Transport in finite size systems: an exit time approach

In the framework of chaotic scattering we analyze passive tracer transport in finite systems. In particular, we study models with open streamlines and a finite number of recirculation zones. In the non trivial case with a small number of recirculation zones a description by mean of asymptotic quantities (such as the eddy diffusivity) is not appropriate. The non asymptotic properties of dispersion are characterized by means of the exit time statistics, which shows strong sensitivity on initial conditions. This yields a probability distribution function with long tails, making impossible a characterization in terms of a unique typical exit time.Comment: 16 RevTeX pages + 6 eps-figures include

Interference phenomena in scalar transport induced by a noise finite correlation time

The role played on the scalar transport by a finite, not small, correlation time, $\tau_u$, for the noise velocity is investigated, both analytically and numerically. For small $\tau_u$'s a mechanism leading to enhancement of transport has recently been identified and shown to be dominating for any type of flow. For finite non-vanishing $\tau_u$'s we recognize the existence of a further mechanism associated with regions of anticorrelation of the Lagrangian advecting velocity. Depending on the extension of the anticorrelated regions, either an enhancement (corresponding to constructive interference) or a depletion (corresponding to destructive interference) in the turbulent transport now takes place.Comment: 8 pages, 3 figure

L\u2019immagine dei siciliani, nei proverbi \u201cblasonatori\u201d di Giuseppe Pitr\ue8

Quando Giuseppe Pitr\ue8 si accinge a raccogliere il corpus dei proverbi siciliani, si accorge che gi\ue0 a partire dal sec. XVII ne erano stati individuati alcuni attinenti allo scontro tra nazioni e citt\ue0. Nel 1880, quindi, individua un nucleo di proverbi che in seguito definir\ue0 \u201cblasoni popolari\u201d e intorno ai quali progetta di produrre un\u2019opera completa riguardante l\u2019intera nazione. Il folklorista palermitano, per\uf2, individua in questi proverbi soprattutto la mancata unit\ue0 del popolo italiano e li considera pi\uf9 una curiosit\ue0 che un oggetto di studio scientifico. Oggi \ue8 possibile, a partire dal corpus di Pitr\ue8, integrare e analizzare questi dati alla luce di categorie interpretative interessanti e nuove.When Giuseppe Pitr\ue8 begins to collect the corpus of Sicilian proverbs, he realizes that as early as the century XVII they had been identified some related to the conflict between nations and cities. In 1880, therefore, he identifies a core of proverbs which later will define "blasoni popolari", and around which plans to produce a complete work on the Italian nation. The folklorist, however, finds in these proverbs especially the failure to unity of the Italian people and considers them more a curiosity than an object of scientific study. Today it is possible, starting from Pitr\ue8 corpus, integrate and analyze these data with interesting and new interpretation categories

Partner selection in indoor-to-outdoor cooperative networks: an experimental study

In this paper, we develop a partner selection protocol for enhancing the network lifetime in cooperative wireless networks. The case-study is the cooperative relayed transmission from fixed indoor nodes to a common outdoor access point. A stochastic bivariate model for the spatial distribution of the fading parameters that govern the link performance, namely the Rician K-factor and the path-loss, is proposed and validated by means of real channel measurements. The partner selection protocol is based on the real-time estimation of a function of these fading parameters, i.e., the coding gain. To reduce the complexity of the link quality assessment, a Bayesian approach is proposed that uses the site-specific bivariate model as a-priori information for the coding gain estimation. This link quality estimator allows network lifetime gains almost as if all K-factor values were known. Furthermore, it suits IEEE 802.15.4 compliant networks as it efficiently exploits the information acquired from the receiver signal strength indicator. Extensive numerical results highlight the trade-off between complexity, robustness to model mismatches and network lifetime performance. We show for instance that infrequent updates of the site-specific model through K-factor estimation over a subset of links are sufficient to at least double the network lifetime with respect to existing algorithms based on path loss information only.Comment: This work has been submitted to IEEE Journal on Selected Areas in Communications in August 201

Nominare per perifrasi: alcuni spunti a partire da un\u2019analisi pragmatica sulle slot machine

Il breve contributo nasce dalla sollecitazione casuale, all'interno di una ricerca pragmatica, del trattamento dei nomi degli apparecchi d'intrattenimento detti slot machine. Dalle telefonate registrate in area palermitana, \ue8 emerso che gli esercenti dei locali che richiedono servizi di assistenza per la manutenzione di queste macchine, solitamente contrassegnate da ideonimi in inglese, sono costretti a perifrasi che agganciano preferenzialmente il nome al contenuto del gioco. Nell'interessante sovrapporsi di codici linguistici la Fowl Play Gold diventa "Quella delle uova" o "Quella con le galline".This shorts paper arises from some casual remarks within a pragmatic research on the onomastic features of the slot machine names. By analysing a series of recorded phone calls of retailers from Palermo asking for maintenance service assistance, the present work shows the interesting habit (or rather, the inclination) to refer to slots machines, generally named through English ideonyms, through periphrases dealing with the content of each game. Thus, through a peculiar overlapping of linguistic codes, the name Fowl Play Gold turns into \u201cthe one of eggs\u201d or \u201cthe one with chickens\u201d