34 research outputs found
Stability of equilibria and bifurcations for a fluid-solid interaction problem
No full textWe study certain significant properties of the equilibrium configurations of a rigid body subject to an undamped elastic restoring force, in the stream of a viscous liquid in an unbounded 3D domain. The motion of the coupled system is driven by a uniform flow at spatial infinity, with constant dimensionless velocity lambda. We show that if lambda is below a critical value, lambda(c )(say), there is a unique and stable time-independent configuration, where the body is in equilibrium and the flow is steady. We also prove that, if lambda < lambda(c) , no oscillatory flow may occur. Successively, we investigate possible loss of uniqueness by providing necessary and sufficient conditions for the occurrence of a steady bifurcation at some lambda(s) >= lambda (c) . (c) 2024 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons .org /licenses /by -nc -nd /4 .0/)
Operation of Cs-Sb-O activated GaAs in a high voltage DC electron gun at high average current
No full textNegative Electron Affinity (NEA) activated GaAs photocathodes are the most popular option for generating a high current (>1 mA) spin-polarized electron beam. Despite its popularity, a short operational lifetime is the main drawback of this material. Recent works have shown that the lifetime can be improved by using a robust Cs-Sb-O NEA layer with minimal adverse effects. In this work, we operate GaAs photocathodes with this new activation method in a high voltage environment to extract a high current. We demonstrate that improved chemical resistance of Cs-Sb-O activated GaAs photocathodes allowed them to survive a day-long transport process from a separate vacuum system using a vacuum suitcase. During beam running, we observed spectral dependence on lifetime improvement. In particular, we saw a 45% increase in the lifetime at 780 nm on average for Cs-Sb-O activated GaAs compared to Cs-O activated GaAs. © 2022 Author(s)
Teoremi di unicità della magnetoidrodinamica in domini illimitati
No full textThe Author establishes two solution uniqueness theorems for the problem of homogeneous, incompressible, perfect, electrically conducting fluid motion around a fixed, electrically conducting solid body. In the first theorem displacemt current is disregarded, in the other one this current is considered. The proof is obtained by using the "weight function method" adopted by G. P. Galdi and S. Rionero in an analogous uniqueness theorem for viscous magnetofluids. © 1979 Università degli Studi di Ferrara
Syntactic and stylistic remarks on the Epitome de Caesaribus
No full textThe so called Epitome de Caesaribus, whose author is unknown, is a short historical work, written between 395 and 408 AD, which deals with the reigns of the Roman emperors from Augustus to Theodosius the Great. The text follows different sources, notably Aurelius Victor and Eutropius. Due to the frequent use of these texts, which are sometimes copied word for word, modern commentators have often expressed a harsh judgment on the style and language of the author, denying him any sort of originality. The aim of this paper is to examine the syntax and style of the text, focusing on subordinate clauses. Specifically, through the presentation of some statistical data and their comparison with other historical works, we shall discuss certain specific features of the Epitome and its relation with the sources.Galdi Giovanbattista. Syntactic and stylistic remarks on the Epitome de Caesaribus. In: Latin vulgaire – latin tardif IX. Actes du IXe colloque international sur le latin vulgaire et tardif, Lyon 2-6 septembre 2009. Lyon : Maison de l'Orient et de la Méditerranée Jean Pouilloux, 2012. pp. 921-932. (Collection de la Maison de l'Orient méditerranéen ancien. Série philologique, 49
Searching for order in the Rule : the contribution of philology and linguistics to the study of Saint Benedict’s Latin
No full textBenedict’s Regula (ca. AD 540) was handed down by hundreds of manuscripts dating from the early 8th cent. AD onwards. Many of them display a large number of non-standard linguistic features, but it is unknown how many of them were extant in Benedict’s original. Our contribution discusses three interrelated questions. First, we focus on the most authoritative manuscript (Sangallensis 914), illustrating a new methodological approach that allows us to better assess its reliability. Second, we examine various instances of variation in the text, suggesting that they can be attributed to the author himself. Finally, we show how the study of Benedict’s Latin can greatly benefit from the application of some criteria recently established in historical linguistics studies
Stationary Navier-Stokes equations in an exterior domain, and some integral identities for Euler and Navier-Stokes equations
No full textWe study: 1) the stationary Navier-Stokes equations in a two-dimensional exterior domain, 2) some integral identities for the Euler and the Navier-Stokes equations. For the first topic, we consider the non-homogenous boundary value problem in a two-dimensional exterior domain together with a prescribed condition at infinity and establish existence of a solution to the problem provided that the boundary value on the boundary of the domain is close to a potential flow; this assumption allows some large boundary value. Indeed, we utilize results of Galdi in 2004 on the Oseen equations, a linearization around a constant nonzero vector. Then we apply ideas used in Russo and Starita's work (in 2008) in three dimension, which is to perturb around a potential flow; in conjunction with the compactness of some linear operator related to the Oseen equations, which is a result again of Galdi in 2004.
