Physical Sciences and Mathematics Commons^™

The Structure And Stability Of Expanding And Converging Near-Stoichiometric Flames, Raymond Addabbo

Dissertations

The stability of expanding and converging premixed flames is investigated theoretically. These configurations are inherently unsteady and represent simple examples of positively (expanding) and negatively (converging) stretched flames. A new model is employed in this study that incorporates both hydrodynamic and diffusional-thermal effects. The model expands earlier works by incorporating variable transport properties, variations in the mixture strength and a more realistic dependence on viscosity.

The expanding flame is shown to remain stable at small radii provided the thermal diffusivity exceeds the mass diffusivity of the deficient reactant. However, once the flame achieves a critical size, a cellular instability appears, …

Asymptotic Methods In Applied Waveguide Problems, Helen Martynov

Dissertations

Some of the most challenging problems in acoustics and electromagnetics involve the study of scattered fields in waveguides caused by targets of elaborate shape. The complexity of the resulting scattered field depends on the geometry of the scatterer, and exact solutions exist only for the simple geometries.

The asymptotic methods developed in this dissertation give the approximate solutions for the scattered fields in two practically important geometries: an object placed inside a stratified waveguide, and a waveguide with multiple abrupt width transitions. The solutions for these geometries are obtained by approximating the field near the target or junction by the …

Structural, Transport And Magnetic Studies Of Perovskite Bi1-X Cax Mn O3, Hyungje Woo

Dissertations

This dissertation presents an investigation of the fundamental physics of the perovskite system Bi_1-xCa_xMn0₃. This material belongs to a group of simple perovskites called the manganites which are of technological importance for magnetic device applications as read-head sensors.

The Bi_1-xCa_xMnO₃ system is known to exhibit charge ordering (and high sensitivity to magnetic fields) for a much broader range of x than the well-characterized La_1-xCa_xMnO₃ system. However, the properties of Bi_1-xCa_xMnO₃ over the entire doping range are not well understood. …

Detection Of Vapor Phase Mercury Species By Laser Fluorescence Methods, Xiaomei Tong

Dissertations

Elemental and compound mercury are often both volatile and air stable. Several mercury species emissions have been identified in off-gases from industrial processes. The high toxicity of mercury species and the presence of mercury species in municipal waste and coal have prompted a demand for a cost-effective, accurate, and rugged technique for real-time, continuous detection of mercury species vapors. Real-time, continuous emission measurements are important for process control, monitoring, and remediation. At present, there is no commercial continuous emission monitoring (CEM) technique or instrumentation to reliably monitor volatile mercury species emissions from industrial stacks. Conventional measurement methods, such as cold …

Electrostatic Micro Actuators For Mirror And Other Applications, Xingtao Wu

Dissertations

Micro-electro-mechanical systems (MEMS) based electrostatic micro actuators are becoming important building blocks for innovations in optical signal processing and computing systems due to their inherently small size, high density, high speed and low power consumption. Generally, the principle of operation in these systems can be described as: an electrostatic attractive force causes a mechanical rotation, translation or deformation of a mirror plate, controlling the power, phase or direction of a light beam while it propagates through some medium or through free space. The fast paced, competitive research and development efforts widely being undertaken, both in academia and industry, are demanding …

Vortex-Defect Interactions In High-Temperature Superconductors, Valentina Tobos

Dissertations

The topics covered in this thesis are related to two objectives: one refers to the search for methods of improving die critical current density of high-temperature superconductors, a subject which remains of continuing interest for its importance in technological applications. The other direction is aimed at clarifying the phase diagram of high-Tc materials.

The interaction between the structural defects and the vortex system plays a significant role in the capability of these materials to carry large electrical transport currents. Through proton irradiation induced defects we follow the evolution of the critical current density, and its enhancement with increasing point-like defects …

Empirical Spectral Analysis Of Random Number Generators, David Zeitler

Dissertations

Computer simulation procedures have become a staple of research and development in many fields, including statistics. The generation of pseudo random number sequences is the core of computer simulation procedures. Validity of research results often depend on the underlying validity of the generator being used.

In this work we develop the machinery for a class of tests of spatial uniformity based on a multi-dimensional Fourier transform of the empirical probability density function. The test can be adapted to specific requirements and has the added advantage that it has computational complexity that is relatively independent of the number of data points …

Quantification Of Benzo[A]Pyrene-Guanine Adducts In In Vitro And In Vivo Tissue Samples By Lc Tandem Mass Spectrometry, Po-Chang Chiang

Dissertations

No abstract provided.

