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Full-Text Articles in Engineering
Adaptive Analytic Continuation For The State Transition Tensors Of The Two-Body Problem, Tahsinul Haque Tasif
Adaptive Analytic Continuation For The State Transition Tensors Of The Two-Body Problem, Tahsinul Haque Tasif
Electronic Theses and Dissertations, 2020-
In the past few decades, Kessler syndrome (named after Donald J. Kessler) has become a point of concern in the field of Space Situational Awareness and the future of space missions. It refers to a scenario, where space debris in Earth's orbits collides and creates an exponential increase in space debris numbers leading to more collisions and more debris. In order to handle the resulting challenges like conjunction analysis, tracking, and probability of collisions, the State Transition Matrix (STM) and Tensors (STTs) of the orbit problem play a significant role. In addition, STM and STTs are ubiquitous in spaceflight dynamics, …
Synthesis, Characterization, And Modeling Of Thermo-Responsive Hydrogels With Improved Mechanical Strength And Swelling Kinetics, Marilu Ortiz Nieves
Synthesis, Characterization, And Modeling Of Thermo-Responsive Hydrogels With Improved Mechanical Strength And Swelling Kinetics, Marilu Ortiz Nieves
Electronic Theses and Dissertations, 2020-
Hydrogels have been extensively studied for use in applications such as tissue engineering, drug delivery systems, wound dressing, actuators, valves, and sensors in Micromechanical Systems (MEMS), among others. Thermo-responsive hydrogels in particular pose various advantages such as their capability to respond to an external stimulus and reverse the response when the stimulus is removed and the ability to imbibe a significant amount of solvent and increase their volume by over 1000%. Extensive research has been conducted to tune and improve hydrogel’s rate and degree of swelling and mechanical properties. Previous work showed that when synthetic clay (Laponite) is cross-linked with …
Data-Driven Diagnostics And Prognostics For Complex Systems: Methods And Applications, Junchuan Shi
Data-Driven Diagnostics And Prognostics For Complex Systems: Methods And Applications, Junchuan Shi
Electronic Theses and Dissertations, 2020-
Recent advances in artificial intelligence or machine learning have the potential to significantly improve the effectiveness and efficiency of diagnostic and prognostic techniques. The objective of this research is to develop novel data-driven predictive models with machine learning and deep learning algorithms that allow one to model the degradation, detect the faults, as well as predict the remaining useful life (RUL) of complex systems, including bearings, gearboxes, and Lithium-ion (Li-ion) batteries. First, an enhanced ensemble learning algorithm is developed to improve the accuracy of RUL prediction by selecting diverse base learners and features at different degradation stages. The proposed method …
Computational Modeling Of Respiratory Airflow In Human Distal Airways Using Hybrid Lung Model, Adnan Islam
Computational Modeling Of Respiratory Airflow In Human Distal Airways Using Hybrid Lung Model, Adnan Islam
Electronic Theses and Dissertations, 2020-
A major challenge in the Computational Fluid Dynamics (CFD) modeling of the human respiratory system is the complex variation of geometric scale from the trachea to the peripheral airways. The current literature on image-based lung flow analysis is limited to a few (typically 5) generations beyond the trachea. Such studies, which are limited largely by computational intensity and computational cost, also have limited accuracy. In this study we propose a hybrid methodology that enables CFD analysis from the middle to the distal airways through to the alveolar level. A hybrid lung model is generated where the middle airways are reconstructed …
The Fluid Dynamics Of A Spanwise-Morphing Wing: An Experimental And Analytical Study, Kamlesh Joshi
The Fluid Dynamics Of A Spanwise-Morphing Wing: An Experimental And Analytical Study, Kamlesh Joshi
Electronic Theses and Dissertations, 2020-
The unsteady forces and fluid flow structure of a morphing wing are investigated for low Reynolds number (Re) flows, i.e., Re < 20,000. The morphing wing is designed to change shape in the spanwise direction in a controlled manner using internal actuation. The two types of wing morphing are studied in this work, i.e., spanwise bending and spanwise twisting. The wing morphing is named based on the overall shape of the wing after it is dynamically morphed.
