Digital Commons Network^™

A Sensory-Based Adaptive Walking Control Algorithm For Variable Speed Biped Robot Gaits, Andrew L. Kun

Doctoral Dissertations

A balance scheme for handling variable speed gaits was implemented on an experimental biped. The control scheme used pre-planned but adaptive motion sequences in combination with closed loop reactive control. CMAC neural networks were responsible for the adaptive control of side-to-side and front-to-back balance. The biped performance improved with neural network training. The biped was able to walk with variable speed gaits, and to change gait speeds on the fly. The slower gait speeds required statically balanced walking, while the faster speeds required dynamically balanced walking. It was not necessary to distinguish between the two balance modes within the controller. …

Contributions To The Theory Of Neighborhoods And Its Applications, Michael Joseph Cullinane

Doctoral Dissertations

Neighborhoods have played a fundamental role in general topology since the birth of the field. This work outlines the historial evolution of the notion of neighborhood and employs neighborhood assignments, weak neighborhood assignments, and a naturally induced notion of duality in a study of non-Hausdorff topological spaces. Neighborhood characterizations of various classes of spaces, among them the developable and the pseudometrizable spaces, are obtained. A generalization of topological spaces based upon a primitive notion of neighborhood is explored and examples are supplied to motivate the investigation.

Adaptive Multiresolution Visualization Of Large Multidimensional Multivariate Scientific Datasets, Pak Chung Wong

Doctoral Dissertations

The sizes of today's scientific datasets range from megabytes to terabytes, making it impossible to directly browse the raw datasets visually. This presents significant challenges for visualization scientists who are interested in supporting these datasets. In this thesis, we present an adaptive data representation model which can be utilized with many of the commonly employed visualization techniques when dealing with large amounts of data. Our hierarchical design also alleviates the long standing visualization problem due to limited display space. The idea is based on using compactly supported orthogonal wavelets and additional downsizing techniques to generate a hierarchy of fine to …

Perfect Matchings: Modified Aztec Diamonds, Covering Graphs Andn-Matchings, Adriana Badauta Cransac

Doctoral Dissertations

In the Introduction, we present the problems we are going to study and we establish the basic definitions, concepts and results that are used throughout.

We begin the first chapter with a presentation of the Aztec diamond and the behaviour of its random domino tilings. We introduce the dual-matching-problem and we explore the structure of the perfect matchings of modified Aztec diamonds. We show that some of these matchings can be extended to matchings of the dual Aztec diamond, pointing out a bijection between these types of matchings. We determine the number of perfect matchings for each of the modified …

Modeling Of The Electromagnetic Radiation From Shielded Enclosures With Apertures And Attached Wires In A Real-World Environment, Bruce Roy Archambeault

Doctoral Dissertations

A hybrid modeling technique using the Finite-Difference Time-Domain (FDTD) approach in conjunction with the Method of Moments (MoM) approach was developed to allow simulation of electromagnetic interference (EMI) emissions through apertures due to sources within a shielded enclosure. These apertures can include air ventilation openings, option card slots, mating cover seams, or any other opening in the metal shielded enclosure. Modeled emission results can now be directly compared to U.S. and other countries' regulations to allow engineers to predict compliance before hardware prototypes are built. The effects of the test environment, including ground plane and specified measurement distance, as well …

Contributions To The Theory Of Distance Functions And Its Application In General Topology, Lawrence Valery Neveu

Doctoral Dissertations

As non-Hausdorff spaces are becoming more important in topology, there is a need to consider new notions in topology to supplement the usual structures. This work uses distance functions to find useful generalizations (in a non-Hausdorff context) of the classes of spaces that are important in the Hausdorff setting. We begin, in the first part, with a historical overview that traces the evolution of the notion of distance and its role in the development of general topology.

In the second part of this work, we launch our study of distance functions. Using non-symmetric distance functions, called asymmetric, we generalize the …

Numerical Analysis For Blood Distribution In Complete Flow Cross-Section Microvascular Networks, Jewen Xiao

Doctoral Dissertations

As the blood flows through a bifurcation, the axisymmetric red blood cell concentration profile is skewed by plasma skimming. In the downstream segment of the bifurcation the concentration profile of red blood cells recovers symmetry by the red blood cell dispersion process.

