Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 29 of 29
Full-Text Articles in Engineering
A Framework For The Design And Characterization Of Advanced Gaskets, Sannmit Shinde
A Framework For The Design And Characterization Of Advanced Gaskets, Sannmit Shinde
Electronic Theses and Dissertations, 2020-
Most industrial manufacturing or processing plants use bolted connections between pipes that transfer media from one location to another. Gaskets are often used to seal these systems as they offer elevated levels of leak mitigation; however, despite their nearly universal usage, the current understanding of gasket mechanics at the meso-scale is still limited. Contemporary gaskets feature viscoelastic materials, fillers, textures, and are fabricated at various thicknesses. They are used in a wide range of thermal, mechanical, chemical, and temporal conditions. The current work characterizes polytetrafluoroethylene (PTFE) gaskets made with several different filler materials and having vastly different geometries. The chemically …
Topology Optimization Of Internal Cooling Channels In Turbulent Flows, Shinjan Ghosh
Topology Optimization Of Internal Cooling Channels In Turbulent Flows, Shinjan Ghosh
Electronic Theses and Dissertations, 2020-
Topology optimization, introduced by Bendsoe and Sigmund in 1988 has been a topic of research in the structural mechanics field for several decades. This technique is commonly used to optimize system performance of structural components with minimum material usage by varying the distribution of materials in a given domain. Fluid dynamic topology optimization, a relatively new research topic uses a method of adding or subtracting materials to a given flow domain to obtain an optimal flow-path for a given objective function. While the structural TO creates a solid structure by introducing holes into the domain, fluid TO introduces solid into …
Anomaly Detection And Failure Prediction In Gas Turbines, Vipul Goyal
Anomaly Detection And Failure Prediction In Gas Turbines, Vipul Goyal
Electronic Theses and Dissertations, 2020-
This study is based on time-series data taken from the combined cycle heavy-duty utility gas turbines. For analysis, first, a multi-stage vector autoregressive model is constructed for the nominal operation of powerplant assuming sparsity in the association among variables, and this model is used as a basis for anomaly detection and prediction. This prediction is compared with the time-series data of the powerplant test data containing anomalies. Granger causality networks, which are based on the associations between the time series streams, can be learned as an important implication from the vector autoregressive modelling. This method suffers from the disadvantage that …
Synthesis And Assessment Of Sustainable Fuels For Transportation And Space Exploration, Katerina Chagoya
Synthesis And Assessment Of Sustainable Fuels For Transportation And Space Exploration, Katerina Chagoya
Electronic Theses and Dissertations, 2020-
As global energy sources transition towards renewable energy, the demand for sustainable fuels has never been greater. The sheer scale of this transition will require numerous solutions to accommodate for the diverse and complex situations worldwide. This dissertation will discuss 3 studies: the utilization of CO2 waste gas to produce fuels sustainably, characterizing biofuels for efficient use in automobiles, and developing a solid, emissonless fuel intended for spaceflight but also applicable on Earth. The hydrogenation of CO2 into value-added molecules could reduce greenhouse gas emissions if waste stream CO2 were captured for conversion. We found that atomic vacancies induced in …
Tailoring Of The Left Ventricular Assist Device Cannula Implantation Using Coupled Multi-Scale Multi-Objective Patient Specific Optimization., Abubakar Dankano
Tailoring Of The Left Ventricular Assist Device Cannula Implantation Using Coupled Multi-Scale Multi-Objective Patient Specific Optimization., Abubakar Dankano
Electronic Theses and Dissertations, 2020-
Despite advancements in device design and anti-coagulation treatments, there are numerous adverse events that may occur following implantation of LVADs. The most devastating involves the embolization of thrombus into the brain causing a stroke, with incidence of up to 14-47% over a 6–12-month period. This study aims to elucidate ways to reduce this risk by surgical maneuvers guided by a multi-scale computational fluid dynamics analysis wrapped around a multi-objective shape optimization scheme which optimizes the anastomosis location of the VAD outflow graft (OG) along the ascending aorta to minimize the incidence of thrombi reaching the cerebral vessels and reduce particle …
