Stability, viscous dissipation and local thermal non-equilibrium in fluid saturated porous media

In this thesis, the field of study related to the stability analysis of fluid saturated porous media is investigated. In particular the contribution of the viscous heating to the onset of convective instability in the flow through ducts is analysed. In order to evaluate the contribution of the viscous dissipation, different geometries, different models describing the balance equations and different boundary conditions are used. Moreover, the local thermal non-equilibrium model is used to study the evolution of the temperature differences between the fluid and the solid matrix in a thermal boundary layer problem. On studying the onset of instability, different techniques for eigenvalue problems has been used. Analytical solutions, asymptotic analyses and numerical solutions by means of original and commercial codes are carried out.

Multilevel Analysis in Household Survey: An Application to Health Condition Data

The aim of this thesis is to apply multilevel regression model in context of household surveys. Hierarchical structure in this type of data is characterized by many small groups. In last years comparative and multilevel analysis in the field of perceived health have grown in size. The purpose of this thesis is to develop a multilevel analysis with three level of hierarchy for Physical Component Summary outcome to: evaluate magnitude of within and between variance at each level (individual, household and municipality); explore which covariates affect on perceived physical health at each level; compare model-based and design-based approach in order to establish informativeness of sampling design; estimate a quantile regression for hierarchical data. The target population are the Italian residents aged 18 years and older. Our study shows a high degree of homogeneity within level 1 units belonging from the same group, with an intraclass correlation of 27% in a level-2 null model. Almost all variance is explained by level 1 covariates. In fact, in our model the explanatory variables having more impact on the outcome are disability, unable to work, age and chronic diseases (18 pathologies). An additional analysis are performed by using novel procedure of analysis :"Linear Quantile Mixed Model", named "Multilevel Linear Quantile Regression", estimate. This give us the possibility to describe more generally the conditional distribution of the response through the estimation of its quantiles, while accounting for the dependence among the observations. This has represented a great advantage of our models with respect to classic multilevel regression. The median regression with random effects reveals to be more efficient than the mean regression in representation of the outcome central tendency. A more detailed analysis of the conditional distribution of the response on other quantiles highlighted a differential effect of some covariate along the distribution.

Framing Death. La morte in diretta, tra cinema e media digitali

Come dimostrano i sempre più numerosi casi di cronaca riportati dai notiziari, la preoccupazione per la gestione delle immagini di morte si configura come un nodo centrale che coinvolge spettatori, produttori di contenuti e broadcaster, dato che la sua emersione nel panorama mediale in cui siamo immersi è sempre più evidente. Se la letteratura socio-antropologica è generalmente concorde nel ritenere che, rispetto al passato, oggi la morte si manifesti con meno evidenza nella vita comune delle persone, che tendono a rimuovere i segni della contiguità vivendo il lutto in forma privata, essa è però percepita in modo pervasivo perché disseminata nei (e dai) media. L'elaborato, concentrandosi in maniera specifica sulle produzioni audiovisive, e quindi sulla possibilità intrinseca al cinema – e alle sue forme derivate – di registrare un evento in diretta, tenta di mappare alcune dinamiche di produzione e fruizione considerando una particolare manifestazione della morte: quella che viene comunemente indicata come “morte in diretta”. Dopo una prima ricognizione dedicata alla tensione continua tra la spinta a considerare la morte come l'ultimo tabù e le manifestazioni che essa assume all'interno della “necrocultura”, appare chiaro che il paradigma pornografico risulta ormai inefficace a delineare compiutamente le emersioni della morte nei media, soggetta a opacità e interdizioni variabili, e necessita dunque di prospettive analitiche più articolate. Il fulcro dell'analisi è dunque la produzione e il consumo di precisi filoni quali snuff, cannibal e mondo movie e quelle declinazioni del gore che hanno ibridato reale e fittizio: il tentativo è tracciare un percorso che, a partire dal cinema muto, giunga al panorama contemporaneo e alle pratiche di remix rese possibili dai media digitali, toccando episodi controversi come i Video Nasties, le dinamiche di moral panic scatenate dagli snuff film e quelle di contagio derivanti dalla manipolazione e diffusione delle immagini di morte.

