Engineering Commons^™

Preliminary Test Predictions For Scale Ram-Air Parachute Testing, Christian A. Guzman Zurita

Doctoral Dissertations and Master's Theses

The present thesis proposes a preliminary analysis to predict the aerodynamic performance for experimental tests of ram-air parachutes in a wind tunnel. A scaled experimental test setup is developed for determining the aerodynamic coefficients of lift (𝐶𝐿) and drag (𝐶𝐷) conducted in a wind tunnel. Additionally, a CFD approach where a steady-state parachute shape defined based on experiments, photographs, and literature, is presented. The accuracy of the simulation depends considerably on the ability to resolve the canopy geometry. Therefore, a CAD geometry generation is implemented for flexible control of the canopy structure by implementing design parameters, e.g., chord, span and …

Development Of Robust Control Laws For Disturbance Rejection In Rotorcraft Uavs, Johannes Verberne

Doctoral Dissertations and Master's Theses

Inherent stability inside the flight envelope must be guaranteed in order to safely introduce private and commercial UAV systems into the national airspace. The rejection of unknown external wind disturbances offers a challenging task due to the limited available information about the unpredictable and turbulent characteristics of the wind. This thesis focuses on the design, development and implementation of robust control algorithms for disturbance rejection in rotorcraft UAVs. The main focus is the rejection of external disturbances caused by wind influences. Four control algorithms are developed in an effort to mitigate wind effects: baseline nonlinear dynamic inversion (NLDI), a wind …

A Behavioral Research Model For Small Unmanned Aircraft Systems For Data Gathering Operations, Paul Leonard Myers Iii

Doctoral Dissertations and Master's Theses

According to Hitlin (2017) of the Pew Research Center, only 8% of U.S. citizens own an unmanned aircraft. Additionally, regarding feelings if U.S. citizens saw an unmanned aircraft flying close to where they live, 26% say they would be nervous, 12% feel angry, and 11% are scared. As of March 9, 2018, there were 1,050,328 U.S. small unmanned aircraft system (sUAS) registrations compared to 947,970 November 29, 2017. While sUAS use has increased in the U.S., it has lagged when compared to other items for personal use available to U.S. citizens as 92% own cell phones (Anderson, 2015). This slower …

Low-Tip-Speed High-Torque Proprotor Noise Approximation For Design Cycle Analysis, Xavier G. Santacruz

Doctoral Dissertations and Master's Theses

Noise reduction in aviation would enable urban missions that cannot be own with current generation helicopters because of their noisiness. This goal can be achieved by using electric motors as they are quieter and can produce higher torque at lower RPMs. Therefore, a proprotor system can be designed to exploit this characteristic potentially abating noise levels. This research performed noise approximations included with rotor aerodynamics for a single, electric-driven, hovering proprotor by creating a code meant to be used in design cycle analysis. The approximation was based on geometry by using the blade element momentum theory, and calculating the pressure …

Covering Shock Wave Induced Interfacial Mixing: Numerical Study And A Control Primer, Erik S. Proaño

Doctoral Dissertations and Master's Theses

This document is aiming toward deepening the understanding of the phenomena of mixing and the effect of the initial conditions in the cylindrical & spherical Richtmyer-Meshkov and Rayleigh-Taylor Instabilities. This work is focused on identifying the most energetic structures of the ow in order to define a reduced order model intended for modeling the evolution of the mixing layer after reshocking the density interface. Initially, Simulations are implemented for the two dimensional case of a cylindrical shock wave convergently approaching an initially wave-like perturbed density discontinuity formed by a target of Sulfur Hexauoride immersed into unshocked air with Atwood number …

Cfd Study Of Taylor-Like Vortices In Swirling Flows, Sattar Panahandehgar

Doctoral Dissertations and Master's Theses

Swirling flows are complex fluid motions that appear in various natural phenomena and man-made devices. Numerous engineering applications such as turbomachinery, jet engine combustion chambers, mixing tanks and industrial burners involve swirling flows. This wide range of applications is due to unique characteristics offered by swirling flows such as increase in mixing rate, heat transfer rate and wall shear stress. In this study the axisymmetric swirling flow behavior in the context of a hybrid rocket engine have been analyzed. While modeling the flow inside a cylindrical chamber using CFD, a similarity with the Taylor vortices instability has been observed. Similar …

