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131.
Multicomponent seismic data are acquired by orthogonal geophones that record a vectorial wavefield. Since the single components are not independent, the processing should be performed jointly for all the components. In this contribution, we use hypercomplex numbers, specifically quaternions, to implement the Wiener deconvolution for multicomponent seismic data. This new approach directly derives from the complex Wiener filter theory, but special care must be taken in the algorithm implementation due to the peculiar properties of quaternion algebra. Synthetic and real data examples show that quaternion deconvolution, either spiking or predictive, generally performs superiorly to the standard (scalar) deconvolution because it properly takes into account the vectorial nature of the wavefields. This provides a better wavelet estimation and thus an improved deconvolution performance, especially when noise affects differently the various components. 相似文献
132.
Alessandro Tibaldi Claudia Corazzato Andrey Kozhurin Alfredo F.M. Lagmay Federico A. Pasquar Vera V. Ponomareva Derek Rust Daniel Tormey Luigina Vezzoli 《Global and Planetary Change》2008,61(3-4):151-174
This paper aims to aid understanding of the complicated interplay between construction and destruction of volcanoes, with an emphasis on the role of substrate tectonic heritage in controlling magma conduit geometry, lateral collapse, landslides, and preferential erosion pathways. The influence of basement structure on the development of six composite volcanoes located in different geodynamic/geological environments is described: Stromboli (Italy), in an island arc extensional tectonic setting, Ollagüe (Bolivia–Chile) in a cordilleran extensional setting, Kizimen (Russia) in a transtensional setting, Pinatubo (Philippines) in a transcurrent setting, Planchon (Chile) in a compressional cordilleran setting, and Mt. Etna (Italy) in a complex tectonic boundary setting. Analogue and numerical modelling results are used to enhance understanding of processes exemplified by these volcanic centres. We provide a comprehensive overview of this topic by considering a great deal of relevant, recently published studies and combine these with the presentation of new results, in order to contribute to the discussion on substrate tectonics and its control on volcano evolution. The results show that magma conduits in volcanic rift zones can be geometrically controlled by the regional tectonic stress field. Rift zones produce a lateral magma push that controls the direction of lateral collapse and can also trigger collapse. Once lateral collapse occurs, the resulting debuttressing produces a reorganization of the shallow-level magma migration pathways towards the collapse depression. Subsequent landslides and erosion tend to localize along rift zones. If a zone of weakness underlies a volcano, long-term creep can occur, deforming a large sector of the cone. This deformation can trigger landslides that propagate along the destabilized flank axis. In the absence of a rift zone, normal and transcurrent faults propagating from the substrate through the volcano can induce flank instability in directions respectively perpendicular and oblique to fault strike. This destabilization can evolve to lateral collapse with triggering mechanisms such as seismic activity or magmatic intrusion. 相似文献
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136.
Thiago J.F. Costa Hudson T. Pinheiro João Batista Teixeira Eric F. Mazzei Leonardo Bueno Mike S.C. Hora Jean-Christophe Joyeux Alfredo Carvalho-Filho Gilberto Amado-Filho Claudio L.S. Sampaio Luiz A. Rocha 《Marine pollution bulletin》2014
Invasive coral species of the genus Tubastraea have been increasingly recorded in Southwestern Atlantic waters since the 1980s. Their invasion and infestation are mainly related to port and oil exploration activities. For the first time the presence of Tubastraea tagusensis colonies is reported in Espírito Santo State, colonizing a port shore area, and incrusting oil/gas platform structures situated in the southern Abrolhos Bank, which is part of the most important coral reef system of the South Atlantic Ocean. Tubastraea colonies exhibit fast growth and high recruitment rates, and colonized 40% of the analyzed structures in just four years. The projection of port and oil/gas industry growth for the Espírito Santo State (more than 300%) highlights an alert to the dispersal of this alien species to natural areas. 相似文献
137.
A. B. Nunes H. F. Campos Velho P. Satyamurty G. Degrazia A. Goulart U. Rizza 《Boundary-Layer Meteorology》2010,134(1):23-39
A major factor that influences the diurnal variation of turbulent kinetic energy (TKE) is the sensible heat flux at the surface.
