Digital Commons Network^™

Attenuation Properties Of Cement Composites: Experimental Measurements And Monte Carlo Calculations, Raul Florez

Masters Theses

"Developing new cement based materials with excellent mechanical and attenuation properties is critically important for both medical and nuclear power industries. Concrete continues to be the primary choice material for the shielding of gamma and neutron radiation in facilities such as nuclear reactors, nuclear waste repositories, spent nuclear fuel pools, heavy particle radiotherapy rooms, particles accelerators, among others. The purpose of this research was to manufacture cement pastes modified with magnetite and samarium oxide and evaluate the feasibility of utilizing them for shielding of gamma and neutron radiation. Two different experiments were conducted to accomplish these goals. In the first …

Seismic Anisotropy And Mantle Dynamics Beneath The Southeastern United States Inferred From Shear-Wave Splitting Analysis, Yunhua Liu

Masters Theses

"Systematic spatial variations of mantle azimuthal anisotropy are revealed by over 3000 pairs of high-quality shear-wave splitting parameters (fast polarization orientations and splitting times) recorded at ~400 USArray and other network stations in the SE United States (75⁰-90⁰ W, and 24⁰-40⁰ N). The fast polarization orientations observed in the continental interior are subparallel to the absolute plate motion (APM) direction of the North American plate with apparent larger-than-normal splitting times, indicating a significant asthenospheric contribution. Fast orientations parallel to the edge of the North American craton are revealed along the southern and eastern margins of the continent. A portion of …

Radiation Noise Source Modeling And Near-Field Coupling Estimation In Rf Interference, Liang Li

Masters Theses

"With increasing complexities and shrinking size of modern electronic devices, the near-field RF interference issues are becoming challenging for RF-digital mixed circuit design. Predicting the coupling from digital module to RF antennas and mitigating RF interference is important to the system performance. The ultimate goal of this study is to address the desensitization issues existing in modern electronic devices that have mixed high speed digital-RF circuits, such as cellphone and wearable devices.

In order to estimate the near-field noise coupling from digital module to RF antennas, the noise source is anticipated to be replaced by its equivalent radiation model which …

Study Jitter Amplification Of A Passive Channel And Investigation Of S₂₁ Magnitude Extraction Methodologies Using A Pattern Generator And Oscilloscope, Xinyun Guo

Masters Theses

"Recently the clock channel jitter amplification has been observed in several publications. Currently in many high-speed I/O systems, to avoid the cost and the complex clock recovery circuit design, people use traces forwarding clock signal from transmitting IC to receiving IC. When these clock traces are long enough, the amount of attenuation will induce not only inter-symbol-interference (ISI) but also modulate with the input jitter. Eventually it will lead some type of jitter been amplified after the channel. Similarly, the high speed communication channel (data channel) will also face this issue. Since there are no studies on the jitter amplification …

Deterministic Simulation Of Thermal Neutron Radiography And Tomography, Rajarshi Pal Chowdhury

Masters Theses

"In recent years, thermal neutron radiography and tomography have gained much attention as one of the nondestructive testing methods. However, the application of thermal neutron radiography and tomography hindered by their technical complexity, radiation shielding, and time-consuming data collection processes. Monte Carlo simulations have been developed in the past to improve the neutron imaging facility's ability. In this present work, a new deterministic simulation approach has been proposed and demonstrated to simulate neutron radiographs numerically using a ray tracing algorithm. This approach has made the simulation of neutron radiographs much faster than by previously used stochastic methods (i.e Monte Carlo …

Composite Model Representation For Computer Aided Design Of Functionally Gradient Materials, Fangquan Wang

Masters Theses

"Functionally Gradient Materials (FGMs) feature smooth transition from one material to another within a single object. FGMs modeling is considered to be one of the new challenges in Computer Aided Design (CAD) area. To overcome this challenge, this thesis presents a composite approach to model FGMs. The input in STL format can be meshed and voxelized in FGMs modeling system. The material composition in each voxel can be generated from multiple different types of control features. And LTI filters including Gaussian Filter and Average Filter are applied to blur default material features in order to generate FGMs inside models. The …

