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Ensemble of binary classifiers: combination techniques and design issues
Get PDFIn this thesis the problem of the combination of binary classifiers ensamble is faced. For each pattern a binary classifier (or binary expert) assigns a similarity score, and according to a decision threshold a class is assigned
to the pattern (i.e., if the score is higher than the threshold the pattern is assigned to the “positive” class, otherwise to the “negative” one). An example
of this kind of classifier is an authentication biometric expert, where the expert must distinguish between the “genuine” users, and the “impostor” users. The combination of different experts is currently investigated by researchers to increase the reliability of the decision. Thus in this thesis the following two aspects are investigated: a score “selection” methodology, and
diversity measures of ensemble effectiveness.
In particular, a theory on ideal score selection has been developed, and a number of selection techniques based on it have been deployed. Moreover some of them are based on the use of classifier as a selection support, thus different use of these classifier is analyzed.
The influence of the characteristics of the individual experts to the final performance of the combined experts have been investigated. To this end some measures based on the characteristics of the individual experts were
developed to evaluate the ensemble effectiveness. The aim of these measures is to choose which of the individual experts from a bag of experts have to be used in the combination. Finally the methodologies developed where extensively tested on biometric datasets
I sedimenti superficiali della piattaforma interna del golfo di Cagliari. Relazioni tra moto ondoso, correnti indotte e processi di sedimentazione su sistemi di spiaggia campione
No full textLa presente tesi di dottorato ha come fine principale l’approfondimento delle conoscenze sedimentologiche sui fondali marini dell’area compresa tra Capo Spartivento e Capo Carbonara e dei meccanismi di apporto, ridistribuzione e sedimentazione attuale nella piattaforma interna. Particolare attenzione è stata posta sui processi di interazione tra moto ondoso e fondali marini di acqua bassa (shallow water) che generano correnti costiere (long-shore, offshore-inshore, upwelling, sinking e rip current) e controllano i processi di erosione, trasporto e sedimentazione sui sistemi di spiaggia oggetto di studio. Primo obiettivo della tesi è contribuire a migliorare le conoscenze finalizzate a realizzare una cartografia dei sedimenti superficiali in scala 1:50.000 del Golfo di Cagliari, base indispensabile per raggiungere il secondo obiettivo che è quello di entrare nei dettagli relativi ai meccanismi delle dinamiche sedimentarie che si attivano sui sistemi di spiaggia per effetto dei diversi eventi meteomarini e comprendere quantitativamente assetto e scenari evolutivi. Contestualmente si è sperimentata per la prima volta sui litorali del Golfo di Cagliari la modellizzazione basata su misure topografiche di alta precisione di spiaggia emersa e batimetriche di spiaggia sommersa e relativi assetti sedimentari nelle diverse stagioni. Inoltre utilizzando come modello le due spiagge campione di Santa Margherita di Pula e Solanas (Sinnai) sono state studiate le differenti risposte idrodinamiche e morfo-batimetriche della surf-zone (zona più dinamica della spiaggia sottomarina) per le quattro principali direzioni di vento comprese nel settore di traversia e per gli eventi con intensità di 5, 10, 15, 25 m/s
Near-Infrared Luminescent Lanthanide Complexes of Quinolinol Ligands: Structure/Properties Relationship
Get PDFThe synthesis and the characterisation of lanthanide complexes with quinolinolato ligands, a class of complexes proposed as near-infrared emitters for several optical applications, with a full investigation of the structure/property relationship, valuable for a reliable interpretation of their photo-physical properties, are described in this thesis.
