A Combined Remote Sensing–Numerical Modelling Approach to the Stability Analysis of Delabole Slate Quarry,Cornwall, UK     

Mohsen Havaej  John Coggan  Doug Stead  Davide Elmo 《Rock Mechanics and Rock Engineering》2016,49(4):1227-1245

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The Spatio-temporal Statistical Structure and Ergodic Behaviour of Scalar Turbulence Within a Rod Canopy     

Khaled Ghannam  Davide Poggi  Amilcare Porporato  Gabriel G. Katul 《Boundary-Layer Meteorology》2015,157(3):447-460

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Structure and properties of the Adriatic crust in the central‐eastern Southern Alps (Italy) from local earthquake tomography     

Alfio Viganò  Davide Scafidi  Silvana Martin  Daniele Spallarossa 《地学学报》2013,25(6):504-512

Structure and properties of the Adriatic crust were determined from local earthquake tomography around the Giudicarie fault zone (central‐eastern Southern Alps, Italy). Tomographic results, based on well‐suited 436 revised earthquakes (period 1994–2007), have a resolution comparable to the scale of regional geological domains and tectonic structures. The observed strong velocity anomalies correlate well with lithological variations corresponding to different geological domains (particularly magmatic complexes at depth) and with high fracturing and/or presence of fluids along active fault systems (South Giudicarie and Valsugana–Bassano del Grappa–Montello thrusts).  相似文献   

Snow water equivalent estimation in the Mallero basin using snow gauge data and MODIS images and fieldwork validation     

Davide Bavera  Carlo De Michele 《水文研究》2009,23(14):1961-1972

Snow accumulation and ablation rule the temporal dynamics of water availability in mountain areas and cold regions. In these environments, the evaluation of the snow water amount is a key issue. The spatial distribution of snow water equivalent (SWE) over a mountain basin at the end of the snow accumulation season is estimated using a minimal statistical model (SWE‐SEM). This uses systematic observations such as ground measurements collected at snow gauges and snow‐covered area (SCA) data retrieved by remote sensors, here MODIS. Firstly, SWE‐SEM calculates local SWE estimates at snow gauges, then the spatial distribution of SWE over a certain area using an interpolation method; linear regressions of the first two order moments of SWE with altitude. The interpolation has been made by both confining and unconfining the spatial domain by SCA. SWE‐SEM is applied to the Mallero basin (northern Italy) for calculating the snow water equivalent at the end of the winter season for 6 years (2001–2007). For 2007, SWE‐SEM estimates are validated through fieldwork measurements collected during an ‘ad hoc’ campaign on March 31, 2007. Snow‐surveyed measurements are used to check SCA, snow density and SWE estimates. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Debris flow burial of ancient wall system in the Upper Po River valley     

William C. Mahaney  Pierre Tricart  Rene W. Barendregt  Christopher Carcaillet  Davide Rabufetti  Volli Kalm 《Geology Today》2010,26(6):209-215

The regrouping area, where Hannibal is thought to have reformed his army after forging a path through a massive rockfall in the Cottian Alps, has been reshaped by a blanket of sediment deposited from debris flows following heavy rain in spring, 2008. Analysis of precipitation data for the period mid‐May to mid‐June, 2008, shows that 722 mm of rain fell at 2150 m, falling off to half that amount at 3325 m on the flanks of Mon Viso. Following exhaustive analysis of environmental factors connected with the invasion of Italy at the start of the Second Punic War (218 bc ), identification of the regrouping area for the Carthaginian Army centred on the presence of an ancient stone wall system which possibly dates from Hannibalic times. Lichen cover, lichen diameters, weathering characteristics, degree to which boulders had sunk into the resident soil, and presence of ancient hearths all combined to make this area a choice locale for reconstructive geoarchaeology. Large scale mass wasting off a prominent bedrock bar adjacent to the wall system in the Upper Po River Valley resulted in burial of most of the prominent wall structures which will complicate any exploration geoarchaeology attempts in future.  相似文献   

Photochemincal processes involving nitrite in surface water samples     

Claudio Minero  Serge Chiron  Gianpaolo Falletti  Valter Maurino  Ezio Pelizzetti  Roberto Ajassa  Maria Eugenia Carlotti  Davide Vione 《Aquatic Sciences - Research Across Boundaries》2007,69(1):71-85

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The ejection-sweep cycle over bare and forested gentle hills: a laboratory experiment     

