Digital Commons Network^™

Processing To Enable Direct-Write Additive Manufacturing Of Ceramics And Ceramic Composites, Austin Martin

Doctoral Dissertations

"This research focuses on the processing of novel feedstocks for and during direct-write additive manufacturing (AM), specifically the direct ink writing (DIW) and Ceramic On-Demand Extrusion (CODE) manufacturing processes, in order to produce ceramic and ceramic-based composite components. Strongly dispersed, concentrated (φ = 0.42), nanoparticle (d₅₀ ~0.3 µm), zirconia (ZrO₂) pastes were used to print densely filled, large continuous volume (≳ 1 cm³) ceramic components. An elastic shear modulus (G’) of 56,000 Pa and yield stresses between 6 and 10 Pa allowed for printed components of 34.5 mm in height over 115 layers without slumping …

Surface Modification To Improve The Electrochemical Performance Of Cathode Materials For Lithium-Ion Batteries And Sodium-Ion Batteries, Han Yu

Doctoral Dissertations

"The specific capacity of active materials as well as their cycling stability are the main limiting factors for the performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIB). Atomic layer deposition (ALD) is considered as a promising surface modification method to enhance the electrochemical performance of active materials for LIBs and SIBs.

In this research, we are committed to using ALD to modify the cathode materials of LIB, by coating different films on the surface of different cathode materials and constructing a stable and favorable interface layer for lithium-ion transport, so that we can protect the active materials from the …

Corrosion Resistance Performance Investigation Of Mild Steel Bar Coated With Magnesium Phosphate Cement Paste, Fan Zhang

Doctoral Dissertations

"In this research study, the anti-corrosion mechanism of reinforcement embedded in magnesium potassium phosphate cement (MKPC) is explored. In addition, one type of additives, metakaolin, and one type of retarder, boric acid, are employed in MKPC to modify its properties in order to further investigate corrosion resistance and to achieve mass-production coating reinforcement at the work site. This coating method may be practical for some underwater construction and some traditional reinforcement concrete structures to reduce the reinforcement corrosion rate and to eventually extend service life in both repair and new construction applications.

By comparing the electrochemical properties of bare ribbed …

Processing And Characterization Of Tini-Based Alloys Fabricated By Laser Aided Manufacturing, Yitao Chen

Doctoral Dissertations

"Laser powder-based directed energy deposition (DED) is a major laser aided additive manufacturing (AM) process for metals. It applies laser energy to deposit metal powders to form 3D metal parts. Apart from manufacturing traditional alloys, DED can also be used to develop advanced alloys with the novel idea of elemental powder mixture feedstock. TiNi-based alloy is a type of shape memory alloy (SMA), a smart material with unique shape memory effects. Using laser powder DED to synthesize TiNi-based SMAs from elemental powder mixture can create more possibilities in new compositions and properties. It can also overcome the limitations of conventional …

Engineering Ni/Al2o3 Catalysts By Atomic Layer Deposition For Methane Reforming, Baitang Jin

Doctoral Dissertations

"Dry reforming of methane (DRM) could be a promising choice to utilize natural gas (mainly methane or CH₄), recycle captured CO₂, and produce valuable syngas. Promoters (e.g., CeO₂ and MgO) on Ni/Al₂O₃ prepared by atomic layer deposition (ALD) and ALD-prepared ultrathin overcoating (e.g., ZrO₂ and CeO_x) on Ni/Al₂O₃ prepared by incipient wetness method were investigated for methane reforming.

MgO and CeO₂ prepared by traditional incipient wetness method were used to promote the performance of ALD-prepared Ni nanoparticles (NPs) supported on four-channel α-Al₂O_{3 …}

Oxidation Of Silicon Carbide And Graphite For High Temperature Gas-Cooled Reactor Applications, Adam Thomas Bratten

Doctoral Dissertations

"This research focuses on the oxidation behavior of silicon carbide and matrix grade graphite, specifically as it pertains to accident scenarios in Gen IV thermal spectrum high temperature gas cooled nuclear reactors. It is imperative to understand the oxidation behavior of such materials to predict their response to off-normal environments and certify their accident tolerance to implement Gen IV reactors. The onset of oxidation temperature of matrix graphite was found to have a strong dependence on the microstructure, and therefore processing parameters, of the materials. The A3-3 type grade contained regions of partially graphitized carbon that were more disordered and …

