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Electronic Theses and Dissertations

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Articles 3121 - 3150 of 4195

Full-Text Articles in Physical Sciences and Mathematics

Higher-Order Physic For Modeling Ice Streams In Ice Sheets, Debra A. Kenneway Jan 2010

Higher-Order Physic For Modeling Ice Streams In Ice Sheets, Debra A. Kenneway

Electronic Theses and Dissertations

Ice streams are transitional between inland glaciers and ice shelves. Hence no stresses can be neglected. Ice streams are important dynamic features of a glacier; it is well known that ice streams drain up to 90% of the ice from an ice sheet. Herein I model ice streams as a multiphysics system of coupled components. This includes treating ice as a non-Newtonian fluid since empirical measurements show a power law relation between stress and strain rate. Sliding is a physical feature that must be included. This is done with a novel approach to sliding by way of a slippery layer. …


Search For Gas Giants Around Late-M Dwarfs, Rohit Deshpande Jan 2010

Search For Gas Giants Around Late-M Dwarfs, Rohit Deshpande

Electronic Theses and Dissertations

We carried out a near-infrared radial velocity search for Jupiter-mass planets around 36 late M dwarfs. This survey was the first of its kind undertaken to monitor radial velocity variability of these faint dwarfs. For this unique survey we employed the 10-m Keck II on Mauna Kea in Hawaii. With a resolution of 20,000 on the near-infrared spectrograph, NIRSPEC, we monitored these stars over four epochs in 2007. In addition to the measurement of relative radial velocity we established physical properties of these stars. The physical properties of M dwarfs we determined included the identification of neutral atomic lines, the …


Synthesis And Applications Of Ring Opening Metathesis Polymerization Based Functional Block Copolymers, Sanchita Biswas Jan 2010

Synthesis And Applications Of Ring Opening Metathesis Polymerization Based Functional Block Copolymers, Sanchita Biswas

Electronic Theses and Dissertations

Ring opening metathesis polymerization (ROMP) is established as one of the efficient controlled living polymerization methods which have various applications in polymer science and technology fields. The research presented in this dissertation addresses several applications of multifunctional well-defined norbornene-based block copolymers synthesized by ROMP using ruthenium-based Grubbs catalysts. These novel block copolymers were applied to stabilize maghemite nanoparticles, creating the superparamagnetic polymeric nanocomposites. The Jaggregation properties of the porphyrin dyes were improved via self-assembly with a customized norbornene polymer. Novel multimodal copolymer probes were synthesized for two-photon fluorescence integrin-targeted bioimaging. In Chapter 1 a brief overview of ROMP along with …


Species Composition And Spatiotemporal Pattern Of The Seed Bank And Vegetation In Native And Degraded Florida Rosemary Scrub, Jennifer J. Navarra Jan 2010

Species Composition And Spatiotemporal Pattern Of The Seed Bank And Vegetation In Native And Degraded Florida Rosemary Scrub, Jennifer J. Navarra

Electronic Theses and Dissertations

The soil seed bank plays a dynamic role in the regeneration of plant communities after natural and anthropogenic disturbance. In this thesis, I addressed how disturbances influence the vegetation and seed bank of Florida rosemary scrub. In Chapter One I evaluated changes in species composition and spatiotemporal pattern of the vegetation and seed bank along a gradient of disturbance. During the summers and winters of 2007-2009 percent ground cover and seed bank species composition were assessed among replicates of three vegetation types subjected to minimal, moderate, and extreme anthropogenic disturbance (native rosemary scrub, degraded scrub, and agriculturally improved pasture, respectively). …


Controlled Assembly And Electronic Transport Studies Of Solution Processed Carbon Nanotube Devices, Paul Stokes Jan 2010

Controlled Assembly And Electronic Transport Studies Of Solution Processed Carbon Nanotube Devices, Paul Stokes

