Engineering Commons^™

Fabrication And Characterization Of Nanoelectronic Devices For Electron Beam Lithography Applications, Xiaojing Yang

Doctoral Dissertations

Vertically aligned carbon nanofibers (VACNFs) have shown promise for use as field emission electron sources. Dual-gate field emission structures (triodes) have been fabricated and characterized. The electron beams can be successfully focused in these triodes. These studies show VACNF based field emission devices are promising for electron beam lithography applications. In this thesis, work is continued on triode device investigation. Methods to improve the device fabrication, to understand/optimize the device performance, and to repair defective triodes are presented.

Numerical simulation of the triode performance is included. Depth of field (DOF) of these triode structures is calculated by simulation and is …

Novel Approaches In The Thermal Management Of Electronics Involving Coupled Electrical, Thermal And Cfd Analysis, Bahram Zandi

Doctoral Dissertations

The cooling of electronic components is one of the most important tasks in the design packaging of electronic equipments as insufficient thermal control can lead to low reliability, short life, and failure of the electronic components. According to a study conducted by Philips Corporation, every ten degree Celsius increase in temperature causes a fifty percent decrease in the operating life of many integrated circuits.

With the increasing design complexities and reliability requirements, today’s electronic design engineers rely significantly on software packages (often based on methods of Computational Fluid Dynamics, or CFD) for the prediction of electronics operational temperature. In the …

Coupling Analysis, Simulation, And Experimentation In Natural And Engineered Biological Systems At The Molecular Scale, Derek W. Austin

Doctoral Dissertations

Cellular functions are controlled by genetic regulatory networks called gene circuits. Recently, there has been much interest in how gene circuits deal with or even exploit stochastic fluctuations in molecular species within the cellular environment. Through a coupling of analysis and simulation with experimentation, this dissertation work furthers the understanding of gene circuit noise behavior and makes significant contributions to the analytical and experimental tools that are currently available for the study and design of natural and synthetic gene circuits. In this study, models are developed for unregulated and autoregulated gene circuits. Results from the analysis are compared to computer …

On-Line Structural Integrity Monitoring And Defect Diagnosis Of Steam Generators Using Analysis Of Guided Acoustic Waves, Baofu Lu

Doctoral Dissertations

Integrity monitoring and flaw diagnostics of flat beams and tubular structures was investigated in this research using guided acoustic signals. The primary objective was to study the feasibility of using imbedded sensors for monitoring steam generator and heat exchanger tubing. A piezo-sensor suite was deployed to activate and collect Lamb wave signals that propagate along metallic specimens. The dispersion curves of Lamb waves along plate and tubular structures were generated through numerical analysis. Several advanced techniques were explored to extract representative features from acoustic time series. Among them, the Hilbert-Huang transform (HHT) is a recently developed technique for the analysis …

Adaptive Control Of Axisymmetric Jets By Cavities, Abraham Joseph Meganathan

Doctoral Dissertations

Actuators capable of producing large amplitude oscillations at desired frequencies are needed in many flow control applications. In this dissertation, turbulent jets were actuated using self-sustaining oscillations in axisymmetric cavities. Tested geometries include baseline turbulent jets passing through axisymmetric cavities, with and without peripheral walls. Cavity length to depth ratio (Lc/Dc) was varied from 1 to 5 and data were collected at several intermediate steps. Tests were performed with air over a Reynolds number, based on jet exit diameter, range of 40,000 to 225,000 in low to high subsonic jet flow conditions. Pressure signals, 2D velocity data obtained using Particle …

Energy Efficient Designs For Collaborative Signal And Information Processing Inwireless Sensor Networks, Yingyue Xu

Doctoral Dissertations

Collaborative signal and information processing (CSIP) plays an important role in the deployment of wireless sensor networks. Since each sensor has limited computing capability, constrained power usage, and limited sensing range, collaboration among sensor nodes is important in order to compensate for each other’s limitation as well as to improve the degree of fault tolerance. In order to support the execution of CSIP algorithms, distributed computing paradigm and clustering protocols, are needed, which are the major concentrations of this dissertation.

