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31.
32.
The carbon dioxide solubility in alkali basalts: an experimental study   总被引:1,自引:1,他引:0  
Experiments were conducted to determine CO2 solubilities in alkali basalts from Vesuvius, Etna and Stromboli volcanoes. The basaltic melts were equilibrated with nearly pure CO2 at 1,200°C under oxidizing conditions and at pressures ranging from 269 to 2,060 bars. CO2 solubility was determined by FTIR measurements. The results show that alkalis have a strong effect on the CO2 solubility and confirm and refine the relationship between the compositional parameter Π devised by Dixon (Am Mineral 82:368–378, 1997) and the CO2 solubility. A general thermodynamic model for CO2 solubility in basaltic melts is defined for pressures up to 2 kbars. Based on the assumption that O2− and CO32− mix ideally, we have:
_boxclose_3^2 - ^m (P,T)X_^2 - ^m f__2 (P,T) K(P,T) = X__3^2 - ^m (P,T) ( X_^2 - ^m f__2 (P,T) ). \begin{gathered} K(P,T) = {\frac{{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)}}{{X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)}}} \hfill \\ K(P,T) = {{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)} \mathord{\left/ {\vphantom {{X_{{{\text{CO}}_{3}^{2 - } }}^{m} (P,T)} {\left( {X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)} \right).}}} \right. \kern-\nulldelimiterspace} {\left( {X_{{{\text{O}}^{2 - } }}^{m} \times f_{{{\text{CO}}_{2} }} (P,T)} \right).}} \hfill \\ \end{gathered}  相似文献   
33.
Acta Geotechnica - Bentonite pellet mixtures are candidate material for the sealing of galleries in radioactive waste disposals. The hydromechanical behaviour of assemblies of bentonite pellets is...  相似文献   
34.
SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450?C900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5?C10?AU) from nearby stars (<25 pc) with masses ranging from a few Jupiter masses to Super Earths (??2 Earth radii, ??10 M??) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.  相似文献   
35.
Determination of spherical harmonic coefficients of the Earth’s gravity field is often an ill-posed problem and leads to solving an ill-conditioned system of equations. Inversion of such a system is critical, as small errors of data will yield large variations in the result. Regularization is a method to solve such an unstable system of equations. In this study, direct methods of Tikhonov, truncated and damped singular value decomposition and iterative methods of ν, algebraic reconstruction technique, range restricted generalized minimum residual and conjugate gradient are used to solve the normal equations constructed based on range rate data of the gravity field and climate experiment (GRACE) for specific periods. Numerical studies show that the Tikhonov regularization and damped singular value decomposition methods for which the regularization parameter is estimated using quasioptimal criterion deliver the smoothest solutions. Each regularized solution is compared to the global land data assimilation system (GLDAS) hydrological model. The Tikhonov regularization with L-curve delivers a solution with high correlation with this model and a relatively small standard deviation over oceans. Among iterative methods, conjugate gradient is the most suited one for the same reasons and it has the shortest computation time.  相似文献   
36.
Résumé

En douze paragraphes, qui balaient l’âge de la Terre depuis ses origines jusqu’à Homo sapiens, nous tenterons de montrer la richesse conceptuelle qu’engendre l’étude de la biosphère actuelle et des biosphères passées. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献   
37.
Tropical instability waves (TIWs) are not easily simulated by ocean circulation models primarily because such waves are very sensitive to wind forcing. In this study, we investigate the impact of assimilating sea surface height (SSH) observations on the control of TIWs in an observing system simulation experiment (OSSE) context based on a regional model configuration of the tropical Atlantic. A Kalman filtering method with suitable adaptations is found to be successful when altimetric data are assimilated in conjunction with sea surface temperature and some in situ temperature/salinity profiles. In this rather realistic system, the TIW phase is roughly controlled with a single nadir observing satellite. However, a right correction of the TIW structure and amplitude requires at least two nadir observing satellites or a wide swath observing satellite. The significant impact of orbital parameters is also demonstrated: in particular, the Jason or GFO satellite orbits are found to be more suitable than the ENVISAT orbit. More generally, it is found that as soon as adequate sub-sampling exists (with periods of 5–10?days), the length of the repetitivity cycle of orbits does not have a significant impact.  相似文献   
38.
It has recently been postulated that lithogenic particles such as Saharan dust strongly influence particulate organic carbon export to the deep ocean by acting as mineral ballast. However, our understanding of the processes involved remains scant. In the present study, optical measurements were performed to monitor variations in the concentration, composition and size distribution of particles in suspension within the water column after simulating a Saharan dust event in very clear Mediterranean waters off Corsica in June 2010. A new methodology set up in large mesocosms proved very successful in this regard. Values obtained simultaneously from three instruments (WetLabs ECO-BB3, WetLabs ac-9, Sequoia Scientific LISST-100) provided evidence that (1) part of the Saharan dust pool has a rapid settling velocity (∼24–86 m day−1), (2) particulate export following a dust event is a nonlinear multi-step process and (3) export is controlled in part by the formation of organic-mineral aggregates. This experimental study provides the first insight of the complex export processes occurring after a dust event involving both physical and biogeochemical forcings in clear oligotrophic waters.  相似文献   
39.
40.
A small-scale pile has been developed in the laboratory to investigate the thermo-mechanical behavior of energy piles subjected to a significant number of thermal cycles. The pile (20 mm external diameter), installed in dry sand, was initially loaded at its head to 0, 20, 40 and 60% of its ultimate bearing capacity (500 N). At the end of each loading step, 30 heating/cooling cycles were applied. The long-term behavior of the pile was observed in terms of head settlement, axial force profile, soil and pile temperature, and stress in soil. The results evidence the irreversible settlement of the pile head induced by thermal cycles under constant load head. In addition, the incremental irreversible settlement that accumulates after each thermal cycle decreases when the number of cycles increases. The evolution of irreversible pile head settlement versus number of cycles can be reasonably predicted by an asymptotic equation.  相似文献   
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