1,720,973 research outputs found
Disponibilità idrica dell'acquifero freatico costiero della Regione Emilia-Romagna e analisi dei fattori di rischio
No full textSurface water-groundwater interaction and nitrate persistence in unconfined high-conductivity aquifers investigated via time series analysis
No full textGroundwater monitoring and protection are crucial issues within the environmental policies of the European Union. European directives require to (i) identify and characterize groundwater bodies, and (ii) reach specific quantitative/qualitative standards for each identified aquifer. The Italian laws incorporate these indications and provide technical criteria to characterize groundwater bodies. In this context, strategies aimed at preventing groundwater depletion play a relevant role in the conservation of water resources. In this study, we focus on the analysis of the underlying mechanisms of natural recharge for an unconfined high-conductivity aquifer. In particular, we refer to the area of the Apennines alluvial fan of the Emilia-Romagna Region. The portion of the cones close to the Apennines consists in high-permeable deposits that extend up to several hundred meters underground. A monolayer phreatic aquifer, connected directly to the surface, is located in this area. Widespread water withdrawals are present for agricultural and industrial purposes. For this reason, the analysis of nitrate concentration in groundwater represents a crucial issue. The use of nitrogen fertilizers and spreading of sewage and sludge in the soil are considered the main sources of nitric pollution. Based on time series analysis, we investigate the natural recharge dynamics by observing the influence of hydrometric variations on the piezometry, and the relationship between water level and nitrate concentration in the aquifer. We do this by means of autoregressive moving average models. The basic idea is to represent hydrological time series as single realizations of stochastic processes. In this context, we provide a basis to estimate groundwater vulnerability through an insight on surface water-groundwater interaction, and the persistence associated with nitrate concentration in an unconfined high-conductivity aquifer
NON-NEWTONIAN FLOW IN A VARIABLE APERTURE FRACTURE: EFFECT OF FLUID RHEOLOGY
Full text linkA conceptual model is presented for non-Newtonian fluid flow in fractured media. The fluid is represented via a
truncated power-law model, the fracture aperture via a stochastic model
The fracture flowrate is derived for flow perpendicular to aperture variation as a function of the parameters
describing the fluid rheology and the variability of the aperture field
Adoption of the pure power law model leads to overestimation of the flowrate with respect to the truncated model,
more so for large external pressure gradient and/or aperture variabilit
Data-driven models of groundwater salinization in coastal plains
No full textSalinization of shallow coastal aquifers is particularly critical for ecosystems and agricultural activities. Management of such aquifers is an open challenge, because predictive models, on which science-based decisions are to be made, often fail to capture the complexity of relevant natural and anthropogenic processes. Complicating matters further is the sparsity of hydrologic and geochemical data that are required to parameterize spatially distributed models of flow and transport. These limitations often undermine the veracity of modeling predictions and raise the question of their utility. As an alternative, we employ data-driven statistical approaches to investigate the underlying mechanisms of groundwater salinization in low coastal plains. A time-series analysis and auto-regressive moving average models allow us to establish dynamic relations between key hydrogeological variables of interest. The approach is applied to the data collected at the phreatic coastal aquifer of Ravenna, Italy. We show that, even in absence of long time series, this approach succeeds in capturing the behavior of this complex system, and provides the basis for making predictions and decisions
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
Analisi di ingressione marina a Bellocchio (Fe) negli scenari di breve, medio e lungo termine con l'ausilio della modellazione matematica 2DH
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