118,806 research outputs found
A. Cardone; L. Buffoni, L’applicazione extraterritoriale della Costituzione: il caso della tutela del lavoro italiano all’estero, in Scritti in onore di Antonio Ruggeri
No full textExponentially-fitted quadrature methods for evolution problems with periodic solution
No full textThe interest for numerical solution of physical and biological problems with oscillating and/or periodic
behaviour requires the use of special-purpose methods. Examples include the electromagnetic scattering, the response of nonlinear circuits to a periodic input and the evolution of an age-structuredpopulation. These problems are characterized by either infinite integrals where the integrand function is oscillatory function, or by Volterra integral equations of type with periodic solution. By exploting the Exponential Fitting theory [1, 2, 3, 4,
5], a new class of quadrature rules, that are a generalization of the usual Gauss-Laguerre formulae, for
problem (1) and a new direct quadrature (DQ) method for problem (2) are derived, respectively. Two extra problems appear in the context of building the exponentially-fitted (ef ) DQ method. The first one is the construction of a two-nodes ef quadrature rule of Gaussian type, that is a generalization of the usual two-nodes Gauss-Legendre formula, on which the DQ method is based. The second problem is the building of a suitable ef interpolation technique on four points which preserves the order of
convergence of the overall method. These works are in collaboration with L. Gr. Ixaru (National Institute of Physics and Nuclear Engineering, Bucharest, Romania), B. Paternoster, A. Cardone and D. Conte (University of Salerno).
References
[1] Ixaru, L.Gr.; Vanden Berghe, G., Exponential fitting, Kluwer Academic Publishers, Dordrecht
(2004).
[2] A. Cardone, B. Paternoster, G. Santomauro, Exponential fitting quadrature rule for functional equations, AIP Conference Proceedings 1479 (2012) 1169-1172.
[3] A. Cardone, L. Gr. Ixaru, B. Paternoster, G. Santomauro, Ef-Gaussian direct quadrature methods
for Volterra integral equations with periodic solution, Mathematics and Computers in Simulation (submitted).
[4] D. Conte, B. Paternoster, G. Santomauro, An exponentially fitted quadrature rule over unbounded
intervals, AIP Conference Proceedings 1479 (2012) 1173-1176.
[5] D. Conte, L. Gr. Ixaru, B. Paternoster, G. Santomauro, Gauss-Laguerre quadrature rule for oscillatory integrands, Computational and Applied Mathematics (submitted)
Henderson and Cardone at Montgomery Awards
No full text(l to r) Cadet Richard Henderson and Major Tommy Cardone pose for a photograph after the awards ceremony
Numerical schemes specially tuned for some evolutionary problems
No full textThe effective numerical integration of evolutionary problems arising from real-life applications requires the analysis of the characteristics of the phenomenon and of the corresponding mathematical model. The resulting numerical methods will therefore be able to reproduce the behavior of the analytical solution and to exploit the knowledge on the problem to reduce the computational effort. This approach has been developed for some classes of differential systems and for some classes of problems with memory modeled by integral or fractional equations.
Problems like advection-diffusion or reaction-diffusion problems are usually solved by a semidiscretization along space, which gives raise to (large) systems of ordinary differential systems characterized by a stiff part and a non-stiff one. IMEX methods treat implicitly the stiff part and explicitly the non-stiff one, in order to have strong stability properties and to reduce the computational cost. We introduce a class of IMEX general linear methods which have no coupling order conditions, do not suffer of the order reduction phenomenon thanks to the high stage order, and have optimal stability properties.
Periodic phenomena with memory, like the spread of seasonal diseases, are modeled by Volterra integral equations with periodic solution. Classical methods require a small stepsize to follow the oscillations.We apply the exponential fitting technique [8] to derive direct quadrature methods with parameters depending on an estimate of the frequency. The error is smaller than the error of classical methods, when periodic problems are treated; the numerical stability is not affected by the accuracy of the estimate of the frequency.
