Physical Sciences and Mathematics Commons^™

The Effects Of Radiation Damage On The Vortex Dynamics Of High Temperature Superconductors, Andra Petrean

Dissertations

This work focuses on the interaction between magnetic vortices in high temperature superconductors and defects introduced by irradiation with protons and heavy ions. The study concentrates on the high temperature superconductor YBa;Cu30 7J5. This material is used to investigate the role of disorder in phase transitions, a topic of great interest in Solid State Physics. In addition, this study analyzes the interaction between vortices and columnar defects in various doses and defect morphologies, including the thermal stability of columnar defects.

We present experimental evidence of the vortex glass phase in proton irradiated Y B a:Cu:!0 -.15. For the first time, …

Information Retrieval And Mining In High Dimensional Databases, Xiong Wang

Dissertations

This dissertation is composed of two parts. In the first part, we present a framework for finding information (more precisely, active patterns) in three dimensional (3D) graphs. Each node in a graph is an undecoraposable or atomic unit and has a label. Edges are links between the atomic units. Patterns are rigid substructures that may occur in a graph after allowing for an arbitrary number of whole-structure rotations and translations as well as a small number (specified by the user) of edit operations in the patterns or in the graph. (When a pattern appears in a graph only after the …

Knowledge Discovery In Biological Databases : A Neural Network Approach, Qicheng Ma

Dissertations

Knowledge discovery, in databases, also known as data mining, is aimed to find significant information from a set of data. The knowledge to be mined from the dataset may refer to patterns, association rules, classification and clustering rules, and so forth. In this dissertation, we present a neural network approach to finding knowledge in biological databases. Specifically, we propose new methods to process biological sequences in two case studies: the classification of protein sequences and the prediction of E. Coli promoters in DNA sequences. Our proposed methods, based oil neural network architectures combine techniques ranging from Bayesian inference, coding theory, …

Deactivation And Enhancement Effects Of Sulfur On Supported Platinum Oxidation Catalysts, Mark Ladolcetta

Dissertations

The effects of sulfur poisoning on the oxidation activity of 1.5 % Pt/γ-Al₂O₃, Pt/TiO₂, Pt/ZrO₂, and Pt/SiO₂, were investigated in this study. Each catalyst was poisoned with an H₂S/air or SO₂/air mixture at 400°C for 24 hours and a sulfur concentration of 200 ppm. The complete oxidation of mixtures of I % CO, methane, ethane, ethene, ethyne, propane, propene, and n-butane in air were measured over fresh and sulfurpoisoned catalysts.

Non-methane alkane oxidation activity was enhanced significantly after sulfur poisoning on all four catalysts. The temperatures …

An Investigation Into Relationships Between Alternative Assessment And Pre-Service Elementary Teachers’ Beliefs About Mathematics, David Charles Coffey

Dissertations

The purpose of this study was to examine how including alternative assessments in a reform-based mathematics course affects pre-service teachers’ mathematical beliefs. A single section of a mathematics course designed for elementary education majors that employed three different alternative assessments was the setting for the study.

A pre- and post-belief survey completed by students enrolled in the section under study represented the first level of data collection and analysis. The results of the pre-belief survey guided the selection of seven informants from the section and provided belief statements for the informants to verify during subsequent interviews. Based on the data …

Rainbow Ramsey Numbers, Linda Eroh

Dissertations

No abstract provided.

Study Of Architecture And Protocols For Reliable Multicasting In Packet Switching Networks, Shiwen Chen

Dissertations

Group multicast protocols have been challenged to provide scalable solutions that meet the following requirements: (i) reliable delivery from different sources to all destinations within a multicast group; (ii) congestion control among multiple asynchronous sources. Although it is mainly a transport layer task, reliable group multicasting depends on routing architectures as well.

This dissertation covers issues of both network and transport layers. Two routing architectures, tree and ring, are surveyed with a comparative study of their routing costs and impact to upper layer performances. Correspondingly, two generic transport protocol models are established for performance study. The tree-based protocol is rate-based …

Time Domain Measurement Of The Nonlinear Refractive Index In Optical Fibers And Semiconductor Film, Hernando Garcia

Dissertations

A new technique to measure the nonlinear refractive index n₂ in optical fibers and semiconductor films has been developed. It is based on the time delay two-beam coupling of very intense picosecond laser pulses that have been self-phase modulated in the nonlinear optical medium. The two beams are coupled in a slow responding medium that is sensitive to time dependent phase distortions. We determine that the amount of phase distortion experienced by the pulse is proportional to the nonlinear refractive index of the medium, This time domain approach can also be applied to optical fiber amplifiers in the presence …

Genetically Evolved Dynamic Control For Quadruped Walking, Giorgio Grasso

Dissertations

The aim of this dissertation is to show that dynamic control of quadruped locomotion is achievable through the use of genetically evolved central pattern generators. This strategy is tested both in simulation and on a walking robot. The design of the walker has been chosen to be statically unstable, so that during motion less than three supporting feet may be in contact with the ground.

