Engineering Commons^™

Controlled Pre-Wetting Of Spread Powder And Its Effects On Part Formation And Printing Parameters In Binder Jetting Additive Manufacturing, Colton G. Inkley

Theses and Dissertations

Binder jetting is an additive manufacturing process that layer by layer builds a 3D model by selectively binding regions of powder using binder deposited though an inkjet printhead. The process offers several advantages over other additive manufacturing processes including fast build rates, vast material selection, decreased cost, and part resolution. The main disadvantage of binder jetting is poor mechanical properties, stemming from a poor understanding of the process physics. Porosity in final parts is not uncommon, but there is little understanding of where the porosity originates. The purpose of this thesis is to report the investigation of increased powder bed …

Demonstration Of A Transient Hot Wire Measurement System Towards A Carbide-Based Sensor For Measuring The Thermal Conductivity Of Molten Salts, Peter Charles Kasper

Theses and Dissertations

This thesis documents research done for a transient hot wire system that will be used in future thermal conductivity measurements of molten salts. Research done with molten salts have been limited because of erroneous measurement capabilities, but the current research strives to introduce a new technique to accurately record thermal conductivity over a wide range of temperatures. This work follows up on past transient hot wire researchers whose designs and tests produced an instrument that can measure the thermal conductivity of molten metals up to 750 K. The transient hot wire (THW) technique has been selected to be used in …

Autoignition Temperatures Of Pure Compounds: Data Evaluation, Experimental Determination, And Improved Prediction, Mark Edward Redd

Theses and Dissertations

The Design Institute for Physical Properties (DIPPR) maintains the DIPPR 801 database for the American Institute of Chemical Engineers. Autoignition temperature (AIT) is one of the properties included in the database and is the focus of this work including improvement of the overall state of AIT in the database. Phenomena related to AIT as well as the relevant literature are reviewed. Likewise, the database is presented to respond to significant misuse of the DIPPR 801 database in the literature. The database is evaluated, respecting AIT, as a whole to show where improvement is needed. An experimental study of minimum autoignition …

Understanding Microstructure Heterogeneity In Li-Ion Battery Electrodes Through Localized Measurement Of Ionic Transport, Baichuan Liu

Theses and Dissertations

Electrode microstructure influences ionic transport and electronic transport and is a key factor that affects lithium-ion battery performance. Non-uniform microstructure or heterogeneity in battery electrodes has long been observed and leads to non-uniform transport properties. This work provides a better understanding of in-plane heterogeneity at millimeter length scale and through-plane heterogeneity at micrometer length scale, through a combination of experiment and modeling. The first part of this work develops the aperture probe technique, which is an experimental method and associated model to locally estimate ionic transport, represented by MacMullin number, in the electrode. By generating contour maps of MacMullin number, …

Material Development Toward An Index-Matched Gadolinium-Based Heterogenous Capture-Gated Neutron Detector, Aaron J. Thorum

Theses and Dissertations

Neutron detection is important in several fields, especially detection of illicit nuclear material. Historically, 3He has been the basis for these technologies. Modern realities have necessitated the development of new technologies and the exploration of new materials to meet this need. One potential solution is known as capture-gating, which is a measurement approach that is good at differentiating between incident neutrons and gamma rays. The key issue is that materials used in current capture-gating devices can suffer from poor optical performance. This is due to the fact that the these detectors, whether composed of a heterogeneous or homogeneous mixture of …

Design And Development Of A Dynamic Web App Library For Hydroshare, Alexander Hart Henrichsen

Theses and Dissertations

This paper documents the design and creation of an App Library for HydroShare water resources data and software discovery and sharing system. This App Library was developed to simplify the discovery process for using environmental web applications and to lower hosting requirements for such a repository. To accomplish this goal, I created the HydroShare App Library as a standalone web application using the React JavaScript framework. The App Library application uses the existing HydroShare resource connectors to allow the registration of all web applications within the App Library without having external software requirements. This allows the HydroShare App Library to …

Improvement Of Ex Vivo Testing Methods For Spine Biomechanical Characterization, Aubrie Lisa Taylor