For the second topic, Dobrokhotov and Shafarevich in 1994 proved some integral identities for the Euler and Navier-Stokes equations. Chae in 2012 proved these integral identities on a hyperplane for a weak solution with some integrability assumptions on the solution. In this thesis, we prove the integral identities on a hyperplane with some different integrability assumptions. It also furnishes a Liouville type theorem as an immediate application, providing a different approach to some of the results of Hamel and Nadirashvili in 2017, 2019, Chae and Constantin in 2015.Ph.D.Includes bibliographical reference
Magnetic orbital and transport properties in LaMnO3 based based heterostructures
No full text2009 - 2010This thesis work deals with the magnetic, orbital and transport properties of (LaMnO3)2N(SrMnO3)N digital superlattices and of LaxMnO3-d thin films, both deposited by molecular beam epitaxy (MBE) technique on SrTiO3 substrates. The (LaMnO3)2N(SrMnO3)N digital superlattices represent the new kind of heterostructure, actually under intensive study, composed by an integer number of unit cells, where electronic reconstruction effects at the (clean) interface are expected.
In the first part of the thesis work, optical lithography techniques and different deposition techniques are employed in order to perform transport measurement in current perpendicular to plane (CPP) configuration and field effect measurements. The CPP technique would allow to gain more information respect to the in-plane measurements as the ones used in the first part of the thesis. Field effect has been widely investigated in manganite (especially LMO-based) systems, as it represents a method to tune the carrier density, and in order to engineer all oxide field effect devices. The results of the optimization of such techniques, together with the optimization of the materials needed as base electrode, side and gate insulators and top electrode is reported.
In the second part of the thesis, both LaMnO3-based systems were studied by traditional techniques (transport measurements, SQUID magnetometer) and soft X-ray absorption and emission techniques by synchrotron radiation. Collecting the data from different measurement techniques, precious information about ferromagnetism, antiferromagnetism and orbital ordering is obtained. [edited by Author]IX n.s
Some remarks on the language of the Itinerarium Antonini Placentini
No full textThe text of the Itinerarium Antonini Placentini, the anonymous account of a travel to the Holy Land dated to ca. 570 AD, is transmitted by two main families of manuscripts: the recensio prior (a), represented by the Sangallensis 133 (G), 8th-9th cent., and the Rhenaugiensis (R), 9th cent. and the recensio altera (13), preserved in several manuscripts. There is broad consensus among scholars that the Latin of (13) largely results from a later normalization in Carolingian times. It is disputed, instead, whether the original text is better preserved in G, which often 'deviates' from standard Latin, or in R, which is much closer to classical canons. In our paper, we will concentrate on noun morphology and on the treatment of final -m. Through the presentation of statistical data and the discussion of selected examples, we shall show that, although G occasionally modifies the text of its archetype, several morphological errors occurring in it may be put down to the author himself. Conversely, R displays a clear tendency to correct the text. Additionally, we will claim that the frequent use, in G, of the endings -a and -as in the accusative singular and nominative plural, respectively, of feminine names are likely to reflect the gradual extension of a casus unicus, which is also found in Romance
Building functional neuromarkers from resting state fMRI to describe physiopathological traits
No full text2016 - 2017The overarching goal of this work has been that of devising novel methods
for building functional neuromarkers from resting-state fMRI data to describe
healthy and pathological human behaviour. Observing spontaneous uctuations
of the BOLD signal, resting-state fMRI allows to have an insight into the
functional organisation of the brain and to detect functional networks that are
consistent across subjects. Studying how patterns of functional connectivity
vary both in healthy subjects and in subjects a ected by a neurodegenerative
disease is a way to shed light on the physiological and pathological mechanisms
governing our nervous system.
