Engineering Commons^™

Phase-Field Models For Simulating Physical Vapor Deposition And Microstructure Evolution Of Thin Films, James Stewart Jr.

Graduate Theses and Dissertations

The focus of this research is to develop, implement, and utilize phase-field models to study microstructure evolution in thin films during physical vapor deposition (PVD). There are four main goals to this dissertation. First, a phase-field model is developed to simulate PVD of a single-phase polycrystalline material by coupling previous modeling efforts on deposition of single-phase materials and grain evolution in polycrystalline materials. Second, a phase-field model is developed to simulate PVD of a polymorphic material by coupling previous modeling efforts on PVD of a single-phase material, evolution in multiphase materials, and phase nucleation. Third, a novel free energy functional …

Validation Of A Confocal Light Sheet Microscope Using Push Broom Translation For Biomedical Applications, Joshua Hutcheson

Graduate Theses and Dissertations

There exists a need for research of optical methods capable of image cytometry suitable for point-of-care technology. To propose am optical approach with no moving parts for simplification of mechanical components for the further development of the technology to the poin-of-care, a linear sensor with push broom translation method. Push broom translation is a method of moving objects by the sensor for an extended field of view. A polydimethylsiloxane (PDMS) microfluidic chamber with a syringe pump was used to deliver objects by the sensor. The volumetric rate of the pump was correlated to the integration time of the sensor to …

Genotoxicity Of Graphene In Escherichia Coli, Ananya Sharma

Graduate Theses and Dissertations

Rapid advances in nanotechnology necessitate assessment of the safety of nanomaterials in the resulting products and applications. One key nanomaterial attracting much interest in many areas of science and technology is graphene. Graphene is a one atom thick carbon allotrope arranged in a two-dimensional honeycomb lattice. In addition to being extremely thin, graphene has several extraordinary physical properties such as its exceptional mechanical strength, thermal stability, and high electrical conductivity. Graphene itself is relatively chemically inert and therefore pristine graphene must undergo a process called functionalization, which is combination of chemical and physical treatments that change the properties of graphene, …

Correcting Current Imbalances In Three-Phase Four-Wire Distribution Systems, Vinson Joseph Jones

Graduate Theses and Dissertations

The objective of this thesis is to present the theory, design, construction, and testing of a proposed solution to unbalanced current loading on three-phase four-wire systems. The Unbalanced Current Static Compensator is the name of the prototype; herein referred to as the UCSC. The purpose of this prototype is to redistribute current between the three phases of a distribution system. Through this redistribution, negative- and zero-sequence currents are eliminated and a balanced system is seen upstream from the point of installation.

The UCSC consists of three separate single-phase H-bridge inverters that all share the same dc-link capacitor. Each of these …

Prevention Of Drone Jamming Using Hardware Sandboxing, Joshua Mead

Graduate Theses and Dissertations

In this thesis, we concern ourselves with the security of drone systems under jamming-based attacks. We explore a relatively new concept we previously devised, known as hardware sandboxing, to provide runtime monitoring of boundary signals and isolation through resource virtualization for non-trusted system-on-chip (SoC) components. The focus of this thesis is the synthesis of this design and structure with the anti-jamming, security needs of drone systems. We utilize Field Programmable Gate Array (FPGA) based development and target embedded Linux for our hardware sandbox and drone hardware/software system.

We design and implement our working concept on the Digilent Zybo FPGA, which …

Investigation Of Optical Properties Of Zinc Oxide Photodetector, Tyler Chism

Graduate Theses and Dissertations

UV photodetection devices have many important applications for uses in biological detection, gas sensing, weaponry detection, fire detection, chemical analysis, and many others. Today’s photodetectors often utilize semiconductors such as GaAs to achieve high responsivity and sensitivity. Zinc oxide, unlike many other semiconductors, is cheap, abundant, non-toxic, and easy to grow different morphologies at the micro and nano scale. With the proliferation of these devices also comes the impending need to further study optics and photonics in relation to phononics and plasmonics, and the general principles underlying the interaction of photons with solid state matter and, specifically, semiconductors. For this …

Achieving A Better Balance Between Productivity And Performance On Fpgas Through Heterogeneous Extensible Multiprocessor Systems, Abazar Sadeghian

Graduate Theses and Dissertations

Field Programmable Gate Arrays (FPGAs) were first introduced circa 1980, and they held the promise of delivering performance levels associated with customized circuits, but with productivity levels more closely associated with software development. Achieving both performance and productivity objectives has been a long standing challenge problem for the reconfigurable computing community and remains unsolved today. On one hand, Vendor supplied design flows have tended towards achieving the high levels of performance through gate level customization, but at the cost of very low productivity. On the other hand, FPGA densities are following Moore's law and and can now support complete multiprocessor …

Use Of Response Surfaces In The Design Of A Simple Step Stress Accelerated Test Plan, Alexander H. Wong

Graduate Theses and Dissertations

In designing accelerated testing plans, cost is a factor that is missing in much of the literature. This paper explicits considers cost by developing an optimization model with the objective to minimize costs for a simple step stress accelerated test plan. Two methodologies are employed. One is an optimization approach in which an attempt is made to quantify the behavior of a series-parallel hardware system over all stages of testing using a response surface, and then an optimization model is used to determine the settings for stresses and failure mode modifications for all stages of testing prior to the start …

