Crown condition assessment at the CONECOFOR Permanent Monitoring Plots.

A detailed crown condition assessment is currently being carried out at the CONECOFOR (CONtrollo ECOsistemi FORestali, Control of Forest Ecosystems) plots. The assessment began in 1996, and during the first two years (1996 and 1997) an assessment form based on previous regional experience was used; in 1998 the new official EU form was adopted. The resulting loss of comparability means that only a few indices can be used in the temporal series 1996-1999. Much effort was devoted to Quality Assurance (QA) procedures. The QA program is structured as follows: (i) specific field manuals have been adopted and are continuously updated; (ii) a national training and intercalibration course (NT&IC) is undertaken yearly before beginning the assessment campaign;( iii) field checks are carried out yearly on a large number of plots. The results of the QA program have shown that for several indices the quality objectives were not reached, but the quality of the data is improving with time. To express the change in crown conditions in each area, a complex index (CCI = Crown Condition Index) was adopted. This index is the result of the sum of the relativized values of all the common indices used during the four years. The following parameters were used: transparency, ramification type, leaf colour alteration extension, leaf damage extension, alteration of leaf distension extension. The range within which the CCI fluctuates was evaluated taking into account all the observations carried out at a given plot throughout the years. The number of cases over a given threshold (outliers) was calculated for each year. The threshold for outliers was calculated as the median value plus 2 times the range of the interquartile value. All individual cases exceeding this value are considered outliers. The results are presented for all the areas in which the data set is complete for the four years. The yearly fluctuations are discussed and related to possible causes

Global and exponential attractors for a Ginzburg-Landau model of superfluidity

The long-time behavior of the solutions for a non-isothermal model in superfluidity is investigated. The model describes the transition between the normal and the superfluid phase in liquid 4He by means of a non-linear differential system, where the concentration of the superfluid phase satisfies a non-isothermal Ginzburg-Landau equation. This system, which turns out to be consistent with thermodynamical principles and whose well-posedness has been recently proved, has been shown to admit a Lyapunov functional. This allows to prove existence of the global attractor which consists of the unstable manifold of the stationary solutions. Finally, by exploiting recent techniques of semigroups theory, we prove the existence of an exponential attractor of finite fractal dimension which contains the global attractor.Comment: 39 page

On the influence of a dissipative boundary on the energy decay for a porous elastic solid

In this paper we study the asymptotic behavior of a porous elastic solid with a dissipative boundary. We prove that the energy exponentially decays when the porosity viscosity is present

On the energy decay of a linear hyperbolic thermoelastic system with dissipative boundary

We study the asymptotic behavior of the solutions of a 3-D hyperbolic system arising in linear homogeneous anisotropic thermoelasticity with a dissipative boundary condition with memory for the displacement. By introducing a boundary free energy, we prove that, if the memory kernel exponentially decays in time then also the energy exponentially decays

Exponential decay for Maxwell equations with a boundary memory condition

We study the asymptotic behavior of the solution of the Maxwell equations with a boundary condition of memory type. We consider a `Graffi' type free energy and we prove that, if the memory kernel satisfies an exponential decay condition, and the domain is strongly star shaped, then the energy of the solution exponentially decays. We also prove that the exponential decay of the kernel is a necessary condition for the exponential decay of the solution

Energy decay in thermoelastic diffusion theory with second sound and dissipative boundary

We study the energy decay of the solutions of a linear homogeneous anisotropic thermoelastic diffusion system with second sound and dissipative linear boundary condition which well describes a material for which the domain outside the body consists in a material of viscoelastic type. The thermal and diffusion disturbances are modeled by Cattaneo-Maxwell law for heat and diffusion equations to remove the physical paradox of infinite propagation speed in the classical theory within Fourier\u2019s law. The system of equations in this case is a coupling of three hyperbolic equations. By introducing a boundary free energy, we prove that, if the memory kernel exponentially decays in time then also the energy exponentially decays. Finally, we generalize the obtained results to the Gurtin-Pipkin model

A principle of constrained minimum in electromagnetism

A minimum variational approach is developed for Maxwell's equations. The existence and uniqueness of strong solutions is shown to be equivalent to the existence of a point of strict minimum for an appropriate functional, using some thermodynamical restrictions on the constitutive equations. One of Maxwell's equations is treated as a constraint in defining the domain of such a functional. Suitable functionals are constructed for several cases

The J-S model versus a non-ideal MHD theory

A new non-ideal electromagnetic interpretation of the J-S type viscoelastic model for polymeric fluids is given and a generalized resisto-elastic magneto-hydrodynamic scenario for collisionless plasmas is proposed. The influence of the new theory on the incompressible transverse Alfv \u301en waves is thoroughly investigated

Asymptotic stability in linear viscoelasticity with supplies

We present some results about the asymptotic behavior of a linear viscoelastic system making use of the approach based on the concept of minimal state. This approach allows to obtain results in a larger class of solutions and data with respect to the classical one based on the histories of the deformation gradient. Recently, a lot of attention has been paid to find unified approaches which permit to study the asymptotic behavior with memory kernels presenting a temporal decay of which the exponential and polynomial decays are only special cases. Here we extend this unified approach to the dynamic problem in presence of supplies by using the minimal state and compare our results with those present in literature

A viscous boundary condition with memory in linear elasticity

We study the asymptotic behavior of a linear elastic medium with a boundary condition with memory. By introducing a boundary free energy, we prove that, if the memory kernel $lambda$ exponentially decays and the domain is strongly star shaped, then the energy exponentially decays. We also prove that the exponential decay of $lambda$ is a necessary condition for the exponential decay of the solution