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Dissertations and Theses

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Articles 1 - 30 of 161

Full-Text Articles in Mechanical Engineering

Dynamic Effects Of Inertial Particles On The Wake Recovery Of A Model Wind Turbine, Sarah E. Smith Jul 2020

Dynamic Effects Of Inertial Particles On The Wake Recovery Of A Model Wind Turbine, Sarah E. Smith

Dissertations and Theses

Impacting particles such as rain, dust, and other debris can have devastating structural effects on wind turbines, but little is known about the interaction of such debris within turbine wakes. This study aims to characterize behavior of inertial particles within the turbulent wake of a wind turbine and relative effects on wake recovery. Here a model wind turbine is subjected to varied two-phase inflow conditions, with wind as the carrier fluid (Re[lambda]=49-88) and polydisperse water droplets (26 to 45µ m in diameter) at varied concentrations (Φv=0.24 x 10-5 - 1.3 x 10-5), comparing ...


Droplet Ejections During Wet Lab Operations Aboard Spacecraft, Caleb Cushman Turner Jul 2020

Droplet Ejections During Wet Lab Operations Aboard Spacecraft, Caleb Cushman Turner

Dissertations and Theses

The breakup and rupture of liquid bridges, thin films, bubbles, droplets, rivulets, and jets can produce satellite droplets that are subsequently ejected into their surrounding environment. For example, when any solid object is withdrawn from a liquid bath, the formation of an ever-thinning columnar liquid bridge eventually ruptures along the axis of the bridge. When rupture occurs under typical pipetting conditions the dynamics governing the rupture almost always produce at a minimum a satellite droplet. When these droplets occur they are often too small and too fast to be observed by the human eye. In a terrestrial environment they are ...


Monocular Visual Inertial Odometry Using Learning-Based Methods, Yuan Tian Jul 2020

Monocular Visual Inertial Odometry Using Learning-Based Methods, Yuan Tian

Dissertations and Theses

Precise pose information is a fundamental prerequisite for numerous applications in robotics, Artificial Intelligent and mobile computing. Many well-developed algorithms have been established using a single sensor or multiple sensors. Visual Inertial Odometry (VIO) uses images and inertial measurements to estimate the motion and is considered a key technology for GPS-denied localization in the real world and also virtual reality and augmented reality.

This study develops three novel learning-based approaches to Odometry estimation using a monocular camera and inertial measurement unit. The networks are well-trained on standard datasets, KITTI and EuROC, and a custom dataset using supervised, unsupervised and semi-supervised ...


Active Drag Reduction Of Ground Vehicles Using Air-Jet Wheel Deflectors, Kaloki Nabutola May 2020

Active Drag Reduction Of Ground Vehicles Using Air-Jet Wheel Deflectors, Kaloki Nabutola

Dissertations and Theses

Seven turbulence models were used to simulate the flow within the wheelhouse of a simplified vehicle body. The performance of each model was evaluated by comparing the aerodynamic coefficients obtained using computational fluid dynamics (CFD) to data collected from wind tunnel experiments. The performance of large eddy simulation (LES) and detached eddy simulation (DES) was largely dependent on the time step and grid size to accurately resolve turbulent eddies. The standard k-e, realizable k-e, k-w, DES, and LES all trended towards a drag coefficient which was 20% lower than the experimental value. In all numerical cases, the lift coefficient was ...


A Numerical Investigation Of Microgravity Evaporation, Daniel Peter Ringle Apr 2020

A Numerical Investigation Of Microgravity Evaporation, Daniel Peter Ringle

Dissertations and Theses

Evaporation is important to myriad engineering processes such as cooling, distillation, thin film deposition, and others. In fact, NASA has renewed interest in using cabin air pressure evaporation as a means to recycle waste water in space. As one example, NASA recently conducted experiments aboard the International Space Station (ISS) to measure evaporation rates in microgravity and to determine the impacts of porous structure on the process. It has long been assumed that differences in evaporation rates between 1-g0 and microgravity are small. However, discrepancies by as much as 40% have been observed in practice. The assumption now ...


