Radial basis functions with compact support for multivariate geostatistics   总被引：3，自引：3，他引：0  

Emilio Porcu  Daryl J. Daley  Martin Buhmann  Moreno Bevilacqua 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(4):909-922

Matrix-valued radially symmetric covariance functions (also called radial basis functions in the numerical analysis literature) are crucial for the analysis, inference and prediction of Gaussian vector-valued random fields. This paper provides different methodologies for the construction of matrix-valued mappings that are positive definite and compactly supported over the sphere of a d-dimensional space, of a given radius. In particular, we offer a representation based on scaled mixtures of Askey functions; we also suggest a method of construction based on B-splines. Finally, we show that the very appealing convolution arguments are indeed effective when working in one dimension, prohibitive in two and feasible, but substantially useless, when working in three dimensions. We exhibit the statistical performance of the proposed models through simulation study and then discuss the computational gains that come from our constructions when the parameters are estimated via maximum likelihood. We finally apply our constructions to a North American Pacific Northwest temperatures dataset.  相似文献   

Effect of ground-motion asynchronism on the equivalent acceleration of earth dams     

Emilio Bilotta  Luca PaganoStefania Sica 《Soil Dynamics and Earthquake Engineering》2010

Under seismic loads the deformability of an earth dam may induce several effects, including ground-motion amplification and asynchronism between different points of the dam embankment. The paper analyses the asynchronous effects occurring in two existing earth dams, representing well-documented case histories: the El Infiernillo Dam (Mexico) and the Camastra Dam (Italy). Asynchronous effects are analysed by theoretical predictions of the dam seismic response by adopting an advanced dynamic approach, which takes into account the main features that dam soils exhibit under cyclic loading conditions. For different potentially unstable masses within the dam embankment, equivalent accelerations were computed as the ratio between the resultant of the inertial forces and the weight of the volume V associated to the unstable mass. With the exception of very cortical sliding surfaces – not significant for dam stability – in most of the analysed cases the equivalent seismic coefficients do not exceed the peak acceleration at the dam base.  相似文献   

Spatial prediction for infinite-dimensional compositional data     

Elías Salazar  Ramón Giraldo  Emilio Porcu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(7):1737-1749

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A rootless suture and the loss of the roots of a mountain chain: The Variscan belt of NW Iberia     

José R. Martínez Catalán  Ricardo Arenas  Jacobo Abati  Sonia Sánchez Martínez  Florentino Díaz García  Javier Fernández Suárez  Pablo González Cuadra  Pedro Castiñeiras  Juan Gómez Barreiro  Alejandro Díez Montes  Emilio González Clavijo  Francisco J. Rubio Pascual  Pilar Andonaegui  Teresa E. Jeffries  James E. Alcock  Rubén Díez Fernández  Alicia López Carmona 《Comptes Rendus Geoscience》2009,341(2-3):114-126

Ophiolites of different Paleozoic ages occur in North-West (NW) Iberia in a rootless suture representing the remnants of the Rheic Ocean. Associated allochthonous terranes in the hanging- and foot-walls of the suture derive from the former margins, whereas the relative autochthon corresponds to the Paleozoic passive margin of northern Gondwana. The Paleozoic tectonic evolution of this part of the circum-Atlantic region is deduced from the stratigraphical, petrological, structural and metamorphic evolution of the different units and their ages. The tectonic reconstruction covers from Cambro-Ordovician continental rifting and the opening of the Rheic Ocean to its Middle to Upper Devonian closure. Then, the Variscan Laurussia–Gondwana convergence and collision is briefly described, from its onset to the late stages of collapse associated with the demise of the orogenic roots.  相似文献   

Genetic impact of the Prestige oil spill in wild populations of a poor dispersal marine snail from intertidal rocky shores     

Piñeira J  Quesada H  Rolán-Alvarez E  Caballero A 《Marine pollution bulletin》2008,56(2):270-281

In November 2002, the sinking of the Prestige cargo ship produced an oil spill of 60,000 tons that affected many areas along the Galician coast (in the northwest of Spain). In a number of rocky shore sites, most organisms (particularly marine mollusks) were nearly extinct at a local scale. We tested whether the local bottleneck/extinction that occurred in affected localities caused any detectable reduction of the genetic diversity in the marine snail Littorina saxatilis, an ovoviviparous rocky shore model species characterized by a low dispersal ability, high population density, and wide distribution range. We compared the level of genetic variation and population differentiation between affected (polluted) and control sites located in seven geographical areas (three sites per area, one impacted and two controls, and two replicates per site) one and a half years after the spill. The analysis included molecular marker variation (microsatellite and AFLP loci) and quantitative trait genetic variation for shell variables in embryos extracted from pregnant females. Our results indicate that the affected populations did not show a significant overall reduction in genetic diversity when compared to the controls, suggesting that the species is highly resistant to losing genetic variability as a consequence of a local short-term pollution process in spite of its low dispersal ability and direct development. However, some genetic effects were detected in the polluted populations, particularly for quantitative shell traits and AFLPs, consistent with local adaptations resulting from the fuel contamination.  相似文献   

