Comparative Analysis among DSP and FPGA-based Control Capabilities in PWM Power Converters

PWM power converters are close to be mature for standard diffusion. New FPGA technologies could now realise at best the digital control key-points: flexible performance and time to market. The paper deals with the new digital control properties of FPGA-based techniques. On the basis of reference structures, a comparative analysis is carried-out trading-off dynamic performances and immunity to PWM environment. All possible sampled control or DSP techniques are firstly analysed and compared to each other. A breakthrough concept for FPGAs is defined, definitely solving for PWM feedback immunity by practical over-sampling and parallel processing while improving dynamic performances. Simulation tests and the application of dead-beat control clearly point-out the respective dynamic properties

Tecniche di mitigazione del multipath in sistemi di posizionamento satellitari

La precisione nel processo di misura della distanza (range) satellite-utente effettuata dal ricevitore di un sistema satellitare di posizionamento è limitata da una serie di fenomeni legati principalmente alla propagazione del segnale di navigazione trasmesso dai satelliti. Gli effetti di alcuni di questi fenomeni sono tenuti in considerazione e corretti dal ricevitore tramite l’utilizzo di modelli standard o di altri metodi. Il fenomeno del multipath si riferisce all’esistenza di ulteriori cammini di propagazione del segnale oltre a quello diretto (line of sight) dovuti principalmente a riflessioni su ostacoli di varia natura; in questo caso al ricevitore sono presenti più repliche sovrapposte del medesimo segnale, caratterizzate da ritardi diversi l’uno dall’altro. Dato che i ricevitori standard sono progettati per sincronizzarsi con una sola replica di segnale, il multipath introduce un errore nelle misure di pseudorange che a seconda degli scenari può assumere valori anche dell’ordine delle decine di metri. In questa Tesi viene investigata la potenziale applicazione di alcuni algoritmi di stima dei parametri di canale come tecniche per la mitigazione degli effetti del multipath in un contesto di positioning. Nei capitoli I e II vengono spiegati i principi di funzionamento di un generico sistema di navigazione satellitare e descritte le diverse componenti del GPS e del futuro sistema GALILEO insieme alle loro principali caratteristiche tecniche. Nel capitolo III viene fornita una caratterizzazione del comportamento in ambiente multipath dei ricevitori dotati di circuiti di sincronizzazione convenzionali, ovvero basati sul DLL; a tale scopo vengono ricavate le curve degli errori di pseudorange indotti dal multipath tramite anche l’ausilio di simulazioni di un DDLL per il caso di canale statico a due raggi. Nel capitolo IV vengono presentati due algoritmi iterativi per la stima di canale basati sul principio della stima a massima verosimiglianza e utilizzati originariamente nei campi dell’array processing e dei sistemi di comunicazione radio mobili. In particolare, dopo le adeguate modifiche, verrà studiata la potenziale applicazione di uno dei due in un ricevitore per sistemi di navigazione e i risultati ottenuti dalle simulazioni di laboratorio saranno confrontati con i corrispondenti risultati ottenuti per il DDLL nel capitolo precedente

Optical Nanofibers for Multiphoton Processes and Selective Mode Interactions with Rubidium

Optical nanofibers (ONFs) interfaced with atoms have found numerous applications for the development of quantum technologies. They feature a strong evanescent held at their waist, thereby providing an intense and tightly focused beam over long distances. Thiscan be used to achieve strong interactions between light and matter, enabling trapping, probing, and control of atoms along the waist. However, little experimental work has been done with the higher-order fiber guided modes (HOM). These feature inhomogeneous polarization distributions around the waist and some carry more than h of angular momentum (AM). Owing to the intense held gradient in their evanescent held, ONFs make excellent platforms to excite quadrupole-allowed transitions which could be used to store high-density information encoded on the AM of guided light. We predicted a transition probability up to 6 times stronger than for free-space beams using the fundamental mode and up to 4 times stronger using linearly polarized HOMs. We also studied a singlecolor, two-photon transition at 993 nm between the 5SI/2 and 6S1/2 atomic levels in a hot rubidium vapor and showed its suitability as a frequency reference. We experimentally verihed the particular selection rules for this transition and showed that they may be used to characterize the polarization at the waist of an ONF embedded in a cloud of atoms formed by a magneto-optical trap. Finally, we developed a method to generate HOM-likebeams in free-space, inject them into an ONF, and decompose the modal excitation at the output via transfer matrix calculation. This approach combined with absorption of guided-light by cold atoms may be used to infer the mode excitation at the waist and allow us to selectively excite HOMs.Okinawa Institute of Science and Technology Graduate Universit

The complexity of the climate-economy nexus: agent-based modelling and policy evaluation

