Digital Commons Network^™

Quality Of Service Provisioning Through Resource Allocation And Data Aggregation In Wireless Sensor Networks, Carl Larsen

Doctoral Dissertations

"In this dissertation, improvement of quality of service (QoS) provisioning in wireless sensor networks (WSN) is examined using four different methods. The first two focus on allocation of limited resources in the face of changing network and channel conditions, and thus improving performance in terms of throughput and delay. The second two methods focus on using data aggregation to minimize the size and number of packet transmissions reducing the energy consumption and improving network lifetime.

Therefore, in the first paper a novel adaptive and distributed fair scheduling (ADFS) protocol for WSN is presented that allocates the channel bandwidth in proportion …

Advanced Control Techniques For Doubly Fed Induction Generator-Based Wind Turbine Converters To Improve Low Voltage Ride-Through During System Imbalances, Murali M. Baggu

Doctoral Dissertations

A doubly-fed induction generator (DFIG) applied to wind power generation is under study for low voltage ride-through application during system disturbances. Conventional dq axis current control using voltage source converters for both the grid side and the rotor side of the DFIG are analyzed and simulated. DFIG operation is investigated under balanced and unbalanced system disturbances. A conventional d-axis and q-axis control applied to a voltage source converter (VSC) during a system imbalance exhibits oscillations in the stiff DC link voltage as well as in the real and reactive powers of the converter. Multiple advanced control methods are explored and …

Investigating The Impact Of Microbial Interactions With Geologic Media On Geophysical Properties, Caroline A. Davis

Doctoral Dissertations

"The goals of this study were to investigate the effect of: (1) microbial metabolic byproducts, microbial growth, and biofilm formation on the low frequency electrical properties of porous media, (2) biofilm formation on acoustic wave properties, and (3) the natural electrical (self-potential) signatures associated with an in-situ biological permeable reactive barrier (PRB). The results suggest: (1) increases in electrolytic conductivity are consistent with increased concentrations of organic acids and biosurfactants; (2) mineral weathering promoted by organic acids causes increases in electrolytic conductivity, concomitant with increases in major cation concentrations; (3) interfacial conductivity generally parallels microbial cell concentrations and biofilm formation; …

Formation Control Of Mobile Robots And Unmanned Aerial Vehicles, Travis Alan Dierks

Doctoral Dissertations

"In this dissertation, the nonlinear control of nonholonomic mobile robot formations and unmanned aerial vehicle (UAV) formations is undertaken and presented in six papers. In the first paper, an asymptotically stable combined kinematic/torque control law is developed for leader-follower based formation control of mobile robots using backstepping. A neural network (NN) is introduced along with robust integral of the sign of the error (RISE) feedback to approximate the dynamics of the follower as well as its leader using online weight tuning. Subsequently, in the second paper, a novel NN observer is designed to estimate the linear and angular velocities of …

Microstructural Influence On Dynamic Properties Of Age Hardenable Femnal Alloys, Ryan A. Howell

Doctoral Dissertations

"A lightweight castable alloy was sought to reduce the MIL-PRF-32269 class II cast steel perforated armor's weight with the requirement that the material had to be manufactured utilizing existing foundry technology and without incurring large alloy cost increases to meet property requirements. Literature on wrought age hardenable Fe-Mn-Al-C alloys suggested this alloy system could achieve weight reduction through high aluminum concentrations with the highest reported strengths exceeding 2 GPa for a Fe-30Mn-9Al-0.9C composition. Even though ballistic testing had not been conducted on this system, high strain rate data of wrought alloys showed excellent work hardenability; greater than existing ballistic metals. …

Integration Of Energy Storage Components With Cascaded H-Bridge Multilevel Converters, Jingsheng Liao