Electronic Theses and Dissertations

Developing techniques for the parallel fabrication of Complementary Metal Oxide Semiconductor (CMOS) compatible single walled carbon nanotube (SWNT) electronic devices is of great importance for nanoelectronic applications. In this thesis, solution processed SWNTs in combination with AC dielectrophoresis (DEP) were utilized to fabricate CMOS compatible SWNT field effect transistors (FETs) and single electron transistors (SETs) with high yield and their detailed electronic transport properties were studied. Solution processing of SWNTs is attractive not only for the high throughput and parallel manufacturing of SWNT devices but also due to the ease of processing at room temperature, and compatibility with various substrates. …


New Laser Technologies Analysis Of Quantum Dot And Lithographic Laser Diodes, Abdullah Demir Jan 2010

New Laser Technologies Analysis Of Quantum Dot And Lithographic Laser Diodes, Abdullah Demir

Electronic Theses and Dissertations

The first part of this dissertation presents a comprehensive study of quantum dot (QD) lasers threshold characteristics. The threshold temperature dependence of a QD laser diode is studied in different limits of p-doping, hole level spacing and inhomogeneous broadening. Theoretical analysis shows that the threshold current of a QD laser in the limit of uniform QDs is not temperature independent and actually more temperature sensitive than the quantum well laser. The results also explain the experimental trends of negative characteristic temperature observed in QD lasers and clarify how the carrier distribution mechanisms inside and among the QDs affect the threshold …


Initial-Value Technique For Singularly Perturbed Two Point Boundary Value Problems Via Cubic Spline, Luis G. Negron Jan 2010

Initial-Value Technique For Singularly Perturbed Two Point Boundary Value Problems Via Cubic Spline, Luis G. Negron

Electronic Theses and Dissertations

A recent method for solving singular perturbation problems is examined. It is designed for the applied mathematician or engineer who needs a convenient, useful tool that requires little preparation and can be readily implemented using little more than an industry-standard software package for spreadsheets. In this paper, we shall examine singularly perturbed two point boundary value problems with the boundary layer at one end point. An initial-value technique is used for its solution by replacing the problem with an asymptotically equivalent first order problem, which is, in turn, solved as an initial value problem by using cubic splines. Numerical examples …


Statistical Analysis Of Visible Absorption Spectra And Mass Spectra Obtained From Dyed Textile Fibers, Katie Margaret White Jan 2010

Statistical Analysis Of Visible Absorption Spectra And Mass Spectra Obtained From Dyed Textile Fibers, Katie Margaret White

Electronic Theses and Dissertations

The National Academy of Sciences recently published a report which calls for improvements to the field of forensic science. Their report criticized many forensic disciplines for failure to establish rigorously-tested methods of comparison, and encouraged more research in these areas to establish limitations and assess error rates. This study applies chemometric and statistical methods to current and developing analytical techniques in fiber analysis. In addition to analysis of commercially available dyed textile fibers, two pairs of dyes are selected based for custom fabric dyeing on the similarities of their absorbance spectra and dye molecular structures. Visible absorption spectra for all …


The Development Of Scalable Pump Techniques For Gg Iag Fiber Lasers And Passive Athermalization Techniques For Solid State Laser, William Hageman Jan 2010

The Development Of Scalable Pump Techniques For Gg Iag Fiber Lasers And Passive Athermalization Techniques For Solid State Laser, William Hageman

Electronic Theses and Dissertations

This dissertation consists of two parts: research pertaining to the development of scalable pump techniques for gain guided index-antiguided fiber lasers and research relating to the development of passive athermalization schemes for solid state lasers. The first section primarily details the development of a side pump scheme that allows for power scaling of gain-guided index anti-guided fibers. While these fibers have been demonstrated in past research, none have used a pump technology capable of pumping with the efficiencies, uniformity, and necessary length to allow for scaling of the fiber lasers to high output powers. The side pumped scheme developed in …


Near-Field Optical Interactions And Applications, David Haefner Jan 2010

Near-Field Optical Interactions And Applications, David Haefner

Electronic Theses and Dissertations

The propagation symmetry of electromagnetic fields is affected by encounters with material systems. The effects of such interactions, for example, modifications of intensity, phase, polarization, angular spectrum, frequency, etc. can be used to obtain information about the material system. However, the propagation of electromagnetic waves imposes a fundamental limit to the length scales over which the material properties can be observed. In the realm of near-field optics, this limitation is overcome only through a secondary interaction that couples the high-spatial-frequency (but non-propagating) field components to propagating waves that can be detected. The available information depends intrinsically on this secondary interaction, …


