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Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
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In the pursuit of optimum performance, materials engineering seeks to design the microstructure and thus the properties of a material through the control of the material composition and processing. Functionally graded materials (FGM) are designed to incorporate location-specific material properties through compositional changes within the part. Moving toward location-specific design of material properties requires the ability to produce material gradients in three dimensions which can be accomplished through the use of additive manufacturing (AM). This research examines the composition-process-structure-property relationship of early iteration titanium (Ti) and tantalum (Ta) graded alloys built in a novel laser powder bed fusion (LPBF) process …
Design And Implementation Of Fully Integrated Cmos On-Chip Bandpass Filter With Wideband High-Gain Low Noise Amplifier, Yu Wang
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Current trends of fully integrated CMOS on-chip bandpass filter are classified into 1) the component level (i.e., active inductor, Q-enhanced passive inductor, negative resistance cancellation), and 2) the circuit level (i.e., adding transmission zeros on stopband, applying the zigzag technique for fewer inductors, superposition of different resonators). The demand for monolithic designs for portable devices attracts market interest in a fully integrated CMOS on-chip bandpass filter. Optimized minimal inductors (OMI) bandpass filter is a good platform for use in both active and passive bandpass filters, mainly because 1) it provides good stopband rejection for high interface attenuation, and 2) the …
Phase Transformation In The Aluminum/Tungsten System, Ammar Azeez Mahdi Al Yasari
Phase Transformation In The Aluminum/Tungsten System, Ammar Azeez Mahdi Al Yasari
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Formation and growth mechanisms of intermetallic compounds in the aluminum/tungsten system were studied during consolidation and subsequent heat treatment. Three different processes, spark plasma sintering (SPS), laser powder bed fusion (LPBF), and metal inert gas welding (MIG) were used, and each of these processes were followed up with heat treatment at different conditions. Al12W, Al5W and Al4W are the three intermetallics that are stable in the system in room temperature, and they were expected to form at the interface between tungsten and aluminum at different temperature ranges. Contrary to expectations, the Al5W phase was not observed during this study and …
Noninvasive Blood Flow And Oxygenation Measurements In Diseased Tissue, Benjamin S. Rinehart
Noninvasive Blood Flow And Oxygenation Measurements In Diseased Tissue, Benjamin S. Rinehart
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The research presented in this dissertation focused on the application of optical imaging techniques to establish blood flow and oxygen saturation as effective biomarkers for two disease cases, Autism Spectrum Disorder (ASD) and Huntington’s Disease (HD). The BTBR mouse model of ASD was utilized to validate measurements of cerebral blood flow and oxygenation as biomarkers for autism. The R6/2 mouse model of juvenile HD was utilized to validate measurements of skeletal muscle blood flow following tetanic muscle contractions induced by electrical nerve stimulation. Next, a noncontact, camera-based system to measure blood flow and oxygen saturation maps was implemented to improve …
The Course Scheduling Problem With Room Considerations, Lijian Xiao
The Course Scheduling Problem With Room Considerations, Lijian Xiao
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The course scheduling problem (CSP), more commonly referred to as the university timetabling problem, belongs to the larger family of general scheduling problems, where the aim is to assign students, faculties, exams, or lectures to a limited number of rooms over time in accordance under real-world constraints. Such problems are known to be NP-complete and have been the subject of study for the optimization society for many decades. This research extends the classical CSP to the CSP with Room Considerations (CSP-R) by incorporating two room-related considerations; cohort-to-room preference and topic-to-room preference. While the former refers to students in each cohort …
Texture Evolution In Materials With Layered Crystal Structures, Vamsi Krishna Vempati
Texture Evolution In Materials With Layered Crystal Structures, Vamsi Krishna Vempati
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Materials with a layered structure consist of crystalline layers that are bonded to each other with secondary bonds (van der Waals interactions). The bonding between crystalline layers is relatively weak compared to the interatomic bonding within the crystalline layers. This research hypothesizes that under appropriate conditions, such as elevated temperature, the deformation of layered materials occurs like the classic “deck of cards” with no preferred direction of slip on the slip planes. The motivation for this study is from the experimental texture evolution of one such material, Bismuth Telluride ,(Bi2Te3), commonly used materials for thermoelectric applications in the range of …
Unraveling The Etiologies Of Discrete Subaortic Stenosis: A Focus On Left Ventricular Outflow Tract Hemodynamics, Jason A. Shar
Unraveling The Etiologies Of Discrete Subaortic Stenosis: A Focus On Left Ventricular Outflow Tract Hemodynamics, Jason A. Shar
