Engineering Commons^™

Ultraviolet Light Emitting Diode Use In Advanced Oxidation Processes, Kelsey L. Duckworth

Theses and Dissertations

Cleanup from a hazardous chemical release can result in large volumes of water containing hazardous materials, such as organophosphates. Unfortunately, this water cannot be treated in a municipal wastewater treatment plant without adversely affecting the performance of the plant. A known method for pretreating this water to prepare it for processing in a traditional treatment plant includes the addition of hydrogen peroxide, followed by ultraviolet (UV) light exposure to form reactive hydroxyl radicals which oxidize the chemical. Light emitting diodes (LEDs) are explored as a UV source as they are durable; compact; can be powered by low voltage, direct current …

Design And Analysis Of An Attitude Determination And Control Subsystem (Adcs) For Afit's 6u Standard Bus, Erin R. Dannemeyer

Theses and Dissertations

The design and testing of AFIT's 6U Attitude Determination and Control Subsystem (ADCS) are explored to establish 3-axis attitude control. The development of AFIT's 6U CubeSat standard bus is an on-going research effort designed to create in-house CubeSat bus components and software. The 6U chassis measures approximately 11 x 24 x 37 cu cm and can have a mass up to 12 kg. The larger bus size (as compared to the more common 3U CubeSat) allows for increased power capabilities and potential to host multiple or larger payloads. Individual ADCS hardware components were either commercially purchased or built in-house and …

Influence Of Mach Number And Dynamic Pressure On Cavity Tones And Freedrop Trajectories, Justin D. Merrick

Theses and Dissertations

Weapons release at supersonic speeds from an internal weapons bay is a highly desirable capability. To ensure a successful release at multiple Mach numbers, the aerodynamic environment must be well-understood and repeatable, with a robust system for safe testing of store separation. For this reason, experimental methods were used to investigate the characteristics of a scaled WICS bay with a length-to-depth ratio of 4.5 at multiple Mach numbers and stagnation pressures. Three new nozzles were designed, manufactured, and characterized for the AFIT small supersonic tunnel, yielding freestream Mach numbers of 2.22, 1.84, and 1.43. In addition, a control valve was …

Thermal Loss Determination For A Small Internal Combustion Engine, Joshua A. Rittenhouse

Theses and Dissertations

Three analysis techniques were used to measure the heat rejection of a 55 cc air-cooled two-stroke engine. This study was performed as part of a larger effort aimed at extending range and endurance limitations of Group 1 & 2 Remotely Piloted Aircraft (RPA). The engine selected for the study was a 55 cc gasoline-fueled, carbureted, spark-ignition engine made by 3W-Modellmotoren and is representative of RPA engines in these groups. With a surface area to volume ratio of 1.48 ¹/_cm, the engine is in a size region where thermal losses begin to dominate engine efficiency and thermal efficiencies …

Experimental Investigation Of Mechanical Behavior Of An Oxide/Oxide Ceramic Composite In Interlaminar Shear And Under Combined Tension-Torsion Loading, Skyler R. Hilburn

Theses and Dissertations

Creep behavior in interlaminar shear of an oxide-oxide ceramic composite, Nextel 720™/aluminosilicate (N720/AS), was investigated at 1100°C in laboratory air and in steam. The interlaminar shear strength (ILSS) was determined as 7.65 MPa. The creep behavior was examined for interlaminar shear stresses in the 2-6 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. Tertiary creep was noted in the tests performed at 6 MPa. Larger creep strains and higher creep strain rates were produced in steam. Surprisingly, the presence of steam had a beneficial effect on creep lifetimes. It appears …

Environmentally Friendly And Sustainable Stream Stability In The Vicinity Of Bridges, Evan David Cope

Theses and Dissertations

This report was sponsored by the Utah Department of Transportation (UDOT) to determine if stream restoration structures could be used as scour countermeasures near state highways and bridges. Scour countermeasures that are effective in preventing erosion exist but that are not so friendly for aquatic organisms. UDOT is interested in finding a countermeasure that is both effective in preventing erosion while not harming aquatic organisms. Stream restoration structures are friendly for aquatic organisms but are prone to failure when flows exceed the design levels. David Rosgen has developed restoration structures that are friendly for aquatic organisms and that have provided …

