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31.
Elisa Maria Alessi Giulia Schettino Alessandro Rossi Giovanni B. Valsecchi 《Celestial Mechanics and Dynamical Astronomy》2018,130(5):34
We present the main findings of a dynamical mapping performed in the Low Earth Orbit region. The results were obtained by propagating an extended grid of initial conditions, considering two different epochs and area-to-mass ratios, by means of a singly averaged numerical propagator. It turns out that dynamical resonances associated with high-degree geopotential harmonics, lunisolar perturbations and Solar radiation pressure can open natural deorbiting highways. For area-to-mass ratios typical of the orbiting intact objects, these corridors can be exploited only in combination with the action exerted by the atmospheric drag. For satellites equipped with an area augmentation device, we show the boundary of application of the drag, and where the Solar radiation pressure can be exploited. 相似文献
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Maiorano Luigi; Bartolino Valerio; Colloca Francesco; Abella Alvaro; Belluscio Andrea; Carpentieri Paolo; Criscoli Alessandro; Jona Lasinio Giovanna; Mannini Alessandro; Pranovi Fabio; Reale Bruno; Relini Giulio; Viva Claudio; Ardizzone Gian Domenico 《ICES Journal of Marine Science》2009,66(1):137-146
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Jafar Amiri Parian Alessandro Cozzani Matteo Appolloni Gianluca Casarosa 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(3):317-327
In the frame of the development of a photogrammetric system to be used in thermal/vacuum chambers at the European Space Research and Technology Centre (ESTEC) of European Space Agency (ESA) and other sites across Europe, the design of a network using micro-cameras was specified by ESA-ESTEC. A thermal/vacuum qualified photogrammetric system, which is able to work and acquire images in vacuum and at cryo-temperatures, was constructed by ESA-ESTEC Test Centre Division. The current system uses four space qualified one-mega pixel cameras and is able to measure large space structures in vacuum and at temperatures down to ?170 °C with a global accuracy better than 1 part per 100,000 in object space. Several tests aiming at the qualification of the sensors and system in terms of operation and accuracy have been carried out. Special measures have been developed and special attention has been taken into account specifically for the first application of the photogrammetric system. It is to verify the ESA’s Herschel Telescope Flight Model alignment positioning. 相似文献
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Tobias Lung Carlo Lavalle Roland Hiederer Alessandro Dosio Laurens M. Bouwer 《Global Environmental Change》2013,23(2):522-536
To better prioritise adaptation strategies to a changing climate that are currently being developed, there is a need for quantitative regional level assessments that are systematic and comparable across multiple weather hazards. This study presents an indicator-based impact assessment framework at NUTS-2 level for the European Union that quantifies potential regional changes in weather-related hazards: heat stress in relation to human health, river flood risk, and forest fire risk. This is done by comparing the current (baseline) situation with two future time periods, 2011–2040 and 2041–2070. The indicator values for the baseline period are validated against observed impact data. For each hazard, the method integrates outcomes of a set of coherent high-resolution regional climate models from the ENSEMBLES project based on the SRES A1B emission scenario, with current and projected non-climatic drivers of risk, such as land use and socio-economic change. An index of regional adaptive capacity has been developed and compared with overall hazard impact in order to identify the potentially most vulnerable regions in Europe. The results show strongest increases in impacts for heat stress, followed by forest fire risk, while for flood risk the sign and magnitude of change vary across regions. A major difference with previous studies is that heat stress risk could increase most in central Europe, which is due to the ageing population there. An overall assessment combining the three hazards shows a clear trend towards increasing impact from climaterelated natural hazards for most parts of Europe, but hotspot regions are found in eastern and southern Europe due to their low adaptive capacities. This spatially explicit assessment can serve as a basis for discussing climate adaptation mainstreaming, and priorities for regional development in the EU. 相似文献
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Ancient carbonate buildups may contain extraordinarily large amounts of early diagenetic precipitates. In some, host rock lamination may be traced into inclusion bands within the 'cement' crystals, suggesting that the crystals are replacive. By analogy with a Pleistocene speleothem from the Sorrento Peninsula, however, these relationships can be explained differently. In the speleothem, large, repeatedly split and dendritic calcite crystals occur within a laminated carbonate. Lamination consists of sub-mm alternations of micrite and microspar. Micritic laminae pass laterally into inclusion-rich growth bands in the dendritic calcite crystals, and have replaced an aragonitic cement, whereas the microspar laminae were primary calcite cements. Three types of inclusion-rich bands occur in the dendrite crystals: (1) with aragonite relicts, (2) 'ribbon calcite' and (3) with oriented micropores. When aragonite precipitated, the calcite dendrite branches were unable to keep growing as single crystals and split into crystallites (separated by micropores, some forming ribbon calcite), whereas during episodes of calcite lamina precipitation, the larger crystals were regenerated by crystallite coalescence. Calcite crystals are primary: they did not replace a micritic precursor. By analogy with the Italian speleothem, some ancient reefal sparry carbonates may not be replacements of earlier laminated sediments, but may have grown concurrently with them. It is also probable that some ancient laminated sediments were instead sea-floor precipitates, and that stromatolites containing cross-cutting crystal fabrics, and the alternating micrite-microspar laminae typical of Archaeolithoporella , could be largely abiotic crystal growths. 相似文献
39.
Warmuth Alexander Hanslmeier Arnold Messerotti Mauro Cacciani Alessandro Moretti Pier Francesco Otruba Wolfgang 《Solar physics》2000,194(1):103-120
NOAA 8210 has been a region showing a remarkable level of activity well before solar maximum. Dominated by a large, rapidly rotating spot, it produced several intense flares during its disk passage at the end of April–beginning of May 1998. We examine the development of AR 8210 in H and white light (WL) and study the evolution of its complex magnetic topology. While the other principal flares are briefly reviewed, the great X1.1/3B flare of 2 May, which was observed at Kanzelhöhe Solar Observatory during a SOHO/UVCS ground support campaign, is studied in detail. This event has been documented in full-disk H and Na-D intensitygrams, Dopplergrams, and magnetograms, with a time cadence of one minute each. The flare was associated with a CME and produced significant geomagnetic effects. Furthermore, we point out the perspectives for our planned Flare Monitoring and Alerting System, since the two new instruments (Magneto-Optical Filter and Digital H camera), which made their first operational run with the campaign, are crucial components for this program. 相似文献
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