This work has been addressed to a detailed investigation of the proper synthetic procedures useful to prepare pure products suitable for structural, spectroscopic and photo-physical studies. Several types of lanthanide quinolinolates have been identified and characterised depending on reaction’ conditions and on the nature of the ligand. The spectroscopic properties are discussed with the view to provide suitable tools to identify and characterise univocally the structural features of this class of complexes. The excited-state dynamics and light emission properties of Er-complexes have been investigated applying a reliable quantitative description of the non-radiative decay processes induced by the dipolar coupling between quencher groups and the lanthanide ion. It has been also demonstrated that the ligand emission is significantly affected by the supramolecular interactions in the crystal packing. The study of the magnetic properties of erbium quinolinolates evidences small magnetic interactions, due to the supramolecular arrangement, relevant in the optical behaviour of optically active ErIII derivatives. The lanthanide quinolinolates have also been incorporated into sol-gel glasses as promising low-cost materials for optical applications, with the aim to investigate the processing potential of this class of emitting molecules
New materials for eco-sustainable electrochemical processes: oxygen evolution reaction at different electrode materials
Get PDFIn this thesis, the issue concerns the study of the oxygen evolution reaction (OER) at different electrode materials. The idea to carry out such research is connected with the key role, which OER plays in several electrochemical processes. In a future energy scenario based on renewable energy hydrogen is an attractive energy carrier. Among the others, hydrogen production by water electrolysis is a clean and simple way of storing energy from sources such as solar, wind, and hydroelectric power the hydrogen can then subsequently be utilized in fuel cells without concern of contaminants. In this contest water electrolysis acquires a particular strategic role. OER is very often the most difficult of the two electrolytic reaction and it is the most important side reaction of many other electrochemical applications. In this work the performances of both “active” and “non active” electrodes have been evaluated. The attention had been firstly paid on the spinel-type Co3O4 electrodes obtained by a sol-gel method to obtain specific information about mechanism and kinetics of the OER. Moreover, the behaviour of SnO2-RuO2 electrodes, mechanically processed for different times, was investigated in acid media during oxidattive runs. Finally the attention has been focused on the evolution of electronic structure and electrochemical acitivity of BDD samples during oxidative ageing tests
Uomo, ambiente e istituzioni nella Sardegna della seconda metà dell'Ottocento : sfruttamento forestale e disordine idraulico
Get PDFLa tesi intende approfondire parallelamente le vicende che hanno riguardato lo sfruttamento intensivo della risorsa legno e i primi tentativi di ovviare al paludismo nella seconda metà dell'Ottocento in Sardegna, considerando il legame indissolubile che esiste tra regime dei boschi e regime delle acque.
Nella prima parte vengono affrontate le questioni metodologiche che caratterizzano la storia dell'ambiente, il filone storiografico basato sullo studio delle interazioni tra uomo e ambiente. Successivamente viene proposto un confronto tra il Mezzogiorno d'Italia e la Sardegna in epoca preunitaria, rispetto all'assetto territoriale e alle politiche di intervento su di esso. Viene poi analizzato l'impatto dell'unificazione legislativa e amministrativa, all'indomani dell'Unità, della politica dei governi della Destra storica e del prevalere dell'utilizzo privatistico del territorio sull'ambiente sardo. Viene di seguito affrontato lo studio dei mutamenti nelle politiche ambientali attuati a partire dall'ascesa al potere della Sinistra storica, con l'analisi dei dibattiti parlamentari che porteranno alla promulgazione della legislazione forestale unitaria, di cui vengono soprattutto analizzate le conseguenze della sua applicazione in Sardegna, e con l'esame della produzione legislativa in tema di bonifiche e di opere idrauliche e dei progetti di bonifica redatti nell'isola. Infine viene evidenziato come, negli ultimi anni dell'Ottocento, riprenda vigore la lezione dei tecnici meridionali preunitari e la visione dei bacini idrografici come nucleo base degli interventi sul territorio, e come, attraverso questa ritrovata consapevolezza, si giunga alla promulgazione dei Provvedimenti speciali per la Sardegna
Palazzi e dimore signorili nella Sardegna del XVIII secolo
Get PDFIn the second half of XVIII century the civil architecture had, in Sardinia, an incresing in production and quality terms. Private investments in building sector determined the development of dwelling market, with initiative setted up by nobilty, of ancient and recent lignace, and by bourgeois class. The government encouraged the achievment of the new well-off classes through the selling of nobility titols, on the financing of civil buildings or the cultivation of huge estates. The works were concentrated in the biggest urban cities of the isle, though we have examples in the inner villages. The buildings don't embrace big palaces. Rich families transformed their houses according to the canons of pedmont baroc architecture. The restiling of the facades was determined by the need to elevate the ancient buildings, in order to obtain new dwellings to be rent. It was clear the will of imitate the prestigious civil architecture financed by the state and built from 1765. The diffusion of savoy `700 language was determined by the partecipation of pedmont designer, many of them military engeeners, to the ideative phase. Decoration and archive sources denotate the contribution of pedmont officials. They featured sardinian architecture of the last `700 with a modern aestetic inspirated to the middle europe, with clear ties to the padan building tradition
Descrizione, funzionamento e analisi prestazionale delle macchine di scavo meccanizzato
Get PDFLa presente tesi si propone di definire delle linee guida da un punto di vista tecnico per la realizzazione di tunnel in sotterraneo con tecnologie di scavo meccanizzato (TBM ed EPB).
