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排序方式: 共有123条查询结果,搜索用时 15 毫秒
91.
92.
Marcello Lappa 《地球物理与天体物理流体动力学》2016,110(4):348-386
Different phenomena related to the spontaneous accumulation of solid particles dispersed in a fluid medium in microgravity conditions are discussed, with an emphasis on recent discoveries and potential links with the general field of astrophysical fluid-dynamics on the one hand, and with terrestrial applications in the field of materials science on the other hand. With special attention to the typical physical forces at play in such an environment, namely, surface-tension gradients, oscillatory residual gravity components, inertial disturbances and forces of an electrostatic nature, specific experimental and numerical examples are presented to provide inputs for an increased understanding of the underlying cause-and-effect relationships. Studying these systems can be seen as a matter of understanding how macroscopic scenarios arise from the cooperative behaviour of sub-parts or competing mechanisms (nonlinearities and interdependencies on various spatial and temporal scales). Through a critical assessment of the properties displayed by the resulting structures (which appear in the form of one-dimensional circuits formed by aligned particles, planar accumulation surfaces, three-dimensional compact structures resembling “quadrics”, micro-crystallites or fractal aggregates), we discuss a possible classification of the related particle attractors in the space of parameters according to the prevailing effect. 相似文献
93.
Francesco De Pascale Marcello Bernardo Francesco Muto Dante Di Matteo Valeria Dattilo 《Natural Hazards》2017,86(2):569-586
The last few years have seen the debate on the geoethics of environmental and climatic protection growing to include resilience as a central idea within this new discipline, which holds many similarities with geography. Resilience analysis often looks at the capacity to re-establish conditions of equilibrium within a system which has been hit by a serious shock, e.g. a natural or man-made disaster. Geoethics works, in tandem with geological analyses and the geography of risk, to inform a population and develop integrated risk management in such a way as to strengthen a community’s resilience. The aim of this work is to study some people’s capacity to overcome what was potentially a disastrous event and, through a process of reconstruction, turn it into an occasion for growth. The experiment, carried out in the primary and middle schools in Aiello Calabro (Calabria, southern Italy), was conducted on the basis of the belief that there is a close relationship between a population’s having a realistic understanding of the risk of such an event, e.g. an earthquake, and high levels of resilience. We also tried to gain an insight into the relationship that may exist between resilience in primary and secondary school children and methods of coping which give an appropriate management of seismic risk. To be more precise, we try to discover whether there is a link between good/appropriate resilience and good/appropriate risk management. 相似文献
94.
Daniel J. Lehrmann Marcello Minzoni Paul Enos Caroline Kelleher Leanne Stepchinski Xiaowei Li Jonathan L. Payne Meiyi Yu 《Sedimentology》2020,67(6):3167-3198
Sector-collapse structures ranging up to 27 km wide with up to 7.7 km bankward erosion (scalloped margins) and linear escarpments occur along the east-north-east-trending, south-facing margins of the Yangtze Platform and Great Bank of Guizhou. Exposure of one of the structures on the rotated limb of a syncline displays the geometry in profile view. Declivities range from 65° to 90° in the upper wall and decrease asymptotically to the toe. Catastrophic collapses of the margins in both platforms occurred during the late Ladinian as constrained by the ages of strata truncated along the margins and the siliciclastic turbidites that onlap collapse structures. Middle Triassic Anisian and Ladinian platform-edge reef facies and platform-interior facies were truncated along both the Yangtze and Great Bank of Guizhou margins. Lower Triassic facies were also truncated along the Great Bank of Guizhou margin. Gravity transport during the main episodes of collapse occurred as mud-rich debris-flows and as mud-free hyper-concentrated flows. Clasts, several to tens of metres and, exceptionally, hundreds of metres across, were transported to the basin. Following collapse, talus, carbonate turbidites and periplatform-mud accumulated at the toe of slope. Shedding of skeletal grains and carbonate mud indicates active carbonate factories at the margin. Preserved sections of the margins demonstrate that the platforms evolved high-relief, accretionary escarpments prior to collapse. High-relief, without buttressing by basin-filling sediments, predisposed the margins to collapse by development of tensile strain and fracturing within the margin due to the lack of confining stress. The linear geometry of margins and active tectonics in the region supports tectonic activity triggering the collapse. Collapse is thus interpreted to have been triggered by fault movement and seismic shock. Comparison with other systems indicates that evolution from high-relief accretion to tectonic collapse of largely lithified margins resulted in large sector-collapse structures and deposition of a coarse, generally mud-poor breccia apron. 相似文献
95.
