855 resultados para Orleans
Resumo:
During the summer of 2007 the United Kingdom experienced some of the worst flooding in its history, with the city of Hull amongst the worst affected. Meanwhile, the city of New Orleans, USA was subject to severe flooding in August 2005 as a result of Hurricane Katrina. The study has found that both the UK and US government disaster management programmes were ill prepared for these flood events. Many parallel issues have been discovered and discussed. The conditions of vulnerability that are evident in developing countries are not widely present in the UK or US but this must not be allowed to lead to complacency and lack of preparation and awareness. The cost in terms of mortality is relatively low compared to similar events in developing countries; however, the economic implications are considerable and must be addressed.
Resumo:
The nonlinear aspects of charged dust grain motion in a one-dimensional dusty plasma (DP) monolayer are discussed. Both horizontal (longitudinal, acoustic mode) and vertical (transverse, optic mode) displacements are considered, and various types of localized excitations are reviewed, in a continuum approximation. Dust crystals are shown to support nonlinear kink-shaped supersonic longitudinal solitary excitations, as well as modulated envelope (either longitudinal or transverse) localized modes. The possibility for Discrete Breather (DB-) type excitations (Intrinsic Localized Modes, ILMs) to occur is investigated, from first principles. These highly localized excitations owe their existence to lattice discreteness, in combination with the interaction and/or
substrate (sheath) potential nonlinearity. This possibility may open new directions in DP- related research. The relation to previous results on atomic chains as well as to experimental results on strongly-coupled dust layers in gas discharge plasmas is discussed.