Numerical methods for the dispersion analysis of Guided Waves

The use of guided ultrasonic waves (GUW) has increased considerably in the fields of non-destructive (NDE) testing and structural health monitoring (SHM) due to their ability to perform long range inspections, to probe hidden areas as well as to provide a complete monitoring of the entire waveguide. Guided waves can be fully exploited only once their dispersive properties are known for the given waveguide. In this context, well stated analytical and numerical methods are represented by the Matrix family methods and the Semi Analytical Finite Element (SAFE) methods. However, while the former are limited to simple geometries of finite or infinite extent, the latter can model arbitrary cross-section waveguides of finite domain only. This thesis is aimed at developing three different numerical methods for modelling wave propagation in complex translational invariant systems. First, a classical SAFE formulation for viscoelastic waveguides is extended to account for a three dimensional translational invariant static prestress state. The effect of prestress, residual stress and applied loads on the dispersion properties of the guided waves is shown. Next, a two-and-a-half Boundary Element Method (2.5D BEM) for the dispersion analysis of damped guided waves in waveguides and cavities of arbitrary cross-section is proposed. The attenuation dispersive spectrum due to material damping and geometrical spreading of cavities with arbitrary shape is shown for the first time. Finally, a coupled SAFE-2.5D BEM framework is developed to study the dispersion characteristics of waves in viscoelastic waveguides of arbitrary geometry embedded in infinite solid or liquid media. Dispersion of leaky and non-leaky guided waves in terms of speed and attenuation, as well as the radiated wavefields, can be computed. The results obtained in this thesis can be helpful for the design of both actuation and sensing systems in practical application, as well as to tune experimental setup.

Mercato dell'informazione, posizionamento dei media e distorsioni: Un'analisi attraverso l'algoritmo Wordfish

Una stampa libera e plurale è un elemento fondante di ogni sistema democratico ed è fondamentale per la creazione di un’opinione pubblica informata e in grado di esercitare controllo e pressione sulle classi dirigenti. Dal momento della loro creazione i giornali si sono imposti come un’importantissima fonte di informazione per l’opinione pubblica. La seconda metà del Novecento, inoltre, ha conosciuto innovazioni tecnologiche che hanno portato grandi cambiamenti nel ruolo della carta stampata come veicolo di trasmissione delle notizie. Partendo dalla diffusione della televisione fino ad arrivare alla rivoluzione digitale degli anni ’90 e 2000, la velocità di creazione e di trasmissione delle informazioni è aumentata esponenzialmente, i costi di produzione e di acquisizione delle notizie sono crollati e una quantità enorme di dati, che possono fornire moltissime informazioni relative alle idee e ai contenuti proposti dai diversi autori nel corso del tempo, è ora a disposizione di lettori e ricercatori. Tuttavia, anche se grazie alla rivoluzione digitale i costi materiali dei periodici si sono notevolmente ridotti, la produzione di notizie comporta altre spese e pertanto si inserisce in un contesto di mercato, sottoposto alle logiche della domanda e dell'offerta. In questo lavoro verrà analizzato il ruolo della domanda e della non perfetta razionalità dei lettori nel mercato delle notizie, partendo dall’assunto che la differenza di opinioni dei consumatori spinge le testate a regolare l’offerta di contenuti, per venire incontro alla domanda di mercato, per verificare l’applicabilità del modello utilizzato (Mullainhatan e Shleifer, 2005) al contesto italiano. A tale scopo si è analizzato il comportamento di alcuni quotidiani nazionali in occasione di due eventi che hanno profondamente interessato l'opinione pubblica italiana: il fenomeno dei flussi migratori provenienti dalla sponda sud del Mediterraneo nel mese di ottobre 2013 e l'epidemia di influenza H1N1 del 2009.

Linear and nonlinear thermal instability of Newtonian and non-Newtonian fluid saturated porous media

The present work aims to investigate the influence of different aspects, such as non-standard steady solutions, complex fluid rheologies and non-standard porous-channel geometries, on the stability of a Darcy-Bénard system. In order to do so, both linear and nonlinear stability theories are considered. A linear analysis focuses on studying the dynamics of the single disturbance wave present in the system, while its nonlinear counterpart takes into consideration the interactions among the single modes. The scope of the stability analysis is to obtain information regarding the transition from an equilibrium solution to another one, and also information regarding the transition nature and the emergent solution after the transition. The disturbance governing equations are solved analytically, whenever possible, and numerical by considering different approaches. Among other important results, it is found that a cylinder cross-section does not affect the thermal instability threshold, but just the linear pattern selection for dilatant and pseudoplastic fluid saturated porous media. A new rheological model is proposed as a solution for singular issues involving the power-law model. Also, a generalised class of one parameter basic solutions is proposed as an alternative description of the isoflux Darcy--Bénard problem. Its stability is investigated.

