1,721,101 research outputs found
On the computation of long period seismograms in a 3-D earth using normal mode based approximations
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Gradients de champ d'ondes et hétérogénéités à petite échelle
No full textComme toutes les sources sismiques produisent non seulement des translations mais aussi ses gradients, c'est-à-dire des déformations et des rotations, ces trois mouvements sont également cruciaux en sismologie. Seule la mesure de tous ces mouvements permet d'accéder complètement au mouvement du sol. Toutefois, contrairement aux translations, les déformations et les rotations sont affectées par des hétérogénéités locales à petite échelle, telles que des inhomogénéités géologiques, des topographies de surface et des cavités. Dans ce travail, nous étudions l'effet des hétérogénéités à petite échelle sur les gradients de champ d'onde dans le contexte de problèmes à la fois direct et inverse. Dans le contexte du problème direct, nous montrons que les structures à petite échelle peuvent affecter la phase, l'amplitude et le temps de parcours des gradients de champ d'onde. Cependant, l'effet des structures à petite échelle sur un récepteur donné peut être capté par un tenseur J, qui ne dépend pas de la source et du temps. Par conséquent, J peut être déterminé par une inversion linéaire. Une fois trouvé, il peut également être utilisé pour corriger tous les futurs gradients de champ d'onde au niveau de ce récepteur. Dans le contexte du problème inverse, nous montrons que les déformations et les rotations n'apportent pas d'améliorations substantielles aux inversions complètes de la forme d'onde. Elles peuvent récupérer le même modèle que celui des déplacements lorsque le nombre de données est suffisant (pour les rotations) et lorsque les récepteurs sont placés loin des hétérogénéités (pour les déformations et les rotations). Lorsque les récepteurs sont placés près des hétérogénéités, le modèle récupéré à partir des gradients de champ d'onde n'est pas correct.Since all seismic sources produce not only translations but also its gradients, i.e strains and rotations; all three motions are equally crucial in seismology. Only with the measurement of all these motions can ground motion be completely accessed. Unlike translations, however, strains and rotations are shown to be affected by local small-scale heterogeneities, such as geological inhomogeneities, surface topographies, and cavities. In this work, we study the effect of small-scale heterogeneities on wavefield gradients in the context of both forward and inverse problems. In the context of the forward problem, we show that small-scale structures can affect phase, amplitude, and travel time of the wavefield gradients. However, the effect of small-scale structures at any given receiver can be captured by a tensor J, which does not depend on source and time. Therefore, J can be determined through linear inversion. Once found, it can also be used to correct all future wavefield gradients at that receiver. In the context of the inverse problem, we show that strains and rotations do not bring substantial improvements to full waveform inversions. They can recover the same model that is recovered from displacements when the number of data is sufficient (for rotations) and when the receivers are placed far away from heterogeneities (for both strains and rotations). When the receivers are placed near heterogeneities, the model recovered from wavefield gradients is not correct
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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