Polymer blends constitute a valuable way to produce relatively low cost new materials. A still open question concerns the miscibility of polyethylene blends. Deviations from the log-additivity rule of the newtonian viscosity are often taken as a signature of immiscibility of the two components. The aim of this thesis is to characterize the rheological behavior in shear and elongation of five series of LLDPE/LDPE blends whose parent polymers have been chosen with different viscosity and SCB content and length. Synergistic effects have been measured for both zero shear viscosity and melt strength. Both SCB length and viscosity ratio between the components have been found to be key parameters for the miscibility of the pure polymers. In particular the miscibility increases with increasing SCB length and with decreasing the LDPE molecular weight and viscosity. This rheological behavior has significant effects on the processability window of these blends when the uni or biaxial elongational flows are involved. The film blowing is one of the processes for which the synergistic effects above mentioned can be crucial. Small scale experiments of film blowing performed for one of the series of blends has demonstrated that the positive deviation of the melt strength enlarges the processability window. In particular, the bubble stability was found to improve or disappear when the melt strength of the samples increased. The blending of LDPE and LLDPE can even reduce undesired melt flow instability phenomena widening, as a consequence, the processability window in extrusion. One of the series of blends has been characterized by means of capillary rheometry in order to allow a careful morphological analysis of the surface of the extruded polymer jets by means of Scanning Electron Microscopy (SEM) with the aim to detect the very early stages of the small scale melt instabilty at low shear rates (sharksin) and to follow its subsequent evolution as long as the shear rate was increased. With this experimental procedure it was possible to evaluate the shear rate ranges corresponding to different flow regions: smooth extrudate surface (absence of instability), sharkskin (small scale instability produced at the capillary exit), stick-slip transition (instability involving the whole capillary wall) and gross melt fracture (i.e. a large scale "upstream" instability originating from the entrance region of the capillary). A quantitative map was finally worked out using which an assessment of the flow type for a given shear rate and blend composition can be predicted.

Membrane-based separation processes are acquiring, in the last years, an increasing importance because of their intrinsic energetic and environmental sustainability: some types of polymeric materials, showing adequate perm-selectivity features, appear rather suitable for these applications, because of their relatively low cost and easy processability. In this work have been studied two different types of polymeric membranes, in view of possible applications to the gas separation processes, i.e. Mixed Matrix Membranes (MMMs) and high free volume glassy polymers. Since the early 90’s, it has been understood that the performances of polymeric materials in the field of gas separations show an upper bound in terms of permeability and selectivity: in particular, an increase of permeability is often accompanied by a decrease of selectivity and vice-versa, while several inorganic materials, like zeolites or silica derivates, can overcome this limitation. As a consequence, it has been developed the idea of dispersing inorganic particles in polymeric matrices, in order to obtain membranes with improved perm-selectivity features. In particular, dispersing fumed silica nanoparticles in high free volume glassy polymers improves in all the cases gases and vapours permeability, while the selectivity may either increase or decrease, depending upon material and gas mixture: that effect is due to the capacity of nanoparticles to disrupt the local chain packing, increasing the dimensions of excess free volume elements trapped in the polymer matrix. In this work different kinds of MMMs were fabricated using amorphous Teflon® AF or PTMSP and fumed silica: in all the cases, a considerable increase of solubility, diffusivity and permeability of gases and vapours (n-alkanes, CO2, methanol) was observed, while the selectivity shows a non-monotonous trend with filler fraction. Moreover, the classical models for composites are not able to capture the increase of transport properties due to the silica addition, so it has been necessary to develop and validate an appropriate thermodynamic model that allows to predict correctly the mass transport features of MMMs. In this work, another material, called poly-trimethylsilyl-norbornene (PTMSN) was examined: it is a new generation high free volume glassy polymer that, like PTMSP, shows unusual high permeability and selectivity levels to the more condensable vapours. These two polymer differ each other because PTMSN shows a more pronounced chemical stability, due to its structure double-bond free. For this polymer, a set of Lattice Fluid parameters was estimated, making possible a comparison between experimental and theoretical solubility isotherms for hydrocarbons and alcoholic vapours: the successfully modelling task, based on application of NELF model, offers a reliable alternative to direct sorption measurement, which is extremely time-consuming due to the relevant relaxation phenomena showed by each sorption step. For this material also dilation experiments were performed, in order to quantify its dimensional stability in presence of large size, swelling vapours.

No description available.

No description available.