In order to facilitate collaboration among sensor nodes, we present a mobile-agent computing paradigm, where instead of each sensor node …

Charge Transport Measurements Of Vertically Aligned Carbon Nanofiber, Lan Zhang

Doctoral Dissertations

Vertically aligned carbon nanofibers (VACNFs) have found a variety of electronic applications. To further realize these applications, a good understanding of the charge transport properties is essential. In this work, charge transport properties have been systematically measured for three types of VACNF forests with Ni as catalyst, namely VACNFs grown by direct current PECVD, and inductively coupled PECVD at both normal pressure (3.6 Torr) and low pressure (50 mTorr).

The structure and composition of these nanofibers have also been investigated in detail prior to the charge transport measurements. It has been found that the dc VACNF body consists of three …

An Integrated Approach To Performance Monitoring And Fault Diagnosis Of Nuclear Power Systems, Ke Zhao

Doctoral Dissertations

In this dissertation an integrated framework of process performance monitoring and fault diagnosis was developed for nuclear power systems using robust data driven model based methods, which comprises thermal hydraulic simulation, data driven modeling, identification of model uncertainty, and robust residual generator design for fault detection and isolation. In the applications to nuclear power systems, on the one hand, historical data are often not able to characterize the relationships among process variables because operating setpoints may change and thermal fluid components such as steam generators and heat exchangers may experience degradation. On the other hand, first-principle models always have uncertainty …

Development Of An Electronic System For Field-Scale Geomorphometric Measurements, Roberto Negrão Barbosa

Doctoral Dissertations

Terrain attributes are among the most studied soil characteristics. Although important, in only a few areas are topographic features mapped at the field-scale level. These features play an important role in assessing the crop production potential and erosion susceptibility of agricultural fields. Therefore high-resolution mapping of terrain attributes are vital to a better management of production fields. Today, terrain attributes are derived from elevation measurement.
A more direct form of measurement was developed by Rowe and Spencer (1976), pitch and roll angles were used to derive slope gradient and vehicle attitude. Yang (1997) related vehicle attitude to slope aspect. The …

Multimodal Three Dimensional Scene Reconstruction, The Gaussian Fields Framework, Fayçal Boughorbel

Doctoral Dissertations

The focus of this research is on building 3D representations of real world scenes and objects using different imaging sensors. Primarily range acquisition devices (such as laser scanners and stereo systems) that allow the recovery of 3D geometry, and multi-spectral image sequences including visual and thermal IR images that provide additional scene characteristics. The crucial technical challenge that we addressed is the automatic point-sets registration task. In this context our main contribution is the development of an optimization-based method at the core of which lies a unified criterion that solves simultaneously for the dense point correspondence and transformation recovery problems. …

Crystallization Of Random Propylene-Ethylene Copolymers At Atmospheric And High Pressures, Anita Dimeska

Doctoral Dissertations

One of the main goals of the polymer research is to modify the properties of polymers in order to increase the range of their end−use applications. This is especially true in the case of isotactic polypropylene (

i−PP). By simple modification of the molecular structure of i−PP with small amount of comonomer a variety of polymer grades with different characteristics can be produced. Random propylene copolymers with low ethylene content have lower crystallinity and melting temperatures than the homopolymer, as well as ability to crystallize into γ−crystal form of i−PP at atmospheric pressure. Isothermal crystallization of i−PP under high pressure …

Active Harmonic Elimination In Multilevel Converters, Zhong Du

Doctoral Dissertations

The modulation technique for multilevel converters is a key issue for multilevel converter control. The traditional pulse width modulation (PWM), space vector PWM, and space vector control methods do not completely eliminate specified harmonics. In addition, space vector PWM and space vector control method cannot be applied to multilevel converters with unequal DC voltages. The carrier phase shifting method for traditional PWM method also requires equal DC voltages. The number of harmonics that can be eliminated by the selective harmonic elimination method is restricted by the number of unknowns in the harmonic equations and available solutions.

