Engineering Commons^™

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 …

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 …

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 …

Electromagnetic Compatibility In Power Inverter Design, Natalia Bondarenko

Doctoral Dissertations

"Power inverter systems generate significant electromagnetic emissions. Methods were studied to model these systems and to reduce their emissions. Three topics are presented in this dissertation.

Methods were developed to obtain simple SPICE models for complex systems which relate circuit components to physical geometry within the system. These models were derived using measurements or using partial element equivalent circuit (PEEC) and model size reduction techniques developed in this dissertation. Methods were proposed for developing a measurement-based model and were applied to a real power inverter/motor system. The model was used to identify system geometries responsible for critical resonances and to …

Performance Analysis And Modelling Of Hybrid Photovoltaic-Thermal Solar Panels, Nicole C. Annis

Doctoral Dissertations

A photovoltaic-thermal (PVT) panel was constructed, tested, and modelled using both MATLAB and TRNSYS. During the experimental testing, which took place on the Missouri University of Science and Technology campus in Rolla, Missouri; two identical PVT panels were tested alongside two PV panels to gather an electrical baseline for comparison. Approximately 69 days’ worth of data were of data were collected during the summer of 2014. The PV electrical, PVT electrical, PVT thermal and PVT combined (electrical and thermal) efficiencies were 3.5-5.6%, 3.4-5.4%, 20.9-11.6%, and 24.3-17.0%, respectively.

A MATLAB program was developed using existing equations for one-dimensional, quasi-steady model of …

The Radiation Physics, Mitigation Approaches And Design Guidelines Of High-Speed Connectors And Cables Analyzed With Numerical Modeling, Analytical Formulation And Measurements, Jing Li

Doctoral Dissertations

The dissertation is composed of three papers, which cover the radiation and mitigation of high-speed connectors and cables analyzed with full wave simulation, numerical modeling, analytical formulation and measurements.

In the first paper, the radiation from the optical cage connector in the frequency range of 4-28 GHz is analyzed with validated full-wave simulation model and analytical formulas. The radiation from the optical cage connector is suppressed with absorbing materials, and the coupling path in optical link is verified, together with the optical cage and module enclosure.

In the second paper, radiation from antenna-mode current and TL-mode current is briefly reviewed …

Advanced Control Of Grid-Connected Multilevel Power Electronic Rectifiers, Sangin Lee

Doctoral Dissertations

"Multilevel power electronic converters have been gaining attention due to their ability to supply high amounts of power and to handle high voltage levels. In this dissertation, grid connected AC-DC rectifier application is investigated with different topologies and control scheme.

At first, neutral point clamped (NPC) rectifier is employed to transfer power from the grid to the load. The NPC rectifier has two capacitors in order to build multilevel output voltage. However, it causes voltage unbalancing problem. Therefore, the new method has been proposed to regulate each capacitor voltage at the same voltage level. Experimental results show that it is …

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 …

Reliability And Security In Low Power Circuits And Systems, Hui Geng

Doctoral Dissertations

"With the massive deployment of mobile devices in sensitive areas such as healthcare and defense, hardware reliability and security have become hot research topics in recent years. These topics, although different in definition, are usually correlated. This dissertation offers an in-depth treatment on enhancing the reliability and security of low power circuits and systems. The first part of the dissertation deals with the reliability of sub-threshold designs, which use supply voltage lower than the threshold voltage (V_th) of transistors to reduce power. The exponential relationship between delay and V_th significantly jeopardizes their reliability due to process variation …

The Engagement Of Expert Opinions In The Modeling Of Multi-Attribute Decision Making For The Selection Of Project Delivery Methods In Building Construction, Issam H. Algraiw

Doctoral Dissertations

"Choosing the most appropriate project delivery method (PDM) available is acknowledged as a crucial issue in the construction industry. Both the choice and application of an unsuitable PDM can result in project failure. Likewise, the selection of a suitable PDM can increase the chance for project success. A method of selecting from among the seven PDMs recognized by the Construction Specifications Institute (CSI) was created in an attempt to address this issue.

This research was comprised of three objectives. The first objective was to determine the influential factors needed to select the appropriate PDMs available to the US construction industry. …

Flow Mechanisms And Numerical Simulation Of Gas Production From Shale Reservoirs, Chaohua Guo

Doctoral Dissertations

"Shale gas is one kind of the unconventional resources which is becoming an ever increasing component to secure the natural gas supply in U.S. Different from conventional hydrocarbon formations, shale gas reservoirs (SGRs) present numerous challenges to modeling and understanding due to complex pore structure, ultra-low permeability, and multiple transport mechanisms.

