Tesi di dottoratohttp://hdl.handle.net/10556/452019-02-18T18:50:53Z2019-02-18T18:50:53ZOn Vector-Valued Schrodinger Operators in Lp-spacesMaichine, Abdallahhttp://hdl.handle.net/10556/31312019-02-06T01:01:27Z2018-04-06T00:00:00ZOn Vector-Valued Schrodinger Operators in Lp-spaces
Maichine, Abdallah
... We construct a realization Ap of A in the spaces Lp(Rd;Cm), 1 p < 1,
that generates a contractive strongly continuous semigroup. First, by using form
methods, we obtain generation of holomorphic semigroups when the potential V
is symmetric. In the general case, we use some other techniques of functional
analysis and operator theory to get a m-dissipative realization. But in this case
the semigroup is not, in general, analytic.
We characterize the domain of the operator Ap in Lp(Rd;Cm) by using rstly
a non commutative version of the Dore-Venni theorem and then a perturbation
theorem due to Okazawa.
We discuss some properties of the semigroup such as analyticity, compactness
and positivity. We establish ultracontractivity and deduce that the semigroup is
given by an integral kernel. Here, the kernel is actually a matrix whose entries
satisfy Gaussian upper estimates.
Further estimates of the kernel entries are given for potentials with a diagonal
of polynomial growth. Suitable estimates lead to the asymptotic behavior of the
eigenvalues of the matrix Schr odinger operator when the potential is symmetric. [edited by Author]
2016 - 2017
2018-04-06T00:00:00ZUnraveling biomarkers in Parkinson’s disease: the role of Insulin-like growth factor-1 (IGF-1) and DAT imagingPicillo, Marinahttp://hdl.handle.net/10556/31212019-01-27T01:06:12Z2018-02-28T00:00:00ZUnraveling biomarkers in Parkinson’s disease: the role of Insulin-like growth factor-1 (IGF-1) and DAT imaging
Picillo, Marina
Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's
disease, affecting up to 10 million individuals worldwide. Although symptomatic treatment
ameliorates motor symptoms, currently there are no disease-modifying treatments.
A biomarker is defined by the National Institutes of Health as “a characteristic that is objectively
measured and evaluated as an indicator of normal biological processes, pathogenic processes or
pharmacological responses to a therapeutic intervention”. Thus, biomarkers include clinical
data, measurements of biological samples (e.g., plasma, serum, cerebrospinal fluid) and application
of brain imaging techniques to detect changes in brain structure and function.
As for PD, biomarkers represent tools potentially suitable for either clinical or research settings and
useful in predicting onset, confirming diagnosis, detecting progression and evaluating the response
to disease-modifying treatments. In addition, biomarkers’ trends in different stages of disease may
reflect the widespread neurochemical and neuroanatomical changes that occur throughout the
course of PD and, thus, possibly suggest new insights in the pathophysiological mechanisms
underlying disease progression. The range of available biomarkers in PD is fast
expanding and includes an increasing number of laboratory, clinical and imaging data. ... [edited by Author]
2015 - 2016
2018-02-28T00:00:00ZMethods and algorithms for power devices losses behavioral modelingMigliaro, Mariohttp://hdl.handle.net/10556/31202019-01-27T01:05:54Z2017-08-07T00:00:00ZMethods and algorithms for power devices losses behavioral modeling
Migliaro, Mario
Power electronics is since decades in the focus of very important technology innovations, as the
characteristics and the performances of power supplies can severely condition and limit the performances
of the system to be fed. In almost all the applications there is the demand to increase as much as possible
the ratio between the maximum power the power supplies can deliver and their volume, defined as the
power-density while, at the same time, the cost must be as reduced as possible. For this reason, electronic
system designers have the task of finding, in a reasonable time, ever better performing solutions, choosing
the best semiconductor devices and magnetic components.