The rst part of this thesis is devoted to the description of fully data-driven
feature extraction techniques based on clustering aimed at supporting the diagnosis
of neurodegenerative diseases (e.g., amyotrophic lateral sclerosis and
Parkinson's disease). The high-dimensional nature of resting state fMRI data
implies the need of suitable feature selection techniques. Traditional univariate
techniques are fast and straightforward to interpret, but are unable to unveil
relationships among multiple features. For this reason, this work presents a
methodology based on consensus clustering, a particular approach to the clustering
problem that consists in combining di erent partitions of the same data
set to produce more stable solutions. One of the objectives of fMRI data analysis
is to determine regions that show an abnormal activity with respect to a healthy
brain and this is often attained with comparative statistical models applied to
single voxels or brain parcels within one or several functional networks. Here,
stochastic rank aggregation is applied to identify brain regions that exhibit a
coherent behaviour in groups of subjects a ected by the same disorder. The
proposed methodology was validated on real data and the results are consistent
with previous literature, thus indicating that this approach might be suitable
to support early diagnosis of neurodegenerative diseases... [edited by Author]XXX cicl
Diritto dei contribuenti nei principali ordinamenti europei
No full text2014 - 2015The object of this research is to compare the experience of different national legal systems on the scope of the rights granted to the taxpayer to the tax authorities before and in particular to the meaning attributed to the participation of the private part of the investigation procedure, in order defense of their rights and interests in advance with respect to the adoption of tax. . And 'it analyzed, into French law, Italian, Portuguese and English, the legislative framework that governs the verification activities along with its most recent jurisprudence. The taxing jurisdictions examined have not, to date, developed uniformly the procedural guarantees. Some countries, as you granted, place a strong emphasis on the need for protection of the taxpayer with respect to the view prior formalization of assessment and governed the defensive contradiction as a moment before the adoption of the tax measure. The contradictory expression of the right of defense, is recognized by law in certain jurisdictions, as a general principle and as a prerogative of all assessment activities in the broadest sense. The defensive function is to be recognized in the participation of the taxpayer's examine the facts and documents acquired by the Directors during the exercise of the powers of control and are therefore equally guaranteed both the defensive contradictory as participation in the audit. In this way, he finds himself in some national legal affirmation of the adversarial principle underlying the recognition of the centrality of the right of defense of the taxpayer within the assessment in a broad sense; the contradictory as procedural time is the main expression of this principle, which however also emphasized with reference to the actions of the taxpayer that can be placed on a collaborative control. In other countries, however, the assessment does not provide for positive discipline adversarial moment prior to the formalization of the opinion of the investigation and the legal system is less open to ensure the protection of the taxpayer forms of facilitating the exercise of the right of defense in the verification process, for both the control activities for both the next relative to the predisposition of the assessment order. It prefers, in these
countries, reserving the context of legal proceedings the exercise of fair hearing of the taxpayer. In research is carried out further comparisons between the experiences of national legal systems and trends currently present in Community law, to the influence that it exerts on the development of national systems examined, following the signing of the Treaty on ' European Union. [edited by author]XIV n.s
