1,720,982 research outputs found
Use of Functionally Graded Material Layers in a Two-Layered Pressure Vessel
No full textThis work explores the possibilities of using functionally graded material (FGM) layers to reduce normal and shear stress gradients due to internal pressure and thermal loadings at the interface of a two-layered wall pressure vessel. The two walls are made of an internal thin metallic layer (titanium used as a liner to avoid a chemical/physical reaction between the gas and the external layer) and an external thick layer (carbon fiber used as a structural restraint). Two main geometrical elements are investigated: a cylindrical shell and a spherical panel. The shell analysis has been made by referring to mixed layerwise theories, which lead to a three-dimensional description of the stress/strain fields in the thickness shell direction; results related to the first order shear deformation theory are given for comparison purposes. It has been concluded that it is convenient to use FGM layers to reduce shear and normal stress gradients at the interfaces. Furthermore, the FGM layers lead to benefits as far as buckling load is concerned; lower values of in-plane shear and longitudinal compressive stresses are, in fact, obtained with respect to a pure two-layered wall.</jats:p
Accurate Vibration Analysis of Multilayered Plates Made of Functionally Graded Materials
No full textClosed form solutions of free vibration problems in simply supported multilayered plates made of Functionally Graded Material (FGM) are dealt with in the present paper. Various refined plate theories are compared in the cases of both equivalent single-layer and layer-wise variable descriptions. Classical theories are compared to advanced ones, in which higher orders of expansion in the thickness direction are used for the transverse displacement. The plate governing equations are provided by applying Carrera's Unified Formulation (CUF) which, in this paper, is extended to the dynamics and free vibration response of plates embedding FGM layers. CUF permits one to handle the governing equations of the whole theory in a unified manner and a hierarchical evaluation of the natural frequencies of plates is therefore obtained. The results are given for one-layer and multi-layer plates embedding FGM layers. Conclusions are drawn regarding the accuracy of classical and advanced plate modelling for various vibration modes. Copyright © Taylor & Francis Group, LLC
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
Effects of thickness stretching in functionally graded plates and shells
No full textThe present work evaluates the effect of thickness stretching in plate/shell structures made by materials which are functionally graded (FGM) in the thickness directions. That is done by removing or retaining the transverse normal strain in the kinematics assumptions of various refined plate/shell theories. Variable plate/shell models are implemented according to Carrera's Unified Formulation. Plate/shell theories with constant transverse displacement are compared with the corresponding linear to fourth order of expansion in the thickness direction ones. Single-layered and multilayered FGM structures have been analyzed. A large numerical investigation, encompassing various plate/shell geometries as well as various grading rates for FGMs, has been conducted. It is mainly concluded that a refinements of classical theories that include additional in-plane variables could results meaningless unless transverse normal strain effects are taken into account. © 2010 Elsevier Ltd. All rights reserved
Evaluation of various theories of the thickness and curvature approximations for free vibrational analysis of cylindrical and spherical shells
No full textCylindrical and spherical shells are largely used in several engineering fields, especially in aerospace vehicles as structural elements and in automotive vehicles as shafts or exhaust and induction systems. Due to their particular relations with vibrations of automotive structures, this work compares various significant shell theories to evaluate the free vibration response. Thin shell theories and shear deformation shell theories are compared with refined theories for both in-plane and out-of-plane displacement components (including transverse normal strain effects). As far as approximation of the curvature terms is concerned, Donnell, Love and exact Flügge theories are been considered. A quite comprehensive analysis has been conducted for the case of simply supported shells. Fundamental and higher frequency parameters are compared by varying the various geometrical parameters of the considered cylindrical and spherical shells . Conclusions are drawn on the use of the most appropriate shell theories for a given shell geometry. Copyright © 2011 Inderscience Enterprises Ltd
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
Variable kinematic models applied to free-vibration analysis of functionally graded material shells
No full textClosed-form solutions of free-vibration problems of simply supported multilayered shells made of Functionally Graded Material have been examined in the present paper. A variable kinematic shell model, which is based on Carrera's Unified Formulation is extended, in this work, to dynamic shell cases. Classical shell theories are compared to refined ones as well as to layer-wise kinematics and mixed assumptions based on the Reissner mixed variational theorem. A comparison with the few results available in the open literature is presented and conclusions are drawn regarding the accuracy of classical and advanced shell modeling to evaluate lower and higher vibration modes as well as the behavior of these modes in the shell thickness direction. © 2010 Elsevier Masson SAS. All rights reserved
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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