1,721,218 research outputs found
3D Multiple-Point Statistics for facies simulation using 2D and 1D conceptual models
No full textModeling geological reservoirs is a crucial step for understanding underground systems. Several
activities such as oil and gas exploration, CO 2 sequestration, or geothermal energy production, need a
realistic 3D characterization of reservoirs with uncertainty assessment. Multiple-Point Statistics (MPS)
simulation is widely used for that task, because it allows for integrating complex conceptual models,
honoring field data and taking into account for non stationarities in a stochastic framework.
MPS methods require a training image (TI) from which the spatial arrangements are borrowed for the
simulations. Therefore, 3D TIs are needed for 3D simulations in classical implementations. However,
in practice, we often have access only to 2D or 1D informations from outcrops or boreholes in analog
sites.
Here, we propose a MPS technique allowing to generate 3D simulations based on 2D orthogonal TIs or
on 2D and 1D orthogonal TIs. The algorithm consists in successively simulating sections and/or lines
according to the orientation of the input 2D/1D TIs, until the 3D block is filled. Each section/line is
simulated by using the TI(s) for the same orientation and by also taking into account for the spatial
statistics in the transversal 2D or 1D section(s) provided by the corresponding TI(s). Therefore, the
proposed method exploits as much as possible the input models. It is based on IMPALA, a parallel
MPS algorithm for facies simulations, and, in addition to overcome the lack of 3D TIs in practical
applications, the method is much faster than a classical 3D simulation based on a full 3D TI
Introducing wwhypda : a world-wide collaborative hydrogeological parameters database
Full text linkFin dalla publicazione dei primi importanti lavori di Henry Darcy (datati 1880) sono stati misurati e pubblicati moltissimi valori delle diverse proprietà delle rocce (ad esempio conducibilità idrauliche, permeabilità, compressibilità, porosità e così via). Tuttavia questi risultati sono dispersi e di non facile accesso. Per sopperire a queste difficoltà e per fornire uno strumento utile nella caratterizzatione di siti, in particolare dal punto di vista stocastico, si propone una banca dati mondiale di parametri idrogeologici (world-wide hydrogeological parameter database: wwhypda). wwhypda é uno strumento di collaborazione che permette agli utilizzatori di contribuire con i propri dati e/o di consultare liberamente la banca dati, il tutto tramite una interfaccia web (http://wwhypda.org). Singole misure e distribuzioni di probabilità sono fornite e catalogate in funzione della litologia, della scala di osservatione, della localizzazione e dell’ambiente geologico relativi.Since the seminal publication of Henry Darcy’s work in the 1880s, a very large number of rock property values (such as hydraulic conductivity, permeability, compressibility, porosity, etc.) has been measured and published. These data are, however, dispersed and difficult to access. To overcome this problem and to facilitate site characterization (especially stochastic), a worldwide hydrogeological parameter database (wwhypda) is proposed. It is an open and collaborative catalog allowing users to store and retrieve measurements. The catalog is accessible through a web interface (http://wwhypda.org). Presently, it provides individual values and probability density functions of the properties as a function of lithology, scale of observation, location, and geological environment.Depuis la publication des travaux originaux de Henry Darcy (datés 1880) de très nombreuses valeurs de propriétés physiques des roches (conductivité hydraulique, perméabilité, compressibilité, porosité, etc.) ont été obtenues expérimentalement et publiées. Ces données sont toutefois dispersées et donc difficiles d’accès. Pour palier à ce problème et pour ainsi faciliter la caractérisation des aquifères (en particulier par des méthodes stochastiques), cet article propose une base de donnée mondiale de paramètres hydrogéologiques. Il s’agit d’un catalogue librement accessible sur Internet (http://wwhypda.org) pour la consultation et la publication des données. Le catalogue contient actuellement des mesures individuelles et permet de calculer des histogrammes des propriétés en fonction de la lithologie, de l’échelle d’observation, de la localisation et de l’environnement géologique.Desde la publicación originaria del trabajo de Henry Darcy’s en los 1880, una gran cantidad de valores de propiedades de roca (tales como conductividad hidráulica, permeabilidad, compresibilidad, porosidad, etc.) ha sido medidos y publicados. Sin embargo, estos datos están dispersos y son de acceso dificultoso. Para solucionar este problema y facilitar la caracterización de un sitio (especialmente estocástico), se propone una base de datos mundial de parámetros hidrogeológicos (wwhypda). Es un catálogo abierto y colaborativo que permite a los usuarios almacenar y recuperar mediciones. El catálogo está accesible a través de una interfaz web (http://wwhypda.org). Actualmente, provee valores individuales y funciones de densidad de probabilidad de las propiedades en función de la litología, la escala de observación, ubicación y medio geológico
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
A new perspective to model subsurface stratigraphy in alluvial hydrogeological basins, introducing geological hierarchy and relative chronology
Full text linkThis paper presents a novel perspective for modelling alluvial stratigraphy. It integrates the spatial geological
information, geological maps and well-log descriptions, with the rules describing the hierarchy and relative
chronology of the geological entities. As geological modelling tools are moving fast forward, the urgent need for
expert geological input, codified as modelling rules, persists. Concerning subsurface alluvial architectures, the
concepts of “stratigraphic hierarchy” and “relative chronology” provide the most relevant rules which permit to
link the modelling procedure to the geo-history of a region.
The paper shows how to formalize this knowledge into modelling rules. This is illustrated and implemented in
a PythonTM module named HIEGEO which is applied on a 2-D cross-section from the Po Basin (N-Italy). The
stratigraphic correlation yields 2-D pictures of the hierarchic stratigraphy and relative chronology of the units.
The input are: an attribute table of stratigraphic boundaries expressing their hierarchy and chronology; contact
points where these boundaries cross the control logs. Since the aim of HIEGEO is to illustrate the principle of the
method but not to replace existing 3-D geological modelling tools, it implements a linear interpolation algorithm
which creates joins between contact points. It plots linear joins framing polygons based on their hierarchy, at any
user’s desired detail. HIEGEO highlights potential inconsistencies of the input dataset, helping to re-evaluate the
geological interpretation.
The proposed workflow allows to: i) translate geological knowledge into modelling rules; ii) compute stratigraphic
models constrained by the hierarchy of stratigraphic entities and the relative chronology of geological
events; iii) represent internal geometries of the stratigraphic units, accounting for their composite nature; iv)
reduce uncertainty in modelling alluvial architectures. It represents a starting point for multi-scale applications
and could be easily integrated into 3-D modelling packages, to couple the hierarchical concept proposed here
with existing advanced interpolation methods
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