Digital Commons Network^™

Graded-Index Fiber Collimator Enhanced Extrinsic Fabry-Perot Interferometer, Yinan Zhang

Masters Theses

"In this thesis, we studied a fringe visibility enhanced extrinsic Fabry-Perot interferometer (EFPI) by fusion splicing a quarter-pitch graded-index fiber (GIF) fiber to the lead-in single-mode fiber (SMF). The performance of the GIF collimator is theoretically analyzed using a ray matrix model and experimentally verified through beam divergence angle measurements. The fringe visibility of the GIF-collimated EFPI is measured as a function of the cavity length and compared with that of a regular SMF-EFPI. At the cavity length of 500µm, the fringe visibility of the GIF-EFPI is 0.8 while that of the SMF-EFPI is only 0.2. The visibility enhanced GIF-EFPI …

Controlling Strength And Permeability Of Silica Investment Casting Molds, Darryl M. Kline

Masters Theses

"Investment casting is a metal casting process in which a ceramic mold is created around a disposable pattern using dip coating. The fine silica flour making up most of the mold gives the benefits of a smooth internal mold surface and high density. The high density allows for investment casting molds to be thinner and lighter than sand-based molds, but gives substantially smaller gaps between particles for air flow. This research focused on the design and improvement of the formulation for making investment casting molds with customizable physical properties. Properties of the molds, specifically flexural strength, permeability, and physical structure, …

Reverberation Reduction In A Room For Multiple Positions, Raghavendra Ravikumar

Masters Theses

"Reverberation in a room occurs when the direct path sound from a sound source undergoes multiple reflections from the walls of the room before reaching the listener. An impulse response of the room can be measured called the room impulse response (RIR) which captures the effects of the room. This can be represented digitally on a computer. A filter is designed to cancel the effects of the room using the information in the room impulse response. This filter is called an equalization filter and is usually placed between the source signal and loudspeaker to perform the equalization. The RIR changes …

Quantification Of Uncertainty In Aerodynamic Heating Of A Reentry Vehicle Due To Uncertain Wall And Freestream Conditions, Benjamin R. Bettis

Masters Theses

"The primary focus of this study is to demonstrate an efficient approach for uncertainty quantification of surface heat flux to the spherical non-ablating heatshield of a generic reentry vehicle due to epistemic and aleatory uncertainties that may exist in various parameters used in the numerical solution of hypersonic, viscous, laminar blunt-body flows with thermo-chemical non-equilibrium. Two main uncertainty sources were treated in the computational fluid dynamics (CFD) simulations: (1) aleatory uncertainty in the freestream velocity and (2) epistemic uncertainty in the recombination efficiency for a partially catalytic wall boundary condition. The Second-Order Probability utilizing a stochastic response surface obtained with …

Methodology And Applications Of Electrostatic Discharge Current Reconstruction By Near-Field Scanning Technique, Wei Huang

Masters Theses

"Electrostatic discharge (ESD) can cause interference in or damage to circuits or systems in many ways e.g., by E- field or H- field coupling or via conduction paths. Although one can roughly estimate the voltage and current at the injection location during an ESD event, the real offending parameter is mostly the ESD current spreading throughout the system. Those currents can be simulated if great simplifications of the system are acceptable. However, even in moderately complex systems, the ability to simulate is limited by a lack of models and computational resources. Independent of the complexity, but obviously not free of …

Automation Of Cad Model Based Assembly Simulations Using Motion Capture, Anup Madhav Vader

Masters Theses

"The manufacturing industry often uses text and video as a supplement for worker training procedures. Unfortunately, text is often difficult to follow and video lends itself to occlusion issues. CAD based animations of assembly operations can overcome these shortcomings while offering greater potential for operations analysis and simulation flexibility. However, creating such CAD based training simulations manually is a time intensive task and many a times fail to reveal the practical assembly issues faced in the real world. Thus, it is highly beneficial to be able to automate these simulations using motion capture from a physical environment. This thesis research …

