Engineering Commons^™

Understanding Corrosion Of Ni₃(Si,Nb) Alloys In Hot Sulfuric Acid, Jen-Hsien Hsu

Doctoral Dissertations

"The Sulfur-Iodine thermochemical cycle has been proposed as a method for producing large quantities of hydrogen gas from water. However, the extreme operating environments involved limit the possible materials for construction.

Through proper heat treatment and composition control, the modified patented Ni₃(Si,Nb) alloy keeps high temperature strength to greater than 750⁰C and can be deformed by cold rolling more than 50% using multiple passes and intermediate anneals. The corrosion resistance is reproducible and maintains less than 5 mpy for a broad range of boiling sulfuric acid concentrations, including 70 wt%.

In the boiling 70 wt% sulfuric acid corrosion tests, kinetic …

Ceramic Dielectrics For High Energy Density Capacity Application, Sheng Chao

Doctoral Dissertations

"The objective of this dissertation is to investigate the relationship between the processing parameters, microstructural development, defect chemistry and electrical properties of titanium oxide (TiO₂) dielectrics for high energy density capacitor applications. The effects of aliovalent dopants on the dielectric properties of TiO₂ ceramics were investigated, aiming to further improve the desired dielectric properties especially at elevated temperatures (up to 200°C). Due to the segregation of acceptor type impurities in the starting powders, space charge polarization took place in TiO₂ ceramics with relative large grain size (>̲500nm), leading to high dielectric loss and low energy storage efficiency. Increased ratio …

Sensor Data-Based Decision Making, Ahmet Soylemezoglu

Doctoral Dissertations

"Increasing globalization and growing industrial system complexity has amplified the interest in the use of information provided by sensors as a means of improving overall manufacturing system performance and maintainability. However, utilization of sensors can only be effective if the real-time data can be integrated into the necessary business processes, such as production planning, scheduling and execution systems. This integration requires the development of intelligent decision making models that can effectively process the sensor data into information and suggest appropriate actions. To be able to improve the performance of a system, the health of the system also needs to be …

Advanced Dynamic Response Improvement Methods For Dc-Dc Power Electronic Converters, Lisheng Shi

Doctoral Dissertations

"Dc-dc power electronic converters supplying electric power to digital processors, data centers, and telecommunication systems are required to exhibit a fast dynamic response in response to their instantaneous electric load variations. This requirement is becoming more and more stringent as the operating voltage of such loads is continuously reducing. This voltage level reduction has reached a point where conventional control approaches can barely meet the dynamic response demanded by such loads. In order to overcome this issue, several approaches focusing on the dynamic response improvement for dc-dc converters have been proposed in the literature. Unfortunately, most of them have at …

The Functionalization Of Single Wall Carbon Nanotubes For Bioapplications, Pu Zhang

Doctoral Dissertations

"In the past few years, the functionalization of carbon nanotubes has received considerable attention due to their extraordinary mechanical, electrical, optical and thermal properties. Using single wall carbon nanotube as a platform in bioanalytical and biomedical applications has also been extensively studied. This dissertation consists of four papers. In the first paper, various methods to functionalize single wall carbon nanotubes with immobilized enzyme for bioanalytical application were investigated. It was found that the covalent functionalization method was not an ideal methodology for enzyme addition neither in terms of enzyme loading amount nor activity retention compared to other methods. Use of …

Low-Thrust Control Of Orbital Elements, Nathan Harl

Doctoral Dissertations

"This dissertation presents a method for controlling the orbital elements of a spacecraft using continuous low-thrust systems. The method involves the use of a general performance index, which is designed to minimize the difference between the instantaneous orbital elements of a spacecraft and some desired set of orbital elements. Due to the generality of the controller design, the resultant controller can be applied to a wide variety of scenarios about various bodies in space. To minimize the designed performance index, a shooting method and a Sequential Quadratic Programming algorithm are utilized and compared.

