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Analisi termica di motori a magneti permanenti per applicazioni ascensoristiche
No full textIn questa tesi è stato studiato un motore sincrono a magneti permanenti ed è stata creata una rete termica a parametri concentrati per poter effettuare studi termici. Il modello creato è supportato da test sperimentali che hanno contribuito alla calibrazione e alla validazione del modello stesso. Sono quindi riportati i risultati ottenuti sia con il modello sia sperimentalmente con le dovute considerazioni riguardo la loro bontà
Regolazione del mercato farmaceutico: un'analisi delle politiche di prezzo e rimborsabilità in Europa e in Italia
Full text linkLa Macchina di Antikythera e il Realismo di Tolomeo
Full text linkChe nella stesura della sua opera fondamentale, l’Almagesto, Caludio Tolomeo abbia attinto dai risultati dell’astronomia ellenistica è fatto acclarato. L’esistenza di alcuni antichi manufatti quali la Macchina di Antikythera sembrano, però, in contraddizione con alcune affermazioni presenti nell’Almagesto circa lo stato delle conoscenze sul cosmo raggiunto dai pensatori del IV-I secolo a.C. Scopo della presente disamina è quello di approfondire il rapporto tra Tolomeo e le sue fonti ellenistiche, indagando se egli avesse o meno coscienza dell’esistenza di una teoria planetaria antecedente il suo lavoro.
It is well known that in drafting his fundamental work, the Almagest, Caludius Ptolemy drew on the results of Hellenistic astronomy. The existence of some ancient artifacts such as the Antikythera Mechanism seem in contradiction with some statements in the Almagest about the state of knowledge on the cosmos reached by thinkers of the IV-I century BC. The purpose of this work is to deepen the relationship between Ptolemy and his Hellenistic sources, investigating whether or not he was aware of the existence of a planetary theory prior to his work
Wandering in the cosmological consistency relations: a critical assessment
Full text linkAbstract in inglese:
The thesis project deals with the so-called cosmological consistency relation, as predicted by inflationary models of the Early Universe. Such relation links the primordial power spectrum of the so-called comoving curvature perturbation (a gauge-invariant measure of primordial density perturbations) or the tensor perturbations (i. e. primordial gravitational waves) with the corresponding bispectrum (the Fourier counterpart of the 3-point function), in the so-called squeezed limit, which means sending one momentum to zero in the 3-point correlator. This property is phenomenologically very important, since it holds in any single-field model of inflation, but many other models of inflation (such as multi-field inflation) do not respect it. This implies that a measurement of a deviation from the consistency relation would authomatically rule out all single-field models of inflation. However, some works have recently claimed that this relation is trivial and non-physical, because according to them the squeezed bispectrum can be set to zero through an appropriate gauge transformation. In this work we introduce all the tools necessary to discuss this issue, but we also provide some arguments that this cancellation argument is not valid and this
relation indeed remains observable and phenomenologically very interesting. More specifically, the impossibility to cancel mixed bispectra involving the scalar curvature and the tensor perturbations of the metric is presented for the first time in this work. Abstract in italiano:
Questo progetto di tesi discute le cosiddette relazioni di consistenza inflazionarie, predette da alcuni modelli d'inflazione dell'universo primordiale. Questa relazione lega lo spettro di potenza primordiale della cosiddetta perturbazione comovente della curvatura (ovvero una misura gauge invariante della perturbazione primordiale della densità) o le perturbazioni tensoriali della metrica (ovvero le onde gravitazionali primordiali) con il corrispondente bispettro (ovvero la controparte della funzione di correlazione a 3 punti nello spazio di Fourier), nel cosiddetto limite squeezed, ovvero quando uno dei tre momenti tende a zero nel correlatore. Questa proprietà è fenomenologicamente molto importante, poiché vale in ogni modello di inflazione a singolo campo, ma altri modelli inflazionari la violano (fra cui i modelli a più campi). Ciò implica che una misura di una deviazione dalla relazione di consistenza eliminerebbe automaticamente tutti i modelli a singolo campo come candidati a descrivere l'Universo primordiale. Tuttavia, alcuni recenti lavori hanno proposto che la relazione di consistenza non sia fisicamente misurabile, in quanto hanno portato argomenti che dimostrano come il bispettro si annulli attraverso un'appropriata trasformazione di gauge. In questo lavoro di tesi sono introdotte tutte le basi necessarie a discutere la questione, ma inoltre vengono proposti argomenti a sostegno del fatto che l'argomento di