Numerical Study Of Flow Of Supercritical Carbon Dioxide Inside Microchannels With Heat Transfer, Uday Manda
Numerical Study Of Flow Of Supercritical Carbon Dioxide Inside Microchannels With Heat Transfer, Uday Manda
Electronic Theses and Dissertations, 2020-
Heat transfer inside microscale geometries is a complex and a challenging phenomenon. As supercritical fluids display large variations in their properties in the vicinity of the critical point, their usage could be more beneficial than traditional coolants. This numerical study, in two parts, primarily focuses on the physics that drives the enhanced heat transfer characteristics of carbon dioxide (CO2) near its critical state and in its supercritical state. In the first part of the study, the flow of supercritical Carbon Dioxide (sCO2) over a heated surface inside a microchannel of hydraulic diameter 0.3 mm was studied using three-dimensional computational fluid …
Modeling And Simulation Of A Power Plant Boiler Including The Dynamics Of Swell And Shrink, Richard Perman
Modeling And Simulation Of A Power Plant Boiler Including The Dynamics Of Swell And Shrink, Richard Perman
Electronic Theses and Dissertations, 2020-
Renewables such as photovoltaics and wind turbines have seen consistent growth in markets across the globe. While renewables increase grid capacity and reduce the use of fossil fuels, their generation rates fluctuate subject to external factors. As the ratio of renewables to nonrenewables increases, so does variability of net load on intermediate and peaking power plants. Power plants with heat recovery steam generators (HRSG) constitute a significant proportion in these categories. There are several interconnected systems within HRSGs, including drum boilers which exhibit interesting transient phenomena known as swell and shrink. Improved understanding, dynamic modeling, and real-time simulation (RTS) of …
A Study Of Autorotation: Samara Seed Pods And Tethered Autogyros, Jonathan Mcconnell
A Study Of Autorotation: Samara Seed Pods And Tethered Autogyros, Jonathan Mcconnell
Electronic Theses and Dissertations, 2020-
This work presents an exploration of autorotational behavior, observing naturally occurring structures to provide insight into the stability and design of autorotative mechanisms. A rotor is said to be in autorotation when, in the presence of airflow, a natural rotation generates lift to either suspend or slow the descent of a rotor. This phenomenon is observed in nature in the form of samaras, a seed pod morphology evolved in parallel by maple trees and many other organisms around the world. Simulation and experimental observation of samara vertical descent behavior provides insight into the stability of naturally evolved autorotative structures. A …
Non-Invasive Detection Of Elevated Intracranial Pressure Using Spontaneous Tympanic Membrane Pulsation, Rajkumar Dhar
Non-Invasive Detection Of Elevated Intracranial Pressure Using Spontaneous Tympanic Membrane Pulsation, Rajkumar Dhar
Electronic Theses and Dissertations, 2020-
Monitoring intracranial pressure (ICP) is a standard diagnostic tool for various neurological conditions such as head injury, ruptured aneurysms, intracerebral and intracranial hemorrhage, and hydrocephalus. Currently, ICP monitoring relies on invasive pressure measurements. These include intraventricular catheter, subdural screw, epidural sensor, and lumbar puncture. Invasive methods pose the risk of infection and hemorrhage, are expensive, and require special clinical skills. A noninvasive method that is reliable, simple to use, low-cost, and provides easily interpretable results can help avoid the complications associated with the invasive methods. This study proposes a novel method for noninvasive ICP monitoring using tympanic membrane pulsation (TMp). …
Simulation Of A Comprehensive Heat Recovery Steam Generator, Jose Chalarca Castro
Simulation Of A Comprehensive Heat Recovery Steam Generator, Jose Chalarca Castro
Electronic Theses and Dissertations, 2020-
With the increasing prevalence of renewables, it is important to optimize combined cycle power plants during transient conditions to better compliment the variable generation of renewable energy generators. There is a demand for dynamic heat recovery steam generators (HRSG) models that may enable improved control designs. Sufficiently accurate real-time simulations of HRSGs may serve as soft sensors and state estimators during transient conditions. Furthermore, real-time simulations of HRSGs can be used for operator training which does not incur the inherit risk of using plant hardware. The focus of this research is on the development towards an integrated dynamic closed loop …
