1,721,005 research outputs found
Fitting hyperelastic models to experimental data
No full textThis paper is concerned with determining material parameters in incompressible isotropic elastic strain–energy functions on the basis of a non-linear least squares optimization method by fitting data from the classical experiments of Treloar and Jones and Treloar on natural rubber. We consider three separate forms of strain-energy function, based respectively on use of the principal stretches, the usual principal invariants of the Cauchy-Green deformation tensor and a certain set of lsquoorthogonalrsquo invariants of the logarithmic strain tensor. We highlight, in particular, (a) the relative errors generated in the fitting process and (b) the occurrence of multiple sets of optimal material parameters for the same data sets. This multiplicity can lead to very different numerical solutions for a given boundary-value problem, and this is illustrated for a simple example
Computational aspects of Worm-Like-Chain interpolation formulas
No full textWe show that the polynomial Worm-Like-Chain (WLC) interpolation formula introduced in [C. Bouchiat, M.D. Wang, J.-F. Allemand, T. Strick, S.M. Block, V. Croquette, Estimating the persistence length of a Worm-Like Chain molecule from force-extension measurements, Biophys. J. 76 (1) (1999) 409-413] in order to improve data fitting with respect to the WLC interpolation formula in [C. Bustamante, J.F. Marko, E.D. Siggia, S. Smith, Entropic elasticity of lambda-phage DNA, Science 265 (1994) 1599. Technical comment] is not unique. Ill-conditioning of the over-determined linear system associated with interpolation of synthetic data from [C. Bouchiat, M.D. Wang, J.-F Allemand, T. Strick, S.M. Block, V. Croquette, Estimating the persistence length of a Worm-Like Chain molecule from force-extension measurements, Biophys. J. 76 (1) (1999) 409-413] is highlighted. Moreover, if the coefficients in the associated polynomial correction are considered as free parameters in the least squares fitting procedure for actual experimental data, then more than one solution with a low residual can be identified. For these reasons we propose modification of the interpolation formula in [C. Bustamante, J.F. Marko, E.D. Siggia, S. Smith, Entropic elasticity of lambda-phage DNA, Science 265 (1994) 1599. Technical comment] so that, for moderate extensions, quadratic contributions are included and no additional parameters are required. We show that relative errors for the fit of synthetically generated data are less than 2% and for actual data they are comparable with and sometimes better than those obtained by using polynomial WLC interpolation formulas
Shear Behavior of a Non-crimp 3D Orthogonal Weave E-Glass Composite Reinforcement
No full textIn this work, the deformability of a single layer E-glass non-crimp 3D orthogonal woven reinforcement is experimentally investigated.
The attention is mainly dedicated to the behavior during shear loading because this is considered the primary deformation mechanism in the reinforcement shaping. The mechanism occurring when the material is subjected to in-plane shear is studied by two different tests: bias
and picture frame. The nonlinear response of the material from both tests are compared in term of macroscopic shear force vs. shear strain. The shear deformation is observed and measured at the macroscale, to have the initiation of wrinkling phenomenon, as well as at the unit cell level to study sliding and rotation of the tows. For these
purposes, the tests are assisted by digital image correlation (DIC) technique
Straightening wrinkles
No full textWe consider the elastic deformation of a circular cylindrical sector composed of an incompressible isotropic soft solid when it is straightened into a rectangular block. In this process, the circumferential line elements on the original inner face of the sector are stretched while those on the original outer face are contracted. We investigate the geometrical and physical conditions under which the latter line elements can be contracted to the point where a localized incremental instability develops. We provide a robust algorithm to solve the corresponding two-point boundary value problem, which is stiff numerically. We illustrate the results with full incremental displacement fields in the case of Mooney–Rivlin materials and also perform an asymptotic analysis for thin sectors
On worm-like chain models within the three-dimensional continuum mechanics framework
No full textIn this paper, we review critically some basic models derived from the statistics of long chain molecules and then discuss the status of such models within the three-dimensional nonlinear theory of elasticity. We draw attention to some deficiencies of certain wormlike chain (WLC) models when viewed within the three-dimensional continuum mechanics framework. Modifications of the WLC models motivated by such considerations and avoiding these deficiencies are then discussed and shown to correspond well with data generated by the exact WLC model
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
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