1,721,103 research outputs found
An empirical method for modelling and simulating some complex macroscopic phenomena by cellular automata
No full textNovel parallel computing models sometime represent a valid alternative to standard differential equation methods inmodelling complex phenomena. In particular, Cellular Automata (CA) provide such an alternative approach for some complexnatural systems, whose behaviour can be described in terms of local interactions of their constituent parts. This paper illustratesan empirical method applied with interesting results in modelling and simulating some complex macroscopic phenomena.While classical CA are based upon elementary automata, with few states and a simple transition function, in order to dealwith macroscopic phenomena it is often necessary to allow a large number of different states a more complicated transition.The notion of substate is introduced in the macroscopic case for decomposing the state of the cell. The values associatedto substates can change in time either due to interactions among substates inside the cell (internal transformations) or to localinteractions among neighbouring cells.The internal transformations are treated in a way similar to ordinary difference equations.The local interactions among cells can be often treated according to an algorithm for the minimisation of differences, whichdescribes a tendency of conserved quantities to reach an equilibrium distribution.A large class of complex macroscopic phenomena seem to satisfy the applicability conditions of such an empirical method;some of them are briefly reviewed
La dinamica della legislazione elettorale nella Russia post-Sovietica: le elezioni libere tra forma e sostanza
Full text linkNegli ultimi decenni in Russia si è potuto osservare un continuo declino delle istituzioni rappresentative ed elettorali. Tale tendenza – legata da un lato allo svuotamento del contenuto democratico del meccanismo elettorale e dall’altro allo scivolamento graduale dell’ordinamento verso una forma di presidenzialismo sempre più personalistico – ha portato molti a ripensare in termini meno ottimistici il processo di democratizzazione nel Paese. Oggi, infatti, come mai prima, è divenuto chiaro quanto il modello politico-istituzionale della Russia si discosti dal modello occidentale di democrazia rappresentativa pluralista
Environmental applications of genetic algorithms
No full textAn application of genetic algorithms to a problem of environmental restoration is presented. The application concerns the in-situ bioremediation of contaminated soils, where indigeneous bacteria are stimulated to degrade the contaminant, by introducing a suitable nutrient solution directly in the soil. Forecasting the results of field operations from laboratory and pilot plant data is very important, and it requires the use of simulation models, which describe the interaction between different physical, chemical and biological phenomena. The main features are briefly summarized of a bioremediation model based on the paradigm of cellular automata, which successfully describes data obtained at a pilot plant scale. Genetic algorithms have been used in order to tailor the model to a specific case, namely contamination by phenol
Analisi sull’abbondanza di una comunità presente in ambiente ipogeo in relazione al ciclo giorno/notte
No full textFrom classical infinite space–time CA to a hybrid CA model for natural sciences modeling
No full textComplex phenomena occurring in natural sciences are usually characterized by a non trivial interplay between microscopic and macroscopic dynamics, which can be successfully captured by the cellular automata (CA) computational paradigm. In this paper we show that some approximation of the classical CA paradigm is needed in order to properly deal with complex dynamical systems. Real phenomena can be efficiently modeled and simulated by introducing a modified CA approach, the CANv2. In this way one takes into account multiscale dynamics, through approximate infinite and/or infinitesimal dynamical stages, by means of a hybrid network of standard CA components and global operators. The power of the CANv2 approach is fully exploited by discussing three examples borrowed from the realm of natural science: debris flows after a landslide, superconductive devices and forest fires spread. Advantages and limitations of our computational model explicitly arise when examples are discussed
Metodo implementato mediante computer per la simulazione del flusso sanguigno miocardico in condizioni di stress
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Elicitation of phytoalexin and hypersensitive necrosis response in carrot cell suspension cultures
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