment of isotropic large-deformation elastoplasticity models with Lode angle dependence
Full text linkThis study aims at assessing formulations of large-deformation elastoplasticity dependent on the Lode angle. The focus is both on the accuracy of the predictions and on the computational efficiency. Although the analysis is limited to isotropic response and isochoric plastic deformation, the proposed assessment has required the extension of an Eulerian model relying on the left Cauchy-Green elastic strain, to include the influence of the Lode angle in the plastic rate tensor. Also, the computational algorithm for more commonly implemented models, derived by assuming the Bilby-Kröner-Lee multiplicative form of the deformation gradient and adopting the logarithmic strain measure, has been significantly improved by using a relatively accurate approximate derivative of the logarithmic strain. While the models implemented in this study assume hyperelasto-plastic behavior, the assessment also includes the hypoelasto-plastic model available in the commercial finite element code Abaqus. For all the specified constitutive equations, some numerical algorithms for small-deformation elastoplasticity can be used for finite deformations. Conclusions are drawn on the basis of some analysis and three benchmark problems, i.e. plane-strain cyclic shearing of a square block, necking of a circular cylindrical bar, and drawing of a bar with a rectangular cross-section. All these problems consider both von Mises plasticity and Tresca plasticity, the latter leading to significant differences among the models in terms of the Lode angle, mostly under plane-strain conditions. The main result is that the considered models overall provide similar engineering responses, but the numerical efficiency of the Eulerian model relying on the left Cauchy-Green elastic strain and the ease of its implementation have advantages over the other models
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
Bone pose estimation in the presence of soft tissue artifact using triangular cosserat point elements
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