D. Poggi  G. Katul 《Boundary-Layer Meteorology》2007,122(3):493-515

Progress on practical problems such as quantifying gene flow and seed dispersal by wind or turbulent fluxes over nonflat terrain now demands fundamental understanding of how topography modulates the basic properties of turbulence. In particular, the modulation by hilly terrain of the ejection-sweep cycle, which is the main coherent motion responsible for much of the turbulent transport, remains a problem that has received surprisingly little theoretical and experimental attention. Here, we investigate how boundary conditions, including canopy and gentle topography, alter the properties of the ejection-sweep cycle and whether it is possible to quantify their combined impact using simplified models. Towards this goal, we conducted two new flume experiments that explore the higher-order turbulence statistics above a train of gentle hills. The first set of experiments was conducted over a bare surface while the second set of experiments was conducted over a modelled vegetated surface composed of densely arrayed rods. Using these data, the connections between the ejection-sweep cycle and the higher-order turbulence statistics across various positions above the hill surface were investigated. We showed that ejections dominate momentum transfer for both surface covers at the top of the inner layer. However, within the canopy and near the canopy top, sweeps dominate momentum transfer irrespective of the longitudinal position; ejections remain the dominant momentum transfer mode in the whole inner region over the bare surface. These findings were well reproduced using an incomplete cumulant expansion and the measured profiles of the second moments of the flow. This result was possible because the variability in the flux-transport terms, needed in the incomplete cumulant expansion, was shown to be well modelled using “local” gradient-diffusion principles. This result suggests that, in the inner layer, the higher-order turbulence statistics appear to be much more impacted by their relaxation history towards equilibrium rather than the advection-distortion history from the mean flow. Hence, we showed that it is possible to explore how various boundary conditions, including canopy and topography, alter the properties of the ejection-sweep cycle by quantifying their impact on the gradients of the second moments only. Implications for modelling turbulence using Reynolds-averaged Navier Stokes equations and plausible definitions for the canopy sublayer depth are briefly discussed.  相似文献   

The relative importance of ejections and sweeps to momentum transfer in the atmospheric boundary layer     

Gabriel Katul  Davide Poggi  Daniela Cava  John Finnigan 《Boundary-Layer Meteorology》2006,120(3):367-375

Using an incomplete third-order cumulant expansion method (ICEM) and standard second-order closure principles, we show that the imbalance in the stress contribution of sweeps and ejections to momentum transfer (ΔS _o ) can be predicted from measured profiles of the Reynolds stress and the longitudinal velocity standard deviation for different boundary-layer regions. The ICEM approximation is independently verified using flume data, atmospheric surface layer measurements above grass and ice-sheet surfaces, and within the canopy sublayer of maturing Loblolly pine and alpine hardwood forests. The model skill for discriminating whether sweeps or ejections dominate momentum transfer (e.g. the sign of ΔS _o ) agrees well with wind-tunnel measurements in the outer and surface layers, and flume measurements within the canopy sublayer for both sparse and dense vegetation. The broader impact of this work is that the “genesis” of the imbalance in ΔS _o is primarily governed by how boundary conditions impact first and second moments.  相似文献   

Fluidization and injection in the deep-water sandstones of the Eocene Alba Formation (UK North Sea)   总被引：4，自引：0，他引：4  

Davide Duranti  Andrew Hurst 《Sedimentology》2004,51(3):503-529

The Nauchlan Member of the Late Eocene Alba Formation (UK North Sea) consists of a deep‐water channel fill that was extensively modified by post‐depositional sand remobilization and injection. Sandstone textures, facies associations and the geometry of the channel fill were affected. A suite of sand‐rich facies was produced by large‐scale fluidization and injection within the channel fill and above it. These facies, termed here unstratified facies, are characterized by the absence of stratification surfaces and by discordant relationships with bedding in the adjacent succession. They reflect variable degrees of disruption of the primary sedimentary structures caused by escaping pore fluid, the velocity of which is estimated at least in the order of 0·1 ms^?1. Adjacent mudstones were severely disrupted by hydraulic fracturing, and fragments of fractured mudstone were incorporated into the fluidized sand. Average porosity was decreased in the sandstones affected by fluidization. Two main phases of sand injection are inferred to occur at different burial depths. A shallow burial phase (below 100 m) produced thin dykes with ptygmatic folds. The second phase occurred at the boundary between Eocene and Oligocene (≈ 300 m burial depth) and resulted in large‐scale tabular wing‐like dykes that project from the edges of the channel fill. The significant pore‐fluid overpressure, which was required to hydraulically fracture the thick mudstone seal and to fluidize the large volume of sand, was likely to be built up by static liquefaction of the source sand and was possibly enhanced by hydrocarbon gas influx.  相似文献   

Application of newly developed ensemble machine learning models for daily suspended sediment load prediction and related uncertainty analysis     

Ahmad Sharafati  Seyed Babak Haji Seyed Asadollah  Davide Motta 《水文科学杂志》2020,65(12):2022-2042

ABSTRACT

Ensemble machine learning models have been widely used in hydro-systems modeling as robust prediction tools that combine multiple decision trees. In this study, three newly developed ensemble machine learning models, namely gradient boost regression (GBR), AdaBoost regression (ABR) and random forest regression (RFR) are proposed for prediction of suspended sediment load (SSL), and their prediction performance and related uncertainty are assessed. The SSL of the Mississippi River, which is one of the major world rivers and is significantly affected by sedimentation, is predicted based on daily values of river discharge (Q) and suspended sediment concentration (SSC). Based on performance metrics and visualization, the RFR model shows a slight lead in prediction performance. The uncertainty analysis also indicates that the input variable combination has more impact on the obtained predictions than the model structure selection.  相似文献