Fractional models can represent memory effects of natural processes and also the anomalous kinetics of some processes in physics, chemistry, pharmacokinetis. Here we focus on the numerical solution of time-fractional reaction-diffusion systems, by a spectral technique along time and a finite difference scheme along space, which are specially designed to reproduce the behavior of the analytical solution and to simplify the overall computation.
The results presented here have been obtained by various collaborations, with K. Burrage, R. D’Ambrosio, L.Gr. Ixaru, Z. Jackiewicz, B. Paternoster, A. Sandu, G. Santomauro, H. Zhang.
References
[1] Ascher, U.M., Ruuth, S.J., Spiteri, R.J. Implicit-explicit Runge-Kutta methods for timedependent partial differential equations. Appl. Numer. Math. 25, 151–167 (1997).
[2] Cardone, A., Jackiewicz, Z., Sandu, A., Zhang, H., Extrapolated implicit-explicit Runge-Kutta methods. Math. Model. Anal. 19, 18–43 (2014).
[3] Cardone, A., Jackiewicz, Z., Sandu, A., Zhang, H., Extrapolation-based implicit-explicit general linear methods. Numer. Algorithms 65, 377–399 (2014).
[4] Cardone, A., Jackiewicz, Z., Sandu, A., Zhang, H., Construction of highly stable implicit-explicit general linear methods, accepted for publication in Discrete Contin. Dyn. Systs.
[5] A. Cardone, L. Gr. Ixaru, and B. Paternoster, Exponential fitting direct quadrature methods for Volterra integral equations, Numer. Algorithms 55, no. 4, 467-480 (2010).
[6] A. Cardone, L.Gr. Ixaru, B. Paternoster, and G. Santomauro, Ef-gaussian direct quadrature methods for Volterra integral equations with periodic solution, Math. Comput. Simul., in press.
[7] V. Gafiychuk, B. Datsko, and V. Meleshko, Mathematical modeling of time fractional reaction-diffusion systems, J. Comput. Appl. Math. 220(1-2), 215-225 (2008).
[8] L.Gr. Ixaru, G. Vanden Berghe, (2004) Exponential Fitting. Kluwer Academic Publishers, Dordrecht.
[9] L. Pareschi, G. Russo, Implicit-explicit Runge-Kutta schemes and applications to hyperbolic systems with relaxation, J. Sci. Comput. 25(1-2), 129–155 (2005)
STABILITY OF COLLOCATION METHODS FOR FRACTIONAL DIFFERENTIAL EQUATIONS
No full textCollocation methods for fractional differential equations have been introduced by Blank [1] and later on rigorously analyzed by Pedas and Tamme [3,4]. Recently Cardone, Conte and Paternoster [2] introduced two step collocation methods, which raise the order of convergence, by using additional information from the past, without increasing the computational cost. Here
we study the stability of both classes of methods, in order to nd methods with unbounded stability regions.
This is a joint work with D. CONTE and B. PATERNOSTER from UNIVERSITY OF SALERNO.
[1 ] L. Blank, Numerical treatment of differential equations of fractional order, Nonlinear World, 4 (1997), 473-491.
[2 ] A. Cardone, D. Conte, B. Paternoster, Two-step collocation methods forfractional dierential equations, to appear in Discrete Cont.Dyn.-B. [3 ] A. Pedas and E. Tamme, On the convergence of spline collocation methods for solving fractional differential equations, J. Comput. Appl.Math., 235 (2011), 3502-3514.