cancellazione non sia corretto, cosicché la relazione di consistenza rimanga osservabile e fenomenologicamente molto interessante. In particolare, l'impossibilità di cancellare bispettri misti, ovvero contenenti anche perturbazioni tensoriali, è presentata per la prima volta in questo lavoro
High-resolution video characterisation of vulcanian plumes at Sabancaya Volcano, Peru
No full textSince November 2016, volcanic activity at Sabancaya volcano (Peru) has been characterized by multiple short-lived Vulcanian explosions per day. These Vulcanian-type explosions and related volcanic plumes were also recorded in visible light during July and August 2018. Specific objectives of this work are to: i) develop a new algorithm to identify and isolate the plume pixels; ii) extract the main geometrical parameters of the eruptive column, such as the height and width as a function of time; iii) determine quantitative information related to the plume motion (e.g. the rise velocity and air entrainment coefficient), based on the physical quantities obtained through the first-order analysis; iv) characterize the eruption dynamics of Vulcanian plumes at Sabancaya. The results show that the algorithm traces well the plume boundaries and is also capable of automatically calculating the geometrical parameters (height of the top, maximum width and rise velocity of the plume head). We focussed on 8 explosions that are characterized by optimal weather and plume rise conditions. The calculated height for these selected explosions ranges from 180 to 715 m within 30 seconds after ejection, while the exit velocities are up to 96.5 m/s. The air entrainment coefficients were also estimated, and lie around 0.15 ± 0.04. Moreover, we found that plumes at Sabancaya have a transient/thermal behaviour, dominated by an unsteady release of pyroclastic material that strongly controls its features and evolution. Thus, high resolution video analysis, quantitative measurements and numerical modelling are merged here to improve the understanding of volcanic explosions at Sabancaya volcano and of volcanic plumes in general
Evaluation of biomarkers in the European nightcrawler Dendrobaena veneta exposed to PFAS under controlled conditions
No full textFrom the scientific relevance findings concerning the PFASs effects, it is necessary to extend the scientific knowledge about their effects on organisms in the natural environment. In the present research study, different stress biomarkers have been evaluated to assess the possible effects that PFASs' mixtures at environmentally detected concentrations may have on Dendobaena veneta. The results show that, in the short term (30 days), PFASs induce an increase in ROS levels and consequent increase in genomic damage. Moreover, PFASs tend to reduce the organisms antioxidant capacity and enhances both transcriptional and translational levels of metallothioneins
Adaptive evolution strategies for black box optimization
Full text linkOptimization of black-box functions has been of interest to researchers for
many years and has become more relevant since the advent of reinforcement learning problems, which goes along with the development of machine learning. One of the ways used to tackle the problem is the use of evolutionary strategy algorithms. These are able to optimize the given function without the need to compute the gradient of the function itself, which is the main problem while dealing with black-box functions, and they also have theoretical guarantees for their ability to converge to an optimum. After a brief discussion of state-of-the-art algorithms, in this thesis a novel algorithm is presented and compared to them. The algorithm, called ASHGF, implements adaptivity of parameters to escape local global minima and use of historical gradients in order to deal with the exploration-exploitation trade-off. Some theoretical results are given, and it is further numerically validated. All the algorithms are first compared on a standard testbed and then on a set of reinforcement learning problems. It will be shown that the algorithm can outperform all the other state-of-the-art algorithms
