Engineering Commons^™

Develop Novel Frap Techniques For Determining Anisotropic Solute Diffusion In Cartilaginous Tissues, Changcheng Shi

All Dissertations

Cartilaginous tissue is a connective tissue composed of specialized cells (e.g., chondrocytes and fibroblasts) that produce a large amount of extracellular matrix (ECM), which is comprised mostly of collagen fibers, abundant ground substance rich in proteoglycan, and elastic fibers. It is characterized by its avascular structures within the tissue, implying that nutrition for normal tissue cells, for maintaining a healthy ECM, is mainly supplied through diffusion from nearby vascularized tissues and synovial fluid. Poor nutritional supply to the cartilaginous tissue is believed to be an important factor leading to tissue degeneration. Moreover, due to the complex collagen fiber structures, the …

Phase Transformation In Ti-Mo-O, Herbert Boeckels

All Dissertations

The present dissertation has investigated the effect of oxygen on the ù and á phase stability in metastable Ti-Mo â titanium alloys using thermal analysis, hardness measurements, electron microscopy, and x-ray diffraction.
Single crystal x-ray diffraction has shown that oxygen atoms are located in the tetrahedral interstitial lattice sites in the rapidly cooled bcc Ti crystal structure, interfering directly with the reversible displacive formation of ù, with this transformation involving collapse of the bcc lattice along â. Subsequent thermal exposure of reversible ù, as occurring during slower cooling, heating, and aging, prompts short range diffusion and the formation of chemical …

Network Traffic Analysis Using Stochastic Grammars, Chen Lu

All Dissertations

Network traffic analysis is widely used to infer information from Internet
traffic. This is possible even if the traffic is encrypted. Previous work uses
traffic characteristics, such as port numbers, packet sizes, and frequency,
without looking for more subtle patterns in the network traffic. In this work,
we use stochastic grammars, hidden Markov models (HMMs) and probabilistic
context-free grammars (PCFGs), as pattern recognition tools for traffic
analysis.
HMMs are widely used for pattern recognition and detection. We use a HMM
inference approach. With inferred HMMs, we use confidence intervals (CI) to
detect if a data sequence matches the HMM. To …

Stochastic Tools For Network Security: Anonymity Protocol Analysis And Network Intrusion Detection, Lu Yu

All Dissertations

With the rapid development of Internet and the sharp increase of network crime, network security has become very important and received a lot of attention.
In this dissertation, we model security issues as stochastic systems. This allows us to find weaknesses in existing security systems and propose new solutions. Exploring the vulnerabilities of existing security tools can prevent cyber-attacks from taking advantages of the system weaknesses. We consider The Onion Router (Tor), which is one of the most popular anonymity systems in use today, and show how to detect a protocol tunnelled through Tor. A hidden Markov model (HMM) is …

Phoneme Weighting And Energy-Based Weighting For Speaker Recognition, Eric Fang

All Dissertations

This dissertation focuses on determining specific vowel phonemes which work best for speaker identification and speaker verification, and also developing new algorithms to improve speaker identification accuracy. Results from the first part of our research indicate that the vowels /i/, /E/ and /u/ were the ones having the highest recognition scores for both the Gaussian mixture model (GMM) and vector quantization (VQ) methods (at most one classification error). For VQ, /i/, /I/, /e/, /E/ and /@/ had no classification errors. Persons speaking /E/, /o/ and /u/ have been verified well by both GMM and VQ methods in our experiments. For …

Improving Accuracy In Ultra-Wideband Indoor Position Tracking Through Noise Modeling And Augmentation, Salil Banerjee

All Dissertations

The goal of this research is to improve the precision in tracking of an ultra-wideband (UWB) based Local Positioning System (LPS). This work is motivated by the approach taken to improve the accuracies in the Global Positioning System (GPS), through noise modeling and augmentation. Since UWB indoor position tracking is accomplished using methods similar to that of the GPS, the same two general approaches can be used to improve accuracy.
Trilateration calculations are affected by errors in distance measurements from the set of fixed points to the object of interest. When these errors are systemic, each distinct set of fixed …

