Engineering Commons^™

Radiation Effects On Metastable States Of Superheated Water, Charles William Alvord

Doctoral Dissertations

Radiation Effects on Metastable States of Superheated Water covers theory, application, and experimentation into the behavior of water at temperatures above the boiling point. The backgrounds of Positron Emission Tomography target design, bubble chambers, and superheat measurements are presented. The quantitative theory of metastable liquids and their characteristic waiting time is discussed. Energetics of bubble formation from two different perspectives are included. Finally, the design of an apparatus for measuring liquid superheats in the presence of radiation is covered in some detail, including several design iterations, first measurements made on the apparatus, and techniques for data reduction.

Multispectral Imaging For Face Recognition Over Varying Illumination, Hong Chang

Doctoral Dissertations

This dissertation addresses the advantage of using multispectral narrow-band images over conventional broad-band images for improved face recognition under varying illumination. To verify the effectiveness of multispectral images for improving face recognition performance, three sequential procedures are taken into action: multispectral face image acquisition, image fusion for multispectral and spectral band selection to remove information redundancy.

Several efficient image fusion algorithms are proposed and conducted on spectral narrow-band face images in comparison to conventional images. Physics-based weighted fusion and illumination adjustment fusion make good use of spectral information in multispectral imaging process. The results demonstrate that fused narrow-band images outperform …

Modeling Of Algan/Gan High Electron Mobility Transistor For Sensors And High-Temperature Circuit Applications, Sazia Afreen Eliza

Doctoral Dissertations

With the most advanced and mature technology for electronic devices, silicon (Si) based devices can be processed with practically no material defects. However, Si technology has difficulty meeting the demand for some high-power, high-speed, and high-temperature applications due to limitations in its intrinsic properties. Wide bandgap semiconductors have greater prospects compared to Si based devices. The wide band gap material system shows higher breakdown voltage, lower leakage, higher saturation velocity, larger thermal conductivity and better thermal stability suitable for high-power, high-speed, and high-temperature operations of the devices. In recent years, GaN based devices have drawn much research attention due to …

Nanostructured Chitosan Membranes For Filtration, Keyur Desai

Doctoral Dissertations

Chitosan is a non-toxic and biodegradable biopolymer derived from naturally occurring chitin. It has excellent metal binding and anti-microbial properties which could be beneficial in air and water filtration applications. Nanofibers have distinctly high surface area to volume ratio.

Electrospinning is a process by which nano-sized polymer fibers can be produced using an electrostatically driven jet of polymer solution. The fibers are collected as a non-woven mat and offer a high surface area to volume ratio.

Electrospinning of pure chitosan is hindered by its limited solubility in aqueous acids and high molecular weight with high degree of inter and intra …

Development Of A Computational Model To Predict The In Vivo Contact Mechanics Of Modern Total Knee Arthroplasty, Adrija Sharma

Doctoral Dissertations

This dissertation focuses on the development of a computationally efficient and fast method that incorporates the kinematics obtained from fluoroscopy and extends it to the prediction of the in-vivo contact mechanics at the femoro-tibial articulation in modern knee implants for the deep knee bend activity. In this endeavor, this dissertation deals with the use of an inverse dynamic rigid body model characterizing the slip and roll behavior observed in the femoro-polyethylene articulation and a coupled deformation model where the polyethylene in knee implants are modeled as hexahedral discrete element networks. The performance of this method is tested by comparing force …

A Study Of The Indentation Size Effect In Copper, Jeremy Harper Strader

Doctoral Dissertations

A simple model for an expanding array of screw dislocations is developed to evaluate the size of the containment zone of the geometrically necessary dislocations as it relates to the indentation size effect. The model as developed predicts the same functional form as the Nix-Gao model, H²=H₀²(1+h^*/h), but a new relation for h^* applies that depends only on the Burgers vector and the Taylor constant, where as the Nix-Gao model predicts a strong dependence of the macroscopic hardness and the tip angle. The continuous stiffness method, CSM, is critically examined using experimental …

Uncertainty Minimization In Robotic 3d Mapping Systems Operating In Dynamic Large-Scale Environments, Sreenivas Rangan Sukumar

Doctoral Dissertations

This dissertation research is motivated by the potential and promise of 3D sensing technologies in safety and security applications. With specific focus on unmanned robotic mapping to aid clean-up of hazardous environments, under-vehicle inspection, automatic runway/pavement inspection and modeling of urban environments, we develop modular, multi-sensor, multi-modality robotic 3D imaging prototypes using localization/navigation hardware, laser range scanners and video cameras.