Disturbi dell'informazione, nuovi media e libertà di manifestazione del pensiero

L’elaborato affronta il tema della massiccia diffusione di disinformazione tramite internet sotto il profilo del diritto costituzionale, nell’ottica di indagare se le dimensioni del fenomeno richiedano l’elaborazione di principi e soluzioni nuove ovvero se i paradigmi costituzionali enucleati dalla tradizione costituzionalistica con riferimento alla libertà d’espressione forniscano gli strumenti sufficienti per un intervento efficace. In tale ottica, il lavoro premette una ricostruzione del fenomeno della disinformazione nel tentativo di individuare il perimetro socio-cognitivo e tecnologico entro cui la medesima prolifera, descrivendo gli elementi che distinguono l’informazione diffusa dai nuovi media rispetto a quella veicolata dai media mainstream. Ciò premesso, lo studio passa a delineare lo “statuto costituzionale” del falso, indagando la rilevanza che la menzogna assume sotto il profilo costituzionale nel suo rapporto con la libertà di manifestazione del pensiero negli ordinamenti interno, europeo e statunitense. L’analisi prosegue poi con l’esame delle politiche di contrasto alla disinformazione introdotte da singoli Stati (prevalentemente Germania, Francia e Italia), Unione europea, e piattaforme, con l’obiettivo di mettere in luce vantaggi e limiti dei modelli di eteroregolamentazione, coregolamentazione e autoregolamentazione. Da ultimo, l’elaborato scompone alcune delle azioni e misure passate in rassegna e le analizza con la lente d’ingrandimento della libertà di manifestazione del pensiero, ordinandone i contenuti secondo la specifica propensione a comprimere la libertà d’espressione. L’indagine si conclude con alcuni brevi spunti conclusivi che evidenziano l’esigenza, in base ai principi costituzionali analizzati, che eventuali interventi normativi siano se del caso volti alla regolazione delle piattaforme, ovvero dei “contenitori”, lasciano i contenuti al libero scambio delle idee.

Populism as a battlefield Populist actors and their representation on social and legacy media during the european parliament elections 2019 in Finland, Italy and the Netherlands

The objective of the present research is to describe and explain populist actors and populism as a concept and their representation on social and legacy media during the 2019 EU elections in Finland, Italy and The Netherlands. This research tackles the topic of European populism in the context of political communication and its relation to both the legacy and digital media within the hybrid media system. Departing from the consideration that populism and populist rhetoric are challenging concepts to define, I suggest that they should be addressed and analyzed through the usage of a combination of methods and theoretical perspectives, namely Communication Studies, Corpus Linguistics, Political theory, Rhetoric and Corpus-Assisted Discourse Studies. This thesis considers data of different provenance. On the one hand, for the Legacy media part, newspapers articles were collected in the three countries under study from the 1st until the 31st of May 2019. Each country’s legacy system is represented by three different quality papers and the articles were collected according to a selection of keywords (European Union Elections and Populism in each of the three languages). On the other hand, the Digital media data takes into consideration Twitter tweets collected during the same timeframe based on particular country-specific hashtags and tweets by identified populist actors. In order to meet the objective of this study, three research questions are posed and the analysis leading to the results are exhaustively presented and further discussed. The results of this research provide valuable and novel insights on how populism as a theme and a concept is being portrayed in the context of the European elections both in legacy and digital media and political communication in general.

What do rendering options tell us about the translating mind? Testing the choice network analysis hypothesis

Frame. Assessing the difficulty of source texts and parts thereof is important in CTIS, whether for research comparability, for didactic purposes or setting price differences in the market. In order to empirically measure it, Campbell & Hale (1999) and Campbell (2000) developed the Choice Network Analysis (CNA) framework. Basically, the CNA’s main hypothesis is that the more translation options (a group of) translators have to render a given source text stretch, the higher the difficulty of that text stretch will be. We will call this the CNA hypothesis. In a nutshell, this research project puts the CNA hypothesis to the test and studies whether it does actually measure difficulty. Data collection. Two groups of participants (n=29) of different profiles and from two universities in different countries had three translation tasks keylogged with Inputlog, and filled pre- and post-translation questionnaires. Participants translated from English (L2) into their L1s (Spanish or Italian), and worked—first in class and then at home—using their own computers, on texts ca. 800–1000 words long. Each text was translated in approximately equal halves in two 1-hour sessions, in three consecutive weeks. Only the parts translated at home were considered in the study. Results. A very different picture emerged from data than that which the CNA hypothesis might predict: there was no prevalence of disfluent task segments when there were many translation options, nor was a prevalence of fluent task segments associated to fewer translation options. Indeed, there was no correlation between the number of translation options (many and few) and behavioral fluency. Additionally, there was no correlation between pauses and both behavioral fluency and typing speed. The discussed theoretical flaws and the empirical evidence lead to the conclusion that the CNA framework does not and cannot measure text and translation difficulty.