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61.
Salvatore Giammanco Massimo Ottaviani Enrico Veschetti 《Pure and Applied Geophysics》2007,164(12):2523-2547
Data for major, minor and trace elements in groundwaters from Mt. Etna volcano collected in 1994, 1995 and 1997 were analyzed
using Cluster Analysis (CA). Two groups of sampling sites were identified (named clusters A and B), mainly on the basis of
their different salinity and content of dissolved CO2. The highest levels of both of these parameters were observed in the sites of cluster A, located in the lower south-western
and central eastern flanks of the volcano. For both of the statistical groups CA was repeated, taking into account the mean
values of each parameter in time, and the results allowed us to recognize four distinct groups of parameters for each group
of sites on the basis of their temporal patterns. Four different types of temporal patterns were recognized: concave, convex,
increasing, decreasing. The observed changes were basically interpreted as a result of the different response of dissolved
chemical elements to changes in the aqueous environment and/or in their solubility/mobility in water due to different rates
of input of magmatic gases to Etna’s aquifers. The main changes occurred in 1995, when Etna’s volcanic activity resumed after
a two-year period of rest. The temporal changes of the majority of the studied parameters (water temperature, water conductivity,
Eh, pH, Al, Mg, B, Ca, Cl−, Hg, Mn, Mo, Na, Ni, Se, Si, Sr, Cr Zn and pCO2) were not cluster-dependent, therefore they were not apparently affected by differences in water salinity between the two
groups of sampling sites. A limited number of parameters (Ti, K, Li, HCO3−, As, Fe, SO42−, Cu and V), however, manifested different behaviors, depending on the cluster of sites to which they belonged, thus suggesting
their apparent dependency on water salinity. 相似文献
62.
63.
64.
Anita Mohan Bhola N. Dwivedi Enrico Landi 《Journal of Astrophysics and Astronomy》2000,21(3-4):407-411
Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft
SOHO (Solar and Heliospheric Observatory), we investigate the height dependence of electron density, temperature and abundance
anomalies in the solar atmosphere. In particular, we present the behaviour of the solar FIP effect (the abundance enhancement
of elements with first ionization potential < 10 eV in the corona with respect to photospheric values) with height
above an active region observed at the solar limb, with emphasis on the so-called transition region lines. 相似文献
65.
We present some algebraic and numerical simulations of the stable boundary layer. We also discuss the problem of the existence
of a critical Richardson number (Ri), beyond which the turbulence is suppressed. We compare the results of a second-order algebraic model with those of a third-order
numerical model and, to this purpose, numerical simulations of a wind-tunnel flow, which is characterized by various Richardson
numbers, were performed. As far as the second-order model is concerned, solutions, for the Richardson number greater than
any critical value, can be obtained by modifying the time scales of the second-order equation pressure correlation terms in
order to account for a buoyancy damping factor. We show that using a third-order model allows the same results (no critical
Richardson number) to be obtained without modifications to the time scales. It is suggested that the non-locality, accounted
for by the third-order moments, could allow the turbulence to persist also for Ri > 1. 相似文献
66.
Global and regional ocean carbon uptake and climate change: sensitivity to a substantial mitigation scenario 总被引:1,自引:0,他引:1
Marcello Vichi Elisa Manzini Pier Giuseppe Fogli Andrea Alessandri Lavinia Patara Enrico Scoccimarro Simona Masina Antonio Navarra 《Climate Dynamics》2011,37(9-10):1929-1947
Under future scenarios of business-as-usual emissions, the ocean storage of anthropogenic carbon is anticipated to decrease because of ocean chemistry constraints and positive feedbacks in the carbon-climate dynamics, whereas it is still unknown how the oceanic carbon cycle will respond to more substantial mitigation scenarios. To evaluate the natural system response to prescribed atmospheric ??target?? concentrations and assess the response of the ocean carbon pool to these values, 2 centennial projection simulations have been performed with an Earth System Model that includes a fully coupled carbon cycle, forced in one case with a mitigation scenario and the other with the SRES A1B scenario. End of century ocean uptake with the mitigation scenario is projected to return to the same magnitude of carbon fluxes as simulated in 1960 in the Pacific Ocean and to lower values in the Atlantic. With A1B, the major ocean basins are instead projected to decrease the capacity for carbon uptake globally as found with simpler carbon cycle models, while at the regional level the response is contrasting. The model indicates that the equatorial Pacific may increase the carbon uptake rates in both scenarios, owing to enhancement of the biological carbon pump evidenced by an increase in Net Community Production (NCP) following changes in the subsurface equatorial circulation and enhanced iron availability from extratropical regions. NCP is a proxy of the bulk organic carbon made available to the higher trophic levels and potentially exportable from the surface layers. The model results indicate that, besides the localized increase in the equatorial Pacific, the NCP of lower trophic levels in the northern Pacific and Atlantic oceans is projected to be halved with respect to the current climate under a substantial mitigation scenario at the end of the twenty-first century. It is thus suggested that changes due to cumulative carbon emissions up to present and the projected concentration pathways of aerosol in the next decades control the evolution of surface ocean biogeochemistry in the second half of this century more than the specific pathways of atmospheric CO2 concentrations. 相似文献
67.
