Engineering Commons^™

Experimental Investigation Of Drag Reduction By Trailing Edge Tabs On A Square Based Bluff Body In Ground Effect, Scott R. Sawyer

Master's Theses

This thesis presents an experimental investigation of drag reduction devices on a bluff body in ground effect. It has previously been shown that the addition of end-plate tabs to a rectangular based bluff body with an aspect ratio of 4 is effective in eliminating vortex shedding and reducing drag for low Reynolds number flows. In the present study a square based bluff body, both with and without tabs, will be tested under the same conditions, except this time operating within proximity to a ground plane in order to mimic the properties of bounded aerodynamics that would be present for a …

Evaluating The Effectiveness Of Cranial Molding For Treatment Of Positional Plagiocephaly Using Finite Element Analysis, Maziyar Keshtgar

Master's Theses

Since the advent of recommendations for placing infants in the supine position during sleep to reduce the incidence of sudden infant death syndrome, clinicians have noted an increase in the frequency of cranial asymmetry due to deformation of suture sections of the infants’ skulls as a result of constant concentrated stress in one area at the back of their head. This specific form of cranial deformation is known as positional plagiocephaly and its rate of occurrence has increased from 0.3% in 8.2% within the past 30 years.

Current treatments and methodologies for preventing and correcting positional plagiocephaly such as stretching …

Tio 2 Fibers: Tunable Polymorphic Phase Transformation And Electrochemical Properties, Edna Garcia, Qiang Li, Xing Sun, Karen Lozano, Yuanbing Mao

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

A series of one-dimensional (1D) nanoparticle-assembled TiO2 fibers with tunable polymorphs were prepared via a novel and large scale ForceSpinning® process of titanium tetraisopropoxide (TTIP)/polyvinylpyrrolidone (PVP) precursor fibers followed with a thermal treatment at various calcinations temperatures. The thermal and structural transformations were characterized by thermogravimetric analysis/differential scanning calorimetry, scanning electron microscopy, and X-ray diffraction. The influence of polymorphic phase of the TiO2 fibers on the electrochemical performance in neutral aqueous 1 M Na2SO4 electrolyte was investigated. The polymorphic amorphous/anatase/rutile TiO2 fibers prepared at 450 °C achieved a highest capacitance of 21.2 F g−1 (6.61 mF cm−2) at a current …

Inventory Management And Control "For A Cause", John Michael Miller

Graduate Theses and Dissertations

Companies today are changing the culture of business and beginning to involve more than just labor and money in overall decisions. Just as sustainability issues and humanitarian logistics are gaining popularity, so is the idea of using business to make a difference on society in addition to making a profit. As companies position themselves across the globe to make an impact, they employ people in third-world environments that create uncertainties on both the supply and demand sides. Also, the idea of strategically planning work with the goal of minimizing costs has been replaced by companies wanting to give more work …

Using The Triple Bottom Line To Select Sustainable Suppliers For A Major Oil And Gas Company, Pandarinath Adarsh Sunkari

Graduate Theses and Dissertations

Companies have primarily been focusing on the financial bottom line i.e., on increasing profits by increasing revenues and reducing costs. With high energy usage and environmental change posing threats to the environment and business operations, companies are now considering sustainability. Since some global suppliers have low cost labor, Social well-being and human development has also emerged as major goals of a company performing global operations. Focusing on these three goals is termed the "Triple Bottom Line" (TBL). We study and explore the TBL benefits that could be realized by an oil and gas company by focusing on sustainable suppliers. A …

Software In Military Aviation And Drone Mishaps: Analysis And Recommendations For The Investigation Process, Veronica Foreman, Francesca Favaro, Joseph Saleh, Christopher Johnson

Faculty Publications

Software plays a central role in military systems. It is also an important factor in many recent incidents and accidents. A safety gap is growing between our software-intensive technological capabilities and our understanding of the ways they can fail or lead to accidents. Traditional forms of accident investigation are poorly equipped to trace the sources of software failure, for instance software does not age in the same way that hardware components fail over time. As such, it can be hard to trace the causes of software failure or mechanisms by which it contributed to accidents back into the development and …

Manipulating The Mass Distribution Of A Golf Putter, Paul J. Hessler Jr.

