Digital Commons Network^™

Model Based Fault Diagnosis And Prognosis Of Class Of Linear And Nonlinear Distributed Parameter Systems Modeled By Partial Differential Equations, Jia Cai

Doctoral Dissertations

"With the rapid development of modern control systems, a significant number of industrial systems may suffer from component failures. An accurate yet faster fault prognosis and resilience can improve system availability and reduce unscheduled downtime. Therefore, in this dissertation, model-based prognosis and resilience control schemes have been developed for online prediction and accommodation of faults for distributed parameter systems (DPS). First, a novel fault detection, estimation and prediction framework is introduced utilizing a novel observer for a class of linear DPS with bounded disturbance by modeling the DPS as a set of partial differential equations.

To relax the state measurability …

Models Of Leader Elections And Their Applications, Stephen Curtis Jackson

Doctoral Dissertations

"New research about cyber-physical systems is rapidly changing the way we think about critical infrastructures such as the power grid. Changing requirements for the generation, storage, and availability of power are all driving the development of the smart-grid. Many smart-grid projects disperse power generation across a wide area and control devices with a distributed system. However, in a distributed system, the state of processes is hard to determine due to isolation of memory. By using information flow security models, we reason about a process's beliefs of the system state in a distributed system. Information flow analysis aided in the creation …

Low-Complexity Iterative Receiver Algorithms For Multiple-Input Multiple-Output Underwater Wireless Communications, Weimin Duan

Doctoral Dissertations

"This dissertation proposes three low-complexity iterative receiver algorithms for multiple-input multiple-output (MIMO) underwater acoustic (UWA) communications. First is a bidirectional soft-decision feedback Turbo equalizer (Bi-SDFE) which harvests the time-reverse diversity in severe multipath MIMO channels. The Bi-SDFE outperforms the original soft-decision feedback Turbo equalizer (SDFE) while keeping its total computational complexity similar to that of the SDFE. Second, this dissertation proposes an efficient direct adaptation Turbo equalizer for MIMO UWA communications. Benefiting from the usage of soft-decision reference symbols for parameter adaptation as well as the iterative processing inside the adaptive equalizer, the proposed algorithm is efficient in four aspects: …

Modeling Gas Inflow For Extremely Low Permeability Shale Using Cfd, Chatetha Chumkratoke

Doctoral Dissertations

"Computational fluid dynamics (CFD) has been used to model 2-D well inflow over a range of permeabilities to study the impact of various well completion strategies (Augustine, 2011). Augustine's 2-D model was subsequently extended for 3-D flow by Thepporprapakorn (2013), for gas flow in the permeability range of tight gas (0.01 mD).

This work presents a 3-D CFD model of gas inflow valid for extremely low ranges of permeability (0.00001 mD). In extremely low permeability, gas flow is complex and includes flow from fractures, flow through porous media, and diffusive gas transport. Diffusive gas transport is important when strong density …

Methodology Investigations For Shear Wave Splitting Analysis, Fansheng Kong

Doctoral Dissertations

"Over the past several decades, shear wave splitting analyses have been increasingly utilized to delineate mantle structure and probe mantle dynamics. However, the reported splitting parameters (fast polarization orientations and splitting times) are frequently inconsistent among different studies, partially due to the different techniques used to estimate the splitting parameters. Here the study conduct research on methodology investigations for shear wave splitting analysis, which are composed of two sub-topics, i.e., a systematic comparison of the transverse minimization (TM) and the splitting intensity (SI) techniques and applicability of the multiple-event stacking technique (MES). Numerical experiments are conducted using both synthetic and …

Detecting, Segmenting And Tracking Bio-Medical Objects, Mingzhong Li

Doctoral Dissertations

"Studying the behavior patterns of biomedical objects helps scientists understand the underlying mechanisms. With computer vision techniques, automated monitoring can be implemented for efficient and effective analysis in biomedical studies. Promising applications have been carried out in various research topics, including insect group monitoring, malignant cell detection and segmentation, human organ segmentation and nano-particle tracking.

