Sviluppo di un sistema per la misura della coppia di sterzo di motorscooter

La tesi, svolta in collaborazione con Piaggio S.p.a., è finalizzata alla progettazione e allo sviluppo di un dispositivo che consenta di misurare la coppia di sterzo applicata dal pilota durante la guida di un motorscooter. In passato alcune soluzioni sono state sviluppate nel tentativo di risolvere il problema; in una fase preliminare di questo lavoro esse sono state analizzate evidenziandone i limiti e le problematiche connesse. La soluzione finale che viene proposta prevede una modifica alla forcella originale del veicolo e l'installazione di un componente caratterizzato da bassa rigidezza torsionale, appositamente realizzato per ospitare un ponte completo di estensimetri a resistenza e consentirne il corretto funzionamento. É previsto, inoltre, un dispositivo di sicurezza che consente al pilota di mantenere il controllo del veicolo qualora si verifichi il cedimento del suddetto elemento di misura. Per fornire un elaborato esaustivo, completo e non incentrato esclusivamente sugli aspetti teorici legati alla progettazione, la soluzione sviluppata è stata realizzata, installata a bordo di un motorscooter e provata in pista: ciò ha consentito di verificarne il funzionamento, valutarne la sensibilità e fornire le linee guida per le opportune ottimizzazioni

On the Multi-Interval Ulam-R\'enyi Game: for 3 lies 4 intervals suffice

We study the problem of identifying an initially unknown $m$-bit number by using yes-no questions when up to a fixed number $e$ of the answers can be erroneous. In the variant we consider here questions are restricted to be the union of up to a fixed number of intervals. For any $e \geq 1$ let $k_e$ be the minimum $k$ such that for all sufficiently large $m$, there exists a strategy matching the information theoretic lower bound and only using $k$-interval questions. It is known that $k_e = O(e^2)$. However, it has been conjectured that the $k_e = \Theta(e).$ This linearity conjecture is supported by the known results for small values of $e$. For $e\leq2$ we have $k_e = e.$ We extend these results to the case $e=3$. We show $k_3 \leq 4$ improving upon the previously known bound $k_3 \leq 10.$Comment: 31 pages, 5 figures, extension of the result to non-asymptotic strategie

General Defocusing Particle Tracking: fundamentals and uncertainty assessment

General Defocusing Particle Tracking (GDPT) is a single-camera, three-dimensional particle tracking method that determines the particle depth positions from the defocusing patterns of the corresponding particle images. GDPT relies on a reference set of experimental particle images which is used to predict the depth position of measured particle images of similar shape. While several implementations of the method are possible, its accuracy is ultimately limited by some intrinsic properties of the acquired data, such as the signal-to-noise ratio, the particle concentration, as well as the characteristics of the defocusing patterns. GDPT has been applied in different fields by different research groups, however, a deeper description and analysis of the method fundamentals has hitherto not been available. In this work, we first identity the fundamental elements that characterize a GDPT measurement. Afterwards, we present a standardized framework based on synthetic images to assess the performance of GDPT implementations in terms of measurement uncertainty and relative number of measured particles. Finally, we provide guidelines to assess the uncertainty of experimental GDPT measurements, where true values are not accessible and additional image aberrations can lead to bias errors. The data were processed using DefocusTracker, an open-source GDPT software. The datasets were created using the synthetic image generator MicroSIG and have been shared in a freely-accessible repository

Bubble-Flip---A New Generation Algorithm for Prefix Normal Words

We present a new recursive generation algorithm for prefix normal words. These are binary strings with the property that no substring has more 1s than the prefix of the same length. The new algorithm uses two operations on binary strings, which exploit certain properties of prefix normal words in a smart way. We introduce infinite prefix normal words and show that one of the operations used by the algorithm, if applied repeatedly to extend the string, produces an ultimately periodic infinite word, which is prefix normal. Moreover, based on the original finite word, we can predict both the length and the density of an ultimate period of this infinite word.Comment: 30 pages, 3 figures, accepted in Theoret. Comp. Sc.. This is the journal version of the paper with the same title at LATA 2018 (12th International Conference on Language and Automata Theory and Applications, Tel Aviv, April 9-11, 2018

