Engineering Commons^™

Prediction Of Fluid Dielectric Constants, Jiangping Liu

Theses and Dissertations

The dielectric constant or relative static permittivity of a material represents the capacitance of the material relative to a vacuum and is important in many industrial applications. Nevertheless, accurate experimental values are often unavailable and current prediction methods lack accuracy and are often unreliable. A new QSPR (quantitative structure-property relation) correlation of dielectric constant for pure organic chemicals is developed and tested. The average absolute percent error is expected to be less than 3% when applied to hydrocarbons and non-polar compounds and less than 18% when applied to polar compounds with dielectric constant values ranging from 1.0 to 50.0. A …

Mechanical Characterization Of The Interspinous Ligament Using Anisotropic Small Punch Testing, Rachel Jane Bradshaw

Theses and Dissertations

Objective: The objective of this work was to characterize the nonlinear anisotropic material constitutive response of the interspinous ligament (ISL).

Methods: Cadaveric test samples of the interspinous ligament were tested using the anisotropic small punch test. The measured force-displacement response served as experimental input into a system identification optimization routine to determine the constitutive material parameters that replicated the measured material response.

Results: The constitutive behavior of the ISL is notably different from that reported for knee, shoulder, and hip ligaments. Specifically, the high collagen fiber content and unique collagen architecture provided a stiffer material response. The results from the …

Friction Bit Joining Of 5754 Aluminum To Dp980 Ultra-High Strength Steel: A Feasibility Study, Britney Weickum

Theses and Dissertations

In this study, the dissimilar metals 5754 aluminum and DP980 ultra-high strength steel were joined using the friction bit joining (FBJ) process. The friction bits were made using one of three steels: 4140, 4340, or H13. Experiments were performed in lap shear, T-peel, and cross tension configurations, with the 0.070" thick 5754 aluminum alloy as the top layer through which the friction bit cut, and the 0.065" thick DP980 as the bottom layer to which the friction bit welded. All experiments were performed using a computer controlled welding machine that was purpose-built and provided by MegaStir Technologies. Through a series …

Characterization Of The Mechanical Response Of The Lumbar Spine, Shannon Alisa Zirbel

Theses and Dissertations

The primary objective of this research is to associate lumbar segmental mechanical response with intervertebral disc degeneration under physiologic testing conditions. Because no mathematical model exists for lumbar spine segmental rotations, a portion of this thesis evaluates potential methods for curve fitting the torque-rotation curves. The Dual Inflection Point (DIP) Boltzmann equation was developed during the course of this research and is presented here as a method for fitting spinal motion data wherein a physical meaning can be assigned to each of the model coefficients. This model can tell us more about the effects of degeneration, testing conditions, and other …

Fpga Communication Framework For Communication, Debugging, Testing, And Rapid Prototyping, Peter Andrew Lieber

Theses and Dissertations

FPGA-CF is an open-source, portable, extensible communications framework that consists of a small hardware core (less than 600 slices) and a software library/API (Java and C++). It enables a host PC to transmit data at 120 Mb/s to Xilinx-based FPGA boards via Ethernet using standard inter-networking protocols (UDP/IP). A custom lightweight connection-oriented protocol guarantees reliability. The hardware core is directly connected to the Xilinx internal configuration port (ICAP) and supports all ICAP functionality. The core also provides an extensible user-channel interface and provides up to 15, 8-bit user-data channels that can be connected to user circuitry (configurable by the user). …

Integration Of Micropore And Nanopore Features With Optofluidic Waveguides For Single Particle Sensing, Matthew R. Holmes

Theses and Dissertations

This dissertation outlines the research and development of ground-breaking nanometer sized openings (nanopores) integrated with an on-chip optofluidic platform. This platform represents a significant advancement for single nanoparticle sensing. In this work specifically, the integrated optofluidic platform has been used to electrically and optically filter and detect single nanoparticles using ionic current blockade and fluorescence experiments. The correlation of electrical and optical signal has provided the highest sensitivity single nanoparticle measurements ever taken with integrated optofluidic platforms. The particular optofluidic platform used for this work is an antiresonant reflecting optical waveguide (ARROW). ARROW hollow and solid core waveguides are interference …

