700 research outputs found
On the constrained mock-Chebyshev least-squares
The algebraic polynomial interpolation on uniformly distributed nodes is
affected by the Runge phenomenon, also when the function to be interpolated is
analytic. Among all techniques that have been proposed to defeat this
phenomenon, there is the mock-Chebyshev interpolation which is an interpolation
made on a subset of the given nodes whose elements mimic as well as possible
the Chebyshev-Lobatto points. In this work we use the simultaneous
approximation theory to combine the previous technique with a polynomial
regression in order to increase the accuracy of the approximation of a given
analytic function. We give indications on how to select the degree of the
simultaneous regression in order to obtain polynomial approximant good in the
uniform norm and provide a sufficient condition to improve, in that norm, the
accuracy of the mock-Chebyshev interpolation with a simultaneous regression.
Numerical results are provided.Comment: 17 pages, 9 figure
“Youth for future”: Qualitative survey of Italian youth and the environment. Tools for an ecopedagogy
El 2020, l’Institut Universitari Salesià de Venècia va efectuar l’enquesta amb mètodes mixtos «Joventut per al Futur» a dues mostres de joves italians: 1.821 d’edat entre 14 i 18 anys, i 1.523 d’entre 19 i 29. L’enquesta preguntava sobre la relació entre la qüestió ambiental en els joves i el futur. La recerca es va dissenyar per dur a terme l’estudi amb diferents instruments i assolir troballes des de perspectives quantitatives i qualitatives, que sovint competeixen en lloc de concórrer.Més enllà de la comparació amb els companys, ens preocupava sobretot la recerca qualitativa i aquesta és la part que es discuteix en l’article. Atès el gran nombre de participants, aquesta secció es va basar en una sola pregunta: una sol·licitud als joves perquè parlessin dels seus suggeriments sobre la relació humà / medi ambient.Com que el nostre bagatge és semiòtic i pedagògic, el propòsit de la nostra recerca era comprendre el sentiment respecte a l’entorn i les formes en què es construeix el significat dins de les llengües juvenils, més enllà dels estereotips i els enganys interpretatius del llenguatge. També proposar elements i oportunitats formatives per aproximar-nos a «l’estat de les coses» interceptant l’extensa (des)informació de la infoesfera, destacant els elements que transmeten les representacions a través de les quals construïm i mapem la nostra imatge del món. És un tema actualment ineludible per a l’educació.The environmental issue has become central in the public debate, but the new scenario of the infosphere within which it takes place with its informal formation, does not seem to increase awareness but rather confusion and cognitive difficulty that holds citizens back from participating in public decisions on the environment. An alarm for pedagogy, ecopedagogy and science in general that should foster a dialogue based on a different approach to the co-construction of knowledge between expert and lay knowledge and new education
Regular Black Holes and Horizonless Ultra-Compact Objects in Lorentz-Violating Gravity
There is growing evidence that Ho\v{r}ava gravity may be a viable quantum
theory of gravity. It is thus legitimate to expect that gravitational collapse
in the full, non-projectable version of the theory should result in geometries
that are free of spacetime singularities. Previous analyses have shown that
such geometries must belong to one of the following classes: simply connected
regular black holes with inner horizons; non-connected black holes "hiding" a
wormhole mouth (black bounces); simply connected or non-connected horizonless
compact objects. Here, we consider a singular black hole in the low-energy
limit of non-projectable Ho\v{r}ava gravity, i.e. khronometric theory, and
describe examples of its possible "regularisations", covering all of the viable
classes. To our knowledge, these examples constitute the first instances of
black holes with inner universal horizons, of black bounces and of stars with a
de Sitter core in the context of Lorentz-violating theories of gravity.Comment: 30 pages, 5 figures; comments welcom
Spectral behavior of preconditioned non-Hermitian multilevel block Toeplitz matrices with matrix-valued symbol
This note is devoted to preconditioning strategies for non-Hermitian
multilevel block Toeplitz linear systems associated with a multivariate
Lebesgue integrable matrix-valued symbol. In particular, we consider special
preconditioned matrices, where the preconditioner has a band multilevel block
Toeplitz structure, and we complement known results on the localization of the
spectrum with global distribution results for the eigenvalues of the
preconditioned matrices. In this respect, our main result is as follows. Let
, let be the linear space of complex matrices, and let be functions whose components
belong to .
Consider the matrices , where varies
in and are the multilevel block Toeplitz matrices
of size generated by . Then
, i.e. the family
of matrices has a global (asymptotic)
spectral distribution described by the function , provided
possesses certain properties (which ensure in particular the invertibility of
for all ) and the following topological conditions are met:
the essential range of , defined as the union of the essential ranges
of the eigenvalue functions , does not
disconnect the complex plane and has empty interior. This result generalizes
the one obtained by Donatelli, Neytcheva, Serra-Capizzano in a previous work,
concerning the non-preconditioned case . The last part of this note is
devoted to numerical experiments, which confirm the theoretical analysis and
suggest the choice of optimal GMRES preconditioning techniques to be used for
the considered linear systems.Comment: 18 pages, 26 figure
From material rent to immaterial rent: continuity or theoretical rupture?