Exergoeconomic Analysis And Optimization Of Novel Cogeneration Systems For Freshwater Production, Power And Cooling, Sattam Alharbi
Exergoeconomic Analysis And Optimization Of Novel Cogeneration Systems For Freshwater Production, Power And Cooling, Sattam Alharbi
Electronic Theses and Dissertations, 2020-
Global consumption of energy and freshwater is increasing continuously due to population growth and improving living standards. The world energy consumption is anticipated to increase by around 50% by 2050 according to the U.S Energy Information Administration (EIA). There is also very limited access to freshwater and cooling in many developing countries. Therefore, developing an efficient energy system, recovering the waste heat (cogeneration system or multigeneration) to produce freshwater and cooling, and using a renewable energy source are promising solutions to meet the energy demand and to reduce environment pollution associated with fossil fuels. In this study, several novel cogeneration …
Signals As Symbols: Applying Normalization Of Deviance To Improve User-Centered Design, Amy Vanschaik
Signals As Symbols: Applying Normalization Of Deviance To Improve User-Centered Design, Amy Vanschaik
Electronic Theses and Dissertations, 2020-
Mistakes can happen in the process of designing and developing interactive digital projects. Sometimes these mistakes negatively impact users' perception and trust of digital interfaces. This research applies the concept of normalization of deviance to identify potential missed opportunities in user-centered design data within the context of a website redesign. By doing this I explore how through observing accidental deviant behaviors or processes we can identify ways to improve the usability and user experience of digital environments. I review the concepts of normalized deviant behavior as addressed by Diane Vaughan in the field of engineering and identify a process for …
Studies On Powder Compaction And Wire Extrusion Of Pure Metals And Metal/Cnt Nano Composites, Qiang Zhou
Studies On Powder Compaction And Wire Extrusion Of Pure Metals And Metal/Cnt Nano Composites, Qiang Zhou
Electronic Theses and Dissertations, 2020-
The goal of this dissertation is to fabricate wires made of Cu/CNT and Al/CNT composites with good mechanical strength and super thermal/electrical conductivities using powder compaction and wire extrusion manufacturing processes. Powder compaction was studied using both test and simulation. Cold compaction, hot compaction and vibration assisted (cold) compaction tests were conducted to achieve different density ratios. Hot compaction tests improved about 6% compared with cold compaction under the same compression pressure. Although the relative density ratio does not obviously improve at vibration assisted (cold) compaction, the strength of the specimens made under vibration loading is much better than those …
Damping And Ejection Of Sloshing Liquid Drops From Elastic Substrates, Md Erfanul Alam
Damping And Ejection Of Sloshing Liquid Drops From Elastic Substrates, Md Erfanul Alam
Electronic Theses and Dissertations, 2020-
Liquid slosh is a potential source of disturbance of the motion of a moving structure. In this thesis, we probe the damping technique of sessile drop by absorbing a portion of the kinetic energy. The sloshing dynamics are typically represented by a mechanical model of a spring mass damper. However, damping by drop sloshing is dependent on viscosity, surface tension, drop size and drop location. We explore highly-coupled fluid-solid mechanics using singular liquid drop with varying viscosity and surface tension resting on a millimetric cantilever. Cantilevers are displaced 0.6 mm and their free end is allowed to vibrate freely. Cantilever …
An Evaporation Based Micro-Synthetic Jet In Microchannel And Its Applications, Ehsan Sourtiji
An Evaporation Based Micro-Synthetic Jet In Microchannel And Its Applications, Ehsan Sourtiji
Electronic Theses and Dissertations, 2020-
An approach to create synthetic jets at micro-scales using periodic bubble growth and collapse was presented and studied over a range of operating frequencies (0.1 to 2.5 Hz) and heating powers (3 to 4.5 Watt). The microfluidic device uses an interfacial layer between vapor and liquid phases which substitutes the requirement for a physical flexible membrane and any other moving parts. The bubble explosion and implosion in the chamber was triggered by periodically powering a micro-heater, which in turn generated the synthetic jet. High-speed camera photography and a microscope were used to capture sequential images of bubble nucleation, growth and …
