Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed April 26, 2007). PDF text: vii, 164 p. : ill. UMI publication number: AAT 3229555. Includes bibliographical references. Also available in microfilm and microfiche formats.

For robots to move out of the lab and into the real-world, they must be able to plan routes not only through space but through time as well. The introduction of a time factor to the planning process implies that robots must reason about other processes and agents that move through space independently of the robot's actions. This thesis presents an integrated route planner and spatial representation system for planning real-time paths through dynamic domains called Robonav. Robonav will find the safest 9 most efficient route through time and space as described by an evaluation function. Due to the design of the spatial representation and the mechanics of the algorithm, Robonav has an isomorphic mapping onto a machine with a highly parallel SIMD architecture. When Robonav is operated in a predictable domain, paths are found in O(p) time (where p is the length of a path). In unpredictable domains, where Robonav is operated in incremental mode, paths are found and executed in O(p²) time. / Master of Science

This study examines the relationship between voluntary associations and the psychological well-being of older people through path analysis. The goals of the study were: (1) to ascertain whether differential research findings are due to measurement artifact, (2) to evaluate the assertions of traditional activity theory versus those of a modified activity theory taking quality into account, and (3) to isolate factors which contribute to and/or mediate the relationship of voluntary-association participation and psychological well-being. Analysis was conducted at two levels. First, a model was developed to study individual participation in voluntary associations, satisfaction with participation, and well-being. Second, a model was developed to examine types of volimtary associations and their effects on satisfaction with participation and on well-being. Subjects were 50 members of voluntary associations who were recruited from target groups in the Durham, North Carolina area. There were 26 males and 24 females. They ranged in age from 61 to 90. The results of the individual path analysis indicate that differential findings due to measurement artifact is likely. After controlling for the effects of health, education, income, and social desirability bias in the model, voluntary-association activity as measured by the Chapin scale was significantly correlated with psychological well-being as measured by the Bradburn scale; however, measurement of volantary-association activity by an average number of meetings measure was not correlated significantly with any measure of well-being. In addition, the Chapin measure did not correlate significantly with the LSI-Z or with the Cantril Ladder. The examination of traditional activity theory versus modified activity theory was somewhat inconclusive, although the results did suggest that mere participation may have effects on psychological well-being that are equal to or greater than the effects of satisfaction with participation. The results of the voluntary association path analysis indicate that their characteristics have consequences both for satisfaction with voluntary associations and for psychological well-being. People who belonged to larger groups were significantly more satisfied with those groups and also were significantly happier. Also, even though people who belonged to age-graded groups were slightly more satisfied with these groups, they were significantly less happy. In addition, people who belonged to church-related groups were slightly more satisfied with these groups, but were significantly less happy. Finally, people who belonged to instrumental groups were slightly less satisfied with these groups than with more expressive groups and were slightly less happy. Discussion focused on possible explanations for the findings. It was suggested that a "happiness" measure seems more sensitive to effects such as those of voluntary-association activity. As for satisfaction with voluntary associations, it was acknowledged that the mere fact that respondents are taking an active part in life may be a key factor to their well-being. As explanations for the findings related to size of voluntary associations, it was suggested that large group activity may be less emotionally demanding and/or may allow contact with more potential friends. For age-graded groups, it was suggested that many older people may maintain a view of themselves as "younger" as the result of non-age-graded activities. For church- related groups, it was suggested that prior findings are due to the relationship between religiosity and well-being rather than characteristics of such groups. Finally, for the instrumental-expressive variable, it was suggested that older people such as in this sample may not value "feeling useful" as much as has been thought. Suggestions for future research included alternative methods of measuring association satisfaction, longitudinal analysis with representative sampling, and further investigation of voluntary-association characteristics. / This thesis was digitized as part of a project begun in 2014 to increase the number of Duke psychology theses available online. The digitization project was spearheaded by Ciara Healy.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 72-95).

The aim of the research project that is the subject of this thesis is to apply mathematical techniques, especially those in the area of operations research, to the problem of maritime minefield transit. We develop several minefield models applicable to different aspects of the minefield problem. These include optimal mine clearance, shortest time traversal and time constrained traversal. We hope the suite of models and tools developed will help make mine field clearance and traversal both safer and more efficient and that exposition of the models will bring a clearer understanding of the mine problem from a mathematical perspective. In developing the solutions to mine field models, extensive use is made of network path planning algorithms, particularly the Weight Constrained Shortest Path Problem (WCSPP) for which the current state-of-the-art algorithm is extended. This is done by closer integration of Lagrangean relaxation and preprocessing to reduce the size of the network. This is then integrated with gap-closing algorithms based on enumeration to provide optimal or near optimal solutions to the path planning problem. We provide extensive computational evidence on the performance of our algorithm and compare it to other algorithms found in the literature. This tool then became fundamental in solving various separate minefield models. Our models can be broadly separated into obstacle models in which mine affected regions are treated as obstacles to be avoided and continuous threat in which each point of space has an associated risk. In the later case, we wish to find a path that minimizes the integral of the risk along the path while constraining the length of the path. We call this the Continuous Euclidean Length Constrained Minimum Cost Path Problem (C-LCMCPP), for which we present a novel network approach to solving this continuous problem. This approach results in being able to calculate a global lower bound on a non-convex optimization problem.