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Un marco para la modelación de flujo hiporreico en escala hidrodinámica
No full textilustraciones, gráficas, tablasIn tropical countries, like Colombia and in other parts of the world, free surface streams play a key role either as freshwater supply for human settlements, or as wastewater receivers from households and industrial compounds. Population growth, internal migration of people towards cities and the effects of climate change make that pressure on aquatic ecosystems become a topic of interest for science and public administration. Therefore, understanding different water bodies, their interaction and their integral modelling process are a research topic of great interest in earth sciences and engineering. In fact, in the last 30 years, academia has studied the interaction between free surface streams and aquifers beneath them, focusing on the effects of these type of flows. This milestone marked the beginning of the studies of Hyporheic Flow (HF) and Hyporheic Zone (HZ).
Hyporheic Zone (HZ) is defined as "a subsurface flowpath along which water 'recently' from the stream will mix with subsurface water to 'soon' return to the stream''. This place has a great relevance in ecologic, biologic and chemical processes such as contaminant attenuation, nutrient, sediment and heat transport for biota growth, nitrification processes in water bodies and river restoration. These phenomena are closely related with chemical water quality and are modeled usually with conservative and reactive transport equations. Nevertheless, species transport in HZ depends on water flow and the patterns it follows.
The flow within the HZ is known as Hyporheic Flow (HF) and its main feature is the wide range of scales in which it acts. Hence, within HZ there is flow from the pore scale and it is controlled by pressure gradients, to the scale of flows controlled by the stream morphology. This wide variety of scales, along with media heterogeneity make the study of processes within the HZ a challenge for the scientific community. Moreover, in countries like Colombia, streams play a key role in society since they are the main freshwater supply and also receive the water disposal.
The main goal of this research project is to formulate a methodological frame for HZ modelling from the continuous media perspective. To that end, this work presents the study of HF, starting from different numerical models, proposing simplifications that can portray HF. In the same way, the use of numerical models allows the decomposition of the physical phenomena to characterize their individual contribution to the HF. The models' results are compared with experimental results to validate their practical usefulness and propose their use in different case studies related with biological, chemical and ecological processes.
To accomplish the main goal, this document presents three different approaches to HF driven by hydrodynamics, using different numerical tools. These approaches are based in continuum media mechanics, despite using different numerical schemes; each one of the presents pros and cons, but above all, each one of them gives key information about Hyporheic Flow that, in the near future, can be upscaled and used for decision making regarding hydraulic resources.
The first numerical model proposed uses Burgers' Equation (BE) to represent HF in a bed with cubical packed spheres. The main goal is to study turbulent velocity decay within uniform media to characterize HF through a simple expression as the BE taking into account the interaction between non linear effects and energy dissipation, characteristic within multiscale flows. For the computational model a Spectral Multidomain Penalty method (SMPM) to avoid numerical errors associated with traditional numerical schemes as finite differences, elements or volumes. The BE model is presented as a first approach of HF in a lab scale.
In second place, the use of the Navier-Stokes Equations (NSE) to represent the combination of free surface flow and a sand bed. Again, the main goal is to determine a mean velocity profile representing the transition between free surface flow in a flume and a regular bed. To achieve this goal the Finite Volume Method was used along with an open source code that was modified to include different viscosity values and source/sink terms that are able to capture the velocity decay. The results of flow are compared with different numerical and experimental models. This analysis includes also a conservative transport model that was also compared with experimental results.
For the final approach, a numerical particle-tracking model is proposed to assess their influence of HF in fine sediment deposition in river beds. The main goal of this part is to evaluate the process of deposition taking into account different flow scenarios within the HZ. Besides flow in porous media, this model includes particle filtration within the bed to retain particles and show places where deposition is more prone to occur. The results, once again, are compared with flume experiments of kaolinite deposition in a recirculating flume.