While deploying our multi-modality complementary approach to pose and structure recovery in dynamic real-world operating conditions, we observe several data fusion issues that state-of-the-art methodologies are not able to handle. Different bounds on the noise model of heterogeneous sensors, the …

Mechanical Behavior Of A Ni-Based Crystalline And A Zr-Based Amorphous Materials Subjected To Surface Severe Plastic Deformation, Jiawan Tian

Doctoral Dissertations

A surface-treatment process, surface-severe-plastic deformation (S²PD), is developed and applied on both crystalline and amorphous materials to introduce the plastic deformation in the near-surface layer. A S²PD-processed crystalline component is expected to have enhanced fatigue properties because the refined grains in the near-surface layer and the coarse grains in the interior have good resistance to the crack initiation and propagation, respectively.

The near-surface structures of the processed specimens were characterized by means of the optical microscopy, scanning-electron microscopy (SEM), X-ray diffraction (XRD), and transmission-electron microscopy (TEM). Mechanical properties, such as the microhardness, yield strength, and four-point-bend …

Reliability Analysis Of Hafnium Oxide Dielectric Based Nanoelectronics, Rui Wan

Doctoral Dissertations

With the physical dimensions ever scaling down, the increasing level of sophistication in nano-electronics requires a comprehensive and multidisciplinary reliability investigation. A kind of nano-devices, HfO₂-based high-k dielectric films, are studied in the statistical aspect of reliability as well as electrical and physical aspects of reliability characterization, including charge trapping and degradation mechanisms, breakdown modes and bathtub failure rate estimation.

This research characterizes charge trapping and investigates degradation mechanisms in high-k dielectrics. Positive charges trapped in both bulk and interface contribute to the interface state generation and flat band voltage shift when electrons are injected from the gate …

Localized Corrosion Behavior Of Zr-Based Bulk Metallic Glasses In Neutral Nacl Electrolytes, Brandice Annette Green

Doctoral Dissertations

The electrochemical behaviors the Zr₅₀Cu₄₀Al₁₀, Zr₅₀Cu₃₃Al₁₀Pd₇, and Zr_52.5Cu_17.9Al₁₀Ni_14.6Ti_5.0 BMGs were investigated in NaCl solutions. Both Zr₅₀Cu₄₀Al₁₀ and Zr₅₀Cu₃₃Al₁₀Pd₇ exhibited poor corrosion behaviors. Zr₅₀Cu₄₀Al₁₀ was vulnerable to localized corrosion at the open-circuit conditions (OCC). Zr₅₀Cu₃₃Al₁₀Pd₇ experienced localized corrosion at OCC or at slightly higher potentials. Anodic-polarization of both alloys demonstrated that small increases in …

Investigation Of Propagation Characteristics Of Twisted Hollow Waveguides For Particle Accelerator Applications, Joshua Lee Wilson

Doctoral Dissertations

A new class of accelerating structures employing a uniformly twisted waveguide is investigated. Twisted waveguides of various cross-sectional geometries are considered and analyzed. It is shown that such a twisted waveguide can support waves that travel at a speed slower than the speed of light c. The slow-wave properties of twisted structures are of interest because these slow-wave electromagnetic fields can be used in applications such as electron traveling wave tubes and linear particle accelerators.

Since there is no exact closed form solution for the electromagnetic fields within a twisted waveguide or cavity, several previously proposed approximate methods are examined, …

System-On-Package Low-Power Telemetry And Signal Conditioning Unit For Biomedical Applications, Mohammad Rafiqul Haider

Doctoral Dissertations

Recent advancements in healthcare monitoring equipments and wireless communication technologies have led to the integration of specialized medical technology with the pervasive wireless networks. Intensive research has been focused on the development of medical wireless networks (MWN) for telemedicine and smart home care services. Wireless technology also shows potential promises in surgical applications. Unlike conventional surgery, an expert surgeon can perform the surgery from a remote location using robot manipulators and monitor the status of the real surgery through wireless communication link. To provide this service each surgical tool must be facilitated with smart electronics to accrue data and transmit …

