Digital Commons Network^™

Optical Spectroscopic Studies Of Two Star Forming Regions, Kristen Leilani Erickson

Doctoral Dissertations

"The ρ Ophiuchi and Serpens molecular clouds are sites of low mass star formation. The goals of this study were to identify young stellar objects (YSOs) and estimate ages and masses in order to infer an initial mass function (IMF), investigate disk evolution, and determine the star-forming history. Optical spectroscopic surveys of an unbiased sample of candidate young stars have been completed. Optical images taken in different photometric bands were used to create color-magnitude diagrams from which sources were selected for spectroscopic observation. In combination with published data, 135 association members in ρ Ophiuchi and 63 association members plus 16 …

Optimized Techniques For Real-Time Microwave And Millimeter Wave Sar Imaging, Joseph T. Case

Doctoral Dissertations

"Microwave and millimeter wave synthetic aperture radar (SAR)-based imaging techniques, used for nondestructive evaluation (NDE), have shown tremendous usefulness for the inspection of a wide variety of complex composite materials and structures. Studies were performed for the optimization of uniform and nonuniform sampling (i.e., measurement positions) since existing formulations of SAR resolution and sampling criteria do not account for all of the physical characteristics of a measurement (e.g., 2D limited-size aperture, electric field decreasing with distance from the measuring antenna, etc.) and nonuniform sampling criteria supports sampling below the Nyquist rate. The results of these studies demonstrate optimum sampling given …

Phase Transitions In Disordered Systems, Fawaz Y. Hrahsheh

Doctoral Dissertations

"Disorder can have a wide variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this thesis we study the effects of disorder on several classical and quantum phase transitions in condensed matter systems. After a brief introduction, we study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte-Carlo simulations. Our results provide numerical evidence for the exotic infinite-randomness scenario. We study classical and quantum smeared phase transitions in substitutional alloys A₁₋ₓBₓ. Our results show that the disorder completely destroys the phase …

Phytoforensics On Energetics: Novel Plant Tissue Measure Approach And Modeling, Yuan Yuan

Doctoral Dissertations

"Explosives and energetics are common soil and groundwater pollutions. This research was to develop novel phytoforensics approaches on energetics. Four different plants species, including woody perennial trees and monocot grasses, were planted both in soil and sand reactors with continuous exposure to a mixture of explosives in the greenhouse. Time dependent assessments were carried out to determine kinetic mechanisms of uptake, transport and accumulation. Plant concentrations were analyzed by both traditional solvent extraction and novel sap analysis methods. A dynamic soil-plant system model was developed to quantify the relationship between tissue concentration and soil pore water concentration for non-volatile organic …

Quantum Phase Transitions In Impurity Models And Percolating Lattices, Manal M. Al-Ali

Doctoral Dissertations

"This thesis investigates the influence of random disorder and dissipation on zero-temperature quantum phase transitions. Both phenomena can fundamentally change the character of the phases of a quantum many-particle system and of the transitions between them. If dissipation and disorder occur simultaneously in a system undergoing a quantum phase transition, particularly strong effects can be expected. In the first paper reproduced in this thesis, we study a single quantum rotor coupled to a sub-Ohmic dissipative bath. We find that this system undergoes a quantum phase transition from a delocalized phase to a localized phase as the dissipation strength is increased. …

Processing, Microstructural Evolution And Electrochemical Performance Relationships In Solid Oxide Fuel Cells, Ayhan Sarikaya

Doctoral Dissertations

"The relationships between the processing parameters, microstructures and electrochemical performance of solid oxide fuel cell (SOFC) components were investigated. The operating regimes (i.e., reducing vs. oxidizing) as well as the elevated temperatures (e.g. 800°C) for their operation introduce several material challenges. Therefore, composite materials are employed to withstand operating conditions while providing sufficient electrochemical performance for fuel cell operation. Analyses on lanthanum-strontium manganite (LSM) - yttria stabilized zirconia (YSZ) compositions (45 vol%-55 vol%) by impedance spectroscopy demonstrated that two competing polarization mechanisms (i.e. charge-exchange and surface adsorption-diffusion of oxygen) limit performance. Optimization of microstructures resulted in total resistances as low …

