Digital Commons Network^™

Bootstrap-Based Confidence Intervals In Partially Accelerated Life Testing, Ahmed Mohamed Eshebli

Doctoral Dissertations

"Accelerated life testing (ALT) is utilized to estimate the underlying failure distribution and related parameters of interest in situations where the components under study are designed for long life and therefore will not yield failure data within a reasonable test period. In ALT, life testing is carried out under two or more higher than normal stress levels, with the resulting acceleration of the failure process yielding a sufficient amount of un-censored life-span data within a practical test duration. Usually one (or more) parameters of the life distribution is linked to the stress level through a suitably selected model based on …

A Functional Data Analytic Approach For Region Level Differential Dna Methylation Detection, Mohamed Salem F. Milad

Doctoral Dissertations

"DNA methylation is an epigenetic modification that can alter gene expression without a DNA sequence change. The role of DNA methylation in biological processes and human health is important to understand, with many studies identifying associations between specific methylation patterns and diseases such as cancer. In mammals, DNA methylation almost always occurs when a methyl group attaches to a cytosine followed by a guanine (i.e. CpG dinucleotides) on the DNA sequence. Many statistical methods have been developed to test for a difference in DNA methylation levels between groups (e.g. healthy vs disease) at individual cytosines. Site level testing is often …

Studies On Neutron Diffraction And X-Ray Radiography For Material Inspection, Fahima Fahmida Islam

Doctoral Dissertations

"Among the different probes to study the structures of the bio and structural materials, X-ray and neutron are widely used because of their distinctive usefulness in investigating different structures. X-ray radiography and neutron diffraction are two widely known non-destructive techniques for material inspection. Here we demonstrate the design of neutron diffractometer with low power source and analyze the digital image produced by the X-ray radiography instead of neutron diffraction because of the availability of the data. Neutron diffraction is a powerful tool for understanding the behavior of crystal structures and phase behaviors of materials. While neutron diffraction capabilities continue to …

Thermomechanical Fatigue Life Investigation Of An Ultra-Large Mining Dump Truck Tire, Wedam Nyaaba

Doctoral Dissertations

The cost benefits associated with the use of heavy mining machinery in the surface mining industry has led to a surge in the production of ultra-large radial tires with rim diameters in excess of 35 in. These tires experience fatigue failures in operation. The use of reinforcing fillers and processing aids in tire compounds results in the formation of microstructural inhomogeneity in the compounds and may serve as sources of crack initiation in the tire. Abrasive material cutting is another source of cracks in tires used in mining applications. It suffices, then, to assume that every material plane in the …

Gamma Spectroscopy By Artificial Neural Network Coupled With Mcnp, Huseyin Sahiner

Doctoral Dissertations

"While neutron activation analysis is widely used in many areas, sensitivity of the analysis depends on how the analysis is conducted. Even though the sensitivity of the techniques carries error, compared to chemical analysis, its range is in parts per million or sometimes billion. Due to this sensitivity, the use of neutron activation analysis becomes important when analyzing bio-samples. Artificial neural network is an attractive technique for complex systems. Although there are neural network applications on spectral analysis, training by simulated data to analyze experimental data has not been made. This study offers an improvement on spectral analysis and optimization …

Modeling Dynamic Community Acceptance Of Mining Using Agent-Based Modeling, Mark Kofi Boateng

Doctoral Dissertations

"This research attempts to provide fundamental understanding into the relationship between perceived sustainability of mineral projects and community acceptance. The main objective is to apply agent-based modeling (ABM) and discrete choice modeling to understand changes in community acceptance over time due to changes in community demographics and perceptions. This objective focuses on: 1) formulating agent utility functions for ABM, based on discrete choice theory; 2) applying ABM to account for the effect of information diffusion on community acceptance; and 3) explaining the relationship between initial conditions, topology, and rate of interactions, on one hand, and community acceptance on the other …

Theoretical Calculations For Electron Impact Ionization Of Atoms And Molecules, Sadek Mohamed Fituri Amami

