Digital Commons Network^™

A Globalized Optimization Schema For Automated Fiber Placement Processing Parameters, Matthew John Godbold

Theses and Dissertations

Automated Fiber Placement is an advanced manufacturing technique for industrial-scale composite structures. Advanced robotics coupled with composite manufacturing results in faster and more consistent results than previously obtained through hand layup. The complexity and interconnectedness of the automated fiber placement process provides a difficult challenge for traditional modeling techniques. Modeling within automated fiber placement currently utilizes physics-based modeling to inform the translation of a design to a manufacturing plan. The intricacy of the automated fiber placement process dictates that attempts at modeling or optimizing these processes are often limited in their scope. Physics-based modeling for manufacturing typically involves numerous interacting …

Comprehensive Process Planning Optimization Framework For Automated Fiber Placement, Alex Ryan Brasington

Theses and Dissertations

Advanced composite materials came about in 1966 and have since been widely used due to the possibility of superior structural performance while also achieving weight reductions. Such opportunities have led to composite materials being used to fabricate complex components, often in the aerospace sector. Most components, especially in aviation, are on a large scale and are outside the capabilities of traditional composite manufacturing techniques. Traditional manufacturing methods are also labor intensive, time consuming, have a high level of material scrap, and are prone to human error. This has led to the need for innovative manufacturing solutions to withstand the ever-increasing …

Closed Form Implicitly Integrated Models For Computationally Efficient Simulation Of Power Electronics, Andrew Wunderlich

Theses and Dissertations

This work describes novel closed-form, implicitly integrated (CF-implicit) models of switched-mode power converters which feature implicit integration but require no iterative numerical solving algorithm for evaluation because they are explicitly solved prior to model execution. The derived models capture the large-signal dynamic behavior of the power converters, so their use and accuracy are not limited to any one set of operating conditions. These models can be implemented in any computational environment, including directly on an existing embedded controller as a digital twin. Since no iterative solver is required, the models are highly computationally efficient and have a very predictable worst-case …

Development Of A Multi-Scale Mechano-Electrochemical Battery Model, Drew J. Pereira

Theses and Dissertations

As the automotive industry moves towards large format electric vehicles, such as trucks and SUVs, the need for highly efficient, energy-dense electrodes rapidly increases. Several promising active materials have been studied and proposed, however, many of these materials undergo significant volume change upon lithiation and de-lithiation. Cell and pack designers struggle to understand and predict how active material volume change at the particle scale will affect mechano-electrochemical behavior on the electrode, cell, and pack scales. Additionally, many of these active materials suffer in their cycle life due to a mechanically-driven degradation of the electrode matrix. Therefore, the focus of this …

Groundwater Flow And Transport At The Forest-Marsh Boundary: A Modeling Study, Sophia Chason Sanders

Theses and Dissertations

The forest-marsh boundary, where tidally influenced salt marshes meet a forested upland, is hydrologically complex due to its multiple water inputs. Groundwater flow and salinity transport at this boundary are not well understood. In order to make predictions about salinity at this boundary as it responds to climatic factors, a two-dimensional model was built to simulate groundwater flow and solute transport at a salt marsh on Sapelo Island, Georgia. After calibration based on observed data from wells at the study site, the model can be used to identify patterns in groundwater movement and solute transport that may influence the vegetation …

Vascular Endothelial Dysfunction And Effects On Arterial Wall Microstructure, Jeffrey Thomas Rodgers

Theses and Dissertations

Vascular endothelial cell dysfunction (ECD) is a disease characterized by the inability of the vascular endothelial cells to transmit signaling molecules, namely nitric oxide (NO), in response to changes in blood flow rate. This disease is shown to be incident in the onset of more severe vascular disease such as hypertension, atherosclerosis, and heart failure. Long-term ECD is shown to cause long-term remodeling such as decreased flow-mediated dilation, increased pulse-wave velocity, intimal-medial thickening, and increased wall stiffness due to collagen deposition. We used second harmonic generation (SHG) microscopy to analyze this change in the collagen microstructure of the arterial extracellular …

Computational Modeling Of Radiation Damage In A Multi-Phase Ceramic Waste Form Using Moose, Zeyu Chen