For these reasons, this …

Mosfet Modeling, Simulation And Parameter Extraction In 4h- And 6h- Silicon Carbide, Md Hasanuzzaman

Doctoral Dissertations

This thesis presents the work on analytical modeling and simulation of a silicon carbide (SiC) power MOSFET, model verification with test data, and device characterization and parameter extraction of the SPICE model. The development of temperature models for a lateral as well as a vertical MOSFET in SiC are also presented.

The model takes into account the various short channel effects in the DIMOS channel region as well as the velocity saturation effect in the drift region. Considering the SiC material processing limitations and feedback from the system level application group, an application specific SiC power MOSFET structure has been …

Effects Of Heavy-Duty Diesel Vehicle Idling Emissions On Ambient Air Quality At A Truck Travel Center And Air Quality Benefits Associated With Advanced Truck Stop Electrification Technology, Guenet Tilahun Indale

Doctoral Dissertations

United States Department of Transportation (DOT) requires truck drivers to rest for 10 hours after every 14 hours of driving. During this time and while waiting for loading and unloading of their trucks, truck drivers idle their engine to provide heat or air conditioning for the cab and sleeping compartment, keep the engine warm during cold climate, and provide electrical power for their onboard appliances. At large truck stops, 200 or more trucks may be idling at the same time. At these truck stops idling emissions can significantly contribute to the concentrations of NOx and PM_2.5 pollutants in the …

Load Balancing In Parallel And Distributed Databases, Zhong Tang

Doctoral Dissertations

This dissertation addresses the load balancing problem for parallel computations in the presence of time delays from a control system design perspective. Extensive experiments in a parallel computing environment have been made to evaluate load balancing strategies, and have driven the continued evolution of the parallel computation model and the load balancing strategies.

The critical feature of the load balancing problem is the delayed receipt of information and transferred load. In this work, load balancing in a parallel computer architecture is first modeled as a deterministic time-delay system with saturations. Three essential properties of the load balancing strategy, including consistency, …

Dynamic Response Analysis Of The Human Knee Joint, Brandi L. Bohleber

Masters Theses

Objective. To perform frequency response analysis of passive intact and rneniscectomized human knee joints under body mass. The knee dynamic system parameters and their alterations with different preloads and displacement amplitudes will be determined.

Design. Using an Instron Mechanical Testing System, specially designed fixtures, and the following softwares: WaveMaker, Excel, LabView, and Matlab, the knees were dynamically tested and analyzed.

Background. Studies have been performed to analyze the dynamic behavior of the human knee. However, no experimental study has investigated the dynamic response of the knee joint under an axial compressive dynamic loading condition considering the effect of the upper …

Modeling Of Unreinforced Construction Joints In Plain Concrete Using Gt Strudl, James Christopher Carroll

Masters Theses

The purpose of this study was to develop a method to predict the behavior of unreinforced concrete construction joints using the computer program GT STRUDL. Two three-dimensional finite element models of a navigation lock wall were constructed. The wall was subjected to eccentric prestress forces, which brought about concern for lift-off within the lock wall.

Eleven loading combinations were evaluated, which were created from seven independent loading conditions. Stresses for each loading combination were compared to nominal strength values as detennined by ACI 318-02, Chapter 22, for plain concrete. Results show the stresses to be acceptable throughout the wall and …

An Evaluation Of Alternative Permissive Periods On Non-Coordinated Phase Performance In Coordinated Traffic Signal Systems, Manoel Mendonca De Castro-Neto

Masters Theses

Currently, there are some concerns regarding coordinated-actuated traffic signal operations. First of all, there is no consistent nomenclature to describe coordination modes. Different traffic signal controller manufacturers use different terminologies and their terms are not necessarily meaningful or intuitive. Actually, one can find inconsistency in the terminology used even by a specific manufacturer just by trying to understand (or decipher) the manual. Secondly, and this might be just a consequence of the first concern, it seems that many traffic engineers and technicians are not aware of the particularities and differences among the coordination modes.