Engine Sound Simulation And Generation In Driving Simulator, Shuang Wu

Masters Theses

"Simulating a driving environment that provides engine sound as auditory feedback to the driver is a challenging task due to the complexity of engine sound, a wide range of operating speeds, and repeated sound clicking during playback. This thesis describes a method of engine sound simulation and generation for a driving simulator. By analyzing sample sounds, spectral modeling synthesis was used to decompose the sound samples into deterministic and stochastic components. Then, the modeled deterministic and stochastic signals were employed to resynthesize the sounds. To represent engine sounds not available in the recorded database, sound interpolation was applied to two …

Fluid Flow Through Deformation Band, Huining Zhang

Masters Theses

"Cataclastic deformation bands, which are common in porous sandstone, have the potential to restrict fluid flow. Geological studies have shown that permeability of deformation band shear zones can be one to five orders of magnitude less than for the sandstone host rock. However, recent studies based on simplified analytical estimates have shown that fluid flow in jointed deformation bands may not be retarded since joints play an important role in conducting fluids. In this study, 2 dimensional finite element analysis (FEA) is used to simulate the total discharge flow rate through jointed deformations. Variations of single planar and conjugate jointed …

A Linear Matrix Inequality-Based Approach For The Computation Of Actuator Bandwidth Limits In Adaptive Control, Daniel Robert Wagner

Masters Theses

"Linear matrix inequalities and convex optimization techniques have become popular tools to solve nontrivial problems in the field of adaptive control. Specifically, the stability of adaptive control laws in the presence of actuator dynamics remains as an important open control problem. In this thesis, we present a linear matrix inequalities-based hedging approach and evaluate it for model reference adaptive control of an uncertain dynamical system in the presence of actuator dynamics. The ideal reference dynamics are modified such that the hedging approach allows the correct adaptation without being hindered by the presence of actuator dynamics. The hedging approach is first …

Design And Analysis Of An Axisymmetric Aerospike Supersonic Micro-Nozzle For A Refrigerant-Based Cold-Gas Propulsion System For Small Satellites, Abdalla Ali Bani

Masters Theses

"The cold-gas propulsion system being developed by M-SAT requires improvements to its original nozzle design. This study documents the research, design, and analysis of a supersonic plug nozzle concept that could be integrated to the refrigerant-based cold-gas propulsion system to possibly improve its performance. As documented in this thesis, CFD analysis showed that the outlined nozzle design method resulted in a feasible nozzle concept that has the ability to out-perform a conventional nozzle of the same area ratio. The flow-fields and thrust of the aerospike nozzle, for the full and truncated nozzles, were investigated. The purpose of this study is …

Voltage Control In A Distribution System Using Active Power Loads, Mounika Chava

Masters Theses

"High penetration of renewable energy resources such as rooftop solar photovoltaic (PV) systems is exacerbating violations of the voltage limits in power distribution networks. Existing solutions to these over-/under-voltage issues include tap-changing transformers and shunt capacitors. However, tap changers only allow voltage changes in discrete steps and shunt capacitors cannot handle over-voltage situations. To overcome these problems, this thesis proposes voltage control in a distribution system by adjusting active power loads. The proposed solution can be used for both under- and over-voltage cases at any levels of voltage adjustment. First, the active power that needs to be adjusted at selected …

An Investigation Of Plugging And Increasing Oil Recovery In Sandstone Porous Media By Micrometer-Size Particle Gel, Haifeng Ding

Masters Theses

"Micrometer-size particle gel (microgel) has been developed and successfully applied to improve conformance in mature reservoirs. However, quite few researches have been published to address on their effect on oil recovery and rock permeability modification.

This work conducted a series of core flooding experiments to investigate the injectivity, plugging efficiency and improving oil recovery potentials of a couple of microgels synthesized in our lab.

