1,720,959 research outputs found
A dynamic homogenization approach for modelling hybrid piezoelectric nanogenerators
Get PDFEnergy scavenging, from green and sustainable energy resources, is increasingly attracting the atten- tion of researchers and industries in several engineering fields. The main aim is capturing the energy, naturally available in the environment, and converting it into electrical energy. Emerging applica- tions, such as in flexible/strechable micro and nano electronics, biomedical monitoring, wearable technology, micro and nano robotics and extreme technology, require devices of smaller and smaller size and high performances
Homogenization of Random Composite Materials: Sensitivity to Mechanical Parameters and Scaling Measures
No full textSeveral composite materials used in engineering, such as rocks, ceramic materials, concrete,
masonry-like materials, innovative meta-materials, have an internal micro-structure characterized
by a random distribution of inclusions embedded in a matrix. Mechanical properties of this type
of materials depend on the characteristics of the microstructure: mechanical properties of
components, geometrical shape and size of inclusions. The evaluation of effective mechanical
properties of this typology of materials is a topical issue.
A statistically-based homogenization procedure, previously developed by some of the authors
[1‐3], is adopted. This procedure allows us obtaining effective elastic properties of homogeneous
micro-polar continua able to naturally account for scale and skew–symmetric shear effects. The
so‐called Representative Volume Element (RVE) used to perform the homogenization procedure
is obtained by increasing a scale factor representing the ratio between the size of a control
window, referred as Statistical Volume Element (SVE), and the particle size until the statistical
convergence is reached.
In this work, in order to evaluate the effect of microstructure on the properties of such
materials, a series of parametric analyses are developed for two dimensional samples of
composites with disk-shaped inclusions. Two material cases are considered: inclusions stiffer or
softer than the matrix. Attention is paid to the phase contrast in elastic moduli (ratio between
inclusions and matrix moduli). The sensitivity of the effective material parameters to several
material contrast is investigated. Moreover, the convergence trend of properly defined
scaling‐measures is analyzed.
The results obtained for different kind of composites - ranging from metal or ceramic matrix
composites up to concrete, masonry-like and geo-materials - highlight the importance of taking
into account the spatial randomness of inclusions in identifying the bulk, shear and bending
behavior of composites as well as the effectiveness of the micro-polar continuum modeling.Several composite materials used in engineering, such as rocks, ceramic materials, concrete,
masonry-like materials, innovative meta-materials, have an internal micro-structure characterized
by a random distribution of inclusions embedded in a matrix. Mechanical properties of this type
of materials depend on the characteristics of the microstructure: mechanical properties of
components, geometrical shape and size of inclusions. The evaluation of effective mechanical
properties of this typology of materials is a topical issue.
A statistically-based homogenization procedure, previously developed by some of the authors
[1‐3], is adopted. This procedure allows us obtaining effective elastic properties of homogeneous
micro-polar continua able to naturally account for scale and skew–symmetric shear effects. The
so‐called Representative Volume Element (RVE) used to perform the homogenization procedure
is obtained by increasing a scale factor representing the ratio between the size of a control
window, referred as Statistical Volume Element (SVE), and the particle size until the statistical
convergence is reached.
In this work, in order to evaluate the effect of microstructure on the properties of such
materials, a series of parametric analyses are developed for two dimensional samples of
composites with disk-shaped inclusions. Two material cases are considered: inclusions stiffer or
softer than the matrix. Attention is paid to the phase contrast in elastic moduli (ratio between
inclusions and matrix moduli). The sensitivity of the effective material parameters to several
material contrast is investigated. Moreover, the convergence trend of properly defined
scaling‐measures is analyzed.
The results obtained for different kind of composites - ranging from metal or ceramic matrix
composites up to concrete, masonry-like and geo-materials - highlight the importance of taking
into account the spatial randomness of inclusions in identifying the bulk, shear and bending
behavior of composites as well as the effectiveness of the micro-polar continuum modeling
Homogenization of Random Composite Materials: Sensitivity to Mechanical Parameters and Scaling Measures
No full textSeveral composite materials used in engineering, such as rocks, ceramic materials, concrete,
masonry-like materials, innovative meta-materials, have an internal micro-structure characterized
by a random distribution of inclusions embedded in a matrix. Mechanical properties of this type
of materials depend on the characteristics of the microstructure: mechanical properties of
components, geometrical shape and size of inclusions. The evaluation of effective mechanical
properties of this typology of materials is a topical issue.