In this study, the deviation against conventional gas flow have been detected in the lab experiments for gas flow through nano membranes. Based on the experimental results, a new apparent permeability expression is proposed with considering viscous flow, Knudsen diffusion, and slip flow. The gas flow mechanisms of gas …

Quantum Inspired Algorithms For Learning And Control Of Stochastic Systems, Karthikeyan Rajagopal

Doctoral Dissertations

"Motivated by the limitations of the current reinforcement learning and optimal control techniques, this dissertation proposes quantum theory inspired algorithms for learning and control of both single-agent and multi-agent stochastic systems.

A common problem encountered in traditional reinforcement learning techniques is the exploration-exploitation trade-off. To address the above issue an action selection procedure inspired by a quantum search algorithm called Grover's iteration is developed. This procedure does not require an explicit design parameter to specify the relative frequency of explorative/exploitative actions.

The second part of this dissertation extends the powerful adaptive critic design methodology to solve finite horizon stochastic optimal …

A Novel Powder Factor Based Bench Blast Design Method For Large Surface Coal Mines, Andrew Clifford Blair

Doctoral Dissertations

"Large surface coal mines in Wyoming's Powder River Basin ship millions of tons of coal per annum, moving millions of cubic yards of overburden to mine the coal. Much of this volume is blasted in the form of benches, a common mining technique. Increases in production and scale of equipment in the past thirty-five years have created a paradigm shift for drill and blast personnel at these large surface mines, and the explosives industry has yet to create a blast design method specifically tailored for large surface coal mine bench blasting.

This research examines the typical scale of bench blasting …

Models Predicting The Performance Of Ic Component Or Pcb Channel During Electromagnetic Interference, Chunchun Sui

Doctoral Dissertations

"This dissertation is composed of three papers, which cover the prediction of the characteristics of jitter due to crosstalk and due to simultaneous switching noise, and covers susceptibility of delay locked loop (DLL) to electromagnetic interference.

In the first paper, an improved tail-fit de-convolution method is proposed for characterizing the impact of deterministic jitter in the presence of random jitter. A Wiener filter de-convolution method is also presented for extracting the characteristics of crosstalk induced jitter from measurements of total jitter made when the crosstalk sources were and were not present. The proposed techniques are shown to work well both …

Modelling Of Interconnects In 3dic Based On Layered Green Functions, Siming Pan

Doctoral Dissertations

As traditional CMOS scaling pace gradually slows down, three-dimensional (3D) integration offers another dimension of in the ”More-than-Moore” era. In this dissertation, a number of investigations were conducted to better model interconnects in 3D integrated circuit (IC), to evaluate electrical behavior including delay, power consumption, signal integrity (SI), and power integrity (PI) for 3D ICs. Partial Element Equivalent Circuit (PEEC) method with layered Green’s function is studied here, since it consumes less computational resources and provides better physical insight to model the interconnects in 3DIC for high-speed digital circuits. The work is organized as a series of papers. The first …

Cormem Digital Reasoning Architecture Using Cmos Technology, Indira Priyadarshini Dugganapally

Doctoral Dissertations

”This dissertation describes the application of a multi-level, memory-based approach for building digital circuits. To reflect the alternative approach, the basic science is termed digital reasoning and the specific CorMem technology is based on recent patents. CMOS transistors are used in a non-traditional way for multi-level operations and memory manipulation. The combination of multi-level architectures and matrix algebra principles can create flexible, modular systems using standard fabrication methods and can avoid many of the limitations of other multi-valued logic approaches.

Quaternary, memory-based systems are developed to implement logic-gate-type functions, digital adder circuits, a complete arithmetic and logic unit (ALU), quaternary-to-binary …

Iterative Ct Reconstruction From Few Projections For The Nondestructive Post Irradiation Examination Of Nuclear Fuel Assemblies, Muhammad Imran Khan Abir

Doctoral Dissertations

The core components (e.g. fuel assemblies, spacer grids, control rods) of the nuclear reactors encounter harsh environment due to high temperature, physical stress, and a tremendous level of radiation. The integrity of these elements is crucial for safe operation of the nuclear power plants. The Post Irradiation Examination (PIE) can reveal information about the integrity of the elements during normal operations and off‐normal events. Computed tomography (CT) is a tool for evaluating the structural integrity of elements non-destructively. CT requires many projections to be acquired from different view angles after which a mathematical algorithm is adopted for reconstruction. Obtaining many …

Investigating New Accident Causation, Risk Assessment, And Mitigation Strategy Selection Tools In The Petroleum Industry, Mohammad A. Alkazimi

Doctoral Dissertations

"The inherent complexity of the processes and the volatile nature of petroleum products compel the petroleum industry to continually seek and develop tools and techniques to identify, evaluate, and mitigate potential risks that can negatively impact their process operations. Additionally, government agencies and nonprofit professional societies guide the petroleum industry with regulatory guidelines, standards, and recommended best practices. The industry and these agencies and societies work to improve operational management, to ensure safe working conditions, and to minimize risk of all kinds, so that if failures occur, damage is contained within tolerable limits (Health and Safety Executives, 2013).

