Engineering Commons^™

Fatigue Damage Prognosis Of Internal Delamination In Composite Plates Under Cyclic Compression Loadings Using Affine Arithmetic As Uncertainty Propagation Tool, Audrey J-M Gbaguidi

Doctoral Dissertations and Master's Theses

Structural health monitoring (SHM) has become indispensable for reducing maintenance costs and increasing the in-service capacity of a structure. The increased use of lightweight composite materials in aircraft structures drastically increased the effects of fatigue induced damage on their critical structural components and thus the necessity to predict the remaining life of those components. Damage prognosis, one of the least investigated fields in SHM, uses the current damage state of the system to forecast its future performance by estimating the expected loading environments. A successful damage prediction model requires the integration of technologies in areas like measurements, materials science, mechanics …

Vision-Aided Navigation For Gps-Denied Environments Using Landmark Feature Identification, Tennyson Samuel John

Doctoral Dissertations and Master's Theses

In recent years, unmanned autonomous vehicles have been used in diverse applications because of their multifaceted capabilities. In most cases, the navigation systems for these vehicles are dependent on Global Positioning System (GPS) technology. Many applications of interest, however, entail operations in environments in which GPS is intermittent or completely denied. These applications include operations in complex urban or indoor environments as well as missions in adversarial environments where GPS might be denied using jamming technology.

This thesis investigate the development of vision-aided navigation algorithms that utilize processed images from a monocular camera as an alternative to GPS. The vision-aided …

Development, Analysis, And Comparison Of Electromechanical Properties And Electrode Morphology Of Ionic Polymer Metal Composites, Balaji Sivasubramanian

Doctoral Dissertations and Master's Theses

With smart materials and adaptive structures being nudged into mainstream technology progressively, the smart composites are donning a predominant role as indispensable structures. Among these, the Ionic Polymer Metal Composites (IPMC), with their large bending deformation and relaxation characteristics at very low voltages are attractive as transducers in many areas of application. The actuation and sensing properties of IPMC have been sought after for various engineering functions. The paper focuses on manufacturing various types of IPMC. Combining the ionic polymer with platinum electrodes, gold sputter coated electrodes and multi-walled carbon nanotube Bucky paper electrodes to create enhanced IPMCs, comparative analysis …

Enhancement Techniques Of Boiling Heat Transfer, Basim Qasim Ali Al-Sukaini

Doctoral Dissertations and Master's Theses

The aim of this study is to investigate pool boiling performance of water under atmospheric pressure by two techniques. The first method is by adding small amounts of surfactants, and the second way is by using structured surfaces.

The first technique is investigated experimentally with environmentally friendly surfactants. The surfactants chosen for the study are an ionic sodium lauryl sulfate (SLS), nonionic ECOSURF™ EH-14, and nonionic ECOSURF™ SA-9. It is observed that adding a small amount of surfactant alters the water boiling phenomenon significantly. Boiling curves for different concentrations are shifted to the left. The wall temperature drops greatly with …

Development Of A System Architecture For Unmanned Systems Across Multiple Domains, Charles Randall Breingan Jr.

Doctoral Dissertations and Master's Theses

In the unmanned systems industry, there is no common standard for systems components, connections and relations. Such a standard is never likely to exist. Needless to say, a system needs to have the components that are required for the application, however, it is possible to abstract the common functionality out of an individual implementation. This thesis presents a universal unmanned systems architecture that collects all of the common features of an unmanned system and presents them as a set of packages and libraries that can be used in any domain of unmanned system operation. The research and design of the …

Speaker Dependent Voice Recognition With Word-Tense Association And Part-Of-Speech Tagging, Theodore Philip King Ernst

Doctoral Dissertations and Master's Theses

Extensive Research has been conducted on speech recognition and Speaker Recognition over the past few decades. Speaker recognition deals with identifying the speaker from multiple speakers and the ability to filter out the voice of an individual from the background for computational understanding. The more commonly researched method, speech recognition, deals only with computational linguistics. This thesis deals with speaker recognition and natural language processing. The most common speaker recognition systems are Text-Dependent and identify the speaker after a key word/phrase is uttered. This thesis presents Text-Independent Speaker recognition systems that incorporate the collaborative effort and research of noise-filtering, Speech …

