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R. L. Jennings 《Solar physics》1993,143(1):1-17
The role of nonlinearity is explored in a mean-field dynamo model. Magnetic fields are amplified by the combined action of the and-effects, and as the field's intensity increases the Lorentz force becomes important. Torsional oscillations and meridional circulations are driven by the Lorentz force, and the oscillations are consistent with those measured on the surface of the Sun. The torsional oscillations feedback in the induction equation and saturate the magnetic field's growth by quenching differential rotation. This model can also help us understand the processes responsible for the range of periods seen in the activity cycles of other stars like the Sun. 相似文献
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Gorka Merino Manuel Barange Julia L. Blanchard James Harle Robert Holmes Icarus Allen Edward H. Allison Marie Caroline Badjeck Nicholas K. Dulvy Jason Holt Simon Jennings Christian Mullon Lynda D. Rodwell 《Global Environmental Change》2012,22(4):795-806
Expansion in the world's human population and economic development will increase future demand for fish products. As global fisheries yield is constrained by ecosystems productivity and management effectiveness, per capita fish consumption can only be maintained or increased if aquaculture makes an increasing contribution to the volume and stability of global fish supplies. Here, we use predictions of changes in global and regional climate (according to IPCC emissions scenario A1B), marine ecosystem and fisheries production estimates from high resolution regional models, human population size estimates from United Nations prospects, fishmeal and oil price estimations, and projections of the technological development in aquaculture feed technology, to investigate the feasibility of sustaining current and increased per capita fish consumption rates in 2050. We conclude that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish. Ineffective fisheries management and rising fishmeal prices driven by greater demand could, however, compromise future aquaculture production and the availability of fish products. 相似文献
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Local uplift of the tank wall is perhaps the most important characteristic of the seismic behaviour of unanchored liquid storage tanks made out of steel. Such uplift is necessary, because unanchored tanks rely primarily on the weight of the liquid resting on an uplifted portion of the base plate to balance the overturning moments that occur during strong shaking. A simplified method of analysis for static lateral loads is developed, based on the assumption that the restraining action of the base plate can be modelled with equivalent, non-linear springs. This assumption, together with a Fourier decomposition of the displacements, simplifies the problem to the extent that it can be solved on a personal computer. The solutions are compared with those from experiments and those from current U.S. design analysis methods. 相似文献
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The effect of salinity-dependent hydraulic conductivity on saltwater intrusion episodes 总被引：2，自引：0，他引：2
The ionic strength of percolating water can greatly alter a soil's hydraulic conductivity. This appears to be the result of dispersion and/or swelling of clay particles, and can alter hydraulic conductivity by several orders of magnitude.
In this paper, the potential effects of salinity-dependent changes in hydraulic conductivity during saltwater intrusions are analyzed. Results are presented to show that this can increase the degree to which brackish water will penetrate a coastal aquifer. This can also increase the width of the dispersed salt front, and can lead to a much greater circulation of saltwater within the intruding saltwater toe. These results may help to explain field observations that have previously been attributed to “scale-dependent” dispersivity and domain heterogeneity. 相似文献
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