In general, applications of computer vision techniques in monitoring biomedical objects include the following stages: detection, segmentation and tracking. Challenges in each stage will potentially lead to unsatisfactory results of automated monitoring. These challenges include different foreground-background contrast, fast motion blur, clutter, object overlap and …

Modeling And Control Of Fuel Cell-Battery Hybrid Energy Sources, Nima Lotfi

Doctoral Dissertations

"Environmental, political, and availability concerns regarding fossil fuels in recent decades have garnered substantial research and development in the area of alternative energy systems. Among various alternative energy systems, fuel cells and batteries have attracted significant attention both in academia and industry considering their superior performances and numerous advantages. In this dissertation, the modeling and control of these two electrochemical sources as the main constituents of fuel cell-battery hybrid energy sources are studied with ultimate goals of improving their performance, reducing their development and operational costs and consequently, easing their widespread commercialization. More specifically, Paper I provides a comprehensive background …

Pointwise And Uniform Convergence Of Fourier Series On Su(2), Donald Forrest Myers

Doctoral Dissertations

"Let f be a Lipschitz function on the special unitary group SU (2). We prove that the Fourier partial sums of f converge to f uniformly on SU (2), thereby extending theorems of Caccioppoli, Mayer, and a special case of Ragozin. Pointwise convergence theorems for the Fourier series of functions on SU (2), due to Liu and Qian, were obtained by Clifford algebra techniques. We obtain similar versions of these theorems using simpler proof techniques: classical harmonic analysis and group theory"--Abstract, page iii.

Modeling Explosive Lensing On A Cylindrical Body In Air: A First Step Towards Sealing An Underwater Offshore Oil Spill, Phillip R. Mulligan

Doctoral Dissertations

"In 2010, the British Petroleum (BP) Deepwater Horizon accident leaked oil into the Gulf of Mexico for 87 days. A fast response method that can seal an oil pipe and stop the release of oil is needed in order to prevent future oil leaks from turning into ecological and financial disasters. Explosives can serve this need.

This research examined how a circular implosive discontinuous explosive lens interacts with a cylindrical surface. The following research was designed to study the applicability of the Method this author developed to predict the peak pressure from multiple shockwaves converging on a centrally located cylinder. …

Lifetime And Effectiveness Evaluation Of Ceramic Pot Filters, Carlo Salvinelli

Doctoral Dissertations

"Poor water quality is a major contributing factor to disease in developing countries. Ceramic pot filters (CPFs) represent an effective and sustainable technology for poor communities, but the characterization of CPF lifetimes is on-going, and the water production seems to be the limiting factor. This dissertation describes laboratory and field investigations conducted to characterize the parameters that impact CPF effectiveness and lifetime in terms of water production and treatment efficacy, both under controlled and real use conditions.

CPF initial flow rate is the most common quality control parameter, but it may not be representative of the long-term effectiveness of the …

A Control Theoretic Approach For Security Of Cyber-Physical Systems, Haifeng Niu

Doctoral Dissertations

"In this dissertation, several novel defense methodologies for cyber-physical systems have been proposed. First, a special type of cyber-physical system, the RFID system, is considered for which a lightweight mutual authentication and ownership management protocol is proposed in order to protect the data confidentiality and integrity. Then considering the fact that the protection of the data confidentiality and integrity is insufficient to guarantee the security in cyber-physical systems, we turn to the development of a general framework for developing security schemes for cyber-physical systems wherein the cyber system states affect the physical system and vice versa. After that, we apply …

Algorithms Leveraging Smartphone Sensing For Analyzing Explosion Events, Srinivas Chakravarthi Thandu

Doctoral Dissertations

"The increasing frequency of explosive disasters throughout the world in recent years have created a clear need for the systems to monitor for them continuously to improve the post-disaster emergency events such as rescue and recovery operations. Disasters both man-made and natural are unfortunate and not preferred, however monitoring them may be a lifesaving phenomenon in emergency scenarios. Dedicated sensors deployed in the public places and their associated networks to monitor such events may be inadequate and must be complemented for making the monitoring more pervasive and effective. In the recent past, modern smartphones with significant processing, networking and storage …

Seismic Anisotropy And Mantle Dynamics Beneath The Central And Western United States, Bin Yang