Doctoral Dissertations

"In recent years, multilevel converters have gained considerable attention in medium-voltage motor drive and grid applications. This popularity is owed to their reduced voltage stress on the semiconductor devices used in their structure. In addition, multilevel converters generate near sinusoidal outputs with low harmonic distortions. Other advantages of such converters include inherent modularity and low dv/dt stresses. In general, multilevel power electronic converters are classified into three main topologies: diode-clamped, flying-capacitor, and cascaded H-bridge. A cascaded H-bridge multilevel converter is created when several H-bridge cells are placed in series. Each H-bridge cell must be fed by a stiff voltage source. …

Guidance, Navigation And Control System For Autonomous Proximity Operations And Docking Of Spacecraft, Daero Lee

Doctoral Dissertations

"This study develops an integrated guidance, navigation and control system for use in autonomous proximity operations and docking of spacecraft. A new approach strategy is proposed based on a modified system developed for use with the International Space Station. It is composed of three "V-bar hops" in the closing transfer phase, two periods of stationkeeping and a "straight line V-bar" approach to the docking port. Guidance, navigation and control functions are independently designed and are then integrated in the form of linear Gaussian-type control. The translational maneuvers are determined through the integration of the state-dependent Riccati equation control formulated using …

Wind Power Applications To Groundwater Remediation, Ronald E. Gallagher

Doctoral Dissertations

"The use of renewable energy systems to power groundwater remediation systems seems like an inherently good idea because of potential cost savings and environmental benefits associated with reduced greenhouse gas emissions. Small wind turbine systems marketed for single residence applications may be the appropriate size for remediation systems, and such wind turbines are readily available at reasonable cost. Another benefit of using domestic wind turbine systems is that they are straightforward to install and operate with minimal training. One of the major drawbacks associated with using wind turbines at remediation sites is that site-specific wind velocity data is typically used …

Modeling And Simulation Of High Pressure Composite Cylinders For Hydrogen Storage, Jianbing Hu

Doctoral Dissertations

"Composite hydrogen cylinders provide an efficient means of storage of hydrogen gas for modern hydrogen vehicles. Safety issues arising from the high gas pressure, temperature variation, fire attack, and fracture failures are the main concerns. The focus of this study is to develop a Finite Element (FE) model to predict the performance of composite cylinders subjected to extreme mechanical/thermal loadings and provide guidance for design optimization"--Abstract, page iv.

A Study Of The Beneficial Role Of Thiol Antioxidant Supplementation In Various Forms Of Glutathione Deficiency, Linu Sara Abraham

Doctoral Dissertations

"Oxidative stress plays a major role in the pathology of numerous disorders afflicting humans, ranging from neurodegenerative diseases, to cancer, and heavy metal toxicity. Scientists are on the constant lookout for new and better antioxidants that have the ability to slow, if not stop the harmful degenerative effects of free radicals in oxidative stress related disorders. Both synthetic and naturally occurring compounds are being constantly screened for their antioxidant properties. This study attempted to evaluate the abilities of a thiol antioxidant, N-Acetylcysteine amide (NACA), to protect cells from the harmful effects of glutathione depletion in two different models of oxidative …

A Qualitative Study Of An E-Commerce Organization In Transition, Steven C. Lopez

Doctoral Dissertations

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Advanced Current-Mode Control Techniques For Dc-Dc Power Electronic Converters, Kai-Tak Wan

Doctoral Dissertations

"There are many applications for dc-dc power electronic converters in industry. Considering the stringent regulation requirements, control of these converters is a challenging task. Several analog and digital approaches have already been reported in the literature. This work presents new control techniques to improve the dynamic performance of dc-dc converters"--Abstract, page iv.

