1,720,960 research outputs found
Comparison of Different Local Unrefined Beam Theories for Bending and Nano Beams Buckling Analysis
Full text linkIn this study, non unified local shear deformation theory is proposed to consider the bending and buckling of nano beams. This theory is based on the assumption that the cross-sectional and planar displacements consist of bending and shear components, shear components do not contribute to the bending moments. Motion equations are derived using the Hamilton’s principle. Analytical solutions for deformation, buckling load, and the natural frequency are presented to a nano simply supported beam, and the results obtained are compared to those proposed by the nonlocal Timoshenko beam theory and Reddy beam theorie
Etude de la vibration transversale pour les nanotubes en carbone
Full text linkThis study concerns the dynamic behavior of composite beams gradually evaluated through the thickness materials. Our work is devoted to the analysis of natural frequencies of composite beams FGM used in building structures in civil engineering often subjected to vibration loads due to earthquakes. The vibration characteristics of specific beams such as free and orthotropic fixed beams are studied without including deformation due to shear and rotational inertia. We introduce the effects of transverse deformation due to shear and rotational inertia for the accurate prediction of normal frequencies. An application to carbon nanotubes was investigated. Cette étude est consacrée sur le comportement dynamique des poutres composites en matériaux graduellement évalués à travers l’épaisseur. Notre travail est consacré à l’analyse des fréquences normales des poutres composites en FGM utilisées dans le renforcement des structures en génie civil souvent soumises à des chargements vibratoires dus aux séismes. Les caractéristiques de vibration des poutres spécifiques telles que les poutres encastrées libres et orthotropiques sont étudiées sans inclure la déformation due au cisaillement et à l’inertie de rotation. Nous introduisons les effets de la déformation transversale due au cisaillement et l’inertie de rotation pour la prévision précise des fréquences normales. Une application aux nanotubes en carbone a été étudiée.Cette étude est consacrée sur le comportement dynamique des poutres composites en matériaux graduellement évalués à travers l’épaisseur. Notre travail est consacré à l’analyse des fréquences normales des poutres composites en FGM utilisées dans le renforcement des structures en génie civil souvent soumises à des chargements vibratoires dus aux séismes. Les caractéristiques de vibration des poutres spécifiques telles que les poutres encastrées libres et orthotropiques sont étudiées sans inclure la déformation due au cisaillement et à l’inertie de rotation. Nous introduisons les effets de la déformation transversale due au cisaillement et l’inertie de rotation pour la prévision précise des fréquences normales. Une application aux nanotubes en carbone a été étudiée
A New Four Variable Refined Shear Deformation Theory for Buckling and Vibration of Functionally Graded Plates
No full textEtude d’une console en matériaux piézo-thermo-élastique
Full text linkIn the first part of this work, analytical expressions were determined for the stresses through the thickness of a composite beam submitted to electrical excitation. In the second part of this study we are interested in the theory of elasticity, which is used to obtain exact solutions of piezo-thermo-elastic consoles gradually coupled evaluated under different loads. These solutions are used to identify the piezoelectric parameter and thermal coefficients of the materials. In addition, numerical results are obtained for the analysis of the loaded console by two different types of loading. In this study we show also that changing the linear thermal parameters of the material does not affect the distribution of the stress and the induction of the beam. However it affetcs the components of the deformation, electric field, the displacement and the electric potential of the console. Dans la première partie de ce travail, des expressions analytiques ont été déterminées pour les contraintes à travers l'épaisseur d'une poutre composite soumise à une excitation électrique. Dans la deuxième partie de cette étude, on s’intéresse à la théorie de l'élasticité qui est utilisée pour obtenir des solutions exactes des consoles piezo-thermo-élastique graduellement évaluée sous différents chargements couplés. Ces solutions sont utilisées pour identifier le paramètre piézoélectrique et les coefficients thermiques des matériaux. En outre, des résultats numériques sont obtenus pour l’analyse de la console chargée par deux différents types de chargement. Dans cette partie d’étude on montre aussi que le changement linéaire des paramètres thermiques du matériau n’influe pas sur la distribution de la contrainte et l'induction de la poutre. Cependant il influe sur les composants de la déformation, champ électrique, le déplacement et le potentiel électrique de la console. Dans la première partie de ce travail, des expressions analytiques ont été déterminées pour les contraintes à travers l'épaisseur d'une poutre composite soumise à une excitation électrique. Dans la deuxième partie de cette étude, on s’intéresse à la théorie de l'élasticité qui est utilisée pour obtenir des solutions exactes des consoles piezo-thermo-élastique graduellement évaluée sous différents chargements couplés. Ces solutions sont utilisées pour identifier le paramètre piézoélectrique et les coefficients thermiques des matériaux. En outre, des résultats numériques sont obtenus pour l’analyse de la console chargée par deux différents types de chargement. Dans cette partie d’étude on montre aussi que le changement linéaire des paramètres thermiques du matériau n’influe pas sur la distribution de la contrainte et l'induction de la poutre. Cependant il influe sur les composants de la déformation, champ électrique, le déplacement et le potentiel électrique de la console
Nonlinear Behavior Of A Non-homogeneous Plate In Cylindrical Bending Under Uniform Loading
No full textIn this work, we will study the non-linear behavior of a plate in cylindrical bending using an exponential function with gradient of material properties (Commonly called E-FG). The plates are subjected to uniform loading and geometric nonlinearity is introduced into relationship the stress-strain using the expressions nonlinear deformations of Von Karman\u27s. The material properties of the plate, except the Poisson coefficient, are assumed to vary in the direction of thickness z in the form of an exponential law distribution. The solution is obtained by using the Prince of Hamilton. Numerical results by an exponential function with gradient of properties are given in the form of graphs non-dimensional; and determine the effect of the material properties on the deflection and the normal stress across the thickness
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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