Hardware Development Of An Ultra-Wideband System For High Precision Localization Applications, Cemin Zhang

Doctoral Dissertations

A precise localization system in an indoor environment has been developed. The developed system is based on transmitting and receiving picosecond pulses and carrying out a complete narrow-pulse, signal detection and processing scheme in the time domain. The challenges in developing such a system include: generating ultra wideband (UWB) pulses, pulse dispersion due to antennas, modeling of complex propagation channels with severe multipath effects, need for extremely high sampling rates for digital processing, synchronization between the tag and receivers’ clocks, clock jitter, local oscillator (LO) phase noise, frequency offset between tag and receivers’ LOs, and antenna phase center variation. For …

Magnetic Field Effects On Photocurrent And Photovoltaic Processes In Organic Solar Cells, Zhihua Xu

Doctoral Dissertations

Two mechanisms were investigated to understand the magnetic field effects on photocurrent (MFP), a phenomenon whereby an external magnetic field (MF) can increase or decrease photocurrent in organic solar cells (OSCs). The first one relates to MF-modulated intersystem crossing (ISC) between singlet and triplet polaron pairs and charge transfer (CT) complexes, accounting for the positive MFP in low and high magnetic field, respectively. The second mechanism originates from the interaction between triplet excited states and charge carriers, namely triplet-charge reaction (TCR). External magnetic field was found to reduce the rate constant of TCR, leading to negative MFP.

MFP measurements were …

Mrf Stereo Matching With Statistical Estimation Of Parameters, Mohammad Shafikul Huq

Doctoral Dissertations

For about the last ten years, stereo matching in computer vision has been treated as a combinatorial optimization problem. Assuming that the points in stereo images form a Markov Random Field (MRF), a variety of combinatorial optimization algorithms has been developed to optimize their underlying cost functions. In many of these algorithms, the MRF parameters of the cost functions have often been manually tuned or heuristically determined for achieving good performance results. Recently, several algorithms for statistical, hence, automatic estimation of the parameters have been published. Overall, these algorithms perform well in labeling, but they lack in performance for handling …

Label-Free Mapping Of Near-Field Transport Properties Of Micro/Nano-Fluidic Phenomena Using Surface Plasmon Resonance (Spr) Reflectance Imaging, Iltai Kim

Doctoral Dissertations

My doctoral research has focused on the development of surface plasmon resonance (SPR) reflectance imaging technique to detect near-field transport properties such as concentration, temperature, and salinity in micro/nano fluidic phenomena in label-free, real-time, and full-field manner. A label-free visualization technique based on surface plasmon resonance (SPR) reflectance sensing is presented for real-time and full-field mapping of microscale concentration and temperature fields. The key idea is that the SPR reflectance sensitivity varies with the refractive index of the near-wall region of the test mixture fluid. The Fresnel equation, based on Kretschmann’s theory, correlates the SPR reflectance with the refractive index …

Reliability In Lean Systems, Robert S. Keyser

Doctoral Dissertations

Implementation of Lean manufacturing systems often turn into expensive hit-or-miss propositions. Whereas many organizations that lack immediate success quickly abandon their ‘Lean’ plans in hopes that the next great marketing panacea will solve their efficiency woes, organizations that experience early success often have difficulty in sustaining their Lean efforts. To further exacerbate the dilemma, knowledge of the reliability of Lean systems is currently inadequate. This paper proposes a contemporary Lean paradigm – reliability in Lean systems – through the development of an innovative Lean System Reliability model (LSRM). Principally, LSRM models the reliability of Lean subsystems as a basis for …

Stochastic Modeling And Estimation Of Wireless Channels With Application To Ultra Wide Band Systems, Yanyan Li

Doctoral Dissertations

This thesis is concerned with modeling of both space and time variations of Ultra Wide Band (UWB) indoor channels. The most common empirically determined amplitude distribution in many UWB environments is Nakagami distribution. The latter is generalized to stochastic diffusion processes which capture the dynamics of UWB channels. In contrast with the traditional models, the statistics of the proposed models are shown to be time varying, but converge in steady state to their static counterparts.

