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排序方式: 共有197条查询结果,搜索用时 93 毫秒
91.
Riccardo Campana Mauro Orlandini Ettore Del Monte Marco Feroci Filippo Frontera 《Experimental Astronomy》2014,37(3):599-613
Low-inclination, low altitude Earth orbits (LEO) are of increasing importance for astrophysical satellites, due to their low background environment. Here, the South Atlantic Anomaly (SAA) is the region with the highest amount of radiation. We study the radiation environment in a LEO (500–600 km altitude, 4° inclination) through the particle background measured by the Particle Monitor (PM) experiment onboard the BeppoSAX satellite, between 1996 and 2002. Using time series of particle count rates measured by PM we construct intensity maps and derive SAA passage times and fluences. The low-latitude SAA regions are found to have an intensity strongly decreasing with altitude and dependent on the magnetic rigidity. The SAA extent, westward drift and strength vs altitude is shown. 相似文献
92.
Teresa Mineo George W. Fraser Adrian Martindale Charly Feldman Riccardo Campana Giancarlo Cusumano Marco Feroci 《Experimental Astronomy》2014,37(1):69-84
The Large Observatory For X-ray Timing (LOFT) is one of the candidate missions selected by the European Space Agency for an initial assessment phase in the Cosmic Vision programme. It is proposed for the M3 launch slot and has broad scientific goals related to fast timing of astrophysical X-ray sources. LOFT will carry the Large Area Detector (LAD), as one of the two core science instruments, necessary to achieve the challenging objectives of the project. LAD is a collimated detector working in the energy range 2-50 keV with an effective area of approximately 10 m 2at 8 keV. The instrument comprises an array of modules located on deployable panels. Lead-glass microchannel plate (MCP) collimators are located in front of the large-area Silicon Drift Detectors (SDD) to reduce the background contamination from off-axis resolved point sources and from the diffuse X-ray background. The inner walls of the microchannel plate pores reflect grazing incidence X-ray photons with a probability that depends on energy. In this paper, we present a study performed with an ad-hoc simulator of the effects of this capillary reflectivity on the overall instrument performance. The reflectivity is derived from a limited set of laboratory measurements, used to constrain the model. The measurements were taken using a prototype collimator whose thickness is similar to that adopted in the current baseline design proposed for the LAD. We find that the experimentally measured level of reflectivity of the pore inner walls enhances the off-axis transmission at low energies, producing an almost flat-top response. The resulting background increase due to the diffuse cosmic X-ray emission and sources within the field of view does not degrade the instrument sensitivity. 相似文献
93.
Several sea-level curves, from the classical ones to some of the most recently published, are analysed and compared. Although this short paper is not a review of the original data and analytical methods used by the different authors, similarities and mainly differences between published sea-level curves are emphasised especially as concern the suggested height and age of the highstand sea-level peaks during the last 450 ka. The perplexities of an end-user when attempting to exploit different curves for investigating uplifted marine terraces are discussed and recommendations are suggested. 相似文献
94.
Beatrice Cappelli Luigi Carmignani Francesca Castorina Anselmo Di Pisa Giacomo Oggiano Riccardo Petrini 《Geodinamica Acta》2013,26(1-2):101-118
AbstractThe Hereynian basement of Northern Sardinia consists of two main teetonometamorphic complexes : the Southern Paleozoic Low to Medium Grade Metamorphic Complex (LMGMC) and the Northern (Precaimbrian ?) High Grade Metamorphic Complex (HGMC). These complexes are separateli bu the “Posada-Asinara Line” which is a several kilometer-wide mylonitie belt consisting of micaschist. parag-neiss and quartzite that cuts across all Northern Sardinia and contains scattered hodies of amphibolites with granulile and eclogite facies relies.Major element composition of ampbibolites indicates they were derived from metamorphosed basalts of tholciitie affinity. REE and the relative abundances of HKS elements strongly suggest an oceanic basaltie prololith (N- and T-typc MORB). A whole-rock Sm-Nd isochron for the amphibolite protoliths yields an age of ea. 960 Ma.The Northern Sardinia basement can he interpreted as a continental collisional zone with the “Posada-Asinara Line” representing a suture zone squeezed between a crustal nappe (HGMC), which represents the overthrust continental margin. and (he inner portion of the Varisean orogenie wedge, which represents the underthrust continental margin with its Paleozoic cover (LMGMC).Geological and geochemical evidence indicate that the “Posada-Asinara Line” may he considered as part of the South European Hereynian Suture Zone. 相似文献
95.