Application Of Carbon Dioxide Towards The Development Of Smart Materials, Green Reaction Schemes And Metallic Nanoparticle Synthesis, Fiaz Mohammed

All Dissertations

Global carbon dioxide (CO₂) emissions have steadily risen over the last 50 years, with 34 billion tons of CO₂ released in 2009 alone. Its potential as a greenhouse gas has negatively affected of our lives and environment by the resulting ocean acidification and climate change. To mitigate atmospheric CO₂, various strategies have been implemented for CO₂ separation, capture, storage and use as a chemical feedstock. The use of CO₂ in various chemical industries is attractive as its non-flammable, non-toxic, and relatively inert properties have made it an inherently safer alternative to traditional organic …

On-Line Transient Stability Studies Incorporating Wind Power, Zhenhua Wang

All Dissertations

Transient stability is a major concern in power system security and reliability because it is the most common type of instability and its impacts can cause greatest economic losses. For enhancing the energy security, it requires the power system operation to be evaluated during both the planning and the operation stage. Many online/offline transient stability assessment techniques have already been developed for this purpose. However, due to the increase in energy demand, the modern power system has grown to a very sophisticated and large system for which extent transient stability assessment methods may not be able to handle. In addition, …

A Mechanism For Organizing Last-Mile Service Using Non-Dedicated Fleet, Shih-Fen Cheng, Duc Thien Nguyen, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

Unprecedented pace of urbanization and rising income levels have fueled the growth of car ownership in almost all newly formed megacities. Such growth has congested the limited road space and significantly affected the quality of life in these megacities. Convincing residents to give up their cars and use public transport is the most effective way in reducing congestion; however, even with sufficient public transport capacity, the lack of last-mile (from the transport hub to the destination) travel services is the major deterrent for the adoption of public transport. Due to the dynamic nature of such travel demands, fixed-size fleets will …

Lagrangian Relaxation For Large-Scale Multi-Agent Planning, Geoff Gordon, Pradeep Varakantham, William Yeoh, Hoong Chuin Lau, Shih-Fen Cheng

Research Collection School Of Computing and Information Systems

Multi-agent planning is a well-studied problem with various applications including disaster rescue, urban transportation and logistics, both for autonomous agents and for decision support to humans. Due to computational constraints, existing research typically focuses on one of two scenarios: unstructured domains with many agents where we are content with heuristic solutions, or domains with small numbers of agents or special structure where we can provide provably near-optimal solutions. By contrast, in this paper, we focus on providing provably near-optimal solutions for domains with large numbers of agents, by exploiting a common domain-general property: if individual agents each have limited influence …

Knowledge-Driven Autonomous Commodity Trading Advisor, Yee Pin Lim, Shih-Fen Cheng

Research Collection School Of Computing and Information Systems

The myth that financial trading is an art has been mostly destroyed in the recent decade due to the proliferation of algorithmic trading. In equity markets, algorithmic trading has already bypass human traders in terms of traded volume. This trend seems to be irreversible, and other asset classes are also quickly becoming dominated by the machine traders. However, for asset that requires deeper understanding of physicality, like the trading of commodities, human traders still have significant edge over machines. The primary advantage of human traders in such market is the qualitative expert knowledge that requires traders to consider not just …

De-Embedding In High Speed Design, Don Degroot, David Dunham

Faculty Publications

No abstract provided.

