Engineering Commons^™

Costs And Benefits Of Flood Mitigation In Louisiana, Arash Taghi Nezhad Bilandi

LSU Doctoral Dissertations

Assessing the costs and benefits of hazard mitigation efforts is an essential component of disaster management, planning, and resilience assessment. These calculations are particularly important in locations vulnerable to multiple hazards with high frequencies, such as coastal Louisiana. This study aims to provide an improved understanding of the costs and benefits of flood mitigation efforts in Louisiana funded by federal government grants between 2005 and 2015. Project data provided by the Governor’s Office of Homeland Security and Emergency Preparedness (GOHSEP) were summarized and missing values were imputed using robust statistical approaches. Elevation project cost was investigated for prediction by statistical …

Coating Component Migration In Paper Coatings, Emilia Purington

Electronic Theses and Dissertations

In many applications such as in paints and coatings, pigments are mixed with polymeric binders to generate the final product. In the coating of paper, properties like strength, durability, and print quality are affected not only by the binder type, but the final location of the binder relative to the pigments and the fibers. During the application and drying of a paper coating, binder is known to migrate. A number of methods are available to measure the migration of latex or starch. However, all of these methods have some limitations, especially when starch, latex and kaolin are components of the …

Metal Thin Film Stiffness Extraction Technique For Surface Acoustic Wave Filters, Travis R. Weismeyer

Electronic Theses and Dissertations

Accurate knowledge of the surface acoustic wave (SAW) properties propagating at the surface of a piezoelectric substrate with thin films, electrodes or temperature compensated films, is critical in SAW filter design to meet the target frequency response, power durability and performance prior to device fabrication. While reliable material constants exist for substrates such as LiNbO3 used in SAW filters, the absolute elastic constants associated with operational thin films used for electrodes or temperature compensation do not exist. Although the bulk values of the constituent materials are known, the composite film/substrate properties are difficult to predict since they depend strongly on …

Tunable Electronic And Optical Properties Of Low-Dimensional Materials, Shiyuan Gao

Arts & Sciences Electronic Theses and Dissertations

Two-dimensional (2D) materials with single or a few atomic layers, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), and the heterostructures or one-dimensional (1D) nanostructures they form, have attracted much attention recently as unique platforms for studying many condensed-matter phenomena and holds great potentials for nanoelectronics and optoelectronic applications. Apart from their unique intrinsic properties which has been intensively studied for over a decade by now, they also allow external control of many degrees of freedom, such as electrical gating, doping and layer stacking. In this thesis, I present a theoretical study of the electronic and …

Optimization Of Useful Hard X-Ray Photochemistry, David Lewis Goldberger

UNLV Theses, Dissertations, Professional Papers, and Capstones

X-ray induced damage is generally considered a nuisance, but in the field of Useful Hard X-ray Photochemistry we harness the highly ionizing and penetrating properties of hard X-rays (> 7 keV) to initiate novel photochemical decomposition and synthesis at ambient and extreme conditions. Preliminary experiments suggest that the energy of irradiating photons and the sample pressure play roles in determining the nature of X-ray induced damage. Here, we present the X-ray energy dependence of damage induced in strontium oxalate, strontium nitrate, and barium nitrate, as well as the pressure dependence of X-ray induced damage of strontium oxalate. Our results indicate …

Linking Structure And Dynamics In Metallic Liquids: A Combined Experimental And Molecular Dynamics Approach, Robert Ashcraft

Arts & Sciences Electronic Theses and Dissertations

A major outstanding problem in condensed matter physics is the nature of the glass transition, in which a rapidly cooled liquid can bypass the transition into a crystalline state and the liquid structure is "frozen-in" due to kinetic arrest. To characterize the fundamental features behind this transition the liquid, both in the high temperature (equilibrium) and supercooled state, needs to be better understood. By examining the relationship between structure and dynamics a better characterization of the liquid state and a determination of the mechanisms that are ultimately important for the formation of the glass can be gained. In this dissertation, …

Multifunctional Nanocomposites Based On Bacterial Cellulose, Qisheng Jiang

McKelvey School of Engineering Theses & Dissertations

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to …

Multifunctional Nanocomposites Based On Bacterial Cellulose, Qisheng Jiang

McKelvey School of Engineering Theses & Dissertations

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to …

Measuring Characteristic Shrinkage Variability Due To Metal Loading Effects In Low Temperature Co-Fired Ceramic Using Image Processing, John Ezekiel Zumbro

