20,681 research outputs found
Studying the capacity of cellular encoding to generate feedforward neural network topologies
Proceeding of: IEEE International Joint Conference on Neural Networks, IJCNN 2004, Budapest, 25-29 July 2004Many methods to codify artificial neural networks have been developed to avoid the disadvantages of direct encoding schema, improving the search into the solution's space. A method to analyse how the search space is covered and how are the movements along search process applying genetic operators is needed in order to evaluate the different encoding strategies for multilayer perceptrons (MLP). In this paper, the generative capacity, this is how the search space is covered for a indirect scheme based on cellular systems, is studied. The capacity of the methods to cover the search space (topologies of MLP space) is compared with the direct encoding scheme.Publicad
Survival Probabilities at Spherical Frontiers
Motivated by tumor growth and spatial population genetics, we study the
interplay between evolutionary and spatial dynamics at the surfaces of
three-dimensional, spherical range expansions. We consider range expansion
radii that grow with an arbitrary power-law in time:
, where is a growth exponent, is the
initial radius, and is a characteristic time for the growth, to be
affected by the inflating geometry. We vary the parameters and
to capture a variety of possible growth regimes. Guided by recent results for
two-dimensional inflating range expansions, we identify key dimensionless
parameters that describe the survival probability of a mutant cell with a small
selective advantage arising at the population frontier. Using analytical
techniques, we calculate this probability for arbitrary . We compare
our results to simulations of linearly inflating expansions (
spherical Fisher-Kolmogorov-Petrovsky-Piscunov waves) and treadmilling
populations (, with cells in the interior removed by apoptosis or a
similar process). We find that mutations at linearly inflating fronts have
survival probabilities enhanced by factors of 100 or more relative to mutations
at treadmilling population frontiers. We also discuss the special properties of
"marginally inflating" expansions.Comment: 35 pages, 11 figures, revised versio
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