The Effects Of Energy Beverages In Counteracting The Symptoms Of Mild Hypoxia At Legal General Aviation Altitudes, Daniel Mark Bull

Doctoral Dissertations and Master's Theses

The purpose of this thesis was to conduct preliminary research, in the form of a pilot study, concerning the natural effects of hypoxia compared to the effects of hypoxia experienced after the consumption of an energy beverage. The study evaluated the effects of hypoxia on FAA certificated pilots at a simulated legal general aviation altitude, utilizing the normobaric High Altitude Lab (HAL) located at Embry Riddle Aeronautical University, Daytona Beach, Florida. The researcher tested 11 subjects, who completed three simulated flight tasks within the HAL using the Frasca International Mentor Advanced Aviation Training Device (AATD). The flight tasks were …

Implementation Of Microwave Transmissions For Rocket Exhaust Plume Diagnostics, Nicholas George Coutu

Doctoral Dissertations and Master's Theses

Rocket-launched vehicles produce a trail of exhaust that contains ions, free electrons, and soot. The exhaust plume increases the effective conductor length of the rocket. A conductor in the presence of an electric field (e.g. near the electric charge stored within a cloud) can channel an electric discharge. The electrical conductivity of the exhaust plume is related to its concentration of free electrons. The risk of a lightning strike in-flight is a function of both the conductivity of the body and its effective length. This paper presents an approach that relates the electron number density of the exhaust plume to …

Novel Airframe Design For The Dual-Aircraft Atmospheric Platform Flight Concept, Eric Michael Mckee

Doctoral Dissertations and Master's Theses

A high-altitude, long-endurance unmanned aerial airframe was designed for the innovative Dual-Aircraft Atmospheric Platform flight concept that exploits stratospheric wind velocity gradients to remain aloft indefinitely. Classical aircraft preliminary design techniques and high-fidelity tools were used to establish a baseline configuration.

Performance characteristics of numerous airfoil profiles were evaluated with two-dimensional flow software in an effort to determine the best-candidate airfoil for the unique application. Vortex-Lattice method tools were used to investigate the sensitivity of three-dimensional design parameters upon overall vehicle aerodynamic performance and determine both static and dynamic stability characteristics of the airframe. Performance capabilities of the finalized airframe …

Investigation Of Shroud Geometry To Passively Improve Heat Transfer In A Solar Thermal Storage Tank, Matthew Keene Zemler

Doctoral Dissertations and Master's Theses

A shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The shroud and baffle are used to create a vena contracta near the surface of the heat exchanger, which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder, which is situated at the top of a solar thermal …

Design And Analysis Of An Adaptive Asynchronous System Architecture For Energy Efficiency, Brent Michael Hollosi

Graduate Theses and Dissertations

Power has become a critical design parameter for digital CMOS integrated circuits. With performance still garnering much concern, a central idea has emerged: minimizing power consumption while maintaining performance. The use of dynamic voltage scaling (DVS) with parallelism has shown to be an effective way of saving power while maintaining performance. However, the potency of DVS and parallelism in traditional, clocked synchronous systems is limited because of the strict timing requirements such systems must comply with. Delay-insensitive (DI) asynchronous systems have the potential to benefit more from these techniques due to their flexible timing requirements and high modularity. This dissertation …

Titanium Aluminum Nitride Films Deposited By Ac Reactive Magnetron Sputtering: Study Of Positioning Effect In An Inverted Cylindrical Magentron Sputtering System, George C. Vandross Ii

Graduate Theses and Dissertations

TiAlN films were deposited on glass substrates by AC magnetron sputtering at 2 kW with constant Argon and Nitrogen gas flow rates to study the effects of positioning on the deposited films. The deposition system used was an ICM-10 IsoFlux cylindrical magnetron sputtering chamber. The samples were placed in different positions and tilts with respect to the location of the Titanium and Aluminum targets in the chamber. It was found that with change in position and application of tilts, deposited films acquired different physical and chemical properties. It is believed that the differences in these properties were caused by to …

On The Maintenance Modeling And Optimization Of Repairable Systems: Two Different Scenarios, Suzan Alaswad

Graduate Theses and Dissertations

The use of mathematical modeling for the purpose of analyzing and optimizing the performance of repairable systems is widely studied in the literature. In this dissertation, we study two different scenarios on the maintenance modeling and optimization of repairable systems. First, we study the long-run availability of a traditional repairable system that is subjected to imperfect corrective maintenance. We use Kijima's second virtual age model to describe the imperfect repair process. Because of the complexity of the underlying probability models, we use simulation modeling to estimate availability performance and meta-modeling to convert the reliability and maintainability parameters of the repairable …

