171,281 research outputs found
Exact reachability for second-order integro-differential equations
No full textIn this Note we analyze a reachability problem for an integro-differential equation by using a harmonic analysis approach. To cite this article: P Loreti, D. Sforza, C R. Acad. Sci. Paris, Ser. I 347 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved
On the topological structure of univoque sets
No full textErdos, Horvath and Joo discovered some years ago that for some real numbers 1 < q < 2 there exists only one sequence c(i) of zeroes and ones such that Sigma c(i) q(-i) = 1. Subsequently, the set U of these numbers was characterized algebraically in [P. Erdos, I. Joo, V. Komornik, Characterization of the unique expansions 1 = Sigma q(-ni) and related problems, Bull. Soc. Math. France 118 (1990) 377-390] and [V. Komornik, P. Loreti, Subexpansions, superexpansions and uniqueness properties in non-integer bases, Period. Math. Hungar. 44 (2) (2002) 195-216]. We establish an analogous characterization of the closure (U) over bar of U. This allows us to clarify the topological structure of these sets: (U) over bar U is a countable dense set of (U) over bar, so the latter set is perfect. Moreover, since U is known to have zero Lebesgue measure, (U) over bar is a Cantor set. (C) 2006 Elsevier Inc. All rights reserved
Modeling Adaptation with Klaim
No full textIn recent years, it has been argued that systems and applications, in order to deal with their increasing complexity, should be able to adapt their behavior according to new requirements or environment conditions. In this paper, we present an investigation aiming at studying how coordination languages and formal methods can contribute to a better understanding, implementation and use of the mechanisms and techniques for adaptation currently proposed in the literature. Our study relies on the formal coordination language Klaim as a common framework for modeling some well-known adaptation techniques: the IBM MAPE-K loop, the Accord component-based framework for architectural adaptation, and the aspect- and context-oriented programming paradigms. We illustrate our approach through a simple example concerning a data repository equipped with an automated cache mechanism
Effectiveness of overlay multicasting in mobile ad-hoc network
No full textThis paper investigates the effectiveness of the application level multicasting, named overlay multicasting, with respect to the network layer one in Mobile Ad Hoc Networks (MANET). With respect to network layer multicasting, in overlay multicasting only the mobile nodes participating to the multicast group exploit the multicast routing at application level, while the other nodes of the MANET simply perform unicast IP routing. This constraint in the possibility of use multicast routing in all nodes leads to a loss of efficiency in the bandwidth usage that we aims to discuss in this paper. The parameter used for the comparison is the cost of the multicast distribution tree, which is built by means of Steiner based algorithms. We measure this parameter by means of an exhaustive simulation campaign, analysing the performance dependence versus different parameters: device coverage range, number of MANET nodes, multicast group size and mobility model
Modeling adaptation with a tuple-based coordination language
No full textIn recent years, it has been argued that systems and applications, in order to deal with their increasing complexity, should be able to adapt their behavior according to new requirements or environment conditions. In this paper, we present a preliminary investigation aiming at studying how coordination languages and formal methods can contribute to a better understanding, implementation and usage of the mechanisms and techniques for adaptation currently proposed in the literature. Our study relies on the formal coordination language Klaim as a common framework for modeling some adaptation techniques, namely the MAPE-K loop, aspect- and context-oriented programming
Controllability for the Burgers model
No full textIn this paper we study vibrations of viscoelastic materials, whose behaviour can be represented by mechanical models given as combinations of springs and dashpots, and establish reachability results.(c) 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/)
A uniform definition of stochastic process calculi
No full textWe introduce a unifying framework to provide the semantics of process algebras, including their quantitative variants useful for modeling quantitative aspects of behaviors. The unifying framework is then used to describe some of the most representative stochastic process algebras. This
provides a general and clear support for an understanding of their similarities and differences. The framework is based on State to Function Labeled Transition Systems, FuTSs for short, that are state-transition structures where each transition is a triple of the form (s; α;P). The first andthe second components are the source state, s, and the label, α, of the transition, while the third component is the continuation function, P, associating a value of a suitable type to each state s0. For example, in the case of stochastic process algebras the value of the continuation function on s0 represents the rate of the negative exponential distribution characterizing the duration/delay of the action performed to reach state s0 from s. We first provide the semantics of a simple formalism used to describe Continuous-Time Markov Chains, then we model a number of process algebras that permit parallel composition of models according to the two main interaction paradigms (multiparty and one-to-one synchronization). Finally, we deal with formalisms where actions and rates are kept separate and address the issues related to the coexistence of stochastic, probabilistic, and non-deterministic behaviors. For each formalism, we establish the formal correspondence between the FuTSs semantics and its original semantics
Implementing a distributed mobile calculus using the IMC framework
No full textIn the last decade, many calculi for modelling distributed mobile code have been proposed. To assess their merits and encourage use, implementations of the calculi have often been proposed. These implementations usually consist of a limited part dealing with mechanisms that are specific of the proposed calculus and of a significantly larger part handling recurrent mechanisms that are common to many calculi. Nevertheless, also the "classic" parts are often re-implemented from scratch. In this paper we show how to implement a well established representative of the family of mobile calculi, the distributed [pi]-calculus, by using a Java middleware (called IMC - Implementing Mobile Calculi) where recurrent mechanisms of distributed and mobile systems are already implemented. By means of the case study, we illustrate a methodology to accelerate the development of prototype implementations while concentrating only on the features that are specific of the calculus under consideration and relying on the common framework for all the recurrent mechanisms like network connections, code mobility, name handling, etc
Towards a Formal Verification Methodology for Collective Robotic Systems
No full textWe introduce a UML-based notation for graphically modeling
systems’ security aspects in a simple and intuitive
way and a model-driven process that transforms graphical
specifications of access control policies in XACML. These
XACML policies are then translated in FACPL, a policy
language with a formal semantics, and the resulting policies
are evaluated by means of a Java-based software tool
Optimal expansions of Kakeya sequences
No full textWe investigate optimal expansions of Kakeya sequences for the presentation of real numbers. Expansions of Kakeya sequences generalize the expansions in non-integer bases and they display analogous redundancy phenomena. In this paper, we characterize optimal expansions of Kakeya sequences, and we provide conditions for the existence of unique expansions with respect to Kakeyasequences
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