We generalize a result of Dar{\'o}czy and K{\'a}tai, on the characterization of univoque numbers with respect to a non-integer base \cite{DarKat95} by relaxing the digit alphabet to a generic set of real numbers. We apply the result to derive the construction of a B\"uchi automaton accepting all and only the greedy sequences for a given base and digit set. In the appendix we prove a more general version of the fact that the expansion of an element $x\in \QQ(q)$ is ultimately periodic, if $q$ is a Pisot number.

We study the L^2 stability of a classical solution of the one-dimensional energy transport model for semiconductors on the whole rel line, under the assumption that the thermodynamic variables remain bounded. The solution converges asymptotically in time to a state in thermodynamic equilibrium.

The discrete Fourier transform of even complex sequences involves, in matrix formulation, a cosine matrix and, in the same way, the discrete Fourier transform of odd complex sequences is related with a sine matrix. Using structural characteristics of the two matrices, whose order is half the length of the symmetric input data, some recursive expressions of them will be constructed. Unlike the previous classical forms of the discrete Fourier transform of an even or odd real vector, the recursive terms in the matrix expressions derived here only involve the same cosine and sine matrices, with halved order. That is, it is shown that, as for the FFT of a general complex sequence, a divide and conquer approach can also be used to compute the DFT of even or odd sequences. The recursion is closed in the family of the sine and cosine matrices used to describe the DFT of even and odd sequences and no other kind of sine or cosine based matrices are required in recursive terms. Although the obtained results give a new theoretical view on the problem of computing the DFT of even and odd complex sequences, these are not of immediate practical use since the computational cost is higher than other currently employed algorithms. Copyright © 2005 John Wiley & Sons, Ltd.

A new fast iterative algorithm is proposed to denoise images affected by Gaussian additive noise, by solving a constrained optimization problem. A family of functionals parameterized by a few hyperparameters already proposed in the literature to solve denoising problems is considered. The algorithm estimates jointly the image and the hyperparameters, therefore providing an automatic method. Each member of the family is made up of a coherence with the data term and a term enforcing a roughness penalty and preserving jump discontinuities. Assuming we know the noise variance, an adequacy constraint is also considered. The algorithm computes a member of the family and a minimizer of it which satisfies the constraint. A convergence proof is provided. We then consider a heuristic version of the algorithm which gives restorations of comparable quality whose computational complexity is a linear function of the pixels number. Experimental results on synthetic and real data are presented. Moreover, numerical comparisons with several fast denoising methods are provided.

Marine phytoplankton are known to produce surface-active materials as part of their metabolism. The surface tension gradient due to the presence of plankton-produced surfactants leads to a surface shear stress, commonly known as Marangoni stress. In this work we try to gain some understanding on these complex phenomena while, at the same time, obtaining some information on the order of magnitude of the surface stress and the resulting velocity in the bulk flow. As the direct modelling of the surfactants is extremely difficult due to the complexity (and uncertainty) of their chemical composition and to the absence of information on the rate of production by marine phytoplankton, we have formulated a model of their effects based on the data of surface activity of seawater samples as they are presented by ?uti? et al. (1981) [?uti?, V., ?osovi?, B., Mar?enko, E., Bihari, N., 1981. Surfactant production by marine phytoplankton. Mar. Chem. 10, 505-520] and ?uti? and Legovic (1990) [?uti?, V., Legovic, T., 1990. Relationship between phytoplankton blooms and dissolved organic matter in the Northern Adriatic. In: Final reports on research projects dealing with eutrophication and plankton blooms (activity h). Mediterranean Action Plan (MAP) Technical Reports Series No. 37. United Nations Environment Program (UNEP), Athens]. Using satellite data and a chlorophyll concentration profile reported in the literature we predict a Marangoni stress whose maximum order of magnitude is 10- 6 N m- 2. We also present the results of a numerical test, where we evaluate the Marangoni stress caused by horizontal variations of the plankton distribution due to the converging flows in a thermal bar, obtaining a Marangoni stress of order of magnitude 10- 5 N m- 2 and a corresponding velocity in the bulk that is at most equal to 10- 4 m s- 1, with values of film pressure within the range of the data available in the literature.

This paper presents two examples of application of Synthetic Aperture Radar (SAR) interferometry (InSAR) to typical geomorphological problems. The principles of InSAR are introduced, taking care to clarify the limits and the potential of this technique for geomorphological studies. The application of InSAR to the quantification of landform, attributes such as the slope and to the estimation of landform variations is investigated. Two case studies are presented. A first case study focuses on the problem of measuring landform attributes by interferometric SAR data. The interferometric result is compared with the corresponding one obtained by a Digital Elevation Model (DEM). In the second case study, the use of InSAR for the estimation of landform variations caused by a landslide is detailed. (c) 2004 Elsevier B.V. All rights reserved.

Our paper describes an example of how new sophisticated applications can be introduced to support the management of large and widely distributed organizations belonging to the Public Sector and in particular to Research, Development and Education. We present SIGLA, the integrated planning and financial accounting system developed and maintained by CNR (the Italian National Research Council) in order to support the financial resource management process, from guideline and objective definition, to budget production and result verification. This application allows strict control of the actual financial resource usage and a crosscheck between objectives and results of research activities. The design and implementation of the system started at the end of the year 2000 and the system is still evolving, following the re-organization of the Council. We start with a brief description of the circumstances which lead to re-defining CNR's organizational model and thus to designing and implementing CNR's new financial accounting system from scratch. We then provide an overview of the organizational model supported by the application. Afterwards we describe the application in terms of code metrics, programming languages, high level inputs and outputs, technology platforms, documentation and hosting environment. An important point in successfully introducing complex tools into a large organization like CNR is to ensure fast learning of the basic (and possibly the advanced) functionalities. Exhaustive documentation is surely a good asset but may not be sufficient, especially when time is a critical factor. In the paper we describe the training strategy we established, mainly based on tutorials and distance learning tools. Last but not least, we present the structure of the helpdesk service which supports users in their daily routine. We conclude the paper with the description of our field experience in running the application and some remarks about SIGLA's reusability.

La scelta degli strumenti di finanziamento del debito pubblico nell'era del Trattato di Maastricht e del Patto di Stabilità e Crescita: analisi normativa, scenari macroeconomici, analisi del rischio-rendimento dei titoli, metodi di simulazione e modelli per la scelta ottima delle emissioni.

Il progetto si basa sull'ipotesi che un modello basato sulla conoscenza che si avvalga di strumenti automatici di restauro digitale possa ampliare opportunità di valorizzazione e di fruibilità delle immagini d'epoca, se si considera l'enorme quantità di fotografie che documentano i momenti della storia del bacino del mediterraneo. La finalità ultima del modello proposto è di svincolare i possibili utenti, interessati al restauro digitale, dall'oneroso compito, ad oggi spesso condotto manualmente, di analizzare le immagini, individuarne i difetti e per ognuno di essi impegnarsi nella scelta del migliore algoritmo e, unitamente, dell'insieme dei parametri ottimi per il conseguimento del miglior risultato.

Il Progetto riguarda tre ambiti di ricerca; 1. Sensoristica virtuale non invasiva per il monitoraggio di parametri ambientali; 2. Metodologie per la determinazione ottimale di posizioni di prelievo di dati di composizione chimica relative a regioni di interesse (ROI) evidenziate sul monumento da strumenti di elaborazione delle immagini e segmentazione basata sul colore delle stesse; 3. Metodologie per la determinazione di griglie ottime di sensori di misura di dati ambientali (quali temperatura ed umidità) sulla base di dati acquisiti da un numero iniziale sottodimensionato di sensori.