1,732,654 research outputs found
Jack D'Ambrosio Diary, 1977-1979
No full textDiaries, from Janurary 1977 to January 1979, of Jack D'Ambrosio, a pharmacist living in Englewood, Ohio. Mr. D'Ambrosio worked at the Veterans Affairs hospital in Dayton, Ohio, and later additionally employed at Elder Beerman, a department store and local pharmacy. He also generated income from his hobby of book collecting/trading and makes several entries regarding book purchases and sales. Entries are made several times a week and are very detailed. Entries include discussion about the weather, family life, health, social life, sports and current events reports and politics. Mr D'Ambrosio also provides in his entries perspectives on: marriage, work life at the VA, the state of the country, growing old, and race relations. Found in: Mss. Acc. 2010.005 and 2012.268, Jack D'Ambrosio Diary, Special Collections Research Center, Swem Library, College of William and Mary
D'Ambrosio
No full textPrinted for a 1983 exhibit at the Colophon Club of San Francisco: "D'Ambrosio: The Book as an Art Medium."Numbered 94 / 10
Ted D'Ambrosio
No full text"Ted D'Ambrosio 1939 - to raid 19 Feb 42 then 4.12.45 to 28.3.92 I shall return!!
Intervista a Mario D'Ambrosio, Presidente nazionale AIDP
No full textIntervista a Mario D'Ambrosio, presidente nazionale AIDP Associazione Italiana Direzione del Personale, realizzata al Congresso Nazionale AIDP, 2-3 maggio 2008 nell'ambito del progetto CEK-lab, sul diversity management
Multivalue numerical methods for partitioned differential problems: from second order ODEs to separable Hamiltonians
No full textThis talk introduces general families of multivalue methods for the numerical solution of partitioned differential problems which includes, as special cases, second order ODEs of special type and Hamiltonian problems with separable Hamiltonian. We present the family of General Nystrom methods, introduced in [2] with the initial aim to provide an unifying approach for the analysis of minimal accuracy and stability demandings. Within this family, we derive high order P-stable formulae which result to be competitive with respect to classical Runge-Kutta-Nystrom methods in numerically solving
periodic sti problems [3]. As regards problem (2), the family of partitioned general linear methods is introduced [1]. With the aim of obtaining a long-term near conservation of the Hamiltonian of (2), we present suitable notions of G-symplecticity and symmetry for these methods. A technique for the generation of numerical solutions with bounded parasitic components is also discussed. Numerical experiments on a selection of separable Hamiltonian problems are reported. The talk deals with a series of joint papers with John Butcher (University of Auckland) and Beatrice Paternoster (University of Salerno). References 1. J. C. Butcher, R. D'Ambrosio, Partitioned general linear methods for separable Hamiltonian problems, in preparation.
2. R. D'Ambrosio, E. Esposito, B. Paternoster, General linear methods for y'' = f(y(t)), Numer. Algor. 61(2), 331{349 (2012). 3. R. D'Ambrosio, B. Paternoster, P-stable General Linear Nystrom methods, submitted
Long-term structure-preserving numerical methods for Hamiltonian problems in Physics and Medicine
No full textIt is the purpose of this talk to analyze the structure preservation properties of multi-value methods for the numerical solution of Hamiltonian problems, originating from Celestial Mechanics, Molecular Dynamics and Immunology. In particular, we aim to achieve accurate and ecient numerical energy preservation and orbits computation in the dynamics of Solar system planets, by employing real data desumed by Nasa Horizons System, as well as numerical modeling of T-cell dynamics by discretization of suitable models arising from Mechanical Statistics is object of the investigations. It is known that, in the spirit of numerical conservation of the invariants of Hamiltonian problems, the classical symplecticity property play a crucial role. However, only certain Runge-Kutta methods are candidate for symplecticity. Even if multivalue methods cannot be symplectic, it is possible to lead them possess a computationally cheap nearly preserving behavior through the properties of G-symplecticity, symmetry and zero-growth parameters for the parasitic components. We are particularly interested in the long-time behavior of multi-value methods. Hence, we provide long-term error estimates by backward error analysis arguments, which permits to get sharp estimates for the parasitic solution components and for the error in the Hamiltonian. We prove that the eects of parasitism on the numerical solution are then negligible on time intervals of length O(h2), where h is the stepsize of integration. The theoretical expectations are then conrmed by the numerical evidence. References: 1. R. D'Ambrosio, G. De Martino, B. Paternoster, Numerical integration of Hamiltonian problems by G-symplectic methods, Adv. Comput. Math. 40(2), 553-575 (2014). 2. R. D'Ambrosio, E. Hairer, Long-term stability of multi-value methods for ordinary dierential equations, J. Sci. Comput. doi: 10.1007/s10915-013-9812-y (2013). 3. R. D'Ambrosio, E. Hairer, C. Zbinden, G-symplecticity implies conjugate-symplecticity of the underlying one-step method. BIT vol. 53, 867-872 (2013)
Structure-preserving numerical methods for differential problems
No full textIt is the purpose of this talk to analyze the behaviour of multi-value numerical methods acting as structure-preserving integrators for the numerical solution of ordinary and partial differential equations (PDEs), with special emphasys to Hamiltonian problems, reaction-diffusion problems and stochastic differential equations (SDEs).
