Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

Dissertations and Theses

Discipline
Institution
Keyword
Publication Year

Articles 1 - 30 of 1088

Full-Text Articles in Engineering

Comparing The Promise And Reality Of E-Scooters: A Critical Assessment Of Equity Improvements And Mode-Shift, Michael Glenn Mcqueen Sep 2020

Comparing The Promise And Reality Of E-Scooters: A Critical Assessment Of Equity Improvements And Mode-Shift, Michael Glenn Mcqueen

Dissertations and Theses

In just three years, e-scooters have substantially disrupted and altered the urban mobility landscape. Throughout this period, they have been commonly touted as part of a larger micromobility solution that promises to erase equity barriers and solve the first-mile/last-mile problem. However, few studies in the nascent e-scooter literature have considered these claims. In this study, we surveyed students at Portland State University (n = 1,968) about the role that e-scooters, among other modes, played in meeting their general and university-related travel needs. We then estimated models that incorporated demographics, travel behavior, and latent attitudes distilled using exploratory factor analysis ...


Theoretical And Experimental Validation Of A Cubesat's L-Band Communication System, Evangelos Mastrogiannis Sep 2020

Theoretical And Experimental Validation Of A Cubesat's L-Band Communication System, Evangelos Mastrogiannis

Dissertations and Theses

An L-band uplink communication system was designed and validated in the lab for a CubeSat satellite operating in low Earth orbit (LEO). This paper investigates communication link analysis, discusses the design strategy for an inexpensive CubeSat receiver operating in L-band with a moderate power Earth station transmitter, and validates the link budget with prototype hardware using an anechoic chamber.

A receiver's required carrier-to-noise ratio (CNR) establishes the basis for a link budget. The requirement for a digital communication link is set by the bit-error-rate (BER) requirement of a chosen communication protocol which is inversely related to the energy per ...


Aeroacoustics Of Supersonic Jet Interacting With Solid Surfaces And Its Suppression, Seyyed Saman Salehian Aug 2020

Aeroacoustics Of Supersonic Jet Interacting With Solid Surfaces And Its Suppression, Seyyed Saman Salehian

Dissertations and Theses

The noise generated by supersonic jet is of primary interest in the high-speed flight. In several flight conditions jet exhaust of the propulsion system interacts with solid surfaces. For example, jet impingement on ground for a rocket lift-off, or interactions influenced by the integration of the engine with the airframe. Such complex applications require consideration of the role of acoustic-surface interactions on the noise generation of the jet and its radiation. Numerical analysis of supersonic jet noise involved in these scenarios is investigated by employing Hybrid Large Eddy Simulation – Unsteady Reynolds Averaged Simulation approach to model turbulence.

First, the supersonic ...


Uas Model Identification And Simulation To Support In-Flight Testing Of Discrete Adaptive Fault-Tolerant Control Laws, Mansi Subhash Bakori Aug 2020

Uas Model Identification And Simulation To Support In-Flight Testing Of Discrete Adaptive Fault-Tolerant Control Laws, Mansi Subhash Bakori

Dissertations and Theses

In mission-critical applications of unmanned and autonomous aerial systems(UAS), it is of significant importance to develop robust strategies for fault-tolerant systems that can countermeasure system degradation and consequently support the integration into the National Airspace (NAS). This thesis research illustrates the results of systems identification that is performed using DATCOM followed by the flight test data. This data is acquired from conducting an intensive flight testings program of a fixed-wing UAS to determine the state-space model of the aircraft. A discrete state-space system is reconstructed from these models to derive Auto-Regressive Moving-Average (ARMA) models used to design a Discrete ...


Synthesizing Expressive Behaviors For Humanoid Robots, Mathias Irwan Sunardi Jul 2020

Synthesizing Expressive Behaviors For Humanoid Robots, Mathias Irwan Sunardi

Dissertations and Theses

Humanoid robots are expected to be able to communicate with expressive gestures at the same level of proficiency as humans. However, creating expressive gestures for humanoid robots is difficult and time consuming due to the high number of degrees of freedom (DOF) and the iterations needed to get the desired expressiveness.

Current robot motion editing software has varying levels of sophistication of motion editing tools ranging from basic ones that are text-only, to ones that provide graphical user interfaces (GUIs) which incorporate advanced features, such as curve editors and inverse kinematics. These tools enable users to create simple motions; but ...


