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331.
Maria Izquierdo Nikolaos Koukouzas Sofia Touliou Kyriakos D. Panopoulos Xavier Querol Grigorios Itskos 《Applied Geochemistry》2011,26(9-10):1599-1606
The mobility of inorganic pollutants is of key concern for a range of industrial and engineering applications of fly ash produced during the combustion of lignite in power generation. This paper investigates the role that the geochemical features of lignite, the ash composition and the partitioning of elements during combustion play in determining leaching properties of lignite fired by-products. The work is based on surveys on three lignite-fired power plants in Greece. Calcium-rich ashes show a high abatement potential for SO2 and other gaseous pollutants. For most elements, the concentrations in the parent lignite and the ashes follow the same trend. Relative enrichments in Cd, Co, Cr, Cu, Mo, Ni, Pb, U, V, W, Zn fingerprint the regional and local geological settings of the lignite basins. The total and leachable concentrations of highly volatile elements are strongly influenced by the interaction with ubiquitous free lime. A broad array of elements is highly insoluble in alkaline ash, while a few oxyanionic-forming elements display substantial mobility. Their mode of occurrence in the parent lignite plays a primary role in the leaching of combustion ashes. The outcomes of this study may assist in addressing the impact of co-firing high ash or high Ca alternative fuels on the leaching properties of combustion by-products. 相似文献
332.
Enric Vicens M. Eugenia Arribas Xavier Clop M. Rita Estrada Eudald Maestro Oriol Oms David Serrat Miquel Molist 《Geoarchaeology》2010,25(2):195-219
The Puigseslloses megalith tomb (Barcelona, Spain) is located on the summit of a hill in the Vic Plain where the sedimentary rocks that were used in its construction do not crop out. A sedimentological and petrological characterization of the monument's slabs and a multidisciplinary analysis of the outcropping materials in nearby areas has allowed the identification of three possible source areas associated with the Paleogene Banyoles Marls Formation and the Folgueroles Sandstone Formation and allows us to propose possible routes by which the slabs were transported from the catchment site to the place where the monument was built. In addition, the lithology and position of different slabs within the megalith denote the intention to separate the chamber from the corridor by using different types of slab. The position of the monument also reveals that tomb location was more of a priority than proximity to the slab sources. © 2010 Wiley Periodicals, Inc. 相似文献
333.
We calculate chemical evolution models for 4 dwarf spheroidal satellites of the Milky Way (Carina, Ursa Minor, Leo I and Leo
II) for which reliable non-parametric star formation histories have been derived. We find that galaxies showing one single
burst of star formation (Ursa Minor and Leo II) require a dark halo slightly larger that the current estimates for their tidal radii for the gas heated by supernovae to be retained until the observed stellar population has formed. Systems showing extended
star formation histories however (Carina and Leo I), are consistent with the idea that their tidally limited dark haloes provide
the necessary gravitational potential wells to retain their gas.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
334.
Jean-Claude Sibuet Shu-Kun Hsu Xavier Le Pichon Jean-Pierre Le Formal Donald Reed Greg Moore Char-Shine Liu 《Tectonophysics》2002,344(1-2)
15 Ma ago, a major plate reorganization occurred in East Asia. Seafloor spreading ceased in the South China Sea, Japan Sea, Taiwan Sea, Sulu Sea, and Shikoku and Parece Vela basins. Simultaneously, shear motions also ceased along the Taiwan–Sinzi zone, the Gagua ridge and the Luzon–Ryukyu transform plate boundary. The complex system of thirteen plates suddenly evolved in a simple three-plate system (EU, PH and PA). Beneath the Manila accretionary prism and in the Huatung basin, we have determined magnetic lineation patterns as well as spreading rates deduced from the identification of magnetic lineations. These two patterns are rotated by 15°. They were formed by seafloor spreading before 15 Ma and belonged to the same ocean named the Taiwan Sea. Half-spreading rate in the Taiwan Sea was 2 cm/year from chron 23 to 20 (51 to 43 Ma) and 1 cm/year from chron 20 (43 Ma) to 5b (15 Ma). Five-plate kinematic reconstructions spanning from 15 Ma to Present show implications concerning the geodynamic evolution of East Asia. Amongst them, the 1000-km-long linear Gagua ridge was a major plate boundary which accommodated the northwestward shear motion of the PH Sea plate; the formation of Taiwan was driven by two simple lithospheric motions: (i) the subduction of the PH Sea plate beneath Eurasia with a relative westward motion of the western end (A) of the Ryukyu subduction zone; (ii) the subduction of Eurasia beneath the Philippine Sea plate with a relative southwestward motion of the northern end (B) of the Manila subduction zone. The Luzon arc only formed south of B. The collision of the Luzon arc with Eurasia occurred between A and B. East of A, the Luzon arc probably accreted against the Ryukyu forearc. 相似文献
335.
