Digital Commons Network^™

Improving Effects Of Sampling Time In Fast Adaptation-Based Control Algorithms With Applications, John R. Cooper

Doctoral Dissertations

Over the past decade, L1 adaptive control has emerged as viable control architecture for systems with unmodeled dynamics and time-varying uncertainties. L1 control uses a concept known as "fast adaptation" to estimate uncertainties. This means the controller relies on high sampling rates. However, in any real-world application, sampling speed is limited by hardware capabilities. Thus the question of how to obtain better performance at slower sampling rates in fast adaptation-based algorithms has become an important research topic. This dissertation presents two methods of online modeling to solve this problem. The first of these is function approximation using artificial neural networks. …

Advanced Manufacturing And Microenvironment Control For Bioengineering Complex Microbial Communities, Andrea Kadiak

Doctoral Dissertations

Archival abstract submitted

Developing A Flexible Disaster Relief Supply Chain Model, Eric Hoffman

Doctoral Dissertations

Archival abstract submitted

Modeling Enhancement And Intelligent Inference Of Impedance-Based Structural Health Monitoring, Qi Shuai

Doctoral Dissertations

Archival abstract submitted

From The Science Of Nanorod Growth To Low Temperature Metallic Attachment, Paul R. Elliott

Doctoral Dissertations

To move nanotechnology out of the lab and into common use requires understanding and experience of the structures and processes involved. The technological maturity allowing the widespread use of nanotechnology is practically nonexistent outside of the integrated circuit industry. This work provides a synergy of the science of nanorod growth and the technology of metallic glue in ambient. Starting from the science, this thesis presents the design and control of the structure and morphology of nanorods grown by physical vapor deposition. We demonstrate the use of deposited seeds as a method to control the diameter and spacing of surface grown …

In-Situ Tem Lithiation Of Alternative Battery Electrode Materials, Matthew T. Janish

Doctoral Dissertations

The world-wide effort to produce and use cleaner energy also necessitates more advanced energy storage capabilities. For example, clean sources of electricity, such as wind or solar, are intermittent and require load leveling. Electric vehicles require more energy- and power-dense batteries in order to truly compete with fossil-fuel-based combustion engines. Lithium-ion batteries (LIBs) currently dominate the secondary battery market. However, in order to build a better LIB, there is a clear need for a better understanding of the fundamentals of lithiation processes. Transmission electron microscopy (TEM) is unique in its ability to correlate structural data with chemical information; as such, …

A Grounded Theoretical Analysis Of Team Resilience In The Us Army, Megan L. Dove-Steinkamp

Doctoral Dissertations

In order to develop a scientific understanding of team resilience, the three primary goals of the current research effort were to (1) summarize the research literature on resilience in and of small groups and systems, (2) articulate a framework to direct the synthesis of existing and future resilience-related research, and (3) construct a substantive theory of team resilience. This exploratory research used a grounded theory approach to explore resilience phenomena experienced by small unit members in the US Army. Participants were sampled from military occupational specialties within Combat Arms, as classified by the US Army Regimental System, and included members …

Analytic Methods For Geometric Modeling, Morad Behandish

Doctoral Dissertations

Current practice in mechanical product description and computational processing is rooted in the theory of solid modeling whose principles were established almost four decades ago. Despite providing a concrete foundation for computerizing the product development process at the time, the limited capacity of the traditional models to answer the growing design and manufacturing needs is only recently being recognized in the scientific and engineering communities.

I propose an alternative approach that employs spatial functions (i.e., 3D signals) instead of (or in addition to) topological pointsets in the Euclidean 3-space to abstract physical objects and their various geometric, physical, and material …

Numerical And Analytical Investigation Of Satellite Precipitation Error Propagation In Hydrologic Simulations, Yiwen Mei

Doctoral Dissertations

The overarching goal of the research described in this dissertation is to understand the hydrologic implications of error propagation from satellite precipitation products to hydrologic simulations. The complex interaction between precipitation error and corresponding hydrologic response is examined following a numerical- and an analytical-based method. The application of a hydrologic model forced by various satellite precipitation products is adopted as the numerical-based framework that was used to identify the properties of error propagation with respect to a number of factors (e.g. basin scale, seasonality, severity of rainfall and flow). Results show better consistency between gauges for events occurred over larger …

Modeling Of Multi-State Spatial Wavefunction Switched (Sws) Fets For Logic Gates And Memories, Bander Saman M

Doctoral Dissertations

This dissertation aims at developing circuit models for complementary (n- and p-channel) spatial wavefunction switched field-effect transistors (SWS-FETs). Unlike conventional FETs, SWS-FETs are comprised of two or more vertically stacked coupled quantum well or quantum dot channels, and the spatial location of carriers within these channels is used to encode the logic states (00), (01), (10) and (11). The development of SWS-FET logic gates and quaternary logics using sub 25 nm FETs is presented. In addition, simulation of compact 3-bit Analog-to-Digital Converters (ADCs) is presented. The accuracy of the SWS-FET circuits is verified by SWS-FET models in Cadence. The models …