Devices And Methods For Electro-Physical Transport Of Dna Across Cell Membranes, Quentin Theodore Aten

Theses and Dissertations

A novel method for charged macromolecule delivery, called nanoinjection, has been developed at Brigham Young University. Nanoinjection combines micro-fabrication technology, mechanism design, and nano-scale electrical phenomenon to transport exogenous DNA across cell membranes on a nano-featured lance. DNA is electrically accumulated on the lance, precision movements of microelectromechanical systems (MEMS) physically insert the lance into cell, and DNA is electrically released from the lance into the cell. Penetration into the cell is achieved through a two-phase, self-reconfiguring metamorphic mechanism. The surface-micromachined, metamorphic nanoinjector mechanism elevates the lance above the fabrication substrate, then translates in-plane at a constant height as the …

A Wideband Precision Quadrature Phase Shifter, Steve T. Noall

Theses and Dissertations

A new circuit is proposed that uses an RC-CR filter in a feedback configuration to achieve a wideband precision quadrature phase shift with constant amplitude response. Such a circuit can be used to perform image rejection in a low IF receiver using the Hartley method. Simulation results show that the circuit can achieve an average image rejection ratio of 50 dB over a 16 MHz bandwidth. The feedback loop enables the circuit to maintain high accuracy over process and temperature.

Magnetic Field Sensing With Slab Coupled Optical Fiber Sensors, Bryson J. Shreeve

Theses and Dissertations

This thesis reports an in-fiber magnetic field sensor that is able to detect magnetic fields as low as 2 A/m at a spatial resolution of 1 mm. The small sensor consists of a magneto-optic slab waveguide, bismuth-doped rare earth iron garnet (Bi-RIG) that is coupled to an optical fiber. By coupling light from the fiber to the slab waveguide, it becomes an in-fiber magnetic field sensor. This is due to the Magneto-Optic Kerr effect; a change in refractive index is proportional to the applied magnetic field. When an AC field is applied, an AC component in the output power can …

An Evaluation Of Constitutive Laws And Their Ability To Predict Flow Stress Over Large Variations In Temperature, Strain, And Strain Rate Characteristic Of Friction Stir Welding, Katherine Lynn Kuykendall

Theses and Dissertations

Constitutive laws commonly used to model friction stir welding have been evaluated, both qualitatively and quantitatively, and a new application of a constitutive law which can be extended to materials commonly used in FSW is presented. Existing constitutive laws have been classified as path-dependent or path-independent. Path-independent laws have been further classified according to the physical phenomena they capture: strain hardening, strain rate hardening, and/or thermal softening. Path-dependent laws can track gradients in temperature and strain rate characteristic to friction stir welding; however, path-independent laws cannot. None of the path-independent constitutive laws evaluated has been validated over the full range …

Photogrammetric Measurement Of Recession Rates Of Low Temperature Ablators Subjected To High Speed Flow, David W. Callaway

Theses and Dissertations

This research advances a technique to simulate high temperature/high speed effects in a high speed/low temperature environment and to capture recession of the test article in three-dimensions. A method of fabricating dry ice test articles was developed, and the AFIT Mach 3 pressure-vacuum wind tunnel was used in combination with the dry ice test articles to collect three-dimensional ablation data for models of different shapes at stagnation pressures ranging from approximately 0.4 atm to 3 atm and stagnation temperatures equivalent to room temperature. High speed Schlieren photography was used for visualization, and the three dimensional shape change was quantified with …

Optimization Of A Tri-Layered Vascular Graft: The Influence Of Cellular And Mechanical Properties, Michael Mcclure

Theses and Dissertations

Electrospinning is a polymer processing technique which allows for the production of nano to micro size fibers and scaffolds which can be composed of numerous synthetic biodegradable materials and natural biopolymers. Natively, elastin and collagen are the main components of vascular tissue. Arranged in a tri-layered structure, they create a specific mechanical environment that can withstand the rigors of circulation. The goal of this study was to develop a mechanically ‘biomimicking’ vascular graft composed of three distinct layers through the process of electrospinning. We hypothesize that the use of bioactive agents such as elastin, collagen, and silk to supplement poly(caprolactone) …

