3,896 research outputs found
Motivi letterari nei libri per l’infanzia di Paolo Di Paolo
No full textThe article, organised in the form of a discussion, aims to analyse the themes and motifs of Paolo Di Paolo’s works that are addressed to young audiences. The author has recently published a large number of volumes directed just at younger readers. When beholding the titles that constitute the author’s bibliography, the reader is struck by Di Paolo’s predisposition to transform literary classics: as much in Giacomo il signor bambino as in the edition of the Divina Commedia, the author’s goal is to try to reach his new readers. Therefore, Di Paolo proves to be a prolific author of the genre; in fact, in his bibliography, volumes of fairy tales with a classic slant, such as La mucca volante, are listed as well.L’articolo contiene un’analisi di temi e di motivi delle opere di Paolo Di Paolo dirette al pubblico più piccolo. L’autore negli ultimi anni ha pubblicato un cospicuo numero di volumi indirizzati, infatti, proprio ai lettori più giovani. Ciò che stupisce scorgendo i titoli che costituiscono la bibliografia dell’autore, è la predisposizione a trasformare i classici della letteratura: tanto in Giacomo il signor bambino quanto nell’edizione della Divina Commedia l’obiettivo è cercare di raggiungere i lettori più giovani. Di Paolo si dimostra, quindi, un autore prolifico del genere, tant’è che nell’elenco non mancano volumi fiabeschi dal taglio classico come La mucca volante. Analizzare le opere giovanili dello scrittore costituisce un fatto inedito
Silicon oxycarbide foams from a silicone preceramic polymer and polyurethane
No full textCeramic open-cell foams were obtained from a preceramic polymer (a silicone resin) and blown polyurethanes, by pyrolysis at 1200 degrees C in nitrogen. Silicon carbide submicron powders were also added to the silicone resin to give SiOC + SiC composite foams. The morphology of the foams was dependent on the architecture of the blown polyurethanes. The crushing strength as well as the elastic modulus increased with increasing relative density, reaching values as high as 14 and 450 MPa, respectively. Some of the foams displayed an excellent thermal stability (resistance to oxidation in air and decomposition in inert atmosphere) up to elevated temperatures
Verified security protocol modeling and implementation with AnBx
No full textAnBx è un'estensione della notazione Alice & Bob per la descrizione di protocolli, ed è utilizzato come linguaggio di specifica per la modellazione puramente dichiarativa dei protocolli distribuiti. AnBx è costituito da un insieme di astrazioni sui dati e sui modi di comunicazione che forniscono il supporto di base per le proprietà di sicurezza ad alto livello, schermando i dettagli della infrastruttura crittografica sottostante.
AnBx, essendo implementato sul tool di verifica OFMC, è utilizzabile non solo per specifica e la progettazione ma anche per l'analisi della sicurezza dei protocolli distribuiti. Inoltre il framework consente la generazione automatica del codice Java di protocolli descritti in AnBx, mantenendo separate la logica del protocollo dalla logica dell'applicazione. L'efficacia del nostro approccio è mostrata nella specifica ed nell'analisi di due protocolli di pagamento elettronico usati nel mondo reale, realizzando proprietà di sicurezza più forti e più scalabili rispetto a quelle delle versioni originali.
Nella seconda parte della tesi analizziamo in maniera formale il sistema di comunicazione veicolare sicura (SeVeCom) utilizzando il framework AIF, che è basato su una nuova tecnica di set-abstraction.
Nel corso del lavoro abbiamo trovato due nuovi attacchi, e verificato che sotto ragionevoli ipotesi il sistema è sicuro.AnBx is an extension of the Alice & Bob notation for protocol narrations to serve as a specification language for a purely declarative modelling of distributed protocols. AnBx is built around a set of communication and data abstractions which provide primitive support for the high-level security guarantees, and help shield from the details of the underlying cryptographic infrastructure.