Senior Honors Projects

Putting may appear to be the easiest but is actually the most technically challenging part of the game of golf. The ideal putting stroke will remain parallel to its desired trajectory both in the reverse and forward direction when the putter head is within six inches of the ball. Deviation from this concept will cause a cut or sidespin on the ball that will affect the path the ball will travel.

Club design plays a large part in how well a player will be able to achieve a straight back and straight through club head path near impact; specifically the …

Effect Of Void Geometry On Strength, Stiffness, And Failure Modes Of Rock-Like Materials, Omed Yousif

UNLV Theses, Dissertations, Professional Papers, and Capstones

The host rock of portion of the first proposed high-level nuclear waste repository in the United States of America (Yucca Mountain, Nevada) is tuff rock that contains voids (lithophysae) with different shapes, sizes, and distributions. The existence of these voids can cause a dramatic change in the rock's mechanical properties such as uniaxial compressive strength, UCS, and Young's modulus, E. Accordingly, in an experimental program, the effects of void existence on the engineering properties of the tuff rocks was explored in a work of US Department of Energy conducted in the Department of Civil and Environmental Engineering and Construction of …

Evaluating The Level Of Harmonic Distortion In A Typical Distribution Feeder, Wessen S. Bogale

UNLV Theses, Dissertations, Professional Papers, and Capstones

Steady-state analysis of electrical power systems is largely based on linear and sinusoidal AC circuits which allow the concept of impedance, phasors and well-defined power quantities (i.e., real, reactive and apparent powers). In reality, however, the electric load which was once composed of linear elements (e.g., induction motors, incandescent lighting, etc …) is becoming more and more nonlinear due to the wide-spread use of electronic components such as fluorescent lighting and variable-frequency drives that power the majority of electric motors. As a consequence, the current drawn by such devices is often distorted, thus containing a number of high frequency harmonics …

Direct Electrical Arc Ignition Of Hybrid Rocket Motors, Michael I. Judson Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Hybrid rockets motors provide distinct safety advantages when compared to traditional liquid or solid propellant systems, due to the inherent stability and relative inertness of the propellants prior to established combustion. As a result of this inherent propellant stability, hybrid motors have historically proven difficult to ignite. State of the art hybrid igniter designs continue to require solid or liquid reactants distinct from the main propellants. These ignition methods however, reintroduce to the hybrid propulsion system the safety and complexity disadvantages associated with traditional liquid or solid propellants. The results of this study demonstrate the feasibility of a novel direct …

Transportation Economics And Energy, Ali Soltani Sobh

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Transportation is one of the major energy consuming sectors in the United States. The continued growth in fuel consumption not only increases dependency on foreign oil but also causes environmental issues due to the emissions of greenhouse gas (GHG). High gasoline consumption in the US transportation sector not only raises concerns regarding national energy security, but also poses many questions regarding the resulting environmental impacts of greenhouse gases emissions. Improvement in automobile fuel economy, increase the use of natural gas vehicles and electric vehicles have been proven to be as the policies in controlling oil demand and GHG emissions in …

Effect Of Manufacturing Processes On The Loss Factor And Other Mechanical Properties Of Kenaf Fiber-Reinforced Composites, Brian P. Spackman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The characteristics essential for manufacturing parts and products are not well known for natural fiber-reinforced composite materials. Natural fibers display properties similar to glass fibers, and present a more environmentally friendly option for manufacturing composite materials. This research investigates various parameters in the manufacture of kenaf fiber-reinforced composites including cure time, density, matrix hardener ratio, surface treatment, and fiber length and examines the effect they have on mechanical properties of the composite material. Several samples were created and subjected to a vibrational test. Using known relationships, mechanical properties were extracted from the test results. Samples were found to exhibit repeatable …