7-Dof Robotic Arm Xy-Plane Translational Stability, Christopher Dean Alkire Apr 2020

7-Dof Robotic Arm Xy-Plane Translational Stability, Christopher Dean Alkire

Dissertations and Theses

Robotic arms are traditionally mounted to rigid structures as they perform tasks. As a result, the arm’s movement would not affect the position of its mount and its operational space that it is performing a task within would remain constant. If a robotic arm were to function in orbit, the motion of the arm would cause it to rotate and translate about its center of mass, which changes as the joints of the arm rotate.

The purpose of this thesis is to focus on the two-dimensional translational effects of an arm operating on a simulated zero-friction surface and provide ...


Theoretical And Computational Analyses On Transition And Turbulence In Purely Oscillating Pipe Flow, Ali Ahmed Abdulrasool Mar 2020

Theoretical And Computational Analyses On Transition And Turbulence In Purely Oscillating Pipe Flow, Ali Ahmed Abdulrasool

Dissertations and Theses

The hydrodynamic instability of purely oscillating pipe flows is investigated in terms of the quasi-steady formulation assuming the temporal changes of the laminar base flow relative to disturbances are slow. A simple model equation is introduced to compare the exact solution of the current approach with those of the major theories dedicated for unsteady flows. The results of the analysis show that the quasi-steady assumption and the multiple scales method are more efficient and accurate than the formal Floquet theory in predicting the transient instabilities within a period in addition to the long-term growth or decay of disturbances. The most ...


Large Deformable Soft Actuators Using Dielectric Elastomer And Origami Inspired Structures, Jangho Park Nov 2019

Large Deformable Soft Actuators Using Dielectric Elastomer And Origami Inspired Structures, Jangho Park

Dissertations and Theses

There have been significant developments in the field of robotics. Significant development consists of new configurations, control mechanisms, and actuators based upon its applications. Despite significant improvements in modern robotics, the biologically inspired robots has taken the center stage. Inspired by nature, biologically inspired robots are called ‘soft robots’. Within these robots lies a secret ingredient: the actuator. Soft robotic development has been driven by the idea of developing actuators that are like human muscle and are known as ‘artificial muscle’. Among different materials suitable for the development of artificial muscle, the dielectric elastomer actuator (DEA) is capable of large ...


A Data Mining Methodology For Vehicle Crashworthiness Design, Xianping Du Oct 2019

A Data Mining Methodology For Vehicle Crashworthiness Design, Xianping Du

Dissertations and Theses

This study develops a systematic design methodology based on data mining theory for decision-making in the development of crashworthy vehicles. The new data mining methodology allows the exploration of a large crash simulation dataset to discover the underlying relationships among vehicle crash responses and design variables at multiple levels and to derive design rules based on the whole-vehicle safety requirements to make decisions about component-level and subcomponent-level design. The method can resolve a major issue with existing design approaches related to vehicle crashworthiness: that is, limited abilities to explore information from large datasets, which may hamper decision-making in the design ...


Tracking Center Of Mass With Limited Inertial Measurement Units, Connor Nathaniel Morrow Sep 2019

Tracking Center Of Mass With Limited Inertial Measurement Units, Connor Nathaniel Morrow

Dissertations and Theses

Wearable motion tracking systems pose an opportunity to study and correct human balance and posture during movement. Currently, these observations are either being conducted in laboratories with the use of camera systems and markers placed on the body, or through the use of suits containing large numbers (15-20) of inertial measurement units. However, to aid with rehabilitation of individuals with impaired balance, there needs to be an option to collect these observations outside of clinics and without incurring much cost from the user. I have focused on three inertial measurement units, one placed on each shank and one placed on ...


