Integrable approximation of J 2-perturbed relative orbits     

M. Lara  P. Gurfil 《Celestial Mechanics and Dynamical Astronomy》2012,114(3):229-254

Most existing satellite relative motion theories utilize mean elements, and therefore cannot be used for calculating long-term bounded perturbed relative orbits. The goal of the current paper is to find an integrable approximation for the relative motion problem under the J ₂ perturbation, which is adequate for long-term prediction of bounded relative orbits with arbitrary inclinations. To that end, a radial intermediary Hamiltonian is utilized. The intermediary Hamiltonian retains the original structure of the full J ₂ Hamiltonian, excluding the latitude dependence. This formalism provides integrability via separation, a fact that is utilized for finding periodic relative orbits in a local-vertical local-horizontal frame and determine an initialization scheme that yields long-term boundedness of the relative distance. Numerical experiments show that the intermediary-based computation of orbits provides long-term bounded orbits in the full J ₂ problem for various inclinations. In addition, a test case is shown in which the radial intermediary-based initial conditions of the chief and deputy satellites yield bounded relative distance in a high-precision orbit propagator.  相似文献   

Depth of faulting and ancient heat flows in the Kuiper region of Mercury from lobate scarp topography     

Isabel Egea-González  Javier Ruiz  Carlos Fernández  Jean-Pierre Williams  Álvaro Márquez  Luisa M. Lara 《Planetary and Space Science》2012,60(1):193-198

Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittle–ductile transition (BDT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for which Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury.The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m^?2 for the Kuiper region, and between 22 and 43 mW m^?2 for Discovery Rupes. Both BDT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation.  相似文献   

Seasonal temperature responses to land-use change in the western United States   总被引：2，自引：0，他引：2  

Lara M. Kueppers  Mark A. Snyder  Lisa C. Sloan  Dan Cayan  Jiming Jin  Hideki Kanamaru  Masao Kanamitsu  Norman L. Miller  Mary Tyree  Hui Du  Bryan Weare 《Global and Planetary Change》2008,60(3-4):250-264

In the western United States, more than 79 000 km² has been converted to irrigated agriculture and urban areas. These changes have the potential to alter surface temperature by modifying the energy budget at the land–atmosphere interface. This study reports the seasonally varying temperature responses of four regional climate models (RCMs) – RSM, RegCM3, MM5-CLM3, and DRCM – to conversion of potential natural vegetation to modern land-cover and land-use over a 1-year period. Three of the RCMs supplemented soil moisture, producing large decreases in the August mean (− 1.4 to − 3.1 °C) and maximum (− 2.9 to − 6.1 °C) 2-m air temperatures where natural vegetation was converted to irrigated agriculture. Conversion to irrigated agriculture also resulted in large increases in relative humidity (9% to 36% absolute change). Modeled changes in the August minimum 2-m air temperature were not as pronounced or consistent across the models. Converting natural vegetation to urban land-cover produced less pronounced temperature effects in all models, with the magnitude of the effect dependent upon the preexisting vegetation type and urban parameterizations. Overall, the RCM results indicate that the temperature impacts of land-use change are most pronounced during the summer months, when surface heating is strongest and differences in surface soil moisture between irrigated land and natural vegetation are largest.  相似文献   

The next step in shallow coral reef monitoring: Combining remote sensing and in situ approaches     

Julie Scopélitis  Serge Andréfouët  Lara Arroyo  Annick Cros  Pascale Chabanet 《Marine pollution bulletin》2010,60(11):1956-1968

Most current coral reef management is supported by mapping and monitoring limited in record length and spatial extent. These deficiencies were addressed in a multidisciplinary study of cyclone impacts on Aboré Reef, New-Caledonia. Local knowledge, high thematic-resolution maps, and time-series satellite imagery complemented classical in situ monitoring methods. Field survey stations were selected from examination of pre- and post-cyclone images and their post-cyclone coral communities documented in terms of substrata, coral morphologies, live coral cover, and taxonomy. Time-series maps of hierarchically defined coral communities created at spatial scales documenting the variability among communities (29-45 classes) and suggesting the processes that affected them. The increased spatial coverage and repeatability of this approach significantly improved the recognition and interpretation of coral communities’ spatio-temporal variability. It identified precise locations of impacted areas and those exhibiting coral recovery and resilience. The approach provides a comprehensive suite of information on which to base reef-scale conservation actions.  相似文献   

Detrital Cr-spinel in the Šambron–Kamenica Zone (Slovakia): evidence for an ocean-spreading zone in the Northern Vardar suture?     