System identification algorithms are used to extract various channel parameters using received signal measurement data, which are usually available at the receiver. The expectation maximization …

Safdetection:Sensor Analysis Based Fault Detection In Tightly-Coupledmulti-Robot Team Tasks, Xingyan Li

Doctoral Dissertations

This dissertation addresses the problem of detecting faults based on sensor analysis for tightly-coupled multi-robot team tasks. The approach I developed is called SAFDetection, which stands for Sensor Analysis based Fault Detection, pronounced “Safe Detection”. When dealing with robot teams, it is challenging to detect all types of faults because of the complicated environment they operate in and the large spectrum of components used in the robot system. The SAFDetection approach provides a novel methodology for detecting robot faults in situations when motion models and models of multi-robot dynamic interactions are unavailable. The fundamental idea of SAFDetection is to build …

The Future Of The Operating Room: Surgical Preplanning And Navigation Using High Accuracy Ultra-Wideband Positioning And Advanced Bone Measurement, Brandon C. Merkl

Doctoral Dissertations

This dissertation embodies the diversity and creativity of my research, of which much has been peer-reviewed, published in archival quality journals, and presented nationally and internationally. Portions of the work described herein have been published in the fields of image processing, forensic anthropology, physical anthropology, biomedical engineering, clinical orthopedics, and microwave engineering.

The problem studied is primarily that of developing the tools and technologies for a next-generation surgical navigation system. The discussion focuses on the underlying technologies of a novel microwave positioning subsystem and a bone analysis subsystem. The methodologies behind each of these technologies are presented in the context …

Deformation And Fatigue Behavior Of Bulk-Metallic Glasses (Bmgs), Dongchun Qiao

Doctoral Dissertations

The objectives of the thesis research are 1) to study the strain rate effect on the deformation behavior of bulk-metallic glasses (BMGs), 2) to investigate the loading mode effect on the fatigue behavior of BMGs.

The main results are obtained as follows. At room temperature, during the inhomogeneous deformation, BMGs show the strain softening caused by the increase of the free volume in the shear bands. However, BMGs have a high-energy state and trend to crystallize, especially in the shear bands with the maximum shear stress and the increasing temperature. The instability of BMGs makes it possible for strain hardening. …

Person-Environment Fit And Readiness For Change: Exploring The Moderating Role Of Leader-Member Exchange And Perceived Organizational Support, Joana R.C. Pimentel

Doctoral Dissertations

This paper was aimed at investigating the interplay of multiple facets of personenvironment fit with individual readiness for change; and to expose potential moderators of this relationship, namely organizational support and quality of relationship with supervisors. The extant research on the relationships between person-environment fit and a number of individual- and organization-level outcomes reveals considerable discrepancies, mainly attributed to the measurement of person-environment fit and to potential moderators. With this in mind, moderated multiple regressions (MMR) were conducted in order to test the hypotheses of existing interaction effects.

The results revealed no significant interactions between facets of personenvironment fit and …

Imaging Of Buried Utilities By Ultra Wideband Sensory Systems, Arun Prakash Jaganathan

Doctoral Dissertations

Third-party damage to the buried infrastructure like natural gas pipelines, water distribution pipelines and fiber optic cables are estimated at $10 billion annually across the US. Also, the needed investment in upgrading our water and wastewater infrastructure over the next 20 years is estimated by Environmental Protection Agency (EPA) at $400 billion, however, non-destructive condition assessment technologies capable of providing quantifiable data regarding the structural integrity of our buried assets in a cost-effective manner are lacking. Both of these areas were recently identified several U.S. federal agencies as 'critical national need'. In this research ultra wideband (UWB) time-domain radar technology …

Dose Modeling And Statistical Assessment Of Hot Spots For Decommissioning Applications, Eric Warner Abelquist

Doctoral Dissertations

A primary goal of this research was to develop a technically defensible approach for modeling the receptor dose due to smaller "hot spots" of residual radioactivity. Nearly 700 combinations of environmental pathways, radionuclides and hot spot sizes were evaluated in this work. The hot spot sizes studied ranged from 0.01 m² to 10 m², and included both building and land area exposure pathways. Dose modeling codes RESRAD, RESRAD-BUILD, and MicroShield were used to assess hot spot doses and develop pathway-specific area factors for eleven radionuclides. These area factors are proposed for use within the existing Multiagency Radiation …