Real-Time Damage Detection For Civil Structures Using Big Data, Chenhao Jin

Doctoral Dissertations

The overall goal of the research in this dissertation is to develop efficient and accurate algorithms to detect damages in real time for civil structures using large scale of monitoring data. First, big data analysis is performed using one-year monitoring weigh-in-motion data collected from an in-service highway bridge located in Meriden, Connecticut. In order to quickly evaluate the structural condition from large scale of weight-in-motion data, two structural reliability-based methods were developed based on yield strength limit state and fatigue limit state. Then, in order to estimate structural parameter from structural dynamic response data, extended Kalman filter is used to …

Nonlinear Optical Processes For Spectral Broadening And Short Pulse Generation, Hongyu Hu

Doctoral Dissertations

The dramatic progress in optical communication is attributed to the development of wavelength-division multiplexing and time-division multiplexing technologies, which employ broadband light source and ultrashort optical pulses respectively to carry signals in optical fibers. Supercontinuum generation is the spectral broadening of narrow-band incident pulses by the propagation through optical waveguides made of nonlinear materials. In this PhD dissertation, I show the design of a tapered lead-silicate optical fiber for supercontinuum generation. The physical mechanisms of optical pulse evolution are explained, which involve various nonlinear optical effects including self-phase and cross-phase modulation, stimulated Raman scattering, four-wave mixing, modulation instability and optical …

Coastal Ecosystem Processing Of Nitrogen Rich High Explosives, Mark L. Ballentine

Doctoral Dissertations

2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5 (RDX) have been used extensively by the world’s militaries for more than a century. Millions of tons of these compounds have been released into marine environments globally. Contamination levels and biological accumulation of TNT and RDX in marine systems from both legacy and new environmental exposures are neither well documented nor understood.

TNT and RDX synthesized with a stable nitrogen isotope (¹⁵N) label were used to trace the uptake, biotransformation, and retention of, both parent compounds, their primary organic derivatives, and associated nitrogen-containing breakdown products in coastal marine biota. The experimental approach consisted of …

Investigation On The Structural Variation Of Self-Assembled Lipid Bicellar Mixtures Upon Environmental Stimuli And Addition Of Pegylated Compounds, Ying Liu

Doctoral Dissertations

Bilayered mixed micelle, known as “bicelle”, has been extensively used as the biological membrane models in deciphering membrane-associated proteins. The bicellar mixtures normally constitute of long-chain and short-chain phospholipids in aqueous solutions. Disc-like morphology has been assumed for such mixtures where a bilayer fragment of long-chain phospholipids is sequestered by short-chain lipids at the rim.

Recently, other structures such as vesicles, elongated micelles, and lamellae have also been found in bicelles as temperature, concentration, and salinity vary.

The nano-sized bicellar discs (nanodiscs) and vesicles have great potential to be used as ingredient carriers for imaging and therapy. The research motivation …

Three-Dimensional Manganese Oxide Nanoarray-Based Monolithic Catalysts For Exhaust Gas Treatment, Sheng-Yu Chen

Doctoral Dissertations

This study focused on the design and synthesis of manganese oxide nanomaterials with nanoarray architectures. First of all, a straightforward synthetic strategy was discovered to fabricate manganese oxide nanoarrays on two-dimensional substrates (e.g. Si wafers and conductive FTO glass). Then, the generic one-pot hydrothermal synthesis route has been successfully utilized to in-situ grow uniform manganese oxide nanoarrays onto the cordierite honeycomb monolithic substrates, forming a series of nanoarray-based monolithic catalysts with different morphology, surface area, and reactivity of carbon monoxide (CO) oxidation., denoted as HM-DCM, HM-PCR, and HM-PSF, respectively. Next, copper manganese oxide (CuMn₂O₄) was combined …

Influence Of Moisture Content Distribution In Soil On Pavement And Geothermal Energy, Md Adnan Khan

Doctoral Dissertations

Moisture content in soil has a great implication in engineering design, and it has been heavily investigated by soil engineers and scientists. If moisture content in expansive soil changes drastically, it will create significant volume change in the soil. If expansive soil is present in building foundation or pavement subgrade, it may result in structural failure. On the other hand, if sufficient moisture content is present in soil, it will increase the production of geothermal energy from the ground soil. This dissertation is an effort to understand the effects of moisture content on both expansive soils and geothermal energy that …

Design, Modeling, Fabrication, And Testing Of A Multistage Micro Gas Compressor With Piezoelectric Unimorph Diaphragm And Passive Microvalves For Microcooling Applications, Shawn Thanhson Le

Doctoral Dissertations

This dissertation investigates the development of a multistage micro gas compressor utilizing multiple pump stages cascaded in series to increase the pressure rise with passive microvalves and piezoelectric unimorph diaphragms. This research was conducted through modeling, simulation, design, and fabrication of the microcompressor and its components. A single-stage and a two-stage microcompressor were developed to demonstrate and compare the performance and effectiveness of using a cascaded multistage design.