The currently …

Application Of Unified Invariants For Cyber Physical Systems In Smart Grids, Tamal Paul

Doctoral Dissertations

Cyber-Physical Systems (CPS) are complex engineered systems which consist of physical components with an underlying cyber network. The three main components of a cyber-physical System are: physical system, networking and communications element and a distributed cyber system. The primary challenge for cyber-physical systems is to understand what happens when various sub-systems, which have been developed in an isolated environment, are integrated. CPS studies need to ensure sub-systems that had been designed in isolation to meet certain specifications, when combined, do not cause the overall system to fail. The crux of cyber-physical research is thus to find a common platform to …

Describing Local Community Acceptance With Discrete Choice Theory For Enhanced Community Engagement, Sisi Que

Doctoral Dissertations

This research sought to facilitate improved community (stakeholder) analysis by providing further insight on the determinants of local community acceptance using discrete choice theory. Specifically, the goals were to: (1) Identify, classify, and verify the important project characteristics and key demographic factors which affect local community acceptance of a mining project; (2) Account for the large number of relevant factors inherent in discrete choice experiments for mining community acceptance evaluation; and (3) Examine discrete choice models to select the most appropriate model for mining community consultation. The research will test the hypotheses that various discrete choice models can describe the …

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 …

Investigation Of Lost Circulation Materials Impact On Fracture Gradient, Mortadha Turki Alsaba

Doctoral Dissertations

"Lost circulation is a challenging problem to be prevented or mitigated during drilling. Lost circulation treatments are widely applied to mitigate losses using a corrective approach or to prevent losses using preventive approaches, also known as "wellbore strengthening". The disagreement among the different wellbore strengthening theories and the lack of understanding the strengthening mechanism resulted in the absence of a standardized method to evaluate the effectiveness of lost circulation materials (LCM) for wellbore strengthening application.

An extensive experimental investigation was performed by constructing a high pressure LCM test apparatus to investigate the effects of different parameters on the sealing efficiency …

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 …

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 …

Development Of Ionic Liquid Multi-Mode Spacecraft Micropropulsion Systems, Steven Paul Berg

Doctoral Dissertations

"This dissertation presents work on development of multi-mode specific spacecraft propulsion systems. Specifically, this work attempts to realize a single propellant capable of both chemical monopropellant and electric electrospray rocket propulsion, develop methods to characterize multi-mode propulsion system performance, and realize a system capable of both monopropellant and electrospray propulsion for a small spacecraft. Selection criteria for ionic liquid propellants capable of both monopropellant and electrospray propulsion are developed. These are based on desired physical properties and performance considering use in both propulsive modes. From these insights, a monopropellant mixture of 1-ethyl-3-methylimidazolium ethyl sulfate and hydroxylammonium nitrate is selected and …

Microstructure And Geotechnical Properties Of St. Peter Sandstone In Clayton, Iowa, Amir Hossein Bagherieh

Doctoral Dissertations

"The St. Peter Sandstone is significantly different from the minerals and rocks which have been studied extensively in mining. It is brittle and characterized by an unusually high friction angle. On the other hand it is friable, and it is nearly cohesionless. The scarcity of the ground control techniques for this particular mining environment has created many difficulties for mine operators. This research aims to establish a fundamental understanding of the basic mechanical and strength properties of the St. Peter Sandstone for engineering design and scientific research. The specific objectives are 1) characterizing the strength of the St. Peter Sandstone, …

Detection And Recognition Of R/F Devices Based On Their Unintended Electromagnetic Emissions Using Stochastic And Computational Intelligence Methods, Shikhar Prasad Acharya

Doctoral Dissertations

"Radio Frequency (RF) devices produce some amount of Unintended Electromagnetic Emissions (UEEs). UEEs are generally unique to a device and can be thought of as a signature of the device. This property of uniqueness of UEEs can be used to detect and identify the device producing the emission. The problem with UEEs is that they are very low in power and are often buried deep inside the noise band which makes them difficult to detect. There are two types of UEE detection methods. The first one is called stimulated detection method where the UEEs of a device are enhanced using …

Investigation Of Effect Of Process Parameters On Multilayer Builds By Direct Metal Deposition, Tarak Amine

Doctoral Dissertations

"Multilayer direct laser deposition (DLD) is a fabrication process through which parts are fabricated by creating a molten pool into which metal powder is injected as. During fabrication, complex thermal activity occurs in different regions of the build; for example, newly deposited layers will reheat previously deposited layers. The objective of this study was to provide insight into the thermal activity that occurs during the DLD process. This work focused on the effect of the deposition parameters of deposited layers on the microstructure and mechanical properties of the previously deposited layers. Varying the parameters was shown to produce different effects …