Engineering Commons^™

Rebalancing Shared Mobility Systems By User Incentive Scheme Via Reinforcement Learning, Matthew Brian Schofield

Theses and Dissertations

Shared mobility systems regularly suffer from an imbalance of vehicle supply within the system, leading to users being unable to receive service. If such imbalance problems are not mitigated some users will not be serviced. There is an increasing interest in the use of reinforcement learning (RL) techniques for improving the resource supply balance and service level of systems. The goal of these techniques is to produce an effective user incentivization policy scheme to encourage users of a shared mobility system to slightly alter their travel behavior in exchange for a small monetary incentive. These slight changes in user behavior …

Turtle: A Fault Injection Platform For Sram-Based Fpgas, Corbin Alma Thurlow

Theses and Dissertations

SRAM-Based FPGAs provide valuable computation resources and reconfigurability; however, FPGA designs can fail during operation due to ionizing radiation. As an SRAM-based device, these FPGAs store operation-critical information in configuration RAM, or CRAM. Testing, through radiation tests, can be performed to prove the effectiveness of SEU mitigation techniques by comparing the SEU sensitivity of an FPGA design with and without the mitigation techniques applied. However, radiation testing is expensive and time-consuming. Another method for SEU sensitivity testing is through fault injection. This work describes a low-cost fault injection platform for evaluating the SEU sensitivity of an SRAM-based FPGA design by …

Software Defined Radio Short Range Radar, Nicholas Everett Kohls

Theses and Dissertations

High cost is a current problem with modern radar systems. Software-defined radios (SDRs) offer a possible solution for low-cost customizable radar systems. An SDR is a radio communi- cation system where, instead of the traditional radio components implemented in hardware, many of the components are implemented in software on a computer or embedded system. Although SDRs were originally designed for wireless communication systems, the firmware of an SDR can be configured into a radar system. With new companies entering the market, various types of low- cost SDRs have emerged. This thesis explores the use of a LimeSDR-Mini in a short-range …

Regional Water Quality Data Viewer Tool: An Open-Source To Support Research Data Access, Danisa Dolder

Theses and Dissertations

Water quality data collection, storage, and access is a difficult task and significant work has gone into methods to store and disseminate these data. We present a tool to disseminate research in a simple method that does not replace but extends and leverages these tools. In the United States, the federal government maintains two systems to fill that role for hydrological data: the U.S. Geological Survey (USGS) National Water Information System (NWIS) and the U.S. Environmental Protection Agency (EPA) Storage and Retrieval System (STORET), since superseded by the Water Quality Portal (WQP). The Consortium of the Universities for the Advancement …

Effects Of Whole Body Vibration On Inhibitory Control Processes, Bennett Alan Mortensen

Theses and Dissertations

Vibrations are often experienced in the workplace and may influence performance and executive function. Research has shown that vibrations may have an affect effect on drowsiness and tests related to inhibitory control. Previous work investigating whole body vibrations (WBV) and their effect was evaluated to inform the decisions for this study. WBV effects on cognitive abilities were examined and the different tests used in these studies were identified and compared. Electroencephalogram (EEG) and event related potentials (ERP) were selected to be used to measure inhibitory and cognitive processes. The N2 ERP, which reflects inhibitory control processes, was examined as well …

Design And Fabrication Of Zinc Oxide Optofluidic Laser Elements, Kyle T. Bodily

Theses and Dissertations

This thesis systematically goes through the derivation, simulation, and experimentation of Zinc Oxide optofluidic micro laser elements. Single and coupled ring resonators were simulated to show single mode transmission as well as enhanced coupling capabilities when surrounded by high refractive index liquid. Devices with diameters ranging from 100-500 µm were successfully fabricated inexpensively through standard cleanroom procedures. The devices were tested using two different pump laser systems. Testing included such factors as high pump intensity, various angles of excitation, and low temperature. In all cases PL emission was observed and recorded.

