1,720,979 research outputs found
Disequazioni variazionali, problemi di ottimo e convessita' generalizzata
Full text linkIl lavoro fatto nella tesi propone un'estensione dei principali teoremi sulle disequazioni variazionali vettoriali (VVI), considerando l'ordinamento indotto da un generico cono C di R^p (convesso, chiuso, puntato e con interno non vuoto) anziche' dal classico cono d'ordine R^p_+ . Uno dei principali risultati e' l'estensione di un risultato in [2], che lega le VVI ad una famiglia di disequazioni variazionali scalari dipendenti da un parametro. Da esso seguono alcuni dei principali teoremi di esistenza mediante il riconducimento al caso scalare. Il risultato, inoltre, insieme ad opportune ipotesi di C-convessita' generalizzata sulla funzione obiettivo, garantisce l'esistenza di soluzioni per problemi di ottimo vettoriale.
Il lavoro si conclude con le dimostrazioni di due nuove condizioni sufficienti di buona posizione per una disequazione variazionale vettoriale debole (nel seguito VVI^w) il cui operatore ammette primitiva. La prima amplia la classe delle funzioni per cui viene garantita la buona posizione di VVI^w(X, Jf ), facendo uso dell'ipotesi di C-pseudo- convessit'a per la funzione f , anziche' di quella di C-convessit'a. L'altra condizione, oltre a far uso di quest'ipotesi piu' debole su f , richiede la connessione di alcuni insiemi coinvolti nella definizione di buona posizione e la limitatezza dell'insieme delle soluzioni del problema di ottimo vettoriale debole (nel seguito VOP^w). Da tali risultati sono poi dedotte altrettante condizioni sufficienti per la buona posizione di VOP^w( f , X)
Frame-Related Sequences in Chains and Scales of Hilbert Spaces
Full text linkFrames for Hilbert spaces are interesting for mathematicians but also important for applications in, e.g., signal analysis and physics. In both mathematics and physics, it is natural to consider a full scale of spaces, and not only a single one. In this paper, we study how certain frame-related properties of a certain sequence in one of the spaces, such as completeness or the property of being a (semi-) frame, propagate to the other ones in a scale of Hilbert spaces. We link that to the properties of the respective frame-related operators, such as analysis or synthesis. We start with a detailed survey of the theory of Hilbert chains. Using a canonical isomorphism, the properties of frame sequences are naturally preserved between different spaces. We also show that some results can be transferred if the original sequence is considered—in particular, that the upper semi-frame property is kept in larger spaces, while the lower one is kept in smaller ones. This leads to a negative result: a sequence can never be a frame for two Hilbert spaces of the scale if the scale is non-trivial, i.e., if the spaces are not equal
Frames and weak frames for unbounded operators
Full text linkIn 2012 G\u{a}vru\c{t}a introduced the notions of -frame and of atomic
system for a linear bounded operator in a Hilbert space , in
order to decompose its range with a frame-like expansion. In
this article we revisit these concepts for an unbounded and densely defined
operator in two different ways. In one case we
consider a non-Bessel sequence where the coefficient sequence depends
continuously on with respect to the norm of .
In the other case we consider a Bessel sequence and the coefficient sequence
depends continuously on with respect to the graph norm of
.Comment: 24 page
Topological aspects of quasi *-algebras with sufficiently many *-representations
Full text linkQuasi *-algebras possessing a sufficient family M of invariant positive sesquilinear forms carry several topologies related to M which make every *-representation continuous. This leads to define the class of locally convex quasi GA*-algebras whose main feature consists in the fact that the family of their bounded elements, with respect to the family M, is a dense C*-algebra
Studio sperimentale del moto di un carrello su un piano inclinato: una proposta didattica
No full textIl presente lavoro riguarda una proposta didattica sulla cinematica, formulata durante il Tirocinio Formativo Attivo (TFA) per la
classe A049 “Matematica e Fisica” che, a parere dell’autrice, è spendibile in tutti gli Istituti di istruzione superiore dotati delle
necessarie attrezzature di laboratorioThe present paper concerns a didactical proposal about cinematics, developed during the TFA (a one-year program for
secondary school teacher training) which, according to the author, is spendable in every school which is endowed with the
necessary laboratory equipment
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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