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21.
Troy A. Henderson John L. Junkins Gianmarco Radice 《Celestial Mechanics and Dynamical Astronomy》2009,104(4):355-368
A complex exponential solution has been derived which unifies the elliptic and hyperbolic trajectories into a single set of
equations and provides an exact, analytical solution to the unperturbed, Keplerian two-body problem. The formulation eliminates
singularities associated with the elliptic and hyperbolic trajectories that arise from these orbits. Using this complex exponential
solution formulation, a variation of parameters formulation for the perturbed two-body problem has been derived. In this paper,
we present the analytical formulation of the complex exponential solution, numerical simulations, a comparison with classical
solution methods, and highlight the benefits of this approach compared with the classical developments.
Previously presented as AAS 07-136 at the 17th AAS/AIAA Spaceflight Mechanics Meeting Sedona, Arizona, AAS 08-206 and AAS
08-230 at the 18th AAS/AIAA Spaceflight Mechanics Meeting Galveston, Texas. 相似文献
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Chemical parameters characterizing the sedimentary environment in a NW Adriatic coastal area (Italy)
Organic matter constituents (C, N, P) have been measured in surficial sediment samples from a coastal area often subjected to eutrophication phenomena. Chemical and physico-chemical parameters are substantially homogeneous throughout the area investigated, indicating a mainly autochthonous origin of the sedimented organic matter and allowing some considerations on the diagenetic processes possibly occurring at the sediment-water interface in relation to nutrient release. 相似文献
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Vincenzo Minganti Renzo Capelli Giuliana Drava Rodolfo De Pellegrini Giorgio Brunialti Paolo Giordani Paolo Modenesi 《Journal of Atmospheric Chemistry》2003,45(3):219-229
The concentrations of Cd, Cu, Mn, Ni, Pb, V, and Zn were measured in four different species of lichens (Parmelia caperata, P. pastillifera, P. saxatilis, P. sulcata) sampled in North-West Italy, in order to obtain maps showing metal distribution and the degree of deviation from background (natural) conditions. Significant differences among the species were found for Zn, Mn, Pb and V, suggesting that the combined use of mixed species in biomonitoring surveys can affect the interpretation of results. Results obtained for Parmelia caperata samples have been compared with background (natural) levels, and maps showing the distribution of each metal expressed as deviation from background levels have been obtained. Overall such maps show a medium to high alteration degree in the study area. 相似文献
25.
Jolita Petkuviene Mindaugas Zilius Irma Lubiene Tomas Ruginis Gianmarco Giordani Arturas Razinkovas-Baziukas Marco Bartoli 《Estuaries and Coasts》2016,39(5):1386-1402
The availability of reactive phosphorus (P) may promote cyanobacterial blooms, a worldwide increasing phenomenon. Cyanobacteria may also regulate benthic P cycling through labile organic input to sediments, favouring reduced conditions and P release, ultimately acting as self-sustainment mechanism for the phytoplankton blooms. To analyse P–cyanobacteria feedbacks and compare external versus internal loads, we investigated P cycling in the Curonian Lagoon, a freshwater estuary with recurrent summer blooms. At two sites representing the dominant sediment types, we characterised P pools and mobility, via combined pore water analysis, calculation of diffusive exchanges and flux measurements via sediment core incubations. Annual P budgets were also calculated, to analyse the whole lagoon role as net sink or source. Muddy sediments, representing nearly 50 % of the lagoon surface, displayed higher P content if compared with sandy sediments, and most of this pool was reactive. The muddy site had consequently higher pore water dissolved inorganic phosphorus (DIP) concentrations maintaining high diffusive gradients. However, measured fluxes suggested that both sediment types were mostly P sinks except for a large DIP regeneration (nearly 30 μmol m?2 h?1) recorded at the muddy site during an intense cyanobacteria bloom. Such internal regeneration had the same order of magnitude as the annual external P load and may offset the net annual DIP sink role of the estuary. It may also prolong the duration of the bloom. Our results suggest that positive feedbacks can regulate N-fixing cyanobacteria blooms and internal P recycling, through either diffusive fluxes or sediment settling and resuspension. 相似文献
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P. Magni D. Tagliapietra L. Balthis S. Como G. Giordani F. Maltagliati A. Rismondo P. Tomassetti 《Marine pollution bulletin》2009,58(4):478-337
We investigated the applicability of the Pearson-Rosenberg (P-R) conceptual model describing a generalized pattern of response of benthic communities in relation to organic enrichment to Mediterranean Sea coastal lagoons. Consistent with P-R model predictions, benthic diversity and abundance showed two different peaks at low (>2.5-5 mg g−1) and high (>25-30 mg g−1) total organic carbon (TOC) ranges, respectively. We identified TOC thresholds indicating that risks of reduced benthic diversity should be relatively low at TOC values < about 10 mg g−1, high at TOC values > about 28 mg g−1, and intermediate at values in-between. Predictive ability within these ranges was high based on results of re-sampling simulation. While not a direct measure of causality, it is anticipated that these TOC thresholds should serve as a general screening-level indicator for evaluating the likelihood of reduced sediment quality and associated bioeffects in such eutrophic systems of the Mediterranean Sea. 相似文献
28.
