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61.
Alessandra Celletti Cătălin Galeş Giuseppe Pucacco Aaron J. Rosengren 《Celestial Mechanics and Dynamical Astronomy》2017,127(3):259-283
We provide a detailed derivation of the analytical expansion of the lunar and solar disturbing functions. Although there exist several papers on this topic, many derivations contain mistakes in the final expansion or rather (just) in the proof, thereby necessitating a recasting and correction of the original derivation. In this work, we provide a self-consistent and definite form of the lunisolar expansion. We start with Kaula’s expansion of the disturbing function in terms of the equatorial elements of both the perturbed and perturbing bodies. Then we give a detailed proof of Lane’s expansion, in which the elements of the Moon are referred to the ecliptic plane. Using this approach the inclination of the Moon becomes nearly constant, while the argument of perihelion, the longitude of the ascending node, and the mean anomaly vary linearly with time. We make a comparison between the different expansions and we profit from such discussion to point out some mistakes in the existing literature, which might compromise the correctness of the results. As an application, we analyze the long-term motion of the highly elliptical and critically-inclined Molniya orbits subject to quadrupolar gravitational interactions. The analytical expansions presented herein are very powerful with respect to dynamical studies based on Cartesian equations, because they quickly allow for a more holistic and intuitively understandable picture of the dynamics. 相似文献
62.
On October 10, 1995, an ML= 4.8 (ING) earthquake occurred in the region of Lunigiana (northwestern Italy). The shock was felt over a large area and produced significant damage. We performed a macroseismic survey and damage zonation and assessed a maximum intensity VII MCS in the epicentral area. The damage pattern, that we investigated in detail for some of the villages in the most heavily damaged area, emphasises the role of surface geology in amplifying the effects. Topographic effects and near-surface geology are largely responsible for broadening the damage area. Given the moderate size of the earthquake, many of the macroseismic observations, including rotations of objects and the propagation of visible waves in the ground, are suggestive of amplification phenomena. 相似文献
63.
64.
In this study we examined the spatial and temporal dynamics of planktonic bacterial assemblages at four different sites in the Lagoon of Venice. Samples were collected in January, April, July and October 2005 and several parameters (temperature, salinity, dissolved oxygen, chlorophyll a, dissolved macronutrients, dissolved and particulate organic carbon, viral and heterotrophic nanoplanktonic abundances) were determined in order to highlight the most important factors which are implied in shaping such assemblages. Furthermore we tested the relationship between similar assemblages and the patterns of activities (prokaryotic carbon production and several hydrolytic activities) that they perform in order to establish if, in this highly variable environment, similar assemblages behave in analogous ways. Results indicate that seasonality act as the main forcing on the communities. Moreover, we found a mismatch between community structure and patterns of activity possibly as a consequence of the heterogeneity of the lagoon which can affect in turn the assemblages' metabolic requirements (and thus their responses). 相似文献
65.
Suspended‐sediment concentration data are a missing link in reconstructions of the River Waal in the early 1800s. These reconstructions serve as a basis for assessing the long‐term effects of major interventions carried out between 1850 AD and the early 20th century. We used a 2D physics‐based morphodynamic model accounting for the influence of floodplain vegetation to fill in this gap. Historical discharge hydrographs were derived from a correlation between flow discharge records at Cologne and water level measurements of the Rhine branches in the Netherlands, taking into account the discharge distribution between the branches. Historical floodplain sedimentation rates were estimated using old cartographic information and recent geomorphologic field work. The computed historical sedimentation rates are found to be within the range of measured data, which suggests that fine suspended sediment concentrations in the early 1800s were comparable to contemporary ones. The computations show also how vegetation enhances the formation of natural levees close to the main channel and at the same time decreases the sedimentation rates in farther areas of the floodplain. A sensitivity analysis shows suspended sediment composition to have a strong influence on the resulting quantities and patterns of floodplain deposition. The reconstruction has also provided validation of the modelling tools to reproduce the effects of vegetation on sediment dynamics, enabling their implementation to study other cases. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
66.
Alessandra Romolo Giovanni Malara Giuseppe Barbaro Felice Arena 《Applied Ocean Research》2009,31(1):31-36
This paper deals with the random forces produced by high ocean waves on submerged horizontal circular cylinders. Arena [Arena F, Interaction between long-crested random waves and a submerged horizontal cylinder. Phys Fluids 2006;18(7):1–9 (paper 076602)] obtained the analytical solution of the random wave field for two dimensional waves by extending the classical Ogilvie solution [Ogilvie TF, First- and second-order forces on a cylinder submerged under a free surface. J Fluid Mech 1963;16:451–472; Arena F, Note on a paper by Ogilvie: The interaction between waves and a submerged horizontal cylinder. J Fluid Mech 1999;394:355–356] to the case of random waves. In this paper, the wave force acting on the cylinder is investigated and the Froude Krylov force [Sarpkaya T, Isaacson M, Mechanics of wave forces on offshore structures, Van Nostrand Reinhold Co.; 1981], on the ideal water cylinder, is calculated from the random incident wave field. Both forces represent a Gaussian random process of time. The diffraction coefficient of the wave force is obtained as quotient between the standard deviations of the force on the solid cylinder and of the Froude Krylov force. It is found that the diffraction coefficient of the horizontal force Cdo is equal to the Cdv of the vertical force. Finally, it is shown that, since a very large wave force occurs on the cylinder, it may be calculated, in time domain, starting from the Froude Krylov force. It is then shown that this result is due to the fact that the frequency spectrum of the force acting on the cylinder is nearly identical to that of the Froude–Krylov force. 相似文献
67.