Run-Time Hev Engine-Generator Power-Speed Optimization For Fuel Consumption And Emissions Reduction, Chester Paul Rowe Ii

Doctoral Dissertations and Master's Theses

As fuel economy and emissions standards become more stringent, Plug-in Hybrid Electric Vehicles (PHEV) using series architectures are being increasingly explored. Due to the decoupling of the Internal Combustion Engine (ICE) from the road, the primary control challenge in this architecture is the optimization of an ICE control law. A run-time Genset speed controller is presented for use during the charge-sustaining mode in a Series PHEV to find the optimal operating parameters for a conventional diesel engine coupled to an electric generator in terms of minimized fuel consumption and emissions generation. On board vehicle sensors provide real time data to …

Development Of An Exteroceptive Sensor Suite On Unmanned Surface Vessels For Real-Time Classification Of Navigational Markers, Christopher Lloyd Kennedy

Doctoral Dissertations and Master's Theses

This thesis presents the development of an exteroceptive sensor suite for real-time detection and classification of navigational markers on Unmanned Surface Vessels. Three sensors were used to complete this task: a 3D LIDAR and two visible light cameras. First, all LIDAR points were transformed from the sensor’s reference frame to the local frame using a Kalman filter to estimate instantaneous vehicle pose. Next, objects were chosen from the LIDAR data to be classified using either Multivariate Gaussian or Parzen Window Classifiers. Both produce 96% accuracy or better, however, multivariate Gaussian ran considerably faster than the Parzen and was simpler to …

Design And Dynamic Analysis Of A Variable-Sweep, Variable-Span Morphing Uav, Nirmit Prabhakar

Doctoral Dissertations and Master's Theses

Morphing wings have the potential to optimize UAV performance for a variety of flight conditions and maneuvers. The ability to vary both the wing sweep and span can enable maximum performance for a diverse range of flight regimes. For example, low-speed missions can be optimized using a wing with high aspect ratio and no wing sweep whereas high-speed missions are optimized with low aspect ratio wings and large wing sweep. Different static morphing wing configurations clearly result in varying aerodynamics and, as a result, varying dynamic modes. Another important consideration, however, is the transient dynamics that occur when transitioning between …

Experimental Validation Of A New Distributed Cooperative Control Algorithm For Multi-Agent Systems With Switching Communication Topologies And Time-Delays, Junzhen Shao

Doctoral Dissertations and Master's Theses

In this thesis, we present practical experimental results to demonstrate a control law for consensus of multiagent systems with switching topologies and time delays. The nonlinear control law utilizes discontinuous cooperative control gains and uses contraction mapping to achieve consensus of multiagent systems. The testing platform we used consists of a number of mobile robots and software simulations both in Matlab and Microsoft Studio C++. We present the effectiveness of the control law design by Aria mobile robots with applications in distributed cooperative formation control. Computer simulations and hardware experiments presented include point consensus control and formation control, both with …

Human Behavior During Spaceflight: Evidence From An Analog Environment, Kenny Mikael Arnaldi

Doctoral Dissertations and Master's Theses

Spaceflight offers a multitude of stressors to humans living and working in space, originating from the external space environment and the life-support system. Future space participants may be ordinary people with different medical and psychosocial backgrounds who may not receive the intense spaceflight preparation of astronauts. Consequently, during a mission, a space participant’s mood and behavior could differ from a trained astronaut. This study was an exploratory research project that used an artificial habitat to replicate an orbital environment and the activities performed by humans in space. The study evaluated whether the type of environment affects mood and temperament. Two …

Characterization Of Electron Number Density Of Rocket Exhaust Plumes Through Microwave Transmissions, Jorge Torres

Doctoral Dissertations and Master's Theses

Charged rocket plumes generally exceed the length of their source vehicles, and offer lightning a favorable path to ground. Rocket plumes enhance the induced transient currents in flight electronics, and increase the risk of vehicle failure. The affinity of lightning to the plume can be associated with the plume's electrical properties, which are coupled to plasma characteristics including the electron number density. However, the electron number density of rocket plumes is not well-known. In this study, the electron number density is characterized through data from static rocket firings. A model of the plume in finite difference time domain (FDTD) simulations …

