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151.
Sebastiano Ghigna Ben Moore Fabio Governato George Lake Thomas Quinn & Joachim Stadel 《Monthly notices of the Royal Astronomical Society》1998,300(1):146-162
We examine the properties of dark matter haloes within a rich galaxy cluster using a high-resolution simulation that captures the cosmological context of a cold dark matter universe. The mass and force resolution permit the resolution of 150 haloes with circular velocities larger than 80 km s−1 within the cluster virial radius of 2 Mpc (with Hubble constant H 0 = 50 km s−1 Mpc−1 ). This enables an unprecedented study of the statistical properties of a large sample of dark matter haloes evolving in a dense environment. The cumulative fraction of mass attached to these haloes varies from close to zero per cent at 200 kpc to 13 per cent at the virial radius. Even at this resolution the overmerging problem persists; haloes that pass within 100–200 kpc of the cluster centre are tidally disrupted. Additional substructure is lost at earlier epochs within the massive progenitor haloes. The median ratio of apocentric to pericentric radii is 6:1, so that the orbital distribution is close to isotropic, circular orbits are rare and radial orbits are common. The orbits of haloes are unbiased with respect to both position within the cluster and the orbits of the smooth dark matter background, and no velocity bias is detected. The tidal radii of surviving haloes are generally well-fitted using the simple analytic prediction applied to their orbital pericentres. Haloes within clusters have higher concentrations than those in the field. Within the cluster, halo density profiles can be modified by tidal forces and individual encounters with other haloes that cause significant mass loss —'galaxy harassment'. Mergers between haloes do not occur inside the cluster virial radius. 相似文献
152.
Erosion and morphology of a debris flow caused by a glacial lake outburst flood,Western Norway 总被引:5,自引:2,他引:3
This article documents a 240,000-m3 debris flow resulting from a glacial lake outburst flood in Fjærland, Western Norway, May 8, 2004. The event started when a glacial lake breached a moraine ridge. The ensuing debris flow was able to erode material along its path, increasing in volume from about 25,000 to 240,000 m3 before depositing about 3 km from its starting point. Field investigations, pre- and post-flow aerial photographs as well as airborne laser scanning (LIDAR) were used to describe and investigate the flow. The most striking and unusual feature of this case study is the very pronounced erosion and bulking. We have made a detailed study of this aspect. Erosion and entrainment is quantified and the final volume of the debris flow is determined. We also present geometrical and sedimentological features of the final deposit. Based on the Fjærland data, we suggest that a self-sustaining mechanism might partly explain the extreme growth of debris flows traversing soft terrain. 相似文献
153.
154.
Aybige Akinci Luca Malagnini Fabio Sabetta 《Soil Dynamics and Earthquake Engineering》2010,30(5):320-335
An Mw 6.25 earthquake occurred on April 6, 2009 at 03:33 a.m. local time, in the Abruzzo region (Central Italy), close to the city of L’Aquila. The earthquake ruptured a North-West (NW)–South-East (SE) oriented normal fault dipping toward the South-West (SW), with the city of L’Aquila lying a few kilometers away on the hanging wall.The main shock has been recorded by fifty-eight accelerometric stations: the highest number of digital recordings ever obtained in Italy for a single earthquake, one of the best-recorded earthquakes with a normal fault mechanism. Very high values of peak ground acceleration (0.3–0.65 g) were observed close to the center of L’Aquila (6 stations at zero JB distance from the fault). The earthquake caused severe loss of lives (299 victims and 1500 injured) and damage (about 18000 unusable buildings) in the epicentral area.In this study we analyze the ground motion characteristics of both the main shock in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo-acceleration response spectra (5% of damping ratio). In particular, we compare the pseudo-acceleration response spectra for horizontal directions with the EC8 design spectrum and the new Italian building code (NTC08). In order to understand the characteristics of the ground motions induced by L’Aquila earthquake, we also study the source-related effects and site response of the strong motion stations that recorded the seismic sequence. A novel method is used for the analysis of inter-station and site-specific H/V spectral ratios for the main event and for 12 aftershocks. 相似文献
155.
Riccardo Tortini Fabio L. Bonali Claudia Corazzato Simon A. Carn Alessandro Tibaldi 《地学学报》2014,26(4):273-281
Measuring surface deformation is critical in analogue modelling of Earth science phenomena. Here, we present a novel application of the Microsoft Kinect sensor to measure vertical deformation in a scaled analogue model of Nisyros volcano (Greece), simulating two magmatic sources and related surface deformation. The Kinect permits capture of real time, 640 × 480 pixel, true‐colour images (RGB) and a grid of distances to the modelled surface with a horizontal and vertical resolution of ±1 mm. Using recorded distances permits quantification of vertical deformation in terms of maximum and average down‐ and uplift during deflation and inflation phases respectively, which is of crucial importance for defining the kinematics of faults formed during the modelling, determined from interpretation of the RGB images. Although other techniques have demonstrated similar or higher accuracy, our study demonstrates the cost‐effectiveness of the Kinect in analogue modelling of volcanoes. 相似文献
156.