In this study, the concentration convective equation, which models the red blood cell dispersion process, is solved with the method of finite differences in cylindrical coordinates. In the computation, a shear-induced diffusivity coefficient is used. The computed hematocrit ratios at the second bifurcation are compared with in vitro experimental data obtained from 50 $\mu$m serial trees with two …

Student Interactions And Mathematics Discourse: A Study Of The Development Of Discussions In A Fifth-Grade Classroom, Sharon Marie Soucy Mccrone

Doctoral Dissertations

Mathematics reform efforts are gaining attention and support in the years since the dissemination of the National Council of Teachers of Mathematics (NCTM) Standards documents. Encouraging student interactions in small and large group settings, and promoting discussion and argumentation of mathematical ideas among students are two possible implications of the vision presented in the Standards. The goal of having mathematics discussions, however, can present a variety of classroom challenges. Many factors influence classroom discourse and need to be addressed in ways that inform teachers as they work toward creating a more interactive, discussion-based mathematics classroom.

The study examines the development …

Relativistic Thinking And Identity Development In College Students, Rebecca Anne Regeth

Doctoral Dissertations

The relationship between relativistic thinking and identity formation was examined. Relativistic thinking is the ability to accept the subjective nature of knowledge and values and has been shown to develop during college. It was predicted that as students become more relativistic in their thinking, they also realize that their own perception of reality is relative too. This causes an identity crisis, resulting in a mature identity. A one-year longitudinal study showed that changes in identity (increased moratorium) were related to changes in thinking (increased relativism). Students in different college majors were shown to think differently about the nature of knowledge …

Response Of Outer Radiation Belt Electrons To A Magnetic Storm, Donald Hugh Brautigam

Doctoral Dissertations

To advance our understanding of the magnetic storm dynamics of the outer radiation belt relativistic electrons, the magnetic storm which commenced on 9 October 1990 was analyzed in detail using data from the Combined Release and Radiation Effects Satellite (CRRES) and the Los Alamos National Laboratory geosynchronous satellite 1989enspace 046. Electron differential flux was transformed into phase space density as a function of the three adiabatic invariants. The invariants were determined by magnetic field data from CRRES and the Tsyganenko 1989 Kp driven model. The unique work of this thesis is the storm time radial diffusion modeling performed using time …

Preparing The Way Of The Lord: Three Case Studies Of Ministerial Preconditioning In Congregations Before The Great Awakening, 1675-1750, Douglas Kevin Fidler

Doctoral Dissertations

This study demonstrates that ministerial predecessors in three northern New England communities actually preconditioned community reactions to the Great Awakening during the years preceding the revival itself. "Preconditioning" is not the ordinary "influence" of pastors within their churches and professional circles suggested in other works. This kind of influence might cause parishioners to consider various behavioral alternatives when confronted by spiritual circumstances. Preconditioned congregations would already have established paradigms for responding to spiritual stimulus. While individual parishioners might act in ways consistent with their own personalities, psychological needs, and spiritual sensitivities, congregations as a whole would apply a predetermined set …

On Some Range Inclusions, Mihaela Anca Poplicher

Doctoral Dissertations

The de Branges-Rovnyak spaces have been introduced by Louis de Branges and James Rovnyak, and have been studied by several authors, in particular by Donald Sarason. The object of this thesis is to study more extensively some properties of this class of spaces. In particular, which of these spaces are invariant under the action of which composition operators, or adjoints of composition operators.