Determinants Of Student Information Technology Adoption, Hans P. Vanderschaaf Jul 2020

Determinants Of Student Information Technology Adoption, Hans P. Vanderschaaf

Dissertations and Theses

Innovating service delivery in higher education is central to supporting institutional and societal goals of increasing the numbers of college graduates and for transforming higher education institutions to center on the needs of today's students. Within this context, technology plays a critical role. This research seeks to contribute to institutional, academic and educational technology sector efforts to dramatically enhance service quality, in support of improving undergraduate student outcomes (student success), by identifying the determinants of student information technology adoption and removing barriers to accessing higher education.

Using a mixed-methods and empirical approach based on the Unified Theory of Acceptance ...


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 ...


Exploring Policies And Strategies For The Diffusion Of Remote Patient Monitoring (Rpm) For The Care Of Senior Population, Hamad Asri Alanazi Jul 2020

Exploring Policies And Strategies For The Diffusion Of Remote Patient Monitoring (Rpm) For The Care Of Senior Population, Hamad Asri Alanazi

Dissertations and Theses

Telemedicine offers great promise in addressing some of the healthcare challenges such as the increase of healthcare expenditure, a growing population, and a projected physician shortage; telemedicine is increasingly being included in the discussion of medicine's future. Telemedicine offers the capabilities to deliver healthcare across distances at reduced costs while maintaining or even increasing the quality of treatment and services.

The objective of this research is to develop a model to evaluate alternative solutions to increase the adoption of RPM for the senior population. Also, the research provides a systematic approach for a comprehensive assessment of teleconsultation adoption, develop ...


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 ...


Evaluating R&D Projects In Regulated Utilities: The Case Of Power Transmission Utilities, Edwin Garces Jul 2020

Evaluating R&D Projects In Regulated Utilities: The Case Of Power Transmission Utilities, Edwin Garces

Dissertations and Theses

R&D project selection is essential for many organizations; however, it is a complex decision since it is affected by many factors. These factors vary among organizations because of their different objectives and conditions. There are limited budgets for the investments, and the current R&D project selection methods are focused on financial analysis or complex mathematical probabilistic calculations. Therefore, the main motivation of this research is to create a method to help improve the ex-ante selection of R&D projects in regulated organizations. More importantly, the case application is the electric transmission utilities sector, which plays one of the most critical roles in the entire electric power ...


A Market Diffusion Potential (Mdp) Assessment Model For Residential Energy Efficient (Ee) Technologies In The U.S., Momtaj Khanam Jul 2020

A Market Diffusion Potential (Mdp) Assessment Model For Residential Energy Efficient (Ee) Technologies In The U.S., Momtaj Khanam

Dissertations and Theses

The Diffusion of Residential Energy Efficient (EE) Technologies has been studied for many years. Finding ways to bridge the energy efficiency gap and increase the diffusion of these technologies have been of much interest to researchers and practitioners alike. However, in most studies, diffusion is equated to adoption of EE technologies by consumers. The present study tries to break this mindset and develops a model to assess the diffusion of residential EE technologies from the market's perspective. The model assesses diffusion of an EE technology based on the market's ability to provide benefits to customers that are identified ...


Ce-Qual-W2 Hydrodynamic And Water Quality Model Of The Cedar River Municipal Watershed, Amory Spencer Cervarich Jul 2020

Ce-Qual-W2 Hydrodynamic And Water Quality Model Of The Cedar River Municipal Watershed, Amory Spencer Cervarich

Dissertations and Theses

The laterally averaged, two-dimensional model CE-QUAL-W2 was used to develop a water quality model of the Cedar River Municipal Watershed as a reservoir management and climate change scenario tool. The 90,638-acre watershed, located 56 kilometers southeast of Seattle, WA, provides drinking water to over 1.4 million people. The watershed relies on two waterbodies for storage, Chester Morse Lake and the Masonry Pool. The Masonry Dam is the main storage structure in the watershed. The Cedar River flows downstream from the Masonry Dam for 57 kilometers to Lake Washington. The reservoir model simulated Chester Morse Lake and the Masonry ...