Model-Form Uncertainty Quantification In Prognosis And Fleet Management With Physics-Informed Neural Networks, Arinan De Piemonte Dourado
Model-Form Uncertainty Quantification In Prognosis And Fleet Management With Physics-Informed Neural Networks, Arinan De Piemonte Dourado
Electronic Theses and Dissertations, 2020-
Prognosis and health management play an important role in the control of costs associated with the operation of large industrial equipment. By properly comprehending hardware degradation and accurately predicting the remaining useful life of such equipment, we can significantly lower operational costs by reducing asset downtime and maintenance interventions. However, complex interactions between operational conditions and component capability make accurately modeling damage accumulation for large fleets a daunting task. Unforeseen factors such as aggressive missions introduced by operators, exposure to harsh environments, manufacturing issues, amongst many others, can lead to large discrepancies between predicted and observed useful life. Motivated by …
Mechanical Properties And Spectral Vibrational Response Of Si-O-C With And Without Graphene Toughening, Anthony Vozza
Mechanical Properties And Spectral Vibrational Response Of Si-O-C With And Without Graphene Toughening, Anthony Vozza
Electronic Theses and Dissertations, 2020-
The mechanical behavior of silicon oxycarbide polymer derived ceramics (SiOC-PDC) without and with a graphene toughening phase was studied under uniaxial compressive load with zero dwell time and with 200 second dwell time step loading in combination with in-situ Raman spectroscopy to determine spectral vibrational response of SiOC under compressive stress. SiOC without and with graphene ceramic samples were produced through the replica templating technique. The compressive strengths of SiOC without and with a graphene toughening phase measured with zero dwell time was determined to be equal to 165.65 (SD 54.21) and 163 (SD 24.2) MPa, respectively, while compressive strengths …
Influence Of Ecm Composition And Intracellular Calcium On Endothelial Biomechanics And Prediction Of Cellular Stresses Using Machine Learning, Vignesh Aravind Subramanian Balachandar
Influence Of Ecm Composition And Intracellular Calcium On Endothelial Biomechanics And Prediction Of Cellular Stresses Using Machine Learning, Vignesh Aravind Subramanian Balachandar
Electronic Theses and Dissertations, 2020-
Endothelial cells, which form the inner layer of the vasculature, constantly interact with their external microenvironment called the extracellular matrix (ECM) by exerting contractile cell-substrate stresses called tractions and cell-cell stresses called intercellular stresses. This cellular mechanosensing can become aberrant and act as a precursor for many vascular pathological and physiological processes such as cancer metastasis, atherosclerosis, cell differentiation, migration, and morphogenesis. Also, intracellular calcium signalling plays an important role in endothelial cell motility and in maintaining vascular tone. Alteration in ECM composition has been linked to several pathologies, in fact, a transition to a fibronectin-rich matrix from a type …
The Mechanics And Multiphysics Of Biomimetic Discrete Exoskeleton Substrates, Hessein Ali
The Mechanics And Multiphysics Of Biomimetic Discrete Exoskeleton Substrates, Hessein Ali
Electronic Theses and Dissertations, 2020-
Biological structures have inspired synthetic materials with unparalleled performances such as ultra-lightweight design, tunable elasticity, camouflaging, and antifouling. Among biological structures, exoskeletal scales that cover the exterior surfaces of fishes, fur, and many reptiles. These exoskeletal scales had appeared in the earliest stages of evolution of complex multicellular life and continued their existence in spite of millions of years of evolutionary pressures. This makes them an attractive candidate for biomimicry to produce high performance multifunctional materials with applications to soft robotics, wearables, energy efficient smart skins, antifouling surfaces and on-demand tunable materials. Canonically speaking, biomimetic samples can be fabricated by …
Mechanics Of Low Dimensional Biomimetic Scale Metamaterials, Hossein Ebrahimi
Mechanics Of Low Dimensional Biomimetic Scale Metamaterials, Hossein Ebrahimi
Electronic Theses and Dissertations, 2020-