Theses and Dissertations

Ceramic waste forms have been proposed to replace the traditional glassy waste forms for long term stabilization of radionuclides. These waste forms are constantly exposed to self-irradiation emitted from the constituent radionuclides causing their material properties to change accordingly. It has been known that the radiation damage in waste forms is dominated by alpha particles emitted from transuranic (TRU) radionuclides. Since alpha particles usually have a range of 10~20 μm in such waste forms, some fraction of any non-transuranic containing phases (for a multiphase waste form) will be undamaged (or less damaged) if containing large enough grain sizes. Modeling and …

Molecular Modeling Of Tethered Polyelectrolytes For Novel Biomedical Applications, Merina Jahan

Theses and Dissertations

Current research trends throughout the world focus on designing intelligent materi- als and systems for diverse applications in all courses of life. Biomaterials research encompasses a major part in this revolution due to the increased effort in fulfilling unmet medical needs to treat complex physiological and neurodegenerative disorders. Polymers play inevitable roles in these research endeavors for their ubiquitous pres- ence in biological systems. Therefore, it is crucial to understand how the polymeric molecules interact within diverse biological environments, to efficiently engineer them for various drug delivery and biosensing systems. The use of experimental design and selection of different polymers …

Modeling Neutron Interaction Inside A 2d Reactor Using Monte Carlo Method, A. S. M. Fakhrul Islam

Theses and Dissertations

Scientists and engineers have been working for many years to develop accurate approaches to analyzing nuclear power reactors using computer codes that closely model the behavior of neutrons in a reactor core. The Monte Carlo simulation method is capable of treating complex geometries with a high level of resolution and fidelity to model neutron interactions inside a reactor core. With the requirement of accurate modeling in reactor physics and dynamics and great innovation of computer technology, Monte Carlo method is becoming an ever more powerful tool and receiving rising attention. In this study, Monte Carlo method is used to model …

Three-Dimensional Collagen Tubes For In Vitro Modeling, Rebecca Jones

Theses and Dissertations

Collagen type I represents a novel material for three-dimensional in vitro models. While two-dimensional models are typically inadequate for recreating the complex processes of the body, collagen provides a three-dimensional basis with a variety of applications, including remodeling of vascular cells under tension and vascular stenosis. Smooth muscle cells reorganize and reconstruct their environment differently under conditions of tensions, such as with sutures, or under conditions without applied external tension. Vascular stenosis, the abnormal narrowing of blood vessels, arises from defective developmental processes or atherosclerosis-related adult pathologies. Stenosis triggers a series of adaptive cellular responses that induces adverse remodeling, which …

The Restoration Of The Nile River And Its Delta, Egypt. Numerical Modeling, Basim Mohammed Naseef Al-Zaidi

Theses and Dissertations

The construction of the High Aswan Dam significantly reduced the flood flows and the sediment supply to the Egyptian portion of the Nile River. Consequences of this changes in river hydrology are diffuse channel bed erosion in the upstream part of the river, in- channel sedimentation in the downstream part of the system, delta recession, habitat deterioration, wetlands loss, water pollution, and environmental problems. The feasibility of a Nile River-Delta restoration project with controlled flow releases and sediment augmentations at Aswan is here investigated with the aid of site-specific one-dimensional morphodynamic models. The water source for the restoration project, based …

Theory, Computation, And Modeling Of Cancerous Systems, Sameed Ahmed

Theses and Dissertations

This dissertation focuses on three projects. In Chapter 1, we derive and implement the compact implicit integration factor method for numerically solving partial differential equations. In Chapters 2 and 3, we generalize and analyze a mathematical model for the nonlinear growth kinetics of breast cancer stem cells. And in Chapter 4, we develop a novel mathematical model for the HER2 signaling pathway to understand and predict breast cancer treatment. Due to the high order spatial derivatives and stiff reactions, severe temporal stability constraints on the time step are generally required when developing numerical methods for solving high order partial differential …

Modeling Early Archaic Mobility And Subsistence: Evaluating Resource Risk Across The South Carolina Landscape, Joseph E. Wilkinson

Theses and Dissertations

Previous models predicting Early Archaic mobility and subsistence strategies in South Carolina have evaluated behavioral negotiations of specific resource distributions. A new model is presented using empirical datasets that quantify and evaluate the quality and geographic distributions of lithic raw materials and drainage systems in the state. By utilizing datasets from private collections and landscape elevation data, this model is generated using Geographic Information Systems (GIS) software in order to produce a "Risk Landscape" from which predictions of site density, artifact density, lithic raw material diversity, and the condition of lithic toolkit assemblages can be generated based on landscape location. …

Modeling Of Tow Wrinkling In Automated Fiber Placement Based On Geometrical Considerations, Roudy Wehbe

