Direct Printing Of Single-Crystal Silicon By Microscale Nanoparticle Printing And Confined Laser Melting And Crystallization, Wan Shou

Doctoral Dissertations

"The transport and interfacial phenomena in laser melting and crystallization of silicon in micro-/nano-scale confinement lacks sufficient understanding. Uncovering the underlying mechanisms, and hence harness the melting and crystallization processes can help the formation of controllable single-crystal structures or patterns. In this dissertation, a molecular dynamics (MD) simulation was conducted to calculate the interfacial free energy of the silicon system in contact with flat and structured walls. Then the calculated interfacial energies were employed to predict the nucleation mechanisms in a slab of liquid silicon confined by two walls and compared with MD simulation results. Further, in combination with a …

Investigation Of Additively Manufactured Polymer And Transparent Polymer Composites, Gregory Taylor

Doctoral Dissertations

"The objective of this study is an investigation of both the characterization of fused deposition modeling (FDM) of polymer thermoplastics and the manufacture of glass-reinforced transparent composites. The flexural behavior and fracture toughness of FDM parts are critical for the evaluation and optimization of both material and process. This study focuses on the performance of FDM Ultem 1010 specimens intended to be used as composite tooling due the material's high heat resistance. A three-point bend test is performed for flexure properties while a single edge notch bend test is performed for fracture toughness. For each of the tests, the build …

Atomic Layer Deposition Prepared Nanostructured Materials For Various Catalytic Reactions, Xiaofeng Wang

Doctoral Dissertations

"Atomic layer deposition (ALD) has been widely used for thin film coating and metal nanoparticles (NPs) preparation. In this report, the applications of ALD prepared nanostructured materials in catalysis were examined.

Highly dispersed Pt monometallic catalysts with different substrates and multi-walled carbon nanotubes (MWCNTs) supported Pt-Co bimetallic catalysts were synthesized by ALD for selective hydrogenation of α, β-unsaturated aldehydes to unsaturated alcohols (UA). Pt/MWCNTs showed the highest selectivity of UA in selective hydrogenation of citral, as compared to Pt/SiO₂, Pt/ALD-Al₂O₃, and Pt/γ-Al₂O₃. After adding Co, the highest selectivity was achieved …

Long-Term Behavior Of Fiber Reinforced Polymer (Frp) Confined Concrete Cylinders Subjected To Severe Weather And Seawater Solution Conditions, Song Wang

Doctoral Dissertations

"This study presents an experimental investigation on durability of fiber-reinforced polymer (FRP) confined concrete cylinders subjected to various environmental conditions. Two types of cylinders were tested in this experiment: concrete-filled FRP tube (CFFT) and hollow-core FRP-concrete-steel (HC-FCS), with FRP tubes having two different constitutive resin components: polyester and epoxy. The specimens were subjected to three different environmental conditions: combined freeze/thaw, wet/dry and heating/cooling cycles with options of continuous water immersion and sustained axial load in an environmental chamber, UV exposure in an UV chamber, and seawater immersion in water tanks with sustained axial load. Mechanical and material characterization tests were …

Development Of Antimicrobial Chitosan Based Nanofiber Dressings For Wound Healing Applications, Lee Cremar, Jorge Gutierrez, Jennifer Martinez, Luis A. Materon, Robert Gilkerson, Fenghua Xu, Karen Lozano

Mechanical Engineering Faculty Publications

Objective(s): Chitosan based composite fine fibers were successfully produced via a centrifugal spinning technology. This study evaluates the ability of the composites to function as scaffolds for cell growth while maintaining an antibacterial activity.

Materials and Methods: Two sets of chitosan fiber composites were prepared, one filled with anti-microbial silver nanoparticles and another one with cinnamaldeyhde. Chitosan powder was dissolved in trifluoroacetic acid and dichloromethane followed by addition of the fillers. The fiber output was optimized by configuring the polymer weight concentration (7, 8, and 9 w/w% chitosan) and applied angular velocity (6000-9000 RPM) within the spinning process.

