1,721,058 research outputs found
Geostatistical characterisation of internal structure of mass-transport deposits from seismic reflection images and borehole logs
Full text linkSeismic reflection images of mass-transport deposits often show apparently chaotic, disorded or low-reflectivity internal seismic facies. The lack of laterally coherent reflections can prevent horizon-based interpretation of internal structure. This study instead inverts for geostatistical parameters which characterise the internal heterogeneity of mass-transport deposits from depth-domain seismic reflection images. A Bayesian Markov Chain Monte Carlo inversion is performed to estimate posterior probability distributions for each geostatistical parameter. If the internal heterogeneity approximates an anisotropic von Kármán random medium these parameters can describe the structural fabric of the imaged mass-transport deposit in terms of lateral and vertical dominant scale lengths and the Hurst number (roughness). To improve the discrimination between vertical and lateral dominant scale lengths, an estimate of the vertical dominant scale length from a borehole is used as a prior in the inversion. The method is first demonstrated on a synthetic multi-channel seismic reflection image. The vertical and lateral dominant scale lengths are estimated with lower uncertainty when data from a synthetic borehole data are included. We then apply the method to a real data example from Nankai Trough, offshore Japan, where a large mass-transport deposit is imaged in a seismic profile and penetrated by a borehole. The results of the inversion show a downslope shortening in lateral scale length, consistent with progressive down-slope disaggregation of the mass-flow during transport. The dominant scale lengths can be used as a proxy for strain history, which can improve understanding of post-failure dynamics and emplacement of subacqueous mass-movements, important for constraining the geohazard potential from future slope failure
Geophysical characterisation of the internal structure of mass-transport deposits
Full text linkSubaqueous mass-movements are a significant marine geohazard, with the potential to cause large-scale tsunami and damage seafloor infrastructure. Their sedimentary deposits (mass-transport deposits, or MTDs) can show complex but well-defined internal structure across many scales in outcrop examples. In seismic images, however, the internal character of MTDs often appears chaotic, disordered or lacking coherent internal reflectors. Conversely, cores sampled from MTDs with such seismic response can show little evidence of deformation. As a consequence, previous studies have struggled to integrate core-, outcrop- and seismic-scale observations of MTDs, preventing the full use of geophysical data for geohazard assessment.
This thesis examines the major controls on the seismic response of MTDs. Chapter 1 develops a geostatistical method to characterise MTDs lacking in coherent internal seismic reflections. The method provides probabilistic estimates of the lateral and vertical dominant scale lengths and Hurst number (roughness) from a seismic image and co-incident borehole log. Chapter 2 applies diffraction imaging to two seismic profiles acquired in the Gulf of Cadiz to characterise the heterogeneous internal structure of MTDs. The resulting images are able to image internal structure and are better able to identify small and thin deposits compared to conventional full-wavefield imaging. Chapter 3 introduces a series of conceptual models for the geophysical properties of shallow sediments to explore the mechanisms that could generate an apparently chaotic-to-transparent response, common to sub-bottom profiler images of MTDs. Full-wavefield seismic modelling experiments show that stratal disruption alone can generate a reduction in seismic amplitudes, without reducing the magnitude of internal impedance contrasts. This discrepancy may explain the frequent contradiction between core-scale and seismic-scale observations of the internal structure of MTDs. Chapter 4 models the seismic response of a fossil MTD outcropping at Vernasso Quarry, north east Italy. A workflow is developed to efficiently model seismic experiments with different source bandwidths and streamer lengths. The results of these experiments indicate that the resolution of the image depends strongly on the source bandwidth, and less strongly on the length of the streamer, likely due to the large proportion of diffracted energy in the seismic response
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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