Combination of topology and material could play an important role in giving rise to nontraditional behavior in mechanical structures and is a typical strategy in nature. Topology is concerned with the geometrical and spatial properties of the objects, which are preserved under continues mechanical deformation of the object such as stretching, bending, twisting, etc. In this work, we focus on structures based on fish scale inspired surface topology. The utilized idea for surface topology is a bioinspired design on the substrate of biological scale-covered systems. Scales are a path breaking evolutionary adaptation that accompanied vertebrate evolution for the past 500 …
The Effect Of Dynamic Span Wise Bending On The Forces Of A Pitching Flat Plate, Manoj Prabakar Sargunaraj
The Effect Of Dynamic Span Wise Bending On The Forces Of A Pitching Flat Plate, Manoj Prabakar Sargunaraj
Electronic Theses and Dissertations, 2020-
A novel experiment has been conducted to investigate the effect of dynamic spanwise bending on the formation of a dynamic stall vortex on a rapidly pitching flat plate. Experiments have been performed in a towing tank at different nondimensional pitch rates (Kp) in the range of 0.4112 < Kp < 0.8225, and four maximum pitch angles (30° , 45°, 60°, and 90°) at a Reynolds number of 12,000. Synchronized direct force measurements and particle image velocimetry (PIV) are used to characterize the effect of bending on the unsteady forces and the flow field. An unsteady analytical model based on the bending and pitching kinematics is used to model the lift force histories. It is found that a spanwise bending of a pitching wing alleviated the unsteady lift forces. However, the main contribution was found to come from the non-circulatory forces. The circulation and pressure analysis of the pitching wing revealed little or no sensitivity to the wing bending motions examined.
Econometric Frameworks For Energy Prediction, Naveen Chandra Iraganaboina
Econometric Frameworks For Energy Prediction, Naveen Chandra Iraganaboina
Electronic Theses and Dissertations, 2020-
Global warming and associated role of energy consumption across various sectors is a well-researched topic in recent years. Understanding current urban energy consumption patterns will allow us to understand how future energy consumption patterns will evolve. With electrification of vehicles and potentially altering culture of work from home, the energy usage at regional level would see a significant change in the future. The current PhD dissertation contributes to energy consumption analysis of a region by analyzing residential energy consumption, commercial energy consumption and transportation energy use by households. The aggregation of these energy consumption within a region contributes to the …
Hotspot Cooling Performance For Confined Jet Impingement Cooling, Tanvir Ahmed Chowdhury
Hotspot Cooling Performance For Confined Jet Impingement Cooling, Tanvir Ahmed Chowdhury
Electronic Theses and Dissertations, 2020-
The current trend in microelectronics is to manufacture devices with increased computational powers and reduced size. These devices with increased power densities are consequently subject to extreme thermal loads. Thermal management of these power loads is extremely challenging. The presence of the hotspots can make this challenge even more difficult. Jet impingement cooling is one of the top candidates for removing such extreme heat fluxes in microelectronics. Jet impingement cooling can achieve heat transfer coefficients (HTCs) due to its normal incident flow-field and ability to thin the local thermal boundary layer in the stagnation region. This dissertation presents the hotspot …
Diffusion Biomarkers To Characterize Tissue Microstructure In Chronic Myocardial Infarction, Mohammad Tanjib Rahman
Diffusion Biomarkers To Characterize Tissue Microstructure In Chronic Myocardial Infarction, Mohammad Tanjib Rahman
Electronic Theses and Dissertations, 2020-
Non-invasive imaging techniques to detect and characterize infarcted myocardium are critical for myocardial infarction (MI) prognosis and post-MI risk assessment. Many existing imaging techniques (such as T1-mapping) for MI detection require the use of contrast agents, which are not recommended for patients with renal failure. Cardiac diffusion tensor magnetic resonance imaging (cDTI), a non-contrast imaging technique, allows estimating the aggregate cardiomyocyte microstructure in healthy subjects and its remodeling as a result of cardiac diseases. Two main questions are investigated in this thesis: 1) how cDTI based biomarkers can characterize microstructural changes occurring post-MI; and 2) if cDTI based biomarkers can …
Understanding Forearm Muscle Coordination In Children, Miguel Gonzalez
Understanding Forearm Muscle Coordination In Children, Miguel Gonzalez
Electronic Theses and Dissertations, 2020-
