Spatial collinear restricted four-body problem with repulsive Manev potential     

Esther Barrabés  Josep M. Cors  Claudio Vidal 《Celestial Mechanics and Dynamical Astronomy》2017,129(1-2):153-176

We outline some aspects of the dynamics of an infinitesimal mass under the Newtonian attraction of three point masses in a symmetric collinear relative equilibria configuration when a repulsive Manev potential (\(-1/r +e/r^{2}\)), \(e>0\), is applied to the central mass. We investigate the relative equilibria of the infinitesimal mass and their linear stability as a function of the mass parameter \(\beta \), the ratio of mass of the central body to the mass of one of two remaining bodies, and e. We also prove the nonexistence of binary collisions between the central body and the infinitesimal mass.  相似文献   

Editorial to the special issue on <Emphasis Type="Italic">Particle background for space instrumentation in the context of the Athena mission</Emphasis>     

Lorenzo Natalucci  Claudio Macculi 《Experimental Astronomy》2017,44(3):261-261

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Detection of Miocene saucer‐shaped sills (offshore Senegal) via integrated interpretation of seismic,magnetic and gravity data     

Sergio Rocchi  Alfredo Mazzotti  Michele Marroni  Luca Pandolfi  Paolo Costantini  Bertozzi Giuseppe  Davide di Biase  Francesco Federici  Papa Goumbo L 《地学学报》2007,19(4):232-239

The Atlantic margin offshore Senegal has been explored by seismic reflection and GRAV‐MAG surveys. High‐amplitude, laterally transgressive seismic reflectors are found to coincide with gravimetric and magnetic highs. Once seismic data are integrated with potential fields modelling, these reflectors can be safely interpreted as saucer‐shaped igneous sills, up to some hundreds of metres thick, some km wide. The occurrence of hydrothermal vent complexes and forced folds in the stratigraphic sequence above the sills constrain the intrusion age to the Miocene. Field observations and in‐situ magnetic susceptibility measurements of Oligocene–Miocene and Quaternary igneous rocks emplaced in coastal Senegal support this interpretation.  相似文献   

Laboratory experiments of slab break‐off and slab dip reversal: insight into the Alpine Oligocene reorganization     

Vincent Regard  Claudio Faccenna  Olivier Bellier  Joseph Martinod 《地学学报》2008,20(4):267-273

We present laboratory experiments to study the consequence of the rupture of a subducting slab on the deep geometry of the subduction zone. In our experiments, slab break‐off occurs after the entrance of buoyant material at trench causing a slowing down of the subduction and producing an increase of the shortening rate and a transient episode of subduction dip reversal. We discuss the potential application of these processes to the recent collisional evolution of the Alps proposing that the rupture of the slab produced a reorganization of the belt with a transition from one sided to a doubly vergent orogen.  相似文献   

Modelling of coupled fluid‐mechanical problems in fractured geological media using enriched finite elements          下载免费PDF全文

Jose Roberto Silvestre  Euripedes do Amaral Vargas Jr.  Luiz Eloy Vaz  Antonio Claudio Soares 《国际地质力学数值与分析法杂志》2015,39(10):1104-1140

Geological environments, such as petroleum reservoirs, normally exhibit physical discontinuities, for example, fractures and faults. Because of the reduced thickness of these discontinuities, finite element formulations with strong discontinuity have been applied to the numerical modelling of geological environments. Until now, two relevant characteristics of petroleum reservoirs have not been addressed by these formulations. The first is the pore pressure jump in the direction normal to a discontinuity in a fluid‐mechanical coupling condition, which is present primarily in sealing faults owing to the contrast of permeability with the porous medium. The absence of this jump can affect the prediction of the deformability of a physical discontinuity. Furthermore, reservoir models frequently use coarse meshes. Thus, the method used to evaluate the pore pressure in the discontinuity may exhibit a strong dependence relative to the mesh refinement. Based on these characteristics, in this study, a formulation of an enriched finite element for application to coupled fluid‐mechanical problems with pre‐existing physical discontinuities saturated by a single fluid is presented. The formulation employs discontinuous interpolation functions and enables the reproduction of jumps of displacement and pore pressure associated with a discontinuity inside the element without the need to discretise it. An approximation to estimate the pore pressure in the discontinuity was developed, one which seeks to minimise the influence of refinement. The element's response is verified by comparison with a one‐dimensional analytical solution and simple examples that are simulated using commercial software. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Phylogeography of Ophryotrocha labronica (Polychaeta,Dorvilleidae) along the Italian coasts          下载免费PDF全文