Doctoral Dissertations

"In the last twenty years, significant progress has been made for the theoretical treatment of electron impact ionization (e,2e) of atoms and molecules and, for some cases, very nice agreement between experiment and theory has been achieved. In particular, excellent agreement between theory and experiment and theory has been achieved for ionization of hydrogen and helium. However, agreement between experiment and theory is not nearly as good for ionization of larger atoms and molecules. In the first part of this dissertation, different theoretical approaches will be employed to study the triply differential cross section (TDCS) for low and intermediate energy …

Efficient Algorithms For Analyzing Large Scale Network Dynamics: Centrality, Community And Predictability, Sima Das

Doctoral Dissertations

"Large scale networks are an indispensable part of our daily life; be it biological network, smart grids, academic collaboration networks, social networks, vehicular networks, or the networks as part of various smart environments, they are fast becoming ubiquitous. The successful realization of applications and services over them depend on efficient solution to their computational challenges that are compounded with network dynamics. The core challenges underlying large scale networks, for example: determining central (influential) nodes (and edges), interactions and contacts among nodes, are the basis behind the success of applications and services. Though at first glance these challenges seem to be …

Event-Triggering Architectures For Adaptive Control Of Uncertain Dynamical Systems, Ali Talib Oudah Albattat

Doctoral Dissertations

"In this dissertation, new approaches are presented for the design and implementation of networked adaptive control systems to reduce the wireless network utilization while guaranteeing system stability in the presence of system uncertainties. Specifically, the design and analysis of state feedback adaptive control systems over wireless networks using event-triggering control theory is first presented. The state feedback adaptive control results are then generalized to the output feedback case for dynamical systems with unmeasurable state vectors. This event-triggering approach is then adopted for large-scale uncertain dynamical systems. In particular, decentralized and distributed adaptive control methodologies are proposed with reduced wireless network …

Geophysical Assessment Of Soil And Rock In The New Madrid Seismic Zone, Faraj Mohamed Eljabri

Doctoral Dissertations

"The research presented here consists of two case studies: the first from a study site in Illinois and the second from a site in Arkansas. In both instances, geophysical investigations were conducted to characterize the subsurface. At the Illinois site, borehole control, downhole seismic (DHS), seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW) data were acquired for the purpose of seismic site characterization. Shear wave and compressional wave velocities were used to estimate depth to bedrock and to generate 1-D plots depicting variations in Poisson's Ratio, elastic moduli and density. The average shear wave velocity in the …

Modal Based Bga Modeling In High-Speed Package, Shuai Jin

Doctoral Dissertations

"In the Section 1, the improved "Root-Omega" method for extracting dielectric properties from fabricated multilayer printed circuit boards is proposed. Based on the electrical properties of fabricated transmission lines, the improved "Root-Omega" method applied to cases with smooth and rough conductors is validated using simulations. Error sensitivity analysis is performed to demonstrate the potential errors in the original "Root-Omega" procedure and the error sensitivity is significantly reduced by the proposed improvements.

In the Section 2, a fast modal-based approach is developed to accurately and efficiently capture the proximity effect. Image theory is also applied in the proposed approach to reduce …

Characterization And Numerical Simulation Of The Microstructural And Micromechanical Viscoelastic Behavior Of Oil Sands Using The Discrete Element Method, Eric Kofi Gbadam

Doctoral Dissertations

"Oil sands are naturally geologic formations of predominantly quartz sand grains whose void spaces are filled with bitumen, water, and dissolved gases. The electric rope shovel is the primary equipment used for excavating the Athabasca oil sand formations. The equipment's static and dynamic loads are transferred to the formation during excavation and propel. These loads cause ground instability leading to sinkage or rutting, crawler wear, and fracture failures. These problems result in unplanned downtimes, production losses, and high maintenance costs. In order to address these problems, there is a need to develop valid models that capture the behavior and performance …

Lhd Vibrations Analysis And Numerical Modeling During Operations, Kgosietsile Kolobe

Doctoral Dissertations

"Load-haul-dump vehicles (LHDs) are extensively used as primary loaders in mining operations. LHDs have proven to be vigorous, extremely productive and reliable in mining applications. They have a wide range of tramming capacities that have enabled them to become an essential component in the hard rock mining industry.