Theses and Dissertations

This dissertation contributed three main areas to flexibility testing and biomechanical characterization of human spinal segments. The first was a literature review of existing testing methodology, the second examined common spine fixation procedures, and the third developed an improved fixation method. Spine biomechanical characterization is the primary technique for assessing the healthy, diseased, and surgically treated response of spinal tissues. However, despite decades of use, no standard testing protocol or reporting methodology for flexibility testing conditions has been established. As part of the present work, a comprehensive, systematic literature review was performed, and the methods sections of 242 relevant journal …

Airship Systems Design, Modeling, And Simulation For Social Impact, Daniel C. Richards

Theses and Dissertations

Although there have been oscillations in airship interest since their use in the early 1900s, technological advancements and the need for more flexible and environmentally friendly transportation modes have caused a stream of study and surge in airship development in recent years. For companies and governments to understand how airships can be incorporated into their fleets to fulfil new or existing mission types, system design space exploration is an important step in understanding airships, their uses, and their design parameters. A decision support system (DSS), Design Exploration of Lighter-Than-Air Systems (DELTAS), was developed to help stakeholders with this task. DELTAS …

Analysis Of A Full-Stack Data Analytics Solution Delivering Predictive Maintenance To A Lab-Scale Factory, Nathan Wesley Hoyt

Theses and Dissertations

With the developments of industry 4.0, data analytics solutions and their applications have become more prevalent in the manufacturing industry. Currently, the typical software architecture supporting these solutions is modular, using separate software for data collection, storage, analytics, and visualization. The integration and maintenance of such a solution requires the expertise of an information technology team, making implementation more challenging for small manufacturing enterprises. To allow small manufacturing enterprises to more easily obtain the benefits of industry 4.0 data analytics, a full-stack data analytics framework is presented and its performance evaluated as applied in the common industrial analytics scenario of …

Midfoot Motion And Stiffness: Does Structure Predict Function?, Kirk Evans Bassett

Theses and Dissertations

In clinical settings, dynamic foot function is commonly inferred from static and passive foot measurements; however, there is little evidence that static foot structure can predict dynamic foot function during walking gait. Previous research seeking to find correlations between the two have focused primarily on sagittal plane midfoot angles even though the midfoot has triplanar motion, which misses potentially important information. Additionally, the focus on kinematics alone may miss the contributions that forces play in midfoot mechanics. To address the angle limitations, a novel Signed Helical Angle (SHA) was developed to capture the triplanar motion of the midfoot from a …

A Direct-Read, A Posteriori Golden Copy Method For Measuring Soc Cache Upsets, Evan D. Poff

Theses and Dissertations

A method for measuring system-on-a-chip (SoC) cache upsets is presented and evaluated. In contrast to methods that predict cache contents through analysis or memory access patterns, this method uses system registers to read cache memories directly, thereby creating and checking golden copies to detect individual memory upsets during operation. The test method is driven by the device under test itself and does not require a user to set or know a priori the cache contents. A bare-metal implementation of this “direct golden method” on a Zynq UltraScale+ MPSoC logged upsets in the device’s data cache, data tag, and TLB RAM …

Evaluating A Statistical-Based Assessment Tool For Stratifying Risk Among U.S. Air Force Organizations, Tiffany A. Low

Theses and Dissertations

The Air Force Inspection System is a proponent of utilizing a risk-based sampling strategy (RBSS) for conducting inspections from major command levels down to the unit level. The strategy identifies areas deemed most important or risky by commanders and prioritizes them accordingly for an independent assessment by the Inspector General. While Air Force regulation specifies the need to use a RBSS for inspection, the implementation process is delegated to individual commands and, subsequently, wings. The 23rd Wing, the sponsor for this research, directed us to analyze a RBSS tool highlighted as an example from which to adopt for those units …

Reconciliation, Restoration And Reconstruction Of A Conflict Ridden Country, Muhammad S. Riaz

Theses and Dissertations

Conflict has sadly been a constant part of history. Winning a conflict and making a lasting peace are often not the same thing. While a peace treaty ends a conflict and often dictates terms from the winners’ perspective, it may not create a lasting peace. Short of unconditional surrender, modern conflict ends with a negotiated cessation of hostilities. Such accords may have some initial reconstruction agreements, but Reconciliation, Restoration and Reconstruction (RRR) is a long term process. This study maintains that to achieve a lasting peace: 1) The culture and beliefs of the conflict nation must be continuously considered and …