Recycling Of Electronic Waste: Printed Wiring Boards, Alex Luyima

Doctoral Dissertations

"Pyrolysis and leaching are the dominant techniques applied in the recycling of waste printed wiring boards (PWBs). Waste PWB pyrolysis is a highly polluting technology and produces brominated pyrolysis oils in addition to hydrogen bromide (HBr) gas. Moreover, leaching as a treatment process of waste PWBs is not well investigated. In this work, the pyrolysis of waste PWBs has been studied with the aim of reducing the amount of brominated oils and HBr gas evolved. The effects of powder inorganic chemicals (CaO, CaCO₃, Fe₂O₃, Al₂O₃, Y-Zeolite, and ZSM-5) additions on the pyrolysis of waste PWBs has been studied through experiments …

Social-Context Based Routing And Security In Delay Tolerant Networks, Roy A. Cabaniss

Doctoral Dissertations

"Delay Tolerant Networks (DTNs) were originally intended for interplanetary communications and have been applied to a series of difficult environments: wireless sensor networks, unmanned aerial vehicles, and short-range personal communications. There is a class of such environments in which nodes follow semi-predictable social patterns, such as wildlife tracking or personal devices. This work introduces a series of algorithms designed to identify the social patterns present in these environments and apply this data to difficult problems, such as efficient message routing and content distribution. Security is also difficult in a mobile environment. This is especially the case in the event that …

The Role Of Face-To-Face Interactions In The Success Of Virtual Project Teams, Lawrence Raymond Blenke

Doctoral Dissertations

"This dissertation examines the importance of in-person Face-To-Face (FTF) interactions in virtual engineering development projects. The basis for this investigation will be the hypothesis that FTF interactions increase the effectiveness, quality of communication, and the trust between participants beyond that achieved with purely computer mediated communication. Through a combination of a literature review and empirical research, this dissertation addresses the following questions: * How important is FTF interaction in virtual development work? * Do various functional areas and age groups rate the importance of FTF interactions differently? * How does FTF interaction affect the levels of trust and communication within …

Data Fusion Techniques For Nondestructive Evaluation And Medical Image Analysis, Soumya De

Doctoral Dissertations

"Data fusion is a technique for combining data obtained from multiple sources for an enhanced detection or decision. Fusion of data can be done at the raw-data level, feature level or decision level. Applications of data fusion include defense (such as battlefield surveillance and autonomous vehicle control), medical diagnosis and structural health monitoring. Techniques for data fusion have been drawn from areas such as statistics, image processing, pattern recognition and computational intelligence. This dissertation includes investigation and development of methods to perform data fusion for nondestructive evaluation (NDE) and medical imaging applications. The general framework for these applications includes region-of-interest …

Bioactive Glass Scaffolds For The Regeneration Of Load-Bearing Bone, Xin Liu

Doctoral Dissertations

"Biocompatible scaffolds that replicate the structure and function of bone would be ideal bone substitutes for structural bone loss, provided they have the requisite mechanical properties for reliable long-term loading. In this dissertation, strong porous scaffolds of silicate 13-93 bioactive glass, created with two different microstructures, were evaluated to determine their mechanical properties and their capacity to regenerate bone in a rat calvarial defect model. Scaffolds with an oriented microstructure of columnar pores were prepared by unidirectional freezing of camphene-based suspensions, followed by thermal annealing and sintering. By optimizing the freezing conditions, annealing time, and sintering temperature, constructs (porosity = …

Nanoscale Metal Oxide And Supported Metal Catalysts For Li-Air Battery, Kan Huang

Doctoral Dissertations

"The dissertation work focuses on research and development of durable nanoscale catalysts and supports for rechargeable Li-air batteries that use aqueous catholytes. Transition metal oxides, TiO₂ and Nb₂O₅ in particular, were prepared from a sol-gel process in the form of nanocoatings (5~50 nm) on carbon nanotubes (CNTs) and studied as catalyst supports. Carbon doping in the oxides and post annealing significantly increased their electronic conductivity. Pt catalyst on the support with TiO₂ (Pt/c-TiO₂/CNTs) showed a much better oxygen reduction reaction (ORR) activity than a commercial Pt on carbon black (Pt/C). Negligible loss ( …

