Engineering Commons^™

System Efficient Esd Design Concept For Soft Failures, Giorgi Maghlakelidze

Doctoral Dissertations

"This research covers the topic of developing a systematic methodology of studying electrostatic discharge (ESD)-induced soft failures. ESD-induced soft failures (SF) are non-destructive disruptions of the functionality of an electronic system. The soft failure robustness of a USB3 Gen 1 interface is investigated, modeled, and improved. The injection is performed directly using transmission line pulser (TLP) with varying: pulse width, amplitude, polarity. Characterization provides data for failure thresholds and a SPICE circuit model that describes the transient voltage and current at the victim. Using the injected current, the likelihood of a SF is predicted. ESD protection by transient voltage suppressor …

Design And Fabrication Of Field-Effect Iii-V Schottky Junction Solar Cells, Amirhossein Ghods

Doctoral Dissertations

“A new concept of field-effect photovoltaic devices with a focus on design and fabrication of single and multi-junction solar cells using III-V materials has been shown and proved. Schottky solar cells based on metal-(insulator)-semiconductor (M-I-S) structure have been designed and fabricated using various wide bandgap semiconductors, such as GaAs and Al_0.3Ga_0.7As. A secondary bias layer has been introduced to the device structure, in which it creates additional band bending and subsequently depletion region at the flat band regions on the top surface of the device. It should be mentioned that the bias layer is designed to …

Catalytic Utilization Of Carbon Dioxide As Renewable Feedstock For Production Of Chemicals And Fuels, Abbas Alaa Jawad

Doctoral Dissertations

"The utilization of CO₂ as a renewable feedstock for producing commodity chemicals and fuels is an interesting challenge to explore new concepts and opportunities in catalysis and industrial chemistry. This sustainable approach not only leads to production of useful chemicals, but also has the potential to mitigate anthropogenic CO₂ emissions to the atmosphere. CO₂ itself is a sustainable and inexhaustibly available carbon source, however, it is inextricably linked to its inherent inertness. It is a thermodynamically stable molecule (ΔG_f = -394.01 kJ.mol^-1) with high oxidation state, hence, reactions of CO₂ must be combined …

Studies On The Stability Of Plasma Proteins And Their Fragments, Paul Praveen Nakka

Doctoral Dissertations

“The stability of a protein-based biological drug is an important concern during processing, storage or patient administration. There are various forces which contribute to the stabilizing of proteins. Both hydrogen bonds and hydrophobic interactions play an important role in protein stability. Improper folding or misfolding of proteins leads to aggregation, which is a major problem found in the bioprocessing industry. The objectives of this research are: 1) to determine the effect of environmental factors such as pH, temperature, additives or salts, and cosolvents on the stability human serum albumin (HAS), which is the most abundant protein in plasma, 2) to …

Geophysical Characteristics Of Nickel And Copper Deposits In Wadi Al Khadra Prospect, Southwestern Of Saudi Arabia, Abdulrahman Ahmed Aljabbab

Doctoral Dissertations

“Three geophysical datasets (self-potential, magnetics, and time - domain electromagnetics) were acquired at Wadi Al Khadra Ni-Cu prospect in southwest Saudi Arabia, and were processed and interpreted for the Saudi Geological Survey. The primary objectives were to map the distribution of metallic mineralization, map structures, verify the integration of the geophysical interpretations and its signatures in conjunction with boreholes information, distinguish the similarities and differences in the integrated interpretation of geophysical data, and design optimal processing and interpretation data parameters. The self-potential tool was used to map the variation in natural surface potential differences to map lateral variations in the …

Behavior Of Negative Stiffness Metamaterial Systems In Structural Engineering Applications, Yasser Darwish

Doctoral Dissertations

“Metamaterial systems with negative stiffness behavior became a point of interest in many energy dissipation applications due to their ability to dissipate high levels of energy. Negative stiffness metamaterial elements can dissipate energy through non-linear elastic behavior when transferred from one stable mode of buckling to another. Hence, the ability of such elements to be reusable for multiple loading cycles exists. Such unique properties made the metamaterial systems a perfect candidate for structural applications such as impact protection of bridges against collision. This research provides innovative metamaterial shell structure that can exhibit negative stiffness behavior by deforming from one shape …

