1,720,961 research outputs found
Modello matematico di flusso e trasporto nei sistemi acquiferi dell'Alto Vicentino
Full text linkFor the past thirty-five years, the layered aquifer system of Central Veneto (Italy) has seen an increasing demand of water for domestic and private uses and a significant reduction of groundwater heads. During these years the origin and development of important groundwater pollution phenomena in the relevant aquifers has been revealed by a quality monitoring system. These aquifers are particularly vulnerable because of the presence of industrial activity in areas characterized by high permeability soils highly susceptible to contaminants transport.
The presenti thesis deals with mathematical models of the relevant processes (flow and transport), jointly with their field validations.
The regional groundwater flux model developed is a large scale scheme originating from detailed studies of the hydrogeological system including: accurate reconstruction of the geological model; hydrogeological characterization; estimates of the groundwater fluxes for mass balance. The three-dimensional flow model allows for the establishment of causal relationships between withdrawal of water (whatever the production layer, and the extracted flow rates) and the fluctuations of piezometric heads anywhere in the system. Its purpose is to provide boundary conditions for the study of flow models and specifically of transport models at smaller scale.
The chief aim of this work is to develop a three-dimensional transport model of solutes within the heterogeneous aquifer systems, in order to obtain long-term predictions of pollutant migration into geologic deposits characterized by variable hydraulic properties. The transport model is implemented according to different numerical approaches: first, a finite elements method is adopted, secondly a Lagrangian approach (Particle Tracking) is taken into account and, finally, the advection-dispersion equation in groundwater, used to describe solute transport in porous media, is solved by a time-splitting technique.
During the present study field experiments have been carried out, which consisted in monitoring solute plume via tracer tests in a heterogeneous aquifer. Concentration data are then used for aquifer parameter identification, necessary for model calibration. The movement of a saline tracer in the subsurface has been monitored via electrical resistivity tomography (ERT) from the surface. The spreading of the solute plume measured in the field experiment permits for an estimate of the actual transport properties in the heterogeneous medium in terms of dispersivity parameters. These parameters are then applied to transport models on a regional scale.
The transport model implemented has allowed for a better understanding of the regional groundwater system and of its transport-related properties. The model is suggested to predict well the evolution of real transport phenomena, so it is deemed of a certain importance for the management of water resources in the area.Negli ultimi anni gli acquiferi dell'Alto Vicentino (Veneto Centrale) sono stati interessati da una crescente domanda idrica accompagnata da un evidente abbassamento dei livelli freatici e da una depressurizzazione delle falde artesiane. Nello stesso periodo l'attività di controllo e di monitoraggio della qualità della risorsa idrica ha fatto emergere alcuni importanti fenomeni di inquinamento che hanno interessato i corpi idrici sotterranei dell'Alto Vicentino, resi vulnerabili dalla presenza di importanti poli industriali in zone ad alta permeabilità, che facilitano il trasporto degli inquinanti in falda.
La presente tesi propone modelli matematici (e le loro validazioni) per lo studio della gestione delle risorse idriche negli acquiferi profondi del Veneto Centrale.
Il modello matematico generale di flusso sviluppato si prefigge di fornire uno strumento qualitativo per la gestione delle risorse idriche e le condizioni al contorno per l'implementazione di
modelli di trasporto. Il modello è stato realizzato sulla base di un'accurata analisi idrogeologica del territorio allo studio, in particolare con la ricostruzione di dettaglio del modello geo-strutturale del sistema multi-acquifero e la stima quantitativa dei termini del bilancio idrologico.
L'obiettivo principale del lavoro è lo sviluppo di un modello di trasporto nel sistema acquifero di interesse, che consenta di prevedere l'andamento spazio-temporale di fenomeni di inquinamento
in atto o futuri; tale modello è stato implementato con differenti approcci numerici: il metodo agli elementi finiti, l'approccio Lagrangiano (Particle Tracking) e l'approccio time-splitting.
Propedeutica all'implementazione del modello matematico di trasporto è la realizzazione di prove sperimentali con traccianti, che consentono di raccogliere informazioni a scala locale sui parametri idro-dispersivi del processo, necessarie alla taratura del modello. Nell'ambito della presente tesi è stato condotto un monitoraggio elettrico ad alta risoluzione per lo studio di dettaglio delle proprietà di trasporto in un'acquifero superficiale, con l'obiettivo di applicare i risultati ottenuti dall'osservazione del comportamento del tracciante iniettato a scala locale nel trasporto a scala regionale.
Il modello di trasporto implementato ha permesso di migliorare la conoscenza delle dinamiche di trasporto nel sistema multiacquifero allo studio, e si è dimostrato in grado di riprodurre l'evoluzione di reali episodi di inquinamento in falda: esso appare quindi di interesse applicativo generale nel campo della gestione delle risorse idriche con riferimento al contesto territoriale del Veneto Centrale
MONITORAGGIO ELETTRICO AD ALTA RISOLUZIONE PER LO STUDIO DELLE PROPRIETA' DI TRASPORTO IN UN ACQUIFERO SUPERFICIALE
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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
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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