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961.
We derive a new formulation for the compositional compressible two-phase flow in porous media. We consider a liquid–gas system with two components: water and hydrogen. The formulation considers gravity, capillary effects, and diffusivity of each component. The main feature of this formulation is the introduction of the global pressure variable that partially decouples the system equations. To formulate the final system, and in order to avoid primary unknowns changing between one-phase and two-phase zones, a second persistent variable is introduced: the total hydrogen mass density. The derived system is written in terms of the global pressure and the total hydrogen mass density. The system is capable of modeling the flows in both one and two-phase zones with no changes of the primary unknowns. The mathematical structure is well defined: the system consists of two nonlinear parabolic equations, the global pressure equation, and the total hydrogen mass density equation. The derived formulation is fully equivalent to the original one. Numerical simulations show ability of this new formulation to model efficiently the phase appearance and disappearance. 相似文献
962.
Andreas Richter Marta Marcos Sebastià Monserrat Damià Gomis Simon Ruiz Gunter Liebsch 《Marine Geodesy》2013,36(4):271-289
Two sea-level records, spanning eight months of simultaneous data in 2002, have been derived from pressure tide gauge measurements at Sant Antoni harbor (Eivissa Island, Western Mediterranean) and off Es Vedrà island, 15 km SW from Sant Antoni. The two time series are compared and used to characterize the sea-level variability in the Balearic Sea. The main forcings for the observed variations, astronomic tides, and meteorologic forcing by the inverse barometer effect are quantified. In a further step, an amplitude transfer function is determined, reflecting the frequency dependent amplification or damping of the nontidal sea-level residuals between both locations due to their local topography. The interpretation of the obtained transfer function indicates sea-level modulating topographic specifics not only for the coastal record at Sant Antoni, but also at the Es Vedrà site. In general, the application of such a transfer function allows the prediction of off-shore sea-level variations from coastal tide gauge measurements. In the present study, ellipsoidal sea-surface heights for Es Vedrà are inferred from Sant Antoni tide gauge data with an accuracy of about 1.5 cm by applying the determined transfer function and a geoid model. 相似文献
963.
Jos I Saiz Nuria Anadn Javier Cristobo Oscar Garca-Alvarez Gerardo Garca-Castrillo Eduardo Lpez Cruz Palacn Jess S Troncoso Ana Ramos 《海洋学报(英文版)》2013,32(6):47-55
Insular marine biotas are often richer in faunal diversity than those from the open sea in the same geographical region. The existence of particular island effects were tested under polar conditions by comparing infaunal benthic assemblages on Peter I Island with those of similar latitudes in the open ocean at the Bellingshausen Sea and also from the coast of the Antarctic Peninsula. Sampling was carried out aboard the R/V Hespérides during the expedition named BENTART-2003 from 24 January to 3 March 2003. Benthic samples were collected at 18 stations ranging from 90 to 2 044 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 32 higher taxa of invertebrates were found. Univariate and multivariate analyses revealed various patterns in the data. First, significant differences in polychaete abundance were detected between the stations located in the open sea and the remaining sites (island plus mainland sites). Bivalve abundances were also distinct between island and mainland sampling sites. Sediment columns taken from the island seafloor exhibited the highest rate of bioturbation by the infauna. These findings confirm the model that islands develop distinct assemblages characterized by the enhancement of the benthic communities even in cold waters. Several abiotic factors were measured simultaneously at the seafloor and along the water column to investigate faunal distribution patterns. Significant correlations were found between the benthic assemblages and a combination of two environmental variables: "island effect" (measured as a categorical variable) and the redox state of sediments. Richer and more complex benthic assemblages were found in Peter I Island’s sea bottom, whereas the more depauperate bottoms remained in the open sea. 相似文献
964.
Gustavo M. Martins Rita F. Patarra Nuno V. Álvaro Afonso C. L. Prestes Ana I. Neto 《Marine Ecology》2013,34(3):289-297
A better understanding of biological systems can only be gained if we understand what processes are important and how they operate to determine the distribution of organisms. Coastal orientation and depth can influence environmental conditions, including the degree of water motion and availability of light, which in turn may influence the horizontal and vertical patterns of organism distribution. Here, we used a mixed‐model design to examine the effects of coastal orientation and depth on the structure of benthic assemblages by comparing the abundance and distribution of macroalgae and invertebrates in shallow and deep waters on the opposing coasts of São Miguel. Generally, coastal orientation had little influence on the distribution of most taxa. In contrast, significant differences were generally associated with depth, although patterns were spatially variable at the scale of locations. This study suggests that depth, and processes operating at the scale of location, but not at the scale of the coast, have an important influence on these assemblages, and that failure to recognise such a scale of variability may hamper our ability to better understand the processes that structure these communities. 相似文献
965.
Boris Shustov Mikhail Sachkov Ana I. Gómez?de?Castro Klaus Werner Norbert Kappelmann Alexander Moisheev 《Astrophysics and Space Science》2011,335(1):273-282
Continuous access to the UV domain has been considered of importance to astrophysicists and planetary scientists since the
mid-sixties. However, the future of UV missions for the post-HST era is believed by a significant part of astronomical community
to be less encouraging. We argue that key science problems of the coming years will require further development of UV observational
technologies. Among these hot astrophysical issues are: the search for missing baryons, revealing the nature of astronomical
engines, properties of atmospheres of exoplanets as well as of the planets of the Solar System etc. We give a brief review
of UV-missions both in the past and in the future. We conclude that UV astronomy has a great future but the epoch of very
large and efficient space UV facilities seems to be a prospect for the next decades. As to the current state of the UV instrumentation
we think that this decade will be dominated by the HST and coming World Space Observatory-Ultraviolet (WSO-UV) with a 1.7 m
UV-telescope onboard. The international WSO-UV mission is briefly described. It will allow high resolution/high sensitivity
imaging and high/low resolution spectroscopy from the middle of the decade. 相似文献
966.
Javier Ruiz Patrick J. McGovern Valle López Jean-Pierre Williams Rosa Tejero 《Icarus》2011,215(2):508-517
Lithospheric strength can be used to estimate the heat flow at the time when a given region was deformed, allowing us to constrain the thermal evolution of a planetary body. In this sense, the high (>300 km) effective elastic thickness of the lithosphere deduced from the very limited deflection caused by the north polar cap of Mars indicates a low surface heat flow for this region at the present time, a finding difficult to reconcile with thermal history models. This has started a debate on the current heat flow of Mars and the implications for the thermal evolution of the planet. Here we perform refined estimates of paleo-heat flow for 22 martian regions of different periods and geological context, derived from the effective elastic thickness of the lithosphere or from faulting depth beneath large thrust faults, by considering regional radioactive element abundances and realistic thermal conductivities for the crust and mantle lithosphere. For the calculations based on the effective elastic thickness of the lithosphere we also consider the respective contributions of crust and mantle lithosphere to the total lithospheric strength. The obtained surface heat flows are in general lower than the equivalent radioactive heat production of Mars at the corresponding times, suggesting a limited contribution from secular cooling to the heat flow during the majority of the history of Mars. This is contrary to the predictions from the majority of thermal history models, but is consistent with evidence suggesting a currently fluid core, limited secular contraction for Mars, and recent extensive volcanism. Moreover, the interior of Mars could even have been heating up during part of the thermal history of the planet. 相似文献
967.