Complexities Observed During The Development Of A Rheological Testing Procedure For Small Cement Paste Samples, Aida Margarita Ley-Hernandez

Doctoral Dissertations

“Rheology has been widely used to describe the flow properties of fresh cement-based suspensions. The use of a rheometer to characterize these properties is not a straightforward task due to the dependency to different preparation conditions, mixing processes, testing procedures and measuring instruments employed. In addition, shear and time dependency of the material which undergoes chemical and physical particle bonding, caused by hydration of cement and flocculation. Nevertheless, the characterization and understanding of the rheological behavior of cement-based materials have become essential with the recent introduction of novel applications like digital construction in the field of civil engineering, among others. …

Operation And Analysis Of High-Voltage-Gain Dc-Dc Converters With Voltage Multipliers, Mohammad Rashed M. Altimania

Doctoral Dissertations

"This research analyzes and investigates the steady-state operations of four different high-voltage-gain step-up dc- dc converters to achieve a high gain. These topologies consist of a two-phase interleaved boost stage with three various voltage multiplier (VM) stages. The first stage of the first three topologies is the same, which is a two-phase interleaved boost stage implemented by using inductors. The first family used in this research is based on a modified Dickson charge pump voltage multiplier stage, and this family has been studied in discontinuous conduction mode (DCM). The second family relies on a non-inverting or inverting diode-capacitors voltage multiplier …

Observer-Based Event-Triggered And Set-Theoretic Neuro-Adaptive Controls For Constrained Uncertain Systems, Abdul Ghafoor

Doctoral Dissertations

"In this study, several new observer-based event-triggered and set-theoretic control schemes are presented to advance the state of the art in neuro-adaptive controls. In the first part, six new event-triggered neuro-adaptive control (ETNAC) schemes are presented for uncertain linear systems. These comprehensive designs offer flexibility to choose a design depending upon system performance requirements. Stability proofs for each scheme are presented and their performance is analyzed using benchmark examples. In the second part, the scope of the ETNAC is extended to uncertain nonlinear systems. It is applied to a case of precision formation flight of the microsatellites at the Sun-Earth/Moon …

Trajectory Control Of A Wheeled Robot Using Interaction Forces For Intuitive Overground Human-Robot Interaction, George Leno Holmes Jr.

Doctoral Dissertations

"Effective and intuitive physical human robot interaction (pHRI) requires an understanding of how humans communicate movement intentions with one another. It has been suggested that humans can guide another human by hand through complex tasks using force information only. However, no clear and applicable paradigm has been set forth to understand these relationships. While the human partner can readily understand and adhere to this expectation, it would be difficult for anyone to explain their intuitive motions with strict rules, algorithms, or steps. Uncovering such a procedural framework for the control of robotic systems to execute expected performance simply from force …

Modeling A Nuclear Research Reactor And Radiation Dose Estimation In An Accident Scenario, Abdulaleem Abdulmajeed Bugis

Doctoral Dissertations

“A detailed, flexible three-dimensional (3D) model of the Missouri S&T Reactor (MSTR) with a heterogeneous core geometry was developed using the Standardized Computer Analyses for Licensing Evaluation (SCALE). A Graphical User Interface (GUI) was developed for SCALE, which allows the user to generate an input file automatically. The SCALE model was validated with a Monte Carlo N-Particle Transport (MCNP) model of the MSTR. The validation process was based on the criticality calculations using the Criticality Safety Analysis Sequence (CSAS6). Three geometrical models were examined. The SCALE model that has the full detailed geometry showed a good agreement with the MCNP …

Effect Of Turbulence Model Closure Coefficient Uncertainty On Scramjet Flow Field Analysis, Martin Albert Di Stefano

Doctoral Dissertations

“The numerical modeling of supersonic combustion ramjet (scramjet) engine flow paths plays an important role in the design of hypersonic air-breathing propulsion systems. Due to the complexity of the flow field physics and limited experimental data, numerical models possess uncertainties which should be addressed to improve the prediction accuracy of the simulations. In this study, the effect of turbulence model closure coefficient uncertainty on the Reynolds-averaged Navier-Stokes solution of a scramjet isolator and scramjet strut fuel injector flow field is investigated with an uncertainty quantification and sensitivity analysis study for commonly used turbulence models. Turbulence models considered in this work …