Micro-Electro-Mechanical Systems (Mems) And Agile Lensing-Based Modules For Communications, Sensing And Signal Processing., Syed Reza Jan 2010

Micro-Electro-Mechanical Systems (Mems) And Agile Lensing-Based Modules For Communications, Sensing And Signal Processing., Syed Reza

Electronic Theses and Dissertations

This dissertation proposes the use of the emerging Micro-Electro-Mechanical Systems (MEMS) and agile lensing optical device technologies to design novel and powerful signal conditioning and sensing modules for advanced applications in optical communications, physical parameter sensing and RF/optical signal processing. For example, these new module designs have experimentally demonstrated exceptional features such as stable loss broadband operations and high > 60 dB optical dynamic range signal filtering capabilities. The first part of the dissertation describes the design and demonstration of digital MEMS-based signal processing modules for communication systems and sensor networks using the TI DLP (Digital Light Processing) technology. Examples of …


Structural, Electronic, Vibrational And Thermodynamical Properties Of Surfaces And Nanoparticles, Handan Yildirim Jan 2010

Structural, Electronic, Vibrational And Thermodynamical Properties Of Surfaces And Nanoparticles, Handan Yildirim

Electronic Theses and Dissertations

The main focus of the thesis is to have better understanding of the atomic and electronic structures, vibrational dynamics and thermodynamics of metallic surfaces and bi-metallic nanoparticles (NPs) via a multi-scale simulational approach. The research presented here involves the study of the physical and chemical properties of metallic surfaces and NPs that are useful to determine their functionality in building novel materials. The study follows the 'bottom-up' approach for which the knowledge gathered at the scale of atoms and NPs serves as a base to build, at the macroscopic scale, materials with desired physical and chemical properties. We use a …


Modeling And Design Of A Photonic Crystal Chip Hosting A Quantum Network Made Of Single Spins In Quantum Dots That Interact Via Single Photons, Hubert P. Seigneur Jan 2010

Modeling And Design Of A Photonic Crystal Chip Hosting A Quantum Network Made Of Single Spins In Quantum Dots That Interact Via Single Photons, Hubert P. Seigneur

Electronic Theses and Dissertations

In this dissertation, the prospect of a quantum technology based on a photonic crystal chip hosting a quantum network made of quantum dot spins interacting via single photons is investigated. The mathematical procedure to deal with the Liouville-Von Neumann equation, which describes the time-evolution of the density matrix, was derived for an arbitrary system, giving general equations. Using this theoretical groundwork, a numerical model was then developed to study the spatiotemporal dynamics of entanglement between various qubits produced in a controlled way over the entire quantum network. As a result, an efficient quantum interface was engineered allowing for storage qubits …


Long Cavity Quantum Dot Laser Diode And Monolithic Passively Mode-Locked Operation, K Shavitranuruk Jan 2010

Long Cavity Quantum Dot Laser Diode And Monolithic Passively Mode-Locked Operation, K Shavitranuruk

Electronic Theses and Dissertations

Advantage of the single QD active layer is its potential for very low threshold current density, which in turn can produce low internal optical loss. The low threshold current density and low internal loss thus enable a significant increase in laser diode cavity length. Because of the importance of the threshold current density in heatsinking, future technology of broad-area monolithic laser diodes can be implemented. The dissertation describes the development and the unique characteristics of single QD active layer laser with long cavity. The data are presented on single layer QD laser diodes that reach threshold current densities values of …


Novel Improvements On The Analytical Chemistry Of Polycyclic Aromatic Hydrocarbons And Their Metabolites, Wang Huiyong Jan 2010

Novel Improvements On The Analytical Chemistry Of Polycyclic Aromatic Hydrocarbons And Their Metabolites, Wang Huiyong

