Digital Commons Network^™

Multiaxial Mechanics Of Human Articular Cartilage In Health And Osteoarthritis, Franz Maier

Doctoral Dissertations

Cartilage covers the articulating bones in all synovial joints throughout the body, providing a wear-resistant, low-friction surface. Complex interactions of solid (collagen and proteoglycans) and fluid (water and dissolved ions) maintain the tissue’s load- bearing properties. Osteoarthritis burdens approximately 20% of the population in the United States, and its prevalence is projected to increase. With progressing disease, the tissue’s constituents alter in composition and structure, resulting in a downward cascade of degeneration. In this work we determined the location dependent multiaxial properties of human cartilage. We found strain dependent anisotropy and significant inter-joint variability in mechanical strength and energy dissipation …

Investigations Of The Effects Of Reading Skill And Epistemological Beliefs On Learning In General Chemistry, And How Students Use Textbooks To Study, Rene Buell

Doctoral Dissertations

Understanding how student characteristics affect learning in chemistry can influence the pedagogical strategies employed by chemistry instructors. Previous studies have investigated the effects of characteristics including prior knowledge, math ability, and motivations on course performance. Student characteristics can also influence study strategies employed by students. Few studies, however, have focused on the role of language and reading comprehension skill on learning in chemistry, and fewer have investigated the levels of epistemological beliefs of general chemistry students. Three studies are presented in this dissertation. In the first study, the effects of prior knowledge and reading comprehension skill on learning from reading …

Improved Seismic Design Of Non-Structural Components (Nscs) And Development Of Innovative Control Approaches To Enhance The Seismic Performance Of Buildings And Nscs, Hamidreza Anajafimarzijarani

Doctoral Dissertations

Post-earthquake reconnaissance following past earthquakes in the US and other seismic-prone countries illustrates that the majority of building losses (injury, dollar loss and downtime) resulted from damage to nonstructural components (NSCs) and building contents. NSCs damages can severely compromise a building functionality, even if the building does not suffer significant structural damages. NSCs can be classified either as primarily displacement/deformation-sensitive or acceleration-sensitive. This study focuses on acceleration-sensitive components.

Previous studies on NSCs are mostly based on the responses of simplified models of primary systems and components. These models, while providing valuable insight into understanding the influential parameters on NSCs seismic …

Biophysical Properties Of An Antifreeze Protein And The Effects Of Ionic Liquids On The Model Protein Gb1, Korth Wade Elliott

Doctoral Dissertations

Antifreeze proteins (AFPs) are a unique class of protein characterized by their ability to depress the freezing point of water sufficient to prevent the formation of ice crystals by adsorbing to the surface of ice crystals. This unique ability allows organisms (e.g. plants, fish, insects, etc.) which live in extremely cold climates to survive. Because of these proteins’ ability to prevent and slow the rate of ice crystal formation, they have great potential in the application of cryopreservation in medicine, agriculture and food science. Antifreeze proteins have been known for over five decades, however, their exact mechanism of action is …

Manganese Oxide Based Electrode Materials For Aqueous Sodium-Ion Electrochemical Energy Storage, Xiaoqiang Shan

Doctoral Dissertations

Aqueous electrochemical energy storage (EES) has been investigated as a potential alternative to commonly used non-aqueous lithium-ion batteries since it can achieve high power performance, long cycle life and good safety. Manganese oxide based materials using Na-ions as charge carriers for aqueous storage have been studied with the advantages of low cost, high earth abundance, and environmental friendliness. However, the applications of oxide materials in aqueous Na-ion storage are limited by low energy density due to low specific capacity and the narrow potential window (~ 1.23 V). To address these two issues, this research work have been focused on the …

A Triaxiality-Dependent Constitutive Model For Predicting Damage-Induced Softening In 3d-Printed Soft Suture Layer, Lei Liu