High Step-Up/Down Transformerless Multilevel Converter For Renewable Energy Applications, Haider Ghazi Mhiesan

Graduate Theses and Dissertations

This thesis focuses on a high step-up/down transformerless dc-dc modular multilevel converter (MMC) that would be applicable to dc power systems. The design achieves high voltage ratios for interfacing renewable energy sources such as photovoltaic and line interactive Uninterruptible Power System (UPS) systems. The circuit topology provides for high step-up/down dc-dc conversion ratios using an MMC approach operating in resonant mode in order to improve overall efficiency. This topology operates to step-up the input voltage with 1:10 or larger conversion ratio. As a bidirectional converter, it also provides step-down capability at the same voltage ratio (10:1 or greater). The MMC …

Cloning, Fed-Batch Expression And Purification Of A Novel Anti-Candida Peptide And Development Of A Cleavage Resistant Variant Of Green Fluorescence Protein, Rudra Palash Mukherjee

Graduate Theses and Dissertations

This work illustrates that the intelligent design of a bioprocess for the production of peptides of various length is possible by having a prior knowledge of desired product, cell line, fermentation conditions, and choices for downstream recovery. Cloning, expression, and recovery of a novel 12-mer anti-Candida peptide served as an illustrative case for a proposed Escherichia coli platform. The antifungal peptide, expressed as a fusion to GFPUV during high call density fed-batch, was recovered from cell lysate, concentrated using ion exchange chromatography, and finally cleaved with cyanogen bromide. The platform was capable of producing active peptide capable of arresting the …

Control Design Of A Single-Phase Dc/Ac Inverter For Pv Applications, Haoyan Liu

Graduate Theses and Dissertations

This thesis presents controller designs of a 2 kVA single-phase inverter for photovoltaic (PV) applications. The demand for better controller designs is constantly rising as the renewable energy market continues to rapidly grow. Some background research has been done on solar energy, PV inverter configurations, inverter control design, and hardware component selection. Controllers are designed both for stand-alone and grid-connected modes of operation. For stand-alone inverter control, the outer control loop regulates the filter capacitor voltage. Combining the synchronous frame outer control loop with the capacitor current feedback inner control loop, the system can achieve both zero steady-state error and …

Designing Sewn Circuits And Stem Self-Efficacy In Middle School Girls, Kara Kaiser

Graduate Theses and Dissertations

The purpose of this study is to determine if the experience of designing and sewing LilyPad Arduino circuits in crafts projects can increase middle school girls’ STEM self-efficacy. Boys STEM self-efficacy will also be assessed to determine if LilyPad Arduino circuits can also increase boys’ STEM self-efficacy. Researchers have been wondering why there is a male dominance in STEM (science, technology, engineering and mathematics) fields and why some women do not have a particular interest in these subjects. There are several reasons this could happen; stereotypes conveyed to them by parents and/or teachers, they genuinely are not interested in STEM …

Experimental And Computational Studies Of Cortical Neural Network Properties Through Signal Processing, Wesley Patrick Clawson

Graduate Theses and Dissertations

Previous studies, both theoretical and experimental, of network level dynamics in the cerebral cortex show evidence for a statistical phenomenon called criticality; a phenomenon originally studied in the context of phase transitions in physical systems and that is associated with favorable information processing in the context of the brain. The focus of this thesis is to expand upon past results with new experimentation and modeling to show a relationship between criticality and the ability to detect and discriminate sensory input. A line of theoretical work predicts maximal sensory discrimination as a functional benefit of criticality, which can then be characterized …

Assessment Of An Industrial Type Radiant Heating System For Drying Rough Rice, Anne Adhiambo Okeyo

Graduate Theses and Dissertations

Rough rice is normally harvested at moisture contents (MCs) higher than that for safe storage. The objective for this study was to investigate the effectiveness of scaled-up infrared (IR) heating followed by tempering steps to dry freshly-harvested rough rice. An industrial type, pilot scale, IR drying equipment, designed to convey rough rice on a vibrating conveyor belt was used in this study. The heating zone of the equipment had catalytic IR emitters powered by natural gas. Freshly-harvested rough rice of long-grain pureline (cv. Cheniere), long-grain hybrid (cv. 6XP 756) and medium-grain (cv. CL 271) cultivars at initial moisture contents (IMCs) …

Evaluation Of Poisson’S Ratio Of Asphalt Concrete, Elvis Alexander Castillo Camarena

Graduate Theses and Dissertations

Poisson´s ratio can be defined as the negative ratio of strains perpendicular to the load direction to the strains parallel to the loading direction. If elastic or viscoelastic models are used, Poisson´s ratio, together with elastic modulus, is a main input used to predict distresses in flexible pavement structures such as rutting and cracking. In asphalt concrete, Poisson’s ratio is commonly measured using two different testing configurations: indirect tension (IDT) and uniaxial. However, results from these two testing configuration can potentially have differences. Design methodologies such as the Mechanistic Empirical Design Guide (MEPDG, now PavementME) have been shown to be …