Engineering Commons^™

Analysis And Design Of Non-Hermitian Optical Systems, Ali Kazemi Jahromi

Electronic Theses and Dissertations

From a very general perspective, optical devices can be viewed as constructions based on the spatial engineering of the optical index of refraction. Sculpting the real part of the refractive index produces the wide variety of known passive optical devices, such as waveguides, resonators, gratings, among a plethora of other possibilities for managing the transport of light. Less attention has been directed to engineering the imaginary part of the refractive index – that is responsible for optical gain and absorption – in conjunction with the real part of the refractive index. Optical gain is the building block of amplifiers and …

Nonlinear Dynamics In Multimode Optical Fibers, Mohammad Amin Eftekhar

Electronic Theses and Dissertations

Multimode optical fibers have recently reemerged as a viable platform for addressing a number of long-standing issues associated with information bandwidth requirements and power-handling capabilities. The complex nature of heavily multimoded systems can be effectively exploited to observe altogether novel physical effects arising from spatiotemporal and intermodal linear and nonlinear processes. Here, we have studied nonlinear dynamics in multimode optical fibers (MMFs) in both the normal and anomalous dispersion regimes. In the anomalous dispersion regime, the nonlinearity leads to a formation of spatiotemporal 3-D solitons. Unlike in single-mode fibers, these solitons are not unique and their properties can be modified …

Single Mode Wavelength-Tunable Thulium Fiber, Dong Jin Shin

Electronic Theses and Dissertations

Thulium fiber lasers have the broadest emission wavelength bandwidth out of any rare-earth doped fiber lasers. The emission wavelength starts from 1.75μm and ends at around 2.15μm, covering a vast swath of the eye safe wavelength region and intersecting with a large portion of mid-infrared atmospheric transmission window. Also, thulium fiber lasers provide the highest average output power of any other rare-earth doped fiber lasers in these wavelength regimes, making them uniquely suited for applications such as remote sensing. At the moment, high power beam propagation of continuous wave laser through the atmosphere in the mid-infrared range is yet to …

2 Micron Fiber Lasers: Power Scaling Concepts And Limitations, Alex Sincore

Electronic Theses and Dissertations

Thulium- and holmium-doped fiber lasers (TDF and HDF) emitting at 2 micron offer unique benefits and applications compared to common ytterbium-doped 1 micron lasers. This dissertation details the concepts, limitations, design, and performance of four 2 micron fiber laser systems. While these lasers were developed for various end-uses, they also provide further insight into two major power scaling limitations. The first limitation is optical nonlinearities: specifically stimulated Brillouin scattering (SBS) and modulation instability (MI). The second limitation is thermal failure due to inefficient pump conversion. First, a 21.5 W single-frequency, single-mode laser with adjustable output from continuous-wave to nanosecond pulses …

Cementless Tibial Base Micromotion During Activities Of Daily Living, Hayden Wilson

Electronic Theses and Dissertations

Initial stability of cementless total knee replacement (TKR) components is directly related to long-term fixation and success, as excess motion hinders bony ingrowth. To assess implant stability, there is a need for more physiologically accurate loading conditions, incorporating forces and displacements in all 6 degrees-of-freedom found in the knee joint, as well as understanding the impact of femoral flexion on conformity of tibiofemoral articulation. Understanding how different activities of daily living generate tibial micromotion yields insight into surgical technique considerations, and rehabilitation strategies post-operatively. ASTM F3141-15, which specifies knee flexion, Internal-External moment, Medial-Lateral, Anterior-Posterior and Superior-Inferior forces during gait and …

Habitat Use Of Blacktip Sharks (Carcharhinus Limbatus) At Fishing Piers, Kelsey L. Spencer

Electronic Theses and Dissertations

Blacktip sharks (Carcharhinus limbatus) can be observed near fishing piers throughout the summer along the northeast coast of South Carolina. These piers attract and support a wide variety of potential prey and sharks are able to forage on fishers’ discards with minimal energetic cost. I tagged 12 blacktip sharks with acoustic transmitters, monitored piers with acoustic receivers, and conducted pier-creel surveys to determine the habitat use of blacktip sharks at fishing piers, factors that influenced residence time and presence/absence at piers, and any cyclical patterns in visits to piers. Data were analyzed with pier association indices (PAI), mixed models, and …