First, this work studied the impact of permeability and crosslinker concentration on PAM type microgel treatment. Results shows that microgel treatment would have a less plugging efficiency in lower permeability rocks, which could be caused by …

Addressing The Influence Of Carbon Monoxide On The Behavior Of An Hcci Engine, Allen Charles Ernst

Masters Theses

"Homogeneous Charge Compression Ignition (HCCI) may be the next leap of improvement to internal combustion engines due to its decreased emissions and improved engine efficiencies. However, such a jump possesses challenges owing to its strict reliance on the inherent physics that dictate start of combustion and limit the reach of stable operation. This work investigates the role and fundamental influence of carbon monoxide on the cycle-to-cycle combustion dynamics present in the region of incomplete combustion that frames the limited HCCI operating region. An improved understanding will open doors to enhanced control methodologies and an expanded stable operating envelope. A constant …

Single Phase Gas Flow Response Of Fractured Horizontal And Vertical Wells To Repeated Production, Divya Kandlakunta

Masters Theses

"Historically, the conventional approach to well production has been to produce continuously, minimizing interruptions to flow insofar as possible. Yet some operators have observed improved well flow rates and ultimate recovery after a significant well shut-in periods. These production increases have not been documented. This study investigates the production impact of cyclic production/shut-in on fractured vertical and horizontal gas well performance.

A numerical reservoir model in Stimplan software was used to model production in fracture stimulated vertical and horizontal gas wells. Reservoir permeability is varied over a range of 0.0001 md to 1 md, and the shut-in period was varied …

Protection Of A 138/34.5 Kv Transformer Using Sel 387-6 Relay, Aamani Lakkaraju

Masters Theses

"Schweitzer Engineering laboratories (SEL) donated the SEL 387, SEL 311L, and SEL 351S relays and the SEL AMS to Missouri University of Science and Technology. This thesis documents the demonstration approach to set the SEL 387 relay to protect a grounded wye-grounded wye transformer and then test these settings by injecting fault currents into the relay using the SEL AMS. This thesis explains the approach to set the differential element of the SEL 387 relay to protect a transformer against internal faults and the overcurrent element of the SEL 387 relay to protect transformer against external faults. A radial power …

Periclinal Folding In Ozark Plateau: A Record Of Local Karst Collapse Or Regional Tectonic Forces?, Chao Liu

Masters Theses

"The Ordovician Rubidoux Formation of the Ozark Plateau, Missouri is typically identified as mechanically competent sub-horizontal beds of medium grained sandstone. North of Licking, MO, the Rubidoux Formation was deformed into a series of dome-and-basin shaped buckle folds, exposed in road cuts over a distance of ~10 km. Such folds are highly unusual within the Ozark Plateau and their origin remains controversial. Three major hypotheses have been proposed based on field observations and stereographic analysis. Given the pervasive distribution of karst collapse throughout Missouri, one hypothesis to explain these folds is that the Roubidoux Formation sagged into collapsed caverns. A …

Origin Of Lacustrine Carbonate-Dominated Clinoforms In The Lower-Permian Lucaogou Low-Order Cycle, Southern Bogda Mountains, Nw China, Yiran Lu

Masters Theses

"Lacustrine carbonate clinoforms deposit can reflect ancient lake condition like paleoclimate and lake type. Complex lithofacies of a carbonate-dominated clinoform package in lower Permian Lucaogou low order cycle, Bogda Mountains, NW China, provide clues on clinoform-forming processes in a half-graben lake. The clinoform package is ~5.2 m thick, prograding from S to N for ~200 m with a maximum 15o dip angle, and spans ~4 km laterally. A clinoform consists of a lower siliciclastic-rich and an upper carbonate-rich beds, forming a clinoform cycle. Results of petrographic study of 30 thin sections suggest that the clinoform package is composed of mixed …

Construction And Validation Of Tl-Ipm Generator, Jamaluddin Mohammad

Masters Theses

"Hydrokinetic energy is one of the potential sources of energy that can be extracted and converted to electrical energy using linear generator. This work discusses about construction and validation of tubular linear internal permanent magnet (TL-IPM) generator, a kind of linear generator. The generator could produce electricity by converting linear motion generated from vortex induced vibrations induced due from a flowing fluid, such as a river. A simulation model of the generator is created using Ansoft's Maxwell software, which uses finite element analysis to perform electromagnetic analysis of the generator. Then a practical generator was built and tested. The results …

Computational Fluid Dynamics (Cfd) Simulations Of Molten Steel Flow Patterns And Particle-Wall Adhesion In Continuous Casting Of Steels, Mahdi Mohammadi-Ghaleni

