1,721,029 research outputs found
Linking soil properties to permittivity data: beyond the refractive index model
No full textThe availability of reliable constitutive models linking the bulk electric properties
of porous media to their inner structure is a key requirement for useful quantitative
applications of non invasive methods. In this paper we focus on the use of dielectric
measurements for (time-lapse) monitoring of fluid saturation changes in porous
materials, e.g. via Time Domain Reflectometry (TDR) or ground penetrating radar
(GPR). A number of empirical, semi-empirical and theoretical relationships have been
proposed, linking the bulk dielectric constant with volumetric water content. Among
the most popular are mixing models that involve some form of weighted average of the
dielectric constants of the components. One such model, named CRIM (complex
refractive index model) or LR (Lichteneker-Rother) has found extensive application in
recent years. In this paper we first analyze the characteristics of the CRIM by means
of theoretical considerations, thus drawing a link between the CRIM and the well
known Archie's law used for the analysis of DC resistivity in porous media. Next, we
use pore-scale modelling and experimental results to show other characteristics of
the CRIM, and in particular the dependence of its parameters on dielectric properties
of the components, as well as on porosity. We then proceed to assess the robustness
of the identification of CRIM parameters in presence of synthetic data error, thus
concluding that CRIM parameters cannot, in general, be independently identified on
the basis of bulk dielectric constant versus moisture content data. A novel
theoretical model for the dielectric response of saturated porous media is proposed
in the second section. The new constitutive relationship incorporates the theoretical
link with Archie's law as well as a combination of the well established Hashin and
Shtrikman bounds. The proposed model is shown to be able to match both experimental
and pore-scale modelling data with no use of ad-hoc fitting parameters.Presenters:
name: Brovelli, Alessandro
affiliation: Dipartimento di Scienze dell'Ambiente e del Territorio, University of Milano-Bicocc
Assessment of earthquake location uncertainties for the design of local seismic networks
Full text linkThe ability to estimate earthquake source locations, along with the appraisal of relevant uncertainties, is paramount in monitoring both natural and human-induced micro-seismicity. For this purpose, a monitoring network must be designed to minimize the location errors introduced by geometrically unbalanced networks. In this study, we first review different sources of errors relevant to the localization of seismic events, how they propagate through localization algorithms, and their impact on outcomes. We then propose a quantitative method, based on a Monte Carlo approach, to estimate the uncertainty in earthquake locations that is suited to the design, optimization, and assessment of the performance of a local seismic monitoring network. To illustrate the performance of the proposed approach, we analyzed the distribution of the localization uncertainties and their related dispersion for a highly dense grid of theoretical hypocenters in both the horizontal and vertical directions using an actual monitoring network layout. The results expand, quantitatively, the qualitative indications derived from purely geometrical parameters (azimuthal gap (AG)) and classical detectability maps. The proposed method enables the systematic design, optimization, and evaluation of local seismic monitoring networks, enhancing monitoring accuracy in areas proximal to hydrocarbon production, geothermal fields, underground natural gas storage, and other subsurface activities. This approach aids in the accurate estimation of earthquake source locations and their associated uncertainties, which are crucial for assessing and mitigating seismic risks, thereby enabling the implementation of proactive measures to minimize potential hazards. From an operational perspective, reliably estimating location accuracy is crucial for evaluating the position of seismogenic sources and assessing possible links between well activities and the onset of seismicity
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
A multi-disciplinary study of deformation of the basaltic cover over fine-grained valley fills: a case study from Eastern Sardinia, Italy
No full textThe Pliocene to Early Pleistocene volcanic activity which generated the basaltic plateau of the Orosei-Dorgali area in Eastern Sardinia led to the disruption of the local hydrographic network by damming some tracts of the fluvial valleys incised in the granite basement. This resulted in the formation of lacustrine basins, whose fine-grained fills were partly interfingered and eventually covered by younger lava flows. In the SW part of the plateau, close to the Galtellì village, a number of unknown depressions, locally named “Paules,” were formed. In order to reconstruct their subsurface structure, two electrical resistivity tomography surveys were carried out across these depressions. The geophysical results, which demonstrate the existence of a disrupted layered system, were used to build a numerical geomechanical model that suggest the depressions originated by local collapses of the basaltic cover due to the compaction of the underlying fine-grained valley fills
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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