Approximate Dynamic Programming Based Solutions For Fixed-Final-Time Optimal Control And Optimal Switching, Ali Heydari

Doctoral Dissertations

"Optimal solutions with neural networks (NN) based on an approximate dynamic programming (ADP) framework for new classes of engineering and non-engineering problems and associated difficulties and challenges are investigated in this dissertation. In the enclosed eight papers, the ADP framework is utilized for solving fixed-final-time problems (also called terminal control problems) and problems with switching nature. An ADP based algorithm is proposed in Paper 1 for solving fixed-final-time problems with soft terminal constraint, in which, a single neural network with a single set of weights is utilized. Paper 2 investigates fixed-final-time problems with hard terminal constraints. The optimality analysis of …

Polarization And Opinion Analysis In An Online Argumentation System For Collaborative Decision Support, Ravi Santosh Arvapally

Doctoral Dissertations

"Argumentation is an important process in a collaborative decision making environment. Argumentation from a large number of stakeholders often produces a large argumentation tree. It is challenging to comprehend such an argumentation tree without intelligent analysis tools. Also, limited decision support is provided for its analysis by the existing argumentation systems. In an argumentation process, stakeholders tend to polarize on their opinions, and form polarization groups. Each group is usually led by a group leader. Polarization groups often overlap and a stakeholder is a member of multiple polarization groups. Identifying polarization groups and quantifying a stakeholder's degree of membership in …

Real Options Modeling And Valuation Of Price Adjustment Flexibility With An Application To The Leasing Industry, Ahmed A. A. Al Sharif

Doctoral Dissertations

"Uncertainty poses not only threats but also opportunities. This study sought to build the scientific foundation for introducing a real options (ROs) methodology for price risk management to the leasing industry. A price risk management that allows for both coping with threats and taking advantage of opportunities. In the leasing industry, fixed rate long-term lease contracts help contract parties stabilize cash flows within volatile markets. The contract's term, however, may be extended long enough that prevent capturing the opportunities of gaining greater profits or reducing expenses. Therefore, the flexibility that enables participants to take advantage of favorable market price is …

Advances In Blind Source Separation, Christopher Osterwise

Doctoral Dissertations

"Blind Source Separation (BSS) is a classic problem that attempts to separate unknown sources from observed mixtures. A common framework of this is the Cocktail Party problem, where multiple individuals speaking in a noisy room are recorded by a configuration of microphones, with the challenge being to split the observed signals into individual conversations. This dissertation covers the evaluation of an existing algorithm known as Cascaded ICA with Intervention Alignment (CICAIA), the establishment of a new parameter for characterizing blind mixtures, and three new algorithms, of which two are capable of separating any number of sources given more microphones than …

Behavior And Effects Of Nanoparticles In Complex Fluid Systems, Chen Wang

Doctoral Dissertations

"The development of nanoscale technologies has greatly expanded the scientific and engineering horizons and also has the potential to turn molecular discoveries into worldwide benefits on multiple fronts. Despite recent extensive efforts, the focus of nanoparticle studies has been on their synthesis and various possible derivatives. In this dissertation, molecular based modeling and simulation studies have been performed to characterize and understand the behavior, properties, and effects of nanoparticles in some important material systems. The results show that small nanoparticles that are highly faceted have significant shape effects, which are not captured by classical continuum-based approaches. When dissolved in confined …

Development Of An Integrative Commissioning Methodology For New-Building Construction, William L. Gillis Iii

Doctoral Dissertations

"Commissioning (Cx) is a quality process for building construction used to verify that the owner's project requirements (OPR) are being met by the final design, construction, and operations and maintenance. The goal is to confirm that each phase of the project is linked back to the OPR through quality assurance methods. Leadership in Energy and Environmental Design (LEED) certification is an OPR which contributes to difficulties within the design and construction (D&C) process. Though LEED certification is only part of the OPR, too often the design drifts from the OPR and simply focuses on meeting the LEED certification.