Inverse Volume-Of-Fluid Meshless Method For Efficient Non-Destructive Thermographic Evaluation, Hussein Awad Kurdi Saad

Doctoral Dissertations and Master's Theses

A novel computational tool based in the Localized Radial-basis Function (RBF) Collocation (LRC) Meshless method coupled with a Volume-of-Fluid (VoF) scheme capable of accurately and efficiently solving transient multi-dimensional heat conduction problems in composite and heterogeneous media is formulated and implemented. While the LRC Meshless method lends its inherent advantages of spectral convergence and ease of automation, the VoF scheme allows to effectively and efficiently simulate the location, size, and shape of cavities, voids, inclusions, defects, or de-attachments in the conducting media without the need to regenerate point distributions, boundaries, or interpolation matrices. To this end, the Inverse Geometric problem …

To Study The Effect Of Catalyst On The Physical Parameters Of Carbon Spheres, Tejas Shailesh Mehta

Doctoral Dissertations and Master's Theses

The discovery of fullerenes has opened up modern studies in carbon materials. Carbon nanoparticles have a large surface area and demonstrate good conductivity. Their unique properties has gained attention in many areas such as water filtration, hydrogen storage and battery electrodes. In this research, carbon spheres with high specific area and uniformity were grown using the Chemical Vapor Deposition (CVD) process with silicon substrates, ethylene (C2H4) as a carbon precursor and argon as the inert gas. We observe that the morphology of carbon spheres largely depend on the experimental conditions, including CVD time duration, temperature, catalyst and flow of gases. …

A Continuous/Discontinuous Fe Method For The 3d Incompressible Flow Equations, Nikolaos Kyriazis

Doctoral Dissertations and Master's Theses

A projection scheme for the numerical solution of the incompressible Navier-Strokes equation is presented. Finite element discontinuous Galerkin (dG) discretization for the velocity in the momentum equations is employed. The incompressibility constraint is enforced by numerically solving the Poisson equation for pressure using a continuous Galerkin (cG) discretization. The main advantage of the method is that is does not require the velocity and pressure approximation spaces to satisfy the usual inf-sup condition, thus equal order finite element approximations for both velocity and pressure can be used. Furthermore, by using cG discretization for the Poisson equation, no auxiliary equations are needed …

A Cfd Investigation Of The Hydrodynamic Characteristics Of Fluid Flow Through An Impeller And Multi-Objective Design Optimization Of A Centrifugal Pump, Mohammed Khammat Sagban

Doctoral Dissertations and Master's Theses

In this thesis, the first part is conducting an investigation of the hydrodynamic characteristics (pressure and velocity) of fluid flow (water) through an impeller of a centrifugal pump. To illustrate a one-dimensional model is used to identify an impeller of a GDM 10 x 12 HD centrifugal pump using Vista CPD design and BladeGen tool. A three-dimensional model is then built with a commercial software package ANSYS Blade Modeler. The structured mesh of the impeller blade is obtained by using TurboGrid system. The volute of the centrifugal pump is built in ANSYS geometry, and an unstructured mesh is accomplished by …

Modeling Hydrodynamic Stability Of Incline-Liquid Airblast Nozzle For Gas Turbine Combustion, Kevin Matiko

Doctoral Dissertations and Master's Theses

Fuel is a major cost item for civil transport airplanes. Minimizing fuel consumption of these crafts is a stream of economic opportunity and a stage for innovation, competition and exploration. Regardless of the fuel type, bio or crude oil based, the civil transport stakeholders would like to minimize fuel consumption of their airplanes. The mixing of fuel and air is a critical process for optimum combustion in gas turbine engines due to its high influence on the downstream combustion process. The need for minimizing fuel consumption coupled with the requirement for combustion systems to perform well at all flight conditions …

Exploration Of A Computational Fluid Dynamics Integrated Design Methodology For Potential Application To A Wind Turbine Blade, Gaurav Kapoor

Doctoral Dissertations and Master's Theses

The main purpose of this thesis is to conduct a parametric sensitivity study on the blade design of AOC 15/50 wind turbine based on a CFD approach and optimize the blade design for maximizing the power output. The ANSYS® Fluent® flow solver using the k-ω SST turbulence model was validated by simulating the flow over two dimensional airfoils comprising the AOC 15/50 wind turbine blade. The CFD results have shown a considerable agreement with the experimental data for the airfoils. Parametric correlation study and sensitivity analysis were conducted by performing actual flow simulations over the turbine blade using ANSYS® Fluent®. …

Reduction Of Secondary Flow Losses In A Turbine For Use In Man-Portable Power Generation, Andrew J. Yatsko E.I.