Topics On Light-Emitting-Diode Driver Research, Jaber Hasan

Graduate Theses and Dissertations

In this dissertation, light-emitting-diode (LED) drivers are investigated for efficiency issues related to driving Red-Green-Blue (RGB) pixels and multiple LED strings in parallel. A high-efficiency digitally controlled RGB LED driver was designed for driving a 3x3 RGB LED display panel. A multiplexer was used to sense the voltage drop across the current controllers. This driver maintained a minimum drive voltage across the RGB LED pixels required to keep it in regulation leading to a reduction of unwanted power losses in the RGB LED pixels by selecting the minimum drop across the current-controllers as the reference voltage of the digital controller. …

Energy And Spectral Efficient Wireless Communications, Guoqing Zhou

Graduate Theses and Dissertations

Energy and spectrum are two precious commodities for wireless communications. How to improve the energy and spectrum efficiency has become two critical issues for the designs of wireless communication systems. This dissertation is devoted to the development of energy and spectral efficient wireless communications. The developed techniques can be applied to a wide range of wireless communication systems, such as wireless sensor network (WSN) designed for structure health monitoring (SHM), medium access control (MAC) for multi-user systems, and cooperative spectrum sensing in cognitive radio systems.

First, to improve the energy efficiency in SHM WSN, a new ultra low power (ULP) …

Thermal And Electrical Parasitic Modeling For Multi-Chip Power Module Layout Synthesis, Zihao Gong

Graduate Theses and Dissertations

This thesis presents thermal and electrical parasitic modeling approaches for layout synthesis of Multi-Chip Power Modules (MCPMs). MCPMs integrate power semiconductor devices and drive electronics into a single package. As the switching frequency of power devices increases, the size of the passive components are greatly reduced leading to gains in efficiency and cost reduction. In order to increase switching frequency, electrical parasitics in MCPMs need to be reduced through tighter electronic integrations and smaller packages. As package size is decreased, temperature increases due to less heat dissipation capability. Thus, it is crucial to consider both thermal and electrical parasitics in …

Study Of Current Optocoupler Techniques And Applications For Isolation Of Sensing And Control Signals In Dc-Dc Converters, Jake Williams

Graduate Theses and Dissertations

There is a need for power switches that can operate at high voltage, high temperature, and high switching frequencies with low losses. Power switches fabricated from wide bandgap materials such as silicon carbide (SiC) or gallium nitride (GaN) can outperform conventional silicon switches due to material property advantages. Another common problem in grid-connected applications is the need for high voltage-isolation of gate drivers and control circuitry while operating efficiently at the high switching frequencies, high power density, and high temperatures made possible by wide bandgap devices. Transformers cannot operate at the temperatures of these wide bandgap devices and a new …

Refractive Index Chemical Sensing With Noble Metal Nanoparticles, Phillip Blake

Graduate Theses and Dissertations

Chemical sensing is a key component in modern society, especially in engineering applications. Because of their widespread impact, improvements to chemical sensors are a significant area of research. One class of sensors, plasmonic sensors, is being heavily researched because of their ability to detect low levels of analyte in near real time without destroying the analyte. This work studies a new class of plasmonic sensor that utilizes diffractive coupling to improve sensor performance. Specifically, this work outlines the first study of diffractive coupling sensors with typical nanoparticle shapes. Sensitivity of this new class of sensor is directly compared to typical …

Trans-Dimensional Geoacoustic Inversion Of Wind-Driven Ambient Noise, Jorge E. Quijano, Stan E. Dosso, Jan Dettmer, Lisa M. Zurk, Martin Siderius

Electrical and Computer Engineering Faculty Publications and Presentations

This letter applies trans-dimensional Bayesian geoacoustic inversion to quantify the uncertainty due to model selection when inverting bottom-loss data derived from wind-driven ambient-noise measurements. A partition model is used to represent the seabed, in which the number of layers, their thicknesses, and acoustic parameters are unknowns to be determined from the data. Exploration of the parameter space is implemented using the Metropolis–Hastings algorithm with parallel tempering, whereas jumps between parameterizations are controlled by a reversible-jump Markov chain Monte Carlo algorithm. Sediment uncertainty profiles from inversion of simulated and experimental data are presented.