L'approfondita ricerca bibliografica sullo stato dell'arte delle opere in sotterraneo realizzate con TBM, cogliendo le principali e fondamentali differenze tra scavo convenzionale e meccanizzato dal punto di vista, tecnico, organizzativo ed economico, si affianca a tre importanti esperienze in cantiere in ambiente urbano e non, riportano un dettagliato lavoro di reporting sui dati di funzionamento delle TBM impiegate per la realizzazione dei lavori, in funzione del materiale scavato.
Particolare importanza ha rivestito la parte dedicata al problem solving svolto in cantiere e riportato nella tesi in oggetto.
L'ultima parte è stata dedicata all'interpretazione statistica dei dati e alla definizione di un modello probabilistico che consenta di prevedere le prestazioni delle TBM a partire dalla conoscenza di parametri noti relativi alla geologia e alla TBM stessa
Optimal retrofit and process design of distillation plants for energy saving and process intensification
Get PDFThis work is divided in two principal sections. The first concerns the application of more convenient structures to intensive energy consuming plants built before the energy crisis. Two case studies are considered. The first regards the implementation of a preflash device (drum or column) on a crude distillation unit. The limitations of both apparatuses are considered together with the energy saving realized. Particular emphasis is given to the evaluation of the best structure that matches the scope in the energy plant reduction and the respect of the production specifications. The second case considered regards a light ends distillation plant. Different separation sequences derived from the plant configuration are considered. The possibility to reach a reduction of the energy consumption is considered together with the maximum reusage
of the plant apparatus, that allows to minimize the capital cost investment. The total annual cost is associated to the required heat exchanger area for the condensers and the reboilers and to the column section diameter. The best solution, that satisfy the scope of the retrofit work minimizing at the same time the employing of new equipment and the energy consumption, is then identified.
In the second section of the work the column sequence design is considered. The starting point was the separation of a four components mixture considered with five different feed compositions. All the possible simple column sequences were first analyzed using different sets of heuristic rules and after with more rigorous evaluation. The different solutions are compared to put in evidence the limitations of the heuristic rules, which anyway remain a good tool for a first screening of the most promising structures. The best distillation sequence for each feed composition case is also considered for the implementation of a divided wall column to perform a three component separation. The resulting “hybrid” sequences are made by a simple column that follows or precedes a divided wall column. This type of column was modeled using the modified Underwood-Fenske-Gilliland method to obtain the first design parameters to be utilized as the input to a more rigorous simulation performed with the Aspen Plus simulation package. The different hybrid configurations are then compared with respect to the best simple column structures from which are derived.
In the last part of the work a new method to map the space of distillation columns with less than n-1 columns is proposed. Up to now this configuration space was never predicted in a systematic way and only heuristic rules are available to predict only a few of all the possible configurations. Including more distillation column
configurations in the research space increases the possibility to identify the sequence that satisfies the research scope. The generation method is presented for a four components mixture but is absolutely general and can be applied for any number of components
Experimental analysis and modeline of gasoil hydrotreatment process
No full textOil industry is continuously evolving chasing the fast development of the contrasting requirements of modern life. From one side, it tries to satisfy the growing energy demand adopting its production to provide the energy resources requred by the market while considering at the same time the increasing pressure to the environmental protection. For this reason, the increasing demand for diesel fuels coupled with the progressive tightening of environmental specifications has brought new emphasis on the research on gasoil production. Worldwide refineries, also in consideration of the varyng quality of the feedstock, are tryng to optimaze the current process operation to maximize the utilization of the available sources. Depending of the specific constraints, this is realizable through the construction of the new plants or the revamp of pre-existing units coupled to the utilization of state of the art catalysts. In any case, optimization of operating conditions is crucial. In this context, this thesis proposes a phenomenological model that could be used to optimize the operating conditions of hydroprocessing plants that, due to their hydrogenation, hydrodesulfurization and hydrodenitrogenation reactions, are the refinery plants devoted to the improvement of gasoil quality. In this way the optimization of the process can always guarantee the satisfaction of more critical specifications