Doctoral Dissertations

"Various tectonic features and the recent availability of high-quality broadband seismic data from the USArray and other seismic stations in the central and western United States (CWUS) provide a distinct opportunity to test different anisotropy-forming mechanisms. For the first part of the study, a total of 4138 pairs of well-defined shear wave splitting (SWS) parameters observed at 445 stations on the northern Great Plains show systematic spatial variations of anisotropic characteristics. Azimuthally invariant fast orientations subparallel to the absolute plate motion (APM) direction are observed at most of the stations on the Superior Craton and the southern Yavapai province, indicating …

Dft Investigations Of Hydrogen Storage Materials, Gang Wang

Doctoral Dissertations

"Hydrogen serves as a promising new energy source having no pollution and abundant on earth. However the most difficult problem of applying hydrogen is to store it effectively and safely, which is smartly resolved by attempting to keep hydrogen in some metal hydrides to reach a high hydrogen density in a safe way. There are several promising metal hydrides, the thermodynamic and chemical properties of which are to be investigated in this dissertation.

Sodium alanate (NaAlH₄) is one of the promising metal hydrides with high hydrogen storage capacity around 7.4 wt. % and relatively low decomposition temperature of …

High-Voltage-Gain Dc-Dc Power Electronic Converters -- New Topologies And Classification, Bhanu Prashant Reddy Baddipadiga

Doctoral Dissertations

"This dissertation proposes two new high-voltage-gain dc-dc converters for integration of renewable energy sources in 380/400V dc distribution systems. The first high-voltage-gain converter is based on a modified Dickson charge pump voltage multiplier circuit. The second high-voltage-gain converter is based on a non-inverting diode-capacitor voltage multiplier cell. Both the proposed converters offer continuous input current and low voltage stress on switches which make them appealing for applications like integration of renewable energy sources. The proposed converters are capable for drawing power from a single source or two sources while having continuous input current in both cases. Theoretical analysis of the …

Unconventional Phase Transitions In Random Systems, Hatem Nuri Barghathi

Doctoral Dissertations

"In this thesis we study the effects of different types of disorder and quasiperiodic modulations on quantum, classical and nonequilibrium phase transitions. After a brief introduction, we examine the effect of topological disorder on phase transitions and explain a host of violations of the Harris and Imry-Ma criteria that predict the fate of disordered phase transitions. We identify a class of random and quasiperiodic lattices in which a topological constraint introduces strong anticorrelations leading to modifications of the Harris and Imry-Ma criteria for such lattices. We investigate whether or not the Imry-Ma criterion, that predicts that random field disorder destroys …

Spectroscopic And Spectro-Astrometric Analysis Of T Tauri Stars, Logan Ryan Brown

Doctoral Dissertations

"To understand our own solar origins, we must investigate the composition of the protoplanetary disk from which the solar system formed. To infer this, we study analogs to the early solar system called T Tauri stars. These objects are low-mass, pre-main sequence stars surrounded by circumstellar disks of material from which planets are believed to form. We present high-resolution, near-infrared spectroscopic data for the T Tauri stars DR Tau and AA Tau using NIRSPEC at the Keck II telescope. For DR Tau, a spectro-astrometric analysis was performed, obtaining sub-seeing spatial information on water emission. Alongside a disk model, we constrained …

Multiphase Field Modeling Of The Formation Path Of Delta Hydrides In Zirconium, Jacob Luke Bair

Doctoral Dissertations

"Zirconium alloys are commonly used in nuclear fuel rod claddings due to their high ductility, good corrosion resistance, and low neutron absorption cross section. Among the most important weaknesses of zirconium alloys is their affinity for hydrogen, resulting in formation of hydrides in the cladding, and leading to embrittlement and mechanical failure. Despite numerous studies on hydride precipitation in zirconium alloys, the nucleation and formation path of stable δ hydrides in α zirconium matrix are not yet fully understood.

