3,759 research outputs found
Surface Resistance of Superconductors in the Presence of a DC Magnetic Field: Frequency and Field Intensity Limits
No full textWe revisit the classical rigid-fluxon model which describes the effect of an applied magnetic flux on the RF surface resistance of a superconductor and discuss explicit formulations for a few limit cases. As an application, we discuss the role of magnetic flux on the enhanced surface resistance of RF accelerating cavities based on niobium, depending on its material properties. We also assess the conditions for the use of high-temperature superconductors for carrying the beam image RF currents in future high-energy circular hadron colliders such as the future circular collider being studied at CERN
CLUSTERING FINANCIAL TIME SERIES BY NETWORK COMMUNITY ANALYSIS
No full text In this paper, we describe a method for clustering financial time series which is based on community analysis, a recently developed approach for partitioning the nodes of a network (graph). A network with N nodes is associated to the set of N time series. The weight of the link (i, j), which quantifies the similarity between the two corresponding time series, is defined according to a metric based on symbolic time series analysis, which has recently proved effective in the context of financial time series. Then, searching for network communities allows one to identify groups of nodes (and then time series) with strong similarity. A quantitative assessment of the significance of the obtained partition is also provided. The method is applied to two distinct case-studies concerning the US and Italy Stock Exchange, respectively. In the US case, the stability of the partitions over time is also thoroughly investigated. The results favorably compare with those obtained with the standard tools typically used for clustering financial time series, such as the minimal spanning tree and the hierarchical tree. </jats:p
Communities in Italian corporate networks
No full textThe community structure of two real-world financial networks, namely the board network and the ownership network of the firms of the Italian Stock Exchange, is analyzed by means of the maximum modularity approach. The main result is that both networks exhibit a strong community structure and, moreover, that the two structures overlap significantly. This is due to a number of reasons, including the existence of pyramidal groups and directors serving in several boards. Overall, this means that the ``small world'' of listed companies is actually split into well identifiable ``continents'' (i.e., the communities)
Advances in the study of HTS superconductors for the beam impedance mitigation in CERN-FCC: the thermal runaway problem
No full textIn CERN Future Circular Collider (FCC-hh), a possible next-generation high-energy hadron–hadron collider, the center-of-mass collision energy will be of 100 TeV, with opposite proton beams of 50 TeV steered in a 100-km circumference tunnel by 16 T superconducting magnets. The synchrotron radiation, emitted by the beams, is absorbed by a beam-facing screen held at 50 K. The surface impedance of this screen has a strong impact on the beam stability, and copper at 50 K allows only tight beam stability margin. This has motivated investigating the possibility of high-temperature superconductors (HTSs) coatings on the beam screen internal surface, as a possible solution. In this communication, we will briefly review the general theory of the surface resistance of HTS in high field, low frequency regimes and will present specific calculations for REBCO commercial tapes that represent one of the possible envisaged solutions. The possible “thermal runaway” problems arising using REBCO tapes are then discussed. In particular, the upper limit for the transverse thermal resistance that guarantees thermal stability is quantitatively determined as a function of the REBCO superconducting properties at FCC operating conditions
Simple model for the rf field amplitude dependence of the trapped flux sensitivity in superconducting rf cavities
No full textThe improvement of the performance of superconducting rf cavities has recently motivated a considerable research effort in order to elucidate the effect of trapped magnetic flux on the surface resistance R_{s}. In this paper, we show that, by introducing a nonlinear pinning force in the Gittleman-Rosenblum equations for the rf power dissipation due to a trapped magnetic flux in a superconductor, we can empirically describe the linear dependence on the rf field amplitude B_{rf0} of the additional surface resistance R_{fl}. We also show that the proportionality between the rf-field-dependent and -independent terms R_{fl}^{1} and R_{fl}^{0} and the frequency dependence of R_{fl}^{1} follow naturally from this approach
