166 research outputs found
JESUITS AND THE ITALIAN UNIFICATION: THE FORM AND ECONOMIC ROLE OF THE STATE IN THE WRITINGS OF TAPARELLI
No full textwe firstly highlight the peculiar theoretical aspects of Taparelli’s view of the interaction between the State and the economy. We discuss his theory on the basis of a classic-legal view of liberty and agency. Secondly, we discuss the concept of common good as a theoretical instrument. In particular, the relationship between the common good and subsidiarity will be discussed. Thirdly, we discuss the specific role and nature of the State, including the justification of progressive taxation. Finally, we attempt to evaluate the extent to which Taparelli’s position was affected by contingent events and the extent to which his view affected the subsequent development of this subject
Mechanism of fluorine redistribution and incorporation during solid phase epitaxial regrowth of pre-amorphized silicon
No full textThe redistribution of impurities during phase transitions is a widely studied phenomenon that has a great relevance in many fields and especially in microelectronics for the realization of Ultra Shallow Junctions (USJs) with abrupt profiles and high electrical activation. The redistribution of fluorine during solid phase epitaxial regrowth (SPER) of pre-amorphized Si has been experimentally investigated, explained and simulated, for different F concentrations and temperatures. We demonstrate, by a detailed analysis and modelling of F secondary ion mass spectrometry chemical concentration profiles, that F segregates in amorphous Si during SPER by splitting in three possible states: i) a diffusive one that migrates in amorphous Si; ii) an interface segregated state evidenced by the presence of a F accumulation peak at the amorphous-crystal interface; iii) a clustered F state. The interplay among these states and their roles in the F incorporation into crystalline Si are fully described in this thesis. It is shown that diffusive F moves by a trap limited diffusion and interacts with the advancing interface by a sticking-release dynamics that regulates the amount of F segregated at the interface. We demonstrate that this last quantity regulates the regrowth rate by an exponential law. On the other hand we show that nor the diffusive F nor the one segregated at the interface can directly incorporate into the crystal but clustering has to occur in order to have incorporation. This is in agreement with the element specific structural information on the F incorporated in crystalline Si given by a specific X-ray absorption spectroscopy analysis performed in this thesis, and also with recent experimental observations, reported in literature. The trends of the model parameters as a function of the temperature are shown and discussed obtaining a clear energetic scheme of the F redistribution in pre-amorphized Si. The above physical understanding and the model could have a strong impact on the use of F as a tool for optimising the doping profiles in the fabrication of ultra-shallow junctions.La redistribuzione di impurezze durante le transizioni di fase è un fenomeno ampiamente studiato che ha una grande rilevanza in molti campi di ricerca e specialmente nella microelettronica per la realizzazione di giunzioni ultra sottili (USJs) caratterizzate da profili di drogante ben confinati e da un’alta attivazione elettrica.
La redistribuzione del fluoro durante la ricrescita epitassiale in fase solida (SPER) del silicio pre-amorfizzato è stata studiata sperimentalmente, descritta e simulata in un ampio range di concentrazioni di F impiantato e temperature di ricrescita. Mediante una dettagliata analisi modellizzazione matematica dei profili in concentrazione di F misurati tramite la spettrometria di massa di ioni secondari, dimostriamo che il F segrega in silicio amorfo durante la SPER suddividendosi in tre possibili stati: i) uno stato diffusivo che migra in silicio amorfo; ii) uno stato segregato all’interfaccia evidenziato dalla presenza di un picco di accumulazione di F all’interfaccia amorfo-cristallo; iii) uno stato di F clusterizzato.
