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Rome, Italy

Ducci D.,University of Naples | Ducci D.,CNR Water Research Institute | de Melo M.T.C.,University of Lisbon | Preziosi E.,CNR Water Research Institute | And 4 more authors.
Science of the Total Environment | Year: 2016

The natural background level (NBL) concept is revisited and combined with indicator kriging method to analyze the spatial distribution of groundwater quality within a groundwater body (GWB). The aim is to provide a methodology to easily identify areas with the same probability of exceeding a given threshold (which may be a groundwater quality criteria, standards, or recommended limits for selected properties and constituents). Three case studies with different hydrogeological settings and located in two countries (Portugal and Italy) are used to derive NBL using the preselection method and validate the proposed methodology illustrating its main advantages over conventional statistical water quality analysis. Indicator kriging analysis was used to create probability maps of the three potential groundwater contaminants. The results clearly indicate the areas within a groundwater body that are potentially contaminated because the concentrations exceed the drinking water standards or even the local NBL, and cannot be justified by geogenic origin. The combined methodology developed facilitates the management of groundwater quality because it allows for the spatial interpretation of NBL values. © 2016 Elsevier B.V. Source

Carlevaro N.,ENEA | Falessi M.V.,Romatre University | Montani G.,ENEA | Montani G.,University of Rome La Sapienza | Zonca F.,ENEA
Journal of Plasma Physics | Year: 2015

In this paper we study transport features of a one-dimensional beam-plasma system in the presence of multiple resonances. As a model description of the general problem of a warm energetic particle beam, we assume η cold supra-thermal beams and investigate the self-consistent evolution in the presence of the complete spectrum of nearly degenerate Langmuir modes. A qualitative transport estimation is obtained by computing the Lagrangian Coherent Structures of the system on given temporal scales. This leads to the splitting of the phase space into regions where the local transport processes are relatively faster. The general theoretical framework is applied to the case of the nonlinear dynamics of two cold beams, for which numerical simulation results are illustrated and analysed. © 2015 Cambridge University Press. Source

Pischiutta M.,Italian National Institute of Geophysics and Volcanology | Savage M.K.,Victoria University of Wellington | Holt R.A.,Victoria University of Wellington | Salvini F.,Romatre University
Journal of Geophysical Research B: Solid Earth | Year: 2015

We investigate seismic signatures of fracturing in a newly ruptured strike-slip fault by determining the wavefield polarization in the New Zealand Canterbury Plains area and across the Greendale Fault, which was responsible for the 3 September 2010 Darfield Mw 7.1 earthquake. Previous studies suggested that fractured rocks in fault damage zones cause directional amplification and ground motion polarization in the fracture-perpendicular direction as an effect of stiffness anisotropy, and cause velocity anisotropy with shear wave velocity larger in the fracture-parallel component. An array of 14 stations was installed following the Darfield earthquake. We assess polarization both in the frequency and time domains through the individual-station horizontal-to-vertical spectral ratio and covariance matrix analysis, respectively, and compare the results to previously reported anisotropy measurements from shear wave splitting. Stations installed in the Canterbury Plains have an amplification peak between 0.1 and 0.3 Hz for both earthquakes and ambient noise. We relate the amplification to the resonance of a considerable thickness (c. 1 km) of soft sediments lying over the metamorphic bedrock. Analysis of seismic events revealed the existence of another peak in amplification between 2 and 5 Hz at two on-fault stations, which was not visible in the noise analysis. In contrast to the lower frequency peak, the ones between 2 and 5 Hz are more strongly anisotropic, attaining amplitudes up to a factor of 4 in the N52 direction. To interpret this effect we model the fracture pattern in the fault damage zone produced by the fault kinematics. We conclude that the horizontal polarization is orthogonal to extensional fractures, which predominate in the shallow layers (<2 km) with an expected strike of N139. Fracture orientation is consistent with coseismic surface rupture observations, confirming the reliability of the model. S wave splitting is produced by velocity anisotropy in the entire rock volume crossed along the seismic path; thus, it is affected by deeper material than the amplification study. We explain the rotation of S wave fast component observed by Holt et al. (2013) near the fault in terms of the dominant synthetic cleavages at greater depths (>2 km), expected in N101 direction on the basis of the model. Thus, different fracture distribution at different depths may explain different results for amplification compared to anisotropy. We propose polarization amplification analysis as a complementary method to S wave splitting analysis. Polarization analysis is rapidly computed and robust, and it can be applied to either earthquakes or ambient noise recordings, giving useful information about the predominant fracture patterns at various depths. ©2015. American Geophysical Union. All Rights Reserved. Source

Preziosi E.,CNR Water Research Institute | Rossi D.,CNR Water Research Institute | Parrone D.,CNR Water Research Institute | Parrone D.,Romatre University | Ghergo S.,CNR Water Research Institute
Rendiconti Lincei | Year: 2016

The evaluation of the chemical status of groundwater bodies, pursuant to the European Groundwater Directive 2006/118/EC, requires the assessment of the natural background levels when concentration exceeds the national standards. In large part of Italy, including the case-study region Latium, the presence of substances of natural origin has long been recognized. Nonetheless, a systematic assessment of background levels is still missing. Guidelines have been published both at the European and Italian level, but there are still unanswered questions, including the appropriate geographical scale, the time and spatial variation. In this paper, the evaluation of the groundwater chemical status at the groundwater body scale for the Latium region for the above-mentioned elements is presented. We used the preselection method, choosing the 95th percentile of the preselected datasets for various groundwater bodies. Results show that the natural background levels differ at the groundwater body scale reflecting the complexity of the geological asset. At a smaller scale, the variation of the background even at short distances may be dramatic, and this should be considered especially when dealing with site scale assessment. Conversely, the time variation of the considered parameters seems to be modest. In the case-study region, the chemical status assessment considering the background levels would result “good” as for the exceedances of arsenic and fluoride, solving the problem of erroneous classification of water bodies characterized by contamination of natural origin. © 2015, Accademia Nazionale dei Lincei. Source

Vissicchio S.,Catholic University of Louvain | Cittadini L.,Romatre University | Bonaventure O.,Catholic University of Louvain | Xie G.G.,Naval Postgraduate School, Monterey | Vanbever L.,Princeton University
Proceedings - IEEE INFOCOM | Year: 2015

Network operators can and do deploy multiple routing control-planes, e.g., by running different protocols or instances of the same protocol. With the rise of SDN, multiple control-planes are likely to become even more popular, e.g., to enable hybrid SDN or multi-controller deployments. Unfortunately, previous works do not apply to arbitrary combinations of centralized and distributed control-planes. In this paper, we develop a general theory for coexisting control-planes. We provide a novel, exhaustive classification of existing and future control-planes (e.g., OSPF, EIGRP, and Open-Flow) based on fundamental control-plane properties that we identify. Our properties are general enough to study centralized and distributed control-planes under a common framework. We show that multiple uncoordinated control-planes can cause forwarding anomalies whose type solely depends on the identified properties. To show the wide applicability of our framework, we leverage our theoretical insight to (i) provide sufficient conditions to avoid anomalies, (ii) propose configuration guidelines, and (iii) define a provably-safe procedure for reconfigurations from any (combination of) control-planes to any other. Finally, we discuss prominent consequences of our findings on the deployment of new paradigms (notably, SDN) and previous research works. © 2015 IEEE. Source

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