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Plastic Strain Accommodation And Acoustic Emission During Melting Of Embedded Indium Particles In Aluminum, Michael M. Kuba

Masters Theses

"Melting of micron-sized (0.2 to 3 µm diameter) indium particles embedded in an aluminum matrix was discovered to produce acoustic emission. Melting of embedded immiscible particles produces a pure dilation during the phase transformation and has no long-range diffusion field to control the speed of transformation. It was found that acoustic emission can no longer be considered as a criterion of displacive transformations and that melting of micron-sized embedded particles is strain energy controlled. Acoustic emission was confirmed to result from the rapid relaxation of aluminum around indium particles embedded on grain boundaries. Prismatic punching of dislocation loops is proposed …

Maximum Power Point Tracking Control Of Hydrokinetic Turbine And Low-Speed High-Thrust Permanent Magnet Generator Design, Hailong Zhou

Masters Theses

"River-based hydrokinetic turbine power generation systems have been studied to introduce an effective energy flow control method. Hydrokinetic turbine systems share a lot of similarities with wind turbine systems in terms of physical principles of operation, electrical hardware, and variable speed capability for optimal energy extraction. A multipole permanent magnet synchronous generator is used to generate electric power because of its ability to reach high power density and high thrust at low speed. A 3-phase diode rectifier is used to convert AC power from the generator into DC power and a boost converter is used to implement energy flow control. …

Physiochemical Characteristics Contributing To The Cytotoxicity Of Transition Metal Oxides, Chi-Heng Wu

Masters Theses

"In the past ten years nanotechnology has not only evolved to play a prominent role in our economy but also increased the concern over potential adverse effects caused by nanomaterials to human health and the environment. Nanotoxicity is to understand the nature and origin of the toxicity imposed by nanomaterials. Studies from our laboratory have shown that nanoparticle induces oxidative stress, perturbs calcium homeostasis, alter gene expression, and produces pro-inflammatory responses. We also identified a trend of toxicity: TiO₂ < Cr₂O₃ < Fe₂O₃ < Mn₂O₃ < NiO < ZnO < CuO. We then asked a question: what are physiochemical factors of transition metal nanoparticles that contributed to this increasing cytotoxicity. In this thesis I investigated the correlation between physicochemical properties and toxicity of the transition metal oxides in the 4th Period of the Periodic Table of Elements. Particle size, BET surface area, point of zero charge, metal dissolution, and degree of surface adsorption of transition metal oxide nanoparticles were measured. There were no increasing trends in both particle size and specific surface area. The point of zero charge showed an increasing trend as TiO₂ < Cr₂O₃ < Fe₂O₃ < NiO < CuO = ZnO < Mn₂O₃. The number of available binding sites of nanoparticle showed an increasing trend as Cr₂O₃ > ZnO > CuO > NiO > Fe₂O₃ > Mn₂O₃ > TiO₂. The degree of adsorption on the surface of nanoparticles showed an increasing trend with atomic …

Blast And Impact Resistance Of "Long" Carbon Fiber Reinforced Concrete, Darwin Ishmael Keener

Masters Theses

"Traditional reinforced concrete is one of the most commonly used materials for protective structures. However, conventional reinforced concrete (RC) is susceptible to significant spalling (small to medium sized chunks of concrete detaching from the original member) during blast events. The force of the blast turns spalled concrete into projectiles, resulting in secondary fragmentation. Furthermore, the concrete debris makes for difficult and uncertain footing. Both phenomena endanger personnel and complicate post-blast recovery efforts. Changes need to be made to conventional reinforced concrete structures to improve their blast and impact survivability and fragmentation resistance in order to protect personnel and facilitate post-blast …

A Novel Cantilever For Bi-Harmonic Atomic Force Microscopy, Muthukumaran Loganathan

Masters Theses

"Tapping mode (TM) AFM is a popularly used AFM technique in which an oscillating sharp tip mounted on a micro cantilever is used to probe the surface of interest with nanoscale resolution by making intermittent (tapping) contact with the surface. Any change in surface profile affects the tip amplitude, and is detectable only if it results in an amplitude change that is significant enough to be measured by the laser detector. Hence, it is desirable to have a micro cantilever that is sensitive to surface changes so as to provide sharper images and better surface resolution.