Davide Lenaz  Claudio Mazzoli  Jan Spišiak  Francesco Princivalle  Lara Maritan 《International Journal of Earth Sciences》2009,98(2):345-355

The Šambron–Kamenica Zone is situated on the northern margin of the Levočské vrchy mountains and Šarišskà vrchovina Highland, where the Central Carpathian Paleogene joins the Pieniny Klippen Belt. Sandstone outcrops in this area. From Cretaceous to Late Oligocene in age, these sediments suggest transport directions from S and SE. The heavy mineral assemblages of this sandstone include Cr-spinel grains, mainly displaying types II and III alpine-peridotite affinities, and are representative of Ocean Island Basalt volcanism. A sample from Upper Eocene sediments at Vit’az shows a clear change in Cr-spinel composition, which turns out to have types I and II peridotite affinities, and to derive from arc and Middle Ocean Ridge Basalt volcanism, with sediment transport directions from SW and WSW. These data indicate major variations in the Upper Eocene tectonic setting, giving constraints to paleogeographic reconstruction of the Slovak Central Carpathians.  相似文献   

Post-imbrian global lunar tectonism: Evidence for an initially totally molten Moon     

Alan B. Binder 《Earth, Moon, and Planets》1982,26(2):117-133

Evaluation of all reasonable sources of stress in the lunar crust indicates that compressional thermoelastic stresses are the only ones which have been tectonically significant on the global scale during the last 3.5×10⁹ yr of lunar history — i.e., the post-Imbrian. However, the thermoelastic stresses calculated for lunar models which have accretional heating profiles at the beginning of lunar history; i.e., a molten zone only a few hundred kilometers deep and a cool deep interior, are less than 1 kbar in the crust. Such stresses are lower than the more than 1 to 7 kbar needed to initiate thrust faulting in the outer crust according to Anderson's theory of thrust faulting. Thus such accretional models predict that no significant global thrust faulting has occurred during the post-Imbrian and that the crust should currently be seismically quiet on the global scale.In contrast, the compressional thermoelastic stresses generated in a Moon which was initially totally molten, as is the case if the Moon formed by fission, are up to 3.5 kbar in the outer few km of the crust at present. These stresses are well within the range needed to cause thrust faulting in the outer 4 km of the crust. According to this model there should be modest scale (10 km), young ( 0.5 to 1×10⁹ yr old) thrust fault scarps in the highlands.Photoselenological investigations confirm that scarps with the expected age and geometric characteristics are found in the highlands. Thus the currently available photoselenological data support the stress model derived for an initially totally molten Moon, but not one which was molten only in the outer few hundreds of km.  相似文献   

On the heat flow of a gravitationally-differentiated moon of fission origin     

Alan B. Binder 《Earth, Moon, and Planets》1975,14(2):237-245

It is shown that the mean value for the heat flow of a gravitationally-differentiated Moon of fission origin is about 13 erg cm^?2 s^?1 and that the heat flow varies regionally from about 3 erg cm^?2s^?1 to more than 45 erg cm^?2s^?1. These regional variations in the heat flow are caused by a non-uniform distribution of K, U and Th in the KREEP zone at the crust-upper mantle boundary and the redistribution of crustal materials and K, U and Th rich KREEP materials by basin-forming impacts. The scale of these regional variations is hundreds of km. The models presented are in accord with the Apollo 15 and 17 heat flow measurements.  相似文献   

Tidal variations of some physico-chemical parameters in Blanca Bay,Argentina     

Marta Susana Orozco Storni  Rubén José Lara  Adán Edgardo Pucci 《Estuarine, Coastal and Shelf Science》1984,19(4):485-491

Oxygen, alkalinity, nutrients, pH, temperature and salinity were measured through tidal cycles in two points of Blanca Bay. A clear dependence of nutrients, oxygen and alkalinity with salinity and tide conditions was observed in the inner point, being attenuated in the outer one.  相似文献   

Giant Maps as Pedagogical Tools for Teaching Geography and Mathematics     

Peter Anthamatten  Lara M. P. Bryant  Beverly J. Ferrucci  Steve Jennings  Rebecca Theobald 《The Journal of geography》2018,117(5):183-192

Giant maps offer a potentially useful pedagogical tool for teaching mathematics and map skills. In this pilot study, giant maps were distributed to elementary schools in Colorado and New Hampshire and teachers were provided with guided activities designed to integrate mathematics and geography skills. In an assessment of student skills, it was found that there were improvements in map-use skills and that students improved in some skills more than others. Additionally, there were differences in gender; girls improved more in their scores for some skills and less than boys in others. The teaching benefits of giant maps merit additional investigation.  相似文献   

Expert views - and disagreements - about the potential of energy technology R&D     

Laura Diaz Anadon  Erin Baker  Valentina Bosetti  Lara Aleluia Reis 《Climatic change》2016,136(3-4):677-691

Mitigating climate change will require innovation in energy technologies. Policy makers are faced with the question of how to promote this innovation, and whether to focus on a few technologies or to spread their bets. We present results on the extent to which public R&D might shape the future cost of energy technologies by 2030. We bring together three major expert elicitation efforts carried out by researchers at UMass Amherst, Harvard, and FEEM, covering nuclear, solar, Carbon Capture and Storage (CCS), bioelectricity, and biofuels. The results show experts believe that there will be cost reductions resulting from R&D and report median cost reductions around 20 % for most of the technologies at the R&D budgets considered. Although the improvements associated to solar and CCS R&D show some promise, the lack of consensus across studies, and the larger magnitude of the R&D investment involved in these technologies, calls for caution when defining what technologies would benefit the most from additional public R&D. In order to make R&D funding decisions to meet particular goals, such as mitigating climate change or improving energy security, or to estimate the social returns to R&D, policy makers need to combine the information provided in this study on cost reduction potentials with an analysis of the macroeconomic implications of these technological changes. We conclude with recommendations for future directions on energy expert elicitations.  相似文献