The atmospheric stable boundary layer: Data analysis and comparison with similarity theories

The objective of this dissertation is to study the structure and behavior of the Atmospheric Boundary Layer (ABL) in stable conditions. This type of boundary layer is not completely well understood yet, although it is very important for many practical uses, from forecast modeling to atmospheric dispersion of pollutants. We analyzed data from the SABLES98 experiment (Stable Atmospheric Boundary Layer Experiment in Spain, 1998), and compared the behaviour of this data using Monin-Obukhov's similarity functions for wind speed and potential temperature. Analyzing the vertical profiles of various variables, in particular the thermal and momentum fluxes, we identified two main contrasting structures describing two different states of the SBL, a traditional and an upside-down boundary layer. We were able to determine the main features of these two states of the boundary layer in terms of vertical profiles of potential temperature and wind speed, turbulent kinetic energy and fluxes, studying the time series and vertical structure of the atmosphere for two separate nights in the dataset, taken as case studies. We also developed an original classification of the SBL, in order to separate the influence of mesoscale phenomena from turbulent behavior, using as parameters the wind speed and the gradient Richardson number. We then compared these two formulations, using the SABLES98 dataset, verifying their validity for different variables (wind speed and potential temperature, and their difference, at different heights) and with different stability parameters (zita or Rg). Despite these two classifications having completely different physical origins, we were able to find some common behavior, in particular under weak stability conditions.

One dimensional extended Hubbard model: two-particle bound states and resonances.

In questo lavoro di tesi è stato svolto uno studio analitico sul modello di Hubbard esteso unidimensionale al fine di osservare la presenza di eventuali risonanze che possano dare origine alla formazione di stati legati di due particelle. L'esistenza di uno stato legato stabile ha suscitato grande interesse negli ultimi anni, sia in ambito teorico che sperimentale, poichè è alla base di molti fenomeni che vengono osservati nei sistemi a molti corpi a basse temperature, come il BCS-BEC crossover. Pertanto si è ritenuto utile studiare il problema a due corpi nel modello di Hubbard esteso, che in generale non è integrabile. Il modello considerato contiene interazioni a primi e secondi vicini, in aggiunta all'interazione di contatto presente nel modello di Hubbard. Il problema è stato indagato analiticamente attraverso il Bethe ansatz, che consente di trovare tutti gli autovalori e le autofunzioni dell'Hamiltoniana. L'ansatz di Bethe sulla funzione d'onda è stato generalizzato per poter tener conto dei termini di interazione a più lungo raggio rispetto all'interazione di contatto. Si trova che, in questo modello, nel limite termodinamico, possono avvenire delle risonanze (o quasi-risonanze) in cui la lunghezza di scattering diverge, contrariamente a quanto avviene nel modello di Hubbard. Tale fenomeno si verifica quando il livello energetico discreto degli stati legati “tocca” la banda di scattering. Inoltre, con l'aggiunta di nuovi termini di interazione emergono nuovi stati legati. Nel caso in esame, si osservano due famiglie di stati legati, se lo spin totale delle due particelle è 1, e tre famiglie di stati legati, se lo spin totale è 0.

Uno Two Drei: la televisione nella promozione linguistica per i giovani. Un caso italiano nel contesto europeo.

The aim of this work is to assess the effectiveness of a project carried out in the Autonomous Province of Trento to promote language learning among young people. The project consisted in a television quiz show featuring games in Italian, English and German. Eight classes from five high schools took part in the game show, which was aired between November 2014 and January 2015 by the local channel Trentino TV. Since multilingualism has been part of the European Union policy, legislation and practices for many decades, the first chapter of this dissertation offers an overview of the main EU language education policies which seek to promote language learning among all citizens. It then focuses on the commitment of the EU and its member States to find new strategies to show the benefits of language learning outside formal education, also using both old and new media. Some TV and radio shows on multilingualism broadcast in Italy and in other EU countries are also briefly described. The second chapter is devoted to Uno Two Drei, the quiz show created by the Autonomous Province of Trento and Trentino TV to promote the learning of English and German among students while enhancing their personal growth and development. The role of everyone involved in the project is outlined, as well as the concept and planning phases and the realization stage. The third chapter focuses largely on the impacts of the initiative on the target group, namely 17-year-old students. Opinions of the participants were first collected in January, when a final meeting was held between the organizers and the schools. Since the researcher has managed the German part of the project, in the following months a questionnaire was administered to the 48 students who played in the German team and to their teachers as well. From both the meeting and the questionnaires it has emerged that the main goals of the initiative were achieved: generally speaking, students have been motivated to study languages and learn new things, the bonds between them have been strengthened and their sense of solidarity has been enhanced.