Piezoresistive Hybrid Nanocomposites For Strain And Damage Sensing: Experimental And Numerical Analysis, Audrey Jean-Miche Gbaguidi Jul 2020

Piezoresistive Hybrid Nanocomposites For Strain And Damage Sensing: Experimental And Numerical Analysis, Audrey Jean-Miche Gbaguidi

Dissertations and Theses

Carbon nanomaterials such as carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) demonstrate remarkable electrical and mechanical properties, which suggest promising structural and functional applications as fillers for polymer nanocomposites.

The piezoresistive behavior of these nanocomposites makes them ideal for sensing applications. Besides, hybrid nanocomposites with multiple fillers like carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) are known to exhibit improved electrical and mechanical performance when compared to mono-filler composites.

To comprehensively understand the mechanisms of electrical percolation, conductivity, and piezoresistivity in hybrid nanocomposites, the author develops a two-dimensional (2D) and a three-dimensional (3D) computational Monte Carlo percolation network models for ...


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 ...


Three-Dimensional, Vision-Based Proportional Navigation For Uav Collision Avoidance, Guanhong Gao Jul 2020

Three-Dimensional, Vision-Based Proportional Navigation For Uav Collision Avoidance, Guanhong Gao

Dissertations and Theses

As the number of potential applications for Unmanned Aerial Vehicles (UAVs) keeps rising steadily, the chances that these devices will operate in close proximity to static or dynamic obstacles also increases. Therefore, collision avoidance is an important challenge to overcome for Unmanned Aerial Vehicle operations. Electro-optical devices have several advantages such as light weight, low cost, low algorithm requirements with respect to computational power and possibly night vision capabilities. Therefore, vision-based Unmanned Aerial Vehicle collision avoidance has received considerable attention. Although much progress has been made in collision avoidance systems (CAS), most approaches are focused on two-dimensional environments. In order ...


An Open Source, Autonomous, Vision-Based Algorithm For Hazard Detection And Avoidance For Celestial Body Landing, Daniel Posada Jul 2020

An Open Source, Autonomous, Vision-Based Algorithm For Hazard Detection And Avoidance For Celestial Body Landing, Daniel Posada

Dissertations and Theses

Planetary exploration is one of the main goals that humankind has established as a must for space exploration in order to be prepared for colonizing new places and provide scientific data for a better understanding of the formation of our solar system. In order to provide a safe approach, several safety measures must be undertaken to guarantee not only the success of the mission but also the safety of the crew. One of these safety measures is the Autonomous Hazard, Detection, and Avoidance (HDA) sub-system for celestial body landers that will enable different spacecraft to complete solar system exploration. The ...


Contributions To The Understanding Of Ship Airwakes Using Advanced Flow Diagnostic Techniques, Dhuree Seth Jul 2020

Contributions To The Understanding Of Ship Airwakes Using Advanced Flow Diagnostic Techniques, Dhuree Seth

Dissertations and Theses

The objective of this research was to better characterize the complex, three dimensional, unsteady aerodynamic flows produced by the superstructure of a ship, which is referred to as an airwake. This problem is relevant and important because the turbulent airwake significantly and adversely affects the ability for rotorcraft to operate safely from the decks of Navy ships. To this end, a series of wind tunnel measurements were performed on the SFS2 simplified frigate shape, which has a flight deck at its stern. The measurements were performed with and without a simulated atmospheric boundary layer (ABL), which included the aerodynamic scaling ...


How Does Robotic Surgery Influence Communication, Leadership, And Team Outcomes? A Multimethod Examination., Jordan E. Rogers Jul 2020

How Does Robotic Surgery Influence Communication, Leadership, And Team Outcomes? A Multimethod Examination., Jordan E. Rogers

Dissertations and Theses

The practice of delivering surgical care has evolved to be less invasive to the patients undergoing surgery. Minimally-invasive surgery can be practiced through traditional laparoscopic methods as well as with robotic technology that displaces the surgeon from the operating table. Robotic surgery has been cited to be safer and more effective than traditional laparoscopic surgery; however, little research has endeavored to investigate the role of surgical modality upon aspects of teamwork. This dissertation contributes to the human factors and teamwork literature by evaluating how surgical modality may influence communication, shared leadership, and team outcomes. Multiple methods were employed to study ...