Theses and Dissertations

Automated manufacturing of fiber reinforced composite structures via numerically controlled hardware yields parts with increased accuracy and repeatability as compared to hand-layup parts. Automated fiber placement (AFP) is one such process in which structures or parts are built by adding bands of prescribed number of tows or slit-tape with prescribed width using robotic machine heads over 3D surfaces following prescribed paths. Despite the improved accuracy, different types of defects or manufacturing features arise during fabrication. These defects can be due to geometrical features, materials, and process planning parameters and are detected in the form of wrinkling, tow twist, tow folding, …

Modeling And Loss Analysis Of Wide Bandgap Power Semiconductor Devices, Kang Peng

Theses and Dissertations

In recent times, the development of high power density and high efficiency power converters has become critical in power electronics applications like electric vehicles, aircrafts, electric ships and so on. High-switching-frequency and high-temperature operation are required to achieve this target. However, these requirements are exceeding the theoretical material-related limits of silicon (Si) based devices. The emerging wide bandgap power semiconductor technology is a promising solution to meet these requirements. Silicon Carbide (SiC) and Gallium Nitride (GaN) are the most promising among all wide bandgap semiconductor materials. SiC and GaN have almost a three times larger bandgap (about 3eV), compared with …

Modeling Human-Structure Interaction Using A Controller System, Albert Ricardo Ortiz Lasprilla

Theses and Dissertations

The effects of human loads on structures are difficult to predict because they depend on the type of activity people are performing. However, models for typical activities such as standing, sitting and jumping have been proposed in the literature. Traditional models represent the human body as a system of lumped masses, dampers and springs arranged in a system with multiple degrees of freedom. Arguably, these models might not fully represent the human body because lumped masses, dampers and springs cannot add energy to the overall system. Furthermore, people could react differently to different levels of excitation and other environmental conditions. …

Modeling Of Structural Relaxation By A Variable-Order Fractional Differential Equation, Su Yang

Theses and Dissertations

In physical point of view, relaxation usually describes the return from a perturbed system into equilibrium and each process has its own characteristic relaxation time. In 1946, Tool first formulated the notion of fictive temperature to characterize the structure of a glass-forming melt. Since then, people used to simulate structural relaxation by first order model. Since fractional-based models have not widely applied in modeling the fictive temperature, I want to explore the the possibility of modeling structural relaxation by fractional differential equation.

In this thesis, I will first introduce the definitions of two different kinds of fractional derivatives: Riemann-Liouville fractional …

Automated Image Analysis And Spatial Computational Modeling Of Nf-Kb In Cerebrovascular Endothelial Cells, Kasey Catalfomo

Theses and Dissertations

Cerebrovascular endothelial cells play a key part in the inflammatory response of the blood-brain barrier in pathological conditions such as Alzheimer’s disease. Specifically, the NF-κB signaling pathway plays a central role. Better understanding of the factors in inflammatory disease progression can lead to more effective treatments for such devastating illnesses like Alzheimer’s, asthma, arthritis, cancer, diabetes and many more inflammatory diseases. The proposed approach analyzes spatial NF-κB distribution contained in multispectral stacked micrograph images of cerebrovascular endothelial cells indexed based on dose of the activating protein and the length of activation. Image analysis code identifies the location of nuclear boundaries …

Modeling Embankment Breach Due To Overtopping, Ali Asghari Tabrizi

Theses and Dissertations

Despite numerous embankment failures around the world, in-depth assessments as well as reliable, comprehensive sets of data of such failures are limited. Detailed understanding of the earthen embankment failure process and the dominant parameters affecting the failure are needed to predict and model the breach process precisely. Therefore, a series of laboratory experiments on embankment (i.e., dam and levee) overtopping as well as erodibility measurements using the Submerged Jet test are conducted. Also, to study the influence of different model parameters (e.g., turbulence model, bedload formula), one of the dam embankment experiments is simulated. The main goal of this research …

Intercode Advanced Fuels And Cladding Comparison Using Bison, Frapcon, And Femaxi Fuel Performance Codes, Aaren Rice

Theses and Dissertations

The high density uranium-based fuels are regaining popularity as the current fleet of LWR’s are showing interest in uprating plants to increase accident tolerance and performance. Fuels such as U3Si2, UN, and UC all contain a higher uranium loading and thermal conductivity than that of UO2 making them attractive in combination with an advanced cladding type such as the ceramic SiC cladding. In addition to adding more mass uranium to the core without surpassing current enrichment limits, these advanced fuels and claddings are designed with increased accident tolerance performance in a LOCA type scenario in mind. One of the possible …