The control strategy adopted is capable of propelling the artificial walker at a forward locomotion speed of ~1.5 Km/h on rugged terrain and provides for stability of motion. The learning of walking, based on simulated …

Modeling, Design And Fabrication Of Thin-Film Microcrystalline Silicon Solar Cells, Wei Chen

Dissertations

The modeling, design and fabrication of low-cost thin-film microcrystalline silicon(µcSi) solar cells is studied in this thesis. The cell, considered in this investigation, utilizes low-cost glass as the substrate and microcrystalline Si (µc-Si) as the active layer. A comprehensive refractive index (n) and extinction coefficient (k) model of silicon as function of doping, temperature and wavelength is developed to assist the optical design of the cell. In order to obtain acceptable short circuit current density (Jsc) from the cell, it is found that the thickness of the silicon thin film should be more than 10µm. To get the best light …

A Meta-Semantic Language For Smart Component-Adapters, Leon K. Jololian

Dissertations

The issues confronting the software development community today are significantly different from the problems it faced only a decade ago. Advances in software development tools and technologies during the last two decades have greatly enhanced the ability to leverage large amounts of software for creating new applications through the reuse of software libraries and application frameworks. The problems facing organizations today are increasingly focused around systems integration and the creation of information flows.

Software modeling based on the assembly of reusable components to support software development has not been successfully implemented on a wide scale. Several models for reusable software …

Active Feedback Control Of A Wake Flow Via Forced Oscillations Based On A Reduced Model, Fu Li

Dissertations

As it is well known, the flow past a cylinder consists of a symmetric recirculation bubble of vortices at small Reynolds numbers. As Reynolds number increases, the bubble becomes unstable and develops into a Karman vortex street of alternating vortices. This instability is responsible for the occurrence of large amplitude oscillations in the lift and an increase in the mean drag. It was previously shown by numerical simulation that the mechanism driving the bubble instability is well mimicked by Foppl's four dimensional potential flow model where the bubble is represented by a saddle point. In this work, we design two …

Component-Based Software Engineering, Zhiyuan Wang

Dissertations

To solve the problems coming with the current software development methodologies, component-based software engineering has caught many researchers' attention recently. In component-based software engineering, a software system is considered as a set of software components assembled together instead of as a set of functions from the traditional perspective. Software components can be bought from third party vendors as off-the-shelf components and be assembled together.

Component-based software engineering, though very promising, needs to solve several core issues before it becomes a mature software development strategy. The goal of this dissertation is to establish an infrastructure for component-based software development. The author …

Applications Of Agent Architectures To Decision Support In Distributed Simulation And Training Systems, Plamen V. Petrov

Dissertations

This work develops the approach and presents the results of a new model for applying intelligent agents to complex distributed interactive simulation for command and control. In the framework of tactical command, control communications, computers and intelligence (C₄I), software agents provide a novel approach for efficient decision support and distributed interactive mission training. An agent-based architecture for decision support is designed, implemented and is applied in a distributed interactive simulation to significantly enhance the command and control training during simulated exercises. The architecture is based on monitoring, evaluation, and advice agents, which cooperate to provide alternatives to the …

A Study Of Droplet Burning In The Nearly Adiabatic Limit, Juan C. Gomez

Dissertations

We consider a small drop of liquid fuel that burns in an oxidizing gaseous environment and translates slowly (relative to flow 'at infinity') under the action of gravity. Practical applications include the burning of liquid fuels as sprays in domestic and industrial oil-fired burners, diesel engines, and liquid-propellant rocket motors. More relevant to the simple physical set-up of the present study are wellcharacterized laboratory experiments on the burning of a single, isolated fuel drop.

The drop burns in a nearly spherical, diffusion flame, flame sheet regime. We consider a specific example, or limit, referred to as 'nearly adiabatic burning', in …

Numerical Study Of Particle Dynamics In A Falling-Ball Viscometer, Peiwen Hou

Dissertations

The falling-ball viscometer is a device where a spherical particle falls along the axis of a circular cylinder filled with viscous fluid. The various classical results for this device are developed under the assumption that the Reynolds number of the flow is zero, i.e., Stoke's flow. Inertial effects are not taken into account. To better understand the dynamics of the particle sedimentation process and the role of inertia in this process, we implemented a numerical simulation.