Non-Contact Distillation, Rawand Muzafar Rasheed Aug 2019

Non-Contact Distillation, Rawand Muzafar Rasheed

Dissertations and Theses

Leidenfrost phenomenon has been studied extensively for its role in applications ranging from nuclear reactor cooling, to metals manufacturing, combustion, and other fields. Herein, Leidenfrost phenomenon is pursued towards non-contact distillation processes with hopes of reducing or even eliminating contaminant fouling. In particular, the microgravity environment of a drop tower is exploited to demonstrate the facility with which droplets achieve and sustain the Leidenfrost state. Dynamic Leidenfrost impacts in microgravity are presented for impacts on hydrophilic and superhydrophobic planar substrates, macro-pillar arrays, confined passageways, and others. Nearly ideal elastic non-contact impacts and droplet oscillation modes are observed. Dynamic Leidenfrost impacts ...


Design Of A Canine Inspired Quadruped Robot As A Platform For Synthetic Neural Network Control, Cody Warren Scharzenberger Jul 2019

Design Of A Canine Inspired Quadruped Robot As A Platform For Synthetic Neural Network Control, Cody Warren Scharzenberger

Dissertations and Theses

Legged locomotion is a feat ubiquitous throughout the animal kingdom, but modern robots still fall far short of similar achievements. This paper presents the design of a canine-inspired quadruped robot named DoggyDeux as a platform for synthetic neural network (SNN) research that may be one avenue for robots to attain animal-like agility and adaptability. DoggyDeux features a fully 3D printed frame, 24 braided pneumatic actuators (BPAs) that drive four 3-DOF limbs in antagonistic extensor-flexor pairs, and an electrical system that allows it to respond to commands from a SNN comprised of central pattern generators (CPGs). Compared to the previous version ...


Characterizing Tilt Effects On Wind Plants, Ryan Scott Jun 2019

Characterizing Tilt Effects On Wind Plants, Ryan Scott

Dissertations and Theses

Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen ...


Infinite Photovoltaic Solar Arrays: Considering Flux Of Momentum And Heat Transfer, Andrew D. S. Glick Jun 2019

Infinite Photovoltaic Solar Arrays: Considering Flux Of Momentum And Heat Transfer, Andrew D. S. Glick

Dissertations and Theses

Large scale solar farms supply an increasing amount of the worlds electricity supply. However, in order to reach cost parity with fossil fuels, further reductions are necessary. Towards this end, photovoltaic (PV) panel cooling becomes increasingly important; high temperatures both decrease efficiency and panel lifetime. To better understand, characterize, and exploit the natural convective cooling of utility scale solar farms, a model solar farm was created. Using both thermal measurements and particle image velocimetry to characterize heat transfer and velocity fields, wind tunnel experiments were conducted using the model solar farm. Three parameters were examined for their effect on heat ...


Fatigue Characteristics Of New Eco Series Aluminum 7175 Alloy, Chinh Q.L. Vu May 2019

Fatigue Characteristics Of New Eco Series Aluminum 7175 Alloy, Chinh Q.L. Vu

Dissertations and Theses

In this dissertation, the fatigue characteristics of three newly developed experimental compositions for aluminum 7175, with improved mechanical strength, that uses magnesium-calcium alloy instead of pure magnesium are studied.

Specimens of each variant were fabricated and subjected to fatigue life testing, fatigue life data analysis, and observation of their fracture characteristics through optical microscopy and scanning electron microscopy (SEM), and metallography to study their grains and surface characteristics.

Fatigue life testing shows all three variants have a fatigue strength that is approaching approximately 200 MPa. ECO7175v3 is shown to have the highest fatigue strength of approximately 220 MPa at 5x10 ...


A Study Of Thermal Energy Storage Of Phase Change Materials: Thermophysical Properties And Numerical Simulations, Kyung-Eun Min Apr 2019

A Study Of Thermal Energy Storage Of Phase Change Materials: Thermophysical Properties And Numerical Simulations, Kyung-Eun Min

Dissertations and Theses

A Thermal Energy Storage (TES) system is meant for holding thermal energy in the form of hot or cold materials for later utilization. A TES system is an important technological system in providing energy savings as well as efficient and optimum energy use. The main types of a TES system are sensible heat and latent heat. A latent heat storage is a very efficient method for storing or releasing thermal energy due to its high energy storage density at constant temperatures, and a latent heat storage material can store 5-14 times more heat per unit volume than a sensible heat ...