Development And Regional Application Of Sub-Seasonal Remote- Sensing Chlorophyll Detection Models, Carly Adeline Hyatt

Theses and Dissertations

Remote sensing has been used as an effective chlorophyll-a detection method in inland lakes and reservoirs. Concentration estimates of chlorophyll-a approximate the amounts of algae and phytoplankton in a body of water, can indicate the existence of large blooms and high nutrient loading, and can be used as an indicator of water quality. These biomasses pose potential threats to the quality of the water and the local environment by depleting oxygen, influencing the taste of the drinking water and detrimentally affecting aesthetics and recreation. Deer Creek Reservoir exhibited eutrophic tendencies in the early 1990's, caused by phosphorus pollution. This was …

Comparative Analysis Of Reconstructed Image Quality In A Simulated Chromotomographic Imager, Ryan L. Tervo

Theses and Dissertations

A hyperspectral chromotomographic instrument has been developed to determine the spatial and spectral distribution of a target. It does this by recording the dispersed images produced by a rotating direct vision prism with a high speed camera. The recorded images are processed through a tomographic reconstruction algorithm to produce a reconstructed hypercube. A physics-based system model was developed to investigate three areas. The first was how the prism angle selection and range of angles used impacted the reconstructed image quality. The second was an assessment of a new iterative reconstruction algorithm developed to remove artifacts produced in the Back Projection …

Opportunistic Access In Frequency Hopping Cognitive Radio Networks, Ethan S. Hennessey

Theses and Dissertations

Researchers in the area of cognitive radio often investigate the utility of dynamic spectrum access as a means to make more efficient use of the radio frequency spectrum. Many studies have been conducted to find ways in which a secondary user can occupy spectrum licensed to a primary user in a manner which does not disrupt the primary user's performance. This research investigates the use of opportunistic access in a frequency hopping radio to mitigate the interference caused by other transmitters in a contentious environment such as the unlicensed 2.4 GHz region. Additionally, this work demonstrates how dynamic spectrum access …

An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud

Theses and Dissertations

A lab and eld based hyperspectral chromotomographic imager has been developed at the Air Force Institute of Technology. It is a prototype used to study the requirements for a space-based system. The imager uses a high speed visible band camera behind a direct-vision prism to image both spatial dimensions and the spectral dimension at the same time. Capturing all 3 simultaneously allows for the hyperspectral imaging of transient events. The prism multiplexes the spectral and spatial information, so tomographic reconstruction algorithms must be used to separate hyperspectral channels. Experiments were conducted to compare reconstructed image quality as a function of …

Polarimetric Calibration And Characterization Of The Telops Field Portable Polarimetric-Hyperspectral Imager, Joel G. Holder

Theses and Dissertations

The Telops polarimetric-hyperspectral imager combines polarimetric and hyperspectral technologies to enable enhanced scene characterization. The Defense Threat Reduction Agency funded research at AFIT to leverage this capability to provide more accurate scene information to radiation transport models that will allow for more effective location of radiation sources within a region of interest. To support the objectives of the DTRA effort, there is a requirement for highly accurate radiometric, polarimetric, and spectral data on a pixel-by-pixel basis. The complex nature of the Telops instrument combined with working in the thermal IR waveband makes achieving this accuracy a challenge. This thesis develops …

U-Pu-Zr Alloy Design By Ternary Potts-Phase Field Modeling, Jordan Jeffrey Cox

Theses and Dissertations

U-Pu-Zr nuclear fuels experience a redistribution of constituents and a number of phase transformations when subjected to the thermal gradient present in nuclear reactors. This redistribution and phase separation leads to several undesirable fuel performance issues. In an effort to better understand how different alloys compositions are affected by this thermal gradient, we utilize the recently introduced Hybrid Potts-phase Field Method to study the U-Pu-Zr system. The recently introduced Hybrid method couples microstructural and compositional evolutions of a system so that the two phenomena can be studied together rather than separately, as is frequently done. However, simulation of the U-Pu-Zr …

Compact Fmcw Radar For Gps-Denied Navigation And Sense And Avoid, James David Mackie

