1,720,963 research outputs found
Separation of a single mode of Rayleigh waves using quaternion SVD in vertically-heterogeneous media
No full textI propose a wave-separation method that separates a single Rayleigh-wave mode from body waves and
from other modes, using quaternions to represent the multi-component seismic data recorded by an array
of vector-sensors. This method decomposes the signal into narrow-frequency bands, which are subjected
to both a velocity correction and a polarisation correction. The aim of these corrections is to reduce the
mode of interest to a quasi-monochromatic wave packet with infinite apparent velocity and quasi-circular
polarisation. Once written in quaternion notation, I refer to this wave packet as “quaternion brick”. It can
be proved that this quaternion brick maps into the first quaternion eigenimage of the quaternion SVD
(QSVD). I apply this method to vertically-heterogeneous elastic models. The method seems to correctly
extract the selected Rayleigh-wave mode and to separate it from body waves. The separation between
different modes is more challenging. It results that, when two modes interfere in the near-offset portion, a
more accurate separation can be obtained by characterising the mode of interest in the far-offset portion
and then extrapolating it in the near-offset portion (where the two modes overlap) using the properties of
the right singular vector of the QSVD
Strain Accumulation Mechanisms in Unconsolidated Sediments during Compression
No full textPride and Berryman (2009) proposed a model to predict pressure dependence of effective elastic bulk modulus for
unconsolidated sediments, by progressively allowing the creation of new contacts during compression. They
assume that the gaps around rattlers are distributed according to a power law with distance, in addition, the model
allows two different strain-accumulation mechanisms: linear or quadratic, the latter being associated with grain
rotation (Goddard, 1990). We have observed that the model of Pride and Berryman can be simplified without losing
its generality, assuming a flat distribution of gaps around rattlers, given appropriate values for the maximum gap.
We have used this simplified model to study how the strain-accumulation mechanism affects the coordination
number during isotropic compression. We tested our model on sand data from Zimmer (2003). We observed that
the majority of the experimental trends lay between the pure linear and the pure quadratic accumulation trends.
We conclude that the strain accumulation in unconsolidated sediments can be well described as a combination of
the two mechanisms. We noted also that rotation affects larger grains (diameter approx. 500 micron) more than
smaller grains (diameter approx. 100 micron)
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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