The near-sea surface meteorological conditions associated with the Mediterranean heavy precipitation events constitute, on
a short time scale, a strong forcing on the ocean mixed layer. This study addresses the question of the optimal time frequency
of the atmospheric forcing to drive an ocean model in order to make it able to capture the fine scale ocean mixed layer response
to severe meteorological conditions. The coupling time frequency should allow the ocean model to reproduce the formation of
internal low-salty boundary layers due to sudden input of intense precipitation, as well as the cooling and deepening of the
ocean mixed layer through large latent heat fluxes and stress under the intense low-level jet associated with these events.
In this study, the one-dimensional ocean model is driven by 2.4-km atmospheric simulated fields on a case of Mediterranean
heavy precipitation, varying the time resolution of the atmospheric forcing. The results show that using a finer temporal
resolution than 1 h for the atmospheric forcing is not necessary, but a coarser temporal resolution (3 or 6 h) modifies the
event course and intensity perceived by the ocean. Consequently, when using a too coarse temporal resolution forcing, typically
6 h, the ocean model fails to reproduce the ocean mixed layer fine scale response under the heavy rainfall pulses and the
strong wind gusts. 相似文献
29.
Shake table testing on restoring capability of double concave friction pendulum seismic isolation systems 
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下载免费PDF全文 Felice Carlo Ponzo Antonio Di Cesare Gianmarco Leccese Domenico Nigro 《地震工程与结构动力学》2017,46(14):2337-2353
After an earthquake, non‐negligible residual displacements may affect the serviceability of a base isolated structure, if the isolation system does not possess a good restoring capability. The permanent offset does not affect the performance unless the design is problematic for utilities, also considering possible concerns related to the maintenance of the devices. Starting from experimental and analytical results of previous studies, the restoring capability of Double Concave Friction Pendulum bearings is investigated in this paper. A simplified design suggestion for the estimation of maximum expected residual displacements for currently used friction pendulum systems is then validated. The study is based on controlled‐displacement and seismic input experiments, both performed under unidirectional motion. Several shaking table tests have been carried out on a three‐dimensional isolated specimen structure. The same sequence of seismic inputs was applied considering three different conditions of sliding surfaces corresponding to low, medium and high friction. The accumulation of residual displacements is also investigated by means of nonlinear dynamic analysis. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
30.
Genuario Belmonte Gianmarco Ingrosso Marco Poto Gianluca Quarta Marisa D'Elia Raffaele Onorato & Lucio Calcagnile 《Marine Ecology》2009,30(3):376-382
Submarine caves at the Cape of Otranto (SE, Italy) host pseudostalactites. Only recently have they been recognised as originating mainly from the marine tube worm Protula tubularia (Serpulidae, Polychaeta). Their formation depends on the adaptability, life history and behaviour of that species in the cave habitat. The dating of calcareous tubes in the pseudostalactite core represents the first attempt to describe the formation of such bio-construction, and the gregarious behaviour of the species. Calcareous tubes along the core axis of three pseudostalactites removed from the cave lu Lampiùne (Otranto, South East Italy) have been dated using the 14 C method. Measures established ages from 2600 to 5000 years for the three structures. This extremely long period (when compared with the life span of each worm) suggests that each tube aggregation is the result of punctuated growth periods alternated with long standstill phases. At the end of a growth period, each tube aggregation was covered with a brownish concretion, completing the pseudostalactite. 相似文献