Autonomous Mission Planning For Spacecraft Rendezvous And Proximity Operations, Julia C. Bell

Theses and Dissertations

The evolving space environment has created a demand for autonomous spacecraft that can maneuver in complex and sometimes contentious environments. Constraint enforcement, such as an avoidance zone to prevent collision with a target, is a key component of autonomous control to ensure safety and performance requirements are met. Finite-horizon Model Predictive Control (MPC) is a popular control method due to its improved computation time while optimizing performance. Two areas of MPC in need of expansion are time-varying constraints and phase transitions in multi-phase applications. In this work, MPC is employed to track the reference trajectory of a multi-phase satellite inspection …

Developing A Basic Formal Supply Chain Ontology To Improve Communication And Interoperability, David Morrow

Theses and Dissertations

Information is crucial to supply chain performance because it is used to make decisions and trigger actions. Organizations across world-class supply chains increasingly use information technology to analyze and process supply chain data. However, supply chain management lacks a common language, making information exchange difficult. An ontology can provide a standardized framework that organizes a given knowledge domain. This research proposes a common language for developing a supply chain ontology that can be built into a basic formal ontology understood by both humans and computers. According to current research, an established and widely used supply chain framework is a good …

Statistically Defensible Wind Tunnel Models, Timothy A. Roche

Theses and Dissertations

Wind tunnels are used to test scale-model air frames in order to collect aerodynamic data. The Subsonic Aerodynamic Research Laboratory (SARL) Wind Tunnel is a low speed wind tunnel located at Wright-Patterson Air Force Base. The SARL Wind Tunnel team approached AFIT for assistance in creating statistically defensible models for the conditions inside the wind tunnel. During a wind tunnel test, pressure sensors cannot be placed at the test model. Instead, pressure is measured by a pitot probe permanently mounted in the corner of the test chamber. The pressure at the model location is predicted from the measurements taken by …

Six Degree-Of-Freedom Mission Planning For Reentry Trajectories, Peter Davis

Theses and Dissertations

Traditional reentry dynamics and planning has typically explored 3 Degrees-of- Freedom (3 DOF) or pseudo 6-DoF problem formulations. This research expands upon previous work and presents a path-constrained optimal control formulation of a fully 6 Degrees-of-Freedom (3 DOF) dynamic system for an unpowered Reentry Vehicle (RV). In a full 6-DoF dynamic system, the translation, rotation and rotational rates are continually tracked. A system of equations of motion are developed to express the dynamics of the RV in terms of defined states and the RV's physical control detections. A neural-network is used to approximate the aerodynamic database of an exemplary RV. …

Sar Collection Planning And Data Quality Assessment, Jacob M. Brumfield

Theses and Dissertations

Radar resource management is an important research topic in the radar community. Identifying the performance of a synthetic aperture radar image early into a data processing chain can improve intelligence collection mission performance. To achieve that goal, separate flags can be presented to a radar technician along a data processing chain to identify various errors within a data collection. Toward the end, this thesis analyzes he radar image processing chain and identifies data quality checks that could be implemented. The first quality check is to identify canonical targets and the necessary Nyquist-Shannon sampling requirements. Then, observations can be made to …

Dynamic Body Armor Shape Sensing Using Fiber Bragg Gratings And Photoassisted Silicon Wire-Edm Machining, Ivann Civi Lomas-E Velasco

Theses and Dissertations

In this thesis, a method to improve survivability is developed for fiber Bragg gratings under high velocity impact in dynamic body armor shape sensing applications by encasing the fiber in silicone. Utilizing the slipping of the fiber within the silicone channel, a proportionality relationship between the strain of the fiber to the acceleration of the impacting projectile is found and is used to obtain the rate of the back-face deformation. A hybrid model is developed to handle errors caused by the stick-slip of the fiber by fitting an inverse exponential to stuck sections found in a captured strain profile and …

Medical Signal Recognition System Based On Machine Learning, Deep Learning, And Internet Of Things, Arwa Hameed Mohammed Taqi

