Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1000°C In Air And In Silicic Acid-Saturated Steam,
2018
Air Force Institute of Technology
Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1000°C In Air And In Silicic Acid-Saturated Steam, Brian G. Kroeger
Theses and Dissertations
Advanced SiC/SiC ceramic matrix composites (CMCs) are being considered for a variety of applications. Of interest is their ability to withstand exposure to high temperature in an aggressive oxidizing environment. The presence of steam creates such an environment. As steam traverses across a SiC/SiC composite and through cracks in the SiC matrix, it becomes saturated with silicic acid, Si(OH)4. It is essential to understand the long-term impacts and durability of SiC/SiC CMCs that have been exposed to such a demanding environment. The present research investigated creep of Hi-Nicalon™ S SiC fibers at 1000°C in air and in silicic …
The Subject Librarian Newsletter, Engineering And Computer Science, Spring 2018,
2018
University of Central Florida
The Subject Librarian Newsletter, Engineering And Computer Science, Spring 2018, Buenaventura "Ven" Basco
Libraries' Newsletters
No abstract provided.
Nonlinear Control Of Underactuated And Constrained Systems,
2018
Embry-Riddle Aeronautical University
Nonlinear Control Of Underactuated And Constrained Systems, Derek Hoffman
Doctoral Dissertations and Master's Theses
It is the purpose of this document to elaborate on the control of systems that are underactuated or otherwise constrained. To do so, local- and global-coordinate formulations are implemented to generate well-defined system dynamics for a multitude of scenarios. These dynamics are shown to lie on manifolds defined by mathematical restrictions, allowing for singularity-free modeling for global considerations. Feed-back controllers by extension share these benefits, facilitating singularity-free control algorithms as a result. Further, unactuated degrees of freedom can be treated as additional constraints, resulting in an embedded manifold upon the original dynamics. A transformation between a provided set of dynamical …
Estimation Of 3d Orientation From Inertial Sensors With Different/Nonuniform Sampling,
2018
[email protected]
Estimation Of 3d Orientation From Inertial Sensors With Different/Nonuniform Sampling, Soulaimane Berkane
Western Research Forum
No abstract provided.
A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity,
2018
Air Force Institute of Technology
A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello
Theses and Dissertations
The research this paper focuses on is comparing the structural differences between the icosahedron and hexakis icosahedron frame and skin for use as a vacuum lighter than air vehicle (VLTAV), analyzing the stress concentrations in the hexakis icosahedron both with and without the skin, and finding the optimal location and size of the air evacuation method for creating the internal vacuum. Previous research to date has identified dynamic loading on the structure and optimization of the structure, but this will be the first research to analyze the manufacturing of the structure through the development of the air evacuation design. Findings …
Developing Motion Platform Dynamics For Studying Biomechanical Responses During Exercise For Human Spaceflight Applications,
2018
University of South Florida
Developing Motion Platform Dynamics For Studying Biomechanical Responses During Exercise For Human Spaceflight Applications, Kaitlin Lostroscio
USF Tampa Graduate Theses and Dissertations
In future human spaceflight missions, with prolonged exposure to microgravity, resistive and aerobic exercises will be countermeasures for bone loss, muscle loss, and decreased aerobic capacity. Two of the exercises of interest are squats and rowing. The cyclic forces produced during these exercises are at relatively low frequencies which are likely to excite structural resonances of space vehicles. Vibration Isolation Systems (VIS) are being designed to be paired with future exploration exercise devices in order to prevent these cyclic exercise forces from impacting the space vehicle. The VIS may be configured such that a platform supports the human and exercise …
Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack,
2018
United States Air Force Academy
Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack, Matthew J. Satchell, Jeffrey M. Layng, Robert B. Greendyke
Faculty Publications
The effect of thermal and chemical boundary conditions on the structure and chemical composition of the wake behind a 3D Mach 7 sphere-cone at an angle of attack of 5 degrees and an altitude of roughly 30,000 m is explored. A special emphasis is placed on determining the number density of chemical species which might lead to detection via the electromagnetic spectrum. The use of non-ablating cold-wall, adiabatic, and radiative equilibrium wall boundary conditions are used to simulate extremes in potential thermal protection system designs. Non-ablating, as well as an ablating boundary condition using the “steady-state ablation” assumption to compute …
2018 Oklahoma Research Day Guide Book,
2018
Southwestern Oklahoma State University
2018 Oklahoma Research Day Guide Book, Southwestern Oklahoma State University
Oklahoma Research Day Abstracts
This is the 2018 Oklahoma Research Day Guide Book. This book does not contain abstracts.