Global Estimation Methodology For Wave Adaptation Modular Vessel Dynamics Using A Genetic Algorithm, Marco Alan Schoener Apr 2019

Global Estimation Methodology For Wave Adaptation Modular Vessel Dynamics Using A Genetic Algorithm, Marco Alan Schoener

Dissertations and Theses

Determining parameters for a system model for marine vessels becomes more difficult as the model is made more complex. Work has been done to determine the equations of motion, but not to fully define how to estimate all of the system parameters. This work utilizes a global optimization methodology for estimating the system parameters using a genetic algorithm. The optimizer uses training data sets created from a set of ship maneuvering standards to minimize the error in the 3 degree-of-freedom equations of motion. The model has been optimized using a “No Surge-Yaw” model (minimal surge coupling) and a “Full” model ...


Finite Element Model Validation And Testing Of An Off-Road Vehicle Under Dynamic Loading Conditions, Mackenzie Susan Cunningham Apr 2019

Finite Element Model Validation And Testing Of An Off-Road Vehicle Under Dynamic Loading Conditions, Mackenzie Susan Cunningham

Dissertations and Theses

In the vehicle design life cycle, validation tests consume a significant portion of the available development time. With a short, one-year design cycle, the Embry-Riddle Baja Team leverages computer-aided engineering (CAE) tools to simulate critical test cases whose loading conditions can be accurately represented by a series of static loads and constraints. Using these conditions, a Finite Element Model (FEM) can be employed to accurately predict the effects of the loading conditions in the components. During the initial design of the front suspension, one major load case was determined to be the main failure load. However, after validation testing the ...


The Influence Of Size And Progression Of Intra-Cerebral Hematoma On The Lateral Ventricles, Muhammad J. Ashraf Jan 2019

The Influence Of Size And Progression Of Intra-Cerebral Hematoma On The Lateral Ventricles, Muhammad J. Ashraf

Dissertations and Theses

Cerebrovascular diseases like intra cerebral hemorrhage are quite deadly and may disturb functioning of the brain, expanding and resulting in formation of an intra cerebral hematoma(ICH). It is imperative to comprehend how hematoma and its expansion inside the brain endangers human life. One of the influences of an ICH inside brain tissue is on the Lateral Ventricles(LV). When the hemorrhage occurs close enough to the lateral ventricles, filled with cerebrospinal fluid(CSF), it disrupts the balance of fluid in LV. A minor pressure change in LV can negatively influence the production of CSF as well as an increase ...


Shape-Stabilization Of Pcm/Hdpe Composites With 3d-Printing Applications For Battery Thermal Management, Thomas Benjamin Freeman Dec 2018

Shape-Stabilization Of Pcm/Hdpe Composites With 3d-Printing Applications For Battery Thermal Management, Thomas Benjamin Freeman

Dissertations and Theses

Phase-change materials (PCMs) are a useful alternative to more traditional methods of thermal management of Li-ion batteries in electric or hybrid-electric vehicles. PCMs are materials which absorb large amounts of latent heat and undergo solid-to-liquid phase change at near-constant temperature. The goal of this thesis is to experimentally investigate the thermal properties of a novel shape-stabilized PCM/HDPE composite extruded filament. The extruded filament can then be used in a 3D printer for custom PCM/HDPE shapes. These custom PCM/HDPE shapes can be used to help reduce weight, energy consumption, and complexity of the thermal management of the ESS ...


