Digital Commons Network^™

Characterization Of Investment Shell Thermal Properties, Mingzhi Xu

Doctoral Dissertations

Thermal properties of investment casting shells have a great influence on the solidification of metal and thus control the properties of the cast product. Computational simulation requires accurate thermal properties to better represent the real process. Due to the porosity and meta-stable materials used in the investment shells, it is difficult to determine the real time thermal properties as a function of components and thermal processing history. Previous studies measured the thermal properties using a variety of methods, but very few results can be directly used in simulations due to lack of accuracy.

This research developed a new methodology that …

Resistance Switching Of Electrodeposited Cuprous Oxide, Sanaz Yazdanparast

Doctoral Dissertations

In this work, the resistance switching behavior of electrodeposited cuprous oxide (Cu₂O) thin films in Au/Cu₂O/top electrode (Pt, Au-Pd, Al) cells was studied. After an initial FORMING process, the fabricated cells show reversible switching between a low resistance state (16.6 Ω) and a high resistance state (0.4 x 10⁶ Ω). Changing the resistance states in cuprous oxide films depends on the magnitude of the applied voltage which corresponds to unipolar resistance switching behavior of this material. The endurance and retention tests indicate a potential application of the fabricated cells for nonvolatile resistance switching random access …

Local Alternative Sources For Cogeneration Combined Heat And Power System, Abdulhakim Amer Agll

Doctoral Dissertations

"Global demand for energy continues to grow while countries around the globe race to reduce their reliance on fossil fuels and greenhouse gas emissions by implementing policy measures and advancing technology. Sustainability has become an important issue in transportation and infrastructure development projects. While several agencies are trying to incorporate a range of sustainability measures in their goals and missions, only a few planning agencies have been able to implement these policies and they are far from perfect. The low rate of success in implementing sustainable policies is primarily due to incomplete understanding of the system and the interaction between …

Imaging Beneath Standing Bodies Of Water In Karst Terrain, Abdulrahman Masfer Alotaibi

Doctoral Dissertations

"Side scan sonar and down scan sonar, sub bottom profiling, electrical resistivity tomography profiling (underwater cables), and continuous resistivity profiling (towed cable) surveys were conducted to characterize the lake sediments (rock and soil) beneath the man-made Little Prairie Lake, in central Missouri. Sub bottom profiling and electrical resistivity (with marine cables and towed cable) were used to determine variability in the lithology and thickness of sediments (soil and rock) beneath the lake, while side scan sonar was used to map the variations in the lithology/nature of exposed lakebed sediments and to locate the potential hazard of trees. Down scan sonar …

Unmanned Aircraft Systems Image Collection And Computer Vision Image Processing For Surveying And Mapping That Meets Professional Needs, James Preston Peterson Ii

Doctoral Dissertations

"Unmanned Aerial Systems (UAS) are rapidly blurring the lines between traditional and close range photogrammetry, and between surveying and photogrammetry. UAS are providing an economic platform for performing aerial surveying on small projects. The focus of this research was to describe traditional photogrammetric imagery and Light Detection and Ranging (LiDAR) geospatial products, describe close range photogrammetry (CRP), introduce UAS and computer vision (CV), and investigate whether industry mapping standards for accuracy can be met using UAS collection and CV processing. A 120-acre site was selected and 97 aerial targets were surveyed for evaluation purposes. Four UAS flights of varying heights …

Pulsed Inductive Plasma Studies By Spectroscopy And Internal Probe Methods, Warner C. Meeks

Doctoral Dissertations

The broad effort of the Missouri Plasmoid Experiment is to elucidate the energy conversion processes in a pulsed inductive discharge due to the presence of plasma. The test article is a 440 to 490 kHz theta-pinch (or solenoidal) geometry coil with a stored energy of around 80 joules. In this work experimental hydrogen, helium, argon and xenon data at back-fill pressures of 10 to 100 mTorr (1.3 to 133.3 Pa) are obtained and interpreted. Spectral and internal probe studies were performed on MPX Mk.I and Mk.II devices, respectively. IR spectra were acquired in the Mk.I device for argon and xenon. …

