1,721,446 research outputs found
Ibo Island in the Quirimbas Archipelago. An Architectural Heritage Within a Natural Heritage
Full text linkThis paper presents the method adopted in the study of Ibo, a small island of the Quirimbas Archipelago in northern Mozambique. Ibo is part of a larger study, begun in 2004 which is still ongoing. In the first phase, the author's attention was focused on the restoration of the historic architecture built with coral limestone. But very soon it became evident that it was necessary to study the context in which these coral architectures were built. After a few years of careful observation, it was apparent that coral stone architecture is strongly conditioned by the knowledge and conservation of the natural environment in which it is built. And in the case of Ibo, the beauty of its heritage and its conservation lies in the delicate balance between architecture and nature
Homoclinics and chaotic behaviour for perturbed second order systems
No full textThis paper deals with perturbed dynamical systems of the form:
−u¨+u=∇V(u)+ε∇uW(t,u)
where u(t)∈Rn(n⩾1). By means of a variational approach the existence of multibump homoclinics is proved under general assumptions on the Melnikov function. As a particular case, if (W; u) is T-periodic, the existence of approximate and complete Bernoulli shift structures is proved. An application to partial differential equations is also given
An Atlantic bridge for comparing EU and US views on the prospects of second-generation biofuels
No full textThe aim of the special issue, An Atlantic bridge for comparing EU and US
views on the prospects of second-generation biofuels, is to compare and
confront the opinions and comments of esteemed European and US
scientists on advanced biofuels, mindful of respective short-term mandates
on renewable energies in the EU-27 and the USA. We gathered seven
articles focused on potential feedstock, crop portfolios, land availability, and
potential food/fuel competition, environmental sustainability, policy regimes,
commercialization, and production facilities, each co-authored by US and EU
authors working in tandem
La Biblioteca di Alessandria. Storia di un paradiso perduto
No full textLa storia del Museo e della Biblioteca di Alessandria dalla fondazione, per opera dei primi due re della dinastia dei Tolemei (inizi del III secolo a.C.) alla conquista araba dell'Egitto (640 d.C.)The story of the Museum and the ancient Library of Alexandria from its foundation under the first two Ptolemies(beginnings of the 3rd c. BC) to the Arab conquest of Egypt (640 AD)
Bifurcation of free vibrations for completely resonant wave equations
No full textWe prove existence of small amplitude, 2π/ω-periodic in time solutions of completely resonant nonlinear wave equations with Dirichlet boundary conditions for any frequency to belonging to a Cantor-like set of positive measure and for a generic set of nonlinearities. The proof relies on a suitable Lyapunov-Schmidt decomposition and a variant of the Nash-Moser Implicit Function Theorem
Fast Arnold diffusion in systems with three time scales
No full textWe consider the problem of Arnold Diffusion for nearly integrable partially isochronous Hamiltonian systems with three time scales. By means of a careful shadowing analysis, based on a variational technique, we prove that, along special directions, Arnold diffusion takes place with fast (polynomial) speed, even though the “splitting determinant” is exponentially small
Periodic solutions of Hamiltonian PDEs
No full textThis paper surveys some recent results about periodic solutions for Hamiltonian PDEs, which involve the small denominators difficulty. We considers in particular periodic orbits for completely resonant nonlinear wave equations and "Birkhoff-Lewis'' orbits with applications to a semilinear beam equation and to the nonlinear Schrödinger equation. The common key technique is a variational Lyapunov-Schmidt decomposition, while for the Birkhoff-Lewis case a suitable normal form theory for PDEs is also needed. For every result a statement is presented, with the main ideas of the proof, and with suggestions for further developments
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