Prediction And Validation Of Residual Stresses In Additively Manufactured Metal Parts, Jose Mayi Rivas
Prediction And Validation Of Residual Stresses In Additively Manufactured Metal Parts, Jose Mayi Rivas
Electronic Theses and Dissertations, 2020-
Selective Laser Melted (SLM) Additively Manufactured (AM) metal parts are of special interest to many industries because their designs can be made arbitrarily complex while still maintaining bulk type mechanical properties. However, the large thermal gradients inherent to the SLM process generate residual stresses (RS) and distortions that are detrimental to the fit, functionality and integrity of parts. Predicting the state of stresses in as-built 3D printed parts is a difficult problem that currently has only been approached with the use of transient thermomechanical Finite Element Models (FEMs). The nonlinearities associated with AM processes are difficult to capture in these …
Lithium-Ion Battery Prognosis With Variational Hybrid Physics-Informed Neural Networks, Renato Giorgiani Do Nascimento
Lithium-Ion Battery Prognosis With Variational Hybrid Physics-Informed Neural Networks, Renato Giorgiani Do Nascimento
Electronic Theses and Dissertations, 2020-
Lithium-ion batteries are an increasingly popular source of power for many electric applications. Applications range from electric cars, driven by thousands of people every day, to existing and future air vehicles, such as unmanned aircraft vehicles (UAVs) and urban air mobility (UAM) drones. Therefore, robust modeling approaches are essential to ensure high reliability levels by monitoring battery state-of-charge (SOC) and forecasting the remaining useful life (RUL). Building principled-based models is challenging due to the complex electrochemistry that governs battery operation, which would entail computationally expensive models not suited for prognosis and health management applications. Alternatively, reduced-order models can be used …
An Investigation Of The Relationship Between Respiration And Seismocardiographic Signals Using Signal Processing, Machine Learning And Finite Element Analysis, Tanvir Hassan
Electronic Theses and Dissertations, 2020-
Cardiovascular disease (CVD) is one of the major causes of death worldwide. Disease management, as well as patient health, can be significantly improved by early detection of patient deterioration and proper intervention. Review of the patient's medical history and physical examination including stethoscope auscultation and electrocardiograms (ECG), echocardiography imaging, numerous blood testing, and computed tomography are common means of evaluating cardiac function. Seismocardiographic (SCG) signals are the vibrations of the chest wall due to the mechanical activity of the heart. These signals can provide useful information about heart function and could be used to diagnose cardiac problems. The variability in …
Vibrations Of Rotationally Periodic Structures: A Metric For Mistuning Characterization And Vibration Localization, Andres Rodriguez
Vibrations Of Rotationally Periodic Structures: A Metric For Mistuning Characterization And Vibration Localization, Andres Rodriguez
Electronic Theses and Dissertations, 2020-
Blisk components are an integral part of jet engines and power generation systems. Composed of a single monolithic structure, integral blisks combine the blade-and-disk portion of primary components such as the fan, compressor stage, or turbine stage. This design modification increases the aerodynamic performance while decreasing the cost and eliminating time of assembly. However, these benefits come with the loss of blade-disk connection interfaces, which greatly reduces the structure's damping and its ability to attenuate unwanted structural vibrations. Blisk dynamics are impacted by mistuning, which is a disruption of the periodic symmetry of otherwise identical bladed sections. This disruption degrades …
Thermofluidic Characterization Of Carbon Dioxide Near Critical Conditions At Microscale, Anatoly Parahovnik
Thermofluidic Characterization Of Carbon Dioxide Near Critical Conditions At Microscale, Anatoly Parahovnik
Electronic Theses and Dissertations, 2020-