In the first part …

The Effect Of Sulfur On Structure And Conversion Of Bioactive Borate Glasses, Ali Mohammadkhah

Masters Theses

"The effect of sulfur on glass structure and the conversion process of bioactive CaO-LI₂O-B₂O₃ glasses were studied. One glass without and two glasses with different amounts of sulfur were made using conventional melting and dry quenching techniques. These glasses reacted with a phosphate solution and converted to hydroxyapatite. Particles (150-355µm) were reacted in 0.25 and 0.5 molar K₂HPO₄ solutions at 37⁰C for 2 to 96 hours. The weight loss of the particles and the final pH of the solution were measured. The weight loss measurements indicated that the reaction rate increases with …

Transient Growth And Instability Control Using Iteration-Varying Filter Ilc In Flexible Dual Flywheel System, Tong Mu

Masters Theses

"In the field of precision motion control, many industrial systems have flexible modes. This is especially true for very high performance nanopositioning systems where traditional bearing systems are replaced with flexible structures in order to eliminate sliding friction. The precision motion control is difficult in flexible systems because the rapid phase transition around the resonant frequency must be accurately modeled in order to actively control the resonant motion. In order to experimentally study the effectiveness of various control algorithms on flexible systems, a dual-flywheel flexible system is constructed. The mechatronics system design strategy is presented in this thesis. The control …

Synthesis Of Nickel Nanoparticles By Gamma-Radiation And Femtosecond Laser Ablation, Vivek Murlidhar Rao

Masters Theses

"Nickel nanoparticles were synthesized by gamma-radiation and femtosecond laser ablation. Aqueous precursors were prepared by uniformly dispersing nickel chloride in a 2:1 ratio of water and isopropanol. Stabilizers employed were Sodium Dodecyl Sulfate (SDS) and Poly Vinyl Pyrrolidone (PVP). Gamma-ray radiolysis of aqueous nickel precursors was investigated as a reducing agent for nickel cations to form atomic seeds for nucleation on multi-walled carbon nanotubes (MWCNTs). 30-60kGy was the dosage used in increments of 10kGy, at a rate of 10kGy/hr. Isopropanol was added to consume the excess of oxidizing species produced by irradiation and form stable secondary radicals. The influence of …

Logistics Modeling And Project Management Practices For Contingency Basing, Amanda Jo Gealy

Masters Theses

"Contingency basing is a critical factor in mission success but requires significant logistical and commander support. Designing and constructing a camp that is safe, secure, and self-sustaining can be a difficult task for a Contingency Basing engineering manager. The infrastructure for basic needs such as electricity, fuel, water, food, and waste management is critical and needs to be flexible.

This research focuses on assisting the Contingency Basing engineering manager in designing and constructing a feasible base camp using project management and modeling tools. Measuring scalability and resiliency with in the contingency base was studied as well. The methodology concentrates on …

Decreasing Time To Market For A Medical Device: New Methods For The Product Development Process, Kelly Marie Davis

Doctoral Dissertations

"Through an example, led at a leading medical device company, this dissertation will demonstrate that by applying certain lean principals and tools to the development of a medical device, shortened development times can be obtained. The two papers presented in the dissertation will fill a gap in current literature. Literature presents lean techniques and applications used in many different industries. But, due to the uniqueness of the medical device industry, these general techniques are not ideal. New methods will be used and validated at a medical device company, Covidien. Instead of trying to implement many general lean principals to their …

Design And Experimental Study Of Turbo Equalization For Multiple Antenna Systems, Amirhossein Rafati

Doctoral Dissertations

"Multiple-input multiple-output (MIMO) wireless communication systems have attracted a lot of interest in the past decade due to their capability in delivering high spectral efficiency as well as their robust performance against fading. In MIMO inter-symbol interference (lSI) channels, a severe interference problem occurs due to the lSI and co-channel interference. Thus, the error propagation problem becomes more serious, and its mitigation has to be considered when designing the receiver. In this regard, a turbo equalizer which exchanges soft information between the equalizer and the decoder has been shown to be an effective method to combat the lSI caused by …

Discrete Fiber-Reinforced Polyurea Systems For Infrastructure Strengthening And Blast Mitigation, Natalia L. Carey

Doctoral Dissertations

"The research presented in this dissertation focused on evaluating the effectiveness of various blast mitigation materials and coating technologies to be used for enhancing blast resistance of structural members. Mechanical properties and blast mitigation performance of different discrete fiber-reinforced polyurea (DFRP) systems were investigated through experimental and analytical work. Four technical papers discuss the research efforts conducted within this dissertation.