Electronic Theses and Dissertations

Polycyclic aromatic hydrocarbons (PAH) are important environmental pollutants originating from a wide variety of natural and anthropogenic sources. Because many of them are highly suspect as etiological agents in human cancer, chemical analysis of PAH is of great environmental and toxicological importance. Current methodology for PAH follows the classical pattern of sample preparation and chromatographic analysis. Sample preparation preconcentrates PAH, simplifies matrix composition, and facilitates analytical resolution in the chromatographic column. Among the several approaches that exist to pre-concentrate PAH from water samples, the Environmental Protection Agency (EPA) recommends the use of solid-phase extraction (SPE). High-performance liquid chromatography (HPLC) and …


Development Of Optical Coherence Tomography For Tissue Diagnostics, Panomsak Meemon Jan 2010

Development Of Optical Coherence Tomography For Tissue Diagnostics, Panomsak Meemon

Electronic Theses and Dissertations

Microvasculature can be found in almost every part of the human body, including the internal organs. Importantly, abnormal changes in microvasculature are usually related to pathological development of the tissue cells. Monitoring of changes in blood flow properties in microvasculature, therefore, provides useful diagnostic information about pathological conditions in biological tissues as exemplified in glaucoma, diabetes, age related macular degeneration, port wine stains, burn-depth, and potentially skin cancer. However, the capillary network is typically only one cell in wall thickness with 5 to 10 microns in diameter and located in the dermis region of skin. Therefore, a non-invasive flow imaging …


Supported Mono And Bimetallic Platinum And Iron Nanoparticles Electronic, Structural, Catalytic, And Vibrational Properties, Jason Robert Croy Jan 2010

Supported Mono And Bimetallic Platinum And Iron Nanoparticles Electronic, Structural, Catalytic, And Vibrational Properties, Jason Robert Croy

Electronic Theses and Dissertations

Catalysis technologies are among the most important in the modern world. They are instrumental in the realization of a variety of products and processes including chemicals, polymers, foods, pharmaceuticals, fuels, and fuel cells. As such, interest in the catalysts that drive these processes is ongoing, and basic research has led to significant advances in the field, including the production of more environmentally friendly catalysts that can be tuned at the molecular/atomic level. However, there are many factors which influence the performance of a catalyst and many unanswered questions still remain. The first part of this work is concerned with the …


Strong Orbit Equivalence And Residuality, Brett M. Werner Jan 2010

Strong Orbit Equivalence And Residuality, Brett M. Werner

Electronic Theses and Dissertations

In this dissertation, we consider notions of equivalence between minimal Cantor systems, in particular strong orbit equivalence. By constructing the systems, we show that there exist two nonisomorphic substitution systems that are both Kakutani equivalent and strongly orbit equivalent. We go on to define a metric on a strong orbit equivalence class of minimal Cantor systems and prove several properties about the metric space. If the strong orbit equivalence class contains a finite rank system, we show that the set of finite rank systems is residual in the metric space. The last result shown is that set of systems with …


Fabrication Of Integrated Optofluidic Circuits In Chalcogenide Glass Using Femtosecond Laser Direct Writing, Troy P. Anderson Jan 2010

Fabrication Of Integrated Optofluidic Circuits In Chalcogenide Glass Using Femtosecond Laser Direct Writing, Troy P. Anderson

Electronic Theses and Dissertations

Femtosecond laser direct writing (FLDW) is a versatile process that uses focused femtosecond pulses to modify the physical structure of a material, which can result in a shift of optical properties such as the linear and nonlinear refractive index. If the photon energy of the femtosecond pulses lies below the material bandgap, nonlinear absorption rather than linear absorption becomes the dominant mechanism of energy transfer to the material. In this manner, a focused femtosecond pulse train can be used to fabricate functional features such as optical waveguides, diffractive optical elements, or micro-fluidic elements within the volume of a transparent medium. …


Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim Jan 2010

Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim

Electronic Theses and Dissertations

In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-Perot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot lasers is studied. Cavity length dependent lasing via ground state and/or excited state transitions is observed from quantum dot lasers and the optical gain from both transitions is measured. Stable optical pulse trains via ground and excited state transitions are generated using a grating coupled external cavity with a curved two-section device. …