Theses and Dissertations

Internet of Things (IoT) technology is becoming increasingly common in the healthcare industry. The significant benefits of IoT are decreased operational costs, improved outcomes of the treatment through virtual infrastructures and accessibility of real-time information for making informed decisions, improved disease management, reduced errors, and enhanced patient experience. This enables hospitals to address the demands of the ever-growing population in this world. On the other hand, medical signal classification systems are systems that recognize normal from abnormal medical signals. These systems depend on two modes, training mode in which the system learns about the dominant features of the signals, and …

Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh

Theses and Dissertations

Piezoelectric contour mode resonator technology has the unique advantage of combining low motional resistance with the ability to define multiple frequencies on the same substrate. Contour mode resonators can be mechanically coupled together to form robust band-pass filters for the next generation of GPS satellites with extreme size reduction compared to electrically coupled filters. Piezoelectric zinc oxide (ZnO) contour mode resonators have the potential for monolithic integration with current ZnO transistor further reducing size, power consumption, and cost of filter modules. Barium strontium titanate (BST) contour mode resonators have incredible frequency tunability due to the fundamental nature of the thin …

Examining The Influence Of Source Dependence On Supplier Performance In The Usaf Organic Supply Chain, Thomas A. Counter

Theses and Dissertations

The purpose of this study is to examine the U.S. Air Force's dependence toward sole sourcing and how that influences procurement outcomes in terms of supplier performance. This research used linear regression to explain the effect of source dependence and supplier size on performance categories for 326 suppliers. The five supplier performance categories in the study included timeliness, cost control, quality, business relations, and regulatory compliance. The research found that the USAFs dependence on sole sourcing had a small but statistically significant influence on all five aspects of supplier performance, with timeliness being the most adversely impacted.

One Dimensional Study Of Magnetoplasmadynamic Thrusters For A Potential New Class Of Heavy Ion Drivers For Plasma Jet Driven Magnetoinertial Fusion, Patrick M. Brown

Theses and Dissertations

Plasma Jet Driven Magnetoinertial Fusion (PJMIF) requires high velocity heavy ion drivers in order to compress a magnetized target to fusion conditions. Previous work with heavy ion drivers has revealed sub-par accelerations due to plasma instabilities; thus, it is necessary to investigate new methods of heavy ion plasma acceleration. One such method is Magnetoplasmadynamic (MPD) thrusters. Past studies of these thrusters have been conducted at an initial temperature at or below the energy of full ionization. Here MPD thrusters are investigated using a Godunov type MHD solver with a Harten-Lax van Leer-D (HLLD) flux solving scheme assuming the plasma is …

An Analysis Of The Air Force Installation Development Plan And Its Energy Benchmarking Effectiveness, Jacob P. Hyman

Theses and Dissertations

Installation Development Plan (IDP) is a comprehensive long-term base planning document, which includes an inventory of sustainable development goals including energy use and climate indicators. This study analyzed 32 different IDPs among the various installations in the continental United States, identifying regional trends and behaviors across their 16 Sustainability Development Indicators (SDI). To study the IDPs more in depth, specific focus was placed on SDI 1, which concerns energy consumption and generation. This study investigated the different variations in energy benchmarking across local climate conditions, SDI ratings, and units used. Major inconsistencies were found across these three domains. Subsequently, the …

Improving The Stability And Operability Of A Small-Scale Rotating Detonation Engine, Nathan T. Fiorino

Theses and Dissertations

A small scale RDE was designed with a channel diameter of 28 mm and channel gap of 2 mm and operated on nitrous oxide (N₂O) and ethylene (C₂H₄) as the oxidizer and fuel respectively. Changes to the original Jets in Crossflow (JIC) injection scheme and spark plug ignition method were implemented to counteract previously observed wave instabilities. Successful detonation was observed over a range of mass flows (0.035-0.068 kg/s) and equivalence ratios (ɸ = 0.6-1.4) and a stable single wave mode with frequency up to 16.8 kHz was observed for the first time. Injection …

Estimation And Simulation Of Daily Activity Patterns For Individuals Using Wheelchairs, Nathan John Lant