Doctoral Dissertations and Master's Theses

As the world has moved into a more energy-demanding environment, there has been the push for higher energy density in a smaller package. One of the potential solutions is through the application of a gas turbine engine; yet the challenge is extracting the energy efficiently through the small components. The focus of the research is on the turbine components and how the secondary flow losses from the generated airfoil shapes can be reduced to improve component performance. One of the secondary flow loss items to be addressed is the generation of the Horseshoe Vortex. The Horseshoe Vortex is an aerodynamic …

Investigation Of Pulse Detonation Engine Flow Conditions For Turbomachinery Integration, Luis Estefano Ferrer-Vidal Espa˜Na-Heredia

Doctoral Dissertations and Master's Theses

Pressure gain combustion has been known to be more thermodynamically efficient than its constant pressure counterpart, which employs deflagration. Integration of pressure gain combustors into gas turbine engines has been and still is one of the most important challenges facing the gas turbine industry. Pressure gain combustion devices are inherently unsteady. This unsteadiness affects turbomachinery components designed using steady operation assumptions, and results in mechanical inefficiencies which could outweigh the thermal efficiency benefits. Understanding of turbine components specifically made to operate in the exhaust conditions provided by a pressure gain combustor may yield new turbine design paradigms. As a first …

National Culture: Understanding The Impact Of Cross-Culture On Airline Pilots' Safety Performance In The Middle-East And North Africa (Mena) Region, Shareef Abdulla Kaddas Al-Romaithi

Doctoral Dissertations and Master's Theses

The continuous expansion of Middle Eastern airlines has created a pilot shortage. Since the local pilot population in the Middle East is relatively small, airlines have been relying on foreign pilots to satisfy their operational requirements. Consequently, pilots with diverse cultural perspectives have been operating together. In order to manage this cultural diversity and ensure safe operations, airlines have been applying a number of training and operational strategies such as Crew Resource Management (CRM) with emphasis on adherence to Standard Operating Procedures (SOP). However, CRM was designed and implemented by North Americans as a solution for human factor intricacies among …

Effect Of Air Carrier Restructuring Strategies On Post-Bankruptcy Performance, Harold Dale Townsend

Doctoral Dissertations and Master's Theses

Air carrier bankruptcy is a common occurrence in the aviation industry. However, there is a paucity of research on the topic of air carrier restructuring during the post-bankruptcy period. General restructuring literature has identified four types of actions: operational, financial, managerial, and portfolio. The purpose of this study was to partially fill the large literature gap in the area of air carrier post-bankruptcy performance through theoretical and practical contributions.

A multilevel exploratory factor analysis was conducted to explore whether the same restructuring areas were found in air carrier specific metrics. All four restructuring areas were found in the factor analysis. …

Evaluation And Flight Assessment Of A Scale Glider, Alvydas Anthony Civinskas

Doctoral Dissertations and Master's Theses

The objective of this project is to do a flight assessment of a Phoenix K8B radio controlled glider to see what process is needed to verify its glide slope and stability characteristics. The flight test analysis, plus a computational fluid dynamics analysis, and an industry-like component build-up aerodynamic analysis were done to provide comparable estimates for the aircraft glide slope. A stability and control derivative analysis was also completed and compared using SURFACES, USAF Datcom, and MIT AVL software. The glide slope estimate and stability and control derivatives obtained from flight test data showed considerable range and uncertainty. Potential sources …

Unsteady Viscous Cavity Flow Using Computational Fluid Dynamics, Chandramouli Vadlamudi

Doctoral Dissertations and Master's Theses

The problem of unsteady viscous incompressible flow in a two-dimensional cavity is treated using the unsteady incompressible Navier-Stokes equations with various initial and boundary conditions. First the case of a square cavity with one inlet and one outlet is treated in steady and unsteady flows. The software package ANSYS FLUENT was used in the CFD simulations. This approach captures the appearance of separation bubbles and vortex formation inside the cavity. Steady state flows are also obtained from the unsteady simulations after convergence of the time dependent solutions. Then the case of a cavity with a synthetic jet and two outlets …