Thermally (Un-) Stratified Wind Plants: Stochastic And Data-Driven Reduced Order Descriptions/Modeling, Naseem Kamil Ali Nov 2018

Thermally (Un-) Stratified Wind Plants: Stochastic And Data-Driven Reduced Order Descriptions/Modeling, Naseem Kamil Ali

Dissertations and Theses

Wind energy is one of the significant sources of renewable energy, yet a number of challenges preclude optimal operation of wind plants. Research is warranted in order to minimize the power losses and improve the productivity of wind plants. Here, a framework combining turbulence theory and data mining techniques is built to elucidate physics and mechanisms driving the energy extraction of the wind plants under a number of atmospheric/operating conditions. The performance of wind turbines is subjected to adverse effects caused by wake interactions. Therefore, it is crucial to understand wake-to-wake interactions as well as wake-to-atmospheric boundary layer interactions ...


Ozone-Surface Exchange And Transport And Transformation Near Ventilation Air Supply, Pradeep Ramasubramanian Sep 2018

Ozone-Surface Exchange And Transport And Transformation Near Ventilation Air Supply, Pradeep Ramasubramanian

Dissertations and Theses

Ozone in indoor environments can pose a health risk to human occupants; around half of exposure to this pollutant occurs inside buildings. One approach to reducing indoor O3 levels is to mitigate O3 as it enters a building via outdoor air ventilation supply. Often, mechanical systems that introduce outdoor air into buildings are placed on building rooftops. At the urban scale, greenery has been shown to reduce levels of some harmful pollutants, including ozone and cities like Portland, OR, are mandating green roofs be built on large commercial buildings to increase urban green surfaces. We investigate if rooftop ...


Chemo-Thermo Cure Of Viscoelastic Materials For Semiconductor Packaging Applications, Anjali Pradeep Kumar Aug 2018

Chemo-Thermo Cure Of Viscoelastic Materials For Semiconductor Packaging Applications, Anjali Pradeep Kumar

Dissertations and Theses

Viscoelastic polymer materials are being actively considered as a novel material for semiconductor packaging applications as a result of their ability to develop strong adhesive bonds at lower temperatures. Viscoelastic thermoset materials are impacted by the stresses generated during the curing process, which is also accompanied by a dissipation of thermal energy. There is a need to develop a generic modeling formulation that is applicable to any material of interest in order to enable the study of different bonding materials and develop optimized curing cycles. This study reports a numerical formulation to evaluate the stress generated and energy dissipated during ...


Reliability Of Solder Joints In Embedded Packages Using Finite Element Methods, Valeri Aisha Yunusa Jul 2018

Reliability Of Solder Joints In Embedded Packages Using Finite Element Methods, Valeri Aisha Yunusa

Dissertations and Theses

Solder joints serve as both mechanical and electrical connections between elements in a package. They are subjected to shear strains generated as a result of the different behaviors of the elements in the package (tension and compression) due to the differences in coefficients of thermal expansion during service conditions.

Some of the causes of solder joint failures are due to the following:

Vibration: small rapid displacements of parts of the assembly. This is not necessarily an issue with electronic components but larger parts like automobiles.

Humidity: the package being exposed to water or ionic species can undergo corrosion if an ...


Emulating Balance Control Observed In Human Test Subjects With A Neural Network, Wade William Hilts Jul 2018

Emulating Balance Control Observed In Human Test Subjects With A Neural Network, Wade William Hilts

Dissertations and Theses

Human balance control is a complex feedback system that must be adaptable and robust in an infinitely varying external environment. It is probable that there are many concurrent control loops occurring in the central nervous system that achieve stability for a variety of postural perturbations. Though many engineering models of human balance control have been tested, no models of how these controllers might operate within the nervous system have yet been developed. We have focused on building a model of a proprioceptive feedback loop with simulated neurons. The proprioceptive referenced portion of human balance control has been successfully modeled by ...


