Physical Sciences and Mathematics Commons^™

Efficient Inversion Methods In Underwater Acoustics, Xiaoqun Ma

Dissertations

This dissertation describes efficient methods developed and implemented for source localization and sound speed and bottom depth estimation using sound propagation in the ocean. The proposed inversion techniques are based on the linearization of the generally non-linear inverse problem of parameter estimation in underwater acoustics. These techniques take into account properties of the ocean environment and are accurate in their estimation results without being prohibitively computationally intensive. For the inversion, select ray paths are taken into account: the direct, first surface bounce, and first bottom bounce. Ray travel time derivatives with respect to parameters that affect path arrival times are …

Near-Field Imaging With Terahertz Pulses, Oleg Mitrofanov

Dissertations

High spatial resolution imaging is implemented with a novel collection mode near-field terahertz (THz) probe. Exceptional sensitivity of the probe allows imaging with spatial resolution of few microns using THz pulses with spectral content of 120 to 1500 microns. In the present study, the principle of the probe operation as well as the probe design and characteristics are described.

The probe performance is related to effective detection of radiation coupled into the probe aperture. Propagation of short single-cycle electromagnetic pulses through apertures as small as 1/300 of the wavelength is experimentally and numerically studied. Finite-difference time-domain method is used to …

Gated Multi-Cycle Integration (Gmci) For Focal Plane Array (Fpa) Applications, Haijiang Ou

Dissertations

In this thesis, the model and the theory of gated multi-cycle integration (GMCI) were first developed specifically for focal plane array dealing with repetitive or modulated image. The operational modes of GMCI include gated integration (GI), phase sensitive integration (PSI), multi-point summation, multi-point subtraction, multi-sample averaging and some of their combinations. Thus, the analytic theory of GMCI somehow unifies the theories of gated integration, phase sensitive detection, multiple summation and average. PSI works with background and/or dark current subtraction. As a result, the storage well of a pixel is mainly used for signal integration even if there exists a strong …

A Near-Infrared Filter System And Study Of Solar Umbral Dots At 1.6 Μm, Jingshan Wang

Dissertations

The observations of solar magnetic fields are very important because they influence events on the sun. Almost all of magnetographs in the world work in the visible wavelength and they are powerful instruments for measuring strong magnetic fields (above 1000 Gauss) on the sun. To measure the weak solar magnetic fields (below 1000 Gauss), a new filter system (magnetograph) working in near-IR wavelength has been developed in this work. This system includes an interference prefilter (FWHM - 40Å), a liquid crystal magnetic analyzer, a near-IR bireffingent filter (FWHM - 2.5Å), a near-IR Fabry-Perot filter (FWHM - 0.12Å), a near-IR InGaAs …

Software And Hardware Improvements For Digital Solar Magnetograph System, Shu Yang

Dissertations

Digital solar imaging systems have been widely used in solar observations. Their high resolution, high rate of image acquisition and convenience for off-line image processing have provided significant improvements to solar physics research. In this project, two digital magnetograph systems established at Big Bear Solar Observatory (BBSO) have been described. One is used to provide a high frame rate magnetogram system, and the other provides a real-time image alignment, i.e., a correlation tracker system.

The developed correlation tracker system consists of a high-speed 64x64 CCD camera, an EDT image grabbing board, an agile mirror, a D/A board and a Sun …

A Comparison Of Methods For Detection Of Qualitative Interaction In Multicenter Trials, Boyd Jay Hanson

Dissertations

This research evaluated and compared three methods for the detection of qualitative treatment-by-center interaction proposed by Azzalini and Cox, Gail and Simon and Ciminera et al., through the analysis of simulated data for multicenter studies of two and three centers with two treatments. The effect of unequal sample size and the presence of an overall treatment effect on characteristics of the methods were examined.

The approach, underlying assumptions and theory of the three methods differ. For this study, they were adapted to establish a common basis for evaluation, thus allowing a meaningful comparison of the methods. For the test presented …

Comparison Of Optical Density, Total Cell Protein, And Number Of Viable Cells (Via Fluorescent Straining) As Measures Of Microbial Growth Kinetics In Suspended And Biofilm Cultures During Biodegradation Of Naphthalene, Jeong Seop Shim

Dissertations

Most studies on bacterial growth kinetics have been dependent on theoretical modeling with general biomass measurements using either dry weight or optical density (OD), without distinguishing live from dead bacteria or debris. As a result, there remains considerable uncertainty in reliably predicting rates of biodegradation for design of treatment processes for environmental pollutants.

This research focused on measurement of bacterial growth rates and activities in suspended cultures and biofilms using Pseudomonas putida (ATCC 17484) for biodegradation of naphthalene. As expected, the rates of biodegradation differed between suspended and immobilized cultures. A comparison was made of the impact of three biomass …

Environmental Science In The New Millennium : A Model To Give Structure And Guidance, James M. Lipuma

Dissertations

This work proposes a template for successful interdisciplinary Environmental Science (EVSQ) programs at four-year American learning institutions. The first conclusion reached is that there is no one "perfect" program. Only by identifying clear goals for EVSC can programs improve. It was determined that a clear definition of EVSC and mission statements related to these definitions are necessary first steps to allow improvement to occur. One major outcome of the work is the educational model built to understand EVSC education. The model identifies methods by which the goals and objectives of EVSC can be identified and accomplished. The research found that …

Multi-Mode Cavity Effects In The Microwave Heating Of A Ceramic Slab, Stuart J. Walker

Dissertations

In order to gain insight into hot spot development in microwave heated ceramics, a partially insulated, two dimensional ceramic slab situated in a TE_M01 cavity is modeled in the small Biot number limit. If the electrical conductivity is an exponential function of temperture and E₀ is the strength of the incident mode, then the relationship between the spatially uniform, steady state leading order temperature, v₈, and E₀¹ is characterized by the well known bi-stable, or S shaped, response curve. The steady state second order temperature, v₁, is described by a boundary …

Analysis Of Discrete Dynamical System Models For Competing Species, Jerry J. Chen

Dissertations

A discrete version of the Lotka-Volterra (LV) differential equations for competing population species is analyzed in detail, much the same way as the discrete form of the logistic equation has been investigated as a source of bifurcation phenomena and chaotic dynamics. Another related system, namely, the Exponentially Self Regulating (ESR) population model, is also thoroughly analyzed. It is found that in addition to logistic dynamics - ranging from the very simple to manifestly chaotic regimes in terms of the governing parameters - the discrete LV model and the ESR model exhibit their own brands of bifurcation and chaos that are …

A More Efficient Document Retrieval Method For Texpros, Yin Dong

Dissertations

Document processing is a critical element of office automation. Through document classification, extraction and filing, documents are automatically placed into a knowledge base according to certain rules. Document retrieval is a process to get a document back according to a user's requirements and to show the results to the user. Hence, a good user-interface and an efficient retrieval algorithm become core parts of document retrieval.

Unlike previous browsers that have been proposed for this purpose, this dissertation develops a new browser that has a user interface with more tools, and one that has a more efficient retrieval algorithm that can …

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 …

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 …

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 …

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 …

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 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 …