1,720,971 research outputs found
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
Numerical solution of a piezoelectric contact problem
Get PDFWe consider a mathematical model, which describes a contact problem between a piezoelectric body and a conductive foundation. The linear electro-elastic constitutive law is employed to model the piezoelectric material. The process is static, the contact is frictionless and described with the normal compliance condition and an electric contact condition. Our aim is to present a detailed description of the numerical modelling of the problem. To this end, we introduce a discrete scheme, based on the finite element method to approximate the spatial variable. Then we treat the contact conditions by using a penalized approach and a version of Newton's method. Finally, we provide numerical simulations in the study of a two-dimensional example and compare the regularized problem with the original one
Numerical solution of a viscoelastic contact problem with normal compliance and unilateral constraint
Get PDFA numerical method is presented for a mathematical model which describes the frictional contact between a viscoelastic body and an obstacle. The process is quasistatic and the material’s behavior is described by means of a viscoelastic constitutive law with long memory. The contact is modelled with normal compliance condition restricted by unilateral constraint, and associated to a version of Coulomb's law of dry friction. A solution algorithm is discussed and implemented. Finally, numerical simulation results are reported on a two-dimensional test problem. These simulations show the efficiency of the algorithm and the corresponding mechanical interpretations
Numerical solution of a viscoelastic contact problem with normal compliance and unilateral constraint
Get PDFA numerical method is presented for a mathematical model which describes the frictional contact between a viscoelastic body and an obstacle. The process is quasistatic and the material’s behavior is described by means of a viscoelastic constitutive law with long memory. The contact is modelled with normal compliance condition restricted by unilateral constraint, and associated to a version of Coulomb's law of dry friction. A solution algorithm is discussed and implemented. Finally, numerical simulation results are reported on a two-dimensional test problem. These simulations show the efficiency of the algorithm and the corresponding mechanical interpretations
Contribution à l'étude mathématique et numérique des structures piézoélectriques en contact
No full textThe topic of this thesis belongs both to applied mathematics and mechanics. It deals with the mathematical study of piezoelectric problems, i.e problems including a coupling between mechanical and electrical actions, involving contact and friction. We study the variational and numerical analysis of these problems. The thesis is structured in four parts. The first one contains the background in Mathematics and Mechanics needed in the rest of the manuscript. The second part deals with two static frictional contact problems between an electro-elastic body and a foundation. We provide the existence, uniqueness and continuons dependence of the solution of the primal problems, formulated in terms of displacement and electric potential fields. A dual formulation, in terms of stress and electric displacement fields is studied too, for which existence and uniqueness results are presented, as well. The third part concern two models of quasistatic piezoelectric contact. For each model we present existence results. The fourth part deals with the numerical analysis and simulations obtained by using Euler scheme in time and finite elements in space. We consider a static electro-elastic problem with normal compliance and friction for which we provide error estimates. The problem is written in the form of an augmented Lagrangian algorithm coupled with a generalized Newton method. Some two-dimensional simulations are presented in order to recover the error estimates. Similar results are also presented in the study of a quasistatic electro-viscoelastic problem contact.Le sujet de cette thèse se situe à la frontière entre les mathématiques appliquées et la mécanique. Il s'agit d'étudier, sous un angle mathématique, des problèmes piézoélectriques, c'est à dire des problèmes couplant action mécanique et action électrique, en présence de contact et de frottement. On s'intéresse notamment à l'analyse variationnelle et numérique de ces problèmes. La thèse comporte quatre parties. La première partie contient l'ensemble des outils mathématiques, numériques et mécaniques nécessaires à une bonne compréhension du travail réalisé par la suite. La deuxième partie aborde deux problèmes statiques de contact frottant entre un corps électro-élastique et une fondation. Dans le cas des formulations primales des problèmes, nous prouvons l'existence, l'unicité, et la dépendance continue des solutions faibles, exprimées en termes de déplacements et de potentiel électrique. Une formulation duale équivalente au problème précédent, exprimée en termes de contraintes et de déplacement électrique, est étudiée pour laquelle des résultats d'existence et d'unicité sont établis. La troisième partie aborde deux modèles de contact piézoélectrique dans un cadre évolutif de type quasistatique. Pour chaque modèle, on présente un résultat d'existence. Dans la quatrième partie, le travail porte sur l'analyse numérique et les simulations par différences finies en temps (Euler implicite) et éléments finis en espace. Dans le cas statique, on traite un problème électro-élastique avec contact frottant de type compliance. Le problème discret est posé et les estimations a priori de l'erreur sont obtenues. Le problème est écrit sous forme d'un Lagrangien augmenté couplé à un algorithme de type Newton généralisé. S'ensuit une simulation numérique en dimension deux d'espace et des vérifications numériques de convergence. Des résultats similaires sont obtenus dans le cas d'un problème de contact quasistatique électro-viscoélastique
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
Numerical analysis of a frictional contact problem for thermo-electro-elastic materials
No full textA numerical method is presented for a mathematical model which describes the frictional contact between a thermo-electro-elastic body and a conductive foundation. The contact is described by Signorini’s conditions and Tresca’s friction law including electrical and ther- mal conductivity conditions. Our aim is to present a detailed description of the numerical modelling of the problem. To this end, we introduce a discrete scheme based on the finite element method. Under some regularity assumptions imposed on the true solution, optimal order error estimates are derived for the linear element solution. This theoretical result is illustrated numerically
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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