35,191 research outputs found
Il problema del taglio massimo: algoritmo di approssimazione tramite programmazione semidefinita
Lo scopo di questa tesi è presentare un algoritmo che in tempo polinomiale
approssima la soluzione del problema del taglio massimo. Il problema,
infatti, è un problema NP-completo e pertanto, non esistendo algoritmi in
grado di risolverlo all’ottimo in tempo polinomiale, può essere approssimato tramite algoritmi di approssimazione. L’algoritmo analizzato risulta fornire una soluzione molto vicina all’ottimo del problema. Tale risultato è ottenuto a partire dalla risoluzione di un rilassamento, in forma di programma semidefinito, del problema originario
Grandi deviazioni applicate alla Legge di Taylor in ambienti Markoviani
La Legge di Taylor (TL) è una legge empirica e dichiara che la varianza di una variabile aleatoria non negativa è una funzione potenza della sua media. La TL è stata ampiamente verificata in ecologia e l'esponente osservato della media si attesta tipicamente intorno al valore 2. Nella tesi, ci occuperemo di studiare il comportamento di tale esponente nel caso di un modello matematico di crescita moltiplicativo in un ambiente Markoviano. Mostreremo che la causa per cui l'esponente osservato assuma
spesso valori vicino a 2 potrebbe derivare dal sottocampionamento. Inoltre, dimostreremo come il valore dell'esponente possa essere utile per cogliere informazioni ecologicamente importanti riguardo alla popolazione sottostante
Thermal Energy Storage Tanks as a Source of Flexibility in District Heating Networks
After a review of district heating generation and storage technologies, a simple model of a stratified tank is developed. It is then validated by means of comparison with an established model, and integrated into a representation of the whole Verona disrict network. The aim is to evaluate the flexibility that can be provided by a tank. It is found to be satisfactory when compared with using the network as storage, however it entails costs of a different nature
Quantum Computer Simulation via Tensor Networks
In recent years lots of efforts have been spent in the realization of quantum computers able to reproduce quantum circuits involving increasing number of qubits with the
greatest possible accuracy. The final goal is to reach the limit, the so-called quantum supremacy, where a classical computer is no longer able to reproduce the results of
a quantum machine. Indeed, simulating quantum many-body systems is very computationally demanding due to the exponential scaling of the Hilbert space with the number of qubits.
In order to perform a classical simulation of a quantum circuit acting on a qubits register, one must choose between two possible approaches: the first is an exact description
of the qubits’ state, possible up to a maximum reachable number of qubits. The second, instead, consists of representing the state approximately. But, even quantum processors
are not able to reproduce exactly a given quantum circuit: their coupling with the environment, which is minimized but not removed by the experimental implementation, induces
errors through quantum channels like decoherence or bit-flip. Therefore an approximate representation of the qubits' state is acceptable as long as its errors are comparable
with the experimental ones. The tensor network methods allow one to approximate a quantum state by efficiently compressing its information, introducing a controllable error.
In this thesis, these methods will be used to simulate a quantum computer on a large computational cluster, to push as far as possible the classical simulation framework
Search for a Higgs or a Z boson decaying to a J/ or meson and a photon
The discovery of the Higgs boson at the CMS and ATLAS experiments in 2012 represents a milestone in the understanding of the electroweak sector of the Standard Model (SM) of elementary particles. The discovery started a new era of measurements at CMS aiming to determine to the highest possible accuracy the couplings of the Higgs boson to the other particles in the SM. A discrepancy between the experimental measurement and the theoretical expectation from the SM would imply a ``new physics'', hinting to new particles yet to be discovered.
In particular, studying the couplings of the Higgs boson to the second generation quarks represents the real challenge of High-Luminosity LHC. A very rare but promising channel is the decay of the Higgs boson in an energetic photon () and a \PJPsi \equiv \PPsiS or \PPsiPrime \equiv \PPsiSS meson, followed by the decay of the \PPsiNS to a pair of muons. The \PH \to \PPsiNS\gamma decay takes place also through charm quark loops, therefore an accurate measurement would allow to determine its couplings with the Higgs boson. The channel is experimentally very clean, thanks to the very low SM backgrounds and the excellent resolution on the invariant mass peak, but also very rare, thus requiring large amounts of data. The observation of the \PZ \to \PPsiNS\gamma , whose rate is 100 times larger than the similar process with the Higgs boson and has never been observed before, is an intermediate objective that can be achieved with a reasonable amount of data.
The thesis work holds on the previous premises and it presents a complete analysis for the search of these processes. The analysis is performed with data from proton-proton collisions corresponding to an integrated luminosity of 137 \si{fb^{-1}} at \sqrt{s} = 13 \ \si{TeV} , collected with the CMS detector during the full LHC Run 2. Since the considered processes are still likely not observable, the aim of the work is to set an upper limit on the cross section at a certain confidence level, using signal Monte Carlo samples. This study would allow to have a perspective of how the analysis could evolve with a larger amount of data during the next phases of LHC, after which the experimental observation of rare decays of the Higgs and Z bosons might become a reality
Validazione di una pinza adattiva per la mediazione dell'impatto tra robot e pezzo
In ottica di una teleoperazione di sortig, realizzare un end-effector capace di mediare l'urto tra robot e pezzo da movimentare. L'end-effector realizzato inoltre, doveva essere in grado di ridurre la velocitĂ del pezzo dopo l'urto
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