Theses and Dissertations

Individuals who use wheelchairs or who have other mobility challenges often are unable to access modern mobility systems "“ including application-based ride hailing and on-demand microtransit. Even designing a system targeted at these users is challenging, given the limited prior analysis of their travel behavior and activity patterns. Simulation tools are used by cities around the world to understand novel and complex transportation systems, yet few are including the needs of users with disabilities in these simulation studies. This thesis examines the travel patterns of wheelchair users from the 2017 National Household Travel Survey and presents a model of daily …

Stock Markets Performance During A Pandemic: How Contagious Is Covid-19?, Yara Abushahba

Theses and Dissertations

Background and Motivation: The coronavirus (“COVID-19”) pandemic, the subsequent policies and lockdowns have unarguably led to an unprecedented fluid circumstance worldwide. The panic and fluctuations in the stock markets were unparalleled. It is inarguable that real-time availability of news and social media platforms like Twitter played a vital role in driving the investors’ sentiment during such global shock.

Purpose:The purpose of this thesis is to study how the investor sentiment in relation to COVID-19 pandemic influenced stock markets globally and how stock markets globally are integrated and contagious. We analyze COVID-19 sentiment through the Twitter posts and investigate its …

Integrating Vibratory Membrane-Based Water Recovery Systems For Sustainable Food And Beverage Production, Michael Vincent O. Laurio

Theses and Dissertations

A vibratory nanofiltration (NF) system was investigated for the preconcentration of coffee extracts for soluble coffee production. The simulated coffee extracts studied contained mostly suspended and colloidal organic components that, although were effectively rejected by the NF membrane (>99% turbidity rejection), affected the vibratory NF performance. The vibratory NF operation improved permeate flux, rejection efficiencies, and reduced flux decline from those observed in crossflow (CF) operation. Further, the effects of applied transmembrane pressure (TMP) and vibrational frequency (F) at corresponding displacement (d) were investigated and modeled. A semi-empirical resistance-in-series model was employed to characterize the mass transfer mechanism, osmotic …

A Self-Tunable Piezoelectric Energy Harvester, Ashraf Hussein

Theses and Dissertations

In this study, a new technique to harvest energy using inertial vibration energy harvesters is introduced. A triple-layer piezoelectric beam with a self-tunable frequency was developed in order to respond to variable-frequency excitations, thereby maintaining the beam in a state of resonance for maximum power output. The tuning mechanism managed to change the natural frequency of the beam in the range of 2.27 ���� to 6.25 ����. In this case, the output voltage could be raised from 12�� to 23��.

A mathematical model was developed to investigate the natural frequency, the output voltage, and the output power of the beam …

Small-Target Detection And Observation With Vision-Enabled Fixed-Wing Unmanned Aircraft Systems, Hayden Matthew Morgan

Theses and Dissertations

This thesis focuses on vision-based detection and observation of small, slow-moving targets using a gimballed fixed-wing unmanned aircraft system (UAS). Generally, visual tracking algorithms are tuned to detect motion of relatively large objects in the scene with noticeably significant motion; therefore, applications such as high-altitude visual searches for human motion often ignore target motion as noise. Furthermore, after a target is identified, arbitrary maneuvers for transitioning to overhead orbits for better observation may result in temporary or permanent loss of target visibility. We present guidelines for tuning parameters of the Visual Multiple Target Tracking (Visual MTT) algorithm to enhance its …

Design And Sensitivity Analysis Of Blood Supply Chain Network, The Merits Of Lateral Resupply, Mohammad Arani

Theses and Dissertations

The vibrant subject of blood banking and blood distribution is addressed where lateral resupply of blood products is allowed. In this research, a blood supply chain network design (BSCND) consisting of four conventional levels each of which corresponding to one entity in the real world is comprehensively studied: donors, blood collection facilities, blood centers, and hospitals. Two important properties are considered within the blood supply chain network (BSCN): ABO-Rh factors and shelf lives of blood products. Moreover, an integrated inventory system for sharing hospitals’ inventory levels is designed to investigate the two performance indicators of the network in terms of …