Nei processi di progettazione e produzione tramite tecnologie di colata di componenti in alluminio ad elevate prestazioni, risulta fondamentale poter prevedere la presenza e la quantità di difetti correlabili a design non corretti e a determinate condizioni di processo. Fra le difettologie più comuni di un getto in alluminio, le porosità con dimensioni di decine o centinaia di m, note come microporosità, hanno un impatto estremamente negativo sulle caratteristiche meccaniche, sia statiche che a fatica. In questo lavoro, dopo un’adeguata analisi bibliografica, sono state progettate e messe a punto attrezzature e procedure sperimentali che permettessero la produzione di materiale a difettologia e microstruttura differenziata, a partire da condizioni di processo note ed accuratamente misurabili, che riproducessero la variabilità delle stesse nell’ambito della reale produzione di componenti fusi. Tutte le attività di progettazione delle sperimentazioni, sono state coadiuvate dall’ausilio di software di simulazione del processo fusorio che hanno a loro volta beneficiato di tarature e validazioni sperimentali ad hoc. L’apparato sperimentale ha dimostrato la propria efficacia nella produzione di materiale a microstruttura e difettologia differenziata, in maniera robusta e ripetibile. Utilizzando i risultati sperimentali ottenuti, si è svolta la validazione di un modello numerico di previsione delle porosità da ritiro e gas, ritenuto ad oggi allo stato dell’arte e già implementato in alcuni codici commerciali di simulazione del processo fusorio. I risultati numerici e sperimentali, una volta comparati, hanno evidenziato una buona accuratezza del modello numerico nella previsione delle difettologie sia in termini di ordini di grandezza che di gradienti della porosità nei getti realizzati. / The possibility to predict defects in aluminium alloy cast component, from the very beginning of the design and production phases is a crucial issue. Among the most common defects of a casting, microporosities (i.e. porosities with dimension up to hundreds of m) are highly detrimental for mechanical performances. In this work, after an in-depth bibliographic research, experimental casting devices and procedures were designed in order to produce specimen with controlled defects and microstructure, related to process condition which could be varied in the range of the actual ones, measured on the shop floor. The whole design phase of the casting devices and procedure was carried out using process simulation software which were extensively fine tuned through experimental activities. The experiment proved to be effective in producing specimen with controlled defects and microstructure, in a consistent way. Numerical models for the prediction of gas and shrinkage porosity were evaluated in terms of accuracy in the description of all of the phenomena involving nucleation and growth of porosity and possibility of implementation on industrial cases. The one considered at the state of the art underwent a validation process with the experimental data. The comparison of numerical results and experimental data showed a good match, thus the good capability of the model to predict porosity, both in magnitude and trend throughout the casting.

Il presente lavoro mira ad analizzare l’organizzazione della gestione aeroportuale come venutasi a delineare a seguito dei processi di privatizzazione nella gestione stessa e di liberalizzazione nella prestazione dei servizi nonché ad esaminare gli effetti di tali processi sulla concorrenza tra aeroporti. Per affrontare tali profili di ricerca, il lavoro è suddiviso in quattro capitoli. Nel primo capitolo viene analizzata l’organizzazione amministrativa dell’aviazione civile e quindi i principali soggetti che operano e/o interagiscono nel mercato aeroportuale e le relative competenze. Nel secondo capitolo si analizza il ruolo del gestore aeroportuale quale soggetto a cui è affidato il compito di amministrare e gestire le infrastrutture aeroportuali e di coordinare e controllare le attività dei vari operatori privati presenti nello scalo. Pertanto si prenderà in esame l’evoluzione dei modelli di gestione aeroportuale, il rapporto tra concessionario e concedente, la qualificazione dell’attività di gestione dell’infrastruttura come servizio pubblico e la regolazione pubblicistica della stessa, volta a correggere le imperfezioni che possono distorcere il normale funzionamento dei meccanismi di mercato e a perseguire il benessere sociale. Nel terzo capitolo, si affronta il tema della liberalizzazione dei servizi, in particolari aerei e c.d. di handling. Infine, nel quarto e ultimo capitolo, si studia la concorrenza tra aeroporti e la sua interrelazione con l’infrastruttura ferroviaria. / The present work analyses, from a legal point of view, the organization of Airport Management, particulary with regard to impact of Privatization and Liberalitazion Policies of Airport Services and the effects of these Policies on competition between airports. Special attention is given to competition and complementarity among transport network.

Extrusion is a process used to form long products of constant cross section, from simple billets, with a high variety of shapes. Aluminum alloys are the materials most processed in the extrusion industry due to their deformability and the wide field of applications that range from buildings to aerospace and from design to automotive industries. The diverse applications imply different requirements that can be fulfilled by the wide range of alloys and treatments, that is from critical structural application to high quality surface and aesthetical aspect. Whether one or the other is the critical aspect, they both depend directly from microstructure. The extrusion process is moreover marked by high deformations and complex strain gradients making difficult the control of microstructure evolution that is at present not yet fully achieved. Nevertheless the evolution of Finite Element modeling has reached a maturity and can therefore start to be used as a tool for investigation and prediction of microstructure evolution. This thesis will analyze and model the evolution of microstructure throughout the entire extrusion process for 6XXX series aluminum alloys. Core phase of the work was the development of specific tests to investigate the microstructure evolution and validate the model implemented in a commercial FE code. Along with it two essential activities were carried out for a correct calibration of the model beyond the simple research of contour parameters, thus leading to the understanding and control of both code and process. In this direction activities were also conducted on building critical knowhow on the interpretation of microstructure and extrusion phenomena. It is believed, in fact, that the sole analysis of the microstructure evolution regardless of its relevance in the technological aspects of the process would be of little use for the industry as well as ineffective for the interpretation of the results.

