Showing papers on "Crossover published in 1988"

Non-linear genetic algorithms for solving problems

Abstract: The present invention is a non-linear genetic algorithm for problem solving. The iterative process of the present invention operates on a population of problem solving entities. First, the activated entities perform, producing results. Then the results are assigned values and associated with the producing entity. Next, entities having relatively high associated values are selected. The selected entities perform either crossover, reproduction, or permutation operations. Lastly, the newly created entities are added to the population.

Crossover networks and their optical implementation

Abstract: Crossover networks are introduced as a new type of interconnection network for applications in optical computing, optical switching, and signal processing. Crossover networks belong to the class of multistage interconnection network. Two variations are presented, the half-crossover network and the full crossover network. An optical system which implements both networks is proposed and demonstrated. Crossover networks can be implemented using the full space-bandwidth product of the optical system with minimal loss of light. It is shown that crossover networks are isomorphic to other multistage networks such as the Banyan and perfect shuffle.

Geosat crossover analysis in the tropical Pacific: 1. Constrained sinusoidal crossover adjustment

Abstract: A new method (constrained sinusoidal crossover adjustment) for removing the orbit error in satellite altimetry is tested (using crossovers accumulated in the first 91 days of the Geosat non-repeat era in the tropical Pacific) and found to have excellent qualities. Two features distinguish the new method from the conventional bias-and-tilt crossover adjustment. First, a sine wave (with wavelength equaling the circumference of the Earth) is used to represent the orbit error for each satellite revolution, instead of the bias-and-tilt (and curvature, if necessary) approach for each segment of the satellite ground track. Secondly, the indeterminacy of the adjustment process is removed by a simple constraint minimizing the amplitudes of the sine waves, rather than by fixing selected tracks. Overall the new method is more accurate, more efficient, and much less cumbersome than the old. The idea of restricting the crossover adjustment to crossovers between tracks that are less than certain days apart in order to preserve the large-scale long-term oceanic variability is also tested with inconclusive results because the orbit error was unusually nonstationary in the initial 91 days of the GEOSAT mission.

Diffusion in a random medium with long-range correlations

Abstract: A renormalisation group analysis of anomalous diffusion in a random medium with constrained long-range correlations is carried out to two-loop order. The crossover between the long-range correlated model and its short-range correlated counterpart is investigated and the dynamic exponent z is shown to be continuous at the crossover.

Using the maximum test statistic in the two-period crossover clinical trial.

Abstract: In a two-period crossover trial where residual carryover is suspected, it is often advised that first-period data only be used in an analysis appropriate for a parallel design. However, it has been shown (Willan and Pater, 1986, Biometrics 42, 593-599) that the crossover analysis is more powerful than the parallel analysis if the residual carryover, expressed as a proportion of treatment effect, is less than 2- square root of 2(1 - rho), where rho is the intrasubject correlation coefficient. Choosing between the analyses based on the empirical evaluation of this condition is equivalent to choosing the analysis with the larger corresponding test statistic. Approximate nominal significance levels are presented that maintain the desired level when basing the analysis on the maximum test statistic. Furthermore, the power and precision of the analysis based on the maximum test statistic are compared to the crossover and parallel analyses.

Models of multilocus recombination: nonrandomness in chiasma number and crossover positions

Abstract: Cytological evidence indicates that genetic interference can be partitioned into two empirical components: nonrandomness in the number of chiasmata that occur and nonrandomness in the locations of multiple chiasmata. Previous studies have incorporated the first effect into genetic models for analyzing multipoint data. An extension to this approach is presented which allows for the second component of interference by modeling the probability density function of the locations of multiple crossovers. Results of reanalyses of multilocus data for the Drosophila X chromosome show that models that incorporate only the first effect give a better fit to these data than do standard mapping functions and that the extended model significantly improved the fit by decreasing the predicted frequency of multiple crossovers in nearby regions. Our results demonstrate that chiasma-based models of multilocus recombination, which are unique in incorporating direct estimates of the frequency of multiple crossovers for a chromosome region, can provide a powerful and realistic means of accounting for genetic interference when applied to the problems of gene localization, locus ordering, and exclusion mapping.

Optical crossover network

Abstract: A crossover network is obtained by using a plurality of similar optical crossover stages. Each stage includes two light paths that combine at an output plane. One path provides the direct connection while the other path provides the crossover connection. To realize this crossover capability, each stage comprises a beam splitter element that accepts a beam containing an image array and develops therefrom two beams that are each directed in two different paths. Along one path, means are provided for reversal of selected segments of the image array and for sending of the reversed or crossed-over image through a beam combiner. Along the second path, means are provided for applying the light to a beam combiner without the image reversal. One disclosed means for image reversal is a prismatic mirror. The number of corners in such a mirror differs from stage to stage.

Prediction of Zero-Shear Viscosity of Linear Polybutadienes from the Crossover Point Using Doi-Edwards Theory

Abstract: Based upon the Doi-Edwards theory, a simple expression has been obtained for zero-shear viscosity in terms of the plateau modulus and the crossover frequency. There are no adjustable parameters in the expression. The model is in very good agreement with the zero-shear viscosity values for linear polybutadienes, the typical discrepancy being ∼5–10%. If the model can be validated for other linear amorphous polymers, it may become possible to estimate the zero-shear viscosity by measuring a single Theological parameter (the crossover frequency).