Detection Of Low Cost Radio Frequency Receivers Based On Their Unintended Electromagnetic Emissions And An Active Stimulation, Sarah A. Seguin

Doctoral Dissertations

"Detection of super-regenerative receivers using their unintended electromagnetic emissions at a significant distance is challenging due to high levels of ambient noise. The evolution of an approach used to solve this problem is chronicled within the three papers that combine to form this dissertation. First, a passive detection method was created for detecting devices based on the characterization of their unintended emissions and utilized a cascading correlation method to confirm detection. Using a simple sine-wave stimulation to modify these unintended emissions produced better results over passive detection techniques by improving the signal quality and the consistency of the unintended emissions, …

A Control-Theoretical Fault Prognostics And Accommodation Framework For A Class Of Nonlinear Discrete-Time Systems, Balaje T. Thumati

Doctoral Dissertations

"Fault diagnostics and prognostics schemes (FDP) are necessary for complex industrial systems to prevent unscheduled downtime resulting from component failures. Existing schemes in continuous-time are useful for diagnosing complex industrial systems and no work has been done for prognostics. Therefore, in this dissertation, a systematic design methodology for model-based fault prognostics and accommodation is undertaken for a class of nonlinear discrete-time systems. This design methodology, which does not require any failure data, is introduced in six papers. In Paper I, a fault detection and prediction (FDP) scheme is developed for a class of nonlinear system with state faults by assuming …

Hydrogen Infrastructure: Resource Evaluation And Capacity Modeling, Kevin B. Martin

Doctoral Dissertations

"A hydrogen economy could offer energy stability, economical, and environmental benefits. Several issues are involved in the design and implementation of a hydrogen economy such as the selection of feedstocks, generation and storage technologies, transportation methods, appropriate equipment capacity, codes/standards and public awareness. The design of a hydrogen infrastructure may seem insurmountable; however, as the system is deconstructed a proper design can be achieved. In order to better understand how a hydrogen system for light duty vehicles might operate, both hydrogen resource and capacity analysis and modeling is conducted. Specifically, an evaluation of leading near term production and distribution technologies …

Decentralized Adaptive Neural Network Control Of Interconnected Nonlinear Dynamical Systems With Application To Power System, Shahab Mehraeen

Doctoral Dissertations

"Traditional nonlinear techniques cannot be directly applicable to control large scale interconnected nonlinear dynamic systems due their sheer size and unavailability of system dynamics. Therefore, in this dissertation, the decentralized adaptive neural network (NN) control of a class of nonlinear interconnected dynamic systems is introduced and its application to power systems is presented in the form of six papers. In the first paper, a new nonlinear dynamical representation in the form of a large scale interconnected system for a power network free of algebraic equations with multiple UPFCs as nonlinear controllers is presented. Then, oscillation damping for UPFCs using adaptive …

Information Archival And Reuse: Drawing Conclusions From The Past, Matt R. Bohm

Doctoral Dissertations

"Over the last few decades design researchers have put forward theories and proposed methodologies that increase the chance that a design team will reliably arrive at the optimal solution to a given design problem. Studies, however, bear out that theories and methodologies alone will not guarantee an optimal or even good design solution. Instead, a breadth of knowledge across multiple engineering domains and the time and tools to thoroughly evaluate the design space are as important as any prescriptive design method. This work presents a set of underlying engineering technologies to define, archive and reuse product design knowledge to provide …

An Experimental And Numerical Investigation Of Flapping And Plunging Wings, Taylor A. Swanson

Doctoral Dissertations

"Micro air vehicles, or MAVs, are of current interest for a multitude of uses to which they, being small, unmanned vehicles, are uniquely suited. Among the proposed uses are exploration, reconnaissance, and communications. They can be deployed inside buildings, where their small size, hovering capability, and maneuverability, are important factors. Due to their small size, they operate at low Reynolds numbers where conventional flying mechanisms are not advantageous. Thus, attempts have been made to learn from natural flyers like insects and birds. Natural flight is accomplished by flapping wings, and this idea has been proposed for certain types of MAVs …

Seismic Behavior Of Circular Reinforced Concrete Bridge Columns Under Combined Loading Including Torsion, Suriya Prakash Shanmugam

Doctoral Dissertations

"Reinforced concrete (RC) columns of skewed and curved bridges with unequal spans and column heights can be subjected to combined loading including axial, flexure, shear, and torsion loads during earthquakes. The combination of axial loads, shear force, and flexural and torsional moments can result in complex failure modes of RC bridge columns. This study carried out experimental and analytical studies to investigate the seismic performance of circular RC columns under combined loading including torsion. The main variables considered here were (i) the ratio of torsion-to-bending moment (T/M), (ii) the ratio of bending moment-to-shear (M/V) or shear span (H/D), and (iii) …

