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451.
This work reports on the application and experimental validation, for idealized geometries, of a multiple-fluid Navier–Stokes model of waves generated by rigid and deforming slides, with the purpose of improving predictive simulations of landslide tsunamis. In such simulations, the computational domain is divided into water, air, and slide regions, all treated as Newtonian fluids. For rigid slides, a penalty method allows for parts of the fluid domain to behave as a solid. With the latter method, the coupling between a rigid slide and water is implicitly computed (rather than specifying a known slide kinematics). Two different Volume of Fluid algorithms are tested for tracking interfaces between actual fluid regions. The simulated kinematics of a semi-elliptical block, moving down a water covered plane slope, is first compared to an earlier analytical solution. Results for the vertical fall of a rectangular block in water are then compared to earlier experimental results. Finally, more realistic simulations of two- and three-dimensional wedges sliding down an incline are compared to earlier experiments. Overall, in all cases, solid block velocities and free surface deformations are accurately reproduced in the model, provided that a sufficiently resolved discretization is used. The potential of the model is then illustrated on more complex scenarios involving waves caused by multi-block or deformable slides. 相似文献
452.
The present study explored ontogenetic shifts in habitat associations by coral reef fishes between recently settled juvenile and adult life stages (Moorea Island: Tiahura and Papetoai sites). Visual censuses highlighted four ontogenetic patterns in habitat associations: (1) no change in habitat associations between the juvenile and adult stages; (2) a decrease in the number of habitats used by adults compared to juveniles; (3) an increase in the number of habitats used during the adult stage; and (4) use of nursery areas by juveniles followed by an extensive movement to an entirely different adult habitat. The comparative analysis of spatial distribution of fish at Tiahura and Papetoai highlighted no-spatial variability in ontogenetic patterns (i.e., 10 of the 15 recorded species have spatial consistency in ontogenetic patterns). Overall, the shifts in habitat associations are of interest in the perspective of understanding flexibility and adaptation capability of coral reef fish, at least at the settlement time. 相似文献
453.
C. Denis K.R. Rybicki A.A. Schreider S. Tomecka‐Sucho P. Varga 《Astronomische Nachrichten》2011,332(1):24-35
In this paper, we study quantitatively the effect of the Earth's core formation on the secular rate of change of the length of day (LOD). We find that for the present epoch, a growth rate of the core comprised between 1 and 10 mm/cy seems to be a plausible guess, leading to a relative de crease of LOD comprised roughly between 10 and 100 μs/cy. Such values do not affect significantly the observed secular in crease of LOD caused by tidal braking, which amounts to about 1.79 ms/cy. However, in the remote geological past, before the Phanerozoic, the effects of core growth may have been much more important, because the total change of LOD associated with core formation has been estimated by Birch in 1965 to be 2.4 hours for an initially undifferentiated cold Earth, and 3.1 hours for an initially undifferentiated hot Earth. We consider a number of scenarios, some of them corresponding to very early and/or very fast core formation, others corresponding to slow and/or late core formation. We show that palaeo‐LOD measurements seem to favour slow core formation during the Proterozoic, contrarily to the now largely prevailing hypothesis based on geochemical arguments that the iron core formed very early in the Earth's history and during a geologically short time interval (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
454.
Rick Verberne Hugo W. van Schrojenstein Lantman Steven M. Reddy Matteo Alvaro David Wallis Denis Fougerouse Antonio Langone David W. Saxey William D. A. Rickard 《Journal of Metamorphic Geology》2023,41(1):3-24
The trace-element composition of rutile is commonly used to constrain P–T–t conditions for a wide range of metamorphic systems. However, recent studies have demonstrated the redistribution of trace elements in rutile via high-diffusivity pathways and dislocation-impurity associations related to the formation and evolution of microstructures. Here, we investigate trace-element migration in low-angle boundaries formed by dislocation creep in rutile within an omphacite vein of the Lago di Cignana unit (Western Alps, Italy). Zr-in-rutile thermometry and inclusions of quartz in rutile and of coesite in omphacite constrain the conditions of rutile deformation to around the prograde boundary from high pressure to ultra-high pressure (~2.7 GPa) at temperatures of 500–565°C. Crystal-plastic deformation of a large rutile grain results in low-angle boundaries that generate a total misorientation of ~25°. Dislocations constituting one of these low-angle boundaries are enriched in common and uncommon trace elements, including Fe and Ca, providing evidence for the diffusion and trapping of trace elements along the dislocation cores. The role of dislocation microstructures as fast-diffusion pathways must be evaluated when applying high-resolution analytical procedures as compositional disturbances might lead to erroneous interpretations for Ca and Fe. In contrast, our results indicate a trapping mechanism for Zr. 相似文献