Classical Molecular Dynamics Study For Defect Sink Behavior In Oxide Dispersed Strengthened Alloys,
2018
Missouri University of Science and Technology
Classical Molecular Dynamics Study For Defect Sink Behavior In Oxide Dispersed Strengthened Alloys, M. Mustafa Azeem, Zhongyu Li, Qingyu Wang, Qazi Muhammad Nouman Amjad, Muhammad Zubair, O. M.H. Ahmed
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
Oxide Dispersed Strengthened (ODS) alloys are considered as a potential candidate for future generation reactors and can even be graded as better radiation resistant materials than the ones already in use. Molecular dynamics (MD) simulation study for defect sinks properties of ODS alloys have been investigated at 700K using LAMMPS (Atomic/Molecular massively parallel simulator software. SRIM (stopping range of ions in matter) code was used to see the approximate range of the ions and damage cascade profile. It has been observed that the oxide particle attracts vacancies/interstitials produced in the base matrix near the interface. The modeled structure looked amorphous …
Study Of Abnormal Grain Growth In Beta Annealed Ti-6al-4v Forgings,
2018
Air Force Institute of Technology
Study Of Abnormal Grain Growth In Beta Annealed Ti-6al-4v Forgings, Lee R. Morris
Theses and Dissertations
Beta annealed Ti-6Al-4V has been used extensively in current aerospace platforms due to properties such as high strength to weight ratio. Recent inspections during aircraft production have revealed regions of excessive grain sizes, resulting in quarantined parts and excessive time spent on root cause analysis and risk mitigation efforts. Uncertainty surrounding these parts has led to increased costs and may cause future aircraft production delays. Part manufacturers have intermittently reported problems with abnormal grain growth in these alloys for years, but to date no supplier has been able to determine the source of this microstructural phenomenon. Leveraging common Finite Element …
Analysis Of Additively Manufactured Injectors For Rotating Detonation Engines,
2018
Air Force Institute of Technology
Analysis Of Additively Manufactured Injectors For Rotating Detonation Engines, Michael C. Waters
Theses and Dissertations
This research represents an experimental and computational analysis of additively manufactured injectors for Rotating Detonation Engines (RDEs) for use in rocket propulsion. This research was based on the manufacture and testing of existing injector element designs using additive techniques. The designs were modeled from geometries gathered from Sutton and Biblarz Elements of Rocket Propulsion [23]. The goal of this research was to characterize the viscous losses of each design based on the discharge coefficient. The designs were computationally simulated to gain insight to the flow characteristics using multiple sets of conditions for surface roughness and inlet pressure. The results were …
Numerical Study Of Lateral Migration Of Elliptical Magnetic Microparticles In Microchannels In Uniform Magnetic Fields,
2018
Missouri University of Science and Technology
Numerical Study Of Lateral Migration Of Elliptical Magnetic Microparticles In Microchannels In Uniform Magnetic Fields, Jie Zhang, Cheng Wang
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This work reports numerical investigation of lateral migration of a paramagnetic microparticle of an elliptic shape in a plane Poiseuille flow of a Newtonian fluid under a uniform magnetic field by direct numerical simulation (DNS). A finite element method (FEM) based on the arbitrary Lagrangian–Eulerian (ALE) approach is used to study the effects of strength and direction of the magnetic field, particle–wall separation distance and particle shape on the lateral migration. The particle is shown to exhibit negligible lateral migration in the absence of a magnetic field. When the magnetic field is applied, the particle migrates laterally. The migration direction …
Ultra-Broadband Infrared Absorption By Tapered Hyperbolic Multilayer Waveguides,
2018
Missouri University of Science and Technology
Ultra-Broadband Infrared Absorption By Tapered Hyperbolic Multilayer Waveguides, Huixu Deng, Cherian J. Mathai, Shubhra Gangopadhyay, Jie Gao, Xiaodong Yang
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Ultra-broadband strong absorption over 92% covering the infrared wavelength range of 1 ~ 6μm is demonstrated by using the tapered hyperbolic Au-SiO2 multilayer waveguides on glass substrates. Such broadband absorption is formed by the stop-light modes at various wavelengths located at different waveguide widths. A planar hyperbolic waveguide model is built to determine the stop-light modes by considering both forward and backward guided modes. The stop-light modes located inside the Au-SiO2 multilayer waveguide are simulated at the absorption peaks by reducing the Au loss. Tapered multilayer waveguides with varying top widths are further simulated, fabricated and measured, indicating …
Wavelength-Selective Mid-Infrared Metamaterial Absorbers With Multiple Tungsten Cross Resonators,
2018
Missouri University of Science and Technology
Wavelength-Selective Mid-Infrared Metamaterial Absorbers With Multiple Tungsten Cross Resonators, Zhigang Li, Liliana Stan, David A. Czaplewski, Xiaodong Yang, Jie Gao
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Wavelength-selective metamaterial absorbers in the mid-infrared range are demonstrated by using multiple tungsten cross resonators. By adjusting the geometrical parameters of cross resonators in single-sized unit cells, near-perfect absorption with single absorption peak tunable from 3.5 µm to 5.5 µm is realized. The combination of two, three, or four cross resonators of different sizes in one unit cell enables broadband near-perfect absorption at mid-infrared range. The obtained absorption spectra exhibit omnidirectionality and weak dependence on incident polarization. The underlying mechanism of near-perfect absorption with cross resonators is further explained by the optical mode analysis, dispersion relation and equivalent RLC circuit …