Coverage Of Continuous Regions In Euclidean Space Using Homogeneous Resources With Application To The Allocation Of The Phased Array Radar Systems, Kassandra M. Merritt

Theses and Dissertations

Air surveillance of United States territory is an essential Department of Defense function. In the event of an incoming aerial attack on North America, the DoD, Department of Homeland Security, and Federal Aviation Administration surveillance capabilities are critical to discovering and tracking the threat so that it can be eliminated. Many of the currently used surveillance radar will reach the end of their design life within ten to twenty years. By replacing the current radar network with a single integrated network of Multifunction Phased Array Radar (MPAR) units, surveillance capabilities can be enhanced and life cycle cost can be reduced. …

Solar Warning Architecture For Manned Missions To Mars, James S. Bohren, John K. Howard

Theses and Dissertations

Solar radiation storms represent a dire threat to manned interplanetary space travel. Earth's current solar forecasting architecture is Earth-focused and insufficient to provide timely warnings to a manned mission to Mars, therefore a "best value" solar warning architecture must be identified. A total of 14 solar warning architectures were developed by varying 5 solar sensor locations, 2 processing locations, and 2 communications strategies. Using Satellite Tool Kit, performance of the candidate architectures in terms of Warning Time and Solar Coverage was quantified during a Mars mission scenario based on NASA's Design Reference Architecture 5.0. Cost of each candidate architecture was …

Spacecraft Demand Tasking And Skip Entry Responsive Maneuvers, Robert A. Bettinger

Theses and Dissertations

The purpose of this research was to parametrically investigate the viability of skip entry maneuvers as an alternative to vacuum-only maneuvers, and to identify whether skip entry maneuvers can extend spacecraft mission lifetime by limiting propellant expenditure through the exploitation of the aerodynamic interaction between the upper atmosphere and an example entry vehicle and remote-sensing orbital platform. Employing the X-37B Orbital Test Vehicle (OTV) and a notional satellite design as the example entry vehicles, the entry profile dynamics of a skip entry maneuver were characterized with varying trajectory initial conditions such as entry altitude, entry flight-path angle, and vehicle aerodynamics. …

A Relay-Rover Differential Game, Youngdong Choi

Theses and Dissertations

Guidance laws are developed to optimally position a relay Micro-UAV (MAV) to provide an operator at the base with real-time Intelligence, Surveillance, and Reconnaissance (ISR) by relaying communication and video signals when the rover MAV performing the ISR mission is out of radio contact range with the base. The ISR system is comprised of two MAVs, the Relay and the Rover, and a Base. The Relay strives to minimize the radio frequency (RF) power required for maintaining communications, while the Rover performs the ISR mission, which may maximize the required RF power. The optimal control of the Relay MAV entails …

Study Of Varying Boundary Layer Height On Turret Flow Structures, Renato Jelic

Theses and Dissertations

The Air Force Institute of Technology and the Air Force Research Labs are investigating flows over turrets which are commonly encountered in directed energy integrations with air vehicles. In this work, the computational study was performed using the NASA developed time-marching finite volume code OVERFLOW 2.2 to analyze the effect of boundary layer height on symmetrical and non-symmetrical turret geometries. The effects of aerodynamics yield to the aberration of the laser beam through two methods, aero-optical and aero-mechanical jitter. The analysis of the flow features, pressure fluctuations, density fluctuations, and forces and moments on the various geometries was conducted to …

Simulations For The Test Flight Of An Experimental Hale Aircraft, Brooke E. Kaszynski

Theses and Dissertations

Recent events, such as the crash of NASA's Helios aircraft during a test flight, show that more must be known about the nonlinear control of HALE aircraft. Shearer, Cesnik and their co-workers have developed a code that is a practical solution to the coupled nonlinear aeroelasticity and flight dynamics of very flexible aircraft called the University of Michigan's Nonlinear Aeroelastic Simulation Toolbox (UM/NAST). They are also in the process of developing a model HALE aircraft called X-HALE which will be used to validate this code experimentally. This research performs flight simulations with UM/NAST so as to make predictions about X-HALE's …