Doctoral Dissertations

Adhesive interfacial layers are ubiquitous in both engineering and natural material systems. They are essential in governing the mechanical behaviors of these materials. Especially, in the field of biological and bio-inspired materials, soft interfacial layer plays very important role in mechanics of them. The rapid development of 3D printing enables high quality bonding between dissimilar materials, providing an opportunity to fabricate biomimetic composites with arbitrary morphology. Along with this new development, new challenges appear in constitutive modeling and the prediction of damage initiation and evolution of 3D printed materials. To meet this need in the field, the model and methodology …

Physics-Based Modeling Framework Incorporating Microstructural Evolution For Predicting Deformation And Recrystallization Of Metallic Materials, Miroslav Zecevic

Doctoral Dissertations

Large number of metallic parts is produced from the raw materials by a set of mechanical shaping and heating operations. Considering the need for metallic components in the modern industry, the field of thermo-mechanical processing of metallic materials is of immense importance. Even modest improvements of the existing thermo-mechanical processes could potentially result in great savings of time, recourses and energy. Finite element modeling of the forming and heating operations introduced in the past decades has allowed for the optimization of the thermo-mechanical processes and has thus resulted in significant advancements. However, due to the limitations of the presently used …

The Effect Of Ionospheric Conductivity On Magnetospheric Dynamics, Benjamin Joseph Jensen

Doctoral Dissertations

The connection between ionospheric conductivity and the dynamics of the magnetosphere was investigated, using several methods to change the ionospheric conductivity and then study the resultant changes to the magnetosphere. Computer simulations of the Earth's geospace environment were utilized using OpenGGCM coupled with an ionosphere model CTIM and a ring current model RCM.

Three methods were used to modify ionospheric conductivity. The incoming particle precipitation was modified by several orders of magnitude $\alpha=.01,.1,1,10$, the ionospheric conductivity was increased or decreased by factors $\beta=.25, .5, 1, 2,$ and $4$, and for the last method differing values of $F_{10.7}$, $70,110, 150, 200,$ …

Performance Evaluation Of Shear Connectors Embedded In Ultra-High Performance Concrete As Part Of A Bridge Repair Method, Dominic Kruszewski

Doctoral Dissertations

Corrosion is one of the most dominant forms of deterioration in steel bridge girders. U.S. federal and state agencies spend billions of dollars annually on bridge rehabilitation as a direct result of corrosion. Even with these efforts, approximately $125 billion is needed to address the current backlog of structures in need of repair. Over time, corrosion leads to section loss of critical load bearing components, hindering the structural integrity of the bridge. To strengthen weakened girders ends with section loss, a structurally efficient repair option has been developed. In this repair, headed shear studs are welded to the intact portion …

Bayesian Variable Selection With Applications To Neuroimaging Data, Shariq Mohammed

Doctoral Dissertations

In this dissertation, we discuss Bayesian modeling approaches for identifying brain regions that respond to certain stimulus and use them to classify subjects. We specifically deal with multi-subject electroencephalography (EEG) data where the responses are binary, and the covariates are matrices, with measurements taken for each subject at different locations across multiple time points. EEG data has a complex structure with both spatial and temporal attributes to it. We use a divide and conquer strategy to build multiple local models, that is, one model at each time point separately both, to avoid the curse of dimensionality and to achieve computational …

Three-Dimensional Image Sensing And Visualization With Augmented Reality, Xin Shen

Doctoral Dissertations

In recent decades, there have been significant technological advancements in sensors, devices, materials, algorithms, and computational hardware, resulting in extensive improvements for visualization capabilities applied to real world objects. Among these improvements, three-dimensional (3D) imaging technologies have received interest from many research groups and may offer advantages over conventional two-dimensional (2D) approaches. In comparison with 2D sensing techniques, which record only the intensity of the scene, passive 3D imaging also includes depth and directional information. Many techniques for 3D imaging have been proposed, such as holography and interferometry, time-of-flight, two-view based stereoscopy, and multi-view techniques for autostereoscopic 3D imaging, to …

An Algorithmic Framework For Gait Analysis And Gait-Based Biometric Authentication, Ioannis Papavasileiou

