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151.
Time domain simulations of nonlinear motions of two-dimensional floating bodies in waves are presented. The so called `body exact' approach is adopted in a numerical wave tank. A new scheme for pressure evaluation on the wetted hull is developed and systematically used with good results in terms of accuracy and stability. Strongly flared geometries are successfully handled even at very large amplitude motions. The validation of the code is carried out according to the 20th ITTC Seakeeping Committee recommendations through internal checks of consistency and through comparisons with available experimental data. 相似文献
152.
Eleazar Padrón Pedro A. Hernández Theofilos Toulkeridis Nemesio M. Pérez Rayco Marrero Gladys Melián Giorgio Virgili Kenji Notsu 《Journal of Volcanology and Geothermal Research》2008
We report herein the first results of two soil CO2 efflux surveys carried out at Cuicocha lake-filled and Pululahua caldera volcanic systems, Ecuador. A total of 172 and 217 soil CO2 efflux measurements were taken at the surface environment of Pululahua and Cuicocha calderas respectively, by means of the “accumulation chamber” method during the summer of 2006 to constrain the total CO2 output from the studied area. Soil CO2 efflux values ranged from non-detectable up to 48.5 and 141.7 g m− 2 d− 1 for Cuicocha and Pululahua calderas respectively. In addition, probability graphs were used to distinguish the existence of different geochemical populations. Sequential Gaussian Simulation was used to construct an average map for 100 simulations and to compute the total CO2 emission at each studied area: 106 and 270 t d− 1 (metric tons per day) for Cuicocha (13.3 km2) and Pululahua (27.6 km2) volcanoes respectively. 相似文献
153.
Cristina G. Di Camillo Igor Bartolucci Carlo Cerrano Giorgio Bavestrello 《Marine Ecology》2013,34(1):62-71
A mass mortality episode involving three marine dyctioceratid sponges, Ircina variabilis, Sarcotragus spinosulus and Spongia officinalis, was observed on ‘Scoglio del Trave’ (Conero Promontory, North Adriatic Sea) in late summer 2009. In this area, calm sea and high temperatures throughout summer created unfavorable environmental conditions, leading to the outbreak of the disease. Affected specimens showed evident necrotic areas and portions with bare skeleton, and many specimens of S. spinosulus were covered with a white mat of cyanobacteria. In September 2009, about 22% of these demosponges suffered from this disease. The mortality event ceased when sea temperature dropped below 20 °C. Small specimens turned out to be more sensitive to the diseases, whereas the damaged tissues of large specimens were able to recover. In October, the damaged specimens were detached by the rough sea and more than 900 beached sponges were found along the 1‐km‐long beach, showing the seriousness of the phenomenon, which probably involved not only the area studied but also areas adjacent to it. 相似文献
154.
Giorgio?RivalentiEmail author Alberto?Zanetti Maurizio?Mazzucchelli Riccardo?Vannucci Carlos?A.?Cingolani 《Contributions to Mineralogy and Petrology》2004,147(6):647-670
Amphibole ± phlogopite ± apatite-bearing mantle xenoliths at Gobernador Gregores display modal, bulk-rock and phase geochemical characteristics held as indicators of carbonatitic metasomatism. However, part of these xenoliths has high TiO2/Al2O3 and those displaying the most pronounced carbonatitic geochemical markers modally trend towards harzburgite. Bulk-rock, clinopyroxene and amphibole show Zr, Hf and Ti negative anomalies, which increase at decreasing Na2O and high field strength elements (HFSE) concentrations. Steady variation trends between xenoliths which have and do not have carbonatitic characteristics suggest a control by reactive porous flow of only one agent, inferred to be initially a ne-normative hydrous basalt (because of the presence of wehrlites) evolving towards silica saturation. Variation trends exhibit cusps when amphibole appears in the mode. Appearance of amphibole may explain the Ti anomaly variations, but not those of Zr and Hf. Numerical modelling [Plate Model (Vernières et al. in J Geophys Res 102:24771–24784, 1997)] gives results consistent with the observed geochemical features by assuming the presence of loveringite. Modest HFSE anomalies in the infiltrating melt may be acquired during percolation in the garnet-facies.In memory of Carlo Rivalenti 相似文献
155.
