Engineering Commons^™

Mechanical Properties Of Brittle Ceramics: Case Study Of Boron Rich Ceramics And Acropora Cervicornis Coral Skeleton, Alejandro Carrasco-Pena

Electronic Theses and Dissertations

Ceramics are ubiquitous in man-made and natural structures. Their mechanical properties highly depend on their composition, microstructure and level of defects in the bulk of the material, the latter affecting the integrity of the components; such is the case of boron-rich ceramics where large agglomerates create high stressed regions, or coral skeleton where porosity determines their strength against hydrodynamic forces present in the ocean tides. Therefore, studying the properties of ceramic materials using invasive and non-invasive methods helps in the understanding of the link between the properties and the performance of the structures. The aim of this research was to …

Streamflow Prediction In Ungauged Basins Located Within Data-Scarce Regions, Mohammadhossein Alipour

Electronic Theses and Dissertations

Preservation and or restoration of riverine ecosystem requires quantification of alterations inflicted by water resources development projects. Long records of streamflow data are the first piece of information required in order to enable this analysis. Ungauged catchments located within data-scarce regions lack long records of streamflow data. In this dissertation, a multi-objective framework named Streamflow Prediction under Extreme Data-scarcity (SPED) is proposed for streamflow prediction in ungauged catchments located within large-scale regions of minimal hydrometeorologic observation. Multi-objective nature of SPED allows for balancing runoff efficiency with selection of parameter values that resemble catchment physical characteristics. Uncertain and low-resolution information are …

Variable Fluid Flow Regimes Alter Endothelial Adherens Junctions And Tight Junctions, Dilshan Ranadewa

Electronic Theses and Dissertations

Variable blood flow regimes influence a range of cellular properties ranging from cell orientation, shape, and permeability: all of which are dependent on endothelial cell-cell junctions. In fact, cell-cell junctions have shown to be an integral part of vascular homeostasis through the endothelium by allowing intercellular signaling and passage control through tight junctions (TJs), adherens junctions (AJs), and gap junctions (GJs). It was our objective to determine the structural response of both AJs and TJs under steady and oscillatory flow. Human brain microvascular endothelial cells (HBMECs) were cultured in a parallel plate flow chamber and exposed to separate trails of …

Leveraging The Intrinsic Switching Behaviors Of Spintronic Devices For Digital And Neuromorphic Circuits, Steven Pyle

Electronic Theses and Dissertations

With semiconductor technology scaling approaching atomic limits, novel approaches utilizing new memory and computation elements are sought in order to realize increased density, enhanced functionality, and new computational paradigms. Spintronic devices offer intriguing avenues to improve digital circuits by leveraging non-volatility to reduce static power dissipation and vertical integration for increased density. Novel hybrid spintronic-CMOS digital circuits are developed herein that illustrate enhanced functionality at reduced static power consumption and area cost. The developed spin-CMOS D Flip-Flop offers improved power-gating strategies by achieving instant store/restore capabilities while using 10 fewer transistors than typical CMOS-only implementations. The spin-CMOS Muller C-Element developed …

Conceptualization And Fabrication Of A Bioinspired Mobile Robot Actuated By Shape Memory Alloy Springs, Lietsel Richardson

Electronic Theses and Dissertations

This work is an experimental study and fabrication of design concepts to validate the feasibility of smart materials and their applications in bio-inspired robotics. Shape-Memory Alloy (SMA) springs are selected as the smart material actuators of interest to achieve locomotion in the proposed mobile robot. Based on a previous design of the robot, this work focuses on both implementing a new locomotion concept and reducing size and weight of the previous design, both using SMA based actuators. Objectives are met in consideration of the conceptual mechanics of circular robot locomotion. The first prototype is a variation of the original design. …

Value-Of-Information Based Data Collection In Underwater Sensor Networks, Fahad Khan

Electronic Theses and Dissertations

Underwater sensor networks are deployed in marine environments, presenting specific challenges compared to sensor networks deployed in terrestrial settings. Among the major issues that underwater sensor networks face is communication medium limitations that result in low bandwidth and long latency. This creates problems when these networks need to transmit large amounts of data over long distances. A possible solution to address this issue is to use mobile sinks such as autonomous underwater vehicles (AUVs) to offload these large quantities of data. Such mobile sinks are called data mules. Often it is the case that a sensor network is deployed to …

Fundamental Core Effects In Co-Cr-Fe-Ni Based High Entropy Alloys, Abhishek Mehta

Electronic Theses and Dissertations

High entropy alloys (HEAs) are near equiatomic multi-principal-element-alloys (MPEAs) which are different from traditional solvent-based multicomponent alloys. Based on initial work by Yeh and Co-workers, they were proposed to exhibit four "core" effects: high entropy, sluggish diffusion, lattice distortion, and cocktail effect. Present work investigates two of the four "core" effects, i.e. high entropy and sluggish diffusion effects, in Co-Cr-Fe-Ni based transition metal high entropy alloys. Solid-to-solid diffusion couple approach was adopted to investigate, these core effects. Experimental results contradicts the "high entropy" effect based on thermodynamics analysis: that the HEAs with low entropy of mixing may be thermodynamically more …

Resource Optimization In Visible Light Communication Using Internet Of Things, Akash Dey

Electronic Theses and Dissertations

In the modern day, there is a serious spectrum crunch in the legacy radio frequency (RF) band, for which visible light communication (VLC) can be a promising option. VLC is a short-range wireless communication variant which uses the visible light spectrum. In this thesis, we are using a VLC-based architecture for providing scalable communications to Internet-of-Things (IoT) devices where a multi-element hemispherical bulb is used that can transmit data streams from multiple light emitting diode (LED) boards. The essence of this architecture is that it uses a Line-of-Sight (LoS) alignment protocol that handles the hand-off issue created by the movement …