The methodology we aim to follow is unifying, i.e. we propose problem-oriented numerical solvers, able to accurately and efficiently reproduce typical properties and behaviors of the above mentioned problems. Thus, according to this clear perspective, the methods we consider are adapted to the problem, in contrast with general purpose solvers that, on the contrary, do not take into account specific features of the problems. A descriptions of the issues regarding each of the above mentioned problems now follows, with the aim to describe how this unifying structure-preserving approach is adapted in concrete to each of the mentioned operators.
As regards Hamiltonian problems, we analyze the nearly conservative behavior of multi-value numerical methods. Such methods, even though they cannot be symplectic, may act as structure-preserving integrators if the fulfill the properties of G-symplecticity \cite{bh2}, symmetry and bounded parasitic components which come into the numerical solution due to the multi-value nature of the solver. In particular, we provide a rigorous long-term error analysis regarding energy conservation for Hamiltonian problems \cite{bh1}, obtained by means of backward error analysis arguments, leading to sharp estimates for the parasitic solution components and for the error in the Hamiltonian. We also discuss the way these features characterize partitioned multi-value methods, specific for solving separable Hamiltonian problems, by pointing out how they can lead to overall explicit numerical schemes, also in comparison with existing symplectic partitioned Runge-Kutta methods \cite{but}.
As regards PDEs, we present novel finite difference schemes for problems with periodic or oscillatory solutions of interest in the mathematical modeling of oscillatory biological systems \cite{sherratt94,sherratt09}. We mainly focus our attention on problem-oriented numerical schemes as in \cite{ref2,ref1}, based on adapted finite difference formulae arising from a twofold level of adaptation to the problem: along space, by approximating the spatial derivatives appearing in the operator by means of finite differences based on non-polynomial fitting techniques; along time, by integrating the semi-discretized problems via special purpose numerical solvers. The coefficients of the resulting methods will depend on the unknown values of parameters related to the problem (e.g. the values of the frequencies of the oscillations): suitable techniques leading to estimates of the parameters will be discussed. Moreover, further issues on the possibility to improve the efficiency of the solvers by assessing adapted IMEX numerical schemes will also be briefly described.
As regards SDEs, the perspective is that of analyzing the potential of stochastic linear multistep methods to act as structure-preserving integrators, with special emphasys to numerically retaining dissipativity properties possessed by the problem \cite{bd}. Exponential mean square contractivity is analyzed, through results revealing some conditional nonlinear stability properties leading to accurate bounds for the stepsize. Numerical experiments on a selection of nonlinear problems are presented.
The presented results deal with a series of joint works in collaboration with Evelyn Buckwar (Johannes Kepler University of Linz), John C. Butcher (University of Auckland), Ernst Hairer (University of Geneva) and Beatrice Paternoster (University of Salerno).
\begin{thebibliography}{4}
\bibitem{bd} E. Buckwar, R. D'Ambrosio, {\em Mean square contractivity of stochastic linear multistep methods}, in preparation.
\bibitem{but} J.C. Butcher, R. D'Ambrosio, {\em Partitioned general linear methods for separable Hamiltonian problems}, in preparation.
\bibitem{bh1} R. D'Ambrosio, E. Hairer, {\em Long-term stability of multi-value methods for ordinary differential equations}, J. Sci. Comput. 60(3), 627--640 (2014).
\bibitem{bh2} R. D'Ambrosio, E. Hairer, C.J. Zbinden, {\em G-symplecticity implies conjugate-symplecticity of the underlying one-step method}, BIT 53, 867-872 (2013).
\bibitem{ref2} R. D'Ambrosio, B. Paternoster, {\em Numerical solution of a diffusion problem by exponentially fitted finite difference methods}, Springer Plus 3, 425--431 (2014).
\bibitem{ref1} R. D'Ambrosio, B. Paternoster, {\em Numerical solution of reaction-diffusion systems of - type by trigonometrically fitted methods}, submitted.
\bibitem{sherratt94} J.A. Sherratt, {\em On the evolution of periodic plane waves in reaction-diffusion systems of - type}, SIAM J. Appl. Math. 54(5), 1374--1385 (1994).
\bibitem{sherratt09} M.J. Smith, J.D.M. Rademacher, J.A. Sherratt, {\em Absolute stability of wavetrains can explain spatiotemporal dynamics in reaction-diffusion systems of lambda-omega type}, SIAM J. Appl. Dyn. Systems 8, 1136--1159 (2009).
\end{thebibliography
Algoritmi di motion cuening per simulatori di veicolo
Full text linkLa necessità di sviluppare un sistema che controlli in modo intelligentemente un simulatore di guida è un argomento che si sta sempre più sviluppando negli ultimi anni. Dato un certo riferimento proveniente da una simulazione virtuale, l’obiettivo di inseguire al meglio la traiettoria è limitata dal fatto che la struttura hai dei vincoli in posizione. Fin dai primi anni 70 algoritmi di motion cuieng erano basati su una combinazione di filtri. L’uso di un controllo MPC vuole portare un approccio metodologico, attraverso l’inserimento in un modello della piattaforma e del modello percettivo umano, nel inseguimento di una traiettoria di accelerazione desiderata anche utilizzando metodi come tilt-coordination e washout filte
Carta d'Ambrosio Rafael
No full textCarta d'Ambrosio Rafael sobre un concert a Palamós del dia 22/05/194
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