Tecniche di progetto di sistemi radar per la rivelazione di detriti spaziali

L’obiettivo di questo lavoro sarà quindi quello di inquadrare il problema relativo agli scenari attuali e alle proiezioni future degli space debris individuando quindi quelli scenari considerati di maggior interesse. Successivamente verranno presentate una serie di simulazioni, adottando un software della NASA, che forniranno dati concreti sulla popolazione dei detriti relativamente alle ipotesi fatte in precedenza. La chiave di questa tesi sarà però la simulazione della RCS (Radar Cross Section) dei detriti orbitanti descritta nel terzo capitolo e che ci fornirà un possibile ventaglio di tali valori espressi in dBsm. Tali simulazioni verranno fatte per semplici strutture al variare della frequenza e dell’angolo di vista; molta importanza verrà data alla simulazione della sfera che permetterà di valutare la correttezza di tali simulazioni. Poi, anche mediante lo studio di alcuni sensori esistenti, si andranno a ricercare le caratteristiche ottimali per la loro rivelazione. Verranno infine individuate alcune frequenze ottime per la rivelazione degli space debris e che verranno usate in seguito come base per la stima dei parametri del radar. Come appena accennato si studieranno le caratteristiche di alcuni elementi radianti di possibile utilizzo valutandone geometrie e guadagni e verranno quindi esaminati tutti i parametri del radar alle frequenze scelte. Questo ci porterà alla fase del lavoro che prevede l’inserimento di tutti i dati fin qui collezionati nell’equazione del radar per stilare una tabella sulle potenze di picco necessarie per effettuare la rivelazione di detriti di determinata taglia, ad una data frequenza, in regioni di spazio ben precise e con caratteristiche altrettanto precise sul tipo di sensore. La fase conclusiva del lavoro prevede uno studio sulle caratteristiche dei sistemi radar di tipo bistatici (con estensione al caso multistatico) per la rivelazione dei detriti spaziali. Tale trattazione risulterà necessaria per comprendere come poter applicare le caratteristiche di questi sistemi in un contesto nazionale per la realizzazione di una “Network” in grado di coadiuvare lo studio di questo fenomeno

Liquid and gas products from lead acid battery (LAB) derived plastics via pyrolysis: a techno-economic assessment to maximize the value

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Malattia, salute, salvezza nei Dialogi di Gregorio Magno

Il concetto di malattia/male della società costituisce il leit-motiv dei quattro libri dei Dialogi di Gregorio Magno, declinandosi in carestie, calamità naturali, invasioni, guerre, interventi del demonio, ma soprattutto in patologie fisiche e psichiche contro le quali sono chiamati ad intervenire i viri Dei, in veste di medici speciali mandati da Dio. Il contributo è frutto di un’indagine preliminare, finalizzata ad inquadrare il significato della malattia nel sistema religioso-culturale dell’opera. Ne emerge che, superando la prospettiva agiografica, il discorso sulla malattia attiene ad un più ampio progetto teologico-dottrinale perseguito dall’autore, il cui sguardo è rivolto non tanto alla salute del corpo, quanto alla salvezza dell’anima

Photonic generation of phase-modulated RF signals for pulse compression techniques in coherent radars

A novel and flexible photonics-based scheme is proposed for generating phase-coded RF pulses suitable for coherent radar systems with pulse compression techniques. After selecting two modes from a mode-locked laser (MLL), the technique exploits an optical in-phase/quadrature modulator driven by a low-sample rate and low-noise direct digital synthesizer to modulate the phase of only one mode. The two laser modes are then heterodyned in a photodiode, and the RF pulse is properly filtered out. The scheme is experimentally validated implementing a 4-bit Barker code and a linear chirp on radar pulses with a carrier frequency of about 25 GHz, starting from an MLL at about 10 GHz. The measures of phase noise, amplitude- and phase-transients, and autocorrelation functions confirm the effectiveness of the scheme in producing compressed radar pulses without affecting the phase stability of the optically generated high-frequency carriers. An increase in the radar resolution from 150 to 37.5 m is calculated. The proposed scheme is capable of flexibly generating software-defined phase-modulated RF pulses with high stability, even at very high carrier frequency, using only a single commercial device with potentials for wideband modulation. It can therefore allow a new generation of high-resolution coherent radars with reduced complexity and cost. © 1983-2012 IEEE