Geophysical Delineation Of Megaporosity And Fluid Migration Pathways For Geohazard Characterization Within The Delaware Basin, Culberson County, Texas, Jonathan David Woodard

Electronic Theses and Dissertations

ABSTRACT

Differential dissolution of gypsum karst within the Delaware Basin poses a significant threat to infrastructure that society depends on. The study area is located in Culberson County, Texas and traverses a distance of approximately 54 kilometers along RM 652 within the Gypsum Plain which is situated on the northern margin of the Chihuahua Desert and includes outcrops of Castile and Rustler strata that host karst geohazards. Regions of karst geohazard potential have been physically surveyed proximal to the study area in evaporites throughout the Castile Formation outcrop; minimal hazards, in comparison to the Castile Formation, have been documented in …

A Novel Approach To Assess Minimally Invasive Surgical Device Failure Utilizing Adverse Event Outcome Severity And Design Complexity., Marie K. Riggs

Electronic Theses and Dissertations

Medical device failure and misuse have the potential to cause serious injury and death. Given the intricate nature of the instruments utilized specifically in minimally invasive surgery (MIS), users and manufacturers of surgical devices share a responsibility in preventing user error and device failure. A novel approach was presented for the evaluation of minimally invasive device failures, which involved assessing the severity of adverse event outcomes associated with the failures modes and investigating aspects of the devices’ design that may contribute to failure. The goals of this research were to 1) characterize the design attributes, failure modes, and adverse events …

Heterogenization Of Complexes With Redox Active Ligands For Hydrogen Evolution Reaction., Wuyu Zhang

Electronic Theses and Dissertations

Hydrogen fuel is a promising future energy carrier with many applications. Thermodynamically, 1.23 V is needed for the water electrolysis, which is a clean method to generate hydrogen gas. In practice excess potential is required, which is called overpotential, due to kinetic barriers. Catalysts to reduce the overpotential for the hydrogen evolution reaction (HER) include many homogeneous catalysts and heterogeneous catalysts. Heterogenization of homogeneous catalysts on electrode surfaces is an ideal way to study a catalyst by combining homogeneous and heterogeneous study together. In this dissertation, several characterization techniques have been employed, include cyclic voltammetry, linear sweep voltammetry, electrochemical impedance …

Design, Analysis, And Application Of A Cellular Material/Structure Model For Metal Based Additive Manufacturing Process., Shanshan Zhang

Electronic Theses and Dissertations

Powder bed fusion additive manufacturing (PBF-AM) has been broadly utilized to fabricate lightweight cellular structures, which have promising potentials in many engineering applications such as biomedical prosthesis, aerospace, and architectural structures due to their high performance-to-weight ratios and unique property tailorabilities. To date, there is still a lack of adequate understanding of how the cellular materials are influenced by both the geometry designs and process parameters, which significantly hinders the effective design of cellular structures fabricated by PBF-AM for critical applications. This study aims to demonstrate a cellular structure design methodology that integrates geometrical design and process-material property designs. Utilizing …

Fused Filament Fabrication 3d Printing Using Low-Melting Alloys., Nirupama Warrier

Electronic Theses and Dissertations

Fused Filament Fabrication (FFF) 3D printing technology has been a popular method of creating prototypes using plastics in the timeliest and most affordable manner for electronic, automotive, and biomedical applications. 3D printing of metals and alloys using FFF technology could provide low-cost alternatives and solutions to the Laser-Powder Bed Fusion Process (L-PBF) and Binder Jetting processes (BJ). In current work, low melting alloys have been used as a starting material and evaluated for FFF 3D printing using two methodologies. In the first methodology, Sn60Bi40 alloy in the form of wire was used as the feedstock for FFF extrusion and process …

A Framework For Clustering And Adaptive Topic Tracking On Evolving Text And Social Media Data Streams., Gopi Chand Nutakki