Execution Of A Hybrid Vehicle Controls Development Effort Utilizing Model-Based Design, Hardware-In-The-Loop Testing, Agile Scrum Methods And Requirements Engineering, Derek Simon Bonderczuk

Doctoral Dissertations and Master's Theses

Modern hybrid vehicles require sophisticated supervisory control systems in order to realize competitive efficiency gains. Processes such as model-based design, HIL simulation and Agile Scrum methods can allow for quicker and less costly development of a complex product. The design of a supervisory control system for a prototype PHEV vehicle was executed with the intent of developing a mule vehicle into a 99% production ready vehicle. The control system design process was carried through from requirements definition to operating parameter optimization of utilizing model-based design, HIL simulation and the Scrum model. A prototype vehicle that has a fully functioning hybrid …

Investigation Of Traditional And Alternate Living Hinge Designs For Fused Deposition Modeling Additive Manufacturing Process, Cassandra Sue Gribbins

Doctoral Dissertations and Master's Theses

A manuscript-style thesis composed of three studies covered the application of living hinge designs in the additive manufacturing process of fused deposition modeling. Initial research included comparing numerical and analytical linear analyses on a traditional living hinge design. The second research consisted of tensile testing for the material properties of the Acrylonitrile Butadiene Styrene (ABS) used in fused deposition modeling (FDM) process by the MakerBot 2X as well as adjusting the traditional design to be printed. The third study explored alternate living hinge designs that utilize the geometric freedom provided by additive manufacturing to more evenly distribute stress across the …

Axial Compressor Design With Counter-Rotation And Variable Rpm For Stall Mitigation, Madhur Tiwari

Doctoral Dissertations and Master's Theses

Compressor Stall, an aerodynamic instability due to abnormal air flow in the compressor resulting in loss of total pressure and compressor performance. One of the reasons of compressor stall is due to rise in static back pressure at compressor exit which may result from an imbalance of incidence angle at the rotor and stator and rotational speed. The paper presents the results of a new axial compressor design with counter rotation and variable RPM. Counter-Rotation is used to push compressor performance during stall by moving the operating point away from surge line with a higher pressure ratio rise. Initially an …

Aerodynamic Study Of Forces Due To Wind Velocity And Angle Of Attack On Parabolic Solar Troughs, Brian Northshield

Doctoral Dissertations and Master's Theses

Scant literature exists of the atmospheric effects on parabolic solar troughs. The technology is relatively new, so supporting studies by consequence are as well.

This study examines the effects of wind at various speeds, with various angles of attack on parabolic solar troughs. This begins by picking up on previous study, corroborating previously found data, then introduces new angles of attack. The model includes the presence of the solar tube where other studies omit.

The purpose of this study is to build a data set which is useful for structural consideration. During the course of this study, it was found …

Early Damage State Criterion From A Fault-Seeded Helicopter Gear Using Acoustic Emission And Neural Networks, Rudy L. Baum

Doctoral Dissertations and Master's Theses

In response to five failures since 2008 of the tail gearbox of multiple models of Sikorsky's H-60 helicopter, acoustic emission (AE) data collected from a rotating gearbox test stand at the Naval Air Station in Patuxtent River, MD, was used to monitor the initiation and propagation of a flaw from an electro-discharge machined (EDM) notch seeded on the face of a gear tooth. A period of testing was considered which spanned ~300,000 seconds or ~83 hours and culminates to a damage state such that a flaw has initiated on both ends of the EDM notch. AE data was analyzed for …

Extreme Value Analysis Of Rainfall Events Over The Kennedy Space, Adam David Schnapp

Doctoral Dissertations and Master's Theses

The use of observational datasets to determine the occurrence frequencies of extreme weather events has gained a lot of recent interest due to concerns about the potential regional impacts from global climate change. Extreme-value theory can quantify the return frequency of the most extreme events, using climatologically short data sets and the assumption that such short climatological periods are stationary. However, the resulting analyses must be used with caution since they may not accurately reflect the potential of extreme events in the future due to climate change and variability. Accurately predicting extreme-event likelihood is important for building realistic long-range planning …