Some known facts and a couple of new properties are included in Chapter 1. There it is shown that the norm of the kernel function for evaluation at a point in the unit disc (in the de …

The Use Of An Artificial Light System To Assess The Influence Of Relative Light Change On Diel Activity Cycles Of Nymphs Of The Mayfly, Stenonema Modestum, In The Presence And Absence Of Predators, Annette L. Schloss

Doctoral Dissertations

A mechanism by which light controls diel changes in locomotor activity and surface location of mayfly nymphs (Stenonema modestum Banks), named the Stimulus-based Timing and Activity-Rate (STAR) Model, was tested. Nymph movements were video-recorded in time-lapse from underneath unglazed artificial substrates in a laboratory stream. Light/dark cycles were simulated using computer-controlled halogen lamps. Light increases and decreases were generated to maintain constant rates of relative light change throughout simulated twilight periods. Nymph locomotor activity and position on the substrate were measured in response to rate of light change. Experiments tested whether adaptation light intensity (10$\sp{-4}$ or 10$\sp{-6}$ W cm$\sp{-2}$), time …

Ecological Database Development And Analyses Of Soil Variability In Northern New England, Michael Anayo Okoye

Doctoral Dissertations

The 1983 Forest Inventory and Analysis (FIA) data of the states of Maine, New Hampshire and Vermont (the study area) contain large amounts of field-measurements of many ecologically important variables. Despite the vast potential usefulness of the FIA data for scientific research, the data were until now, literally unused except for a few administrative purposes, because of problems in the way the data were organized, summarized, and coded for storage. The primary objective of this research was to solve the problems that had thus precluded these FIA data from use in scientific applications, and present the data in a form …

A Metric-Based Scientific Data Model For Knowledge Discovery, David T. Kao

Doctoral Dissertations

Scientific data, which include multimedia (e.g., images, audio, and video) and non-standard data (e.g., finger prints and DNA sequences), is characterized by rich and complex inter-instance relationships in addition to the inter-entity relationships found in traditional data. Conventional data models are insufficient for modeling such inter-instance relationships. This thesis proposes a metric-based scientific data model from the notions of data-as-functions and pseudo-quasimetrics, which are used to model inter-entity and inter-instance relationships respectively. Compared to other scientific data models, the metric-based conceptual model can be applied to many data sets where geometric views might not otherwise be available.

A detailed approach …

Analysis Of Cured-In-Place Pipes (Cipp) Installed In Circular And Oval Deteriorated Host Pipes, Abdel-Aziz Mabrouk Omara

Doctoral Dissertations

This dissertation presents new analytical models for the structural analysis of Cured-In-Place Pipes (CIPP) used in the rehabilitation process of deteriorated pipelines. Both cases of partially and fully deteriorated pipelines are considered. Specifically, analytical models for the stability of CIPP encased in either circular or oval partially deteriorated host pipes are presented. The proposed models for the case of partially deteriorated host pipes were compared with the results of experimental works. Results of the experimental work, which was done during the course of this research, were used in the comparison. Other, previously done, related experimental work were also added to …

Vehicle Performance Optimization Utilizing The Air Turbo-Ramjet Propulsion System; Methodology Development And Applications, Kirk Christensen

Doctoral Dissertations

"The ATR (Air TurboRocket) is an air breathing propulsion system in which the turbocompressor turbine is powered by a hot drive gas which is generated independently of the air flow through the compressor. The ATR has a lower specific impulse (Isp) and higher thrust compared to a similar size turbojet but a lower thrust and higher Isp compared to similar size solid rocket motor (SRM). This work defines the benefits of ATR propulsion for tactical vehicles.

ATR simulation codes were developed to support analysis of hypothetical ATR powered vehicles. Both turbojet powered and SRM powered vehicles were also evaluated against …

Multiobjective Optimum Design Of Static And Seismic-Resistant Structures With Genetic Algorithm, Fuzzy Logic And Game Theory, Dan Li

Doctoral Dissertations

"The goal of this research is to develop a constrained multiobjective optimization method in the form of a robust, practical, problem-independent algorithm, and to investigate the effect of multiobjective optimization on structural design.