Increased mining economic challenges and global competition means the mining industry has to maximize productivity by cutting down operating and capital costs. Also, improvements in safety standards have led to the demand for safer and efficient machines.

LHD operators are at a high risk of whole-body vibrations (WBVs) exposure leading to musculoskeletal …

Optimization Of Solvent Suppression Sequences For Nmr Analysis Of Aqueous Solutions, Annalise Rose Pfaff

Doctoral Dissertations

"When the use of deuterated solvents is precluded in the NMR analysis of biomolecules in their natural environment, pre-saturation solvent suppression pulse sequences are frequently employed to avoid interference from the overbearing solvent signal. However, these sequences generally require extensive re-adjustment of NMR parameters between samples. For this reason, the EXCEPT (EXponentially Converging Eradication Pulse Train) solvent suppression sequence was developed, which exhibits a tolerance of over an order of magnitude in sample T₁ variation. EXCEPT uses an innovative version of "inversion-recovery nulling" with frequency-selective, low-power adiabatic pulses and exponentially decreasing interpulse delays that effectively reduce solvent net magnetization by …

Cognition-Based Approaches For High-Precision Text Mining, George John Shannon

Doctoral Dissertations

"This research improves the precision of information extraction from free-form text via the use of cognitive-based approaches to natural language processing (NLP). Cognitive-based approaches are an important, and relatively new, area of research in NLP and search, as well as linguistics. Cognitive approaches enable significant improvements in both the breadth and depth of knowledge extracted from text. This research has made contributions in the areas of a cognitive approach to automated concept recognition in.

Cognitive approaches to search, also called concept-based search, have been shown to improve search precision. Given the tremendous amount of electronic text generated in our digital …

Characterizing Long-Term Groundwater Conditions And Lithology For The Design Of Large-Scale Borehole Heat Exchangers, David Charles Smith

Doctoral Dissertations

"Construction of large scale ground coupled heat pump (GCHP) systems that operate with hundreds or even thousands of boreholes for the borehole heat exchangers (BHE) has increased in recent years with many coming on line in the past 10 years. Many large institutions are constructing these systems because of their ability to store energy in the subsurface for indoor cooling during the warm summer months and extract that energy for heating during the cool winter months.

Despite the increase in GCHP system systems constructed, there have been few long term studies on how these large systems interact with the subsurface. …

Design And Performance Of Cost-Effective Ultra High Performance Concrete For Bridge Deck Overlays, Mahdi Valipour

Doctoral Dissertations

"The main objective of this research is to develop a cost-effective ultra-high performance concrete (UHPC) for bonded bridge deck overlays. The high durability and mechanical properties of such repair material can offer shorter traffic closures and prolong the service life of the pavement. The UHPC was optimized using supplementary cementitious materials (SCMs), proper combinations of sands, and adequate selection of fiber types and contents. Packing density studies included paste, sand, and fiber combinations. The robustness of optimized UHPC mixtures to variations of mixing and curing temperatures was examined. The efficiency of various shrinkage mitigation approaches in reducing autogenous and drying …

The Maculoprotective Effect Of A Thiol Antioxidant In Retinal Degeneration Models, Hsiu-Jen Wang

Doctoral Dissertations

"Age-related macular degeneration (AMD) is a leading cause of irreversible blindness among adults, age 60 and older, in developed countries. While oxidative stress is implicated in the pathogenesis of AMD, clinical studies have shown that dietary antioxidants can delay progression of AMD. Currently, there is no FDA-approved treatment for AMD. Therefore, we hypothesized that N-acetylcysteine amide (NACA), a thiol antioxidant, would protect retinal pigment epithelium and impede the progression of retinal degeneration. The goal of this work was to evaluate the efficacy of NACA in preventing retinal pigment epithelial cell and photoreceptor death in AMD models. To achieve this, we …

The Influence Of Caprock On Blast Fragmentation Distribution, Matthew Kurtis Coy

Doctoral Dissertations

"This dissertation describes the development of a small-scale model of a caprock-laden quarry blast and discusses the results from that testing. The purpose of this testing was to provide insight into the reasons for poor caprock breakage during blasting.