Electrokinetic Flow In A Nanochannel With An Overlapped Electrical Double Layer, Zhuorui Song

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research is a theoretical study aiming to improve the understanding of nanofluidic flows. Nanofluidic flows have a wide range of potential application in many fields, such as DNA analysis, drug delivery, analyte separation, power generation, and so on. The most common material used in nanofluidic flows is silica whose surfaces are charged mainly due to proton exchange with the fluids. Charges on the surfaces as well as near the surfaces in the fluid side cause a significantly different response of the fluids to the applied electric field or pressure difference compared to those at normal scale. In the previous …

Molecular Sensing And Imaging Of Human Disease Cells And Their Responses To Biochemical Stimuli, Lifu Xiao

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Advancement in microscopic and spectroscopic techniques could significantly improve our ability in the study and diagnosis of diseases. Especially, being able to image and detect human diseases at the cellular and molecular level allows people to diagnose diseases at early stages and to study the molecular mechanisms behind various diseases. Currently, histopathological techniques are most widely used for prognosis and diagnosis of human diseases. However, conventional histopathology requires a complex process of sample preparation, which limits the diagnostic efficiency of this technique. More importantly, it requires fixation of tissue or cell sample, making it unsuitable for the study of dynamic …

Laboratory Study On The Effects Of Exit Face Inclination Of Critical Gradients, Richard Allen Keizer Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The objective of this research is to help better understand the effects of exit face inclinations on critical gradients. This will lead to more practical ways to predict critical hydraulic gradients and slope stability using soil properties and exit face conditions. Current geotechnical engineering does not consider these factors because they are not thoroughly understood. Despite the attempts to better predict critical gradients, methods developed over 70 years ago to model the heave mechanism are used to model failure mechanisms such as backward erosion (or piping). This critical hydraulic gradient is only calculated by means of the buoyant unit weight …

Techno-Economic Feasibility And Life Cycle Assessment Of Dairy Effluent To Biofuel Via Hydrothermal Liquefaction, Hailey M. Summers

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Delactosed whey permeate (delac) is a low valued by-product in the dairy industry with 90 million tons annually disposed of worldwide. Upgrading delac to bioproducts, specifically biofuel, has been demonstrated at laboratory scale through yeast fermentation. However, the large-scale environmental impact and economic feasibility of this process is yet to be quantified. Further research, focused on evaluating the sustainability, scalability and economic feasibility of the fermentation pathway, directs research and development to move the technology towards commercialization. The enclosed research incorporates biological experimentation with engineering systems modeling to evaluate the large-scale environmental impacts and economic feasibility of generating bioproducts from …

Energy Harvesting And Storage: The Catalyst To The Power Constraint For Leveraging Internet Of Things (Iot) On Trains, Kelechi Nwogu

Department of Computer Electronics and Engineering: Dissertations, Theses, and Student Research

The success of Wireless Sensor Networks is heavily constrained by its reliance on storage technology like batteries, which are a finite resource. Whilst the number of transistors in an IC doubles every 18 months, the energy density of batteries is relatively flat during the same time period. This is a key challenge in leveraging the Internet of Things on trains.

The gravity of this problem is increased by an order of magnitude when the network is to be scaled up to hundreds or thousands of nodes. Comprehensive research and development efforts have been devoted to building ultra-low power sensors. These …

Velocity Distributions And Wall Pressures In A Scale Model Gated Box Culvert Control Structure, Alexander L. Evans

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

The South Florida Water Management District (SFWMD) manages a system of canals and structures that control the flow through several large storm water treatment areas (STA). The present project was initiated because of the partial failure of a three-barrel, gated box culvert structure that belongs to the system. The structure has a forebay with three sluice gates that control the flow into three 8 ft by 8 ft box culverts. Settling and partial failure of the culverts in the structure was presumably caused by piping of sediment through joints in pre-cast sections of culvert. It was hypothesized that both unsteady …

Mitochondrial Dysfunction And Loss Of Glutamate Uptake In Primary Astrocytes Exposed To Titanium Dioxide Nanoparticles, Christina L. Wilson