Results: …

Responsiveness Comparison Between A Lift-Type And Drag-Type Rotor In Waves, Yingchen Yang, Fredrick A. Jenet, Deyanira Jimenez, Brandon Benavides, Jesus Cerda, Angel Lopez

Mechanical Engineering Faculty Publications

Our recent progress on development of a vertical-axis unidirectional rotary wave energy converter (WEC) is discussed in this work. The WEC features a vertical-axis rotor that preforms unidirectional rotation in waves. The vertical axis arrangement makes the WEC respond well to waves from any direction with no realignment needs. And, the unidirectional behavior of the rotor promises no wave frequency discrimination, which is in comparison to reciprocating WECs that employ the resonant principle and are very frequency-specific. In our earlier proof-of-concept studies, we have successfully demonstrated two types of rotor designs: a lift type employing hydrofoil blades and a drag …

Gender Effects Of Robotics Programs On Stem-Related Self-Efficacy Of High School Students, Sandra Hall-Lay

Walden Dissertations and Doctoral Studies

Lack of STEM-related self-efficacy has impeded the growth of women in STEM fields. Out of school (OST) robotics programs and other STEM-related OST programs provide secondary students with opportunities to work in groups, brainstorm, and formulate ideas that require communication and teamwork. The purpose of this quantitative, quasi-experimental study was to compare STEM-related self-efficacy scores among male and female students who participated in OST robotics programs or other OST STEM-related programming. Independent variables were type of OST STEM program and gender. The dependent variable was students' STEM-related self-efficacy as measured by the Coping Self-Efficacy Scale. Responses from 149 students in …

Creative 3d Plant Optimization (C3po) System For The Exploration Systems And Habitation (X-Hab) 2018 Academic Innovation Challenge, Carter Bodnar, Joanna Boyd, Rebecca Brown, Kaitlin Burnash, Amanda Dennis, Brandon Furman, Camren Hansen, Skyler Heiner, Cameron Lebaron, Nicholas Narrell, Ty Nicholas, Adreann Peel, Andrew Poulos, David Redd, Joshua Wallace, Iren Bencze

Biological Engineering

As work in space continues to progress, many different ideas are being explored to improve life for astronauts. One factor that has been extensively researched is the viability of growing plants on the international space station(ISS). As plants provide a fresh source of food and psychological benefits for the astronauts providing their care, growing plants has remained a point of interest for NASA over the years. Currently the VEGGIE system provides a platform for growing plants on the ISS; however, the system creates a large amount of waste (the substrate after use) and requires regular interaction from the astronauts, as …

Designing A Synthetic Spider Silk Based Coating For Urinary Catheters To Reduce The Risk Of Cautis, Tess Armbrust, Alexander Cook, Andrea Grebil, Matthew Potter, Rachel Müller, Harshit Singh, Riannon Smith, Randolph Lewis

Biological Engineering

• Catheter-associated urinary tract infections (CAUTIs) are a leading cause of morbidity and mortality in patients with life-threatening conditions.¹

• Foley catheters are the most common urinary catheters used but can become burdened with microbes which lead to CAUTIs, the most common source of hospital acquired infection (HAI).¹

• The attached bacteria can form biofilms on the catheter which are difficult to treat using oral antibiotics and can lead to chronic infections.²

• Synthetic spider silk as a catheter coating shows great promise because of demonstrated strength, biocompatibility, and antimicrobial properties.

• Chlorhexidine can enhance the antimicrobial …

A Time-Efficient Cmos-Memristive Programmable Circuit Realizing Logic Functions In Generalized And-Xor Structures, Muayad Aljafar, Marek Perkowski, John M. Acken, Robin Tan

Electrical and Computer Engineering Faculty Publications and Presentations

This paper describes a CMOS-memristive Programmable Logic Device connected to CMOS XOR gates (mPLD-XOR) for realizing multi-output functions well-suited for two-level {NAND, AND, NOR, OR}-XOR based design. This structure is a generalized form of AND-XOR logic where any combination of NAND, AND, NOR, OR, and literals can replace the AND level. For mPLD-XOR, the computational delay, which is measured as the number of clock cycles, equals the maximum number of inputs to any output XOR gate of a function assuming that the number of XOR gates is large enough to calculate the outputs of the function simultaneously. The input levels …

Terahertz Imaging Of Thin Film Layers With Matched Field Processing, Scott Schecklman, Lisa M. Zurk

Electrical and Computer Engineering Faculty Publications and Presentations

Terahertz (THz) time of flight (TOF) tomography systems offer a new measurement modality for non-destructive evaluation (NDE) of the subsurface layers of protective coatings and/or laminated composite materials for industrial, security and biomedical applications. However, for thin film samples, the time-of-flight within a layer is less than the duration of the THz pulse and consequently there is insufficient range resolution for NDE of the sample under test. In this paper, matched field processing (MFP) techniques are applied to thickness estimation in THz TOF tomography applications, and these methods are demonstrated by using measured THz spectra to estimate the the thicknesses …