Process Design, Dynamics, And Techno-Economic Analysis Of A Sustainable Coal, Wind, And Small Modular Nuclear Reactor Hybrid Energy System, Kyle Lee Buchheit

Doctoral Dissertations

"The availability of cheap electricity is one of the biggest factors for improving quality of life. With the debate on the effects of carbon dioxide emissions continuing, several countries have either implemented or are considering the reduction of emissions through various economic means. The inclusion of a monetary penalty on carbon emissions would increase the prices of electricity produced by carbon-based sources. The push for large-scale renewable sources of energy has met problems with regards to energy storage and availability. The proposed coal, wind, and nuclear hybrid energy system would combine a renewable energy source, wind, with traditional and stable …

Analysis Of Effects Of Surface Roughness And Local Surface Imperfections On Measured Pressure, Laurin Ashley Bookout

Doctoral Dissertations

"When tests using pressure to characterize the performance or effects of an explosive are conducted in laboratory or other small scale, highly controlled settings, it is expected that any gages will be ideally mounted and there will not be any surface imperfections or roughness near the gage location. However, when explosive tests are scaled up, the test beds typically do not have perfect surfaces. Instead there may be rough surfaces with various types of geometry or situations where it is extremely difficult to get the gage flush mounted with a flat surface. In a time where tests with multiple replications …

Analysis Of Production And Pressure Data To Characterize The Performance Of Oil And Gas Reservoirs, Abuagila Ramadan Elgmati

Doctoral Dissertations

"Production data analysis is an important tool for estimating important reservoir parameters. In particular, determining the average reservoir pressure (p_av) and tracking its change with time is critical to analyzing and optimizing reservoir performance. The traditional method for determining p_av involves pressure buildup tests. A direct method for estimating (p_av) from flowing pressures and rate data is available. However, the method is for an idealized case that assumes constant production rate during pseudo steady-state (PSS) flow, which is not generally true for real wells. This research extends that approach so that it can …

Privacy-Preserving Query Processing Over Encrypted Data In Cloud, Yousef M. Elmehdwi

Doctoral Dissertations

"The query processing of relational data has been studied extensively throughout the past decade. A number of theoretical and practical solutions to query processing have been proposed under various scenarios. With the recent popularity of cloud computing, data owners now have the opportunity to outsource not only their data but also data processing functionalities to the cloud. Because of data security and personal privacy concerns, sensitive data (e.g., medical records) should be encrypted before being outsourced to a cloud, and the cloud should perform query processing tasks on the encrypted data only. These tasks are termed as Privacy-Preserving Query Processing …

Synthesis And Characterization Of Vanadium Oxide Nanomaterials, Tyler M. Fears

Doctoral Dissertations

"This dissertation focuses on the synthesis and characterization of vanadium oxide nanomaterials and neutron-transparent Li-ion battery electrolytes.

Vanadium oxide gels were synthesized via the epoxide-assisted gelation of VOCl₃ using epichlorohydrin in ethanol. This represents the first epoxide-assisted gelation developed for vanadium oxide gels and serves as a potential economical replacement for the fabrication of vanadium oxide gels via the hydrolysis of vanadium alkoxides. Though epoxide-assisted gelation has been demonstrated for a number of transition metal oxides, the gelation mechanism observed here for VOCl₃ appears to be unique.

While investigating the electrochemical and structural properties of lithium vanadates, it …

Non-Invasive Imaging And Assessment Of Pavements, Adel Mohamed Elkrry

Doctoral Dissertations

"Eight electrical resistivity tomography (ERT) and multi-channel analysis of surface wave (MASW) case studies are presented. The objective is to assess the condition of pavement, base, native soil, and rock all the way down to the top of the bedrock. Each segment of road way is approximately 1000 ft. long. The cases include US 63 north of Rolla, US 54 in Camden County, Rte. 179 in Jefferson City, HWY AT in Franklin County, I-55 in Pemiscot County, I-55 in Perry County, HWY U in Dent County, I-35 in Daviess County. In addition, there are only three types of pavement in …