Optimal Battery Weight Fraction For Serial Hybrid Propulsion System In Aircraft Design, Tsz Him Yeung

Doctoral Dissertations and Master's Theses

This thesis focuses on electric propulsion technology associated with serial hybrid power plants most commonly associated with urban air mobility vehicles. While closed form analytical solutions for parallel hybrid aviation cases have been determined, optimized serial hybrid power plants have not seen the same degree of fidelity. Presented here are the analytical relationships between several preliminary aircraft design objectives and the battery weight fraction. These design objectives include aircraft weight, range, operation cost, and carbon emissions. The relationships are based on a serial hybrid electric propulsion architecture from an energy standpoint, and can be applied to hybrid aircraft of different …

A Hybrid Vortex Solution For Radial Equilibrium In Axial Compressors, Wenyu Li

Doctoral Dissertations and Master's Theses

A hybrid vortex solution using the radial equilibrium equation for three dimensional design in axial compressors is generated. One of the most common used vortex solutions is Free Vortex. However, it ignores the fact that axial velocity varies with radius. The Hybrid Vortex includes axial velocity distribution with radius, which gives a more effective design. A single stage is first designed using the Free Vortex design method. A low hub-to-tip ratio is set to ensure subsonic flow. The axial velocity profile is exported from the CFX solver of the inlet diffuser. Using the Hybrid Vortex solution to the radial equilibrium …

Hypervelocity Impact Analysis Of Hybrid Nanocomposite Sensors For Inflatable Space Structures, Yachna Gola

Doctoral Dissertations and Master's Theses

Future space exploration requires easy-to-transport, and easy-to-build and deploy space habitats. NASA and Bigelow Aerospace have collaborated so that human habitation can be made safe and easy with inflatable space habitats (Litteken, 2017). One of the biggest threats faced by these structures in outer space is impact damage by micrometeoroid orbital debris (MMOD) traveling at velocities as high as 15 km/s (Lemmens, Krag, Rosebrock, & Carnelli, 2013). This work presents fabrication and testing of hybrid nanocomposites with carbon nanotubes (CNT) and coarse graphene nanoplatelets (GNP) as fillers and flexible epoxy matrix, that are proposed to be used for sensing the …

The Effects Of Bone Morphogenic Protein 2 On The Viability And Proliferation Of Dental Pulp Stem Cell Isolates, Joseph Cinelli

UNLV Theses, Dissertations, Professional Papers, and Capstones

Growth factor is an umbrella term used to describe a signaling molecule present in organisms that serves the purpose of influencing a stimulatory or inhibitory response from the target cell it acts on. Growth factors are categorized and classified by the types of tissues they act on and the cellular responses they illicit. For example, there are growth factors that act primarily in connective tissue on fibroblasts and they are aptly classified as the fibroblast growth factor family. Similarly, there is another family of growth factors that act on bone forming cells, among others, and they are known as bone …

The Development Of A Viscoelastic Ellipsoidal Model For Use In Measuring Plantar Tissue Material Properties During Walking, Jessica Lee Deberardinis

UNLV Theses, Dissertations, Professional Papers, and Capstones

Introduction: The mechanical characteristics of the plantar tissues during walking is not well understood as most of the current research focuses on testing specific plantar regions in cadavers or while the feet of the participants are raised. In this work, it is hypothesized that a viscoelastic geometric ellipsoid model used to assess multiple structures of the foot would be accurate and robust. This model would be participant-specific and applicable to the entire stance phase of gait.

Methods: The proposed viscoelastic ellipsoid model would represent several key anatomical areas: Heel, Posterior Midfoot, Anterior Midfoot, Metatarsals 1-2, Metatarsals 3-5, Toe 1, Toe …

Equation Of State Of H2o Ice Using Melt-Recrystallization, Zachary Michael Grande

UNLV Theses, Dissertations, Professional Papers, and Capstones

The recent surge in exoplanet discoveries due to advancements in astrophysical technology and analysis has brought the reliability of early equation of state measurements into question as they are the limiting factor when modeling composition of these planets. H2O content is among the most important for the search of habitable planets as well as in understanding planetary dynamics and atmosphere formation. Over the last three decades the equation of state of H2O has been investigated with various techniques but, has suffered from anisotropic strain and poor powder statistics resulting in a large discrepancy in equation of state fits. At pressures …

Numerical Analysis And Fluid Flow Modeling Of Incompressible Navier-Stokes Equations, Tahj Hill

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Navier-Stokes equations (NSE) are an essential set of partial differential equations for governing the motion of fluids. In this paper, we will study the NSE for an incompressible flow, one which density ρ = ρ0 is constant.