The primary application of the general controller …

Scaled Experimental Study On Excavation Of Lunar Regolith With Rakes/Rippers And Flat Blade, Masafumi Iai

Doctoral Dissertations

"As humanity's activities expand to the Moon, Mars, and other extra-terrestrial bodies, it will be necessary to use local resources rather than bringing everything from the Earth. This concept is called In-Situ Resource Utilization (ISRU), which starts with excavation and earthmoving. The present study focuses on loosening and moving of the lunar regolith by a ripper (or rake) and a wide blade with consideration of gravel content. After characterizing the lunar regolith and two of its simulants (JSC-1A and FJS-1), the relationship between the excavation energy and different conditions, namely gravel content, relative density, and tine spacing on a rake, …

Robust Frequency-Domain Turbo Equalization For Multiple-Input Multiple-Output (Mimo) Wireless Communications, Jian Zhang

Doctoral Dissertations

"This dissertation investigates single carrier frequency-domain equalization (SC-FDE) with multiple-input multiple-output (MIMO) channels for radio frequency (RF) and underwater acoustic (UWA) wireless communications. It consists of five papers, selected from a total of 13 publications. Each paper focuses on a specific technical challenge of the SC-FDE MIMO system. The first paper proposes an improved frequency-domain channel estimation method based on interpolation to track fast time-varying fading channels using a small amount of training symbols in a large data block. The second paper addresses the carrier frequency offset (CFO) problem using a new group-wise phase estimation and compensation algorithm to combat …

Intelligent Power System Operation In An Uncertain Environment, Yusuf Yare

Doctoral Dissertations

"This dissertation presents some challenging problems in power system operations. The efficacy of a heuristic method, namely, modified discrete particle swarm optimization (MDPSO) algorithm is illustrated and compared with other methods by solving the reliability based generator maintenance scheduling (GMS) optimization problem of a practical hydrothermal power system. The concept of multiple swarms is incorporated into the MDPSO algorithm to form a robust multiple swarms-modified particle swarm optimization (MS-MDPSO) algorithm and applied to solving the GMS problem on two power systems. Heuristic methods are proposed to circumvent the problems of imposed non-smooth assumptions common with the classical approaches in solving …

Borate Based Bioactive Glass Scaffolds For Hard And Soft Tissue Engineering, Steven B. Jung

Doctoral Dissertations

"The main objectives of this dissertation were to evaluate bioactive borate glass scaffolds for hard and soft tissue applications and determine the potential toxicity of the borate glasses on the adjacent and systemic tissues. Porous randomly oriented fiber scaffolds composed of bioactive borate glass were implanted in subcutaneous soft tissue sites and in calvaria defects of laboratory rats and no signs of toxicity (necrotic tissue, increase in macrophages or other immune cells) were detected in any of the adjacent tissues (hard or soft). Systemic organs (kidney and liver) of laboratory rats implanted with bioactive borate scaffolds were analyzed for possible …

Identifying Multiple Steady States In The Design Of Reactive Distillation Processes, Thomas Karl Mills

Doctoral Dissertations

"Global homotopy continuation is used to identify multiple steady states in ideal reactive flash and reactive distillation systems involving a reaction of the form A+B [symbol for <--> C taking place in the liquid phase. The choice of specifications has an influence on the existence of multiple solutions for both the flash and the column. For the flash, specification of the heat input or withdrawal can give rise to multiplicities while specification of the split fraction does not. Specification of one internal energy balance variable and one external material balance variable does not produce multiplicities in the column; however, specification of …

Dynamic Reconfiguration And Control Of Smart Power Systems, Pinaki Mitra

Doctoral Dissertations

"To address the increasing demand and complexity, modern power systems need intelligence at almost all levels which can transform them into 'smart' power systems. The term 'smart power systems' not only refers to the terrestrial power systems with a significant penetration of distributed energy resources and energy storage such as plug-in electric vehicle parking lots (SmartParks), but also includes other isolated power systems, such as the power systems of naval electric ships. The research presented in this dissertation contributes to the dynamic reconfiguration and control of both terrestrial and ship power system with the application of computational intelligence methods.