Quality function …

Effect Of Dense Heat Exchanging Internals On The Hydrodynamics Of Bubble Column Reactors Using Non-Invasive Measurement Techniques, Mohammed Khloofh Al Mesfer

Doctoral Dissertations

"Given their efficiency and capital cost reduction, bubble/slurry bubble column reactors are the reactors of choice for Fischer-Tropsch (FT) synthesis, offering clean alternative fuels and chemicals. FT synthesis is an exothermic process that requires many heat exchanging tubes in order to remove heat efficiently and maintain the desired temperature and isothermal operating condition. The impact of the heat exchanging tubes (internals) on the hydrodynamics is not fully understood. Reliably designing and scaling up bubble column reactors requires proper understanding of hydrodynamics, as well as heat and mass transfer parameters.

The main objective of this work is to advance the understanding …

Integration Of Nanoporous Zeolite With Optical Fiber Devices For Chemical Sensing, Xinwei Lan

Doctoral Dissertations

"Label-free optical fiber chemical sensors have provoked significant research interest in recent years due to their unique advantages of small size, low cost, potential for distributed sensing, capability of in situ and remote operation, and tolerance to harsh environments. However, existing optical fiber chemical sensors lack the desired sensitivity and specificity for many applications such as chemical and biological analysis, industrial process control, environmental monitoring, and national security.

The dissertation summarizes our research efforts and results in functional integration of nanoporous zeolites with optical fiber devices for development of label-free optical fiber chemical sensors with high sensitivity and selectivity. Fundamental …

Minimizing Formation Damage For Preformed Particle Gels Treatment In Mature Reservoirs, Mahmoud Omran Elsharafi

Doctoral Dissertations

"This research studied the effect of preformed particle gels (PPGs) on unswept, low-permeable zones/areas. The objective was to find methods that minimized the damage caused by PPGs on unswept, low-permeable zones/areas, thus improving PPG treatment efficiency. These results can help to identify of the best PPG types, particle sizes, and brine concentrations for specific reservoirs and treatments. This study used sandstone core samples with various degrees of permeability. Two types of particle gels, a strong Daqing gel (DQ) and a weak Liquiblock™ 40k gel (40K), were used, each with a different strength.

This research included two stages. Firstly, both a …

Modeling And Analysis Of Dynamic Behavior Of Adsorption Stratified Column Beds Packed With Partially Fractal Porous Adsorbent Particles, Min Li

Doctoral Dissertations

"In this work novel porous adsorbent media having partially fractal structures and stratified packed-beds are constructed and their dynamic performance with respect to their adsorptive capacity through the construction and solution of rigorous models is studied. The results show that conventional columns packed with partially fractal porous adsorbent particles provide larger breakthrough times and dynamic utilization of the adsorptive capacity of the column when compared with those of conventional columns employing conventional adsorbent particles which do not possess a partially fractal structure. Furthermore, stratified column beds exhibit superior species separation performance than conventional columns when they are packed with either …

Source Reconstructions For Ic Radiated Emissions Based On Magnitude-Only Near-Field Scanning, Ji Zhang

Doctoral Dissertations

"In this dissertation, a source reconstruction method is proposed to model the emission behavior of an IC by using magnitude-only information during near-field scanning. The phase-retrieval is accomplished during the back-forth iterations between two scanning planes of different heights. The magnitudes of fields on two planes of different heights are recorded and used to constrain the amplitude of the calculated fields during iterations. Three essential transformations among dipoles and fields are continued at each iteration step, until the convergence condition is achieved. The proposed algorithm has been verified by using a set of dipole-array as the original emitting sources, and …

Spatial Variation Of Amd Related Co₂ Emissions On Reclaimed Mine Spoil, Moagabo Mathiba

Doctoral Dissertations

"Carbon dioxide (CO₂) from acid mine drainage (AMD)-carbonate neutralization reactions in reclaimed mine spoils, can intermittently invade homes and structures constructed on or adjacent to these spoils in hazardous and even lethal concentrations (>15%) and rendering them uninhabitable. This phenomenon is beginning to be recognized as an emerging environmental, safety and health threat with potential environmental and financial liability for mine operators, developers and owners.

