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Innovative methodologies for the synthesis of large array antennas for communications and space applications.
No full textModern communication and space systems such as satellite communication devices, radars, SAR and radio astronomy interferometers are realized with large antenna arrays since this kind of radiating systems are able to generate radiation patterns with high directivity and resolution. In such a framework conventional arrays with uniform inter-element spacing could be not satisfactory in terms of costs and dimensions. An interesting alternative is to reduce the array elements obtaining the so called "thinned arrays". Large isophoric thinned arrays have been exploited because of their advantages in terms of weight, consumption, hardware complexity, and costs over their filled counterparts.
Unfortunately, thinning large arrays reduces the control of the peak sidelobe level (PSL) and does not give automatically optimal spatial frequency coverage for correlators. First of all the state of the art methodologies used to overcome such limitations, e.g., random and algorithmic approaches, dynamic programming and stochastic optimization algorithms such as genetic algorithms, simulated annealing or particle swarm optimizers, are analyzed and described in the introduction. Successively, innovative guidelines for the synthesis of large radiating systems are proposed, and discussed in order to point out advantages and limitations. In particular, the following specific issues are addressed in this work:
1. A new class of analytical rectangular thinned arrays with low peak sidelobe level (PSL). The proposed synthesis technique exploits binary sequences derived from McFarland difference sets to design thinned layouts on a lattice of P(P+2) positions for any prime P. The pattern features of the arising massively-thinned arrangements characterized by only P(P+1) active elements are discussed and the results of an extensive numerical analysis are presented to assess advantages and limitations of the McFarland-based arrays.
2. A set of techniques is presented that is based on the exploitation of low correlation Almost Difference Sets (ADSs) sequences to design correlator arrays for radioastronomy applications. In particular three approaches are discussed with different objectives and performances. ADS-based analytical designs, GA-optimized arrangements, and PSO optimized arrays are presented and applied to the synthesis of open-ended "Y" and "Cross" array configurations to maximize the coverage u-v or to minimize the peak sidelobe level (PSL). Representative numerical results are illustrated to point out the features and performances of the proposed approaches, and to assess their effectiveness in comparison with state-of-the-art design methodologies, as well. The presented analysis indicates that the proposed approaches overcome existing PSO-based correlator arrays in terms of PSL control (e.g., >1.0dB reduction) and tracking u-v coverage (e.g., up to 2\% enhancement), also improving the speed of convergence of the synthesis process.
3. A genetic algorithm (GA)-enhanced almost difference set (ADS)-based methodology to design thinned planar arrays with low-peak sidelobe levels (PSLs). The method allows to overcome the limitations of the standard ADS approach in terms of flexibility and performance. The numerical validation, carried out in the far-field and for narrow-band signals, points out that with affordable computational efforts it is possible to design planar array arrangements that outperform standard ADS-based designs as well as standard GA design approaches
Security Policy Enforcement in Service-Oriented Middleware
No full textPolicy enforcement, or making sure that software behaves in line with a set of rules, is a problem of interest for developers and users alike. In a single machine environment, the reference monitor has been a well-researched model for enforcing policies. However, applying the same reference model in distributed applications is complicated by the presence of multiple users and concerns, and by the dynamism of the system and policies.
This thesis deals with building, assessing and configuring a tool for distributed policy enforcement that acts at application runtime. In a service-oriented architecture setting, the thesis proposes a set of adaptive middleware controls able to enact policies across applications. A core contribution of this thesis is the first message-level enforcing mechanism for access and usage control policies across services. In line with the idea that no security mechanism can be perfect from the beginning, the thesis also proposes a method to assess and amend how correctly a security mechanism acts across a distributed system. Another contribution is the first method to configure an authorisation system to satisfy conflicting security and performance requirements. This approach is based on the observation that policy violations can be caused by inappropriately fitting the enforcing mechanisms onto a target system. Putting these three contributions together gives a set of middleware tools to enforce cross-service policies in a dynamic environment. These tools make the user in control over continuous and improvable security policy enforcement
Music signal processing for automatic extraction of harmonic and rhythmic information
No full textThis thesis is concerned with the problem of automatic extraction of harmonic and rhythmic information from music audio signals using statistical framework and advanced signal processing methods.
