Prediction of satellite orbits contraction due to diurnally varying oblate atmosphere and altitude-dependent scale height using KS canonical elements     

Xavier James Raj 《Planetary and Space Science》2009,57(11):1312-1320

A new non-singular analytical theory for the motion of near-Earth satellite orbits with the air drag effect is developed in terms of uniformly regular KS canonical elements. Diurnally varying oblate atmosphere is considered with variation in density scale height dependent on altitude. The series expansion method is utilized to generate the analytical solutions and terms up to fourth-order terms in eccentricity and c (a small parameter dependent on the flattening of the atmosphere) are retained. Only two of the nine equations are solved analytically to compute the state vector and change in energy at the end of each revolution, due to symmetry in the equations of motion. The important drag perturbed orbital parameters: semi-major axis and eccentricity are obtained up to 500 revolutions, with the present analytical theory and by numerical integration over a wide range of perigee height, eccentricity and inclination. The differences between the two are found to be very less. A comparison between the theories generated with terms up to third- and fourth-order terms in c and e shows an improvement in the computation of the orbital parameters semi-major axis and eccentricity, up to 9%. The theory can be effectively used for the re-entry of the near-Earth objects, which mainly decay due to atmospheric drag.  相似文献   

Contraction of near-Earth satellite orbits using uniformly regular KS canonical elements in an oblate atmosphere with density scale height variation with altitude     

M. Xavier James Raj 《Planetary and Space Science》2009,57(1):34-41

A new non-singular analytical theory for the contraction of near-Earth satellite orbits under the influence of air drag is developed in terms of uniformly regular Kustaanheimo and Stiefel (KS) canonical elements using an oblate atmosphere with variation of density scale height with altitude. The series expansions include up to fourth power in terms of eccentricity and c (a small parameter dependent on the flattening of the atmosphere). Only two of the nine equations are solved analytically to compute the state vector and change in energy at the end of each revolution, due to symmetry in the equations of motion. It is observed that the analytically computed values of the semi-major axis and eccentricity are consistent with the numerically integrated values up to 500 revolutions over a wide range of the drag-perturbed orbital parameters. The theory can be effectively used for re-entry of near-Earth objects.  相似文献   

Variations of levels and composition of PM₁₀ and PM_2.5 at an insular site in the Western Mediterranean     

Jorge Pey  Xavier Querol  Andrs Alastuey 《Atmospheric Research》2009,94(2):285-299

The insular suburban site of Castillo de Bellver was selected for the study of the variability of PM levels and composition in the Western Mediterranean Basin (WMB).Mean annual (in 2004) PM₁₀ and PM_2.5 levels at this site were 29 and 20 µg/m³, respectively. These levels may be regarded as relatively low when compared with other suburban insular locations in the Eastern Mediterranean Basin (EMB), but they are higher than those recorded at most of the European suburban sites, especially in Northern and Western Europe. Seasonal variability of PM levels at this site is governed by meteorology rather than local emissions, whereas the daily cycles are clearly defined by the anthropogenic emissions, mainly coming from the urban area of Palma de Mallorca and the harbour area of the same city.Concerning the aerosol composition at this site, the main PM constituent is the mineral matter (29% in PM₁₀ and 16 % in PM_2.5), more than 50% (in PM₁₀) being attributable to African dust. The amount of secondary inorganic aerosols is also very high (27% in PM₁₀ and 34% in PM_2.5), with the predominance of fine ammonium sulphate, and in a less proportion fine ammonium nitrate (in winter) and coarse Ca and Na nitrate (with higher importance in summer). The carbonaceous particles, dominantly fine, account for 17% of PM₁₀ and 25% of PM_2.5. The elemental carbon/organic carbon (EC/OC) ratio reached a mean value of 0.17, similar to those observed at regional background sites in the WMB coast of Spain. The sea spray aerosols (mainly coarse) represented around 10% of PM₁₀, and only 4% in PM_2.5. Finally, the unaccounted fraction increased from 15% to 20% in PM_2.5, being mostly attributed to water.The concentrations of trace elements in PM₁₀ and PM_2.5 were usually in the range to those observed in regional background sites in the Iberian Peninsula, with the exception of the typical tracers of road traffic such as Cu, Sb, Zn, Sn and Ba, which presented concentrations in the range of urban sites of Iberia. Other elements such as Cr, Zr, Hf and Co have been identified as the main tracers of the harbour contributions.  相似文献   

Mesozoic Evaniidae (Insecta: Hymenoptera) in Spanish Amber: Reanalysis of the Phylogeny of the Evanioidea     

Enrique PE?ALVER  Jaime ORTEGA-BLANCO  André NEL  Xavier DELCLòS 《《地质学报》英文版》2010,84(4):809-827

<正>One new genus and five new species of the family Evaniidae are described from the Early Cretaceous (Albian)Spanish amber of Penacerrada-Ⅰ(Province of Burgos),San Just and Arroyo de la Pascueta(both in the Province of Teruel):Cretevania alonsoi sp.nov.,C.montoyai sp.nov.,C.alcalai sp.nov.,C.rubusensis sp.nov.,and Iberoevania roblesi gen.and sp.nov.Taxonomic changes include Cretevania pristina(Zhang and Zhang,2000) comb.nov.,C.exquisita(Zhang,Rasmtsyn,Wang and Zhang,2007)comb.nov.,C.vesca(Zhang,Rasnitsyn,Wang and Zhang,2007)comb.nov.,and C.cyrtocerca(Deans,2004)comb.nov.,as a result of the reinterpretation of the genera Procretevania and Eovernevania.The new well preserved specimens of the genus Cretevania,together with the characters shown by the type specimens of the synonymized genera,give new information about their anatomical characters of taxonomical importance,and the genus Cretevania Rasnitsyn,1975 is re-diagnosed.The holotypes of the Russian species in amber have been revised.A cladistic analysis of fossil and extant groups of the superfamily Evanioidea is included.Cretevania had a wide palaeogeographic distribution,with the highest diversity known from Spain.The 13 known Cretevania species show a high interspecific variation mainly in wing characteristics,and a wide range of body and wing size.  相似文献   