VALUTAZIONE DEI LEGAMENTI INTRINSECI DEL POLSO CON ARTRO-RM

OBIETTIVO Questa tesi si prefigge di dimostrare la validità della metodica dell’artroRm nello studio delle lesioni a eziologia traumatica dei legamenti intrinseci del carpo e in particolare del legamento scafo-lunato ( SL) comparando i risultati ottenuti con le valutazioni dell’artroscopia. La lesione del SL è molto frequente in sportivi come sciatori o motociclisti, ma anche in persone comuni nel tentativo di ripararsi in una caduta, in incidenti in automobile per l’urto con il volante, etc,ed è dovuta alla posizione del polso in estensione e rotazione in senso radiale. L’eziologia è prevalentemente traumatica, però le perforazioni nel legamento possono essere presenti in pazienti asintomatici, e talvolta ritrovate in cadaveri senza nessun riscontro di ferita, frattura o dolore al polso, presenti raramente prima di 20 anni, e raggiungono circa il 50 % a 80 anni; la sezione completa del legamento determina un malallineamento con lo scafoide instabile prossimalmente, aumento della motilità radio-scafoidea e riduzione di quella del semilunare. MATERIALI E METODI Lo studio comprende 17 pazienti 15 uomini e 2 donne, con età compresa tra 18 e 65 anni( età media 39,2) con lesioni traumatiche di polso, i quali sono stati tutti prima visitati da un ortopedico e solo dopo sottoposti a artro-RM ( che prevede l’iniezione nel compartimento radio-carpale di gadolinio con diluizione 1\250) e viene seguita da copertura antibiotica profilattica. Le sequenze utilizzate sono state SPIN ECHO T1, SPIN ECHO T1 FAT SAT,STIR coronale, GRADIENT T2 coronale e assiale e SPIN ECHO 3d T2 coronale. RISULTATI Sono stati valutati segni diretti di lesione SL( riscontrate 2 lesioni parziali, 5 lesioni totali con monconi visualizzabili, 9 lesioni totali senza monconi visualizzabili, 1 riscontro di falso negativo) e segni indiretti di lesione SL( 12 casi di diastasi tra lo scafoide e il semilunare,3 lesioni condrali con fenomeni di sofferenza ossea subcondrale quali l’edema midollare e la presenza di geodi. Il tipo di instabilità più frequentemente riscontrata è tipo DISI( dorsal intercalated segmental instability) e 1 solamente VISI. CONLUSIONI La metodica non viene effettuata in tutti i centri di diagnostica per immagini e la casistica disponibile risulta essere inoltre limitata in quanto pazienti con trauma di polso vengono valutati con il solo esame rx e in alcuni casi con valutazione dinamica sotto esame amplioscopico. L’affidabilità della metodica è alta ma richiede esperienza interventistica da parte dell’operatore. Il valore aggiunto risulta costituito dalla possibilità di visualizzare contemporaneamente sia il contenente che il contenuto, cioè sia le strutture tendinee e le parti molli superficiali che le strutture capsulari, i legamenti intrinseci e i segmenti scheletrici, a cui si aggiunge l’utilità nei casi in cui non risulti apprezzabile diastasi scafo-lunata in condizioni statiche, in quanto l’introduzione del mezzo di contrasto determina separazione forzata dei due segmenti scheletrici consentendo la visualizzazione dei legamenti e delle loro eventuali lesioni. Il limite di questa metodica è che purtroppo non è dinamica e quindi non consente di valutare sotto stress l’articolazione come invece effettuano gli ortopedici sotto fluoroscopia e in fase artroscopica, individuando i casi di instabilità dinamica e consentendo, attraverso movimenti forzati dell’articolazione di distendere strutture legamentose che in condizioni statiche sono meno visualizzabili

Algorithms and Data Structures for Coding, Indexing, and Mining of Sequential Data

In recent years, the production of sequential data has been rapidly increasing. This requires solving challenging problems about how to represent information, how to retrieve information, and how to extract knowledge, from sequential data. These questions belong to the areas of coding, indexing, and mining, respectively. In this thesis, we investigate problems from those three areas. Coding refers to the way in which information is represented. Coding aims at generating optimal codes, that are codes having a minimum expected length. Codes can be generated for different purposes, from data compression to error detection/correction. The Lempel-Ziv 77 parsing produces an asymptotically optimal code in terms of compression. We study algorithms to efficiently decompress strings from the Lempel-Ziv 77 parsing, using memory proportional to the size of the parsing itself. We provide the first implementation of an algorithm by Bille et al., the only work we are aware of on this problem. We present a practical evaluation of this approach and several optimizations which improve the performance on all datasets we tested. Through the Ulam-R{'e}nyi game, it is possible to provide optimal adaptive error-correcting codes. The game consists of discovering an unknown $m$-bit number by asking membership questions the answers to which can be erroneous. Questions are formulated knowing the answers to all previous ones. We want to find an optimal strategy, i.e., a strategy that can identify any $m$-bit number using the theoretical minimum number of questions. We studied the case where questions are a union of up to a fixed number of intervals, and up to three answers can be erroneous. We first show that for any sufficiently large $m$, there exists a strategy to identify an initially unknown $m$-bit number which uses at most four intervals per question. We further refine our main tool to turn the above asymptotic result into a complete characterization of those instances of the Ulam-R{'e}nyi game that admit optimal strategies. Indexing refers to the way in which information is retrieved. An index for texts permits finding all occurrences of any substring, without traversing the whole text. Many applications require to look for approximate substrings. One of these is the problem of jumbled pattern matching, where two strings match if one is a permutation of the other. We study combinatorial aspects of prefix normal words, a class of binary words introduced in this context. These words can be used as indices for the Indexed Binary Jumbled Pattern Matching problem. We present a new recursive generation algorithm for prefix normal words that is competitive with the previous one but allows to list all prefix normal words sharing the same prefix. This sheds lights on novel insights that may help solving the problem of counting the number of prefix normal words of a given length. We then introduce infinite prefix normal words, and we show that one of the operations used by the algorithm, when repeatedly applied to extend a word, produces an infinite prefix normal word. This motivates the seeking for other operations that produce infinite prefix normal words. We found that one of these operations establishes a connection between prefix normal words and Sturmian words. We also explored the relationship between prefix normal words and Abelian complexity, as well as between prefix normal words and lexicographic order. Mining refers to the way in which information is converted into knowledge. The process of knowledge discovery covers several processing steps, including knowledge extraction. We analyze the problem of mining assertions for an embedded system from its simulation traces. This problem can be modeled as a pattern discovery problem on colored strings. We present two problems of pattern discovery on colored strings: patterns for one color only, or for all colors at the same time. We present two suffix tree-based algorithms. The first algorithm solves both the one color problem and the all colors problem. We then, introduce modifications which improve performance of the algorithm both on synthetic and on real data. We implemented and evaluated the proposed approaches, highlighting time trade-offs that can be obtained. A different way of knowledge extraction is based on the information-theoretic perspective of Pearl's model of causality. It has been postulated that the true causality direction between two phenomena A and B is related to the problem of finding the minimum entropy joint distribution between A and B. This problem is known to be NP-hard, and greedy algorithms have recently been proposed. We provide a novel analysis of one of the proposed heuristic showing that this algorithm guarantees an additive approximation of 1 bit. We then, provide a general criterion for guaranteeing an additive approximation factor of 1. This criterion may be of independent interest in other contexts where couplings are used