This work revealed the thermo physical characteristics of near critical and supercritical carbon dioxide at the micro scale. The results include the extension of flow boiling heat transfer correlations, boiling inception, near critical bubble dynamics, thermalization mode shift, Joule Thomson effect and pressure drop evaluation. It was found that extremely low superheat temperatures are required for boiling inception near the critical conditions (i.e., T=31.4 °C, and P=7.37 MPa), and boiling heat transfer correlations were extended up to a reduced pressure of 0.99. The work also revealed a significant enhancement of the heat transfer coefficient as the critical conditions approached, which …
Autoignition Delay Time Measurements And Chemical Kinetic Modeling Of Hydrogen/Ammonia/Natural Gas Mixtures, Jessica Baker
Autoignition Delay Time Measurements And Chemical Kinetic Modeling Of Hydrogen/Ammonia/Natural Gas Mixtures, Jessica Baker
Electronic Theses and Dissertations, 2020-
In recent years, hydrogen-carrying compounds have accrued interest as an alternative to traditional fossil fuels due to their function as zero-emission fuels. As such, there is interest in investigating hydrogen-carrying compounds to improve understanding of the fuels' characteristics for use in high pressure systems. In the current study, the oxidation of ammonia/natural gas/hydrogen mixtures was carried out to study CO formation profiles as well as the ignition delay times behind reflected shock waves in order to refine chemical kinetic models. Experiments were carried out in the University of Central Florida's shock tube facility by utilizing chemiluminescence to obtain OH* emission …
Heat Transfer Characterization Of Carbon Dioxide In Micro Impinging Jet(S) Near Critical Conditions, Stephen Adeoye
Heat Transfer Characterization Of Carbon Dioxide In Micro Impinging Jet(S) Near Critical Conditions, Stephen Adeoye
Electronic Theses and Dissertations, 2020-
The continuous growth and demand of increased operating performances of electronics has brought about an increase in the chip power density posing threat to the thermal management of these devices. Although numerous thermal solutions ranging from passive to active cooling together with a variety of working fluids have been adopted, however, the question whether these available cooling methods could meet up with the ever-growing need for increased operating performances is a concerning one. Jet impingement cooling has been effectively used in many industrial applications due to its high heat transfer capability. The limited study at the micro scale suggests that …
Data-Driven Modeling Of Mechanical Behaviors Of Additively Manufactured Materials, Ziyang Zhang
Data-Driven Modeling Of Mechanical Behaviors Of Additively Manufactured Materials, Ziyang Zhang
Electronic Theses and Dissertations, 2020-
Additive manufacturing (AM) is a revolutionary technology that greatly improves the flexibility of fabricating parts with complex structures and eliminates the cost of making molds. While AM techniques offer unique benefits over traditional manufacturing processes, it is challenging to predict the mechanical behaviors of additively manufactured parts based on design and process parameters. With recent advances in machine learning, data-driven methods have the potential to overcome such limitations. In this work, data-driven modeling frameworks were proposed to predict the tensile, flexural, and compressive behaviors of additively manufactured plastics and composites. Ensemble learning was used to predict the tensile strength of …
Decentralized Digital Fabrication Of Flexible Micro/Nano Devices Using A Laserjet Printer, Arshya Bamshad
Decentralized Digital Fabrication Of Flexible Micro/Nano Devices Using A Laserjet Printer, Arshya Bamshad
Electronic Theses and Dissertations, 2020-
The fabrication of traditional micro/nano devices requires access to cleanrooms, complex and expensive tools, and highly-skilled labor. A facile and digital do-it-yourself (DIY) technique for the fabrication of low-cost devices on flexible substrates (paper, cloth, and plastic films) is presented in this work. A set of office-grade equipment (i.e., laserjet printer, thermal laminator, computer-aided paper cutter), and commercially available supplies (i.e., baking wax paper, furniture restoration metal-leaf) are utilized. The presented technology enables community-embedded production by removing a high technological barrier. The validity of the proposed technology was proved by designing three levels of experiments, i.e., patterns, devices, and systems. …
A Flexible 3d Architecture For Cooling Future Generation Devices, Khan Mohammad Rabbi
A Flexible 3d Architecture For Cooling Future Generation Devices, Khan Mohammad Rabbi
Electronic Theses and Dissertations, 2020-