Use Of Cellular Concrete For Air Convection Embankment To Protect Permafrost Foundation In Cold Regions, Hanli Wu

Doctoral Dissertations

"Crushed-rock air convection embankment (ACE) has been used to mitigate thaw settlement, and pavement distresses caused by climatic extremes in permafrost regions for over three decades. However, the desired crushed rocks needed for ACE are not readily available in many areas of interior Alaska. Burdened by the need to ship suitable rocks to remote locations, the cost of constructing an ACE is often prohibitively high, which prevents its wide use in Alaska. An existing cementitious material, cellular concrete, may provide the solution.

This study intends to systematically characterize the heat transfer patterns of ACE and identify the performance benefits of …

Accuracy Improvement Of Cable Harness Modeling & Analytical Modeling Of Multi-Reflections In High-Speed Signal Channels, Muqi Ouyang

Doctoral Dissertations

"Cable harnesses are widely used in modern vehicles to power electric systems locating at different locations throughout the vehicle and to establish signal channels for data communications between these systems. Generally, a cable harness consists of multiple wires and its geometry can be very complicated, making full-wave modeling and simulation approaches computational resource-intensive. To cut down the computational effort, the hybrid multiconductor transmission-line (MTL) method has been developed, and the generalized MTL (GMTL) method and the multiple scattering (MS) method have been developed to improve the accuracy of the hybrid MTL method. In this research, the convergence issue in the …

Computational Fluid Dynamics Techniques For Multiphase Flow Systems, Jose Sebastian Uribe Lopez

Doctoral Dissertations

"Mathematical modelling of multiphase flow systems has been a major and persistent challenge over the last decades. Vast attempts to obtain predictive models can be found reported in literature, where major advances can be recognized in recent years, paired to enhancements in computer science and engineering. Notwithstanding, universally valid models with a mechanistic development are far from being achieved. The current status of modelling any multiphase flow system relies on the model order reduction of purely theoretical models. Such reductions and simplifications become the source of deviations in the predictions of the experimentally measured parameters and will constrain the applicability …

Theoretical Determination Of The Yield Curve For Unsaturated Soils, Sara Fayek

Doctoral Dissertations

"An important step to developing a good understanding of the behavior of unsaturated soils is to adopt a formal and simple constitutive framework and to conduct high-quality and short-time experiments. Barcelona Basic Model (BBM) was the first elastoplastic constitutive model for unsaturated soils. The yield curve, which separates the elastic region from the elastoplastic region, is an important aspect of constitutive modeling for unsaturated soils. Most concepts for unsaturated soils were developed based upon the results from suction-controlled triaxial (SCTX) tests. Though, the SCTX tests on unsaturated soils are costly, time-consuming, and laborious, and their results are questionable. This study …

Pi And Emi Analysis Of 3d Ic System With Tsvs And Co-Packaged Optics, Wei Zhang

Doctoral Dissertations

"With the demand for developing high-capacity, high-density, high-power optical links for data center communications, co-packaged optics is a promising solution. When the three-dimensional (3D) IC and optic engines are integrated into the same package, the design of such systems in terms of signal integrity, power integrity, and electromagnetic interference will be more challenging.

This first paper mainly focuses on modeling the bias-voltage-dependent, temperature-dependent, and light-intensity-dependent hysteresis behavior of a through-silicon-vias (TSV) structure in 3D IC and analyzing its effect on the power integrity of a system with 3D IC.

This second paper investigates the scaled tendency of the emissions in …

Strain And Temperature Measurement From Distributed Fiber Optic Sensors In Performance-Based Fire Engineering, Yanping Zhu

Doctoral Dissertations

"Strain and temperature measurement of steel and concrete structures under fires is critical to the understanding of structural performance yet historically challenging due to a significant gap in measurement science. This Ph.D. study characterizes in six parts low-cost distributed fiber optic sensors and applies them to strain, and temperature measurements based on Rayleigh and Brillouin light scattering. The first part aims to quantify the Rayleigh scattering based measurement accuracy of distributed fiber optic sensors under a heating-holding load protocol and characterize the effect of polymer coating on the sensors as the polymer softens and melts at elevated temperatures. The second …

Multi-Stage Multi-Market Optimal Bidding Strategy In Electricity Markets, Hossein Mehdipourpicha