Alessandra Ascione Alessandro Iannace Pamela Imbriale Nicoletta Santangelo Antonio Santo 《地学学报》2014,26(1):1-13
Continental carbonates of Quaternary age in southern Italy commonly exhibit the facies of calcareous tufa, often reported as related to shallow aquifers fed by meteoric waters and to organic processes. A close spatial relationship exists between the mappable tufa deposits and major Quaternary extensional faults. With respect to the Ca‐Mg‐HCO3 composition of limestone aquifers’ springs, tufa‐depositing springs exhibit higher salinity and alkalinity, are slightly warmer, have lower pH and are enriched in SO4 and CO2. Their δ13C values are systematically positive and compatible with a deep‐seated carbon source. A clear input of soil‐derived organic carbon is indicated only for small, non‐mappable tufas deposited by perched springs. The dataset indicates that the large tufa deposits owe their origin to a supplementary source of CO2 advected by degassing through active faults, as a necessary prerequisite for inducing a rise of total dissolved salts and alkalinity. Meteoric waters that have come from a shallow aquifer are able to precipitate only limited amount of carbonates. 相似文献
68.
Paola Del Negro Mauro Celussi Erica Crevatin Alessandro Paoli Fabrizio Bernardi Aubry Alessandra Pugnetti 《Marine Ecology》2008,29(3):375-386
The prokaryotic community, both in terms of abundance and activity (exoenzymatic hydrolysis of proteins, polysaccharides and phosphorylated molecules and leucine uptake), was investigated seasonally for a 3‐year period (2004–2006) in the Gulf of Venice (northern Adriatic Sea). By focusing on spatial and temporal variability, the prokaryote dynamics showed significant variations on a horizontal and seasonal scale, but no substantial differences were observed among years. The basin‐scale variability was mainly influenced by allochthonous inputs from the Po river and the Venice Lagoon, which were the main source of nutrients, acting as a ‘bottom up’ control on prokaryotes. On a seasonal scale, all the microbial parameters (except the polysaccharide degradation) showed significant variations following the temperature fluctuations. The annual rate of change was very low for all the chemical, physical and biological parameters and only the abundance and phosphatase activity of the prokaryotes differed significantly among years. 相似文献
69.
Maria Alessandra Iannotta Francesco Toscano & Francesco Paolo Patti 《Marine Ecology》2009,30(1):106-115
Strong environmental selection may give rise to complex species and/or camouflage the presence of sibling species in brackish waters. The prosobranch gastropod Nassarius corniculus (Olivi, 1792) is a common scavenger widely distributed in Mediterranean brackish and marine areas. We examined the morphological and molecular features of N. corniculus populations and related these features to the environmental complexity of brackish habitats. Morphological data revealed differences in radular features between specimens collected from two Mediterranean lagoons (Lake Faro, Messina, Sicily and Lake Fusaro, Gulf of Gaeta). Analysis of with the mitochondrial marker mt 16S rRNA revealed genetic variability within the Lake Faro population but did not show the different geographic structure between the two lagoons indicated by morphological data. We also predicted the gene flow of N. corniculus by comparing populations of two marine areas (Faro Sea and Ischia). 相似文献
70.
Roberto Carlucci Lembo Giuseppe Maiorano Porzia Capezzuto Francesca Marano Chiara Alessandra Sion Letizia Spedicato Maria Teresa Ungaro Nicola Tursi Angelo Gianfranco D'Onghia 《Estuarine, Coastal and Shelf Science》2009,83(4):529-538
The spatial pattern of the nursery areas of red mullet (Mullus barbatus), hake (Merluccius merluccius) (Linnaeus, 1758) and deep-water rose shrimp (Parapenaeus longirostris) (Lucas, 1846) was studied in the South Adriatic and North Ionian Seas (Eastern-Central Mediterranean) applying geostatistical techniques and data from time series trawl surveys conducted in the area. The analysed variables were: R (number of recruits/km2) and R/Tot (fraction of recruits on the total sampled population). The structural analysis showed a spatial pattern of both variables characterized by continuity on a small scale. Predictions of nursery area localization with probability of finding recruits at different threshold values were obtained through median indicator kriging. For the red mullet the nurseries were mainly identified in the South Adriatic Sea off the Gargano peninsula and between Molfetta and Monopoli within 50 m in depth. The main concentration of hake juveniles was found to be between 100 and 200 m in depth along the Gargano peninsula and between Otranto and Santa Maria di Leuca, where a nursery of deep-water rose shrimp was also detected. An overlapping depth, between 100 and 200 m, was identified for hake and deep-water rose shrimp nurseries. Protection of these areas through limitations of fishing pressure is discussed. 相似文献