Among different research directions, automatic extraction of chords and key has always been of a great interest to Music Information Retrieval (MIR) community. Chord progressions and key information can serve as a robust mid-level representation for a variety of MIR tasks.
We propose statistical approaches to automatic extraction of chord progressions using Hidden Markov Models (HMM) based framework. General ideas we rely on have already proved to be effective in speech recognition.
We propose novel probabilistic approaches that include acoustic modeling layer and language modeling layer. We investigate the usage of standard N-grams and Factored Language Models (FLM) for automatic chord recognition.
Another central topic of this work is the feature extraction techniques. We develop a set of new features that belong to chroma family. A set of novel chroma features that is based on the application of Pseudo-Quadrature Mirror Filter (PQMF) bank is introduced. We show the advantage of using Time-Frequency Reassignment (TFR) technique to derive better acoustic features.
Tempo estimation and beat structure extraction are amongst the most challenging tasks in MIR community.
We develop a novel method for beat/downbeat estimation from audio. It is based on the same statistical approach that consists of two hierarchical levels: acoustic modeling and beat sequence modeling.
We propose the definition of a very specific beat duration model that exploits an HMM structure without self-transitions. A new feature set that utilizes the advantages of harmonic-impulsive component separation technique is introduced.
The proposed methods are compared to numerous state-of-the-art approaches by participation in the MIREX competition, which is the best impartial assessment of MIR systems nowadays
The economic well-being of married women in a comparative perspective: The effect of income, work and union on financial satisfaction.
No full textThe thesis looks at three major determinants of economic well-being of a modern woman: 1) individual financial resources 2) decisions about work and career, 3) the choice of partnership. The economic well-being is thus reflected in both individual achievements (income and work) and collective conditions (partnership). I compare the situation in five European countries- Italy, Denmark, France, United Kingdom and Ireland using the data on perceived individual financial satisfaction.
In the first chapter, I investigate how economic well-being of women changes with the presence of their personal income. Economics suggests various theories that explain the way family performs its functions and determine the well-being of its members. The theory of Gary Becker idealizes family seeing it as a rational unit where both wife and husband aim at the maximization of family resources. On the other hand, the bargaining perspective highlights that the household behaviour depends largely on family dynamics and a bargain between the partners. There is large empirical evidence against unitary models of household behavior and this chapter presents another contribution to the relevant empirics. I further enrich the analysis by: 1) incorporating the social context in explaining the bargaining between partners and woman’s economic well-being, 2) testing the unified model of household behaviour at different household income levels.
The second chapter goes beyond the current studies on woman’s economic independence. Economic theory is rather limiting because it relies only on income in explaining the economic well-being of women. The sociological perspective is broader because it encompasses the employment patterns, future career prospects and commitment to personal occupation (Gerson, 1993, Hakim, 2000). I employ diversity of work choices and career orientation in the analysis of woman’s economic well-being and her financial position within family. Career stability and attachment to work are analysed and compared to a choice of a more flexible path in various European countries. Flexibility is popular in globalized labour markets and is a frequent choice for women because it offers them the opportunity to balance work and family. But how much is it really beneficial for women themselves? I hypothesize that it is not relative incomes or pure employment that matter the most for woman’s economic wellbeing but more likely the choice of relatively continuous and full-time working careers. I also analyse the value of a full time homemaking as a career, so called ‘marriage career’ for woman’s well-being. The results are commented considering the potential intra-household dynamics.
In the third chapter, economic bargaining perspective is enriched with the transaction costs approach (Pollak, 1985) and the theories of money management (Pahl 1983, Treas 1993) to deal with the differences in income sharing between married and cohabiting couples. There is a growing tendency to see cohabitation as an equivalent alternative to marriage and I investigate how different these two unions are for woman’s economic well-being. The type of union as a governing structure is a collective determinant of woman’s economic well-being that adds to the bargaining process
General Aspects of Modified Theories of Gravity
No full textThe aim of this work is to investigate the both, some mathematical and physical general aspect of modified gravity, and, more specifically, the proprieties of viable, realistic models of modified gravity which can be used to reproduce the inflation and the dark energy epoch of universe today
Intertextuality and Intratextuality in the Pessoan Epic: Mensagem
No full textThe thesis is articulated in three main chapters which try to explore how the dynamics of intertextuality is translatable, within the Pessoan oevre, also in an intratextual manner. Actually, I tried to explore progressively how the system of literary genres combines with the Pessoan introjection and subversion of literary genres and models.