While the consensus on the urgency of climate actions has grown in the last decades, what is the pathway to be followed to translate proposal into actions is still argument of debates in the climate change economics literature. Most economists believe that carbon pricing is the main and the most efficient option to reduce GHGs emissions, however a growing number of works point out that this result is highly dependent on the type of model used, claiming the superiority of a policy mix when a more realistic representation of the economy is used. My research work deals with the study of different climate policies with a complex system science approach, in particular, using the Eurace macroeconomic agent-based model. This work has two main objectives: first, to test the common belief that the carbon tax policy is the main and powerful instrument we have to induce the desired climate transition; second, to study the policy mix problem within the Eurace model economy, in particular, a mix of a carbon tax and a feed-in tariff policy. I enriched the Eurace model with a new agent, the climate module, to account for the climate-economy feedback. The economy affects the climate through greenhouse gas emissions from fossil fuels use for the energy production while the climate affects the economy damaging physical capital, with damages dependent on the temperature anomaly. Moreover, I introduced heterogeneity in the capital good sector, in order to include energy intensity improvements as a factor of technological change. In order to establish a relation between real world and model quantities, I followed an initialization procedure based on imposing physical constraints on model's quantities. I have developed an extended multi-criteria analysis method to evaluate policies performance accounting for both multiple objectives and variability of the outcomes of computational experiments. To pursue the research objectives I performed a set of computational experiments with the Eurace model, in which I analyzed a carbon tax policy, a feed-in tariff policy, and a mix of the two policies. Results of computational experiments show that the carbon tax is not the best performing climate policy when analyzed with the Eurace model, both the feed-in tariff and the policy mix perform better. This result is independent from the presence of climate damages. In absence of climate damages the PM performs better than its components, however, climate damages reduce the positive effects of the interaction between the components leading to higher economic costs for the same emission reduction obtained. According to the extended multi-criteria analysis, in presence of climate damages, the feed-in tariff policy is almost always preferred to the policy mix

Il canto di Agatone nelle 'Tesmoforiazuse': ‘deificazione’ della musica e vanificazione del contenuto

Il lavoro propone una correzione o revisione della valutazione espressa più di 40 anni fa daP.Rau (‘Paratragodia’) sul canto di Agatone nelle ‘Tesmoforiazuse’ (vv. 101-29): valutazione alla quale sostanzialmente si attiene tuttora la maggioranza, se non la totalità degli studiosi. Secondo Rau la parodia riguarderebbe essenzialmente il ritmo e la musica (edonistica, virtuosistica), mentre sotto l’aspetto degli usi linguistici lo stile risulterebbe perfettamente appropriato al tipo di canto. Attraverso una puntuale analisi si mette in evidenza che a essere presi di mira, insieme agli aspetti musicali, sono anche quelli linguistico-espressivi e contenutistici, caratterizzati da un’estrema elaborazione formale, ma assolutamente vacui ed inconsistenti sul piano concettuale.This work aims at correcting and revising the judgement passed more than forty years ago by P.Rau (‘Paratragodia’) on Agathon s’ song in ‘Thesmophoriazusae’ (vv. 101-129), judgement shared even to these days by the majority, if not by the totality of scholars. According to Rau, parody would concern essentially rhythm and music (from an edonistic, virtuosistic point of view), while as regards the linguistic choice, the style would appear perfectly appropriate to this type of song. Through a detailed analysis we highlight the fact that, together with musical, linguistic-expression and aspects of content are targeted since they are characterized by an extreme formal working out, but they are absolutely empty and inconsistent on a conceptual level

I Nuovi dati sull'Eneolitico sardo dagli scavi 1993 nella necropoli di Filigosa-Macomer (NU)

I relativamente poco numerosi ma interessanti frammenti ceramici prenuragici rinvenuti negli scavi 1993 della necropoli di Filigosa permettono alcune considerazioni sulla fine del Neolitico e sull'avvento dell'età del Rame, in cui, a seguito di influssi esterni, appaiono elementi culturali precedentemente sconosciuti come la metallurgia, il santuario e le muraglie difensive. Nelle tombe di Filigosa, a differenza degli insediamenti Monte Claro, che secondo l'Autrice furono costruiti da invasori, si è riscontrata una presenza prevalente di materiali che, pur essendo innovativi rispetto alla cultura di Ozieri, ne mantengono la tradizione. Il ritrovamento di un'ansa a canale decorata con festone dentellato di stile Ozieri "rigido", che si confronta con le ceramiche della tomba di Janna Ventosa, e la comune presenza del focolare nell'anticella e del dromos, forniscono un aggancio fra la fine di Ozieri e il nascere di Abealzu-Filigosa

Individuality

Emerson’s thought played an important and well recognized role in the development of American pragmatism, but the role exerted by the Transcendentalist in some other philosophical European contexts was even more direct and incisive. On some circumstances, the “adventure” of Emerson’s seminal ideas carried out a journey to/from Europe whose “rebound effect” on the American context is useful to evaluate. The widely attested influence of Emerson on Nietzsche sets an expressive example of this outward/inwards journey; other plain indications suggest now to reconsider the Emerson-Bergson relation and the peculiar outcomes that this relation produced in James’ pragmatism. In this paper, the controversy between William James and Henri Bergson is considered as from the topic of individuality and the very similar way in which the two philosophers theorized its temporalistic and pluralistic constitution. Both of them have been deeply influenced by Emerson, even though in different measure and sometimes with different – if not diverging – philosophical results. Nevertheless, just their common reference to Emerson can contribute to a better understanding of their controversial relation and of the consequences of this relation on the development of James’ ethical views