1,721,238 research outputs found
Monte Carlo Markov chains constrained on graphs for a target with disconnected support∗
Full text linkThis paper presents a theoretical Monte Carlo Markov chain procedure in the framework of graphs. It specifically deals with the construction of a Markov chain whose empirical distribution converges to a given reference one. The Markov chain is constrained over an underlying graph so that states are viewed as vertices, and the transition between two states can have positive probability only in the presence of an edge connecting them. The analysis focuses on the relevant case of support of the target distribution not connected in the graph. Some general arguments on the speed of convergence are also carried out
Nomenclatural Synopsis, Revised Distribution and Conservation Status of Ranunculus gracilis (Ranunculaceae) in Italy
Full text linkRanuculus gracilis is endemic to the SE Euro-Mediterranean area and its presence in Italy is controversial. Based on analysis of the relevant literature, field surveys and examination of herbarium specimens, a revised distribution of this species in Italy is presented and its conservation status is assessed. Ranunculus agerii, described by Antonio Bertoloni from Bologna (Emilia-Romagna, Northern Italy), and R. schowii, described by Vincenzo Tineo from Vittoria and Terranova (Sicily), usually regarded as synonyms of R. gracilis, are here lectotypified and their taxonomic status discussed. Thanks to our study, the presence of R. gracilis in Italy is confirmed and, now, it is reported in a national conservation framework
Stochastic Precedence and Minima Among Dependent Variables
Full text linkThe notion of stochastic precedence between two random variables emerges as a relevant concept in several fields of applied probability. When one consider a vector of random variables X1,..,Xn, this notion has a preeminent role in the analysis of minima of the type minj∈AXj for A ⊂{1,...n}. In such an analysis, however, several apparently controversial aspects can arise (among which phenomena of “non-transitivity”). Here we concentrate attention on vectors of non-negative random variables with absolutely continuous joint distributions, in which a case the set of the multivariate conditional hazard rate (m.c.h.r.) functions can be employed as a convenient method to describe different aspects of stochastic dependence. In terms of the m.c.h.r. functions, we first obtain convenient formulas for the probability distributions of the variables minj∈AXj and for the probability of events {Xi=minj∈AXj}. Then we detail several aspects of the notion of stochastic precedence. On these bases, we explain some controversial behavior of such variables and give sufficient conditions under which paradoxical aspects can be excluded. On the purpose of stimulating active interest of readers, we present several comments and pertinent examples
Decentralized control of finite state systems: A game theoretic approach
Full text linkIn this paper we consider a pair of interconnected, nondeterministic and metric finite state systems and address a control problem where controllers are designed for enforcing local specifications expressed in terms of regular languages, up to a desired accuracy. The control architecture considered is decentralized, that is each controller can only communicate with the corresponding plant. Since plant systems are interconnected, the part of the specification that can be enforced on one system depends on the part that can be applied on the other one. We show how this dependency can be formalized in terms of equilibria, by extending game theory to the present framework. We introduce notions of equilibria, Nash equilibria and dominant equilibria. When controlled plants are at an equilibrium, they satisfy a part of their specification; when they are at a Nash equilibrium, deviation of each plant from its control strategy may correspond to a loss in terms of the part of specification enforced; when they are at a dominant equilibrium, there is no other equilibrium where plants can achieve larger parts of the corresponding specifications. A characterization of these notions is derived and checkable conditions are discussed. An example in the context of multi-agent systems with shared resources is also included. (c) 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Risultati della discectomia percutanea in una casistica omogenea di ernie del disco lombari
No full textZero-temperature stochastic Ising model on planar quasi-transitive graphs
Full text linkWe study the zero-temperature stochastic Ising model on some connected planar
quasi-transitive graphs, which are invariant under rotation and translation.
The initial spin configuration is distributed according to a Bernoulli product
measure with parameter . In particular, we prove that if
and the graph underlying the model satisfies the planar shrink property (which
causes each finite cluster to shrink to a site and then vanish with positive
probability) then all vertices flip infinitely often almost surely
H-Systems
No full textIn this chapter, H-systems are defined and their expressive power is discussed with
respect to other formalisms, such as Impulsive Systems and Piecewise-Affine (PWA)
systems. Some illustrative examples of H-systems are also presented
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