Systems that consume and convert energy produce thermal energy as a byproduct. This generation of thermal energy, if not dissipated properly, contributes to the significant temperature rise of the overall system. This temperature rise can lead to reduced efficiency and system-level failure. Future technologies will continue to face such thermal challenges. In fact, next-gen devices will demand flexible thermal management architectures for high-performance operation. To tackle these challenges, innovative liquid cooling technologies and high-speed thermal diagnostic systems must be developed simultaneously. Active and passive pulsation-liquid-cooling techniques are currently an attractive thermal management solution. In an active cooling mode, the influence …
Quantitative Metallurgy Of Anisotropic Nickel-Base Superalloys Under Tensile And Fatigue Loading, Dominic Devito
Quantitative Metallurgy Of Anisotropic Nickel-Base Superalloys Under Tensile And Fatigue Loading, Dominic Devito
Electronic Theses and Dissertations, 2020-
Nickel-base superalloys are ideal materials for application in high temperature and high stress environments. Their resistance to both heat and corrosion makes these metals well-suited for use as components in engines and turbines. There has been much interest in characterizing the mechanical properties of Ni-base superalloys under severe conditions. Either large monotonic loads or cyclic loads are the most investigated. Also, research efforts tend to focus on the influence of microstructural features of fatigue life, and they accomplish this through qualitative observation. Presented here is both quantitative and qualitative analysis done on Ni-base superalloy specimens that have been subjected to …
Generative Adversarial Networks For Extrapolation Of Corrosion In Automobile Images, Andre Von Zuben
Generative Adversarial Networks For Extrapolation Of Corrosion In Automobile Images, Andre Von Zuben
Electronic Theses and Dissertations, 2020-
Deep learning has shown success in several applications involving pattern recognition, expert systems, and scientific discovery. However, existing methods struggle with industrial applications, which are often challenged by non-ideal datasets. In many cases, the datasets are small, poorly labeled, noisy, or have unbalanced class distribution or any combination of such problems. In this Master's research, we propose a generative adversarial network (GAN) strategy that is able to circumvent limitations imposed by tiny datasets. As a case study, we use the extrapolation of corrosion in automobiles and feed our deep learning framework with only a few dozen images instead of the …
Crystal Viscoplastic Modeling Of Single Crystal And Directionally Solidified Nickel-Base Superalloys, Navindra Wijeyeratne
Crystal Viscoplastic Modeling Of Single Crystal And Directionally Solidified Nickel-Base Superalloys, Navindra Wijeyeratne
Electronic Theses and Dissertations, 2020-
Nickel-base superalloys (NBSAs) are widely used in engineering applications for many turbomachinery component designs. Superior material properties at high temperatures such as high tensile strength, superior fatigue strength, excellent resistance to thermal shocks, and strong corrosion resistance are primarily responsible for their extensive application. This proposal focuses on modeling generic single crystal (SX) and directionally solidified (DS) Ni-base superalloy. Compared to polycrystal superalloys, SX superalloys exhibit superior thermal fatigue and creep resistance which is attributed to the absence of grain boundaries in the SX crystalline structure. Directional solidification procedures enable the solidification structure of the materials to be comprised of …
Experimental And Computational Heat Transfer Study Of Sco2 Single Jet Impingement, John Richardson
Experimental And Computational Heat Transfer Study Of Sco2 Single Jet Impingement, John Richardson
Electronic Theses and Dissertations, 2020-
The present study experimentally investigates the heat transfer capability of supercritical carbon dioxide (sCO2) single-jet impingement. The evaluated jet Reynolds number range is between 80,000 and 1,000,000, with a non-dimensional jet-to-target surface spacing of 2.8. CO2-impinging jet stagnation conditions were maintained at approximately 20 MPa and a temperature of 673 K for most experiments. The goal is to understand how changes in the aforementioned parameters influence heat transfer between the working fluid and the heated surface. Additionally, due to the elevated Reynolds numbers and difference in thermodynamic properties between air and CO2, air-derived impingement correlations may not be appropriate for …