Electronic Theses and Dissertations

Recent advances and widespread usage of online web services and social media platforms, coupled with ubiquitous low cost devices, mobile technologies, and increasing capacity of lower cost storage, has led to a proliferation of Big data, ranging from, news, e-commerce clickstreams, and online business transactions to continuous event logs and social media expressions. These large amounts of online data, often referred to as data streams, because they get generated at extremely high throughputs or velocity, can make conventional and classical data analytics methodologies obsolete. For these reasons, the issues of management and analysis of data streams have been researched extensively …

Material Properties Design Using Simulations And Experiments For Powder Injection Molding Of Lead Zirconate Titanate (Pzt)., Bhushan Pramod Bandiwadekar

Electronic Theses and Dissertations

Powder injection molding (PIM) process simulations can be performed to minimize the number of injection molding experiments by estimating material properties necessary for PIM simulations. In current work, lead zirconate titanate (PZT) powder-polymer binder feedstock was compounded for 45 vol. % and 52 vol. % solids loading. PIM experiments on designed micro-pillar array geometry were performed using 52 vol. % PZT. Using PIM experiments results as basis, PIM simulations were performed on designed micro-pillar array geometries to understand the effectiveness of PIM simulations with the use of estimated feedstock properties in predicting molding behavior that have micro-features. Additionally, PIM simulations …

Queue Stability Analysis In Network Coded Wireless Multicast., Nadieh Mohamadi-Moghadam

Electronic Theses and Dissertations

In this dissertation queue stability in wireless multicast networks with packet erasure channels is studied. Our focus is on optimizing packet scheduling so as to maximize throughput. Specifically, new queuing strategies consisting of several sub-queues are introduced, where all newly arrived packets are first stored in the main sub-queue on a first-come-first-served basis. Using the receiver feedback, the transmitter combines packets from different sub-queues for transmission. Our objective is to maximize the input rate under the queue stability constraints. Two packet scheduling and encoding algorithms have been developed. First, the optimization problem is formulated as a linear programming (LP) problem, …

Control Of Power Electronic Interfaces In Distributed Generation., Mohammad Mohebbi

Electronic Theses and Dissertations

Renewable energy has gained popularity as an alternative resource for electric power generation. As such, Distributed Generation (DG) is expected to open new horizons to electric power generation. Most renewable energy sources cannot be connected to the load directly. Integration of the renewable energy sources with the load has brought new challenges in terms of the system’s stability, voltage regulation and power quality issues. For example, the output power, voltage and frequency of an example wind turbine depend on the wind speed, which fluctuate over time and cannot be forecasted accurately. At the same time, the nonlinearity of residential electrical …

Artificial Olfactory System For Multi-Component Analysis Of Gas Mixtures., Alexander Aleksandrovich Larin

Electronic Theses and Dissertations

Gas analysis is an important part of our world and gas sensing technology is becoming more essential for various aspects of our life. A novel approach for gas mixture analysis by using portable gas chromatography in combination with an array of highly integrated and selective metal oxide (MOX) sensors has been studied. We developed a system with small size (7 x 13 x 16 inches), low power consumption (~10 W) and absence of special carrier gases designed for portable field analysis (assuming apriori calibration). Low ppb and even sub-ppb level of detection for some VOCs was achieved during the analysis …

Testing And Modeling Of The Thixotropic Behavior Of Cementitious Materials., Bashir Hasanzadeh

Electronic Theses and Dissertations

During construction, concrete goes under various operations. It is normally transported to the job site, be placed and consolidated in the formwork, etc. The easiness and quality of these operations are very much related to the intrinsic rheological properties of concrete. Therefore, a good understanding of rheological behavior of concrete under various conditions are needed. Thixotropy is an important part of rheology. The thixotropic behaviors of concrete can be good representatives of its flow behaviors on the job site. For example, the breakdown aspect of thixotropy can help to explain how its flow behavior can impact concrete pumping and its …

A Comparison Of Mean Age Theory And Residence Time Distributions In Mixed Systems., Nolan Theaker