Design And Critical Performance Evaluation Of Horizontal Axis Hydrokinetic Turbines, Suchi Subhra Mukherji

Masters Theses

"The current work discusses the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkT) under different turbine geometries and flow conditions. Hydrokinetic turbines are a class of zero-head hydropower systems which utilize kinetic energy of flowing water to drive a generator. However, such turbines often suffer from low-efficiency. A detailed computational fluid dynamics study was performed using a low-order k-[omega] SST (Shear Stress Transport) turbulence model to examine the effect of each of tip-speed ratio, solidity, angle of attack and number of blades on the performance of small HAHkTs with a power capacity of 10 kW. The numerical models (both two-dimensional …

Slip Ramp Spacing Design For Truck Only Lanes Using Microscopic Simulation, Manoj Vallati

Masters Theses

"This research work proposes recommendations for slip ramp spacing between the TOLs and the general GPLs along Missouri rural interstate highways using a microscopic simulation model, VISSIM. Simulation of peak period rural traffic conditions indicated that heavy vehicle speeds were directly proportional to the lengths of the merge, diverge, and link sections. The proposed design recommendations for slip ramp spacing are based on the results of these section lengths. Design of experiments was carried out using a central composite design. As the slip ramp spacing depended heavily on the lane change behavior of drivers, a sensitivity analysis was performed of …

An Analysis Of The Integration Of Lean And Safety, Pankaj Mahesh Pai

Masters Theses

"The lean philosophy has proven potential to help businesses improve productivity and reduce its losses. Lean can give businesses a cutting edge in this age of global competition. The fundamental principle of lean is to identify wastes in the system and reduce or eliminate them. There is a concern that during lean implementations, the focus on productivity may result in health and safety issues being ignored or worse, changes driven by lean may introduce new hazards. The relationship between lean and safety is not clearly understood. Lean and safety should be compatible. Both strive to improve processes. Both are against …

Event Detection From Click-Through Data Via Query Clustering, Prabhu Kumar Angajala

Masters Theses

"The web is an index of real-world events and lot of knowledge can be mined from the web resources and their derivatives. Event detection is one recent research topic triggered from the domain of web data mining with the increasing popularity of search engines. In the visitor-centric approach, the click-through data generated by the web search engines is the start up resource with the intuition: often such data is event-driven. In this thesis, a retrospective algorithm is proposed to detect such real-world events from the click-through data. This approach differs from the existing work as it: (i) considers the click-through …

Multi Axis Slicing For Rapid Prototyping, Divya Kanakanala

Masters Theses

"With multi-axis capability, direct laser deposition process can produce a metal part without the usage of support structures. In order to fully utilize such a capability, a slicing method for multi-axis metal deposition process is discussed. Using the geometry information of adjacent layers, the slicing direction and layer thickness can be changed as needed. A hierarchy structure is designed to manage the topological information which is used to determine the slicing sequence. The parallel slicing process is studied to build hollow type structure. With such a character, the hole like feature can be deposited directly to save the required machining …

Prediction Of Soft Error Response Of Integrated Circuits To Electrostatic Discharge Injection Via Simulation Field; Package Interaction For Electrostatic Discharge Soft Error Prediction; Full Wave Model For Simulating Noise Ken Electrostatic Discharge Generator, Argha Nandy

Masters Theses

"In the first section, a concept for analyzing soft error response in ICs to ESD via coupling through flex cable structures is presented. Its novelty lies in accounting for the transient electromagnetic fields radiated by the ESD generator that couples to the flex cable PCB thereby causing disturbance on the IC under test. This is accomplished in three stages; first by developing a full wave model of the DUT which includes modeling the PCB and flex cable geometry and validating it in frequency domain with regard to the transfer impedance. This followed by combining the ESD generator with the DUT …

Design And Development Of Microwire Feeder For Laser Applications, Amogh J. Shenoy