In …

Emerging Technology Supply Chain Model For Additive Manufacturing, David M. Dietrich

Doctoral Dissertations

"This research concerns developing an emerging manufacturing technology, additive manufacturing (AM), into a mature and flexible, cost-effective supply chain for aerospace production. The field of additive manufacturing is an approach to low volume manufacturing of plastic or metal parts using three dimensional Computer Aided Design data. As an emerging technology, AM's supply chain is not established compared to conventional aerospace manufacturing technologies, such as injection molding or composite manufacturing. Technical and business challenges limit the robustness of the additive manufacturing system for aerospace applications. The overall intent of this research is to: first, provide an introduction to two main polymer …

Improvised Explosive Device Crater Repair For Enduring Route Remediation, Daniel Roman Kienitz

Doctoral Dissertations

"Recent road repairs performed on main supply routes (MSRs) and alternative supply routes (ASRs) in Iraq and Afghanistan revealed several deficiencies in current repair techniques. Temporary solutions such as aggregate backfill, asphalt, and traditional concrete repairs were unacceptable due to the ease of emplacement of additional improvised explosive devices (IEDs). In addition to the threat of IED placement, the threat from exposure of the repair teams to enemy attack during placement and curing was substantial. In order to address these problems, this project investigated rapid hardening materials for improvised explosive device crater repair. A laboratory test program along with performance …

Dependency Of Machinability In Gray Cast Iron On Nitride-Induced Age Strengthening, Jared Teague

Doctoral Dissertations

"Work of previous researchers has suggested that room temperature age strengthening in gray cast irons improves machinability. Verification and quantification of the machinability improvement is important to industry. Improved machinability will reduce overall manufacturing costs and reduce raw material consumption by decreasing the rate at which tools are replaced. Experimental work was performed to determine a connection between improved machinability in gray cast iron and changes in machining mechanics. An industrial tool wear study verified that age strengthening improved machinability by reducing tool wear to less than one-quarter of the unaged value. Laboratory tests on iron castings from the same …

Dead Time And Count Loss Determination For Radiation Detection Systems In High Count Rate Applications, Amol Patil

Doctoral Dissertations

"This research is focused on dead time and the subsequent count loss estimation in radiation detection systems. The dead time is the minimum amount of time required between two events to permit detection of those events individually by a radiation detection system. If events occur during the system dead time, they are lost. Such lost information can be important in many applications including high-precision spectroscopy, positron emission tomography (PET), and the scanning of spent nuclear fuel. Understanding of the behavior of radiation detection systems is important; thus this work included a comprehensive review of dead time and pulse pile-up models …

Analysis Of Laminated Architectural Glazing Subjected To Combined Wind And Debris Impact Loading, Mahesh Shibarooru Shetty

Doctoral Dissertations

"Laminated glazing has been a popular form of window glazing in recent years and is found to be effective during extreme weather conditions like hurricane. Laminated glass is composed of two glass layers with a polymer as an interlayer. The main objective of this work involves studying the stress response, failure and damage analysis of rectangular laminated architectural glazing against combined wind and windborne debris impact. Here both small-hard (like roof gravel) and large-soft (like timber) windborne debris are considered. The stress response of the rectangular laminated architectural glazing was modeled using the finite element code ABAQUS. The effect of …

A Case Study In Quantitative Analysis Of Cyber-Physical Systems: Reliability Of The Smart Grid, Ayman Z. Faza

Doctoral Dissertations

"A cyber-physical system is the integration of a physical infrastructure with a cyber infrastructure, which provides control over its physical counterpart. The goal is to improve certain aspects of the physical infrastructure, such as its reliability. The Smart Grid, in which intelligent cyber control is added to improve the operation of the traditional power grid, is a prime example of a cyber-physical system. Quantitative models are needed in order to better understand the benefits and risks of adding intelligence to physical systems. To this end, we have developed an integrated cyber-physical reliability model, with a focus on the Smart Grid …

Optimal Excitation Controllers, And Location And Sizing Of Energy Storage For All-Electric Ship Power System, Chuan Yan