Il contributo di Sergio Torsello alla renaissance salentina del primo quindicennio del 2000
No full textQuesto contributo mira a descrivere le tre “anime” di Sergio Torsello – Direttore Artistico del Festival La Notte della Taranta, Consulente Scientifico dell’Istituto Diego Carpitella, e Mediatore Culturale tra e per i talenti artistici del suo territorio. Il punto di partenza della narrazione è un articolo di Sergio Torsello, pubblicato nel 2011 in un volume di cui l’autore della narrazione è stato curatore. L’autore sottolinea la stretta connessione tra le tre anime di Sergio Torsello, che emerge non solo dal suo articolo del 2011 ma anche dalle numerose interazioni avvenute tra Sergio Torsello e l’autore. La descrizione del rilievo scientifico della figura di Sergio Torsello è sicuramente parziale, circoscritta nel tempo (gli 8 anni, dal 2007 al 2015 in cui ha interagito con l’autore) e nello spazio (inteso come insieme di argomenti delle loro conversazioni scientifiche e culturali). Ma rende merito del cruciale contributo di Sergio Torsello alla renaissance culturale salentina degli anni dal 2001 al 2015.This contribution aims to describe the three “souls” of Sergio Torsello – Artistic Director of “La Notte della Taranta” Festival, Scientific Consultant of “Diego Carpitella” Institute, and Cultural Mediator
between and for the artistic talents of his territory. The starting point of the description is an article by Sergio Torsello, published in 2011 in a book of which the author of the description was the editor. The author highlights the close connection between the three souls of Sergio Torsello, which emerges not only from the above-mentioned article, but also from the numerous interactions between Sergio Torsello and the author. The description of the scientific significance of Sergio Torsello’s figure is certainly partial, limited in time (the 8 years, from 2007 to 2015, in which he interacted with the author) and in space (in terms of set of topics of their scientific and cultural conversations). But it gives merit to Sergio Torsello’s key contribution to the cultural renaissance of Salento in the years from 2001 to 2015
Stochastic Generalized Nash Equilibrium-Seeking in Merely Monotone Games
No full textWe solve the stochastic generalized Nash equilibrium (SGNE) problem in merely monotone games with expected value cost functions. Specifically, we present the first distributed SGNE-seeking algorithm for monotone games that require one proximal computation (e.g., one projection step) and one pseudogradient evaluation per iteration. Our main contribution is to extend the relaxed forward–backward operator splitting by the Malitsky (Mathematical Programming, 2019) to the stochastic case and in turn to show almost sure convergence to an SGNE when the expected value of the pseudogradient is approximated by the average over a number of random samples.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Sergio GrammaticoTeam Bart De Schutte
Sergio Bettini e la critica d’arte
No full textOn the occasion of the publication of two books about Sergio Bettini’s works (unpublished studies, conference proceedings and critical apparatus) the author analyzes the scientific production of this scholar during his life (1930-1986). Furtherly this essay analyzes the great scholar’s relationship with the School of Wien and first of all his deep connection with all European different critical and comparative points of view
Guest Editorial: Introduction to IEEE Control Systems Letters Special Section on Multi-Agent Coordination for Energy Systems: From Model Based to Data-Driven Methods
No full textEditorialGreen Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Sergio GrammaticoTeam Bart De Schutte
Cromatismo, ritmo, memoria: sulla narrativa di Sergio Atzeni
No full textSergio Atzeni’s works are many and really heterogeneous, both in style and contents. But if we dig up deeply into his texts, we discover that the currents followed by the author are always the same, and that texts that are apparently different have actually significant common aspects.Le opere di Sergio Atzeni sono numerose e molto eterogenee, sia nello stile che nei contenuti. Ma se andiamo a scavare nel profondo, ci rendiamo conto che i filoni seguiti dall’autore sono sempre gli stessi, e che esiti testuali apparentemente distinti hanno in realtà importanti aspetti in comune
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