In this Ph.D. research project, two novel quantitative phase-field models were developed and utilized to advance our understanding of mechanisms of …

Uncertainty Quantification Applied To The Analysis And Design Of A Hypersonic Inflatable Aerodynamic Decelerator For Spacecraft Reentry, Andrew J. Brune

Doctoral Dissertations

"The primary objective of this research is to investigate the uncertainty in the multidisciplinary analysis of a Hypersonic Inflatable Aerodynamic Decelerator configuration for Mars entry, subject to uncertainty sources in the high-fidelity computational models and the operating conditions. Efficient uncertainty quantification methods based on stochastic expansions are applied to the analysis of the hypersonic flowfield, fluid-structure interaction, and flexible thermal protection system response of a deformable inflatable decelerator. Uncertainty analysis is first applied to the hypersonic flowfield simulations to quantify the uncertainty in the surface convective and radiative heat flux, pressure, and shear stress of a fixed inflatable decelerator, subject …

Bayesian Inference For Dynamic Pose Estimation Using Directional Statistics, Jacob E. Darling

Doctoral Dissertations

"The dynamic pose of an object, where the object can represent a spacecraft, aircraft, or mobile robot, among other possibilities, is defined to be the position, velocity, attitude, and angular velocity of the object. A new method to perform dynamic pose estimation is developed that leverages directional statistics and operates under the Bayesian estimation framework, as opposed to the minimum mean square error (MMSE) framework that conventional methods employ. No small attitude uncertainty assumption is necessary using this method, and, therefore, a more accurate estimate of the state can be obtained when the attitude uncertainty is large.

Two new state …

Methodology For Analysis Of Stress, Creep, And Fatigue Behavior Of Compliant Mechanisms, Joshua Allen Crews

Doctoral Dissertations

"A methodology is developed for analyzing stress within homogeneous and metallic-reinforced, fixed-free compliant segments and small-length flexural pivots. Boundary conditions related to the inclusion of metallic reinforcing components within a polymer compliant segment are investigated. The analysis method outlined herein relies on key outputs from the pseudo-rigid-body models (PRBMs). A method is presented for the redesign of compliant mechanisms to include metallic reinforcement to reduce stress while maintaining force-deflection behavior. Examples are provided in which a compliant segment is redesigned to include metallic reinforcement by using the stress equations developed from the PRBM. The effect of bonding between the polymer …

Using Wireless Sensors And Networks Program For Chemical Particle Propagation Mapping And Chemical Source Localization, Xiang Gao

Doctoral Dissertations

"Chemical source localization is a challenge for most of researchers. It has extensive applications, such as anti-terrorist military, Gas and oil industry, and environment engineering. This dissertation used wireless sensor and sensor networks to get chemical particle propagation mapping and chemical source localization. First, the chemical particle propagation mapping is built using interpolation and extrapolation methods. The interpolation method get the chemical particle path through the sensors, and the extrapolation method get the chemical particle beyond the sensors. Both of them compose of the mapping in the whole considered area. Second, the algorithm of sensor fusion is proposed. It smooths …

Static And Dynamic Characterization Of Tied Arch Bridges, John Edward Finke

Doctoral Dissertations

"Tied arch bridges have been designed and constructed since the late 19th century. With their open vista owing to minimalist features tied arch bridges continue to appeal the public. Tied arch bridges are both aesthetic and economical alternates to long span bridges holding a place in the hierarchy of major bridges. They fit in a niche between viable and economical plate girder spans and short cable stayed bridge spans. There are several variations of the tied arch with the most common form being those having vertical hangers, stiff tie girders and slender arch ribs. This tied arch variation is examined …

Adaptive Consensus Based Formation Control Of Unmanned Vehicles, Haci Mehmet Guzey

Doctoral Dissertations

"Over the past decade, the control research community has given significant attention to formation control of multiple unmanned vehicles due to a variety of commercial and defense applications. Consensus-based formation control is considered to be more robust and reliable when compared to other formation control methods due to scalability and inherent properties that enable the formation to continue even if one of the vehicles experiences a failure. In contrast to existing methods on formation control where the dynamics of the vehicles are neglected, this dissertation in the form of four papers presents consensus-based formation control of unmanned vehicles-both ground and …

Development And Evaluation Of A Coaxial Cable Sensing System For Co₂ Sequestration Wellbore Integrity Monitoring, Yurong Li

Doctoral Dissertations

"Downhole monitoring plays a crucial part in geological carbon dioxide (₂) sequestration. Various downhole monitoring technologies have been explored and applied, but they are either expensive or have system longevity issues. To address this issue, a robust and cost-effective downhole sensing system based on distributed coaxial cable sensors is developed and evaluated in laboratory, and a numerical simulation with staged finite element model is conducted to study the feasibility of using the coaxial cable sensing system for monitoring and evaluation of wellbore stability during CO₂ injection.

