Heat transfer and the onset of chaos in a spherical,axisymmetric, anelastic model of whole mantle convection     

L. P. Solheim  W. R. Peltier 《地球物理与天体物理流体动力学》2013,107(4):205-255

Abstract

An isochemical uni-phase model of whole mantle convection has been developed in terms of which factors influencing the onset of time dependent chaotic behavior may be assessed. The model is spherical but restricted in generality to the analysis of axisymmetric solutions. In this paper we have employed it to examine the impact of compressibility and sphericity on the nature and onset of time dependence. Particular attention has been given to an examination of the impact that the onset of time dependence has upon the power law relation that connects the heat transfer (represented by the Nusselt number) to the strength of the thermal forcing (represented by the Rayleigh number). In order to obtain these results very extensive numerical simulations were required and the results themselves should be rather useful in the context of models of the thermal history of the planet.  相似文献   

Origin and extent of fresh groundwater, salty paleowaters and recent saltwater intrusions in Red River flood plain aquifers, Vietnam   总被引：1，自引：0，他引：1  

Luu T. Tran  Flemming Larsen  Nhan Q. Pham  Anders V. Christiansen  Nghi Tran  Hung V. Vu  Long V. Tran  Hoan V. Hoang  Klaus Hinsby 《Hydrogeology Journal》2012,20(7):1295-1313

A model has been established on the origin and extent of fresh groundwater, salty paleowaters and saltwater from recent seawater intrusions in the Red River flood plain in Vietnam. This was done with geological observations, geophysical borehole logging and transient electromagnetic methods. Salt paleowater is present up to 50–75?km from the coastline, with occurrence controlled by the Holocene transgression. A density-driven leaching of salty porewater has occurred from high-permeability Holocene sediments into underlying Pleistocene deposits, whereas diffusion has dominated in low-permeability layers. In the Pleistocene aquifer, the highest content of dissolved solids is found below two intrinsic valleys with Holocene marine sediments and along the coastline. Recent intrusion of saltwater from the South China Sea is observed in shallow groundwater 35?km inland, probably a result of transport of salty water inland in rivers or leaching of paleowaters from very young near-coast marine sediments. The observed inverted salinity profile, with high saline water overlying fresher groundwater, has been formed due to the global eustatic sea-level changes during the last 8,000–9,000?years. The proposed model may therefore be applicable to other coastal aquifers, with a proper incorporation of the local geological environments.  相似文献   

Experimental study of strain localization in sensitive clays     

Anders Samstad Gylland  Hans Petter Jostad  Steinar Nordal 《Acta Geotechnica》2014,9(2):227-240

For evaluation of slope stability in materials displaying strain-softening behavior, knowledge concerning the failed state material response is of importance. Here, soft sensitive clay is studied. Such clays behave contractant at failure, which for undrained conditions yields a strain-softening behavior governed by the generation of excess pore water pressure. Strain softening is further linked with material instability and the phenomenon of strain localization. In the case of shear band formation, internal pore pressure gradients are then expected to be present for globally undrained conditions in the sensitive clay due to its low permeability. In the present study, this hypothesis and its implications on the global response and shear band properties are investigated. Utilizing an experimental setup with a modified triaxial cell allowing for shear band formation, the effect of varying the displacement rate is studied. Onset of strain localization is interpreted to occur just before or at the peak shear strength. A strong rate dependency of the softening response is observed. Increasing displacement rates give raised brittleness in terms of the slope of the global softening curve due to accumulating pore pressure. Also, reduced shear band thickness and a shear band inclination approaching 45° are obtained for increasing rates. In the context of slope failure in such materials, the rate dependency in the post-peak state opens up for a large variation in behavior, all depending on time as an important factor.  相似文献   

Finiteness of spatial central configurations in the five-body problem   总被引：1，自引：0，他引：1  

Marshall Hampton  Anders Jensen 《Celestial Mechanics and Dynamical Astronomy》2011,109(4):321-332

We strengthen a generic finiteness result due to Moeckel by showing that the number of spatial central configurations of the Newtonian five-body problem with positive masses is finite, apart from some explicitly given special cases of mass values.  相似文献   

Precise U–Pb baddeleyite ages of mafic dykes and intrusions in southern West Greenland and implications for a possible reconstruction with the Superior craton     

Mimmi K.M. Nilsson  Ulf Söderlund  Richard E. Ernst  Michael A. Hamilton  Anders Scherstén  Paul E.B. Armitage 《Precambrian Research》2010

The Archaean block of southern Greenland constitutes the core of the North Atlantic craton (NAC) and is host to a large number of Precambrian mafic intrusions and dyke swarms, many of which are regionally extensive but poorly dated. For southern West Greenland, we present a U–Pb zircon age of 2990 ± 13 Ma for the Amikoq mafic–ultramafic layered intrusion (Fiskefjord area) and four baddeleyite U–Pb ages of Precambrian dolerite dykes. Specifically, a dyke located SE of Ameralik Fjord is dated at 2499 ± 2 Ma, similar to a previously reported ⁴⁰Ar/³⁹Ar age of a dyke in the Kangâmiut area. For these and related intrusions of ca. 2.5 Ga age in southern West Greenland, we propose the name Kilaarsarfik dykes. Three WNW-trending dykes of the MD3 swarm yield ages of 2050 ± 2 Ma, 2041 ± 3 Ma and 2029 ± 3 Ma. A similar U–Pb baddeleyite age of 2045 ± 2 Ma is also presented for a SE-trending dolerite (Iglusuataliksuak dyke) in the Nain Province, the rifted western block of the NAC in Labrador. We speculate that the MD3 dykes and age-equivalent NNE-trending Kangâmiut dykes of southern West Greenland, together with the Iglusuataliksuak dyke (after closure of the Labrador Sea) represent components of a single, areally extensive, radiating swarm that signaled the arrival of a mantle plume centred on what is presently the western margin of the North Atlantic craton. Comparison of the magmatic ‘barcodes’ from the Nain and Greenland portions of the North Atlantic craton with the established record from the north-eastern Superior craton shows matches at 2500 Ma, 2214 Ma, 2050–2030 Ma and 1960–1950 Ma. We use these new age constraints, together with orientations of the dyke swarms, to offer a preliminary reconstruction of the North Atlantic craton near the north-eastern margin of the Superior craton during the latest Archaean and early Palaeoproterozoic, possibly with the Core Zone craton of eastern Canada intervening.  相似文献   

The 33rd International Geological Congress in Norway, 2008     

Anders Solheim Sylvi Haldorsen 《《幕》》2007,30(4):303-304

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