To wrap up, the three models presented in this work offer a novel vision on Hyporheic Flow within scales driven by hydrodynamical effects. Mainly, the free flow conditions driving flow in porous media and high Reynolds number flows presence within porous media determine hydrodynamics and processes associated with it, such as fine sediment deposition.En paises tropicales como Colombia y en gran parte del mundo, las corrientes superficiales juegan un rol importante como fuente de agua potable para grandes asentamientos humanos, a la vez que receptores de vertimientos domésticos e industriales. El crecimiento de la población, la migración interna a las ciudades y los efectos del cambio climático, hacen que la presión sobre los ecosistemas acuáticos se vuelva un tema de interés para la ciencia y la administración pública. En consecuencia, el entendimiento de los diferentes cuerpos de agua, las relaciones entre ellos y su modelación integral son un tema de investigación con gran acogida en las geociencias y la ingeniería. De hecho, desde hace cerca de 30 añnos, la academia se ha fijado en las realciones entre las corrientes de agua y los acuíferos debajo de las mismas para estudiar diferentes fenómenos ocasionados por este tipo de flujos. De esta forma nace el estudio del Flujo Hiporreico (HF) y la Zona Hiporreica (HZ). La Zona Hiporreica (HZ) se define como "la trayectoria de flujo de agua que ha abandonado un cuerpo de agua superficial hace "poco'' tiempo, para mezclarse con agua subterránea y "pronto'' volver al mismo cuerpo de agua''. Este lugar tiene gran importancia en procesos ecológicos, biológicos y químicos como la atenuación de contaminantes, el transporte de nutrientes, sedimentos y calor para el crecimiento de biota, los procesos de nitrificación de los cuerpos de agua y la restauración de cuerpos de agua. Estos fenómenos están ligados estrechamente con el concepto de calidad y química del agua, y son modelados con ecuaciones de transporte conservativo o reactivo. No obstante, el transporte de sustancias en este medio depende del flujo de agua y los patrones que este sigue. Al flujo de agua en la HZ se le denomina Flujo Hiporreico (HF), y su principal característica es el amplio rango de escalas en el que está presente. De esta forma, dentro de la HZ se pueden observar flujo desde la escala de poros, controlado por gradientes de presión, hasta la escala de flujos controlados por la morfología de las corrientes de agua. Esta amplia variedad de escalas, sumada a la heterogeneidad de los medios naturales, hacen que el estudio de procesos en la HZ se transforme en un reto para la comunidad científica. El objetivo del presente trabajo de investigación es el de formular un marco metodológico para la modelación de la HZ desde la perspectiva de la mecánica del medio continuo. Para tal fin, este trabajo presenta un estudio del HF, a partir de diferentes modelos numéricos, proponiendo simplificaciones que puedan representar el HF. Asimismo, el uso de modelos numéricos permite descomponer los fenómenos físicos para caracterizar la contribución de cada uno al HF. Los resultados de los modelos son comparados con resultados experimentales para verificar su utilidad práctica y proponer su uso en diferentes casos de estudio relacionados con procesos biológicos, químicos y ecológicos. Para el cumplimiento del objetivo general se presentan tres aproximaciones de modelación de Flujo Hiporreico dominado por factores hidrodinámicos, por medio de diferentes herramientas numéricas. Estas aproximaciones se basan en la mecánica del medio continuo, a pesar de utilizar diferentes esquemas numéricos; presentan diferentes fortalezas y debilidades y, sobre todo, brindan información sobre el Flujo Hiporreico que, en un futuro, puede ser escalada para contribuir con la toma de decisiones en lo referente al recurso hídrico. El primer modelo numérico propuesto utiliza la ecuación de Burgers (BE) para representar el HF en un lecho de esferas dispuestas en forma cúbica. El objetivo principal es estudiar el decaimiento de las velocidades turbulentas dentro de un medio uniforme para caracterizar el HF mediante una expresión simple como la BE teniendo en cuenta la interacción de efectos no lineales y disipación de energía, propios de los flujos multiescala. Para el modelo computacional se utilizó un método de multidominio espectral (SMPM) para evitar errores numéricos asociados a los métodos tradicionales como las diferencias, elementos o volúmenes finitos. Este modelo se presenta como una primera aproximación hacia el HF a escala de laboratorio. En segundo lugar, se propone un modelo basado en las ecuaciones de Navier-Stokes (NSE) modificada para representar la combinación de un flujo libre y el lecho de un canal. De nuevo, el objetivo es determinar un perfil de velocidades promedio que represente la transición entre el flujo de un canal y un lecho de forma regular. Para este fin se utilizó el método de los volúmenes finitos y un paquete de software de código abierto que fue modificado para incluir viscosidades diferentes y términos de fuente/sumidero que representen el decaimiento de velocidades. Los resultados de flujo son comparados con diferentes modelos numéricos y experimentales. De igual manera, este análisis incluye además una implementación de transporte conservativo de especies que fue también comparado con resultados experimentales. Como última aproximación, se propone un modelo de rastreo numérico de partículas para evaluar la influencia del HF en la depositación de sedimentos finos en lechos de ríos. El objetivo principal de este aparte es analizar el proceso de depositación de sedimentos, teniendo en cuenta diferentes escenarios de flujo en la HZ. Además del flujo en el medio poroso, el modelo implementado utiliza la filtración de materiales dentro del lecho para retener partículas finas y mostrar los lugares donde se espera que haya mayor depositación de estas. Los resultados, una vez más, son validados de forma cualitativa con experimentos de laboratorio realizados con kaolinita en canales recirculantes experimentales. En síntesis, los tres modelos presentados en este trabajo ofrecen una visión novedosa sobre el Flujo Hiporreico en escalas dominadas por efectos hidrodinámicos. Principalmente, el dominio de las condiciones de flujo libre presentes sobre el flujo en el medio poroso y la presencia de flujos con altos números de Reynolds dentro del medio poroso dominan la hidrodinámica y los procesos asociados a la misma, como la despositación de sedimentos finos.Convocatoria 647/2014 de Colciencias - Doctorados nacionales
Cohorte 2016 - Beca estudiante doctoral colombiano - Comisión Fulbright ColombiaDoctoradoDoctor en Ingeniería - Ingeniería CivilAgua y medio ambient
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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