Subspace Clustering Using Ensembles Of K-Subspaces, John Lipor, David Hong, Yan Shuo Tan, Laura Balzano

Electrical and Computer Engineering Faculty Publications and Presentations

Subspace clustering is the unsupervised grouping of points lying near a union of low-dimensional linear subspaces. Algorithms based directly on geometric properties of such data tend to either provide poor empirical performance, lack theoretical guarantees, or depend heavily on their initialization. We present a novel geometric approach to the subspace clustering problem that leverages ensembles of the K-subspaces (KSS) algorithm via the evidence accumulation clustering framework. Our algorithm, referred to as ensemble K-subspaces (EKSS), forms a co-association matrix whose (i,j)th entry is the number of times points i and j are clustered together by several runs of KSS with random …

Private Sector Defense Contractor Management Strategies For Contract Fulfillment, Rachel Stallworth

Walden Dissertations and Doctoral Studies

Private sector U.S. defense contractors failing to meet contract objectives experience lower profitability, pay costly penalties, and risk survivability. Using the theory of contracts, the purpose of this multiple case study was to the explore strategies that some leaders of U.S. defense contracting businesses use to meet all the contract terms with the U.S. Department of Defense. Data were collected from 5 leaders of private sector defense contracting companies in northwest Florida through face-to-face, semistructured interviews and through a review of operations manuals, quality assurance policy manuals, and archived U.S. Department of Defense contracts. During data analysis using Yin's 5-step …

Developing Technology For Environmental Response To Harmful Algal Blooms (Habs), Ammon Balle, Jason Eldredge, Michael Flores, Kyle Hillman, Ammon Hooper, Jeffrey Jarman, Bethany Jensen, Tyler Lewis

Biological Engineering

• Toxic to humans, domestic animals, fish, and other wildlife

• Immediate symptoms: nausea, vomiting, diarrhea, headache, and skin rash

• Carcinogen

• Liver Toxin

• Withstands high temperatures, changes in pH, photolysis, and hydrolysis

• A main toxin of concern in Utah HABs

Microfluidic Device For Decellularization Of Murine Brain Slices, Christian Morrill, Adam Talbot, Ian Wadsworth, Melena Garrett, Elaine Castro, Holly Saatzer, Yu Huang

Biological Engineering

In the body, nearly all cells in tissues reside in an extracellular matrix (ECM) consisting of a complex three-dimensional (3D) microenvironment created through cell-cell and cell-ECM interactions that maintain specificity and homeostasis of the tissue. Accurate representation of microenvironments is pivotal in furthering our understanding of several fields, including disease mechanisms, drug discovery, tissue engineering, and regenerative medicine. Current 3D tissue models are limited in their ability to reproduce tissue-specific biochemical and mechanical cues present in vivo¹.

Decellularization is the chemical, physical, or enzymatic means of stripping cells from a tissue, producing a bare 3D ECM that is …

Springstepper: An Alternative To Traditional Crutches, Jennifer Smith, Garrett Jones, Wm. Paul Gilson, Jeremiah Woodall, Matthew Clegg

Biological Engineering

Axillary crutches are the most common type of crutch. They are cheap and readily accessible, which makes them a popular option. However, when used incorrectly they can cause a host of problems, including blood clots (Brooks) and nerve damage (Chang). Even when used correctly they can cause carpal tunnel syndrome and other injuries due to the large amount of force placed on the hand and wrist (Goh). Several different crutches have been created, but each comes with its own issues (Malkan).

Tire-Derived Geo-Cylinders And Polymer Products For Enhancing The Properties Of Base/Sub Base Materials In Pavement Systems, Justin Scott Smith

Graduate Theses, Dissertations, and Problem Reports (ETD)

As a critical part of the transportation network, pavements offer a safe means for vehicular traffic. Pavements are subjected to many forms of stress during their service life, and they are susceptible to environment related cracking and failures. Failures can be attributed to poor subgrade, freeze-thaw variations, and fatigue under repetitive axle loadings. Reinforcement products such as tire-derived geo-cylinders (TDGC) which make-up mechanical concrete and geo-polymers have been utilized in civil engineering practice, and this research aims to understand the potential life of tested pavement system components set at displacement limitations when reinforced with TDGCs and geo-polymers from exposure to …

Thermal-Fatigue And Thermo-Mechanical Equivalence For Transverse Cracking Evolution In Laminated Composites, Javier Cabrera Barbero

