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81.
Massimo Caccia 《Oceanic Engineering, IEEE Journal of》2006,31(3):711-727
A laser-triangulation optical-correlation sensor for estimating the motion of underwater vehicles at low speed in the proximity of the seabed is described. Experimental results, obtained by processing image sequences acquired by the instrument mounted below the Romeo remotely operated vehicle (ROV) in operating conditions, are presented 相似文献
82.
Federico Spagnoli Antonietta Specchiulli Tommaso Scirocco Gerardo Carapella Paolo Villani Giovanni Casolino Primiano Schiavone Massimo Franchi 《Marine Ecology》2002,23(S1):384-394
Abstract. The Lago di Varano is situated on the north side of the Gargano National Park (southeast Italy) and covers a surface area of about 65 km2 . It communicates with the Adriatic Sea through two artificial canals (Foce Capoiale and Foce Varano) located at the two ends of a long and narrow coastal dune. This work presents preliminary results of four seasonal surveys (1999–2000) carried out to measure chemical and physical parameters of the water column (temperature, salinity, dissolved oxygen and pH) and to analyse a number of biogeochemical characteristics of surface sediments (organic matter, total phosphorus, total nitrogen and total Hg, As, Pb, Cd, Cr, Cu and Ni content). Water analysis indicated poor exchange between the coastal pond and the open sea, limited to autumn and winter. Surface sediments were rich in organic matter, whose distribution was influenced by chemical-physical and hydrodynamic variations in the water column. At the sediment level, the highest values of Cd were found in the central zone of the basin, while the highest Cr values were measured in the central and southeastern areas. With the exception of Cd and Pb, the metal content did not indicate anthropogenic pollution, in particular when compared with the Venice Lagoon and the Central Adriatic Sea. 相似文献
83.
Massimo Azzali rea De Felice Manlio Luna Giulio Cosimi Flavio Parmiggiani 《Marine Ecology》2002,23(S1):78-91
Abstract. The paper provides an overview of the state of the small pelagic fish in the Adriatic Sea. The North Adriatic is reviewed for the 1976–1998 period and the South Adriatic for the 1987–1998 period. First the fluctuations in time and in space of the pelagic biomass, as a whole and per species, are presented. Then the dramatic collapse of anchovy stock and its apparent association with the decrease of surface temperature is discussed. Finally the changes of the anchovy and sardine catches are compared and analysed with respect to their abundances in the sea. The conclusion is that acoustic and satellite methods are able to provide a large amount of information on the variability in the pelagic populations; this is essential for an appropriate management of these resources. There is still a need, however, to refine the methods and to integrate this kind of information with further environmental data (including natural predators). 相似文献
84.
Massimo Mazzoni 《Solar physics》1987,108(2):221-225
The energy differences between 1s
22p 1s2p3p transitions and the corresponding 1s
2 1s3p resonances are expressed by means of a polynomial function of the atomic number. The agreement with experimental data from lithium to potassium is very good. Interpolated values for nitrogen to sodium and argon as well as extrapolation for calcium are reported. 相似文献
85.
Microscopic impactor debris in the soil around Kamil crater (Egypt): Inventory,distribution, total mass,and implications for the impact scenario 下载免费PDF全文
Luigi Folco Massimo D'Orazio Agnese Fazio Carole Cordier Antonio Zeoli Matthias van Ginneken Ahmed El‐Barkooky 《Meteoritics & planetary science》2015,50(3):382-400
We report on the microscopic impactor debris around Kamil crater (45 m in diameter, Egypt) collected during our 2010 geophysical expedition. The hypervelocity impact of Gebel Kamil (Ni‐rich ataxite) on a sandstone target produced a downrange ejecta curtain of microscopic impactor debris due SE–SW of the crater (extending ~300,000 m2, up to ~400 m from the crater), in agreement with previous determination of the impactor trajectory. The microscopic impactor debris include vesicular masses, spherules, and coatings of dark impact melt glass which is a mixture of impactor and target materials (Si‐, Fe‐, and Al‐rich glass), plus Fe‐Ni oxide spherules and mini shrapnel, documenting that these products can be found in craters as small as few tens of meters in diameter. The estimated mass of the microscopic impactor debris (<290 kg) derived from Ni concentrations in the soil is a small fraction of the total impactor mass (~10 t) in the form of macroscopic shrapnel. That Kamil crater was generated by a relatively small impactor is consistent with literature estimates of its pre‐atmospheric mass (>20 t, likely 50–60 t). 相似文献
86.
Alain Cheilletz Dominique Gasquet Fouad Filali Douglas A. Archibald Massimo Nespolo 《Mineralium Deposita》2010,45(4):323-329
El Hammam is the only fluorite mine in Morocco (production 100,000 t/year). The fluorite mineralization is in an array of
fluorite–calcite veins and is characterized by unusually high REE content in carbonate minerals (1,400 ppm in calcite; up
to 2,000 ppm in siderite) and in fluorite (about 600 ppm). Since the 1960s, the genesis of the deposit has been attributed
to a mesothermal hydrothermal event connected with late-Variscan granitic intrusions. Precise 40Ar/39Ar dating of hydrothermal K-feldspar yields an age of formation of the El Hammam deposit at 205 ± 1 Ma. Its genesis is therefore
associated in time and space with the development of the Triassic–Jurassic basins and the associated anorogenic continental
flood basalts of the Moroccan Mesetian Middle Atlas. The source of the hydrothermal mineralization (magmatic and/or metamorphic)
is discussed. 相似文献
87.
