Optimizing Epochal Evolutionary Search: Population-Size Dependent Theory

Epochal dynamics, in which long periods of stasis in an evolving population are punctuated by a sudden burst of change, is a common behavior in both natural and artificial evolutionary processes. We analyze the population dynamics for a class of fitness functions that exhibit epochal behavior using a mathematical framework developed recently, which incorporates techniques from the fields of mathematical population genetics, molecular evolution theory, and statistical mechanics. Our analysis predicts the total number of fitness function evaluations to reach the global optimum as a function of mutation rate, population size, and the parameters specifying the fitness function. This allows us to determine the optimal evolutionary parameter settings for this class of fitness functions.We identify a generalized error threshold that smoothly bounds the two-dimensional regime of mutation rates and population sizes for which epochal evolutionary search operates most efficiently. Specifically, we analyze the dynamics of epoch destabilization under finite-population sampling fluctuations and show how the evolutionary parameters effectively introduce a coarse graining of the fitness function. More generally, we find that the optimal parameter settings for epochal evolutionary search correspond to behavioral regimes in which the consecutive epochs are marginally stable against the sampling fluctuations. Our results suggest that in order to achieve optimal search, one should set evolutionary parameters such that the coarse graining of the fitness function induced by the sampling fluctuations is just large enough to hide local optima.     

Quantitative applications of high-resolution proton magnetic resonance measurements in the characterization of detergent chemicals

Quantitative hydrogen nuclear magnetic resonance measurements are used for the determination of average structures of detergent chemicals. For alkylbenzenes, alkylphenols, and ethylene oxide (EO) adducts of alkylphenols, the following quantities can be measured: average lengths of alkyl chains, average molecular weights, degree and kind of branching in the alkyl chain, ortho-para distribution of aryl substituents, and average lengths of BO chains. Accuracy is of the the order of ± 2% of the total hydrogen. The method is nondestructive, and sample volumes as small as 0.007 ml have been used.     

Organic builders: A review of worldwide efforts to find organic replacements for detergent phosphates

Continuing pressures to reduce phosphates in wastewaters have sustained an intensive worldwide search to develop acceptable substitutes. Organic polycarboxylate salts have been most extensively investigated because there are a large number of structural possibilities, and the possibility for biodegradation to innocuous CO₂ and H₂O offers an optimal answer to most environmental questions. In addition to testing known compounds, many novel structures have been synthesized in efforts to tailor materials with optimum properties. Stringent requirements for functional effectiveness, human safety, environmental acceptability, practical processability, and acceptable costs have limited the number of viable alternatives. Compounds that have been proposed are reviewed with particular attention to recent developments.     

Parallelization of structured,hierarchical adaptive mesh refinement algorithms

We describe an approach to parallelization of structured adaptive mesh refinement algorithms. This type of adaptive methodology is based on the use of local grids superimposed on a coarse grid to achieve sufficient resolution in the solution. The key elements of the approach to parallelization are a dynamic load-balancing technique to distribute work to processors and a software methodology for managing data distribution and communications. The methodology is based on a message-passing model that exploits the coarse-grained parallelism inherent in the algorithms. The approach is illustrated for an adaptive algorithm for hyperbolic systems of conservation laws in three space dimensions. A numerical example computing the interaction of a shock with a helium bubble is presented. We give timings to illustrate the performance of the method. Received: 28 April 1999 / Accepted: 25 November 1999     

Resource sharing and coevolution in evolving cellular automata

Coevolution, between a population of candidate solutions and a population of test cases, has received increasing attention as a promising biologically inspired method for improving the performance of evolutionary computation techniques. However, the results of studies of coevolution have been mixed. One of the seemingly more impressive results to date was the improvement via coevolution demonstrated by Juille and Pollack (1998) on evolving cellular automata to perform a classification task. Their study, however, like most other studies on coevolution, did not investigate the mechanisms giving rise to the observed improvements. In this paper, we probe more deeply into the reasons for these observed improvements and present empirical evidence that, in contrast to what was claimed by Juille and Pollack, much of the improvement seen was due to their "resource sharing" technique rather than to coevolution. We also present empirical evidence that resource sharing works, at least in part, by preserving diversity in the population.     

HDTV Delivery to the Consumer Work of the Advanced Television Systems Committee

Technical development of advanced television systems has reached a level where major changes in consumer products can be expected on the market in the foreseeable future. Super VHS, already being sold, offers pictures from prerecorded tapes which are significantly better than can be delivered via conventional broadcast. The Japan Broadcasting Corporation has announced it will begin direct satellite broadcasting of high definition television (HDTV) in Japan in 1990, and consumer HDTV equipment will be sold in Japan, and likely elsewhere, at that time.     

Dimensions of air traffic control tower information needs: From information requests to display design.

In an effort to determine the information needs of tower air traffic controllers, instructors from the Federal Aviation Administration's Academy in Oklahoma City were asked to control traffic in a high-fidelity tower cab simulator. Information requests were made apparent by eliminating access to standard tower information sources. Instead, controllers were required to ask for precisely the information they needed during the scenarios. The information requests were classified using an elaboration of Zwaan and Radvansky's (1998) dimensions of situation models. The vast majority of requests were about three of the dimensions originally developed for reading comprehension: the protagonist, intentionality, and space. The information requests were also classified into 28 operational categories (e.g., aircraft identification, destination). From these results, the data were summarized, not just statistically, but by the creation of display-hypotheses. The display-hypotheses were organized according to the situation-model dimensions. Controllers preferred data blocks organized by the situation-model principle over those that violated this organization. The summary display-hypotheses were quite simple and accounted for the vast majority of the information requests controllers made. The display-hypotheses accounted for the information needs of controllers during routine as well as off-nominal events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computation in Sofic Quantum Dynamical Systems

We analyze how measured quantum dynamical systems store and process information, introducing sofic quantum dynamical systems. Using recently introduced information-theoretic measures for quantum processes, we quantify their information storage and processing in terms of entropy rate and excess entropy, giving closed-form expressions where possible. To illustrate the impact of measurement on information storage in quantum processes, we analyze two spin-1 sofic quantum systems that differ only in how they are measured.