Xavier Fettweis Hubert Gallée Filip Lefebre Jean-Pascal van Ypersele 《Climate Dynamics》2006,27(5):531-541
Measurements from ETH-Camp and JAR1 AWS (West Greenland) as well as coupled atmosphere-snow regional climate simulations have highlighted flaws in the cross-polarized gradient ratio (XPGR) technique used to identify melt from passive microwave satellite data. It was found that dense clouds (causing notably rainfall) on the ice sheet severely perturb the XPGR melt signal. Therefore, the original XPGR melt detection algorithm has been adapted to better incorporate atmospheric variability over the ice sheet and an updated melt trend for the 1988–2003 period has been calculated. Compared to the original algorithm, the melt zone area increase is eight times higher (from 0.2 to 1.7% year−1). The increase is higher with the improved XPGR technique because rainfall also increased during this period. It is correlated to higher atmospheric temperatures. Finally, the model shows that the total ice sheet runoff is directly proportional to the melt extent surface detected by satellites. These results are important for the understanding of the effect of Greenland melting on the stability of the thermohaline circulation. 相似文献
336.
Frdric O. Vandermeirsch Xavier J. Carton Yves G. Morel 《Dynamics of Atmospheres and Oceans》2003,36(4):271-296
In a two-and-a-half-layer quasi-geostrophic model, a process study is conducted on the interaction between a vortex and a zonal jet, both with constant potential vorticity. The vortex is a stable anticyclone, initially located north of the eastward jet. The potential vorticity of the jet is allowed to have various vertical structures, while the vortex is concentrated in only one layer. The flow parameters are set to values characteristic of the Azores region.First, the jet is stable. Weak vortices steadily drift north of the jet without crossing it while strong vortices can cross the jet and tear off a cyclone with which they pair as a heton (baroclinic dipole). This heton often breaks later in the shear exerted by the jet; the two vortices finally drift apart. When crossed by deep anticyclones, the jet develops meanders with 375 km wavelength. These results exhibit a noticeable similarity with the one-and-a-half-layer case studied in Part I.Secondly, the jet is allowed to be linearly unstable. In the absence of the vortex, it develops meanders with 175 km wavelength and 25-day e-folding time on the β-plane. For various vertical structures of the jet, baroclinic instability is shown to barely affect jet–vortex interaction if the linear growth rate of unstable waves is smaller than 1/(14 days). Further simulations with a linearly unstable, nonlinearly equilibrated jet evidence its strong temporal variability when crossed by a deep vortex on the β-plane. In particular, long waves can dominate the spectrum for a few months after jet crossing by the vortex. Again in this process, the deep vortex couples with a surface cyclone and both drift southwestward. 相似文献
337.
338.
Jesús Carrera Xavier Sánchez-Vila Inmaculada Benet Agustín Medina Germán Galarza Jordi Guimerà 《Hydrogeology Journal》1998,6(1):178-190
Matrix diffusion has become widely recognized as an important transport mechanism. Unfortunately, accounting for matrix diffusion
complicates solute-transport simulations. This problem has led to simplified formulations, partly motivated by the solution
method. As a result, some confusion has been generated about how to properly pose the problem. One of the objectives of this
work is to find some unity among existing formulations and solution methods. In doing so, some asymptotic properties of matrix
diffusion are derived. Specifically, early-time behavior (short tests) depends only on φ
m
2
R
m
D
m
/ L
m
2, whereas late-time behavior (long tracer tests) depends only on φ
m
R
m
, and not on matrix diffusion coefficient or block size and shape. The latter is always true for mean arrival time. These
properties help in: (a) analyzing the qualitative behavior of matrix diffusion; (b) explaining one paradox of solute transport
through fractured rocks (the apparent dependence of porosity on travel time); (c) discriminating between matrix diffusion
and other problems (such as kinetic sorption or heterogeneity); and (d) describing identifiability problems and ways to overcome
them.
Received, October 1997 · Revised, November 1997 · Accepted, December 1997 相似文献
339.
Spectral phases of surface waves radiated at the seismic source are recovered by means of the Hilbert transform of spectral amplitudes. Through numerical simulations as well as the study of an earthquake with well known focal mechanism, it is shown that the recovered phases satisfy a criterion of coherency, so that they can be used in an inversion process for the retrieval of the seismic moment tensor. 相似文献
340.
In the eigenvalue eigenvector decomposition used in inversion techniques, we can sometimes obtain eigenvalues close to zero. Related to these eigenvalues close to zero, a set of stratified earth models is generated. These are compatible with the theoretical observations according to a given model. The method is applied to ellipticities and phase velocities of Rayleigh waves, and supply proof of the advantage of working with both sets of data together. 相似文献