The first paper examined the development and characterization of different DFRP systems for infrastructure strengthening and blast retrofit. The behavior of various systems which consisted of chopped E-glass fibers discretely integrated in with the polyurea matrix was evaluated through coupon …

Economics And Finance On Time Scales, Julius Severin Heim

Doctoral Dissertations

"This thesis consists of 6 papers that investigate models in economics and finance based on so-called dynamic equations on time scales. The first paper covers multiplier-accelerator models that can be described by linear second-order dynamic equations. The possibility of taxes as well as the possibility of foreign trade is taken into consideration. The second paper discusses cobweb models, which describe cyclical supply and demand in markets, where the supply is determined before the observation of the price. Cobweb models that can be formulated with first-order linear, second-order linear, and nonlinear dynamic equations are being considered. The third and fourth papers …

Development Of Third Generation Advanced High Strength Steels, Meghan C. Mcgrath

Doctoral Dissertations

"Lightweight duplex steels with combinations of either bainite, acicular ferrite, and austenite or martensite and austenite were investigated as third generation advanced high strength steels targeted for automotive applications. Large additions of manganese (>13 wt%) and carbon (

Duplex steels with different volume fractions of primary δ -ferrite were used to study the crystallography of austenite formed during the peritectic reaction. Solute profiles across the peritectic interface showed aluminum segregated near the interface which promoted bainitic ferrite formation. Thermal treatments were used to manipulate the concentration and type of oxides and the ferrite plate density was found to correlate …

Fractal Oxidation Kinetics And Risk Evaluation Of Spontaneous Combustion In Coal Mines, Yutao Zhang

Doctoral Dissertations

"The spontaneous combustion of coal occurs when air supply is sufficient for the oxidation of coal and air velocity is insufficient for the dissipation of generated heat. Spontaneous combustion, if not eradicated immediately, may lead to coal ignition and even a full-blown fire. The fire may engulf a large area and spread further if they are not immediately attended to. This will not only endanger miners and mining operations, but also result in possible mine closures and even fatalities.

Porous structure has a significant effect on coal adsorption and spontaneous combustion. In this research, fractal theory was utilized to quantitatively …

Impact Of Plug-In Hybrid Electric Vehicles On The Power Grid In A Smart Environment, Zahra Darabi

Doctoral Dissertations

This dissertation focuses on the interactions between plug-in hybrid electric vehicles (PHEVs) and the power grid. This study has used the data available through the national household travel survey (NHTS) to obtain realistic information such as the arrival time of vehicles, miles driven, and vehicles types. After data manipulation, the aggregated PHEV charging load profiles (PCLP) have been developed. The results show that the peak of PCLP overlaps with the domestic load peak. In order to alleviate this issue, several charging policies have been developed and their impacts on PCLP have been investigated. As a next contribution, the data obtained …

Identification And Visualization Of Electromagnetic Coupling Paths & Nonlinear Capacitors For Esd Protection, Hongyu Li

Doctoral Dissertations

"The first topic of this dissertation focuses on developing methods to identify and visualize electromagnetic coupling paths. The basis of the approach is to utilize an analogy between electromagnetic energy flow and fluid flow. This allows one to apply the theories and algorithms of fluid dynamics to electromagnetics and thereby to visualize the electromagnetic energy flow. This in turn can be utilized to identify the electromagnetic coupling path.

The second topic of this dissertation investigates the nonlinearity of capacitors and suggests improved trade-off between electrostatic discharge (ESD) protection and data bandwidth by using the antiferroelectric (AFE) capacitors as ESD protection. …

Influence Of Temperature And Microstructural Modification On Formability Of Magnesium Alloys, Arun Mohan

Doctoral Dissertations

"The ß-precipitate free AZ31, ß-precipitate rich AZ91 and a few Mg-Y-Zn alloys were studied to understand the dependence of Mg formability on microstructural condition and temperature. Friction stir processing (FSP) was used to refine the grain size and to obtain desirable distribution of precipitates in the matrix. Since Mg alloys exhibit challenges in achieving room temperature formability, superplastic deformation was utilized. This work focused on high strain rate superplasticity (HSRS, ≥10⁻² s⁻¹) which is more attractive for industrial applications as compared to the slower rates of conventional superplasticity.