Doctoral Dissertations

Small or large deviations present in someone's gait patterns could be attributed to either their unique muscular-skeletal structure or possible neurological disorders, such as Parkinson’s Disease (PD) or stroke. With the rapid development of wearable technologies, it is now possible to quantitatively measure such deviations. In this thesis we develop an algorithmic framework that identifies the deviations caused from neurological disorders, that can have applications in gait physical therapy, or from unique individual behavior, which can have applications in behavioral biometrics. First, to objectively extract gait phases, an infinite Gaussian mixture model is presented to classify different gait phases, and …

Propargyl-Linked Antifolates As Inhibitors Of The Folate Biosynthetic Pathway In Mycobacterium Tuberculosis And M. Avium, Behnoush Hajian

Doctoral Dissertations

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), has co-evolved with humans since the dawn of our species. Despite advances in antibiotic therapy, TB global burden is till enormous. Antimicrobial resistance and HIV epidemic challenge the ongoing efforts to control TB. Novel anti-TB agents are required to address the issues associated with current drug regimens and to improve the outcomes of TB therapy. In this work, we have evaluated the antimycobacterial activity of propargyl-linked antifolates against drug-susceptible and drug-resistant M. tuberculosis. Antifolates exerts their antimicrobial effect by interruption of folate biosynthetic pathway and one-carbon metabolism. We have successfully …

Bio-Inspired Stimuli Responsive Smart Soft Materials, Songshan Zeng

Doctoral Dissertations

Smart soft materials, which are commonly integrated with function-oriented surface engineering and substrate configuration, capable of reversibly changing transparency, fluorescence, coloration, are playing critical part in the emerging optical/electronic applications. Inspired by the vivid displaying tactics in marine life, a series of intriguing bilayer or multi-layer devices based on a rigid thin film tightly bonded to a soft stretchable substrate was achieved in this dissertation. These devices exhibit versatile multi-stimuli responsive characteristics which can dynamically change their optical properties (such as transparency, fluorescent intensity/coloration, reflective color) as exposed to specific stimulus (such as heat, UV, moisture, electrical field and/or mechanical …

Thickness Scaling Of Ferroelectricity In Bifeo3 By Tomographic Atomic Force Microscopy, James Steffes

Doctoral Dissertations

Intrinsic and extrinsic properties of ferroelectric materials are known to have strong dependencies on electrical and mechanical boundary conditions, resulting in finite-size effects at length scales below several hundred nanometers. In ferroelectric thin films, equilibrium domain size is proportional to the square root of film thickness, which precludes the ability for current tomographic microscopies to accurately resolve complex domain morphologies in sub-micron films. Nanometer-scale three-dimensional imaging of spontaneous polarization is critical for understanding equilibrium states in polar materials, as well as for engineering devices based on such phenomena, however such capabilities remain a substantial experimental challenge. Tomographic atomic force microscopy …

In-Situ Micromechanical Characterization Of Materials With High Mechanical Potential Energy Absorption Capacity, Keith Dusoe

Doctoral Dissertations

The storage, and subsequent release, of mechanical potential energy during the deformation of a material is an important phenomenon that allows for the working principles of engineered spring devices to be realized. The recovery of the released mechanical potential energy, stored as atomic configurational changes, can be utilized and harnessed to perform work on an element in the surrounding environment. This interplay between storage and release of mechanical potential energy in materials plays important roles not only in the engineering of advanced “spring” devices such as sporting equipment and resonators in microelectromechanical systems (MEMS) devices but also in the fast …

Higher-Order Accurate Finite Difference Method For Thermal Analysis In Double-Layered Solid Structures -- Gradient Preserved Method, Yun Yan

Doctoral Dissertations

Layered structures have appeared in many systems such as biological tissues, micro-electronic devices, thin films, fins, reactor walls, thermoelectric power conversion, thermal coating, metal oxide semiconductors, and thermal processing of DNA origami nanostructures. Analyzing heat transfer in layered structures is of crucial importance for the design and operation of devices and the optimization of thermal processing of materials. There are many numerical methods dealing with the layered structures or interface problems. The existing numerical methods such as the immersed interface method and the matched interface boundary method, if using threegrid points across the interface, usually provide only a second-order truncation …

Wastewater Pipe Condition And Deterioration Modeling For Risk-Based Decision-Making, Greta J. Vladeanu