Brian M. Kelley Daniel J. Lehrmann Meiyi Yu Adam B. Jost Katja M. Meyer Kimberly V. Lau Demir Altiner Xiaowei Li Marcello Minzoni Ellen K. Schaal Jonathan L. Payne 《Sedimentology》2020,67(6):3119-3151
Carbonate platforms spanning intervals of global change provide an opportunity to identify causal links between the evolution of marine environment and depositional architecture. This study investigates the controls on platform geometry across the Palaeozoic to Mesozoic transition and yields new stratigraphic and palaeoenvironmental constraints on the Great Bank of Guizhou, a latest Permian to earliest Late Triassic isolated carbonate platform in the Nanpanjiang Basin of south China. Reconstruction of platform architecture was achieved by integrating field mapping, petrography, biostratigraphy, satellite imagery analysis and δ13C chemostratigraphy. In contrast to previous interpretations, this study indicates that: (i) the Great Bank of Guizhou transitioned during Early Triassic time from a low-relief bank to a platform with high relief above the basin floor (up to 600 m) and steep slope angles (preserved up to 50°); and (ii) the oldest-known platform-margin reef of the Mesozoic Era grew along steep, prograding clinoforms in an outer-margin to lower-slope environment. Increasing platform relief during Early Triassic time was caused by limited sediment delivery to the basin margin and a high rate of accommodation creation driven by Indosinian convergence. The steep upper Olenekian (upper Lower Triassic) slope is dominated by well-cemented grainstone, suggesting that high carbonate saturation states led to syndepositional or rapid post-depositional sediment stabilization. Latest Spathian reef initiation coincided with global cooling following Early Triassic global warmth. The first Triassic framework-building metazoans on the Great Bank of Guizhou were small calcareous sponges restricted to deeper water settings, but early Mesozoic reef builders were volumetrically dominated by Tubiphytes, a fossil genus of uncertain taxonomic affinity. In aggregate, the stratigraphic architecture of the Great Bank of Guizhou records sedimentary response to long-term environmental and biological recovery from the end-Permian mass extinction, highlighting the close connections among marine chemistry, marine ecosystems and carbonate depositional systems. 相似文献
96.
Jan-Olaf Meynecke Elisa Seyboth Jasper De Bie Jan-Lukas Menzel Barraqueta Abdoulkadri Chama Subhra Prakash Dey Serena Blyth Lee Vivitskaia Tulloch Marcello Vichi Ken Findlay Alakendra Narayan Roychoudhury Brendan Mackey 《Marine Ecology》2020,41(6):e12616
Globally, baleen whales were severely depleted by historic whaling. Recovering populations have been observed to alter their behaviour. These changes have been attributed to climate change in some cases and raise concerns over the successful recovery of baleen whale populations. Current data-driven statistical habitat and behavioural models have proven useful for addressing questions of whale distribution changes within their limitations. Given observed changes in oceanic conditions, a new approach to managing baleen whale population recovery is necessary. Model predictions of future whale movements and distributions under climate change scenarios are vital to enable adequate conservation management. This paper presents a new perspective on understanding the impacts of climate change on humpback whales, arguing the need for a system-based multidisciplinary research approach. Our approach includes coupled, mechanistic models based upon robust ecological principles, and integrates key physical, biogeochemical, biological and ecological modules to address long-term changes associated with climate change. To illustrate the need for this system-based multidisciplinary approach, we focus on Southern Hemisphere humpback whales, the recovery of which may be impacted by rapid changes in habitat conditions brought about by anthropogenic climate change. 相似文献
97.
98.
Massimo Vellante Matthias Förster Michael Pezzopane Norbert Jakowski Tie Long Zhang Umberto Villante Marcello De Lauretis Bruno Zolesi Werner Magnes 《Earth, Moon, and Planets》2009,104(1-4):25-27
Cross-spectral analysis of ULF wave measurements recorded at ground magnetometer stations closely spaced in latitude allows accurate determinations of magnetospheric field line resonance (FLR) frequencies. This is a useful tool for remote sensing temporal and spatial variations of the magnetospheric plasma mass density. The spatial configuration of the South European GeoMagnetic Array (SEGMA, 1.56 < L < 1.89) offers the possibility to perform such studies at low latitudes allowing to monitor the dynamical coupling between the ionosphere and the inner plasmasphere. As an example of this capability we present the results of a cross-correlation analysis between FLR frequencies and solar EUV irradiance (as monitored by the 10.7-cm solar radio flux F10.7) suggesting that changes in the inner plasmasphere density follow the short-term (27-day) variations of the solar irradiance with a time delay of 1–2 days. As an additional example we present the results of a comparative analysis of FLR measurements, ionospheric vertical soundings and vertical TEC measurements during the development of a geomagnetic storm. 相似文献
99.
100.
Petko Nenovski Maria Chamati Umberto Villante Marcello De Lauretis Patrizia Francia 《Acta Geophysica》2013,61(2):311-337
We apply detrended fluctuation analysis (DFA) on fluxgate and search-coil data in ULF range (scales 10–90 s or 0.1–0.011 Hz) for the months January–April 2009 available from the South European GeoMagnetic Array stations: Castello Tesino (CST), Ranchio (RNC), and L’Aquila (AQU) in Italy; Nagycenk (NCK) in Hungary; and Panagyuriste (PAG) in Bulgaria. DFA is a data processing method that allows for the detection of scaling behaviors in observational time series even in the presence of non-stationarities. The H and Z magnetic field components at night hours (00-03 UT, 01–04 LT) and their variations at the stations CST, AQU, NCK, and PAG have been examined and their scaling characteristics are analyzed depending on geomagnetic and local conditions. As expected, the scaling exponents are found to increase when the K p index increases, indicating a good correlation with geomagnetic activity. The scaling exponent reveals also local changes (at L’Aquila), which include an increase for the Z (vertical) component, followed by a considerable decrease for the X (horizontal) component in the midst of February 2009. Attempts are made to explain this unique feature with artificial and/or natural sources including the enhanced earthquake activity in the months January–April 2009 at the L’Aquila district. 相似文献