Doctoral Dissertations

"Restructuring of power industry created the competitive situations for different MPs through designing appropriate electricity markets. Typically, in pool-based electricity markets, MPs submit their offers, and ISO clears the market and notifies MPs of the cleared power amounts and market prices. In this situation, designing an effective bidding strategy for MPs who seek to maximize their profits has thus become one of the crucial yet difficult tasks that still need further exploration. The majority of recent studies overlooked this problem for the purely financial players. Therefore, designing an efficient strategy for virtual bidder in the pool-based electricity markets is studied …

Laterally Heterogeneous Seismic Anisotropy Investigated By Shear Wave Splitting Analyses, Yan Jia

Doctoral Dissertations

"Numerous geophysical studies suggest that seismic anisotropy is a nearly ubiquitous property of the Earth’s crust and upper mantle. In this study, we utilize the shear wave splitting technique to investigate the piercing-point-dependent azimuthal anisotropy beneath the northeastern edge of the Sichuan Basin in central China, and the spatial and temporal variations of anisotropy near the 2019 M7.1 Ridgecrest earthquake in California, respectively. A clear back azimuthal dependence of the splitting parameters and the lack of a 90° or 180° periodicity of azimuthal variation in the observed fast orientations provide strong evidence for the existence of piercing-point-dependent anisotropy beneath the …

Influences Of The Internal Residual On Combustion Instabilities In The Misfire And Partial Burn Regimes Of A Dilute Spark-Ignition Engine, Rachel Inez Stiffler

Doctoral Dissertations

"Dilution in spark-ignition (SI) engines can improve fuel consumption and reduce emissions; however, increased levels of dilution either from excess oxidizer or exhaust gas recirculation (EGR) causes combustion to become more strained and cycle-to-cycle variations increase. At high levels of dilution incomplete combustion events (i.e. misfires and partial burns) start to occur, which cause combustion instabilities and eventually a dilute limit is reached. It is known the combustion instabilities seen are primarily due to the feed-forward mechanism present in the residual gases, but it is still unknown what about the residual is influencing the dynamics under high levels of dilution …

Evaluation Of Novel Preformed Particle Gels For Conformance Control And Acid Stimulation Through Core Flooding Tests, Shuda Zhao

Doctoral Dissertations

"Acid stimulation and conformance control are two major methods to improve oil production. This study systematically evaluates two newly developed gels: Degradable Preformed Particle Gel (DPPG) and Re-crosslinkable Preformed Polymer Gel (RPPG). DPPG is designed to be a temporary plugging agent for acid stimulation and can self-degrade into a water-like fluid. RPPG is designed for reservoir sweep efficiency improvement and can re-crosslink to each other and form an immobile bulk gel after being placed in fractures or fracture-like conduits.

For DPPG, this study evaluates the effect of monomer, crosslinker, and initiator concentration on the swelling and degradation performance. Results show …

Using Computational Methods To Optimize High Heat Flux Component Thermal Performance In Magnetic Confinement Fusion Reactor Research, Monica Gehrig

Doctoral Dissertations

"Heat transfer enhancement by means of internally modified geometries in tubes and channels is an important mechanism to improve the survivability of components in extreme high-heat flux environments. Various features such as ribs and fins are studied using computational fluid dynamics in both uniform and one-sided heating in tubes and rectangular channels respectively to determine the most effective geometries across a variety of different flow and heating conditions. This work examines heat transfer enhancement and rib geometry optimization to support experimental research for nuclear fusion applications. The project begins by designing and analyzing test sections supporting a helium flow loop …

Molten Steel Interactions With Tundish Linings And Refractory Glazes, Tyler Michael Richards

Doctoral Dissertations

"In the final stages of casting, molten steel is in contact with two main types of refractories: the working lining of the tundish used to serve as an intermediate vessel between the ladle and copper mold, and the various glazed carbon-bearing refractories used to control the flow of steel from the ladle to the tundish and from the tundish to the mold. If steel interacts with these refractories in such a way as to result in the formation of inclusions, it may be too late to remove them, leading to degradation of the steel’s mechanical properties. Understanding these interactions and …

Depositional Conditions, Stratigraphic Evolution, And Allo- And Autogenic Controls Of Lower Permian Non-Marine Carbonate Rocks, Lucaogou Low-Order Cycle, Bogda Mountains, Nw China, Yiran Lu