First, we will present the derivation of the NSE and discuss solutions and boundary conditions for the equations. We will then discuss the Reynolds number, a dimensionless number that is important in the observations of fluid flow patterns. We will study the NSE at various Reynolds numbers, and use the Reynolds number to write the NSE in a nondimensional form.

We will …

A Monolithic Arbitrary Lagrangian-Eulerian Finite Element Method For An Unsteady Stokes/Parabolic Interface Problem, Ian Kesler

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this thesis, a non-conservative arbitrary Lagrangian-Eulerian (ALE) method is developed

and analyzed for a type of linearized Fluid-Structure Interaction (FSI) problem in a

time dependent domain with a moving interface - an unsteady Stokes/parabolic interface

problem with jump coefficients. The corresponding mixed finite element approximation is

analyzed for both semi- and full discretization based upon the so-called non-conservative

ALE scheme. The stability and optimal convergence properties in the energy norm are

obtained for both schemes.

Modeling Driver-Pedestrian-Infrastructure Interactions At Signalized Midblock Crosswalks, Boniphace Kutela

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cities and metropolitan areas are increasingly facilitating pedestrians’ movement by the provision of pedestrian walking facilities. As pedestrian traffic increases, the risk of crash involvement increases, especially at midblock locations, where pedestrians are exposed to unsafe interactions with vehicular traffic. To improve pedestrians’ safety at midblock locations, various countermeasures are provided, which include signalized crosswalks. Several studies have analyzed driver-pedestrian interactions, as well as pedestrian-infrastructure interactions at signalized midblock crosswalks. However, more in-depth studies are necessary, due to shortfalls of study assumptions, which have led to the application of improper statistical models, as seen in the literature. Improved models are …

Opportunities And Challenges Of Modular Construction In A Hospitality Centric Environment, Shreyansh Paliwal

UNLV Theses, Dissertations, Professional Papers, and Capstones

Modular construction techniques can substantially decrease project schedules and costs, effectively maintaining or increasing the quality of an end product by shifting a percentage of site-based work to an off-site fabrication shop. Modular construction can also significantly contribute to sustainability by reducing site disruption, reducing waste generated, creating better relocatability and reusability, causing less dust and noise pollution, and reducing the probability of loss, theft, and damage to equipment. The primary goal of this research is to identify the opportunities and challenges of implementing modular construction techniques in a hospitality-centric environment, by investigating the current situation and characteristics of modular …

Cesium Platinum Iodide Perovskite Synthesis, Development And Application In Photovoltaic Devices, Dakota Schwartz

UNLV Theses, Dissertations, Professional Papers, and Capstones

Third generation photovoltaics, including perovskites, are essential to improving solar technology for widespread future use. Perovskite solar cells have surpassed 23.7% power conversion efficiency, comparable to traditional silicon photovoltaic panels. However, these perovskites are fabricated using lead-based compounds, posing toxicity issues. Furthermore, existing perovskites have limited thermal and moisture stability in ambient environments. In order to address toxicity and stability concerns, as well as to maximize photon absorption in solar cells through bandgap optimization, this effort focuses on the development of novel leadfree perovskite materials. A cesium platinum iodide composition is selected as a model system due to the theoretical …

Estimation Of Stage-Area-Storage Relationships In Reservoirs And Stage-Discharge Relationships In Rivers Using Remotely Sensed Data, Sailuj Shakya

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis estimates the relationships between the water surface levels and quantities of water in reservoirs and rivers using remotely sensed data without any field measurements. However, the accuracies of the estimates were validated using the field measurements from ground stations. The relationships between the water surface levels and quantities are fundamental for monitoring water quantities for the operation of hydraulic structures, as well as analyzing variability and changes in hydrology. Accessibility and transparency are big issues in establishing a monitoring system that can provide field validation of efforts to model global climate systems. Remote sensing has a capability of …

Assessing Simulated Transmissivity In Numerical Flow Models Of Complex Hydrogeology, Afan Tarar

UNLV Theses, Dissertations, Professional Papers, and Capstones

Accurately extracting a meaningful transmissivity, a target value within one order of magnitude of field estimates, in numerical models poses a significant challenge when modeling complex groundwater systems. Aquifer transmissivity is directly proportional to the aquifer thickness and the estimated aquifer hydraulic conductivity. In complex geologic conditions (especially in fractured systems) with multiple heterogeneous and anisotropic hydrogeologic units, transmissivity can vary over several orders of magnitude.

