1,721,083 research outputs found
Using fumarolic inert gas composition to investigate magma dynamics at Campi Flegrei (Italy)
No full textSimulation of heavy gas dispersion based on depth-averaged equations
No full textMany volcanic and non-volcanic areas in Italy emit a huge amount of gas into the atmosphere. Non-volcanic sources in central Italy emit a huge amount of carbon dioxide (CO2) which has a molecular mass greater than that of air. Under stable atmospheric conditions and/or in presence of topographic depressions, its concentration can reach high values resulting fatalities to humans or animals. Several episodes of this phenomenon have been recorded in central Italy and elsewhere. Although from a theoretical point of view, gas dispersion can be fully studied by solving the complete equations system for mass, momentum and energy transport, in actual practice, simplified models able to describe specific phases or aspects of the dispersion problem have to be used. In order to simulate dispersion of a heavy gas and to assess the consequent hazard, we used the established TWODEE model, which is based on a shallow layer approach. This technique uses depth-averaged variables to describe the flow behaviour of dense gas over complex topography represents a good compromise between the complexity of CFD models and the simpler integral models. We present preliminary results for a vented CO2 release in central Italy using the TWODEE model. We find that the dispersion pattern is strongly affected by the steep terrain, and the ambient windspeed
Probabilistic hazard analysis of the gas emission of Mefite d'Ansanto, southern Italy
Full text linkThe emission of gas species dangerous to human health and life is a widespread source of hazard in various natural contexts. These mainly include volcanic areas but also non-volcanic geological contexts. A notable example of the latter occurrence is the Mefite d'Ansanto area in the southern Apennines in Italy. Here, large emissions of carbon dioxide (CO2) occur at rates that make this the largest non-volcanic CO2 gas emissions area in Italy and probably on Earth. Given the topography of the area, in certain meteorological conditions a cold-gas stream forms in the valleys surrounding the emission zone, which has proved to be potentially lethal to humans and animals in the past. In this study, we present a gas hazard modelling study that considers the main species, CO2, and the potential effect of another notable species, hydrogen sulfide (H2S). For these purposes, we used VolcanIc Gas dIspersion modeLling v1.3.7 (VIGIL), a tool that manages the workflow of gas dispersion simulations in both the dense- and dilute-gas regimes and is specifically optimised for probabilistic hazard applications. In its latest version, VIGIL can automatically detect the most appropriate regime to simulate based on the gas emission properties and meteorological conditions at the source. Results are discussed and presented in the form of maps of CO2 and H2S concentration and persistence at various exceedance probabilities, which consider the gas emission rates and their possible ranges of variation defined in previous studies. The effect of seasonal variations is also presented and discussed
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
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