In this paper we will try to represent in mathematical form some of the characteristics of a Post-Fordist economic system. In particular, we will focus on the theory of distribution, and on the role of income. We will try to identify the process that led to the crisis of Fordism by modifiyng the Ricardian framework presented in Pasinetti 1966. Rent in Fordist system of production is linked to the diminishing returns. In Post-Fordist production process we will assume a law of formation of (immaterial) rent related to increasing returns .Capitalismo Cognitivo; Fordismo; Pasinetti; Ricardo; rendita; Postfordismo
From individual to collective immunity: The role of the venom as antimicrobial agent in the Stenogastrinae wasp societies
Separation of heat and charge currents for boosted thermoelectric conversion
In a multi-terminal device the (electronic) heat and charge currents can
follow different paths. In this paper we introduce and analyse a class of
multi-terminal devices where this property is pushed to its extreme limits,
with charge heat currents flowing in different reservoirs. After
introducing the main characteristics of such
regime we show how to realise it in a multi-terminal device with
normal and superconducting leads. We demonstrate that this regime allows to
control independently heat and charge flows and to greatly enhance
thermoelectric performances at low temperatures. We analyse in details a
three-terminal setup involving a superconducting lead, a normal lead and a
voltage probe. For a generic scattering region we show that in the regime of
heat-charge current separation both the power factor and the figure of merit
are highly increased with respect to a standard two-terminal system. These
results are confirmed for the specific case of a system consisting of three
coupled quantum dots.Comment: 12 pages, 8 figure
Implementazione e analisi di algoritmi dinamici per trasmissione MPEG-DASH su client Android
Attualmente, la maggior parte dei dati che transitano sulla rete appartiene a contenuti multimediali. Più nello specifico, è lo Streaming Video ad avere la predominanza nella condivisione di Internet; vista la crescita che tale servizio ha subìto negli ultimi anni, si sono susseguiti diversi studi volti allo sviluppo di tecniche e metodologie che potessero migliorarlo. Una di queste è sicuramente l'Adaptive Video Streaming, tecnica utilizzata per garantire all'utente una buona Quality of Experience (QoE) mediante l'utilizzo dei cosiddetti "algoritmi di rate adaptation".
Il lavoro svolto in questi studi si è voluto concentrare su due filoni distinti, ma allo stesso tempo confrontabili: la prima parte della tesi riguarda lo sviluppo e l'analisi di alcuni algoritmi di rate adaptation per DASH, mentre la seconda è relativa all'implementazione di un nuovo algoritmo che li possa affiancare, migliorando la QoE nel monitorare lo stato della connessione.
Si è quindi dovuta implementare un'applicazione Android per lo streaming video, che fosse conforme allo standard MPEG-DASH e potesse fornire le informazioni di testing da utilizzare per le analisi.
La tesi è suddivisa in quattro capitoli: il primo introduce l'argomento e definisce la terminologia necessaria alla comprensione degli studi; il secondo descrive alcuni dei lavori correlati allo streaming adattivo e introduce i due filoni principali della tesi, ovvero gli algoritmi di rate adaptation e la proposta di algoritmo per la selezione dinamica del segmento; il terzo presenta l'app SSDash, utilizzata come mezzo per le analisi sperimentali; infine, il quarto ed ultimo capitolo mostra i risultati delle analisi e le corrispondenti valutazioni
Could time detect a faking-good attitude? A study with the MMPI-2-RF
Background and Purpose: Research on the relationship between response latency (RL) and faking in self-administered testing scenarios have generated contradictory findings. We explored this relationship further, aiming to add further insight into the reliability of self-report measures. We compared RLs and T-scores on the MMPI-2-RF (validity and restructured clinical [RC] scales) in four experimental groups. Our hypotheses were that: the Fake-Good Speeded group would obtain a different completion time; show higher RLs than the Honesty Speeded Group in the validity scales; show higher T-Scores in the L-r and K-r scales and lower T-scores in the F-r and RC scales; and show higher levels of tension and fatigue. Finally, the impact of the speeded condition in malingering was assessed. Materials and Methods: The sample was comprised of 135 subjects (M = 26.64; SD = 1.88 years old), all of whom were graduates (having completed at least 17 years of instruction), male, and Caucasian. Subjects were randomly assigned to four groups: Honesty Speeded, Fake-Good Speeded, Honesty Un-Speeded, and Fake-Good Un-Speeded. A software version of the MMPI-2-RF and Visual Analog Scale (VAS) were administered. To test the hypotheses, MANOVAs and binomial logistic regressions were run. Results: Significant differences were found between the four groups, and particularly between the Honest and Fake-Good groups in terms of test completion time and the L-r and K-r scales. The speeded condition increased T-scores in the L-r and K-r scales but decreased T-scores in some of the RC scales. The Fake groups also scored higher on the VAS Tension subscale. Completion times for the first and second parts of the MMPI-2-RF and T-scores for the K-r scale seemed to predict malingering. Conclusion: The speeded condition seemed to bring out the malingerers. Limitations include the sample size and gender bias
Differences in the development of nitrate tolerance and in its reversal with N-acetylcisteine between arterial and venous vessels in man
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