109 research outputs found
A study of order based genetic and evolutionary algorithms in combinatorial optimization problems
In Genetic and Evolutionary Algorithms (GEAs) one is faced with a given number of parameters, whose possible values are coded in a binary alphabet. With Order Based Representations (OBRs) the genetic information is kept by the order of the genes and not by its value. The application of OBRs to the Traveling Salesman Problem (TSP) is a well known technique to the GEA community. In this work one intends to show that this coding scheme can be used as an indirect representation, where the chromosome is the input for the decoder. The behavior of the GEA's operators is compared under benchmarks taken from the Combinatorial Optimization arena.(undefined
On Meme Self-Adaptation in Spatially-Structured Multimemetic Algorithms
NMA 2014Multimemetic algorithms (MMAs) are memetic algorithms that explicitly exploit the evolution of memes, i.e., non-genetic expressions of problem-solving strategies. We consider a class of MMAs in which these memes are rewriting rules whose length can be fixed during the run of the algorithm or self-adapt during the search process. We analyze this self-adaptation in the context of spatially-structured MMAs, namely MMAs in which the population is endowed with a certain topology to which interactions (from the point of view of selection and variation operators) are constrained. For the problems considered, it is shown that panmictic (i.e., non-structured) MMAs are more sensitive to this self-adaptation, and that using variable-length memes seems to be a robust strategy throughout different population structures.This work is partially supported by MICINN project ANYSELF (TIN2011-28627-C04-01), by
Junta de AndaluĂa project DNEMESIS (P10-TIC-6083) and by Universidad de Málaga, Campus de Excelencia Internacional AndalucĂa Tech
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
Negative Impacts of Human Land Use on Dung Beetle Functional Diversity
The loss of biodiversity caused by human activity is assumed to alter ecosystem
functioning. However our understanding of the magnitude of the effect of these
changes on functional diversity and their impact on the dynamics of ecological
processes is still limited. We analyzed the functional diversity of
copro-necrophagous beetles under different conditions of land use in three
Mexican biosphere reserves. In Montes Azules pastures, forest fragments and
continuous rainforest were analyzed, in Los Tuxtlas rainforest fragments of
different sizes were analyzed and in Barranca de Metztitlán two types of
xerophile scrub with different degrees of disturbance from grazing were
analyzed. We assigned dung beetle species to functional groups based on food
relocation, beetle size, daily activity period and food preferences, and as
measures of functional diversity we used estimates based on multivariate
methods. In Montes Azules functional richness was lower in the pastures than in
continuous rainforest and rainforest fragments, but fragments and continuous
forest include functionally redundant species. In small rainforest fragments
(<5 ha) in Los Tuxtlas, dung beetle functional richness was lower than in
large rainforest fragments (>20 ha). Functional evenness and functional
dispersion did not vary among habitat types or fragment size in these reserves.
In contrast, in Metztitlán, functional richness and functional dispersion
were different among the vegetation types, but differences were not related to
the degree of disturbance by grazing. More redundant species were found in
submontane than in crassicaule scrub. For the first time, a decrease in the
functional diversity in communities of copro-necrophagous beetles resulting from
changes in land use is documented, the potential implications for ecosystem
functioning are discussed and a series of variables that could improve the
evaluation of functional diversity for this biological group is proposed
Biodiversity, Disparity and Evolvability
A key problem in conservation biology is how to measure biological diversity. Taxic diversity (the number of species in a community or in a local biota) is not necessarily the most important aspect, if what most matters is to evaluate how the loss of the different species may impact on the future of the surviving species and communities. Alternative approaches focus on functional diversity (a measure of the distribution of the species among the different 'jobs' in the ecosystem), others on morphological disparity, still others on phylogenetic diversity. There are three major reasons to prioritize the survival of species which provide the largest contributions to the overall phylogenetic diversity. First, evolutionarily isolated lineages are frequently characterized by unique traits. Second, conserving phylogenetically diverse sets of taxa is valuable because it conserves some sort of trait diversity, itself important in so far as it helps maintain ecosystem functioning, although a strict relationships between phylogenetic diversity and functional diversity cannot be taken for granted. Third, in this way we maximize the "evolutionary potential" depending on the evolvability of the survivors. This suggests an approach to conservation problems focussed on evolvability, robustness and phenotypic plasticity of developmental systems in the face of natural selection: in other terms, an approach based on evolutionary developmental biology
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