Middleware per la gestione di interfacce di comunicazione e di sorgenti di contesto in ambienti wireless eterogenei

The full exploitation of multi-hop multi-path connectivity opportunities offered by heterogeneous wireless interfaces could enable innovative Always Best Served (ABS) deployment scenarios where mobile clients dynamically self-organize to offer/exploit Internet connectivity at best. Only novel middleware solutions based on heterogeneous context information can seamlessly enable this scenario: middleware solutions should i) provide a translucent access to low-level components, to achieve both fully aware and simplified pre-configured interactions, ii) permit to fully exploit communication interface capabilities, i.e., not only getting but also providing connectivity in a peer-to-peer fashion, thus relieving final users and application developers from the burden of directly managing wireless interface heterogeneity, and iii) consider user mobility as crucial context information evaluating at provision time the suitability of available Internet points of access differently when the mobile client is still or in motion. The novelty of this research work resides in three primary points. First of all, it proposes a novel model and taxonomy providing a common vocabulary to easily describe and position solutions in the area of context-aware autonomic management of preferred network opportunities. Secondly, it presents PoSIM, a context-aware middleware for the synergic exploitation and control of heterogeneous positioning systems that facilitates the development and portability of location-based services. PoSIM is translucent, i.e., it can provide application developers with differentiated visibility of data characteristics and control possibilities of available positioning solutions, thus dynamically adapting to application-specific deployment requirements and enabling cross-layer management decisions. Finally, it provides the MMHC solution for the self-organization of multi-hop multi-path heterogeneous connectivity. MMHC considers a limited set of practical indicators on node mobility and wireless network characteristics for a coarsegrained estimation of expected reliability/quality of multi-hop paths available at runtime. In particular, MMHC manages the durability/throughput-aware formation and selection of different multi-hop paths simultaneously. Furthermore, MMHC provides a novel solution based on adaptive buffers, proactively managed based on handover prediction, to support continuous services, especially by pre-fetching multimedia contents to avoid streaming interruptions.

Ingegneria di sistemi auto‐organizzanti con il paradigma multiagente

Self-organisation is increasingly being regarded as an effective approach to tackle modern systems complexity. The self-organisation approach allows the development of systems exhibiting complex dynamics and adapting to environmental perturbations without requiring a complete knowledge of the future surrounding conditions. However, the development of self-organising systems (SOS) is driven by different principles with respect to traditional software engineering. For instance, engineers typically design systems combining smaller elements where the composition rules depend on the reference paradigm, but typically produce predictable results. Conversely, SOS display non-linear dynamics, which can hardly be captured by deterministic models, and, although robust with respect to external perturbations, are quite sensitive to changes on inner working parameters. In this thesis, we describe methodological aspects concerning the early-design stage of SOS built relying on the Multiagent paradigm: in particular, we refer to the A&A metamodel, where MAS are composed by agents and artefacts, i.e. environmental resources. Then, we describe an architectural pattern that has been extracted from a recurrent solution in designing self-organising systems: this pattern is based on a MAS environment formed by artefacts, modelling non-proactive resources, and environmental agents acting on artefacts so as to enable self-organising mechanisms. In this context, we propose a scientific approach for the early design stage of the engineering of self-organising systems: the process is an iterative one and each cycle is articulated in four stages, modelling, simulation, formal verification, and tuning. During the modelling phase we mainly rely on the existence of a self-organising strategy observed in Nature and, hopefully encoded as a design pattern. Simulations of an abstract system model are used to drive design choices until the required quality properties are obtained, thus providing guarantees that the subsequent design steps would lead to a correct implementation. However, system analysis exclusively based on simulation results does not provide sound guarantees for the engineering of complex systems: to this purpose, we envision the application of formal verification techniques, specifically model checking, in order to exactly characterise the system behaviours. During the tuning stage parameters are tweaked in order to meet the target global dynamics and feasibility constraints. In order to evaluate the methodology, we analysed several systems: in this thesis, we only describe three of them, i.e. the most representative ones for each of the three years of PhD course. We analyse each case study using the presented method, and describe the exploited formal tools and techniques.

Studio del comportamento meccanico di smalti porcellanati per substrati metallici