Questo lavoro ha descritto nel dettaglio quali scambi avvengono tra questi stati e che ruolo hanno nell’incorporazione del F nel silicio cristallino. È stato osservato che il F diffusivo è soggetto ad una diffusione limitata dalle trappole presenti nel substrato amorfo. Il F che diffonde in amorfo interagisce con l’interfaccia che avanza tramite una dinamica di tipo “attacca-stacca”, che regola l’ammontare del F segregato all’interfaccia. Dimostriamo che questa ultima quantità regola la velocità di ricrescita tramite una legge esponenziale. Dall’altra parte noi mostriamo che né il F diffusivo né quello segregato all’interfaccia possono incorporarsi direttamente nel cristallo ma del clustering deve accadere per avere l’incorporazione del F. Questa osservazione è in accordo con le informazioni strutturali del F incorporato in Silicio cristallino ottenute da una specifica analisi tramite spettroscopia di assorbimento a raggi X svolta in questa tesi e anche con le recenti osservazioni sperimentali riportate in letteratura. Gli andamenti dei parametri del modello in funzione della temperatura sono mostrati e discussi ottenendo un chiaro schema energetico della redistribuzione del F in silicio pre-amorfizzato. La suddetta comprensione fisica dei meccanismi coinvolti e il relativo modello predittivo da noi sviluppato potrebbero avere una forte impatto sull’uso del F come strumento per ottimizzare i profili dei droganti nella fabbricazione di giunzioni ultra-sottili
Formation and incorporation of SiF4 molecules in F-implanted preamorphized Si
No full textThe local structure of fluorine incorporated in crystalline silicon following solid phase epitaxial regrowth was investigated by means of x-ray absorption spectroscopy at the F K-edge. We clearly demonstrate that most F is found in SiF4 molecules in the crystalline matrix. A kinetic pathway, which explains our observation and which is also able to rationalize previous results in a common and coherent framework, is proposed
Microstructural evolution of René N4 during high temperature creep and aging
No full textThe main scope of this work is to describe the microstructure evolution of single-crystal (SX) superalloy René N4 during creep and static aging at high temperatures, in function of time, stress and temperature. During creep at high temperatures, SX microstructure evolves from a dense and ordered distribution of cuboidal γ′ particles to a configuration characterized by alternate rafts of γ′ phase and γ matrix, through a process known as rafting. The microstructural evolution of superalloys is very important to derive models able to predict service conditions of a component through microstructural analysis. In this work two microstructural parameters were identified and analyzed for René N4: matrix channels width w along the [001] lattice direction and periodicity width λ, given by the sum of w and the width of the γ′ precipitates along [001]. Both parameters were measured on some creep-damaged and some statically aged specimens, as well as on the virgin material to analyze their trends in function of time, temperature and stress. In particular, the parameter Δλ looks independent of both the stress level and the microstructural morphology and could be used in future works to develop microstructural evolution model of René N4 in function of service time and temperature. Keywords: Single-crystal, Superalloy, Microstructure, René N
Fluorine redistribution and incorporation during solid phase epitaxy of preamorphized Si
No full textThe redistribution of fluorine during solid phase epitaxial regrowth (SPER) of preamorphized Si has been experimentally investigated, explained, and simulated, for different F concentrations and temperatures. We demonstrate, by a detailed analysis and modeling of F secondary ion mass spectrometry chemical-concentration profiles, that F segregates in amorphous Si during SPER by splitting in three possible states: (i) a diffusive one that migrates in amorphous Si; (ii) an interface segregated state evidenced by the presence of a F accumulation peak at the amorphous-crystal interface; (iii) a clustered F state. The interplay among these states and their roles in the F incorporation into crystalline Si are fully described. It is shown that diffusive F migrates by a trap limited diffusion mechanism and also interacts with the advancing interface by a sticking-release dynamics that regulates the amount of F segregated at the interface. We demonstrate that this last quantity determines the regrowth rate through an exponential law. On the other hand we show that neither the diffusive F nor the one segregated at the interface can directly incorporate into the crystal but F has to cluster in the amorphous phase before being incorporated in the crystal, in agreement with recent experimental observations. The trends of the model parameters as a function of the temperature are shown and discussed obtaining a clear energetic scheme of the F redistribution and incorporation in preamorphized Si. The above physical understanding and the model could have a strong impact on the use of F as a tool for optimizing the doping profiles in the fabrication of ultrashallow junctions
On the Effects of the Rejuvenation Treatment on Mechanical and Microstructural Properties of IN-738 Superalloy
No full textThe main scope of this paper is to show the effects of a specific rejuvenation treatment studied for IN-38 on both the microstructure and the mechanical properties of the creep-damaged superalloy and to compare the tests results with the virgin material and with the recovery obtained through the standard heat treatment. This work will show that this rejuvenation treatment is able to recover the microstructure of creep-damaged specimens and that the creep and tensile properties of the rejuvenated alloy are even better than the virgin material for the tests performed. Moreover, it will be shown that the standard heat treatment provided for IN-738 is not able to fully recover the microstructure and that the creep properties of the superalloy during the tests have been lower than the virgin material
Participatory action research in the age of social media: Literacies, affinity spaces and learning
No full textThis article summarizes the developments, methodological design, and some of the theories framed within a PhD research about the integration of social media in higher education. Its aims are to determine significant issues, challenges and opportunities that emerge when social media are integrated into learning environments in higher education. ‘Doing Online Relearning through Information Skills’ (DORIS) is proposed as a research framework to address the aims, objectives, and research questions of this study. It was conceived from a Participatory Action Research perspective. This approach is intended to help discover and reflect upon teaching and learning practices in a technologically mediated educational setting. Furthermore, the concept of affinity spaces is discussed, together with its distinction from the concept of communities of practice. The data collection methods planned to conduct the study are: diagnostic questionnaire, blog, social learners' input and reports, a second questionnaire, and semi-structured interviews. The theory of affinity spaces offers a powerful way of thinking about teaching and learning processes mediated by different technologies. The heuristics that will focus the data collection and analysis are: a) on the function of content, and b) on the function of participants’ interactions with the content and/or with one another. DORIS is proposed as a powerful way to organize learning interventions through the structure of information literacy skills. It is grounded on action research and on constructivist, blended, and problem based learning. Researchers, librarians or educators can adapt this model for teaching, learning and researching about and with social media or for other technologically mediated learning environments, or could be adapted for information literacy programs
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