Theses and Dissertations

Location information is vital for any type of aircraft and even more crucial for Unmanned Aerial Systems (UAS). GPS is a readily available solution but signals can easily be jammed or lost. In this thesis, radar is explored as a backup system for self-localization when GPS signals are not available. The method proposed requires that an area be pre mapped by collecting radar data with known latitude and longitude coordinates. New radar data is then collected and compared to previously stored values. Channel matrices are stored at each point and are used as the basis for location comparisons. Various methods …

A Systematic Study Of The Optical And Electrical Properties Of Ge1-YSnY And Ge1-X-YSiXSnY Semiconductor Alloys, Thomas R. Harris

Theses and Dissertations

In order to fully utilize newly developed Ge_1-ySn_y and Ge_1-x-ySi_xSn_y materials for new novel optoelectronic devices, the optical and electrical properties of these alloys were investigated using photoluminescence (PL) and Hall-effect measurements. Direct bandgap PL emission was observed from almost all the samples, making them very promising candidates for Si-based light emitting devices. T-dependent PL studies also indicate that the indirect-to-direct bandgap transition of Ge_1-ySn_y alloys might take place at a much lower Sn content than the theory predicts. T-dependent Hall-effect measurements showed both degenerate parallel conducting layers as …

High-Resolution Mri For 3d Biomechanical Modeling: Signal Optimization Through Rf Coil Design And Mr Relaxometry, James A. Badal

Theses and Dissertations

Computed Tomography (CT) is often used for building 3D biomechanical models of human anatomy. This method exposes the subject to a significant x-ray dose and provides limited soft-tissue contrast. Magnetic Resonance Imaging (MRI) is a potential alternative to CT for this application, as MRI offers significantly better soft-tissue contrast and does not expose the subject to ionizing radiation. However, MRI requires long scan times to achieve 3D images at sufficient resolution, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). These long scan times can make subject motion a problem. This thesis describes my work to reduce scan time while achieving sufficient …

Development Of Tailsitter Hover Estimation And Control, Jason M. Beach

Theses and Dissertations

UAVs have become an essential tool in many market segments, particularly the military where critical intelligence can be gathered by them. A tailsitter aircraft is a platform whose purpose is to efficiently merge the range and endurance of fixed-wing aircraft with the VTOL capabilities of rotorcraft and is of significant value in applications where launch and recovery area is limited or the use of launch and recovery equipment is not desirable. Developing autopilot software for a tailsitter UAV is unique in that the aircraft must be autonomously controlled over a much wider range of attitudes than conventional UAVs. Assumptions made …

Experimental And Numerical Investigation Of The Behavior Of Screen Grid Icf Walls, Yosra Hesham El Maghraby

Theses and Dissertations

The current research addresses Screen Grid ICF walls, an innovative system that combines structural strength and sustainability. The system however is still in its infancy with relatively few researches and yet not acknowledged by several design codes. The aim of this work is to further gain knowledge in the structural behavior of SGICF walls that will lead to introducing design guidelines. To accomplish this, a test program was prepared and performed. Nonetheless, the experimental program did not entirely address every aspect required to deeply understand the structural behavior of the new system. Finite Element Modeling was performed in order to …

Impact Of Structure, Material Properties, Temperature Curling, And Trafficking On Load Transfer Efficiency, Charles Cunliffe

Theses and Dissertations

This study examines the impact of structure, material properties, temperature gradient and trafficking on load transfer efficiency of rigid airfield pavements. The current FAA mechanistic design procedure for rigid pavements assumes constant stress-based load transfer efficiency (LTE (S)) of 25% at the joints. The design procedure assumes the material properties remain constant throughout the life of the pavement. Furthermore, the design procedure does not directly consider the effect that temperature induced slab curling can have on joint LTE (S). Analysis is conducted from full scale accelerated pavement test data from the National Airport Pavement Test Facility (NAPTF) operated by the …

A New Software Tool To Environmentally And Economically Evaluate Solvent Recovery In The Pharmaceutical Industry, Eduardo Cavanagh

