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101.
Wave-induced steady streaming,mass transport and net sediment transport in rough turbulent ocean bottom boundary layers 总被引:1,自引:0,他引:1
The interaction between two important mechanisms which causes streaming has been investigated by numerical simulations of the seabed boundary layer beneath both sinusoidal waves and Stokes second order waves, as well as horizontally uniform bottom boundary layers with asymmetric forcing. These two mechanisms are streaming caused by turbulence asymmetry in successive wave half-cycles (beneath asymmetric forcing), and streaming caused by the presence of a vertical wave velocity within the seabed boundary layer as earlier explained by Longuet-Higgins. The effect of wave asymmetry, wave length to water depth ratio, and bottom roughness have been investigated for realistic physical situations. The streaming induced sediment dynamics near the ocean bottom has been investigated; both the resulting suspended load and bedload are presented. Finally, the mass transport (wave-averaged Lagrangian velocity) has been studied for a range of wave conditions. The streaming velocities beneath sinusoidal waves (Longuet-Higgins streaming) is always in the direction of wave propagation, while the streaming velocities in horizontally uniform boundary layers with asymmetric forcing are always negative. Thus the effect of asymmetry in second order Stokes waves is either to reduce the streaming velocity in the direction of wave propagation, or, for long waves relative to the water depth, to induce a streaming velocity against the direction of wave propagation. It appears that the Longuet-Higgins streaming decreases as the wave length increases for a given water depth, and the effect of wave asymmetry can dominate, leading to a steady streaming against the wave propagation. Furthermore, the asymmetry of second order Stokes waves reduces the mass transport (wave-averaged Lagrangian velocity) as compared with sinusoidal waves. The boundary layer streaming leads to a wave-averaged transport of suspended sediments and bedload in the direction of wave propagation. 相似文献
102.
Erik Mostert 《Physics and Chemistry of the Earth》2009,34(3):142-149
The management of the Rhine is often seen as an exemplary case of international river basin management. In the Rhine basin, countries that went to war with each other twice in the last century have managed to reach agreements on many issues and water quality has improved considerably. The improvement in water quality is often attributed to the activities of the International Commission for the Protection of the Rhine and in particular to its Rhine Action Plan. In order to test this assertion, this paper describes and analyzes the development of international co-operation on the water quality of the Rhine since 1945. It concludes that water quality improvement cannot be attributed to any single factor. Instead, a whole array of interrelated factors are at play, including the European Union, other international fora such as the North Sea Ministerial Conferences, domestic legislation, the activities of environmental NGOs and waterworks, growing environmental awareness, and the changing structure of the industry in the basin. Because of the importance of contextual factors, the Rhine experiences cannot simply be applied to basins with a different context. In many cases, international river basin management may be promoted most effectively by promoting co-operation at the river basin level. In many other cases, however, it may be more effective to identify and then work on the contextual factors that (1) have the biggest leverage effect in the specific case and (2) can be influenced most effectively. 相似文献
103.
Lui-Heung Chan John C. Lassiter Erik H. Hauri Stanley R. Hart Jerzy Blusztajn 《Earth and Planetary Science Letters》2009,277(3-4):433-442
Radiogenic isotope variations in lavas from the Cook–Austral volcanic chain have delineated three distinct mantle sources: a HIMU component, a depleted component (DM), and an enriched component (EM). To better constrain the mantle sources for South Pacific hot spot volcanism, we determined lithium isotopic compositions of lavas from Raivavae, Rapa, Mangaia and Tubuai of the volcanic chain. The study includes whole rock and mineral analyses. In general, δ7Li of most olivines resemble bulk rock composition whereas clinopyroxenes are variably lighter. This implies that clinopyroxene is more susceptible to diffusion-induced fractionation, in agreement with previous studies. Olivine δ7Li values span a narrower range than whole rock values, and do not extend to the very heavy compositions previously reported in HIMU bulk lavas. This discrepancy likely reflects alteration of bulk lavas, and suggests that Li-isotope analyses of bulk lavas should be interpreted with caution. Olivines from HIMU lavas have heavy δ7Li values (up to 6.2‰), and extend beyond the range reported for fresh MORB. Correlations between Li-isotopes and radiogenic isotopes suggest that the heavy δ7Li values in HIMU olivines are a source characteristic and not the result of post-magmatic alteration. Although the Li-isotope composition of recycled, dehydrated oceanic crust is currently under debate, our results suggest that HIMU lavas derive from a source containing recycled dehydrated oceanic crust, and that the “heavy” Li-isotope signature of altered oceanic crust is partially preserved during passage through the subduction factory. 相似文献
104.
