1,720,957 research outputs found
Inverse modeling of geochemical and mechanical compaction in sedimentary basins through Polynomial Chaos Expansion
Full text linkWe present an inverse modeling procedure for the estimation of model parameters of sedi-
mentary basins subject to compaction driven by mechanical and geochemical processes. We consider a
sandstone basin whose dynamics are governed by a set of unknown key quantities. These include geophys-
ical and geochemical system attributes as well as pressure and temperature boundary conditions. We derive
a reduced (or surrogate) model of the system behavior based on generalized Polynomial Chaos Expansion
(gPCE) approximations, which are directly linked to the variance-based Sobol indices associated with the
selected uncertain model parameters. Parameter estimation is then performed within a Maximum Likeli-
hood (ML) framework. We then study the way the ML inversion procedure can benefit from the adoption of
anisotropic polynomial approximations (a-gPCE) in which the surrogate model is refined only with respect
to selected parameters according to an analysis of the nonlinearity of the input-output mapping, as quanti-
fied through the Sobol sensitivity indices. Results are illustrated for a one-dimensional setting involving
quartz cementation and mechanical compaction in sandstones. The reliability of gPCE and a-gPCE approxi-
mations in the context of the inverse modeling framework is assessed. The effects of (a) the strategy
employed to build the surrogate model, leading either to a gPCE or a-gPCE representation, and (b) the type
and quality of calibration data on the goodness of the parameter estimates is then explored
Uncertainty propagation in sandstone compaction modeling
No full textThe diagenesis of sedimentary basins is the result of a set of contributing processes taking place after deposition. Among these geochemical reactions and mechanical compaction play the most relevant role. Geochemical reaction models entail the definition of basin scale reaction parameters and are typically temperature dependent. Geological evolutionary scales of basin diagenesis do not allow a straightforward evaluation of modeling parameter and are plagued by uncertainty. In this communication we analyze the uncertainty in porosity vertical distributions given by the effects of several uncertain parameters, such as large scale reaction rate and the mechanical compaction coefficients, and boundary conditions. We employ a model driven parametric uncertainty quantification methodology. The technique is based on a sparse grid sampling in the uncertain parameters space. The original mathematical model is then recast in terms of a generalized Polynomial Chaos Expansion. This methodology allows to (i) obtain a computationally efficient surrogate model of the system and (ii) to compute the complete set of the variance based Sobol indices. Uncertainty propagation is analyzed considering the probability density distribution of porosity and temperature in selected locations along the vertical direction. Results are illustrated on a one dimensional basin compaction problem, involving quartz precipitation in sandstones
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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