Process For Refining And Validating A Finite Element Model Of An Experimental High-Altitude, Long-Endurance (Hale) Aircraft, Nicholas A. Sinnokrak

Theses and Dissertations

The work presented here focuses on finite element (FE) modeling of X-HALE, a test aircraft designed and built by the University of Michigan, in conjunction with the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory (AFRL). This scaled vehicle is representative of high-altitude, long-endurance (HALE) aircraft and was designed to provide controlled aeroelastic and flight data. FE models of portions of the X-HALE wing structure were created and analysis results were compared against two separate laboratory static bending tests conducted on X-HALE wing sections. The process documented here should improve future efforts to refine FE models of …

Optical Flow-Based Odometry For Underground Tunnel Exploration, Terra Kier

Theses and Dissertations

As military operations in degraded or GPS-denied environments continue to increase in frequency and importance, there is an increased necessity to be able to determine precision location within these environments. Furthermore, authorities are finding a record number of tunnels along the U.S.-Mexico border; therefore, underground tunnel characterization is becoming a high priority for U.S. Homeland Security as well. This thesis investigates the performance of a new image registration technique based on a two camera optical- flow configuration using phase correlation techniques. These techniques differ from other image based navigation methods but present a viable alternative increasing autonomy and answering the …

Host-Based Systemic Network Obfuscation System For Windows, Kevin E. Huber

Theses and Dissertations

Network traffic identifies the operating system and services of the host that created the traffic. Current obfuscation programs focus solely on the Transport and Internet layer protocols of the TCP/IP model. Few obfuscation programs were developed to run on a Windows operating system to provide host-based obfuscation. Systemic Network Obfuscation System (SNOS) was developed to provide a thorough obfuscation process for network traffic on the Windows operating system. SNOS modifies the protocols found at all layers of the TCP/IP model to effectively obfuscate the Windows operating system and services running on the host.

Performance Analysis And Optimization Of The Winnow Secret Key Reconciliation Protocol, Kevin C. Lustic

Theses and Dissertations

Currently, private communications in public and government sectors rely on methods of cryptographic key distribution that will likely be rendered obsolete the moment a full-scale quantum computer is realized, or efficient classical methods of factoring are discovered. There are alternative methods for distributing secret key material in a post-quantum era. One example of a system capable of securely distributing cryptographic key material, known as Quantum Key Distribution (QKD), is secure against quantum factorization techniques as its security rests on generally accepted laws of quantum physics. QKD protocols typically include a phase called Error Reconciliation, a clear-text classical-channel discussion between legitimate …

Design And Characterization Of A Space Based Chromotomographic Hyperspectral Imaging Experiment, Jason D. Niederhauser

Theses and Dissertations

This research focuses upon the design, analysis and characterization of several systems related to a spacebased chromotomographic experiment (CTEx), a hyperspectral imager, currently in development at the Air Force Institute of Technology. Three interrelated subject-areas were developed. The initial focal point was a generic, system-level mechanical layout and integration analysis of the space-based instrument. The scope of this work was intended to baseline the space-based system design in order to allow for further trade-space refinement and requirements development. Second, development of an iteration upon the ground-based version of CTEx was accomplished in an effort to support higher-fidelity field data-collection. This …

Operational Characteristics Of A Rotating Detonation Engine Using Hydrogen And Air, Rachel M. Russo

Theses and Dissertations

Rotating detonation engines (RDE) are pressure gain combustion engines that have the potential for greater efficiency than traditional, constant pressure, deflagration engines. RDEs are smaller and mechanically simpler than pulsed detonation engines. A small diameter (3 in) engine was successfully run on hydrogen and air. Most of the tests were conducted using air with a slightly lower diluents percentage (77% nitrogen as opposed to 79% nitrogen). These tests provided the foundation for determining the operational space (mass flow rate and equivalence ratio) of the rotating detonation engine. From the tests conducted with the lower diluents air, the appropriate run conditions …