A combination of surface electromyography (EMG) and pattern recognition algorithms have led to improvements in the functionality of upper limb prosthetics. This method of control relies on user's ability to repeatedly generate consistent muscle contractions. Research in EMG based control of prosthesis has mainly utilized adult subjects who have fully developed neuromuscular control. Little is known about children's ability to generate consistent EMG signals necessary to control artificial limbs with multiple degrees of freedom. To address this gap, two experiments were designed to validate and benchmark an experimental protocol that quantifies the ability to coordinate forearm muscle contractions in able-bodied …
Mid-Infrared Laser Absorption Spectroscopy And Ignition Delay Time Measurements Of Advanced Renewable Fuels At High Pressure In A Shock Tube, Erik Ninnemann
Mid-Infrared Laser Absorption Spectroscopy And Ignition Delay Time Measurements Of Advanced Renewable Fuels At High Pressure In A Shock Tube, Erik Ninnemann
Electronic Theses and Dissertations, 2020-
The United States government has set 2050 as the target for net-zero greenhouse gas emissions due to their increasing levels and the subsequent rise in global temperatures. To meet this target, there has been renewed interest in the combustion of high-energy biofuels that could combat these issues. Thus, the Department of Energy started the Co-Optimization of Fuels and Engines program to find bioderived blendstocks that can harmonize with current and future generation engines to increase power and efficiency, all while reducing overall emissions. As part of this program, it is crucial to understand the combustion of these fuels at the …
Corticomuscular Adaptation To Mechanical Perturbations In A Seated Locomotor Task, Seyed Yahya Shirazi
Corticomuscular Adaptation To Mechanical Perturbations In A Seated Locomotor Task, Seyed Yahya Shirazi
Electronic Theses and Dissertations, 2020-
Cortical control during walking is most pronounced when the person is perturbed. Although seated locomotor tasks such as cycling or recumbent stepping improve walking performance, the electrocortical correlates of perturbed seated tasks have not been studied in detail. The primary purpose of this research was to quantify cortical and muscular responses to mechanical perturbations during recumbent stepping. We also aimed to quantify possible differences between young and older adults' responses to perturbed stepping. A secondary aim of this research was to determine the accuracy of electroencephalography (EEG) source imaging to interpret the electrocortical findings adequately. We hypothesized that both young …
Wind Turbine Main Bearing Fatigue Prognosis With Physics-Informed Machine Learning, Yigit Yucesan
Wind Turbine Main Bearing Fatigue Prognosis With Physics-Informed Machine Learning, Yigit Yucesan
Electronic Theses and Dissertations, 2020-
Unexpected main bearing failure on a wind turbine causes unscheduled maintenance and increased operation costs (mainly due to crane, parts, labor, and production loss). Unfortunately, historical data indicates that failure can happen far earlier than the component designed lives (due to manufacturing problems, for example). For the legacy fleet, which composes the majority of the installed basis, fatigue has become a major issue. Although bearing fatigue can be expressed with physics-informed models, they often inherent large uncertainties due to operation and unknown lubricant degradation mechanism. Apart from the unknown physics of failure, additional uncertainties associated with the grease that surrounds …
Experimental And Chemical Kinetics Investigation Of High-Temperature Combustion Of Diisopropyl Methylphosphonate., Ramees Khaleel Rahman
Experimental And Chemical Kinetics Investigation Of High-Temperature Combustion Of Diisopropyl Methylphosphonate., Ramees Khaleel Rahman
Electronic Theses and Dissertations, 2020-
Due to the high toxicity of chemical warfare (CW) agents, laboratory experiments are carried out using CW surrogates. Diisopropyl Methylphosphonate (DIMP), an organophosphate compound (OPC), is a crucial CW surrogate that has a chemical structure like the deadly nerve agent Sarin (GB). In this work, high-temperature combustion of DIMP is studied in a shock tube to understand the kinetics of destruction of DIMP. Laser absorption spectroscopy was used to obtain carbon monoxide mole fraction time-histories during high-temperature combustion of DIMP. Since combustion involves complex mixing phenomena involving different fuel to oxidizer ratios, experiments were conducted at conditions relevant to a) …
On The Interaction Of Creep And High-Cycle Fatigue In Cm 247 Lc, Thomas Bouchenot
On The Interaction Of Creep And High-Cycle Fatigue In Cm 247 Lc, Thomas Bouchenot