Department of Chemical and Biomolecular Engineering: Dissertations, Theses, and Student Research

The proper function of astrocytes is critical for brain health as they are the most abundant cells in the brain which monitor ion homeostasis, recycle neurotransmitters and respond to tissue damage therefore disruption in astrocyte function can result in overall detrimental effects and has been linked with neurodegenerative diseases. Titanium Dioxide (TiO₂) nanoparticles are currently the second most produced engineered nanomaterial in the world with vast usage in consumer products leading to recurrent human exposure. Animal studies indicate significant nanoparticle accumulation in the brain while cellular toxicity studies demonstrate negative effects on neuronal cell viability and function. However, …

Using Controlled Curing In A Custom Stereolithography-Based 3d Printing Machine To Obtain Graded Property Variations, Evan S. Schwahn

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

In an effort to construct materially graded parts, a strategy was studied that is based on varying ratios of interpenetrating polymer networks (IPNs) in a manner that can be adapted to 3D printing. Using IPNs has the benefit of allowing access to a broad range of property variation. The strategy used involves controlled partial curing of the first network, followed by washing of that network to remove uncured components, then swelling of the structure with a second polymer component and curing.

This method was utilized to control final IPN properties by controlling the extent of crosslinking of the initial network, …

Ultrahigh Density Sub-10 Nm Cobalt Nanowire Arrays: Simulation, Fabrication, And Characterization, Yuan Tian

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The simulation, fabrication, and characterization of self-assembled ultrahigh density sub-10nm Co nanowire arrays are presented in this dissertation. The general phase separation nanowire growth simulation was operated based on a modified Ising model. The fabrication process can be summarized as the binary Co-X systems lateral phase separation during physical vapor deposition – the plasma layer deposition with a single alloy Co-X target. The “X” stands for Al or Si. The nanowire fabrication and diameter deduction was achieved by balancing the growth rate and surface diffusivity. For Co-Al binary system, the formed sub-10 nm Co nanowires are of face-centered cubic structure …

Investigating Polymer Based Scaffolds For Urinary Bladder Tissue Engineering, Srikanth Sivaraman

All Dissertations

Current surgical treatments for urinary bladder disorders rely on the use of autologous intestinal segments and xenografts such as small intestinal submucosa, which suffer from various complications including mechanical mismatch and graft shrinkage. Despite early promises of bladder tissue engineering, a recent report of unsuccessful clinical trials suggests that the technology needs further improvement and evaluation through animal models of bladder dysfunction. Therefore, the objective of this doctoral dissertation was to characterize a viable bladder tissue scaffold (patch) which mimics the mechanical properties of the bladder, maintains the phenotype of the BSMC seeded in it and finally, tested in vivo …

Decision Environments To Encourage More Sustainable Infrastructure Outcomes, Earl Shealy

All Dissertations

Physical infrastructure (i.e. roads, pipelines, airports, dams, landfills, and water treatment systems) contributes directly to sustainability outcomes such as energy and water use and climate changing emissions. The infrastructure built today will likely impact future generations for many years. Planning, design and development decisions about infrastructure are critical to the future performance of these systems. Such decisions about infrastructure are complex with multiple variables, alternative options, and design stages. To manage decisions that exceed cognitive capacity to consider all options, decision makers often create mental shortcuts (heuristics), and accompanied errors (biases). The potential cognitive biases when dealing with complex decisions …

Mechanically- And Electrochemically- Induced Damage At Metal Interfaces Of Joint Replacements And The Biological Consequences, Pooja Panigrahi

All Dissertations

Retrieval analysis has emerged as one of the most direct and informative ways to analyze mechanisms of orthopaedic device failure. With a rising projected demand for revision joint arthroplasty, 268,200 revision total knee replacements (TKR) and 96,700 revision total hip replacements (THR) in 2030, metal interfaces in joint replacements are currently under intense scientific focus as the interactions among mechanical and electrochemical processes continue to challenge the orthopaedic device industry. The objective of these studies was to use implant retrieval and in in vitro analyses to determine the effects of material and mechanical properties on wear and corrosion, and to …