Characterization Of Florida Landfills With Elevated Temperatures, Ryan Joslyn

Electronic Theses and Dissertations

The occurrence of elevated temperatures within landfills is a very challenging issue for landfill operators to detect and correct. Little is known regarding the causes of elevated temperatures (ETs) and the number of landfills currently operating under such conditions. Therefore, the goal of this research was to determine which landfills within Florida have been impacted by ETs, and to develop a more complete understanding of the factors that may lead to these landfills becoming elevated temperature landfills (ETLFs). Historical landfill gas wellhead data, waste deposition reports, and landfill site geometry were collected for 27 landfill cells through the FDEP OCULUS …

Dynamic Behavior And Performance Of Different Types Of Multi-Effect Desalination Plants, Mohamed Abdelkareem

Electronic Theses and Dissertations

Water and energy are two of the most vital resources for the socio-economic development and sustenance of humanity on earth. Desalination of seawater has been practiced for some decades and is a well-established means of water supply. However, this process consumes large amounts of energy and the global energy supply is also faced with some challenges. In this research, multi-effect desalination (MED) has been selected due to lower cost, lower operating temperature and efficient in terms of primary energy and electricity consumption compared to other thermal desalination systems. The motivation for this research is to address thermo-economics and dynamic behavior …

Fluctuations In Walking Speeds And Spatiotemporal Gait Parameters When Walking On A Self-Paced Treadmill At Level, Incline, And Decline Slopes, Cesar Castano

Electronic Theses and Dissertations

On a daily basis, humans walk over a variety of terrains. Studies have shown that spatiotemporal gait parameters, such as stride length, stride frequency, stride variability, etc., change when humans walk down a decline and up an incline compared to level ground. However, these studies have been limited to using fixed speed treadmills or analyzing a small number of strides when conducted over ground. Thus, there is a need to investigate the fluctuations in spatiotemporal gait parameters of humans walking at their self-selected speed, which requires recording hundreds of strides. Here we hypothesized that subjects will walk with a slower …

Modeling Of Complex Parts For Industrial Waterjet Cleaning, Braden James

Graduate Theses and Dissertations

Industrial high-pressure waterjet cleaning is common to many industries. The modeling in this paper functions inside a collaborative robotic framework for high mix, low volume processes where human robot collaboration is beneficial. Automation of pressure washing is desirable for economic and ergonomic reasons. An automated cleaning system needs path simulation and analysis to give the operator insight into the predicted cleaning performance of the system. In this paper, ablation, the removal of a substrate coating by waterjet, is modeled for robotic cleaning operations. The model is designed to work with complex parts often found in spray cleaning operations, namely parts …

Incentivizing Collaboration In A Competition, Arunesh Sinha, Michael P. Wellman

Research Collection School Of Computing and Information Systems

Research and design competitions aim to promote innovation or creative production, which are often best achieved through collaboration. The nature of a competition, however, typically necessitates sorting by individual performance. This presents tradeoffs for the competition designer, between incentivizing global performance and distinguishing individual capability. We model this situation in terms of an abstract collaboration game, where individual effort also benefits neighboring agents. We propose a scoring mechanism called LSWM that rewards agents based on localized social welfare. We show that LSWM promotes global performance, in that social optima are equilibria of the mechanism. Moreover, we establish conditions under which …

Granny Pod Virtual Assistant, David Connolly, Bing Chen

Theses/Capstones/Creative Projects

Dr. Chen is working on a sustainable small house (SSH) project, sometimes called the “Granny Pod”. Regulations will soon allow homeowners to house their parents on their property, which can be an opportunity live independently in a cheap, sustainable, and convenient alternative to a retirement community. To help achieve this vision, a Virtual Assistant system for the SSH was developed. The system uses a Google Home or Amazon Echo to respond to the voice command “Hey Google (or Alexa), I need help” by contacting the nearby homeowner or caretaker. It alerts the resident who is at the door when the …

Experimental And Computational Analysis Of A 3d Printed Wing Structure, Aryslan Malik

Doctoral Dissertations and Master's Theses

Correct prediction of aeroelastic response is a crucial part in designing flutter or divergence free aircrafts within a designated flight envelope. The aeroelastic analysis includes specifically tailoring the design in order to prevent flutter (passive control) or eliminate it by applying input on control surfaces (active control). High-fidelity models such as coupled Computational Fluid Dynamics (CFD) - Computational Structural Dynamics (CSD) can obtain full structural and aerodynamic behavior of a deformable aircraft. However, these models are so large that pose a significant challenge from the control systems design perspective. Thus, the development of an aeroelastic modeling software that can be …

Adaptive Commanding Of Control Moment Gyroscopes With Backlash, Justin G. Bourke

Doctoral Dissertations and Master's Theses

The existence of backlash in mechanical systems provides significant challenges when attempting to control these systems to a high degree of precision. The imperfect meshing of gear or belt teeth deteriorates the performance of position controllers and tracking of small commands, producing unacceptable steady-state offsets, increased rise and settling times. Agile spacecraft often use control moment gyroscopes (CMGs) equipped with gear trains to efficiently provide torque for the fine attitude adjustments used in docking and precision stabilization maneuvers. A theoretical examination and a practical model is developed to study the effectiveness of both proportional-integral (PI) and model referencing adaptive controllers …

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.