Electronic Theses and Dissertations

A comparison between mean age theory and conventional residence time distributions over a range of quantified mixing levels was conducted using computational fluid dynamics (CFD). The system was a stirred tubular reactor. The model was validated by comparing computationally derived RTD curves with experimentally obtained RTD curves, with quantified differences less than 3%. Mixing was quantified using the Tanks-in-Series model. Mixing levels were set by varying flow rate and impeller rpm. Mean age distributions at the outlet, where experimental RTD’s were measured, were very narrow for all levels of mixing studied. RTD’s showed expected characteristics; a wider distribution and long …

Design, Development, And Characterization Of Breathforce : A Respiratory Training System For Patients With Spinal Cord Injuries., Kevin L Tran

Electronic Theses and Dissertations

Pulmonary and cardiovascular dysfunction are consistently reported as the leading causes of morbidity and mortality among the 1,275,000 people who are living with chronic spinal cord injury (SCI) in the United States. Respiratory-cardiovascular complications from neurological disorders (primarily COPD and sleep apnea) are currently the number one cause of death and disability in the US.

The main goal of this project is to develop an inspiratory-expiratory training device for use in the rehabilitation of patients with respiratory motor and cardiovascular deficits that incorporates existing technologies and promotes successful training methodologies performed at the clinic and at home.

An embedded microprocessor …

Computational Prediction Of Conductivities Of Disk-Shaped Particulate Composites, Jian Qiu

Electronic Theses and Dissertations

The effective conductivities are determined for randomly oriented disk-shaped particles using an efficient computational algorithm based on the finite element method. The pairwise intersection criteria of disks are developed using a set of vector operations. An element partition scheme has been implemented to connect the elements on different disks across the lines of intersection. The computed conductivity is expressed as a function of the density and the size of the circular disks or elliptical plates. It is further expressed in a power-law form with the key parameters determined from curve fittings. The particle number and the trial number of simulations …

The Application Of Proper Orthogonal Decomposition To Numerically Modeled And Measured Ocean Surface Wave Fields Remotely Sensed By Radar, Andrew Joseph Kammerer

Electronic Theses and Dissertations

Phase-resolved ocean surface wave elevation maps provide important information for many scientific research areas (e.g., rogue waves, wave-current interactions, and wave evolution/growth) as well as for commercial and defense applications (e.g., naval and shipping operations). To produce these maps, measurements in both time and space are necessary. While conventional wave sensing techniques are limited spatially, marine radar has proven to be a complex yet promising remote sensing tool capable of providing both temporal and spatial wave measurements. The radar return from the sea surface is complex because it contains contributions from many sources only part of which provide information about …

Engineering Applications Of Organic Surfactant Modified Bentonite In Sorptive Soil Barriers., Sadra Javadi

Electronic Theses and Dissertations

Earthen barriers such as CCLs and GCLs have been employed in geotechnical practices to provide a low permeability hydraulic barrier since long time ago. These types of barriers exhibited satisfactory performance for many applications such as landfills. The performance of low permeability barriers is based on the swelling potential of their component, which is mostly Na-bentonite, in contact with polar fluids such as water. However, the acceptable range of conductivity cannot be achieved by traditional earthen barriers when they are permeated by non-polar fluids such as gasoline. This phenomenon occurs due to the incompatibility of earthen barrier constituent with non-polar …

Dynamic Adversarial Mining - Effectively Applying Machine Learning In Adversarial Non-Stationary Environments., Tegjyot Singh Sethi

Electronic Theses and Dissertations

While understanding of machine learning and data mining is still in its budding stages, the engineering applications of the same has found immense acceptance and success. Cybersecurity applications such as intrusion detection systems, spam filtering, and CAPTCHA authentication, have all begun adopting machine learning as a viable technique to deal with large scale adversarial activity. However, the naive usage of machine learning in an adversarial setting is prone to reverse engineering and evasion attacks, as most of these techniques were designed primarily for a static setting. The security domain is a dynamic landscape, with an ongoing never ending arms race …

An Interactive Interface For Nursing Robots., Ankita Sahu

Electronic Theses and Dissertations

Physical Human-Robot Interaction (pHRI) is inevitable for a human user while working with assistive robots. There are various aspects of pHRI, such as choosing the interface, type of control schemes implemented and the modes of interaction. The research work presented in this thesis concentrates on a health-care assistive robot called Adaptive Robot Nursing Assistant (ARNA). An assistive robot in a health-care environment has to be able to perform routine tasks and be aware of the surrounding environment at the same time. In order to operate the robot, a teleoperation based interaction would be tedious for some patients as it would …