Quantification Of Information Flow In Cyber Physical Systems, Li Feng

Doctoral Dissertations

"In Cyber Physical Systems (CPSs), traditional security mechanisms such as cryptography and access control are not enough to ensure the security of the system since complex interactions between the cyber portion and physical portion happen frequently. In particular, the physical infrastructure is inherently observable; aggregated physical observations can lead to unintended cyber information leakage. Information flow analysis, which aims to control the way information flows among different entities, is better suited for CPSs than the access control security mechanism. However, quantifying information leakage in CPSs can be challenging due to the flow of implicit information between the cyber portion, the …

Methods And Algorithms For Service Selection And Recommendation (Preference And Aggregation Based), Kenneth Kofi Fletcher

Doctoral Dissertations

"In order for service users to get the best service that meets their requirements, they prefer to personalize their non-functional attributes, such as reliability and price. However, the personalization makes it challenging because service providers have to deal with conflicting non-functional attributes when selecting services for users. In addition, users may sometimes want to explicitly specify their trade-offs among non-functional attributes to make their preferences known to service providers. Typically, users' service search requests with conflicting non-functional attributes may result in a ranked list of services that partially meet their needs. When this happens, it is natural for users to …

Application Of Colloidal Unimolecular Polymer (Cup) Particles In Coatings, Sagar Vijay Gade

Doctoral Dissertations

"Colloidal unimolecular polymer (CUP) particles were prepared by the process of water reduction on copolymers containing hydrophobic and hydrophilic monomers at definite ratio using free radical polymerization. The CUPs are formed by the effect of hydrophilic /hydrophobic interactions of the polymer with a change in the solvent environment around them. Once formed these colloidal particles are thermodynamically stable with collapsed hydrophobic groups forming a spheroidal core and hydrophilic charges on the surface stabilizing the particle by the charge repulsion. CUPs contain only the charged CUP particles, water and counterions with all the functionality on the surface for further chemistry. CUP …

Impact Of Thorium Based Molten Salt Reactor On The Closure Of The Nuclear Fuel Cycle, Safwan Qasim Mohammad Jaradat

Doctoral Dissertations

"Molten salt reactor (MSR) is one of six reactors selected by the Generation IV International Forum (GIF). The liquid fluoride thorium reactor (LFTR) is a MSR concept based on thorium fuel cycle. LFTR uses liquid fluoride salts as a nuclear fuel. It uses ²³²Th and ²³³U as the fertile and fissile materials, respectively. Fluoride salt of these nuclides is dissolved in a mixed carrier salt of lithium and beryllium (FLiBe). The objective of this research was to complete feasibility studies of a small commercial thermal LFTR. The focus was on neutronic calculations in order to prescribe core design …

Localization And Tracking Of Electronic Devices With Their Unintended Emissions, Nurbanu Guzey

Doctoral Dissertations

"The precise localization and tracking of electronic devices via their unintended emissions has a broad range of commercial and security applications. Active stimulation of the receivers of such devices with a known signal generates very low power unintended emissions. This dissertation presents localization and tracking of multiple devices using both simulation and experimental data in the form of five papers.

First the localization of multiple emitting devices through active stimulation under multipath fading with a Smooth MUSIC based scheme in the near field region is presented. Spatial smoothing helps to separate the correlated sources and the multipath fading and results …

Mechanical Characteristics Of Organically Modified Fly Ash-Kaolinite Mixtures, Xin Kang

Doctoral Dissertations

"Fly ash is a hazardous waste material to the environment. Beneficial reuse of fly ash, however, brings economic and environmental benefits, i.e., decreases the cost of disposal, reduces greenhouse gas emission, and improves mechanical properties of construction materials. Due to the lack of pozzolanic properties, the reuse rate of Class F fly ash in geotechnical engineering is relatively low (ACAA 2013). In order to promote the effectiveness and sustainability of high volume reuse of class F fly ash in geotechnical engineering, biopolymers (Chitosan, and Xanthan gum) and synthetic polymers (Polyethylene Oxide, PEO) were used instead of the traditional stabilizers to …

Selective Laser Sintering Of Bioactive Glass Scaffolds And Their Biological Assessment For Bone Repair, Krishna C. R. Kolan