Electronic Theses and Dissertations, 2020-
Industrial gas turbines constitute a considerable portion of global power generation, from large engines for centralized grids, to smaller frames for decentralized demand. Power output, efficiency, and reliability are chief criteria regarding the development of next-generation turbines, whose components are expected to operate in ever harsher environments. Turbine blades are subjected to high temperatures, an array of mechanical loads, and dynamic fluid fields, all contained within a non-isothermal profile, making creep and high-cycle fatigue critical aspects of turbine blade design. Current analysis tools and methods have resulted in the development of many successful components; however, improved life prediction models with …
Harvesting Heat From Safer, Energy-Dense Slow Pyrolant Mixtures For Future Space Missions, Katerina Chagoya
Harvesting Heat From Safer, Energy-Dense Slow Pyrolant Mixtures For Future Space Missions, Katerina Chagoya
Electronic Theses and Dissertations, 2020-
Energy sources powering space missions range from highly energetic nuclear reactions to short-lifetime and low-output batteries. The proper selection of a power system is dependent on the mission duration and destination and oftentimes energy sources that may be optimal for the former may be unsuitable for the latter. Various limitations of these power sources hinder the capacity for regular and frequent space exploration. However, the ability to harvest heat for electrical power generation would allow for long-distance and long-duration missions at a reduced cost. By employing a regulated, self-propagating, exothermic chemical reaction between solid fuel and oxidizer, we hope to …
Laser-Microdrop Interactions In Nanoparticle Deposition On Solid Substrates, Tianyi Li
Laser-Microdrop Interactions In Nanoparticle Deposition On Solid Substrates, Tianyi Li
Electronic Theses and Dissertations, 2020-
Nanoparticle suspensions are utilized for depositing thin films on solid substrates by a process called nano electrospray laser deposition. In this research, three deposition methods, contact liquid line laser printing, nano-electrospray laser sintering and evaporative optical Marangoni convection are investigated experimentally and analytically. Thin silver lines are printed on indium tin oxide-coated silicon substrates by dispensing silver nanoparticle suspension with a micropipe of inner diameter 51µm and subsequently sintering the nanoparticles with a CO2 laser beam of Bessel intensity profile. The deposited silver lines of 65µm width and 1µm height have good resistivity which can be used to manufacture silver …
Mechanical Behavior Of Bioceramic Materials: Case Study Of The Skeleton Of The Staghorn Coral, Acropora Cervicornis And The Tibia Of The Laboratory Mouse, Mus Musculus, Mahmoud Omer
Electronic Theses and Dissertations, 2020-
I studied two types of bioceramics: (A) the aragonite CaCO3 skeleton of the staghorn coral, Acropora cervicornis and (B) the hydroxyapatite Ca10(PO4)6(OH)2 bones of the laboratory mouse, Mus musculus. The research aimed to analyze coral deformation behavior and study dietary and estrogen depletions effects on bone strength. I compared the mechanical and structural properties of staghorn coral skeletons cleaned by chemical bleaching and biological processes. Optical microscopy and computed tomography (CT) revealed a sophisticated microstructure of non-homogenously distributed pores. Staghorn coral skeletons showed ''gracious" fracture, where the unique pore arrangements resisted catastrophic crack growth and prevented instantanous failure. Elastic moduli …
Material Properties Of 17-4ph Stainless Steel Fabricated With Cooling Holes By Atomic Diffusion Additive Manufacturing (Adam), Nandhini Raju
Material Properties Of 17-4ph Stainless Steel Fabricated With Cooling Holes By Atomic Diffusion Additive Manufacturing (Adam), Nandhini Raju
Electronic Theses and Dissertations, 2020-
The objective of this study is to investigate the material properties of 17-4PH stainless steel printed with cooling holes in different build orientations by the Atomic Diffusion Additive manufacturing technique. Samples with film cooling holes printed in different build orientations, with impingement inserts, impingement cavities were manufactured in a Markforged Metal-X machine. The presence of the holes in these samples helps to understand the printability and accuracy of internal cooling holes, as manufactured by the Metal-X machine. Manufactured samples were first washed to remove the plastic binder. These pre-sintered samples were tested, for density, microstructure analysis, roughness, Energy Dispersive X-ray …