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Discrete subaortic stenosis (DSS) is an obstructive cardiac disease characterized by the formation of a thin fibromuscular ring of tissue in the left ventricular (LV) outflow tract (LVOT). Although its etiology is unknown, the association between DSS, pediatric age, and morphological LVOT abnormalities points to a potential hemodynamic etiology. Here, altered subaortic flow dynamics, stemming from deviated LVOT anatomy, may promote lesion formation through local fluid shear stress abnormalities triggering membrane formation. The assessment of this hypothetical pathway requires elucidation of the complex LV wall shear stress (WSS) environment. The central hypothesis of this dissertation is that altered LV hemodynamics, …
Bayesian Inspired Multi-Fidelity Optimization With Aerodynamic Design, Christopher Corey Fischer
Bayesian Inspired Multi-Fidelity Optimization With Aerodynamic Design, Christopher Corey Fischer
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In most engineering design problems, there exist multiple models of varying fidelities for use in predicting a single system response such as Computational Fluid Dynamics (CFD) models constructed using Potential Flow, Euler equations, or full physics Navier Stokes implementation. Engineering design is constantly pushing the forefront of the field through imposing stricter and more complex constraints on system performance, thus elevating the need for use of high-fidelity models in the design process. Increasing fidelity level often correlates to an increase in cost (financial, computational time, and computational resources). Traditional design processes rely upon low-fidelity models for expedience and resource savings. …
Development And Application Of A Computational Modeling Scheme For Periodic Lattice Structures, Abdalsalam Fadeel
Development And Application Of A Computational Modeling Scheme For Periodic Lattice Structures, Abdalsalam Fadeel
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Sandwich structures are widely used for aerospace, marines and other applications due to their light-weight, strength, and strain energy absorption capability. The cores of the sandwich structure are typically fabricated by using high strength cellular materials such as aluminum and titanium alloys, or polymer foams, and honeycombs. Lattice cell structures (LCS) of different configurations such as body centered cubic (BCC), tetrahedron and pyramidal are being investigated as core material due to their design freedom and periodic nature. Due to the recent advent of additive manufacturing (AM), new research is being sought in the areas of designing and developing application-specific LCS …
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Browse all Theses and Dissertations
In the pursuit of optimum performance, materials engineering seeks to design the microstructure and thus the properties of a material through the control of the material composition and processing. Functionally graded materials (FGM) are designed to incorporate location-specific material properties through compositional changes within the part. Moving toward location-specific design of material properties requires the ability to produce material gradients in three dimensions which can be accomplished through the use of additive manufacturing (AM). This research examines the composition-process-structure-property relationship of early iteration titanium (Ti) and tantalum (Ta) graded alloys built in a novel laser powder bed fusion (LPBF) process …
The Effect Of Winding Curvature And Core Permeability On The Power Losses And Leakage Inductance Of High-Frequency Transformers, Daniel J. Whitman
The Effect Of Winding Curvature And Core Permeability On The Power Losses And Leakage Inductance Of High-Frequency Transformers, Daniel J. Whitman
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At the frequencies used in switching dc-dc converters, the skin and proximity effects have a significant effect on both the losses and leakage inductance of the transformers used in these circuits. Analytical expressions that have been derived to calculate ac resistance and leakage inductance have primarily used a 1-D approximation. They also have used Cartesian coordinates or approximations that are equivalent to Cartesian coordinates, as well as usually assuming an ideal core of infinite permeability. The classical result in the case of the resistance/losses is Dowell’s equation, and there are analogous results for leakage inductance. This dissertation derives new equations …
Gated Hall And Field-Effect Transport Characterization Of E-Mode Zno Tfts, Jason C. Anders
Gated Hall And Field-Effect Transport Characterization Of E-Mode Zno Tfts, Jason C. Anders
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Amorphous and nano-crystalline metal oxide semiconductors are an important class of materials under continuing investigation for emerging technologies. Accurate measurements of electron mobility in these materials is critical for furthering overall device development. This is complicated due to the fact that device measurements such as current response, transistor input and output characteristics, as well as mobility are affected by transport-limiting factors, such as charge trapping effects at the dielectric / active layer interface, and restriction of electronic transport across grain boundaries. In this work, we focus on the binary metal oxide thin film transistor (ZnO TFT), a normally-off (e-mode) transistor …