1,721,009 research outputs found
Glauconitic-rich strata from Oligo-Miocene shallow-marine siliciclastic deposits of the northern margin of Africa (Tunisia): geochemical approach for basin analysis
No full textGlauconitic minerals have long been appreciated as a reliable tool for sequence stratigraphic interpretation. A degree of maturity and occurrence of glauconite are closely related within a system tract context and substrate paleoenvironmental conditions. Within Oligo-Miocene shallow marine deposits of northern Tunisian outcrops, the glauconite occurs as thin (few centimeters) to moderate thick (1 m) clay and fine grain size sandstone horizons which are superbly exposed at many localities. Sedimentological investigations data indicate that these glaucony-bearing strata are deposited under shallow water shelfal and lagoonal siliciclastic depositional systems. Geochemical analysis from nine glaucony samples shows that Oligocene glaucony is invariably more evolved (K2O = 6–8 %) than Miocene glaucony, which is typically slightly evolved (K2O = 4–6 %). Vertical changes in glaucony maturity are consistent with sequence-stratigraphic interpretation, showing in general an upward increase in the transgressive systems tract. Maximum glaucony concentration is recorded corresponding to the maximum flooding surface/condensed section. Comparison of glaucony characteristics across different depositional systems at the same stratigraphic level shows a slight decrease in maturity and abundance from distal to proximal locations. This lateral tendency reflects more suitable conditions for glauconitization in open-marine environments than in shallow waters
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
De la conception physique aux outils d'administration et de tuning des entrepôts de données
No full textThe main goal of this thesis is to propose a set of approaches to optimize performance of data warehouses and assist the data warehouse administrator (DWA) to well perform this optimization. Our approaches use three optimization techniques: primary and derived horizontal partitioning and bitmap join indexes (BJI). First, we propose a partitioning approach, which takes into account both the performance (reducing the response time) and manageability (controlling the number of fragments). Then, we propose a greedy approach that selects a set of BJI. The use of FH and BJI independently cannot exploit the various similarities existing between these two techniques. We propose an approach for multiple selection of FH and BJI. This approach can be used for tuning data warehouses. We conducted several experiments to validate our approaches. Finally, we develop a tool to assist the DWA in physical design and tuning.Nous visons à travers cette thèse à proposer un ensemble d'approches permettant d'optimiser les entrepôts de données et d'aider l'AED à bien mener cette optimisation. Nos approches d'optimisation reposent sur l'utilisation de trois techniques d'optimisation : la fragmentation horizontale primaire, dérivée et les index de jointure binaires (IJB). Nous commençons par proposer une approche de fragmentation qui prend en considération à la fois la performance (réduction du coût d'exécution) et la manageabilité (contrôle du nombre de fragments générés). Nous proposons ensuite une approche gloutonne de sélection d'IJB. L'utilisation séparée de la fragmentation horizontale (FH) et des IJB ne permet pas d'exploiter les similarités existantes entre ces deux techniques. Nous proposons une approche de sélection conjointe de la FH et des IJB. Cette approche peut être utilisée pour le tuning de l'entrepôt. Nous avons mené plusieurs expériences pour valider nos différentes approches. Nous proposons par la suite un outil permettant d'aider l'AED dans ses tâches de conception physique et de tuning.Mots clés : Conception physique, Tuning, Techniques d'optimisation, Fragmentation Horizontale, Index de Jointure Binaires
De la conception physique aux outils d'administration et de tuning des entrepôts de données
No full textThe main goal of this thesis is to propose a set of approaches to optimize performance of data warehouses and assist the data warehouse administrator (DWA) to well perform this optimization. Our approaches use three optimization techniques: primary and derived horizontal partitioning and bitmap join indexes (BJI). First, we propose a partitioning approach, which takes into account both the performance (reducing the response time) and manageability (controlling the number of fragments). Then, we propose a greedy approach that selects a set of BJI. The use of FH and BJI independently cannot exploit the various similarities existing between these two techniques. We propose an approach for multiple selection of FH and BJI. This approach can be used for tuning data warehouses. We conducted several experiments to validate our approaches. Finally, we develop a tool to assist the DWA in physical design and tuning.Nous visons à travers cette thèse à proposer un ensemble d'approches permettant d'optimiser les entrepôts de données et d'aider l'AED à bien mener cette optimisation. Nos approches d'optimisation reposent sur l'utilisation de trois techniques d'optimisation : la fragmentation horizontale primaire, dérivée et les index de jointure binaires (IJB). Nous commençons par proposer une approche de fragmentation qui prend en considération à la fois la performance (réduction du coût d'exécution) et la manageabilité (contrôle du nombre de fragments générés). Nous proposons ensuite une approche gloutonne de sélection d'IJB. L'utilisation séparée de la fragmentation horizontale (FH) et des IJB ne permet pas d'exploiter les similarités existantes entre ces deux techniques. Nous proposons une approche de sélection conjointe de la FH et des IJB. Cette approche peut être utilisée pour le tuning de l'entrepôt. Nous avons mené plusieurs expériences pour valider nos différentes approches. Nous proposons par la suite un outil permettant d'aider l'AED dans ses tâches de conception physique et de tuning.Mots clés : Conception physique, Tuning, Techniques d'optimisation, Fragmentation Horizontale, Index de Jointure Binaires
De la conception physique aux outils d'administration et de tuning des entrepôts de données
No full textThe main goal of this thesis is to propose a set of approaches to optimize performance of data warehouses and assist the data warehouse administrator (DWA) to well perform this optimization. Our approaches use three optimization techniques: primary and derived horizontal partitioning and bitmap join indexes (BJI). First, we propose a partitioning approach, which takes into account both the performance (reducing the response time) and manageability (controlling the number of fragments). Then, we propose a greedy approach that selects a set of BJI. The use of FH and BJI independently cannot exploit the various similarities existing between these two techniques. We propose an approach for multiple selection of FH and BJI. This approach can be used for tuning data warehouses. We conducted several experiments to validate our approaches. Finally, we develop a tool to assist the DWA in physical design and tuning.Nous visons à travers cette thèse à proposer un ensemble d'approches permettant d'optimiser les entrepôts de données et d'aider l'AED à bien mener cette optimisation. Nos approches d'optimisation reposent sur l'utilisation de trois techniques d'optimisation : la fragmentation horizontale primaire, dérivée et les index de jointure binaires (IJB). Nous commençons par proposer une approche de fragmentation qui prend en considération à la fois la performance (réduction du coût d'exécution) et la manageabilité (contrôle du nombre de fragments générés). Nous proposons ensuite une approche gloutonne de sélection d'IJB. L'utilisation séparée de la fragmentation horizontale (FH) et des IJB ne permet pas d'exploiter les similarités existantes entre ces deux techniques. Nous proposons une approche de sélection conjointe de la FH et des IJB. Cette approche peut être utilisée pour le tuning de l'entrepôt. Nous avons mené plusieurs expériences pour valider nos différentes approches. Nous proposons par la suite un outil permettant d'aider l'AED dans ses tâches de conception physique et de tuning.Mots clés : Conception physique, Tuning, Techniques d'optimisation, Fragmentation Horizontale, Index de Jointure Binaires
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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