Carbon Nanotube Field Emission Arrays, Benjamin L. Crossley

Theses and Dissertations

This effort exploits the unique physical and electrical characteristics of carbon nanotubes (CNTs) for field emission applications. Carbon nanotube field emission devices are designed, fabricated, and tested. Two reliable CNT synthesis methods, microwave plasma enhanced chemical vapor deposition (MPE-CVD) and thermal chemical vapor deposition (T-CVD), are developed. The physical properties of the resulting CNTs are analyzed using Raman spectroscopy and Scanning electron microscopy (SEM) and then tested for field emission performance. The T-CVD grown CNTs are shown to have fewer growth defects, but suffer from less process control making integration into devices difficult without further process development. Field emission testing …

Characterizing Cyclostationary Features Of Digital Modulated Signals With Empirical Measurements Using Spectral Correlation Function, Mujun Song

Theses and Dissertations

Signal detection is widely used in many applications. Some examples include Cognitive Radio (CR) and military intelligence. CRs use signal detection to sense spectral occupancy. Without guaranteed signal detection, a CR cannot reliably perform its role. Similarly, signal detection is the first step for garnering an opponent's information. Wireless signal detection can be performed using many different techniques. Some of the most popular include matched filters, energy detectors (which use measurements such as the Power Spectral Density (PSD) of the signal), and Cyclostationary Feature Detectors (CFD). Among these techniques, CFD can be viewed as a compromise technique, in that it …

Face Recognition Via Ensemble Sift Matching Of Uncorrelated Hyperspectral Bands And Spectral Pcts, Mohd Fairul Mohd-Zaid

Theses and Dissertations

Face recognition is not a new area of study, but facial recognition using through hyperspectral images is a somewhat new concept which is still in its infancy. Although the conventional method of face recognition using Red-Green-Blue (RGB) or grayscale images has been advanced over the last twenty years, these methods are still shown to have weak performance whenever there are variations or changes in lighting, pose, or temporal aspect of the subjects. A hyperspectral representation of an image captures more information that is available within a scene than a RGB image therefore it is beneficial to study the performance of …

Risks Associated With Federal Construction Projects, Krishna R. Surajbally

Theses and Dissertations

The rise in terrorism, corporate espionage, cyber attacks, and federal fiscal constraints play an important role in the federal construction process. The risks associated with these occurrences are studied to aid in the risk management of the military construction process. This paper presents the status of research into these areas to identify how methods, policies, applications, and information obtained from case studies can be used by stakeholders to manage risk in the United States Air Force construction process. The author reviewed research on risk associated with four essential components of the military construction process – Critical Infrastructure, Information Technology, Contracts, …

Enterprise Requirements And Acquisition Model, David A. Leach, Chad T. Searle

Theses and Dissertations

In support of senior leadership emphasis on improving early systems engineering and analysis, the Enterprise Requirements and Acquisition Model (ERAM) is a quantitative discrete-event process simulation model that accounts for activities from the identification of a desired space capability early in the JCIDS process through Milestone C of the acquisition system resulting in a probabilistic schedule distribution for a given concept. This model of the DoD's space capability development process will provide valuable decision making information for Concept Characterization and Technical Descriptions referenced during Analysis of Alternatives. The research focused on identifying activities, assigning historical triangular distributions and probabilities at …

Numerical Analysis On The Effects Of Blade Loading On Vortex Shedding And Boundary Layer Behavior In A Transonic Axial Compressor, Kenneth Phillip Clark

Theses and Dissertations

Multiple high-fidelity, time-accurate computational fluid dynamics simulations were performed to investigate the effects of upstream stator loading and rotor shock strength on vortex shedding characteristics in a single stage transonic compressor. Various configurations of a transonic axial compressor stage, including three stator/rotor axial spacings of close, mid, and far in conjunction with three stator loadings of decreased, nominal, and increased were simulated in order to understand the flow physics of transonic blade-row interactions. Low-speed compressors typically have reduced stator/rotor axial spacing in order to decrease engine weight, and also because there is an increase in efficiency with reduced axial spacing. …