1,720,959 research outputs found
Data for publication "Development of a dual-domain karst flow model under consideration of preferential film-flow dynamics and analysis of compartment-specific parameter sensitivities"
No full textData for publication "Development of a dual-domain karst flow model under consideration of preferential film-flow dynamics and analysis of compartment-specific parameter sensitivitie
CFPy —A Python Package for Pre‐ and Postprocessing of the Conduit Flow Process of MODFLOW
No full textBundesministerium für Bildung und Forschung https://doi.org/10.13039/501100002347Deutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Development of a Dual‐Domain Karst Flow Model Under Consideration of Preferential Film‐Flow Dynamics and Analysis of Compartment‐Specific Parameter Sensitivities
No full textAbstract The characterization and management of karst systems is a challenging task due to their inherently heterogeneous nature and vulnerability with respect to contamination. Highly conductive features of the vadose zone (e.g., dissolution shafts and faults) induce flow channeling and preferential flow. This complicates any efforts to simulate rapid recharge dynamics in deep porous‐fractured vadose zones in the context of flood and contamination risk assessment. Therefore, a strong need for numerical modeling strategies arises that employ conceptually sound formulations of these dynamics based on physical processes. Here, we present a novel modeling strategy by extending the numerical discrete‐continuum flow model MODFLOW‐CFPv2 to allow the simultaneous computation of diffuse fluxes and film‐flow in the vadose zone, thus simulating infiltration via preferential pathways. We conduct a global sensitivity analysis of a synthetic karst system that addresses the importance of including such processes in karst modeling. While event‐averaged sensitivities are in alignment with commonly observed dominance of the phreatic zone properties, results of time‐dependent sensitivities suggest that during strong infiltration events the consideration of film‐flow and its controlling parameters, that is, the fracture facial area density and an applied upper threshold for its activation, can become important. Our distributed numerical method assists in the development of karst modeling strategies where a sufficiently large and developed vadose zone offers the capacity for preferential flow that may not be accurately reproduced by most bulk‐effective methods. Hence, it benefits the unique characterization of such systems and can be easily implemented in existing workflows such as CFPv2.Key Points We developed a novel karst flow model under consideration of diffuse as well as process‐based film flow dynamics within the vadose zone A global sensitivity analysis is carried out to highlight the importance of rapid infiltration in the vadose zone via preferential pathways Results of time‐dependent sensitivities show the importance of film‐flow and its controlling parameters during strong infiltration eventsAbstract The characterization and management of karst systems is a challenging task due to their inherently heterogeneous nature and vulnerability with respect to contamination. Highly conductive features of the vadose zone (e.g., dissolution shafts and faults) induce flow channeling and preferential flow. This complicates any efforts to simulate rapid recharge dynamics in deep porous‐fractured vadose zones in the context of flood and contamination risk assessment. Therefore, a strong need for numerical modeling strategies arises that employ conceptually sound formulations of these dynamics based on physical processes. Here, we present a novel modeling strategy by extending the numerical discrete‐continuum flow model MODFLOW‐CFPv2 to allow the simultaneous computation of diffuse fluxes and film‐flow in the vadose zone, thus simulating infiltration via preferential pathways. We conduct a global sensitivity analysis of a synthetic karst system that addresses the importance of including such processes in karst modeling. While event‐averaged sensitivities are in alignment with commonly observed dominance of the phreatic zone properties, results of time‐dependent sensitivities suggest that during strong infiltration events the consideration of film‐flow and its controlling parameters, that is, the fracture facial area density and an applied upper threshold for its activation, can become important. Our distributed numerical method assists in the development of karst modeling strategies where a sufficiently large and developed vadose zone offers the capacity for preferential flow that may not be accurately reproduced by most bulk‐effective methods. Hence, it benefits the unique characterization of such systems and can be easily implemented in existing workflows such as CFPv2.Key Points We developed a novel karst flow model under consideration of diffuse as well as process‐based film flow dynamics within the vadose zone A global sensitivity analysis is carried out to highlight the importance of rapid infiltration in the vadose zone via preferential pathways Results of time‐dependent sensitivities show the importance of film‐flow and its controlling parameters during strong infiltration eventsDeutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Analogue fracture experiments and analytical modeling of unsaturated percolation dynamics in fracture cascades
No full textInfiltration and recharge dynamics in fractured aquifer systems often strongly deviate from diffuse Darcy–Buckingham type flows due to the existence of a complex gravity-driven flow component along fractures, fracture networks, and fault zones. The formation of preferential flow paths in the unsaturated or vadose zone can trigger rapid mass fluxes, which are difficult to recover by volume-effective modeling approaches (e.g., the Richards equation) due to the nonlinear nature of free-surface flows and mass partitioning processes at unsaturated fracture intersections. In this study, well-controlled laboratory experiments enabled the isolation of single aspects of the mass redistribution process that ultimately affect travel time distributions across scales. We used custom-made acrylic cubes (20 by 20 by 20 cm) in analog percolation experiments to create simple wide-aperture fracture networks intersected by one or multiple horizontal fractures. A high-pre-cision multichannel dispenser produced gravity-driven free-surface flow (droplets or rivulets) at flow rates ranging from 1 to 5 mL min −1 . Total inflow rates were kept constant while the fluid was injected via 15 (droplet flow) or three inlets (rivulet flow) to reduce the impact of erratic flow dynamics. Normalized fracture inflow rates were calculated and compared for aperture widths of 1 and 2.5 mm. A higher efficiency in filling an unsaturated fracture by rivulet flow observed in former studies was confirmed. The onset of a capillary-driven Washburn-type flow was determined and recovered by an analytical solution. To upscale the dynamics and enable the prediction of mass partitioning for arbitrary-sized fracture cascades, a Gaussian transfer function was derived that reproduces the repetitive filling of fractures, where rivulet flow is the prevailing regime. Results show good agreement with experimental data for all tested aperture widths. © Soil Science Society of America.This work was funded by the Deutsche Forschungsgemeinschaft (DFG; German Research Foundation) under Grant no. KO 53591/1-1 and supported by the Open Access Publication Funds of the University of Göttingen. Marco Dentz acknowledges the funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement no. 617511 (MHetScale).Peer reviewe
Effect of Unsaturated Flow Modes on Partitioning Dynamics of Gravity-Driven Flow at a Simple Fracture Intersection: Laboratory Study and Three-Dimensional Smoothed Particle Hydrodynamics Simulations
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Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
No full textWe 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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