In the first chapter I focused on the relationships between the Sebastianist myth and the Portuguese imperialism both from a diachronic and synchronous perspective trying to pinpoint the consequences this issues acquire in a literary ambit. I took under consideration the relationship with the Camonian epic model and attempted to demonstrate that the revision of the Camoes' pattern stems from a much profounder need to revise the Lusitanian imperialistic ideal. Moreover, I have also scrutinezed the presence and the echoes of the European historical avant-gardes affecting Alvaro De Campos' Odes' epic tendencies.
The second chapter is more centered on the influence of some Victorian poets upon Mensagem's texturing and which is mainly perceivable through the analysis of some Victorian devises such as the use of "persona" developped by a few Victorian poets such as Robert Browning and futher on amplified by some modernist poets such as T.S. Eliot and Ezra Pound for instance and, emblematically exasperated by Pessoa in his distinguishing heteronymia. Interestingly, this feature reveals itself particularly pivotal to Mensagem's structuring as it affects the Pessoan weaving of his Luistanian modernist epic as well.
In the third chapter, I took under consideration the influence of brief genres upon Mensagem, some of which are typical of Classicism, such as epitaphs, epigrams, and epitaphs on Pessoa's epic imaginary. Furthermore, in spite of the undeniable ascendancy of fragment upon the Pessoan production, the bewitchment for classicism Pessoa shows in many critical essays finds a concrete form by the poetics of Antonio Mora, Alberto Caieiro and Ricardo Reis but also offers a possible interpretative chink in Mensagem as well
An Ecoritical Approach to Chaucer. Representations of the Natural World in the English Literature of the Middle Ages
No full textStarting from an introduction on ecocriticism the work traces the development of the idea and the representations of nature in the ancient world which so much influenced the Middle Ages; it focuses on the English world by offering an interpretation of the natural world in Beowulf, and draws conclusion on possible eco-oriented ideas of the relationship between humans and the natural world in the ancient Classic and in the Anglo-Saxon worlds. Then the work surveys representations of the natural world in the English Literature of the Middle Ages, considering the fundamental influence of the 12th century philosophical ideas and also offering various examples of different philosophical and cultural approaches to the idea and to the representation of nature and oh humanity's relation with it. From these premises the work finally proceeds to offer an eco-oriented interpretation of some of Chaucer's works: Troilus and Criseyde, the House of Fame, the Parlement of Foules, and a small selection from the Canterbury Tales. The study of these works shows how Chaucer, albeit not deeply or exclusively involved with the specific matter of an "ecological" idea of the relationship between humanity and nature (also due to the fact that culture in the Middle Ages was seen as a composite but at the same time monolithic system, with little disciplinary specialization), was definitely interested in the subject and in his portrait of human interior and social life both on an individual and on a collective level, he does not miss the chance to exhort his audience to keep an ethical behavior not only toward the other humans, but toward the natural world itself, which is the source for human life and human imagination alike
Structural-model experiments revealing bifurcation, instability and localization
No full textSmall scale experiments are invented to analyze several aspects of instability and bifurcation occurring in structures and within materials. Photoelasticity is employed to analyze the localization of stress in ordered granular materials and near stiff and thin inclusions embedded in an elastic matrix. Prototypes have been designed and realized of elastic structures evidencing buckling under tensile dead loading and flutter and divergence instabilities as related to dry friction. All the experiments have been performed at the Laboratory for Physical Modeling of Structures and Photoelasticity of the Department of Mechanical and Structural Engineering of the University of Trento
Synthesis, characterization, and field-test of nanocatalysts for hydrogen production by hydrolysis of chemical hydrides
