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Rocío?Isabel?PáezEmail author Ugo?Locatelli Christos?Efthymiopoulos 《Celestial Mechanics and Dynamical Astronomy》2016,126(4):519-541
A number of studies, referring to the observed Trojan asteroids of various planets in our Solar System, or to hypothetical Trojan bodies in extrasolar planetary systems, have emphasized the importance of so-called secondary resonances in the problem of the long term stability of Trojan motions. Such resonances describe commensurabilities between the fast, synodic, and secular frequency of the Trojan body, and, possibly, additional slow frequencies produced by more than one perturbing bodies. The presence of secondary resonances sculpts the dynamical structure of the phase space. Hence, identifying their location is a relevant task for theoretical studies. In the present paper we combine the methods introduced in two recent papers (Páez and Efthymiopoulos in Celest Mech Dyn Astron 121(2):139, 2015; Páez and Locatelli in MNRAS 453(2):2177, 2015) in order to analytically predict the location of secondary resonances in the Trojan problem. In Páez and Efthymiopoulos (2015), the motion of a Trojan body was studied in the context of the planar Elliptic Restricted Three Body or the planar Restricted Multi-Planet Problem. It was shown that the Hamiltonian admits a generic decomposition \(H=H_b+H_{sec}\). The term \(H_b\), called the basic Hamiltonian, is a model of two degrees of freedom characterizing the short-period and synodic motions of a Trojan body. Also, it yields a constant ‘proper eccentricity’ allowing to define a third secular frequency connected to the body’s perihelion precession. \(H_{sec}\) contains all remaining secular perturbations due to the primary or to additional perturbing bodies. Here, we first investigate up to what extent the decomposition \(H=H_b+H_{sec}\) provides a meaningful model. To this end, we produce numerical examples of surfaces of section under \(H_b\) and compare with those of the full model. We also discuss how secular perturbations alter the dynamics under \(H_b\). Secondly, we explore the normal form approach introduced in Páez and Locatelli (2015) in order to find an ‘averaged over the fast angle’ model derived from \(H_b\), circumventing the problem of the series’ limited convergence due to the collision singularity at the 1:1 MMR. Finally, using this averaged model, we compute semi-analytically the position of the most important secondary resonances and compare the results with those found by numerical stability maps in specific examples. We find a very good agreement between semi-analytical and numerical results in a domain whose border coincides with the transition to large-scale chaotic Trojan motions. 相似文献
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Marco Barbera Fabio Gastaldello Luisa Sciortino Simonpietro Agnello Gianpiero Buscarino Alfonso Collura Nicola La Palombara Ugo Lo Cicero Nicola Sartore Andrea Tiengo Salvatore Varisco Anna Maria Venezia 《Experimental Astronomy》2016,42(2):179-197
After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions. 相似文献
24.
LIDAR monitoring of mass wasting processes: The Radicofani landslide, Province of Siena, Central Italy 总被引：1，自引：0，他引：1
Marco Baldo Claudio Bicocchi Ugo Chiocchini Daniele Giordan Giorgio Lollino 《Geomorphology》2009,105(3-4):193-201
The Radicofani Basin, stretching about 30 km NW–SE, is an intra-Central Apennine basin connected to Pliocene–Pleistocene extensional tectonics. It consists of an Early to Middle Pliocene succession including essentially shelf pelites. In the Radicofani area, province of Siena (Tuscany region), morphodynamic processes are very frequent with widespread badlands and rapidly evolving mudflows. In order to evaluate the general instability of the Radicofani area, geological and geomorphological surveys were carried out. The 1954, 1990 and 2003 aerial surveys allowed a comparison of the changes in the various morphological aspects of the study area, which suggested an increase in slope instability with time. A new complex translational landslide evolving into mudflows, activated during the winter of 2003, was monitored using an experimental system based on terrestrial LIDAR (Light Detection and Ranging) and GPS (Global Positioning System) technologies. This system allowed the monitoring of the morphologic and volumetric evolution of the landslide. A comparison of the monitoring data of October 2004, June 2005, May 2006 and May 2007 points out that the evolution is characterised by the sliding of displaced materials. A volume of about 1300 m3 of materials was removed during the period 2004–2005, 300 m3 for 2005–2006, and 400 m3 for 2006–2007. The greater initial mass movement probably reflects a greater static imbalance during the early period of landslide movement and increased rainfall. Therefore, the proposed monitoring system methodology allows the numerical evaluation of the landslide morphological evolution and to validate the landslide evolution model based on geological and geomorphological field surveys. 相似文献
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Over the past five years or so, Anglo-American hegemony in human geography has been widely debated. This debate has highlighted
the obstacles put in the way of the building of a more international geographical discipline. In this paper, we reflect on
the possibilities and also the limitations of Europe as a context for the experimentation with a more cross-national discipline.
In doing so, we notice on the one hand the increasing attention towards the Europeanisation of human geography, particularly
at an institutional level, but on the other hand we also notice the lack of some basic forms and tools of communication and
exchange that might facilitate the mobilisation of scholars around the ‘European project’. The paper tries to offer a contribution
to this issue by discussing the ways in which a European journal of human geography might be conceived and also concretely
organised. In this respect the paper takes into account issues of language, access to scientific knowledge and recognition
of cultural and academic diversities.