Masters Theses

"This thesis focuses on the design and development of a microwire feeder for laser applications. The use of wire-feeders in laser welding and electrical discharge machining applications has been prominent which can handle wire of 0.25 mm and it can go up to 10.0 mm in other applications. Development of microwire handling devices is complicated and difficult due to its low buckling strength; the need for high accuracy for its use; and the harsh environment it is exposed to, in laser applications. This paper presents a systematic methodology for the design and development of a high-precision microwire handling device. This …

Incorporating New Technology Into Healthcare: An Analysis Of Performance, Acceptance, And Safety, Anthony Joseph Strawhun

Masters Theses

"Each year, advances in the healthcare industry allows for better patient care and increased ability to save lives. Looking at standardized and common healthcare devices for both inside and outside the hospital environment, this research studied the tradeoffs and human factors that affect operator performance and patient survival. This research studied the impact of human factors and technology in the development and implementation of the automated external defibrillator for out-of-hospital use and the incremental advantages of SMArT infusion pump technology over traditional intravenous infusion pumps for in-hospital care. The study highlights the complex human factors of both products and establishes …

Biodiesel Production Using Supercritical Methanol, Dhaval Nitin Modi

Masters Theses

"The catalyst-free transesterification of oil (triglycerides) in supercritical methanol at a temperature and pressure above 239⁰C and 8.1MPa, respectively, provides a new way of producing biodiesel. High reaction temperature and pressure help to accelerate the transesterification because the supercritical methanol becomes non-polar and has enhanced contact with oil. The supercritical transesterification of soybean oil was carried out in a 170 ml volume high-pressure batch reactor. The pressure within the batch reactor was self-generated from heating the contents since no pumps were used. Transesterification of soybean oil with supercritical methanol readily produced biodiesel. Since the supercritical transesterification is carried out without …

Inverse Limits With Upper Semi-Continuous Set Valued Bonding Functions: An Example, Christopher David Jacobsen

Masters Theses

"While there is a wealth of information pertaining to inverse limits with single valued bonding maps, comparatively little is known about inverse limits with upper semi-continuous set valued bonding functions. In order to add somewhat to the communal knowledge on the subject, this paper provides an example of an inverse limit with a single upper semi-continuous set valued bonding function. It is then shown that the space is a continuum, and its structure is examined via its arc components and through various of its properties, such as dimension and decomposability"--Abstract, page iii.

Resistance Switching In Electrodeposited Magnetite Thin Films, Samantha Glen Matthews

Masters Theses

"The resistance switching phenomenon has been extensively studied in metal oxide thin films for its applications in the non-volatile memory industry. The research presented here focuses on magnetite thin films which have been electrodeposited onto gold-sputtered glass substrates via the electrochemical reduction of a Fe(III)-triethanolamine complex in aqueous alkaline solution. Magnetite was chosen for its usefulness in read/write memory applications, its high Curie temperature, its metal-to-insulator (Verwey) transition, and its half-metallic character and attendant spintronic properties. Resistance switching behavior caused by a reversible redox reaction at the anode was observed in the films, demonstrating that electrodeposited films show the same …

Dynamic Ant Colony Optimization For Globally Optimizing Consumer Preferences, Pavitra Dhruvanarayana

Masters Theses

"Consumer preference for any product or product feature can be expressed in the form of a utility function. Many such utility functions form a part of a preference map, where each of these are expressed in terms of the attributes defining the product or the product feature. In order to optimize the design, it is required to optimize the overall utility function obtained by a mathematical combination of individual utility functions defined in the preference map. The objective of this research is to devise and implement an algorithm to optimize all the individual utility functions comprised in a preference map …

Emi Suppression Of Dc-Dc Synchronous Buck Converters By Layout Optimizations And Emi Prediction Using Non-Linear And Spice Circuit Co-Simulation, Ankit Bhargava