Graduate Theses and Dissertations

Low temperature co-fired ceramic (LTCC) has many benefits when it comes to electronic packaging due to the low dielectric loss, reliability in extreme environments, and high breakdown voltage. Though the ceramic has a lot of benefits it is not widely used due to the high cost and complexities associated with manufacturing. One of these issues with manufacturing is compensating for the shrinkage of the ceramic, this is accomplished by using an expansion factor, creating the “green” or manufactured design. This expansion factor is approximated through knowledge of the ceramic factors such as the metal loading, layers of ceramic tape, firing …

Comparative Study Of Power Semiconductor Devices In A Multilevel Cascaded H-Bridge Inverter, Kenneth Mordi

Graduate Theses and Dissertations

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET …

Reinventing The Wheel, Esther K. Unti, Ahmed Z. Shorab, Patrick B. Kragen, Adam M. Menashe

Mechanical Engineering

Reinventing the Wheel selected tires and designed wheels for the 2018 Cal Poly, San Luis Obispo Formula SAE combustion vehicle. Available tire options were evaluated for steady-state and transient performance as well as vehicle integration. A single-piece composite wheel with hollow spokes was designed to meet stiffness, strength, and tolerance requirements. A detailed study of wheel loading and geometric structural efficiency was performed. Finite element analysis was used to iterate the geometry and laminate. A two-piece male mold was designed and machined to manufacture the wheel. Removable silicone inserts were used to create the hollow spokes.

Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh

Doctoral Dissertations

Metamaterials (MMs) are nanocomposite materials consisting of metal-dielectric resonators much smaller in size than the wavelength of the incident light. Common examples of metamaterials are based on split ring resonators (SRRs), parallel wires or strips and fishnet structures. These types of materials are designed and fabricated in order to provide unique optical responses to the incident electromagnetic radiation that are not available in naturally existing materials. The MMs can exhibit unusual properties such as strong magnetism at terahertz (THz) and optical frequencies. Additionally, negative index materials (NIMs) can provide negative index of refraction which can be used in many applications …

Metal Segregation During The Solidification Of Titanium-Aluminum Alloys For 3d Printing Applications, Jwala Parajuli

Master's Theses

Titanium-Aluminum alloys are one of the widely used alloys in multiple engineering applications. They are highly preferred in Selective Laser Melting (SLM) processes due to their low density, high melting temperature, and good strength. Segregation occurs during the solidification of most alloys and produces a non-uniform distribution of atoms. In SLM, segregation may depict the type of adhesion between the two deposited interfacial layers and the strength between the interphase between an already solidified layer and a new one, and overall, the quality of the printed part. In order to avoid segregation, the understanding of the segregation behavior at atomistic …

A Study Of The Diffusion Characteristics Of Tungsten Bar Stock And Tungsten Produced Via Direct Metal Laser Sintering (Dmls), Jonathan Robert Bruss

Master's Theses (2009 -)

Using a vacuum hot extraction method diffusivity and concentration of hydrogen were measured in samples of tungsten bar stock and direct metal laser sintered (DMLS) tungsten. It was found that the tungsten bar stock closely adhered to the model established by Frauenfelder. The DMLS samples approximately follow a downward sloping trend over the 500K-1200K temperature range. The trend is opposite of what is expected suggesting processing has a major effect on diffusion behavior. A CFD model was created using ANSYS Fluent to simulate the diffusion behavior. The model functions by separating out diffusion mechanisms and solving Fick’s law with each …

Electrospun Collagen Fibers For Tissue Regeneration Applications, Ying Li

Electronic Thesis and Dissertation Repository

Tissue engineering aims to regenerate damaged and deceased tissue by combining cells with scaffold made from an appropriate biomaterial and providing a conducive environment to guide cell growth and the formation or regeneration of new tissue or organ. While collagen, an important material of the extracellular matrix (ECM), is a natural choice as a scaffold biomaterial, the conducive environment can only be created by having the ability to control the geometry, organization, structural and mechanical properties of the scaffold. Moreover, degradability and degradation rate control of the scaffold has to be taken into consideration too. In this work, we aim …

Development Of Self-Healing Mechanisms For Asphalt Pavements, Max Abelardo Aguirre Deras

LSU Doctoral Dissertations

Self-healing mechanisms, such as microcapsules or hollow-fibers, filled with an asphalt rejuvenator present an emerging technology that would enhance an asphalt mixture’s resistance to cracking damage caused by vehicular and environmental loading. The objectives of this study were to: (a) Evaluate the effects of asphalt rejuvenators on hot-mix asphalt mixtures in order to test its effects on the fundamental engineering properties of the mixtures at high and intermediate temperatures; (b) Develop a synthesis procedure for production of microcapsules and hollow-fibers containing an asphalt rejuvenator; (c) Evaluate the self-healing efficiency of double-walled microcapsules and hollow-fibers filled with an asphalt rejuvenator, through …