相似文献
| Ugo RossiEmail: |
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Quan Hua Mike Barbetti David Fink Klaus Felix Kaiser Michael Friedrich Bernd Kromer Vladimir A. Levchenko Ugo Zoppi Andrew M. Smith Fiona Bertuch 《Quaternary Science Reviews》2009,28(25-26):2982-2990
Atmospheric radiocarbon variations over the Younger Dryas interval, from 13,000 to 11,600 cal yr BP, are of immense scientific interest because they reveal crucial information about the linkages between climate, ocean circulation and the carbon cycle. However, no direct and reliable atmospheric 14C records based on tree rings for the entire Younger Dryas have been available. In this paper, we present (1) high-precision 14C measurements on the extension of absolute tree-ring chronology from 12,400 to 12,560 cal yr BP and (2) high-precision, high-resolution atmospheric 14C record derived from a 617-yr-long tree-ring chronology of Huon pine from Tasmania, Australia, spanning the early Younger Dryas. The new tree-ring 14C records bridge the current gap in European tree-ring radiocarbon chronologies during the early Younger Dryas, linking the floating Lateglacial Pine record to the absolute tree-ring timescale. A continuous and reliable atmospheric 14C record for the past 14,000 cal yr BP including the Younger Dryas is now available. The new records indicate that the abrupt rise in atmospheric Δ14C associated with the Younger Dryas onset occurs at 12,760 cal yr BP, 240 yrs later than that recorded in Cariaco varves, with a smaller magnitude of 40‰ followed by several centennial Δ14C variations of 20–25‰. Comparing the tree-ring Δ14C to marine-derived Δ14C and modelled Δ14C based on ice-core 10Be fluxes, we conclude that changes in ocean circulation were mainly responsible for the Younger Dryas onset, while a combination of changes in ocean circulation and 14C production rate were responsible for atmospheric Δ14C variations for the remainder of the Younger Dryas. 相似文献
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Christopher P. Woods Mark T. Stoelinga Johnd. Locatelli Peter V. Hobbs 陈跃 陈添宇 《干旱气象》2008,26(3):82-94
2001年12月13—14日,一个强劲的气旋风暴影响了西北太平洋地区,在俄勒冈州喀斯喀特山区产生了强地形降水。这个风暴是“改进微物理参数的观测验证试验（Improvement of Microphysical Parameterization through Observational Verification Experiment,IMPROVE）”第二阶段外场研究的气旋风暴之一。在风暴移过俄勒冈州喀斯喀特山区期间,获得了大量的实测和遥感探测数据,形成了由气象状态参数（温、压、湿、风向风速和垂直气流速度）、极化多普勒雷达探测数据和云微物理参数（云液态水、粒子浓度、粒子谱及图像）组成的完整数据库。12月13—14日的过程具有对流层底层前倾锋演变的特点,锋面向前上方伸展到了强烈发展的高空冷锋雨带中,云发展到了8～9km的高度。与以前华盛顿喀斯喀特山区分析的风暴重要差别是,这个风暴在俄勒冈州喀斯喀特山上空的锋前低层气流是与弱东风气流相反的强西风爬山气流。结果当高空冷锋雨带过境时,在高空产生了大量冰晶的同时在低层地形抬升地区又产生了丰富的液态水。机载实测、地基微波辐射计观测以及雪晶观测证实,同时存在高冰晶浓度和高空相对大的云水含量,地面冰晶凇附也严重。分析表明,锋面和地形的相互促进作用使降水得到了增强。 相似文献
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Claude Froeschlé Robert Gonczi Elena Lega Ugo Locatelli 《Celestial Mechanics and Dynamical Astronomy》1997,69(1-2):235-254
The study of the stochasticity of the asteroid belt requires the analysis of a large number of orbits. We detect the dynamical
character of a set of 5 400 asteroids using the Fast Lyapunov Indicator, a method of analysis closely related to the computation
of the Lyapunov Characteristic Exponents, but cheaper in computational time. For both regular and chaotic orbits we try to
associate the motion to the underlying resonances network. For it we consider different methods of classification of rational
numbers proposed by number theory, and we choose the one which seems to be strictly related to the dynamical behaviour of
a system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Marco Sansottera Ugo Locatelli Antonio Giorgilli 《Celestial Mechanics and Dynamical Astronomy》2011,111(3):337-361
We adapt the Kolmogorov’s normalization algorithm (which is the key element of the original proof scheme of the KAM theorem)
to the construction of a suitable normal form related to an invariant elliptic torus. As a byproduct, our procedure can also
provide some analytic expansions of the motions on elliptic tori. By extensively using algebraic manipulations on a computer,
we explicitly apply our method to a planar four-body model not too different with respect to the real Sun–Jupiter–Saturn–Uranus
system. The frequency analysis method allows us to check that our location of the initial conditions on an invariant elliptic
torus is really accurate. 相似文献
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A geological-geophysical expedition (Ev-K2–CNR 1988) visited the area from West Kun Lun to Karakorum (K2–Gasherbrum). Seven tectonic units including sedimentary, magmatic and metamorphic rocks were distinguished in this area; the northernmost are suggested to belong to the Kun Lun and Qiangtang Microplates. The sedimentary sequence of Shaksgam is proved to extend from the Permian to the Jurassic, with Carboniferous and Cretaceous ages more doubtful. This sequence shows intermediate affinities between the Karakorum and the Qiangtang. The two southernmost units belong to the Karakorum Microplate. The Karakorum Fault Zone comprises a complex pattern of faults and thrusts, with brittle deformation and uplifting of granitoid bodies. 相似文献