Small-scale test blocks were poured using a weak mortar mix to represent a limestone formation at a small scale. A cold joint was created in the upper portion of the test specimens to represent the bedding plane that separates caprock and substrate layers in a caprock-laden limestone bench. The scale-model test blocks were blasted using detonating cord. The primary configuration for …

Programming Problems On Time Scales: Theory And Computation, Rasheed Basheer Al-Salih

Doctoral Dissertations

"In this dissertation, novel formulations for several classes of programming problems are derived and proved using the time scales technique. The new formulations unify the discrete and continuous programming models and extend them to other cases "in between." Moreover, the new formulations yield the exact optimal solution for the programming problems on arbitrary isolated time scales, which solve an important open problem. Throughout this dissertation, six distinct classes of programming problems are presented as follows. First, the primal as well as the dual time scales linear programming models on arbitrary time scales are formulated. Second, separated linear programming primal and …

Dirac Surface States Of Magnetic Topological Insulators, Seng Huat Lee

Doctoral Dissertations

"Magnetic topological insulator (TI) has been theoretically proposed to be a platform for inducing magnetic monopole and exhibit fascinating quantum phenomena, whereas topological superconductor can host Majorana fermions, particles that are their own antiparticles, which can be manipulated for topological quantum computing. In this dissertation, we experimentally demonstrated that by intercalation of different transition metals in the van der Waals gaps of Bi₂Se₃ TI, magnetism and even superconductivity can be induced. In Fe_xBi₂Se₃, antiferromagnetism is induced with a transition temperature at ~ 100 K. Coexistence of the Dirac surface state with …

Depositional Systems, Sequence Architecture, And Controlling Factors Of An Eocene Stratigraphic Sequence At Minfeng Steep Margin Of Dongying Depression, Eastern China, Zhixin Li

Doctoral Dissertations

“This study is carried out in Minfeng area, the steep margin of Dongying half graben, eastern China, by integrating 3-D seismic, wireline log, and core data, and aims to interpret the depositional systems, reconstruct sequence stratigraphic architecture, and understand the controlling processes and factors at the steep margin of a rift basin. In the first part of this work, an Eocene stratigraphic sequence is divided into three systems tracts, corresponding to different stages of lake evolution, as early expansion (EEST), late expansion-early contraction (LEECST), and late contraction (LCST). EEST is the thickest and diagnostic by the best-developed marginal and basinal …

Designing High Performance Overall Water Splitting Electrocatalysts From Non-Precious Metal Selenides, Abdurazag T. Swesi

Doctoral Dissertations

“The energy production has been depending mostly on fossil fuel which will be depleted someday in the near future. Aspects such as the loss of energy resources and destruction of the environment have motivated researchers for pursuing transition away from fossil fuels to renewable solar-fuels. Therefore, in order to meet the continuous increasing demand for energy, the hydrogen, with the largest energy density stored in it, can then efficiently be used in fuel cells without concern of contaminants. Water splitting reaction to generate H₂ and O₂ is one promising method of converting solar energy into fuels. The major …

Balanced Truncation Model Reduction Of Nonlinear Cable-Mass Pde System, Madhuka Hareena Lochana Weerasinghe

Doctoral Dissertations

We consider model order reduction of a cable-mass system modeled by a one dimensional wave equation with interior damping and dynamic boundary conditions. The system is driven by a time dependent forcing input to a linear mass-spring system at the left boundary of the cable. A mass-spring model at the right end of the cable includes a nonlinear stiffening force. The goal of the model reduction is to produce a low order model that produces an accurate approximation to the displacement and velocity of the mass in the nonlinear mass-spring system at the right boundary. We believe the nonlinear cable-mass …

Acquisition Of Active Multichannel Analysis Of Surface Waves (Masw) Data In Karst Terrain, Ghassan Salem Alsulaimani

Doctoral Dissertations

"This study was designed to verify the effects and data reproducibility when the length of receiver array, receiver spacing, source offset and array orientation parameters are changed for data acquired using multichannel analysis of surface waves (MASW), at intended target depth of 30ft (9m), and to compare the results with electrical resistivity tomography (ERT) data obtained for the same study site.