Graduate Theses, Dissertations, and Problem Reports (ETD)

Carbon fiber reinforced plastics (CFRP) are potential materials for many aerospace and aeronautical applications due to their high specif strength/weight and a low coeffcient of thermal expansion (CTE) resulting in a high long-term stability. Among candidate structures, the re-entry reusable launch vehicles (RLV), the fuel oxidant storage and transportation at cryogenic temperature, space satellites, and aircraft structure (frame, wings, etc...) can be highlighted. However, CFRP are prone to internal damage as a result of high residual stresses and thermal fatigue loading. In this study, micro-cracking damage evolution in laminated composites subjected to monotonic cooling and thermal cyclic loads is developed …

The Effect Of Waco2 Ratio On Co2 Geo-Sequestration Efficiency In Homogeneous Reservoirs, Emad A. Al-Khdheeawi, Stephanie Vialle, Ahmed Barifcani, Mohammad Sarmadivaleh, Stefan Iglauer

Research outputs 2014 to 2021

Various factors such as reservoir temperature, wettability, caprock properties, vertical to horizontal permeability ratio, salinity, reservoir heterogeneity, injection well configuration affect the CO2 geo-sequestration efficiency. Furthermore, it was previously investigated that CO2 storage efficiency can be improved by using water alternating CO2 (WACO2) technology. However, the effect of the WACO2 ratio (the ratio of the total amount of injected CO2 to the total amount of injected water) on CO2 storage efficiency has not been addressed adequately. Thus, in this paper, a 3D homogeneous reservoir simulation model has been developed to study the impact of the WACO2 ratio on CO2 mobility …

Co2 Saturated Brine Injected Into Fractured Shale: An X-Ray Micro-Tomography In-Situ Analysis At Reservoir Conditions, Hongyan Yu, Yihuai Zhang, Maxim Lebedev, Zhenliang Wang, Jinfeng Ma, Zhihao Cui, Michael Verrall, Andrew Squelch, Stefan Iglauer

Research outputs 2014 to 2021

Fracture morphology and permeability are key factors in enhanced gas recovery (EOR) and Carbon Geo-storage (CCS) in shale gas reservoirs as they determine production and injection rates. However, the exact effect of CO2-saturated (live) brine on shale fracture morphology, and how the permeability changes during live brine injection and exposure is only poorly understood. We thus imaged fractured shale samples before and after live brine injection in-situ at high resolution in 3D via X-ray micro-computed tomography. Clearly, the fractures’ aperture and connectivity increased after live brine injection.

Influence Of Substrate Stage Temperature And Rotation Rate On The Magneto-Optical Quality Of Rf-Sputtered Bi2.1dy0.9fe3.9ga1.1o12 Garnet Thin Films, Mohammad E. Alam, Mikhail Vasiliev, Kamal Alameh

Research outputs 2014 to 2021

Highly bismuth-substituted iron garnet thin films are prepared on quartz substrates by using a radio frequency (RF) magnetron sputtering technique. We study the factors (process parameters associated with the RF magnetron sputter deposition technique) affecting the magneto-optical (MO) properties of ferrite garnet films of composition Bi2.1Dy0.9Fe3.9Ga1.1O12. All films show high MO response across the visible range of wavelengths after being annealed. In particular, the effects of substrate stage temperature and rotation rate on the various properties of films are studied. Experimental results reveal that the characteristics of garnet films of this type can be tuned and optimized for use in …

Magneto-Optic Properties Of Ultrathin Nanocrystalline Ferrite Garnet Films In The 8k To 300k Temperature Interval, Viatcheslav Kotov, Vladimir Shavrov, A. Popkov, Mikhail Vasiliev, Kamal Alameh, Mohammad Alam, L. Alyabyeva, Dmitry Balabanov, Vladimir Burkov, M Virchenko

Research outputs 2014 to 2021

A study of the initial stages of crystallization in RF magnetron-sputtered ferrite garnet films is reported, in which a series of ultrathin Bi2Dy1Fe4Ga1O12 layers is fabricated and characterized. The spectral and temperature dependencies of magnetic circular dichroism (MCD) of these films are studied in the temperature range from 300 K down to 8 K. Measured magneto-optical properties are reported in the spectral range between 300 and 600 nm. In ultrathin garnets at temperatures below 160 K, we found that between 360 and 520 nm, the spectral MCD dependencies were typical of bismuth-substituted garnets with high levels of gallium dilution in …