Steady fluid flow through static microvalves structure was studied to gain insight on its gas flow dynamics and characteristics. Transient analysis combined with the structure's interaction was investigated with an analytical model …

A Study Of Mathematics Achievement, Placement, And Graduation Of Engineering Students, Sara Hahler Blazek

Doctoral Dissertations

The purpose of this study was to determine how background knowledge impacts freshmen engineering students' success at Louisiana Tech University in terms of grades in two different freshman classes and graduation. To determine what factors impact students, three different studies were implemented. The first study used linear regression to analyze which demographic and academic variables significantly impacted freshman math and engineering courses. Using regression discontinuity, the second study determined if the university's placement requirement for Pre-Calculus was appropriate. The final study analyzed factors that impact graduation for engineering students as well as other disciplines to determine which significant variables were …

Expanding The Applications Of Poly(Dimethylsiloxane) In Biomicrofluidics, Sawyer D. Stone

Doctoral Dissertations

This work aims to create novel applications for poly(dimethylsiloxane) (PDMS) in the field of biomicrofluidics through oxidative stress detection, doping of the polymer for intentional leaching into microdevices, and the development of low-cost implements for fabricating PDMS microfluidic devices. PDMS has become the polymer of choice for research in microfluidics due to its optical clarity, ease of fabrication, flexibility in design, good mechanical properties, and the ability to chemically modify the surface.

Biomicrofluidics enables the rapid throughput and analysis of small biological samples requiring less time investment and reagent use than traditional macroscale laboratory techniques. Polymer devices are inexpensive, easily …

The Mediating Influence Of Career Aspirations And Career Decision-Making Self-Efficacy On Self-Differentiation, Vocational Identity, And Career Indecision, Jay Justin Middleton

Doctoral Dissertations

Research indicates that numerous family variables influence the career-development process (Osipow, 1983). Bowen's family systems theory is one model through which to view the development and influence of the family on career development (Bowen, 1972). According to his theory, individuals begin life highly dependent on family members for all forms of support. As people grow into adults, they slowly become independent of their family, or self-differentiated. Adults low in self-differentiation have been found to make decisions in order to appease their families. Further, low levels of self-differentiation have been related to greater mental health problems (Skowron & Friedlander, 1998) and …

The Use Of Geophysical Methods For Dam Seepage Investigations And Dredged Oyster Deposit Characterization, Stanley Chinedu Nwokebuihe

Doctoral Dissertations

"The dissertation is made up of three papers, which discuss the utility of geophysical tools in earthfill dam investigations and dredged oyster bed characterization.

In the first paper, an earthfill dam in Warren County, Missouri was effectively investigated for seepage through the dam and its outlet works using an integration of the electrical resistivity tomography, induced polarization and spontaneous potential geophysical tools. Recommendations were subsequently made based on the results of the study on grout locations to prevent further seepage. In the second paper, a similar study of earthfill dam seepage was conducted on a different dam in Southern Missouri. …

Development Of A Nonlinear Model For The Prediction Of Response Times Of Glucose Affinity Sensors Using Concanavalin A And Dextran And The Development Of A Differential Osmotic Glucose Affinity Sensor, Louis G. Reis

Doctoral Dissertations

With the increasing prevalence of diabetes in the United States and worldwide, blood glucose monitoring must be accurate and reliable. Current enzymatic sensors have numerous disadvantages that make them unreliable and unfavorable among patients. Recent research in glucose affinity sensors correct some of the problems that enzymatic sensors experience. Dextran and concanavalin A are two of the more common components used in glucose affinity sensors. When these sensors were first explored, a model was derived to predict the response time of a glucose affinity sensor using concanavalin A and dextran. However, the model assumed the system was linear and fell …

An Improved Imaging Method For Extended Targets, Sui Zhang

Doctoral Dissertations

The dissertation presents an improved method for the inverse scattering problem to obtain better numerical results. There are two main methods for solving the inverse problem: the direct imaging method and the iterative method. For the direct imaging method, we introduce the MUSIC (MUltiple SIgnal Classification) algorithm, the multi-tone method and the linear sampling method with different boundary conditions in different cases, which are the smooth case, the one corner case, and the multiple corners case. The dissertation introduces the relations between the far field data and the near field data.