Terrestrial laser scanning for rockfall stability analysis in the cultural heritage site of Pitigliano (Italy) 总被引:2,自引:1,他引:1
Riccardo Fanti Giovanni Gigli Luca Lombardi Deodato Tapete Paolo Canuti 《Landslides》2013,10(4):409-420
Traditional surveying methods are often not sufficient to achieve a complete geomechanical characterization of the rock mass, to analyze the instability mechanisms threatening the cultural heritage of hilltop historic towns. In Pitigliano (Tuscany, Central Italy), terrestrial laser scanning was employed complementarily to conventional geomechanical techniques. The overall 3D survey of the exposed surfaces was combined with scanlines of the inner walls of the subterranean cavities running underneath the historic centre. The rock mass discontinuities geometry was extracted, and the most critical instability mechanisms were mapped, with particular interest in the potential impacts on the ancient buildings located along the cliff edge. The geomechanical analysis of the surveyed joint sets confirmed a structural control on the cliff morphology by two main joint sets. Thanks to the laser scanner-based kinematic analysis, flexural toppling and wedge failure were found as the main hazardous instability mechanisms in Pitigliano. Finally, the conservation criticalities were identified and a pilot monitoring system was installed in a sector highly susceptible to block detachment. 相似文献
96.
Characterization of active fault scarps from LiDAR data: a case study from Central Apennines (Italy)
Carlo Alberto Brunori Riccardo Civico Francesca Romana Cinti 《International journal of geographical information science》2013,27(7):1405-1416
A high-resolution digital elevation model (DEM, 1 ms spacing) derived from an airborne light detection and ranging (LiDAR) campaign was used in an attempt to characterize the structural and erosive elements of the geometry of the Pettino fault, a seismogenic normal fault in Central Apennines (Italy). Four 90- to 280 m-long fault scarp segments were selected and the surface between the base and the top of the scarps was analyzed through the statistical analysis of the following DEM-derived parameters: altitude, height of the fault scarp, and distance along strike, slope, and aspect. The results identify slopes of up to 40° in faults lower reaches interpreted as fresh faces, 34° up the faces. The Pettino fault maximum long-term slip rate (0.6–1.1 mm/yr) was estimated from the scarp heights, which are up to 12–19 m in the selected four segments, and the age (ca. 18 ka) of the last glacial erosional phase in the area. The combined analysis of the DEM-derived parameters allows us to (a) define aspects of three-dimensional scarp geometry, (b) decipher its geomorphological significance, and (c) estimate the long-term slip rate. 相似文献
97.
Federico Carturan Carlo Pellegrino Riccardo Rossi Massimiliano Gastaldi Claudio Modena 《Bulletin of Earthquake Engineering》2013,11(2):543-559
In this work an integrated procedure for the evaluation of the seismic vulnerability of bridges included in the transportation network and a rational resource allocation for retrofitting with the aim of minimizing the consequences of an earthquake is shown at a network level. Both normal service and post-earthquake emergency conditions are considered as possible scenarios. The final result consists in global delay in the network versus seismic action occurring time. An iterative procedure finally defines the priority for optimal budget allocation for retrofitting. The procedure has been tested on a wide bridge network located in the North-eastern part of Italy. 相似文献
98.
