1,720,961 research outputs found
On the effects of suitably designed space microstructures in the propagation of waves in time modulated composites
Full text linkIn the one-dimensional case, the amplitude of a pulse that propagates in a homogeneous material whose properties are instantaneously changed in time will undergo an exponential increase due to the interference between the reflected and transmitted pulses generated at each sudden switch. Here, we resolve the issue by designing suitable reciprocal PT-symmetric space-time microstructures so that the interference between the scattered waves is such that the overall amplitude of the wave will be constant in time in each constituent material. Remarkably, for the geometries proposed here, a pulse will propagate with constant amplitude regardless of the impedance between the constituent materials, and for some, regardless of the wave speed mismatch. We extend, then, these results to the two-dimensional case, by proposing suitable geometries that avoid the blow up of the wave amplitude at the source point due to the scattering associated with time modulation. Given that the energy associated with the wave will increase exponentially in time, this creates the possibility to exploit the stable propagation of the pulse to accumulate energy for harvesting
IMPLICIT MESH DISCONTINUOUS GALERKIN FOR VARIABLE ANGLE TOW MULTILAYERED PLATES
No full textThis works presents a novel computational scheme for variable angle tow (VAT) multilayered
plates [1]. The characteristic features of the proposed scheme are the combined
use of a discontinuous Galerkin (dG) formulation and an implicitly defined mesh. The
formulation is based on the principle of virtual displacements (PVD) and the Equivalent
Single Layer (ESL) assumption for the mechanical behavior of the VAT plates [2].
The problem is first placed within the dG framework by suitably introducing an auxiliary
variable and by rewriting the set of equations governing ESL VAT plates as a firstorder
system of differential equations. Following Arnold et al.[3] and by introducing
suitably defined average and jump operators, the primal formulation for ESL theories of
VAT multilayered plates is obtained. Two dG formulations are considered, namely the
Internal Penalty and the Compact Discontinuous Galerkin methods, which are obtained
by suitably specifying the corresponding numerical fluxes.
Subsequently the numerical implementation is discussed. First, the mesh elements are
defined using a reference background quad-tree grid and the implicit representation of the
considered domain’s boundaries. Then, the elemental matrices are computed using the
algorithm proposed by Saye [4] for the integration over implicitly defined domains and
boundaries. To show the potential of the scheme, numerical tests are performed on VAT
plates with simple and more complex geometries such as curved edges and cutouts
NONLOCAL LAYER-WISE ADVANCED THEORIES FOR LAMINATED PLATES
No full textEringen nonlocal layer-wise models for the analysis of multilayered plates are formulated in the framework of the Carrera Unified Formulation and the Reissner Mixed Variational Theorem (RMVT). The use of the layer-wise approach and RMVT ensures the fulfilment of the transverse stress equilibrium at the layers’ interfaces and allows the analysis of plates with layers exhibiting different characteristic lengths in their nonlocal behaviour. A Navier solution has been implemented and tested for the static bending of rectangular simply-supported plates. The obtained results favourably compare against available three-dimensional analytic results and demonstrate the features of the proposed theories
A BOUNDARY ELEMENT FORMULATION FOR MICROMECHANICAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PIEZOELECTRIC COUPLING
No full textA novel boundary element formulation for the evaluation of the effective properties of threedimensional polycrystalline aggregates with piezoelectric coupling is presented. The aggregates are modelled at the scale of their constituent crystals and are artificially generated through Voronoi-Laguerre tessellations. The electro-mechanical behaviour of each crystal is represented upon introducing an ad-hoc mesh of its boundary and a generalised integral representation of the governing equations of the piezoelectric problem. The behaviour of the whole aggregate is then retrieved upon introducing a suitable set of electro-mechanical interface conditions at the grain boundaries. With respect to classic FE formulations, the present approach has the advantages of: i) expressing the problems in term of boundary values only, thus allowing a natural expression of the interface conditions; ii) requiring the grain boundary mesh only, thus reducing the meshing effort; iii) reducing the number of degrees of freedom of the problem, which is highly desirable in three-dimensional problems. Numerical analyses are performed to study the effect of the statistical distribution of the grains’ orientation on the effective properties of BaTiO3 aggregates. The obtained results are consistent with theoretical estimates and the results available in the literature, showing the potential and accuracy of the proposed formulation
Coupling VLM and DG methods for the aeroelastic analysis of composite wings
Full text linkIn this work, a novel computational tool is introduced for rapid aeroelastic analysis of composite wings, integrating an aerodynamic Vortex Lattice Method with a structural Interior Penalty Discontinuous Galerkin method.
After the mathematical description of the aeroelastic model, some results for a composite wing are presented to investigate the influence of varying lamination angles on the wing displacement, twist, and divergence speed.
Validation against commercial software confirms the effectiveness of the approach
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
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