Future changes in Central Europe heat waves expected to mostly follow summer mean warming     

Joan Ballester  Xavier Rodó  Filippo Giorgi 《Climate Dynamics》2010,35(7-8):1191-1205

Daily output from the PRUDENCE ensemble of regional climate simulations for the end of the twentieth and twenty-first centuries over Europe is used to show that the increasing intensity of the most damaging summer heat waves over Central Europe is mostly due to higher base summer temperatures. In this context, base temperature is defined as the mean of the seasonal cycle component for those calendar days when regional heat waves occur and is close, albeit not identical, to the mean temperature for July–August. Although 36–47% of future Central Europe July and August days at the end of the twenty-first century are projected to be extreme according to the present day climatology, specific changes in deseasonalized heat wave anomalies are projected to be relatively small. Instead, changes in summer base temperatures appear much larger, clearly identifiable and of the same order of magnitude as changes in the whole magnitude of heat waves. Our results bear important consequences for the predictability of central European heat wave intensity under global warming conditions.  相似文献   

Practical aspects of demand and capacity evaluation of RC members in the context of EC8‐3     

Xavier Romo  Raimundo Delgado  Aníbal Costa 《地震工程与结构动力学》2010,39(5):473-499

The structural safety assessment procedures proposed in Part 3 of Eurocode 8 (EC8‐3) for the case of reinforced concrete structures are addressed. The practical evaluation of the member chord rotation demand according to EC8‐3 is examined in detail along with several alternative formulations. The need for these formulations is demonstrated by presenting example situations where the EC8‐3 proposal is difficult to apply. The effectiveness of the proposed approaches is assessed through an example application and recommendations for their practical use are defined. Given the importance of the shear span in this context, a sensitivity analysis of the EC8‐3 capacity models with respect to this parameter is carried out and discussed in a later section. This analysis aims to assess the validity of the simplifications proposed by a previous research study for the quantification of the EC8‐3 capacity values. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Organic matter in sediments of canyons and open slopes of the Portuguese,Catalan, Southern Adriatic and Cretan Sea margins     

Antonio Pusceddu  Silvia Bianchelli  Miquel Canals  Anna Sanchez-Vidal  Xavier Durrieu De Madron  Serge Heussner  Vasilios Lykousis  Henko de Stigter  Fabio Trincardi  Roberto Danovaro 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(3):441-457

We describe the quantitative and compositional (phytopigment, protein, carbohydrate and lipid) patterns of sedimentary organic matter along bathymetric gradients in seven submarine canyons and adjacent open slopes located at four European regions: one along the NE Atlantic and three along the Mediterranean continental margins. The investigated areas are distributed along a putative longitudinal gradient of decreasing primary production from the Portuguese (northeastern Atlantic Ocean), to the Catalan (western Mediterranean Sea), Southern Adriatic (central Mediterranean Sea) and Southern Cretan (eastern Mediterranean Sea) margins. Sediment concentrations of organic matter differed significantly between the Portuguese margin and the Mediterranean regions and also from one study area to the other within the Mediterranean Sea. Differences in quantity and composition of sediment organic matter between canyons and open slopes were limited and significant only in the eutrophic Portuguese margin, where the differences were as large as those observed between regions (i.e. at the mesoscale). These results suggest that the overall trophic status of deep margin sediments is controlled mostly by the primary productivity of the overlying waters rather than by the local topography. Moreover, we also report that the quantity and nutritional quality of sediment organic matter in canyons and adjacent open slopes do not show any consistent depth-related pattern. Only the Nazaré and Cascais canyons in the Portuguese margin, at depths deeper than 500 m, displayed a significant accumulation of labile organic matter. The results of our study underline the need of further investigations of deep margins through sampling strategies accounting for adequate temporal and spatial scales of variability.  相似文献   

Giuliano F. Panza, Mircea Radulian and Cesar-Ioan Trifu (eds.), Seismic Hazard of the Circum-Pannonian Region, Pageoph Topical Volumes, Vol. 157.     

Xavier Goula 《Surveys in Geophysics》2001,22(1):97-99

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Development of a Data Visualization and Analysis Tool to Study the Particle Dynamics in the Coastal Zone   总被引：1，自引：0，他引：1  

Dimitra Kitsiou  Xavier Durrieu de Madron  Pedro Antonio Arnau 《Marine pollution bulletin》2001,43(7-12):262-269

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Modified equations for the determination of odd zonal harmonics     

Dr. Xavier Berger  Pr. Georges Ligier 《Journal of Geodesy》1978,52(2):101-105

The development of the analytical theory of the motion of an artificial satellite (Berger, 1972–1975) points out the great importance of the second, third order and coupling terms between zonal harmonics. These terms have been added to the equations established byKing-Hele andCook (1968–1973) for the determination of odd zonal harmonics. This solution is compared with theirs. It satisfies all the equations much better and especially the equations relating to near-critical inclination satellites.  相似文献