Integrated Approach To Investigate The Wellbore Integrity Under Downhole Conditions, Weicheng Zhang

Doctoral Dissertations

“The integrity of the cement sheath is the key part to maintain zonal isolation and prevent the inter-zonal communication. Loads arising from multiple stages of wellbore life span may induce various modes of cement failure within the cement (disking and radial cracks) and at the cement-casing and the cement-formation interfaces (debonding fractures). This research utilizes the integrated laboratory and numerical approach to investigate the cement hardening process, to predict the cement failure under various loading conditions. An innovative experimental setup is established to measure the cement pore pressure variation during the hardening process under downhole conditions, and a staged 3D …

Enabling Flexibility Through Strategic Management Of Complex Engineering Systems, Walter Louis Barnes Ii

Doctoral Dissertations

”Flexibility is a highly desired attribute of many systems operating in changing or uncertain conditions. It is a common theme in complex systems to identify where flexibility is generated within a system and how to model the processes needed to maintain and sustain flexibility. The key research question that is addressed is: how do we create a new definition of workforce flexibility within a human-technology-artificial intelligence environment?

Workforce flexibility is the management of organizational labor capacities and capabilities in operational environments using a broad and diffuse set of tools and approaches to mitigate system imbalances caused by uncertainties or changes. …

Integrating Resilience Into Military Infrastructure Mission Assurance Assessments And Decision Making, John Richards

Doctoral Dissertations

“This research created the Mission Assurance Resilience Matrix, a decision framework that integrates existing infrastructure assessment methods with emerging resilience research to model resilience under uncertainty as part of a detailed infrastructure management system. This framework enables military decision makers to easily visualize deficiencies in infrastructure resilience and assess where to most efficiently allocate resources. This research further extends results by including modules on training and education as a component of the scope of work.

There are three significant contributions of this research. The first identifies the gaps of how and where modeling under uncertainty, infrastructure systems management, and resilient …

Geophysical Assessment Of The Lake Chesterfield Site, Missouri, Diya Ali Ahmad Alfuqara

Doctoral Dissertations

"Since construction of the Lake Chesterfield, Missouri in 1986, significant leaks have occurred causing the lake to lose substantive volumes of water. Mitigation efforts, have not solved the problem. Indeed, in June of 2017, the water level in Lake Chesterfield dropped at an alarmingly rapid rate. Prior to authorizing additional mitigation work, the Lake Chesterfield. Home Owners Association (LCHOA) decided to acquire geophysical data across the drained and dry lake bed. These information would help a geotechnical engineering firm determine the most appropriate mitigation plan.

In the summer of 2018, electrical resistivity tomography, multichannel analysis of surface wave, and spontaneous-potential …

Physical And Biological Factors Affecting Oxygen Transfer In The Activated Sludge Wastewater Treatment Process, Kenneth A. Campbell

Doctoral Dissertations

“The activated sludge (AS) process is widely utilized for wastewater treatment due to its versatility and general resiliency, but is energy intensive, requiring aeration and mixing energy inputs to maintain the biochemical reaction and optimize treatment performance. This study is focused on determining different factors that influence oxygen transfer and consequently its energy demand.

AS morphology, as described by the d₁₀, d₂₀, d₃₂, specific filament length (SFL), 30 min settleability (SV₃₀), etc., does influence the OTE. Filamentous organisms increase the hydrodynamic radius of suspended particles, which dilates mixed liquor apparent viscosity (µ …

Computational Model For Neural Architecture Search, Ram Deepak Gottapu

Doctoral Dissertations

"A long-standing goal in Deep Learning (DL) research is to design efficient architectures for a given dataset that are both accurate and computationally inexpensive. At present, designing deep learning architectures for a real-world application requires both human expertise and considerable effort as they are either handcrafted by careful experimentation or modified from a handful of existing models. This method is inefficient as the process of architecture design is highly time-consuming and computationally expensive.

