Ioannis Karafyllidis

A model for predicting forest fire spreading using cellular automata

Abstract The model presented, for the first time, in this paper can predict the spreading of fire in both homogeneous and inhomogeneous forests and can easily incorporate weather conditions and land topography. An algorithm has been constructed based on the proposed model and was used for the determination of fire fronts in a number of hypothetical forests, which were found to be in good agreement with the experience on fire spreading in real forests.

A cellular automaton model for the effects of population movement and vaccination on epidemic propagation

A cellular automaton model for the effects of population movement and vaccination on epidemic propagation is presented. Each cellular automaton cell represents a part of the total population that may be found in one of three states: infected, immunized and susceptible. As parts of the population move randomly in the cellular automaton lattice, the disease spreads. We study the effect of two population movement parameters on the epidemic propagation: the distance of movement and the percentage of the population that moves. Furthermore, the model is extended to include the effect of the vaccination of some parts of the population on epidemic propagation. The model establishes the acceleration of the epidemic propagation because of the increment, of the percentage of the moving population, or of the maximum distance of population movement. On the contrary, the effect of population vaccination reduces the epidemic propagation. The proposed model can serve as a basis for the development of algorithms to simulate real epidemics based on real data.

Simulation of electrical tree growth in solid dielectrics containing voids of arbitrary shape

In this paper the electrical tree growth in solid insulating materials containing voids of arbitrary shape is modelled using von Neumanns cellular automata (CA). The model is based upon the assumption that the electric stress at the end of a conducting tip quite often approaches the dielectric strength of the material and that progressive breakdown may occur by electrical tree formation. Because of tree advancement, the potential distribution within the insulating material changes with time, and it is calculated at each time step. An algorithm, based on this model, for the simulation of electrical tree growth in solid dielectrics containing voids of arbitrary shape has been developed. Simulation results show that voids constitute a danger for solid insulation, because they act as sources of secondary electrical trees. An interaction mechanism between voids within a dielectric is proposed and discussed.

Simulation of two-dimensional photoresist etching process in integrated circuit fabrication using cellular automata

A new algorithm for the simulation if photoresist etching, based on cellular automata, is presented in this paper. The algorithm is fast and robust and has been successfully tested using all known etch-rate distribution test functions. The algorithm performs very well, even in areas where the fluctuation in etch rates is wide and sharp.

A CAD system for the construction and VLSI implementation of Cellular Automata algorithms using VHDL

Abstract Cellular Automata (CAs) are models of physical systems where space and time are discrete and interactions are only local. CAs are very effective in simulating physical systems and solving scientific problems, because they can capture the essential features of systems in which global behaviour arises from the collective effect of simple components which interact locally. CAs have been applied successfully to the simulation of several physical systems and processes, and have been extensively used as a very large-scale integrated (VLSI) architecture. We present a CAD system that builds a bridge between CAs as models of physical systems and processes, and CAs as a VLSI architecture. The inputs to our CAD system are the CA dimensionality, lattice size, local rule, and the initial and boundary conditions imposed by the particular problem. Our system produces as output the corresponding VHDL code, which leads to VLSI implementation of the CA algorithm. No prior knowledge of VHDL is required by the user. We have tested our CAD system using well-known one- and two-dimensional CAs, namely the game of life and the rule 90 CAs. The VHDL code produced in all these cases has been used for the automated design of the corresponding VLSI system, using a commercial VLSI CAD system. Simulations of the operation of these VLSI systems showed that the corresponding CA has been successfully implemented into hardware.

Reconstruction of DNA sequences using genetic algorithms and cellular automata : Towards mutation prediction?

Change of DNA sequence that fuels evolution is, to a certain extent, a deterministic process because mutagenesis does not occur in an absolutely random manner. So far, it has not been possible to decipher the rules that govern DNA sequence evolution due to the extreme complexity of the entire process. In our attempt to approach this issue we focus solely on the mechanisms of mutagenesis and deliberately disregard the role of natural selection. Hence, in this analysis, evolution refers to the accumulation of genetic alterations that originate from mutations and are transmitted through generations without being subjected to natural selection. We have developed a software tool that allows modelling of a DNA sequence as a one-dimensional cellular automaton (CA) with four states per cell which correspond to the four DNA bases, i.e. A, C, T and G. The four states are represented by numbers of the quaternary number system. Moreover, we have developed genetic algorithms (GAs) in order to determine the rules of CA evolution that simulate the DNA evolution process. Linear evolution rules were considered and square matrices were used to represent them. If DNA sequences of different evolution steps are available, our approach allows the determination of the underlying evolution rule(s). Conversely, once the evolution rules are deciphered, our tool may reconstruct the DNA sequence in any previous evolution step for which the exact sequence information was unknown. The developed tool may be used to test various parameters that could influence evolution. We describe a paradigm relying on the assumption that mutagenesis is governed by a near-neighbour-dependent mechanism. Based on the satisfactory performance of our system in the deliberately simplified example, we propose that our approach could offer a starting point for future attempts to understand the mechanisms that govern evolution. The developed software is open-source and has a user-friendly graphical input interface.

SECS: A New Single-Electron-Circuit Simulator

Downscaling of the devices of integrated circuits (ICs) has reached the verge of nanometer scale. On this scale, new phenomena of a quantum nature are starting to appear in ICs. The necessity of the development of new tools for studding the behavior of such circuits that take into account these phenomena is evident. For this reason, a new system for the design and simulation of single electron circuits called SECS has been developed. The operation of single electron circuits is based on the tunneling effect. The stochastic nature due to tunneling is incorporated in the simulation of single electron circuits using the Monte Carlo method. The novelty of the SECS system is that it provides the behavior of single electron circuits in an actual time scale, making thus easier and more complete the study of the phenomena that take place at an arbitrary single electron circuit.

A cellular automaton for the determination of the mean velocity of moving objects and its VLSI implementation

Abstract A new algorithm for the determination of the mean velocity of a moving object, using the properties of Cellular Automata, is presented in this paper. The mean velocity is calculated along the centra axis perpendicular to the lens of the vision system. The motion of the object is restricted to translation (angular velocity is zero) and to one moving object in the scene. Experimental results for the determination of the mean velocity and its computational error are also presented. The algorithm presented in this paper does not require the calculation or the extraction of image features, such as area and shape, line segments, characteristic points, corners, etc. The design and VLSI implementation of a Cellular Automaton architecture is also presented for the efficient realisation of the algorithm.

A single-electron XOR gate

A new single-electron circuit implementing the logic function XOR is presented in this paper. The logic gate proposed consists of five tunnel junctions, two capacitors and four islands. The operation of this gate is analysed using Monte Carlo simulation. The simulation results show that the gate operates in stable regions.

A methodology for VLSI implementation of Cellular Automata algorithms using VHDL

A methodology for the VLSI implementation of Cellular Automata (CA) algorithms using the VHSIC Hardware Description Language (VHDL) is proposed for the first time. This methodology builds a bridge between the CAs as models of physical systems and processes and the CAs as a VLSI architecture. A translation algorithm is developed that has as input the CA algorithms that simulate physical systems and processes, and as output the corresponding VHDL code. The parameters of this translation algorithm are defined by the user and can be automatically mapped into synthesizable VHDL. An example, where this methodology is applied to the hardware implementation of a CA algorithm for automated visual inspection, is presented.