The real-time distributed sensing system is composed of Fabry-Perot interferometer based …

Properties Of Amorphous Transparent Conducting And Semiconducting Oxides From First Principles, Rabi Khanal

Doctoral Dissertations

"Amorphous transparent conducting and semiconducting oxides possess properties superior or comparable to their crystalline counterparts. The structure-property relationship in amorphous oxides is not nearly as well understood as in the case of the crystalline transparent conducting oxides. We have employedab initio molecular dynamics and a liquid quench approach to simulate amorphous oxide structures and performed density functional-based calculations to study the electronic properties of several amorphous conducting and semiconducting oxides with various cation compositions.

The effect of amorphization in oxides was investigated by taking indium oxide as a progenitor of the system. From the thorough study it was confirmed …

Palynological Studies Of Holocene Lake Sediments In The Missouri Ozarks, Robert D. Haselwander

Doctoral Dissertations

"Five small lakes in southeast Missouri (Frisco, Pine Forest, and Bray Area lakes [Phelps County], and Cypress and Blue ponds [Bollinger County]) were cored for paleolimnological studies. Cores were evaluated for their sedimentology, palynology, and geochemistry. In two of these lakes (Bray Area and Pine Forest lakes) the planktonic algae were also studied in the water column, along with ecological parameters. Algae in the sediments were compared to algae in the water to understand the resistance of different species to decay, and a suggested methodology for this work is described. Reconstructions of the past environments around each lake were created …

Advancing Microalgae Culturing Via Bubble Dynamics, Mass Transfer, And Dynamic Growth Investigations, Aastha Ojha

Doctoral Dissertations

"The major hindrances to large scale cultivation of microalgae are the problems associated with the design, operation, and scale-up of airlift photobioreactors (PBRs), due to a lack of a comprehensive understanding of the gas-liquid interaction process in real microalgae cultures. Thus, the overall objective of this work is to advance the fundamental understanding of microalgae culturing via gas holdup, bubble dynamics, mass transfer, and dynamic growth investigations.

First, a four-point optical fiber probe technique was employed to study the local gas holdup, and bubble dynamics properties such as bubble passage frequency, chord length and bubble velocity distribution, and interfacial area …

Analysis And Mitigation Of Wellbore Breakout And Fracturing, Reza Rahimi

Doctoral Dissertations

"Mechanical wellbore integrity problems while drilling are mainly due to wellbore shear failure or tensile failure. To ensure wellbore integrity, breakout and fracture geomechanical analysis is conducted to estimate minimum and maximum drilling fluid densities. Currently, there is no agreement as to which rock failure criterion to use for estimating breakout or fracture criteria to use for analyzing drilling induced fractures. However, when wellbore integrity issues arise while drilling, mitigation strategies can be applied to rectify these problems.

This dissertation analyzes criteria for wellbore breakout and fracturing. Also, mitigation strategies for breakout and fracturing while drilling were experimentally investigated. Thirteen …

Mechanisms For Improving Information Quality In Smartphone Crowdsensing Systems, Francesco Restuccia

Doctoral Dissertations

"Given its potential for a large variety of real-life applications, smartphone crowdsensing has recently gained tremendous attention from the research community. Smartphone crowdsensing is a paradigm that allows ordinary citizens to participate in large-scale sensing surveys by using user-friendly applications installed in their smartphones. In this way, fine-grained sensing information is obtained from smartphone users without employing fixed and expensive infrastructure, and with negligible maintenance costs.

Existing smartphone sensing systems depend completely on the participants' willingness to submit up-to-date and accurate information regarding the events being monitored. Therefore, it becomes paramount to scalably and effectively determine, enforce, and optimize the …