Domenico Pileggi David Rossi Enrico Lunedei Dario Albarello 《Bulletin of Earthquake Engineering》2011,9(6):1839-1854
The problem of seismic characterization of rock-mass or stiff-soil outcrops by the use of passive seismic prospecting techniques
is discussed. Difficulties in the application of this kind of procedure in the presence of rugged morphology, high surface
wave velocities and low ambient vibration powers, typical of stiff-soil/rock-mass sites are examined. A methodology to face
these problems is here proposed, which is based on the strict synergy of detailed geologic surveys and application of robust
seismic prospecting techniques, jointly considering single-station and multi-station tools. The application of this approach
for the characterization of a number of sites belonging to the Italian Accelerometric Network is described, focusing on two
representative case histories. 相似文献
68.
Enrico Foti Ivan Cáceres Rabionet Alberto Marini Rosaria E. Musumeci Agustín Sánchez-Arcilla 《Coastal Engineering》2011
Optical systems can provide very accurate measurements of bottom morphology in wave flumes. However, it is often necessary, e.g. when laser scanners are used, to stop the experiments and disturbing significantly the sandy bed itself, by emptying the flume. In the present work measurement strategies based on computer vision techniques which permit measurements also in the presence of water are applied in wave flumes at small and at large scale. Such techniques, based on the use of structured light, are demonstrated to be able to perform measurements of 2D and 3D bed evolution also in a very active area, such as the swash zone, where the alternating presence and absence of water makes it difficult to recover the bed morphology in a dynamic way. 相似文献
69.
Daniele Spiga Gianpiero Tagliaferri Paolo Soffitta Oberto Citterio Stefano Basso Ronaldo Bellazzini Alessandro Brez Wolfgang Burkert Vadim Burwitz Enrico Costa Luca de Ruvo Ettore Del Monte Sergio Fabiani Gisela Hartner Benedikt Menz Massimo Minuti Fabio Muleri Giovanni Pareschi Michele Pinchera Alda Rubini Carmelo Sgrò Gloria Spandre 《Experimental Astronomy》2014,37(1):37-53
The Joint European X-ray Telescope (JET-X) was the core instrument of the Russian Spectrum-X- γ space observatory. It consisted of two identical soft X-ray (0.3–10 keV) telescopes with focusing optical modules having a measured angular resolution of nearly 15 arcsec. Soon after the payload completion, the mission was cancelled and the two optical flight modules (FM) were brought to the Brera Astronomical Observatory where they had been manufactured. After 16 years of storage, we have utilized the JET-X FM2 to test at the PANTER X-ray facility a prototype of a novel X-ray polarimetric telescope, using a Gas Pixel Detector (GPD) with polarimetric capabilities in the focal plane of the FM2. The GPD was developed by a collaboration between INFN-Pisa and INAF-IAPS. In the first phase of the test campaign, we have re-tested the FM2 at PANTER to have an up-to-date characterization in terms of angular resolution and effective area, while in the second part of the test the GPD has been placed in the focal plane of the FM2. In this paper we report the results of the tests of the sole FM2, using an unpolarized X-ray source, comparing the results with the calibration done in 1996. 相似文献
70.