Oxygen Flux And Dielectric Response Study Of Mixed Ionic-Electronic Conducting (Miec) Heterogeneous Functional Materials, Fazle Rabbi

Theses and Dissertations

Dense mixed ionic-electronic conducting (MIEC) membranes consisting of ionic conductive perovskite-type and/or fluorite-type oxides and high electronic conductive spinel type oxides, at elevated temperature can play a useful role in a number of energy conversion related systems including the solid oxide fuel cell (SOFC), oxygen separation and permeation membranes, partial oxidization membrane reactors for natural gas processing, high temperature electrolysis cells, and others. This study will investigate the impact of different heterogeneous characteristics of dual phase ionic and electronic conductive oxygen separation membranes on their transport mechanisms, in an attempt to develop a foundation for the rational design of such …

The Development Of A Performance Progression For Science Teachers' Implementation Of Model-Based Teaching, Christopher Bogiages

Theses and Dissertations

The Next Generation Science Standards (NGSS) call for science teachers to implement pedagogical strategies that can approximate authentic scientific practices. One such strategy, Model-Based Teaching, engages students in learning the disciplinary core ideas of science through the process of developing and using Scientific Models. Model-Based Teaching is a difficult pedagogical strategy for teachers to learn and implement. Factors such as Knowledge of Scientific Models and Modeling (KSM), understanding of the Nature of Science (NOS), and use of questioning to facilitate whole class discussions play important roles in the development of teachers' ability to implement Model-Based Teaching. This study employed a …

New Approach For Modeling Hybrid Pressure Swing Adsorption-Distillation Processes, Fan Wu

Theses and Dissertations

A new methodology for modeling hybrid pressure swing adsorption (PSA)-distillation processes has been developed. Two hybrid systems were simulated as examples. One is for ethanol dehydration, and the other is for propane/propylene separation. Firstly, a distillation process simulator such as Chemsep was used to simulate the distillation process of the hybrid system, in which the PSA unit was treated as a "black box" with an assumed process performance. In this way, a hybrid PSA-distillation process can be analyzed simply by performing mass balances around these units and running Chemsep to determine the possibility of energy saving compared to a reference …

Modeling Of Sic Power Semiconductor Devices For Switching Converter Applications, Ruiyun Fu

Theses and Dissertations

Thanks to recent progress in SiC technology, SiC JFETs, MOSFETs and Schottky diodes are now commercially available from several manufactories such as Cree, GeneSiC and Infineon. SiC devices hold the promise of faster switching speed compared to Si devices, which can lead to superior converter performance, because the converter can operate at higher switching frequencies with acceptable switching losses, so that passive filter size is reduced. However, the ultimate achievable switching speed is determined not only by internal semiconductor device physics, but also by circuit parasitic elements. Therefore, in order to accurately predict switching losses and actual switching waveforms, including …

Multi-Physicochemical Modeling Of Solid Oxide Fuel Cells And Electrolyzer Cells, Yuanyuan Xie

Theses and Dissertations

Multi-physicochemical models are developed for solid oxide fuel cells and electrolysis cells. The models describe the complicated transport processes of charge (electron/ion) conservation, mass/species conservation, momentum conservation, and energy conservation. Transport processes are coherently coupled with chemical reforming processes, surface elementary reaction processes, as well as electro-oxidation processes of both hydrogen and carbon monoxide. The models are validated with experimental data and utilized for fundamental mechanism studies of SOFCs fueled with different type of fuels, such as hydrogen, hydrocarbon, e.g., methane, H2S, and their mixtures. The fundamental mechanisms associated with syngas generation using electrolysis cell are also extensively investigated using …

A Geographic Modeling Framework For Assessing Critical Infrastructure Vulnerability: Energy Infrastructure Case Study, Leanne Sulewski

Theses and Dissertations

Vulnerability of critical infrastructure systems is of the utmost importance to a nation's national security interests, especially the electric grid. Despite the importance of these systems, disruptions continue to occur at an alarming rate, thus indicating that there is a fundamental flaw in the way critical infrastructure systems are analyzed for vulnerability.

Critical infrastructure systems are typically analyzed using mathematical approaches such as graph theory, which strip systems of their important geographic information, and only look at their connections to each other. While these relationships and metrics provide useful information, they cannot provide the entire picture. As such, this research …