Data preprocessing for river flow forecasting using neural networks: Wavelet transforms and data partitioning   总被引：7，自引：0，他引：7  

Barbara Cannas  Alessandra Fanni  Linda See  Giuliana Sias 《Physics and Chemistry of the Earth》2006,31(18):1164-1171

The evaluation of surface water resources is a necessary input to solving water management problems. Neural network models have been trained to predict monthly runoff for the Tirso basin, located in Sardinia (Italy) at the S. Chiara section. Monthly time series data were available for 69 years and are characterized by non-stationarity and seasonal irregularity, which is typical of a Mediterranean weather regime. This paper investigates the effects of data preprocessing on model performance using continuous and discrete wavelet transforms and data partitioning. The results showed that networks trained with pre-processed data performed better than networks trained on undecomposed, noisy raw signals. In particular, the best results were obtained using the data partitioning technique.  相似文献   

Absolute Tilt from a Laser Guide Star: A First Experiment     

S. Esposito  R. Ragazzoni  A. Riccardi  C. O'Sullivan  N. Ageorges  M. Redfern  R. Davies 《Experimental Astronomy》2000,10(1):135-145

Absolute tip–tilt recovery using a tilt signal measured on a Laser Guide Star is a central problem in the framework of the development of Adaptive Optics Systems reaching full sky coverage down to visible wavelengths. In the past few years, various techniques aimed at solving this problemhave been proposed. However only a couple of these has been recentlytested in practice.We report about an experiment aimed at evaluating the performance of one of these techniques called the Elongation Perspective technique. Our experiment has been performed using the ALFA system inCalar-Alto (Spain) and involves the simultaneous operation of the 3.6 m and the 2.2 m telescopes at the Observatory.This article describes the telescope configuration used, as well as the datareduction process carried out in order to estimate the scientific objecttilt. The technique performances are discussed in terms of the residualtilt error variance and related correlation coefficient. The analysisshows that, despite the low SNR of our measurements, the atmospheric tiltvariance is reduced to 80% of its initial value corresponding to acorrelation coefficient of about 0.6. To get a betterestimate of the performance achievable using this technique,the tilt error variance due to photon noise in the laser measurementis estimated and removed from the obtained tilt error variance.When this correction is done, thisvariance is reduced to about 50% of its initial value, showingthat the use of this technique can give rise to a significant reduction of the scientific object image motion.  相似文献   

Normal Form Invariants Around Spin-orbit Periodic Orbits     

Alessandra Celletti  Corrado Falcolini 《Celestial Mechanics and Dynamical Astronomy》2000,78(1-4):227-241

We consider a model of spin-orbit interaction, describing the motion of an oblate satellite rotating about an internal spin-axis and orbiting about a central planet. The resulting second order differential equation depends upon the parameters provided by the equatorial oblateness of the satellite and its orbital eccentricity. Normal form transformations around the main spin-orbit resonances are carried out explicitly. As an outcome, one can compute some invariants; the fact that these quantities are not identically zero is a necessary condition to prove the existence of nearby periodic orbits (Birkhoff fixed point theorem). Moreover, the nonvanishing of the invariants provides also the stability of the spin-orbit resonances, since it guarantees the existence of invariant curves surrounding the periodic orbit.  相似文献   

Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O concentration and soil degassing at Vulcano (Aeolian islands: Italy)     

Maurizio De Rosa  Gianluca Gagliardi  Alessandra Rocco  Renato Somma  Paolo De Natale  Giuseppe De Natale 《Geochemical transactions》2007,8(1):5

We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO₂ and H₂O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-μm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO₂ and H₂O concentrations, and CO₂ soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater – FOG- and Valley of Palizzi, PAL). CO₂/H₂O values, measured on the ground, are very similar (around 0.019 (± 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS – Baia Levante beach) obtaid during the 1977–1993 heating phase of the crater fumaroles.  相似文献   

A multidisciplinary procedure to evaluate and optimize the efficacy of hydraulic barriers in contaminated sites: a case study in Northern Italy     

Alessandro Chelli  Andrea Zanini  Emma Petrella  Alessandra Feo  Fulvio Celico 《Environmental Earth Sciences》2018,77(6):246

In the last decades, hydraulic barriers have been activated in a large number of polluted sites with the aim of preventing groundwater pollution outside the contaminated area. From a regulatory point of view, there is the need of evaluating the efficacy of these barriers. For this reason, the goal of the present study is to apply a coupled experimental modelling approach aimed at evaluating the efficacy of the barrier and providing management strategies. In particular, a case study in Italy is investigated. The study case is of main interest because of its complexity due to a heterogeneous aquifer and the presence of surface water that interacts with the below aquifer. The study has been carried out through the experimental characterization of the aquifer system (coupling the classic stratigraphic techniques with the results of radiocarbon dating, as well as through pumping and injection tests) and its hydrogeological behaviour (by means of hydraulic- and the stream-head measurements, as well as some isotopic investigations), and the implementation of a numerical model (through MODFLOW 2005). The results show the effectiveness of the coupled experimental modelling approach to analyse and simulate the hydrodynamics within the test aquifer system, as well as to evaluate the efficacy of the hydraulic barrier. Based on the results of the numerical model, easy solutions were designed to manage the barrier.  相似文献   

On the Use of Interferometric Synthetic Aperture Radar Data for Monitoring and Forecasting Natural Hazards     

Bernardi  Mara S.  Africa  Pasquale C.  de Falco  Carlo  Formaggia  Luca  Menafoglio  Alessandra  Vantini  Simone 《Mathematical Geosciences》2021,53(8):1781-1812