A New Framework For Qos Provisioning In Wireless Lans Using The P-Persistent Mac Protocol, Kiran Babu Anna Jan 2010

A New Framework For Qos Provisioning In Wireless Lans Using The P-Persistent Mac Protocol, Kiran Babu Anna

Electronic Theses and Dissertations

The support of multimedia traffic over IEEE 802.11 wireless local area networks (WLANs) has recently received considerable attention. This dissertation has proposed a new framework that provides efficient channel access, service differentiation and statistical QoS guarantees in the enhanced distributed channel access (EDCA) protocol of IEEE 802.11e. In the first part of the dissertation, the new framework to provide QoS support in IEEE 802.11e is presented. The framework uses three independent components, namely, a core MAC layer, a scheduler, and an admission control. The core MAC layer concentrates on the channel access mechanism to improve the overall system efficiency. The …


Weighted Inverse Weibull And Beta-Inverse Weibull Distribution, Jing Xiong Kersey Jan 2010

Weighted Inverse Weibull And Beta-Inverse Weibull Distribution, Jing Xiong Kersey

Electronic Theses and Dissertations

The weighted inverse Weibull distribution and the beta-inverse Weibull distribution are considered. Theoretical properties of the inverse Weibull model, weighted inverse Weibull distribution including the hazard function, reverse hazard function, moments, moment generating function, coefficient of variation, coefficient of skewness, coefficient of kurtosis, Fisher information and Shanon entropy are studied. The estimation for the parameters of the length-biased inverse Weibull distribution via maximum likelihood estimation and method of moment estimation techniques are presented, as well as a test for the detection of length-biasedness in the inverse Weibull model. Furthermore, the beta-inverse Weibull distribution which is a weighted distribution is presented, …


Improving Parallel I/O Performance Using Interval I/O, Jeremy Logan Jan 2010

Improving Parallel I/O Performance Using Interval I/O, Jeremy Logan

Electronic Theses and Dissertations

Today's most advanced scientific applications run on large clusters consisting of hundreds of thousands of processing cores, access state of the art parallel file systems that allow files to be distributed across hundreds of storage targets, and utilize advanced interconnections systems that allow for theoretical I/O bandwidth of hundreds of gigabytes per second. Despite these advanced technologies, these applications often fail to obtain a reasonable proportion of available I/O bandwidth. The reasons for the poor performance of application I/O include the noncontiguous I/O access patterns used for scientific computing, contention due to false sharing, and the somewhat finicky nature of …


Climate Investigations Using Ice Sheet And Mass Balance Models With Emphasis On North American Glaciation, Sean David Birkel Jan 2010

Climate Investigations Using Ice Sheet And Mass Balance Models With Emphasis On North American Glaciation, Sean David Birkel

Electronic Theses and Dissertations

This dissertation describes the application of the University of Maine Ice Sheet Model (UM-ISM) and Environmental Change Model (UM-ECM) to understanding mechanisms of ice-sheet/climate integration during ice ages. The UM-ECM, written by the author for this research, calculates equilibrium biome and snow/ice mass balance solutions for the globe based on modern input climatology and user-defined parameter values. The program was produced in conjunction with a National Science Foundation ITEST grant meant to seed inquiry-based classroom study of Earth systems using computer models. To that end, the UM-ECM serves as both a research and teaching tool. The model has a web-based …


Item Order Effects On Attitude Measures, Pei-Hua Chen Jan 2010

Item Order Effects On Attitude Measures, Pei-Hua Chen

Electronic Theses and Dissertations

The purpose of this dissertation was to examine the effects of altered item order on attitude measures for both computerized adaptive and conventional survey formats. Based on items modified from a dissertation/thesis completion survey (Green & Kluever, 1997) with three scales, three survey versions were generated with items ordered by difficulty as hard-to-easy (H-E), easy-to-hard (E-H), and five medium trait level items presented first followed by randomly ordered items (M-R) for conventional survey format. Significant differences in item difficulty and item discrimination were found for two of the three scales. Differences in scale reliability were detected for the procrastination and …


Dft Study Of Geometry And Energetics Of Transition Metal Systems, Satyender Goel Jan 2010