Evaluation Of Bio-Asphalt Binders Modified With Biochar: A Pyrolysis By-Product Of Mesua Ferrea Seed Cover Waste, Abhinay Kumar, Rajan Choudhary, Rumi Narzari, Rupam Kataki, Sanjay K. Shukla

Research outputs 2014 to 2021

With growing global concerns related to energy security and sustainability, interest in bio-fuels has increased significantly. Production of biofuel mostly begins with pyrolysis, a process that converts the biomass to liquid biooil, solid biochar and gases. A large amount of carbonaceous biochar is generated as a by-product during the pyrolysis. However, no major effort has been made in the past decade to utilize the biochar in pavement applications, especially as a bio-modifier to asphalt binders. In this study, an attempt was made to evaluate the carbonaceous biochar, obtained during bio-fuel production through pyrolysis of Mesua ferrea seed cover waste, as …

The Effect Of Friction Stir Processing On The Microstructure And Tensile Behavior Of Aluminum Alloys, Nelson Gomes Affonseca Netto

UNF Graduate Theses and Dissertations

Friction Stir Processing (FSP) is a promising thermomechanical technique that is used to modify the microstructure of metals locally, and thereby locally improve mechanical properties of the material. FSP uses a simple and inexpensive tool, and has been shown to eliminate pores and also reduce the sizes of intermetallics in aluminum alloys. This is of great interest for research on solidification, production and performance of aluminum alloy castings because FSP can enhance the structural quality of aluminum casting significantly by minimizing the effect of those structural defects.

In the literature, there is evidence that the effectiveness of FSP can change …

Effect Of Vessel-Generated Waves In Near Low Tide Conditions On Shorelines In The Intracoastal Waterways, Mackenzie Lee Sanchez

UNF Graduate Theses and Dissertations

Erosion is caused when there is a net loss of sediment in a coastal system, i.e. when the amount of sediment leaving a system is more than the amount of sediment entering that same system. This investigation will focus on vessel-generated waves and their effect on the shorelines of the Jacksonville, Florida Intracoastal Waterways near low tide conditions. The investigation conducted herein examines variations in turbidity and pressure measurements in response to passing vessels at a single site location previously selected in 2016. The primary water/shoreline interaction recorded during this investigation is located below the visible scarp (near low tide …

Profile Analysis Of Mobile Application Security, Adetunji A. Olunuga

UNF Graduate Theses and Dissertations

ABSTRACT

This thesis conducts profile analysis on the mobile application security using peer-review articles that were published from 2010 to 2018. From the analysis, we will identify prolific authors, intuitions, and geographic regions as well as the topics addressed by the articles. The profile analysis will reveal most frequently used research methods, research approaches (quantitative, qualitative and mixed), and theories used to study the field. This thesis reveals that none of the researchers have made significant contributions to the field, and researches are not collaborating to solve their research problems. The profile analysis shows that surveys and experiments are the …

Investigation Of Near-Bottom Current Characteristics Along An Open-Ocean Coast, Nikole S. Ward

UNF Graduate Theses and Dissertations

Near-bottom current data was collected over a period of 8 years at the U.S. Army Corps of Engineers Field Research Facility in Duck, North Carolina. This data set consisted of currents measured up to three elevations above the bottom at deployment depths of 5 meters, 8 meters and 13 meters, as well as continuous real-time wind and wave data collected at the pier. The data was collated, quality checked and analyzed to define a climatology of near bottom currents along the study area using current moments. This data set had previously never been available for analysis due to the large …

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 …

Targeting Metastatic Breast Cancer With Statin Drugs And Coq10, Jacob Thrasher

Honors Theses

Statin drugs are commonly prescribed to lower cholesterol levels in patients, but recently statins have been under investigation as a potential anti-cancer drug. Statins are HMG-CoA reductase inhibitors and subsequently inhibit the mevalonate pathway and cholesterol synthesis. Since cholesterol trafficking is vital in the growth and metastasis of cancer, statin drugs are being studied to explore their effects on cancer cells. CoQ10, one of the products from the mevalonate pathway, also has shown some potential anti-cancer properties, but its use to combat cancer is controversial. While some studies have shown that CoQ10 supplements can be synergistic with other cancer treatment …

Patient Friendly Kidney Function Screening, Ragwa El Sayed, Rathna Ramesh, Alessandro Bellofiore, David Anastasiu, Melinda Simon

Faculty Publications

No abstract provided.