Doctoral Dissertations

"Bone scaffold fabrication using powder-bed based additive manufacturing techniques, like the selective laser sintering (SLS) process, provides control over pore interconnectivity, pore geometry, and the overall shape of the scaffold, which aids in repairing different regions of the bone. The main objectives of this dissertation were to develop bioactive glass (BG) scaffolds using the SLS process and evaluate the scaffolds for their effectiveness in bone repair both in vitro and in vivo. 13-93 glass, a silicate based BG, and 13-93B3 glass, a borate based BG, are designed to accelerate the body's natural ability to heal itself and are used …

Advanced Approaches For Bridge Deck Assessment Using Ground Penetrating Radar, Aleksey Kamilevich Khamzin

Doctoral Dissertations

"Ground penetrating radar (GPR) data were acquired across four bridge decks with the objective of developing an advanced workflow for GPR operation that would allow the bridge owners to estimate repair quantities for certain bridge decks, based on GPR data. The primary contributions from this research are as follows: 1. It was demonstrated that the conditions of bridge decks can be cost-effectively and efficiently assessed using the GPR tool. 2. The GPR tool's ability to provide rapid and reliable results in comparison with conventional bridge deck condition assessment techniques was established. 3. The qualitative and quantitative relationships between the GPR …

Computational Approaches For Voltage Stability Monitoring And Control In Power Systems, Kangombe Joseph Makasa

Doctoral Dissertations

"The electric power grid is a complex, non-linear, non-stationary system comprising of thousands of components such as generators, transformers, transmission lines and advanced power electronics based control devices, and customer loads. The complexity of the grid has been further increased by the introduction of smart grid technologies. Smart grid technology adds to the traditional power grids advanced methods of communication, computation and control as well as increased use of renewable energy sources such as wind and solar farms and a higher penetration of plug-in electric vehicles among others. The smart grid has resulted in much more distributed generation, bi-directional powerflows …

Approximation Methods In Relativistic Eigenvalue Perturbation Theory, Jonathan Howard Noble

Doctoral Dissertations

"In this dissertation, three questions, concerning approximation methods for the eigenvalues of quantum mechanical systems, are investigated: (i) What is a pseudo-Hermitian Hamiltonian, and how can its eigenvalues be approximated via numerical calculations? This is a fairly broad topic, and the scope of the investigation is narrowed by focusing on a subgroup of pseudo-Hermitian operators, namely, PT-symmetric operators. Within a numerical approach, one projects a PT-symmetric Hamiltonian onto an appropriate basis, and uses a straightforward two-step algorithm to diagonalize the resulting matrix, leading to numerically approximated eigenvalues. (ii) Within an analytic ansatz, how can a relativistic Dirac Hamiltonian be …

Near-Field Scanning Study For Radio Frequency Interference Estimation, Jingnan Pan

Doctoral Dissertations

"This dissertation discusses the novel techniques using near-fields scanning to do radio frequency interference (RFI) estimation. As the electronic products are becoming more and more complicated, the radio frequency (RF) receiver in the system is very likely interfered by multiple noise sources simultaneously. A method is proposed to identify the interference from different noise sources separately, even when they are radiating at the same time. This method is very helpful for engineers to identify the contribution of the coupling from different sources and further solve the electromagnetic interference issues efficiently. On the other hand, the equivalent dipole-moment models and a …

Holocene Sedimentology And Stratigraphy Of Coastal Sediments In An Arid Climate, Al Qahmah, Southern Red Sea, Saudi Arabia, Abdullah Ibrahim Nabhan

Doctoral Dissertations

"Holocene sedimentary deposits in Al Qahmah coast, southern Red Sea, in Saudi Arabia have been accumulated on an arid siliciclastic coast in a rift tectonic setting. This study provides a detail interpretation and analysis of sedimentary facies, stratigraphy, depositional environment, and major geological processes. Two studies have been undertaken. First, petrological study of composition and texture of modern sediments and facies mapping delineate facies distribution and mechanisms of sediment transport and deposition. A unique suite of complex riverine, wave, tidal, wind, and chemical and biological processes affect the composition, texture, and distribution of the facies. Second, the depositional environments of …

