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301.
Ariadna Farrés Jacques Laskar Sergio Blanes Fernando Casas Joseba Makazaga Ander Murua 《Celestial Mechanics and Dynamical Astronomy》2013,116(2):141-174
Using a Newtonian model of the Solar System with all 8 planets, we perform extensive tests on various symplectic integrators of high orders, searching for the best splitting scheme for long term studies in the Solar System. These comparisons are made in Jacobi and heliocentric coordinates and the implementation of the algorithms is fully detailed for practical use. We conclude that high order integrators should be privileged, with a preference for the new $(10,6,4)$ method of Blanes et al. (2013). 相似文献
302.
Jacques P. Vallée 《New Astronomy Reviews》2011,55(3-4):91-154
Here I present a survey of magnetic fields in large objects, from the interstellar supershells (10 pc) up to the edge of the Universe (near a redshift z of 10), with an emphasis on discoveries made in the last decade, be they through particle astronomy or electromagnetic astronomy.For each type of object, the basic observational properties are summarized, and the best theoretical scenario which accounts for the large body of observations is discussed.The strength of these large-scale fields can vary from mGauss to μGauss. Magnetism acts as a tracer of the dynamical histories of cosmological and intracluster events, it guides the motion of the interstellar ionised gas, and it aligns the charged dust particles. 相似文献
303.
Jacques P. Vallée 《New Astronomy Reviews》2011,55(3-4):23-90
Here I present a survey of planetary, stellar and clumpy interstellar magnetic fields, with an emphasis on discoveries made in the last decade. Ground-based and Earth–satellite observations of magnetic fields in astronomical objects are cataloged, as obtained at all multiple electromagnetic wavelengths.For each type of object, the basic observational properties are summarized, and the best theoretical scenario which accounts for the large body of observations is discussed. There is no single unifying magnetic model for all objects (although dynamo theory comes close for many compact objects, and helical theory for many extended objects).The strength of the observed magnetic fields reaches exagauss values (1018 G) in compact objects such as magnetars, and decreases to microgauss values (10?6 G) in the clumpy interstellar medium. 相似文献
304.
Colin Frank Wilson Eric Chassefière Emmanuel Hinglais Kevin H. Baines Tibor S. Balint Jean-Jacques Berthelier Jacques Blamont Georges Durry Csaba S. Ferencz Robert E. Grimm Takeshi Imamura Jean-Luc Josset Fran?ois Leblanc Sebastien Lebonnois Johannes J. Leitner Sanjay S. Limaye Bernard Marty Ernesto Palomba Sergei V. Pogrebenko Scot C. R. Rafkin Dean L. Talboys Rainer Wieler Liudmila V. Zasova Cyrill Szopa 《Experimental Astronomy》2012,33(2-3):305-335
The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an ‘M-class’ mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55?km, where temperatures and pressures are benign (~25°C and ~0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond. 相似文献
305.
Mamadou Adama Sarr Philippe Gachon Ousmane Seidou Christopher Robin Bryant Jacques André Ndione Jacques Comby 《水文科学杂志》2013,58(9):1538-1549
AbstractDaily precipitation data from 31 Senegalese stations spanning the period from 1950 to 2007 were used to examine the inter-annual variations of seven rainfall indices: the annual mean precipitation (MEAN); the annual standard deviation of daily precipitation (STD); the frequency of wet days (Prcp1); the maximum number of consecutive dry days (CDD); the maximum 3-day rainfall total (R3D); the wet day precipitation intensity (SDII); and the 90th percentile of rain-day precipitation (Prec90p). The indices were spatially averaged over three agro-climatic regions in Senegal. Trends in the time series of the averaged indices were assessed using both visual examination and a modified version of the Mann-Kendall (MM-K) test. Initially negative significant trends in all seven indices suggest gradually drier conditions over the three agro-climatic regions between 1950 and 1980. In contrast, no significant trends, or even positive significant trends, were observed from the mid-1980s to 2007. The MM-K test was applied to all available data (1950–2007) and the period from 1971 to 2000. While several indices were found to have significant trends towards drier conditions for the 1950–2007 period, only PRCP1 showed a positive significant trend for the 1971–2000 period. The MM-K test did not detect a significant trend for the other indices. It was found that the rainfall deficit and therefore drought is no longer intensifying, and that the region may even become wetter. However, the period covered by the observations is still too short to resolve the question of whether there is now a trend towards wetter conditions.
