1,720,973 research outputs found
Development of a numerical workflow based on μ-CT imaging for the determination of capillary pressure–saturation-specific interfacial area relationship in 2-phase flow pore-scale porous-media systems: a case study on Heletz sandstone
Full text linkIn this case study, we present the implementation of a finite element method (FEM)-based numerical pore-scale model that is able to track and quantify the propagating fluid–fluid interfacial area on highly complex micro-computed tomography (μ-CT)-obtained geometries. Special focus is drawn to the relationship between reservoir-specific capillary pressure (pc), wetting phase saturation (Sw) and interfacial area (awn). The basis of this approach is high-resolution μ-CT images representing the geometrical characteristics of a georeservoir sample. The successfully validated 2-phase flow model is based on the Navier–Stokes equations, including the surface tension force, in order to consider capillary effects for the computation of flow and the phase-field method for the emulation of a sharp fluid–fluid interface.
In combination with specialized software packages, a complex high-resolution modelling domain can be obtained. A numerical workflow based on representative elementary volume (REV)-scale pore-size distributions is introduced. This workflow aims at the successive modification of model and model set-up for simulating, such as a type of 2-phase problem on asymmetric μ-CT-based model domains. The geometrical complexity is gradually increased, starting from idealized pore geometries until complex μ-CT-based pore network domains, whereas all domains represent geostatistics of the REV-scale core sample pore-size distribution. Finally, the model can be applied to a complex μ-CT-based model domain and the pc–Sw–awn relationship can be computed
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
An integrated core-based analysis for the characterization of flow, transport and mineralogical parameters of the Heletz pilot CO2 storage site reservoir
No full textHeltez, Israel is the location for an onshore deep saline CO2 storage pilot site. The 'Heletz sandstone' is the building unit of the deep saline reservoir. Based on core samples of sandstone and caprock taken from the newly drilled injection (H18A) and monitoring wells (H18B), this article examines and reports the petrophysical properties of the Heletz Formation reservoir important for the short and long term trapping of CO2. A suite of laboratory and pore-scale CT-based modeling techniques are employed to determine the flow and transport parameters used by the continuum-scale numerical simulators and the mineral composition necessary for the understanding of mineral trapping processes. The effect of diagenesis on the reservoir parameters was determined in the laboratory using sedimentological, petrological, and petrophysical analyses. Variations in Sr-87/Sr-86 isotope composition and fluid inclusion analysis bring additional information about the diagenetic development and define the status quo of fluid-mineral reactions before CO2 injection. Cathodoluminescence microscopy and SEM/XRD revealed the amounts of minerals in the sandstone samples and caprock and explained the poor binding of the sandstone which may lead to mobilized material during injection. Digital image analysis on thin sections, cathodoluminescence, and SEM were integrated with attributes derived from mercury intrusion porosimetry, steady state gas permeametry or nuclear magnetic resonance to form an essential outline for the Heletz Formation reservoir. This relates storage space, injectivity and storage efficiency to features such as grain size, pore size distribution, effective porosity, intrinsic permeability, or tortuosity. Furthermore, the laboratory and numerical CT-based investigation techniques are compared and discussed. The benefit of combining experimental methods and numerical simulations on pore-scale models is the increase in confidence of the parameter accuracy, fundamental for the success of the planned activities at Heletz. (C) 2016 Elsevier Ltd. All rights reserved.European Community [227286, 282900, 309067
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
Anwendung und Bewertung der Gitter Boltzmann Methode für die Modellierung des Fluid Transports in porösen Gesteinen