Doctoral Dissertations

The dissertation research work described here has four primary objectives: (1) the development of a comprehensive wastewater pipe condition rating model that incorporates a large number of environmental, structural, and hydraulic parameters of the pipe; (2) the development of a wastewater pipe deterioration model used to predict future overall condition states of the pipe, as well as determining the probability of failure at any given age of the pipe; (3) the development of a comprehensive consequence of failure model that assesses the consequence of wastewater pipe failure using economic, social, and environmental cost factors; and (4) the development of a …

Investigating The Role Of Operating Parameters And Surface Treatments Of Carbon Based Electrodes In Capacitive Deionization, Md Ashique Ahmed

Doctoral Dissertations

This research focused on studying salt ion removal behavior and regeneration of electrodes used in capacitive deionization (CDI). CDI is a novel deionization technology that utilizes electrochemical processes to extract ions from water and either hold them electrostatically on the electrode surface or trap them in a double layer formed next to surface of electrodes. The use of porous carbon materials as electrodes in CDI enhances ion removal capacity because of availability of high surface area, conductivity, porosity, non-corrosive behavior, and other favorable properties. Experiments were conducted with a synthetic NaCl solution prepared in the laboratory. The first part of …

Development Of A Longitudinal Imaging System For Murine Brain Injury Models, Chelsea D. Pernici

Doctoral Dissertations

Following traumatic brain injury (TBI) and stroke, secondary injury cascades can lead to axonal damage and persistent microglia activation, respectively, in subcortical regions of mice. Current techniques, such as diffusion tensor imaging (DTI) and histology are used to observe features related to damage, but DTI lacks cellular resolution and histology is conducted on fixed tissue, preventing longitudinal studies in the same mouse. The combination of cranial windows and multiphoton microscopy (MPM) is used to image cells in the upper layers of the mouse cortex, but resolution rapidly degrades with imaging depth, making it difficult to observe white matter and subcortical …

Development And Analysis Of Engineered Brain Cell Microenvironments Mimicking Healthy And Diseased Neuronal Circuits, Kahla St. Marthe

Doctoral Dissertations

Astrocytes and microglia (glial cells) are active elements of the brain maintaining numerous homeostatic functions. Disturbances result in worsening of neuro-inflammation, traumatic brain injury, and various stages of brain tumors. Glial cells contribute to homeostasis for dynamic second messengers in the CNS, including intracellular calcium concentration ([Ca2+] i). Calcium is a central secondary messenger which signals for example, through the N-methyl-D-aspartate (NMDA) glutamate receptor on the neuronal membrane. A large, dynamic Ca2+ influx ensues after glutamate binds to the NMDA receptor. This influx initiates several molecular mechanisms within the cell. Disturbances in calcium homeostasis can lead to neurological diseases such …

Validation Of Spatial Hysteresis As The Internal Damping Mechanism In An Unmanned Micro Aerial Vehicle Model, Ashleigh Chambers

Doctoral Dissertations

Unmanned aerial vehicles have been an area of interest in both research and industry for the past several decades. Advancements in technology have allowed such aircraft to decrease in size. UAVs are less expensive than traditional aircraft and are less restricted in where they can fly due to their compact size, leading to shifts in the way infrastructure, agriculture, and transportation surveillance and operations are handled.

However, small aerial vehicles and flexible, composite ones are more susceptible to crashes. This has led to an increased interest in methods to control such aircraft. In order to accurately model for a composite, …

Smoothed Particle Hydrodynamics For Computational Fluid Dynamics, Wennan Ma

Doctoral Dissertations

Smoothed particle hydrodynamics (SPH) is a simple and effective numerical method that can be used to solve a variety of challenging problems in computational mechanics. It is a Lagrangian mesh-free method ideal for solving deformation problems. In the SPH method, the state of a system is represented by a set of particles, which possesses individual material properties and interact with each other within a specific range defined as a support domain by a weight function or smoothing function. SPH features flexibility in handling complex flow fields and in including physical effects.