Doctoral Dissertations

"The Navy's future all-electric ship power system is based on the integrated power system (IPS) architecture consisting of power generation, propulsion systems, hydrodynamics, and DC zonal electric distribution system (DC-ZEDS). To improve the power quality, optimal excitation systems, and optimal location and sizing of energy storage modules (ESMs) are studied. In this dissertation, clonal selection algorithm (CSA) based controller design is firstly introduced. CSA based controller design shows better exploitation ability with relatively long search time when compared to a particle swarm optimization (PSO) based design. Furthermore, 'optimal' small population PSO (SPPSO) based excitation controller is introduced. Parameter sensitivity analysis …

Behavior Of Externally Bonded Fiber Reinforced Polymer Systems For Strengthening Concrete Girders In Shear, Michael Shawn Murphy

Doctoral Dissertations

"Deficiencies in shear resistance are a primary concern in concrete members due to the sudden and unpredictable nature of shear failures. Shear deficiencies in concrete structures can arise due to improper design, long-term deterioration, man-made damages, increases in loads, or as a result of over strengthening in flexure. A number of shear strengthening techniques offer a cost effective means for restoring or enhancing the shear capacity of a concrete member. The use of externally bonded fiber reinforced polymers (FRP) is one such technique that has gained recent recognition for its high strength-to-weight ratio and simplicity of application. The development of …

Computational Intelligence Methods In Wireless Sensor Networks, Raghavendra V. Kulkarni

Doctoral Dissertations

"Wireless sensor networks (WSNs) are networks of autonomous nodes that sense, compute and communicate in order to monitor an environment collectively. Ad hoc deployment, dynamic environment and resource constraints in nodes need to be considered while addressing WSN challenges such as deployment, localization, routing and scheduling. Adaptive mechanisms that exhibit intelligent behavior in complex and dynamic environments are desirable to address these challenges. The potential of computational intelligence ( CI) based approaches for addressing WSN challenges is investigated in this study. Contributions of this dissertation are in the following three areas: critical literature analysis, new architectures and approaches, and new …

Application Of Quality Engineering To Investment Portfolio Selection And Optimization, Vivek Kulinchandra Jikar

Doctoral Dissertations

"The Taguchi System of Quality Engineering (TSQE) is a widely accepted philosophy and set of tools and techniques to rapidly design and manufacture high quality, low cost products and services. It is heavily focused on creating stable system designs that allow a product or system to perform as desired by customers in the environment of their choice. This research demonstrates the power of the TSQE to manage an investment portfolio. In particular, it uses the concept of design stability to select investments and optimize portfolios. It proposes a new design stability-based investment screening metric and discusses its application. Further, this …

Characterization Of Diamond Thin Films And Related Materials, Travis K. Mckindra

Doctoral Dissertations

"Thin carbon films including sputtered deposited graphite and CO₂ laser-assisted combustion-flame deposited graphite and diamond thin films were characterized using optical and electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Amorphous carbon thin films were deposited by DC magnetron sputtering using Ar/O₂ gases. The film morphology changed with the oxygen content. The deposition rate decreased as the amount of oxygen increased due to oxygen reacting with the growing film. The use of oxygen in the working gas enhanced the crystalline nature of the films. Graphite was deposited on WC substrates by a CO₂ laser-assisted O₂/C₂H₂ combustion-flame method. Two distinct microstructural areas …

Phase Equilibria In Iron Phosphate System, Liying Zhang

Doctoral Dissertations

"The main objectives of this research were to synthesize iron phosphate compounds, study phase equilibria in the iron phosphate system, focusing on the glass forming area, and investigate glass formability and properties based on the liquidus regions. Twelve iron phosphate compounds were successfully prepared and studied in terms of liquidus temperature or decomposition behavior. The liquidus surface of the Fe₃PO₇- Fe(PO₃)₃ system was re-determined and found to be significantly different from that originally presented by Wentrup in 1935. Eutectic points exist at 58.0 mole% Fe₂O₃ (1070⁰C), 42.7 mole% Fe₂O₃ (925°C), and 37.0 mole% Fe₂O₃ (907°C). The latter two eutectic points …

Adaptive Resource Allocation For Cognitive Wireless Ad Hoc Networks, Behdis Eslamnour

Doctoral Dissertations

"Widespread use of resource constrained wireless ad hoc networks requires careful management of the network resources in order to maximize the utilization. In cognitive wireless networks, resources such as spectrum, energy, communication links/paths, time, space, modulation scheme, have to be managed to maintain quality of service (QoS). Therefore in the first paper, a distributed dynamic channel allocation scheme is proposed for multi-channel wireless ad hoc networks with single-radio nodes. The proposed learning scheme adapts the probabilities of selecting each channel as a function of the error in the performance index at each step.