This work presents the results of theoretical and experimental characterization of thermodynamic, mechanical and transport properties in polymer solvent systems. The polymer solvent pairs considered ranged to those in which the polymer is rubbery, to those in which the initially glassy polymeric matrix is plasticized by the action of the low molecular weight species. Advanced Equation of State models have been adopted for thermodynamic modeling,along with a rigorous procedure that enables to extend their applicability to the non equilibrium, glassy region. Mass sorption kinetics had been modeled with phenomenological models and with advanced kinetic models. / Questo lavoro verte sulla caratterizzazione teorica e sperimentale delle proprietà termodinamiche, meccaniche e di trasporto di sistemi polimero-solvente. In particolare sono stati presi in considerazione sia sistemi polimero-solvente in cui la matrice polimerica si trova allo stato di gomma, che sistemi in cui la matrice polimerica esibisce comportamento vetroso, nonché sistemi nei quali si verifica la transizione vetrosa indotta dall'effetto plasticizzante del solvente. La modellazione termodinamica è stata effettuata utilizzando equazioni di stato avanzate e metodi idonei ad estenderne il campo di utilizzo alla condizione di non equilibrio, propria dello stato vetroso. Cinetiche di assorbimento non Fickiane sono state modellate utilizzando approcci fenomenologici e modelli cinetici avanzati.

Chromatography is the most widely used technique for high-resolution separation and analysis of proteins. This technique is very useful for the purification of delicate compounds, e.g. pharmaceuticals, because it is usually performed at milder conditions than separation processes typically used by chemical industry. This thesis focuses on affinity chromatography. Chromatographic processes are traditionally performed using columns packed with porous resin. However, these supports have several limitations, including the dependence on intra-particle diffusion, a slow mass transfer mechanism, for the transport of solute molecules to the binding sites within the pores and high pressure drop through the packed bed. These limitations can be overcome by using chromatographic supports like membranes or monoliths. Dye-ligands are considered important alternatives to natural ligands. Several reactive dyes, particularly Cibacron Blue F3GA, are used as affinity ligand for protein purification. Cibacron Blue F3GA is a triazine dye that interacts specifically and reversibly with albumin. The aim of this study is to prepare dye-affinity membranes and monoliths for efficient removal of albumin and to compare the three different affinity supports: membranes and monoliths and a commercial column HiTrapTM Blue HP, produced by GE Healthcare. A comparison among the three supports was performed in terms of binding capacity at saturation (DBC100%) and dynamic binding capacity at 10% breakthrough (DBC10%) using solutions of pure BSA. The results obtained show that the CB-RC membranes and CB-Epoxy monoliths can be compared to commercial support, column HiTrapTM Blue HP, for the separation of albumin. These results encourage a further characterization of the new supports examined.

Giovanni Paisiello's Barber of Seville, although no longer an opera that is frequently performed, was very popular in the eighteenth and early nineteenth centuries. Based on a play by Pierre-Augustin Caron de Beaumarchais, Le barbier de Seville (1775), was translated into many different languages, and performed by companies all over Europe and America. Paisiello's work was so successful that Mozart, inspired by the idea, wrote a sequel in 1786, The Marriage of Figaro in collaboration with Da Ponte. When Rossini presented his own version of Barber of Seville in Rome in 1816, the public hissed with indignation and outrage to demonstrate a predilection for Paisiello. Giovanni Paisiello (1740 - 1816) was a Neapolitan composer who worked at St. Petersburg, Russia from 1776 - 1784 in the court of Catherine II where he was appointed Kapelmeister of Italian opera. The composer chose the French play by Beaumarchais as his point of departure, having it adjusted and rewritten in Italian verse in order to please his patroness. Due to the restrictions set upon the duration of the spectacle and the subject matter, the comedy was shortened and its socio-political critique eliminated. Thus Le barbier de Seville, which the Empress essentially considered democratizing and harmful to the absolute monarchy, was transformed into an opera buffa, Il barbiere di Siviglia, that involved harmless clowning. Il barbiere is significant because its creation demonstrates how Italian opera buffa became a vehicle to distract the public from considering the issues that were in the air prior to the French Revolution. This thesis examines the many contradictory factors involved in allowing this sort of entertainment at the Imperial Court. The study explores Catherine the Great and her character, as well as her clever ability to maintain a successful image as an Enlightened Despot. The differences and similarities between the French play and the Italian libretto are surveyed in order to demonstrate the simplifications that had to be made. A discussion treating the shift of focus that resulted by moving attention away from Figaro toward Dr. Bartholo, will indicate how the play was transformed into a libretto which proved to be emasculated and irregular. The music and how the composer dealt with the text will be discussed. Paisiello's buffo characterization of the old miserly doctor will be considered through use of musical examples. Additionally, the composer's setting of ensembles will be examined given their particular prominence in this work. The use of unifying elements will also be surveyed. The ideas of the era of Enlightenment affected both the bourgeoisie and the aristocracy. However, each group interpreted education and rationalism in its own way. While the members of the middle class attempted to change the structure of society (ancien regime), the authorities needed to maintain it. Through Italian opera buffa, however, both seemed to find the middle ground for compromise. It was acceptable because it was musical theatre that was made to appear harmless.