Synthesis Of Crumpled Graphene And Titanium Dioxide Based–Nanomaterials And The Application To Carbon Dioxide Photoreduction, Yao Nie

McKelvey School of Engineering Theses & Dissertations

With the rapid development of the economy, increasing combustion of fossils fuels has caused an increase in the atmospheric carbon dioxide (CO2) level, and has led to global climate change. As a mitigation approach, CO2 capture and conversion (CCC) can not only capture CO2, but also convert it to useable products, such as hydrocarbon fuels. Photocatalytic reduction is an attractive CCC option that directly harnesses inexpensive and abundant solar energy. Titanium dioxide (TiO2) is a widely used semiconductor for photocatalysis, and graphene nanosheets are a promising material for use in fabricating graphene-TiO2 hybridized photocatalysts. To realize the application of these …

Ice Adhesion Analysis Of Severely Aged Pdms Rubbers, Theodore R. Woll

Electronic Theses and Dissertations

The goal of this study was to evaluate and optimize the ice adhesion test initially developed by the University of Denver and to examine Polydimethylsiloxane (PDMS) based silicone rubbers for their ice-phobicity as a function of their physical and chemistry properties, and under severe oxidative aging. The test is based on an ice block bonded to a silicone rubber substrate and subjected to shear. In its original state, the test had severe limitations that caused the ice to be dislodged through a mixture of shear and peeling. Several steps were taken in this research to improve the test, and the …

Modeling And Validations Of Control Parameters For Material Extrusion-Based Additive Manufacturing Of Thixotropic Aluminum Alloys., Lars Herhold

Electronic Theses and Dissertations

Additive Manufacturing (AM) with metals has been accomplished mainly through powder bed fusion processes. Initial experiments and simulations using Material Extrusion Additive Manufacturing (MEAM) have been performed by various researchers especially using low melting alloys. Recently Stratasys Inc. submitted a patent application for the use of their Material Extrusion technology also called Fused Deposition Modeling (FDM) where they describe the process using thixotropic semi-solid alloys. Currently this process using semi-solid, engineering type alloys such as A356 or THIXALLOY 540 aluminum have not been researched to evaluate the control parameters. This research combines the in-depth knowledge of applying thixotropic semi-solid aluminum …

Engineering Next Generation Anisotropic Materials And Composites, Nihal Kanbargi

Doctoral Dissertations

Polymer-based composite systems have been developed for a wide variety of applications ranging from aerospace to electronics. My work has focused on the structure-process-property relationships of anisotropic polymeric materials and composites, aimed primarily for structural applications. Anisotropic materials such as fibers have superior mechanical properties along the axial direction and this property can be exploited to engineer exceptionally strong and light materials. In the first chapter, we discuss the physics of degradation of Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. PBO, a fiber of extraordinary tensile modulus and strength has been found to degrade rapidly under moderate conditions of humidity and heat. Solid-state NMR …

High Strain Rate Dynamic Response Of Aluminum 6061 Micro Particles At Elevated Temperatures And Varying Oxide Thicknesses Of Substrate Surface, Carmine Taglienti

Masters Theses

Cold spray is a unique additive manufacturing process, where a large number of ductile metal micro particles are deposited to create new surface coatings or free-standing structures. Metallic particles are accelerated through a gas stream, reaching velocities of over 1 km/s. Accelerated particles experience a high-strain-rate microscopic ballistic collisions against a target substrate. Large amounts of kinetic energy results in extreme plastic deformation of the particles and substrate. Though the cold spray process has been in use for decades, the extreme material science behind the deformation of particles has not been well understood due to experimental difficulties arising from the …

Dynamic Behavior Of Granular Earth Materials Subjected To Pressure-Shear Loading, Jeff Wilson Lajeunesse

Dissertations (1934 -)

The dynamic response of granular earth materials such as sand has been of interest for many years. Multiple previous works have explored the shock response of sand in various grain shapes, sizes, and moisture contents, but the response during rapid combined loading has been relatively unexplored. The current study contributes to that lack of data by performing pressure-shear experiments on Oklahoma #1 silica sand, with quasi-smooth grains of 63 - 120 micron diameter and 99.8 wt.% Si02 composition. In these experiments, an oblique flyer plate impacts an equally inclined target, imparting a longitudinal (pressure) and transverse (shear) wave into a …

Continuous Flow Process For Recovery Of Metal Contaminants From Industrial Wastewaters With Magnetic Nanocomposites, David Hutchins

Graduate Theses & Non-Theses

Remediation of metal-containing industrial effluents presents both a technical challenge and an economic opportunity. Many industrial waste streams contain low levels of metal ions requiring treatment prior to discharge. Existing treatment technologies are frustrated by disparate compositions and low metal concentrations. Chemical precipitation is effective; however, it requires excessive reagents and discourages selective recovery. Ion-exchange enables recovery, but requires a batch process with extensive operational and maintenance demands, and is rarely implemented in large-scale applications. A continuous flow process capable of selective recovery would present many advantages over existing technologies.