Understanding The Fusion And Maturation Of Tissue Engineered Linear Blood Vessels Using Magnetic Cellular Spheroids, Timothy R. Olsen

All Dissertations

Cellular spheroids are attractive for tissue fabrication due to having precise control over cell and extracellular matrix (ECM) composition, the ability for upscaled production and repeatability, their three-dimensional nature and the fact that spheroids will produce their own ECM over time. A critical process in the fabrication of complex tissue structures with cellular spheroids is related to their fusion and maturation. Tissue fusion is a self-assembly process in which two or more distinct cell populations, or tissues, make contact and coalesce to form a single cohesive structure. Maturation of tissue engineered constructs involves developing the mechanical properties and ECM compositions …

High Resolution Multi-Spectral Imagery And Learning Machines In Precision Irrigation Water Management, Leila Hassan-Esfahani

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The goals of preserving scarce water resources, cultivating more lands, and saving on irrigation water bills have directed the attention of water resources managers toward the concepts of precision agriculture and, in particular, to precision irrigation. The purpose of precision irrigation is to increase irrigation efficiency to avoid crop water stress, avoid yield reduction due to under-irrigation and leaching of nutrients, runoff, and reduce soil erosion due to over-irrigation. In this study, irrigation efficiency has been defined in terms of irrigation uniformity and the response of the crop to irrigation. Crop water demand, soil moisture, evapotranspiration rate, and potential water …

Experimental Validation Data For Cfd Of Steady And Transient Mixed Convection On A Vertical Flat Plate, Blake W. Lance

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In this computer age, simulations are becoming common in science and engineering. One category of simulation, Computational Fluid Dynamics (CFD), begins with physical equations but adds approximations and calibrations in order to complete solutions. Translating these equations into computer languages may cause unintended errors. If simulation results are to be used for decision making, their accuracy needs to be assessed. This accuracy assessment is the theory behind the field of Verification & Validation.

Verification involves confirming the translation of physical equations to computer language was per- formed correctly. It also features methods to detect many types of code errors. Validation …

Testing Of Rainflow Histograms Of Strain For Implementation As A Bridge Weigh-In-Motion Technique, Nephi R. Johnson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The highways and bridges that make up the nation’s infrastructure are becoming older and need replacement or maintenance. In order to determine the best use of funds, bridges are being monitored and studied. This paper was part of a long term study with the goal of monitoring multiple bridges for several years in order to develop an extensive network of bridge information. This particular study was on a bridge in Utah that was instrumented with permanent measurement and monitoring devices. Monitoring of bridges provides information on how the temperature and weather cause the bridge to move, change and age. It …

Systems Optimization Models To Improve Water Management And Environmental Decision Making, Omar Alminagorta Cabezas

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The degradation of water quality and wetlands is one of the most challenging environmental problems around the world. In spite of the magnitude of these environmental problems, few efforts identify how scarce resources (e.g., water, budget) can be more efficiently used to solve these problems. This dissertation presents a set of tools to help solve environmental problems related to excess phosphorus levels in water bodies and wetland degradation caused by water shortages and invasive vegetation. These tools are presented in three studies. The first study presents a simple optimization model that identifies the cost-effective combination of management practices to reduce …

Methods Of Processing Kenaf Chopped Strand Mats For Manufacturing Test Specimens And Composite Structures, Joshua W. Heil

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Every year in the United States, 10 to 11 million vehicles reach the end of their life cycle. Nearly all of these go to a recycling facility. After the recycling process is complete an average of 25% of each vehicle, by weight, goes to waste. This demonstrates the need to use natural fibers in parts that could be recycled, like parts that can be made from kenaf. There are many reasons to consider using natural/bio-fiber composites (bio-composites). These reasons include human health and environmental factors as well as advantages that natural fibers have over fiberglass, such as: lower costs and …