Theses and Dissertations

The environmental impact reduction and operating costs savings associated with the purification and reuse of solvent waste in the manufacture of active pharmaceutical ingredients (API's) were investigated. A software toolbox has been developed that combines Aspen Plus(R) process simulation with SimaPro(R) and Ecosolvent life cycle assessment (LCA) databases. The feasibility of a relatively small flexible skid capable of recovering multiple solvent waste streams was evaluated. Fractional distillation and pervaporation were considered to separate binary solvent waste mixtures. Optimum distillation reflux ratio and feed stage were determined to maximize the environmental impact reductions and operating cost savings. The optimum reflux ratio …

Novel Technologies For The Detection And Mitigation Of Drowsy Driving, Samuel Lawoyin

Theses and Dissertations

In the human control of motor vehicles, there are situations regularly encountered wherein the vehicle operator becomes drowsy and fatigued due to the influence of long work days, long driving hours, or low amounts of sleep. Although various methods are currently proposed to detect drowsiness in the operator, they are either obtrusive, expensive, or otherwise impractical. The method of drowsy driving detection through the collection of Steering Wheel Movement (SWM) signals has become an important measure as it lends itself to accurate, effective, and cost-effective drowsiness detection. In this dissertation, novel technologies for drowsiness detection using Inertial Measurement Units (IMUs) …

Mobile Indoor Positioning For Augmented Reality Systems, Robert B. Glass

Theses and Dissertations

This thesis explores the creation and setup of a prototype that allows users of the device to interact within an indoor real world environment and a virtual environment simultaneously using high-tech common technology. The prototype is comprised of a small mobile device such as a cellular mobile phone, Raspberry Pi computer, a battery powered handheld Pico projector, and software developed for the Android OS. The software can easily be ported to other mobile and non-mobile operating systems. The mobile device must contain accelerometer, magnetometer, and gyroscope embedded sensors as well as 802.11 wireless network chip. The prototype software implements an …

Analysis And Modeling Of The Roles Of Actin-Myosin Interactions In Bladder Smooth Muscle Biomechanics, Seyed Omid Komariza

Theses and Dissertations

Muscle mechanical behavior potentially plays an important role in some of the most common bladder disorders. These include overactive bladder, which can involve involuntary contractions during bladder filling, and impaired contractility or underactive bladder, which may involve weak or incomplete contractions during voiding. Actin-myosin cross-bridges in detrusor smooth muscle (DSM) are responsible for contracting and emptying the bladder. The total tension produced by muscle is the sum of its preload and active tensions. Studies suggest that actin-myosin cross-links are involved in adjustable preload stiffness (APS), which is characterized by a preload tension curve that can be shifted along the length …

Dispatch, Delivery, And Location Logistics For The Aeromedical Evacuation Of Time-Sensitive Military Casualties Under Uncertainty, Benjamin Grannan

Theses and Dissertations

Effective aeromedical evacuation of casualties is one of the most important problems in military medical systems because high-priority casualties will not survive without timely medical care. The decision making process for aeromedical evacuation consists of the following components: (1) identifying which aeromedical evacuation asset (see figure 1) to dispatch to the casualty, (2) locating aeromedical evacuation assets strategically in anticipation of incoming demand, and (3) deciding which medical treatment facility to transport the casualty. These decisions are further complicated because prioritization of casualties is based on severity of injury while aeromedical evacuation assets and medical treatment facilities operate with varying …

Modeling Acute Changes In Bladder Wall Tension, Shape And Compliance During Filling, Firdaweke Habteyes

Theses and Dissertations

The bladder wall consists primarily of detrusor smooth muscle. Tension-sensitive nerves in the bladder wall are responsible for providing bladder fullness information that is interpreted as urgency. Bladder wall tension, and therefore nerve output, is a function of bladder volume, shape and material properties. Studies have shown that the bladder wall exhibits acutely regulated detrusor compliance. In addition, bladder shape throughout filling depends on intra-abdominal forces and material properties of the bladder wall, such as regulated detrusor compliance. This thesis focused on modeling the potential influence of acute changes in bladder compliance, shape and bladder wall tension during filling. Laplace’s …

Volume Swing Frequency Response Method For Determining Mass Transfer Mechanisms In Microporous Adsorbents, Mohammad Iftekhar Hossain