Doctoral Dissertations

"The overall objective of this study is to interpret the depositional conditions of lacustrine carbonate deposits of the lower Permian Lucaogou low-order cycle in the greater Turpan-Junggar continental rift basin, NW China. The depositional environments of ten carbonate lithofacies in the Tarlong-Taodonggou half graben and the Zhaobishan section were interpreted. Allo- and autogenic factors were identified. They controlled characteristics and distribution pattern of carbonate deposits in regional and local scale, respectively. Allogenic factors include the amount and direction of regional siliciclastic input, basin geometry, cyclic humidity/aridity oscillation, temperature, and regional tectonics. Autogenic factors include local siliciclastic input, local topography, local …

Mantle Flow And Transition Zone Discontinuities Beneath The Carribean Plate: Constraints From Shear Wave Splitting And Receiver Function Analyses, Tu Xue

Doctoral Dissertations

"Azimuthal anisotropy quantified by teleseismic SKS, SKKS, PKS (“XKS”) and local S wave splitting parameters is used to investigate lithospheric deformation and asthenospheric flow beneath the boundary zone of the North American and Caribbean plates and adjacent areas. A total of 4915 XKS and 1202 pairs of local S wave splitting parameters were obtained at 24 broad band seismic stations. The XKS observations can be divided into two groups based on the spatial distribution of the resulting fast polarization orientations. Those observed on the Caribbean Plate are mostly WNW-ESE which are roughly trench-parallel. In contrast, the fast orientations observed on …

Disorder Effects In Frustrated Magnets And Absorbing State Transitions, Xuecheng Ye

Doctoral Dissertations

"Correlation, topology, and disorder can fundamentally affect the properties of interacting many-particle systems. After a short introduction which covers the basic concepts of phase transitions and scaling as well as the physics of Josephson junctions, the dissertation focuses on three separate projects.

The first project is motivated by the stripe and nematic phases observed e.g. in cuprate superconductors and iron pnictides. To understand the effects of disorder on such phases, we have investigated the behavior of the diluted J₁-J₂ Ising model. Spinless impurities generate a random-field disorder for the spin-density (stripe) order parameter, which destroys the stripe …

Application Of Machine Learning In Geophysics: Ranking Teleseismic Shear Wave Splitting Measurements And Classifying Different Types Of Earthquakes, Yanwei Zhang

Doctoral Dissertations

"During the past decades, applications of Machine Learning have been explosively developed to solve various academic and industrial problems, and over-human performance has been shown in diverse areas. In geophysical research, Machine Learning, especially Convolutional Neural Network (CNN), has been applied in numerous studies and demonstrated considerable potential. In this study, we applied CNN to solve two geophysical problems, ranking teleseismic shear splitting (SWS) measurements and classifying different types of earthquakes.

For ranking teleseismic SWS measurements, we utilized a CNN-based method to automatically select reliable SWS measurements. The CNN was trained by human-verified teleseismic SWS measurements and tested using synthetic …

Resistivity Imaging Of Prominent Seepage Pathways In Karst Terrain, Abdullah Hadi Zaid Alhaj

Doctoral Dissertations

"An integrated research approach was conducted to evaluate subsurface karstic conditions in Greene County, southwestern Missouri. Electrical resistivity tomography (ERT) was employed to image anomalously low resistivity zones associated with the presence of seepage pathways that were anthropogenic and/or natural in origin. Techniques including visual inspection (VI), multichannel analysis of surface waves (MASW), borehole control (BC), and aerial imagery (AI) were supplementally used to constrain the ERT data interpretations.

This research addressed six objectives. First, the ERT data interpretations were verified in terms of depth to the top of bedrock, fractures/voids, and moisture changes using the MASW, borehole control, and …

Optimization Of Energy Storage Scheduling In Electricity Markets, Jian Liu

Doctoral Dissertations

"In the existing literature, merchants' trading actions are usually assumed not to affect market prices; however, a large-scale energy storage merchant’s actions can affect market prices. This work examined two electricity merchant scenarios: one with only energy storage and the other with both energy storage and renewable power plants. We approximated market impact via a linear function of the electricity traded by the merchant. This study began by applying dynamic programming to the optimal economic dispatch policy of electricity merchants and it considered the market impact, physical characteristics of storage systems, and the uncertainty of renewable energy sources. Then, this …