Sandrine Roy Riccardo Vassallo Joseph Martinod Matías C. Ghiglione Christian Sue Pascal Allemand 《地学学报》2020,32(1):1-10
Across the extreme south of Patagonia, the Magallanes‐Fagnano Fault (MFF) accommodates the left‐lateral relative motion between South America and Scotia plates. In this paper, we present an updated view of the geometry of the eastern portion of the MFF outcropping in Tierra del Fuego. We subdivide the MFF in eight segments on the basis of their deformation styles, using field mapping and interpretation of high‐resolution imagery. We quantify coseismic ruptures of the strongest recorded 1949, Mw7.5 earthquake, and determine its eastern termination. We recognize several co‐seismic offsets in man‐made features showing a sinistral shift up to 6.5 m, greater than previously estimated. Using 10Be cosmogenic nuclides depth profiles, we date a cumulated offset in post‐glacial morphologies and estimate the long‐term slip rate of the eastern MFF. We quantify a 6.4 ± 0.9 mm/a left‐lateral fault slip rate, which overlaps geodetic velocity and suggests stable fault behaviour since Pleistocene. 相似文献
99.
The Italian strong motion network 总被引:2,自引:2,他引:0
Antonella Gorini Mario Nicoletti Paolo Marsan Riccardo Bianconi Rita De Nardis Luisa Filippi Sandro Marcucci Franco Palma Elisa Zambonelli 《Bulletin of Earthquake Engineering》2010,8(5):1075-1090
The Italian Strong Motion Network is a permanent monitoring system run by the Italian national emergency management department
(Dipartimento della Protezione Civile, DPC). The network is known as RAN (Rete Accelerometrica Nazionale). An extensive project
for updating and improving the technology of RAN instruments as well as the number of recording points was performed in the
last 10 years. A wide site selection survey was carried out from eastern Sicily along the Italian peninsula, covering high
seismic risk areas. The recording station density and the choice of high-quality digital strong motion instruments ensure
reliability of the RAN network in the long-term. At the end of 2008, the free field sites selection and instruments installation,
planned in the project, were quite completed. In planning and drawing the new RAN, special attention has been devoted to the
robustness of the transmission systems, and to the distribution of new stations in order to ensure plenty of data during a
seismic emergency. We spent special care both in the estimation of the RAN site responses and in the diffusion of the strong
motion data. In order to better identify damaged earthquake areas, improved ground motion parameters need to be set. Such
parameters will also assist future progress for engineering seismic design techniques as well as disaster mitigation. 相似文献
100.
Federico Betti Giorgio Bavestrello Marzia Bo Valentina Asnaghi Mariachiara Chiantore Simone Bava Riccardo Cattaneo‐Vietti 《Marine Ecology》2017,38(3)
During the last several decades, the Mediterranean littoral shallow water benthic communities have suffered significant changes in their structure and taxa composition. Despite numerous studies conducted to characterize these changes at various levels, it has always been very difficult to disentangle the effects of natural factors from anthropic ones. The main purpose of this work was to evaluate possible changes, over a 10‐year scale, in diversity and abundance of the most representative species of the benthic communities considered to be primarily and potentially affected by natural stressors in a highly protected area. Sets of macro‐photographs were taken in 2002–2003 of three sites inside a small bay called Ca’ dell'Oro, which is the “no entry—no take” zone of the Marine Protected Area of Portofino, in order to analyse the structure of the benthic communities at different depths over a short time scale. The same sampling was repeated 10 years later in 2013. In the 10‐year span, a significant change in the macroalgal coverage and composition was observed, while the overall richness and coverage of species remained almost unchanged. This process resulted in a significant reduction of the habitat complexity of the three‐dimensional algal components. Likewise, a remarkable change in terms of presence and abundance occurred among all zoobenthic components. The benthic communities seem to have suffered from detrimental effects probably caused by climatic events that have been occurring in recent years in the Ligurian Sea. 相似文献