Theses and Dissertations

Because of their numerous important applications in industrial catalytic, separation, and purification processes, miroporous materials have attracted considerable attention. Understanding the dynamic behavior of various gases in these porous materials is a critical step in designing, developing and effective operation of such kind of industrial processes. Frequency response (FR) methods have proven to be one of the best recently developed techniques and have been widely used to investigate kinetics behavior of various gas-solid systems due to their ability to discriminate among different rate limiting mechanisms. The current work has been focusing on the development of a volume swing frequency response …

Classification Of Low Velocity Impactors Using Spiral Sensing Of Acousto-Ultrasonic Waves, Chijioke Agbasi

Theses and Dissertations

The non-linear elastodynamics of a flat plate subjected to low velocity foreign body impacts is studied, resembling the space debris impacts on the space structure. The work is based on a central hypothesis that in addition to identifying the impact locations, the material properties of the foreign objects can also be classified using acousto-ultrasonic signals (AUS). Simultaneous localization of impact point and classification of impact object is quite challenging using existing state-of-the-art structural health monitoring (SHM) approaches. Available techniques seek to report the exact location of impact on the structure, however, the reported information is likely to have errors from …

Heat Transfer Enhancement By Three-Dimensional Surface Roughness Technique In Nuclear Fuel Rod Bundles, Kang Liu

Theses and Dissertations

DISS_abstract> This thesis investigate thermal characteristic of a single-phase nano-fluid in a single heater element loop tester and provides a comparison between heat transfer enhancement results achieved using water as a coolant and using nano-fluids with different volume percentage. The experimental investigation is performed on two simulated nuclear fuel rods with two different types of modified outer surfaces roughness. The fuel rod surfaces modified are termed as two-dimensional surface roughness (square transverse ribbed surface) and three-dimensional surface roughness (Diamond shaped blocks). The nano-fluid used are 0.5% and 2% ZnO-Deionized water based nano-fluid. The maximum heat transfer co-efficient enhancement achieved compared …

Understanding Hydrothermal Carbonization Of Mixed Feedstocks For Waste Conversion, Xiaowei Lu

Theses and Dissertations

Hydrothermal carbonization (HTC) is an environmentally beneficial means to convert waste materials to value-added solid and liquid products with minimal greenhouse gas emission. Research is lacking on understanding the influence of critical process conditions on product formation and environmental implication associated with HTC of waste streams. This work was conducted to determine how reaction conditions and heterogeneous compound mixtures (representative of municipal wastes) influence hydrothermal carbonization processes. The specific experiments include: (1) determine how carbonization product properties are manipulated by controlling feedstock composition, process conditions, and catalyst addition; (2) determine if carbonization of heterogeneous mixtures follows similar pathways as that …

High Frequency Ac Power Systems, Huaxi Zheng

Theses and Dissertations

High Frequency AC (HFAC) power systems - systems having frequencies higher than the usual 60 Hz - may have advantages in some applications, especially where small size and weight are important (aircraft, ships, etc), or where variable operating speed increases efficiency. While 400 Hz systems are widely used in aircraft, these generally do not include parallel-connected generators that operate at megawatt power levels, which is our domain of interest in this research. In particular, we are interested in micro-grid power systems in the 10-100 MW range, consisting of several generators operating in parallel at system frequencies above 60 Hz. This …

Discovery And Characterization Of Multi-Target Directed Ligands As Inhibitors Of Amyloid-Β Aggregation And Regulators Of Alzheimer's Disease, Jui-Heng Tseng

Theses and Dissertations

Alzheimer's disease (AD) is the most common neurodegenerative disease in the world. As the disease advances, symptoms include confusion, language skill breakdown, and long term memory loss - and culminate in death. Existing therapies for AD provide symptomatic benefits but cannot halt or slow the disease pathogenesis.

Increasing evidence reveals the multi-factorial nature of AD. Numerous factors, including amyloid-β (Aβ) aggregation, calcium homeostasis dysregulation, and oxidative stress, contribute to disease development and interplay with each other. Therefore, multi-target directed ligands (MTDLs) may present an effective AD treatment. Among all factors, Aβ aggregation is suggested to play the most crucial role. …