1,721,145 research outputs found
On the industrial fitness of WCET analysis
No full textThe process requirements that govern the development of high-integrity real-time systems make timing analysis an ineludible concern. Conceptually, the problem space of timing analysis includes the determination of the best, average and worst-case bounds for the execution time of the program parts of interest. As the problem space is vast, as often is the program to analyse, industry seeks tools and methods that can address its need effectively, that is to say, with a decent cost-benefit ratio. Static analysis is widely acknowledged as the most authoritative means to derive safe bounds on the worst-case execution time (WCET). The WCET in turn is the prerequisite input to feasibility analysis. Without WCET, feasibility analysis is just pointless. In terms of cost-benefit ratio, the value of feasibility analysis must be not inferior to the joint cost of obtaining the WCET values, ensuring the compliance of the system (at least in the worst case) to the analysis model, and running the analysis itself. It is not a given that this equation always holds in practice. When it does not, it is important to understand what are the impediments and how they can be slashed. Static WCET analysis is exposed to known fragilities in terms of cost efficiency and value tightness. Yet, the important progress achieved in the research around it suggests that the "WCET problem" is virtually solved, and quite satisfactorily so for simple single-processor architectures. The industrial ground, however, is the sole terrain where the truth of that claim can be ascertained. In this paper we discuss lessons learned from an experiment, massive for size, duration and effort, aimed to the timing analysis of a significant component of the software application embedded onboard a commercial satellite system. We discuss the limitations which we incurred in our application of static WCET analysis, highlighting those which we consider intrinsic to the method itself when confronted with the challenges of industrialscale systems
L'Unione Matematica Italiana nelle sue carte. Testimonianze dall'Archivio Storico
No full textL’Archivio storico dell'Unione Matematica Italiana - UMI - è stato di recente riordinato e messo a disposizione degli studiosi. Nello specifico, una parte, relativa al periodo 1938-1950, è stata aperta per la prima volta. Sono emersi interessanti documenti inerenti all'atteggiamento dell'UMI riguardo alle leggi razziali, che evidenziano il ruolo giocato dai matematici, come da altri intellettuali e scienziati, nel consolidamento del regime fascista
On a class of first order congruences of lines
No full textWe study a class of new examples of congruences of lines of order one, i.e. the congruences associated to the completely exceptional Monge-Ampère equations. We prove that they are in general not linear, and that through a general point of the focal locus there passes a planar pencil of lines of the congruence. In particular, the completely exceptional Monge-Ampère equations are of Temple type
Vector spaces of skew-symmetric matrices of constant rank
No full textWe study the orbits of vector spaces of skew-symmetric matrices of
constant rank 2r and type (N + 1) x (N + 1) under the natural action of
SL(N + 1), over an algebraically closed field of characteristic zero. We
give a complete description of the orbits for vector spaces of dimension
2, relating them to some 1-generic matrices of linear forms. We also
show that, for each rank two vector bundle on P^2 defining a triple
Veronese embedding of P^2 in G(1, 7), there exists a vector space of 8
x 8 skew-symmetric matrices of constant rank 6 whose kernel bundle is
the dual of the given rank two vector bundle
Erratum to: ``On the Hilbert scheme of Palatini threefolds'' [Adv. Geom. 2 (2002), no. 4, 371--389; MR1940444]
No full textIn our paper "On the Hilbert scheme of Palatini threefolds", we studied the regularity of the map ρ : G(3, (P^14)^*) − − → H, where H is the irreducible component of the Hilbert scheme of threefolds in P5 containing the Palatini scrolls. The map ρ associates to a web of linear complexes of lines in its singular set X. We have realized that there is one exception in Theorem 4.3 e we correct the result
On the Hilbert Scheme of Palatini threefolds
No full textIn this paper we study the Hilbert scheme of Palatini threefolds X in P-5. We prove that such a scheme has an irreducible component containing X which is birational to the Grassmannian G(3, P^14) and we determine the exceptional locus of the birational map
Transizioni costituzionali e consolidamento democratico in Asia agli albori del XXI secolo
No full textPercorsi delle transizioni costituzionali e processi di consolidamento degli ordinamenti asiatici agli albori del XXI secol
On congruences of linear spaces of order one
Full text linkAfter presenting the main notions and results about
congruences of k-planes, we dwell upon congruences of lines, mainly of order one. We survey the classification results in the projective spaces of dimension 3 and 4, which are almost complete, and the (partial) results and some conjectures in higher
dimension. Finally we present some new results, in particular a degree bound for varieties with one apparent double point, a new class of examples with focal locus of high degree, and some general results about the classification of first order congruences of lines in P^4 with reducible focal surface
Perazzo 3-folds and the weak Lefschetz property
Full text linkWe deal with Perazzo 3-folds in P4, i.e. hypersurfaces X = V(f) subset of P4 of degree d defined by a homogeneous polynomial f(x0, x1, x2, u, v) = p0(u, v)x0 +p1(u, v)x1 + p2(u, v)x2 + g(u, v), where p0, p1, p2 are algebraically dependent but linearly independent forms of degree d - 1 in u, v, and g is a form in u, v of degree d. Perazzo 3-folds have vanishing hessian and, hence, the associated graded Artinian Gorenstein algebra Af fails the strong Lefschetz Property. In this paper, we determine the maximum and minimum Hilbert function of Af and we prove that if Af has maximal Hilbert function it fails the weak Lefschetz Property while it satisfies the weak Lefschetz Property when it has minimum Hilbert function. In addition, we classify all Perazzo 3-folds in P4 such that Af has minimum Hilbert function.(c) 2023 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/)
Principi costituzionali e obblighi convenzionali di tutela penale nel contesto del controllo di convenzionalità.
No full textIl principio di legalità in materia penale, tradizionalmente espresso dal brocardo nullum crimen sine lege, e, più in generale, i principi costituzionali, stanno subendo significativi processi di torsione sotto l’influsso delle fonti internazionali e sovranazionali nonché della giurisprudenza di Strasburgo e Lussemburgo. Un’ipotesi paradigmatica del fenomeno è rappresentata dalla materia penale, presi-diata da una ricca grammatica di principi costituzionali che devono confrontarsi con le indicazioni provenienti dall’elaborazione pretoria di origine esterna. In tale contesto, la riflessione si concentrerà sulle relazioni tra il principio costituzionale di legalità in materia penale e gli obblighi di incrimina-zione provenienti dalla Corte di Strasburgo. La tensione tra questi due termini si manifesta in modo significativo nel contesto del controllo di convenzionalità, ossia all’interno della sequenza di operazioni logico-giuridiche nelle quali si articola la verifica della Corte costituzionale circa la conformità delle disposizioni giuridiche interne alla Cedu. Rispetto ad ipotesi di inerzia del legislatore italiano nell’adempiere gli obblighi positivi di tutela penale, il controllo di convenzionalità mostra un’aporia, che si sostanzia nell’impossibilità per la Corte costituzionale di pronunciare sentenze additive in ma-lam partem in materia penale e di assicurare, quindi, l’osservanza degli obblighi internazionali richiamati dall’art. 117, comma 1 Cost., norma di copertura della Cedu secondo l’impostazione ricostruttiva sviluppata dalla Corte costituzionale a partire dalle sentenze 348 e 349 del 2007. Emerge, pertanto, una problematica relazione tra l’art. 25, comma 2 Cost. e l’art. 117, comma 1 Cost., sulla quale si intende svolgere alcune riflessioni
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