When we use direct imaging methods for solving inverse …

Synthesis, Characterization, And Activity Of Co/Fe Alumina/Silica Supported Ft Catalysts And The Study Of Promoter Effect Of Ruthenium, Sunday Azubike Esumike

Doctoral Dissertations

The alumina and hybrid alumina-silica FT catalyst were prepared by one-step solgel/oil-drop methods using metal-nitrate-solutions (method-I), and nanoparticle-metaloxides (method-2). The nanoparticle-metal-oxides did not participate in solubility equilibria in contrast to metal nitrate in method-1 causing no metal ion seepage; therefore, method-2 yields higher XRF metal loading efficiency than method-1. The thermal analysis confirmed that the metal loading by method-1 and method-2 involved two different pathways. Method-1 involves solubility equilibria in the conversion of metal-nitrate to metal- hydroxide and finally to metal-oxide, while in method-2 nanoparticle-metal-oxide remained intact during sol-gel-oil-drop and calcination steps.

The alumina supported catalysts were dominated by γ-alumina …

Investigation Of Local Velocities And Phase Holdups, And Flow Regimes And Maldistribution Identification In A Trickle Bed Reactor, Mohd Fitri Bin Abdul Rahman

Doctoral Dissertations

"Trickle bed reactors are packed beds of catalyst on which gas and liquid reactants flow concurrently downward. In this work, the experimental work was carried out in 0.14 m diameter Plexiglas column using air-water system flowing over a packed bed of 3 mm glass bead particles. The local liquid and gas velocities, phase saturation and their time series have been investigated for the first time by developing, validating, and implementing a new two-tip optical fiber probe technique. It was found the radially and axially the liquid and gas velocities and their saturation vary and they also vary with times. In …

Magneto Inductive Communication System For Underwater Wireless Sensor Networks, Niaz Ahmed

Doctoral Dissertations

"Underwater wireless sensor networks have found a number of applications in underwater environment monitoring, infrastructure monitoring, military applications and ocean exploration. Among the four possible means of underwater wireless communication, namely acoustic, electromagnetic (EM), magneto-inductive (MI) and optics communication, MI communication enjoys the advantages of being low cost and robust equally in air, water and soil. This dissertation presents design and implementation of a low-power and low-cost MI sensor network node that is suited for long-term deployment of underwater and underground infrastructure monitoring, such as bridge scour and levee scour monitoring. The designed MI sensor node combat the directionality of …

Application Of Nearly Linear Solvers To Electric Power System Computation, Lisa L. Grant

Doctoral Dissertations

"To meet the future needs of the electric power system, improvements need to be made in the areas of power system algorithms, simulation, and modeling, specifically to achieve a time frame that is useful to industry. If power system time-domain simulations could run in real-time, then system operators would have situational awareness to implement and avoid cascading failures, significantly improving power system reliability. Several power system applications rely on the solution of a very large linear system. As the demands on power systems continue to grow, there is a greater computational complexity involved in solving these large linear systems within …

Processing, Microstructure, And Mechanical Properties Of Zirconium Diboride-Molybdenum Disilicide Ceramics And Dual Composite Architectures, Ryan Joseph Grohsmeyer

Doctoral Dissertations

"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB₂-MoSi₂ ceramics at room temperature (RT) and 1500⁰C in air, and fabrication of ZrB₂-MoSi₂ dual composite architectures (DCAs) for use near 1500⁰C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500⁰C for 15 ZrB₂-MoSi₂ ceramics hot pressed using fine, medium, or coarse ZrB₂ starting powder with 5-70 vol.% MoSi₂, referred to as FX, MX, and CX respectively where X is the nominal MoSi₂ content. MoSi₂ decomposed during sintering, resulting in …

Fusion Of Non-Visual And Visual Sensors For Human Tracking, Wenchao Jiang

Doctoral Dissertations

"Human tracking is an extensively researched yet still challenging area in the Computer Vision field, with a wide range of applications such as surveillance and healthcare. People may not be successfully tracked with merely the visual information in challenging cases such as long-term occlusion. Thus, we propose to combine information from other sensors with the surveillance cameras to persistently localize and track humans, which is becoming more promising with the pervasiveness of mobile devices such as cellphones, smart watches and smart glasses embedded with all kinds of sensors including accelerometers, gyroscopes, magnetometers, GPS, WiFi modules and so on. In this …

Mass Transfer Studies In Heavy Oil Recovery Using Solvents, Vijitha Mohan

Doctoral Dissertations

"Heavy oil, sometimes called bitumen, is known for its high viscosity (above 100 cp) and low API gravity (below 22⁰). In most cases, viscosity reduction is needed for the final product. There is a considerable amount of heavy oil in Alberta, Canada and the world's largest heavy oil deposit is in Venezuela. Yet less than 1% of it can be recovered because of its high viscosity. For shallow reservoirs, it is possible to resort to open cast mining. For deeper reservoirs, steam is used at ~ 350 ⁰C which gets the oil viscosity reduced to 1cp, which can now be …