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Petersen A.M.,IMT Lucca Institute for Advanced Studies | Succi S.,Istituto Applicazioni Calcolo | Succi S.,Freiburg Institute for Advanced Studies
Journal of Informetrics | Year: 2013

We present a simple generalization of Hirsch's h-index, Z≡h2+C/5, where C is the total number of citations. Z is aimed at correcting the potentially excessive penalty made by h on a scientist's highly cited papers, because for the majority of scientists analyzed, we find the excess citation fraction (C-h2)/C to be distributed closely around the value 0.75, meaning that 75% of the author's impact is neglected. Additionally, Z is less sensitive to local changes in a scientist's citation profile, namely perturbations which increase h while only marginally affecting C. Using real career data for 476 physicists careers and 488 biologist careers, we analyze both the distribution of Z and the rank stability of Z with respect to the Hirsch index h and the Egghe index g. We analyze careers distributed across a wide range of total impact, including top-cited physicists and biologists for benchmark comparison. In practice, the Z-index requires the same information needed to calculate h and could be effortlessly incorporated within career profile databases, such as Google Scholar and ResearcherID. Because Z incorporates information from the entire publication profile while being more robust than h and g to local perturbations, we argue that Z is better suited for ranking comparisons in academic decision-making scenarios comprising a large number of scientists. © 2013 Elsevier Ltd. Source


Buscemi M.G.,IMT Lucca Institute for Advanced Studies | Montanari U.,University of Pisa
Journal of Logic and Algebraic Programming | Year: 2011

Service composition in Service Oriented Computing concerns not only integration of heterogeneous distributed applications but also dynamic selection of services. Quality of Service (QoS) plays a key role in service composition as services providing the same functionalities can be differentiated according to their QoS guarantees. At subscription time, a service requester and a provider may sign a contract recording the QoS of the supplied service. The cc-pi calculus has been introduced as a constraint-based model of QoS contracts. In this work we propose a variant of the cc-pi calculus in which the alternatives in a choice rather than being selected non-deterministically have a dynamic priority. Basically, a guard cj:πj in a choice is enabled if the constraint cj is entailed by the store of constraints and the prefix πj can be consumed. Moreover, the j-th branch can be selected not only if the corresponding guard cj:πj is enabled but also if cj is weaker than the constraints ci of the other enabled alternatives. We prove that our choice operator is more general than a choice operator with static priority. Finally, we exploit some examples to show that our prioritised calculus allows arbitrarily complex QoS negotiations and that a static form of priority is strictly less expressive than ours. © 2010 Elsevier Inc. All rights reserved. Source


Barbuti R.,University of Pisa | Levi F.,University of Pisa | Milazzo P.,University of Pisa | Scatena G.,IMT Lucca Institute for Advanced Studies
Theoretical Computer Science | Year: 2012

In this paper, we present a formalization of biological systems based on multiset rewriting and we investigate the use of abstract interpretation on its semantics. We consider a probabilistic semantics, which is well suited to represent the non-deterministic evolution of real biological systems. Abstract interpretation allows us to deal with systems in which the kinetic rates of the evolution rules are not precisely known. On the (abstract) systems, we perform probabilistic model checking obtaining lower and upper bounds for the probabilities of reaching states satisfying the given properties. We apply abstract probabilistic model checking to verify reachability properties in a model of tumor growth. © 2011 Elsevier B.V. All rights reserved. Source


Bonchi F.,French National Center for Scientific Research | Buscemi M.G.,IMT Lucca Institute for Advanced Studies | Ciancia V.,University of Amsterdam | Gadducci F.,University of Pisa
Journal of Automated Reasoning | Year: 2012

Name passing calculi are nowadays one of the preferred formalisms for the specification of concurrent and distributed systems with a dynamically evolving topology. Despite their widespread adoption as a theoretical tool, though, they still face some unresolved semantic issues, since the standard operational, denotational and logical methods often proved inadequate to reason about these formalisms. A domain which has been successfully employed for languages with asymmetric communication, like the π-calculus, are presheaf categories based on (injective) rela-bellings, such as Set I. Calculi with symmetric binding, in the spirit of the fusion calculus, give rise to novel research challenges. In this work we examine the explicit fusion calculus, and propose to model its syntax and semantics using the presheaf category Set E, where E is the category of equivalence relations and equivalence preserving morphisms. © 2012 Springer Science+Business Media, LLC. Source


Cimino M.G.C.A.,University of Pisa | Lazzerini B.,University of Pisa | Marcelloni F.,University of Pisa | Ciaramella A.,IMT Lucca Institute for Advanced Studies
Expert Systems with Applications | Year: 2012

Situation awareness is a powerful paradigm that can efficiently exploit the increasing capabilities of handheld devices, such as smart phones and PDAs. Indeed, accurate understanding of the current situation can allow the device to proactively provide information and propose services to users in mobility. Of course, to recognize the situation is a challenging task, due to such factors as the variety of possible situations, uncertain and imprecise data, and different user's preferences and behavior. In this framework, we propose a robust and general rule-based approach to manage situation awareness. We adopt Semantic Web reasoning, fuzzy logic modeling, and genetic algorithms to handle, respectively, situational/contextual inference, uncertain input processing, and adaptation to the user's behavior. We exploit an agent-oriented architecture so as to provide both functional and structural interoperability in an open environment. The system is evaluated by means of a real-world case study concerning resource recommendation. Experimental results show the effectiveness of the proposed approach. © 2012 Elsevier Ltd. All rights reserved. Source

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