Fabio V. De Blasio 《Geotechnical and Geological Engineering》2012,30(1):269-276
The paper presents a numerical method to simulate the dynamics of a cohesive debris flow. The model is based on a molecular
dynamics algorithm where the equation of motion is calculated for an ensemble of interacting particles. In addition to the
hard-core repulsion and to the other forces commonly introduced to simulate granular media, in this work an attractive force
between particles is added as a model for cohesion. The model is computationally straightforward and devoid of a series of
cumbersome problems affecting fluid mechanical codes. Preliminary simulations presented here look promising, and indicate
directions of study for a better comparison and test against field data. 相似文献
157.
Landslides in Valles Marineris (Mars): A possible role of basal lubrication by sub-surface ice 总被引:1,自引:0,他引:1
Fabio Vittorio De Blasio 《Planetary and Space Science》2011,59(13):1384-1392
There is much interest on the occurrence of water and ice in the past history of Mars. Because landslides on Mars are much better conserved than their terrestrial counterparts, a physical examination and morphological analysis can reveal significant details on the depositional environment at the instant of failure. A study of the landslides in Valles Marineris based on their physical aspect is presented and the velocity of the landslides is calculated with a stretching block model. The results show that the landslides were subject to strong basal lubrication that made them travel at high speed and to long distances. We use physical analysis to explore the four alternative possibilities that the natural lubricant of the landslides in Valles Marineris was either ice, deep water, a shallow carpet of water, or evaporites. Examination of the furrows present on the surface of the landslide deposits shows that either sub-surface ice or evaporites were likely present on the floor of Valles Marineris during the mass failures. 相似文献
158.
Francesco Di Benedetto Francesco D’Acapito Fabio Capacci Gabriele Fornaciai Massimo Innocenti Giordano Montegrossi Werner Oberhauser Luca A. Pardi Maurizio Romanelli 《Physics and Chemistry of Minerals》2014,41(3):215-225
We investigated the speciation of Fe in bulk and in suspended respirable quartz dusts coming from ceramic and iron-casting industrial processes via X-ray absorption spectroscopy, with the aim of contributing to a better understanding of the variability of crystalline silica toxicity. Four different bulk industrial quartz powders, nominally pure quartz samples with Fe contents below 200 ppm, and three respirable dusts filters were selected. Fe speciation was determined in all samples through a coupled study of the X-ray absorption near-edge structure and extended X-ray absorption fine structure regions, operating at the Fe–K edge. Fe speciation revealed common features at the beginning of the different production processes, whereas significant differences were observed on both respirable dusts and bulk dusts exiting from the production process. Namely, a common pollution of the raw quartz dusts by elemental Fe was evidenced and attributed to residuals of the industrial production of quartz materials. Moreover, the respirable samples indicated that reactivity occurs after the suspension of the powders in air. The gravitational selection during the particle suspension consistently allowed us to clearly discriminate between suspended and bulk dusts. On the basis of the obtained results, we provide an apparent spectroscopic discrimination between the raw materials used in the considered industrial processes, and those that are effectively inhaled by workers. In particular, an amorphous FeIII oxide, with an unsaturated coordination sphere, can be related to silica reactivity (and health consequences). 相似文献
159.
Fabio Manca Giuseppe Capelli Francesco La Vigna Roberto Mazza Annalisa Pascarella 《Environmental Earth Sciences》2014,72(4):1083-1095
The wind effect on river water quality was illustrated by means of thermohaline measurements carried out in the Tiber River in May 2012. The survey was carried out using a boat, in stations located in the two Tiber branches: Fiumara Grande and Traiano Canal. Thermohaline variables (salinity and temperature) were used to describe the water-type patterns and to define the salt-wedge position. Although the river flow rate was rather high, saltwater intrusion happened. Wind data suggested that the more probable cause of salt-wedge intrusion was the wind action. Especially wind speeds higher than 4 m/s are able to dominate the sea current at surface layers, determining an increase in the sea level. Therefore, westerly winds determined a seawater inflow in the river mouths. 相似文献
160.
Ugo Chiocchini Fabio Castaldi Maurizio Barbieri Valeria Eulilli 《Hydrogeology Journal》2010,18(6):1319-1341
The stratigraphic and structural setting of the Cimini Mountains and Viterbo area of Italy has been reconstructed. The architecture of the tectonic edifice, below the Pleistocene Cimino and Vicano volcanic districts cover, is characterized by the Mesozoic–Cenozoic Tuscan Nappe and the similar Umbria-Marche Succession; both are capped by the overthrusted Ligurian Late Cretaceous–Eocene Tolfa Flysch. A shallow unconfined volcanic aquifer is separated, by a thick aquiclude, from the deep confined carbonate aquifer consisting of the Tuscan Nappe and the Umbria-Marche Succession. The volcanic aquifer hosts cold waters, whilst the carbonate aquifer hosts hot sulphate–alkaline earth waters that emerge in the thermal area of Viterbo with a temperature of 30–60°C. The recharge area of cold waters is located in the Cimini Mountains. Thermal waters of the Viterbo hot springs are derived from a circuit of waters that emerge along the River Nera near Narni (about 34 km ENE of Viterbo), with a high salinity, a temperature of 16–18°C, a sulphate–alkaline earth composition, and a discharge of 13 m3/sec, whose recharge area is located in the central pre-Apennines reliefs. 相似文献