1,721,047 research outputs found
Existence and uniqueness for a non-isothermal dynamical Ginzburg-Landau model of superconductivity
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Parabolic-hyperbolic time-dependent Ginzburg-Landau-Maxwell equations
No full textThis article is devoted to the long-term dynamics of a parabolic-hyperbolic system arising in superconductivity. In the literature, the existence and uniqueness of the solution have been investigated but, to our knowledge, no asymptotic result is available. For the bi-dimensional model we prove that the system generates a dissipative semigroup in a proper phase-space where it possesses a (regular) global attractor. Then, we show the existence of an exponential attractor whose basin of attraction coincides with the whole phase-space. Thus, in particular, this exponential attractor contains the global attractor which, as a consequence, is of finite fractal dimension
A thermodynamically consistent Ginzburg-Landau model for superfluid transition in liquid helium
No full textIn this paper, we propose a thermodynamically consistent model for superfluid-normal phase transition in liquid helium, accounting for variations of temperature and density. The phase transition is described by means of an order parameter, according to the Ginzburg-Landau theory, emphasizing the analogies between superfluidity and superconductivity. The normal component of the velocity is assumed to be compressible, and the usual phase diagram of liquid helium is recovered. Moreover, the continuity equation leads to a dependence between density and temperature in agreement with the experimental data
A non-isothermal Ginzburg-Landau model in superconductivity: existence, uniqueness and asymptotic behaviour
No full textApproaches of data analysis from multi‐parametric monitoring systems for landslide risk management
Full text linkIn the last decades, several approaches were proposed accounting for early warning
systems to manage in real time the risks due to fast slope failures where important
elements, such as structures, infrastructures and cultural heritage are exposed. The
challenge of these approaches is to forecast the slope evolution, thus providing alert
levels suitable for managing infrastructures in order to mitigate the landslide risk and
reduce the “response” time for interventions.
Three different strategies can be defined in this regard: an Observation‐Based
Approach (OBA), a Statistic‐Based Approach (SBA) and a Semi‐Empirical Approach
(SEA). These approaches are focused on searching relations among destabilizing
factors and induced strain effects on rock mass.
At this aim, some experiments are being performed at different scales in the
framework of consulting activities and research projects managed by the Research
Centre for the Geological Risk (CERI) of the University of Rome “Sapienza”. These
experiments are testing different kind of sensors including extensometers, strain
gauges, rock‐thermometers, interferometers, optical cams connected to Artificial
Intelligence (AI) systems, for detecting changes in rock properties and detecting stressstrain
changes, as well as pluviometers, anemometers, hygrometers, air‐thermometers,
micro‐ or nano‐ accelerometers and piezometers for detecting possible trigger of
deformational events.
The results of this Ph.D. thesis demonstrate that the data analysis methods allowed
the identification of destabilizing actions responsible for strain effects on rock mass at
different dimensional scale and over several time‐window, from short‐ to long‐ period
time scale. Furthermore, the three approaches were to be suitable to recognize
precursor signals of rock mass deformation and demonstrated the possibility to
provide an early warning
A thermodynamic approach to isotropic-nematic phase transitions in liquid crystals
No full textWe propose a dynamical model for (non-isothermal) phase transitions in liquid crystals. Macroscopic motions of the liquid crystal (LC) are neglected, while the coupling with the electromagnetic field is considered. The LC is described in terms of the classical order tensor Q, which is split as Q=s N, where N is a normalized tensor; two independent evolution laws are given for s and N. The model includes an evolutive equation for the temperature field obtained from an appropriate form of the energy balance, in which the internal powers associated to the equations for s and N are accounted for. The thermodynamic restrictions in the constitutive relations which ensure the Clausius-Duhem inequality have been pointed out
Well-posedness of an isothermal diffusive model for binary mixtures of incompressible fluids
No full textWe consider a model describing the behaviour of a mixture of two incompressible fluids with the same density under isothermal conditions. The model consists of three balance equations: a continuity equation, a Navier-Stokes equation for the mean velocity of the mixture and a diffusion equation (Cahn-Hilliard equation). We assume that the chemical potential depends on the velocity of the mixture in such a way that an increase in the velocity improves the miscibility of the mixture. We examine the thermodynamic consistence of the model which leads to the introduction of an additional constitutive force in the motion equation. Then, we prove the existence and uniqueness of the solution of the resulting differential problem
Gauge invariance and asymptotic behavior for the Ginzburg-Landau equations of superconductivity
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