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排序方式: 共有192条查询结果,搜索用时 31 毫秒
71.
Giovanni Spagnoli Pierpaolo Oreste Salvatore Grancuore 《Marine Georesources & Geotechnology》2013,31(6):739-745
AbstractThe estimation of excavation rates in specific geological and geotechnical conditions is one of the most delicate aspects for mining and geotechnical operations particularly offshore. Many models have been developed to study the effectiveness of a drilling tool in contact with the ground. In this article, the results of laboratory cutting tests on concrete specimens are shown. The comparison of the results of laboratory tests with different predictive models, helped to identify the most representative models. The models were then used to study in more detail, the effectiveness of the excavation tools through a parametric analysis. The research helped to define how to obtain rubrics, which can estimate the theoretical net cutting production of an excavation machine, when the power of its engines is known, or to evaluate, when the requested net cutting production is available, the power that the cutting machine must have. The findings were also applied to a sandstone previously investigated. The results are based on theoretical models and cannot be used on geomaterials with the same (or similar) geotechnical properties. 相似文献
72.
Francesca Zuccarello Salvatore L. Guglielmino Viviana Battiato Lidia Contarino Daniele Spadaro Pado Romano 《Acta Geophysica》2009,57(1):15-23
This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high
resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising
flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially
characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline
of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following
legs of the flux tubes. These results are briefly discussed in the light of most recent models. 相似文献
73.
Ilia Louban Nicole Bobrowski Dmitri Rouwet Salvatore Inguaggiato Ulrich Platt 《Bulletin of Volcanology》2009,71(7):753-765
The simultaneous quantitative determination of two-dimensional bromine monoxide (BrO) and sulphur dioxide (SO2) distributions in volcanic gas plumes is described. Measurements at the fumarolic field on the island Vulcano (autumn 2004)
and in the plume of Mt. Etna volcano (spring 2005) were carried out with an Imaging DOAS instrument. The SO2 fluxes of several fumaroles were estimated from two-dimensional distributions of SO2. Additionally, the first two-dimensional distributions of BrO within a volcanic plume were successfully retrieved. Slant
column densities of up to 2.6 × 1014 molecules per square centimetre were detected in the plume of Mt. Etna. The investigation of the BrO/SO2 ratio, calculated from the two-dimensional distributions of SO2 and BrO, shows an increase from the centre to the edge of the volcanic plume. These results have significance for the involvement
of ozone during BrO formation processes in volcanic emissions. 相似文献
74.
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76.
Enrico Ciliberto Carmelo Crisafulli Fabio Carmelo Manuella Filippo Samperi Salvatore Scirè Vittorio Scribano Marco Viccaro Ezio Viscuso 《Chemical Geology》2009,258(3-4):258-268
Many tholeiite gabbro xenoliths from the Hyblean tuff-breccia deposits (Sicily, southern Italy) present mineralogical and geochemical evidence for hydrothermal alteration at different temperatures and water/rock ratios. In some cases, the primary mineral assemblage has been entirely replaced by Na-rich alkali feldspar, chlorite/smectite interlayers, zeolites, aegirine–augite, titanite, zircon etc. Hence the chemical composition of such metasomatic rocks displays larger amounts of volatiles, alkalis, Zr, Hf, U, Th and lower Ca, Mg, Fe with respect to the original gabbro. Five hydrothermally altered gabbroic xenoliths were selected for thermal decrepitation and bulk gas analyses by quadrupole mass spectrometry. All the samples analyzed display the same Electron Impact-Direct Pyrolysis Mass spectra (EI-DPMS). These show a series of peaks differing by 14 mass units due to loss of methylene groups (–CH2), by a fragmentation process typical of saturated aliphatic and aliphatic–aromatic hydrocarbons. In addition, Fourier Transform Infrared (FT-IR) spectra of the samples present several bands typical of vibration frequencies of aliphatic hydrocarbons. The high-molecular-weight hydrocarbons observed probably originated from Fischer–Tropsch-type (FT-t) synthesis in the high temperature section of a serpentinite-hosted hydrothermal system. This suggestion may lend support to the recent hypothesis regarding the original oceanic nature of the Hyblean lithospheric basement. 相似文献
77.
78.
Mario Mattia Marco Aloisi Giuseppe Di Grazia Salvatore Gambino Mimmo Palano Valentina Bruno 《Journal of Volcanology and Geothermal Research》2008
In this work, we report the results of an integrated approach using both seismological and geodetic data provided by the INGV-CT (Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania) Stromboli volcano monitoring systems, in order to improve the knowledge of its plumbing system. In particular, we investigated the relationships between the June 1999 seismic swarm, occurring in the area of Stromboli, and the possible activation of the NE–SW oriented volcano-tectonic structure. We analyzed this seismic swarm proposing new locations and a morphological analysis of the waveforms. This approach allowed us to demonstrate that there are relationships between the tectonic activity near Stromboli and the rising of magma. This evidence supports the hypothesis that during the 1999 swarm an intrusive process started from a crustal level where earthquakes were located (about 10–15 km b.s.l.). 相似文献
79.
The common shrimps of the genus Palaemon are often reported as living in Mediterranean submarine caves. The present study quantifies the distribution pattern of a Palaemon spp. populations throughout 1 year of observations in a shallow submarine cave in South‐eastern Italy, Ionian Sea. The cave was subdivided into six sectors from the entrance towards the inner portion of the ‘blind cave’ and 16 dives (four per season, during both day and night) were performed with SCUBA equipment. The population was estimated in situ using visual census. Four different species of Palaemon were identified. This study has shown that Palaemon spp. assemblages live throughout the year in submarine caves. Moreover, the results suggest submarine caves play an important role in the biology of Palaemon spp. populations, by providing refuge, juvenile recruitment and food resources. 相似文献
80.
Marine genetic resources both within and beyond national jurisdiction have been the focus of international negotiations in a range of forums in recent years. One recurrent theme throughout these discussions has been the absence of detailed information upon which policy responses to the emerging issue of the conservation and sustainable use of marine genetic resources (especially in areas beyond national jurisdiction) could be based. In an effort to address some of these knowledge gaps, this article examines the level and nature of scientific and commercial interest in marine genetic resources, including in areas beyond national jurisdiction. It also examines the changing perspectives of the scientific community in relation to the potential of marine genetic resources. 相似文献