Composite porcelain enamels are inorganic coatings for metallic components based on a special ceramic-vitreous matrix in which specific additives are randomly dispersed. The ceramic-vitreous matrix is made by a mixture of various raw materials and elements and in particular it is based on boron-silicate glass added with metal oxides(1) of titanium, zinc, tin, zirconia, alumina, ecc. These additions are often used to improve and enhance some important performances such as corrosion(2) and wear resistance, mechanical strength, fracture toughness and also aesthetic functions. The coating process, called enamelling, depends on the nature of the surface, but also on the kind of the used porcelain enamel. For metal sheets coatings two industrial processes are actually used: one based on a wet porcelain enamel and another based on a dry-silicone porcelain enamel. During the firing process, that is performed at about 870°C in the case of a steel substrate, the enamel raw material melts and interacts with the metal substrate so enabling the formation of a continuous varying structure. The interface domain between the substrate and the external layer is made of a complex material system where the ceramic vitreous and the metal constituents are mixed. In particular four main regions can be identified, (i) the pure metal region, (ii) the region where the metal constituents are dominant compared with the ceramic vitreous components, (iii) the region where the ceramic vitreous constituents are dominant compared with the metal ones, and the fourth region (iv) composed by the pure ceramic vitreous material. It has also to be noticed the presence of metallic dendrites that hinder the substrate and the external layer passing through the interphase region. Each region of the final composite structure plays a specific role: the metal substrate has mainly the structural function, the interphase region and the embedded dendrites guarantee the adhesion of the external vitreous layer to the substrate and the external vitreous layer is characterized by an high tribological, corrosion and thermal shock resistance. Such material, due to its internal composition, functionalization and architecture can be considered as a functionally graded composite material. The knowledge of the mechanical, tribological and chemical behavior of such composites is not well established and the research is still in progress. In particular the mechanical performances data about the composite coating are not jet established. In the present work the Residual Stresses, the Young modulus and the First Crack Failure of the composite porcelain enamel coating are studied. Due to the differences of the porcelain composite enamel and steel thermal properties the enamelled steel sheets have residual stresses: compressive residual stress acts on the coating and tensile residual stress acts on the steel sheet. The residual stresses estimation has been performed by measuring the curvature of rectangular one-side coated specimens. The Young modulus and the First Crack Failure (FCF) of the coating have been estimated by four point bending tests (3-7) monitored by means of the Acoustic Emission (AE) technique(5,6). In particular the AE information has been used to identify, during the bending tests, the displacement domain over which no coating failure occurs (Free Failure Zone, FFZ). In the FFZ domain, the Young modulus has been estimated according to ASTM D6272-02. The FCF has been calculated as the ratio between the displacement at the first crack of the coating and the coating thickness on the cracked side. The mechanical performances of the tested coated specimens have also been related and discussed to respective microstructure and surface characteristics by double entry charts.

Metodi numerici per lo studio di centri di lavoro ad alta velocità

A Machining Centre is nowadays a complex mechanical, electronic, electrical system that needs integrated design capabilities which very often require a high time-consuming effort. Numerical techniques for designing and dimensioning the machine structure and components usually requires different knowledge according to the system that have to be designed. This Ph. D Thesis is related about the efforts of the Authors to develop a system that allows to perform the complete project of a new machine optimized in its dynamic behaviour. An integration of the different systems developed, each of which respond to specific necessities of designer, is here presented. In particular a dynamic analysis system, based on a lumped mass approach, that rapidly allows to setup the drives of the machine and an Integrated Dynamic Simulation System, based on a FEM approach, that permit a dynamic optimization, are shown. A multilevel Data Base, and an operator interface module provide to complete the designing platform. The proposed approach represents a significant step toward the virtual machining for the prediction of the quality of the worked surface.

L'Ottica di Euclide e la scienza della visione

La presente tesi concerne il trattato "Ottica" scritto da Euclide nel III secolo a.C. quando, nell'area del bacino del Mediterraneo, si verificò una rivoluzione scientifica che diede origine alla nascita della scienza moderna. Si colloca nel filone delle ricerche volte a ricostruire la verità storica ed il contenuto scientifico del pensiero dello scienziato ed a meglio illustrare i contributi dati, dalla scienza ellenistica, alla conoscenza del fenomeno visivo. Si sono presi in esame dunque il momento storico e la situazione economica, sociale e scientifica verificatasi nel III secolo a.C., in particolare ad Alessandria d'Egitto, dove l'incontro del pensiero greco con le culture preesistenti portò alla nascita del metodo scientifico moderno; si sono considerati il pensiero filosofico del tempo e le teorie scientifiche sviluppatesi, con particolare riguardo alla matematica ed alla scienza medica, fondata dal medico alessandrino Erofilo. Si è poi preso in esame il contenuto del trattato. L' "Ottica" è il primo trattato di ottica geometrica della storia e la prima teoria scientifica che si occupi della visione. È basato sul metodo ipotetico-deduttivo, su conoscenze di oftalmologia e sulla scienza matematica degli Elementi. È un modello geometrico di un processo fisiologico e riconferma la matematica quale strumento principe per la costruzione del sapere scientifico. Crea modelli utili per altre teorie scientifiche (ad es. l'astronomia) e per le arti figurative ed ha applicazioni tecnologiche (ad es. l'astrolabio e la diottra). È il testo di base della moderna ottica geometrica. Non si pone come una verità assoluta ma come un'ipotesi di lavoro. Si sono esaminati il difficile percorso storico e bibliografico dell'opera caratterizzato da incomprensioni e manomissioni nonché la ricerca filologica volta a ricostruire l'integrità del testo. Si ritenne infatti che la sua validità fosse inficiata da alcuni "errori", in realtà dovuti all'incomprensione dei concetti e del metodo euclidei ed alle successive manomissioni. Emerge come la scienza non abbia avuto un progresso costante, continuo, aprioristico e come sia incerta ed instabile la conservazione nel tempo del sapere scientifico. Appare inoltre evidente come la scienza sia un prodotto della cultura umana e pertanto come la conoscenza della storia sia una condizione fondante per il progresso scientifico.

Proprietà statistiche delle caratteristiche topologiche del grafo di un "hub" generato da un social network

Questa tesi affronta lo studio delle proprietà statistiche della topologia di un grafo, che rappresenta le relazioni interpersonali in un gruppo di utenti di Facebook. Perché è interessante? Quali informazioni produce? Anzitutto va osservato che dalla nascita di Internet in poi la globalizzazione ha reso le relazioni sociali un fenomeno di massa con numeri sorprendentemente alti di connessioni. Questo e la disponibilità dei dati forniscono una occasione preziosa per analizzarne la struttura.