A Process Analysis Of Engineering Problem Solving And Assessment Of Problem Solving Skills, Sarah Grigg

All Dissertations

In the engineering profession, one of the most critical skills to possess is accurate and efficient problem solving. Thus, engineering educators should strive to help students develop skills needed to become competent problem solvers. In order to measure the development of skills, it is necessary to assess student performance, identify any deficiencies present in problem solving attempts, and identify trends in performance over time. Through iterative assessment using standard assessment metrics, researchers/instructors are able to track trends in problem solving performance across time, which can serve as a gauge of students' learning gains.
This research endeavor studies the problem solving …

Synthesis And Characterization Of Nanoscale Fluorescent Polymer Films, Maryus Chyasnavichyus

All Dissertations

Performance of the chemical sensing devices is based sensitivity to the targeted analytes and accuracy of the measurements. Of many different types of chemical sensors, fluorescence based sensing devices draw much attention as efficient yet small and straightforward devices, capable of detection of various analytes at extremely small quantities.
Polymeric materials provide support for the fluorescent materials and usually serve as a host for the chromophores, protecting them from harsh environments, and serve as a transport media for the analyte.
In the present study thin fluorescent polymer films, sensitive to the environment are synthesized and studied. Poly(glycidyl methacrylate) was used …

Induced Elastic Matrix Synthesis Within 3-Dimensional Collagen Constructs, Lavanya Venkataraman

All Dissertations

Elastin, a primary component of elastic arteries, maintains structural stability of the cyclically recoiling artery, and critically regulates vascular cell behavior. Accelerated degradation of elastic matrix, such as that seen in vascular pathologies like abdominal aortic aneurysms (AAA), can therefore severely compromise vessel homeostasis. Tissue engineering and in-situ matrix repair strategies evaluated so far are primarily limited in inducing adult vascular cells to replicate the complex elastic matrix assembly process, and restore lost matrix integrity. Previously, our lab established the elastogenic benefits of concurrent delivery of TGF-β1 and HA-oligomers (together termed elastogenic factors, EFs), within 2D cultures of rat aortic …

Towards Trustworthy, Efficient And Scalable Distributed Wireless Systems, Ze Li

All Dissertations

Advances in wireless technologies have enabled distributed mobile devices to connect with each other to form distributed wireless systems. Due to the absence of infrastructure, distributed wireless systems require node cooperation in multi-hop routing. However, the openness and decentralized nature of distributed wireless systems where each node labors under a resource constraint introduces three challenges: (1) cooperation incentives that effectively encourage nodes to offer services and thwart the intentions of selfish and malicious nodes, (2) cooperation incentives that are efficient to deploy, use and maintain, and (3) routing to efficiently deliver messages with less overhead and lower delay. While most …

Photo-Thermal Processing Of Semiconductor Fibers And Thin Films, Nishant Gupta

All Dissertations

Furnace processing and rapid thermal processing (RTP) have been an integral part of several processing steps in semiconductor manufacturing. The performance of RTP techniques can be improved many times by exploiting quantum photo-effects of UV and vacuum ultraviolet (VUV) photons in thermal processing and this technique is known as rapid photo-thermal processing (RPP). As compared to furnace processing and RTP, RPP provides higher diffusion coefficient, lower stress and lower microscopic defects. In this work, a custom designed automated photo assisted processing system was built from individual parts and an incoherent light source. This photo-assisted processing system is used to anneal …