Masters Theses

"In this research, the measurements of clog deposit thickness on the interior surfaces of a continuous casting nozzle were compared with Computational Fluid Dynamics (CFD) predictions of melt flow patterns and particle-wall interactions to identify the mechanisms of nozzle clogging. A hybrid turbulent approach, Detached Eddy Simulation (DES), was configured to simulate both turbulent structures and particle-wall interactions inside the nozzle accurately. For experimental measurements of nozzle clogging, a nozzle received from industry was encased in epoxy and carefully sectioned to allow measurement of the deposit thickness on the internal surfaces of the nozzle. CFD simulations of melt flow patterns …

Provenance And Depositional Environments Of Fluvial-Lacustrine Sandstones Of Lower Permian Lucaogou Low-Order Cycle, Bogda Mountains, Nw China, Xiaowei Peng

Masters Theses

"Compositional and textural maturity of sandstones may reflect provenance lithology and sediment transport distance, which are useful for paleogeographic reconstruction. 37 sandstones in six outcrop stratigraphic sections in Tarlong-Taodonggou and Zhaobishan areas in the greater Turpan-Junggar rift basin were studied to investigate the fluvial-lacustrine sandstone provenance in lower Permian Lucaogou (LCG) low-order cycle, Bogda Mountains, NW China. 400 points were counted in each thin section. All the samples are classified into lithic arenites, subarenites, wackes, and mudrocks. Three Petrofacies are defined. Petrofacies A is characterized by a high lithic content which is dominantly basaltic lithics with minor sedimentary lithics and …

Event-Sampled Direct Adaptive Neural Network Control Of Uncertain Strict-Feedback System With Application To Quadrotor Unmanned Aerial Vehicle, Nathan Szanto

Masters Theses

"Neural networks (NNs) are utilized in the backstepping approach to design a control input by approximating unknown dynamics of the strict-feedback nonlinear system with event-sampled inputs. The system state vector is assumed to be unknown and an observer is used to estimate the state vector. By using the estimated state vector and backstepping design approach, an event-sampled controller is introduced. As part of the controller design, first, input-to-state-like stability (ISS) for a continuously sampled controller that has been injected with bounded measurement errors is demonstrated and, subsequently, an event-execution control law is derived such that the measurement errors are guaranteed …

Hydrodynamic Of A Co-Current Gas Liquid Upflow In A Moving Packed Bed Reactor With Porous Catalysts, Ali Jabbar Toukan

Masters Theses

"In this study, the hydrodynamic, i.e. flow regime identification, line average liquid holdup, and the internal liquid holdup of a co-current moving packed bed reactor were studied. For the sake of hydrodynamics study, moving bed reactor is investigated as two-phase upflow packed bed reactor. Scaled down configuration was used to simulate of the moving bed reactors utilized in the industrial process. First, line average liquid holdup is measured with different geometrical configurations covering empty, dry, wet, and packed column under flowrates operation conditions. A new methodology has been developed to determine the line average liquid holdup for a porous catalyst. …

Reduction Of Emi Due To Common Mode Current Using Common Mode Filter Or Lossy Material, Qian Liu

Masters Theses

"This thesis consists of four papers. In the first paper, two new common mode filter structures were designed, fabricated, and measured. A "sandwich-type" EBG structure that resonates at the desired filter frequency is designed to suppress common mode filter on differential signals. The new filters are placed on top of the PCB as a surface-mount component, instead of being implemented within the PCB stackup. The total radiated power (TRP) of the implemented filter is investigated and discussed. RF absorbing material and traditional shielding are considered to reduce the TRP.

In the second paper and third paper, new PCB-embedded common mode …

Pim Source Identification Using Vibration Modulation Method, Sen Yang

Masters Theses

“In Section 1, passive intermodulation (PIM) is introduced and the mechanism of it is briefly explained. Then, the up-to-date PIM testing and source identification method in the industrial and academia worlds will be summarized.

The vibration modulation method for PIM source identification is proposed in Section 2. Different vibration sources were tested and compared, and the test results showed that the vibration modulation method is able to identify PIM source with good accuracy.