Photonic Technologies for Radar and Telecomunications Systems

The growing interest in flexible architectures radio and the recent progress in the high speed digital signal processor make a software defined radio system an enabling technology for several digital signals processing architecture and for the flexible signal generation. In this direction wireless radar\telecommunications receiver with digital backend as close as possible to the antenna, as well as the software defined signal generation, reaches several benefits in term of reconfigurabilty, reliability and cost with respect to the analogical front-ends. Unfortunately the present scenario ensures direct sampling and digital downconversion only at the intermediate frequency. Therefore these kinds of systems are quite vulnerable to mismatches and hardware non-idealities in particular due to the mixers stages and filtering process. Furthermore, since the limited input bandwidth, speed and precision of the analog to digital converters represent the main digital system‘s bottleneck, today‘s direct radio frequency sampling is only possible at low frequency. On the other hand software defined signals can be generated exploiting direct digital synthesizers followed by an up-conversion to the desired carrier frequency. State-of-the-art synthesizers (limited to few GHz) introduce quantization errors due to digital-to-analog conversion, and phase errors depending on the phase stability of their internal clock. In addition the high phase stability required in modern wireless systems (such as radar systems) is becoming challenging for the electronic RF signal generation, since at high carrier frequency the frequency multiplication processes that are usually exploited reduce the phase stability of the original RF oscillators. Over the past 30 years microwave photonics (MWP) has been defined as the field that study the interactions between microwave and optical waves and their applications in radar and communications system as well as in hybrid sensor‘s instrumentation. As said before software defined radio applications drive the technological development trough high speed\bandwidth and high dynamic range systems operating directly in the radio frequency domain. Nowadays, while digital electronics represent a limit on system performances, photonic technologies perfectly engages the today‘s system needs and offers promising solution thanks to its inherent high frequency and ultrawide bandwidth. Moreover photonic components with very high phase coherence guarantees highly stable microwave carriers; while strong immunity to the electromagnetic interference, low loss and high tunability make a MWP system robust, flexible and reliable. Historical research and development of MWP finds space in a wide range of applications including the generation, distribution and processing of radio frequency signals such as, for example, analog microwave photonic link, antenna remoting, high frequency and low noise photonic microwave signal generation, photonic microwave signal processing (true time delay for phased array systems, tunable high Q microwave photonic filter and high speed analog to digital converters) and broadband wireless access networks. Performances improvement of photonic and hybrid devices represents a key factor to improve the development of microwave photonic systems in many other applications such as Terahertz generation, optical packet switching and so on. Furthermore, advanced in silicon photonics and integration, makes the low cost complete microwave photonic system on chip just around the corner. In the last years the use of photonics has been suggested as an effective way for generating low phase-noise radio frequency carriers even at high frequency. However while a lot of efforts have been spent in the photonic generation of RF carriers, only few works have been presented on reconfigurable phase coding in the photonics-based signal generators. In this direction two innovative schemes for optically generate multifrequency direct RF phase modulated signals have been presented. Then we propose a wideband ADC with high precision and a photonic wireless receiver for sparse sensing. This dissertation focuses on microwave photonics for radar and telecommunications systems. In particular applications in the field of photonic RF signal generation, photonic analog to digital converters and photonic ultrawideband radio will be presented with the main objective to overcome the limitations of pure electrical systems. Schemes and results will be further detailed and discussed. The dissertation is organized as follows. In the first chapter an overview of the MWP technologies is presented, focusing the attention of the limits overcame by using hybrid optoelectronic systems in particular field of applications. Then optoelectronic devices are introduced in the second chapter to better understand their role in a MWP system. Chapters 3,4, and 5 present results on photonic microwave signal generation, photonic wideband analog to digital converters and photonic ultrawideband up\down converter for both radar and telecommunications applications. Finally in the chapter 6 an overview of the photonic radar prototype is given

Phase coding of RF pulses in photonics-aided frequency-agile coherent radar systems

An innovative optical scheme to generate software-defined phase-modulated radio frequency (RF) pulses with carrier frequency agility from a mode-locked laser (MLL) is proposed. The technique exploits a direct digital synthesizer and a Mach-Zehnder modulator to apply an intermediate frequency modulation to the MLL's modes. The heterodyne detection of the optical signal allows the generation of amplitude- and phase-modulated RF carriers with very high phase stability, suitable for coherent radar applications. Further, a single MLL can be used to generate carriers simultaneously at different frequencies, enabling frequency hopping or multifunctional radars, with no need to increase the complexity of the transmitter. Results show chirped and Barker-coded pulses at around 10 or 40 GHz in a single setup, without any performance degradation while increasing the carrier frequency. The proposed technique allows the practical realization of compressed pulses for coherent radars over a wide carrier frequency range, allowing the development of software-defined radar systems with improved functionalities. © 1965-2012 IEEE