Full text linkDie Modellierung physikalischer Eigenschaften und Phänomene von natürlichen Festgesteinen stellt inzwischen einen wichtigen Arbeitsbereich innerhalb der modernen Gesteinsphysik dar. In den letzten Jahren hat dabei die Röntgen-Computertomografie als schnelles, zerstörungsfreies sowie bildgebendes Verfahren die Grenzen des Verständnisses der Fluid Dynamik in komplexen Systemen signifikant vorangetrieben. Diese Promotionsschrift reiht sich konsequent in die komplexe Thematik mit ein und gibt zunächst einen umfassenden Einblick in den Stand der Technik von Strömungssimulationen in porösen Medien, bevor neue Ansätze für hochgenaue Modellrechnungen in echten Porennetzwerken aufgezeigt werden. Zielführend werden dabei zunächst die theroretischen Grundlagen bezüglich der Fluid Dynamik, dem bildgebenden Verfahren sowie der Modellierungstechnik gegeben. Diesem theoretischen Teil folgt eine ausführliche, interdisziplinäre Gesteinscharakterisierung, bevor die Ergebnisse der Strömungssimulationen an synthetischen und realen Porennetzwerken dargestellt werden. Besonderes Augenmerk dieser Arbeit liegt dabei auf zwei thematischen Bereichen. Zum Einen, wird der essentielle Arbeitsablauf zur Gewinnung hochaufgelöster 3D Datensätze für die Extraktion der in-situ Porennetzwerke analysiert. Aufgrund der hohen erreichbaren Auflösung moderner CT-Systeme (wenige Mikrometer, teils einige hundert Nanometer) können erstmalig auch sehr kleine Porenstrukturen für die Modellierung aufbereitet werden. Dazu wird ein verbesserter Extraktions-Algorithmus getestet, der in der Lage ist, die segmentierten Strukturen mit hoher Genauigkeit und Zuverlässigkeit in numerische Gitter zu transferieren. Zum Anderen wird ein neues Verfahren zur Überprüfung der Repräsentativität von Transportmodellierungen eingeführt. Die so ermittelten repräsentativen Volumina werden im Anschluss daran mittels der Gitter Boltzmann Methode auf ihre Transporteigenschaften hin untersucht. Aufgrund dieser numerisch sehr einfachen, aber dennoch eleganten Methode können beliebige Strukturen (z.B. grobe und feine Porennetzwerke, sekundäre Porositäten, Tonporositäten, etc.) auf beliebigen Skalen mit hoher Auflösung modelliert und gleichfalls charakterisiert werden. Ergänzend dazu werden vergleichende Simulationen mit gebräuchlichen Softwarepaketen evaluiert und mit den Ergebnissen der Boltzmann Modellierung auf verschiedenen (Mikro-) Skalen gegenübergestellt. Abschließend werden die Ergebnisse aller Teilbereiche zusammengefasst, beurteilt und diskutiert.Modeling physical properties and phenomena of natural rocks forms an important field of work for modern petrophysics. In recent years, the fast and non-destructive X-ray computed micro tomography has pushed the knowledge and understanding of fluid dynamics in complex pore systems extensively forward. This PhD thesis is in accordance to this wide and complex field of research and gives a comprehensive overview about state of the art transport modeling in porous media. New approaches for high precisely modeling aspects in real pore geometries are shown. Conducive to this thesis, theoretical background on fluid dynamics, modern CT imaging and modeling techniques is introduced first. Afterwards, a detailed and interdisciplinary rock characterization is performed, before results of transport modeling on a synthetic and on real pore networks are given. Special attention is given onto two main topics. On the one hand, the essential workflow to obtain high resolution 3D data sets for the advanced pore network extraction is introduced in detail. Since modern CT devices are able to scan samples with micron to submicron resolution, even very small pore structures can be taken into account for modeling purposes. For this, a special network extraction algorithm, which is able to preserve these small sample features with high accuracy during grid generation, is tested. On the other hand, an advanced method to evaluate the representiveness of transport modeling phenomena, depending on the voxel size of the scanned data, is introduced. The so derived representative elementary volumes (REV) are then used to apply the Lattice Boltzmann Method (LBM) for the estimation of fluid transport properties of these structures. Due to this numerically easy but elegant approach, even structures of arbitrary complexity (e.g. coarse and fine pore networks, secondary porosities, clay related porosities, etc.) can be investigated and taken into account on different scales as well. Additionally, comparative simulations with a commonly used modeling technique are performed and evaluated in close combination with the results of the Boltzmann transport modeling on different scales. Finally, results of each partition of this thesis are combined, assessed, discussed and summarized
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