1,720,955 research outputs found
Adaptive multilevel space-time-stepping scheme for transport in heterogeneous porous media (ADM-LTS)
Get PDFWe present ADM-LTS, an adaptive multilevel space-time-stepping scheme for transport in heterogeneous porous media. At each time step, firstly, the flow (pressure) solution is obtained. Then, the transport equation is solved using the ADM-LTS method, which consists of two stages. In the first stage, an initial solution is obtained by imposing the coarsest space-time grid. This initial solution is then improved, in the second stage, by imposing a space-time adaptive grid on the cells where the solution does not satisfy the desired quality. The quality control is based on error estimators with user-defined threshold values. The time-integration procedure, in which the coarsest-scale solution provides local flux boundary conditions for sub-domains with local time refinement, is strictly mass conservative. In addition, the method employs space-time fine grid cells only at the moving saturation fronts. In order to ensure local mass conservation at all levels, finite-volume restriction operators and unity prolongation operators are developed. Several numerical experiments have been performed to analyze the efficiency and accuracy of the proposed ADM-LTS method for both homogeneous and heterogeneous permeability fields on two and three dimensional domains. The results show that the method provides accurate solutions, at the same time it maintains the computational efficiency. The ADM-LTS implementation is publicly available at https://gitlab.com/darsim2simulator.Reservoir Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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 Dynamic Multilevel Multiscale Framework for Accurate and Efficient Simulation of CO2-Brine Multiphase Flow in Heterogeneous Porous Media
No full textOne of the most important challenges facing academic, industrial and policy-making sectors is meeting with the increasing energy demand while preserving the affordability of the energy and maintaining the quality of the planet earth (including the environment, specially by reducing its greenhouse gas footprint). This global challenge demands for exploiting the subsurface formations as giant storage space for industrial by prod- ucts, e.g., CO2, while a future utilisation is found for them. Exploitation of subsurface formations for CO2 storage depends on our capacity to “accurately” and “efficiently” simulate the multiphase nonlinear flow in heterogeneous large-scale natural formations. An accurate and efficient simulation would allow for proper predictive understanding for several operational aspects including: (1) capacity of the storage; (2) life-time long behaviour of the injected CO2 in the subsurface formation, and (3) safety and integrity of the capturing procedure. The challenge of extreme scale dissimilarity between the heterogeneous coefficients (rock con- ductivity and fluid physics, e.g., mixing) and the reservoir has been known in the scientific literature as one of the main simulation challenges. Classically, to resolve this mismatch, reservoir models have been exces- sively upscaled to a resolution which can be solved affordably with the state-of-the-art commercial-grade simulators. However, as the rapid extension of the computational capacity, as well as the newly developed multiscale scalable nonlinear solvers, one needs to revisit our simulation frameworks to provide a scalable (to field scale) and accurate CO2 simulation framework. This thesis work focuses on extension of the recently developed Algebraic Dynamic Multilevel Method (ADM) to highly-nonlinear simulations of CO2-Brine multi- phase flow problems. ADM maintains simulation scalability by imposing fine-scale grids only where needed; and imposing coarser grids paired with accurate prolongation operators far from the sub-domains with sharp gradients. In this work, to provide a systematic study, the developed ADM framework is formulated such that it allows for both multiscale-based basis functions and also upscaling-based procedure. This is crucially im- portant as it reveals how the "solution-based” interpolations based on fine-scale heterogeneity can impact the simulation results; compared with the “effective-coefficient-based” approach.In brief, the novelty and contribution of this research is two fold: (1) development of a multiscale-based ADM method for CO2-Brine simulator and (2) systematic study to find the best model order reduction strat- egy when it comes to complex multiphase characteristics and rock heterogeneity. Two different classes of simulations are studied: (1) injection and evolution of the injected CO2 phase into the brine with capillary effects; and (2) miscible mixing process in which resolving front fingers into the residing less-mobile fluid imposes computational challenges. The study, as such, intends to reveal the details in “upscaling-based” vs. “multiscal-based” approach; and tends to provide a generic framework in which the scalability of the simu- lations are preserved by employing fine-scale grids only where and when needed.Several challenging sensitivity analysis are performed in which fine-scale solutions are compared with the multi-scale ADM and upscaling ADM solutions for immiscible and miscible fluid flow displacement. From these numerical experiments can be concluded that Multiscale-ADM outperforms the Upscaling-based ADM approach. More precisely with similar active grid cells, it provides a more accurate simulation method. As such, Multiscale-ADM casts a promising approach for next-generation simulators for CO2-Brine systems.Applied Earth Science
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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