Section 3 outlines a special PIM source identification system built based on the vibration modulation system. The two subsystems, PIM receiver and PIM vibrator, are illustrated in …

Avon Alkaline Igneous Province, Missouri: Characterization Of Subcontinental Mantle Source And Evolution Via Chemical Analysis Of Olivine, Zachary William Freeman

Masters Theses

"This article presents the crystallization age of, and composition of olivine phenocrysts within an alnoite of, the Avon Alkaline Igneous Province (AAIP) of Ste. Genevieve County, Missouri. The AAIP is an ultramafic igneous province consisting of approx. 80 known intrusives of diverse lithology and texture. ⁴⁰Ar/³⁹ Ar geochronology indicates an emplacement age of 386 +/- 1 Ma, which establishes the AAIP as the only known Devonian-age ultramafic igneous body in the Midwestern U.S. Study of the AAIP provides a unique opportunity to characterize the Devonian-age subcontinental mantle and the processes that generated the suite of ultramafic rocks present …

Paleogeogra Detrital Zircon Geochronology Of Upper Cambrian To Lower Mississippian Siliciclastic Strata Of The Ozark Dome And Vicinity, Bing Li

Masters Theses

"Siliciclastic strata exposed in the Ozark Dome provide Late Cambrian to Late Cretaceous snapshots of an evolving paleogeology and regional to far-field tectonic events. U-Pb ages of detrital zircons from the arkosic base of the Upper Cambrian Lamotte Formation reflect first cycle derivation from the adjacent ca. 1.31-1.48 Ga Granite-Rhyolite province, with subsidiary input from ca. 1.6-1.7 Ga Mazatzal basement. Feldspathic arenites near the top of the Lamotte Sandstone also contain significant quantities of detrital zircon grains of these ages, with additional peaks centered at ca. 2.7 and ca. 1.1 Ga, signaling the onset of extra-regional detrital input most likely …

Pricing Of Geometric Asian Options In General Affine Stochastic Volatility Models, Johannes Ruppert

Masters Theses

"In this thesis, we look at the general affine pricing model introduced in [11]. This model allows to price geometric Asian options, which are of big interest due to their lower volatility in comparison to, for example, European options. Because of their structure and in order to be able to price these options, we look at the basic theory of Lévy processes and stochastic calculus. Furthermore, we provide the detailed description of the parameters of the pricing formulas for some popular specific single-factor stochastic volatility models with jumps and generalize the approach of [11] to multi-factor models"--Abstract, page iii.

A Novel Anthropomorphic Flow Phantom For The Quantitative Evaluation Of Prostate Dce-Mri Acquisition Techniques, Silvin Knight, Jacinta Browne, James Meaney, David Smith, Andrew Fagan

Articles

A novel anthropomorphic flow phantom device has been developed which can be used for quantitatively assessing the ability of MRI scanners to accurately measure signal / concentration time-intensity curves (CTCs) associated with dynamic contrast-enhanced (DCE) MRI. Modelling of the complex pharmacokinetics of contrast agents as they perfuse through the tumour capillary network has shown great promise for cancer diagnosis and therapy monitoring. However, clinical adoption has been hindered by methodological problems, resulting in a lack of consensus regarding the most appropriate acquisition and modelling methodology to use and a consequent wide discrepancy in published data. A heretofore overlooked source of …

Controllable Growth Of Vertically Aligned Graphene On C-Face Sic, Yu Liu, Lianlian Chen, Donovan Hilliard, Qing-Song Huang, Fang Liu, Mao Wang, Roman Böttger, René Hübner, Alpha T. N’Diaye, Elke Arenholz Elke Arenholz, Viton Heera Viton Heera, Wolfgang Skorupa Wolfgang Skorupa, Shengqiang Zhou

Articles

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d0 magnetism is realized …

Investigation Of A Scalable Barrel Atmospheric Plasma Reactor For The Treatment Of Polymer Particles, Hisham Abourayana, Vladimir Milosavljevic, Peter Dobbyn, Patrick J. Cullen, Denis Dowling

Articles

This study reports on the performance of a scalable barrel atmospheric plasma system for the treatment of polymer particles. A novel feature of the barrel system design is the use of a biased electrode, which also acts as the roller for the glass barrel. The plasma is generated using either helium or helium / oxygen gas mixtures. The reactor was used to activate 20 g batches of silicone, polypropylene (PP), acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate (PET) particles, each with diameters in the range 3 to 5 mm. The effect of plasma treatment time and gas flow rate on …