University of Alabama

About: University of Alabama is a education organization based out in Tuscaloosa, Alabama, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 27323 authors who have published 48609 publications receiving 1565337 citations. The organization is also known as: Alabama & Bama.

Control system optimization using genetic algorithms

Abstract: The use of genetic algorithms as a technique for solving aerospace-related control system optimization problems is explored in this paper. Genetic algorithms are parameter search procedures based on the mechanics of natural genetics. They combine a Darwinian survival-of-the-fittest strategy with a random yet structured information exchange among a population of artificial chromosomes. The genetic algorithm technique is used to design a lateral autopilot and a windshear controller. The results show that a variety of aerospace control system optimization problems can be addressed using genetic algorithms with no special problem-dependent modifications. Suggestions for other uses related to aerospace control system optimization are presented.

Where are youth active? Roles of proximity, active transport, and built environment.

Abstract: GROW, H. M., B. E. SAELENS, J. KERR, N. H. DURANT, G. J. NORMAN, and J. F. SALLIS. Where Are Youth Active? Roles of Proximity, Active Transport, and Built Environment. Med. Sci. Sports Exerc., Vol. 40, No. 12, pp. 2071–2079, 2008. Purpose: This study examined factors related to two sources of physical activity for youth: active use of recreation sites and active transport to recreation sites. Methods: Parents of children (n = 87) and matched pairs of parents and adolescents (n = 124 pairs) in three US cities reported on youths’ active use of, proximity to, and walking/biking to 12 recreation sites and on neighborhood walkability and safety. Multivariate regression models evaluated factors associated with youths’ frequent site use and active transport to sites. Results: Proximity to the site was associated with frequent use of large parks and public open space. Walking/biking to the site was associated with frequent use of most sites (indoor recreation sites, small and large parks, basketball courts, walking/running tracks, school recreation sites, playgrounds, and public open space). After controlling for proximity and demographic factors, active transport to sites remained significantly associated (P G 0.05) with frequent use of four sites for children (indoor recreation, walking/running tracks, school recreation facilities, and public open space) and all but three sites for adolescents (indoor recreation, playfields/courts, and beach/ lake/rivers). Adolescents’ active transport to more sites was most positively related to higher perceived traffic safety and to better pedestrian infrastructure and was negatively related to crime threat. Adolescents with driver’s licenses walked/biked to recreation sites less often. Conclusions: Active transport was strongly associated with the use of multiple recreation sites by children and adolescents, even when accounting for proximity and demographic factors. Adolescents living in neighborhoods with better traffic safety walked/ biked to more recreation sites for physical activity. Findings support the need for built environments and transportation policies that

Patterns of Transnational Terrorism, 1970–1999: Alternative Time-Series Estimates

Abstract: Using alternative time-series methods, this paper investigates the patterns of transnational terrorist incidents that involve one or more deaths. Initially, an updated analysis of these fatal events for 1970–1999 is presented using a standard linear model with prespecified interventions that represent significant policy and political impacts. Next, a (regime-switching) threshold autoregressive (TAR) model is applied to this fatality time series. TAR estimates indicate that increases above the mean are not sustainable during high-activity eras, but are sustainable during low-activity eras. The TAR model provides a better fit than previously tried methods for the fatality time series. By applying a Fourier approximation to the nonlinear estimates, we get improved results. The findings in this study and those in our earlier studies are then applied to suggest some policy implications in light of the tragic attacks on the World Trade Center and the Pentagon on September 11, 2001.

Using genetic algorithms to explore pattern recognition in the immune system

Abstract: This paper describes an immune system model based on binary strings. The purpose of the model is to study the pattern-recognition processes and learning that take place at both the individual and species levels in the immune system. The genetic algorithm (GA) is a central component of the model. The paper reports simulation experiments on two pattern-recognition problems that are relevant to natural immune systems. Finally, it reviews the relation between the model and explicit fitness-sharing techniques for genetic algorithms, showing that the immune system model implements a form of implicit fitness sharing.