1,720,956 research outputs found
Attitudine all’infiltrazione e capacità di ritenzione di suoli nei confronti di fluidi inquinanti tipo DNAPL
No full textA partire dal 1994 è stata avviata, dal Dipartimento di Scienze della Terra e dal Dipartimento di Ingegneria Civile dell’Università di Firenze, una sperimentazione riguardante il flusso di inquinanti tipo DNAPL (Dense Non Aqueous Phase Liquids), come il tetracloroetilene, attraverso sedimenti lacustri, e suoli sviluppati al di sopra dei sedimenti stessi, simili per caratteristiche a quelli che proteggono il primo acquifero alluvionale nella pianura del Valdarno Medio in Toscana; in particolare la sperimentazione è avvenuta tramite l’impiego di monoliti indisturbati cilindrici di terreno, di dimensioni metriche, prelevati ad attrezzati sul medesimo sito di prelievo. I risultati della sperimentazione hanno mostrato, tramite ricostruzione della distribuzione del “plume”inquinante entro il monolite, la estrema mobilità dei solventi clorurati, soprattutto in condizioni di suoli non saturi, alla capacità di campo e fessurati per pedogenesi e strutturazione idraulica.Nel presente lavoro si vuole concentrare l’attenzione sulle evidenze sperimentali dirette del comportamento dei DNAPL in mezzi a bassa permeabilità, fra l’altro maggiormente interessanti da un punto di vista della protezione della risorsa, mettendo in risalto le implicazioni applicative in termini di valutazione dei tempi d’arrivo specifici.Fra le principali evidenze sperimentali ottenute dalla sperimentazione sul monolite si è osservato che la velocità effettiva media di migrazione della fase NAPL libera è comparabile con quella dell’acqua in condizioni sature, almeno finchè la saturazione in fase libera non scende al di sotto di quella residua; inoltre si è osservato un tempo di primo arrivo della fase disciolta in acqua (flusso convettivo-dispersivo) pari a circa 1⁄4 del tempo di arrivo dell’acqua in condizioni sature. La Kns della fase libera, inoltre, varia di più di 1 ordine di grandezza tra il momento iniziale dell’infiltrazione e le fasi successive (da 5x10-7 a 2x10-8 m/s)
Transmission of climate, sea-level, and tectonic singals across river systems
No full textThis thesis investigates the impact of climatic, tectonic, and sea-level changes (external forcing) on river systems (source-to-sink) and how these changes are recorded in the stratigraphic record. It describes a newly developed numerical tool (PaCMod) to simulate the complex fluvial system sediment flux response to external forcing on a geological time scale. Numerical modelling simulations, combined with field data indicated that the late Quaternary evolution of the Golo River system (France) was controlled by a complex interaction of sea-level and climatic forcing. Stratigraphic analysis in the Panther Tongue delta (Utah) showed how different parts of an ancient shoreline reacted differently to the same changes in external forcing, which consequently, have a different stratigraphic expression along depositional strike.Geoscience & EngineeringCivil Engineering and Geoscience
Disentangling Sea Level, and Sediment Supply Signals From The Panther Tongue Parasequence
No full textTo assess, and validate the most recent interpretations on the Panther Tongue\rq{}s depositional history we use the conceptual process-response model, 2Dstratsim. The focus of this study is on the Ksp040 parasequence which reflects the wave-dominated shoreface along the southern Wasatch Plateau. The associated Panther Tongue delta to the north is considered as the dominant sediment source for the Ksp040 parasequence. As a result of the complex 3D nature of the individual Panther Tongue delta lobes it is infeasible to correlate it to a 2D simulated profile of 2Dstratsim. Before field data is used in the 2Dstratsim model, the model is first brought to a workable level through debugging, and rewriting of the C++ source code. Then the model uses parameterised equations together with user implemented input signals in a forward routine to generate a cross-sectional profile of a shoreface on a linear decreasing initial surface. This forward routine is used through inversion techniques to automatically correlate measured, and simulated logs with the data format average grain-size to depth. By generating a best match between these logs, the forcing signals of the geologic environment are disentangled. To disentangle the forcing signals of the Panther Tongue first the cross-sectional diagram of the Panther Tongue\rq{}s shoreface is modified to prepare it for a visual correlation to the simulated cross-sections based on observed bedset characteristics. Then, the measured average grain-size log data is digitised to enable a detailed correlation calculation between the measured, and simulated logs. New tools are added to examine the model\rq{}s output graphically, in addition existing ones are enhanced. Four forward scenarios are created based on the bedset characteristics of the shoreface to set preliminary parameters, and constrain the statistical functions of the inversion routine. This improves the automated correlation procedure between the measured logs and the simulated logs. The forward scenarios use two different geologic settings, with, and without back-barrier formation on the shoreface profile. These settings are again subdivided into a scenario where solely the sea level is changed to match the simulated profile to the measured cross-sectional diagram. The other scenario primarily uses fluctuations in the sediment supply to match the cross-sections, and uses the sea level to a minimal extent. In the inversion scenario the model is matched to the simulated logs of the forward scenario, that was created without back-barrier formation, and only changes in sea level. Because the model requires additional work to generate a profile from the field measured logs. This issue is related to the stability and sensitivity of the 2Dstratsim model, the difference in average grain-size classification between the model and the field, and the gaps in the individual measured logs. Thus, 2Dstratsim can be used to create sedimentary environments using the forward routine. The model is also able to use its inversion routine to automatically recreate sedimentary environments to a limited extent as no geologic constraints are considered in this routine. Therefore, there is no assurance that the final result is geologically plausible. Additionally, extensive preliminary work is required to use the inversion routine.Petroleum EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
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
Untangling Sea Level and Sediment Supply History of the Panther Tongue Delta, Utah, USA
No full textThe Panther Tongue is a fluvio-deltaic parasequence in the lower part of the Star Point Sandstone formation in the Wasatch Plateau, central Utah, deposited during the late Cretaceous period. The sedimentology of the Panther Tongue and adjacent beach ridges parasequence has been extensively described by Hwang & Heller (2002) and Hampson et al. (2011). This study aims to produce an estimate of the magnitude of the sediment supply and the sea level fluctuations at the time when the Panther Tongue delta was formed. First, two delta sections and a beach ridges section were constructed by interpreting and correlating available logs, using the Manti geological map (Witkind et al., 1987) and geological interpretations from Hwang & Heller (2002) and Hampson et al. (2011). Next, a numerical delta and beach ridges model ‘2DStratSim’ in MATLAB was used to simulate the delta and beach ridges sections. Forward simulations with different sea level and sediment supply scenarios were run in order to determine a model that best fits the constructed delta and beach ridges sections. The input variables of the best matching simulation are the following. The relative sea level falls 28 meters over 80 000 years. The sea level decreases 4 meters over the first 40 000 years and 24 meters over the next 40 000 years. The average bed sediment load supply is 0,03 m3/s. The average suspended sediment load supply is 0,04 m3/s. The bed sediment load supply varies between 0,15 m3/s and 0,005 m3/s. The suspended sediment load supply varies between 0,1 m3/s and 0,005 m3/s. The total bed sediment volume was 1,92??10?^11 m3. The average suspended sediment load supply was 0,04 m3/s. The total suspended sediment volume was 1,55??10?^11 m3/s.Applied GeologyGeoscience & EngineeringCivil Engineering and Geoscience
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
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