Sensitivity Of The Two-Fluid Model To Constitutive Correlations For Large Diameter Pipes, Alexander Lee Swearingen

Doctoral Dissertations

"Multiphase flows are a significant factor in nuclear reactor operations. In order to understand this behavior in reactor systems, system analysis codes are used to simulate reactor conditions. Due to the nature of the nuclear industry, simulations predicting the void development in the core are required to be highly accurate. This work evaluated the sensitivity of the void fraction and interfacial area concentration predictions to changes in correlations used to calculate three parameters that are used to complete the interfacial drag calculation. The three parameters evaluated were drift-flux, void fraction covariance, and interfacial area concentration. The change in drift-flux correlation …

Mobility Analysis And Topology Synthesis Of Compliant Mechanism Using Compliance Number And Pseudo-Rigid-Body Model (Prbm), Pratheek Bagivalu Prasanna

Doctoral Dissertations

"Establishing and understanding the kinematic properties of a compliant mechanism has been a relatively recent endeavor and has proved to be a challenging task. A concept of compliance number was offered earlier; the development of terminologies was emphasized that aided in its determination. It also hypothesized that the compliance number (C) and stored strain energy, or mode shapes, are strongly correlated. This compliance number (C) concept is revisited, and a more lucid interpretation of its significance is provided. A fundamental understanding of the concept of deformation mode shapes in compliant mechanisms is formalized using two distinct categories: (i) segmental and …

Deep Learning-Based Surrogate Models For Post-Earthquake Damage Assessment, Xinzhe Yuan

Doctoral Dissertations

"Seismic damage assessment is a critical step to enhance community resilience in the wake of an earthquake. This study aims to develop deep learning-based surrogate models for widely used fragility curves to achieve more accurate and rapid assessment in practice. These surrogate models are based on artificial neural networks trained from the labelled ground motions whose resulting damage classes on targeted structures are determined by nonlinear time history analyses. The development of various surrogate models is progressed in four phases. In Phase I, the multilayer perceptron (MLP) is used to develop multivariate seismic classifiers with up to 50 hand-crafted intensity …

Effects Of Static And Dynamic Visuals On The Learning Of Science Concepts In The Secondary-School Classroom, Theodore Johnson

Doctoral Dissertations

The current study is grounded in the cognitive theory of multimedia learning. The investigator considered how embedding science text with visuals could affect secondary-school students' ability to retain the information they learn (rote learning) and transfer the new knowledge to an unfamiliar problem (meaningful learning). Furthermore, this study explored how the type of visuals (static versus vs. dynamic visual) and text (audio vs. print) affect science learning. The data generated was sourced from student participants in a secondary-school biology classroom. The purpose of this study was to investigate how prior knowledge and the integration of information modalities (i.e., text, audio, …

Investigation Of Control Parameters, Strategies, And Transport Modeling For Effective Electrokinetic Nanoparticle Treatment Of Cementitious Materials, Huayuan Zhong

Doctoral Dissertations

Various deleterious chemical species (including sulfates, chlorides, and others) contaminate concrete structures which are inherently porous and thus suffer from compromised durability. Several technologies have been developed for repairing concrete or enhancing the service life. Nevertheless, their efficiency, practicability, and cost can vary widely. Compared with chemical grout, fiber wrap, and traditional repair technology, electrokinetic nanoparticle treatment (EN) has been found to provide remarkable benefits for strength restoration and mitigation of durability problems via porosity reduction. Nanoparticle instability and over dosage issues can arise and lead to problems during treatments. In many cases, these treatment processes have been accompanied by …

Gradient Preserved And Artificial Neural Network Method For Solving Heat Conduction Equations In Double Layered Structures, Aniruddha Bora

Doctoral Dissertations

Layered structures have appeared in many engineering systems such as biological tissues, micro-electronic devices, thin  lms, thermal coating, metal oxide semiconductors, and DNA origami. In particular, the multi-layered metal thin  lms, gold-coated metal mirrors for example, are often used in high-powered infrared-laser systems to avoid thermal damage at the front surface of a single layer  lm caused by the high-power laser energy. With the development of new materials, functionally graded materials are becoming of more paramount importance than materials having uniform structures. For instance, in semiconductor engineering, structures can be synthesized from di erent polymers, which result in various values …