Il fantastico di essere donna: spose, massaie e madri nell'opera di Paola Masino

This article focuses on the uncanny of women’s bodies in Paola Masino’s works and aims to show how Masino’s rhetorical devices and writing style reflected Freud’s Unheimliche.L’articolo si propone di rintracciare il topos del corpo femminile perturbante nella narrativa di Paola Masino, le cui eroine in negativo ricoprono per lo più i ruoli banalissimi e prosaici di spose, massaie e madri. Se da un lato le metamorfosi del femminile si riducono nell’opera di questa autrice al loro grado zero – contro la varietà di apparizioni diaboliche ed epifanie angeliche che caratterizzano la rappresentazione della donna nella letteratura del fantastico e del soprannaturale –  dall’altro la scrittura che ne descrive le trasfigurazioni mette in scena una retorica della metafora e dell’allegoria che interpreta l’essere come caduta e il corpo come condanna e sofferenza della carne. Così come il corpo femminile appare martoriato dall’inchiesta sul male e sul peccato e dal processo intentato a quelle forme di potere che costringono la donna al sacrificio della propria vita e all’annullamento di sé, anche il corpo della scrittura, implodendo nell’accumulazione caotica delle sue figure, manifesta il rapporto tormentato che lega la scrittrice alla creazione artistica, fino alla competizione e alla rivalità con la divinità creatrice, maschile e paterna

Technical, economic and environmental assessement of bioethanol biorefinery from waste biomass

This study presents a sequential three-steps methodology for the technical, economic and environmental assessment (TEEA) of bioethanol production from waste biomass. In EU the most abundant waste biomasses produced in 2018 could be ascribed to three main categories: lignocellulosic (329.41 Mt), starch (160 Mt) and sugar-based (58.56 Mt). The technical assessment compiled an inventory of the waste biomasses and subsequently designed their biological conversion into ethanol through integrated biorefinery processes by means of material flow analysis (MFA); the economic assessment was aimed at the definition of the cut-off size of the biorefinery plant necessary to achieve profitability; the environmental assessment was based on Life Cycle Analysis (LCA) and energy balance (i.e. energy input consumption). For each of the three waste biomass categories, at least one that was significant as available amount and representative in terms of physico-chemical characteristics, was evaluated: sugarcane for sugar-based, potatoes for starch-based and rice straw, cattle manure and organic fraction of municipal solid waste (OFMSW) for lignocellulosic biomasses. The technical assessment of the biorefinery routes lead to the following yields (kg of bioethanol per kg of biomass): 0.16, 0.17, 0.22, 0.19 and 0.14 respectively. The economic profitability was reached by all biorefineries and Net Present Value (M€) were: 0.85 for sugarcane, 0.11 for potatoes, 0.09 for rice straw, 0.11 for cattle manure and 0.39 for OFMSW. From the environmental perspective, cattle manure reached the highest reduction of climate change and acidification impacts compared to other biomasses, while sugarcane achieved the lowest energy input consumption (around 64%)

«Il desiderio è tutto» Voglie, fantasie, ossessioni di collezionisti e antiquari

The aim of this essay is to intersect the figures of the collector and the antiquarian with the dynamics of desire, and identify the possible connections between the three themes. Therefore, a thematic and comparative approach was chosen, while the sample text were drawn from the Italian literature of the late nineteenth and twentieth centuries. The textual analysis will reveal the various desires moving collectors and antiquarians in search of the items that make up their collections: greed, pathological need of wealth, fantasies of martyrdom, love, ambition to excel, dreams of omnipotence, libido, jealousy, Illusion of immortality, attraction to the perverse, flâneuristic curiosity. But at the top of this list there is undoubtedly the desire to listen to literature’s description of life.Lo scopo che si propone questo saggio è far interagire le figure del collezionista e dell’antiquario con le dinamiche del desiderio e individuare le possibili connessioni esistenti fra i tre temi. Si è scelto dunque di adottare un approccio di analisi dei testi di tipo tematico e comparatistico e di privilegiare un campione di esempi tratti dalla narrativa italiana di fine Ottocento e Novecento, non trascurando di mostrare come gli scrittori presi in esame oscillino fra il consapevole riferimento alla tradizione letteraria e il tentativo di tracciare percorsi originali di rivisitazione e riscrittura. L’analisi testuale rivelerà i desideri disparati che muovono collezionisti e antiquari alla ricerca dei reperti che compongono le loro collezioni: avidità maniacale, bisogno patologico di ricchezza, fantasie di martirio, amor proprio, ambizione di eccellere, sogni di onnipotenza, libido, gelosia, illusione di immortalità, attrazione per il perverso, curiosità da flâneur. Ma in cima a questo elenco vi è senza dubbio il desiderio di ascoltare il racconto che la letteratura può fare della vita