1,720,970 research outputs found
Accurate modelling of the linear elastic flexure of composite beams warped by midlayer slip, with emphasis on concrete-timber systems
No full textWe focus on the modelling of the linear elastic flexure of composite beams in which the external layers are connected by a midlayer allowing a conspicuous slip between the external layers. In particular, we consider the case of concrete-timber systems in which the midlayer consists of steel shear connectors passing through a wooden plank. To model these structures, we extend the Newmark theory, originally developed for connection of negligible thickness. Also, we apply Jourawski's technique to the Newmark model to obtain accurate analytic predictions of the shear stress. We provide analytic solutions for the cases of simply-supported, cantilever, and propped-cantilever beams, all subject to uniform load, and we compare the results with those obtained from both accurate plane stress Finite Element simulations and the First-Order Shear Deformation (FOSD) theory. For the latter we provide the explicit expression of the shearing rigidity based on a classical energy criterion. We show the inability of the FOSD modelling to accurately predict the deflection and explain the unexpected too large compliance characterising the FOSD estimate. Instead, the Newmark model turns out to be highly accurate for sufficiently slender beams, even in terms of shear stress if the "Jourawski-like" post-processing proposed here is used. We also consider a further extension of Newmark's theory to accurately model not-too-slender composite beams. In such an extension, henceforth called the Newmark-Timoshenko model, the wooden element is allowed to follow a Timoshenko kinematics, richer than the Euler-Bernoulli kinematics assigned to both the external layers in the Newmark model. The results of the novel Newmark-Timoshenko model are numerically obtained by the Rayleigh-Ritz method in which the analytic solution of Newmark's model is used to construct optimal approximating functions of the field entering the Total Potential Energy functional
Multiple arylations of aromatics via removable palladacycle scaffolds: polycyclic compounds and their way of formation
No full textHydrogen charging of carbon and low alloy steel by electrochemical methods
Full text linkAtomic hydrogen can be the result of different processes like electroplating, chemical and electrochemical pickling treatments, in welding or by cathodic processes in corrosive fluids. Moreover, adsorption of atomic hydrogen can affect materials in contact with high pressure gaseous hydrogen. Once entered the material, atomic hydrogen interacts with the metal structure and may produce a "damage" of various forms, such as Hydrogen Induced Cracking (HIC), delayed fracture, blistering and hydrogen embrittlement. In particular, when H2S is present ("sour service"), metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Sour service materials must be used in compliance with international accepted standards, used worldwide in oil and gas activities, when fluids are classified as sour. The present study has been carried out in order to set up an electrochemical method to charge with hydrogen two typical pipeline materials, carbon and low alloy steels. The reason of the use of an electrochemical method is to avoid any critical conditions from the point of view of preparation, safety and disposal. Hydrogen content in the specimens was measured by two different methods: hot glycerol bath and Inert Gas Fusion (IGF) analysis. Hydrogen content in the specimens is about 0.6-2 ppm; mechanical performances were assessed by means of J integral tests: a pronounced decrease of fracture toughness was observed for H charged specimens.{GRAPHIACAL ABSTRACT
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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