Giorgio Graziani Sergio Lucchesi Eugenio Scandale 《Physics and Chemistry of Minerals》1990,17(5):379-384
Growth marks of pegmatite beryls can be divided into general and specific in relation to their types and distributions. Dislocation absence and growth bands have been recognized as general growth marks of the environment while minor element concentrations and optical anomalies as specific to the local growth medium. 相似文献
156.
Luisa?Frati Giorgio?Brunialti Stefano?LoppiEmail author 《Journal of Atmospheric Chemistry》2005,52(3):221-230
The results of a transplant experiment with the fruticose lichen Evernia prunastri aimed at monitoring the trends of trace elements deposition in a repeated biomonitoring study are reported. Data comparability
between the two surveys and interpretation of the results were addressed in this study. The ratio between the concentration
of each element after the exposure and in control samples prior to exposure (exposed-to-control ratio, EC ratio), as well
as an appropriate interpretative scale, were adopted as a means of determining the temporal trends of element accumulation
by lichen transplants. The results showed that the method adopted is indeed a reliable tool, pinpointing a Zn smelting plant
and an oil refinery as principal pollution sources in the area, which indicate that elements associated with the former were
similarly accumulated in both 2002 and 2003, while elements associated with the latter tended to decrease in 2003. 相似文献
157.
Stefano Bianchi Giorgio Matt Fabrizio Nicastro Delphine Porquet Jacques Dubau 《Monthly notices of the Royal Astronomical Society》2005,357(2):599-607
We have calculated the equivalent widths of the absorption lines produced by Fe xxv and Fe xxvi in a Compton-thin, low-velocity photoionized material illuminated by the nuclear continuum in active galactic nuclei. The results, plotted against the ionization parameter and the column density of the gas, are a complement to those presented by Bianchi & Matt for the emission lines from the same ionic species. As an extension to the work by Bianchi & Matt, we also present a qualitative discussion on the different contributions to the He-like iron emission line complex in the regimes where recombination or resonant scattering dominates, providing a useful diagnostic tool to measure the column density of the gas. Future high-resolution missions (e.g. Astro-E2 ) will allow us to fully take advantage of these plasma diagnostics. In the meantime, we compare our results with an up-to-date list of Compton-thick and unobscured (at least at the iron line energy) Seyfert galaxies with emission and/or absorption lines from H- and He-like iron observed with Chandra and XMM–Newton . 相似文献
158.
Projection, or conjugate gradient like, methods are becoming increasingly popular for the efficient solution of large sparse sets of unsymmetric indefinite equations arising from the numerical integration of (initial) boundary value problems. One such problem is soil consolidation coupling a flow and a structural model, typically solved by finite elements (FE) in space and a marching scheme in time (e.g. the Crank–Nicolson scheme). The attraction of a projection method stems from a number of factors, including the ease of implementation, the requirement of limited core memory and the low computational cost if a cheap and effective matrix preconditioner is available. In the present paper, biconjugate gradient stabilized (Bi‐ CGSTAB) is used to solve FE consolidation equations in 2‐D and 3‐D settings with variable time integration steps. Three different nodal orderings are selected along with the preconditioner ILUT based on incomplete triangular factorization and variable fill‐in. The overall cost of the solver is made up of the preconditioning cost plus the cost to converge which is in turn related to the number of iterations and the elementary operations required by each iteration. The results show that nodal ordering affects the perfor mance of Bi‐CGSTAB. For normally conditioned consolidation problems Bi‐CGSTAB with the best ILUT preconditioner may converge in a number of iterations up to two order of magnitude smaller than the size of the FE model and proves an accurate, cost‐effective and robust alternative to direct methods. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
159.
160.
Massimiliano Favalli Fabrizio Innocenti Maria Teresa Pareschi Giorgio Pasquarè Stefano Branca 《Geodinamica Acta》2013,26(5):279-290
AbstractA Digital Elevation Model (DEM) of Mt. Etna is presented; it has altimetric and planimetric resolution of 1 m and 5 m, respectively, and covers an area of about 120 km . This 3-D view of Mt. Etna allowed both recognition and location of the main morphostructural and volcano-tectonic features of the volcano. A slope map has been generated from the DEM; on the basis of slope distributions and surface textures, five acclivity domains have been recognized. The largest domain, south of the summit craters, reflects the occurrence of old plateau lavas, distinct from central volcanoes which built the present Etnean volcanic system. Interaction between the central volcanoes, with their summit calderas and failed slopes, produced the other recognised domains. Furthermore, newly identified relevant morphostructural lines are discussed. © Elsevier, Paris 相似文献