Erik Tihelka 《Geology Today》2020,36(5):188-191
The majority of organisms that ever lived on the Earth, and hence the majority of evolutionary innovations, are now extinct. Only fragments of this past diversity are observable in the form of the fossil record. Biomimicry and biotechnology seek to utilize the astonishing diversity of living organism's solutions to complex biological problems as inspiration for human technology. This feature reviews the potential industrial applications of fossil-inspired technologies, an emerging area of research here referred to as ‘palaeobiotechnology’ or ‘brown biotechnology’. Examples from vertebrate, invertebrate and molecular palaeontology illustrate the diverse potential applications of extinct organisms, including the design of new materials such as bone substitutes, development of pharmaceuticals, robots and anchoring devices for submarines. Palaeobiotechnological approaches are able to both inspire modern sustainable technologies and at the same time illuminate the biology of ancient organisms. 相似文献
105.
Megan Damon Masanori C. Kameyama Michael Knox David H. Porter Dave Yuen Erik O. D. Sevre 《Visual Geosciences》2008,13(1):49-57
The current availability of thousands of processors at many high performance computing centers has made it feasible to carry
out, in near real time, interactive visualization of 3D mantle convection temperature fields, using grid configurations having
10–100 million unknowns. We will describe the technical details involved in carrying out this endeavor, using the facilities
available at the Laboratory of Computational Science and Engineering (LCSE) at the University of Minnesota. These technical
details involve the modification of a parallel mantle convection program, ACuTEMan; the usage of client–server socket based
programs to transfer upwards of a terabyte of time series scientific model data using a local network; a rendering system
containing multiple nodes; a high resolution PowerWall display, and the interactive visualization software, DSCVR. We have
found that working in an interactive visualizastion mode allows for fast and efficient analysis of mantle convection results.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
106.
107.
Clemens Reimann Belinda Flem Arnold Arnoldussen Peter Englmaier Tor Erik Finne Friedrich Koller Øystein Nordgulen 《Applied Geochemistry》2008
Rock, soil, and plant (terrestrial moss, European mountain ash leaves, mountain birch leaves, bark and wood, and spruce needles and wood) samples, collected at 3 km intervals along a 120 km long transect (40 sites) cutting the city of Oslo, Norway, were analysed for their Pb concentration and Pb-isotope ratios. A general decrease in 206Pb/207Pb, 208Pb/207Pb and 206Pb/208Pb ratios, with a characteristic low variability in all plant materials and the plant-derived O-horizon of soil profiles, compared to rocks and mineral soils, is observed along the transect. It is demonstrated that minerogenic and biogenic sample materials belong to two different spheres, the lithosphere and biosphere, and that geochemical processes determining their chemical and isotopic compositions differ widely. Background variation for both sample materials needs to be established and documented at the continental and global scale before the anthropogenic influence on the geochemistry of the earth’s surface can be reliably estimated. 相似文献
108.
Erik Jönsson 《社会与自然资源》2017,30(7):844-859
ABSTRACTIn this article, I scrutinize three art, design, and architecture projects engaging with “cultured,” or “in vitro,” meat (primarily muscle cells cultured outside of bodies) to illuminate the entanglements of academic and extra-academic environments that have characterized cultured meat’s history to date, and the conversations that this technology has spurred. In envisioning new ways of eating, and living, these projects (a book of hypothetical recipes, The In Vitro Meat Cookbook, Catts and Zurr’s bioartistic engagements with tissue engineering, and Terreform1’s tissue-house prototype “The In Vitro Meat Habitat”) illustrate cultural practices thought to be enabled by cell culturing’s new applications. Emphasizing such visions and conversations allows me to highlight an inattention to discursive dynamics within research on natures subsumed to industrial production processes (Boyd, Prudham, and Schurman 2001). But engaging with the “subsumption of nature” framework simultaneously allows me to problematize artistic visions presenting nature as fully malleable. 相似文献
109.
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