The hydrography and biology of a bloom of the coccolithophorid Emiliania huxleyi in the northern North Sea     

Robert N. Head  David W. Crawford  Jorun K. Egge  Roger P. Harris  Svein Kristiansen  David J. Lesley  Emilio Maran  David Pond  Duncan A. Purdie 《Journal of Sea Research》1998,39(3-4)

In June/July 1994 a study was made of a small bloom of the coccolithophorid Emiliania huxleyi in an area of the North Sea to the east of the Shetland Islands. Observations on the hydrography of the study area indicated the bloom was associated with Atlantic water and was confined to an area in which a stable shallow mixed layer had formed. There was no evidence to suggest association of horizontal physical structure with the bloom development. High cell densities of >1– cells dm⁻³, together with low concentrations of PIC (<50 μg dm⁻³) and detached liths (2– liths cm⁻³) indicated that the bloom was studied at an early stage of development. Biochemical and physiological observations indicated active growth was taking place. The results presented are discussed in comparison with previous studies carried out in both oceanic and shelf seas.  相似文献   

The econometric estimation and testing of DARP models     

Emilio Casetti  Ayse Can 《Journal of Geographical Systems》1999,1(2):91-106

DARP, acronym for Drift Analysis of Regression Parameters, originated as a heuristic technique for the investigation of parametric drift in any arbitrary `expansion space', geographic or otherwise. DARP was intended as an exploratory tool useful to aid with the formal specification of parametric drift. In this paper, the DARP technique is reformulated in terms of `DARP models', and the estimation and testing of these models by GLS, FGLS, and ML are discussed. The ML estimation of a spatial DARP model is demonstrated using empirical data. Received: 4 March 1998/Accepted: 23 December 1998  相似文献   

Hickin, Edward J., River geomorphology     

Emilio Biagini 《GeoJournal》1998,44(2):162-163

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Intensive use of ground water and sustainability     

Custodio E 《Ground water》2005,43(3):291-291

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Di un nuovo accelerometro e relativo metodo di lettura differenziale per la determinazione rapida delle forze sismiche massimali     

Dott. Ing. Emilio Perri 《Pure and Applied Geophysics》1941,3(1):1-11

Riassunto Un metodo differenziale di lettura concernente l'uso del nuovo tipo di accelerometro ideato dall'A. e descritto in altra nota di questo periodico, viene qui esposto. Si dimostra che, disponendo di una coppia di pendoli accelerometrici del tipo descritto e senza far uso di alcun frequenzimetro, un valore fortemente approssimato dell'accelerazione è ricavabile dalla sola nozione dei due spostamenti delle masse pendolari sotto l'effetto della stessa scossa. Una semplice formula collega il valore dell'accelerazione ai suddetti elementi cinematici che è sufficiente conoscere con approssimazione. Si conclude affermando che le qualità di semplice automatismo e razionalità del nuovo accelerometro ideato dall'A. lo rendono indispensabile per il rilievo delle accelerazioni massimali esplicantisi in zona pleistosismica, più ancora come apparato tipico per la costituzione di reti accelerometriche permanenti da distendersi sulle zone prevalentemente sismiche.

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Zusammenfassung Der Verf. hat vor kurzem einen neuen Beschleunigungsmesser erdacht, gebaut und in dieser ZS. beschreibt. Für diesen Apparat beweist nun die Möglichkeit durch eine differentielle Methode die Beschleunigung zu bestimmen und zwar durch eine doppelte Ablesung mittels zwei gleichen Apparate von fast gleicher Empfindlichkeit aber mit verschiedenen Schwing-Perioden, Die abgeleiteten Formeln werden dann vom Verf. auch benutzt um die gute Annäherung des Verfahrens zu überprüfen, wofür zeigt, dass die Bestimmung de Beschleunigung normalerweise mit einer Annäherung von 2–3%, in jedem Falle höchstens von 5%, möglich ist.

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