11,229 research outputs found
Effects of external global noise on the catalytic CO oxidation on Pt(110)
Oxidation reaction of CO on a single platinum crystal is a reaction-diffusion
system that may exhibit bistable, excitable, and oscillatory behavior. We
studied the effect of a stochastic signal artificially introduced into the
system through the partial pressure of CO. First, the external signal is
employed as a turbulence suppression tool, and second, it modifies the
boundaries in the bistable transition between the CO and oxygen covered phases.
Experiments using photoemission electron microscopy (PEEM) together with
numerical simulations performed with the Krischer-Eiswirth-Ertl (KEE) model are
presented.Comment: 15 pages, 7 figures, accepted in J. Chem. Phy
Noise-Induced Spatial Pattern Formation in Stochastic Reaction-Diffusion Systems
This paper is concerned with stochastic reaction-diffusion kinetics governed
by the reaction-diffusion master equation. Specifically, the primary goal of
this paper is to provide a mechanistic basis of Turing pattern formation that
is induced by intrinsic noise. To this end, we first derive an approximate
reaction-diffusion system by using linear noise approximation. We show that the
approximated system has a certain structure that is associated with a coupled
dynamic multi-agent system. This observation then helps us derive an efficient
computation tool to examine the spatial power spectrum of the intrinsic noise.
We numerically demonstrate that the result is quite effective to analyze
noise-induced Turing pattern. Finally, we illustrate the theoretical mechanism
behind the noise-induced pattern formation with a H2 norm interpretation of the
multi-agent system
Contribution of cellular automata to the understanding of corrosion phenomena
We present a stochastic CA modelling approach of corrosion based on spatially
separated electrochemical half-reactions, diffusion, acido-basic neutralization
in solution and passive properties of the oxide layers. Starting from different
initial conditions, a single framework allows one to describe generalised
corrosion, localised corrosion, reactive and passive surfaces, including
occluded corrosion phenomena as well. Spontaneous spatial separation of anodic
and cathodic zones is associated with bare metal and passivated metal on the
surface. This separation is also related to local acidification of the
solution. This spontaneous change is associated with a much faster corrosion
rate. Material morphology is closely related to corrosion kinetics, which can
be used for technological applications.Comment: 13 pages, 9 figure
Debates—Stochastic subsurface hydrology from theory to practice: why stochastic modeling has not yet permeated into practitioners?
This is the peer reviewed version of the following article: [Sanchez-Vila, X., and D. Fernàndez-Garcia (2016), Debates—Stochastic subsurface hydrology from theory to practice: Why stochastic modeling has not yet permeated into practitioners?, Water Resour. Res., 52, 9246–9258, doi:10.1002/2016WR019302], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/2016WR019302/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingWe address modern topics of stochastic hydrogeology from their potential relevance to real modeling efforts at the field scale. While the topics of stochastic hydrogeology and numerical modeling have become routine in hydrogeological studies, nondeterministic models have not yet permeated into practitioners. We point out a number of limitations of stochastic modeling when applied to real applications and comment on the reasons why stochastic models fail to become an attractive alternative for practitioners. We specifically separate issues corresponding to flow, conservative transport, and reactive transport. The different topics addressed are emphasis on process modeling, need for upscaling parameters and governing equations, relevance of properly accounting for detailed geological architecture in hydrogeological modeling, and specific challenges of reactive transport. We end up by concluding that the main responsible for nondeterministic models having not yet permeated in industry can be fully attributed to researchers in stochastic hydrogeology.Peer ReviewedPostprint (author's final draft
Lattice Gas Automata for Reactive Systems
Reactive lattice gas automata provide a microscopic approachto the dynamics
of spatially-distributed reacting systems. After introducing the subject within
the wider framework of lattice gas automata (LGA) as a microscopic approach to
the phenomenology of macroscopic systems, we describe the reactive LGA in terms
of a simple physical picture to show how an automaton can be constructed to
capture the essentials of a reactive molecular dynamics scheme. The statistical
mechanical theory of the automaton is then developed for diffusive transport
and for reactive processes, and a general algorithm is presented for reactive
LGA. The method is illustrated by considering applications to bistable and
excitable media, oscillatory behavior in reactive systems, chemical chaos and
pattern formation triggered by Turing bifurcations. The reactive lattice gas
scheme is contrasted with related cellular automaton methods and the paper
concludes with a discussion of future perspectives.Comment: to appear in PHYSICS REPORTS, 81 revtex pages; uuencoded gziped
postscript file; figures available from [email protected] or
[email protected]
Stochastic Turing Patterns on a Network
The process of stochastic Turing instability on a network is discussed for a
specific case study, the stochastic Brusselator model. The system is shown to
spontaneously differentiate into activator-rich and activator-poor nodes,
outside the region of parameters classically deputed to the deterministic
Turing instability. This phenomenon, as revealed by direct stochastic
simulations, is explained analytically, and eventually traced back to the
finite size corrections stemming from the inherent graininess of the
scrutinized medium.Comment: The movies referred to in the paper are provided upon request. Please
send your requests to Duccio Fanelli ([email protected]) or Francesca
Di Patti ([email protected]
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