A statistically-based homogenization procedure, previously developed by some of the authors
[1‐3], is adopted. This procedure allows us obtaining effective elastic properties of homogeneous
micro-polar continua able to naturally account for scale and skew–symmetric shear effects. The
so‐called Representative Volume Element (RVE) used to perform the homogenization procedure
is obtained by increasing a scale factor representing the ratio between the size of a control
window, referred as Statistical Volume Element (SVE), and the particle size until the statistical
convergence is reached.
In this work, in order to evaluate the effect of microstructure on the properties of such
materials, a series of parametric analyses are developed for two dimensional samples of
composites with disk-shaped inclusions. Two material cases are considered: inclusions stiffer or
softer than the matrix. Attention is paid to the phase contrast in elastic moduli (ratio between
inclusions and matrix moduli). The sensitivity of the effective material parameters to several
material contrast is investigated. Moreover, the convergence trend of properly defined
scaling‐measures is analyzed.
The results obtained for different kind of composites - ranging from metal or ceramic matrix
composites up to concrete, masonry-like and geo-materials - highlight the importance of taking
into account the spatial randomness of inclusions in identifying the bulk, shear and bending
behavior of composites as well as the effectiveness of the micro-polar continuum modeling
SENSITIVITY TO MATERIAL CONTRAST AND SCALING MEASURES IN STATISTICALLY‐BASED HOMOGENIZATION PROCEDURE FOR RANDOM COMPOSITE MATERIALS
No full textA statistically based homogenization procedure, previously developed by some of the authors [1‐3], is
adopted. This procedure allow us to obtain the effective elastic properties of micropolar continua able to
describe composite materials exhibiting an internal microstructure characterized by random distributions
of particles inside a matrix. The so‐called Representative Volume Element (RVE) used to perform the
homogenization procedure is obtained by increasing a scale factor representing the ratio between the size
of a control window, referred as Statistical Volume Element (SVE), and the particle size until the statistical
convergence is reached.
In this article, an evaluation of the sensitivity to material contrast (ratio between inclusion and matrix
moduli) in the identification of the classical and micropolar constitutive coefficients of the homogenized
continuum is investigated, and the convergence trend of properly defined scaling‐measures is analyzed. To
this aim a series of parametric analyses on two dimensional samples of composites with disk‐shaped
inclusions are performed by varying both the inclusion density and the material contrast. The results
obtained for different kind of composites ‐ ranging from metal or ceramic matrix composites up to
concrete, masonry‐like and geo‐materials ‐ highlight the importance of taking into account the spatial
randomness of inclusions in identifying the bulk, shear and bending behavior of composites as well as the
effectiveness of the micropolar continuum modeling.A statistically based homogenization procedure, previously developed by some of the authors [1‐3], is
adopted. This procedure allow us to obtain the effective elastic properties of micropolar continua able to
describe composite materials exhibiting an internal microstructure characterized by random distributions
of particles inside a matrix. The so‐called Representative Volume Element (RVE) used to perform the
homogenization procedure is obtained by increasing a scale factor representing the ratio between the size
of a control window, referred as Statistical Volume Element (SVE), and the particle size until the statistical
convergence is reached.
In this article, an evaluation of the sensitivity to material contrast (ratio between inclusion and matrix
moduli) in the identification of the classical and micropolar constitutive coefficients of the homogenized
continuum is investigated, and the convergence trend of properly defined scaling‐measures is analyzed. To
this aim a series of parametric analyses on two dimensional samples of composites with disk‐shaped
inclusions are performed by varying both the inclusion density and the material contrast. The results
obtained for different kind of composites ‐ ranging from metal or ceramic matrix composites up to
concrete, masonry‐like and geo‐materials ‐ highlight the importance of taking into account the spatial
randomness of inclusions in identifying the bulk, shear and bending behavior of composites as well as the
effectiveness of the micropolar continuum modeling
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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