No full textAbstract There is a growing concern related to increasing energy requirement and greenhouse gas emissions. Hydrogen gas is recognised as a desirable clean fuel and may be a sustainable solution. Hydrogen gas can be directly used as an anodic fuel for Proton Exchange Membrane Fuel Cell that converts chemical energy of hydrogen into electrical energy with no environmentally harmful by-products. Chemical hydrides with high hydrogen storage capacity in terms of gravimetric and volumetric efficiencies are the most promising candidates to supply pure hydrogen at room temperature. Among them, Sodium borohydride (SBH) and Ammonia borane (AB) have drawn a lot of interest as they are stable, non-flammable, nontoxic, and have a high hydrogen storage capability. Large amount of pure hydrogen gas is released during the hydrolysis of these chemical hydrides in presence of certain catalysts. The by-products are non-toxic, environmentally safe and can be recycled. Noble catalysts like Pt and Pd, used in the past to enhance the hydrogen production rate, do not seem to be viable for industrial application considering their cost and availability. Co and Ni borides are considered as good candidates for catalyzed hydrolysis owing to their good catalytic activity, low cost and effortlessly synthesis. Transition metals with varying (metal)/(Co + metal) molar ratio were doped in Co-B catalyst and the effect of metal doping on surface morphology, electronic interaction, and catalytic efficiency of the alloy catalyst powder on hydrogen production by hydrolysis of SBH and AB were studied. On the basis of characterization results, the role of each metal species, involved in hydrolysis and enhanced catalytic performance is discussed. The stability, reusability, and durability of these catalysts have also been investigated. Nanoparticle-assembled Co-B-P thin films on Ni foam (by electroless deposition), along with supported and unsupported Co-B nanoparticles over carbon films were synthesized by Pulsed Laser Deposition and studied for catalytic hydrolysis
La simulazione delle pratiche lavorative nei contesti formativi medici
No full textIl tema affrontato in questo elaborato di tesi costituisce un argomento di grande interesse sotto il profilo dello studio organizzativo, quello delle forme organizzative attraverso le quali si trasmette la conoscenza nei luoghi di lavoro.
La ricerca parte da un punto di osservazione specifico e con un interrogativo principale che contraddistinguono l’intero percorso della tesi: gli attori organizzativi che attivano il processo di formazione e che lo gestiscono in un contesto di simulazione delle pratiche lavorative, attraverso quali modalità organizzative mettono in pratica la comunicazione e trasmissione di saperi esperti? Detto altrimenti, quali sono le pratiche sociali di questa specifica attività di docenza che viene a realizzarsi grazie alla simulazione e alle recenti innovazione tecnologiche che la compongono?
Cardine dell’analisi è il lavoro di una figura apparentemente non centrale della docenza e che è rappresentato dalle pratiche sociali svolte dalle e dai tutor. Osservandole e analizzandole, nella ricerca si mette a fuoco il principale registro soggiacente sulla base del quale l’intero impianto formativo è reso plausibile: quello per cui fare formazione in medicina attivando delle simulazioni di pratiche lavorative caratteristiche di contesti medici specifici non relega queste esperienze formative alla condizione di mere copie di quanto può avvenire nei luoghi di lavoro. Al contrario, le pratiche formative del dare un volto al manichino sulla base di rituali specifici, del mobilitare la materialità degli ambienti di lavoro per attivare le sale virtuali che costituiscono i contesti formativi, di assegnare emozioni e ritmicità al processo formativo e di dare ad esso configurazioni specifiche con l’ausilio di pratiche discorsive, stimolano e accompagnano tanto le esperienze estetiche multisensoriali, che le consapevolezze cognitive, enfatizzando il frame di realismo della simulazione; frame che costituisce il patto di verosimiglianza che si instaura tra la figura del tutor e quella di chi partecipa alla formazione.
La ricerca è stata realizzata attraverso la tecnica dell'osservazione partecipante presso un centro di formazione medica basata sulla simulazione (in una città del Nord Italia) ed è ispirata ai principi metodologici della prospettiva sociologica della Grounded Theory. Come framework teorico della ricerca la tesi si basa su un’accurata rassegna critica della letteratura sulla simulazione in generale e su quella specifica dei contesti medici, letteratura che viene fatta dialogare con la prospettiva di studio nell’ambito del filone di studi sociologici del lavoro e dell’organizzazione rappresentato dai Practice-Based-Studies.
Si tratta di un elaborato che cerca di inserirsi in maniera innovativa nel contesto della letteratura sulla simulazione nei processi di formazione in medicina e in maniera interessante in quella sulle pratiche lavorative che conducono all’attivazione di forme organizzative specifiche per la trasmissione dei saperi esperti