Novel Modulated Antennas And Probes For Millimeter Wave Imaging Applications, Mohamed A. Abou-Khousa

Doctoral Dissertations

"Microwave and millimeter wave (300 MHz - 300 GHz) imaging techniques have shown great potential for a wide range of industrial and medical applications. These techniques are fundamentally based on measuring relative and coherent electromagnetic fields distributions, e.g., electric fields, around the object to be imaged. Various imaging systems can be devised for measuring relative electric field distributions; each with it own advantages and limitations. This dissertation is focused on addressing critical challenges related to the practical implementation of various microwave and millimeter wave imaging systems. Specifically, this research is meant to achieve three main objectives related to designing efficient …

Material Flow And Microstructure Evolution In Friction Stir Welding Of Aa6111 Alloy Sheets, Manasij Kumar Yadava

Doctoral Dissertations

"Material flow and microstructure evolution are the two important aspects of the Friction stir welding (FSW) technique, which control the properties and performance of the friction stir welds. The present work investigates these two aspects of the FSW with main emphasis on the friction stir lap joints (FSLJs) on the AA6111 sheets. Due to the characteristic material flow during FSW, the faying surfaces in FSLPs are deposited in and around the weld nugget and create unavoidable defects. These defects reduce the load carrying thickness of the joints by providing an easy path for the weld failure. Therefore, to control the …

Protein Responsive Synthetic Materials For Biomedical Applications, Youyou Zheng

Doctoral Dissertations

"The production of synthetic materials with molecular recognition abilities towards biomacromolecules has been widely researched because of its potential applications in separations, sensing, therapeutics, etc. While molecular imprinting has become a commercially viable method for the production of synthetic materials with molecular recognition abilities towards small molecules, little success has been recorded towards protein targets. Proteins are difficult to imprint as they present a number of epitopes for imprinting, are difficult to remove from the completed material, and are incompatible with the densely crosslinked structures required. As a result, a novel surface molecular imprinting technique was developed to synthesize polymeric …

Rational Construction By Molecular Dynamics Modeling And Simulations Of Porous Adsorbent Media For Bioseparation, Enrico Riccardi

Doctoral Dissertations

"Ion-exchange chromatography employing porous adsorbent particles or monoliths in which charged ligands are immobilized onto polymeric extender molecules grafted on the pore surfaces of a base matrix has become a very important method for bioseparations. In this dissertation, a novel fundamental and systematic methodology has been developed that uses the molecular dynamics (MD) modeling and simulation approach to rationally design, construct, and characterize polymeric porous adsorbent media and study the transport and adsorption of a charged biomolecule (desmopressin) in a representative adsorbent medium. The MD results have also been utilized in a macroscopic model to study the large-scale dynamic behavior …

The Role Of Friction Stir Processing On The Microstructure And Mechanical Properties Of A Cast Aluminum Alloy, Saumyadeep Jana

Doctoral Dissertations

"Al-7Si-0.6Mg is one of the most important cast aluminum alloys because of its attractive mechanical properties and high castability. Microstructurally, the alloy consists of primary aluminum dendrites with eutectic Si particles in the interdendritic region. This makes the alloy quasi-brittle in nature which affects the ductility of the alloy to a great extent. In order to improve the ductility, the eutectic Si particles need to be refined which so far has been achieved by chemical and/or thermal modification. Friction stir processing (FSP) on the other hand can achieve the same through plastic deformation, and therefore replace the cast structure with …

Emi Failure Analysis Techniques And Noise Prediction For Trace Crossing Split Planes, Weifeng Pan