Cost Domination In Graphs, David John Erwin

Dissertations

Let G be a connected graph having order at least 2. A function f : V (G) —> {0 , 1 , . . . , diam G} for which f ( v ) < e(v) for every vertex v of G is a cost function on G. A vertex v with f ( v ) > 0 is an f-dominating vertex, and the set Vj~ = {v 6 V(G) : f(v) > 0} of f-dominating vertices is the f-dominating set. An /-dominating vertex v is said to f-dominate every vertex u with d(n, v) < f(u ), while …

E-Docspros : Exploring Texpros Into E-Business Era, Zhenfu Cheng

Dissertations

Document processing is a critical element of office automation. TEXPROS (TEXt PROcessing System) is a knowledge-based system designed to manage personal documents. However, as the Internet and e-Business changed the way offices operate, there is a need to re-envision document processing, storage, retrieval, and sharing. In the current environment, people must be able to access documents remotely and to share those documents with others. e-DOCPROS (e-DOCument PROcessing System) is a new document processing system that takes advantage of many of TEXPROS's structures but adapts the system to this new environment. The new system is built to serve e-businesses, takes advantage …

Ultrathin Silicon Wafer Bonding Physics And Applications, Michael H. Beggans

Dissertations

Ultrathin silicon wafer bonding is an emerging process that simplifies device fabrication, reduces manufacturing costs, increases yield, and allows the realization of novel devices. Ultrathin silicon wafers are between 3 and 200 microns thick with all the same properties of the thicker silicon wafers (greater than 300 microns) normally used by the semiconductor electronics industry. Wafer bonding is one technique by which multiple layers are formed.

In this thesis, the history and practice of wafer bonding is described and applied to the manufacture of microelectomechanical systems (MEMS) devices with layer thickness on the scale of microns. Handling and processing problems …

Waqs : A Web-Based Approximate Query System, George Jyh-Shian Chang

Dissertations

The Web is often viewed as a gigantic database holding vast stores of information and provides ubiquitous accessibility to end-users. Since its inception, the Internet has experienced explosive growth both in the number of users and the amount of content available on it. However, searching for information on the Web has become increasingly difficult. Although query languages have long been part of database management systems, the standard query language being the Structural Query Language is not suitable for the Web content retrieval.

In this dissertation, a new technique for document retrieval on the Web is presented. This technique is designed …

Broadband Whole Package Fdtd Simulation, Shenjun Li

Dissertations

Whole package analysis is becoming more and more important with the rapid expansion of high frequency electronics. The motivation of this thesis is to find and implement a new method for broadband whole package simulation. 3-dimension (3-D) whole package Finite Difference Time Domain (FDTD) simulation result was first reported in detail in this thesis.

The FDTD method is a widely used full-wave time-domain simulation method used in the design and analysis for electromagnetic (EM) systems, such as antennas, wave propagating, and microwave circuits. Absorbing boundary condition (ABC), such as the perfect matched layer (PML) method, makes it possible to accurately …

Augmenting Applications With Hyper Media, Functionality And Meta-Information, Roberto Galnares

Dissertations

The Dynamic Hypermedia Engine (DHE) enhances analytical applications by adding relationships, semantics and other metadata to the application's output and user interface. DHE also provides additional hypermedia navigational, structural and annotation functionality. These features allow application developers and users to add guided tours, personal links and sharable annotations, among other features, into applications. DHE runs as a middleware between the application user interface and its business logic and processes, in a n-tier architecture, supporting the extra functionalities without altering the original systems by means of application wrappers.

DHE automatically generates links at run-time for each of those elements having relationships …

Volume Change Behavior Of Clay Soils And The Effect On Discrete Fractures, Heather Ann Hall

Dissertations

This study examines the behavior of subsurface fractures in fine-grained soil such as clays in response to changing environmental conditions. Fractures serve as conduits for moisture transfer, which can lead to substantial shrinking and swelling of the surrounding fracture boundary soils. These volume changes, in turn, affect fracture geometry and moisture transmission rates. A new predictive model, termed the 'Fracture Volume Change Model' (FVC Model), has been developed to relate moisture transfer, soil volume change and associated changes in fracture aperture. The model assumes a discrete horizontal fracture in a laterally-infinite, saturated, expansive clay with rigid, outer no-flow boundaries and …

A Dynamical Model Of The Distributed Interaction Of Intracellular Signals, Adrienne C.N. James

Dissertations

A major goal of modern cell biology is to understand the regulation of cell behavior in the reductive terms of all the molecular interactions. This aim is made explicit by the assertion that understanding a cell's response to stimuli requires a full inventory of details. Currently, no satisfactory explanation exists to explain why cells exhibit only a relatively small number of different behavioral modes.

In this thesis, a discrete dynamical model is developed to study interactions between certain types of signaling proteins. The model is generic and "connectionist" in nature and incorporates important concepts from the biology. The emphasis is …

Knowledge-Based Document Retrieval With Application To Texpros, Fang Sheng

Dissertations

Document retrieval in an information system is most often accomplished through keyword search. The common technique behind keyword search is indexing. The major drawback of such a search technique is its lack of effectiveness and accuracy. It is very common in a typical keyword search over the Internet to identify hundreds or even thousands of records as the potentially desired records. However, often few of them are relevant to users' interests.

This dissertation presents knowledge-based document retrieval architecture with application to TEXPROS. The architecture is based on a dual document model that consists of a document type hierarchy and, a …

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 …

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 …

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 …