Utilizing Supercomputing To Analyze Risks Of An Emergent Large-Scale Debris Field In Low Earth Orbit,
2018
Air Force Institute of Technology
Utilizing Supercomputing To Analyze Risks Of An Emergent Large-Scale Debris Field In Low Earth Orbit, David J. Buehler
Theses and Dissertations
The likelihood of on-orbit breakups, whether spontaneous or the result of collision, will likely continue to grow as the barriers of entry to and use of space are reduced. In all orbital regimes, especially low Earth orbit (LEO), preparation to respond quickly when the next breakup occurs is critical. This research utilizes high-performance parallel computation along with python-driven Systems Tool Kit (STK) to model a large-scale on-orbit breakup in LEO, with the goal of returning data in less than 90 minutes. The breakup is characterized by the National Aeronautics and Space Administration (NASA) EVOLVE 4.0 breakup model and is both …
Navigation Using Vector And Tensor Measurements Of The Earth's Magnetic Anomaly Field,
2018
Air Force Institute of Technology
Navigation Using Vector And Tensor Measurements Of The Earth's Magnetic Anomaly Field, Lauren A. Mount
Theses and Dissertations
This research explores the viability of using a navigation system that relies on measurements of the magnetic anomaly field as an alternative to GPS navigation. Previous research has been conducted on developing a navigation system using the intensity of the Earth's magnetic anomaly field as an alternative signal. This research focuses on using vector and tensor measurements, as opposed to scalar measurements of the anomaly field, as a means of obtaining accurate position and orientation solutions. This paper presents two navigation systems. The first uses an Extended Kalman Filter (EKF) with vector measurements of the magnetic anomaly field to aid …
Effects Of Position Uncertainty On Passive Multistatic Sar Resolution Measures,
2018
Air Force Institute of Technology
Effects Of Position Uncertainty On Passive Multistatic Sar Resolution Measures, Duy K. Nguyen
Theses and Dissertations
Given numerous exciting potentials including substantial cost savings, passive multistatic synthetic aperture radar (PMSAR) has been gaining more attention in the radar community. However, PMSAR research efforts such as emitters of opportunity selection thus far have not considered radar position uncertainty. Seeking to fill this knowledge gap, we run Monte Carlo trials to simulate transmitter position uncertainty and examine the effects on the multistatic resolution of radar sets of different geometries, center frequencies and bandwidths. By monitoring the 3dB contour of the multistatic point spread function, we find that the multistatic resolution worsens on average and the data spread grows …
Assessing The Reliability Of The B-1b Lancer Using Survival Analysis,
2018
Air Force Institute of Technology
Assessing The Reliability Of The B-1b Lancer Using Survival Analysis, Francisco J. Rodriguez
Theses and Dissertations
During the 2017 posture statement to the US Senate Armed Services Committee, the Secretary of the Air Force and Chief of Staff of the Air Force stated the Air Force suffers from shrinking aircraft inventory, aging aircraft fleets, and flying beyond the expected service life. These trends are not an exception to the B-1B Lancer, which has been in service since 1986. Recently, the B-1B Lancer has maintained the lowest mission capable (MC) rates of 47.7 percent. The purpose of this research is to explore the failure rates of the B-1B Lancer using survival analysis that investigates the failure behavior …
Space-Based Maneuver Detection And Characterization Using Multiple Model Adaptive Estimation,
2018
Air Force Institute of Technology
Space-Based Maneuver Detection And Characterization Using Multiple Model Adaptive Estimation, Justin D. Katzovitz
Theses and Dissertations
An increasingly congested space environment requires real-time and dynamic space situational awareness (SSA) on both domestic and foreign space objects in Earth orbits. Current statistical orbit determination (SOD) techniques are able to estimate and track trajectories for cooperative spacecraft. However, a non-cooperative spacecraft performing unknown maneuvers at unknown times can lead to unexpected changes in the underlying dynamics of classical filtering techniques. Adaptive estimation techniques can be utilized to build a bank of recursive estimators with different hypotheses on a system's dynamics. The current study assesses the use of a multiple model adaptive estimation (MMAE) technique for detecting and characterizing …
Quasi-Static Nonlinear Analysis Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle,
2018
Air Force Institute of Technology
Quasi-Static Nonlinear Analysis Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Kyle D. Moore
Theses and Dissertations
Due to the many drawbacks associated with a traditional lighter than air vehicle (LTAV), there is a desire for a LTAV which generates lift from an internal vacuum. To date, two feasible designs (the icosahedron and the hexakis icosahedron) for this so called vacuum lighter than air vehicle (VLTAV) have been studied at the Air Force Institute of Technology (AFIT). This research looks to show the feasibility of a new design for a VLTAV, the celestial icosahedron. This research includes a boundary condition study which proves the symmetric nature of the celestial icosahedron's frame with laterally constrained and unconstrained vertices. …
