1,721,002 research outputs found
G. Parravicini, La politica fiscale e le entrate effettive del Regno ď Italia : 1860-1890
No full textRomano Ruggiero. G. Parravicini, La politica fiscale e le entrate effettive del Regno ď Italia : 1860-1890. In: Annales. Economies, sociétés, civilisations. 17ᵉ année, N. 4, 1962. pp. 819-820
"Pragmatism and Theories of Emergence" in "European Journal of Pragmatism and American Philosophy" XI-2 | 2019
No full textSingle- and Dual-domain Models of Solute Transport in Alluvial Sediments: the Effects of Heterogeneity Structure and Spatial Scale
No full textFine-scale heterogeneity of alluvial aquifers controls solute transport in groundwater at the scales relevant for practical applications: the architecture of sedimentary structures might create preferential flow paths (PFPs) or hydraulic barriers, which affect the breakthrough curves (BTCs). Objective of this paper was the assessment of the relevance of single- and dual-domain models for different heterogeneity patterns and scale lengths in alluvial sediments. Three case studies have been analysed with a classical single-domain model (SDM) and with three dual-domain models (DDMs): a dual-porosity model (DPorM) and two dual-permeability models (DPerM), which differ for the presence or the absence of solute exchange between the two domains. The first case study includes numerical tracer tests in metre-scale blocks of alluvial sediments; the second is a laboratory experiment of tracer injection in a decimetre-scale column of homogeneous sand; the third is a field tracer test performed at hectometre scale at the Cape Cod site. The relevance of the solute exchange in the DDMs is analysed with the characteristic advection and exchange times and with the Péclet and Damköhler numbers. The SDM is satisfactory for alluvial sediments with unstructured heterogeneity. The uncoupled DPerM is shown to be a better approach than the DPorM in sediments with PFPs; in this case, the coupled DPerM does not improve significantly the results of the uncoupled DPerM. A minor difference between the results of the three DDMs is observed for sediments in which the non-Fickian behaviour is not clearly determined by the presence of PFPs
Why are very short times so long and very long times so short in elastic waves?
No full textIn a first study of thermoelastic waves, such as in the textbook of Landau
and Lifshitz, one might at first glance understand that when the given period
is very short, waves are isentropic because heat conduction does not set in,
while if the given period is very long, waves are isothermal because there is
enough time for thermalization to be thoroughly accomplished. When one
pursues the study of these waves further, by the mathematical inspection of the
complete thermoelastic wave equation one finds that if the period is very short,
much shorter than a characteristic time of the material, the wave is isothermal,
while if it is very long, much longer than the characteristic time, the wave is
isentropic. One also learns that this fact is supported by experiments: at low
frequencies the elastic waves are isentropic, while they are isothermal when
the frequencies are so high that can be attained in few cases. The authors
show that there is no contradiction between first-glance understanding and the
mathematical treatment of the elastic wave equation: for thermal effects very
long periods are so short and very short periods are so long
A new method for the identification of distributed transmissivities
No full textFor two-dimensional groundwater flow in an isotropic confined aquifer, it has been shown elsewhere that two independent steady state sets of data, ie, piezometric heads and source terms corresponding to different steady state flow conditions, and the value of transmissivity at one point suffice to determine transmissivity uniquely in a connected domain. The data are independent if the hydraulic gradients are not parallel anywhere over the domain. The applicability of this technique to real cases is tested with two synthetic examples. The fit is good. The relative error for the identified internode transmissivities is very low when error-free data are used, and it varies by an amount approximately constant over the entire aquifer when an error on the initial value of transmissivity is introduced. The errors on the piezometric heads bear more relevance, but nonetheless, the affected results are still good. -from Author
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