To extract a meaningful value of transmissivity from a numerical model, a simple five-layer MODFLOW model was constructed. Each layer in the model was assigned a fixed hydraulic conductivity and thickness. The model simulates …

Multi-Resolution Spatio-Temporal Change Analyses Of Hydro-Climatological Variables In Association With Large-Scale Oceanic-Atmospheric Climate Signals, Kazi Ali Tamaddun

UNLV Theses, Dissertations, Professional Papers, and Capstones

The primary objective of the work presented in this dissertation was to evaluate the change patterns, i.e., a gradual change known as the trend, and an abrupt change known as the shift, of multiple hydro-climatological variables, namely, streamflow, snow water equivalent (SWE), temperature, precipitation, and potential evapotranspiration (PET), in association with the large-scale oceanic-atmospheric climate signals. Moreover, both observed datasets and modeled simulations were used to evaluate such change patterns to assess the efficacy of the modeled datasets in emulating the observed trends and shifts under the influence of uncertainties and inconsistencies. A secondary objective of this study was to …

The Affective Perceptual Model: Enhancing Communication Quality For Persons With Pimd, Jadin Tredup

UNLV Theses, Dissertations, Professional Papers, and Capstones

Methods for prolonged compassionate care for persons with Profound Intellectual and Multiple Disabilities (PIMD) require a rotating cast of import people in the subjects life in order to facilitate interaction with the external environment. As subjects continue to age, dependency on these people increases with complexity of communications while the quality of communication decreases. It is theorized that a machine learning (ML) system could replicate the attuning process and replace these people to promote independence. This thesis extends this idea to develop a conceptual and formal model and system prototype.

The main contributions of this thesis are: (1) proposal of …

Application-Specific Memory Subsystem Benchmarking, Mahesh Lakshminarasimhan

Boise State University Theses and Dissertations

Application performance often depends on achieved memory bandwidth. Achieved memory bandwidth varies greatly given specific combinations of instruction mix and order, working set size, and access pattern. Achieving good application performance depends on optimizing these characteristics within the constraints of the given application. This task is complicated due to the lack of information about the impact of small changes on the performance. Some information is provided by benchmarks, but most memory benchmarks are confined to simple access patterns that are not representative of patterns found in real applications.

This thesis presents AdaptMemBench, a configurable benchmark framework designed to explore the …

Design Of Remote Datalogger Connection And Live Data Tweeting System, Zachary Wofford

Biological and Agricultural Engineering Undergraduate Honors Theses

Low-Impact Development (LID) is an attempt to sustainably respond to the potential hazards posed by urban expansion. Green roofs are an example of LID design meant to reduce the amount of runoff from storm events that are becoming more intense and less predictable while also providing insulation to buildings. LID has not yet been widely adopted as it is often a more expensive alternative to conventional infrastructure (Bowman et. al., 2009). However, its benefits are apparent. The University of Arkansas Honors College awarded a grant to research the large green roof atop Hillside Auditorium. One part of this grant is …

Internal Design Of A Hydroponics Greenhouse For Tri Cycle Farms, Sarah Gould

Biological and Agricultural Engineering Undergraduate Honors Theses

Hydroponics is the agricultural technique of growing plants without soil, using other growing media and added nutrients in a solvent. It is an attractive agricultural method over conventional agriculture because it is more water efficient, is less labor intensive, yields higher quality crops in less time, and is easier to control. According to the Digital Journal, “hydroponics crop value is anticipated to grow to USD 27.29 Billion by 2022 at an estimated CAGR of 6.39% from 2015 to 2020” (Sawant, 2016). Alongside this growing market acceptance for hydroponics, there is also a local demand that requires only a small transportation …