This research examines and develops a continuous flow process for …

A Coupled Thermo-Mechanical Theory Of Strain Gradient Plasticity For Small And Finite Deformations, Yooseob Song

LSU Doctoral Dissertations

In this work, a thermodynamically consistent coupled thermo-mechanical gradient enhanced continuum plasticity theory is developed for small and finite deformations. The proposed model is conceptually based on the dislocations interaction mechanisms and thermal activation energy. The thermodynamic conjugate microstresses are decomposed into energetic and dissipative components. This work incorporates the thermal and mechanical responses of microsystems. It addresses phenomena such as size and boundary effects and in particular microscale heat transfer in fast-transient processes. Not only the partial heat dissipation caused by the fast transient time, but also the distribution of temperature caused by the transition from the plastic work …

Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian

Electronic Thesis and Dissertation Repository

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is …

Analysis Of The Low-Cycle Fatigue Behavior Of Silicone Rubber For Biomedical Balloons, Chase Cooper

Materials Engineering

The development of a medical drug delivery device that allows for the deployment drugs into the adventitial tissue of blood vessels requires the inflation of a silicone elastomer. The inflated silicone must be able to consistently endure multiple loading cycles without failing so that the device can operate reliably. There are multiple methods of processing the silicone for the device and the goal of this study is to examine the effect of the various processing methods on the characteristics of the silicone. The Dynamic Mechanical Analysis Machine (DMA) is used to model the conditions of the device’s application by performing …

High Performance Thermal Insulation: Silica Aerogels In Construction Technology, Matthew Giarrusso

Honors Theses

The United States is a world leader in the production and expenditure of energy, accounting for 18% of the total global energy consumption in 2016, 40% of which was used for the heating, cooling, and lighting of commercial and residential buildings. Currently, traditional air-based insulation products are being used in thicker and more numerous layers in an attempt to keep up with contemporary codes and standards. One promising alternative to traditional insulation is silica aerogel. With a remarkably low density and thermal conductivity, silica aerogel could save energy, space, and weight in new and retrofit structures. Silica aerogels are currently …

Modeling Kidney Transplantation Decisions: Regulatory Oversight, Information Sharing, And Post-Transplant Drug Choice, Zahra Gharibi

Operations Research and Engineering Management Theses and Dissertations

The United States and many other nations are encountering a disturbing obstacle: A shortage of available organs for patients who are in need of kidney transplantation. This dissertation strives to analyze this trend and present potential solution by focusing on three different aspects, namely regulatory oversight, information sharing, and post-transplant immunosuppressant drug choice. In my first essay, I propose a stochastic model that identifies a socially-optimal kidney transplant choice given the inherent trade-off between the expected wait time (driven by supply and demand) and the quality of received donor kidney.

I modify the model to account for changes made by …

Preliminary Investigation Of Tensile Strength And Impact Characterization Of Cementitious Composite Incorporating Carbon Nanotubes, Robabeh Jazaei

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cement has been largely used in the construction industry, specifically as a matrix for concrete. Recently, a new generation of cement-based composite that greatly increases mechanical properties is replacing conventional concrete. With periodic advances in the field, researchers considered particles with high-aspect ratios such as Carbon Nanotubes (CNTs) to reinforce cement matrices. Although there is not much literature to draw upon in research, some research on improving the tensile strength of cementitious composite incorporating with CNTs does exist. However, there had been no evidence of investigation into impact strength until this study.

Most papers presented examined the effect of multi-walled …

Morphological And Energy Transport Optimization Of Spectrally-Selective Solar Absorber Coatings At Mesoscale, Dale Karas

UNLV Theses, Dissertations, Professional Papers, and Capstones

A special class of cuprous-based inorganic oxide materials, synthesized as nanoparticles via hydrothermal and co-precipitation methods, are portable to spectrally-selective absorber coatings with high solar-thermal energy conversion efficiency. Operating reliably at elevated temperatures when used in tandem with solar concentrators, these materials enable cost-competitive solar energy conversion technology that can be incorporated with thermal energy storage systems, supporting the viability of novel renewable power generation; notably, optimizing absorptive performance while mitigating thermal losses through re-radiated waste heat motivates sustainable energy production particular to desert climates, where water conservation and ecological sensitivity needs are paramount.

This work targets the chemical synthesis …