Editor Z.W. Kundzewicz; Associate editor K. Hamed 相似文献
306.
Imprints of hydrocarbon-bearing basinal fluids on a karst system: mineralogical and fluid inclusion studies from the Buda Hills,Hungary 总被引:1,自引:1,他引:0
Zsófia?PorosEmail author Andrea?Mindszenty Ferenc?Molnár Jacques?Pironon Orsolya?Gy?ri Paola?Ronchi Zoltán?Szekeres 《International Journal of Earth Sciences》2012,101(2):429-452
Calcite veins and related sulphate–sulphide mineralisation are common in the Buda Hills. Also, abundant hypogenic caves are
found along fractures filled with these minerals pointing to the fact that young cave-forming fluids migrated along the same
fractures as the older mineralising fluids did. The studied vein-filling paragenesis consists of calcite, barite, fluorite
and sulphides. The strike of fractures is consistent—NNW–SSE—concluding a latest Early Miocene maximum age for the formation
of fracture-filling minerals. Calcite crystals contain coeval primary, hydrocarbon-bearing- and aqueous inclusions indicating
that also hydrocarbons have migrated together with the mineralising fluids. Hydrocarbon inclusions are described here for
the first time from the Buda Hills. Mixed inclusions, i.e., petroleum with ‘water-tail’, were also detected, indicating that
transcrystalline water migration took place. The coexistence of aqueous and petroleum inclusions permitted to establish the
entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded
since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1.7 NaCl eq. wt%) implies that hydrocarbon-bearing
fluids were diluted by regional karst water. FT-IR investigations revealed that CO2 and CH4 are associated with hydrocarbons. Groundwater also contains small amounts of HC and related gases on the basin side even
today. Based on the location of the paleo- and recent hydrocarbon indications, identical migration pathways were reconstructed
for both systems. Hydrocarbon-bearing fluids are supposed to have migrated north-westward from the basin east to the Buda
Hills from the Miocene on. 相似文献
307.
AbstractLarge structures, lineations, foliations and sense of shear criteria are examined on the scale of the whole Ibero-Armorican Arc. Four sections (Galicia, Brittany-Vendée, Limousin and Eastern Massif Central) exemplify the major thrust sheets observed around the Arc. Stretching lineations are contemporaneous with the siluro-devonian metamorphism and are either transverse, oblique or parallel to the collision zone. A kinematic analysis shows that these lineations have resulted from a dominanüy transverse shear deformation which was followed by, or combined with, a longitudinal shear direction. On the scale of the entire Arc, this variation in the shear direction is interpreted as resulting from an early head on thrusting relative movement evolving to large scale movements parallel to the plate boundaries. Experiments with sand-silicone models support a model which generates the Arc by interaction between a transform sinistral direction, and a converning zone at a high angle to the transform direction. 相似文献
308.