Lighting And Economic Considerations For A Hydroponic S-Based Greenhouse At Tri Cycle Farms, Laura Gray

Biological and Agricultural Engineering Undergraduate Honors Theses

Hydroponics is an agricultural technology that involves growing plants without soil, instead using other growth media with added nutrients, typically inside a controlled facility such as a greenhouse. Hydroponics-based agriculture has a number of benefits, namely that it is more water efficient, requires less intensive labor, yields higher quality crops consistently in shorter time, and is easier to control. It also has the potential to be economically advantageous, due to its ability to grow certain crops in the off-season. In Fayetteville, Arkansas, a non-profit urban farm known as Tri Cycle Farms has been seeking a way to design, build, and …

Effectiveness Of Titanium And Iron Nanoparticles In Treating M. Aeruginosa For Harmful Algal Bloom Remediation, Natalie Von Tress

Biological and Agricultural Engineering Undergraduate Honors Theses

Harmful Algal Blooms (HABs) are a growing issue worldwide, posing harm to both aquatic ecosystems and drinking water quality. This issue could be potentially mitigated using nanoparticle (NP) treatment, simultaneously removing cyanobacteria and associated cyanotoxins in HABs. This research seeks to discern the effectiveness of using titanium dioxide and iron (III) oxide NP treatment at removing cyanobacteria via flocculation and sedimentation. Each NP at 25 mg/L and 50 mg/L were used to treat suspended culture of Microcystis aeruginosa, the representative cyanobacteria, up to 72 hours. Cell concentration and morphology in the supernatant were measured via a Coulter counter and …

Simulating Delayed Flood And Alternate Wetting And Drying Rice Production In Arkansas Using Apex, Jaden Tatum

Biological and Agricultural Engineering Undergraduate Honors Theses

Rice is a staple food for billions of people, and rice production will need to grow with global populations. One potential solution to decrease the environmental impacts associated with rice production is alternate wetting and drying (AWD) management which, as opposed to sustained flooding, allows a reduction of water use and methane emissions. Studies into AWD have shown that yield levels may be conserved when using this practice, which would be necessary for widespread implementation. Modeling AWD management changes successfully would help to determine where and to what extent this practice may be effective in the US. The management and …

Ecological Co2 Flux Of A Green Roof Ecosystem And A Typical Grassland Ecosystem, Madeline Oxner

Biological and Agricultural Engineering Undergraduate Honors Theses

The Hillside Auditorium Green Roof is a low impact development feature on the University of Arkansas campus. It retains storm water and allows plants living on the roof to take up and transpire the water. Green roofs work to mimic natural ecosystems in urban environments. A key property is ecosystem respiration, which plays a large role in the global carbon cycle and is an important biologic activity indicator. The ecosystem respiration of Hillside Auditorium Green Roof was compared to a typical grassland ecosystem at the University of Arkansas farm to determine how closely the green roof is able to mimic …

Quantifying Litter Decomposition Rates On A Semi-Intensive Green Roof, Eli Lasalle

Biological and Agricultural Engineering Undergraduate Honors Theses

The overall goal of this study was to provide a measure of the decomposition rate constant on a semi- intensive green roof located in Fayetteville, Arkansas. The specific approach chosen was the use of the Tea Bag Index (TBI), a standardized plant litter decomposition test. There was some heterogeneity observed on site and the locations of samples tested were chosen based on this. Additional laboratory tests were conducted in order to determine whether there would be a large impact of temperature on decomposition or if it would be outweighed by other factors. The temperatures compared were 5°C, 20°C, and 30°C. …

A Unified Risk-Based Framework For Assessing Sustainability And Resiliency Of Civil Infrastructure, Thomas Adam Robbins

Boise State University Theses and Dissertations

As of February 2019, the National Aeronautics and Space Administration (NASA) has reported since 1880 the average global temperature has increased 1°C, with the warmest year on record being 2016. As the years continue to pass, it is becoming more evident that climate change is occurring, which is known to be a catalyst for climatic weather events. Statistically speaking, these events are more prevalent, and catastrophic exemplified as hurricanes, earthquakes, flooding, and fires. In addition to the increase of potentially catastrophic events, society as a whole has become more conscientious in the use and preservation of natural resources, waste generation, …