In theory, the basic concept of the SPH method …

The Role Of Jasmonate In The Shade Response Of Perennial Ryegrass, Rania Eltanbouly

Doctoral Dissertations

'Archival abstract submitted'

Three-Dimensional Imaging, Visualization And Recognition In Low Light Environments, Adam Markman

Doctoral Dissertations

There has been significant research in developing novel image sensors to capture a scene in low illumination environments. Using conventional passive imaging sensors that operate in the visible spectrum, camera read-noise becomes higher than the signal information from the scene resulting in read-noise dominant images. These images suffer from poor signal-to-noise ratio making scene visualization unobtainable. Thus, imaging in photon-limited environments has been viewed as a nuisance. This dissertation will consist of three separate parts that discuss utilizing photon-counting principals for secure information storage or imaging in photon-limited environments. First, an optical security system for information storage is introduced that …

Reliable Physical Unclonable Function Design And Algorithm For Authentication And Key Generation, Wei Yan

Doctoral Dissertations

Security is becoming an increasing concern in electronic devices recently. Specifically, since the embedded systems and Internet of Things (IoTs) have become necessary parts of our life, more and more vulnerabilities are detected and made use of by attackers. Moreover, as the electronic component supply chain grows more complex due to globalization, with parts coming from a diverse set of suppliers, counterfeit electronics have been a major challenge that calls for immediate solutions. This is because the traditional solutions that using static digital ID and keys can be easily obtained or cloned. The current best practice is to place a …

Retinoic Acid Receptor Signaling During Paraxial Mesoderm Differentiation Of Pluripotent Stem Cells, Ryan Patrick Russell

Doctoral Dissertations

The treatment of severe musculoskeletal injuries is currently limited to surgical intervention and natural healing during recovery, which are not always sufficient to repair critical defects. Various cell-based approaches for repair augmentation have gained traction, however a reliable cell therapy approach has not been realized. Pluripotent stem cells (PSCs) retain the developmental potential to become any cell in the human body and are a valuable model for studying cell differentiation that hold tremendous promise for treating orthopedic injuries. The goal of our research has been to develop an efficient in vitro differentiation method to generate skeletal progenitor cells, the forerunners …

Contributions Of Angular Momentum In Gyroscopes To Perception Of Heaviness And Controllability, Thomas Brooks

Doctoral Dissertations

Haptic touch by wielding exploits a number of physical object properties in supporting perception and action. In particular, moments of an object’s mass influence judgments of its weight, length, and orientation. It has been suggested that these judgments are about something other than the physical dimensions themselves. However, manipulations of force fields in perception-action tasks requires participants to relearn how to manipulate objects or limbs.

The experiments here exploit the properties of a perceptual novelty—the gyroscope—to explore the role of an altered force field in perceptual judgment and its role in learning. Experiment 1 demonstrates that gyroscopic forces bring about …

School Counselors Meeting High School Students’ Social And Emotional Needs, Lorrie-Anne Monte

Doctoral Dissertations

The purpose of this research is to understand how school counselors are meeting the social and emotional needs of their ninth through twelfth grade high school students. The Delphi Method was used to create consensus among school counselor experts to identify the most prevalent social and emotional needs of their high school students, as well as the prevention and intervention techniques that school counselors are using to meet those needs. Twenty school counselors who work in high schools that have an American School Counselor Association (ASCA) Recognized ASCA Model Program (RAMP) agreed to participate as experts in this study (Round …

Synthesis And Modeling Of Ferroelectric Nanocomposites, Yomery Espinal

Doctoral Dissertations

Nanocomposites consisting of a ferroelectric oxide embedded within a non-ferroelectric matrix are a unique class of materials with potential to improve performance in next-generation electronics and non-volatile memory. Dielectric losses and breakdown due to processing and intrinsic properties of a monolithic ferroelectric point to low figures of merit. Therefore, it is necessary to develop composite materials with an active ferroelectric that is physically confined within a low-loss dielectric matrix while maintaining significant dielectric and pyroelectric properties inherent to ferroelectrics. The purpose of this work is to explore the behavior of ferroelectric nanocomposites as a function of dimensionality, and composition. The …