An Aviation Weather Preflight Decision Support Tool To Improve Ga Pilots Preflight And Inflight Performance, Jayde M. King Jul 2020

An Aviation Weather Preflight Decision Support Tool To Improve Ga Pilots Preflight And Inflight Performance, Jayde M. King

Dissertations and Theses

Low hour, inexperienced General Aviation (GA) pilots account for the majority of weather-related incidents, which often result in fatalities. Previous research identifies poor preflight planning practices and a lack of aviation weather knowledge as key contributing factors to the high novice private pilot accident and fatality rate. Research invested into resolving these issues often attempt to introduce new inflight weather technology to assist pilots with weather avoidance. However, these interventions usually result in pilots using the information to strategically navigate closer to degraded weather conditions (Beringer & Ball, 2004; Burgess & Thomas, 2004). Therefore, the purpose of this study was to investigate the effect ...


An Assessment Of The Decision-Making Units' Efficiency In Service Systems, Maoloud Yakhlif Dabab Jun 2020

An Assessment Of The Decision-Making Units' Efficiency In Service Systems, Maoloud Yakhlif Dabab

Dissertations and Theses

Most tools and models of performance and quality of service management are generic and do not solve complex technical systems. The critical components of the system need such tools to assess their efficiency to make a better decision about them. One of the primary objectives in the service systems is to improve the ability of efficiency, effectiveness, and sustainability of critical assets. One of the challenges with improving critical assets is the amount of major capital spending needed to upgrade a technology infrastructure with a high obsolescence rate. This along with usage and reliability issues, makes evaluating mobile cells to ...


Design Of A 7-Mhz Portable Direct Conversion Transceiver With Digitally Controlled Keying, Abram Morphew Jun 2020

Design Of A 7-Mhz Portable Direct Conversion Transceiver With Digitally Controlled Keying, Abram Morphew

Dissertations and Theses

This thesis outlines the design of a portable direct conversion transceiver system for the 7-MHz (or 40m) band. This band is popular due to its propagation characteristics which allow for world-wide communication with very low power. The transceiver utilizes a crystal-stabilized local oscillator optimized for frequency agility, low power consumption, and an optimal drive level of +7 dBm. A low power 8-bit microcontroller acts as an interface for either a straight key providing manual Morse code operation or digital logic control from a personal computer. It also acts as a side tone oscillator providing audio feedback to the operator during ...


Designing Gates And Architectures For Superconducting Quantum Systems, Sahar Daraeizadeh Jun 2020

Designing Gates And Architectures For Superconducting Quantum Systems, Sahar Daraeizadeh

Dissertations and Theses

Large-scale quantum computers can solve certain problems that are not tractable by currently available classical computational resources. The building blocks of quantum computers are qubits. Among many different physical realizations for qubits, superconducting qubits are one of the promising candidates to realize gate model quantum computers. In this dissertation, we present new multi-qubit gates for nearest-neighbor superconducting quantum systems. In the absence of a physical hardware, we simulate the dynamics of the quantum system and use the simulated environment as a framework for test, design, and optimization of quantum gates and architectures. We explore three different simulation-based gate design methodologies ...


Development Of A State-Space Aeroelastic Model Of A Flexible T-Tail Aircraft For Flutter Analysis, Patrick S. Downs Jun 2020

Development Of A State-Space Aeroelastic Model Of A Flexible T-Tail Aircraft For Flutter Analysis, Patrick S. Downs

Dissertations and Theses

Flutter prediction is an important part of the preliminary design process of any new aircraft. Current analysis methods include coupled fluid structure interaction codes and doublet lattice panel codes. The computation resources and time required for CFD solutions makes them unattractive for preliminary design and doublet lattice models require considerable pre and post processing to provide satisfactory results. Thus, a process for developing an analytical model to facilitate rapid design changes and the implementation of active control systems is the main motivation of this thesis. An analytical model is developed by first deriving the equations of motion of the structure ...