Being implemented on top of the OFMC verification tool, AnBx serves not only for specification and design, but also for security analysis of distributed protocols. Moreover the framework, keeping apart the protocol logic from the application logic, allow for automatic generation of Java source code of protocols specified in AnBx.
We demonstrate the practical effectiveness of our approach with the specification and analysis of two real-life e-payment protocols, obtaining stronger and more scalable security guarantees than those offered by the original ones.
In the second part of the thesis we formally analyze the Secure Vehicle Communication system (SeVeCom), using the AIF framework which is based on a novel set-abstraction technique. We report on two new attacks found and verify that under some reasonable assumptions, the system is secure
SILICON OXYCARBIDE CERAMIC FOAMS FROM A PRECERAMIC POLYMER
No full textOpen-cell ceramic foams were obtained from the pyrolysis, at 1000 degrees to 1200 degrees C under nitrogen, of a preceramic polymer (a silicone resin) and blown polyurethanes. The morphology of the expanded polyurethane was reproduced in the final architecture of the ceramic foam. The foams produced in this way consisted of an amorphous silicon oxycarbide ceramic (SiOC), having a bulk density ranging from 0.1 to 0.4 g/cm(3) and variable cell size (300 to 600 mu m). Young's modulus ranged from 20 to 170 MPa, and the compression strength from 1 to 5 MPa. The foams displayed excellent dimensional stability up to their pyrolysis temperature
DNS of turbulent flows in ducts with omplex shape
No full textWe carry out Direct Numerical Simulation (DNS) of flows in closed straight ducts with complex peripheral shape. To perform the simulations the Navier-Stokes equations in cylindrical coordinates are discretized by a second-order finite difference scheme, and the immersed-boundary technique is used to resolve the flow close to walls of complex shape. The basic geometry is a circular pipe of radius R, with imposed sinusoidal perturbations of the type ηRsin (Nw). Simulations by varying Nwat fixed η were performed to investigate the effect of the perturbation wavenumber. Additional simulations by fixing Nwand varying η also allow to investigate the influence of the amplitude of the wall corrugations. The modifications of the near-wall structures due to change in the shape of the walls are well depicted through contour plots of the radial component of the vorticity. The presence of geometrical disturbances anchors the structures at the locations where curvature changes, and the shape of the structures is strongly linked to the amplitude of the wall corrugation. Our interest is also in understanding the influence of the shape of the surface on wall friction. We were expecting some changes in the profile of the total stress with respect to that of the circular pipe, which instead were not found. This is a first indication that changes in the near-wall region do not affect the outer region, and that Townsend’s similarity hypothesis holds
CERAMIC FOAMS FROM PRECERAMIC POLYMER AND POLYURETHANE: PREPARATION AND MORPHOLOGICAL INVESTIGATIONS
No full textOpen-cell ceramic foams were obtained from a preceramic polymer (silicone resin) and blown polyurethanes. The preceramic polymer, which is crosslinked by condensation of silanol groups, was dissolved in CH2Cl2 and added to a liquid polyol containing the surfactant and the amine catalyst. Isocyanate was then added to the mixture and the foam was obtained through a twofold blowing mechanism (physical and chemical blowing). The morphology of the expanded polyurethane, which can be flexible or semirigid, characterized the final structure of the ceramic foam. The materials obtained were pyrolyzed in a nitrogen flux at temperatures of 1000-1200 degrees C, thus allowing for the polymer-to-ceramic transformation to occur in the preceramic polymer. The ceramic foams produced in this way consisted of an amorphous silicon oxycarbide ceramic (SiOC). They presented a density ranging from 0.1 to 0.3 g/cm(3) The average pore diameter ranged from 200 to 400 mu m and they possessed 80 to 90 % open porosity
Thermal and thermal-oxidative degradation of polyurethane foams filled with ammonium phosphate
No full textCeramic foams from a preceramic polymer and polyurethanes: preparation and morphological characterization
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