The main purpose of this study …

The Evaluation Of The Low Probability Of Intercept Altimeter (Lpia) And Its Impact On Ea-6b Operations, Daniel Philip Covelli

Masters Theses

The purpose of this study was to evaluate the performance of the Low Probability of Intercept Altimeter (LPIA) Radar Altimeter (RADALT), which was selected to replace the AN/APN-194 RADALT, as installed in the EA-6B Prowler and conclude how the new system will impact the tactical operation of the EA-6B aircraft if allowed to proceed to and pass the operational phase of testing in its current status.

The LPIA was selected to replace the APN-194 as part of the overall EA-6B aircraft Block III test program in order to comply with the Chief of Naval Operations’ (CNO’s) mandate to install the …

Polyampholyte Hydrogel Characteristics And Detecting The Bacterial Interactions With These Hydrogels Using Digital Image Processing Methods, Ram Pratap Gangadharan

Masters Theses

In recent years, the unique physical properties of synthetic hydrogels have been exploited in a number of interesting and novel applications. In particular polyampholytes have been the subject of many theoretical studies since they provide a model for studying the longrange interactions found in proteins and other forms of soft condensed matter. In balanced polyampholytes the net electrostatic forces are attractive so that in low ionic salt concentration, the chains have a tendency to collapse into compact globules. Addition of salt, which screens these interactions, induces a swelling of the chain. However the electrostatic interactions between polymeric and mobile charges …

Modeling And Simulation Of A Trailer With Band Track Over Wheels, Hemmant Gopal

Masters Theses

No abstract provided.

Comparison Between Tapered Element Microbalance (Teom) And Federal Reference Method (Frm) For Pm2.5 Measurement In East Tennessee, David Scott Greene

Masters Theses

Particulate matter (PM) of 2.5 microns or less is linked to serious negative health and visibility effects, and consequently is gaining increased regulatory attention. Therefore, accurate and timely measurement of ambient PM_{2.5 is an essential task for both researchers pursuing productive investigations, and local air quality administrators in evaluating, modeling, planning for compliance, and generally making the highest productive use of their control resources. However, accurate and timely may be conflicting needs.}

Many studies have concluded that a significant difference in measurements exists between the Tapered Element Oscillating Microbalance Monitors (TEOM) and the Federal Reference Method (FRM). The difference …

Using Helmet Mounted Displays To Designate And Locate Targets In The Urban Environment, Freddie Paul Henderson

Masters Theses

Technologies have developed within the last ten years to allow the Helmet Mounted Display (HMD) to be much more effective as an air-to-ground (A/G) weapons cue. HMD A/G accuracy and performance requirements should be added to the Joint Helmet Mounted Cueing System (JHMCS) specifications, detailed to be as good or better than the FA-18 heads-up-display (HUD). Because of target ranging and line-of-sight (LOS) errors, the JHMCS is only used as an area sensor cue in the urban close air support (CAS) role. Therefore, for use against point targets, improvements to JHMCS are needed. LOS errors have to be reduced from …

Long Range Interdiction: Effects Based Justification Of The B-1b Lancer Aircraft, Stanley Clay Jones

Masters Theses

The purpose of this study was to evaluate the B-1B aircraft for the land-based, long-range, ground attack mission and to use that evaluation to support my belief that the B-1B aircraft provides a better platform than U.S. Naval fighter aircraft for the same, based on the effects that each aircraft delivers.