Due to frequent changes in topology and …

Development Of Embedded Modulated Scatterer Technique: Single- And Dual-Loaded Scatterers, Kristen M. Donnell

Doctoral Dissertations

"Health monitoring of infrastructure is an important ongoing issue. Therefore, it is important that a cost-effective and practical method for evaluating complex composite structures be developed. A promising microwave-based embedded sensor technology is developed based on the Modulated Scatterer Technique (MST). MST is based on illuminating a probe, commonly a dipole antenna loaded with a PIN diode (also referred to as a single-loaded scatterer, or SLS), with an electromagnetic wave. This impinging wave induces a current along the scatterer length, which causes a scattered field to be reradiated. Modulating the PIN diode also modulates the signal scattered by the probe, …

Electrochemical Characterization Of Cerium-Based Conversion Coatings On Al 7075-T6, Simon Joshi

Doctoral Dissertations

"This research used electrochemical techniques to characterize the deposition and corrosion protection behavior of cerium-based conversion coatings on AI 7075-T6. Alkaline activation decreased native oxide impedance (5.9 kΩ-cm²) by ~25% promoting deposition of 250-500 mn coatings. Activation in NaOH solutions deposited coatings with large cracks and craters, whereas Na₂C0₃ activation resulted in uniform coatings, i.e., fewer cracks and almost no craters. Uniformly deposited coatings exhibited better cathodic inhibition and higher impedance (~200 kΩ-cm²) than on NaOH activated substrates (~100 kΩ-cm²). Subsurface crevices, caused by Cl⁻ and H₂O₂ in the deposition solution, were found under large cracks and craters. Thus, Na₂CO₃ …

Synthesis And Characterization Of Metal Decorated Bamboo Structured Carbon Nanotubes For Hydrogen Storage, Sean Charles Mickey

Doctoral Dissertations

"Although hydrogen has been considered as a viable alternative fuel, the storage systems used to contain the hydrogen must be improved for large scale use. A variety of conceivable storage options exist ranging from compressed gas, cryogenic liquid, chemical solid state storage, and adsorptive surfaces. Carbon nanotubes (CNTs) provide a potentially viable option for hydrogen storage applications as a high surface area, lightweight media for adsorptive storage, but do not efficiently store hydrogen at ambient temperatures. Metal hydrides, on the other hand, are able to store large weight percents of hydrogen in a chemical solid state, but generally have unfavorable …

Fluid Flow Related Phenomena And Inclusion Motion In Continuous Casting Strands, Yufeng Wang

Doctoral Dissertations

"To improve the efficiency of the continuous casting process and the quality of its products, this dissertation mainly investigated fluid flow related phenomena and inclusion motion in continuous casting. Mathematical simulation was performed for this purpose. Both a slab caster and a billet caster were investigated. In the study of the slab caster, the application of electromagnetic brake field on the slab mold was evaluated. The results indicated that the magnetic force decelerated the high speed steel jet, stabilized the top fluctuation, and prevented the bias flow inside the mold. The other study of this slab caster involved the fluid …

Characterization Of The Corrosion Protection Mechanism Of Cerium-Based Conversion Coatings On High Strength Aluminum Alloys, William R. Pinc

Doctoral Dissertations

"The aim of the work presented in this dissertation is to investigate the corrosion protection mechanism of cerium-based conversion coatings ( CeCCs) used in the corrosion protection of high strength aluminum alloys. The corrosion resistance of CeCCs involves two general mechanisms; barrier and active. The barrier protection mechanism was influenced by processing parameters, specifically surface preparation, post-treatment, and the use of gelatin. Post-treatment and the addition of gelatin to the coating solution resulted in fewer cracks and transformation of the coating to CeP0₄, which increased the corrosion resistance by improving the barrier aspect of CeCCs. CeCCs were found to best …