Fault Modeling And Test Vector Generation For Asic Devices Exposed To Space Single Event Environment, Ahmed Mohamed

Theses and Dissertations

This work aims at providing a concise automated flow to predict the effect of Single Event Transients (SETs) on ASIC chips by developing a method to characterize the circuit susceptibility to SET pulses propagation and then generation of the required input vectors that sensitize the victim paths. A new enhanced method for SET electrical propagation modeling is proposed and compared to a previously published analytical model. The method was applied on different standard cells libraries built over XFAB Xh018 technology and verified for accuracy against simulations. The new method showed enhancement in accuracy compared with previous work in literature. Industrial …

Engineering A Prophylactic Cap For Multi-Dose Vial Disinfection, Rebecca Lee Charboneau

Theses and Dissertations

Recently, multi-dose vials (MDVs) have demonstrated significant bioburden, with randomized studies revealing bacterial contamination rates up to 27%. When the proper protocol of disinfecting the vial diaphragm with a pre-saturated wipe is followed, MDV bioburden is eliminated. However, when this sterilization protocol is neglected, the susceptibility of MDV to house potential nosocomial pathogens intensifies. In this work, the usability and effectiveness of a novel device, referred to as the Vial Cap, are investigated to gauge the feasibility and acceptability of this device as a method of MDV disinfection. The usability of the Vial Cap was evaluated using principle human factors …

Exploring The Performance Impacts Of Harmful Fpga Configurations, Tanner Gaskin

Theses and Dissertations

In this work a new technique for accelerating the aging of FPGA devices is proposed and demonstrated. The proposed technique uses harmful configurations (short circuits) to accelerate the aging process on targeted portions of an FPGA chip. A testbed is developed for the purpose of measuring FPGA degradation. Using this testbed it is shown that implementing thousands of short circuits in FPGA fabric generates enough heat to cause significant damage to the chip, reducing switching speeds by up to 8%. It is also demonstrated that different parts of the FPGA fabric can be aged at different rates, with some parts …

Assessment Of Contract Terms And Conditions For Lump-Sum Contracts, Omar Othman

Theses and Dissertations

A Contract is a tool that defines the obligations of the contracting parties and assigns the risk between them. Contracts are usually drafted to meet the interests of the owner by addressing the legal issues and liabilities. Meanwhile, less emphasis is placed on clearly communicating the contract terms and ensuring that all contracting parties comprehend their risks and obligations. In a country like Egypt, which has faced drastic economic and political changes in the past few years, and yet is experiencing a boom in the construction sector, many developers tend to draft contracts that might be legally complicated or lacks …

Data-Driven Modeling And Control Of A Two-Link Flexible Manipulator (Tlfm), Samuel Ayankoso

Theses and Dissertations

Two-link flexible manipulators (TLFMs) are used in different application domains, and their merits include lightweight, low energy consumption, high operational speed, transportability, maneuverability, and low cost. Despite the merits of TLFMs, the flexibility of the links introduces modeling and control problems. The existing mathematical modeling techniques of a TLFM, such as the assumed mode method (AMM), finite element method (FEM) and finite difference method (FDM are mathematically complex and do not accurately match the physical system dynamics. Lumped parameter method (LPM) model is a simplified model, but it is also inaccurate. Moreover, different forms of control problems are applicable to …

Effects Of Genipin Crosslinking On The Properties Of Tendon Derived Extracellular Matrix Hydrogels, Alicia Cheyenne Coombs

Theses and Dissertations

Extracellular matrix (ECM) hydrogels are a useful biomaterial in the tissue engineering field used for injectables in drug delivery systems, wound dressing, tissue regeneration and many other applications. ECM hydrogels are highly biocompatible, contain proper ratios of biomolecules required for complex bioactivity of tissues and they promote tissue repair. However, ECM hydrogels typically have poor mechanical strength, which leads to hydrogel instability, and a limitation in their ability to be modified for translational applications. In this research, genipin, a natural crosslinker derived from plants, was utilized in an attempt to improve upon the mechanical limitations of ECM hydrogels. Genipin has …