Here, the TKE variations are analysed during the morning transition phase because subsequent to the neutral or stable stratification
during the night, peaks of concentration of scalars develop. The characteristics of the TKE during the growth phase of convection
are analysed with the help of two analytical models. For this purpose, a three-dimensional spectral model of the growth of
convection, starting from a neutral layer, and other formulations of micrometeorological parameters such as the convective
and neutral spectra, velocity variance and dissipation rates are utilised. The peak values in the TKE spectra in the lower,
middle and upper levels of the convective boundary layer showed a migration to higher wavelengths as the convection increased
with time. The TKE evolutions generated by the analytical models agree fairly well with the results of large-eddy simulation
for three vertical levels. 相似文献
138.
500-year temperature reconstruction in the Mediterranean Basin by means of documentary data and instrumental observations 总被引:3,自引:1,他引:2
Dario Camuffo C. Bertolin M. Barriendos F. Dominguez-Castro C. Cocheo S. Enzi M. Sghedoni A. della Valle E. Garnier M.-J. Alcoforado E. Xoplaki J. Luterbacher N. Diodato M. Maugeri M. F. Nunes R. Rodriguez 《Climatic change》2010,101(1-2):169-199
The paper reports the main results of the EU project Millennium in the Mediterranean area over the last 500 years. It analyses a long series of temperature from Portugal, Spain, France, Italy and Greece. The series are obtained by combining indices from documentary sources from AD 1500 to the onset of regular instrumental observations. There is an ongoing discussion regarding the proper way of combining documentary and instrumental data and how to translate accurately the conventional indices from ??3 to +?3 into modern units, i.e. degree Celsius. This paper produces for the first time a number of early instrumental observations, in some cases (i.e. Italy and France) covering 350 years, including thereby the earliest regular observations after the invention of the thermometer. These Mediterranean data show that anomalous temperatures usually had only a locally limited effect, while only few extreme events had a widespread impact over the whole region, such as the summer of 2003. During the period from 1850 to the present day, the Mediterranean temperature anomaly was close to the Northern Hemisphere in spring and summer, while it was warmer in autumn and winter. Compared with the long-term instrumental records (i.e. 1655 onwards), the recent warming has not exceeded the natural past variability characterized by heating–cooling cycles with no significant long-term trends. 相似文献
139.
William R. Tavares Rodrigo M. Nunes Sidney S. Avancini Ricardo L. S. Farias 《Astronomische Nachrichten》2024,345(2-3):e230168
The Nambu–Jona-Lasinio model is known for its simplicity and capacity to reproduce some of the basic characteristics of the quantum chromodynamics phase diagram. However, since it is a nonrenormalizable model, there are regularization issues that should be treated conveniently. This is the case when considering the quark anomalous magnetic moment (AMM) when external constant magnetic fields are present. Regularization procedures based on entangled functions between the magnetic field and the cutoff of the model can predict first-order phase transitions for chiral symmetry restoration at finite values of magnetic fields and inverse magnetic catalysis. The strengths of magnetic fields explored in NJL model and lattice QCD do not show first-order phase transition. In the present work, we show that some of the previous results are regularization-dependent effects and how to handle the divergences using the vacuum magnetic regularization scheme. 相似文献
140.
An analysis tool for the study of wind speed profiles over the water has been developed. The profiles are analysed using a
modified dimensionless wind speed and dimensionless height, assuming that the sea surface roughness can be predicted by Charnock’s
roughness length model. In this form, the roughness dependency on wind speed is extracted and the variations on the wind profile
are due solely to atmospheric stability. The use of the Charnock’s non-dimensional wind profile is illustrated using data
collected from a meteorological mast installed in the Danish North Sea. The best fit with the observed mean non-dimensional
wind profile under neutral atmospheric conditions is found using a value of 1.2 × 10−2 for Charnock’s parameter. The stability correction on the neutral wind profile suggested by the Businger-Dyer relations was
found to perform well over the sea. 相似文献