Mathematical Geosciences - Recent advances in satellite technologies, statistical and mathematical models, and computational resources have paved the way for operational use of satellite data in...  相似文献   

Sr,Nd,Pb and trace element systematics of the New Caledonia harzburgites:Tracking source depletion and contamination processes in a SSZ setting     

Arianna Secchiari  Alessandra Montanini  Delphine Bosch  Patrizia Macera  Dominique Cluzel 《地学前缘(英文版)》2020,11(1):37-55

The New Caledonia ophiolite(Peridotite Nappe)consists primarily of harzburgites,locally overlain by mafic-ultramafic cumulates,and minor spinel and plagioclase lherzolites.In this study,a comprehensive geochemical data set(major and trace element,Sr-Nd-Pb isotopes)has been obtained on a new set of fresh harzburgites in order to track the processes recorded by this mantle section and its evolution.The studied harzburgites are low-strain tectonites showing porphyroclastic textures,locally grading into protomylonitic textures.They exhibit a refractory nature,as attested by the notable absence of primary clinopyroxene,very high Fo content of olivine(91-93 mol.%),high Mg#of orthopyroxene(0.91-0.93)and high Cr#of spinel(0.44-0.71).The harzburgites are characterised by remarkably low REE concentrations(<0.1 chondritic values)and display"U-shaped"profiles,with steeply sloping HREE(DyN/YbN=0.07-0.16)and fractionated LREE-MREE segments(LaN/SmN=2.1-8.3),in the range of modern fore-arc peridotites.Geochemical modelling shows that the HREE composition of the harzburgites can be reproduced by multi-stage melting including a first phase of melt depletion in dry conditions(15%fractional melting),followed by hydrous melting in a subduction zone setting(up to 15%-18%).However,melting models fail to explain the enrichments observed for some FME(i.e.Ba,Sr,Pb),LREE-MREE and Zr-Hf.These enrichments,coupled with the frequent occurrence of thin,undeformed films of Al2 O3,and CaO-poor orthopyroxene(Al2O3=0.88-1.53 wt.%,CaO=0.31-0.56 wt.%)and clinopyroxene with low Na2 O(0.03-0.16 wt.%),Al2 O3(0.66-1.35 wt.%)and TiO2(0.04-0.10 wt.%)contents,point to FME addition during fluid-assisted melting followed by late stage metasomatism most likely operated by subductionrelated melts with a depleted trace element signature.Nd isotopic ratios range from unradiogenic to radiogenic(-0.80<εNdi≤+13.32)and negatively correlate with Sr isotopes(0.70257≤87Sr/86Sr≤0.70770).Pb isotopes cover a wide range,trending from DMM toward enriched,sediment-like,compositions.We interpret the geochemical signature displayed by the New Caledonia harzburgites as reflecting the evolution of a highly depleted fore-arc mantle wedge variably modified by different fluid and melt inputs during Eocene subduction.  相似文献   

Occurrence of brominated flame retardants, polycyclic musks, and chlorinated naphthalenes in seal blubber from Antarctica: Comparison to organochlorines     

Alessandra Schiavone  Kurunthachalam Kannan  Yuichi Horii  Silvano Focardi  Simonetta Corsolini 《Marine pollution bulletin》2009,58(9):1415-1419

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Evaluation of out‐of‐plane seismic performance of column‐to‐column precast concrete cladding panels in one‐storey industrial buildings          下载免费PDF全文

Andrea Belleri  Fabrizio Cornali  Chiara Passoni  Alessandra Marini  Paolo Riva 《地震工程与结构动力学》2018,47(2):397-417

Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of precast cladding panels, typically associated with a connection system not designed to account for displacement and rotation compatibility between the panels and the supporting structure. Experimental investigations were performed in the past to investigate the in‐plane performance of cladding panels and design recommendations have been made accordingly; however, in the case of out‐of‐plane seismic loads, the load demand is commonly evaluated in the design practice by means of formulations for nonstructural components. This paper summarizes the results obtained from parametric analyses conducted to estimate the out‐of‐plane load demand in column‐to‐column cladding panels typical of one‐storey commercial and industrial buildings. Empirical equations suitable for both new and existing panels are proposed and compared with the design equations given in Eurocode 8 and ASCE 7. The paper also considers the effects of the development of plastic hinges at the column base and of the roof flexibility on the load demand in panel‐to‐column connections. The roof flexibility may generate the torsion of the panels; consequently, an analytical procedure to account for such effects is proposed. Finally, general design recommendations are made.  相似文献   

Cokriging for multivariate Hilbert space valued random fields: application to multi-fidelity computer code emulation     

Ognjen?GrujicEmail authorView author&#;s OrcID profile  Alessandra?Menafoglio  Guang?Yang  Jef?Caers 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(7):1955-1971

In this paper we propose Universal trace co-kriging, a novel methodology for interpolation of multivariate Hilbert space valued functional data. Such data commonly arises in multi-fidelity numerical modeling of the subsurface and it is a part of many modern uncertainty quantification studies. Besides theoretical developments we also present methodological evaluation and comparisons with the recently published projection based approach by Bohorquez et al. (Stoch Environ Res Risk Assess 31(1):53–70, 2016.  https://doi.org/10.1007/s00477-016-1266-y). Our evaluations and analyses were performed on synthetic (oil reservoir) and real field (uranium contamination) subsurface uncertainty quantification case studies. Monte Carlo analyses were conducted to draw important conclusions and to provide practical guidelines for all future practitioners.  相似文献