463,997 research outputs found
Interface Simulation Distances
The classical (boolean) notion of refinement for behavioral interfaces of
system components is the alternating refinement preorder. In this paper, we
define a distance for interfaces, called interface simulation distance. It
makes the alternating refinement preorder quantitative by, intuitively,
tolerating errors (while counting them) in the alternating simulation game. We
show that the interface simulation distance satisfies the triangle inequality,
that the distance between two interfaces does not increase under parallel
composition with a third interface, and that the distance between two
interfaces can be bounded from above and below by distances between
abstractions of the two interfaces. We illustrate the framework, and the
properties of the distances under composition of interfaces, with two case
studies.Comment: In Proceedings GandALF 2012, arXiv:1210.202
Linear and Branching System Metrics
We extend the classical system relations of trace\ud
inclusion, trace equivalence, simulation, and bisimulation to a quantitative setting in which propositions are interpreted not as boolean values, but as elements of arbitrary metric spaces.\ud
\ud
Trace inclusion and equivalence give rise to asymmetrical and symmetrical linear distances, while simulation and bisimulation give rise to asymmetrical and symmetrical branching distances. We study the relationships among these distances, and we provide a full logical characterization of the distances in terms of quantitative versions of LTL and μ-calculus. We show that, while trace inclusion (resp. equivalence) coincides with simulation (resp. bisimulation) for deterministic boolean transition systems, linear\ud
and branching distances do not coincide for deterministic metric transition systems. Finally, we provide algorithms for computing the distances over finite systems, together with a matching lower complexity bound
Vortex annihilation in the ordering kinetics of the O(2) model
The vortex-vortex and vortex-antivortex correlation functions are determined
for the two-dimensional O(2) model undergoing phase ordering. We find
reasonably good agreement with simulation results for the vortex-vortex
correlation function where there is a short-scaled distance depletion zone due
to the repulsion of like-signed vortices. The vortex-antivortex correlation
function agrees well with simulation results for intermediate and long-scaled
distances. At short-scaled distances the simulations show a depletion zone not
seen in the theory.Comment: 28 pages, REVTeX, submitted to Phys. Rev.
Linear Distances between Markov Chains
We introduce a general class of distances (metrics) between Markov chains,
which are based on linear behaviour. This class encompasses distances given
topologically (such as the total variation distance or trace distance) as well
as by temporal logics or automata. We investigate which of the distances can be
approximated by observing the systems, i.e. by black-box testing or simulation,
and we provide both negative and positive results
Solvent-mediated interactions between nanoparticles at fluid interfaces
We investigate the solvent mediated interactions between nanoparticles
adsorbed at a liquid-vapor interface in comparison to the solvent mediated
interactions in the bulk liquid and vapor phases of a Lennard-Jones solvent.
Molecular dynamics simulation data for the latter are in good agreement with
results from integral equations in the reference functional approximation and a
simple geometric approximation. Simulation results for the solvent mediated
interactions at the interface differ markedly from the interactions of the
particles in the corresponding bulk phases. We find that at short interparticle
distances the interactions are considerably more repulsive than those in either
bulk phase. At long interparticle distances we find evidence for a long-ranged
attraction. We discuss these observations in terms of interfacial interactions,
namely, the three-phase line tension that would operate at short distances, and
capillary wave interactions for longer interparticle distances.Comment: 22 pages, 6 figure
Censoring Distances Based on Labeled Cortical Distance Maps in Cortical Morphometry
Shape differences are manifested in cortical structures due to
neuropsychiatric disorders. Such differences can be measured by labeled
cortical distance mapping (LCDM) which characterizes the morphometry of the
laminar cortical mantle of cortical structures. LCDM data consist of signed
distances of gray matter (GM) voxels with respect to GM/white matter (WM)
surface. Volumes and descriptive measures (such as means and variances) for
each subject and the pooled distances provide the morphometric differences
between diagnostic groups, but they do not reveal all the morphometric
information contained in LCDM distances. To extract more information from LCDM
data, censoring of the distances is introduced. For censoring of LCDM
distances, the range of LCDM distances is partitioned at a fixed increment
size; and at each censoring step, and distances not exceeding the censoring
distance are kept. Censored LCDM distances inherit the advantages of the pooled
distances. Furthermore, the analysis of censored distances provides information
about the location of morphometric differences which cannot be obtained from
the pooled distances. However, at each step, the censored distances aggregate,
which might confound the results. The influence of data aggregation is
investigated with an extensive Monte Carlo simulation analysis and it is
demonstrated that this influence is negligible. As an illustrative example, GM
of ventral medial prefrontal cortices (VMPFCs) of subjects with major
depressive disorder (MDD), subjects at high risk (HR) of MDD, and healthy
control (Ctrl) subjects are used. A significant reduction in laminar thickness
of the VMPFC and perhaps shrinkage in MDD and HR subjects is observed when
compared to Ctrl subjects. The methodology is also applicable to LCDM-based
morphometric measures of other cortical structures affected by disease.Comment: 25 pages, 10 figure
Some new less conservative criteria for impulsive synchronization of a hyperchaotic Lorenz system based on small impulsive signals
In this Letter the issue of impulsive Synchronization of a hyperchaotic Lorenz system is developed. We propose an impulsive synchronization scheme of the hyperchaotic Lorenz system including chaotic systems. Some new and sufficient conditions on varying impulsive distances are established in order to guarantee the synchronizability of the systems using the synchronization method. In particular, some simple conditions are derived for synchronizing the systems by equal impulsive distances. The boundaries of the stable regions are also estimated. Simulation results show the proposed synchronization method to be effective. (C) 2009 Elsevier Ltd. All rights reserved
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