Optimal management of flows arising in the bioventing techniques (BV) for soil remediation problems is considered. The aim is to determine optimal locations and flow rates of injection and extraction wells, in order to cover the contaminated region by a uniform air velocity flow field. An air flow optimization criterion is considered leading to a mathematical programming problem. Several numerical experiences have been employed: in all tests we show that wells are placed outside the contaminated zone and they surround it.

In this article we obtain rates of convergence to equilibrium of marked Hawkes processes in two situations. Firstly, the stationary process is the empty process, in which case we speak of the rate of extinction. Secondly, the stationary process is the unique stationary and non trivial marked Hawkes process, in which case we speak of the rate of installation. The first situation models small epidemics, whereas the results in the second case are useful in deriving stopping rules for simulation algorithms of Hawkes processes with random marks.

The dynamics of a system quenched into a state with lamellar order and subject to an uniform shear flow is solved in the large-N limit. The description is based on the Brazovskii free energy and the evolution follows a convection-diffusion equation. Lamellas order preferentially with the normal along the vorticity direction. Typical lengths grow as gammat(5/4) (with logarithmic corrections) in the flow direction and logarithmically in the shear direction. Dynamical scaling holds in the two-dimensional case while it is violated in D=3.

The numerical construction of a symmetric Toeplitz matrix having prescribed eigenvalues is faced by a two-step method using the continuation idea. The Cayley transform is exploited in order to integrate flows in the linear subspace of skew-symmetric and centro-symmetric matrices.

Si discutono le definizione di soluzioni ad ODE discontinue in relazione al problema della ricostruzione delle traiettorie ottime da un feedback. In particolare si danno condizioni su feedback stratificati alla Boltianskii-Brunovsky per avere l'uguaglianza fra soluzioni alla Krasowskii e treiettorie ottime.

In this paper we obtain the rate of convergence to equilibrium of a class of interacting marked point processes, introduced by Kerstan, in two different situations. Indeed, we prove the exponential and subexponential ergodicity of such a class of stochastic processes. Our results are an extension of the corresponding results in a paper by Bremaud, Nappo and Torrisi (JAP, 2002). The generality of the dynamics which we take into account allows the application to the so-called loss networks, and multivariate birth-and-death processes.

In this paper we deal with high oscillatory systems and numerical methods for the approximation of their solutions. Some classical schemes developed in the literature are recalled and a recent approach based on the expression of the oscillatory solution by means of the exponential map is considered. Moreover we introduce a new method based on the Cayley map and provide some numerical tests in order to compare the different approaches

In particolare nell'ultima fase, il progetto e' stato orientato alla caratterizzazione di processi di transizione liquido/solido in presenza di deformazioni della fase solida. Su segnalazione di esperti in Scienza dei Materiali, sono state svolte delle simulazioni numeriche per individuare l'entita' dell'effetto di tali deformazioni sul processo. Stiamo lavorando su un test che portera' auspicabilmente a chiarire la necessita' che il modello matematico includa anche la descrizione delle deformazioni.

The approximation of a function affected by noise in several dimensions suffers from the so-called "curse of dimensionality". In this paper a Fourier series method based on regularization is developed both for uniform and random design when a restriction on the complexity of the curve such as additivity is considered in order to circumvent the problem. Optimal convergence theorems are stated and numerical experiments are shown on several test problems available in the literature together with comparisons with alternative methods. © 2002 Elsevier Science B.V. All rights reserved.

Remote sensing of atmosphere is changing rapidly thanks to the development of high spectral resolution infrared space-born sensors. The aim is to provide more and more accurate information on the lower atmosphere, as requested by the World Meteorological Organization (WMO), to improve reliability and time span of weather forecasts plus Earth's monitoring. In this paper the performance of the Infrared Atmospheric Sounding Interferometer (IASI) is analyzed looking directly at the products: temperature and water vapour.

A novel mesoscopic simulation technique -multi-particle collision dynamics- which has been suggested very recently, is used to study the two-dimensional flow around a square and a circular cylinder. The method is described and new proper boundary conditions are proposed to deal with wall collisions. The flow is analyzed in a wide range of Reynolds numbers in order to cover both the steady and unsteady regimes, resulting in symmetric steady vortices and periodic vortex shedding, respectively. The numerical results for integral flow parameters, such as the recirculation length, the drag and lift coefficients, the Strouhal number, as well as the spatial dependence of the velocity field, are compared with previous numerical and experimental studies. The qualitative and quantitative agreement is very good, validating the method as a promising technique to describe the hydrodynamic effects of solvent on embedded particles.

The phase separation of two-dimensional binary mixtures has been studied through numerical Langevin simulations based on a Ginzburg-Landau free energy. We have considered not symmetric mixtures with and without imposed shear flow. In the sheared case our main results are as follows: (1) domains are distorted by the flow; (2) the structure factor has four peaks; (3) excess viscosity shows a peak whose position is independent of shear rate but its height decreases increasing shear rate.