Evaluation Of Experimental Bridges In Tennessee, David P. Chapman

Doctoral Dissertations

This dissertation presents an overview and evaluation of an effort of the Tennessee Department of Transportation (TDOT) to design multispan steel girder bridges that can be erected with minimal disruption to traffic passing under the proposed spans. TDOT has developed the Pier-Plate Moment Connection in order to facilitate the accelerated construction of steel girder bridges. This connection allows the girders of a multispan steel bridge to be erected as simple spans and then to be made continuous prior to the dead load of the deck being applied. Since 2003, the Department of Civil and Environmental Engineering at the University of …

Elastic Properties Of Bulk-Metallic Glasses Studied By Resonant Ultrasound Spectroscopy, Zhiying Zhang

Doctoral Dissertations

The elastic properties of a solid are of considerable interest to both science and technology. Not only do they contain fundamental information about the nature of the inter-atomic bonding in the material, but they also determine the mechanical behavior of solids. In the past few years, considerable effort has been devoted to the study of elastic properties of bulk metallic glasses (BMGs), a relatively new class of metallic materials that display a unique combination of mechanical and physical properties. Our research has focused on Zr-based, Cu-based and Ca-based metallic glasses. Zr-based BMGs are known to have superior glass forming ability …

Integration Of Spatial And Spectral Information For Hyperspectral Image Classification, Zheng Du

Doctoral Dissertations

Hyperspectral imaging has become a powerful tool in biomedical and agriculture fields in the recent years and the interest amongst researchers has increased immensely. Hyperspectral imaging combines conventional imaging and spectroscopy to acquire both spatial and spectral information from an object. Consequently, a hyperspectral image data contains not only spectral information of objects, but also the spatial arrangement of objects. Information captured in neighboring locations may provide useful supplementary knowledge for analysis. Therefore, this dissertation investigates the integration of information from both the spectral and spatial domains to enhance hyperspectral image classification performance.

The major impediment to the combined spatial …

Extraction Of Proteins By Winsor Iii Microemulsion Systems, Javier Alejandro Gomez Del Rio

Doctoral Dissertations

Purification of proteins by microemulsion was improved through use of a 3-phase (“Winsor-III”) microemulsion system instead of the traditionally employed 2-phase (“Winsor-II”) water-in-oil microemulsion system. As a consequence, two of the main problems of the traditional method were improved: the low and slow rate of recovery of proteins encapsulated by the microemulsions and the low protein solubilization capacity of the microemulsions.

Microemulsion systems employed a mixture of surfactants, two pH-degradable “cyclic ketal” alkyl ethoxylates (O-[(2-tridecyl, 2-ethyl-1,3-dioxolan-4-yl) methoxy]–O’- methoxy poly(ethylene glycol)_n , where n, the average degree of polymerization for the ethoxylate group, equaled 3.0 or 5.45, CK3 and CK7, …

Development And Implementation Of Mathematical Modeling, Vibration And Acoustic Emission Technique To Correlate In Vivo Kinematics, Kinetics And Sound In Total Hip Arthroplasty With Different Bearing Surfaces, Diana Andreeva Glaser

Doctoral Dissertations

The evaluation of Total Hip Arthroplasty (THA) outcome is difficult and invasive methods are often applied. Fluoroscopy has been used as an in vivo diagnostic technique to determine separation which may lead to vibration propagation and audible interactions. The objective of this study was to develop a new, non-invasive technique of digitally capturing vibration and sound emissions at the hip joint interface and to correlate those with the hip kinematics derived from fluoroscopy. Additionally, an examination of the role of hip mechanics on walking performance in THA subjects of various bearings surfaces was performed.

In vivo kinematics, kinetics, corresponding vibration …

Antennas And Arrays For Mobile Platforms -- Direct Broadcast Satellite And Wireless Communication, Songnan Yang

Doctoral Dissertations

Flexibility of any proposed communication links is becoming one of the most challenging features. Direct broadcasting satellite services, for example, will be greatly enhanced by providing service-on-the-move. This market is very demanding as it necessitates the development of a low cost, low profile antenna that can be mounted on top of SUVs and minivans, which is capable of continuously tracking the satellite. Another example is the wireless antennas for laptops and smart-phones, where the antennas should fit within an extremely small volume and should be capable of addressing many services over wide frequency range. In this dissertation, both DBS and …