Doctoral Dissertations

"A variety of methods exist that help locate the source, coupling path, and antenna in an electromagnetic interference (EMI) problem. No single method is the best option in all cases. A good electromagnetic compatibility (EMC) engineer should understand and have experience with a wide range of failure analysis methods and thus, be able to select the most appropriate ones for a given problem. The first three papers are from a series of articles, which explains a set of methods for the analysis of EMI failures. Each method is categorized based on two criteria: 1) the elements in an EMI problem …

Energy And Voltage Management Methods For Multilevel Converters For Bulk Power System Power Quality Improvement, Atousa Yazdani

Doctoral Dissertations

"Electric arc furnaces (EAFs) are prevalent in the steel industry to melt iron and scrap steel. EAFs frequently cause large amplitude fluctuations of active and reactive power and are the source of significant power quality disturbances. Also EAFs comprise a major portion of industrial loading on the bulk power system. Typically, a static VAR compensator (SVC) or Static Synchronous compensator (STATCOM) are use to provide the reactive power support in order to alleviate the fluctuations in voltage at PCC. Static Synchronous Compensators (STATCOMs) provide a power electronic-based means of embedded control for reactive power support. Integrating an energy storage system …

Novel Optofluidic Sensor Systems For Quantitative Chemical Imaging And On-Chip Sensor Calibration, Jongwon Park

Doctoral Dissertations

"The design, fabrication and characterization of optofluidic biosensor systems for quantitative oxygen imaging with a color charge-coupled device (CCD) camera as well as on-chip self-calibration of sensors utilizing gas bubbles was investigated. This dissertation was prepared in publication format. The first and second papers demonstrate that color imaging devices can be used in quantitative chemical analysis. The final paper explores the feasibility of using electrolytically generated bubbles for a novel functionality of reagentless, on-chip, in situ calibration of optical biosensors. Work in the first paper includes the use of a color CCD camera for fluorescence intensity imaging. This involves extracting …

Real-Time And Portable Microwave Imaging System, Mohammad Tayeb Ahmad Ghasr

Doctoral Dissertations

"Microwave and millimeter wave imaging has shown tremendous utility in a wide variety of applications. These techniques are primarily based on measuring coherent electric field distribution on the target being imaged. Mechanically scanned systems are the simple and low cost solution in microwave imaging. However, these systems are typically bulky and slow. This dissertation presents a design for a 2D switched imaging array that utilizes modulated scattering techniques for spatial multiplexing of the signal. The system was designed to be compact, coherent, possessing high dynamic range, and capable of video frame rate imaging. Various aspects of the system design were …

Spacecraft Formation Flight At Sun-Earth/Moon Libration Points, Douglas Robert Tolbert

Doctoral Dissertations

"Formations of spacecraft, positioned near the libration points of the Sun- Earth/Moon system, have recently received an increase in interest in response to a variety of mission needs. Specifically, missions such as the Micro Arcsecond X-Ray Imaging Mission (MAXIM), Terrestrial Pathfinder (TPF), Stellar Imager (SI) and the European Space Agency's DARWIN all baseline formations of spacecraft to satisfy mission requirements. Replacing the traditional single spacecraft mission with multiple small spacecraft flying in formation is advantageous for these missions, especially when establishing a virtual aperture. These types of formations allow for higher resolution observations than with a single, conventional aperture. The …

Membrane Properties Of Intact Rock Cores Of Burlington Limestone, Jefferson Dolomite, Darrington Phyllite, And Low Permeability Concrete, Megan Hart

Doctoral Dissertations

"A number of laboratory studies have shown that clays exhibit membrane properties. However, little research has been performed on lithologies outside of pure clays. Recently, research focusing on mixed sand and clay membrane properties for engineering applications was performed. Still, literature only suggests the possibilities of membrane properties, osmotic or reverse-osmotic, associated with other naturally occurring 'tight' rock types. Therefore, the objectives of this research was to perform a series of hyperfiltration experiments using actual rock discs of Quarry Ridge Jefferson Dolomite, Darrington Phyllite, Lower Burlington Limestone, and low permeability concrete to determine if tight lithologies can function as membranes"--Abstract, …