3,268 research outputs found
A review of wildland fire spread modelling, 1990-present 3: Mathematical analogues and simulation models
In recent years, advances in computational power and spatial data analysis
(GIS, remote sensing, etc) have led to an increase in attempts to model the
spread and behvaiour of wildland fires across the landscape. This series of
review papers endeavours to critically and comprehensively review all types of
surface fire spread models developed since 1990. This paper reviews models of a
simulation or mathematical analogue nature. Most simulation models are
implementations of existing empirical or quasi-empirical models and their
primary function is to convert these generally one dimensional models to two
dimensions and then propagate a fire perimeter across a modelled landscape.
Mathematical analogue models are those that are based on some mathematical
conceit (rather than a physical representation of fire spread) that
coincidentally simulates the spread of fire. Other papers in the series review
models of an physical or quasi-physical nature and empirical or quasi-empirical
nature. Many models are extensions or refinements of models developed before
1990. Where this is the case, these models are also discussed but much less
comprehensively.Comment: 20 pages + 9 pages references + 1 page figures. Submitted to the
International Journal of Wildland Fir
Cellular automaton supercolliders
Gliders in one-dimensional cellular automata are compact groups of
non-quiescent and non-ether patterns (ether represents a periodic background)
translating along automaton lattice. They are cellular-automaton analogous of
localizations or quasi-local collective excitations travelling in a spatially
extended non-linear medium. They can be considered as binary strings or symbols
travelling along a one-dimensional ring, interacting with each other and
changing their states, or symbolic values, as a result of interactions. We
analyse what types of interaction occur between gliders travelling on a
cellular automaton `cyclotron' and build a catalog of the most common
reactions. We demonstrate that collisions between gliders emulate the basic
types of interaction that occur between localizations in non-linear media:
fusion, elastic collision, and soliton-like collision. Computational outcomes
of a swarm of gliders circling on a one-dimensional torus are analysed via
implementation of cyclic tag systems
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
Reaction-diffusion fronts with inhomogeneous initial conditions
Properties of reaction zones resulting from A+B -> C type reaction-diffusion
processes are investigated by analytical and numerical methods. The reagents A
and B are separated initially and, in addition, there is an initial macroscopic
inhomogeneity in the distribution of the B species. For simple two-dimensional
geometries, exact analytical results are presented for the time-evolution of
the geometric shape of the front. We also show using cellular automata
simulations that the fluctuations can be neglected both in the shape and in the
width of the front.Comment: 11 pages, 3 figures, submitted to J. Phys.
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