1,721,486 research outputs found
Size dependent effect on the buckling and vibration analysis of double-bonded nanocomposite piezoelectric plate reinforced by boron nitride nanotube based on modified couple stress theory
No full textIn this article, the buckling and vibration analysis of a double-bonded nanocomposite piezoelectric plate reinforced by a boron nitride nanotube based on the Eshelby-Mori-Tanaka approach is developed using modified couple stress theory under electro-thermo-mechanical loadings surrounded by an elastic foundation. Using Hamilton's principle, the governing equations of motion are obtained by applying a modified couple stress theory and the Eshelby-Mori-Tanaka approach for piezoelectric material and Kirchhoff plate. These equations are coupled for the double-layer plate using the Pasternak foundation and solved using Navier's type solution. Then the dimensionless frequencies and critical buckling load for simply-supported boundary conditions are obtained. The effects of material length scale parameter, elastic foundation coefficients, aspect ratio (a/b), length to thickness ratio (a/h), transverse and longitudinal wave numbers on the dimensionless natural are investigated. The dimensionless frequency of a double-bonded nanocomposite piezoelectric plate increases with increasing length to thickness ratio and decreases with increasing aspect ratio. In addition, the effect of the elastic foundation on the dimensionless frequency of double-bonded nanocomposite piezoelectric plates is more considerable for higher elastic medium parameters. The critical buckling load also decreases with an increase in the dimensionless material length scale parameter
A Multi-Pier MP method for the non-linear static analysis of out-of-plane loaded masonry walls
No full textThe aim of this paper is to propose a novel 3D truss-like approach called Multi Pier (MP) to analyze the out-of-plane non-linear static behavior of masonry walls. The use of truss elements allows the model to be time-saving, accurate and implementable into a commercial FE software equipped with only non-linearity for 1D elements; consequently, it is characterized by a drastic reduction of the computational effort required and by impressive robustness, being possible an immediate utilization by inexperienced users. In the model, the wall is divided in the horizontal and vertical directions into 3D braced truss frames, with horizontal and vertical elements called piers and diagonal elements called braces. The axial, flexural, and torsional behavior, and their mutual interaction at the meso-scale level (masonry unit cell) are accurately reproduced. Nine experimental masonry walls in two-way bending, in presence or absence of openings and complex boundary conditions, are numerically analyzed to assess the ability of the model at a structural level to reproduce global load–displacement curves obtained experimentally and crack patterns at collapse. A satisfactory match between numerical predictions and experimental evidence is systematically found, meaning that the procedure proposed can represent a simple and valuable tool for all those practitioners not familiar with advanced computations in masonry field, but interested in a reliable prediction of the behavior of masonry walls out-of-plane loaded by means of standard commercial codes
A Multi-Pier MP procedure for the non-linear analysis of in-plane loaded masonry walls
No full textSeveral simplified and advanced methods have been proposed to evaluate the behavior of masonrywalls under in-plane loads, but their implementation in standard commercial software remains still an exception. In this paper, a novel 1D approach called Multi-Pier MP method, which has the advantage that can be used in a commercial software and requires only truss elements with a non-linear softening behavior, is presented. In the model, a masonry structure in-plane loaded is transformed in an assemblage of piers (vertical trusses) and diagonal connecting elements (braces), ensuring by elastic stiffness equivalence that a masonry representative element of volume behaves in the same manner as the 1D system constituted by two vertical trusses and two diagonal braces. After a validation at a unit cell level, where geometric and mechanical properties of the trusses are set in order to reproduce correctly masonry behavior respectively under axial loads, combined shear and compression stresses and bending and shear actions, four masonry full scale shear walls with different length to width ratios and presence or absence of openings are analyzed in the non-linear static range. In addition to experimental results, two Heterogeneous Discrete Element and Finite Element Methods were used with validation purposes. Excellent match among MP Method results, experimental evidences and alternative advanced numerical heterogeneous approaches is found, as far as the prediction of ultimate load, post peak behavior, initial stiffness and failure mechanisms is concerned. The model is also capable to follow at each step of loading the spreading and position of tensile and shear cracks
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
Leakage flow flutter in a low-speed axial-flow fan with shrouded blades
No full textA large-amplitude axial vibration of a rotor fan with shrouded blades has been experimentally observed. The analysis of the Campbell diagram shows that the vibration is related to a backward-whirl vibrational mode of the rotor which is always present, with different amplitudes depending on the operating conditions and configuration. Modifications of the shroud roughness and insertion of small obstacles in the gap region have independently shown that leakage flow fluctuations constitute the excitation of the large-amplitude vibration. This indicates that the phenomenon is likely a flutter, as it is also suggested by the observed intermittency and aerodynamic stiffening. The feedback of the vibration on the flow is likely due to the variations of the gap size
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