Sensitivity Analyses Of Optimized Attitude Estimators Using Sensor Fusion Solutions For Low-Cost Mems Configurations, Ryan W. Hoffman Jul 2018

Sensitivity Analyses Of Optimized Attitude Estimators Using Sensor Fusion Solutions For Low-Cost Mems Configurations, Ryan W. Hoffman

Dissertations and Theses

Since the 1990’s, there has been increased focus on creating navigation systems for small unmanned systems, particularly small unmanned aerial systems (SUAS). Due to size, weight, and cost restrictions, compared to larger more costly manned systems, navigation systems for SUAS have evolved to be quite different from the proven systems of the past. Today, there are many solutions for the problem of navigation for SUAS. The problem has now become choosing the most fitting navigation solution for a given application/mission. This is particularly true for evaluating solutions that are fundamentally different.

This research analyses the performance and sensitivity ...


Improving Seaglider Efficiency: An Analysis Of Wing Shapes, Hull Morphologies, And Propulsion Methods, Christopher James Hockley Jul 2018

Improving Seaglider Efficiency: An Analysis Of Wing Shapes, Hull Morphologies, And Propulsion Methods, Christopher James Hockley

Dissertations and Theses

Autonomous underwater gliders are a family of autonomous underwater vehicles used for long-term observation of oceanic environments. These gliders leverage changes in buoyancy and the resulting vertical motion, to generate forward locomotion via hydrodynamic surfaces. In order to function for extended periods, these systems operate in a low-speed, low-drag regime. This research examines factors impacting the operational efficiencies of gliders, including morphological changes, configuration changes, and propulsion. An interesting question arises when considering the operational efficiencies of conventionally propelled systems at the operating speeds typical of gliders. Can a conventional propulsion system match the efficiency of an underwater glider buoyancy ...


Biomimetic Design And Construction Of A Bipedal Walking Robot, Alexander Gabriel Steele Jun 2018

Biomimetic Design And Construction Of A Bipedal Walking Robot, Alexander Gabriel Steele

Dissertations and Theses

Human balance and locomotion control is highly complex and not well understood. To understand how the nervous system controls balance and locomotion works, we test how the body responds to controlled perturbations, the results are analyzed, and control models are developed. However, to recreate this system of control there is a need for a robot with human-like kinematics. Unfortunately, such a robotic testbed does not exist despite the numerous applications such a design would have in mobile robotics, healthcare, and prosthetics.

This thesis presents a robotic testbed model of human lower legs. By using MRI and CT scans, I designed ...


Wind Energy And Wind-Energy-Inspired Turbulent Wakes: Modulation Of Structures, Mechanisms And Flow Regimes, Elizabeth H. Camp Jun 2018

Wind Energy And Wind-Energy-Inspired Turbulent Wakes: Modulation Of Structures, Mechanisms And Flow Regimes, Elizabeth H. Camp

Dissertations and Theses

The interaction of turbulent wakes with one another and with the adjacent fluid directly impacts the generation of electricity in wind turbine arrays. Computational modeling is well suited to the repeated iterations of data generation that may be required to inform understanding of the function of wind farms as well as to develop control schemes for plant function. In order to perform such computational studies, a simplified model of the turbine must be implemented. One of the most computationally efficient parametrizations of the blade utilizes a stationary disk which has a prescribed drag and produces a wake. However, since accurate ...


An Underwater Vehicle Navigation System Using Acoustic And Inertial Sensors, Khalid M. Alzahrani May 2018

An Underwater Vehicle Navigation System Using Acoustic And Inertial Sensors, Khalid M. Alzahrani

Dissertations and Theses

Unmanned Underwater Vehicles (UUVs) have become an essential tool for different underwater tasks. Compared with other unmanned systems, the navigation and localization for UUVs are particularly challenging due to the unavailability of Global Positioning System (GPS) signals underwater and the complexity of the unstable environment. Alternative methods such as acoustic positioning systems, Inertial Navigation Systems (INS), and the geophysical navigation approach are used for UUV navigation. Acoustic positioning systems utilize the characteristics of acoustic signals that have a lower absorption rate and a more extended propagation distance than electromagnetic signals underwater. The significant disadvantage of the INS is the “drift ...