1,720,997 research outputs found
Nonlinear modeling of carbon nanotube composites dissipation due to interfacial stick-slip.
No full textA nonlinear constitutive theory is proposed to describe and characterize the hysteretic elastoplastic response of nanocomposite materials caused by the inelastic shear stick–slip between carbon nanotubes and the surrounding matrix. The theory combines the mean-field homogenization method based on the Eshelby equivalent inclusion theory, the Mori–Tanaka homogenization approach, and the concept of inhomogeneous inclusions affected by inelastic eigenstrains. The shear stick–slip is accounted for as an incremental plastic eigenstrain in the inclusions. The evolution of the introduced plastic eigenstrain is regulated by a constitutive law based on a micromechanical adjustment of the von Mises function based on the interfacial stress discontinuity. Parametric studies show that the investigated carbon nanotube composites can exhibit superior damping capacities by determining optimal nano/micro-scale constitutive parameters to maximize the nanofrictional energy dissipation
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
On the hysteretic properties of debonding nanostructured materials
No full textA new paradigm for vibrational energy dissipation can be devised exploiting nanostructured materials
made of carbon nanotubes (CNTs). The high interfacial area of CNTs together with the poor
bonding properties (when immersed in a polymeric or epoxy matrix) enhances interfacial slippage
thus providing high levels of nano/micro-structural hysteresis under cyclic loadings.
We present a theoretical and computational framework, based on the Eshelby-Mori-Tanaka approach
(e.g., see [1]), for the elastodynamic response of CNT-based composites. The description of
hysteresis is achieved within a thermodynamically consistent constitutive characterization that stems
from the definition of an effective micromechanically-derived yield criterion. Such criterion is based
on the models developed by Ju et al. (e.g., see [2]) and Zhou et al. (e.g., see [3]). In particular, the
constitutive laws here proposed describe the composite as a three-phase material which gradually
evolves. The three phases refer to perfectly bonded fibers, partially/completely debonded fibers, and
to the elastic hosting matrix, respectively. The evolving laws obey to the Weibull statistics, in terms
of average interfacial strength and debonding rate (e.g., see [4]).
The present approach aims to improve the knowledge of the vibrational characterization of CNT
composites, previously described within the context of equivalent linear elasticity with perfect bonding
[5], and it provides a first-order analytical foundation for the estimation of the effective damping
properties and optimal tuning of the dissipation parameters for different applications, as the numerical
testing campaigns illustrate
General-Purpose Finite Element-Based Path Following of Nonlinear Dynamical Systems
No full textThis paper summarizes ongoing efforts toward an advanced integration of algorithmsfrom the finite-element and bifurcation domains, thus enabling an accurate and effective unfoldingof the bifurcation and post-bifurcation scenarios of nonautonomous PDEs typical of nonlinearstructural dynamics including multi-physics applications. The developed tools rely on a nonlinearfinite-element (FE) formulation coupled with a MATLAB-based platform for continuation of periodicorbits called COCO.The paper demonstrates the versatility of the approach through a comparison between the predictionsof the frequency-response curves for a hinged-hinged nonlinear beam subject to a primaryresonanceharmonic transverse load using an in-house FE discretization of the approximate Mettlermodel and using a FE discretization of the special Cosserat model of rods implemented in COMSOLMultiphysics. As the latter accounts for the full nonlinearities and extensional/flexural/shearing deformations,it is expected to yield physically more realistic results. As demonstrated in this paper, italso allows for a straightforward analysis of different sets of boundary conditions without the needfor further simplifications or model reductions
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
Coupled diffusion-damage modeling of historical masonry walls
No full textThe causes of deterioration of historical masonry structures can be subdivided in two main groups: physical/chemical and mechanical ones. Few are the contributions which address the modeling of the deterioration of these structures accounting for both the above causes and their coupling [1], while some contributions can be found for other materials (see [2], [3]). Within this context, in this work a model for the analysis of masonry walls which couples the mechanical damage process with the environmental deterioration is developed. The mechanics is inspired by the Lagrangean model proposed in [4] and the environmental action is modelled with the diffusion of penetrating agents inside the masonry. The mass flux of external agents is influenced by the mechanical damage and, on the other hand, the constitutive relations for stresses accounts for the environmental effects. Numerical tests show the effectiveness of the proposed approach
Fully coupled diffusion-damage analysis in historical masonry walls
No full textHistorical masonry structures are affected by a complex deterioration process, mainly due by the interaction of mechanical and physical/chemical condition. For this reason, in this field of
constructions the mechanical performance cannot be evaluated apart from the the environmental deterioration. Considering this scenario a preliminary work has been recently proposed in
[1] for a mechanical model of damage and friction analysis of masonry walls, embedding also the environmental deterioration. The model employed is capable, for a particular mechanical
damage state, to simulate the mass flux of external agents as influenced by the mechanical damage. Due by a lacking of specific literature for these types of structures, diffusion has been
accounted addressing to models which couple these phenomena for other materials, see for example [2]-[3].
In this paper we address the extension of this preliminary work to a full coupling of these two deterioration agents. The time evolution of the mechanical damage, based on the model of brick-by-brick interaction proposed in [4] within a computational multi-scale approach, is coupled with the time evolution of the environmental action. The diffusion of penetrating agents inside the masonry affects the constitutive relations step by step during the considered time slot. The aim is to evaluate possible equilibrium condition between the two phenomena even though they have very different evolution time, in order to assess valuable structural information.
Numerical tests are used to show the effectiveness of the proposed approach
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