420 research outputs found
Vesicle computers: Approximating Voronoi diagram on Voronoi automata
Irregular arrangements of vesicles filled with excitable and precipitating
chemical systems are imitated by Voronoi automata --- finite-state machines
defined on a planar Voronoi diagram. Every Voronoi cell takes four states:
resting, excited, refractory and precipitate. A resting cell excites if it has
at least one excited neighbour; the cell precipitates if a ratio of excited
cells in its neighbourhood to its number of neighbours exceed certain
threshold. To approximate a Voronoi diagram on Voronoi automata we project a
planar set onto automaton lattice, thus cells corresponding to data-points are
excited. Excitation waves propagate across the Voronoi automaton, interact with
each other and form precipitate in result of the interaction. Configuration of
precipitate represents edges of approximated Voronoi diagram. We discover
relation between quality of Voronoi diagram approximation and precipitation
threshold, and demonstrate feasibility of our model in approximation Voronoi
diagram of arbitrary-shaped objects and a skeleton of a planar shape.Comment: Chaos, Solitons & Fractals (2011), in pres
Slime mould computes planar shapes
Computing a polygon defining a set of planar points is a classical problem of
modern computational geometry. In laboratory experiments we demonstrate that a
concave hull, a connected alpha-shape without holes, of a finite planar set is
approximated by slime mould Physarum polycephalum. We represent planar points
with sources of long-distance attractants and short-distance repellents and
inoculate a piece of plasmodium outside the data set. The plasmodium moves
towards the data and envelops it by pronounced protoplasmic tubes
Development of multiscale approach to modeling mechanical response of high-strength intermetallic alloys on the basis of movable cellular automaton method
On the basis of movable cellular automaton method (MCA) was developed a multiscale two-dimensional structural and rheological model of hard-strength intermetallic alloy Ni3Al. In this model, the intermetallic alloy is regarded as multiscale composite system. Developed approach takes into account the properties of grain boundaries, the characteristics of the geometry and internal structure of the grains and their size distribution. Internal grain structure of hard-strength alloy is constructed in the framework of MCA method using the algorithm of Voronoi tessellation. To simulate the processes of deformation and fracture of such complex systems by MCA method the two-dimensional model of elastic-plastic interaction of cellular automata is used. This model is based on the use of many-particle potentials/forces of interaction of cellular automata. An incremental theory of plasticity of isotropic medium with von Mises plasticity criterion was used to model deformation of intermetallic alloy. Radial return algorithm of Wilkins was adopted for this purpose. Twoparameter criterion of Drucker-Prager was used as fracture criterion in proposed model. When modeling of the mechanical response of hard-strength alloy peculiarities of its multiscale internal structure (the presence of subgrains in grains) at lower scales with respect to the considered one was taken into account implicitly using a specially developed multiscale approach. Verification of the developed model is performed by simulation of tests on the uniaxial tension of Ni3Al samples and comparing the simulation results with the experimental data. Comparison of the obtained “theoretical” loading diagrams with experimental data showed good qualitative and quantitative similarity. This indicates the adequacy of the developed model and the possibility of its use to describe the deformation and fracture of such complex heterogeneous systems
Cellular Automata Applications in Shortest Path Problem
Cellular Automata (CAs) are computational models that can capture the
essential features of systems in which global behavior emerges from the
collective effect of simple components, which interact locally. During the last
decades, CAs have been extensively used for mimicking several natural processes
and systems to find fine solutions in many complex hard to solve computer
science and engineering problems. Among them, the shortest path problem is one
of the most pronounced and highly studied problems that scientists have been
trying to tackle by using a plethora of methodologies and even unconventional
approaches. The proposed solutions are mainly justified by their ability to
provide a correct solution in a better time complexity than the renowned
Dijkstra's algorithm. Although there is a wide variety regarding the
algorithmic complexity of the algorithms suggested, spanning from simplistic
graph traversal algorithms to complex nature inspired and bio-mimicking
algorithms, in this chapter we focus on the successful application of CAs to
shortest path problem as found in various diverse disciplines like computer
science, swarm robotics, computer networks, decision science and biomimicking
of biological organisms' behaviour. In particular, an introduction on the first
CA-based algorithm tackling the shortest path problem is provided in detail.
After the short presentation of shortest path algorithms arriving from the
relaxization of the CAs principles, the application of the CA-based shortest
path definition on the coordinated motion of swarm robotics is also introduced.
Moreover, the CA based application of shortest path finding in computer
networks is presented in brief. Finally, a CA that models exactly the behavior
of a biological organism, namely the Physarum's behavior, finding the
minimum-length path between two points in a labyrinth is given.Comment: To appear in the book: Adamatzky, A (Ed.) Shortest path solvers. From
software to wetware. Springer, 201
Three-dimensional virtual microstructure generation of porous polycrystalline ceramics
Various numerical methods have been recently employed to model microstructure of ceramics with different level of accuracy. The simplicity of the models based on regular morphologies results in a low computational cost, but these methods produce less realistic geometries with lower precision. Additional methods are able to reconstruct irregular structures by simulating the grain-growth kinetics but are restricted due to their high computational cost and complexity. In this paper, an innovative approach is proposed to replicate a three-dimensional (3D) complex microstructure with a low computational cost and the realistic features for porous polycrystalline ceramics.
We present a package, written in MATLAB, that develops upon the basic Voronoi tessellation method for representing realistic microstructures to describe the evolution during the solid-state sintering process. The method is based on a cohesive prism that links the interconnect cells and thus simulates the neck formation. Spline surfaces are employed to represent more realistic features. The method efficiently controls shape and size and is able to reconstruct a wide range of microstructures composed of grains, grain boundaries, interconnected (open) and isolated (closed) pores. The numerical input values can be extracted from 2D imaging of real polished surfaces and through theoretical analysis. The capability of the method to replicate different structural properties is tested using some examples with various configurations
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