Effects Of Motion Measurement Errors On Radar Target Detection, Darnell D. Parker

Theses and Dissertations

This thesis investigates the relationships present between signal-to-clutter ratios, motion measurement errors, image quality metrics, and the task of target detection, in order to discover what factor merit greater focus in order to attain the highest probability of target detection success. This investigation is accomplished by running a high number of Monte Carlo trials through a coherent target detector and analyzing the results. The aforementioned relationships are demonstrated via sample synthetic aperture radar imagery, histograms, receiver operating characteristics curves, and error bar plots.

Polarization-Based Image Segmentation And Height Estimation For Interferometric Sar, Augusta J. Vande Hey

Theses and Dissertations

To find scatterers in a synthetic aperture radar (SAR) image, a modification is proposed to improve peak region segmentation (PRS) with region merging. The modification considers the polarization of each pixel before it is added to a segment to ensure the segment only contains pixels of the same polarization. Prior to region merging, the polarization of the segments is compared, so that only segments with the same polarization are merged into a single region. The segmented regions are used to find the height of each scatterer through interferometric SAR (IFSAR) processing. Multiple methods of IFSAR are examined to find the …

Methods For Focal Plane Array Resolution Estimation Using Random Laser Speckle In Non-Paraxial Geometries, Phillip J. Plummer

Theses and Dissertations

The infrared (IR) imaging community has a need for direct IR detector evaluation due to the continued demand for small pixel pitch detectors, the emergence of strained-layer-super-lattice devices, and the associated lateral carrier diffusion issues. Conventional laser speckle-based modulation transfer function (MTF) estimation is dependent on Fresnel propagation and a wide-sense-stationary input random process, limiting the use of this approach for lambda (wavelength)-scale IR devices. This dissertation develops two alternative methodologies for speckle-based resolution evaluation of IR focal plane arrays (FPAs). Both techniques are formulated using Rayleigh-Sommerfield electric field propagation, making them valid in the non-paraxial geometries dictated for resolution …

Identification And Characterization Of Point Defects In Nonlinear Optical Crystals: Barium Gallium Selenide And Lithium Triborate, Brian C. Holloway

Theses and Dissertations

Increased interest in developing new nonlinear optical materials has led to 3rd generation materials, such as BaGa4Se₇ and LiB₃O₅. These two nonlinear optical crystals have the potential to enable development of tunable lasers operating across the mid-wave infrared and the ultraviolet regions, respectively. Coherent light sources are used in the development of enhanced technologies with commercial and defense-based applications such as: health and environmental monitoring devices, next-generation infrared countermeasures, and ballistic missile booster exhaust plume characterization. The performance of optical materials in high-powered military applications is largely limited by the presence of defects. These defects …

Influence Of Materials And Design Parameters On Zinc Oxide Surface Acoustic Devices, Samuel B. Dewhitt

Theses and Dissertations

This thesis presents research into Zinc Oxide (ZnO) based resonators to include Width Extensional Mode (WEM), Length Extensional Mode (LEM), and Surface Acoustic Wave (SAW) devices. The design and operation of ZnO based SAW devices are investigated further to characterize design parameters and operating modes. Their design, fabrication, and results are discussed in detail. SAW device testing in conjunction with X-Ray Diffractometry (XRD) and Atomic Force Microscopy (AFM) are utilized to characterize ZnO and its deposition parameters on a variety of different substrates and interlayers, with different deposition temperatures and annealing parameters. These substrates include silicon, silicon oxide-on-silicon, and sapphire …

Theory And Design Of A Highly Compressed Dropped-Channel Polarimetric Synthetic Aperture Radar, John T. Becker

Theses and Dissertations

Compressed sensing (CS) is a recent mathematical technique that leverages the sparsity in certain sets of data to solve an underdetermined system and recover a full set of data from a sub-Nyquist set of measurements of the data. Given the size and sparsity of the data, radar has been a natural choice to apply compressed sensing to, typically in the fast-time and slow-time domains. Polarimetric synthetic aperture radar (PolSAR) generates a particularly large amount of data for a given scene; however, the data tends to be sparse. Recently a technique was developed to recover a dropped PolSAR channel by leveraging …