Pilot’S Willingness To Operate In Unmanned Aircraft System Integrated Airspace, Lakshmi Vempati May 2020

Pilot’S Willingness To Operate In Unmanned Aircraft System Integrated Airspace, Lakshmi Vempati

Dissertations and Theses

The interest in Unmanned Aircraft Systems (UAS) use for private, civil, and commercial purposes such as package delivery, inspection, surveillance, and passenger and cargo transport has gained considerable momentum. As UAS infiltrate the National Airspace System (NAS), there is a need to not only develop viable, safe, and secure solutions for the co-existence of manned and unmanned aircraft, but also determine public acceptance and pilot’s willingness to operate an aircraft in such an integrated environment. Currently there is little or no research on pilot’s perceptions on their willingness to operate an aircraft in UAS integrated airspace and airports ...


Viscoplastic Study Of 3d Printed Carbon Fiber Composites, Alexander M. Seifans May 2020

Viscoplastic Study Of 3d Printed Carbon Fiber Composites, Alexander M. Seifans

Dissertations and Theses

The research presented here involves an attempt to model the viscoplastic response of 3D printed carbon fiber composites made using the Mark Two 3D printer by Markforged. The ability to manufacture composites through the use of 3D printers is relatively new and contains gaps in the various mechanical properties of the material, of interest is the viscoplastic response.

Due to the fabrication method, the properties of the composites cannot be assumed to be similar to that of conventionally made composites as the fused deposition in printing alters the material properties. In order to understand the effects of the printed fiber ...


Shape Optimization Of Microfiber Composite Energy Harvesters, Suyash Lahoti May 2020

Shape Optimization Of Microfiber Composite Energy Harvesters, Suyash Lahoti

Dissertations and Theses

A model of energy harvesting beam with a piezoelectric material, microfiber composite (MFC), in a unimorph configuration was setup in Matlab using the governing equations of motions of a coupled electromechanical system. The equations of motion were derived using Hamilton’s variational principles and constitutive relations of a piezoelectric material. The mathematical model developed in Matlab was validated with an experiment and frequency response functions. The validated model was used to perform shape optimization so as to obtain the shape of the beam and the patch that harvests the largest voltage. The shape variables were length of the beam (LB ...


Unsteady Internal Ballistics Of A Hybrid Rocket, Naveen Sri Uddanti May 2020

Unsteady Internal Ballistics Of A Hybrid Rocket, Naveen Sri Uddanti

Dissertations and Theses

With the recent progress made in the field of space tourism, hybrid rocket engines have gained a renewed interest due to their simplicity, low cost, operational flexibility, and safety. The flow in the ports of a hybrid rocket motor involves several coupled unsteady phenomena like moving walls, combustion in a boundary layer flow and mass addition along the port, through the regression of the solid fuel wall. The flow in the combustion chamber of a hybrid rocket is inherently unsteady because the geometry of the port varies as a function of space and time. In the current research, we develop ...


Dmd And Pod Modal Analysis For Store Separation, Nicholas Peters May 2020

Dmd And Pod Modal Analysis For Store Separation, Nicholas Peters

Dissertations and Theses

Store separation from aircraft and spacecraft has historically been a critical and in some cases fatal issue for the aerospace industry. Given the severity of the issue much effort has been spent on the development of processes to identify failure flight conditions for store separation. The processes currently used for identifying potential failure conditions however are both resource intensive and iterative processes. A potential remedy to reducing resource use and improve turn around time in this process is the implementation of a mode based reduced order model (ROM) for modeling store separation. The objective of this study was to first ...


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 ...


Analysis Of Local Convection Heat Transfer Rates Of Supercritical Carbon Dioxide In Tubes, Yang Chao May 2020

Analysis Of Local Convection Heat Transfer Rates Of Supercritical Carbon Dioxide In Tubes, Yang Chao

Dissertations and Theses

Numerical investigation on thermodynamic characteristics of pure supercritical carbon dioxide (𝑆𝐶𝑂2) and mixtures of Helium and 𝑆𝐶𝑂2 in horizontal straight tubes with diameter of 6mm under cooling and heating conditions is carried out by using SST 𝑘 − 𝜔 turbulence model. The computations are conducted at operating pressure of 8MPa with various operating conditions. Simulations are conducted by using the latest poly-hexcore mesh method in ANSYS FLUENT 19.2 and tetrahedral mesh method in CFX 19.2, results and solving time are compared. The effect of heat flux, mass flux, inlet temperature and buoyancy on heat transfer performance are studied, pressure ...