[4 ] A. Pedas and E. Tamme, Numerical solution of nonlinear fractional differential equations by spline collocation methods, J. Comput. Appl.Math., 255 (2014), 216-230
GPU accelerated solution of time fractional diffusion systems
No full textFractional diffusion systems model a number of important applications, as for example water diffusion magnetic resonance imaging, since the biological tissues are heterogeneous and the signal exhibits a heavy tail which is characteristic of anomalous diffusion [3]. In this talk, we consider a time-fractional diffusion system discretized by a mixed method, consisting of a spectral method along time and a finite difference scheme along space [1]. As the spatial mesh becomes finer, the computational cost becomes very large and prevents getting high accuracy. In this context, our contribution is a suitable parallel implementation on GPUs (Graphics Processing Units) of this model. This massively multi-processors architecture has been recently used in several scientific applications to improve performance of software [4] and to get accurate and accelerated solutions in similar fractional diffusion problems [2]. Experiments show the gain of performance in execution time and accuracy terms of the parallel implementation.
References
[1] Burrage, K. and Cardone, A. and D’Ambrosio, R. and Paternoster, B. 2017 Numerical solution of time fractional diffusion systems, Appl. Numer. Math. 116, 82–94.
[2] De Luca, P., Galletti, A., Ghehsareh, H.R., Marcellino, L., & Raei, M. A gpucuda framework for solving a two-dimensional inverse anomalous diffusion problem.In: Foster, I., Joubert, G.R., Kučera, L., Nagel, W.E., Peters, F. (eds) Parallel Computing: Technology Trends, Advances in Parallel Computing. Vol 36. pp 311 -320. IOS Press, 2020.
[3] Höfling, F. and Franosch, T. 2013 Anomalous transport in the crowded world of biological cells, Rep. Prog. Phys. 76, 046602.
[4] Kurzak, J., Gates, M., Charara, A., YarKhan, A., Yamazaki, I., & Dongarra, J. (2019, August). Linear systems solvers for distributed-memory machines with gpu accelerators. In European Conference on Parallel Processing (pp. 495-506). Springer, Cham
Erranti e impreviste
No full textOn the Italian silver screens as well as in the cities, the feminine bodies have been crossing the most various landscapes. In so doing, they have been tracing peculiar, often unpredicted trajectories, as unpredicted and forbidden their presence was, if not accompanied by a man, in the spaces of the streets. This essay aims at proposing a first glance on these walking women, crossing the steps described in feminine writings to those appearing in films, from the Thirties to the aftermath of the war
Il successo di EGA presso gli studiosi italiani / EGA’s success amongst Italian academics,
No full text[EN] Since a long time I have been convinced that EGA is the best architectural representation magazine – or maybe of all graphic representation ones – and it’s not a mistery. It is obvious that not everyone will share this oppinion and someone could get angry when I say it, but it is meditated oppinion, supported by irrefutable data, released from my personal relationship with the magazine and the colleagues who participate in it.[IT] Da molti anni sono convinto che EGA sia la migliore rivista di rappresentazione dell’architettura – se non addirittura di tutte quelle che si interessano di rappresentazione grafica – e non ne faccio mistero. È ovvio che non tutti condividono e qualcuno si arrabbia quando lo affermo, ma si tratta di opinione meditata, suffragata da dati inoppugnabili, svincolati dal mio personale rapporto con la rivista e i colleghi che la curano.Cardone, V. (2018). Il successo di EGA presso gli studiosi italiani. EGA. Revista de Expresión Gráfica Arquitectónica. 