Full Pattern Analysis And Comparison Of The Center Fed And Offset Fed Cassegrain Antennas With Large Focal Length To Diameter Ratios For High Power Microwave Transmission, Derek W. Mantzke

Theses and Dissertations

High power microwaves (HPM) have been a topic of research since the Cold War era. This paper will present a comparison between two Cassegrain-type antennas: the axially, or center fed, and the offset fed. Specifically, the 10 GHz operating frequency will be investigated with large focal length to diameter () ratios. Beam patterns which encompass the entire radiation pattern will be included for data validation and optimization. The simulations will follow a design of experiments factorial model to ensure all possible combinations of prescribed parameters are included, including an analysis of variance (ANOVA) study to find parameter influence on the …

A Model-Based Approach To Cubesat Propulsion And Payload Analysis, Madeline H. Johnson

Theses and Dissertations

Currently, there are only limited ways to increase mission success of CubeSats in terms of component and mission compatibility. The Payload Analysis Tool (PAT), developed by Air Force Institute of Technology (AFIT) students, combines the power of multiple tools to analyze payload compatibility on a single CubeSat bus. The PAT simulates a CubeSat mission with a variety of payloads to better understand how the payloads interact with the bus in terms of power, data rate, and memory, but it lacks a propulsion system. This thesis research advances the PAT by including a propulsion system which allows for increased mission time …

Performance Study Of Post-Processed Additively Manufactured Low Thrust Nozzles, Tyler W. Gerhold

Theses and Dissertations

This research explores metal post-processing techniques to effectively reduce the large anomalous protrusions found in small additively manufactured low thrust rocket nozzles. Research has found that nozzles of this kind can experience losses in thrust of over 40%. Analytic theory of adiabatic nozzle flow with viscous losses for additively manufactured nozzles does not align with what has been found when tested experimentally. Compressible flow losses, such as shock wave formation inside the nozzle diverging cone, are likely the leading causes of such loss. Reduction in nozzle irregularities can likely yield results seen in analytic theory with similar performance to traditional …

Integrated Circuits Parasitic Capacitance Extraction Using Machine Learning And Its Application To Layout Optimization, Mohamed Saleh Abouelyazid Saleh

Theses and Dissertations

The impact of parasitic elements on the overall circuit performance keeps increasing from one technology generation to the next. In advanced process nodes, the parasitic effects dominate the overall circuit performance. As a result, the accuracy requirements of parasitic extraction processes significantly increased, especially for parasitic capacitance extraction. Existing parasitic capacitance extraction tools face many challenges to cope with such new accuracy requirements that are set by semiconductor foundries (< 5% error). Although field-solver methods can meet such requirements, they are very slow and have a limited capacity. The other alternative is the rule-based parasitic capacitance extraction methods, which are faster and have a high capacity; however, they cannot consistently provide good accuracy as they use a pre-characterized library of capacitance formulas that cover a limited number of layout patterns. On the other hand, the new parasitic extraction accuracy requirements also added more challenges on existing parasitic-aware routing optimization methods, where simplified parasitic models are used to optimize layouts.

This dissertation provides new solutions for interconnect parasitic capacitance extraction and parasitic-aware routing optimization methodologies in order to cope with the new accuracy requirements of advanced process nodes as follows. …

Educational Data Mining For Predicting University Students' Performance, To Enhance University Admission Criteria, Youssef Amr Naga

Theses and Dissertations

This thesis aims to propose and evaluate possible predictors of success for incoming university students to the American University in Cairo (AUC) who wish to enroll in its engineering programs, by considering their overall grade point average (GPA) at graduation as the measure of their success (output variable). This study is composed of two phases. First, available university admission variables; i.e., gender, high school diploma, high school score, and proficiency level in the English language (the language of instruction at AUC) at the time of application are evaluated as a predictor of students’ performance using five different data mining techniques. …

Novel Compact Mimo Antenna Array Structures For 5g, Wi-Fi 6 And Vehicular Applications, Sulaiman Tariq