The Macro-Modelling Of Steel Fiber Reinforced Concrete/Mortar Flexural Tensile Behavior And Mix Optimization For Flexural Strength., Li Liu

Electronic Theses and Dissertations

With the continuous advances in materials’ technology, the performance of the commonly used concrete building material has continued to improve. Compressive strengths exceeding 75 MPa are now being used in applications throughout the world. However, the concrete becomes less ductile and more susceptible to sudden failures with increases in its compressive strength. Although the behavior of concrete is generally governed by its compressive strength, its tensile strength, although much lower, is also important. This tensile strength impacts appearance, the serviceability and durability of concrete elements. In addition, minimum levels of tensile strength are required for many concrete applications including, earthquake …

Observation And Estimation Study For Sensorless Control Of Linear Vapor Compressors., Joseph Latham

Electronic Theses and Dissertations

Linear vapor compressors have become widely investigated for refrigeration applications due to their high efficiency in comparison to the more common rotary type compressors. However, the nature of the linear compressor adds complexity to the control of these machines. The unconstrained motion of the piston in a linear compressor allows for continuous modulation of the compressor output, but requires knowledge of the mechanical dynamics to effectively control the compressor and prevent collision of the piston with the cylinder head. This control is made more difficult by the highly nonlinear nature of the force of gas compression acting against the piston. …

Applications Of Polarized Metallic Nanostructures., Jasmin Beharic

Electronic Theses and Dissertations

Gold nanostructures exhibit technologically useful properties when they are polarized in an electric field. In two projects we explore instances where the polarized metal can be used in real world applications. The first project involves gold nanoparticles (GNP) for use in light actuated microelectromechanical systems (MEMS) applications. Although the GNPs were originally designed for volumetric heating in biomedical applications, we treat them as a thin film coating, opening the door for these particles to be used in MEMS applications. This work characterizes the thermal properties of gold nanoparticles on surfaces for spatially-targeted thermal actuation in MEMS systems. The second project …

A Data Science Pipeline For Educational Data : A Case Study Using Learning Catalytics In The Active Learning Classroom., Asuman Cagla Acun Sener

Electronic Theses and Dissertations

This thesis presents an applied data science methodology on a set of University of Louisville, Speed School of Engineering student data. We used data mining and classic statistical techniques to help educational researchers quickly see the data trends and peculiarities. Our data includes scores and information about two Engineering Fundamental Class. The format of these classes is called an inverted classroom model or flipped class. The purpose of this study is to analyze the data in order to uncover potentially hidden information, tell interesting stories about the data, examine student learning behavior and learning performance in an active learning environment, …

Fabrication And Characterization Of A Mcro/Nanofluidic Platform For Electroporation., Hanwen Yuan

Electronic Theses and Dissertations

For traditional electroporation devices, there are a number of problems associated with these devices such as insufficient understanding of its theoretical mechanism, low cell viability, inadequate electroporation efficiency, excess voltage applied to generate required electric field due to the large size of these devices and sample contamination. Although newly developed microfluidic electroporation devices have solved most of the above existing problems in traditional bulk electroporation devices, they appear to lack the ability to control the precise dose of biomolecules or genes transfecting into cells and, from a manufacturing perspective, the fabrication methods do not enable repeatable production of such devices …

Magnetic Field-Induced Intramolecular Cyclization As A Trigger For Nanoparticle-Based Delivery Systems., Sara Katherine Biladeau

Electronic Theses and Dissertations

Magnetic nanoparticles (MNPs) are used in a variety of applications, including as agents for magnetic resonance imaging, generation of local hyperthermia, and as platforms for drug delivery. Iron-based MNPs are often coated with a shell, such as silica or gold, to increase biocompatibility for drug delivery applications. Many MNPs used for cancer therapy rely on either an internal trigger, such as a difference in pH, or an external trigger, such as light or an alternating magnetic field (AMF), to cause release of a payload, typically a chemotherapeutic drug. Internal triggers are appealing because drug release can be targeted to a …