23(34):206-211. https://doi.org/10.4995/ega.2018.10852SWORD2062112334AMORUSO, G., 2018. El espacio ilusorio barroco en las perspectivas arquitectónicas de Girolamo Curti y Angelo Michele Colonna en el Palacio de la Ciudad de Bolonia, EGA Expresión Gráfica Arquitectónica, 33, pp. 78-89. https://doi.org/10.4995/ega.2018.10389Barba, S., Messina, B. (in charge of), 2005. Il disegno dei viaggiatori. Salerno: CUES.Bartolomei, C., Ippolito, A., 2015. Faros italianos entre geometría y simbolismo, EGA Expresión Gráfica Arquitectónica, 25, pp. 192-199. https://doi.org/10.4995/ega.2015.3679Borja Molero, A., Barba, S., Álvaro Tordesillas, A., 2016., Documentación del patrimonio cultural. Método basado en la fusión de técnicas fotogramétricas y de escaneado óptico de triangulación, EGA Expresión Gráfica Arquitectónica, 28, pp. 236-245. https://doi.org/10.4995/ega.2016.6308Cabezos Bernal, P., Rossi, A., 2017. Técnicas de musealización virtual. Los capiteles del Monasterio de San Cugat, EGA Expresión Gráfica Arquitectónica, 29, pp. 48-57. https://doi.org/10.4995/ega.2017.7340Calisi, D., Cianci, M.G., 2018. De lo virtual a lo real. Un modelo de madera para la reconstrucción filológica del barrio Alessandrino en la zona arqueológica central de Roma, EGA Expresión Gráfica Arquitectónica, 33, pp. 90-102. https://doi.org/10.4995/ega.2018.8924Capone, M., Nigro, E., 2017. Desde la geometría hasta la representación generativa. La búsqueda de una solución optimizada en el proyecto del Club Táchira (Caracas, 1955), E GA Expresión Gráfica Arquitectónica, 31, pp. 172-183.Cardone, V., 2002. Pedro Luis Escrivá: forma e funzione nel disegno delle fortificazioni, EGA Expresión Gráfica Arquitectónica, 7, pp. 36-47.Cardone, V., 2003. Pedro Luis Escrivá, ingegnere militare del Regno di Napoli. Salerno: CUES.Cardone, V., 2005. A proposito di nome, contenuti, programmi e prospettive per la nostra area culturale, EGA Expresión Gráfica Arquitectónica, 10, pp. 48-57. https://doi.org/10.4995/ega.2005.10329Cardone, V., 2017. Editoriale, diségno, n.1, luglio-dicembre 2017, pp. 5-8.Cipriani, L., Fantini, F., Bertacchi, S., 2015. El color en las piedras y en los mosaicos de Rávena: nuevas imágenes de los monumentos antiguos a través de la fotogrametría no convencional de última generación, EGA Expresión Gráfica Arquitectónica, 26, pp. 190-201. https://doi.org/10.4995/ega.2015.4052De Sanctis, A., Fortunato, G., Zappani, A.A., 2017. Nuevos levantamientos y documentos de archivo para el conocimiento de los bienes arquitectónicos: la construcción en el siglo xvii de un nuevo vestíbulo en el Convento- Santuario de San Francisco de Paula (Paula- Italia), EGA Expresión Gráfica Arquitectónica, 30, pp. 118-129. https://doi.org/10.4995/ega.2017.7835Fantini, F., 2012. Modelos con nivel de detalle variable realizados mediante un levantamiento digital aplicados a la arqueología, EGA Expresión Gráfica Arquitectónica, 19, pp. 306-317. https://doi.org/10.4995/ega.2012.1383Gombrich, E.H., 1993. Historia del arte y psicología en Viena, hace cincuenta años, EGA Expresión Gráfica Arquitectónica, 1, pp. 38-41.Leserri, M., Rossi, G., 2013. Arquitecturas de piedra seca, un levantamiento problemático, EGA Expresión Gráfica Arquitectónica, 22, pp. 184-195. https://doi.org/10.4995/ega.2013.1532Maestri, D., 1993. Axonometría, dibujo y arquitectura, EGA Expresión Gráfica Arquitectónica, 1, pp. 99-108.Rossi, A., Palmero, L., DeGregorio, S., 2018. El análisis de la forma en el diseño arquitectónico: desde el proyecto a la ejecución, EGA Expresión Gráfica Arquitectónica, 32, pp. 186-197. https://doi.org/10.4995/ega.2018.894
Il cannocchiale rovesciato e la dialettica dello sguardo in "Queimada"
No full textIl saggio propone una lettur di "Queimada" attraverso un'analisi fondata sulla gestione dello sguardo, che mette in rilievo il contributo dello sceneggiator
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