The MASW data acquired for 34 sites, along four profiles for each site using variable source offsets of 10ft (3m) and 30ft (9.1m), and variable receiver spacings of 2.5ft (0.76m) and 5.0ft (0.76m), concurrently. Out of the 272 profiles …

Local Holomorphic Extension Of Cauchy Riemann Functions, Brijitta Antony

Doctoral Dissertations

"The purpose of this dissertation is to give an analytic disc approach to the CR extension problem. Analytic discs give a very convenient tool for holomorphic extension of CR functions. The type function is introduced and showed how these type functions have direct application to important questions about CR extension. In this dissertation the CR extension theorem is proved for a rigid hypersurface M in C² given by y = (Re ω)^m(Im ω)ⁿ where m and n are non-negative integers. If the type function is identically zero at the origin, then there is no CR extension. …

Numerical Investigation On Nonlocal Problems With The Fractional Laplacian, Siwei Duo

Doctoral Dissertations

"Nonlocal models have recently become a powerful tool for studying complex systems with long-range interactions or memory effects, which cannot be described properly by the traditional differential equations. So far, different nonlocal (or fractional differential) models have been proposed, among which models with the fractional Laplacian have been well applied. The fractional Laplacian (-Δ)^α/2 represents the infinitesimal generator of a symmetric α-stable Lévy process. It has been used to describe anomalous diffusion, turbulent flows, stochastic dynamics, finance, and many other phenomena. However, the nonlocality of the fractional Laplacian introduces considerable challenges in its mathematical modeling, numerical simulations, and mathematical …

Data Analytics Methods For Attack Detection And Localization In Wireless Networks, Yi Ling

Doctoral Dissertations

"Wireless ad hoc network operates without any fixed infrastructure and centralized administration. It is a group of wirelessly connected nodes having the capability to work as host and router. Due to its features of open communication medium, dynamic changing topology, and cooperative algorithm, security is the primary concern when designing wireless networks. Compared to the traditional wired network, a clean division of layers may be sacrificed for performance in wireless ad hoc networks. As a result, they are vulnerable to various types of attacks at different layers of the protocol stack. In this paper, I present real-time series data analysis …

Repair Of Metallic Components Using Hybrid Manufacturing, Renwei Liu

Doctoral Dissertations

"Many high-performance metal parts users extend the service of these damaged parts by employing repair technology. Hybrid manufacturing, which includes additive manufacturing (AM) and subtractive manufacturing, provides greater build capability, better accuracy, and surface finish for component repair. However, most repair processes still rely on manual operations, which are not satisfactory in terms of time, cost, reliability, and accuracy. This dissertation aims to improve the application of hybrid manufacturing for repairing metallic components by addressing the following three research topics. The first research topic is to investigate and develop an efficient best-fit and shape adaption algorithm for automating 3D models' …

Zero-Dimensional Spaces And Their Inverse Limits, Sahika Sahan

Doctoral Dissertations

"In this dissertation we investigate zero-dimensional compact metric spaces and their inverse limits. We construct an uncountable family of zero-dimensional compact metric spaces homeomorphic to their Cartesian squares. It is known that the inverse limit on [0,1] with an upper semi-continuous function with a connected graph has either one or infinitely many points. We show that this result cannot be generalized to the inverse limits on simple triods or simple closed curves. In addition to that, we introduce a class of zero-dimensional spaces that can be obtained as the inverse limits of arcs. We complete by answering a problem by …