AbstractThe Vestfirdir Peninsula of northwestern Iceland mainly consists of tholeiitic lava flows, 8–14 Ma old, gently dipping to the southeast. A detailed study of strike-slip and normal faulting allowed identification of two main paleostress regimes. Two sets of normal faults were recognized. The largest set trends ENE-WSW to NNE-SSW; the minor set trends NW-SE to WNW-ESE. Concerning the major extension, the reconstruction of paleostress trajectories shows a gradual change in trend from ESE-WNW, in the northern half of the peninsula, to NNW-SSE to the south. The minor extension also shows a gradual change from NNE-SSW to ENE-WSW trends, from north to south. The nearly constant perpendicularity between the major and minor trends of extension is accounted for by permutation of stress axes within the general pattern of extension related to oceanic rifting. The progressive azimuthal change of the major extension trend, from northeast to southwest across the peninsula, is interpreted as the expression of a change in trend of the extinct Skagi-Snaefells rift, a structure that cannot be reconstructed directly through geological mapping. The average trends of extension in the southern Vestfirdir Peninsula, N150°E, suggest a N60°E trend for the ancient Snaefells rift segment. Likewise, the N100–110°E trends of extension in northern Vestfirdir suggest a N10–20°E trend for the Skagi paleo-rift., © Elsevier, Paris 相似文献
309.
Lilya Djarar Hua Wang Michel Guiraud Jacques Clermonté Louis Courel Michel Dumain 《Geodinamica Acta》2013,26(5):193-221
RésuméLa nature syn-sédimentaire des failles bordières du bassin houiller stéphanien des Cévennes est mise en évidence par la distribution des dépôts conglomératiques et gréseux de cône alluvial au pied des paléoreliefs de socle. Elle est également attestée par les fortes variations d’épaisseur caractérisant les niveaux gréseux, silteux et de charbon se distribuant au centre des sous-bassins ainsi que par les directions centripètes d’apport sédimentaire.A l’échelle du bassin, la nature extensive de la structuration syn-sédimentaire est mise en évidence par des failles normales d’orientation NW-SE, NE-SW et NNW-SSE, à fort pendage, structurant les sous-bassins en demi-graben à géométrie synclinale ou à configuration divergente. Dans le secteur SE du bassin de la Grand’Combe, les structures syn-sédimentaires extensives coexistent avec des plis précoces reliés à un décollement généralisé au niveau des couches de charbon « Sans Nom ».L’intégration des données structurales et microtectoniques collectées dans les dépôts stéphaniens et dans le socle montre que la structuration syn-sédimentaire extensive du bassin stéphanien est associée au cours du temps à une rotation progressive antihoraire de la direction d’extension principale successivement NE-SW à NW-SE.L’ensemble des données tectono-sédimentaires nous permet de proposer une nouvelle interprétation du bassin stéphanien des Cévennes dans le cadre de la tectonique extensive tardi- orogénique de la chaîne varisque. Cette interprétation est illustrée par un modèle de bassin extensif intégrant une structuration générale en demi-graben et une tectonique gravitaire locale. La tectonique gravitaire s’exprime par la mise en place de décollements superficiels en liaison avec la surrection du horst dissymétrique du Rouvergue, en position axiale dans le bassin. 相似文献
310.
Clement Ubelmann Jacques Verron Jean-Michel Brankart Pierre Brasseur Emmanuel Cosme 《Ocean Dynamics》2012,62(6):867-880
Tropical instability waves (TIWs) are not easily simulated by ocean circulation models primarily because such waves are very sensitive to wind forcing. In this study, we investigate the impact of assimilating sea surface height (SSH) observations on the control of TIWs in an observing system simulation experiment (OSSE) context based on a regional model configuration of the tropical Atlantic. A Kalman filtering method with suitable adaptations is found to be successful when altimetric data are assimilated in conjunction with sea surface temperature and some in situ temperature/salinity profiles. In this rather realistic system, the TIW phase is roughly controlled with a single nadir observing satellite. However, a right correction of the TIW structure and amplitude requires at least two nadir observing satellites or a wide swath observing satellite. The significant impact of orbital parameters is also demonstrated: in particular, the Jason or GFO satellite orbits are found to be more suitable than the ENVISAT orbit. More generally, it is found that as soon as adequate sub-sampling exists (with periods of 5–10?days), the length of the repetitivity cycle of orbits does not have a significant impact. 相似文献