The research presents an approach to automate the process of deep learning architecture design through a modeling procedure. In particular, it first introduces a framework that treats …

The Combined Toxic Effect Of Nanoparticles And Lead In The Presence Of Algae (Raphidocelis), Xuesong Liu

Doctoral Dissertations

"The elevated toxicity of toxic metals in the presence of nanoparticles (NPs) has raised significant concerns on the NP environmental safety. This research focuses on the impact of environmental conditions, specifically algae, on this type of toxicity. An indicator aquatic organism, Ceriodaphnia dubia (C. dubia), was used to examine the combined toxicity and toxicity mitigation from algae by monitoring its 24-h mortality. Four papers are included in this research, which focus on four aspects of the combined toxicity and the corresponding algae (Raphidocelis) impact. The first paper examines the algae impact on the combined toxicity of …

Experimental And Modeling Studies Using Packed Bed Reactors: Liquid Phase Ethylene Production By Hydrogenation Of Acetylene, Humayun Shariff

Doctoral Dissertations

"Gas-phase catalytic hydrogenation of acetylene to produce ethylene, commonly practiced in industries, has green oil formation, which leads to catalyst deactivation and sometimes reactor runaway risks due to high exothermicity. To overcome these issues as well as to increase the selectivity and conversion, liquid-phase hydrogenation of acetylene was investigated in packed bed reactors (PBR) using a commercial catalyst. The reactor performance of two-phase flow PBRs was assessed experimentally complemented by a validated mathematical model at different scales.

The selective hydrogenation of acetylene in the liquid phase over a commercial 0.5 wt% Pd/Al₂O₃ catalyst was investigated in a …

Minimizing The Detrimental Effects Of Hydro-Peaking On Riverbank Instability: The Lower Osage River Case, Wesam Sameer Mohammed-Ali

Doctoral Dissertations

"The fluctuation of water level downstream from dams due to hydropower flow releases negatively affects the riverbank stability. Therefore, this research aims to examine the feasibility of using an optimization technique to mitigate the riverbank instability resulting from the outflow variation of hydropower plants. The effects of the water releases from the Bagnell Dam were investigated by computing a series of safety factors for 78 cross sections along the 81-mile stretch of the lower Osage River in relation to outflow events by using the integrated BSTEM model incorporated into the HEC-RAS model. The 1-D sediment transport and unsteady flow in …

Experimental Investigation Of Ionic Liquid Mixtures For Electrospray Propulsion, Mitchell J. Wainwright

Doctoral Dissertations

"In recent years, there has been a dramatic increase in the number of small satellites (namely MicroSats, NanoSats, and CubeSats) in earth orbit; many of these are launched without propulsion systems. Multi-mode propulsion systems, capable of operating in either chemical or electric mode, have been proposed as attractive candidates for use in small satellites. Such systems are mass and volume optimal and flexible in terms of thrust requirements. Most previous work on multi-mode systems has focused on chemical mode performance.The work in this dissertation focuses on the electric mode performance of these propulsion systems.

The work in this research is …

Understanding The Deformation Mechanisms In Ni-Based Superalloys With Using Crystal Plasticity Finite Element Method, Tianju Chen

Doctoral Dissertations

“Ni-based superalloy is considered as a good candidate due to its excellent resistance to elevated temperature deformation for long term period application. Understanding the deformation and failure mechanisms of Ni-Based superalloys is very helpful for providing design guidelines for processing Ni-based superalloys. Experimental characterization indicates that the deformation mechanisms of Ni based superalloy is strongly microstructure dependent. Besides, damage transform from the void nucleation to the macro cracks by voids growth leading to the failure of the Ni-based superalloys are also showing strong microstructure sensitivity. Therefore, this work focuses on the prediction and comprehension of the deformation and void growth …

Development Of A System Architecture For The Prediction Of Student Success Using Machine Learning Techniques, Tatiana A. Cardona