Distributed State Verification In The Smart Grid Using Physical Attestation, Thomas Patrick Roth

Doctoral Dissertations

"A cyber process in a distributed system can fabricate its internal state in its communications with its peers. These state fabrications can cause other processes in the distributed system to make incorrect control decisions. Cyber-physical systems have a unique advantage in the detection of falsified states because processes typically have observable effects on a shared physical infrastructure. This physical infrastructure acts as a high-integrity message channel that broadcasts changes in individual process states. The objective of this research is to demonstrate that there are cases where physical feedback from the shared infrastructure can be used to detect state fabrications. To …

Analytical And Numerical Studies Of Photo-Injected Charge Transport In Molecularly-Doped Polymers, Amrita Roy Chowdhury

Doctoral Dissertations

"The mobility of photo-injected charge carriers in molecularly-doped polymers (MDPs) exhibits a commonly observed, and nearly universal Poole-Frenkel field dependence, µ ~ exp [square root (ß₀E)], that has been shown to arise from the correlated Gaussian energy distribution of transport sites encountered by charges undergoing hopping transport through the material. Analytical and numerical studies of photo-injected charge transport in these materials are presented here with an attempt to understand how specific features of the various models developed to describe these systems depend on the microscopic parameters that define them. Specifically, previously published time-of-flight mobility data for the molecularly …

On The Deployment Of On-Chip Noise Sensors, Tao Wang

Doctoral Dissertations

"The relentless technology scaling has led to significantly reduced noise margin and complicated functionalities. As such, design time techniques per se are less likely to ensure power integrity, resulting in runtime voltage emergencies. To alleviate the issue, recently several works have shed light on the possibilities of dynamic noise management systems. Most of these works rely on on-chip noise sensors to accurately capture voltage emergencies. However, they all assume that the placement of the sensors is given. It remains an open problem in the literature how to optimally place a given number of noise sensors for best voltage emergency detection. …

Synthesis And Electrochemical Studies Of Novel Ionic Liquid Based Electrolytes, Avinash Raju Vadapalli

Doctoral Dissertations

"Room temperature ionic liquids (RTILs) have received substantial interest as nonaqueous electrolytes in lithium ion- and metal-air batteries in recent years due to their low volatility, non-flammability, wide liquid range, and thermal stability characteristics. Towards developing a new generation of high specific energy lithium ion batteries, a series of imidazolium and pyrrolidinium based ionic liquids were synthesized and explored as nonaqueous electrolytes in lithium-, lithium ion-, and lithium-air batteries. Pyrrolidinium-TFSI based ionic liquids have wide electrochemical stability (5.7 - 6.2 V vs Li/Li⁺); however, they show limited thermal stabilities and lithium cell discharge characteristics. TFSI-based ionic liquids are …

Essays On Unit Root Testing In Time Series, Xiao Zhong

Doctoral Dissertations

"Unit root tests are frequently employed by applied time series analysts to determine if the underlying model that generates an empirical process has a component that can be well-described by a random walk. More specifically, when the time series can be modeled using an autoregressive moving average (ARMA) process, such tests aim to determine if the autoregressive (AR) polynomial has one or more unit roots. The effect of economic shocks do not diminish with time when there is one or more unit roots in the AR polynomial, whereas the contribution of shocks decay geometrically when all the roots are outside …

Evolutionary Dynamics Of Speciation And Extinction, Dawn Michelle King

Doctoral Dissertations

Presented here is an interdisciplinary study that draws connections between the fields of physics, mathematics, and evolutionary biology. Importantly, as we move through the Anthropocene Epoch, where human-driven climate change threatens biodiversity, understanding how an evolving population responds to extinction stress could be key to saving endangered ecosystems. With a neutral, agent-based model that incorporates the main principles of Darwinian evolution, such as heritability, variability, and competition, the dynamics of speciation and extinction is investigated. The simulated organisms evolve according to the reaction-diffusion rules of the 2D directed percolation universality class. Offspring are generated according to one of three reproduction …