The attention of this thesis has been on the modeling of power losses of magnetic components and
semiconductor devices, considering that they have the biggest impact on the system efficiency. The model
classically adopted are usually calculated in different conditions from the operative conditions, require long
time simulations, need the knowledge input variables that cannot be easily measured and have coefficients
difficult to be identified. For this reason, the aim of this thesis has been to investigate a general approach to
identify power losses models of devices, obtained from experimental data. In particular, sufficiently accurate
and at the same time simple and intelligible loss model are desired.
The approach adopted is based on Genetic Programming (GP), that is an evolutionary method able to return
output models, in order to minimize a given fitness function that is a metric of the quality of the solution.
The goal of the algorithm has been to obtain models accurate, but at the same time simple and intelligible
for the user. These two desired conditions are often conflicting, being complicated models usually accurate
and simple models usually inaccurate. For this reason, a Multi Objective (MO) approach, returning a Pareto
Front composed non-dominated solutions, has been adopted. Moreover, the GP has been modified to return
parametric functions, having the same structure, but different coefficients for all the devices to characterize.
In this way, it is supposed to have a more general model, that is sufficiently good for all the devices. ... [edited by Author]
2015 - 2016
2017-08-07T00:00:00ZRisorse Umane, pratiche di gestione ad alta prestazione e performance d’aziendaMatarazzo, Giuseppehttp://hdl.handle.net/10556/31192019-02-05T01:06:20Z2018-01-30T00:00:00ZRisorse Umane, pratiche di gestione ad alta prestazione e performance d’azienda
Matarazzo, Giuseppe
Lo scopo di questa tesi è quello di descrivere ed esplorare la relazione tra la presenza di pratiche di gestione del lavoro ad alta prestazione ed il contesto aziendale, inteso sia come struttura che come composizione della forza lavoro. Per farlo è stato utilizzato il database Eurofound sulle aziende europee alla sua terza edizione (dati relativi all’annualità 2013), il cui campione è rappresentato da circa 27000 aziende rappresentative di 32 paesi. La tecnica utilizzata è quella di un modello di regressione lineare multipla in cui dagli scarti tra l’intercetta (i cui valori noti corrispondono all’Italia per il paese ed al punteggio più basso delle altre variabili) e le altre modalità fosse possibile vedere a parità di condizioni di partenza quali paesi e quali caratteristiche – raggruppabili in due macro aree grazie a variabili di struttura e di composizione della forza lavoro – favorissero la crescita e lo sviluppo di sistemi HR. La variabile dipendente, costruita per addizione, è data dalla somma di variabili dicotomiche – o dicotomizzate secondo le indicazioni della letteratura – di tipo categoriale. La validità del modello è stata testata con gli opportuni test di significatività e di robustezza. ... [abstract a cura dell'Autore]; The aim of this thesis is to describe and explore the relationship between the presence of High
Performance Work Practices (HPWP) and the business context, this one intended both as structure
and workforce arrangement. For the purpose, the Eurofound database has been used, at its third
edition (data related to 2013). This dataset is composed by about 27000 firms representative of 32
counties.
The technique used is the one of a multiple linear regression model where, from the deviation of the
intercept (whose known values correspond to Italy as country and to the other variables lower score)
and the other values, it could be possible to see - the starting conditions being equal - which countries
and what characteristics – possibly and subsequently grouped in two macro areas referred to firm
structure and workforce arrangement - will facilitate the growth and development of HR systems.
The dependent variable, built by addition, is given by the sum of dichotomous variables – or
dichotomised according to the literature indications - of categorical type. The validity of the model
was examined through appropriate significance and robustness tests. The results, consistent with the
expectations, have shown, with regard to the structure, a strong impact not only from the number of
employees but also from the presence or absence of departments connected to development and
innovation.
Regarding the workforce, a well-defined relationship was found between the dissemination of HR
practices and the employee’s education level and between the dissemination of HR practices and the
presence of a highly skilled workforce. ... [edited by Author]
2015 - 2016
2018-01-30T00:00:00Z