Piero Cossu  Ferruccio Maltagliati  Federica G. Pannacciulli  Roberto Simonini  Gloria Massamba‐N'Siala  Marco Casu  Claudio Lardicci  Daniela Prevedelli  Alberto Castelli 《Marine Ecology》2015,36(4):1088-1097

Species of the genus Ophryotrocha are a well‐studied group of organisms but, despite the relatively large body of biological studies, little is known about their intra‐specific patterns of genetic diversity. In the present study, we analysed the patterns of genetic variation in samples of Ophryotrocha labronica (Polychaeta, Dorvilleidae) collected along the Italian coasts within three regions with different thermal regimes: the Northern Adriatic Sea (NAS), the Ligurian Sea (LS), and the South/Southeast Sicilian Sea (SS). A partial sequence of the cytochrome c oxidase subunit I (COI) gene was used as a genetic marker. An analysis of molecular variance (AMOVA) showed significant genetic differentiation between the NAS and the other regions. Conversely, little or no genetic structuring was found between the LS and the SS or amongst locations within a given region. A Bayesian phylogenetic tree and a median‐joining network provided evidence for the occurrence of two highly divergent genetic lineages characterized by a high average sequence divergence (17.2%, Kimura two‐parameter distance). The spatial patterns of genetic variation found in O. labronica may reflect the signature of past expansion events of the two genetic lineages. Although the high sequence divergence suggested that cryptic speciation within O. labronica may have occurred, other traits such as the absence of reproductive isolation, pattern of phenotypic variation and habitat specificity prompted us to regard the two groups as distinct COI lineages of O. labronica.  相似文献   

On a planar circular restricted charged three-body problem     

Abimael Bengochea  Claudio Vidal 《Astrophysics and Space Science》2015,357(1):1-15

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The trapezoidal collinear four-body problem     

Martha Alvarez-Ramírez  Mario Medina  Claudio Vidal 《Astrophysics and Space Science》2015,358(1):1-18

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Impact of network geometry, observation schemes and telescope structure deformations on local ties: simulations applied to Sardinia Radio Telescope     

Claudio Abbondanza  Pierguido Sarti 《Journal of Geodesy》2012,86(3):181-192

The 64-m Sardinia Radio Telescope (SRT) is currently under construction in Sardinia (Italy). To ensure future surveying and monitoring operations at an utmost level of accuracy, we aim at selecting the optimal design and the most cost-effective solution for the establishment of the local ground control network (LGCN). We simulate and test 45 data sets corresponding to 5 different network configurations. We investigate the influence of 2 LGCN geometries (14 or 8 ground markers) and 3 terrestrial observation schemes (based on redundant forward intersections or side shots) on the precision and accuracy of the conventional reference point (CRP) of SRT and the simulated tie vector with a global navigation satellite system (GNSS) station. In addition, thermal and gravitational deformations of the radio telescope structure are simulated as systematic errors introduced into the observations and their effects on the CRP estimates are quantified. The state-of-the-art of CRP surveying and computation, based on terrestrial indirect methods, is applied. We show how terrestrial indirect methods can estimate the position of the radio telescope CRP to the millimeter precision level. With our simulations, we prove that limiting the LGCN to a 8-point configuration ensures the same precision on the CRP obtained with a 14-point network. Furthermore, we demonstrate that in the absence of telescope deformations, side shots, despite the lower redundancy, preserve a precision similar to that of redundant forward intersections. We show that the deformations due to gravitational flexure and thermal expansion of the radio telescope cannot be neglected in the tie vector computation, since they may bias the CRP estimate by several millimeters degrading its accuracy but not impacting on its formal precision. We highlight the dependency of the correlation matrices of the solutions on the geometry of the network and the observation schemes. Similarly, varying the extent of telescope deformations, we show that the CRP estimate again depends on the combination of the network geometry and the observation schemes.  相似文献   

Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations     

Robert P. C. Wiersma  Joop Schaye  Tom Theuns  Claudio Dalla Vecchia  Luca Tornatore 《Monthly notices of the Royal Astronomical Society》2009,399(2):574-600

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