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Heuristic and Metaheuristic Techniques for Optimization
Published in Michael W. Carter, Camille C. Price, Ghaith Rabadi, Operations Research, 2018
Michael W. Carter, Camille C. Price, Ghaith Rabadi
After selection, pairs of chromosomes are formed at random and are subjected to certain genetic manipulations; that is, modifications to the genes in the parent chromosomes. A process called crossover swaps a part of the genetic information contained in two chromosomes. Typically, a substring position in the chromosome is randomly chosen and the genes (string elements) within that substring are exchanged, forming two new offspring to replace the parents. The exact nature of crossovers is application specific, and must be done in such a way that resulting strings correspond to meaningful and feasible problem solutions. The recombination process can introduce improved genetic building blocks but will, on occasion, inadvertently disrupt favorable genetic structures. This (together with the selection of the fittest) may have the effect of driving the evolutionary process toward a local optimum. To overcome this, mutations are allowed to occur.
Adaptation and Deadaptation Kinetics of Activated Sludge
Published in John M. Bell, Proceedings of the 43rd Industrial Waste Conference May 10, 11, 12, 1988, 1989
P.R. Senthilnathan, J. J. Ganczarczyk
Adaptation can be either phenotypic or genotypic. In phenotypic adaptation, the genetic information content of the cells is unchanged; only the degree of expression of genes is altered. Phenotypic adaptation may be common during short-term fluctuations in the environment. Genotypic adaptation occurs through genetic modifications, and the modified genes are transmitted to daughter cells. There are two basic methods of genetic change: mutation and recombination. Mutation, a common means of genotypic adaptation, is a change in the nucleotide sequence of the DNA occurring within an individual cell. Recombination is any process by which genes from two separate organisms are brought together into one cell by several means namely: transformation, conjugation, plasmid transfer, transduction, and genetic engineering. Genotypic adaptation may be common during chronic changes in the environment.
Biosynthesis
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
Genetic recombination refers to the exchange of genes between two DNA molecules to form a new combination of genes. The recombination takes place naturally but can be carried out in the laboratory, using established laboratory methods. Genetic material can be transferred between prokaryotic cells by such ways as conjugation, transformation, and transduction.
Evaluation of the influence of dominance rules for the assembly line design problem under consideration of product design alternatives
Published in Engineering Optimization, 2018
Jonathan Oesterle, Amodeo Lionel
The role of recombination is to generate new solutions from the selected solutions, in preference such that the offspring contains the desirable features of both parents. The recombination step is carried out with probability , otherwise the individual with the best fitness value is copied into the offspring population. The recombination process between two solutions X and Y contains one component, F, and is formulated as follows: where f represents either: (i) a single-point crossover used by the evolutionary algorithms and the genetic operators of the imperialist competitive algorithm; or (ii) a random binary crossover used by the classical imperialist competitive algorithm. Figure 7 shows an example of each crossover type. The single-point crossover is represented in Figure 7(a), and the random binary crossover Figure 7(b). Due to the verification of the preservation of the various constraints (e.g. cycle time, precedence constraints), some tasks and their respective resources have, after the crossover process, no valid workstation. To produce feasible individuals, these tasks must be reassigned through a reassignment procedure. These non-valid elements are represented by dashes.