1,720,991 research outputs found
Edge wrinkling in elastically supported pre-stressed incompressible isotropic plates
Full text linkThe equations governing the appearance of flexural static perturbations at the edge of a semi-infinite thin elastic isotropic plate, subjected to a state of homogeneous bi-axial pre-stress, are derived and solved. The plate is incompressible and supported by a Winkler elastic foundation with, possibly, wavenumber dependence. Small perturbations superposed onto the homogeneous state of pre-stress, within the three-dimensional elasticity theory, are considered. A series expansion of the plate kinematics in the plate thickness provides a consistent expression for the second variation of the potential energy, whose minimization gives the plate governing equations. Consistency considerations supplement a constraint on the scaling of the pre-stress so that the classical Kirchhoff-Love linear theory of pre-stretched elastic plates is retrieved. Moreover, a scaling constraint for the foundation stiffness is also introduced. Edge wrinkling is investigated and compared with body wrinkling. We find that the former always precedes the latter in a state of uni-axial pre-stretch, regardless of the foundation stiffness. By contrast, a general bi-axial pre-stretch state may favour body wrinkling for moderate foundation stiffness. Wavenumber dependence significantly alters the predicted behaviour. The results may be especially relevant to modelling soft biological materials, such as skin or tissues, or stretchable organic thin-films, embedded in a compliant elastic matrix
Localized bulging in an inflated hyperelastic tube: the effects of rotation, multi-layering and torsion
Full text linkIn this thesis, we start by considering a hyperelastic circular solid cylinder or tube that is rotating about its axis of symmetry with angular velocity ω. If the resultant axial force F is fixed, it is shown that the bifurcation condition for a solid cylinder or a tube that is shrink-fitted to a rigid circular cylindrical spindle is simply given by dω/dλz = 0, where λz is the axial stretch. When the spindle is absent (the case of unconstrained rotation), we also allow for the possibility that the tube is additionally subjected to an internal pressure P. It is shown that with P fixed, and ω and F both viewed as functions of the circumferential stretch λa and λz, the bifurcation condition for localized bulging is that the Jacobian of ω and F should vanish. The second part of the thesis studies localized bulging in an inflated bilayer tube under inflation and axial extension. Firstly, bulging prevention in a hyperelastic bilayer tube composed of the Gent material is investigated. We determine several critical parameter regimes where localized bulging disappears, when one layer (layer I) of the tube cannot bulge whereas the other part (layer II) can. Surprisingly, we find that localized bulging still occurs if the proportion of layer II exceeds a critical value, no matter whether it occupies the inner layer or outer layer. Secondly, we focus on the effect of modulus ratio between two layers on the bulge formation. If the thickness of the bilayer tube is specified, the composite tube is more stable when the stiffer part occupies the outer layer. Moreover, the critical volume ratio vcr as a function of the interfacial radius D has a maximum if s > 1 but a minimum if s > 1 but a minimum if s < 1, where s is the ratio of the shear modulus of the outer layer to that of the inner layer. Finally, we turn our attention to study the effect of torsion on the onset of localized bulging. When the twisting moment M is fixed, the bifurcation condition for localized bulging is that the Jacobian of the internal pressure P and the resultant axial force F should vanish. It is found that the onset of localized bulging can be delayed or removed when a torsion is applied to the tube
A study of mechanical and capillary bifurcation phenomena in soft elastic materials
Full text linkStress-induced pattern formations in soft elastic materials are bifurcation phenomena which can be localized or periodic. Certain localized pattern formations such as necking or bulging are associated with zero wavenumber, whereas periodic pattern formations such as wrinkling or buckling are associated with a strictly positive wavenumber. Whilst the near-critical behaviour of the periodic case is well understood, studies of the localized case have only recently gathered momentum, and are conceptually more challenging to undertake. Despite this, a remarkable amount of analytical progress can be made. We will highlight this generally underappreciated fact by studying theoretically the complete bifurcation behaviour of localized patterns, as well as the competition from periodic patterns, in elastic materials under various effects. Firstly, the bifurcation behaviour of soft incompressible hollow tubes under elasto-capillary effects is studied. Analytical bifurcation conditions for localized pattern formation are initially derived using established results from a prototypical problem. A linear bifurcation analysis then shows that an axi-symmetric zero wavenumber bifurcation mode is favoured over periodic modes for a range of boundary conditions and loading scenarios. A weakly non-linear analysis provides an explicit connection between this zero wavenumber mode and localized necking or bulging, and a phase-separation-like evolution of these localized patterns into a final Maxwell state is described analytically. The effect of material compressibility on localized pattern formation in soft cylinders is also studied analytically, and comparisons with recently published numerical simulation results are made. We then consider the formation of a self-contacting crease on the free surface of a compressed elastic half-space. This is a highly unique localized pattern since its inception is an inherently non-linear bifurcation phenomenon. Therefore, unlike localized bulging or necking, it is undetectable through a linear analysis. We derive a new analytical bifurcation condition for creasing by reformulating the analysis of a recent ground-breaking study
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
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
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