Doctoral Dissertations

“ The goals of higher education have evolved through time based on the impact that technology development and industry have on productivity. Nowadays, jobs demand increased technical skills, and the supply of prepared personnel to assume those jobs is insufficient. The system of higher education needs to evaluate their practices to realize the potential of cultivating an educated and technically skilled workforce. Currently, completion rates at universities are too low to accomplish the aim of closing the workforce gap. Recent reports indicate that 40 percent of freshman at four-year public colleges will not graduate, and rates of completion are even …

Multi-Physics-Based Approach To Active Microwave Thermography, Seyed Ali Mirala

Doctoral Dissertations

“The goal of this work is to advance a novel nondestructive testing (NDT) method for controlled, rapid, and effective inspection of a structure through the integration of microwave NDT and thermography, referred to as Active Microwave Thermography (AMT). In AMT, the structure under test is exposed to microwave radiation and the thermal profile of the structure is monitored via a thermal camera in order to obtain desired information regarding the structure. This new technique is applicable across a wide range of NDT needs including detection of voids, delamination, water ingress, debonding, and cracks in numerous structures such as carbon fiber …

A Framework For A Successful Additive Repair System, Todd E. Sparks

Doctoral Dissertations

“The goal of this research is to generate a revolutionary improvement to the usability and usefulness of additive repair technology by integrating a set of tools into a seamless work flow. Insufficient automation in the current repair process is a huge hurdle in achieving cost-effective, reliable repairs. Many opportunities have been missed due to inconsistency, quality issues and lack of robustness and flexibility. The present work addresses deficiencies in preparatory steps such as 2D and 3D geometry processing, parameter estimation, and path planning as well as on-machine execution of the path plan. The bulk of the effort is focused on …

Accurate Modeling Techniques For Power Delivery, Jingdong Sun

Doctoral Dissertations

“Power delivery is essential in electronic systems to provide reliable power from voltage sources to load devices. Driven by the ambitious user demands and technology evolutions, the power delivery design is posed serious challenges. In this work, we focus on modeling two types of power delivery paths: the power distribution network (PDN) and the wireless power transfer (WPT) system.

For the modeling of PDN, a novel pattern-based analytical method is proposed for PCB-level PDN impedance calculations, which constructs an equivalent circuit with one-to-one correspondences to the PCB’s physical structure. A practical modeling methodology is also introduced to optimize the PDN …

Geo-Engineered Induced Seismicity And The Effects On Federal Infrastructure, Merissa L. Zuzulock

Doctoral Dissertations

“The study of human-induced seismicity and the effects on civil engineering systems are not completely understood or often studied. Moreover, existing studies are focused on the cause of the seismicity and not on the potential damage to infrastructure from these seismic events. There are recent studies that are beginning to focus on shallow induced seismic activity and the effects on infrastructure by establishing innovative ways to quantify that damage. These studies that focus on the potential damage neglect to included considerations for small magnitude cluster events. As geo-induced seismic events increase, soil fatigue becomes of greater concern to structures within …

Bond Behavior Of Advanced Fiber Reinforced Composite-Concrete Joints, Xingxing Zou

Doctoral Dissertations

“Externally bonding advanced composite materials to concrete structures is an effective way to improve their strength, ductility, and durability. The interfacial bond behavior is fundamental to understand the overall structural performance of concrete structures strengthened with advanced composite materials. This study includes a comprehensive investigation of the bond behavior of composite-concrete joints with different fiber reinforced composite types. First, a direct approach to determine the bond-slip relationship for fiber reinforced cementitious matrix (FRCM)-concrete joints based on fiber strain measurements was proposed. Then, an analytical solution to predict the full-range response of FRCM-concrete joints was derived by assuming a trilinear bond-slip …

An Approach To System Of Systems Resiliency Using Architecture And Agent-Based Behavioral Modeling, Paulette Bootz Acheson

Doctoral Dissertations

”In today’s world it is no longer a question of whether a system will be compromised but when the system will be compromised. Consider the recent compromise of the Democratic National Committee (DNC) and Hillary Clinton emails as well as the multiple Yahoo breaches and the break into the Target customer database. The list of exploited vulnerabilities and successful cyber-attacks goes on and on. Because of the amount and frequency of the cyber-attacks, resiliency has taken on a whole new meaning. There is a new perspective within defense to consider resiliency in terms of Mission Success.

This research develops a …