The Pandemic is forcing everyone to become aware of the need for a change in the cultural and socio-economic paradigms of recent decades.
During the twentieth century, on the one hand, entire populations concentrated in urban areas with ever higher population densities, at the same time giving rise to the phenomenon of “urban sprawl” or “suburbanization”.
On the other hand, entire territories have been abandoned (the so-called “inner areas”).
Now, we can define territorial rebalancing strategies based precisely on the reactivation of “inner areas”. Strategies that, in the Post (post) COVID era will have to be not only resilient, but anti-fragile. And the key is precisely in the future of the smaller historical centres.
This article aims to review the strengths and weaknesses of small historic centres, outlining possible scenarios for their “smart” revitalization and for a true sustainable and inclusive development.
This paper follows the propagation of pollution in a river with a rectangular cross-section of the river bed and a variable cross-sectional velocity. The calculations were made for steady flows and steady pollutant concentrations. To approximate the velocity distribution in the river bed a set of equations for current and vorticity functions was solved. The distribution of pollutant concentrations in the river was calculated from a bidirectional advection and turbulent diffusion equation. Analysis of the distribution of concentrations leads to the conclusion that the effects of transverse advection associated with a lateral inflow of pollutants disappear relatively quickly. Therefore, the distribution of concentrations in cross sections further downstream from the point of pollutant discharge can be determined quite accurately just from an advection-diffusion model, with no transverse advection effects included. Such a level of accuracy is usually sufficient to assess the impact of a pollution source on the aquatic environment. The transverse mixing of pollutants in the stream proceeds slowly and creates a large mixing zone in which the concentrations of pollutants (low but still significant for water quality) can be detected in cross-sections that are remote from the pollutant discharge point. Transverse advection may be ignored while calculating concentrations in remote cross sections at straight watercourse sections and in steady state conditions.
The article presents an overview of materials which can be employed used to camouflage objects on the modern battlefield in the radar frequency range.