Pietro Mosca Riccardo Polino Sergio Rogledi Massimo Rossi 《International Journal of Earth Sciences》2010,99(4):833-849
Alps and Apennines are juxtaposed within an approximately 100 km-wide area covered by the Upper Eocene to Miocene successions
of the Tertiary Piedmont Basin. The Upper Eocene–Oligocene evolution of this area was characterized to the north and west
by the propagation of the SE-verging Southalpine thrust-fold belt that can be traced from the Po Plain subsurface until the
Torino Hill-Saluzzese area, and to the south by a high-angle, broadly E–W oriented megashear zone that led to the juxtaposition
of different crustal levels and controlled the development of a mosaic of partly independent sub-basins. Since the latest
Oligocene the N-verging Apenninic tectonics prevailed in the collisional system and the Tertiary Piedmont Basin evolved as
a wide thrust-top basin, bounded to the north by the N-verging Monferrato arc and characterized by a tectono-sedimentary evolution
recording changes of subsidence and shift of depocentres in relation to crustal structures. 相似文献
88.
The low annual and seasonal variability of the shallow groundwater temperature in the alluvial plain aquifers of the Piemonte
region (NW Italy) confirmed the potentiality of the low-enthalpy open-loop groundwater heat pumps (GWHP) diffusion to contribute
to the reduction of regional greenhouse gas emissions. The distribution of mean groundwater temperatures ranged from a minimum
of 10.3°C to a maximum of 17.9°C with a mean of 14.0°C. Differences among diverse areas were slight according with the modest
variations in the general climatic condition. Like the air, temperature distribution of the shallow groundwater temperatures
is generally similar to topographic elevations in reverse manner. Higher temperature values recorded were typical of summer
months (June, July). On the opposite lower values were measured in January and February. No significant difference phase (time)
difference between air and groundwater temperature appeared in the data analysis. Besides air-temperature influence (seasonal
variability) seemed strictly connected to the depth to groundwater in the measure point and it was negligible when the value
was over 9.5 m. For the application of the open-loop systems, extensive examinations of the hydrogeological local conditions
should be conducted at site scale and groundwater heat transport modelling should be developed. 相似文献
89.
Folco Giacomini Vittorio Boerio Simona Polattini Massimo Tiepolo Riccardo Tribuzio Alberto Zanetti 《Environmental Earth Sciences》2010,61(8):1621-1639
This work is part of the project study for a road tunnel bypassing the town of Genova and was aimed at evaluating the amount of asbestos fibres in the metaophiolites belonging to the Voltri Group and the Sestri–Voltaggio Zone (Liguria, Northern Italy). The 85 studied rock samples (mainly mafic and ultramafic rocks) derive from exposed outcrops and prospecting boreholes. The study of field relations and petrographic/microtextural investigations under the optical microscope allowed for the identification and characterisation of asbestos-bearing settings and lithotypes. Mineralogy and concentration of asbestos fibres in powdered specimens were determined by means of a scanning electron microscope equipped with an energy-dispersive X-ray spectroscopy device. These investigations were combined with petrography on thin-section, X-ray diffraction analysis and phase contrast optical microscopy on rock powders. Mafic and ultramafic rocks commonly contain asbestos in concentrations below 1,000 mg/kg (considered as the contamination threshold under Italian law). However, the fibre concentration rises abruptly within localised zones, where the metaophiolite sequences were involved into late ductile to brittle tectono-metamorphic events. Two groups of asbestos-bearing settings have been so far identified in the area: (a) fracture networks within serpentinites (dominated by fibrous chrysotile), and (b) boudins of chlorite-tremolite schists, likely deriving from dynamic recrystallisation of mafic rocks under greenschist facies conditions (dominated by fibrous amphibole). Even considering the low volumetric incidence of these settings (metres to few tens of metres), their high asbestos content locally controls the total fibre amount in the excavation products, thus requiring special prevention measures during excavation, management and final storage of the contaminated debris. 相似文献
90.
New Sr isotopic data on lavas and xenoliths from Somma-Vesuvius and other nearby volcanic areas (Phlegrean Fields and Ischia) are presented. Chemical and isotopic evidences show that not all the Phlegrean Fields rocks belong to the low K series, but some of them may be interpreted as low pressure differentiates of Somma magmas, i.e. as a part of the high K series. Two rock groups are defined in the Ischia low K series, which are well identified both in time and in chemical and isotopic features, and cannot be derived from the same magma source. The low K series in the studied area generally has lower Sr isotopic values than the high K series.Historical Vesuvian lavas show two distinct linear trends with negative slopes when87Sr/86Sr ratios are plotted against their ages of eruption. Such trends are interpreted to result from mixing of magmas in two separate reservoirs. Evidence from the Vesuvian ejecta shows that Somma-Vesuvius magmas underwent high or low pressure fractionation, in connection with different events of the Vesuvian activity. Distinct magma reservoirs developed episodically at different depths. Isotopic and geochemical evidences do not favour large scale assimilation of crustal materials by Somma-Vesuvius magmas, but instead appear to reflect mantle characteristics.A minimum of three different (inhomogeneous) source regions is necessary to account for the isotopic features of the studied rocks. 相似文献