Masters Theses

"The oscillation on the phase voltage is due to the resonant structure formed by a parasitic loop (consisting of two FETs and the input decoupling capacitors) inductance and the output capacitance of the low side FET. Therefore, it is important to minimize this parasitic loop inductance. A simulation guideline is developed on full-wave modeling and simulation of buck converter layouts to estimate the parasitic loop inductances. Furthermore, this method is taken one step further to estimate the far-field radiation from the loop. These simulations were verified on six PCB variants of the buck converter and were compared with measurements in …

Developing A Model For Evaluating Software Tools In Education, Vedant Jain

Masters Theses

"This thesis proposes a research model to evaluate computer-mediated learning technology, user acceptance of the technology, and the effect of the technology on learning outcomes. This thesis also introduces two innovative research techniques for such evaluations, that is, eye-tracking and the think aloud protocol. Think aloud protocol allows us to understand a user's state of mind while he/she is interacting with the system. Eye-tracking provides additional insights into a user's cognitive state while using the system and can help triangulate the results. We demonstrated the application of the research model and research techniques in evaluating visualization software designed in a …

Calibration Of Resistance Factors For Axial Capacity Of Driven Pile Into Missouri Soil, Mulugeta Abay Kebede

Masters Theses

"Over the past two decades the load resistance factor design (LRFD) has been accepted by the American Association for Transportation and Highway Officials (AASHTO) for the design of bridges. This approach is now gaining widespread popularity in the United States for substructure bridge design, including the design of driven pile foundations, as the states calibrate the geotechnical resistance factors for local geological conditions and practices. This study presents the geotechnical resistance factors calibrated for axially driven pile using the first-order reliability method (FORM) for the target reliability index of 2.33 and 3.0 based on 64 end-of-drives (EOD) and 22 beginning-of …

Evaluation Of Alternative Methods For Surface Preparation And Deposition Of Cerium-Based Conversion Coatings On Aluminum Alloys, William J. Gammill

Masters Theses

"This thesis investigates alternative surface preparation and deposition methods for cerium-based conversion coatings (CeCC) on high strength aluminum alloys. Cerium-based conversion coatings are being investigated as a more environmentally friendly replacement for chromium-based conversion coatings. Currently, the alloys are immersed in strong alkaline and acidic solutions to prepare the aluminum surfaces for conversion coating, in which immersion may not be suitable for all situations. Alternatives to this method were investigated, including wipe application of solution, ultrasonic processing in deionized water, and abrasive blasting with alumina. AI 7075-T6 test panels were prepared using each of these methods and compared to a …

Thrust Measurement Of Dielectric Barrier Discharge Plasma Actuators And Power Requirements For Aerodynamic Control, Joseph William Ferry

Masters Theses

"Plasma-based aerodynamic actuators are of interest to researchers because they do not require moving control surfaces or a source of pressurized air to modify a flow field. Dielectric barrier discharge (DBD) plasma actuators have the added advantages of simple installation and low power consumption.

DBD plasma actuators are AC devices. This work measured actuator power consumption and thrust production for driving frequencies between 1 and 18 kHz, and for driving voltages of 6 and 9 kV peak to peak. The actuator consumed between 3 and 22 W of power and produced thrust levels between 0.05 and 0.2 mN per meter …

Experimental And Modeling Comparison Of Modular Photovoltaic-Thermal Solar Panels, Nicole C. Annis

Masters Theses

"Three different prototype photovoltaic-thermal panels using water as the cooling fluid were tested simultaneously. The first two panels (Panel A and B) consisted of a highly conductive thermal sheeting and different sized copper tubing. The third panel (Panel C) consisted of copper tubing with an aluminum fin. Thermal images were used to verify the heat transfer across the panels and compare the amount of heat radiating off the back of the photovoltaic-thermal panels versus the standard photovoltaic paneleaf Three A type panels were thermally connected in series. Three photovoltaic panels were also tested for an electrical comparison. The purpose of …

Influence Of Flow Baffles On Mixing Of Two Air Streams Flowing In A Mixing Chamber With Dissimilar Temperatures: A Computational Study, Abdulmunam Salem Shaban