Observing and Verifying the Quantum Trajectory of a Mechanical Resonator

Continuous weak measurement allows localizing open quantum systems in state space, and tracing out their quantum trajectory as they evolve in time. Efficient quantum measurement schemes have previously enabled recording quantum trajectories of microwave photon and qubit states. We apply these concepts to a macroscopic mechanical resonator, and follow the quantum trajectory of its motional state conditioned on a continuous optical measurement record. Starting with a thermal mixture, we eventually obtain coherent states of 78% purity--comparable to a displaced thermal state of occupation 0.14. We introduce a retrodictive measurement protocol to directly verify state purity along the trajectory, and furthermore observe state collapse and decoherence. This opens the door to measurement-based creation of advanced quantum states, and potential tests of gravitational decoherence models.Comment: 20 pages, 4 figure

Monetary Policy under Rule-of-Thumb Consumers and External Habits

This paper develops and estimates a simple New Keynesian Dynamic Stochastic General Equilibrium (DSGE) model with rule-of-thumb consumers and external habits. Our theoretical model has a closed-form solution which allows the analytical derivation of its dynamical and stability properties. These properties are analyzed and discussed in the light of their implications for the efficacy and the calibration of the conduct of the monetary policy. The model is then evaluated empirically, employing numerical simulations based on Monte Carlo Bayesian estimates of the structural parameters and impulse response analyses based on weakly identified SVECMs. The estimates are repeated for each of the G7 national economies. Providing single country estimates and simulations, we derive some indications on the relative efficacy of monetary policy and of its potential asymmetric effects resulting from the heterogeneity of the estimated models.Rule-of-thumb, habits, monetary policy transmission, price puzzle, DSGE New Keynesian model, monetary policy, SVECM and Monte Carlo Bayesian estimators.

Monetary Policy, Rule-of-Thumb Consumers and External Habits: An International Comparison

This paper extends the standard New Keynesian dynamic stochastic general equilibrium (DSGE) model to agents who cannot smooth consumption (i.e. spenders) and are affected by external consumption habits. Although these assumptions are not new, their joint consideration strongly affects some theoretical and empirical results addressed by the recent literature. By deriving closed-form solutions, we identify different demand regimes and show that they are characterized by specific features regarding dynamic stability and monetary policy effectiveness. We also evaluate our model by stochastic simulations obtained from the Bayesian parameters estimates for the G7 economies. From posterior impulse response we address the empirical relevance of the different regimes and provide comparative evidence on the asymmetric effects of monetary policy, resulting from the heterogeneity of the estimated model structures.Rule-of-thumb, habits, monetary policy transmission, determinacy, New Keynesian

Monetary Policy, Rule-of-Thumb Consumers and External Habits: A G7 Comparison

This paper extends the standard New Keynesian dynamic stochastic general equilibrium (DSGE) model to agents who cannot smooth consumption (i.e. spenders) and are affected by external consumption habits. Although these assumptions are not new, their joint consideration strongly affects some theoretical and empirical results addressed by the recent literature. By deriving closed-form solutions, we identify different demand regimes and show that they are characterized by specific features regarding dynamic stability and monetary policy effectiveness. We also evaluate our model by stochastic simulations obtained from the Bayesian parameters estimates for the G7 economies. From posterior impulse responses we address the empirical relevance of the different regimes and provide comparative evidence on the heterogeneity of monetary policy effects among countries.Rule-of-thumb, habits, monetary policy transmission, determinacy, New Keynesian DSGE model, monetary policy, Monte Carlo Bayesian estimators.