This research studies the properties and characteristics of multiobjective optimization and solutions. Design objectives, constraints and design variables as well as their effect on structural design and behaviors are investigated. Dynamic input energy for a multidegree-of-freedom structure is formulated. A multiobjective optimization algorithm based on game theory is developed. Fuzzy set theory is introduced to construct a fuzzy constrained environment. A Pareto genetic algorithm is developed based …

Heat Transfer In Microchannels, Xianming Wang

Doctoral Dissertations

The objective of this research was to develop an analytical solution to the heat transfer problem in microchannels with slip-flow--a heat transfer problem for gases at low pressures or in extremely small geometries, and to verify this solution experimentally. In this investigation, an analytical expression for the velocity distribution with slip-flow was obtained which involved the Knudsen (Kn) number in an infinite series form. The result showed that the velocity always increased as the Knudsen number was increased. The Knudsen number for extremely small channels may become large enough to affect significantly the velocity distribution and consequently affect the heat …

The Use Of Prior Knowledge In Learning From Examples, Stephen B. Blessing '89

Doctoral Dissertations

This dissertation examines the way people acquire procedures from examples, and provides a computational model of the results. In four experiments, people learned an analog of algebra. For each experiment, the initial know ledge that people had of the task was varied. In two experiments (Experiments 1 and 3), the syntactic know ledge that people had concerning the task w as manipulated. The knowledge of syntax that participants had, particularly the ability to correctly parse the character string, was found to be a major determiner in the way participants acquired the rules. Experiment 2 explicitly manipulated participant's awareness as to …

Implementation Of Alf Results To Designing Flexible Pavements In Louisiana, Ludfi Djakfar

Doctoral Dissertations

The Louisiana Transportation Research Center (LTRC) recently conducted a research effort using the Accelerated Loading Facility (ALF). The objective of the research was to evaluate a limited number of alternative base materials and construction techniques envisioned to provide a significant reduction in the occurrence of shrinkage and reflected block cracking in the cement-stabilized bases. Nine test sections were constructed for this research, using the same wearing course material but having different thicknesses of crushed stone and soil cement bases and subbases. The soil cement base is the most commonly used base material in Louisiana, whereas crushed stone is a preferred …

Snow And Ice Chemistry Study Of The Greenland Ice Sheet, Qinzhao Yang

Doctoral Dissertations

The Greenland ice sheet preserves high resolution records of environmental and climate change spanning seasons to hundreds and thousands of years. In this study, we utilize major chemical species measurements of surface snowpit samples and ice cores collected at GISP2, 20D, Mount Logan, and Sentik Glacier to investigate major chemical species spatial distribution, temporal variations, and possible sources for the major chemical species in these ice cores.

A two-sided t-distribution test (a = 0.05) was applied for the study of major chemical species spatial distribution over a portion of central Greenland. The results suggest that concentrations of major chemical species …

Cross-Tail Current Carriers In A Two-Dimensional Equilibrium Magnetotail Model, Douglas Johnston Larson

Doctoral Dissertations

The purpose of this study is to gain physical insight into how charged particles, that violate the guiding center approximations, contribute to cross-tail current in a self-consistent plasma sheet. A technique to generate self-consistent two-dimensional (2D) current sheets is described. Groups of monoenergetic protons are followed in a model magnetic field. The sample current sheets are characterized by resonant quasiadiabatic and stochastic orbits. Several ion and electron groups are combined to produce a plasma sheet in which the charged particles carry the currents needed to generate the magnetic field in which the orbits are traced. An electric field also is …

Assessing Land Use/Cover Change In Costa Rica, Gerardo-Arturo Sanchez-Azofeifa

Doctoral Dissertations

The need for accurate estimates of forest cover and forest fragmentation is a critical issue for developing countries such as Costa Rica. Accurate estimates of forest cover can help in several sectors related to the environment and economic development. This dissertation focuses on providing an accurate and precise estimate of forest cover in Costa Rica. The year 1991 was used as a baseline. Landsat Thematic Mapper was the remote sensing sensor used in this analysis. This dissertation concludes that: (1) Twenty-nine percent ($\sim$1,400,000 ha) of the country was under primary forest (80% canopy closure) in 1991. Of the total forest …