Theses and Dissertations

Due to the fast development of wireless communication applications, the study of Multiple Input Multiple Output (MIMO) communication systems has lately gained comprehensive research interests since it can significantly increase the channel capacity and link reliability without sacrificing bandwidth and/or power transmitted. However, the user equipment is constantly shrinking in size to support more applications and satisfy aesthetic needs, which increases the need for more compact, high-performance antenna array designs. Many techniques are being constantly developed to combat the effects of mutual coupling that arise with the miniaturization of MIMO arrays. This dissertation focuses on designing, testing, and evaluating new …

Temperature And Radiation Measurements In A Pressurized Oxy-Coal Reactor, Dustin Peter Badger

Theses and Dissertations

To understand the behavior and performance of a new 100 kW pilot scale pressurized oxy-coal reactor, radiation measurements of the flame have been made using a Fourier Transform Infrared (FTIR) spectrometer. From these radiation measurements, gas temperatures were obtained using integrated spectral infrared (ISIR) emission from the CO2 and water vapor of the combustion product gases. Radiative emission from the product gases in the reactor were collected through a quartz window 1.524 m downstream of the burner. An optical probe focused culminated emission from the combustion chamber into a silica fiber which transported the radiative signal to the spectrometer. The …

Multi-Material 3d-Printed Silicone Vocal Fold Models, Clayton Adam Young

Theses and Dissertations

Self-oscillating synthetic vocal fold (VF) models are often used to study human voice production. In this thesis, a method for fabricating multi-layer self-oscillating synthetic VF models using silicone 3D printing is presented. Multi-material 3D printing enables faster fabrication times with more complex geometries than traditional casting methods and builds a foundation for producing VF models with potentially more life-like geometries, materials, and vibratory characteristics. The printing method in this study used a custom dual extruder and slicing software to print UV-curable liquid silicone into a gel-like support matrix. The extruder was fabricated using high-torque stepper motors with high resolution leadscrews …

Experimental Characterization And Manufacture Of Polymer Nanocomposite Dielectric Coatings For High-Temperature Superconductor Applications, Jacob Ryan Mahon

Theses and Dissertations

Increased implementation of high-temperature superconducting (HTS) power transmission has the potential to revolutionize the efficiency of electrical grids and help unlock a fully electric transportation infrastructure. Realizing the benefits of HTS systems has been impeded by a lack of available dielectric insulation materials that can 1) withstand the extreme cryogenic operating environment of superconductors and 2) demonstrate low temperature processing that is compatible with existing superconductor manufacturing methods. Solving this problem necessitates a high-performance dielectric material with multifunctional properties specifically suited for operation in HTS systems. A polyamide and silicon dioxide (PA/SiO2) nanocomposite material with exceptional thermal stability has been …

A Model For The Sustainable Achievement Of The Optimum Return For Crops In Greenhouses, Eman Elnahas

Theses and Dissertations

This study provides a tool for accurate estimation of the irrigation water needs for various crop combinations under different environmental conditions; and employs a genetic optimization algorithm to reach optimum combinations. In the interest of sustainability, the source of energy required to drive the pumps is selected to be a renewable source, namely solar energy, which is converted to electricity employing photovoltaic (PV) modules. Having a single crop will lead to an uneconomical system because the PV installed capacity will not be exploited most of the time.

This research was conducted by establishing the required database, generating different scenarios, assessing …

A Modular Synthesis Of Processable And Thermally Stable Semi-Fluorinated Aryl Ether Polymers Via Step-Growth Polymerization Of Fluoroalkenes, Ketki Eknath Shelar

Theses and Dissertations

Tailored fluoropolymers remain the leading choice for a wide variety of advanced high-performance applications, including electronic/optical and energy conversion, owing to their unique blend of complementary high-performance properties. Amorphous semi-fluorinated polymers exhibit improved solubility and melt processability when compared to traditional perfluoropolymers. A leading class of semi-fluorinated aryl ether polymers includes perfluorocyclobutyl (PFCB), perfluorocycloalkenyl (PFCA), and fluoroarylene vinylene ether (FAVE) polymers. Monomers containing aromatic trifluorovinyl ethers (TFVE) are used to synthesize PFCB polymers via radical-mediated [2+2] cyclodimerization. On the other hand, FAVE and PFCA polymers are polymerized via base-mediated nucleophilic addition/elimination of bisphenols with TFVE monomers and decafluorocyclohexene respectively. The …