Thermally stable fine grains and pinning particles at HSRS temperatures were essential …

Handel's Maser-Solution Theory Of Ball Lightning: The Creation Of Stable Three-Dimensional Cavitons By An Atmospheric Maser With An Open Resonator, Glenn Andrew Carlson

Doctoral Dissertations

"This dissertation develops details of Handel's Maser-Soliton Theory of ball lightning. The atmosphere between a thundercloud and the Earth's surface is modeled as an idealized stable open resonator with water vapor as the active medium and the thundercloud and Earth's surface as reflecting surfaces. The stable resonator generates a maser beam that narrows to the beam waist at the Earth's surface, which is assumed to be planar. Two candidate rotational transitions are identified within the v₁v₂v₃ = 010 vibrational band of water having wavelengths of 13.9 cm and 1.12 cm, and relevant spectroscopic parameters are retrieved from the HITRAN 2008 …

Global Homotopy Continuation And Stability Analysis: Optimal Application To Chemical Engineering Design, David Anthony Harney

Doctoral Dissertations

"The design of chemical engineering process equipment routinely necessitates the solution of large systems of non-linear equations. The processing speed of standard desktop computers have allowed for equation-oriented process simulators to become commercially viable. For a fully equation-oriented simulator to be competitive with standard iterative solvers, a robust and reliable non-linear equation solver is required and standard Newton methods fail to provide the necessary reliability.

Homotopy continuation methods have been proposed as a way to greatly expand the domain of convergence of the process simulator's equation solving algorithm. This research expands upon existing homotopy continuation algorithms, investigates bounding algorithms, corrector …

Imaging The Subsurface In Karst Terrain Using Electrical Resistivity Tomography, Evgeniy V. Torgashov

Doctoral Dissertations

"Five electrical resistivity tomography (resistivity) case studies are presented. The first case study, entitled "Springfield Underground", includes ERT data acquired with the purpose of imaging the ceiling of an limestone aggregate mine following simultaneous localized roof failure. The interpretation of the ERT data indicates roof rock failure occurred at the intersection of two previously unmapped near-vertical solution-widened fractures.

At the "Chesterfield Dam" site, resistivity data were acquired to identify the zone of seepage through an earthfill dam. The seepage pathway beneath the dam is interpreted as through a solution-widened fracture, the top of which constituted a segment of the original …

Investigation Of Different Approaches To Combine Cable Information And Near-Field Scan Data For Radiated-Field Estimation, Keong W. Kam

Doctoral Dissertations

"Near-field scanning is often used to solve EMC problems. Aside from the purpose of visualization of near-fields, measured near-field data can be used to estimate far-field. One of many challenges associated with using near-field to far-field transform (NFFFT) technique for EMC application is the handling of attached cables. The objective of this investigation is to evaluate different methods to add cable information to the near-field data for far-field estimation. The investigation is carried out using numerical experiments in EMCoS EMC studio, which is a commercial MoM (Method of Moment) tool for EM simulation. Measurement results from a test structure are …

Modeling Carbon Sequestration In Transition Zone To Optimize Storage Potential, Fang Yang

Doctoral Dissertations

"Shallow aquifers are potential candidates for carbon sequestration because of their wide distribution and low injection cost. Injected CO₂ in a shallow region segregates into two zones according to CO₂ phases within the initial reservoir pressure and the maximum bottom hole pressure: gas zone and transition zone. Transition zone is a better option because of favorable CO₂ properties. This work investigated the CO₂ storage potential in transition zone using the compositional simulator CMG-GEM and a design of experiment software iSIGHT. First, it addressed the basic characteristics of CO₂ sequestration in transition zone, and then modeled CO₂ injection with simultaneous water …

Small Sample Inference For Exponential Survival Times With Heavy Right-Censoring, Noroharivelo Volaniaina Randrianampy