The ADI (Alternating Direction Implicit) scheme is widely used to solve the vorticity-stream function formulation of the Navier-Stokes equation in axisymmetric geometries. However, a …

A Mathematical Model Of Wheelchair Racing, Susan J. Schenk

Dissertations

Wheelchair racing strokes are very complicated movements, which involve a coupling between the athlete and his or her racing chair. Each body segment, as well as the wheel, follows a distinct trajectory as the motion is performed. Understanding the kinematics and kinetics of various stroke techniques would provide the athletes and their coaches with information, which could help guide the racers toward improved performances.

In this thesis, a mathematical model is developed, which is capable of providing such valuable kinematic and kinetic information. This two-dimensional model represents the body segments as a coupled pendulum system of point masses and the …

Experiment, Thermodynamic Properties And Modeling On Combustion Of Methyl Tert-Butyl Ether : Isobutane And Isobutene And Thermodynamic Properties Of Chloro Alkanes And Alkenes, Chiung-Ju Chen

Dissertations

The reaction systems: methyl tert-butyl ether (MTBE) unimolecular decomposition, MTBE radicals + O₂, tert-butyl radical +O₂, isobutene + HOO. (HO₂),isobutene + OH, sobutene-OH adducts + O₂, and allylic isobutenyl radical + O₂, are important systems in the understanding the oxidation chemistry of MTBE, tertiary butyl radical (C3C.), and sobutene, are analyzed. Thermochemical parameters are determined by ah initio Møller-Plesset (MP2(full)/6-31g(d)), complete basis set model chemistry (CBS-4 and CBS-q with MP2(full)/6-31g(d) and B3LYP/6-31g(d) optimized geometries), density functional (B3LYP/631g(d)), semi-empirical MOPAC (PM3) molecular orbital calculations, and by group additivity estimation. Thermochemical …

Collaborative Software Agents Support For The Texpros Document Management System, Jrtian Lin

Dissertations

This dissertation investigates the use of active rules that are embedded in markup documents. Active rules are used in a markup representation by integrating Collaborative Software Agents with TEXPROS (abbreviation for TEXt PROcessing System) [Liu and Ng 1996] to create a powerful distributed document management system. Such markup documents with embedded active rules are called Active Documents. For fast retrieval purposes, when we need to generate a customized Internet folder organization, we first define the Folder Organization Query Language (FO-QL) to solve data categorization problems. FO-QL defines the folder organization query process that automatically retrieves links of documents deposited into …

Polymer Pyrolysis And Oxidation Studies In A Continuous Feed And Flow Reactor : Cellulose, Polystyrene, And Polyethylene, Byung-Ik Park

Dissertations

A dual zone, continuous feed tubular reactor is developed to assessthe potential for formation of products from incomplete combustion in thermal oxidation of common polymers. Solid polymer powder (cellulose,polystyrene, or polyethylene) is fed continuously into a volatilization oven where it fragments and vaporizes under continuous steady state conditions. The gas phase polymer fragments flow directly into a second, main flow reactor oven and undergo further pyrolysis and oxidation reaction. Temperatures in the main flow reactor are varied independently of the volatilization zone to observe conditions needed to convert the initial polymer fragmentsto CO₂ and H₂O. Combustion products …

Hytexpros : A Hypermedia Information Retrieval System, Hong Shen

Dissertations

The Hypermedia information retrieval system makes use of the specific capabilities of hypermedia systems with information retrieval operations and provides new kind of information management tools. It combines both hypermedia and information retrieval to offer end-users the possibility of navigating, browsing and searching a large collection of documents to satisfy an information need. TEXPROS is an intelligent document processing and retrieval system that supports storing, extracting, classifying, categorizing, retrieval and browsing enterprise information. TEXPROS is a perfect application to apply hypermedia information retrieval techniques. In this dissertation, we extend TEXPROS to a hypermedia information retrieval system called HyTEXPROS with hypertext …

Experimental And Phenomenological Study Of Persistent Photoconductivity In Yba2cu3o6 Thin Films, Daniel-Dennis Mcalevy Bubb

Dissertations

Persistent Photoconductivity in YBa₂Cu₃O_6+x thin films is studied by means of infrared photoconductivity measurements after the films have been illuminated with visible light at low temperature. Experimentally, the effect is characterized by the samples' electrical response to infrared light, either causing the resistance to decrease or increase.

A cellular automata model is proposed in explanation of these results and is shown to be consistent with current experimental understanding of this unusual effect, both our results and those of others. The cellular automata model may have application to other unusual optical phenomena exhibited by YBa_{2 …}