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We consider numerical identification of the piecewise constant permeability function in a nonlinear parabolic equation, with the augmented Lagrangian method. By studying this problem, we aim at also gaining some insight into the potential ability of the augmented Lagrangian method to handle permeability estimation within the full two-phase porous-media flow setting. The identification is formulated as a constrained minimization problem. The parameter estimation problem is reduced to a coupled nonlinear algebraic system, which can be solved efficiently with the conjugate gradient method. The methodology is developed and numerical experiments with the proposed method are presented. 相似文献
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Feeding habits of harp and hooded seals in drift ice waters along the east coast of Greenland in summer and winter 总被引：2，自引：0，他引：2
Results of analyses of stomach and intestinal contents from hooded ( Cystophora cristata ) and harp ( Phoca groenlandica ) seals captured in the pack ice belt of the Greenland Sea in summer (July-August) in 2000 and winter (February-March) in 2001 revealed that the diet of both species were comprised of relatively few prey taxa. Pelagic amphipods of the genus Parathemisto , the squid Gonatus fabricii , polar cod ( Boreogadus saida ) and capelin ( Mallotus villosus ) constituted 63-99% of the observed diet biomass in both seal species, irrespective of sampling period, but their relative contribution to the diet varied both with species and sampling period/area. For hooded seals, G. fabricii and capelin were the dominant food items in winter 2001, but the summer 2000 diet comprised a mixture of this squid and polar cod. Parathemisto was most important for the harp seals during summer 2000; in winter 2001 the contribution from krill and capelin were comparable to that of Parathemisto . Multivariate analyses revealed differences in the intestinal contents of hooded and harp seals in areas where the two species' occurrence spatially overlapped. Different foraging depths of the two species may have contributed to the observed differences in diets. 相似文献
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We present a generic, semi-automated algorithm for generating non-uniform coarse grids for modeling subsurface flow. The method is applicable to arbitrary grids and does not impose smoothness constraints on the coarse grid. One therefore avoids conventional smoothing procedures that are commonly used to ensure that the grids obtained with standard coarsening procedures are not too rough. The coarsening algorithm is very simple and essentially involves only two parameters that specify the level of coarsening. Consequently the algorithm allows the user to specify the simulation grid dynamically to fit available computer resources, and, e.g., use the original geomodel as input for flow simulations. This is of great importance since coarse grid-generation is normally the most time-consuming part of an upscaling phase, and therefore the main obstacle that has prevented simulation workflows with user-defined resolution. We apply the coarsening algorithm to a series of two-phase flow problems on both structured (Cartesian) and unstructured grids. The numerical results demonstrate that one consistently obtains significantly more accurate results using the proposed non-uniform coarsening strategy than with corresponding uniform coarse grids with roughly the same number of cells. 相似文献
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Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples 总被引：2，自引：0，他引：2
Xiande Liu Piet Van Espen Freddy Adams Jan Cafmeyer Willy Maenhaut 《Journal of Atmospheric Chemistry》2000,36(2):135-155
Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 m equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 m EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K2SO4,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine. 相似文献
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Numerical identification of diffusion parameters in a nonlinear convection–diffusion equation is studied. This partial differential
equation arises as the saturation equation in the fractional flow formulation of the two-phase porous media flow equations.
The forward problem is discretized with the finite difference method, and the identification problem is formulated as a constrained
minimization problem. We utilize the augmented Lagrangian method and transform the minimization problem into a coupled system
of nonlinear algebraic equations, which is solved efficiently with the nonlinear conjugate gradient method. Numerical experiments
are presented and discussed.
This work was partially supported by the Research Council of Norway (NFR), under grant 128224/431. 相似文献
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Darija Vukić Lušić Dražen Lušić Denis Pešut Vladimir Mićović Marin Glad Lovorka Bilajac Vesna Peršić 《Marine pollution bulletin》2013
The quality of bathing water is of considerable public importance due to the possibility of fecal contamination. In 2009, Croatia implemented the new European Bathing Water Directive (BWD, 2006/7/EC) establishing stricter microbiological standards for new parameters with new reference methods. This study aims to evaluate the equivalence of different methods according to the old and revised BWD and to provide the possibility of data comparison. Furthermore, the directive requires the establishment of the bathing water profile (BWP) for pollution risk assessment. The estimation of consistency of pollution risk assessment with obtained microbiological results was also performed. 相似文献
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Three-dimensional (3D) seismic data acquired for hydrocarbon exploration reveal that gas accumulations are common within the
2–3 km thick Plio-Pleistocene stratigraphic column of the south-western Barents Sea continental margin. The 3D seismic data
have relatively low-frequency content (<40 Hz) but, due to dense spatial sampling, long source-receiver offsets, 3D migration
and advanced interpretation techniques, they provide surprisingly detailed images of inferred gas accumulations and the sedimentary
environments in which they occur. The presence of gas is inferred from seismic reflection segments with anomalously high amplitude
and reversed phase, compared with the seafloor reflection, so-called bright spots. Fluid migration is inferred from vertical
zones of acoustic masking and acoustic pipes. The 3D seismic volume allows a spatial analysis of amplitude anomalies inferred to reflect the presence of gas and fluids. At several locations, seismic attribute
maps reveal detailed images of flat spots, inferred to represent gas–water interfaces. The data indicate a focused fluid migration
system, where sub-vertical faults and zones of highly fractured sediments are conduits for the migration of gas-bearing fluids
in Plio-Pleistocene sediments. Gas is interpreted to appear in high-porosity fan-shaped sediment lobes, channel and delta
deposits, glacigenic debris flows and sediment blocks, probably sealed by low-permeability, clayey till and/or (glacio)marine
sediments. Gas and fluid flow are here attributed mainly to rapid Plio-Pleistocene sedimentation that loaded large amounts
of sedimentary material over lower-density, fine-grained Eocene oozes. This probably caused pore-fluid dewatering of the high-fluid
content oozes through a network of polygonal faults. The study area is suggested to have experienced cycles of fluid expulsion
and hydrocarbon migration associated with glacial–interglacial cycles. 相似文献