Like in natural soils, soil temperature and moisture, and possibly elevation are likely to influence CO₂ emissions from reclaimed mine spoils. However, mine spoil soils are heterogeneous and have significant convective transport due to …

Topics In Voice Echo Cancellation, Pratik Vijay Shah

Doctoral Dissertations

"Acoustic echo cancellation (AEC) is a well studied problem. The underlying assumption in most echo cancellation solutions is that the echo path following the reference signal is completely linear. However, in many handheld devices, the echo path following the reference signal is nonlinear. The reason for this nonlinearity in the echo path is the use of smaller and cheaper loudspeakers. In order to cut the manufacturing cost, device manufactures use cheaper loudspeakers such that they satisfy the carrier specifications. Such loudspeaker can be easily over driven in to their nonlinear region and thus add nonlinearities to the downlink path. This …

Field Performance Of Alternative And Cost Efficient Cast In Place And Precast Prestressed Concrete Bridge Approach Slabs, Nathan Price Muncy

Masters Theses

"In December of 2010, the Missouri Department of Transportation (MoDOT) investigated alternative cost-efficient bridge approach slabs (BASs). New BAS designs were subsequently developed and had a projected cost savings up to twenty-four percent with anticipated equal or better structural performance. A precast-prestressed (PCPS) BAS was introduced as an alternative to traditional BASs that offers advantages such as rapid construction and improved long-term durability. The three new BAS designs were implemented into in-situ bridge projects by MoDOT and the field performance was evaluated within this research study.

Field testing of each BAS was performed using two MoDOT HS20 trucks. Various instrumentation …

Automatic Detection Of Polypoid Skin Lesions: The Squash Sign, Saurabh G. Karnik

Masters Theses

“Earlier detection of malignant melanoma can save lives. Automatic in-vivo methods of melanoma detection including smart-phone applications are now available, but specificity is low, i.e. too many benign lesions are detected as possible melanomas. Polypoids, elevated and rounded lesions are one class of benign lesions. These raised lesions with piecewise circular borders, predominantly intradermal nevi and cutaneous polyps (IDNs), are always benign. Variegated coloring present in polypoid lesions can lead physicians to perform an unneeded biopsy. Contact dermatoscope plates with gel squash these lesions, leaving a “squash sign” marker of benignancy which can be automatically detected. We present a method …

Significance And Analysis Of Milia-Like Cysts In Dermoscopy Skin Lesion Images, Sneha K. Mahajan

Masters Theses

“Milia-like cysts (MLCs) are dermoscopic structures frequently observed in seborrheic keratoses(SKs), which are the most common type of skin lesions. Diverse appearances of these skin lesions make them difficult to differentiate from melanoma, a deadly type of skin cancer. Classified by size into two main groups, starry MLCs and cloudy MLCs, the presence of these structures in a skin lesion has been known to help differentiate benign lesions from melanoma. Though the presence of cloudy MLCs is not exclusively associated with SKs, they can be a useful tool to differentiate SKs from melanoma. This research study determines the statistical occurrence …

High Temperature Sensor Based On Fabry-Perot Interferometer In Ceramic Coaxial Cable, Kenneth Paul Smith Jr.

Masters Theses

"In this thesis, the application of a coaxial cable Fabry-Perot interferometer (CCFPI) as a high temperature sensor is analyzed. Coaxial cable sensors provide the advantages of fiber optic sensors, such as the ability to be embedded and multiplexed, while overcoming the limitations created by the fragility of fibers. The fabrication process of the CCFPI, using a computer controlled drill system to create holes in the cable is discussed. By analyzing the amplitudes of the created reflections, the diameter of the holes is optimized. A new fabrication process, in which holes are drilled 180⁰ apart from each other to create a …

A Conforming Method For Regional Marginal Loss Surplus Allocation, Xiaolong Wang

Masters Theses

"The marginal transmission loss model is used in electricity markets across the United States to measure a resource's marginal contribution to system loss. This model prices loss into the locational marginal price as a marginal loss component. Marginal loss pricing will render a net revenue surplus within an energy balanced system. This marginal loss surplus (MLS) is typically allocated back to scheduling coordinators in proportion to the measured demand on a system-wide basis. However, when the system experiences heterogeneous loss across different regions, the system-wide allocation method fails to recognize the regional differences in actual loss costs. As a result, …