Biped Dynamic Walking Using Reinforcement Learning, Hamid Benbrahim

Doctoral Dissertations

This thesis presents a study of biped dynamic walking using reinforcement learning. A hardware biped robot was built. It uses low gear ratio DC motors in order to provide free leg movements. The Self Scaling Reinforcement learning algorithm was developed in order to deal with the problem of reinforcement learning in continuous action domains. A new learning architecture was designed to solve complex control problems. It uses different modules that consist of simple controllers and small neural networks. The architecture allows for easy incorporation of modules that represent new knowledge, or new requirements for the desired task. Control experiments were …

Analysis And Design Of Ac Induction Motors With Squirrel Cage Rotors, Shine Ho

Doctoral Dissertations

The traditional approach to modelling the AC induction motor revolves around the well-known equivalent "T" circuit model. In this approach, the direct connection from geometry to performance is suppressed. For better understanding of magnetic, electrical, and thermal behaviors, three lumped models based on the actual geometry are developed in this dissertation. Based on these lumped models, an iterative design model is also developed.

In order to analyze and design induction motors, the relationships of basic motor variables to motor performance must be known. For determining the relationships, three new mathematical lumped models are developed. The magnetic model describes flux behavior. …

Composition Operators On Riemann Surfaces, Ioana Crenguta Mihaila

Doctoral Dissertations

General background. Composition operators are defined on a Hilbert (or Banach) spaces of complex valued functions defined on some set X. For the big majority of cases the set X is the unit disc in the complex plane, and the space of functions is one of the Hardy or Bergman spaces (weighted or not). This is due, without doubt, to the richness of those spaces, and the high degree of interest in them. There have been also important papers on the study of the Hardy spaces on the unit ball of n-dimensional complex space.

I have been working with my …

Investigation Of Pd(A)(20)Pd(T)(20) In The Analytical Electrophoresis Apparatus, John Oliver Wooll

Doctoral Dissertations

The analytical electrophoresis apparatus (AEA) is capable of generating and monitoring the electrophoretic migration of macroions. The oligonucleotide pd(A)$\sb{20}\cdot$pd(T)$\sb{20}$ was use as a model to compound to evaluate the range and validity of AEA measurements under a variety of electric fields and solvent conditions. A broad range of electric fields yield consistent, reproducible values. The charge determination from different procedures, steady state electrophoresis (SSE) and electrophoretic mobility, have not been consolidated into a consistent theory but advancements in the scope and understanding of the AEA's potential have been made. The apparent charge from the AEA measured electrophoretic mobility, $\mu$, of …

The Evolutionary Dimension Within Economic Thought, James Julius Neidhart

Doctoral Dissertations

This dissertation integrates the concepts of circular causality, emergence, and hierarchical organization through an investigation of the evolutionary dimension within economic thought. The different sections of this dissertation represent complementary perspectives on this theme.

The first chapter introduces the concept of circular causality and the technique of causal diagramming. These tools are used in the second and third chapters to highlight the evolutionary dimension within the history of economic thought. The particular theorists and groups of articles discussed include Adam Smith, Alfred Marshall, the Increasing Returns debates of the 1920's, Gunnar Myrdal, and Nicholas Kaldor. The significance of the Increasing …

Profiles Of Reform In The Teaching Of Calculus: A Study Of The Implementation Of Materials Developed By The Calculus Consortium Based At Harvard (Cch) Curriculum Project, Alice Darien Lauten

Doctoral Dissertations

The research question addressed in this study is: What profiles of interpretation and implementation of reform in the teaching of calculus emerge from data obtained from mathematics faculty members using Calculus Consortium Based at Harvard (CCH) Curriculum Project materials? Site liaisons from mathematics departments using CCH Curriculum Project materials in 117 academic institutions, consisting of 13 secondary schools, 30 two-year colleges, 19 doctoral and research universities, and 55 other colleges and universities, completed Initial and Site Liaison Surveys. Site liaisons and 266 other instructors from 117 academic institutions completed a Faculty Survey. Six clustering scales were developed from the survey …