On Correcting Radial Orbit Errors for Altimetric Satellites Using Crossover Analysis

Abstract: A method is proposed for correcting radial orbit error in measurements of sea surface height using a satellite altimeter. Traditionally, the orbit error is modeled in terms of a Fourier series with the Fourier coefficients determined by minimizing the residual crossover difference in a least-squares sense. In this method an a priori constraint must be imposed to obtain a unique solution. It is shown that by using singular value decomposition, no such constraint is needed. This proposed method leaves the geographically dependent errors unchanged and makes only those corrections warranted by the information contained in crossover differences. Thus, the resultant ocean topography is free from any undue distortion which might be incurred by an a priori constraint. It is suggested that the method is useful for application to high-accuracy altimetric mission, because the orbit error can be reduced without compromising the accuracy of the measured mean ocean topography.

Linkage Mapping of Marker Genes in Common Bean

Abstract: Linkage maps are really chromosome maps, which assign genes to specific chromosomes (or linkage groups) and provide an indication of the location of these genes in a linear arrangement along each chromosome. The map distances between genes in the map are based on crossover data produced in various types of genetic experiments. Although the correspondence between physical distance and the map distance is not exact, the map distances are instructive, useful, and reflect accurately the potential for crossover frequency along the chromosome.

“Thermodynamical formalism” for an infinite hierarchy of fractal resistor networks

Abstract: where N is the number of resistors. We find a generic phase transition at/3 =/3c = -1. Also, we develop a transfer matrix technique which determines all even positive moments. The thermodynamical formalism is applied to the Hilfer-Blumen hierarchy of generalized Sierpinski gasket fractal networks, and the crossover from fractal to lattice behavior is studied. At this crossover we find a sharp phase transition in the second moment (/3 = 2).

Bit-vector optimization algorithms for control of learning in neurons with second-messenger dynamics

Abstract: The authors describe comparatively simple; evolutionary algorithms that can utilize point mutation or crossover operators or both. The algorithms are first tested on two predefined functions of excitase configurations, and their basic strengths and weaknesses are revealed. They are then tested in vivo, coupled with the reaction-diffusion dynamics of the cell to execute a particular task (here, the motion of a robot on a plane). This provides insight into the interaction between the fast dynamics of cellular processing, and the choice of slow dynamics, or motion through the parameter spaces of learning. >

Critical dynamics of ferromagnets

Abstract: The crossover in the dynamics from isotropic to dipolar critical behaviour has been a matter of debate over many years We review a mode coupling theory for dipolar ferromagnets which gives a unified explanation of the seemingly contradictory experimental situation The shape functions, the scaling functions for the damping coefficients and the precise position of the crossover are computed Below Tc only the exchange interaction is taken into account

An Optimum Design of FIB System with a Beam Crossover

Abstract: A study was made to optimize an electrostatic ion optical system with an intermediate beam crossover between two focusing lenses. A description was given of an optimization technique with respect to the relative displacement of the crossover between the two lenses with short working distances. It was shown that a system with the objective lens operated in the bipotential mode had better focusing properties than that in the unipotential mode. Some numerical examples were presented for the high performance lens system designed with this technique.

Free-space optical crossover interconnects for parallel computers

Abstract: The crossover network is introduced as a novel type of interconnection network for applications in optical digital computing, optical switching, and signal processing. It is isomorphic to other log/sub 2/(N) networks such as the perfect shuffle and the Banyan network. This means that algorithms which are based on the Banyan, such as FFT (fast Fourier transform) algorithms, can be translated to a crossover-based implementation. Using free-space optics it is possible to implement as many as 128*128 connections between two chips of optical logic devices. A setup for the implementation of crossover networks is proposed and demonstrated. >

Critical dynamics of dipolar ferromagnets (invited)

Abstract: In real ferromagnets both exchange and dipolar forces are of importance. The crossover in the dynamics from isotropic to dipolar critical behavior has been a matter of debate for a long time. While neutron scattering experiments gave a dynamical critical exponent z= (5)/(2) and no crossover to z=2, the linewidth did not agree with the scaling function for isotropic ferromagnets. On the other hand, a crossover to dipolar critical behavior was found in hyperfine interaction experiments and the presence of the dipolar interaction also manifests itself in electron spin resonance experiments. We review a recent mode coupling theory for dipolar ferromagnets by means of which these phenomena all can be explained in a unified fashion. It turns out that the crossover in the transverse linewidth occurs at a wave number which is smaller than qD, the position of the static crossover. The dynamical scaling functions and the shape function are in agreement with experiment. Further experiments are proposed.

Lossless implementation of optical crossover networks using reflective SEED devices

Abstract: The use of optics in digital computers and switching systems offers the potential for massively parallel operation. The performance of an optical computer, however, will depend strongly on the efficiency of interconnecting different layers of logic arrays. Recently, crossover networks were proposed for this purpose [1].

Crossover in the one-dimensional self-directed walk

Abstract: The self-directed walk is studied in one dimension. In this walk with memory the jump probability is given by WN+or-(i)=(1+exp(+or-g Delta N(i)))-1 where Delta N is the difference between the number of times the sites in the forward and backward directions have been visited after N steps. When g>O there is a crossover between a Gaussian random walk and an intermediate regime where the radius of gyration grows like N2 followed by a crossover to the asymptotic regime where the walk is directed. When g<0 a single crossover is obtained between the Gaussian random walk and a saturation regime at large N when the walk is self-attracting.

A dynamic model for printed circuit crossover interconnects

Abstract: Crossover printed conductors may be used as multilevel chip-to-chip interconnects for high-frequency high-speed circuits, in VLSI applications, microwave directional couplers, etc. A theoretical model for crossover interconnects is presented in this article. The model accounts for dispersion effects and radiation loss and it may be used for the design of maximum or minimum power transfer between interconnects.