Doctoral Dissertations

"We develop a saddlepoint-based method and several generalized Bartholomew methods for generating confidence intervals about the rate parameter of an exponential distribution in the presence of heavy random right-censoring. Butler's conditional moment generating function formula is used to derive the relevant moment generating function for the rate parameter score function which provides access to a saddlepoint-based bootstrap method. Moment generating functions also play a key role in the generalized Bartholomew methods we develop. Since heavy censoring is assumed, the possible non-existence of the rate parameter maximum likelihood estimate (MLE) is nonignorable. The overwhelming majority of existing methods condition upon the …

Therapeutic Effects Of N-Acetylcysteine Amide In The Treatment Of Eye Disorders, Joshua W. Carey

Doctoral Dissertations

"The loss of vision from age-related eye diseases now affects over 30 million people in the United States and is expected to reach twice that number within the next couple of decades. Among these disorders, age-related macular degeneration and cataract formation represent the largest percentage of these cases. Therapeutic options available for treating age-related macular degeneration are limited and there is no noninvasive form of treatment for cataracts current available. Several studies have indicated that oxidative stress plays an important role in the pathology of these age-related eye disorders. If oxidative stress is responsible for the initiation and progression of …

Underground Mine Fire Simulation Using Multiscale Modeling Approach, Xichen Zhang

Doctoral Dissertations

"Underground mine fires have always been a major concern. Past events show that fire poses a severe safety hazard to mine workers, and causes tremendous economic loss to the mine and surrounding communities. A good understanding of the interaction between a mine fire and the mine ventilation network is crucial for effective fire emergency planning and hazard control. Unfortunately our understanding of a fire is still limited due to the complex nature of mine fires and a lack of adequate resource for studying them.

A new multiscale modeling approach coupling conventional 1D and 3D techniques has shown to be a …

Stress Corrosion Cracking Behavior Of Friction Stir Processed Ultrafine Grained Light Metal Alloys, Gaurav Ramchandra Argade

Doctoral Dissertations

"The influence of friction stir processing (FSP), a microstructural modification tool, on the corrosion behavior of Al-Mg, Al-Mg-Sc, Mg-Al-Zn and Mg-Y-RE alloys has been studied. An attempt has been made to establish correlation between processing parameters and the subsequent microstructural evolution especially matrix grain size on the corrosion and stress corrosion properties of the alloys. A relationship between grain size and corrosion rate for Mg-Y-RE alloys was envisaged and power law type behavior was proposed. Ultrafine fine grained (UFG) microstructure showed one order magnitude lower corrosion rate.

Grain refinement achieved through different FSP parameters showed lower corrosion currents for Al-Mg …

Two Essays On The Domain Translation From Financial Options To Real Options, Hongyan Chen

Doctoral Dissertations

"Real options (ROs) extend the financial option pricing theory to the valuation of real asset investment and managerial flexibility under uncertainty. However, differences between financial and non-financial markets, and the complex real world environment of applications, build obstacles for the domain translation from financial options to ROs.

This dissertation is motivated by the challenges of domain translation and developed in two essays. The first essay studies the incentive function of ROs (named the RO incentive). The essay develops an option-game framework to model the RO incentive, examines the change of investment behavior caused by the RO incentive, and values the …

Theoretical Studies Of Few-Body Problems, Uttam Chowdhury

Doctoral Dissertations

"Heavy ion collisions with atomic and molecular targets produce many outcomes. The Schrödinger equation is not analytically soluble for more than two mutually interacting particles. As a result, theory must resort to using approximations, the validity of which is determined by comparison with experiment. This work is focused on finding better approximations to describe ionization and capture processes in proton collisions.

Proton-impact ionization of molecular hydrogen is treated as a 3-body problem. Usually the target is treated as an atomic target and the results are multiplied by an ad hoc factor to account for the molecular structure. Measured cross sections …

Modelling Interruptions Of Human-In-The Loop Tasks, Muhammet Servet Gulum

Doctoral Dissertations

"Interruptions are a part of our everyday experience and are increasingly becoming a part of our work. Systems are typically not designed with consideration of the effects of interrupting a user during a task sequence. Research is being done in the field of interruptions and its effects. There have been various claims about the effects of interruptions on human task performance. It has been shown that interruptions may not only increase the time to perform a task but also decrease the performance. It has also been analyzed that the effect of interruptions depends on many parameters including task complexity, point …