Masters Theses

"One of the most important components of heating, ventilation, and air conditioning (HVAC) is an air handling unit (AHU) which is used to condition and mix air that arrives from outside the building (OA) and return air (RA) that exits from the indoor space. Poor mixing between the warm return air and the cold outside air often leads to air stratification in AHU, which results in various problems, such as, nuisance trips of low temperature safety thermostats, freezing of chilled or hot water coils in a stratified subfreezing air stream and loss of control when sensors cannot read the true …

Performance Evaluation Of Energy Efficient Lighting Associated With Renewable Energy Applications, Allison Nicole Sperber

Masters Theses

"The present study demonstrated lighting loads as an energy end use associated with renewable energy system applications. Incorporating an energy efficient end use within a renewable energy system can be especially beneficial regarding size and portability. Light-emitting diodes (LEDs) are an energy efficient alternative to traditional outdoor lighting, which is currently dominated by high intensity discharge source lamps. LEDs provide the ability to mitigate the negative impacts of diesel consumption when a diesel generator is used independently or as a backup for renewable energy applications in remote localities. In-field data was collected of traditional metal halide lamps and two comparable …

Embedded Optimal Control Of Mobile Robot Formations Using Neural Networks, Bryan M. Brenner

Masters Theses

"This work first presents the development of a nearly-optimal control scheme and then evaluates the effectiveness of this nearly-optimal control scheme by comparing it to a non optimal controller in Paper I. It is shown that the proposed nearly-optimal scheme is a significant improvement over the non optimal one in both simulation and hardware tests. The test was carried out on a differentially driven robotic vehicle in both obstacle free and obstacle ridden environments. On the other hand, the controller introduced for the obstacle avoidance in Paper II will also function in the absence of obstacles so that no switching …

Palynology Of The Middle To Upper Eocene Esmeraldas Formation In The Nuevo Mundo Syncline Area, Middle Magdalena Valley Basin, Colombia, Guillermo Rodriguez-Forero

Masters Theses

"The palynology of the Eocene Esmeraldas Formation in the Middle Magdalena Valley Basin, Colombia was analyzed in order to constrain the age of the unit. This formation is a very important oil reservoir in the Middle Magdalena Valley Basin, which is a product of a fragmentation of a Cenozoic foreland basin by the Northern Andes. It created structural complexities and syntectonic deposition. The lateral continuity of the formation, as well as its correlations with lithostratigraphic units is adjacent basins, are not clearly understood. The Los Corros Fossil Horizon, a mollusk horizon in the upper part of the Esmeraldas Formation, is …

Automatic Detection Of Malignant Melanoma Using Boundary Gradient Information In Dermoscopy Images, Yogesh Ajit Dandekar

Masters Theses

"This thesis demonstrates an algorithm which uses local border features, primarily derived from the border gradient, to help determine whether the lesion is a malignant melanoma or a benign lesion. Although this algorithm uses manually-marked lesion borders, it could be included in a fully automatic routine. A Prewitt algorithm with a window size proportional to the area of the lesion is used to calculate the gradient over the entire lesion boundary. This gradient value is used to calculate various boundary features, such as mean, standard deviation, and direction of maximum gradient. The dark and white areas inside the lesion combined …

Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Nikhil D. Doiphode

Masters Theses

"We have investigated Freeze Extrusion Fabrication (FEF) of 13-93 bioactive glass to fabricate three dimensional scaffolds for bone tissue engineering. Bioactive glass paste was prepared for consistent extrusion through micro-nozzle and controlled porosity scaffolds were fabricated using additive manufacturing FEF. CAD models were prepared for different scaffold designs and computer controlled layer-by-layer deposition of pseudoplastic paste was carried out to in accordance. Liquid nitrogen assisted freezing of pastes was used for the consolidation of deposited layers. Post processing binder burnout and sintering schedules were designed for evaporation of organic binder and densification of glass. Sintering shrinkage was measured, and X-ray …