Dft Study Of Geometry And Energetics Of Transition Metal Systems, Satyender Goel

Electronic Theses and Dissertations

This dissertation focuses on computational study of the geometry and energetics small molecules and nanoclusters involving transition metals (TM). These clusters may be used for various industrial applications including catalysis and photonics. Specifically, in this work we have studied hydrides and carbides of 3d-transition metal systems (Sc through Cu), small nickel and gold clusters. Qualitatively correct description of the bond dissociation is ensured by allowing the spatial and spin symmetry to break. We have tested applicability of new exchange-correlation functional and alternative theoretical descriptions (spin-contamination correction in broken symmetry DFT and ensemble Kohn-Sham (EKS)) as well. We studies TM hydrides …


Using Landscape Genetics To Assess Population Connectivity In A Habitat Generalist, Tyler Duncan Hether Jan 2010

Using Landscape Genetics To Assess Population Connectivity In A Habitat Generalist, Tyler Duncan Hether

Electronic Theses and Dissertations

Understanding the nature of genetic variation in natural populations is an underlying theme of population genetics. In recent years population genetics has benefited from the incorporation of landscape and environmental data into pre-existing models of isolation by distance (IBD) to elucidate features influencing spatial genetic variation. Many of these landscape genetics studies have focused on populations separated by discrete barriers (e.g., mountain ridges) or species with specific habitat requirements (i.e., habitat specialists). One difficulty in using a landscape genetics approach for taxa with less stringent habitat requirements (i.e., generalists) is the lack of obvious barriers to gene flow and preference …


Physicochemical And Thermochemical Properties Of Sulfonated Poly(Etheretherketone) Electrolyte Membranes, Stephen Rhoden Jan 2010

Physicochemical And Thermochemical Properties Of Sulfonated Poly(Etheretherketone) Electrolyte Membranes, Stephen Rhoden

Electronic Theses and Dissertations

Fuel cells have long been seen as an alternative to combustion powered and diesel powered engines and turbines. Production of energy via a fuel cell conversion method can generate up to 60% efficiency in comparison to 30% using a combustion powered engine, with low co-production of harmful side-products. The polymer electrolyte membrane (PEM) adapted for the fuel cell application is one of the main components that determines the overall efficiency. This research project was focused towards novel PEMs, such as sulfonated poly(etheretherketone) or SPEEK, which are cost-efficient and robust with high proton conductivities under hydrated conditions. The degree of sulfonation …


Nonlinear Absorption And Free Carrier Recombination In Direct Gap Semiconductors, Peter D. Olszak Jan 2010

Nonlinear Absorption And Free Carrier Recombination In Direct Gap Semiconductors, Peter D. Olszak

Electronic Theses and Dissertations

Nonlinear absorption of Indium Antimonide (InSb) has been studied for many years, yet due to the complexity of absorption mechanisms and experimental difficulties in the infrared, this is still a subject of research. Although measurements have been made in the past, a consistent model that worked for both picosecond and nanosecond pulse widths had not been demonstrated. In this project, temperature dependent two-photon (2PA) and free carrier absorption (FCA) spectra of InSb are measured using femtosecond, picosecond, and nanosecond IR sources. The 2PA spectrum is measured at room temperature with femtosecond pulses, and the temperature dependence of 2PA and FCA …


Silicon-Sensitized Erbium Excitation In Silicon-Rich Silica For Integrated Photonics, Oleksandr Savchyn Jan 2010

Silicon-Sensitized Erbium Excitation In Silicon-Rich Silica For Integrated Photonics, Oleksandr Savchyn

Electronic Theses and Dissertations

It is widely accepted that the continued increase of processor performance requires at least partial replacement of electronic interconnects with their photonic counterparts. The implementation of optical interconnects requires the realization of a silicon-based light source, which is challenging task due to the low emission efficiency of silicon. One of the main approaches to address this challenge is the use of doping of silicon based matrices with optical centers, including erbium ions. Erbium ions incorporated in various hosts assume the trivalent state (Er3+) and demonstrate a transition at 1.54 μm, coinciding with optical transmission windows in both silicon and silica. …