One flight totaling 6.5 hours was flown by the author in the B-1B aircraft during daylight visual meteorological conditions (VMC) and included low level flight, aerial refueling, low altitude weapons delivery, threat simulation at an Electronic warfare range, and terminal area operations. This flight was used to evaluate the …

Investigation Of A Phase Transition In Pure And Magnesia- And Titania-Substituted Hexacelsian, Melanie Jean Kirkham

Masters Theses

Hexacelsian, the hexagonal polymorph of BaAl_{2Si2O8, experiences a phase transition near 300ºC with an accompanying large volume change, which can lead to cracking and thermal shock, limiting the potential applications of hexacelsian. It has previously been reported that certain additions, including MgO and TiO2, can suppress the undesirable phase transition. Room-temperature neutron and high-temperature X-ray diffraction have been used to study the structure and thermal behavior of hexacelsian, both pure and substituted with varying amounts of MgO and TiO2. The diffraction data of the pure sample was refined using the}

P-3 space group. Attempting to refine the substituted sample …

Time-Varying Autoregressive Modeling Of Nonstationary Signals, Xiaolin Luo

Masters Theses

Nonstationary signal modeling is a research topic of practical interest. In this thesis, we adopt a time-varying (TV) autoregressive (AR) model using the basis function (BF) parameter estimation method for nonstationary process identification and instantaneous frequency (IF) estimation. The current TVAR model in direct form (DF) with the blockwise least-squares and recursive weighted-least-squares BF methods perform equivalently well in signal modeling, but the large estimation error may cause temporary instabilities of the estimated model.

To achieve convenient model stability monitoring and pole tracking, the TVAR model in cascade form (CF) was proposed through the parameterization in terms of TV poles …

Assessments Of Vibratory Handheld Tools And Handle Interactions, Douglas Alan Logsdon

Masters Theses

There has been a broad history of injuries occurring as the result of vibratory hand-tool use. Following these findings, three human safety standards have been proposed. These standards declare that the dynamic properties with respect to acceleration frequency spectra must be determined for vibratory hand tools. These properties must meet specific tolerances in order to be considered acceptable for use.

The standards, however, do not recognize the significance of the coupling characteristics and the energy transfer between the user and vibrating handle. This interaction reveals the amount of vibratory energy that enters the user's hands. Epidemiological data for VWF shows …

A Performance Analysis Of The Cmaq Model And Its Sensitivity To Ozone Precursors In East Tennessee, Karthikeyan Ramaswamy

Masters Theses

This paper presents the results of sensitivity analyses and its effect on ozone concentrations in East Tennessee. The objective of this research was to conduct a sensitivity analysis on ozone precursor emissions. In this research, the Models- 3/Community Multiscale Air Quality (CMAQ) and Sparse Matrix Operator Kernel Emissions (SMOKE) models were utilized to predict base case ozone concentrations based on 1999 National Emission Inventory (NEI) in East Tennessee from August 27th to September 9th, 1999. The modeling domain consisted of a three tiered nested domain with grid resolutions of 36 km, 12 km and 4km. The 4 km domain covered …

Synthesis And Analysis Of Anionic Hydrogel Scaffolds For Endothelial Cell Tissue Engineering, Abitha Sundararajan

Masters Theses

Acidic hydrogels are cross-linked polymer networks that contain neutral and negatively charged monomers. The degree of negative charge on these soft materials plays a critical role in their biomedical applications. In particular, their use as a scaffold for cardiovascular applications depends on their charged and swollen states. The amount of negative charge, however, is a complicated function of the fabrication conditions, monomeric dissociation constants, ionic strengths and pH of the surround bath solution. This study, therefore, considered four representative acidic hydrogels and their physical properties and interactions with endothelial cells. The acidic monomers methacrylic acid (MAAc) and sulfoethylmethacrylate (SEMA) were …

Evaluation Of The Effects On Human Performance Characteristics And Peak Head Accelerations With The Use Of Various Intra-Oral Appliances, Katie Lin Padgett

Masters Theses

Various studies have investigated the relationship between the mandibular position and its affect on human performance characteristics. To maintain the jaw in an optimal position Mandibular Orthopedic Repositioning Appliances (MORA) have been produced. A protective mouthguard is an appliance worn in the mouth which helps prevent injuries to the teeth, lips, cheek, tongue, and jaw as a result of impact. More recently, it has been hypothesized that mouthguards reduce the risk of concussion by attenuating the impact to the jaw rather than transferring the force to the brain. Currently, there are no standards for testing protective mouthguards. Such a test …