Modelli della sensibilità allo strain-rate e identificazione dei parametri caratteristici di lamiere di acciaio

È ormai ampiamente riconosciuto che i materiali hanno un comportamento che varia con la velocità di deformazione. L'influenza della velocità sulle proprietà del materiale viene modellata tramite modelli costitutivi. I modelli che sono stati proposti sono numerosi e differenti fra di loro e non esistono dei criteri ben definiti per la loro scelta. I dati caratteristici dei vari materiali non sempre sono disponibili anche perché la loro identificazione è piuttosto difficoltosa. Scopo del lavoro è di implementare una procedura numerica per l'identificazione dei parametri di influenza rispetto alla velocità di deformazione, tramite la simulazione di una prova sperimentale. Per questo scopo sono stati considerati e confrontati diversi modelli. Di questi modelli si sono messi in evidenza i vantaggi e le principali limitazioni e si sono potuti determinare i parametri per i due materiali considerat

Transfer process and typicality of noisy quantum systems with discrete time dynamics

In the thesis, models of quantum systems characterized by discrete time dynamics are presented and applied to different problems. More specifically, aspects of excitation transport, quantum state transfer and thermalization are investigated mainly within the framework of quantum cellular automata (QCA), which are discrete time evolution quantum systems defined on a regular lattice of, in this case, qubits. The peculiarities of QCA, together with the restriction to the first excitation sector of the Hilbert space, make it possible to define a transport dynamics on a one dimensional lattice that encompasses all classical Markov chains, as well as maps where quantum coherence between sites can build up over time. This allows for the possibility to make a direct comparison between a fully classical dynamics and a dynamics affected by quantum effects, which is of relevance both in the field of quantum biology, especially regarding the transport of electronic excitations in photosynthetic systems, and in quantum computing when dealing with the transport of an unknown quantum state. In a quantum thermodynamics context, instead, QCA can serve the purpose to validate arguments of tipicality that have been brought forward in recent years in order to demonstrate the thermalization of closed quantum systems (i.e. the tendency of any small subsystems to evolve towards the maximally mixed state). Numerical results concerning this issue are presented. Finally, a modelization of scattering-like processes, where the scattering consists of random unitary interactions between an environment and part of a quantum bipartite system is discussed. Relevant properties of the resulting state such as its mean purity and the correlations between the interacting and the “sheltered” part of the system can be analitically evaluated, and their fluctuations bounded

Formal Verification of Security Protocol Implementations: A Survey

Automated formal verification of security protocols has been mostly focused on analyzing high-level abstract models which, however, are significantly different from real protocol implementations written in programming languages. Recently, some researchers have started investigating techniques that bring automated formal proofs closer to real implementations. This paper surveys these attempts, focusing on approaches that target the application code that implements protocol logic, rather than the libraries that implement cryptography. According to these approaches, libraries are assumed to correctly implement some models. The aim is to derive formal proofs that, under this assumption, give assurance about the application code that implements the protocol logic. The two main approaches of model extraction and code generation are presented, along with the main techniques adopted for each approac